Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed October 13, 2009). PDF text: xiv, 183 p. : ill. (some col.) ; 1 Mb. UMI publication number: AAT 3358961. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thèse de doctorat : Dispositifs de l'électronique intégrée : Villeurbanne, INSA : 2002. / Thèse : 2002ISAL0056. Titre provenant de l'écran-titre. Bibliogr. p.127-130.

Thesis (D. Min.)--Liberty Baptist Theological Seminary, 2003. / Description based on print version record. Includes bibliographical references.

Thesis (D. Min.)--Trinity International University, 2003. / Abstract. Includes bibliographical references (leaves 207-211).

Thesis (M.A.)--Briercrest Biblical Seminary, 2000. / Abstract. Includes bibliographical references (leaves 78-81).

The pressing need for clean renewable energy sources has aroused worldwide research interest on the exploration of biofuels produced from lignocellulosic feedstock (e.g. forestry or agricultural residues and municipal wastes). The general absence of cost-effective method to overcome the recalcitrant nature of cellulosic biomass is the major challenge for the industrialization of this so-called second-generation biofuel. With the purpose to enhance our understanding of the fundamental mechanism of thermophilic microbial cellulose conversion process, we used culture-independent metagenomic analysis based on Next Generation Sequencing to explore the physiological ecology of thermophilic cellulolytic microbial community and more importantly to discover metabolic potentials. During the enrichment of thermophilic cellulolytic consortium, noticeable effects of co-substrate and pH was observed and subsequently investigated. Based on the community structure revealed by 16S rRNA gene sequencing at various pH values, we concluded that keeping pH higher than 6.0 was crucial to maintain effective cellulose conversion because the growth of Thermoanaerobacterium over other more efficient cellulolytic populations could be practically avoided. Given in mind that uncharacterized microbial populations may possess critical enzymatic components that are essential for the breakdown of cellulosic feedstock, gene-centric metagenomic pipeline was developed to discover genes that are functionally beneficial for thermophilic cellulose hydrolysis. Aside from that, metagenomic gene mining based on functional prediction using HMM (Hidden Markov Model) showed higher positive ratio in identifying novel carbohydrate-active genes than that of functional screening. Without cultivation, near complete genomes of the major thermophilic cellulose degraders were recovered from the metagenome by a gene binning pipeline combining tetranucleotide frequency based primary k-means clustering and subsequent scaffolding with paired-end relationship between two reads (sequences). Furthermore, by quantifying the transcriptional activities of various carbohydrate-active genes in the metatranscriptome of the enriched thermophilic cellulose-degrading consortium, we disclosed significance of enzymes of GH09 and GH48 which had been underestimated by previous metagenomic studies. Eventually, metagenomic survey of various sludge samples collected at specific operational conditions helped to confirm the metabolism potential of thermophilic sludge in cellulose up taking by possessing more enzymes of GH05 and GH04 families. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

By utilizing the electric motor as the propulsion system, the electric vehicle (EV) establishes a new bridge between renewable energies and our daily life, which meanwhile has to face with a brand new technical issue, namely the energy management and conversion. Then, the performance of energy conversion systems has become a new evaluation criteria for EVs. Accordingly, this study works on the analysis and control of the EV energy conversion system, including the secure charging system via wireless power transmission (WPT), advanced driving control via electric propulsion system, and bidirectional power interface via electromagnetic interference (EMI) mitigation technique. First, this study proposes a novel energy encryption algorithm for WPT systems. In the presented scheme, the energy can be encrypted by chaotically regulating the frequency of the power source based on the unpredictable security key. The authorized receptor can effectively receive the energy by simultaneously adjusting the circuit to decoding the encrypted energy based on the acquired security key, while the unauthorized receptor cannot obtain the energy without knowledge of the security key. In this study, both simulation and experimental results are provided to verify the feasibility of the proposed secure WPT system. Subsequently, this study proposes a new dynamic model of EV powering steering systems, by synthetically taking into account characteristics of the electric propulsion motor, driver’s operation, and uncertain disturbances caused by irregularities of the road surface. By using various nonlinear analysis methods, the unstable chaotic behaviors can be revealed in the power steering system, especially when the vehicle turns a concern at a high speed. Additionally, a new control algorithm is designed and implemented to stabilize the EV power steering system, and corresponding validity is also mathematically proved in this study. Thirdly, an integrated driving control system is designed based on the aforementioned dynamic analysis, which is used to enhance the stability and maneuverability performances of four-in-wheel independently-driven (4WID) EVs. By adopting the supervisor-actuator structure, the proposed driving control scheme not only effectively improves the performance of tracking reference paths, but also optimally distribute the desired yaw moment to each in-wheel motor. In this study, the mathematical proof and the simulation are both conducted to demonstrate the feasibility of the proposed integrated driving control strategy. Lastly, this study also works on the EMI issue caused by switch-mode energy conversion devices for EVs. In this section, a new pulse-width-modulation (PWM) method is designed by utilizing the random-like sequence, aiming to suppress the conducted peaky EMI over the whole power spectrum, thereby ensuring the working performance for electronic instruments in EVs. For demonstrating the effectiveness of the proposed soft-chaoizing scheme, this study takes two exemplifications such as the electric propulsion drive system and the bidirectional power interface for vehicle-to-grid (V2G) systems. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

The distillation of sea water is of importance for the future demands for potable water and other uses in the world. A novel technique, based on electrohydrodynamic (EHD) principles, was used in this realm to desalinate artificial sea water of 3.3% (w/V) concentration. A single point corona electrode was operated at a potential of 5.3 kV (maximum output current 0.3 mA), and was installed one cm over the surface of sea water. The flux of air ions was about 3.0 $ times$ 10$ sp{12}$ cm$ sp{-2}$ s$ sp{-1}$ which produced an average electric wind of 1.72 m s$ sp{-1}$ at the sea water surface. Space charge from a corona electrode generated forces in the media to enhance the evaporation rate by about a factor of three compared with a control freely evaporating sea water. Water vapour was condensed and the condensate's purity was evaluated by chemical and physical analyses. Electrical conductivity and pH of the EHD distillate were found to be 14 $ mu$S cm$ sp{-1}$ and 5.5, respectively. In the absence of Joule heating, the energy required for EHD-distillation was comparable to the latent heat of vaporization of 2.3 $ times$ 10$ sp3$ kJ kg$ sp{-1}$ for water. The steady-state temperature of EHD solution was below that of the corresponding unventilated freely evaporating sea water. Electric wind caused by the ionic drag is considered to be the principal driving force for the enhancement.

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