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Statistical Safety Analysis of Maintenance Management Process of Excavator Units

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International Journal of Automation and computing 2010年第2期7卷 146-152页

作者： Ljubisa Papic Milorad Pantelic Joseph Aronov ajit kumar verma Research Center of Dependability and Quality Management Kolubara Metal Company Federal Scientific Research Institute of Standardization Indian Institute of Technology Bombay

Within this paper, the process of statistical safety analysis has been presented, which involves the following steps： formulation of basic principles of statistical safety analysis, initial events analysis, accident sceneries progress analysis, risk calculation, and risk calculation results analysis. On this basis, it has been concluded that the bucket wheel excavator SRs 1200×24/4×0（400 kW）＋VR safety criteria is the mechanism for the hoist of rotor＇s arrow failure modes, because in that case whole bucket wheel excavator failure would necessarily happen （excavator falling down on counterweight）. Therefore, excavator units statistical safety analysis is accomplished preventively to obtain its effective maintenance management.

关键词： Safety maintenance management statistical analysis event tree accident scenarios risk analysis excavator units.

Effect of ultrasonic assisted sintering on mechanical properties and degradation behaviour of Mg15Nb3Zn1Ca biomaterial

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Journal of Magnesium and Alloys 2021年第6期9卷 1989-2008页

作者： ajit kumar Pulak M Pandey Department of Mechanical Engineering Indian Institute of TechnologyDelhiNew Delhi 110016India

The present work investigates the effect of ultrasonic power(%)and the time of ultrasonic vibration on the sintered density and ultimate compressive strength(UCS)of Mg15Nb3Zn1Ca fabricated using ultrasonic assisted conventional sintering(UACS).The customized UACS setup was designed and manufactured to conduct the experimentations.A customized ultrasonic stepped horn assembly was used for providing vibrations to the sample during ***,to evaluate the efficacy of ultrasonic vibration parameters,the developed setup was used to sinter Mg15Nb3Zn1Ca composite *** study unveiled an increased sintered density and UCS of the fabricated sample by the increase in ultrasonic power(%).Moreover,a decrease in sintered density and UCS was observed with an increase in the time of ultrasonic vibration beyond a certain *** sintered with the assistance of ultrasonic vibration at 100%ultrasonic power,and 20 min of ultrasonic vibration resulted in a sintered density of 1.928±0.062 g·cm^(-3)and UCS of 234.9±12.3 *** obtained mechanical properties of the fabricated sample were comparable to the properties of cortical *** surface morphology and elemental compositions of samples fabricated using UACS declared a fair dispersion of reinforcement in the matrix containing merely the source *** results of corrosion test have showed that the assistance of ultrasonic vibration suppressed the degradation behaviour of the sintered sample after performing electrochemical study of samples using 3-electorde cell ***15Nb3Zn1Ca fabricated using UACS showed a 50.18%and 9.08%of reduction in corrosion rate over conventionally sintered pure Mg and Mg15Nb3Zn1Ca *** addition,electrochemical impedance spectroscopy(EIS)results indicated an enhanced corrosion resistance of the Mg15Nb3Zn1Ca composite material when fabricated at 100%of ultrasonic power with 20 min of vibration *** from that,electrochemical equivalent circuits also result

关键词： Ultrasonic assisted sintering Magnesium Corrosion EIS Mechanical properties

Experimental investigation for machinability aspects of graphene oxide/carbon fiber reinforced polymer nanocomposites and predictive modeling using hybrid approach

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Defence Technology（防务技术） 2021年第5期17卷 1671-1686页

作者： Jogendra kumar Rajesh kumar verma Department of Mechanical Engineering Madan Mohan Malaviya University of TechnologyGorakhpur273010India

This article explores the drilling behavior of polymer nanocomposites reinforced by Graphene oxide/Carbon fiber using a hybrid method of Grey theory and Principal component analysis(GR-PCA).An online digital dynamometer was employed for the evaluation of Thrust Force and *** image processing technique computes the *** surface methodology(RSM)considers the parameters,namely,drilling speed(S),feed rate(F),Graphene Oxide wt.%(G)in designing the experimentation *** component analysis(PCA)was used to tackle the response priority weight during the combination of multiple *** of variance(ANOVA)scrutinized the influence of parameters and intended the regression models to predict the ***-PCA evaluated the optimal parametric setting and remarked that feed rate acts as the most predominant *** higher feed rate and wt.%of G is responsible for surface damages like fiber pull-out,fiber fracture and cracks.A significant improvement in drilling responses has been obtained and also validates through confirmatory test and microstructure investigations.

