动态投入产出系统的稳定性分析

The dynamic input-output model is well known in economic theory and practice. In this paper, the asymptotic stability and balanced growth solutions of the dynamic input-output system are considered. Under some natural assumptions which do not require the technical coefficient matrix to be indecomposable,it has been proved that the dynamic input-output system is not asymptotically stable and the closed dynamic input-output model has a balanced growth solution.     

Dynamic Modelling and Identification of a Waterjet Cutting System

This paper describes a new dynamic model for a waterjet cutting system that includes a double-acting reciprocating intensifier pump. Since the system operates at high pressures the fluid flow is assumed to be compressible. The dynamic model includes the characteristics of the intensifier pump, the check valves, the accumulator, the system piping and compressible jet flow through the nozzle. The system model is presented as a set of differential-algebraic equations. Experimental results for an actual system are used to identify the discharge coefficient of the nozzle, certain unknown parameters associated with the check valve, and to determine the velocity profile of the piston in the intensifier pump. This is accomplished by formulating and solving a parameter optimization problem. The paper also includes numerical simulation results that validate the dynamic model.     

二系悬挂条件下的车-路垂向耦合系统的动力模型

在车辆的走行过程中,上部与下部是相互作用和影响的．因此,轨道交通问题实际上就是线路下部结构和车辆系统的体系匹配问题．在一系悬挂条件下的车-路系统耦合动力分析模型基础上,考虑了包含转向架在内的车辆的实际构成和轨下基础包括路基和地基的参振特性,利用轨道维护标准模拟行走不平顺激励,通过位移相容条件,从理论上研究车辆-轨道-路基体系的动力相互作用,建立了二系悬挂条件下的车辆-轨道-路基系统的垂向动力分析模型．为高速铁路路基的动力特性分析和设计提供参考．     

非均匀介质GL型热弹性问题解的存在唯一性

We study a new model named the Green-Lindsay type therm-elastic model for nonhomogeneous media that consists of a system of dynamic thermoelasticity equations of displacement and dynamic heat conduction equation. We construct the model based on the classical GL-model for homogeneous material. This system is coupled dynamic problem and the displacement field and heat field must be solved at the same time. By using Fadeo-Galerkin method, we proved that the problem we proposed exist unique weak solution under some regular assumption.     

利用传递函数——噪声模型表达经济变量间的动态影响机制

传递函数———噪声模型是一类多变量时间序列模型,它在表达系统动态影响机制方面有着独到的优势。本文将这种模型的建模方法应用于经济系统,建立了一个表达产值和出口间动态关系的传递函数———噪声模型。近几个月的实际数据表明模型的拟合是理想的。     

货币供给动态调控模型及其稳定性

根据我国货币政策传导机制并结合目前经济金融形势,建立了货币供给系统的一般动态模型,为了便于分析系统的稳定性,在此基础上建立前向离散货币供给系统简化模型并用经济控制论的方法分析了系统的稳定性。     

关于M/M/n排队模型的动态解及稳定性

文章讨论动态 M/M/n排队模型 ,运用算子半群理论证明了该模型动态正解的存在唯一性 .并进一步表明零点是系统的一个本征值 ,相应的本征函数为系统的一个定态正解 ,系统的动态正解强稳定到定态解     

A predator-prey model with Beddington-DeAngelis functional response: a non-standard finite-difference method

In this paper, we transform a continuous-time predator-prey model with Beddington–DeAngelis functional response into a discrete-time model by nonstandard finite difference scheme (NSFD). The NSFD model shows complete dynamic consistency with its continuous counterpart for any step size. However, the discrete model of same continuous system obtained by Euler forward method shows dynamic inconsistency for larger step size. Extensive numerical simulations have been done to compare the dynamics of NSFD system and Euler system. Our analysis reveals that dynamics of NSFD model is independent of the step-size, whereas the dynamics of the standard discrete model completely depends on the step-size and produces spurious dynamics like chaos.     

基于人机耦合的下肢外骨骼动力学分析及仿真

建立了一种包含人机交互力的人体-外骨骼模型，对人体和外骨骼分别采用7连杆的刚体模型进行建模，建立其D-H坐标系，得到人机模型在运动过程中的变化矢量.采用Newton-Euler方程建立动力学方程式，将人机之间的交互力简化为弹力，根据运动中人体和外骨骼质心之间的距离变化得到其相对位移，从而求得运动过程中交互力的大小.最终在ADAMS(automatic dynamic analysis of mechanical system)仿真软件中对动力学模型进行仿真，并将动力学方程得到的关节力矩代入到仿真中，验证了该人体-外骨骼模型的正确性.     

害虫综合防治建模驱动“半连续动力系统理论”兴起

以害虫综合防治数学建型为启迪,对生物数学研究的一些相关问题开展了一系列的研究.从实际问题出发,我们分别建立了"常微分方程模型"以及对应的"周期脉冲控制模型";随着害虫综合防治常态化管理和环境污染常态化防治的兴起,我们建立了"状态脉冲反馈控制系统"模型,简称"半连续动力系统"模型,提出了"半连续动力系统"相关的概念,创建了其基本理论,并且作了系统性的研究,例如:半连续动力系统的周期解以及周期解的稳定性、同宿轨和同宿分支、异宿轨和异宿分支以及"双边控制系统"等概念及其判定定理的研究;进一步将"半连续动力系统"相应的理论和方法应用于生物数学其他方面的一些相关问题的研究.本文以数学模型为载体,归纳总结了近十多年来对生物数学的研究历程,指出了当前研究中尚待解决的问题.     

