Dynamics of Front Driven by Convection Field in Bistable Media

The front dynamics driven by a convection field in a model of FitzHugh-Nagumo type is studied both analytieMly and numerically. Saddle-node bifurcation induced by the convection field is found by using a singular perturbation analysis of front solutions. Convection field accelerates the B1och front propagating opposite the direction of convection field, but inhibits the Bloch front propagating along the direction of convection field. In addition convection field drives Ising front to travel opposite the direction of convection field.     

Spatial and Temporal Properties of a Nonlinear Optical Feedback System

We experimentally investigate the spatial and temporal properties of a nonlinear optical system composed of an optically addressed spatial light modulator and a two-dimensional optical feedback. The system property is examined using fringes with only one spatial wave vector. The fringes are spontaneously generated using a spatial frequency filter in the optical feedback. We also experimentally investigate the properties of the spatial light modulator in the system using ordinary interference fringes in order to compare with the system property. We demonstrate that the spatial frequency response of the nonlinear optical system is identical to that of the spatial light modulator. We also demonstrate the distinctive temporal behavior of diffraction lights from the fringes generated in the system.     

Controlling the transition between Turing and antispiral patterns by using time-delayed-feedback

The controllable transition between Turing and antispiral patterns is studied by using a time-delayed-feedback strategy in a FitzHugh-Nagumo model.We treat the time delay as a perturbation and analyse the effect of the time delay on the Turing and Hopf instabilities near the Turing-Hopf codimension-two phase space.Numerical simulations show that the transition between the Turing patterns(hexagon,stripe,and honeycomb),the dual-mode antispiral,and the antispiral by applying appropriate feedback parameters.The dual-mode antispiral pattern originates from the competition between the Turing and Hopf instabilities.Our results have shown the flexibility of the time delay on controlling the pattern formations near the Turing-Hopf codimension-two phase space.     

Time Delay Induced Stochastic Resonance in One Species Competition Ecosystem without a Periodic Signal

One-species competition ecosystem with noise and time delay was investigated as not driven by a periodic force.The results show that the time delay is responsible for stochastic resonance of the system as delay time is smaller than critical point of the Hopf bifurcation.     

Influence of Dark Energy on Gravitational Time Delay

We investigate the gravitational time delay of light in the Schwarzschild black hole space-time surrounded by quintessence. With the analysis and numerical methods, we find that the gravitational time delay of light in the Schwarzschild black hole space-time surrounded by quintessence increases when the normalization factor c increases, and that the gravitational time delay also decreases when the quintessential state parameter ωq increases.     

Influence of Dark Energy on Gravitational Time Delay

We investigate the gravitational time delay of light in the Schwarzschild black hole space-time surrounded by quintessence. With the analysis and numerical methods, we find that the gravitational time delay of light in the Schwarzschild black hole space-time surrounded by quintessence increases when the normalization factor c increases, and that the gravitational time delay also decreases when the quintessential state parameter ω_q increases.     

Control of the patterns by using time-delayed feedback near the codimension-three Turing–Hopf–Wave bifurcations

Control of the spatiotemporal patterns near the codimension-three Turing–Hopf–Wave bifurcations is studied by using time-delayed feedback in a three-variable Brusselator model. Linear stability analysis of the system shows that the competition among the Turing-, Hopf- and Wave-modes, the wavenumber, and the oscillation frequency of patterns can be controlled by changing the feedback parameters. The role of the feedback intensity Pu played on controlling the pattern competition is equivalent to that of Pw, but opposite to that of Pv. The role of the feedback intensity Pu played on controlling the wavenumber and oscillation frequency of patterns is equivalent to that of Pv, but opposite to that of Pw. When the intensities of feedback are applied equally, changing the delayed time could not alter the competition among these modes, however, it can control the oscillation frequency of patterns. The analytical results are verified by two-dimensional （2D） numerical simulations.     

