景区外文翻译现状实证调查和研究
摘 要：普陀山作为我国5A级旅游景区以及中国佛教四大名山之一，吸引着国内外游客和佛教团体前来交流参访。目前，普陀山虽然具备了英、日、韩3种语言翻译，但依旧存在翻译不规范、不全面的问题。本文以分析现状为主要导向，以功能对等理论为理论框架，笔者实地考察分析普陀山外语普及情况，重点就英语翻译存在的问题提出规范化建议。
关键词：外文翻译;功能对等;普陀山
景区外文翻译不仅是外籍游客了解景区的工具，更是回顾历史、弘扬中国文化的重要窗口。普陀山作为我国5A级风景名胜区以及中国佛教四大名山之一，宗教文化底蕴深厚，历年来举办的大型南海观音文化节，吸引着各国游客和佛教团体前来交流参访。目前，普陀山虽然具备了英、日、韩三种语言翻译，但依旧存在翻译缺失和不规范的问题。我国学者对此做了不少有价值的研究，其研究手段以翻译学理论为基础，一般分为两类。第一类如赵平和吴彬(2007)、曾景婷(2009)等对旅游景点公示语翻译错误分析及翻译技巧探讨;第二类如陈刚(2002)、田文菡和张枫(2010)等对翻译质量的提高对促进城市形象的跨文化传播意义的研究[1-4]。
本文以分析现状为主要导向，以功能对等理论为理论框架，实地考察分析普陀山外语普及情况，重点就英语翻译存在的问题提出针对性地规范化建议，以期推动景区高质量、高水平的旅游翻译服务发展，提高普陀山景区在传播中华文明、扩大中华文化的影响力。
一、功能对等理论
奈达理论的核心概念是“功能对等”，是我国引进较早的理论之一，是一种比较客观的等效翻译理论。所谓“功能对等”，就是说翻译时不求文字表面的死板对应，而要在两种语言间达成功能上的对等。为使源语和目的语之间的转换有一个标准，减少差异。在这一理论中，他指出翻译是用最恰当、自然和对等的语言从语义到文体再现源语的信息。功能对等理论的核心是“译文读者对原文的反应与原文读者对原文的反应应该是一致的”，因而奈达将翻译定义为“从语义到文体在译语中用最近似的自然对等值再现源语的信息”[5]。
为了准确地再现源语文化和消除文化差异，译者可以遵循以下3个步骤。第一，努力创造出既符合原文语义又体现原文文化特色的译作。然而，两种语言代表着两种完全不同的文化，文化可能有类似的因素，但不可能完全对等。因此，完全展现原文文化内涵的完美的翻译作品是不可能存在的，译者只能最大限度地再现源语文化。第二，如果意义和文化不能同时兼顾，译者只有舍弃形式对等，通过在译文中改变原文的形式达到再现原文语义和文化的目的。第三，如果形式的改变仍然不足以表达原文的语义和文化，可以采用“重创”这一翻译技巧来解决文化差异，使源语和目的语达到意义上的对等[6]。
普陀山景区的翻译主要是为境外游客以及佛教团体交流来访服务，在提供便利的基础上使他们了解中国佛教文化，身临其境体会中国文化的独特魅力，实现交际的功能。所以从这个角度来说，“功能对等”理论对旅游景区英语的翻译具有指导意义。
二、功能对等理论视角下普陀山英文翻译文本存在的问题
笔者经过实地考察拍摄，收集文献资料，发现普陀山外文翻译普及情况并不乐观，标识语不足甚至不准确占了较大比例。在这里着重就英文翻译情况通过功能对等理论进行分析，存在以下5个方面的问题。
(一)逐字翻译或以拼音代替翻译的情况
中国大部分景区的译文采用通名意译和专名音译(拼音)的规则，但普陀山情况比较特殊，由于其核心因素是观音佛教文化，景点名的选择通常和佛经传说相关，佛教色彩较浓厚，这种通用的规则不能完全适用。该景区译者为了便捷或是直观的目的直接以拼音代替，结果是景点名仅具有导向作用，丧失了交际功能。虽然可能达到了形式上的统一，却掩盖了原语的文化意义。例如普济寺“Puji Temple”、万佛宝塔“Wanfo Pagoda”、海天佛国石“Haitianfoguo Rock”等。其中普济寺有“普济群灵”之意，整个氛围肃穆端庄，呈示吉祥、顺缘之意;国人很容易地从名称的字面意思上推断出这些景点的内涵，但外国友人不仅无法体会到名称里的风雅和庄严，还理解不了名称背后的奥妙所在。因此，依据功能对等理论中“最大限度地再现源语文化”的翻译策略，可以舍弃形式对等，通过调整形式达到再现原文文化的目的。普济寺的译法建议改为“Temple of Universal Relief”，万佛宝塔为“Pagoda of a Million Bodhisattvas”，海天佛国石为“Rock Inscribed with Chinese Characters ‘Hai Tain Fo Guo’”。
(二)翻譯错误
拼写错误和中式英语较为突出。例如紫竹林“Purple Bamboo Forset”，“Forset”明显是低级失误，应为“Forest”。但“Forest”表示森林，用在此处范围太大，用“Woods”较为合适。其次，“紫竹”对应英文为“Black Bamboo”或“Phyllostachys Nigra”，译者的惯性思维占了上风，套用汉语的表达习惯，直接译为了“Purple Bamboo”。
(三)翻译不统一、不规范
笔者在考察过程中，发现了同一个景点在不同告示牌上没有固定翻译的问题。单单就“普陀山”这个最重要的景区名称来讲，就有“Putuoshan”和“Mount Putuo”两种不同的译法。这两种译法都是正确的，但会给外国友人造成一定的困扰，没有达到功能对等理论中“形式恰当，吸引读者”的标准。除此以外，景点中南天门“Southern Paradise Gate/Nantianmen”、海天佛国崖“Cliff of Buddhist Paradise/Haitianfoguo Cliff”、紫竹林停车场“Parking of Zizhulin/Parking of Purple Bamboo Woods”的译文也存在不统一的问题。
(四)翻译过于呆板，忽视文化内涵
外国友人因文化差异和社会环境的不同，对富含文化背景的译文往往会有理解上的困难，这时译者应该调节信息，增加相应的文化背景解释或注释。为了易于译文的读者更有效地接收信息，译者可选择添加新信息来加强传播效果[7]。
例如，不肯去观音院“Unwilling-to-go Guanyin Mon stery”。据史料记载，唐大中十三年(859年)，日本僧侣慧锷从五台山得观世音圣像回国，船经普陀山洋面搁浅于暗礁之上，他以为菩萨不愿东去，便靠岸留下佛像由当地居民供奉，称为“不肯去观音院”，是为普陀开山供佛之始。根据功能对等理论，对富含文化背景的译文需增加相应的解释。假如在告示牌上能补充院名的由来，能更好地实现交际的功能。同时，其译名也存在问题。“不肯去”意为不愿离开，“Unwilling-to-leave”更恰当;而“Guanyin”用“观音”的英文专有名词“Avalokitevara”更合适;“Monstery”不能拆分为两个单词且拼写有误。所以这个寺院建议译为“Unwilling-to-leave Avalokitevara Monastery”。
(五)翻译缺失
首先，景区内双语或是多语的警示牌甚少。例如“请勿坐栏杆上，造成后果自负”等警示牌只有中文版本。普陀山位于海岛，拥有众多孤峰突兀的风景地貌。若是游客没有注意安全隐患，极易发生事故。其次，笔者还从游客咨询服务中心获悉，景区内没有设置外语导游。随着人工智能的不断发展，国家相关部门倡议各景区大力发展“智慧景区”。App智慧导航和电子讲解是《关于促进智慧旅游发展的指导意见》中重点提及的旅游景区改善措施。外籍游客若是没有外语导游的指引和讲解，只能单纯地游览景点，无法领会普陀山精彩绝伦的佛教文化。如若外国友人在来访交流过程中遇到语言不通、交流困难，再加上潜在的文化差异影响，会降低对普陀山的好感度。普陀山的整体形象和对外开放程度会随之降低。
三、改善普陀山外语翻译的规范性建议
(一)以读者为中心
奈达认为“翻译的主要服务对象是译文读者”“最主要的是比较译文读者和原文读者的反应”。为了使外籍游客更好地理解中国佛教文化，译者应该考虑到中外文化差异、思维方式的不同以及语言结构差异，而不是仅仅拘泥于原文形式的对等。译者可以使用增译法和意译，或是在译名下增加注释，提供更多佛教教义和仪式的背景信息，使译名忠实地表达原文的信息与风格。更好地使目标读者在欣赏和理解译文时所做出的反应与源文本的读者一致。
(二)提高译者自身的素质
译者是外文翻译中最直接的因素，译者文化修养、工作态度直接影响景区外文翻译水平。普陀山景区的译者应掌握较深广的佛教文化知识，同时拥有跨文化交际的意识，在功能对等理论的指导下采用合适的翻译技巧。例如，翻译梵音洞“Fanyin Cave”时，“梵音”指佛、菩萨的声音，因此“梵音洞”可译为“Cave of the Sound of Buddha and Bodhisattva”。寺庙名称通常含有“禅寺”“讲寺”“庵”“苑”等，了解传统佛教建筑通用术语，有助于预防翻译错误。
(三)建设现代化的翻译解说系统
王淑芳等(2004)提出全面研究国外的旅游景区解说系统，从中找出外国人对旅游吸引物的理解习惯，为规范我国的旅游景区解说系统英译作参考与借鉴[8]。由于普陀山景区内缺少App智慧导航，景区可以在研究外国人对旅游吸引物理解习惯的基础上，提高智慧App的开发力度，增加双语甚至是多语电子讲解的显示屏或者通过扫码的线上外语讲解服务，使用便携式可选择语音导游播放器。
(四)景区管理部门加大监管力度
旅游景区管理部门要重视外文翻译，设立相关部门进行管理、检查和维护;为了提高景区标识语的翻译质量，相关部门应该鼓励公示语翻译专家、高校外国语学院师生参与景区翻译，对不规范的译文进行重译，最重要的是根据国际游客的反馈来修改译文。对译文的评估和维护程序是基于译者对目标游客的假设，无论这些假设多么合理，都不能完全排除外语文本存在缺陷的情况。为了从国际游客那里得到反馈，建议管理部门设计问卷调查等形式采集游客的意见和建议。
四、结语
随着我国对外交流开放，境外游客人数稳步增加，外文翻译和外语导游服务在此背景下显得尤为重要。普陀山有特定的佛教文化背景，景区内的译文应基于功能对等理论，考虑释义的目的和目标读者，尽量准确地再现源语文化和消除文化差异，使译文和原文在功能上达到最大限度地对等，从而引起游客的“相似反应”。本文着重分析了英语翻译存在的问题，从4个方面针对性地提出规范化建议，以推动普陀山景区高质量、高水平的旅游翻译服务发展，推动景区智慧化发展。
参考文献
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作者：王艺臻 吴佳怡 袁秀凤
河北工程大学土木工程学院
毕业设计外文资料翻译
专
业 学
生 指导教师
河北工程大学土木工程学院
2014年6月4号
未来个人运输在世界大城市中的发展
Schafer, Jacoby, Heywood and Waitz(2009)研究认为一个人平均每天花大约70分钟的时间使用交通工具。这个时间预算在过去各个国家中是相对稳定的。所以，富有的人开始倾向于跑的更快，跑的更远。
而在不久的将来，全世界将会全面提高机动车的机动性。例如：Schafer and Victor (2000)推测，预计到2050年世界公民行驶的整体平均路程将比欧洲在1990年跑的整体平均路程多。从2000年到2050年，美国的平均机动性将提高2.6倍，达到每年58000千米。Schafer and Victor (2000)还预估，到2050年印度的平均机动性将增加到每年6000千米，达到了欧洲1970年早期的水平。总的来说，人们在2000年能行驶230亿公里，到了2050年，有望增加到1050亿公里。
与此同时，城市人口正持续增大。根据World Bank(2002)研究，拥有1000多万居民的大城市的数量有望在下一代翻倍。随着城市的扩大和富裕，车辆所有制以及其使用会快速增加，相反，这将影响车辆的行速，加大道路拥挤和空气污染。
上述趋势使得人们对大城市可持续发展交通展开了广泛地讨论。从广义上讲，城市交通的可持续运动涉及到可操作性以及通过公平高效手段产生的财富问题，同时还要维护身体健康，将自然资源消耗和放射性污染减到最低。通常，广泛使用公共交通和快速轨道交通是可行的。例如：像东京，香港这样的大城市，它们在私人车流行前就投资建设公共交通，以提供广泛的，优质的公共交通系统。在这些城市，直到快速轨道交通的建立，公交远行还一直处于高水平阶段。
然而，个人交通工具已成为现代城市生活的一部分。不管是作为独有的、分享的还是用于飞行的交通工具，它们都给个人和社会带来了很大的便利。因此，Kennedy et al. (2005)指出，对于城市的可持续发展来说，为新一代可持续个人交通工具做规划是至关重要的。同时技术创新和工业生态学观念的应用，让可持续个人交通工具成为了可能。
另外，许多应用智能型运输系统将充分影响未来城市交通运输。这些应用程序包括需求管理(需求感应公共交通、汽车共乘共享、通路管制以及道路使用要求)、 旅行计划系统/实时旅游者信息、公共交通信号优先系统。
为了研究大城市中个人交通运输目前及将来的状况，本文选取了世界15大都市，根据地理位置划分可如下所示：
北美洲：芝加哥、纽约 欧洲：伦敦、莫斯科、巴黎 中美洲、南美洲：布宜诺斯艾利斯(阿根廷首都)、墨西哥城、里约热内卢、圣保罗 印度：班加罗尔、加尔各答、新德里、孟买 中国：香港、上海
对于各个大城市来说，一系列影响未来交通的关键指标是已检定的。主要包括人口和财富、私人电动客运车辆、公共交通模式操作、运具选择、旅行速度模式、交通事故。以人口和财富为列，因为人口的大小以及人群的富有程度起到至关重要的作用，因此对选定大城市的人口预期增长和大城市所在国的人均财富预期增长作出相应比较。
结果显示，从2005年到2025年预计出现人口增长最高比例(超过预期30%)的地区有班加罗尔、加尔各答、新德里、孟买和上海，其次为适度增加12%-18%的芝加哥、香港、墨西哥城、、里约热内卢和圣保罗，增长最慢的(低于12%)主要有布宜诺斯艾利斯、伦敦、莫斯科、纽约和巴黎。总体上说，人口增长最快的现象将出现在印度和中国。而从2010年到2014年，预计收入增长最快的是中国，接着是印度、俄罗斯、墨西哥、香港、巴西、英国、阿根廷、法国和美国。
然后，对选定大城市的计划策略进行分析，这些大城市主要有：纽约、伦敦、圣保罗、孟买和上海。同时，目前的结论不需完整描述一个策略。例如：在国家、地区和地方上，城市交通规划会涉及很多政府的结构，并且每个层次都有它自己的策略。所以，策略分析的主要目的是突出已定大城市在未来10到20年内的主要目标、实施重点以及措施计划。其关注点是计划出行方式即该策略如何预想私人车辆、公共车辆以及非机动车辆在未来的作用。
以纽约为列，区域交通规划的目标是从2030年开始，满足城市和地区的交通需求，并提高行驶速度。这个计划策略包括改善交通网络，通过更好的道路管理和拥挤定价来减少交通堵塞。具体措施如下：1)提高关键拥堵路线的承载力2)提供新通勤火车进入曼哈顿3)增加到稠密地区的交通4)改善、增加公共汽车服务5)改善当地通勤火车的服务。
另外，纽约近期推出了自己的战略计划。主要目标包括：例如城市交通事故减少50%;实施快速公交线路措施，以提高全市汽车的行速;到2015年使自行车通行翻一倍;启动全市停车政策来管理空间，以此减少巡航和拥堵;采用完整街道设计模版为重建项目;提供更好的街道面等。
最后，对选定城市的未来运输方式进行了讨论。主要包括个人车辆人均所有权、在城市内部个人车辆行驶的人均距离、用于通勤的个人车辆行驶的人均距离、用于休闲旅游的个人车辆行驶的人均距离、道路死亡人均数量、新的机动网络。 基于上述研究，我们预测到2025年各大城市都或多或少会有些改变，主要改变有个人交通工具的所有权、由个人交通工具内在核心决定的人均距离、道路死亡人均数量等。这预测主要包括以下几方面：
1) 个人车辆所有权大幅增加的现象将出现在印度的四大城市和上海 2) 在任何大城市中，使用内核个人交通工具的数量将不会增加 3) 预计用于通勤的个人交通工具的使用也将不会增加
4) 用于休闲旅行的个人交通工具数量将增加(并且交通事故增长最快的)， 这种现象主要出现在上海，其次是印度的四大城市，里约热内卢和圣保罗
总的来说，在未来的15年内，可以预见到在选定大城市的各个地方不会出现大幅度降低对个人交通工具依赖的现象。相反，我们预计在印度、中国、巴西的大城市中，个人交通工具的作用将会不断上升。
上述趋势的出现是由于我们视不同的交通运输方式为独立唯一的选择。然而，越来越多的实施和新机动网络正处于使用中，即综合网络——提供多链接，高技术，门到门的交通运输方式选择。虽然，这些网络有望减少人们对个人交通运输的依赖度，但这种特性的大小和影响仍有待确定。
