Influence of behaviour of alumina slurry on quality of alumina powder prepared by jet wheel impact atomization

Alumina slurries prepared in pilot plant scale have been characterized in terms of slurry rheology and stability and processed in a spray drier based on jet wheel impactor for atomization. Spheroidal alumina granules have been produced and their density, particle size and flowability behaviour are determined. Microstructure of the spheroidal granules has been observed under SEM and results are reported. The powders find application in plasma spray coatings, production of dense ceramic parts, components and tiles.     

A DEM Analysis of Flow Characteristics of Noncohesive Particles in Hopper

Flow characteristics of material in hoppers, silos, and bins are critical issues for operational stability as well as structural integrity of these units. In this work, flow of noncohesive particles in hopper is studied using the discrete element method (DEM) where each particle is tracked for its position, velocity, and acceleration. Material properties tend to alter during hopper flow due to compaction, expansion, and segregation. These features are difficult to model with a continuum approach. In the first part, material flow patterns are correlated with hopper angle and hopper opening, the two main design parameters. The typical shift from mass flow to funnel flow depending on the hopper angle was successfully simulated. In the second part, the discharge rate of material was quantitatively analyzed as function of hopper design parameters. Beverloo model 1 was tested on these simulated flow rates and it was shown that the simulated flow rates follow the model for this specific granular system. However, the DEM analysis was also able to demonstrate the failure of the traditional Beverloo model in the restricted flow regime. Simulated flow rates also follow the empirical correlations with hopper angle as stated in literature. DEM simulations were validated with experimental data for both material flow pattern and discharge rates.     

Development and applications of quaternary ammonium (QA) membrane electrodes in pharmaceutical preparation and in bioavailability of Prostaglandin E1 and Deoxycholate

The two novel ion-pairs (PB-TPB and NB-TPB) of quaternary ammonium drugs; propantheline bromide (PB), N,N-Diisopropyl-N-methyl-N-[2-(xanthen-9ylcarbonyloxy)ethyl] ammonium bromide and neostigmine bromide (NB), 3-(dimethylcarbamoyloxy) phenyl]-trimethylazanium have been synthesized, respectively and incorporated in poly (vinyl chloride)-based membrane electrodes for the quantification of propantheline bromide and neostigmine bromide in different pharmaceutical preparations. The influences of membrane compositions on the potentiometric responses of membrane electrodes have been found to substantially improve the performance characteristics. The best performance was reported with membranes having composition (w/w) of PB-TPB or NB-TPB (6%): PVC (34%): o-NPOE (60%). The proposed electrodes exhibit nernstian response in the concentration ranges of 2.1 × 10⁻⁷ M to 1.0 × 10⁻² M and 4.4 × 10⁻⁷ M to 1.0 × 10⁻² M with detection limit of 1.5 × 10⁻⁷ M and 3.3 × 10⁻⁷ M, respectively. Both the membrane electrodes perform satisfactorily over pH ranges of (3.5–7.5 and 4.0–7.0) with fast response times (11 s and 13 s), respectively. These drugs (PB and NB) were further utilized as different ion-pairs of Prostaglandin E₁ (PGE₁) and Deoxycholate (DOC) in poly (vinyl chloride)-based membrane electrodes for the determination of bioavailability of Prostaglandin E₁ and Deoxycholate in plasma of different patients.     

Numerical analysis of solidification of a 3-D semitransparent medium in presence of volumetric radiation

Solidification of a 3-D cubical semitransparent absorbing, emitting and scattering semitransparent medium in the presence of volumetric radiation is analyzed. An enthalpy based lattice Boltzmann method is used to analyze the solidification process. Radiative information is computed using the finite volume method. Over a range of temperatures, a distinct liquid-, mushy- and solid-zones are considered. Cases of both Dirichlet and Neumann boundary conditions are taken up. Liquid fraction and temperature distributions in the medium are analyzed for the effects of the extinction coefficient, the scattering albedo, the conduction-radiation parameter and the latent heat.     

Pure H2 Production by Decomposition of Methane Over Ni Supported on Hydroxyapatite Catalysts

The catalytic decomposition of CH₄ for the production of pure H₂ is carried out over Ni supported on hydroxyapatite [Ca₅(PO₄)₃(OH)] catalysts at 650 °C and atmospheric pressure. CH₄ decomposition activity is decreased with time on stream and finally deactivated completely. The physicochemical properties of the fresh catalysts are characterized by XRD, DTA/TG, TPR and SEM techniques along with CHNS analyses of the used samples. It is found that the 30 wt% Ni/HAp displayed higher H₂ production rates over the other Ni loadings, which is correlated with Ni metal surface area measured by O₂ pulse chemisorption. IICT communication number: 051211.     

Effect of protein concentration on the surface composition,water sorption and glass transition temperature of spray-dried skim milk powders

The effects of dilution of protein content in skim milk (34–8.5% protein content), by lactose addition, on the surface composition, water sorption property and glass transition temperatures of spray-dried powders were investigated. The X-ray photoelectron spectroscopy (XPS) study of spray-dried powders showed preferential migration of proteins toward the surface of the milk particles whereas the lactose remained in the bulk. Sorption studies showed that the lower protein concentration in milk powders is linked to an increased water adsorption property and lowering of water activity (a_w) for lactose crystallization. Analysis of glass transition temperature (T_g) of the powders sorbed at different humidities showed no distinct change in T_g values, indicating the dominant effect of lactose on the glass transition temperature of all the powders.     

Second law based optimisation of crossflow plate-fin heat exchanger design using genetic algorithm

A genetic algorithm based optimisation technique has been developed for crossflow plate-fin heat exchangers using offset-strip fins. The algorithm takes care of large number of continuous as well as discrete variables in the presence of given constraints. The optimisation program aims at minimising the number of entropy generation units for a specified heat duty under given space restrictions. The results have also been obtained and validated through graphical contours of the objective function in the feasible design space. The effect of variation of heat exchanger dimensions on the optimum solution has also been presented.     

Ion implanted AlGaN-GaN HEMTs with nonalloyed Ohmic contacts

In this letter, the incorporation of Si implantation into AlGaN-GaN high-electron mobility transistor (HEMT) processing has been demonstrated. An ultrahigh-temperature (1500/spl deg/C) rapid thermal annealing technique was developed for the activation of Si dopants implanted in the source and drain. In comparison to control devices processed by conventional fabrication, the implanted device with nonalloyed ohmic contact showed comparable device performance with a contact resistance of 0.4 /spl Omega//spl middot/mm, I/sub max/ of 730 mA/mm, f/sub t//f/sub max/ of 26/62 GHz, and a power of 3.4 W/mm on sapphire. These early results demonstrate the feasibility of implantation incorporation into GaN-based device processing as well as the potential to increase yield, reproducibility, and reliability in AlGaN-GaN HEMTs.