Analysis of a Diffusion-Convection System Modeling a Contamination Problem

A system of coupled diffusion-convection equations which model a contamination problem are analyzed. The equations are reformu-lated as an abstract problem which is used to obtain existence, uniqueness and posit ivity results for the solutions. A minimum principle is also proved and a special class of solutions which have bearing on the model are derived     

Exact Solutions of Discrete Kinetic Models and Stationary Problems for the Plane Broadwell Model

A review of exact solutions of discrete velocity models is given. Different methods of constructing the solutions are discussed. New methods are proposed for the stationary Broadwell model, and new class of solutions is obtained. Two-dimensional flows in channel are studied on the basis of exact solutions and analogy with the Carleman model. Explicit example of non-unique solution to a boundary value problem is given. Exact hydrodynamic equations are derived for the stationary Broadwell model. A role of the Navier–Stokes approximation is discussed in detail by comparison with these exact equations.     

一般两速离散Illner模型的1 1维精确解

Ｉｌｎｅｒ模型是最一般的Ｂｏｌｔｚｍａｎｎ方程的两速模型，它包括Ｃａｒｌｅｍａｎ模型和ＭｃＫｅａｎ模型作为两种特殊情形·离散Ｉｌｎｅｒ模型１＋１维精确解能够以一种简洁的方式进行研究·前人的结论需要修正·我们得到了一类新的１＋１维精确解·这给出了研究类似的离散Ｂｏｌｔｚｍａｎｎ方程精确行波解的一般方法·     

Asymptotic behavior of solutions of a periodic diffusion system of plankton allelopathy

This paper is concerned with the existence and asymptotic behavior of periodic solutions for a periodic reaction diffusion system of a planktonic competition model under Dirichlet boundary conditions. The approach to the problem is by the method of upper and lower solutions and the bootstrap argument of Ahmad and Lazer. It is shown under certain conditions that this system has positive or semi-positive periodic solutions. A sufficient condition is obtained to ensure the stability and global attractivity of positive periodic solutions.     

Numerical investigation of a new class of waves in an open nonlinear heat-conducting medium

The paper contributes to the problem of finding all possible structures and waves, which may arise and preserve themselves in the open nonlinear medium, described by the mathematical model of heat structures. A new class of self-similar blow-up solutions of this model is constructed numerically and their stability is investigated. An effective and reliable numerical approach is developed and implemented for solving the nonlinear elliptic self-similar problem and the parabolic problem. This approach is consistent with the peculiarities of the problems — multiple solutions of the elliptic problem and blow-up solutions of the parabolic one.     

Existence and Characterization of Optimal Locations

A general model for optimal location problems is given and the existence of solutions is proved under practical conditions. Conditions that all possible solutions must satisfy are given; these conditions form the basis of a method of finding solutions.     

Wave features of a hyperbolic prey–predator model

A hyperbolic predator–prey model is proposed within the context of extended thermodynamics. The nature of the steady state solutions for the uniform and non‐uniform perturbations are analyzed. The existence of smooth traveling wave‐like solutions, related to the invasion of the predator population into a prey‐only state is discussed. Validation of the model in point is also accomplished by searching for numerical solutions of the system, which also points out limit cycles in the populations. Copyright © 2010 John Wiley & Sons, Ltd.     

一类两参数非线性奇摄动边值问题解的渐近性态

本文研究了一类两参数非线性奇摄动边值问题的基本模型.利用奇摄动方法,对该问题解的结构在两个小参数相互关联的三种不同情形下作了讨论,得到了该问题的渐近解并证明了在三种情形下不同的解的结构与渐近性态.     

Existence and Uniqueness of Solutions for a Semiconductor Device Model with Current Dependent Generation-recombination Term

A drift-diffusion model for a semiconductor device is studied. It is assumed that mobilities saturate for large densities of current carriers. The model includes the generation-recombination term of Shockley–Read–Hall and Auger as well as the avalanche term. The existence of weak solutions is proved for space dimensions=1, 2, 3 and uniqueness of solutions is showed in the case of one space dimension.     

Modeling of thermoelastic processes in heterogeneous anisotropic shells with initial deformations

A refined mathematical model of the dynamic problem of coupled thermoelasticity of heterogeneous anisotropic shells taking into account the anisotropy of thermomechanical properties of the material both in the median surface and in the transversal direction is developed. The model includes initial deformations and is based on the assumption that the components of the vector of displacements and temperature are linearly distributed over the thickness. The reliability of the proposed model is evaluated by comparing the solutions obtained on its basis with the corresponding solutions obtained by using the theory of elasticity.     

A parameter study of epitaxial crystal growth

A third order autonomous ordinary differential equation is studied that is derived from a mathematical model of epitaxial crystal growth on misoriented crystal substrates. The solutions of the ODE correspond to the traveling wave solutions of a nonlinear partial differential equation which is related to the Kuramoto–Sivashinsky equation. The fixed points, the periodic solutions, and the heteroclinic orbits of the ODE are analysed, and stability results are given. A variety of nonlinear phenomena are observed, including Gavrilov–Guckenheimer bifurcations, homoclinic bifurcations, and a cascade of period doublings.     

