[pt] Este trabalho faz parte do desenvolvimento do núcleo de estudos de redes de computadores que utilizam canais de rádio PRNET ( Packet Radio Networks). Aborda-se a especificação e implementação do três primeiros níveis dos protocolos de comunicação segundo o padrão OSI/ISO: e a especificação e implementação de um serviço de execução remota de programas que visa utilizar a capacidade computacional da rede que está distribuída entre vários sistemas independentes de capacidade individual reduzida, usando as estações ociosas para a execução remota dos programas. / [en] The aim of this work is to develop a research nucleus as a support for studying packet radio networks. The scope of this work is the specification and implementation of the first three levels of the ISO reference model and the specification and implementation of a remote program execution service, that uses all the network’s computational resources, distributed among several independent systems with a limited capability of execution, taking advantage of idle stations, to execute programs.

[pt] Programas de computador já vem sendo utilizados há muito tempo no projeto de circuitos integrados, principalmente para verificação e simulação. Os anos 80 viram surgir os compiladores de silício, novas ferramentas para a geração automática de estruturas e leiautes. O sistema apresentado nesse trabalho permite a geração automática do leiaute de uma via de dados (conjunto de registradores e ALUs) a partir de uma descrição de seu tamanho e componentes. É também apresentado um gerador de leiautes gate matrix com facilidades para posicionamento de terminais, utilizando para a criação das células da biblioteca do gerador de vias. São discutidos também os problemas envolvidos nas diversas etapas de geração, assim como as soluções encontradas. / [en] Computer programs have been used for a long time in the design of integrated circuits, specially for verification and simulation. In the 80s silicon compilers appeared, a newkind of tool used for circuit synthesis and layout generation. The system here presented permits the automatic generation of the layout of a datapath (a collection of registers and ALUs) from a specification containing the number of bits and functions desired. A gate matrix layout generator with facilities for placing terminals is also presented, as a tool for creating the necessary cells for the datapath library. The several problems involved on layout generation are discussed, as well as the solutions employed.

Submitted by Pedro Barros (pedro.silvabarros@ufpe.br) on 2018-09-28T20:54:12Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Gilberto Fernandes Silva de Abreu.pdf: 5096470 bytes, checksum: d6a92a0826077650bed9728eb062b33c (MD5) / Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-11-20T20:47:10Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Gilberto Fernandes Silva de Abreu.pdf: 5096470 bytes, checksum: d6a92a0826077650bed9728eb062b33c (MD5) / Made available in DSpace on 2018-11-20T20:47:11Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) TESE Gilberto Fernandes Silva de Abreu.pdf: 5096470 bytes, checksum: d6a92a0826077650bed9728eb062b33c (MD5) Previous issue date: 2017-03-03 / Introdução: As derivações biliodigestivas, usualmente praticadas nesses casos, nem sempre produzem resultados satisfatórios, por isso o reparo da lesão da via biliar extra-hepática utilizando a membrana de biopolímero de cana-de-açúcar (BPCA) se apresenta como uma alternativa de tratamento promissora e de baixo custo. Métodos: Trata-se de um estudo prospectivo, randomizado, do tipo experimental analítico, realizado com 02 grupos de trabalho alocados de forma aleatória. A amostra foi composta por 20 suínos (Sus domesticus), machos e fêmeas, adultos jovens, com 3 a 6 meses de idade e peso médio variando entre 66,73 e 98,56kg. No BPCAM E1 (n=5) e BPCAM E2 (n=5), foi produzido um defeito crítico no colédoco de 10mm, com retirada das bordas da incisão, seguida de implantação ajustada de fragmento medindo 10x20mm de BPCA. No grupo controle (n=10) foram produzidas duas secções transversais no colédoco, distando 10mm entre si, que foram anastomosadas em sequência. Os animais foram reoperados e avaliados em tempos distintos, 150 (BPCAM E1), 225 (Controle) e 330 (BPCAM E2) dias, sendo submetidos a exames laboratoriais, radiológicos, ultrassonográficos e análises histológicas do segmento biliar tratado. Resultados: Não houve diferença estatística nas variáveis GGT (U/L), BT (mg/dL) TGP (U/L), INR e Cr, entre os grupos Controle x BPCAM (E1 e E2). Na análise histológica do grupo BPCAM E2 houve aumento da intensidade da inflamação, reação granulomatosa, fibrose e número de vasos, sem produzir alterações das enzimas canaliculares e dilatação das vias biliares à ultrassonografia. O tecido fibroso resultante da anastomose colédoco-colédoco complicada produziu considerável frequência de estreitamento ductal e obstrução ao fluxo biliar. Conclusão: O BPCA, quando utilizado na forma de