关键词： Graphene oxide Polymer Carbon fiber RSM ANOVA GR-PCA

Development of Mg based biomaterial with improved mechanical and degradation properties using powder metallurgy

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Journal of Magnesium and Alloys 2020年第3期8卷 883-898页

作者： ajit kumar Pulak M.Pandey Department of Mechanical Engineering Indian Institute of TechnologyDelhi110016India

In the present work,biocompatible materials such as niobium(Nb),zinc(Zn)and calcium(Ca)have been blended with magnesium(Mg)to develop a novel biomaterial(BM)with improved mechanical and corrosion resistant *** metallurgy(PM)technique was used to fabricate Mg based *** powder of all aforementioned materials were mixed homogenously in specific quantities to create a uniform composite *** order to analyse the influence of process parameters on the mechanical properties of the fabricated part,experiments were performed considering central composite design(CCD).The effect of powder metallurgical parameters namely percentage Nb,compaction pressure,heating rate,sintering temperature and soaking time on the ultimate compressive strength(UCS)and sintered density was studied in the present *** was found that the UCS and sintered density increased with increase in compaction pressure,heating rate and sintering *** results also revealed that the increase in soaking time and percentage Nb,increased sintered density and UCS to a certain *** increase in these two parameters,sintered density and UCS *** electron microscopy(SEM)images of the fabricated samples showed reduction in porosity with the increase in heating ***,X-ray diffraction(XRD)results revealed that no other phase or impurities were found during sintering of Mg based *** optimum process parameters were obtained to develop Mg based BM for maximum UCS and sintered ***,the Mg based BM samples fabricated at optimum process parameters were used for corrosion testing in simulated body fluid(SBF)solution at a temperature of 37±0.5℃.The Mg based BM yielded improved mechanical properties with reduced corrosion rates as compared to pure Mg.

关键词： Biomaterials Powder metallurgy Magnesium Corrosion Metal matrix composite

Development of a new coated electrode with low nickel content for welding ductile iron and its response to austempering

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International Journal of Minerals,Metallurgy and Materials 2018年第9期25卷 1090-1103页

作者： Tapan Sarkar ajit kumar Pramanick Tapan kumar Pal Akshay kumar Pramanick Welding Technology Centre Jadavpur University Department of Forge Technology NIFFT

Coated Electrodes with small amounts of nickel were developed for welding ductile iron(DI) and conversion of the same into austempered ductile iron(ADI) after austempering. Among six electrodes, Trials 3 and 4 were selected for establishing crack-free weld deposits via preheating and post-weld heat treatment. Austenitization was performed at 900°C for 2 h and austempering at 300 or 350°C for three different holding times to observe the results of austempering with respect to the microstructure, hardness, and austempering kinetics of the samples. The microstructures of the weld deposits showed needle-like bainitic ferrite with small amounts of retained austenite when treated at 300°C and feathery bainitic ferrite with large amounts of retainedaustenite when treated at 350°C. The electrode labeled with Trial 3 revealed greater austenite contents than that labeled with Trial 4 when treated with a 2 h holding time regardless of the austempering temperature applied. The transformation rate of the bainitic ferrite of Trial 3 was relatively higher than that of Trial 4 and showed a lower rate constant, leading to a higher diffusion rate of carbon in austenite.

关键词： electrode development microstructure XRD analysis transformation kinetic microhardness

Surface Modification Aspects for Improving Biomedical Properties in Implants:A Review

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Acta Metallurgica Sinica(English Letters) 2024年第2期37卷 213-241页

作者： J.Sharath kumar Rakesh kumar Rajeev verma Industrial and Production Department Dr B R Ambedkar National Institute of Technology JalandharJalandharPunjab144008India

The primary focus during surgery is to ensure successful implantation by achieving long-term and stable fixation of *** surgery is now more focused on the development of novel biomaterials intended to improve implant *** obtain a better understanding of metal implants,this article investigated the causes of material failures in certain cases and analysed a few case *** interaction between the implant and bone tissue was a crucial aspect of successful implantation,and this study explored the factors influencing this interaction as well as ways to improve *** modern approaches used for modifying implant surfaces were systematically illustrated and briefly *** spray coatings were often favoured because of their wide range of coating materials,but other substantial surface modifications(such as friction stir processing and laser surface texturing)were also used for a selection of ***,implant surfaces with desirable features,such as biocompatibility,antibacterial properties,corrosion resistance,and wear resistance,were essential for optimising implant *** systematic review's main aim is to provide exhaustive reference information and a broad overview to advance the production and design of orthopaedic implants.

