Teses e Dissertações defendidas fora da UFPA

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/7305

Teses e Dissertações defendidas fora do âmbito da Universidade Federal do Pará cujos autores(as) sejam servidores(as) técnicos administrativos ou docentes da UFPA

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Agora exibindo 1 - 6 de 6

Acesso aberto (Open Access)
Correlação entre condições de solidificação, microestrutura a resistência mecânica
(Universidade Estadual de Campinas, 1999-02-02) QUARESMA, José Maria do Vale; GARCIA, Amauri; http://lattes.cnpq.br/1721691084829002
Correlation among solidification conditions, microstructure and mechanical behavior / The imposition of a wide range of operational conditions in foudry and static casting generates, as a direct consequence, a diversity of solidification structures. Structural parameters such as grain size and interdendrictic spacings are highly influenced by the thermal behavior of the metal/mold system. during solidification, consequently imposing a close correlation between the described system and the resulting microstructure. The mechanical properties of an alIoy in its crude state of solidification depend on the microstructural arrangement defined in the solidification process. Under the circumstances, the mechanical behavior of the alIoy, represented by stresses and/or strains, wilI be defined by grain size, interdendritic spacings, casual porosities, segregated products and other phases. Expressions correlating the mechanical behavior with microstructural parameters are very useful in order to search for a type of previous planning of the solidification conditions in terms of a determined leveI of mechanical resistance which is intended to be attained, e.g. to settle a way of programming the microstructure and the mechanical properties as well. Particularly, the literature in this field presents relations between the yield strength of the material and the grain size, such as the renowned HalI-Petch's equation. The present work advances in that direction, in search of relations among mechanical behavior in the plastic field, secondary dendritic spacings and solidification conditions. In order to analyze an important variable of solidification in molds with good heat diffusivity, like the metal/mold heat transfer coefficient, alloys of the Sn-Pb system - with compositions Sn- 5%Pb, Sn- 10%Pb, Sn- 20%Pb, Sn- 38,1%Pb (eutectic) - besides the element tin, were chosen. The choice was made because such alloys are easily handled in laboratory and chiefly because their thermophysical properties are well known. Particularly the influences of the following operational conditions on hi were investigated: mold thickness, liquid metal superheating and magnitude of the solidification range. Experimental results related to the distribution of temperatures in metal and mold during solidification, as compared with the results of simulation with a numerical model, made it possible to attain of expressions, for each case, by relating hi in terms of time. Heat transfer from the external surface of the mold to the environment was also analyzed; in the same manner, expressions were developed correlating the mold/environment heat transfer coefficient hAmb in terms of time as well. To correlate parameters of dendritic structures and mechanical properties, the following alloys of the Al-Cu system were chosen: Al- 4,5%Cu; Al- 15%Cu. The same aforementioned analysis referring to hi and hAmb was extended to those alloys including the one of eutectic composition (Al- 33%Cu) and pure aluminum. Based upon results of standardized solidification tests, secondary dendritic spacing ( EDS ) and upon mathematical models of heat transfer and dendritic growth, expressions were developed correlating the ultimate tensile strength (σu) and specific elongation (δ) as a function of variables of the metallmold system. Thus it was a way towards the programming of the dendritic structure and the leveI of resistance as a function of preestablished operational conditions in the solidification process.
Acesso aberto (Open Access)
Estudo experimental do secador pneumático vertical
(Universidade Estadual de Campinas, 1986-02-17) FARIA, Lênio José Guerreiro de; SANTANA, Cesar Costapinto; http://lattes.cnpq.br/8458559657676452
