Η άθροιση μεγάλων αριθμών είναι μια χρονοβόρα και ενεργοβόρα διαδικασία. Πολλές μέθοδοι έχουν αναπτυχθεί για να μειωθεί η καθυστέρηση υπολογισμού του αθροίσματος λόγω της μετάδοσης κρατουμένου. Τέτοιες είναι η πρόβλεψη κρατουμένου (carry look ahead) και η επιλογή κρατουμένου (carry select). Αυτές οι αρχιτεκτονικές δεν είναι επαρκώς επεκτάσιμες για μεγάλους αριθμούς (με πολλά bits) ή πολλούς αριθμούς, διότι παράγονται μεγάλα και ενεργοβόρα κυκλώματα. Στην παρούσα εργασία μελετάται η μέθοδος υπολοίπου (RNS), η οποία χρησιμοποιεί συστήματα αριθμών μεγαλύτερα από το δυαδικό. Ορίζεται μια βάση τριών αριθμών και οι αριθμοί αναπαρίστανται στα εκάστοτε τρία συστήματα της βάσης. Η άθροιση γίνεται παράλληλα σε κάθε σύστημα και τέλος οι αριθμοί μετατρέπονται πάλι στο δυαδικό. Τα πλεονεκτήματα αυτής της προσέγγισης είναι η παραλληλία και η απουσία μεγάλων κυκλωμάτων διάδοσης κρατουμένου. Το μειονέκτημα είναι ότι χρειάζονται κυκλώματα μετατροπής από και προς το δυαδικό σύστημα. Αυτού του είδους οι αθροιστές συγκρίνονται για κατανάλωση ενέργειας με τους γνωστούς carry look ahead και carry select. Διαπιστώθηκε ότι οι RNS αθροιστές καταναλώνουν λιγότερη ενέργεια. / The addition of many-bits numbers is a time and power consuming task. Many methods are developed to reduce the sum calculation delay due to carry propagation. Such techniques are Carry Look Ahead and Carry Select, Those techniques are not scalable to many bits numbers or a set of many numbers: the circuits needed are big and power consuming. In this thesis, the the RNS technique is investigated. This technique uses radix bigger than binary. A 3-numbers base is defined and the numbers that participate in the sum are represented uniquely in each element radix. The addition is performed in parallel in each radix. Finally the result is transformed back to the binary numbers system. The advantages of this technique are the parallelization of the process and the lack of carry propagation circuits. The disadvantage is that transformation circuits are need from/to binary system. The RNS adders are compared to CLA and CS for power. Such adders are compared to CLA and CS for power consumption. It is found that RNS adders consume less energy.

[pt] Este trabalho apresenta uma análise detalhada de uma recente proposta de combinação da transmissão em blocos com portadora única e a técnica CDMA, referida como CS-CDMA (Chip Spread CDMA). Uma característica marcante desta técnica de transmissão é que diferentemente do que ocorre nos sistemas DS-CDMA, a ortogonalidade entre os códigos dos diferentes usuários é mantida mesmo quando a transmissão é feita através de um canal multipercurso seletivo em frequência, suposto invariante no tempo, permitindo assim que os usuários possam ser identicamente desacoplados na recepção. Além desta vantagem, resultados de desempenho indicaram uma significativa superioridade deste sistema sobre o tradicional DS-CDMA. Entretanto comparações existentes, consideraram apenas o up-link, do sistema e adotaram algumas premissas, que incluem, a utilização de códigos ortogonais pelos diversos usuários e a suposição de canais de transmissão invariantes no tempo. O presente trabalho apresenta uma análise detalhada da técnica (CS-CDMA e uma análise comparativa dos sistemas em condições menos favoráveis. Os sistemas operam em ambientes invariante e variante no tempo, com códigos ortogonais e não ortogonais e em dois cenários diferentes, down- link e up-link. Os resultados consideram recepção com equalização no domínio da frequência utilizando equalizadores do tipo ZF (Zero Forcing) e MMSE (Minimum Mean Squared Error). Simulações foram realizadas no intuito de se avaliar o desempenho dos dois sistemas considerados. Curvas de probabilidade de erro foram obtidas e ilustram e comparam tais desempenhos em diferentes situações e cenários de interesse. / [en] This dissertation proposes detailed analysis of a recent combined mechanism for transmission in blocks with a single carrier and CDMA technique known as Chip Spread CDMA (CS-CDMA). An important feature of this transmission technique is that unlike what happens in Direct Sequence (DS-CDMA) systems, the orthogonality between codes of different users is maintained even when the transmission, considered time-invariant, is made through a selective multipath channel frequency, which ideally allows users to be uncoupled in reception. However, existing comparisons only consider the up-link transmission and adopt certain assumptions, which include orthogonal codes for different users and time invariant channels. This technique have shown a significant superiority as compared with the traditional DS-CDMA. A comparison of (CS-CDMA systems in more realistic conditions are presented in this work. Various environments were tested in the presence of BPSK modulation systems, as well as invariant and time-varying transmission. Comparison between scenarios down-link and up-link are also presented. The results consider equalized reception in the frequency domain using the ZF (Zero Forcing) equalizers and MMSE (Minimum Mean Squared Error). Simulations were carried out in order to evaluate the performance of the two systems considered. Error probability curves were obtained to illustrate and compare the performances in different situations and scenarios.

