Programmable logic controller
A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.
1.History
The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed.
Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay.
In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner. One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84
moniker at the end of its product range until the 984 made its appearance.
The automotive industry is still one of the largest users of PLCs.
2.Development
Early PLCs were designed to replace relay logic systems. These PLCs were programmed in "ladder logic", which strongly resembles a schematic diagram of relay logic. This program notation was chosen to reduce training demands for the existing technicians. Other early PLCs used a form of instruction list programming, based on a stack-based logic solver.
Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and C. Another method is State Logic, a very high-level programming language designed to program PLCs based on state transition diagrams.
Many early PLCs did not have accompanying programming terminals that were capable of graphical representation of the logic, and so the logic was instead represented as a series of logic expressions in some version of Boolean format, similar to Boolean algebra. As programming terminals evolved, it became more common for ladder logic to be used, for the aforementioned reasons. Newer formats such as State Logic and Function Block (which is similar to the way logic is depicted when using digital integrated logic circuits) exist, but they are still not as popular as ladder logic.
A primary reason for this is that PLCs solve the logic in a predictable and repeating sequence, and ladder logic allows the programmer (the person writing the logic) to see any issues with the timing of the logic sequence more easily than would be possible in other formats.
2.1Programming
Early PLCs, up to the mid-1980s, were programmed using proprietary programming panels or special-purpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were very minimal due to lack of memory capacity. The very oldest PLCs used non-volatile magnetic core memory.
More recently, PLCs are programmed using application software on personal computers. The computer is connected to the PLC through Ethernet, RS-232, RS-485 or RS-422 cabling. The programming software allows entry and editing of the ladder-style logic. Generally the software provides functions for debugging and
troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC though a programming board which writes the program into a removable chip such as an EEPROM or EPROM.
3.Functionality
The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems and networking. The data handling, storage, processing power and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combined with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications. Regarding the practicality of these desktop computer based logic controllers, it is important to note that they have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. In addition to the hardware limitations of desktop based logic, operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the logic may not always respond to changes in logic state or input status with the extreme consistency in timing as is expected from PLCs. Still, such desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs.
In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have become more common and accepted. These are very much like PLCs, and are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are involved, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have between 8 and 12 digital inputs, 4 and 8 digital outputs, and up to 2 analog inputs. Size is usually
about 4" wide, 3" high, and 3" deep. Most such devices include a tiny postage stamp sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic.
4.PLC Topics
4.1.Features
The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.
4.2System scale
A small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O.
Modular PLCs have a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O modules is customised for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special high speed serial I/O link is used so that racks can be distributed away from the processor, reducing the wiring costs for large plants.
4.3User interface
PLCs may need to interact with people for the purpose of configuration, alarm
reporting or everyday control.
A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use a programming and monitoring software installed on a computer, with the PLC connected via a communication interface.
4.4Communications
PLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or Ethernet. Modbus, BACnet or DF1 is usually included as one of the communications protocols. Other options include various fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protocols.
Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser.
PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations.
4.5Programming
PLC programs are typically written in a special application on a personal computer, then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or some other non-volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays.
Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. Initially most PLCs utilized Ladder Logic Diagram Programming, a model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today.
IEC 61131-3 currently defines five programming languages for programmable control systems: FBD (Function block diagram), LD (Ladder diagram), ST (Structured text, similar to the Pascal programming language), IL (Instruction list,
similar to assembly language) and SFC (Sequential function chart). These techniques emphasize logical organization of operations.
While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addressing, memory organization and instruction sets mean that PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly compatible.
5.PLC compared with other control systems
PLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a "generic" solution, and where the non-recurring engineering charges are spread over thousands or millions of units.
For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.
A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit busses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomic.
Very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customized solutions; for
example, aircraft flight controls.
Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements.
PLCs may include logic for single-variable feedback analog control loop, a "proportional, integral, derivative" or "PID controller". A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has become less distinct.
PLCs have similar functionality as Remote Terminal Units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs and DCSs are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments.
