共查询到20条相似文献，搜索用时 468 毫秒
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研究相空间中二阶非完整力学系统的Lie对称与守恒量．首先利用系统运动微分方程在无限小变换下的不变性建立Lie对称的确定方程和限制方程，得到Lie对称的结构方程和守恒量；其次研究上述问题的逆问题；最后举例说明结果的应用． 相似文献
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准坐标下Poincaré-Chetaev方程的Lie对称性与守恒量 总被引：1，自引：0，他引：1
赵淑红 《商丘师范学院学报》2002,18(2):3-7
建立准坐标下完整力学系统的Poincare-Chetaev方程.给出准坐标下系统的无限小生成元的定义,利用常微分方程在无限小变换下的不变性质研究它的Lie对称性,得到确定方程、结构方程和守恒量的形式.并举例说明结果的应用. 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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广义Birkhoff系统的对称性与守恒量（英文） 总被引：1，自引：0，他引：1
研究了广义Birkhoff系统的3种对称性及其相应的守恒量.首先,基于Pfaffian作用量在无限小变换下的不变性,建立了广义Birkhoff系统的Noether理论;其次,基于微分方程在无限小变换下的不变性,建立了广义Birkhoff系统的Lie对称性的定义和判据,给出了由系统的Lie对称性直接导致的Hojman守恒量;最后,基于力学系统运动微分方程中出现的动力学函数在经历无限小变换后仍然满足原来方程的一种不变性,建立了广义Birkhoff系统的Mei对称性的定义和判据,给出了由系统的Mei对称性直接导致的Mei守恒量.举例说明了结果的应用. 相似文献
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《商丘师范学院学报》1998,(Z3)
作者为物理系博景和、韶关大学刘荣万和北京理工大学梅凤翔,全文发表于国际EI收录期刊《JournaofBIT》1998,SI（3）。系梅凤翔主持的国家自然科学基金项目和高校博士点基金资助项目的子课题。物理系统所处的状态和运动规律往往以某些对称性为其基本特征。寻束系统守恒星的近代方法是woetner方法和Lie方法,Lie方法引入力学系统的研究始于Lutzky等人的工作,近年来Lie对称方法的研究迅速发展。本文研究准坐标下完整力学系统的Lie对称性和守恒星问题。首先引入准坐标系不无限小变换,利用微分方程在无限小变换下的不变性,得到了准坐… 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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研究了在群的无限小变换下有多余坐标完整系统Tzenoff方程的对称性，给出了该系统Tzenoff方程的Mei对称性和Lie对称性的定义和判据方程．给出了这种Mei对称性导致Lie对称性的充要条件，分别通过特殊Lie对称性或特殊Mei对称性条件下的Lie对称性，找到了有多余坐标完整系统Tzenoff方程的Hojman守恒量． 相似文献
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高维增广相空间中广义力学系统的Lie对称定理及其逆定理 总被引：5，自引：0，他引：5
给出高维增广相空间中广义力学系统的Ｌｉｅ对称定理及其逆定理,首先,分析运动微分方程在无限小变换下的不变性建立完整非保守广义力学系统Ｌｉｅ对称的确定方程。得到Ｌｉｅ对称的结构方程和守恒方程,其次,讨论了Ｌｉｅ对称的逆问题,最后举例说明结果的应用。 相似文献
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研究非Chetaev型非完整系统相对非惯性系的Lie对称性与守恒量、首先，利用微分方程在无限小群变换下的不变性建立了Lie对称性所满足的确定方程，给出了结构方程和守恒量：其次讨论了系统的Lie对称逆问题；最后举例说明结果的应用． 相似文献
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研究了在群的无限小变换下非完整系统Tzenoff方程的Mei对称性，给出了非完整系统Tzenoff方程Mei对称性的定义和判据方程．给出了这种Mei对称性导致Lie对称性的充要条件，通过特殊Mei对称性条件下的Lei对称性，找到了非完整系统Tzenoff方程的Hojman守恒量． 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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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 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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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献