The implementation of a disambiguation marching cubes algorithm

This thesis first systematically analyzes a classic surface generation algorithm, the marching cubes algorithm, in computer volume visualization, with emphasis on the mathematical background and the ambiguity problem of the algorithm. A simple and elegant disambiguation algorithm is then described and implemented. Finally, generated data from mathematical functions and real world data from scientific experiment are used to test the original marching cubes algorithm and the disambiguation algorithm

Interactive volume visualization in a virtual environment.

by Yu-Hang Siu.Thesis (M.Phil.)--Chinese University of Hong Kong, 1998.Includes bibliographical references (leaves 74-80).Abstract also in Chinese.Abstract --- p.iiiAcknowledgements --- p.vChapter 1 --- Introduction --- p.1Chapter 1.1 --- Volume Visualization --- p.2Chapter 1.2 --- Virtual Environment --- p.11Chapter 1.3 --- Approach --- p.12Chapter 1.4 --- Thesis Overview --- p.13Chapter 2 --- Contour Extraction --- p.15Chapter 2.1 --- Concept of Intelligent Scissors --- p.16Chapter 2.2 --- Dijkstra's Algorithm --- p.18Chapter 2.3 --- Cost Function --- p.20Chapter 2.4 --- Summary --- p.23Chapter 3 --- Volume Cutting --- p.24Chapter 3.1 --- Basic idea of the algorithm --- p.25Chapter 3.2 --- Intelligent Scissors on Surface Mesh --- p.27Chapter 3.3 --- Internal Cutting Surface --- p.29Chapter 3.4 --- Summary --- p.34Chapter 4 --- Three-dimensional Intelligent Scissors --- p.35Chapter 4.1 --- 3D Graph Construction --- p.36Chapter 4.2 --- Cost Function --- p.40Chapter 4.3 --- Applications --- p.42Chapter 4.3.1 --- Surface Extraction --- p.42Chapter 4.3.2 --- Vessel Tracking --- p.47Chapter 4.4 --- Summary --- p.49Chapter 5 --- Implementations in a Virtual Environment --- p.52Chapter 5.1 --- Volume Cutting --- p.53Chapter 5.2 --- Surface Extraction --- p.56Chapter 5.3 --- Vessel Tracking --- p.59Chapter 5.4 --- Summary --- p.64Chapter 6 --- Conclusions --- p.68Chapter 6.1 --- Summary of Results --- p.68Chapter 6.2 --- Future Directions --- p.70Chapter A --- Performance of Dijkstra's Shortest Path Algorithm --- p.72Chapter B --- IsoRegion Construction --- p.7

Microscale modeling of fluid flow in porous medium systems

Proper mathematical description of macroscopic porous medium flows is essential for the study of a wide range of subsurface contamination scenarios. Existing mathematical formulations, however, demonstrate inadequacies that preclude the accurate description of many systems. Multi-scale models developed using thermodynamically constrained averaging theory (TCAT) rigorously define macroscopic variables in terms of more well-understood microscopic counterparts, permitting detailed analysis of macroscopic model forms based on microscale simulation and experiment. Within this framework, the primary objectives of microscale modeling are to elucidate important physical mechanisms and to inform both the form of macroscale closure relations as well as associated parameter values. In order to meet these goals, numerical tools must include: (1) simulations that provide accurate microscopic solutions for physical phenomena in large, complex domains; (2) morphological analysis tools that can be used to upscale simulation results to larger scales as dictated by the associated theoretical framework. Development of a numerical toolbox for microscale porous medium studies is considered in line with these objectives, including both implementation and optimization strategies. High-performance implementations of the lattice Boltzmann method are developed to simulate one- and two-phase flows using several computing platforms. A modified marching cubes algorithm is developed to explicitly construct all entities in a two-phase system, including all interfaces between the fluid and solid phases in addition to the three phase contact curve. These entities serve as a numerical skeleton for upscaling multiphase porous medium simulation results to the macroscale. Based on these tools, development of macroscopic constitutive laws is illustrated for a special case of anisotropic flow in porous media. In this example, microscale simulation is used to demonstrate a limitation of existing macroscopic forms for cases in which the momentum resistance depends on the flow direction in addition to the orientation. A modified macroscopic form is proposed in order to properly account for this phenomenon

NASA Tech Briefs, July 1995

Topics include: mechanical components, electronic components and circuits, electronic systems, physical sciences, materials, computer programs, mechanics, machinery, manufacturing/fabrication, mathematics and information sciences, book and reports, and a special section of Federal laboratory computing Tech Briefs

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences