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Theoretical study of ferroelectric triglycine sulphate (TGS) crystal in external electric fields

100%

Upadhyay T. C. , Nautiyal A.

International Letters of Chemistry, Physics and Astronomy

2013

tom Vol. 6

54-65

A modified two sub-lattice pseudospin-lattice coupled mode model of Mitsui et al [Phys. Rev., 111 (1958) 1259] by adding third, fourth order phonon anharmonic interaction and external electric field terms has been applied to ferroelectric triglycine sulphate crystal. Electric field dependence of ferroelectric, dielectric and acoustical properties has been studied. With the help of double time temperature dependent Green’s function method, expressions for shift, width, soft mode frequency, dielectric constant, loss tangent and acoustic attenuation have been derived. Numerically calculations have been made and results have been compared with experimental data reported by Bye et al [Ferroelectrics 4 (1974) 243] and Shreekumar et al [Ferroelectrics 160 (1994) 23] for TGS crystal and a good agreement has been observed.

Optimum transportation of relief materials aftermath the disaster

80%

Nautiyal A. , Kumar A. , Poddar A. , Parajuli N.

tom Vol. 109, nr 1

26--41

Purpose: Natural disasters disrupt not only the lives of individuals but also the functioning of society. Given the unpredictability of disasters and the uncertainty associated with them, preparation is the best way to mitigate and reduce the effects of the disaster. Design/methodology/approach: The study presents a mathematical model in the form of a multi-objective linear programming problem for the relief distribution from the airports which minimizes the total operational cost as well as travel time. Further, the solution approach and analytical results have also been discussed. Findings: The main aims at the preparedness stage are to identify and build infrastructures that might function as useful operation centres during a disaster. The study also provides decisions that include the type and number of vehicles for each affected location. Research limitations/implications: Airports can function as centres for relief collection and distribution. However, relief operations carried out through airports are often subject to problems such as stockpiling. Further, various modes are available for the transport of relief supplies- air, water, and land transport modes primarily. While aircraft and helicopters are faster, their costs of operation are too high. Instead, trucks are economical but very slow as compared to aircraft. Practical implications: The choice of model depends on many factors including the availability of vehicles, availability of routes, and criticality of situations. The choices made in turn affect the costs and the time of operations. Originality/value: The model converts a disaster scenario into a demand-supply problem with the aim being to decide allocations at specified intervals of time.