Study of thermal conduction in bismuth-thallium specimens between 1.5 K and50 K

Three samples of bismuth-thallium, in which the thallium consent was low and varied between 2 to 9 %, were found to be superconducting with transition temperatures dependent on thallium concentration. The thermal conductivities of these samples have been measured over the temperature range from 1.5 to 50 K both in normal and superconducting states. Addition of low concentration of thallium in bismuth results in a gradual distortion of the bismuth lattice. This is evident from the Laue back reflection x-ray photographs taken on these samples. The thermal conductivity data on these specimens at low temperatures show considerable departure from the usual temperature dependence of thermal conductivity that is generally observed for an elemental or alloy superconductor. This deviation is particularly marked in the normal strte conductivity variation. The results have been discussed and analysed in order to identify the scattering mechanisms operative in these samples over the studied temperature range.     

Influence of prior-austenite grain size and fracture mode on the fracture toughness of 12% Cr steel

The prior-austenite grain size of a 12% Cr steel has been varied by altering the austenitising temperature. The effect of these variations on the K _Ic fracture toughness has been studied for the as-quenched condition and after subsequently tempering at temperatures up to 550°C. The fact that different fracture modes occurred within this range of heat-treatment has allowed the effect of grain size variations on fracture toughness to be compared for specific fracture morphologies.

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Résumé En modifiant la température d'austénitisation d'un acier à 12% Cr, on a fait varier son grain austénitique primaire et l'on a étudié l'effet de ces variations sur la ténacité à la rupture K _Ic dans l'état brut de trempe et après des revenus allant jusqu'à 550°C. Pour ces divers traitements thermiques, on a constaté des modes de rupture différents, ce qui a permis d'évaluer les effets de variations de la taille du grain sur la ténacité à la rupture, pour des morphologies de rupture bien spécifiques.

     

An efficient hierarchical clustering technique

An efficient divisive clustering technique based on hierarchical partitioning of space is proposed. It may be executed in O(N) time at each level of hierarchy. The technique along with some of its modifications are implemented on typical data sets and the results is discussed.     

Absorption of ultrasound in the intermediate state of indium

The attenuation of longitudinal ultrasonic waves has been measured in spectroscopically pure single crystals of indium in the intermediate state over the frequency range of 10–30 MHz. It is shown that the total attenuation in the intermediate state can be divided into two parts. The superconducting layers give rise to the oscillatory temperature-dependent attenuation, while the normal layers and the boundary effect between the normal and superconducting layers produce a temperature-independent constant attenuation. A plausible explanation of the observed experimental results is discussed.     

A socio-technical view of performance impact of integrated quality and sustainability strategies

This research seeks to examine the direct effects of social and technical integration on deployment of quality and sustainability management programmes and the indirect effect of those on quality and sustainability performance. We also seek to test the spillover effects of quality and sustainability management programmes on sustainability and quality performance, respectively. Socio-technical systems (STSs) theory is used to test the role of social and technical integration on quality and sustainability management programmes. The framework of integrated management system, as supported by both STSs and complementarity theory, is used to test the direct and spillover effects of quality and sustainability management programmes. A large multi-country sample is used to empirically test our theory-induced hypotheses. The findings support that social and technical integration are indeed significant enablers for the positive relationships that quality and sustainability programmes have on quality performance and sustainability performance. Specifically, the results show that while social integration has both direct and indirect effects on quality and sustainability performance, technical integration impacts quality and sustainability performance only through the mediation effect of the respective programmes. The results do not support the spillover effects of quality and sustainability management programmes on sustainability and quality performance. Implications of the findings on academic knowledge and managerial practice are offered.     

Dielectric behaviour of porcelain in relation to constitution

The dielectric properties of porcelain bodies prepared with and without the incorporation of mineralisers were investigated at different frequencies (1–10 MHz) and room temperature (25°C). The phase compositions and microstructures of the porcelain bodies were also determined. The influence of concentrations of mullite, quartz, cristobalite and glass as well as size of mullite crystals and the asymmetry of mullite crystal size distribution on dielectric constant, tanδ and loss factor were examined. The results suggested that frequency of the order of 10⁶ Hz had almost no effect on the dielectric constant but influenced the loss factor substantially. Multiple regression equations connecting loss factor with the constitutional parameters of porcelain bodies were developed to calculate loss factor and the calculated and experimental values were compared.     