6.Digital and analog signals
Digital or discrete signals behave as binary switches, yielding simply an On or Off signal (1 or 0, True or False, respectively). Push buttons, limit switches, and photoelectric sensors are examples of devices providing a discrete signal. Discrete signals are sent using either voltage or current, where a specific range is designated as On and another as Off. For example, a PLC might use 24 V DC I/O, with values above 22 VDC representing On, values below 2VDC representing Off, and intermediate values undefined. Initially, PLCs had only discrete I/O.
Analog signals are like volume controls, with a range of values between zero and full-scale. These are typically interpreted as integer values (counts) by the PLC, with various ranges of accuracy depending on the device and the number of bits available to store the data. As PLCs typically use 16-bit signed binary processors, the integer values are limited between -32,768 and +32,767. Pressure, temperature, flow, and weight are often represented by analog signals. Analog signals can use voltage or
current with a magnitude proportional to the value of the process signal. For example, an analog 0 - 10 V input or 4-20 mA would be converted into an integer value of 0 - 32767.
快速外文文献翻译 在科研过程中阅读翻译外文文献是一个非常重要的环节，许多领域高水平的文献都是外文文献，借鉴一些外文文献翻译的经验是非常必要的。由于特殊原因我翻译外文文献的机会比较多，慢慢地就发现了外文文献翻译过程中的三大利器：Google“翻译”频道、金山词霸（完整版本）和CNKI“翻译助手"。 具体操作过程如下： 1.先打开金山词霸自动取词功能，然后阅读文献； 2.遇到无法理解的长句时，可以交给Google处理，处理后的结果猛一看，不堪入目，可是经过大脑的再处理后句子的意思基本就明了了； 3.如果通过Google仍然无法理解，感觉就是不同，那肯定是对其中某个“常用单词”理解有误，因为某些单词看似很简单，但是在文献中有特殊的意思，这时就可以通过CNKI的“翻译助手”来查询相关单词的意思，由于CNKI的单词意思都是来源与大量的文献，所以它的吻合率很高。 另外，在翻译过程中最好以“段落”或者“长句”作为翻译的基本单位，这样才不会造成“只见树木，不见森林”的误导。 注： 1、Google翻译：https://www.doczj.com/doc/3a16308433.html,/language_tools google，众所周知，谷歌里面的英文文献和资料还算是比较详实的。我利用它是这样的。一方面可以用它查询英文论文，当然这方面的帖子很多，大家可以搜索，在此不赘述。回到我自己说的翻译上来。下面给大家举个例子来说明如何用吧比如说“电磁感应透明效应”这个词汇你不知道他怎么翻译， 首先你可以在CNKI里查中文的，根据它们的关键词中英文对照来做，一般比较准确。 在此主要是说在google里怎么知道这个翻译意思。大家应该都有词典吧，按中国人的办法，把一个一个词分着查出来，敲到google里，你的这种翻译一般不太准，当然你需要验证是否准确了，这下看着吧，把你的那支离破碎的翻译在google里搜索，你能看到许多相关的文献或资料，大家都不是笨蛋，看看，也就能找到最精确的翻译了，纯西式的！我就是这么用的。 2、CNKI翻译：https://www.doczj.com/doc/3a16308433.html, CNKI翻译助手，这个网站不需要介绍太多，可能有些人也知道的。主要说说它的有点，你进去看看就能发现：搜索的肯定是专业词汇，而且它翻译结果下面有文章与之对应（因为它是CNKI检索提供的，它的翻译是从文献里抽出来的），很实用的一个网站。估计别的写文章的人不是傻子吧，它们的东西我们可以直接拿来用，当然省事了。网址告诉大家，有兴趣的进去看看，你们就会发现其乐无穷！还是很值得用的。https://www.doczj.com/doc/3a16308433.html, 3、网路版金山词霸（不到1M）：https://www.doczj.com/doc/3a16308433.html,/6946901637944806 翻译时的速度： 这里我谈的是电子版和打印版的翻译速度，按个人翻译速度看，打印版的快些，因为看电子版本一是费眼睛，二是如果我们用电脑，可能还经常时不时玩点游戏，或者整点别的，导致最终SPPEED变慢，再之电脑上一些词典（金山词霸等）在专业翻译方面也不是特别好，所以翻译效果不佳。在此本人建议大家购买清华大
