Dispersion Relation of a Ferrofluid Layer of Any Thickness and Viscosity in a Normal Magnetic Field; Asymptotic Regimes

We have calculated the general dispersion relationship for surface waves on a ferrofluid layer of any thickness and viscosity, under the influence of a uniform vertical magnetic field. The amplification of these waves can induce an instability called peaks instability (Rosensweig instability). The expression of the dispersion relationship requires that the critical magnetic field and the critical wavenumber of the instability depend on the thickness of the ferrofluid layer. The dispersion relationship has been simplified into four asymptotic regimes: thick or thin layer and viscous or inertial behaviour. The corresponding critical values are presented. We show that a typical parameter of the ferrofluid enables one to know in which regime, viscous or inertial, the ferrofluid will be near the onset of instability.Comment: 21 pages, 6 eps figures, Latex, to be published in Journal de Physique I

Gestão Centrada No Ser Humano: O Caso de dois Coordenadores de Cursos de IES de Foz do Iguaçu

No artigo analisa-se a mudança de paradigma que ocorreu no gerenciamento a partir do desenvolvimento da teoria dos sistemas abertos. Caracteriza-se e analisa-se, também, de maneira comparativa o estilo tradicional de gerenciamento baseado no modelo Estratégia- Estrutura-Sistemas, orientado para tarefas com o estilo gerencial baseado no modelo Objetivos-Processos-Pessoas, orientado para pessoas. Descreve-se e analisa-se a evolução do conceito de organização na era industrial. Enfatiza-se a importância da compreensão de que se vive numa sociedade de organizações. Descreve-se a importância das organizações como mecanismo de crescimento econômico e de controle social. Finaliza-se o texto enfatizando a importância do ser humano para se atingir resultados organizacionais na chamada sociedade do conhecimento

A Temporal Map in Geostationary Orbit: The Cover Etching on the EchoStar XVI Artifact

Geostationary satellites are unique among orbital spacecraft in that they experience no appreciable atmospheric drag. After concluding their respective missions, geostationary spacecraft remain in orbit virtually in perpetuity. As such, they represent some of human civilization's longest lasting artifacts. With this in mind, the EchoStar XVI satellite, to be launched in fall 2012, will play host to a time capsule intended as a message for the deep future. Inspired in part by the Pioneer Plaque and Voyager Golden Records, the EchoStar XVI Artifact is a pair of gold-plated aluminum jackets housing a small silicon disc containing one hundred photographs. The Cover Etching, the subject of this paper, is etched onto one of the two jackets. It is a temporal map consisting of a star chart, pulsar timings, and other information describing the epoch from which EchoStar XVI came. The pulsar sample consists of 13 rapidly rotating objects, 5 of which are especially stable, having spin periods < 10 ms and extremely small spindown rates. In this paper, we discuss our approach to the time map etched onto the cover and the scientific data shown on it; and we speculate on the uses that future scientists may have for its data. The other portions of the EchoStar XVI Artifact will be discussed elsewhere.Comment: Accepted for publication in Astronomical Journa

Exomoon habitability constrained by energy flux and orbital stability

Detecting massive satellites of extrasolar planets has now become feasible, which led naturally to questions about their habitability. In a previous study we presented constraints on the habitability of moons from stellar and planetary illumination as well as from tidal heating. Here I refine our model by including the effect of eclipses on the orbit-averaged illumination. Moons in low-mass stellar systems must orbit their planet very closely to remain bound, which puts them at risk of strong tidal heating. I first describe the effect of eclipses on stellar illumination of satellites. Then I calculate the orbit-averaged energy flux including illumination from the planet and tidal heating. Habitability is defined by a scaling relation at which a moon loses its water by the runaway greenhouse process. As a working hypothesis, orbital stability is assumed if the moon's orbital period is less than 1/9 of the planet's orbital period. Due to eclipses, a satellite in a close orbit can experience a reduction in orbit-averaged stellar flux by up to about 6%. The smaller the semi-major axis and the lower the inclination of the moon's orbit, the stronger the reduction. I find a lower mass limit of ~0.2M_sun for exomoon host stars to avoid the runaway greenhouse effect. Precise estimates depend on the satellite's orbital eccentricity. Deleterious effects on exomoon habitability may occur up to ~0.5M_sun. Although the habitable zone lies close to low-mass stars, which allows for many transits of planet-moon binaries within a given observation cycle, resources should not be spent to trace habitable satellites around them. Gravitational perturbations by the star, another planet, or another satellite induce eccentricities that likely make any moon uninhabitable. Estimates for individual systems require dynamical simulations that include perturbations among all bodies and tidal heating in the satellite.Comment: 4 pages, 2 figures, accepted by A&

