40 resultados para Particulas


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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O estudo analisa a significação das particulas pronominais entre as quais se incluem os determinantes, os pronomes substantivos e os advérbios pronominais. Para esta análise se adota o critério dos traços constrativos (Chomsky, 2). Os resultados do trabalho mostram que as categorias semânticas dos pronomes (lato sensu) se associam, de uma forma ou de outra, às nações de DEFINIDADE e PESSOA DO DISCURSO.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Since the early twenty-first century, the construction sector has been the second largest on the rise in the Brazilian industrial sector, with a growth of 1.4% in 2012, and is likely to remain at this level for a long time. However, unlike decades ago, the industry has been seeking in its manufacturing process, sustainable materials, encompassing in their works the concept of sustainability. Thus, the timber sector seeks to satisfy a market increasingly demanding, innovating techniques and utilization being less aggressive to the environment. The purpose of this study was to produce and evaluate the mechanical strength of the composite cement with the addition of wood residues and slag low oven. Therefore, it was made 42 specimen cement-slag-wood, carried out in two steps. Since at the first, it was varied only the slag particle size, and at the second, through the best result of the previous step, it was varied the wood particles granulometry. The mechanical performance of the composite was evaluated by the results obtained in the compression test and the physical test for determining the density of the material. In the first step of the process can be concluded that the best result was achieved with the use of slag particles retained on the 60 mesh sieve. In the second phase of the study concluded that the best results were achieved with wood particles with the large particles, i.e. particles retained on the 10 mesh sieve. Both in the first and in the second step it can be seen that there has been the influence of the particle size of the waste materials. With the obtained results, could be evaluated that the use of waste for the production of cement-slag-wood composite showed lower performance when compared to the results obtained in studies without the use of waste. However, some applications are feasible to be performed with the use of composite wood-cement-slag

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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This paper presents a study about the operation of the major system’s components of a linear particle acclerator (Linac). It addresses the components mainly responsible for the formation of the beam, through the inclusion of several block diagrams showing the details of the structure. Among the systems discussed may be mentioned the system modulator, automatic frequency control, dosimetry and auxiliary systems. The main objective is the dissemination of basic technology applied in linear accelerators and create literature about this subject in national language. Despite the high complexity and large number of devices that comprise a linear accelerator, it has been developed an easy to understand text that adresses the most relevant issues to the operation of the linear accelerator from the point of view of electrical engineering

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The Boron Neutron Capture Therapy (BNCT), based on the 10B(n,α)7Li reaction, represents a promising modality for the treatment of cancers that are resistents to conventional treatments. So, it is necessary to find drugs (boron compounds) with high selectivity for each type of cancer, the neutrons source should be well characterized and the rate of 10B(n,α)7Li reaction should be measured with great accuracy as possible. This study aimed to develop a method for manufacturing thin films of boron, for measure the 10B(n,α)7Li reaction, and analyze the uniformity of the films. Five thin films of boron were manufactured with three different concentrations of boric acid, heated to transform the acid in boron, irradiated with thermic neutrons coupled to CR-39 detectors, in BNCT line at the reactor IEA-R1 IPEN/CNEN, São Paulo. After the irradiation, the detectors were chemically attacked with NaOH to reveal the tracks. The methodology presented is effective because it resulted in deposition of boron as thin film enabling the quantitative analysis of 10B(n,α)7Li reaction. The analysis of the uniformity of density of the induced tracks in CR-39 shows that, in most of the films, there is no uniformity in surface distribution of boron, but when the film is divided, we obtain some uniform sectors

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Cosmic radiation has been identi ed as one of the main hazard to crew, aircraft and sensitive equipments involved in long-term missions and even high-altitude commercial ights. Generally, shields are used in spatial units to avoid excessive exposure, by holding the incident radiation. Unfortunatelly, shielding in space is problematic, especially when high-energy cosmic particles are considered, due to the production of large number of secondary particles, mainly neutrons, protons and alpha particles, caused by spallation reactions and quasi-elastic processes of the corpuscular radiation with the shield. Good parameters for checking the secondary particle production at target material are diferential cross section and energy deposited in the shield. Addition experiments, some computer codes based on Monte Carlo method show themselves a suitable tool to calculate shield parameters, due to have evaluated nuclear data libraries implemented on the algorithm. In view of this, the aim of this work is determining the parameters evaluated in shielding materials, by using MCNPX code, who shows good agreement with experimental data from literature. Among the materials, Aluminium had lower emission and production of secondary particles