分数Brown运动时变随机种群收获系统数值解的均方散逸性

讨论了一类带分数Brown运动时变随机种群收获系统数值解的均方散逸性.在一定条件下,利用It公式和Bellman-Gronwall-Type引理,研究了方程(1)具有均方散逸性.分别利用带补偿的倒向Euler方法和分步倒向Euler方法讨论数值解的均方散逸性存在的充分条件,并通过数值算例对所给出的结论进行了验证.     

广义Khasminskii-type条件下与年龄相关随机时滞种群系统的数值解

给出了一类带时滞随机种群系统,通过Ito公式,在局部Lipschitz条件和广义Khasminskii-type条件下.运用Euler-Maruyama法讨论了带时滞随机种群系统数值解,并给出了渐进估计,通过数值算例对主要结果进行验证.     

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。     

带Poisson跳年龄相关随机时滞种群系统的均方稳定性

本文研究了带Poisson跳年龄相关随机时滞种群系统均方稳定性的问题.在一定条件下,给出了数值解均方稳定的定义.利用补偿随机θ法讨论系统数值解的均方稳定性,给出数值解稳定的充分条件.获得了当1/2≤θ≤1时,对于任意的步长?τ/m,数值解是均方稳定的;当0≤θ1,时,如果步长?t∈(0,?t0),数值解是指数均方稳定的的结果.最后通过数值算例推广并验证了结果的有效性和正确性.     

一类与年龄相关的种群系统的数值解

本文采用同时离散时间和年龄的逼近方法,根据控制收敛定理,H(o)lder不等式及Gronwall不等式讨论了随机年龄种群系统在[0,y]时间内系统总的种群数量的数值收敛问题.通过建立逼近模式给出了数值解逼近解析解的充分条件,最后通过算例对本文提供的方法进行了验证.     

具有年龄结构随机种群系统数值解的渐近有界性

本文研究了一类具有年龄结构的随机种群系统的数值解问题.在线性增长条件下,利用Euler-Maruyama(EM)方法讨论了具有年龄结构的随机种群系统的数值解的p阶矩渐近有界性,并获得了渐近有界性准则.最后,通过数值算例对所得的结论进行了验证.     

具有环境污染的随机Lotka-Volterra模型周期解的存在性与种群的灭绝性

种群系统在受到环境噪声干扰的同时,还会受到环境污染的影响.讨论了具有环境污染的非自治随机Lotka-Volterra模型.通过构造Lyapunov函数证明了系统正周期解的存在性.运用Ito公式和鞅的强大数定律给出了种群灭绝的充分条件.通过数值例子验证了所得到的结论.     

具最终状态观测的种群扩散系统最优生育率控制的非线性问题

讨论了一类与年龄相关的时变种群扩散系统最优生育率控制的非线性问题,证明了最优生育率控制的存在性,并给出了控制为最优的必要条件及其由偏微分方程组和变分不等式组成的最优性组.这些结果可为时变种群扩散系统最优控制问题的实际研究提供理论基础.     

一类单种群系统正周期解及其稳定性

考虑周期单种群模型 dxdt=xg( t,x)± p( t,x)的正周解及其稳定性 .证明了在一定条件下 ,系统存在全局吸引的正周期解 .给出了系统存在两个正周期解的充分条件 ,同时也给出了种群灭绝的条件 .这些结果用于 Logistic模型和 Odum模型 ,得到了被开发的周期 Logistic模型存在全局吸引的正周期解 ;被开发了的周期 Odum模型只存在两个正周期解 ,其中之一吸引初值大于一个定数的所有解 ,另一个周期解则是种群灭绝的分界线     

一类种群系统的适定性及最优收获问题

本文研究了一类非线性时变种群扩散系统的适定性及最优收获问题.利用压缩不 动点原理讨论了该种群系统的解的存在唯一性.证明了最优收获控制的存在性,并且获 得了最优控制的唯一性和所满足的必要条件.     

Convergence of numerical solutions to neutral stochastic delay differential equations with Markovian switching

Recently, numerical solutions of stochastic differential equations have received a great deal of attention. It is surprising that there are not any numerical methods established for neutral stochastic delay differential equations yet. In the paper, the Euler–Maruyama method for neutral stochastic delay differential equations is developed. The key aim is to show that the numerical solutions will converge to the true solutions under the local Lipschitz condition.     

Investigation of Multi-soliton, Multi-cuspon Solutions to the Camassa-Holm Equation and Their Interaction

The authors study the multi-soliton,multi-cuspon solutions to the CamassaHolm equation and their interaction.According to the solution formula due to Li in 2004and 2005,the authors give the proper choi...     

