The main focus of this work was to investigate the nature of unsteady boundary-layer development over finite domains, with the behaviour of the boundary layer on a rotating sphere in an unbounded, rotating fluid used as a prototype. The sphere and its surrounding fluid are assumed to be initially rotating as a solid body, and the evolution of a boundary layer on the sphere is analysed in cases where the sphere has been smoothly slowed, or brought to a state of rotation in an opposite sense to its initial conditions. It may be seen that a characteristic property of this flow is that the boundary layer is bi-directional; over most of the streamwise domain for the flow, whether the flow is positive or negative in the streamwise coordinate direction depends on the transverse location being considered. This fact leads to challenges in the numerical evaluation of the flow field due to the parabolic nature of the boundary-layer equations. A further consideration is the implication that these regions of reversed flow cause the flow field to contain minima and maxima in the streamwise velocity component. This has been shown in a little-known study by Cowley et al. (1985) to cause the boundary layer to become susceptible to asymptotically short-scale perturbations with large frequencies. The unsteady boundary layer on a rotating sphere under these conditions is consequently shown to be extremely challenging to compute numerically. It is also found that using local approximations at the ends of the finite domain, which in the case of the sphere are the pole and equator, to investigate the two-dimensional boundary layer can cause difficulties, as in some cases there exist steady, spatial perturbations to a boundary-layer state which introduce short spatial scales. The instabilities and other features analysed in this work are framed largely in the context of the rotating sphere, but the causes of the phenomena are found to be sufficiently generic that they may be observed in other physical contexts. To demonstrate this, the shallow katabatic flow down a cooled slope is briefly investigated, and the above mathematical features are again uncovered.

The boundary layer problems in periodic homogenization arise naturally from the quantitative analysis of convergence rates. Formally they are second-order linear elliptic systems with periodically oscillating coefficient matrix, subject to periodically oscillating Dirichelt or Neumann boundary data. In this dissertation, for either Dirichlet problem or Neumann problem, we establish the homogenization results and obtain the nearly sharp convergence rates, provided the domain is strictly convex. Also, we show that the homogenized boundary data is in W1,p for any p ∈ (1,∞), which implies the Cα-Hölder continuity for any α ∈ (0,1).

Graduation date: 1984

The "n-like layer" is important in multilayer layer amorphous selenium (a-Se) based Xray detector structures because it blocks the injection of holes from the positive electrode. The dark current in these devices is controlled primarily by hole injection,and the introduction of the n-like layer to block hole injection was a key development in the commercialization of a-Se X-ray detectors. An n-like a-Se layer is defined as a layer in which the electron range is much greater than the hole range, ¦Ìe¦Óe >> ¦Ìh¦Óh, where ¦Ó and ¦Ì are the lifetime and drift mobility of the charge carriers and the subscript e and h represent electrons and holes.<p> This thesis examines the effect of doping a-Se with Group II elements (in particular Mg) towards finding a better n-like layer ¨C that with relatively long electron range (drift mobility ¡Á lifetime) , trap limited hole transport and which is stable against crystallization. Conventional Time of Flight (TOF) and Interrupted Field Time of Flight (IFTOF) transient photoconductivity measurements were used to characterize the electron and hole transport in various Group II doped a-Se layers. The dependence of the electron and hole lifetimes and drift mobilities on the composition of the n-like layer was examined. The addition of Group II materials converts the a-Se starting material from p-like into n-like. It was found that increasing the concentration of Mg increases the electron range while limiting the hole range by modifying the population of deep traps. The addition of As further limits the hole transport but does not alter the electron range. The clear reproducibility of the thermal properties obtained from the Differential Scanning Calorimetry (DSC) implies that small amounts of Mg can be used as a suitable n-type dopant.

The "n-like layer" is important in multilayer layer amorphous selenium (a-Se) based Xray detector structures because it blocks the injection of holes from the positive electrode. The dark current in these devices is controlled primarily by hole injection,and the introduction of the n-like layer to block hole injection was a key development in the commercialization of a-Se X-ray detectors. An n-like a-Se layer is defined as a layer in which the electron range is much greater than the hole range, ¦Ìe¦Óe >> ¦Ìh¦Óh, where ¦Ó and ¦Ì are the lifetime and drift mobility of the charge carriers and the subscript e and h represent electrons and holes.<p> This thesis examines the effect of doping a-Se with Group II elements (in particular Mg) towards finding a better n-like layer ¨C that with relatively long electron range (drift mobility ¡Á lifetime) , trap limited hole transport and which is stable against crystallization. Conventional Time of Flight (TOF) and Interrupted Field Time of Flight (IFTOF) transient photoconductivity measurements were used to characterize the electron and hole transport in various Group II doped a-Se layers. The dependence of the electron and hole lifetimes and drift mobilities on the composition of the n-like layer was examined. The addition of Group II materials converts the a-Se starting material from p-like into n-like. It was found that increasing the concentration of Mg increases the electron range while limiting the hole range by modifying the population of deep traps. The addition of As further limits the hole transport but does not alter the electron range. The clear reproducibility of the thermal properties obtained from the Differential Scanning Calorimetry (DSC) implies that small amounts of Mg can be used as a suitable n-type dopant.

