Simulation of a non-stationary stochastic process with respect to its probability density function

Various relationships are developed for simulation of a non-stationary stochastic process. They are based on modelling of its time-dependent amplitude probability density, expressed analytically. Although the approach presented has a general application, its main purpose is to reproduce an environmental loading process and use it as the on-line input of computer controlled loading machines.     

温度为T时量子谐振子系统处在第n态的概率

研讨了温度为T时量子谐振子系统处在第n态的概率,并讨论了结果的物理意义．     

Dromion solutions for an electron acoustic wave and its application to space observations

The nonlinear evolution of an electron acoustic wave is shown to obey the Davey-Stewartson I equation which admits so called dromion solutions. The importance of these two dimensional localized solutions for recent satellite observations of wave structures in the day side polar cap regions is discussed and the parameter regimes for their existence is delineated.     

Coherence coefficient measuring system and its application to some acoustic measurements

The coherence coefficient defined by the so-called zero-delayed correlations for two sine functions can be given as a function of the phase difference only. Consequently, some acoustic responses resulting from the phase synthesis are capable of being analysed making use of this characteristic of the coherence coefficient.The measuring system based on the definition of coherence coefficient and some examples applying the system to acoustic measurement are discussed in this paper. In addition, the paper shows that the measured values agree well with the theoretical ones.     

分数阶状态空间系统的稳定性分析及其在分数阶混沌控制中的应用

基于Lyapunov稳定性理论,针对分数阶状态空间系统模型,提出一种稳定性判定方法,并给出了数学证明. 运用该稳定性理论无需求解平衡点,而方便地选择出控制项,对分数阶状态空间系统进行控制. 本文以分数阶统一混沌系统作为控制对象,将所提出的稳定性理论应用于该系统的控制中,仿真结果验证了该理论的有效性. 关键词： 分数阶 状态空间系统 稳定性 统一混沌系统     

负跃层浅海声传播问题的解析解及其在水下脉冲声传播研究中的应用

提出一个基于波数积分理论的解析解,可用于计算包含海面下均匀层、负跃层、海底上方均匀层以及液态均匀海底的负跃层浅海波导中的声场。对声源位于水体不同层中的情况给出详细的推导,给出深度格林函数的解析解,并介绍了如何利用其计算点源和线源这两种情况下的声场.通过一个典型的负跃层浅海算例,验证了本文所提方法的精度,以及处理点源及线源问题的能力.此外,将本文提出的方法应用于水下脉冲声传播研究。针对某次实验的实际海洋环境,利用本文方法研究接收到的脉冲信号的波形特点,并与利用射线理论分析得到的相邻脉冲到达时间间隔等理论结果进行比较·结果表明,利用本方法得到的相邻脉冲到达时间数值结果与理论值高度一致。本方法非常适用于需要大量重复计算声场的情况,如水下脉冲声传播、海底声学参数反演等问题的计算机仿真研究。     

Wigner function and the entanglement of a quantized Bessel-Gaussian vortex state of a quantized radiation field

A new kind of quantum non-Gaussian state with a vortex structure,termed a Bessel-Gaussian vortex state,is constructed,which is an eigenstate of the sum of squared annihilation operators a2+b2.The Wigner function of the quantum vortex state is derived and exhibits negativity which is an indication of nonclassicality.It is also found that a quantized vortex state is always in entanglement.And a scheme for generating such quantized vortex states is proposed.     

重力场中原子的衍射态及其概率分布

使用量子力学中Feynman的路径积分方法,导出了重力场中原子经单缝、双缝及多缝衍射后的量子态及其概率分布.在一定近似条件下,证明了干涉条纹的移动与重力加速度有关,而条纹间隔与重力加速度无关.     

Separation of variables in the Klein-Gordon quation for superposition of a quantized and a classical field

A study is made of the problem of separation of variables in the Klein-Gordon equation for fields that are a superposition of a classical field and the field of a quantized plane wave. Six types of fields are found for which the Klein-Gordon equation reduces to a specific equation, the operators of creation and annihilation occurring quadratically in this equation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 23–27, January, 1976.     

