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71.
P. Torline G. du Plessis N. Schnautz J. C. Thompson 《Journal of separation science》1979,2(10):613-616
A detailed method for the routine preparation of glass capillary columns is presented. The method consists of coating a glass tube with quartz powder prior to pulling the tube into a capillary. The inner surface of the capillary consists of an even distribution of quartz particles fused to the walls. This surface has been found readily deactivated by standard procedures and ideal for the preparation of thick-film glass capillary columns. The method has been thoroughly tested in two independent laboratories to ensure that the procedures described are reproducible. 相似文献
72.
A High-Order Finite Difference Scheme for 3D Unsteady Convection Diffusion Reaction Equations北大核心CSCD 下载免费PDF全文
针对三维非稳态对流扩散反应方程,构造了一种高精度紧致有限差分格式,对空间的离散采用四阶紧致差分方法,对时间的离散采用Taylor级数展开和余项修正技术,所提格式在时间上的精度为二阶、在空间上的精度为四阶。利用Fourier稳定性分析法证明了该格式是无条件稳定的。最后给出数值算例验证了理论结果。 相似文献
73.
We describe a new branch-and-bound algorithm for the exact solution of the maximum cardinality stable set problem. The bounding phase is based on a variation of the standard greedy algorithm for finding a colouring of a graph. Two different node-fixing heuristics are also described. Computational tests on random and structured graphs and very large graphs corresponding to real-life problems show that the algorithm is competitive with the fastest algorithms known so far.This work has been supported by Agenzia Spaziale Italiana. 相似文献
74.
L. A. Dunyushkina A. V. Kuz’min V. B. Balakireva V. P. Gorelov 《Russian Journal of Electrochemistry》2006,42(4):375-380
Transport numbers for oxygen ions and protons are measured by an emf method in the system CaTi1?x FexO3?δ (x = 0.1–0.5) in the oxidizing and reducing atmospheres in the temperature interval 973–1173 K. It is shown that the compounds under study are mixed ion-electron conductors at small iron concentrations and electron conductors, at large iron contents. The proton conductivity in the compounds is very poor and does not exceed 0.5% in air. On the basis of the temperature dependences of transport numbers for ions and linear expansion, it is established that the CaTi0.9Fe0.1O3?δ system has a phase transition of a second order in a reducing environment at 1020–1050 K. The total and partial electron conductivities of CaTi0.9Fe0.1O3?δ are studied as a function of the partial pressure of oxygen at 1173 K. The nature of electroconduction in CaTi1?x FexO3?δ is discussed. 相似文献
75.
The semiconductive properties of a series of pyrenyl polyenes of the type R-(CH=CH)n-R, are studied as a function of the adsorption of different amount of a vapour. With regard to the compensation temperature
(T
0) the compounds are divided into two groups. For compounds which have odd number of double bonds,T
0 is infinite and in compounds having even number double bonds,T
0 is finite.T
0 for II2 is higher while that of II4 is lower than the experimental temperature. DifferentT
0 for the compounds having odd or even number of double bonds suggests a physical basis for the compensation rule, which we
believe, is related to the molecular and crystalline structure of the compounds 相似文献
76.
Heat conduction, convection and radiolysis of the
The calorimeter allows the water absorbed dose, a measure of radiotherapy, to be measured according to its definition. Different detector types are used in the PTB calorimeter; this paper discusses heat conduction, convection and the radiolysis of the
system for a ‘sealed’ detector. The ‘sealed’ detector allows the calorimeter to be operated at room temperature in the case of 60Co-γ-radiation. 相似文献
Full-size image
77.
A. Krauss 《Thermochimica Acta》2006,445(2):126-132
A transportable water calorimeter for the determination of the quantity of absorbed dose to water in radiotherapy beams has been developed at the PTB and is presented in detail in this investigation. Heat conduction effects occurring in the calorimeter are studied for different lateral sizes of high-energy photon beams, for different depth dose distributions of electron beams and for a scanned-beam irradiation with a heavy ion beam. The corresponding correction factors are calculated and arguments are given under which conditions these can adequately be applied. 相似文献
78.
V. Ya. Kavun N. F. Uvarov A. B. Slobodyuk V. K. Goncharuk A. Yu. Kotenkov I. A. Tkachenko A. V. Gerasimenko V. I. Sergienko 《Russian Journal of Electrochemistry》2005,41(5):501-509
Methods of (19F, 1H) NMR and impedance spectroscopy are used to investigate the internal mobility and ionic conduction in solid solutions arising in the system PbF2-ZrF4 and polycrystals KSnZrF7, Li(Na)(NH4)6Zr4F23, and M2ZrF6 (M = K, NH4). Factors responsible for the form of ionic motions and their energetics at 170–550 K are considered. It is established that the phase transitions in these compounds are connected with the crystal transition to a superionic state and that the high ionic (superionic) conductivity of beta phases is due to the diffusion of fluoride ions, ammonium cations, and possibly alkali metal cations. The obtained data testify to a substantial role of chainlike aggregation of anionic groupings and a variableness of structural mechanisms of formation of such chains in fluorozirconates for the development of translational diffusion in these compounds.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 573–582.Original Russian Text Copyright © 2005 by Kavun, Uvarov, Slobodyuk, Goncharuk, Kotenkov, Tkachenko, Gerasimenko, Sergienko. 相似文献
79.
Herbert Spohn 《Journal of statistical physics》1977,17(6):385-412
A single (nonrelativistic, spinless) electron subject to a constant external electric field interacts with impurities located on an infinitely extended lattice by a potential of random strength. The random strength is given by a field of Gaussian random variables. We show the existence of the averaged dynamics and prove that in the weak coupling limit, 0, 2
t= fixed, one obtains the usual transport equation for the velocity distribution.Work supported by a Max Kade Foundation fellowship.On leave of absence of the Fachbereich Physik der Universität München. 相似文献
80.
Electrophysical properties of single crystals of nonstoichiometric phases R1 − y
M
y
F3 − y
, where R = La-Lu, M = Ca, Sr, or Ba, with the tysonite (LaF3) structure, which are present in a metastable state after being grown and cooled, are measured in the temperature interval
extending from 300 to 1073 K. It is discovered that, during a sufficiently long high-temperature investigation, solid solutions
R1 − y
Ca
y
F3 − y
, where R = Tb, Dy, or Ho, undergo irreversible variations in the phase composition in the temperature region 723 to 823 K.
This level of temperatures, which correspond to partial decomposition of phases R1 − y
Ca
y
F3 − y
with the rare-earth elements of the end of the period, lies above the temperatures to which the fluoride solid electrolytes
are usually heated when used in solid-state electrochemical devices. The temperature and concentration dependences of the
phases’ electroconduction are explained in the framework of the vacancy mechanism of anionic transport.
Original Russian Text ? N.I. Sorokin, B.P. Sobolev, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 4, pp. 420–431.
The paper is dedicated to the memory of Prof. M.W. Breiter, formerly of the Vienna Technical University, Austria. 相似文献