Numerical studies of time-independent and time-dependent scattering by several elliptical cylinders

A numerical solution to the problem of time-dependent scattering by an array of elliptical cylinders with parallel axes is presented. The solution is an exact one, based on the separation-of-variables technique in the elliptical coordinate system, the addition theorem for Mathieu functions, and numerical integration. Time-independent solutions are described by a system of linear equations of infinite order which are truncated for numerical computations. Time-dependent solutions are obtained by numerical integration involving a large number of these solutions. First results of a software package generating these solutions are presented: wave propagation around three impenetrable elliptical scatterers. As far as we know, this method described has never been used for time-dependent multiple scattering.     

Exact Solutions of Extended Boussinesq Equations

The problem addressed in this paper is the verification of numerical solutions of nonlinear dispersive wave equations such as Boussinesq-like system of equations. A practical verification tool for numerical results is to compare the numerical solution to an exact solution if available. In this work, we derive some exact solitary wave solutions and several invariants of motion for a wide range of Boussinesq-like equations using Maple software. The exact solitary wave solutions can be used to specify initial data for the incident waves in the Boussinesq numerical model and for the verification of the associated computed solution. The invariants of motions can be used as verification tools for the conservation properties of the numerical model.     

一类非线性延迟微分方程数值解的振动性分析

本文考虑一类非线性延迟微分方程-带有单调造血率的造血模型数值解的振动性.通过研究特征方程根的情况得到数值解振动的条件并且讨论了非振动的数值解的一些性质.为了更有力的说明我们的结果,最后给出了相应的算例.     

A multiple-scales solution of the undular hydraulic jump problem

A non-linear third-order ODE governing the free surface of an undular hydraulic jump is solved by means of a multiple-scales analysis. The resulting solutions are compared with direct numerical solutions of the ODE, and good agreement is found. Furthermore, new flow features, which are not evident in the numerical solutions, are revealed by the multiple-scales solutions. The results of the analysis are also compared with numerical solutions of the full equations of motion and with experimental data, and satisfactory agreement is obtained. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Exponential stability of numerical solutions for a class of stochastic age-dependent capital system with Poisson jumps

Recently, numerical solutions of stochastic differential equations have received a great deal of attention. Numerical approximation schemes are invaluable tools for exploring their properties. In this paper, we introduce a class of stochastic age-dependent (vintage) capital system with Poisson jumps. We also give the discrete approximate solution with an implicit Euler scheme in time discretization. Using Gronwall’s lemma and Barkholder-Davis-Gundy’s inequality, some criteria are obtained for the exponential stability of numerical solutions to the stochastic age-dependent capital system with Poisson jumps. It is proved that the numerical approximation solutions converge to the analytic solutions of the equations under the given conditions, where information on the order of approximation is provided. These error bounds imply strong convergence as the timestep tends to zero. A numerical example is used to illustrate the theoretical results.     

Numerical approximations of the 10-moment Gaussian closure

We propose a numerical scheme to approximate the weak solutions of the 10-moment Gaussian closure. The moment Gaussian closure for gas dynamics is governed by a conservative hyperbolic system supplemented by entropy inequalities whose solutions satisfy positiveness of density and tensorial pressure. We consider a Suliciu-type relaxation numerical scheme to approximate the solutions. These methods are proved to satisfy all the expected positiveness properties and all the discrete entropy inequalities. The scheme is illustrated by several numerical experiments.

     

多维马尔科夫转制随机微分方程的数值解

由于多维马尔科夫转制随机微分方程不存在解析解,利用Euler—Maruyama方法给出多维马尔科夫转制随机微分方程的渐进数值解,并证明了此数值解收敛到方程的解析解．将单一马尔科夫转制随机微分方程的数值解问题延伸到多维马尔科夫转制情形,增强了马尔科夫转制随机微分方程的适用性．     

New analytical and CWENO numerical solutions for axisymmetric horizontal flows with heat sources

Some new nonlinear analytical solutions are found for axisymmetric horizontal flows dominated by strong heat sources. These flows are common in multiscale atmospheric and oceanic flows such as hurricane embryos and ocean gyres. The analytical solutions are illustrated with several examples. The proposed exact solutions provide analytical support for previous numerical observations and can be also used as benchmark problems for validating numerical models. A central weighted essentially non-oscillatory (CWENO) reconstruction is also employed for numerical simulation of the corresponding integro-differential equations. Due to the use of the same polynomial reconstruction for all derivatives and integral terms, the balance between those terms is well preserved, and the method can precisely reproduce the exact solutions, which are hard to capture by traditional upwind schemes. The developed analytical solutions were employed to evaluate the performance of the numerical method, which showed an excellent performance of the numerical model in terms of numerical diffusion and oscillation.