The Future of Personal Transportation in Megacities of The World On average, a person spends about 70 minutes per day traveling (Schafer, Jacoby, Heywood, and Waitz, 2009). This time budget is relatively constant over time and across countries. Consequently, wealthy people tend to travel faster and over longer distances. In the future there will be an overall increase in mobility throughout the world. For example, Schafer and Victor (2000) projected that by 2050 the average citizen of the world will travel (by all modes) as much overall distance as the average Western European did in 1990. From 2000 to 2050, the mobility of the average American will increase by a factor of 2.6, to 58,000 km/year. Schafer and Victor (2000) forecast that the average Indian will increase his/her travel to 6,000 km/year by 2050, comparable to the level of West Europeans in the early 1970s.In total, in 2000, people traveled 23 billion km, and by 2050 that figure is expected to grow to 105 billion km (Schafer and Victor, 2000). At the same time, urban population continues to expand, and the number of megacities—cities with over 10 million inhabitants—is expected to double within a generation (World Bank, 2002). As cities grow and become richer, vehicle ownership and use tend to increase rapidly. This, in turn, has an influence on travel speed, congestion, and air pollution. The above trends have resulted in wide discussion about sustainable transportation in metropolitan areas. In broad terms, movement to sustainable urban transportation involves accessibility and the generation of wealth by cost-effective and equitable means, while safeguarding health and minimizing the consumption of natural resources and the emission of pollutants (Kennedy, Miller, Shalaby, Maclean, and Coleman, 2005). Frequently, this has been feasible with wide use of public transportation in general, and rapid rail transportation in particular. For example, there are cities such as Tokyo and Hong Kong that invested in public transport to provide extensive, high-quality, public transport systems before private vehicle ownership was high (Barter, Kenworthy, and Laube, 2003). In these cities, bus travel was at a high level until rapid mass transit was built and became affordable. However, personal vehicles are an integral part of modern city life, providing a number of benefits to individuals and society no matter how they are used—as single occupancy vehicles or as shared or shuttle vehicles. Consequently, as pointed out by Kennedy et al. (2005), planning for a new generation of sustainable personal vehicles is critical for the sustainable development of cities. Through technical innovation and the application of concepts of industrial ecology, there are several possible candidates for the sustainable personal vehicles of the future (Kennedy et al., 2005). In addition, it is likely that many applications of intelligent transportation systems will substantially affect future urban transportation. These applications include, for example, demand management (demand-responsive public transportation, car pooling and sharing, access control, road-use charging), trip planning systems/real-time traveler information, and signal priorities for public transport. To study current and future personal transportation in megacities, 15 metropolitan areas worldwide were selected. The selected metropolitan areas were classified by region as follows: North America: Chicago, New York Europe: London, Moscow, Paris Central and South America: Buenos Aires, Mexico City, Rio de Janeiro, Sao Paulo India: Bangalore, Calcutta, Delhi, Mumbai China: Hong Kong, Shanghai For each metropolitan area, a set of key indicators affecting future transportation was examined. It includes population and health, Private motorized passenger vehicles, Public transportation modes operated, Modal split, Travel speed by mode, Road fatalities. As population and wealth, Size of the population and wealth of the population play vital roles. Consequently, Figure 1 and Table 1 present the expected growth in population of the examined megacities, and Table 2 presents the expected growth in wealth per capita for the countries in which the megacities are located. The results indicate that the highest proportional increases from 2005 to 2025 (more than0%) is predicted for Bangalore, Calcutta, Delhi, Mumbai, and Shanghai, followed by modest increases (12-18%) for Chicago, Hong Kong, Mexico City, Rio de Janeiro, and São Paulo. The lowest increases (less than 12%) are predicted for Buenos Aires, London, Moscow, New York, and Paris. Overall, the highest increase of population will take place in the examined Indian and Chinese metropolitan areas.Table 2 indicates that the highest increase of incomes from 2010 to 2014 is expected for China, followed by India, Russia, Mexico, Hong Kong, Brazil, United Kingdom, Argentina, France, and the United States. Then the chapter studies the Selected urban transportation plans and strategies. The cities involve New York, London, Sao Paulo, Mumbai, Shanghai. Meanwhile, The presented summaries do not necessarily convey a complete description of the strategies. For example, the urban transportation plans of large metropolitan areas typically involve many government structures at national, regional, and local levels (see e.g., Urban Age, 2009), and each level can have its own strategy. Consequently, the presented summaries are designed to highlight the main objectives, focuses, and measures planned by the selected metropolitan areas for the next 10 to 20 years. The emphasis is on the planned modal split (i.e., how the strategies envision the future role of private vehicles, public transportation, and nonmotorized transportation. As New York, the goal of the regional transportation plan (PLANYC, 2007) is to meet the city’s and region’s transportation needs through 2030 and beyond, and to improve travel speed. The plan includes strategies to improve the transit network and reduce growing gridlock on the roads through better road management and congestion pricing. The specific initiatives include the following: (1) to increase the capacity on key congested routes, (2) to provide new commuter rail access to Manhattan, (3) to expand transit access to underserved areas, (4) to improve and expand bus service, and (5) to improve local commuter rail service. In addition, New York City has recently introduced its own strategic plan (NYCDOT, 2008). Its major goals include, for example cutting city traffic fatalities by 50% from the 2007 levels, implementing bus rapid transit lines and measures to increase bus speeds city-wide, doubling bicycle commuting by 2015, initiating city-wide parking policies to manage curb space to reduce cruising and congestion, adopting complete-street design templates for reconstruction projects, launching a Main Street Initiative to develop people-friendly boulevards in key corridors across the city, and delivering better street surfaces. At last, we discuss the future transportation in the examined metropolitan areas. It includes Personal vehicle ownership per capita, Distance driven by personal vehicles per capita within cities’ inner core, Distance driven by personal vehicles per capita for commuting, Distance driven by personal vehicles per capita for leisure trips, Number of road fatalities per capita, New mobility networks. Based on the analysis, projections through 2025 were made for each megacity for changes in ownership of personal vehicles; distance traveled per capita by personal vehicle within inner core, for commuting, and for leisure; and for number of road fatalities per capita. The forecasts include the following: • The largest increases in personal vehicle ownership will occur in the four Indian megacities and Shanghai. • There will be no increase in the use of personal vehicles for inner-core transportation in any of the megacities. • No increases are expected in the use of personal vehicles for commuting.
