Made available in DSpace on 2014-06-12T18:30:57Z (GMT). No. of bitstreams: 2 arquivo8522_1.pdf: 885088 bytes, checksum: 731a54bbce606e1245c5b0ca84497abf (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2003 / Este trabalho consiste em estudar o movimento de uma partícula, de massa infinitesimal, submetida unicamente à força de atração gravitacional induzida por um fio circular homogêneo fixo, contido no espaço tri-dimensional. Iniciamos este trabalho apresentando a formulação do problema e um estudo preliminar do potencial. Fazemos o estudo das simetrias e dos conjuntos invariantes. No capítulo 2, verificamos que todas as singularidades do problema do fio circular são devidas à colisão. No capítulo 3, verificamos que o potencial ou o gradiente da função potencial V, pode ser visto como uma aproximação de outros potenciais, ou do gradiente de outros potenciais de m,ais fácil manipulação. E, no capítulo 4, provamos a existência de soluções periódicas de problemas perturbados próximas a soluções circulares de problemas não perturbados. No capítulo 5, apresentamos o estudo da dinâmica do problema do fio circular homogêneo. Inicialmente estudamos a dinâmica da partícula restrita aos conjuntos invariantes. No estudo da dinâmica restrita ao eixo z verificamos a existência de soluções periódicas, e soluções ilimitadas, as que escapam para o infinito. Além disso, observamos que a origem é ponto de equilíbrio estável do sistema restrito e que todas as soluções deste problema estão definidas em todo tempo. No estudo no plano horizontal verificamos a existência de soluções circulares passando por qualquer ponto no exterior do fio circular e a não existência de soluções circulares no interior do fio. Fazemos um estudo sobre a existência de soluções circulares no exterior do fio circular para um certo momento angular fixado. No interior do fio circular, provamos que as soluções ou colidem ou convergem para a origem ( a menos da solução de equilíbrio). Verificamos que todas as soluções não radicais descrevem uma curva cujo traço tem uma forma particular. No exterior do fio circular, fazemos também uma análise da dinâmica, a partir do retrato de fase. Por fim, apresentamos a região de Hill do problema e o estudo da solução de equilíbrio restrito a este plano. No estudo no plano vertical provamos a existência de soluções periódicas longe do fio circular e soluções periódicas próximas ao fio circular, intersectando a região planar interior ao fio circular, com um raio qualquer. Além disso, verificamos a existência de soluções em forma de oito, passando pela origem. Provamos também a existência de certas soluções periódicas no espaço tri-dimensional, perto do fio circular e apresentamos a análise da solução de equilíbrio do problema

Submitted by Israel Vieira Neto (israel.vieiraneto@ufpe.br) on 2015-03-05T17:09:49Z No. of bitstreams: 2 DISSERTAÇÃO Francinaldo Junior.pdf: 3351371 bytes, checksum: d51e55bbc480ac940c502e8b1eace90f (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-05T17:09:49Z (GMT). No. of bitstreams: 2 DISSERTAÇÃO Francinaldo Junior.pdf: 3351371 bytes, checksum: d51e55bbc480ac940c502e8b1eace90f (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2014-08-29 / Peças de concreto armado com seções transversais circulares vazadas são usadas com muita frequência na engenharia. Em Recife, particularmente, o número de edificações com mais de 30 pavimentos tem apresentado crescimento notável; Muitas dessas edificações são projetadas sobre fundações de estacas circulares vazadas. Os elementos estruturais dessas edificações devem transmitir, de forma segura, momentos, carregamentos axiais e esforços cortantes para as suas fundações. Desta forma, com o aumento da altura das edificações, ocorre também o aumento dos esforços cisalhantes que são transmitidos para suas fundações. Por outro lado, estes elementos vazados são mais críticos em relação ao cisalhamento devido ao seu núcleo vazio. As normas e diretrizes para avaliação da resistência ao cisalhamento de peças com tais seções transversais são praticamente não existentes, e a maioria dos requisitos das normas existentes, dentre elas a NBR 6118, foram baseados em modelos de cisalhamento para seções retangulares. Este estudo buscou avaliar, de forma comparativa, a resistência ao cisalhamento de peças com seções transversais circulares vazadas, obtidas de ensaios experimentais encontrados na literatura, com valores calculados utilizando a Teoria do Campo de Compressão Modificada através da norma canadense (CSA A23.3-04). Ao final, foi proposto, baseado nas normas existentes e nos dados experimentais, parâmetros para avaliação da altura útil, d, e largura efetiva, bw, a serem sugeridos para a NBR 6118, de forma a possibilitar o calculo das forças cortantes resistentes em peças com seções circulares vazadas, e ao mesmo tempo garantir que cada resistência calculada seja menor que a obtida experimentalmente.

