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
2013-01-12
25
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.
The author implies that villagers liked LED bulbs very much, because they______.
选项
A、were given by Irvine-Halliday
B、are rugged
C、are cheap
D、are easily-recharged
答案
D
解析
这是一道引申判断题。第2段提到,村民们每晚用电4个小时,然后用脚踏的方式来给电池充电。可以想象,在一个遥远的小村庄,这可能是最理想的充电方式了。
转载请注明原文地址:https://kaotiyun.com/show/RO9O777K
0
考博英语
相关试题推荐
Woodyarrivedatamost______moment;Iwasjustgettingintothebath.
Jameshasjustarrived,butIdidn’tknowhe______untilyesterday.
______ifIhadarrivedyesterdaywithoutlettingyouknowbeforehand?
Thebusmovedslowlyinthethickfog.Wearrivedatour______almosttwohourslater.
IarrivedattheairportsolatethatI_____missedtheplane.
Myauntlosthercatlastsummer,butit____aweeklateratahomeinthenextvillage.
IarrivedattheairportsolatethatI_____missedtheplane.
随机试题
预算管理制
消化性溃疡患者最常见的并发症是
A、刃状边缘B、凿状边缘C、凹形边缘D、肩台形边缘E、斜面形边缘铸造金属全冠一般为
设,则秩r(AB—A)等于()。
[2011年第11题]设L为连接点(0,2)与点(1,0)的直线段,则对弧长的曲线积分(x2+y2)ds=()。
扬帆集团是一家中药制造企业。2015年以前,扬帆集团主打的Q产品治疗热毒肿痛功效显著,很受市场欢迎,被认为是国家名药。近年来中药市场需求依然旺盛,然而扬帆集团的Q产品销售增长缓慢,公司的业绩和市值增长指标不如其他著名中药企业。根据SWOT分析,扬帆集团目前
因急需新设销售门店,甲公司委托中介代为寻找门市房,并约定中介费用为10万元。2×16年2月1日,经中介介绍,甲公司与丙公司签订了经营租赁合同。合同约定:租赁期自2×16年2月1日起3年,年租金为420万元,丙公司同意免除前两个月租金;丙公司尚未支付的物业费
卢梭反对天赋观念,提出了白板说。
北大西洋公约组织
有以下程序structS{intn;inta[20];};voidf(struct*P){inti,j,t;for(i=0;i<p->n-1;i++)for(j=i+1;j<p->n.j++)if(p->a[i]>p->a[j]
最新回复
(
0
)