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781.
We have studied conversion and interaction of a Bessel laser beam of zero order in photorefractive crystals. We have established
that in a cubic gyrotropic crystal, two Bessel light beams propagate with different wave vectors and cone angles, but with
identical conicity parameters. As the power in the Bessel light beam increases, we have experimentally observed a new optical
effect: self-action of a Bessel light beam. We have studied the effect of external influences and the parameters of the beam
itself on the process of self-refraction in photorefractive crystals.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 488–493, July–August, 2006. 相似文献
782.
Jean Paul Morniroli 《Interface Science》1997,4(3-4):273-283
A new method using Large Angle Convergent Beam Electron Diffraction (LACBED) patterns is proposed to measure accurately the grain boundary misorientation. The LACBED patterns which are obtained with a defocused convergent electron beam having a convergence semi-angle in the range 1 to 5o contain very sharp deficiency lines. Due to the good quality of the LACBED patterns, these sharp deficiency lines can be used to measure with great accuracy the grain boundary misorientation. In addition, since the LACBED method is a defocus mode method, the patterns contain at the same time information on the reciprocal space (the deficiency lines typical of the crystal orientation of the two grains on each side of the grain boundary) and on the real space (the image of the grain boundary). We describe a method which allows the identification of the misorientation from these LACBED patterns. The main point to consider is the accuracy which is about 0.05o. It is much better than the one obtained from other conventional methods used to measure this misorientation. 相似文献
783.
784.
本文对扫描棱镜在转动过程中各个位置的尺寸的计算公式作了详细的推导,首次实现了对扫描棱镜尺寸的计算机处理,为扫描棱镜及其相关附件的最佳优化设计提供了可靠的理论依据 相似文献
785.
The MIDI! basis set is extended to three new atoms: silicon, bromine, and iodine. The basis functions for these heteroatoms
are developed from the standard 3-21G basis set by adding one Gaussian-type d subshell to each Si, Br, or I atom. The exponents of the d functions are optimized to minimize errors in the geometries and charge distributions that these basis functions yield when
they are used in Hartree-Fock calculations with all atoms represented by the MIDI! basis. The MIDI! basis is defined to use
five spherical d functions in a d subshell. We present a detailed comparison of such calculations to calculations employing six Cartesian d functions in each d subshell; these studies show that 5D and 6D options give very similar results for molecular geometries and dipole moments,
not only for compounds containing Si, Br, and I but also for compounds containing N, O, F, P, S, and Cl. The MIDI! basis set
is also tested successfully for hypervalent Si compounds.
Received: 7 January 1998 / Accepted: 7 January 1998 相似文献
786.
Alan S. Carroll 《Pramana》2003,61(5):847-858
In this contribution we summarize the results of two experiments to measure the transparency of nuclei in the (p,2p) quasi-elastic scattering process near 90‡ in thepp center-of-mass. The incident momenta went from 6 to 14.4 GeV/c, corresponding to 4.8 <Q
2
< 127 (GeV/c)2. First, we describe the measurements with the newer experiment, E850, which has more complete kinematic definition of quasi-elastic
events. E850 covers a larger range of incident momenta, and thus provides more information regarding the nature of the unexpected
fall in the transparency above 9 GeV/c. Second, we review the techniques used in an earlier experiment, E834, and show that
the two experiments are consistent for the carbon data. We use the transparencies measured in the five nuclei from Li to Pb
to set limits on the rate of expansion for protons involved in quasi-elastic scattering at large momentum transfer. 相似文献
787.
分析了色散棱镜的特性及其顶角设计问题。讨论了色散棱镜和扩束棱镜在布鲁斯特角入射状态下,可组合使用的形式及单程角色散。提出将色散棱镜与扩束棱镜组合使用,可减少色散棱镜个数而获得更大角色散的方法。并据此设计了两个色散棱镜组,在Ti∶S激光器中得到实际使用。 相似文献
788.
Characteristic features of low frequency transverse wave propagating in a magnetised dusty plasma have been analysed considering
the effect of dust-charge fluctuation. The distinctive behaviours of both the left circularly polarised and right circularly
polarised waves have been exhibited through the analysis of linear and non-linear dispersion relations. The phase velocity,
group velocity, and group travel time for the waves have been obtained and their propagation characteristics have been shown
graphically with the variations of wave frequency, dust density and amplitude of the wave. The change in non-linear wave number
shift and Faraday rotation angle have also been exhibited with respect to the plasma parameters. It is observed that the effects
of dust particles are significant only when the higher order contributions are considered. This may be referred to as the
‘dust regime’ in plasma. 相似文献
789.
高维单形Bartos体积公式的推广 总被引:2,自引:0,他引:2
本文给出单形K维顶点角的概念,建立单形新的一类体积公式,导出单形K维顶点角的正弦定理,并获得关于单形K维顶点角的一个几何不等式. 相似文献
790.
An MR imaging technique has been developed producing head and body images of diagnostic quality in only a few seconds acquisition time. The Fourier type imaging technique uses excitation with relatively small excitation angels, echoes produced by gradient inversion, and extremely fast profile repetition. A typical result at 0.5 T is an artifact-free head image of 128 x 128 resolution, 10 mm slice thickness in an acquisition time of 2 seconds. 相似文献