Linear programming solutions and distance functions under a constant returns to scale technology

This note generalizes analytical relationships among activity variables of DEA models previously derived by Boussemart, Briec and Leleu (2007). We relax the asumption of constant returns to scale by showing that the key results hold under a weaker asumption of homogeneity. We use the notion of alpha-returns to scale to extend the analysis to strictly increasing and decreasing returns, covering now the whole range of returns to scale for multi-output homogenous technologies.Data envelopment analysis, Methodology, Production

More evidence on technological catching-up in the manufacturing sector

Production frontiers for the manufacturing sector are estimated to determine a “country specific” catching-up process of Total Factor Productivity (TFP).TFP gains are gauged at the manufacturing industry level for 14 OECD countries over the 1970-2001 period. Our TFP measure does not assume technical or allocative efficiency which are inherent drawbacks of usual TFP indices. We show that catching-up processes can be very different between sub-periods and across countries. A significant catching-up process was at work in the manufacturing sector between 1970 and 1986 then it overturned over the period 1987-2001. During the first sub-period, the speed of technological catching-up of the euro-zone countries is definitely higher than those of the other European or OECD nations whereas the divergence noted in second sub-period has the same order of magnitude among the three groups.Catching-up; TFP change index; Technology adoption; Production Frontier

Acoustic response of a rigid frame porous medium slab with a periodic set of inclusions

The acoustic response of a rigid frame porous slab with a periodic set of inclusions is calculated by use of a multipole method. The acoustic properties, in particular the absorption, of such a structure are then derived and studied. Numerical results together with a modal analysis show that the addition of a periodic set of high-contrast inclusions leads to quasi-modes excitation of both the slab and the gratings, and to a large increase of the acoustic absorption of the initial slab, this being partly due to the quasi-modes excitation.Comment: submitted to Journal of Sound and Vibratio

Short- and Long-Run Credit Constraints in French Agriculture: A Directional Distance Function Framework Using Expenditure-Constrained Profit Functions

This empirical application investigates the eventual presence of credit constraints using a panel of French farmers. This is the first European application using a direct modelling approach based upon axiomatic production theory. The credit constrained profit maximisation model proposed by Färe, Grosskopf and Lee is extended in three ways. First, we rephrase the model in terms of directional distance functions to allow for duality with the profit function. Second, we model the presence of credit constraints in the short-run and investment constraints in the long-run using short- respectively long-run profit functions. Third, we lag the expenditure constraint one year to account for the separation between planning and production. We find empirical evidence of both credit and investment constraints, though their relative impact on the degree of financial inefficiency is rather low in the short-run. Financially unconstrained farmers are larger, perform better, and seem to benefit from a virtuous circle where access to financial markets allows better productive choices. In the long-run, almost all farms seem to suffer from credit constraints for financing their investments.proportional distance function, profit function, credit constraint

Materials Testing

International audienceIn recent years, a number of models to calculate the acoustical behaviour of porous materials (sound absorption, sound insulation and vibration damping) have been developed [1]. Although these models are based on physical sound theories, they require a number of material parameters and the output of a calculation will depend on the accuracy of the input parameters. Depending on the complexity of the porous material and the configuration to be modeled, up to seven parameters may be needed

Long wave expansions for water waves over random topography

In this paper, we study the motion of the free surface of a body of fluid over a variable bottom, in a long wave asymptotic regime. We assume that the bottom of the fluid region can be described by a stationary random process $\beta(x, \omega)$ whose variations take place on short length scales and which are decorrelated on the length scale of the long waves. This is a question of homogenization theory in the scaling regime for the Boussinesq and KdV equations. The analysis is performed from the point of view of perturbation theory for Hamiltonian PDEs with a small parameter, in the context of which we perform a careful analysis of the distributional convergence of stationary mixing random processes. We show in particular that the problem does not fully homogenize, and that the random effects are as important as dispersive and nonlinear phenomena in the scaling regime that is studied. Our principal result is the derivation of effective equations for surface water waves in the long wave small amplitude regime, and a consistency analysis of these equations, which are not necessarily Hamiltonian PDEs. In this analysis we compute the effects of random modulation of solutions, and give an explicit expression for the scattered component of the solution due to waves interacting with the random bottom. We show that the resulting influence of the random topography is expressed in terms of a canonical process, which is equivalent to a white noise through Donsker's invariance principle, with one free parameter being the variance of the random process $\beta$. This work is a reappraisal of the paper by Rosales & Papanicolaou \cite{RP83} and its extension to general stationary mixing processes