共查询到20条相似文献,搜索用时 62 毫秒
1.
Richard E. Ewing 《Journal of Mathematical Analysis and Applications》1979,71(1):167-186
Numerical approximation of the solution of the Cauchy problem for the linear parabolic partial differential equation is considered. The problem: (p(x)ux)x ? q(x)u = p(x)ut, 0 < x < 1,0 < t? T; ; ; p(0) ux(0, t) = g(t), 0 < t0 ? t ? T, is ill-posed in the sense of Hadamard. Complex variable and Dirichlet series techniques are used to establish Hölder continuous dependence of the solution upon the data under the additional assumption of a known uniform bound for ¦ u(x, t)¦ when 0 ? x ? 1 and 0 ? t ? T. Numerical results are obtained for the problem where the data ?1, ?2 and g are known only approximately. 相似文献
2.
For parabolic initial boundary value problems various results such as , where u satisfies , are demonstrated via the maximum principle and potential theoretic estimates. 相似文献
3.
Consider the renewal equation in the form (1) , where is a probability density on [0, ∞) and limt → ∞g(t) = g0. Asymptotic solutions of (1) are given in the case when f(t) has no expectation, i.e., . These results complement the classical theorem of Feller under the assumption that f(t) possesses finite expectation. 相似文献
4.
Min Ming Tang 《Journal of Mathematical Analysis and Applications》1977,57(2):368-381
In this paper we study the behavior of solutions of some quasilinear parabolic equations of the form as t → ∞. In particular, the solutions of these equations will decay to zero as t → ∞ in the L∞ norm. 相似文献
5.
Arthur Lubin 《Journal of Functional Analysis》1974,17(4):388-394
Let m and vt, 0 ? t ? 2π be measures on T = [0, 2π] with m smooth. Consider the direct integral = ⊕L2(vt) dm(t) and the operator on , where e(s, t) = exp ∫st ∫Tdvλ(θ) dm(λ). Let μt be the measure defined by for all continuous ?, and let ?t(z) = exp[?∫ (eiθ + z)(eiθ ? z)?1dμt(gq)]. Call {vt} regular iff for all for 1 a.e. 相似文献
6.
F.J. Massey 《Journal of Differential Equations》1976,22(2):416-427
Analyticity in t of solutions u(t) of nonlinear evolution equations of the form , is established under suitable conditions on . An application is given to quasilinear parabolic equations. 相似文献
7.
Beny Neta 《Journal of Mathematical Analysis and Applications》1982,89(2):598-611
Galerkin's method with appropriate discretization in time is considered for approximating the solution of the nonlinear integro-differential equation , 0 < x < 1, 0 < t < T.An error estimate in a suitable norm will be derived for the difference u ? uh between the exact solution u and the approximant uh. It turns out that the rate of convergence of uh to u as h → 0 is optimal. This result was confirmed by the numerical experiments. 相似文献
8.
Results on partition of energy and on energy decay are derived for solutions of the Cauchy problem . Here the Aj's are constant, k × k Hermitian matrices, x = (x1,…, xn), t represents time, and u = u(t, x) is a k-vector. It is shown that the energy of Mu approaches a limit , where M is an arbitrary matrix; that there exists a sufficiently large subspace of data ?, which is invariant under the solution group U0(t) and such that depending on ? and that the local energy of nonstatic solutions decays as . More refined results on energy decay are also given and the existence of wave operators is established, considering a perturbed equation at infinity. 相似文献
9.
10.
R Lowen 《Journal of Mathematical Analysis and Applications》1978,64(2):446-454
Starting from a defining differential equation of the kernel of an exponential operator with normalization ∫?∞∞W(λ, t, u) du = 1, we determine Sλ for various p(t) including; for example, p(t) a quadratic polynomial, all the known exponential operators are recovered and some new ones are constructed. It is shown that all the exponential operators are approximation operators. Further approximation properties of these operators are discussed. For example, functions satisfying are characterized. Several results of C. P. May are also improved. 相似文献
11.
R.E OMalley 《Journal of Mathematical Analysis and Applications》1974,45(2):468-484
We shall examine the control problem consisting of the system on the interval 0 ? t ? 1 with the initial values x(0, ?) and z(0, ?) prescribed, where the cost functional J(?) = π(x(1, ?), z(1, ?), ?) + ∝01V(x(t, ?), z(t, ?), u(t, ?), t, ?) dt is to be minimized. We shall restrict attention to the special problem where the fi's are linear in z and u, V is quadratic in z and independent of z when ? = 0, π and V are positive semidefinite functions of x and z, and V is a positive definite function of u. Under appropriate conditions, we shall obtain an asymptotic solution of the problem valid as the small parameter ? tends to zero. The techniques of constructing such asymptotic expansions will be stressed. 相似文献
12.
