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41.
B.I. Sturman A.S. Gorkunova K.H. Ringhofer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):291-297
We investigate analytically and numerically the influence of the type of the photorefractive nonlinear response on the periodic
states (attractors) which occur during feedback controlled 2W-coupling and correspond to almost 100% diffraction efficiency
of the dynamic index grating. In addition to the case of the local response typical, for example, for LiNbO3 crystals we consider the cases of nonlocal (diffusive) response (BaTiO3, SBN) and resonant response (DC-biased BSO, BTO, and BGO crystals). It is shown that the conditions for the transition to
the periodic states and their apparent characteristics are strongly different for the two limiting cases above.
Received 16 July 2002 / Received in final form 29 October 2002 Published online 4 March 2003 相似文献
42.
We predict ultraslow collapse of “tubular image states” (TIS) on material surfaces. TIS are bound Rydberg-like electronic states formed at large distances (∼30 nm) from the surfaces of suspended circularly-symmetric nanowires, such as metallic C nanotubes. The states are formed in potential wells, resulting from a combination of the TIS-electron attraction to image charges in the nanotube and its centrifugal repulsion, caused by spinning around the tube. We demonstrate that TIS can collapse on the tube surface by passing their angular momentum l to circularly polarized flexural phonons excited in the tube. Our analysis shows that for highly detached TIS with l ? 6 the relaxation lifetimes are of the order of 10 ns-1 μs, while for l < 6 these lifetimes are reduced by several orders of magnitude. 相似文献
43.
3-Hydroxy-4-hydroxymethyl pyrrolidin-2-ones, easily prepared from the Baylis–Hillman adduct 1-ethyl-4-methyl-2-hydroxy-3-methylenebutanedioate, are useful intermediates in the synthesis of bioactive compounds. In order to understand the mechanism involved in this reaction, vibrational and Montecarlo molecular mechanics conformational analysis on 1-ethyl-4-methyl-2-hydroxy-3-methylenebutanedioate were carried out, confirming the existence of a low energy intramolecular H-bonded five-member ring. 相似文献
44.
用三维TRS(totalrouthiansurface)自洽理论对奇奇核164Lu的位能面进行了计算,计算结果与实验上得到的ε2=0.38基本一致,从而从理论上确认了164Lu是三轴超形变核,并且指出了存在三轴超形变带的两个组态. Total routhian surface in~(164)Lu nuclei is calculated according to the three dimensional Total Routhian Surface (TRS) theory. The result of the calculation is in agreement with the experiment. At the same time, two TSD bands could be assigned to the configuration(π\(1/2), α=1/2)(ν\(5/2), α=1/2), (π\(1/2), α=1/2)(ν\(3/2), α=-1/2). 相似文献
45.
使用Monte Carlo模拟的方法得出了随机粗糙表面,在Kirchhoff近似的基础上,利用数值分析的方法分析了一维随机粗糙表面的散射特征,得出了一维随机粗糙表面散射分布曲线,我们还考虑了遮蔽效应的影响,并且讨论了Kirchhoff近似的有效性。 相似文献
46.
陈海珍 《宁波大学学报(理工版)》2004,17(4):444-448
选用了钛酸丁酯、硬脂酸和乙二醇作为表面活性剂,采用表面化学修饰和表面物理修饰2种方法修饰纳米氧化钛,然后分散在乙二醇溶剂中形成溶胶溶液.并通过红外光谱仪、紫外分光计、原子力显微镜,分析了表面化学修饰后的纳米氧化钛表面化学结构的变化,观测了纳米氧化钛溶胶在乙二醇溶剂中稳定性.试验结果表明表面活性剂与纳米氧化钛的表面的不饱和键之间形成了新的化学结构,粒子表面可能接枝上有机长链,提高了纳米粒子在溶剂中的相容性.表面化学修饰后的纳米氧化钛与乙二醇溶剂形成了较稳定的溶胶体系,而且纳米溶胶粒径较小.表面活性剂添加量与纳米粒子添加量控制在(1~1.2):1时,可以获得纳米溶胶粒径较小,同时溶胶稳定性较好的纳米氧化钛-乙二醇溶胶体系. 相似文献
47.
The Raman shifts of nanocrystalline GaSb excited by an Ar^ ion laser at wavelengths 514.5, 496.5, 488.0, 476.5,and 457.9nm are studied by an SPEX-1403 laser Raman spectrometer respectively, and they are explained by phonon confinement, tensile stress, resonant Raman scattering and quantum size effects. The Stokes and anti-Stokes Raman spectra of GaSb nanocrystals strongly support the Raman feature of GaSb nanocrystals. The calculated optical spectra compare well with experimental data on Raman scattering GaSb nanocrystals. 相似文献
48.
Richard Brown 《Geometriae Dedicata》2003,97(1):129-150
In this note, we show that given a closed, orientable genus-g surface S
g
, any hyperbolic toral automorphism has a positive power which induces a quadratic, orientable pseudo-Anosov homeomorphism on S
g
. To show this, we lift Anosov toral automorphisms through a ramified topological covering and present the lifted homeomorphism via a standard set of Lickorish twists. This construction provides a general method of producing pseudo-Anosov maps of closed surfaces with predetermined orientable foliations and quadratic dilatation. Since these lifted automorphisms have orientable foliations, this construction is a sort of converse to that of Franks and Rykken [Trans. Amer. Math. Soc. 1999], who established that one can associate to a quadratic pseudo-Anosov homeomorphism with oriented unstable foliation a hyperbolic toral automorphism. 相似文献
49.
50.
Ray Leslie Withers Carlos Otero-Diaz Adrian Gómez-Herrero Albert Prodan Lasse Norén 《Journal of solid state chemistry》2005,178(10):3159-3168
Ternary derivatives of 1T-TaS2 have been synthesized and the variation in the highly structured diffuse intensity distributions characteristic of such materials carefully monitored to investigate the effect that such substitution has upon the band structures and Fermi surfaces (FSs) of the materials. Removal of d electrons via the replacement of Ta ions with lower valent transition metal ions leads to a systematic increase in the radii of the characteristic structured diffuse intensity distribution. Extended Hückel tight binding calculations of the FSs of the doped samples are carried out and used to predict possible nesting wave-vectors. The results are in reasonably good agreement with the radii of the experimentally observed diffuse intensity distributions. 相似文献