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1.
In this paper, two new nonconforming hexagonal elements are presented, which are based on the trilinear function space Q1^(3) and are edge-oriented, analogical to the case of the rotated Q1 quadrilateral element. A priori error estimates are given to show that the new elements achieve first-order accuracy in the energy norm and second-order accuracy in the L^2 norm. This theoretical result is confirmed by the numerical tests.  相似文献   

2.
王鸣 《数学进展》1994,23(3):238-250
本文讨论了下述情形:1非嵌套网格;2曲边有限元;3非协调元;4拟协调元;5有限元的型函数有特殊性质,都能导致非嵌套的有限元空间.对一个包括上述情形的问题给出了非嵌套有限元的W循环多重网格方法,并证明了它的收敛性。  相似文献   

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4.
抛物型积分微分方程的变网格有限元法   总被引:19,自引:2,他引:17  
众所周知,对通常的抛物型边值问题的解法就是对空间区域采用有限元法,对时间区间采用差分方法,并且不同时刻采用相同的网格。1985年,梁国平在文[5]中提出了一种解抛物型初边值问题的新思想,即变网格有限元法。此后许多数值分析学者就相继采用这一思想来解决其它问题。本文我们采用变网格有限元方法来处理抛物型积分微分方程问题,给出  相似文献   

5.
Navier—Stokes方程的变网格非协调有限元法   总被引:1,自引:0,他引:1  
本文通过所谓的速度-压力型公式讨论了Navier-Stokes方程的变网格非协调有限元逼近,得到了在模意义下的速度,压力误差估计,且在一定条件下,某些误差估计能达到最优。  相似文献   

6.
通过对方程的对流部分采用沿着特征线方向向后两步差分格式进行离散,而对扩散部分采用混合有限元格式进行离散,从而利用多步特征-混合有限元方法对平面非均匀水沙模型进行了数值模拟,给出了相应的误差分析及数值算例.  相似文献   

7.
有关有限元法的校正技术,文[1]林群、杨一都作了较为系统的综述。文[2]林群、周爱辉提出了几个算子相乘的观点,并对二维一次有限元作了三重校正。文[3]朱起定等对两点边值问题和带光滑核边界积分方程的有限元解给出了多重校正公式。从理论上讲,这些问题可以任意次校正。然而,对多角形域上边界积分方程,由于角点的存在,解函数在角点有奇性,文[3]的方法失效。本文采用局部加密网格方法,对角域上边界有限元给出了多重校正公式。本文采用的符号同文[4]。  相似文献   

8.
一阶双曲问题的间断流线扩散法   总被引:7,自引:0,他引:7  
1.引言众所周知,求解一阶双曲问题的Galerkin有限元法,仅具有次最优LZ一收敛阶估计,难于建立H\误差估计【‘1,且Gderkill有限元解常呈现伪数值振荡.为改善计算精度与稳定性,诸多非标准有限元解法相继提出,其中,间断(Discontinuous)Galerkin有限元法(以下简称DG方法)与流线扩散(StreamlineDiffusion)有限元法(以下简称SD法)是两种具有鲜明特点,较为成功的算法.具体地,DG方法是一种迎风型显式算法,它从入流边界开始,沿流场方向,自上游往下游,逐个单元进行解算,计算十分简便且可局部并行化.SD方法则是一种P…  相似文献   

9.
段火元 《计算数学》1998,20(4):403-408
0.弓I言稳定化有限元方法[2][4][12][15]ro[18]在固体和流体力学的数值计算中构造有效的格式发挥着很大的作用.从理论分析的角度看,该方法(Galerkin一局部最小二乘方法)是完备的、确定的,但是在实际计算中稳定化参数。E(0,CI)的如何选取直接影响到逼近解的质量.数值实验【9川叫'川'到表明。取得太小会造成。伪l。压力模式rI.因此,对of的估计是一个值得注意的重要问题.文[8]虽然估训一了一些逆常数,但其未能给出确定逆估计常数的一般公式,而且技巧性太强,过于依赖区域剖分的性质,使得逆常数的计算复杂化,不…  相似文献   

10.
将特征有限元方法和混合有限元方法进行耦合,对页岩气藏渗流模型进行了数值模拟,给出了详细的误差分析,得到了最优的L~2模误差估计,并用数值实验验证了方法的有效性.  相似文献   

