Performance analysis of single relay selection in cooperative communication over Nakagami-m fading channels

We derive closed-form expressions for outage probability and symbol error rate(SER) of opportunistic relaying(OR) and selection cooperation(SC).For the amplify-and-forward relay selection scheme,comparison between two selection strategies over independent non-identically distributed Nakagami-m fading channels via analytical and simulation results is given in terms of the outage probability and SER.Simulation results show that OR performs better than SC.     

全双工中继选择策略的性能研究

为了提高协同通信系统的频谱效率,对全双工中继通信系统进行了研究.首先,介绍了传统的主动机会中继策略和最优的全双工中继选择策略,并在最优全双工中继选择策略的基础上提出了增强型全双工中继选择策略;其次,分析了主动机会中继选择策略应用在全双工中继网络中的中断性能,推导了3种策略中断概率的闭式精确结果和高信噪比(SNR)下的近似逼近结果;最后,通过数值仿真分析验证了理论推导结果的正确性.研究结果表明:在高SNR范围时,最优全双工中继选择策略和主动机会中继选择策略的中断性能趋于平台效应;增强型全双工中继选择策略的中断性能会随着SNR的增大而一直提高,且增强型全双工中继选择策略的中断性能明显最优,主动机会中继选择策略的性能最差.      

Performance Analysis of AF Relaying Based on Water-filling Power Allocation over Nakagami-m Fading

This paper investigates exact performance of an amplify-and-forward(AF) relay system based on water-filling power allocation in Nakagami-m fading environment, where m is a nonnegative integer plus one half.We first offer the cumulative distribution function(CDF) and probability density function(PDF) of the received signal-to-noise ratio(SNR) at a destination. Then outage probability, moments of SNR, higher-order statistics of the capacity are explicitly conducted. Especially, average symbol error rate(SER) under an additive white generalized Gaussian noise(AWGGN) is developed for water-filling power allocation scheme. While the average SER subjected by an additive white Gaussian noise(AWGN) can be regarded as a special case. Finally, all theoretical formulas are truly attested by various simulation results.     

基于改进合同网的多Agent系统协作机理研究

针对传统合同网协作模型的不足和舰船动力辅助系统的特点,从三个方面对合同网加以改进,给出了一种适合于舰船动力辅助系统多Agent控制系统的改进合同网模型,该模型不但能够提高协作效率,而且能够有效的解决被控系统在突发事件和故障状态下的交互协作问题.以简化的冷却水系统为例,以JADE为开发平台,将该模型应用于其多Agent控制系统开发中,通过仿真模拟了Agent之间的协作过程,并将协作结果与理论结果比较验证了其正确性,为深入研究多Agent系统的协作机理提供了通用的方法.     

Performance analysis of AF relaying based on water-filling power allocation over Nakagami-<Emphasis Type="Italic">m</Emphasis> fading

This paper investigates exact performance of an amplify-and-forward (AF) relay system based on water-filling power allocation in Nakagami-m fading environment, where m is a nonnegative integer plus one half. We first offer the cumulative distribution function (CDF) and probability density function (PDF) of the received signal-to-noise ratio (SNR) at a destination. Then outage probability, moments of SNR, higher-order statistics of the capacity are explicitly conducted. Especially, average symbol error rate (SER) under an additive white generalized Gaussian noise (AWGGN) is developed for water-filling power allocation scheme. While the average SER subjected by an additive white Gaussian noise (AWGN) can be regarded as a special case. Finally, all theoretical formulas are truly attested by various simulation results.     

CDMA 网络中基于 QoS 保证的呼叫接纳控制策略

基于CDMA（code division multipleaccess）系统接纳控制（call admission control，CAC）机制没有完全考虑各种多媒体业务的现状，研究了CDMA系统中剩余容量的计算方法，采用更加符合目前无线多媒体网络中业务实际情况的业务模型，给出了一种针对多媒体业务的基于QoS（quality of service）保证的动态CAC算法．分析与仿真结果表明，该算法在保证各种业务QoS要求的情况下，可以显著改善CDMA系统的呼叫等待延时和中断率等性能，提高系统资源的利用率．     

Outage performance of amplify-and-forward multiple-input multiple-output relay networks with outdated channel state information and co-channel interference

In this paper, we investigate the outage performance of a dual-hop amplify-and-forward(AF) multipleinput multiple-output(MIMO) relay network, considering beamforming transmission with outdated channel state information(CSI) and an arbitrary number of co-channel interferers at both the relay and the destination. The exact closed-form expression for the outage probability is derived, and the asymptotic behavior of the outage probability is also presented to provide further insights into the system performance. Our results show that the system suffers a diversity gain loss caused by the outdated CSI, and the interference only degrade the coding gain of the system. Moreover, increasing antennas can achieve more performance gains, however, the gains decrease as the delay of the CSI increases.     

