T**********e
发帖数: 29576 | 1 全球公开竞标的卫星发射，SpaceX和阿里亚娜各得9个，波音落马ULA一个，小日一个。
毛子的火箭发射估计苏联的库存用完了过期了，走下坡路。
Arianespace, SpaceX Battled to a Draw for 2014 Launch Contracts
Of the 19 commercial launch contracts competitively awarded in 2014,
Arianespace and SpaceX took home nine apiece.
Commercial launch service providers in 2014 booked 19 orders open to
competitive bidding for satellites to launch into geostationary orbit.
Another eight satellites, including Indian and Chinese spacecraft, were
booked, or soon will be, by national l... 阅读全帖 |
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T**********e
发帖数: 29576 | 2 SpaceX制造发射几百个近地卫星（750哩)，因为轨道低信号速度比同步卫星要快，而且
因为光速在真空里比光纤里快40%，最终网络速度要超过现有地面网。
以后扩大系统，信号可以达到火星殖民地。
Elon Musk's Plan to Build a Space Internet
Musk is tonight hosting a SpaceX event in Seattle, where the company is
opening a new office. The talk will mostly be about SpaceX’s plans for
hiring aerospace and software engineers in the Pacific Northwest to boost
the company’s rocket-building efforts. But he'll also use the talk to
announce his newest idea, which would launch a vast network of communicat... 阅读全帖 |
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d*********o
发帖数: 6388 | 3 http://www.dailymail.co.uk/sciencetech/article-2982537/Indian-M
This spectacular image reveals Phobos, one of the two moons orbiting Mars (
the other is Deimos), silhouetted against the Martian surface (shown).
Although Phobos is the larger of the two moons, it is still only about 14
miles (22km) across, and completes an orbit of Mars once every seven Earth
hours. The odd colour of Mars is due to the specific filters used by the
camera
This image, showing the limb of Mars against the void of spa... 阅读全帖 |
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d*********o
发帖数: 6388 | 4 http://www.dailymail.co.uk/sciencetech/article-2982537/Indian-M
This spectacular image reveals Phobos, one of the two moons orbiting Mars (
the other is Deimos), silhouetted against the Martian surface (shown).
Although Phobos is the larger of the two moons, it is still only about 14
miles (22km) across, and completes an orbit of Mars once every seven Earth
hours. The odd colour of Mars is due to the specific filters used by the
camera
This image, showing the limb of Mars against the void of spa... 阅读全帖 |
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T**********e
发帖数: 29576 | 5 看着和波音的设计类似，只不过一级发动机自己用机翼飞回跑到降落，不像波音一样半
空中用直升机抓降落伞。但最后估计只剩20-30%发射成本。SpaceX的一级整体回收可以
发展成登火星返回的手段，空客的回收纯粹是节约成本。
Herve Gilibert, technical director for Airbus’ Space Systems division, said
the Adeline propulsion unit — engine and avionics — is where lies most of
the value of the first stage. The Airbus team concluded that SpaceX’s
design of returning the full stage to Earth could be simplified by
separating the propulsion bay from the rest of the stage, protecting the
motor on reentry and, using th... 阅读全帖 |
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j****3
发帖数: 2836 | 6 http://www.chinadefenseobservation.com/?p=4243
China claims to have a working version of NASA’s impossible engine orbiting
the Earth
Scientists in China claim they’ve created a working prototype of the ‘
impossible’ reactionless engine – and they say they’re already testing it
in orbit aboard the Tiangong-2 space laboratory. And will use it in
satellites ‘imminently’.
