调研的英文 study survey 哪个比较合适?为什么?

Base on a questionnaire, this article explored the current condition of personalization in city libraries. It also analyzed such condition and therefore proposed urgent development in personalized service for most the libraries. The author of this article had sought causes from both the readers and the workers in libraries.He(she) articulated readers'demand on personalized service in libraries in which they could achieve high-speed,accurate and updated information service according to their needs at low cost, by simply using their mobile phones and laptops. He (she) also provided his own proposal on how to develop personalized service.

求具体题目啊!

第二节 液体的压强
课内练习
1、由于受到_________作用，液体对支持它的容器底有压强；液体还具有_________性，因此对容器的侧壁也会产生压强。
2、液体内部的压强与_________和_________有关，同一深度，液体向下的压强_________(填“＞”或“＜”＝。
3、增大液体压强的方法有（1）__________________；（2）__...

1-5CEDBA 6-10CACBB 11 park 12.on 13.sunday 14.friend 15.seal 16.and 17.met 18.actress 19.a 20.souvenir 21.OnFeb6.1973 22.started to play tennis 23.In1983 24.she joined the National Team 25.IN1997 26.capital 27.tired 28.wash 29.alone30.leader 31.impression 32.independent 33.inventor's 34.Italian 35.private 36-50DBCBDBABBDCCADA
50-55 FBGDA 56.Will you please say it again moreslowly 57.Are YOU FROM Paris 58.How long have you lived there 59.You think 60.It was nice talking to you 61-71BBDCDABCAD 71-75CBCAB 76-80CFEBD 81-85ceabd 86-90 FFTTF

已经发你邮箱.查收.也可去空间看一下.

http://chem.hengqian.com/html/2008/3-16/r16224282.shtml

设每个提价x元,即每个售价为(50＋x)元,销量为(500-10x)个,则获利
y=(50+x)(500-10x)-40(500-10x)=-10(x-20)2＋9000．
所以x=20时,获利y取得最大值,即销售单价为70元时,获得利润最大．
- -

设种甲种x株
400x+(3x+10)*300≤30000
(760-400)*x+(540-300)*(3x+10)≥21600
17.7≤x≤20.7
x=18 3x+10=64
x=19 3x+10=67
x=20 3x+10=70 或甲x 乙3x+10
x*(760-400)+(3x+10)*(540-300)>=21600
400x+300*(3x+10)

1.A2,A3,无4、C酒精是非电解质,A液氯是单质也不属于电解质5、C6、A7、C8、B9、D10、B

设每台冰箱的定价应为x元,
每天可以售出的冰箱数为8+(2900−x)/50×4=-2（x-3000）/25
利润为
（x-2500）[-2（x-3000）/25]
=-2（x²-5500x+7500000)/25
=-2（x-2750）²/25+5000
（1）由题意得-2（x-2750）²/25+5000=4800
解得x=2400
-2×（2400-3000）/25=48
每台冰箱的定价应为2400元,平均每天可以售出48台冰箱,利润平均每天达到4800元
（2）每天的销售利润4800元不是最大利润
当x=2750时,利润有最大值-2（2750-2750）²/25+5000=5000
每台冰箱的定价为2750元时利润最高,最高是5000元

镇江成语是管中窥豹,炙手可热,作文是寻找一盏灯,都江堰,一样吗

链接http://img.jxjyzy.com/ResourceHtml/2011/06/11/2319268.html有试题和答案

a survey on "thousands of villages & towns"

