摘要:

AbstractLet ω0, …, ωp−1ϵS1bepdistinct directions and letRdenote the Radon transform. The functionsfwith support in the unit disc and withRf(s, ωj) = 0 forsϵ [−1, 1] andj= 0, …,p− 1 are given. „Ghosts”︁ are constructed, i.e. functions in the null space that pretend not existent tumors. Methods to avaoid such

ISSN:0170-4214    

DOI:10.1002/mma.1670030102

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractWe consider the problem whereaandfare 1‐periodic int, ais positive,fsatisfies appropriate decreasing conditions; smoothness ofa, f, ∂Ω is also assumed. Denote by λ0the principal eigenvalue of Δ with zero Dirichlet boundary conditions, and define . We prove: (a) if ε ≤ 0, then no non‐negative periodic solution exists but zero, and any solution with continuous non‐negative initial datum converges to zero uniformly ast→ ∞; (b) if ε>0, then a unique non trivial non‐negative 1‐periodic solutionu* exists, and any solution with continuous, non‐negative not identically zero initial datum appro

ISSN:0170-4214    

DOI:10.1002/mma.1670030103

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractIn the paper it is considered the generalized telegraphic equation represented by the system of four evolution equations, containing a small positive parameter multiplying some of the time derivatives. It is shown that if the small parameter tends to zero, the solution to the telegraphic equation tends asymptotically to the solution of the diffusion equation obtained from the former one by putting the small parameter equal to zero.

ISSN:0170-4214    

DOI:10.1002/mma.1670030104

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThis work is devoted to Free Boundary Problems with Laplace equation Δu=fin the domain and the two conditions on the Free Boundaryu= 1 and |gradu| = λ = const. In the model problems which we study, three cases arise: 1)f= 0, λ is given, 2)f= 0, λ is unknown and the length of the Free Boundary is given, 3)f≠ 0, λ = 0 (Obstacle Pr

ISSN:0170-4214    

DOI:10.1002/mma.1670030105

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractWe formulate the assumptions under which RiceJintegral and the critical energy release rate, which occur in fragile fracture mechanic, are equivalent.

ISSN:0170-4214    

DOI:10.1002/mma.1670030106

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractWe prove asymptotic estimates for the Green's function of irregular multipoint eigenvalue problems, these estimates are fundamental for the expansion of functions into a series of eigenfunctions of irregular eigenvalue problems.

ISSN:0170-4214    

DOI:10.1002/mma.1670030107

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe (exterior) oblique derivative problem of potential theoryis considered wherelis aC(1,λ)‐vector field on a regular boundary ∂Gein Euclidean spaceR3and the directionlat any point of ∂Geforms with the outside normalnan angle ∢ (l, n) satisfying cos ∢ (l, n) ≥c>0. An approximation of the uniquely determined solution is given by use of trial functions {Φn}n=0,1,…harmonic in some region containingGeand suitable for numerical purpose (for instance: solid spherical harmonics, certain sequences of fundamental solutions). The system {l▽Φn+hΦn}n=0,1,…defined on ∂Geis shown to be closed and complete in the pre‐Hilbert spaceC(0,λ)(∂Ge) of

ISSN:0170-4214    

DOI:10.1002/mma.1670030108

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAn Uzawa algorithm of Temam is improved so that the Navier‐Stokes boundary value problem is reduced to a sequence of linear Poisson problems. A simple finite element method is shown to give a convergent sequence of approximate solutions. Finally a penalty variant is discusse

ISSN:0170-4214    

DOI:10.1002/mma.1670030109

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractWe prove that for positive initial datau0,v0ϵC1(R) ∩L1(R) vanishing at infinity, the solutionu(x, t)v(x, t) of the Carleman model satisfies the estimate The constantCdepends only on the initial mas

ISSN:0170-4214    

DOI:10.1002/mma.1670030110

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

In this paper we consider the reflection of acoustic waves at an unbounded surface which coincides with a plane outside a sufficiently large sphere. We prove uniqueness and existence theorems for the corresponding boundary value problems for the reduced wave equation with Dirichlet and Neumann data by employing integral equation methods.

ISSN:0170-4214    

DOI:10.1002/mma.1670030111

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY