963 resultados para Regime
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エジプトではムバーラク大統領の国内政策と域内におけるエジプトの影響力低迷が引き金となって、2011年1月25日に抗議運動起こった。抗議運動はエジプト全土に拡がり、18日間の民衆的な反体制運動によってムバーラクは軍に見捨てられ、失脚に追い込まれた。この民衆蜂起によって警察は街頭から撤退し、シナイ半島の警察署は焼き放たれ、ムバーラクが率いていた国民民主党の建物や国内治安機関の本部は襲撃され、国家機関が数ヶ月にもわたって機能不全となり、ムバーラク体制の崩壊は国内的な混乱を招くこととなった。振り返れば、エジプトでの政治的大変動は社会的な革命へと展開することはできなかった。その理由は独裁体制からの移行を先導できる組織化された反体制勢力が存在しなかったためである。民衆による抗議運動は一時的に体制を転覆できても旧体制のエリートを分裂させることはできず、軍の影響下にある体制の復活を防ぐこともできなかった。2011年以降のエジプトは現在まで混乱状態に陥ったままであるが、1カ月に及ぶエジプト軍最高評議会(SCAF)の暫定統治、エジプト史上初の自由な大統領選挙によって選出された文民大統領のムルスィーによる一年余りの統治、そして2013年7月の軍事クーデターによって権力の座に就いたスィースィーの統治といった過程で、民衆蜂起がエジプトの外交関係に及ぼした影響はごく僅かであった。本稿は、現在のエジプトの外交政策が2011年の革命にほとんど影響を受けていないのはなぜか、またエジプトの統治者たちが政権の正統性、体制の強化および政治的な安定性を確保し、国内的な課題に対処するための戦略をいかに策定しているのかを説明することを試みる。本稿での主張は、ムバーラク以降のエジプトが体制の強化と保全のために外交政策を進めており、国内的な混乱によって地域内アクターへの依存度が高まっていることである。
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An earlier analysis of the Hall-magnetohydrodynamics (MHD) tearing instability [E. Ahedo and J. J. Ramos, Plasma Phys. Controlled Fusion 51, 055018 (2009)] is extended to cover the regime where the growth rate becomes comparable or exceeds the sound frequency. Like in the previous subsonic work, a resistive, two-fluid Hall-MHD model with massless electrons and zero-Larmor-radius ions is adopted and a linear stability analysis about a force-free equilibrium in slab geometry is carried out. A salient feature of this supersonic regime is that the mode eigenfunctions become intrinsically complex, but the growth rate remains purely real. Even more interestingly, the dispersion relation remains of the same form as in the subsonic regime for any value of the instability Mach number, provided only that the ion skin depth is sufficiently small for the mode ion inertial layer width to be smaller than the macroscopic lengths, a generous bound that scales like a positive power of the Lundquist number
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The one-dimensional self-similar motion of an initially cold, half-space plasma of electron density 0,produced by the (anomalous) absorption of a laser pulse of irradiation
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Thermal smoothing in the plasma ablated from a laser target under weakly nonuniform irradiation is analyzed, assuming absorption at nc and a deflagration regime (conduction restricted to a thin quasisteady layer next to the target). Magnetic generation effects are included and found to be weak. Differences from results available in the literature are explained; the importance of the character of the underdense flow at uniform irradiation is emphasized.
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Refractive smoothing of weak non-uniformities in the illumination of laser targets is analyzed, assuming absorption at the critical density and restricting conduction to a thin layer, and using results from thermal smoothing, which is uncoupled from the refraction. Magnetic effects are included. Non-uniformity wavelengths comparable to the thickness of the conduction layer are considered; efficient smoothing exists at both short and long wavelengths in this range. Thermal focusing could make the ablated plasma unstable.
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An asymptotic analysis of electron collection at high bias Fp serves to determine the domain of validity of the orbital-motion-limited regime of cylindrical Langmuir probes, which is basic for the workings of conductive bare tethers. The radius of a wire collecting OML current in an unmagnetized plasma at rest cannot exceed a value, Rmax , which is found to exhibit a minimum as a function of Fp ; atFp values of interest, Rmax is already increasing and is larger than the electron Debye length lDe . The breakdown of the regime relates to conditions far fromthe probe, at electron energies comparable to the ion thermal energy, kTi ; Rmax is found to increase with Ti . It is also found that ~1! the maximumwidth of a thin tape, if used instead of a wire, is 4Rmax ; ~2! the electron thermal gyroradius must be larger than both R and lDe for magnetic effects to be negligible; and ~3! conditions applying to the tether case are such that trapped-orbit effects are negligible.
