Radiation-induced robust oscillation [2mm]and non-Gaussian fluctuation

There have been many recent studies devoted to the consequences of stochasticity in protein circuitry. Stress conditions, including DNA damage, hypoxia, heat shock, nutrient deprivation, and oncogene activation, can result in the activation and accumulation of p53. Several experimental studies show that oscillations can be induced by DNA damage following nuclear irradiation. To explore the underlying dynamical features and the role of stochasticity, we discuss the oscillatory dynamics in the well-studied regulatory network motif. The fluctuations around the fixed point of a delayed system are Gaussian in the limit of sufficiently weak delayed feedback, and remain Gaussian along a limit cycle when viewed tangential to the trajectory. The experimental results are recapitulated in this study. We illustrate several features of the p53 activities, which are robust when the parameters change. Furthermore, the distribution in protein abundance can be characterized by its non-Gaussian nature.     

基于不确定油液光谱数据的综合传动装置剩余寿命预测

原子发射光谱分析得到的磨损微粒元素浓度是综合传动装置性能劣化评估和剩余寿命预测的重要监测指标。由于系统随机劣化过程和光谱测量误差的影响,油液光谱数据中不可避免包含系统劣化随机性和光谱测量不确定性。然而,现有基于油液光谱数据的剩余寿命预测研究中,没有考虑劣化过程的随机性和测量的不确定性对剩余寿命预测的影响。因此,针对综合传动装置劣化随机性和油液光谱数据测量不确定性对寿命预测的影响,提出一种考虑系统随机劣化和数据不确定测量的综合传动装置劣化过程建模方法。基于随机过程首中时间的概念,定义了综合传动装置的剩余寿命;基于Wiener随机过程,建立了考虑系统随机劣化和不确定测量数据的综合传动装置劣化模型,利用极大似然估计方法,估计了劣化过程模型的参数;利用卡尔曼滤波技术,实现了综合传动装置劣化状态的实时估计与更新,进一步得到了考虑系统劣化随机性和光谱数据测量不确定性的剩余寿命分布。研究结果表明,提出的劣化建模方法能够准确估计装置的运行状态,避免了采用条件维护时间对装置进行维护与保养的局限性;综合传动装置的维护时间预测值比条件维护时间延长了193 Mh（113.5%）;考虑光谱数据测量不确定性的剩余寿命预测方法优于不考虑测量不确定性的方法。     

The dissipative effects on stochasticity of the nonlinear oscillator

The effects of dissipation on the stochasticity of a nonlinear oscillator in the presence of a perturbing field are studied analytically. It is shown that the dissipation has two different and opposite effects on the stochasticity depending on the external frequency in the non time asymptotic domain. In the low frequency regime the stochasticity is enhanced while high frequency diminishes the stochasticity. These results may be related to some aspects of recent numerical studies.     

Stochasticity in many-dimensional nonlinear oscillating systems

Qualitative analytic estimates of the stochasticity limit of one- and many-dimensional nonlinear oscillating systems are derived using the overlapping of first-order resonances as a criterion for stochasticity. Computational results obtained with several very simple transformations are compared with the analytic estimates. Numerical studies significantly below the stochasticity limit of a many-dimensional nonlinear system reveal an example of a very slow instability, the first, to the best of our knowledge.     

动力学系统中非线性项的跳跃随机性

计算机计算和实验的结果表明:动力学系统中非线性函数有一种特殊性质,即跳跃随机性。这种性质使确定的非线性函数中产生了许多不同于自身曲线的跳跃随机曲线。 关键词：     

Noise-driven intermittency in tidal dynamics

Summary The tide nonstationarity in the Adriatic Sea is described. We show how this phenomenon can be related to the stochasticity of sea fetch by a nonlinear noise-forced oscillator model. The experimental series correlation dimension reveals a strong lifting with respect to the astronomic tide. The lifting is related to space-time intermittency.     

统计物理的微观动力学基础

统计的基本出发点是研究系统具有的随机性,不同系统在不同情形下的宏观热力学性质起源于系统内部随机性的差异,通过对宏观热力学系统的微观非线性动力学进行研究探索，我们可以进一步更为深入地理解物态方程、相变等诸多的宏观热力学现象。本文通过哈密顿系统的非线性动力学研究，以及遍历性理论的动力学随机性研究对此问题进行了分析，研究表明，动力学系统的全局性混沌是系统统计成立的根本要素，系统的无限大自由度（热力学极限）已不是决定性的因素，人们可以在此基础上建立少自由度系统的统计力学及热力学。     

Stochastic behaviour in presence of an electrostatic wave due to the crossing of multiple cyclotron resonances in an inhomogeneous magnetic field

The criterion for the occurence of stochastic behaviour of particle trajectories in the field of an electrostatic wave is obtained taking into account the longitudinal inhomogeneity of the ambient magnetic field. The origin of the stochasticity is explained. The optimum conditions for particle heating are obtained at a wave amplitude below the threshold of stochasticity in a homogeneous plasma.     

Small-scale vorticity filaments and structure functions of the developed turbulence

We develop a theory of turbulence based on the Navier-Stokes equation, without using dimensional or phenomenological considerations. A small scale vortex filament is the main element of the theory. The theory allows to obtain the scaling law and to calculate the scaling exponents of Lagrangian and Eulerian velocity structure functions in the inertial range. The obtained results are shown to be in very good agreement with numerical simulations and experimental data. The introduction of stochasticity into the equations and derivation of scaling exponents are discussed in details. A weak dependence on statistical propositions is demonstrated. The relation of the theory to the multifractal model is discussed.     

