两种群植物病虫害模型的正平衡点的稳定性

考虑了病虫害存在区域内的害虫和植物的关系,根据单位时间内植物在人工喷洒杀虫剂的作用下所呈现的三种状态,建立了一个两种群植物病虫害模型.然后给出了它的唯一正平衡点,利用稳定性第一近似方法讨论了正平衡点的存在性和稳定性.最后利用MATLAB软件进行相应的数值模拟,充分地体现了结论的合理性,最终得出了针对该病虫害模型的最佳解决办法.     

反馈控制Lotka-Volterra合作系统稳定性研究

研究具有反馈控制的两种群Lotka-Volterra合作系统正平衡点的稳定性.通过构造适当的Lyapunov函数得到一组保证正平衡点全局吸引的充分性条件.我们的结果表明在原系统存在正平衡点时,反馈控制变量仅能改变正平衡点的位置,而不会改变正平衡点的稳定性.     

私企同部门技术工人再培训的微分动力学模型构建及其稳定性分析北大核心CSCD

针对私企同部门技术工人再培训问题,构建了动力学模型.分析了技术工人再培训的唯一正平衡点与非负平衡点的局部稳定性和正平衡点的全局稳定性,进一步利用Matlab对相关结果进行拟合验证.     

具有双时滞偏利模型的稳定性分析

主要研究了带有时滞的种群偏利合作模型.首先通过Hurwitz准则得到正平衡点及边界平衡点的局部稳定性条件,然后构造合适的Lyapunov函数给出了正平衡点及边界平衡点的全局稳定性的充分条件.可以看到局部稳定性的充分条件同样也是全局稳定性的充分条件,这一结果补充完善了一些已有的结果.     

具有脉冲种间偏利关系的Lotka-Volterra模型的稳定性分析

通过对具有偏利关系的病虫害种群的研究,建立了具有固定时刻脉冲的偏利关系系统,并构造频闪映射,利用Jury判定证明了该系统解的最终有界性及平衡点的稳定性,并结合理论上的结果给出了防治病虫害方面的一些建议.     

Ivlev型捕食系统的全局动力学分析

研究捕食者与食饵均具有线性密度制约的Ivlev型捕食动力系统.应用常微分方程定性方法,得到了正平衡点的全局稳定性和非小振幅极限环的存在唯一性的充分条件.特别地,在一定条件下,证明了极限环的存在唯一性与正平衡点的局部不稳定性是等价的,正平衡点的局部稳定性隐含它的全局稳定性,因此,系统的全局动力学性质完全由正平衡点的局部性质所决定.     

具反馈控制的一方不能独立生存偏利合作系统的稳定性

研究具反馈控制的一方不能独立生存的两种群偏利合作系统正平衡点和边界平衡点的稳定性,通过构造适当的Lyapunov函数分别得到保证正平衡点和边界平衡点全局渐近稳定的充分性条件,并通过MATLAB进行数值模拟.研究结果表明,在原系统存在正平衡点时,适当的反馈控制变量仅改变正平衡点的位置,不会改变正平衡点的稳定性;但不适当的反馈控制变量将导致系统中不能独立生存的种群绝灭.     

带Lotka-Volterra互惠源的多种群趋化模型的稳定性

主要研究带Lotka-Volterra互惠源项的多种群趋化模型的唯一正平衡点的稳定性.首先应用非奇M-矩阵理论给出该模型存在唯一正平衡点的充分条件;然后用线性化方法分析正平衡点的局部稳定性;最后结合该模型与一个相应的常微分方程组之间的关系讨论正平衡点的全局渐近稳定性.     

时滞谣言传播模型的动力学分析

研究了一个具有心理调节因子和时滞效应的谣言传播模型.首先验证平衡点的存在性;利用谱半径法计算谣言传播的基本再生数.其次通过线性系统特征方程的特征根判断边界平衡点的局部稳定性.进一步,给出了时滞状态下的正平衡点的局部稳定性与发生Hopf分岔的判别条件.最后,通过模拟正平衡点的局部稳定性来验证理论的可靠性.     

