Input impedance of a probe-fed circular microstrip antenna with thick substrate

A method of computing the input impedance for the probe fed circular microstrip antenna with thick dielectric substrate is presented. Utilizing the framework of the cavity model, the fields under the microstrip patch are expanded in a set of modes satisfying the boundary conditions on the eccentrically located probe, as well as on the cavity magnetic wall. A mode-matching technique is used to solve for the electric field at the junction between the cavity and the coaxial feed cable. The reflection coefficient of the transverse electromagnetic (TEM) mode incident in the coaxial cable is determined, from which the input impedance of the antenna is computed. Measured data are presented to verify the theoretical calculations. Results of the computation of various losses for the circular printed antenna as a function of substrate thickness are also included.     

Brief therapy prevalence and training: A national survey of psychologists.

Psychologists find themselves ill-prepared to meet the increasing demand for briefer and briefer therapies. Members of APA Divisions 12 (Clinical Psychology) and 29 (Psychotherapy) were surveyed (N?=?1,250; return rate?=?57%) regarding their practice of and training in brief therapy. Results indicate that almost all (89%) of the respondents perform some brief therapy and, on average, spend half their time doing it. With regard to training, however, half of those conducting brief therapy have never taken any brief therapy courses. Additional findings indicate theoretical orientation, gender, region, practice site, and setting are significantly related to the amount of brief therapy delivered. Overall, the amount and helpfulness of brief therapy training are significantly related to one's skill, satisfaction, and positive attitude toward brief therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Finite element method of lines analysis of open, periodic structures

The applicability of the finite element method of lines to the analysis of open, periodic structures is demonstrated. To validate the method and study its characteristics, the problem of transverse electric (TE) plane wave scattering from a metallic waveguide array is considered. Convergence of the solution is investigated both as a function of the mesh density and the order of the polynomial approximation used in the construction of basis functions.<>     

Leaders as attachment figures: Leaders' attachment orientations predict leadership-related mental representations and followers' performance and mental health.

In 3 studies, the authors examined the contribution of leaders' attachment styles to their leadership motives and beliefs and to followers' outcomes. In Study 1, participants completed measures of attachment orientation, leadership motives, self-representations, and leadership style. Studies 2 and 3 were conducted within Israeli military units either during a leadership workshop or during intensive combat training. Israeli military officers and their soldiers (followers) reported on their attachment styles, and the soldiers reported on the officers' leadership qualities and on the soldiers' own performance and mental health. Leaders' attachment anxiety was associated with more self-serving leadership motives and with poorer leadership qualities in task-oriented situations. Leaders' attachment anxiety also predicted followers' poorer instrumental functioning. Leaders' attachment-related avoidance was negatively associated with prosocial motives to lead, with the failure to act as a security provider, and with followers' poorer socioemotional functioning and poorer long-range mental health. Results are discussed with respect to the value of attachment theory for the study of leadership. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Approach to model order reduction for angular response calculationsin periodic structures

A framework for implementing model order techniques for periodic structure analysis is presented. Appropriate choice of the problem formulation, in combination with straightforward Pade approximations, permit the entire angular response to be extrapolated from the solution at a single aspect angle     

Semi-discrete finite element method analysis of arbitrarymicrostrip elements-static solution

The semi-discrete finite-element method (FEM) is applied to solve the Poisson equation for a class of microstrip structures. This numerical technique is a variant of the conventional FEM. Its name stems from the fact that finite-element approximation is implemented only along two of the Cartesian coordinates, while the solution dependence on the third is handled analytically. When applicable, this method is simpler and more economical than the conventional fully-discrete version. Convergence properties of the solution are examined, and its validity tested for a number of geometries through comparison with other solutions and published data     

Failure modes and fracture mechanisms in flexure of Kevlar-epoxy composites

The results of testing in three-point bending of aramid fibre-reinforced epoxy composites are described. This loading mode has been chosen in order to increase the variety of failure modes and of fracture mechanisms. The main failure modes observed are tensile and delamination, with a transition at a fibre volume fraction of about 46%. This mode transition is detectable by monitoring various mechanical properties and acoustic emission data against the fibre volume fraction. The tensile mode comprises a fracture mechanism of fibre splitting and pull-out and the delamination comprises fibre bending, tearing off of fibre skin and shearing of individual filaments. Other effects such as the shifting of the neutral axis and the compressive failure at the compression side are also reported.     

Continuous spectrum and characteristic modes of the slot line infree space

The continuous spectrum of the slot in an infinite ground plane is expressed in terms of the Mathieu functions. The so-called characteristic values and field modes of the slot are stated explicitly     

Extension of Kennaugh's optimal polarization concept to the asymmetric scattering matrix case

The polarization scattering matrix measured by a bistatic radar system generally will be asymmetric. The scattering matrix will also be asymmetric when the radar system is monostatic, but the intervening propagation medium is anisotropic. Kennaugh's optimal polarizations theory is generalized to the case of the asymmetric scattering matrix. The radar antenna polarizations to be used for maximum and zero power receptions are defined and geometrically interpreted on the Poincare sphere. These polarizations, termed optimal polarizations, may be used to enhance the level of target echo return, to discriminate against undesired interference sources, or to classify radar targets.     

Rigorous analysis of a circular patch antenna excited by amicrostrip transmission line

Boundary conditions are enforced on a portion of the microstrip feed line as well as the patch antenna. The integral equation for the unknown currents on the antenna and feed is solved by applying the Galerkin method of moments in the Fourier transform domain. The validity of the solution is tested by comparison of computed results with experimental data. The theoretical treatment proves to be applicable to the most common feeding arrangements, namely, the direct edge-feed and proximity coupling excitation. In the latter case, two-layer substrates having distinct dielectric constants are studied. The purpose of the study is to deduce, for a given overall substrate thickness, the smallest line-ground plane separation for which a match of the radiator to the feed line is still possible. The advantages of such a configuration are discussed