与年龄相关的模糊随机种群扩散系统的指数稳定性

讨论了一类与年龄相关的模糊随机种群扩散系统,系统受两种不确定性因素的影响,即随机和模糊.在有界和Lipschitz条件下,利用Ito公式和Gronwall引理,建立了均方意义下与年龄相关的模糊随机种群扩散系统指数稳定性的判定准则并通过数值例子对所给出的结论进行了验证.     

与年龄相关的模糊随机种群系统的半隐式Euler法的收敛性

介绍了一类与年龄相关的模糊随机种群系统的半隐式Euler法.系统同时受到两种不确定性因素的影响:即,随机和模糊.在有界的条件(弱于线性增长条件)和Lipschitz条件下,讨论了与年龄相关的模糊随机种群系统在半隐式Euler法下的收敛性.方法具有克服线性计算不稳定的优点.最后通过例子对算法进行了验证.     

与年龄相关的模糊随机种群扩散系统的均方散逸性

讨论了一类与年龄相关的模糊随机种群扩散系统,该系统受随机和模糊两种不确定性因素的影响.在有界的条件(弱于线性增长条件)和Lipschitz条件下,利用It公式和Bellman-Gronwall-Type引理,建立了均方意义下与年龄相关的模糊随机种群扩散系统均方散逸性的判定准则.并通过数值例子对所给出的结论进行了验证.     

与年龄相关的模糊随机种群扩散系统的数值解

讨论了一类与年龄相关的模糊随机种群扩散系统的数值解。系统同时受两种不确定性因素的影响。即,随机和模糊。并根据Euler-Maruyama方法给出了模糊随机种群扩散系统的数值解表达式,在有界的条件(弱于线性增长条件)和Lipschitz条件下,证明了方程的数值解在均方意义下收敛于解析解。通过例子对本文的算法进行了验证。     

与年龄相关的随机分数阶种群系统温和解的存在性、唯一性

本文研究了一类与年龄相关的随机分数阶种群动态系统.利用不动点定理、随机分析和算子半群理论,讨论了与年龄相关的随机分数阶种群系统温和解的存在性、唯一性.本文是随机整数阶种群系统的推广.     

具有年龄和加权的非线性随机种群系统的最优边界控制

讨论了与年龄相关的非线性随机种群系统的最优边界控制问题,在外界环境对种群系统产生影响的条件下,考虑了种群的加权系数,应用积分-偏微分方程和变分不等式导出控制为最优的必要条件,得到最优性组.     

分数阶与年龄相关的随机种群系统的逼近控制

讨论了一类分数阶与年龄相关的随机种群系统的逼近控制.通过不动点原理,分数阶性质和随机微分方程基本理论,建立了分数阶与年龄相关的随机种群控制系统弱解存在的必要条件,并给出了该系统逼近控制的条件,最后通过数值例子对所给出的结论进行了验证.     

更一般与年龄相关随机时滞种群方程的全局稳定性

讨论更一般的与年龄相关随机时滞种群方程的全局稳定性.如果传统假设(Lipschitz条件)缺失,与年龄相关随机时滞种群方程可能有多于一个弱解.然而,大量文献研究结果是在此类方程有唯一强解前提下获得.因此,有必要对更一般的有多于一个弱解情况进行相关概念推广.对更一般的与年龄相关随机时滞种群方程,随机稳定性概念被提出,一般的Barbashin-Krasovskii定理和Lasalle定理被建立,涵盖了多于一个弱解的情况.显然,这两个定理给出随机时滞种群方程稳定性的判定标准,并且通过实例说明定理的有效性.     

与年龄相关的随机时滞种群方程的指数稳定性

本文研究了与年龄相关的随机时滞种群方程,运用Burkholder-Davis-Gundy定理和改进的coercivity条件,建立了均方意义和几乎处处意义下与年龄相关的随机时滞种群方程稳定性的判定准则,得到了保证强解稳定的若干充分条件.     

带跳的随机年龄相关种群方程解的存在唯一性（英文）

本文给出具有Poisson跳的随机年龄相关种群方程.在局部非Lipschitz条件下,证明了Hilbert空间中随机年龄相关种群方程解的存在唯一性.     

Determining a Rotation of a Tetrahedron from a Projection

The following problem, arising from medical imaging, is addressed: Suppose that T is a known tetrahedron in ?³ with centroid at the origin. Also known is the orthogonal projection U of the vertices of the image ?T of T under an unknown rotation ? about the origin. Under what circumstances can ? be determined from T and U?     

Symmetry-based solution of a model for a combination of a risky investment and a riskless investment

Benth and Karlsen [F.E. Benth, K.H. Karlsen, A note on Merton's portfolio selection problem for the Schwartz mean-reversion model, Stoch. Anal. Appl. 23 (2005) 687-704] treated a problem of the optimisation of the selection of a portfolio based upon the Schwartz mean-reversion model. The resulting Hamilton-Jacobi-Bellman equation in 1+2 dimensions is quite nonlinear. The solution obtained by Benth and Karlsen was very ingenious. We provide a solution of the problem based on the application of the Lie theory of continuous groups to the partial differential equation and its associated boundary and terminal conditions.     

Calculating a function of a matrix with a real spectrum

Let T be a square matrix with a real spectrum, and let f be an analytic function. The problem of the approximate calculation of f(T) is discussed. Applying the Schur triangular decomposition and the reordering, one can assume that T is triangular and its diagonal entries t_ii are arranged in increasing order. To avoid calculations using the differences t_ii ? t_jj with close (including equal) t_ii and t_jj, it is proposed to represent T in a block form and calculate the two main block diagonals using interpolating polynomials. The rest of the f(T) entries can be calculated using the Parlett recurrence algorithm. It is also proposed to perform some scalar operations (such as the building of interpolating polynomials) with an enlarged number of significant decimal digits.

     

On a mapping of a projective space into a sphere

We obtain an exact estimate for the minimum multiplicity of a continuous finite-to-one mapping of a projective space into a sphere for all dimensions. For finite-to-one mappings of a projective space into a Euclidean space, we obtain an exact estimate for this multiplicity for n = 2, 3. For n ≥ 4, we prove that this estimate does not exceed 4. Several open questions are formulated.     

Approaching a vertex in a shrinking domain under a nonlinear flow

We consider here the homogeneous Dirichlet problem for the equation , in a noncylindrical domain in space-time given by . By means of matched asymptotic expansion techniques we describe the asymptotics of the maximal solution approaching the vertex x=0, t=T, in the three different cases p>1/2, p=1/2(vertex regular), p<1/2 (vertex irregular).     

Folding a surface to a polygon

A concept of folding for compact connected surfaces, involving the partition of the surface into combinatorially identical n-sided topological polygons, is defined. The existence of such foldings for given n and given surfaces is explored, with definitive results for the sphere and the torus. We obtain necessary conditions for the existence of such foldings in all other cases.Supported by Kuwait University Grant SM 043.