复线性微分方程解的增长性的几个结果

本文研究了复线性微分方程解的增长性问题.利用两类具有某种渐进增长性质的函数作为线性微分方程的系数,讨论了两类二阶线性微分方程解的增长性,获得了方程解为无穷级.这些结果推广了先前的一些结果.     

偏泛函微分方程系统解的强迫振动性

本文研究两类偏泛函微分方程系统的强迫振动性.建立了这两类偏泛函微分方程系统解的强迫振动的若干判据.     

一阶线性微分方程与求导计算

利用一阶线性齐次微分方程的求解公式,建立了两类重要函数的求导公式,从而揭示了线性微分方程与函数导数之间的紧密联系.     

一类非线性中立型抛物微分方程边值问题解的振动性

讨论了一类非线性中立型抛物微分方程,得到了该类方程的两类边值问题解振动的充分条件.     

具有连续偏差变元的非线性双曲方程的振动准则(英文)

讨论了一类双曲偏泛函微分方程边值问题,给出了在两类边值条件下解振动的充分条件。     

二阶变系数线性微分方程与Riccati方程的关系

揭示了二阶变系数线性微分方程和Riccati方程之间的内在联系,证明了在对这两类方程求解时可以相互转化,从而对二阶变系数线性微分方程和Riccati方程的求解提供更多的思路和途径..     

两类二阶线性微分算子的分解及应用

本文根据两类Ｒｉｃｃａｔｉ方程解的结果，给出两类二阶线性微分算子可分解的条件及分解结果的应用，并由此得到两类微分方程组的解．     

带多阈值的两类索赔风险模型中的期望折现罚函数

本文考虑了带多阈值两类索赔到达风险模型,在假定两类索赔到达过程均为phase-type 分布时,建立了期望折现罚函数所满足的积分-微分方程.并通过拉普拉斯变换讨论了方程的解.     

相关风险和模型的折扣惩罚函数的期望

本文研究了包含两类相关风险和模型的Gerber-Shiu函数,利用积分-微分方程和构造指数鞅,获得了破产时Gerber-Shiu函数的Laplace变换.当两类索赔额均服从指数分布时,求出了相应的显式.     

两种类似于齐次方程的微分方程的解法

本文介绍两类可化为齐次方程的微分方程的解法.     

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.     

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).     

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.     

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.