182 resultados para Friedmann, MoritzFriedmann, MoritzMoritzFriedmann
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In considering the position of community engagement within planning in a time of neo-liberalism and a context of ‘neo-communitarian localism’ (cf. Jessop, 2002; DeFilippis, 2004), this paper reviews the role and relevance of Planning Aid in terms of its performance and aspirations in guiding and transforming planning practice (Friedmann, 1973; 1987; 2011) since its inception in 1973. In doing this we reflect on the critiques of Planning Aid performance provided by Allmendinger (2004) and bring the account up-to-date following on from past considerations (e.g. Bidwell and Edgar, 1982; Thomas, 1992; Brownill and Carpenter, 2007a,b; Carpenter and Brownill, 2008) and prompted by the 35 years since the University of Reading produced the first published work reviewing Planning Aid (Curtis and Edwards, 1980). Our paper is timely given renewed attacks on planning, the implementation of a form of localism and reductions in funding for planning in a time of austerity. Our view is that the need for forms of ‘neo-advocacy’ planning and community development are perhaps even more necessary now, given the continuing under-representation of lower income groups, minority groups and to allow for the expression of alternative planning futures. Thus further consideration of how to ensure that Planning Aid functions are sustained and understood requires the attention of policymakers and the planning profession more widely.
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We present a thermodynamical description of the interaction between holographic dark energy and dark matter. If holographic dark energy and dark matter evolve separately, each of them remains in thermodynamic equilibrium. A small interaction between them may be viewed as a stable thermal fluctuation that brings a logarithmic correction to the equilibrium entropy. From this correction we obtain a physical expression for the interaction which is consistent with phenomenological descriptions and passes reasonably well the observational tests: (c) 2008 Elsevier B.V. All rights reserved.
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This paper investigates the predictions of an inflationary phase starting from a homogeneous and anisotropic universe of the Bianchi I type. After discussing the evolution of the background spacetime, focusing on the number of e-folds and the isotropization, we solve the perturbation equations and predict the power spectra of the curvature perturbations and gravity waves at the end of inflation. The main features of the early anisotropic phase is (1) a dependence of the spectra on the direction of the modes, (2) a coupling between curvature perturbations and gravity waves and (3) the fact that the two gravity wave polarizations do not share the same spectrum on large scales. All these effects are significant only on large scales and die out on small scales where isotropy is recovered. They depend on a characteristic scale that can, but a priori must not, be tuned to some observable scale. To fix the initial conditions, we propose a procedure that generalizes the one standardly used in inflation but that takes into account the fact that the WKB regime is violated at early times when the shear dominates. We stress that there exist modes that do not satisfy the WKB condition during the shear-dominated regime and for which the amplitude at the end of inflation depends on unknown initial conditions. On such scales, inflation loses its predictability. This study paves the way for the determination of the cosmological signature of a primordial shear, whatever the Bianchi I spacetime. It thus stresses the importance of the WKB regime to draw inflationary predictions and demonstrates that, when the number of e-folds is large enough, the predictions converge toward those of inflation in a Friedmann-Lemaitre spacetime but that they are less robust in the case of an inflationary era with a small number of e-folds.
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Para avaliar, in virtro, uma metodologia que visa a reprodutividade de radiografias periapicais, obtidas com posicionadores individualizados através de registros oclusais, de incisivos centrais superiores, submetidos à movimentação ortodôntica simulada - através da obtenção de medidas lineares do comprimento dos dentes, da comparação visual de imagens observadas lado a, nomonitor; e da subtração radiogrráfica digital qualitativa ded imagens - foram utilizados 29 dentes incisivos centrais extraídos de humanos. Os dentes foram radiografados em um simulador de tecidos ósseo e moles, em diferentes inclinações no sentido vestíbulo-palatino (0º incial, 0º contrle, -10º, -5º, +5º e 10º). As radiografias foram digitalizadas e submetidas, inicialmente, à análise quantitativa do comprimento dentário, através de régua eletrônica. Posteriormente, pares de imagens domesmo dente (inicial X inclinação) foram exibidos a um observador, que as avaliou quanto apresença ou ausência de imagem compatível com reabsorção apical, atribuindo-lhes escores de 1 a 5. As imagens resultantes da subtração dos mesmos pares de radiografias foram avaliadas pelos mesmos critérios. As medidas lineares de copmprimento dentário foram reprodutíveis (r=0,99) tanto na repetição das avaliações quanto na comparação entre as imagens 0º incial e 0º controle, não diferindo significativamente (ANOVA, p+ 0,827) nas radiografias com diferentes angulações. A avaliação por subtração digital de imagens apresentou boa correlação (r=0,798) quando repetida em 20% da amostrra, não diferindo, signitivamente (Teste não paramétrico dee Friedmann, p = 0,379), em relação aos escores atribuídos às imagens provenientes de diferentes angulações. A avaliação de pares de imagens apresentou em média correlação (r=0,413) quando repetida em 20% da amostra, porém também não apresentou diferenças estatisticamente significativas (Teste não paramétrico de Friedman, p=0,700) nos escores atribuídos às imagens de acordo com a inclinação os dentes. Tais resultados permitem concluir que a metodologia proposta para a obtenção, in vitro, de radiografias periapicais de incisivos superiores, através do uso de um posicionador individualizado por registro oclusal, resultou em imagens reprodutíveis de comprimento dentário, mesmo quando a movimentação ortodôntica foi simulada através da inclinação do dente em até 20% nos sentido vestibulo-palatino, quando avaliadas através das medidas de comprimento dentário e da subtração digital.
