A fast and efficient load flow technique for unbalanced distribution system

This paper presents a fast and efficient load flow technique for unbalanced distribution system. The proposed load flow technique is derived by promulgating the concept of conventional backward forward sweep (BFS) technique of power flow study for distribution system. The proposed technique employs a novel load-impedance matrix (LIM) to calculate the bus voltages in a single step unlike the conventional BFS approach which involves two separate steps (backward sweep and forward sweep) to perform the same and this improvement is claimed as the novelty of this work. This distinctive feature makes the proposed algorithm faster in operation. Nodal voltages, at any iteration, may be calculated, directly, from the values obtained in the previous iteration by utilizing LIM. A simple concept of set theory is adopted here to construct the LIM. Special treatments are also included in this method to analyze weakly meshed systems. The proposed technique is flexible enough to accommodate any sort of changes in the existing network topology through LIM. It is tested on different three-phase balanced and unbalanced radial distribution systems as well as weakly meshed networks for load flow study. A separate case study is also presented to check the validity of the proposed load flow technique for various transformer connections. The obtained results demonstrate the effectiveness of the proposed technique. Furthermore, performance comparison reveals that the proposed algorithm is, computationally, faster and robust than the conventional power flow techniques reported in the recent state-of-the-art literatures.     

Image Segmentation via Iterative Fuzzy Clustering Based on Local Space-Frequency Multi-Feature Coherence Criteria

Fuzzy set theory has recently attracted much attention in the field of image classification, image understanding and image processing. One of the major topics in fuzzy image processing is the image classification problem. This paper presents a fast and accurate iterative fuzzy clustering (I.F.C.) method dynamically adapted to the classification process. This is used for high performance fuzzy segmentation which forms the basis for reliable image understanding. The proposed fuzzy segmentation scheme examines the image connectivity in the space and frequency domains. The detected fuzzy features are combined via a block synthesis and local correlation algorithmic procedure. Some results showing that the performance of the proposed I.F.C./clustering method is superior from that of the standard fuzzy c-means method are provided.     

新的价连接性指数~mX用于有机化合物的QSAR

定义新的价连接性指数 m X、m X′,并用于有机化合物的定量结构 -活性相关性研究中 ,发现 m X、m X′与有机物的毒性具有良好的线性关系 ,相关系数均在 0 .92以上 ,优于文献方法。该法具有计算简单 ,物理意义明确等优点。     

A kind of conditional vertex connectivity of Cayley graphs generated by 2-trees

Let G be a graph. Then T ⊆ V(G) is called an R^k-vertex-cut if G − T is disconnected and each vertex in V(G) − T has at least k neighbors in G − T. The size of a smallest R^k-vertex-cut is the R^k-vertex-connectivity of G and is denoted by κ^k(G). In this paper, we determine the numbers κ¹ and κ² for Cayley graphs generated by 2-trees, including the popular alternating group graphs.     

基于图论的河道-滩区系统连通性评价方法

河流系统的连通性是维持河流生态系统健康的重要因素。基于图论连通度理论，将河道-滩区系统中的水流通道、鬃岗地形、小型封闭水域和牛轭湖等微地貌单元概化为图模型，并利用ArcGIS平台和DEM模型实现其表述。在此基础上，建立图的邻接矩阵，进行连通性分析和水流通道连通度计算，实现了河道-滩区系统连通程度分析的定量化。最后以瓯江丽水河段的河道-滩区系统为例，进行了一定水位条件下的连通状况模拟和连通程度定量分析。案例分析结果表明：通过确定关键性水流通道和水流通道汇合点，可对河流生态修复工程设计方案进行优化；利用本文所提出的方法对河道-滩区系统的连通性进行定量评价是有效可行的。该方法可用于河流健康评估、河流生态修复工程优化、河湖水网连通程度的定量分析等。     

Graph theoretic characterization and reliability of the generalized Boolean n-cube network

In this paper, a general class of Boolean n-cube structures is investigated. The interconnection is based on a mixed radix number system which results in a variety of generalized Boolean n-cube structures for a given number of processors , where x and y are positive integers. A number of interesting properties of the network are revealed. By a constructive method, the node connectivity of this network is found. Finally, we show that the graph is super-λ and is an optimal reliable structure for interconnection networks.     

