共查询到20条相似文献,搜索用时 31 毫秒
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A novel approach for calculating the density of surface states in a disordered system is presented. It is shown that the node counting method for calculating the energy spectrum of a system holds for the Bethe lattice. An exact method for calculating the total density of states of a disordered Bethe system terminating on a closed surface, as well as the contribution of the bulk and surface states to it is then developed and applied to the cases of Lorentzian and Gaussian randomness. The results are discussed in connection to relevant material from the literature. 相似文献
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A fundamental assumption embraced in conventional use of the ultrasonic pulse-echo immersion technique to measure attenuation in solid materials is revisited. The cited assumption relies on perfect and immutable adhesion at the water to sample interface, a necessary condition that allows calculating the reflection coefficient at any interface from elastic wave propagation theory. This parameter is then used to correct the measured signal and obtain the real attenuation coefficient of the sample under scrutiny. In this paper, cases in which the perfectly cohesive interfacial condition is not satisfied are presented. It is shown also that in those cases, the repeatability of the conditions at the interface is always uncertain. This implies that the reflection coefficients are unknown, even when density is known. A new method of simultaneously measuring the reflection coefficients for both exposed interfaces that are normal to the transducer, and the attenuation coefficient of the specimen is developed and is presented here. The robustness of the new method is proven, as we demonstrate that the proper value of attenuation is achieved independently of the continuously varying interfacial conditions of these non-ideal cases. 相似文献
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估算供体-受体对荧光共振能量传递效率的研究 总被引:2,自引:2,他引:0
在有机白光LED的研究中,能量传递效率计算方法的研究是一项很有意义的工作。作者在总结前人工作的基础上,提出了一种利用有机分子发射谱和激发谱估算有机分子荧光共振能量传递(FRET)效率相对值的新方法,这种方法的优点是数据处理过程简单,对实验仪器设备要求不高,并且不需要通常计算方法所需的荧光量子产率等参数,缺点是只能计算能量传递的相对值。利用这种方法计算了甲萘酚、溴甲酚紫、萤光素钠盐三种能量受体和能量供体核黄素在不同浓度下能量传递效率的相对值,计算结果与实验结果基本符合,验证了此方法的合理性。 相似文献
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The definition of the time varying force on a tip with internal degrees of freedom in atomistic molecular dynamics (MD) simulations of scanning force microscopy experiments is discussed. We show that the static expression for the tip force is inadequate for calculating force fluctuations within the MD simulations and suggest a different method of calculating the tip force. By studying the size of tip force fluctuations for different tip models and various tip positions with respect to the surface, we demonstrate that the new method works equally well in both static and dynamic cases. 相似文献
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CHEN Xiaoyu 《理论物理通讯》1998,30(2):293-296
The exact solutions of the closed evolution of spin states in rotating magnetic fields are described for the most general cases via eigenstate method. A simple algorithm for calculating the geometric phase is exploited. 相似文献
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A method on how to take into account pump statistics and spontaneous atomic decays when calculating the photon-number distribution of lasers in photon-number representation is presented. The intracavity phonon-number and extracavity photocount distributions with binomial pump and spontaneous atomic decays are calculated. In two limit cases, the results of calculations transit respectively to the photon-number distributions of systems with common Poissonian pump and regular pump, and both with the spontaneous atomic decays being suppressed. 相似文献
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A. M. Fedorovskii V. A. Shcheglov A. A. Stepanov 《Journal of Russian Laser Research》1998,19(2):160-174
A method for calculating the ray paths in optical systems composed of axially symmetric reflecting and refracting surfaces is outlined. It is assumed that there is no common symmetry axis in the system, so that the ray paths are substantially three-dimensional. For the sake of generality, both the simplest cases admitting of an analytic solution and the more intricate cases when iterative procedure has to be used are considered. Particular attention is given to the computation features which make the algorithm both universal and robust. The method proposed allows for the use of a wide range (five types of the surfaces specified) of optical elements. Furthermore, the approach suggested is universal and, as such, makes it possible also to pass on with relative ease to other cases of specifying the surfaces. 相似文献
