A novel method of suppressing the inrush current of transformers by using a series‐connected voltage‐source PWM converter

This paper proposes a novel method of suppressing the inrush current of transformers. A small‐rated voltage‐source PWM converter is connected in series to the transformers through a matching transformer. As the connected PWM converter serves as a resistor for the source current, no inrush phenomena occurs. The required rating of the PWM converter, which serves as the damping resistor for the inrush phenomena, is 1/400 that of the main transformers in single‐phase circuits. In three‐phase circuits, it is 1/900. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 56–65, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20174     

Connecting parameters optimization on unsymmetrical twin-tower structure linked by sky-bridge

Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge, the frequency response functions, the displacement power spectral density （PSD） functions, and the time-averaged total vibration energy were derived, by assuming the white noise as the earthquake excitation. The effects of connecting parameters, such as linking stiffness ratio and linking damping ratio, on the structural vibration responses were then studied, and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure. The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed. Finally, the distribution characteristics of the top displacement PSD and the structural responses, excited by El Centro, Taft and artificial waves, were compared in both frequency and time domain. It is found that the connecting parameters at either end of connection interactively affect the responses of the towers. The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness, but are unable to reduce the seismic responses of the towers to the best extent simultaneously. It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers. The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio. The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.     

REMARKS ON JOHN DISKS

Let D■R2 be a Jordan domain,D*=R2\D,the exterior of D.In this article,the authors obtained the following results:(1)If D is a John disk,then D is an outer linearly locally connected domain;(2)If D* is a John disk,then D is an inner linearly locally connected domain;(3)A homeomorphism f:R 2 →R 2 is a quasiconformal mapping if and only if f(D)is a John disk for any John disk D■R 2 ;and(4)If D is a bounded quasidisk,then D is a John disk,and there exists an unbounded quasidisk which is not a John disk.     

一个计算网络可靠度的递归算法

给出一个计算网络可靠度的有效算法,该算法的特点是结合概率论的有关知识和布尔代数运算：递归地调用一个简单、有效的概率公式来计算网络可靠度。该算法易于在计算机上操作和实现,从而适用于大型网络可靠度的定量计算。最后通过实例验证所给算法的有效性。     

Parallelization of a dynamic SVD clustering algorithm and its application in information retrieval

We describe an implementation of a parallel document clustering scheme based on latent semantic indexing, which uses singular value decomposition. Given a set of documents, the clustering algorithm is dynamic in the sense that it automatically infers the number of clusters to be output. The parallel version has been implemented on a LAN and on a dual‐core system. Experimental evaluation of the algorithm shows an average speed‐up of 6.22 for the LAN implementation and an average speed‐up of 3.71 for the dual‐core implementation, while still maintaining a precision and recall in the range [0.85, 1]. To put these implementations in the context of information retrieval, we use the parallel clustering algorithm and develop a document similarity search system. The similarity search system shows good performance in terms of precision and recall. Copyright © 2010 John Wiley & Sons, Ltd.     

正数和与积的对偶不等式

给出了在个数相同的两组正数之积相等的情形下,判定这两组正数之和大小的一个充分条件,由此得出了正数和最大值存在的链式条件．应用这一链式条件解决了将,nl个正数分成等个数的n个数组后,每组之积的和与每组之和的积的最值问题．对于正数积的最小值问题,证明了与正数和最大值类似的结果,且相应的定理之间互为对偶定理．     

河网非恒定流隐式方程组的汊点分组解法

本文在现有研究成果的基础上，提出了一种汊点分组解法其特点是能够根据实际问题的需要，灵活方便地将河网中的汊点划分为任意多组，使汊点方程组的系数矩阵压缩到与分组后每组中的汊点数相同的阶数不仅极大地压缩了系数矩阵的贮存量，而且计算量大幅度减少，计算精度也得到了保证     

关于细胞神经网络无性模板的设计

本文以连通片检测器无性模板的设计为例，给出了细胞神经网络中无性模板的设计方法及连通片检测器无性模板中各元素的数值范围。     

基于K-means聚类和LVQ神经网络的OLED缺陷像素识别

提出改进的K-means聚类分割和LVQ神经网络分类的方法，用于有机发光二极管显示面板喷墨打印制程中缺陷像素的识别。首先采用改进的K-means聚类算法对预处理后的打印像素进行分割，然后采用连通域水平矩形确定每一个打印像素的坐标及几何特征，再通过灰度共生矩阵提取其纹理特征，最后通过LVQ神经网络对所述特征进行分类，完成缺陷像素的标记及分类统计。结果表明，本文算法的识别率明显优于其他常用分类识别算法，平均缺陷检测率为100%，分类准确率达到98.9%，单像素检测时间为8.3 ms。     

IUINet: 基于Shift的双流映射3D医学分割模型

为了提高特征融合, 我们设计了动态全连接层(DyFC), 该方法重新定义了权重和偏置, 使用基向量来代表新的权重和偏置, 基向量的系数是根据每一个输入特征进行学习得到的, 权重和偏置不再是共享的, 而是特有的, 这对于每一个特征的表达更具有专向性. 在本文中, 我们提出了一种双流映射结构模型IUINet. IUINet是通过3DShift操作、空间可分离卷积的组合来实现医学图像分割任务, 同时保持精度和效率之间的平衡. 所提出来的IUINet遵循编码器-解码器结构, 其中编码器一部分包含Shift操作、逐点Conv1×1操作, 另一部分包含空间可分离卷积操作. IUINet运用了多尺度输入以及多尺度特征映射层, 提高反向传播速度, 降低反向传播的平均距离. 提高模型的精确度, 增加模型泛化能力, 减少过拟合.