Hoje em dia com o crescente aumento da exploração de petróleo e gás em águas profundas, há um aumento na demanda por operações offshore envolvendo a cooperação entre unidades flutuantes. Tais operações requerem um alto nível de planejamento e coordenação, o que na maioria dos casos é feito com a troca de informação no nível de operação, com cada unidade flutuante comandada independentemente. Exemplos de operações deste tipo vão desde operações de alívio passando por operações de instalação de equipamento submarino, até operações de pesquisa envolvendo múltiplas unidades flutuantes dotadas de sistema de posicionamento dinâmico (DP). As vantagens do controle cooperativo surgem com a redução do erro da distância relativa durante a manutenção do posicionamento ou durante a execução de manobras de posicionamento conjuntas. No presente trabalho, os conceitos de controle de consenso são aplicados de forma combinada com o sistema DP de cada navio. A influência dos ganhos do controlador cooperativo no sistema como um todo será discutida, utilizando-se técnicas de análise da resposta em frequência. Simulações completas no domínio do tempo e experimentos usando modelos em escala serão utilizados para se demonstrar o funcionamento do controle cooperativo. Todas as simulações serão conduzidas no simulador Dynasim e os ensaios experimentais no tanque de provas da Engenharia Naval da Escola Politécnica da Universidade de São Paulo. Além disso, serão feitas comparações entre os experimentos em tanque de provas e simulações numéricas equivalentes, demonstrando-se a validade dos ensaios numéricos. Será também demonstrado que os requisitos de projetos adotados são atendidos pelos ensaios em tanque de provas. . / With the increasing of deep water oil & gas exploration, there is also an increase in the demand by offshore operations involving muti-vessels. Such operations require a high level of planning and coordination, which in most of the cases is made by information exchange at the operation level, being each vessel commanded independently. Examples of such operations are offloading, subsea equipment installation and subsea research operation; all of them involving multiples dynamically positioned (DP) vessels. The advantage of the cooperative control arises with the reduction of the relative positioning error during station keeping or transient maneuvers. In this work, the consensus control concepts are applied combined with the DP System of each ship. The cooperative DP controller will be investigated with the analysis of the coupled dynamics of the vessels. The influence of the cooperative control gains on the whole system will be discussed, using the frequency response of the open loop system. Fully nonlinear time-domain simulations and experimental results will be used to demonstrate the operation of the cooperative control. Besides that, comparisons between the small-scale experiments and equivalent numerical simulations will be carried out, validating the experimental results. It will also be demonstrated that the adopted design requirements are met. All tests will be carried out using the Dynasim numerical simulator and the small-scale experiments will be carried on the academic towing tank in the Naval Architecture and Ocean Engineering Department, Polytechnic School of University de São Paulo.

