3,385 research outputs found
Thou Shalt is not You Will
In this paper we discuss some reasons why temporal logic might not be
suitable to model real life norms. To show this, we present a novel deontic
logic contrary-to-duty/derived permission paradox based on the interaction of
obligations, permissions and contrary-to-duty obligations. The paradox is
inspired by real life norms
Susceptibilidade à Erosão Hídrica na Bacia da Ribeira Seca (Santiago, Cabo Verde)
Na Ilha de Santiago, em Cabo Verde, a erosão hídrica é o processo que afecta áreas
mais extensas. A ocorrência de aguaceiros intensos e concentrados no tempo e no espaço
promovem uma marcada erosividade das precipitações, com forte irregularidade regional. A
grande variabilidade dos declives e das formas das vertentes, associadas à diversidade
litológica, bem como à multiplicidade de ocupação do solo, permitem condições de
erodibilidade muito contrastadas no espaço.
O objectivo deste trabalho é obter um mapa de susceptibilidade à erosão hídrica para a bacia
da Ribeira Seca (Santiago oriental) com base no modelo digital do terreno (MDT), nos mapas
geológico e de ocupação do solo e na distribuição da erosividade das precipitações.
Verifica-se que o sector sudeste da bacia é o mais susceptível à erosão hídrica, pois nele
ocorrem a maior concentração diária das precipitações e as condições geomorfológicas e de
coberto do solo de mais elevada erodibilidade.In Santiago Island, Cape Verde, the hidric erosion is the most widespread process. The
rainfall events are high concentred and intense promoting strong precipitation erosivity and
have a great spatial variability. The high diversity of slopes steepness, lanforms, geological
units and land cover is responsible for the great spatial contrast of erodibility conditions.
The goal of this study is to produce a susceptibility hidric erosion map for Ribeira Seca basin
(Santiago oriental) based on a Digital Elevation Model (DEM) and on geological, land cover
and rain erosivity maps.
The results show that the south-eastern area of the basin is the most susceptible to hidric
erosion, due to local daily rainfall concentration and geomorphological and land cover
conditions of higher erodibility
On the differential geometry of curves in Minkowski space
We discuss some aspects of the differential geometry of curves in Minkowski
space. We establish the Serret-Frenet equations in Minkowski space and use them
to give a very simple proof of the fundamental theorem of curves in Minkowski
space. We also state and prove two other theorems which represent Minkowskian
versions of a very known theorem of the differential geometry of curves in
tridimensional Euclidean space. We discuss the general solution for torsionless
paths in Minkowki space. We then apply the four-dimensional Serret-Frenet
equations to describe the motion of a charged test particle in a constant and
uniform electromagnetic field and show how the curvature and the torsions of
the four-dimensional path of the particle contain information on the
electromagnetic field acting on the particle.Comment: 10 pages. Typeset using REVTE
Interplay between bending and stretching in carbon nanoribbons
We investigate the bending properties of carbon nanoribbons by combining
continuum elasticity theory and tight-binding atomistic simulations. First, we
develop a complete analysis of a given bended configuration through continuum
mechanics. Then, we provide by tight-binding calculations the value of the
bending rigidity in good agreement with recent literature. We discuss the
emergence of a stretching field induced by the full atomic-scale relaxation of
the nanoribbon architecture. We further prove that such an in-plane strain
field can be decomposed into a first contribution due to the actual bending of
the sheet and a second one due to edge effects.Comment: 5 pages, 6 figure
Magnetovac Cylinder to Magnetovac Torus
A method for mapping known cylindrical magnetovac solutions to solutions in
torus coordinates is developed. Identification of the cylinder ends changes
topology from R1 x S1 to S1 x S1. An analytic Einstein-Maxwell solution for a
toroidal magnetic field in tori is presented. The toroidal interior is matched
to an asymptotically flat vacuum exterior, connected by an Israel boundary
layer.Comment: to appear in Class. Quant. Gra
Distribuição Espacial da Susceptibilidade à Erosão Hídrica nas Bacias das Ribeiras de Picos e Seca (Santiago, Cabo Verde)
Os processos de erosão hídrica em Cabo Verde são os mais marcantes da
dinâmica actual das vertentes, pois são os mais comuns e que afectam áreas extensasdurante a curta estação húmida de três meses. A ocorrência de episódios chuvosos
concentrados no tempo e com uma evidente irregularidade espacial permitem umaacentuada erosividade das precipitações, marcada por uma forte irregularidade regional.
A forte variabilidade das formas de relevo, a diversidade da natureza das unidadesgeológicas e a multiplicidade de ocupação do solo favorecem condições deerodibilidade muito contrastadas no espaço.
O objectivo deste trabalho é estabelecer um modelo desusceptibilidade à erosão hídricaem função de factores geomorfológicos (declive, perfil e traçado das vertentes eerodibilidade das unidades litológicas e dos materiais de cobertura), climáticos(intensidade pluviométrica) e de ocupação do solo para as bacias das ribeiras dos Picose Seca. Os resultados foram obtidos com recurso ao ambiente de Sistemas deInformação Geográfica (SIG). Este trabalho surge na sequência de outros já realizadospelos autores, onde se apresentaram as condições de erodibilidade e erosividade paraáreas mais restritas da Ilha de Santiago.
O modelo de susceptibilidade à erosão hídrica resultou do cruzamento dos mapas dedeclives, de perfil e do traçado das vertentes, obtidos a partir do modelo digital deterreno (DTM), do mapa geológico, da distribuição espacial da intensidadepluviométrica e da densidade de ocupação do solo, tendo em conta que são estas asprincipais condicionantes de erosão hídrica, referidas pelos autores que estudaram estaregião. Cada um destes mapas foi reclassificado com base numa análise qualitativa dograu de erodibilidade, sendo atribuído um número de ordem a cada classe, em função da
sua susceptibilidade à erosão hídrica, conforme foi localmente reconhecido.