The radical, fuel-free EmDrive recently stirred up controversy after a paper
published by a team of NASA researchers appeared to ... 阅读全帖 |
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d*****l
发帖数: 8441 | 7 https://www.zhihu.com/question/52288132/answer/130094296
1.1 本次航天发射的有效载荷
实践17号科学应用卫星，主要用来验证纯电推进、地球同步轨道卫星在轨服务、通讯等
高大上功能，都是中国卫星工程技术重大突破。跑个题先，看到实践就想起老祖宗很早
就教育我们一个道理，
而又有伟人告诉我们了
所以实践系列卫星一直都是中国秘而不宣的卫星系列，你懂得。
还有一个很重要的不同，本次火箭只有一级和二级，上面级带了一个远征二号，有双发
动机拥有多次点火能力，所以可以执行复杂入轨程序，也可以做多个大型卫星的多次入
轨，非常高大上，比常规火箭第三级水平不知道高到哪里去了。
所以这次火箭发射，无论是从测试新型火箭、测试新型上面级、测试崭新的发射场（重
型任务）、测试新型卫星，都有着极其重要的意义。如果把远征二号和实践17都算作有
效载荷的话，他们的总重大约在12吨，也有说14吨级别的（没有官方数据），刚好是长
征五号的极限GTO（地球同步转移轨道，马上介绍）。
1.2 本次涉及到的轨道类型
目前地球附近航天发射最主流的轨道是两种（其他的就不介绍了）... 阅读全帖 |
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S******8
发帖数: 24594 | 8 -Paz established contact with a ground control center in southern Germany
shortly after arriving in orbit Thursday, according to Airbus. Control of
the satellite will be handed over to a facility near Madrid operated by INTA
— the Spanish space agency — and Hisdesat in about five days.
-SpaceX planned to place the two Starlink prototypes, developed by the
company’s division in Redmond, Washington, into the same 317-mile-high
orbit as Paz.
The two test satellites will boost themselves into a high... 阅读全帖 |
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发帖数: 1 | 9 刚刚！SpaceX首次发射新版猎鹰9(block 5)成功，可12次连续发射无需维护保养！ 第
八次发射将载人！！
SpaceX launches its newest Falcon 9 rocket
by Jackie Wattles @jackiewattles May 11, 2018: 5:29 PM ET
A new version of SpaceX's Falcon 9 rocket that could eventually take
astronauts to space took flight for the first time Friday.
Liftoff occurred around 4:14 pm ET out of Kennedy Space Center in Florida --
a day later than originally planned. The Falcon 9 Block 5 rocket, as the
latest version is called, carried the Bangabandhu Satellite-1... 阅读全帖 |
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发帖数: 1 | 10 An asteroid could destroy humanity like it did dinosaurs. A Hopkins team has
a plan to save the world.
Andy Cheng, chief scientist at the Johns Hopkins Applied Physics Laboratory
in Laurel, is co-lead investigator on the Double Asteroid Redirection Test
mission, NASA's first test of a defense mission to deflect an asteroidt by
smashing a spacecraft into it. (Kim Hariston/Baltimore Sun)
By Tim Prudente February 4 at 6:53 PM
A team of scientists, astronomers and engineers meets weekly in a confere... 阅读全帖 |
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发帖数: 1 | 11 Stone Cold Word
Longboat Key, Florida4m ago
AG Barr investigating a missing Twinkie is a joke.
So I am reading all these comments laughing and calling out "conspiracy
theories". It's easy to "throw shade"..... getting "shade to stick" is
another story.
I know this. A high profile prisoner, who supposedly tried to kill
himself just two weeks ago, this guy could not get near a 6 inch piece of
thread. Now that's not a "conspiracy theory".
The "shade slingers" want us to believe that this ego ... 阅读全帖 |
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发帖数: 1 | 12 [99] APOLLO. In July 1960 NASA was preparing to implement its long-range
plan beyond Project Mercury and to introduce a manned circumlunar mission
project-then unnamed-at the NASA/Industry Program Plans Conference in
Washington. Abe Silverstein, Director of Space Flight Development, proposed
the name "Apollo" because it was the name of a god in ancient Greek
mythology with attractive connotations and the precedent for naming manned
spaceflight projects for mythological gods and heroes had been s... 阅读全帖 |
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t******t
发帖数: 15246 | 13 China is advancing its space capabilities by developing staged combustion,
an engine technology that is likely to offer greater performance for the
Long March 6 and 7, two of a family of launchers that the country will field
around the middle of the decade.
The smaller of the two, the Long March 6, may be the first to go into
service, beating the flagship third member of the family, the Long March 5
heavy launcher.
A new 18-metric-ton-thrust engine “is a high-altitude liquid oxygen and
kerosene ... 阅读全帖 |
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v**e
发帖数: 8422 | 14 China adds space tracking spot
2011-11-05 14:01
Hong Kong - China has acquired a space tracking station in Australia, its
first such facility in a close US ally, a report said on Saturday.
The station in remote Dongara, about 350km north of Perth in western
Australia, was used during Tuesday's launch of the Shenzhou VIII mission,
Hong Kong daily the South Morning China Post reported.