[pt] Com o objetivo de se aumentar a confiabilidade de um sistema de micro-ondas tem-se utilizado, em alguns casos, a polarização circular. De modo a se evitar o emprego de vários dispositivos para a obtenção de fontes de polarização circular (os quais concorrem para um aumento do coeficiente de onda estacionária global do sistema) utiliza-se um único componente capaz de efetuar a transformação da polarização circular desejada. Tal componente é conhecido como polarizador. Este trabalho de tese visa apresentar o desenvolvimento e o projeto de um polarizador construído em guia circular, para a faixa de SHF. O efeito da transformação de polarização é conseguido através de diafragmas indutivos e capacitivos dispostos ao longo do guia circular. O coeficiente de onda estacionária máximo encontrado em um modelo construído para a faixa de 6,8 a 7,8 GHz foi de 1,1 e a relação axial de 1,2 dB. Devido a não utilização de dielétricos com perdas na estrutura, pode-se esperar baixos valores de perda por inserção. Nestas medidas incluem-se a transição guia retangular-guia circular. Na Introdução do presente trabalho é apresentada a obtenção de polarização circular em guia circular através de dois modos TE 11, ortogonais, defasados de 90 0. no Capítulo 1 são analisados os fundamentos teóricos em que se apóia o polarizador e no Capítulo 2 é analisada a sistemática de projeto da estrutura. Os Capítulos 3 e 4 descrevem, respectivamente, o projeto de um modelo experimental e os ensaios efetuados. / [en] Circular polarization hás been used in some cases to increase the capability and reliability of microwave systems. The desing employed here avoids introduccing several components to generate circular polarization (as such elements tend to increase the total voltage standing wave ratio of the system) by utilizing a single component capable of making the transformation from the original linear polarization in the retangular guide to the desired circular polarization. This component is known as a polarizer. This paper presents the development and results of a thesis project involving the construction of a polarizer in circular waveguide for the SHF band. The transformation from linear to circular polarization is obtained by using inductive and capacitive diaphrams dispposed longitudinaly in circular guide. The maximum voltage standing wave ratio measured in the model constructed was 1,1 and the maximum axial ratio was 1.2 dB for the band 6,8 to 7.8 GHz. Because lossy dielectric materials were not used in this polarizer low values of insertion loss are expected. The effects of the transition from retangular to circular guide are included in the measurements. In the introduction section of this paper the author describes the method for realizing circular polarization in circular waveguides by the use of two orthogonal TE 11 modes phased 90 0 apart with respect to each other. In Chapter 1 the theoretical fundamentals upon which the polarizer is based are analysed and in Chapter 2 a systematic analysis of the structure is reported, Chapter 3 and 4 describe, respectively, the investigations of the experimental model and the test results achieved.

