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A Novel Coverage Holes Discovery Algorithm Based on Voronoi Diagram in Wireless Sensor Networks
Guoyong Dai,Hexin Lv,Luyi Chen,Binbin Zhou,Ping Xu 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.3
Coverage is a key and fundamental problem in wireless sensor networks. To provide high quality of service, high coverage ratio of sensor nodes in monitored area should be assured. Coverage holes may lead to routing failure and degrade the quality of service. A novel coverage hole discovery algorithm, VCHDA, is proposed for wireless sensor networks in this paper. The proposed algorithm is based on the well-known Voronoi diagram. It can recognize coverage holes and label the border nodes of coverage holes effectively. Simulations are conducted and the results show that the proposed algorithm is effective and with high accuracy.
Di Tang,Shiyi Bao,Binbin Lv,Hao Cui,Lijia Luo,Min Xu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6
Shedding vortices in cross flow are of much practical importance in the analysis of flow induced vibrations of a steam generator. However, studies of shedding vortex are still few in present, especially in shedding patterns and its influences on lift performances. In this paper, five basic shedding patterns were investigated by numerical simulations of a 2D unsteady flow around a bundle with 253 cylinders. The numerical results clearly demonstrated that flow in line is the most common pattern. On the hand, the other four shedding patterns, cross in line, cross near line near, cross near line far and cross far line near, appear randomly. Influences of shedding vortices on lift performances were concluded as lift enhancement, lift pit and lift lag. These numerical results can provide a basic knowledge of shedding vortices for cylinders and can precisely quantify their influences on unsteady lift performances.