The United States and the European Space Agency, have long had tracking
facilities in Australia, including the jo... 阅读全帖 |
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r********n
发帖数: 7441 | 15 Iran Missile Milestones
http://www.iranwatch.org/wmd/wponac-missilemilestones.htm
Updated July 2011
1985: Then-speaker of the Iranian Majlis Ali Akbar Hashemi Rafsanjani leads
a high-level delegation to Libya, Syria, North Korea and China, reportedly
to acquire missiles.
1985: Iran receives its first Scud-Bs from Libya.
1987: China sells Iran "Silkworm" anti-ship cruise missiles.
1987: Iran reportedly receives approximately 100 Scud B missiles from North
Korea. Iran had allegedly agreed to finan... 阅读全帖 |
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m******e
发帖数: 536 | 16 【 以下文字转载自 Military 讨论区 】
发信人: meditate (meditate), 信区: Military
标 题: 中国可能近一两周内进行新的反卫星武器试验
发信站: BBS 未名空间站 (Sat Jan 5 00:58:39 2013, 美东)
中国可能近一两周内进行新的反卫星武器试验
Will China Launch an Anti-Satellite Test Soon?
Associated Press, By SPACE.com Staff | SPACE.com – 7 hrs ago..
China may be gearing up to perform a controversial anti-satellite test this
month, perhaps in the next week or two, some experts say.
For several months, rumors have been circulating within the United States
defense and intelligence... 阅读全帖 |
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h********o
发帖数: 3320 | 17 这个活我自己干过，说说感受。原来的漆去掉可以先用一下stripper，高压水枪，然后
用wood brightener。如果漆比较厚的化，stripper一次不一定能全部去掉。如果漆不
是很厚的化，有时候stripper加高压水枪就能基本把原来的漆去掉。sanding有时候是
为了表面比较平整一些，这个要简单一些。但是如果是把原来的漆打磨掉，那可是要费
老鼻子劲儿了，可不是个好活。orbit sander不推荐，建议至少用belt sander。如果
地面平整的化，建议去home depot去租那种手推的立式sander，但是这个也只能管地面
，而且地面不平整还不好用。如果你用orbit sander，打磨地面加栏杆，20x20的deck
， 一个人两三天根本就干不完，因为你不可能连续干，会累死你，一星期不知道够不
够用，特别是栏杆，麻烦死了，一跟木条有四个面，有时候sander好够不着。地面不建
议刷漆，因为时间长了漆会起皮，建议用oil based stain。栏杆可以用漆，因为漆用
在竖的平面上比用在水平平面上要牢固。栏杆和地面建议用两个不同颜色的，最好有对
比，这样更好看。
总... 阅读全帖 |
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a******e
发帖数: 36306 | 18 ☆─────────────────────────────────────☆
ssssgg (ssssgg) 于 (Thu Apr 16 17:45:07 2009) 提到:
不幸被雷。
由于我是H1B签证，公司在Orbit reserve 一张单程到北京的机票。但我近期没想回去
，给Orbit打了电话问能不能refund, 得到的回复说可以，但只能回到公司用于reserve
的信用卡上，而不能到我的信用卡上。不知道这种情况如何能拿回机票的钱呢？
☆─────────────────────────────────────☆
fryking (赤道企鹅) 于 (Thu Apr 16 17:54:16 2009) 提到:
这个不是你出钱的票，怎么可能到你的另一张卡上去？
看看和公司私下商量一下，能否退掉票，给你支票(估计公司官僚的话，够呛，涉及移
民身份问题它们可能会比较谨慎)。试试看说比如你不准备直接回中国，而是到X国去找
朋友什么的行不？(时间，行程未定)不知道，可能是馊主意。
最不济，让公司给orbit改改票日期？没准有用得着的时候。
☆─────────── |
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d**y
发帖数: 32 | 19 摘要如下。 请有兴趣及方向相符的发站内信，附上简要介绍及联系方法
"Thermal Analysis of Nano Satellite Using Thermal Desktop 5.0"
Abstract
The analysis of nano satellites have been done for hot and cold case
orbital heating rates on material body as knowledgement and learning for
engineers especially thermal subsystem. This analysis has done intends for
calculating amount of temperature distribution from material body satellite
when happened heating rates in orbit. For prevented which happened of brutal
condition so we used mate... 阅读全帖 |
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b******m
发帖数: 222 | 20 重要的事你看的懂你哥的文章，我看都看不懂。你帮我看看这句啥意思，
gently pulling hernia orbital fat , blunt separation of the outer envelope,
so that fat ball fully hernia, hemostat
clamp on the horizontal plane of orbital septum after Canada cut off fat,
full electric coagulation to stop
bleeding, relax fat to natural back satisfied that the orbital septum. |
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c********i
发帖数: 1489 | 21 前一周，听CNN, NPR,92.9等等新闻，最后退役的四架航天飞机，居然没有一个留在了
Houston Johnson Space Center，让人愤怒感慨，特别是本地电台里的人讽刺说 "too
bad we do not have a 212 number".
http://www.nasa.gov/topics/shuttle_station/features/shuttle_map
Atlantis - Florida, Kennedy Space Center
Endeavour - Los Angeles, California Science Center
Discovery - Virgina, Smithsonian
Enterprise - NYC, Air & Space Museum.
大概这又是一个基于政治倾向而非公平性的决定。
凭什么和航空半文钱关系都没有的NYC都可以拿到一个，
而作为关键控制中心的Houston却因为现任总统的愚蠢倾向和党派之争落选？
"Houston, we have a problem"，
不记得有哪个宇航员曾经说过 “New Yo... 阅读全帖 |
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a**p
发帖数: 13 | 22 Here was the reason that provided by Mr. Waynehale.
Wayne Hale is retired from NASA after 32 years. In his career he was the
Space Shuttle Program Manager.
Why Houston Did Not Get A Shuttle
Posted on April 14, 2011 by waynehale
Immediate reaction from many people in the Houston area was that the Orbiter
disposition decision was politically tainted. For example, this was the
explanation of my old Rice classmate Annise Parker, her honor the Mayor of
Houston.
Maybe there is some truth to that. It... 阅读全帖 |
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T********n
发帖数: 528 | 23 月底一向是赌场比较冷清的时候（payday是最热闹的）。可是为了make up4月一开始
run bad的打算多clock in一些时间让这个月hourly好看一点.
Things rarely go as planned.
This Friday I got to the card room at ～4 PM. 40/80 list was super long and
I played 20/40 first. New table of 20/40, in first 2 orbits I missed 5
flush draws, bye-bye ~1 rack+. Next three orbits I make 5 sets and all
snapped off (4 of them by the same lady chasing mostly runner runners), now
total -3.5 racks. Before long, I was in for 5 racks.
同时，看到了坐在我旁边的同胞在看mitbbs，马上跟她指出本版（Hi！！）... 阅读全帖 |
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D**********e
发帖数: 147 | 24 Libra Horoscope for November 2010
Â
By Susan Miller
Â
Â
Lately you may have felt like the famous Tantalus from Greek mythology.
Immortal Tantalus, having
committed unspeakable crimes and having stolen food from the gods, sits in a
pool of crystal clear water
that recedes from him each time bends to drink. As he reaches for the
delicious, ripe grapes hanging
directly overhead, he finds that they are just a little too far for his
fingers to grasp. No matter how hard he
tries, the fr... 阅读全帖 |
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D**********e
发帖数: 147 | 25 Sagittarius Horoscope for November 2010
By Susan Miller
The planets are sending you two different messages as November opens. On one
hand, you have Mars now
in Sagittarius giving you remarkable favor and pushing you to go, go, go at
great speed. Mars will make
you impatient, but you need to resist moving so fast. Jupiter, your ruling
planet, whose job it is to take
good care of you, has been retrograde (and therefore asleep) since July 23.
If you feel like nothing is
happening fast enough for yo... 阅读全帖 |
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l*********d
发帖数: 21519 | 26 你看看我昨晚下的order：
Items You Ordered
Qty Description Price Total
5 31389 Orbit Irrigation 58288N Brass Telescoping 3-Arm Sprinkler with
Aluminum Step Spike (Hot Deal!) $16.25 $81.25
1 31303BR DIG Corp. SHB112 100 Foot Spool of ¼ Inch Soaker Hose
with In-Line Drippers every 12 Inches - Brown (Hot Deal!) $8.15 $8.
