Browsing by Author "Chang, Chih-Han"
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Item Automatic mesh generation of two-dimensional objects(1988) Chang, Chih-Han; Akin, John Edward.An approach for the fully automatic generation of two-dimensional finite element meshes is presented. The method follows from the basic concept of the quadtree encoding technique with the specific modifications made to produce valid, user controllable finite element meshes. The use of quadtree method for mesh generation was pioneered by Shephard and Yerry, (6). Our work is similar but more general than theirs. In this thesis after giving an overview of finite element method and mesh requirements, the quadtree and modified quadtree techniques are introduced. Then paper emphasizes on those algorithmic aspects of the mesh generator especially on transferring quadtree code to finite mesh. Finally, examples are included to demonstrate this technique and conclusions are given.Item Computer-aided design of femoral stem prostheses(1991) Chang, Chih-Han; Akin, John Edward.In the design of femoral stem prostheses, both biologic factors and prosthetic design features influence the long-term performance of the implant. The analysis of all these influences is difficult, if not impossible, at the present time. This research presents a computational approach, using automatic contour detection, octree automesh and a special finite element program, that allows the stress analysis of different prostheses to be performed with minimal human interaction. Using computed tomography scans of a femur, the stress pattern in the femur when subjected to physiologic loading with or without a implanted prosthesis can be generated. A variety of prosthetic designs can be evaluated and the most suitable design can be selected for a particular patient prior to the operation. With an accurate inner contour generated by the computer algorithm developed in this study, a femoral prosthesis can be designed which most closely reproduces the stress pattern in the intact femur. Based on this study, different design parameters can be evaluated and the optimal prosthetic design can then be carried out with more advanced computer hardware.