[pt] A estimação de direção de chegada (DoA) é uma importante área de processamento de arranjos de sensores que é encontrada em uma ampla gama de aplicações de engenharia. Este fato, juntamente com o desenvolvimento da área de Compressed Sensing (CS) nos últimos anos, são a principal motivação desta dissertação. Nesta dissertação, é apresentada uma formulação do problema de estimação de direção de chegada como um problema de representação esparsa da sinal e vários algoritmos de recuperação esparsa são derivados e investigados para resolver o problema atual. Os algoritmos propostos são baseados na incorporação da informação prévia sobre o sinal esparso no processo de estimativa. Na primeira parte, nos concentramos no desenvolvimento de dois algoritmos Bayesianos , que se baseiam principalmente no algoritmo iterative hard thresholding (IHT). Devido ao desempenho inferior dos algoritmos convencionais de estimação de chegada em cenários com fontes correlacionadas, nós prestamos atenção especial ao desempenho dos algoritmos propostos nesta condição. Na segunda parte, o problema de otimização baseados na minimização da norma l1 é apresentado e um algoritmo bayesiano é proposto para resolver o problema chamado basis pursuit denoising (BPDN). Os resultados da simulação mostram que os estimadores Bayesianos superam os estimadores não Bayesianos e que a incorporação do conhecimento prévio da distribuição do sinal melhorou substancialmente o desempenho dos algoritmos. / [en] Direction of arrival (DoA) estimation is a key area of sensor array processing which is encountered in a broad range of important engineering applications. This fact together with the development of the Compressed Sensing (CS) area in the last years are the principal motivation of this thesis. In this dissertation, a formulation of the source localization problem as a sparse signal representation problem is presented and several sparse recovery algorithms are derived and investigated for solving the current problem. The proposed algorithms are based on the incorporation of the prior information about the sparse signal in the estimation process. In the first part, we focus on the development of two Bayesian greedy algorithms which are principally based on the iterative hard thresholding (IHT) algorithm. Due to the inferior performance of the conventional DoA estimation algorithm in scenarios with correlated sources, we pay special attention to the performance of the proposed algorithms under this condition. In the second part, the optimization problem using a l1 penalty is introduced and a Bayesian algorithm for solving the basis pursuit denoising problem is presented. Simulation results shows that Bayesian estimators which take into account the prior knowledge of the signal distribution outperform and improve substantially the performance of the non-Bayesian estimators.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-04-14T16:10:05Z No. of bitstreams: 1 Dissertação - Aline Soares Freire - FINAL.pdf: 4503064 bytes, checksum: 1e469a75225eda50cf3c49c6ab32c87a (MD5) / Made available in DSpace on 2016-04-14T16:10:05Z (GMT). No. of bitstreams: 1 Dissertação - Aline Soares Freire - FINAL.pdf: 4503064 bytes, checksum: 1e469a75225eda50cf3c49c6ab32c87a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ / A análise de amostras hipersalinas ainda é um problema analítico a ser resolvido, tendo em vista que a presença de sais dissolvidos é fonte freqüente de interferências em espectrometria atômica. Atualmente, tem ocorrido um grande aumento da demanda para caracterização de águas de alta salinidade, como as águas produzidas, pelo fato de estas serem um dos maiores descartes da indústria de petróleo. Devido a isto, metodologias analíticas para sua caracterização têm sido amplamente desenvolvidas para a determinação de metais-traço em amostras salinas e dentre as técnicas analíticas destaca-se a Espectrometria de Absorção Atômica de Alta Resolução com Fonte Contínua, uma renovação da AAS convencional. Contudo, para a obtenção de resultados acurados, é imprescindível que