Dissertations / Theses on the topic 'Field of two elements'

The finite element method is a powerful analysis tool which has facilitated a better understanding of the behaviour of reinforced concrete structures. Its use in the research field is widespread and complements experimental tests and the development of new analytical models. Its application in practice engineering has permitted to deal with complex elements. However, the general structural engineer is still reluctant to consider finite element modelling for his work as he finds most of these models excessively sophisticated for his needs and knowledge. In particular, complexity of many finite element tools usually derives from the adoption of advanced concrete constitutive models. Implementation of more simple models based on engineering practice could facilitate its use by less experienced finite element users. In structural engineering practice finite element analysis can be of great usefulness to deal with those more problematic elements and/or where the application of traditional analysis methods presents limitations. This includes the so-called D-regions with a 3D behaviour. The strut-and-tie method and the stress field method are consistent and rational tools for the analysis and design of D-regions, but while their application to 2D elements is well covered in literature, its extension to 3D is problematic. This generally explains why excessively conservative assumptions are still common in the design of these elements. Refinement of current analytical and design approaches or the use of finite element analysis could lead to more rational solutions which in turn will reduce material requirements and costs. A 3D nonlinear finite element-based tool was developed in this thesis oriented towards the analysis and design of 3D D-regions by less experienced finite element users. Regarding material modelling, an orthotropic concrete model was adopted to permit the use of uniaxial stress-strain relationships. Only one single parameter, the uniaxial compressive strength of concrete, needs to be defined. Additionally, several aid functions were implemented, among which the following can be highlighted: a comprehensive, embedded reinforcement model to facilitate the introduction of complex rebar geometries; special support and load elements permitting an integrated and simple treatment of the boundary conditions imposed by them; and a simple design algorithm for the automatic determination of the required rebar areas. Three examples of applications to representative 3D D-regions are presented to show the capabilities of the tool. In particular, the analyses of fourteen four-pile caps, three socket base column-to-foundations connections and one anchorage block are described in the third part of the thesis. Results prove that realistic response predictions can be obtained considering relatively simple constitutive models. The capacity of the tool to configure consistent stress field models depending on the reinforcement arrangement is also demonstrated. The generation of rational reinforcement configurations by applying the implemented design algorithm is also shown. A strut-and-tie-based method for the analysis and design of four-pile caps with rectangular geometries is proposed in the fourth part. The method is based on a refined 3D strut-and-tie model and the consideration of three potential modes of failure: exceeding the reinforcement strength, crushing of the diagonal strut at the base of the column with narrowing of the strut and splitting of the diagonal strut due to transverse cracking. The main innovation is that the strut inclination is not fixed as in current strut-and-tie-based design procedures, but determined by maximizing the pile cap strength. The method accounts for strength softening of cracked concrete, compatibility constraints and reinforcement details. Its application to 162 specimens of literature led to very good predictions of the ultimate strength and, to a lesser extent, of the mode of failure.
El método de los elementos finitos es una potente herramienta de análisis que ha facilitado un mejor conocimiento del comportamiento de las estructuras de hormigón armado. Su uso en el ámbito de la investigación está ampliamente extendido. Su aplicación en la práctica ingenieril ha permitido la resolución de elementos complejos. Sin embargo, el ingeniero estructural común todavía es reticente a usar la modelización por elementos finitos ya que considera que la mayoría de estos modelos son excesivamente sofisticados para sus necesidades. La complejidad de muchas herramientas de elementos finitos suele derivarse de la adopción de modelos constitutivos de hormigón avanzados. La implementación de modelos más sencillos podría facilitar su uso por usuarios menos experimentados. En la práctica ingenieril el análisis con elementos finitos puede ser de gran utilidad para tratar aquellos elementos más problemáticos y/o donde la aplicación de los métodos de análisis tradicionales presenta limitaciones. Esto incluye las llamadas regiones D con comportamiento 3D. El método de bielas y tirantes y el método de campos de tensiones son herramientas racionales para el análisis y dimensionamiento de regiones D, pero su extensión a 3D es problemática. Este hecho explica por qué se adoptan todavía hipótesis excesivamente conservadoras en el dimensionamiento de estos elementos. La propuesta de métodos analíticos y de diseño más adecuados o la modelización con elementos finitos podría conducir a soluciones más racionales, lo que a su vez reduciría las necesidades de material y los costes. Como parte de esta tesis se ha desarrollado una herramienta de cálculo no lineal basada en el método de los elementos finitos orientada al análisis y dimensionamiento de regiones D tridimensionales por usuarios con menos experiencia en la modelización con elementos finitos. Se ha adoptado un modelo ortotrópico para el hormigón para permitir el uso de relaciones uniaxiales de tensión-deformación. Sólo es necesario definir un único parámetro, la resistencia a compresión uniaxial del hormigón. Adicionalmente, se han implementado varias funciones de ayuda, entre las que destacan: un modelo de armadura embebida para facilitar la introducción de geometrías de armado complejas; elementos especiales de apoyo y de carga que permiten un tratamiento integral de las condiciones de contorno; y un algoritmo de diseño para la determinación automática del área de armado necesaria. Se presentan tres ejemplos de aplicación a regiones D 3D representativas para mostrar las capacidades de la herramienta. En concreto, en la tercera parte del documento se describen los análisis de catorce encepados, tres cálices de cimentación y un bloque de anclaje. Los resultados muestran que se pueden obtener predicciones bastante realistas considerando modelos constitutivos relativamente sencillos. También se demuestra la capacidad de la herramienta para configurar modelos de campo de tensiones consistentes dependiendo de la configuración de armado. Además se muestra la capacidad del algoritmo de diseño para configurar disposiciones de armado racionales. En la cuarta parte se propone un método para el análisis y dimensionamiento de encepados sobre cuatro pilotes con geometría rectangular. El método se basa en un modelo 3D de bielas y tirantes refinado y la consideración de tres modos de fallo posibles: rotura del acero, aplastamiento de la biela diagonal en la base de la columna con estrechamiento de la misma y splitting de la biela diagonal debido a la fisuración transversal. La principal novedad es que el ángulo de la biela no se fija como en otros modelos, sino que se determina mediante la maximización de la resistencia del encepado. El método considera el debilitamiento de la resistencia del hormigón fisurado, condiciones de compatibilidad de deformaciones y detalles de armado. Su aplicación a 162 especímenes dio luga
El mètode dels elements finits és una potent eina d'anàlisi que ha facilitat un millor coneixement del comportament de les estructures de formigó armat. El seu ús en l'àmbit de la investigació està àmpliament estès. La seua aplicació en la pràctica enginyeril ha permès la resolució d'elements més complexos. No obstant això, l'enginyer estructural comú encara és reticent a fer servir la modelització per elements finits ja que considera que la majoria d'aquests models són excessivament sofisticats per a les seues necessitats i el seu conèixement. En concret, la complexitat de moltes eines d'elements finits sol derivar-se de l'adopció de models constitutius avançats de formigó. La implementació de models més senzills basats en la pràctica enginyeril podria facilitar el seu ús per a usuaris menys experimentats en la modelització amb elements finits. A la pràctica enginyeril l'anàlisi amb elements finits pot ser de gran utilitat per a tractar aquells elements més problemàtics i/o on l'aplicació dels mètodes d'anàlisi tradicionals presenta limitacions. Això inclou les anomenades regions D amb comportament 3D. El mètode de bieles i tirants i el mètode de camps de tensions són eines racionals per a l'anàlisi i dimensionament de regions D, però la seua extensió a 3D és problemàtica. Aquest fet explica per què s'adopten encara hipòtesis excessivament conservadores en el dimensionament d'aquests elements. La proposta de mètodes analítics i de disseny més adequats o la modelització amb elements finits podria conduir a solucions més racionals, amb el que també es reduirien les necessitats de material i els costos. Com a part d'aquesta tesi s'ha desenvolupat una eina de càlcul no lineal basada en el mètode dels elements finits orientada a l'anàlisi i dimensionament de regions D tridimensionals per a usuaris amb menys experiència en la modelització amb elements finits. S'ha adoptat un model ortotròpic per al formigó per permetre l'ús de relacions uniaxials de tensió-deformació. Només cal definir un únic paràmetre, la resistència a compressió uniaxial del formigó. Addicionalment, s'han implementat diverses funcions d'ajuda, entre les quals destaquen: un model d'armadura embeguda per facilitar la introducció de geometries d'armat complexes; elements especials de suport i de càrrega que permeten un tractament integral i senzill de les condicions de contorn; i un algoritme de disseny per a la determinació automàtica de l'àrea d'armat necessari. Es presenten tres exemples d'aplicació a regions D 3D representatives per mostrar les capacitats de l'eina. En particular, en la tercera part del document es descriuen les anàlisis de catorze enceps sobre quatre pilons, 3 calzes de fonamentació i un bloc d'ancoratge. Els resultats mostren que es poden obtenir prediccions prou realistes considerant models constitutius relativament senzills. També es demostra la capacitat de l'eina per configurar models de camp de tensions consistents depenent de la configuració d'armat. A més es mostra la capacitat de l'algoritme de disseny per configurar disposicions d'armat racionals. En la quarta part es proposa un mètode per a l'anàlisi i dimensionament d'enceps sobre quatre pilons amb geometria rectangular. El mètode es basa en un model 3D de bieles i tirants refinat i la consideració de tres modes de fallada possibles: trencament de l'acer, aixafament de la biela diagonal a la base de la columna amb estrenyiment de la mateixa i splitting de la biela diagonal per causa de la fissuració transversal. La principal novetat és que l'angle de la biela no es fixa com en els models actuals de bieles i tirants, sinó que es determina mitjan\c{c}ant la maximització de la resistència de l'encep. El mètode proposat considera el debilitament de la resistència del formigó fissurat, condicions de compatibilitat de deformacions i detalls d'armat. La seua aplicació a 162 espècimens de la liter
Meléndez Gimeno, C. (2017). A finite element-based approach for the analysis and design of 3D reinforced concrete elements and its applications to D-regions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86193
TESIS