基于啁啾光纤光栅时分延时的相控阵波束形成

利用脉冲调制雷达信号的间歇性工作特点,不同波长的激光与雷达信号进行时分调制。啁啾光纤光栅将已调制射频信号的一串光脉冲序列进行反射延时,不同波长的激光序列在不同位置反射后产生不同时延。对载波频率等于4GHz的脉冲雷达信号进行实验测量,结果表明4个阵元的延时值与波束指向的理论延迟值一致,满足系统设计要求。     

反应扩散系统中反螺旋波与反靶波的数值研究

采用三变量Brusselator扩展模型在二维空间对反应扩散系统中反螺旋波和反靶波进行了数值模拟,利用色散关系和参量的时空变化研究了反螺旋波与反靶波的形成机制和时空特性,分析了方程参数对反螺旋波与反靶波的影响,获得了多种不同臂数的反螺旋波.模拟结果表明：反螺旋波源于波失稳、霍普失稳,或两种失稳的共同作用,而在反靶波中除上述两种失稳外还同时存在图灵失稳,波的传播方向均由外向内;反螺旋波波头的相位运动方向与波的走向相同,且旋转周期随臂数的增加逐渐增大;多臂数的反螺旋波由于受微扰及边界条件的影响,在波头的持续旋转运动中可以向臂数少的反螺旋波发生转变,并且在一定条件下单臂反螺旋波可实现到反靶波的转变;当不活跃中间物质的浓度的扩散系数超过临界值时,波的传播方向发生改变,系统可以实现反螺旋波到螺旋波以及反靶波到靶波的转变.     

Duffing Oscillator’s Vibration Control under Resonance with a Negative Velocity Feedback Control and Time Delay

An externally excited Duffing oscillator under feedback control is discussed and analyzed under the worst resonance case. Multiple time scales method is applied for this system to find analytic solution with the existence and nonexistence of the time delay on control loop. An appropriate stability analysis is also performed and appropriate choices for the feedback gains and the time delay are found in order to reduce the amplitude peak. Different response curves are involved to show and compare controller effects. In addition, analytic solutions are compared with numerical approximation solutions using Rung-Kutta method of fourth order.     

Investigation of the Influence of Overvoltage,Auxiliary Glow Current and Relaxation Time on the Electrical Breakdown Time Delay Distributions in Neon

Results of the statistical analysis of the electrical breakdown time delay for neon‐filled tube at 13.3 mbar are presented in this paper. Experimental distributions of the breakdown time delay were established on the basis of 200 successive and independent measurements, for different overvoltages, relaxation times and auxiliary glows. Obtained experimental distributions deviate from usual exponential distribution. Breakdown time delay distributions are numerically generated, usingMonte‐Carlo method, as the compositions of the two independent random variables with an exponential and a Gaussian distribution. Theoretical breakdown time delay distribution is obtained from the convolution of the exponential and Gaussian distribution. Performed analysis shows that the crucial parameter that determines the complex structure of time delay is the overvoltage and if it is of the order of few percentage, then distribution of time delay must be treated as an convolution of two random variables. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

实现空间高分辨成像的数字域时间延迟积分CMOS相机设计及分析

为使具有诸多优点的互补金属氧化物半导体(CMOS)传感器更适合空间高分辨成像,寻求空间高分成像的新型技术,提出了更利于微光成像和推扫成像的卷帘数字域时间延迟积分(TDI)算法。同时研究数字域TDICMOS相机成像质量,详细分析了其噪声来源和特性,并建立了数字域积分图像信噪比(SNR)与积分级数的关系模型,讨论了积分时间和光照度对SNR的影响。最后利用设计的IBIS5-B-1300卷帘数字域TDI CMOS原理样机开展验证实验。实验结果表明本文算法能明显提高成像质量,数字域10级积分图像SNR由未积分的19.07dB提高至29.21dB,而且级数越大,SNR越大。理论分析和实验验证均表明M级卷帘数字域TDI可使图像SNR提高M(σAD+σCMOS)/(MσAD+槡MσCMOS)倍,其中σAD和σCMOS与选择的CMOS传感器有关,另外σCMOS还受积分时间和光照度的影响。     

Control Strategy of True Time Delay Lines

This article presents the control of adjustable true time delays applied to an optical beamforming system. First is introduced the response of ring resonators of two and four ports and the cascade and lattice structures. The coupling factor and the phase modulation are employed as the control parameters for the adjustable group delay. The strategy of control is proposed and applied to a cascade of five ring resonators for producing wideband true time delays in the picosecond–nanosecond range with 2-GHz bandwidth and extremely low ripple. Ripples lower than 0.1% were obtained for the adjusted group delays. The proposed strategy can be simply extended if more resonators are added to increase the bandwidth of the system.     

