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991.
V. I. Sardyko 《Journal of Applied Spectroscopy》2001,68(1):73-82
An exact solution to the equations that describe the operation of a ring laser having nonstationary parameters is obtained. An iterative formula is derived and the conditions under which a quasi–stationary solution can be used are determined. Lasers with vibrating and reversing differences of the frequencies of opposite waves are considered. In the case of a reversing shift, it is always possible to isolate a quasi–stationary regime when transient processes are completed. 相似文献
992.
We analytically study the nonlinear localized gap modes in a
one-dimensional atomic chain with uniform atomic mass but two periodically
alternating force constants between the nearest neighbors by means of
a quasi-continuum approximation. This model simulates a row of atoms
in the <111> direction of a diamond-structure type of crystals or
molecular crystals with alternating double and single bonds. For this
lattice system, we find that the harmonic plus quartic anharmonic terms
of inter-site potential produce a new type of nonlinear localized gap modes
with a slightly asymmetry distribution of atomic displacements. These localized
gap modes are somewhat different from widely studied localized gap
modes with a symmetry atomic displacement distribution in diatomic ion lattices. 相似文献
993.
毛永华 《北京师范大学学报(自然科学版)》2000,36(2):152-155
通过构造业列双线性算子得到可逆Markov过程的生成的多个特征值估计的一种递推公式,在某些情况下这些估计是精确的。 相似文献
994.
995.
996.
M. P. Sampedro M. A. Cerezo Jcome D. Ramírez Martínez M. Mndez Otero M. Palomino Ovando 《Crystal Research and Technology》2006,41(7):683-688
It is, well know that some, optical materials to change his refractive index when these exposed to light, depending on particular conditions, they can generate several distributions of refractive index. In this work, an experimental periodic arrangement of refractive index generated on the Bi12TiO20 photorrefractive crystal is presented, the initial condition used was generated by superposing two He‐Ne laser linearly polarized beams in a perpendicular direction to the external field applied to the crystal at 632.8 nm. The diagrams of bands generated with this arrangement is studied, based on the similarities presented by the periodic refractive index with the photonic bandgap (PBG) diagrams one‐dimensional superlattices composed of alternating layers of two distinct materials. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
997.
冷轧机辊缝预设定计算机操作指导控制系统 总被引:1,自引:0,他引:1
采用冷轧机辊缝预定操作指导控制系统,在CRT上显示出轧机调整参数,指导轧制操作者调整辊缝,并且在一幅画上显示出轧制过程全部参数,为用户控制和分析轧制过程提供支持。 相似文献
998.
Min Fu Ze-shan Hu Min Tang Xiao-ping Wei Min-hao Shao Lan-hua Li Yu-lin Deng 《化学物理学报(中文版)》2007,20(6):811-815
"Nanoparticle ZnO was synthesized in non-aqueous medium. UV adsorption spectra were measured and effective mass model was used to calculate particle size in situ. A technique method named as supersaturation control growth was developed, which dealt with addition of nanoparticle suspension with small size to another suspension with big size. As a result, those small particles completely dissolved and those big ones totally grew because of dissolution degree difference between small particles and the big ones. The particle number of big particle suspension kept being a constant and the growth rate was much higher than Ostwald ripening. Main characteristic of this technique is that size distribution of nanoparticles can be narrowed provided original size difference of two suspension is big enough and original size distribution is not too broad." 相似文献
999.
Existing conditions of full bandgaps and absolute negative refraction in metallic-dielectric photonic crystal 总被引:1,自引:0,他引:1
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This paper has theoretically studied the characteristic frequencies
of band structures in two-dimensional metallic-dielectric photonic
crystals. It is demonstrated that a large filling fraction benefits
the existence of absolute photonic band gap, while a smaller filling
fraction benefits an absolute negative refraction band. In addition,
it also finds that the relation between the cut-off frequency of
E-polarized wave and the filling fraction exceeding 10{\%} is content
with a linear increasing function, whose coefficients are exponential
to the normalized lattice constant. These investigations have
significant implications for tuning the operational frequencies to
desired applications and manufacturing photonic crystals. 相似文献
1000.
ZHOUBang-Rong 《理论物理通讯》2003,40(6):669-674
High density phase transitions in a 4-dimensional Nambu-dona-Lasinio model containing a single symmetry breaking order parameter coming from the fermion-antifermion condensates are researched and expounded by means of both the gap equation and the effective potential approach. The phase transitions are proven to be second-order at a high temperature T; however at T = 0 they are first- or second-order, depending on whether A/m(0), the ratio of the momentum cutoff A in the fermion-loop integrals to the dynamical fermion mass m(0) at zero temperature, is lessthan 3.387 or not. The former condition cannot be satisfied in some models. The discussions further show complete effectiveness of the critical analysis based on the gap equation for second order phase transitions including determination of the condition of their occurrence. 相似文献