外文翻译及中文译文
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外文翻译原文及译文学院计算机学院专业计算机科学与技术班级学号姓名指导教师负责教师Java(programming language)Java is a general-purpose, concurrent, class-based, object-oriented computer program- -ming language that is specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" (WORA), meaning that code that runs on one platform does not need to be recompiled to run on another. Java applications are typically compiled to byte code (class file) that can run on any Java virtual machine(JVM) regardless of computer architecture. Java is, as of 2012, one of the most popular programming languages in use, particularly for client-server web applications, with a reported 10 million users. Java was originally developed by James Gosling at Sun Microsystems (which has since merged into Oracle Corporation) and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++, but it has fewer low-level facilities than either of them.The original and reference implementation Java compilers, virtual machines, and class libraries were developed by Sun from 1991 and first released in 1995. As of May 2007, in compliance with the specifications of the Java Community Process, Sun relicensed most of its Java technologies under the GNU General Public License. Others have also developed alternative implementations of these Sun technologies, such as the GNU Compiler for Java and GNU Classpath.Java is a set of several computer software products and specifications from Sun Microsystems (which has since merged with Oracle Corporation), that together provide a system for developing application software and deploying it in across-platform computing environment. Java is used in a wide variety of computing platforms from embedded devices and mobile phones on the low end, to enterprise servers and supercomputers on the high end. While less common, Java appletsare sometimes used to provide improved and secure functions while browsing the World Wide Web on desktop computers.Writing in the Java programming language is the primary way to produce code that will be deployed as Java bytecode. There are, however, byte code compilers available forother languages such as Ada, JavaScript, Python, and Ruby. Several new languages have been designed to run natively on the Java Virtual Machine (JVM), such as Scala, Clojure and Groovy.Java syntax borrows heavily from C and C++, but object-oriented features are modeled after Smalltalk and Objective-C. Java eliminates certain low-level constructs such as pointers and has a very simple memory model where every object is allocated on the heap and all variables of object types are references. Memory management is handled through integrated automatic garbage collection performed by the JVM.An edition of the Java platform is the name for a bundle of related programs from Sun that allow for developing and running programs written in the Java programming language. The platform is not specific to any one processor or operating system, but rather an execution engine (called a virtual machine) and a compiler with a set of libraries that are implemented for various hardware and operating systems so that Java programs can run identically on all of them. The Java platform consists of several programs, each of which provides a portion of its overall capabilities. For example, the Java compiler, which converts Java source code into Java byte code (an intermediate language for the JVM), is provided as part of the Java Development Kit (JDK). The Java Runtime Environment(JRE), complementing the JVM with a just-in-time (JIT) compiler, converts intermediate byte code into native machine code on the fly. An extensive set of libraries are also part of the Java platform.The essential components in the platform are the Java language compiler, the libraries, and the runtime environment in which Java intermediate byte code "executes" according to the rules laid out in the virtual machine specification.In most modern operating systems (OSs), a large body of reusable code is provided to simplify the programmer's job. This code is typically provided as a set of dynamically loadable libraries that applications can call at runtime. Because the Java platform is not dependent on any specific operating system, applications cannot rely on any of the pre-existing OS libraries. Instead, the Java platform provides a comprehensive set of its own standard class libraries containing much of the same reusable functions commonly found in modern operating systems. Most of the system library is also written in Java. For instance, Swing library paints the user interface and handles the events itself, eliminatingmany subtle differences between how different platforms handle even similar components.The Java class libraries serve three purposes within the Java platform. First, like other standard code libraries, the Java libraries provide the programmer a well-known set of functions to perform common tasks, such as maintaining lists of items or performing complex string parsing. Second, the class libraries provide an abstract interface to tasks that would normally depend heavily on the hardware and operating system. Tasks such as network access and file access are often heavily intertwined with the distinctive implementations of each platform. The and java.io libraries implement an abstraction layer in native OS code, then provide a standard interface for the Java applications to perform those tasks. Finally, when some underlying platform does not support all of the features a Java application expects, the class libraries work to gracefully handle the absent components, either by emulation to provide a substitute, or at least by providing a consistent way to check for the presence of a specific feature.The success of Java and its write once, run anywhere concept has led to other similar efforts, notably the .NET Framework, appearing since 2002, which incorporates many of the successful aspects of Java. .NET in its complete form (Microsoft's implementation) is currently only fully available on Windows platforms, whereas Java is fully available on many platforms. .NET was built from the ground-up to support multiple programming languages, while the Java platform was initially built to support only the Java language, although many other languages have been made for JVM since..NET includes a Java-like language called Visual J# (formerly named J++) that is incompatible with the Java specification, and the associated class library mostly dates to the old JDK 1.1 version of the language. For these reasons, it is more a transitional language to switch from Java to the .NET platform, than a first class .NET language. Visual J# was discontinued with the release of Microsoft Visual Studio 2008. The existing version shipping with Visual Studio 2005will be supported until 2015 as per the product life-cycle strategy.In June and July 1994, after three days of brainstorming with John Gage, the Director of Science for Sun, Gosling, Joy, Naughton, Wayne Rosing, and Eric Schmidt, the team re-targeted the platform for the World Wide Web. They felt that with the advent of graphical web browsers like Mosaic, the Internet was on its way to evolving into the samehighly interactive medium that they had envisioned for cable TV. As a prototype, Naughton wrote a small browser, Web Runner (named after the movie Blade Runner), later renamed Hot Java.That year, the language was renamed Java after a trademark search revealed that Oak was used by Oak Technology. Although Java 1.0a was available for download in 1994, the first public release of Java was 1.0a2 with the Hot Java browser on May 23, 1995, announced by Gage at the Sun World conference. His announcement was accompanied by a surprise announcement by Marc Andreessen, Executive Vice President of Netscape Communications Corporation, that Netscape browsers would be including Java support. On January 9, 1996, the Java Soft group was formed by Sun Microsystems to develop the technology.Java编程语言Java是一种通用的,并发的,基于类的并且是面向对象的计算机编程语言,它是为实现尽可能地减少执行的依赖关系而特别设计的。
温室大棚智能传感器中英文外文翻译文献(含:英文原文及中文译文)英文原文Smart Infrared Temperature SensorsP RayKeeping up with continuously evolving process technologies is a major challenge for process engineers. Add to that the demands of staying current with rapidly evolving methods of monitoring and controlling those processes, and the assignment can become quite intimidating. However, infrared (IR) temperature sensor manufacturers are giving users the tools they need to meet these challenges: the latest computer-related hardware, software, and communications equipment, as well as leading-edge digital circuitry. Chief among these tools, though, is the next generation of IR thermometers— the smart sensor.Today’s new smart IR sensors represent a union of two rapidly evolving sciences that combine IR temperature measurement with high-speed digital technologies usually associated with the computer. These instruments are called smart sensors because they incorporate microprocessors programmed to act as transceivers for bidirectional, serial communications between sensors on the manufacturing floor and computers in the control room (see Photo 1). And because the circuitry is smaller, the sensors are smaller, simplifying installation in tight orawkward areas. Integrating smart sensors into new or existing process control systems offers an immediate advantage to process control engineers in terms of providing a new level of sophistication in temperature monitoring and control.Integrating Smart Sensors into Process LinesWhile the widespread implementation of smart IR sensors is new, IR temperature measurement has been successfully used in process monitoring and control for decades (see the sidebar, “How Infrared Temperature Sensors Work,” below). In the past, if process engineers needed to ch ange a sensor’s settings, they would have to either shut down the line to remove the sensor or try to manually reset it in place. Either course could cause delays in the line, and, in some cases, be very dangerous. Upgrading a sensor usually required buying a new unit, calibrating it to the process, and installing it while the process line lay inactive. For example, some of the sensors in a wire galvanizing plant used to be mounted over vats of molten lead, zinc, and/or muriatic acid and accessible only by reaching out over the vats from a catwalk. In the interests of safety, the process line would have to be shut down for at least 24 hours to cool before changing and upgrading a sensor.Today, process engineers can remotely configure, monitor, address, upgrade, and maintain their IR temperature sensors. Smart models with bidirectional RS-485 or RS-232 communications capabilities simplifyintegration into process control systems. Once a sensor is installed on a process line, engineers can tailor all its parameters to fit changing conditions—all from a PC in the control room. If, for example, the ambient temperature fluctuates, or the process itself undergoes changes in type, thickness, or temperature, all a process engineer needs to do is customize or restore saved settings at a computer terminal. If a smart sensor fails due to high ambient temperature conditions, a cut cable, or failed components, its fail-safe conditions engage automatically. The sensor activates an alarm to trigger a shutdown, preventing damage to product and machinery. If ovens or coolers fail, HI and LO alarms can also signal that there is a problem and/or shut down the line.Extending a Sensor’s Useful LifeFor smart sensors to be compatible with thousands of different types of processes, they must be fully customizable. Because smart sensors contain EPROMs (erasable programmable read only memory), users can reprogram them to meet their specific process requirements using field calibration, diagnostics, and/or utility software from the sensor manufacturer.Another benefit of owning a smart sensor is that its firmware, the software embedded in its chips, can be upgraded via the communications link to revisions as they become available — without removing the sensor from the process line. Firmware upgrades extend the working life of asensor and can actually make a smart sensor smarter.The Raytek Marathon Series is a full line of 1- and 2-color ratio IR thermometers that can be networked with up to 32 smart sensors. Available models include both integrated units and fiber-optic sensors with electronic enclosures that can be mounted away from high ambient temperatures.(see Photo 1). Clicking on a sensor window displays the configuration settings for that particular sensor. The Windows graphical interface is intuitive and easy to use. In the configuration screen, process engineers can monitor current sensor settings, adjust them to meet their needs, or reset the sensor back to the factory defaults. All the displayed information comes from the sensor by way of the RS-485 or RS-232 serial connection.The first two columns are for user input. The third monitors the sensor’s parameters in real time. Some parameters can be changed through other screens, custom programming, and direct PC-to-sensor commands. Parameters that can be changed by user input include the following:∙Relay contact can be set to NO (normally open) or NC (normally closed).∙Relay function can be set to alarm or setpoint.∙Temperature units can be changed from degrees Celsius to degreesFahrenheit, or vice versa.∙Display and analog output mode can be changed for smart sensors that have combinedone- and two-color capabilities.∙Laser (if the sensor is equipped with laser aiming) can be turned on or off.∙Milliamp output settings and range can be used as automatic process triggers or alarms. ∙Emissivity (for one-color) or slope (for two-color) ratio thermometers values can be set. Emissivity and slope values for common metal and nonmetal materials, and instructions on how to determine emissivity and slope, are usually included with sensors.∙Signal processing defines the temperature parameters returned. Average returns an object’s average temperature over a period of time; peak -hold returns an object’s peak temperature either over a period of time or by an external trigger.∙HI alarm/LO alarm can be set to warn of improper changes in temperature. On some process lines, this could be triggered by a break in a product or by malfunctioning heater or cooler elements.∙Attenuation indicates alarm and shut down settings for two-color ratio smart sensors. In this example, if the lens is 95% obscured, an alarm warns that the temperature results might be losing accuracy (known as a “dirty window” alarm). More than 95% obscurity can trigger anautomatic shutdown of the process.Using Smart SensorsSmart IR sensors can be used in any manufacturing process in which temperatures are crucial to high-quality product.Six IR temperature sensors can be seen monitoring product temperatures before and after the various thermal processes and before and after drying. The smart sensors are configured on a high-speed multidrop network (defined below) and are individually addressable from the remote supervisory computer. Measured temperatures at all sensor locations can be polled individually or sequentially; the data can be graphed for easy monitoring or archived to document process temperature data. Using remote addressing features, set points, alarms, emissivity, and signal processing, information can be downloaded to each sensor. The result is tighter process control. Remote Online Addressability In a continuous process similar to that in Figure 2, smart sensors can be connected to one another or to other displays, chart recorders, and controllers on a single network. The sensors may be arranged in multidrop or point-to-point configurations, or simply stand alone.In a multidrop configuration, multiple sensors (up to 32 in some cases) can be combined on a network-type cable. Each can have its own “address,” allowing it to be configured separately with different operating parameters. Because smart sensors use RS-485 or FSK (frequency shiftkeyed) communications, they can be located at considerable distances from the control room computer — up to 1200 m (4000 ft.) for RS-485, or 3000 m (10,000 ft.) for FSK. Some processes use RS-232 communications, but cable length is limited to <100 ft.In a point-to-point installation, smart sensors can be connected to chart recorders, process controllers, and displays, as well as to the controlling computer. In this type of installation, digital communications can be combined with milliamp current loops for a complete all-around process communications package.Sometimes, however, specialized processes require specialized software. A wallpaper manufacturer might need a series of sensors programmed to check for breaks and tears along the entire press and coating run, but each area has different ambient and surface temperatures, and each sensor must trigger an alarm if it notices irregularities in the surface. For customized processes such as this, engineers can write their own programs using published protocol data. These custom programs can remotely reconfigure sensors on the fly—without shutting down the process line.Field Calibration and Sensor UpgradesWhether using multidrop, point-to-point, or single sensor networks, process engineers need the proper software tools on their personal computers to calibrate, configure, monitor, and upgrade those sensors.Simple, easy-to-use data acquisition, configuration, and utility programs are usually part of the smart sensor package when purchased, or custom software can be used.With field calibration software, smart sensors can be calibrated, new parameters downloaded directly to the sensor’s circuitry, and the sensor’s current parameters saved and stored as computer data files to ensure that a complete record of calibration and/or parameter changes is kept. One set of calibration techniques can include one-point offset and two- and three-point with variable temperatures:• One-point offset. If a single temperature is used in a particular process, and the sensor reading needs to be offset to make it match a known temperature, one-point offset calibration should be used. This offset will be applied to all temperatures throughout the entire temperature range. For example, if the known temperature along a float glass line is exactly 1800°F, the smart sensor, or series of sensors, can be calibrated to that temperature.• Two-point. If sensor readings must match at two specific temperatures, the two-point calibration shown in Figure 3 should be selected. This technique uses the calibration temperatures to calculate a gain and an offset that are applied to all temperatures throughout the entire range. • Three-point with variable temperature. If the process has a wide range of temperatures, and sensor readings need to match at threespecific temperatures, the best choice is three-point variable temperature calibration (see Figure 4). This technique uses the calibration temperatures to• Three points If the process has a wi de temperature range, the sensor reading must meet three specific temperatures. The best choice is a three-point temperature calibration. This technique uses the calibration temperature to calculate two gains and two offsets. The first gain and offset apply to all temperatures below the midpoint temperature and at all midpoints above the second plate. Three-point calibration is less common than multiple single-dot, but occasionally manufacturers need to implement this technology to meet specific standards.On-site calibration software also allows the use of routine diagnostic methods, including power supply voltage and relay tests that are run on smart sensors. The result is that the process engineer knows that the sensor works best and it makes it easier to do some necessary troubleshooting.3. ConcludesThe new generation of intelligent infrared temperature sensors requires process engineers to keep up with changes brought about by new production technologies and increased production. They can now configure as many sensors as possible to meet the needs of their particular control process and extend the lifespan of these sensors, far beyond theprevious “not smart” designs. Due to the increased production speed, equipment downtime must be reduced. By monitoring equipment as much as possible and fine-tuning temperature variables without the need for shutdown processes, engineers can maintain efficient processes and deliver high-quality products. The digital processing components and communication capabilities of smart infrared sensors provide a degree of flexibility, security, and ease of use that have not been achieved to date.Infrared (IR) radiation is an electromagnetic spectrum that includes radio waves, microwaves, visible light, and ultraviolet light, as well as gamma rays and X-rays. The IR is between the visible part of the spectrum and radio waves. Infrared wavelengths are usually expressed in micrometers and the spectral range is from 0.7 to 1000 microns. Only the 0.7-14 micron band is used for infrared temperature measurement.Using advanced optical systems and detectors, non-contact infrared thermometers can focus on almost any part or part of the 0.7-14 μm band. Because each object (except blackbody) emits the best infrared energy at a specific point along the infrared wavelength of the line, each process may require a unique sensor model with specific optics and detector types. For example, a sensor, a narrow concentration of polyethylene and related materials concentrated in the 3.43 μm spectral ran ge suitable for measuring surface temperature. A sensor is set at 5 microns to measure the glass surface. Light sensors are used for metal and metal foils. Thebroader spectral range is used to measure lower temperature surfaces such as paper, cardboard, poly, and aluminum foil composites.An object reflects the increase or decrease of emission infrared energy through its temperature. It is emitted energy, measured at the target emissivity, which indicates the temperature of an object.Emissivity is a term used to quantify the energy and light emitting properties of different materials and surfaces. Infrared sensors have an adjustable emissivity setting, usually from 0.1 to 1.0, allowing accurate measurement of several surface types of temperature. The emitted energy comes from an object and reaches the infrared sensor through its optical system, which focuses on one or more light-sensitive detectors on the energy source. The detector's infrared energy is then converted into electrical signals, which in turn are converted into temperature values based on the sensor's calibration equation and the target's emissivity. This temperature value can be displayed on the sensor or converted to a digital output in a smart sensor and displayed on the computer terminal.中文译文智能红外温度传感器P Ray跟上不断发展的工艺技术对工艺工程师来说是一向重大挑战。
