Comparison of backwards and forwards scalar relative dispersion in turbulent shear flow

Turbulent mixing is characteristically identifiable with backwards relative dispersion, where pairs of particles get transported to the mixing location. However, relative dispersion models are insensitive to this fact and predominantly apply forwards relative dispersion concepts. The goal of the current study is to highlight and interpret differences, if any, between the forwards and backwards relative dispersion. Direct numerical simulation is used to obtain the flow field in an infinitely long channel. A Lagrangian technique is used in conjunction with the direct numerical simulation to track scalar markers released into this flow field. Two different types of flow, Poiseuille channel flow, where the walls of the channel are stationary, and plane Couette flow, where the walls of the channel move in opposite directions relative to each other, are simulated. Forwards relative dispersion is found to be faster in the viscous sub-layer, the transition region and the logarithmic regions of the Poiseuille channel flow, while the backwards relative dispersion is faster in the center of the channel. Faster forwards relative dispersion is seen in the center of the Couette flow channel and the logarithmic region, while higher rate of backwards relative dispersion is observed in the viscous sub-layer and the transition region. The underlying reason for differences in relative dispersion is related to the turbulence velocity structure and the velocity fluctuation probability density function that the particle pairs experience while traveling towards or away from a point. It is also found that the Prandtl number affects rates of forwards and backwards relative dispersion in a systematic manner.     

Microstructure and properties of an infra-red transmitting chalcogenide glass-ceramic

A chalcogenide glass-ceramic (0.3 PbSe-0.7 Ge_1.5 As_0.5 Se₃) which transmits in the infra-red region between 8 and 12 m was produced from a phase separated parent glass. The glass transition temperature (T _g) was increased from 280 to 340°C by crystallizing the phase with the lowerT _g. Further heat-treatment produced a glass-ceramic that was up to 60% crystalline and contained PbSe, PbSe₂ and GeSe₂ crystals with a gran size of 0.5 m. The infra-red transmission of the glass-ceramic decreased with increased crystallinity. The glass-ceramic modulus of rupture (38 MN m^–2) was increased to as much as twice that of the glass and the Vickers hardness increased by 30% to 280 kg mm^–2.     

Optimum anamorphic image generation using image rotation and relative entropy

Multimedia Tools and Applications - Anamorphosis is related to the art that gives illusion (distortion) over the image or object when the viewer looks the original image or from the random...     

Stochastic meshfree method for elasto-plastic damage analysis

This paper presents a stochastic meshfree method for solving boundary-value problems in damage mechanics under elasto-plastic conditions. Isotropic ductile damage evolution law is used to model the coupled elasto-plastic damage growth. Uncertainty associated with initial damage in materials is considered as random field. Moving least squares shape function method and Karhunen Loève expansion method are used for random field discretization. Statistical parameters of the response quantities are computed using perturbation method. The proposed method involves a new stochastic stress update procedure to solve the nonlinear equations in terms of discretized random variables arising from perturbation of equilibrium equations system. Numerical examples comprising of one and two dimensional problems are presented to illustrate the effectiveness of proposed method.     

Studies on applications of room temperature ionic liquids

Room temperature ionic liquids (RTILs) have many potential applications in nuclear fuel cycle, especially actinide and fission product separations. This paper outlines the results of work in our Centre directed towards identifying specific applications with respect to recovery of uranium and palladium from nitric acid media. The use of RTILs as diluents for extraction processes as well as electrolysis media have been explored. The extraction of uranium(VI) and palladium(II) from nitric acid medium by tri-n-butyl phosphate solution in RTIL has been studied. Voltammetric investigations on the suitability of RTIL as electrolytic medium for the electrodeposition of uranium and palladium at near ambient conditions are reported. The feasibility of electrodeposition of uranium as uranium oxide (UO₂) and palladium(II) as metallic palladium from the loaded organic phase has been demonstrated.     

Temperature changes and loads during hot-die forging of a gamma titanium–aluminide alloy

Non-isothermal forging is a non-steady state deformation process since temperatures of die, workpiece and environment are different from each other. The workpiece temperature decreases during the process by heat transfer to the dies and the environment. On the other hand, deformation heating can increase the workpiece temperature. The deformation loads depend not just on the initial temperature of the workpiece and the strain rate, but also on the duration of the deformation. This paper presents the results of a study that involved both physical experiments and finite element simulation of the non-isothermal deformation of a gamma titanium–aluminide.     

Influence of β-carotene-rich vegetables on the bioaccessibility of zinc and iron from food grains

Widespread deficiencies of iron and zinc, commonly found in populations dependent on plant foods, necessitate food-based strategies to maximise their bioavailability from plant foods. In this study, β-carotene-rich vegetables were evaluated for their effects on the bioaccessibility of iron and zinc from cereals and pulses by employing a simulated gastrointestinal digestion procedure involving equilibrium dialysis. Addition of carrot or amaranth (2.5 g and 5 g per 10 g of grain) significantly enhanced the bioaccessibility of iron and zinc from the food grains, the percent increase being 13.8–86.2 in the case of carrot and 11–193% in the case of amaranth. Pure β-carotene added at an equivalent level also enhanced the bioaccessibility of iron (19.6–102% increase) and zinc (16.5–118.0% increase) from the cereals examined. This is the first report on the beneficial influence of β-carotene on iron and zinc bioaccessibilities.     

Regional validity of the parameters of a distributed runoff-erosion model in the semi-arid region of Brazil

The present paper examines the validity of the application of a distributed rainfall-runoff-erosion model on a regional basis in a semi-arid region of Brazil. The model tested is known as WESP (Water Erosion Simulation Program) developed by Lopes (1987). The model simulates the hydrograph and the sediment graph for individual events and thus, the model when properly calibrated can serve as a predictive tool for runoff and soil erosion on an individual or a continuous basis. The possibility of the existence of regionally applicable values for the parameters of the model WESP would be very interesting from the point of view of predictability of runoff and soil erosion from ungauged basins in the region. For this purpose, data collected in several experimental units in the experimental basin of Sumé as well as in the experimental basin of São João de Cariri have been used. The model was calibrated and validated in each of the experimental units (consisting of erosion plots and micro-basins) and the average value from all of the units for each of the parameters was considered to be the regional value. With these average values, all the events in all the experimental units were simulated. The results show that the runoff and erosion values simulated with this single parameter set were very good in all the units, being well within the acceptable deviations.