964 resultados para Expressions


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A pesquisa de doutorado que apresento teve como objeto de estudo cartas escritas por diferentes sujeitos, enviando ideias para a Constituição brasileira promulgada em outubro de 1988. As cartas selecionadas são todas documentos manuscritos por diferentes sujeitos, componentes de um largo acervo documental, que apresenta indícios de que seus autores não concluíram o ensino fundamental, do tempo e do espaço em que foram escritas, hoje parte do fundo patrimonial do Museu da República. Esta pesquisa inseriu-se na temática sobre pluralidade de conhecimentos/saberes que circulam socialmente, especialmente os traduzidos por expressões escritas de sujeitos jovens e adultos. Entendi essa produção como um processo de participação política, ou seja, minha hipótese central pode ser assim resumida: sujeitos, em seus processos de produção de cidadania, ao escreverem cartas à elaboração da Constituição, em exercício de participação política, se autoproduzem como cidadãos, pela escrita. Mais do que exercício de cidadania, a abordagem e interpretação que fiz das escritas epistolares mostraram também que os sujeitos tinham conhecimentos que talvez ignorassem, e que independiam de conhecimentos formais para expressaram outros sentidos de cidadania, afirmando direitos tantas vezes negados. Esse reconhecimento levou-me à certeza de que estava diante de práticas sociais em que a noção de justiça cognitiva podia ser identificada, pelo fato de as pessoas, fora do espaço do conhecimento formal, revelarem outros conhecimentos indispensáveis ao exercício da cidadania, demonstrando a condição de iguais a pessoas escolarizadas em espaços formais. Assim sendo, devo admitir que o conhecimento formal não é condição para o exercício da cidadania, e que a presença de outros conhecimentos para além dos formais da cultura escrita, constituídos em redes, porque forjados na vida, no cotidiano em que os sujeitos vivem, e enredados em suas mais diferentes histórias que os constituem, e assim representados no modo como escreviam, permitiu reconhecer politicamente esses sujeitos de direito, fora do espaço da chamada educação formal. Esse reconhecimento levou-me à certeza (sempre provisória) de uma prática social em que a justiça cognitiva podia ser identificada, pelo fato de as pessoas, fora do espaço do conhecimento formal, revelarem outros conhecimentos indispensáveis ao exercício da cidadania, porque se reconheciam em patamar de igualdade com pessoas escolarizadas.

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A 5V/1 V Switched Capacitor (SC) dc-dc converter designed for a 0.18μm CMOS process is analysed in detail, in this paper. Analytical equations are derived for the voltages and currents through the main components of the SC converter. The model includes switches, capacitors, equivalent series resistances and the load. The switches in the converter are represented by MOSFETs in the UMC 0.18μm CMOS process. The impact of system parameters on output voltage ripple are studied using the analytical expressions.

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In order to understand how the performance of a liquid-crystal laser depends on the physical properties of the low molar mass nematic host, we have studied the energy threshold and slope efficiency of ten optically pumped liquid-crystal lasers based on different hosts. Specifically, this leads to a variation in the birefringence, the orientational order parameter, and the order parameter of the transition dipole moment of the dye. It is found that low threshold energies and high slope efficiencies correlate with high order parameters and large birefringences. To a first approximation this can be understood by considering analytical expressions for the threshold and slope efficiency, which are derived from the space-independent rate equations for a two-level system, in terms of the macroscopic liquid crystal properties.

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Coupling of the in vacuo modes of a fluid-loaded, vibrating structure by the resulting acoustic field, while known to be negligible for sufficiently light fluids, is still only partially understood. A particularly useful structural geometry for the study of this problem is the simply supported, rectangular flat plate, since it exhibits all the relevant physical features while still admitting an analytical description of the modes. Here the influence of the fluid can be expressed in terms of a set of doubly infinite integrals over wave number: the modal acoustic impedances. Closed-form solutions for these impedances do not exist and, while their numerical evaluation is possible, it greatly increases the computational cost of solving the coupled system of modal equations. There is thus a need for accurate analytical approximations. In this work, such approximations are sought in the limit where the modal wavelength is small in comparison with the acoustic wavelength and the plate dimensions. It is shown that contour integration techniques can be used to derive analytical formulas for this regime and that these formulas agree closely with the results of numerical evaluations. Previous approximations [Davies, J. Sound Vib. 15(1), 107-126 (1971)] are assessed in the light of the new results and are shown to give a satisfactory description of real impedance components, but (in general) erroneous expressions for imaginary parts.

