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151.
本文刻划了一类幂零根基为二步幂零李代数的新的非可解对称自对偶李代数.当其Levi因子同构于sl(2,C)时,用半单李代数的表示理论具体构造了它们.最后,给出了■2中对称自对偶李代数是CS李代数的一个判别准则。 相似文献
152.
Zhao Zifeng Bian Mengying Lin Chenjian Fu Xuzheng Yu Gang Wei Huibo Liu Zhiwei Bian Zuqiang Huang Chunhui 《中国科学:化学(英文版)》2021,64(9):1504-1509
Science China Chemistry - Electroluminescence of f-f transition lanthanide complex is a traditional topic for display over decades. Here we report highly efficient organic light-emitting diodes... 相似文献
153.
In this paper, we investigate a stochastic non‐autonomous SIRS (susceptible‐infected‐recovered‐susceptible) model. The extinction and the prevalence of the disease are discussed, and so, the threshold is given. Especially, we show there is a positive nontrivial periodic solution. At last, some examples and simulations are provided to illustrate our results. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
154.
Grady B. Wright Robert D. Guy Jian Du Aaron L. Fogelson 《ournal of non Newtonian Fluid Mechanics》2011,166(19-20):1137-1157
An important class of gels are those composed of a polymer network and fluid solvent. The mechanical and rheological properties of these two-fluid gels can change dramatically in response to temperature, stress, and chemical stimulus. Because of their adaptivity, these gels are important in many biological systems, e.g. gels make up the cytoplasm of cells and the mucus in the respiratory and digestive systems, and they are involved in the formation of blood clots. In this study we consider a mathematical model for gels that treats the network phase as a viscoelastic fluid with spatially and temporally varying material parameters and treats the solvent phase as a viscous Newtonian fluid. The dynamics are governed by a coupled system of time-dependent partial differential equations which consist of transport equations for the two phases, constitutive equations for the viscoelastic stresses, two coupled momentum equations for the velocity fields of the two fluids, and a volume-averaged incompressibility constraint. We present a numerical method based on a staggered grid, second order finite-difference discretization of the momentum equations and a high-resolution unsplit Godunov method for the transport equations. The momentum and incompressibility equations are solved in a coupled manner with the Generalized Minimum Residual (GMRES) method using a multigrid preconditioner based on box-relaxation. We present results on the accuracy and robustness of the method together with an illustration of the interesting behavior of this gel model for the four-roll mill problem. 相似文献
155.
An improved transverse Ising model is proposed by taking the
depolarization field effect into account. Within the framework of
mean-field theory we investigate the behavior of the ferroelectric thin
film. Our results show that the influence of the depolarization field
is to flatten the spontaneous polarization profile and make the films
more homogeneous, which is consistent with Ginzburg-Landau theory.
This fact shows that this model can be taken as an effective model to
deal with the ferroelectric film and can be further extended to refer
to quantum effect. The competition between quantum effect and
depolarization field induces some interesting phenomena on ferroelectric thin films. 相似文献
156.
《Solid State Communications》1987,64(4):543-547
We have investigated the effect of a uniaxial stress on the transverse optical and longitudinal optical phonon frequencies of In-hardened GaAs using a cw Nd:YAG laser. We find that for a stress along [1 1 1] the single-doublet phonon frequency splittings are smaller in comparison with those in pure GaAs. A possible explanation of this effect may lie in a hardening of the internal stress parameter ζ due, at least in part, to the increase in lattice constant. Plastic deformation and fracture at the highest stresses reached is also discussed and compared with observations for pure GaAs. 相似文献
157.
《Journal of Physics and Chemistry of Solids》1987,48(7):683-685
Following the perturbation theory of Bajaj et al. the ground state energy of a bound piezopolaron is computed for ZnS, ZnSe, ZnTe and CdTe. Extending this theory to the excited states, the L.A. phonon contributions to the Lamb-shifts in these piezoelectric semiconductors are obtained. It is found that these contributions are smaller by seven to eight orders when compared to the L.O. phonon contributions. 相似文献
158.
159.
《Comptes Rendus de l''Academie des Sciences Series IV Physics》2001,2(10):1389-1406
Sub-10-fs pulse generation has reached a maturity and robustness that gave rise to a rapid increase of new ultrafast applications. Some of these novel applications rely on the octave-spanning spectral width, the coherence properties, or the extremely high peak intensity of femtosecond lasers, which sets them apart from the traditional use of femtosecond lasers in ultrafast spectroscopy. In this review, we concentrate on the sub-10-fs regime and first discuss the state of the art in ultrashort pulse generation. We then report on ultrabroadband wavelength conversion schemes and dispersion control by chirped mirrors. We also review advances in pulse characterization methods, with which we can measure pulse properties with much higher accuracy than simple autocorrelation methods and which support even a bandwidth in the single-cycle regime. With the recent demonstrations of pulses with a duration of merely two optical cycles, a regime is entered where the relative phase between the carrier and the envelope of the pulse starts to play a role. We discuss methods to measure and control the carrier–envelope phase and point out applications in frequency metrology. A wealth of further novel directions and developments in femtosecond research is reviewed in this article. 相似文献
160.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1991,47(3-4):509-512
We report the first near IR FT-Raman spectroscopy of normal diseased human artery. In normal human aorta, two bands at 1669 cm−1 and 1452 cm−1 dominate the spectrum and can be assigned to protein amide I and C-H in-plane bending vibrations, respectively. Weaker bands are also observed between 1250 and 1350 cm−1. Non-calcified atherosclerotic lesions with a large amount of necrotic debris below the tissue surface show a relative increase in the intensity of the 1452 cm−1 band. In atherosclerotic aortas which contain calcified deposits several hundred microns below the tissue surface, a strong 961 cm−1 band is observed due to the symmetric stretch of phosphate groups in the calcified salts. The results show that this method provides the capability to probe biological substituents several hundred microns below the tissue surface. 相似文献