11.
EXISTENCEANDUNIQUENESSOFSOLUTIONSFORNONLINEARBOUNDARYVALUEPROBLEMSOFVOLTERRA-HAMMERSTEINTYPEINTEGRODIFFERENTIALEQUATION¥WangG...  相似文献   

12.
We define the generalized potential polynomials associated to an independent variable, and prove an explicit formula involving the generalized potential polynomials and the exponential Bell polynomials. We use this formula to describe closed type formulas for the higher order Bernoulli, Eulerian, Euler, Genocchi, Apostol-Bernoulli, Apostol-Euler polynomials and the polynomials involving the Stirling numbers of the second kind. As further applications, we derive several known identities involving the Bernoulli numbers and polynomials and Euler polynomials, and new relations for the higher order tangent numbers, the higher order Bernoulli numbers of the second kind, the numbers , the higher order Bernoulli numbers and polynomials and the higher order Euler polynomials and their coefficients.  相似文献   

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The modified lower box dimension can be redefined in terms of the d-measure [4]. In this note we prove a decomposition theorem for this measure and show that strong regularity can be interpreted as this d-measure regularity in Rn. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

15.
D3-Modules     
A right R-module M is called a D3-module, if M 1 and M 2 are direct summands of M with M = M 1 + M 2, then M 1M 2 is a direct summand of M. Following the work of Bass on projective covers, we introduce the notion of D3-covers and provide new characterizations of several well-known classes of rings in terms of D3-modules and D3-covers.  相似文献   

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That we are morally responsible for what we do willingly and knowingly is a commonplace. That our moral responsibility extends as far as to cover at least the intended consequences of our voluntary actions and perhaps also the ones we did not intend, but could or did foresee, is equally beyond dispute. But what about omissions? Are we, or can we be, (equally) morally responsible for the harm that has occured because we did not prevent it, even though we could have done so? Say, for all the enormous suffering, caused daily by famine, deprivation and curable diseases in the Third World countries?Moral intuitions and practices that one could consult in this matter seem to leave us in the dark. We regularly ascribe responsibility to people for harms resulting from their negligence or failure to fulfill professional duties. On the other hand, we tend to think that unless there is some evidence of the causal contribution that agents made to a harmful event and/or state, it is not really fair to blame it on them. And finally, to complicate things even more, most of us deny that omissions could effect anything (any change) in the world and consequently regard them as causally impotent (as well as possibly harmless).Most of the proposed solutions to this perplexing issue simply take negative moral responsibility for granted and then either try to revise our ordinary notion of causation accordingly or, alternatively, weaken the conditions for holding someone morally responsible. In the paper I present and defend the relative merits of the third approach, one sceptical of the notion of moral responsibility for the ‘outcomes’ of omissions. I try to show that for some identifiable core notion of moral responsibility and paradigmatic cases of omissions, the prospects for a happy marriage are rather slim.  相似文献   

18.
his paper presents concentration inequalities and laws of large numbers under weak assumptions of irrelevance that are expressed using lower and upper expectations. The results build upon De Cooman and Miranda’s recent inequalities and laws of large numbers. The proofs indicate connections between the theory of martingales and concepts of epistemic and regular irrelevance.  相似文献   

19.
Let G=(V,E) be a (directed) graph with vertex set V and edge (arc) set E. Given a set P of source-sink pairs of vertices of G, an important problem that arises in the computation of network reliability is the enumeration of minimal subsets of edges (arcs) that connect/disconnect all/at least one of the given source-sink pairs of P. For undirected graphs, we show that the enumeration problems for conjunctions of paths and disjunctions of cuts can be solved in incremental polynomial time. Furthermore, under the assumption that P consists of all pairs within a given vertex set, we also give incremental polynomial time algorithm for enumerating all minimal path disjunctions and cut conjunctions. For directed graphs, the enumeration problem for cut disjunction is known to be NP-complete. We extend this result to path conjunctions and path disjunctions, leaving open the complexity of the enumeration of cut conjunctions. Finally, we give a polynomial delay algorithm for enumerating all minimal sets of arcs connecting two given nodes s1 and s2 to, respectively, a given vertex t1, and each vertex of a given subset of vertices T2.  相似文献   

20.
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