Tangent-ball techniques for shape processing

Shape processing defines a set of theoretical and algorithmic tools for creating, measuring and modifying digital representations of shapes.  Such tools are of paramount importance to many disciplines of computer graphics, including modeling, animation, visualization, and image processing.  Many applications of shape processing can be found in the entertainment and medical industries. In an attempt to improve upon many previous shape processing techniques, the present thesis explores the theoretical and algorithmic aspects of a difference measure, which involves fitting a ball (disk in 2D and sphere in 3D) so that it has at least one tangential contact with each shape and the ball interior is disjoint from both shapes. We propose a set of ball-based operators and discuss their properties, implementations, and applications.  We divide the group of ball-based operations into unary and binary as follows: Unary operators include: * Identifying details (sharp, salient features, constrictions) * Smoothing shapes by removing such details, replacing them by fillets and roundings * Segmentation (recognition, abstract modelization via centerline and radius variation) of tubular structures Binary operators include: * Measuring the local discrepancy between two shapes * Computing the average of two shapes * Computing point-to-point correspondence between two shapes * Computing circular trajectories between corresponding points that meet both shapes at right angles * Using these trajectories to support smooth morphing (inbetweening) * Using a curve morph to construct surfaces that interpolate between contours on consecutive slices The technical contributions of this thesis focus on the implementation of these tangent-ball operators and their usefulness in applications of shape processing. We show specific applications in the areas of animation and computer-aided medical diagnosis.  These algorithms are simple to implement, mathematically elegant, and fast to execute.Ph.D.Committee Chair: Jarek Rossignac; Committee Member: Greg Slabaugh; Committee Member: Greg Turk; Committee Member: Karen Liu; Committee Member: Maryann Simmon

Gearing

Gearing technology in its modern form has a history of only 100 years. However, the earliest form of gearing can probably be traced back to fourth century B.C. Greece. Current gear practice and recent advances in the technology are drawn together. The history of gearing is reviewed briefly in the Introduction. Subsequent sections describe types of gearing and their geometry, processing, and manufacture. Both conventional and more recent methods of determining gear stress and deflections are considered. The subjects of life prediction and lubrication are additions to the literature. New and more complete methods of power loss predictions as well as an optimum design of spur gear meshes are described. Conventional and new types of power transmission systems are presented

A feature-based approach to the Computer-Aided Design of sculptured products

Computer-Aided Design systems offer considerable potential for improving design process efficiency. To reduce the 'ease of use' barrier hindering full realisation of this potential amongst general mechanical engineering industries, many commercial systems are adopting a Feature-Based Design (FBD) metaphor. Typically the user is allowed to define and manipulate the design model using interface elements that introduce and control parametric geometry clusters, with engineering meaning, representing specific product features (such as threaded holes, slots, pockets and bosses). Sculptured products, such as golf club heads, shoe lasts, crockery and sanitary ware, are poorly supported by current FBD systems and previous research, because their complex shapes cannot be accurately defined using the geometrically primitive feature sets implemented. Where sculptured surface regions are allowed for, the system interface, data model and functionality are little different from that already provided in many commercial surface modelling systems, and so offer very little improvement in ease of use, quality or efficiency. This thesis presents research to propose and develop an FBD methodology and system suitable for sculptured products. [Continues.

Introduction to Surface-Mount Technology

In chapter 1, the surface-mount technology and reflow soldering technology are overviewed. A brief introduction is presented into the type of electronic components, including through-hole- and surface-mounted ones. Steps of reflow soldering technology are outlined, and details are given regarding the properties of solder material in this technology. The rheological behavior of solder pastes is detailed, and some recent advancements in addressing the thixotropic behavior of this material are summarized. The process of stencil printing is detailed next, which is the most crucial step in reflow soldering technology; since even 60–70% of the soldering failures can be traced back to this process. The topic includes the structures of stencils, discussion of the primary process parameters, and process optimization possibilities by numerical modeling. Process issues of component placement are presented. The critical parameter (process and machines capability), which is used extensively for characterizing the placement process is studied. In connection with the measurement of process capability, the method of Gage R&R (repeatability and reproducibility) is detailed, including the estimation of respective variances. Process of the reflow soldering itself is detailed, including the two main phenomena taking place when the solder is in the molten state, namely: wetting of the liquid solder due to surface tension, and intermetallic compound formation due to diffusion. Solder profile calculation and component movements during the soldering (e.g., self-alignment of passive components) are presented too. Lastly, the pin-in-paste technology (reflow solder of through-hole components) is detailed, including some recent advancements in the optimization of this technology by utilizing machine learning techniques

