Dispersion compensation in an open-loop all-optical chaotic communication system

The optical chaotic communication system using open-loop fiber transmission is studied under strong injection conditions. The optical chaotic communication system with open-loop configuration is studied using fiber transmission under strong injection conditions. The performances of fiber links composed of two types of fiber segments in different dispersion compensation maps are compared by testing the quality of the recovered message with different bit rates and encrypted by chaotic modulation （CM） or chaotic shift keying （CSK）. The result indicates that the performance of the pre-compensation map is always worst. Two types of symmetrical maps are identical whatever the encryption method and bit-rate of message are. For the transmitting and the recovering of message of lower bit rate （1 Gb/s）, the post-compensation map is the best scheme. However, for the message of higher bit rate （2.5 Gb/s）, the parameters in communication system need to be modified properly in order to adapt to the high-speed application. Meanwhile, two types of symmetrical maps are the best scheme. In addition, the CM method is superior to the CSK method for high-speed applications. It is in accordance with the result in a back-to-back configuration system.

ATM Open-Loop Shuffleout网络丢失率新的计算方法

文献 [1]提出了Open LoopShuffleout的ATM交换结构 .它是基于多级自路由、输出排队的Banyan结构 .文献[9]在文献 [1]的基础上构造了多递ATMShuffleout交换结构 .这种Open LoopShuffleout的ATM交换结构的信元丢失率包括三部分 ,其中之一就是网络丢失率πn.文献 [1]计算网络丢失率是在假设任意一级交换单元中每一输出端口的负载相同的前提下进行的 .本文考虑了更一般的情况 ,给出了精确计算网络丢失率的分析模型 ,不仅能够处理随机业务 ,而且还能处理热点业务 .模型分析和仿真的数字结果显示了在热点业务下一些有益的结论 .

Instability of cylinder wake under open-loop active control

Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic actuator located on the cylinder surface,adjusts the base flow to affect the three-dimensional wake instability and achieve wake stabilization and transition delay. The instability mode at a Reynolds number Re = 300 can be transformed from B to A with N = 1.0, where N is an interaction number representing the strength of the Lorentz force relative to the inertial force in the fluid. The wake flow is Floquet stable when N increases to 1.3. The spanwise perturbation wavelengths are 3.926 D and 0.822 D in the modes A and B, respectively, where D is the cylinder diameter. In addition, the oscillating amplitudes of drag and lift are reduced with the increase in the interaction number. Particle tracing is used to explore the essential physical mechanism for mode transformation. The path lines show that suppression of flow separation hinders the fluid deformation and rotation, leading to the decrease in elliptic and hyperbolic instability regions, which is the material cause of mode transformation.All of the results indicate that wake stabilization and transition delay can be achieved under open-loop active control via the streamwise Lorentz force.

Open-loop frequency response for a chaotic masking system

In this paper, a new numerical simulation approach is proposed for the study of open-loop frequency response of a chaotic masking system. Using Chua＇s circuit and the Lorenz system as illustrative examples, we have shown that one can employ chaos synchronization to separate the feedback network from a chaotic masking system, and then use numerical simulation to obtain the open-loop synchronization response, the phase response, and the amplitude response of a chaotic masking system. Based on the analysis of the frequency response, we have also proved that changing the amplitude of the exciting （input） signal within normal working domain does not influence the frequency response of the chaotic masking system. The new numerical simulation method developed in this paper can be extended to consider the open-loop frequency response of other systems described by differential or difference equations.

Analytical solution for a class of linear quadratic open-loop Nash game with multiple players

In this paper, the Nash equilibria for differential games with multiple players is studied. A method for solving the Riccati-type matrix differential equations for open-loop Nash strategy in linear quadratic game with multiple players is presented and analytical solution is given for a type of differential games in which the system matrixcan be diagonalizable. As the special cases, the Nash equilibria for some type of differential games with particular structure is studied also, and some results in previous literatures are extended. Finally, a numerical example is given to illustrate the effectiveness of the solution procedure.