membrana para reparação tecidual da via biliar principal, produziu processo cicatricial completo e continuidade do fluxo biliar. / Introduction: As bilio-digestive bypass surgery, usually carried out to resolve these cases, does not always produce satisfactory results, the repair of extrahepatic bile duct lesions using sugarcane biopolymer membrane has arisen as a promising low-cost alternative treatment. Methods: A prospective randomized analytical experimental study was conducted on two working groups. The sample consisted of 20 male and female pigs (Sus domesticus) from the Suidae family of the Piau breed, young adults with three to six months of age and body weight between 66.73 and 98.56kg. In the group BPCAM E1 (n=5) e BPCAM E2 (n=5), a 10mm critical defect was produced in the bile duct with removal of the edges of the incision, followed by the precision implantation of a 10x20mm fragment of sugarcane biopolymer membrane (BPCAM). In the control group (n=10), two sections of the common bile duct were made 10mm apart and then anastomosed. The animals in each group were re-operated and evaluated after 150 (BPCAM E1), 225 (Control) and 330 (BPCAM E2) days, the treated biliary segment undergoing laboratory, radiological and ultrasound tests and histological analysis. Results: No statistical difference was found in the variables GGT (U/L), BT (mg/dL), TGP (U/L), INR and Cr between the Control and BPCAM (E1 and E2) groups. The histological analysis of the BPCAM E2 group showed an increase in intensity of inflammation, granulomatous reaction, fibrosis and number of vessels, without producing changes in hepatic enzymes and bile duct dilation under ultrasound. Conclusion: When used as a membrane for main bile duct tissue repair, BPCA was a biocompatible material that produced a complete healing process and continuity of bile flow.

Thesis advisor: Eileen Sweeney / Motion is the central phenomenon that Aristotle's physics endeavors to explain, and the whole superstructure of his natural philosophy is bound to it. This was certainly understood by Thomas Aquinas, who produced a most careful and thorough account of the Aristotelian theory of motion. What is rarely recognized is that in so doing he developed and improved that theory in a number of respects. This dissertation is a study of the theory of physical motion in Aquinas. It has two principal results. The first regards the concept of motion itself. Aquinas accepts Aristotle's definition of motion, but gives his own explanation of it, one which employs non-Aristotelian ideas like participation, and places motion in a more general and cohesive system of relations between non-being and being. The second regards what is called natural motion, i.e., that which inanimate matter exhibits of its own accord. How Aquinas explains this has rarely been understood and has frequently been misunderstood. I provide a thorough, systematic treatment that sets forth the principles underlying Aquinas's theory of natural motion, explains in what sense such motion is said to be caused, and notes – what commentators are prone to overlook – the critical role played by analogy as an aid to grasp the causality of natural motion. Chapter 1 briefly introduces Aquinas as a medieval "physicist", i.e., natural philosopher, specifies the scope of the dissertation, and lays out the path to be followed in the succeeding chapters. Chapter 2 summarizes what Aristotle says about motion in his Physics. His definition of motion is presented, and the terms in which it is given are analyzed. As the definition is famously perplexing, and its meaning a matter of debate, the opinions of a number of modern commentators are reviewed. After having explained the primacy that Aristotle assigns to locomotion and the connection he establishes between motion and time, the chapter concludes with a section on the causes of motion. This covers Aristotle's arguments for the eternity of motion, his denial of pure self-motion, introduces his views on animal, natural, and violent motion, and concludes with the first mover and first motion reached at the end of the Physics. Chapter 3 is a short introduction to the tradition of Aristotelian commentary. It contains brief reviews of some of what Simplicius, John Philoponus, Averroes, and Avicenna say about the Aristotelian theory of motion, with especial attention given to those aspects of it with which they disagree or which they find troublesome. The next three chapters are devoted to Aquinas. Chapter 4 covers how Aquinas interprets Aristotle's definition of motion and how he integrates it into his own metaphysics. The chapter begins with two preparatory notes. First, it introduces Aquinas as a commentator, and stresses the importance of having the context of the commentary tradition in mind when reading Aquinas, because he belongs to it and approached Aristotle in much the same way as earlier commentators. This has the consequence that his own developments are somewhat concealed, since what he