毕业设计相关外文材料（推荐阅读）

第一篇：毕业设计相关外文材料

Estimating Hydropower’s Contribution

to the Control of Greenhouse Gas Emissions

ABSTRACT One of the environmental effects of hydropower operation that should be evaluated in licensing decisions is the general benefit to air quality.Hydropower’s contribution to the reduction of greenhouse gas(GHG)emissions is an increasingly important component of these air quality benefits.The Oak Ridge Competitive Electricity Dispatch(ORCED)computer model is one method that can be used to quantify these benefits.ORCED provides a relatively simple method that is applicable and cost-effective and that has been successfully applied in other GHG studies.ORCED can be used to calculate a region-specific value of the carbon intensity factor(CIF, kg carbon/MWh)that would be associated with likely replacement power(i.e., a regionally representative mix of coal, gas, and other energy sources).The project’s plant factor and operational mode(e.g, baseload versus peaking)can also be incorporated in the CIF calculation.The resulting parameter can then be multiplied by the energy output of the hydropower project that is being analyzed to estimate a CO2 emission value that is avoided by the project’s operation.Valuing Energy Production Hydropower’s contribution to GHG emission control is related to avoided emissions(i.e.emissions that would occur if hydroelectricity had to be replaced by another fossil-fueled energy source).The estimation of an appropriate value for avoided emissions is complicated, because there is not a single equation to calculate the emissions that are not produced at hydropower projects.The characteristics of avoided emissions depend on the type of power that is displaced by hydropower generation.If a kilowatt-hour were not generated at the hydro plant, what plant would have generated it? The answer depends on a range of factors: the time of day, the plants already on the system, the plants available, their variable costs, the type of fuel they use, their efficiencies, even the transmission losses and constraints.These factors are regionally and seasonally variable.GHG Measurement Units A common unit for measuring GHG is metric tons of carbon.Although carbon is largely emitted as carbon dioxide gas(CO2)when it is burned, small percentages are also emitted as carbon monoxide(CO)and methane(CH4), which eventually convert to CO2 in the atmosphere.Other GHGs are ozone(O3)and nitrous oxide(N2O).The atmospheric warming effect of GHGs other than CO2 can be represented relative to the effect of CO2.The exact relationship between the gases is complicated by factors such as the wavelength of radiation absorbed, decomposition of gases in the atmosphere, and other atmospheric chemical reactions that can increase or decrease greenhouse gas effects.The warming value will change over time as the other gases are converted to CO2 or otherwise removed from the atmosphere.In general, CH4 is 56 times more potent than CO2 over a twenty year period, but over 100 years this difference drops to 21 times, and over 500 years it drops to 7 times the effect of CO2(EIA 1999b).Nitrogen oxide(NOx)is not a greenhouse gas on its own, but it can combine with CO to promote the formation of ozone.However, the greenhouse impact of power plant NOx emissions compared to CO2 emissions is several orders of magnitude less.Estimation Methods Different levels of modeling complexity can be used in estimating GHG benefits.The simplest approach is to make an a priori assumption of the type of power that would replace hydropower production and then use a representative carbon intensity factor to calculate the relevant carbon emissions.Average carbon intensity factors range from 266kg C/MWh for a coal-fired steam electric plant to 90 kg C/MWh for an advanced gas combined cycle plant(EIA 1999a and 1999b).For example, if the loss of a hydro facility would be replaced by increased coal-fired production at 33 percent efficiency then carbon emissions would increase 266 kg per MWh.If the facility had a capacity of five MW and a plant factor of 50%, replacement with coal-fired production would generate about 5,800 tons of carbon per year.This is equivalent to 4,500 vehicles.Conclusions The production of hydroelectricity is associated with significant reductions in the nation’s GHG emissions, although the specific amount of this benefit is difficult to measure directly.ORCED provides a relatively simple method to estimate the GHG benefits of hydropower.If more precise answers are required, then other large-load flow or capacity expansion models may need to be used.However, for most cases ORCED provides a mechanism to get results without the high cost or long time of these large models.ORCED can be used to calculate a region-specific value of the carbon intensity factor that would be associated with likely replacement power, and that factor can be adjusted to account for the hydropower projects plant factor.The resulting carbon intensity factor can then be multiplied by the energy output of the hydropower project that is being analyzed to produce a CO2 savings that is associated with the project’s operation.This GHG emission can then be converted to an equivalent value the number of cars needed to produce the same emission or to some other common measure, to put this savings in a more easily understood measure.This analytical approach can be adapted to evaluating alternative plant operations, such as shifts from peaking to baseload.The model also generates the marginal cost of power for a given region, allowing the user to determine the economic impact of the generation.估算水电的贡献的控制温室气体排放

摘要

水电的操作应在许可决定的环境影响评价的一般利益之一，是空气质量。水电的贡献，是温室气体（GHG）的排放量减少是这些空气质量效益越来越重要的组成部分。Oak Ridge竞争性电力调度（ORCED）计算机模型是一种方法，可以用来量化这些利益。ORCED提供了一个相对简单的方法是可行和符合成本效益，并且已成功地应用在其他温室气体的研究。ORCED可以用来计算一个地区的碳强度因子的特定值（CIF，公斤碳/兆瓦时），将与可能的替换电源（即煤、气区域代表性的组合，和其他能源的来源）有关。该项目的植物因子和运作模式（如基荷与峰值）也可纳入到CIF计算。由此产生的参数，然后可以乘上水电项目正在分析估计二氧化碳排放值，是由该项目的运作避免能量的输出。

重视能源生产

水电的贡献，与控制温室气体排放有关，避免排放量（即排放量会发生变化，如果水电必须由另一个化石燃料能源替代）。为避免排放量估计一个适当的值是复杂的，因为没有一个公式来计算未在水电项目产生的排放量。对避免的排放量的特性取决于对能源的类型，是由水电发电流失。如果一千瓦小时未在水力发电厂产生的，哪种植物会产生呢？答案取决于一系列因素：一天的时间，植物已在系统中，提供的生产基地，他们使用的燃料类型，它们的效率，甚至是传输损耗和可变成本的限制。这些因素是区域和季节的变量。

温室气体计量单位

用于测量温室气体常用的单位是公吨碳。虽然主要的碳排放是二氧化碳气体（CO2），当它燃烧，而一氧化碳（CO）和甲烷（CH4）占很小的比例，最终转化为二氧化碳排放在大气中和其他温室气体的臭氧（O3）和氧化亚氮（N2O）。其他的温室气体等使大气变暖的影响可以表示相对于二氧化碳的效果。气体之间的确切关系有复杂的因素，如吸收波长的辐射，大气中的气体分解，和其他气体的化学反应，可以增加或减少温室气体的影响。气候变暖的价值将随时间而改变为其他气体，转化为二氧化碳或以其他方式存在于大气中。一般情况下，甲烷是56倍以上，过去20年间二氧化碳更主要，但这种差异在100年下降到21倍，超过500年就降到了7倍的二氧化碳的影响（环境影响评估1999b）。氮氧化物（NOx）的温室气体是不针对自己的，但它可以与CO结合，促进臭氧的形成。然而，与电厂氮氧化物排放量相比，二氧化碳温室气体排放的影响是少几个数量级

估计方法

由于建模的复杂程度不同，可用作估算温室气体排放的好处。最简单的方法是使一个假想的电源类型，以取代水电生产，然后使用具有代表性的碳强度因子计算碳排放有关的假设。平均碳强度因子范围从266公斤的C /兆瓦的燃煤蒸汽电热设备厂到90公斤先进的燃气联合循环电厂的C /兆瓦时（环评1999a和1999b）。例如，如果一个水电设施损失将通过增加燃煤改为生产效率33%的碳排放量将增加到每兆瓦时266公斤。如果工厂有五兆瓦和50％植物因子，与燃煤生产替代将会每年产生约5,800吨二氧化碳。这相当于4500辆的排放量。