This thesis contains eight chapters, dealing with machine analysis and representation. A definition and a brief survey of previous investigation devoted to shaded-pole motors and the application of finite element method for solving the two-dimensional electromagnetic field is given in Chapter 1. An outline of the present investigation is also given. In Chapter 2, the experimental requirements and details of the equipment are given. This includes the techniques of recording the transient torque patterns and the method of measuring the complete torque-speed characteristics. The experimental methods for parameters determination are also mentioned. The finite element method is outlined in Chapter 3. This chapter deals also with the assumptions made, the formulation of the non-linear energy function, the solution of Poisson's equation and an example of a simple shape contianing 16 elements for illustrating the method. In Chapter 4, the computer program for the finite element is outlined. The iteration process and the numerical representation of the magnetization curve are mentioned. Application of the finite element method to the shaded-pole motor is also given. Calculation of parameters by finite element technique is given in Chapter 5. Self inductance is calculated using the concept of stored energy and the results of self and mutual inductances are tabulated. Basic performance equations of an electrical machine are derived in Chapter 6. Solution of the basic performance equations, by a step-by-step numerical method, is also given. In Chapter 7, the steady state performance equations are established in terms of harmonic currents and inductance coefficients. The flux linkages are evaluated by the approximated functions of mutual inductances. The electromagnetic torque is calculated from the stored energy in the magentic field. General conclusions and suggestion for further work are mentioned in Chapter 8.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
The continuous casting technique in the last four decades has been large used for to production of semi-finished steel. The heat transfer is major mechanism and it occurs in various steps during the continuous casting. The quality of steel is directly related to the way the heat transfer occur because the thermal variations produce mechanical loads as well as contact forces which are generated through the rollers and shake of the mold. Such factors may cause defects such as fractures or cracks in the final product if the resulting stresses and strains exceed critical values. The technique must be improved in order to reduce the appearance of defects and the production time. For this a good understanding of physical phenomena involved during the solidification process is critical. The focus of this work is to apply the EbFVM (Element based Finite-Volume Method) approach to study the effects of linear tensions unidirectionally coupled with the temperature applied to continuous casting of the steel 1013D (0,3% of carbon) In the simulations we adopted some simplifications such as the Plane Strain and isotropic material. We also neglected the body forces contact with the rollers the liquid pressure on the walls of the steel ingot (ferrostatic pressure) and the convective effect. However despite of the simplifications adopted this work provides quantitative informations on the linear tensions accumulation that point out to areas of possible of cracks formations
A tÃcnica de lingotamento contÃnuo nas Ãltimas quatro dÃcadas à cada vez mais utilizada na produÃÃo de aÃo semiacabado. A transferÃncia de calor à o principal mecanismo dominante e ocorre em todas as etapas do processo. A qualidade do aÃo no lingotamento està diretamente relacionada à forma que ocorrem as trocas de calor pois as variaÃÃes tÃrmicas produzem carregamentos mecÃnicos assim como as forÃas de contato as quais sÃo geradas por intermÃdio dos rolos e da oscilaÃÃo do molde. Tais fatores podem causar defeitos como fraturas ou trincas no produto final caso as tensÃes e deformaÃÃes resultantes excedam valores crÃticos. O aprimoramento da tÃcnica tem a finalidade de evitar o surgimento de defeitos e reduzir o tempo de produÃÃo. Para isso à fundamental uma boa compreensÃo dos fenÃmenos fÃsicos envolvidos ao longo do processo de solidificaÃÃo. O foco deste trabalho à aplicar a abordagem do EbFVM (Element based Finite-Volume Method) no estudo dos efeitos das tensÃes lineares acopladas unidirecionalmente com a temperatura aplicado ao lingotamento contÃnuo do aÃo 1013D (0,3% de carbono) Nas simulaÃÃes adotou-se algumas simplificaÃÃes com o estado plano de tensÃes e isotropia do material. Descartando-se as forÃas de corpo o contato com os rolos a pressÃo do aÃo lÃquido nas paredes do lingote (pressÃo ferrostÃtica) e o efeito convectivo. Contudo apesar das simplificaÃÃes adotadas este trabalho traz informaÃÃes quantitativas quanto a formaÃÃo do acÃmulo das tensÃes lineares que apontam para regiÃes de possÃveis formaÃÃes de trincas

