Electrosintering of iron powder compacts

The influence of a nominal external electric field E=3 to 10 kV/cm on the sintering of iron powder compacts for 30 minutes at 1140 °C in a vacuum of ∼10⁻⁶ torr was investigated. It was found that the field reduced the porosity by as much as 29 to 73 pct compared to sintering without a field, the magnitude depending on the procedure employed to measure the density of the specimen. Optical microscopy revealed that the specimen electrosintered with E=10 kV/cm had a skin of ∼0.2 mm in thickness, where the porosity was significantly less than in the interior. This was also the depth of carburization that was obtained upon carburizing the electrosintered specimens. It is proposed that the decrease in porosity produced by the field results from a decrease in the chemical potential of vacancies at or just below the charged external surface. Vacancy flux equations employed to calculate the porosity as a function of distance below the external surface showed that the porosity becomes approximately zero at a distance of x _c=0.4 to 0.5 mm below the surface, which is in reasonable accord with the microscopy measurements. Similar values of x _c were obtained by assuming that the entire porosity decrease given by the density measurements occurred in a ring of thickness of x _c below the external surface. The difference in the density measured by two Archimedes-principle procedures and microscopy observations suggests that the cavities open to the external surface of the electrosintered specimens are smaller or narrower than those for specimens sintered without a field.     

Shaping cocaine abstinence by successive approximation.

Cocaine-using methadone-maintenance patients were randomized to standard contingency management (abstinence group, n?=?49) or to a contingency designed to increase contact with reinforcers (shaping group, n?=?46). For 8 weeks, both groups earned escalating-value vouchers based on thrice-weekly urinalyses: The abstinence group earned vouchers for cocaine-negative urines only; the shaping group earned vouchers for each urine specimen with a 25% or more decrease in cocaine metabolite (first 3 weeks) and then for negative urines only (last 5 weeks). Cocaine use was lower in the shaping group, but only in the last 5 weeks, when the response requirement was identical. Thus, the shaping contingency appeared to better prepare patients for abstinence. A 2nd phase of the study showed that abstinence induced by escalating-value vouchers can be maintained by a nonescalating schedule, suggesting that contingency management can be practical as a maintenance treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retardation of grain growth and cavitation by an electric field during superplastic deformation of ultrafine-grained 3Y-TZP at 1,450–1,600 °C

The influence of a continuous dc electric field applied orthogonal to the tensile direction on the flow stress, grain growth, and cavitation during superplastic deformation (SPD) of ultrafine-grained 3Y-TZP at 1,450–1,600 °C was determined. The field gave a significant reduction in the level of the stress-strain curve, and reduced grain growth and cavitation. The decrease in flow stress by the field was attributed mainly to the retardation of grain growth. The decrease in cavitation correlated with the retardation of grain growth and was attributed largely to the reduction in flow stress by the field.     

KINETICS OF LIQUID PHASE CATALYTIC DEHYDRATION OF METHANOL TO DIMETHYL ETHER

The kinetics of the liquid phase catalytic dehydration of methanol to dimethyl ether were investigated. The experiments were carried out under low concentrations of feed in a 1-L stirred autoclave, according to a statistical experimental design. The inert liquid phase used for this investigation was a 78:22 blend of paraffinic and naphthenic mineral oils. A complete thermodynamic analysis was carried out in order to determine the liquid phase concentrations of the dissolved species. A global kinetic model was developed for the rate of dimethyl ether synthesis in terms of the liquid phase concentration of methanol. The activation energy of the reaction was found to be 18,830 cal/gmol. Based on a step-wise linear regression analysis of the kinetic data, the order of the reaction which gave the best fit was 0.28 with respect to methanol. Effects of the solid to liquid and the gas to liquid mass transfer resistances on the kinetic rate have also been investigated.     

Cross-language computational investigation of the length effect in reading aloud.

The authors examined whether 2 computational models of reading, the dual-route cascaded model (M. Coltheart, K. Rastle, C. Perry, R. Langdon, and J. C. Ziegler, 2001) and the connectionist 2-layer model (M. Zorzi, G. Houghton, and B. Butterworth, 1998), were able to predict the pattern that the length effect found in reading aloud is larger in German than in English (J. C. Ziegler, C. Perry, A. M. Jacobs, and M. Braun, 2001). The results showed that the dual-route cascaded model, which uses a serial mechanism for assembling phonology, successfully predicted this cross-language difference. In contrast, the connectionist model of Zorzi et al. (1998) predicted the opposite: a larger length effect in English than in German. Both the success of one model and the failure of the other highlight fundamental differences between 2 major classes of computational models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microstructure coarsening during static annealing of 60Sn40Pb solder joints: I stereology

The phase size distributions (PSDs) of the Sn, Pb, and the combined Pb and Sn phases, and the shape factor δ were determined for as-reflowed 60Sn40Pb solder joints and following their annealing at 50°C to 150°C. The PSDs in all cases had a positive skew which was approximated by a log-normal function. The PSDs were time invariant and were in accord with the Bitti and Nunzio model for phase coarsening. The shape factor, δ, decreased with the mean of the combined Pb and Sn phase size, and with temperature. Whether or not δ affects the PSDs is not clear.     

Temperature reduction due to the application of phase change materials

Overheating is a major problem in many modern buildings due to the utilization of lightweight constructions with low heat storing capacity. A possible answer to this problem is the emplacement of phase change materials (PCM), thereby increasing the thermal mass of a building. These materials change their state of aggregation within a defined temperature range. Useful PCM for buildings show a phase transition from solid to liquid and vice versa. The thermal mass of the materials is increased by the latent heat. A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. For realistic investigations, test rooms were erected where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding. The experimental data was finally reproduced by dint of a mathematical model.