• The largest increases in the use of personal vehicles for leisure traveling (and the largest increases in road fatalities) will take place in Shanghai, followed by the four megacities in India, Rio de Janeiro, and São Paulo. Overall, no substantial decrease in the reliance on personal vehicles is foreseen in the next 15 years anywhere in the examined megacities. To the contrary, an increased role of personal vehicles is forecasted for the megacities in India, China, and Brazil. The above trends are based on treating the different transportation modes as independent and exclusive options. However, there is growing implementation and use of new mobility networks—integrated networks that provide a variety of connected and IT-enhanced transportation options door-to-door. Although such networks are expected to reduce the reliance on personal vehicles, the magnitude and nature of this effect remain to be ascertained.
交通事故分析的可能性和局限性
S.Oppe 关键字：后果;目的;描述;限制;关注;事故分析;可能性
摘要：交通事故的统计数字，尤其国家一级的数据对监控和预测事故的发展，积极或消极检测事故的发展，以及对定义安全目标和评估工业安全特别有益。事故分析是应用非常有限的分析，是前瞻性分析和回顾性分析，能够对新开发的交通安全系统和特殊过程的安全措施进行评价。目前迫切需要一个将实时事故分析与研究相结合的行为。将自动检测和视频录制相结合的研究交通事故的科研论文会比较容易接受。这种类型的研究最终会对交通理念有个完善的认识。
1.简介
本文主要是基于个人的经验，研究有关交通安全、安全分析以及事故分析等在研究中的作用。由这些经验推导出的哲学思考就像通过研究和统计得出的实践观点。而这些调查数字已经在其他地方发表了。
在缺少直接观察的事故中，许多方法论问题的产生，导致不能直接测试对结果持续讨论。通过看事故视频来讨论是富有成效的。事实证明，用来解释事故的大部分有关信息就是事故中缺少的记录。深入研究还无法回忆起所有的必要的用来测试有关事故发生的假设数据，。尤其是车-车相撞发生的车祸，这是在荷兰城市道路交叉口录制的视频，一辆从岔路驶来的汽车与主干路的汽车相撞，下列问题可以问：为什么汽车来自次干路上，突然加速后又几乎停止，撞上了在左侧主路的一辆汽车呢?为什么没有注意到正在驶来的车?是不是因为两车从右边驶来，司机因为前面的交叉为他们提供了可能性而斤斤计较?难道他向左看过，但他认为停在拐角处的绿色货车能让他停下来?当然，交通状况并不复杂。目前这个事故中没有骑自行车或行人在拥挤路口分散他的注意。如果停着的绿色车能够在五分钟内消失，这两辆车可能就不会相撞。在事故发生的相关条件下，几乎不可能观察下一个交通行为，因为交通事故是不可预见的。由于新的视频设备和自动检测事故设备的不断发展，如在收集数据方面不需要很高的成本就能变得越来越逼真。必要的增加数据类型也能更好的解释交通中存在的危险因素。关于事故分析的可能性和限制性的问题是不容易回答的，我们不能确切的分析交通事故。因为事故分析涵盖了每一个活动中的不同背景，并根据不同的信息来源范围来补充资料，特别是收集事故的数据，背景资料等，我们首先要看看在交通安全领域的活动周期然后再回答事故分析的可能性与限制。这些行为主要是与交通系统的安全管理有关，有些则是相关的研究活动。
应该用下面的步骤来加以区分： ——检测交通安全问题;
——描述问题和它的主要特征; ——分析其原因分析和改进建议; ——选择和执行安全措施; ——评价所采取的措施。
虽然这个周期可以由同一人或一群人做出来，而问题在每个阶段(政治/管理或科学)都有不同的背景。我们用事故分析来描述这一阶段。做这个决定是重要的。很多关于分析结果的方法的讨论由于忽视之间的区别而成为徒劳的。政治家或道路管理人员对道路的个别事故不是很留意。他们对事故的看法往往都是一视同仁，因为总的结果比整个事故中的每个人的因素重要。因此，每次事故看做一个个体，之间相互协调就会达成安全的结果。
研究人员研究事故发生时一连串事件中每个人的兴趣。希望从中得到关于每次事故的详细信息并能发现其发生的原因和有关的条件。政治家们希望只是因为细节决定行动。在最高一级事故总数减少。信息的主要来源是国家数据库及其统计学处理系统。对他来说，统计意外数字及其统计的波动来进行事故分析。这适用于事故分析中的交通安全领域。因此，我们将首先描述了事故的这些方面。 2.事故的性质和它们的统计特性
事故基本概念是意外，不管是其发生的原因还是引起事故出现的过程。两个简单的假设通常是来描述交通事故的形成过程：
-事故发生的概率与以往发生的事故之间是独立; -事故发生在时间上是同性质的
如果这两个假设成立，那么事故是泊松分布。第一个假设与大多数的批判不符。事故是罕见的事件，因此不会受到以前事故的影响。在某些情况下，有一个直接的因果链(例如，大量的车开到一起)这一系列的事故被认为是一个个体事故但包含许多的车。这个假设并不适用于统计人员伤亡。伤亡人数往往与同一事故有关，因此，独立性假设不成立。第二个假设乍一看似乎不太容易理解。穿越空间或在不同地点发生的的事故同样具有可能性。然而，假设需要很长一段时间并且没有缓缴期。其性质是根据理论的假设。如果其短时间内能成立，那么它也适用于长时间，因为泊松分布变量的总和，即使他们的泊松率是不同的，但也属于泊松分布。对于这些时期的总和泊松率则等于为这些地方的泊松率的总和。假设与一个真正的情况相比较计数，无论是从一两个结果还是总情况来看都有一个基本情况比较符合。
例如，对比在一年中特定的一天例如下一天，下一个星期的一天发生的交通事故。如果条件是相同的(同一时间，交通情况相同，同样的天气条件等)，那么由此产生的意外数字是相同的泊松过程的结果。这一假设可以通过估算进行测试的两个观测值的基础上(估计是两个值的平均值)的速度参数。概率理论能够
考虑到这两个观察值的平均，用于计算的平等假设的可能性。这是一个相当强大的统计过程。泊松假设是研究了很多次，来获得证据支持。它已经应用于许多情况，数的差异表明在安全性的差异然后确定是否发生意外。这一程序的主要目的是检测在安全分歧。这可能是一个时间上的差异，或不同的地方或不同的条件。这种差异可以指导改进的过程。由于主要关注的是，以减少意外的发生，这种分析可能导致对治疗中最有前途的领域。为这样一个测试应用程序的必要条件是，那意外的数字进行比较是大到足以证明存在的分歧。在许多地方情况下，一个应用程序是不可能的。事故黑点分析往往阻碍了这一限制，例如，如果应用这种测试，找出事故是否在特定的位置数是高于平均水平。该程序的描述，也可以使用，如果发生意外乃根据数的特点找到有前途的安全目标。不仅聚集，而且还与分类泊松假设成立，而意外数字可以相互测试的泊松假设的基础。这种测试是相当麻烦的，因为每个特定的情况下，每一个不同的泊松参数，即，对所有可能结果的概率必须计算应用测试。然后，泊松分布近似为正态分布，均值和方差等于泊松参数。一旦均值和方差的正态分布，给出了所有的测试可以改写了标准零均值和
方差的正态分布条件。没有任何更多的必要计算，但测试统计，需要利用表绘制。3. 行车安全政策事故统计的应用
分析那些假设的基础上描述的测试程序的类型及其优点。这种应用最好的例子是为一个国家或地区进行超过一年的安全监测，用事故的总体数据(最终的特定类型，如死亡事故)与前几年的数据相比较。根据数年的事故序列，能够分析出它的发展趋势，并大致预测以后几年的事故数量。一旦建立了这样一种趋势，那么在误差范围内未来一年或几年都可以预见。从一个给定趋势的偏差也可以进行预测新的事件。最有名的是斯米德在1949年进行的分析。我们将讨论这个事故类型分析更详细的内容。
1、该测试应用推广到高阶分类。Foldvary和Lane(1974)，在衡量强制佩戴安全带的效果，谁是最早应用于值的4路表高阶相互作用的总卡方分配的。
2、测试不局限于总体影响，但卡方值就可以分解模型内子假说。另外，在双向表，卡方总可以分解成零件表互动的作用。对1的优势。和2。比以前的情况是，这对许多相互关联的(子)表和相应的智广场卡方检验是由大量分析，取而代之的是一个一卡方的确切划分。
3、投入更多关注的是参数估计。例如，在卡方分割使人们有可能以测试有关行参数的线性或二次限制或趋势的不连续性。
4、分析的单位是从数到广义加权计数。这对于道路安全分析，那里一段时间，道路使用者的数量，地点或公里数的车辆往往是必要的修正有利。最后一个选项是没有发现在许多统计软件包。安徒生1977年给出了一个用于道路双向安全分析表的例子。工资保障运动的一个计算机程序。这一级没有说明事故原因分
析。它会尝试检测安全问题需要特别注意。所需的基本信息包括事故数字，来形容不安全总额，暴露的数据来计算风险，并找到一个高风险的情况下或(团体)道路使用者。
4. 事故分析研究目的
交通安全的研究是有关的事故及其后果的发生。因此，人们可能会说，研究对象是意外。然而研究人员的兴趣较少集中在这个最后的结果本身，而是多在进程更多的结果(或不结果)的事故。因此，最好是把作为他的研究对象，在流量的重要事件。一个在交通意外的过程，结果是，该实际发生是由研究者未落观测研究的主要问题。
调查一宗交通意外，他将努力重建了间接来源的事件，如涉及的道路使用者，所提供的资料或目击者有关情况，车辆，道路和司机的特点。因此这不是科学独特的，也有一个间接的研究对象的研究更多的例子。但是，第二个困难是，该研究的对象不能被诱发。有系统的控制实验手段研究只对问题方面的可能，而不是问题本身。
间接观察和缺乏系统的控制组合使调查人员很难发现在什么情况下造成事故的因素。虽然研究人员主要是在事故处理领导有兴趣，他几乎完全信息的后果，它的产品，意外。此外，事故背景是复杂的。一般来说，可分为以下几个方面：
-考虑到交通系统，交通量和组成国家，道路使用者，他们的速度，天气条件下，路面情况，车辆，道路使用者和他们的相互作用的演习，意外可以或无法预防。
-由于发生事故，也对这样的速度和车辆质量的因素，大量的不同，碰撞角度，对道路使用者和他们的脆弱性，影响等位置的保护，伤害是严重或或多或少物质损失是多还是少可观。虽然这些方面不能独立研究从理论的角度看，它也从由此产生的结果的优势，区分交通情况有潜在危险的数字，是由有一个意外的可能性，在这种潜在的危险局势，给定一个特定事故。
这个概念框架是对风险的关于个别道路使用者，以及上级的决定控制器的决定制定的一般基础。在风险的数学公式，我们需要一个明确的概率空间的介绍，基本事件(的情况)，可能导致事故组成，每个类型的事件的概率，最终收在一次事故中，最后的具体成果，损失，鉴于事故的类型。
另一种方法是看事故特征组合，然后找出关键因素。这种类型的事故分析是通过分析事故的共组或子群来开展。事故本身是一个研究的单位，但也要研究道路因素：道路位置，道路设计(如一个弯道)等。
原文出处：SWOV institute for road safety research Leidschendam(会议记录)，记录者，S.Oppe.