says in his commentary on the Physics is presented as straightforward exposition, without any suggestion of originality. Second, modern readers are cautioned not to import modern senses of "motion" unwittingly into Aquinas, as this leads to confusion. The point is made that his Latin usage is regular and well-defined. After this, Aquinas's interpretation of the definition of motion is presented and what he means by calling it "imperfect act" is explained. This involves a sophisticated theory of the order of act to act, and incorporates the Neoplatonic language of participation and perfection. The next section of the chapter presents some of the analyses that Aquinas makes of motion, including its mental character and categorization. It is noteworthy, yet in fact quite unnoticed, that Aquinas provides a subtle and inventive solution to a modern debate over the proper interpretation of the definition of motion (the so-called "process" vs. "non-process" debate) which reconciles the two sides. Finally, I present a visual analogy as an aid for grasping how motion fits into a larger Thomistic metaphysical scheme concerning the relationship between non-being and being. Chapter 5 treats Aquinas's account of natural motion. It begins by noting some of the problems involved with Aristotle's explanation of natural motion, including, critically, that of the cause of such motion. It then highlights the work of James Weisheipl, who rejected a motor coniunctus interpretation of natural motion and offered in its stead his own, one which has since become well-known. But a careful examination of what Aquinas says shows that Weisheipl's interpretation of him is incorrect, and must also be rejected. The chapter then lays out (1) the principles of motion and their schematic organization; (2) Aquinas's theory of efficient causality and how we are to understand his denial of the possibility of action at a distance; (3) his use of analogies to indicate how we are to understand the efficient cause of natural motion; and then finally (4) shows, first, how the multiplicity and variation of the analogies lead commentators to misread Aquinas, and, then, how they illuminate other aspects of his theory of motion. Chapter 6 treats, in turn, the much debated principle that "everything that is moved is moved by another", and then the arguments that Aquinas gives for the existence of an unmoved mover, which he takes to be God. With regard to the first, it is pointed out that the theory of inertia is not nearly so fatal to the principle as many historians of science assume. Indeed, understood in light of what was said about Aquinas's understanding of the efficient causality involved in natural motion in the preceding chapter, it is compatible with inertia. However, a review of the three arguments Aquinas takes from Aristotle purporting to prove the principle are all found to be subject to serious objections. Greatest attention is given to the argument drawn from the claim that a thing cannot simultaneously be in act and in potency in the same respect. With regard to the second, it is shown that what Aquinas has to say about the unmoved mover is perplexed and inconsistent. Aquinas accepts two series of arguments from Aristotle, one from the Physics that concludes to a first moving cause, another from the Metaphysics that concludes to a final cause. From the former, Aquinas constructs his own argument from motion, most famously presented as the prima via, but at times he attempts to combine the two Aristotelian series. It is shown that these attempts at harmonization involve Aquinas in inconsistencies. What the prima via revision concludes to is also discussed. An important observation is that the prima via is manifestly intended by Aquinas to be an argument from physical motion. Yet numerous commentators, perceiving its weakness, attempt to recast it in a non-physical form, such that "motion" no longer signifies what Aquinas intends. The chapter ends with some cautious remarks on the state of these highly controversial topics. Chapter 7 concludes the dissertation, first, with a brief recapitulation of some of its major points, and then with some speculation as to what use its results may have for future scholarship. / Thesis (PhD) — Boston College, 2023. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Philosophy.

In this paper, processing effects of electroplating and post- plating annealing on via extrusion are investigated. The study is based on two TSV structures with identical geometry but different processing conditions. Via extrusion, stress and material behaviors of the TSV structures were first compared. Electron backscatter diffraction (EBSD) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) were used to characterize the microstructure of TSVs and the additives incorporated during electroplating. Based on the results, processing effects on via extrusion and its mechanism are discussed, including grain growth, local plasticity, and diffusional creep.