Programmable logic controller A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result. 1.History The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay. In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner. One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84
中等分辨率制备分离的 快速色谱技术 W. Clark Still,* Michael K a h n , and Abhijit Mitra Departm(7nt o/ Chemistry, Columbia Uniuersity,1Veu York, Neu; York 10027 ReceiLied January 26, 1978 我们希望找到一种简单的吸附色谱技术用于有机化合物的常规净化。这种技术是适于传统的有机物大规模制备分离，该技术需使用长柱色谱法。尽管这种技术得到的效果非常好，但是其需要消耗大量的时间，并且由于频带拖尾经常出现低复原率。当分离的样本剂量大于1或者2g时，这些问题显得更加突出。近年来，几种制备系统已经进行了改进，能将分离时间减少到1-3h，并允许各成分的分辨率ΔR f≥（使用薄层色谱分析进行分析）。在这些方法中，在我们的实验室中，媒介压力色谱法1和短柱色谱法2是最成功的。最近，我们发现一种可以将分离速度大幅度提升的技术，可用于反应产物的常规提纯，我们将这种技术称为急骤色谱法。虽然这种技术的分辨率只是中等（ΔR f≥），而且构建这个系统花费非常低，并且能在10-15min内分离重量在的样本。4 急骤色谱法是以空气压力驱动的混合介质压力以及短柱色谱法为基础，专门针对快速分离，介质压力以及短柱色谱已经进行了优化。优化实验是在一组标准条件5下进行的，优化实验使用苯甲醇作为样本，放在一个20mm*5in.的硅胶柱60内，使用Tracor 970紫外检测器监测圆柱的输出。分辨率通过持续时间（r）和峰宽（w,w/2）的比率进行测定的（Figure 1），结果如图2-4所示，图2-4分别放映分辨率随着硅胶颗粒大小、洗脱液流速和样本大小的变化。
五分钟搞定5000字－外文文献翻译 在科研过程中阅读翻译外文文献是一个非常重要的环节，许多领域高水平的文献都是外文文献，借鉴一些外文文献翻译的经验是非常必要的。由于特殊原因我翻译外文文献的机会比较多，慢慢地就发现了外文文献翻译过程中的三大利器：Google“翻译”频道、金山词霸（完整版本）和CNKI“翻译助手"。 具体操作过程如下： 1.先打开金山词霸自动取词功能，然后阅读文献； 2.遇到无法理解的长句时，可以交给Google处理，处理后的结果猛一看，不堪入目，可是经过大脑的再处理后句子的意思基本就明了了； 3.如果通过Google仍然无法理解，感觉就是不同，那肯定是对其中某个“常用单词”理解有误，因为某些单词看似很简单，但是在文献中有特殊的意思，这时就可以通过CNKI的“翻译助手”来查询相关单词的意思，由于CNKI的单词意思都是来源与大量的文献，所以它的吻合率很高。 另外，在翻译过程中最好以“段落”或者“长句”作为翻译的基本单位，这样才不会造成“只见树木，不见森林”的误导。 注： 1、Google翻译：https://www.doczj.com/doc/3a16308433.html,/language_tools google，众所周知，谷歌里面的英文文献和资料还算是比较详实的。我利用它是这样的。一方面可以用它查询英文论文，当然这方面的帖子很多，大家可以搜索，在此不赘述。回到我自己说的翻译上来。下面给大家举个例子来说明如何用吧 比如说“电磁感应透明效应”这个词汇你不知道他怎么翻译， 首先你可以在CNKI里查中文的，根据它们的关键词中英文对照来做，一般比较准确。
在此主要是说在google里怎么知道这个翻译意思。大家应该都有词典吧，按中国人的办法，把一个一个词分着查出来，敲到google里，你的这种翻译一般不太准，当然你需要验证是否准确了，这下看着吧，把你的那支离破碎的翻译在google里搜索，你能看到许多相关的文献或资料，大家都不是笨蛋，看看，也就能找到最精确的翻译了，纯西式的！我就是这么用的。 2、CNKI翻译：https://www.doczj.com/doc/3a16308433.html, CNKI翻译助手，这个网站不需要介绍太多，可能有些人也知道的。主要说说它的有点，你进去看看就能发现：搜索的肯定是专业词汇，而且它翻译结果下面有文章与之对应（因为它是CNKI检索提供的，它的翻译是从文献里抽出来的），很实用的一个网站。估计别的写文章的人不是傻子吧，它们的东西我们可以直接拿来用，当然省事了。网址告诉大家，有兴趣的进去看看，你们就会发现其乐无穷！还是很值得用的。https://www.doczj.com/doc/3a16308433.html, 3、网路版金山词霸（不到1M）：https://www.doczj.com/doc/3a16308433.html,/6946901637944806 翻译时的速度： 这里我谈的是电子版和打印版的翻译速度，按个人翻译速度看，打印版的快些，因为看电子版本一是费眼睛，二是如果我们用电脑，可能还经常时不时玩点游戏，或者整点别的，导致最终SPPEED变慢，再之电脑上一些词典（金山词霸等）在专业翻译方面也不是特别好，所以翻译效果不佳。在此本人建议大家购买清华大学编写的好像是国防工业出版社的那本《英汉科学技术词典》，基本上挺好用。再加上网站如：google CNKI翻译助手，这样我们的翻译速度会提高不少。 具体翻译时的一些技巧（主要是写论文和看论文方面） 大家大概都应预先清楚明白自己专业方向的国内牛人，在这里我强烈建议大家仔
