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Search Results: 1 - 10 of 605890 matches for " Elvio A. de;Oliveira "
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Crystallization Mechanism and Kinetics of BaO-Li2O-ZrO2-SiO2 Glasses
Silveira, Cristian Berto da;Campos, Sílvia Denofre de;Campos, Elvio A. de;Oliveira, Ant?nio Pedro Novaes de;
Materials Research , 2002, DOI: 10.1590/S1516-14392002000100004
Abstract: differential thermal analysis and scanning electron microscopy were used to determine the influence of the addition of bao on the crystallization mechanism of li2o-zro2-sio2 systems. as the concentration of bao in the samples increased, a transition occurred in the predominant crystallization mechanism, which passed from superficial to volumetric. to determine the maximum nucleation rate, the crystallization kinetics of the sample containing 20 mole % bao, which showed the most uniform crystallization, was studied by counting the nuclei with an image analyzer. the first nuclei appeared at the first endothermic inflection point (at the start of tg, at 440 °c), while the maximum number of nuclei was counted at the midpoint of the glass transition region (446 °c). these results are similar to those observed for other materials that crystallize in volume, and confirm scanning electron microscopy data.
Crystallization Mechanism and Kinetics of BaO-Li2O-ZrO2-SiO2 Glasses
Silveira Cristian Berto da,Campos Sílvia Denofre de,Campos Elvio A. de,Oliveira Ant?nio Pedro Novaes de
Materials Research , 2002,
Abstract: Differential thermal analysis and scanning electron microscopy were used to determine the influence of the addition of BaO on the crystallization mechanism of Li2O-ZrO2-SiO2 systems. As the concentration of BaO in the samples increased, a transition occurred in the predominant crystallization mechanism, which passed from superficial to volumetric. To determine the maximum nucleation rate, the crystallization kinetics of the sample containing 20 mole % BaO, which showed the most uniform crystallization, was studied by counting the nuclei with an image analyzer. The first nuclei appeared at the first endothermic inflection point (at the start of Tg, at 440 °C), while the maximum number of nuclei was counted at the midpoint of the glass transition region (446 °C). These results are similar to those observed for other materials that crystallize in volume, and confirm scanning electron microscopy data.
Modelos matemáticos para a secagem intermitente de arroz em casca Mathematical models for intermittent drying of rice
Volnei L. Meneghetti,Elvio Aosani,Jeferson C. da Rocha,Maurício de Oliveira
Revista Brasileira de Engenharia Agrícola e Ambiental , 2012, DOI: 10.1590/s1415-43662012001000012
Abstract: Prop s-se, com este trabalho, ajustar modelos matemáticos aos valores experimentais em fun o do teor de água e estudar os efeitos das rela es de intermitência na secagem de gr os de arroz na eficiência da opera o. Utilizaram-se gr os de arroz com casca produzidos na Regi o Sul do Rio Grande do Sul. As amostras com teor de água próximo a 20% b.u. foram secadas sob três condi es de rela o de intermitência: 1:1, 1:2 e 1:4; em todas as condi es foram utilizados os mesmos manejos térmicos em temperaturas graduais crescentes do ar: 70, 90, 110 ± 5 °C, respectivamente, na 1 a e na 2 a e a partir da 3 a hora. Para os ajustes dos modelos matemáticos foi realizada análise de regress o n o-linear pelo método Simplex e Quasi-Newton, cujos valores s o os parametros dos modelos estimados em fun o da temperatura do ar de secagem. Comparando-se os coeficientes de determina o ajustados (R2ajustado), o erro médio relativo (P) e estimado (SE) e a distribui o de resíduos, os resultados obtidos permitem concluir que: a rela o de intermitência altera o tempo de opera o e a taxa horária de secagem dos gr os de arroz e, ainda, o modelo de Midilli foi o que melhor representou a secagem intermitente do arroz em casca. This study aimed to adjust mathematical models to experimental values in function of the water content and study the effects of intermittent relations in drying of paddy grains in the efficiency of operation. Paddy grains produced in the southern region of Rio Grande do Sul were used. The samples with approximately 20% water content were dried under three intermittent relation conditions: 1:1, 1:2, 1:4. In all these conditions the same thermal procedures were utilized, gradual increase in air temperature 70, 90, 110 ± 5 oC respectively, in the 1st, 2nd and 3rd hour. For the adjustments of the mathematical models, a non linear regression analysis through the Simplex and Quasi-Newton methods was carried out. The values of the parameters of the models being estimated in function of the temperature of the drying air. A comparison was carried out of the adjusted coefficient of determination (R 2adjusted), the relative mean error (P), the estimated mean error (SE) and the distribution of residues. The results showed that the intermittent relation modifies the operating time and the houR Ly rate of drying of the rice grains and the MidiLλi model was the one which best represented the intermittent drying of paddy.
