最新PLC中英文资料外文翻译 (1)资料
可编程控制器技术讨论与未来发展
摘自《可编程控制器技术讨论与未来发展》
数字媒体系 08165110 多衡随着时代的发展,当今的技术也日趋完善、竞争愈演愈烈;单靠人工的操作已不能满足于目前的制造业前景,也无法保证更高质量的要求和高新技术企业的形象.
人们在生产实践中看到,自动化给人们带来了极大的便利和产品质量上的保证,同时也减轻了人员的劳动强度,减少了人员上的编制.在许多复杂的生产过程中难以实现的目标控制、整体优化、最佳决策等,熟练的操作工、技术人员或专家、管理者却能够容易判断和操作,可以获得满意的效果.人工智能的研究目标正是利用计算机来实现、模拟这些智能行为,通过人脑与计算机协调工作,以人机结合的模式,为解决十分复杂的问题寻找最佳的途径我们在各种场合看到了继电器连接的控制，那已经是时代的过去，如今的继电器只能作为低端的基层控制模块或者简单的设备中使用到；而PLC的出现也成为了划时代的主题，通过极其稳定的硬件穿插灵活的软件控制，使得自动化走向了新的高潮。
PLC的最大特点在于：电气工程师已不再电气的硬件上花费太多的心计，只要将按钮开关或感应器的输入点连接到PLC的输入点上就能解决问题，通过输出点连接接触器或继电器来控制大功率的启动设备，而小功率的输出设备直接连接就可以。
PLC的内部包含了具有中央处理器的CPU，并带有外部I/O口扩展的I/O接口地址和存储器三大块组成，CPU的核心是由一个或者多个累加器组成，它们具有逻辑的数学运算能力，并能读取程序存储器的内容通过计算后去驱动相应的存储器和I/O接口；I/O口将内部累加器和外部的输入和输出系统连接起来，并将相关的数据存入程序存储器或者数据存储器中；存储器可以将I/O口输入的数据存入存储器中，并在工作时调转到累加器和I/O接口上，存储器分程序存储器ROM和数据存储器RAM,ROM可以将数据永久的存入存储器中，而RAM只能作为CPU计算时临时计算使用的缓冲空间。
PLC的抗干扰是极其优秀的，我们根本不用去关心它的使用寿命和工作场合的恶劣，这些所有的问题已不再成为我们失败的主题，而留给我们的是关心如何来利用PLC的内部资源为我们加强设备的控制能力，使我们的设备更加的柔性。
PLC的语言并不是我们所想象的汇编语言或C语言来进行编程，而是采用原有的继电器控制的梯形图，使得电气工程师在编写程序时很容易就理解了PLC的语言，而且很多的非电气专业人士也对PLC很快认识并深入。
以上仅仅是PLC的优点之一，这也是人们比较容易理解的一部分，在很多的设备中，人们已不再希望看到太多的控制按钮，它们不但容易损坏而且极易产生人为的失误，小的并不是主要的失误也许你还能够接受；但过大的甚至是致命的失误是我们无法容忍的。新的技术总是为了给我们带来更安全和便捷的操作，使得我们面临的一大堆问题一扫而光，你有了解过HMI吗？这里说HMI你根本不清楚它是什么，也没有兴趣了解，换一个中文把它说明为触摸屏或者人机界面你就知道了，它和PLC的结合给了我们更大的空间。
HMI控制不仅仅是减少了控制按钮，增加控制的灵活性，更主要的它是可顺序性的，而且在能够改变数据输入和数据输出反馈，在温度控制曲线的模拟也能直观的显示出来。并且能够通过编写功能帮助程序来提供各种力所能及的帮助，使得操作者减少不必要的失误。HMI 的厂商目前也越来越多，功能也越来越强，价格也越来越低，使用的面越来越广。HMI的前景可以说十分的看好。
在很多场合，单靠单机的控制是无法保证设备的顺畅运行，而通过设备与设备的信息交流达到我们想要的效果。比如在前包装和后工序的检测，我们就要将包装的信息反馈到检测处，而检测处的信息也要反馈到包装来。这样通过信息共享来使得两者之间链接起来，形成一个共体，从而使的两者间的配合更加的紧密，在彼此间达到映影相挥的效果。
PLC的通信已经愈来愈体现它的价值，在PLC与PLC之间的通信，能够通过信息的沟通和数据的共享来保证设备之间的相互协调，已达到互补的效果。PLC之间的数据转换采用RS232接口来传送数据，而RS232接口只能保证10米的传输距离，如果在1000米的距离内我们可以通过RS485来进行通信，更长的距离只能通过MODEL来进行传输。
PLC的数据传送只是将内部的数据传送到对方的一块连续的地址中，我们把它称为一个表，对方的PLC通过读取表中的数据来进行操作。如果表中的数据是一个一般设置的数据的话，那只是一般的数据传送，比如今天的油价上升了，我要把油价的价格传送到所有的输油机上，那就是数据的共享；而当表中的数据是一段控制PLC的指令程序，那就很有难度了，比如你要控制一台机器人来按你想象的动作工作，你会给它编制一段程序并以数据的形式发送过去。
信息输送的形式有单工位、半双工位和全双工位的分别。单工位的意义也就是说两者之间，一个只能发送，而一个只能接收，比如一个特务他只能接收上司的指示，而无法给上司回复；半双工位也就是两个能都能发送和接受数据，但不能同时发送和接受，比如你打电话时是不能接电话,对方也一样；而全双工位是两者之间都能发送和接受数据，并可同时发送和接受。像互联网就是典型的例子。
信息输送的过程也有同步和异步之分：同步的意义在于发送数据时数据线和时钟线是同步的，也就是数据信号和时钟信号同时由CPU进行发送，这需要彼此都要专门的时钟信号来进行传送和接送，并且是强制性的，这种方法的特点在于它的速度极快、但相应占用CPU 的工作时间也相对的要长、同时技术难度也非常的大。它的要求在于在一帧的数据传送中不能有一位的误差，不然的话整个数据将发生错误，这在硬件上是一个比较大的难度。在一些专用的设备中应用的越来越广泛，像专用的医疗设备、数字信号设备等，在比较单一数据的传输中，它的效果非常的好。