POSSIBILITIES AND LIMITATIONS OF ACCIDENT
ANALYSIS
S.Oppe Keyword：Consequences; purposes; describe; Limitations; concerned; Accident Analysis; possibilities Abstraet：Accident statistics, especially collected at a national level are particularly useful for the description, monitoring and prognosis of accident developments, the detection of positive and negative safety developments, the definition of safety targets and the (product) evaluation of long term and large scale safety measures. The application of accident analysis is strongly limited for problem analysis, prospective and retrospective safety analysis on newly developed traffic systems or safety measures, as well as for (process) evaluation of special short term and small scale safety measures. There is an urgent need for the analysis of accidents in real time, in combination with background behavioural research. Automatic incident detection, combined with video recording of accidents may soon result in financially acceptable research. This type of research may eventually lead to a better understanding of the concept of risk in traffic and to well-established theories. 1. Introduction. This paper is primarily based on personal experience concerning traffic safety, safety research and the role of accidents analysis in this research. These experiences resulted in rather philosophical opinions as well as more practical viewpoints on research methodology and statistical analysis. A number of these findings are published already elsewhere. From this lack of direct observation of accidents, a number of methodological problems arise, leading to continuous discussions about the interpretation of findings that cannot be tested directly. For a fruitful discussion of these methodological problems it is very informative to look at a real accident on video. It then turns out that most of the relevant information used to explain the accident will be missing in the accident record. In-depth studies also cannot recollect all the data that is necessary in order to test hypotheses about the occurrence of the accident.For a particular car-car accident, that was recorded on video at an urban intersection in the Netherlands, between a car coming from a minor road, colliding with a car on the major road, the following questions could be asked:Why did the driver of the car coming from the minor road, suddenly accelerate after coming almost to a stop and hit the side of the car from the left at the main road? Why was the approaching car not noticed? Was it because the driver was preoccupied with the two cars coming from the right and the gap before them that offered him the possibility to cross? Did he look left before, but was his view possibly blocked by the green van parked at the corner? Certainly the traffic situation was not complicated. At the moment of the accident there were no
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bicyclists or pedestrians present to distract his attention at the regularly overcrowded intersection. The parked green van disappeared within five minutes, the two other cars that may have been important left without a trace. It is hardly possible to observe traffic behaviour under the most relevant condition of an accident occurring, because accidents are very rare events, given the large number of trips. Given the new video equipment and the recent developments in automatic incident and accident detection, it becomes more and more realistic to collect such data at not too high costs. Additional to this type of data that is most essential for a good understanding of the risk increasing factors in traffic, it also important to look at normal traffic behaviour as a reference base. The question about the possibilities and limitations of accident analysis is not lightly answered. We cannot speak unambiguously about accident analysis. Accident analysis covers a whole range of activities, each originating from a different background and based on different sources of information: national data banks, additional information from other sources, specially collected accident data, behavioural background data etc. To answer the question about the possibilities and limitations, we first have to look at the cycle of activities in the area of traffic safety. Some of these activities are mainly concerned with the safety management of the traffic system, some others are primarily research activities. The following steps should be distinguished:description of the problem and its main characteristics;selection and implementation of safety measures;the probability of an accident to occur is independent from the occurrence of previous accidents; -the occurrence of accidents is homogeneous in time. If these two assumptions hold, then accidents are Poisson distributed. The first assumption does not meet much criticism. Accidents are rare events and therefore not easily influenced by previous accidents. In some cases where there is a direct causal chain (e.g. , when a number of cars run into each other) the series of accidents may be regarded as one complicated accident with many cars involved.The assumption does not apply to casualties. Casualties are often related to the same accident and therefore the independency assumption does not hold. The second assumption seems less obvious at first sight. The occurrence of accidents through time or on different locations are not equally likely. However, the assumption need not hold over long time periods. It is a rather theoretical assumption in its nature. If it holds for short periods of time, then it also holds for long periods, because the sum of Poisson distributed variables, even if their Poisson rates are different, is also Poisson distributed. The Poisson rate for the sum of these periods is then equal to the sum of the Poisson rates for these parts. The assumption that really counts for a comparison of (composite) situations, is whether two outcomes from an aggregation of situations in time and/or space, have a comparable mix of basic situations. E.g. , the comparison of the number of accidents on one particular day of the year, as compared to another day (the next day, or the same day of the next week etc.). If the conditions are assumed to be the same (same duration, same mix of traffic and situations, same weather conditions etc.) then the resulting numbers of accidents are the outcomes of the same Poisson process. This assumption can be tested by estimating the rate parameter on the basis of the two observed values (the estimate being the average of the two values). Probability theory can be used to compute the likelihood of the equality assumption, given the two observations and their mean. This statistical procedure is rather powerful. The Poisson assumption is investigated many times and turns out to be supported by a vast body of empirical evidence. It has been applied in numerous situations to find out whether differences in observed numbers of accidents suggest real differences in safety. The main purpose of this procedure is to detect differences in safety. This may be a difference over time, or between different places or between different conditions. Such differences may guide the process of improvement. Because the main concern is to reduce the
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number of accidents, such an analysis may lead to the most promising areas for treatment. A necessary condition for the application of such a test is, that the numbers of accidents to be compared are large enough to show existing differences. In many local cases an application is not possible. Accident black-spot analysis is often hindered by this limitation, e.g., if such a test is applied to find out whether the number of accidents at a particular location is higher than average. The procedure described can also be used if the accidents are classified according to a number of characteristics to find promising safety targets. Not only with aggregation, but also with disaggregation the Poisson assumption holds, and the accident numbers can be tested against each other on the basis of the Poisson assumptions. Such a test is rather cumbersome, because for each particular case, i.e. for each different Poisson parameter, the probabilities for all possible outcomes must be computed to apply the test. In practice, this is not necessary when the numbers are large. Then the Poisson distribution can be approximated by a Normal distribution, with mean and variance equal to the Poisson parameter. Once the mean value and the variance of a Normal distribution are given, all tests can be rephrased in terms of the standard Normal distribution with zero mean and variance one. No computations are necessary any more, but test statistics can be drawn from tables. 3. The use of accident statistics for traffic safety policy. The testing procedure described has its merits for those types of analysis that are based on the assumptions mentioned. The best example of such an application is the monitoring of safety for a country or region over a year, using the total number of accidents (eventually of a particular type, such as fatal accidents), in order to compare this number with the outcome of the year before. If sequences of accidents are given over several years, then trends in the developments can be detected and accident numbers predicted for following years. Once such a trend is established, then the value for the next year or years can be predicted, together with its error bounds. Deviations from a given trend can also be tested afterwards, and new actions planned. The most famous one is carried out by Smeed 1949. We will discuss this type of accident analysis in more detail later. 1. The application of the Chi-square test for interaction is generalised to higher order classifications. Foldvary and Lane (1974), in measuring the effect of compulsory wearing of seat belts, were among the first who applied the partitioning of the total Chi-square in values for the higher order interactions of four-way tables.
2. Tests are not restricted to overall effects, but Chi-square values can be decomposed regarding sub-hypotheses within the model. Also in the two-way table, the total Chisquare can be decomposed into interaction effects of part tables. The advantage of 1. and 2. over previous situations is, that large numbers of Chi-square tests on many interrelated (sub)tables and
corresponding Chi-squares were replaced by one analysis with an exact portioning of one Chi-square. 3. More attention is put to parameter estimation. E.g., the partitioning of the Chi-square made it possible to test for linear or quadratic restraints on the row-parameters or for discontinuities in trends. 4. The unit of analysis is generalised from counts to weighted counts. This is especially advantageous for road safety analyses, where corrections for period of time, number of road users, number of locations or number of vehicle kilometres is often necessary. The last option is not found in many statistical packages. Andersen 1977 gives an example for road safety analysis in a two-way table. A computer programme WPM, developed for this type of analysis of multi-way tables, is available at SWOV (see: De Leeuw and Oppe 1976). The accident analysis at this level is not explanatory. It tries to detect safety problems that need special attention. The basic information needed consists of accident numbers, to describe the total amount of unsafety, and exposure data to calculate risks and to find situations or (groups of) road users with a high level of risk. 4. Accident analysis for research purposes. Traffic safety research is concerned with the occurrence of accidents and their consequences. Therefore, one might say that the object of research is the accident. The researchers interest however is less focused at this final outcome itself, but much more at the process that results (or does not result) in accidents. Therefore, it is better to regard the critical event in traffic as his object of study. One of the major problems in the study of the traffic process that results in accidents is, that the actual occurrence is hardly ever observed by the researcher. Investigating a traffic accident, he will try to reconstruct the event from indirect sources such as the information given by the road users involved, or by eye-witnesses, about the circumstances, the characteristics of the vehicles, the road and the drivers. As such this is not unique in science, there are more examples of an indirect study of the object of research. However, a second difficulty is, that the object of research cannot be evoked. Systematic research by means of controlled experiments is only possible for aspects of the problem, not for the problem itself. The combination of indirect observation and lack of systematic control make it very difficult for the investigator to detect which factors, under what circumstances cause an accident. Although the researcher is primarily interested in the process leading to accidents, he has almost exclusively information about the consequences, the product of it, the accident. Furthermore, the context of accidents is complicated. Generally speaking, the following aspects can be distinguished: Given an accident, also depending on a large number of factors, such as the speed and mass of vehicles, the collision angle, the protection of road users and their vulnerability, the location of impact etc., injuries are more or less severe or the material damage is more or less substantial. Although these aspects cannot be studied independently, from a theoretical point of view it has advantages to distinguish the number of situations in traffic that are potentially dangerous, from the probability of having an accident given such a potentially dangerous situation and also from the resulting outcome, given a particular accident.
This conceptual framework is the general basis for the formulation of risk regarding the decisions of individual road users as well as the decisions of controllers at higher levels. In the mathematical formulation of risk we need an explicit description of our probability space, consisting of the elementary events (the situations) that may result in accidents, the probability for each type of event to end up in an accident, and finally the particular outcome, the loss, given that type of accident.
A different approach is to look at combinations of accident characteristics, to find critical factors. This type of analysis may be carried out at the total group of accidents or at subgroups. The accident itself may be the unit of research, but also a road, a road location, a road design (e.g. a roundabout) etc.