具反馈控制的单方不能独立生存合作系统稳定性研究

研究具有反馈控制的单方不能独立生存两种群合作系统正平衡点和边界平衡点的稳定性.通过构造适当的Ly印unov函数分别得到一组保证正平衡点和边界平衡点全局吸引的充分性条件.我们的结果表明在原系统存在唯一的全局吸引的正平衡点时,反馈控制变量控制在一定的范围,则所研究系统仍然具有唯一的全局吸引的正平衡点;反馈控制变量足够大,则第二个种群将最终绝灭;在原系统只有一个全局稳定的边界平衡点时,反馈控制变量仅改变正平衡点的位置,而不会改变边界平衡点的稳定性.     

Linear birth and death models and associated Laguerre and Meixner polynomials

We study birth and death processes with linear rates λ_n = n + α + c + 1, μ_{n + 1} = n + c, n 0 and μ₀ is either zero or c. The spectral measures of both processes are found using generating functions and the integral transforms of Laplace and Stieltjes. The corresponding orthogonal polynomials generalize Laguerre polynomials and the choice μ₀ = c generates the associated Laguerre polynomials of Askey and Wimp. We investigate the orthogonal polynomials in both cases and give alternate proofs of some of the results of Askey and Wimp on the associated Laguerre polynomials. We also identify the spectra of the associated Charlier and Meixner polynomials as zeros of certain transcendental equations.     

Distributive and Multiplication Modules and Rings

We study rings in which every ideal is a finitely generated multiplication right ideal.     

Affine-inscribed and affine-circumscribed polygons and polytopes

Five theorems on polygons and polytopes inscribed in (or circumscribed about) a convex compact set in the plane or space are proved by topological methods. In particular, it is proved that for every interior point O of a convex compact set in ℝ³, there exists a two-dimensional section through O circumscribed about an affine image of a regular octagon. It is also proved that every compact convex set in ℝ³ (except the cases listed below) is circumscribed about an affine image of a cube-octahedron (the convex hull of the midpoints of the edges of a cube). Possible exceptions are provided by the bodies containing a parallelogram P and contained in a cylinder with directrix P. Bibliography: 29 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 231, 1995, pp. 286–298. Translated by B. M. Bekker.     

Partitions and pairwise sums and products

A seven cell partition of N is constructed with the property that no infinite set has all of its pairwise sums and products in any one cell. A related Ramsey Theory question is shown to have different answers for two and three cell partitions.     

Ritz and harmonic Ritz values and the convergence of FOM and GMRES

The Ritz and harmonic Ritz values are approximate eigenvalues, which can be computed cheaply within the FOM and GMRES Krylov subspace iterative methods for solving non‐symmetric linear systems. They are also the zeros of the residual polynomials of FOM and GMRES, respectively. In this paper we show that the Walker–Zhou interpretation of GMRES enables us to formulate the relation between the harmonic Ritz values and GMRES in the same way as the relation between the Ritz values and FOM. We present an upper bound for the norm of the difference between the matrices from which the Ritz and harmonic Ritz values are computed. The differences between the Ritz and harmonic Ritz values enable us to describe the breakdown of FOM and stagnation of GMRES. Copyright © 1999 John Wiley & Sons, Ltd.     

Beliefs and beyond: affect and the teaching and learning of mathematics

The importance of beliefs for the teaching and learning of mathematics is widely recognized among mathematics educators. In this special issue, we explicitly address what we call “beliefs and beyond” to indicate the larger field surrounding beliefs in mathematics education. This is done to broaden the discussion to related concepts (which may not originate in mathematics education) and to consider the interconnectedness of concepts. In particular, we present some new developments at the conceptual level, address different approaches to investigate beliefs, highlight the role of student beliefs in problem-solving activities, and discuss teacher beliefs and their significance for professional development. One specific intention is to consider expertise from colleagues in the fields of educational research and psychology, side by side with perspectives provided by researchers from mathematics education.