关键词： Biomaterials Surface treatments Thermal spray coatings Antibacterial Biocompatibility Corrosion resistance Wear resistance

Mitigation on self-discharge behaviors via morphological control of hierarchical Ni-sulfides/Ni-oxides electrodes for long-life-supercapacitors

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Journal of Materials Science & Technology 2022年第18期113卷 217-228页

作者： Dhananjay Mishra Niraj kumar ajit kumar SeungGi Seo SungHun Jin Department of Electronic Engineering Incheon National UniversityIncheon 406-772 and also with Convergence Research Center for Insect VectorsIncheon National UniversityRepublic of Korea

To cope up with the sustainable energy storage goals for supercapacitors(SCs),the self-discharge in SC electrodes is a significant hurdle,and thereby,nickel sulfide(NS)with high conductivity is adopted as a test vehicle for understanding the morphological evolution effects for long-life ***,honeycomb-like NS is hierarchically formed over hydrothermally grown nickel oxide(NO)via successive ionic layer adsorption reaction(SILAR)*** heterostructure shows a fivefold improvement in specific capacitance from 348 F g^(−1) to 2077 F g^(−1)at 1 mV s^(−1) over bare ***,the remarkable upliftment of capacitance retention is achieved from 60.7%to 92.3%even after 3000 cycles via morphological control of NS/NO hetero-structure with the help of highly conductive *** importantly,the self-discharge behaviors and synergistic role of leakage current associated with morphological evolution via NS overcoating are studied in *** particular,the self-discharge mitigation from 45%(NO)to 35%(NS20/NO)due to the NS/NO heterostructure and the behind mechanism are ascribed to the activated-controlled Faradaic reaction coupled with a charge *** study emphasizes the potential importance of composite heterostructure by tuning the electrical conductivity and morphological adjustment NO via consecutive overcoating of NS through SILAR as a novel *** enhances charge storage,redox kinetics,and the mitigation of self-discharge properties of the active electrode *** practical validation on sustainable energy storage,NS20/NO supercapacitors illuminate the LED for 35%longer than NO after one-time charging,potentially beneficial for the next generation SCs.

关键词： Morphological evolution Self-discharge SILAR overcoating Supercapacitors Heterostructure

Battery energy storage-based system damping controller for alleviating sub-synchronous oscillations in a DFIG-based wind power plant

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Protection and Control of Modern Power Systems 2023年第2期8卷 260-277页

作者： Neevatika verma Narendra kumar Rajeev kumar Department of Electrical Engineering Delhi Technological UniversityNew DelhiIndia Electrical Engineering Department Jamia Millia IslamiaNew DelhiIndia Electrical and Electronics Engineering Department KIET Group of InstitutionsGhaziabadIndia

This paper presents the issue of the Sub-synchronous resonance(SSR)phenomenon in a series compensated DFIG-based wind power plant and its alleviation using a Battery Energy Storage-based Damping Controller(BESSDCL).A supplementary damping signal is developed considering the angular speed deviation and is incorporated into the BESS control ***-area Measurement System data is used to determine the angular speed deviation.A lin-earized system model is developed to perform eigenvalue analysis,and to detect and examine unstable SSR *** variation of wind speed and three-phase fault are also taken into consideration to validate the robustness of the *** further verify the efficacy of the proposed damping controller,time-domain simulations are performed using MATLAB/*** application of the proposed BESSDCL stabilizes all the unstable system modes effectively at wind speeds of 7 m/s,9 m/s,and 11 m/s,and at 40%,50%,and 60%series compensation levels,as well three-phase fault conditions.

关键词： Battery energy storage system Damping controller Doubly-fed induction generator(DFIG) Series

Modeling the effect of time delay in implementation of mitigation policies on the control of atmospheric greenhouse gases

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International Journal of Biomathematics 2023年第8期16卷 75-108页

作者： Alok kumar verma Maitri verma Department of Mathematics School of Physical and Decision Science Babasaheb Bhimrao Ambedkar University Lucknow India

Mitigation of the enhanced greenhouse gas(GHG)concentrations in the Earth's atmosphere is imperative to meet the climate change mitigation *** of many countries are developing and implementing various mitigation strategies to reduce their GHG ***,a time delay between the formulation and implementation of these mitigation policies can affect their effectiveness in controlling greenhouse gas levels in the *** work presents a nonlinear mathematical model to investigate the effect of application of mitigation strategies and the delay involved in their implementation over the reduction of atmospheric greenhouse *** model formulation,it is assumed that the mitigation strategies work two-fold;first they reduce the GHG emission rate from the anthropogenic source and second they increase the removal rate of greenhouse gas from the atmosphere.A comprehensive stability analysis of the proposed model system is made to examine its long-term *** model analysis shows that an increase in the implementation rate of mitigation strategies and their efficiencies to cut down the GHG emission rate from point sources and increase the GHG uptake rate lead to reduction in equilibrium GHG *** is found that a long delay in the execution of mitigation policies can destabilize the system dynamics and leads to the generation of periodic *** expression for the threshold value of the delay parameter at which periodic oscillations arise via Hopf-bifurcation is *** stability and direction of bifurcating periodic solutions are discussed.A sensitivity analysis is performed to investigate the effect of changes in key parameters over system dynamics.

关键词： Mathematical model greenhouse gases global warming mitigation strategies time delay Hopf-bifurcation