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192 results on '"Shekhar, Mayank"'

21. Automated detection of credit card fraud through machine learning.

Author

Shekhar, Mayank, Khawas, Krishna, and Murugan, Suganiya

Subjects
*CREDIT card fraud, *CREDIT cards, *SMART cards, *DATA science, *MACHINE learning
Abstract

Credit card companies must identify fraudulent credit card transactions in order to prevent consumers from being charged for goods they did not buy. Data science can address these problems, so machine learning and data science as a combined field shouldn't be underestimated. The project's objective is to compile a catalogue of all datasets used for machine learning to detect credit card theft. The use of data from credit card transactions that are later discovered to be fraudulent to simulate earlier credit card transactions is one of the problems with identifying credit card fraud. Then, using this approach, the validity of new deals is assessed. Our intention is to reduce the number of erroneous deals by detecting all fraudulent ones. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Development and Experimental Study of Electrochemical Diamond Drilling Process on Ti6Al4V.

Author

Shekhar, Mayank and Singh Yadav, Sanjeev Kumar

Subjects
BORING & drilling (Earth & rocks), TITANIUM alloys, CHEMICAL processes, MECHANICAL abrasion, INDUSTRIAL diamonds, SURFACE roughness, MACHINE tools
Abstract

Electrochemical diamond drilling (ECDD) process is a chemical energy-based hybrid machining technique where the removal of material from the workpiece occurs with the help of both anodic dissolution and mechanical abrasion. Titanium alloys have remarkable mechanical as well as chemical properties, however, excellent properties enhance the difficulty in machining of titanium. Ti6Al4V, alloy of titanium contains α and β phase which have different dissolution potentials and produces poor surface when electrochemically machined. Here electrochemical diamond drilling of Ti6Al4V is done with a diamond abrasive tool which helps in mechanical abrasion and further by electrochemical dissolution hence this increases the rate of material removal and minimizes surface roughness. From the experiments, the suitable machining range was found to be, voltage 13–17 V, tool feed rate 0.09–0.15 mm/min, and electrolyte concentration of electrolyte from 225 g/l to– 275 g/l, with tool rotation ranging between 800 RPM and 1200 RPM. The MRR range found was between 30.57 mg/min and 53.11 mg/min with Ra values ranging between 2.66 μ m and –5.76 μ m. The variation of machining with ECDD tool and bare ECD tool has also been graphically represented which highlights the benefits of diamond abrasive-based ECDD tool. [ABSTRACT FROM AUTHOR]

Published
2024
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32. The optimal machining parameters of electrochemical diamond drilling process: RSM approach.

Author

Shekhar, Mayank and Yadav, Sanjeev Kumar Singh

Subjects
*BORING & drilling (Earth & rocks), *ELECTROCHEMICAL cutting, *MECHANICAL abrasion, *RESPONSE surfaces (Statistics), *CHROMIUM-cobalt-nickel-molybdenum alloys, *MANUFACTURING processes, *SURFACE finishing, *TITANIUM alloys
Abstract

Electrochemical diamond drilling (ECDD) is a novel hybrid machining process that offers an efficient solution for machining of super alloys without distressing their internal properties. The material removal process in ECDD occurs through a combination of anodic dissolution and mechanical abrasion, making it an effective solution for machining two-phase alloys that are prone to differential dissolution of phases. Ti6Al4V alloy is one such example, which has poor surface finish when electrochemically machined due to the different dissolution potentials of its α and β phases. The present study suggests the use of response surface methodology (RSM) for optimizing the ECDD process. Using central composite design (CCD), 30 experimental runs were performed to analyze the effect of input parameters—voltage, tool feed rate, concentration of electrolyte and tool RPM on material removal rate (MRR) and surface roughness (Ra). The result showed that the use of diamond abrasive tool in ECDD enhances the surface finish by removing the TiO2 layer and burrs through mechanical abrasion, while increasing MRR through electrolytic dissolution. The study found that the optimized conditions for ECDD produced an MRR of 0.041 gm/min and Ra of 3.986 µm which were 5.12% and 2.1% different from the values predicted by the regression model. The study concludes that ECDD can be used to produce high-quality surfaces on two phase alloys while preserving their internal properties, making it a valuable tool for machining of wide range of materials. [ABSTRACT FROM AUTHOR]