Case of a Boltzmann gas leading to the Smoluchowski coagulation equation

A special model of a rarefied hard-sphere gas is considered. The hard-sphere particles undergo absolutely elastic collisions. It is assumed that particles can collide only if their nonzero velocities are orthogonal to each other. The model makes it possible to proceed from the Boltzmann equation to the Smoluchowski coagulation equation, where coagulation means that the kinetic energies of the colliding particles are added. A Monte Carlo scheme for simulation of the phenomenon is described, and the convergence of the simulation algorithm is proved. The convergence of numerical results to exact solutions of the Smoluchowski equation and to finite-difference solutions is tested.     

Construction of Strongly Time-Consistent Subcores in Differential Games with Prescribed Duration

A Couette flow of a viscoelastic medium is considered that is described by the Johnson–Segalman–Oldroyd model with two relaxation times. The development of singularities related to the appearance of internal discontinuities is studied both analytically and numerically within one-dimensional nonstationary hyperbolic models of viscoelastic Maxwell-type media. A numerical model for calculating nonstationary one-dimensional discontinuous solutions is constructed, discontinuous solutions are studied, and the hysteresis phenomenon, i.e., the dependence of the structure of a steady Couette flow on the prehistory of its formation, is analyzed.     

B-transform method and its application in obtaining solutions of some impulsive models

A new method is developed for finding solutions of impulsive systems. The method has been applied to finding solutions to the followings models: impulsive population, sickel cell anaemia, gas enclosure problem and a simple model of the heart.     

Solitary solutions to an androgen-deprivation prostate cancer treatment model

A model of androgen deprivation treatment for prostate cancer is considered in this paper. Bright/dark solitary solutions to the model are constructed using inverse balancing and generalized differential operator techniques. It is shown that solitary solutions correspond to biomedically relevant sets of model parameters. Dynamical properties of solitary solutions are analyzed in the phase plane. It is demonstrated that such solutions closely reflect the real-world phenomena observed during androgen deprivation treatment. Computational experiments are used to illustrate these effects.     

垃圾填埋气体渗流过程中压力分布的滑脱解

考虑气体滑脱效应条件下,建立了垃圾填埋场气体渗流的数学模型．采用摄动法及积分变换法对模型进行解析求解,定量研究填埋气体的压力分布特征,并结合监测数据对模型参数与模型可靠性进行灵敏度分析和验证．结果表明:滑脱效应对气体渗流有较大影响,考虑滑脱效应条件的气体压力小于未考虑滑脱效应条件的气体压力,且得到的滑脱解与实测数值吻合较好．因此,研究填埋气体渗流时不能忽略滑脱效应．这不仅对于填埋场释放气体控制系统的设计和管理提供理论依据,而且可为低渗透油气藏工程开发过程中试井数据的确定提供科学的技术支持．     

小展弦比波的Green-Naghdi渐进模型的行波解

本文研究了小展弦比波的Green-Naghdi渐进模型. 利用平面自治系统的稳定性分析方法, 在不同的参数条件下, 讨论了它的行波系统的分岔并且给出了对应的相图, 得到了光滑周期波解, 广义扭波解, 广义反扭波解, 广义紧波解, 周期尖波解, 孤波解和孤立尖波解的精确表达式. 进一步, 通过数学软件Maple模拟了这些解.     

一类带有交叉扩散的捕食模型的共存问题

研究带有齐次Dirichlet边界条件的捕食-食饵模型,得到了平凡解存在的条件,并给出半平凡解存在的充分条件以及解的先验估计,最后利用Shauder不动点定理,得到问题至少有一个正解存在的充分条件.该结果说明只要捕获率足够小,物种的交叉扩散相对弱,问题就至少存在一个正解.     

On the existence of multivortices in a generalized Bogomol'nyi system

An interesting feature of the generalized Abelian Higgs vortex model introduced by M. Lohe is that it allows a wider class of Higgs self-interaction potential functions, yet, noninteracting multivortices are still present in the critical coupling phase as the solutions of a modified Bogomol'nyi system. In this paper, we add two new classes of multivortex solutions to Lohe's model. We prove that, under the 't Hooft boundary condition, there are solutions realizing a periodic lattice structure and a quantized flux. A necessary and sufficient condition is obtained for the existence of such solutions. We also show that the Meissner effect occurs in the model. Moreover, we establish for any given vortex distribution in the plane, the existence of a one-parameter family of gauge-distinct solutions of infinite energy.     

具有时滞及B-D功能反应的食物链系统周期解的存在性与全局渐近稳定性

研究了具有时滞和Beddington-DeAngelis功能反应的一类食物链系统,通过运用Mawhin重合度理论中的延拓定理,得到了系统至少存在一个周期解的充分条件,并通过构造Lyapunov泛函的方法得到了系统周期解的全局稳定性.