共查询到20条相似文献，搜索用时 62 毫秒
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研究了特殊Ⅲ类二次微分系统(x)＝-y lx2 mxy,(y)＝x(1 ax by)的极限环的最大个数问题. 纠正了索明霞和岳锡亭的文章(微分方程年刊, 2003,19(3):397401)中的一些错误. 通过将所研究的系统化为Liénard型系统并利用其相关性质给出了几个定理, 在某些条件下证明了系统最多存在2个极限环, 改进了上述一文中的结果. 相似文献
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运用分支的方法,通过分析未扰系统的同宿轨在小扰动下的稳定流形和不稳定流形之间的相对位置,研究了一类含四个自由参数的平面二次微分系统(Ⅰ)类方程(x)=-y+(бx)+ lx2 +mxy+ny2,y=x,n≠0的极限环的存在性问题,给出了系统存在极限环的条件. 相似文献
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《临沂师范学院学报》2013,(3):95-99
通过分析未扰系统的同宿轨在小扰动下产生的稳定和不稳定流形之间的相对位置,利用环域定理,研究了一类平面二次系统(Ⅱ)类微分方程的极限环的存在性问题,给出了系统存在唯一稳定及不稳定极限环的条件. 相似文献
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鄢玉英 《江西广播电视大学学报》2004,24(4):79-80
本文利用极限平衡条件，对内外支座为简支的环板进行了塑性极限分析，得出了环板极限状态时内力计算公式，公式中的系数α1、α2的取值，使内外支座为简支的环板的计算问题大为简化，便于在工程中应用。 相似文献
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李艳梅 《楚雄师范学院学报》2008,23(9)
利用判定函数法研究了一类线性系统在11次扰动下的极限环分支,证明了这类系统至多产生5个极限环,并给出了正好产生5个极限环的条件,最后给出了一个能产生五个极限环的具体例子。 相似文献
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讨论一类食饵种群具有常数存放率的n+2次kolmogorov系统:x′=x(a0+a1x-a2x2-a3yn-a4xyn)+F,y′=y(x2-1),得到系统不存在极限环和存在唯一极限环充分条件,并推广了前人的部分结果。 相似文献
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丰建文 《郧阳师范高等专科学校学报》1997,(2)
本文对一个放牧有相互干扰的食—植系统(E)极限环的存在性与唯一性进行了重新讨论,首先通过对奇点性态的分析得到了系统(E)极限环的存在性,接着通过一系列变换将其化为广义Li(?)bard方程,最后分析方程的性质得到了极限环唯一性的猜测. 相似文献
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研究一类分四片的非光滑平面系统,讨论其中2类特殊系统的Hopf分支情况,并证明至多存在4个极限环,同时给出极限环的存在条件。 相似文献
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通过分析未扰系统的同宿轨在小扰动下的稳定流形和不稳定流形之间的相对位置,研究了平面二次微分系统具有如下形式的（Ⅲ）类方程x=-y＋δx＋mxy＋ny^2,y=x（1＋ax＋by）（b≠0,n≠0）的同宿分支极限环的问题．给出了系统分别存在稳定极限环和不稳定极限环的条件． 相似文献
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Francis S. Broadway 《Cultural Studies of Science Education》2011,6(2):293-304
In order to advance the purpose of education as creating a sustainable world yet to be imagined, educationally, queer (v.)
queer (v.) expounds curriculum, pedagogy and being, which has roots in sexuality—the public face of the private confluence
of sexuality, gender, race and class, are a necessary framework for queer. If queer is a complicated conversation of strangers’
eros, then queer facilitates the creation of space, revolution and transformation. In other words, queer, for science education,
is more than increasing and privileging the heteronormative and non-heteronormative science content that extends capitalism’s
hegemony, but rather science as the dignity, identity, and loving and caring of and by one’s self and fellow human beings
as strangers. 相似文献
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G. D. Shlasko 《Equity & Excellence in Education》2013,46(2):123-134
A great deal of research on multiculturalism looks at different approaches to multicultural education and visions of multicultural teaching and learning. Though some research theorizes about how preservice teachers might learn about race or gender, there is very little work that helps teacher educators understand what learning about diversity more broadly, might look like. This study uses the conceptual framework developed by Paine to raise questions about and illuminate differences in the learning outcomes of preservice teachers who participated in two similar yet notably different service-learning experiences. Through examinations of writing tasks we find that teacher learning did indeed depend on the opportunities to learn provided by service-learning placements. Service-learning experiences that facilitated non-traditional power dynamics, engaged out-of-school contexts, and connected to teaching pedagogy were associated with more complex understandings of diversity. We suggest that attention to the relationships between service experiences and learning will help us better manage service learning limitations, better understand the impact of service-learning, and better understand the opportunities to learn inherent in such activities. 相似文献
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MOGHANI Ghorban Ali ASHRAFI Ali Reza HAMADANIAN Masood 《Journal of Zhejiang University. Science. B》2005,(3)
INTRODUCTION The simplicity and elegance of some of theapplications of graph theory to chemistry can perhapsonly be compared with the results from group theorydealing with symmetry as a basic quality of a system.In some problems connectivity and symmetry arecombined and the question of determining symmetryproperties of graph becomes important. Given here are some definitions and notations.An automorphism of a graph G is a permutation g ofthe vertex set of G with the property that, for an… 相似文献
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本文给出了数列{A（u,v）=u^2＋v^2,u,v∈N}的定义及其若干性质． 相似文献
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MOGHANI Ghorban Ali ASHRAFI Ali Reza HAMADANIAN Masood 《Journal of Zhejiang University. Science. B》2005,(3)
Let G be a weighted graph with adjacency matrixA=[aij]. An Euclidean graph associated with a molecule is defined by a weighted graph with adjacency matrix D=[dij], where for i≠j, dij is the Euclidean distance between the nuclei i andj. In this matrix dij can be taken as zero ifall the nuclei are equivalent. Otherwise, one may introduce different weights for different nuclei. Balasubramanian (1995) computed the Euclidean graphs and their automorphism groups for benzene, eclipsed and staggered forms of ethane and eclipsed and staggered forms of ferrocene. This paper describes a simple method, by means of which it is possible to calculate the automorphism group of weighted graphs. We apply this method to compute the symmetry of tetraammine platinum(Ⅱ) with C2v and C4v point groups. 相似文献
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Let G be a weighted graph with adjacency matrix A=[aij]. An Euclidean graph associated with a molecule is defined by a weighted graph with adjacency matrix D=[d/ij], where for i≠j, dij is the Euclidean distance between the nuclei i and j. In this matrix dij can be taken as zero if all the nuclei are equivalent. Otherwise, one may introduce different weights for different nuclei.Balasubramanian (1995) computed the Euclidean graphs and their automorphism groups for benzene, eclipsed and staggered forms of ethane and eclipsed and staggered forms of ferroeene. This paper describes a simple method, by means of which it is possible to calculate the automorphism group of weighted graphs. We apply this method to compute the symmetry of tetraammine platinum(Ⅱ) with C2v and C4v point groups. 相似文献
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对最大公凶式的表达式d（x）=uCx）f（x）＋v（x）g（x）中用辗转相除法所得出的u（x）和v（x）所具有的唯一性和次数最低性进行一下证明． 相似文献
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徐熙君 《青岛大学师范学院学报》1998,(2)
本文给出了多项式最大公因式等式u（x）f（x）＋v（x）g（x）＝（f（x）,g（x））中u（x）和v（x）的矩阵表示,并讨论以u（x）和v（x）的有关性质。 相似文献