【精品】科技英语4低通滤波器原文和翻译
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科技英语阅读教材ESTreadingunit4原文及译文高教出版Unite4 Electronic Information(robots)Remote-controlled Robot Surrogate Could Attend Your Next Meeting. for You(译文见下端)1It may look like a floor lamp mounted on a vacuum claener , but Anybots Inc.'s new QB is actually the latest in surrogate robotics . QB is designed to serve as your eyes ,ears and voice when you can't be there in person ,Even better , it's mobile , rolls around on two wheels like Rosie and can be navigated remotely via the Web and a Wi-Fi connection .2Telecommuting workers and traveling executives alike could us QB (so named because it is the next in line after the company's prototype QB bot) as a virtual extension of themselves. allowing them to attend meetings , tour facilities or perform walk-throughs of real estate properties , all while controlling the robot from a computer keyboard.3Anybots formally unveiled the remotely controlled robot on Tuesday and plans to start selling QBs by the end of the year .A five-megapixel vedio camera serves as one eye, whlie the other is a laser pointer. A speaker on the crown of QB's head gives it a mouthpiece, a touch-screen monitor on on its forehead enables software maintenance and other input , and a ring of protective rubber around its head makes it look a bit like Olivia Newton-John circa 1981.4Along with the wheels,a self-balancing system and a motor with a top speed of five kilometers per our make the robot mobile . The two-wheel-as opposed to a tricycle or quad-design makes it more maneuverable in tight spaces and helps keep its weight down to about 16 kilograms . The area between the QB'shead and base consists of a length of telescoping plastic that can be adjusted to let the QB stand as tall as 175 centimeters or as short as 81 centimeter.5Although it's unclear if the capacity for remote operation. willUS$15,000 Price tag .Anybots believe its technology will appeal to a new generation of workers who expect to be in contact at all times and in all places .The QB is designed to enable this connectivity without sacrificing “presence”,says Bob Christopher,president and chief operating officer of Anybots ,based in Moutain View,Calif . Bandwidth speed and vedio qu ality continue to improve , but they can’t replace being there , he adds .A test-drive reveals valuable Wi-Fi lesson6 To see how this might work in practice , Scientific American test-drove (from our editorial offices in New York) a QB located at Anybots’s facility in California . Our mossion was to drive across the building’s lobby and ask a second QB (remotely controlled by an Anybots employee) where we could find Erin Rapacki , who does product development for the company , and then proceed to Erin’s l ocation. The session began with logging on to a website set up by Anybots and selecting the IP address of the QB we were to inhabit.7 Once our robot “woke up” and connected to Anybots’s local Wi-Fi network, we used the arrow keys on our keyboard to navigate the QB across the lobby. The controls take some getting used to. Particularly because rugs and other materials on the floor may prevent the Qb from travelling a completely straight line . We easily found the other QB but had difficulty aligning our came ra so that we were staring directly into the other QB’s camera. This wasn’t necessary , because we could hearthe person controlling the other QB loud and clear through the microphone on our robot. Using the arrow keys,we were able to swivel our QB to the left and follow the relatively basic directions we had been given to our destination.8 With a bit more practice, navigation would have been smoother, THE QB features a buit-in lidar(light detection and ranging) system that warns the robot when it is getting too close to an object and slows the robot down to avoid(or at least reduce the impact of) a collision. The QB also has a camera located on the bottom of its “”chin” that points down at its wheels so you can see whether you’re about to drive over a lowe r obstacle(such as someone’s foot).9 The QB’s laser-pointer eye turned out to be useful when greeting people we encountered, including Anybots founder and CEO Trevor Blackwell, who accepted a laser beam in the palm of his hand in lieu of a handshake (a relief ,since the QB has no hands).10 By the time we were ready to leave , we were able to drive our QB back to the Anybots lobby and out the front door. Just past the building’s threshold, we learned a valuable lesson in surrogate navigation: never drive outside the range of your Wi-Fi network. A dropped connection means no cameras and no control over the robot’s navigation, which was especially unfortunate in our case because we were approaching the top ofa ramp down to the parking lot when we lost the signal.11 Danger,Will Robinson.Unit4译文今后远程控制的代理机器人可以为您参加的会议它可能看起来像装在一个真空吸尘器落地灯,但实际上它是Anybots公司最新的代理机器人的QB。
Space explorationRobots will not only help us on this world. But will also help us explore other worlds. In fact, space exploration is one of the most promising usages for robots. Since these machines are not so susceptible to the elements that could hurt or kill people. Robots can withstand radiation, heat, cold and can function without an atmosphere. Also robots have a much longer life span. So voyages to other solar systems as well as other planets would be possible. Robots could communicate with us and if something went wrong and destroyed, the space vehicle and a machine would be lost, not a human being.机器人用于空间探索机器人不仅会在这个星球上帮助我们,而且还将帮助我们探索别的星球。
实际上,空间探索就是机器人最有前途的用途之一,知识因为机器人对于机器人会使人伤亡的自然环境和条件不很敏感。
机器人能经受得住辐射,耐热又耐寒,而且能在没有大气的环境中的工作。
此外,机器人的使用寿命长得多。
因此不但可飞往别的行星,而且可飞往别的星系。
机器人可跟我们进行通信联络,要是有什么东西除了毛病,而损坏了宇宙飞行器的话,失去的是机器人而不是人。
新视野⼤学英语4:Unit4TextA课⽂+译⽂新视野⼤学英语4:Unit4 TextA(课⽂+译⽂) 新视野⼤学英语都讲哪些知识吗?你对新视野⼤学英语了解吗?下⾯是yjbys⼩编为⼤家带来的新视野⼤学英语4:Unit4 TextA(课⽂+译⽂),欢迎阅读。
新视野⼤学英语4:Unit4 TextA(课⽂+译⽂) 1.Environmental sensitivity is now as required an attitude in polite society as is, say, belief in democracy or disapproval of plastic surgery. But now that everyone from Ted Turner to George H. W. Bush has claimed love for Mother Earth, how are we to choose among the dozens of conflicting proposals, regulations and laws advanced by congressmen and constituents alike in the name of the environment? Clearly, not everything with an environmental claim is worth doing. How do we segregate the best options and consolidate our varying interests into a single, sound policy? 1.在上流社会,对环境的敏感就如同信仰民主、反对整容⼀样,是⼀种不可或缺的态度。
然⽽,既然从泰德•特纳到乔治•W.H.布什,每个⼈都声称⾃⼰热爱地球母亲,那么,在由议员、选民之类的⼈以环境名义⽽提出的众多的相互⽭盾的提案、规章和法规中,我们⼜该如何做出选择呢?显⽽易见,并不是每⼀项冠以环境保护名义的事情都值得去做。
使用自动缝合显微镜图像自动拼接斌MAA,* b,蒂莫·齐默尔曼,曼弗雷德·罗德Ç,西门Winkelbachð何锋,沃纳Linden一个Kurt E.J.的一个DITTMAR一个分子生物技术部,德国生物技术研究中心,的Mascheroder Weg1,D-38124,德国不伦瑞克b高级光学显微镜基金,EMBL海德堡,海德堡,德国丙部门微生物Pathogencity,德国生物技术研究中心,德国不伦瑞克,ð机器人研究所和过程控制,布伦瑞克技术大学,德国不伦瑞克。
2006年收到修改稿2006年7月26日;接收2006年7月28日抽象图像拼接多个图像相结合的过程中产生的全景或放大图像。
在许多生物医学研究,包括癌症和感染的,这种方法的使用是非常可取的,以便获得大面积的某些结构或整个部分,而保留微观决议。
在这项研究中,我们描述了应用程序,即自动缝合。
软件的产生通常是用于全景摄影,在显微镜图像的无缝拼接。
首先,我们测试这个软件图像设置手动收购光镜和正常的表现相比,Paint Shop Pro的进行手动拼接方法。
其次,这个软件施加到由自动显微镜获取图像堆栈。
然后拼接结果与产生由selfprogrammed的相比长方形瓦片宏集成在图像J.第三,这个方案被应用在电子图像拼接图像显微镜观察。
因此,这里所描述的自动拼接方案可能会发现应用程序方便的图像拼接和虚拟显微镜生物医学研究。
2006年Elsevier公司保留所有权利。
关键词:自动缝合;图像拼接,自动显微镜图像masaicing;虚拟显微镜1.介绍图像拼接过程的combiningmultiple图像的产生一个全景或放大图像(深Szeliski的,1997年;陈1999年Klette; Zomet等,2006),并发现许多应用程序在收购的高分辨率图像。
例如,对于明场或荧光显微镜,分析全段高几厘米不能被执行的分辨率,即使在低功率的目标而且,即使具有高的分辨率的摄像机被应用。
【关键字】精品The simulation and the realization of the digital filterWith the information age and the advent of the digital world, digital signal processing has become one of today's most important disciplines and door technology. Digital signal processing in communications, voice, images, automatic control, radar, military, aerospace, medical and household appliances, and many other fields widely applied. In the digital signal processing applications, the digital filter is important and has been widely applied.1、figures Unit on :Analog and digital filtersIn signal processing, the function of a filter is to remove unwanted parts of the signal, such as random noise, or to extract useful parts of the signal, such as the components lying within a certain frequency range.The following block diagram illustrates the basic idea.There are two main kinds of filter, analog and digital. They are quite different in their physical makeup and in how they work. An analog filter uses analog electronic circuits made up from components such as resistors, capacitors and op amps to produce the required filtering effect. Such filter circuits are widely used in such applications as noise reduction, video signal enhancement, graphic equalisers in hi-fi systems, and many other areas. There are well-established standard techniques for designing an analog filter circuit for a given requirement. At all stages, the signal being filtered is an electrical voltage or current which is the direct analogue of the physical quantity (e.g. a sound or video signal or transducer output) involved. A digital filter uses a digital processor to perform numerical calculations on sampled values of the signal. The processor may be a general-purpose computer such as a PC, or a specialised DSP (Digital Signal Processor) chip. The analog input signal must first be sampled and digitised using an ADC (analog to digital converter). The resulting binary numbers, representing successive sampled values of the input signal, are transferred to the processor, which carries out numerical calculations on them. These calculations typically involve multiplying the input values by constants and adding the products together. If necessary, the results of these calculations, which now represent sampled values of the filtered signal, are output through a DAC (digital to analog converter) to convert the signal back to analog form.Note that in a digital filter, the signal is represented by a sequence of numbers, rather than a voltage or current.The following diagram shows the basic setup of such a system.Unit refers to the input signals used to filter hardware or software. If the filter input, output signals are separated, they are bound to respond to the impact of the Unit is separated, such as digital filters filter definition. Digital filter function, which was to import sequences X transformation into export operations through a series Y.According to figures filter function 24-hour live response characteristics, digital filters can be divided into two, namely, unlimited long live long live the corresponding IIR filter and the limited response to FIR filters. IIR filters have the advantage of the digital filter design can use simulation results, and simulation filter design of a large number of tables may facilitate simple. It is the shortcomings of the nonlinear phase; Linear phase if required, will use the entire network phase-correction. Image processing and transmission of data collection is required with linear phase filters identity. And FIR linear phase digital filter to achieve, but an arbitrary margin characteristics. Impact from the digital filter response of the units can be divided into two broad categories : the impact of the limited response (FIR) filters, and unlimited number of shocks to (IIR) digital