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Este trabalho aborda o tema Análise de Preferência (Conjoint Analysis). É uma metodologia para mensuração da preferência dos consumidores por determinado produto ou serviço. O conhecimento da preferência dos consumidores auxilia as empresas a otimizar seus produtos ou serviços buscando vantagens competitivas. Inicialmente foram analisadas as etapas que compõem um estudo de Análise de Preferência. A seguir foi realizado uma pesquisa de Análise de Preferência em uma situação real onde foi avaliada a preferência dos consumidores por Cursos de Especialização.
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Identifica-se a gestão por processos como uma abordagem eficaz para alavancar os resultados da organização. Para que isso possa ocorrer porem é necessário modificar os processos de negócio existentes. Pessoas são o único elemento comum na gestão por processos e na mudança. Para realizar os benefícios pretendidos, a ação organizacional deve focalizar seus esforços na consecução do apoio das pessoas. A revisão bibliográfica identificou mais de uma centena de fatores de influência na mudança. Esses fatores foram classificados em 4 grupos, a saber: características do indivíduo – Tipo 1, características do indivíduo – Tipo 2, características da organização e fatores de influência. Somente os identificados como fatores de influência exercem um impacto direto sobre o indivíduo. Estes fatores foram reclassificados nos 15 atributos utilizados para realizar o estudo empírico. O primeiro estudo, qualitativo, selecionou dos 15 fatores de influência no indivíduo para a mudança, os 10 mais importantes. Com esses 10 fatores, foi realizada uma pesquisa quantitativa pela internet visando identificar a importância relativa destes. Foram utilizados dois métodos para estimar a importância de cada fator para cada respondente que participou do estudo: Adaptive Conjoint Analysis (ACA) e Ordenação. Utilizando-se o método estatístico Analise de Agrupamento, foram formados, por semelhança, de 2 a 10 grupos com as importâncias relativas resultantes. Esses agrupamentos foram posteriormente confrontados com as variáveis de controle e com o fato da mudança avaliada, ter sido ou não gerada por uma demanda de tecnologia da informação (TI). Nos grupos formados pelo método ACA, há indícios de que as variáveis de controle e o fator gerador da mudança impactam o comportamento dos indivíduos. Nos grupos formados pelo método ordenação, os indícios revelam que não há impacto nem das variáveis de controle (salvo poucas exceções), nem do fator gerador da mudança. No teste não paramétrico de Friedman e nas comparações múltiplas de Dunn-Bonferroni utilizados para priorizar as importâncias calculadas no método ACA, foram encontrados dois grupos distintos. Pelo método de ordenamento, o resultado da amostra mostrou três grupos com priorização distinta dos atributos.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
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Recent astronomical observations (involving supernovae type Ia, cosmic background radiation anisotropy and galaxy clusters probes) have provided strong evidence that the observed universe is described by an accelerating, flat model whose space-time properties can be represented by the FriedmannRobertsonWalker (FRW) metric. However, the nature of the substance or mechanism behind the current cosmic acceleration remains unknown and its determination constitutes a challenging problem for modern cosmology. In the general relativistic description, an accelerat ing regime is usually obtained by assuming the existence of an exotic energy component endowed with negative pressure, called dark energy, which is usually represented by a cosmological constant ¤ associated to the vacuum energy density. All observational data available so far are in good agreement with the concordance cosmic ¤CDM model. Nevertheless, such models are plagued with several problems thereby inspiring many authors to propose alternative candidates in the relativistic context. In this thesis, a new kind of accelerating flat model with no dark energy and fully dominated by cold dark matter (CDM) is proposed. The number of CDM particles is not conserved and the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational particle creation. In order to have a transition from a decelerating to an accelerating regime at low redshifts, the matter creation rate proposed here depends on 2 parameters (y and ߯): the first one identifies a constant term of the order of H0 and the second one describes a time variation proportional to he Hubble parameter H(t). In this scenario, H0 does not need to be small in order to solve the age problem and the transition happens even if there is no matter creation during the radiation and part of the matter dominated phase (when the ß term is negligible). Like in flat ACDM scenarios, the dimming of distant type Ia supernovae can be fitted with just one free parameter, and the coincidence problem plaguing the models driven by the cosmological constant. ACDM is absent. The limits endowed with with the existence of the quasar APM 08279+5255, located at z = 3:91 and with an estimated ages between 2 and 3 Gyr are also investigated. In the simplest case (ß = 0), the model is compatible with the existence of the quasar for y > 0:56 whether the age of the quasar is 2.0 Gyr. For 3 Gyr the limit derived is y > 0:72. New limits for the formation redshift of the quasar are also established
