【正文】 管和接收管并列一起，平時(shí)接收管始終無光照，只在發(fā)光管發(fā)出的紅外光遇到反射物時(shí)，接收管收到反射回來的紅外線才工作。紅外通信系統(tǒng)組成結(jié)構(gòu)包括:發(fā)射器部分，信道部分，接收器部分。再接收到原信息后可在接收部分連接驅(qū)動(dòng)電路以完成預(yù)期的各種功能。（1）發(fā)射器部分：目前己有紅外無線數(shù)字通信系統(tǒng)的信息源包括語音、數(shù)據(jù)、圖像等。LOS方式是方向性的，它具有信道特性好等優(yōu)點(diǎn)，但存在“陰影”效應(yīng)，難于實(shí)現(xiàn)漫游功能。需傳輸?shù)男盘?hào)經(jīng)數(shù)化后(被采樣量化)，一般需要進(jìn)行基帶調(diào)制、傳輸調(diào)制，有時(shí)還進(jìn)行信號(hào)源壓縮編碼，以上所得電信號(hào)驅(qū)動(dòng)光電變換電路完成光信號(hào)發(fā)射。一方面采用各種方法提高光發(fā)射功率，另一方面采用空間分集、全息漫射片等使其光發(fā)射器的光功率空間分布均勻。由于自然光及人工光源等背景光信號(hào)的介入，信源以及端設(shè)備中電學(xué)的、光學(xué)的噪聲與干擾的影響，紅外無線數(shù)字通信在有些場(chǎng)合質(zhì)量較差，此時(shí)還需加入信道編碼部分。紅外無線數(shù)字通信信道中常使用的光學(xué)元件主要有光學(xué)濾光片、聚光鏡等，它們的作用是:整形、濾波、視場(chǎng)變換、頻段劃分等，如可用透鏡對(duì)發(fā)射光進(jìn)行聚焦，利用光學(xué)濾光片濾除雜散光，利用透鏡擴(kuò)大光接收機(jī)的視場(chǎng)，還可利用光學(xué)元件進(jìn)行鏈路的頻分復(fù)用等。（3）接收器部分：信道中的光信號(hào)由光接收部分實(shí)現(xiàn)光電變換，為了去除噪聲及碼間干擾等功能。紅外無線光接收機(jī)常采用放大器，并要求為帶寬大、增益高、噪聲低、干擾小、頻率響應(yīng)與信道脈沖響應(yīng)匹配。為了獲得大的光接收機(jī)工作范圍及瞬時(shí)視場(chǎng)，常采用球形光學(xué)透鏡。頻率高，波長(zhǎng)短，所發(fā)射的能量集中空間傳播時(shí)的衰減系數(shù)小，可保證信號(hào)的有效傳送；傳播范圍不受局限，不存在頻率干擾問題，與無線電波方式相比，不必就頻譜資源問題向有關(guān)部門進(jìn)行申請(qǐng)和登記，易于實(shí)施；紅外線不能穿過或繞過人和物體，在數(shù)據(jù)傳輸時(shí)，不能阻斷光路； 通常，紅外遙控收發(fā)器將信號(hào)(二進(jìn)制脈沖碼)調(diào)制在38KHz的載波上，經(jīng)緩沖放大后送至紅外發(fā)光二極管，轉(zhuǎn)化為紅外信號(hào)發(fā)射出去。前者以寬脈沖表示1，窄脈沖表示0。遙控編碼脈沖信號(hào)（以PPM碼為例）通常由引導(dǎo)碼、系統(tǒng)碼、系統(tǒng)反碼、功能碼、功能反碼等信號(hào)組成。系統(tǒng)碼也叫識(shí)別碼，它用來指示遙控系統(tǒng)的種類，以區(qū)別其它遙控系統(tǒng)，防止各遙控系統(tǒng)的誤動(dòng)作。系統(tǒng)反碼與功能反碼分別是系統(tǒng)碼與功能碼的反碼，反碼的加入是為了能在接收端校對(duì)傳輸過程中是否產(chǎn)生差錯(cuò)。地址碼和數(shù)據(jù)碼都用寬度不同的脈沖來表示，兩個(gè)窄脈沖表示“0”；兩個(gè)寬脈沖表示“1”；一個(gè)窄脈沖和一個(gè)寬脈沖表示“F”也就是地址碼的“懸空”。下半部分是放大的一組字碼：一個(gè)字碼由12位AD碼（地址碼加數(shù)據(jù)碼，比如8位地址碼加4位數(shù)據(jù)碼）組成，每個(gè)AD位用兩個(gè)脈沖來代表：兩個(gè)窄脈沖表示“0”；兩個(gè)寬脈沖表示“1”；一個(gè)窄脈沖和一個(gè)寬脈沖表示“F”也就是地址碼的“懸空”。第三篇：電氣工程及其自動(dòng)化專業(yè)英語翻譯Electric Power modern society depends on the electricity supply more heavily than ever can not be imagined what the world should be if the electricity supply were interrupted all over the power systems(or electric energy systems), providing electricity to the modern society, have bee indispensable ponents of the industrial first plete electric power system(prising a generator, cable, fuse, meter, and loads)was built by Thomas Edison – the historic Pearl Street Station in New York City which began operation in September was a DC system consisting of a steamenginedriven DC generator supplying power to 59 customers within an area roughly km in load, which consisted entirely of incandescent lamps, was supplied at 110 V through an underground cable system..Within a few years similar systems were in operation in most large cities throughout the the development of motors by Frank Sprague in 1884, motor loads were added to such was the beginning of what would develop into one of the largest industries in the spite of the initial widespread use of DC systems, they were almost pletely superseded by AC 1886, the limitations of DC systems were being increasingly could deliver power only a short distance from keep transmission power losses(I 2 R)and voltage drops to acceptable levels, voltage levels had to be high for longdistance power high voltages were not acceptable for generation and consumption of power。如果世界各地電力供應(yīng)中斷了,無法想象世界會(huì)變成什么樣。歷史上第一個(gè)完整的電力系統(tǒng)（包括發(fā)電機(jī)，電纜，熔斷器，計(jì)量，加載）由托馬斯愛迪生所建——紐約市珍珠街電站，始于1882年9月運(yùn)作。他們的負(fù)載，其中包括白熾燈，通過地下電纜系統(tǒng)提供110V電壓。隨著弗蘭克斯普拉格在1884年對(duì)馬達(dá)的發(fā)展，電機(jī)負(fù)載被添加到這些系統(tǒng)，從此開始發(fā)展成為世界上最大的產(chǎn)業(yè)之一。