Unsteady free convection flow over an infinite vertical porous plate due to the combined effects of thermal and mass diffusion, magnetic field and Hall currents

The unsteady free convection flow over an infinite vertical porous plate, which moves with time-dependent velocity in an ambient fluid, has been studied. The effects of the magnetic field and Hall current are included in the analysis. The buoyancy forces arise due to both the thermal and mass diffusion. The partial differential equations governing the flow have been solved numerically using both the implicit finite difference scheme and the difference-differential method. For the steady case, analytical solutions have also been obtained. The effect of time variation on the skin friction, heat transfer and mass transfer is very significant. Suction increases the skin friction coefficient in the primary flow, and also the Nusselt and Sherwood numbers, but the skin friction coefficient in the secondary flow is reduced. The effect of injection is opposite to that of suction. The buoyancy force, injection and the Hall parameter induce an overshoot in the velocity profiles in the primary flow which changes the velocity gradient from a negative to a positive value, but the magnetic field and suction reduce this velocity overshoot.

Microscopic study of the 2/5 fractional quantum Hall edge

This paper reports on our study of the edge of the 2/5 fractional quantum Hall state, which is more complicated than the edge of the 1/3 state because of the presence of edge sectors corresponding to different partitions of composite fermions in the lowest two Lambda levels. The addition of an electron at the edge is a nonperturbative process and it is not a priori obvious in what manner the added electron distributes itself over these sectors. We show, from a microscopic calculation, that when an electron is added at the edge of the ground state in the [N(1), N(2)] sector, where N(1) and N(2) are the numbers of composite fermions in the lowest two Lambda levels, the resulting state lies in either [N(1) + 1, N(2)] or [N(1), N(2) + 1] sectors; adding an electron at the edge is thus equivalent to adding a composite fermion at the edge. The coupling to other sectors of the form [N(1) + 1 + k, N(2) - k], k integer, is negligible in the asymptotically low-energy limit. This study also allows a detailed comparison with the two-boson model of the 2/5 edge. We compute the spectral weights and find that while the individual spectral weights are complicated and nonuniversal, their sum is consistent with an effective two-boson description of the 2/5 edge.

Multiscaling in Hall-Magnetohydrodynamic Turbulence: Insights from a Shell Model

We show that a shell-model version of the three-dimensional Hall-magnetohydrodynamic (3D Hall-MHD) equations provides a natural theoretical model for investigating the multiscaling behaviors of velocity and magnetic structure functions. We carry out extensive numerical studies of this shell model, obtain the scaling exponents for its structure functions, in both the low-k and high-k power-law ranges of three-dimensional Hall-magnetohydrodynamic, and find that the extended-self-similarity procedure is helpful in extracting the multiscaling nature of structure functions in the high-k regime, which otherwise appears to display simple scaling. Our results shed light on intriguing solar-wind measurements.

Compensator Design for Closed Loop Hall-Effect Current Sensors

Closed loop current sensors used in power electronics applications are expected to have high bandwidth and minimal measurement transients. In this paper, a closed loop compensated Hall-effect current sensor is modeled. The model is used to tune the sensor's compensator. Analytical expression of step response is used to evaluate the performance of the PI compensator in the current sensor. This analysis is used to devise a procedure to design parameters of the PI compensator for fast dynamic response and for small dynamic error. A prototype current sensor is built in the laboratory. Simulations using the model are compared with experimental results to validate the model and to study the variation in performance with compensator parameters. The performance of the designed PI compensator for the sensor is compared with a commercial current sensor. The measured bandwidth of the designed current sensor is above 200 kHz, which is comparable to commercial standards. Implementation issues of PI compensator using operational amplifiers are also addressed.

