PMU based voltage security assessment of power systems exploiting principal component analysis and decision trees

The need for feature selection and dimension reduction is felt as a fundamental step in security assessment of large power systems in which the number of features representing the state of power grids dramatically increases. These large amounts of attributes are not proper to be used for computational intelligence (CI) techniques as inputs, because it may lead to a time consuming procedure with insufficient results and they are not suitable for on-line purposes and updates.This paper proposes a combined method for an online voltage security assessment in which the dimension of the token data from phasor measurement units (PMUs) is reduced by principal component analysis (PCA). Then, the features with different stability indices are put into several categories and feature selection is done by correlation analysis in each category. These selected features are then given to decision trees (DTs) for classification and security assessment of power systems.The method is applied to 39-bus test system and a part of Iran power grid. It is seen from the results that the DTs with reduced data have simpler splitting rules, better performance in saving time, reasonable DT error and they are more suitable for constant updates.     

弹性波衍射CT

本文直接从等价于弹性动力学Ｎａｖｉｅｒ方程的耦合齐次与非齐次矢量波动方程组出发，围绕弹性波衍射ＣＴ展开了理论研究，尤其是其非齐次方程含有震源项，同时适合Ｐ波和Ｓ波，考虑爆炸震源，引进塑性半径，运用张量运算，推导了Ｂｏｒｎ近似下散射波谱与目标函关系，得到二种数据采集方式下的层析成像ＦＢＰ公式，可同时适用于Ｐ波和Ｓ波，尽管与以往不涉及震源项的结果相似，但本结果更符合地震勘探情况。     

图像处理中自适应数学形态学的研究

实际图像处理中当视场的变化引起目标变形时,固定大小的形态学算子很难达到较好的处理效果。研究了利用距离变换自适应地调整结构元大小的方法,即根据图像的不同位置来调整结构元素的大小,从而实现图像的形态学运算,并由此推导出了快速计算方法,最后测试了这种新算法的有效性。实验结果表明,该算法取得了较为理想的效果。     

影响DT岩石粉状铵梯炸药爆速的因素探索

文章从ＤＴ岩石粉状铵梯炸药的原材料细度，复合油相，混药时间，投料顺序，混药药温，装药密度等方面，探讨了该炸药爆速的影响因素。     

Diffusion tensor interpolation profile control using non-uniform motion on a Riemannian geodesic

Tensor interpolation is a key step in the processing algorithms of diffusion tensor imaging (DTI), such as registration and tractography. The diffusion tensor (DT) in biological tissues is assumed to be positive definite. However, the tensor interpolations in most clinical applications have used a Euclidian scheme that does not take this assumption into account. Several Rie-mannian schemes were developed to overcome this limitation. Although each of the Riemannian schemes uses different metrics, they all result in a ‘fixed’ interpolation profile that cannot adapt to a variety of diffusion patterns in biological tissues. In this paper, we propose a DT interpolation scheme to control the interpolation profile, and explore its feasibility in clinical applications. The profile controllability comes from the non-uniform motion of interpolation on the Riemannian geodesic. The interpolation experiment with medical DTI data shows that the profile control improves the interpolation quality by assessing the reconstruction errors with the determinant error, Euclidean norm, and Riemannian norm.     

一种基于混合决策树的调度知识获取算法*

提出了一种基于混合决策树的调度知识获取算法。将模拟退火算法融入遗传算法中,作为一种具有自适应变概率的变异操作,构成一种混合优化方法。利用这种混合方法求解在不同调度目标下制造系统的最优特征子集,同时确定控制决策树规模的最优参数;使用决策树评价混合方法中染色体编码的适应度,在得到不同调度目标下的最优特征子集和最优决策树参数后,生成调度知识。仿真实验结果表明,该算法在性能上优于其他算法。     

一种改进AVQ的主动队列算法

在讨论了各种算法的基础上，分析和比较了现有的几种主动队列管理算法：随机早期检测算法（RED），自适应RED算法（ARED），自适应虚拟队列（AVQ）算法，动态阈值（DT）算法以及队列长度阈值（QLT）的分组调度算法等，并对AVQ算法进行了改进，将原算法维持单个虚拟队列改为维持多个虚拟队列，从而使其在原性能的基础上增加了区分服务的功能，以达到适应下一代网络发展的需要。     

多站数据采集在探地雷达中的应用

由于地下介质组成相当复杂,且具有非均匀、损耗和色散等特性,以及各种杂散回波的存在,探地雷达(GroundPene-tratingRadar,GPR)信号处理与一般的空间雷达有较大差别,其成像效果不尽如人意。本文将衍射层析成像(DiffractionTo-mography,DT)中的多站数据采集应用在探地雷达中来实现高质量成像,并经过数值验证,说明了多站数据采集较传统单站数据采集有很大的优越性。     

Data-mining model based adaptive protection scheme to enhance distance relay performance during power swing

The paper presents a data-mining model based adaptive protection scheme enhancing distance relay performance during power swing for both compensated and uncompensated power transmission networks. In the power transmission network, the distance relays are sensitive to certain system event such as power swings, which drive the apparent impedance trajectories into the protection zones of the distance relay (zone-3) causing mal-operation of the distance relay, leading to subsequent blackouts. Further, three-phase balanced symmetrical fault detection during power swing is one of the serious concerns for the distance relay operation. This paper proposed a new adaptive protection scheme method based on data-mining models such as DT (decision tree) and RF (random forests) for providing supervisory control to the operation of the conventional distance relays. The proposed scheme is able to distinguish power swings and faults during power swing including fault zone identification for series compensated power transmission network during stress condition like power swing. The proposed scheme has been validated on a 39-bus New England system which is developed on Dig-Silent power factory commercial software (PF4C) platform and the performance indicate that the proposed scheme can reliably enhance the distance relay operation during power swing.     

采用纯铁中间层热轧钛合金/不锈钢复合板显微结构和性能

针对钛/不锈钢不易直接热轧复合的问题,通过添加工业纯铁为中间层材料,采用真空轧制的方法制得钛合金/不锈钢复合板。利用扫描电子显微镜、能谱仪、X射线衍射仪和拉剪实验,研究纯铁中间层和不同温度对复合板界面组织特征和性能的影响。结果表明:添加纯铁中间层后,在轧制温度为750～950℃、压下率为20%时,随着轧制温度的升高,复合面抗剪切强度增加,在轧制温度为950℃时,复合效果最好,复合界面抗剪切强度达到248 MPa;在高温1050℃时,纯铁和钛合金的交界面上生成β-Ti和Fe_2Ti化合物会降低复合强度。