This thesis presents numerical techniques for solving problems of incompressible flow coupled to scalar transport equations using finite element discretizations in space. The two applications considered in this thesis are multi-phase flow, modeled by level set or phase field methods, and planetary mantle convection based on the Boussinesq approximation. A systematic numerical study of approximation errors in evaluating the surface tension in finite element models for two-phase flow is presented. Forces constructed from a gradient in the same discrete function space as used for the pressure are shown to give the best performance. Moreover, two approaches for introducing contact line dynamics into level set methods are proposed. Firstly, a multiscale approach extracts a slip velocity from a micro simulation based on the phase field method and imposes it as a boundary condition in the macro model. This multiscale method is shown to provide an efficient model for the simulation of contact-line driven flow. The second approach combines a level set method based on a smoothed color function with a the phase field method in different parts of the domain. Away from contact lines, the additional information in phase field models is not necessary and it is disabled from the equations by a switch function. An in-depth convergence study is performed in order to quantify the benefits from this combination. Also, the resulting hybrid method is shown to satisfy an a priori energy estimate. For the simulation of mantle convection, an implementation framework based on modern finite element and solver packages is presented. The framework is capable of running on today's large computing clusters with thousands of processors. All parts in the solution chain, from mesh adaptation over assembly to the solution of linear systems, are done in a fully distributed way. These tools are used for a parallel solver that combines higher order time and space discretizations. For treating the convection-dominated temperature equation, an advanced stabilization technique based on an artificial viscosity is used. For more efficient evaluation of finite element operators in iterative methods, a matrix-free implementation built on cell-based quadrature is proposed. We obtain remarkable speedups over sparse matrix-vector products for many finite elements which are of practical interest. Our approach is particularly efficient for systems of differential equations.

Architectural orientation of wood surfaces is the primary study of this thesis. To understand different wood surfaces, they are ordered into 4 elements of Architecture; Earth, Air, Fire, Water. This thesis is structured from these 4 elements in a simple legible form. Deer Field Inn would serve the local communities of Ritchie County, West Virginia for family, social, and organization gatherings.
Master of Architecture

