Cementitiously stabilized soils or soil-cement is a commonly used solution for highway subbase and base course construction, particularly in regions where higher quality soils and aggregates are limited. Even though the utilization of soil-cement as an engineered material has been around for over 70 years, there is still room for advancement with respect to characterizing the performance of these mixtures both in the laboratory and in the field. The first objective of this thesis was to examine the Mississippi Department of Transportation soil-cement database to determine current soil-cement practices in Mississippi. The second objective of this thesis was to develop thermal measurement techniques to characterize compacted cementitiously stabilized soils. Over 800 compacted specimens were prepared and tested to investigate the feasibility and usefulness of performing thermal measurements on soil-cement mixtures.

abstract: Advancements in thermal interface materials (TIMs) allows for the creation of new and more powerful electronics as they increase the heat transfer from the component to the heat sink. Current industrial options provide decent heat transfer, but the creation of TIMs with higher thermal conductivities is needed. In addition, if these TIMs are elastic in nature, their effectiveness can greatly increase as they can deal with changing interfaces without degradation of their properties. The research performed delves into this idea, creating elastic TIMs using liquid metal (LM), in this case galinstan, along with other matrix particles embedded in Polydimethylsiloxane (PDMS) to create an easy to use, relatively inexpensive, thermally conductive, but electrically insulative, pad with increased thermal conductivity from industrial solutions. The pads were created using varying amounts of LM and matrix materials ranging from copper microspheres to diamond powder mixed into PDMS using a high-speed mixer. The material was then cast into molds and cured to create the pads. Once the pads were created, the difficulty came in quantifying their thermal properties. A stepped bar apparatus (SBA) following ASTM D5470 was created to measure the thermal resistance of the pads but it was determined that thermal conductivity was a more usable metric of the pads’ performance. This meant that the pad’s in-situ thickness was needed during testing, prompting the installation of a linear encoder to measure the thickness. The design and analysis of the necessary modification and proposed future design is further detailed in the following paper. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2017

Modern high frequency electronic devices are continually becoming smaller in area but capable of generating higher RF power, thereby increasing the dissipated power density. For many microwave devices, for example the planar Gunn diode, standard thermal management may no longer be sufficient to effectively remove the increasing dissipated power. The work has looked at the design and development of an active micro-cooler, which could be fully integrated with the planar Gunn diode at wafer level as a monolithic microwave integrated circuit (MMIC). The work also resulted in the further development of novel thermal measurement techniques, using micro-particle sensors with infra-red (IR) thermal microscopy and for the first time to measure thermal profiles along the channel of the planar Gunn diode. To integrate the gallium arsenide (GaAs) based planar Gunn diode and micro-cooler, it was first necessary to design and fabricate individual GaAs based planar Gunn diodes and micro-coolers for thermal and electrical characterisation. To obtain very small area micro-coolers, superlattice structures were investigated to improve the ratio between the electrical and thermal conductivities of the micro-cooler. To measure the specific contact resistivity of the superlattice based micro-cooler contacts, the Reeves & Harrison TLM (transmission line method) was used as it included both horizontal and vertical components of the contact resistance. It was found, for the GaAs based micro-cooler, only small amounts of cooling (< 0.4 °C) could be obtained, therefore the novel temperature measurement method using micro-particle sensors placed on both the anode and cathode contacts was utilised. The bias probes used to supply DC power to the micro-coolers were found to thermally load these very small structures, which led to anomalously high measured cooling temperatures of > 1°C. A novel approach of determining if the measured cooling temperature was due to cooling or probe loading was developed. A 1D model for the integrated micro-cooler was developed and the results indicated that when the micro-cooler was used as a cooling element in a monolithic microwave integrated circuit, the supporting substrate thickness was very important. Simulation showed to obtain cooling the substrate thickness had to be very thin (< 50 μm), which may preclude the use of GaAs micro-coolers as part of a monolithic microwave integrated circuit.