数字通信第四版
Digital Communications,Fourth Edition
作者：John Proakis 起止页码：1-10
出版日期(期刊号)：2003年1月 出版单位：电子工业出版社
外文翻译译文：
第1章 引 言
在本书中,我们将介绍作为数字通信系统分析和设计基础的基本原理。数字通信的研究主题包括数字形式的信息从产生该信息的信源到一个或多个目的地的传输问题。在通信系统的分析和设计中，特别重要的是信息传输所通过的物理信道的特征。信道的特征-般会影响通信系统基本组成部分的设计。下面阐述一个通信系统的基本组成部分及其功能。
1.1数字通信系统的基本组成部分
图1-1-1 显示了一个数字通信系统的功能性框图和基本组成部分。输出的可以是模拟信号，如音频或视频信号;也可以是数字信号，如电传机的输出，该信号在时间上是离散的，并且只有有限个输出字符。在数字通信系统屮，由信源产生的消息变换成二进制数字序列。理论上，应当用尽可能少的二进制数字表示信源输出(消息)。换句话说.我们要寻求一种信源输出的有效的表示方法,使其很少产生或不产生冗余。将模拟或数宇信源的输出有效地变换成二进制数字序列的处理过程称为信源编码或数据压缩。
由信源编码器输出的二进制数字序列称为信息序列，它被传送到信道编码器。信道编码器的目的是在二进制信息序列中以受控的方式引人一些冗余，以便于在接收机中用来克服信号在信道中传输时所遭受的噪声和干扰的影响。因此，所增加的冗余是用来提高接收数据的可靠性以及改善接收信号的逼真度的。实际上，信息序列中的冗余有助于接收机译出期望的信息序列。例如,二进制信息序列的一种(平凡的)形式的编码就是将每个二进制数字简单重复m次.这里m为一个正整数。更复杂的(不平凡的)编码涉及到一次取k个信息比特,并将毎个k比特序列映射成惟一的n比特序列，该序列称为码字。以这种方式对数据编码所引人的冗余度的大小是由比率n/k作来度擞的。该比率的倒数，即k/n，称为码的速率或简称码率。信道编码器输出的二进制序列送至数宇调制器，它是通信信道的接口。因为在实际中遇到的几乎所有的通信信道都能够传输电信号(波形),所以数字调制的主要目的是将二进制信息序列映射成信号波形。为了详细说明这一点，假定已编码的信息序列以均匀速率R(b/s)―次一个比特传输,数字调制器可以简单地将二进制数字“0”映射成波形s0(t)而二进制数字“1”映射成波形s1(t)。在这种方式中，信道编码器输出的毎一比特是分别传输的。我们把它称为二进制调制。另一种方式，调制器目一次传输b个已编码的信息比特，其方法是采用M = 2s个不同的波形ST(t)i=1,2，…，M,每一个波形用来传输2s个可能的b比特序列中的一个序列。我们称这种方式为M元调制(M〉2)。注意，每b/R秒就有一个新的b比特序列进入调制器。因此，当信道比特率R固定,与一个b比特序列相应的似个波形之一的传输时间量是二进制调制系统时间周期的b倍。
图1-1-1
数字通信系统的基本模型
通信信道是用来将发送机的信号发送给接收机的物理媒质。在无线传输中，信道可以是大气(自由空间)另一方面，电话信道通常使用各种各样的物理媒质，包括有线线路、光缆和无线(微波)等。无论用什么物理媒质来传输信息，其基本特点是发送信号随机地受到各种可能机理的恶化，例如由电子器件产生的加性热噪声、人为噪声(如汽车点火噪声)及大气噪声(如在雷赛雨时的闪电)。
在数字逋信系统的接收端,数字解调器对受到信道恶化的发送波形进行处理，并将该波形还原成一个数的序列，该序列表示发送数据符号的估计值〔二进制或M元〕。这个数的序列披送至信道译码器，它根据信进编码器所用的关于码的知识及接收数据所含的冗余度重构初始的信息序列。
解调器和译码器工作性能好坏的—个度量是译码序列中发生差错的频度。更准确地说，在译码器输出端的平均比特错误概率是解调器-译码器組合性能的一个度量。一般地，错误概率是下列各种因素的函数:码特征、用来在信道上传输信息的波形的类型、发送功率信道的特征(即噪声的大小、干扰的性质等)以及解调和译码的方法。在后续各章中将详细讨论这些因素及其对性能的影晌。
作为最后一步，当需要模拟输出时，信源译码器从信道译码器接收其输出序列并根据所采用的信源编码方法的有关知识重构由信源发出的原始信号。由于信道译码的差错以及信源编码器可能引入的失真,在信源译码器输出端的信号只是原始信源输出的—个近似。在原始信号与重构信号之间的信号差或信号差的函数是数字通信系统引入失真的一种度量。
1.2通信信道及其特征
正如前面指出的，通信信道在发送机与接收机之间提供了连接。物理信道也许是携带电信号的一对明线;或是在已调光波束上携带信息的光纤;或是水下海洋信道其中信息以声波形式传输;或是自由空间，携带信息的信号通过天线在空间辐射传输。可被表征为通信信道的其他媒质是数据存储媒质如磁带、磁盘和光盘。
在信号通过任何信道传输中的一个共同的问题是加性噪声。一般地，加性噪声是由通信系统内部组成元器件所引起的，例如电阻和固态器件。有时将这种噪声称为热噪声。其他噪声和干扰源也许是系统外面引起的，例如来自信道上其他用户的干扰。当这样的噪声和干扰与期望信号占有同频带时，可通过对发送信号和接收机中解调器的适当设计来使它们的影响最小。信号在信道上传输时可能会遇到的其他类型损伤有信号衰减、幅度和相位失真、多径失真等。
可以通过增加发送信号功率的方法使噪声的影响最小。然而，设备和其他实际因素限制了发送信号的功率电平，另一个基本的限制是可用的信道带宽。带宽的限制通常是由于媒质以及发送机和接牧机中组成器件和部件的物理限制产生的。这两种限制因素限制了在任何通信信道上能可靠传输的数据量,我们将在以后各章中讨论这种情况。下面描述几种通信信道的重要特征。
1.有线信道
电话网络扩大了有线线路的应用，如话音信号传输以及数据和视频传输。双绞线和同轴电缆是基本的导向电磁信道，它能提供比较适度的带宽。通常用来连接用户和中心机房的电话线的带宽为几百千赫(khz)另一方面同轴电缆的可用宽带是几兆赫(Mhz)。信号在这样的信道上传输时，其幅度和相位都会发生失真，还受到加性噪声的恶化。双绞线信道还易受到来自物理邻近信道的串音干扰。因为在全国和全世界有线信道上通信在日常通信中占有相当大的比例，因此,人们对传输特性的表征以及对信号传输时的幅度和相位失真的减缓方法作了大量研究。在第9章中，我们将阐述最佳传输信号及其解调的设什方法。在笫10章和第11章中，我们将研究信道均衡器的设计,它是用来补偿信道的幅度和相位失真的。
2.光纤信道
光纤提供的信道带宽比同轴电缆信道大几个数量级。在过去的20年屮，已经研发出具有较低倌号衰减的光缆，以及用于信号和信号检测的可靠性光子器件。这些技术上的进展导致了光纤信道应用的快速发展，不仅应用在国内通信系统中，也应用于跨大西洋和跨太平洋的通信中。由于光纤信道具有大的可用带宽，因此有可能使电话公司为用户提供宽系列电店业务，包括话音、数据、传真和视频等。
在光纤通信系统中，发送机或调制器是一个光源.或者是发光二极管(LED)或者是激光。通过消息信号改变(调制)光源的强度来发送信息。光像光波一样通过光纤传播，并沿着传输路径被周期性地放大以补偿信号衰减(在数宇传输中，光由中继器检测和再生)。在接收机中，光的强度由光电二极管检测，它的输出电信号的变化直接与照射到光电二极管上的光的功率成正比。光纤信道中的噪声源是光电二极管和电子放大器。
3.无线电磁信道
在无线通信系统中，电磁能是通过作为辐射器的天线耦合到传播媒质的。天线的物理尺寸和配置主要决定于运行的频率。为了获得有效的电磁能量的辐射，天线必须比波长的1/10更长。因此,在调幅(AM)频段发射的无线电台，譬如说在f=1MHz时(相当于波长= C/f=300m)要求天线至少为30m。无线传输天线的其他重要特征和属性将在第5章阐述。
在大气和自由空间中，电磁波传播的模式可以划分为3种类型，即地波传播、天波传播和视线传播。在甚低频(VLF)和音频段，其波长超过10km，地球和电离层对电磁波传播的作用如同波导。在这些频段,通信信号实际上环绕地球传播，由于这个原因，这些频段主要用来在世界范围内提供从海洋到船舶的导航帮助。在此频段中可用的带宽较小(通常是中心频率的1% ~10%)因此通过这些信道传输的信息速率较低，且一般限于数字传输。在这些频率上，最主要的一种噪声是由地球上的雷暴活动产生的，特别是在热带地区。干扰来自这些频段上的用户。
在高频(HF)频段范围内，电磁波经由天波传播时经常发生的问题是信号多径。信号多径发生在发送信号经由多条传播路径以不同的延迟到达接收机的时侯，一般会引起数字通信系统中的符号间干扰。而且经由不同传播路径到达的各信号分量会相互削弱，导致信号衰落的现象.许多人在夜晚收听远地无线电台广播时会对此有体验。在夜晚，天波是主要的传播模式。HF频段的加性噪声是大气噪声和热噪声的组合。
在大约30MHZ之上的频率,即频段的边缘，就不存在天波电离层传播。然而，在30~60MHZ频段有可能进行电离层散射传播，这是由较低电离层的信号散射引起的。也可利用在40~300MHZ频率范围内的对流层散射在几百英里的距离通信。对流层散射是由在10mile或更低高度大气层中的粒子引起的信号散射造成的，一般地，电离层散射和对流层散射具有大的信号传播损耗，要求发射机功率大和天线比较长。
在30MHZ以上频率通过电离层传播具有较小的损耗,这使得卫里和超陆地通信成为可能。因此,在甚高频(VHF)频段和更高的频率，电磁传播的最主要模式是LOS传播。对于陆地通信系统这意味着发送机和接收机的天线必须是直达LOS,没有什么障碍。由于这个原因VHF和特高频(UHF)频段发射的电视台的天线安装在髙塔上,以达到更宽的覆盖区域。
一般地LOS传播所能覆盖的区域受到地球曲度的限制。如果发射天线安装在地表面之上H米的高度,并假定没有物理障碍(如山)那么到无线地平线的距离近似为d=15H KM，例如电视天线安装在300m高的塔上.它的覆盖范围大约67km另一个例子，工作在1GHZ以上频率，用来延伸电话和视频传输的微波中继系统将天线安装在离塔上或高的建筑物顶部。
对工作在VHF和UHF频率范围的通信系统限制性能的最主要噪声是接收机前端所产生的热噪声和天线接收到的宇宙噪声。在10GHZ以上的超髙频(SHF)频段，大气层环境在信号传播中担负主要角色。例如,在10GHZ频率，衰减范围从小雨时的0.003 dB/KM左右到大雨时的0.3dB/KM;在100GHZ,衰减范围从小雨时的0.1dB左右到大雨时的6dB左右。因此，在此频率范围,大雨引起了很大的传播损耗，这会导致业务中断(通信系统完全中断)。
在极高频(EHF)频段以上的频率是电磁频谱的红外区和可见光区，它们可用来提供自由空间的LOS光通信。到目前为止,这些频段已经用于实验通信系统,例如，卫星到卫星的通信链路。
4.水声信道
在过去的几十年中.海洋探险活动不断增多。与这种增多相关的是对传输数据的需求。数据是由位于水下的传感器传送到海洋表面的,从那里可能将数据经由卫星转发给数据采集中心。
除极低频率外，电磁波在水下不能长距离传播。在低频率的信号传输的延伸受到限制，因为它需要大的且功率强的发送机。电磁波在水下的衰减可以用表面深度来表示,它是信号衰减l/e的距离。对于海水,表面深度 250/f，其中f以HZ为单位。例如，在10 khz上,表面深度是2.5m。声信号能在几十甚至几百千米距离上传播。
水声信道可以表征为多径信道,这是由于海洋表面和底部对信号反射的缘故。因为波的运动,信号多径分量的传播延迟是时变的，这就导致了信号的衰落。此外,还存在与频率相关的衰减，它与信号频率的平方近似成正比。声音速度通常大约为1 500m/s，实际值将在正常值上下变化,这取决于信号传播的深度。
海洋背景噪声是由虾、鱼和各种哺乳动物引起的。在靠近港口处，除了海洋背景噪声外也有人为噪声。尽管有这些不利的环境，还是可能设计并实现有效的且高可靠性的水声通信系统,以长距离地传输数字信号。
5.存储信道
信息存储和恢复系统构成了日常数据处理工作的非常重要的部分。磁带(包括数字的声带和录像带)、用来存储大量计箅机数据的磁盘、用作计箅机数据存储器的光盘以及只读光盘都是数据存储系统的例子,它们可以表征为通信信道。在磁带或磁盘或光盘上存储数据的过程，等效于在电话或在无线信道上发送数据。回读过程以及在存储系统中恢复所存储的数据的信号处理等效于在电话和无线通信系统中恢复发送信号。
由电子元器件产生的加性噪声和来自邻近轨道的干扰一般会呈现在存储系统的回读信号中，这正如电话或无线通信系统中的情况。
所能存储的数据量一般受到磁盘或磁带尺寸及密度(每平方英寸存储的比特数)的限制，该密度是由写/读电系统和读写头确定的。例如在磁盘存储系统中，封装密度可达每平方英寸比特(1 in=2.54cm)。磁盘或磁带上的数据的读写速度也受到组成信息存储系统的机械和电子子系统的限制。
信道编码和调制是良好设计的数字磁或存储系统的最重要的组成部分。在回读过程中，信号被解调。由信道编码器引入的附加冗余度用于纠正回读信号中的差错。
1.3 通信信道的数学模型
在通过物理信道传输信息的通信系统设计中，我们发现，建立一个能反映传输媒质最重要特征的数学模型是很方便的。信道的数学模型可以用于发送机中的信道编码器和调制器，以及接收机中的解调器和信道译码器的设计。下面，我们将简要的描述信道的模型，它们常用来表征实际的物理信道。 1. 加性噪声信道
通信信道最简单的数学模型是加性噪声信道，如图1-3-1所示。在这个模型中，发送信号s(t)被加性随机噪声过程n(t)恶化。在物理上，加性噪声过程由通信系统接收机中的电子元部件和放大器引起，或者由传输中的干扰引起(正如在无线电信号传输中那样)。
如果噪声主要是由接收机中的元部件和放大器引起，那么，它可以表征为热噪声。这种模型的噪声统计地表征为高斯噪声过程。因此，该信道的数学模型通常称为加性高斯噪声信道。因为这个信道模型适用于很广的物理通信信道，并且因为它在数学上易于处理，所以是在通信系统分析和设计中所用的最主要的信道模型。信道的衰减很容易加入到该模型。信号通过信道传输而受到衰减时，接收信号是
r(t)s(t)n(t) 式中，是衰减因子。
图1-3-1 加性噪声信道
2. 线性滤波器信道
在某些物理信道中，例如有线电话信道，采用滤波器来保证传输信号不超过规定的带宽限制，从而不会引起相互干扰。这样的信道通常在数学上表征为带有加性噪声的线性滤波器，如图1-3-2所示。因此，如果信道输入信号为s(t)，那么信道输出信号是
r(t)s(t)c(t)n(t)
c()s(t)dn(t)
式中，c()是信道的冲激响应，表示卷积。
图1-3-2 带有加性噪声的线性滤波器信道 3. 线性时变滤波器信道
像水声信道和电离层无线电信道这样的物理信道，它们会导致发送信号的时变多径传播，这类物理信道在教学上可以表征为时变线性滤波器。该线性滤波器可以表征为时变信道冲激响应c(τ;t)，这里c(τ;t)是信道在t-τ时刻加入冲激而在τ时刻的响应。因此，τ表示“历时(经历时间)”变量。
上面描述的三种数学模型适当的表征了实际中的绝大多数物理信道。本书将这3 种模型用于通信系统的分析和设计。
1.4 数字通信发展的回顾与展望 值得注意的是，最早的电通信形式，即电报，是一个数字通信系统。电报由S•莫尔斯研制，并在1837年进行了演示试验。莫尔斯设计出一种可变长度的二进制码，其中英文字母用点划线的序列(码字)表示。在这种码中，较频繁发生的字母用短码字表示，不常发生的字母用较长的码字表示。因此，莫尔斯码是第三章所述可变长度信源编码方法的先驱。
差不多在40年之后，1875年，E博多设计出一种电报码，其中每一个字母编成一个固定长度为5的二进制码字。在博多码中，二进制码的元素是等长度的，且指定为传号和空号。