15
1 31391 DIG Corp. B38100B 1/4 Inch Vinyl Micro Tubing, 100 Foot Coil,
Black (Hot Deal!) $5.21 $5.21
2 31003 Orbit 67403 DripMaster... 阅读全帖 |
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O*******d
发帖数: 20343 | 28 美国的火星探测器，用了两套软件，一套用英制，一套用公制，两套之际的数据交换没
有转换，直接使用。导致降落高度错误，直接在火星大气层中烧毁。
The Mars Climate Orbiter (formerly the Mars Surveyor '98 Orbiter) was a 338
kilogram (750 lb) robotic space probe launched by NASA on December 11, 1998
to study the Martian climate, atmosphere, surface changes and to act as the
communications relay in the Mars Surveyor '98 program, for Mars Polar Lander
. However, on September 23, 1999, communication with the spacecraft was lost
as the spacecraft went into orbital insertion, d... 阅读全帖 |
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b*****r
发帖数: 321 | 29 发信人: slli (老良), 信区: SFworld
标 题: Foundation and Earth 33
发信站: BBS 水木清华站 (Thu Aug 26 20:07:00 1999)
Foundation and Earth
Part Three
Aurora
Chapter 8
Forbidden World
33.
The Far Star was in polar orbit about the Forbidden World, at a
distance great enough to keep the orbital period at a little in excess of six
days. Trevize seemed in no hurry to come out of orbit.
"Since the planet is i |
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c****t
发帖数: 19049 | 30 2011 is shaping up to an amazing year for Speculative Fiction at large not
just Fantasy although that is looking damn good all by itself. My Sci-Fi
list last year was only 7 books long, which grew a little with the year, but
it was so short I combined it with UR and Steampunk picks. This year Sci-Fi
warrants a post all its own with loads of debuts and returning stars. The
people claiming Sci-fi is dying or already dead should shear the wool off
their eyes and see what is brewing.
Science Fictio... 阅读全帖 |
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s*****t
发帖数: 1994 | 31 A Star Cluster in Motion
Credit: Adam Block (NOAO)
Explanation: Star clusters are a swarm of complex motions. The stars that compose globular
clusters and many open clusters all orbit the cluster center, occasionally interacting,
gravitationally, with a close-passing star. The orbits of stars around the cluster are typically not
as circular as the orbits of planets in our solar system. Cluster stars frequently fall more
directly toward the center and many times trace out un |
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z***j
发帖数: 23 | 32 not all orbits are known by everyone. only unclassified orbits are published,
but some amateurs publish orbits of classified satellites derived from their
own observation (this practice may have discontinued after 9/11).
i don't know how the satellites avoid each other, but for geosynch satellites
each one has a defined window within which they can drift around -- this is to
save propellant since keeping `true geostationary' would be very hard and
would need far more frequent adjustment. at t |
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s*****t
发帖数: 1994 | 33 The Satellites that Surround Earth
Illustration Credit: P. C.-W. Fu & A. Hanson (Indiana), P. Frisch (Chicago), NASA
Explanation: Thousands of satellites orbit the Earth. Costing billions of dollars, this swarm
of high altitude robots is now vital to communication, orientation, and imaging both Earth
and space. One common type of orbit is geostationary where a satellite will appear to hover
above one point on Earth's equator. Geostationary orbits are very high up -- over five times
the radius |
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s*****t
发帖数: 1994 | 34 Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA
Explanation: Why is this small object orbiting Mars? The origin of Phobos,
the larger of the two moons orbiting Mars, remains unknown. Phobos and
Deimos appear very similar to C-type asteroids, yet gravitationally
capturing such asteroids, circularizing their orbits, and dragging them into
Mars' equatorial plane seems unlikely. Pictured above is Phobos as it
appeared during last week's flyby of ESA's Mars Express, a robotic
spacecraft |
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Z**R
发帖数: 1233 | 35 By Peter B. de Selding
Space News Staff Writer
posted: 22 October 2008
11:11 a.m. ET
PARIS - India's first space mission beyond Earth orbit was launched
successfully Wednesday (Local Time) when an upgraded version of India's
Polar Satellite Launch Vehicle (PSLV) placed the Chandrayaan-1 lunar orbiter
into an elliptical transfer orbit, the Indian Space Research Organization (
ISRO) announced.