结论

水电的生产使全国的温室气体排放量大幅减少，但这样做的收益的具体数额是难以直接测量。ORCED提供了一个相对简单的方法来估算温室气体在水电生产中的好处。如果需要更精确的答案，然而更大流量或负载容量扩充模型可能需要使用。然而，在大多数情况下ORCED提供一种机制来获得无高成本或为这些大型模型花很长一段时间的结果。ORCED可用于计算的碳强度的因素，就是可能与更换电源相关区域的具体值，这个因素可以调整，以考虑水电工程机组的使用率。由此产生的碳排放强度因子然后乘上水电项目的能源输出，它是正在分析以产生一个与该项目的操作有关的二氧化碳排放。这种温室气体排放可以被转换为等值的需要产生同样的排放，或其他一些常见的措施，或放在更加容易理解衡量这一储蓄。这种分析方法可以适用于其他植物评估业务，如从峰值到基荷变化。该模型还生成一个特定区域电力边际成本，使用户能够确定产生的经济影响。

第二篇：毕业设计外文翻译

外文原文

Overview of JSp Technology

Benefits of JSp

JSp pages are translated into servlets.So, fundamentally, any task JSp pages can perform could also be accomplished by servlets.However, this underlying equivalence does not mean that servlets and JSp pages are equally appropriate in all scenarios.The issue is not the power of the technology, it is the convenience, productivity, and maintainability of one or the other.After all, anything you can do on a particular computer platform in the Java programming language you could also do in assembly language.But it still matters which you choose.JSp provides the following benefits over servlets alone:

•It is easier to write and maintain the HTML.Your static code is ordinary HTML: no extra backslashes, no double quotes, and no lurking Java syntax.•You can use standard Web-site development tools.Even HTML tools that know nothing about JSp can be used because they simply ignore the JSp tags.•You can divide up your development team.The Java programmers can work on the dynamic code.The Web developers can concentrate on the presentation layer.On large projects, this division is very important.Depending on the size of your team and the complexity of your project, you can enforce a weaker or stronger separation between the static HTML and the dynamic content.Now, this discussion is not to say that you should stop using servlets and use only JSp instead.By no means.Almost all projects will use both.For some requests in your project, you will use servlets.For others, you will use JSp.For still others, you will combine them with the MVC architecture.You want the appropriate tool for the job, and servlets, by themselves, do not complete your toolkit.Advantages of JSp Over Competing Technologies

A number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology.Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language.Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington.During the discussion, the moderator brought up the subject of Jini, which at that time was a new Java technology.The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea.He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual “embrace and extend” strategy.At this point, Gosling lightheartedly interjected “You mean disgrace and distend.”

Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes.But guess what? The shoe is on the other foot here.The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with special tags.For example, ColdFusion did it years earlier.Even ASp(a product from the very software company of the aforementioned manager)popularized this approach before JSp came along and decided to jump on the bandwagon.In fact, JSp not only adopted the general idea, it even used many of the same special tags as ASp did.So, the question becomes: why use JSp instead of one of these other technologies? Our first response is that we are not arguing that everyone should.Several of those other technologies are quite good and are reasonable options in some situations.In other situations, however, JSp is clearly better.Here are a few of the reasons.Versus.NET and Active Server pages(ASp)

.NET is well-designed technology from Microsoft.ASp.NET is the part that directly competes with servlets and JSp.The advantages of JSp are twofold.First, JSp is portable to multiple operating systems and Web servers;you aren't locked into deploying on Windows and IIS.Although the core.NET platform runs on a few non-Windows platforms, the ASp part does not.You cannot expect to deploy serious ASp.NET applications on multiple servers and operating systems.For some applications, this difference does not matter.For others, it matters greatly.Second, for some applications the choice of the underlying language matters greatly.For example, although.NET's C# language is very well designed and is similar to Java, fewer programmers are familiar with either the core C# syntax or the many auxiliary libraries.In addition, many developers still use the original version of ASp.With this version, JSp has a clear advantage for the dynamic code.With JSp, the dynamic part is written in Java, not VBScript or another ASp-specific language, so JSp is more powerful and better suited to complex applications that require reusable components.You could make the same argument when comparing JSp to the previous version of ColdFusion;with JSp you can use Java for the “real code” and are not tied to a particular server product.However, the current release of ColdFusion is within the context of a J2EE server, allowing developers to easily mix ColdFusion and servlet/JSp code.Versus pHp

pHp(a recursive acronym for “pHp: Hypertext preprocessor”)is a free, open-source, HTML-embedded scripting language that is somewhat similar to both ASp and JSp.One advantage of JSp is that the dynamic part is written in Java, which already has an extensive ApI for networking, database access, distributed objects, and the like, whereas pHp requires learning an entirely new, less widely used language.A second advantage is that JSp is much more widely supported by tool and server vendors than is pHp.Versus pure Servlets

JSp doesn't provide any capabilities that couldn't, in principle, be accomplished with servlets.In fact, JSp documents are automatically translated into servlets behind the scenes.But it is more convenient to write(and to modify!)regular HTML than to use a zillion println statements to generate the HTML.plus, by separating the presentation from the content, you can put different people on different tasks: your Web page design experts can build the HTML by using familiar tools and either leave places for your servlet programmers to insert the dynamic content or invoke the dynamic content indirectly by means of XML tags.Does this mean that you can just learn JSp and forget about servlets? Absolutely not!JSp developers need to know servlets for four reasons:

1.JSp pages get translated into servlets.You can't understand how JSp works without understanding servlets.2.JSp consists of static HTML, special-purpose JSp tags, and Java code.What kind of Java code? Servlet code!You can't write that code if you don't understand servlet programming.3.Some tasks are better accomplished by servlets than by JSp.JSp is good at generating pages that consist of large sections of fairly well structured HTML or other character data.Servlets are better for generating binary data, building pages with highly variable structure, and performing tasks(such as redirection)that involve little or no output.4.Some tasks are better accomplished by a combination of servlets and JSp than by either servlets or JSp alone.Versus JavaScript

JavaScript, which is completely distinct from the Java programming language, is normally used to dynamically generate HTML on the client, building parts of the Web page as the browser loads the document.This is a useful capability and does not normally overlap with the capabilities of JSp(which runs only on the server).JSp pages still include SCRIpT tags for JavaScript, just as normal HTML pages do.In fact, JSp can even be used to dynamically generate the JavaScript that will be sent to the client.So, JavaScript is not a competing technology;it is a complementary one.It is also possible to use JavaScript on the server, most notably on Sun ONE(formerly iplanet), IIS, and BroadVision servers.However, Java is more powerful, flexible, reliable, and portable.Versus WebMacro or Velocity

JSp is by no means perfect.Many people have pointed out features that could be improved.This is a good thing, and one of the advantages of JSp is that the specification is controlled by a community that draws from many different companies.So, the technology can incorporate improvements in successive releases.However, some groups have developed alternative Java-based technologies to try to address these deficiencies.This, in our judgment, is a mistake.Using a third-party tool like Apache Struts that augments JSp and servlet technology is a good idea when that tool adds sufficient benefit to compensate for the additional complexity.But using a nonstandard tool that tries to replace JSp is a bad idea.When choosing a technology, you need to weigh many factors: standardization, portability, integration, industry support, and technical features.The arguments for JSp alternatives have focused almost exclusively on the technical features part.But portability, standardization, and integration are also very important.For example, the servlet and JSp specifications define a standard directory structure for Web applications and provide standard files(.war files)for deploying Web applications.All JSp-compatible servers must support these standards.Filters can be set up to apply to any number of servlets or JSp pages, but not to nonstandard resources.The same goes for Web application security settings.Besides, the tremendous industry support for JSp and servlet technology results in improvements that mitigate many of the criticisms of JSp.For example, the JSp Standard Tag Library and the JSp 2.0 expression language address two of the most well-founded criticisms: the lack of good iteration constructs and the difficulty of accessing dynamic results without using either explicit Java code or verbose jsp:useBean elements.10.4 Misconceptions About JSp

Forgetting JSp Is Server-Side Technology

Here are some typical questions Marty has received(most of them repeatedly).•Our server is running JDK 1.4.So, how do I put a Swing component in a JSp page?

