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RISS 인기검색어
- 검색키워드
- 저자 : Uma Gandhi (검색결과 5 건)
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Sakthivel Gandhi,Swaminathan Sethuraman,Uma Maheswari Krishnan 한국고분자학회 2013 Macromolecular Research Vol.21 No.8
Biocompatible and biodegradable polyesters have immense potential in medical applications as drug delivery vehicles and tissue engineering scaffolds. In this study, we synthesized biodegradable aliphatic polyesters,namely poly(butylene pimelate) (PBPi), poly(butylene succinate) (PBSu), and poly(butylene sebacate) (PBSe), by the polycondensation of equimolar quantities of dicarboxylic acid and diol using mesoporous SBA-15 silica as heterogeneous catalyst. We then compared its performance with a conventional homogenous catalyst, SnCl2·2H2O, which did not form these polymers. The synthesized SBA-15 catalyst was characterized by electron microscopy, nitrogen adsorption-desorption isotherm and infrared spectroscopy. The synthesized polyesters were evaluated using infrared spectroscopy, X-ray diffraction, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, gel permeation chromatography, scanning electron microscopy and goniometry. The combined results demonstrate that the SBA-15 mesoporous catalyst formed higher molecular weight degradable polyesters in addition to higher yield and purity, thus confirming the superiority of the mesoporous silica catalyst for polymer formation.
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Measurement of Diesel Exhaust Fluid Concentration in Urea-SCR after-Treatment System
PalaniKumar Gurusamy,Uma Gandhi,Umapathy Mangalanathan,Karl Marx LR 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.8
In an effort to meet the established emission standards Selective Catalytic Reduction (SCR) is used to reduce NOx emissions with diesel exhaust fluid (DEF) as additive in the exhaust of diesel engines. ISO 22241-1:2006 specifies the quality characteristics of DEF in order to maintain efficiency and hence, it is essential that the concentration of urea in DEF is accurately monitored. In this paper, a measurement system is designed, developed and tested for measuring the concentration of urea in DEF. The design involves piezoelectric ultrasound transmitter and receiver with associated electronics operating at a frequency of 4 MHz. The concentration of urea in DEF is measured (i) by measuring the time of flight of ultrasound waves between transmitter and receiver (ii) by measuring the amplitude of received signal in terms of frequency using voltage-to-frequency converter. The measurement system is modeled using two-port network model for piezoelectric transmitter/receiver and transmission line model for DEF medium. The prototype of measurement system is fabricated with all associated electronics and tested for variation in concentration of urea in DEF. The results from prototype are in close agreement with the results obtained from analytical model. The measurement system is tested for repeatability and sensitivity to temperature.
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Design of High Output Broadband Piezoelectric Energy Harvester with Double Tapered Cavity Beam
Ramalingam Usharani,Gandhi Uma,Mangalanathan Umapathy 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.3 No.4
Design of piezoelectric energy harvester for a wide operating frequency range is a challenging problem and is currently being investigated by many researchers. Widening the operating frequency is required, as the energy is harvested from ambient source of vibration which consists of spectrum of frequency. This paper presents a technique to increase the operating frequency range and to enhance the amplitude of the generated voltage in the operating frequency range. The wider operating frequency range is achieved by designing a harvester using propped cantilever beam with variable overhang and the amplitude of the generated voltage is enhanced by introducing a double tapered cavity. The proposed piezoelectric energy harvester is modeled analytically using Euler Bernoulli beam theory. The results from the modeling and analysis reveal that the maximum voltage is generated from the energy harvester designed with the double tapered cavity having the taper angle of α =2.25o. Hence the experimental investigations are carried out with this energy harvester and the generated voltage measured is in close agreement with the results obtained from the model. The simulation and experimental results presented in this paper demonstrate that the proposed harvester design not only widens the operating frequency range but also it enhances the amplitude of the generated voltage in large extent.
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Raja V,Umapathy Mangalanathan,Uma Gandhi,Praveen kumar B,Premkumar S 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11
Energy harvesting from rotational motion has drawn attention over the years to energise low-power wireless sensor networks in a rotating environment. The harvester works efficiently in a small frequency range which has to be similar to the driving frequency. Because of the constraints of size, precision, and the energy harvester’s weight, it is challenging to design it to suit micro applications. To deal with this problem, this paper proposes a rotational piezoelectric energy harvester (RPEH), which generates a voltage output from rotational motion. This design increases the gravitational force acting on the system by increasing the length of the beam, which in turn increases its vibration in a transverse direction. EulerBernoulli’s theory is utilized to derive the mathematical model of the RPEH under rotational motion, and harvester dynamic equations are derived using the electromechanical Lagrange equations. A prototype of RPEH is developed and the exactness of the proposed mathematical model is verified using experimental results and numerical simulation. Maximum power of 43.77 µW is produced at a rotating frequency of 21 Hz (1260 rpm) with an optimum load resistance of 1141.3 kΩ.
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Cantilever Beam with Trapezoidal Cavity for Improved Energy Harvesting
Annapureddy Rami Reddy,Mangalanathan Umapathy,Deenadayalan Ezhilarasi,Gandhi Uma 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
This paper presents a cantilever structure as energy harvester by introducing a trapezoidal cavity to increase the amplitude of the generated voltage and the overall mechanical to electrical energy conversion efficiency. An analytical model of the proposed structure is developed using Euler-Bernoulli beam theory. The effect of taper angle of the trapezoidal cavity and the neutral axis shift on the generated voltage is analyzed using analytical model and through experimentation. The generated output voltage from the energy harvester with trapezoidal cavity is compared with the beam having rectangular cavity and the beam without cavity. The generated voltage for the beam with trapezoidal cavity is 97.5% and 108% higher as compared with the beam having rectangular cavity and the beam without cavity. The characteristics of the energy harvester are evaluated through analytical model and experimentation and the results are in close agreement.
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