955 resultados para Institute for Numerical Analysis (U.S.)


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A década de 1950 foi marcada por inúmeras transformações, sociais, políticas e econômicas, decorrentes da industrialização em curso no Brasil. Alguns setores da sociedade, como as elites políticas e um grupo de intelectuais, sentiram a necessidade de pensar as políticas educacionais entendendo o processo educacional como dimensão essencial da realidade brasileira por meio de publicações de numerosos trabalhos. Assim, foi criado no dia 14 de julho de 1955, o ISEB (Instituto Superior de Estudos Brasileiros), ainda no governo Café Filho, mas iniciou suas atividades no mandato de Juscelino Kubitschek. Era um instituto ligado ao Ministério da Educação e Cultura (MEC), porém gozava de autonomia administrativa e seus integrantes possuíam liberdade de pesquisa. Tinha como objetivo ser um local de estudos e debates para discutir o desenvolvimento do Brasil. Eram reflexões voltadas para o âmbito das Ciências Sociais como: Economia, Filosofia, Sociologia, História e Política, e a partir delas, buscava-se instaurar o debate, dialogar com a sociedade mediante palestras em institutos importantes na época e ainda, conferências em São Paulo, patrocinadas pelo Centro da Federação das Indústrias (FIESP). Seus trabalhos principais foram: a publicação de livros, artigos, jornais e a realização de conferências, além de São Paulo, em outras cidades, como Brasília e Rio de Janeiro. Por ser constituído de intelectuais de diferentes vertentes ideológicas, emergiam muitos atritos de ideias, o que, consequentemente, provocou várias crises dentro do instituto. Alguns, como Hélio Jaguaribe, defendiam que a instauração de um processo de desenvolvimento teria como direção a burguesia industrial. Em face do exposto, esta pesquisa investigou o papel pedagógico do ISEB, por meio da análise de suas publicações e dos cursos por ele ministrados. A proposta se deu no sentido de compreender seus dois momentos: o primeiro, durante o governo de Juscelino Kubitschek, e o segundo, no governo de João Goulart, buscando qualificar ideológica e pedagogicamente cada um deles. O estudo evidenciou que o ISEB possuía uma dimensão pedagógica, a qual, apesar de não estar descrita em seu estatuto, encontrava-se implícita em suas publicações, cursos e palestras.

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We present theoretical and numerical analysis of the femtosecond processing of silica by laser beam with power below self-focusing threshold.

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Cold roll forming is an extremely important but little studied sheet metal forming process. In this thesis, the process of cold roll forming is introduced and it is seen that form roll design is central to the cold roll forming process. The conventional design and manufacture of form rolls is discussed and it is observed that surrounding the design process are a number of activities which although peripheral are time consuming and a possible source of error. A CAD/CAM system is described which alleviates many of the problems traditional to form roll design. New techniques for the calculation of strip length and controlling the means of forming bends are detailed. The CAD/CAM system's advantages and limitations are discussed and, whilst the system has numerous significant advantages, its principal limitation can be said to be the need to manufacture form rolls and test them on a mill before a design can be stated satisfactory. A survey of the previous theoretical and experimental analysis of cold roll forming is presented and is found to be limited. By considering the previous work, a method of numerical analysis of the cold roll forming process is proposed based on a minimum energy approach. Parallel to the numerical analysis, a comprehensive range of software has been developed to enhance the designer's visualisation of the effects of his form roll design. A complementary approach to the analysis of form roll design is the generation of form roll design, a method for the partial generation of designs is described. It is suggested that the two approaches should continue in parallel and that the limitation of each approach is knowledge of the cold roll forming process. Hence, an initial experimental investigation of the rolling of channel sections is described. Finally, areas of potential future work are discussed.