参考答案
参考答案：
1—5 CBBCA 6—10 BCBAC 11—15 CABAA 16—20 CCABA
21—25 BDACD 26—30 ADACB 31—35 CCBDB
36—40 BADBA 41—45 CDCAD 46—50 BCADA 51—55 CBCBD
56—60 DBBCA 61—65 DACBB 66—70 ACBAD
71. speaking / talking72. important / vital / significant 73. how 74. choose
75. positive76. influence / impact 77. rid
78. enables / allows / helps 79. humor 80. Working
One possible version:
Volunteer spirit is rooted in the hearts of many people, especially young people in China. In recent years, there have been large numbers of volunteers devoting their time and effort to people in need.
The picture shows us a touching moment when two volunteers help a disabled man in a wheelchair. Realizing it would be impossible for the man to get to the top all by himself, the volunteers carry the wheelchair with difficulty step by step up the stairs.
This picture reminds me of many volunteers in my school, my community and our country, helping not just the disabled, but also those who can’t find their way around, or those who suffer from misfortune. Volunteers make a difference to these people when they bring them warmth, comfort and relief.
I would be happy to be a volunteer, too, and help the senior citizens in the House for the Aged regularly so that they will not feel lonely but enjoy their life to the full.
听力材料：
Text 1
W: Bob, you are reading this book? I thought you disliked it.
M: Yes, it’s full of strange ideas with common photos, but it provides some technical data that might be useful in my study.
Text 2
W: Come on. Plenty of room here. Fares, please!
M: Two to the beach. How much is it?
W: Three dollars.
Text 3
W: Excuse me! I don’t have time to waste. I’ve been here almost one full hour!
M: Sorry, madam. You have to wait your turn. There’s no place for parking now.
Text 4
W: Bill, your work is too messy.
M: I’ll pay attention to my handwriting next time.
W: Is this a promise?
M: Yes, I’m serious this time.
Text 5
W: Oh, dear! It’s eight flights up!
M: That’s all right. We’ll get used to it. After all, we’re a little further away from the street and traffic noise and there’s no one living over us.
Text 6
W: I’m having a hard time getting the information for my report.
M: That’s easy. You only have to search the Internet to get what you want.
W: Really? But how?
M: So click here, then up to the top. Then open that window. Yeah, that one.
W: Er...Hum...Got it.
M: And that’s it. You’re done.
W: I see. That is pretty easy after all. Now I can get what I need in my room!
Text 7
W: Sir, may I please see your license? Do you know how fast you were going?
M: No, I’m not sure. I think about 65 miles per hour, right?
W: You’re not sure? You were going at 90 miles per hour! That’s 25 miles per hour over the legal speed limit! How can you explain your behavior?
M: Well, I was using a cell phone. While I did that I was listening to music, and eating some food.
W: I’ll have to give you a ticket. Be more careful next time.
Text 8
M: What are you reading about in that science magazine?
W: There are several interesting articles in it. I’ve just finished reading one about cloning.
M: I don’t like the idea of that. I don’t want people to copy me or any other people. It could be very confusing.
W: According to the article, you have no real need to worry. Research nowadays is focusing on cloning parts of a human body to replace damaged or lost parts, not on recreating a whole human being.
M: If so, we can benefit from it.
W: In this article, scientists say that if you took the genes from someone and tried to create a copy of a person, there’s no guarantee that the copy would look or act like the original!
M: Really? What else have you discovered?
W: I read about how scientists are using material from plants and animals to create new medicines.
M: That’s great, because it uses natural materials rather than ones that scientists make themselves. I prefer natural medicines to man-made ones.
