Tesile toughness of microcellular foams of polystyrene,styrene-acrylonitrile copolymer,and polycarbonate,and the effect of dissolved gas on the tensile toughness of the same polymer matrices and microcellular foams

This paper reports on the tensile properties of microcellular foams of three different thermoplastics, since there have been several reports in the literature, but with indefinite conclusions so far, that microbubbles act in a manner similar to rubber particles in toughening thermoplastics. Polystyrene (PS), styreneacrylonitrile copolymer (SAN), and polycarbonate (PC), were selected based on their different intrinsic ductilities. The gas supersaturation technique was used to generate samples with microbubbles. The effect of the presence of microbubbles inside the polymer matrix was separated from the effects of the pressure and thermal history experienced by the samples. Nitrogen gas dissolved into PS, and to a lesser extent into SAN, caused and increase of the tensile toughness, but this increased decayed with time as nitrogen gas diffused out of the samples. Furthermore, microcellularly foamed PS samples showed some limited improvement in terms of tensile toughness after all the nitrogen gas diffused out. SAN and PC showed deterioration of the tensile toughness in the presence of microbubbles.     

Refractive‐index matching between liquid crystals and photopolymers

Abstract— Refractive indices of two photocurable polymers, NOA65 and NOA81 (Norland Optical Adhesive), and two series of Merck liquid crystals, E‐series (E44, E48, and E7) and BL‐series (BL038, BL003 and BL006), and two UCF high‐birefringence liquid‐crystal mixtures were measured using an Abbe refractometer in the visible spectral region and 15–55°C temperature range. Some liquid crystals have excellent index matching with NOA65 in the red, while some fit better in the blue spectral region. To validate this index‐matching property found in the material level, we prepared some polymer‐dispersed liquid‐crystal devices. Good correlations between material and device performances are obtained.     

Race and sex as determinants of ratings by potential employers in a simulated work-sampling task.

Examined the way the sex and race of the rater and the sex and race of the ratee influence assessments of ratee performance on a simulated work-sampling task. 36 undergraduates assumed the role of a manager and rated all 8 combinations of male-female and black-white performers. Results indicate that sex-race stereotypes do influence assessments of behavior on a work-sampling task even when objective measures are defined. Findings are discussed in terms of potential methods of overcoming these biases to use more effectively the work samples for selection and promotion decisions are discussed. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wall friction in oscillating liquid columns

Rates of energy dissipation in an oscillating column of liquid in a pipe have been measured by a pressure-volume diagram technique. The measured rates are up to 150 per cent greater than prediction by laminar boundary layer theory, with the deviation increasing as the liquid viscosity is reduced from 42 to 1·0 cSt. This effect is believed due to periodic turbulence in the boundary layer. Some energy dissipation measurements were also made with a sand—water mixture. Less energy is required to suspend the sand in an oscillatory flow than would be required in a steady flow.     

Application of laser fusion to the radiolytic production of hydrogen

A preliminary conceptual design of a plant to produce hydrogen by laser-fusion-induced steam radiolysis has been developed. It consists of a suppressed ablation lithium wetted wall cavity surrounded by pure and borated steam regions in which fusion neutrons deposit a substantial fraction of their energy, causing nuclear heating in the steam and structural materials, as well as radiolysis of water molecules. Coupled photon-neutron transport calculations have been performed to determine the energy deposited in the different regions of the reactor, and subsequently the amount of hydrogen and nuclear heating generated for various sets of reactor dimensions. The results of these calculations have been used to perform an economic analysis based on scaled costs of the corresponding component systems of proposed laser fusion power plants and hydrogen-generating or handling facilities. The production costs of hydrogen and electric power produced by the laser fusion hydrogen/electric plant considered have been estimated. It has been found that within the uncertainty of these estimates, and for laser fusion output parameters reasonably expected for a first-generation reactor, the computed hydrogen and electric power production costs are not competitive with current prices of natural gas and oil, and electrical power generated by alternate means. However, with an extension of the expected range of output values to significantly higher pellet gains, hydrogen production could become economically attractive.     

Radium in uranium mill tailings - Some observations on retention and removal

The various mechanisms by which radium can be retained by uranium mill tailings are discussed. These include coprecipitation (solid solutions), adsorption on silica and hydroxides, ion exchange in clay minerals, and retention in pores. Previous work on radium removal from mill tailings and on radioactive disequilibrium in uranium deposits is critically reviewed in relation to these mechanisms. Fresh data are presented, indicating the roles of charge-depressant ions and of organic complexing agents in radium removal. The addition of reducing agent has been found effective in the presence of complexing agents because it can convert some low-solubility metal hydroxides to their more soluble, lower valency form, thereby eliminating radium adsorption sites. A radium level of 30 pCi/g in the tailings is concluded to be environmentally safe for surface disposal of tailings.     

Coextraction of uranium and radium from ore with ferric chloride

Ferric chloride leaching, at temperatures around 74°C, is found to remove up to remove up to 97% of the uranium from ores occurring in the Elliot Lake area of Canada. Radium removal is poor due to the formation of sulphates from the sulphides present in the ore. However, if the sulphides are removed initially by flotation, then ferric chloride can extract as much as 92% of the radium, giving tailings which are sulphide-free and with radium levels approaching 24 pCi/g. The main steps in a ferric chloride leaching process have been tested at the bench scale. Radium may be removed by adsorption on manganese dioxide and uranium is removed by liquid extraction with D2EHPA (DAPEX process). The ferric chloride may be recirculated for further leaching and the net usage is expected to be in the order of 5 kg/Mg of solids treated. Because of the recycle, it is possible to keep chloride ion levels in the effluent below the prescribed level of 750 mg/L.     

Recent experimental results in near-field antenna measurements

Recent experimental results on determination of antenna pattern and power gain from near-field measurements are described. Two new antenna measurement theorems were applied. Measurements were made on an electrically large horn lens, a standard-gain horn and a nominal duplicate of the measuring antenna. Some comparisons with direct far-field measurement results were made.