Estimation of the Hall-Petch strengthening coefficient of steels through nanoindentation

A method to estimate the Hall-Petch coefficient k for yield strength and flow stress of steels through nanoindentation experiments is proposed. While determination of k(f) for flow stress is on the basis of grain boundary strengthening evaluated by sharp indentation, k(y) for yield strength was computed with pop-in data from spherical indentations. Good agreement between estimated and literature data, obtained from the tensile tests, validates the proposed methodology. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Hall viscosity to entropy ratio in higher derivative theories

In this paper based on the basic principles of gauge/gravity duality we compute the hall viscosity to entropy ratio in the presence of various higher derivative corrections to the dual gravitational description embedded in an asymptotically AdS(4) space time. As the first step of our analysis, considering the back reaction we impose higher derivative corrections to the abelian gauge sector of the theory where we notice that the ratio indeed gets corrected at the leading order in the coupling. Considering the probe limit as a special case we compute this leading order correction over the fixed background of the charged black brane solution. Finally we consider higher derivative (R-2) correction to the gravity sector of the theory where we notice that the above ratio might get corrected at the sixth derivative level.

Room-temperature bandlike transport and Hall effect in a high-mobility ambipolar polymer

The advent of a new class of high-mobility semiconducting polymers opens up a window to address fundamental issues in electrical transport mechanism such as transport between localized states versus extended state conduction. Here, we investigate the origin of the ultralow degree of disorder (E-a similar to 16 meV) and the ``bandlike'' negative temperature (T) coefficient of the field effect electron mobility: mu(e)(FET) (T) in a high performance (mu(e)(FET) > 2.5 cm(2) V-1 s(-1)) diketopyrrolopyrrole based semiconducting polymer. Models based on the framework of mobility edge with exponential density of states are invoked to explain the trends in transport. The temperature window over which the system demonstrates delocalized transport was tuned by a systematic introduction of disorder at the transport interface. Additionally, the Hall mobility (mu(e)(Hall)) extracted from Hall voltage measurements in these devices was found to be comparable to field effect mobility (mu(e)(FET)) in the high T bandlike regime. Comprehensive studies with different combinations of dielectrics and semiconductors demonstrate the effectiveness of rationale molecular design, which emphasizes uniform-energetic landscape and low reorganization energy.

Homogeneous isotropic superfluid turbulence in two dimensions: Inverse and forward cascades in the Hall-Vinen-Bekharevich-Khalatnikov model

We present the first direct-numerical-simulation study of the statistical properties of two-dimensional superfluid turbulence in the simplified, Hall-Vinen-Bekharevich-Khalatnikov two-fluid model. We show that both normalfluid and superfluid energy spectra can exhibit two power-law regimes, the first associated with an inverse cascade of energy and the second with the forward cascade of enstrophy. We quantify the mutual-friction-induced alignment of normal and superfluid velocities by obtaining probability distribution functions of the angle between them and the ratio of their moduli.

Intrinsic large gap quantum anomalous Hall insulators in LaX (X = Br,Cl,I)

We report a theoretical prediction of a new class of bulk and intrinsic quantum anomalous Hall (QAH) insulators LaX (X=Br, Cl, and I) via relativistic first-principles calculations. We find that these systems are innate long-ranged ferromagnets which, with the help of intrinsic spin-orbit coupling, become QAH insulators. A low-energy multiband tight-binding model is developed to understand the origin of the QAH effect. Finally, integer Chern number is obtained via Berry phase computation for each two-dimensional plane. These materials have the added benefit of a sizable band gap of as large as similar to 25 meV, with the flexibility of enhancing it to above 75 meV via strain engineering. The synthesis of LaX materials will provide the impurity-free single crystals and thin-film QAH insulators for versatile experiments and functionalities.

Apuntes en torno al pensamiento político de Joseph Ratzinger

Un ameno libro de circunstancia sobre la elección de Benedicto XVI, publicado apenas un mes después de esta, me servirá para iniciar mi exposición sobre la persona y labor de Joseph Ratzinger. Allí el autor, Alfredo Urdaci, ensaya una interesante tesis, ¿cómo fue posible tal elección? Porque si bien Ratzinger estaba entre los papables, no era muy probable que realmente fuera elegido. Tenía y –por qué no decirlo– sigue teniendo oposición dentro de la Curia y dentro de algunos sectores de la Iglesia. Y cómo no habría de levantarla un cardenal tan políticamente incorrecto como Ratzinger. No me detengo en sus distintas declaraciones a lo largo de su carrera, pero sí me gustaría presentar un par de frases suyas dichas tan solo días antes de su elección como Papa.