Nataf变换的桥梁系统多维地震易损性分析方法

在多维性能极限状态理论框架下,考虑桥梁各构件地震响应参数相关性,引入Nataf变换,提出了改进的桥梁系统多维地震易损性分析方法;以一座三跨V撑连续梁桥为例,利用OpenSees软件建立桥梁系统非线性动力分析模型,从美国太平洋地震研究中心强震数据库中选取20条地震波进行增量动力分析,并获得桥梁结构在地震作用下的最大响应样...     

基于风险网络的轨道交通车辆风险评价

针对轨道交通车辆系统的风险网络和关键部件风险评价开展研究，以系统部件和部件连接关系作为节点和边，建立了风险网络模型，分析了节点固有风险的影响因素和计算方法.根据节点之间故障传播概率得到边的作用强度和路径风险.对节点固有风险和路径风险进行分析，得到节点综合风险，并通过幂法对节点综合风险进行求解，从而识别部件对系统的影响程度.以转向架系统为例进行综合风险计算，结果表明：部件固有风险大小不能完全决定综合风险大小，还与部件连接关系和作用强度相关；与实际经验得出的关键部件综合风险排序对比，利用本文方法得到的关键部件排序一致性与其他方法相比有明显提升.     

基于风险网络的轨道交通车辆风险评价

针对轨道交通车辆系统的风险网络和关键部件风险评价开展研究，以系统部件和部件连接关系作为节点和边，建立了风险网络模型，分析了节点固有风险的影响因素和计算方法.根据节点之间故障传播概率得到边的作用强度和路径风险.对节点固有风险和路径风险进行分析，得到节点综合风险，并通过幂法对节点综合风险进行求解，从而识别部件对系统的影响程度.以转向架系统为例进行综合风险计算，结果表明：部件固有风险大小不能完全决定综合风险大小，还与部件连接关系和作用强度相关；与实际经验得出的关键部件综合风险排序对比，利用本文方法得到的关键部件排序一致性与其他方法相比有明显提升.     

First passage probability of structures under non-Gaussian stochastic behavior

An analytical moment-based method was proposed for calculating first passage probability of structures under non-Ganssian stochastic behaviour. In the method, the third-moment standardization that constants can be obtained from first three-order response moments was used to map a non-Ganssian structural response into a standard Gaussian process; then the mean up-crossing rates, the mean clump size and the initial passage probability of some critical barrier level by the original structural response were estimated. Finally, the formula for calculating first passage probability was established on the assumption that the corrected up-crossing rates are independent. By a nonlinear single-degree-of-freedom system excited by a stationary Gaussian load,it is demonstrated how the procedure can be used for the type of structures considered. Further, comparisons between the results from the present procedure and those from Monte-Carlo simulation are performed.     

基于实测数据的高铁牵引变电所负序电流概率分析

为了研究高速铁路牵引供电系统三相电流不平衡问题, 通过分析高速铁路牵引供电系统负荷及V/v接线牵引变压器负序电流,基于概率理论建立了牵引变电所负序电流的概率分析模型.用该模型对京沪高铁某牵引变电所的负序电流进行了仿真分析和实测数据验证,结果表明,利用该牵引变电所的设计参数仿真得到的负序电流概率分布与利用实测数据的分析结果一致,该牵引变电所负序电流概率分析模型能够真实地模拟高速铁路牵引变电所的负序电流分布情况.      

