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Articles by Jun Dai
Total Records ( 2 ) for Jun Dai
  Yanli Zhang , Jun Dai and Dasheng Zhu
  It is necessary to calculate the "Probability of Failure on Demand" (PFD) and "Probability of Failure of Safety" (PFS) for the assessment of the "Safety Integrity Level" (SIL) of a Safety Instrumented System (SIS) in the international standard IEC 61508 (2000). To fulfill the high safety and availability requirements redundant channels are often used which are normally homogeneous. Whereas, in order to minimize the potential Common Cause Failures (CCF) for very high safety requirements (e.g. SIL4) it may be advisable to build up a heterogeneous system with different hardware/software platforms. For such type of heterogeneous systems the calculation of the PFD is a challenge because the failure rates of the particular channels are different in general and no formulas are included in the standard. Within the scope of this work, the physical block diagram and the voting diagram for 2oo3 redundant system are introduced, then based on them, the Markov-model method is used to simulate these redundant systems, including both the homogeneous and the heterogeneous systems.
  Lin Chen , Jun Dai , Junjie Feng , Bing Fu and Haihong Pan
  To reduce time for collision detection among articulated models, the collision detection algorithm of Hybrid Bounding Volume Hierarchy Tree (HBVHT) was proposed to accelerate the speed of culling away triangles. The HBVHT was composed of two phases: A broad phase and a narrow phase. The broad phase consisted of Axis-Aligned Bounding Box (AABB) and the Bounding Volume (BV) was used to build a Multi-Level Hierarchy Tree (MLHT); the narrow phase was made up of the Oriented Bounding Box (OBB) hierarchy trees and triangles. Furthermore, according to the characteristic of hierarchical structure of the HBVHT, an improved cost function was given to analyze the performance of the HBVHT. Experiments were performed between two 6-DOF robots under the Open GL environment. Two robots with the same number of triangles moved with the same trajectory for the collision experiments. Experimental results show that the efficiency of HBVHT algorithm is higher than that of the RAPID and the other two HBVHTs with different structure. The results indicate that the HBVHT algorithm can effectively improve the efficiency of collision detection among the articulated model robots.
 
 
 
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