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The current I to a cylindrical probe at rest in an unmagnetized plasma, with probe bias highly positive, is determined. The way I lags behind the orbital-motion-limited OMLcurrent, 1 OML R, as the radius R exceeds the maximum radius for the OML regime to hold, is of interest for space-tether applications. The ratio I/I OML is roughly a decreasing function of R/lD R max /lDe , which is independent of bias, with lDe the electron Debye length and Rmax /l De roughly an increasing function of the temperature ratio, Ti /Te. The dependence of current on ion energy is used to discuss the effect of probe motion through the plasma, a case applying to tethers in low orbit.
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In this work the spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated for a wide range of plasma conditions which cover situations where corona, local thermodynamic and non-local thermodynamic equilibrium regimes are found. An analysis of the influence of the thermodynamic regime on these magnitudes is also carried out by means of comparisons of the results obtained from collisional-radiative, corona or Saha–Boltzmann equations. All the calculations presented in this work were performed using ABAKO/RAPCAL code.
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The determination of the plasma potential Vpl of unmagnetized plasmas by using the floating potential of emissive Langmuir probes operated in the strong emission regime is investigated. The experiments evidence that, for most cases, the electron thermionic emission is orders of magnitude larger than the plasma thermal electron current. The temperature-dependent floating potentials of negatively biased Vpmenor queVpl emissive probes are in agreement with the predictions of a simple phenomenological model that considers, in addition to the plasma electrons, an ad-ditional electron group that contributes to the probe current. The latter would be constituted by a fraction of the repelled electron thermionic current, which might return back to the probe with a different energy spectrum. Its origin would be a plasma potential well formed in the plasma sheath around the probe, acting as a virtual cathode or by collisions and electron thermalization pro-cesses. These results suggest that, for probe bias voltages close to the plasma potential Vp?Vpl, two electron populations coexist, i.e., the electrons from the plasma with temperatureTeand a large group of returned thermionic electrons. These results question the theoretical possibility of measuring the electron temperature by using emissive probes biased to potentials Vp about lower equal than ?Vpl.
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One key issue in the simulation of bare electrodynamic tethers (EDTs) is the accurate and fast computation of the collected current, an ambient dependent operation necessary to determine the Lorentz force for each time step. This paper introduces a novel semianalytical solution that allows researchers to compute the current distribution along the tether efficient and effectively under orbital-motion-limited (OML) and beyond OML conditions, i.e., if tether radius is greater than a certain ambient dependent threshold. The method reduces the original boundary value problem to a couple of nonlinear equations. If certain dimensionless variables are used, the beyond OML effect just makes the tether characteristic length L ∗ larger and it is decoupled from the current determination problem. A validation of the results and a comparison of the performance in terms of the time consumed is provided, with respect to a previous ad hoc solution and a conventional shooting method.
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La gestión de los recursos hídricos se convierte en un reto del presente y del futuro frente a un panorama de continuo incremento de la demanda de agua debido al crecimiento de la población, el crecimiento del desarrollo económico y los posibles efectos del calentamiento global. La política hidráulica desde los años 60 en España se ha centrado en la construcción de infraestructuras que han producido graves alteraciones en el régimen natural de los ríos. Estas alteraciones han provocado y acrecentado los impactos sobre los ecosistemas fluviales y ribereños. Desde los años 90, sin embargo, ha aumentado el interés de la sociedad para conservar estos ecosistemas. El concepto de caudales ambientales consiste en un régimen de caudales que simula las características principales del régimen natural. Los caudales ambientales están diseñados para conservar la estructura y funcionalidad de los ecosistemas asociados al régimen fluvial, bajo la hipótesis de que los elementos que conforman estos ecosistemas están profundamente adaptados al régimen natural de caudales, y que cualquier alteración del régimen natural puede provocar graves daños a todo el sistema. El método ELOHA (Ecological Limits of Hydrological Alteration) tiene como finalidad identificar las componentes del régimen natural de caudales que son clave para mantener el equilibrio de los ecosistemas asociados, y estimar los límites máximos de alteración de estas componentes para garantizar su buen estado. Esta tesis presenta la aplicación del método ELOHA en la cuenca del Ebro. La cuenca del Ebro está profundamente regulada e intervenida por el hombre, y sólo las cabeceras de los principales afluentes del Ebro gozan todavía de un régimen total o cuasi natural. La tesis se estructura en seis capítulos que desarrollan las diferentes partes del método. El primer capítulo explica cómo se originó el concepto “caudales ambientales” y en qué consiste el método ELOHA. El segundo capítulo describe el área de estudio. El tercer capítulo realiza una clasificación de los regímenes naturales de la cuenca (RNC) del Ebro, basada en series de datos de caudal mínimamente alterado y usando exclusivamente parámetros hidrológicos. Se identificaron seis tipos diferentes de régimen natural: pluvial mediterráneo, nivo-pluvial, pluvial mediterréaneo con una fuerte