而异步是应用范围最广泛的，这得益于它的技术难度相对要小、同时不需要配制专门的时钟信号、它的特点在于，它的数据是间隔性的，离散性的发送和接受，当CPU太忙的时候可以停顿性去工作，在硬件上也减少了难度，同时数据的丢失相对要少，我们可以通过数据的检测来观察我们发送的数据是否有错误，像奇偶法、累加法和八位效验法等，都可以用来帮助我们检测发送的数据是否有错误发生，通过反馈来进行辨别。
信息的传送口线有串口和并口之分：通常的PLC是8位机，当然也有16位机。我们在发送数据的时候可以是一位一位的发送给对方，也可以8位8位的将数据发送到对方，一位和8位区别也就是我们所说的串口发送数据和并口发送数据。串口速度比较慢，但只要两条或者三条口线就能解决问题，并能借用电话线来进行远程控制。而并口的传送速度是极快的，它是串口的256倍，在短距离占有优势，由于是TTL电平，一般限于1米的范围，它并不适用于长距离的数据传送，这样成本太昂贵了。
很多的情况下我们总喜欢采用串并转换芯片来进行传输，这种情况下不需要我们进行过于复杂的寄存器设置了，而直接通过数据传送指令进行数据交流，但在通信中并不是一个十分可行的办法，因为在发送数据的时候对方的PLC必须一直等待你的数据输出，它不能去做其他的工作。
当你在看书的时候，你听到有人敲门、你停下手上的事情、去打开门、并同敲门者对话、这个时候电话响了、你示意接个电话、在接完电话后、回过头来同敲门者继续对话、对话完毕后、你再继续看你的书，这种情况我们把它称为中断，它具有权威性，也具有优先性，PLC 具备了这样的功能。它的特点在于我们在设备的操作过程中可能会遇到紧急的突发事件，我们要立刻的停下手上的工作，去处理更重要的事情，这种情况是我们经常所遇到的，PLC在去执行紧急的任务时，总会先保存目前的状态，比如程序的地址，CPU的累加器数据等，就像我们去开门时要记下我们看的书在第几页了或者干脆作个记号，因为我们待会还要继续接着看后面的书。CPU总是按照我们的意愿去做应该做的事情，但你错误的给它一件事情，它
也会同样的去做，这一点我们必须注意。
中断并不是只有一个，有时会同时存在几个中断，中断具有优先的级别，他们会根据人的要求去执行更高级别的中断。这种中断中的中断也就形成了中断嵌套。当然中断的级别根据各种PLC内部CPU的资源有关，同时也跟堆栈的容量大小也有关系。
中断的内容有很多种，比如外部中断、通信中的发送和接受中断、定时和计数的时钟中断、还有WDT复位中断等，它们丰富了CPU在处理各种事务时响应种类。这样讲也许你并不能完全理解中断的内部结构和操作顺序，我们做一个小小的例子来说明.
每一个设备总是不会忘记有一个按钮，它也是在我们遇到紧急情况时使用的，那就是急停按钮。当我们遇到人身事故和意外情况时我们只要按下它，机器立即停止所有的操作，并等待处理完意外后再恢复操作。急停按钮连接PLC内部CPU的内部I/O接口上，当按钮给CPU一个外部触发信号时，CPU对I/O进行再次检测，当确认有外部触发信号时，CPU保护现场并将程序计数器自动转到相应的外部I/O中断程序中去，当外部中断程序处理完毕，程序计数器返回到主程序继续工作。有一点可以说明的是我们一般会把急停按钮的外部中断升至最高级别，从而保证安全。
当我们在工作完一个工件时，给PLC一个信号，将PLC的内部计数器加1来计算我们一天的工作量时，一个简单的计数器能解决问题，当然它们也能够在掉电的情况下保持数据，促使数据不丢失，这也是我们所渴望的。
PLC还具有高级计数器的功能，当我们在接受一些高速的数据时，这里所说的高速是在在微秒级的数据，比如条码扫描机在不断的扫描数据，数据处理器DSP计算的高速信号等，我们就要采用到高级计数器来帮助我们进行计数。它在PLC执行程序时一旦发现高级计数器对应的中断，就会立即放下手上的工作。经过再次编程的梯形图程序说明我们在执行程序时高级计数器会自动的执行对应的工作，从而将高级计数器的级别升至高一级别。
你也许听过太多的这个词:“死机”，大致的意思是CPU工作量过大，内部资源不足等情况造成程序无法运行。PLC也有类似的情况，在PLC内部有一个看门狗WDT，我们可以设置WDT一个程序运行的时间，当程序运行过程中出现程序跳转错误时或者程序繁忙时，程序的运行时间超过WDT的设置时间，CPU转而WDT复位状态。程序重新开始运行，但对中断不会进行破坏。
PLC的发展已经从单一的模式进入了通信的网络时代，并同其它的工控网板和I/O卡板轻易的进行共享。组态软件可以将所有的这些硬件连接起来，通过更直观的动画图片来进行控制，并可以通过互联网在异地进行控制，像神舟五号的发射就是采用这种办法来使飞船升
空。
更高层次的发展需要我们不断的努力来取得。PLC的出现已经足足影响了几代人，我们也从上一辈的经验中获取了更多的知识和教训，来不断的发展PLC技术，将它推向更高浪潮。
英文原稿
PLC technique discussion and future development
Along with the development of the ages, the technique that is nowadays is also gradually perfect, the competition plays more more strong; the operation that list depends the artificial has already can't satisfied with the current manufacturing industry foreground, also can't guarantee the request of the higher quantity and high new the image of the technique business enterprise.
