Spin-dependent transport in four-terminal rings in the presence of the Rashba spin-orbit coupling

Spin dependent transport in one-dimensional four-terminal rings (FTRs) is investigated in the presence of the Rashba spin-orbit coupling (RSOC). In the absence of the RSOC, the conductances as a function of the electron wave vector show resonant behavior for symmetrical configurations. For asymmetrical configurations, the conductances show peculiar zero-conductance resonances, and two kinds of conductance zeros have been found. In the presence of the RSOC, the original conductance zeros disappear as new conductance zeros are generated. Moreover, two kinds of symmetry relations have been found in the conductances, the spin dependent conductances and the spin polarizations. For the FTRs with axial or central symmetry, the phase-locking effect has been found in terminal 2, where there is no spin polarization. Under a weak magnetic field, the Zeeman term is treated by a perturbation, and it is found that the Zeeman effect is obvious for weak RSOC.     

Property study of coherent annular beam generated by the annular phase-locking laser

An annular phase-locking laser with annular gain media is presented. In this paper, the light field distribution of coherent annular beam (CAB) can be given by an analytical expression based on the Collins formula. Typical numerical examples are given to illustrate the application of our analytical result and the propagation property of a CAB through a paraxial ABCD optical system.     

Transition from quasi-periodicity to chaos in a system of coupled nonlinear oscillators

The global bifurcation structure for a model of coupled nonlinear oscillators has been analysed numerically. It is shown that destruction of the two-torus preceding chaos is usually observed in this system. The critical surface of the invariant two-torus and its collapse in the course of rotation are firstly observed in a realistic differential equation system. A scaling property for the fine structure of phase-locking regions has also been confirmed.     

Phase-locking of the tunable two-dimensional axisymmetrical folded-combined CO2 laser

The frequency modulation of the two-dimensional (2D) axisymmetrical folded and combined (ASFC) CO₂ laser is performed by a blazed grating. Its principle of phase-locking is studied in detail. The properties of the injected mode in ASFC and the mode coupling coefficient, which are analyzed, will be considered to be the main factors of the phase-locking. It is shown that the effect of phase-locking will not be influenced when the blazed grating is adjusted. However, it will influence the distribution of the light intensity to some degree.     

Principle of phase-locking of axisymmetric concentric cavity CO2 laser

Based on the phase-locking principle of Gaussian beam, the phase-locking mechanisms of the spherical wave from axisymmetric concentric cavity (ASCC) CO₂ laser are analyzed. And then we study the variety laws of the equiphase surfaces and the light spots of the injected beam. The numerical calculations show that the injected beam could be considered as a spherical wave approximately in the ASCC. The phase-locking of the spherical wave is different from the phase-locking of the Gaussian beam; there are different field distributions between Gaussian beam and spherical wave. And the phase-locking method could improve the maximum value of the light intensity, the encircled energy reflects the degree of phase-locking.     

基于样本熵的听觉神经锁相机理的实验分析

锁相是指系统的响应与周期性刺激的特定相位同步的物理现象. 听觉神经的锁相对揭示人的听觉认知基本的神经机理及改善听觉感知有重要意义. 然而, 现有研究主要集中于心理物理方法和幅度谱分析, 不能有效区分包络响应和时域细节结构响应, 不能直观反映神经锁相. 本文主要利用拔靴法和离散傅里叶变换, 提出了基于样本熵的时域细节结构频率跟随响应(temporal-fine-structure-related frequency following response, FFR_T)的神经锁相值(phase locking value, PLV)计算方法, 用于分析神经物理实验数据. 两个脑电实验结果表明: FFR_T的PLV样本熵显著大于包络相关频率跟随响应(envelope-related frequency following response, FFR_E)的PLV, 且二者正交独立, 新方法能有效地分别反映听觉系统对包络和时间细节结构的锁相机理; 基频处的响应主要来源于FFR_E的锁相; 基频处, 不可分辨谐波成分包络的锁相能力优于对可分辨谐波; 基频缺失时, 畸变产物是不同的听觉神经通路的FFR_E的混合; 谐波处, FFR_E 集中于低频, FFR_T则集中于中、高频; 听觉神经元锁相能力与声源的频率可分辨性相关. FFR_T的PLV方法克服了现有FFR分析的局限性, 可用于深入研究听觉神经机理.     

A model of neural control of the heart rate

A simple model of heart rate regulation is proposed, using the assumption that the nervous system regulates the generation of pulses of the pacemaker. Previous values of intervals between heart beats (RR intervals) are used for this regulation, which is described by a nonlinear feedback loop with time delay. The conductance of the excitation in the heart is phenomenologically described by one nonlinear function (recovery curve). The model reproduces time series of RR intervals. Different known patterns of heart rate variability are observed, depending on the type of control and the parameter values.     

