Submitted by Edisangela Bastos (edisangela@ufpa.br) on 2013-01-31T21:08:44Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_OtimizacaoAntenasLineares.pdf: 900502 bytes, checksum: a9a4cd9879a83fe826fe2618f846c352 (MD5) / Approved for entry into archive by Ana Rosa Silva(arosa@ufpa.br) on 2013-02-05T11:55:34Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_OtimizacaoAntenasLineares.pdf: 900502 bytes, checksum: a9a4cd9879a83fe826fe2618f846c352 (MD5) / Made available in DSpace on 2013-02-05T11:55:34Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_OtimizacaoAntenasLineares.pdf: 900502 bytes, checksum: a9a4cd9879a83fe826fe2618f846c352 (MD5) Previous issue date: 2009 / FAPESPA - Fundação Amazônia de Amparo a Estudos e Pesquisas / O objetivo deste trabalho é a otimização da largura de banda de antenas linear e planar para aplicações em sistemas de banda larga. Nesse sentido, foi feito um estudo das técnicas de análise, aumento da largura de banda e otimização adequadas para o problema em questão. Como técnica de análise, foi utilizado o método dos momentos, o qual está apresentado no capítulo II. Para aumentar a largura de banda, foram utilizadas as técnicas de colocação de elementos parasitas e construção de fendas no radiador, descritos sucintamente no capítulo III. Como algoritmo de otimização, foi utilizado o algoritmo genético, descrito sucintamente no capítulo II. Neste trabalho, são apresentadas duas propostas de antenas, uma antena dipolo linear combinada com quatros espiras parasitas, capítulo IV, e uma antena planar do tipo espira, capítulo V. No primeiro caso, foram utilizados elementos parasitas e o algoritmo genético para aumentar a largura de banda e, no segundo, foram empregadas fendas no radiador e a otimização paramétrica para este objetivo. / The objective of this work is the bandwidth optimization of linear and planar antennas for broadband system applications. For achieving this goal, it was made a study of the analysis, bandwidth enlargement and optimization techniques appropriated for the problem in question. As analysis technique, the method of moments was utilized, which is presented in chapter II. For bandwidth enlargement, the techniques of collocation of parasitic elements and building slots in the radiator were employed, briefly described in chapter III. As optimization algorithm, the genetic algorithm was utilized, briefly described in chapter II. In this work, two antenna proposals are presented, a linear dipole antenna combined with four parasitic elements, chapter IV, and a planar antenna of loop type, chapter V. In the first case, it was utilized parasitic elements and the genetic algorithm to enlarge the bandwidth, and in the second, it was employed slots in the radiator and the parametric optimization to this objective.