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Alginate is widely used as a viscosity enhancer in many different pharmaceutical formulations. The aim of this thesis is to quantitatively describe the functions of this polyelectrolyte in pharmaceutical systems. To do this the techniques used were Viscometry, Light Scattering, Continuous and Oscillatory Shear Rheometry, Numerical Analysis and Diffusion. Molecular characterization of the Alginate was carried out using Viscometry and Light Scattering to determine the molecular weight, the radius of gyration, the second virial coefficient and the Kuhn statistical segment length. The results showed good agreement with similar parameters obtained in previous studies. By blending Alginate with other polyelectrolytes, Xanthan Gum and 'Carbopol', in various proportions and with various methods of low and high shear preparation, a very wide range of dynamic rheological properties was found. Using oscillatory testing, the parameters often varied over several decades of magnitude. It was shown that the determination of the viscous and elastic components is particularly useful in describing the rheological 'profiles' of suspending agent blends and provides a step towards the non-empirical formulation of pharmaceutical disperse systems. Using numerical analysis of equations describing planar diffusion, it was shown that the analysis of drug release profiles alone does not provide unambiguous information about the mechanism of rate control. These principles were applied to the diffusion of Ibuprofen in Calcium Alginate gels. For diffusion in such non-Newtonian systems, emphasis was placed on the use of the elastic as well as the viscous component of viscoelasticity. It was found that the diffusion coefficients were relatively unaffected by increases in polymer concentration up to 5 per cent, yet the elasticities measured by oscillatory shear rheometry were increased. This was interpreted in the light of several theories of diffusion in gels.

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The creep rupture properties of cast ½Cr½Mo¼V and 1Cr1Mo¼V alloy steel used in the manufacture of power station steam generating plant. have been investigated. The effects of constraint and geometry on the creep rupture properties are also considered. The validity of various criteria controlling macroscopic creep crack growth in cast CrMoV alloys has been examined. It is found that neither the stress intensity factor nor reference stress correlate satisfactorily the creep crack growth rates at the test temperature of 550°C. Certain minimum displacements must be achieved for crack initiation and propagation. It is found that this displacement as measured by crack opening displacement or crack aspect ratio, is the same in both compact tension and centre-cracked panel geometries, is invariant with crack length and decreases with increasing constraint. The effect of constraint on creep crack growth rate in the two geometries is less conclusive. A new model describing creep crack growth in cast CrMoV alloy steels has been developed. The model is based on the results from a numerical finite element creep analysis of the relaxation and redistribution of stress ahead of an incubating creep crack . It is found that macroscopic creep crack growth in a material undergoing either plane stress or plane strain deformation can be described by a fracture stress which is based on the Von Mises equivalent stress. It has been shown that this model is capable of rationalising all of the experimental crack velocity data from the cast CrMoV alloys. The resultant degree of data correlation is far superior to that obtained when using the stress intensity factor or reference stress. A cumulative damage creep fracture model based upon the results from the numerical analysis has been developed. It is found that the model is capable of predicting the behaviour of propagating creep cracks in cast CrMoV alloys from smooth bar creep rupture data.

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We demonstrate the development of femtosecond laser inscribed superstructure fiber gratings (fsSFG) in silica optical fibre. We utilise a single step process, to inscribe low loss and polarisation independent, sampled gratings in optical fibres using the point by point femtosecond laser inscription method. Our approach results in a controlled modulated index change with complete suppression of any overlapping LPG structure leading to highly symmetric superstructure spectra, with the grating reflection well within the Fourier design limit. We also solve Maxwell's equations and calculate the back reflection spectrum using the bidirectional beam propagation method (BiBPM). Experimental results validate our numerical analysis and the estimation of inscription parameters such as ac index modulation, wavelength and the relative peak strength. We also explore how changes in the grating's period influence the reflection spectrum.

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The present dissertation investigates the influence of brand as well as substance-related marketing attributes on prescription pharmaceutical sales within a state-controlled market. For this purpose, a systematic literature review was conducted in the first instance, during which knowledge about the most relevant research within this field was gathered. Consequently, over 538 publications were reviewed and indicated as being potentially relevant, leading to an eventual count of 98 core publications. However, most of these studies had been conducted in the mainly unrestricted US market. These findings were then summarised and statistically evaluated. In a second step, based on the literature review, a qualitative study, containing focus and Delphi groups, was then performed. The participants in these studies were involved in pharmaceutical marketing within a state-controlled prescriptions pharmaceuticals market. Consequently, the findings were slightly different to those derived by the systematic literature review. Based on this second step, seven hypotheses were proposed. In the third step, these hypotheses were tested, using collected data and a secondary market dataset provided by a market research institute. A statistical analysis was then performed, applying descriptive as well as multiple regression analytical methods. The evaluation of the results resulted in a conceptual model of physician targeting, leading to several theoretical, methodological and managerial implications.