Application of PLC PLC is one kind specially for the digital operation operation electronic installation which applies under the industry environment designs. It uses may the coding memory, uses for in its internal memory operation and so on actuating logic operation, sequence operation, time, counting and arithmetic operation instructions, and can through digital or the simulation-like input and the output, controls each type the machinery or the production process. PLC and the related auxiliary equipment should according to form a whole easy with the industrial control system, easy to expand its function the principle to design.” In the 1970s the last stage, the programmable controller entered the practical application development phase, the computer technology has introduced in comprehensively the programmable controller, causes its function to have the leap. The higher operating speed, the subminiature volume, the more reliable industry antijamming design, the simulation quantity operation, the PID function and the extremely high performance-to-price ratio has established it in the modern industry status. In the early-1980s, the programmable controller has obtained the widespread application in the advanced industrial nation. This time programmable controller develops the characteristic is large-scale, the high velocity, the high performance, the product seriation. This stage's another characteristic is in the world produces the programmable controller's country to increase day by day, the output rises day by day. This symbolizes that the programmable controller marched into the mature stage. The 20th century last stage, the programmable controller's development characteristic was even more adapts in the modern industry need. From the control scale, this time has developed the large-scale machinery and subminiature machine; From the control, was born various special function unit, used in the pressure, the temperature, the rotational speed, the displacement and so on all kinds of control situation; From product necessary ability, has produced each kind of man-machine contact surface unit, the correspondence unit, caused to apply the programmable controller's industrial control equipment necessary to be easier. At present, the programmable controller in domain and so on machine manufacture, petroleum chemical industry, metallurgy steel and iron, automobile, light industry applications obtained the considerable development.