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A method for calculating the fluctuations and correlations in cascade processes is outlined, on the basis of deriving random cascade curves from their spatial (longitudinal) moment. The method reduces the problem of calculating cascade fluctuations in a homogeneous medium to calculating the covariational matrix of random moments, depending only on the energy variable. The set of elements of this matrix allows the fluctuations and core correlations of any track characteristics of the cascade to be calculated. The method is intended for calculations of high-energy cascades, when the influence of fluctuations of high-order longitudinal moments (n 5) may be neglected.Translated from Izvestiya Vysskikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 17–23, March, 1987. 相似文献
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Kin S. Chiang 《Optical and Quantum Electronics》1990,22(3):239-257
In calculating the modal characteristics of a finitely clad optical waveguide, if the wavelength is much shorter than the core of the waveguide, then the cladding of the waveguide can be assumed to be infinite. On the other hand, if the wavelength is much longer than the core, the core can be ignored. These two approximations, although simple and accurate in the two respective extreme cases, do not provide adequate information in the transition region, where many tapered devices are operated. To overcome this a novel perturbation method is devised, in which these two approximations are combined in such a way that a result that is accurate in all cases can be obtained. Analytical expressions based on this method for describing the dispersion characteristics of finitely clad slab waveguides and circular step-index fibres are derived and compared with other conventional approximations. The combined use of this method and the coupled-mode theory for the analysis of optical couplers is also described. 相似文献
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B.A. Mamedov A.S. Ekeno?lu 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(3):527-530
A new algorithm is presented for calculating the Bernoulli numbers valid for all values of their argument. We introduce a simple, new analytical computer method for calculating the Bernoulli numbers on the basis of their integral expressions. The formula given in this study for the evaluation of Bernoulli numbers shows good rate of convergence and numerical stability with existing formulas. 相似文献
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A. B. Podlaskin 《Technical Physics》1998,43(6):644-647
The method of calculating the nonlinear aerodynamic characteristics of objects from trajectory data, based on the differential
correction principle, is well known [N. P. Mende, FTI Preprint No. 1326, A. F. Ioffe Physicotechnical Institute, Leningrad
(1989); G. T. Chapman and D. B. Kirk, AIAA J. 8, 753 (1970)]. A modification of this method is proposed here, in which the solution is to be obtained in the form of a spline.
This new approach, which has been tested on model problems, can provide a more reliable guarantee of adequacy of the solutions
and an improvement in accuracy in cases where the functional relations sought have a complicated form.
Zh. Tekh. Fiz. 68, 32–36 (June 1998) 相似文献
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在多计算步的非定常输运问题的蒙特卡罗模拟中,为自动调整每一步的样本数以获得较高的计算效率,可以有多种准则.一种可选的方法是在每一步每隔若干样本监测一次系统中未死亡粒子属性分布对应的香农熵的收敛情况以决定何时停止追加样本,此种方法需要在每一步频繁计算香农熵值.由于在MPI消息传递并行编程环境下香农熵的经典计算方法必须广播大量的数据,导致每一步的计算时间随香农熵计算频率的提高而快速增大,这显然是不能满足实际需求的.本文提出了一种适应于消息传递并行编程环境的香农熵计算新方法,该方法计算得到的香农熵值并不等价于经典方法,但二者之间的差别会随着样本数的增加而趋于零.新方法的最大优势是高频计算香农熵值的时间代价大为降低,为最终实现基于香农熵收敛判断的每步样本数的自动调整奠定了必要的基础. 相似文献
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The presence of chaos in the classical dynamics is not necessarily the destructive element it was thought to be for semiclassical approximations in the time domain. The method of calculating the semiclassical propagation of initial states and correlation functions for nonlinear and chaotic dynamics is shown, and the excellent accuracy is noted for rather long times. The breakdown timescale is much longer than the infamous "log time" for the cases investigated here. 相似文献