Orientadores: Aloisio Ernesto Assan, Persio Leister de Almeida Barros / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-11T01:26:45Z (GMT). No. of bitstreams: 1 BobadillaGuadalupe_Ulises_D.pdf: 1151597 bytes, checksum: 005fbfba6e1ebd787b740be4f94cbf34 (MD5) Previous issue date: 2008 / Resumo: As características que determinam o comportamento de uma estrutura sob carregamento dinâmico são as massas dos vários elementos, a rigidez dos seus membros e a dissipação de energia. Para avaliar corretamente a resposta dinâmica de uma estrutura levando em conta os efeitos da interação, é necessário incorporar as propriedades dinâmicas do solo dentro da formulação matemática do modelo físico adotado. Referido à superestrutura, os efeitos da interação alteram a resposta estrutural final, devido à inter-relação dinâmica entre o movimento do solo e o movimento da base de fundação. Conseqüentemente, se primeiro se avalia o movimento da base de fundação [produto da interação solo-estrutura (SSI)], a resposta estrutural final poderá ser resolvida depois via análise modal da superestrutura. Esta conceituação é utilizada no presente trabalho. Aqui, todo o processo de análise é feito no domínio da freqüência. A resposta estrutural é avaliada através da chamada Transformada Implícita de Fourier (ImFT), implementando-se para isto um algoritmo computacional que avalia a resposta dinâmica utilizando a ImFT eficientemente. A ImFT é uma avaliação racional das matrizes envolvendo as transformadas discretas de Fourier (DFT), para num mesmo processo matricial achar a resposta dinâmica estrutural diretamente no domínio do tempo. Correntemente, para a análise no domínio da freqüência tem-se utilizado a FFT (Fast Fourier Transform); embora a FFT seja computacionalmente eficiente, apresenta-se aqui a ImFT, um outro processo computacional alternativo à FFT e bastante eficiente para certos tipos de carregamento tais como uma excitação sísmica, que é o carregamento utilizado nesta pesquisa / Abstract: The characteristics that determine the behavior of a structure under dynamic loading are the masses of various elements, the rigidity of its members and the dissipation of energy. To properly evaluate the dynamic response of a structure taking into account the effects of the interaction, it is necessary to incorporate the dynamic properties of the soil within the mathematical formulation of the physical model adopted. Referred to the superstructure, the effects of interaction modify the final structural response due to the dynamic interrelationship between the soil motion and the base of foundation motions. Consequently, if that first assesses the base of foundation motions [product of the soil-structure interaction effects (SSI)], the final structural response can be assessed later by modal analysis of the superstructure. This concept is used in this work. Here, the whole process of analysis is done in frequency domain. The structural response is evaluated by the so-called Implicit Fourier Transform (ImFT), implementing to this a computational algorithm that assesses the structural dynamic response using the ImFT efficiently. The ImFT is a rational assessment of matrices involving the Discrete Fourier Transform (DFT) for a same matrix process find structural dynamics response directly on time domain. Commonly, for the analysis in the frequency domain has been used the FFT (Fast Fourier Transform), although the FFT is efficiently, presents itself here the ImFT, another alternative computational algorithm and quite competent to certain types of loading such as a seismic excitation which is the loading used in this study / Doutorado / Estruturas / Doutor em Engenharia Civil

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2016-08-10T19:31:03Z No. of bitstreams: 2 Dissertação - Weder Cabral Mendes - 2016.pdf: 1214460 bytes, checksum: 14588573f8f81fe4836a9945adacf37d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-15T13:25:32Z (GMT) No. of bitstreams: 2 Dissertação - Weder Cabral Mendes - 2016.pdf: 1214460 bytes, checksum: 14588573f8f81fe4836a9945adacf37d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-08-15T13:25:32Z (GMT). No. of bitstreams: 2 Dissertação - Weder Cabral Mendes - 2016.pdf: 1214460 bytes, checksum: 14588573f8f81fe4836a9945adacf37d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Gait recognition via computer vision attracted increasing interest for its noninvasive characteristic and mainly for your advantage of recognizing people at distance. Recognition is performing extracting features included in gait, this features are extracted from images