Nonclassical Potential Symmetries and New Explicit Solutions of Burgers Equation

A new method is used to determine the nonclassical potential symmetry generators of Burgers equation.Some classes of new explicit solutions, which cannot be obtained by Lie symmetry group of Burgers equation or its integrated equation, are obtained by using these new nonclassical potential symmetry generators.     

Explicit square conserving schemes of Landau-Lifshitz equation with Gilbert component

1　IntroductionandProblemsTotheordinarydifferentialequationsdY dt=A(t,Y)Y ,Y∈Rn,t≥ 0 ,( 1 )A(t,Y)isskewsymmetrymatrix .Fromd(YTY) dt=(Y′) TY YTY′=YT(AT A)Y =0 ,and‖Y( 0 )‖ =a ,aisapositivenumber,wecanget‖Y(t)‖ =a .Totheordinarydifferentialequationsofthesquareconservingproperty ( 1 ) ,classicalnumericalmethods,suchasexplicitRunge_Kuttamethods,multiplestepmethods,cannotpreservethesquareconservingproperty.Theimplicitmiddleschemecanpreservethesquareconservingproperty ,butitis…     

拉伸半无限圆孔板的应力集中系数表达式

首次推出拉伸半无限圆孔板孔边最大应力集中系数的显式表达式,此式不但形式简单而且具有良好的精度,目前献中尚无类似表达式。同时指出,Jeffery给出的仅有的几个具体理论值在圆孔比较靠近直线边界时误差较大。此外,采用本新定义的应力集中系数,当圆孔非常靠近直线边界时有一个极限值。     

近三正则3—连通平面地图的计数

本文提供了便于依根点次,边数和根面次计数近三正则3－连通有根平面地图的一个函数方程,继之得到其参数形式解,并由此通过Lagrange反演导出了它的计数显示,本文推广了[3]和[4]的结果。     

对流扩散方程的一种显式有限体积——有限元方法

本文给出非线性对流扩散问题的一种有限体积的有限元方法相结合的显式离散方法,证明了数值解的稳定性,并给出了一个实际算例。     

冲压板材拉伸筋阻力的一种有效数值计算方法

将弹塑性有限变形的拟流动角点本构理论和厚向各向异性屈服函数引入弹塑性动力显式有限元列式,对板材通过拉伸筋的变形过程及拉伸筋阻力进行了数值模拟,并与有关实验结果进行了比较很好的一致性,表明了该计算方法的有效性。进而,数值研究了拉伸筋形状、界面摩擦状况以及材料的厚向各向异性对拉伸筋阻力的影响,为实际覆盖件冲压成形中拉伸筋的设置提供了重要的定量依据。     

连续支付红利的美式障碍期权定价的数值方法

本文利用显式差分格式为连续支付红利的向下触销型美式障碍期权定价.由于障碍的影响,定价模型的边值条件含有间断,故把结点设在障碍水平上,并在障碍附近的区域内运用局部网格加密技术,这样就可以得到较精确的期权价格.本文给出数值算例,验证算法的有效性,并分析障碍对期权价格的影响.     

An immersed boundary vector potential-vorticity meshless solver of the incompressible Navier–Stokes equation

We present a strong form meshless solver for numerical solution of the nonstationary, incompressible, viscous Navier–Stokes equations in two (2D) and three dimensions (3D). We solve the flow equations in their stream function-vorticity (in 2D) and vector potential-vorticity (in 3D) formulation, by extending to 3D flows the boundary condition-enforced immersed boundary method, originally introduced in the literature for 2D problems. We use a Cartesian grid, uniform or locally refined, to discretize the spatial domain. We apply an explicit time integration scheme to update the transient vorticity equations, and we solve the Poisson type equation for the stream function or vector potential field using the meshless point collocation method. Spatial derivatives of the unknown field functions are computed using the discretization-corrected particle strength exchange method. We verify the accuracy of the proposed numerical scheme through commonly used benchmark and example problems. Excellent agreement with the data from the literature was achieved. The proposed method was shown to be very efficient, having relatively large critical time steps.     

VARIATIONS ON A THEME BY EULER

1.IntroductionAHallliltolliansystemofdifferentialequationsonRZnisgivedbyP~~H,(P,q),q=HP(P,q),(1)wherep=(pl,'.,P.),q=(ql,',q.)eR"arethegeneralizedcoordinatesandmolllentarespectivelyandH(P,q)istheellergyofthesystem.Thesystem(1)canberewrittenasthecompactf…     

二维等熵流的线性化方程的具轴对称初值的柯西问题

The explicit solution to Cauchy problem for linearized system of two-dimensional isentropic flow with axisymmetrical initial data in gas dynamics is given.