To obtain the profiles of dry bulb and wet bulb temperature, specific humidity, q, and air density, ρ, to a height of 200 meters above the ground, a precise lightweight thermocouple psychrometer was designed. To lift the thermocouple psychrometer and the attached wires in obtaining the ρq profiles, a rigid polyethylene balloon augmented with 5.5-feet outdoor or 100-g meteorological balloons were used. Using the height dependent eddy exchange coefficient and a one-dimensional time-dependent profile model, the nighttime variations of ρq as a function of height were predicted and compared with observed values. It was found that the general shape of the eddy exchange coefficient, K(Z), was approximately the same as found in recent literature.

Geóloga / Como objetivos se busca estimar el potencial de climatización con bombas de calor en sectores residenciales de la Región Metropolitana e indicar dónde se cumplen los aspectos físicos necesarios para su implementación. Por un lado, se analizan los intercambiadores horizontales enterrados aproximadamente a un metro y medio del suelo. Se calcula el área de las tuberías a enterrar, considerando la demanda térmica de calefacción de viviendas con distintas dimensiones y la eficiencia del sistema. Se estima que el área de intercambiadores varía entre el triple a doble de la superficie que se desea climatizar. Junto a esto, se analizan los planes reguladores comunales para obtener las superficies mínimas prediales de las zonas residenciales y ver dónde es probable encontrar espacio para instalar el sistema. Se observa que son las zonas periféricas y el sector nororiente del Gran Santiago los que presentan las condiciones requeridas. Otro tipo de intercambiadores son los verticales abiertos. Para analizar su potencial se calculan los caudales de extracción de agua subterránea típicos en la Cuenca de Santiago y el rendimiento del sistema. Con estos caudales se tiene que las potencias generadas superan con creces las demandas térmicas residenciales. También se estima la profundidad de los intercambiadores considerando los abatimientos generados por la actual extracción de agua en la zona, los cuales no son significativos por la extensa presencia de arenas y grava, y el máximo nivel del agua subterránea en los últimos 30 años, donde se detectan zonas con un descenso sostenido en el último tiempo, que requieren mayor cuidado al determinar la profundidad. La profundidad de los intercambiadores se estima por sobre los 150 metros en las comunas cercanas a la zona apical del Abanico del Maipo, para luego ir disminuyendo radialmente, hacia el norte y el este del abanico, y llegar a 20 metros. Considerando los potenciales generados, aspectos físicos y costos de instalación, los intercambiadores horizontales son recomendados para viviendas unifamiliares y los intercambiadores abiertos para edificaciones mayores como edificios o viviendas distritales. / Este trabajo ha sido financiado por el Centro de Excelencia en Geotermia de Los Andes (CEGA), proyecto FONDAP 15090013

The major objective of this project was to assess the application of atmospheric pressure microwave induced plasmas to the control of trichloroethene vapour emissions from industrial cleaning processes. Laboratory experiments, chemical modelling and chemical analysis were the three major elements of the project. A typical stream to be treated, as measured at the project test site, was 60 lmin-1 of air contaminated with 2 % trichloroethene vapour. The practical experiments carried out were trichloroethene dissociation by microwave plasma, propane-assisted microwave plasma and conventional propane combustion. Flow rates of 4 � 12 lmin-1, trichloroethene concentrations of 0 � 6 % in air and plasma powers of up to 3 kW were investigated. The processes were simulated using both equilibrium and kinetic modelling in CHEMKIN. Chemical analysis was done using gas chromatography with an electron capture detector, with gas chromatography/mass spectrometry to identify eluted compounds. The destruction and removal efficiencies, by-products, temperature and robustness of each process were investigated. A simple economic and environmental analysis was done, and the results were compared with currently available processes.

