Chhaya Ravi Kant

Metal cluster's effect on the optical properties of cesium bromide thin films

Cesium bromide (CsBr) films grown on glass substrates by thermal evaporation showed prominent absorption peaks in the UV-visible region. Interestingly, these absorption spectra showed peaks which red shifted over time in ambient exposure. Structural and morphological studies suggested decrease in particle size overtime which was unusual. Electron micrographs show the formation of “daughter” cesium nanorods from parent CsBr particles. Theoretical calculations show the optical behavior observed to be due to localized surface plasmon resonance resulting from cesium nanorods.

Characterization of ZnO:Si nanocomposite films grown by thermal evaporation

Composite films were fabricated by co-evaporating Zinc Oxide with Silicon at room temperatures. The resulting films had polycrystalline grains of Zinc Oxide whose grain size were few hundred nanometers, embedded in the silicon matrix. These nanocrystalline grains of ZnO showed good photoluminescence emission at 520 nm along with a photoluminescence emission at 620 nm being contributed by the silicon background. Thus, the nanocomposite films gave a board emission, making it a potentially useful candidate for optoelectronic devices. The photo-luminescent property of the films was found to be stable since the homgenously dispersed ZnO nanocrystals were not allowed to agglomerate by the silicon background.

Two-level single-chain pointer forwarding strategy: a new scheme for location management in mobile communication

A new strategy called ‘two-level single-chain pointer (TLSCP) Forwarding strategy is proposed to reduce location management cost for mobile users. A two-level hierarchy of level-1 and level-2 pointer forwarding chains that are reduced to a single chain in a distributed database environment to locate a mobile user is used in this strategy. An analytical model is developed to evaluate the signalling and location tracking cost. Performance analysis shows that the proposed TLSCP scheme significantly reduces the network signalling traffic cost for mobile users with low mobility.

DATA ACQUISITION SYSTEM FOR ARC-DRIVEN HF/DF CHEMICAL LASERS

The article focuses on the development of a data acquisition system (DAS) working in a noisy and hostile environment for an arc-operated hydrogen fluoride/deuterium fluoride (HF/DF) chemical laser. PC-based DAS has been configured using Advantech plug and play modules with fiber link connectivity. This article also focuses on implementation of an orifice-based precise gas flow control system. The plasma arc discharge in an arc heater/generator is essentially employed for inducing thermal dissociation of sulfur hexafluoride SF6 for production of fluorine atoms, and DAS has been used for performance optimization of the composition of the lasing mixture by independently varying the flow rate, pressure, and temperature of its constituents. Since arc load is complex with high voltage transients and electromagnetic noise, an optical fiber link has been implemented for data transmission. This article also discusses digital output interface circuitry for various electro-pneumatic actuators/solenoid valves. The developed DAS has been used for monitoring and performance evaluation of parameters for 50 kW arc tunnel.