Kankar P.K.,PDPM Indian Institute of Information Technology, Design & Manufacturing |
Sharma S.C.,Indian Institute of Technology Roorkee |
Harsha S.P.,Indian Institute of Technology Roorkee
Neurocomputing | Year: 2013
Fault diagnosis of bearings under localized defects is essential in the design of high performance rotor bearing system. Traditionally, fault diagnosis of rolling element bearings is carried out performed by the use of signal processing methods, which assume statistically stationary signal features. This paper presents a feature-recognition system for rolling element bearings fault diagnosis, which utilizes cyclic autocorrelation of raw vibration signals. Cyclostationary analysis of non-stationary signals clearly indicates the appearance of several distinct modulating frequencies. The coefficients of wavelet transform are calculated using six different base wavelets, after calculating cyclic autocorrelation of vibration signals. The base wavelet that maximizes the Energy to Shannon Entropy ratio is selected to extract statistical features from wavelet coefficients. Finally, a comparative study is carried out with the calculated statistical features as input to soft computing techniques. Three soft computing techniques are used for faults classifications, out of which two are supervised techniques i.e. Support vector machine, Artificial Neural Network and other one is an unsupervised technique i.e. Self-Organizing Maps. The Complex Gaussian wavelet is selected based on maximum Energy to Shannon Entropy ratio. The results show that the support vector machine identifies the fault categories of rolling element bearing more accurately and has a better diagnosis performance. © 2013 Elsevier B.V.
Kumar Singh V.,Indian Institute of Technology Kanpur |
Kumar Singh V.,PDPM Indian Institute of Information Technology, Design & Manufacturing |
Mazhari B.,Indian Institute of Technology Kanpur
Applied Physics Letters | Year: 2013
Conventional method used for measurement of linearly extrapolated threshold voltage from the slope of I SD vs. VGS characteristics in organic thin film transistors (OTFTs) suffers from the influence of gate dependence of field mobility and its use for comparing different devices can result in anomalous trends. In the present work, an improved method is described, which eliminates the effects of mobility and yields a unique value of threshold voltage. Experimental results obtained with pentacene OTFTs with two different dielectric materials are presented, which show that actual threshold voltage can be very different than the values estimated using the conventional technique. © 2013 AIP Publishing LLC.
Mukherjee B.,PDPM Indian Institute of Information Technology, Design & Manufacturing
AEU - International Journal of Electronics and Communications | Year: 2015
In this paper, effect of loading of a circular metallic patch on a half Hemispherical Dielectric Resonator Antenna (HDRA) with array of slots is investigated. The half HDRA with array of slots operate from 5.3GHz to 6.05GHz. The circular patch controls the frequency tuning of the antenna geometry. The radius of the patch governs the resonant frequency and subsequently the bandwidth of operation. The patch also plays a role of reflector to improve the gain of the antenna. An optimized radius of patch of r =0.6cm on the proposed geometry offers 0.82GHz of impedance bandwidth (S 11 <-10dB) at 4.55GHz. The gain is significantly improved to 8.5dBi at 5.05GHz. A prototype is fabricated and the measured results are found to be in good agreement with the simulations. The resonant frequency is most suitable for standard wireless communications with wide band and high gain applications. © 2015 Elsevier GmbH.
Jha R.K.,PDPM Indian Institute of Information Technology, Design & Manufacturing |
Biswas P.K.,Indian Institute of Technology Kharagpur |
Chatterji B.N.,Indian Institute of Technology Kharagpur
IET Image Processing | Year: 2012
Two stochastic resonance (SR)-based techniques are introduced for enhancement of very low-contrast images. In the proposed SR-based image enhancement technique-1, an expression for optimum threshold has been derived. Gaussian noise of increasing standard deviation has been added iteratively to the low-contrast image until the quality of enhanced image reaches maximum. A quantitative parameter 'distribution separation measure (DSM)' is used to measure the enhancement quality. In order to reduce the required number of iterations in the second enhancement technique the author's have derived an expression for optimum noise standard deviation σ optimum that maximises signal-to-noise ratio (SNR). Image enhancement is obtained by iterating only with few noise standard deviations around σ optimum. This reduces number of iterations drastically. Comparison with the existing methods shows the superiority of the proposed method. © 2012 The Institution of Engineering and Technology.
Kumar A.,PDPM Indian Institute of Information Technology, Design & Manufacturing |
Rafi S.M.,PDPM Indian Institute of Information Technology, Design & Manufacturing |
Singh G.K.,Indian Institute of Technology Roorkee
Digital Signal Processing: A Review Journal | Year: 2012
In this work, a hybrid method in frequency domain for design of a linear-phase quadrature mirror filter bank is proposed. The nonlinear least square hybrid method based on Levenberg-Marquardt (LM) and Quasi-Newton (QN) is developed for the design of a low-pass prototype filter whose responses in the passband and stopband are ideal, and the filter bank response at quadrature frequency is 0.707. The proposed method is employed to optimize the quadratic measure of ideal characteristics of the prototype filter and filter bank at quadrature frequency. Performance and effectiveness of the proposed method in terms of peak reconstruction error (PRE), mean squares error in passband and stopband regions, and error in transition band at quadrature frequency are shown through numerical examples and comparison of the results with other existing method. It was found that the proposed method is very simple and easy to implement for QMF bank design problem. © 2012 Elsevier Inc. All rights reserved.