The 3,042-pound (1,380-kg) Chandrayaan-1, carrying 11 experiments including
three from the European Space |
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Z**R
发帖数: 1233 | 36 【 以下文字转载自 Military 讨论区 】
发信人: ZZGR (闲逛), 信区: Military
标 题: 印度的月球卫星进入工作轨道了
发信站: BBS 未名空间站 (Wed Nov 12 12:36:27 2008)
Chandrayaan-1 Successfully Reaches its Operational Lunar Orbit
November 12, 2008
Today, Chandrayaan-1 spacecraft has successfully reached its intended
operational orbit at a height of about 100 km from the lunar surface. This
followed a series of three orbit reduction manoeuvres conducted during the
past three days by repeatedly firing the spacecraft’s 440 Newton Liquid
Engine. A |
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c****r
发帖数: 576 | 37 最简单的Logistic Map: X(n+1) = r*X(n)*(1-X(n))
function x = orbit(x0,r1,r2,m,n)
% draw the orbit diagram when r(lambda) change, nesting function iter.m
% orbit(x0,r1,r2,m,n)
% x0: initial condition
% r1
% m: the sampling times between the r interval
% n: the iteration times for the logistic equation, in reality, n is the
% number of time points
if r1>=r2
error('r1 should be smaller than r2!!!');
else
if m==1
x = zeros(1,n);
x(1,:) = iter(r1,x0,n);
pl |
|
c****r
发帖数: 576 | 38 最简单的Logistic Map: X(n+1) = r*X(n)*(1-X(n))
function x = orbit(x0,r1,r2,m,n)
% draw the orbit diagram when r(lambda) change, nesting function iter.m
% orbit(x0,r1,r2,m,n)
% x0: initial condition
% r1
% m: the sampling times between the r interval
% n: the iteration times for the logistic equation, in reality, n is the
% number of time points
if r1>=r2
error('r1 should be smaller than r2!!!');
else
if m==1
x = zeros(1,n);
x(1,:) = iter(r1,x0,n);
pl... 阅读全帖 |
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h***f
发帖数: 4541 | 39 先介绍咱中国人写的一篇计算化学论文，发在浙大学报上
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1389895/
J Zhejiang Univ Sci B. 2005 June; 6(6): 584
Jun-na Liu, Zhi-rong Chen, and Shen-feng Yuan
检索发现，它已经成了“高被抄”率（借用一下highly-cited这个词）的文章。其中有
一段“Nature bond orbital analysis provides an efficient method for ...”（
其中Nature应为Natural），用google搜索
"Natural bond orbital analysis provides an efficient method for"
或缩写形式
"NBO analysis provides an efficient method for"
或错误的形式
"Nature bond orbital analysis provides an efficient method f... 阅读全帖 |
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t**********m
发帖数: 205 | 40 来自主题: Mathematics版 - 伟哥之乐 The joy of viXra
https://telescoper.wordpress.com/2011/05/19/
Posted in The Universe and Stuff with tags arXiv, astronomy, Cosmology,
Physics, scientific publishing, viXra on May 19, 2011 by telescoper
From time to time on this blog I post rants about the state of scientific
publishing, open access, the importance of the arXiv for astronomy and
cosmology, and so on.
This morning, however, I discovered an “alternative” side to the whole
business of online science, a site by the name of viXra. Mos... 阅读全帖 |
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D**o
发帖数: 2653 | 41 注意作者 \author{YHBKJ}
Atiyah-Bott Localization 1
2012-09-05 09:24:19
\documentclass[a4paper,12pt]{article}
\usepackage{amsfonts}
\usepackage{amsmath,amsthm,amssymb}
\usepackage{CJK,graphicx}
\usepackage{amscd}
\usepackage{amssymb}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}{Corollary}[section]
\newtheorem{definition}{Definition}[section]
\newtheorem{lemma}{Lemma}[section]
\begin{document}
\title{\textbf{\Huge{Atiyah-Bott Localization 1}}}\author{YHBKJ}\date{}\
maketitle
\begin{ab... 阅读全帖 |
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t**********m
发帖数: 205 | 42 The joy of viXra
https://telescoper.wordpress.com/2011/05/19/
Posted in The Universe and Stuff with tags arXiv, astronomy, Cosmology,
Physics, scientific publishing, viXra on May 19, 2011 by telescoper
From time to time on this blog I post rants about the state of scientific
publishing, open access, the importance of the arXiv for astronomy and
cosmology, and so on.
