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991.
Carl Droms 《Proceedings of the American Mathematical Society》2003,131(8):2305-2311
We associate to each right-angled Coxeter group a 2-dimensional complex. Using this complex, we show that if the presentation graph of the group is planar, then the group has a subgroup of finite index which is a 3-manifold group (that is, the group is virtually a 3-manifold group). We also give an example of a right-angled Coxeter group which is not virtually a 3-manifold group.
992.
Thomas C. W. Mak Hilbert J. Bruins Slot Paul T. Beurskens 《Journal of inclusion phenomena and macrocyclic chemistry》1986,4(3):295-302
Crystals of (C2H5)4NCl·4H2O are orthorhombic, space groupCcca, witha=19.104(3),b=23.084(4),c=13.330(3) , andZ=16. The structure features an anionic host lattice constructed from the linkage of (H2O)4Cl– tetrahedra by hydrogen bonds between vertices, generating two open linear channel systems which accommodate the ordered cations. FinalR
F
=0.080 for 1516 observed MoK data measured at 22°C.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82035 (12 pages)Dedicated to Professor G. A. Jeffrey 相似文献
993.
Dana Rihova-Skabrahova 《Applications of Mathematics》2001,46(2):103-144
The computation of nonlinear quasistationary two-dimensional magnetic fields leads to a nonlinear second order parabolic-elliptic initial-boundary value problem. Such a problem with a nonhomogeneous Dirichlet boundary condition on a part 1 of the boundary is studied in this paper. The problem is discretized in space by the finite element method with linear functions on triangular elements and in time by the implicit-explicit method (the left-hand side by the implicit Euler method and the right-hand side by the explicit Euler method). The scheme we get is linear. The strong convergence of the method is proved under the assumptions that the boundary is piecewise of class C3 and the initial condition belongs to L2 only. Strong monotonicity and Lipschitz continuity of the form a(v,w) is not an assumption, but a property of this form following from its physical background. 相似文献
994.
995.
The notes here presented are of the modifications introduced in
the application of WKB method. The problems of two- and
three-dimensional harmonic oscillator potential are revisited by WKB and
the new formulation of quantization rule respectively. It is found
that the energy spectrum of the radial harmonic oscillator, which
is reproduced exactly by the standard WKB method with the Langer
modification, is also reproduced exactly without the Langer
modification via the new quantization rule approach. An
alternative way to obtain the non-integral Maslov index for
three-dimensional harmonic oscillator is proposed. 相似文献
996.
Heat transfer correlation for boiling flows in small rectangular horizontal channels with low aspect ratios 总被引:8,自引:0,他引:8
In the present experimental study, a correlation is proposed to represent the heat transfer coefficients of the boiling flows through horizontal rectangular channels with low aspect ratios. The gap between the upper and the lower plates of each channel ranges from 0.4 to 2 mm while the channel width being fixed to 20 mm. Refrigerant 113 was used as the test fluid. The mass flux ranges from 50 to 200 kg/m2 s and the channel walls were uniformly heated up to 15 kW/m2. The quality range covers from 0.15 to 0.75 and the flow pattern appeared to be annular. The modified Lockhart–Martinelli correlation for the frictional pressure drop was confirmed to be within an accuracy of ±20%. The heat transfer coefficients increase with the mass flux and the local quality; however the effect of the heat flux appears to be minor. At the low mass flux condition, which is more likely to be with the smaller gap size, the heat transfer rate is primarily controlled by the liquid film thickness. A modified form of the enhancement factor F for the heat transfer coefficient in the range of ReLF200 well correlates the experimental data within the deviation of ±20%. The Kandlikar's flow boiling correlation covers the higher mass flux range (ReLF>200) with 10.7% mean deviation. 相似文献
997.
二维各向异性弹性力学的Stroh公式及其推广 总被引:1,自引:0,他引:1
Stroh公式是解决各向异性弹性体二维变形的强有力的工具。该公式形式上简洁优美、应用上方便有力。它的推广形式也日益在混合边值问题、压电材料、非对称弯曲板、三维各向异性弹性体、稳态运动、多自由度系统振动等方面得到广泛应用。本文简要介绍Stroh公式及其推广形式的研究状况与进展。 相似文献
998.
滑移流区内微环缝槽道中的层流流动与换热 总被引:7,自引:0,他引:7
本文针对微环缝槽道采用速度滑移和温度跳跃边界条件求解了不可压缩气体的N-S方程和能量方程,理论分析了微环缝槽道在单侧或双侧不同热流密度加热条件下的流动与层流换热特性,讨论了Kn数、内外径比对流动阻力及换热特性的影响。结果表明:滑移流区微环继通道内的流阻和Nusselt数明显低于连续流区;且随着Kn数的增加,流阻和Nusselt数均减小;但其随内外径比r*的变化趋势与连续流区相似。 相似文献
999.
As the SG-DBR laser is among the most attractive sources for WDM and DWDM systems, it is important and necessary to investigate its wavelength switching characteristics. This behaviour will affect wavelength routing and the capability limits for channel re-allocation in future optical networks. This paper presents detailed experimental studies on a high-speed SG-DBR laser by using a Fabry–Perot Interferometer technique adapted for the non-continuous wave case. Measurements of fast intra-modal (i.e. cavity mode) and inter-modal (i.e. super-mode) wavelength switching and insights into the device's dynamic behaviour are obtained. Implications are given for transmitter design in dynamic wavelength routing and channel re-allocation. 相似文献
1000.