filters.FIR filters can be strictly linear phase, but because the system FIR filter function extremity fixed at the original point, it can only use the higher number of bands to achieve their high selectivity for the same filter design indicators FIR filter called band than a few high-IIR 5-10 times, the cost is higher, Signal delay is also larger. But if the same linear phase, IIR filters must be network-wide calibration phase, the same section also increase the number of filters and network complexity. FIR filters can be used to achieve non-Digui way, not in a limited precision of a shock, and into the homes and quantitative factors of uncertainty arising from the impact of errors than IIR filter small number, and FIR filter can be used FFT algorithms, the computational speed. But unlike IIR filter can filter through the simulation results, there is no ready-made formula FIR filter must use computer-aided design software (such as MATLAB) to calculate. So, a broader application of FIR filters, and IIR filters are not very strict requirementson occasions.Unit from sub-functions can be divided into the following four categories :(1) Low-filter (LPF);(2) high-filter (HPF);(3) belt-filter (BPF);(4) to prevent filter (BSF).The following chart dotted line for the ideals of the filter frequency characteristics :A1(f) A2(f)f(a) (b)A3(f) A4(f)f f(c) (d)(a)LPF (b)HPF (c)BPF (d)BSF2、MATLAB introducedMATLAB is a matrix laboratory (Matrix Laboratory) is intended. In addition to an excellent value calculation capability, it also provides professional symbols terms, word processing, visualization modeling, simulation and real-time control functions. MATLAB as the world's top mathematical software applications, with a strong engineering computing, algorithms research, engineering drawings, applications development, data analysis and dynamic simulation, and other functions, in aerospace, mechanical manufacturing and construction fields playing an increasingly important role. And the C language function rich, the use of flexibility, high-efficiency goals procedures. High language both advantages as well as low level language features. Therefore, C language is the most widely used programming language. Although MATLAB is a complete, fully functional programming environment, but in some cases, data and procedures with the external environment of the world is very necessary and useful. Filter design using Matlab, could be adjusted with the design requirements and filtercharacteristics of the parameters, visual simple, greatly reducing the workload for the filter design optimization.In the electricity system protection and secondary computer control, many signal processing and analysis are based on are certain types Yeroskipou and the second harmonics of the system voltage and current signals (especially at D process), are mixed with a variety of complex components, the filter has been installed power system during the critical components. Current computer protection and the introduction of two digital signal processing software main filter. Digital filter design using traditional cumbersome formula, the need to change the parameters after recalculation, especially in high filters, filter design workload. Uses MATLAB signal processing boxes can achieve rapid and effective digital filter design and simulation.MATLAB is the basic unit of data matrix, with its directives Biaodashi mathematics, engineering, commonly used form is very similar, it is used to solve a problem than in MATLAB C, Fortran and other languages End precision much the same thing. The popular MATLAB 5.3/Simulink3.0 including hundreds of internal function with the main pack and 30 types of tool kits (Toolbox). kits can be divided into functional tool kits and disciplines toolkit. MATLAB tool kit used to expand the functional symbols terms, visualization simulation modelling, word processing and real-time control functions. professional disciplines toolkit is a stronger tool kits, tool kits control, signal processing tool kit, tool kits, etc. belonging to such communicationsMATLAB users to open widely welcomed. In addition to the internal function, all the packages MATLAB tool kits are readable document and the document could be amended, modified or users through Yuanchengxu the construction of new procedures to prepare themselves for kits.3、Digital filter designDigital filter design of the basic requirementsDigital filter design must go through three steps :(1) Identification of indicators : In the design of a filter, there must be some indicators. These indicators should be determined on the basis of the application. In many practical applications, digital filters are often used to achieve the frequency operation. Therefore, indicators in the form of general jurisdiction given frequency range and phase response. Margins key indicators given in two ways. The first is absolute indicators. It provides a function to respond to thedemands of the general application of FIR filter design. The second indicator is the relative indicators. Its value in the form of answers to decibels. In engineering practice, the most popular of such indicators. For phase response indicators forms, usually in the hope that the system with a linear phase frequency bands human. Using linear phase filter design with the following response to the indicators strengths:①it only contains a few algorithms, no plural operations;②there is delay distortion, only a fixed amount of delay; ③the filter length N (number of bands for N-1), the volume calculation for N/2 magnitude.(2) Model approach : Once identified indicators can use a previous study of the basic principles and relationships, a filter model to be closer to the target system.(3) Achieved : the results of the above two filters, usually by differential equations, system function or pulse response to describe. According to this description of hardware or software used to achieve it.4、Introduced FPGAProgrammable logic device is a generic logic can use a variety of chips, which is to achieve ASIC ASIC (Application Specific Integrated Circuit) semi-customized device, Its emergence and development of electronic systems designers use CAD tools to design their own laboratory in the ASIC device. Especially FPGA (Field Programmable Gate Array) generated and development, as a microprocessor, memory, the figures for electronic system design and set a new industry standard (that is based on standard product sales catalogue in the market to buy). Is a digital system for microprocessors, memories, FPGA or three standard building blocks constitute their integration direction.Digital circuit design using FPGA devices, can not only simplify the design process and can reduce the size and cost of the entire system, increasing system reliability. They do not need to spend the traditional sense a lot of time and effort required to create integrated circuits, to avoid the investment risk and become the fastest-growing industries of electronic devices group. Digital circuit design system FPGA devices using the following main advantages(1)Design flexibleUse FPGA devices may not in the standard series device logic functional limitations. And changes in system design and the use of logic in any one stage of the process, and only through the use of re-programming the FPGA device can be completed, the system design provides for great flexibility.(2) Increased functional densityFunctional density in a given space refers to the number of functional integration logic. Programmable logic chip components doors several high, a FPGA can replace several films, film scores or even hundreds of small-scale digital IC chip illustrated in the film. FPGA devices using the chip to use digital systems in small numbers, thus reducing the number of chips used to reduce the number of printed size and printed, and will ultimately lead to a reduction in the overall size of the system.(3) Improve reliabilityPrinting plates and reduce the number of chips, not only can reduce system size, but it greatly enhanced system reliability. A higher degree of integration than systems in many low-standard integration components for the design of the same system, with much higher reliability. FPGA device used to reduce the number of chips required to achieve the system in the number printed on the cord and joints are reduced, the reliability of the system can be improved.(4) Shortening the design cycleAs FPGA devices and the programmable flexibility, use it to design a system for longer than traditional methods greatly shortened. FPGA device master degrees high, use printed circuit layout wiring simple. At the same time, success in the prototype design, the development of advanced tools, a high degree of automation, their logic is very simple changes quickly. Therefore, the use of FPGA devices can significantly shorten the design cycle system, and speed up the pace of product into the market, improving product competitiveness.(5) Work fastFPGA/CPLD devices work fast, generally can reach several original Hertz, far larger than the DSP device. At the same time, the use of FPGA devices, the system needed to achieve circuitclasses and small, and thus the pace of work of the entire system will be improved.(6) Increased system performance confidentialityMany FPGA devices have encryption functions in the system widely used FPGA devices can effectively prevent illegal copying products were others(7) To reduce costsFPGA device used to achieve digital system design, if only device itself into the price,sometimes you would not know it advantages, but there are many factors affecting the cost of the system, taken together, the cost advantages of using FPGA is obvious. First, the use of FPGA devices designed to facilitate change, shorten design cycles, reduce development costs for system development; Secondly, the size and FPGA devices allow automation needs plug-ins, reducing the manufacturing system to lower costs; Again, the use of FPGA devices can enhance system reliability, reduced maintenance workload, thereby lowering the cost of maintenance services for the system. In short, the use of FPGA devices for system design to save costs.FPGA design principles :FPGA design an important guiding principles : the balance and size and speed of exchange, the principles behind the design of the filter expression of a large number of certification.Here, "area" means a design exertion FPGA/CPLD logic resources of the FPGA can be used to the typical consumption (FF) and the search table (IUT) to measure more general measure can be used to design logic equivalence occupied by the door is measured. "pace" means stability operations in the chip design can achieve the highest frequency, the frequency of the time series design situation, and design to meet the clock cycle -- PADto pad, Clock Setup Time, Clock Hold Beijing, Clock-to-Output Delay, and other characteristics of many time series closely related. Area (area) and speed (speed) runs through the two targets FPGA design always is the ultimate design quality evaluation criteria. On the size and speed of the two basic concepts : balance of size and speed and size and speed of swap.One pair of size and speed is the unity of opposites