共查询到20条相似文献,搜索用时 93 毫秒
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从Lagrange观点出发,采用分裂格式法求解一维辐射流体力学方程组中的三温方程,用于紧凑等离子体环与靶碰撞产生的X射线辐射的数值模拟研究。提出了求解电子、离子、辐射场三温相脱离的能量方程的隐式差分格式,介绍了能量交换项与压力做功及热传导项分开计算的分裂格式方法,数值模拟得到了其对温度变化的影响。 相似文献
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提出一种以各物相的X射线衍射系数K为未知量组成的方程组求解K值,进而求解各物相含量的无标定量相分析方法.该方法不需加入参比物相,允许待测样品含有一个非晶相.采用了最小二乘方程组的抛弃平均法处理数据求其最优解.
关键词: 相似文献
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在三维三温辐射流体力学方程组求解过程中,为解决复杂的等离子体流场和难度大的三维网格计算,提出了用物理量迁移法求解方程组,并对三温能量方程采用了一种改进的显示算法。由此获得了较好的数值结果。 相似文献
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将时域传输线模型与漂移-扩散模型相结合,提出一种耦合数值计算方法,研究计算了带二极管负载的电缆在X射线辐照下的瞬态响应。该耦合数值计算方法首先利用时域传输线模型计算电缆在X射线辐照下的各节点电参数,然后将得到的终端节点的电压代入漂移-扩散模型中求解二极管的内部参数与偏置电流,最后将得到的偏置电流代入到下一时间步的传输线模型中继续进行计算。该方法能够直接反映出电缆在X射线辐照下的瞬态响应与所连接的负载状态改变之间的耦合关系,利用该方法求解X射线辐照简单电子系统的典型算例,计算结果表明,X射线辐照下,同轴电缆上各处的响应电流会随着PIN二极管状态的改变而发生明显变化,与理论分析相符合,耦合模型适用于此类问题。 相似文献
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GEAR算法在随机轨道模型计算中的应用 总被引:3,自引:0,他引:3
本文对随机轨道模型中颗粒相常微分方程组的刚性问题进行了分析,结果表明:当采用常规算法如四阶Runge-kutta法求解方程组时,方程组的刚性是导致某些情况下计算发散或计算时间过长的原因。为此,本文将适用于求解刚性方程组的Gear算法应用于随机轨道模型的计算中,取得了良好的效果. 相似文献
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以差分方程代替微分方程给大气原始方程组求解带来了诸多难以解决的问题, 对于(半)拉格朗日模式来说质点轨迹的计算与Helmholtz方程的求解是两大难题. 本文通过对气压变量代换, 并在积分时间步长内将原始方程组线性化, 近似为常微分方程组, 求出方程组的半解析解, 再采用精细积分法求解半解析解. 半解析方法可同时计算风、气压和位移, 无需求解Helmholtz方程, 质点的位移采用积分风的半解析解得到, 相比采用风速外推的计算方法, 半解析方法更科学合理. 非线性密度流试验检验表明: 半解析模式能够清晰地模拟Kelvin-Helmholtz 切变不稳定涡旋的发生和发展过程; 模拟的气压场和风场环流结构与标准解非常相似, 且数值解是收敛的, 同时, 总质量和总能量具有较好的守恒性. 试验初步证明了采用半解析方法求解大气原始方程组是可行的, 为大气数值模式的构建提供了一个新的思路. 相似文献
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本文是文献[1]的续篇。在麦克斯韦方程组和速率方程组及其差分格式保持不变的条件下,采用欧拉方法求解初级电子数方程组。推导了平面一维和柱二维守恒形式的初级电子方程组的差分格式,同时对柱二维作了数值计算。计算结果和[1]的结果一并放在[2]中讨论。 相似文献
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A. A. Zabolotskii 《Journal of Experimental and Theoretical Physics》2011,112(4):642-648
The possibility of forming stable bound plasmon-polariton states in an extended metallic cylinder surrounded by a two-level
medium has been investigated. The dynamics of plasmons is described in the hydrodynamic approximation. It has been shown that
the equations of motion of charge-density bunches and the Bloch equations for the two-level medium are reduced in certain
approximations to integrable equations for both transverse and longitudinal plasmons. In the former case, the initial system
of equations after the application of the slow-envelope approximation is reduced to equations equivalent to the Maxwell-Bloch
equations. In the latter case, the equations describe wave dynamics beyond the slow-envelope approximation. In the approximation
of unidirectional wave propagation, the initial system of equations is reduced to equations related to the reduced Maxwell-Bloch
equations. Soliton and breather-like solutions of the derived equations describe plasmon-exciton self-induced transparency. 相似文献
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It is shown that the equations of motion for a charged massive particle are consequences of the field equations in Kaluza unification theory of gravitation and electromagnetism, i.e., the equations of motion for the particle can be deduced from Kaluza field equations, just as that in Einstein's theory of motion of general relativity the equations of motion for a massive particle are consequences of the Einstein equations. Furthermore, the Lorentz equations for a particle maving in the Maxwell electromagnetic field on the Minkowskian space-time can also be obtained from the Maxwell equations by means of the Kaluze mechanism of the Maxwell theory. 相似文献
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Joshua N. Goldberg 《General Relativity and Gravitation》1974,5(2):183-200
The object of this paper is to relate three equations in the Newman-Penrose system of equations to the conservation laws and, hence, to the equations of motion. To do so, the corresponding result is first obtained using the Einstein equations in a null coordinate system. The Newman-Penrose equations are then analyzed. They are separated into hypersurface, propagation, supplementary, and conservation equations. When all field equations except the three conservation equations have been appropriately satisfied, the desired result follows.Research supported by the National Science Foundation under Grant GP-34641X. 相似文献