外文文献原稿和译文原稿DATABASEA database may be defined as a collection interrelated data store together with as little redundancy as possible to serve one or more applications in an optimal fashion .the data are stored so that they are independent of programs which use the data .A common and controlled approach is used in adding new data and in modifying and retrieving existing data within the data base .One system is said to contain a collection of database if they are entirely separate in structure .A database may be designed for batch processing , real-time processing ,or in-line processing .A data base system involves application program, DBMS, and database.THE INTRODUCTION TO DATABASE MANAGEMENT SYSTEMSThe term database is often to describe a collection of related files that is organized into an integrated structure that provides different people varied access to the same data. In many cases this resource is located in different files in different departments throughout the organization, often known only to the individuals who work with their specific portion of the total information. In these cases, the potential value of the information goes unrealized because a person in other departments who may need it does not know it or it cannot be accessed efficiently. In an attempt to organize their information resources and provide for timely and efficient access, many companies have implemented databases.A database is a collection of related data. By data, we mean known facts that can be recorded and that have implicit meaning. For example, the names, telephone numbers, and addresses of all the people you know. You may have recorded this data in an indexed address book, or you may have stored it on a diskette using a personalcomputer and software such as DBASE Ⅲor Lotus 1-2-3. This is a collection of related data with an implicit meaning and hence is a database.The above definition of database is quite general. For example, we may consider the collection of words that made up this page of text to be usually more restricted. A database has the following implicit properties:● A database is a logically coherent collection of data with some inherent meaning. A random assortment of data cannot be referred to as a database.● A database is designed, built, and populated with data for a specific purpose. It has an intended group of user and some preconceived applications in which these users are interested.● A database represents some aspect of the real world, sometimes called the miniworld. Changes to the miniworld are reflected in the database.In other words, a database has some source from which data are derived, some degree of interaction with events in the real world, and an audience that is actively interested in the contents of the database.A database management system (DBMS) is composed of three major parts: (1) a storage subsystem that stores and retrieves data in files; (2)a modeling and manipulation subsystem that provides the means with which to organize the data and to add, delete, maintain, and update the data; and (3) an interface between the DBMS and its users. Several major trends are emerging that enhance the value and usefulness of database management systems.●Managers who require more up-to-date information to make effective decisions.●Customers who demand increasingly sophisticated information services and more current information about the status of their orders, invoices, and accounts.●Users who find that they can develop custom applications with database systems in a fraction of the time it takes to use traditional programming languages.●Organizations that discover information has a strategic value; they utilize their database systems to gain an edge over their competitors.A DBMS can organize, process, and present selected data elements from the database. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions that aren’t available in regular reports. These questions might initially be vague and/or p oorly defined, but people can “browse” through the database until they have the needed information. In short, the DBMS will “mange” the stored data items and assemble the needed items from the common database in response to the queries of those who aren’t programmers. In a file-oriented system, user needing special information may communicate their needs to a programmer, who, when time permits, will write one or more programs to extract the data and prepare the information. The availability of a DBMS, however, offers users a much faster alternative communications path.DATABASE QUERYIf the DBMS provides a way to interactively enter and update the database ,as well as interrogate it ,this capability allows for managing personal database. However, it does not automatically leave an audit trail of actions and does not provide the kinds of controls necessary in a multi-user organization .There controls are only available when a set of application programs is customized for each data entry and updating function.Software for personal computers that perform some of the DBMS functions has been very popular .Individuals for personal information storage and processing intended personal computers for us .Small enterprises, professionals like doctors, architects, engineers, lawyers and so on have also used these machines extensively. By the nature of intended usage ,database system on there machines are except from several of the requirements of full-fledged database systems. Since data sharing is not intended, concurrent operations even less so ,the software can be less complex .Security and integrity maintenance are de-emphasized or absent .as data volumes will be small, performance efficiency is also less important .In fact, the only aspect of a database system that is important is data independence. Data independence ,as stated earlier ,means that application programs and user queries need not recognize physical organization of data on secondary storage. The importance of this aspect , particularly for the personal computer user ,is that this greatly simplifies database usage . The user can store ,access and manipulate data at ahigh level (close to the application)and be totally shielded from the low level (close to the machine )details of data organization.DBMS STRUCTURING TECHNIQUESSpatial data management has been an active area of research in the database field for two decades ,with much of the research being focused on developing data structures for storing and indexing spatial data .however, no commercial database system provides facilities for directly de fining and storing spatial data ,and formulating queries based on research conditions on spatial data.There are two components to data management: history data management and version management .Both have been the subjects of research for over a decade. The troublesome aspect of temporal data management is that the boundary between applications and database systems has not been clearly drawn. Specifically, it is not clear how much of the typical semantics and facilities of temporal data management can and should be directly incorporated in a database system, and how much should be left to applications and users. In this section, we will provide a list of short-term research issues that should be examined to shed light on this fundamental question.The focus of research into history data management has been on defining the semantics of time and time interval, and issues related to understanding the semantics of queries and updates against history data stored in an attribute of a record. Typically, in the context of relational databases ,a temporal attribute is defined to hold a sequence of history data for the attribute. A history data consists of a data item and a time interval for which the data item is valid. A query may then be issued to retrieve history data for a specified time interval for the temporal attribute. The mechanism for supporting temporal attributes is to that for supporting set-valued attributes in a database system, such as UniSQL.In the absence of a support for temporal attributes, application developers who need to model and history data have simply simulated temporal attributes by creating attribute for the time interval ,along with the “temporal” attribute. This of course may result in duplication of records in a table, and more complicated search predicates in queries. The one necessary topic of research in history data management is to quantitatively establish the performance (and even productivity) differences betweenusing a database system that directly supports attributes and using a conventional database system that does not support either the set-valued attributes or temporal attributes.Data security, integrity, and independenceData security prevents unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database of the database, called subschemas. For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data.Data integrity refers to the accuracy, correctness, or validity of the data in the database. In a database system, data integrity means safeguarding the data against invalid alteration or destruction. In large on-line database system, data integrity becomes a more severe problem and two additional complications arise. The first has to do with many users accessing the database concurrently. For example, if thousands of travel agents book the same seat on the same flight, the first agent’s booking will be lost. In such cases the technique of locking the record or field provides the means for preventing one user from accessing a record while another user is updating the same record.The second complication relates to hardware, software or human error during the course of processing and involves database transaction which is a group of database modifications treated as a single unit. For example, an agent booking an airline reservation involves several database updates (i.e., adding the passenger’s name and address and updating the seats-available field), which comprise a single transaction. The database transaction is not considered to be completed until all updates have been completed; otherwise, none of the updates will be allowed to take place.An important point about database systems is that the database should exist independently of any of the specific applications. Traditional data processing applications are data dependent.When a DMBS is used, the detailed knowledge of the physical organization of the data does not have to be built into every application program. The application program asks the DBMS for data by field name, for example, a coded representationof “give me customer name and balance due” would be sent to the DBMS. Without a DBMS the programmer must reserve space for the full structure of the record in the program. Any change in data structure requires changes in all the applications programs.Data Base Management System (DBMS)The system software package that handles the difficult tasks associated with creating ,accessing and maintaining data base records is called a data base management system (DBMS). A DBMS will usually be handing multiple data calls concurrently.It must organize its system buffers so that different data operations can be in process together .It provides a data definition language to specify the conceptual schema and most likely ,some of the details regarding the implementation of the conceptual schema by the physical schema.The data definition language is a high-level language, enabling one to describe the conceptual schema in terms of a “data model “.At the present time ,there are four underling structures for database management systems. They are :List structures.Relational structures.Hierarchical (tree) structures.Network structures.Management Information System(MIS)An MIS can be defined as a network of computer-based data processing procedures developed in an organization and integrated as necessary with manual and other procedures for the purpose of providing timely and effective information to support decision making and other necessary management functions.One of the most difficult tasks of the MIS designer is to develop the information flow needed to support decision making .Generally speaking ,much of the information needed by managers who occupy different levels and who have different levels and have different responsibilities is obtained from a collection of exiting information system (or subsystems)Structure Query Language (SQL)SQL is a data base processing language endorsed by the American NationalStandards Institute. It is rapidly becoming the standard query language for accessing data on relational databases .With its simple ,powerful syntax ,SQL represents a great progress in database access for all levels of management and computing professionals.SQL falls into two forms : interactive SQL and embedded SQL. Embedded SQL usage is near to traditional programming in third generation languages .It is the interactive use of SQL that makes it most applicable for the rapid answering of ad hoc queries .With an interactive SQL query you just type in a few lines of SQL and you get the database response immediately on the screen.译文数据库数据库可以被定义为一个相互联系的数据库存储的集合。
外文资料及中文译文作者姓名***专业财务管理指导教师姓名***专业技术职务副教授外文资料FIVE WAYS TO IMPROVE RETURN ON EQUITYThe Du Pont Model: A Brief HistoryThe use of financial ratios by financial analysts, lenders, academic researchers, and small business owners has been widely acknowleged in the literature. (See, for example, Osteryoung & Constand (1992), Devine & Seaton (1995), or Burson (1998) The concepts of Return on Assets (ROA hereafter) and Return on Equity (ROEhereafter) are important for understanding the profitability of a business enterprise. Specifically, a “return on” ratio illustrates the relationship between profits and the investment needed to generate those profits. However, these concepts are often “too far removed from normal activities” to be easily understood and useful to many managers or small business owners. (Slater and Olson, 1996)In 1918, four years after he was hired by the Du Pont Corporation to work in its treasury department, electrical engineer F. Donaldson Brown was given the task of untangling the finances of a company of which Du Pont had just purchased 23 percent of its stock. (This company was General Motors!) Brown recognized a mathematical relationship that existed between two commonly computed ratios, namely net profit margin (obviously a profitability measure) and total asset turnover (an efficiency measure), and ROA. The product of the net profit margin and total asset turnover equals ROA, and this was the original Du Pont model, as illustrated in Equation 1 below.Eq. 1: (net income / sales) x (sales / total assets) = (net income / total assets) i.e. ROAAt this point in time maximizing ROA was a common corporate goal and the realization that ROA was impacted by both profitability and efficiency led to the development of a system of planning and control for all operating decisions within a firm. This became the dominant form of financial analysis until the 1970s. (Blumenthal, 1998)In the 1970s the generally accepted goal of financial management became “maximizing the wealth of the firm’s owners” (Gitman, 1998) and focus shifted from ROA to ROE. This led to the first major modification of the original Du Pontmodel. In addition to profitability and efficiency, the way in which a firm financed its activities, i.e. its use of “leverage” became a third area of attention for financial managers. The new ratio of interest was called the equity multiplier, which is (total assets / equity). The modified Du Pont model is shown in Equations 1 and 2 below.Eq. 2: ROA x (total assets / equity) = ROEEq. 3: (net income / sales) x (sales / total assets) x (total assets / equity) = ROE The modified Du Pont model became a standard in all financial management textbooks and a staple of introductory and advanced courses alike as students read statements such as: “Ultimately, the most important, or“bottom line” accounting ratio is the ratio of net income to common equity (ROE).” (Brigham and Houston, 2001)The modified model was a powerful tool to illustrate the interconnectedness of a firm’s income statement and its balance sheet, and to develop straight-forward strategies for improving the firm’s ROE.More recently, Hawawini and Viallet (1999) offered yet another modification to the Du Pontmodel. This modification resulted in five different ratios that combine to form ROE. In their modification they acknowlege that thefinancial statements firms prepare for their annualreports (which are of most importance to creditorsand tax collectors) are not always useful tomanagers making operating and financialdecisions. (Brigham and Houston, p. 52) T heyrestructured the traditional balance sheet into a“managerial balance sheet” which is “a moreappropriate tool for assessing the contribution ofoperating decisions to the firm’s financialperformance.” (Hawawini and Viallet, p.68)This restructured balanc e sheet uses the conceptof “invested capital” in place of total assets, andthe concept of “capital employed” in place oftotal liabilities and owner’sequity found on thetraditional balance sheet. The primary differenceis in the treatment of the short-ter m “workingcapital” accounts. The managerial balance sheet uses a net figure called “working capital requirement” (determined as: [accounts receivable + inventories + prepaid expenses] – [accounts payable + accrued expenses]) as a part of invested capital. These accounts then individually drop out of the managerial balance sheet. A more detailed explanation of the managerial balance sheet is beyond the scope of this paper, but will be partially illustrated in an example. The “really” modified Du Pont mode l is shown below in Equation 4.Eq. 4: (EBIT / sales) x (sales / invested capital) x (EBT / EBIT) x (invested capital / equity) x (EAT / EBT) = ROE(Where: invested capital = cash + working capital requirement + net fixed assets) This “really” modified model still maintains the importance of the impact of operating decisions (i.e. profitability and efficiency) and financing decisions (leverage) upon ROE, but uses a total of five ratios to uncover what drives ROE and give insight to how to improve this important ratio.The firm’s operating decisions are those that involve the acquisition and disposal of fixed assets and the management of the firm’s operating assets (mostly inventories and accounts receivable) and operating liabilities (accountspayable and accruals). These are captured in thefirst two ratios of the “really” modified Du Pontmodel. These are:1. operating profit margin: (Earnings Before Interest & Taxes or EBIT / sales)2. capital turnover: (sales / invested capital)The firm’s financing decisions are those that determine the mix of debt and equity used to fund the firm’s operating decisions. These are captured in the third and fourth ratios of the “really” modified model. These are:3. financial cost ratio: (Earnings Before Taxes or EBT / EBIT)4. financial structure ratio: (invested capital / equity)The final determinant of a firm’s ROE is the incidence of business taxation. The higher the taxrate applied to a firm’s EBT, the lower its ROE. This is cap tured in the fifth ratio ofthe “really”modified model.5. tax effect ratio: (Earnings After Taxes or EAT / EBT)The relationship that ties these five ratios together is that ROE is equal to their combined product. (See Equation 4.)Example of A pplying the “Really” Modified Du Pont ModelTo illustrate how the model works, consider the income statement and balance sheet for the fictitious small firm of Herrera & Company, LLC.Income StatementNet Sales …………………………………………………….. $766,990C ost of Goods Sold ………………………………………….. (560,000) Selling, General, & Administrative Expenses ………………. (143,342) Depreciation Expense ……………………………………….. (24,000) Earnings Before Interest & Taxes …………………………… $ 39,648Interest Expense ……………………………………………... (12,447) Earnings Before Taxes ………………………………………. $ 27,201Taxes ………………………………………………………… (8,000) Earnings After Taxes (net profit) ……………………………. $ 19,201Balance SheetCash ……………………….$ 40,000 Notes Payable ………………… $ 58,000 Pre-paid Expenses ………... 12,000 Accounts Payable …………….. 205,000 Accounts Receivable ……… 185,000 Accrued Expenses ……………. 46,000 Inventory ………………….. 200,000 Current Liabilities ……………. $309,000 Current Assets ……………. $437,000 Long-Term DebtL and/Buildings …………… 160,000 Mortgage ……………………. 104,300Equipment ………………… 89,000 8-Year Note ………………… 63,000Less: Acc. Depreciation …... (24,000) Owner’s Equity ……………….. 185,700Net Fixed Assets ………….. $225,000 Total Liabilities & Equity …….. $662,000 Total Assets ………………. $662,000Computation of ROE1. Operating Profit Margin = $39,648 / $766,990 = .05172. Capital Turnover = $766,990 / $411,000* = 1.86623. Financial Cost Ratio = $27,201 / $39,648 = .68614. Financial Structure Ratio = $411,000 / $185,700 = 2.21325. Tax Effect Ratio = $19,201 / $27,201 = .7059ROE = .0517 x 1.8662 x .6861 x 2.2132 x .7059 = .1034** or 10.34%* Invested Capital = Cash ($40,000) + Working Capital Requirement [$185,000 + $200,000 + $12,000] –[$205,000 + $46,000] (or $146,000) + Net Fixed Assets ($225,000) = $411,000** Note that this is the same as conventional computation of ROE: $19,201 / $185,700 = .1034Conclusions & ImplicationsThe “really” modified Du Pont model of ratio analysis can demystify relatively complex financial analysis and put strategic financial planning at the fingertips of any small business owner or manager who takes the (relatively little) time needed to understand it. Each operating and financial decision can be made within a framework of how that decision will impact ROE. Easily set up on a computer model (such as a spreadsheet), one can see how decisions “flow through” to the bottom line, which facilitates coordinated financial planning. (Harrington & Wilson,1986).In its simplest form, we can say that to improve ROE the only choices one has are to increase operating profits, become more efficient in using existing assets to generate sales, recapitalize to make better use of debt and/or better control the cost of borrowing, or find ways to reduce the tax liability of the firm. Each of these choices leads to a different financial strategy.For example, to increase operating profits one must either increase sales (in a higher proportionthan the cost of generating those sales) or reduce expenses. Since it is generally more difficult toincrease sales than it is to reduce expenses, a small business owner can try to lower expenses by determining: 1) if a new supplier might offer equivalent goods at a lower cost, or 2) if a website might be a viable alternative to a catalog, or 3) can some tasks currently being done by outsiders be done in-house. In each case net income will rise without any increase in sales and ROE will rise as well. Alternatively, to become more efficient, one must either increase sales with the same level of assets or produce the same level of sales with less assets. A small business owner might then try to determine: 1) if it is feasible to expand store hours by staying open later or on weekends, or 2) if a less expensive piece of equipment is available that could replace an existing (more expensive) piece of equipment, or 3) if there is a more practical way to produce and/or deliver goods or services than is presently being used.Further, small business owners can determine if they are using debt wisely. Refinancing an existing loan at a cheaper rate will reduce interest expenses and, thus, increase ROE. Exercising some of an unused line of credit can increase the financial structure ratio with a corresponding increase in ROE. And, taking advantage of tax incentives that are often offered by federal, state,and local taxing authorities can increase the tax effect ratio, again with a commensurate increase in ROE.In conclusion, ROE is the most compre-hensive measure of profitability of a firm. It considers the operating and investing decisions made as well as the financing andtax-related decisions. The “really” modified Du Pont model dissects ROE into five easily computed ratios that can be examined for potential strategies for improvement. It should be a tool that all business owners, managers, and consultants have at their disposal when evaluating a firm and making recommendations for improvement.中文译文真实修改的杜邦分析:五种方式改善股东权益回报率杜邦模型:简史运用财务比率进行分析已经被财务分析家,贷款人,学术研究人员和小企业主在文献资料里广泛运用。
