共查询到20条相似文献，搜索用时 62 毫秒
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文章研究了一类多项式系统:dx/dt=-y+δx+lx2+mxy+ax3,dy/dt=x+b1xy+b2xy2+…+bnxyn(bn≠0)基于Liapunov形式级数法理论,得到了O(0,0)是该系统的焦点或中心的一个充分条件,同时分析了该系统依赖于参数δ的Hopf分支问题其补充了文献[5]的结论。 相似文献
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研究了一类具有两个离散时滞的中立型Logistic微分方程dy(t)/dt=ry(t)[(1-y(t-τ1)/k) cd/dt(1-y(t-τ2)/k)]的Hopf分支，其中τ1，τ2不相等且不同时为零．首先给出零解局部稳定的定理和超越方程零点分布的一般理论，再选择一个时滞为分支参数来分析其特征方程，证明Hopf分支的存在性，并找到了分支点． 相似文献
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以时滞为参数，研究了一类时滞捕食一食饵系统的正平衡点的稳定性及局部Hopf分支的存在性．应用一般泛函微分方程的全局Hopf分支定理，讨论了该系统的全局Hopf分支的存在性． 相似文献
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通过讨论多时滞中立型捕食-食饵系统正平衡点的稳定性与Hopf分支，分析其特征方程，发现当时滞穿越某些值时出现了分支，给出了寻找Hopf分支点的计算方法． 相似文献
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研究一类具时滞同源的Nicholson微分方程模型的Hopf分支的数值逼近问题．以滞量为参数，应用Cooke和J．Hale的方法，得到Hopf分支存在的条件；利用欧拉方法将得到的差分方程表示为映射，给出差分方程Hopf分支存在的条件及连续模型与其数值逼近间的关系．证明该模型在,τ=τ0产生Hopf分支时，其数值逼近也在相应的参数τh处具有Hopf分支，并且τh=τ0＋0（h）． 相似文献
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考虑了蛋白质分子能量与信息传输方程的局域普适开折，在此基础上研究了方程的Hopf分支，普适开折的Hopf分支是通有的，这有利于生命体内蛋白质分子能量与信息传输的合理解释． 相似文献
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山东省2009年高考数学试题数列与不等式的解答题为:等比数列{an}的前n项和为Sn,已知对任意的nEN+,点(n,Sn)均在函数y=b+r(b＞0且b≠1,b,r均为常数)的图像上.(1)求r的值;(2)当b=2时,记bn=2(㏒2an+1)(n∈N+),证明:对任意的n∈N+,不等式b1+1/b1·b2+1/b2……bn+1/bn＞√n+1成立. 相似文献
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张潜 《淮南职业技术学院学报》2003,3(1):83-84
不利用Newton-leibniz公式,而从Riemann积分的定义出发,得出:integral from n=a to b(dx/x′)=1/r-1[(1/a~(r-1))-(1/b~(r-1))](a>0,r为正整数,且r≥2)integral from n=a to b(x′dx)=b~(r 1)-a~(r 1)/r 1(a>0,r为正整数)About the Research of Two Integral Problems 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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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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《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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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
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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