Text 9
W: Let’s have seafood tonight and then go see the new movie at Mall Cinema. It’s a beautiful love story.
M: Oh, goodness, please not again. That’s what we did last week.
W: No, we didn’t. Last week we went to see that movie about a man’s struggle against illness.
M: Right, that was intended for women, just like this one. Besides, this is the last week for Rush Hour. And action movies like that need to be seen in a theatre on a big screen.
W: Oh, yeah, I did promise to see it with you. But you liked that movie, didn’t you?
M: Oh, sure, it was great. I had popcorn for dinner and paid the price of a movie ticket to get a two-hour sleep.
W: It wasn’t that bad and we went to an excellent restaurant.
M: That place doesn’t have a single meat dish. Just fish and you know I don’t like fish that much.
W: And I don’t like meat that much. The only meat I eat is chicken.
M: But when I pick the restaurant, I always respect your food preferences.
W: Well, I suppose that, to be fair, you should get to pick the movie and we can go to a restaurant that serves meat.
Text 10
Hi, everyone! I’d like to talk about healthy diets in this period. First of all, why should we eat healthy? Eating a healthy diet is important for long-lasting energy and illness prevention. Learning how to eat healthier and what it really means to do so will help you lose weight and feel great. It also helps you realize that no matter how busy your life is, you can take the time to have good meals and snacks throughout the day.
The importance of a healthy diet used to be just about having enough food to eat. In earlier times, this usually meant growing your own food and raising pigs, sheep or cows to feed your family. There were no such things as artificial colorings or flavorings or even so much worry about the different types of fats and what sugar calories can do to your weight.
The main problem with many diets today is that they are based on cutting out whole food groups to lose weight. It is true, for example, that if you cut your body off from carbs like potatoes and rice, you may lose pounds quicker but you are not really eating healthfully. By cutting out certain aspects of food, you are not giving your body what it needs to stay well. Eating right, having a balanced diet instead of eating the same things all the time is still the best way to lose weight safely without any bad effects to your body. Dieting is merely eating less and sometimes not getting the nutrients you need to stay in good health.
评分说明
任务型阅读：
第80题答案Working的首字母必须大写,写成小写不给分.
书面表达：
1．本题总分为25分,按5个档次给分.（参见附录）
2．评分时,先根据文章的内容和语言（内容要点、应用词汇和语法结构的数量和准确性、上下文的连贯性及语言的得体性）初步确定其所属档次,然后以该档次的要求来衡量,确定或调整档次,最后给分.（如果没有使用较复杂的句子结构,评分时将分数降低1个档次）.
3．词数少于130或多于170的,从总分中减去2分.
4．文章应分为三大块：1）简述图片内容；2）结合自身实际谈感想；3）考生举例说明.
缺少其中一块,文章为三档及以下.
5．遗漏支撑三大块主要内容的细节（如：情景、人物、动作、自身实际、活动内容、陈述原因等等）,每处扣2分.
6．语言形式错误分为大错和小错.大错包括“时态、语态、主谓一致”等,小错包括“单词拼写错误、小品词用法错误”等.
如出现1个大错,从总分中减去1分.如出现1个小错,从总分中减去半分.
7．如书写较差,以至影响交际,将分数降低1个档次.
8．如层次不清楚,写作没分段,从总分中减去2分.
附录：各档次的给分范围和要求
第五档 (很好)：(21—25分)
1．完全完成了试题规定的任务.2．覆盖所有内容要点.3．应用了较多的语法结构和词汇.4．语法结构或词汇方面有些许错误,但为尽力使用较复杂结构或较高级词汇所致；具备较强的语言运用能力.5．有效地使用了语句间的连接成分,使全文结构紧凑.6．完全达到了预期的写作目的.
第四档 (好)：(16—20分)
1．完全完成了试题规定的任务.2．虽漏掉1、2个次重点,但覆盖所有主要内容.3．应用的语法结构和词汇能满足任务的要求.4．语法结构或词汇方面应用基本准确,些许错误主要是因尝试较复杂语法结构或词汇所致.5．应用简单的语句间的连接成分,使全文结构紧凑.6．达到了预期的写作目的.
第三档 (适当)：(11—15分)
1．基本完成了试题规定的任务.2．虽漏掉一些内容,但覆盖所有主要内容.3．应用的语法结构和词汇能满足任务的要求.4．有一些语法结构或词汇方面的错误,但不影响理解.5．应用简单的语句间的连接成分,使全文内容连贯.6．整体而言,基本达到了预期的写作目的.
第二档 (较差)：(6—10分)
1．未恰当完成试题规定的任务.2．漏掉或未描述清楚一些主要内容,写了一些无关内容.3．语法结构单调、词汇项目有限.4．有一些语法结构或词汇方面的错误,影响了对写作内容的理解.5．较少使用语句间的连接成分,内容缺少连贯性.6．信息未能清楚地传达给读者.
第一档 (差)：(1—5分)
1．未完成试题规定的任务.2．明显遗漏主要内容,写了一些无关内容,原因可能是未理解试题要求.3．语法结构单调、词汇项目有限.4．较多语法结构或词汇方面的错误,影响对写作内容的理解.5．缺乏语句间的连接成分,内容不连贯.6．信息未能传达给读者.
不得分：（0分）
未能传达给读者任何信息：内容太少,无法评判；写的内容均与所要求内容无关或所写内容无法看清.