An Inexact Restoration Package for Bilevel Programming Problems  [PDF]
Elvio A. Pilotta, Germán A. Torres
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.330181
Abstract: Bilevel programming problems are a class of optimization problems with hierarchical structure where one of the con-straints is also an optimization problem. Inexact restoration methods were introduced for solving nonlinear programming problems a few years ago. They generate a sequence of, generally, infeasible iterates with intermediate iterations that consist of inexactly restored points. In this paper we present a software environment for solving bilevel program-ming problems using an inexact restoration technique without replacing the lower level problem by its KKT optimality conditions. With this strategy we maintain the minimization structure of the lower level problem and avoid spurious solutions. The environment is a user-friendly set of Fortran 90 modules which is easily and highly configurable. It is prepared to use two well-tested minimization solvers and different formulations in one of the minimization subproblems. We validate our implementation using a set of test problems from the literature, comparing different formulations and the use of the minimization solvers.
Existence of a Walrasian Equilibrium in Locally Convex Topological Vector Spaces, with Interdependent Utility Functions  [PDF]
Elvio Accinelli, Aramando García, Marisol Torres
Theoretical Economics Letters (TEL) , 2017, DOI: 10.4236/tel.2017.71005
Abstract: In this paper we extend the well known result of existence of Walrasian equilibrium given in Debreu (1952) to economies modeled over topological vector spaces. Our work is closely related to the previous results of Yannelis-Pranhakar (1983), and Tan and Yuan (1999), but unlike these papers we prove the existence of a Walrasian equilibrium in infinite dimensional economies with interdependent and price-dependent utilities.
A??o dos térmitas no solo
Ferreira, Eric Victor de Oliveira;Martins, Vanessa;Inda Junior, Alberto Vasconcellos;Giasson, Elvio;Nascimento, Paulo César do;
Ciência Rural , 2011, DOI: 10.1590/S0103-84782011005000044
Abstract: the order isoptera is well known by its potential as a plague, although the number of species that are plagues is small within the group. termites are the dominant invertebrates in tropical terrestrial environments and are spread from tropical rainforests to the savannahs, being found even in arid regions, in various habitats. these insects have a major role and are still little studied in tropical ecosystems. nutrient cycling, aeration, water infiltration of soil, bioturbation, aggregates formation and organic material decomposition, are processes influenced by the action of termites, which , directly or indirectly, affect soil and landscape formation wherever they are. we suggest that a better approach must be addressed in future researches about these insects influence in the soil under specified conditions of use and management, in sustainable food production and climate changes.
Experimental poisoning of goats by Ipomoea carnea subsp. fistulosa in Argentina: a clinic and pathological correlation with special consideration on the central nervous system
Ríos, Elvio E.;Cholich, Luciana A.;Gimeno, Eduardo J.;Guidi, María G.;Acosta de Pérez, Ofelia C.;
Pesquisa Veterinária Brasileira , 2012, DOI: 10.1590/S0100-736X2012000100007
Abstract: ipomoea carnea subsp. fistulosa, aguapei or mandiyura, is responsible for lysosomal storage in goats. the shrub contains several alkaloids, mainly swansonine which inhibits lysosomal α-mannosidase and golgi mannosidase ii. poisoning occurs by inhibition of these hydrolases. there is neuronal vacuolation, endocrine dysfunction, cardiovascular and gastrointestinal injury, and immune disorders. clinical signs and pathology of the experimental poisoning of goats by ipomoea carnea in argentina are here described. five goats received fresh leaves and stems of ipomoea. at the beginning, the goats did not consume the plant, but later, it was preferred over any other forage. high dose induced rapid intoxication, whereas with low doses, the course of the toxicosis was more protracted. the goats were euthanized when they were recumbent. cerebrum, cerebellum, medulla oblongata, pons and colliculi, were routinely processed for histology. in nine days, the following clinical signs developed: abnormal fascies, dilated nostrils and abnormal postures of the head, cephalic tremors and nystagmus, difficulty in standing. subsequently, the goats had a tendency to fall, always to the left, with spastic convulsions. there was lack in coordination of voluntary movements due to purkinje and deep nuclei neurons damage. the cochlear reflex originated hyperreflexia, abnormal posture, head movements and tremors. the withdrawal reflex produced flexor muscles hypersensitivity at the four legs, later depression and stupor. abnormal responses to sounds were related to collicular lesions. thalamic damage altered the withdrawal reflex, showing incomplete reaction. the observed cervical hair bristling was attributed to a thalamic regulated nociceptive response. depression may be associated with agonists of lysergic acid contained in ipomoea. these clinical signs were correlated with lesions in different parts of the cns.
