Papers by Author: Shi Jun Ji

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Authors: Shu Dong Xiu, Shi Jun Ji, Yang Wang
Abstract: A fast algebraic grid generation algorithm is proposed and a improved Kamaugh map data structure for the new algorithm is designed in the paper. The new created vertex inside of the region is based on algebraic operation of the corner vertices and the middle vertices of boundary broken lines on the region and the program data structure is a improved Kamaugh map data structure, so the algorithm has the merit of simple algebraic formula, quickly executing speed and powerful technology for the four-sided region enclosed by four broken lines, the algorithm is realized on the four-sided region and B-spline surface on the complex surface. The algorithm is extensively applicable for shape modeling in computer aided geometric design, industrial prototype design and reverse engineering.
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Authors: Yang Wang, Shi Jun Ji, Li Jun Yang
Abstract: Subdivision algorithms have emerged recently as a powerful and useful technique in modeling free-form surfaces. Subdivision algorithms exited at present however, being their disadvantages, can’t meet the demand of wide application in modeling surfaces and don’t still belong to a general theory. In this paper, a general subdivision algorithm is presented which is a general conclusion inferred from classical Catmull-Clark subdivision algorithm and can produce existing subdivision algorithm by selecting reasonable vertical weights and horizontal weights. The subdivision algorithm is an ideal resolution for keeping shape feature such as crease, corner and dart contrast to all existing subdivision algorithms, it also have the advantage of flexible weights selection, easily control of shape and high compute speed. Therefore, the algorithms are extensively applicable for shape modeling in computer aided geometric design, industrial prototype design and reverse engineering.
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Authors: S.J. Lv, Yang Wang, Shi Jun Ji
Abstract: This paper presents the experiments of Nd:YAG pulsed laser cutting of GH3536 superalloy sheet and investigates the influences of different cutting parameters on laser cut quality factors including recast layer, kerf width and dross formation. The results show that the recast layer possesses finer granularity and higher hardness than those of the matrix, and the thickness of recast layer increases with increased pulse energy and decreases as the cutting speed and gas pressure increase. Oxygen-assisted cutting comes with thick recast layers and argon-assisted cutting acquires thin layers. The low-strength oxide layer worsens the kerf surfaces in oxygen-assisted cutting while argon-assisted cutting produces unaffected surface quality and is suitable for applications with subsequent welding.
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Authors: Yang Wang, Han Ming Lv, Shi Jun Ji
Abstract: A triangle mesh was reconstructed from an unorganized point cloud through two phases of mesh growing based on different strategies, where regions with high point density usually grow at the first phase and the remaining regions grow later. In each phase of mesh growing, the smoothest regions always grow firstly and then largely avoid errors emerging in sharp regions. The presented test technique of geometric integrity as well as the abnormality disposing method pledged the reconstructed mesh has correct geometry structure. Experiments show that the algorithm is efficient and effective.
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