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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

On Existence of Primitive Normal Elements of Cubic Form over Finite Fields

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Algebra Colloquium 2022年第1期29卷 151-166页

作者： Himangshu hazarika Dhiren kumar Basnet Department of Mathematical Sciences Tezpur UniversityAssamIndia

For a prime p and a positive integer k,let q=p^(k) and F_(q)^(n) be the extension field of F_(q).We derive a sufficient condition for the existence of a primitive element α in F_(q)^(n) such that α^(3)-α+1 is also a primitive element of F_(q)^(n) ,a sufficient condition for the existence of a primitive normal element a in F_(q)^(n) over F_(q) such that α(3)-α+1 is a primitive element of F_(q)^(n) ,and a suficient condition for the existence of a primitive normal element a in F_(q)^(n) over F_(q) such that а^(3)-а+1 is also a primitive normal element of F_(q)^(n) over F_(q).

关键词： finite field primitive element free element normal basis character

Remote Sensing Image Retrieval Based on 3D-Local Ternary Pattern(LTP)Features and Non-subsampled Shearlet Transform(NSST)Domain Statistical Features

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Computer Modeling in Engineering & Sciences 2022年第4期131卷 137-164页

作者： Hilly Gohain Baruah Vijay kumar Nath Deepika hazarika Department of Electronics and Communication Engineering Tezpur UniversityAssam784028India

With the increasing popularity of high-resolution remote sensing images,the remote sensing image retrieval(RSIR)has always been a topic of major issue.A combined,global non-subsampled shearlet transform(NSST)-domain statistical features(NSSTds)and local three dimensional local ternary pattern(3D-LTP)features,is proposed for high-resolution remote sensing *** model the NSST image coefficients of detail subbands using 2-state laplacian mixture(LM)distribution and its three parameters are estimated using Expectation-Maximization(EM)*** also calculate the statistical parameters such as subband kurtosis and skewness from detail subbands along with mean and standard deviation calculated from approximation subband,and concatenate all of them with the 2-state LM parameters to describe the global features of the *** various properties of NSST such as multiscale,localization and flexible directional sensitivity make it a suitable choice to provide an effective approximation of an *** order to extract the dense local features,a new 3D-LTP is proposed where dimension reduction is performed via selection of‘uniform’*** 3D-LTP is calculated from spatial RGB planes of the input *** proposed inter-channel 3D-LTP not only exploits the local texture information but the color information is captured ***,a fused feature representation(NSSTds-3DLTP)is proposed using new global(NSSTds)and local(3D-LTP)features to enhance the discriminativeness of *** retrieval performance of proposed NSSTds-3DLTP features are tested on three challenging remote sensing image datasets such as WHU-RS19,Aerial Image Dataset(AID)and PatternNet in terms of mean average precision(MAP),average normalized modified retrieval rank(ANMRR)and precision-recall(P-R)*** experimental results are encouraging and the NSSTds-3DLTP features leads to superior retrieval performance compared to many well known existing descriptors such as Gabor RGB,Granulometry,loc

关键词： Remote sensing image retrieval laplacian mixture model local ternary pattern statistical modeling,KS test,texture,global features

Polymer flooding and its effects on enhanced oil recovery special reference to Upper Assam Basin

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Petroleum Research 2023年第1期8卷 54-62页

作者： Kalpajit hazarika Subrata Borgohain Gogoi Amit kumar Presidency University BangaloreIndia Dibrugarh University AssamIndia Rajiv Gandhi Institute of Petroleum Technology JaisAmethiIndia

