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M. J. Dias Carneiro Cesar S. Eschenazi Regina Radicchi 《Bulletin of the Brazilian Mathematical Society》2010,41(1):139-160
In this paper we study the topological properties of integral curves of a system of implicit differential equations associated
to rarefaction curves of a system of three conservation laws. This system of equations becomes singular at the points of eigenvalue
of multiplicity greater or equal to two. We focus our attention to the generic case of multiplicity two and three. We give
local weak topological models for these equations. 相似文献
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Cesar S. Eschenazi Carlos Frederico B. Palmeira 《Bulletin of the Brazilian Mathematical Society》2013,44(2):255-272
Local 1-shock curve arcs and local reverse 2-shock curve arcs were constructed, in the geometric context of the wave manifold, in a previous paper. In that geometric context, sonic and sonic’ surfaces are the boundaries of admissible shock curve arcs; in order to introduce the concept of non-local 1-shock curve arcs and non-local reverse 2-shock curve arcs it is necessary to understand how a hugoniot curve intersects the sonic and sonic’ surfaces; intersections of such curves with sonic’ surface are well known. In this paper we present a complete study on how Hugoniot curves intersect the sonic surface for a quadratic system of two conservation laws. 相似文献
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Subham Majumdar EV Sampathkumaran St Berger M Della Mea H Michor E Bauer M Brando J Hemberger A Loidl 《Pramana》2002,58(5-6):777-782
Recently, the solid solution Ce2Au1−
x
Co
xSi3 has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo
effect. Here we report high pressure electrical resistivity of Ce2AuSi3, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these
alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which
are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions
before attaining non-magnetism for the Co end member. 相似文献
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We have grown single crystals of the psuedo-one-dimensional compound Sr3CuIrO6, a K4CdCl6-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior
of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence
for at least two magnetic transitions, at 5 K (T
1) and 19 K (T
2), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of
both the forms is found to be widely different, exhibiting unexpected time dependence. 相似文献
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We report the separate and combined effects of humic acid and Ca2+ ions on the transport of colloidal particles through a sand-packed column. Polystyrene latex particles with a sulfate functional
group were used as model colloids. The concentrations of both the inlet solution and the effluent solutions were measured
during each experimental run. Breakthrough curves were obtained by taking the ratios of each effluent sample concentration
to the inlet solution concentration. In the absence of humic acid, the results indicate that increasing the concentration
of Ca2+ increases particle attachment to the sand, thus causing decreased transport rates of latex particles through the porous bed
matrix. Once 4 mg/l humic acid was added to the system, changes were observed in the effect that Ca2+ has on latex particle breakthrough. In a system containing calcium, increasing the humic acid concentration was shown to reduce
particle attachment and increase transport rates. In the absence of calcium, the ratios for the outlet-to-inlet concentrations
were similar for each concentration of humic acid. The electrophoretic mobility was also measured in order to determine the
role of electrostatic repulsion in the latex particle transport. The electrophoretic mobility of the latex particles was found
to be dependent on humic acid concentration in the absence of Ca2+ but not in its presence.
Received: 2 February 2001 Accepted: 6 2001 相似文献
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Jianzhong Fu Elia V Eschenazi Kyriakos D Papadopoulos 《Microscopy and microanalysis》2007,13(5):358-364
In using microscopic imaging techniques, unbiased selection of sampling areas is often critical when judgment has to be used to find regions of interest. A conditional random sampling was designed to survey hematite particles on a mica surface using tapping-mode atomic force microscopy, based on three adapted-systematic-sampling methods designed to exclude subjective bias by limiting the freedom of arbitrarily selecting sampling areas. The results of these surveying methods were compared with the average particle surface density modeled by Poisson distribution. It was found that the conditional random sampling could survey particles effectively and improve the data reliability significantly. Ten population-known images from the same mica sheet were used to evaluate these methods, and an average relative error of 12% (maximum 21%) was obtained using the conditional random method with six sampling areas. It was used to investigate the effects of common organic pollutants, benzene, toluene, ethylbenzene, and xylenes on the transport of soil colloids. 相似文献
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