Verifica-se que as áreas de maior susceptibilidade à erosão hídrica são as do sectorsudeste da bacia da Ribeira Seca e as vertentes dos principais vales da bacia da Ribeira dos Picos, onde se encontram as unidades geológicas mais friáveis, os declives mais
acentuados e onde predominam sectores das vertentes de traçado côncavo, a que seassocia pontualmente a mais elevada intensidade pluviométrica.In Cape Verde the hydric erosion is common during the short wet station of three
months and is the most dynamic slope process and the most widespread in spatial terms.
The rainy events are short and intense, with a great regional irregularity, which allows
an high regional variability of the erosivity conditions.
The erodibility conditions register also a strong spatial variability due to the landforms
contrasts, the diversity lithology and structure of the geological units, and the regional
multiplicity of land cover density conditions.
The main objective of the study is to develop a geographical model of susceptibility to
hydric erosion in Ribeira Seca and Picos basins, based on geomorphological factors
(slope angle, profile and tangential curvatures, lithological units and sedimentary cover
materials erodibility), climatic one (pluviometric intensity) and land cover density. This
study is carried out in the sequence of other ones developed by the authors on more
limited areas of Santiago Island or using a more restricted number of factors.
The model results from the sum in rank of the maps of spatial distribution of the main
factors of hydric erosion, referred by several authors to Santiago: the landform maps
obtained from the digital elevation model (DEM); the geological map; the pluviometric
intensity spatial distribution; and the land cover density. A hierarchic number of
susceptibility to hydric erosion was attributed to each class of these maps, based on
qualitative analysis and field work measures evaluation of the relative degree of
erodibility or erosivity.
The south-east sector of the Ribeira Seca basin and the slopes of the main valleys of the
Picos one are the more susceptible to hydric erosion, due to the local friability of the
geological unities, the steepness of the slopes, and the frequent sectors of concave
curvature, and locally the highest pluviometric intensity
Condiciones ambientales y diferenciación social en los patrones de movilidad: el caso de las desigualdades de género en el Área Metropolitana de Lisboa
Place determinants and social dimensions interact to produce mobility patterns. The article
seeks to measure to what extent the physical and social conditions of the residency place modulate
the intensity of mobility particularly in what concerns gender inequalities. To do so, we first present
the theoretical framework, which guides our perspective on mobility inequalities and the geographical
focus: Lisbon Metropolitan Area (LMA). Secondly, using logistic regression on representative data
from a survey to LMA inhabitants we elaborate on the concept of environmental motility and its
relationship to various types of inequality. Lastly, we systematize a view on accumulated inequalities
examining how local environments may increase the mobilities gender gap.info:eu-repo/semantics/publishedVersio
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Affluence and Objective Environmental Conditions: Evidence of Differences in Environmental Concern in Metropolitan Brazil
In an age of climate change, researchers need to form a deepened understanding of the determinants of environmental concern, particularly in countries of emerging economies. This paper provides a region-specific investigation of the impact of socio-economic status (SES) and objective environmental conditions on environmental concern in urban Brazil. We make use of data collected from personal interviews of individuals living in the metropolitan areas of Baixada Santista and Campinas, in the larger São Paulo area. Results from multilevel regression models indicate that wealthier households are more environmentally concerned, as suggested by affluence and post-materialist hypotheses. However, we also observe that increasing environmental concern correlates with a decline in objective environmental conditions. Interactions between objective environmental conditions and SES reveal some intriguing relationships: Among poorer individuals, a decline in environmental conditions increases environmental concern as suggested by the objective problems hypothesis, while for the wealthy, a decline in environmental conditions is associated with lower levels of environmental concern
Riemannian Geometry of Noncommutative Surfaces
A Riemannian geometry of noncommutative n-dimensional surfaces is developed
as a first step towards the construction of a consistent noncommutative
gravitational theory. Historically, as well, Riemannian geometry was recognized
to be the underlying structure of Einstein's theory of general relativity and
led to further developments of the latter. The notions of metric and
connections on such noncommutative surfaces are introduced and it is shown that
the connections are metric-compatible, giving rise to the corresponding Riemann
curvature. The latter also satisfies the noncommutative analogue of the first
and second Bianchi identities. As examples, noncommutative analogues of the
sphere, torus and hyperboloid are studied in detail. The problem of covariance
under appropriately defined general coordinate transformations is also
discussed and commented on as compared with other treatments.Comment: 28 pages, some clarifications, examples and references added, version
to appear in J. Math. Phy
Minimal resonances in annular non-Euclidean strips
Differential growth processes play a prominent role in shaping leaves and
biological tissues. Using both analytical and numerical calculations, we
consider the shapes of closed, elastic strips which have been subjected to an
inhomogeneous pattern of swelling. The stretching and bending energies of a
closed strip are frustrated by compatibility constraints between the curvatures
and metric of the strip. To analyze this frustration, we study the class of
"conical" closed strips with a prescribed metric tensor on their center line.
The resulting strip shapes can be classified according to their number of
wrinkles and the prescribed pattern of swelling. We use this class of strips as
a variational ansatz to obtain the minimal energy shapes of closed strips and
find excellent agreement with the results of a numerical bead-spring model.
Within this class of strips, we derive a condition under which a strip can have
vanishing mean curvature along the center line.Comment: 14 pages, 13 figures. Published version. Updated references and added
2 figure
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