This morning, however, I discovered an “alternative” side to the whole
business of online science, a site by the name of viXra. Mos... 阅读全帖 |
|
w********i
发帖数: 795 | 43 PhD student positions at IFW
Dresden (Germany)
We are looking for a PhD student within the Emmy-Noether group
Spin-orbital entanglement and dynamic properties of spin-orbital systems
at the Institute for Theoretical Solid State Physics within the Leibniz
Institute for Solid
State and Materials Research Dresden (IFW Dresden). The group works on
correlated
electron systems, i.e., on materials where many-body (electron-electron)
interactions are
important and can lead to a large variety of { someti... 阅读全帖 |
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c******7
发帖数: 439 | 44 谢谢回复!
对于spin没有经典对应. 我的理解是,
我不会纠结于产生, 我只把它当做一个有这么多角动量, 这么多磁矩的客体.
然后当电子在强电场下高速运动的时候容易有比比较强的spin-orbit耦合.
所以我关心电子轨道运动会不会离原子核近,
如果近的话, 电场强,电子速度快这两点就同时满足了.
我觉得一阶近似下,spin-orbit耦合就是看orbit的形态 |
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t*******e
发帖数: 216 | 45
电子自旋产生的磁矩是一个固定量（符号+/-), 因此orbit的就决定了产生的B场大小，
所以也不是一阶近似，这个是精确解析。
我觉得一阶近似下,spin-orbit耦合就是看orbit的形态 |
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T******y
发帖数: 128 | 46 The full Moon will loom larger in the sky on Friday than it has since 1993,
as it will be nearly as close as it ever comes to Earth in its orbit.
The Moon does not orbit Earth in a perfect circle. Instead, it follows an
elliptical path that brings it 50,000 kilometres closer to our planet on one
side of its orbit (called perigee) than the other (apogee).
It'll be in year 2016 for such a close distance. |
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s*****t
发帖数: 1994 | 47 A Star Cluster in Motion
Credit: Adam Block (NOAO)
Explanation: Star clusters are a swarm of complex motions. The stars that compose globular
clusters and many open clusters all orbit the cluster center, occasionally interacting,
gravitationally, with a close-passing star. The orbits of stars around the cluster are typically not
as circular as the orbits of planets in our solar system. Cluster stars frequently fall more
directly toward the center and many times trace out un |
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z***j
发帖数: 23 | 48 not all orbits are known by everyone. only unclassified orbits are published,
but some amateurs publish orbits of classified satellites derived from their
own observation (this practice may have discontinued after 9/11).
i don't know how the satellites avoid each other, but for geosynch satellites
each one has a defined window within which they can drift around -- this is to
save propellant since keeping `true geostationary' would be very hard and
would need far more frequent adjustment. at t |
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s*****t
发帖数: 1994 | 49 The Satellites that Surround Earth
Illustration Credit: P. C.-W. Fu & A. Hanson (Indiana), P. Frisch (Chicago), NASA
Explanation: Thousands of satellites orbit the Earth. Costing billions of dollars, this swarm
of high altitude robots is now vital to communication, orientation, and imaging both Earth
and space. One common type of orbit is geostationary where a satellite will appear to hover
above one point on Earth's equator. Geostationary orbits are very high up -- over five times
the radius |
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s*******y
发帖数: 988 | 50 先简单说说X37吧,X37确实具有非常重的军民两用特性,它以较小的体积达到了传统航天
器无法达到的空间机动能力.由于空间变轨需要大量的燃料,一般机动性能较好的航天器
意味着较大较昂贵.X37以一种独特的方式达到了强悍的机动能力,这种方式叫做"利用气
动辅助的SMV轨道机动方案"(Concept for Operationally Responsive Space Mission
Planning Using Aeroassisted Orbital Transfer),具体方法是利用“减速脱轨进入大
气层-大气上层飞行-脱离大气层重新入轨”（Exo-Atmospheric Deorbit —
Atmospheric Flight — Exo-Atmospheric Re-orbit）三个连续机动在一个轨道周期内
完成轨道倾角改变。也就是说X37在改变轨道的时候将减速进入大气层,依靠大气层的气
动力,象传统的飞机一样改变航向,然后点燃发动机再次进入轨道.这种设计大大的节省
了空间变轨的燃料消耗,赋予了X37强大的机动能力. |
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