如果作为一道数学题可以这么算,但实际经营中降价带来的营业额增加不能按这种计算方法算

1-5、BBCCD
6-10、
11-17
18.△ABC中,AB=AC=2,∠A=36°,
所以
∠B=72°,∠C=72°
从B点作角B的平方线BD交AC于D,
则
∠DBC=36°=∠DBA=36°,∠CDB=72°=∠C
所以
BC=BD=AD,
三角形ABC相似于三角形BCD
从而
AB/BC=BC/CD
CD=AC-AD=AC-BC=2-BC
即
2/BC=BC/(2-BC)
BC^2+2BC-4=0
BC>0
所以
BC=-1+√5.
19、自己画图
P点落在双曲线上的情况有（2,-1）（1,-2）两种情况,
所以P=2/6=1/3
你看一下是不是,还有些没做完,如果是的话,待会做完了再告诉你
我自己做的,

解题思路：（1）根据所给数据易得方程和方程组，解之得函数表达式；
（2）设同时投资两种产品获利W万元，w=y_A+y_B，得出利润表达式，运用函数性质求解．

（1）∵当x=5时，y_A=2，
∴2=5k，
∴k=0.4．
∴y_A=0.4x．
当x=2时，y_B=2.4；
当x=4时，y_B=3.2
∴

2.4＝4a+2b
3.2＝16a+4b，
解得

a＝−0.2
b＝1.6．
∴y_B=-0.2x²+1.6x．

（2）设投资B种商品x万元，则投资A种商品（10-x）万元，获得利润W万元．
根据题意可得：
W=-0.2x²+1.6x+0.4（10-x）=-0.2x²+1.2x+4．
∴W=-0.2（x-3）²+5.8．
当投资B种商品3万元时，可以获得最大利润5.8万元，
所以投资A种商品7万元，B种商品3万元，这样投资可以获得最大利润5.8万元．

点评：
本题考点： 二次函数的应用．

考点点评： 此题难点在第二个问题，求出利润表达式，运用函数性质求最值，常用配方法或公式法．

解题思路：利润=投入资金×获利百分率，需要注意的是第一种出售方式中下月是在上月的基础上获利．

设投入资金x元，
如果本月初出售，到下月初可获利y₁元，
则y₁=10%x+（1+10%）x•10%=0.1x+0.11x=0.21x，
如果下月初出售，可获利y₂元，
则y₂=25%x-8000=0.25x-8000，
当y₁=y₂时，0.21x=0.25x-8000时，解得x=200000，
当y₁＞y₂时，0.21x＞0.25x-8000时，解得x＜200000，
当y₁＜y₂时，0.21x＜0.25x-8000时，解得x＞200000，
∴若商场投入资金20万元，两种销售方式获利相同；若商场投入资金少于20万元，本月初出售获利较多，若投入资金多于20万元，下月初出售获利较多．

点评：
本题考点： 一次函数的应用．

考点点评： 本题为方案选择问题，分情况讨论是不错的解法之一．当然也可以利用与一次函数相结合根据图象来求解．

（1）2÷（32+9+7+2）×100%
=2÷50×100%
=4%
答：不及格的人数占全班人数的百分之四；

（2）1-4%=96%
答：全班及格率是百分之九十六．

我不在扬州市维扬区!