1 Bit Logic Instructions 1.1 Overview of Bit Logic Instructions 1.1.1 Description Bit logic instructions work with two digits, 1 and 0. These two digits form the base of a number system called the binary system. The two digits 1 and 0 are called binary digits or bits. In the world of contacts and coils, a 1 indicates activated or energized, and a 0 indicates not activated or not energized. The bit logic instructions interpret signal states of 1 and 0 and combine them according to Boolean logic. These combinations produce a result of 1 or 0 that is called the “result of logic operation” (RLO). The logic operations that are triggered by the bit logic instructions perform a variety of functions. There are bit logic instructions to perform the following functions: ---| |--- Normally Open Contact (Address) ---| / |--- Normally Closed Contact (Address) ---(SAVE) Save RLO into BR Memory XOR Bit Exclusive OR ---( ) Output Coil ---( # )--- Midline Output ---|NOT|--- Invert Power Flow The following instructions react to an RLO of 1: ---( S ) Set Coil ---( R ) Reset Coil SR Set-Reset Flip Flop RS Reset-Set Flip Flop Other instructions react to a positive or negative edge transition to perform the following functions: ---(N)--- Negative RLO Edge Detection ---(P)--- Positive RLO Edge Detection NEG Address Negative Edge Detection POS Address Positive Edge Detection
Analysis on the Chinese Enterprise Financing Abstract:The main sources of financing for small and medium sized enterprises (SMEs) are equity, trade credit paid on time, long and short term bank credits, delayed payment on trade credit a nd other debt. The marginal costs of each financing instrument are driven by asymmetric informatio n and transactions costs associated with nonpayment. According to the Pecking Order Theory, firms will choose the cheapest source in terms of cost. In the case of the static trade-off theory, firms cho ose finance so that the marginal costs across financing sources are all equal, thus an additional Euro of financing is obtained from all the sources whereas under the Pecking Order Theory the source is determined by how far down the Pecking Order the firm is presently located. In this paper, we argue that both of these theories miss the point that the marginal costs are dependent of the use of the fun ds, and the asset side of the balance sheet primarily determines the financing source for an additiona l Euro. An empirical analysis on a unique dataset of Portuguese SMEs confirms that the compositio n of the asset side of the balance sheet