Position and Velocity Time Delay for Suppression Vibrations of a Hybrid Rayleigh-Van der Pol-Duffing Oscillator

In this paper, we used time delay feedback to minimize the vibrations of a hybrid Rayleigh–van der Pol–Duffing oscillator. This system is a one-degree-offreedom containing the cubic and fifth nonlinear terms and an external force. We applied the multiple scales method to get the solution from first approximation. Graphically and numerically, we studied the system before and after adding time delay feedback at the primary resonance case (Ω ≌ ω). We used MATLAB program to simulate the efficacy of different parameters and the time delay on the main system.     

领导-跟随多智能体系统的滞后一致性

近年来,随着应用的需要和技术的发展,多智能体系统的一致性逐渐成为研究热点.在通信网络和工程应用中,由于信号传播的延迟效应,系统中智能体的状态可能表现为滞后一致.本文提出多智能体系统的滞后一致性概念,研究了有向网络环境下一阶领导-跟随多智能体系统的滞后一致性问题.通过设计合适的控制协议,利用矩阵理论和稳定性理论,获得该系统达到滞后一致的充分条件.数值模拟验证了理论结果的正确性.     

Transient Properties of a Bistable System with Delay Time Driven by Non-Gaussian and Gaussian Noises: Mean First-Passage Time

The mean first-passage time of a bistable system with time-delayed feedback driven by multiplicative non-Gaussian noise and additive Gaussian white noise is investigated. Firstly, the non-Markov process is reduced to the Markov process through a path-integral approach; Secondly, the approximate Fokker-Planck equation is obtained by applying the unified coloured noise approximation, the small time delay approximation and the Novikov Theorem. The functional analysis and simplification are employed to obtain the approximate expressions of MFPT. The effects of non-Gaussian parameter (measures deviation from Gaussian character) r, the delay time τ, the noise correlation time τ₀, the intensities D and α of noise on the MFPT are discussed. It is found that the escape time could be reduced by increasing the delay time τ, the noise correlation time τ₀, or by reducing the intensities D and α. As far as we know, this is the first time to consider the effect of delay time on the mean first-passage time in the stochastic dynamical system.     

啁啾光栅色散及时延特性研究

基于耦合模理论，通过对耦合波方程进行相位共轭变换，将反向耦合波方程变换为Ｒｉｃｃａｔｉ微分方程，利用数值解法对常耦合系数和高斯型耦合系数线性啁啾光栅的反射特性、色散特性和时延特性进行了详细分析，为设计具有理想效果的色散补偿器件提供了有效的理论方法。     

JP-10点火延时的激波管研究

在预加热激波管上测定了JP-10的点火延时时间．采用高精度真空仪直接测定注入激波管中JP-10蒸气压力，获得了JP-10气相浓度，解决了高碳数碳氢燃料点火延时激波管实验时管壁吸附影响燃料气相浓度确定的困难．采用压力传感器、单色仪和光电倍增管记录得到了完整的点火过程引起的压力变化和OH或CH自由基发射强度变化．自由基发射信号作为诊断点火发生的手段．当实验压力为151?556 kPa，温度为1000?2120 K，JP-10摩尔百分比为0.1%?0.55%，化学当量比为0.25、0.5、1.0、2.0时，获得了点火延时时间与实验温度、JP-10浓度、O2浓度的依赖关系，结果还表明，高温区和低温区呈现出不同的依赖关系．     

Second-Order Consensus of Multiple Agents with Coupling Delay

In this paper, we investigate two kinds of second-order consensus algorithms for multiple agents with coupling delay under general fixed directed information topology. Stability analysis is performed based on Lyapunov- Krasovskii functional method. Delay-dependent asymptotical stability condition in terms of linear matrix inequalities （LMIs） is derived for the second-order consensus algorithm of delayed dynamical networks. Both delay-independent and delay-dependent asymptotical stability conditions in terms of LMIs are derived for the second-order consensus algorithm with information feedback.     

一种飞行试验FC航电系统的采集网络时延测试方法

针对飞行试验FC总线测试的特点,文章提出了一种飞行试验FC航电系统的采集网络时延测试方法,在不影响原航电系统信息传输结构与特性的前提下,测试到通信消息从航电子系统端口发出的精准时刻,解决了航电FC采集网络时延测试难题;通过对某试验机的FC采集网络时间延迟测试,提高了飞行试验某航电子系统的试验计算精度,证明了该方法在工程中的有效性。