Malgré l'augmentation constante de l'efficacité des cellules photovoltaïques multi-jonctions destinées au photovoltaïque concentré, des pertes de performances subsistent à haute concentration solaire. Elles sont principalement causées par un ombrage excessif dû aux métallisations ou par effet Joule à cause de la résistance série. Une des solutions à ce problème est de reporter le contact métallique en face avant sur la face arrière grâce à des vias métallisés et isolés électriquement. Avec cette architecture, les pertes dues à l'effet Joule et à l'ombrage seront limitées et des gains en efficacité sont attendus. Toutefois, l'intégration de vias sur des cellules photovoltaïques triple jonction favorise la recombinaison électron-trou en surface et peut provoquer une perte de performances de ces dispositifs. Ce mémoire présente les travaux de recherche effectués visant à étudier précisément cette problématique ainsi qu'à proposer des solutions pour limiter ces pertes. L'objectif est d'évaluer les pertes de performances de cellules photovoltaïques triple jonction suite à l'intégration de vias. Dans un second temps, l'objectif secondaire vise à limiter les pertes grâce à des traitements de passivation. Les résultats et solutions qu'apporte ce projet représentent une étape clé dans la réalisation de cette nouvelle architecture de contact électrique pour cellules photovoltaïques. En effet, les conclusions de ce projet de recherche permettent de valider la possibilité d'obtenir des gains en efficacité grâce à cette architecture. De plus, les procédés de microfabrication présentés dans ce projet de recherche proposent des solutions afin d'intégrer des vias sur ces hétérostructures tout en limitant les pertes en performances.

L’amélioration des microsystèmes grâce à leur intégration en 3 dimensions (3D) est liée au développement des interconnexions verticales, appelées through silicion via (TSV). Afin d’obtenir une densité d’intégration maximum et les meilleures performances électriques possibles, ces interconnexions sont d’un diamètre le plus petit possible (facteur de forme élevé) et idéalement remplies de cuivre. Dans ces conditions, la fabrication de TSV représente un défi. L’une des étapes les plus critiques est l’isolation électrique du TSV de cuivre qui doit être réalisée sans endommager les microdispositifs déjà présent sur le substrat. Cette étape est traditionnellement accomplie par le dépôt de dioxyde de silicium (SiO2), compliqué à mettre en œuvre et coûteux pour des TSV de cuivre à facteur de forme élevés. Le procédé d’électrogreffage d’un film isolant de poly-4-vinylpirydine (P4VP) a été proposé comme alternative au SiO2. Ce procédé a déjà été prouvé pour isoler des TSV usinés dans du silicium ne contenant aucun dispositif, mais reste a être démontré dans les conditions d’intégration 3D. Cette thèse a pour but de démontrer la compatibilité du procédé d’isolation par électrogreffage de P4VP de TSV de cuivre à facteur de forme élevé, dans les conditions d’intégration 3D et d’en déduire l’impact sur la fiabilité des microdispositifs à leur proximité. Cette thèse rapporte la fabrication des premiers TSV de cuivre à facteur de forme élevé, isolés par P4VP, dans les conditions d’intégration 3D d’un microsystème. Nous avons observé la vulnérabilité des microdispositifs aux attaques successives des solutions traditionnellement utilisées pour préparer le substrat de silicium à l’électrogreffage. Cependant, en remplaçant les solutions les plus agressives par des techniques plus douces, la fabrication des TSV isolés par P4VP a été démontrée. L’influence de la préparation de surface du silicium sur l’épaisseur du film greffé a ensuite été étudiée. L’analyse comparative des voltammogrammes révèle que la présence d’un oxyde créé chimiquement permet d’obtenir des films de P4VP plus épais que lorsque le substrat est désoxydé. Le rôle des états de surface générés par la présence de l’oxyde a été investigué par l’analyse de courbes Mott-Schottky. Ces expériences ont mis en évidence l’influence des états de surface sur la création d’une zone d’inversion dans le silicium, favorisant l’accumulation d’électrons nécessaire à l’électro-initiation du procédé d’électrogreffage. Enfin, la thèse rapporte la première mesure des contraintes résiduelles associées à la conception de TSV isolés par P4VP. Ces mesures révèlent que l’utilisation de l’isolant électrogreffé, comparativement au SiO2, permet de réduire considérablement les contraintes dans le silicium à proximité des TSV. Ainsi, l’utilisation du polymère de P4VP devrait permettre d’augmenter la densité d’intégration d’un microsystème tout en assurant sa fiabilité.