componente del caudal base, pluvial oceánico, pluvio-nival oceánico y Mediterráneo. En el cuarto capítulo se realiza una regionalización a toda la cuenca del Ebro de los seis RNC encontrados en la cueca. Mediante parámetros climáticos y fisiográficos se extrapola la información del tipo de RNC a puntos donde no existen datos de caudal inalterado. El patrón geográfico de los tipos de régimen fluvial obtenido con la regionalización resultó ser coincidente con el patrón obtenido a través de la clasificación hidrológica. El quinto capítulo presenta la validación biológica de los procesos de clasificación anteriores: clasificación hidrológica y regionalización. La validación biológica de los tipos de regímenes fluviales es imprescindible, puesto que los diferentes tipos de régimen fluvial van a servir de unidades de gestión para favorecer el mantenimiento de los ecosistemas fluviales. Se encontraron diferencias significativas entre comunidades biológicas en cinco de los seis tipos de RNC encontrados en la cuenca. Finalmente, en el sexto capítulo se estudian las relaciones hidro-ecológicas existentes en tres de los seis tipos de régimen fluvial encontrados en la cuenca del Ebro. Mediante la construcción de curvas hidro-ecológicas a lo largo de un gradiente de alteración hidrológica, se pueden sugerir los límites de alteración hidrológica (ELOHAs) para garantizar el buen estado ecológico en cada uno de los tipos fluviales estudiados. Se establecieron ELOHAs en tres de los seis tipos de RNC de la cuenca del Ebro Esta tesis, además, pone en evidencia la falta de datos biológicos asociados a registros de caudal. Para llevar a cabo la implantación de un régimen de caudales ambientales en la cuenca, la ubicación de los puntos de muestreo biológico cercanos a estaciones de aforo es imprescindible para poder extraer relaciones causa-efecto de la gestión hidrológica sobre los ecosistemas dependientes. ABSTRACT In view of a growing freshwater demand because of population raising, improvement of economies and the potential effects of climate change, water resources management has become a challenge for present and future societies. Water policies in Spain have been focused from the 60’s on constructing hydraulic infrastructures, in order to dampen flow variability and granting water availability along the year. Consequently, natural flow regimes have been deeply altered and so the depending habitats and its ecosystems. However, an increasing acknowledgment of societies for preserving healthy freshwater ecosystems started in the 90’s and agreed that to maintain healthy freshwater ecosystems, it was necessary to set environmental flow regimes based on the natural flow variability. The Natural Flow Regime paradigm (Richter et al. 1996, Poff et al. 1997) bases on the hypothesis that freshwater ecosystems are made up by elements adapted to natural flow conditions, and any change on these conditions can provoke deep impacts on the whole system. Environmental flow regime concept consists in designing a flow regime that emulates natural flow characteristics, so that ecosystem structure, functions and services are maintained. ELOHA framework (Ecological Limits of Hydrological Alteration) aims to identify key features of the natural flow regime (NFR) that are needed to maintain and preserve healthy freshwater and riparian ecosystems. Moreover, ELOHA framework aims to quantify thresholds of alteration of these flow features according to ecological impacts. This thesis describes the application of the ELOHA framework in the Ebro River Basin. The Ebro River basin is the second largest basin in Spain and it is highly regulated for human demands. Only the Ebro headwaters tributaries still have completely unimpaired flow regime. The thesis has six chapters and the process is described step by step. The first chapter makes an introduction to the origin of the environmental flow concept and the necessity to come up. The second chapter shows a description of the study area. The third chapter develops a classification of NFRs in the basin based on natural flow data and using exclusively hydrological parameters. Six NFRs were found in the basin: continental Mediterranean-pluvial, nivo-pluvial, continental Mediterranean pluvial (with groundwater-dominated flow pattern), pluvio-oceanic, pluvio-nival-oceanic and Mediterranean. The fourth chapter develops a regionalization of the six NFR types across the basin by using climatic and physiographic variables. The geographical pattern obtained from the regionalization process was consistent with the pattern obtained with the hydrologic classification. The fifth chapter performs a biological validation of both classifications, obtained from the hydrologic classification and the posterior extrapolation. When the aim of flow classification is managing water resources according to ecosystem requirements, a validation based on biological data is compulsory. We found significant differences in reference macroinvertebrate communities between five over the six NFR types identified in the Ebro River basin. Finally, in the sixth chapter we explored the existence of significant and explicative flow alteration-ecological response relationships (FA-E curves) within NFR types in the Ebro River basin. The aim of these curves is to find out thresholds of hydrological alteration (ELOHAs), in order to preserve healthy freshwater ecosystem. We set ELOHA values in three NFR types identified in the Ebro River basin. During the development of this thesis, an inadequate biological monitoring in the Ebro River basin was identified. The design and establishment of appropriate monitoring arrangements is a critical final step in the assessment and implementation of environmental flows. Cause-effect relationships between hydrology and macroinvertebrate community condition are the principal data that sustain FA-E curves. Therefore, both data sites must be closely located, so that the effects of external factors are minimized. The scarce hydro-biological pairs of data available in the basin prevented us to apply the ELOHA method at all NFR types.
