Asymptotic Behavior of Solutions to the Diffusion Equation

We study asymptotic behavior of solutions to an initial value problem posed for heat equation. For which, we construct an approximate solution to the initial value problem in terms of derivatives of Gaussian by incorporating the moments of initial function. Spatial shifts are introduced into the leading order term as well as penultimate term of the approximation. This paper is continuation to the work of Yanagisawa [14].     

Singularly Perturbed Population Models with Reducible Migration Matrix: 2. Asymptotic Analysis and Numerical Simulations

The paper is concerned with asymptotic analysis of a singularly perturbed system of McKendrick equations of population with age and geographical structure. It is assumed that the migration between geographical patches occurs on a much faster time scale than the demographic processes and is described by a reducible Kolmogorov matrix. We apply a novel regularizing technique which makes the error estimates easier than that in previous papers and provide a numerical illustration of theoretical results.     

Global Null Controllability of the 1-Dimensional Nonlinear Slow Diffusion Equation

The authors prove the global null controllability for the 1-dimensional nonlinear slow diffusion equation by using both a boundary and an internal control. They assume that the internal control is only time dependent. The proof relies on the return method in combination with some local controllability results for nondegenerate equations and rescaling techniques.     

On an Asymptotic Behavior of Exponential Functional Equation

The stability problems of the exponential （functional） equation on a restricted domain will be investigated, and the results will be applied to the study of an asymptotic property of that equation. More precisely, the following asymptotic property is proved： Let X be a real （or complex） normed space. A mapping f ： X → C is exponential if and only if f（x ＋ y） - f（x）f（y） → 0 as ｜｜x｜｜ ＋ ｜｜y｜｜ → ∞ under some suitable conditions.     

On Tests to Distinguish Distribution Tails Invariant with Respect to the Scale Parameter

Doklady Mathematics - We propose two tests to distinguish between separable classes of distribution tails, the first of which is invariant with respect to the scale parameter and the second is...     

一种特殊条件下的扩散方程的数值解法及物理分析

利用有限差分方法中的预估校正格式求解裂变产物在燃料芯块中的扩散方程,并进行了灵活的边界条件处理,取得了令人满意的计算精度,为有效开展对反应堆燃料元件破损探测信号的定量分析提供了条件.对数值计算过程进行了一定的物理分析,从物理意义上解释了数值计算过程中一些特殊处理的合理性.     

Numerical Exact Controllability of the 1D Heat Equation: Duality and Carleman Weights

This article is devoted to the numerical computation of distributed null controls for the 1D heat equation. The goal is to compute a control that drives (a numerical approximation of) the solution from a prescribed initial state exactly to zero. We extend the earlier contribution of Carthel, Glowinski, and Lions, which is devoted to the computation of controls of minimal square-integrable norm. We start from some constrained extremal problems (involving unbounded weights in time), introduced by Fursikov and Imanuvilov, and we apply appropriate duality techniques. Then, we provide numerical approximations of the associated dual problems, and apply conjugate gradient algorithms. Finally, several experiments are presented, and we highlight the influence of the weights and analyze this approach in terms of robustness and efficiency. Also, the results are compared with others in a previous article of the authors, where primal methods were considered.     

具源项的奇异扩散方程解的存在性及渐近性

讨论了一类具源项的奇异扩散方程的第二初边值问题,证明了经典解的存在性以及时间充分大时解的渐近性质.     

On the Exact Controllability of the Wave Equation with Interior and Boundary Controls

The exact controllability of the wave equation in a bounded domain of Rⁿ, with controls on a part of the boundary and in the interior, is studied. Feedback laws are established.     

A Ray Method for the Asymptotic Solution of the Diffusion Equation

A general method is presented for finding asymptotic solutionsof problems posed for linear partial differential equationscontaining lower order (dispersive) terms. Powers of a largeparameter appear in these equations multiplying the lower orderterms. The expansion procedure is a "ray method", i.e. all ofthe functions that appear in the expansion satisfy ordinarydifferential equations along certain curves called rays. Special attention is paid to the equation of heat conduction.In this case, 1/ is related to the thermal conductivity of themedium. For this equation several problems are considered inwhich the parameter enters the data or the inhomogeneous (source)term in various ways.     

On Asymptotic Series Expansions of Solutions to the Riccati Equation

Mathematical Notes - We consider scalar real Riccati equations with coefficients expanding in convergent power series in a neighborhood of infinity. Continued solutions of such equations are...     

cauchy核奇异积分方程关于积分曲线的稳定性

当E为复平面上的有界连通区域,所有已知函数在E上满足Holder条件,光滑封闭曲线гсE时,借助广义逆,讨论了正则型Cauchy核奇异积分方程在г发生某种光滑扰动时的稳定性问题,给出了相应的误差估计,并建立了收敛性定理.     

Asymptotic Analysis of Solutions to a Riccati Equation

A Riccati equation with coefficients expandable into convergent power series in a neighborhood of infinity is considered. Continuable solutions to equations of this type are studied. Conditions for the expansion of these solutions into convergent series in a neighborhood of infinity are obtained by methods of power geometry.     

C0-半群关于参数的可微性及其应用

考虑了C0-半群关于参数的可 微性,而参数含在半群的无穷小生成元中. 证明了：无穷小生成元关于参数的广义连续 性及强可微性蕴含着该C0-半群关于参数的可微性. 这些结果被应用于证明线性延 滞微分方程的解关于延滞量的可微性质.     

线性控制系统对小时滞的鲁棒能控性

对于在Banach空间中线性控制系统对时滞的鲁棒能控性．给出一个充分条件,在这个条件下,证明对一个能控的线性系统施加某个小的时滞扰动之后,其能控性保持不变．     

线性控制系统对小时滞的鲁棒能控性

对于在Banach空间中线性控制系统对时滞的鲁棒能控性.给出一个充分条件,在这个条件下,证明对一个能控的线性系统施加某个小的时滞扰动之后,其能控性保持不变.     

The Continuity of Barrier Function with Respect to the Parameter

The authors study the continuity of barrier function Be（x） with respect to the parameter. A sufficient condition which makes Be（x） be continuous with respect to c is obtained, and an example of discontinuity when the condition is not satisfied is also constructed.     

Inverse Problems of Finding the Absorption Parameter in the Diffusion Equation

Mathematical Notes - The paper is devoted to the study of inverse problems of finding, together with a solution u(x, t) of the diffusion equation $${u_t} - \Delta u + [c(x,t) + a{q_0}(x,t)]u =...