We study electromagnetic plane wave diffraction by a hollow circular cone with thin walls modelled by the so-called impedance-sheet boundary conditions. By means of Kontorovich–Lebedev integral representations for the Debye potentials and a ‘partial’ separation of variables, the problem is reduced to coupled functional difference (FD) equations for the relevant spectral functions. For a circula...

In this article, a hybrid optimization method has been proposed consisting of modified ant colony systems (ACSs) and constrained nonlinear programming (NLP) to solve the problems of null synthesis of concentric rings circular array antenna consist of parallel center feeding dipoles elements with two complex nonlinear optimization problems. In the first problem, a synthesis of concentric circula...

The theory of the dielectric cone antenna has been known since the early seventies. On their own, this antenna has a reasonably circular symmetric radiation pattern but exhibits an undesirably high side-lobe level. A properly designed metallic shield, which does not interfere with the field structure of the dielectric cone, may be used to reduce the side-lobe level. Although in principle this a...

In single photon emission computed tomography (SPECT), a varying-focal-length cone-beam collimator can be used to reduce the truncation problem and to maintain sensitivity when imaging the organ of interest. The collimator is constructed so that the collimator holes focus to a circular symmetric, spatially varying, focal point function. The focal length increases radially from the shortest foca...

We develop an active set method for solving second-order cone programs that may have an arbitrary number of linear constraints but are restricted to have only one second-order cone constraint. Problems of this form arise in the context of robust optimization and trust region methods. The proposed active set method exploits the fact that a second-order cone program with only one second-order con...

This study investigated the effects of screwdriver handle shape, surface, and workpiece orientation on subjective discomfort, number of screw-tightening rotations, screw-insertion time, axial screwdriving force, and finger contact forces in a screwdriving task. Handles with three longitudinal cross-sectional shapes (circular, hexagonal, triangular), four lateral shapes (cylindrical, double frus...

In this paper we study a special class of convex optimization problems called conically ordered convex programs (COCP), where the feasible region is given as the level set of a vector-valued nonlinear mapping, expressed as a nonnegative combination of convex functions. The nonnegativity of the vectors is defined using a pre-described conic ordering. The new model extends the ordinary convex pro...

A “facial reduction”-like regularization algorithm is established for general conic optimization problems by relaxing requirements on the reduction certificates. This yields a rapid subspace reduction algorithm challenged only by representational issues of the regularized cone. A condition for practical usage is analyzed and shown to always be satisfied for single second-order cone optimization...