Chemical Enhance oil Recovery(CEOR)technology is getting more attention since energy crises are getting worse and *** application of polymer flooding depends on the evaluation of rheological and solution properties of injected slug at reservoir conditions,which is function of polymer concentration,salinity,temperature and shear *** acryl amide(PAM)is commonly used polymer in polymer flooding ***,comparative study with other polymers such as xanthan gum(XG)is required while selection of appropriate polymer for *** present study,the recovery efficiency of PAM and XG as a polymer has been evaluated for application as chemical EOR agent for tertiary phase polymer flooding in Upper Assam *** comparative study between PAM and XG has been done in terms of rheological *** flooding experiment of polymer flooding has also been tested to determine the recovery efficiency of the PAM and XG polymer *** results showed that these polymers exhibit favorable salt tolerance,temperature resistance,and recoverable viscosity after shearing,reasonable thickening behavior and improved viscosity enhancement properties due to presence of hydrophobic association in the polymer main *** flooding experiment of polymer flooding has also been tested to determine the recovery efficiency of the PAM and XG polymer *** show that macroscopic sweep efficiency is the dominant factor during *** an injection of hydrogel polymer to the reservoir is to increase a viscosity of fluid containing water so that the fluid is more difficult to flow than the oil,and as a result,the oil production *** thinning behavior was observed in case of PAM indicating predominance of the frontal advance *** PAM seems to be following both piston like movement and frontal advance theory it can be efficiently enhancing the macroscopic sweep efficiency as well as microscopic displacement *** overall

关键词： Rheology Polymer Macroscopic Microscopic EOR

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

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

Chlorination roasting-coupled water leaching process for potash recovery from waste mica scrap using dry marble sludge powder and sodium chloride

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International Journal of Minerals,Metallurgy and Materials 2020年第9期27卷 1203-1215页

作者： Sandeep kumar Jena Jogeshwar Sahu Geetikamayee Padhy Swagatika Mohanty ajit Dash Mineral Processing and Central Characterization Department Council of Scientific and Industrial Research(CSIR)-Institute of Minerals and Materials Technology(IMMT)BhubaneswarOdisha 751013India

The present paper reports the effective utilization of marble sludge powder(MSP)for the recovery of potash values from waste mica scrap using chlorination roasting-water leaching *** studies indicated the presence of dolomite as the major mineral phase in MSP,whereas muscovite and quartz were observed in the mica *** acid leaching studies suggest a maximum of 22%potash recovery under conditions:4 M H2SO4 acid,particle size of^100μm,stirring speed of 600 r/min,leaching temperature of 75℃,and leaching time of 90 *** chlorination roasting-water leaching process was adopted to achieve the lowest level of 80%-90%potash *** optimum conditions for the recovery of^93%potash from mica(~8.6wt%K2O)requires 900℃ roasting temperature,30 min roasting time,and 1:1:0.75 mass ratio of mica:MSP:*** roasting temperature and amount of NaCl are found to be the most important factors for the recovery *** reaction mechanism suggests the formation of different mineral phases,including sylvite(KCl),wollastonite,kyanite,and enstatite,during roasting,which were confirmed by X-ray diffraction(XRD)analyses and scanning electron microscopy(SEM)*** MSP-blended NaCl additive is more effective for potash recovery compared with the other reported commercial roasting additives.

关键词： potash recovery mica scrap marble sludge powder chlorination roasting water leaching

Abundance of Carbonic Fluid Inclusions in Hira-Buddini Gold Deposit, Hutti-Maski Greenstone Belt, India: Inferences from Petrography and Volume Ratio Estimation of Fluid Components

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Journal of Earth Science 2020年第3期31卷 492-499页

作者： Rajagopal Krishnamurthi ajit kumar Sahoo Rajesh Sharma Prabhakar Sangurmath Department of Earth Sciences Indian Institute of TechnologyRoorkeeRoorkee-241661India Department of Geology Banaras Hindu UniversityVaranasi-221005India Wadia Institute of Himalayan Geology Dehradun-24S001India Hutti Gold Mines Company Limited Hutti-584115India

Low saline aqueous carbonic fluids are considered to be the ore forming solutions for orogenic lode gold *** separation/fluid immiscibility of the ore fluid is quite common and is one of the major reasons for deposition of gold in these *** carbonic fluid inclusions have been observed in quartz grains of Hira-Buddnini Gold *** estimation indicates that more volume of H2O compared to CO2 is likely to be trapped in inclusions at different P-T *** loss of H2O from fluid inclusions during ductile deformation of quartz grains have been attributed as the suitable reason for abundance of carbonic fluid inclusions.

关键词： orogenic lode gold deposit carbonic fluid inclusions Redlich-Kwong Equation fluid immiscibility Hira-Buddini Gold Deposit