contradictions body. Requirements for the design of a design while the smallest, highest frequency of operation is unrealistic. More scientific goal should be to meet the design requirements of the design time series (includes requirements for the design frequency) premise, the smallest chip area occupied. Or in the specified area, the design time series cushion greater frequency run higher. This fully embodies the goals of both size and speed balanced thinking. On the size and speed requirements should not be simply interpreted as raising the level and design engineers perfect sexual pursuit, and should recognize that they are products and the quality and cost of direct relevance. If time series cushion larger design, running relatively high frequency, that the design Jianzhuangxing stronger, more quality assurance system as a whole; On the other hand, the smaller size of consumption design is meant to achieve in chip unit more functional modules, the chip needs fewer, the entire system has been significantly reduced cost. As a contradiction of the twocomponents, the size and speed is not the same status. In contrast, meet the timetables and work is more important for some frequency when both conflicts, the use of priority guidelines.Area and the exchange rate is an important FPGA design ideas. Theoretically, if a design time series cushion larger, can run much higher than the frequency design requirements, then we can through the use of functional modules to reduce the consumption of the entire chip design area, which is used for space savings advantages of speed; Conversely, if the design of a time series demanding, less than ordinary methods of design frequency then generally flow through the string and data conversion, parallel reproduction of operational module, designed to take on the whole "string and conversion" and operate in the export module to chip in the data "and string conversion" from the macro point of view the whole chip meets the requirements of processing speed, which is equivalent to the area of reproduction - rate increase.For example. Assuming that the digital signal processing system is 350Mb/s input data flow rate, and in FPGA design, data processing modules for maximum processing speed of 150Mb/s, because the data throughput processing module failed to meet requirements, it is impossible to achieve directly in the FPGA. Such circumstances, they should use "area-velocity" thinking, at least three processing modules from the first data sets will be imported and converted, and then use these three modules parallel processing of data distribution, then the results "and string conversion," we have complete data rate requirements. We look at both ends of the processing modules, data rate is 350Mb/s, and in view of the internal FPGA, each sub-module handles the data rate is 150Mb/s, in fact, all the data throughput is dependent on three security modules parallel processing subsidiary completed, that is used by more chip area achieve high-speed processing through "the area of reproduction for processing speed enhancement" and achieved design.FPGA is the English abbreviation Field of Programmable Gate Array for the site programmable gate array, which is in Pal, Gal, Epld, programmable device basis to further develop the product. It is as ASIC (ASIC) in the field of a semi-customized circuit and the emergence of both a customized solution to the shortage circuit, but overcome the original programmable devices doors circuit few limited shortcomings.FPGA logic module array adopted home (Logic Cell Array), a new concept of internal logic modules may include CLB (Configurable Logic Block), export import module IOB (Input Output Block) and internal links (Interconnect) 3. FPGA basic features are :(1) Using FPGA ASIC design ASIC using FPGA circuits, the chip can be used,while users do not need to vote films production.(2) FPGA do other customized or semi-customized ASIC circuits throughout the Chinese specimen films.3) FPGA internal capability and rich I/O Yinjue.4) FPGA is the ASIC design cycle, the shortest circuit, the lowest development costs, risks among the smallest device5) FPGA using high-speed Chmos crafts, low consumption, with CMOS, TTL low-power compatibleIt can be said that the FPGA chip is for small-scale systems to improve system integration, reliability one of the bestCurrently FPGA many varieties, the Revenue software series, TI companies TPC series, the fiex ALTERA company seriesFPGA is stored in films from the internal RAM procedures for the establishment of the state of its work, therefore, need to programmed the internal Ram. Depending on the different configuration, users can use a different programming methodsPlus electricity, FPGA, EPROM chips will be read into the film, programming RAM中data, configuration is completed, FPGA into working order. Diaodian, FPGA resume into white films, the internal logic of relations disappear, FPGA to repeated use. FPGA's programming is dedicated FPGA programming tool, using generic EPROM, prom programming device can. When the need to modify functional FPGA, EPROM can only change is. Thus, with a FPGA, different programming data to produce different circuit functions. Therefore, the use of FPGA very flexible.There are a variety of FPGA model : the main model for a parallel FPGA plus a EPROM manner; From the model can support a number of films FPGA; serial prom programming model could be used serial prom FPGA programming FPGA; The external model can be engineered as microprocessors from its programming microprocessors.Verilog HDL is a hardware description language for the algorithm level, doors at the level of abstract level to switch-level digital system design modelling. Modelling of the target figure by the complexity of the system can be something simple doors and integrity of electronic digital systems. Digital system to the levels described, and in the same manner described inHin-time series modelling.Verilog HDL language with the following description of capacity : design behaviour characteristics, design data flow characteristics, composition and structure designed to control and contain the transmission and waveform design a certification mechanism. All this with the use of a modelling language. In addition, Verilog HDL language programming language interface provided by the interface in simulation, design certification from the external design of the visit, including specific simulation control and operation.Verilog HDL language grammar is not only a definition, but the definition of each grammar structure are clear simulation, simulation exercises. Therefore, the use of such language to use Verilog simulation models prepared by a certification. From the C programming language, the language inherited multiple operating sites and structures. Verilog HDL provides modelling capacity expansion, many of the initial expansion would be difficult to understand. However, the core subsets of Verilog HDL language very easy to learn and use, which is sufficient for most modelling applications. Of course, the integrity of the hardware description language is the most complex chips from the integrity of the electronic systems described.historyVerilog HDL language initially in 1983 by Gateway Design Automation companies for product development simulator hardware modelling language. Then it is only a dedicated language. Since their simulation, simulation devices widely used products, Verilog HDL as a user-friendly and practical language for many designers gradually accepted. In an effort to increase the popularity of the language activities, Verilog HDL language in 1990 was a public area. Open Verilog International (OVI) is to promote the development of Verilog international organizations. 1992, decided to promote OVI OVI standards as IEEE Verilog standards. The effort will ultimately succeed, a IEEE1995 Verilog language standard, known as IEEE Std 1364-1995. Integrity standards in Verilog hardware description language reference manual contains a detailed description.Main capacity:Listed below are the main Verilog hardware description language ability*Basic logic gate, and, for example, or have embedded in the language and nand* Users of the original definition of the term (UDP), the flexibility. Users can be defined in the original language combinations logic original language, the original language of logic couldalso be time series* Switches class infrastructure models, such as the nmos and pmos also be embedded in the language* Hin-language structure designated for the cost of printing the design and trails Shi Shi and design time series checks.* Available three different ways to design or mixed mode modelling. These methods include : acts described ways - use process of structural modelling; Data flow approach - use of a modelling approach Fuzhi expression; Structured way - using examples of words to describe modular doors and modelling.* Verilog HDL has two types of data : data types and sequence data line network types. Line network types that the physical links between components and sequence types that abstract data storage components.* To describe the level design, the structure can be used to describe any level module example * Design size can be arbitrary; Language is design size (size) impose any restrictions* Verilog HDL is no longer the exclusive language of certain companies but IEEE standards.* And the machine can read Verilog language, it may as EDA tools and languages of the world between the designers* Verilog HDL language to describe capacity through the use of programming language interface (PLI) mechanism further expansion. PLI is to allow external functions of the visit Verilog module information, allowing designers and simulator world Licheng assembly* Design to be described at a number of levels, from the switch level, doors level, register transfer level (RTL) to the algorithm level, including the level of process and content* To use embedded switching level of the original language in class switch design integrity modelling* Same language can be used to generate simulated incentive and certification by the designated testing conditions, such as the value of imports of the designated*Verilog HDL simulation to monitor the implementation of certification, the certification process of implementing the simulation can be designed to monitor and demonstrate value. These values can be used to compare with the expectations that are not matched in the case of print news reports.