奥氏体化时间对AISI 4340钢贝氏体连续转变动力学的影响

利用AISI 4340钢热膨胀实验,研究了奥氏体化时间对贝氏体连续转变动力学的影响.将热膨胀试样加热到950℃,经10-120min奥氏体化,在20s内迅速冷却到550℃,在随后的120min缓慢冷却到350℃,然后以100℃/s迅速冷却至室温.贝氏体连续冷却转变起始温度（Bs）和50%转变温度（Bm）随奥氏体化时间而显著增加,贝氏体相变结束温度（Bf）几乎不变.Bs可能与AlN等碳、氮化合物粒子在原奥氏体晶界的析出及合金元素的作用有关.贝氏体连续冷却转变速率随贝氏体体积分数的变化可以分成三个阶段：快速增长阶段、缓慢减小阶段和快速减小阶段.产生这种现象的原因可能是由于在连续转变过程中温度的降低、碳的扩散及合金元素的作用等造成的.     

基于轨迹灵敏度的暂态稳定约束最优潮流计算

为将暂态稳定约束最优潮流问题转化为最优潮流和暂态稳定两个子问题,根据暂态稳定计算结果求出发电机转角及转速相对于机械输入功率的轨迹灵敏度。基于轨迹灵敏度,计算出在最领先发电机和最落后发电机之间转移的有功功率,据此修改其在最优潮流模型中的有功功率上下限,从而实现两个子问题的交替求解。并且推导出准确的轨迹灵敏度及初值计算公式,利用上述公式,得更小的转移功率值,从而使功率转移后系统的优化程度更高。同时在惯性中心坐标下采用最大转角判据找出最领先机和最落后机,并以3机9节点和10机39节点系统为例,验证了该方法的可行性。     

基于GPU的Viterbi并行解码算法的设计与实现

针对GPU并行计算特征,对Viterbi解码自身做了并行处理探索,并提出使用Zero-Termination卷积码来实现基于GPU的Viterbi解码分块并行处理.设计的实现结果表明:Zero-Termination卷积码的简单而适用于GPU分块并行;误码率降低,特别是在信噪比低的情况下,Zero-Termination卷积码误码率比不损失码率的卷积码要低.同时,还实现了基于GPU的7,9,15三种不同约束长度的Viterbi解码,获得了良好的误码性能曲线及高吞吐率表现.     

NEURAL NETWORK MODELING FOR ESTIMATION OF SCOUR DEPTH AROUND BRIDGE PIERS

It is essential to predict the scour depth around bridge piers for hydraulic engineers involved in the economical design of bridge pier foundation. Conventional investigations have long been of the opinion that empirical scour prediction equations based on laboratory data over predict scour depths. In this article, the Back-Propagation Neural Network (BPN) was applied to predict the scour depth in order to overcome the problem of exclusive and the nonlinear relationships. The observations obtained from thirteen states in USA was verified by the present model. From the comparison with conventional experimental methods, it can be found that the scour depth around bridge piers can be efficiently predicted using the BPN.     

暂态能量函数法在地区电网黑启动辅助决策中的应用

电网黑启动是一个包含了发电厂启动、电网调度和运行的复杂动态过程，其电网路径及孤立电网闭环点的选择一直是困扰调度人员的核心问题。由于黑启动中的电网处于孤立状态，其暂态稳定性是衡量电网强壮程度的一个重要指标，文中提出利用暂态能量函数法对黑启动路径和闭环等问题进行量化分析和择优选择。根据该方法编制的黑启动辅助决策软件已成功应用于广东多个地方电网的黑启动方案设计中，通过2个应用实例说明了该方法的有效性。     

基于非线性 PCA的微气体传感器阵列信号处理

在线性叠加模型基础上提出了气体传感器对混合气体的非线性叠加模型,并引入了非线性主成分分析(Nonlinear Principal Component Analysis,NLPCA)法对微传感器阵列的信号进行处理。使用该模型对由4个微热板式气体传感器组成的阵列的信号进行了分析,对照基于线性叠加模型的主成分分析法(Principal Component Analysis,PCA)的识别结果,说明该方法能够提高对混合气体识别和量化的准确度。     

Load selection of automated guided vehicles in flexible manufacturing systems

This paper examines the operation of multiple-load AGVs in a flexible manufacturing system where AGVs in the system are capable of carrying two or more loads. The load selection problem arises when an AGV stops at a pick-up queue and has to decide which part(s) should be picked up. Five heuristic rules that may be used to select the load to be carried were suggested and evaluated under a hypothetical flexible manufacturing system with the aid of computer simulation. The results revealed that the variable-route-part-priority (VP) rule and fixed-route-part-priority (FP) rule generated significantly higher throughput than their counterparts, while the ’pick-all-send-nearest’ (PN) rule outperformed the other rules in part flowtime and work-in-process level. The results also suggest that when the carrying capacity of the AGV increases, the performance differences among the rules also increase. This finding sustains the need to explore an efficient operation strategy of multiple-load AGVs in flexible manufacturing systems.     

观光车环境感知系统的探讨与分析

阐述了观光车装备环境感知系统的意义,对实现环境感知系统所需的传感器进行了探讨与分析,最终设计了视频摄像头结合毫米波雷达组成环境感知的硬件系统,并对此多传感器系统的数据融合给出了要求和方法。     

The relationship between sensitisation and small punch test behaviour in a high-nitrogen austenitic stainless steel at cryogenic temperatures

Austenitic stainless components used in nuclear fusion reactors must be capable of maintaining reasonable mechanical properties to thermal ageing caused by welding and in‐service. Recently, high‐nitrogen (High‐N) austenitic stainless steels (SS) are receiving increased attention because of their strength advantages, but they have been found to be susceptible to dichromium nitride (Cr₂N) precipitation during thermal exposure at 823–1073 K. The susceptibility to sensitisation at thermal ageing temperature for high‐N austenitic SS is examined using the single‐loop electrochemical potentiokinetic reactivation (EPR) test. High‐N SS were found to be susceptible to sensitisation caused by grain boundary precipitation of Cr₂N, with the degree of sensitisation increasing systematically with ageing time and temperature. In particular, it was found that the precipitates, which effected sensitisation, were changed from carbides (M₂₃C₆) to nitrides (Cr₂N) with increasing ageing time and temperature. The deterioration of mechanical properties associated with thermal ageing in high‐N SS was investigated by a small punch (SP) test using miniature specimens at cryogenic temperatures. Results indicated that the degradation of mechanical properties in this alloy was caused by a decrease of cohesive strength resulting from carbides (Cr₂₃C₆) and nitrides (Cr₂N) precipitated in grain boundaries.