Physical model of the rotation of a tropical cyclone

A physical mechanism for the intense rotation of a spiral cyclonic vortex in a laboratory model of a tropical cyclone is described on the basis of experimental results. The results obtained are compared with the equation describing the vertical component of the vorticity. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 1, 25–28 (10 January 1996)     

Influence of strong single-ion anisotropy on phase states of 3D and 2D frustrated magnets

We investigated the influence of strong single-ion anisotropy, exceeding exchange interaction, and frustrated exchange interaction on spin-wave excitation spectra and phase states using the Hubbard operators’ technique, allowing the exact account of single-ion anisotropy. The results show that both the homogeneous phases (ferromagnetic and quadrupolar) and the spatially inhomogeneous phase (spiral structure) are possible in the 3D magnetic crystal. The region of existence of the spiral structure is considerably smaller than that in the analogues system, but with weak single-ion anisotropy. The situation is more complex in the 2D system; another spatially inhomogeneous state (the domain structure) can be realized in addition to the spiral magnetic structure. The phase diagrams for both the 3D and 2D systems were plotted.     

旋风分离器固体颗粒浓度三维电容层析成像分布

本文采用12电极电容传感器测量得到旋风分离器锥体部分的电容信号,利用线性逆反推算法得到断面固体颗粒的二维浓度分布。基于二维断面浓度分布,采用电容三维图像重建算法,得到锥体部分的三维颗粒浓度分布。图像重建结果与旋风分离器实际运行状况和数值计算结果吻合,说明电容层析成像及三维图像重建方法的准确性和可行性。     

Modified diffusion with memory for cyclone track fluctuations

Fluctuations in a time series for tropical cyclone tracks are investigated based on an exponentially modified Brownian motion. The mean square displacement (MSD) is evaluated and compared to a recent work on cyclone tracks based on fractional Brownian motion (fBm). Unlike the work based on fBm, the present approach is found to capture the behavior of MSD versus time graphs for cyclones even for large values of time.     

干气密封三维微间隙流场数值模拟

采用三维流动求解器CFD-ACE ,以空气作为工作介质,对干气密封不同工况下的内部微间隙三维流场进行了数值模拟,得到了流场的压力分布及其产生的开启力,通过与文献中试验结果的比较和分析,三维流场的计算结果与文献中试验结果吻合较好.在考虑气体的可压缩性的情况下,直接求解N-S方程可对干气密封微间隙内的三维流场进行正确的描述.     

传导延迟对螺旋波动力学行为的影响

采用Greenberg-Hastings离散激发介质模型研究传导延迟对螺旋波动力学行为的影响.模拟结果表明:某些情况下,延迟对螺旋波动力学行为无影响;在适当参数下,可观察到螺旋波波长和波速的改变、呼吸螺旋波、多臂螺旋波以及螺旋波和反螺旋波共存现象,对产生这些现象的物理机制作了简要的解释.     

Strong dynamical heterogeneities in the violation of the fluctuation-dissipation theorem in spin glasses

We analyze numerically the violation of the fluctuation-dissipation theorem (FDT) in the +/-J Edwards-Anderson (EA) spin-glass model. Using single spin probability densities we reveal the presence of strong dynamical heterogeneities, which correlate with ground-state information. The physical interpretation of the results shows that the spins can be divided into two sets. In 3D, one set forms a compact structure which presents a coarseninglike behavior with its characteristic violation of the FDT, while the other asymptotically follows the FDT. Finally, we compare the dynamical behavior observed in 3D with 2D.     

Tropical cyclones: Structure,computer simulation models,and operational prediction

Over the past two decades, observational studies using aircraft and satellite data to supplement conventional surface and upper air data have revealed much about the structure of tropical cyclones. During this same period, numerical weather prediction models have been developed to study the dynamics and energetics of these intense, destructive storms. This article reviews the structure of mature tropical cyclones and discusses the physical processes that are important in their genesis and maintenance. Some examples of computer simulation models are presented. Finally, the operational prediction of actual tropical storms by statistical and dynamical methods is summarized.     

