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Hanumantharao R.,Vignans Institute of Information Technology | Kalainathan S.,Vellore Institute of Technology
Bulletin of Materials Science | Year: 2013

Vickers and Knoop microhardness tests were carried out on grown L-alanine single crystals by slow evaporation technique over a load range of 10-50 g on selected broad (2 0 3) plane. Vickers (Hv) and Knoop (Hk) microhardness for the above loads were found to be in the range of 60-71 kg/mm2 and 35-47 kg/mm2, respectively. Vickers microhardness number (Hv) and Knoop microhardness number (H k) were found to increase with increasing load. Meyer's index number (n) calculated from Hv shows that the material belongs to the soft material category. Using Wooster's empirical relation, the elastic stiffness constant (c11) was calculated from Vickers hardness values. Young's modulus was calculated using Knoop hardness values. Hardness anisotropy has been observed in accordance with the orientation of the crystal. © Indian Academy of Sciences. Source

Reddi C.V.S.N.,Vignans Institute of Information Technology | Padmanabhan C.,Indian Institute of Technology Madras
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2015

Helmholtz resonators are used to control low-frequency noise in cavities. One of the ways to reduce the resonance frequency of a resonator without changing its volume is to introduce an intrusion. Similarly, the introduction of multiple orifices can increase the resonance frequency without changing the resonator volume. These features provide an ability to accommodate slight changes in the cavity/enclosure frequencies during the design process. However, one has to rely on extensive three-dimensional finite element or boundary element simulations to predict the resonator characteristics with the introduction of these features. To reduce the computational burden, a design relation, between the first resonance frequency of a single orifice intruded resonator with that of a multi-orifice intruded resonator, is proposed in this paper. In developing this design relation, the total cross-sectional area of the resonator with multiple orifices is the same as that of the single orifice resonator. It is shown that this design relation is independent of the shape/size of the orifices and resonator cavity. Using this relation, a new end correction formula for the orifice lengths of multi-orifice intruded resonators has been proposed. The end correction formula can be used to calculate the reactance of multi-orifice intruded Helmholtz resonators analytically. These expressions are derived by carrying out extensive simulations of the resonators using the boundary element method. Limited experiments have been carried out to validate the proposed approach. The use of these expressions will reduce the computational cost of simulating cavities embedded with resonators as one can avoid modeling the resonators and use impedance boundary conditions instead. © Institution of Mechanical Engineers 2015. Source

SasiKiran P.,Vignans Institute of Information Technology | Manohar T.G.,Andhra University
Ain Shams Engineering Journal | Year: 2016

The Dynamic Voltage Restorer (DVR) is identified as the best solution for mitigation of voltage sag and swell related problems in the much taped distribution system. The compensation performance of the DVR very much depends on its control algorithm. In the paper, an estimation method based on Unscented Kalman Filter (UKF) is proposed for mitigating the voltage swell concern. The proposed UKF based estimation technique is used to assist the control algorithm for generating reference signals of Voltage Source Converter (VSC) of DVR. DVR presents the compensation voltage as output which is included in the connected line. With this estimation method, voltage swell issues are discovered with accuracy and faster performance to retract out the swell problem in sensitivity load linked distribution systems. In MATLAB/Simulink platform the suggested method is executed and its performance is assessed and contrasted with the Linear Kalman Filter (LKF) and Extended Kalman Filter (EKF). © 2016. Source

Sridhar R.,Vignans Institute of Information Technology | Ravinder D.,Osmania University | Vijaya Kumar K.,Jawaharlal Nehru Technological University
Journal of Alloys and Compounds | Year: 2015

Synthesized Ni-Cu nano ferrites with the compositional formula Ni1-xCuxFe2O4 (x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) were prepared by the citrate-gel auto combustion technique. The prepared samples were characterized using X-ray difractrograms (XRD), Transmission electron microscope (TEM) and Fourier transforms infrared (FTIR). The X-ray difractrograms (XRD) clearly exhibited the existence of single phase cubic spinel structure and the crystallite size was found in the range of 36-58 nm. TEM micrographs indicated the nanostructure nature with platelet shape. FTIR absorption spectra revealed the presence of two significant absorption bands ν1 and ν2 around 580 cm-1 and 410 cm-1 characteristic of spinel ferrite. This confirms the formation of single phase spinel structure with two sub-lattices tetrahedral (A) site and octahedral (B) site. The thermoelectric properties were carried out by the differential method from room temperature to well beyond the transition temperature. The seebeck coefficient is negative for all the compositions showing that these ferrites behave as n-type semiconductors. The transition temperature determined from thermoelectric power studies, it was found that the transition temperature decreases with increase of Cu concentration. The values of the charge carrier concentration and charge carrier mobility have been computed from the observed values of the seebeck coefficient. The temperature variation of the seebeck coefficient and carrier concentration is also discussed. On the basis of these results an explanation for the conduction mechanism in Ni-Cu nano ferrites is suggested. © 2015 Elsevier B.V. All rights reserved. Source

Premamayudu B.,Andhra University | Venkata R.K.,Vignans Institute of Information Technology | Suresh V.P.,Adikavi Nannaya University
International Journal of Applied Engineering Research | Year: 2014

Key management is the one of the fundamental requirement for securing the hierarchical wireless sensor networks (HWSN) and also prevents adversarial activities. This paper presents a new pairwise key management scheme using matrix for HWSNs. In HWSN, cluster headers are more powerful than cluster members in all the resources like power, storage, communication and processing data. This heterogeneity alleviates the overhead of cluster members during the key establishment. All the expensive computations can be given to cluster headers in the network. Compared with other popular key management schemes, our scheme has many advantages in consuming the resources. The experiment and analysis show that our scheme can maintain the full network connectivity, easy configuration management, neighbor cluster members directly establish pairwise keys during the communication and reduce storage overhead. © Research India Publications. Source

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