It is common practice to design water chiller units and heat exchangers in such a way that they do not operate within the transition region. This is mainly due to the perceived chaotic behaviour as well as the paucity of information in this region. Due to design constraints or change of operating conditions, however, exchangers are often forced to operate in this region. This is even worse for enhanced tubes as much less information within this region is available. It is also well known that the entrance has an influence on where transition occurs, adding to the woes of available information. The purpose of this study is thus to obtain heat transfer and friction factor data in the transition region of fully developed and developing flows inside smooth and enhanced tubes, using water as the working fluid, and to develop correlations from these results. The use of different inlets, tube diameters and enhanced tubes was also investigated with regards to the commencement of transition. Heat transfer and pressure drop data were obtained from six different types of tubes with diameters of 15.88 mm (5/8′′) and 19.02 mm (3/4′′). Low fin enhanced tubes with a fin height to diameter ratio of 0.4 and helix angles of 18◦ and 27◦ were investigated. Heat transfer was obtained by means of an in-tube heat exchanger with the cooling of water being used as the test fluid. Reynolds numbers ranged between 1 000 and 20 000 while Prandtl numbers were in the order of 4 to 6. Uncertainties in heat transfer coefficient and friction factors were on average below 2.5% and 10% respectively. Adiabatic friction factor results showed that the use of different inlets influenced the commencement of transition. The smoother the inlet profile the more transition was delayed, confirming previous work done. The effect of increasing tube diameters had a slight delay in transition. Enhanced tubes caused transition to occur at lower Reynolds numbers which was accounted for by the fin height and not the helix angle. Heat transfer results showed that transition occurred at approximately the same Reynolds number for all the different inlets and enhanced tubes. This was attributed to the secondary flow forces influencing the growing hydrodynamic boundary layer. These secondary flow forces also influenced the laminar heat transfer and diabatic friction factors with both these parameters being higher. Turbulent enhanced tube heat transfer results were higher than those of the smooth tube, with the tube with the greatest helix angle showing the greatest increase. Correlations were developed for all the tubes and their inlets and predicted all the data on average to within 3%. / Thesis (PhD)--University of Pretoria, 2010. / Mechanical and Aeronautical Engineering / unrestricted

Terahertz (THz) devices are designed to operate from 0.1-10 THz. The THz spectra have unique properties such as penetration through soft materials and reflecting from hard materials, which make THz technologies, a prime candidate for imaging. Plasmons are longitudinal charge oscillations in carrier rich materials. Plasmons can be generated over the channel of transistors inducing a voltage between the source-drain when conditions are satisfied. In this thesis, plasmonic devices operating in the THz region have been studied both theoretically and experimentally investigating GaN/AlGaN and Graphene based transistors. First, we report on a detailed study of dispersion properties of uniform grating gate THz plasmonic crystals, asymmetric dual grating gate plasmonic crystals and with symmetry-breaking defect-like cavities in order to understand the physics behind THz plasmons. For the first time, we defined the dispersion of plasmons in terms of effective plasmonic index. By adding an additional grating on top of the grating gate with a different periodicity, doubles the amount of absorption. Plasmons can be excited when polarization is perpendicular to the gate. We then showed focusing and exciting of THz plasmons polarization independent using circular grating lenses. Sub-micron THz ring resonators are presented showing THz guiding in plasmonic waveguides. So far, resonant sensing has been observed only at cryogenic temperatures since electron mobility is high enough at low temperatures to sustain resonant plasmonic excitation at the channel of the detector. Recently, graphene attracted the attention of the researchers because of its high mobility at room temperature. Room temperature detection has been attempted and achieved, however the detectors have very small responsivity with non-resonant behavior since the graphene is sandwiched and fabrication of such detectors in large scale is impossible with the methods used. Here, we present a resonant room temperature detection of THz with upside down free standing graphene FETs having more than a 400 quality factor, a record high number in the field which is up to 50 times higher than GaN detectors and hundreds of responsivity values with a maximum around 400 V/W which is record high for graphene (10,000 times higher than previously reported graphene detector).

Recent natural disasters, such as major tsunamis, have prompted researchers and practicing engineers to improve their understanding of the impacts of bore-like waves on structures and their foundations. The high velocity and the relatively short duration of hydraulic bores causes local scouring which is different from that generated by river flows and waves. The present study uses an experimental model to simulate the propagation of a hydraulic bore over a movable sediment bed placed around a circular pier-like structure. Measurements of water surface elevation, bore propagation velocity and scour distribution were taken. The linear relationship between reservoir depth and bore depth led to an increase in flow acceleration, and thus to an increase in flow velocity. Final scour bed elevations indicated that scour depth was highly dependent on the bore velocity. The scour depth ratios suggested in current design guidelines were significantly lower than those obtained in this study.