虽然莫尔斯在研制第一个点的数字通信系统(电报)中起了重要的作用，但是现在我们所指的现代数字通信系统起源于奈奎斯特的研究。奈奎斯特研究了再给定带宽的电报信道上，无符号间干扰的最大信号传输速率。他用公式表达了一个电报系统的模型，其中发送信号的一般形式为
s(t)anng(tnT)
式中，g(t)表示基本的脉冲形状，an是以速率1/T bit/s发送的二进制数据序列。奈奎斯特提出了带宽限于W Hz的最佳脉冲形状，并且在脉冲抽样时刻Kt(k=0，1，。。。)无符号间干扰的条件下的最大比特率。他得出结论：最大脉冲速率是2W脉2，冲/s，该速率称为奈奎斯特速率。
1. INTRODUCTION In this book, we present the basic principles that underlie the analysis and design of digital communication systems.The subject of digital communications involves the transmission of information in digital form from a source that generates the information to one or more destinations. Of particular importance in the analysis and design of communication systems are the characteristics of the physical channels through which the information is transmitted. The characteristics of the channel generally affect the design of the basic building blocks of the communication system. Below, we describe the elements of a communication system and their functions. 1-1 ELEMENTS OF A DIGITAL COMMUNICATION SYSTEM Figure 1-1-1 illustrates the functional diagram and the basic elements of a digital communication system. The source output may be either an analog signal, such as audio or video signal, or a digital signal, such as the output of a teletype machine, that is discrete in time and has a finite number of output characters. In a digital communication system, the messages produced by the source are converted into a sequence of binary digits. Ideally, we should like to represent the source output (message) by as few binary digits as possible. In other words, we seek an efficient representation of the source output that results in little or no redundancy. The process of efficiently converting the output of either an analog or digital source into a sequence of binary digits is called source encoding or data compression. The sequence of binary digits from the source encoder, which we call the information sequence, is passed lo the channel encoder. The purpose of the channel encoder is to introduce, in a controlled manner, some redundancy in the binary information sequence that can be used at the receiver to overcome the effects of noise and interference encountered in the transmission of the signal through the channel. Thus, the added redundancy serves to increase the reliability of the received data and improves the fidelity of the received signal.In effect, redundancy in the information sequence aids the receiver in decoding the desired information sequence. For example, a (trivial) form of encoding of the binary information sequence is simply to repeat each binary digit m times,where m is some positive integer. More sophisticated (nontrivial) encoding involves talcing k information bits at a time and mapping each k-bit sequence into a unique n-bit sequence, called a code word. The amount of redundancy introduced by encoding the data in this manner is measured by the ratio n/k.The reciprocal of this ratio, namely k/n, is called the rate of the code or,simply, the code rate.
The binary sequence at the output of the channel encoder is passed to the digital modulator, which serves as the interface to the communications channel.Since nearly all of the communication channels encountered in practice are capable of transmitting electrical signals (waveforms), the primary purpose of the digital modulator is to map the binary information sequence into signal waveforms. To elaborate on this point, let us suppose that the coded information sequence is to be transmitted one bit at a time at some uniform rate R bits/s. The digital modulator may simply map the binary digit 0 into a waveform s0(t) and the binary digit 1 into a waveform j,(i). In this manner,each bit from the channel encoder is lransmitted separately. We call this binary modulation. Alternatively, the modulator may transmit b coded information bits at a time by using M = 2s distinct waveforms j.(r), i = 0,1
M1 MHz (corresponding to a wavelength of A = cffr = 300m).requires an antenna of at least 30m. Other important characteristics and attributes of antennas for wireless transmission are described in Chapter 5.
Figure 1-2-2 illustrates the various frequency bands of the electromagneticspectrum. The mode of propagation of electromagnetic waves in the atmo- sphere and in free space may be subdivided into three categories, namely,ground-wave propagation, sky-wave propagation, and line-of-sight (LOS) propagation. In the VLF and audio frequency bands, where the wavelengths exceed 10 km, the earth and the ionosphere act as a waveguide for electromagnetic wave propagation. In these frequency ranges, communication signals practically propagate around the globe. For this reason, these frequency bands are primarily used to provide navigational aids from shore to ships around the world. The channel bandwidths available in these frequency bands are relatively small (usually 1-10% of the center frequency), and hence the information that is transmitted through these channels is of relatively slow speed and generally confined to digital transmission. A dominant type of noise at these frequencies is generated from thunderstorm activity around the globe,especially in tropical regions. Interference results from the many users of these frequency bands. Ground-wave propagation, as illustrated in Fig. 1-2-3, is the dominant mode of propagation for frequencies in the MF band (0.3-3 MHz). This is the frequency band used for AM broadcasting and maritime radio broadcasting. In AM broadcasting, the range with groundwave propagation of even the more powerful radio stations is limited to about 150 km. Atmospheric noise,man-made noise, and thermal noise from electronic components at the receiver are dominant disturbances for signal transmission in the MF band. Sky-wave propagation, as illustrated in Fig. 1-2-4 results from transmitted signals being reflected (bent or refracted) from the ionosphere, which consists of several layers of charged particles ranging in altitude from 50 to 400 km above the surface of the earth. During the daytime hours, the heating of the lower atmosphere by the sun causes the formation of the lower layers at altitudes below 120 km. These lower layers, especially the D-layer, serve to absorb frequencies below 2 MHz, thus severely limiting sky-wave propagation of AM radio broadcast. However, during the night-time hours, the electron density in the lower layers of the ionosphere drops sharply and the frequency absorption that occurs during the daytime is significantly reduced. As a consequence, powerful AM radio broadcast stations can propagate over large distances via sky wave over the F-layer of the ionosphere, which ranges from 140 to 400 km above the surface of the earth.
