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International audienceThe paper proposes a primal-dual algorithm for solving an equality constrained minimization problem. The algorithm is a Newton-like method applied to a sequence of perturbed optimality systems that follow naturally from the quadratic penalty approach. This work is first motivated by the fact that a primal-dual formulation of the quadratic penalty provides a better framework than the standard primal form. This is highlighted by strong convergence properties proved under standard assumptions. In particular, it is shown that the usual requirement of solving the penalty problem with a precision of the same size as the perturbation parameter, can be replaced by a much less stringent criterion, while guaranteeing the superlinear convergence property. A second motivation is that the method provides an appropriate regularization for degenerate problems with a rank deficient Jacobian of constraints. The numerical experiments clearly bear this out. Another important feature of our algorithm is that the penalty parameter is allowed to vary during the inner iterations, while it is usually kept constant. This alleviates the numerical problem due to ill-conditioning of the quadratic penalty, leading to an improvement of the numerical performances

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Stereolithography is an additive manufacturing process which makes it possible to fabricate useful com plex 3D ceramic parts, with a high dimensional resolution and a goo d surface finish. Stereolithography is based on the selective UV polymerization of a reactive system consisting in a dispersion of ceramic partides in a curable monomer/oligomer resin. In order to reach a homogeneous polymerization in the green part, and to limit the risk of cracking and/or deformation during subsequent stages of debinding and sintering due to internai stresses, the influence of various fabrication parameters (laser power, scanning speed, number of irradiations) on the degree of polymerization was investigated. In addition, the impact of the irradiation of the subsequent upper layers onto the previously deposited and irradiated layers was evaluated. The degree of conversion was determined by Fourier Transform lnfr ared Spectroscopy (FTIR). Raman spectroscopy was also used and a brief comparison between these two methods is given.