THE INFLUENCE OF HYDROLOGICAL CONNECTIVITY ON FOOD WEB STRUCTURE IN FLOODPLAIN LAKES

Hydrological connectivity is an important driver of ecosystem structure in floodplain rivers; however, little is known of how hydrological connectivity affects the structure and functioning of food webs in these systems. This study examines aquatic food web structure in 10 floodplain lakes on a dryland river floodplain in eastern Australia across a connectivity gradient. Results for fishes suggest that benthic carbon sources are more important in high connectivity billabongs than in low connectivity billabongs and that pelagic sources are more important in low connectivity billabongs than in high connectivity billabongs. Fishes in less connected billabongs were also found to feed at higher trophic levels than in more connected billabongs. We hypothesize that in high connectivity billabongs, where suitable benthic primary sources are abundant, common fish species such as carp and bony bream feed as detritivores or herbivores; while in low connectivity billabongs, where benthic sources are less abundant, the same species feed as planktivores, insectivores or piscivores. This dietary difference may also be promoted by greater predation efficiency in less structurally complex low connectivity billabongs. The feeding behaviour of these fish species subsequently influences the trophic positions of fishes higher in the food chain and ultimately the total food chain lengths that high and low connectivity billabongs support. The results of this study highlight the importance of hydrological connectivity to the structure of food webs in these systems and the potential for them to be affected by water resource development. Copyright © 2011 John Wiley & Sons, Ltd.     

Coverage‐aware connectivity‐constrained unattended sensor deployment in underwater acoustic sensor networks

Careful deployment of nodes in underwater acoustic sensor networks in a distributed manner with the goal of maximized coverage and guaranteed connectivity is a challenging problem because it is very difficult and costly to access the 3D underwater environment. This paper presents a novel algorithm for self‐deployment of nodes in underwater acoustic sensor networks assuming that the nodes are randomly dropped to the water surface and form a densely populated connected network at the water surface. The idea of the algorithm is based on calculating an optimized depth for each node in the network in such a way that the possible sensing coverage overlaps are minimized and the connectivity of final topology is guaranteed. The algorithm has three main phases. In the first phase, nodes are organized in a tree structure that is rooted at the surface station. In the second phase, the depths for all nodes are computed iteratively at surface station. In the final phase, the calculated depths are distributed to nodes so that the nodes start sinking. The performance of the proposed approach is validated through simulation. We observed that the proposed approach performs at least 10% better in terms of network coverage than contemporary schemes in the literature. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of longitudinal structural connectivity on seismic performance of three-hinged precast arch culverts

The hinge type of precast concrete arch culvert was introduced to Japan from France in the 1990s in consideration of the saving of labor, shortening of the construction period, and high quality control of the concrete members. However, due to the 2011 off the Pacific Coast of Tohoku Earthquake (March 11, 2011), the three-hinged precast arch culverts that had been constructed in Japan at the beginning of the period when precast arch culverts were firstly introduced, suffered damage, which spoiled their serviceability. According to the extent of the damage and the type of culverts that were damaged, the longitudinal structural connectivity of the culverts was assumed to be one of the possible reasons for the reported damage mechanism. Therefore, the objective of this paper was to clarify how strongly the longitudinal structural connectivity influenced the longitudinal seismic behavior of the three-hinged arch culverts. To achieve this objective, an elasto-plastic finite element analysis was conducted with an analytical model that could capture the characteristics of the damaged culverts. Simultaneously, a penalty method with the bi-linear spring model was applied as a solution to the contact-impact problems of the precast segmental arch members. As a result, it was found that the weaker longitudinal structural connectivity in the damaged culverts allowed the torsional displacements of the arch members to induce critical damage to the arch members, namely, edge defects in the arch crown and concrete foundation. The numerical results proved the unignorable influence of the longitudinal structural connection on the possible damage to three-hinged arch culverts.     

An adaptive joining mechanism for improving the connection ratio of ZigBee wireless sensor networks

Wireless sensor networks (WSNs) are well suited to many applications, including environment surveillance and target tracking. ZigBee is an IEEE 802.15.4‐based standard that is considered suitable for WSNs. The functional operations of a ZigBee network rely on self‐organized network connections and the proper deployment of sensor devices. However, the devices comprising a ZigBee network may become isolated from the network after the joining phase due to the configuration constraints of the ZigBee standard. This means that some deployed devices cannot join the network even though they can communicate with other joined nodes. These isolated devices reduce the efficiency of network operation and increase deployment costs. This paper proposes a ZigBee‐compatible adaptive joining mechanism with connection shifting schemes to improve the connectivity of ZigBee networks, allowing them to operate at the expected efficiency. Simulation results show that the proposed mechanism significantly improves the join ratio of deployed sensor devices in ZigBee WSNs. Copyright © 2009 John Wiley & Sons, Ltd.