* Acts described in the class, not only in the RTL level Verilog HDL design description, and todescribe their level architecture design algorithm level behavioural description* Examples can use doors and modular structure of language in a class structure described* Verilog HDL mixed mode modelling capabilities in the design of a different design in each module can level modelling* Verilog HDL has built-in logic function, such as*Structure of high-level programming languages, such as conditions of expression, and the cycle of expression language, language can be used* To it and can display regular modelling* Provide a powerful document literacy* Language in the specific circumstances of non-certainty that in the simulator, different models can produce different results; For example, describing events in the standard sequence of events is not defined.5、In troduction of DSPToday, DSP is w idely used in the modern techno logy and it has been the key part of many p roducts and p layed more and mo re impo rtant ro le in our daily life.Recent ly, Northw estern Po lytechnica lUniversity Aviation Microelect ronic Center has comp leted the design of digital signal signal p rocesso r co re NDSP25, w h ich is aim ing at TM S320C25 digital signal p rocesso r of Texas Inst rument TM S320 series. By using top 2dow n design flow , NDSP25 is compat ible w ith inst ruct ion and interface t im ing of TM S320C25.Digital signal processors (DSP) is a fit for real-time digital signal processing for high-speed dedicated processors, the main variety used for real-time digital signal processing to achieve rapid algorithms. In today's digital age background, the DSP has become the communications, computer, and consumer electronics products, and other fields based device.Digital signal processors and digital signal processing is inseparably, we usually say "DSP" can also mean the digital signal processing (Digital Signal Processing), is that in this digital signal processors Lane. Digital signal processing is a cover many disciplines applied to many areas and disciplines, refers to the use of computers or specialized processing equipment, the signals in digital form for the collection, conversion, recovery, valuation, enhancement, compression, identification, processing, the signals are compliant form. Digital signal processors for digital signal processing devices, it is accompanied by a digital signal processing to produce. DSP development process is broadly divided into three phases : the 20th century to。
Unit 3 lesson 1\2\6 Unit 4 lesson 1\2\6 Unit 5 1\4\6这学期课程范围Final TestSection 1 Listening comprehension (20 points)CET-4听力Section 2 Reading comprehension (30 points/3 passages)两篇选自《快速阅读》,一篇选自课文Section 3 Vocabulary, structure and grammar (25 points)考察课文学过的词汇、短语Section 4 Cloze (or matching, 10 points)选自课文Section 5 Composition (15 points)选自口语话题English for Science and EngineeringReview EssentialsUnit 3 Lesson 1Language points (words, expressions and sentence patterns)layout 布局most advantageous 最有利的efficient deployment 高效部署manufacturing facilities 生产设施optimize the use of human resources 优化人力资源的使用personnel (全体)员工running the plant 经营管理工厂placement 安置、部署schedule 排定,安排supervise 监督;管理;指导raw material 原材料component 组成部分food processing plant 食品加工厂health care facilities 卫生机构consulting company 咨询公司efficiency 效率effectiveness 效力productivity 生产力profitability 盈利key points 要点element 要素be concerned with…in the broadest sense of the word…in terms of…a wide variety of…Input (Reading Page 31 Exercise g)Output topic (for speaking and writing):On a variety of engineering fields (or On differences between electrical engineering, electronic engineering and communications)You may be asked in your oral test or in the composition section of your final exam to share your knowledge in a variety of engineering fields (or On differences between electrical engineering, electronic engineering and communications).In your composition test, you will be required to write for no less than 120 words, following the outline as below:1.What is engineering? (Introduction, preferably 2-4 sentences)2.List the three fields in which you are most interested. Provide some respective details. (Main body,preferably 3-5 sentences for each of 3 paragraphs)3.What is the one which you are going to be engaged in? (Conclusion, preferably 2-4 sentences)In your oral test, you are expected to speak for no less than 3 minutes (with timing subject to the teacher). To prepare your oral test, you may work with other partners in a group of no more than 3 people; or you can prepare alone and be joined by no more than 3 people during the test, or you alone may just interact with the teacher, as the case may be .Words for reference: civil engineering, mechanical engineering, electrical engineering, electronic engineering, communications engineering, chemical engineering, software engineering,Unit 3 Lesson 2Language points (words, expressions and sentence patterns)branch 分支diversify 多样化generate 产生invent 发明discipline 分支utilization 利用,使用transmission systems 传输系统transistor 晶体管computer hardware 计算机硬件processing 加工ergonomically 能发挥工作者最大效能地radar 雷达navigation system 导航系统component 组成部件automobile 汽车flatscreen 平板,平面显示器power station 发电站work on…work for…specialize in…Grammatical highlights: simple present vs. present continuous tense (Page 81, page 33 exercise c)Input (Reading Page 32 Exercise a)Language points (words, expressions and sentence patterns)overlap 叠盖discipline 学科aerospace 航空航天nuclear 核的define 解释,下定义device 装置,器件theoretical 理论的conversant 熟识dynamics 动力学statics 静力学solid mechanics 固体力学fluid dynamics 流体动力学thermodynamics 热力学kinematics 运动学mechatronics 机电一体化,机械电子学heat transfer 传热学strength of materials 材料力学steam turbine 汽轮机gas turbine 燃气轮机internal combustion engine 内燃机escalator 扶手电梯robot 机器人to be closely related to…a number of…all sorts of…to be conversant with…to be acquainted with…to be aware of…to be expert in...to be familiar with...to be proficient in...to be well-versed in...to have some knowledge of...to have the know-how...to know backwards...to know your stuff...to master...to know something like the back of your hand...to know the basics…Grammatical highlights: Connecting Phrases (Page 77; Page 6 Exercise b) Input (Listening Page 103 Unit 3, Lesson 6, Exercise A)Language points (words, expressions and sentence patterns) NASA = National Aeronautics and Space Administration 国家航空航天管理局space shuttle 航天飞机winged orbiter 有翼轨道飞行器cargo 货物fuel tank 燃料箱liquid 液体的,液态的hydrogen 氢气oxygen 氧气oxidizer 氧化剂solid-propellant 固体推进剂booster 助推器,多级火箭的第一级private citizen 普通公民launch 发射cylindrical 圆柱体的,圆柱形的by-product 副产品joint 接缝,接头brittle 易碎的,脆的rupture 裂开,断裂prematurely 提前的,过早的O-ring O形密封圈immediate 直接的aftermath 后果;余波investigation 调查involvement 参与deliver 递交、递送Ronald Reagan 罗纳德. 里根Presidential Commission 总统委员会Rogers Commission 罗杰斯委员会Task Force 特别工作组modification 修正、修改assurance 保证procedure 程序fleet 舰队ground 着陆incorporate 吸收be subjected to 使经受stringent 严格的thorough 彻底地、全面的ground-testing (飞弹、火箭等)的地面试验equivalent 相当于…的事情,对等物be certified to 获得认证demonstrate 证明、展示margin 范围、极限authority 权利consist ofa pair ofplay a vital part inhold something in positionburn throughbreak offas a result ofapart fromInput (Reading Page 44 Exercise B)Grammatical highlights: Unreal conditionals in the past (Page 84)Unit 4 Lesson 2Language points (words, expressions and sentence patterns) maintenance engineer 技术维护工程师safeguard 保护hazardous 危险的occupation 职业oversee 监督,监视inspection 检查insurance 保险compensation 补偿,赔偿specialty 专业adopt 接受,采纳initial 最初的principal 主要的,首要的likelihood 可能,可能性conceal 遮住,隐藏eliminate 排除,消除initiate 开始,着手maintain保持,继续,保养, 维护modify 修改,修饰prevent 预防propose 提议,建议reduce 降低seek 寻找in most casesput forwardcut downget rid ofcover upmake surelook forcarry outset upInput (Reading Page 47 Exercise e)Unit 4 Lesson 6Language points (words, expressions and sentence patterns) finished product 成品keep on doing 继续做、坚持做…reliability 可靠性maintainability 可维护性safety 安全性inspections and testsmeasuring equipmentquality inspection/auditionquality inspector/auditorquality requirementscustomer requirementscustomer feedbackproduct specificationscomponents and materialsprocurement departmentmarketing departmentwarehousemanufacturing/production departmentafter-sales servicescustomer servicesmaintenancestatistical quality control 统计质量控制implementation 实施、贯彻specification 规格;详述;说明书sufficiently 充足地take into account 考虑到factor 因素characteristics 特征、特色neglect 疏忽、忽略vacuum cleaner 真空吸尘器outdated 过时的definition 定义up-to-date 最新的conformance 一致性、适应性verify 验证、检验track record 跟踪记录component 部件conform 使一致,使顺从bear in mind 牢记feedback 反馈dimension 维度parameter 变量envisage 想象、展望it is no good doing…rather thanbe equal tobear in mindbe worth doingbe used to doingbe able toconform to/conformance toInput (Reading Page 55 exercise e)Output topic (for speaking and writing):On a “total quality control” approachYou may be asked in your oral test or in the composition section of your final exam to share your view on a “total quality control” approach.In your composition test, you will be required to write for no less than 120 words, following the outline as below:1. What is quality control? What is a “total quality control” approach? (Introduction, preferably 2-4 sentences)2. List the essential factors (and/or procedures) which shall be considered in a “total quality control approach”, and explain respectively. (Main body, preferably 3-5 sentences for each of 3 paragraphs)3. Why is the approach so important to a company? (Conclusion, preferably 2-4 sentences)In your oral test, you are expected to speak for no less than 3 minutes (with timing subject to the teacher). To prepare your oral test, you may work with other partners in a group of no more than 3 people; or you can prepare alone and be joined by no more than 3 people during the test, or you alone may just interact with the teacher, as the case may be .computerization 计算机的使用、计算机化complex 复杂的handle 处理store 存贮generate 生成vast 大量的quantity 数量aided 辅助drawing 图样、制图model 模型prototype 原型、样品time-consuming 耗时间的defect 缺点trend 趋势time-study 工时研究muscle 肌肉human-factor 人为因素ergonomics 人类工程学criteria 标准complex 复杂的panel 面板reactor 反应堆interdisciplinary 交叉学科的specialist 专家legal 法律的behavioral 行为的regarding 有关、关于licensure 从业许可、专业认证approval 认可、同意to play an increasingly important role inin recent yearsor soas well asthe vast quantity ofused to dogrow in importanceto find outhave a big effect onGrammatical highlightsPresent perfect tense (Page 88)Will for predictions (Page 89)Input (Reading Page 105 Unit 5, Lesson 1, Exercise B)Initial 最初的,开头的Fundamentals 基础Acquire 获得; 学到Relevant 有关的,相关的Principles 原理Accredit 承认资格,官方认可Accrediting Board for Engineering and Technology 工程和技术认证委员会(ABET) meet/exceed requirements满足/超过要求Mandatory 强制要求的;必须的continuing education 继续教育normally 通常,一般来说seminar 研究会,讨论会assign 分派/布置(任务)technical specialist 技术专家supervise 监督; 指导; 管理technician 技术人员eventually 最终managerial or sales fields 管理和销售领域as long asbe referred to asunder the supervision ofgo intoInput (Reading Page 64 Exercise b)wastage 消耗;废物layoff 停工,停止活动;临时解雇competitive 竞争的,比赛的insist 坚持outlook 展望, 前景opportunity 机会, 时机occupation 职业in balance with 与……保持平衡available 可用的, 可获得的optimize 使最优化point of view 观点assessment 评估;评价delivery 传送,投递obsolete 废弃的;老式的,已过时的promote 促进,推进pace 步幅,步调vary 变化;不同vulnerable 易受攻击的;易受伤的;potential 潜在的,有可能的reward 报酬;报答hold downbe in balance withdepend onbe vulnerable topass overInput (Reading Page 69 Exercise h)Output topic (for speaking and writing):My career outlook as an engineerYou may be asked in your oral test or in the composition section of your final exam to share your career outlook as an engineer.In your composition test, you will be required to write for no less than 120 words, following the outline as below:1. What engineering specialty are you learning? (Introduction, preferably 2-4 sentences)2. List no less than three jobs you are going to take one after another? (Main body, preferably 3-5 sentences for each of 3 paragraphs)3. Why do you plan your career this way? (Conclusion, preferably 2-4 sentences)In your oral test, you are expected to speak for no less than 3 minutes (with timing subject to the teacher). To prepare your oral test, you may work with other partners in a group of no more than 3 people; or you can prepare alone and be joined by no more than 3 people during the test, or youalone may just interact with the teacher, as the case may be.Words for reference: technician, engineer intern, professional engineer, technical specialist, certified, licensed, engineer supervisor, department manager, senior engineer, technical director, CTO (chief technology officer), start my own business, engineering consultancy firm, construction firm…。
