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991.
Photon statistics of the micromaser with a Kerr medium   总被引:2,自引:0,他引:2       下载免费PDF全文
吴曙东  詹志明  金丽霞 《中国物理》2002,11(12):1272-1275
We have established the master equation for the micromaser with a Kerr medium,we have studied the photon statics of the micromaser with a Kerr medium field and analysed the influence of the Kerr effect on the photon statistics,The influence of the Kerr effect on the photon statistics is different in two regimes,In the thermal-atom regime,the Kerr effect produces quantum noise,and decreases the mean photon number.In the ultracold-atom regime,with the increase of the nonlinear parameter of the Kerr medium,the stability of the mean photon number and the normalized variance enhances the mean photon number,and the normalized variance exhibits collapse-revival phenomena periodically,their resonance peaks become lower,and the photon statistics of more and more regions are sub-Poissonian.  相似文献   
992.
以粗粒化的多肽链模型进行了SARS病毒包膜中E蛋白的计算机模拟,描述了该蛋白质空间构象的概貌.首先扩展了多肽链的HP模型,使之能够用于研究在水或脂环境下蛋白质折叠的行为,并且考虑了全部氨基酸残基疏水相互作用能的差异.相关格子链的MonteCarlo模拟显示了很高的计算效率.模拟再现了蛋白质的coil-globule转变,验证了蛋白质序列分布的重要性.结果表明,在水环境中,E蛋白质空间结构由紧致的疏水内核和部分向外延伸的亲水片段组成;在脂环境中,中部疏水片段会成为向外延伸的环,而当两侧紧致的亲水片段分开时,则形成桥.  相似文献   
993.
程南璞  郑仁蓉  朱顺泉 《物理学报》2001,50(6):1035-1039
用粒子转子理论模型计算奇奇核84Y的能谱,通过分析能谱的最近邻能级间距分布函数和能谱刚性度的变化特点,研究了准粒子特征对奇奇核84Y能谱统计特点的影响,发现奇奇核84Y的能谱总体上接近混沌;在采用的理论模型中,准粒子特征通过反冲项和科氏力作用项影响能谱,同时能谱具有随着费米能和能隙参量的减小从接近混沌逐渐转变到接近规则的特点 关键词: 奇奇核 粒子转子模型 准粒子特征 能谱统计 NNS分布函数 能谱刚性度  相似文献   
994.
基于区间分析的结构非概率可靠性模型   总被引:106,自引:9,他引:97  
本文用非概率的凸集模型模拟结构的不确定性,将结构的不确定参数描述为区间变量,基于区间分析,提出了一种新的非概率可靠性度量体系分析方法,从物理、几何意义等方面解释了文中理论的合理性,其计算方法简便,衫,给出了算例分析。  相似文献   
995.
This note studies A , a condition number used in the linear programming algorithm of Vavasis and Ye [14] whose running time depends only on the constraint matrix A∈ℝ m×n , and (A), a variant of another condition number due to Ye [17] that also arises in complexity analyses of linear programming problems. We provide a new characterization of A and relate A and (A). Furthermore, we show that if A is a standard Gaussian matrix, then E(ln A )=O(min{mlnn,n}). Thus, the expected running time of the Vavasis-Ye algorithm for linear programming problems is bounded by a polynomial in m and n for any right-hand side and objective coefficient vectors when A is randomly generated in this way. As a corollary of the close relation between A and (A), we show that the same bound holds for E(ln(A)). Received: September 1998 / Accepted: September 2000?Published online January 17, 2001  相似文献   
996.
An analytical one-dimensional model of the microphase separation in symmetric diblock copolymers is developed. Three stages of the process of the microphase segregation of a quenched diblock copolymer system into a lamella structure are predicted. The first stage involves a fast increase of the amplitude of the quasi-periodical lamella structure (with the average wave vector q0) up to a nearly equilibrium value; the second stage is a slow phase diffusion process which is characterized by increasing coherency of the lamella structure; the third stage is the slow process of the lamella swelling, which is driven by the thermally activated process of the spontaneous deletion of excessive lamellas, the lamella size increasing from the initial value 2π/q 0 to the equilibrium 2π/q eq > 2π/q 0 during the process. The last two stages are described with the specially introduced coarse-grained “amplitude-phase” approximation. It is shown that the relaxation of the gradient of the phase of the lamellar structure is the slowest relaxation process and, thus, can be used as an effective order parameter of the lamellar structure at the later stages of the microphase segregation. Received 10 March 2000 and Received in final form 5 June 2000  相似文献   
997.
We present Monte Carlo simulations of the ripening of 2D islands in the case when the formation of the monomer-monomer bonds is kinetically limited. The results obtained indicate that such limitations may modify the early stage of the kinetics. Asymptotically, the ripening is described by the Lifshitz-Slyozov law. Received 29 August 2000  相似文献   
998.
Scaling properties of the Gibbs distribution of a finite-size one-dimensional Ising model are investigated as the thermodynamic limit is approached. It is shown that, for each nonzero temperature, coarse-grained probabilities of the appearance of particular energy levels display multiscaling with the scaling length ℓ = 1/M n, where n denotes the number of spins and Mn is the total number of energy levels. Using the multifractal formalism, the probabilities are argued to reveal also multifractal properties. Received 10 July 2000 and Received in final form 6 November 2000  相似文献   
999.
We study by theoretical analysis and by direct numerical simulation the dynamics of a wide class of asynchronous stochastic systems composed of many autocatalytic degrees of freedom. We describe the generic emergence of truncated power laws in the size distribution of their individual elements. The exponents α of these power laws are time independent and depend only on the way the elements with very small values are treated. These truncated power laws determine the collective time evolution of the system. In particular the global stochastic fluctuations of the system differ from the normal Gaussian noise according to the time and size scales at which these fluctuations are considered. We describe the ranges in which these fluctuations are parameterized respectively by: the Lévy regime α < 2, the power law decay with large exponent ( α > 2), and the exponential decay. Finally we relate these results to the large exponent power laws found in the actual behavior of the stock markets and to the exponential cut-off detected in certain recent measurement. Received 29 July 2000 and Received in final form 25 September 2000  相似文献   
1000.
The widely observed enthalpy-entropy compensation in chemistry and biophysics is still in a state of great confusion, because the reported enthalpy-entropy correlations in literature were often found to be false1-3. This problem has promoted Exner4. Krug5, Linert6, and others to develop some statistical methods to examine the compensation between the enthalpies and entropies obtained from the indirect van't Hoff method. However, as pointed out by Connors in a recent review7, it remains untou…  相似文献   
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