Irradiation effects on the abrasive wear of glassfibre-vinylester composites

Thermoset resins derived from vinylesters show improvedproperties over general purpose resins. Polymer composites basedon vinylester show improved wear resistant properties whenexposed to gamma-irradiation and laser beams. The improvement inoverall wear resistance of the composite is attributed to thefact that irradiation increases the resistance to crackpropagation which, in turn, increases the hardness due to a veryhigh concentration defect around the interface through adiffusion mechanism. Irradiation changes the interfacialmicrostructure to improve the fibre-matrix interfacial bonding.This is well supported by micrographs of the worn surface of thecomposite taken on a scanning electron microscope.     

A de novo interstitial deletion of chromosome 15 band q25 as revealed by FISH-technique

We report a new chromosomal finding in a 20 month-old girl. The minor clinical features included: moderate mental retardation, microcephaly, mild hypotonia and hypertelorism. Initially, what appeared to be a terminal deletion of the long arm of one chromosome 15 [15q26-->qter] was determined to be an interstitial deletion involving band 15q25 as revealed by FISH-technique, showing the presence of intact telomeric hybridization signals. The cytogenetic diagnosis was thus modified to 46,XX, del (15) (pter-->q24::q26--> qter). Nevertheless, the function of the enzyme telomerase should not be ignored, as healing could occur following such terminal deletions. Consequently, it will remain a difficult task to distinguish terminal deletions from those that are interstitial.     

Manager personality, manager service quality orientation, and service climate: Test of a model.

This article conceptually and empirically explores the relationships among manager personality, manager service quality orientation, and climate for customer service. Data were collected from 1,486 employees and 145 managers in grocery store departments (N = 145) to test the authors' theoretical model. Largely consistent with hypotheses, results revealed that core self-evaluations were positively related to managers' service quality orientation, even after dimensions of the Big Five model of personality were controlled, and that service quality orientation fully mediated the relationship between personality and global service climate. Implications for personality and organizational climate research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compromise: An effective approach for the design of pressure vessels using composite materials

The factors involved in designing structures made of metals and composite materials differ significantly because of the inherent non-isotropy associated with the latter. In this paper, a compromise Decision Support Problem template for the design of pressure vessels made of composite materials is presented. Membrane theory and classical laminate analysis have been utilized for the structural analysis. A novel criterion for reducing the stress concentration at the “knuckle” region of the pressure vessel has been used. To support the design methodology, a mathematical template for the design of the pressure vessel is detailed and solved. The results are examined and insights noted and discussed. The emphasis, however, is on the method and its capabilities and not on numbers obtained as a result of solving the template.     

Characteristics of single- and two-dimensional phase coupled arraysof vertical cavity surface emitting GaAs-AlGaAs lasers

Two-dimensional arrays of 3×3 vertical cavity surface emitting GaAs-AlGaAs lasers with 7-μm center spacing are described. The lasers were grown by molecular beam epitaxy and contain one grown GaAs-AlAs mirror under the active layer and a second, thermally deposited, high-reflectivity, SiO₂-Si mirror on top of the epitaxial layer. The array has a 295-K threshold of 90 mA, corresponding to 10 mA per laser. The individual lasers in the array have Gaussian beam profiles both spatially in the near field and angularly in the far field. When all the lasers in the array are operating in a coupled manner, the emission exhibits a lobed far-field pattern with a 5° separation in the direction parallel to the contact edge and a 2.5° separation perpendicular to the contact edge     

On fatigue reliability under random loads

We consider the problem of estimating the probability of survival (non-failure) and the probability of safe operation (strength greater than a limiting value) of structures subjected to random loads. These probabilities are formulated in terms of the probability distributions of the loads and the material strength. For the material strength, the Weibull distribution is assumed, the parameters of which are estimated by a statistical analysis of the experimental tensile strength of steel specimens subjected to different periods of random loads. The statistical analysis shows that, with the application of random loads, the initial homogeneous distribution of strength changes to a two-component distribution, reflecting the two-stage fatigue damage. In the crack initiation stage, the strength increases initially and then decreases, while an abrupt decrease of strength is seen in the crack propagation stage. The consequences of this behaviour on the fatigue reliability are discussed.     

Morphology-property relationships in oriented PET films: A role of in-plane crystalline orientation distribution on the film properties

The role of in-plane crystalline, amorphous, and overall molecular orientation on various properties in the plane of the films was investigated using a variety of techniques. It is shown that for a fixed value of crystallinity the in-plane crystalline orientation and the nature of the constraint imposed by the crystallites on the molecules play an important role in obtaining isotropic in-plane expansion or shrinkage properties. Achievement of in-plane isotropic tensile strength and elongation at the break are found to depend entirely upon an isotropic distribution of the amorphous orientation; the orientation of crystallites plays no detectable role. Furthermore, the deformation mechanisms of sequential and simultaneous biaxial stretching processes have been investigated and compared. The simulteneous stretching process is considered to be a more controlled film-fabricating method compared to sequential stretching in achieving balanced, in-plane film properties. © 1993 John Wiley & Sons, Inc.