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在果实采后贮藏过程中,病原真菌的侵染会引起果实腐烂,造成巨大的经济损失。利用生物和非生物因子诱导果实抗病性,已经成为采后病害防治领域的一个研究热点。本文主要利用RT-PCR和RACE技术克隆果实抗病相关基因,通过分子杂交和蛋白羰基化免疫检测技术,研究了外源SA和酵母拮抗菌诱导果实抗病性机理,结果表明: 1. 通过优化RNA提取方法,能从含有多糖的冬枣、葡萄、甜樱桃、桃、番茄等果实中提取到质量较好的RNA,用于RT-PCR和Northern杂交。 2. 采用RT-PCR和RACE方法,从甜樱桃果实克隆了两个抗氧化相关基因CAT2(Genbank:EF165590)和GPX(Genbank:EF165591)和两个PR基因GLU-1(Genbank:EF177487)和GLU-3(Genbank:EF177488)。其中CAT2全长cDNA序列为1479 bp,编码492个氨基酸;GPX全长cDNA序列为513 bp,编码170个氨基酸;GLU-1全长cDNA序列为1050 bp,编码349个氨基酸;GLU-3部分cDNA序列为454 bp,编码141个氨基酸。 3. 酵母拮抗菌Pichia membranaefaciens处理不同成熟度的甜樱桃果实,能显著降低果实贮藏期间青霉病(Penicillium expansum)的发生,并且对低成熟度果实的病害防治效果更为明显。酵母拮抗菌的抑病机理与减轻了甜樱桃果实蛋白羰基化程度,诱导了果实抗氧化酶基因(CAT和GPX)和PR基因(GLU-1)的表达和提高了抗氧化酶(CAT和GPX)和β-1,3-葡聚糖酶的活性有关。 4. 四种酵母拮抗菌P. membranaefaciens, Cryptococcus laurentii, Candida guilliermondii和Rhodotorula glutinis处理桃果实,可显著降低贮藏期间的褐腐病(Monilinia fructicola)。这是由于酵母拮抗菌能抑制病原菌侵染造成的氧化胁迫和蛋白羰基化。此外,酵母拮抗菌处理还能显著诱导CAT、POD、几丁质酶、β-1,3-葡聚糖酶活性及相应基因的表达。 5. 水杨酸(SA,2 mM)处理采后不同成熟度的甜樱桃果实,能显著降低青霉病的危害。其抑病机理与SA处理能减轻P. expansum侵染引起的果实蛋白羰基化程度,显著提高CAT、GPX和β-1,3-葡聚糖酶基因的表达和相关的酶的活性有关。而2 mM的SA处理对P. expansum的生长没有直接抑制作用。 6. 水杨酸(SA,2 mM)与P. membranaefaciens(1×108 CFU/ml)配合处理能显著降低低温贮藏期间桃果实的褐腐病,并能提高几丁质酶、β-1,3-葡聚糖酶和POD的活性和相关基因的表达。另外,2 mM的SA对拮抗菌P. membranaefaciens的生长没有影响,但能够抑制病原菌M. fructicola的孢子萌发和菌丝扩展。

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The GTO model presented in this paper uses analytical expressions to describe the internal physics of the device. It has been implemented to run as compiled code in the SPICE simulation package and as a MAST template in the Saber simulator. A rigorous comparison of measured simulated waveforms and performance parameters (including turn-off energies) for a 3000A device is described and discussed.

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In this paper, an introduction to Bayesian methods in signal processing will be given. The paper starts by considering the important issues of model selection and parameter estimation and derives analytic expressions for the model probabilities of two simple models. The idea of marginal estimation of certain model parameter is then introduced and expressions are derived for the marginal probability densities for frequencies in white Gaussian noise and a Bayesian approach to general changepoint analysis is given. Numerical integration methods are introduced based on Markov chain Monte Carlo techniques and the Gibbs sampler in particular.

