某网络设备EMC 测试超标的分析和结构优化

某设备带插卡EMC测试中辐射超标,文中从插卡PCB和机箱导槽的电容耦合效应入手,分析了EMC测试超标的原因,通过在机箱导槽和PCB之间设计一个铍铜弹性夹片零件,增强了PCB的单板地和机箱之间的电气连接可靠性,从而有效减少了电磁波的电容耦合效应,解决了EMC测试超标问题。同时运用有限元分析方法并进行样品实物测试对比,分析了该铍铜弹性夹片零件在实际生产应用中出现的夹持不可靠问题的原因,并通过更换合适的铍铜材料型号和选择正确的热处理方式解决了该零件的夹持不可靠问题。     

FPGA设计中的亚稳态及其缓解措施

亚稳态是异步数字电路设计中的固有现象。针对FPGA产品研制中的亚稳态问题,分析了其产生的原因,阐述了亚稳态对系统可靠性的影响和评估方法,并针对单比特异步传输、多比特异步传输和复位三种情况下的亚稳态提出缓解措施。该措施可以在工程实践中参考使用。     

南四湖水体富营养化时空比较分析与评价

南四湖是南水北调东线工程重要的输水通道和调蓄湖泊之一,随着通水时间的临近,其水质安全和水体富营养化状况备受关注．根据2006、2007、2010和2011年4次32个采样点的南四湖水质空间分布监测数据,采用综合营养状态指数法进行评价．结果表明,4个监测年枯水期南四湖水体总体平均处于富营养轻度水平,在南四湖水质得到大幅度改善的情况下,各年营养水平变化不大;南阳湖和独山湖水体的综合营养状态指数出现下降趋势,而昭阳湖（下）和微山湖岛北水体的综合营养状态指数出现上升趋势,这与全湖总磷出现均一化趋势有关．2010-2011年除微山湖岛南水体处于中营养水平外,其他湖区水体均处于富营养轻度水平．对南四湖水质空间分布监测数据的分析表明,南四湖藻类水华的繁殖生长主要受水体中TP的制约．     

稳态分数阶Kalman滤波器

基于CARMA新息模型对线性离散分数阶状态空间系统提出一种稳态分数阶Kalman滤波器。分数阶描述比整数阶描述更精确,所提出的滤波器相比已有的整数阶系统的相关研究结果更具普遍性和实用性。仿真实例表明了该滤波器的有效性。     

双重迭代变分贝叶斯自适应卡尔曼滤波算法

提出了一种新的自适应卡尔曼滤波算法。该算法假设系统过程噪声方差和量测噪声方差之间存在的函数关系已知,两种噪声方差随着时间变化且均未知。先令当前时刻的过程噪声方差等于前一时刻的过程噪声方差,通过变分贝叶斯近似的方法,在卡尔曼滤波框架下迭代求解当前时刻的量测噪声方差和状态估计,再利用假设中的函数关系获得新的过程噪声方差。对上述过程多次迭代,最终获得状态估计及协方差。仿真实验结果表明,该算法具有较高的滤波精度;在假设条件不确知的情况下仍具有较强的鲁棒性。     

一种与材料状态相关的砂土剪胀性理论模型

结合密砂和中密砂的相变点的概念,提出了以相变状态为参考状态的状态参量表达式,并将此状态参数引入剪胀比的计算公式.在修正剑桥模型的基础上,提出了新的塑性势函数和硬化参数表达式以消除应力路径的影响.在增量塑性理论的基础上,建立了一种适合于密砂和中密砂的与材料状态相关的剪胀性理论模型.     

Optimization of axial symmetrical FGM under thetransient-state temperate field

A numerical procedure for analyzing the temperature distribution in a hollow axisymmetric cylinder,made of functionally gradient material (FGM),was investigated.Based on the thermal elasticity theory and the arbitrary difference precise integration (ADPI) method,temperature distribution through the FGM cylinder in the ring section under a transient-state temperature field was developed and presented.A genetic algorithm (GA) was applied to the thermal stress optimal design of an FGM hollow cylinder,and as a result,the minimum thermal stress distribution in the FGM cylinder was obtained.A corresponding numerical procedure regarding to a ceramic-metal FGM cylinder was performed,and the computational results were discussed.     

MSMSE-based optimal beamforming design and simplification on AF MIMO two-way relay channels

An optimal cooperative beamforming for the amplify-and-forward (AF) MIMO two-way relay channels was designed. Supposing the channel state information (CSI) was perfectly known by the receiver and transmitter as well as the relay, optimal beamforming vectors (matrices) of all nodes were jointly designed based on the criterion of minimizing the sum mean square errors (MSMSE). The analysis result shows that the performance effect of transmitting and receiving beamforming pairs is to maximize the receive signal-to-noise ratio (SNR) at two communication nodes, and the rank of the optimal relay beamforming matrix is no larger than two when there is only one data stream at each source node. A simplified algorithm was put forward to accomplish the design based on the analysis conclusions. Simulation results provide that the system performance, which is characterized in terms of bit error rates (BER), is significantly improved by cooperative beamforming, and the performance of the simplified method is not only very close to the optimal one but also with faster iteration speed and much lower computational complexity.     

航天军转民数据库

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