外文文献翻译(含:英文原文及中文译文)文献出处:Gao Q, Wang X, Xie G. License Plate Recognition Based On Prior Knowledge[C]// IEEE International Conference on Automation and Logistics. IEEE, 2007:2964-2968.英文原文License Plate Recognition Based On Prior KnowledgeQian Gao, Xinnian Wang and Gongfu XieAbstract - In this paper, a new algorithm based on improved BP (back propagation) neural network for Chinese vehicle license plate recognition (LPR) is described. The proposed approach provides a solution for the vehicle license plates (VLP) which were degraded severely. What it remarkably differs from the traditional methods is the application of prior knowledge of license plate to the procedure of location, segmentation and recognition. Color collocation is used to locate the license plate in the image. Dimensions of each character are constant, which is used to segment the character of VLPs. The Layout of the Chinese VLP is an important feature, which is used to construct a classifier for recognizing. The experimental results show that the improved algorithm is effective under the condition that the license plates were degraded severely.Index Terms - License plate recognition, prior knowledge, vehiclelicense plates, neural network.I. INTRODUCTIONV ehicle License-Plate (VLP) recognition is a very interesting but difficult problem. It is important in a number of applications such as weight-and-speed-limit, red traffic infringement, road surveys and park security [1]. VLP recognition system consists of the plate location, the characters segmentation, and the characters recognition. These tasks become more sophisticated when dealing with plate images taken in various inclined angles or under various lighting, weather condition and cleanliness of the plate. Because this problem is usually used in real-time systems, it requires not only accuracy but also fast processing. Most existing VLP recognition methods [2], [3], [4], [5] reduce the complexity and increase the recognition rate by using some specific features of local VLPs and establishing some constrains on the position, distance from the camera to vehicles, and the inclined angles. In addition, neural network was used to increase the recognition rate [6], [7] but the traditional recognition methods seldom consider the prior knowledge of the local VLPs. In this paper, we proposed a new improved learning method of BP algorithm based on specific features of Chinese VLPs. The proposed algorithm overcomes the low speed convergence of BP neural network [8] and remarkable increases the recognition rate especially under the condition that the license plate images were degrade severely.II. SPECIFIC FEA TURES OF CHINESE VLPSA. DimensionsAccording to the guideline for vehicle inspection [9], all license plates must be rectangular and have the dimensions and have all 7 characters written in a single line. Under practical environments, the distance from the camera to vehicles and the inclined angles are constant, so all characters of the license plate have a fixed width, and the distance between the medium axes of two adjoining characters is fixed and the ratio between width and height is nearly constant. Those features can be used to locate the plate and segment the individual character. B. Color collocation of the plateThere are four kinds of color collocation for the Chinese vehicle license plate .These color collocations are shown in table I.TABLE IMoreover, military vehicle and police wagon plates contain a red character which belongs to a specific character set. This feature can be used to improve the recognition rate.C. Layout of the Chinese VLPSThe criterion of the vehicle license plate defines the characters layout of Chinese license plate. All standard license plates contain Chinese characters, numbers and letters which are shown in Fig.1. The first one is a Chinese character which is an abbreviation of Chineseprovinces. The second one is a letter ranging from A to Z except the letter I. The third and fourth ones are letters or numbers. The fifth to seventh ones are numbers ranging from 0 to 9 only. However the first or the seventh ones may be red characters in special plates (as shown in Fig.1). After segmentation process the individual character is extracted. Taking advantage of the layout and color collocation prior knowledge, the individual character will enter one of the classes: abbreviations of Chinese provinces set, letters set, letters or numbers set, number set, special characters set.(a)Typical layout(b) Special characterFig.1 The layout of the Chinese license plateIII. THE PROPOSED ALGORITHMThis algorithm consists of four modules: VLP location, character segmentation, character classification and character recognition. The main steps of the flowchart of LPR system are shown in Fig. 2.Firstly the license plate is located in an input image and characters are segmented. Then every individual character image enters the classifier to decide which class it belongs to, and finally the BP network decides which character the character image represents.A. Preprocessing the license plate1) VLP LocationThis process sufficiently utilizes the color feature such as color collocation, color centers and distribution in the plate region, which are described in section II. These color features can be used to eliminate the disturbance o f the fake plate ’ s regions. The flowchart of the plate location is shown in Fig. 3.Fig.3 The flowchart of the plate location algorithmThe regions which structure and texture similar to the vehicle plate are extracted. The process is described as followed:Here, the Gaussian variance is set to be less than W/3 (W is the character stroke width), so 1P gets its maximum value M at the center of the stroke. After convolution, binarization is performed according to a threshold which equals T * M (T<0.5). Median filter is used to preserve the edge gradient and eliminate isolated noise of the binary image. An N * N rectangle median filter is set, and N represents the odd integer mostly close to W.Morphology closing operation can be used to extract the candidate region. The confidence degree of candidate region for being a license plate is verified according to the aspect ratio and areas. Here, the aspect ratio is set between 1.5 and 4 for the reason of inclination. The prior knowledge of color collocation is used to locate plate region exactly. The locating process of the license plate is shown in Fig. 4.2) Character segmentationThis part presents an algorithm for character segmentation based on prior knowledge, using character width, fixed number of characters, the ratio of height to width of a character, and so on. The flowchart of the character segmentation is shown in Fig. 5.Firstly, preprocess the license the plate image, such as uneven illumination correction, contrast enhancement, incline correction and edge enhancement operations; secondly, eliminating space mark which appears between the second character and the third character; thirdly, merging the segmented fragments of the characters. In China, all standard license plates contain only 7 characters (see Fig. 1). If the number of segmented characters is larger than seven, the merging process must be performed. Table II shows the merging process. Finally, extracting the individual character’ image based on the number and the width of the character. Fig. 6 shows the segmentation results. (a) The incline and broken plate image, (b) the incline and distort plate image, (c)the serious fade plate image, (d) the smut license plate image.where Nf is the number of character segments, MaxF is the number of the license plate, and i is the index of each character segment.The medium point of each segmented character is determined by:(3)where 1i Sis the initial coordinates for the character segment, and 2i S is thefinal coordinate for the character segment. The d istance between two consecutive medium points is calculated by:(4)Fig.6 The segmentation resultsB. Using specific prior knowledge for recognitionThe layout of the Chinese VLP is an important feature (as described in the section II), which can be used to construct a classifier for recognizing. The recognizing procedure adopted conjugate gradient descent fast learning method, which is an improved learning method of BP neural network[10]. Conjugate gradient descent, which employs a series of line searches in weight or parameter space. One picks the first descent direction and moves along that direction until the minimum in error is reached. The second descent direction is then computed: this direction the “ conjugate direction” is the one along which the gr adient does not change its direction will not “ spoil ” the contribution from the previous descent iterations. This algorithm adopted topology 625-35-N as shown in Fig. 7. The size of input value is 625 (25*25 ) and initial weights are with random values, desired output values have the same feature with the input values.As Fig. 7 shows, there is a three-layer network which contains working signal feed forward operation and reverse propagation of error processes. The target parameter is t and the length of network outputvectors is n. Sigmoid is the nonlinear transfer function, weights are initialized with random values, and changed in a direction that will reduce the errors.The algorithm was trained with 1000 images of different background and illumination most of which were degrade severely. After preprocessing process, the individual characters are stored. All characters used for training and testing have the same size (25*25 ).The integrated process for license plate recognition consists of the following steps:1) Feature extractingThe feature vectors from separated character images have direct effects on the recognition rate. Many methods can be used to extract feature of the image samples, e.g. statistics of data at vertical direction, edge and shape, framework and all pixels values. Based on extensive experiments, all pixels values method is used to construct feature vectors. Each character was reshaped into a column of 625 rows’ feature vector. These feature vectors are divided into two categories which can be used for training process and testing process.2) Training modelThe layout of the Chinese VLP is an important feature, which can be used to construct a classifier for training, so five categories are divided. The training process of numbers is shown in Fig. 8.As Fig. 8 shows, firstly the classifier decides the class of the inputfeature vector, and then the feature vector enters the neural network correspondingly. After the training process the optimum parameters of the net are stored for recognition. The training and testing process is summarized in Fig. 9.(a) Training process(b)Testing processFig.9 The recognition process3) Recognizing modelAfter training process there are five nets which were completely trained and the optimum parameters were stored. The untrained feature vectors are used to test the net, the performance of the recognition system is shown in Table III. The license plate recognition system is characterized by the recognition rate which is defined by equation (5).Recognition rate =(number of correctly read characters)/ (number of found characters) (5)IV. COMPARISON OF THE RECOGNITION RA TE WITH OTHER METHODSIn order to evaluate the proposed algorithm, two groups of experiments were conducted. One group is to compare the proposed method with the BP based recognition method [11]. The result is shown in table IV. The other group is to compare the proposed method with themethod based on SVM [12].The result is shown in table V. The same training and test data set are used. The comparison results show that the proposed method performs better than the BP neural network and SVM counterpart.V. CONCLUSIONIn this paper, we adopt a new improved learning method of BP algorithm based on specific features of Chinese VLPs. Color collocation and dimension are used in the preprocessing procedure, which makes location and segmentation more accurate. The Layout of the Chinese VLP is an important feature, which is used to construct a classifier for recognizing and makes the system performs well on scratch and inclined plate images. Experimental results show that the proposed method reduces the error rate and consumes less time. However, it still has a few errors when dealing with specially bad quality plates and characters similar to others. This often takes place among these characters (especially letter and number): 3—8 4—A 8—B D—0.In order to improve the incorrect recognizing problem we try to add template-based model [13] at the end of the neural network.中文译文基于先验知识的车牌识别Qian Gao, Xinnian Wang and Gongfu Xie摘要- 本文介绍了一种基于改进的BP(反向传播)神经网络的中国车牌识别(LPR)算法。
汽车发动机外文文献翻译(含:英文原文及中文译文)文献出处:Talom M. AUTOMOTIVE ENGINE[J]. Applied Thermal Engineering, 2013, 2(3):39-45.英文原文AUTOMOTIVE ENGINETalom M1 Engine Classification and Overall MechanicsThe automobile engines can be classified according to: (1) cycles, (2) cooling system, (3) fuel system, (4) ignition method, (5) valve arrangement, (6) cylinder arrangement, (7) engine speed.Engines used in automobiles are the internal combustion heat engines. The burning of gasoline inside the engine produces high pressure in the engine combustion chamber. This high pressure force piston to move, the movement is carried by connecting rods to the engine crankshaft. The crankshaft is thus made to rotate: the rotary motion is carried through the power train to the car wheels so that they rotate and the car moves.The engine requires four basic systems to run (Fig. 2-1). Diesel engines require three of these systems. They are fuel system, ignition system (except diesel), lubricating system andcooling system. However, three other related systems are also necessary. These are the exhaust system, the emission-control system, and the starting system. Each performs a basic job in making the engine run.2 Engine Operating PrinciplesThe term “stroke” is used to describe the movem ent of the piston within the cylinder. The movement of the piston from its uppermost position (TDC, top dead center) to its lowest position (BDC, bottom dead center) is called a stroke. The operating cycle may require either two or four strokes to complete. Most automobile engines operate on the four stroke cycle.In four-stroke engine, four strokes of the piston in the cylinder are required to complete one full operating cycle. Each stroke is named after the action. It performs intake, compression, power, and exhaust in that order.The intake strokeThe intake stroke begins with the piston near the top of its travel. As the piston begins its descent, the exhaust valve closes fully, the intake valve opens and the volume of the combustion chamber begins to increase, creating a vacuum. As the piston descends, an air/fuel mixture is drawn from the carburetor into the cylinder through the intake manifold. The intake stroke endswith the intake valve close just after the piston has begun its upstroke.Compression strokeAs the piston is moved up by the crankshaft from BDC, the intake valve closes. The air/fuel mixture is trapped in the cylinder above the piston. Future piston travel compresses the air/fuel mixture to approximately one-eighth of its original volume (approximately 8:1 compression ratio) when the piston has reached TDC. This completes the compression stroke. Power strokeAs the piston reaches TDC on the compression stroke, an electric spark is produced at the spark plug. The ignition system delivers a high-voltage surge of electricity to the spark plug to produce the spark. The spark ignites, or sets fire to, the air/fuel mixture. It now begins to burn very rapidly, and the cylinder pressure increases to as much as 3-5MPa or even more. This terrific push against the piston forces it downward, and a powerful impulse is transmitted through the connecting rod to the crankpin on the crankshaft. The crankshaft is rotated as the piston is pushed down by the pressure above it.Exhaust strokeAt the end of the power stroke the camshaft opens theexhaust valve, and the exhaust stroke begins. Remaining pressure in the cylinder, and upward movement of the piston, force the exhaust gases out of the cylinder. At the end of the exhaust stroke, the exhaust valve closes and the intake valve opens, repeating the entire cycle of events over and over again.3 Engine Block and Cylinder HeadEngine BlockThe engine block is the basic frame of the engine. All other engine parts either fit inside it or fasten to it. It holds the cylinders, water jackets and oil galleries (Fig. 2-4). The engine block also holds the crankshaft, which fastens to the bottom of the block. The camshaft also fits in the block, except on overhead-cam engines. In most cars, this block is made of gray iron, or an alloy (mixture) of gray iron and other metals, such as nickel or chromium. Engine blocks are castings.Some engine blocks, especially those in smaller cars, are made of cast aluminum. This metal is much lighter than iron. However, iron wears better than aluminum. Therefore, the cylinders in most aluminum engines are lined with iron or steel sleeves. These sleeves are called cylinder sleeves. Some engine blocks are made entirely of aluminum.Cylinder SleevesCylinder sleeves are used in engine blocks to provide a hard wearing material for pistons and piston rings. The block can be made of one kind of iron that is light and easy to cast while the sleeves uses another that is better able to stand up wear and tear.There are two main types of sleeves: dry and wet (Fig. 2-5).Dry sleeve Wet sleeveCylinder HeadThe cylinder head fastens to the top of the block, just as a roof fits over a house. The underside forms the combustion chamber with the top of the piston. In-line engine of light vehicles have just one cylinder head for all cylinders; larger in-line engines can have two or more. Just as with engine blocks, cylinder heads can be made of cast iron or aluminum alloy. The cylinder head carries the valves, valve springs and the rockers on the rocker shaft, this part of valve gear being worked by the pushrods. Sometimes the camshaft is fitted directly into the cylinder head and operates on the valves without rockers. This is called an overhead camshaft arrangement.GasketThe cylinder head is attached to the block with high-tensile steel studs. The joint between the block and the head must begas-tight so that none of the burning mixture can escape. This is achieved by using cylinder head gasket. Gaskets are also used to seal joins between the other parts, such as between the oil pan, manifolds, or water pump and the blocks.Oil PanThe oil pan is usually formed of pressed steel. The oil pan and the lower part of cylinder block together are called the crankcase; they enclose, or encase, the crankshaft. The oil pump in the lubricating system draws oil from the oil pan and sends it to all working parts in the engine. The oil drains off and run down into the pan. Thus, there is a constant circulation of oil between the pan and the working parts of the engine.4 Piston Assembly, piston rings, The piston pin ,Connecting Rods, Crankshafts And FlywheelPistonPiston rings and the piston pin are together called the piston assembly.The piston is an important part of a four-stroke cycle engine. Most pistons are made from cast aluminum. The piston, through the connecting rod, transfers to the crankshaft the force created by the burning fuel mixture. This force turns the crankshaft.To withstand the heat of the combustion chamber, the piston must be strong. It also must be light, since it travels at high speeds as it moves up and down inside the cylinder. The piston is hollow. It is thick at the top where it takes the brunt of the heat and the expansion force. It is thin at the bottom, where there is less heat. The top part of the piston is the head, or crown. The thin part is the skirt. Most pistons have three ring grooves at the top. The sections between the ring grooves are called ring lands.piston ringsPiston rings fit into ring grooves near the top of the piston. In simplest terms, piston rings are thin, circular pieces of metal that fit into grooves in the tops of the pistons. In modern engines, each piston has three rings. (Piston in older engines sometimes had four rings, or even five.) The inside surface of the ring fits in the groove on the piston. The ring's outside surface presses against the cylinder walls. Rings provide the needed seal between the piston and the cylinder walls. That is, only the rings contact the cylinder walls. The top two rings are to keep the gases in the cylinder and are called compression rings. The lower one prevents the oil splashed onto the cylinder bore fro m entering the combustion chamber, and is called an oil ring.The piston pinThe piston pin holds together the piston and the connecting rod. This pin fits into th e piston pin holes and into a hole in the top end of the connecting rod. The top end of t he rod is much smaller than the end that fits on the crankshaft. This small end fits inside the bottom of the piston. The piston pin fits through one side of the piston, through the small end of the rod, and then through the other side of the piston. It holds the rod firmly in place in the center of the piston. Pins are made of high-strength steel and have a hollow center. Many pins are chrome-plated to help them wear better. A piston pin fits into a round hole in the piston. The piston pin joins the piston to the connecting rod. The thick part of the piston that holds the piston pin is the pin boss. Connecting RodsThe connecting rod little end is connected to the piston pin.A bush made from a soft metal, such as bronze, is used for this joint. The lower end of the connecting rod f its the crankshaft journal. This is called the big end. For this big-end bearing, steel-backed lead or tin shell bearings are used. These are the same as those used for the main bearings. The split of the big end is sometimes at an angle, so that it is small enough t o be withdrawn through the cylinder bore. The connecting rod ismade from forged alloy steel.CrankshaftsThe crankshaft is regarded as the “backbone” of the engine (Fig. 2-7). The crankshaft, in conjunction with the connecting rod, converts the reciprocating motion of the piston to the rotary motion needed to drive the vehicle. It is usually made from car-bon steel which is alloyed with a small proportion of nickel. The main bearing journals fit into the cylinder block and the big end journals align with the connecting rods. At the rear end of the crankshaft is attached the flywheel, and at the front end are the driving wheels for the timing gears, fan, cooling water and alternator. The throw of the crankshaft, . the distance between the main journal and the big end centers, controls the length of the stroke. The stroke is double the throw, and the stroke length is the distance that the piston travels from TDC to BDC and vice versa.中文译文汽车发动机Talom M1发动机分类和一般力学(1)循环,(2)冷却系统,(3)燃料系统,(4)点火方法,(5)阀门布置,(6)气缸布置,(7)发动机速度。
步行机器人中英文对照外文翻译文献(文档含英文原文和中文翻译)图1 远程脑系统的硬件配置图2 两组机器人的身体结构图3 传感器的两个水银定位开关图4 层次分类图5 步行步态该输入处理器是作为参考程序块和一个图像搜索窗口形象该大小的搜索窗口取决于参考块的大小通常高达16 * 16且匹配。
该处理器计算价值块在搜索窗口,还找到最佳匹配块,这就是其中的最低当目标平移时块匹配是非常有力的。
然而,普通的块匹配方法当它旋转时无法跟踪目标。
为了克服这一困难,我们开发了一种新方法,跟随真正旋转目标的图6 双足步行图6 双足步行图7 双足步行实验图8 一系列滚动和站立运动通过集成传感器网络转型的综合为了使上述描述的基本动作成为一体,我们通过一种方法来描述一种被认为是根据传感器状况的网络转型。
图9显示了综合了基本动作机器人的状态转移图:两足行走,滚动,坐着和站立。
这种一体化提供了机器人保持行走甚至跌倒时的problems and advance the study of vision-based behaviors, we have adopted a new approach through building remote-brained robots. The body and the brain are connected by wireless links by using wireless cameras and remote-controlled actuators.As a robot body does not need computers on-board,it becomes easier to build a lightweight body with many DOFS in actuation.In this research, we developed a two-armed bipedal robot using the remote-brained robot environment and made it to perform balancing based on vision and getting up through cooperating arms and legs. The system and experimental results are described below.2 The Remote-Brained SystemThe remote-brained robot does not bring its own brain within the body. It leaves the brain in the mother environment and communicates with it by radio links. This allows us to build a robot with a free body and a heavy brain. The connection link between the body and the brain defines the interface between software and hardware. Bodies are designed to suit each research project and task. This enables us advance in performing research with a variety of real robot systems[10].A major advantage of remote-brained robots is that the robot can have a large and heavy brain based on super parallel computers. Although hardware technology for vision has advanced and produced powerful compact vision systems, the size of the hardware is still large. Wireless connection between the camera and the vision processor has been a research tool. The remote-brained approach allows us to progress in the study of a variety of experimental issues in vision-based robotics.Another advantage of remote-brained approach is that the robot bodies can be lightweight. This opens up the possibility of working with legged mobile robots. AsFigure 4 shows some of the classes in the programming environent for remote-brained robot written in Euslisp. The hierachy in the classes provides us with rich facilities for extending development of various robots.4 Vision-Based BalancingThe robot can stand up on two legs. As it can change the gravity center of its body by controling the ankle angles, it can perform static bipedal walks. During static walking the robot has to control its body balance if the ground is not flat and stable.In order to perform vision-based balancing it is re-quired to have high speed vision system to keep ob-serving moving schene. We have developed a tracking vision board using a correlation chip[l3]. The vision board consists of a transputer augmented with a special LSI chip(MEP[14] : Motion Estimation Processor) which performs local image block matching.The inputs to the processor MEP are an image as a reference block and an image for a search window.The size of the reference blsearch window depends on the size of the reference block is usually up to 32 by 32 pixels so that it can include 16 * 16 possible matches. The processor calculates 256 values of SAD (sum of absolute difference) between the reference block and 256 blocks in the search window and also finds the best matching block, that is, the one which has the minimum SAD value.Clock is up to 16 by 16 pixels.The size of the search window depends on the size of the reference block is usually up to 32 by 32 pixels so that it can include 16 * 16 possible matches. The processor calculates 256 values of SAD (sum of absolute difference) between the reference block and 256 blocks in the search window and also finds the best matching block, that is, the one which has the minimum SAD value.Block matching is very powerful when the target moves only in translation. However, the ordinary block matching method cannot track the target when it rotates. In order to overcome this difficulty, we developed a new method which follows up the candidate templates to real rotation of the target. The rotated template method first generates all the rotated target images in advance, and several adequate candidates of the reference template are selected and matched is tracking the scene in the front view. It remembers the vertical orientation of an object as the reference for visual tracking and generates several rotated images of the reference image. If the vision tracks the reference object using the rotated images, it can measures the body rotation. In order to keep the body balance, the robot feedback controls its body rotation to control the center of the body gravity. The rotational visual tracker[l5] can track the image at video rate.5 Biped WalkingIf a bipedal robot can control the center of gravity freely, it can perform biped walk. As the robot shown in Figure 2 has the degrees to left and right directions at the ankle position, it can perform bipedal walking in static way.The motion sequence of one cycle in biped walking consists of eight phases as shown in Figure 6. One step consists of four phases; move-gravity-center-on-foot,lift-leg, move-forward-leg, place-leg. As the body is described in solid model, the robot can generate a body configuration for move-gravity-center-on-foot according to the parameter of the hight of the gravity center. After this movement, the robot can lift the other leg and move it forward. In lifting leg, the robot has to control the configuration in order to keep the center of gravity above the supporting foot. As the stability in balance depends on the hight of the gravity center, the robot selects suitable angles of the knees.Figure 7 shows a sequence of experiments of the robot in biped walking6 Rolling Over and Standing UpFigure 8 shows the sequence of rolling over, sitting and standing up. This motion requires coordination between arms and legs.As the robot foot consists of a battery, the robot can make use of the weight of the battery for the roll-over motion. When the robot throws up the left leg and moves the left arm back and the right arm forward, it can get rotary moment around the body. If the body starts turning, the right leg moves back and the left foot returns its position to lie on the face. This rollover motion changes the body orientation from face up to face down. It canbe verified by the orientation sensor.After getting face down orientation, the robot moves the arms down to sit on two feet. This motion causes slip movement between hands and the ground. If the length of the arm is not enough to carry the center of gravity of the body onto feet, this sitting motion requires dynamic pushing motion by arms. The standing motion is controlled in order to keep the balance.7 Integration through Building Sensor-Based Transition NetIn order to integrate the basic actions described above, we adopted a method to describe a sensor-based transition network in which transition is considered according to sensor status. Figure 9 shows a state transition diagram of the robot which integrates basic actions: biped walking, rolling over, sitting, and standing up. This integration provides the robot with capability of keeping walking even when it falls down.The ordinary biped walk is composed by taking two states, Left-leg Fore and Right-leg Fore, successively.The poses in ‘Lie on the Back’ and ‘Lie on the Face’are as same as one in ‘Stand’. That is, the shape ofthe robot body is same but the orientation is different.The robot can detect whether the robot lies on the back or the face using the orientation sensor. When the robot detects falls down, it changes the state to ‘Lie on the Back’ or ‘Lie on the Front’ by moving to the neutral pose. If the robot gets up from ‘Lie on the Back’, the motion sequence is planned to exe cute Roll-over, Sit and Stand-up motions. If the state is ‘Lie on the Face’, it does not execute Roll-over but moves arms up to perform the sitting motion.8 Concluding RemarksThis paper has presented a two-armed bipedal robot which can perform statically biped walk, rolling over and standing up motions. The key to build such behaviors is the remote-brained approach. As the experiments have shown, wireless technologies permit robot bodies free movement. It also seems to change the way we conceptualize robotics. In our laboratory it has enabled the development of a new research environment, better suited to robotics and real-world AI.The robot presented here is a legged robot. As legged locomotion requires dynamic visual feedback control, its vision-based behaviors can prove the effectiveness of the vision system and the remote-brained system. Our vision system is based on high speed block matching function implemented with motion estimation LSI. The vision system provides the mechanical bodies with dynamic and adaptive capabilities in interaction with human. The mechanical dog has shown adaptive behaviors based on distance。
电容器中英文对照外文翻译文献(文档含英文原文和中文翻译)译文:1电容器的选择本文为电化学双层电容器或超级电容器提供在一台常规电容器,简明的介绍新生的电化学双电层电容器或超级电容器。
电容器是存放电能并且协助过滤的根本电路元素。
电容器有二个主要应用; 其中之一是充电或释放电的作用。
这个作用适用于电源平流滤波电路,微型计算机备用电路和利用期间充电或释放电的定时器电路。
其他是阻拦DC 流程的作用。
这个作用适用于提取或消灭特殊频率的过滤器。
这是其中不可或缺的优秀电路所需的频率特性。
电解电容是在充分的标度商业化的下一代电容器。
他们类似电池在细胞建筑,但是阳极和负极材料依然保持不变。
他们是铝,钽和两个陶瓷电容电解质的地方与他们所使用的液体固体分离器/ 对称的电极。
电化学电容器(EC),往往被称为超级电容器或超级电容,存储电荷的双层电荷在1层表面电解质界面,主要在高电位表面的碳。
由于高电位表面是薄的双重层,所以这些设备可以有一个非常高的比和体积电容。
这使得他们能够结合以前无法实现的电容用无限的电荷密度/放电循环寿命。
每单元的工作电压,只受击穿电位电解质的影响,通常<1或“<3伏的每个细胞水性或有机电解质分别。
该存储的概念电力能源双电层这是形成于界面之间的固体电解质和一直都知道自19世纪末期。
第一电气设备使用双层充电储存在报告1957年H.I.贝克尔的通用电气(美国专利2800616)。
不幸的是,贝克尔的设备是不切实际的,同样一个充斥电池,电极都需要沉浸在一个容器电解质,并且该设备从未商业化。
贝克尔那样做了,但是随后发现电容值已经被标准石油化学家公司俄亥俄州(索奥)的罗伯特A赖特迈尔发明并且现在正在普遍使用。
他的专利(美国3288641),在1962年年底提出并获1966年11月,和一个后续专利(美国专利3536963)由资深研究员索奥唐纳德L.布斯在1970年,形式为基础随后的专利和期刊数百文章涉及ec技术的所有方面。
外文翻译资料外文原文:Washing machinesLet’s look inside one of today’s fully automatic washing machines that use swirling water to clean the clothes. There are many types of washing machines but this Figure shows you what most of them are basically made up of.。
The reason why a washing machine like this can wash and get the water out of the clothes at the same time is because it has a double layer drum.When1washing and rinsing,the pulsator spins and makes the water swirl..To get the water out of the clothes, the inner wall f the drum spins and the water goes through the holes.These days,the“centrifugal force washing machines”are quite popular.This type of machine does not use a pulsator.Instead,the inner wall spins really quickly.1外文翻译资料When the drum spins,the dirty clothes get stuck to the wall.The water and detergent also try to escape through the holes of the wall but before they do so,they are forced to escape through the clothes.When this happens,the power of the water and detergent removes the dirt form the clothes.Another good thing about this type of machine is that clothes don’t get tangled up so you don’t have to worry about your clothes getting ripped or damaged.Next,let’s look at some different types ofwashing machines!Many of you probably think that the water inside washing machines goes round and round. Actually, different washing machines make water flow in different ways.Whirlpool type:This type of washing machine uses a pulsator to force the water to move like a whirlpool inside the Drum.The spinning water forces the dirt out form the clothes inside the machine. Some of the newer models of this type also make the whirlpool move up and down to make it clean clothes even better!Agitator stirring typeThis type of washing machine has something that looks like a propeller at the bottom of the tub.This Propeller spins around and stirs the water.The water then forces the dirt out from the clothes in the machine.The good thing about this type of machine is that clothes do not get tangled up and clothes get evenly washed.Drum type:This type of machine has a drum with many holes in it. There are also protrusions bumps on the wall of the drum.As the drum turns,the clothes are picked up by the protrusions. When the clothes fall down from the top of the drum through the water,the movement removes dirt from the clothes.Centrifugal force type:2外文翻译资料As we have said before, the spinning drum pushes the water and detergent out through the wall of the inner drum. The power that comes form spinning the drum is called centrifugal force., which is where the name comes from. The water is forced through the clothes and then the holes in the inner wall.After one cycle,the water is recycled back into the tank and the process starts again.This cycle is what cleans the clothes!In Japan,people first started using machines in1930.But then the price of a washing machine was so high that most average persons could not buy one for their homes.Looking back now, there was something strange and funny on some of the first versions of the washing machine .The machine had two rollers that were used to sandwich each shirt and other clothes to squeeze the water out of them.The rollers were turned by hand,and in fact,you needed a lot of strength to turn those things!Still,people then thought it was a really neat invention!This type of water squeezer was used for almost 30 years until something new came along. The spin drier that used“centrifugal force”to get most ofthe water is out of the clothes.In1953,the nozzle type washing machine was first sold in Japan.This washing machine is like the older brother of the swirling washing machine that you see today. The price of these washing machines was lower and because of this, more people bought them. The first fully automatic washing machine was introduced in1968,and after that,washing clothes became a lot easier to do!There are a lot of different types of washing machines. What kind of washing machine do you have in your house?Fully automatic:The fully automatic machine has two drum layers that wash, rinse and removewater from clothes together. All you have to do is add detergent and put in dirty3外文翻译资料clothes and then washing machine will do the rest.There is also a new type of fully automatic washing machine that can dry clothes after they have been washed.Twin tub:This washing machine has one part that dose the washing and another part that does the squeezing.Even though it’s a hassle to take the clothes out and move them to other tub,the good thing is that you can wash and squeeze at the same time with one machine.Front loading:The main feature of front loaders is that they use a lot less water than other types.This is the type of Washing machine that dry cleaners use but a lot of people in western countries have this type of washing machine in their homes too.Let’s try to make the best washing machine in the world!We should already thank the scientists that invented the fully automatic washing machine because it makes washing clothes a piece of cake.Scientists are still trying really hard to find ways to make washing machines a lot handier to use for everyone.Some of the things that they are trying to do are to find better ways of making clothes clean and ways to make washing machines last longer.There are washing machines with d trying function today so you don’t even have to hang clothes after words because it dries them automatically!Amazing!Scientists are also trying to find ways to use less water and less detergent in washing machines at present.This is because that it is better to use less water for preserving the environment.What are washing machines of the future going to be like? Maybe there will be a washing machine that dries and folds your clothes after washing them,or maybe there will be one that will wash your clothes while you are still wearingthem! How handy would that be! Remember, if the first washing machine was like4外文翻译资料a dream to people in the old days, all the dreams you have about washing machines of the future may come true!Now, washing machine is becoming more and more popular. We see the main classification.Washing machine can be divided into automatic type and semi-automatic type two kinds, automatic type washing machine as long as we begin our work proactively set better washing procedure,washing machine began to work until the end without manual intervention. And semi-automatic washing machine washing and dewatering process is divided,is also called the double barrel washing machine, a tong,one takes off a bucket,and put tong inside washing out to artificial add to take off in the barrel dehydration is handled and complete laundry process.Full-automatic washing machine in structure to take off in tong internal bucket suit, two barrels of axis,while working with the clutch to finish washing state and dehydration of the transition of the states,on the key said is automatic washing machine.Full-automatic washing machine press catharsis means to points,can be dividedinto bunt washer and roll barrel type two kinds of washing machine, From the electric control ways to points,can be divided into mechanical program-controlled type and computer board controls type washing machine two kinds.The cylinder and the pulsator washing machine are now the main two kinds.Pulsator washing machine working principle is to add clothing,then open the inlet valve,choose good bibcock of water level and correct working procedures, switch on the power,closed warehouse door,and safety switch closed at water level,the public internal switch contacts are and dehydration contacts are interlinked,inlet valve electrify water,when the barrel water reaches the specifiedheight,in air pressure under the action of water level switch inside public contacts5外文翻译资料disconnect dehydration contacts and connect washing contacts,feed valve power to stop water,motor power is switched on,motor started running,and periodically sometimes are turning,sometimes reverse,mutual alternant,driven by clutch BoLun using the same cycle are turning,inversion,with a certain speed rotating BoLun can drive inside bucket of water and clothing,clothing rotating water formed in the mutual friction and reach the purpose of laundry. When washing process is completed,drainage electromagnetic valve electrify work,drain valve is opened,inside bucket of water exudes,and linkage shaft also the clutch from washing state switch to dehydration state,when drainage is completed,atmospheric pressure drop and inside bucket of water level switch public contacts reset through dehydration contacts,drainage electromagnetic valve keep electrify state,motor driven off running electrify bucket high-speed andjilt dry clothing,laundry program after washing machine disconnect hydropower and stop. As for intermediate process of how many times, laundry to wash the length of time, by process control.Roller-type washing machine of the principle and Pulsator washing machine are basic similar.But110mm drum machine it no clutch variable speed,but its motor is double-speed motor, so when washing machine work in washing state, program-controlled device connected motor washing low-speed windings, motor speed slow, working on dehydration, when they connect dehydration modal high-speed windings,motor high-speed operation,this process is programmed through the device and motor to work together to finish.To sum up, the role of these two kinds of washing machine is same, but different implementation,each has his strong point,Pulsator washing machine is simulated handmade kneaded action to work, 110mm drum type washing machine is by gravity inertial function to finish our work,they realize washing and6dewatering way also have different features,Pulsator washing machine to wear clothes is relatively large,but detergents degree is higher,110mm drum machine for clothing wear small,but detergents degrees,but lower than Pulsator washing machine to save water.So far,washing machine is still towards a higher requirements development.7译文:洗衣机来看一下涡流式全自动洗衣机的构造。
旅行商问题外文文献翻译(含:英文原文及中文译文)文献出处:Mask Dorigo. Traveling salesman problem [C]// IEEE International Conference on Evolutionary Computation. IEEE, 2013,3(1), PP:30-41.