Pressure measurement using a strain gauge bonded with epoxy adhesive to a metallic mechanical support has been, and still is, extensively employed, however, for some applications the use of an epoxy is inadequate, especially when temperatures exceed 120C. There is therefore particular interest in the use of thin film techniques to vacuum deposit strain gauges directly on metallic substrates. Such devices are highly cost effective when produced in large quantities due to the manufacturing techniques involved. This makes them ideally suited for use in large-volume products such as electronic weighing scales and pressure transducers. In this thesis, new techniques for fabricating thin film vapour deposited strain gauge transducers on metal substrates for application as novel pressure sensors in the fastener industry are developed. Clearly, for a vapour deposited strain gauge to function correctly, it is essential that it be deposited on a defect free, high quality electrically insulating film. This was a significant challenge in the present study since all available physical vapour deposition (PVD) equipment was direct current (DC) and insulators of around 4 um thick were needed to electrically isolate the strain gauges from metal. As a result, several methods of depositing insulators using DC were developed. The first involved the use of DC magnetron sputtering from an aluminium target to reactively deposit up to 4 um thick AlN. DC magnetron discharges suffer arc instability as the AlN forms on the target and this limits the maximum thickness that can be deposited. Consequently, the arc instability was suppressed manually by increasing argon gas flow at the onset of arcing. Although the deposited AlN showed a high insulating resistance, it was found that the breakdown voltage could significantly increase by (a) utilising a metallic interlayer between the thin film insulator and the metallic substrate and (b) annealing in air at 300C. A second deposition method involved the use of DC magnetron sputtering to deposit modulated thin film insulators in which an aluminium target was used to reactively deposit alternating layers of aluminium nitride and aluminium oxide. These films showed significant increases in average breakdown voltage when the number of layers within the composite film was increased. The third method involved the deposition of AlN thin film insulators using partially filtered cathodic arc evaporation with shielding. Initially, AlN was deposited under partially filtered conditions to obtain a relatively thick (~ 4 um) coating then, while still depositing under partially filtered conditions, a smooth top coating was deposited by using a shielding technique. The deposition of metal macroparticles is an inherent problem with cathodic arc deposition and shielding is one form of macroparticle filtering. Such particles are highly undesirable in this study as they are electrically conductive. A fourth coating technique for depositing insulators on steel was based on thermal spray technology. Insulating films of Al2O3 were plasma sprayed and then polished to thereby fabricate viable electrical insulators for vapour deposited strain gauges. With respect to depositing strain gauges two methods were employed. The first involved the sputter deposition of chromium through a shadow mask to form a strain gauge with gauge factor sensitivity of around 2. The second used cathodic arc evaporation to fabricate a multi-layered strain gauge composed of alternating CrN and TiAlN layers that yielded a gauge factor of around 3.5. The technique achieves better compatibility between gauge and insulator by allowing a wider selection of materials to form the gauge composition. Finally, a novel pressure sensor in the form of a load cell was developed that consisted of a chromium strain gauge on a steel washer electrically insulated with AlN thin film. The load cell showed good performance when tested under compressive load.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Babatunde Ogunnaike, Dept. of Chemical Engineering, and Robert W. Birkmire, Dept. of Materials Science & Engineering. Includes bibliographical references.

Current leading thin-film solar cell technologies, i.e., cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS), employ elements which are either toxic (Cd), or rare and/or expensive (In, Te, Ga, and Cd). The aim of this thesis is to investigate new, abundant, non-toxic p-type semiconductors for potential solar absorber application. Two ternary chalcogenides, Cu���PSe��� and CuTaS���, were selected for their attractive calculated optical absorption properties. Thin films of both materials were synthesized using physical vapor deposition (PVD) techniques in conjunction with post-deposition annealing. Cu���PSe��� appears promising for solar absorber applications, with a measured optical bandgap of 1.2 eV, an absorption coefficient (��) reaching 10��� cm�����, Hall mobilities of 19.8���30.3 cm��/V���s, and carrier concentrations of 3.3���4.9 10����� cm�����. Optical characterization of CuTaS��� thin-films showed a rapid turn-on of absorption, with �� exceeding 10��� cm����� within 0.5 eV of the bandgap. To date, reproducible synthesis of CuTaS��� thin films has been problematic. Moreover, these films are insulating and thus not yet appropriate for thin-film solar cell absorber applications. / Graduation date: 2013

Vertically aligned carbon nanotubes have been grown using Ni as catalyst by plasma enhanced chemical vapor deposition system (PECVD) in various pre-patterned substrates. Ni was thermally evaporated on silicon substrates with anodized alumina mask prepared in different methods including 2 step anodization of porous alumina template and interference lithography assisted array of pores. The templates helped to define Ni nanodots inside the pores which in turn catalyzed the growth of carbon nanotubes inside the PECVD system at temperature of 700-750C using mixture of ammonia and acetylene gases. The resulting well-aligned multi-walled carbon nanotubes were further investigated using SEM, TEM and Raman spectroscopy. The size, shape and structure of the grown carbon nanotubes were also discussed. / Singapore-MIT Alliance (SMA)

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 189-197).

