An analysis of two-dimensional aligned-field magnetogasdynamic flows

Zusammenfassung Eine zähigkeitslose Flüssigkeit endlicher Leitfähigkeit wird in einem Zustand stationärer zweidimensionaler Bewegung betrachtet, d.h. der Geschwindigkeitsvektor besitzt eine Nullkomponente in einer bestimmten Richtung. Eine Analyse der Strömung wird vorgenommen, wenn die Magnet- und Geschwindigkeitsfelder überall parallel sind. Zwei mögliche Gruppen von Gebietsströmungen sind festzustellen: a) wo das Magnetfeld drallfrei ist, b) wo die Ladungsdichte überall null ist. Durch Anwendung komplexer Variabeln werden die allgemeinen Gleichungen in beiden Fällen beträchtlich vereinfacht; dadurch lassen sich die notwendigen parametrischen Formen der betreffenden physikalischen Grössen bestimmen. Dieses Verfahren lässt sich auch auf andere Arten von Strömungsfeldern anwenden.     

高压密封消化罐在光谱分析样品前处理中的应用

原了吸收光谱法是进行元素定量分析的快捷有效的方法,但固体试样溶解的不完全会对其分析测定的准确度带来很大影响。本文应用高压密封消化罐对电厂难溶的垢样进行消解,对消解条件进行了探索试验,确定了比较方便快捷、溶样完全的消解体系。并对垢样消解液中的一些常规元素作了相应的原子吸收光谱测定。     

A boundary element method for the solution of finite mobility ratio immiscible displacement in a Hele‐Shaw cell

In this paper, the interaction between two immiscible fluids with a finite mobility ratio is investigated numerically within a Hele‐Shaw cell. Fingering instabilities initiated at the interface between a low‐viscosity fluid and a high‐viscosity fluid are analysed at varying capillary numbers and mobility ratios using a finite mobility ratio model. The present work is motivated by the possible development of interfacial instabilities that can occur in porous media during the process of CO₂ sequestration but does not pretend to analyse this complex problem. Instead, we present a detailed study of the analogous problem occurring in a Hele‐Shaw cell, giving indications of possible plume patterns that can develop during the CO₂ injection. The numerical scheme utilises a boundary element method in which the normal velocity at the interface of the two fluids is directly computed through the evaluation of a hypersingular integral. The boundary integral equation is solved using a Neumann convergent series with cubic B‐Spline boundary discretisation, exhibiting sixth‐order spatial convergence. The convergent series allows the long‐term nonlinear dynamics of growing viscous fingers to be explored accurately and efficiently. Simulations in low‐mobility ratio regimes reveal large differences in fingering patterns compared with those predicted by previous high‐mobility ratio models. Most significantly, classical finger shielding between competing fingers is inhibited. Secondary fingers can possess significant velocity, allowing greater interaction with primary fingers compared with high‐mobility ratio flows. Eventually, this interaction can lead to base thinning and the breaking of fingers into separate bubbles. Copyright © 2015 John Wiley & Sons, Ltd.     

混合层流场的特性及其大涡结构的研究

对５０年代以来尤其是近１０年来有关混合层的研究成果，特别是有关大涡拟序结构的成果进行了综述，为进一步开展混合层的研究提供参考     

A general circle theorem

Summary A general circle theorem is obtained which not only unifies all existing circle theorems, but allows new ones to be deduced. The results are extended to allow for certain other finite boundaries, thus providing simple solutions for problems involving difficult boundary shapes.     

Structural Characterization of the Solvate Complexes of the Lithium Salts of Diorganophosphides and Phosphinideneborates; A Pathway to Phosphorus-Boron Double Bonds

Abstract

The structures of several solvated lithium diorganophosphides are described. These may take a variety of structures including chain-like polymers with alternating Li⁺ and PR₂ ^? groups, dimeric species with PR₂ ^? groups bridging two Li⁺ ions or mononuclear species having terminal ^?PR₂ groups which have pyramidal geometries at phosphorus. The Li⁺ ions in all structures are solvated by either THF or Et₂O bases. Separation of the Li⁺ can be effected using 12-crown-4 to coordinate Li⁺ as [Li(12-crown-4)₂]⁺ affording free [PR₂]^? counterions. An extension of these techniques has led to the synthesis of the first compounds which have B-P double bonds. These are the compounds [Li(Et₂O)₂PRBMes₂] and [Li(12-crown-4)₂][PRBMes₂](R=Ph, C₆H₁₁,Mes) which have B-P bond lengths of 1.82 – 1.83Å.