Le phytomanagement compte parmi les méthodes innovantes de gestion des sites et sols pollués en raison de son adéquation avec le développement durable. Pour répondre à la double exigence de performances environnementales et économiques, les phytotechnologies sont désormais combinées à la valorisation de la biomasse produite sur sols pollués. Parmi les filières éco-innovantes et non-alimentaires de valorisation de cette biomasse, la culture de plantes à parfums, aromatiques et médicinales (PPAM) pour la production d’huiles essentielles (HE), substances biosourcées à haute valeur ajoutée, a été proposée dans le cadre du projet PhytEO, financé par l’ADEME. Ainsi, ma contribution à ce projet a permis d‘évaluer la pertinence d’un mode de gestion reposant sur la culture de la sauge sclarée et de la coriandre, en présence ou non d’un amendement mycorhizien, en s’appuyant sur des démonstrateurs in situ à l’échelle de l’hectare, parcelles historiquement polluées ou non par les éléments traces (ET). La coriandre ainsi que la sauge sclarée ont toutes deux montré une bonne capacité à s’installer, à se développer et à produire une quantité importante de biomasse sur des sols présentant une forte pollution historique par les ET. Bien que l’ajout d’un amendement biologique à base de champignons mycorhiziens à arbuscules ait permis d’augmenter de façon significative les taux de mycorhization des racines de coriandre et de sauge sclarée, aucun gain n’a été observé ni au niveau de la croissance de ces deux PPAM, ni au niveau de la quantité et de la qualité des HE. Un effet positif en termes d’immobilisation des ET dans le sol, en particulier du Pb, et une réduction des transferts des ET (Cd et Pb) dans les parties aériennes a toutefois été montré chez la sauge sclarée. D’autre part, les HE distillées à partir de la biomasse de sauge sclarée (inflorescences) ou de coriandre (parties aériennes ou graines) cultivées sur sols pollués présentent une qualité très satisfaisante, caractérisée par leur non contamination en ET ou en résidus de pesticides (traces). Leurs compositions chimiques, non altérées par la pollution en ET et l’inoculation mycorhizienne, affichent divers principes actifs dont le linalol, l’acétate de linalyle, le germacrène, l’α-pinène, le γ-terpinène, le 2-décénal, le décanal et le 2-dodécénal. Ainsi, plusieurs propriétés biologiques potentiellement valorisables dans des domaines à vocation non-alimentaire, tels que la protection des cultures (effets fongistatiques, anti-germinatifs et herbicides) ou la santé humaine (effets anti-inflammatoires et antioxydants) ont été mises en évidence. En revanche, en dépit de son fort pouvoir complexant des HE, la β-cyclodextrine n’a montré aucun effet positif sur les propriétés biologiques testées. Par ailleurs, la végétalisation du sol pollué par la sauge sclarée permet une modulation de la structure des communautés bactériennes et fongiques, telluriques et racinaires. Enfin, l’ensemble des résultats de cette étude et de l’analyse technico-économique de la filière PPAM-HE soulignent le haut potentiel de la sauge sclarée dans une démarche de phytomanagement de sols pollués par les ET
To cope with the soil trace element (TE) pollution, phytomanagement was brought forward as an eco-friendly and feasible approach. To meet the dual requirements of environmental and economic performances, phytotechnologies are now combined with the valorisarion of biomass produced on polluted soils. Among the eco-innovative channels intended for the non-food valorisation of the produced biomass, the cultivation of aromatic and medicinal plants producing essential oils (EO), high-added value biosourced products, has been suggested within the framework of PhytEO project, funded by ADEME. Thus, this thesis contributed to evaluate the relevance of a management approach based on clary sage and coriander cultivation, combined or not with a mycorrhizal inoculum, on in situ experimental plots polluted or not with TE. Both clary sage and coriander have shown a good ability to settle in, to grow and to produce high amounts of biomass, despite the presence of high TE concentrations in the soil. The addition of an amendment based on arbuscular mycorrhizal fungi enhanced the mycorrhizal colonisation rates of both coriander and clary sage roots. However, no significant improvement was observed in terms of plants’ growth, EO amounts and quality. Moreover, mycorrhizal inoculation allowed TE immobilisation in soils, in particular Pb, and reduced TE (Cd and Pb) transfers in aerial parts of clary sage. Besides, the EO distilled from clary sage inflorescences and coriander (aerial parts orseeds) grown on TE polluted soils, displayed a highly satisfactory quality, regarding the absence of contamination by TE or pesticide residues (trace amounts). Their chemical compositions were not altered by both TE pollution and mycorrhizal inoculation and were characterized by several active principles, such as linalool, linalyl acetate, germacrene, α-pinene, γ-terpinene, 2-decenal, decanal and 2-dodecenal. Furthermore, several biological properties with potential applications in non-food fields such as crop protection (antifungal, antigerminative and herbicidal) or human healthcare (antioxidant and anti-inflammatory) have been brought forward. However, despite its ability to form inclusion complexes with EO components, β-cyclodextrin has shown no significant improvement of the tested EO biological activities. On another note, the soil revegetation with clary sage displayed a clear shaping of the bacterial and fungal communities, in both the rhizospheric soil and the roots of the aromatic plant species. Altogether, our results combined with the techno-economic feasibility assessment of the channel “aromatic and medicinal plants/EO” have emphasised clary sage as a good candidate for the phytomanagement of TE-polluted soils

Inflation is currently the most promising paradigm of the Early Universe. The simple paradigm involves a single canonical scalar field minimally coupled to gravity slowly rolling down a potential. In this thesis, we discuss an extension to the simple paradigm, multifield inflation, in which inflation is driven by more than one scalar field. Unlike in the single field paradigm, isocurvature perturbations could be non-vanishing and source curvature perturbation on superhorizon scales. Analytic model predictions during the slow-roll regime in some classes of multifield inflation models have been worked out in the literature. However, curvature perturbation may continue to evolve after slow-roll as isocurvature perturbations are not necessarily exhausted when inflation ends. In this thesis, by using the δ N formalism, we investigate the effects of perturbative reheating on the curvature perturbation and related observables in multifield models. By considering various two-field models, we demonstrate that the subsequent (p)reheating evolution is significant and must be taken into account even for perturbative reheating. How the model predictions evolve during reheating is a model dependent question, implying that models of multifield inflation cannot be compared to observations directly without specifying how reheating takes place. We also discuss a different class of two-field models, conformal inflation, which is locally scale invariant. Universal behaviour emerges as a critical phenomenon near the enhanced SO(1,1) or shift symmetry point, leading to model independent predictions. Going beyond the original model proposed by Kallosh and Linde, we show that this universal behaviour extends to more generalised models involving higher order derivatives for slow-roll potential driven inflation.