has an impact of the type of financing used and the Pecking Order Theory and the traditional Static Trade-off theory are rejected. For SME the main sources of financing are equity (internally generated cash), trade credit, ban k credit and other debt. The choice of financing is driven by the costs of the sources which is primar ily determined by costs of solving the asymmetric information problem and the expected costs assoc iated with non-payment of debt. Asymmetric information costs arise from collecting and analysing i nformation to support the decision of extending credit, and the non-payment costs are from collectin g the collateral and selling it to recover the debt. Since SMEs’ management and shareholders are oft en the same person, equity and internally generated funds have no asymmetric information costs an d equity is therefor e the cheapest source. 1 Asset side theory of SME financing In the previous section we have suggested that SME’s in Portugal are financed using internal g enerated cash, cheap trade credits, long and short-term bank loans and expensive trade credits and o ther loans. In this section the motives behind the different types of financing are discussed. 1.1 Cheap Trade credits The first external financing source we will discuss is trade-credits. Trade credits are interesting
中南大学CentralSouthUniversity 本科毕业设计英文文献翻译 题目 学生姓名 学号 指导教师 学院 专业班级 二○一六年一月八日
Spring 的 web MVC 构架模式 Juergen Hoeller 1、介绍： Spring 的应用构架 当你第一次看到并接触Spring框架的时候，你一定会在心里想到；“哦哦，不不，这又是另一种Web构架”。这篇文章将会指出Spring框架不是什么特殊的web框架，而是一个通用的轻量级的应用程序框架，在专用网络支持下的应用程序框架。并且它会告诉你Spring框架明显区别于其他轻量级application framework，它将专注于web的支持，与struts和webwork有着明显的区别。 在和struts和webwork的对比上之中，Spring框架是一个服务于所有层面上的application framework：提供了bean的配置基础，AOP的支持，JDBC的提取框架，抽象事务支持，等等诸如此类。它有一个非常显著的特点：在某个层面上如果你不需要Spring的支持，它有一个非常显著的特点：在某个层面上如果你不需要Spring 的支持，你就可以不使用Spring框架的class（类），只使用它的某一部分的功能。从它的设计理念，你可以看到Spring框架帮助你实现了真正的逻辑层和web 层的成功分离：例如：一个校验应用将不用依靠controllers，就可以实现。这样的目标是更好的重用和易测：过分依靠不必要的容器和框架将不能实现这一点。 当然，Spring的自己本身的web支持和通常框架模式的细致完整。然而，Spring替换struts，webwork或者其他的web方案非常的容易。这个对于Spring 的web支持或者不同的地方，Spring允许你在web容器里面建立一个中间层，在测试环境或者标准独立的应用里面来设置重用你的商务逻辑。 还有就是在J2EE环境里面，可以让你你的商务逻辑不必依靠容器提供的服务，就比如像JTA，EJB的支持。良好的框架的一个web应用是可以运行在任何容器上，就比如，Tomcat或者Resin这些容器。值得注意的事，Spring不是和已经存在的解决方案进行竞争的关系。我们鼓励结合标准的技术，如Servlet，JSP，JTA，JNDI，JDBC和JDO，和其他非常匹配的工具，比方如Hibernate，Velocity,Log4J,和Caucho’s Hessian/Burlap这类工具。这个框架的设计思想是你的应用处在需要改良的时候，你将可以对其做一些技术的选择：例如，如果你需要分布式事务处理，你可能需要用Spring框架的JTA Transaction Manager 来实现JTA服务。或者，用DataSourceTranscactionM anager 或者HibernateTransction Manager 来实现美妙完美的单个数据库交换。 2、 Web MVC：Spring web框架的设计思想 Spring网络框架通过配置操作mappings可配置的处理程序，展示resolution，本地化和模板集成围绕着分派请求操作的servlet -DispatcherServlet分派请求处理程序，可配置的处理程序映射，决议，决议和语言环境和主题设计的。缺省的操作是一个非常简单的控制器接口，他只是提供了一个“ModelAndView handleRequest（request请求，response响应）”的方法。这已经可以将它应用于一个应用的程序控制器，但是，如果你想包含多个层次的控制，Abstract Controlerr，AbstractCommand Controllers，