The Effect Of Forward Sweep On A Wing/Body Junction

PhDA study has been carried out of the aerodynamic interference flow arising at the junction of a swept-forward wing, which is cambered, but without taper or twist and a flat plate on which a fully-developed, turbulent boundary layer approaches the junction. Initial CFD predictions of the pressures over the wing were carried out by the author at BAe, Hatfield. Flow visualisation tests and surface pressure measurements over the wind tunnel model were conducted at wing incidences from -3' to +9'. With the wing at 0' incidence, a single-tube yawmeter was used to explore the flow field around the leading-edge of the junction and an X-wire anemometer to examine the mean velocity and turbulence fields in the streamwise corners and at the trailing edge. The Reynolds number of the tests, based on the streamwise chord and free stream velocity of 30 m/s, was 1.03 A06. At low incidence,, a very weak separation occurred in the plate boundary layer, a very short distance upstream of the junction. However the oncoming stream converges into the junction, appearing to confine any vortical motion at the leading edge to within a very thin layer below the closest point of measurement to the plate. Rudimentary vortical flow developed slightly downstream of the leading edge, but dissipated further downstream. Although weak vortices were measured in the trailing-edge, cross-plane, these were attributed to comer separations just upstream. The turbulence activity in the streamwise corners was found to be surprisingly low, especially in the compression side of the junction. Estimates of skin-friction showed that it was lower over the majority of the trailing-edge cross-plane than in the plate boundary layer upstream of the junction. At higher incidence, flow visualisation showed that the junction region had severe stall characteristics, with 3-dimensional recirculation regions forming.British Aerospace, Hatfield, Civil Aircraft factory under contracted HY-11070

Feasibility of remotely manipulated welding in space. A step in the development of novel joining technologies

In order to establish permanent human presence in space technologies of constructing and repairing space stations and other space structures must be developed. Most construction jobs are performed on earth and the fabricated modules will then be delivered to space by the Space Shuttle. Only limited final assembly jobs, which are primarily mechanical fastening, will be performed on site in space. Such fabrication plans, however, limit the designs of these structures, because each module must fit inside the transport vehicle and must withstand launching stresses which are considerably high. Large-scale utilization of space necessitates more extensive construction work on site. Furthermore, continuous operations of space stations and other structures require maintenance and repairs of structural components as well as of tools and equipment on these space structures. Metal joining technologies, and especially high-quality welding, in space need developing

Análisis mediante elementos discretos (MED) y evaluación experimental bajo la Norma ASTM G-99 del desgaste en revestimientos duros aplicados por procesos de soldadura en uñas de acero 32MnCrMo6-4-3 de una excavadora hidráulica CAT 336D2 L

El desgaste de materiales es un fenómeno que afecta a todo tipo de industrias, debido a este gran problema, diferentes investigadores vienen desarrollando estudios para minimizar los efectos del desgaste. La presente tesis abarca el estudio de 3 recubrimientos duros aplicado en el acero de las uñas de Acero 32MnCrMo6-4-3 (K-130), utilizado en las excavadoras hidráulicas 336D2 L CAT y su incidencia en el desgaste presentado en la mina Barrick – Lagunas norte. Durante la elaboración de este proyecto se realizarán estudios y pruebas respecto a la resistencia al desgaste de los materiales anteriormente mencionados, mediante la norma ASTM G99 y elementos discretos (MED). Teniendo en cuenta factores como tenacidad, dureza, estructura, corrosión presente, modo y tipo de carga, composición química, rugosidad de la superficie, distancia recorrida, frecuencia de cambio, etc. Expresándolos mediante un marco conceptual y de referencia, la metodología con la cual se procedió en este proyecto y las actividades desarrolladas. Palabras claves: desgaste, uñas de acero, recubrimiento, excavadora hidráulica, elementos discretos, tenacidad, dureza, composición químicaTesi

A History of Aerospace Problems, Their Solutions, Their Lessons

The positive aspect of problem occurrences is the opportunity for learning and a challenge for innovation. The learning aspect is not restricted to the solution period of the problem occurrence, but can become the beacon for problem prevention on future programs. Problems/failures serve as a point of departure for scaling to new designs. To ensure that problems/failures and their solutions guide the future programs, a concerted effort has been expended to study these problems, their solutions, their derived lessons learned, and projections for future programs. This includes identification of technology thrusts, process changes, codes development, etc. However, they must not become an excuse for adding layers upon layers of standards, criteria, and requirements, but must serve as guidelines that assist instead of stifling engineers. This report is an extension of prior efforts to accomplish this task. Although these efforts only scratch the surface, it is a beginning that others must complete

Liquid rocket engine turbopump shafts and couplings

Design criteria and recommended practices are presented for designing tubopump shafts and couplings. Design parameters, material selection, and structural analysis are discussed

Intuitive freeform modeling using subdivision surfaces.

