共查询到17条相似文献,搜索用时 611 毫秒
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基于完全笛卡尔坐标的多体系统微分-代数方程符号线性化方法 总被引:1,自引:0,他引:1
多体系统动力学方程分为两类形式,即微分方程和微分-代数方程。这两类方程都是针对大位移系统,并且方程呈强非线性。为研究多体系统小位移或振动问题,从多体系统动力学方程出发,讨论微分-代数方程线性化计算机代数问题。利用完全笛卡尔坐标描述多刚体系统,建立多刚体系统动力学微分-代数方程。利用逐步线性化方法和计算机代数,分别对多体系统微分-代数方程的广义质量阵,约束方程和广义力阵在平衡位置附近进行Taylor展开。给出一种基于完全笛卡尔坐标的多体系统动力学微分-代数方程符号线性化方法。最后通过两个算例验证该方法的有效性。 相似文献
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波动方程在声学、电磁学和流体动力学等领域上有着广泛的应用.本文针对波动方程,研究了一类新的Schwarz波形松弛方法.经典Schwarz波形松弛方法是一种迭代方法,在求解波动方程时,特别是当子区域间的重叠量特别小的情形下,迭代次数往往较多,计算量较大.而本文构造的加速Schwarz波形松弛方法,即AitkenSchwarz波形松弛方法与Steffensen Schwarz波形松弛方法,是一种直接方法,它通过构造子区域边界信息的映射矩阵,很大程度地提升了计算性能.文中分别分析了这两种方法的收敛性,并且验证了新方法对于波动方程的可行性.数值算例证实了方法的有效性. 相似文献
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建立了物理参数和几何参数均为随机变量,并考虑具有齿轮侧隙、轴承间隙、时变刚度、齿间摩擦力和静态传递误差的齿轮-转子系统非线性振动的动力学方程。利用Newmark-β逐步积分法将此随机参数时变刚度系统的非线性动力学方程转换为随机参数的拟静力学控制方程,利用求解随机变量函数数字特征的代数综合法和矩法,导出了系统动态位移响应的均值和均方差计算公式。算例结果表明:齿轮模数的随机性对系统响应的随机性影响较大,摩擦系数对系统振幅的影响不可忽视,特别当齿轮的间隙大于10?5m时,系统的振幅受其影响增大。关键词:随机参数;齿轮-转子系统;非线性动力学;Newmark-β法;时变刚度 相似文献
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本文将人工智能的关键技术之一演化算法中的遗传算法用于结构可靠度的计算,并在算法中采用实数编码技术及一系列目前较先进的策略和算子,同时将模拟退火的思想引入变异算子。通过算例证明这种改进遗传算法在求解可靠度尤其求解复杂非线性问题可靠度时具有良好收敛性和高效性。 相似文献
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描述芯片或电力系统运行规律的常用数学模型是高维微分代数方程组,其中的微分方程组太大,线性多步法和Runge-Kutta法等经典数值方法均不能有效求解。为求解这些微分方程组,借鉴常微分方程经典数值方法的A稳定定义,提出了波形松弛方法A稳定(强A稳定),给出了基于θ方法的波形松弛方法 A稳定(强A稳定)和非A稳定的条件,以及几个支持理论结果的数值算例。研究结果表明WR方法并非天然继承底层方法的A稳定性,为使波形松弛方法 A稳定,需要使用A稳定的底层方法和适当的分裂函数,这为刚性方程WR方法的构造奠定了理论基础。此外,借鉴经典数值方法的B稳定定义,提出了波形松弛方法的B稳定(强B稳定),给出了波形松弛方法强B稳定的条件。 相似文献
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本文探讨大规模隐式常微分方程初值问题的数值解法,重点讨论波形松弛方法。通过对连续时间交替方向隐式波形松弛(ADIWR)应用线性多步方法,建立离散时间迭代格式。随后,对有限时间区间情形,详细分析迭代矩阵的谱半径并由此获得迭代格式的收敛性结果。此外,应用Z-变换进一步探讨离散ADIWR在无限时间区间上的收敛性。最后,数值实验验证了所获理论结果并表明ADIWR有着良好的收敛速度。 相似文献
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Differential-algebraic equations and singular perturbation methods in recurrent neural learning 总被引:1,自引:0,他引:1
This paper introduces a mathematical framework based on dynamical system theory, differential-algebraic equations (DAEs) and singularly perturbed (SP) systems, oriented to the analysis and design of on-line schemes for fixed point recurrent neural learning. New schemes proposed in this framework make it possible to relax some common assumptions in usual recurrent backpropagation (RBP) implementations. The scope of the work is not necessarily restricted to gradient-based adaptation methods, the results being applicable to more general learning strategies. The presented models clarify the relative timescaling between the network dynamics and the adaptation process in on-line techniques, including adjoint-based approaches. Certain restrictions on the learning speed are formalized through a 'rate of learning' limit appearing in the DAE/SP setting. Local convergence is rigorously stated, and certain Newton-based stabilization techniques are proposed regarding global issues in the presence of bifurcations, which typically introduce severe difficulties in common RBP methods. Some simulation examples concerning the synthesis of associative memories illustrate the applicability of the proposed techniques. 相似文献
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Anjan Bose 《Sadhana》1993,18(5):815-841
The dynamic behaviour of a large interconnected electric power system is characterized by a simultaneous set of nonlinear
algebraic and ordinary differential equations. The solution is obtained by numerical methods and the simulation of the transient
behaviour for a few seconds after a fault is the standard analytical procedure used in planning and operational studies of
the system. The need for on-line simulation in near real time for more efficient operation has encouraged the search for faster
solution methods and the use of parallel computers for this purpose has attracted the attention of many researchers. The success
of parallelization depends on three factors: the problem structure, the computer architecture, and the algorithm that takes
maximum advantage of both. In this problem, the generator equations are only coupled through the electrical network providing
some parallelization in (variable) space, and a solution is needed at each time step leading to some parallelization in time
(waveform relaxation). However, since the problem formulation is not completely decoupled, parallel algorithms can only be
developed by trading off any relaxation with a degradation in convergence. The fastest sequential algorithm used today is
the combination of implicit trapezoidal integration with a dishonest Newton solution. The Newton algorithm is not parallel
at all but has the fastest convergence while a Gauss-Jacobi algorithm is completely parallel but converges very slowly. A
relaxation of the Newton algorithm appears to be a good compromise. As for the parallel hardware, the coupling seems to require
significant communication between processors thus favouring a data-sharing architecture over a message-passing hypercube.
Special architectures to match the problem structure have also been an area of investigation. This paper elaborates on the
above issues and assesses the present state-of-the-art. 相似文献
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图像复原中通常假设图像在梯度域上是稀疏的,而非凸正则化方法会更加促进稀疏性。本文基于近年出现的几类非凸正则项,提出了泊松噪声下图像去模糊问题的几个非凸模型,发展了相应的高效求解算法,并研究了算法的收敛性;数值实验表明所提出的非凸模型可以增强图像在梯度域上的稀疏性,并优于一些现有的方法。 相似文献