This work is related with studies on the performance of a vertical pneumatic dryer on a well instrumented pilot plant. Experiences were rea1ized with sand particles with a mean diameter of 0.46mm and 0.55mm and glass spheres with a mean diameter of 0.24mm, in a drying tube with 4m high and an inside diameter of 5.25cm, aiming the determination of the air humidity, temperature and pressure profiles along the dryer, also entrance and exit moisture contents of solids can be obtained. Psychrometers were designed to measure the air humidity above 1000e and they are used to determine the humidity and temperature profiles. It is presented a1so a dryer simulation study that utilizes a unidimensional model, where the basic of the momentum, energy and mass conservation equations for particulated systems are integrated, and a comparison between the simulated and experimental results is done.
Acesso aberto (Open Access)
Modelagem chuva-vazão em bacias hidrograficas com suporte em redes neurais artificiais
(Universidade Estadual de Campinas, 1999-12-06) BARP, Ana Rosa Baganha; BARBOSA, Paulo Sérgio Franco; http://lattes.cnpq.br/9653654803297649
This work describes the use of two hydrological simulation deterministic models to represent the rainfuJI-runnoff processo The Itapetiniga, Almas and Guarapiranga rivers basin, located in the State of São Paulo and the Guaporé river basin located in the State of Mato Grasso, are taken as a case study. Both deterministic models used parameters optimization, with a nonlinear and unconstrained structure: (a) SMAP - Soil Moisture Accounting Procedure, which uses a first order optimization procedure; (b) Artificial Neural Network (ARN) model, which uses a second order optimzation procedure. Both models assume a montly interval to account rainfall and river flow. Some tests include a mix structure between SMAP and ARN, aiming at an evaluation of ARN potential to replace physical parameters and typical processes of conceptual rainfall-runnoff models.
Acesso aberto (Open Access)
Processos de relaxação em sistemas longe do equilíbrio termodinâmico
(Universidade Estadual de Campinas, 1985-08-16) MACHADO, Carlos José Freire; VASCONCELLOS, Aurea Rosas; http://lattes.cnpq.br/0475932786473160
Acesso aberto (Open Access)
Síntese e atividade biológica de neolignanas 8.0.4' derivados e compostos correlatos
(Universidade Estadual de Campinas, 1991-07-03) SANTOS, Lourivaldo da Silva; BARATA, Lauro Euclides Soares; http://lattes.cnpq.br/1609747051706094
We have synthesized ca. 80 different aromatic compounds (8.0.4' -neolignans several derivatives and correlated compounds containing or 5 at C-8). These substances were submitted to bioassays namely PAF antagonists anti-leishmaniasis antibacteria, anti-schistossomose and anti-fungi. From the Virola surinmensin leaves we have isolated a 8.0.4' -neolignan, (+) -surinamensin whose absolute configuration was determinated as (+)-7S, 8S-surinamensin. Using crown ethers associated with metalic hydrides we have performed studies on the reduction stereoselectivity aiming a high diastereoselectivity of the β-ketoether reductions. We have also developed the first synthetic pathway Ieading to the enantiomerically pure 8.0.4' -neolignans using (+) - and (-) -Dimethyl tartrate as the chiral auxiliary groups which was sucessfulIy applied to the synthesis of (+) -virolin. Also we obtained chiral β -ketosulfides using the same route described earlier in an enantiosselectice pathway. Finnally, using safrol and eugenol abundant Brazilian raw material, we developed an alternative synthetic rout to the neolignans having bromohydrin as intermediate.
Acesso aberto (Open Access)
Transformada seno discreta com rotação de eixos bidimensional (DSTr -2D): aplicações na codificação e interpolação de imagens para redução de efeito de blocos
(Universidade Estadual de Campinas, 1998-10-29) PELAES, Evaldo Gonçalves; IANO, Yuzo; http://lattes.cnpq.br/1819902045004845
This work presents a new tool for image coding and image interpolation based on the two-dimensional discrete sine transform with axis rotation (DSTr-2D). The main characteristics of this transform are the few blocking effects found in the reconstructed image and its computational simplicity. In this work, the DSTr-2D is applied to image interpolation and its performance is compared with results obtained from DCT. A method of interpolation using DCT without extrapolation is also presented. The DSTr-2D achieves a performance better than the other interpolation methods used for comparison purposes. Indeed the better performance is obtained when the sample rate is increased. The DSTr-2D is also applied to the image coding, and it was verified that its advantage relative to DCT in terms of blocking effects in the reconstructed image. The results obtained in image coding using DSTr-2D are compared with results obtained from DCT and LOT. The images were coded using scalar, gaussian, laplacian and Lloid-Max quantization Finally, the DSTr-2D is applied to performs the image coding and the image interpolation, simultaneously.

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