Dispersion analysis of the least‐squares finite‐element shallow‐water system

The frequency or dispersion relation for the least‐squares mixed formulation of the shallow‐water equations is analysed. We consider the use of different approximation spaces corresponding to co‐located and staggered meshes, respectively. The study includes the effect of Coriolis, and the dispersion properties are compared analytically and graphically with those of the mixed Galerkin formulation. Numerical solutions of a test problem to simulate slow Rossby modes illustrate the theoretical results. Copyright © 2003 John Wiley & Sons, Ltd.     

Analysis and finite element simulations of a second‐order fluid model in a bounded domain

This article is concerned with the equations governing the steady motion of a viscoelastic incompressible second‐order fluid in a bounded domain. A new proof of existence and uniqueness of strong solutions is given. In addition, using appropriate finite element methods to approximate a coupled equivalent problem, sharp error estimates are obtained using a fixed point argument. The method is applied to the two‐dimensional lid‐driven cavity problem, at low Reynolds number and in a certain range of values of the viscoelastic parameters, to analyze the combined effects of inertia and viscoelasticity on the flow. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007     

Constructing two-weight codes with prescribed groups of automorphisms

We construct new linear two-weight codes over the finite field with q elements. To do so we solve the equivalent problem of finding point sets in the projective geometry with certain intersection properties. These point sets are in bijection to solutions of a Diophantine linear system of equations. To reduce the size of the system of equations we restrict the search for solutions to solutions with special symmetries.Two-weight codes can be used to define strongly regular graphs. We give tables of the two-weight codes and the corresponding strongly regular graphs. In some cases we find new distance-optimal two-weight codes and also new strongly regular graphs.     

Hilbert algebras as implicative partial semilattices

The infimum of elements a and b of a Hilbert algebra are said to be the compatible meet of a and b, if the elements a and b are compatible in a certain strict sense. The subject of the paper will be Hilbert algebras equipped with the compatible meet operation, which normally is partial. A partial lower semilattice is shown to be a reduct of such an expanded Hilbert algebra i ?both algebras have the same ?lters.An expanded Hilbert algebra is actually an implicative partial semilattice (i.e., a relative subalgebra of an implicative semilattice),and conversely.The implication in an implicative partial semilattice is characterised in terms of ?lters of the underlying partial semilattice.     

Multiscale Finite Element Modeling of Arc Dynamics in a DC Plasma Torch

The dynamics of the electric arc inside a direct current non-transferred arc plasma torch are simulated using a three-dimensional, transient, equilibrium model. The fluid and electromagnetic equations are solved numerically in a fully coupled approach by a multiscale finite element method. Simulations of a torch operating with argon and argon–hydrogen under different operating conditions are presented. The model is able to predict the operation of the torch in steady and takeover modes without any further assumption on the reattachment process except for the use of an artificially high electrical conductivity near the electrodes, needed because of the equilibrium assumption. The results obtained indicate that the reattachment process in these operating modes may be driven by the movement of the arc rather than by a breakdown-like process. It is also found that, for a torch operating in these modes and using straight gas injection, the arc will tend to re-attach to the opposite side of its original attachment. This phenomenon seems to be produced by a net angular momentum on the arc due to the imbalance between magnetic and fluid drag forces.     

Photon interaction studies using 241Am γ-rays

We have carried out some photon interaction measurements using 59.54 keV γ-rays from a ²⁴¹Am source. These include γ attenuation studies as well as photoelectric absorption studies in various samples. The attenuation studies have been made using leaf and wood samples, samples like sand, sugar etc., which contain particles of varying sizes as well as pellets and aqueous solutions of rare earth compounds. In the case of the leaf and wood samples, we have used the γ-ray attenuation technique for the determination of the water content in fresh and dried samples. The variation of the attenuation coefficient with particle size has been investigated for sand and sugar samples. The attenuation studies as well as the photoelectric studies in the case of rare earth elements have been carried out on samples containing such elements whose K-absorption edge energies lie below and close to the γ-energy used. Suitable compounds of the rare earth elements have been chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. A well-shielded scattering geometry was used for the photoelectric measurements. The mixture rule was invoked to extract the values of the mass attenuation coefficients for the elements from those of the corresponding compounds. The results are consistent with theoretical values derived from the XCOM package.     

The Choquet-Deny convolution equation μ=μ*σ for probability measures on Abelian semigroups

In this note, we characterize the regular probability measures satisfying the Choquet-Deny convolution equation =* on Abelian topological semigroups for a given probability measure .     

Synthesis and spectroscopic study of hexadecaalkyl-substituted rare-earth diphthalocyanines

New hexadecaalkyl-substituted diphthalocyanine complexes of lanthanides ^RPc₂Ln (R = Et, or Bu; Ln = Lu, Dy, or Eu) were synthesized by three methods: in solution in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, in a melt of a mixture of the reagents, and under microwave irradiation. The first of the above-mentioned procedures has an advantage for the preparation of Dy and Eu diphthalocyanines, whereas the melt synthesis is a method of choice for the preparation of Lu complexes. The reaction time decreases in going from the first to the third method. The structures of the complexes were confirmed by mass spectrometry, NMR spectroscopy, and electronic absorption spectroscopy.     

微量元素与精神病的研究

一些基础医学实验研究和临床观察的资料表明，精神疾病患者体内的微量元素存在着显著的异常，已引起了国内外学者广泛关注，本文根据近年来的国内外文献报道，概述了微量元素锌（Ｚｎ），铜（Ｃｕ），铁（Ｆｅ）和常量元素钙（Ｃａ），镁（Ｍｇ）的生理作用及与精神病关系的研究进展。     

茶叶中八种微量元素的初级形态分析

本文介绍对市售绿茶中Cu、Zn等八种微量元素进行的初级形态分析。在测定煮、泡茶和茶叶残渣中这些元素含量的基础上,算出有关参数,提供了微量元素浸出的有关信息。