英文原文Traveling salesman problemMask Dorigo1 IntroductionIn operational research and theoretical computer science, the Traveling Salesman Problem (TSP) is a NP-difficult combinatorial optimization problem. By giving pairs of city-to-city distances, find each city exactly one shortest trip. It is a special case of buyer travel problems.The problem was first elaborated in 1930 as one of the most in-depth research questions in mathematics problems and optimization. It becomes a benchmark for many optimization methods. Although the problem is difficult to calculate, a large number of heuristic detections and exact methods are known to solve certain situations that contain tens of thousands of cities.TSP has many applications, even based on its most essential concept itself, such as planning, logistics, and manufacturing microchips. With minor changes, it has emerged as a sub-problem in many areas, such asDNA sequencing. In these applications, the cities in the TSP represent the customers, welding points, or DNA fragments. The distance in the TSP represents the travel time or cost, or similarity measure between DNA fragments. In many applications, additional constraints, such as limited resources or time windows, make the problem quite difficult. In computational complexity theory, the decision version of the TSP (given a length L, the goal is to judge whether there is any travel shorter than L) belongs to the class of np complete problems. Therefore, it is likely that in the worst case scenario, the operating time required to solve any of the TSP's algorithms increases exponentially with the number of cities.2 HistoryThe origin of the traveling salesman problem is still unclear. A manual of 1832 referred to the problem of travel salesmen, including examples from Germany and Switzerland. However, there is no mathematical treatment in the book. The traveling salesman problem was elaborated in the 19th century by the Irish mathematician W.R. and the English mathematician Thomas Kirkman. Hamilton's Icosian game is a casual game based on finding the Hamilton Circle. The general form of TSP, first studied by mathematicians and especially Karl Menger at the Vienna and Harvard universities in 1930, Karl Menger defined the problem, considered the obvious brute force algorithm, and examined the heuristics of non-nearest neighbors:We express the messenger problem (because in practice, every postman must solve this problem, and many tourists do the same), and its task is to know the limited number of points and their paired distances and find the shortest connection route. Of course, this problem is solvable for a limited number of trials. The rule allows the number of trials to be less than the number of species at a given point, but it is not known. First from the starting point to the nearest point, then from that point to the next point from its nearest point, this rule does not generally constitute the shortest possible line.After Hassler Whitney introduced the TSP at Princeton University, this issue quickly became popular in the European and American scientific communities in the 1950s and 1960s. In Dan Monica, the RAND Corporation's George Dantzig, Delbert Ray Fulkerson, and Selmer M. Johnson contributed to this and they solved TSP as an integer linear programming and an improved cutting plane problem. With these new solution methods, they built an optimal tour that solved an instance with 49 cities, and at the same time proved that no other tour can be shorter. In the following decades, the problem was studied by many researchers in mathematics, computer science, chemistry, physics, and other sciences.Richard M. Karp's research in 1972 showed that the Hamiltonian problem is NP-complete, which means that the TSP is NP-hard. Thisprovides a mathematical explanation as to why it is difficult to find the best travel.In the late 1970s and 1980s, there was a major breakthrough in the problem. Together with others, Gröötschel, Padberg, and Rinaldi used cut-plane methods and branch-and-bound methods to successfully solve instances of up to 2,392 cities.In the 1990s, Applegate, Bixby, Chvátal, and Cook developed the "Concordance" program that was used in many recent solutions. In 1991, Gerhard Reinelt published TSPLIB, which collected examples of different difficulties and was used by many research groups to compare results. In 2005, Cook and others found the best travel through 33,810 cities from a chip layout problem. This is the largest example of solving problems in TSPLIB. For many other examples with millions of cities, problem solving can be found and 1% is guaranteed to be the best one.3 Description3.1 As a Graphic ProblemTSP can be transformed into an undirected weighted graph. For example, the city is the vertex of the graph, the path is the edge of the graph, and the path distance is the length of the edge. This is a minimization problem that starts and ends at a specified vertex, and other vertices have exactly one access. A Hamiltonian circle is one of the best travels of the TSP and is proportional to the distance on each side.Normally, the model is a complete graph (ie each pair of vertices is connected by edges). If there is no path between the two cities, adding an edge of any length that does not affect the best travel becomes a complete picture.3.2 Asymmetry and symmetryIn a symmetrical TSP, the distance between two cities in each opposite direction is the same, forming an undirected graph. This symmetry splits the possible solutions in half. In an asymmetric TSP, there may be no two-way paths or two-way paths different to form a directed graph. Traffic accidents, one-way flights, and tickets of different times and prices are examples of disruptions to this symmetry.3.3 Related issuesAn equivalent proposition in graph theory is to give a complete weighted graph (where the vertices represent cities, the paths represented by the edges, and the weights represent costs or distances) and find the Hamiltonian ring with the smallest weight. Returning to the requirements of the departure city does not change the computational complexity of the problem. Look at the Hamilton route problem.Another related problem is the Bottleneck Traveling Salesman Problem (bottlenecks TSP): Find a Hamiltonian ring with the lowest critical edge weight in the weighted graph. The problem is of considerable practical significance, except that in the obvious areas oftransportation and logistics, a typical example is the drilling of drilling holes in PCBs for the manufacture of printed circuit dispatches. In machining or drilling applications, the “city” is the part or drill hole (different in size), and the “overhead of traverse” contains the time for replacement parts (stand-alone job scheduling problem). The general traveling salesman problem involves the “state,” “one or more” “city,” where the salesman visits each “city” from each “state,” and is also referred to as the “travel politician problem.” Surprisingly, Behzad and Modarres found that the general traveling salesman problem can be transformed into a standard traveling salesman problem with the same number of cities as the modified distance matrix.The problem of sequential ordering involves accessing a series of issues that have a city of priority relations with each other.The traveling salesman problem solves the buyer's purchase of a set of products. He can buy these products in several cities, but at different prices, while not all cities offer the same products. The goal is to find a path in all cities to minimize total expenses (travel expenses + purchase expenses).4 Calculation SolutionsThe traditional ideas for solving NP-hard problems are the following:1) Design the algorithm to find the exact solution (only applicable tosmall problems, which will be completed soon).2) Develop a "sub-optimal" or heuristic algorithm, ie the algorithm seems or may provide a good solution, but it cannot be proven to be optimal.3) It is possible to find solutions or heuristics in special cases of problems (sub-problems).4.1 Computational ComplexityThe problem has been proved to be an NP-difficult problem (more precisely, it is a complex class FP NP ), and the decision problem version (given the cost and a number x to determine whether there is a cheaper path than X) is a NP-complete problem. The bottleneck traveling salesman problem is also an NP-hard problem. Cancelling the "visit only once" condition for each city does not eliminate Np-difficulty, because it is easy to see that the best travel in the flat case must be visited once per city (otherwise, as seen by the triangle inequality, A short cut to skip repeat visits will not increase the length of the tour.)4.2 Approximate ComplexityIn general, finding the shortest traveling salesman problem is a NPO-complete. If the distance is measurable and symmetrical, the problem becomes APX-complete. Christofides's algorithm is within about 1.5.If the limits are 1 and 2 (but still a metric), the approximate ratio is7/6. In the case of asymmetry and metering, only the logarithmic performance can be guaranteed. The best performance of the current algorithm is 0.814log n. If there is a constant factor approximation, it is an open problem.The corresponding maximization problem found the longest traveling salesman to travel around 63/38. If the distance function is symmetric, the longest tour can be approximated by 4/3 with a deterministic algorithm and a random algorithm.4.3 Accurate AlgorithmThe most straightforward approach is to try all permutations (ordered combinations) to see which one is the least expensive (use brute force search). The time complexity of this method is O (n !), the factorial of the number of cities, so this solution, even if only 20 cities are unrealistic. One of the earliest applications of dynamic programming was the Held-Karp algorithm. The time complexity of problem solving was O (n 22n ).Dynamic programming solutions require the time complexity of the index. Use inclusion-exclusion to solve problems in 2n time and space.It seems difficult to improve these times. For example, it is not known whether there is an accurate algorithm for TSP and the time complexity is O (1.9999n).4.4 Other methods include1) Different branch and bound algorithms can be used for TSP in 40-60 cities.2) An improved linear programming algorithm that handles TSPs in 200 cities.3) Branch and bounds and specific cuts are the preferred method of solving a large number of instances. The current method has a record of solving 85,900 city examples (2006).A solution for 15,112 German towns was discovered in TSPLIB in 2001 using the cutting plane method proposed by George Dantzig, Ray Fulkerson, and Selmer M. Johnson in 1954 based on linear programming.Rice University and Princeton University have performed calculations on a network of 110 processors. The total computation time is equivalent to a 2.5 MHz processor working 22.6 years. In 2004, the problem of traveling salesman visited all 24,978 towns in Sweden and was about 72,500 kilometers in length. At the same time, it proved that there is no shorter travel.In March 2005, accessing all 33,810 point of travel salesman problems on a circuit board was solved by using the Concord TSP solver: a tour with a length of 66,048,945 units was found, which at the same time proved that there was no shorter tour. Calculated for approximately 15.7 CPU years (Cook et al., 2006). In April 2006, an instance of 85,900 points using the Concord TSP solver solved the CPU time of more than136 years (2006).4) Heuristic approximation algorithmA variety of heuristic approximation algorithms that can quickly produce good solutions have been developed. The current method can solve very large problems (with millions of cities) in a reasonable amount of time, and only 2–3% of the probability is far from the optimal solution.Constructive heuristics The nearest neighbor (neural network) algorithm (or so-called greedy algorithm) lets the salesman choose the nearest city that has not been visited as his next action goal. The algorithm quickly produces a valid short path. For N cities randomly distributed on one plane, the average path generated by the algorithm is 25% longer than the shortest path. However, there are many cities with special distributions that make the neural network algorithm give the worst path (Gutin, Y eo, and Zverovich, 2002). This is a real problem with symmetric and asymmetric traveling salesman problems (Gutin and Y eo, 2007). Rosenkrantz et al. showed that the neural network algorithm satisfies the triangle inequality when the approximation factor Θ(log| V | ).The approximate ratio of the construction based on the minimum spanning tree is 2 . The Christofides algorithm achieved a ratio of 1.5.Bitonic travel is a monotonic polygon made up of the smallest perimeter of a set of points, which can be calculated efficiently throughdynamic planning.Another constructive heuristic, the twice comparison merge (MTS) (Kahng, Reda 2004), performs two consecutive matches, and the second match is executed after all the first matching edges have been removed. Then merge to produce the final travel.Iterative refinements, pairwise exchanges, or Lin-Kernighan heuristics, pairwise exchanges, or 2-technologies involve the repeated deletion of two edges and the replacement of edges that are not needed to create a new and shorter tour. This is a special case of a K-OPT method. Please note that Lin –Kernighan is often a misname of 2-OPT. Lin –Kernighan is actually a more general approach.K-opt heuristics, a given tour, removes k-disjoint edges. Regroup the remaining parts into one tour, leaving the disjoint sub-tours (ie, the end of a disjointed part together). This actually simplifies the TSP under consideration into a much simpler problem. There are 2K-2 other connection possibilities for each part of the endpoint: 2 K total destination can be connected, so this part cannot be considered. This constrained 2K-TSP can then be resolved using brute force methods to find the lowest partial reorganization of the original part. K-opt is a special case of V-opt or variable-opt technology. The most popular K-opt is 3-opt, which was introduced by Shen Lin of Bell Labs in 1965. There is a 3 - OPT special case where the edges do not intersect (adjacent to bothsides). The v-opt heuristic, the variable-opt method is related to the k-opt method, and is a generalization of the K-opt method. While K -opt removes a fixed number (K) from the original tour, the variable-opt method does not delete fixed-size edge sets. Instead, they continue to grow during the search process. The best method known here is Lin-Kernighan's method (mentioned above as a 2-OPT error). Shen Lin and Brian Kernighan first published their method in 1972, which was the most reliable heuristic for solving traveling salesman problems for nearly two decades. The more advanced variable-opt approach was developed at Bell Labs in the late 1980s by David Johnson and his research team. These methods (sometimes referred to as) add methods from tabu search and evolutionary computation to the Lin-Kernighan method. The basic Lin-Kernighan technique gives results that guarantee at least 3 -opt. The Lin–Kernighan–Johnson method calculates Lin–Kernighan's weekly tour, then disrupts the tour through so-called mutations that move at least four sides and connect them in different ways, and then establishes a new tour with the V-opt method. The v-opt method is widely considered to be the most powerful heuristic to solve a problem, and can solve problems under special circumstances, such as the Hamilton ring problem and other non-decimal TSPs, but other heuristics cannot. Over the years, Lin-Kernighan-Johnson has been shown to be the best solution to all TSP solutions that have been tried.中文译文旅行商问题Mask Dorigo1 引言在运筹学和理论计算机科学中,旅行商问题(TSP )是一个NP-困难的组合优化问题。
数据采集外文文献翻译(含:英文原文及中文译文)文献出处:Txomin Nieva. DATA ACQUISITION SYSTEMS [J]. Computers in Industry, 2013, 4(2):215-237.英文原文DATA ACQUISITION SYSTEMSTxomin NievaData acquisition systems, as the name implies, are products and/or processes used to collect information to document or analyze some phenomenon. In the simplest form, a technician logging the temperature of an oven on a piece of paper is performing data acquisition. As technology has progressed, this type of process has been simplified and made more accurate, versatile, and reliable through electronic equipment. Equipment ranges from simple recorders to sophisticated computer systems. Data acquisition products serve as a focal point in a system, tying together a wide variety of products, such as sensors that indicate temperature, flow, level, or pressure. Some common data acquisition terms are shown below.Data collection technology has made great progress in the past 30 to 40 years. For example, 40 years ago, in a well-known college laboratory, the device used to track temperature rises in bronze made of helium was composed of thermocouples, relays, interrogators, a bundle of papers, anda pencil.Today's university students are likely to automatically process and analyze data on PCs. There are many ways you can choose to collect data. The choice of which method to use depends on many factors, including the complexity of the task, the speed and accuracy you need, the evidence you want, and more. Whether simple or complex, the data acquisition system can operate and play its role.The old way of using pencils and papers is still feasible for some situations, and it is cheap, easy to obtain, quick and easy to start. All you need is to capture multiple channels of digital information (DMM) and start recording data by hand.Unfortunately, this method is prone to errors, slower acquisition of data, and requires too much human analysis. In addition, it can only collect data in a single channel; but when you use a multi-channel DMM, the system will soon become very bulky and clumsy. Accuracy depends on the level of the writer, and you may need to scale it yourself. For example, if the DMM is not equipped with a sensor that handles temperature, the old one needs to start looking for a proportion. Given these limitations, it is an acceptable method only if you need to implement a rapid experiment.Modern versions of the strip chart recorder allow you to retrieve data from multiple inputs. They provide long-term paper records of databecause the data is in graphic format and they are easy to collect data on site. Once a bar chart recorder has been set up, most recorders have enough internal intelligence to operate without an operator or computer. The disadvantages are the lack of flexibility and the relative low precision, often limited to a percentage point. You can clearly feel that there is only a small change with the pen. In the long-term monitoring of the multi-channel, the recorders can play a very good role, in addition, their value is limited. For example, they cannot interact with other devices. Other concerns are the maintenance of pens and paper, the supply of paper and the storage of data. The most important is the abuse and waste of paper. However, recorders are fairly easy to set up and operate, providing a permanent record of data for quick and easy analysis.Some benchtop DMMs offer selectable scanning capabilities. The back of the instrument has a slot to receive a scanner card that can be multiplexed for more inputs, typically 8 to 10 channels of mux. This is inherently limited in the front panel of the instrument. Its flexibility is also limited because it cannot exceed the number of available channels. External PCs usually handle data acquisition and analysis.The PC plug-in card is a single-board measurement system that uses the ISA or PCI bus to expand the slot in the PC. They often have a reading rate of up to 1000 per second. 8 to 16 channels are common, and the collected data is stored directly in the computer and then analyzed.Because the card is essentially a part of the computer, it is easy to establish the test. PC-cards are also relatively inexpensive, partly because they have since been hosted by PCs to provide energy, mechanical accessories, and user interfaces. Data collection optionsOn the downside, the PC plug-in cards often have a 12-word capacity, so you can't detect small changes in the input signal. In addition, the electronic environment within the PC is often susceptible to noise, high clock rates, and bus noise. The electronic contacts limit the accuracy of the PC card. These plug-in cards also measure a range of voltages. To measure other input signals, such as voltage, temperature, and resistance, you may need some external signal monitoring devices. Other considerations include complex calibrations and overall system costs, especially if you need to purchase additional signal monitoring devices or adapt the PC card to the card. Take this into account. If your needs change within the capabilities and limitations of the card, the PC plug-in card provides an attractive method for data collection.Data electronic recorders are typical stand-alone instruments that, once equipped with them, enable the measurement, recording, and display of data without the involvement of an operator or computer. They can handle multiple signal inputs, sometimes up to 120 channels. Accuracy rivals unrivalled desktop DMMs because it operates within a 22 word, 0.004 percent accuracy range. Some data electronic automatic recordershave the ability to measure proportionally, the inspection result is not limited by the user's definition, and the output is a control signal.One of the advantages of using data electronic loggers is their internal monitoring signals. Most can directly measure several different input signals without the need for additional signal monitoring devices. One channel can monitor thermocouples, RTDs, and voltages.Thermocouples provide valuable compensation for accurate temperature measurements. They are typically equipped with multi-channel cards. Built-in intelligent electronic data recorder helps you set the measurement period and specify the parameters for each channel. Once you set it all up, the data electronic recorder will behave like an unbeatable device. The data they store is distributed in memory and can hold 500,000 or more readings.Connecting to a PC makes it easy to transfer data to a computer for further analysis. Most data electronic recorders can be designed to be flexible and simple to configure and operate, and most provide remote location operation options via battery packs or other methods. Thanks to the A/D conversion technology, certain data electronic recorders have a lower reading rate, especially when compared with PC plug-in cards. However, a reading rate of 250 per second is relatively rare. Keep in mind that many of the phenomena that are being measured are physical in nature, such as temperature, pressure, and flow, and there are generallyfewer changes. In addition, because of the monitoring accuracy of the data electron loggers, a large amount of average reading is not necessary, just as they are often stuck on PC plug-in cards.Front-end data acquisition is often done as a module and is typically connected to a PC or controller. They are used in automated tests to collect data, control and cycle detection signals for other test equipment. Send signal test equipment spare parts. The efficiency of the front-end operation is very high, and can match the speed and accuracy with the best stand-alone instrument. Front-end data acquisition works in many models, including VXI versions such as the Agilent E1419A multi-function measurement and VXI control model, as well as a proprietary card elevator. Although the cost of front-end units has been reduced, these systems can be very expensive unless you need to provide high levels of operation, and finding their prices is prohibited. On the other hand, they do provide considerable flexibility and measurement capabilities.Good, low-cost electronic data loggers have the right number of channels (20-60 channels) and scan rates are relatively low but are common enough for most engineers. Some of the key applications include:•product features•Hot die cutting of electronic products•Test of the environmentEnvironmental monitoring•Composition characteristics•Battery testBuilding and computer capacity monitoringA new system designThe conceptual model of a universal system can be applied to the analysis phase of a specific system to better understand the problem and to specify the best solution more easily based on the specific requirements of a particular system. The conceptual model of a universal system can also be used as a starting point for designing a specific system. Therefore, using a general-purpose conceptual model will save time and reduce the cost of specific system development. To test this hypothesis, we developed DAS for railway equipment based on our generic DAS concept model. In this section, we summarize the main results and conclusions of this DAS development.We analyzed the device model package. The result of this analysis is a partial conceptual model of a system consisting of a three-tier device model. We analyzed the equipment project package in the equipment environment. Based on this analysis, we have listed a three-level item hierarchy in the conceptual model of the system. Equipment projects are specialized for individual equipment projects.We analyzed the equipment model monitoring standard package in the equipment context. One of the requirements of this system is the ability to use a predefined set of data to record specific status monitoring reports. We analyzed the equipment project monitoring standard package in the equipment environment. The requirements of the system are: (i) the ability to record condition monitoring reports and event monitoring reports corresponding to the items, which can be triggered by time triggering conditions or event triggering conditions; (ii) the definition of private and public monitoring standards; (iii) Ability to define custom and predefined train data sets. Therefore, we have introduced the "monitoring standards for equipment projects", "public standards", "special standards", "equipment monitoring standards", "equipment condition monitoring standards", "equipment project status monitoring standards and equipment project event monitoring standards, respectively Training item triggering conditions, training item time triggering conditions and training item event triggering conditions are device equipment trigger conditions, equipment item time trigger conditions and device project event trigger condition specialization; and training item data sets, training custom data Sets and trains predefined data sets, which are device project data sets, custom data sets, and specialized sets of predefined data sets.Finally, we analyzed the observations and monitoring reports in the equipment environment. The system's requirement is to recordmeasurements and category observations. In addition, status and incident monitoring reports can be recorded. Therefore, we introduce the concept of observation, measurement, classification observation and monitoring report into the conceptual model of the system.Our generic DAS concept model plays an important role in the design of DAS equipment. We use this model to better organize the data that will be used by system components. Conceptual models also make it easier to design certain components in the system. Therefore, we have an implementation in which a large number of design classes represent the concepts specified in our generic DAS conceptual model. Through an industrial example, the development of this particular DAS demonstrates the usefulness of a generic system conceptual model for developing a particular system.中文译文数据采集系统Txomin Nieva数据采集系统, 正如名字所暗示的, 是一种用来采集信息成文件或分析一些现象的产品或过程。