I. Simakovaa, A. Koskina, I. Deliya, A. Simakovb aBoreskov Institute of Catalysis, Siberian Branch of Academy of Sciences, pr. Ak. Lavrentieva, 5, 630090, Novosibirsk, Russia, simakova@catalysis.ru, bCentro de Ciencias de la MateriaCondensada, Universidad NacionalAutónoma de México, Apdo. Postal 2681, Ensenada, B.C., México, andrey@ccmc.unam.mx 摘要 纳米钯催化剂的应用已获得超过过去几年中日益增长的重要性。精细有机合成钯基催化方法允许更换传统的多步有机合成技术的劳动消耗，并从成本和环境影响的角度来看提供改善。已培育的高比表面积活性炭的“Sibunit”的基板作为催化剂的基材使用，无论是在酸性或是碱性介质，同时在其表面超强酸性中心可以促进催化运行过程中产生不良反应情况下的化学惰性。一种转换α-蒎烯商业的生物活性化合物衍生品和香水，以及与太阳紫外线过滤属性屏幕，作为一个重要的中间步骤，涉及催化加氢。目前的工作目的是所要澄清的因素，有利于碳金属Pd的分散。碳还原温度和预处理影响金属的大小在关于“Sibunit”选择性verbenol转换催化剂制备钯表面研究。用电子显微镜法（TEM）来显示钯碳表面影响双氧水，硝酸氧化的金属分散度，硝酸。在Pd / C催化剂样品verbenol加氢反应的催化活性是确定的。最活跃的催化剂样品动力学特性在verbenol加氢反应获得。 关键词：TEM，钯，活性炭，萜类，香料，精细化学品 1．引言 超过钯金属催化剂的选择性加氢是用来生产有机化工原料最令人鼓舞的方式，包括染料等东西，药品，香料，维生素和有价值的商业中间体[1]。因此，给一个成功的工业过程设计以及催化剂的Pd / C氢化植物油的食物中的脂肪含低量的反式异构体，没有致癌的镍[2]。 烷基取代aminomethylpyrrolidine化合物，是合成pyrrolidylquinolines的semiproducts的关键，pyrrolidylquinazolines和苯甲酰胺，是高效的精神药品（“Sulpirid”，“Eglonyl”，“Levoride”，“Betamak”）的基础。学习选择性=饱和的C-债券在N-vinylpyrrolidinone-2与Pd/ C和选择性加氢>=1 - 乙基 -2-nitromethylenepyrrolidine的C-NO2的片段> CH - CH-NH2的碎片1 - 乙基-2 - aminomethylpyrrolidine以上的Pd / C导致了合成高纯度的发展1 - 乙基-2- aminomethylpyrrolidine（高有效的药物“Sulpyrid”的关键产品）[3-6]。 萜烯含氧衍生物- verbenol，verbanol，柠檬醛和isopiperitenol是合成香料 的宝贵的中间产品，化妆品基地，药品和维生素。从α-蒎烯的合成，包括芳樟
1.宗旨：简单.实用.快速 在科研过程中阅读翻译外文文献是一个非常重要的环节，许多领域高水平的文献都是外文文献，借鉴一些外文文献翻译的经验是非常必要的。由于特殊原因我翻译外文文献的机会比较多，慢慢地就发现了外文文献翻译过程中的三大利器：Google“翻译”频道、金山词霸（完整版本）和CNKI“翻译助手"。 具体操作过程如下： 1.先打开金山词霸自动取词功能，然后阅读文献； 2.遇到无法理解的长句时，可以交给Google处理，处理后的结果猛一看， 不堪入目，可是经过大脑的再处理后句子的意思基本就明了了； 3.如果通过Google仍然无法理解，感觉就是不同，那肯定是对其中某个“常 用单词”理解有误，因为某些单词看似很简单，但是在文献中有特殊的意思，这时就可以通过CNKI的“翻译助手”来查询相关单词的意思，由于CNKI的单词意思都是来源与大量的文献，所以它的吻合率很高。 另外，在翻译过程中最好以“段落”或者“长句”作为翻译的基本单位，这样才不会造成“只见树木，不见森林”的误导。 在科研过程中阅读翻译外文文献是一个非常重要的环节，许多领域高水平的文献都是外文文献，借鉴一些外文文献翻译的经验是非常必要的。由于特殊原因我翻译外文文献的机会比较多，慢慢地就发现了外文文献翻译过程中的三大利器：Google“翻译”频道、金山词霸（完整版本）和CNKI“翻译助手"。 具体操作过程如下： 1.先打开金山词霸自动取词功能，然后阅读文献； 2.遇到无法理解的长句时，可以交给Google处理，处理后的结果猛一看，不堪入目，可是经过大脑的再处理后句子的意思基本就明了了； 3. 如果通过Google仍然无法理解，感觉就是不同，那肯定是对其中某个“常用单词”理解有误，因为某些单词看似很简单，但是在文献中有特殊的意思，这时就可以通过CNKI的“翻译助手”来查询相关单词的意思，由于CNKI的单词意思都是来源与大量的文献，所以它的吻合率很高。 另外，在翻译过程中最好以“段落”或者“长句”作为翻译的基本单位，这样才不会造成“只见树木，不见森林”的误导。 注： 1、Google翻译： google，众所周知，谷歌里面的英文文献和资料还算是比较详实的。我利用它是这样的。一方面可以用它查询英文论文，当然这方面的帖子很多，大家可以搜索，在此不赘述。回到我自己说的翻译上来。下面给大家举个例子来说明如何用吧 比如说“电磁感应透明效应”这个词汇你不知道他怎么翻译， 首先你可以在CNKI里查中文的，根据它们的关键词中英文对照来做，一般比较准确。