Immigrants participate in entrepreneurial activity more frequently than other groups, largely resulting from restricted access to traditional occupational advancement. Recent studies have reported that immigrant entrepreneurs focus on their abundance of human and social capital to obtain the financial resources necessary to fund their ventures. Lack of financial resources has been identified as a major barrier for immigrant entrepreneurs; however, as this study indicates, both native and immigrant entrepreneurs face similar financial hurdles in locating initial startup funding. Where major differences arise between native and immigrant entrepreneurs is that native entrepreneurs more frequently transition to business forms of debt, a key component to long-term success. Resulting from their lack of embeddedness in their host context, immigrant entrepreneurs are far more likely to rely on social network based resources to fund growth, which removes their businesses from the opportunities business forms that debt provides. Using the Kauffman public data, I investigated the relationship between financing strategies engaged by "immigrant" versus "native" entrepreneurs.

Space objects are generally defined as any orbiting object around the Earth, both from natural and artificial origin. In the last years, space activities are increasing the number of space objects, raising concern about the likelihood of collisions between operational spacecrafts. To mitigate this dangerous phenomenon, studies about probability of collision and avoidance maneuvers have played an important role in the last decades. Through the Two-Line-Element sets, position and velocity information of space objects can be computed at a known instant of time and then propagated to future time period with the Simplified General Perturbation model. Accurately knowing the motion of each object helps in the detection of collisions. This thesis deals with spacecraft collision probability by drafting a layout of a collision simulator and developing part of it in MATLAB environment. To compute the probability of collision in a validation example, the procedure that has been followed consisted in propagating the trajectory of a European satellite to the time of closest approach. At this instant of time, an encounter region has been defined, finding the likelihood of collision between another object with Foster’s analytical method and with non-linear Monte Carlo simulations. This dissertation ends with a general flowchart of the simulator, which illustrates its functioning and includes the future works to be developed.

A new method called the Direct Method is developed to solve for the propagating modes in waveguides via the finite-element method. The variational form of the Direct method is derived to ensure that an extremum is reached. The Direct method uses Maxwell's equations directly, both zero and first-order, scalar and vector bases that are used in the finite-element formulation. The direct solution method solves for both the magnetic and electric fields simultaneously. Comparisons are made with the traditionally used vector-Helmholtz equation set. The advantages and disadvantages of the newly developed method is described as well as several results displayed using the WR-90 waveguide and a circular waveguide as test waveguides. Results include a partially filled dielectric loaded rectangular waveguide. The effects of including the divergence of the fields in the functional as penalty terms on the quality of results obtained by the Direct method and the vector-Helmholtz method is explored. The quality of results is gauged on the accuracy of the computed modes as well as the elimination or a significant reduction in the number of 'spurious modes' that are often encountered in solutions to waveguide problems. It is shown that computational time for the solution and computer storage requirements exceed the typically used Helmholtz equation method but the results obtained can be more accurate. Future work may include developing a sparse eigenvalue solution method that could reduce the solution time and storage requirements significantly. The Direct method of solution in dynamics resulted after an initial search in magnetostatics for methods to solve for the magnetic field without using the magnetic-vector potential using finite-element methods. A variational derivation that includes the boundary conditions is developed for the magnetic-vector potential method. Several techniques that were used to attempt accurate solutions for the magnetostatic fields with multiple materials and without the use of the magnetic-vector potential are described. It was found that some of the newly developed general techniques for magnetostatics are only accurate when homogeneous media are present. A method using two curl equations is developed which is a Direct method in magnetostatics and reveals the interaction between the bases used. The transition from magnetostatics to dynamics is made and similar Direct methods are applied to the waveguide problem using different bases.
Ph. D.

TWO WAYS OF BURNING A COTTON FIELD is an ethnographic memoir concerning the narrator’s experiences as a Peace Corps volunteer in Paraguay, South America. The plot is structured around a moral crisis in his rural Paraguayan village. The narrator’s neighbor, a man in his late twenties, threatened to kill his partner and her two children. The Paraguayan police were made aware of the situation but did nothing. Peace Corps management also instructed the narrator to do nothing. In TWO WAYS OF BURNING A COTTON FIELD, this moral crisis is explored within the contexts of post-colonial power structures, including economic and ecologic geographies, intersections of community and government, and the colonial-indigenous language continuum of Paraguay (Spanish-Guaraní). Further, these neighbors’ localized trauma is located within historical, colonial trauma. Of particular concern is the role that languages – English, Spanish, and Guaraní – play in constructing power, worldview, and relationships within the village.

Two compact planar crossed-dipole antennas loaded with near-field resonant parasitic (NFRP) elements are reported. The NFRP and crossed-dipole elements are designed for the desired circularly polarized (CP) radiation. By placing the NFRP element over the driven element at angles of 0 degrees and 45 degrees, respectively, dual-band and broadband CP antennas are realized. All radiating elements of antennas are 35 mm x 35 mm x 0.508 mm (0.187 lambda(0) x 0.187 lambda(0) x 0.0027 lambda(0) at 1.6 GHz) in size. The dual-band CP antenna has a measured vertical bar S-11 vertical bar < -10-dB bandwidth of 226 MHz (1.473-1.699 GHz) and measured 3-dB axial ratio (AR) bandwidths of 12 MHz (1.530-1.542 GHz) and 35 MHz (1.580-1.615 GHz) with minimum AR CP frequencies of 1.535 GHz (AR = 0.26 dB) and 1.595 GHz (AR = 2.08 dB), respectively. The broadband CP antenna has a measured vertical bar S-11 vertical bar< -10-dB bandwidth of 218 MHz (1.491-1.709 GHz) and a 3-dB AR bandwidth of 145 MHz (1.490-1.635 GHz). These compact antennas yield bidirectional electromagnetic fields with high radiation efficiency across their operational bandwidths.

Thesis (Ph. D.)--City University of Hong Kong, 2005.
"Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 115-128).

