This thesis details an exploration of the behaviour of spatial optical solitons (self-collimated, self-stabilising light beams) interacting with the interface between classes of nonlinear dielectric materials. Chapter 1 gives the theoretical background to the thesis by introducing the soliton concept, material interfaces and the Helmholtz model. The second chapter discusses the reflection and refraction characteristics of soliton beams incident on the planar boundary between dissimilar cubic-quintic materials. The deployment of Helmholtz soliton theory allows for the simultaneous consideration of: (i) arbitrary angles of incidence, reflection and refraction (relative to the interface), and (ii) finite beam waists (as opposed to infinitely-wide plane waves). Despite an abundance of literature concerning solitons at interfaces, there appears to be no published research addressing refraction in the presence of cubic-quintic optical nonlinearity (and certainly none in arbitrary-angle contexts). Excellent agreement is generally found between theoretical predictions from a generalised Snell’s law and results from extensive computer simulations. In Chapter 3, these novel analyses have been complemented by further investigations into other fundamental aspects of optical refraction, namely Goos-Hänchen shifts and critical angle prediction. Both aspects are the first of their kind in the cubic-quintic regime. The fourth chapter considers surface wave propagation along the interface between two dissimilar power-law materials; this research has already contributed to a published peer reviewed paper [J. M. Christian et al., "Helmholtz bright spatial solitons and surface waves at power-law optical interfaces," Journal of Atomic, Molecular & Optical Physics 2012 (2012), art. no. 137967]. The chapter also expands upon that paper by giving a more detailed account of surface wave stability properties. Chapter 5 provides an in-depth computational study into beam propagation in coupled waveguide arrays (materials whose refractive index is periodically patterned) and there appears to be a link between the beam's critical angle and the depth of the modulation of the array. The thesis concludes with a summary of findings and suggestions surrounding the implications of this novel research.

Graphite based materials are of particular interest as energy materials. Graphite is used as a moderator in nuclear reactors and there have been investigations into the ability of modified graphites, such as expanded or intercalated graphite, to store hydrogen. Poly-crystalline coherent inelastic neutron scattering(poly-CINS) is used to give information on the dynamic properties of materials. typically poly-CINS produces large and difficult to interpret data sets. Neutronplot, a novel analysis software suite described in this work, is used in conjunction with predicted dynamic information to analyse poly-CINS data. X-ray diffraction measurements taken by Keens[1] were used to investigate the bulk structural properties of several natural graphites, one of which was chosen for poly-CINS analysis using IN5 experimental data, simulated data and Neutronplot. These investigations were also replicated with an exfoliated graphite sample. Both x-ray and neutron diffraction were used to investigate the structure of a C60 intercalated graphite sample derived from the exfoliated graphite and a Poly-CINS experiment was conducted using the NEAT spectrometer. We have found that the current IUPAC lattice values for rhombohedral stacking in graphite do not fit with experimental measurements. Also the interlayer spacing of rhombohedrally stacked graphite in natural graphite samples tends to be larger than that of hexagonal graphite. The investigations of exfoliated graphite show how interactions other than the graphene interlayer begin to dominate as disorder is added into the system. Successful C60 intercalation in graphite layers is confirmed by neutron diffraction. Measurements of the elastic constant C33 for natural and exfoliated graphite show good agreement with other graphite measurements. The intercalate poly-CINS measurement suffered from low statistics and shows how Neutronplot can be used for less than ideal data sets. The data shows diffuse C60 in the graphite matrix, this result is reflected in the diffraction measurements.