Unit 4 Meeting the MuseUnderstanding ideasWhat inspires you?Every artist’s wish is to create something that expresses an idea. But where do artists get their ideas from? Who or what inspires them? Here we find out more about the influences behind the successes of three very different artists.express v. ____________ n. __________ influence__________inspire v. _____________ n. ___________ find out ___________段落翻译:________________________________________________________________________________ ________________________________________________________________________________ Florentijn Hofman, visual artist①Florentijn Hofman is a Dutch artist, whose large sculptures are on display all over the world. One way for him to find inspiration is turning to his children’s toys. These objects have given him ideas for his animal sculptures, such as the famous Rubber Duck. A more recent work of his is the huge Floating Fish, which was set among the beautiful landscape of Wuzhen West Scenic Zone.②Hofman’s inspiration for Floating Fish came from Chinese folk tales passed down through the generations. He was particularly interested in the old story about a fish jumping through the “Dragon Gate”. This story came to life for Hofman when he visited Wuzhen and saw how people lived there.③“During the walk and my stay here in the town, I saw the fish being fed by people. You see also some fish sculpted on the wall.” These sights set Hofman’s idea for Floating Fish in motion. visual___________ turn to___________on display____________________ inspiration ___________folk tales___________ in motion___________pass…down through generations ____________________ float___________being fed by people 在句子中作___________成分,修饰____________sculpted on the wall在句子中作___________成分,修饰____________________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ _______________________________________________________________________________ Tan Dun, poser④“There is no territory in the world of music.” These are the words of Chinese poser Tan Dun. He is most widely known for posing music for the film Crouching Tiger, Hidden Dragon and the 2008 Beijing Olympics.⑤To listen to Tan’s music is to experience a mix of Chinese musical traditions and Western influences. Since his first opera, Nine Songs, Tan Dun has been using a bination of Chinese music and sounds from all over the world to tell stories. As Tan once said, Chinese music should carry “universal expression” of the human spirit so as to be recognised by the whole world.territory n. __________ poser n. _____________ v. _____________be widely known for ___________________ a mix of _______________a bination of__________________ v. _______________so as to/in order to _________________ 表_______________________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Yang Liping, dancer⑥Yang Liping’s passion is dancing. After winning a national petition in 1986 with her Spirit ofthe Peacock dance, she has been known as the “Peacock Princess”. The inspiration for her famousdances has e from the time she spent in Xishuangbanna, Yunnan Province.⑦“I feel very grateful for the years in Xishuangbanna,” says Yang. “It gave me a chance to godeeper into the lives of various ethnic groups... Our ethnic groups, especially the Dai people, admire the peacock. They think the peacock represents the beauty of nature. I especially like the dance style of the Dai people and it gives me lots of inspiration. My dance es from their traditional belief and aims to bring out the Dai women’s beauty.”passion ____________be known as ___________________ go deeper into ________________ethnic groups _____________________ princess ____________ 王子____________She spent in Xishuangbanna, Yunnan Province 是一个__________从句,引导词_________在从句中作___________,所以省略了be/feel grateful for sth.__________bring out the Dai women’s beauty_____________________________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ ________________________________________________________________________________________________________________________________________________________________________ Developing ideasART & TECHNOLOGY①Think “art”. What es to your mind? Is it Greek or Roman sculptures in the Louvre, or Chinese paintingsin the Palace Museum? Or maybe, just maybe, it’s a dancing pattern of lights?②The artworks by American artist Janet Echelman look like colourful floating clouds when they are lit up at night. Visitors to one of her artworks in Vancouver could not only enjoy looking at it, they could also interact with it—literally. They did this by using their phones to change its colours and patterns. Exhibits such as these are certainly new and exciting, but are they really art?③Whatever your opinion, people have been expressing their thoughts and ideas through art for thousands of years. To do this, they have used a variety of tools and technologies. Yet Michelangelo and others have been labelled as “artists” rather than “technicians”. This means that art and technology have always been seen as two very separate things.e to your mind __________________ dancing pattern of lights_________________light up_________________interact with_________________ literally______________a variety of_________________ rather than_________________ separate______________exhibits ____________ be labelled as_________________ technician_________________________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ _______________________________________________________________________________ ④Today, however, technological advances have led to a bination of art and technology. As a result, the art world is changing greatly. Now art is more accessible to us than ever before. Take for example one of China’s most famous paintings from the Song Dynasty, Along the River During the Qingming Festival. As this artwork is rarely on display, people have sometimes queued up to six hours for a chance to see it. Once in front of the painting, they only have limited time to spend taking in its five metres of scenes along the Bian River in Bianjing. Thanks to technology however, millions more people have been able to experience a digital version of this painting. Threedimensional (3D) animation means that viewers can see the characters move around and interact with their surroundings. They can also watch as the different scenes change from daylight into nighttime.technological advances________________ lead to ________________is more accessible to ________________ surroundings________________queue______________ up to________________ take in____________________ threedimensional ___________________ animation______________________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ _______________________________________________________________________________ ⑤The arttech bination is also changing our concepts of “art” and the “artist”. Not only can we interact with art, but also take part in its creation. With new technological tools at our fingertips, more and more people are exploring their creative sides. The result has been exciting new art forms, such as digital paintings and videos.⑥However, the increase in the amount and variety of art produced has also raised questions over its overall quality. Can a video of someone slicing a tomato played in slow motion really be called “art”?⑦Similarly, such developments are making the line between art and technology less distinct. Can someone unfamiliar with traditional artists’ tools really call themselves an “artist”? And is the artist the creator of the art itself, or the maker of the technology behind it? A recent project used technology and data in the same way that Rembrandt used his paints and brushes. The end result, printed in 3D, was a new “Rembrandt painting” created 347 years after the artist’s death. These advances are perhaps bringing us closer to a time when puters rather than humans create art.⑧Where technology will take art next is anyone’s guess. But one thing is for sure—with so many artists exploring new possibilities, we can definitely expect the unexpected.the arttech bination____________________ concepts ______________at one’s fingertips ______________ raised questions over ______________overall quality______________ slice______________in slow motion ______________ distinct______________that Rembrandt used his paints and brushes 是____________从句,修饰_______________when puters rather than humans create art是____________从句,修饰_______________________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________。
科技英语阅读1—9单元译文:Unit1罗素悖论的提出是基于这样的一个事例:设想有这样一群理发师,他们只给不给自己理发的人理发。
假设其中一个理发师符合上述的条件,不给自己理发;然而按照要求,他必须要给自己理发.但是在这个集合中没有人会给自己理发。
(如果这样的话,这个理发师必定是给别人理发还要给自己理发)1901年,伯特兰·罗素悖论的发现打击了他其中的一个数学家同事。
在19世纪后期,弗雷格尝试发展一个基本原理以便数学上能使用符号逻辑。
他确立了形式表达式(如:x=2)和数学特性(如偶数)之间的联系.按照弗雷格理论的发展,我们能自由的用一个特性去定义更多更深远的特性。
1903年,发表在《数学原理》上的罗素悖论从根本上揭示了弗雷格这种集合系统的局限性。
就现在而言,这种类型的集合系统能很好的用俗称集的结构式来描述.例如,我们可以用x代表整数,通过n来表示并且n大于3小于7,来表示4,5,6这样一个集合。
这种集合的书写形势就是:x={n:n是整数,3〈n<7}。
集合中的对象并不一定是数字。
我们也可让y={x:x是美国的一个男性居民}。
表面上看,似乎任何一个关于x的描述都有一个符合要求的空间。
但是,罗素(和策梅洛一起)发现x={a:a不再a中}导致一个矛盾,就像对一群理发师的描述一样。
x它本身是在x的集合中吗?否定的答案导致了矛盾的出现。
当罗素发现了悖论,弗雷格立即就发现悖论对他的理论有致命的打击。
尽管这样,他还不能解决这个问题,并且上世纪有很多的尝试,去解决这个问题(但没有成功)。
罗素自己对这个悖论的回答促进了类型理论的形成。
他解释说,悖论的问题在于我们混淆了数集和数集的集合。
所以,罗素介绍了对象的分级系统:数、数集、数集的集合等等.这个系统为形式化数学的形成奠定了基础,至今它还应用于哲学研究和计算机科学分支。
策梅洛对于罗素悖论的解决方法用新的公理:对于任意公式A(x)和任意集合b,都会有一个集合满足y={x:x既在b中又满足A(x)}取代了以前的公理:对于任意公式A(x),都会有一个集合满足y={x:x满足A(x)}。
Automation and Controllingsensor 传感器sufficient and necessary condition 充要条件dry friction 静摩擦follower 跟随器,输出放大器,从动轮,跟踪装置integral 积分duty 工作状态FM(frequency modulation ) 调频Geometry 几何(学)autopilot 自动驾驶仪forced response 强迫响应performance index 性能指数performance specification 性能指标polar plot 极坐标图trial and error 试探法Bar Code 条形码Bill of Materials (BOM) 物料清单CAD (Computer Aided Design) 计算机辅助设计CAM (Computer Aided Manufacturing) 计算机辅助制造Computer Integrated Manufacturing (CIM) 计算机集成制造CMOS (Complimentary Metal-Oxide-Semiconductor) n. 互补金属氧化物半导体——一种应用于大规模集成电路芯片制造的原料)是微机主板上的一块可读写的RAM芯片,用来保存当前系统的硬件配置和用户对某些参数的设定。
ControlNet 控制网,一种高速串行通信系统,适用于需要进行实时应用信息交换的设备之间的通讯。
conveyor 传送带DAC (Digital-to-Analog Converter) 数字模拟信号转换器Data Acquisition 数据采集Fiber Optics 光纤Fieldbus 现场总线Ethernet 以太网GUI (Graphical User Interface) 图形用户界面programming language 程序设计语言program debugger 程序调试器direct current dynamo 直流发电机kinetic energy 动能automatization 自动化human-simulating-intelligent control 仿人工智能控制reference frame 参考系servo 伺服机构extrusion 挤压billet 胚料dual 对偶的,二元的,二体的,双的actuator 激励源(如电流源、电压源);致动器AS-I (Actuator-Sensor Interface) 执行器传感器接口Analog Input Module 模拟信号输入模块Analog Output Module 模拟信号输出模块Brushless Servomotor 无电刷伺服电机Crossdocking 直接转运,一项使产品组合顺利进行的作业。