•How do I put an image into a JSp page? I do not know the proper Java I/O commands to read image files.•Since Tomcat does not support JavaScript, how do I make images that are highlighted when the user moves the mouse over them?

•Our clients use older browsers that do not understand JSp.What should we do?

•When our clients use “View Source” in a browser, how can I prevent them from seeing the JSp tags?

All of these questions are based upon the assumption that browsers know something about the server-side process.But they do not.Thus:

•For putting applets with Swing components into Web pages, what matters is the browser's Java version—the server's version is irrelevant.If the browser supports the Java 2 platform, you use the normal AppLET(or Java plug-in)tag and would do so even if you were using non-Java technology on the server.•You do not need Java I/O to read image files;you just put the image in the directory for Web resources(i.e., two levels up from WEB-INF/classes)and output a normal IMG tag.•You create images that change under the mouse by using client-side JavaScript, referenced with the SCRIpT tag;this does not change just because the server is using JSp.•Browsers do not “support” JSp at all—they merely see the output of the JSp page.So, make sure your JSp outputs HTML compatible with the browser, just as you would do with static HTML pages.•And, of course you need not do anything to prevent clients from seeing JSp tags;those tags are processed on the server and are not part of the output that is sent to the client.Confusing Translation Time with Request Time

A JSp page is converted into a servlet.The servlet is compiled, loaded into the server's memory, initialized, and executed.But which step happens when? To answer that question, remember two points:

•The JSp page is translated into a servlet and compiled only the first time it is accessed after having been modified.•Loading into memory, initialization, and execution follow the normal rules for servlets.Table 1 gives some common scenarios and tells whether or not each step occurs in that scenario.The most frequently misunderstood entries are highlighted.When referring to the table, note that servlets resulting from JSp pages use the _jspService method(called for both GET and pOST requests), not doGet or dopost.Also, for initialization, they use the jspInit method, not the init method.Table 1.JSp Operations in Various Scenarios

JSp page translated into servletServlet compiledServlet loaded into server's memoryjspInit called_jspService called

page first written

Request 1YesYesYesYesYes

Request 2NoNoNoNoYes

Server restarted

Request 3NoNoYesYesYes

Request 4NoNoNoNoYes

page modified

Request 5YesYesYesYesYes

Request 6NoNoNoNoYes

中文翻译

JSp技术概述

一、JSp的好处

JSp页面最终会转换成servler。因而，从根本上，JSp页面能够执行的任何任务都可以用servler来完成。然而，这种底层的等同性并不意味着servler和JSp页面对于所有的情况都等同适用。问题不在于技术的能力，而是二者在便利性、生产率和可维护性上的不同。毕竟，在特定平台上能够用Java编程语言完成的事情，同样可以用汇编语言来完成，但是选择哪种语言依旧十分重要。

和单独使用servler相比，JSp提供下述好处：

JSp中HTML的编写与维护更为简单。JSp中可以使用常规的HTML：没有额外的反斜杠，没有额外的双引号，也没有暗含的Java语法。

能够使用标准的网站开发工具。即使对那些对JSp一无所知的HTML工具，我们也可以使用，因为它们会忽略JSp标签（JSp tags）。

可以对开发团队进行划分。Java程序员可以致力于动态代码。Web开发人员可以将经理集中在表示层（presentation layer）上。对于大型的项目，这种划分极为重要。依据开发团队的大小，及项目的复杂程度，可以对静态HTML和动态内容进行弱分离（weaker separation）和强分离（stronger separation）。

在此，这个讨论并不是让您停止使用servlets，只使用JSp。几乎所有的项目都会同时用到这两种技术。针对项目中的某些请求，您可能会在MVC构架下组合使用这两项技术。我们总是希望用适当的工具完成相对应的工作，仅仅是servlet并不能填满您的工具箱。

二、JSp相对于竞争技术的优势

许多年前，Marty受到邀请,参加一个有关软件技术的小型(20个人)研讨会.做在Marty旁边的人是James Gosling---Java编程语言的发明者。隔几个位置,是来自华盛顿一家大型软件公司的高级经理。在讨论过程中,研讨会的主席提出了Jini的议题,这在当时是一项新的Java技术.主席向该经理询问他的想法.他继续说,他们会持续关注这项技术,如果这项技术变得流行起来,他们会遵循公司的“接受并扩充(embrace and extend)”的策略.此时, Gosling随意地插话说“你的意思其实就是不接受且不扩充(disgrace and distend)。”

在此, Gosling的抱怨显示出，他感到这个公司会从其他公司那里拿走技术,用于他们自己的目的.但你猜这次怎么样?这次鞋子穿在了另一只脚上。Java社团没有发明这一思想----将页面设计成由静态HTML和用特殊标签标记的动态代码混合组成.。ColdFusion多年前就已经这样做了。甚至ASp(来自于前述经理所在公司的一项产品)都在JSp出现之前推广了这种方式。实际上,JSp不只采用了这种通用概念,它甚至使用许多和ASp相同的特殊标签。

因此,问题变成:为什么使用JSp,而不使用其他技术呢?我们的第一反应是我们不是在争论所有的人应该做什么。其他这些技术中,有一些也很不错,在某些情况下也的确是合情合理的选择.然而,在其他情形中,JSp明显要更好一些。下面给出几个理由。

与.NET和Active Server pages(ASp)相比

.NET是Microsoft精心设计的一项技术。ASp.NET是与servlets和JSp直接竞争的技术。JSp的优势体现在两个方面。

首先,JSp可以移植到多种操作系统和Web服务器,您不必仅仅局限于部署在Windows 和IIS上尽管核心.NET平台可以在好几种非Windows平台上运行，但ASp这一部分不可以。您不能期望可以将重要的ASp.NET应用部署到多种服务器和操作系统。对于某些应用，这种差异没有什么影响。但有些应用，这种差异却非常重要。

其次，对于某些应用，底层语言的选择至关重要。例如，尽管.NET的C#语言设计优良，且和Java类似，但熟悉核心C#语法和众多工具库的程序员很少。此外,许多开发者依旧使用最初版本的ASp。相对于这个版本,JSp在动态代码方面拥有明显的优势。使用JSp,动态部分是用Java编写的,而非VBScript过其他ASp专有的语言,因此JSp更为强劲,更适合于要求组件重用的复杂应用。

当将JSp与之前版本的ColdFusion对比时，您可能会得到相同的结论。应用JSp，您可以使用Java编写“真正的代码”，不必依赖于特定的服务器产品。然而，当前版本的ColdFusion满足J2EE服务器的环境，允许开发者容易的混合使用ColdFusion和Servlet/JSp代码。

与pHp相比

pHp（“pHp：Hypertext preprocessor”的递归字母缩写词）是免费的、开放源代码的、HTML嵌入其中的脚本语言，与ASp和JSp都有某种程度的类似。JSp的一项优势是动态部分用Java编写，而Java已经在联网、数据库访问、分布式对象等方面拥有广泛的ApI，而pHp需要学习全新的、应用相对广泛的语言。JSp的第二项优势是，和pHp相比，JSp拥有极为广泛的工具和服务器提供商的支持。