Despite having significant applications in the nuclear industry, there have been virtually no molecular dynamics (MD) simulations of radiation damage in graphite. The difficulties in developing an accurate yet computationally inexpensive description of carbon have limited the number of detailed investigations. Although previous work has reported point defect energies and estimates of threshold displacement energies, very little is known about the cascade behaviour and the evolution of damage at the atomic level. Gaining an understanding of the processes caused by irradiation in graphite is central to extending the life span of the current advanced gas-cooled nuclear reactors in the UK. In addition, this will provide crucial information to aid next-generation nuclear technology such as the high-temperature graphitemoderated reactors, which were recently selected for development in the USA. The Environment Dependent Interaction Potential (EDIP) has been employed along with the Zeigler-Biersack-Littmark potential to model radiation damage in graphite. Statistical sampling of 20 initial directions and over a range of energies has revealed that nuclear graphite behaves in a manner distinct from metals and oxides, with damage primarily in the form of isolated point defects as apposed to connected regions of transient damage. Simulations have given evidence of channelling occurring along the <10¯12> channel which has previously not been observed in graphite simulations. Graphite cascades have exhibited a fractal-like branching structure and binary-collision-type behaviour. Results produced agree with historical defect prediction models. Important quantities such as the range of the primary knock-on atom and the average energy loss per collision have been calculated. Results indicate that graphite cascades are not dependent on the initial cell temperature. EDIP has been further employed to simulate the effects of radiation damage in carbon allotropes. Results reveal how a material’s structure affects the collision cascade and have highlighted the unique radiation response of graphite.

Source: Dissertation Abstracts International, Volume: 41-09, Section: B, page: 3357. / Thesis (Ph.D.)--The Florida State University, 1980.

Source: Dissertation Abstracts International, Volume: 37-07, Section: B, page: 3305. / Thesis (Ph.D.)--The Florida State University, 1976.

Esta dissertação analisa, do ponto de vista técnico, econômico e social, diferentes altemativas de usos finais para a eletricidade deslocada da cocção elétrica no setor residencial da Colômbia. Neste trabalho mostra-se que o cozimento e preparo de alimentos por meio da eletricidade, tem um custo social elevado. Discute-se, portanto, o papel de diversos energéticos substitutos da eletricidade nesse uso final. Analisaram-se projetos de eletrificação no setor de transportes. Os resultados mostram que, a curto prazo, existem opções interessantes do ponto de vista técnico. econômico e ambiental de eletricação de transporte de massa nas grandes cidades (Santafé de Bogotá e Medellín). Contudo, determinou-se que provavelmente as reduções de demanda de eletricidade pelo setor residencial na Colômbia redundarão no adiamento do aumento de oferta e não na conquista de novos e importantes mercados para a eletricidade. / This dissertation analyses, various end-use alternatives for the electricity saved from electric cooking in Colombia; technical, economic and social issues were studied. This document shows that preparation of food, using electricity has a high social cost. Therefore, discussion about the role of several types of energy that could substitute electricity in that end-use was made. There were also analyzed some projects of electrification in the transport sector. The results show that in a short range period of time there are interesting options of massive transport electrication in the largest cities of Colombia (Santafe de Bogota and Medellin) taking into consideration, technical, economic and environmental aspects. However, it was determined that reductions on electricity demand of the residential sector will be more likely reflected in a delay of increasing supply than of new and large electricity market formation.

As redes de Distribuição de Energia Elétrica podem ser submetidas a perturbações, causadas pela proliferação de cargas não-lineares, provocando distúrbios nos alimentadores das sub-estações e afetando cargas sensíveis, obrigando as empresas de energia elétrica e aos consumidores a adotarem medidas preventivas e corretivas. Esses distúrbios quando afetam a forma de onda da tensão ou da corrente, provocando o aparecimento de freqüências múltiplas as da fundamental, é um fenômeno conhecido como distorção harmônica. Para avalia-la, foi desenvolvido um equipamento eletrônico controlado por microprocessadores, possibilitando medições em campo da tensão e corrente harmônica, assim como o módulo e fase de cada harmônico, múltiplo de 60 Hz, até o 40° harmônico. Com base nos dados coletados pelo equipamento, foram avaliados os distúrbios provocados pelas cargas não-lineares num consumidor gerador de harmônicos. Foram realizadas comparações entre os registros de consumo medidos pelo equipamento e o registrado pela concessionária. Foi comparada também a distorção harmônica, na corrente e na tensão, com as normas nacionais e internacionais. Os resultados indicaram, mesmo em se considerando uma série histórica pouco expressiva, coerência com o estado do conhecimento sobre o fenômeno. / The distribution lines can be affected by disturbances, caused by the increase of non- linear loads, provoking disturbances in substation feeders. These disturbances can affect sensitive loads, demanding therefore from the Utilities preventive and remedial actions. When they affect the voltage waveforms, current and voltage, causing the occurrence of multiply frequency at the fundamental frequency, it is a phenomena known as harmonic distortion. An electronic equipment controlled by microprocessors was developed to the disturbance assessment and to make measurements in site possible, sampling the waveform and calculating the rst 40 harmonics of the 60 Hz, fundamental, for both voltage and current waveform. The data bases were collected by the equipment and the disturbances caused by non-linear loads were veried, at a certain consumer who generates harmonics. Two comparisons were performed: the data consumption measured by equipment versus the Utility\'s data consumption and the harmonic distortion current and voltage, versus international and local standards. Results have shown coherence with the state of knowledge. In spite of the presented data being of a short period duration.

