电磁脉冲对埋地电缆耦合的FDTD仿真分析

以有限埋地电缆为研究对象,依据电磁场理论和时域有限差分法建立了物理分析模型.采用多区域FDTD方法对埋地电缆进行分析,通过编程计算出仿真结果,该结果与实测数据比较一致,验证了该方法的正确性.     

计及静态安全风险的输电网短期综合扩展规划

为兼顾输电规划的经济性与可靠性,建立了计及静态安全风险的输电网短期有功和无功综合扩展规划的数学模型,模型中将线路与无功补偿设备投资的年值费用、年运行费用及年风险费用总和作为目标函数,计及了预想事故发生的概率和交流潮流约束。为了基于交流潮流模型进行静态安全风险评估,提出了一种基于有功静态安全域和电压灵敏度循环迭代的2阶段削负荷方法。首先确定最优校正性控制下的负荷削减量,进而用损失电量的社会产值来衡量风险费用。为应对模型求解计算上的复杂性,给出了一个2阶段寻优算法,该法不仅降低了原问题的求解难度,而且最终可获得若干数目的满意解,辅助规划人员决策。通过巴西南部46节点系统算例验证了模型的合理性和算法的有效性。     

A search game model of the scatter hoarder's problem

Scatter hoarders are animals (e.g. squirrels) who cache food (nuts) over a number of sites for later collection. A certain minimum amount of food must be recovered, possibly after pilfering by another animal, in order to survive the winter. An optimal caching strategy is one that maximizes the survival probability, given worst case behaviour of the pilferer. We modify certain ‘accumulation games’ studied by Kikuta & Ruckle (2000 J. Optim. Theory Appl.) and Kikuta & Ruckle (2001 Naval Res. Logist.), which modelled the problem of optimal diversification of resources against catastrophic loss, to include the depth at which the food is hidden at each caching site. Optimal caching strategies can then be determined as equilibria in a new ‘caching game’. We show how the distribution of food over sites and the site-depths of the optimal caching varies with the animal''s survival requirements and the amount of pilfering. We show that in some cases, ‘decoy nuts’ are required to be placed above other nuts that are buried further down at the same site. Methods from the field of search games are used. Some empirically observed behaviour can be shown to be optimal in our model.     

面向跨语言词云可视化的拓扑布局算法研究

针对大范围替换词云中单词后出现的词云拓扑结构不稳定的现象,提出一种词云可视化的拓扑保持布局算法。首先,该算法通过对替换后的词云中单词进行分散处理,使之前或重叠远离的单词按原拓扑相应分离;再利用Delaunay三角剖分算法对离词云风格化,形成控制风格;最后在控制风格的基础上采用紧凑布局的方法将分散词云紧凑为与替换前原词云拓扑一致的词云布局。针对替换的一种具体情况,即跨语言翻译词云的情况做详细介绍。该算法在提高词云而已稳定性,保持原词云拓扑结构方面是一个新的突破。     

具有资源约束的项目调度问题中的量子进化算法

为了将量子进化思想应用到具有资源约束的项目调度领域中,提出了一种基于活动对连接关系的调度解表示方法,进而构成新的搜索解空间。利用新表示方法的二值性,给出了量子进化算法。该算法扩展了前向-后向搜索思想,构造出原问题的反向问题,并把原问题和反向问题以同样的方式进行求解,利用反向搜索一个方向上的解群来更新另一个方向上的解群。此外,算法根据分散搜索的思想,利用新搜索解空间中定义的距离来控制搜索的分散性。最后,通过仿真说明了该算法的有效性。     

纯铜径向微压缩塑性变形行为尺寸效应

对不同晶粒尺寸的纯铜多晶体圆柱试样,开展径向微压缩试样。实验结果表明,随着晶粒尺寸的增大,成形力减弱,分散性增大,并出现不规则表面。提出了基于表层晶粒位错堆积的修正表层模型和基于标准偏差理论和晶粒尺寸分布的流动应力波动性公式,分析了微压缩变形中的成形力尺寸效应。从表层晶粒以旋转为主要变形模式的角度,讨论了表层晶粒非均匀塑性变形。与实验结果吻合很好。     

Rolling contact fatigue life model incorporating residual stress scatter

There has been a considerable body of research concerned with predicting the service life of rolling contact components. It is well known that the prevailing cause of failure in rolling contact components is fatigue crack. Although the trend has been toward the use of surface integrity in fatigue life prediction, one aspect missing in most models has been a consideration of the residual stress scatter in the subsurface. Since the fatigue life of a manufactured component depends on its weakest point, the local extreme is most relevant for the fatigue life prediction. This study thus incorporates the residual stress scatter into the rolling contact fatigue life model to predict the fatigue life closer to the experimental life. It is noted that residual stresses vary significantly at the same depth. After the residual stress scatter is incorporated into the model, the predictions agree well with the experimental lives.     

Assessment of damage in structural steels by the parameters of scatter of hardness characteristics in loaded and unloaded states

The authors discuss new experimental data on hardness of structural steels 25, 45, and 0N9, which were obtained for flat specimens subjected simultaneously to uniaxial tension, including the cases of intermittent unloading at various levels of residual strain. Based on numerous measurements (up to 30), mean values of hardness and their Gumbel scatter parameters have been determined for specimens in the loaded and unloaded states. The paper substantiates the procedure of determination of indices of sensitivity of measured hardness values and their scatter to loading conditions, which make it possible to refine the hardness characteristics as measured during technical diagnostics of equipment in operation. __________ Translated from Problemy Prochnosti, No. 3, pp. 29–37, May–June, 2008.     

基于两空间核鉴别分析的人脸识别

指出了几种线性鉴别分析方法在处理小样本人脸识别问题时存在的不足,结合核方法的思想,提出了一种基于两空间核鉴别分析的人脸识别方法.首先使用KPCA方法在核变换后的特征空间中对样本进行处理;进面将变换后的类内散布矩阵分成非零空间和零空间进行鉴别向量确定和鉴别特征提取,最后将得到的两种鉴别特征融合,从而使用最近邻法进行分类....     

利用EXCEL2000中的图表工具绘制硫化橡胶的老化动力学变化曲线

通过经验公式对硫化橡胶老化试验数据进行拟合,然后根据经验公式的拟合值,用EXCEL中的图表工具作出硫化橡胶的老化动力学变化曲线,以期反映硫化橡胶的动力学变化规律。