se faça a remoção dos sais presentes nessas matrizes hipersalinas. Essa separação prévia pode ser realizada através do emprego de resinas qualantes, que pré-concentram o analito e permitem a remoção da matriz. Sendo assim, este trabalho visa à avaliação do uso da resina quelante comercial Chelex-100® na préconcentração de Co, Cu, Mn, Ni e Pb e posterior determinação destes por Espectrometria de Absorção Atômica de Alta Resolução com Fonte Contínua e Forno de Grafite (HR-CS GF AAS). A metodologia foi validada através do uso dos materiais de referência certificados para água do mar CASS-4, CASS-5 e NASS-5. Os limites de detecção obtidos, em μg L-1, foram de 0,006; 0,070; 0,024; 0,074; e 0,018 para Co, Cu, Mn, Ni e Pb, respectivamente. Amostras de água produzida oriundas de plataformas de petróleo offshore foram analisadas e os resultados mostraram que essas águas possuem baixas concentrações dos elementos determinados ou os mesmos não foram detectados. Os valores encontrados são muito inferiores aos limites preconizados pela legislação brasileira através da Resolução CONAMA 357/05 / The analysis of hypersaline samples is still an analytical problem to be solved, once the presence of dissolved salts is a frequent source of interferences in atomic spectrometry. Actually, there is a large increase in the interest in the caracterization of this kind of sample, as produced waters are one of the largest discharges of petroleum industry. Hence, analytical methodologies to produced water caracterization have been widely developed to trace metals determination in saline samples and among the analytical techniques, there is High Resolution Continuum Source Atomic Absorption Spectrometry, a renovation of conventional AAS. However, to obtain accurated results, it's necessary to remove the salts present in this high salinity matrices. This previous separation can be done employing a chelating resin, that preconcentrates the analyte(s) and allows matrix removal. In this way, the aim this work is to evaluate the use of chelating resin Chelex-100® to preconcentrate Co, Cu, Mn, Ni and Pb, for the later determination by High Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (HR-CS GF AAS). The methodology was validated by the use of sewater certified reference materials CASS-4, CASS-5 e NASS-5. The detection limits in μg L-1, were 0,006; 0,070; 0,024; 0,074; and 0,018 for Co, Cu, Mn, Ni and Pb, respectively. Produced water samples from offshore petroleum platforms were analysed and results showed that this waters have low concentrations of these studied elements or could not be detected. Found values are much lower when compared to limits from Brazilian legislation, in this case CONAMA 357/05 Resolution

La technique d’acquisition comprimée ou compressed sensing (CS) exploite la compressibilité de différents types d’images pour reconstruire des données sous-échantillonnées sans perte d’informations. Cette technique peut être appliquée à l’IRM pour réduire les temps d’acquisition. CS est basée sur trois composantes majeures : (1) la représentation parcimonieuse du signal dans un domaine de transformation, (2) des mesures incohérentes et (3) une méthode de reconstruction non-linéaire avec une contrainte de parcimonie. Dans la première résultats partie de cette thèse, nous proposons un nouveau modèle de sous-échantillonnage basé sur la théorie de l’agrégation limitée par la diffusion (DLA) et montrons qu’il est plus performant que la méthode de sous-échantillonnage aléatoire. Le modèle de sous-échantillonnage DLA a été utilisé pour implémenter la technique de CS pour l’imagerie haute résolution pondérée T2 et T1 sur un champ magnétique très intense (17.2T). Pour chacune des pondérations, le temps d’acquisition a été réduit de 50% tout en conservant la qualité des images en termes de résolution spatiale, rapport contraste sur bruit et quantification de l’intensité du signal. Les deux nouvelles séquences d’impulsions CS (csRARE et csFLASH) ont été implémentées sur le logiciel commercial ParaVision 5.1. La seconde résultats partie de la thèse est centrée sur l’étude de la dépendance en temps de la diffusivité dans le ganglion abdominal de l’Aplysia Californica. Le ganglion abdominal de l’aplysie a été choisi pour cette étude d’imagerie car l’IRM à haute résolution permet la description anatomique fine du réseau cellulaire (taille des neurones individuels et orientation des axones). Utiliser les tissus neuronaux de l’aplysie pour étudier la relation entre la structure cellulaire et le signal d’IRM de diffusion peut permettre de comprendre cette relation pour des organismes plus complexes. Le signal d’IRM de diffusion (IRMd) a été mesuré à différents