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991.
Theoretical and experimental research has been performed on the interaction curves and stress paths of crystallinepolymeric materials PE and POM under tensile-torsional stress with a linearly intensifying model and in terms of the yield points undergoing Von Mises criterion. 相似文献
992.
993.
Xu Jie-Cheng Cheng Ling-Ling Shen Wei-Zhen Wang Shi-Qing Qian Cui-He Huang Jia-Xin 《中国化学》1986,4(2):160-167
DSIP and its fourteen analogs as well as three short peptides were synthesized by solid phase method. The design of the analogs was based on the consideration of the introduction of D-amino acid into the molecules to inhibit the enzymatic hydrolysis and the introduction of amino acids with a hydrophobic side chain. The modification was placed on the position of 1, 3, 4, 5, 8 and 9, e.g. D- Trp1, Tyr1, Tyr1 Phe5, D-Trp1 Phe8, Trp3,4, D-Trp1,3,4 Phe8, D-Trp3,4 Phe8 D-Glu9, D-pF-Phe3,4 Phe8 D-Glu9, Phe5, Glu5 Asp9, Tyr6 Asp9, Asp9 and Ala7-DSIP as well as Trp-Ala-Gly-Gly-Asp, Trp-Ala-Gly-Gly-Glu and Trp-Gly-Glu. DSIP and Phe5-DSIP were also prepared by pentafluorophenyl ester method. The purity of the synthetic peptides was checked by amino acid analysis, elemental analysis, thin layer chromatography and paper electrophoresis. The biological assay showed that the analogs of D-Trp1, Tyr1, Tyr1 Phe5 and Ala7-DSIP as well as three short peptides were inactive whereas Phe5-DSIP showed similar activity as that of synthetic DSIP. 相似文献
994.
Yi‐zhang Chen Zhan‐peng Zhang Jian Yu Zhao‐Xia Guo 《Journal of Polymer Science.Polymer Physics》2009,47(12):1211-1218
Uniform poly(methyl methacrylate) (PMMA)/silica nanocomposite fibers containing up to 20 wt % silica were prepared by electrospinning. The electrospun solutions were prepared by mixing a solution of PMMA in dimethyl formamide (DMF) with colloidal silica in methyl ethyl ketone (MEK). The average fiber diameter decreases from 2.49 μm to 1.69 μm when 20 wt % silica is incorporated as a result of considerably increased solution conductivity, although the solution viscosity increases significantly, which should result in opposite effect. Thinner fibers (down to 350 nm) can be obtained by changing DMF/MEK proportion and by the addition of an ammonium salt. Nano‐sized silica particles (10–40 nm) distributes homogeneously in the fibers, as revealed by transmission electron microscopy. Furthermore, the incorporation of silica nanoparticles can change the thermal properties and surface wettability of the fiber mats. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1211–1218, 2009 相似文献
995.
Qian Wang Dr. Shayu Li Dr. Liming He Dr. Yan Qian Dr. Xiuping Li Dr. Wenhao Sun Dr. Min Liu Dr. Juan Li Dr. Yi Li Prof. Guoqiang Yang Prof. 《Chemphyschem》2008,9(8):1146-1152
A series of dicyanovinyl‐substituted aromatic compounds (Ar‐DCV; Ar=9‐anthracenyl, 1‐naphthyl, 1‐pyrenyl) with dual fluorescence are prepared, and their emission properties—when molecularly dispersed in a polymer medium—are investigated under pressure perturbation. The total emission intensity is enhanced drastically from ambient pressure up to 70 kbar. Emission 30–107 times more intense than that at ambient pressure is observed at higher pressure. In dual emission, the enhancement of the local excited state (LE state) is significantly different from that of the intramolecular charge‐transfer state (ICT state). The intensity of the ICT emission increases faster (30–370 times) than that of the LE emission (less than 20 times). In accordance with spectroscopic data, emission dynamics at different pressures, and computational studies on the molecular conformations of these compounds, a kinetic model is proposed to explain the effect of pressure on the emissive properties of the Ar‐DCV compounds from the point of view of pressure‐dependent populations of the species in the ground state. 相似文献
996.
Monte Carlo simulation of spin-wave excitation for the magnetic films with structure and interaction fluctuations 总被引:1,自引:0,他引:1
Monte Carlo simulation studies are performed to examine influence of structure and interaction fluctuations on magnetic properties of a ferromagnetic system modelled with a Heisenberg Hamiltonian. It is found that the spontaneous magnetization at low temperature for the multilayered films decreases with temperature in a Bloch law of spin-wave excitations. Both Bloch coefficient B and exponent b vary evidently because of a strong surface and size effect in the finite magnetic films with free boundaries. For the disordered bulk FCC magnet with periodic boundary, the Bloch T3/2 law is followed at low temperature and B is greatly influenced by the structure and interaction fluctuations. At the same time, Bloch coefficient B of the amorphous magnet with the coordination and interaction fluctuations has been derived. The simulated results are in good agreement with the theoretical predictions of spin-wave excitation, and explain the experimental facts well. 相似文献
997.
998.
Yi Qian Wang 《数学学报(英文版)》2001,17(2):313-318
In this paper we consider the boundedness of all the solutions for the equation x″ + ax
+−bx
− = f(t) is a smooth 2π-periodic function, a and b are positive constants (a≠b).
Received November 27, 1998, Accepted October 15, 1999 相似文献
999.
1000.
Ming Qian Zhonghua Shen Jian Lu Xiaowu Ni Qiang Li Yimin Xuan 《Optics and Lasers in Engineering》2008,46(6):461-468
Our recent work revealed that speckles can be formed when nanofluids containing a proper volume fraction of nanoparticles are illuminated by a monochromatic laser beam [Qian M, Liu J, Yan M-S, Shen Z-H, Lu J, Ni XW, et al. Investigation on utilizing laser speckle velocimetry to measure the velocities of nanoparticles in nanofluids. Opt Express 2006; 14: 7559–66]. In this paper, two different physical models are established to figure out the speckle-formation mechanism. The photon–nanoparticle-collision model emphasizes the random collisions between photons and nanoparticles, and Monte Carlo method is used to simulate how the incident photons move in the vessel containing nanofluids. However, in the electric-dipole model, each illuminated nanoparticle becomes an electric dipole and sends out scattering lights, and the coherent addition of the scattering lights from nanoparticles is numerically calculated. Finally, from the numerical results, the speckle-formation mechanism is figured out. 相似文献