In Namibia, about one-quarter of children have stunted growth related to poor nutrition; about 120,000 children have lost one or both parents, predominantly to HIV/AIDS, and 26% of all women aged 15 to 49 have had at least one child die."Living more sanitarily may have increased asthma, but in terms of scale and impact, that's tiny compared with the benefit of not dying from disease for lack of hygiene," says Michael Bell, an infectious disease specialist and deputy director of Healthcare Quality Promotion at the Centers for Disease Control and Prevention.Some scientists are searching for ways to harness the immune-priming effects of microorganisms without the fatal diseases. Parasitic worms known as helminthes are leading the way.Clinical trials are under way in the U.S. and Europe testing Trichuris Suis Ova (TSO)—-a species of pig whipworm—as a treatment for peanut allergies, ulcerative colitis, Crohn's disease and MS. A study is being designed to test it with asthma. It's also being tested with adults who have autism, which some researchers believe could be related to immunological function.Enlarge ImageCloseChina Photos/Getty ImagesA vendor's baby sits amid the chickens at a market in Wuhan, Hubei Province, China.Preliminary studies seem promising: In one, when 29 patients with Crohn's disease, a disorder of the digestive tract, were given TSO every three weeks for six months, symptoms improved in 21 of them with no adverse side effects.The ova are suspended in a liquid, invisible to the naked eye. "There's no taste, nothing to feel," says Dr. Weinstock, one of the early developers who could share in the proceeds if TSO proves successful. The microscopic eggs hatch into microscopic whipworms in the gastrointestinal tract, which interact with the host's immune system and can dampen an overactive immune response, he explains. To date, there have been few side effects, he says. "As far as we know, this agent doesn't cause diarrhea," he adds. "Nothing crawls out of you."For those who fear the "ick" factor, Dr. Weinstock notes that even under normal conditions, people are teeming with microorganisms, which outnumber human cells by about 10 to 1, many of which are necessary for human health. Many foods—from yogurt to cheese to bread—also contain live bacteria and fungi.Some daily products now widely advertise that they contain probiotics, or good bacteria. But most immunologists say that those in food products have not been sufficiently studied or standardized to draw scientific conclusions about what health benefits they provide.Scientists are still working on ways to separate good germs from bad ones; in the meantime, they have a few insights: Studies have shown that children who grow up with household pets have fewer allergies and less asthma than those who don't.The CDC's Dr. Bell says that people should be vigilant about wound care since bacteria can cause problems if it gets into the blood stream, and he still advocates hand-washing. "If you're not doing it 10 times a day, you're probably not doing it enough," he says. But he and other experts say that regular soap and water are fine in most cases. Sterilizing hands iscritical mainly for health-care workers and in hospitals, where disease-causing germs are prevalent and can easily spread.Many experts advise common sense. "We don't want to say to children, 'OK, play by the dirty river bank and catch whatever you can,' " says Dr. Weinstock. "But we can say there's nothing wrong with kids playing in the dirt. They don't have to live in total sanitation, and they won't die from eating something off the floor. It's probably more healthy than not."All you need is a wormhole, the Large Hadron Collider or a rocket that goes really, really fast1 Hello. My name is Stephen Hawking. Physicist, cosmologist and something of a dreamer. Although I cannot move and I have to speak through a computer, in my mind I am free. Free to explore the universe and ask the big questions, such as: is time travel possible? Can we open a portal to the past or find a shortcut to the future? Can we ultimately use the laws of nature to become masters of time itself?1' Time travel was once considered scientific heresy. I used to avoid talking about it for fear of being labelled a crank. But these days I'm not so cautious. In fact, I'm more like the people who built Stonehenge. I'm obsessed by time. If I had a time machine I'd visit Marilyn Monroe in her prime or drop in on Galileo as he turned his telescope to the heavens. Perhaps I'd even travel to the end of the universe to find out how our whole cosmic story ends.2 To see how this might be possible, we need to look at time as physicists do - at the fourth dimension. It's not as hard as it sounds. Every attentive schoolchild knows that all physical objects, even me in my chair, exist in three dimensions. Everything has a width and a height and a length.3 But there is another kind of length, a length in time. While a human may survive for 80 years, the stones at Stonehenge, for instance, have stood around for thousands of years. And the solar system will last for billions of years. Everything has a length in time as well as space. Travelling in time means travelling through this fourth dimension.4 To see what that means, let's imagine we're doing a bit of normal, everyday car travel. Drive in a straight line and you're travelling in one dimension. Turn right or left and you add the second dimension. Drive up or down a twisty mountain road and that adds height, so that's travelling in all three dimensions. But how on Earth do we travel in time? How do we find a path through the fourth dimension?5 Let's indulge in a little science fiction for a moment. Time travel movies often feature a vast, energy-hungry machine. The machine creates a path through the fourth dimension, a tunnel through time. A time traveller, a brave, perhaps foolhardy individual, prepared for who knows what, steps into the time tunnel and emerges who knows when. The concept may be far-fetched, and the reality may be very different from this, but the idea itself is not so crazy.6 Physicists have been thinking about tunnels in time too, but we come at it from a different angle. We wonder if portals to the past or the future could ever be possible within the laws of nature. As it turns out, we think they are. What's more, we've even given them a name: wormholes. The truth is that wormholes are all around us, only they're too small to see. Wormholes are very tiny. They occur in nooks and crannies in space and time. You might find it a tough concept, but stay with me.6' A wormhole is a theoretical 'tunnel' or shortcut, predicted by Einstein's theory of relativity, that links two places in space-time - visualised above as the contours of a 3-D map, where negative energy pulls space and time into the mouth of a tunnel, emerging in another universe. They remain only hypothetical, as obviously nobody has ever seen one, but have been used infilms as conduits for time travel - in Stargate (1994), for example, involving gated tunnels between universes, and in Time Bandits (1981), where their locations are shown on a celestial map7 Nothing is flat or solid. If you look closely enough at anything you'll find holes and wrinkles in it. It's a basic physical principle, and it even applies to time. Even something as smooth as a pool ball has tiny crevices, wrinkles and voids. Now it's easy to show that this is true in the first three dimensions. But trust me, it's also true of the fourth dimension. There are tiny crevices, wrinkles and voids in time. Down at the smallest of scales, smaller even than molecules, smaller than atoms, we get to a place called the quantum foam. This is where wormholes exist. Tiny tunnels or shortcuts through space and time constantly form, disappear, and reform within this quantum world. And they actually link two separate places and two different times.8 Unfortunately, these real-life time tunnels are just a billion-trillion-trillionths of a centimetre across. Way too small for a human to pass through - but here's where the notion of wormhole time machines is leading. Some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter.9 Given enough power and advanced technology, perhaps a giant wormhole could even be constructed in space. I'm not saying it can be done, but if it could be, it would be a truly remarkable device. One end could be here near Earth, and the other far, far away, near some distant planet.10 Theoretically, a time tunnel or wormhole could do even more than take us to other planets. If both ends were in the same place, and separated by time instead of distance, a ship could fly in and come out still near Earth, but in the distant past. Maybe dinosaurs would witness the ship coming in for a landing.11 The fastest manned vehicle in history was Apollo 10. It reached 25,000mph. But to travel in time we'll have to go more than 2,000 times faster12 Now, I realise that thinking in four dimensions is not easy, and that wormholes are a tricky concept to wrap your head around, but hang in there. I've thought up a simple experiment that could reveal if human time travel through a wormhole is possible now, or even in the future. I like simple experiments, and champagne.12' So I've combined two of my favourite things to see if time travel from the future to the past is possible.Let's imagine I'm throwing a party, a welcome reception for future time travellers. But there's a twist. I'm not letting anyone know about it until after the party has happened. I've drawn up an invitation giving the exact coordinates in time and space. I am hoping copies of it, in one form or another, will be around for many thousands of years. Maybe one day someone living in the future will find the information on the invitation and use a wormhole time machine to come back to my party, proving that time travel will, one day, be possible.In the meantime, my time traveller guests should be arriving any moment now. Five, four, three, two, one. But as I say this, no one has arrived. What a shame. I was hoping at least a future Miss Universe was going to step through the door. So why didn't the experiment work? One of the reasons might be because of a well-known problem with time travel to the past, the problem of what we call paradoxes.Paradoxes are fun to think about. The most famous one is usually called the Grandfather paradox. I have a new, simpler version I call the Mad Scientist paradox.13 I don't like the way scientists in movies are often described as mad, but in this case, it's true. This chap is determined to create a paradox, even if it costs him his life. Imagine, somehow, he's built a wormhole, a time tunnel that stretches just one minute into the past. Hawking in a scene from Star Trek with dinner guests from the past, and future: (from left) Albert Einstein, Data and Isaac Newton14 Through the wormhole, the scientist can see himself as he was one minute ago. But what if our scientist uses the wormhole to shoot his earlier self? He's now dead. So who fired the shot? It's a paradox. It just doesn't make sense. It's the sort of situation that gives cosmologists nightmares.15 This kind of time machine would violate a fundamental rule that governs the entire