1：不懂
2：设A为2,B为-2,则2÷1/-2 = 2÷(-1/2)=-4 ,则结果为-2A
3:唉,我也在做作业,不想想了.
4:这个比较麻烦.
俄,我至少也想了想,给点分咯

前面等式两边平方 得出 x+1/x+2=24%D%A然后将后面等式也平方得x+1/x-2

还有访谈法也可以,但是一般访谈法是结合问卷使用的,好像很少单独使用.

S1=a1=1,
当n>=2时,由已知,
-Sn*S(n-1)=an=Sn-S(n-1),
两端同除以 Sn*S(n-1) 得
-1=1/S(n-1)-1/Sn,
即 1/Sn-1/S(n-1)=1,
所以 ｛1/Sn｝是以 1 为首项,1 为公差的等差数列,
则 1/Sn=n,
所以 Sn=1/n .

1)请将分类依据代号填入相应的括号内：(　　H2、CO2)两种物质都不是电解质 (　Na2O、NaCl　)两种物质都是钠的化合物(　CO2、Na2O　)两种物质都是氧化物 (　NaCl、FeCl3　)两种物质都是盐(2)用洁净的烧杯取少量蒸馏水,用酒精灯加热至沸腾,向烧杯中逐滴加入饱和的图中某种物质M的溶液加热至呈红褐色.①物质M的化学式为_________FeCl3_______.②证明有红褐色胶体生成的实验操作是 用一束光 照射 可以产生丁达尔效应

解题思路：利润=投入资金×获利百分率，需要注意的是第一种出售方式中下月是在上月的基础上获利．

设投入资金x元，
如果本月初出售，到下月初可获利y₁元，
则y₁=10%x+（1+10%）x•10%=0.1x+0.11x=0.21x，
如果下月初出售，可获利y₂元，
则y₂=25%x-8000=0.25x-8000，
当y₁=y₂时，0.21x=0.25x-8000时，解得x=200000，
当y₁＞y₂时，0.21x＞0.25x-8000时，解得x＜200000，
当y₁＜y₂时，0.21x＜0.25x-8000时，解得x＞200000，
∴若商场投入资金20万元，两种销售方式获利相同；若商场投入资金少于20万元，本月初出售获利较多，若投入资金多于20万元，下月初出售获利较多．

点评：
本题考点： 一次函数的应用．

考点点评： 本题为方案选择问题，分情况讨论是不错的解法之一．当然也可以利用与一次函数相结合根据图象来求解．

D．③①②⑤④

（一滴水在宇宙中不过是一个微小的点，可是它却能反映出整个太阳。这就意味着整个太阳已经被“压缩”进一个水滴之中；我们的眼睛不过几厘米大小，却能看到整个星空，只有整个星空的信息被浓缩进空间的每一个点上，这才有可能。于是，当我们面对清晨绿叶上的串串露珠时，仿佛看到无数的太阳在微风中舞蹈；当我们凝视少女那秋潭般碧澈的眼睛时，似乎看到了一个奥妙无穷的宇宙。）

听力 23123/32123/13332/12132/ 单选 12312/34213/42314/ 31243/43433/21234/12412/ 2423/221/4131/3413

解题思路：利润=投入资金×获利百分率，需要注意的是第一种出售方式中下月是在上月的基础上获利．

设投入资金x元，如果本月初出售，到下月初可获利y1元，则y1=10%x+（1+10%）x•10%=0.1x+0.11x=0.21x，如果下月初出售，可获利y2元，则y2=25%x-8000=0.25x-8000，当y1=y2时，0.21x=0.25x-8000时，解得x=200000，当y1...