Resumo:
Este estudo qualitativo foi elaborado por meio de pesquisa bibliográfica de estudiosos do tema da avaliação do rendimento de alunos, como Luckesi (2005), Hoffmann (2003), Paro (2003), Hadji (1994) e Figari (1996), e de pesquisa de campo, com o objetivo de investigar como está ocorrendo a avaliação do ensino fundamental da rede pública paulista, na vigência do regime de progressão continuada. Considerando que os fundamentos da prática avaliativa distam quase sempre dos apregoados pela política educacional instituída e com o propósito de verificar se isto está ocorrendo com a política de progressão continuada, participei, durante um ano letivo, das atividades educacionais de uma escola pública da periferia da Grande São Paulo, observando, colhendo depoimentos e anotando cuidadosamente tudo o que vivenciei nesse período. Para empreender uma leitura dos dados coletados, busquei também o apoio no construto teórico de Michel de Certeau, para quem aos "produtos impostos" códigos, leis, políticas culturais, etc. rigorosamente organizados de forma a atribuir um lugar, um papel ao homem ordinário, contrapõem-se práticas construídas no processo de apropriação desses produtos. Por meio de suas "artes de fazer", os usuários reinventam o cotidiano. Utilizando-se de "táticas astuciosas", o usuário da cultura reapropria-se dos espaços, altera-lhes os códigos e deles faz uso "a seu jeito". Nesta pesquisa, que enfoca as relações dos protagonistas de processos avaliativos escolares, confirmam-se os postulados de Certeau, que não conferem ao consumidor da política um lugar passivo. Como já foi caracterizado por este instigante pensador, o usuário da política (o instituinte), enquanto portador de astúcias, move-se no campo espacial do outro (o instituído) e, taticamente, fazendo uso de práticas não previstas, escreve uma "outra história". O principal objetivo deste trabalho foi contribuir com reflexões que mostrem a importância de se analisar as tensões geradas por políticas educacionais impostas, desprovidas de sentido para aqueles que não participam de sua elaboração, o que tem provocado movimentos táticos de seus usuários, neste caso, os docentes, os quais, sem as condições objetivas necessárias para promover a política instituída, enunciada no discurso, utilizam-se do seu potencial instituinte de transformação, escrevendo uma "outra história".
Resumo:
Este estudo qualitativo foi elaborado por meio de pesquisa bibliográfica de estudiosos do tema da avaliação do rendimento de alunos, como Luckesi (2005), Hoffmann (2003), Paro (2003), Hadji (1994) e Figari (1996), e de pesquisa de campo, com o objetivo de investigar como está ocorrendo a avaliação do ensino fundamental da rede pública paulista, na vigência do regime de progressão continuada. Considerando que os fundamentos da prática avaliativa distam quase sempre dos apregoados pela política educacional instituída e com o propósito de verificar se isto está ocorrendo com a política de progressão continuada, participei, durante um ano letivo, das atividades educacionais de uma escola pública da periferia da Grande São Paulo, observando, colhendo depoimentos e anotando cuidadosamente tudo o que vivenciei nesse período. Para empreender uma leitura dos dados coletados, busquei também o apoio no construto teórico de Michel de Certeau, para quem aos "produtos impostos" códigos, leis, políticas culturais, etc. rigorosamente organizados de forma a atribuir um lugar, um papel ao homem ordinário, contrapõem-se práticas construídas no processo de apropriação desses produtos. Por meio de suas "artes de fazer", os usuários reinventam o cotidiano. Utilizando-se de "táticas astuciosas", o usuário da cultura reapropria-se dos espaços, altera-lhes os códigos e deles faz uso "a seu jeito". Nesta pesquisa, que enfoca as relações dos protagonistas de processos avaliativos escolares, confirmam-se os postulados de Certeau, que não conferem ao consumidor da política um lugar passivo. Como já foi caracterizado por este instigante pensador, o usuário da política (o instituinte), enquanto portador de astúcias, move-se no campo espacial do outro (o instituído) e, taticamente, fazendo uso de práticas não previstas, escreve uma "outra história". O principal objetivo deste trabalho foi contribuir com reflexões que mostrem a importância de se analisar as tensões geradas por políticas educacionais impostas, desprovidas de sentido para aqueles que não participam de sua elaboração, o que tem provocado movimentos táticos de seus usuários, neste caso, os docentes, os quais, sem as condições objetivas necessárias para promover a política instituída, enunciada no discurso, utilizam-se do seu potencial instituinte de transformação, escrevendo uma "outra história".