universe - that causes happen before effects, and never the other way around. I believe things can't make themselves impossible. If they could then there'd be nothing to stop the whole universe from descending into chaos. So I think something will always happen that prevents the paradox. Somehow there must be a reason why our scientist will never find himself in a situation where he could shoot himself. And in this case, I'm sorry to say, the wormhole itself is the problem.16 In the end, I think a wormhole like this one can't exist. And the reason for that is feedback. If you've ever been to a rock gig, you'll probably recognise this screeching noise. It's feedback. What causes it is simple. Sound enters the microphone. It's transmitted along the wires, made louder by the amplifier, and comes out at the speakers. But if too much of the sound from the speakers goes back into the mic it goes around and around in a loop getting louder each time. If no one stops it, feedback can destroy the sound system.17 The same thing will happen with a wormhole, only with radiation instead of sound. As soon as the wormhole expands, natural radiation will enter it, and end up in a loop. The feedback will become so strong it destroys the wormhole. So although tiny wormholes do exist, and it may be possible to inflate one some day, it won't last long enough to be of use asa time machine. That's the real reason no one could come back in time to my party.18 Any kind of time travel to the past through wormholes or any other method is probably impossible, otherwise paradoxes would occur. So sadly, it looks like time travel to the past is never going to happen. A disappointment for dinosaur hunters and a relief for historians.虫洞是根据爱因斯坦相对论预测的连接时空中两个不同地点的假想“隧道”或捷径,上面的三维图轮廓集中呈现了这一点:负能量将时间和空间拖入一条隧道入口,并在另一个宇宙出现。
3.1 名词的译法第1节翻译练习1In an unusual application, this organization uses a fingerprint scanner to monitor the comings and goings of its residents.A capacitor is used to eliminate sparking when a circuit containing inductance is suddenly opened.一个不同寻常的用途是:这个机构使用指纹扫描器监视居住人员的进出。
当含有电感的电路突然断开时,可用电容器消除火花。
第1节翻译练习2The comparison reveals that the error is due to aliasing. The scans confirmed that the subjects’ brains dealt with words in ways that contradict one hoary old idea.The latest research with radioactive isotopes has shown that this assumption is quite wrong.比较结果表明,误差是由于名称不同而造成的。
扫描结果证实,受试者的大脑处理词的方式同一种古老的旧观念不一致。
对放射性同位素的最新研究结果表明,这种设想是完全错误的。
Metals differ in the ease with which they give up electrons and enter into chemical combination.Internal-shoe drum brakes provide better protection from water and dust.People on earth are protected from the dangerous ultraviolet radiation of the sun by a layer or ozone that spans the planet and absorbs the radiation.各种金属放出电子和参与化学反应的难易程度不一。
Words and Expressionsintegrator n. 积分器amplitude n. 幅值slope n 斜率denominator n. 分母impedance n阻抗inductor n. 电感capacitor n电容cascade n. 串联passband n 通带ringing n. 振铃damping n. 阻尼,衰减conjugate adj. 共轭的stage v. 成为low-pass filters 低通滤波器building block 模块linear ramp 线性斜坡log/log coordinates 对数/对数坐标Bode plot 伯德图transfer function 传递函数complex-frequency variable 复变量complex frequency plane 复平面real component 实部frequency response 频率响应complex function 复变函数Laplace transform 拉普拉斯变换real part 实部imaginary part 虚部angular frequency 角频率frequency response 频率响应transient response 瞬态响应decaying-exponential response 衰减指数响应step function input 阶跃(函数)输入time constant 时间常数first-order filters 一阶滤波器second-order low-pass filters 二阶低通滤波器passive circuit 无源电路active circuit 有源电路characteristic frequency 特征频率quality factor n. 品质因子,品质因数circular path 圆弧路径complex conjugate pairs 共轭复数对switched-capacitor 开关电容negative-real half of the complex plane 复平面负半平面Unit 4 Low-pass FiltersFirst-Order FiltersAn integrator (Figure 2. la) is the simplest filter mathematically, and it forms the building block for most modern integrated filters. Consider what we know intuitively about an integrator. If you apply a DC signal at the input (i.e., zero frequency), the output will describe a linear ramp that grows in amplitude until limited by the power supplies. Ignoring that limitation, the response of an integrator at zero frequency is infinite, which means that it has a pole at zero frequency. (A pole exists at any frequency for which the transfer function's value becomes infinite.)(为什么为极点,为什么低通?)R CIN V OUTV +-Figure A simple RC integratorWe also know that the integrator's gain diminishes with increasing frequency and that at high frequencies the output voltage becomes virtually zero. Gain is inversely proportional to frequency, so it has a slope of -1 when plotted on log/log coordinates (i.e., -20dB/decade on a Bode plot , Figure 2. 1b). Log frequency INOUTV V log Slope=20dB/decadeFigure 2.1 b A Bode plot of a simple integratorYou can easily derive the transfer function ass R sC R X V V C IN OUT 0/1ω=== Where s is the complex-frequency variable ωσj + and 0ωis 1/RC. If we think of s as frequency, this formula confirms the intuitive feeling that gain is inversely proportional to frequency.The next most complex filter is the simple low-pass RC type (Figure 2. 2a). Its characteristic (transfer function) is011/1/1ωω+=+=+=s sCR sC R sC V V IN OUT When 0=s , the function reduces to 00ωω, i.e., 1. When s tends to infinity, the function tends to zero, so this is a low-pass filter. When 0ω-=s , the denominator is zero and the function's value is infinite, indicating a pole in the complex frequency plane . The magnitude of the transfer function is plotted against s in Figure 2. 2b, where the real component of s (σ) is toward us and the positive imaginary part (ωj ) is toward the right. The pole at -0ω is evident. Amplitude is shown logarithmically to emphasize the function's form. For both the integrator and the RC low-pass filter, frequency response tends to zero at infinite frequency; that is, there is a zero at ∞=s . This single zero surrounds the complex plane.But how does the complex function in s relate to the circuit's response to actual frequencies? When analyzing the response of a circuit to AC signals, we use the expression L j ωfor impedance of an inductor and C j ω1for that of a capacitor . When analyzing transient response using Laplacetransforms []1, we use sL and 1/sC for the impedance of these elements. The similarity is apparentimmediately. The ωj in AC analysis is in fact the imaginary part of s, which, as mentioned earlier, is composed of a real part σ and an imaginary part ωj .If we replace s by ωj in any equation so far, we have the circuit's response to an angular frequency . In the complex plot in Figure 2.2b, 0=σand hence ωj s = along the positive j axis. Thus, the function's value along this axis is the frequency response of the filter. We have sliced the function along the ωj axis and emphasized the RC low-pass filter's frequency-response curve by adding a heavy line for function values along the positive j axis. The more familiar Bode plot (Figure 2.2c) looks different in form only because the frequency is expressed logarithmically.(根据图翻译这两句话) INV OUTV RCFigure 2.2a A simple RC low-pass filterWhile the complex frequency's imaginary part (ωj ) helps describe a response to AC signals, the real part (σ) helps describe a circuit's transient response . Looking at Figure 2.2b, we can therefore say something about the RC low-pass filter's response as compared to that of the integrator. The low-pass filter's transient response is more stable, because its pole is in the negative-real half of the complex plane .That is, the low-pass filter makes a decaying-exponential response to a step-function input ; the integrator makes an infinite response. For the low-pass filter, pole positions further down the σ- axis mean a higher 0ω, a shorter time constant, and therefore a quicker transient response. Conversely, a pole closer to the j axis causes a longer transient response.So far, we have related the mathematical transfer functions of some simple circuits to their associated poles and zeroes in the complex-frequency plane . From these functions, we have derived the circuit ’s frequency response (and hence its Bode plot) and also its transient response. Because both the integrator and the RC filter have only one s in the denominator of their transfer functions, they each have only one pole. That is, they are first-order filters.Figure 2.2b The complex function of an RC low-pass filter Log frequencyINOUTV V log RC/10=ωFigure 2.2c A Bode plot of a low-pass filterHowever, as we can see from Figure 2.1b, the first-order filter does not provide a very selective frequency response. To tailor a filter more closely to our needs , we must move on to higher orders. From now on, we will describe the transfer function using f(s) rather than the cumbersome IN OUT V V .Second-Order Low-Pass FiltersA second-order filter has 2s in the denominator and two poles in the complex plane. You can obtain such a response by using inductance and capacitance in a passive circuit or by creating an active circuit of resistors, capacitors, and amplifiers. Consider the passive LC filter in Figure 2.3a, for instance. We can show that its transfer function has the form ()11/1/12++=++=++=RCs LCs sC sL R sC X X R X s f C L C and if we define LC /120=ωand R L Q /0ω=,then()200220/ωωω++=Q s s s f where 0ωis the filter's characteristic frequency and Q is the quality factor (lower R means higher Q). IN V OUTV R L CFigure 2.3a An RLC low-pass filterThe poles occur at s values for which the denominator becomes zero; that is,when 0/2002=++ωωQ s s . We can solve this equation by remembering that the roots of02=++c bx ax are given byaac b b x 242-±-= In this case, a = 1, Q b 0ω=, and 20ω=c .The term (ac b 42-) equals ()4/1220-Q ω, so if Q is less than 0.5 then both roots are real and lie on the negative-real axis. The circuit's behavior is much like that of two first order RC filters in cascade . This case isn't very interesting, so we'll consider only the case where Q > 0.5, which means ()ac b 42-is negative and the roots are complex.Figure 2.3b A pole-zero diagram of an RLC low-pass filterThe real part is therefore a b 2/-, which is Q 2/0ω-, and common to both roots. The roots' imaginary parts will be equal and opposite in signs. Calculating the position of the roots in the complex plane, we find that they lie at a distance of0ωfrom the origin, as shown in Figure 2.3b. Varying 0ω, changes the poles' distance from the origin. Decreasing the Q moves the poles toward each other, whereas increasing the Q moves the poles in a semicircle away from each other and toward the ωj axis. When Q = 0.5, the poles meet at 0ω-on the negative-real axis. In this case, the corresponding circuit is equivalent to two cascaded first-order filters.Now let's examine the second-order function's frequency response and see how it varies with Q. As before, Figure 2.4a shows the function as a curved surface, depicted in the three-dimensional space formed by the complex plane and a vertical magnitude vector . Q =0.707, and you can see immediately that the response is a low-pass filter.The effect of increasing the Q is to move the poles in a circular path toward the ωj axis. Figure2.4b shows the case where Q = 2. Because the poles are closer to the ωj axis, they have a greater effect on the frequency response, causing a peak at the high end of the passband .Figure 2.4a The complex function of a second-order low-pass filter (Q = 0.707)Figure 2.4b The complex function of a second-order low-pass filter (Q = 2)There is also an effect on the filter's transient response. Because the poles' negative-real part is smaller, an input step function will cause ringing at the filter output. Lower values of Q result in less ringing, because the damping is greater. On the other hand, if Q becomes infinite, the poles reach the ωj axis, causing an infinite frequency response (instability and continuous oscillation) at 0ωω=. In the LCR circuit in Figure 2.3a, this condition would be impossible unless R=0. For filters that contain amplifiers, however, the condition is possible and must be considered in the design process.A second-order filter provides the variables 0ωand Q, which allow us to place poles wherever we want in the complex plane. These poles must, however, occur as complex conjugate pairs , in which the real parts are equal and the imaginary parts have opposite signs. This flexibility in pole placement is a powerful tool and one that makes the second-order stage a useful component in many switched-capacitor filters. As in the first-order case, the second-order low-pass transfer function tends to zero as frequency tends to infinity. The second-order function decreases twice as fast, however, because of the 2s factor in the denominator. The result is a double zero (零点) at infinity.低通滤波器一阶滤波器从数学公式上讲,积分器(见图2.1a )是最简单的滤波器;它是构成大多数现代滤波器的基本模块。
