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Competitive costs, rapid recharge, and high-energy density make small direct methanol fuel cells promising power sources for electronic equipment. Cell performance depends on several parameters, including current density, methanol concentration, and catalyst loadings. In this paper, a 1-D analytical model able to simulate the cell performance is interfaced to a stochastic optimization procedure in order to maximize the battery duration while minimizing methanol crossover. Index Terms--Batteries, energy conversion, fuel cells, optimization methods.

In 1996, a superconducting magnetic energy storage arrangement was selected to become a benchmark problem for testing different optimization algorithms, both deterministic and stochastic ones. Since the forward problem can be solved semianalytically by Biot--Savart's law, this benchmark became quite popular. Nevertheless, the demands on optimization software have increased dramatically since then. To give an example, methods looking for Pareto-optimal points rather than for a single solution only have been introduced by several groups. In this paper, a proposal for an extended version of the benchmark problem will be made and some results will be presented. Index Terms--Optimization benchmark problem, Pareto optimality, superconducting magnetic energy storage (SMES) arrangement.

A full-Maxwell numerical algorithm based on the cell method, which is similar to finite-difference time-domain or FIT but allows complete freedom on the mesh, is presented in this paper. The algorithm can be used with tetrahedral or hexahedral primal meshes. The numerical scheme is explicit, does not need the introduction of new variables or local matrix inversions (as, e.g., in the microcell method), and allows the use of phase-matched layer type boundary conditions. Index Terms--FIT, full-Maxwell, time-domain, waveguides.

In this paper, a time-domain formulation for two-dimensional (2-D) eddy-current problems based on a discrete geometric approach is presented. The method bears very strong similarities with a mass-lumped [theta]-type finite-element method (FEM) formulation. Analogies and differences are highlighted, and a numerical experiment is reported. Index Terms--Discrete approaches, eddy-currents, mass lumping, [theta]-method.

In this paper, a proof of the symmetry of the system matrix arising in a class of vector potential cell methods with non-symmetric material matrices is presented. Some remarks on how to construct other schemes with symmetric system matrices are also presented. The explicit expression of the matrix entries derived in order to prove the symmetry is also used to show that this matrix is identical to the one arising in the standard edge finite-element method. Finally, some remarks on discrete regularizations of these formulations are given. Index Terms--Finite-element methods, Maxwell equations.

In this paper, the coupling of discontinuous finite elements (FEs) with standard conforming ones is applied to the special case of rotating electrical machines. The proposed scheme exploits the capability of discontinuous methods of dealing with non-matching grids, and the lower computational cost of conforming methods, by using first ones only where needed. Therefore, the technique is ideally suited for the treatment of the air-gap region of such devices where the rotation of one part of the mesh generates hanging nodes. The resulting purely finite flement scheme is applied to the TEAM 24 benchmark problem. Index Terms--Discontinuous finite elements, electrical machines, variational methods.

In this paper results obtained from the parallelisation of existing 3D electromagnetic Finite Element codes within the ESPRIT HPCN project PARTEL are presented. The parallelisation procedure, based on the Bulk Synchronous Parallel approach, is outlined and the encouraging results obtained in terms of speed-up on some industrially significant test cases are described and discussed. Index terms - finite element methods, electromagnetic simulation software, parallel algorithms, high performance computing

A local error estimation and adaptive meshing method developed by some of the authors for finite element analysis of 2D electrostatic and magnetostatic problems is now extended to 3D problems. The problems are formulated in terms of scalar potentials and discretized on a tetrahedral mesh using linear shape functions. Local error is estimated by approximately solving an independent differential problem in each tetrahedral element. The elements selected for refinement are subdivided by adding nodes inside the element, or along an edge, depending on their geometrical quality factor. Index terms - Error analysis, finite element methods, magnetostatics, electrostatic analysis.

The present paper discusses a technique, based on the combined use of Radial Basis Functions, which provide an analytical approximation of the true cost function, and self adaptive fuzzy sets, which allow a flexible combination of conflicting objectives, for the stochastic optimisation of multiminima problems. The proposed technique is fully described, its features of interest for industrial level design optimisation are outlined and some initial positive results are presented. Index terms - Optimisation methods, fuzzy sets, interpolation.

A mixed variational formulation for the solution of three dimensional magnetostatic problems, based on both the magnetic field H and the magnetic induction field B, has been developed. The approach is based upon the minimisation of the residual in the fulfilment of the constitutive relationship, imposing Maxwell's equations as constraints. A finite element discretisation has been realised by using face and edge elements to interpolate B and H, respectively, in order to guarantee the physical continuity properties. The mathematical formulation, its code development and computational results are presented and discussed in detail. Index terms - Finite element methods, Maxwell's equations, magnetostatics.

Results from a European collaborative project to create an open system for engineering design, with particular emphasis toward electromagnetic devices, are presented. The system, code named MIDAS, is based on the new ISO STEP standard for data exchange and utilises state-of-the-art Graphical User Interfaces, 3D Geometric Modelling and three-dimensional automatic mesh generation with an advanced 2D subset.

In this paper the results obtained in the realization of an automatic procedure for magnet design in 2D, plane and axysimmetric, will be presented. The proposed procedure combines mesh adaption, based on an 'a-posteriori' error estimate, and deterministic optimization techniques. The use of an analysis module with mesh adaption capabilities gives the automatic design procedure a more stable behaviour in the evaluation of the objective function. In particular, one of the most important features of this strategy is to allow wide variations in dimensional parameters, with high accuracy. The procedure has been realized with a modified version of the VF/OPERA 2d code, realized by the authors, and an optimization technique, based either on the 'Response Surface' or on the 'Pattern Search' algorithm, interacting with the analysis code using parametric commands.

A local error estimation and adaptive meshing method developed by the authors for finite element analysis of 2D electrostatic and magnetostatic problems is now extended to 2D steady state time harmonic quasistatic eddy current problems. Local error estimation is based on the approximate solution of an independent differential problem in each triangular element. Mesh refinement is carried out by adding nodes in the centroids of selected elements and then applying the Delaunay algorithm.

A proposal for benchmark problems to test electromagnetic optimization methods, relevant to multiobjective optimization of a Solenoidal Superconducting Magnetic Energy Storage with active and passive shielding is presented. The system has been optimized by means of different optimization procedures based on the Global Search Algorithm, Evolution Strategies, Simulated Annealing and the Conjugate Gradient Method, all coupled to integral or Finite Element codes. A comparison of results is performed and the features of the problem as a test of optimization procedures are discussed.

A procedure to significantly reduce the computational cost of the Simulated Annealing optimization algorithm coupled with analysis methods is proposed. The chosen approach relies on the application of the Simulated Annealing method to an analytical approximation of the true objective function, expressed in the form of a multiquadric expansion. The algorithm is fully described, its potential advantages are pointed out and some test cases showing the effectivness of the implemented strategy are reported and discussed.

In a previous paper the authors proposed a Coulomb gauge A,V-A-Psi formulation for quasi-static transient eddy current problems using V=0, instead of A[center dot]n=0, as gauge condition on the conductor boundary. Further numerical experimentation using either V=0 or A[center dot]n=0 on different parts of the conductor boundary, however, has shown that, rather unexpectedly, J[center dot]n=0 is numerically more weakly enforced where V=0 is used. Hence, in spite of some advantages of V=0, A[center dot]n=0 still seems to be a better choice, after all. A theoretical explanation for this unexpected drawback of V=0 has been found and is presented here in detail.