点评：
本题考点： 一次函数的应用．

考点点评： 本题为方案选择问题，分情况讨论是不错的解法之一．当然也可以利用与一次函数相结合根据图象来求解．

conduct investigatin and resear about the wholesale market

2010年高三英语调研测试
参 考 答 案
听力理解 (每小题2分,满分30分)
5 ABACB 10 CABBB 11~15 BCCBA
听取信息 (每小题1分,满分5分)
16.Golden Star 17.run large programs 18.Watch movies
19.Germany 20.5,500
完形填空 (每小题2分,满分20分)
21~25 CBCDB 26~30 CACBD
语法填空 (共10小题；每小题1.5分,满分15分)
31.from 32.but 33.pulling 34.astonished 35.whose
36.thoughtful 37.thanked 38.himself 39.that 40.in
阅读(每小题2分,满分40分)
41~45 BCDBA 46~50 DBACB 51~55 BABCD 56~60 EAFCB
基础写作（满分15分）
I participated in a fantastic English talent show in People’s Park on Dec.25,2009.Middle school students from all over Guangzhou performed all kinds of programs,like English songs,English short plays and English stories.The purpose of this show is to encourage students to introduce Guangzhou and the 2010 Asian Games in English and to arouse students’ interest in English as well.
I was very excited because I was the leading actor/actress in an English short play at the show.Though I was a little bit nervous at the beginning,later on I felt relaxed and the performance was a great success.
读写任务（满分20分）
Dear Concerned Mum,
In your letter you say that the extra free time your son has is causing him to become lazy and neglect his studies.You fear that this will affect his future both at university and at work.
I quite understand how you feel but still I think you may be worrying unnecessarily.The extra free time may actually help his studies.Using this time to relax and have fun can refresh both his mind and his body,allowing him to study more effectively.Remember the quantity of study isn’t as important as the quality of study.Spending more time with his friends will also help him develop his social skills.This is very important when he finally enters the workforce.
Naturally you don’t want your son to fall behind.But wait until his next exams before judging the effects of the change.If you find there’s a problem then you could send him to private weekend classes or even make him to spend 3 hours on each day of the weekend at home doing extra study.
Yours sincerely
Abby

[－1,2]

∵y＝f(x ² －1)的定义域为[－ ， ]，
∴x∈[－ ， ]，x ² －1∈[－1,2]，
∴y＝f(x)的定义域为[－1,2]．

解题思路：设每台电脑x万元，每台电子白板y万元，根据购买1台电脑和2台电子白板需要3.5万元，购买2台电脑和1台电子白板需要2.5万元，列方程组求解．

设每台电脑x万元，每台电子白板y万元，
由题意得，

x+2y＝3.5
2x+y＝2.5，
解得：

x＝0.5
y＝1.5．
答：每台电脑0.5万元，每台电子白板1.5万元．

点评：
本题考点： 二元一次方程组的应用．

考点点评： 本题考查了二元一次方程组的应用，解答本题的关键是读懂题意，设出未知数，找出合适的等量关系，列方程组求解．

（1）将 和 代入一次函数m=kt+b中,
有 ,
∴ ．
∴m=-2t+96．
经检验,其它点的坐标均适合以上解析式,
故所求函数解析式为m=-2t+96；
（2）设前20天日销售利润为p1元,后20天日销售利润为p2元．
由p1=（-2t+96）（ t+25-20）
=（-2t+96）（ t+5）
=- t2+14t+480
=- （t-14）2+578,
∵1≤t≤20,
∴当t=14时,p1有最大值578（元）．
由p2=（-2t+96）（- t+40-20）
=（-2t+96）（- t+20）
=t2-88t+1920
=（t-44）2-16．
∵21≤t≤40,此函数对称轴是t=44,
∴函数p2在21≤t≤40上,在对称轴左侧,随t的增大而减小．
∴当t=21时,p2有最大值为（21-44）2-16=529-16=513（元）．
∵578＞513,故第14天时,销售利润最大,为578元；
（3）p1=（-2t+96）（ t+25-20-a）=- t2+（14+2a）t+480-96a
对称轴为t= =14+2a．
∵1≤t≤20,
∴当t≤2a+14时,P随t的增大而增大
又每天扣除捐赠后的日利润随时间t的增大而增大,
故：20≤2a+14,
又∵a＜4,
∴3≤a＜4．

ABCBA BACAC BABBC ABBAC
ABACD BADCB CCBAD
CABDA CBBCC DDCAD ACBAC
BCCA ACCB ADAB CCA
South stay wrapped Features everywhere preserved/protected Getting music/noise(s)
spring Preference

已发

大哥,你好歹给偶原题啊

“为寻求业务发展和开发项目等进行考察调研”
go on a survey trip in search of business development and project exploitation.

