Effect of post-deposition annealing on microstructural and optical properties of barium strontium titanate thin films deposited by r.f. magnetron sputtering

The effect of post-deposition annealing on the structural and optical properties of barium strontium titanate, Ba_0.8Sr_0.2TiO₃ film has been investigated. The films have been deposited on oxidized p-silicon substrates by r.f. magnetron sputtering followed by annealing in O₂ atmosphere at different temperatures. In situ deposition has also been carried out at 550 °C for comparison. The nature of the variation of refractive index and extinction coefficient with annealing temperature and wavelength has been studied. Absorption band edges shift towards lower photon energy values as the temperature is increased causing a reduction in the optical band gap energy. Infrared absorption bands show a cubic symmetry at lower frequency and are found to be broadened and even split at higher frequency.     

Evaluation of the nutritional quality of four unexplored aquatic weeds from northeast India for the formulation of cost-effective fish feeds

A study was conducted to evaluate the nutritional potential of four commonly available, unexplored aquatic weeds namely, Salvinia cuculata, Trapa natans, Lemna minor and Ipomoea reptans from northeast India for ascertaining their suitability for utilization as supplementary fish feed with the aim to reduce the cost of commercial feeds. Results of proximate analysis showed that the crude protein content of the aquatic weeds ranged between 11.0% and 32.2% (w/w), whereas crude fibre and ash contents varied between 4.2% and 20% (w/w), and 13.3% and 31.2% (w/w), respectively. Protein to energy ratio (P/E) of these weeds ranged between 30.7 mg/kcal and 95.3 mg/kcal and the highest value was displayed by I. reptans. All these aquatic weeds contained high amounts of vitamins E and C and mineral elements required for the normal growth and development of fish.     

Effect of valency on material removal rate in electrochemical machining of aluminium

Material removal rate (MRR) of aluminium work piece has been obtained by electrochemical machining using NaCl electrolyte at different current densities and compared with the theoretical values. It has been observed that resistance of the electrolyte solution decrease sharply with increasing current densities. The over-voltage of the system initially increases and then attains a saturation value with increasing current densities. The material removal rate, determined experimentally, almost corresponds to theoretical value with Al³⁺ state. On the other hand, taking into account over-voltage, MRR comes out be 72%. It appears that removal of a fraction of aluminium occurs in Al⁺ which subsequently gets converted into Al³⁺ through a series chemical reactions. A mechanism of such chemical reactions is proposed.     

Effect of compact density and preheating temperature of the Al–Ti–C preform on the fabrication of in situ Mg–TiC composites

Magnesium reinforced in situ TiC particulates was successfully synthesized by utilizing the self-propagating high temperature synthesis (SHS) process. The result showed that preform temperature and compact density have effects on the SHS reaction. It is observed that when the compact density was below 68% of the theoretical density, no SHS reaction occurred. However, with an increase in density from 68 to 72%, the successful thermal explosion reaction was observed in the Mg melt. Besides this, the effect of preheat temperature on the fabrication of Mg/TiC composite was extensively studied and found that the preheat temperature below 300 °C failed to give rise to SHS reaction. However, the preheat temperature of 450, 500, and 550 °C favors the reaction inside the liquid melt, but the temperature of 600 °C leads to the ignition reaction in the preheating furnace itself. SEM and EDX study confirms fine distribution of TiC in the matrix.     

Sustaining Urban Water Supplies in India: Increasing Role of Large Reservoirs

Urban water demand is rapidly growing in India due to high growth in urban population and rapid industrialization. Meeting this demand is a big challenge for the urban planners in India. Incidentally, the large urban areas are experiencing faster growth in population, and most of them are in arid and semi arid regions, which are naturally water-scarce. As a result, water supplies from local water resources including aquifers are falling far short of the high and concentrated demands in most urban areas. Under such situations, these large cities have to rely on distant large reservoirs. The analysis of 302 urban centers shows that cities with larger population size have much higher level of dependence on surface water sources. Also, greater the share of surface water in the city water supplies, higher was the level of per capita water supply. Multiple regression models are estimated for Class I cities and Class II towns in India. The results show that Population Elasticity of Water Supply (PEWS) change with time and space—for Class I cities it was 1.127 in 1988, whereas that with respect to 1999 population is 1.289. It also shows that Class I cities have better water supply (PEWS is 1.127 in 1988 and 1.289 in 1999) than Class II towns (PEWS is 0.396 in 1988 and 0.675 in 1999). Given the structure and pattern of urban population growth, economic conditions and water demands, large reservoirs will have a much bigger role in meeting urban water supply needs.     

Pressure dependent phase transitions in (Pb,Ca)TiO3: Determination of structure using high pressure synchrotron X-ray and Raman studies

Pressure dependent studies on technologically important ferroelectric material Pb_0.70Ca_0.30TiO₃ show the occurrence of a new hitherto unreported pressure dependent phase transition around 4 GPa. In the pressure range 4–14 GPa, the parent tetragonal (P4mm) phase of Pb_0.70Ca_0.30TiO₃ transforms in to a monoclinic (Cm) phase before attaining its paraelectric cubic (Pm3m) phase around 15 GPa. High pressure Raman studies reveal the presence of a critical pressure above which the ferroelectric phase starts to reappear in the paraelectric phase. This critical pressure is found to be much lower than the critical pressure observed in pure PbTiO₃. Possible reasons for this lowering of the critical pressure are presented.     

SODAPRETER: A novel approach towards automatic SODAR data interpretation

Instead of piecemeal approaches for detecting specific patterns in the SODAR echograms, an integrated modular approach 'towards' automatic interpretation of the ABL structure patterns, as depicted in the SODAR facsimile records, is presented. Here we propose a unified approach where the user is at liberty to select a wide range of image processing and the pattern recognition techniques required to extract remotely-probed meteorological information from the closest geometric representation of the SODAR pattern boundary. The ultimate goal, part of which is already implemented and reported here, is to generate 'expert-like' interpretation of SODAR echograms.     

Studies of microstructural imperfections of powdered Zirconium-based alloys

Different model based approaches of X-ray diffraction line profile analysis have been applied on the heavily deformed zirconium-based alloys in the powdered form to characterize the microstructural parameters like domain size, microstrain and dislocation density. In characterizing the microstructure of the material, these methods are complimentary to each other. Though the parameters obtained by different techniques are differently defined and thus not necessarily comparable, the values of domain size and microstrain obtained from the different techniques show similar trends.