与纯Servlet相比

原则上，JSp并没有提供Servlet不能完成的功能。实际上，JSp文档在后台被自动转换成Servlet。但是编写（和修改）常规的HTML，要比无数println语句生成HTML要方便得多。另外，通过将表示与内容分离，可以为不同的人分配不同的任务：网页设计人员使用熟悉的工具构建HTML，要么为Servlet程序员留出空间插入动态内容，要么通过XML标签间接调用动态内容。

这是否表示您只可以学习JSp，将Servlet丢到一边呢？当然不是！由于以下4种原因，JSp开发人员需要了解Servlet：

（1）JSp页面会转换成Servlet。不了解Servlet就无法知道JSp如何工作。

（2）JSp由静态HTML、专用的JSp标签和Java代码组成。哪种类型的Java代码呢？当然是Servlet代码！如果不了解Servlet编程，那么就无法编写这种代码。

（3）一些任务用Servlet完成比用JSp来完成要好。JSp擅长生成由大量组织有序的结构化HTML或其他字符数据组成的页面。Servlet擅长生成二进制数据，构建结构多样的页面，以及执行输出很少或者没有输出的任务（比如重定向）。

（4）有些任务更适合于组合使用Servlet和JSp来完成，而非单独使用Servlet或JSp。

与JavaScript相比

JavaScript和Java编程语言完全是两码事，前者一般用于在客户端动态生成HTML，在浏览器载入文档时构建网页的部分内容。这是一项有用的功能，一般与JSp的功能（只在服务器端运行）并不发生重叠。和常规HTML页面一样，JSp页面依旧可以包括用于JavaScript的SCRIpT标签。实际上，JSp甚至能够用来动态生成发送到客户端的JavaScript。因此，JavaScript不是一项竞争技术，它是一项补充技术。

JavaScript也可以用在服务器端，最因人注意的是SUN ONE（以前的iplanet）、IIS和BroadVision服务器。然而，Java更为强大灵活、可靠且可移植。

与WebMacro和Velocity相比

JSp决非完美。许多人都曾指出过JSp中能够改进的功能。这是一件好事，JSp的优势之一是该规范由许多不同公司组成的社团控制。因此，在后续版本中，这项技术能够得到协调的改进。

但是，一些组织已经开发出了基于Java的替代技术，试图弥补这些不足。据我们的判断，这样做是错误的。使用扩充JSp和Servlet技术的第三方工具，如Apache Structs，是一种很好的思路，只要该工具带来的好处能够补偿工具带来的额外复杂性。但是，试图使用非标准的工具代替JSp则不理想。在选择一项技术时，需要权衡许多方面的因素：标准化、可移植性、集成性、行业支持和技术特性。对于JSp替代技术的争论几乎只是集中在技术特性上，而可移植性、标准化和集成性也十分重要。例如，Servlet和JSp规范为Web应用定义了一个标准的目录结构，并提供用于部署Web应用的标准文件（.war文件）。所有JSp兼容的服务器必须支持这些标准。我们可以建立过滤器作用到任意树木的Servlet和JSp页面上，但不能用于非标准资源。Web应用安全设置也同样如此。

此外，业界对JSp和Servlet技术的巨大支持使得这两项技术都有了巨大的进步，从而减轻了对JSp的许多批评。例如，JSp标准标签库和JSp 2.0表达式语言解决了两种最广泛的批评：缺乏良好的迭代结构；不使用显式的Java代码或冗长的jsp:useBean元素难以访问动态结果。

三、对JSp的误解

忘记JSp技术是服务器端技术

下面是Marty收到的一些典型问题（大部分问题不止一次的出现）。

我们的服务器正在运行JDK1.4。我如何将Swing组件用到JSp页面中呢？

我如何将图像放到JSp页面中？我不知道读取图像文件应该使用哪些Java I/O命令。

Tomcat不支持JavaScript，当用户在图像上移动鼠标时，我如何使图像突出显示呢？

我们的客户使用不理解JSp的旧浏览器。我应该怎么做？

当我们的客户在浏览器中使用“View Source”（查看源代码）时，如何阻止他们看到JSp标签？

所有这些问题都基于浏览器对服务器端的过程在有所了解的假定之上。但事实上浏览器并不了解服务器端的过程。因此：

如果要将使用Swing组件的applet放到网页中，重要的是浏览器的Java版本，和服务器的Java版本无关。如果浏览器支持Java 2平台，您可以使用正常的AppLET（或Java插件）标签，即使在服务器上使用了非Java技术也须如此。

您不需要Java I/O来读取图像文件，您只需将图像放在存储Web资源的目录中（即WEB-INF/classes向上两级的目录），并输出一个正常的IMG标签。

您应该用SCRIpT标签，使用客户端JavaScript创建在鼠标下会更改的图像，这不会由于服务器使用JSp而改变。

浏览器根本不“支持”JSp----它们看到的只是JSp页面的输出。因此，如同对待静态HTML页面一样，只需确保JSp输出的HTML与浏览器兼容。

当然，您不需要采取什么措施来阻止客户看到JSp标签，这些标签在服务器上进行处理，发送给客户的输出中并不出现。

混淆转换期间和请求期间

JSp页面需要转换成servlet。Servlet在编译后，载入到服务器的内容中，初始化并执行。但是每一步发生在什么时候呢？要回答这个问题，要记住以下两点：

JSp页面仅在修改后第一次被访问时，才会被转换成servlet并进行编译；

载入到内存中、初始化和执行遵循servlet的一般规则。

表1列出一些常见的情形，讲述在该种情况下每一步是否发生。最常被误解的项已经突出标示出来。在参考该表时，要注意，由JSp页面生成的servlet使用_jspService方法（GET和pOST请求都调用该函数），不是doGet或dopost方法。同样，对于初始化，它们使用jspInit方法，而非init方法。

表1 各种情况下的JSp操作

将JSp 页面转换成servlet编译Servlet 将Servlet 载入到服务器内存中调用jspInit 调用_jspService

页面初次创建

请求 1有有有有有

请求 2无无无无有

服务器重启后

请求3无无有有有

请求 4无无无无有

页面修改后

请求 5有有有有有

请求 6无无无无有

第三篇：毕业设计冷凝器外文翻译

吉林化工学院本科毕业设计（论文）外文翻译

氨制冷系统的节能设计，改造和蒸发式冷凝器的控制

阿卜杜勒穆罕默德和凯利，工业评估中心，代顿大学

摘要

氨制冷系统通常提供了许多节能商机，因为他们的大动力消耗，运行时间长的和动态的操作。氨制冷系统的能源使用高度依赖于冷凝头的压力，而这是一个函数的蒸发式冷凝器容量和控制功能。本文研究系统能源利用中聚光能力和冷凝器的控制之间的关系。它首先开发方法来确定冷凝器的性能，然后以仿真模型模拟压缩机和冷凝器风扇的能源利用。，它使用工程基本面和经验两个数据，准确地捕捉压缩机，冷凝器和环境湿球温度之间的协同效应。节约能源是三种情况：安装在冷凝器风机变频驱动器，采用湿球控制方法战略和提高聚光性能。以说明气候的影响，这些模拟是两个不同的ASHRAE气候区，迈阿密，佛罗里达州和执行明尼阿波利斯，明尼苏达州，这是炎热和寒冷的气候分别。结果表明，提高表现不佳的冷凝器的性能是最经济有效的节能测量。但是节约能源从冷凝器安装变频驱动器球迷和利用湿球的方法策略取决于环境气候条件，与位置无关。接下来，内部收益率的计算方法来安装额外的聚光能力超越在为相同的两个ASHRAE气候区新建筑应用的标准做法。结果表明，安装两次基线聚光能力，内部收益率超过20 ％。综上所述，本文提出的设计，改造的综合方法在氨制冷系统蒸发式冷凝器的控制权。节约能源衍生通过使用这种方法可以显著提高氨的能量效率制冷系统。