As neoplasias mieloproliferativas (NMP) são doenças hematológicas caracterizadas pela proliferação aumentada e acúmulo de células mieloides maduras de uma ou mais séries hematopoéticas: granulocítica, eritrocítica, megacariocítica ou mastocítica. Os pacientes com NMP podem apresentar mutações como a JAK2V617F, MPL e CALR, cujas descrições foram fundamentais para o início da elucidação da fisiopatologia das NMP. As células neoplásicas das NMP apresentam resistência à apoptose e proliferação celular exacerbada. Sabe-se ainda que essas doenças são consideradas oncoinflamatórias e pré-leucêmicas. Apesar de todos esses conhecimentos sobre os mecanismos moleculares e celulares envolvidos na patogênese das NMP, não há até a presente data tratamentos eficazes que curam ou alteram a história natural de progressão dessas desordens para LMA. Pelo exposto, foi aqui investigada a potencial participação dos membros da via de sinalização Hippo na fisiopatologia das NMP BCR-ABL1 negativas mais frequentes, a policitemia vera (PV), trombocitemia essencial (TE) e mielofibrose primária (MF). A via de sinalização Hippo foi descrita como supressora de tumor e é uma das responsáveis pela regulação da proliferação, diferenciação e morte celular. Foi analisada, ainda nesse estudo, a correlação dos níveis de expressão dos genes da via Hippo com o perfil de citocinas plasmáticas dos pacientes com PV, TE e MF, a associação com o \"status mutacional\" e com a expressão dos genes que regulam a apoptose celular pela via intrínseca. Os principais achados nos pacientes com PV foram a diminuição da expressão dos genes supressores de tumor LATS2, MST1 e MST2 acompanhada pela presença de elevada concentração de citocinas pró-inflamatórias e fenótipo de resistência a apoptose. Na TE, os dados relevantes foram a detecção da diminuição da expressão dos genes supressores de tumor LATS1, LATS2 MST1 e SAV1, e o observação da relação entre alta expressão dos genes SAV1 e MOB1B e a mutação da CALR. Em MF destaca-se a redução da expressão dos genes SAV1 e TAZ da via de sinalização Hippo e do gene AURKB do ciclo celular. Em conclusão, os dados indicam que a diminuição da expressão dos genes supressores de tumor da via Hippo contribui para a fisiopatologia e para o fenótipo de resistência das células neoplásicas à apoptose das NMP. / Myeloproliferative neoplasms (MPN) are hematological disorders characterized by increased proliferation of mature myeloids cells of one or more hematopoietic series: granulocytic, erythrocytic, megakaryocytic or mastocytic. Patients with MPN may present mutations such as JAK2V617F, MPL and CALR, which were essential descriptions for the beginning of pathophysiological elucidation of MPN. The NMP neoplastic cells show resistance to apoptosis and exacerbated cell proliferation. It is known that these entities are considered also oncoinflamatory and pre-leukaemic. Despite all this knowledge about the molecular and cellular mechanisms involved in the pathogenesis of MPN, there are no effective treatments that cure or alter the natural history of progression of these disorders to AML. For the above, a participatory potential of the Hippo signaling pathway members in the pathophysiology of the most frequent negative BCR-ABL1 MPN, the polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) were investigated. The Hippo signaling pathway has been described as tumor suppressor and is responsible for the regulation of proliferation, differentiation and cell death. The correlation analysis of the expression levels of the Hippo pathway genes with the plasma cytokine profile of patients with PV, ET and PMF, the association with the mutational status and the expression of the genes that regulate intrinsic cellular apoptosis were performed. The main findings in patients with PV were decreased expression of the tumor suppressor genes LATS2, MST1 and MST2 accompanied by the presence of high concentration of proinflammatory cytokines and phenotype of resistance to apoptosis. In ET, relevant data were the detection of decreased expression of the tumor suppressor genes LATS1, LATS2 MST1 and SAV1, and the observation of the relationship between high expression of the SAV1 and MOB1B genes and the mutation of the CALR. In PMF, stands out the reduction of the SAV1 and TAZ gene expression of the Hippo signaling pathway and the AURKB gene of the cell cycle. In conclusion, the data indicate that decreased expression of the tumor suppressor genes of the Hippo pathway contributes to the pathophysiology and neoplastic cell resistance phenotype to the apoptosis of MPN.

