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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Future of Biofuels: An Economic Analysis of the Design and Operation of a Microalgae Facility in Texas and the Southwestern United States

Allison, Marc S. 2010 August 1900 (has links)
The world of energy is changing. With rising energy costs and concerns over the supply of energy materials, more research is being conducted into alternative sources of fuel and microalgae is one of the sources being researched, although much research had been conducted on it as a part of the Aquatic Species Program from the 1970s to the early 1990s. With the emergence of microalgae as a source of alternative energy, the need for an economic analysis of microalgae has arisen. This research studies the economic feasibility of the design and operation of a microalgae production facility in two Texas locations (Pecos and Corpus Christi) and in southeastern New Mexico using a stochastic simulation model. It examines the production levels needed for the facility to be profitable and also some facility designs necessary for that profitability. It also measures several annual financial indicators so that potential investors have some estimates of the future profitability of the microalgae industry. The results show that for microalgae to become a viable commercial operation, production must be improved beyond the current levels and the levels suggested by the literature. Production needs to be at least 0.8 g/L/day with 40 percent oil content and 24 inches of water depth. Production must be improved through increasing growth rates and oil contents at greater water depths. Production can be improved through nutrient and carbon dioxide usage, two elements that are being heavily researched. Water usage will become a major focus because of the limited resources and the quantities necessary to operate a commercial-scale facility. With the necessary improvements in technology and research, microalgae could prove to be a viable source of alternative energy.
2

Modélisation haute fréquence des effets électromagnétiques induits dans les câblages aéronautiques / Numerical modeling of electromagnetic field effects on aircraft wire harnesses

Chafik, Aymene 20 September 2019 (has links)
La modélisation numérique des réseaux de câbles est devenue une étape indispensable dans la phase de conception d’un projet afin de prédire les disfonctionnements dans les moyens de transport issus de l’augmentation des couplages électromagnétiques. La majorité des modèles repose sur des méthodes analytiques, qui sont certes rapides en comparaison avec les méthodes numériques 3D, mais en contrepartie sont limitées aux basses fréquences et aux géométries uniformes. De plus, des hypothèses concernant les conditions aux limites des conducteurs, comme les plans de masse infinis, sont souvent appliqués dans le but d’obtenir des formules analytiques simples C’est dans ce contexte, que nous avons envisagé l’amélioration de ces modèles en réduisant ces simplifications et ces hypothèses imposées au départ. A cet égard, nous avons développé dans un premier temps un modèle de ligne de transmission filaire qui consiste à prendre en compte les pertes par rayonnement en haute fréquence, la longueur finie et la géométrie non uniforme. Lors de cette étude, nous avons utilisé la théorie des lignes et deux méthodes numériques en l’occurrence les méthodes PEEC et TLST. Nous avons démontré pour le cas des risers que les coefficients de la méthode PEEC peuvent être obtenus analytiquement. Concernant notre deuxième axe de recherche, on s’est intéressé à la modélisation des conduits métalliques notamment les plans de masse finis et les goulottes. Ces derniers ont été modélisés avec un ensemble de câbles. Une étude expérimentale a été menée sur les effets induits par la goulotte sur la propagation des ondes électromagnétiques. Finalement, les résultats de nos modèles ont été validés expérimentalement avec des mesures. Une attention particulière a été portée sur l’effet des extrémités des lignes de transmission. / Considering the increasing awareness of the EM coupling issues inside aircraft and automotive engines, numerical modeling of cable harness networks is currently one of the most important steps in the design process of an engineering project. Most of the relevant softwares that deals with the cable topology simulation relies on the well-known analytical models such as the multiconductor transmission line theory. These techniques are better than the fullwave ones regarding the time calculation and the memory requirement. However, they are available only in the low frequency range because of the assumptions taken into account such as the uniform geometry and the infinite length of the wires. To overcome these restrictions and improve the existing solutions, we come up with a new high frequency model which is based on the transmission line theory and two numerical methods: PEEC and TLST. To keep the analytical approach of our model, we managed to get the analytical expressions of the PEEC’s partial elements. In this thesis, we were also interested by the cable raceways and cable trays. First of all, we developed a raceway model based on transmission line wires. Comparing our results with the FDTD ones, we noticed some differences especially in the high frequency range when the wire ends with the risers. Through an experimental study, we explained the behavior and the impact of these cables trays on the EM wave propagation. Finally, the results of our models have been validated with the measurements. Thanks to these experiments, we highlighted the fact that the termination of a wire has an important impact on the wave propagation.

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