Abstract Using a relation between representation theory of crystallographic space groups and a Dirichlet type of boundary problem for the Laplacian, we derive the solutions for the Dirichlet problem, as well as for a similar Neumann boundary problem, by a complete decomposition of plane waves into irreducible representations of a particular space group. This decomposition corresponds to a basis transformation in L2(Ω) and yields a new set of basis functions adapted to the symmetry of the lattice considered.
We consider a Dirichlet-Neumann boundary problem in a bounded domain for scalar conservation laws. We construct an approximate solution to the problem via an elliptic approximation for which, under appropriate assumptions, we prove that the corresponding limit satisfies the considered equation in the interior of the domain. The basic tool is the compensated compactness method. We also provide numerical examples.
The tool design problem of electrochemical machining (ECM) is formulated by the inverted approach in which the spatial coordinates are treated as the dependent variables on the plane of the complex potential. A general solution of this free boundary problem by analytic continuation provides the basis for a series approximation with correct asymptotic behavior using the method of weighted residues. The procedure is used to determine the noninsulated or partially insulated tool shapes which can be used to machine a prescribed workpiece geometry. The method is generally applicable to inverse (design) problems of potential theory which involve a given equipotential (or streamline) boundary along which a Neumann boundary condition is also prescribed as occurs in heat conduction, ideal flow, and electrostatics. The inverted approach not only eliminates the need for trial-and-error design procedures but also provides the advantage of adjustment in geometry by superposition.
ON THE DIRICHLET-NEUMANN BOUNDARY PROBLEM FOR SCALAR CONSERVATION LAWS
