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A comparative study on microstructural evolution and surface properties of graphene/CNT reinforced Al6061-SiC hybrid surface composite fabricated via friction stir processing

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Transactions of Nonferrous Metals Society of China 2019年第10期29卷 2005-2026页

作者： abhishek SHARMA Vyas Mani SHARMA Jinu PAUL Department of Mechanical Engineering Indian Institute of Technology

A comparative study on the surface properties of Al-SiC-multi walled carbon nanotubes (CNT) and Al-SiC-graphene nanoplatelets (GNP) hybrid composites fabricated via friction stir processing (FSP) was documented. Microstructural characterization reveals a more homogeneous dispersion of GNPs in the Al matrix as compared to CNTs. Dislocation blockade by SiC and GNP particles along with the defect-free interface between the matrix and reinforcements is also observed. Nanoindentation study reveals a remarkable ~207% and ~27% increment in surface nano-hardness of Al-SiC-GNP and Al-SiC-CNT hybrid composite compared to as-received Al6061 alloy, respectively. On the other hand, the microhardness values of Al-SiC-GNP and Al-SiC-CNT are increased by ~36% and ~17% relative to as-received Al6061 alloy, respectively. Tribological assessment reveals ~56% decrease in the specific wear rate of Al-SiC-GNP hybrid composite, whereas it is increased by ~122% in Al-SiC-CNT composite. The higher strength of Al-SiC-GNP composite is attributed to the mechanical exfoliation of GNPs to few layered graphene (FLG) in the presence of SiC. Also, various mechanisms such as thermal mismatch, grain refinement, and Orowan looping contribute significantly towards the strengthening of composites. Moreover, the formation of tribolayer by the squeezed-out GNP on the surface is responsible for the improved tribological performance of the composites. Raman spectroscopy and various other characterization methods corroborate the results.

关键词： friction stir processing graphene carbon nanotube hybrid composite wear

Effects of Nonmonotonic Functional Responses on a Disease Transmission Model:Modeling and Simulation

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Communications in Mathematics and Statistics 2022年第2期10卷 195-214页

作者： abhishek Kumar Nilam Department of Applied Mathematics Delhi Technological UniversityDelhi 110042India

In this article,a novel susceptible-infected-recovered epidemic model with nonmonotonic incidence and treatment rates is proposed and analyzed *** Monod-Haldane functional response is considered for nonmonotonic behavior of both incidence rate and treatment *** model analysis shows that the model has two equilibria which are named as disease-free equilibrium(DFE)and endemic equilibrium(EE).The stability analysis has been performed for the local and global behavior of the DFE and *** the help of the basic reproduction number(R_(0)),we investigate that DFE is locally asymptotically stable when R_(0)*** local stability of DFE at R_(0)=1 has been analyzed,and it is obtained that DFE exhibits a forward transcritical ***,we identify conditions for the existence of EE and show the local stability of EE under certain ***,the global stability behavior of DFE and EE has been ***,numerical simulations have been done in the support of our theoretical findings.

关键词： Monod-Haldane functional Basic reproduction number Local and global stability Bifurcation

Deep Neural Network and Pseudo Relevance Feedback Based Query Expansion

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Computers, Materials & Continua 2022年第5期71卷 3557-3570页

作者： abhishek Kumar Shukla Sujoy Das Department of Mathematics Bio-Informatics and Computer ApplicationsMaulana Azad National Institute of Technology BhopalBhopalMadhya Pradesh462003India

The neural network has attracted researchers immensely in the last couple of years due to its wide applications in various areas such as Data mining,Natural language processing,Image processing,and Information retrieval *** embedding has been applied by many researchers for Information retrieval *** this paper word embedding-based skip-gram model has been developed for the query expansion *** terms are obtained from the top“k”initially retrieved documents using the Pseudo relevance feedback model and then they are trained using the skip-gram model to find the expansion terms for the user *** performance of the model based on mean average precision is *** proposed model compares with other existing *** improvement of 6.61%,6.93%,and 9.07%on MAP value is observed compare to the Original query,BM25 model,and query expansion with the Chi-Square model *** proposed model also retrieves 84,25,and 81 additional relevant documents compare to the original query,query expansion with Chi-Square model,and BM25 model respectively and thus improves the recall value *** per query analysis reveals that the proposed model performs well in 30,36,and 30 queries compare to the original query,query expansion with Chi-square model,and BM25 model respectively.

