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Search Results: 1 - 10 of 4367 matches for " Valdir;Pires "
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Blendas de poliamida 6/elast?mero: propriedades e influência da adi??o de agente compatibilizante
Barra, Guilherme M. O.;Roeder, Jerusa;Soldi, Valdir;Pires, Alfredo T. N.;Agnelli, José A. M.;
Polímeros , 2003, DOI: 10.1590/S0104-14282003000200006
Abstract: this study describes the micro- and macroscopic properties of polyamide 6 (pa6) and ethylene /propylene/diene copolymer (epdm) blends, and the effects from small quantities of epdm or epm grafted with maleic anhydride in this polymer mixture. the components and polymer blends at different compositions were analyzed by differential scanning calorimeter (dsc) and infrared spectroscopy (ftir). the results suggest immiscible mixture in all ranges of the blend's compositions. scanning electron microscopy (sem) micrographs of the blends indicated that the size of rubber aggregates decreases as the functionalized elastomer (epdm-g-ma or epm-g-ma) is added to the pa6/epdm mixture, and the impact strength of the pa6 matrix increases significantly.
Influência do comon?mero e do método de polimeriza??o na cinética de libera??o de fenobarbitona a partir de hidrogéis
Barcellos, Ivonete O.;Katime, Issa A.;Soldi, Valdir;Pires, Alfredo T. Nunes;
Polímeros , 2000, DOI: 10.1590/S0104-14282000000200013
Abstract: the release of water-soluble drugs from initially hydrated hydrogels matrices generally involves the simultaneous water absorption and drug desorption through a swelling-controlled diffusion mechanism. the diffusional behaviour of phenobarbitone from a hydrogel formed by a 2-hydroxyethylmethacrylate (hema) and methyl monoitaconate (mmi) copolymer was reported. the drug release into water was performed by high pressure liquid cromatography and the results showed that the phenobarbitone release from the hydrogels studies, considering the diffusion coefficient values did not change with the temperature and the polymerization method. the activation energy values suggested a more favorable phenobarbitone release from the hydrogels p(hema-co-mmi) polymerized in mass and bulk solution.
Blendas de poliamida 6/elast mero: propriedades e influência da adi o de agente compatibilizante
Barra Guilherme M. O.,Roeder Jerusa,Soldi Valdir,Pires Alfredo T. N.
Polímeros , 2003,
Abstract: Neste trabalho foram estudadas as propriedades micro e macroscópicas de misturas físicas binárias de poliamida 6 [PA6] com copolímero poli(etileno-co-propileno-co-dieno) [EPDM] e em presen a de pequenas quantidades de EPDM ou EPM enxertados com anidrido maleico, atuando como agentes compatibilizantes. Os componentes puros (poliamida 6 e EPDM) e as blendas poliméricas em diferentes composi es foram analisados por calorimetria diferencial de varredura (DSC) e espectroscopia de infravermelho (FTIR). Os resultados indicaram a imiscibilidade dos componentes da mistura em toda a faixa de composi o estudada. A utiliza o das técnicas de análise elementar, microscopia eletr nica de varredura e propriedades mecanicas permitiu avaliar a homogeneidade da mistura, a redu o do tamanho dos domínios do elast mero e o aumento da for a de impacto da matriz de PA6 com a adi o do agente compatibilizante à mistura binária de PA6/EPDM.
Influência do comon mero e do método de polimeriza o na cinética de libera o de fenobarbitona a partir de hidrogéis
Barcellos Ivonete O.,Katime Issa A.,Soldi Valdir,Pires Alfredo T. Nunes
Polímeros , 2000,
Abstract: A libera o de drogas solúveis em água a partir de matrizes de hidrogéis hidratados, geralmente envolve simultaneamente a absor o de água e a libera o da droga via mecanismo de difus o controlada. Foi analisado o comportamento difusional da fenobarbitona no hidrogel do copolímero 2-hidroxietil metacrilato (HEMA) e monoitaconato de metila (MMI). A libera o da droga no meio aquoso foi acompanhada por cromatografia líquida de alta press o e os resultados mostraram que a libera o da fenobarbitona a partir dos hidrogéis estudados, considerando-se os valores dos coeficientes de difus o, n o variou com a temperatura e com o método de polimeriza o. Os valores de energia de ativa o sugerem um favorecimento na libera o da fenobarbitona a partir dos hidrogéis de p(HEMA-co-MMI) polimerizados em massa e em solu o.
Simulation model of a baggage claim device coping with a new large aircraft (NLA)
Rogéria de Arantes Gomes Eller,Milton Valdir de Matos Feitosa,Protógenes Pires Porto
Revista de Literatura dos Transportes , 2011,
Abstract: Este artigo apresenta uma metodologia para avalia o e projeto de um dispositivo de restitui o de bagagens capaz de atender as necessidades de uma aeronave grande do tipo conhecido como New Large Aircraft – NLA, chegando de um voo internacional. Dois modelos de simula o foram desenvolvidos. O primeiro é um modelo determinístico empregando a ferramenta disponível nas Planilhas Excel. O segundo, um modelo estocástico, é desenvolvido na plataforma computacional ARENA. Os parametros da configura o de dados, tais como número de bagagens por passageiro, tamanho médio das bagagens, e velocidade de deslocamento do carrossel (esteira), foram atribuídos com base nas metodologias propostas pela International Air Transport Associacion (IATA), por Hart (Hart, 1985) e por Horonjeff (Horonjeff, 1969). Foram simuladas chegadas desembarcando 650, 750, 850, 950 e 1000 passageiros com a finalidade de verificar, para cada voo, o comportamento da esteira. Dos resultados foram extraídos nomogramas (ábacos) para emprego na tomada tática de decis o pelo supervisor do setor de devolu o de bagagens e para a tomada de decis es estratégicas por parte da autoridade aeroportuária com a finalidade de planejamento. Os resultados comparativos dos dois modelos demonstraram consistência até o nível de 850 passageiros. Além desse nível, os resultados apresentam diferen as ligeiramente crescentes que devem ser levadas em considera o para fins de planejamento.