The people see in produce practice, automate brought the tremendous convenience and the product quantities for people up of assurance, also eased the personnel's labor strength, reduce the establishment on the personnel. The target control of the hard realization in many complicated production lines, whole and excellent turn, the best decision etc., well-trained operation work, technical personnel or expert, governor but can judge and operate easily, can acquire the satisfied result. The research target of the artificial intelligence makes use of the calculator exactly to carry out, imitate these intelligences behavior, moderating the work through person's brain and calculators, with the mode that person's machine combine, for resolve the very complicated problem to look for the best path
We come in sight of the control that links after the electric appliances in various situation, that is already the that time generation past, now of after use in the mold a perhaps simple equipments of grass-roots control that the electric appliances can do for the low level only;And the PLC emergence also became the epoch-making topic, adding the vivid software control through a very and stable hardware, making the automation head for the new high tide.
The PLC biggest characteristics lie in: The electrical engineering teacher already no longer electric hardware up too many calculationses of cost, as long as order the importation that the button switch or the importation of the sensors order to link the PLC up can solve problem, pass to output to order the conjunction contact machine or control the start equipments of the big power after the electric appliances, but the exportation equipments direct conjunction of the small power can.
PLC internal containment have the CPU of the CPU, and take to have an I/ O for expand of exterior to connect a people's address and saving machine three big pieces to constitute, CPU core is from an or many is tired to add the machine to constitute, mathematics that they have the logic operation ability, and can read the procedure save the contents of the machine to drive the homologous saving machine and I/ Os to connect after pass the calculation; The I/ O add inner part is tired the input and output system of the machine and exterior link, and deposit the related data into the procedure saving machine or data saving machine; The saving machine can deposit the data that the I/ O input in the saving machine, and in work adjusting to become tired to add the machine and I/ Os to connect, saving machine separately saving machine RAM of the procedure saving machine ROM and datas, the ROM can can do deposit of the data permanence in the saving machine, but RAM only for the CPU computes the temporary calculation usage of hour of buffer space.
The PLC anti- interference is very and excellent, our root need not concern its service life and the work situation bad, these all problems have already no longer become the topic that we fail, but stay to our is a concern to come to internal resources of make use of the PLC to strengthen the control ability of the equipments for us, make our equipments more gentle.
PLC language is not we imagine of edit collected materials the language or language of Cs to carry on weaving the distance, but the trapezoid diagram that the adoption is original after the electric appliances to control, make the electrical engineering teacher while weaving to write the procedure very easy comprehended the PLC language, and a lot of non- electricity professional also very quickly know and go deep into to the PLC.
Is PLC one of the advantage above and only, this is also one part that the people comprehend more and easily, in a lot of equipmentses, the people have already no longer hoped to see too many control buttons, they damage not only and easily and produce the artificial error easiest, small is not a main error perhaps you can still accept; But lead even is a fatal error greatly is what we can't is tolerant of. New technique always for bringing more safe and convenient operation for us, make we a lot of problems for face on sweep but light, do you understand the HMI? Says the
HMI here you basically not clear what it is, also have no interest understanding, change one inside text explains it into the touch to hold or man-machine interface you knew, it combines with the PLC to our larger space.
HMI the control not only only is reduced the control press button, increase the vivid of the control, more main of it is can sequence of, and at can the change data input to output the feedback with data, control in the temperature curve of imitate but also can keep the manifestation of view to come out. And can write the function help procedure through a plait to provide the help of various what lies in one's power, the one who make operate reduces the otiose error. Currently the HMI factory is also more and more, the function is also more and more strong, the price is also more and more low, the noodles of the usage are wide more and more. The HMI foreground can say that think ° to be good very.
At a lot of situations, the list is is a smooth movement that can't guarantee the equipments by the control of the single machine, but pass the information exchanges of the equipments and equipments to attain the result that we want. For example fore pack and the examination of the empress work preface, we will arrive wrapping information feedback to examine the place, and examine the information of the place to also want the feedback to packing. Pass the information share thus to make both the chain connect, becoming a total body, the match of your that thus make is more close, at each other attain to reflect the result that mutually flick.
The PLC correspondence has already come more more body now its value, at the PLC and correspondence between PLCs, can pass the communication of the information and the share of the datas to guarantee that of the equipments moderates mutually, the result that arrive already to repair with each other. Data conversion the adoption RS232 between PLC connect to come to the transmission data, but the RS232 pick up a people and can guarantee 10 meters only of deliver the distance, if in the distance of 1000 meters we can pass the RS485 to carry on the correspondence, the longer distance can pass the MODEL only to carry on deliver.
The PLC data transmission is just to be called a form to it in a piece of and continuous address that the data of the inner part delivers the other party, we, the PLC of the other party passes to read data in the watch to carry on the operation. If the data that data in the watch is a to establish generally, that is just the general data transmission, for example today of oil price rise, I
want to deliver the price of the oil price to lose the oil ally on board, that is the share of the data; But take data in the watch for an instruction procedure that controls the PLC, that had the difficulty very much, for example you have to control one pedestal robot to press the action work that you imagine, you will draw up for it the form that a procedure combine with the data sends out to pass by.
The form that information transport contain single work, the half a work and the difference of a workses .The meaning of the single work also is to say both, a can send out only, but a can receive only, for example a spy he can receive the designation of the superior only, but can't give the superior reply; A work of half is also 2 and can can send out similar to accept the data, but can't send out and accept at the same time, for example when you make a phone call is to can't answer the phone, the other party also; But whole pair works is both can send out and accept the data, and can send out and accept at the same time. Be like the Internet is a typical example.
The process that information transport also has synchronous and different step cent: The data line and the clock lines are synchronous when synchronous meaning lie in sending out the data, is also the data signal and the clock signals to be carry on by the CPU to send out at the same time, this needs to all want the specialized clock signal each other to carry on the transmission and connect to send, and is constrained, the characteristics of this kind of method lies in its speed very quick, but correspond work time of take up the CPU and also want to be long oppositely, at the same time the technique difficulty also very big. Its request lies in can'ting have an error margins in a datas deliver, otherwise the whole piece according to compare the occurrence mistake, this on the hardware is a bigger difficulty. Applied more and more extensive in some appropriative equipmentses, be like the appropriative medical treatment equipments, the numerical signal equipments...etc., in compare the one data deliver, its result is very good.
