Macroscopic Model of Solid Oxide Fuel Cell Stack for Integrating in a Generator Simulation

International audienceThis paper presents a macroscopic model of solid oxide fuel cell (SOFC) with the aim to perform a simulation of the whole generator. Three sub-models have been developed to take into fluidic, thermal and electrical phenomena. The fluidic sub-model is based on an equivalent circuit based on electrical analogy. Pressure drops in channels are modelled by resistances and the fluid accumulation in the volume is modelled by capacitor. Each electrode compartment (channel+electrode) is represented by two resistances and one capacitor. We have used this model to calculate the pressure at the catalytic sites and gas flows at fuel cell input and output. The electrical response is based on the classical Nernst potential equation, activation, ohmic and concentration overvoltages. The thermal modelling is based on a (2D) nodal network. Two aspects are studied in this article (conduction and the convection heat transfer). Results have been validated on a 5 cell stack

Habitat-dependent outdoor recreation and conservation organizations can enable recreational fishers to contribute to conservation of coastal marine ecosystems

Stakeholder engagement is essential to conserve ecosystems and associated biodiversity. Outdoor recreation specialists represent stakeholder groups that often rely on specific healthy ecosystems and have unique incentives to contribute to conservation and stewardship. We introduce the concept of habitat-dependent outdoor recreation conservation organizations (HDORCOs) and their potential to harness outdoor recreation enthusiasm to achieve ecosystem-scale conservation objectives. We identify potential roles for HDORCOs in nurturing pro-environmental attitudes and facilitating stewardship behavior among recreationists, focusing on examples from recreational fishing specialists and coastal marine ecosystems. While HDORCOs have achieved conservation outcomes in a range of settings, transferability across recreational specializations and ecological, cultural, socioeconomic, and governance contexts could remain challenging and potentially requires further development of the HDORCO concept. Communication with HDORCOs is one strategy to enhance engagement of recreationists, stakeholder groups not traditionally associated with pro-environmental behavior, in ecosystem-scale conservation efforts

Nuclear Medium Effects in the Relativistic Treatment of Quasifree Electron Scattering

Non-relativistic reduction of the S-matrix for the quasifree electron scattering process $A\left(~e, e'p~\right)A-1$ is studied in order to understand the source of differences between non-relativistic and relativistic models. We perform an effective Pauli reduction on the relativistic expression for the S-matrix in the one-photon exchange approximation. The reduction is applied to the nucleon current only; the electrons are treated fully relativistically. An expansion of the amplitude results in a power series in the nuclear potentials. The series is found to converge rapidly only if the nuclear potentials are included in the nuclear current operator. The results can be cast in a form which reproduces the non-relativistic amplitudes in the limit that the potentials are removed from the nuclear current operator. Large differences can be found between calculations which do and do not include the nuclear potentials in the different orders of the nuclear current operator. In the high missing momentum region we find that the non-relativistic calculations with potentials included in the nuclear current up to second order give results which are close to those of the fully relativistic calculation. This behavior is an indication of the importance of the medium modifications of the nuclear currents in this model, which are naturally built into the relativistic treatment of the reaction.Comment: Latex, 26 pages including 5 uuencoded postscript figures. accepted for publication in Phys. Rev. C

P-matrix and J-matrix approaches. Coulomb asymptotics in the harmonic oscillator representation of scattering theory

The relation between the R- and P-matrix approaches and the harmonic oscillator representation of the quantum scattering theory (J-matrix method) is discussed. We construct a discrete analogue of the P-matrix that is shown to be equivalent to the usual P-matrix in the quasiclassical limit. A definition of the natural channel radius is introduced. As a result, it is shown to be possible to use well-developed technique of R- and P-matrix theory for calculation of resonant states characteristics, scattering phase shifts, etc., in the approaches based on harmonic oscillator expansions, e.g., in nuclear shell-model calculations. P-matrix is used also for formulation of the method of treating Coulomb asymptotics in the scattering theory in oscillator representation.Comment: Revtex, 57 pages including 15 figures; to be published in Annals of Physic

European Red List of Marine Fishes

The European Red List is a review of the conservation status of European species according to IUCN regional Red Listing guidelines. It identifies those species that are threatened with extinction at the regional level, so that appropriate conservation action can be taken to improve their status. This Red List publication summarises results for all described native European marine fishes.Postprin

Diffusion des rayons X et des neutrons

Dans un cristal, tout écart de périodicité se traduit par une diffusion anomale des rayons X et des neutrons. Les auteurs examinent les différents types de désordres et les diffusions correspondantes. Ils décrivent les principales techniques et montrent les avantages présentés par les neutrons

Diffusion des rayons X et des neutrons

In a crystal, every deviation from the periodicity involves an anomalous scattering of X-rays and of neutrons. The authors examine the various types of disorders and the corresponding scattering. They describe the principal techniques and point out the advantages of using the neutrons.Dans un cristal, tout écart de périodicité se traduit par une diffusion anomale des rayons X et des neutrons. Les auteurs examinent les différents types de désordres et les diffusions correspondantes. Ils décrivent les principales techniques et montrent les avantages présentés par les neutrons

Modélisation bio économique des stratégies de protection de la vigne, en vue d'une évaluation des politiques environnementales

International audienceThis research had two objectives. The first was to model the behaviour of wine producers, and the second was to assess the effectiveness of policies designed to reduce pesticide use in viticulture. We modeled the decisions of producers aiming to maximize their expected income while subject to a number of constraints and phytosanitary risks. We also examined the impacts of different protection strategies targeting downy mildew, the main grape disease in European Atlantic vineyards. The Vineyard model for Environmental Policy Analysis (VINEPA) model is a multi-periodic stochastic programming model based on panel data of about one hundred representative winegrowing farms from the Farm Accountancy Data Network in the Bordeaux region. The response of vines to fungicide treatments against downy mildew was simulated through the downy mildew potential system, an epidemiologic model initially developed for decision support, using data from multiple weather stations along with special plots of untreated vines, monitored weekly over a 10-year period. The VINEPA model accurately reproduced the current chemical protection strategies in the region. Simulations were then carried out for different types of taxes (ad valorem and volume based) at different rates. In addition, we analysed the effects of policies on spraying practices, along with their potential impact on investment in precision technology equipment

Macroscopic model of a solid oxide fuel cell for integrating in a generator simulation

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Transient thermal behaviour of a solid oxide fuel cell

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