Influence of the solvent on the segmental dynamics and structure in mixed compositions of polyurethane and styrene-acrylonitrile copolymer

The effect of the tetrahydrofuran (THF), methyl ethyl ketone (MEK), ethyl acetate (EA), and acetone (A) solvents on the structure and segmental dynamics of polyurethane (PU)-(styrene-acrylonitrile) (SAN) mixed compositions are studied by spin-probe EPR spectroscopy, differential scanning calorimetry, and infrared spectroscopy. The molecular mobility τ, the degree of crystallinity χ, the modulus of elasticity E alter only slightly in passing from 100% PU to a 50% PU-50% SAN, but the structural and dynamic properties change abruptly at a high SAN content in the composition, regardless of the type of solvent. The values of τ, χ, and elastic modulus for the mixed compositions increases depending on the type of solvent in the following sequence: THF, MEK, EA, A, which can be explained by the thermodynamic affinity between the solvent and solute. It is also shown that, with growing content of SAN in the composition, the number of intermolecular hydrogen bonds between nitrile and urethane groups (3344-cm^?1 band) increases.     

Effect of a Novel Polymeric Coupling Agent on the Water Uptake Property and Warp Stability of Poly(vinyl chloride)/Bamboo Flour Composite

Water uptake property and warp stability of poly(vinyl chloride) (PVC)/bamboo flour composite were investigated employing a novel polymeric coupling agent, poly(styrene-co-maleic anhydride)-block-poly(styrene-co-acrylonitrile) {P[(SMA)-b-(SAN)]}. P[(SMA)-b-(SAN)] was synthesized through controlled/'living' radical polymerization (CRP) technique in an one-pot reaction and incorporated into the composite to improve the interfacial adhesion between PVC and bamboo flour. The structure of P[(SMA)-b-(SAN)] was confirmed by ¹H-NMR, FT-IR and GPC. PVC/bamboo flour composite sheets were then prepared from a single screw extruder and two-roll mill in the presence of P[(SMA)-b-(SAN)] coupling agent. As the content of the coupling agent increased, improved interfacial bonding between PVC and bamboo flour filler was observed. Water uptake property and warp stability were also improved in the presence of the coupling agent. These results suggest that the block copolymer successfully acted as a coupling agent in PVC/bamboo flour composites.     

Research on the phase-locking and beam characteristics of a new axisymmetric-fold-combination CO2 laser

A new type of axisymmetric-fold-combination CO₂ laser, which is constituted by several axisymmetric four-mirror cavities, is studied theoretically in this paper. The mutual energy coupling occurring within the communal discharge region of the unstable resonator to inject seed signals into each sub-resonator is demonstrated by theoretical deduction. The numerical results have proved that phase-locking could be achieved in this cavity, and the beams with phase-locking have both a higher intensity and a smaller light spot than the ones without phase-locking.     

两路双包层光纤激光器互注入锁相实验研究

提出了一种利用45°半透半反分束镜和角锥反射器实现两路光纤激光器的能量相互注入,从而获得相干合成激光输出的新方法,分析了其锁相原理.在实验上成功实现了两路独立振荡双包层光纤激光器的互注入锁相输出,在远场观察到了清晰稳定的干涉条纹（可见度约0.57）,获得了超过10W的相干合成激光输出,功率合成效率约为76%.实验表明,这种互注入锁相方法可以在更高功率条件下运行,是光纤激光相干合成领域一种有前途的新技术. 关键词： 光纤激光器 相干合成 互注入锁相     

Arnold tongues in human cardiorespiratory systems

Arnold tongues are phase-locking regions in parameter space, originally studied in circle-map models of cardiac arrhythmias. They show where a periodic system responds by synchronizing to an external stimulus. Clinical studies of resting or anesthetized patients exhibit synchronization between heart-beats and respiration. Here we show that these results are successfully modeled by a circle-map, neatly combining the phenomena of respiratory sinus arrhythmia (RSA, where inspiration modulates heart-rate) and cardioventilatory coupling (CVC, where the heart is a pacemaker for respiration). Examination of the Arnold tongues reveals that while RSA can cause synchronization, the strongest mechanism for synchronization is CVC, so that the heart is acting as a pacemaker for respiration.     

The model of Josephson junction arrays embedded in resonant cavities and the phase-locking properties

We propose a new model of a Josephson junction array embedded in a resonant cavity. The model considers the excitation of the resonance mode by the array and the influence of the resonance mode on the array. The phase-locking properties of the junction array are investigated in the frame of the model. Resonant steps in the current–voltage characteristics due to the interaction between the array and the resonant cavity and many other features of the phase-locking behaviors have been produced. The results include the influence of the quality factor, the strength of the coupling, as well as the junction number of the array on the phase-locking properties. The model can successfully explain many features of the real situation and provide useful new predictions.     