毕业设计外文翻译材料及译文专业:物流工程班级:物流092 学号:090512208 姓名:李成璋指导教师:吕延昌6.3 Why is shipping different?There are particular obstacles to knowing your customer in the shipping sector, and thus being able to analyse credit risk. In the first place, shipping companies take every advantage possible of the peculiar status of their assets–they can choose anywhere in the world to register them and naturally choose the most tax efficient and the registries that offer the opportunity of least disclosure of corporate and business data to outsiders. They will also set up separate legal vehicles to own each asset. This means that their structure is usually complex and opaque. From a legal perspective, a typical shipping company is more like a group of independent operators working in unison than a single operating legal entity like Exxon Mobil, or Microsoft, or Ford.A bunker supplier needs to know exactly to whom a delivery is being made – not least because this will be crucial to any recovery procedures if there is a payment issue. There will normally be a single, agency/management company representing the group, but this will rarely have assets and the supplier must understand the structure of the business and their counter party within it.The second issue is that since a shipping company is made up of a number of asset-holding entities registered in offshore non-disclosure domiciles, there are no consolidated accounts. In fact, there are often no accounts at all! A third question is whether the potential customer pays its bills. The problem with calling your competitors for references is that they may be reluctant to be truthful about a good customer for fear of losing them, so it is not always easy to tell if a reference is accurate. The shipping industry is getting hotter and hotter as a place to be. Every month that goes by without a major collapse means the likelihood of a serious collapse is that much closer. To stand the best chance of minimising potential loss, it is important to have the most sensitive awareness of the markets and of the players in them that you possibly can. A specialist marine credit report can clarify these issues. 6.4 How to prepare a bunkering credit risk report6.4.1 Understanding the fleetTake the first issue, the opaque structure of a shipping business with every ship owned by a different offshore company. A number of sources list the ships trading in a particular fleet, but the credit report attempts to present more than a list. It should give an idea of the organic structure of the fleet–how it has been built up over time–and thus provide insights into the character, abilities and professionalism of the owner.A tightly run fleet of modern-product tankers with a good mix of long-term and spotwork with top-class shippers is likely to be a better credit risk prospect for a bunkersupplier than an owner whose tonnage is old and badly maintained and only intermittently employed by second or third-tier shippers.A good marine credit report will point out the implications of the fleet and its structure and will also set it in the context of the prevailing market–given today’sfreight rates and the particular balance of supply and demand, how will this fleet be doing today? Is it concentrated into one sector so that business will suffer if that sector is down? Or is it operating across a few markets where the principal is experienced and well-connected, so likely to get the pick of whatever business is available as well as spread its own risk?6.4.2 Assessing financial viabilityThe second point a marine credit report will address is how to assess the financial viability of a shipping company in the absence of consolidated accounts. The credit reporting companies get the information from the same place that the accountants who work for the business get it –generating the profit and lossaccount from the trading results of the fleet, and the costs of running the ships, and the balance sheet from the asset values against likely finance cost, and debtors against creditors.The credit companies know the freight rates for the particular vessel types and trading routes where the fleet works. They will have an idea of roughly how much the vessels have been working. On the balance sheet side, they will know what similar ships cost when the vessels were purchased and they know how long a mortgage usually runs. So from this it is possible to generate an approximate set of consolidated accounts.6.4.3 The crucial questionFinally, the third point. Will the company actually pay up on day 30? The credit-reporting companies are in a slightly better position than the supplier here. They are able to speak to a wide variety of suppliers to get references–and call charterers and other suppliers too. If enough people who supply a company are called, a pattern starts to emerge. Major distorting factors can be adjusted for and discounted and, setting all the references against the market context and trading history of the business, an estimate can be made of what the real position is likely to be and a pretty good guess taken as whether payment will be forthcoming. It is notcertain, but it is a good guide.A good credit risk report will provide an insight into the structure, finances, management style, trading patterns, asset base, historical payments performance, known recent events and market and other factors that might impact on a potential customer. Used in conjunction with the supplier’s own knowledge, a credit report can allow a greater depth and breadth of insight to allow a finer commercial decision to be made.6.5 Content and structure of the marine credit reportEssentially, the marine credit report comprises the following elements:Corporate and legal details: date, place and type of incorporation, ownership, management, banking and share capital information.Operational information:what the company does, where it does it, with what assets and in what kind of markets.Financial assessment: on the rare occasions that realistic and reliable financial figures are available, these will be quoted and commented on. More often the report will include an assessment, based on knowledge of ship values, freight rates and operating costs, of the likely financial position of the business. These latter may not be exact, but they can often prove to be reasonably accurate.Reputation: this will include anonymously quoted comments from a number of suppliers on their experience with this account, payment performance experienced and level of credit given.Appraisal: this summarises the content of the report and assesses the creditworthiness of the company. The appraisal end with a credit recommendation.Usually the report will also include a credit rating and will have fleet and financial data attached, where available.6.6 Steps and advice for preventing credit riskChecking records: The beginning of the process is to check all the records possessed on the purchasing company for previous transactions and any notes and history made by traders and others during the course of the business over time. Look for both patterns and irregularities in the payment behaviour and, especially, where there has been late or unusual payment behaviour, how and at what point has the customer informed your company, and what sort of explanation has been given.Specialist data vendors:The next stage would be to look at the fleet on Sea-web or Seasearcher. A lot can be learned from this about the likely condition of a company. Sovereign risk: It is useful to check where the management company is based because there may be national characteristics in terms of payment practice that could be more than just stereotypes. This can be judged by which nation it is.What vessels? What trades?: Also from Sea-web or Seasearcher, check which sector the company operates in–Dry, Wet or Boxes? Or a niche trade like reefer or feedering? Or a mix of several? It is important to look at both the ages of the ships and also when they were acquired –the age will indicate asset value and the date of purchase will give a rough idea of how much finance cost the principals may be carrying. It is also wise to check on the actual ownership of the vessel seeking to bunker, vessel type and the routings.Initial hypothesis: By checking through the above stages, it is possible to gain a general sense of the account, but there is a need to be constantly alert for indications that counter these findings and the assumptions made. It is important to have a developing hypothesis, but this must not be rigid and it needs to be tested at every point.Trade press:There is a need to check the markets and trades where the potential customer is active. The best source of this is the trade press–Tradewinds, Lloyd’s list, Bunkerspot, Bunkerworld, and its sister online journal Ocean Intelligence Daily. Asking the market: The next stage is to call around the market to see if others will let it be known what their experience has been with this company.Buy a credit report: The final advice is to buy a credit report. This has several advantages: providers are impartial and objective, they have a broad sense of contact across the industry and great experience in sifting useful information and data in a way that allows a clear and unbiased assessment of a company.The point of credit risk analysis is to let credit be provided with as much confidence as possible and thus maximise revenue. The trick is to do as much business with a particular account as possible before pulling out. In particular, the aim should be to develop a long term partnership with particular shipping companies from the supply chain point of view. The most fundamental of all considerations in bunker credit risk assessment, however, is knowledge.Financial assessment: on the rare occasions that realistic and reliable financial figures are available, these will be quoted and commented on. More often the reportwill include an assessment, based on knowledge of ship values, freight rates and operating costs, of the likely financial position of the business. These latter may not be exact, but they can often prove to be reasonably accurate.Table 1: A Major Oil Company Credit ChecklistCriteria MaximumScore Actual ScoreHas the company been in existence for more than five years? 10 Is it five years since the last fundamental restructuring? 10 Is the subject’s financial condition sound or satisfactory? This includes evaluating the following points: operating profit, net result, liquidity, leverage and cash flow, when and where available.10Is the ratio of long term debt/net fixed assets less than 60% (0.60:1.00)? 5 Is the company’s turnover (excluding extraordinary items) in excess ofUS$100 million?10Are the company’s main markets at satisfa ctory or good level? 15 Are the company’s main markets improving?15 Is the company publicly listed? What is the company’s share behaviour, when compared to others in the same industry?5Is the company backed by a larger group, by a government or by (very) wealthy people?15Is the company’s current payments performance and/or reputationregarded as satisfactory or better?15Total 1156.3 为什么传送不同有了解你的客户在航运界,特别是障碍,从而能够分析信贷风险。
外文文献翻译(含: 英文原文及中文译文)文献出处:Jens Clausen, Birgit Blättel-Mink2, Lorenz Erdmann, Christine Henseling .Contribution of Online Trading of Used Goods to Resource Efficiency: An Empirical Study of eBay Users [J].Sustainability, 2010, 2: 10-30.英文原文Contribution of Online Trading of Used Goods to Resource Efficiency:An Empirical Study of eBay UsersJens Clausen, Birgit Blättel-Mink , Lorenz Erdmann and ChristineHenselingAbstractThis paper discusses the sustainability impact (contribution to sustainability, reduction of adverse environmental impacts) of online second-hand trading.A survey of eBay users shows that a relationship between the trading of used goods and the protection of natural resources is hardly realized.Secondly, the environmental motivation and the willingness to act in a sustainable manner differ widely between groups of consumers.Given these results from a user perspective, the paper tries to find some objective hints of online second-hand trading’s environmental impact.The greenhouse gas emissions resulting from theenergy used for the trading transactions seem to be considerably lower than the emissions due to the (avoided) production of new goods.The paper concludes with a set of recommendations for second-hand trade and consumer rmation about the sustainability benefits of purchasing second-hand goods should be included in general consumer information, and arguments for changes in behavior should be targeted to different groups of consumers.Keywords: online marketplaces; online auctions; consumer; electronic commerce; used products; second-hand market; sustainable consumption1.IntroductionOnline auction and trading platforms are increasing the opportunities for sustainable consumption.The potential of online based second-hand trading lies largely in the opportunity to extend the life span of products, thereby avoiding additional environmental stresses due to the purchase of new goods.To date, private households often failed to exploit the potentials for reusing products because of high transaction costs.Trade in second-hand goods remained limited to regional markets.These barriers frequently prevented local and regional used goods markets from attaining critical mass and becoming attractive for both buyers and sellers.In recent years, however, rapidly increasing use of the Internet and trading platforms, such as eBay, have fundamentally transformed the underlying conditions of such markets.Online markets have not only significantly increased the numbers of market participants; they have also changed the roles traditionally assigned to consumers and producers.Exchange sites, auction platforms and other Internet-based trading models where users are not merely buyers, but at the same time, also active sellers of products or services, have shifted the role of consumers.Against this background, this article examines consumption processes using the example of eBay, the world’s largest online trading platform for used goods, by focusing on the following question: Which sustainability potentials are connected with the electronic trading of used goods, and how can these potentials be exploited? This question lies in the center of the research project “From Consumer to Prosumer—Development of new trading mechanisms and auction cultures to promote sustainable consumption.”The project is intentionally linked with various streams of research and insights, especially concerning the intensification of use, lifestyle research, and life-cycle assessment, in the fields of information technology and telecommunications, and integrates them from the perspective of the research guiding question.After giving an overview of the scientific work on environmental attitudes and behavior in the context of internet based used goods trading, and an empirical look on internet usage in Chapter 2, the empirical results of an online survey on online trading and sustainability are presented inChapter 3.Chapter 4 draws conclusions from the empirical study and Chapter 5 focuses on the ecological assessment of used goods trading.The paper concludes with some remarks on the consequences of second-hand trade, online platforms, and consumer policy.2.Internet-Based Used Goods Trading from a Subjective PerspectiveSustainability researchers in the social sciences assume that environmentally-oriented behavior is supported to a non-negligible degree by positive attitudes toward the environment and by knowledge about the environment [1-7].Time and again, however, representative surveys of the population provide evidence for a discrepancy between concern about increasing environmental devastation and its consequences, as well as knowledge about the environment on the one hand, and environmental behavior that is in line with such knowledge on the other.It is possible to identify groups of individuals who display environmentally-friendly behavior, but not the corresponding attitudes toward the environment (e.g., older single women), just as there are groups of individuals who display a high degree of ecological awareness, but whose behavior is nonetheless not consistently environmentally oriented (e.g., families whose environmentally-friendly behavior is organized to the hilt, but who still drive a family car).Three bundles of characteristics that influence the sustainability of styles of consumption have emerged in the research [8]: the household’s social situation(socio-demographic characteristics and time resources), consumer preferences (subjective preferences relating to the selection of products and behaviors), and actual consumption behavior.Socio-demographic characteristics that substantially influence differences in terms of sustainable consumption patterns include age, educational level, gender, marital status, and income, with women, well educated people, and parents striving for consistency of attitudes and behavior.Grunenberg and Kuckartz [1] were able to identify the group they called the “environmentally committed”in their study, which was representative for Germany.“[A group] that takes environmental problems more seriously and is actively committed to solving them.Entirely consistent pro-environment behavior is not demanded of this group; that would require, for example, that these individuals would not just eat exclusively organically-grown food, but would also sell their cars and take bicycling vacations.”(Grunenberg/Kuckartz, p.204 [1]).The following indicators were used to define the group of environmentally-committed individuals: membership in an organization promoting conservation or environmental protection; donation to such an organization in the previous year; familiarity with the term “sustainable development;”high willingness to pay for improved environmental protection; frequenting of information about environmental problems from specialist periodicals; environmental mentality type 1 (motto: “Be arole model when it comes to environmental protection!”); declared shared responsibility for environmental protection (statement: “It isn’t difficult for an individual person to do something for the environment!”) (Grunenberg/Kuckartz, p.204 [1]).Members of this group are often in the familial phase of life, have a relatively high level of education, often live in major cities or small communities, seldom in medium-sized towns or villages, tend to come from West Germany, as a rule have a higher professional position (senior staff, upper-middle-level or upper-level civil servants, the professions), have a medium to high, but not very high income, and tend to live in quiet neighborhoods in single- or two-family houses.Regarding their political preferences, the authors ascertained a more pronounced interest in politics in general, and a clear focus on post-materialist values.As to trading in used goods as a specific area of consumption, a study of West Berlin showed that buying and selling used goods is linked fairly rarely to ecological motives [9].Pragmatic reasons for selling used goods are mentioned more frequently, for instance “making room”or “getting rid of items we no longer need.”In contrast, when purchasing used goods, financial motives are more important.The proportion of men who buy and sell used goods is somewhat higher than that of women.The average age is 36.More than two-thirds of those offering goods on the second-hand market have a job.Housewives and students comprise 10%of sellers each, the unemployed and pensioners about 5% each.The sellers often live in multi-person households, and live less commonly alone.Among the buyers of second-hand goods, 29.4% are in the 19- to 25-year age group and 35.7% are in the 26- to 35-year group.Most people have a job (61%), and students form 15% of the buyers, which is substantially higher than their proportion of the cational levels are above-average among buyers, too, as is the proportion of individuals living in multi-person households.3.Online Trading and Sustainability—Empirical ResultsTaking the example of eBay, the above mentioned relationships were more closely looked at with an online survey that was carried out by the authors in November, 2008.The survey was intended to gain insight into eBay users’consumption patterns, their attitudes, and their ways of dealing with used products on eBay.The survey was directed to private eBay users who use the site, both for buying and selling, and who carried out at least one transaction during the preceding 12 months.In total, 2,511 valid questionnaires were analyzed.In contrast to Germany’s total population, more men (57.1%) than women responded, more persons who live with their partners (73.4%), and more people living in households of three or more (52.4%).The sample also displays a relatively high educational (49.4% level A) and employment status (49.2% working full time), and the respondents tend to live in or near urban areas.The agedistribution of the respondents (biggest cluster 40–49 years old; 29.8%) and their income distribution (40% medium to low income) are comparable with the overall population.More women (45.1%) than men (34.0%) of the sample live in households with children; the proportion of men increases with increasing age.The women who buy or sell on eBay have lower incomes.48.7%, of all female eBay buyers earn less than 2,000 Euros per month compared to 39.8% of all male eBay pared to the group of Internet users mentioned above, the sample analyzed here differs only in relation to income, with Internet users displaying higher incomes.The following subjects will be approached: Attitudes toward the environment and motives for trading on eBay, attitudes of eBay users regarding used products and their handling of used products.Then, a typology of consumer patterns of eBay users that was derived from the data will be presented.4.Conclusions from the Empirical StudyThe results of the survey show that environmental aspects play only a minor role for the majority of the surveyed eBay users when trading used products.When concerning their motivations in particular, other aspects have been more important to date: practical and financial considerations, as well as having fun trading on eBay.Opportunities to make trading on eBay more environmentally friendly lie in providing information about the environmental relevance of used goods trading, e.g.,directly on the eBay platform.In addition, the broad range of motivations that eBay speaks to offers good starting points for creating alliances of motivations that connect ecological aspects with other aspects of use.A concrete strategic point of intervention is the option to provide opportunities for climate-neutral shipping on the eBay platform, and eBay users have indicated a high willingness to use such an option.The survey also made it possible to identify various starting points for intensifying used goods trading.When developing communications strategies in this regard, the value of used goods for others should be emphasized more strongly.This could happen, for example, by pointing more clearly to the quality, as well as the monetary value, of used products in such communications.Interesting approaches that take this direction include quality tests of used products, as well as tools with which users can learn about the prices they can get for used products.The test lab introduced by eBay in mid-2008 is an interesting approach.Certain used products were tested here to show their value in relation to the value of new products.The results highlight the significance of situations of change in life for trading used products.Such phases, for example, the birth of one’s first child or retirement can (under certain circumstances) function as times when people start trading used goods, or they can be situations in which the willingness to buy and to sell second-hand products is especially high.An important aspect for used goods trading is that the effort invested in selling the product must be financially worthwhile.The responses showed, however, that this is not always the case.This aspect must be taken into account when developing measures to intensify used goods trading.Another finding: a central problem of used goods trading lies in the fact that many buyers are unsure of the quality of the products for sale (lack of warranties, doubts about whether the products are in fact in proper working order).In order to address this concern, it is important to develop mechanisms that increase trust in second-hand products and reflect their quality.Initial starting points include initiatives to refurbish used products.One example for this is the initiative which purchases, refurbishes and then resells used cell phones and provides a warranty.Identification of the five consumption patterns in online used goods trading contributed to structuring the various behavior patterns of private eBay users.Above all, the fact that the respondents’differences in socio-demographic characteristics are very small is remarkable.The five types do differ significantly, however, regarding their attitudes and their behavior on eBay.They also differ with respect to their concern for the sustainability-related contexts of eBay trading.The environmentally oriented buyers of used goods and the prosumers, as different as they may be, are those upon whom we pin our hopes for sustainability.Although the former group displays a certain consistency in terms of attitudes andbehavior, which is also characterized by increasing awareness of sustainability, it is the prosumers who treat new and used products with care in order to resell them, thereby contributing to lengthening of the life spans of products, even if they are not aware of this effect.中文译文二手物品网上交易资源效率的贡献:eBay用户的实证研究Jens Clausen , Birgit Blättel-Mink , Lorenz Erdmann ,Christine Henseling 摘要本文探讨了网上二手交易的可持续性的影响(对可持续发展的贡献,减少对环境的不利影响) 。
