如果只能申请到美国CS前100的大学，是出国还...

Copying Birds May Save Aircraft FuelBoth Boeing and Airbus have trumpeted the efficiency of their newest aircraft.The 787 and 350 respectively.Their clever designs and lightweightcompositescertainly make a difference.But a group of researchers at Stanford University,led by Ilan Kroo,has suggested that airlines could take a more naturalisticapproach to cutting jet-fuel use and it would not require them to buy newaircraft.The answer,says Dr Kroo,lies with birds.Since 1914,scientists have known thatbirds flying in formation-a V-shape-expend less energy.The air flowing over abird's wings curls upwards behind the wingtips.a phenomenon known asupwash.Other birds flying in the upwash experience reduced drag,and spendless energy propelling themselves.Peter Lissaman,anaeronautics expert whowas formerly at Caltech and the University of Southern California,has suggestedthat a formation of 25 birds might enjoy a range increase of 71%.When applied to aircraft,the principles are not substantially different.Dr Krooand his team modeled what would happen if three passenger jets departing fromLos Angeles,San Francisco and I as Vegas were to assemble over Utah,assume aninverted V-formation occasionally change places so all could have a turn in themost favourable positions,and proceed to London.They found that the aircraftconsumed as much as 15%less fuel（coupled with a reduction in carbon-dioxideoutput）.Nitrogen-oxide emissions during the cruising portions of the flight fellby around a quarter.There are,of course,knots to be worked out.One consideration is safety,or atleast the perception of it.Would passengers feel comfortable travelling incompanion?Dr Kroo points out that the aircraft could be separated by severalnautical miles,and would not be in the intimate groupings favoured by displayteams like the Red Arrows,A passenger peering out of the window might noteven see the other planes.Whether the separation distances involved wouldsatisfy air-traffic-control regulations is another matter,although a working groupat the International Civil Aviation Organisation has included the possibility offormation flying in a blueprint for new operational guidelines.It remains to be seen how weather conditions affect the air flows that makeformation flight more efficient.In zones of increased turbulence,the planes'wakes will decay more quickly and the effect will diminish.Dr Kroo says this isone of the areas his team will investigate further.It might also be hard for airlinesto co-ordinate the departure times and destinations of passenger aircraft in a waythat would allow them to gain from formation flight.Cargo aircraft,in contrast,might be easier to reschedule,as might routine military flight.As it happens,America's armed forces are on the on case already.Earlier thisyear the country'S Defence Advanced Research Projects Agency announcedplans to pay Boeing to investigate formation flight,though the programme hasyet to begin.There are reports that some military aircraft flew in formation whenthey were low on fuel during the Second World War,but Dr Lissaman says theyare unsubstantiated."My father was an RAF pilot and my cousin the skipper of aLancaster lost over Berlin,"he adds.So he should know
Findings of the Stanford University researchers will promote the sales of newBoeing and Airbus aircraft.

2003年6月1日至7月31日，某百货大楼举办有奖销售活动。活动期间，凡在百货大楼购物满20元者均可获得奖券一张。周某因购物获得数张奖券，其中一张号码为047956。7月31日，百货大楼在公证员的公证下公开摇奖，摇得金奖一个，号码即为047956，奖金5000元。百货大楼当即将中奖号码及奖金额公布于大楼门前的公告牌上，并注明“中奖者须在8月10日前兑奖，逾期作自动放弃处理”。除此之外，百货大楼从未作出任何关于兑奖时限的公开规定。8月4日、9日、11日，该市日报三次公布了百货大楼的中奖号码及奖金额(但未注明兑奖期限)。周某从报上得知自己中奖后，于8月21日到百货大楼兑奖，百货大楼以期限已过为由拒绝。无奈，周某起诉到法院，请求百货大楼兑付其中奖奖金。问：
(1)百货大楼从事有奖销售活动，属于什么性质的行为?为什么?
(2)周某是否有权要求被告交付中奖奖金?为什么?
(3)百货大楼在摇奖后公告领奖期限的行为性质如何认定?对周某是否具有约束力?为什么?

简述判别心理异常的四个标准。