冷却原子在相位调制加速驻波光场作用下动量扩散的动力学

分析了二能级原子在相位调制加速驻波光场作用下动量扩散模型,这个量子系统在经典极限下表现混沌行为.在相同参量条件下,这个系统具有动力学局域特征,但混沌扩散运动没有完全受到抑制 关键词：     

量子参数激励单摆的局域效应研究

分析了二能级原子在振幅调制主波场中动量扩散模型。这是一个量子参数激励单摆系统。这个量子系统在经典极限下表现混沌行为。在相同参数条件下,这个系统具有动力学特征。     

广义热波长:定义、意义和应用

光子气体和低温下强简量子气体都不是经典理想气体,通常的热波长没有意义。但是,它们存在每个粒子的平均动量,因此可以定义广义热波长.这个热波长是系统量子相干性的一个量度,在非简并条件下,实物粒子系统广义热波长回到通常的热波长.简并条件下,热力学系统的线度必须大于广义热波长,因此导致了对热力学系统出现相关现象的最小线度,即最小线度判据.本文利用这一判据给出了一些典型系统的最小线度.     

检测铸件用的“万能”机器人系统

英国铸造研究协会研制了一个检测不同形状和尺寸的铸件的自动超声测试系统.在这个系统中拿探头的是一个机器人,它使这个系统用起来很方便.英国铸造协会研制这个系统.是为了研究它在象铸造这样多用途的制造业中的应用. 系统中的换能器连接在专门设计的超声探伤仪上,这台仪器也可以测量截面厚度、或为确定石墨的形     

振幅相位调制驻波光场中冷却原子的动力学局域

分析了二能级原子在振幅相位调制驻波场作用下动量扩散模型,这是一个双频参数激励的非线性量子单摆模型。这个系统在经典极限下表现混沌行为,在相同参数条件下,这个系统具有动力学局域特征,具有两个不可约频率扰动的系统的局域长度要比单个频率扰动时大得多。     

微重力环境下油滴沉降实验观察与分析

微重力条件下,物体的重力影响几乎消失,这时液体的流动特性会发生不同于重力作用下的变化.为了形象地观察到这个变化过程,根据微重力原理建立了一个短时微重力实验系统.在其模拟的微重力环境下,观测到油滴下降时的形状与速度变化.通过观察该实验,提高了学生的观察能力及总结物理实验规律的能力.     

一个新四维非自治超混沌系统的分析与电路实现

在以Lorenz系统为基础的一个新超混沌系统上,加入一个驱动信号,组成了一个四维非自治超混沌系统.该系统基本动力学特性的变化,主要是通过控制外界输入信号的频率实现的.在不同的频率参数下,该系统体现出了周期轨、二维环面、混沌以及超混沌不同的动力学特性,其中周期轨特性较为显著.这个现象在数值仿真以及分形分析上得到了很好地验证.最后设计一个模拟电路,通过实验结果进一步验证了与数值仿真的一致性.     

非连续反馈控制激发介质中的螺旋波

采用非连续反馈方法来控制Fitz-Hugh-Nagumo方程描述的激发介质中的螺旋波. 在控制过程中,对于系统各个格点快变量的幅值进行观测并和设定的阈值进行比较,当采样格点的快变量的值大于这个阈值时,则对系统进行直接小幅度的负反馈. 研究发现：在对系统所有格点快变量幅值观测时选择比较小的阈值则更容易将系统的螺旋波消除掉并使系统达到稳定均匀态. 在比较大的阈值下,系统的螺旋波则变得稀疏,也可以导致螺旋波的破裂. 在任意选择单个格点的快变量观测下,比较小的反馈强度仍然可以消除螺旋波,系统也达到稳定均匀态. 当 关键词： 螺旋波 Fitz-Hugh-Nagumo方程 反馈控制     