Simulation model of a baggage claim device coping with a new large aircraft (NLA)
Rogéria de Arantes Gomes Eller,Milton Valdir de Matos Feitosa,Protógenes Pires Porto
Journal of Transport Literature , 2011,
Abstract: This paper presents a methodology for assessment and design of a baggage claim device capable of allowing an airport terminal to receive a New Large Aircraft - NLA from an international flight. It was developed two simulation models. The first one is a deterministic model and employs the Microsoft Excel Electronic Spreadsheet. The second one, which is stochastic, is developed in ARENA. The configuration data parameters, such as number of bags per passenger, average baggage size, and carousel velocity, are assigned based on International Air Transport Association (IATA), Hart (1985) and Horonjeff (1969) methodologies. It was simulated flight arrivals disembarking 650, 750, 850, 950 and 1,000 passengers affecting the claim device for each flight. From the results, nomograms were derived to be used as a tool, either for tactical decision-making by a baggage claim device supervisor, or for airport authority planning purposes. The comparative results between the two models show that they are consistent up to a level of 850 passengers. Beyond this level, the results present slightly rising differences that must be considered for planning purposes.
Maleic Anhydride Grafting on EPDM: Qualitative and Quantitative Determination
Barra, Guilherme M.O.;Crespo, Janaina S.;Bertolino, José R.;Soldi, Valdir;Pires, Alfredo T. Nunes;
Journal of the Brazilian Chemical Society , 1999, DOI: 10.1590/S0103-50531999000100006
Abstract: several attempts have been made to compatibilize immiscible blends by introducing suitably-chosen polymer additives. this work studies the epdm elastomer, chemically modified with maleic anhydride (ma), through reaction in solution of epdm and ma, using dibenzoyl peroxide as an initiator. the best conditions for obtaining the maximum grafting were studied at different times and percentage weights of maleic anhydride. the evaluation of ma grafting onto epdm was determined with multiple internal reflectance infrared spectroscopy as discussed in detail.
Moldagem por inje??o de pós ceramicos: remo??o da parafina e do polipropileno utilizados como veículo organico
Oliveira, Ricardo V. B.;Pinheiro, Eduardo A.;Soldi, Valdir;Pires, Alfredo T. N.;Fredel, Márcio C.;
Polímeros , 2004, DOI: 10.1590/S0104-14282004000300009
Abstract: powder injection molding [pim] has become highly attractive as it combines the versatility and productivity of conventional injection molding processes with the intrinsic properties of metallic and ceramic materials. the removal of organic binder, used as vehicles during the process, is one of the most critical stages in the production of ceramic devices in this process. in this work, the influence from the geometry of the injected part on the removal of the organic binder was evaluated for both solvent immersion and thermal degradation processes. alumina powder was mixed with an organic binder, comprising polypropylene [pp], paraffin wax [pw] and stearic acid [sa], and injection molded in different geometries. immersion of ceramic parts in hexane induced the solubilization of pw and sa, confirmed by weight variation. parts porosity, determined through nitrogen adsorption isotherm, showed an increase from 0.5 v% before immersion to ca. 20 v% after immersion. pp burnout produced aliphatic hydrocarbons and unsaturated compounds that flow through a porous structure produced in early stages of this process. parts geometry plays an important role in binder removal, affecting the quality of the sintered part as well as the remaining stages of the process.
A racionaliza??o da vida como processo histórico: crítica à racionalidade econ?mica e ao industrialismo
Fernandes, Valdir;
Cadernos EBAPE.BR , 2008, DOI: 10.1590/S1679-39512008000300002
Abstract: this article analyzes theoretical studies about the concept of rationality and criticizes economic rationality. it discusses the rationalization of life as a historic process, guided by the principal of rationality based on the aristotelian notion of reason and extending through analyses by max weber, karl mannheim, the frankfurt school, ivan illich, andré gorz, karl polanyi and guerreiro ramos. based on this theoretical framework, it constructs a criticism of economic rationality upon which is based the current process of development and its difficulties, and the very notion of progress.
Simonsen: pioneiro da vis?o inercial de infla??o
Ramalho, Valdir;
Revista Brasileira de Economia , 2003, DOI: 10.1590/S0034-71402003000100009
Abstract: in the late 60s, mário henrique simonsen arrived at a view of inflation which he called 'model of inflationary feedback'. this view included, under different names, certain notions that became popular in the 80s, such as inflationary shock, self-perpetuating inflation, and inflation institutionalized through indexation. among eminent brazilian economists, simonsen was the first to defend the thesis that indexation hampers the effectiveness of the fight against inflation. from the early 70s on, he preached this thesis in his classes, his books, articles and speeches as a finance minister, stressing that, due to indexation, price rises in the past determined inflation in the present.
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