M.G. Crandall S.-O. Londen J.A. Nohel 《Journal of Mathematical Analysis and Applications》1978,64(3):701-735
We study the nonlinear Volterra equation , (1) as well as the corresponding problem with infinite delay . (7) Under various assumptions on the nonlinear operators A, B and on the given functions a, F, f, h existence theorems are obtained for (1) and (7, followed by results concerning boundedness and asymptotic behaviour of solutions on (0 ? < ∞); two applications of the theory to problems of nonlinear heat flow with “infinite memory” are also discussed. 相似文献
13.
Douglas Hensley 《Journal of Number Theory》1984,18(2):206-212
For a > 0 let , the sum taken over all n, 1 ≤ n ≤ x such that if p is prime and p|n then a < p ≤ y. It is shown for u < about () that , where pa(u) solves a delay differential equation much like that for the Dickman function p(u), and the asymptotic behavior of pa(u) is worked out. 相似文献
14.
Karen A Ames 《Journal of Mathematical Analysis and Applications》1984,103(1):172-183
Solutions of Cauchy problems for the singular equations (in a Hilbert space setting) and , ω={(x1,…,xM)εm: 0 < xi < ci for each i=1,…,m} are shown to be unique and to depend Hölder continuously on the initial data in suitably chosen measures for 0?t < T < ∞. Logarithmic convexity arguments are used to derive the inequalities from which such results can be deduced. 相似文献
15.
Ethelbert N Chukwu 《Journal of Mathematical Analysis and Applications》1980,76(1):283-296
Sufficient conditions are developed for the null-controllability of the nonlinear delay process (1) when the values of the control functions u lie in an m-dimensional unit cube Cm of Em. Conditions are placed on f which guarantee that if the uncontrolled system is uniformly asymptotically stable and if the linear control system x(t) = L(t, xt) + B(t) u(t) is proper, then (1) is null-controllable. 相似文献
16.
In this paper we study the existence, uniqueness, and regularity of the solutions for the Cauchy problem for the evolution equation is in (0, 1), 0 ? t ? T, T is an arbitrary positive real number,f(s)?C1, and g(x, t)?L∞(0, T; L2(0, 1)). We prove the existence and uniqueness of the weak solutions for (1) using the Galerkin method and a compactness argument such as that of J. L. Lions. We obtain regular solutions using eigenfunctions of the one-dimensional Laplace operator as a basis in the Galerkin method. 相似文献
17.
J.G. Besjes 《Journal of Mathematical Analysis and Applications》1974,48(2):594-609
We consider the first initial-boundary value problem for and L1 are linear elliptic partial differential operators) and investigate the properties of u(x, t, ?) as ? ↓ 0 in the maximum norm. Special attention is paid to approximations obtained by the boundary layer method. We use a priori estimates. 相似文献
18.
Consider the nonlinear integro-differential equation , 0 < x <, 0 < t < T, with appropriate initial and boundary conditions. This problem serves as a model for one-dimensional heat flow in materials with memory. The numerical solution via finite elements was discussed in B. Neta [J. Math. Anal. Appl.89 (1982), 598–611]. In this paper we compare the results obtained there with finite difference approximation from the point of view of accuracy and computer storage. It turns out that the finite difference method yields comparable results for the same mesh spacing using less computer storage. 相似文献
19.
Tomas Schonbek 《Journal of Differential Equations》1985,56(2):290-296
New and more elementary proofs are given of two results due to W. Littman: (1) Let . The estimate cannot hold for all u?C0∞(Q), Q a cube in , some constant C. (2) Let n ? 2, p ≠ 2. The estimate cannot hold for all C∞ solutions of the wave equation □u = 0 in ; all t ?; some function C: → . 相似文献
20.
Christopher K.R.T. Jones 《Journal of Differential Equations》1983,49(1):142-169
Two theorems are proved for the spherically symmetric solutions of the “bistable” reaction-diffusion equation , where ? is cubic-like and x ∈ Rn. The first theorem says that, for a suitable class of initial data, there are only two types of asymptotic behavior, u(x, t) tends to an equilibrium solution as t → + ∞ or u(x, t) → 1 uniformly on compact sets. The second theorem says that in the latter case, if the solution is followed out along any ray, it approaches, in shape, the one-dimensional travelling wave. 相似文献