Time-reversal processing for an acoustic communications experiment in a highly reverberant environment

Time-reversal (T/R) communications is a new application area motivated by the recent advances in T/R theory. Although perceived by many in signal processing as simply an application of matched-filter theory, a T/R receiver offers an interesting solution to the communications problem for a reverberant channel. In this paper, the performance of various realizations of the T/R receiver for an acoustic communications experiment in air is described along with its associated processing. The experiment is developed to evaluate the performance of point-to-point T/R receivers designed to extract a transmitted information sequence propagating in a highly reverberant environment. It is demonstrated that T/R receivers are capable of extracting the transmitted coded sequence from noisy microphone sensor measurements with zero-symbol error. The processing required to validate these experimental results is discussed. These results are also compared with those produced by an equivalent linear equalizer or inverse filter, which provides the optimal solution when it incorporates all of the reverberations.     

Reformulation of the path probability method and its application to crystal growth models

The microscopic master equation of a system is derived within the framework of the path probability method (PPM). Then, by extending Morita's method in equilibrium statistical mechanics, the path probability function constructed microscopically can be systematically decomposed to result in the conventional path probability function of cluster approximation when correlations larger than the chosen basic cluster are neglected. In order to critically compare the master equation method with the PPM, the triangle approximation is treated by both methods for crystal growth models. It is found that the PPM gives physically satisfactory kinetic equations, while the master equation (supplemented with a cluster probability in the superposition approximation) does not. The triangle PPM calculation considerably improves the result of the pair approximation for crystal growth velocity in the solid-on-solid model, and compares well with Monte Carlo results.     

Effect of the state of a quantized electromagnetic field on the interaction with an atom with allowance for the continuum

This paper studies the effect of a transition into the continuous spectrum on the “collapse” and “revival” of population oscillations in an atom. It is shown that at large values of the mean number of photons in a radiation field and in conditions of weak ionization the phenomena of collapse and revival can still be observed, but the amplitude of population oscillations decreases exponentially because of the damping of the level. The interaction of a quantized electromagnetic field with a Λ system of an atom when one state is continuous is examined. Expressions are derived for the probability of “survival” of the atom when the quantized field was initially in a state with a given number of photons and when it was in a coherent state. An approximate calculation of the sum in averaging over the photon number distribution in the case of a coherent field leads to expressions for the probabilities of survival of the atom that transform into expressions, as the mean number of photons tends to infinity, corresponding to the case of a field in the representation of a fixed number of photons. The possibility of a stable state existing in a coherent quantized field is examined. It is found that for a Λ system the condition for the existence of a stable state remains valid in the case of a coherent state of the field when the photon number is large. Zh. éksp. Teor. Fiz. 113, 1193–1205 (April 1998)     

Quasienergy anholonomy and its application to adiabatic quantum state manipulation

The parametric dependence of a quantum map under the influence of a rank-1 perturbation is investigated. While the Floquet operator of the map and its spectrum have a common period with respect to the perturbation strength lambda, we show an example in which none of the quasienergies nor the eigenvectors obey the same period: After a periodic increment of lambda, the quasienergy arrives at the nearest higher one, instead of the initial one, exhibiting an anholonomy, which governs another anholonomy of the eigenvectors. An application to quantum state manipulations is outlined.     

Scattering theory for a model of an atom in a quantized field

We compute the scattering operator for a simplified model of an atom interacting a with a quantized field. The field is restricted to the vacuum and one-particle sectors, and the atom has only two states. We also solve the inverse scattering problem for the same model. The methods used rely on the particular form of the interaction, which is chosen to mimic the interaction between radiation and matter.This work was partially supported by NSF Grant DMS-8922941.     

Performance of a PIV system for a combusting flow and its application to a spray combustor model

The performance of PIV system for combusting flow was evaluated by using artificial images generated from computer graphics and experimental data. The influences of shutter speed, filter, laser power and the PIV algorithms on the measurement uncertainty were studied for optimizing the performance of the PIV system. This system was applied to the spray combustor model for boiler, and the flow patterns with and without combustion were elucidated. Results showed that the burner flow generates complex three-dimensional flow pattern, which contributes to highly mixed fuel flow in the combustor. Although the flow pattern with and without combustion is similar, the growth of burner flow area and an increase in velocity magnitude are found in the flow field by the influence of chemical reactions in combustion.     

Green's function for a system consisting of a charged particle and a quantized plane wave

An integral representation in terms of the intrinsic time is obtained for Green's function of a system consisting of a charged spinless particle intersecting with the field of a quantized plane wave.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 54–58, August, 1978.