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约束力学系统引入待定乘子的两种方式 被引量:2
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作者 丁光涛 《力学与实践》 北大核心 2016年第1期83-86,共4页
讨论约束力学系统中引入待定乘子两种不同的途径及其对应的物理意义.一种方式引入待定乘子是处理非独立坐标变更,乘子与约束反力相关;另一种方式是变分原理条件极值要求,乘子与系统的拉格朗日函数相关.对完整系统由两种途径导出的带乘... 讨论约束力学系统中引入待定乘子两种不同的途径及其对应的物理意义.一种方式引入待定乘子是处理非独立坐标变更,乘子与约束反力相关;另一种方式是变分原理条件极值要求,乘子与系统的拉格朗日函数相关.对完整系统由两种途径导出的带乘子运动方程是相同的,但是对非完整系统则分别导出两种不同的运动方程:罗斯方程和维科(Vacco)方程. 展开更多
关键词 完整约束 非完整约束 待定乘子 罗斯方程 维科方程
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OpenMP-Based PCG Solver for Three-Dimensional Heat Equation
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作者 Dandan Li Qun Wang 《Computer Technology and Application》 2011年第12期963-968,共6页
As one of the most important mathematics-physics equations, heat equation has been widely used in engineering area and computing science research. Large-scale heat problems are difficult to solve due to computational ... As one of the most important mathematics-physics equations, heat equation has been widely used in engineering area and computing science research. Large-scale heat problems are difficult to solve due to computational intractability. The parallelization of heat equation is available to improve the simulation model efficiency. In order to solve the three-dimensional heat problems more rapidly, the OpenMP was adopted to parallelize the preconditioned conjugate gradient (PCG) algorithm in this paper. A numerical experiment on the three-dimensional heat equation model was carried out on a computer with four cores. Based on the test results, it is found that the execution time of the original serial PCG program is about 1.71 to 2.81 times of the parallel PCG program executed with different number of threads. The experiment results also demonstrate the available performance of the parallel PCG algorithm based on OpenMP in terms of solution quality and computational performance. 展开更多
关键词 Three-dimensional heat equation preconditioned conjugate gradient compiler directives OpenMP.
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Nonlinear Exact Solutions of the 2-Dimensional Rotational Euler Equations for the Incompressible Fluid
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作者 安红利 杨金晶 阮文威 《Communications in Theoretical Physics》 SCIE CAS CSCD 2015年第5期613-618,共6页
In this paper, the Clarkson-Kruskal direct approach is employed to investigate the exact solutions of the 2-dimensionai rotationai Euler equations for the incompressible fluid. The application of the method leads to a... In this paper, the Clarkson-Kruskal direct approach is employed to investigate the exact solutions of the 2-dimensionai rotationai Euler equations for the incompressible fluid. The application of the method leads to a system of completely solvable ordinary differential equations. Several special cases are discussed and novel nonlinear exact solutions with respect to variables x and y are obtained. It is'of interest to notice that the pressure p is obtained by the second kind of curvilinear integral and the coefficients of the nonlinear solutions are solitary wave type functions like tanh( kt /2 ) and sech (kt/2) due to the rotational parameter k ≠ O. Such phenomenon never appear in the classical Euler equations wherein the Coriolis force arising from the gravity and Earth's rotation is ignored. Finally, illustrative numerical figures are attached to show the behaviors that the exact solutions may exhibit. 展开更多
关键词 rotational Euler equations incompressible fluids Clarkson-Kruskal direct method similarity re-ductions nonlinear exact solutions
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