Real materials contain structural defects which significantly affect their properties. Defects, in a general sense, are ubiquitous and encompass the diverse variety of elements capable of disrupting the continuity and translational symmetry of a crystalline lattice, both in terms of its structural morphology, and in terms of local modulation of its electrical and optical properties. In this perspective, atomic vacancies, line vacancies, atomic rearrangements, local doping inhomogeneity, chemically adsorbed adatoms, all fall within the broad category of defects. Thus, the nanoscale details of surface structure plays a pivotal role in understanding the impact defects may have on the overall properties of the material, and this is particularly true for "all-surface" materials such as two-dimensional (2-D) crystals. Even the interface between two atomically thin layers has a strong impact on the electronic and optical properties of few-layered stacks; therefore, also the interface associated with stacking and layer orientation can be viewed as an extend defect in two dimensions. While macroscopic morphological characterization methods can provide averaged information over a lateral extent defined by their spatial resolution, high resolution (i.e. nanoscale) imaging has the potential to unveil important insights into the role of defects that dominate several aspects of surface chemistry and physics. On the one hand, defects in 2-D materials can be seen as deleterious as they may alter their electrical, chemical, magnetic and mechanical properties. On the other hand, the intentional creation of nanoscale defects may offer an additional degree of freedom for engineering their properties. In this perspective, having structural defects can be either detrimental or beneficial, depending on the targeted application. Despite the ever expanding literature on the study of the interplay between defects and the optical, electrical and mechanical properties of two dimensional materials, direct and non-destructive imaging of defect formation at the nanoscale remains a significant challenge. Although techniques such as electron microscopies or scanning tunnelling microscopy can be used to resolve individual lattice defects, they may be destructive or restricted to specific (e.g. conductive) substrates. This thesis presents a nanoscale optical investigation of 2-D materials, such as graphene and single-layer MoS2, with a particular focus on the characterisation of defects. The field enhancement at the tip-apex of a metal-coated atomic force microscopy (AFM) tip is used to decrease the spatial resolution beyond the diffraction limit. In the case of the investigation of Raman scattering, this near-field optical technique is known as tip-enhanced Raman spectroscopy (TERS). TERS is here demonstrated to be a valid technique to probe the distribution of point-like defects at the nanoscale, especially in the case of barely defective graphene. An analytical model to describe near-field imaging of pointlike Raman scatterers, which is of general applicability to zero-dimensional scatterers such as molecules, is presented. The near-field image, constructed from the Raman intensity, is found to depend on the Raman tensor and the orientation of the scatterer. The model can be also used to explain the different values of near-field Raman enhancement observed for different Raman bands. Motivated by the successful optical characterization of defects in graphene by means of Raman spectroscopy, it is now timely to expand the study of structural defects to other 2-D materials, such as semiconducting transition metal dichalcogenides. MoS2 is one of the most prominent members of this newly discovered category of chalcogenide monolayers. Defect-induced Raman scattering of single-layer MoS2 is studied by means of a controlled introduction of defects using ion-bombardment. Phonon confinement is used to explain the evolution of peak widths and shifts, and a metric based on Raman intensities is proposed to quantify defects. To gain insight into the defect-induced Raman processes, polarised and resonance Raman spectroscopy are employed.

Cette thèse traite de la RMN en phase liquide à champs multiples, pour la détermination de la structure et de la dynamique de petites molécules et de protéines. La dynamique ps-ns des chaînes latérales de la protéine ubiquitine a été étudiée par la relaxation du 13C des groupes méthyles δ1 des isoleucines, marqués sélectivement. Les vitesses de relaxation mesurées à plusieurs hauts champs magnétiques et les vitesses de relaxation longitudinale de 0.29 T à 9 T obtenues par relaxométrie haute résolution ont été analysées à l'aide du programme ICARUS, adapté à l’occasion pour les groupes méthyle. La matrice de relaxation a été calculée par un programme inédit, nommé RedKite. Un modèle de fonction de densité spectrale a été proposé pour prendre en compte les mouvements complexes des groupes méthyles. Nous avons ainsi pu accéder à une description de la dynamique des groupes méthyle sur trois ordres de grandeur d’échelles de temps. La spectroscopie RMN à deux champs magnétiques a été développée en collaboration avec Bruker. Le spectromètre à deux champs permet le contrôle des spins dans deux centres magnétiques avec une homogénéité suffisante et le transfert rapide de l’échantillon entre ces deux centres. Grâce à l'utilisation de cohérences à zéro-quantum, nous avons mesuré des spectres de corrélation homo- et hétéronucléaires à haute résolution dans lesquels les deux dimensions sont obtenues à deux champs très différents. Cette approche a été utilisée pour réduire considérablement la contribution de l’échange chimique à la relaxation transverse, permettant l’observation des signaux de noyaux en échange chimique invisibles à haut champ
We present the development of multiple-field liquid-state NMR spectroscopy for the determination of the structure and dynamics of small molecules and proteins. Dynamics of proteins side-chains in the pico- to nanosecond range have been studied in the protein ubiquitin, by measuring the relaxation of carbon-13 nuclei in isoleucine-δ1 methyl groups, with site-specific isotope labelling. High-field relaxation rates and longitudinal relaxation rates obtained using high-resolution relaxometry have been analysed using a new version of the program ICARUS, adapted for methyl groups. The relaxation matrix has been calculated with a homemade program called RedKite. Models of spectral density function have been proposed to account for all motions of methyl groups. This unprecedented dataset allows for the description of motions in methyl groups over 3 orders of magnitudes of correlation times. Two-field NMR has been developed in collaboration with Bruker. The two-field NMR spectrometer allows for the control of nuclear spins in two magnetic centres with vastly different magnetic fields, coupled with a sample shuttle. Using zero-quantum coherences, homo and heteronuclear two-field high-resolution spectra have been obtained, where the two dimensions are acquired at very different magnetic fields. Such pulse sequences have been used to reduce the contribution of chemical exchange to transverse relaxation, even when this exchange makes signals invisible at high field. The reduced bandwidth of signals at low field has also been used to perform efficient isotropic mixing in a two-field TOCSY experiment. Correlations have been observed for carbon-13 signals separated by more than 150 ppm

This project is an implementation of an orbit propagation routine called SGP4 that calculates TLE data by means of an estimation algorithm that exploits the Levenberg-Marquardt method. The first chapter is a description of the subject of study and why it is still used; the second chapter describes orbit determination by means of flow diagrams and the orbit propagation routine I have used in this project. Last two chapters are a description of the Matlab codes that have been developed, with some validation test and specific test cases of 5 satellites with both computed and precise orbit determination ephemeris. Finally, a brief conclusion about results and possible improvements of the codes is written at the end of the last chapter.

