Aspects of the Softness and Hardness Concepts of Density-Functional Theory

In the density-functional theory of the ground state of an electronic system there arise the concepts of softness, hardness, local softness, and local hardness. Definitions of these quantities are reviewed, and then local softness and local hardness are discussed in some detail. The local softness of a species, the derivative , is a measure of the chemical reactivity of a site in the molecule. From it can be obtained the total global absolute softness in the sense of Pearson and a normalized chemical reactivity index of frontier type. Several formulas for s( r ) are obtained, including new fluctuation formulas, and its determinative role in chemisorption, catalysis, and frontier-controlled charge-transfer processes is briefly discussed. Local hardness is a corresponding appropriately defined functional derivative η(r) = [δμ/δp(r)]_v(r). Difficulties associated with ambiguities in this definition are discussed and resolved. It is concluded that for most purposes the best working formula for local hardness is , where η(r, r′) is the hardness kernel; , where F[p] is the usual Hohenberg-Kohn functional and f(r) is the Fukui function. With this definition, η(r) = η, a constant which is the global hardness. Just as the chemical potential equalizes in the ground state, so does the hardness. It is demonstrated that hardness can be taken to be an average of orbital contributions.     

Design and simulation of a novel GaN based resonant tunneling high electron mobility transistor on a silicon substrate

For the first time, we have introduced a novel GaN based resonant tunneling high electron mobility transistor (RTHEMT) on a silicon substrate. A monolithically integrated GaN based inverted high electron mobility transistor (HEMT) and a resonant tunneling diode (RTD) are designed and simulated using the ATLAS simulator and MATLAB in this study. The 10% Al composition in the barrier layer of the GaN based RTD structure provides a peak-to-valley current ratio of 2.66 which controls the GaN based HEMT performance. Thus the results indicate an improvement in the current-voltage characteristics of the RTHEMT by controlling the gate voltage in this structure. The introduction of silicon as a substrate is a unique step taken by us for this type of RTHEMT structure.     

An intelligent traffic control system using RFID

Vehicular traffic control at road crossings has always been a matter of concern for administrations in many modern cities around the world. Several attempts have been made to design efficient automated systems to solve this problem. Most of the present day systems use predetermined timing circuits to operate traffic signals, which are not very efficient because they do not operate according to the current volume of traffic at the crossing. It is often seen in today's automated traffic control systems that vehicles have to wait at a road crossing even though there is little or no traffic in the other direction. There are other problems as well, such as ambulances getting caught up by a red traffic signal and wasting valuable time. Congestion is often translated into lost time, missed opportunities, lost worker productivity, delivery delay, and a general increased cost.     

Effect of Formulation Variables on the Preparation and in Vitro-in Vivo evaluation of Cimetidine Release from Ethyl Cellulose Micropellets

Ethyl cellulose embedded prolonged release microparticles containing cimetidine was designed by dispersing the drug-ethyl cellulose mixture in acetone, into a medium of mineral oil and subsequent rigidization of the ethyl cellulose matrix. Significant reproducibility of the manufacturing process was observed. In vitro-in vivo correlation revealed the the dissolution process is the rate determining step in drug absorption and the significant in vivo efficiency of the dosage form is well expected.     

Effects of Solvents, Temperature, and Plasticizer on Film Coating of Tablets

The effects of solvent composition, temperature, solvent retention, plasticizers, and polishing on the disintegration and percent dissolution of various nonaqueous film coated tablets were studied. A mixture of isopropanol-dichloromethane used as solvent systems for the film coating of ranitidine hydrochloride tablets resulted in reduced film peel-off time, decreased disintegration time, and increased percent dissolution. The effect of prewarming the coating bed of cimetidine tablets revealed an increase in percent dissolution compared to no prewarming condition. In contrast, an increase in temperature of the tablet bed resulted in higher disintegration time and lower percent dissolution of ibuprofen tablets. Ranitidine hydrochloride film coated tablets polished with polyethylene glycol showed lower disintegration time and higher percent dissolution than those polished with beeswax. The presence of plasticizer in the coating solution resulted in decreased disintegration time and higher percent dissolution for norfloxacin tablets.     

High-temperature and ageing properties of high-crystalline TOR-filled SBR vulcanizates

The influence of a co-cross-linkable processing aid, Trans-polyoctenylene (TOR), on hightemperature stress-strain properties and ageing of filled styrene butadiene rubber (SBR) vulcanizates, was studied. Three different cross-linking systems, conventional (CV), semiefficient (SEV) and efficient (EV), with respect to SBR were included. A linear regression equation has been obtained between vulcanizate modulus (200%), TOR dosage and sulphur/accelerator ratio at different test temperature. A similar equation has also been found with tensile strength at 120 °C. Thermal analysis, Fourier transform-infrared spectroscopy and a few solid-state ¹³Carbon nuclear magnetic resonance spectroscopic techniques were performed to get insight into the structural changes that occur between TOR and SBR during cross-linking. A plausible mechanism of the interaction between TOR and SBR has been suggested. Based on the property retention of the vulcanizates at room as well as at high working temperature, an optimization of properties between the CV and EV systems has been attempted by the modification of the CV system using TOR.     

Semi-automated object-based landform classification modelling in a part of the Deccan Plateau of central India

Landform mapping holds significance in governing boundary conditions for the underlying processes operative in the fields of natural resource management, yet the automation in recognizing landform occurrence remains difficult. Geospatial object-based image analysis (GEOBIA) technique has evolved as a promising tool for addressing the issue. Majority of the GEOBIA-based landform classification studies document generic approach. The present study undertaken in Katol Tehsil of Nagpur District, a part of Deccan Plateau of central India aims at knowledge-based modelling through a multi-scale mapping workflow comprising multi-resolution segmentation (input raster dataset of IRS-P6 LISS-IV image and Cartosat-1 digital terrain model), knowledge-based classification, and accuracy assessment against a reference landform map. Contour- and drainage-based relative topographic position zone is derived in a novel attempt. Finally, knowledge-based rules are framed using the primary terrain parameters of elevation, slope, profile curvature, and drainage for deriving final output. The results of landform classification indicate the dominance of erosive landform over depositional one; maximum area of 6244 ha being under pediment. An accuracy assessment exercise is carried out in a watershed occurring in the study area, which shows very good statistical agreements between modelled and reference landforms including partial detection. The key constraint of this knowledge-based modelling is its limited adaptability to only localized conditions. However, such kind of object-based and knowledge-based analyses have immense potential with the increasing availability of finer resolution remote-sensing data products that demand the alternative paths of deriving objects that are made up of several pixels.     

Structural,electronic and thermodynamic properties of ZrCo and ZrCoH3: A first-principles study

The ZrCo intermetallic is considered to be strategically important for hydrogen isotope storage and its use in the International Thermonuclear Experimental Reactor (ITER) system. Here we report the structural, electronic and thermodynamic properties of ZrCo and ZrCoH₃ using the first-principles approach. The calculations are performed using a plane-wave based pseudo-potential approach under the framework of spin-polarized density-functional theory. The ground state properties like lattice constants, bulk moduli, and enthalpy of formation have been determined by optimizing the atomic and electronic structure of ZrCo and ZrCoH₃ compounds. From the total energy calculations, the enthalpy of formation of ZrCoH₃ from ZrCo is estimated to be −91 kJ/mol H₂ at 0 K. Both lattice parameters and formation energy are found to be in good agreement with their corresponding experimental values. The nature of chemical bonding in ZrCo and ZrCoH₃ has been analyzed from the electronic density of states spectrum of the constituent materials.