共查询到20条相似文献，搜索用时 343 毫秒
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针对"嫦娥三号"软着陆最优降落位置及能量控制研究,使用积分化和图像二值化方法,构建主下降阶段动力学仿真模型和基于耗能最低的灵敏度分析模型等,运用Matlab7软件编程求解,得到"嫦娥三号"在着陆准备轨道近、远月点位置以及降落月面时的具体位置等结论。 相似文献
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吕海波 《成都航空职业技术学院学报》2010,26(4):43-46
统计资料表明,在造成飞机进近和着陆阶段飞行事故的主要原因中,人为因素占有很大的比重。本文对飞机在下降和进近过程中出现事故的诱因进行了总体分析,经过分步确定目标,核实每一个有疑问的数据,监控每一段飞行中的关键数据,适时调整所需的各项参数,果断地做出正确的决策,进而形成了下降和进近过程中能够确保飞行安全又较为合理的的飞行管理方法。 相似文献
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嫦娥三号已成功完成软着陆,其着陆准备轨道的位置和着陆轨道及其控制策略是嫦娥三号月球着陆的关键问题。运用天体物理相关理论及智能优化算法构建了基于复杂网络的滤波模型和基于粒子群算法的着陆轨道优化模型,并通过matlab计算及matlab仿真,给出了着陆轨道及其控制策略。 相似文献
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美国高校实现新校长“软着陆”的策略 总被引：3，自引：0，他引：3
大学校长的选拔和使用是各国都十分关注的问题。目前,我国高校领导班子正处于新老交替阶段,如何使新任校长在尽可能短的时间内熟悉大学的情况,适应大学运转的需要是我国教育管理工作者和理论工作者探讨的热点问题之一。而美国高校实行的新任校长“软着陆”这一做法,很有启发意义,现介绍如下：“软着陆”是对经济运行状态的一种形象性比喻,即好比飞机经过一段飞行之后,平稳地降落在陆地上。“软着陆”最早是作为经济学术语而出现的,其基本含义是：国民经济的运行经过一段过度扩张之后,平稳地回落到适度增长区间,即在一定时间内,有… 相似文献
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丁明武 《教育前沿(综合版)》2011,(1)
我国的探月工程分三个阶段。第一步是绕,即实施对卫星绕月轨道的控制实验并对月球表面进行探测;第二步是落,即将月球探测器在月球表面着陆并对月球进行实地考察;第三步是回,在完成对月球的实地考察后,将在月球上采集的实物样品带回 相似文献
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《第二课堂(小学)》2002,(12)
万老师: 您好!今年,我国载人航天第三次飞行试验获得圆满成功,“神舟”三号飞船在遨游太空数日之后,飞船返回舱安全降落在内蒙古中部地区。从着陆现场的情况来 相似文献
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沈杨 《中学英语园地(高三版)》2008,(3):24-29
1．1and，drop，fall这三个词用作动词时，都有“落下”之意。land侧重指“（从空中）降落、落下、着陆”，也可指船“上岸、登陆”。例如：The plane landed safely．飞机安全着陆。drop和fall作不及物动词用时，可以互换使用。drop还可作及物动词。fall则不可以。drop侧重指由于地心引力或手没抓住等原因而“落下、使下落”。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献