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Kozo Kobayashi 《Fortschritte der Physik》1989,37(8):599-610
We notice that in the embedding of submanifolds, the fundamental equations are only the Gauss equations for the tangent vectors while the Weingarten equations for the normal equations can essentially be determined by them, and furthermore that the integrability condition of the Weingarten equations, the Ricci equations, are consitently satisfied under that of the Gauss equations. Therefore, the Weingarten and the Ricci equations do not describe essentially independent conditions for embedding. We demonstrate these facts by explicitly constructing the normal vectors from the tangent vectors. 相似文献
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从质点系的牛顿动力学方程出发,引入系统的高阶速度能量,导出完整力学系统的高阶Lagrange方程、高阶Nielsen方程以及高阶Appell方程,并证明了完整系统三种形式的高阶运动微分方程是等价的.结果表明,完整系统高阶运动微分方程揭示了系统运动状态的改变与力的各阶变化率之间的联系,这是牛顿动力学方程以及传统分析力学方程不能直接反映的.因此,完整系统高阶运动微分方程是对牛顿动力学方程及传统Lagrange方程、Nielsen方程、Appell方程等二阶运动微分方程的进一步补充.
关键词:
高阶速度能量
高阶Lagrange方程
高阶 Nielsen方程
高阶Appell方程 相似文献
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Exact solutions of the atmospheric (2+1)-dimensional nonlinear incompressible non-hydrostatic Boussinesq (INHB) equations are researched by Combining function expansion and symmetry method. By function expansion, several expansion coefficient equations are derived. Symmetries and similarity solutions are researched in order to obtain exact solutions of the INHB equations. Three types of symmetry reduction equations and similarity solutions for the expansion coefficient equations are proposed. Non-traveling wave solutions for the INHB equations are obtained by symmetries of the expansion coefficient equations. Making traveling wave transformations on expansion coefficient equations, we demonstrate some traveling wave solutions of the INHB equations. The evolutions on the wind velocities, temperature perturbation and pressure perturbation are demonstrated by figures, which demonstrate the periodic evolutions with time and space. 相似文献
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《Physica D: Nonlinear Phenomena》1988,31(3):339-388
Integrable hierarchies of nonlinear evolution equations are investigated on the basis of linear integral equations. These are (Riemann-Hilbert type of) integral transformations which leave invariant an infinite sequence of ordinary differential matrix equations of increasing order in an (indefinite) parameter k. The potential matrices in these equations obey a set of nonlinear recursion relations, leading to a heirarchy of nonlinear partial differential equations. In decreasing order the same equations give rise to a “reciprocal” hierarchy, associated with Heisenberg ferromagnet type of equations.Central in the treatment is an embedding of the hierarchy into an infinite-matrix structure, which is constructed on the basis of the integral equations. In terms of this infinite-matrix structure the equations governing the hierarchies become quite simple. Furthermore, it leads in a straightforward way to various generalizations, such as to other types of linear spectral problems, multicomponent system and lattice equations. Generalizations to equations associated with noncommuting flows follow as a direct consequence of the treatment. Finally, some results on conserved densities and the Hamiltonian structure are briefly discussed. 相似文献
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Based on the three-order Lagrangian equations, Hamilton's function of acceleration $H^\ast$ and generalized acceleration momentum P_\alpha ^\ast are defined, and
pseudo-Hamilton canonical equations corresponding to three-order Lagrangian
equations are obtained. The equations are similar to Hamilton's canonical equations
of analytical mechanics in form. 相似文献