Computational experience with the Chow—Yorke algorithm

The Chow—Yorke algorithm is a nonsimplicial homotopy type method for computing Brouwer fixed points that is globally convergent. It is efficient and accurate for fixed point problems. L.T. Watson, T.Y. Li, and C.Y. Wang have adapted the method for zero finding problems, the nonlinear complementarity problem, and nonlinear two-point boundary value problems. Here theoretical justification is given for applying the method to some mathematical programming problems, and computational results are presented.This work was partially supported by NSF Grant MCS 7821337.     

A numerical technique for three-dimensional compressible boundary layers

The non-linear two-point boundary value problem for three-dimensional compressible boundary layers is solved through the application of a boundary value technique for a range of parameters characterizing the nature of stagnation point flows. The analytical boundary conditions, at infinity, are applied at the edge of the computational mesh with iterations on the size of the domain. The solutions obtained show excellent agreement with the established similarity solutions for three-dimensional flows. The present method has the potential advantage of yielding the wall values of f″_w, g″_w and θ′_w as a part of the solution, contrary to the previously used ‘shooting’ methods. The algorithm is computationally simple and numerically stable and extremely suitable for engineering design applications.     

Chaotic behavior in stellar dynamos

Slowly rotating main-sequence stars with deep convective zones have activity cycles like the sun's. The solar cycle is aperiodic and modulated to give intervals of reduced activity. A simple sixth-order system, obtained by truncating the dynamo equations, has solutions that mimic this behavior. The transition to chaos is analyzed and the astrophysical significance of these results is discussed.     

A free boundary problem for a fluid flow in a heterogeneous porous medium

In this paper we study the problem of seepage of a fluid through a porous medium, assuming the flow governed by a nonlinear Darcy law and nonlinear leaky boundary conditions. We prove the continuity of the free boundary and the existence and uniqueness of minimal and maximal solutions. We also prove the uniqueness of theS ₃-connected solution in various situations.     

Hilbert's Tenth Problem and Mazur's Conjecture for large subrings of

We give the first examples of infinite sets of primes such that Hilbert's Tenth Problem over has a negative answer. In fact, we can take to be a density 1 set of primes. We show also that for some such there is a punctured elliptic curve over such that the topological closure of in has infinitely many connected components.

     

A multi-wall carbon nanotube–molecular semiconductor composite for bi-layer organic solar cells

A water-soluble composite of oxidised multi-wall carbon nanotubes and sulphonic acid sodium salt derivatised copper phthalocyanine for application in bi-layer organic solar cells is reported. Measurements of the topography of thin films of this novel material and of the valence electronic structure of its two components are used to rationalise the photovoltaic characteristics of a model organic heterojunction utilising the nanocomposite as the hole-extracting electrode and donor layer.     

浅谈关于公司投资问题

本文主要解决的是公司如何合理安排投资取得最大经济效益的非线性规划问题进行了模型讨论,评价了模型的优缺点和现实性意义,对公司的投资问题有一定的借鉴意义。     

高校人事管理信息化建设的探究

人事管理信息化是高校信息化建设的重要内容，目前高校实施人事管理信息化建设具有十分重要的意义。当今高校人事管理信息化建设存在许多问题，因此，提出加强高校人事管理信息化建设的对策与措施，从而加快信息化建设的步伐。     

Spin-orbit-like terms in semileptonic weak Hamiltonian

It is shown that new spin-orbit-like terms appear in the effective nonrelativistic weak Hamiltonian for nucleon provided that nuclear potential is taken into account. Arguments for their considerable enhancement, in particular, in relativistic nuclear model of Walecka are advanced. Received: 29 July 1999