星耀夜阑
排放冷却是对流冷却的另一种。与再生冷却不同，用于排放冷却的冷却剂对推力室冷却吸热后不进入燃烧室参与燃烧，而是排放出去。直接排放冷却剂会降低推力室比冲，因此需要尽可能减少用于排放冷却的冷却剂流量，同时只在受热相对不严重的喷管出口段采用排放冷却。还有一种是辐射冷却，其热流由燃烧产物传给推力室，再由推力室室壁想周围空间辐射散热。辐射冷却的特点是简单、结构质量小。主要应用于大喷管的延伸段和采用耐高温材料的小推力发动机推力室。在组织推力室内冷却时，是通过在推力室内壁表面建立温度相对较低的液体或气体保护层，以减少传给推力室室壁的热流，降低壁面温度，实现冷却。内冷却主要分为头部组织的内冷却（屏蔽冷却）、膜冷却和发汗冷却三种方法。推力室采用内冷却措施后，由于需要降低保护层的温度，所以燃烧室壁面附近的混合比不同于中心区域的最佳混合比（多数情况下采用富燃料的近壁层），造成混合比沿燃烧室横截面分布不均匀，使燃烧效率有一定程度的降低。膜冷却与屏蔽冷却类似，是通过在内壁面附近建立均匀、稳定的冷却液膜或气膜保护层，对推力室内壁进行冷却，只是用于建立保护层的冷却剂不是喷注器喷入的，而是通过专门的冷却带供入。冷却带一般布置在燃烧室或喷管收敛段的一个横截面上。沿燃烧室长度方向上可以有若干条冷却带。为提高膜的稳定性，冷却剂常常经各冷却带上的缝隙或小孔流入采用发汗冷却时，推力室内壁或部分内壁由多孔材料制成，其孔径为数十微米。多孔材料通常用金属粉末烧结而成，或用金属网压制而成。此情况下，尽可能使材料中的微孔分布均匀，是单位面积上的孔数增多。液体冷却剂渗入内壁，建立起保护膜，使传给壁的热流密度下降。当用于发汗冷却的液体冷却剂流量高于某一临界值，在推力室内壁附近形成的是液膜。当冷却剂流量低于临界值流量时，内壁温度会高于当前压力下的冷却剂沸点，部分或全部冷却剂蒸发，形成气膜。除了以上热防护外，还有其他热防护方法如：烧蚀冷却、隔热冷却、热熔式冷却以及室壁的复合防护等。3 高焓气体发生器热防护方案综合上述方法结合实际情况，便得到高焓气体发生器的热防护方法。高焓气体发生器的燃烧室与液体火箭发动机的不同，省去前面的推力室部分，使得其结构更简单而有效。那么，所涉及到的热防护即为对燃烧室室壁的热防护部分。由于燃料进入燃烧室内迅速分解并放出大量
樱花龙女
全新版大学英语听说教程2答案百度网盘免费下载
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《大学英语听说教程》是2005年8月科学出版社出版的图书，作者是冯健。本书重点要求学生掌握和提高英语的语言能力、交际能力和实际运用能力，实用性强。
搁小浅671
高考英语听说练习题及答案
随着国际性大公司纷纷抢占中国市场,若想在其中谋得满意的职位,英语听说能力是必不可少的敲门砖。下面是我整理的高考英语听说试题及答案，希望能帮到大家!
A、对话理解。本部分共有四段对话，每段对话后有两个问题。请根据对话内容，在各题所给的三个选项中选出一个最佳答案，用鼠标在题号前选择。每段对话听两遍。本题共8分。
听第一段对话，回答第1---2小题。
M: Hi, Mary. Last Saturday was your birthday, wasn't it?
W: I had a party that day, but actually, my birthday was on Friday.
M: Oh, I see. How was the party?
W: It was wonderful. I got many gifts.
M: Really? What did you get?
W: Well, my parents gave me a bike, my uncle gave me a pet cat.
M: How about Jack? What did he give you?
W: He gave me beautiful roses.
( ) 1. When was Mary's birthday?
A. Sunday. B. Saturday. C. Friday.
( ) 2. What did Mary get from her uncle?
A. Roses. B. A bike. C. A cat.
听第二段对话，回答第3---4小题。
W: Hi, Tom. I heard you changed your job?
M: Yes, I’m tired of office work.
W: How is your new work?
M: Very good. I like teaching little kids. They are so lovely.
W: How many kids do you teach?
M: There are twenty-two kids in my class, half are boys and half are girls.
W: What do you teach these little kids?
M: Well, some singing and dancing, sometimes I play games with them.
W: They must be very fond of you.
( ) 3. What did Tom do before?
A. A singer. B. An office worker. C. A teacher.
( ) 4. How many boys are there in Tom's class?
A. Eleven. B. Twelve. C. Twenty-two.
听第三段对话，回答第5---6小题。
W: Morning Peter, what are you doing?
M: I'm planning for my summer vacation.
W: You like travelling a lot. Where are you going this summer?
