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Rakesh Singh Tomar,Joydip Dhar,Ajay Kumar 한국전산응용수학회 2023 Journal of applied mathematics & informatics Vol.41 No.1
An epidemic infectious disease model consists of six compartments viz. Susceptible, Exposed, Infected, Quarantine, Recovered, and Virus with nonlinear saturation incidence rate is proposed to know the viral disease dynamics. There exist two biological equilibrium points for the model system. The system's local and global stability is done through Lyapunov's direct method about equilibrium points. The sensitivity analysis has been performed for the basic reproduction number and equilibrium points through the normalized forward sensitivity index. Sensitivity analysis shows that virus growth and quarantine rates are more sensitive parameters. In support of mathematical conclusions, numerical experimentation has been shown.
Avinash Vishwakarma,Sivaiah Bathula,Nagendra S. Chauhan,Ruchi Bhardwaj,Bhasker Gahtori,Avanish K. Srivastava,Ajay Dhar 한국물리학회 2018 Current Applied Physics Vol.18 No.12
SiGe alloy is widely used thermoelectric materials for high temperature thermoelectric generator applications. However, its high thermoelectric performance has been thus far realized only in alloys synthesized employing mechanical alloying techniques, which are time-consuming and employ several materials processing steps. In the current study, for the first time, we report an enhanced thermoelectric figure-of-merit (ZT)∼1.1 at 900 °C in ntype Si80Ge20 nano-alloys, synthesized using a facile and up-scalable methodology consisting of rapid solidification at high optimized cooling rate∼3.4×107 K/s, employing melt spinning followed by spark plasma sintering of the resulting nano-crystalline melt-spun ribbons. This enhancement in ZT>20% over its bulk counterpart, owes its origin to the nano-crystalline microstructure formed at high cooling rates, which results in crystallite size ∼7 nm leading to high density of grain boundaries, which scatter heat-carrying phonons. This abundant scattering resulted in a very low thermal conductivity ∼2.1 Wm−1K−1, which corresponds to ∼50% reduction over its bulk counterpart and is amongst the lowest reported thus far in n-type SiGe alloys. The synthesized samples were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy, based on which the enhancement in their thermoelectric performance has been discussed.