Niklas Luhmann: La compleja incertidumbre de un mundo secularizado
Tell,Elvio A.;
Ciencia, docencia y tecnolog?-a , 2007,
Abstract: niklas luhmann's work invites us to think over society in a new way, leaving behind old habits and traditional thoughts built by the western intellectual heritage since the illustration. lukhmann's reluctance to sustain the basic postulates of the ancient european thought and his concern about proposing an illustration of the illustration are no more that forewords to approaching the requirements of a new theory more suitable to modern times. thus, it could be said that he requires to go beyond modernity tempting to create new intellectual categories. as an example, his work implies a constant concern to conceive a new concept of subject independent from his/her context meant in terms of social systems, and while the analysis of social communication traditionally implies subjects, for the studied author that represents a chimera. even when communication assumes the participation of either several or many people, that is the very reason why it cannot be attributed to any particular one.
Niklas Luhmann: la compleja incertidumbre de un mundo secularizado
Elvio A. Tell
Ciencia, Docencia y Tecnología , 2007,
Abstract: La obra de Niklas Luhmann es una invitación a pensar de un modo nuevo la sociedad, abandonando viejos hábitos y tradiciones de pensamiento que ha forjado la herencia intelectual de Occidente desde la Ilustración. El rechazo de Luhmann a mantener los postulados del pensamiento veteroeuropeo y su preocupación en formular una ilustración de la ilustración no son más que preámbulos para abordar la exigencia de una nueva teoría más acorde con los tiempos modernos. En este sentido, bien puede decirse que exige ir más allá de la modernidad tendiendo a crear nuevas categorías intelectuales. Por ejemplo, su obra es una constante preocupación por pensar un nuevo concepto de sujeto independiente de su entorno que son los sistemas sociales. Tradicionalmente el análisis de la comunicación social supone sujetos. Para el autor, esto representa una quimera. Si bien es cierto que la comunicación presupone la participación de muchas personas, precisamente por eso, no puede ser atribuida a ningún individuo en particular.
Soroprevalência de aglutininas anti-Leptospira spp. em ovinos nas Mesorregi?es Sudeste e Sudoeste do Estado Rio Grande do Sul, Brasil
Herrmann, Geder Paulo;Lage, Andrey Pereira;Moreira, Elvio Carlos;Haddad, Jo?o Paulo Amaral;Resende, José Renato de;Rodrigues, Rogério Oliveira;Leite, R?mulo Cerqueira;
Ciência Rural , 2004, DOI: 10.1590/S0103-84782004000200017
Abstract: the presence of anti-leptospira agglutinins in 1.360 samples of ovine sera was determined. clinically healthy sheep with more than one year of age, raised in pasture in 136 farms of 18 counties, 10 located in the southeast mesorregions and 8 in the southwest mesorregions of the state of rio grande do sul, brazil, between the months of january and march of 1999. were used sera tested by the microscopic agglutination technique (mat), from the 1.360 samples of serum tested, 466 (34.26%) were positive and the titers of anti-leptospira spp. agglutinins varied from 100 to 3.200. the serovars founded were: hardjo (norma), 210 (28.4%), sentot, 152 (16.8%); hardjoprajitno, 133 (14.5%); fortbragg, 73 (6.3%); wolffi, 39 (4.7%); pyrogenes, 25 (1.8%); australis, 21 (1.6%); pomona, 20 (1.6%); sejroe, 19 (2.2%); castellonis, 18 (1.8%); hebdomadis, 17 (1.3%); icterohaemorrhagiae, 16 (0.5%); grippotyphosa, 9 (0.7%); canicola , 8 (0.6%); tarassovi, 7 (0.6%), bratislava, 4 (0.29%), autumnalis, 3 (0.2%). the results demonstrate that leptospira spp are disseminated in the majority of the farms that raise sheep in the southeast and southwest mesorregions of the state of rio grande do sul, brazil.
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