A presente tese procura expor as linhas gerais do projeto estético de Hölderlin, tal como ele procurou realizá-lo entre 1793 e 1797. Anunciado em diversas cartas como uma tentativa de encontrar o princípio esclarecedor das oposições do espírito, tais como natureza e liberdade, sujeito e objeto, eu e não-eu, esse projeto estético toma por base a relação entre filosofia e poesia tal como a estabeleceu Kant na Crítica da Faculdade de Julgar, em especial na seção em que trata das ideias estéticas, da imaginação produtiva e do gênio, bem como aquela estabelecedia por Schiller em Sobre graça e dignidade, na medida em que este último procura fundar uma estética objetiva a partir dos esforços iniciados por Kant nesse mesmo sentido. Mas é principalmente ao entrar em contato com a filosofia da Doutrina-da-ciência, de Fichte, que Hölderlin vislumbra todo o potencial dessa relação entre filosofia e poesia. Em sua obra, afinal, Fichte atribui à imaginação criadora um papel ainda mais importante do que Kant, na medida em que, para aquele, a imaginação constitui a origem das separações encontradas no eu. O fato, porém, de que Hölderlin não realiza sua anunciada estética na forma teórica não impede de vê-la executada poeticamente em seu romance de formação Hipérion ou o eremita na Grécia. Assim como o filósofo da Doutrina-da-ciência reduz as oposições encontradas no eu à imaginação por meio do método da determinação recíproca, também Hipérion, na medida em que realiza a passagem da natureza para o âmbito da liberdade e da poesia, é capaz de unificar as oposições próprias da via excêntrica. / This thesis is intended to render an outline of the aesthetic project Hölderlin sought to carry out between 1793 and 1797. His aesthetic project, which in a number of letters he addressed as an attempt to find the principle enlightening such oppositions of spirit as nature and freedom, subject and object, self and not-self, is based upon the philosophy-poetry relationship as established by Kant in the Kritik der Urteilskraft, especially in the section dealing with aesthetic ideas, productive imagination, and genius, as well as the one Schiller establishes in Über Anmut und Würde to the extent he succeeds in founding an objective Aesthetics upon Kant\'s efforts to this effect. However, it was not before he got in touch with Fichte´s Wissenschaftslehre philosophy that Hölderlin realizes the entire potential of this philosophy-poetry relationship. After all, throughout his work Fichte assigns creative imagination a more important role than Kant does, as imagination, for the former, is the origin of the separations residing in the self. Hölderlin\'s failure to perform his announced Aesthetics in the form of theory, however, did not prevent him from accomplishing it poetically in his novel Hyperion or the Hermit in Greece. Just as the philosopher of the Wissenschaftslehre reduces unto imagination the oppositions in the self using the reciprocal determination method, Hyperion is also capable of unifying the oppositions pertaining to the eccentric path as it leads from nature into the realm of freedom and poetry.

Este trabalho apresenta o estudo do sistema ';pi';/4-DQPSK recentemente escolhido como o esquema de modulacao digital para a segunda geracao do distema de comunicacao movel celular. As propriedades que motivaram sua escolha, a definicao dos sistemas de transmissao e recepcao e as caracteristicas de desempenho em canal tipico de comunicacao movel sao aqui estudadas. E feita uma analise dos fenomenos que ocorrem no canal de radio movel e dos modelos capazes de simular tais fenomenos. Apresenta-se o desenvolvimento de um conjunto de programas de computacao que apontam a simulacao do sistema em questao. Baseados nos resultados de diversas simulacoes verifica-se a validade do modelo de dois percursos para o canal seletivo em frequencia. Verificamos tambem como os diferentes perfis de potencia de multipercurso podem afetar o desempenho global do sistema.