não há resumo / there is no abstract

Lithium ion battery discovered since the 1980s has become pivotal to our energy needs. With the need for a shift to renewable energy and increased use of portable devices, energy storage has become a very important aspect of modern day life and technology. In the thesis, optimization techniques for solid state calcination of lithium olivine batteries are characterized and analyzed. A brief introduction into lithium ion battery is discussed, the chemistry and physics of the materials is studied in details. Emphasis is placed on the olivine structure, industrially utilized synthesis method and the performance of olivine lithium ion batteries are also discussed in details. Olivine structure LiFePO₄ (LFP) was synthesized via solid state processes, using Li₂CO₃, NH₄H₂PO₄ and FeC₂O₄·H₂O and C₁₂H₂₂O₁₁ as precursor materials. The effects of calendaring in terms of charge/discharge capacity, cycle life performance, surface morphology, and ac impedance was analyzed. The resulting LFP electrode was divided in part, Part A was left as is and Part B was calendared. The calendared electrode exhibited lower impedance under electrochemical impedance test. The calendared electrode also exhibited a higher discharge capacity of about 130 mAh/g at 0.1C compared to the as-is electrode with discharge capacity of about 120mAh/g. Olivine structure LiMnPO₄ (LMP) was also synthesized via solid state processes, using Li₂CO₃, NH₄H₂PO₄, MnCO₃ and C₁₂H₂₂O₁₁ as precursor materials. Comparison of the carbon addition process was done by adding sucrose to the initial precursor mix and carbon black at the later stages of fabrication. The 3 step carbon addition exhibited the highest specific capacity of about 72mAh/g, 1 step carbon addition possessed the least capacity of about 45mAh/g, while the 2 step process had a capacity of about 65mA/g. / A Thesis submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the Master of Science. / Summer Semester 2015. / June 29, 2015. / Includes bibliographical references. / Pedro L. Moss, Professor Directing Thesis; Mark H. Weatherspoon, Committee Member; Petru Andrei, Committee Member.

Some eukaryotes are able to gain access to otherwise well-protected carbon sources in plant biomass by exploiting microorganisms in the environment, or harboured in their digestive system. One such organism is the European black slug, Arion ater, which takes advantage of a gut microbial consortium that can break down plant tissues, including the widely available, but difficult to digest, carbohydrate polymers in lignocellulose. This ability is considered to be one of the major factors that have enabled A. ater to become one of the most widespread plant pest species in Western Europe and North America. Here we have identified the A. ater gut environment as a target for metagenomic study through identification of cellulolytic activity of bacterial origin. Next generation sequencing technology was used to characterize the bacterial diversity and functional capability of the gut microbiome of this notorious agricultural pest. Over 6 Gbp of gut metagenomic community sequences were analysed to reveal populations of known lignocellulose-degrading bacteria, along with abundant well-characterized bacterial plant pathogens. This study also revealed a repertoire of more than 3,000 carbohydrate active enzymes (CAZymes), indicating a microbial consortium capable of degradation of all components of lignocellulose, including cellulose, hemicellulose, pectin and lignin. Together, these functions would allow A. ater to make extensive use of plant biomass as a source of nutrients. This thesis demonstrates the importance of studying microbial communities in understudied groups such as the gastropods, firstly with respect to understanding links between feeding and evolutionary success and, secondly, as sources of novel enzymes with biotechnological potential, such as CAZYmes that could be used in the production of biofuel.