S波段相对论速调管放大器锁相特性

对相对论速调管放大器（RKA）锁相特性进行了粒子模拟与实验研究。在2.5维粒子模拟中,研究了电子束电压波形特征对RKA锁相特性的影响,结果表明:电子束电压波形上冲对RKA锁相特性有正面影响,即能够减小相位差达到锁定状态的时间,幅度为20%的上冲导致大约23的相位差变化;波形顶降则对RKA锁相特性有负面影响,可使相位差过早地偏离稳定值,幅度为5%的顶降大约能引起50的相位差偏离;电压波形的上升时间对RKA相位锁定特性也有影响,但规律不明显。在三维粒子模拟和实验中,研究了导引磁场大小对RKA锁相特性的影响,结果表明,在1.6 T以下,RKA输出微波与种子源微波之间的相位差锁定值总体上随导引磁场的增大而减小,在细节上,呈现阶跃形式,即一定范围内导引磁场大小变化不会导致相位差的改变。实验研究表明,在导引磁场范围为0.6~1.2 T时,RKA锁定相位差随导引磁场的增大而减小,阶跃现象不明显。     

Relaxed criteria of the Dobrushin-Shlosman mixing condition

An interacting particle system (Glauber dynamics) which evolves on a finite subset in thed-dimensional integer lattice is considered. It is known that a mixing property of the Gibbs state in the sense of Dobrushin and Shlosman is equivalent to several very strong estimates in terms of the Glauber dynamics. We show that similar, but seemingly much milder estimates are again equivalent to the Dobrushin-Shlosman mixing condition, hence to the original ones found by Stroock and Zegarlinski. This may be understood as the absence of intermediate speed of convergence to equilibrium.     

Multifractal Analysis of Human Heartbeat in Sleep

We study the dynamical properties of heart rate variability （HRV） in sleep by analysing the scaling behaviour with the multifractal detrended fluctuation analysis method. It is well known that heart rate is regulated by the interaction of two branches of the autonomic nervous system： the parasympathetic and sympathetic nervous systems. By investigating the multifractal properties of light, deep, rapid-eye-movement （REM） sleep and wake stages, we firstly find an increasing multifractal behaviour during REM sleep which may be caused by augmented sympathetic activities relative to non-REM sleep. In addition, the investigation of long-range correlations of HRV in sleep with second order detrended fluctuation analysis presents irregular phenomena. These findings may be helpful to understand the underlying regulating mechanism of heart rate by autonomic nervous system during wake-sleep transitions.     

Phase-locking and critical phenomena in lattices of coupled nonlinear oscillators with random intrinsic frequencies

We study phase-locking in a network of coupled nonlinear oscillators with local interactions and random intrinsic frequencies. The oscillators are located at the vertices of a graph and interact along the edges. They are coupled by sinusoidal functions of the phase differences across the edges, and their intrinsic frequencies are independent and identically distributed with finite mean and variance.We derive an exact expression for the probability of phase-locking in a linear chain of such oscillators and prove that this probability tends to zero as the number of oscillators grows without bound. However, if the coupling strength increases as the square root of the number of oscillators, the probability of phase-locking tends to a limiting distribution, the Kolmogorov-Smirnov distribution. This latter result is obtained by showing that the phase-locking problem is equivalent to a discretization of pinned Brownian motion.The results on chains of oscillators are extended to more general graphs. In particular, for a hypercubic lattice of any dimension, the probability of phase-locking tends to zero exponentially fast as the number of oscillators grows without bound. We also consider a less stringent type of synchronization, characterized by large clusters of oscillators mutually entrained at the same average frequency. It is shown that if such clusters exist, they necessarily have a sponge-like geometry.     

二维Hénon-Heiles势及其变形势体系逃逸率与分形维数的研究

采用Chin和Chen的动力学算法追踪粒子在体系中的运动情况, 首次研究并对比了粒子在Hénon-Heiles体系与变形Hénon-Heiles六边形体系中的混沌逃逸规律, 在Hénon-Heiles体系中, 对于不同能量范围, 分形维数与逃逸率随能量而改变, 但在变形Hénon-Heiles六边形体系中, 仅在低能区分形维数与逃逸率随能量的改变而变化, 而高能区逃逸率和分形维数趋于稳定值. 并且得到普遍规律, 即不同混沌体系中粒子的混沌逃逸率和粒子逃逸的分形维数呈现较强的线性相关性. 因而分形维数可以作为工具研究混沌体系中粒子的逃逸规律, 在介观器件设计中可以通过研究混沌电子器件的分形维数来表征粒子在器件中的传输行为.     

Autoresonant excitation of multiphase waves in the sine-Gordon model

Autoresonant excitation and control of multiphase waves of the sine-Gordon equation is discussed. The autoresonance (a persistent nonlinear phase-locking) is achieved by applying chirped frequency wave-like perturbations and passage through resonances with inactive (dormant) degrees of freedom in the system. Successful phase locking requires the amplitude of the driving perturbation to exceed a threshold that scales as 3/4 power of the driving frequency chirp rate. The spectral theory of the inverse scattering transform method is used for diagnostics and analysis of the excited solutions.     

运动后人体心肺节律同步关系及信号的耦合方向

研究运动后青年心肺系统的耦合关系.通过提取在校学生运动后的心跳和呼吸信号,采用经验模态分解的方法对信号进行滤波,分析了心肺信号的相同步行为和心肺节律间耦合作用的相对强弱关系.结果表明,人体在运动后仍然存在心肺系统节律同步现象.这种同步比例不仅因人而异,而且因时而异.由传递熵的计算结果得知,呼吸对于心跳的耦合作用相对较大.