The tropical cyclone (TC) and environmental interaction is not fully understood. Previous studies have demonstrated that this interaction affects intensity change. The studies found that intensification is favored in low shear, moist environments, with high sea surface temperatures (SST). However, little precise quantification was provided, especially in terms of the impact of environmental water vapor on TC intensity change. This work addresses the TC interaction with the environmental water vapor. Results from a comprehensive statistical study show that TC intensification is more likely to occur in an anomalously moist environment than a dry environment. However, only a small amount of the total variance is explained. When assessing the effect of vertical wind shear along with environmental water vapor, more of the variance is explained. Water vapor not only affects TC intensity. Prior modeling studies have demonstrated impacts from environmental water vapor on TC structure. These impacts can also affect intensity change. Specifically, enhanced water vapor content within the TC enhances the rainbands, which can lead to an eyewall replacement cycle, causing a temporary weakening, followed by re-intensification. This thesis evaluates observational and high resolution MM5 model output from Hurricanes Katrina and Rita from the Hurricane Rainband and Intensity Experiment (RAINEX) to evaluate the effects of varying water vapor distributions on TC structure. While the two hurricanes were of similar intensity, they had different water vapor distributions and structures. Rita underwent an eyewall replacement cycle while under RAINEX surveillance while Katrina did not. Rita was also located within a dry environment and had a strong horizontal moisture gradient, while Katrina was in a moist environment and had a weak moisture gradient. Results suggest that a strong horizontal water vapor gradient, with a moist TC and dry outer environment may confine the hurricanes into a pattern that causes them to have high circularity, promoting the formation of a secondary eyewall. The dry outer environment had strong atmospheric stability and was less favorable for deep convection far from the center in the Rita case. The moist environment in the Katrina case was more unstable. This may have allowed for the rainbands to be farther from the center in a less circular pattern than Rita. The results presented in this thesis suggest that this pattern is less favorable for an eyewall replacement cycle.

The present work is focused on the nucleation and growth mechanism of carbon nanotubes (CNT) that we have studied through different field emission techniques (FEM, FIM and atom-probe (PFDMS)). Reaction conditions associated with the CVD synthesis method were modeled inside the microscope aiming at studying nucleation phenomena at high resolution. The interaction between different metals (Fe, Co, Ni, conditioned as sharp tips) and gases (acetylene, ethylene and ethanol) was analyzed operando at high temperatures (500–900K), with the aim of reproducing growth conditions during the imaging process. Ni was, in the end, the only metal studied, due to the poor quality of images acquired from Co and Fe. Aimed at reproducing the conditioning step of the catalyst often observed in CVD protocols, a first study showed that the crystal adopts a polyhedral morphology at the working temperature (873K) in an hydrogen atmosphere or under Ultra-High-Vacuum conditions, by the extension of dense crystal planes like {111} or {100}. The presence of hydrogen in the chamber does not seem to present any influence on the final crystal morphology at temperatures above 600K. When exposed to a carbon-containing gas, nickel crystals present two distinct behaviors following the temperature region that is explored. At temperatures below ~623K, exposing Ni to ethylene or acetylene leads to the formation of a stable and poorly structured nickel carbide layer. The superficiality of this carbide is proven by the ease of its physical (by increasing the electrical field) or chemical (exposure to hydrogen or oxygen) evacuation. These three treatments initiate a clean-off phenomenon that evacuates the carbide layer. Reproducing these experiments in the atom-probe confirmed the carbidic nature of the surface as NiCy compounds were collected. At temperatures above 623K, the carbide layer (formed by exposing Ni to the same gases) becomes unstable. Its formation is related to a transition period that precedes the nucleation of graphenes on the surface. The Ni crystal undergoes a massive morphological transformation when acetylene is introduced in the chamber at 873K. This phenomenon is induced by the presence of carbon on the surface which adsorbs so strongly on step sites that it provokes their creation. Carbon also induces a considerable enhancement of Ni atoms mobility that allows for this transition to occur. Once the new morphology is attained, nucleation of graphenes is observed to start on the extended and carbon-enriched step-containing crystal planes. By reproducing these experiments in the atom-probe, a high surface concentration of carbon dimers and trimers was observed. A kinetic study of their formation was thus achieved and showed that they were formed on the surface by the recombination of Cad. Their potential role as building-blocks of the CNT growth process (which had previously been proposed following theoretical considerations) is thus suggested on the basis of experimental results for the first time. Two critical surface concentrations are highlighted in the present work. The first one is needed for the formation of carbon dimers and trimers and the second one has to be attained, during the morphological transformation, before the onset of graphene nucleation, probably providing a sufficient growth rate of the graphitic nuclei and allowing them to attain their critical size before their decomposition. Finally, the observation of rotational circular patterns, most probably related to carbon nanotubes, suggests that CNT growth (and not only graphene nucleation) occurred episodically in our conditions, confirming the validity of our model.