Vibrational quasicontinuum of polyatomic molecules: New problems for laser spectroscopy

Generally, the subject of the paper is related to the structure of highly excited vibrational states of polyatomic molecules. The problem is treated in terms of intramolecular vibrational dynamics as well as spectroscopy of vibrational transitions. Theoretical approximations which allow us to calculate spectra starting from dynamics are discussed. A microscopic treatment of spectroscopic relaxation timesT ₁ andT ₂ is given. Also, various experimental approaches to study the problem are outlined including the measurements of stochasticity onset in molecules.     

Equipartition and rate of energy exchanges in a model of a radiant cavity

Results of calculations on a model of a radiant cavity, performed in order to explore the relation between stochasticity and geometrical structure of phase space, are presented. The rate of energy exchanges, as indicator of stochasticity, is found to be quite effective. Furthermore, a trend to equipartition for such a quantity is observed at increasing energy, and this implies an increasing rigidity of high harmonic modes also in the stochastic regime of motion. Such a feature may be correlated to the shape of the spectrum which characterizes the radiant cavity with respect to nonlinear chains.     

梯度磁场中静电波引起的粒子随机运动

本文讨论了一般非均匀梯度磁场下任意方向传播的静电波引起粒子随机运动的非线性效应。用正则久期扰动理论给出包含粒子周期运动和波振荡之间非线性共振的哈密顿量。根据Chirikov岛重叠条件给出一般梯度磁场下粒子进入随机态的临界波幅值。分析表明,相对均匀磁场,在弱非均匀情形下,该临界值降低,意味着粒子更易进入随机态。 关键词：     

Magnetic stochasticity in gyrokinetic simulations of plasma microturbulence

Analysis of the magnetic field structure from electromagnetic simulations of tokamak ion temperature gradient turbulence demonstrates that the magnetic field can be stochastic even at very low plasma pressure. The degree of magnetic stochasticity is quantified by evaluating the magnetic diffusion coefficient. We find that the magnetic stochasticity fails to produce a dramatic increase in the electron heat conductivity because the magnetic diffusion coefficient remains small.     

Noisy activation kinetics induces bursting in the Huber-Braun neuron model

We study a physiologically realistic implementation of internal stochasticity in a four-dimensional Hodgkin-Huxley type model of mammalian cold receptors. We show that in a deterministically tonic firing regime, this stochasticity can drive the neuron into a state of complex bursting behaviour. An explanation of the mechanism behind this effect is given in terms of phase space dynamics.     

Design and experimental tests of active control barriers for low-frequency stationary noise reduction in urban outdoor environment

Active noise control (ANC) techniques are based on the emission of an antiphase signal in order to cancel the noise produced by a primary source. ANC has been successfully applied especially for reducing noise in confined environments, such as headphones and ducts. In this study, we present an application of ANC concepts to the design of an anti-noise barrier for an outdoor environment and its experimental testing. Even though passive techniques are effective in noise reduction at middle-high frequencies, they become less efficient at low frequencies (below 300 Hz) due to the limited dimensions of commonly deployable barriers. In this paper, we analyze the properties of a low-cost active noise system able to efficiently operate on stationary, almost pure-tone, low-frequency noise, such as that produced by electrical transformers and reactors in power and transformation plants. A prototype has been implemented and on-the-field experimental tests have been carried out. The results (confirmed also by numerical simulations) demonstrate a remarkable efficiency in the far field, with a reduction up to 15 dB with respect to the absence of the ANC system.     

电子器件散粒噪声测试方法研究

本文分析了超导量子干涉器(SQUID)和超导-绝缘-超导(SIS)约瑟夫森结散粒噪声测试方法的应用局限性,提出了常规器件的散粒噪声测试方案.针对常规电子器件散粒噪声特性,研究了噪声测试基本条件,并建立了低温测试系统.通过采用双层屏蔽结构和超低噪声前置放大器,实现了较好的电磁干扰屏蔽和极低的背景噪声.在10 K温度下对常规二极管散粒噪声进行了测试,通过理论和测试结果对比分析,验证了测试系统的准确和可信性. 关键词： 散粒噪声 电子器件 噪声测试     

Controlling global stochasticity of Hamiltonian systems by nonlinear perturbation

A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust against small external noise. The mechanism underlying this high control efficiency is intuitively explained. Received 15 January 2002 Published online 6 June 2002     

军用运输机机舱有源消声实验系统的设计与实现

为验证有源消声技术在军用运输机机舱低频噪声消除方面的有效性,设计和实现了一套机舱有源消声实验系统。采用“激振器+舱壁板”方式实现了飞机螺旋桨对机舱诱导噪声的声源模拟,设计了基于前馈控制结构的自适应有源噪声控制系统,构建了基于FX-LMS算法的自适应消声控制器,采用监测麦克风组对舱内空间的消声效果进行监测。实验结果验证了自适应有源噪声控制技术在军用飞机舱室消声降噪领域的有效性,并表明初、次级声源间距对自适应有源消声系统的消声效果具有重要的影响。