首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
To get from Kathmandu to the tiny village in Nepal, Dave Irvine-Halliday spent more than two days. When he arrived, he found vil
To get from Kathmandu to the tiny village in Nepal, Dave Irvine-Halliday spent more than two days. When he arrived, he found vil
admin
2015-01-09
24
问题
To get from Kathmandu to the tiny village in Nepal, Dave Irvine-Halliday spent more than two days. When he arrived, he found villagers working and reading around battery-powered lamps equipped with light-emitting diodes, or LEDs—-the same lamps he had left there in 2000.
Irvine-Halliday, an American photonics engineer, was not surprised. He chose to use LED bulbs because they are rugged, portable, long-lived, and extremely efficient. Each of his lamps produces a useful amount of illumination from just one watt of power. Villagers use them about four hours each night, then top off the battery by pedaling a generator for half an hour. The cool, steady beam is a huge improvement over lamps still common in developing Countries. In fact, LEDs have big advantages over familiar incandescent(白炽的)lights as well—so much so that Irvine-Halliday expects LEDs will eventually take over from Thomas Edison’s old lightbulb as the world’s main source of artificial illumination.
The dawn of LEDs began about 40 years ago, but early LEDs produced red or green glows suitable mainly for displays in digital clocks and calculators. A decade ago, engineers invented a semiconductor crystal made of an aluminum compound that produced a much brighter red light. Around the same time, a Japanese engineer developed the first practical blue LED. This small advance had a huge impact because blue, green, and red LEDs can be combined to create most of the colors of the rainbow, just as that in a color television picture.
These days, high-intensity color LEDs are showing up everywhere such as the traffic lights. The reasons for the rapid switchover are simple. Incandescent bulbs have to be replaced annually, but LED traffic lights should last five to yen years. LEDs also use 80 to 90 percent less electricity than the conventional signals they replace. Collectively, the new traffic lights save at least 400 million kilowatt-hours a year in the United States.
Much bigger savings await if LEDs can supplant Mr. Edison’s bulb at the office and in the living room. Creating a white-light LED that is energy-saving, cheap and appealing has proved a tough engineering challenge. But all the major lightbulb makers—including General Electric, Philips, and Osram-Sylvania—are teaming up with semiconductor manufacturers to make it happen.
What does Irvine-Halliday think of LEDs?
选项
A、They are cool and steady, but rugged.
B、They will replace Edison’s lightbulbs someday.
C、They are easily maintained.
D、They are very cheap.
答案
B
解析
第二段接着说,发光二极管比爱迪生的白炽灯具有更大的优越性,所以哈利德期待它能取代白炽灯成为世界的主要人造光源。
转载请注明原文地址:https://kaotiyun.com/show/x5QO777K
0
考博英语
相关试题推荐
Manymentalinstitutionsthroughoutthecountryhavebeenturnedintodumpinggroundsforthousandsofoldsterswhohavenoplac
Inthepast,consumerswereoftencheatedor______intobuyinggoodsbybusinesssandtheycouldhardlydoanythingaboutit.
Howeverimportantwemayregardschoollifetobe,thereisnogainsayingthefactthatchildrenspendmoretimeathomethanin
Television—thatmostpervasive(遍布的)andpersuasiveofmodernofmoderntechnologies,markedbyrapidchangeandgrowth—ismovin
Itcanbeinferredfromthepassagethattheauthorwouldmostlikelydescribetheevolutionoffeministliterarytheoryas_____
Itcanbeinferredfromthepassagethattheauthorwouldmostlikelydescribetheevolutionoffeministliterarytheoryas_____
WhenDonaldarrivedforhisfirstgroup-therapysessionhewasinawheelchair,sufferingfrommalignantmelanomaandseverelyd
Thefundamentaldistinctionbetweenaconstitutionandordinarylawsissimilartothatbetweenlawsingeneralandtheirapplic
Tosurviveintheintensetradecompetitionbetweencountries,wemust______thequalitiesandvarietiesofproductswemaketo
______Irealizedtheconsequences,Iwouldneverhavecontemplatedgettinginvolved.
随机试题
下列关于心尖的描述中,正确的是
注水井封隔器不密封和分层测试期间,不能计算()水量。
正常血小板直方图分布范围在
毒性较小的酯类麻药是血管收缩剂是
胆囊切除手术中,不适合胆总管探查指征的是
轴承是汽车的先行商品,根据汽车的需求量,就可以推断轴承的需求量。这种预测方法是()。
公安教育与科研工作是为公安队伍提供人才和科学技术保障的专门工作。
(91年)试证明n维列向量组α1,α2,…,αn线性无关的充分必要条件是行列式其中αiT表示列向量αi的转置,i=1,2,…,n.
Formanywomenchoosingwhethertoworkornottoworkoutsidetheirhomeisaluxury:they.mustworktosurvive.Othersfacea
Thoreausaideducationoftenmadestraight-cutditchesoutoftwistingsmallstreams.ButnotattheEcoDorm,whichhouses36un
最新回复
(
0
)