temps de diffusion dans le ganglion abdominal et des simulations de la diffusion de l’eau dans des géométries obtenues à partir de la segmentation d’images haute résolution pondérées T2 et l’incorporation d’informations sur la structure cellulaire trouvées dans la littérature ont été réalisées. Pour comparer le signal d’IRMd dans des neurones composés d’une seule cellule avec le signal des simulations numériques, des cellules de grande taille ont été segmentées à partir d’images anatomiques pondérées T2. A l’intérieur des cellules, un noyau à forme irrégulière a été généré manuellement (environ 25-30% en fraction volumique). Les petites cellules ont été modélisées comme des petites sphères avec un petit noyau sphérique concentrique (environ 25% en fraction volumique). Le nerf a été modélisé en combinant des axones (cylindres) de différents diamètres en cohérence avec la littérature. Le signal numérique d’IRMd a été simulé en résolvant l’équation de Bloch-Torrey pour les domaines géométriques décris ci-dessus. En fittant le signal expérimental avec le signal simulé pour différents types de cellules comme les grandes cellules neuronales (diamètre entre 150 et 420 µm), des agrégats de petites cellules neuronales ayant la forme d’un sac (jusqu’à 400 cellule chez l’aplysie adulte dans chaque sac avec une taille cellulaire entre 40 et 100 µm de diamètre), des nerfs (groupes d’axones de forme cylindrique avec un diamètre de moins de 1 à 25 µm) pour une grande gamme de temps de diffusions, nous avons obtenu des estimations du coefficient de diffusion intrinsèque dans le noyau et le cytoplasme (pour les neurones) et le coefficient de diffusion intrinsèque dans les axones (pour les nerfs). Nous avons aussi évalué la pertinence d’utiliser une formule préexistante décrivant la dépendance en temps du coefficient de diffusion pour estimer la taille des cellules. / Compressed sensing (CS) exploits the compressibility of different types of images to reconstruct undersampled data without loss of information. The technique can be applied to MRI to reduce the acquisition times. The CS is based on three major components: (1) sparsity representation of the signal in some transform domain, (2) incoherent measurements, and (3) sparsity-constrained nonlinear reconstruction method. If the total number of points in the image is larger than four times the number of sparse coefficients, then the reconstruction of under sampled data is feasible. In the first results part of this thesis, we propose a new under sampling model based on the diffusion limited aggregation (DLA) theory and show that it performs better than the random variable under sampling method. The DLA under sampling model was used to implement the CS for T2-weighted and T1-weighted high resolution imaging at the ultra-high magnetic field (17.2T). In both cases, the acquisition time was reduced by 50% while maintaining the quality of the images in terms of spatial resolution, contrast to noise ratio, and signal intensity quantification. Both new CS pulse sequences (csRARE and csFLASH) were implemented in ParaVision 5.1 commercial software. The second results part of the thesis is focused on the study of the time-dependent diffusivity in the abdominal ganglion of Aplysia California. The Aplysia abdominal ganglion was chosen in this imaging study because high resolution MR imaging allows the fine anatomical description of the cellular network (size of individual neurons and orientation of axons). Using the Aplysia ganglia to study the relationship between the cellular structure and the diffusion MRI signal can shed light on this relationship for more complex organisms. We measured the dMRI signal at several diffusion times in the abdominal ganglion and performed simulations of water diffusion in geometries obtained after segmenting high resolution T2-weighted images and incorporating known information about the cellular structure from the literature. To match the dMRI signal in the single cell neurons with numerical simulations signal, the large cell outline was segmented from the anatomical T2 weighted image. Inside this cell shape, an irregularly shaped nucleus was manually generated (around 25-30% volume fraction). The small cells were modeled as small spheres with a smaller concentric spherical nucleus (around 25% volume fraction). The nerve was modeled by combining axons (cylinders) of different diameters consistent with the literature. The numerical dMRI signal can be simulated by solving Bloch-Torrey equation under the geometries domain described above. By fitting the experimental signal to the simulated signal for several types of cells such as: large cell neurons (diameter between 150 µm and 420 µm); cluster of small neuron cells gathered in the shape of a bag (up to 400 cells in adult Aplysia in each bag with cell size between 40 µm to 100 µm in diameter); and nerves (group of axons cylindrical shape diameter from less than 1 µm to 25 µm) at a wide range of diffusion times, we obtained estimates of the intrinsic diffusion coefficient in the nucleus and the cytoplasm (for cell neurons) and the intrinsic diffusion coefficient in the axons (for the nerves). We also evaluated the reliability of using an existing formula for the time-dependent diffusion coefficient to estimate cell size.

