共查询到20条相似文献，搜索用时 78 毫秒
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研究非完整相对运动动力学系统的Lagrange对称性,给出非完整相对运动动力学系统的Lagrange对称性的定义和判据,并得到非完整相对运动动力学系统的Lagrange对称性导致守恒量的条件和形式。通过算例说明结果的应用。 相似文献
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张解放 《周口师范学院学报》1995,(4)
在本文中我们建立了非完整力学系统在事件空间中的D'Alembert—Lagrange原理,并由此导出了非完整力学系统在事件空问中的广义型方程和广义Nielsen型方程。 相似文献
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Lagrange力学在类力学系统中有着重要的应用,利用Lagrange方程,可用来处理一些类力学系统的问题.本文运用Lagrange方程处理LRC电路系统,通过引入群的无限小变换,可以获得该类力学系统的对称性和守恒量. 相似文献
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研究了Lagrange力学系统的一种新对称性:Noether-Lie对称性及其守恒量.给出了Lagrange系统的Noether-Lie对称性的定义和判据,提出Lagrange系统的Noether-Lie对称性导致的Noether守恒量和Hojman守恒量.最后给出一个例子说明结果的应用. 相似文献
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赵跃宇 《商丘师范学院学报》1994,(Z2)
完整保守的和非完整非保守的力学系统在受到小干扰力作用的情况下，系统在无干扰时的变分泛函的驻值性与其Ｎｏｅｔｈｅｒ对称性会发生变化．在本文中，我们研究小干扰力作用不改变力学系统原有的极值性和对称性的条件，并给出了几种常见情形下的结果． 相似文献
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研究受Chetaev型非完整的约束和非Chetaev型完整约束的力学系统的Lie对称性与守恒量，首先应用微分方程在无限小变换下的不变性分别建立Chetaev系统和非Chetaev系统Lie对称性所满足的确定方程和限制方程，给出结构方程并求出守恒量。 相似文献
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论文研究了非完整非保守系统的非Noether对称性和Lutzky守恒量．基于非保守非完整系统的运动、非保守力、非完整约束力和Lagrange函数之间的关系，给出了系统的非Noether对称性和Lutzky守恒量．还给出了非Noether对称性和Noether对称性的关系，并且进一步指出Lutzky守恒量可由Noether不变量的完全集给出．最后给出一个说明性例子． 相似文献
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罗绍凯 《商丘师范学院学报》2000,16(2):5-9
研究相对论完整非保守系统的Lie对称性和守恒量,定义相对论力学系统的无限小变换生成元,利用微分方程在无限小变换下的不变性,建立相对论力学系统的Lie对称确定方程,得到结构方程和守恒量的形式,并举例说明其应用. 相似文献
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赵跃宇 《商丘师范学院学报》1996,(Z1)
本文在增广相空间中研究力学系统的对称性与不变量．基于增广相空间中的Ｈａｍｉｌｔｏｎ作用泛函在无穷小变换群的作用下的不变性，我们给出了力学系统相应的不变量，相应的结论被推广到非保守和非完整力学系统．我们还得到了有关结论的逆命题．文章最后，我们讨论了著名的Ｅｍｄｅｎ方程及Ｈａｍｅｌ－Ａｐｐｅｌｌ问题的不变量． 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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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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Rajesh Kanoi 《海外英语》2007,(1):52
Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer. 相似文献