This thesis reports studies of methane dehydro-aromatization (MDA) over Zn-based/HZSM-5 catalysts and the catalytic conversion of acetylene gas (C2H2) on grain surface reactions using time-of-flight mass spectrometry (TOF-MS). Both catalytic reactions generate polycyclic aromatic hydrocarbons (PAHs) as their final products. For the MDA reaction, the performance of Zn-based/HZSM-5 catalysts prepared by wet impregnation method was investigated under the conditions of atmospheric pressure and supersonic jet expansion (SJE). The experimental results revealed that, under the SJE condition, the Zn/HZSM-5 catalysts exhibited high catalytic activity. It was also found that because of the rapid migration of H+ ions on the catalyst, the activation of CH4 at active sites of nano-ZnO is facile. A new reaction mechanism involving an active “ZnO-CH3+...-H-ZnO” intermediate formed as a result of synergetic action between ZnO and HZSM-5 has been proposed for the dissociation of methane and dehydrogenation. However, under atmospheric pressure, the catalytic activity of the Zn/HZSM-5 catalysts was low. The physical properties of the catalyst were characterized by Brunauer-Emmett-Teller (BET), Fourier transform infrared (FT-IR), temperature-programmed reduction of H2 (H2-TPR), temperature -programmed desorption of NH3 (NH3-TPD), X-ray photoelectron spectroscopy (XPS), thermogravimetric and differential thermogravimetric (TG/ DTG), and high-resolution transmission electron microscopy (HRTEM) techniques. For the catalytic conversion reaction of acetylene gas to form PAHs, the grains used were olivine and pyroxene-type silicates as well as alumina. Gas-phase PAHs were produced by the catalytic reaction of acetylene over crystalline silicates and alumina in a pulsed jet expansion condition and the gaseous products detected using time-of-flight mass-spectrometry (TOF-MS). In a separate experiment, further confirmation of the catalytic conversion of PAHs was obtained with the acetylene gas at atmospheric pressure flowing continuously through a fixed-bed reactor. The gas effluent and carbonaceous compounds deposited on the catalysts were dissolved separately in dichloromethane and analyzed using gas-chromatography-mass spectrometry (GC-MS). Amongst the samples studied, alumina showed higher activity than the olivine and pyroxene-type silicates grains. A mechanism for PAH formation is proposed in which the Mg2+ in silicates and Al3+ ions in Al2O3 act as Lewis acid sites for the acetylene reactions. Experimental investigation indicated that these silicates and Al2O3 particles are capable of providing catalytic centers for adsorption and activation of acetylene molecules that are present in the circumstellar environments of mass-losing carbon stars. The structure and physical properties of the particles were characterized by means of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and high-resolution transmission electron microscopy (HRTEM) techniques. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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No description available.

The current streamline formulation is limited to single-porosity systems and is then not suitable for application to naturally fractured reservoirs. Describing the fluid transport in naturally fractured reservoirs has been recognized as a main challenge for simulation engineers due to the complicated physics involved. In this work, we generalized the streamline-based simulation to describe the fluid transport in naturally fractured reservoirs. We implemented three types of transfer function: the conventional transfer function (CTF), the diffusion transfer function (DTF), and the empirical transfer function (ETF). We showed that these transfer functions can be implemented easily in the current single-porosity streamline codes. These transfer functions have been added as a source term to the transport equation that describes the saturation evolution along the streamlines. We solved this equation numerically for all types of transfer functions. The numerical solution of the continuity equation with DTF and ETF requires discretizing a convolution term. We derived an analytical solution to the saturation equation with ETF in terms of streamline TOF to validate the numerical solution. We obtain an excellent match between the numerical and the analytical solution. The final stage of our study was to validate our work by comparing our dual-porosity streamline simulator (DPSS) to the commercial dual-porosity simulator, ECLIPSE. The dual-porosity ECLIPSE uses the CTF to describe the interaction between the matrix-blocks and the fracture system. The dual-porosity streamline simulator with CTF showed an excellent match with the dual-porosity ECLIPSE. On the other hand, dual-porosity streamline simulation with DTF and ETF showed a lower recovery than the recovery obtained from the dual-porosity ECLIPSE and the DPSS with CTF. This difference in oil recovery is not due to our formulation, but is related to the theoretical basis on which CTF, DTF, and ETF were derived in the literature. It was beyond the scope of this study to investigate the relative accuracy of each transfer function. We demonstrate that the DPSS is computationally efficient and ideal for large-scale field application. Also, we showed that the DPSS minimizes numerical smearing and grid orientation effects compared to the dual-porosity ECLIPSE.

Thesis (M.S.)--Rutgers University, 2007. / "Graduate Program in Biomedical Engineering." Includes bibliographical references (p. 23-24).

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 186-201).

Thesis (Ph. D.)--Carleton University, 2000. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 201-237).

An ion scattering surface analysis system using TOF energy-analysis of the scattered ions was improved with a duoplasmatron ion source and new data-handling electronics. The new source gave greater beam current and stability. The new electronics were: a timing filter amplifier and constant fraction discriminator. Much work was done on alignment of the sample in the beam and reduction of the spot size. To add to the flexibility of the beam guidance system a new pair of steering plates was added. Some of the test spectra are presented to show the operation of the system. Relevant material on various aspects of the system are presented in the appendices. / None / Master of Engineering (ME)

Infants and young children with tracheostomies need better respiratory monitors. Mucus in the tracheostomy tube presents a serious choking hazard.  Current devices indirectly detect respiration, often yielding false or delayed alarms.  A compact ultrasonic time-of-flight (TOF) airflow sensor capable of attaching directly to the tracheostomy tube has been developed to address this need.  The ultrasonic flow sensing principle, also known as transit time ultrasound, is a robust method that correlates the timing of acoustic signals to velocity measurement.  The compact prototype developed here can non-invasively measure all airflow into and out of a patient, so that breath interruption can easily be detected. This paper concerns technical design of the sensor, including the transducers, analog/digital electronics, and embedded systems hardware/software integration.   Inside the sensor's flow chamber, two piezoelectric transducers sequentially transmit and receive ping-like acoustic pulses propagating upstream and downstream of flow.  A microcontroller orchestrates measurement cycles, which consist of the transmission, reception, and signal processing of each acoustic pulse.  The velocity and direction of airflow influence transit time of the acoustic signals.  Combining TOF measurements with the known geometry of the flow chamber, average air velocity and volumetric flow rate can be calculated.  These principles have all been demonstrated successfully by the prototype sensor developed in this research. / Master of Science