Measured and predicted root-mean-square errors in square and triangular antenna mesh facets

Deflection shapes of square and equilateral triangular facets of two tricot-knit, gold plated molybdenum wire mesh antenna materials were measured and compared, on the basis of root mean square (rms) differences, with deflection shapes predicted by linear membrane theory, for several cases of biaxial mesh tension. The two mesh materials contained approximately 10 and 16 holes per linear inch, measured diagonally with respect to the course and wale directions. The deflection measurement system employed a non-contact eddy current proximity probe and an electromagnetic distance sensing probe in conjunction with a precision optical level. Despite experimental uncertainties, rms differences between measured and predicted deflection shapes suggest the following conclusions: that replacing flat antenna facets with facets conforming to parabolically curved structural members yields smaller rms surface error; that potential accuracy gains are greater for equilateral triangular facets than for square facets; and that linear membrane theory can be a useful tool in the design of tricot knit wire mesh antennas

Stress decay in an orthotropic half-plane under self-equilibrating sinusoidal loading

An elastic orthotropic half-plane subjected to sinusoidal normal loading along an entire straight edge is analyzed. Stresses are calculated for material property combinations which are representative of some unidirectional fiber reinforced composites and of (+ or - 45) (subs) laminates made from the same unidirectional materials. Plots of the stresses as functions of the distance from the loaded boundary show that they can differ greatly from their counterparts in the isotropic half-plane under the same loading. How the results impact the question of the applicability of St. Venant's principle to orthotropic materials is briefly discussed

Shear-stress intensity factors for elastic sheets with cover plates

Shear stress intensity factors are calculated for three problems concerning inextensible cover plates either bonded to or embedded in an elastic sheet which is under uniaxial tension. The stress intensity factors are small when the ratio of sheet thickness to cover plate length is small and, as the ratio increase, rapidly approach their asymptotic values for infinite sheet thickness. In the problem of the embedded cover plate, the stress intensity factor also depends on the Poisson's ratio of the sheet material. The dependence on Poisson's ratio, however, is significant only when the ratio of sheet thickness to cover plate length is small. Some possible implications of the present results for debonding of reinforced sheets under cyclic loading are briefly discussed

Optimized Integration of Renewable Energy Technologies in MENA: Jordan Case Study

The methodology and the results for an optimized integration of renewable energy technologies in the MENA region is described and the results of a Jordan case study are presente

Stress concentrations in filament-stiffened sheets of finite length

Stress concentrations in filament-stiffened sheets of finite lengt

Load-shortening behavior of an initially curved eccentrically loaded column

To explore the feasibility of using buckled columns to provide a soft support system for simulating a free-free boundary condition in dynamic testing, the nonlinear load-shortening behavior of initially imperfect, eccentrically loaded slender columns is analyzed. Load-shortening curves are obtained for various combinations of load eccentricity and uniform initial curvature and are compared, for reference purposes, with the limiting case of the classical elastica. Results for numerous combinations of initial curvature and load eccentricity show that, over a wide range of shortening, an axially loaded slender column exhibits load-deflection compliance which is of the same order as that of a straight but otherwise identical cantilever beam under lateral tip loading

A finite-element alternating method for two-dimensional Mode-1 crack configurations

A finite-element alternating method is presented for 2-D Mode-1 crack problems. An analytical solution for an arbitrary polynomial normal pressure distribution applied to the crack faces is obtained and used as the basic solution in the method. The method is applied to several crack problems to study its efficiency and the results are compared to accurate stress-intensity factor solutions in the literature. The method gave reasonably accurate stress-intensity factors and crack opening displacements with minimal computing effort. Because the method must model only the uncracked body, finite-element models with many degrees of freedom are not warranted and therefore, the method has been implemented on personal computers

Predictors of course and outcome in hypochondriasis after cognitive-behavioral treatment

Background. Predictors of treatment outcome were evaluated in a clinical sample suffering from hypochondriasis. Methods: The sample consisted of 96 patients with hypochondriacal disorder according to DSM-IV or high syndrome scores on the Illness Attitude Scales (IAS) or Whiteley Index (WI). After intense inpatient cognitive-behavioral treatment (CBT), 60% of the patients were classified as responders because of substantial improvements or recovery from hypochondriacal symptomatology. Results: Non-responders were characterized by a higher degree of pre-treatment hypochondriasis, more somatization symptoms and general psychopathology (SCL-90R), more dysfunctional cognitions related to bodily functioning, higher levels of psychosocial impairments, and more utilization of the health care system as indicated by the number of hospital days and costs for inpatient treatments and medication. No predictive value was found for sociodemographic variables, comorbidity with other mental disorders and chronicity. Multiple linear regression showed that pre-treatment variables significantly predicted IAS scores at post-treatment (R-2 = 0.59), changes during treatment (0.10), IAS scores at follow-up two years later (0.41) and changes between baseline and follow-up (0.25). Conclusions: The results demonstrate the relevance of various psychopathological variables and health care utilization as important indicators for outcome and further course of clinical hypochondriasis. Copyright (C) 2002 S. Karger AG, Basel

All-propulsion design of the drag-free and attitude control of the European satellite GOCE

This paper concerns the drag-free and attitude control (DFAC) of the European Gravity field and steady-state Ocean Circulation Explorer satellite (GOCE), during the science phase. GOCE aims to determine the Earth's gravity field with high accuracy and spatial resolution, through complementary space techniques such as gravity gradiometry and precise orbit determination. Both techniques rely on accurate attitude and drag-free control, especially in the gradiometer measurement bandwidth (5-100mHz), where non-gravitational forces must be counteracted down to micronewton, and spacecraft attitude must track the local orbital reference frame with micro-radian accuracy. DFAC aims to enable the gravity gradiometer to operate so as to determine the Earth's gravity field especially in the so-called measurement bandwidth (5-100mHz), making use of ion and micro-thruster actuators. The DFAC unit has been designed entirely on a simplified discrete-time model (Embedded Model) derived from the fine dynamics of the spacecraft and its environment; the relevant control algorithms are implemented and tuned around the Embedded Model, which is the core of the control unit. The DFAC has been tested against uncertainties in spacecraft and environment and its code has been the preliminary model for final code development. The DFAC assumes an all-propulsion command authority, partly abandoned by the actual GOCE control system because of electric micro-propulsion not being fully developed. Since all-propulsion authority is expected to be imperative for future scientific and observation missions, design and simulated results are believed to be of interest to the space communit

Cognitive behavior therapy in panic disorder and comorbid major depression - A naturalistic study

Background: There is a lack of evidence about the effectiveness of cognitive behavior therapies (CBT) in settings of routine clinical care as well as in the treatment of panic and comorbid disorders. Methods: We investigated a group-oriented CBT approach for 80 patients with panic disorder including 35 patients with current comorbid major depression. Assessments took place 6 months before treatment, at the beginning and end of treatment, and 1 year later. Structured interviews and multiple clinical self-rating scales were used. Results: Panic patients with comorbid major depression showed higher anxiety-specific and nonspecific pathology. The most striking benefits were in reducing avoidance behavior, while improvements concerning catastrophic beliefs were smaller, but still significant. For most self-rating scale results, patients with and without comorbid depression improved to a comparable degree. However, the end-state functioning of patients with panic disorder and current comorbid depression at admission is significantly lower than for patients with panic disorder alone, Conclusions: The results point to the necessity to develop and improve treatment approaches for patients with comorbidity of panic disorder and current major depression. Copyright (C) 2000 S.Karger AG, Basel