t******t
发帖数: 15246 | 1 引 言
吸气式发动机的效率在部分程度上受到内部与环境的最大压比制约，理论上压比高的发
动机效率更高。常规发动机通过压气机把空气压缩，再把压缩空气导入燃烧室燃烧，冲
压发动机和脉冲喷气发动机则不同，它们没有专门的压气部件，冲压发动机通过速度压
缩空气，但只有在进口速度超过M a = 2时才能将速度转换成压力，并具有较高的效率
。脉冲喷气发动机在低压室间隙燃烧，因此效率较低。对推进装置来说，爆震燃烧过程
的高燃气压力( > 1. 01×106Pa～1. 01×107Pa)和温度( > 2 000℃)以及快速燃烧都
很有吸引力。因此，过去数十年来，基于爆震燃烧的脉冲爆震发动机( PDE)已引起人们
的广泛注意。
基本概念和工作原理
脉冲爆震发动机（Pulse Detonation Engine，简称PDE）是一种利用脉冲式、周期性爆
震波所产生的高温、高压燃气来产生推理的全新概念发动机。与一般喷气发动机（等压
稳态燃烧）中的爆燃波不同，脉冲爆震发动机（等容非稳态燃烧）中的爆震波（由激波
后紧跟一道燃烧波组成）是以高超音速传播的，因此它能够产生高的燃气压力（13—55
大气压）、燃气温度（大... 阅读全帖 |
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l****z
发帖数: 29846 | 2 Christopher Helman, 04.13.11, 07:10 PM EDT
For all the outcry over GE, a number of corporate titans are paying much
higher rates than the average citizen.
image
In Detail: What The Top 20 U.S. Companies Pay In Taxes
As many Americans finish up their personal tax returns over the next few
days, they'll marvel with horror at how much hard-earned cash gets siphoned
up by the government. At times like this, it's satisfying to have a
corporate bogeyman to hate--like General Electric, which has faced ... 阅读全帖 |
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P*********0
发帖数: 4321 | 3 Published: September 19, 2012
by Frank James
As Mitt Romney continues to deal with fallout from the secretly recorded "47
percent" fundraiser video that's gone viral, in which he dissed half the
nation, more attention is being given to another recording featuring another
Romney — his mother, Lenore.
President John F. Kennedy was in the White House in 1962 when the current
Republican presidential nominee's mother sat down for an interview to speak
on behalf of her husband, George, who was then ma... 阅读全帖 |
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k****w
发帖数: 72 | 4 An American guy who is very concerned about the radiation sent me below link
. Some American scientists started a petition to the United Nations. Please
take a look and support if you are concerned too. Please feel free to pass
along if you like.
http://act.credoaction.com/sign/fukushima_disaster/?akid=9483.2
Below is the email, in case you want to read.
~~~~~~~~~~~~~~~~~~~
From: "Jordan Krueger, CREDO Action"
Sent: Wednesday, November 20, 2013 6:36:00 AM
Subject: More radiation than 14,000 Hiro... 阅读全帖 |
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T**8
发帖数: 78 | 5 There are only two student from International community school made into the
national merit semi-final in 2014. Interlake has 29.
Check and judge by youself.
National Merit Scholarship semifinalists named
Posted by John Higgins
Lakeside School in Seattle once again topped the list of area semifinalists
named Wednesday in the National Merit Scholarship program, with 33 students.
Bellevue’s Interlake High School has 29 semifinalists, and Garfield High
School in Seattle has 11.
Bellevue
• ... 阅读全帖 |
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T****8
发帖数: 505 | 6 1 Electron Kebebew Medical Officer National Institutes of Health
$350,000.00
2 Randolph Copeland Medical Officer Indian Health Service $
339,507.00
3 Anthony Fauci Director ,national allergy and infectious disease
National Institutes of Health $335,000.00
4 David Poe Medical Officer Indian Health Service $326,913.
00
5 Joseph Frechette Medical Officer Indian Health Service $
326,913.00
6 Richard Nichols Medi... 阅读全帖 |
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y**********g
发帖数: 3071 | 7 一把椅子， 价格跟k5差不多， 到底有多神奇？
看有人说自从坐上他， 腰部痛， 颈椎病也好了， 人都年轻了， 这会不会是托啊 |
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g********r
发帖数: 8017 | 9 站着工作比好椅子有效多了。人的结构进化出来就不是为了适应坐着的。 |
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