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We present the development of superstructure fiber gratings (SFG) in Ge-doped, silica optical fiber using femtosecond laser inscription. We apply a simple but extremely effective single step process to inscribe low loss, sampled gratings with minor polarization dependence. The method results in a controlled modulated index change with complete suppression of mode coupling associated with the overlapping LPG structure leading to highly symmetric superstructure spectra, with the grating reflection well within the Fourier design limit. The devices are characterized and compared with numerical modeling by solving Maxwell's equations and calculating the back reflection spectrum using the bidirectional beam propagation method (BiBPM). Experimental results validate our numerical analysis, allowing for the estimation of inscription parameters such as the ac index modulation change, and the wavelength, position and relative strength of each significant resonance peak. We also present results on temperature and refractive index measurements showing potential for sensing applications.

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Internally heated fluids are found across the nuclear fuel cycle. In certain situations the motion of the fluid is driven by the decay heat (i.e. corium melt pools in severe accidents, the shutdown of liquid metal reactors, molten salt and the passive control of light water reactors) as well as normal operation (i.e. intermediate waste storage and generation IV reactor designs). This can in the long-term affect reactor vessel integrity or lead to localized hot spots and accumulation of solid wastes that may prompt local increases in activity. Two approaches to the modeling of internally heated convection are presented here. These are based on numerical analysis using codes developed in-house and simulations using widely available computational fluid dynamics solvers. Open and closed fluid layers at around the transition between conduction and convection of various aspect ratios are considered. We determine optimum domain aspect ratio (1:7:7 up to 1:24:24 for open systems and 5:5:1, 1:10:10 and 1:20:20 for closed systems), mesh resolutions and turbulence models required to accurately and efficiently capture the convection structures that evolve when perturbing the conductive state of the fluid layer. Note that the open and closed fluid layers we study here are bounded by a conducting surface over an insulating surface. Conclusions will be drawn on the influence of the periodic boundary conditions on the flow patterns observed. We have also examined the stability of the nonlinear solutions that we found with the aim of identifying the bifurcation sequence of these solutions en route to turbulence.

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Chemical turbulence in the oscillatory catalytic CO oxidation on Pt(110) is suppressed by means of focused laser light. The laser locally heats the platinum surface which leads to a local increase of the oscillation frequency, and to the formation of a pacemaker which emits target waves. These waves slowly entrain the medium and suppress the spatiotemporal chaos present in the absence of laser light. Our experimental results are confirmed by a detailed numerical analysis of one- and two-dimensional media using the Krischer-Eiswirth-Ertl model for CO oxidation on Pt110. Different control regimes are identified and the dispersion relation of the system is determined using the pacemaker as an externally tunable wave source.

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We examine the feasibility of optical pulse transmission in dispersion-managed fiber systems with in-line nonlinear optical loop mirrors. Applying numerical analysis, we find regimes of stable propagation over long distances in such lines, with a significant increase in the signal-to-noise ratio. © 2000 Optical Society of America.

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We present the development of superstructure fiber gratings (SFG) in Ge-doped, silica optical fiber using femtosecond laser inscription. We apply a simple but extremely effective single step process to inscribe low loss, sampled gratings with minor polarization dependence. The method results in a controlled modulated index change with complete suppression of mode coupling associated with the overlapping LPG structure leading to highly symmetric superstructure spectra, with the grating reflection well within the Fourier design limit. The devices are characterized and compared with numerical modeling by solving Maxwell's equations and calculating the back reflection spectrum using the bidirectional beam propagation method (BiBPM). Experimental results validate our numerical analysis, allowing for the estimation of inscription parameters such as the ac index modulation change, and the wavelength, position and relative strength of each significant resonance peak. We also present results on temperature and refractive index measurements showing potential for sensing applications.

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We present theoretical and numerical analysis of the femtosecond processing of silica by laser beam with power below self-focusing threshold. © 2006 IEEE.

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A distributed fiber sensing system based on ultraweak FBGs (UWFBGs) assisted polarization optical time-domain reflectometry (POTDR) is proposed for load and vibration sensing with improved signal-to-noise ratio (SNR) and sensitivity. UWFBGs with reflectivity higher than Rayleigh scattering coefficient per pulse are induced into a POTDR system to increase the intensity of the back signal. The performance improvement of the system has been studied. The numerical analysis has shown that the SNR and sensitivity of the system can be effectively improved by integrating UWFBGs along the whole sensing fiber, which has been clearly proven by the experiment. The experimental results have shown that by using UWFBGs with 1.1 x 10-5 reflectivity and 10-m interval distance, the SNR is improved by 11 dB, and the load and vibration sensitivities of the POTDR are improved by about 10.7 and 9 dB, respectively.