PERFORMANCE OF A NEW DECODING METHOD USED IN OPEN-LOOP ALL-OPTICAL CHAOTIC COMMUNICATION SYSTEM

A new decoding method with decoder is used in open-loop all-optical chaotic communication system under strong injection condition.The performance of the new decoding method is numerically investigated by comparing it with the common decoding method without decoder.For new decoding method,two cases are analyzed,including whether or not the output of the decoder is adjusted by its input to receiver.The results indicate the decoding quality can be improved by adjusting for the new decoding method.Meanwhile,the injection strength of decoder can be restricted in a certain range.The adjusted new decoding method with decoder can achieve better decoding quality than decoding method without decoder when the bit rate of message is under 5 Gb/s.However,a stronger injection for receiver is needed.Moreover,the new decoding method can broaden the range of injection strength acceptable for good decoding quality.Different message encryption techniques are tested,and the result is similar to that of the common decoding method,indicative of the fact that the message encoded by using Chaotic Modulation(CM) can be best recovered by the new decoding method owning to the essence of this encryption technique.

Control-Relevant Identification Test Design for Open-Loop Experiment

An optimal experiment design (DED) with respect to the use of designing model-base controller was studied. The mean squared error at the setpoint is chosen as the performance criterion. Simple design formulas are derived based on the asymptotic theory. The signal is used for the open loop experiment. The design constraint is the power of the process signal or the process input signal. The results give guideline for identification application.

Experiments on an Open-Loop Cycle Carbon Dioxide Refrigeration System

An open loop cycle carbon dioxide(CO2)refrigeration system is established,and the cooling performances of high-pressure CO2 under different storage conditions(25℃,30℃,and 35℃)are investigated.Moreover,the experimental mass flow rates of CO2 are compared with the theoretical values at different conditions and refrigeration capacities.The results indicate that the storage condition of CO2 has a significant impact on the refrigeration performance,and the mass flow rate of CO2 increases with the increasing storage temperature in a given refrigeration capacity.

A SEMI-OPEN-LOOP CODING MODE SELECTION ALGORITHM BASED ON EFM AND SELECTED AMR-WB+ FEATURES

To solve the problems of the AMR-WB+(Extended Adaptive Multi-Rate-WideBand) semi-open-loop coding mode selection algorithm,features for ACELP(Algebraic Code Excited Linear Prediction) and TCX(Transform Coded eXcitation) classification are investigated.11 classifying features in the AMR-WB+ codec are selected and 2 novel classifying features,i.e.,EFM(Energy Flatness Measurement) and stdEFM(standard deviation of EFM),are proposed.Consequently,a novel semi-open-loop mode selection algorithm based on EFM and selected AMR-WB+ features is proposed.The results of classifying test and listening test show that the performance of the novel algorithm is much better than that of the AMR-WB+ semi-open-loop coding mode selection algorithm.

Connections Between Induction Generator Effect and Open-loop Modal Proximity to Cause Sub-synchronous Oscillations in Series-compensated Power System

The induction generator effect(IGE)and the openloop modal proximity(OLMP)are two different reasons why subsynchronous oscillations(SSOs)in a series-compensated power system(SCPS)may occur.The IGE attributes the growing SSOs to negative resistance,while the OLMP explains the SSO mechanism from the standpoint of modal conditions.In this paper,we investigate the connections between the IGE and the OLMP through equivalent RLC circuit and open-loop modal analysis.Our investigation is conducted for two types of seriescompensated power systems where either a synchronous generator or a DFIG is connected at the sending end.The investigation reveals the conditions,in which the IGE and the OLMP may jointly cause the growing SSOs,i.e.,both the IGE and the OLMP can explain why the growing SSOs occur.Furthermore,the investigation indicates that the IGE and the OLMP may be totally irrelevant and lead to growing SSOs separately.This implies that it is possible that in a SCPS,the growing SSOs are only due to the IGE,and the OLMP is non-existent,and vice versa.Hence,when the growing SSOs occurs in a SCPS,examination based on both the IGE and the OLMP should be carefully conducted in order to find if the oscillatory instability is due to the IGE,or the OLMP,or both of them.