The aim of this master’s thesis was to analyze the contemporary electronic throttles and the requirements imposed on them. Then to build the mathematical model, identify parameters of the given electronic throttle, proceed the verification and on its basis to build the simulation model. There were selected suitable control and high power components to control the electronic throttle. Due to the knowledge of these parameters the simulation model was extended. For this extended simulation model was designed the position cascade controller with speed and current control loop. Using the designed controller the implementation of the electronic throttle control and the available high power and control module was realized.

[pt] As cadeias de suprimento (CS) estão sendo cada vez mais pressionadas a implementar iniciativas para tornar o seu desempenho mais sustentável. Como exemplo, pode-se citar os desafios impostos pela transição energética para o setor de óleo e gás e suas CS. Orientar a CS em direção a sustentabilidade requer um esforço coordenado, integrado e colaborativo entre os múltiplos parceiros. Um fator crucial para evoluir a trajetória de sustentabilidade das CS é a aprendizagem que ocorre durante a implementação das iniciativas de sustentabilidade colaborativas. Entretanto, não há evidências suficientes na literatura sobre como e em que níveis o processo de aprendizagem ocorre, assim como, sobre suas características e forma de interação entre os parceiros. O objetivo da tese é aprofundar o entendimento sobre as características da dinâmica de aprendizagem e sua influência na trajetória de sustentabilidade nas CS. A tese utiliza os métodos de revisão sistemática da literatura e estudo de caso múltiplo. Como resultados principais, apresenta uma tipologia e framework teórico integrado sobre aprendizagem de sustentabilidade em CS e propõe uma abordagem baseada em processo para investigação empírica do fenômeno. A pesquisa foi conduzida em três grandes multinacionais internacionais e em suas CS atuantes no Brasil. Os resultados mostram que a trajetória de sustentabilidade da CS é cumulativa, recorrente e não-linear, resultante de sucessivas oportunidades de aprendizado emergentes das iniciativas de sustentabilidade colaborativas na CS. Valendo-se do raciocínio abdutivo, a tese fornece um primeiro passo na elaboração de teoria de sobre aprendizagem de sustentabilidade da CS e cunha o conceito de plasticidade da CS. / [en] Supply chains (CS) are pressured to implement initiatives to make their performance more sustainable. For example, the challenges imposed by the energy transition for the oil and gas sector and its SC stand out. Guide SC towards sustainability requires a coordinated, integrated, and collaborative effort between multiple partners. A crucial factor in evolving the sustainability trajectory of SC is the learning that takes place during the implementation of collaborative sustainability initiatives. However, there is not enough evidence in the literature about how and at what levels the learning process occurs, as well as about its characteristics and form of interaction between partners. The objective of the thesis is to deepen the understanding of the characteristics of the learning dynamics and their influence on the sustainability trajectory in the SC. The thesis uses the methods of systematic literature review and multiple case studies. As the main results, it presents a typology and integrated theoretical framework on SC sustainability learning and proposes a process-based approach for empirical investigation of the phenomenon. The research was conducted in three large international multinationals and in their SC operating in Brazil. The results show that SC s sustainability trajectory is cumulative, recurrent, and non-linear, resulting from successive learning opportunities emerging from collaborative sustainability initiatives at SC. Adopting abductive reasoning, the thesis provides a first step in the elaboration of a theory of learning about SC sustainability and coined the concept of SC plasticity.