毕业设计(论文)外文文献翻译文献、资料中文题目:机械设计文献、资料英文题目:Mechanical Design文献、资料来源:文献、资料发表(出版)日期:院(部):专业:班级:姓名:学号:指导教师:翻译日期: 2017.02.14外文资料翻译译文机械设计摘要:机器是由机械装置和其它组件组成的。
它是一种用来转换或传递能量的装置,例如:发动机、涡轮机、车辆、起重机、印刷机、洗衣机、照相机和摄影机等。
许多原则和设计方法不但适用于机器的设计,也适用于非机器的设计。
术语中的“机械装置设计”的含义要比“机械设计”的含义更为广泛一些,机械装置设计包括机械设计。
在分析运动及设计结构时,要把产品外型以及以后的保养也要考虑在机械设计中。
在机械工程领域中,以及其它工程领域中,所有这些都需要机械设备,比如:开关、凸轮、阀门、船舶以及搅拌机等。
关键词:设计流程设计规则机械设计设计流程设计开始之前就要想到机器的实际性,现存的机器需要在耐用性、效率、重量、速度,或者成本上得到改善。
新的机器必需具有以前机器所能执行的功能。
在设计的初始阶段,应该允许设计人员充分发挥创造性,不要受到任何约束。
即使产生了许多不切实际的想法,也会在设计的早期,即在绘制图纸之前被改正掉。
只有这样,才不致于阻断创新的思路。
通常,还要提出几套设计方案,然后加以比较。
很有可能在这个计划最后决定中,使用了某些不在计划之内的一些设想。
一般的当外型特点和组件部分的尺寸特点分析得透彻时,就可以全面的设计和分析。
接着还要客观的分析机器性能的优越性,以及它的安全、重量、耐用性,并且竞争力的成本也要考虑在分析结果之内。
每一个至关重要的部分要优化它的比例和尺寸,同时也要保持与其它组成部分相协调。
也要选择原材料和处理原材料的方法。
通过力学原理来分析和实现这些重要的特性,如那些静态反应的能量和摩擦力的最佳利用,像动力惯性、加速动力和能量;包括弹性材料的强度、应力和刚度等材料的物理特性,以及流体润滑和驱动器的流体力学。
(含:英文原文及中文译文)文献出处:Public Personnel Management, 12(2):159-166.英文原文New Public Management and the Quality of Government: Coping withthe New Political Governance in CanadaPeter AucoinA tension between New Public Management (NPM) and good governance, including good public administration, has long been assumed by those who regard the structures and practices advocated and brought about by NPM as departing from the principles and norms of good governance that underpinned traditional public administration (Savoie 1994). The concern has not abated (Savoie 2008).As this dynamic has played out over the past three decades, however, there emerged an even more significant challenge not only to the traditional structures, practices and values of the professional, non-partisan public service but also to those reforms introduced by NPM that have gained wide, if not universal, acceptance as positive development in public administration. This challenge is what I call New Political Governance (NPG). It is NPG, and not NPM, I argue, that constitutes the principal threat to good governance, including good public administration, and thus the Quality of Government (QoG) as defined by Rothstein and Teorell (2008). It is a threat to the extent that partisans in government, sometimes overtly, mostly covertly, seek to use and overridethe public service –an impartial institution of government –to better secure their partisan advantage (Campbell 2007; MacDermott 2008 a, 2008b). In so doing, these governors engage in a politicization of the public service and its administration of public business that constitutes a form of political corruption that cannot but undermine good governance. NPM is not a cause of this politicization, I argue, but it is an intervening factor insofar as NPM reforms, among other reforms of the last three decades, have had the effect of publicly exposing the public service in ways that have made it more vulnerable to political pressures on the part of the political executive.I examine this phenomenon by looking primarily at the case of Canada, but with a number of comparative Westminster references. I consider the phenomenon to be an international one, affecting most, if not all, Western democracies. The pressures outlined below are virtually the same everywhere. The responses vary somewhat because of political leadership and the institutional differences between systems, even in the Westminster systems. The phenomenon must also be viewed in the context of time, given both the emergence of the pressures that led to NPM in the first instance, as a new management-focused approach to public administration, and the emergence of the different pressures that now contribute to NPG, as a politicized approach to governance with important implications for public administration, and especially forimpartiality, performance and accountability.New Public Management in the Canadian ContextSince the early 1980s, NPM has taken several different forms in various jurisdictions. Adopting private-sector management practices was seen by some as a part, even if a minor part, of the broader neo-conservative/neo-liberal political economy movement that demanded wholesale privatization of government enterprises and public services, extensive deregulation of private enterprises, and significant reductions in public spending –‘rolling back the state’, as it was put a at the outset (Hood 1991). By some accounts, almost everything that changed over the past quarter of a century is attributed to NPM. In virtually every jurisdiction, nonetheless, NPM, as public management reform, was at least originally about achieving greater economy and efficiency in the management of public resources in government operations and in the delivery of public services (Pollitt 1990). The focus, in short, was on ‘management’. Achieving greater economy in the use of public resources was at the forefront of concerns, given the fiscal and budgetary situations facing all governments in the 1970s, and managerial efficiency was not far behind, given assumptions about the impoverished quality of management in public services everywhere.By the turn of the century, moreover, NPM, as improved public management in this limited sense, was well embedded in almost allgovernments, at least as the norm (although it was not always or everywhere referred to as NPM). This meant increased managerial authority, discretion and flexibility:• for managing public resources (financial and human);• for managing public-service delivery systems; and,• for collaborating with othe r public-sector agencies as well as with privatesector agencies in tackling horizontal – multi-organizational and/or multisectoral – issues.This increased managerial authority, flexibility and discretion was, in some jurisdictions, notably the Britain and New Zealand, coupled with increased organizational differentiation, as evidenced by a proliferation of departments and agencies with narrowed mandates, many with a single purpose. “Agencification’, however, was not a major focus reform in all jurisdictions, including Canada and Australia where such change, if not on the margins, was clearly secondary to enhanced managerial authority and responsibility (Pollitt and Talbot 2004).The major NPM innovations quickly led to concerns, especially in those jurisdictions where these developments were most advanced, about a loss of public service coherence and corporate capacity, on the one hand, and a diminished sense of and commitment to public-service ethos, ethics and values, on the other. Reactions to these concerns produced some retreat, reversals, and re-balancing of the systems in questions (Halligan2006). Nowhere, however, was there a wholesale rejection of NPM, in theory or practice, and a return to traditional public administration, even if there necessarily emerged some tension between rhetoric and action (Gregory 2006). The improvements in public management brought about by at least some aspects of NPM were simply too obvious, even if these improvements were modest in comparison to the original claims of NPM proponents.At the same time that NPM became a major force for change in public administration, however, it was accompanied by a companion force that saw political executives seeking to assert greater political control over the administration and apparatus of the state, not only in the formulation of public policies but also in the administration of public services. Accordingly, from the start, at least in the Anglo-American systems, there was a fundamental paradox as political executives, on both the left and the right sides of the partisan-political divide, sought to (re)assert dominance over their public-service bureaucracies while simultaneously devolving greater management authority to them (Aucoin 1990).The impetus for this dynamic lay in the dissatisfaction of many political executives with the ‘responsiveness’ of public servants to the political authority and policy agendas of these elected officials. Public choice and principal-agency theories provided the ideologicaljustifications for taking action against what were perceived as self-serving bureaucrats (Boston 1996). Beyond theory and ideology, however, the practice of public administration by professional public servants in some jurisdictions, notably Australia, Britain and New Zealand, offered more than sufficient evidence to political leaders of a public-service culture that gave only grudging acceptance, at best, to the capacity of elected politicians to determine what constituted the ‘public interest’ in public policy and administration.The Canadian case is of interest, I suggest, for several reasons. In comparative perspective, Canada did not approach public management reform with much of an ideological perspective. When the Conservatives defeated the centrist Liberals in 1984, neither the new prime minister, Brian Mulroney, nor his leading ministers were hardcore neo-conservatives in the Ronald Reagan or Margaret Thatcher mold. At that time, and until the end of the Conservative government in 1993, the party was essentially a centrist party in the Canadian ‘brokerage’ party tradition. While important aspects of neoliberalism unfolded, especially under the umbrella of economic deregulation that came with a free-trade agreement with the United States, there were no major administrative reforms that were politically driven. Pragmatism prevailed (Gow 2004). As a result, the reforms initiated during this period were essentially undertakings of the professional public-service leadership that sought tostay abreast with developments elsewhere. The scope and depth of these reforms were affected, however, by the extent to which ministers wanted to maintain an active involvement in administration (Aucoin 1995).By comparison to developments elsewhere, Canadian ministers were less inclined to worry about the professional public service being unresponsive to their political direction. Nonetheless, the Mulroney regime saw an expansion in the number, roles and influence of ‘political staff’ appointed to ministers’ offices, most notably in the Prime Minister’s Office (PMO). These staff, who have grown continuously in number over the past four decades, are not public servants, although they are employed on the public payroll. Unlike public servants, who are appointed independently of ministers, political staff are appointed and dismissed at the discretion of ministers and, of course, they have no tenure beyond their ministers. And, in official constitutional doctrine, they have no separate authority to direct the public service. In the Canadian tradition, moreover, they are appointed almost exclusively from partisan-political circles and appointees rarely possess any public service experience.For all these reasons, the Canadian government did not go as far down the NPM road as its three major Westminster counterparts (Australia, Britain and New Zealand) in terms of such matters as ‘agencification,’ devolution, term contracts for executives, external recruitment, or contracting-out. And, the reforms that did occur did notfundamentally transform the traditional administrative architecture. Throughout, there was retained, and even further developed:• an integrated public service, with the most senior levels drawn from the career public service and managed and deployed as a corporate executive resource;• departmental organizations, structured hierarchically with the minister as political executive and combining public policy and operational/service delivery responsibilities; and,• public administrative structures for addressing both corporate or governmentwide concerns and horizontal policy and service delivery issues.These features were seen as strengths of the Canadian approach (Bourgon 1998; Lindquist 2006; Dunn 2002).At the same time, reforms were initiated to improve public management that followed the principal NPM script: some measure of devolution of management authority from central management agencies to the senior public-service executives of line departments for (a) achieving greater economy and efficiency in the use of public resources, (b) improving service delivery, and (c) enhancing collaboration across departments to address those wicked ‘horizontal’ problems that defy government’s organizational boundaries (Bakvis and Juillet 2004).Further, in addressing one major challenge that was critical in thefirst years of NPM, namely, the fiscal crisis of the state in the latter part of the 20th century, the record of Canada was at first dismal and then dramatically successful. While the Conservative government, in power from 1984-93, was unable to wrestle annual deficits to the ground, a major program-budget review initiated following the Liberal Party victory in 1993 resulted, in surprisingly short order, in annual multi-billion dollar budget surpluses for over a decade – the best record in the G-8 nations (a group that does not include Australia which has had a similar experience with very large budget surpluses). On this front, political will and discipline, but not ideology, was a decisive force.By the first decade of the 21st century, moreover, Canada also came to be ranked first both in E-Government and in Service Delivery on one major international scorecard. On this front, the fact that the public service has been able to operate essentially on its own has helped spur progress. The Canadian emphasis on citizen-centred service drew inspiration from the NPM focus on ‘customers’ but, at the same time, paid serious attention to the priorities of citizens as defined by citizens –the outside-in perspective that enabled a significant advance in integrated service delivery structures and processes using multiple channels of service (Flumian, Coe and Kernaghan 2007). The Canadian methodology for this performance-based approach to service-delivery measurement and improvement is being adopted elsewhere in the Westminster systems.Finally, and clearly on a much less positive note, a good deal of attention has been required in Canada over the past decade to codes of ethics, public service values, transparency, comptrollership, and public accountability –thanks in large part to a series of alleged and real political-administrative scandals! Not surprisingly, this is where NPG and its effects on the quality of government can be witnessed in spades.中文译文新公共管理与政府素质:加拿大的新政府治理Peter Aucoin新公共管理(NPM)与善治之间的紧张关系,包括良好的公共管理,早已被那些认为公共产品管理倡导和带来的结构和做法背离了支持传统公众的善治原则和规范的人所认可管理(萨瓦1994)。
附录C:外文翻译资料Article Source:Business & Commercial Aviation, Nov 20, 2000. 5-87-88 Interactive Electronic Technical Manuals Electronic publications can increase the efficiency of your digital aircraft and analogtechnicians.Benoff, DaveComputerized technical manuals are silently revolutionizing the aircraft maintenance industry by helping the technician isolate problems quickly, and in the process reduce downtime and costs by more than 10 percent.These electronic publications can reduce the numerous volumes of maintenance manuals, microfiche and work cards that are used to maintain engines, airframes, avionics and their associated components."As compared with the paper manuals, electronic publications give us greater detail and reduced research times," said Chuck Fredrickson, general manager of Mercury Air Center in Fort Wayne, Ind.With all the advances in computer hardware and software technologies, such as high quality digital multimedia, hypertext and the capability to store and transmit digital multimedia via CD-ROMs/ networks, technical publication companies have found an effective, cost-efficient method to disseminate data to technicians.The solution for many operators and OEMs is to take advantage of today's technology in the form of Electronic Technical Manuals (ETM) or Interactive Technical Manuals (IETM). An ETM is any technical manual prepared in digital format that has the ability to be displayed using any electronic hardware media. The difference between the types of ETM/IETMs is the embedded functionality and implementation of the data."The only drawback we had to using ETMs was getting enough computers to meet our technicians' demand," said Walter Berchtold, vice president of maintenance at Jet Aviation's West Palm Beach, Fla., facility.A growing concern is the cost to print paper publications. In an effort to reduce costs, some aircraft manufacturers are offering incentives for owners to switch from paper to electronic publications. With an average printing cost of around 10 cents per page, a typical volume of a paper technical manual can cost the manufacturer over $800 for each copy. When producing a publication electronically, average production costs for a complete set of aircraft manuals are approximately $20 per copy. It is not hard to see the cost advantages of electronic publications.Another advantage of ETMs is the ease of updating information. With a paper copy, the manufacturer has to reprint the revised pages and mail copies to all the owners. When updates are necessary for an electronic manual, changes can either be e-mailed to theowners or downloaded from the manufacturer's Web site.So why haven't more flight departments converted their publications to ETM/IETMs? The answer lies in convincing technicians that electronic publications can increase their efficiency."We had an initial learning curve when the technicians switched over, but now that they are familiar with the software they never want to go back to paper," said Fredrickson.A large majority of corporate technicians also said that while they like the concept of having a tool that aids the troubleshooting process, they are fearful to give up all of their marked-up paper manuals.In 1987, a human factors study was conducted by the U.S. government to compare technician troubleshooting effectiveness, between paper and electronic methodology, and included expert troubleshooting procedures with guidance through the events. Results of the project indicated that technicians using electronic media took less than half the time to complete their tasks than those using the paper method, and technicians using the electronic method accomplished 65 percent more in that reduced time.The report also noted that new technicians using the electronic technical manuals were 12-percent more efficient than the older, more experienced technicians. (Novices using paper took 15 percent longer than the experts.)It is interesting that 90 percent of the technicians who used the electronic manuals said they preferred them to the paper versions. This proved to the industry that with proper training, the older technicians could easily transition from paper to electronic media.Electronic publications are not a new concept, although how they are applied today is. "Research over the last 20 years has provided a solid foundation for today's IETM implementation," said Joseph Fuller of the U.S. Naval Surface Warfare Center. "IETMs such as those for the Apache, Comanche, F-22, JSTAR and V-22 have progressed from concept to military and commercial implementation."In the late 1970s, the U.S. military investigated the feasibility of converting existing paper and microfilm. The Navy Technical Information Presentation System (NTIPS) and the Air Force Computer- based Maintenance Aid System (CMAS) were implemented with significant cost savings.The report stated that transition to electronic publications resulted in reductions in corrective maintenance time, fewer false removals of good components, more accurate and complete maintenance data collection reports, reduction in training requirements and reduced system downtime.The problem that the military encountered was ETMs were created in multiple levels of complexity with little to no standardization. Options for publications range from simple page-turning programs to full-functioning automated databases.This resulted in the classification of ETMs so that the best type of electronic publication could be selected for the proper application.Choosing a LevelWith all of the OEM and second- and third-party electronic publications that are available it is important that you choose the application level that is appropriate for your operation.John J. Miller, BAE Systems' manager of electronic