M: I'm not very sure yet. Last summer, I visited some cities in Shandong.
W: So you won't visit large cities this year, will you?
M: No, I am thinking of going to small cities in Hunan this summer. What about you, Mary?
W: Well, I think I will stay in Guangzhou again and study.
M: Come on. You need a rest.
( ) 5. Where did Peter go last summer?
A. Shandong. B. Hunan. C. Guangzhou.
( ) 6. What do we know about Mary?
A. She likes travelling. B. She studies hard. C. She needs a plan.
听第四段对话，回答第7---8小题。
W: Excuse me, sir. How can I get to the City Museum?
M: Oh, the Museum is in the city center, on the main street.
W: How could I get there?
M: There is a bus stop there. Take bus No.12 and get off at the stop, City Library.
W: How long shall I walk after getting off the bus?
M: You need to walk for about five minutes. The Museum is opposite the library.
W: Thank you very much.
( ) 7. What place is the woman looking for?
A.The library. B. The bus stop. C. The museum.
( ) 8. How long is the distance between the bus stop and the library?
A. About 5 minutes. B. About 8 minutes. C. About 12 minutes.
B、短文理解。你将听到一篇短文，短文后面有5个问题，请根据短文的内容，在每小题所给的.三个选项中选出一个能完成句子的最佳选项。短文听两遍。本题共5分。
Next Sunday is Father’s Day, and Mary wants to buy a special gift for her father. Her father was fifty-eight and would retire in two years. She looked at the Father’s Day advertisements in the newspaper, but they mostly had sales on ties and bottles of beer. Her father doesn’t like to wear ties, and he never drinks beer. He used to go fishing on the weekends, but lately he’s been staying home and working in the garden. Mary can spend about $45 on her father’s gift. She wants to buy him something that he will use every week. Last year she got him a sweater and two T-shirts. She wants to get him something different this year, such as gardening or fishing tools.
( ) 9. Mary wants to buy her father a gift because it’s going to be _________.
A.the Father’s Day B. her father’s birthday C. a big sale day
( ) 10. Mary's father used to _____________ on weekends.
A. drink beers B. go fishing C. work in gardens
( ) 11. Mary could spend _________ on her father's gift.
A. $60 B. $58 C. $45
( ) 12. Last year, Mary gave her father some___________ as gifts.
A. fishing tools B. T-shirts C. gardening tools
( ) 13. Lately, Mary's father likes to __________ on weekends.
A. go fishing B. read newspaper C. work in the garden
听力答案：
A). 1. C 2. C 3. B 4. A 5. A 6. B 7. C 8. A
B) 9. A 10. B 11. C 12. B 13. C
C、朗读短文。你将会在屏幕上看到一篇短文，准备30秒钟，按照提示朗读并在规定时间内录音。本题共3分。
A Man was going to the house of a rich person. As he went along the road, he saw a box of good apples at the side. He said, "I don't want to eat those apples; for the rich man will give me much food; he will give me very nice food to eat." Then he took the apples and threw them away into the dust. He went on and came to a river. The river had become very big; so he could not go over it. He waited for some time, then he said, "I cannot go to the rich man's house today, because I cannot get over the river." He began to go home. He didn't eat anything that day. He came to the apples, and took them out of the dust and ate them.
D、情景对话。请你根据所给的情景与提示扮演角色，进行提问或回答4个问题。在完成每个问题之前，你有5秒钟左右的准备时间，按照提示在规定时间内录音。本题共4分。
角色： Tom和小芳，学生。
情景：两人在讨论各自的兴趣爱好，Tom喜欢球类运动，小芳喜爱音乐舞蹈等。
你将扮演小芳的角色。
Tom: Hi, Xiao Fang. What are you doing? <电脑屏幕显示>
考生:I'm practicing my dancing skills.
Tom: Dancing skills? Do you like dancing? <电脑屏幕显示>
考生: Yes, I like dancing very much.
Tom: What about music? Do you like music?
考生：Yes, music and dancing are my hobbies. What are your hobbies?
Tom: Well, I like playing basketball and football. <电脑屏幕显示>
考生: Who do you often play with?