A new mathematical model has been developed along with a new parameter estimation routine using surface temperature and heat flux measurements to estimate blood perfusion and thermal resistance in living tissue. Dynamic thermal measurements collected at the surface of the sensor before and after imposing a dynamic thermal cooling event are used with the model to estimate the blood perfusion, thermal resistance and core temperature. The Green\'s function based analytical solution does not require calculation of the whole tissue temperature distribution, which was not the case for the previous models. The result from the new model was proved to have better and more consistent results than previous models. The new model was validated to solve one of the unsolved biomedical problems which is the ability of detecting burn severity. The method was tested with a phantom perfusion system. The results matched known blood perfusion and thermal resistance values. The method was also tested with burns on animal models. Inflammation effects associated with the burns were studied using a newly developed term called the Burn Factor. This correlated with the severity of imposed burns. This work consists of three journal papers. The first paper introduces the mathematical model and its validation with finite-difference solutions. The second paper validates the physical aspects of the usage of the model with thermal measurement in detecting simulated burned layers and the associated perfusion. The third paper demonstrates the ability of the model to use thermal measurements to detect different burn severity of an animal model and to study the healing process. / Ph. D.

Les secouristes, par la nature et le cadre de leurs missions, interviennent en environnement à risque et mettent parfois leur santé en danger. Afin de minimiser ce risque, de nouveaux Equipements de Protection Individuelle (veste, tee-shirt et bottes) ont été conçus par un consortium européen de 23 partenaires réunis autour du programme de recherche ProeTEX. Ces travaux de thèse s’inscrivent dans le cadre de ce projet et ont pour objectif de développer un système de monitoring ambulatoire des paramètres thermiques du pompier qui sera intégré aux vêtements intelligents destinés aux secouristes. L’intérêt de cette intégration est le prépositionnement des capteurs afin de réduire le temps de préparation du secouriste. La surveillance s’opère à deux niveaux : l’interface Homme-environnement et le corps. Afin d’évaluer le risque thermique encouru, les paramètres faisant l’objet d’un suivi sont : la température interne, mesurée depuis le tee-shirt, et la température externe et le flux thermique, mesurés dans la veste. Ces paramètres permettent d’apprécier la contrainte thermique imposée par l’environnement et l’état de santé du pompier. Deux méthodes de mesure des paramètres thermiques dans la veste ont été développées. Le projet a abouti au développement de prototypes fonctionnels dont les performances ont été attestées en centre de validation. Des tests ont été conduits en laboratoire et en conditions extrêmes sur le terrain à la Brigade de Sapeurs-Pompier de Paris et au « International Firefighting, Survival and Rescue at Sea Training Center » de Pavie, Italie, pour démontrer la fonctionnalité des EPI en conditions réelles. / Rescuers, within the framework of their missions, operate in hazardous condition and sometimes put their health at risk. To minimize this risk, new personal protective equipment (jacket, t-shirt and boots) were designed by a 23 European partners’ consortium within the research program ProeTEX. This thesis is part of this project and aims to develop an ambulatory monitoring system for firefighters’ thermal parameters; It will be integrated into smart clothes for rescuers. Monitoring is taking place at two levels: Human-environment interface and body. To evaluate the thermal hazard involved, the parameters being monitored are: internal temperature, measured from the tee-shirt and external temperature and heat flux, in the jacket. These parameters are used to assess heat stress imposed by the environment and the health status of the fire-fighter. Two methods of measurement of thermal parameters in the jacket were developed. The project resulted in the development of functional prototypes whose performances have been vouched in validation center. Tests took place in the laboratory and during field trails in extreme conditions.

