Tribological characteristics of few-layer graphene over Ni grain and interface boundaries

Tripathi, Manoj,Awaja, Firas,Paolicelli, Guido,Bartali, Ruben,Iacob, Erica,Valeri, Sergio,Ryu, Seunghwa,Signetti, Stefano,Speranza, Giorgio,Pugno, Nicola Maria The Royal Society of Chemistry 2016 Nanoscale Vol.8 No.12

<P>The tribological properties of metal-supported few-layered graphene depend strongly on the grain topology of the metal substrate. Inhomogeneous distribution of graphene layers at such regions led to variable landscapes with distinguishable roughness. This discrepancy in morphology significantly affects the frictional and wetting characteristics of the FLG system. We discretely measured friction characteristics of FLG covering grains and interfacial grain boundaries of polycrystalline Ni metal substrate<I>via</I>an atomic force microscopy (AFM) probe. The friction coefficient of FLG covered at interfacial grain boundaries is found to be lower than that on grains in vacuum (at 10<SUP>−5</SUP>Torr pressure) and similar results were obtained in air condition. Sliding history with AFM cantilever, static and dynamic pull-in and pull-off adhesion forces were addressed in the course of friction measurements to explain the role of the out-of-plane deformation of graphene layer(s). Finite element simulations showed good agreement with experiments and led to a rationalization of the observations. Thus, with interfacial grain boundaries the FLG tribology can be effectively tuned.</P>

A Comparative Performance Analysis of Feature Extraction Techniques for Hyperspectral Image Classification

Diwaker,Manoj Kumar Chaudhary,Praveen Tripathi,Ashutosh Bhatt,Abhay Saxena 보안공학연구지원센터 2016 International Journal of Software Engineering and Vol.10 No.12

Obtaining thematic maps using image classification techniques from hyperspectral datasets is a very difficult image processing task. In hyperspectral image analysis dimensionality reduction is one of the challenging pre-processing tasks, which is achieved using feature extraction techniques. The beauty of these techniques is that they drastically reduces the dimensionality of image and at the same time preserves the majority of the essential information. In this paper few most frequently used dimensionality reduction methods are being investigated, which helps to get accurateness. This research work presents a relative performance investigation of few mostly frequently used feature extraction techniques like Decision Boundary Feature Extraction (DBFE), Non-Parametric Weighted Feature Extraction (NWFE), Discriminative analysis feature extraction (DAFE) and Principal Component Analysis (PCA). The classification is carried out using two most widely used classification techniques including Gaussian Maximum Likelihood (GML) and neural network (NNs). The results obtained after performing experiments indicates that Decision Boundary Feature Extraction (DBFE) technique has provided the best accuracy among various investigated feature extraction techniques. The application areas of this research include areas like identification of exact location in battle field, drought affected areas, flooded areas and weather forecasting etc.

Laser driven terahertz generation in hot plasma with step density profile

Kumar, Manoj,Tripathi, Vipin Kumar,Jeong, Young Uk American Institute of Physics 2015 Physics of plasmas Vol.22 No.6

Identification of Inrush and Internal Fault in Indirect Symmetrical Phase Shift Transformer Using Wavelet Transform

Shailendra Kumar Bhasker,Manoj Tripathy,Vishal Kumar 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

This paper proposes an algorithm for the differential protection of an Indirect Symmetrical Phase Shift Transformer (ISPST) by considering the different behaviors of the compensated differential current under internal fault and magnetizing inrush conditions. In this algorithm, a criterion function is defined which is based on the difference of amplitude of the wavelet transformation over a specific frequency band. The function has been used for the discrimination between three phase magnetizing inrush and internal fault condition and requires less than a quarter cycle after disturbance. This method is independent of any coefficient or threshold values of wavelet transformation. The merit of this algorithm is demonstrated by the simulation of different faults in series and excitation unit and magnetizing inrush with varying switching conditions on ISPST using PSCAD/EMTDC. Due to unavailability of in-field large interconnected transformers for such a large number of destructive tests, the results are further verified by Real Time Digital Simulator (RSCAD/RTDS). The proposed algorithm has been compared with the conventional harmonic restraint based method that justifies the application of wavelet transform for differential protection of ISPST. The proposed algorithm has also been verified for different rating of ISPSTs and satisfactory results were obtained.

Identification of Inrush and Internal Fault in Indirect Symmetrical Phase Shift Transformer Using Wavelet Transform

Bhasker, Shailendra Kumar,Tripathy, Manoj,Kumar, Vishal The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

This paper proposes an algorithm for the differential protection of an Indirect Symmetrical Phase Shift Transformer (ISPST) by considering the different behaviors of the compensated differential current under internal fault and magnetizing inrush conditions. In this algorithm, a criterion function is defined which is based on the difference of amplitude of the wavelet transformation over a specific frequency band. The function has been used for the discrimination between three phase magnetizing inrush and internal fault condition and requires less than a quarter cycle after disturbance. This method is independent of any coefficient or threshold values of wavelet transformation. The merit of this algorithm is demonstrated by the simulation of different faults in series and excitation unit and magnetizing inrush with varying switching conditions on ISPST using PSCAD/EMTDC. Due to unavailability of in-field large interconnected transformers for such a large number of destructive tests, the results are further verified by Real Time Digital Simulator (RSCAD/RTDS). The proposed algorithm has been compared with the conventional harmonic restraint based method that justifies the application of wavelet transform for differential protection of ISPST. The proposed algorithm has also been verified for different rating of ISPSTs and satisfactory results were obtained.

Material Flow Behavior and Mechanical Properties of Dissimilar Friction Stir Welded Al 7075 and Mg AZ31 Alloys Using Cd Interlayer

Satya Kumar Dewangan,M. K. Tripathi,M. K. Manoj 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.5

Friction Stir Welding (FSW) has great potential over fusion welding for joining dissimilar alloys. However, formation ofintermetallic compounds (IMCs) Al12Mg17and Al3Mg2in FSW of Al/Mg alloys is almost unavoidable and problematic forthe research community. Such IMCs in the form of continuous layer provide easy crack propagation path which increasesbrittleness and reduces the joint strength of the weld. To improve the material flow behavior and reducing brittleness, accurateand precise attempts were taken to join two dissimilar alloys i.e. Al 7075 and Mg AZ31 with the incorporation of cadmiuminterlayer first time. Tool rotational speed of 1300 rpm and traverse speed of 20 mm/min were maintained throughout thewelding process. Various phase formation and their distribution in the nugget zone has been studied in details by using opticalmicroscopy, SEM–EDS and XRD. The supersaturated solid solution (SSSS) of Mg in Al, and a thin layer of Al3Mg2andsmall particles (~ 1 μm) of Al12Mg17have been observed in the stir zone. During processing Cd reacted with Mg and formedCdMg and CdMg3which have been distributed in the upper-middle portion of Mg region as intercalated lamellar structure. Formation of these compound provided micro-mechanical interlocking. Further, Al material has been found to be depositedinto the Mg region in the form of elongated balloon which provided anchoring effect due to mechanical interlocking. Themaximum tensile strength achieved is 129 MPa which is higher than the previously reported dissimilar FSW of Al 7xxxseries alloy with Mg alloy. Fractographic study of the dissimilar FSW tensile sample was carried out to understand crackpropagation path and scope for further improvement in the weld joint strength.