Lai Yuen-hoo.Thesis submitted in: November 2004.Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.Includes bibliographical references (leaves 100-102).Abstracts in English and Chinese.Abstract --- p.i摘要 --- p.iiAcknowledgment --- p.iiiList of Figures --- p.ivTable of Content --- p.viiChapter 1. --- Introduction --- p.1Chapter 1.1. --- Problem Definition --- p.1Chapter 1.2. --- Proposed Solution --- p.2Chapter 1.3. --- Thesis Contributions --- p.2Chapter 2. --- Modeling Approaches --- p.4Chapter 2.1. --- Polygon Modeling --- p.4Chapter 2.2. --- Patch Modeling --- p.6Chapter 2.3. --- Freehand Sketch-based Modeling --- p.7Chapter 2.4. --- Template Based Modeling --- p.8Chapter 2.5. --- Curve Interpolation Method --- p.9Chapter 3. --- Surface Operations --- p.11Chapter 3.1. --- Surface Blending --- p.11Chapter 3.2. --- Surface Trimming --- p.13Chapter 3.3. --- Boolean Operations --- p.14Chapter 4. --- Subdivision Surface --- p.16Chapter 4.1. --- Basic Principle --- p.16Chapter 4.2. --- Catmull-Clark Surface --- p.17Chapter 5. --- Modeling Algorithm Overview --- p.21Chapter 6. --- Subdivision Surface Generation --- p.23Chapter 6.1. --- Input Curves --- p.23Chapter 6.2. --- Surface Sweeping --- p.24Chapter 6.3. --- Subdivision Surface Fitting --- p.29Chapter 7. --- Surface Blending --- p.32Chapter 7.1. --- Introduction --- p.32Chapter 7.2. --- Problem Definition --- p.32Chapter 7.3. --- Algorithm Overview --- p.36Chapter 7.4. --- Blend Region Detection --- p.39Chapter 7.4.1. --- Collision Detection --- p.40Chapter 7.4.2. --- Result and Analysis --- p.42Chapter 7.5. --- "Mesh Refinement, Surface Fitting and Region Removal" --- p.46Chapter 7.5.1. --- Mesh Refinement --- p.46Chapter 7.5.1.1. --- Adaptive Subdivision --- p.46Chapter 7.5.1.2. --- Additional Subdivision Constraint --- p.47Chapter 7.5.2. --- Surface Fitting --- p.49Chapter 7.5.2.1. --- General Approach --- p.49Chapter 7.5.2.2. --- Surface Point Correspondence --- p.50Chapter 7.5.2.3. --- Numerical Fitting Method --- p.51Chapter 7.5.3. --- Unwanted Region Removal --- p.55Chapter 7.5.4. --- Result and Analysis --- p.56Chapter 7.6. --- Boundary Smoothing --- p.58Chapter 7.6.1. --- General Approach --- p.59Chapter 7.6.2. --- Constraint on Deformation Direction of Vertex --- p.61Chapter 7.6.3. --- Result and Analysis --- p.63Chapter 7.7. --- Blend Curves --- p.65Chapter 7.7.1. --- Problem Definition --- p.65Chapter 7.7.2. --- Proposed Solution Overview --- p.66Chapter 7.7.3. --- Maintenance of Regular Vertex Valence along Blend Curve --- p.67Chapter 7.7.3.1. --- Pairing Up Blend Boundary Vertices --- p.70Chapter 7.7.4. --- Minimization of Distortion Caused by Extraordinary Vertices --- p.72Chapter 7.7.5. --- Blend Vertex Position Optimization Function --- p.74Chapter 7.7.5.1. --- Face Normal Expression --- p.74Chapter 7.7.5.2. --- Face Normal Difference Energy Function --- p.77Chapter 7.7.5.3. --- Midpoint Distance Energy Function --- p.78Chapter 7.7.5.4. --- Weighted Least Square Energy Minimization --- p.78Chapter 8. --- Implementation --- p.81Chapter 8.1. --- Data Structure --- p.81Chapter 8.2. --- User Interface --- p.82Chapter 9. --- Results --- p.83Chapter 9.1. --- Surface Generation --- p.83Chapter 9.2. --- Surface Blending --- p.86Chapter 9.2.1. --- Ideal Case --- p.86Chapter 9.2.2. --- Angle of Insertion --- p.87Chapter 9.2.3. --- Surface Feature Near Intersection --- p.88Chapter 9.2.4. --- Comparison --- p.89Chapter 9.2.5. --- Other Examples --- p.92Chapter 9.3. --- Overall Performance --- p.94Chapter 9.4. --- Limitations --- p.97Chapter 9.4.1. --- Limitation on Generated Shape --- p.97Chapter 9.4.2. --- Limitation on Input Surfaces --- p.98Chapter 10. --- Conclusion and Future Work --- p.99References --- p.10