一个刚柔耦合的火箭发射架动力学模型

对刚柔耦合火箭发射架进行了动力学建模．将火箭发射架分成两个子系统,一个是多刚体系统,另一个是空间大位移运动的柔性发射管．先对这两个子系统的动力学分别建模,然后再考虑这两个系统之间的动力学耦合,从而获得整个系统的动力学模型．这种方法把复杂系统离散成简单系统,再由现存的简单系统的动力学模型组合成整个系统的动力学模型,使得整个建模过程高效、方便．     

A new nonlinear dynamic analysis method of rotor system supported by oil-film journal bearings

The strong nonlinear behavior usually exists in rotor systems supported by oil-film journal bearings. In this paper, the partial derivative method is extended to the second-order approximate extent to predict the nonlinear dynamic stiffness and damping coefficients of finite-long journal bearings. And the nonlinear oil-film forces approximately represented by dynamic coefficients are used to analyze nonlinear dynamic performance of a symmetrical flexible rotor-bearing system via the journal orbit, phase portrait and Poincaré map. The effects of mass eccentricity on dynamic behaviors of rotor system are mainly investigated. Moreover, the computational method of nonlinear dynamic coefficients of infinite-short bearing is presented. The nonlinear oil-film forces model of finite-long bearing is validated by comparing the numerical results with those obtained by an infinite-short bearing-rotor system model. The results show that the representation method of nonlinear oil-film forces by dynamic coefficients has universal applicability and allows one easily to conduct the nonlinear dynamic analysis of rotor systems.     

Comportamiento dinámico de viaductos cortos considerando la interacción vehículo-vía-estructura-suelo

The dynamic vehicle-track-bridge-soil interaction is studied on high speed lines. The analysis is carried out using a general and fully three dimensional multi-body-finite element-boundary element model, formulated in the time domain to predict vibrations due to the train passage over the bridge. The vehicle is modelled as a multi-body system, the track and the bridge are modelled using finite elements and the soil is considered as a homogeneous half-space by the boundary element method. Usually, moving force model and moving mass model are employed to study the dynamic response of bridges. In this work, the multi-body system allows one to consider the quasi-static and dynamic excitation mechanisms. Soil-structure interaction is taken into account on the dynamic structure behaviour on simply-supported short span bridges. The influence of soil-structure interaction is analysed in both resonant and non-resonant regimes.     

动态输入率和服务率设定下的M/M/c模型扩展及其应用

为了解决M/M/c模型中恒定输入率和服务率假设与现实现象不符的问题,本文提出了随系统状态变化的输入概率和服务度,并通过新输入概率与平均输入率以及新服务度与平均服务率的结合分别构造了动态输入率和服务率。基于上述动态输入率和动态服务率,建立了依赖系统当前状态的状态转移过程,从状态转换强度方面优化了排队理论及其度量模型,同时,设计了结合系统实际的后确定法求解动态输入率与服务率的相关参数,从而构建了扩展M/M/c模型。由于输入率和服务率的动态性,扩展M/M/c模型具有比原排队论模型更广的适用范围和精度更高的模拟结果。最后,通过一个生活实例对新模型的有效性和实用性进行验证。     

一类区域经济发展的系统动力学模型

本文针对区域经济发展过程中的相互作用问题 ,运用微分动力系统的理论与方法 ,建立了一类区域经济发展的系统动力学模型 ,并就实际问题进行分析 ,得到了相应比较好的结果     

关于非线性自回归模型的几何遍历性

本文讨论带噪声的动态系统，即非线性自由回归模型，若原系统不具有任何压缩性质，但是它的某种拓扑共轭变换后的系统满足一定的压缩性质，本文指出，当噪声适当小时，相应的带噪声的动态系统将有唯一的平稳解，而且是几何遍历的。     

经验正交函数与遗传算法结合的副热带高压位势场非线性模型反演

针对副热带高压的动力预报模型难以准确构建的困难,基于T106数值预报产品500 hPa位势高度场序列,用经验正交函数（EOF）分解方法对位势场序列进行了时、空分解,引入了动力系统重构思想,以EOF分解的空间模态的时间系数序列作为动力模型变量,用遗传算法全局搜索和并行计算优势,进行了动力模型参数的优化反演,建立了客观合理的非线性动力模型．通过对动力模型积分和EOF的时、空重构,实现了副热带高压的中、长期预报．试验结果表明,本文反演的动力模型的副热带高压预报效果优于常规的数值预报产品,该研究工作为副热带高压等复杂天气系统和要素场预报提供了新的方法思路和技术途径．     

On the oil-whipping of a rotor-bearing system by a continuum model

The nonlinear dynamic behavior of a rotor-bearing system is analyzed based on a continuum model. The finite element method is adopted in the analysis. Emphasis is placed on the so-called “oil-whip phenomena” which might lead to the failure of the rotor system. The dynamic response of the system in unbalanced conditions is approached by a direct integration method. It is found that a typical “oil-whip phenomenon” is successfully simulated, and the effect of the refinement of the finite element mesh is also checked. Furthermore, the bifurcation behavior of the oil-whip phenomenon that is of much concern in recent nonlinear dynamics research is analyzed. The rotor-bearing system is also examined by a simple discrete model. Significant differences are found between these two models. It is suggested that a careful examination should be made in modeling the nonlinear dynamic behavior of a rotor system.