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In this work we obtain the cosmological solutions and investigate the thermodynamics of matter creation in two diferent contexts. In the first we propose a cosmological model with a time varying speed of light c. We consider two diferent time dependence of c for a at Friedmann-Robertson- Walker (FRW) universe. We write the energy conservation law arising from Einstein equations and study how particles are created as c decreases with cosmic epoch. The variation of c is coupled to a cosmological Λ term and both singular and non-singular solutions are possible. We calculate the "adiabatic" particle creation rate and the total number of particles as a function of time and find the constrains imposed by the second law of thermodynamics upon the models. In the second scenario, we study the nonlinearity of the electrodynamics as a source of matter creation in the cosmological models with at FRW geometry. We write the energy conservation law arising from Einstein field equations with cosmological term Λ, solve the field equations and study how particles are created as the magnetic field B changes with cosmic epoch. We obtain solutions for the adiabatic particle creation rate, the total number of particles and the scale factor as a function of time in three cases: Λ = 0, Λ = constant and Λ α H2 (cosmological term proportional to the Hubble parameter). In all cases, the second law of thermodynamics demands that the universe is not contracting (H ≥ 0). The first two solutions are non-singular and exhibit in ationary periods. The third case studied allows an always in ationary universe for a suficiently large cosmological term
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The present work investigates some consequences that arise from the use of a modifed lagrangean for the eletromagnetic feld in two diferent contexts: a spatially homogeneous and isotropic universe whose dynamics is driven by a magnetic feld plus a cosmological parameter A, and the problem of a static and charged point mass (charged black hole). In the cosmological case, three diferent general solutions were derived. The first, with a null cosmological parameter A, generalizes a particular solution obtained by Novello et al [gr-qc/9806076]. The second one admits a constant A and the third one allows A to be a time-dependent parameter that sustains a constant magnetic feld. The first two solutions are non-singular and exhibit in ationary periods. The third case studied shows an in ationary dynamics except for a short period of time. As for the problem of a charged point mass, the solutions of the Einstein-Maxwell equations are obtained and compared with the standard Reissner-Nordstrom solution. Contrary to what happens in the cosmological case, the physical singularity is not removed
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
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In this dissertation, after a brief review on the Einstein s General Relativity Theory and its application to the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological models, we present and discuss the alternative theories of gravity dubbed f(R) gravity. These theories come about when one substitute in the Einstein-Hilbert action the Ricci curvature R by some well behaved nonlinear function f(R). They provide an alternative way to explain the current cosmic acceleration with no need of invoking neither a dark energy component, nor the existence of extra spatial dimensions. In dealing with f(R) gravity, two different variational approaches may be followed, namely the metric and the Palatini formalisms, which lead to very different equations of motion. We briefly describe the metric formalism and then concentrate on the Palatini variational approach to the gravity action. We make a systematic and detailed derivation of the field equations for Palatini f(R) gravity, which generalize the Einsteins equations of General Relativity, and obtain also the generalized Friedmann equations, which can be used for cosmological tests. As an example, using recent compilations of type Ia Supernovae observations, we show how the f(R) = R − fi/Rn class of gravity theories explain the recent observed acceleration of the universe by placing reasonable constraints on the free parameters fi and n. We also examine the question as to whether Palatini f(R) gravity theories permit space-times in which causality, a fundamental issue in any physical theory [22], is violated. As is well known, in General Relativity there are solutions to the viii field equations that have causal anomalies in the form of closed time-like curves, the renowned Gödel model being the best known example of such a solution. Here we show that every perfect-fluid Gödel-type solution of Palatini f(R) gravity with density and pressure p that satisfy the weak energy condition + p 0 is necessarily isometric to the Gödel geometry, demonstrating, therefore, that these theories present causal anomalies in the form of closed time-like curves. This result extends a theorem on Gödel-type models to the framework of Palatini f(R) gravity theory. We derive an expression for a critical radius rc (beyond which causality is violated) for an arbitrary Palatini f(R) theory. The expression makes apparent that the violation of causality depends on the form of f(R) and on the matter content components. We concretely examine the Gödel-type perfect-fluid solutions in the f(R) = R−fi/Rn class of Palatini gravity theories, and show that for positive matter density and for fi and n in the range permitted by the observations, these theories do not admit the Gödel geometry as a perfect-fluid solution of its field equations. In this sense, f(R) gravity theory remedies the causal pathology in the form of closed timelike curves which is allowed in General Relativity. We also examine the violation of causality of Gödel-type by considering a single scalar field as the matter content. For this source, we show that Palatini f(R) gravity gives rise to a unique Gödeltype solution with no violation of causality. Finally, we show that by combining a perfect fluid plus a scalar field as sources of Gödel-type geometries, we obtain both solutions in the form of closed time-like curves, as well as solutions with no violation of causality
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)