sequence of people walking. The main challenges of gait recognition is to extract characteristics with unique information for each person, in additional, the use of accessories and clothes difficult the feature extraction process. This paper proposes a gait recognition method using information of people’s contours transformed in domain frequence by Discrete Fourier Transform. A lot of data are generated from the contours, thereby, three different techniques for dimensionality reduction CDA (Class Discrimination Ability), PCA (Principal Component Analysis) and PLS (Partial Least Squares) are employed to reduce the dimensionality of data and generate characteristics that are relevant to the recongnition system. Two classifiers, KNN (K-Nearest Neighbor) and LDA (Linear Discriminant Analysis) classify the characteristics that are returned by the dimensionality reduction methods. The accuracy are achieved by the combination of the dimensionality reduction methods and classifiers, the highest accuracy was 92:67%, which was achieved with the combination between the LDA and PCA (LDAPCA). Therefore, the results show that the information contained in the contours of silhouette are discriminant to recognize people by their gait. / O reconhecimento de pessoas através da marcha humana via visão computacional tem ganhado destaque por ser uma técnica biométrica não invasiva e principalmente por sua vantagem de reconhecer pessoas à distância. O reconhecimento é realizando extraindo características contidas na marcha de cada pessoa, essas características são extraídas de sequências de imagens da pessoa caminhando. Os principais desafios dessa técnica biométrica está em extrair as características com informações que consigam diferenciar uma pessoa da outra, além disso, o uso de acessórios e vestimentas dificultam o processo de extração de características. Este trabalho propõe um método de reconhecimento baseado na marcha humana utilizando informações dos contornos das pessoas transformados para o domínio da frequência por meio da Transformada Discreta de Fourier. Como são geradas muitos dados a partir dos contornos, três técnicas diferentes de redução de dimensionalidade CDA (Class Discrimination Ability), PCA (Principal Component Analysis) e PLS (Partial Least Squares) são empregadas para reduzir a quantidade de dados e gerar características que sejam relevantes para o sistema de reconhecimento. Dois classificadores, KNN (K-Nearest Neighbor) e LDA (Linear Discriminant Analysis) classificam as características retornadas pelos métodos de redução de dimensionalidade. As taxas de acurácia são obtidas pelos resultados gerados entre a combinação dos métodos de redução de dimensionalidade e os classificadores, a maior taxa de acurácia foi de 92;67%, a qual foi alcançada com a combinação entre o LDA e PCA (LDAPCA). Dessa forma, conclui-se que as informações contidas no contorno da silhueta no domínio da frequência são discriminantes para reconhecer pessoas através da marcha.

Le contrôle de la température d'un milieu thermique reste d'une grande importance en raison du coût économique qu'il peut engendrer. Ainsi, un moyen efficace de réduire les coûts de chauffage/refroidissement est de fournir un bon système de contrôle qui limite l'énergie nécessaire pour exécuter ces tâches. À cette fin, nous étudierons le contrôle d'une interface diffusive homogène finie utilisant le contrôleur CRONE de trois générations et contrôlons leurs comportements. La nouveauté de ce travail existe dans l'utilisation d'un contrôleur de commande fractionnaire (le contrôleur CRONE) appliqué à une unité d'ordre fractionnaire et l'utilisation d'un contrôleur complexe (la troisième génération) qui n'est pas si familier dans le domaine des contrôleurs. Les résultats montrent le comportement et la robustesse des contrôleurs CRONE de trois générations. / Controlling thermal medium’s temperature remains of a great importance, because of the economic cost that it may engender. Thus, one effective way to reduce heating/cooling cost is by providing a good control system that limits power needed to run these tasks. For this purpose, we will study the control of a finite homogeneous diffusive interface using the three generations CRONE controller and control their behaviors. The novelty of this work exists in the use of a fractional order controller (the CRONE controller) applied to a fractional order plant and the use of a complex controller (the third generation) which is not so familiar in the controllers domain. The results show the behavior and the robustness of the three generations CRONE controllers.