[pt] O principal objetivo deste trabalho é o desenvolvimento de um programa computacional para a analise não-linear estática e dinâmica de pórticos planos com ligações flexíveis (semi-rígidas). Inicialmente é apresentada a metodologia de solução não-linear e as formulações dos elementos finitos adotados na base computacional implementada. Em seguida, são estudados vários exemplos de sistemas estruturais estáticos com caminhos de equilíbrio fortemente não-lineares com a finalidade de testar os programas implementados. Então é apresentada a formulação do problema dinâmico com a definição das equações diferenciais ordinárias de movimento e as expressões das matrizes de massa e amortecimento. A solução desse sistema de equações diferenciais ordinárias é obtida por métodos de integração numérica implícitos ou explícitos. Alguns destes métodos são apresentados neste trabalho e incorporados ao programa computacional em conjunto com estratégias adaptativas de incremento automático do intervalo de tempo de integração (delta)t. Por fim, o sistema computacional desenvolvido é utilizado na modelagem e obtenção da resposta estrutural estática e dinâmica de alguns sistemas estruturais planos com comportamento eminentemente não-linear. Através destes resultados são analisados alguns fenômenos importantes de instabilidade estática e dinâmica, bem como possíveis mecanismos de colapso e a influência de parâmetros físicos e geométricos no comportamento estrutural. / [en] The main objective of this thesis is to develop a numerical methodology for the nonlinear static and dynamics analysis of plane frames with semi-rigid connections. Initially, the formulations of the adopted finite elements are presented and implemented together with numerical methodologies for the solution of the non-linear equilibrium equations. Then, some examples of strongly nonlinear structural systems under static loads are studied to check the methodology. Subsequently, the ordinary differential equations of motion are derived and the corresponding damping and mass matrices are presented. The solution of this system of ordinary differential equations is obtained by implicit or explicit numerical integration methods. Some of these methods are presented in this work and incorporated into the computational program together with adaptive strategies for the automatic increment of the time step (delta)t. Finally, the computational system here developed is used to study the static and dynamic response of some plain structural systems with an inherent nonlinear behavior. A detailed parametric study is carried out to identify the influence of physical and geometric parameters on the structural behavior. This enables the analysis of some important static and dynamic instability phenomena and identification of possible mechanisms of collapse.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Neste trabalho, os efeitos de um campo magnético oblíquo externo no modelo de Gross- Neveu (2+1)-dimensional, que inclui as componentes paralela e perpendicular do campo em relação ao sistema, são estudados no contexto da simetria quiral e discreta do modelo. Nosso principal interesse está nos efeitos deste campo sobre o diagrama de fase do sistema, onde também incluímos os efeitos combinados de temperatura e potencial químico. Os diagramas de fase são obtidos através do potencial efetivo a 1 loop para o modelo, derivado em primeira ordem na expansão 1=N. Transições de fase relevantes que podem ser estudadas através deste modelo são, por exemplo, metal-isolante em matéria condensada e na teoria quântica de campos de férmions planares em geral. A relação entre a transição de fase com quebra da simetria quiral e discreta e o surgimento de um gap (ou a presença de um valor esperado no vácuo do campo escalar diferente de zero), como função do campo magnético oblíquo, é analisada em detalhes. / In this work, the effects of an external oblique magnetic field in the (2+1)-dimensional Gross-Neveu model, and that therefore includes both parallel and perpendicular components of the applied field, are studied in the context of the models discrete chiral symmetry. Our main concern is in the effects of such a field in the systems phase diagram and that also includes the combined effects of temperature and chemical potential. The phase diagrams are obtained through the one-loop effective potential for the model, derived in the leading order in the 1=N expansion Relevant phase transitions that can be studied through this model are, for example, metal-insulator ones in condensed matter and in the quantum field theory of planar fermions in general. The relation between the phase transition with (discrete) chiral symmetry breaking and the emergence of a gap (or the presence of a chiral nonvanishing vacuum expectation value) in the planar fermionic system, as a function of the external oblique magnetic field, is analyzed in details.

Les systèmes modernes de télécommunication touchent un public de plus en plus large, ce qui induit inexorablement une utilisation intensive de la gamme hyperfréquence. Pour éviter la saturation des services disponibles, les spécifications concernant les systèmes sont de plus en plus exigeantes. Ces contraintes drastiques sont reportées sur les différents éléments et en particulier sur les filtres. C'est dans ce contexte que nous présentons une nouvelle technologie de réalisation de filtres, l'objectif étant d'améliorer les performances électriques des filtres sans renoncer à la facilité de réalisation des circuits. Ainsi, dans le premier chapitre, nous introduisons les deux techniques historiques de fabrication de filtres, les technologies planaire et volumique. Puis une association de ces deux technologies appelée Substrate Integrated Waveguide (SIW) est présentée. Elle consiste à créer des cavités enterrées à l'intérieur d'un substrat planaire. Dans le deuxième chapitre, nous proposons des améliorations concernant cette technique SIW, celles-ci concernent non seulement les topologies des résonateurs mais aussi les possibilités de couplages entre les résonateurs. Enfin, dans le troisième chapitre, nous présentons une nouvelle topologie de filtre basée sur une recombinaison entre éléments planaires et cavités intégrées. La synthèse de ce résonateur est aussi décrite dans cette partie. Les avantages de cette nouvelle topologie sont une conception aisée ainsi que des bonnes performances électriques.