关键词： Information retrieval query expansion word embedding neural network deep neural network

Comparison of Scour and Flow Characteristics Around Circular and Oblong Bridge Piers in Seepage Affected Alluvial Channels

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Journal of Marine Science and Application 2018年第2期17卷 254-264页

作者： Rutuja Chavan B.venkataramana Pratik Acharya Bimlesh Kumar Department of Civil Engineering Indian Institute of Technology GuwahatiGuwahati 781039India

The present study examines scour geometry and turbulent flow characteristics around circular and oblong piers in alluvial channel with downward *** were conducted in plane sand bed of non-uniform sand under no seepage,10%seepage and 15%seepage *** depth at oblong pier is significantly lesser than the scour depth at circular ***,the scour depth at both piers reduces with downward *** measurements show that the velocity and Reynolds stresses are negative near the bed at upstream of piers where the strong reversal *** downstream of oblong pier near the free surface,velocity and Reynolds stresses are less positive;whereas,they are negative at downstream of circular *** streamline shape of oblong pier leads to reduce the strength of wake vortices and consequently reversal flow at downstream of *** application of downward seepage turbulent kinetic energy is *** results show that the wake vortices at oblong pier are weaker than the wake vortices at circular *** strength of wake vortices diminishes with downward *** Strouhal number is lesser for oblong pier and decreases with downward seepage for both oblong and circular piers.

关键词： Downward seepage Oblong pier Scour Strouhal number Turbulent kinetic energy

Three-phase AC-DC Converter for Direct-drive PMSG-based Wind Energy Conversion System

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Journal of Modern Power Systems and Clean Energy 2023年第2期11卷 589-598页

作者： Kumar abhishek Singh Ayushi Chaudhary Kalpana Chaudhary Department of Electrical Engineering Indian Institute TechnologyVaranasiIndia Department of Electrical Engineering Indian Institute TechnologyKanpurIndia

In this paper,a wind energy conversion system(WECS)is presented for the electrification of rural areas with wind energy availability.A three-phase AC-DC converter based on a bridgeless Cuk converter is used for power extraction from the permanent magnet synchronous generator(PMSG).The bridgeless topology enables the elimination of the front-end diode bridge rectifier(DBR).Moreover,the converter has fewer components,simple control,and high efficiency,making it suitable for a small-scale WECS.A squirrel cage induction motor(SCIM)is used to emulate a MOD-2 wind turbine to implement the PMSG-based WECS.A direct-drive eight-pole PMSG is used in this study;thus,a low-input-voltage system is *** converter is designed to operate in the discontinuous inductor current mode(DICM)for inherent power factor correction(PFC)and the maximum power point tracking(MPPT)is achieved through the tip-speed ratio(TSR)*** performance of the developed system is analyzed through simulation,and a 500 W hardware prototype is developed and tested in different wind speed conditions.

关键词： Permanent magnet synchronous generator(PMSG) three-phase AC-DC converter wind energy conversion system(WECS) wind turbine emulator

Implications of REE incorporation and host sediment influence on the origin and growth processes of ferromanganese nodules from Central Indian Ocean Basin

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Geoscience Frontiers 2021年第3期12卷 609-623页

作者： Simontini Sensarma abhishek Saha Arghya Hazra CSIR-National Institute of Oceanography Dona PaulaGoa 403004India Indian Institute of Science BangaloreKarnataka 560012India School of Earth Ocean and Atmospheric SciencesGoa UniversityGoa 403206India

This study presents new major,trace and REE data for thirty-five ferromanganese nodules recovered from areas representing three different sediment types(siliceous,red clay and their transition zone)in the Central Indian Ocean Basin(CIOB)to address their genetic aspects,classification,growth rate,nature of host sediments and influence of REE in the processes of nodule *** nodules from CIOB are mostly either hydrogenetic(metals coming from oxygenated bottom water)and diagenetic(metals coming from suboxic sediment pore water)or a combination of both,depending on the source of supply of ***,a number of biogeochemical processes mediate this supply of metals which again changes from time to time,making the nodule growth process highly *** study suggests that at the initial stage of nodule growth,host sediments do not play much role in controlling the growth processes for which REEs can enter both Mn and Fe oxyhydroxide phases ***,the bottom water signature is imprinted in these early formed nodules irrespective of their host sediment substrate but with gradual growth and burial in the sediment,the main mode of metal enrichment becomes diagenetic through sediment pore *** tends to increase the concentration of Mn,Ni and Cu over other elements which are retained in the sediment *** the REEs,Ce concentration of the nodules shows significant positive anomaly due to variation in redox potential and hence its magnitude can be used to get an idea about the metal enrichment procedure and the genetic type of the ***,based on host sediment only,not much difference is found in the magnitude of Ce anomaly in these *** the other hand,discrimination diagram,based on HFSE and REY chemistry,indicates that most of these nodules are of diagenetic origin under oxic condition with a trend towards hydrogenetic ***,the genetic type of the ferromanganese nodules from the CIOB are more effectively differentiated

关键词： Central Indian Ocean Basin Ferromanganese nodules Deep-sea sediments Rare earth elements Geochemical discrimination

Vasectomy reversal： a clinical update

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Asian Journal of Andrology 2016年第3期18卷 365-371,I0007页

作者： abhishek P Patel Ryan P Smith Department of Urology University of Virginia Charlottesville VA 22908-0422 USA.

