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Thesis (M.S.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaf 51). Also available on the World Wide Web.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted.

High altitude balloons are an effective, inexpensive and readily available conduit for conducting near space and low Reynolds number experimentation. Experiments are being developed that will use high altitude balloons as carriers for near space and low Reynolds test vehicles. The first step in developing this capability is to create a system that is able to log collected data and track and control a high altitude balloon payload. It is also beneficial that this system be flexible enough to accept different sensor types, communication methods and connection and release linkages. By combining the flexibility of microcontroller biased circuitry and the availability of commercial off the shelf products an economical design solution to this problem has been be achieved. Analysis of this system has been performed and the design has been fabricated, tested and specially modified to withstand the extreme conditions of high altitude flight.

In this thesis I will describe the methods used and problems I have faced and attempted to solve during my time developing a math game for younger kids, a game that makes an attempt to teach kids something called number sense. Teaching pre school kids about number sense is something relatively new and the group I have been working with are of the understanding that it’s something that is very likely to be important to prevent children from falling behind in math during the earlier years of school. Number sense basically means the ability to connect symbolic numbers to their meaning interms of sets, amounts and dimensions such as larger-smaller, higher-shorter, more-less, etc. If this proves to be useful then the quality of education will improve as a result of more children being able to keep up with their math from an early stage.

Balloon angioplasty, used to clear clogged blood vessels, is the most common medical intervention in the world. In an effort to improve on an angioplasty balloon currently on the market, extruded tubes were designed that were comprised of different numbers of layers of an 80/20 ratio of polyethylene terephthalate (PET) to a thermoplastic elastomer. Balloons were fabricated from these tubes, and tested for burst strength, puncture resistance, and compliance. Lastly, these properties were correlated to the material configuration of the balloons. It was found that, although the burst strength and compliance of the balloons was not significantly effected, increasing the number of layers while keeping the ratio of materials constant lead to a linear increase in the puncture resistance and toughness of the balloons. This is important because it shows that one of the angioplasty balloons currently sold can be improved simply by changing the configuration of the materials, instead of having to research new medical grade polymers and how to process them.

The plastic deformation of stent during the implantation process, with considering the effect of artery and plaque, was investigated in this thesis. The stress-stretch relationships of porcine coronary arteries and aortas were obtained by the tensile test. The nonlinear ABAQUS finite element software was used in the analysis. The nonlinear-elastic, plastic and linear elastic material models for artery-plaque, stent and balloon were employed respectively. In this thesis, the initial folded balloon model was proposed to simulate the whole inflation and deflation process of balloon deformation. To investigate the effect of artery with plaque on the deformation of stent, the FEM model with considering the artery and plaque was proposed to simulate the expansion process of stents. The plaque¡¦s destruction during the expansion of stent was studied. The effects of plaque¡¦s thickness and the artery models on the expansion of stent were investigated. The effects of geometrical parameters and the influences on the deformation and the stress distribution of Palmaz type stent were discussed. The expansion ability and foreshortening of Chen and Tsai¡¦s stent were also assessed in this work. The results indicate that the limited expansion ability make Chen and Tsai¡¦s stent be not suitable for using as coronary stent. It might be used as the stent of carotid artery if its expansion ability improved by properly designing stent¡¦s diameter and geometry shape. The results reveal the foreshortening of Chen and Tsai¡¦s stent does not approach to zero as mentioned by Chen. A Chen modified and Tsai¡¦s stent was also proposed in this study. The simulation results show that the foreshortening in the Chen modified type is improved.

The dropping of a water-filled latex balloon onto a flat, rigid surface is an experiment that is known and has been performed by many, but on which there is no existing published work. High-speed images taken of the process revealed a range of phenomena, many of which had not been previously observed. After release, a water-filled balloon accelerates down and impacts with the tank floor. Upon impact, the balloon deforms through the propagation of waves up the balloon from the impact point. If the balloon does not rupture during this deformation, it then bounces up off the surface, the whole process similar to that when a water droplet bounces on a hydrophobic surface. Often, however, the balloon ruptures. This occurs through the propagation of one or more cracks through the balloon, leading to the rapid retraction of the membrane over the water’s surface, and consequent ejection of a fine spray of water droplets behind it. If there are any waves on the balloon at the moment of rupture, a larger-scale growth of the interfacial amplitude occurs, of the same wavelength as the preburst waves. Eventually, gravity dominates, as the water slumps down and spreads over the flat surface. In this thesis, the process described above is examined in detail, both experimentally and theoretically. To gain some insight into the behaviour of the latex balloons, their static and quasi-static behaviour is examined. A experimental method better than simply dropping the balloons was derived, permitting the accurate quantitative measurement of the process. In this new method, the balloons were held stationary, forced at a set frequency, then ruptured with a pin. The pre-burst waves are then shown to be accurately modelled by linear theory, with tension in the membrane acting much like a fluid surface tension. The behaviour of the rubber in retraction from large initial stretches is shown to be disperse, in contrast with that observed for retractions from small initial stretches, due to both non-linearity in the rubber and drag from the water on the strip. The spray ejected behind the rubber is explained as consequence of the inherent instability of the Gaussian velocity field in the wake. Finally, the late-time growth of the interfacial amplitude is examined, and argued to be closely-related to the Richtmyer-Meshkov instability. A model is then derived for the case of a balloon oscillated and burst with water both inside and outside, and is shown to be in approximate agreement with experiments.