Aprendizagem Gerencial Construtivista: O Caso de Supervisão em Estágios Acadêmicos

Neste texto, procura-se especular teoricamente a possibilidade de criação de uma pedagogia gerencial ancorada nos fundamentos da pedagogia freireana. O norteamento do texto se dá no pressuposto de que a aprendizagem gerencial deve levar em conta toda a multidimensionalidade do ser humano. O gerente humanista deve ser capaz de complementar a sua aprendizagem formal no seu ambiente de prática por meio da ação e da reflexão. Acredita-se que a aprendizagem é um processo inacabado e infinito. Finaliza-se o ensaio com a convicção de que aprender é o ponto de partida e o ponto de chegada no processo de tornarse um ser humano mais humano e mais flexível

Improving Evacuation Maps by Integrating Needs and Preferences of End-Users in GIS

International audienceAn efficient communication requires knowing the characteristics of the receiver. Even if this rule of communication is the basis in many fields of applications (marketing, education, advertising …), it is still not operationnaly integrated into flood risk cartographic communication. This is surprising since cartographic software and Geographical Information Systems (GIS) have become inevitable in territorial management and engineering assessments and allow the mappers to produce target-oriented communication resources such as maps in an effective and efficient manner. In our contribution we will show how flood evacuation maps may be produced by integrating the needs with respect to stakeholder communication as well as the preferences of different end-users

Caracterizacion economica y productiva de planteles bovinos con sistema de ciclo completo adscritos al programa de carne natural Chile. Estudios de caso: XI y XIV regiones

77 p.El presente estudio realizó una caracterización económica y productiva de planteles bovinos con sistema productivo de ciclo completo adscritos al programa de certificación Programa de Carne Natural Chile, ubicados en las regiones: XI y XIV. El estudio tuvo un carácter exploratorio descriptivo, utilizando medidas de tendencia central y de dispersión. Inicialmente se realizó un análisis descriptivo de los planteles bovinos de manera individual como también de manera conjunta. Enseguida se determinó y analizó los tipos de costos más relevantes y representativos de dichos planteles, para posteriormente, junto con la estimación de los ingresos generados por venta de animal, estimar un margen bruto asociado a cada plantel. A través de lo anterior, se demostró que la carne natural representa una oportunidad para la exportación de carne bovina de mayor valor, enfocándose en la diferenciación del producto por su calidad, en cantidad suficiente para abordar los requerimientos de los mercados más exigentes, incluyendo el nacional. Los planteles adscritos al Programa de Carne Natural Chile mostraron precios de venta superiores que en el mercado local (feria). Sus costos de producción parecieron no ser diferentes a los que presentan los sistemas ganaderos convencionales, por lo que la implementación del Programa de Carne Natural Chile en los planteles bovinos, involucra un sistema de gestión guiado a partir de un protocolo de producción establecido y no necesariamente representa un aumento en los costos de producción en los sistemas ganaderos. Lo anterior justifica la implementación del programa, a pesar de que en la actualidad su adopción en planteles bovinos es limitada./ SUMMARY: This research carried out an economic and productive characterization of bovine institutions with a complete productive cycle associated with the Certification of the Chile Natural Meat Programme located in XI and XIV Regions. This research in an exploratory descriptive one using both mean and dispersion measures. Initially, a descriptive analysis of the bovine institutions both individually and collectively was carried out. Then, the most relevant and representative costs were determined and analyzed, along with an estimate of the incomes generated by the sales of animals so as to be able to estimate a gross margin associated to each institution. Taking into account what is presented above, it was determined that natural meat represents an opportunity for the export of higher value beef, focusing on the differentiation of the product, based on its quality, in sufficient quantity to meet the requirements of the most demanding markets, including the local one. The institutions associated with the Chilean Natural Meat Programme proved to have a very similar feeding system, where meadows represent the staple food for the animals. The gross margins calculated for each institution showed highly profitable values, due mainly to low production costs. The estimated structure of cost, does not seem to have significant differences from that already existing in conventional livestock systems. Therefore, implementing the Chilean Natural Meat Programme in bovine institutions involves a management system based on a previously established production protocol and does not necessarily represents an increase in production costs of the livestock systems. All the above justifies implementing the programme, despite the fact that, at present, its adoption in bovine institutions is very low