And the different step is an application the most extensive, this receive benefit in it of technique difficulty is opposite and want to be small, at the same time not need to prepare the specialized clock signal, its characteristics to lie in, its data is partition, the long-lost send out and accept, be the CPU is too busy of time can grind to a stop sex to work, also reduced the difficulty on the hardware, the data throw to lose at the same time opposite want to be little, we can pass the examination of the data to observe whether the data that we send out has the mistake or not, be
like strange accidentally the method, tired addition and eight efficacies method etc., can use to helps whether the data that we examine to send out have or not the mistake occurrence, pass the feedback to carry on the discriminator.
A line of transmission of the information contain a string of and combine the cent of: The usual PLC is 8 machines, certainly also having 16 machines. We can be an at the time of sending out the data a send out to the other party, also can be 88 send out the data to the other party, an and
8 differentiationses are also the as that we say to send out the data and combine sends out the data.
A speed is more and slowly, but as long as 2 or three lines can solve problem, and can use the telephone line to carry on the long range control. But combine the oscular transmission speed is very quick of, it is a string of oscular of 25600%, occupy the advantage in the short distance, the in view of the fact TTL electricity is even, being limited by the scope of one meter generally, it combine unwell used for the data transmission of the long pull, thus the cost is too expensive.
Under a lot of circumstances we are total to like to adopt the string to combine the conversion chip to carry on deliver, under this kind of circumstance not need us to carry on to depositted the machine to establish too and complicatedly, but carry on the data exchanges through the data transmission instruction directly, but is not a very viable way in the correspondence, because the PLC of the other party must has been wait for your data exportation at the time of sending out the data, it can't do other works.
When you are reading the book, you hear someone knock on door, you stop to start up of affair, open the door and combine to continue with the one who knock on door a dialogue, the telephone of this time rang, you signal hint to connect a telephone, after connecting the telephone through, return overdo come together knock on door to have a conversation, after dialogue complete, you continue again to see your book, this kind of circumstance we are called the interruption to it, it has the authority, also having sex of have the initiative, the PLC had such function .Its characteristics lie in us and may meet the urgently abrupt affairs in the operation process of the equipments, we want to stop to start immediately up of work, the whereabouts manages the more important affair, this kind of circumstance is we usually meet of, PLC while carry out urgent mission, total will keep the current appearance first, for example the address of
the procedure, CPU of tired add the machine data etc., be like to to stick down which the book that we see is when we open the door the page or simply make a mark, because we treat and would still need to continue immediately after book of see the behind. The CPU always does the affair that should do according to our will, but your mistake of give it an affair, it also would be same to do, this we must notice.
The interruption is not only a, sometimes existing jointly with the hour several inside break, break off to have the preferred Class, they will carry out the interruption of the higher Class according to person's request. This kind of breaks off the medium interruption to also became to break off the set. The Class that certainly break off is relevant according to various resources of CPU with internal PLC, also following a heap of capacity size of also relevant fasten.
The contents that break off has a lot of kinds, for example the exterior break off, correspondence in of send out and accept the interruption and settle and the clock that count break off, still have the WDT to reset the interruption etc., they enriched the CPU to respond to the category while handle various business. Speak thus perhaps you can't comprehend the internal structure and operation orders of the interruption completely also, we do a very small example to explain.
Each equipments always will not forget a button, it also is at we meet the urgent circumstance use of, that is nasty to stop the button. When we meet the Human body trouble and surprised circumstances we as long as press it, the machine stops all operations immediately, and wait for processing the over surprised empress recover the operation again.Nasty stop the internal I/ O of the internal CPU of the button conjunction PLC to connect up, be to press button an exterior to trigger signal for CPU, the CPU carries on to the I/ O to examine again, being to confirm to have the exterior to trigger the signal, CPU protection the spot breaks off procedure counts the machine turn the homologous exterior I/ O automatically in the procedure to go to also, be exterior interruption procedure processing complete, the procedure counts the machine to return the main procedure to continue to work.Have 1:00 can what to explain is we generally would nasty stop the button of exterior break off to rise to the tallest Class, thus guarantee the safety.
When we are work a work piece, giving the PLC a signal, counting PLC inner part the machine add 1 to compute us for a day of workload, a count the machine and can solve problem in brief, certainly they also can keep the data under the condition of dropping the electricity, urging the data not to throw to lose, this is also what we hope earnestly.
The PLC still has the function that the high class counts the machine, being us while accept some datas of high speed, the high speed that here say is the data of the in all aspects tiny second class, for example the bar code scanner is scanning the data continuously, calculating high-speed signal of the data processor DSP etc., we will adopt the high class to count the machine to help we carry on count. It at the PLC carries out the procedure once discover that the high class counts the machine to should of interruption, will let go of the work on the hand immediately. The trapezoid diagram procedure that passes by to weave the distance again explains the high class for us to carry out procedure to count machine would automatic performance to should of work, thus rise the Class that the high class counts the machine to high one Class.
You heard too many this phrases perhaps:" crash", the meaning that is mostly is a workload of CPU to lead greatly, the internal resources shortage etc. the circumstance can't result in procedure circulate. The PLC also has the similar circumstance, there is a watchdog WDT in the inner part of PLC, we can establish time that a procedure of WDT circulate, being to appear the procedure to jump to turn the mistake in the procedure movement process or the procedure is busy, movement time of the procedure exceeds WDT constitution time, the CPU turn but the WDT reset the appearance. The procedure restarts the movement, but will not carry on the breakage to the interruption.
The PLC development has already entered for network ages of correspondence from the mode of the one, and together other works control the net plank and I/ O card planks to carry on the share easily. A state software can pass all se hardwares link, more animation picture of keep the view to carries on the control, and cans pass the Internet to carry on the control in the foreign land, the blast-off that is like the absolute being boat No.5 is to adopt this kind of way to make airship go up the sky.
