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Abstract: This paper deals with an approximation problem concerning vector fields through the new notion of div–rot variational splines. The minimizing problem is addressed in a finite element space through the choice of some semi-norms based on decomposition of the divergence operator and vector fields into a form with a rotational part. We study the existence and the uniqueness of the solution of such a problem. Then, a convergence result and an estimation of the error are established. Some numerical and graphical examples are analyzed in order to prove the validity of our method. Furthermore, we compare and show how our method improves upon one existing in the literature. [Copyright &y& Elsevier]

Abstract: An approximation problem of parametric curves and surfaces is studied by a new kind of spline functions from some Lagrange or Hermite data set. We present an interpolation problem by minimizing a functional on a parametric finite element space in order to obtain the new notion of a spline. We call it discrete interpolating variational spline. We show how to compute in practice such spline and we carefully prove a convergence result. To illustrate the generality and practice of this work we give some particular cases and we finish by presenting some numerical and graphical examples. [Copyright &y& Elsevier]

Abstract: This is a note on the paper [A. Kouibia, A.J. López-Linares, M. Pasadas, Approximation of discontinuous curves and surfaces with tangent conditions, J. Comput. Appl. Math. 193 (2006) 51–64]. We consider the constructing problem of a discontinuous parametric curve or surface from a finite set of points and tangent conditions. We develop a method based on the theory of discrete smoothing variational splines conveniently adapted to introduce the tangent conditions and the discontinuity set. We give a convergence result and we analyze some numerical and graphical examples in order to illustrate the effectiveness of the presented method. [Copyright &y& Elsevier]

We present in this paper a discrete problem of constructing some parametric surfaces with parallelism conditions from some given Lagrangean data. We consider the problem of fitting some scattered points with a surface pseudo-parallel to a given reference surface in a finite element space. Some convergence results are shown. Finally, we analyze some graphical examples in order to prove the validity and the effectiveness of this method. [Copyright &y& Elsevier]

We present in this paper an approximation method of curves from sets of Lagrangian data and vectorial tangent subspaces. We define a discrete smoothing fairness spline with tangent conditions by minimizing certain quadratic functional on finite element spaces. Convergence theorem is established and some numerical and graphical examples are analyzed in order to show the validity and the effectiveness of this paper. [Copyright &y& Elsevier]