介绍

约7.5 ％的总生产能耗用于食品加工行业，其中约21％的能量是电能(二零零六年环评)。在这些设备中，氨制冷系统是最大的能源消耗部分。制冷与冷却工艺所用电量是食品加工行业(二零零六年EIA)的用电量的27％。制冷系统使用的能量是高度依赖于冷凝压力，而这又是冷凝器容量和控制性能。因此，提高聚光能力和控制可导致显著的节能效果。

本文首先确定使用的数据从实际的聚光性能制冷控制系统。然后是开发仿真模型来计算每年的能源使用所研究的压缩机和冷凝器风扇。该仿真模型，用来计算节能三

吉林化工学院本科毕业设计（论文）外文翻译

个节能措施(ECMS)：在冷凝器风扇安装变频器，采用湿球的方法策略，提高聚光性能。以说明气候的影响，这些仿真用于执行迈阿密，佛罗里达州和明尼苏达州明尼阿波利斯，这是炎热和寒冷的气候分别。文章最后决定回报的安装额外的容量超出标准规范的内部收益率在新的建筑应用。

系统说明

分析系统是一个两阶段的氨制冷系统具有两个低压侧压缩机和两个高级压缩机。所有的压缩机是螺杆式与滑阀控制和热虹吸油冷却。一种蒸发式冷凝器以恒定的速度从系统散发热量。对于本文的其余部分，术语系统将参考冷凝器风扇和压缩机。从冷凝器泵的能源使用小，并且不评价了本文。关键系统参数，包括电动机电流，氨的压力和温度从制冷控制系统获得。氨性数据的计算使用参考流体热力学和输运性质数据(NIST，2010)也被称为REFPROP。图中显示了制冷系统的替补的示意图。

图1。电路图制冷系统的pH值图上

计算排热到冷凝器

冷凝压力是决定系统能源利用的一个关键变量。为了准确地计算冷凝压力，冷凝器性能必须确定。在第一步骤中确定冷凝器性能是计算从压缩机排出到总热量冷凝器。在系统中的能量平衡显示了总的热拒绝了冷凝器是由低和高级压缩机加两个设置在制冷（QREF0）低和高级压缩机两者的压缩或轴功率（WS）的热量。

QCond.actual = Σ QrefLS +Σ QrefHS +Σ WSLS +Σ WsHS（1）

吉林化工学院本科毕业设计（论文）外文翻译

所有的热拒绝从低温压缩机减去热虹吸拒绝的低级压缩机油冷却（TSOC，LS）将被转移到高压侧制度。因此，由高温压缩机提供（TRprovided，HS）的制冷是：

ΣTRprovided，HS = Σ QrefLS +Σ QrefHS +Σ WLS

吉林化工学院本科毕业设计（论文）外文翻译

量可以使用等式4和来自控制系统的百分之制冷容量，计算如下：

QREF = Qrrated • ％容量

（5）

压缩热由高温级压缩机（WsHS）生产

来自控制系统的数据而获得的每个压缩机的电机电流。至相关电机电流轴功率（WS），电机电流和输入之间的关系权力必须得到发展。这种关系中，可以从点测量开发电机电流和输入功率在整个压缩机的工作范围。通过使用的压缩机（ὴm）的两个铭牌效率和f（A），轴功率或等价每个压缩机的压缩热量可以计算为：

WsHS = F（A）* ὴm

（6）

热虹吸油冷却（TSOC）

考虑了两阶段的低温循环在图1中表示的氨制冷系统。在状态1LS，氨进入压缩机作为饱和蒸汽和离开压缩机的过热蒸汽在状态2LS。路径1LSmref.LS •（h2a.LSh4.LS）（8）

通常，制造商报告的体积流量的空气速率，标称容量，并且热抑制因子（HRF）。体积流量是用于使用计算的质量流率空气的密度在标准条件。该HRF，这既是外部空气湿球温度计的功能温度（TWB）和饱和冷凝温度（Tcond），用于确定在额定容量冷凝器对于一个给定TWB和Tcond为（Manske，Reindl和2001年克莱因）：

额定电容容量=标称容量/ HRF（TWB，Tcond）（10）

等式9b和10可以适用于制造商的规格为蒸发冷凝器，以确定对于一个给定的湿球Tcond和效力之间的关系范围。有效性被发现是线性相关的Tcond为： effM = E0

吉林化工学院本科毕业设计（论文）外文翻译

由于蒸发式冷凝器的运行期间的实际容量已计算的，实际效果可以适合于在等式11的形式的线。测量效力与从所研究的系统Tcond数据被绘制时，无论是蒸发式冷凝器，风机和水泵是在图3满负荷生产。额定制造商从式（11）效果也绘制在同一张图来比较的有效性上一个新的蒸发式冷凝器，以其中一个已经服役了几年。图3表示该蒸发式冷凝器性能已劣化随着时间的推移。实际容量比制造商的额定容量少约40％。此信息可以被用作用于模拟程序的校准参数。例如，在图3中，冷凝器容量为一个新的冷凝器将约为1.69倍，目前的实际能力。

图3。实际和制造商有效性的蒸发式冷凝器

模拟年能源消耗

每年的能量使用的制冷系统的是压缩机和冷凝器的总和风机能耗。冷凝压力是必须正确地计算一个关键的变量正确模拟压缩机和冷凝器风扇的能源使用。以下步骤概述一方法计算压缩机功率，冷凝压力和冷凝器风扇电源。

计算压缩机输入功率

一个给定的压缩机在一定范围抽吸的额定轴功率（bhprated）和冷凝温度可以从制造商处获得。此数据可以被嵌入到一个二阶多项式方程的交互项来确定额定满载

吉林化工学院本科毕业设计（论文）外文翻译

轴功率在给定的吸气和冷凝温度（Manske 2000），如：

bhprated = P0 + P1 • Tcond + P2 • TSUC + P11 • Tcond ² + P22 • TSUC ² + P12 • Tcond • TSUC（12）

在该制冷系统中的压缩机，像许多制冷系统中，在操作碱/修剪方式，表示过去压缩机接通的每个阶段是修剪压缩机。式（4），它类似于公式12中，示出的满负荷容量压缩机吸入的函数和冷凝温度下，该压缩机运行。知道制冷负荷（参考负载）和碱的量被操作（Σ TRBase），则该部分的容量修剪压缩机的压缩机定阶段（FCTrim）可以计算如下：

FCTrim =（参考负载6789

吉林化工学院本科毕业设计（论文）外文翻译

红色=压缩机的能耗，蓝=冷凝器风扇能源，绿色=节能，广场=投资回报率，VFD =常数变速冷凝器风扇，所需时间约=利用湿球的方法和策略PERFOR =提高聚光性能。

在新建筑应用安装额外的电容容量

冷凝器是因为结构支撑，管道和控制成本来安装。因此，这是很少的成本效益来安装额外的冷凝器为唯一目的能量效率。然而，在新建筑中安装额外的冷凝器容量可以成本效益。近似的安装成本与变频驱动和湿球的做法冷凝器控制是指在公式23。增量成本（元）= 17 ·增容（MBH）+ 12,000（23）

在添加额外的冷凝器时收益率（IRR）内部收益率图9显示容量时，冷凝器的寿命是20年，能源涨价率是3 ％。内部收益率计算用于安装的50 ％的额外容量，100％，150 ％和200 ％，比7000 MBH基线能力。在这两个位置，内部收益率超过20％加倍聚光能力。因此，增加聚光能力似乎是一个非常有吸引力的选项的新建筑。

图9。返回的安装额外的电容容量内部收益率

红色=增量成本，绿色=每年节约能源成本，回报广场=内部收益率

小结与讨论

本文开发了一种方法，利用数据来校准聚光性能制冷控制系统。此校准冷凝器性能的仿真中使用模型计算所研究的能源使用的系统。该仿真模型是然后用来计算节能三的ECM ：在冷凝器风扇安装变频器，采用湿球的方法策略，提高聚光性能的两个不同的ASHRAE气候区。