The development of the higher layer needs our continuous effort to obtain.The PLC emergence has already affected a few persons fully, we also obtained more knowledge and
precepts from the top one experience of the generation, coming to the continuous development PLC technique, push it toward higher wave tide.
外文翻译
Load and Ultimate Moment of Prestressed Concrete Action Under Overload-Cracking Load It has been shown that a variation in the external load acting on a prestressed beam results in a change in the location of the pressure line for beams in the elastic range.This is a fundamental principle of prestressed construction.In a normal prestressed beam,this shift in the location of the pressure line continues at a relatively uniform rate,as the external load is increased,to the point where cracks develop in the tension fiber.After the cracking load has been exceeded,the rate of movement in the pressure line decreases as additional load is applied,and a significant increase in the stress in the prestressing tendon and the resultant concrete force begins to take place.This change in the action of the internal moment continues until all movement of the pressure line ceases.The moment caused by loads that are applied thereafter is offset entirely by a corresponding and proportional change in the internal forces,just as in reinforced-concrete construction.This fact,that the load in the elastic range and the plastic range is carried by actions that are fundamentally different,is very significant and renders strength computations essential for all designs in order to ensure that adequate safety factors exist.This is true even though the stresses in the elastic range may conform to a recognized elastic design criterion. It should be noted that the load deflection curve is close to a straight line up to the cracking load and that the curve becomes progressively more curved as the load is increased above the cracking load.The curvature of the load-deflection curve for loads over the cracking load is due to the change in the basic internal resisting moment action that counteracts the applied loads,as described above,as well as to plastic strains that begin to take place in the steel and the concrete when stressed to high levels. In some structures it may be essential that the flexural members remain crack free even under significant overloads.This may be due to the structures’being exposed to exceptionally corrosive atmospheres during their useful life.In designing prestressed members to be used in special structures of this type,it may be necessary to compute the load that causes cracking of the tensile flange,in order to ensure that adequate safety against cracking is provided by the design.The computation of the moment that will cause cracking is also necessary to ensure compliance with some design criteria. Many tests have demonstrated that the load-deflection curves of prestressed beams are approximately linear up to and slightly in excess of the load that causes the first cracks in the tensile flange.(The linearity is a function of the rate at which the load is applied.)For this reason,normal elastic-design relationships can be used in computing the cracking load by simply determining the load that results in a net tensile stress in the tensile flange(prestress minus the effects of the applied loads)that is equal to the tensile strength of the concrete.It is customary to assume that the flexural tensile strength of the concrete is equal to the modulus of rupture of the
外文翻译范例
要求：选择一篇和自己论文或者自己专业相关的外文进行翻译，英文字符数在6000-7000字符（注：可以继续按原文的一部分）。排版格式按照下文 公司的核心竞争力 原文来源：The Core Competence of the Corporation, Research Report on Harvard Business Review,1990 至少有三种检验方法可以用来确定公司的核心竞争力。首先，核心竞争力能够为公司进入多个市场提供方便。举例来说，显示器系统方面的核心竞争力能够使一家公司涉足计算器、微型电视机、手提电脑显示屏以及汽车仪表盘等广泛的业务领域，这就是卡西欧公司进军手持式电视机市场不足为奇的原因。第二，核心竞争力应当对最终产品为客户带来的可感知价值有重大贡献。显然，本田公司的发动机专长满足了这个条件。 最后一点，核心竞争力应当是竞争对手难以模仿的。如果核心竞争力是各项技术和生产技能的复杂的融合，那么这项能力就难以被竞争对手模仿。竞争对手或许能够获得核心竞争力中的几种技术，但是要复制其内部协调与学习的整体模式却非常困难。在20世纪60年代初期，JVC决定致力于录像带技术方面的核心竞争力，这个核心竞争力就通过了我们上述的三项检验。20世纪70年代末美国的RCA公司决心开发以唱针为基础的视频转动式系统，这个项目则不能通过上述三项检验。 。。。。。。。。。。。 