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301.
FU JingLi CHEN LiQun & CHEN BenYong Institute of Mathematical Physics Zhejiang Sci-Tech University Hangzhou China 《中国科学:物理学 力学 天文学(英文版)》2010,(3)
We investigate Noether symmetries and conservation laws of the discrete nonconserved systems with nonregular lattices. The operators of discrete transformation and discrete differentiation to the right and left are introduced for the systems. Based on the invariance of discrete Hamilton action on nonregular lattices of the systems with the nonconserved forces under the infinitesimal transformations with respect to the time and generalized coordinates, we give the discrete analog of generalized variational f... 相似文献
302.
An analysis of seismic attenuation in random porous media 总被引:1,自引:0,他引:1
LIU Jiong BA Jing MA JianWei & YANG HuiZhu Institute of Seismic Exploration School of Aerospace Tsinghua University Beijing China Research Institute of Petroleum Exploration & Development PetroChina Beijing 《中国科学:物理学 力学 天文学(英文版)》2010,(4)
The attenuation of seismic wave in rocks has been one of the interesting research topics, but till now no poroelasticity models can thoroughly explain the strong attenuation of wave in rocks. In this paper, a random porous medium model is designed to study the law of wave propagation in complex rocks based on the theory of Biot poroelasticity and the general theory of stochastic process. This model sets the density of grain, porosity, permeability and modulus of frame as random parameters in space, and only one fluid infiltrates in rocks for the sake of better simulation effect in line with real rocks in earth strata. Numerical simulations are implemented. Two different inverse quality factors of fast P-wave are obtained by different methods to assess attenuation through records of virtual detectors in wave field (One is amplitude decay method in time domain and the other is spectral ratio method in frequency domain). Comparing the attenuation results of random porous medium with those of homogeneous porous medium, we conclude that the attenuation of seismic wave of homogeneous porous medium is far weaker than that of random porous medium. In random porous media, the higher heterogeneous level is, the stronger the attenuation becomes, and when heterogeneity σ = 0.15 in simulation, the attenuation result is consistent with that by actual observation. Since the central frequency (50 Hz) of source in numerical simulation is in earthquake band, the numerical results prove that heterogeneous porous structure is one of the important factors causing strong attenuation in real stratum at intermediate and low frequency. 相似文献
303.
LI ZhiHong SU Jun GUO Bing LI ZhiChang BAI XiXiang LIU JianCheng LI YunJu YAN ShengQuan WANG BaoXiang WANG YouBao LIAN Gang ZENG Sheng LI ErTao CHEN YongShou SHU NengChuan FAN QiWen & LIU WeiPing China Institute of Atomic Energy Beijing China 《中国科学:物理学 力学 天文学(英文版)》2010,(4)
The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm-1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S (E) factors and reaction rates for the 12C(p,γ)13N direct capture reaction at energies of astrophysical relevance. 相似文献
304.
考虑速度和温度同时在加法白噪声扰动下的随机Boussinesq方程组的解的渐近特征.可以接轨道得到该随机方程组的唯一解,并可以验证该解生成随机动力系统,进而证明了该随机动力系统存在随机吸引子. 相似文献
305.
Analytical self-similar solutions of the Ginzburg-Landau equation with three-order dispersion effect
Based on the technique of the symmetry reduction, we find the asymptotic self-similarity analytical resolutions from the constant coefficient Ginzburg-Landau equation considering both influences of the thirdorder dispersion and gain dispersion on the evolution of pulses. We have obtained the self-similar pulse amplitude function, phase function, strict linear chirp function, and the effective temporal pulse width. Numerical simulations show qualitative agreement with these theoretical results. 相似文献
306.
Numerical simulations of the impact of wavefront phase distortions of pump on the beam quality of OPA 总被引:1,自引:0,他引:1
<正>A numerical model of optical parametric amplification(OPA) is introduced to investigate the impact of wavefront phase distortion of pump on the beam quality of signal.Numerical results show that the unidentical walk-off directions of the pump and the idler waves are the main factors leading to the transfer of wavefront phase distortions of the pump to the signal,and by reducing the angle between the two directions,the beam quality factor(M~2) can be greatly decreased and hence the good beam quality of the signal can be maintained. 相似文献
307.
范胜君 《数学年刊A辑(中文版)》2006,(5)
在文[8]的基础上和彭实戈提出的关于g-期望的最基本的条件下,证明了g-期望关于凸(凹)函数的Jensen不等式在一般意义下成立当且仅当g是关于(y,z)的超齐次(次齐次)生成元且不依赖于y. 相似文献
308.
309.
We study transmission properties in configurations composed of two single metal gratings with different thicknesses. Choosing the perfect electric conductor excludes the influence of intrinsic material dispersion on transmission behaviors; and as such, we aim to reveal the contribution of geometric dispersion to electromagnetic transmission. Transmission suppression line, instead of a transmission suppression point, is discovered, denoting the curve of the wavelength versus the interval or the lateral displacement between the two single gratings when the transmission suppression appears. A simplified model is proposed to comprehend the underlying physics of this special phenomenon. 相似文献
310.
Streak camera has high temporal resolution and high sensitivity, and is a powerful tool in biomedical study to measure fluorescence lifetime and perform fluorescence lifetime imaging. However, nonuniformity of the gain in the streak tube and nonlinearity of the sweeping speed limit the precision of fluorescence lifetime measurement, particularly when fluorescence lifetimes are short. We have constructed a two-photon excitation fluorescence lifetime measurement system that is based on a synchroscan streak camera and have developed accordingly a method to correct the effect of gain nonuniformity and nonlinearity of sweeping speed on the measurement precision. A continuous-wave laser of high stability is used to calibrate the gain of the streak camera, and a Fabry-Perot etalon is used to calibrate the nonlinearity of the sweeping speed. Fitting algorithms are used to correct the gain of the streak camera and nonlinearity of the sweeping speed respectively, which significantly improves the measurement precision of the system, as characterized through the fluorescence lifetime of the short-lived fluorescence dye, Rose Bengal. Experimental results show that the measurement fluctuation of the lifetime has been improved from more than 10% to 2% after correcting the effects of gain nonuniformity and sweeping speed nonlinearity. 相似文献