重要的结果是：

1．制冷系统的总功耗是强烈依赖于冷凝器大小，性能和控制。

2．对于现有系统，提高了蒸发式冷凝器性能可能是最成本效益的节能措施。目视检

吉林化工学院本科毕业设计（论文）外文翻译

[4] Manske，K.A.，Reindl酒店，D.T.和克莱因2001年S.A.公司。在工业“蒸发式冷凝器的控制制冷系统制冷24 “国际杂志： 676-691。

[5]米切尔，J.W.博朗，J.E.，1998。“设计，分析和空间调节设备的控制和

系统”。威斯康星大学麦迪逊分校。

[6] 标准与技术，2010年全国学院，参考流体热力学和运输属性数（REFPROP）8.0版 [7] 国家可再生能源实验室，2005年，“用户手册TMY3s ”，http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/ [8] Stoecker，威尔伯特，1998年，工业制冷手册。麦格劳13-

第四篇：毕业设计三相异步电动机外文翻译

中文翻译

异步电动机具有结构简单、运行可靠、价格低、维护方便等一系列的优点，因此，异步电动机被广泛应用在电力拖动系统中。尤其是随着电力电子技术的发展和交流调速技术的日益成熟，使得异步电动机在调速性能方面大大提高。目前，异步电动机的电力拖动已被广泛地应用在各个工业电气自动化领域中。就三相异步电动机的机械特性出发，主要简述电动机的启动，制动、调速等技术问题。三相异步电动机的机械特性文

三相异步电动机的机械特性是指电动机的转速n与电磁转矩Tem之间的关系。由于转速n与转差率S有一定的对应关系，所以机械特性也常用Tem＝f（s）的形式表示。三相异步电动机的电磁转矩表达式有三种形式，即物理表达式、参数表达式和实用表达式。物理表达式反映了异步电动机电磁转矩产生的物理本质，说明了电磁转矩是由主磁通和转子有功电流相互作用而产生的。参数表达式反映了电磁转矩与电源参数及电动机参数之间的关系，利用该式可以方便地分析参数变化对电磁转矩的影响和对各种人为特性的影响。实用表达式简单、便于记忆，是工程计算中常采用的形式。

电动机的最大转矩和启动转矩是反映电动机的过载能力和启动性能的两个重要指标，最大转矩和启动转矩越大，则电动机的过载能力越强，启动性能越好。

三相异步电动机的机械特性是一条非线性曲线，一般情况下，以最大转矩（或临界转差率）为分界点，其线性段为稳定运行区，而非线性段为不稳定运行区。固有机械特性的线性段属于硬特性，额定工作点的转速略低于同步转速。人为机械特性曲线的形状可用参数表达式分析得出，分析时关键要抓住最大转矩、临界转差率及启动转矩这三个量随参数的变化规律。三相异步电动机的启动

小容量的三相异步电动机可以采用直接启动，容量较大的笼型电动机可以采用降压启动。降压启动分为定子串接电阻或电抗降压启动、Y-D降压启动和自耦变压器降压启动。定子串电阻或电机降压启动时，启动电流随电压一次方关系减小，而启动转矩随电压的平方关系减小，它适用于轻载启动。Y-D降压启动只适用于正常运行时为三角形联结的电动机，其启动电流和启动转矩均降为直接启动时的1/3，它也适用于轻载启动。自耦变压器降压启动时，启动电流和启动转矩均降为直接启动时的l/k2（k为自耦变压器的变比），适合带较大的负载启动。

绕线转子异步电动机可采用转子串接电阻或频敏变阻器启动，其启动转矩大、启动电流小，适用于中、大型异步电动机的重载启动。

软启动器是一种集电机软启动、软停车、轻载节能和多种保护功能于一体的新型电动机控制装置，国外称为Soft Starter。它的主要构成是串接于电源与被控电动机之间的三相反并联晶闸管及其电子控制电路。运用串接于电源与被控电动机之间的软启动器，以不同的方法，控制其内部晶闸管的导通角，使电动机输入电压从零以预设函数关系逐渐上升，直至启动结束，赋予电动机全电压，即为软启动。在软启动过程中，电动机启动转矩逐渐增加，转速也逐渐增加。软启动器实际上是个调压器，用于电动机启动时，输出只改变电压并没有改变频率。

三相异步电动机的调速

三相异步电动机的调速方法有变极调速、变频调速和变转差率调速。其中变转差率调速包括绕线转子异步电动机的转子串接电阻调速、串级调速和降压调速。

变极调速是通过改变定子绕组接线方式来改变电机极数，从而实现电机转速的变化。变极调速为有级调速，变极调速时的定子绕组联结方式有三种：Y-YY、顺串Y-反串Y、D-YY。其中Y-YY联结方式属于恒转矩调速方式，另外两种属于恒功率调速方式。变极调速时，应同时对调定子两相接线，这样才能保证调速后电动机的转向不变。

变频调速是现代交流调速技术的主要方向，它可实现无级调速，适用于恒转矩和恒功率负载。

绕线转子电动机的转子串接电阻调速方法简单，易于实现，但调速是有级的，不平滑，且低速时特性软，转速稳定性差，同时转子铜损耗大，电动机的效率低。串级调速克服了转子串接电阻调速的缺点，但设备要复杂得多。

异步电动机的降压调速主要用于风机类负载的场合，或高转差率的电动机上，同时应采用速度负反馈的闭环控制系统。

把电压和频率固定不变的工频交流电变换为电压或频率可变的交流电的装置称作“变频器”。为了产生可变的电压和频率，该设备首先要把电源的交流电变换为直流电（DC），这个过程叫整流。再把直流电（DC）变换为交流电（AC），这个过程叫逆变，把直流电变换为交流电的装置叫逆变器（inverter）。对于逆变为频率可调、电压可调的逆变器我们称为变频器。变频器输出的波形是模拟正弦波，主要用在三相异步动机的调速，又叫变频调速器。附录 二