一类不可逆保守系统中的混沌类吸引子

报道一类不可逆保守系统的性质及在其中发现的混沌类吸引子.这些系统可以看作是一种加过压保护的张弛振荡电路的简化模型.它展示的类吸引性是指这个混沌轨道吸引它之外的迭代,而这种吸引由系统的不可逆性所导致.数值研究发现这个混沌轨道就是系统不连续边界的映象集,而且这很可能是这类系统的普遍性质. 关键词： 不可逆保守系统 混沌类吸引子 张弛振荡     

一种数字控制三相逆变电路的局部振荡行为分析

针对数字控制三相逆变系统, 对其在同步旋转坐标系比例控制下的局部振荡行为进行了分析.通过建立系统各个状态变量离散迭代方程, 针对这个高阶系统提出了各种不稳定行为的解析判别式. 以此为基础,得到了系统产生局部振荡的条件,以及控制参数与局部振荡点的关系. 最后,通过Simulink仿真以及电路实验证明了理论分析的正确性以及有效性. 研究结果揭示了三相逆变系统的运动行为及各相之间的内在耦合关系, 并准确地描述了系统产生的局部振荡现象. 关键词： 三相逆变电路 数字控制 运动行为 局部振荡     

An improved formula for the surface resistance of normal metals at millimetre wavelengths

A number of researchers have reported discrepancies between surface resistance (SR) measurements and classical theoretical predictions in normal metals for millimetre wavelengths (MW). In this paper, a rigorous model is developed for analysing SR of normal metals. This model is based on quantum mechanical analysis of the spatial dispersion within the metal. We use the model to predict SR and eliminate the discrepancies between SR measurements and classical theoretical predictions in normal metals for MW. Moreover, we have compared the results of this model with that of the classical skin-effect model and classical relaxation-effect model. Our analysis shows that the conductivity is not only frequency- but also wave-vector-dependent for MW. We demonstrate that our model has good quantitative agreement with the published experimental data for the room temperature surface resistance of normal metals for MW.     

Quantum walk under coherence non-generating channels

We investigate the probability distribution of the quantum walk under coherence non-generating channels. We definea model called generalized classical walk with memory. Under certain conditions, generalized classical random walk withmemory can degrade into classical random walk and classical random walk with memory. Based on its various spreadingspeed, the model may be a useful tool for building algorithms. Furthermore, the model may be useful for measuring thequantumness of quantum walk. The probability distributions of quantum walks are generalized classical random walkswith memory under a class of coherence non-generating channels. Therefore, we can simulate classical random walkand classical random walk with memory by coherence non-generating channels. Also, we find that for another class ofcoherence non-generating channels, the probability distributions are influenced by the coherence in the initial state of thecoin. Nevertheless, the influence degrades as the number of steps increases. Our results could be helpful to explore therelationship between coherence and quantum walk.     

Classical signal model for quantum channels

Recently it was shown that the main distinguishing features of quantum mechanics (QM) can be reproduced by a model based on classical random fields, the so-called prequantum classical statistical field theory (PCSFT). This model provides a possibility to represent averages of quantum observables, including correlations of observables on subsystems of a composite system (e.g., entangled systems), as averages with respect to fluctuations of classical (Gaussian) random fields. We consider some consequences of the PCSFT for quantum information theory. They are based on our previous observation that classical Gaussian channels (important in classical signal theory) can be represented as quantum channels. Now we show that quantum channels can be represented as classical linear transforms of classical Gaussian signals.     

Lagrangian theoretical framework of dynamics of nonholonomic systems

By the generalized variational principle of two kinds of variables in general mechanics, it was demonstrated that two Lagrangian classical relationships can be applied to both holonomic systems and nonholonomic systems. And the restriction that two Lagrangian classical relationships cannot be applied to nonholonomic systems for a long time was overcome. Then, one important formula of similar Lagrangian classical relationship called the popularized Lagrangian classical relationship was derived. From Vakonomic model, by two Lagrangian classical relationships and the popularized Lagrangian classical relationship, the result is the same with Chetaev's model, and thus Chetaev's model and Vakonomic model were unified. Simultaneously, the Lagrangian theoretical framework of dynamics of nonholonomic system was established. By some representative examples, it was validated that the Lagrangian theoretical framework of dynamics of nonholonomic systems is right.     

