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排序方式: 共有9959条查询结果,搜索用时 625 毫秒
991.
In this paper we prove the existence of global weak solutions of the p-harmonic flow with potential between Riemannian manifolds M and N for arbitrary initial data having finite p-energy in the case when the target N is a homogeneous space with a left invariant metric.
Received March 17, 1999, Revised September 22, 1999, Accepted October 15, 1999 相似文献
992.
This paper is concerned with producing highly accurate solution and bifurcation structure using the pseudo‐spectral method for the two‐dimensional pressure‐driven flow through a horizontal duct of a square cross‐section that is heated by a uniform flux in the axial direction with a uniform temperature on the periphery. Two approaches are presented. In one approach, the streamwise vorticity, streamwise momentum and energy equations are solved for the stream function, axial velocity, and temperature. In the second approach, the streamwise vorticity and a combination of the energy and momentum equations are solved for stream function and temperature only. While the second approach solves less number of equations than the first approach, a grid sensitivity analysis has shown no distinct advantage of one method over the other. The overall solution structure composed of two symmetric and four asymmetric branches in the range of Grashof number (Gr) of 0–2 × 106 for a Prandtl number (Pr) of 0.73 has been computed using the first approach. The computed structure is comparable to that found by Nandakumar and Weinitschke (1991) using a finite difference scheme for Grashof numbers in the range of 0–1×106. The stability properties of some solution branches; however, are different. In particular, the two‐cell structure of the isolated symmetric branch that has been found to be unstable by the study of Nandakumar and Weinitschke is found to be stable by the current study. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
993.
P. Tuĝcu 《Rheologica Acta》1995,34(3):288-297
Finite element analyses of the process of polymer drawing for elastic-thermoviscoplastic material behaviour are performed. The deformation-induced heat generation and its softening effect are accounted for. Non-adiabatic thermal effects are examined from the beginning of the loading process, to the attainment of the nearly steady-state neck propagation stages. Solutions for both polymeric films as well as fibres are presented. 相似文献
994.
The effect of the parameters of heat treatment on the experimental 18% maraging steels was studied using hardness tester,
optical, scanning electron and transmission electron microscopy and X-ray metallography techniques. The specimens were solution
treated at 815, 900, 1000, 1060°C for periods between 1 and 4 h. After air-cooling to room temperature, a bcc martensitic
structure was obtained. The higher temperature (1060°C) and longer time (4 h) of the solution treatment caused essentially
homogeneous, massive martensitic structure. The aging of the steels was studied between 240 and 480°C from 1 to 41 h. As indicated
by the results, the hardness vs. aging time curves show a rapid rate of hardening at 480°C while the response at 240 to 320°C
is slower. The time required to reach peak hardness increases with decreasing temperature. The increase in hardness during
aging can be explained by the precipitation of hardening phases. So, it is necessary to use a high temperature solution treatment
to obtain a better alloy distribution and a tough martensitic structure, and an aging treatment at 480 °C between 4 and 10
h to achieve the desired properties.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
A. Cruz Orea I. Delgadillo H. Vargas J.L. Pichardo J.J. Alvarado-Gil L.C.M. Miranda 《Solid State Communications》1996,100(12):855-859
The photoacoustic technique is used in semiconductor two-layer systems for the determination of thermal properties and thermal expansion coefficient. The two-layer systems studied were amorphous silicon-glass and Al0.2Ga0.8As---GaAs. Our results show that the proposed method is a reliable technique for the characterization of other semiconductor two-layers systems. 相似文献
996.
T. S. Petkevich Yu. G. Egiazarov N. A. Kovalenko T. L. Sen’ko 《Journal of Applied Spectroscopy》1998,65(1):117-123
Activity of alumocopper-palladium catalysts (0.5 at.% Pd, 0.1–3.0 at.% Cu) which differ in preparation method in CO, C2H4 and CH4 oxidation is studied. It is shown that preliminary modification of a carrier by copper leads to an enhancement of catalyst
activity as compared with an alumopalladium one. With the methods of EDRS, TPR-TRS, and TPR of adsorbed CO and O2, the Pd/Cu/Al2O3, Cu/Pd/Al2O3 and (Pd−Cu)/Al2O3, systems are studied. It is established that premodification of the carrier leads to a weakening of its interaction with
the second metal while the combined deposition from one impregnating solution in subsequent thermal treatment is accompanied
by a strong metal aggregation.
Institute of Physicoorganic Chemistry, National Academy of Sciences of Belarus, 13, Surganov St., Minsk, 220072. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 114–120, January–February, 1998. 相似文献
997.
We consider the short-time heat content asymptotics for oblique boundary conditions. The first few coefficients in the asymptotic expansion are calculated. 相似文献
998.
999.
B. Canals D.A. Garanin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):439-447
Thermodynamic quantities and correlation functions (CFs) of the classical antiferromagnet on the checkerboard lattice are
studied for the exactly solvable infinite-component spin-vector model, D↦∞. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances
smaller than the correlation length, r
ξ
c∝ exp(T
*/T), correlations in the checkerboard-lattice model decay already at the scale of the lattice spacing due to the strong degeneracy
of the ground state characterized by a macroscopic number of strongly fluctuating local degrees of freedom. At low temperatures,
spin CFs decay as <
>∝ 1/r
2 in the range a
0≪r≪ξ
c∝T
-1/2, where a0 is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are very similar with
MC simulations, exact and analytical results for the classical Heisenberg model (D = 3) on the pyrochlore lattice. This shows that the ground state of the infinite-component spin vector model on the checkerboard
lattice is a classical spin liquid.
Received 16 November 2001 and Received in final form 12 February 2002 相似文献
1000.
Noël Lohoue 《Annals of Global Analysis and Geometry》1998,16(6):543-571
We give a sufficient condition for stability around 2 of Lp cohomology of a system over locally symmetric space. 相似文献