El problema de la razón moderna y el estado de derecho según Joseph Ratzinger

Resumen: El presente texto analiza dos cuestiones centrales en el pensamiento de Joseph Ratzinger: por un lado, el problema de la racionalidad del derecho y, en segundo lugar, el fundamento del Estado de Derecho en el mundo moderno. Para tal fin, previo diagnóstico sobre la situación jurídica contemporánea, se analizan ambos tópicos de acuerdo a los principales discursos realizados por el Cardenal Ratzinger y luego papa Benedicto XVI llegando a la conclusión de que el problema subyacente a ambos es el problema de la verdad tanto metafísica como moral.

A hall dynamo model for the reversed field pinch

A mechanism for the reversed field pinch (RFP) dynamo is proposed, based on the nonlinear Hall effect of a saturated helical MHD instability. The sign and magnitude of the effect are shown to be those required for the RFP dynamo. Predictions of the model are in accord with RFP fluctuation measurements.

Alvará com força de Ley, porque Vossa Magestade he servido prohibir, que se possam carregar, nem transportar escravos pretos de hum, e outro sexo dos pórtos da America, Africa, e Asia, para os destes Reinos de Portugal, e dos Algarves ; applicando as penas nelle declaradas a todos os que contravierem a dita Ley, passado o termo de seis mezes, a respeito dos primeiros, e segundos dos referidos pórtos, e hum anno a respeito dos terceiros : tudo na fórma que acima se contém : para V. Magestade ver / Joaquim Joseph Borralho o fez

Ao alto do título: Conde de Oeyras.

Voz sagrada, política, rhetorica, e metrica ou supplemento a's Vozes Saudosas da eloquencia do espirito, do zelo, e eminente sabedoria do Padre Antonio Vieira da Companhia de Jesus, pregador de S. Magestade, e príncipe dos oradores evangélicos : offerecida ao Senhor Doutor Joseph de Lima Pinheiro e Aragam

Padre Antônio Vieira nasceu em Lisboa em 6 de novembro de 1608 e morreu na Bahia em 18 de julho de 1697. Ordenado sacerdote em 1634, logo se destacou como excepcional pregador. Exerceu importante papel politico e diplomático durante o reinado de D. João IV e fez do púlpito uma tribuna a serviço da nação, em guerra com a Espanha. De 1652 a 1661 atuou como missionário no Maranhão. Em Portugal foi denunciado como herético ao Tribunal da Inquisição. Doente e encarcerado defendeu-se com extraordinário vigor, mas foi condenado a internamento numa casa jesuítica e proibido de pregar. Retirou-se em 1681 para o Brasil, onde trabalhou na edição completa dos Sermoens, iniciada em 1679. Voz sagrada... é um suplemento às Vozes saudosas. Foi publicado, após a morte do autor, por Francisco Luiz Ameno em 1748. Compõe-se de cartas, poemas e outros escritos em latim e português e uma oração fúnebre celebrada pelo Conde da Ericeira nas exéquias do Padre Vieira

Historia de Portugal restaurado, offerecida ao Illustmo e Excellentmo Senhor D. Joseph Mascarenhas, do Conselhor de sua Magestade, seu mordomo mór... : escrita por D. Luiz de Menezes, conde da Ericeira, do Conselho de Estado de Sua Magestade.

Luis de Menezes, terceiro Conde da Ericeira, nasceu em Lisboa em 1632 e suicidou-se em 1690. Foi chamado de Colbert português por ter estimulado a introdução das artes fabris e industriais em Portugal. Escreveu ‘Historia de Portugal restaurado offerecida ao Illustmo e Excellentmo Senhor D. Joseph Mascarenhas’ em duas partes: a primeira, em 1679 e a segunda, em 1698. A mesma historia obteve depois diversas reimpressões, a saber: Parte I, dividida nos tomos I e II, Lisboa, na Oficina de Domingos Rodrigues, em 1751; Parte II, dividida nos tomos III e IV, Lisboa, na Oficina dos herdeiros de Antonio Pedroso Galram, em 1751. Saiu uma terceira vez em Lisboa em 1759. Segundo Inocêncio, ‘compreende esta historia a narração de todos os sucessos militares e políticos ocorridos em Portugal, desde a restauração de 1640 até o ano de 1668, em que se celebraram as pazes com o reino de Castela’