The world’s 7 billion inhabitants depend on chemical fertilizers to meet the growing demand for food. The phosphorus used in fertilizer is sourced from ancient sedimentary deposits of Phosphate Rock (PR), largely in the form of carbonate calcium phosphate, called carbonate apatite, which resembles bone. PR is non-renewable and Canada’s reserves are extremely limited; currently, all 1,400,000 tonnes of phosphorus products used annually are imported. This project investigates a novel method to recycle phosphorus from municipal wastewater in a form that will enable its reuse as a fertilizer, through a reaction with CaCO3 from limestone and waste CO2 (g). This will contribute to the nascent circular nutrient economy within Canada. A review of the current state of phosphorus and nutrient recycling is presented, including a plan for establishing the Canadian Nutrient Platform. A series of inorganic phosphate (PO4-, or Pi) solutions was prepared to simulate the concentrations found in Ottawa’s municipal wastewater, between 2.5-30 mM Pi. These solutions were mixed with CaCO3 solutions that were highly supersaturated through a carbon capture technique. Batch tests successfully reduced the [Pi] and [Ca2+], as measured by colorimetry, and precipitate formed. These results were subsequently repeated in a continuous stirred lab-scale reactor. These precipitation products were characterized using Scanning Electron Microscopy, Raman Spectroscopy, X-Ray Diffraction, and carbon coulometry to measure carbonate content. This analysis confirmed the presence of both Pi and CO3 in a bone-like, carbonate apatite. Although other technologies are being explored to recycle phosphorus from wastewater streams, this is the first indication that it may be possible to precipitate a carbonate apatite by mixing two waste streams, municipal waste water and CO2 (g), with cost-effective CaCO3.

Understanding the behaviour of polymers which are located in the presence of nuclear materials is important in order to predict the lifespan of the materials. Artificial ageing experiments are undertaken at elevated temperatures to infer how the materials may age. This study was concerned with the monitoring of trace gases (H2O, CO2, CO and acetic acid) within a materials ageing vessel which contained ethylene-vinyl acetate (EVA) polymer and uranium in order to deduce the rate of polymer degradation and/or uptake of the gases by uranium. A novel circular multi-reflective (CMR) cell was designed, developed and deployed in situ in order to extend the optical pathlength within the vessel to improve detection limits of the trace gases. One cell was located at the 6 millimetre solid/solid interfacial region between cylindrical coupons of the EVA polymer and uranium, to enable representative sampling in proximity to where the gases were evolved, adsorbed or reacted. The unique planar star-like beam profile of the CMR cell was crucial in enabling detection within this narrow interfacial region. A second CMR cell was incorporated within the vessel headspace, above the two material coupons, to address a specific research problem which aimed to ascertain whether differences in the gaseous composition existed between the two regions, which would indicate poor gas mixing. Two spectroscopic techniques were employed in conjunction with the CMR cells to monitor the trace gases: these comprised broadband absorption spectroscopy (BBAS) and tunable diode laser absorption spectroscopy (TDLAS). Near-infrared (IR) radiation sources, in the form of diode lasers, a superluminescent light emitting diode (SLED) and supercontinuum (SC) source were utilised in BBAS experiments. TDLAS was used for the detection of CO2, CO and H2O, whilst BBAS was used for the detection of acetic acid, and other potential unknown species. The requirement for using near-IR radiation was a consequence of using flexible silica-based optical fibres to remotely monitor the vessel which was located within a temperature controlled chamber. As a result, this was the first demonstration of CMR cells being used in conjunction with near-IR radiation sources. An optical pathlength of 69 cm was achieved within the materials ageing vessel, which led to the following limits of detection at 75 °C, 150 Torr with a 10 second averaging time: H2O = 3 ppm; acetic acid = 157 ppm; CO2 = 596 ppm and CO = 37500 ppm. Manufacturing issues with the cell optics, coupled with monitoring weak ro-vibrational absorption features led to considerably higher limits of detection than expected. The CMR spectroscopic system was used successfully to observe the outgassing trend of partially cured EVA polymer, which was shown to depend on cure time. A key finding of this research, however, was the observation of a difference between the interfacial gaseous composition versus the headspace gas in a system that contained both a source and sink material (i.e. one that evolved, and one that adsorbed gases). This was only made possible by using the CMR spectroscopic system. This observation was also supported by a computational fluid dynamic (CFD) model.

