共查询到20条相似文献,搜索用时 31 毫秒
1.
A Finite Element Galerkin Method for a Unidimensional Single-Phase Nonlinear Stefan Problem with Dirichlet Boundary Conditions 总被引:1,自引:0,他引:1
Based on straightening the free boundary, an H1-Galerkin methodis proposed and analysed for a single-phase nonlinear Stefanproblem with Dirichlet boundary conditions. Optimal H1 estimatesfor continuous-time Galerkin approximations are derived. 相似文献
2.
Nicolai V. Krylov 《Applied Mathematics and Optimization》2002,46(2):231-261
Sufficient conditions on bounded domains D ² R d={(t,x)} of class C4 are given under which solutions of the heat equation ut=j u+f in D have continuous second-order derivatives with respect to (t,x) in D- . The equation is supplemented with C4 boundary data and it is assumed that f] C2 . 相似文献
3.
On the solvability for the mixed-type Lyapunov equation 总被引:3,自引:0,他引:3
** Email: xsf{at}math.pku.edu.cn*** Email: mscheng{at}math.pku.edu.cn In this paper, the linear matrix equation X = AXB* + BXA* +Q is considered, which is called the mixed-type Lyapunov equation.Some necessary and sufficient conditions for the existence ofa unique solution are presented. Since a Hermitian positivesemidefinite solution is important from the application pointof view, some sufficient conditions for the existence of a Hermitianpositive semidefinite solution are derived. 相似文献
4.
文利用变分方法讨论了方程-△pu=λ a(x)(u^{+})q-1-μ a(x)(u-)q-1+f(x,u), u∈W01,p(Ω), 当 p≠q时的可解性. 其中Ω是 RN(N≥ 3)中的有界光滑区域,权重函数a(x)∈ Lr(Ω), (r≥Np/Np-Nq+pq)且a(x)>0, a.e.于Ω, f满足某些条件. 相似文献
5.
In this paper, the authors investigate the decay of end effectsfor a cross-diffusion problem defined on a semi-infinite cylindricalregion. With homogeneous Dirichlet or Neumann conditions prescribedon the lateral surface of the cylinder, it is shown that forfixed finite time and under certain restrictions on the coefficients,solutions decay point-wise as the distance d from the finiteend of the cylinder tends to infinity at least of order e–kd2.Under less restrictive conditions, it is shown that solutionsdecay in L2 at least as fast as e–kd. In both cases, kis a computable function of time. 相似文献
6.
该文利用变分方法讨论了方程 -△p u=λa(x)(u+)p-1-μa(x)(u-)p-1+f(x, u), u∈W01,p(\Omega)在(λ, μ)\not\in ∑p和(λ, μ) ∈ ∑p 两种情况下的可解性, 其中\Omega是 RN(N≥3)中的有界光滑区域, ∑p为方程 -△p u=α a(x)(u+)p-1-βa(x)(u-)p-1, u∈ W01,p(\Omega)的Fucik谱, 权重函数a(x)∈ Lr(\Omega) (r≥ N/p)$且a(x)>0 a.e.于\Omega, f满足一定的条件. 相似文献
7.
** Email: emmanuel.moulay{at}ec-lille.fr*** Email: wilfrid.perruquetti{at}ec-lille.fr In this paper, the problem of finite time stability is investigatedfor differential inclusion. Two sufficient conditions for finitetime stability, using a smooth Lyapunov function and a non-smoothone, are established. Then, the same idea is used to give twonecessary conditions. Examples are developed using the conceptof Krasovskii solutions for differential equation with discontinuousright-hand sides. 相似文献
8.
栗付才 《数学物理学报(A辑)》2008,28(6):1187-1193
该文研究光滑有界区域Ω( RN (N≥ 1) 上具有齐次Dirichlet边界条件的拟线性退化抛物型方程组
ut-div(|▽u|p-2 ▽u) =avα, vt-div(|▽v|q-2 ▽v) =buβ
的非负解的性质, 其中p, q>2, α, β ≥ 1, a, b> 0是常数. 该文指出上述方程组的解是否在有限时刻爆破依赖于初值、系数 a 与 b以及 αβ 和 (p-1)(q-1)之间的关系. 相似文献
9.
Spin Structures on Lefschetz Fibrations 总被引:1,自引:0,他引:1
Necessary and sufficient conditions for Lefschetz fibrationsover D2 and S2 to carry spin structures are presented. The conditionsare given in terms of vanishing cycles and homology sections. 相似文献
10.
Present address: Department of Mathematics, University of Tabriz, Tabriz, Iran. Accurate end conditions are derived for quintic spline interpolationat equally spaced knots. These conditions are in terms of availablefunction values at the knots and lead to O(h6) convergence uniformlyon the interval of interpolation. 相似文献
11.
该文讨论了偶数阶边值问题 (-1)m y(2m)=f(t,y), 0≤t≤1,ai+1y(2i) (0)-βi+1y (2i+1) (0)=0, γi+1y(2i) (1)+δi+1y(2i+1) (1)=0,0≤i ≤m-1正解的存在性.借助于Leggett-Williams 不动点定理,建立了该问题存在三个及任意奇数个正解的充分条件. 相似文献
12.