Le tube à onde progressive (TOP) est un dispositif où un faisceau d’électrons se déplaçant sur l’axe d’une hélice interagit avec les ondes électromagnétiques propagées par cette hélice. Il est le siège de nombreuses instabilités : des oscillations (génération d’ondes hyperfréquences parasites), mais aussi des instabilités du faisceau qui ont pour conséquence une dissipation parasite due à l'interception du faisceau par l'hélice. L’objectif de cette thèse est de développer une formulation hamiltonienne au problème permettant des modèles approchés plus compacts, plus précis et plus complets. Après l'avoir exposée, nous présentons un schéma numérique contenant notre modèle discret pour la simulation du TOP. Ce modèle discret a été mis au point pour tenir compte des conditions d'adaptation et de changements de géométrie. Le couplage avec les électrons met en jeu des champs de base simples, et le modèle tient compte de la charge d'espace. Différentes méthodes d'intégration numérique sont développées, dont nous comparons l'efficacité. Nous comparons ce modèle discret avec divers modèles d'amplification des ondes à froid, dont le modèle actuellement utilisé chez Thales pour la conception des tubes ({texttt{MVTRAD}}). Nous montrons aussi que les modèles d'amplification des ondes à froid à deux ou trois dimensions comme {texttt{MVTRAD}} ou {texttt{BWIS}} (prenant en compte les ondes inverses) ne respectent pas nécessairement l'équation de Maxwell-Faraday, contrairement au nôtre. Enfin, nous comparons notre modèle discret de circuit et le modèle d'amplification des ondes à froid dans le cas d'un faisceau linéaire. / A traveling-wave tube (TWT) is a device where an electron beam traveling along the axis of a helix interacts with the electromagnetic waves propagated by this helix. It is sensitive to many instabilities : oscillators (generating noise microwave), but also beam instabilities that generate a noise dissipation due to the interception of the beam by the helix. The aim of this thesis is to find a Hamiltonian formulation of the problem to allow more compact, more accurate and more complete approximate models. Having found one, we start to develop a numerical scheme containing our discrete model for the simulation of TOP. This discrete model has been developed to take into account the tapering sections, geometry changes and adaptations. The coupling with electrons involves simple functions of space, and the model takes space charge into account. Different methods of numerical integration are developed, of which we compare the efficiency. We compared the discrete model with various cold waves amplification models, especially with the model currently used at Thales for the design of their tubes ({texttt{MVTRAD}}). Moreover, we showed that two- or three-dimensional cold wave amplification models like {texttt{MVTRAD}} or {texttt{BWIS}} (which takes into account the backward waves) fail to respect the Maxwell-Faraday equation, contrary to ours. Finally we made a comparison between our circuit discrete model and the amplification model of cold waves in the case of a linear beam.

Ultra wideband (UWB) technology plays a significant role in wireless communication. The complex antenna transfer function (CATF) of an UWB antenna provides important information required for better channel designs and communication systems. In this dissertation the CATF of a Double ridge guide horn (DRGH) antenna is determined and used as a standard antenna for UWB measurements. Two methods were used: the two antenna method in an anechoic chamber and a modified gain-transfer method in a compact antenna test range (CATR). Measurements were performed with a vector network analyser (VNA) in the frequency domain, in the anechoic chamber and the CATR. The distance measurements required to calculate the CATF from the S-parameter measurements were performed in the time domain. The CATF of the standard antenna was determined using two identical antennas and then it was shown that a modified gain-transfer method can be used to determine the CATF of any unknown antenna in a CATR, using the standard antenna as a reference. Some of the challenges were to obtain the correct equations and measurement method to obtain the CATF in a CATR. The standard antenna was used to investigate uncertainty contributions for the measurements in the CATR. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted

La stéganographie est l’art de la dissimulation de l’information secrète dans un médium donné (cover) de sorte que le médium résultant (stégo) soit quasiment identique au médium cover. De nos jours, avec la mondialisation des échanges (Internet, messagerie et commerce électronique), s’appuyant sur des médiums divers (son, image, vidéo), la stéganographie moderne a pris de l’ampleur. Dans ce manuscrit, nous avons étudié les méthodes de stéganographie LSB adaptatives, dans les domaines spatial et fréquentiel (DCT, et DWT), permettant de cacher le maximum d’information utile dans une image cover, de sorte que l’existence du message secret dans l’image stégo soit imperceptible et pratiquement indétectable. La sécurité du contenu du message, dans le cas de sa détection par un adversaire, n’est pas vraiment assurée