Published
2023
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40. Tree-Ring Isotopic Records Suggest Seasonal Importance of Moisture Dynamics Over Glacial Valleys of the Central Himalaya

Author

Singh, Nilendu, Shekhar, Mayank, Parida, Bikash Ranjan, Gupta, Anil K., Sain, Kalachand, Rai, Santosh K., Bräuning, Achim, Singh Charkaborty, Joyeeta, Sharma, Vikram, Kamal Tiwari, Reet, Chauhan, Pankaj, and Montagnani, Leonardo

Subjects
ddc:550, General Earth and Planetary Sciences
Abstract

Accelerated glacier mass loss is primarily attributed to greenhouse-induced global warming. Land–climate interactions have increasingly been recognized as an important forcing at the regional-local scale, but the related effects on the Himalayan glaciers are less explored and thought to be an important factor regulating spatial heterogeneity. The aim of the present study is a multi-decadal approximation of glacier—hydroclimate interaction over the western region of the central Himalaya (WCH). Multi-species, highly coherent, tree-ring cellulose δ18O chronologies from three sites across the WCH were used to derive atmospheric humidity (Atmospheric Moisture Content: AMC) record of the last four centuries. Annual-scale AMC reconstruction implies a decreasing regional atmospheric moisture since the mid-19th century and a sharp decline in recent decades (1960s). Coherency analyses between regional AMC and glacier mass balance (GMB) indicate an abrupt phase-shift in the relationship after the 1960s within a common record of the last 273 years. To ascertain the cause of this phase-shift, annual AMC was disintegrated into seasonal-scale, utilizing ∼200 years of δ18O record of a deciduous tree species. Seasonal (winter: October–March; summer: April–September) AMC reconstructions and disaggregation results indicate higher sensitivity of regional ice-mass variability to winter moisture dynamics than summer.Winter season AMC reconstruction confirms a revival of winter westerlies-driven moisture influx in the region since the 1970 s. Meanwhile, the record for the summer season AMC indicates a gradual decline in moisture influx from the beginning of the 20th century. Interestingly, despite a prominent decline in Indian summer monsoon (ISM) precipitation after the mid-20th century, the summer season AMC—GMB relation remained stable. We hypothesize that decadal-scale greening, and consequently increased evapotranspiration and pre-monsoon precipitation might have been recycled through the summer season, to compensate for the ISM part of precipitation. However, isotope-enabled ecophysiological models and measurements would strengthen this hypothesis. In addition, high-resolution radiative forcing and long-term vegetation greening trends point towards a probable influence of valley greening on GMB. Our results indicate that attribution of ice mass to large-scale dynamics is likely to be modulated by local vegetation changes. This study contributes to the understanding of long-term hydroclimate—ice mass variability in the central Himalaya, where predictions are crucial for managing water resources and ecosystems.

Published
2022

41. Tree-Ring Isotopic Records Suggest Seasonal Importance of Moisture Dynamics Over Glacial Valleys of the Central Himalaya

Author

Singh, Nilendu, primary, Shekhar, Mayank, additional, Parida, Bikash Ranjan, additional, Gupta, Anil K., additional, Sain, Kalachand, additional, Rai, Santosh K., additional, Bräuning, Achim, additional, Singh Charkaborty, Joyeeta, additional, Sharma, Vikram, additional, Kamal Tiwari, Reet, additional, Chauhan, Pankaj, additional, and Montagnani, Leonardo, additional

Published
2022
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50. Water-gas shift reaction over supported Au nanoparticles

Author

Shekhar, Mayank, primary, Lee, Wen-Sheng, additional, Akatay, M. Cem, additional, Maciel, Leonardo, additional, Tang, Wenjie, additional, Miller, Jeffrey T., additional, Stach, Eric A., additional, Neurock, Matthew, additional, Delgass, W. Nicholas, additional, and Ribeiro, Fabio H., additional

Published
2022
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