Effect of preparation method on the dispersion and activity of V2O5–Al2O3 catalysts

Al2O3-supported 12 wt% V2O5 catalysts were prepared by physically grinding both the oxides (solid–solid wetting) and by wet impregnation techniques. The physical mixtures (PM) were treated under two different conditions – calcination in the presence of dry oxygen and wet oxygen. The catalysts were characterized by x-ray diffraction, scanning electron microscopy, electron spin resonance and oxygen and carbon dioxide chemisorptions. Vanadia dispersion of the physical mixture calcined in the presence of wet oxygen was found to be very similar to that of the V2O5/Al2O3 catalyst prepared by the standard impregnation method. Methanol partial oxidation activities of these catalysts were also comparable. This revised version was published online in November 2006 with corrections to the Cover Date.     

Changes in wild ass (Equus hemionus khur) habitat conditions in Little Rann of Kutch,Gujarat from a remote sensing perspective

The Rann of Kutch, Gujarat is the only habitat for one of the endangered sub-species of the Asiatic wild ass (Equus hemionus khur) and most of the population survives in the Wild Ass Sanctuary in Little Rann of Kutch. The area is a saline desert with extremely sparse cover of vegetation. In the past, the habitat supported a thriving population of wild asses. However, due to extensive changes in the land-use around the Rann of Kutch, there has been an increase in the conflict of interests between man and the wild ass. The present paper seeks to analyse the situation with respect to changes in land-use, vegetation cover and salt cultivation to plan proper habitat management inside the sanctuary to mitigate the problem of crop predation by the wild ass through the use of high resolution satellite data.

The Survey of India (SOI) topographic maps of 1960 vintage were used to estimate the past habitat, land-use, vegetal cover and salt fields. The SOI topographic maps and false colour composites provided a limited number of land-use classes for a meaningful comparison of land-use changes. This data has been compared with digitally classified SPOT MLA on SIPS (Satellite Image Processing System, Hyderabad). Various techniques such as principal component analysis, normalized difference vegetation index, unsupervised and supervised classifications were carried to classify various features. Of these techniques, supervised classification provided very useful results for an effective interpretation. It was observed that there has been an increase in irrigated crop fields. This has resulted in enhanced crop predation by wild asses thereby triggering human-wild ass conflicts. The digital interpretation provided crucial information on a number of classes of land-use relevant to the habitat of wild ass. An operational basis of deriving such information for formulating effective conservation strategies is presented.     

Effect of T6 heat treatment on damping characteristics of Al/RHA composites

In the present work, effect of T6 heat treatment on the damping behaviour of aluminum/rice husk ash (RHA) composites fabricated by vortex method was studied using dynamic mechanical analyser (DMA) at frequencies ranging from 1 Hz to 25 Hz at room temperature under three-point bending test mode. The matrix material for the present work was A356·2 and reinforced with different weight % of 4, 6 and 8 rice husk ash particles. It was observed that composite exhibits high damping capacities than unreinforced alloy and increases with increase in weight % and the storage modulus increases with the addition of RHA particles but decreases with the increase in weight %. The heat treated composites exhibit higher damping capacity than the composites without heat treatment and increases with the increase in weight % of the reinforcement and loss in the storage modulus was observed and further decreases with the increase in the weight % of reinforcement. The related mechanisms were also discussed.     

Properties of Ternary One Dimensional Plasma Photomic Crystals for an Obliquely Incident Electromagnetic Wave Considering the Effect of Collisions in Plasma Layers

An analytical study is presented on the modal dispersion characteristics, group velocity, and effective group, as well as the phase index of a ternary one dimensional plasma photonic crystal for an obliquely incident electromagnetic wave considering the effect of collisions in plasma layers. The dispersion relation is derived by using the transfer matrix method and the boundary conditions based on electromagnetic theory. The dispersion curves are plotted for both the normal photonic band gap structure and the absorption photonic band gap structure. It is found that the increase in the angle of incidence shifts the photonic band gap toward higher frequencies. Also, the cutoff frequency is independent of collisions.     

