Market Power in Direct Marketing of Fresh Produce: Community Supported Agriculture Farms

CSA farms establish a loyal customer base and, potentially, market power. A new empirical industrial organization (NEIO) approach and survey data from Northeast CSA farms are used to determine whether CSA farms have market power and the extent to which they exercise their market power. Results suggest CSA farms exert about two percent of their potential monopoly power.Community Supported Agriculture; New Empirical Industrial Organization; Market Power; Fresh Produce; Organic Agriculture

Measuring the notched compressive strength of composite laminates: Specimen size effects

Large fibre reinforced composite structures can give much lower strengths than small test specimens, so a proper understanding of scaling is vital for their safe and efficient use. Small size (scale) specimens are commonly tested to justify allowable stresses, but could be dangerous if results are extrapolated without accounting for scaling effects. On the other hand large factors are sometimes applied to compensate for uncertainties, resulting in overweight designs. The most important variables of scaling effects on the strength of composites with open holes have been identified from experimental tests as notch size, ply and laminate thickness. In this study, these have been scaled both independently and simultaneously over a large range of combinations. The specimens are fabricated from commercially available (Hexcel Composites Ltd.) carbon/epoxy pre-impregnated tapes 0.125 mm thick (IM7/8552). The material is laid up by hand in unidirectional [04]ns with n = 2, 3, 4, and 8 (i.e., 2, 3, 4 and 8 mm thick) and multidirectional laminates; two generic quasi-isotropic lay-ups, one fabricated with blocked plies [45n/90n/−45n/0n]s and the other with distributed layers [45/90/−45/0]ns with n = 2, 4 and 8 are examined. It is shown that the critical failure mechanism in these laminates is in the form of fibre microbuckling or kinking. The unnotched compressive strength in unidirectional specimens thicker than 2 mm is found to be limited by the stress concentration developed at the end tabs and manufacturing induced defects in the form of ply waviness, fibre misalignment and voids rather than specimen size (scaling). In the open hole specimens, for both lay-ups, the strength reduction observed is due to hole size effect rather than specimen thickness or volume increase. The open hole (notched) compressive strength results obtained compare favourably to predictions by a linear softening cohesive zone fracture model developed in earlier work by the second author

Simulation et visualisation des transitoires dans un réseau électrique de grande dimension

Les logiciels de simulaton numérique des lignes de transmission dans le domaine du temps en régime transitoire, tel que EMTP, mettent en oeuvre des modèles sophistiqués qui fournissent des résultats précis. Une lacune de ces logiciels demeure l'absence d'une interface de visualisation graphique permettant l'observation spatiale des phénomènes étudiés. Ce mémoire présente la réalisation d'un logiciel permettant de simuler numériquement des lignes de transmission et de visualiser les ondes en trois dimensions. Le logiciel est appliqué à la simulation des réseaux de transport d'énergie électrique. La résolution numérique des lignes est obtenue à l'aide du modèle «Z-Line». Le logiciel est réalisé dans le langage de haut niveau Matlab, qui intègre toutes les fonctionnalités mathématiques et graphiques requises. La possibilité de visualiser les phénomènes transitoires électromagnétiques dans les grands réseaux de transport d'énergie électrique tente d'offrir de nouvelles possibilités d'analyse de ces phénomènes

Pando: Personal Volunteer Computing in Browsers

The large penetration and continued growth in ownership of personal electronic devices represents a freely available and largely untapped source of computing power. To leverage those, we present Pando, a new volunteer computing tool based on a declarative concurrent programming model and implemented using JavaScript, WebRTC, and WebSockets. This tool enables a dynamically varying number of failure-prone personal devices contributed by volunteers to parallelize the application of a function on a stream of values, by using the devices' browsers. We show that Pando can provide throughput improvements compared to a single personal device, on a variety of compute-bound applications including animation rendering and image processing. We also show the flexibility of our approach by deploying Pando on personal devices connected over a local network, on Grid5000, a French-wide computing grid in a virtual private network, and seven PlanetLab nodes distributed in a wide area network over Europe.Comment: 14 pages, 12 figures, 2 table

Vegetation dynamics on an abandoned vacuum-mined peatland: 5 years of monitoring.