The Core Competence of the Corporation The Core Competence of the Corporation Research Report on Harvard Business Review,1990 The distinction we observed in the way NEC and GTE conceived of themselves a portfolio of competencies versus a portfolio of businesses was repeated across many industries. From 1980 to 1988, Canon grew by 264%, Honda by 200%. Compare that with Xerox and Chrysler. And if Western managers were once anxious about the low cost and high quality of Japanese imports, they are now overwhelmed by the pace at which Japanese rivals are inventing new markets, creating new products, and enhancing them. Canon has given us personal copiers; Honda has moved from motorcycles to four wheel off road buggies. Sony developed the 8mm camcorder, Yamaha, the digital piano. Komatsu developed an underwater remote controlled bulldozer, while Casio's latest gambit is a small screen color LCD television. Who would have anticipated the evolution of these vanguard markets? In more established markets, the Japanese challenge has been just as disquieting. Japanese companies are generating a blizzard of features and functional enhancements that bring technological sophistication to everyday products. Japanese car producers have been pioneering four wheel steering, four valve-per cylinder engines, in car navigation systems, and sophisticated
PLC外文翻译
外文翻译 原文：The open system merit of Computer Numerical Control The open system merit is the system simple, the cost low, but the shortcoming is the precision is low. The reverse gap, the guide screw pitch error, stop inferiorly can affect the pointing accuracy by mistake. Following several kind of improvements measure may cause the pointing accuracy distinct improvement. 1. reverse gap error compensates The numerical control engine bed processing cutting tool and the work piece relative motion is depends upon the drive impetus gear,the guide screw rotation, thus the impetus work floor and so on moves the part to produce moves realizes. As traditional part gear, guide screw although the manufacture precision is very high, but always unavoidably has the gap. As a result of this kind of gap existence, when movement direction change, starts the section time to be able to cause inevitably actuates the part wasting time, appears the instruction pulse to push the motionless functional element the aspect. This has affected the engine bed processing precision, namely the instruction pulse and actual enters for the step does not tally,has the processing error therefore, the split-ring numerical control system all establishes generally has the reverse gap error compensatory function, with by makes up which wastes time the step reverse gap difference compensates is first actual reverse enters for the error, converts the pulse equivalent number it, compensates the subroutine as the gap the output, when the computer judgment appears when instruction for counter motion, transfers the gap to compensate the subroutine immediately, compensates the pulse after the output to eliminate the reverse gap to carry on again normally inserts makes up the movement. 2. often the value systematic characteristic position error compensates A kind of storehouse by transfers for the designer. Like this in the components design stage, the designer only must input the characteristic the parameter, the system direct production characteristic example model: We must save the related characteristic class in the database the structure information, the database table collection are use in saving this part of related information. According to the characteristic type definition need, we defined the characteristic class code table, the
PLC外文文献翻译
Programmable logic controller A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result. 1.History The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay. In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner. One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84
毕业设计外文翻译资料
外文出处： 《Exploiting Software How to Break Code》By Greg Hoglund, Gary McGraw Publisher : Addison Wesley Pub Date : February 17, 2004 ISBN : 0-201-78695-8 译文标题： JDBC接口技术 译文： JDBC是一种可用于执行SQL语句的JavaAPI（ApplicationProgrammingInterface应用程序设计接口）。它由一些Java语言编写的类和界面组成。JDBC为数据库应用开发人员、数据库前台工具开发人员提供了一种标准的应用程序设计接口，使开发人员可以用纯Java语言编写完整的数据库应用程序。 一、ODBC到JDBC的发展历程 说到JDBC，很容易让人联想到另一个十分熟悉的字眼“ODBC”。它们之间有没有联系呢？如果有，那么它们之间又是怎样的关系呢？ ODBC是OpenDatabaseConnectivity的英文简写。它是一种用来在相关或不相关的数据库管理系统（DBMS）中存取数据的，用C语言实现的，标准应用程序数据接口。通过ODBCAPI，应用程序可以存取保存在多种不同数据库管理系统（DBMS）中的数据，而不论每个DBMS使用了何种数据存储格式和编程接口。 1．ODBC的结构模型 ODBC的结构包括四个主要部分：应用程序接口、驱动器管理器、数据库驱动器和数据源。应用程序接口：屏蔽不同的ODBC数据库驱动器之间函数调用的差别，为用户提供统一的SQL编程接口。 驱动器管理器：为应用程序装载数据库驱动器。 数据库驱动器：实现ODBC的函数调用，提供对特定数据源的SQL请求。如果需要，数据库驱动器将修改应用程序的请求，使得请求符合相关的DBMS所支持的文法。 数据源：由用户想要存取的数据以及与它相关的操作系统、DBMS和用于访问DBMS的网络平台组成。 虽然ODBC驱动器管理器的主要目的是加载数据库驱动器，以便ODBC函数调用，但是数据库驱动器本身也执行ODBC函数调用，并与数据库相互配合。因此当应用系统发出调用与数据源进行连接时，数据库驱动器能管理通信协议。当建立起与数据源的连接时，数据库驱动器便能处理应用系统向DBMS发出的请求，对分析或发自数据源的设计进行必要的翻译，并将结果返回给应用系统。 2．JDBC的诞生 自从Java语言于1995年5月正式公布以来，Java风靡全球。出现大量的用java语言编写的程序，其中也包括数据库应用程序。由于没有一个Java语言的API，编程人员不得不在Java程序中加入C语言的ODBC函数调用。这就使很多Java的优秀特性无法充分发挥，比如平台无关性、面向对象特性等。随着越来越多的编程人员对Java语言的日益喜爱，越来越多的公司在Java程序开发上投入的精力日益增加，对java语言接口的访问数据库的API 的要求越来越强烈。也由于ODBC的有其不足之处，比如它并不容易使用，没有面向对象的特性等等，SUN公司决定开发一Java语言为接口的数据库应用程序开发接口。在JDK1．x 版本中，JDBC只是一个可选部件，到了JDK1．1公布时，SQL类包（也就是JDBCAPI）