Magnetohydrodynamic mixed convection in a non-Newtonian third-grade fluid flowing through vertical parallel plates: A semianalytical study of flow and heat transfer

Buoyancy assisted and buoyancy opposed mixed convection of a third-grade fluid, which flows through vertically oriented parallel plates, subjected to uniform and constant wall heat fluxes, under the effect of an externally applied magnetic field, are investigated. The coupled, nonlinear conservation equations of momentum and energy are solved employing the collocation method (CM) and velocity and temperature distributions are solved semianalytically. The results produced by the CM and the results of exact solution are compared for the buoyancy assisted and buoyancy opposed flow of a Newtonian fluid through the vertically oriented parallel plates arrangement without the effect of the externally applied magnetic field. An excellent agreement is exhibited by demonstrating the efficacy of the CM. The effects of the third-grade fluid parameter, Hartmann number, and mixed convection parameter on the dimensionless velocity, temperature, and Nusselt number are studied. The results imply that in the case of buoyancy assisted flow, an increment in the non-Newtonian third-grade fluid parameter causes a decrease in the fluid velocity near the plate walls, which finally causes an increase in the velocity in the central core of the plates. In buoyancy opposed flow, the effect of the same parameter is to oppose the flow reversal near the walls and with higher values of this parameter, it can totally prevent the flow reversal near the walls. The results of the present study can be useful in the fields of flow and heat transfer of various grades of polymers, paints, and food processing.     

Thermal characteristics of forced convection in combined pressure and shear-driven flow of a non-Newtonian third-grade fluid through parallel plates

Heat transfer in a non-Newtonian third-grade fluid, flowing under the action of pressure gradient and shear, through two parallel plates, is considered. The upper plate moves with a constant velocity. Constant wall heat fluxes are applied to the plates. Effect of viscous dissipation is included, which has a major role in heat transfer of non-Newtonian fluids. The governing equations are nonlinear and are solved semi-analytically by using the least-square method (LSM). Then, using the solution for velocity in the energy equation, the solution is obtained by a direct integration process. Further, approximate analytical solutions are obtained by the perturbation method, which validates the results generated by the LSM. The effects of the third-grade fluid parameter on the velocity and temperature and also on the physical quantity, such as Nusselt's number, are discussed. Further, viscous dissipation effects on the temperature distribution have been analyzed. Observations show that the movement of the upper plate results in a significant decrease in temperature near the upper plate. For the unit heat flux ratio, the temperature difference between the surface and fluid is more at the upper surface due to the enhanced convective heat transfer caused by the moving upper plate. Nusselt's number increases significantly with an increase in the heat flux ratio.     

On the Occurrences of “Frizzle-Type” Surface Defects in a Hot-Rolled Steel Plate

Metallurgical investigations were directed to probe into the genesis of “frizzle” and fissure-type surface defects on 10-mm hot-rolled steel plates meant for application in flat-bed wagons for carrying heavy machinery. The thin hairline fissures on the steel plates were identified as skin laminations associated with long, shallow, and branched cracks, intruding from the plate surfaces to the interior with curved contours, replete with fragmented oxide scale entrapments and debris. The incidence of these superficial defects on the plates was linked to surface damage to the solidifying skin of continuously cast steel slabs, induced by the extensive pitting and cavitation of caster pinch rolls. It is presumed that during hot rolling of the steel slabs, surface blemishes like indentations and folds got rolled over by metal flow, entrapping copious amounts of primary as well as secondary scales underneath the laminated skin. Under the influence of shear forces during rolling, the defects are believed to have ingressed further into the plate interior leading to the formation of long, shallow, and branched cracks with curved contours and entrapped fragmented oxide scales.