高速模型尾迹流场及其电磁散射特性相似性实验研究

高速目标再入大气层或在临近空间飞行时,空气电离形成的等离子体鞘套和尾迹对目标的雷达散射特性会产生影响.为了研究不同模型尾迹流场及其电磁散射特性规律和相似性,以氧化铝球模型为研究对象,在弹道靶设备上开展了双尺度参数相同的条件下高速球模型尾迹流场及其电磁散射相似性实验研究.由二级轻气炮发射模型,模型直径分别为8.0、10.0、12.0、15.0 mm,速度约6 km/s,靶室压力分别为6.3,5.0,4.2,3.3 k Pa,采用阴影照相系统测量模型激波脱体距离、电子密度测量系统测量模型尾迹的电子密度分布、X波段单站雷达系统测量在视角为40?的模型及流场的雷达散射截面(RCS)分布.实验结果表明:在速度不变、双尺度参数相同的条件下,随着模型尺寸的增加,激波脱体距离逐渐增加,激波脱体距离与模型直径之比近似相同;不同模型尾迹电子密度测量曲线的趋势和数量级一致,表明不同模型的尾迹流场适用于双缩尺律;不同尺寸模型尾迹的总体RCS与分布RCS均不相同,表明不同模型尾迹的电磁散射不适用于二元缩尺律;高速球模型全目标电磁散射能量分布在模型及其绕流区域、等离子体尾迹区域;高速球模型全目标电磁散射能量在模型及绕流场区域出现1个强散射中心,在模型湍流尾迹区域出现多个散射中心;高速球模型尾迹的RCS测量信号呈现随机性分布特性,幅度脉动和频率脉动均没有周期性;随着模型尺寸的增加,模型尾迹的总体RCS增加,尾迹脉动频率的变化范围减小.     

KT—5C边缘等离子体湍流性质的实验研究

利用四探针方法系统地研究了ＫＴ－５Ｃ托卡马克边缘等离子体的湍流性质。实验结果指出，在限制器内０．５ｃｍ处，有一自然产生的径向电场剪切层，由Ｅｒ×Ｂ引起的等离子体整体的极向旋转在剪切层外沿着离子逆磁漂移方向，而在剪切层内则是沿着电子逆漂移方向的。     

差分发射探针在微波等离子体中的应用

本文引入的差分发射探针技术，主要用于测量等主子体电势。其中主要采用了直流加热探针和反馈环控制偏压电路，使等离子体电势的直接、连续和自动指示成为可能。与比较成熟的单探针测量技术相比，本文给出的方法测量结果正确，操作简单，能自动跟踪批示。     

微波共振探针及其在等离子体诊断中的应用

介绍了能够测量稳定和时变等离子体电子密度的微波共振探针,给出了其工作原理和在测量稳定、时变和瞬态等离子体电子密度中的应用。分析了传输模式和反射模式的工作过程及对测量范围、测量精度和空间分辨率等影响因素。结果表明,选用较长的探针有利于提高电子密度的测量范围和精度;选用的微波扫频源高端频率越高,频率分辨率越高,则电子密度的测量范围越大,测量精度越高。理论分析得出系统可测量的电子密度约为1.37×10⁸~4.1×10¹¹cm^-3。     

关于“平板边界层中湍流的发生与混沌动力学之间的联系”一文中的注记

经过进一步地研究，发现在本刊2002年8月的“平板边界层中湍流的发生与混沌动力学之间的联系”一文中，尚存在着一些数据处理上的问题.对此做了修正. 关键词： 湍流发生 混沌动力学 分形     

翼型近尾迹流动的PIV研究

利用在线式互相关PIV系统,在低速风洞中对NACA0012翼型的近尾迹流动进行了实验研究。实验结果表明,翼型近尾迹存在有序的涡街结构,涡街在尾缘处形成后,在向下游的迁移中,会经历一个发展壮大,失稳破碎,最终演化为湍流的过程、本文分析了近尾迹流动结构、流动机制,探讨了近尾迹流动中旋涡和涡街的稳定性．本文指出在翼型尾缘处采用恰当的流动控制措施,可以改变尾流与其下游物体相互作用的形式和机制,以达到兴利除弊的目的。     

环形波导狭缝天线产生的氩等离子体特性研究

研制了一种环形波导腔环绕直径３０ｃｍ,高５０ｃｍ耐热玻璃圆筒真空室构成的新的大面积微波等离子体源。环形波导内侧开有多个用来激励产生等离子体的狭缝,相邻狭缝间的距离为半个波导波长。利用该装置研究了微波功率,工作气体对氩等离子体特性的影响。     