英文文献翻译 题目：赣州市池江中学学生亚健康心理现状的调查研究 学院：体育学院 专业名称：体育教育 班级学号：11102124 学生姓名：谢宝飞 指导教师：张文仙
国外亚健康状态的研究进展 20世纪80年代中期，前苏联学者N。布赫曼（Berkman）提出在健康与疾病之间存在着一种中间状态。20世纪90年代中期，我国学者王育学和孙涛首次提出"亚健康"的概念，定义为：介于健康和疾病的中间状态，在医疗机构县级以上中心医院）经系统检查和单项检查，未发现有疾病，而患者向己确实感觉到了躯体和心理上的种种不适。 1996年，在首届"亚健康学术研讨会"上，亚健康状态的名称和广义概念被正式确定。自"亚健康状态"的概念提出后，许多学者从不同的研究角度对业健康状态做出了定义。 董玉整认为，个体的亚健康状态表现为身心情感方面处于健康与疾病之间的健康低质量状态及体验。刘保延等提出亚健康状态指持续3个月以上出现的不适状态或适应能力显著减退而无明确疾病诊断，或有明确诊断但所患疾病与目前不适状态没有直接因果关系。 Wamg和Yan在国际上提出亚健康状态的英文名称为"Suboptimal health status"（SHS），并将其定义为：以持续3个月以上的感觉不适、虚弱、低体力等为特征的，一种可逆的无病理诊断的介于健康与疾病的中间状态。其理论基础是处于亚健康状态时，所出现的持续不适、虚弱和能力减退等症状足由环境及心理等方面的刺激使机体长期发牛应濑反应所引起。 亚健康状态与中医学治未病的思想相结合且我国亚健康状态的研究主要集中在中医领域，目前较为公认《亚健康中医临床指南》中定义为：一定时间内活力降低、功能和适应能力减退，但不符合现代医学有关疾病的临床或业临床诊断标准的处于健康和疾病之问的一种状念，具体包括躯体、心理和社会交往方丽的症状。 虽然国外没有对亚健康状态的定义，但对一些医学无法解释的症状有研究，将其描述为人体出现的缺乏病理改变的躯体化综合征，以疼痛和躯体功能障碍为常见表现，并常伴随沮丧和焦虑等精神障碍。根据出现的医学无法解释的症状可以具体分为许多综合征：慢性疲劳综合征，肠道易激综合征，肌纤维痛，非心源性胸痛，海湾战争综合征，躯体形式障碍等。虽然涵盖了这一些状态的特征下，但由于并没有揭示出现该症状的原因，目前此定义仍在争议中。 因疲劳是亚健康状态的常见表现之一，有人将亚健康状态与医学无法解释的症状之一的慢性疲劳综合征划等号，也曾有学者将慢性疲劳综合征作为亚健康的诊断标准。但美国疾病控制中心1988年3月将慢性疲劳综合征正式确定为一种以慢性疲劳为主要特征的疾病并制定了诊断标准，其慢性疲劳症状持续时间为6个月以上，且该病的症状群除疲劳表现外，还包括睡眠紊乱、异常情绪表现等。 亚健康状态虽多表现为慢性疲劳，但并不特指符合特殊标准的慢性疲劳综合征，所以两者应有各自不同的诊断标准。 我国学者提出的亚健康状态比国外的"医学无法解释的症状"范围广泛，包括躯体、心理和社
学校代码：11517 学号：201050712108 HENAN INSTITUTE OF ENGINEERING 文献翻译 题目基于P LC的自动售货机控制 系统设计 学生姓名 专业班级电气工程及其自动化0921班 学号 20095071 系（部）电气信息工程系 指导教师(职称) 完成时间 2011年 3 月 2日
摘自《可编程控制器在过程自动化中的应用》 Ahti Mikkor,Lembit Roosimolder Department of Product Development,Institute of Machinery, Tallinn technical University,Ehitajate tee 5,19086Tallinn. 摘要：目前，控制问题解决了各种各样的技术操作部分：电子，液压，气动和机械。函数- nality，可靠性和控制系统的价格是阻止开发的理由。本文集中于可编程逻辑控制器（PLC），以五年在这方面的发展经验为基础。成功的解决方案是问题重点。具体的硬件，控制器编程的问题、数据/信号的交换和人机界面进行审议。实际的建议，需要根据具体的方法来开发可编程控制器。对于可能出现的错误和警告，提出可以帮助避免方法。 关键词：可编程控制器、自动化、自动化系统、过程自动化 1引言 现代的机器包括电子和机械两部分。平衡两方面因素，初步规划和方案选择对最终结果起着至关重要的作用。 在控制方法的选择，继电器，专用设备，可编程逻辑控制器（PLC）和电子制造技术的发展。这篇文章是基于PLC集中- S的经验，拥有超过5年的PLC - S 的实际工作经验中收集的。双方强弱，积极和消极的做法进行了讨论。建议使用可编程控制器帮助解决。 在规划基于PLC系统中最重要的决定是选择处理器类型。误区是意味着修改额外费用或扩展完全新设备的需要。最常见的错误是高估小型处理器编程的可能性。有选择PLC的几种方法。不幸的是，他们大多集中在电气方面的PLC - S 和允许的最大计数信号。他们不涉及分析，以确定用户程序或通信可能的特殊需要。 基于几个现有的方法，实践经验和未来趋势的选择为开PLC的开发提供新的方法。阿赫蒂瓦尔Mikkor已获得通过采取在超过15个大范围的自动化项目的一部分，以他的经验，这些项目包括电力消耗在AS昆达北欧水泥工厂监控系统的开发，更新测试流量计钻机，建设城镇Rakvere和普亚，污水处理厂在城里Jogeva 和发展动力涡轮安全系统，污水处理厂在塔尔图监测网络系统的集中供热。 2可编程控制器在投票站的使用