到1886年，直流系統(tǒng)的局限性也日益明顯。為了保持發(fā)射功率損失（I 2 R）和電壓下降到可接受的水平，長(zhǎng)途輸電電壓必須高。1889年，在北美波特蘭和威拉梅特大瀑布之間的俄勒岡州第一次實(shí)施交流傳輸線。隨著交流的發(fā)展多相系統(tǒng)由尼古拉特斯拉，成為更具吸引力的。西屋公司購買了這些早期的發(fā)明專利，并形成了現(xiàn)在交流系統(tǒng)的基礎(chǔ)。到了世紀(jì)之交時(shí)，下面的原因使交流系統(tǒng)贏過了直流系統(tǒng)：（1）交流系統(tǒng)電壓水平可以很容易地改變，從而提供了傳輸?shù)撵`活性，發(fā)電用不同的電壓和消費(fèi)。（3）交流電機(jī)的馬達(dá)比直流簡(jiǎn)單且便宜得多。在電力傳輸初期交流頻率并不規(guī)范。這對(duì)互連的問題。較長(zhǎng)的距離越來越需要大量的電壓傳輸這激勵(lì)了他們逐步使用高壓。在美國，標(biāo)準(zhǔn)是115，138，161，和230千伏的高電壓（高壓）類，345，500和765千伏級(jí)的特高電壓（超高壓）。第一個(gè)750 kVtransmission線將在不久的將來建在中國西北地區(qū)。高壓直流輸電可用于輸入大塊輸電和長(zhǎng)距離輸電，并提供不同系統(tǒng)間的異步連接，因?yàn)樵诮涣髀?lián)網(wǎng)系統(tǒng)間是不切實(shí)際的，因?yàn)榉€(wěn)定考慮，或因?yàn)橄到y(tǒng)間不同的頻率。由于電力無法用簡(jiǎn)單和經(jīng)濟(jì)的方法大量?jī)?chǔ)存，電力的生產(chǎn)和消費(fèi)必須同時(shí)進(jìn)行。因此，一個(gè)正常的電力系統(tǒng)能連續(xù)運(yùn)行提供可靠的電力供應(yīng)給客戶是至關(guān)重要的。在電力系統(tǒng)的不穩(wěn)定可能會(huì)表現(xiàn)在經(jīng)營方式和多種不同的方式上，這取決于系統(tǒng)配置。由于電力系統(tǒng)的發(fā)電電力，一個(gè)令人滿意的系統(tǒng)運(yùn)行的必要條件是，依靠同步電機(jī)都留在同步或通俗的“步驟”。第四篇：測(cè)繪專業(yè)英語論文外文翻譯The measurement of the surveying and mapping in mine Since the seventy s, as the electronic technology and laser technology development, the type of surveying and mapping instruments with electronics(such as range finder, electronic tachometer, gyroscopes)to the traditional surveying and mapping instruments methods produced profound satellite remote sensing, global positioning system, as a representative of the space on earth observation technology in surveying and mapping application in the science of mature, puter technology, system scientifically based geographic information system and application for the emergence of surveying and mapping information source of access, analyze, management, processing and application fully provide strong technical support, automation and intelligence of surveying and mapping system is already in investigation, therefore we can say, the modern mapping technology is undergoing a profound of measuring technology of an important application field, in the vast coal, metal mines, nonferrous mine production process played an important survey of modern task is: in mine exploration, design, development and production of the different stages of the operation of the ground and underground mining area, the space, resources,(in mineral and land resources and environment are mainly)information acquisition, storage, processing, display and use for reasonable and effective development resources, protecting the resources, protecting the environment, management, industrial and environmental services for the continuous development of the order to realize its modern task, mine measurement must be making full use of modern surveying and mapping instruments and techniques, put the advanced modern technology with mine surveying the actual work, specific characteristics, and the bination of broaden the living space mine survey and business scope, promote the reform and development of mine survey, adapt to the market economy system and mining system reform tachometer, space information technology, the inertial measurement system and other modern surveying and mapping instruments have been in mine survey technology is used to further development and are paper to modern surveying and mapping instruments of the development of the technology and its application in 、Electronic tachometer and its application in mine survey: Electronic tachometer as the most widely used surveying and mapping instruments, is electronic technology and optical technology development of