整流后倒U型管内气液两相流动的稳定性及流型分布

在倒U型管垂直段的两端内分别放置一个整流环，来消除入口弯头对垂直段流动的影响，通过对单相流体在倒U型管内的流动进行数值计算，以及对整流作用下倒U型管内气液流动的稳定性和流型的分布进行实验研究，发现整流环的整流作用可以增强管道内流动的稳定性，实验还发现，倒U型管垂直上升段内的间歇性流动（弹状流和块状流）区域减小，环状流区域增大，流动的稳定性增强。     

ISDN标准接入的多功能数字终端

论述了综合业务数字网（ＩＳＤＮ）及其标准用户──网络接口的基本概念；对用户网络接口的体系结构作了较为详细的说明，给出了具体的软件实现方法和硬件接口电路（ＳＮＩＣ）．在此基础上，提出了ＩＳＤＮ标准数字话音终端和基于基本接入能力（２Ｂ＋Ｄ）的多功能数字终端的设计方案。     

Verbindungsbildung in den quasi-binären Systemen AcX4?MX2 (Ac = Th,U; M = Ca,Sr, Ba,Eu, Ge,Sn, Pb; X = Br,I)

Formation of Compounds in the Quasi-binary Systems AcX₄? MX₂ (Ac = Th, U; M = Ca, Sr, Ba, Eu, Ge, Sn, Pb; X = Br, I) T,x-phase diagrams of the systems ThI₄? SnI₂, ThI₄? PbI₂, ThI₄? CaI₂, and ThI₄? SrI₂ were established using thermoanalysis and x-ray methods. The only ternary compounds have a 1:1 composition. Further AcMX₆ compounds (Ac: Th, U; M: Ca, Sr, Ba, Eu, Ge, Sn, Pb; X: Br, I) were synthesized and their structures investigated. Four structure types are found depending on the temperature and the Ac/M combinations. The structures of γ-ThSnI₆ and β-ThSnI₆ were determined with single crystal methods as representatives of a whole series of isotypic compounds.     

Excitation of analytes and enhancement of emission intensities in a d.c. plasma jet: a critical review leading to proposed mechanistic models

Experimental data and theoretical criteria are used to critically review existing models for analyte emission enhancement in the 3-electrode d.c. plasma (DCP). The analytical zone is characterized as a non-optically thin recombining plasma in partial thermodynamic equilibrium (PTE). Spectrochemical excitation the authors ascribe largely to: (1) argon resonance line radiative transport; (2) inversion of optically pumped argon states; (3) inversion of analyte populations by Franck-Condon collisions with argon; (4) energy cascading in analytes via a multitude of channels. Adding an easily ionized element (EIE): (1) induces additional resonance line radiative transfer; (2) raises electron densities in cooler, analyte-rich plasma margins; (3) locally increases argon optical absorption cross sections via Stark broadening; (4) redistributes ohmic heating. Coupling between the proposed mechanisms is non-linear. Relationships between radiative transfer and collisional redistribution and (1) background suppression by EIE and (2) analyte emission enhancement by helium are also examined. Similarities between DCP and inductively coupled plasma (ICP) excitation mechanisms are noted and practical implications are addressed.     

A case for large Auger recombination cross sections associated with deep centers in semiconductors

It is argued that the recent quantitative results concerning localized defects in semiconductors (e.g. GaAs) are consistent with the possibility of large Auger-type cross sections associated with recombination at these centers.It is proposed that many of the capture cross sections reported to be in the range 10^?13–10^?16cm², which exhibit only weak temperature dependence, and which do not depend on carrier concentration, might be explained by this mechanism.     

The vibrational force field of halogenated aromatic molecules: II. Out-of-plane vibrations of fluoroaromatics

A general quadratic force field is determined for the out-of-plane vibrations of florobenzenes. The force constants for the out-of-plane wagging of both CH and CF bonds decrease by about 10 % for each ortho fluorine substituent. No significant meta dependence could be detected. It is shown that the present field is in excellent accord with the chlorobenzene field of Scherer and with the benzene fields of Whiffen and of Kydd when due allowance is made for differences in coordinate definitions.     

Semilocal rings with <Emphasis Type="Italic">n</Emphasis>-Engel multiplicative group

An associative ring R with unit element is called semilocal if R modulo its Jacobson radical is an artinian ring. It is proved that the multiplicative group R* of a semilocal ring R generated by R* satisfies an n-Engel condition for some positive integer n if and only if R is m-Engel as a Lie ring for some positive integer m depending only on n.Received: 21 January 2003     

Presentations of the unit group of an order in a non-split quaternion algebra

We give an algorithm to determine a finite set of generators of the unit group of an order in a non-split classical quaternion algebra over an imaginary quadratic extension K of the rationals. We then apply this method to obtain a presentation for the unit group of . As a consequence a presentation is discovered for the orthogonal group . These results provide the first examples of a characterization of the unit group of some group rings that have an epimorphic image that is an order in a non-commutative division algebra that is not a totally definite quaternion algebra.     

The realization space of a Π-algebra: a moduli problem in algebraic topology

A Π-algebra A is a graded group with all of the algebraic structure possessed by the homotopy groups of a pointed connected topological space. We study the moduli space R(A) of realizations of A, which is defined to be the disjoint union, indexed by weak equivalence classes of CW-complexes X with , of the classifying space of the monoid of self homotopy equivalences of X. Our approach amounts to a kind of homotopical deformation theory: we obtain a tower whose homotopy limit is R(A), in which the space at the bottom is BAut(A) and the successive fibres are determined by Π-algebra cohomology. (This cohomology is the analog for Π-algebras of the Hochschild cohomology of an associative ring or the André-Quillen cohomology of a commutative ring.) It seems clear that the deformation theory can be applied with little change to study other moduli problems in algebra and topology.