Effective boundary condition at a rough surface starting from a slip condition

We consider the homogenization of the Navier-Stokes equation, set in a channel with a rough boundary, of small amplitude and wavelength $\epsilon$. It was shown recently that, for any non-degenerate roughness pattern, and for any reasonable condition imposed at the rough boundary, the homogenized boundary condition in the limit $\epsilon = 0$ is always no-slip. We give in this paper error estimates for this homogenized no-slip condition, and provide a more accurate effective boundary condition, of Navier type. Our result extends those obtained in previous works, in which the special case of a Dirichlet condition at the rough boundary was examined

Agri-Environmental Policies When the Spatial Pattern of Biodiversity Reserves Matters

The aim of this paper is to compare different policy instruments for cost-effective habitat conservation on agricultural lands, when the desired spatial pattern of reserves is a random mosaic. We use a spatially explicit mathematical programming model which studies the farmers' behavior as profit maximizers under technical and administrative constraints. Facing different policy measures, each farmer chooses its land-use at the field level, which determines the landscape at the regional level. A spatial pattern index (Ripley L function) is then associated to the obtained landscape, indicating on the degree of dispersion of the reserve. We compare a subsidy per hectare of reserve with an auction scheme and an agglomeration malus. We find that the auction is superior to the uniform subsidy both for cost-efficiency and for the spatial pattern of the reserve. The agglomeration malus does better than the auction for the spatial pattern but is more costly.agri-environmental policies, biodiversity, mathematical programming, spatial optimization, reserve design, cost-efficiency, Environmental Economics and Policy, Resource /Energy Economics and Policy, H23, Q57, Q12, Q28,

Hg(II) trace electrochemical detection on gold electrode: Evidence for chloride adsorption as the responsible for the broad baseline

Investigations were performed in order to clarify the origin of the broad baseline observed during Hg(II) trace electrochemical detection on gold electrode in the presence of Cl- anions. The influence of Cl- concentration on the shape of the voltammograms was studied in the presence and in the absence of Bovine Serum Albumin (BSA) in order to bring out adsorption/desorption processes. On the basis of these experiments, and contrary to what has been proposed by several authors in the literature, it was proved that the broad baseline does not result from calomel (Hg2Cl2) formation but is rather related to an interaction between Cl- and polycrystalline Au electrode surface. The evolution of the shape of the baseline was also studied in the presence of other halide anions, namely F-, Br-, and I-. The latter two were found to induce a broad baseline similar to that recorded in the presence of Cl-. Finally, it was shown that BSA addition is not suitable for Hg(II) detection since it prevents Hg(0) deposition onto the electrode surface

High frequency analysis of the unsteady Interactive Boundary Layer model

The present paper is about a famous extension of the Prandtl equation, the so-called Interactive Boundary Layer model (IBL). This model has been used intensively in the numerics of steady boundary layer flows, and compares favorably to the Prandtl one, especially past separation. We consider here the unsteady version of the IBL, and study its linear well-posedness, namely the linear stability of shear flow solutions to high frequencyperturbations. We show that the IBL model exhibits strong unrealistic instabilities, that are in particular distinct from the Tollmien-Schlichting waves. We also exhibit similar instabilities for a Prescribed Displacement Thickness model (PDT), which is one of the building blocks of numerical implementations of the IBL model