系统风险的概念及其计算方法

本文在风险概念的基础上,从风险的特性出发,阐述了风险的本质,并重新定义了风险的含义,对风险的内涵作了进一步延伸和扩展,指出风险是系统不利事件对作用对象的影响程度。衡量这种影响程度需要从不利事件发生的概率以及后果两个方面来刻画。由于不利事件的发生以及作用后果具有不确定性,因此刻画影响程度需要从特征量角度进行分析和计算,给出了风险特征量计算方法。本文提出的风险计算比经典风险的计算更能反映风险的本质,最后给出了系统不利事件发生概率的估计方法。     

Supply Chain Cooperation between Coal Enterprise and Electric Power Enterprise in China

Based on the two-stage Stackelberg game method, value creation of supply chain cooperation between coal enterprise and power utilities is studied by formulating profit functions of coal and power enterprises and calculating the maximum profit. According to the analysis, it is found that the profit from supply chain cooperation between coal and power enterprises is more than that of non- cooperation. The cooperation is validated to be beneficial for both units; however, the profit is mainly taken by the power enterprise. Thus, it is necessary to set up the incentive mechanism to distribute cooperation value between coal and power enterprises to promote their continual cooperation.     

供应链中的企业合作强度

提出评价供应链绩效的供应链企业合作强度的新概念.影响企业间合作强度的主要因素是供应链中企业的竞争力和合作企业之间的合作阻力系数.假设企业合作强度与企业竞争力成正比,与企业合作阻力系数成反比,构建了企业合作阻力系数的计算方法.在此基础上构建了供应链相邻节点企业之间和企业整体合作强度的计算模型.计算模型中考虑了综合收益和综合成本两个参数,并分别针对整个合作过程提出了具体的计算方法.     

A Practical Adaptive TuCM Scheme for Rayleigh Flat Fading Channels

IntroductionAs stated in Ref.[1 ],if the channel state isknown atthe transmitter,then channel capacity isachieved by adapting the transmit power,data rateand coding scheme relative to this fade state.Based on those results,an uncoded adaptive modu-lation was proposed[2 ] .This adaptive modulation is1 7d B more power efficientthan non- adaptive mod-ulation in fading.Combining trellis coded modula-tion ( TCM) with adaptive modulation,an adaptivecoded modulation was studied[3 ] .The results sh…     

燃料电池小型车SOC动态调节的功率跟随控制策略

针对风冷型质子交换膜燃料电池与锂电池组成的小型车用混合动力系统,提出一种根据SOC(state of charge)动态调节功率跟随系数的能量管理方法,完成混合动力观光车样车研制.对构成样车的混合动力系统、氢气储存供给系统、信号控制系统3部分进行了详细阐述,并对不同工况下功率跟随算法调节系数对控制效果的影响进行了分析;...     

风力发电塔系统整体建模与模态分析研究

为了判断风力发电塔系统是否能避开共振,需对其进行模态分析。提出了考虑“桨叶-轮毂-机舱-塔筒”耦合的整体建模的方法,可用于风力发电塔系统模态的计算。分别进行了停机阶段、运行阶段和切出阶段的模态分析,对比其频率和固有振型。对比结果表明：三个阶段的频率基本相同,只须验算停机状态下的频率满足规范即可;塔筒的振动形式主要为侧向弯曲振动、前后弯曲振动和扭转振动;桨叶在前十阶的振动形式主要为挥舞振动和摆振,且三桨叶振动存在一定的规律;相对于停机阶段,运行阶段时振型基本相同,切出阶段时振型有较大差异。     

三端口双向直流变换器的负序平衡应用

基于三端口双向直流变换器能实现各端口之间有功能量自由传输的特点,提出了其在负序电流平衡方面的新型应用方法及电路拓扑．该方法克服了传统负序电流平衡方法不能实现三相桥臂之间有功能量交换的问题,能有效改善三相电网的不平衡问题．本文对三端口双向直流变换器工作原理、负序电流平衡方法,以及基于该方法的负序平衡系统容量关系进行了详细分析,提出了系统控制策略．通过仿真验证了三端口双向直流变换器负序平衡应用的可行性及系统控制策略的有效性．在合适的控制策略下,本拓扑能同时实现包括负序、无功和谐波电流在内的综合补偿．     

基于ANP—Fuzzy方法的物流服务供应链流程对接绩效评价

分析了物流服务供应链协同运作的特点,从流程对接前、中、后3个时间段出发,建立了物流服务供应链协同运作流程对接评价指标体系．在评价方法上,综合考虑ANP和模糊评价法的优点,采用ANP方法来确定各指标的权重,用模糊评价法对各指标原始得分进行评价,建立ANP—Fuzzy综合绩效评价模型,并进行了算例分析．结果表明,该方法可以定量地评价物流服务供应链流程对接绩效,具有一定的推广价值．