Use of geosynthetics for reinforcing soil beds supporting shallow foundations has gained tremendous popularity in recent times. In this thesis, to study and understand the behaviour of geosynthetics reinforced soil foundations, model load tests are carried out on square footings resting on sand beds reinforced with geosynthetics. The effects of various parameters like type and tensile strength of geosynthetic material, depth of reinforced zone, spacing of reinforcement layers, width of reinforcement and form of reinforcement on the performance of square footings on reinforced sand beds are studied. Results from these tests are analyzed to understand the effect of various parameters in improving the bearing capacity and reducing the settlement of footings. An equation is developed to estimate the ultimate bearing capacity of square footings resting on geosynthetic reinforced sand beds by multiple regression analysis of the experimental data. The model loading tests on reinforced soil foundations are simulated in the numerical model using the computer program FLAC3D (Fast Lagrangian Analysis of Continua in 3D). Finally parametric studies on a full scale reinforced soil foundation are conducted. From the experimental, analytical and numerical investigations carried out in this thesis, some important conclusions are drawn regarding the effective depth of reinforced zone, optimum spacing and quantity of reinforcement layers. Relative efficiency of various forms of reinforcement is discussed. Validity of the regression and numerical models developed is verified through experimental data from present study and also for data from other researchers.

Phase Shifters are one of the most important building cells of the applications in microwave and millimeter-wave range, especially for communications and radar applications / to steer the main beam for electronic scanning. This thesis includes all of the stages starting from the theoretical design stage to the measurements of the phase shifters. In detail, all-pass network phase shifter configuration is used to achieve broadband and ultra wide-band differential phase characteristics. For these reasons, 1 to 2 GHz, 2 to 4 GHz, and 3 to 6 GHz 4-bit, 22.5&deg / phase resolution phase shifter realization with surface micromachined lumped components are designed, simulated, fabricated and measured. Basic building blocks of the phase shifters, i.e., surface micromachined lumped components, square planar spiral inductors and Metal-Insulator-Metal capacitors are designed with EM simulation and lumped equivalent model extractions. The validation of the designed square planar spiral inductors is done with fabrication and measurement steps, very low error, below 1%, between the designs and fabricated samples are observed. Using this knowledge on lumped elements finally phase shifters are designed with surface micromachined lumped components, fabricated using an in house technology provided by METU-MEMS facilities, RF MEMS group. Low phase rms error, good return and insertion loss considerations are aimed, and achieved. In addition to the main work of this thesis, a generalized theoretical calculation method for 2n-1 number of stages all-pass network phase shifters is presented for the first time in literature. A different, new, broadband, and combined phase shifter topology using two-stage all-pass filters is presented. Moreover, the implementation of this idea is proved to be practical to 3 to 6 GHz 5.625&deg / and 11.25&deg / combined phase shifter. A new approach for stage numbers other than power of 2 is indicated, which is different from what is already presented in the literature. An example practical implementation results are provided for the three-stage 4-bit 1 to 6 GHz phase shifter. Also, a small improvement in SRF of the high inductance valued inductors is achieved with the mitering of the corners of square planar spiral inductors. Comparison of the measured data between the normal inductors and mitered versions shows that the first SRF of the inductors are increased about 80 MHz, and second SRF of the inductors are increased about 200 MHz.

This dissertation presents a contribution to quantitative microwave imaging for breast tumor detection. The study made in the frame of a joint supervision Ph.D. thesis between University Paris-SUD 11 (France) and Mälardalen University (Sweden), has been conducted through two experimental microwave imaging setups, the existing 2.45 GHz planar camera (France) and the multi-frequency flexible robotic system, (Sweden), under development. In this context a 2D scalar flexible numerical tool based on a Newton-Kantorovich (NK) scheme, has been developed. Quantitative microwave imaging is a three dimensional vectorial nonlinear inverse scattering problem, where the complex permittivity of an object is reconstructed from the measured scattered field, produced by the object. The NK scheme is used in order to deal with the nonlinearity and the ill-posed nature of this problem. A TM polarization and a two dimensional medium configuration have been considered in order to avoid its vectorial aspect. The solution is found iteratively by minimizing the square norm of the error with respect to the scattered field data. Consequently, the convergence of such iterative process requires, at least two conditions. First, an efficient calibration of the experimental system has to be associated to the minimization of model errors. Second, the mean square difference of the scattered field introduced by the presence of the tumor has to be large enough, according to the sensitivity of the imaging system. The existing planar camera associated to a flexible 2D scalar NK code, are considered as an experimental platform for quantitative breast imaging. A preliminary numerical study shows that the multi-view planar system is quite efficient for realistic breast tumor phantoms, according to its characteristics (frequency, planar geometry and water as a coupling medium), as long as realistic noisy data are considered. Furthermore, a multi-incidence planar system, more appropriate in term of antenna-array arrangement, is proposed and its concept is numerically validated. On the other hand, an experimental work which includes a new fluid-mixture for the realization of a narrow band cylindrical breast phantom, a deep investigation in the calibration process and model error minimization, is presented. This conducts to the first quantitative reconstruction of a realistic breast phantom by using multi-view data from the planar camera. Next, both the qualitative and quantitative reconstruction of 3D inclusions into the cylindrical breast phantom, by using data from all the retina, are shown and discussed. Finally, the extended work towards the flexible robotic system is presented. / A dissertation prepared through an international convention for a joint supervision thesis with Université Paris-SUD 11, France / Microwaves in biomedicine