No description available.

Issues of control and causation are central to the Quantum Theory of Computation. Yet there is no place for them in fundamental laws of Physics when expressed in the prevailing conception, i.e., in terms of initial conditions and laws of motion. This thesis aims at arguing that Constructor Theory, recently proposed by David Deutsch to generalise the quantum theory of computation, is a candidate to provide a theory of control and causation within Physics. To this end, I shall present a physical theory of information that is formulated solely in constructor-theoretic terms, i.e., in terms of which transformations of physical systems are possible and which are impossible. This theory solves the circularity at the foundations of existing information theory; it provides a unifying relation between classical and quantum information, revealing the single property underlying the most distinctive phenomena associated with the latter: the unpredictability of the outcomes of some deterministic processes, the lack of distinguishability of some states, the irreducible perturbation caused by measurement and the existence of locally inaccessible information in composite systems (entanglement). This thesis also aims to investigate the restrictions that quantum theory imposes on copying-like tasks. To this end, I will propose a unifying, picture-independent formulation of the no-cloning theorem. I will also discuss a protocol to accomplish the closely related task of transferring perfectly a quantum state along a spin chain, in the presence of systematic errors. Furthermore, I will address the problem of whether self-replication (as it occurs in living organisms) is compatible with Quantum Mechanics. Some physicists, notably Wigner, have argued that this logic is in fact forbidden by Quantum Mechanics, thus claiming that the latter is not a universal theory. I shall prove that those claims are invalid and that the logic of self-replication is, of course, compatible with Quantum Mechanics.

Grid computing systems are suffering from reliability and scalability problems caused by their reliance on centralised middleware. In this thesis, we argue that peer to peer middleware could help alleviate these problems. We show that peer to peer techniques can be used to provide reliable storage systems, which can be used as the basis for peer to peer grid middleware. We examine and develop new methods of providing reliable peer to peer storage, giving a new algorithm for this purpose, and assessing its performance through a combination of analysis and simulation. We then give an architecture for a peer to peer grid information system based on this work. Performance evaluation of this information system shows that it improves scalability when compared to the original centralised system, and that it withstands the failure of participant nodes without a significant reduction in quality of service. New contributions include dynamic replication, a new method for maintaining reliable storage in a Distributed Hash Table, which we show allows for the creation of more reliable, higher performance systems with lower bandwidth usage than current techniques. A new analysis of the reliability of distributed storage systems is also presented, which shows for the first time that replica placement has a significant effect on reliability. A simulation of the performance of distributed storage systems provides for the first time a quantitative performance comparison between different placement patterns. Finally, we show how these reliable storage techniques can be applied to grid computing systems, giving a new architecture for a peer to peer grid information service for the SAM-Grid system. We present a thorough performance evaluation of a prototype implementation of this architecture. Many of these contributions have been published at peer reviewed conferences.