Pressure leaching of copper converter slag using dilute sulphuric acid for the extraction of cobalt, nickel and copper values

In our earlier studies [1–4], conditions were optimized for leaching converter slag with ferric chloride/dilute sulphuric acid for the recovery of cobalt, nickel and copper. By using both leachants most of the copper, nickel and cobalt values could be solubilized. Subsequent treatment of the leach liquors for separation and recovery of metals was difficult due to the presence of large quantities of iron in relation to other metal concentrations. In the present work, an attempt has been made to develop a process based on pressure leaching of the slag with dilute sulphuric acid in which iron contamination could be minimized by oxidation and hydrolysis. Various parameters including leaching time, pulp density, particle size, concentration of acid and oxygen partial pressure were studied to optimize the solubility of metal values. Under optimum conditions about 90% copper and more than 95% each of nickel and cobalt could be extracted with only 0.8% extraction of iron.     

Soft-computing based diagnostic tool for analyzing demyelination in magnetic resonance images

This paper proposes a soft-computing based diagnostic tool for analyzing (white matter changes) demyelination due to radiation therapy given to brain tumor cases. The tool exploits the pattern of changes in gray level distribution using a temporal sequence of magnetic resonance (MR) images. Appearance of white matter changes due to demyelination varies from patient to patient. Further, there exists inherent impreciseness in the white matter change patterns. These characteristics make use of fuzzy features well suited for describing image based temporal patterns. Correlation between these temporal patterns and actual onset of demyelination can be captured by fuzzy rules because of the inherent uncertainty associated with changes in gray level pattern in the image and occurrence of the disease. The tool is based on hybrid approach of two popular approaches of genetic algorithm based machine learning (GBML) techniques namely Michigan and Pittsburgh approach. The genetic algorithm (GA) based machine learning tool generates an optimized rule set to indicate positive (P), negative (N) or doubtful (D) cases of demyelination.     

Interaction of a characteristic shock with a weak discontinuity in a relaxing gas

The evolution of a characteristic shock in a relaxing gas is investigated and its interaction with a weak discontinuity is studied. A particular solution to the governing system, which exhibits space–time dependence, is used to study the evolutionary behaviour of the characteristic shock; the properties of incident, reflected and transmitted waves, influenced by the relaxation mechanism, together with the geometry of the fluid flow and the background state at the rear of the shock, are studied.     

Ferromagnetic GaN--Cr Nanowires

Using first-principles theory, we predict ferromagnetism in Cr-doped GaN nanowires irrespective of the sites that the Cr atoms occupy. This is in contrast to Mn-doped GaN nanowires in which the magnetic coupling between the Mn atoms is sensitive to the Mn--Mn and Mn--N distances, although the ground state of Mn-doped GaN nanowires is ferromagnetic. Each Cr atom carries a magnetic moment of about 2.5 micro(B). The magnetic moment at the N site, however, is small and is aligned antiferromagnetically to the moments at the Cr atom. The magnetization axis is perpendicular to the axis of the wire, but the anisotropy energy is rather small. The easy solubility of Cr in GaN and the lack of sensitivity of ferromagnetic coupling to Cr distribution suggest that Cr-doped GaN nanowires may be a more suitable system for applications in spintronics than Mn-doped GaN nanowires.     

Storage of molecular hydrogen in B-N cage: energetics and thermal stability

Using first principles theory based on density functional formulation we have studied the energetics and thermal stability of storing hydrogen in B-N-based nanostructures. We show that hydrogen molecule enters through the hexagonal face of the B36N36 cage and prefers to remain inside the cage in molecular form. The energy barriers for the hydrogen molecule to enter into or escape from the cage are respectively 1.406 eV and 1.516 eV. As the concentration of hydrogen inside the cage increases, the cage expands and the bond length of the hydrogen molecule contracts, resulting in significant energy cost. At zero temperature, up to 18 hydrogen molecules can be stored inside a B36N36 cage corresponding to a gravimetric density of 4 wt %. However, molecular dynamics simulation by using Nose algorithm at room temperature (T = 300 K) indicates that high weight percentage hydrogen storage cannot be achieved in B-N cage structures and thus these materials may not be good for practical applications.     

Kinetics of low-temperature chlorination of vanadium pentoxide by carbon tetrachloride vapor

Low-temperature chlorination of vanadium pentoxide by carbon tetrachloride vapor in dilution with nitrogen has been carried out. The effect of time, particle size, partial pressure of CCl₄ vapor (0.1 to 0.6 atm), and temperature (553 to 788 K) on the extent of chlorination of V₂O₅ has been investigated. The extent of chlorination of the oxide is found to increase with a decrease in its particle size. In all cases, the reaction followed a topochemical reaction model, obeying the following relationship:

Kinetics of and preparation of nickel by Ni3S2−NiO reaction under reduced pressure

The reaction between Ni₃S₂ (liquid) and NiO (solid) resulting in the formation of Ni and SO₂ was investigated in the temperature range 800° to 1200°C under a reduced pressure of <0.1 mm Hg. From the kinetic studies in the temperature range 950° to 1150°C, the reaction was found to proceed in three stages: i) Up to about 25 pct reduction, the rate of reaction was high and followed approximately a cubic rate law. During this stage, the reaction is thought to be under mixed control. Activation energy for the first 10 pct reduction was found to be approximately 45 kcal per mole. ii) From about 25 to 90 pct reduction, it obeyed the parabolic rate law, with an activation energy of 86±6 kcal per mole. This value is in agreement with the activation energy reported in the literature for the diffusion of sulfur in nickel. iii) Beyond 90 pct reduction, the reaction was very sluggish owing to the poor availability of the reactants. Optimum conditions for preparing nickel sponge by the above reaction and its processing into thin strips have been standardized. Some of the properties of the metal thus produced have also been incorporated.     

FPGA‐based implementation for improved control scheme of grid‐connected PV system with 3‐phase 3‐level NPC‐VSI

The large scale penetration of renewable energy resources has boosted the need of using improved control technique and modular power electronic converter structures for efficient and reliable operation of grid‐connected systems. This study investigates the performance of a grid‐connected 3‐phase 3‐level neutral‐point clamped voltage source inverter for renewable energy integration by using improved current control technique. For medium or high‐voltage grid interfacing, the multilevel inverter structure is generally used to reduce the voltage stress across the switching device as well as the harmonic distortion. The neutral‐point clamped voltage source inverter is controlled by using decoupling technique along with the proper grid synchronization via moving average filter–based phase‐locked loop. The moving average filter–based phase‐locked loop is used to reduce the delay in grid angle estimation under balanced as well as distorted grid conditions. A Lyapunov‐based approach for analysing the stability of the system has also been discussed. In this study, the hardware‐in‐loop (HIL) simulation of the control algorithm and the grid synchronization technique is realized using Virtex‐6 FPGA ML605 evaluation kit. The performance of the system is analyzed by conducting a time‐domain simulation in the Matlab/Simulink platform and its performance is examined in the HIL environment. The simulation and the hardware cosimulation results are presented to validate the effectiveness of the proposed control scheme.