Open-loop Phase Synchronization Method of Positive and Negative Sequences for Three-phase Asymmetric Grid

Currently,a grid-connected inverter is required to inject a dual-sequence current during asymmetric grid sags,which means both positive and negative sequence phases should be tracked.This paper proposes an open-loop phase synchronization(OLS)method of positive and negative sequences for an asymmetric grid based on the moving average filter(MAF),which does not need to separate the positive and negative sequence fundamental components of grid voltage.As a benefit,there is no double-frequency oscillation in the estimated phases at offnominal frequencies since the positive and negative sequence phases are obtained simultaneously.The proposed method not only has the inherent advantages of OLS,but also further improves the dynamic response since the window length of MAF is only 1/6 of the fundamental period.The effectiveness of the proposed OLS is verified by experimental results.

兆瓦级高效紧凑型核动力系统运行特性研究

为研究兆瓦级高效紧凑型核动力系统的运行特性,使用自主开发的热管堆瞬态分析程序TAPIRS(Transient Analysis code for heat Pipe and AMTEC power conversion space Reactor power System)和超临界二氧化碳布雷顿循环的瞬态分析程序SCTRAN/CO_(2)(Super Critical reactors Transient Analysis code/Carbon Dioxide)的耦合程序对其反应性、负荷、冷却水温度和流量等扰动进行了开环动态响应分析,并据此进行了控制系统设计。在此基础上,对线性变负荷、阶梯式变负荷以及甩负荷这三种变负荷运行工况进行了计算分析。结果表明:该核动力系统的转速对扰动的变化较为敏感,需要加以控制;低负荷下旁通会使压缩机流量上升,需对压缩机流量加以控制;系统在控制方案下能以6%FP(Full Power)·min^(−1)的速度实现0%~100%的负荷变动,且可以在任意负荷水平下运行;甩负荷下系统的波动时间变长,但是仍可达到新的稳态进行工作,且各参数处于安全范围内。本研究可为新型核动力系统的概念设计提供参考。

数模—动模混合仿真系统的接口建模与稳定性分析

为满足现代电力系统实时仿真的发展需求,数模-动模混合仿真系统结合实时数字仿真和物理动态模拟仿真的优点,成为现代电力系统研究的重要仿真方法。接口系统是混合仿真系统设计中的核心与难点。为了深入分析混合仿真系统的稳定性,对接口系统各个组成环节进行建模得到系统开环传递函数,分别根据劳斯判据和奈奎斯特判据研究开环传递函数中不同参数对系统稳定性的影响。理论推导表明接口系统中滤波器截止频率、接口延时和阻抗模拟比对系统的稳定性影响较大,并通过所搭建的混合仿真系统进行实验,实验结果表明不同参数对系统的稳定性影响与理论推导一致。

航天器气动角运动学及开环性能分析

对于航天器在大气中飞行的控制设计问题,由于气动角与气动力和气动力矩直接相关,因此一般采用气动角反馈.在研究稳定性等闭环性能时,需要用到气动角运动学方程.但是难以找到气动角运动学的推导方法,因此在应用时对于不同坐标系的定义缺乏灵活性.气动角运动学形式复杂,其推导具有难度.提出推导的方法,给出了气动角运动学方程,并对其开环性能进行了分析,为控制设计提供了基础.所提出的气动角运动学的推导方法,气动角运动学方程,以及开环性能分析的方法和结果,可以应用于带有大气的目标星体的气动进入的控制设计和分析中,从而为其提供了理论支撑.

