摘要:

AbstractThe customary procedure for including resistive effects in turbulent hydraulic and stratified atmospheric flows is to integrate the empirically‐known boundary shears over the entire wetted boundary of a thin fluid slab. A resistive body‐force is then assumed to exist everywhere in each slab to replace the boundary shearing force. For the classical Saint‐Venant model, this body‐force can be shown to have a constant distribution in the vertical direction, and therefore can be evaluated for use in the momentum differential equation. In the newer Dressler theory, however, for unsteady flow over curved beds, it is proved here that a constant body‐force distribution is not possible. We determine its variable distribution and its magnitude for use in the curved‐flow equations. This vasriable distribution acts to produce an equal resultant in every thin layer of fluid parallel to the bed in an angular wedge over the curved channel bed. The new curved‐flow equations are therefore extended to include resi

ISSN:0170-4214    

DOI:10.1002/mma.1670080132

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractIn this paper we prove that the one‐dimensional model of elastic beam is an approximation to the three‐dimensional linear theory of elastic

ISSN:0170-4214    

DOI:10.1002/mma.1670080133

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe stability bound for the classical nonlinear Euler beam is determined in the case that its deflection is limited by an obstacle parallel to the plane of the beam. Let a clamped or simply supported beam be axially compressed by a forceP>P0, whereP0denotes the critical load. So far only a linear theory has been applied to analyze the stability of the solutions in contact with the obstacle and the jumping to a different state. Utilizing a free boundary problem formulation we analytically as well as numerically answer these questions for the nonlinear beam.

ISSN:0170-4214    

DOI:10.1002/mma.1670080134

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractWe prove the local existence of smooth solutions for the Vlasov‐Maxwell equations in three space variables. The existence time for such solutions is independent of the light velocityc. Then we derive regularity results for both the Vlasov‐Poisson and the Vlasov‐Maxwell equations. The last part of the paper is devoted to a proof of weak and strong convergence of the Vlasov‐Maxwell equations towards the Vlasov‐Poisson equations, when the light velocitycgoes to

ISSN:0170-4214    

DOI:10.1002/mma.1670080135

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractIt is proven that for a certain class of singular nonlinear Schrödinger equations there exist stationary ground state and oscillatory solutions. Furthermore the existence of those solitary wave type solutions is considered which do not necessarely vanish at infinity. The results are applied to problems from plasma physics; to superfluid films, and to the Heisenberg ferromagnet spin chain

ISSN:0170-4214    

DOI:10.1002/mma.1670080136

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper discusses the scattering frequencies associated with the scalar wave equation and a time‐periodic, real, potential. It is shown that the scattering frequencies form a discrete set in the complex plane and depend continuously on the potential. Existence of the scattering frequencies is proved for periodic potentials which are perturbations of a time independent, nonnegative, potentia

ISSN:0170-4214    

DOI:10.1002/mma.1670080137

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractFor the solution of the exterior Dirichlet problem for the Helmholtz equation we propose to seek the solution in the form of an acoustic single‐layer potential with a distribution extended over an internal surface. This leads to an ill‐posed integral equation of the first kind which can be approximately solved by the Tikhonov regularization techni

ISSN:0170-4214    

DOI:10.1002/mma.1670080138

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis work is a continuation of [1]. We give a space‐time variational formula to the problem of the scattered acoutic wave by a hard body, using the double layer retarded potential technique. New schemes are constructed from this variationnal formula, for which we prove the stability and errors estimate

ISSN:0170-4214    

DOI:10.1002/mma.1670080139

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper presents a solution procedure for three‐dimensional crack problems via first kind boundary integral equations on the crack surface. The Dirichlet (Neumann) problem is reduced to a system of integral equations for the jump of the traction (of the field) across the crack surface. The calculus of pseudodifferential operators is used to derive existence and regularity of the solutions of the integral equations. With the concept of the principal symbol and the Wiener‐Hopf technique we derive the explicit behavior of the densities of the integral equations near the edge of the crack surface. Based on the detailed regularity results we show how to improve the boundary element Galerkin method for our integral equations. Quasi‐optimal asymptotic estimates for the Galerkin error are

ISSN:0170-4214    

DOI:10.1002/mma.1670080140

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

ISSN:0170-4214    

DOI:10.1002/mma.1670080101

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY