J.-F. Remacle

A decennial control of N-cycle in the Belgian Ardenne forest ecosystems

As a rule, N-supply of mature Ardenne forest ecosystems is satisfactory. Mineralization rates of soil organic matter are generally high and nitrogen is not a frequent nor an important growth limiting factor. Light N-deficiency is likely to depend on unsatisfactory root absorbing power in very acid soils with dysmoder humus. For other major elements, especially for Mg, Ca and P, near optimal nutrition is rarely observed.During the late sixties, fertilizer experiments have shown that nutrition equilibrium of stands growing on acid soils, poor in exchangeable Mg, is very sensitive to artificial NH4-addition. Mg-deficiency symptoms have been induced. The present continuing atmospheric NH4 input is believed to produce similar but lasting nutritional stress which might be accentuated by additional acidity generated during nitrification of excess NH4. Evolving Mg deficiency leads to trees death and developing forest decline is likely to enhance N-output under NO3-form.Awaiting adequate air purification, fertilizing should restore nutrition equilibrium in order to save damaged stands, to slow down soil acidification and to incorporate excess atmospheric N-input into improved biomass production.

Error estimation based on a new principle of projection and reconstruction

A new approach for error estimation in finite element computations is presented. This method may be applied to a wide range of modeling (magnetostatics, magnetodynamics, scattering problems). The main idea is to reconstruct, from the finite element solution of a primal formulation, a field belonging to the space of the dual finite element formulation. The error is then computed through the nonfulfilment of the constitutive relation by the couple: primal solution-dual solution. 2-D problems with analytical solutions are treated to prove the efficiency of the method. Then the error estimator is used to adapt the mesh for a 3-D magnetostatic problem.

Optimization of the width of a thin plate in a transverse flux induction furnace

This paper presents the analysis of a transverse flux induction furnace. The originality of the analysis presented in this paper is to use successively three different formulations in order to solve the magneto-thermal coupled problem. The Whitney elements (node based, edge based, facet based and volume based elements) are shown to be a convenient means to perform naturally that coupling and to fulfil convergence conditions for the iterative solver.