Conventionalization, Bifurcation, and Quality of Life: Certified and Non-Certified Organic Farmers in Texas

Organic agriculture has been advanced as a production system that improves environmental quality and supports rural community development. Recent developments in organics have called into question both assertions. Researchers have argued that the advent of national-level organic standards has contributed to the conventionalization and bifurcation of organics. Conventionalization refers to the process by which organic agriculture increasingly takes on the characteristics of mainstream industrial agriculture. Bifurcation refers to the process by which the organic agriculture adopts a dual-structure of smaller, lifestyle-oriented producers and larger, industrial-scale producers. This research examines the conventionalization and bifurcation theses through a comparison of certified organic and non-certified organic producers in Texas. We conclude that the case of organics in Texas provides mixed support for the conventionalization thesis

Numerical Study of the Stress Response of Two-Dimensional Dense Granular Packings

We investigate the Green function of two-dimensional dense random packings of grains in order to discriminate between the different theories of stress transmission in granular materials. Our computer simulations allow for a detailed quantitative investigation of the dynamics which is difficult to obtain experimentally. We show that both hyperbolic and parabolic models of stress transmission fail to predict the correct stress distribution in the studied region of the parameters space. We demonstrate that the compressional and shear components of the stress compare very well with the predictions of isotropic elasticity for a wide range of pressures and porosities and for both frictional and frictionless packings. However, the states used in this study do not include the critical isostatic point for frictional particles, so that our results do not preclude the fact that corrections to elasticity may appear at the critical point of jamming, or for other sample preparation protocols, as discussed in the main text. We show that the agreement holds in the bulk of the packings as well as at the boundaries and we validate the linear dependence of the stress profile width with depth.Comment: 7 pages, 5 figure

Maximum Likelihood Estimator for Hidden Markov Models in continuous time

The paper studies large sample asymptotic properties of the Maximum Likelihood Estimator (MLE) for the parameter of a continuous time Markov chain, observed in white noise. Using the method of weak convergence of likelihoods due to I.Ibragimov and R.Khasminskii, consistency, asymptotic normality and convergence of moments are established for MLE under certain strong ergodicity conditions of the chain.Comment: Warning: due to a flaw in the publishing process, some of the references in the published version of the article are confuse

Sensitivity of the stress response function to packing preparation

A granular assembly composed of a collection of identical grains may pack under different microscopic configurations with microscopic features that are sensitive to the preparation history. A given configuration may also change in response to external actions such as compression, shearing etc. We show using a mechanical response function method developed experimentally and numerically, that the macroscopic stress profiles are strongly dependent on these preparation procedures. These results were obtained for both two and three dimensions. The method reveals that, under a given preparation history, the macroscopic symmetries of the granular material is affected and in most cases significant departures from isotropy should be observed. This suggests a new path toward a non-intrusive test of granular material constitutive properties.Comment: 15 pages, 11 figures, some numerical data corrected, to appear in J. Phys. Cond. Mat. special issue on Granular Materials (M. Nicodemi Editor

Rapport V.3. Effets mésométéorologiques des plans d’eau ; application au régime des brises à Fos

The coastal breeze system is a mesoscale circulation that finds its origin in the thermic contrast between the earth and the water surfaces. Such a contrast depends on a number of factors such as : changing insolation with latitudes and seasons, nebulosity , rugged surface of the earth, soils nature and background vegetation, watertable importance, etc., so that each coastal site is in possession of a particular breeze regime. Inside the gulf of Fos, coastal breezes are an important element of the local climate as they represent about the third of the meteorological situations that interest all the area during the hot period. Their essential charicteristics are presented herein.Le système des brises côtières est une circulation à moyenne échelle (mesoscale) qui trouve son origine dans le contraste thermique entre la terre et l’eau. Ce contraste dépend de nombreux facteurs tels que l’insolation variable avec la latitude et la saison, la nébulosité, le relief, la nature des sols et la végétation de l’arrière-pays, l’importance de la nappe d’eau, etc., de sorte que chaque site côtier possède son régime de brises particulier. Dans le golfe de Fos, les brises côtières constituent un élément important du climat local puisqu’elles représentent environ le tiers des situations météorologiques intéressant la région durant la saison chaude. On présente ici leurs caractéristiques essentielles.Gland H. Rapport V.3. Effets mésométéorologiques des plans d’eau ; application au régime des brises à Fos. In: Influence des activités de l'homme sur le cycle hydrométéorologique. Compte-rendu des treizièmes journées de l'hydraulique. Paris, 16-18 septembre 1974. Tome 2, 1975

Rapport III. 12 Étude statistique tridimensionnelle des panaches d'aéroréfrigérants. Méthode et résultats relatifs à l’influence de la puissance et des conditions de rejets

Three-dimensional statistical study of cooling tower plumes Method and results on the effects of power and discharge conditions. The three dimensional computer code PANACH which was achieved using laboratory experiments, to calibrate the turbulent mixing parameters, and then validated with on site measurements, is used in order to estimate a three dimensional statistical plume prevision. As the computing time does not allow to calculate each meteorological set of date, a classification of these date was adopted. This method which was developed by the National Meteorology Board is based upon a double classification with basic classes in which all plumes are assumed to be dynamically similar and a sub-classification allowing to take into account the real moisture vertical profiles. This statistical method is applied to the cases of 2 and 4 wet-type natural draft cooling towers of 1300 MWe and of 2 wet-dry and dry.Le code de calcul tridimensionnel PANACH après avoir été mis au point à partir d'essais sur modèle réduit et validé à partir de campagnes de mesures en nature a été utilisé pour estimer une statistique tridimensionnelle de panaches. Les temps de calcul ne permettant pas d'effectuer un calcul pour chaque radiosondage, une méthode de classification a été adoptée. Cette méthode développée par la Météorologie Nationale est basée sur une double classification comprenant des classes de bases dans lesquelles les panaches sont supposés dynamiquement semblables et une sous-classification pour mieux tenir compte des profils réels d'humidité. Cette méthode statistique a ensuite été appliquée au cas de 2 ou 4 tranches de 1300 MWe équipées d'aéroréfrigérants à tirage naturel de types humide, sec et humide-sec.Darles A., Sabaton M., Gland H., Viollet Pierre-Louis. Rapport III. 12 Étude statistique tridimensionnelle des panaches d'aéroréfrigérants. Méthode et résultats relatifs à l’influence de la puissance et des conditions de rejets. In: Rejets de chaleur à l'atmosphère. Gestion des calories et hydraulique associée. Compte-rendu des XVIes journées de l'hydraulique. Paris, 16-18 septembre 1980. Tome 2, 1980