publications, told B/CAthat "When choosing the level of an ETM/IETM, things like complexity of the aircraft and its systems, ease of use, currency of data and commonality of data should be the deciding factors; and, of course, price. If operational and support costs are reduced when you purchase a full-functioning IETM, then you should purchase the better system."Miller is an expert on the production, sustainment and emerging technologies associated with electronic publications, and was the manager of publications for Boeing in Philadelphia.Electronic publications are classified in one of five categories. A Class 1 publication is a basic electronic "page turner" that allows you to view the maintenance manual as it was printed. With a Class 2 publication all the original text of the manual is viewed as one continuous page with no page breaks. In Class 3, 4 and 5 publications the maintenance manual is viewed on a computer in a frame-based environment with increasing options as the class changes. (See sidebar.)Choosing the appropriate ETM for your operation is typically limited to whatever is being offered on the market, but since 1991 human factors reports state the demand has increased and, therefore, options are expected to follow.ETM/IETM ProvidersCompanies that create ETM/IETMs are classified as either OEM or second party provider. Class 1, 3 and 4 ETM/IETMs are the most commonly used electronic publications for business and commercial operators and costs can range anywhere from $100 to $3,000 for each ETM/ IETM. The following are just a few examples ofETM/IETMs that are available on the market.Dassault Falcon Jet offers operatorsof the Falcon 50/50EX, 900/900EX and 2000 a Class 4 IETM called the Falcon Integrated Electronic Library by Dassault (FIELD). Produced in conjunction with Sogitec Industries in Suresnes Cedex, France, the electronic publication contains service documentation, basic wiring, recommended maintenance and TBO schedules, maintenance manual, tools manual, service bulletins, maintenance and repair manual, and avionics manual.The FIELD software allows the user to view the procedures and hot- link directly to the Illustrated parts catalog. The software also enables the user to generate discrepancy forms, quotation sheets, annotations in the manual and specific preferences for each user.BAE's Miller said most of the IETM presentation systems have features called "Technical Notes." If a user of the electronic publication notices a discrepancy or needs to annotate the manual for future troubleshooting, the user can add a Tech Note (an electronic mark-up) to the step or procedure and save it to the base document. The next time that or another user is in the procedure, clicking on the tech note icon launches a pop-up screen displaying the previous technician's comments. The same electronic transfer of tech notes can be sent to other devices by using either a docking station or through a network server. In addition, systems also can use "personal notes" similar to technical notes that are assigned ID codes that only the authoring technician can access.Requirements for the FIELD software include the minimum of a 16X CD-ROM drive,Pentium II 200 MHz computer, Windows 95, Internet Explorer 4 SP 1 and Database Access V3.5 or higher.Raytheon offers owners of Beech and Hawker aircraft a Class 4 IETM called Raytheon Electronic Publication Systems (REPS). The REPS software links the frame-based procedures with the parts catalog using a single CD-ROM.Raytheon Aircraft Technical Publications said other in- production Raytheon aircraft manual sets will be converted to the REPS format, with the goal of having all of them available by 2001. In addition Raytheon offers select Component Maintenance Manuals (CMM). The Class 1 ETM is a stand-alone "page-turner" electronic manual that utilizes the PDF format of Adobe Acrobat.Other manufacturers including Bombardier, Cessna and Gulfstream offer operators similar online and PDF documentation using a customer- accessed Web account.Boeing is one manufacturer that has developed an onboard Class 5 IETM. Called the Computerized Fault Reporting System (CFRS), it has replaced the F-15 U.S. Air Force Fault Reporting Manuals. Technologies that are currently being applied to Boeing's military system are expected to eventually become a part of the corporate environment.The CFRS system determines re-portable faults by analyzing information entered during a comprehensive aircrew debrief along with electronically recovered maintenance data from the Data Transfer Module (DTM). After debrief the technicians can review aircraft faults and schedule maintenance work to be performed. The maintenance task is assigned a Job Control Number (JCN) and is forwarded electronically to the correct work center or shop. Appropriate information is provided to the Air Force's Core Automated Maintenance System (CAMS).When a fault is reported by pilot debrief, certain aircraft systems have the fault isolation procedural data on a Portable Maintenance Aid (PMA). The JCN is selected on a hardened laptop with a wireless Local Area Network (LAN) connection to the CFRS LAN infrastructure. The Digital Wiring Data System (DWDS) displays aircraft wiring diagrams to the maintenance technician for wiring fault isolation. On completion of maintenance, the data collected is provided to the Air Force, Boeing and vendors for system analysis.Third party IETM developers such as BAE Systems and Dayton T. Brown offer OEMs the ability to subcontract out the development of Class 1 through 5 ETM/IETMs. For example, Advantext, Inc. offers PDF and IPDF Class 1 ETMs for manufacturers such as Piper and Bell Helicopters. Technical publications that are available include maintenance manuals, parts catalogs, service bulletins, wiring diagrams, service letters and interactive parts ordering forms.The difference between the PDF and IPDF version is that the IPDF version has the ability to search for text and include hyperlinks. A Class 1 ETM, when printed, is an exact reproduction of the OEM manuals, including any misspellings or errors. Minimum requirements for the Advantext technical publications is a 486 processor, 16 MB RAM with 14 MB of free hard disk space and a 4X CD-ROM or better.Aircraft Technical Publishers (ATP) offers Class 1, 2 and 3 ETM/ IETMsfor the Beechjet 400/400A; King Air 300/ 350, 200 and 90; Learjet 23/24/25/28/29/35/36/55; Socata TB9/10/20/21 and TBM 700A; Sabreliner 265-65, -70 and -80; andBeech 1900. The libraries can include maintenance manuals, Illustrated parts bulletins, wiring manuals, Airworthiness Directives, Service Bulletins, component maintenance manuals and structural maintenance manuals. System minimum requirements are Pentium 133 MHz, Windows 95 with 16 MB RAM, 25 MB free hard disk space and a 4X CD-ROM or better.Additional providers such as Galaxy Scientific are providing ETM/ IETMs to the FAA. This Class 2, 3 and 4 publication browser is used to store, display and edit documentation for the Human Factors Section of the administration."Clearly IETMs have moved from research to reality," said Fuller, and the future looks to hold more promise.The Future of Tech PubsThe use of ETM/IETMs on laptop and desktop computers has led research and development corporations to investigate the human interface options to the computer. Elements that affect how a technician can interface with a computer are the work environment, economics and ease of use. Organizations such as the Office of Naval Research have focused their efforts on the following needs of technicians: -- Adaptability to the environment.-- Ease of use.-- Improved presentation of complex system relationship.-- Maximum reuse and distribution of engineering data.-- Intelligent data access.With these factors in mind, exploratory development has begun in the areas of computer vision, augmented reality display and speech recognition.Computer vision can be created using visual feedback from a head- mounted camera. The camera identifies the relative position and orientation of an object in an observed scene, and the object is used to correlate the object with a three-dimensional model. In order for a computer vision scenario to work, engineering data has to be provided through visually compatible software.When systems such as Sogitech's View Tech electronic publication browser and Dassault Systemes SA's Enovia are combined, a virtual 3D model is generated.The digital mockup allows the engineering information to directly update the technical publication information. If a system such as CATIA could be integrated into a Video Reference System (VRS), then it could be possible that a technician would point the camera to the aircraft component, the digital model identifies the component and the IETM automatically displays the appropriate information.This example of artificial intelligence is already under development at companies like Boeing and Dassault. An augmented reality display is a concept where visual cues are presented to users on a head-mounted, see-through display system.The cues are presented to the technician based on the identification of components on a 3D model and correlation with the observed screen. The cues are then presented as stereoscopic images projected onto the object in the observed scene.In addition a "Private Eye" system could provide a miniature display of the maintenance procedure that is provided from a palm- size computer. Limited success hascurrently been seen in similar systems for the disabled. The user of a Private Eye system can look at the object selected and navigate without ever having to touch the computer. Drawbacks from this type of system are mental and eye fatigue, and spatial disorientation.Out of all the technologies, speech recognition has developed into an almost usable and effective system. The progression through maintenance procedures is driven by speaker-independent recognition. A state engine controls navigation, and launches audio responses and visual cues to the user. Voice recognition software is available, although set up and use has not been extremely successful.Looking at other industries, industrial manufacturing has already started using "Palm Pilot" personal digital assistants (PDAs) to aid technicians in troubleshooting. These devices allow the technician to have the complete publication beside them when they are in tight spaces. "It would be nice to take the electronic publications into the aircraft, so we are not constantly going back to the work station to print out additional information," said Jet Aviation's Berchtold.With all the advantages that a ETM/ IETM offers it should be noted that electronic publications are not the right solution all of the time, just as CBT is not the right solution for training in every situation. Only you can determine if electronic publications meet your needs, and most technical publication providers offer demo copies for your review. B/CA IllustrationPhoto: Photograph: BAE Systems' Christine Gill prepares a maintenance manual for SGML conversion BAE Systems; Photograph: Galaxy Scientific provides the FAA's human factors group with online IETM support.; Photograph: Raytheon's Class 4 IETM "REPS" allows a user to see text and diagrams simultaneously with hotlinks to illustrated parts catalogs.外文翻译资料译文部分文章出处:民航商业杂志,2000-11-20,5-87-88交互式电子技术手册的电子出版物可以提高数字飞机和模拟技术的效率。
毕业设计(论文)译文及原稿免费下载,免费分享。
让论文写得更简单,更舒适。
更容易……译文题目ZigBee:无线技术,低功耗传感器网络原稿题目ZigBee: Wireless Technology for Low-Power Sensor Networks原稿出处电子文献ZigBee:无线技术,低功耗传感器网络加里莱格美国东部时间2004年5月6日上午12:00技师(工程师)们在发掘无线传感器的潜在应用方面从未感到任何困难。
例如,在家庭安全系统方面,无线传感器相对于有线传感器更易安装。
而在有线传感器的装置通常占无线传感器安装的费用80%的工业环境方面同样正确(适用)。
而且相比于有线传感器的不切实际甚至是不肯能而言,无线传感器更具应用性。
虽然,无线传感器需要消耗更多能量,也就是说所需电池的数量会随之增加或改变过于频繁。
再加上对无线传感器由空气传送的数据可靠性的怀疑论,所以无线传感器看起来并不是那么吸引人。
一个低功率无线技术被称为ZigBee,它是无线传感器方程重写,但是。
一个安全的网络技术,对最近通过的IEEE 802.15.4无线标准(图1)的顶部游戏机,ZigBee的承诺,把无线传感器的一切从工厂自动化系统到家庭安全系统,消费电子产品。
与802.15.4的合作下,ZigBee提供具有电池寿命可比普通小型电池的长几年。
ZigBee设备预计也便宜,有人估计销售价格最终不到3美元每节点,。
由于价格低,他们应该是一个自然适应于在光线如无线交换机,无线自动调温器,烟雾探测器和家用产品。
(图1)虽然还没有正式的规范的ZigBee存在(由ZigBee联盟是一个贸易集团,批准应该在今年年底),但ZigBee的前景似乎一片光明。
技术研究公司In-Stat/MDR在它所谓的“谨慎进取”的预测中预测,802.15.4节点和芯片销售将从今天基本上为零,增加到2010年的165万台。
不是所有这些单位都将与ZigBee结合,但大多数可能会。
西京学院本科毕业设计(论文)外文资料翻译教学单位:经济系专业:国际经济与贸易(本)学号:0700090641姓名:王欢外文出处:《国际商务谈判》附件:1.译文;2.原文;3.评分表2010年11月1.译文译文(一)国际商务谈判是国际商务活动中,处于不同国家或不同地区的商务活动当事人为了达成某笔交易,彼此通过信息交流,就交易的各项要件进行协商的行为过程。
可以说国际商务谈判是一种在对外经贸活动中普遍存在的﹑解决不同国家的商业机构之间不可避免的利害冲突﹑实现共同利益的一种必不可少的手段。
国际商务谈判与一般贸易谈判具有共性,即以经济利益为目的,以价格为谈判核心。
因为价格的高低最直接﹑最集中的表明了谈判双方的利益切割,而且还由于谈判双方在其他条件,诸如质量﹑数量﹑付款形式﹑付款时间等利益要素上的得与失,在很多情况下都可以折算为一定的价格,并通过价格的升降而得到体现或予以补偿。
在国际买卖合同中价格术语包括单价和总价。
单价则是由计量单位,单价,计价货币以及贸易术语构成。
例如,一个价格术语可以这样来说:“每吨CIF伦敦1500美元包含3%佣金”。
总价格是合同中交易的总额。
在谈判过程中,应该由谁先出价,如何回应对方的报价,做出多少让步才适当,到最后双方达成都能接受的协议,整个这一过程被称之为谈判之舞。
通常情况下,谈判者的目标价位不会有重叠:卖方想为自己的产品或服务争取的价格,会高出买方愿意付出的价格。
然而,有时候谈判者的保留点却会相互重叠,也就是说大多数买方愿意付出的价格都会高于卖方可以接受的最低价格,在这种议价区间的前提下,谈判的最终结果会落在高于卖方的保留点而低于买方的保留点之间的某个点上。
议价区间可以为正数,也可以为负数。
在正议价区间,谈判者的保留点会互相重叠的,即买方愿意出的最高价格高于卖方可以接受的最低价格。
这意味着谈判者能达成协议的话,那么结果肯定在这个区间之内。
负议价区间可能根本不存在或是负数,这可能会造成花费巨大的时间来做一件毫无结果的协议,谈判者将会浪费时间成本。
车床用于车外圆、端面和镗孔等加工的机床称作车床。
车削很少在其他种类的机床上进行,因为其他机床都不能像车床那样方便地进行车削加工。
由于车床除了用于车外圆还能用于镗孔、车端面、钻孔和铰孔,车床的多功能性可以使工件在一次定位安装中完成多种加工。
这就是在生产中普遍使用各种车床比其他种类的机床都要多的原因。
两千多年前就已经有了车床。
现代车床可以追溯到大约1797年,那时亨利•莫德斯利发明了一种具有把主轴和丝杆的车床。
这种车床可以控制工具的机械进给。
这位聪明的英国人还发明了一种把主轴和丝杆相连接的变速装置,这样就可以切削螺纹。
车床的主要部件:床身、主轴箱组件、尾架组件、拖板组、变速齿轮箱、丝杆和光杆。
床身是车床的基础件。
它通常是由经过充分正火或时效处理的灰铸铁或者球墨铸铁制成,它是一个坚固的刚性框架,所有其他主要部件都安装在床身上。
通常在球墨铸铁制成,它是一个坚固的刚性框架,所有其他主要部件都安装在床身上。
通常在床身上面有内外两组平行的导轨。
一些制造厂生产的四个导轨都采用倒“V”,而另一些制造厂则将倒“V”形导轨和平面导轨结合。
由于其他的部件要安装在导轨上并(或)在导轨上移动,导轨要经过精密加工,以保证其装配精度。
同样地,在操作中应该小心,以避免损伤导轨。
导轨上的任何误差,常常会使整个机床的精度遭到破坏。
大多数现代车床的导轨要进行表面淬火处理。
以减少磨损和擦伤,具有更大的耐磨性。
主轴箱安装在床身一端内导轨的固定位置上。
它提供动力。
使工件在各种速度下旋转。
它基本上由一个安装在精密轴承中的空心轴和一系列变速齿轮---类似于卡车变速箱所组成,通过变速齿轮,主轴可以在许多中转速的旋转。
大多数车床有8~18中转速,一般按等比级数排列。
在现代车床上只需扳动2~4个手柄,就能得到全部挡位的转速。
目前发展的趋势是通过电气的或机械的装置进行无级变速。
由于车床的精度在很大程度上取决于主轴,因此主轴的结构尺寸较大,通常安装在紧密配合的重型圆锤滚子轴承或球轴承中。
主轴中有一个贯穿全长的通孔,长棒料可以通过该孔送料。
主轴孔的大小是车床的一个重要尺寸,因为当工件必须通过主轴孔供料时,它确定了能够加工棒料毛坯的最大外径尺寸。
主轴的内端从主轴箱中凸出,其上可以安装多种卡盘、花盘和挡筷。
而小型的车床长带有螺纹截面供安装卡盘之用。
很多大车床使用偏心夹或键动圆锥。
这些附件组成了一个大直径的圆锥体,以保证对卡盘进行精确地装配,并且不用旋转这些笨重的附件就可以琐定后松开卡盘或花盘。
主轴由电动机经V带或无声链装置提供动力。
大多数现代车床有5~15马力的电动机,为硬质合金和金属陶瓷合金刀具提供足够的动力,进行高速切削。
尾座组件主要有三部分组成。
底座与床身的内侧导轨配合,并可以在导轨上做纵向移动,底座上有一个可以使整个尾座组件夹紧在任意位置上的装置。
尾座安装在底座上,可以沿键槽在底座横向移动,使尾座与主轴箱中的主轴对中并为切削锥体提供方便。
尾座组件的第三部分是尾座套筒,它是一个直径通常在2~3英寸之间的刚制空心圆柱轴。
通过手轮和螺杆,尾座套筒可以在尾座体中纵向移入和移出几英寸。
活动套筒的开口一端具有莫氏锥度,可以用于安装顶尖或诸如钻头之类的各种刀具。
通常在活动套筒的外表面刻有几英寸的刻度,以控制尾座的前后移动。
锁定装置可以使套筒在所需要的位置上夹紧。
拖板组件用于安装和移动切削工具。
拖板上一个相对平滑的H形铸件,安装在床身外侧导轨上,并可在上面移动。
大拖板上有横向导轨,使横向托板可以安装在上面,并通过丝杆使其运动,丝杆由一个小手柄和刻度盘控制。
横拖板可以带动刀具垂直于工件的旋转轴线切削。
大多数车床的刀架安装在复式刀座上,刀座上有底座,底座安装在横拖板上,可绕垂直轴和上刀架转动。
上刀架安装在底座上,可用手轮和刻度盘控制一个短丝杆使其前后移动。
溜板箱装在大拖板前面,通过溜板箱内的机械装置可以手动和动力驱动大拖板以及动力驱动横拖板。
通过转动溜板箱前的手轮,可以手动操作拖板沿床身移动。
手轮的另一端与溜板箱背面的小齿轮连接,小齿轮与齿条啮合,齿条倒装在床身前上边缘的下面。
利用光杆可以将动力传递给大拖板和横拖板。
光杆上有一个几乎贯穿于整个光杆的键槽,光杆通过两个转向相反并用键连接的锤齿轮传递动力。
通过溜板箱前的换向手柄可使啮合齿轮与其中的一个锤齿轮啮合,为大拖板提供“向前”或“向后”的动力。
适当的离合器或者与齿条小齿轮连接或者与横拖板的螺杆连接,使拖板纵向移动或使横拖板横向移动。
对于螺纹加工,丝杆提供了第二种纵向移动的方法。
光杆通过摩擦离合器驱动拖板移动,离合器可能会产生打滑现象。
而丝杆产生的运动是通过溜板箱与丝杆之间的直接机械连接来实现的,对开螺母紧紧包合丝杆。
当对开螺母闭合时,可以沿丝杆直接驱动拖板,而不会出现打滑的可能性。
现代车床有一个变速齿轮箱,齿轮箱的输入端由车床主轴通过合适的齿轮传动驱动。
齿轮箱的输出端与光杆和丝杆连接。
主轴就是这样通过齿轮传动链驱动变速齿轮箱,在带动丝杆和光杆,然后带动拖板,刀具就可以按主轴的转数纵向地或横向地精确移动。
一台典型的车床的主轴每转一圈,通过光杆可以获得从0.002到0.118英寸尺寸范围内的48种进给量;而使用丝杆可以车削从1.5到92牙/英寸范围内的48种不同螺纹。
一些老式的或廉价的车床为了能够得到所有的进给量和加工出所有螺纹,必须更换主轴和变速齿轮箱之间的齿轮系中的一个或两个齿轮。
LATHESThe basic machines that are designed primarily to do turning , facing and boring are called lathes . Very little turning is done on order types of machines tool , and none can do it with equal facility .Because lathe can do boring , facing , drilling , and , reaming in addition to turning ,their versatility permits several operations to be performed with a single setup of the work-piece . This accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool .Lathes in various forms have existed for more than two thousand years . Modern lathes date from about 1797 , when Henry Maud-sley developed one with a lead-screw . It provided controlled , mechanical feed of the tool . This ingenious Englishman also developed a change-gear system that could connect the spindle and lead-screw and thus enables thread to be cut .Lathe Construction . The essential components of a lathe are depicted in the block diagram of Fig.15-1. These are the bed , headstock assembly , tailstock assembly , carriage assembly , quick-change gear box , and the lead-screw and feed rod .The bed is the backbone of a lathe .It is usually made of well-normalized or aged gray or nodular cast iron and provides a heavy , rigid frame on which all the other basic components mounted . Two sets of parallel , longitudinal ways , inner and outer , are contained in the bed , usually on the upper side . Some makes use an inverted V-shape for all four ways , whereas others utilize one inverted V and one flat way in one or both sets . Because several other accuracy of alignment . Similarly , proper precaution should be taken in operating a lathe to assure that the ways are not damaged . Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed .The ways on most modern lathes are surface hardened to offer greater resistance to wear and abrasion .The headstock is mounted in a fixed position on the inner ways at one end of lathe bed . It provides a powered means of rotating the work at various speeds . It consists , essentially , of a hollow spindle , mounted in accurate bearings , and a set of transmission gears-similar to a truck transmission-through which the spindle can be rotated at a number ofspeeds . Most lathes provided from eight to eighteen speeds , usually in a geometric ratio , and on modern lathes all the speeds can be obtained merely by moving from two to four levers . An increasing trend is to provided a continuously variable speed range through electrical or mechanical drives .Because the accuracy of a lathe is greatly dependent on the spindle , it is of heavy construction and mounted in heavy bearings , usually preloaded tapered roller or ball types . A longitudinal hole is an important size dimension of a lathe because it determines the maximum size of bar stock that can be machined when the material must be fed through the spindle .The inner end of the spindle protrudes from the gear box and contains a means for mounting various types of chucks , face plate , and dog plate on it . Whereas small lathes often employ a threaded section to which the chucks are screwed , most large lathes utilize either cam-lock or key-drive taper noses . These provide a large-diameter taper that assures the accurate alignment of the chuck , and a mechanism that permits the chuck or face plate to be locked or unlocked in position without the necessity of having to rotate these heavy attachments .Power is supplied to the spindle by means of an electric motor through a V-belt or silent –chain drive . Most modern lathes have motors of from 5 to 15 horsepower to provide adequate power for carbide and ceramic and ceramic tools at their high cutting speeds .The tailstock assembly consists , essentially , of three parts . A lower casting fits on the inner ways of the bed and can slide longitudinally thereon , with a means for clamping the entire assembly in any desired location . An upper casting fit on the lower one and can be moved transversely upon it on some type of keyed ways . This transverse motion permits aligning the tailstock and headstock spindles and provides a method of turning tapes . The third major component of the assembly is the tailstock quil . This is a hollow steed cylinder , usually about 2 to 3 inches in diameter , that can be moved severed inches longitudinally in and out of the upper casting by means of a handwheel and screw . The open end of the quill hole terminates in a Morse taper in which a lathecenter , or various tools such as drills , can be held . A graduated scale , several inches in length , usually is engraved in the outside of the quill to aid in controlling its motion in and out of the upper casting . A locking device permits clamping the quill any desired position .The carriage assembly provides the means for mounting and moving cutting tools . The carriage is a relatively flat H-shaped casting that rest and moves on the outer set of ways on the bed . The transverse bar of the carriage contains ways on which the cross slide is mounted and can be moved by means of a feed screw that is controlled by a small hand-wheel and a graduated dial . Through the cross slide a means is provided for moving the lathe tool in the direction normal to the axis of rotation of the work .On most lathes the tool post actually is mounted on a compound rest . This consists of a base , which is mounted on the cross slide so that it can be pivoted about a vertical axis , and an upper casting . The upper casting is mounted on ways on this base so that it can be moved back and forth and controlled by means of a shout lead screw operated by a hand-wheel and a calibrated dial .Manual and powered motion for the carriage , and powered motion for the cross slide , is provided by mechanisms within the apron , attached to the front of the carriage . Manual movement of the carriage along the bed is effected by turning a hand-wheel on the front of the apron , which is geared to a pinion on the back side . This pinion engages a rack that is attached beneath the upper front edge of the bed in an inverted position .To impart powered movement to the carriage and cross slide , a rotating feed rod is provided . The feed rod , which contains a keyway throughout most of its length , passes through the two reversing bevel pinions and is keyed to them . Either pinion can be brought into mesh with a mating bevel gear by means of the reversing lever on the front of the apron and thus provide “forward” or “reverse” power to the carriage . Suitable clutches connect either the rack pinion or the cross-slide screw to provide longitudinal motion of the carriage or transverse motion of cross slide .For cutting threads , a second means of longitudinal drive isprovided by a lead screw . Whereas motion of the carriage when driven by the feed-rod mechanism takes place through a friction clutch in which slippage is possible , motion through the lead screw is by a direct , mechanical connection between the apron and the lead screw . This is achieved by a split nut . By means of a clamping lever on the front of the apron , the split nut can be closed around the lead screw . With the spit nut closed , the carriage is moved along the lead screw by direct drive without possibility of slippage .Modern lathes have a quick-change gear box . The input end of this gear box is driven from the lathe spindle by means of suitable gearing . The output end of the gear box is connected to the feed rod and lead screw . Thus , through this gear train , leading from the spindle to the quick-charge gear box , thence to the lead screw and feed rod ,and them to the carriage , the cutting tool can be made to move a specific distances , either longitudinally or transversely , for each revolution of the spindle .A typical lathe provides , through the feed rod , forty-eight feeds ranging from 0.0012 inch to 0.118 inch per revolution of the spindle , and , through the lead screw , leads for cutting forty-eight different threads from 1.5 to 92 per inch . On some older and some cheaper lathes , one or two gears in the train between the spindle and the change gear box must be changed in order to obtain a full range of threads and feeds .。