基于硬件在环仿真的DFIG并网系统开环模式谐振风险及验证

开环模式谐振理论是阐释风电并网引起的电力系统振荡机理的研究成果,其中基于平均模型的离线时域仿真结果可信度存疑。为提升开环模式谐振的工程指导可靠度,首先基于硬件在环仿真,组建了用于验证开环模式谐振的半实物实验平台;其次建立双馈风电场并网系统的小信号模型,提出开环模式分析通用方法评估系统振荡风险;最后以两个算例进行了开环模式谐振现象的分析与实验。得到结论:硬件在环仿真的结果符合开环模式分析的结果,在开环模式谐振条件下,系统稳定性下降。留数法可以较为准确地预测系统闭环模式,系统参数的合理整定可以减小开环模式谐振带来的影响。

A novel control strategy for reproducing the floor motions of high-rise buildings by earthquake-simulating shake tables

To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Table(NEST)has been developed.The testbed consists of three consecutive floors of steel structure.The bottom two floors provide a space to accommodate a full-scale room.To fully explore the flexibility of NEST,we propose a novel control strategy to generate the required shake table input time histories for the testbed to track the target floor motions of the buildings of interest with high accuracy.The control strategy contains two parts:an inverse dynamic compensation via simulation of feedback control systems(IDCS)algorithm and an offline iteration procedure based on a refined nonlinear numerical model of the testbed.The key aspects of the control strategy were introduced in this paper.Experimental tests were conducted to simulate the seismic responses of a full-scale office room on the 21^(st)floor of a 42-story high-rise building.The test results show that the proposed control strategy can reproduce the target floor motions of the building of interest with less than 20%errors within the specified frequency range.

新能源经柔直送出系统的VSG控制及故障穿越策略

对于新能源经柔直送出系统,新能源控制器与柔直控制器参数匹配不佳会引起次/超同步振荡问题。为此,采用了基于VSG(虚拟同步发电机)控制的开环策略,取消了传统闭环控制方式下的内、外环及锁相环节,优化了柔直的阻抗特性,降低了与新能源的次/超同步振荡风险,同时适应孤岛与联网的运行方式。针对开环控制自身特性存在双极功率不平衡及故障后短路电流过高的问题,相应提出了双极功率平衡及故障穿越策略,并基于RTDS仿真验证了所提VSG控制及故障穿越策略的有效性。

开式空气循环热泵干燥系统性能仿真分析

为解决能源使用效率低、HCFC/HFC等非环保制冷剂使用等问题,提出了不同于传统干燥技术的以空气为工质的空气循环热泵干燥(ACHPD)系统新技术。建立了数学仿真模型,通过所构建实验台的实验结果进行验证,干燥速率误差在±0.01%以内,系统功率误差在±7%以内。与传统的电加热器干燥(EHD)系统相比,当水质量蒸发率从0.75 kg/h增至3.45 kg/h时,ACHPD系统的节能率达到15%~27%。进气温度由10℃增至40℃和相对湿度由30%增至80%分别使单位除湿能效比(MER)降低约7%和21%。膨胀机效率由0.55增至0.8和压缩机效率由0.4增至0.9会使系统的能效分别降低17%和36%。

计及调速系统详细模型和调频备用的大扰动下频率最低值预测方法

随着新能源占比的提升,系统惯性降低、调频资源减少,系统频率稳定问题严峻。因此在新型电力系统运行方式多变的背景下,如何快速精准评估大功率扰动下系统频率安全指标显得尤为重要。其中频率最低值指标由于与多种参数存在高度非线性且无法显式表达的量化关系而难以实现快速准确预测,是频率稳定安全指标评估的研究重点。然而,目前频率最低值快速预测方法难以考虑调频备用的影响。为此,基于系统频差曲线抛物线近似的假设,对平均系统频率(average system frequency,ASF)模型进行开环解耦,进一步得出系统频率最低值时间与调速器输出功率之间的量化关系,最终实现考虑调频备用容量的频率最低值快速预测方法。该方法在小系统和ACTIVSg2000算例上的预测精度分别为99.28%和97.71%,算例结果证明了算法的有效性。该方法对频率安全约束下机组组合、频率稳定控制措施的有效性评估以及频率稳定约束下系统新能源运行承载能力评估等问题具有重要意义。