混沌在工程中的应用

介绍一此处理混沌的技术及混沌在工程中的应用     

分离流动的脉冲热线测量方法研究与应用

1引言分离流动经常出现在许多实际流动中，对流体机械和飞行器产生重大影响。但由于这种流动具有方向性，变化快，给测量带来了困难。到目前为止，主要有以下三种测量方法：山激光多普勒测速治（＊D川；（2）飞行热线（F坊In含＊。卜w让e）；O）脉冲热线技术（PulsedAVire。‘脉冲热线”比“激光多普勒测速仪”价格低一个数量级，操作简单，是一种比较理想的测量技术。其原理最初由Baner山提出，随后经过BradburyP］，Eaton问，Castro＊和Fernholz问等人不断发展与完善，目前国外正推广应用在分离流动的研究中。但在国内，尚不多见其…     

混沌神经动力学行为在多自由度机器人上的应用研究

本文把混沌神经动力学行为应用到了一个多自由度的机器人手臂,利用一种简单的神经编码方法使高维的神经网络模式转化成了低维的运动参数。虽然只在神经网络中嵌入了三种简单的姿势动作,但是在混沌神经动力学行为出现时,机器人手臂呈现出复杂的组合运动。利用这一点,提出了一个简单的控制算法用来解决病态问题(不一定有解或者确定的解无法保证的问题)。实装实验进一步表明,尽管只有粗略甚至不确定的光源信息,利用提出的算法机器人手臂可以成功的寻找到光源。     

Experimental observation of intermittent route to chaos in magnetized filamentary discharge plasma due to the cylindrical plasma bubble

We delineate an experimental observation of the effect of the magnetic field along with mesh grid biasing in the presence of a cylindrical plasma bubble in a filamentary discharge magnetised plasma system. The cylindrical mesh grid of 80% optical transparency has been negatively biased and introduced in the plasma for creating a plasma bubble. Plasma floating potential fluctuations have been taken outside (LP1) and inside (LP2) of the plasma bubble. It has been noticed that as the external magnetic field is increased the oscillation pattern shows intermittent route to chaos as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) We have used recurrence quantification analysis (RQA) to the observed intermittency to chaos in the plasma. The main measures of RQA are laminarity (LAM) and determinism (DET). The laminarity measure can be associated with the average time between the chaotic burst in the intermittency. It has also been observed that the DET depends on the control parameter and decreases exponentially, features like a dip in skewness and a hump in the kurtosis with the variation of control parameter have been noticed, which are the strong evidence of intermittent behaviour of the system. Further, a numerical model has been developed to the observed experimental analysis of the intermittent route to chaos.     

Accuracy of semiclassical dynamics in the presence of chaos

We review some of the issues facing semiclassical methods in classically chaotic systems, then demonstrate the long-time accuracy of semiclassical propagation of a nonstationary wave packet using the quantum baker's map of Balazs and Voros. We show why some of the standard arguments against the efficacy of semiclassical dynamics for long-time chaotic motion are incorrect.     

Tsallis non-extensive statistics,intermittent turbulence,SOC and chaos in the solar plasma. Part two: Solar flares dynamics

In this study which is the continuation of the first part (Pavlos et al. 2012) [1], the nonlinear analysis of the solar flares index is embedded in the non-extensive statistical theory of Tsallis (1988) [3]. The q$q$-triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the singular value decomposition (SVD) components of the solar flares timeseries. Also the multifractal scaling exponent spectrum f(a)$f\left(a\right)$, the generalized Renyi dimension spectrum D(q)$D\left(q\right)$ and the spectrum J(p)$J\left(p\right)$ of the structure function exponents were estimated experimentally and theoretically by using theq$q$-entropy principle included in Tsallis non-extensive statistical theory, following Arimitsu and Arimitsu (2000) [25]. Our analysis showed clearly the following: (a) a phase transition process in the solar flare dynamics from a high dimensional non-Gaussian self-organized critical (SOC) state to a low dimensional also non-Gaussian chaotic state, (b) strong intermittent solar corona turbulence and an anomalous (multifractal) diffusion solar corona process, which is strengthened as the solar corona dynamics makes a phase transition to low dimensional chaos, (c) faithful agreement of Tsallis non-equilibrium statistical theory with the experimental estimations of the functions: (i) non-Gaussian probability distribution function P(x)$P\left(x\right)$, (ii) f(a)$f\left(a\right)$ and D(q)$D\left(q\right)$, and (iii) J(p)$J\left(p\right)$ for the solar flares timeseries and its underlying non-equilibrium solar dynamics, and (d) the solar flare dynamical profile is revealed similar to the dynamical profile of the solar corona zone as far as the phase transition process from self-organized criticality (SOC) to chaos state. However the solar low corona (solar flare) dynamical characteristics can be clearly discriminated from the dynamical characteristics of the solar convection zone.     