Abstract We studied from 1998 to 2002 the fine-scale vegetation dynamics of a poorly regenerated vacuum-mined bog located in southern Quebec. We selected mined sites that have been abandoned for 14 years and monitored the vascular and non-vascular plants, and some hydrological characteristics. We focussed our study on the monitoring of cotton-grass (Eriophorum vaginatum L.) tussocks. Major changes in the plant cover were observed during the five-year period, such as a decrease (26-31%) in the number of cotton-grass tussocks and an increase in the ericaceous shrub cover. The water table level (lower than 40 cm below the soil surface) and frost heaving appear to be the main factors explaining the failure of cotton-grass and of other typical bog plant species to colonize abandoned mined surfaces. The ericaceous shrub cover, although increasing, was still sparse even after two decades of abandonment, and it may take several additional decades before a complete shrub cover establishes itself. While the natural revegetation process of this vacuum-mined bog is still dynamic after two decades of abandonment, there is no evidence to suggest that vegetation assemblages will eventually resemble those of undisturbed peatlands

Communication et implantation bureautique dansle franchisage de diffusion

L’informatisation interne verticale des activités de gestion intervient aussi bien dans les pratiques locales des franchisés que dans celles qui gèrent leurs relations commerciales et financières avec le franchiseur. Il est important de retrouver « l’esprit » original de la franchise afin de comprendre les paramètres conceptuels dans lesquels les franchisés vont intéger le projet informatique. En prenant conscience des implications communicationnelles des différents types de franchisage de reproduction ou de « diffusion » sur les structures organisationnelles. le franchiseur doit se donner les moyens de régler les dissonances culturelles (visions des modèles) avant de s’attacher à démonter l’utilité et la faisabilité techniques de son projet

Combined Effects of Acute Temperature Change and Elevated pCO2 on the Metabolic Rates and Hypoxia Tolerances of Clearnose Skate (Rostaraja eglanteria), Summer Flounder (Paralichthys dentatus), and Thorny Skate (Amblyraja radiata)

Understanding how rising temperatures, ocean acidification, and hypoxia affect the performance of coastal fishes is essential to predicting species-specific responses to climate change. Although a population’s habitat influences physiological performance, little work has explicitly examined the multi-stressor responses of species from habitats differing in natural variability. Here, clearnose skate (Rostaraja eglanteria) and summer flounder (Paralichthys dentatus) from mid-Atlantic estuaries, and thorny skate (Amblyraja radiata) from the Gulf of Maine, were acutely exposed to current and projected temperatures (20, 24, or 28 °C; 22 or 30 °C; and 9, 13, or 15 °C, respectively) and acidification conditions (pH 7.8 or 7.4). We tested metabolic rates and hypoxia tolerance using intermittent-flow respirometry. All three species exhibited increases in standard metabolic rate under an 8 °C temperature increase (Q10 of 1.71, 1.07, and 2.56, respectively), although this was most pronounced in the thorny skate. At the lowest test temperature and under the low pH treatment, all three species exhibited significant increases in standard metabolic rate (44–105%; p \u3c 0.05) and decreases in hypoxia tolerance (60–84% increases in critical oxygen pressure; p \u3c 0.05). This study demonstrates the interactive effects of increasing temperature and changing ocean carbonate chemistry are species-specific, the implications of which should be considered within the context of habitat. Associated dataset: Gail D. Schweiterman, Daniel P. Crear et al. 2019. Metabolic Rates and Hypoxia Tolerences of clearnose skate (Rostaraja eglanteria), summer flounder (Paralichthys dentatus), and thorny skate (Amblyraja radiata) https://doi.org/10.25773/qmew-c18

Metabolic Rates and Hypoxia Tolerences of clearnose skate (Rostaraja eglanteria), summer flounder (Paralichthys dentatus), and thorny skate (Amblyraja radiata)

These data were collected following methods described in the associated publication: LINK “Combined Effects of Acute Temperature Change and Elevated pCO2 on the Metabolic Rates and Hypoxia Tolerances of Clearnose Skate (Rostaraja eglanteria), Summer Flounder (Paralichthys dentatus), and Thorny Skate (Amblyraja radiata)”. Schweiterman, G.D. et al. 2019 Biology, 8(3), 56