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1

Analysis of the beam divergence for one-rod core microstructured optical fibres

Sharma D. K., Tripathi S. M.

Opto-Electronics Review

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2019

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Vol. 27, No. 2

224--231

EN

The evolution of microstructured optical fibers with hexagonal array (H-MOFs) of air-holes rooted in the background of undoped silica has led to the realization of an ideal host for encouraging and technologically entitled optical properties. We focus to explore the divergence of radiation into free space from the end-facet of solid-core H-MOFs by using the improved theoretical model. Also, we investigated the wavelength dependence of beam divergence angle for principal core mode of H-MOFs under step-index fiber approximation (SIFA). Experimental results have been included for comparison.

2

A study of indoor radon, thoron and their exhalation rates in the environment of Fazilka district, Punjab, India

Narang S., Kumar D., Sharma D. K., Kumar A.

Acta Geophysica

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2018

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Vol. 66, no. 5

1233--1241

EN

Over the last few decades, the study of radioactive radon gas has gained huge momentum due to its possible role in health related hazards. In the present work, pin-hole twin chamber single entrance dosimeters have been used for track measurements of radon and thoron. The annual average radon concentration varies from 50.3 to 204 Bq/m3 at all locations. Almost all the values are below the safe range provided by ICRP. Radon concentration is found to be higher in winter as compared to other seasons. Variation of radon with quality of dwellings is also discussed. The values of annual effective dose due to radon and thoron are also well within the range provided by ICRP and WHO. Radon and thoron exhalation rates are measured using SMART RnDuo monitor. The radon mass exhalation rates ranged from 11 to 71 mBq/kg/h while the thoron surface values ranged from 36 to 2048 Bq/m2/h. All the values are on the lower side. A weak correlation is found between radon and thoron concentrations and their exhalation rates. When compared with the values of other parts of northern India, the values of present investigation are on higher side.

3

CO2 gasification reactivity and kinetics studies of raw coal, super clean coal and residual coals obtained after organo-refining (solvent extraction)

Sharma D. K., Giri C. C.

Journal of Power Technologies

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2016

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Vol. 96, nr 3

157--169

EN

Gasification of coal is important for the generation of H2. This is also good for Integrated Gasification Combined Cycle (IGCC) power generation which can be easily and relatively cheaply combined with CO2 concentration, storage and utilization systems. Solvent extraction of coal in organic solvents results in the production of super clean coal, mostly having less than 1% ash. The present paper reports the effect of solvent extraction (organo-refining) of Samla coal by using an industrial solvent, such as N-methyl-2-pyrrolidone (NMP), a coal derived solvent, such as, anthracene oil (AO) and a petroleum derived solvent, i.e. cetene (CE), on the CO2 gasification of coal. Different solvents had different effects on the CO2 gasification of super clean coal (SCC) or of residual coal (RC) obtained after the organo-refining of coals in different solvents. The CO2 gasification reactivity of raw coal as well as of solvent treated coals was found to increase with increase in the temperature of the gasification from 900 to 1100C. The treatment of coal with solvents has been found to affect the CO2 gasification reactivity. Super clean coals obtained from the organo-refining in the cetene and NMP showed good CO2 gasification reactivity. Residual coals obtained from the organo-refining in NMP and CE also showed good CO2 gasification reactivity. Kinetics studies have revealed that the activation energies of CO2 gasification reactions are reduced as a result of organo-refining of coal in different solvents. While organo-refining of coals in NMP and if possible in CE as well may help in obviating some of the major engineering problems in IGCC power generation, this integration may not be economically attractive at present. Future IGCC power generation may involve the use of CO2 and O2 as the gasifying medium.