This thesis investigated the apparent effectiveness of environmental education essential elements in school field trip programming. First, the elements essential to environmental education field trips were identified from the literature. Second, these elements were incorporated into a questionnaire that was administered as a pre/post test to elementary school students visiting an extensive indoor environmental education facility located in Montreal. Finally, 24 environmental education programs at eight institutions in Montreal were observed to investigate the extent and methodology of implementation of the essential elements. With regard to the chief institution, it was concluded that (1) the educational programming appeared to significantly increase environmental knowledge, and (2) the environmental attitudes were most strongly correlated with student background. Program observation at the eight institutions demonstrated that a wide array of environmental topics was presented, but there was insufficient instruction of environmental issues and action strategies. The list of observed implementation methodologies and the study conclusions could prove useful as a research-based foundation for effective environmental education field trip program development.

The infiuence of the nuclear Coulombfield on two-pion and two-kaon correlations is investigated for sources with charge number of Z = 160. The source radii extracted from the correlation function determined in sidewards and outwards direction are remarkably affected for meson pairs with average momenta, below 200 MeV/c.

The thesis starts with a short introduction to smooth dynamical systems and Hamiltonian dynamical systems. The aim of the introductory chapter is to collect basic results and concepts used in the thesis to make it self–contained. The second chapter of the thesis deals with the interaction of two charges moving in R2 in a magnetic field B. This problem can be formulated as a Hamiltonian system with four degrees of freedom. Assuming that the magnetic field is uniform and the interaction potential has rotational symmetry we reduce this Hamiltonian system to one with two degrees of freedom; for certain values of the conserved quantities and choices of parameters, we obtain an integrable system. Furthermore, when the interaction potential is of Coulomb type, we prove that, for suitable regime of parameters, there are invariant subsets on which this system contains a suspension of a subshift of finite type. This implies non–integrability for this system with a Coulomb type interaction. Explicit knowledge of the reconstruction map and a dynamical analysis of the reduced Hamiltonian systems are the tools we use in order to give a description for the various types of dynamical behaviours in this system: from periodic to quasiperiodic and chaotic orbits, from bounded to unbounded motion. In the third chapter of the thesis we study the interaction of two charges moving in R3 in a magnetic field B. This problem can also be formulated as a Hamiltonian system, but one with six degrees of freedom. We keep the assumption that the magnetic field is uniform and the interaction potential has rotational symmetry and reduce this Hamiltonian system to one with three degrees of freedom; for certain values of the conserved quantities and choices of parameters, we obtain a system with two degrees of freedom. Furthermore, when the interaction potential is chosen to be Coulomb we prove the existence of an invariant submanifold where the system can be reduced by a further degree of freedom. The reductions simplify the analysis of some properties of this system: we use the reconstruction map to obtain a classification for the dynamics in terms of boundedness of the motion and the existence of collisions. Moreover, we study the scattering map associated with this system in the limit of widely separated trajectories. In this limit we prove that the norms of the gyroradii of the particles are conserved during an interaction and that the interaction of the two particles is responsible for a rotation of the guiding centres around a fixed centre in the case of two charges whose sum is not zero and a drift of the guiding centres in the case of two charges whose sum is zero.

In this Thesis we analyse in detail the Anglo-Australian 2 degree Field Galaxy Redshift Survey (2dFGRS). The goal of this survey is to measure all galaxy redshifts for the 250 000 galaxies brighter than b(_J) = 19.45 spread over ~ 2000 square degrees. At present, the 2dFGRS has obtained redshifts for ~ 190 000 galaxies. It is currently the biggest galaxy redshift survey in existence and represents an order of magnitude increase in size over any previous survey. The study of the large-scale structure of the Universe is undergoing a revolution due to important technological advances in observational astronomy that make surveys like the 2dFGRS possible. This new era in mapping the Universe demands the development of new theoretical analysis tools, both to exploit the large amounts of data, and to take advantage of, for the first time in cosmology, the extraordinary opportunity to push random errors below the level of the systematic errors. By a detailed analysis of the survey construction and observing strategy, we implement a set of maps to estimate, as precisely as possible, the selection function of the 2dFGRS. These maps, which characterize the survey completeness, enable us to estimate accurately fundamental properties of a homogeneous galaxy sample: the galaxy luminosity function and real space galaxy clustering. By combining the 2dFGRS with the near infra-red 2MASS survey, we estimate the K(_s)-band galaxy luminosity function, from which we infer the stellar mass function of galaxies. This yields a total mass fraction in stars between 0.1% and 0.3% of the critical cosmic density. Exploiting the size of the survey, we undertake the first precise measurement of the dependence of galaxy clustering on luminosity and spectral type. Star-forming galaxies as well as more quiescent galaxies show a clear increase in clustering strength with luminosity at a similar rate. This is the first time that we are able to examine in detail the properties of galaxies that drive their spatial distribution.

