The purpose of this study was to evaluate the importance of time-matching separate cine camera views in three-dimensional motion studies and to develop analytical methods to accomplish the time matching. An image space was calibrated using twenty-four control points and motion picture films at about 60 frames per second were taken of a moving bar, and of a subject putting a shot. Combinations of correctly and incorrectly matched views were compared for their accuracy in determining the positions of six object points. An algorithm was derived which included the timing variable in the least squares solution for the X, Y, and Z coordinates. These "best fit" solutions for the timing and for the coordinate locations were compared with criterion values. Alterations in the timing of views tended to introduce a bias into the coordinate locations. The magnitude of the bias was a function of the velocity of the object points and of the camera positioning. To keep final coordinate errors below 5% required the two views to be matched to within 0.008 seconds. The time matching algorithm was able to match the views to within 0.005 seconds. The corresponding coordinates could vary by an average of 2.4% from the correct ones. It was concluded that the analytical time matching algorithm could produce acceptable results if extreme accuracy was not required. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

More and more computer applications are using three-dimensional models for a variety of uses (e.g. CAD, graphics, recognition). A major bottleneck is the acquisition of these models. The easiest method for designing the models is to build them directly from images of the object being modelled. This paper describes the design of a system, MOLASYS (for MOdeL Acquisition SYStem), that allows the user to build object models interactively from underlying images. This would not only be easier for the user, but also more accurate as the models will be built directly satisfying the dimensions, shape, and other constraints present in the images. The object models are constructed by constraining model points and edges to match points in the image objects. The constraints are defined by the user and expressed using a Jacobian matrix of partial derivatives of the errors with respect to a set of camera and model parameters. MOLASYS then uses Newton's method to solve for corrections to the parameters that will reduce the errors specified in the constraints to zero. Thus the user describes how the system will change, and the program determines the best way to accomplish the desired changes. The above techniques, implemented in MOLASYS, have resulted in an intuitive and flexible tool for the interactive creation of three-dimensional models. / Science, Faculty of / Computer Science, Department of / Graduate

Two fundamental problems of celestial mechanics are considered: the stellar or planetary three-body problem and a related form of the restricted four-body problem. Although a number of constraints are imposed, no assumptions are made which could invalidate the final solution. A consistent and rational approach to the analysis of four-body systems has not previously been developed, and an attempt is made here to describe problem evolution in a systematic manner. In the particular three-body problem under consideration two masses, forming a close binary system, orbit a comparatively distant mass. A new literal, periodic solution of this problem is found in terms of a small parameter e, which is related to the distance separating the binary system and the remaining mass, using the two variable expansion procedure. The solution is accurate within a constant error O(e¹¹) and uniformly valid as e tends to zero for time intervals 0(e¹⁴). Two specific examples are chosen to verify the literal solution, one of which relates to the sun-earth-moon configuration of the solar system. The second example applies to a problem of stellar motion where the three masses are in the ratio 20 : 1 : 1. In both cases a comparison of the analytical solution with an equivalent numerically-generated orbit shows .close agreement, with an error below 5 percent for the sun-earth-moon configuration and less than 3 percent for the stellar system. The four-body problem is derived from the three-body case by introducing a particle of negligible mass into the close binary system. Unique uniformly valid solutions are found for motion near both equilateral triangle points of the binary system in terms of the small parameter e, where the primaries move in accordance with the uniformly-valid three-body solution. Accuracy, in this case, is Q maintained within a constant error 0(e⁸), and the solutions are uniformly valid as e tends to zero for time intervals 0(e¹¹). Orbital position errors near L₄ and L₅ of the earth-moon system are found to be less than 5 percent when numerically-generated periodic solutions are used as a standard of comparison. The approach described here should, in general, be useful in the analysis of non-integrable dynamic systems, particularly when it is feasible to decompose the problem into a number of subsidiary cases. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Dissertation (MSc)--University of Pretoria, 2009. / Microbiology and Plant Pathology / Unrestricted

Master of Public Health - MPH / Access to appropriate health care service during childbirth is a great challenge to many women in Africa and Namibia is no exception. More than 70% of women in Otjozondjupa region experienced some form of delay during childbirth, and while maternal mortality continued to rise over the years in Namibia it is currently at about 265/100 000, which is too high for a middle-income country. Hence, this study aimed to get a deeper understanding of the perceptions of women who experienced any of the three delays in accessing appropriate health care during childbirth in Otjiwarongo hospital.