外文原文

Asynchronous motor has a simple structure, reliable operation, low price, convenient maintenance and a series of advantages, therefore, asynchronous motor is widely used in electric drive system.Especially with the development of power electronic technology and AC drive technology becomes more mature, greatly improve the speed performance makes the asynchronous motor.At present, electric drive asynchronous motor has been widely used in various industrial electrical automation.The mechanical properties of three-phase asynchronous motor starting, the main motor starting, braking, speed control technology.The mechanical properties of 1 three-phase asynchronous motor Mechanical characteristics of three-phase asynchronous motor is refers to the relationship between the speed of the motor electromagnetic torque of N and Tem.Due to the speed of N and slip S have a certain relationship, so the mechanical properties are also commonly used Tem = f(s)representation.Electromagnetic torque expression of three-phase asynchronous motor has three forms, namely physical expression, parameters and practical expression.Physical expressions reflect the physical nature of electromagnetic torque of asynchronous motor, the electromagnetic torque is generated by the main flux and rotor active current interaction.Parameter expression reflects the relationship between parameters of electromagnetic torque and power supply parameters and motor, the expression can be used to influence easily analyze the influence of parameter variation on the electromagnetic torque and all kinds of human characteristics.Practical expressions in a simple, easy to remember, is often used in engineering calculation in the form of.The maximum torque of motor and torque are two important indexes reflecting the overload capacity of the motor and starting performance, maximum torque and start torque motor overload capacity is bigger, stronger, better starting performance.The mechanical characteristic of three-phase asynchronous motor is a nonlinear curve, under normal circumstances, with the maximal torque(or critical slip)as a cutoff point, the linear segment for the stable operation region, while the nonlinear section is not stable operating region.Hard characteristic is linear segment inherent mechanical properties, the nominal operating point speed slightly lower than the synchronous speed.Shape parameters available expressions man-made mechanical characteristic curve analysis, analysis the key to grasp the maximum torque, starting torque variation of critical slip and the three with the parameters of.2 three-phase asynchronous motor starting Three-phase asynchronous motor with small capacity can be used to directly start, cage motor with large capacity can adopt step-down start.Step-down start into stator resistance or reactance step-down start, Y-D step-down start and autotransformer start.The stator resistance or motor step-down start, starting current voltage relations with a reduced, and the starting torque with the square of the voltage is reduced, it is suitable for the starting load.Only applicable to motor start to normal operation for the triangle connection Y-D buck, the starting current and starting torque is reduced to direct startup 1/3, which is also suitable for the starting load.Autotransformer start, starting current and starting torque is reduced to direct startup l/k2(k is the self coupling transformer), suitable for large load starting.The wound rotor asynchronous motor with rotor series resistance or frequency sensitive rheostat starting, the starting torque, small starting current, suitable for heavy load starting, large asynchronous motor.The soft starter is a novel control device for motor motor soft start, soft stop, light load energy saving and various protecting functions in one, called Soft Starter.The main structure is connected in series between the power supply and the controlled motor three-phase inverse parallel thyristor and its electronic control circuit.Through the series of soft starter is connected between the power supply and the controlled motor, in different ways, its internal control thyristor conduction angle, so that the motor input voltage from zero to a preset function gradually rise, until the end of the motor start, give full voltage, namely soft start.In the soft start-up process, starting torque motor speed increases gradually, gradually increasing.The soft starter is actually a regulator, for when the motor is started, the output voltage does not change the frequency change.3 speed of three-phase asynchronous motor Control method of the three-phase asynchronous motor with variable speed, variable speed and variable slip speed.The variable slip ratio control includes a rotor winding rotor asynchronous motor series resistance speed control, cascade control and blood pressure control.Variable speed is by changing the stator winding connection mode to change the pole number, so as to realize the change of motor speed.Variable speed is speed-regulation, variable stator winding connection speed of three kinds: Y-YY, Y-, D-YY and Y run.The Y-YY connection is constant torque speed control mode, another two species belong to the constant power control mode.Variable pole speed, should also be on the stator two-phase wiring, so that we can guarantee the speed regulation motor steering.Variable frequency speed control is the main direction of modern AC speed regulation technology, it can realize stepless speed regulation, suitable for constant torque and constant power load.Wound rotor rotor motor series resistance speed control method is simple, easy to implement, but speed is not smooth, level, and low speed characteristics of soft, speed stability is poor, and the rotor copper loss, motor efficiency is low.Cascade speed control to overcome the rotor series resistance speed disadvantage, but the equipment is much more complex.Step-down speed asynchronous motor for fan load, or high slip motor, closed-loop control system should be accompanied by negative feedback of speed.The industrial frequency alternating current voltage and frequency of fixed to variable voltage or frequency of the alternating current.