A frequently occurring problem with electromagnetic wave propagation via sky wave in the HF frequency range is signal multipath. Signal multipath occurs when the transmitted signal arrives at the receiver via multiple propagation paths at different delays, tt generally results in intersymbol interference in a digital communication system. Moreover, the signal components arriving via different propagation paths may add destructively, resulting in a phenomenon called signal fading, which most people have experienced when listening to a distant radio station at night when sky wave is the dominant propagation mode. Additive noise at HF is a combination of atmospheric noise and thermal noise. Sky-wave ionospheric propagation ceases to exist at frequencies above approximately 30 MHz, which is the end of the HF band. However, it is possible to have ionospheric scatter propagation at frequencies in the range 30-60 MHz, resulting from signal scattering from the lower ionosphere. It is also possible to communicate over distances of several hundred miles by use of tropospheric scattering at frequencies in the range 40-300 MHz. Troposcatter results from signal scattering due to particles in the atmosphere at altitudes of 10 miles or less. Generally, ionospheric scatter and tropospheric scatter involve large signal propagation losses and require a large amount of transmitter power and relatively large antennas. Frequencies above 30 MHz propagate through the ionosphere with relatively little loss and make satellite and extraterrestrial communications possible. Hence, at frequencies in the VHF band and higher, the dominant mode of electromagnetic propagation is linc-of-sight (LOS) propagation. For terrestrial communication systems, this means that the transmitter and receiver antennas must be in direct LOS with relatively little or no obstruction. For this reason, television stations transmitting in the VHF and UHF frequency bands mount their antennas on high towers to achieve a broad coverage area.
In general, the coverage area for LOS propagation is limited by the curvature of the earth. If the transmitting antenna is mounted at a height h m above the surface of the earth, the distance to the radio horizon, assuming no physical obstructions such as mountains, is approximately dr Thus,r represents the "age" (elapsed-time) variable.
The three mathematical models described above adequately characterize the great majority of the physical channels encountered in practice. These three channel models are used in this text for the analysis and design of communication systems. 1-4 A HISTORICAL PERSPECTIVE IN THE DEVELOPMENT OF DIGITAL COMMUNICATIONS It is remarkable that the earliest form of electrical communication, namely telegraphy, was a digital communication system. The electric telegraph was developed by Samuel Morse and was demonstrated in 1837. Morse devised the variable-length binary code in which letters of the English alphabet are represented by a sequence of dots and dashes (code words). In this code, more frequently occurring letters are represented by short code words, while letters occurring less frequently are represented by longer code words. Thus, the Morse code*was the precursor of the variable-length source coding methods described in Chapter 3. Nearly 40 years later, in 1875, Emile Baudot devised a code for telegraphy in which every letter was encoded into fixed-length binary code words of length 5. In the Baudot code, binary code elements are of equal length and designated as mark and space. Although Morse is responsible for the development of the first electrical digital communication system (telegraphy), the beginnings of what we now regard as modern digital communications stem from the work of Nyquist(1924), who investigated the problem of determining the maximum signaling rate that can be used over a telegraph channel of a given bandwidth without intersymbol interference. He formulated a model of a telegraph system in which a transmitted signal has the general form
s(t)anng(tnT)
where g(t)represents a basic pulse shape and an is the binary data sequence of {±1} transmitted at a rate of 1/Tbits/s. Nyquist set out to determine the optimum pulse shape that was bandlimited to W Hz and maximized the bit rate under the constraint that the pulse caused no intersymbol interference at the sampling time klT. k =0, ±1, ±2 ……His studies led him to concludc that the maximum pulse rate is 2W pulses/s. This rate is now called Nyquist rate.
当今时代是一个自动化时代，交通灯控制等很多行业的设备都与计算机密切相关。因此，一个好的交通灯控制系统，将给道路拥挤，违章控制等方面给予技术革新。随着大规模集成电路及计算机技术的迅速发展，以及人工智能在控制技术方面的广泛运用，智能设备有了很大的发展，是现代科技发展的主流方向。本文介绍了一个智能交通的系统的设计。该智能交通灯控制系统可以实现的功能有：对某市区的四个主要交通路口进行控制：个路口有固定的工作周期，并且在道路拥挤时中控制中心能改变其周期：对路口违章的机动车能够即时拍照，并提取车牌号。在世界范围内，一个以微电子技术，计算机和通信技术为先导的，一信息技术和信息产业为中心的信息革命方兴未艾。而计算机技术怎样 与实际应用更有效的结合并有效的发挥其作用是科学界最热门的话题，也是当今计算机应用中
研究交通的目的是为了优化运输，人流以及货流。由于道路使用者的不断增加，现有资源和基础设施有限，智能交通控制将成为一个非常重要的课题。但是，智能交通控制的应用还存在局限性。例如避免交通拥堵被认为是对环境和经济都有利的，但改善交通流也可能导致需求增加。交通仿真有几个不同的模型。在研究中，我们着重于微观模型，该模型能模仿单独车辆的行为，从而模仿动态的车辆组。
由于低效率的交通控制，汽车在城市交通中都经历过长时间的行进。采用先进的传感器和智能优化算法来优化交通灯控制系统，将会是非常有益的。优化交通灯开关，增加道路容量和流量，可以防止交通堵塞，交通信号灯控制是一个复杂的优化问题和几种智能算法的融合，如模糊逻辑，进化算法， 和聚类算法已经在使用，试图解决这一问题，本文提出一种基于多代理聚类算法控制交通信号灯。
在我们的方法中，聚类算法与道路使用者的价值函数是用来确定每个交通灯的最优决策的，这项决定是基于所有道路使用者站在交通路口累积投票，通过估计每辆车的好处(或收益)来确定绿灯时间增益值与总时间是有差异的，它希望在它往返的时候等待，如果灯是红色，或者灯是绿色。等待，直到车辆到达目的地，通过有聚类算法的基础设施，最后经过监测车的监测。
我们对自己的聚类算法模型和其它使用绿灯模拟器的系统做了比较。绿灯模拟器是一个交通模拟器，监控交通流量统计，如平均等待时间，并测试不同的交通灯控制器。结果表明，在拥挤的交通条件下，聚类控制器性能优于其它所有测试的非自适应控制器，我们也测试理论上的平均等待时间，用以选择车辆通过市区的道路，并表明，道路使用者采用合作学习的方法可避免交通瓶颈。
本文安排如下：第2部分叙述如何建立交通模型，预测交通情况和控制交通。第3部分是就相关问题得出结论。第4部分说明了现在正在进一步研究的事实，并介绍了我们的新思想。
The times is a automation times nowadays,traffic light waits for much the industey equipment to go hand in hand with the computer under the control of.Therefore,a good traffic light controls system,will give road aspect such as being crowded,controlling against rules to give a technical improvement.With the fact that the large-scale integrated circuit and the computer art promptness develop,as well as artificial intelligence broad in the field of control technique applies,intelligence equipment has had very big development,the main current being that modern science and technology develops direction.The main body of a book is designed having introduccd a intelligence traffic light systematically.The function being intelligence traffic light navar’s turn to be able to come true has：The crossing carries out supervisory control on four main traffic of some downtown area;Every crossing has the fixed duty period,charges centrefor being able to change it’s period and in depending on a road when being crowded;The motro vehicle breaking rules and regulations to the crossing is able to take a photo immediately,abstracts and the vehicle shop sign.Within world range ,one uses the microelectronics technology,the computer and the technology communicating by letter are a guide’s,centering on IT and IT industry information revolution is in the ascendant.But,how,computer art applies more effective union and there is an effect’s brought it’s effect into play with reality is the most popular topic of scientific community,is also that computer applications is hit by the unparalleled active field nowadays.The main body of a book is applied up mainly from slicing machine’s only realizing intellectualized administration of crossroads traffic light,use operation in controlling the vehicular traffic regularity. Transportation research has the goal to optimize transportation flow of people and goods.As the number of road users constantly increases, and resources provided by current infras-tructures are limited, intelligent control of traffic will become a very important issue in thefuture. However, some limitations to the usage of intelligent tra?c control exist. Avoidingtraffic jams for example is thought to be beneficial to both environment and economy, butimproved traffic-flow may also lead to an increase in demand [Levinson, 2003]. There are several models for traffic simulation. In our research we focus on microscopicmodels that model the behavior of individual vehicles, and thereby can simulate dynam-ics of groups of vehicles. Research has shown that such models yield realistic behavior[Nagel and Schreckenberg, 1992, Wahle and Schreckenberg, 2001]. Cars in urban traffic can experience long travel times due to inefficient traffic light con-trol. Optimal control of traffic lights using sophisticated sensors and intelligent optimizationalgorithms might therefore bevery beneficial. Optimization of traffic light switching increasesroad capacity and traffic flow, and can prevent tra?c congestions. Traffic light control is acomplex optimization problem and several intelligent algorithms, such as fuzzy logic, evo-lutionary algorithms, and reinforcement learning (RL) have already been used in attemptsto solve it. In this paper we describe a model-based, multi-agent reinforcement learningalgorithm for controlling traffic lights. In our approach, reinforcement learning [Sutton and Barto, 1998, Kaelbling et al., 1996]with road-user-based value functions [Wiering, 2000] is used to determine optimal decisionsfor each traffic light. The decision is based on a cumulative vote of all road users standingfor a traffic junction, where each car votes using its estimated advantage (or gain) of settingits light to green. The gain-value is the difference between the total time it expects to waitduring the rest of its trip if the light for which it is currently standing is red, and if it is green.The waiting time until cars arrive at their destination is estimated by monitoring cars flowingthrough the infrastructure and using reinforcement learning (RL) algorithms. We compare the performance of our model-based RL method to that of other controllersusing the Green Light District simulator (GLD). GLD is a traffic simulator that allows usto design arbitrary infrastructures and traffic patterns, monitor traffic flow statistics such asaverage waiting times, and test different traffic light controllers. The experimental resultsshow that in crowded traffic, the RL controllers outperform all other tested non-adaptivecontrollers. We also test the use of the learned average waiting times for choosing routes of cars through the city (co-learning), and show that by using co-learning road users can avoidbottlenecks.
