A full-bridge, parallel-loaded, resonant, zero current/zero voltage switching converter has been developed for DC-DC voltage transformation. The power supply was used to condition power sourced by a 28-V, 400-A Neihoff alternator installed in a HMMWV that delivered power to a 5-kW mobile radar. This design focuses on achieving maximum power density at reasonable efficiency (i.e. > 80%) by operating at the highest resonant and switching frequencies possible. A resonant frequency of 392-kHz was achieved while providing rated power. The high resonant frequency was facilitated by the development of an extremely low inductance layout (< 20 nH) capable of conducting the high resonant currents associated with this converter topology. A design methodology is presented for parallel-loaded, resonant voltage boost converters utilizing the development of a converter prototype as a basis. The experimental results are presented as validation of the methodology.

The interfacial heat transfer coefficient is an important variable regarding the subject of metal castings. The error associated with the experimental temperature data must be dealt with appropriately so that they do not significantly affect the resulting interfacial heat transfer coefficient. The systematic and random errors are addressed using a combination of three-dimensional finite element modeling and the matrix transform method, respectively. Experimentally obtained A356 permanent mold casting data was used to estimate the interfacial heat transfer coefficient corresponding to common industrial mold coatings.

No description available.

No description available.

The single family housing sector currently accounts for approximately 15% (US DOE 2002) of the total national energy consumption with the majority of the energy use associated with the HVAC system to provide comfort for the residents. In response to recent concern over the unpredictability of the energy supply and the pollution associated with its consumption, new methods are constantly being developed to improve the energy efficiency of homes. A variety of concrete wall systems including Multi-functional Precast Panel (MPP) systems and Insulating Concrete Form (ICF) systems have been proposed to not only improve the building envelope thermal performance but other important residential characteristics such as durability and disaster and fire resistance. MPPs consist of Precast Concrete Panels (PCPs) that incorporate structural elements, interior and exterior finishes, insulation, and even heating/cooling systems into a single manufactured building panel. The ICF system is a cast-in-place concrete panel system that does not offer the level of integration found in the MPP system but has become increasingly accepted in the building construction industry. This research evaluates the thermal performance benefits of concrete wall systems in detached, single family home applications. The thermal performance benefits of two MPP systems and an ICF system are analyzed within the context of a representative or prototypical home in the U.S. and are compared to two wood frame systems; one representing a typical configuration and the other an energy efficient configuration. A whole wall approach is used to incorporate the two and three dimensional conduction and transient characteristics of the entire wall assembly, including the clear wall and wall detail regions, into a whole building simulation of the prototypical house. The prototypical house heating and cooling energy consumption associated with each wall system is determined for six representative climates throughout the U.S. to evaluate the effect of various ambient conditions on the relative energy savings. For each wall system, the effect of thermal bridging on overall R value, the effect of thermal capacitance, and the role of infiltration on energy use are investigated. The results of the research include a comparison of the prototypical house energy savings associated with each of the wall systems; an assessment of the relative importance of the increased insulation, thermal mass, and improved air tightness on the overall energy load; and a comparison of the cost of ownership for the various wall systems. The results indicate that properly designed concrete wall systems can reduce annual heating and cooling costs. In addition, the results show that the most significant impacts of improved wall systems are, from greatest to least: infiltration reduction, improved insulation configuration, and thermal capacitance. Finally, the results show that while there are energy savings associated with concrete wall systems, economic justification of these systems must also rely on the other attractive features of concrete systems such as greater durability and disaster resistance. / Master of Science

A transient technique was validated for making thermal conductivity measurements. The technique incorporated a small, effectively spherical, heat source and temperature sensing probe. The actual thermal conductivity measurements lasted 30 seconds. After approximately 15 minutes of data reduction, a value for thermal conductivity was obtained. The probe yielded local thermal conductivity measurements. Spherical sample volumes less than 8 cm² were required for the materials tested. Thermal conductivity (and moisture) distributions can be measured for relatively dry or wetted samples. The technique employs an encapsulated bead thermistor. A thermistor, more commonly used as a temperature transducer, has the inherent feature of being readily self-heated. A computer-based data acquisition and control system regulates the power supplied to the thermistor such that its self-heated temperature response approximates a step change. Thermal conductivity is deduced from the transient measurement of the power dissipated by the probe as a function of time. The technique was used to measure the thermal conductivity of fifteen liquids and five insulation materials. Two different thermistor types, glass-encapsulated and Teflon-encapsulated, were evaluated. Capabilities and limitations of each probe type and the measurement technique, in general, were observed. / M.S.