par les méthodes proposées dans la littérature. Afin de résoudre cette question, nous avons adapté et implémenté deux méthodes (connues) de stéganographie LSB adaptatives, en ajoutant un système chaotique robuste permettant une insertion quasi-chaotique des bits du message secret. Le système chaotique proposé consiste en un générateur de séquences chaotiques robustes fournissant les clés dynamiques d’une carte Cat 2-D chaotique modifiée. La stéganalyse universelle (classification) des méthodes de stéganographie développées est étudiée. A ce sujet, nous avons utilisé l’analyse discriminante linéaire de Fisher comme classifieur des vecteurs caractéristiques de Farid, Shi et Wang. Ce choix est basé sur la large variété de vecteurs caractéristiques testés qui fournissent une information sur les propriétés de l’image avant et après l’insertion du message. Une analyse des performances des trois méthodes de stéganalyse développées, appliquées sur des images stégo produites par les deux méthodes de stéganographie LSB adaptatives proposées, est réalisée. L’évaluation des résultats de la classification est réalisée par les paramètres: sensibilité, spécificité, précision et coefficient Kappa. / Steganography is the art of the dissimulation of a secret message in a cover medium such that the resultant medium (stego) is almost identical to the cover medium. Nowadays, with the globalization of the exchanges (Internet, messaging and e-commerce), using diverse mediums (sound, embellish with images, video), modern steganography is widely expanded. In this manuscript, we studied adaptive LSB methods of stéganography in spatial domain and frequency domain (DCT, and DWT), allowing of hiding the maximum of useful information in a cover image, such that the existence of the secret message in the stégo image is imperceptible and practically undetectable. Security of the message contents, in the case of its detection by an opponent, is not really insured by the methods proposed in the literature. To solve this question, we adapted and implemented two (known) methods of adaptive stéganographie LSB, by adding a strong chaotic system allowing a quasi-chaotic insertion of the bits of the secret message. The proposed chaotic system consists of a generator of strong chaotic sequences, supplying the dynamic keys of a modified chaotic 2D Cat map. Universal steganalysis (classification) of the developed methods of stéganography, is studied. On this question, we used the linear discriminating analysis of Fisher as classifier of the characteristic vectors of Farid, Shi and Wang. This choice is based on the wide variety of tested characteristic vectors that give an information about the properties of the image before and after message insertion. An analysis of the performances of three developed methods of steganalysis, applied to the produced stego images by the proposed adaptive methods of stéganography, is realized. Performance evaluation of the classification is realized by using the parameters: sensibility, specificity, precision and coefficient Kappa.

The development of new types of offshore wind turbine on floating platforms requires the development of new approaches to modelling the combined platform-turbine system. In this thesis a linearised frequency-domain approach is developed which gives fast but approximate results: linearised models of the structural dynamics, hydrodynamics, aerodynamics and control system dynamics are brought together to find the overall response of the floating wind turbine to harmonic wind and wave loading. Initially, a nonlinear flexible multibody dynamics code is developed and verified, which is then used to provide reference nonlinear simulation results. The structural dynamics of a wind turbine on a moving platform are shown to be nonlinear, but for realistic conditions the effects are small. An approximate analysis of the second-order response of floating cylinders to hydrodynamic loads suggests slow drift motion may be relatively small for floating wind turbines, compared to other floating offshore structures. The aerodynamic loads are linearised using both harmonic and tangent linearisation approaches; the harmonic linearisation gives improved results when stall occurs. The wake dynamics can also be included. The control system behaviour is linearised using the same method, which works well when the wind speed is far from the rated wind speed; close to the rated wind speed the nonlinearity is stronger, but further improvement should be possible. These sub-models are combined to give a simple but complete model of a floating wind turbine, with flexible blades and a flexible tower, but neglecting the control system behaviour, wake dynamics and nonlinear hydrodynamic loads. For the OC3-Hywind turbine, the accuracy of the results is assessed by comparison to nonlinear time-domain simulations using the commercial code Bladed. Peak-peak errors of less than 5 % are achievable for many harmonic wind and wave inputs, but certain conditions lead to larger errors. The effect of including linearised control system behaviour is demonstrated for a subset of conditions. Overall, the results are promising but more work is needed for practical application.