Esta dissertação trata do tema desenho técnico do vestuário. O objetivo deste trabalho foi sistematizar diretrizes para a representação gráfica técnica de acabamentos, detalhes, linhas e cotas em produtos do vestuário do segmento de malharia circular com vistas à sua normalização. A pesquisa foi classificada como aplicada, qualitativa e exploratória. A coleta de dados ocorreu por meio de entrevistas semiestruturadas e coleta documental realizadas de forma presencial e por meio eletrônico (e-mail). Os participantes foram sete docentes de disciplinas de desenho técnico que atuam em instituições de ensino superior que possuem cursos de moda em nível bacharelado e, oito profissionais do desenvolvimento de produto de empresas de confecção do vestuário que trabalham com malha circular. Com isso, foi possível diagnosticar como é feita a representação de desenhos técnicos do vestuário nestes dois ambientes, o acadêmico e o industrial, localizados em diferentes regiões brasileiras. Os resultados das entrevistas foram apresentados através de quadros comparativos com cruzamento dos dados coletados. Como resultado, apresentam-se diretrizes para a construção do desenho e representação de cores, linhas, cotas/medidas. Outro produto deste trabalho é um catálogo dos principais acabamentos e detalhes utilizados em malha circular com descrições, imagens e representações técnicas dos mesmos. / This dissertation deals with the theme of technical drawing of clothing. The aim of this study was to propose guidelines for graphical representation technique of finishing, details, lines and quotas on clothing products of circular knitting segment to achieve its normalization. The research was classified as applied, exploratory and qualitative. Data collection occurred through semi-structured interviews and documentary collection both conducted face-to-face form and by electronic means (e-mail). Participants consisted of seven professors of technical drawing disciplines who work in institutions of higher education that have fashion courses in the Bachelor level. In addition to the professors, eight product development professionals of knitting clothing companies who work with circular mesh also participated. With this, it was possible to diagnose how is the representation of technical drawings of clothing in these two environments, the academic and the industrial, located in different regions of Brazil. The interview responses were presented through comparative tables including the collected data. As a result, guidelines are presented for the construction of the drawing and representation of colors, lines, dimensions/measurements. Another product of this work is a catalogue of the main finishing and details used in circular knit with descriptions, images and representations of the referred techniques.

This study aims to examine the possibilities and limitations ofresidual products from the Swedish food industry for new uses inpackaging design. The selection in the study is semi strategicallyrandom and through the selection four interviews were conductedvia e-mail, two interviews from RISE and two from the Swedishdesign agencies Snask and Bedow. The interviews are based on thestudy's question issues; What innovative packaging materials withproperties corresponding to plastics are available in the Swedishmarket? And How does a selection of Swedish design agenciesapproach the innovative packaging materials available on theSwedish market? Through results and analysis we have come tothe conclusion that there is a great awareness of design agencieswhen it comes to making environmentally conscious designdecisions and that it is highly relevant in today's society. Duringthe study, interesting packaging material was discovered. What hasalso emerged is that it is a matter of course to have to be climatefriendly as everything depends on demand from customers andconsumers. There are no direct regulations to relate to, but it is upto each individual how to relate to a more sustainabledevelopment. However, in order for a societal transformation totake place, collaboration between the various social sectors isrequired (Svenska vetenskapsrådet Formas, 2018).