外注入激光同步方程和在保密通信中的应用

本文建立了外部光注入半导体激光器的同步系统误差方程 ,实现了外部光注入波长 1 31μm分布反馈激光器的两个激光混沌系统的同步 ,其同步误差几乎为零 .成功数值模拟了该同步系统在长距离光纤传输中的同步 ,其同步误差随着传输距离而增加 ,光纤的自相位调制是限制激光混沌在光纤传输中同步的主要原因 ,分析了这种传输的极限 ,讨论了在不同传输距离上的强度噪声和相位噪声对同步误差的影响 .在长距离光纤模拟和数字保密通信中应用的数值模拟表明 ,无论是在时域还是在频域 ,信息在混沌中都难以分离 。

基于同步方程方法的有源噪声控制

基于同步方程方法基本原理,对有源噪声控制系统中的参考输入信号和测量误差信号进行处理,得到最优的噪声控制滤波器,其无须对次路径进行辨识建模,且具有较好的鲁棒性;就前馈控制结构加以研究,仿真结果表明,该方法不仅在次路径固定不变时,使噪声信号得到明显衰减,并且在次路径发生改变时,依然能很好地控制噪声。

电网对称短路故障下直驱风电并网逆变器暂态同步特性研究

电网在对称短路故障下,风电并网逆变器容易出现暂态失稳问题。文章首先建立直驱风电并网逆变器简化模型,得到了其与电网的频率同步方程,研究了电网电压跌落程度、锁相环参数对直驱风电并网逆变器暂态同步过程中等效功角和频率响应特性。由于电网电压跌落会使得并网逆变器的频率出现较大超调和振荡,严重影响并网逆变器的暂态同步性能,而在故障期间,降低锁相环积分系数可以提高并网逆变器等效惯量和阻尼,从而有利于提高系统暂态稳定性。在Matlab/Simulink中建立了直驱风电并网逆变器的时域仿真模型,通过仿真验证了理论分析的正确性。

基于输出反馈控制理论的HVDC附加次同步阻尼控制器

通过在直流输电系统的整流站装设附加次同步阻尼控制器可以削弱交直流并联输电系统中发生的次同步振荡。利用输出反馈线性最优控制理论设计附加次同步阻尼控制器,选取与控制器密切相关的反馈信号Δω5、ΔαR,求解有约束条件的Levine-Athans方程,得出附加控制器的输出反馈增量。特征值分析和时域仿真结果表明:所设计的附加次同步阻尼控制器在很宽的串联补偿条件下能有效地抑制交直流并联输电系统中发生的次同步振荡。

流域用水系统协调发展分析

采用复合系统和协调发展理论与方法,提出同步协调方程,构建了流域各用水子系统间的协调发展评价方法,并将其运用于福建九龙江流域。结果表明:九龙江流域在过去5年中,用水系统协调发展程度较高,同时存在波动。

Using multi-threads to hide deduplication I/O latency with low synchronization overhead

Data deduplication, as a compression method, has been widely used in most backup systems to improve bandwidth and space efficiency. As data exploded to be backed up, two main challenges in data deduplication are the CPU-intensive chunking and hashing works and the I/0 intensive disk-index access latency. However, CPU-intensive works have been vastly parallelized and speeded up by multi-core and many-core processors; the I/0 latency is likely becoming the bottleneck in data deduplication. To alleviate the challenge of I/0 latency in multi-core systems, multi-threaded deduplication （Multi-Dedup） architecture was proposed. The main idea of Multi-Dedup was using parallel deduplication threads to hide the I/0 latency. A prefix based concurrent index was designed to maintain the internal consistency of the deduplication index with low synchronization overhead. On the other hand, a collisionless cache array was also designed to preserve locality and similarity within the parallel threads. In various real-world datasets experiments, Multi-Dedup achieves 3-5 times performance improvements incorporating with locality-based ChunkStash and local-similarity based SiLo methods. In addition, Multi-Dedup has dramatically decreased the synchronization overhead and achieves 1.5-2 times performance improvements comparing to traditional lock-based synchronization methods.

Equation of state of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) bulk metallic glass

The knowledge of the equation of state(EOS)and the compressibility of a solid are of central importance for the understanding of the behavior and the application of a condensed matter.The compression behavior of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass(BMG)is investigated at room temperature up to 24 GPa using in-situ high pressure energy dispersive X-ray diffraction with synchrotron radiation.A model of basic cell volume has been established and the equation of state of BMG is determined by the calculation of radial distribution function.The experimental results indicate that the BMG contains a large amount of vacancy-like free volume.Low pressure(below 7 GPa)induces the collapse of the free volume to some extent and structure relaxation in the BMG.

