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1

Optimization of a dual-slot waveguide for a refractive index biosensor

Sahu S., Ali J., Singh G.

Optica Applicata

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2018

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Vol. 48, nr 1

161--167

EN

The present article illustrates the modeling and optimization of a dual-slot waveguide for the application of a refractive index biosensor. The nanometer scale waveguide structure uses the silicon-on-insulator platform for the consideration of higher sensitivity and compactness of a resonator biosensor. The modal analysis is performed using the finite difference method based on full vector eigenmode calculation. The maximum field penetration in the lower index region is found for the quasi-TE mode. The sensitivity is maximized through the optimization of the waveguide dimension by relating effective refractive index with the dispersion of a waveguide. The biosensor showed the maximum calculated sensitivity of 461.327 nm/RIU and a limit-of-detection of 2.601 × 10–6 RIU (where RIU denotes refractive index unit).

2

Effectiveness of a cooling jacket with reference to physiological responses in iron foundry workers

Shirish A., Kapadia V., Kumar S., Kumar S., Mishra S., Singh G.

International Journal of Occupational Safety and Ergonomics

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2016

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Vol. 22, No. 4

487--493

EN

Personal cooling garments (PCGs) have gained increased attention in recent years due to heat stress and strain in the working environment. The present study was conducted in hot environments of an iron foundry to evaluate the efficacy of a battery-operated PCG. Twenty-four workers were exposed to climatic conditions of 35.89 ± 1.25 °C, 35% relative humidity during 90-min work with PCG and habitual clothing (HC). Mean weighted skin temperature was significantly lower by 4.84 ± 1.05 °C compared with HC 0.38 ± 1.02 °C (p < 0.05). A statistically significant difference was also observed for 0.492 ± 0.26 g mean sweat loss in the PCG group compared with 0.775 ± 0.42 g in the HC group (p < 0.05). Heart rate, and back and chest skin temperatures were comparatively more reduced in the PCG group compared with the HC group. PCG provides a practical and economical way of alleviating the physiological effects of heat stress when environmental control is not feasible.

3

Modeling of a high performance Mach-Zehnder interferometer all optical switch

Singh G., Janyani V., Yadav R. P.

Optica Applicata

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2012

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Vol. 42, nr 3

613-625

EN

In this work, a detailed performance analysis for a Mach-Zehnder interferometer (MZI) optical switch with a channel profile of titanium-indiffused lithium niobate (Ti:LiNbO3) is presented. The concept of diffusion process controlled modeling has been used to design and optimize its performance. Impacts of Ti-strip thickness on the power imbalance of first 3-dB coupler and crosstalk (CT) levels at the end of the interferometric arms are defined and calculated. Transition losses in the curved waveguides of the structure are maintained at low levels by selecting low less bend structures to increase overall performance of the switch. The best CT levels of - 41.73 dB for cross state and -32.69 dB for bar state at 1.3 mu m wavelength have been achieved. While at 1.55 mum wavelength, a CT of - 41.73 dB for cross state and -33.99 dB for bar state have been observed. The switch designed was found to operate best at 7.25 V and 8.25 V for test wavelengths of 1.3 mu m and 1.55 mu m, respectively. The computed results for its performance are better as compared to the present published data.

4

Stability of superposed viscous-viscoelastic (Rivlin-Ericksen) fluids through porous medium

Kumar P., Mohan H., Singh G.

Studia Geotechnica et Mechanica

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2004

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Vol. 26, nr 1-2

53-61

PL

Badano niestabilność typu Rayleigha-Taylora cieczy Newtona nakładającej się na lepkosprężystą ciecz Rivlina-Ericksena w ośrodku porowatym. Ponieważ zarówno w lepkiej cieczy Newtona, jak i w lepkiej cieczy układ jest stabilny w potencjalnie stabilnym przypadku, a niestabilny w potencjalnie niestabilnym przypadku, wniosek ten odnosi się też do badanego przez nas problemu. Rozważono oddzielnie wpływ jednorodnego poziomego pola magnetycznego i wpływ jednorodnej rotacji na niestabilność. Pole magnetyczne stabilizuje pewne pasmo liczby falowej, podczas gdy układ jest niestabilny dla wszystkich liczb falowych, gdy brak pola magnetycznego dla potencjalnie niestabilnej konfiguracji. Układ jest jednak stabilny w potencjalnie stabilnym przypadku, a niestabilny w potencjalnie niestabilnym przypadku dla bardzo lepkich cieczy poddanych jednostajnej rotacji.

EN

The Rayleigh-Taylor instability of a Newtonian viscous fluid overlying a Rivlin-Ericksen viscoelastic fluid through porous medium is considered. As in both Newtonian viscous-viscous fluids, the system is stable in the potentially stable case and unstable in the potentially unstable case, this holds for the present problem as well. The effects of a uniform horizontal magnetic field and a uniform rotation on the instability problem are also considered separately. The presence of magnetic field stabilizes a certain wave-number band, whereas the system is unstable for all wave-numbers in the absence of the magnetic field for the potentially unstable configuration. However, the system is stable in the potentially stable case and unstable in the potentially unstable case for highly viscous fluids in the presence of a uniform rotation.