Effects of barrier fluctuation on the tunneling dynamics in the presence of classical chaos in a mixed quantum-classical system

We present a numerical investigation of the tunneling dynamics of a particle moving in a bistable potential with fluctuating barrier which is coupled to a non-integrable classical system and study the interplay between classical chaos and barrier fluctuation in the tunneling dynamics. We found that the coupling of the quantum system with the classical subsystem decreases the tunneling rate irrespective of whether the classical subsystem is regular or chaotic and also irrespective of the fact that whether the barrier fluctuates or not. Presence of classical chaos always enhances the tunneling rate constant. The effect of barrier fluctuation on the tunneling rate in a mixed quantum-classical system is to suppress the tunneling rate. In contrast to the case of regular subsystem, the suppression arising due to barrier fluctuation is more visible when the subsystem is chaotic.      

Tsallis non-extensive statistics,intermittent turbulence,SOC and chaos in the solar plasma,Part one: Sunspot dynamics

In this study, the non-linear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis (1988, 2004, 2009) ,  and . The q$q$-triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the sunspot index timeseries. Also the multifractal scaling exponent spectrum f(a)$f\left(a\right)$, the generalized Renyi dimension spectrum D(q)$D\left(q\right)$ and the spectrum J(p)$J\left(p\right)$ of the structure function exponents were estimated experimentally and theoretically by using the q$q$-entropy principle included in Tsallis non-extensive statistical theory, following Arimitsu and Arimitsu (2001, 2000)  and . Our analysis showed clearly the following: (a) a phase transition process in the solar dynamics from high dimensional non-Gaussian SOC state to a low dimensional non-Gaussian chaotic state, (b) strong intermittent solar turbulence and anomalous (multifractal) diffusion solar process, which is strengthened as the solar dynamics makes a phase transition to low dimensional chaos in accordance to Ruzmaikin, Zeleny and Milovanov’s studies (Zelenyi and Milovanov (1991) [21]); Milovanov and Zelenyi (1993) [22]; Ruzmakin et al. (1996) [26]) (c) faithful agreement of Tsallis non-equilibrium statistical theory with the experimental estimations of (i) non-Gaussian probability distribution function P(x)$P\left(x\right)$, (ii) multifractal scaling exponent spectrum f(a)$f\left(a\right)$ and generalized Renyi dimension spectrum _Dq$D_q$, (iii) exponent spectrum J(p)$J\left(p\right)$ of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics.     

平板边界层中湍流的发生与混沌动力学之间的联系

通过对平板边界层流动中的测量数据的仔细分析,证实了在平板边界层的湍流发生的过程中存在着奇怪吸引子.将这一结论与先前的转捩动力学分析结果相比较,证明了湍流的发生本身具有着混沌动力学本质,从而在平板边界层中的湍流发生与混沌之间建立了联系 关键词： 边界层 转捩 湍流的发生 混沌 奇怪吸引子     

Changes of the electron dynamics in hydrogen inductively coupled plasma

Changes of the electron dynamics in hydrogen （H2） radio-frequency （RF） inductively coupled plasmas are investigated using a hairpin probe and an intensified charged coupled device （ICCD）. The electron density, plasma emission intensity, and input current （voltage） are measured during the E to H mode transitions at different pressures. It is found that the electron density, plasma emission intensity, and input current jump up discontinuously, and the input voltage jumps down at the E to H mode transition points. And the threshold power of the E to H mode transition decreases with the increase of the pressure. Moreover, space and phase resolved optical emission spectroscopic measurements reveal that, in the E mode, the RF dynamics is characterized by one dominant excitation per RF cycle, while in the H mode, there are two excitation maxima within one cycle.     

The onset of chaos in the wake of an oscillating cylinder: Experiment and the dynamics of the circle map

This paper deals with a comparison between experimental observations in a low-Reynolds-number wake behind an oscillating cylinder and the universal properties of a sine circle map. When the limit cycle due to the natural vortex shedding in the wake is modulated at a second frequency by oscillating the cylinder transversely, one obtains in phase space a flow on a two torus. The nonlinear interaction between the two oscillators results in Arnol’d tongues due to phase locking, the devil’s staircase along the critical line, and a transition from order to chaosvia the quasiperiodic route. The sine circle map describes these features adequately. A comparison between the experiment and the theory is made in terms of multifractal formalism and trajectory scaling function.     

Intermittency at critical transitions and aging dynamics at the onset of chaos

We recall that at both the intermittency transitions and the Feigenbaum attractor, in unimodal maps of non-linearity of order ζ > 1, the dynamics rigorously obeys the Tsallis statistics. We account for theq-indices and the generalized Lyapunov coefficients λ^q that characterize the universality classes of the pitchfork and tangent bifurcations. We identify the Mori singularities in the Lyapunov spectrum at the onset of chaos with the appearance of a special value for the entropic indexq. The physical area of the Tsallis statistics is further probed by considering the dynamics near criticality and glass formation in thermal systems. In both cases a close connection is made with states in unimodal maps with vanishing Lyapunov coefficients.