Temporal variations of Earth\'s magnetic field provide a great range of geophysical information about the dynamics at different layers of the Earth. Since it is a planetary field, regional and global aspects can be explored, depending on the timescale of variations. In this thesis, the geomagnetic field variations for the last two millennia were investigated. For that, some improvement on the methods to recover the ancient magnetic field intensity from archeological material were done, new data was acquired and a critical assessment of the global archaeomagnetic database was performed. Two methodological advances are reported, comprising: i) the correction for microwave method of the cooling rate effect, which is associated to the difference between the cooling times during the manufactory of the material and that of the heating steps during the archaeointensity experiment; (ii) a test for thermoremanent anisotropy correction from the arithmetic mean of six orthogonal samples. The temporal variation of the magnetic intensity for South America was investigated from nine new data, three from ruins of the Guaraní Jesuit Missions and six from archaeological sites associated with jerky beef farms, both located in Rio Grande do Sul, Brazil, with ages covering the last 400 years. These data combined with the regional archaeointensity database, demonstrates that the influence of significant non-dipole components in South America started at ~1800 CE. Finally, from a reassessment of the global archaeointensity database, a new interpretation was proposed about the geomagnetic axial dipole evolution, where this component falls constantly since ~700 CE associated to the breaking of the symmetry of the advective sources operating in the outer core.
Variações temporais do campo magnético da Terra fornecem uma grande diversidade de informações geofísicas sobre a dinâmica das diferentes camadas da Terra. Por ser um campo planetário, aspectos regionais e globais podem ser explorados, dependendo da escala de tempo das variações. Nesta tese, foram investigadas as variações do campo geomagnético para os dois últimos milênios. Para isso, aprimoramentos nos métodos de aquisição da intensidade geomagnética registrada em materiais arqueológicos foram realizados, bem como a aquisição de novos dados e uma avaliação crítica da base de dados arqueomagnética global. Dois novos avanços metodológicos são aqui propostos, sendo eles: i) correção para o método de micro-ondas do efeito da taxa de resfriamento, que está associada à diferença entre os tempos de resfriamento durante a manufatura do material e o das etapas de aquecimento durante o experimento de arqueointensidade; (ii) teste para correção da anisotropia termorremanente a partir da média aritmética de seis amostras posicionadas ortogonalmente umas às outras durante o experimento de arqueointensidade. A variação temporal da intensidade magnética para a América do Sul foi investigada a partir de nove dados inéditos, sendo três provenientes das ruínas das Missões Jesuíticas Guaraníticas e seis de sítios arqueológicos associados a fazendas de charque, ambos localizados no Rio Grande do Sul, Brasil, com idades que cobrem os últimos 400 anos. Esses dados, combinados com o banco de dados regionais de arqueointensidade, demonstram que a influência significativa de componentes não-dipolares do campo magnético na América do Sul começou em ~1800 CE. Finalmente, a partir de uma reavaliação do banco de dados globais de arqueointensidade uma nova interpretação foi proposta a respeito da evolução do dipolo axial geomagnético, sugerindo que essa componente está decrescendo constantemente desde ~700 CE devido à quebra da simetria das fontes advectivas que operam no núcleo externo.

本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第8127号
理博第2149号
新制||理||1144(附属図書館)
UT51-2000-F31
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)教授 石黒 武彦, 教授 山田 耕作, 助教授 前野 悦輝
学位規則第4条第1項該当

The infiuence of the nuclear Coulombfield on two-pion and two-kaon correlations is investigated for sources with charge number of Z = 160. The source radii extracted from the correlation function determined in sidewards and outwards direction are remarkably affected for meson pairs with average momenta, below 200 MeV/c.

Thesis (Ph. D.)--University of Kentucky, 2006.
Title from document title page (viewed on January 25, 2007). Document formatted into pages; contains: xiii, 162 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 151-157).

The genome of Klebsiella pneumoniae HS11286 carries two integrative and conjugative elements (ICEs), ICEKpnHS-1 and ICEKpnHS-2; the former belongs to the ICEKp1 family and the latter was unexplored. This study was designed to further characterise the two ICEs, and investigate their prevalence in local clinical K. pneumoniae isolates. Sequence analysis showed that ICEKpnHS-2 belonged to the subfamily of PAPI elements with XerC-like integrases and PCR screening revealed that ICEKpnHS-1 associated elements were more (30%) prevalent in local isolates compared to ICEKpnHS-2 (12.5%). Contributions of these elements to cell physiology, virulence and antibiotic resistance were investigated. Deletion of ICEKpnHS-1 reduced siderophore secretion and growth, particularly in iron restricted conditions. The ΔICEKpnHS-1 strain also showed reduced resistance to various antibiotics, especially those known to be affected by the ATP binding cassette (ABC) and major facilitator superfamily (MFS) exporters. Assays in Galleria mellonella provided preliminary evidence that deletion of ICEKpnHS-2 reduced the virulence of K. pneumoniae HS11286. Type IV secretion systems (T4SS) are major component modules of ICEs responsible for conjugative transfer of nucleoprotein complexes. Observed reduction of conjugative transfer of one of the ICEs following deletion of the other led us to study interactions between the two distinct T4SSs encoded on the ICEs in HS11286. A marker plasmid containing oriT of ICEKpnHS-1 (P-oriT1) was constructed and deletion of ICEKpnHS-2 was shown to produce a six–fold reduction in trans-conjugants. Deletion of the mobB (ICEKpnHS-1) orthologue in ICEKpnHS-2 (mob-2) and traI (relaxase of ICEKpnHS-2) both produced similar defects in transconjugants frequencies that could be complemented in-trans. The ATPase Mob-1 was bioinformatically shown to lack a Walker B and it was speculated that Mob-2 might compensate for this. Accordingly, point mutations in Walker motifs of mob-2 provided evidence supporting this complementary function in energy transduction contributing significantly to the crosstalk between the two non-homologous ICEs. Data on frequency of transfer of the native chromosomal ICEKpnHS-1 and its effects on the phenotypes of an E. coli were also shown. However, ICEKpnHS-2 self-conjugation was not detected.