Dynamical evolution of spatiotemporal patterns in mammalian middle cortex

The spatiotemporal structure of brain oscillations are important in understanding neural function. We analyze oscillatory episodes from isotropic preparations from the middle layers of a mammalian cortex which display irregular and chaotic spatiotemporal wave activity, within which spontaneously emerge spiral and plane waves. The dimensionality of these dynamics shows a consistent decrease during the middle of these episodes, regardless of the presence of simple spiral or plane waves. It is important to define the relevant biological order parameters which govern these dynamical bifurcations.     

TiAl/Ti3Al体系剪切变形的分子动力学研究

利用分子动力学方法研究了正化学比的TiAl/Ti3Al双相体系中剪切变形诱发位错形核以及相关结构转变的动态过程以及切变力场对最终结构的影响.研究发现,在TiAl/Ti3Al双相体系中剪切变形诱发黏滞-滑移式的滑移行为;界面在其中起到了传递能量、均衡协变的作用,界面两侧的异相结构保留了单相形变特征.六角密堆积(HCP)-Ti3Al部分各原子层较长时间内呈整体剪切协变,其后形变分化为应力集中诱发层错区和初始完整结构回复区;而面心立方(FCC)-TiAl部分因刚性较大仅存在微协变,其后局部受力区直接诱发相邻原子层间相对滑移,发生FCC向HCP结构转变.变形结构方面,HCP-Ti3Al部分在剪切力较大区域形成连续且稳定的FCC堆垛,近界面区FCC薄层与HCP相交替并存;而FCC-TiAl部分内禀层错和孪晶共存,当力场增大时形成亚稳HCP结构.     

Spiral structures in magnetized rotating plasmas

A theory of spiral structure formation has been formulated to show that spiral structures are rather basic entities in magnetized rotating plasmas subjected to various types of instabilities such as collisional drift wave instability, flute mode instability due to centrifugal force, and Kelvin-Helmhotz instability. The characteristic features of spiral structures observed experimentally in electron cyclotron resonance plasmas are reproduced by our theory.     

含葡萄糖的混浊介质的Mueller矩阵模拟与分析

利用矢量Monte Carlo算法结合葡萄糖的旋光特性模拟了含糖混浊介质的背散射Mueller矩阵.数值模拟表明:含糖混浊介质的背散射Mueller矩阵元素中除Mll、M14、M41、M44外的其它元素花样均发生龙卷风状的不同程度的扭曲,其中M24、M34、M42、M43的扭曲程度更为显著.研究发现M24、M34、M4...     

Dissipation in Lie–Poisson systems and the Lorenz-84 model

The relation between dissipation and the symplectic structure of the momentum-space is studied in so(3) Lie algebra and in 2D fluid dynamics. Three kinds of dissipative mechanisms are discussed and a general bracket formalism is introduced. A chaotic dynamical system due to Lorenz, and largely studied in low-dimensional models of geophysical fluid dynamics, is analysed in its geometric and dynamical features, by means of the formalism previously introduced. A mechanism of energy transfer for this low-order model is discussed.     

Large force fluctuations in a flowing granular medium

We study fluctuations in the force at the boundary of a 2D granular flow. The forces are mainly impulsive at all flow rates. The probability distribution of impulses decays exponentially at large impulses, as do the forces in a static granular medium. At small impulses, the distribution evolves continuously with flow rate with no indication of the transition from collisional flow to intermittently jamming flows. However, the distribution of the time interval between collisions tends to a power law, P(tau) - tau(-3/2), showing a clear dynamical signature of the approach to jamming.     

Water Vapour Potential Vorticity and Its Applications in Tropical Cyclones

A new tracer is presented to diagnose tropical cyclones （TCs） and their correspondent rainfall. It is defined as water vapour potential vorticity （WPV） by replacing potential temperature with specific humidity in the potential vorticity （PV）. The WPV is compared with PV and moist potential vorticity （MPV） in diagnosing three tropical cyclone cases occurred in North-West Pacific during 10 July to 21 July 2005 （Haitang）, 30 July to 9 August 2005 （Matsa） and 25 September to 3 October 2005 （Longwang） separately. The results show that in tracing the track of TCs, WPV is not nicer than PV but better than MPV. While diagnosing TCs＇ onshore rainfall, WPV is better than MPV in all the three cases. Moreover, the advection of WPV is a good indication of TC rainfall after its landing.     

