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An analytical model for the specific gas detection of oxygen, carbon dioxide, and water vapor using zirconia amperometric oxygen sensors has been developed. Sensors of this type have been designed, fabricated, and tested using planar ceramic technology. Furthermore, an experimental setup has been designed and constructed for sensor characterization. This testbed can accurately control gas partial pressures as well as the total system pressure over a wide range of flow rates. Extensive effort has been put into design and construction of this testbed to ensure accurate scientific measurements. Special attention has been paid to ensuring that the apparatus is leak-tight from air to ensure accurate measurements at low oxygen partial pressures. Results of the experimentation for oxygen detection as well as the detection of carbon dioxide and water vapor are presented. The effects of electronic conduction in the zirconia electrolyte at low oxygen partial pressures are examined. Possible applications of the sensor, as well as suggestions for further research are discussed.

The nature of turbulent jet flows is considered. First, the effects of nozzle geometry are examined. A boundary element formulation, which may be used to analyze the stability of vortex-sheet jets of arbitrary geometry, is developed. This formulation is applied to rectangular jets. It is found that rectangular jets support four linearly independent families of instability waves. Within each family there are infinitely many modes. A way to classify these modes according to the characteristics of their eigenfunctions is proposed. It is found that the first and third modes of each family are corner modes. The fluctuations associated with these waves are localized near the corners of the jet. The second mode in each family, however, is a center mode with maximum fluctuations concentrated near the central portions of the jet. The center modes have the largest spatial growth rates. It is anticipated that as the instability waves propagate downstream the center modes would emerge as the dominant instabilities of the jet. Second, a K-$\varepsilon$ turbulence model, which incorporates Pope's nonplaner correction and Sarkar's high convective Mach number correction, is proposed for the computation of time-averaged turbulent jet flows. It is demonstrated that this model does contain the essential ingredients of turbulence physics for adequate jet mean flow prediction. However, the empirical constants that are generally used are found to be inappropriate for jets. A high-order parabolized approach to computing ideally expanded jet flows is presented. A new set of empirical constants is chosen, which better correlates the computations with measurements for a set of jets representative of a variety of nozzle configurations. It is demonstrated that, when the standard constants are replaced by the new ones, the model can offer good mean flow predictions for axisymmetric, / rectangular and elliptic jets with Mach numbers ranging from 0.4 to 2.0 and jet total temperature to ambient temperature ratios ranging from 1.0 to 4.0. Together, the two efforts lay much of the groundwork for a complete study of the effects of nozzle geometry on the mixing and noise generation in high-speed jet flows. / Source: Dissertation Abstracts International, Volume: 56-03, Section: B, page: 1471. / Major Professor: Christopher K. W. Tam. / Thesis (Ph.D.)--The Florida State University, 1995.

Thesis (M.App.Sc.) - Carleton University, 2009. / Includes bibliographical references (p.153-159). Also available in electronic format on the Internet.

With increasing emphasis on reliability in industry, products are now made more robust, and few failures are observed in a short development period. In this circumstance, assessing product reliability based on degradation data at high stress levels becomes necessary. These tests are called accelerated degradation tests. There is a need to scientifically design these test plans. A good test plan can save time and expense, and provide more accurate estimates of reliability for the same number of test units and test time. To address this problem, a four-step-approach for the optimum planning of accelerated degradation tests is proposed in this study. First, a cost model for accelerated degradation tests is given. New analytical methods for obtaining the optimal allocations of the test units to selected stress levels are developed next. The stress considered here is temperature. Then, measurement plans are discussed. Nonlinear mixed effects models are applied and further developed and extended to allow for acceleration in the analysis of accelerated degradation data and to obtain the degradation model's parameters. A simulation method is used to evaluate the test plans' properties. In the simulation step, the mean square error is used as a criterion for comparing the accuracies that can be obtained from the test plans. A linear degradation case is used to illustrate the given approach. An LED example is also given to illustrate this approach. Test plans for obtaining accurate estimates of reliability information within cost budgets are important. The proposed approach enables reliability and test engineers to get the most efficient use of their test resources.

A high-order immersed boundary method (IBM) for the computation of unsteady, incompressible fluid flows on two-dimensional, complex domains is proposed, analyzed, developed and validated. In the IBM, the equations of interest are discretized on a fixed Cartesian grid. As a result, domain boundaries do not always conform to the (rectangular) computational domain boundaries. This gives rise to 'immersed boundaries', i.e., boundaries immersed inside the computational domain. A new IBM is proposed to remedy problems in an older existing IBM that had originally been selected for use in numerical flow control investigations. In particular, the older method suffered from considerably reduced accuracy near the immersed boundary surface where sharp jumps in the solution, i.e., jump discontinuities in the function and/or its derivatives, were smeared out over several grid points. To avoid this behavior, a sharp interface method, originally developed by LeVeque & Li (1994) and Wiegmann & Bube (2000) in the context of elliptic PDEs, is introduced where the numerical scheme takes such discontinuities into consideration in its design. By comparing computed solutions to jump-singular PDEs having known analytical solutions, the new IBM is shown to maintain the formal fourth-order accuracy, in both time and space, of the underlying finite-difference scheme. Further validation of the new IBM code was accomplished through its application to several two-dimensional flows, including flow past a circular cylinder, and T-S waves in a flat plate boundary layer. Comparison of results from the new IBM with results available in the literature found good agreement in all cases.