We present a high-order spectral element method for solving layered media scattering problems featuring an operator that transparently enforces the far-field boundary condition. The incorporation of this Dirichlet-to-Neumann (DtN) map into the spectral element framework is a novel aspect of this work, and the resulting method can accommodate plane-wave radiation of arbitrary angle of incidence....

We present a mixed method for a three-dimensional axisymmetric div-curl system reduced to a two-dimensional computational domain via cylindrical coordinates. We show that when the meridian axisymmetric Maxwell problem is approximated by a mixed method using the lowest order Nédélec elements (for the vector variable) and linear elements (for the Lagrange multiplier), one obtains optimal error es...

In modern DSL systems, multi-user crosstalk is a major source of performance degradation. Optimal Spectrum Balancing (OSB) is a centralized algorithm that mitigates the effect of crosstalk by allocating optimal transmit spectra to all interfering DSL modems. By the use of Lagrange multipliers the algorithm decouples the spectrum management problem into per-tone optimization problems. The remain...

The Maxwell equations in the magnetohydrodynamic (MHD) limit in heterogeneous domains composed of conducting and non-conducting regions are solved by using Lagrange finite elements and by enforcing continuities across interfaces using an Interior Penalty technique à la Baker [Finite element methods for elliptic equations using non-conforming elements, Math. Comp. 31 (137) (1977) 45–59]. The met...

This paper generalizes the fast Fourier transform algorithm to the computationof Fourier transformson compact Lie groups. The basic technique uses factorization of group elements and Gel'fand-Tsetlin bases to simplify the computations, and may be extended to treat the computation of Fourier transforms of nitely supported distributions on the group. Similar transforms may be deened on homogeneou...

There are many motivations for the discrete Fourier transform. Those of you in computer science have probably encountered them first in signal processing and perhaps further in cool theory results like switching lemmas. Those of you in physics have definitely encountered the continuous fourier transform, most likely first in quantum theory where we learn that the fourier transform goes between ...

This paper presents a mixed variational framework and numerical examples to treat a bidimensional friction contact problem in large deformation. Two different contact algorithms with friction are developed using the 2D finite element code PLAST2. The first contact algorithm is the classical node-on-segment, and the second one corresponds to an extension of the mortar element method to a unilate...

Optimization and inverse problems governed with partial differential equations are often formulated as constrained nonlinear programming problems via the Lagrange formalism. The nonlinearity is treated using the sequential quadratic programming. A numerical solution then hinges on an efficient iterative method for the resulting saddle–point systems. In this paper we apply a semi–monotonic augme...

The mortar nite element method allows the coupling of diierent discretization schemes and triangulations across subregion boundaries. In the original mortar approach the matching at the interface is realized by enforcing an orthogonality relation between the jump and a modiied trace space which serves as a space of Lagrange multipliers. In this paper, this Lagrange multiplier space is replaced ...