Green fluorescence of terbium ions in lithium fluoroborate glasses for fibre lasers and display devices

In this paper, for the first time, the visible fluorescence properties, resonance energy transfer mechanism responsible for non-radiative decay rates of ⁵D₄ → ⁷F₅ transition and also quenching of fluorescence intensity of the ⁵D₃ → ⁷F₅ transition of various concentrations of Tb³⁺ ions in LBZLFB glasses are reported. Optical absorption, fluorescence spectra and quantum efficiencies are measured and analysed. Green fluorescence related to ⁵D₄ → ⁷F₅ (548 nm) transition is registered under excitation of 378 nm of Tb³⁺ ions. Based on excitation and fluorescence measurements, several spectroscopic parameters for Tb³⁺ ions are examined as a function of concentration by Judd–Ofelt theory to judge the suitability of studied glasses for display devices and fibre lasers.     

Kinetics of Lime-Enhanced Hydrogen Reduction of Solid Nickel Sulphide

Investigations have been carried out on the hydrogen reduction of solid nickel sulphide (β-NI₃S₂) in the presence of lime. The effects of the charge composition, temperature (500-700°C). hydrogen flow rate, time of reduction and particle size of the sulphide have been studied. Lime was found to tremendously enhance the reduction process and drastically stifle H₂S emission into the off-gas. Temperature as well as hydrogen flow rate were found to affect the reduction process and best results were achieved (in static bed experiments) with 200% CaO addition at 630°C in 2 hr employing a hydrogen flow rate of 0.2 l/min. Thermodynamic considerations and several experimental findings indicate that the progress of the Ni₃S₂-CaO-H₂ reaction is governed by the intrinsic kinetics of the Ni₃S₂-H₂ reaction. Kinetic analysis reveals the observance of Jander's linear rate equation indicative of phase boundary control at the sulphide/gas interface. Scanning electron microscopic studies on the reduced nickel sulphide pellets show that like in solid state transformations, discontinuous precipitation (cellular morphology) is exhibited.     

Generalized approach for model algorithmic control

This paper considers the development of a general model algorithmic control (MAC). It is shown that the proposed structure contains all the features and principles of MAC. The scheme developed allows choices of prediction and reference trajectories. The regulation effect is studied and non-minimum phase systems are also exemplified. The tracking and regulation properties of the proposed MAC depend on the choice of regulator and controller parameters. Results of simulation studies indicate the effectiveness of the developed algorithmic control.     

Modelling the non-linear stochastic characteristics of EMG/tension relationship

A generalized non-linear mathematical model for the identification of EMG/tension relationship is developed. Volterra functional expansions are utilized for identification of the linearities as well as the non-linearities of the system, leading to the development of a generalized methodology. Kernels of the system are computed in the frequency domain using an efficient fast fourier transform (FFT) algorithm. The results obtained for the case of biceps brachii muscle are compared with the corresponding results obtained by using a stochastic state-space model : the Volterra approach appears to provide a more realistic characterization. Symmetry of the kernels reduces storage requirements and computation time on the digital computer considerably. Physiological interpretation of the results obtained reveals diagnostic information about certain pathologies related to human skeletal muscle.     

ENHANCEMENT OF STEADY STATE REACTION RATES THROUGH COOPERATIVE ADSORPTION†

The Elovich model for single component adsorption is extended to treat two components, especially when surface heterogeneity and interactions are present. When only surface heterogeneity is present, the resulting unique steady state is stable; also the steady state rate is decreased in comparison to the Langmuir model. When attractive forces are acting in opposition to surface heterogeneity, the resulting unique steady state displays enhanced rates. When surface heterogeneity has negligible influence, the system can exhibit triple (two stable and one unstable) steady stales. In the present case attractive interactions are present between all types of molecular pairs. However oscillations are not observed for the choice of realistic interaction parameters. In addition the stable steady slates display lower rates in comparison to the single steady state.