Le carbure de silicium (SiC) semble être actuellement le candidat le plus viable des semi-conducteurs à large bande interdite pour remplacer le silicium (Si) dans un avenir proche. En raison de ses propriétés intrinsèques, le SiC permet de développer des dispositifs à semi-conducteurs aux caractéristiques supérieures offrant de grandes améliorations de performances, et se traduisant également par des conceptions plus efficaces et compactes dans diverses applications de l'électronique de puissance. Les MOSFET de 1,2 kV SiC, de loin les composants les plus répandus de la famille pour équiper les sources de puissance, ont rapidement été déployés pour remplacer les modules IGBT Si en raison de leur résistance à l'état passant faible et de leurs excellentes performances de commutation dans toutes les plages de température. Cependant, encore à un stade précoce de développement, les MOSFET SiC présentent leurs problèmes techniques et économiques propres, lesquels problèmes ont freiné leur expansion en électronique de puissance. La caractérisation et la modélisation, en particulier l'état de fonctionnement du MOSFET SiC, ont été examinées dans le cadre de cette thèse afin de mettre en lumière les spécificités et les conséquences qui en découlent sur la conception des convertisseurs de puissance. C’est ainsi qu’une méthodologie de caractérisation statique pour les MOSFET à haute tension a été développée. Les caractéristiques ont été mesurées par méthodes appropriées permettant à la température de la jonction de rester constante pendant la mesure. Les résultats expérimentaux ont été analysés et comparés à ceux relatifs aux dispositifs conventionnels en Si. Ensuite, un nouveau modèle compact du module MOSFET SiC a été mis au point sur le logiciel Saber pour des simulations orientées circuit. Ce modèle prend en compte les phénomènes physiques observés, notamment les effets des pièges d’interface, le comportement JFET intrinsèque, le canal court et la température. En tant que version modifiée de Shichman Hodges, le modèle utilise un nombre raisonnable de paramètres d’ajustement, lesquels sont principalement extraits par identification des courbes de données expérimentales à l’aide d’un logiciel d’optimisation, et pour les autres étant basés sur les données disponibles dans la fiche technique du composant étudié. Finalement, nous avons abordé la caractérisation électro-thermique des MOSFET de SiC. Pour remédier à la présence de pièges d'interface, des bancs de test dédiés ont été développés pour la mesure de la température MOSFET au SiC sur la base du TSEP. Une simulation par éléments finis 3D (FEM) est réalisée pour étudier la distribution thermique à l'intérieur du module. En comparant avec les expériences, le modèle électro-thermique a été validé avec une précision acceptable. / Silicon carbide (SiC) has actively been emerged as the most viable candidate of the wide band gap (WBG) semiconductors to replace silicon (Si) in the near future. Due to its inherent properties, SiC enables the development of new generation semiconductor devices that offer great performance improvements, resulting in more efficient and compact designs in various power electronics applications. The 1.2 kV SiC MOSFETs, which are by far the most important devices in the SiC family, have been quickly used as the replacement of Si IGBTs in many applications due to their superior characteristics. However, at an early stage of development, SiC MOSFETs come with their own list of technical and economic issues which have somehow limited their widespread implementation for power electronics applications. The characterization and modeling, in particular on-state of the SiC MOSFET, have been investigated in this dissertation to develop insight of the unique characteristics along with the effects on the design of power converters. In such a way, the characterization test benches for high voltage power MOSFETs have been developed. The device is characterized using appropriate methods, which allows the junction temperature to remain constant during the measurement. The characteristics are then analyzed and compared to these of Si counterpart to provide further understanding of SiC MOSFETs. Subsequently, a novel compact model has been developed for circuit simulation, taking into account physical phenomena including interface traps, short-channel, intrinsic JFET and temperature effects. As a modified version of the Shichman Hodges, the model employs a few adjustment parameters, which are mostly derived from curve fitting of experimental data, using optimization tool software. The proposed model with fairly simple current equation thus is expedient to represent the DC behavior of power MOSFET for a wide range of operation conditions. In the end, the thermal characterization of SiC MOSFETs is examined. The on-resistance has been proposed as a temperature-sensitive electrical parameter (TSEP) to estimate the junction temperature. In the presence of the interface traps, the dedicated test benches have been developed for SiC MOSFET temperature measurement based on TSEP. 3D Finite element (FEM) simulation is performed to investigate thermal distribution inside the module. By comparing with the experiments, the electro-thermal model is validated with acceptable accuracy.