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Your search keyword '"Kumar, Shashi"' showing total 3 results
Start Over Author "Kumar, Shashi" Publication Year Range Last 10 years Publisher american institute of physics
3 results on '"Kumar, Shashi"'

1. Effects of periodic suction-blowing excitation on the aerodynamic sound generated by a laminar flow past a square cylinder using the direct numerical simulation approach.

Author

Kumar, Shashi, Ganta, Naveen, and Bhumkar, Yogesh G.

Subjects
*AEROACOUSTICS, *ACOUSTIC field, *PROPER orthogonal decomposition, *LAMINAR flow, *COMPUTER simulation, *VORTEX shedding, *DRAG force
Abstract

This paper analyzes the effects of a periodic suction-blowing excitation on the aerodynamic sound generated by a laminar flow past a square cylinder using the direct numerical simulation approach. The periodic suction-blowing excitation has been prescribed on the top and bottom surfaces of the square cylinder. The proper orthogonal mode decomposition (POD) technique has been used to find information about important modes associated with disturbance pressure fields. The POD technique separated the contribution of the dominant lift dipole equivalent sources and the drag dipole equivalent sources to the disturbance pressure field for the no-excitation case. The POD technique also revealed that the periodic suction-blowing excitation introduced an additional monopole equivalent sound source and a drag dipole equivalent sound source due to periodic enhancement and reduction of the body's effective cross-sectional area. Modifications in the sound field due to changes in excitation amplitude, forcing frequency, and the phase delay between the excitation and vortex shedding process have been studied in detail. Although no significant changes in the flow field were noticed due to a small amplitude of excitation, the directivity of the sound field was significantly altered. The sound fields have been classified into five distinct zones for different periodic suction-blowing excitation frequencies. The beats of sounds were noted when the forcing frequency of excitation and the Strouhal frequency associated with vortex shedding were sufficiently close. It is observed that the in-phase excitation in which either blowing or suction is applied on both surfaces of a cylinder at a particular instant introduces a significant bias in the sound field directivity. The interaction between the lift dipole equivalent sources due to vortex shedding and the monopole and the drag dipole equivalent sources due to excitation introduces a bias in the sound field directivity. As a result, a dominant sound field is observed either in the top-left or in the bottom-left parts of the domain. [ABSTRACT FROM AUTHOR]

Published
2022
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2. A MEMS based blood glucose measurement sensor using twin-cantilever structure.

Author

Ropmay, Gaddiella Diengdoh, Kumar, Shashi, Rathore, Pradeep Kumar, Rangababu, Peesapati, Akhtar, Jamil, Gupta, Vinay, Gaol, Ford Lumban, and Korody, Jagannath

Subjects
*BLOOD sugar measurement, *STRAINS & stresses (Mechanics), *BLOOD sugar, *LEAD zirconate titanate, *MECHANICAL energy, *ION sources
Abstract

This paper aims to propose a blood glucose measurement sensor using a MEMS-based twin cantilever structure, which is highly reliable and accurate. Two identical microcantilever beams featuring a dimension of 500 µm x 100 µm x 10 µm, were designed and fabricated using the IntelliFab module of the IntelliSuite MEMS software. One was deposited with a piezoelectric material Lead Zirconate Titanate (PZT), which converts mechanical stress into a change in electric potential, and the other, with doped polysilicon (a piezoresistor), which translates mechanical energy in terms of a change in resistance. Glucose detection in the blood sample was achieved by coating the top surface of a cantilever beam with glucose-sensitive polymer PAA-ran-3-PAAPBA. Mechanical bending of the cantilever beam was observed due to the presence of glucose in blood sample and the output voltage proportional to glucose concentration has been measured using op-amp as a readout circuitry. The resulting output voltage corresponding to a glucose concentration of 162 mg/dL is found to be 47.49 mV. [ABSTRACT FROM AUTHOR]

Published
2020
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3. Sensitivity enhancement of P- and N-MOS based current mirror pressure sensor using differential amplifier.

Author

Kumar, Shashi, Ropmay, Gaddiella Diengdoh, Rathore, Pradeep Kumar, Rangababu, Peesapati, Akhtar, Jamil, Gupta, Vinay, Gaol, Ford Lumban, and Korody, Jagannath

Subjects
*PRESSURE sensors, *CONSTANT current sources, *HOLE mobility, *DIFFERENTIAL amplifiers, *DETECTOR circuits, *TRANSISTORS
Abstract

The aim of this work is to enhance the full scale output voltage and sensitivity of a PMOS based current-mirror integrated pressure sensor. A source coupled differential amplifier has been designed using PMOS transistors and implemented to achieve the same. The proposed sensing structure includes three p-channel MOSFETS connected in current-mirror configuration followed by two p-channel MOSFETS in common source differential amplifier configuration. Transistor M1 (reference transistor) of the mirror circuit serves as constant current source while transistor M2 and transistor M3, integrated on the flexible membrane, are active transistors for sensing pressure. When the sensing membrane is subjected to external pressure, M2 and M3 sense the maximum tensile and compressive stresses respectively. The piezoresistive nature of these MOSFETs allows for the computation of stress- induced variation in hole mobility within the channel of active MOSFETM2 and MOSFET M3. The differential amplifier is made up of the two PMOS transistors M4 and M5 on the same chip. The complete structure is designed in TSpice software using the 5 µm CMOS technology parameters. It amplifies the output voltage from the current-mirror sensing circuit to give enhanced pressure sensitivity. Employing this arrangement, an improvement in pressure sensitivity from 467.4 to 972.5 mV/MPa is achieved. Comparison with the previously reported n-channel MOSFET counterpart shows that NMOS devices exhibit better sensitivity. [ABSTRACT FROM AUTHOR]

Published
2020
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