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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.
A new broadband energy harvester using propped cantilever beam with variable overhang
R. Usharani,G. Uma,M. Umapathy,S.B. Choi 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.5
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 new technique to increase the operating frequency range which is achieved by designing a harvester featured by a propped cantilever beam with variable over hang length. The proposed piezoelectric energy harvester is modeled analytically using Euler Bernoulli beam theory and the effectiveness of the harvester is demonstrated through experimentation. The results from analytical model and from experimentation reveal that the proposed energy harvester generates an open circuit output voltage ranging from 36.43 V to 11.94 V for the frequency range of 27.24 Hz to 48.47 Hz. The proposed harvester produces continuously varying output voltage and power in the broadened operating frequency range.
EFFECTS OF SOURCE POSITION ON THE DH-TYPE II CME PROPERTIES
Shanmugarju, A.,Moon, Y.J.,Cho, K.S.,Umapathy, S. The Korean Astronomical Society 2009 Journal of The Korean Astronomical Society Vol.42 No.3
The properties of SOHO/LASCO CMEs are subjected to projection effects. Their dependence on the source position is important to be studied. Our main aim is to study the dependence of CME properties on helio-longitude and latitude using the CMEs associated with type IIs observed by Wind/WAVES spacecraft (Deca-hecta metric type IIs - DH type IIs). These CMEs were identified as a separate population of geo-effective CMEs. We considered the CMEs associated with the Wind/WAVE type IIs observed during the period January 1997 - December 2005. The source locations of these CMEs were identified using their associated GOES X-ray flares and listed online. Using their locations and the cataloged properties of CMEs, we carried out a study on the dependence of CME properties on source location. We studied the above for three groups of CMEs: (i) all CMEs, (ii) halo and non-halo CMEs, and (iii) limb and non-limb CMEs. Major results from this study can be summarized as follows. (i) There is a clear dependence of speed on both the longitude and latitude; while there is an increasing trend with respect to longitude, it is opposite in the case of latitude. Our investigations show that the longitudinal dependence is caused by the projection effect and the latitudinal effect by the solar cycle effect. (ii) In the case of width, the disc centered events are observed with more width than those occurred at higher longitudes, and this result seems to be the same for latitude. (iii) The dependency of speed is confirmed on the angular distance between the sun-center and source location determined using both the longitude and latitude. (iv) There is no dependency found in the case of acceleration. (v) Among all the three groups of CMEs, the speeds of halo CMEs show more dependency on longitude. The speed of non-halo and non-limb CMEs show more dependency on latitude. The above results may be taken into account in correcting the projection effects of geo-effective CMEs.
SYNTHESIS AND CHARACTERIZATION OF NANOSIZED Mg(OH)2 AND ITS NANOCOMPOSITE WITH POLY (VINYL ALCOHOL)
R. ANBARASAN,M. FATHIMA PARVEEN,S. UMAPATHY,V. DHANALAKSHMI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2009 NANO Vol.4 No.3
Nano-Mg(OH)2 was synthesized by co-precipitation method. Peaks between 500 and 1250 cm-1 in FTIR spectroscopy confirmed the presence of metal hydroxide stretching. TGA inferred that above 600°C, 50% of residue weight remained. HRTEM of nanocomposite gave an idea about the nonspherical morphology of particles of size 25 nm to 30 nm. SEM inferred that flower-like morphology for pristine Mg(OH)2 and higher % weight of aniline-intercalated Mg(OH)2 had agglomerated structure. UV visible spectrum inferred the presence of Mg2+ ion at 275 nm and the presence of amino-group-intercalated Mg(OH)2, which had a sharp peak at 193 nm and the intensity of which increases with the increase in % weight of aniline. PL inferred that aniline-intercalated Mg(OH)2 showed a lower intensity of which increased with higher wavelength value than the pristine and nanocomposite with PVA.
Lawrance, M. B.,Shanmugaraju, A.,Moon, Y. J.,Ibrahim, M. S.,Umapathy, S. D. Reidel Pub. Co 2016 Solar physics Vol.291 No.5
<P>The characteristics and geoeffectiveness of interplanetary coronal mass ejections (ICMEs) are derived and their relationships are investigated. The results are compared for a set of events in the rising phase of Solar Cycles 23 and 24. These events are considered from the reported list of Cane and Richardson (Geophys. Res. Lett. 27, 3591, 2000). The geoeffectiveness is studied independently for ICME and sheath. The results obtained are that i) CMEs of Cycle 23 have generated a higher Dst index than Cycle 24 CMEs and that ii) the southward magnetic component (B-s) and the Dst index of ICMEs correlate well for both Cycles 23 and 24 in their rising phase. These findings agree with the literature, which has described Cycle 24 to be weaker than Cycle 23 and where the ICME/sheath regions of Cycle 23 are found to have a greater B-s that results in stronger storms. In addition, other results obtained are as follows: i) The relation between ICME size and the related Dst index gives a weak correlation for the rising phases of both Cycles 23 and 24. ii) The correlation between sheath size and Dst index is higher in the rising phase of Cycle 24 than in the rising phase of Cycle 23. iii) The average ICME size of the rising phase of Cycle 23 (84 R-circle dot) is greater than that of the rising phase of Cycle 24 (58 R-circle dot). However, the average sheath size is 24 R-circle dot, which is nearly equal to that of Cycle 24 (26 R-circle dot). Thus the differences between the properties of ICME and sheath in both the cycles are demonstrated. Nearly 75 % of geomagnetic storm peaks occurred in the ICME duration in the rising phase of Cycles 23 and 24. This shows that the ICMEs are more important in generating the storms than the sheaths in the rising phase of a solar cycle.</P>
Syed Ibrahim, M.,Shanmugaraju, A.,Moon, Y.-J.,Vrsnak, B.,Umapathy, S. Elsevier 2018 ADVANCES IN SPACE RESEARCH Vol.61 No.1
<P><B>Abstract</B></P> <P>Statistical relationship between major flares and the associated CMEs during rising phases of Solar Cycles 23 and 24 are studied. Totally more than 6000 and 10,000 CMEs were observed by SOHO/LASCO (Solar and Heliospheric Observatory/Large Angle Spectrometric Coronagraph) during 23rd [May 1996–June 2002] and 24th [December 2008–December 2014] solar cycles, respectively. In particular, we studied the relationship between properties of flares and CMEs using the limb events (longitude 70–85°) to avoid projection effects of CMEs and partial occultation of flares that occurred near 90°. After selecting a sample of limb flares, we used certain spatial and temporal constraints to find the flare-CME pairs. Using these constraints, we compiled 129 events in Solar Cycle 23 and 92 events in Solar Cycle 24. We compared the flare-CME relationship in the two solar cycles and no significant differences are found between the two cycles. We only found out that the CME mean width was slightly larger and the CME mean acceleration was slightly higher in cycle 24, and that there was somewhat a better relation between flare flux and CME deceleration in cycle 24 than in cycle 23.</P>