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This paper presents an analytical model for the determination of the basic breakdown properties of three-dimensional (3D)-RESURF/CoolMOS/super junction type structures. To account for the two-dimensional (2D) effect of the 3D-RESURF action, 2D models of the electric field distribution are developed. Based on these, expressions are derived for the breakdown voltage as a function of doping concentration and physical dimensions. In addition to cases where the drift regions are fully depleted, the model developed is also applicable to situations involving drift regions which are almost depleted. Accuracy of the analytical approach is verified by comparison with numerical results obtained from the MEDICI device simulator.

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In this paper, we derive an EM algorithm for nonlinear state space models. We use it to estimate jointly the neural network weights, the model uncertainty and the noise in the data. In the E-step we apply a forwardbackward Rauch-Tung-Striebel smoother to compute the network weights. For the M-step, we derive expressions to compute the model uncertainty and the measurement noise. We find that the method is intrinsically very powerful, simple and stable.

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Previously published expressions for the wear volume in the micro-scale abrasion test for curved specimen surfaces (K.L. Rutherford and I.M. Hutchings, Tribology Letters 2 (1996) 1-11) were based upon erroneous assumptions about the wear-scar geometry. Accurate volumes have now been computed, and the errors in the use of the original analytical equations are shown to be negligibly small (<0.5% error) for all practical cases. © J.C. Baltzer AG, Science Publishers.

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A method is presented for predicting the variance of the energy levels in a built-up system to accompany the mean values predicted by SEA. Closed form expressions for the variance are obtained in terms of the standard SEA parameters and an additional set of parameters αk that describe the nature of the power input to each subsystem k, and αks that describe the nature of the coupling between subsystems k and s.

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In this paper, an introduction to Bayesian methods in signal processing will be given. The paper starts by considering the important issues of model selection and parameter estimation and derives analytic expressions for the model probabilities of two simple models. The idea of marginal estimation of certain model parameter is then introduced and expressions are derived for the marginal probabilitiy densities for frequencies in white Gaussian noise and a Bayesian approach to general changepoint analysis is given. Numerical integration methods are introduced based on Markov chain Monte Carlo techniques and the Gibbs sampler in particular.

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The objective of this paper is to test various available turbulent burning velocity models on an experimental version of Siemens small scale combustor using the commercial CFD code. Failure of burning velocity model with different expressions for turbulent burning velocity is observed with an unphysical flame flashback into the swirler. Eddy Dissipation Model/Finite Rate Chemistry is found to over-predict mean temperature and species concentrations. Solving for reaction progress equation with its variance using scalar dissipation rate modelling produced reasonably good agreement with the available experimental data. Two different turbulence models Shear Stress Transport (SST) and Scale Adaptive Simulation (SAS) SST are tested and results from transient SST simulations are observed to be predicting well. SAS-SST is found to under-predict with temperature and species distribution.

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Computational Fluid Dynamics CFD can be used as a powerful tool supporting engineers throughout the steps of the design. The combination of CFD with response surface methodology can play an important role in such cases. During the conceptual engineering design phase, a quick response is always a matter of urgency. During this phase even a sketch of the geometrical model is rare. Therefore, the utilisation of typical response surface developed for congested and confined environment rather than CFD can be an important tool to help the decision making process, when the geometrical model is not available, provided that similarities can be considered when taking into account the characteristic of the geometry in which the response surface was developed. The present work investigates how three different types of response surfaces behave when predicting overpressure in accidental scenarios based on CFD input. First order, partial second order and complete second order polynomial expressions are investigated. The predicted results are compared with CFD findings for a classical offshore experiment conducted by British Gas on behalf of Mobil and good agreement is observed for higher order response surfaces. The higher order response surface calculations are also compared with CFD calculations for a typical offshore module and good agreement is also observed. © 2011 Elsevier Ltd.

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This work is concerned with the characteristics of the impact force produced when two randomly vibrating elastic bodies collide with each other, or when a single randomly vibrating elastic body collides with a stop. The impact condition includes a non-linear spring, which may represent, for example, a Hertzian contact, and in the case of a single body, closed form approximate expressions are derived for the duration and magnitude of the impact force and for the maximum deceleration at the impact point. For the case of two impacting bodies, a set of algebraic equations are derived which can be solved numerically to yield the quantities of interest. The approach is applied to a beam impacting a stop, a plate impacting a stop, and to two impacting beams, and in each case a comparison is made with detailed numerical simulations. Aspects of the statistics of impact velocity are also considered, including the probability that the impact velocity will exceed a specified value within a certain time. © 2012 Elsevier Ltd. All rights reserved.