3英文文献及翻译格式示例
哈尔滨工业大学毕业设计（论文） 英文原文（原文也可以直接将PDF版打印） ASSESSING CREDIT OR DETERMINING QUANTITY? THE EVOLVING ROLE OF RATING AGENCIES Lynnette D. Purda* This version: April 21, 2011 Abstract Over the past ten years, credit rating agencies have come under intense criticism from both practitioners and academics, first for their failure to identify problems resulting in bankruptcies at Enron and Worldcom and second for providing overly optimistic ratings for structured finance products. While many investors question the value of rating agencies in light of these criticisms, they have proven remarkably resilient. This paper provides a brief background on how rating agencies secured competitive advantages in evaluating credit quality. It then reviews the empirical evidence on the information content of ratings given these advantages. I argue that the information content of ratings stems from two intertwined sources: 1) information related to credit quality and 2) information related to the firm’s ability to access debt. Based on this evidence, I suggest that the dominant role for ratings today is as a benchmark for financial contracting. In this way, ratings remain influential in establishing the supply and demand of debt securities. 译文 评级机构的发展的作用评估信用还是决定数量？ 本文：2011.4.21 摘要 在过去的十年，信用评级机构一直处于来自实践者和学者的激烈的批评中，首先他们未能发现问题，导致安然和世通破产；其次对结构性金融产品提供过于乐观的评级。虽然许多投资者因为这些批评对评级机构的价值提出了质疑，但他们仍然被证明是相当有活力的。这篇文章首先在评估机构如何在信用评级质量中获得竞争优势提供一个简单地背景介绍，然后考虑到这些优势回顾了一些信息内容方面的评级经验证据。个人认为信息内容的评级来自两种交织在一起（错综复杂）的来源：1）和信贷质量相关的信息；2)和公司获取债务资本能力相关的信息。以此为据，我建议当前评级的主导作用是作为基准的金融收缩。以这种方式，在建立债券的供应和需求方面评级仍然是有效的。 - -1
引进外资外文翻译资料
河南科技学院新科学院 2013届本科毕业生论文（设计） 英文文献及翻译 Foreign capital inflows and welfare in an economy with imperfect competition 学生姓名：王艳杰 所在院系：经济系 所学专业：国际经济与贸易 导师姓名：侯黎杰 完成时间：2013年4月15日
Foreign capital inflows and welfare in an economy with imperfect competition Abstract:This paper examines the resource allocational and welfare effects of exogenous inflows of foreign capital in a general-equilibrium model with oligopolistic competition and unemployment. Although the welfare impact for the short run is ambiguous and dependent upon the strength of excess profits and scale economies relative to unemployment in manufacturing, in the long run additional inflows of foreign capital always improve national welfare with capital mobility. Hence, attracting foreign capital remains a sound policy for economies characterized by imperfect competition, scale economies,and regional unemployment. Keywords: International capital mobility; Imperfect competition; Welfare 1.Introduction The welfare effects of exogenous inflows of foreign capital in the presence of trade restrictions have been extensively studied. Brecher and Diaz Alejandro (1977) show that when imports are subject to tariffs, an introduction of fo reign capital inflows accentuates the tariff distortion and hence reduces national welfare if the import-competing sector is relatively capital-intensive. In contrast, Dei (1985) shows that when imports are restricted by quotas,foreign capital inflows in the presence of foreign-owned capital always improve welfare by depressing the rental and so lowering the payments to existing foreign-owned capital. Recently, Neary (1981), using a common framework for both tariffs and quotas, obtains more general results of foreign capital inflows; the welfare effect of such inflows depends crucially on whether foreign-owned capital exists initially in the home country. In addition, Khan (1982) and Grinols (1991) have examined the effects of foreign capital inflows for a generalized Harris-Todaro economy under tariff protection. Khan finds that the result by Brecher and Diaz Alejandro is still valid even in the presence of unemployment, whereas Grinols argues that increased foreign capital need not be detrimental to welfare if the opportunity costs of labor are sufficiently low. Noteworthy is that the models used by these authors are all based upon the premise of perfect competition along with constant returns-to-scale technology. Although perfect competition serves as a useful assumption in crystallizing theoretical insights, it nevertheless fails to depict many of the real-world phenomena. The real-world economy is characterized, to a large extent, by imperfect competition and economies of scale. The policy implications of imperfect competition and economies