Vasectomy is a safe and effective method of contraception used by 42-60 million men worldwide. Approximately 3%-6% of men opt for a vasectomy reversal due to the death of a child or divorce and remarriage, change in financial situation, desire for more children within the same marriage, or to alleviate the dreaded postvasectomy pain syndrome. Unlike vasectomy, vasectomy reversal is a much more technically challenging procedure that is performed only by a minority of urologists and places a larger financial strain on the patient since it is usually not covered by insurance. Interest in this procedure has increased since the operating microscope became available in the 1970s, which consequently led to improved patency and pregnancy rates following the procedure. In this clinical update, we discuss patient evaluation, variables that may influence reversal success rates, factors to consider in choosing to perform vasovasostomy versus vasoepididymostomy, and the usefulness of vasectomy reversal to alleviate postvasectomy pain syndrome. We also review the use of robotics for vasectomy reversal and other novel techniques and instrumentation that have emerged in recent years to aid in the success of this surgery.

关键词： epididymovasostomy microsurgery postvasectomy orchialgia postvasectomy pain syndrome vas deferens vasectomy vasectomy reversal vasoepididymostomy vasovasostomy

Performance, emission and combustion characteristics of DI diesel engine running on blends of honne oil/diesel fuel/kerosene/DMC

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International Journal of Agricultural and Biological Engineering 2011年第3期4卷 48-57页

作者： B.K.Venkanna C.venkataramana Reddy Department of Mechanical Engineering Basaveshwar Engineering CollegeBagalkot 587102KarnatakaIndia Principal Guru Nanak Institute of TechnologyIbrahimpatnamR.R.District-501506Andra PradeshIndia

Honne oil(tamanu)(H),a non-edible vegetable oil is native for northwards of Northern Marianas islands and the Ryukyu Islands in southern Japan and westward throughout *** has remained as an untapped new possible source of alternative fuel that can be used as diesel engine *** pertaining to use of vegetable oil in diesel engine with kerosene and dimethyl carbonate(DMC)is *** present research is aimed to investigate experimentally the performance,exhaust emission and combustion characteristics of a direct injection(DI)diesel engine,typically used in agricultural sector,over the entire load range,when fuelled with neat diesel(ND)and blends of diesel fuel(D)/DMC/H/kerosene(K).DMC/D/H/K blends have a potential to improve the performance and emissions and to be an alternative to *** have been conducted when fuelled with H20(20%H+80%D),HK(20%H+40%K+40%D)and HKD5(20%H+40%K+35D+5%DMC)to HKD15 in steps of 5%DMC keeping H and K percentages *** emissions(CO,HC and smoke density(SD))of fuel blend HKD15 are found to be lowest,with SD dropping *** NOx level is slightly higher with HKD5 to HKD15 as compared to *** brake thermal efficiency of HKD5 to HKD15 is same and it is higher than that of *** is a good trade off between NOx and *** cylinder pressure and premixed combustion phase increases as DMC content increase.

关键词： diesel engine performance emissions combustion vegetable oil kerosene diesel fuel dimethyl carbonates

Large eddy simulations of a turbulent mixing layer periodically excited with fundamental and third harmonic frequency

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Chinese Journal of Aeronautics 2023年第5期36卷 33-40页

作者： Jörg SCHLÜTER Dan ZHAO abhishek SARKAR School of Engineering Deakin UniversityWaurn Ponds 3216Australia College of Engineering University of CanterburyChristchurch 8041New Zealand School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore

A better understanding of the mixing behavior of excited turbulent mixing layers is critical to a number of aerospace *** studies of excited turbulent mixing layers focused on single frequency excitation or the excitation with fundamental and its second harmonic *** is a lack of detailed studies on applying low and higher frequency *** this study,we have performed large-eddy simulations of periodically excited turbulent mixing *** excitation consists of a fundamental frequency and its third *** have used phase-averaging to identify the vortex structure and strength in the mixing layer,and we have studied the vortex *** different vortex paring mechanisms are observed depending on the phase shift between the two excitation *** influence of these two mechanisms on the mixing of a passive scalar is also *** is found that exciting the mixing layer with these low and high frequencies has initially an adverse influence on the mixing process;however,it improves the mixing further downstream of the splitter plate with the excitation using a phase shift ofΔφ=πshowing the best mixing *** present works shed lights on the fundamental vortex dynamics,and has great potential for aeronautical,automotive and combustion engineering applications.

关键词： Flow control Flow excitation Large eddy simulations Turbulent mixing layer Vortex dynamics