第五篇：出租车计价器毕业设计外文资料

ABSTRACT In this paper, a multi-channel taximeter that is able to deal with more than one passenger simultaneously is proposed.In order to demonstrate the theory of operation of the proposed system, a complete design for an experimental three-channel taximeter(whose prototype has been built under grant from the Egyptian Academy for Scientific and Technological Research)is presented.System location, outline, block diagrams as well as detailed circuit diagrams for the experimental taximeter are also included.1.INTRODUCTION Transporting people in the morning from their homes to their works and back in the afternoon has become a big problem in big cities especially in undeveloped countries.As a partial solution of this problem, the authorities in some countries had, unofficially, left the taxicab drivers to carry different passengers to different places at the Same time.For example, a taxicab with four seats may carry four different passengers without any relation between them except that their way of travelling is the same.Accordingly, it has become very difficult to rely on the present conventional single-channel taximeter to determine the fare required from each passenger separately.Accordingly, an unfair financial relation was created between the taxicab driver, owner, passengers and the state taxation department.Under these circumstances, taxicab drivers force the passengers to pay more than what they should pay.In some cases passengers had to pay double fare they should pay.With the present conventional single-channel taximeter, taxicab owners are not able to determine the daily income of their taxicab.In some cases(a taxicab with four seats)they may only get one quarter of the income of the taxicab(collected by the taxicab driver).From which they should pay the salary of the taxicab driver as well as the cost of fuel, minor and major repairs in addition to the car depreciation.As a matter of fact the position of the taxicab owners is not so bad as it seems.A general agreement has been reached between the taxicab drivers and owners such that the drivers should guarantee a fixed daily income to the owners as well as the paying for the cost of fuel as well as the minor repaires.Even though the taxicab drivers still share the large portion ofthe income of the taxicab.Also with the presence of the single-channel taximeter, it has become very difficult for the state taxation department to know the yearly income of the taxicab and accordingly it has become very difficult to estimate the taxes to be paid by the taxicab owners.In order to face this problem, the state taxation department had to impose a fixed estimated taxes for each seat of the taxicab whatever the income of the taxicab.In this paper, we introduced a multichannel taximeter that can deal with more than one passenger simultaneously.I t should be pointed out that by the term passenger we mean a one person or a group of related persons.I t should also be pointed out that our proposed multi-channel taximeter is not, simply, a multi display readouts.As a matter of fact it contains logic circuits that automatically changes the fare per killometer of travelling distance or per minutes of 'waiting time according to the number of passengers hiring the taxicab.In the following part and as an example, we will present a complete design for a three-channel taximeter.Block diagrams as well as detailed circuit diagrams of the experimental three-channel taximeter are also included.A prototype has been built under grant from the Egyptian Academy for Scientific and Technological Research.2.AN EXPERIMENTAL THREECHANNEL TAXIMETER Theory of operation of our experimental device to work as an electronic digital taximeter is based on t h e fact thathe speedometer cable rotates one revolution for each meter of travelling distance.Accordingly, if the speedometer cable is coupled with a speed sensor that generates a single pulse for each meter of travelling distance, then our taximeter could be three up counter modules associated with a speed sensor unit.However, our experimental taximeter is not simply a three display readouts.As a matter offact it contains logic circuits that automatically changes the fare per kilometer of travelling distance or per minutes of waiting time according to the number of passengers hiring the taxicab.The device may be splitted into two main parts: The first is the speed sensor unit which may be located anywhere in the taxicab such that an easy coupling to the speedometer cable can be achieved.The second unit contains the main electronic circuit, the displayand control panel.The unit should be located somewhere in front of both the driver and the passengers.A possible components locations is shown in Figure 1.A.Speed Sensor Unit The main function of this unit is to supply train of pulses whose frequency is proportional to the angular rotation of the wheels.A possible form of a speed sensor is shown in Figure 2.If may consist of a tj.pica1 permanent magnet sine wave generator with its output connected to a pulse shapping circuit(two general purpose silicon diodes, 1K ohms resistor and a schmit trigger inverter).In order to find some way to detect the movement of the taxicab, the output of the sine wave generator is rectified through a general purpose silicon diode Dl then smoothed by a 1000 F capacitor.The output voltage at terminal Q is then limited to the value of 4.7 volts by using a Ik ohms resistor as well as a zener diode ZD.The level of the voltage at terminal Q would be high whenever the taxicab is moving and will be zero otherwise.This voltage can be used for the automatic switching from distance fare to time fare.B.Main Electronic and Display Unit A suggested shape for the main electronic and display unit is shown in Figure 3.The control and display panel contains all ' controls necessary for operating the taximeter as well as four readout displays.The first channel will give the sum of money required from the first passenger, while the second and third readouts are for the second and third passengers, respectively.The fourth readout will give the total income of the taxicab.The contents of the last readout should be nonvolatile and be able to be retained even during parking the taxicab.The channel rotary selector switchs 1 , 2 and 3 have fully clockwise/anticlockwise positions.In the fully anticlockwise position, the counter of the corresponding readout is blancked and disabled.In the fully clockwise position, the counter is unblanked, cleared to zero and enabled to be ready for counting the sum of money required from the first, second and third passengers, respectively.Pushing the total sum pushbutton 4 unblanks the fourth readout enabling any person to retain the readout corresponding to the total income.After the release of the pushbutton, the fourth readout will be blanked again.This unit also contains the main electronic circuit which will be fully described in the following section.3.DESCRIBTION OF THE MAIN ELECTRONIC CIRCUIT The general block diagram of the main electronic circuit is shown in Figure 4.It consists of five subcircuits designated by the symboles CTI up to CT4supporting circuits, these are: The number of passenger deticition circuit CTI, travelling distance scaling circuit CT2, waiting time scaling circuit CT3, circuit CT4 which generates clock pulses for the display circuit.A.Number of Passengers Detection Circuit CT1 As shown from the general block diagram, the circuit CTI has three inputs I, 2 and 3 as well as three outputs J, K and L.The function of the circuit is to supply a high level voltage at terminals J, K or L if and only if one, two or three passengers are hiring the taxicab, respectively.The term passenger, here, means one person or a group of related persons.When a passenger is getting into the cab, we simply turn on a free readout display by turning the corresponding rotary selector switch to a fully clockwise direction.This will automatically disconnect the corresponding terminal I, 2 or 3 from ground.The logical relation between various input terminals I, 2 and 3 and the output terminals J, K and L is shown in Table 1.As a combinational circuit we start the design by deriving a set of boolean functions.A possible simplified boolean functions that gives minimum number of inputs to gates may be obtained from Table I.A possible logical diagram that is based on the above derived expressions is shown in Figure 5.It consists of two inverters, four 2-input AND, to3-input AND two 3-input OR gates B.Tavelling Distance Scaling Circuit CT2 As shown from the block diagram of Figure 4, the circuit CT2 has four input J, K, L and E and one output M.The function of the circuit is to supply a single pulse at the output M for a certain number of pulses generated at the output of the speed sensor(certain number of meters travelled by the taxicab), according to the number of passengers hiring the car.A suggested fare per kilometer of travelling distance is shown in colomn two of Table 2.the circuit, in this case, should supply a single pulse at the output M for every 100, 125 or 143 pulses generated at the input terminal E according to the level of voltage at input terminale 3, K or L, respectively.Our circuit could be, as shown in Figure 5, three decade counters, connected as a three digit frequency divider whose dividing ratios 100, 125 and 143 are automatically selected by the voltage level at terminals J, K and L, respectively.A possible circuit diagram that may verify the above function is shown in Figure 6.It consists of three decade counters type 7490, one BCD-to decimal decoder type 7445, three 4-input AND, one 3-input ANDone 2-input AND two 3-input OR gates.C.Time Scaling Circuit CT3 As shown in the block diagram, the time scalingcircuit will have four inputs J, K, L and F and one output N.The function of this circuit and accordingto colomn three of Table 2(fare per 2 minuts of waiting time)is to supply a single pulse at the output N for every 120, 240 or 360 pulses supplied at the input terminal F from the I Hz clock according to level of voltage at inputs J, K and L, respectively.Time scaling circuit would be similar to the distance scaling circuit but with different diving ratios.A Possible circuit diagram is shown in figure 7.It consists, in this case, of three decade counter type 7490, two 3-input AND, one 5-input AND, one 2-input AND one 3-input OR gates.D.Circuit CT4 Which Generates Clock Pulses for Display Circuit The function of this circuit is to supply one, two or three pulses at the output terminal R for each pulse generated at any of the terminals N or M, according to the voltage level at the input terminals J, K or L, respectively.The output P will receive a pulse for each pulse generated at any of the input terminals N or M.This function can be performed by the circuit shown in Figure 8, it consists of one ripple counter type 7493, one half of a dual JK masterslave flip-flops circuit type 7476, three inverters, three 2-input AND, one 3-input AND, one 2-input OR and one 3-input OR gates.When a pulse is generated at either input terminals N or M, a high level voltage will be generated at the output Q of the flip-flop.This will g a t e t h e I Khz signal to be connected to the input A of the ripple counter as well as to the output terminal R.When one, two or three pulses are counted by the ripple counter, according to the level of voltage at the input terminals J, K and L, respectively, a high is generated to reset the counter and change the state of the flip-flopsuch that Q becomes low.Hence, the 1 KHz signal is disabled to reach the outputerminal R or the input A of the ripple counter.In order to ensure the proper function of the circuit, the flip-flop should be cleared whenever a new channel is operated.This has been achieved by the input 5 and will be explained later when describing the function of the channels rotary selector switchs.E.Display Circuit As shown in Figure 2, the display panel would contain three 4-digit displays that give the sum of money required from each passenger separately as well as a one six-digit display that gives the total income of the taxicab.A possible wiring diagram for the display circuit is shown in Figure 9.Rotating any of the rotary selector switches to fully clockwise direction will supply the corresponding display by5 volts through terminals 1, 2 and 3, respectively.The corresponding display will be unblanked by supplying a low level of voltage through terminals A, C and G, respectively.Keeping terminals 8, D and H, respectively, at low level will keep them reset to zero.The corresponding display is then enabled by removing the low voltage from terminals B, D, and H, respectively, to be ready for counting the sum of money required from the corresponding passenger starting from zero.The counting pulses for these three displays are supplied through terminal P.The total sum display will be enabled whenever any of the three displays is enabled(this is done by a 3-input OR gate as shown in Figure 8).Retaining the contents of the last display will be done by unblanking it by supplying a low level of voltage to terminal I as shown in Figure 10 b.F.Changing Over Between Time and Distance Fares In the following part, two different methods for changing over between time andistance fares are suggested: The first is to switch to time fare whenever the distance fare is less than the time fare.Hence, a simple look to fares table(Table 2)can show that time fare should be used whenever the taxicab moves with speed less than 50 m/min.A possible circuit that can perform this switching action is shown in Figure IO c.It contains one rpm limit switch and a one inverter as well as two 2-input AND gates.The contacts of the limit switch are normally closed and will be opened whenever the angular speed of the speedometer cablexceeds 50 rmp.The second alternation is to connect the input of the inverter in Figure 10 c.to the output terminal Q of the speedometer circuit, Figure 2.In this case, the switching into time fare will be done whenever the taxicab is at stand still.G.Function of the Rotary Selector Switches The voltage levels that should be supplied by the terminals of the rotary selector switches in order to ensure proper operation by the electronic circuit are given in Table 3.Connection of three rotary selector switches each witb four decks of five poles each, that satisfy the logic function of Table 3, is shown in Figure 10 a.Rotating any of the three switches into fully clockwise direction will pass through five positions.The function of the rotary selector switches can be described starting from the first position passing through variousteps until reaching the final position as follows: Initial position: In this position a low voltage level is applied to terminals I, 2 and 3, this will disconnect the 5 volts supply from the three first displays, set the three inputs of the number of passenger detection circuit CTI to low level.A low voltage level is applied to terminals 8, D and H, this is to ensure that the total income display is disabled.Voltage levels at terminals A, C, G and S are at no care condition.Step I: Rotating any of the rotary selector switches one step toward clockwise direction will supply 5 volts to the corresponding display, provides a high level voltage at terminals 1, 2 or 3 indicating that one passenger have entered the taxicab.A high level voltage should be applied to terminals A, C or G in order to ensure that the corresponding display is still blanked.Other terminals B, D, H and S are kept unchanged.Step 2: Rotating the rotary selector switch one step further, will change the state of voltages at terminal A, C or G to be at low level and unblanks the corresponding display.States of voltages at terminals I, 2, 3 and S are remained unchanged.Terminals B, D and H should be remained at low level to ensure that the corresponding readout is cleared to zero while unblanking the display.