Frequency-domain scheduling, multiple antenna techniques, and rate adaptation enable next generation orthogonal frequency division multiple access (OFDMA) cellular systems such as Long Term Evolution (LTE) to achieve significantly higher downlink spectral efficiencies. However, this comes at the expense of increased feedback overhead on the uplink. LTE uses a pragmatic combination of several techniques to reduce the channel state feedback required by a frequency-domain scheduler. In subband-level feedback scheme specified in LTE, the user reduces feedback by only reporting the channel quality indicator (CQI) computed over groups of resource blocks called subbands. LTE also specifies an alternate user selected subband feedback scheme, in which the feedback overhead is reduced even further by making each user feed back the indices of the best M subbands and only one CQI value averaged over all the M subbands. The coarse frequency granularity of the feedback in the above schemes leads to an occasional incorrect determination of rate by the scheduler for some resource blocks. The overall throughput of LTE depends on the method used to generate the CQI and the statistics of the channel, which depends on the multiple antenna technique used. In this thesis, we develop closed-form expressions for the throughput achieved by the user selected and subband-level CQI feedback schemes of LTE. The comprehensive analysis quantifies the joint effects of four critical components on the overall system throughput, namely, scheduler, multiple antenna mode, CQI feedback scheme, and CQI generation method. The performance of a wide range of schedulers, namely, round robin, greedy, and proportional fair schedulers and several multiple antenna diversity modes such as receive antenna diversity and open-and closed-loop transmit diversity is analyzed. The analysis clearly brings out the dependence of the overall system throughput on important parameters such as number of resource blocks per subband and the rate adaptation thresholds. The effect of the coarse subband-level frequency granularity of feedback is explicitly captured. The analysis provides an independent theoretical reference and a quick system parameter optimization tool to an LTE system designer. It also helps us theoretically understand the behavior of OFDMA feedback reduction techniques when operated under practical system constraints. Another contribution of this thesis is a new statistical model for the effective exponential SNR mapping (EESM), which is a highly non-linear mapping that is widely used in the design, analysis, and simulation of OFDMA systems. The statistical model is shown to be both accurate and analytically tractable, and plays a crucial role in facilitating the analysis of the throughput of LTE when EESM is used to generate the CQI.

Tall buildings are wind-sensitive structures and could experience high wind-induced effects. Aerodynamic boundary layer wind tunnel testing has been the most commonly used method for estimating wind effects on tall buildings. Design wind effects on tall buildings are estimated through analytical processing of the data obtained from aerodynamic wind tunnel tests. Even though it is widely agreed that the data obtained from wind tunnel testing is fairly reliable the post-test analytical procedures are still argued to have remarkable uncertainties. This research work attempted to assess the uncertainties occurring at different stages of the post-test analytical procedures in detail and suggest improved techniques for reducing the uncertainties. Results of the study showed that traditionally used simplifying approximations, particularly in the frequency domain approach, could cause significant uncertainties in estimating aerodynamic wind-induced responses. Based on identified shortcomings, a more accurate dual aerodynamic data analysis framework which works in the frequency and time domains was developed. The comprehensive analysis framework allows estimating modal, resultant and peak values of various wind-induced responses of a tall building more accurately. Estimating design wind effects on tall buildings also requires synthesizing the wind tunnel data with local climatological data of the study site. A novel copula based approach was developed for accurately synthesizing aerodynamic and climatological data up on investigating the causes of significant uncertainties in currently used synthesizing techniques. Improvement of the new approach over the existing techniques was also illustrated with a case study on a 50 story building. At last, a practical dynamic optimization approach was suggested for tuning structural properties of tall buildings towards attaining optimum performance against wind loads with less number of design iterations.