Thermomechanical behaviour of composites

This paper derives the governing equations for the thermomechanical behaviour of composites. When the basic equations for the thermoelastic behaviour of solids were first derived in the nineteenth century several approximations were made. The effect of these assumptions are discussed and illustrated by the results of a simple laboratory test. The implications of this work on the analysis of impact damaged laminates are then discussed.     

Toughening of Dental Porcelain by Tetragonal ZrO2 Additions

The effect on mechanical behavior of ZrO₂ additions to a dental porcelain was investigated. The ZrO₂ was introduced into the glassy matrix phase of the porcelain by refritting the all-glass porcelain constituent. X-ray diffraction indicated that a sizeable fraction of the ZrO₂ was retained in the tetragonal form after the porcelain was fired. Zirconia additions to the porcelain produced substantial improvements in fracture toughness, strength, and thermal shock resistance.     

Power spectral density of CMI-coded TV signal transmitted through fibre-optic heterodyne system

An expression is derived for the power spectral density of a coded mark inversion (CMI) TV signal transmitted through a fibre-optic heterodyne system. An illustrative example is given, and its power spectral density has been computed numerically.     

Ultra-strong, well-apodised Bragg gratings in chalcogenide rib waveguides

The first ultra-strong, near-perfect, raised-apodised Bragg gratings in As/sub 2/S/sub 3/ chalcogenide rib waveguides using /spl lambda/=532 nm light and a modified Sagnac holographic writing setup are demonstrated. Good agreement is achieved between the experimental results and the numerical modelling of the gratings using the transfer matrix analysis for thin film structures.     

Physical parameters of fiber affecting passage from the rumen

Our objective was to review the factors that affect fiber passage from the rumen. Rumen residence time and passage from the rumen are important in control of intake, digestibility, protein metabolism, and protein escape. Physical factors associated with particle size and particle specific gravity affect passage from the rumen. Although particles of 5 cm may pass through the reticulo-omasal orifice, most particles leaving the rumen are smaller than 1 mm. Polypropylene ribbon cut into 7-cm lengths, introduced into the rumen, markedly reduced intake and were ruminated to fine particle size before being passed. Materials with specific gravity less than 1.0 are ruminated extensively and are passed slowly. As specific gravity of plastic particles increase, rumination of particles is decreased and passage is increased. Particles with specific gravities between 1.17 and 1.42 pass most rapidly. Increasing specific gravities further results in a decline in passage and a further lowering of rumination of particles. Natural hay and fresh forages are hydrated in the rumen, which causes functional specific gravity to increase. Some factors that affect rate of change of functional specific gravity of forages have been investigated. Small particle size, autoclaved rumen fluid, buffer solutions, and specific salts increased the rate of change of functional specific gravity of particles. Understanding of these factors may enable us to make better decisions in managing ruminant productions systems.     

Effect of orienting fields on agglomeration in dilute dispersions of magnetic fine particles

Static light scattering was used to investigate dilute dispersions of fine gamma -Fe/sub 2/O/sub 3/ magnetic particles. The particles were acicular and on average 0.39 mu m long and 0.056 mu m in diameter. They were dispersed in organic solvents at concentrations of approximately 10/sup -4/ vol%, corresponding to an average interparticle separation of 9 mu m. Computer programs using a coupled dipole algorithm to predict the scattering from the particles were written. Experimental results do not agree with computer calculations of the light scattering from single particles, but are consistent with scattering from thick ropelike agglomerates of particles. The size of these agglomerates was estimated after 10 s to be less than 100 particles, while the thickness of the ropes is at least 5 particles.<>     

Crystallization of some anorthite-diopside glass precursors

Anorthite and diopside have been obtained from complete devitrification of glasses belonging to the quaternary system MgO-CaO-Al₂O₃-SiO₂. Microstructure, the natural trend of the nucleation mechanism and kinetic studies on the crystallization phenomenon have been investigated by means of optical and electron microscopies, thermal and thermomechanical techniques and X-ray powder diffractometry. All the glasses investigated show a complete crystallization starting from a simple surface nucleation process. The activation energy for the crystallization process proved to be higher than that for viscous flow, leading to an important aspect modification in the sample during ceramization. Thermal stability and physical properties of both glass and glass-ceramic materials have been tested, suggesting the possible use of these materials in industrial application.     

ESD–RF co-design methodology for the state of the art RF-CMOS blocks

This paper describes an approach to design ESD protection for integrated low noise amplifier (LNA) circuits used in narrowband transceiver front-ends. The RF constraints on the implementation of ESD protection devices are relaxed by co-designing the RF and the ESD blocks, considering them as one single circuit to optimise. The method is applied for the design of 0.25 μm CMOS LNA. Circuit protection levels higher than 3 kV HBM stress are achieved using conventional highly capacitive ggNMOS snapback devices. The methodology can be extended to other RF-CMOS circuits requiring ESD protection by merging the ESD devices in the functionality of the corresponding matching blocks.     

A prospective investigation of the impact of childhood sexual abuse on the development of sexuality.

The sexual attitudes and activities of 77 sexually abused and 89 comparison women (mean age=20.41, SD=3.38) were assessed 10 years after disclosure in a longitudinal, prospective study of the long-term effects of childhood sexual abuse. Abused participants were more preoccupied with sex, younger at first voluntary intercourse, more likely to have been teen mothers, and endorsed lower birth control efficacy than comparison participants. When psychological functioning earlier in development was examined, sexual preoccupation was predicted by anxiety, sexual aversion was predicted by childhood sexual behavior problems, and sexual ambivalence (simultaneous sexual preoccupation and sexual aversion) was predicted by pathological dissociation. Findings also indicate that biological father abuse may be associated with greater sexual aversion and sexual ambivalence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)