Exponential synchronization for delayed nonlinear Schr?dinger equation and applications in optical secure communication

For further exploring the confidentiality of optical communication,exponential synchronization for the delayed nonlinear Schrodinger equation is studied.It is possible for time-delay systems to generate multiple positive Lyapunov exponents without the limitation of system dimension.Firstly,the homoclinic orbit analysis is carried out by using the bifurcation theory,and it is found that there are two homoclinic orbits in the system.According to the corresponding relationship,solitary waves also exist in the system.Secondly,the Melnikov method is used to prove that homoclinic orbits can evolve into chaos under arbitrary perturbations,and then chaotic signals are used as the carriers of information transmission.The Lyapunov exponent spectrum,phase diagram and time series of the system also prove the existence of chaos.Thirdly,an exponential synchronization controller is designed to achieve the chaotic synchronization between the driving system and the response system,and it is proved by the Lyapunov stability theory.Finally,the error system is simulated by using MATLAB,and it is found that the error tends to zero in a very short time.Numerical simulation results demonstrate that the proposed exponential synchronization scheme can effectively guarantee the chaotic synchronization within 1 s.

Theory of Dynamics In-Phase Locking and Quasi-Period Synchronization in Two Mutually Coupled Multi-Quantum-Well Lasers

Abstract We study dynamics in two mutually coupling multi-quantum-well lasers. We carry out theoretical and numerical analysis of synchronization, anti-synchronization, in-phase locking in the two identical lasers but detuning, in detain. It is proved that the coupling level determines stability of the lasers by analyzing the eigenvalue equation. Critical case of locking is discussed via the phase difference equation. Quasi-period and stable states in the two lasers are investigated via varying the current, detuning and coupling level.

Three Lemmas on Dynamic Cavity Method

We study the dynamic cavity method for dilute kinetic Ising models with synchronous update rules. For the parallel update rule we find for fully asymmetric models that the dynamic cavity equations reduce to a Markovian dynamics of the (time-dependent) marginal probabilities. For the random sequential update rule, also an instantiation of a synchronous update rule, we find on the other hand that the dynamic cavity equations do not reduce to a Markovian dynamics, unless an additional assumption of time factorization is introduced. For symmetric models we show that a fixed point of ordinary Belief propagation is also a fixed point of the dynamic cavity equations in the time factorized approximation. For clarity, the conclusions of the paper are formulated as three lemmas.

Chaos Synchronization of Nonlinear Bloch Equations Based on Input-to-State Stable Control

In this paper, we propose a new input-to-state stable （ISS） synchronization method for chaotic behavior in nonlinear Bloch equations with external disturbance. Based on Lyapunov theory and linear matrix inequality （LMI） approach, for the first time, the ISS synchronization controller is presented to not only guarantee the asymptotic synchronization but also achieve the bounded synchronization error for any bounded disturbance. The proposed controller can be obtained by solving a convex optimization problem represented by the LMI. Simulation study is presented to demonstrate the effectiveness of the proposed synchronization scheme.

Performance Analysis of PMSM Equations Computation

The paper deals with the comparison of three different digital devices used for the computing of permanent magnet synchronous motor （PMSM） model. Model is used for virtual high frequency injection method （VHFIM） sensorless control, where injection and acting voltages are virtual ones. For computing the whole PMSM model, differential equations are used. The paper is focused on performance analysis of computing speed and accuracy of field-programmable gate array （FPGA） device, digital signal controller and Power PC microcontroller and results are compared.

Exact Boundary Synchronization for a Coupled System of Wave Equations with Neumann Boundary Controls

In this paper, for a coupled system of wave equations with iNeumann boundary controls, the exact boundary synchronization is taken into consideration. Results are then extended to the case of synchronization by groups. Moreover, the determination of the state of synchronization by groups is discussed with details for the synchronization and for the synchronization by 3-groups, respectively.

Exact Synchronization for a Coupled System of Wave Equations with Dirichlet Boundary Controls

In this paper, the exact synchronization for a coupled system of wave equations with Dirichlet boundary controls and some related concepts are introduced. By means of the exact null controllability of a reduced coupled system, under certain conditions of compatibility, the exact synchronization, the exact synchronization by groups, and the exact null controllability and synchronization by groups are all realized by suitable boundary controls.

Synchronized bioluminescence behavior of a set of fireflies involving fractional operators of Liouville-Caputo type

In this paper, a system of fractional differential equations that model the synchronized bioluminescence behavior of a set of fireflies put on two spatial arrangements is presented; the alternative representation of these equations contains fractional operators of IAouvillc-Caputo type. The objective of the model is to qualitatively recover synchronization and show that it is persistent. It is shown that the effort made by each firefly glow changes with respect to the number of male competitors and the distance between them. The conditions on biological parameters are interpreted.

Riccati difference equation in optimal control formagnetic bearings

A model predictive optimal control method for magnetically suspended flywheel is presented.In order to suppress the conical whirl of the rotor caused by gyroscopic effect,the synchronization error is added to the traditional quadratic performance index.The target performance index is composed of the translatory error,the synchronization error,and the control output predicted by the discrete-time state model.The optimal controller is obtained by means of iterating a Riccati difference equation(RDE).Stability of the control scheme is investigated through fake algebraic Riccati technique(FART).The robust performance of the controller with respect to control parameters is studied by simulation.Results of the simulation and experiment on a compact magnetically suspended flywheel demonstrate that the proposed controller with consideration of the synchronization error is very effective to suppress the conical whirl caused by gyroscopic effect.