Benchmark instance indicators and computational comparison of methods

chapter 7This chapter is devoted to extensive computational experiments on the resource-constrained project scheduling problem. Its objective is twofold. First, a selection of representative exact and heuristic methods among the ones presented in the previous chapters are tested and compared under a common experimental framework on four different instance sets. Second, classical and new instance difficulty indicators are evaluated through the experiments and their discriminating power is discussed

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating

Traditionally stellar radiation has been the only heat source considered capable of determining global climate on long timescales. Here we show that terrestrial exoplanets orbiting low-mass stars may be tidally heated at high enough levels to induce a runaway greenhouse for a long enough duration for all the hydrogen to escape. Without hydrogen, the planet no longer has water and cannot support life. We call these planets "Tidal Venuses," and the phenomenon a "tidal greenhouse." Tidal effects also circularize the orbit, which decreases tidal heating. Hence, some planets may form with large eccentricity, with its accompanying large tidal heating, and lose their water, but eventually settle into nearly circular orbits (i.e. with negligible tidal heating) in the habitable zone (HZ). However, these planets are not habitable as past tidal heating desiccated them, and hence should not be ranked highly for detailed follow-up observations aimed at detecting biosignatures. Planets orbiting stars with masses <0.3 solar masses may be in danger of desiccation via tidal heating. We apply these concepts to Gl 667C c, a ~4.5 Earth-mass planet orbiting a 0.3 solar mass star at 0.12 AU. We find that it probably did not lose its water via tidal heating as orbital stability is unlikely for the high eccentricities required for the tidal greenhouse. As the inner edge of the HZ is defined by the onset of a runaway or moist greenhouse powered by radiation, our results represent a fundamental revision to the HZ for non-circular orbits. In the appendices we review a) the moist and runaway greenhouses, b) hydrogen escape, c) stellar mass-radius and mass-luminosity relations, d) terrestrial planet mass-radius relations, and e) linear tidal theories. [abridged]Comment: 59 pages, 11 figures, accepted to Astrobiology. New version includes an appendix on the water loss timescal

Oscillations in the Habitable Zone around Alpha Centauri B

The Alpha Centauri AB system is an attractive one for radial velocity observations to detect potential exoplanets. The high metallicity of both Alpha Centauri A and B suggest that they could have possessed circumstellar discs capable of forming planets. As the closest star system to the Sun, with well over a century of accurate astrometric measurements (and Alpha Centauri B exhibiting low chromospheric activity) high precision surveys of Alpha Centauri B's potential exoplanetary system are possible with relatively cheap instrumentation. Authors studying habitability in this system typically adopt habitable zones (HZs) based on global radiative balance models that neglect the radiative perturbations of Alpha Centauri A. We investigate the habitability of planets around Alpha Centauri B using 1D latitudinal energy balance models (LEBMs), which fully incorporate the presence of Alpha Centauri A as a means of astronomically forcing terrestrial planet climates. We find that the extent of the HZ is relatively unchanged by the presence of Alpha Centauri A, but there are variations in fractional habitability for planets orbiting at the boundaries of the zone due to Alpha Centauri A, even in the case of zero eccentricity. Temperature oscillations of a few K can be observed at all planetary orbits, the strength of which varies with the planet's ocean fraction and obliquity.Comment: 10 pages, 9 figures, accepted for publication in MNRA