binding of either tyrosine or 6MPH4 alone does not change the coordination. However, when both tyrosine and 6MPH4 are bound, the active site becomes 5-coordinate, creating an open site for reaction with O2. Investigation of the kinetics of oxygen reactivity of TyrH complexes in the absence and presence of tyrosine and/or 6MPH4 indicated that there is a significant enhancement in reactivity in the 5-coordinate complex in comparison to the 6-coordinate form. Similar investigations with E332A TyrH showed that Glu332 residue plays a role in directing the protonation of the bridged complex that forms prior to the formation of Fe(IV)O. Rapid chemical quench analyses of DOPA formation showed a burst of product formation, suggesting a slow product release step. Steady-state viscosity experiments established a diffusional step as being significantly rate-limiting. Further studies with stopped-flow spectroscopy indicated that the rate of TyrH reaction is determined by a combination of a number of physical and chemical steps. Investigation of the NO complexes of TyrH by means of optical absorption, electron paramagnetic resonance (EPR) and electron spin echo envelope modulation (ESEEM) techniques revealed the relative positions of the substrate and cofactor with respect to NO, an O2 mimic, and provided further insight into how the active site is tuned for catalytic reactivity upon substrate and cofactor binding. The second theory is that a decreased vertical temperature lapse rate, dT/dp, would slow cloud growth, creating a mode of cloud-top heights at the stable layer as clouds lose buoyancy. The signal for lapse rate changes in the AIRS data, however, is not as strong as the signal for RH differences. Near 600-400 hPa, roughly the region where congestus cloud-top heights are located, no significant difference in lapse rates is noted between congestus and deep clouds; in fact, the mean values suggest that congestus clouds appear in more unstable atmospheres than deep clouds. Only slight differences in temperature and lapse rate are noted in ERA data as well. These results suggest that drier air may play a greater role in limiting congestus cloud-top heights than increased atmospheric stability. Five years of relative humidity (RH) observations from the Atmospheric Infrared Sounder (AIRS) instrument aboard the Aqua satellite are then analyzed to identify areas of anomalously dry air between 600 and 400 hPa over deep convective regions of the tropical oceans. Back trajectories are then calculated for each observed parcel.

In a conventional nonvolatile memory (NVM), charge is stored in a ploy-silicon floating gate (FG) surrounded by dielectrics. But, it will suffer some limitations for continued scaling of the device structure. Therefore, the nanocrystal nonvolatile memory devices have been investigated to overcome the limit of the conventional floating gate NVM in recently years. Nanocrystal charge storage offers several advantages, the main one being the potential to use thinner tunnel oxide without sacrificing nonvolatility. This is a quite attractive proposition since reducing the tunnel oxide thickness is a key to lowering operating voltage and/or increasing operating speeds. In this thesis, we have fabricated tungsten (W) nanocrystals nonvolatile memory devices. A thin tungsten silicide (W5Si3) layer was deposited on tunnel oxide layer first. The following oxidation was performed in furnace system. The W element tends to segregate downward and precipitate on the tunnel oxide after thermal oxidation. In addition, the silicon element is oxidized into silicon dioxide surrounded tungsten nanocrystals. Also, the carrier gas, such as O2 and N2, were also added as the tungsten silicide deposition. The memory effect and the electrical reliability for W nanocrystals surrounded in different dielectric were also investigated in this study. In addition, the formation mechanism of W nanocrystals with additional silicon oxide capped on tungsten silicide was also investigated. The thicker silicon oxide can effectively control the thermal oxidation condition and prevent thin film degradation. However, the overall oxidation cause the memory window reduction and the electrical characteristics degradation, resulted from the partially oxidation of W nanocrystal to metal-incorporated dielectric. By contrast, we also demonstrated the structure that deposited the charge trapping layer by co-sputtered W and dielectric material as SiO2 or Si3N4 to directly form the W nanocrystal embedded in dielectrics. Besides, the W and Si directly deposited by co-sputtered to adjust the two elements contained ratio had investigated as well in this study. Furthermore, the memory effect and electrical characteristics for germanium (Ge) element incorporated W nanocrystal memory were also discussed. The additional storage element contributes the memory effect. In summary, the memory effect for W nanaocrystal embedded in different dielectric, the effect of the thermal treatment for additional silicon oxide incorporation, and the contribution of the Ge element to the memory effect can be obtained from the fabrication of W nanocrystal memory were finished in this study.