Prequantum Classical Statistical Field Theory: Schrödinger Dynamics of Entangled Systems as a Classical Stochastic Process

The idea that quantum randomness can be reduced to randomness of classical fields (fluctuating at time and space scales which are essentially finer than scales approachable in modern quantum experiments) is rather old. Various models have been proposed, e.g., stochastic electrodynamics or the semiclassical model. Recently a new model, so called prequantum classical statistical field theory (PCSFT), was developed. By this model a “quantum system” is just a label for (so to say “prequantum”) classical random field. Quantum averages can be represented as classical field averages. Correlations between observables on subsystems of a composite system can be as well represented as classical correlations. In particular, it can be done for entangled systems. Creation of such classical field representation demystifies quantum entanglement. In this paper we show that quantum dynamics (given by Schrödinger’s equation) of entangled systems can be represented as the stochastic dynamics of classical random fields. The “effect of entanglement” is produced by classical correlations which were present at the initial moment of time, cf. views of Albert Einstein.     

Quantum discord and classical correlation signatures of mobility edges in one-dimensional aperiodic single-electron systems

We investigate numerically the quantum discord and the classical correlation in a one-dimensional slowly varying potential model and a one-dimensional Soukoulis–Economou ones, respectively. There are well-defined mobility edges in the slowly varying potential model, while there are discrepancies on mobility edges in the Soukoulis–Economou ones. In the slowly varying potential model, we find that extended and localized states can be distinguished by both the quantum discord and the classical correlation. There are sharp transitions in the quantum discord and the classical correlation at mobility edges. Based on these, we study “mobility edges” in the Soukoulis–Economou model using the quantum discord and the classical correlation, which gives another perspectives for these “mobility edges”. All these provide us good quantities, i.e., the quantum discord and the classical correlation, to reflect mobility edges in these one-dimensional aperiodic single-electron systems. Moreover, our studies propose a consistent interpretation of the discrepancies between previous numerical results about the Soukoulis–Economou model.     

Equilibriumizing all food chain chaos through reproductive efficiency

The intraspecific interference of a top-predator is incorporated into a classical mathematical model for three-trophic food chains. All chaos types known to the classical model are shown to exist for this comprehensive model. It is further demonstrated that if the top-predator reproduces at high efficiency, then all chaotic dynamics will change to a stable coexisting equilibrium, a novel property not found in the classical model. This finding gives a mechanistic explanation to the question of why food chain chaos is rare in the field. It also suggests that high reproductive efficiency of top-predators tends to stabilize food chains.     

STUDY ON EXCESS CONDUCTION LOSS IN NORMAL METALS AT/BELOW SUB-MILLIMETER WAVELENGTHS

We have used the spatial dispersion theory to develop a rigorous model to investigate excess conduction loss in normal metals. We have used the model to account excess conduction loss and dissect the discrepancies between excess conduction loss measurements and classical theoretical predictions in normal metals at/below sub-millimeter wavelengths. Moreover, we have compared the results of this model with the results of the classical skin-effect model and classical relaxation-effect model. Our analysis shows that the conductivity is not only frequency but also wave vector dependent. The results of the calculations indicate a good quantitative agreement with the published experimental data for the room temperature excess conduction loss of normal metals at/below sub-millimeter wavelengths.     

Dirac's extended electron model

Dirac's extended electron model is elaborated here both on the classical and quantum level. The classical equations of motion are deduced from Dirac's action principle. It is shown that the model is free of the troublesome runaway solutions in the classical theory. The quantum theory of the radial oscillations is worked out in detail and the spectrum is discussed. The stability of the model is studied and it is found that Dirac's extended electron is unstable against quadrupole deformations.