The accurate measurement of total temperature in engine diagnostics is a challenging task which is subject to several sources of error. Conduction error is predominant among these sources since total temperature sensors are embedded into a cooled strut for measurement. This study seeks to understand the effect of conduction error on total temperature probe performance from an analytical and experimental standpoint and to provide an effective calibration procedure. The review of historical low-order models, as well as results from a developed thermal resistance model, indicates that conduction error is driven by dimensionless parameters, including the Biot, Nusselt, and Reynolds Numbers, as well as a non-dimensional temperature characterizing the flow/strut temperature difference. A conduction error calibration procedure for total temperature probes is experimentally tested in this study. Data were acquired for nominal flow total temperatures ranging from 550 °F to 850 °F with the probe Reynolds number varying from 2,000 to 12,000 for varying conduction conditions with axial temperature gradients up to 1150 °F per inch. A physics-based statistical model successfully expressed total temperature probe performance as a function of dimensionless conduction driver and probe Reynolds number. This statistical model serves as a “calibration surface” for a particular total temperature probe. Due to the scaling of the problem, this calibration is experimentally obtained in moderate temperature regimes, then implemented in higher temperature regimes. The calibration yields an overall uncertainty in total temperature measurement to be ±4% of the total temperature for flow conditions typical in engine diagnostics, with extreme uncertainties in input conditions. Conduction error is successfully shown to be independent of any temperature regime and driven by dimensionless parameters. / Master of Science

Sudden cardiac death occurs due to aberrations in the multifactorial process that is cardiac conduction. Conduction velocity (CV) and its modulation by several determinants, like cellular excitability, tissue structure and electrical coupling by gap junctions (GJ), have been extensively studied. However, there are several discrepancies in cardiac electrophysiology research that have extended over decades, suggesting elements that are still not completely understood about this complex phenomenon. This dissertation will focus on one such mechanism, ephaptic coupling (EpC). The purpose of this work is twofold, 1) to identify ionic determinants of EpC, and its interactions with gap junctional coupling (GJC) and, 2) to investigate the possible role of serum ion modulation in cardiac arrhythmia therapy. First, the effects of altering extracellular ion concentration – sodium, potassium and calcium at varying GJ protein expression were studied. Briefly, reducing sodium was related to CV slowing under conditions of reduced EpC (wide intercalated disc nanodomains – perinexi) and GJC (reduced GJ protein – Connexin43). On the other hand, increasing potassium slowed CV in hearts with wide perinexi independent of GJC. Elevating calcium, reduced perinexal width and was associated with fast CV during physiologic sodium concentration. However, under conditions associated with disease, like hyponatremia, elevating calcium still reduced perinexal width but slowed CV. These findings are the first to suggest that ionic modulators of EpC could modulate CV during health and disease. Next, the potential of perfusate ion modulation in cardiac arrhythmia therapy was investigated. Briefly, in a model of myocardial inflammation, TNFα, a pro-inflammatory cytokine, slowed CV relative to control conditions and this was associated with widening of the perinexus (reduced EpC). Increasing extracellular calcium restored CV to control values by improving not only EpC but also GJC. Finally, in a model of metabolic ischemia in the heart, CV response due to solutions with varying sodium and calcium concentrations were tested. The solutions that were associated with wider perinexi and elevated sodium performed best during ischemia by attenuating CV slowing, reducing arrhythmias and increasing time to asystole. Taken together, these findings provide evidence for the possibility of ionic determinants of EpC in cardiac arrhythmia therapy. / Ph. D.

The increasing use of non-sustainable materials in technology has led to severe environmental consequences, prompting a global search for more sustainable and eco-friendly alternatives. Clay, with its low cost, non-toxicity, recyclability, natural abundance, and versatile properties, has emerged as a beacon of hope for a greener future. Since prehistoric times, clay has found extensive use in the pharmaceutical, petroleum, biomedical, and energy industries. Its high surface area, cation exchange capacity, intrinsic porosity, and ease of functionalization make it a versatile and sustainable choice for a variety of applications. The dissertation focuses on synthesizing hybrid clays functionalized with zwitterionic molecules for antimicrobial and ionic membrane applications. It also studies the rheological properties of bentonite clay modified with betaines of different carbon chain lengths. The research aims to investigate the flow and stability of these functionalized clays. In addition, it offers valuable insights into how carbon chain length and pH affect the rheological properties of clays. This is followed by engineering pathogen-resistant clay composites embedded with antimicrobial agents like silver ions and terbinafine hydrochloride against pathogens (viz. S. aureus, E. coli, and C. albicans). Another part of the dissertation focuses on developing and investigating flexible and durable betaine-functionalized clay membranes as ion-conducting separators for batteries and fuel cells. The low-cost membranes exhibit excellent ionic conductivity, chemical-thermal stability, recyclability, and ease of engineering making them an exceptional material for such applications. Overall, this dissertation presents a comprehensive study of the structure-property relationship of hybrid clays, bridging the fields of chemistry, materials engineering, electrochemistry, and biology. The research is poised to inspire the scientific and industrial communities with the potential of novel clay-based materials, encouraging them to embrace cleaner technologies and reduce their carbon footprints.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.