Reduced models of atmospheric low-frequency variability: Parameter estimation and comparative performance

Low-frequency variability (LFV) of the atmosphere refers to its behavior on time scales of 10–100 days, longer than the life cycle of a mid-latitude cyclone but shorter than a season. This behavior is still poorly understood and hard to predict. The present study compares various model reduction strategies that help in deriving simplified models of LFV.Three distinct strategies are applied here to reduce a fairly realistic, high-dimensional, quasi-geostrophic, 3-level (QG3) atmospheric model to lower dimensions: (i) an empirical–dynamical method, which retains only a few components in the projection of the full QG3 model equations onto a specified basis, and finds the linear deterministic and the stochastic corrections empirically as in Selten (1995) [5]; (ii) a purely dynamics-based technique, employing the stochastic mode reduction strategy of Majda et al. (2001) [62]; and (iii) a purely empirical, multi-level regression procedure, which specifies the functional form of the reduced model and finds the model coefficients by multiple polynomial regression as in Kravtsov et al. (2005) [3]. The empirical–dynamical and dynamical reduced models were further improved by sequential parameter estimation and benchmarked against multi-level regression models; the extended Kalman filter was used for the parameter estimation.Overall, the reduced models perform better when more statistical information is used in the model construction. Thus, the purely empirical stochastic models with quadratic nonlinearity and additive noise reproduce very well the linear properties of the full QG3 model’s LFV, i.e. its autocorrelations and spectra, as well as the nonlinear properties, i.e. the persistent flow regimes that induce non-Gaussian features in the model’s probability density function. The empirical–dynamical models capture the basic statistical properties of the full model’s LFV, such as the variance and integral correlation time scales of the leading LFV modes, as well as some of the regime behavior features, but fail to reproduce the detailed structure of autocorrelations and distort the statistics of the regimes. Dynamical models that use data assimilation corrections do capture the linear statistics to a degree comparable with that of empirical–dynamical models, but do much less well on the full QG3 model’s nonlinear dynamics. These results are discussed in terms of their implications for a better understanding and prediction of LFV.     

Spin dynamics of qqq wave function on light front in high momentum limit of QCD: Role of qqq force

The contribution of a spin-rich qqq force (in conjunction with pairwise qq forces) to the analytical structure of the qqq wave function is worked out in the high momentum regime of QCD where the confining interaction may be ignored, so that the dominant effect is Coulombic. A distinctive feature of this study is that the spin-rich qqq force is generated by a ggg vertex (a genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on as many quark lines, giving rise to a (Mercedes-Benz type) Y-shaped diagram. The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these ingredients, the differential equation for the 3D wave function ? receives well-defined contributions from the qq and qqq forces. In particular a negative eigenvalue of the spin operator iσ₁ · σ₂ × σ₃ which is an integral part of the qqq force, causes a characteristic singularity in the differential equation, signalling the dynamical effect of a spin-rich qqq force not yet considered in the literature. The potentially crucial role of this interesting effect vis-a-vis the so-called ‘spin anomaly’ of the proton, is a subject of considerable physical interest.     

热敏神经元网络中螺旋波死亡和破裂的数值模拟

实验发现大脑皮层内出现螺旋波且螺旋波对神经元电信号传递有积极作用.利用细胞网络方法从对大脑皮层观察到的螺旋波进行数值模拟.以包含温度因子的热敏神经元模型在二维空间构造规则网络,研究了神经元膜片温度参数对神经元网络中螺旋波演化影响;定义了一类统计同步因子来刻画温度因子引起螺旋波相变(破裂和死亡)的临界条件.发现在规则网络下,当温度超过一定值后螺旋波会死亡和消失而导致整个网络达到均匀同步;在考虑了弱通道噪声情况下,螺旋波温度超越一定临界值则引起螺旋波的破裂.进一步分析了暂时性发烧昏迷的可能机制在于神经系统某些功能区螺旋波传播电信号的中断.     

Spiral breakup as a model of ventricular fibrillation

The phenomenon of spiral breakup in a 2D and a 3D excitable medium is described. Differences between breakup in two dimensions and in three dimensions are discussed. Spiral breakup in an anatomical model of the ventricles of the heart is also studied. The patterns of excitation in the heart are presented at different wavelengths together with their electrocardiograms. Finally it is suggested that the phenomenon of spiral breakup is a possible mechanism of the ventricular fibrillation (VF). (c) 1998 American Institute of Physics.