A. Ursini 《Algebra Universalis》2000,43(1):51-78
In a congruence modular subtractive variety there are both the commutator of ideals and the commutator of congruences. We prove that, if I' is the smallest congruence having an ideal I as a congruence class, then [I,J] = 0 /[I', J']. The general identity [0/ !,0 / #] = 0/[!,#] for !, # congruences, does not always hold; we give several conditions equivalent to this identity and sufficient conditions for it to hold. In the meantime, we get some other characterizations of the commutator of ideals. We also deal with the equational definability of principal commutators in a subtractive variety and with the extension property of the commutator from ideals of a subalgebra to the commutator of ideals of the whole algebra. 相似文献
13.
T. Ando 《Archiv der Mathematik》2001,77(1):76-84
We present necessary and sufficient conditions for a set of matrices to coincide with a set of the form {A: HA + A*H > 0} or {T : T*HT < H} for some (hidden) positive definite matrix H. 相似文献
14.
文中研究了对应于α-带尺度函数的小波紧框架,这个小波紧框架是由V1中的n个函数ψ1,ψ2,...,ψn构成. 首先给出了这n个函数构成小波紧框架的充分条件, 并借助尺度函数给出了构造小波紧框架的显式公式. 如果尺度函数的符号是有理函数,则可以构造出符号为有理函数的小波紧框架. 其次给出类似于正交小波的小波紧框架的分解与重构算法,并构造了小波紧框架的数值算例. 相似文献
15.
In this paper, a semidiscrete finite element Galerkin methodfor the equations of motion arising in the 2D Oldroyd modelof viscoelastic fluids with zero forcing function is analysed.Some new a priori bounds for the exact solutions are derivedunder realistically assumed conditions on the data. Moreover,the long-time behaviour of the solution is established. By introducinga StokesVolterra projection, optimal error bounds forthe velocity in the L(L2) as well as in the L(H1)-norms andfor the pressure in the L(L2)-norm are derived which are validuniformly in time t > 0. 相似文献
16.
Farouki Rida T.; Manni Carla; Sestini Alessandra 《IMA Journal of Numerical Analysis》2003,23(2):175-195
The interpolation of a planar sequence of points p0, ..., pNby shape-preserving G1 or G2 PH quintic splines with specifiedend conditions is considered. The shape-preservation propertyis secured by adjusting tension parameters thatarise upon relaxing parametric continuity to geometric continuity.In the G2 case, the PH spline construction is based on applyingNewtonRaphson iterations to a global system of equations,commencing with a suitable initialization strategythisgeneralizes the construction described previously in NumericalAlgorithms 27, 3560 (2001). As a simpler and cheaperalternative, a shape-preserving G1 PH quintic spline schemeis also introduced. Although the order of continuity is lower,this has the advantage of allowing construction through purelylocal equations. 相似文献
17.
We present a new fourth-order finite difference method for thegeneral second-order non-linear differential equation yN = f(x,y, y') subject to mixed two-point boundary conditions. An interestingfeature of our method is that each discretization of the differentialequation at an interior grid point is based on just three evaluationsof f. We establish, under appropriate conditions, O(h4)-convergenceof the finite difference scheme. In the case of linear differentialequations, our finite difference scheme leads to tridiagonallinear systems. Numerical examples are considered to demonstratecomputationally the fourth order of the method. 相似文献
18.
TRIANTAFILLIDIS S.; LEACH J. A.; OWENS D. H.; TOWNLEY S. 《IMA Journal of Mathematical Control and Information》1996,13(3):251-277
A problem of universal adaptive stabilization in Rn is approachedin a qualitative manner to relate the form of the trajectoriesin the extended state space Rn+1 to the root locus of the associatedfixed-parameter linear system. Relationships are derived betweenthe values of the limit gain and the initial conditions. Numericalstudies are used to illustrate and support these ideas by computationof generic trajectories and attempted computation of certainnon-generic possibilities. The implications of the study formore general dynamic situations are outlined.
These authors are also with the Department of Mathematics,University of Exeter, EX4 4QE. 相似文献
19.
SANTOS JUAN ENRIQUE; DOUGLAS JIM JR; MORLEY MARY E.; LOVERA OSCAR M. 《IMA Journal of Numerical Analysis》1988,8(4):415-433
A model is defined to simulate the propagation of waves in aradially symmetric, isotropic, composite system consisting ofa fluid-filled well bore f through a fluid-saturated poroussolid p. Biot's equations of motion are chosen to describe thepropagation of waves in p, while the standard equation of motionfor compressible inviscid fluids is used for f, with appropriateboundary conditions at the contact surface between f and p.Also, absorbing boundary conditions for the artificial boundariesof p are derived for the model, their effect being to make themtransparent for waves arriving normally First, results on the existence and uniqueness of the solutionof the differential problem are given and then a discrete-time,explicit finite element procedure is defined and analysed, withfinite element spaces suited for radially symmetric problemsbeing used for the spatial discretisation. 相似文献
20.
Daverman Robert J.; Im Young Ho; Kim Yongkuk 《Journal London Mathematical Society》2003,68(1):206-222
The main result provides mild conditions under which a closed,orientable, PL 4-manifold N = N1#N2 with 1(Ne) residually finite(e=1,2) is a codimension-5 PL fibrator. The paper also presentsa rich variety of conditions on a closed 4-manifold N4 underwhich every PL map between manifolds, where the domain is orientableand all point inverses are copies of N4, must be an approximatefibration. 相似文献