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Derivatives of eigenvalues and eigenvectors with respect to parameters in symmetric quadratic eigenvalue problem are studied. The first and second order derivatives of eigenpairs are given. The derivatives are calculated in terms of the eigenvalues and eigenvectors of the quadratic eigenvalue problem, and the use of state space representation is avoided, hence the cost of computation is greatly reduced. The efficiency of the presented method is demonstrated by considering a spring-mass-damper system. 相似文献
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污染环境中三维竞争系统的生存阈值 总被引:4,自引:0,他引:4
本文用积分均值法,首次讨论了带有毒素影响的三维竞争系统的Lotka-Volterra模型,得到了各种群平均持续生存与绝灭的阈值.文中所得结论对环境污染以及生物种群影响的理论研究和实际应用有重要意义.文[5,6]的主要结论包含在本文的结果中. 相似文献
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冷备系统可靠性评定的统计方法 总被引:5,自引:0,他引:5
贮备是提高系统可靠性可行且有效的途径.关于冷备系统的可靠性评定问题,前人仅在设备均为指数型部件的情况给出了WCF方法.文中对实际中常用的指数-威布尔混合型冷备系统,提出了两种可靠性评定方法:WCF方法和Fiducial方法,并在中小样本下对两种方法进行了模拟研究,说明了这两种方法的实用性. 相似文献
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提出了一种敏感性问题问卷调在技术.在相同的样本量下,提出的问卷调查技术可以获得调查者所关心的两项敏感指标(敏感比例π_x和敏感指标均值μ_x).此外,还定义了关于敏感指标的极大似然估计形式,给出一种问卷调查装置对个体隐私保护的度量方法.利用Monte Carlo方法模拟计算了在简单随机有放回抽样设计方案下估计量的精度和装置的保护度. 相似文献
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路见可 《数学年刊A辑(中文版)》2002,(5)
对非线性奇异积分方程其中L为一封闭光滑曲线;a,b,c为常数,在H(?)lder连续函数空间中求解时将其化为一个带根号的Riemann边值问题而得出其一般解.本文得知;一般说来,它具有非平凡解.其解的表达式以及可解条件均已得出. 相似文献
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则称二阶完全非线性组(1)是一致抛物的.我们在矩形域Q_T={0≤x≤l,0≤t≤T}(l>0,T>0)上研究方程组(1)满足边界条件 相似文献
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在考虑强阻尼效应的情形下,建立了一类轴向载荷作用下的波动方程.研究一类具有强阻尼的非线性波动方程的初边值问题的整体解的性态.以Sobolev空间的性质为工具,利用Faedo-Galerkin方法,证明了该方程在线性边界条件下弱解的存在唯一性,为力学中具有阻尼结构的振动问题的研究提供了重要依据. 相似文献
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§1. Introduction Let ? ? Rn (n ≥1) be an open set, p ≥1. We consider functions u ∈W1 (?), such ,pthat, for some α> 0, |u|? < ∞. α (1.1) ?When p = 1, it is also natural to consider u ∈BV (?) which satis?es (1.1). For any u ∈W1 (?), p ≥1 or u ∈BV (?), we de?ne its zero set by … 相似文献
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从另一个角度研究线性广义系统Ex=Ax的平衡点邻域的定性行为,并对正则性概念作了有益的推广. 相似文献
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《代数通讯》2013,41(4):965-986
ABSTRACT An exact sequence of Witt groups, motivated by exact sequences obtained by Lewis and by Parimala, Sridharan and Suresh, is constructed. The behavior of the maps involved in these sequences with respect to isotropy is completely determined in the case of division algebras. In particular, the kernels of the maps involved in the previous sequences are explicitly given, leading to a new proof of their exactness. Similar exact sequences of equivariant Witt groups are constructed. As an application, relations between the cardinality of certain Witt groups are obtained. 相似文献
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Daniel Goodman 《Natural Resource Modeling》1987,1(2):205-234
A generalized birth–and–death process serves as a simple, flexible model for computing the expected persistence time of a small population in a random world. We may reparametrize the model in ways that allow explicit incorporation of density dependence, random differences in events experienced by different individuals, and random environmental variation experienced by all individuals in concert. This model seems to capture the important features of real population dynamics for purposes of computing the mean persistence time, even though the underlying mechanisms presumed in the mathematics of the model are decidedly unrealistic. The lack of isomorphism between birth and death rates, as they feature in the model, and vital rates of real biological populations can lead to extremely misleading results, if the classic formulation, rather than the reparametrization is applied without due circumspection. Using the reparametrized model, we find that environmental variation poses a greater problem for population persistence than does individual variation. In particular, with purely individual variation, the expected persistence time increases approximately with the power of the ceiling on population size; but with purely environmental variation, the expected persistence time increases somewhat less than linearly with the size of the population ceiling. The birth–and–death process model can also be applied to calculating the persistence time of a population on an ensemble of reserves which are linked by natural migration or by deliberate reintroduction programs. Results of this model, for an idealized ensemble, show that multiple independent reserves with a sufficient recolonization rate (natural or otherwise) will confer a longer persistence time than a single reserve with the same total carrying capacity, but in the absence of recolonization, the system of smaller separate reserves confers a shorter persistence time than the single large reserve. 相似文献
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Ten regular tetrahedra can be arranged in such a way that their vertices are coincident with the vertices of a regular dodecahedron
and that two tetrahedra meet at each vertex of the dodecahedron. If the resultant structure is considered as a bar-and-joint
structure, there will be 60 bars, lying along the edges of the tetrahedra, and 20 joints at the vertices of the dodecahedra;
six bars meet at each joint. Although the structure more than satisfies Maxwell's rule, it is known to admit finite mechanisms.
Recently, a new method for detecting symmetric finite mechanisms in symmetric bar-and-node structures has been developed.
The method only requires a count of the number of bars, and the number of nodes, that are left unmoved by each of the symmetry
operations allowable for the structure. This paper will describe the application of this method to the structure described
above. The structure has icosahedral symmetry, I
h
, and the analysis confirms the existence of the mechanisms with C
3v
and C
5v
symmetry that have previously been detected using ad-hoc methods.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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混合Weibull分布参数估计的ECM算法 总被引:1,自引:0,他引:1
混合威布尔分布是寿命数据分析中一个重要的统计模型.但是利用传统的统计方法,如矩估计、极大似然估计等估计模型的参数比较困难.应用ECM算法详细研究了混合威布尔分布在正常工作条件下,完全数据场合、Ⅰ-型截尾和Ⅱ-截尾场合的参数估计问题.数据模拟表明利用ECM算法来估计混合威布尔分布是一种有效的方法. 相似文献