In this paper, a method for determining ground plane features in a sequence of images captured by a mobile camera is presented. The hardware of the mobile system consists of a monocular camera that is mounted on an inertial measurement unit (IMU). An image processing procedure is proposed, first to extract image features and match them across consecutive image frames, and second to detect the ground plane features using a two-step algorithm. In the first step, the planar homography of the ground plane is constructed using an IMU-camera motion estimation approach. The obtained homography constraints are used to detect the most likely ground features in the sequence of images. To reject the remaining outliers, as the second step, a new plane normal vector computation approach is proposed. To obtain the normal vector of the ground plane, only three pairs of corresponding features are used for a general camera transformation. The normal-based computation approach generalizes the existing methods that are developed for specific camera transformations. Experimental results on real data validate the reliability of the proposed method. / <p>QC 20121107</p>

The studies in this dissertation mainly utilize planar antennas for ultra-wideband antenna designs not only on the investigation of antenna performance but also towards exploiting attractive features of ultra-wideband antennas for practical applications, such as WMAN access-point antennas, omnidirectional WiMAX access-point antennas, band-notched UWB (Ultra-wideband, 3.1 ~ 10.6 GHz) antennas, and so on. To begin with, the effects of the ground-plane size and the asymmetrical ground plane on ultra-wideband antennas are studied in Chapter 2. Following up, from the conclusive results, an antenna for WMAN operation in access-point applications and an omnidirectional monopole for USB wireless network card device are proposed and analyzed. Characteristics of ultra-wideband antenna radiation in relation to the antenna's width for obtaining omnidirectional radiation are addressed. In Chapter 3, several ultra-wideband access-point antennas are presented for achieving good omnidirectional radiation in the azimuthal plane across the bandwidth. Furthermore, in Chapter 4, band-notching techniques are applied to ultra-wideband antennas for avoiding the interference between the UWB and the WLAN systems.

This thesis reports the development of Vanadium Tungsten Oxide (VWO) film as an active detector material for uncooled infrared detectors by using the reactive DC magnetron co-sputtering method. VWO is a doped form of the Vanadium Oxide (VOx) which is known as a prominent material for uncooled infrared detectors with its high TCR, low resistivity, and low noise properties. VOx is a widely preferred material for commercialized uncooled infrared detectors along with its drawbacks. Fabrication is fairly difficult due to its unstable material properties and the need for low process temperatures for a monolithic, CMOS compatible surface micromachining process. Hence, a new material with high performance and easier fabrication is needed. This thesis is the first study at METU on the development of high-performance VWO as an active detector material for uncooled infrared detectors. Deposition studies of VWO primarily started by measuring the effects of deposition parameters upon the magnetron sputtering system. Because the high effectiveness of the tungsten doping has been obtained for the doping level below 10% according to literary information, maximum vanadium (V) deposition rate together with minimum tungsten (W) deposition rate has been initially aimed. TCR of the VWO films has been measured between -2.48 %/K and -3.31 %/K, and the variation of noise corner frequency from 0.6 kHz to 8 kHz has been observed. In addition to these results of VWO, a favorable VOx recipe which has the highest performance done at METU in terms of resistance, TCR, noise and uniformity has also attained during the studies. Structural characterization of VWO is achieved using XPS, XRD, and AFM characterization techniques. Other than the sputtering parameters, post-annealing process and oxygen plasma exposure was examined as well. A general observation of the post-annealing is that it decreases not merely the TCR but also the noise of the deposited film. A short-period oxygen plasma exposure has a constructive effect on the noise behavior. Fabricated vanadium tungsten oxide with sandwich type resistor structure shows very close but better bolometric properties when compared with the yttrium barium copper oxide (YBCO), which is another material being studied in scope of other theses at METU. XPS, XRD and AFM characterization methods have been used for the structural characterization of vanadium-tungsten-oxide.