In this thesis¡M As-grown and H-treated polycrystalline diamond film Metal-Insulator-Semiconductor Field-Effect-Transistor on the p-type surface semiconductive layers of undoped hydrogen-terminated CVD diamond films were successfully fabricated using a new fabrication process[1-2]. This new fabrication process of the polycrystalline diamond film MISFET exploits selected area deposition (SAD)[3] with Shadow Mask and indeed possesses low cost and less process¡Mso it was a best alternation for diamond device fabrication recently. Next, a modified equivalent circuit of the polycrystalline diamond film MISFET on the p-type surface semiconductive layers of undoped hydrogen-terminated CVD diamond films is also proposed, which consists of FET and the parasitic current conduction paths. The FET current path represents the currents flowed through the P-type conductive layer, and the parasitic current conductance paths represents the currents flowed through the barrier of metal/diamond and through both of the grain boundary and bulk diamond, respectively. In addition, the I-V characteristics of As-grown and H-treated polycrystalline diamond film MISFET has been successfully simulated by using this modified equivalent circuit. The simulation results show good agreements with the measurement. In addition, the I-V characteristics of As-grown polycrystalline diamond film MISFET, from measurement and simulation results, were great affected by the grain boundaries and bulk diamond crystallites, and their shape is similar to that of Schottky diode. Whereas, the effect of the bulk diamond crystallites and diamond grain boundaries was great decreased after hydrogen plasma treatment and the shape of the I-V characteristics is similar to that of Si-MISFET. This result is believed to have important impacts for the application of diamond device in the nearest future.

Most design of experiments assumes predetermined design regions. Design regions with uncertainty are of interest in the first chapter. This chapter proposes optimal designs under a two-part model to handle the uncertainty in the design region. In particular, the logit model in the two-part model is used to assess the uncertainty on the boundary of the design region. The second chapter proposes an efficient and effective multi-layer data collection scheme (Layers of Experiments) for building accurate statistical models to meet tight tolerance requirement commonly encountered in nano-fabrication. "Layers-of-Experiments" (LOE) obtain sub-regions of interest (layer) where the process optimum is expected to lie and collect more data in the sub-regions with concentrated focus. The third chapter contributes a new design criterion combining model-based optimal design and model-free space-filling design in a constraint manner. The proposed design is useful when the fitted statistical model is required to have both characteristics: accuracy in statistical inference and design space exploration. The fourth chapter proposes adaptive combined designs in the layers of experiments. This chapter also develops methods to improve model quality by combining information from various layers and from engineering models. Combined designs are modified to improve its efficiency by incorporate collected field data from several layers of experiments. Updated engineering models are used to build more accurate statistical models.

This study focused on the improvement of film cooling for gas turbine vanes using both computational and experimental techniques. The experimental component used a matched Biot number model to measure scaled surface temperature (overall effectiveness) distributions representative of engine conditions for two new configurations. One configuration consisted of a single row of holes on the pressure surface while the other used numerous film cooling holes over the entire vane including a showerhead. Both configurations used internal impingement cooling representative of a 1st vane. Adiabatic effectiveness was also measured. No previous studies had shown the effect of injection on the mean and fluctuating velocity profiles for the suction surface, so measurements were made at two locations immediately upstream of film cooling holes from the fully cooled cooling configuration. Different blowing conditions were evaluated. Computational tools are increasingly important in the design of advanced gas turbine engines and validation of these tools is required prior to integration into the design process. Two film cooling configurations were simulated and compared to past experimental work. Data from matched Biot number experiments was used to validate the overall effectiveness from conjugate simulations in addition to adiabatic effectiveness. A simulation of a single row of cooling holes on the suction side also gave additional insight into the interaction of film cooling jets with the thermal boundary layer. A showerhead configuration was also simulated. The final portion of this study sought to evaluate the performance of six RANS models (standard, realizable, and renormalization group k-ε; standard k-ω; k-ω SST; and Transition SST) with respect to the prediction of thermal boundary layers. The turbulent Prandtl number was varied to test a simple method for improvement of the thermal boundary layer predictions. / text