一、选择题
5 B B B B D 10 C D C C D
11～15 B D C C A 16～20 C C D A C
21～25 B C B B D 26～30 D D B B B
二、简答题
31．（1）8 纤维素
（2）6 液泡 8 细胞壁
（3）5 12
（4）生长点细胞没有叶绿体和（大型）液泡
32．（1）无水乙醇
（2）石蜡油 CO2
（3）唾液腺 大 具有横纹
（4）用解剖针捣毁脊髓 完成反射需要完整的反射弧
33．（1）光反应 H2O ATP 光 ATP NADPH
（2）暗反应 糖（有机物） 化学
34．（1）胰高血糖素 胰岛素 糖原
（2）胰岛
（3）增加 ①
（4）增加 ②
35．（1）样方
（2）四角的顶点 用绳连起样方的四个顶点
（3）物种数 每个物种的个体数
（4）多样性（丰富程度）
36．（1）乙 数目 形态结构
（2）甲和乙
（3）甲
（4）初级精母
37．（1）① 近亲婚配 ② 三代以内旁系血亲 增加 增大 ③ B
（2）① 常 显性 ② 100 ③ 手术没有改变该男生的致病基因
38．（1）B
（2）转录 翻译 蛋白质
（3）全能性
39．（1）真空渗水法 空气 水分 小 细胞间隙 上浮 上浮所需时间
（4）③ 温度 叶圆片上浮所需时间 不同的温度（5℃、25℃、45℃）

语文 文言文会出三峡和答谢中书书

有疑问可提交讨论

31分的同学要加油了.

大气湍流: 激光束通过湍流大气传输时,由于湍流大气中折射率的随机不均匀分布,其强度、相位和传输方向会受到扰动而出现随机变化,变化情况与激光束宽w,和湍流尺度l的相对大小有关；当2w/l1时,光束截面内包含许多湍流漩涡,引起光束强度起伏、相位起伏和光束扩展.记在弱湍流下,折射率改变很小,但由于存在大量的不均匀元,以致在一定距离之外,积累效应就十分显著,包括光束漂移、光束扩展、到达角起伏、大气闪烁等.

崇明 2010学年 初二
在“百度文库”中键入以上三个关键词,即可搜索到.第一个文档就是.

解题思路：（1）连接AC，由四边形ABCD为圆内接四边形，利用圆内接四边形对角互补得到∠ABC+∠ADC=180°，在三角形ABC与三角形ADC中，分别利用余弦定理表示出AC²，将各自的值代入求出cos∠ABC的值，进而确定出∠ABC与∠ADC的度数，代入计算即可求出AC的长；
（2）四边形ABCD面积=三角形ABC面积+三角形ADC面积，求出即可；在三角形ABC中，利用正弦定理即可求出R的值．

（1）连接AC，
∵四边形ABCD为圆的内接四边形，
∴∠ABC+∠ADC=180°，
∵AB=AD=4千米，BC=6千米，CD=2千米，
∴由余弦定理得：AC²=4²+6²-2×4×6cos∠ABC=4²+2²-2×2×4cos∠ADC，
∴cos∠ABC=[1/2]，
∵∠ABC为三角形内角，
∴∠ABC=60°，∠ADC=120°，
∴AC²=4²+6²-2×4×6×[1/2]=28，即AC=2
7（千米）；
（2）根据题意得：S_{四边形ABCD}=[1/2]×4×6sin60°+[1/2]×2×4sin120°=8
3（平方千米），
由正弦定理得：2R=[AC/sinB]=
2
7


3
2=
4
21
3（千米），
则R=
2
21
3（千米）．

点评：
本题考点： 余弦定理；正弦定理．

考点点评： 此题考查了正弦、余弦定理，以及特殊角的三角函数值，熟练掌握定理是解本题的关键．