【关键字】精品Words and Expressionsintegrator n. 积分器amplitude n. 幅值slope n 斜率denominator n. 分母impedance n 阻抗inductor n. 电感capacitor n 电容cascade n. 串联passband n 通带ringing n. 振铃damping n. 阻尼,衰减conjugate adj. 共轭的stage v. 成为low-pass filters 低通滤波器building block 模块linear ramp 线性斜坡log/log coordinates 对数/对数坐标Bode plot 伯德图transfer function 传递函数complex-frequency variable 复变量complex frequency plane 复平面real component 实部frequency response 频率响应complex function 复变函数Laplace transform 拉普拉斯变换real part 实部imaginary part 虚部angular frequency 角频率frequency response 频率响应transient response 瞬态响应decaying-exponential response 衰减指数响应step function input 阶跃(函数)输入time constant 时间常数first-order filters 一阶滤波器second-order low-pass filters 二阶低通滤波器passive circuit 无源电路active circuit 有源电路characteristic frequency 特征频率quality factor n. 品质因子,品质因数circular path 圆弧路径complex conjugate pairs 共轭复数对switched-capacitor 开关电容negative-real half of the complex plane 复平面负半平面Unit 4 Low-pass FiltersFirst-Order FiltersAn integrator (Figure 2. la) is the simplest filter mathematically, and it forms the building block for most modern integrated filters. Consider what we know intuitively about an integrator. If you apply a DC signal at the input (i.e., zero frequency), the output will describe a linear ramp that grows in amplitude until limited by the power supplies. Ignoring that limitation, the response of an integrator at zero frequency is infinite, which means that it has a pole at zero frequency. (A pole exists at any frequency for which the transfer function's value becomes infinite.)(为什么为极点,为什么低通?)Figure A simple RC integratorWe also know that the integrator's gain diminishes with increasing frequency and that at high frequencies the output voltage becomes virtually zero. Gain is inversely proportional to frequency, so it has a slope of -1 when plotted on log/log coordinates (i.e., -20dB/decade on a Bode plot, Figure 2. 1b).Figure 2.1 b A Bode plot of a simple integratorYou can easily derive the transfer function asWhere s is the complex-frequency variable and is 1/RC. If we think of s as frequency, this formula confirms the intuitive feeling that gain is inversely proportional to frequency.The next most complex filter is the simple low-pass RC type (Figure 2. 2a). Its characteristic (transfer function) isWhen, the function reduces to , i.e., 1. When s tends to infinity, the function tends to zero, so this is a low-pass filter. When, the denominator is zero and the function's value is infinite, indicating a pole in the complex frequency plane. The magnitude of the transfer function is plotted against s in Figure 2. 2b, where the real component of s () is toward us and the positive imaginary part () is toward the right. The pole at - is evident. Amplitude is shown logarithmically to emphasize the function's form. For both the integrator and the RC low-pass filter, frequency response tends to zero at infinite frequency; that is, there is a zero at. This single zero surrounds the complex plane.But how does the complex function in s relate to the circuit's response to actual frequencies? When analyzing the response of a circuit to AC signals, we use the expression for impedance of an inductor and for that of a capacitor. When analyzing transient response using Laplace transforms, we use sL and 1/sC for the impedance of these elements. The similarity is apparent immediately. The in AC analysis is in fact the imaginary part of s, which, as mentioned earlier, is composed of a real part and an imaginary part.If we replace s by in any equation so far, we have the circuit's response to an angular frequency. In the complex plot in Figure 2.2b, and hence along the positive j axis. Thus, the function's value along this axis is the frequency response of the filter. We have sliced the function along the axis and emphasized the RC low-pass filter's frequency-response curve by adding a heavy line for function values along the positive j axis. The more familiar Bode plot (Figure 2.2c) looks different in form only because the frequency isexpressed logarithmically.(根据图翻译这两句话)Figure 2.2a A simple RC low-pass filterWhile the complex frequency's imaginary part () helps describe a response to AC signals, the real part() helps describe a circuit's transient response. Looking at Figure 2.2b, we can therefore say something about the RC low-pass filter's response as compared to that of the integrator. The low-pass filter's transient response is more stable, because its pole is in the negative-real half of the complex plane. That is, the low-pass filter makes a decaying-exponential response to a step-function input; the integrator makes an infinite response. For the low-pass filter, pole positions further down the axis mean a higher, a shorter time constant, and therefore a quicker transient response. Conversely, a pole closer to the j axis causes a longer transient response.So far, we have related the mathematical transfer functions of some simple circuits to their associated poles and zeroes in the complex-frequency plane . From these functions, we have derived the circuit ’s frequency response (and hence its Bode plot) and also its transient response. Because both the integrator and the RC filter have only one s in the denominator of their transfer functions, they each have only one pole. That is, they are first-order filters .Figure 2.2b The complex function of an RC low-pass filterFigure 2.2c A Bode plot of a low-pass filterHowever, as we can see from Figure 2.1b, the first-order filter does not provide a very selective frequency response. To tailor a filter more closely to our needs , we must move on to higher orders. From now on, we will describe the transfer function using f(s) rather than the cumbersome IN OUT V V . Second-Order Low-Pass FiltersA second-order filter has 2s in the denominator and two poles in the complex plane. You can obtain such a response by using inductance and capacitance in a passive circuit or by creating an active circuit of resistors, capacitors, and amplifiers. Consider the passive LC filter in Figure 2.3a, for instance. We can show that its transfer function has the formand if we defineLC /120=ωand R L Q /0ω=,then where 0ωis the filter's characteristic frequency and Q is the quality factor (lower R means higher Q).Figure 2.3a An RLC low-pass filterThe poles occur at s values for which the denominator becomes zero; that is,when 0/2002=++ωωQ s s . We can solve this equation by remembering that the roots of 02=++c bx ax are given byIn this case, a = 1, b 0ω=, and 20ω=c .The term (ac b 42-) equals ()4/1220-Q ω, so if Q isless than 0.5 then both roots are real and lie on the negative-real axis. The circuit's behavior is much like that of two first order RC filters in cascade . This case isn't very interesting, so we'll consider only the case where Q > 0.5, which means ()ac b 42-is negative and the roots are complex.Figure 2.3b A pole-zero diagram of an RLC low-pass filterThe real part is therefore a b 2/-, which is Q 2/0ω-, and common to both roots. The roots' imaginary parts will be equal and opposite in signs. Calculating the position of the roots in the complex plane, we find that they lie at a distance of0ωfrom the origin, as shown in Figure 2.3b. Varying 0ω, changes the poles' distance from the origin. Decreasing the Q moves the poles toward each other, whereas increasing the Q moves the poles in a semicircle away from each other and toward the ωj axis. When Q = 0.5, the poles meet at 0ω-on the negative-real axis. In this case, the corresponding circuit is equivalent to two cascaded first-order filters.Now let's examine the second-order function's frequency response and see how it varies with Q. As before, Figure 2.4a shows the function as a curved surface, depicted in the three-dimensional space formed by the complex plane and a vertical magnitude vector . Q =0.707, and you can see immediately that the response is a low-pass filter.The effect of increasing the Q is to move the poles in a circular path toward the ωj axis. Figure2.4b shows the case where Q = 2. Because the poles are closer to the ωj axis, they have a greater effect on the frequency response, causing a peak at the high end of the passband .Figure 2.4a The complex function of a second-order low-pass filter (Q = 0.707)Figure 2.4b The complex function of a second-order low-pass filter (Q = 2)There is also an effect on the filter's transient response. Because the poles' negative-real part is smaller, an input step function will cause ringing at the filter output. Lower values of Q result in less ringing, because the damping is greater. On the other hand, if Q becomes infinite, the poles reach the ωj axis, causing an infinite frequency response (instability and continuous oscillation) at 0ωω=. In the LCR circuit in Figure 2.3a, this condition would be impossible unless R=0. For filters that contain amplifiers, however, the condition is possible and must be considered in the design process.A second-order filter provides the variables 0ωand Q, which allow us to place poles wherever we want in the complex plane. These poles must, however, occur as complex conjugate pairs , in which the real parts are equal and the imaginary parts have opposite signs. This flexibility in pole placement is a powerful tool and one that makes the second-order stage a useful component in many switched-capacitor filters. As in the first-order case, the second-order low-pass transfer function tends to zero as frequency tends to infinity. The second-order function decreases twice as fast, however, because of the 2s factor in the denominator. The result is a double zero (零点) at infinity. 低通滤波器一阶滤波器从数学公式上讲,积分器(见图2.1a )是最简单的滤波器;它是构成大多数现代滤波器的基本模块。