毕业设计外文翻译格式实例.
理工学院毕业设计(论文)外文资料翻译 专业：热能与动力工程 姓名：赵海潮 学号：09L0504133 外文出处：Applied Acoustics, 2010(71):701~707 附件： 1.外文资料翻译译文；2.外文原文。
附件1：外文资料翻译译文 基于一维CFD模型下汽车排气消声器的实验研究与预测Takeshi Yasuda, Chaoqun Wua, Noritoshi Nakagawa, Kazuteru Nagamura 摘要目前，利用实验和数值分析法对商用汽车消声器在宽开口喉部加速状态下的排气噪声进行了研究。在加热工况下发动机转速从1000转/分钟加速到6000转/分钟需要30秒。假定其排气消声器的瞬时声学特性符合一维计算流体力学模型。为了验证模拟仿真的结果，我们在符合日本工业标准（JIS D 1616）的消声室内测量了排气消声器的瞬态声学特性，结果发现在二阶发动机转速频率下仿真结果和实验结果非常吻合。但在发动机高阶转速下（从5000到6000转每分钟的四阶转速，从4200到6000转每分钟的六阶转速这样的高转速范围内），计算结果和实验结果出现了较大差异。根据结果分析，差异的产生是由于在模拟仿真中忽略了流动噪声的影响。为了满足市场需求，研究者在一维计算流体力学模型的基础上提出了一个具有可靠准确度的简化模型，相对标准化模型而言该模型能节省超过90％的执行时间。 关键字消声器排气噪声优化设计瞬态声学性能 1 引言 汽车排气消声器广泛用于减小汽车发动机及汽车其他主要部位产生的噪声。一般而言，消声器的设计应该满足以下两个条件：（1）能够衰减高频噪声，这是消声器的最基本要求。排气消声器应该有特定的消声频率范围，尤其是低频率范围，因为我们都知道大部分的噪声被限制在发动机的转动频率和它的前几阶范围内。（2）最小背压，背压代表施加在发动机排气消声器上额外的静压力。最小背压应该保持在最低限度内，因为大的背压会降低容积效率和提高耗油量。对消声器而言，这两个重要的设计要求往往是互相冲突的。对于给定的消声器，利用实验的方法，根据距离尾管500毫米且与尾管轴向成45°处声压等级相近的排气噪声来评估其噪声衰减性能，利用压力传感器可以很容易地检测背压。 近几十年来，在预测排气噪声方面广泛应用的方法有：传递矩阵法、有限元法、边界元法和计算流体力学法。其中最常用的方法是传递矩阵法（也叫四端网络法）。该方
基于PLC相关的毕业设计外文翻译(可编辑修改word版)
毕业论文（设计）外文翻译 题目：可编程逻辑控制器技术 系部名称：信息工程系专业班级： 学生姓名：学号： 指导教师：教师职称： 2014 年3 月XX 日
译文 可编程逻辑控制器技术 引言 PLC（可编程逻辑控制器）实际是一个工业控制系统（近来我们看到更多的是用处理器来取代微控制器），在软件和硬件都配备的条件下，适合应用于工业环境。PLC 的发明是相当必要的，它代替了传统的依靠由继电接触器电路来控制电机。PLC 的工作原理是根据它的输入信号和工作状态来确定输出。用户通常是通过软件或编程输入一个程序，来输出所需要的结果。 如图 8-1 所示，PLC 是由典型的黑色构件组成。特别需要注意的是它的输入和输出， 因为在这些模块上，工业环境会给 CPU 一个输入线，所以很有必要将 CPU 模块隔离以保护其免遭有害的影响。程序单元通常是用计算机来编写程序（一般是梯形图）。 1.1CPU 的中央处理单元 中央处理单元（CPU）是一个 PLC 的主控制器。一般 CPU 本身是一个微控制器。通常这些都是 8 位微控制器，如 8051 ，现在的这些是 16 位和 32 位微控制器。潜规则是，你会发现用在 PLC 控制器上的微控制器多数是由日本生产的日立和富士通，欧洲的西门子控制器，和美国的摩托罗拉微控制器。CPU 也负责通讯，与 PLC 控制器的其它部分相互联系，如程序执行，内存操作，监督输入和设置输出。PLC 控制器拥有复杂的程序用于内存检查，以确保 PLC 内存不被损坏（内存检查是为了安全原因而作出的）。一般来说，CPU 单元多数用来检查 PLC 控制器本身，所以有可能出现的错误很早就会被发现。你可以简单地看任何 PLC 控制器,查看错误信号在发光二极管上的种种指示形式。 1.2内存 系统内存（今天主要是在 FLASH 技术上实现）用于一台 PLC 的过程控制系统。除了 这个操作系统它还包含用户程序将梯形图翻译成二进制的形式。 FLASH 存储器的内容仅在 用户程序改变下可以改变。PLC 控制器较早被用来代替闪存，EPROM 存储器代替了那些只能依靠紫外线灯等擦除内存并依靠程序员来编程的 FLASH 存储器。在 FLASH 技术的作用下这个过程被大大的缩短了。重组程序内存通过程序中的串行通讯用于应用程序开发。使用内存被划分成多个具有特殊功能的模块。存储器某些部分用来存储输入状态和输出状态。一个 输入信号的实际状态是用 1 或0 存储在一个特定的存储位。每一个输入信号和输出信号在内存里都有一个位与之相对应。内存的其他部分用来存储用户程序中使用的变量以及变量的内容。例如，定时器的值和计数器的值都将被存储在这部分内存里。 1.3PLC 控制器的编程 PLC 控制器可以通过计算机（常用的方式）进行编程，还可以通过手动编程器（控制台）编程。这实际上意味着如果你有需要的编程软件那么每个 PLC 控制器都可以通过计算机进行编程。今天的传输计算机是非常适合在工厂对 PLC 控制器进行编程的。这对工业有着非常重要的意义。一旦系统被刷新，重新读取正确的程序到 PLC 就很重要。还可以定期检查 PLC 中的程序是否改变了。这有助于避免在工厂车间发生危险状况（部分汽车制造商建立了通信网络，定期检查项目中的 PLC 控制器，以确保执行的程序是正确的）。
中英文对照资料外文翻译文献
中英文对照资料外文翻译文献 平设计任何时期平面设计可以参照一些艺术和专业学科侧重于视觉传达和介绍。采用多种方式相结合，创造和符号，图像和语句创建一个代表性的想法和信息。平面设计师可以使用印刷，视觉艺术和排版技术产生的最终结果。平面设计常常提到的进程，其中沟通是创造和产品设计。共同使用的平面设计包括杂志，广告，产品包装和网页设计。例如，可能包括产品包装的标志或其他艺术作品，举办文字和纯粹的设计元素，如形状和颜色统一件。组成的一个最重要的特点，尤其是平面设计在使用前现有材料或不同的元素。平面设计涵盖了人类历史上诸多领域，在此漫长的历史和在相对最近爆炸视觉传达中的第20和21世纪，人们有时是模糊的区别和重叠的广告艺术，平面设计和美术。毕竟，他们有着许多相同的内容，理论，原则，做法和语言，有时同样的客人或客户。广告艺术的最终目标是出售的商品和服务。在平面设计，“其实质是使以信息，形成以思想，言论和感觉的经验”。
在唐朝（618-906 ）之间的第4和第7世纪的木块被切断打印纺织品和后重现佛典。阿藏印在868是已知最早的印刷书籍。在19世纪后期欧洲，尤其是在英国，平面设计开始以独立的运动从美术中分离出来。蒙德里安称为父亲的图形设计。他是一个很好的艺术家，但是他在现代广告中利用现代电网系统在广告、印刷和网络布局网格。于1849年，在大不列颠亨利科尔成为的主要力量之一在设计教育界，该国政府通告设计在杂志设计和制造的重要性。他组织了大型的展览作为庆祝现代工业技术和维多利亚式的设计。从1892年至1896年威廉?莫里斯凯尔姆斯科特出版社出版的书籍的一些最重要的平面设计产品和工艺美术运动，并提出了一个非常赚钱的商机就是出版伟大文本论的图书并以高价出售给富人。莫里斯证明了市场的存在使平面设计在他们自己拥有的权利，并帮助开拓者从生产和美术分离设计。这历史相对论是，然而，重要的，因为它为第一次重大的反应对于十九世纪的陈旧的平面设计。莫里斯的工作，以及与其他私营新闻运动，直接影响新艺术风格和间接负责20世纪初非专业性平面设计的事态发展。谁创造了最初的“平面设计”似乎存在争议。这被归因于英国的设计师和大学教授Richard Guyatt，但另一消息来源于20世纪初美国图书设计师William Addison Dwiggins。伦敦地铁的标志设计是爱德华约翰斯顿于1916年设计的一个经典的现代而且使用了系统字体设计。在20世纪20年代，苏联的建构主义应用于“智能生产”在不同领域的生产。个性化的运动艺术在2俄罗斯大革命是没有价值的，从而走向以创造物体的功利为目的。他们设计的建筑、剧院集、海报、面料、服装、家具、徽标、菜单等。J an Tschichold 在他的1928年书中编纂了新的现代印刷原则，他后来否认他在这本书的法西斯主义哲学主张，但它仍然是非常有影响力。Tschichold ，包豪斯印刷专家如赫伯特拜耳和拉斯洛莫霍伊一纳吉，和El Lissitzky 是平面设计之父都被我们今天所知。他们首创的生产技术和文体设备，主要用于整个二十世纪。随后的几年看到平面设计在现代风格获得广泛的接受和应用。第二次世界大战结束后，美国经济的建立更需要平面设计，主要是广告和包装等。移居国外的德国包豪斯设计学院于1937年到芝加哥带来了“大规模生产”极简到美国;引发野火的“现代”