湖北理工学院 毕业设计(论文)外文文献翻译
核电厂的液位控制系统的设计
作者:邱永胜
摘要——MSR的液位控制系统(水气分离器再热器)储油槽的关键部分是传统岛核仪器和控制设备正常运行的核电站在调节中起着非常重要的作用。这种方案是基于分布式控制系统(DCS)的设计和实现液位控制系统。设计改变了在过去MSR储油槽的核电站控制方法,选择成熟、可靠、先进的DCS控制系统来满足其要求液位控制。正常排泄水调节阀,紧急排水阀门实现独立控制和操作功能(手动/自动)。增加舒缓的水压力,温度,并调整阀门反馈信号。提供设备完整的工艺参数和自诊断功能。提高了控制系统的可用性,降低缺陷率的控制设备,控制设备转换为实现“零缺陷”,满足电站的长期安全运行。
关键字——核能计划ˈ液位控制ˈ系统配置分布式控制系统。
I介绍
我国在“十一五”计划中建立了“积极发展核电”政策,积极推进核电建设先进技术的使用。由于核能的特殊性质,仪表和控制系统的安全性和可靠性比其先进和创新更重要。
审查发生在过去重大核电站的事故中的那些相关的仪表和控制系统的问题。
II MSR
系统工作流程
气分离器再热器(MSR)用于核电站,其根本目的是提高蒸汽循环的热效率。 每一个分离器再热器再热储油槽,水平再热储油槽,II级再热储油槽,分离器储油槽,每个储油槽是提供一组基本类型监管机构控制器。控制系统控制的一个正常的排水阀,紧急排水阀控制疏水槽水位。MSR疏水液位系统的合理设计汽轮机的安全运行,具有十分重要的意义。如果不正常疏水,影响水分分离器再热器身体安全。
DAS(数据采集系统)是用于收集疏水槽的压力、温度数据信号,实时监控和显示的运行状态系统。疏水箱的水位信号(4 ~ 20 ma)被送到模拟输入卡。系统预设值比较运算符在水位信号的人机界面,通过调整PID回路,控制信号从模拟输出卡输出阀(4 ~ 20 ma),来调整阀门开度,从而达到控制的目的疏水槽水位,水位调节循环1 #、2 # MSR储油槽,分别由6组12每个正常排水监管和应急排水阀门,从各自的分段处理液位控制器控制信号来调整阀门开度,液位保持在控制范围内,控制储油 1
湖北理工学院 毕业设计(论文)外文文献翻译
槽液位稳定。
III控制系统方案
DCS需要几个控制站之间的许多工业过程控制的控制点的控制站可以通过网络交换数据连接。硬件设备主要的工作站系统处理器(WP),应用处理器(美联社),应用工作站(AW70),现场控制处理器(FCP)、通信处理器(COMMP),现场总线模块(FBM)。
DCS控制系统的硬件连接图和具体功能和配置。
A硬件需求除了满足核级仪表设备需求(1 e)安全(RCC-E(2002)标准)[2],核功率计的计算机控制系统应该是结构化,模块化,灵活,操作方便,控制网络。系统通道或保护和控制系统必须实现电气隔离和功能隔离用于光纤通信,系统必须有一个持续的在线自测诊断能力。作为一个整体,硬件系统具有较强的抗电磁干扰、高功率瞬变能力和满足电磁兼容性要求。水气分离器再热器之外的这种技术的控制系统可以被认为是通过识别的智能传感器和现场总线技术,实现信息采集和现场控制。这种技术大大简化了仪器控制布局的结构和分布的过程。 B .可靠性设计
(a)冗余设计:由于核电站的特殊性质,为了确保DCS的高可靠性要求,I / O模块,和具体的现场控制站控制器、电源、网络和服务器,将冗余配置。
(b)隔离设计:特殊要求或信号,如信号安全non-security-level DCS和DCS是一个共安全级别DCS将孤立从non-security-level DCS,避免非安全性系统导致损失的安全特性。
(c)多样性设计:多样性是一种保护的性能故障和共模故障。保护的特定功能,需要非常高的可靠性,如反应堆关闭系统,必须设置为两个相互独立的,没有属性,因此可以避免共模故障的发生。设计通常是应用于冗余系统的多样性。
(d)容错设计:设计系统的容错技术是指误动作不响应技术。至于键盘不允许键屏蔽,如运营商在操作员站不按照规则操作系统没有响应,而不是输出操作指令,或提示操作错误信息。
IV
配置控制软件的设计
控制配置,准备了一个程序(模块),设置参数,这样就可以构建所需的用户主体和额外的功能,或功能块的软连接,完成过程控制系统。
湖北理工学院 毕业设计(论文)外文文献翻译
配置软件需求: 首先,软件具有较强的可移植性,连接和互操作性; 其次、安全、高效的数据通信中,友好和视觉界面; DCS系统应用程序配置软件作为软件平台,控制工程师,从如何编写软件程序来实现控制和显示功能,并花更多的时间和精力在控制电路的设计和实际控制和显示在打印相关信息,如使用这种模块化的配置方法,可以完成各种项目的配置。
这个设计使用一个控制配置央行图。央行是包括所有仪器控制系统的控制图。 # 1 MSR正常/紧急疏水槽排水阀控制,例如,给央行的配置图和描述。液位的分段控制,即正常排水阀调节正常水平间隔,紧急排水阀高度间隔。液位控制一直很稳定,在扰动发生时,液位控制响应快,如果液面达到极限,正常和紧急陷阱都打开,关闭完全正确(高液位报警有强制性全面紧急控制水阀,低水平报警而强制关闭正常排水阀)。控制系统的失败后,设备正确响应,以确保机组的安全。
# 1 msr二级央行的正常储油槽陷阱配置图
通过配置,DCS控制程序称为中位数选择器模块、PID控制模块,两个位置控制模块,手动模块等正常排水阀是强迫开放、积极行动,紧急排水阀空气关闭,相反的效果。
使用HART协议DVC6010PD智能定位器(精度±1%)取代了现有的3582克气动阀门定位器。阀门管理安装AMS ValveLink软件和相关硬件支持# 1,# 2 msr在线和离线诊断,管理的控制阀门。
PID控制模块、模拟输入模块(AIN)和模拟输出模块(差异)连接有机地形成一个参数控制电路,。首先,是模块主要修改测量信号,FBM缩放、警报和其他操作,然后输出处理过的数据测量值输入参数PID控制模块的量。其次,PID模块考虑偏差的测量值和设置和设置p,我,d处理和调优参数,最终,传输数据量的差异模块。最后,对模块的输出数据,作为修改,然后路由到FBM的输出点。为了提高控制质量,单回路控制方案的基础上,还可以使用串级控制的程序员。串级控制回路由2模拟输入模块(AIN),2 PID控制模块和一个模拟输出模块(差异)。当循环工作状态,二级调节器的设置状态,参数的设置值是一个数据连接和通信和输出参数的主要监管机构。无扰转移到闭环控制,您通常需要将初始化二级调节器的输出信号初始化主调节器的输入信号。同时二级调节器的输出信号反演计算的输入信号传输逆计算的主要监管机构。对模块的初始化输出信号需要被转移到初始化二级调节器的输入信
湖北理工学院 毕业设计(论文)外文文献翻译
号。
V系统电源、地表和环境设计
DCS是公认的双向交流220 v±10%,50赫兹±2.5赫兹单相电源,由两个不间断电源(UPS),隔离变压器抑制高频干扰传输到网格中的力量。冗余电源配置合适的开关装置和循环保护电路。这两个主要力量提要内阁。适当的地面点的选择,完美的接地系统,接地设计,系统接地,保护接地,屏蔽地面分离。抑制噪声,确保系统的安全运行,各种抗噪声技术用于设计。这些技术包括opto-isolated、高共,必要的接地和电磁屏蔽。加强DCS系统抗干扰能力的ˈ当其他设备工作在470 mhz的频率,功率5 w,和从系统中超过1.2米,电磁干扰和射频干扰不会影响系统的稳定性。振动强度要求:5855。
[6]凡X触摸DCS系统在核电站中的应用[J]。机械和电气信息,2010(4):191 - 192。
作者的传记
邱永胜出生于西安,中国,在1973年。他收到第二炮兵工程学院BS,中国在1996年和1999年,ˈ分别。现在他是一个工程师在电子和工程学院,南京大学的职位和通讯ˈ中国。他的研究兴趣包括计算机测量和控制技术,通信技术。
湖北理工学院 毕业设计(论文)外文文献翻译
Low Voltage Flyback DC-DC Converter For
Power Supply Applications Hangzhou Liu1, John Elmes2, Kejiu Zhang1, Thomas X. Wu1, Issa Batarseh1
Department of Electrical Engineering and Computer Science, University of Central Florida, Orlando, FL 32816, USA Advanced Power Electronics Corporation, Orlando, FL 32826, USA Abstract ：In this paper, we design a low voltage DC-DC converter with a flyback transformer. The converter will be used as a biased power supply to drive IGBTs. The flyback transformer using planar EI-core is designed and simulated using ANSYS PExprt software. Besides, anLT3574 IC chip from Linear Technology has been chosen for converter control. Finally, the converter modeling and simulation are presented and PCB layout is designed. Keywords：Flyback, anLT3574IC, PCB
I. INTRODUCTION The goal of this project is to develop and build a prototype of a high-efficiency, high-temperature isolated DC-DC converter to be used as a biased power supply for driving a complementary IGBT pair. It is important that the converter can deliver the required power at an ambient temperature of up to 100℃; therefore it has to be efficient so that its components do not exceed their maximum temperature ratings. The final converter will be completely sealed and potted in a metal case. The input voltage range for this converter is from 9V to 36V. The output sides have two terminals, one is﹢16V and the other one is﹣6V. In order to get the desired performance, anLT3574 IC chip from Linear Technology is used. The key to this design is the flyback transformer. The transformer using planar EI-core is designed and simulated using ANSYS PExprt software. Finally, the PCB layout of the converter will be presented.
II. KEY DESIGN OUTLINE For this flyback topology, the output voltage can be determined by both the transformer turns ratio and the flyback loop resistor pairs. Therefore, at the initial design stage, we can choose a convenient turn’s ratio for the transformer, and modify it later on if necessary to make sure the output performance is desirable and the transformer will not saturate [1]. The relationship between transformers turns ratio and duty cycle can be found as
Where n is the transformer turns ratio, D is the duty cycle, VO` is the sum of the output voltage plus the rectifier drop voltage, VIN is the input voltage of the transformer. The value of feedback resistor can be calculated as
Where RREF is the reference resistor, whose value is typically 6.04kΩ; α is a constant of 0.986;VBG is the internal band gap reference voltage, 1.23V; and VTC is normally 0.55V [1]. With a specific IC chosen, the converter circuit can be designed based on a demo circuit and some parameters may need to be modified if necessary to optimize the performance. Furthermore, in LT Spice, a large number of simulations need to be done with different conditions such as load resistor values and input voltage levels. It is important to make sure that the output voltage can be regulated well with all these different conditions. The most critical part of the design is the flyback transformer. With high switching frequency, the AC resistance can only be estimated based on some traditional methods such as Dowell’s curve rule [2].In order to get more accurate values of AC resistance values; we propose to use finite element electromagnetic software ANSYS PExprt to do the design [3]. At the initial design stage, key parameters such as the worst-case input voltage, frequency, material, inductance values will be decided. After that, these data will be imported to the software, from which an optimized solution will be generated. III. CONVERTER SIMULATION RESULTS We choose LT3574 chip in this design. From the simulation results in Figure 1 and Table 1, it clearly shows that the output voltages which are﹢16V and -6V respectively can be regulated pretty well with the input voltage range from 9V to 36V. The voltage tolerance ranges are from ﹢15V to ﹢19V and -12V toDC converter for low voltage power supply application has been designed. The modeling and simulation results are presented. Based on the design specifications, a suitable IC from Linear Technology is chosen. A large amount of circuit simulations with different conditions such as load resistor values and input voltage levels are presented to get the desirable output voltage and current performance. The transformer has been designed including electrical, mechanical and thermal properties. With all the specific components decided, the PCB layout of the converter has been designed as well.
REFERENCE
[1] Linear Technology Application Notes , Datasheet of Isolated Flyback Converter Without an Opto-Coupler, http://cds.linear.com/docs /Datasheet/3574f.pdf. [2] P.L.Dowell, “Effect of eddy currents in transformer windings” Proceedings of the IEE, NO.8 PP.1387-1394, Aug 1966. [3] S.Xiao, “Planar Magnetics Design for Low- Voltage DC-DC Converters” MS, 2004.
[4] ANSYS Application Notes, PEmag Getting Started: A Transformer Design Example, http:///download/ EDA/Maxwell9/planarGS0601.pdf. [5] K. Zhang; T. X.Wu; H.Hu; Z. Qian; F.Chen.; K.Rustom; N.Kutkut; J.Shen; I.Batarseh; "Analysis and design of distributed transformers for solar power conversion" 2011 IEEE Applied Power Electronics Conference and Exposition (APEC), v l., no., pp.1692-1697, 6-11 March 2011. [6] Zhang.; T.X.Wu.; N.Kutkut; J.Shen; D.Woodburn; L.Chow; W.Wu; H.Mustain; I. Batarseh; ,"Modeling and design optimization of planar power transformer for aerospace applic ation," Proceedings of the IEEE 2009 National, Aerospace & Electronics Conference (NAECON) , vol., no., pp.116-120, 21-23 July 2009. [7] Ferroxcube Application Notes, Design of Planar Power Transformer,
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