High temperature flow and failure processes in an Al–13 wt% Si eutectic alloy

A maximum elongation of 250% was achieved in a Al–13 wt% Si eutectic alloy (∼ 18 μm grain size) when deformation was carried out at 557°C at a strain rate of 1×10^-2 s^-1. The shapes of the true stress–true strain curves obtained in this investigation are different from those reported by Chung and Cahoon [1]. It is felt that this is due to differences in the processing of the alloys used in the two investigations. The higher elongation obtained at a strain-rate of 1×10^-2 s^-1 as compared to 4.6×10-4 s-1 is attributed to a higher strain rate sensitivity, lower rain and particle coarsening and a lower level of cavitation at the former strain rate. It is believed that the mechanism of high temperature flow in this system is by grain boundary sliding accommodated by dislocation motion. The latter is rate controlled by the climb of dislocations over hard Si particles. This revised version was published online in November 2006 with corrections to the Cover Date.     

ACHIEVEMENT VALUES AND SCIENTIFIC PRODUCTIVITY.

50 COLLEGE SCIENCE TEACHERS WERE TESTED ON MUKHERJEE'S SENTENCE COMPLETION TEST (SCT), A FORCED CHOICE SCALE FOR MEASURING ACHIEVEMENT VALUES (V ACH). THE HYPOTHESIS OF A POSITIVE RELATIONSHIP BETWEEN V ACH AND SCIENTIFIC PRODUCTIVITY WAS TESTED. RESULTS INDICATED A SIGNIFICANT POSITIVE CORRELATION. MOST TEACHERS WERE ADVANCED RESEARCH DEGREES WERE FOUND TO HAVE HIGH V ACH SCORES. THE STUDY PROVIDES EVIDENCE OF THE CONSTRUCT VALIDITY OF THE SCT AS A MEASURE OF V ACH AND DEMONSTRATES THE IMPORTANCE OF V ACH IN PREDICTING SCIENTIFIC PRODUCTIVITY. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural Studies of Gels and Gel-Glasses in the SiO2-GeO2 System Using Vibrational Spectroscopy

GeO₂ gel and gels in the SiO₂-GeO₂ system synthesized by the hydrolytic polycondensation of metal alkoxides have been studied by infrared and Raman spectroscoptic techniques. The molecular structures, hydroxyl contents, and crystallinity of gels and gel-glasses in relation to the thermal history and GeO₂ concentration were investigated. The binary compositions having up to 70 mol% GeO₂ were examined.     

Slow Surface Wave along a Compressible Plasma Slab

Slow surface wave phenomena are studied in a compressible plasma—dielectric interface, the structure being rectangular. Cases with plasma dielectric constant εp positive (i.e. plasma frequency is less than excitation frequency) and negative (i.e. plasma frequency is greater than excitation frequency) are both considered. The existence of tho ‘ forward ’ surface wave is observed in all cases. The Philbrick repetitive SK5-Analog Computer was used for computation. Limiting case of incompressible plasma slab is also discussed.     

Precision universal temperature ( −200°C to +200°C) controller with fast solid state on-off system

A simple, rugged, reliable, low cost temperature display-cum-controller has been designed and constructed using standard integrated circuits and a 3½ digit LED display. The controller, utilising semiconductor controlled rectifiers as fast solid state on–off switches capable of maintaining the set temperature constant within the temperature range -200^°C to + 200^°C with a resolution of ±0·05^°C. A thermocouple (specifically, a copper-constantan type) sensor has been used because of its fast response time and tolerance of high magnetic fields.     

Transient stability of a double-excited synchronous machine by the second method of Lyapunov

Lyapunov functions are generated for doubly-excited and conventional singly-excited synchronous machines. A comparison of the stability boundaries of these two machines in the state-plane shows that the doubly-excited machine hag a larger zone of transient stability.     

Heat conduction and thermal stabilization in YBCO tape

Yttrium barium copper oxide (YBCO) coated conductors are widely used in the conduction-cooled superconducting magnets with rapid development in refrigeration technologies at present. ‘Quench’ is a state that refers to the irreversible and uncontrolled superconductor to resistive transitions in the superconductor. The propagation of ‘quench’ or ‘normal zone’ has different characteristics in these high temperature superconductors (HTS) compared to low temperature superconductors. The superconductor to normal index, known as ‘n’ is much flatter in HTS. The hot spot emerging in local region due to quench and non-uniform critical current may cause permanent damage to whole HTS tape and hence the magnet winding pack. Thus it is necessary to determine the temperature profile along the length of HTS tape under a given energy (joule heating) such that propagation of the hot spot developed locally can be prevented early. In this study, a one dimensional, time dependent heat diffusion equation with appropriate boundary conditions are used to describe the consequences of the normal zone propagation resulting in the temperature diffusion in a HTS tape. The results demonstrate the necessity of adequate cooling of the edges of the flat HTS tapes to prevent irreversible normal zone transitions.