In this study, topology optimisation for heat-conducting paths in a three-dimensional domain was investigated. The governing equations for the temperature distribution were solved using the finite volume method, the sensitivities of the objective function (average temperature) were solved using the adjoint method, and finally, the optimal architecture was found with the method of moving asymptotes (MMA) using a self programmed code. A two-dimensional domain was evaluated first as a validation for the code and to compare with other papers before considering a three-dimensional cubic domain. For a partial Dirichlet boundary, it was found that the converged architecture in three dimensions closely resembled the converged architectures from two dimensions, with the main branches extending to the outer corners of the domain. However, the partial Dirichlet boundary condition was not realistic, and to represent a more realistic case, a full Dirichlet boundary was also considered. In order to investigate a full Dirichlet boundary condition, the domain had to be supplied with an initial base for the architecture to allow variation in the sensitivities. It was found that the width and height of this base had a significant effect on the maximum temperature. A height of 0.04 with a base width of 0.24 proved to be the most effective, since this small base gave the MMA enough freedom to generate a tree structure. It was first assumed that this base should be in the centre of the bottom boundary and this was later proved. The results showed again that the maximum temperature decreased with an increase in the conductivity ratio or volume constraint. The architectures were similar to the partial Dirichlet boundary, again with the main branches extending to the outer corners of the domain. The main branches were thinner compared with the partial Dirichlet boundary and fewer secondary branches were observed. It was concluded that a full Dirichlet boundary could be solved using topology optimisation, if the boundary was supplied with an initial base. With the successful implementation of the full Dirichlet boundary with one initial base, multiple bases were investigated. First, two bases were used and it was assumed that the optimal placement for these bases was in the centre of each respective half of the bottom boundary, which was later confirmed. The optimal width and height of 0.24 and 0.04 respectively were again optimal for each specific base. The same procedure was followed for four bases and it was assumed that the optimal placement was in the centre of each respective quadrant of the bottom boundary, which was also later confirmed. The optimal width and height of 0.12 and 0.04 respectively were found for this case. With this established, optimisation runs for different conductivity ratios and volume constraints were completed for two and four bases. It was found that two bases offered increased performance in terms of the maximum temperature compared with one base. An increase in performance was also observed when using four bases compared with two bases. A maximum of 20.4% decrease in the maximum temperature was observed when comparing four bases with one. Keywords: topology, optimisation, conduction, three-dimensional / Dissertation (MSc)--University of Pretoria, 2014. / gm2014 / Mechanical and Aeronautical Engineering / Unrestricted

Indiana University-Purdue University Indianapolis (IUPUI) / Background: The advancement of three-dimensional visualization technology provides exciting new opportunities in medical education, including new methods for teaching complex anatomical relationships and promising tools for the training of postgraduate physicians. Information on how faculty use three-dimensional visualization technology for anatomy education is essential for informed discussions surrounding their effectiveness as a teaching tool and use in the medical curriculum, yet the current literature lacks necessary contextual details on how faculty integrate these technologies into actual medical curricula. Methods: Fifteen medical educators from North American medical schools and teaching hospitals completed semi-structured interviews and discussed how they use three-dimensional visualization technology for teaching in preclinical courses, clinical clerkships, and postgraduate programs. Transcripts were analyzed using the constant comparative method and resulting themes were used to inform the creation of a questionnaire. Results: The resulting themes of analysis were organized according to a curricular framework that describes how faculty use these technologies as an instructional resource and how this use is related to the purposes, content, sequence, instructional processes and evaluation of medical curricula. The results demonstrate how three-dimensional visualization technology is being is implemented in a variety of ways in the curriculum and revealed numerous similarities of use across the levels of medical education. Analyses revealed minimal use of three-dimensional visualization technology for assessment and indicated faculty face significant challenges in designing such assessment. Conclusions: Results suggest continuing assessment of the effectiveness of these technologies as a teaching tool needs to encompass broader aspects of use, such as those described in this study. Additionally, results showing similarities of use across levels suggest that educators and administrators should consider how threedimensional visualization technology can be thoughtfully integrated to address the changing needs of learners as they progress through medical education. Findings also suggest that administrators who want to support the integration of three-dimensional visualization technology into the curriculum need to provide adequate support and training to help faculty overcome time limitations and difficulties designing assessment methods.

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The study of three-dimensional percolation paths through materials is important in its contribution to understanding defect sensitive properties of materials. This work shows the importance of grain boundary character in modeling defect sensitive boundaries. Also presented are trends of percolation of sensitized grain boundaries in 304 stainless steel (304SS). Of particular interest is how open paths form in a three-dimensional model created through serial sectioning. Evidence is presented that triple or quadruple points that contain typically two boundaries with special character that intersect the percolation path break up the path. Some grains with no known special qualities (i.e., CSL) have observable special behavior.

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