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Modified Green's Functions for Shallow Water Acoustic Wave Propagation
This article presents an assessment of alternative forms of the Green’s function for boundary element simulations of acoustic wave propagation in shallow water. It is assumed that the problem is two-dimensional, the source of acoustic disturbance is time-harmonic, the velocity of sound is constant and the medium in the absence of perturbations is quiescent.
Efficient implementations of the boundary element method for underwater acoustics should employ Green's functions which directly satisfy the boundary conditions on the free surface and the horizontal parts of the bottom boundary. In the present work, these Green's functions are constructed by using different techniques, namely the method of images, eigenfunction expansions and the Ewald’s method
Comparing Organic Urban Consumers in Developing and Developed Countries: First Results in Brazil and France
Despite numerous studies reporting on sustainable consumption or organic consumer profiles, there is a gap in thorough understanding of organic consumers in different places, since most of studies only investigate organic consumption in most developed countries. The goal of this paper is thus to compare French and Brazilian organic consumers, so as to know if people think and behave differently or similarly in different places. Individual interviews were conducted in each country, with consumers in organic producers market in Brazil, and consumers who buy organic products from farmers markets or local organic food network in France. Products were selected to cover examples of different choice situations such as imported organic products that compete with comparable products of local origin, or organic local products in supermarkets that compete with similar products from other distribution outlets. Results show common consumer concerns such as quality or personal and family health, and common preference for local and organic products but for different reasons. However, results also shed light on different patterns related to environmental concerns or commitment to supporting small or local farmers. The impacts of the findings of this study relate to a diversity of topics such as social mobilization for sustainable agriculture, local organic food networks and environmental concerns. ...French Abstract : De nombreuses recherches portent sur la consommation durable et le profil des consommateurs de produits biologiques, mais ces recherches portent sur la consommation dans les pays développés, et ne permettent pas de savoir s'il existe des différences de consommation entre pays développés et pays en développement. Le but de cet article est de comparer le comportement de consommateurs de produits biologiques en France et au Brésil, sur la base d'entretiens individuels permettant de comparer plusieurs situations de choix : produits biologiques importés en concurrence avec des produits locaux comparables, produits biologiques locaux disponibles en supermarché ou d'en d'autres circuits de distribution,... Les résultats mettent en évidence des attentes communes, comme la qualité ou la santé, et des préférences partagées pour les produits biologiques et locaux, mais pour des raisons différentes dans les deux échantillons. Les résultats montrent également que l'importance accordée aux préoccupations environnementales et au soutien aux petits producteurs locaux n'est pas la même dans les deux échantillons. Cette recherche conduit à des pistes de réflexion portant sur la mobilisation des consommateurs pour la consommation durable, les réseaux de production et consommation de produits biologiques et les préoccupations environnementales des consommateurs.ORGANIC FOOD; LOCAL FOOD; SUSTAINABLE CONSUMPTION; QUALITATIVE STUDY
Generalizing a Unified Model of Dark Matter, Dark Energy, and Inflation with Non Canonical Kinetic Term
We study a unification model for dark energy, dark matter, and inflation with
a single scalar field with non canonical kinetic term. In this model the
kinetic term of the Lagrangian accounts for the dark matter and dark energy,
and at early epochs a quadratic potential accounts for slow roll inflation. The
present work is an extension to the work by Bose and Majumdar [1] with a more
general kinetic term that was proposed by Chimento in [2]. We demonstrate that
the model is viable at the background and linear perturbation levels.Comment: 8 pages, 2 figures. Minor changes to text and formulae, and added 3
references to match the published version in Phys. Rev.
Phase and Charge reentrant phase transitions in two capacitively coupled Josephson arrays with ultra-small junction
We have studied the phase diagram of two capacitively coupled Josephson
junction arrays with charging energy, , and Josephson coupling energy,
. Our results are obtained using a path integral Quantum Monte Carlo
algorithm. The parameter that quantifies the quantum fluctuations in the i-th
array is defined by . Depending on
the value of , each independent array may be in the semiclassical or
in the quantum regime: We find that thermal fluctuations are important when
and the quantum fluctuations dominate when . We have extensively studied the interplay between vortex and charge
dominated individual array phases. The two arrays are coupled via the
capacitance at each site of the lattices. We find a {\it
reentrant transition} in , at low temperatures, when one of
the arrays is in the semiclassical limit (i.e. ) and the
quantum array has , for the values considered for
the interlayer capacitance. In addition, when , and
for all the inter-layer couplings considered above, a {\it novel} reentrant
phase transition occurs in the charge degrees of freedom, i.e. there is a
reentrant insulating-conducting transition at low temperatures. We obtain the
corresponding phase diagrams and found some features that resemble those seen
in experiments with 2D JJA.Comment: 25 Latex pages including 8 encapsulated poscript figures. Accepted
for publication in Phys. Rev B (Nov. 2004 Issue
Exploring associations between micro-level models of innovation diffusion and emerging macro-level adoption patterns
A micro-level agent-based model of innovation diffusion was developed that
explicitly combines (a) an individual's perception of the advantages or
relative utility derived from adoption, and (b) social influence from members
of the individual's social network. The micro-model was used to simulate
macro-level diffusion patterns emerging from different configurations of
micro-model parameters. Micro-level simulation results matched very closely the
adoption patterns predicted by the widely-used Bass macro-level model (Bass,
1969). For a portion of the domain, results from micro-simulations were
consistent with aggregate-level adoption patterns reported in the literature.
Induced Bass macro-level parameters and responded to changes in
micro-parameters: (1) increased with the number of innovators and with the rate
at which innovators are introduced; (2) increased with the probability of
rewiring in small-world networks, as the characteristic path length decreases;
and (3) an increase in the overall perceived utility of an innovation caused a
corresponding increase in induced and values. Understanding micro to macro
linkages can inform the design and assessment of marketing interventions on
micro-variables - or processes related to them - to enhance adoption of future
products or technologies.Comment: 20 pages, 4 figures and a table of supplementary data. Accepted for
publicatio
Compositional uniformity, domain patterning and the mechanism underlying nano-chessboard arrays
We propose that systems exhibiting compositional patterning at the nanoscale,
so far assumed to be due to some kind of ordered phase segregation, can be
understood instead in terms of coherent, single phase ordering of minority
motifs, caused by some constrained drive for uniformity. The essential features
of this type of arrangements can be reproduced using a superspace construction
typical of uniformity-driven orderings, which only requires the knowledge of
the modulation vectors observed in the diffraction patterns. The idea is
discussed in terms of a simple two dimensional lattice-gas model that simulates
a binary system in which the dilution of the minority component is favored.
This simple model already exhibits a hierarchy of arrangements similar to the
experimentally observed nano-chessboard and nano-diamond patterns, which are
described as occupational modulated structures with two independent modulation
wave vectors and simple step-like occupation modulation functions.Comment: Preprint. 11 pages, 11 figure
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