Tom: I often play basketball with my roommates. <电脑屏幕显示>
E、口头作文。下面是Xiao Bin上周五的一次经历。请你根据所给的图片进行1分钟的口头作文。在进行口头作文前，你有50秒左右的准备时间，按照提示在规定时间内录音。本题共5分。
给分点建议：1) Last Friday, Xiao bin was passing a basin; 2)He found that the tap was not shut well and water was dropping; 3) He went over to turn off the tap to stop water dropping; 4) He was praised by a teacher; 5) Everyone has the duty to save water;
一纯佛雨
新视野大学英语听说教程2答案 (Unit 1-6) Unit1Warming up1.T 2.F 3.NGShort conversations1.B 2.D 3.C 4.D 5.C 6.C 7.B 8.B 9.A 10.CLong conversation1.D 2.D 3,A 4.B 5.CUnderstanding a passage1.C 2.D 3.B 4.C 5.BMovie dialog1. upset 2.sick 3.law 4.harmless 5.break 6.replaced 7.memories 8.natural 9.birthday 10.appreciateListening and speaking 1.sit quietly and listen to 2.a blank stare 3.put it a different way 4.speak up in class 5.in turn 6.a great deal of HomeworkTask11.D 2.C 3.B 4.D 5.BTask21.C 2.A 3.B 4.A 5.CTask31.the age,size and future 2.Seventy years ago 3.increase with distance 4.Late last month 5.A light year 6.distances in space7.other measurements 8.support the idea 9.slow down and break up 10.or possibly even olderUint2Warming up1. passion 2.make sacrifices 3.the meaning of greatnessShort conversations1~5.BBCCC 6~10.AAACALong conversation1D 2.B 3.C 4.D 5.DUnderstanding a passage1.C 2.B 3.C 4.D 5.D Movie dialog1. training 2.touch 3.understand 4.appreciate 5.trouble 6.fighting 7.three 8.honest 9.cry 10.borrowListening and speakingHomeworkTask11.D 2.C 3.D 4.B 5.ATask21.A 2.B 3.C 4.B 5.DTask31.on the ball 2.did something unexpected 3.at the job or activity 4.hit it out of the park 5.think it over 6.is very successful 7.complete a job or activity 8.did something wrong 9.how much it ia worth 10.close to myUnit3Warming up3~2~1Short conversations1~5.DABCD 6~10ADBABLong conversation1.A 2.B 3.D 4.D 5.AUnderstanding a passage1.B 2.D 3.D 4.A 5.B Movie dialog1.night 2.definitely 3.love 4.wise 5.My wife 6.26 7.died 8.youngest 9.goea by 10.gotten oldListening and speaking 1. physically OK 2.To the kitchen 3.a bowl of ice cream with strawberries 4.I don’t need to write it down 5.a plate of bacon and eggsHomeworkTask11.A 2.B 3.D 4.C 5.DTask21.B 2.D 3.B 4.C 5.ATask31. they care about 2.performed marriages 3.wait longer to get married 4.bring people together 5.plan a blind date 6.follow their cultural 7.meant for the other 8.establishing a relationship 9.improve their chances 10.meet someone over the InternetUnit4Warming up1.c 2.A 3.AShort conversations1~5DBCAB 6~10DACCBLong conversations1.B 2.A 3.C 4.D 5.BUnderstanding a passage1.C 2.B 3.D 4.B 5.AUnderstanding a Movie Speech1. certain 2.occasionally 3.come along 4.receiving 5.delight 6.gathering 7.natural 8.special 9.welcoming 10.remindingListening and speaking1.a class of adults 2.the ruler,the book,the pen and so on3.Give me the keys4.looked surprised and somewhat at a loss5.threw his arms around the teacher’sneck and kissed him on both cheeksSupplementary listeningListening and speakingHomeworkTask11.A 2.C 3.A 4.B 5.BTask21.D 2.C 3.A 4.C 5.BTask31.answer a question 2.to be admitted 3.copies of all school records 4.the results of the TOEFL score5.minimum accept students 6.additional English training 7.conditionally accept students 8.taking regular classes9.provides more information 10.successfully pass classesUnit5 Warming up1.F 2.T 3.TShort conversations1~5CDACA 6~10BDDDCLong conversations1.B 2.D 3.A 4.D 5.AUnderstanding a passage1.D 2.C 3.B 4.A 5.CMovie dialog1. Everything the light touches 2.rises and falls 3.will rise with you 4.shadowy place 5.never go there6.getting your way 7.exists together 8.respect all the creatures 9.let me explain 10.in the great circle of lifeListening and speaking1.He smoked ,drank,and acted in a manner generally bad for his health2.He learned how to be a good person 3.He died early ,along and sad 4.Open-ended 5. Open-endedHomeworkTask11.B 2.A 3.D 4.B 5.CTask2 1.A 2.C 3.D 4.D 5.BTask31.one million new cases 2.have increased 3.drug treatments 4.gathered results 5.145.000 6.before it has spread 7.from coming back 8.reduce by half 9.within 15 years 10.middle-aged womenUnit6Warming up1.T 2.F 3.NGShort conversations1~5.BADBB 6~10.CCABCLong conversations1.A 2.D 3.D 4.C 5.BUnderstanding a passage1.C 2.A 3.B 4.C 5.DMovie dialog1.important decision 2.As in 3.agreed on 4.What’s wrong with 5.I mean 6.wait a minute 7.what a challenge 8.what he’s doing 9.gets his way 10.ever imaginedListening and speakingHomeworkTask11.B 2.C 3.B 4.C 5.CTask21.B 2.C 3.D 4.B 5.DTask31. federal government 2.education reform law 3.be forced to 4.place top importance on 5.calls for 6.main goal 7.by 40 percent 8.low-income and minority 9.poorly performing students 10.free after-school help
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