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Journal of Magnesium and Alloys 2019年第4期7卷 661-671页

作者： prakash Kumar Sahu nikhil p vasudevan Bipul Das Sukhomay pal Department of Mechanical Engineering and IDM Joint Lab Tsinghua UniversityBeijing 100084China Larsen and Toubro Limited HaziraSuratGujarat 394510India Department of Mechanical Engineering National Institute of Technology Silchar788010 AssamIndia Department of Mechanical Engineering Indian Institute of Technology Guwahati781039 AssamIndia

Research work presented in this study has the primary target of exploring joint attributes of AZ31 magnesium alloys using friction stir welding process with a modified tool referred as bobbin *** of inert and open atmosphere on mechanical properties are evaluated over a wide range of welding speed and tool rotation *** of the research findings from the inert atmosphere bobbin tool were made with the traditional process of friction stir *** results depicted improved joint properties for inert atmosphere *** and intermediate range of tool rotational speed is found to be favorable for bobbin tool friction stir welding without and with an inert medium,*** atmosphere due to inert medium leads to less oxidation of the AZ31 Mg alloy leading to superior joint *** investigations are also made with the aim of evaluating the impact of bobbin tool and inert medium on joint *** each aspect for joining of AZ31 Mg alloy,bobbin tool with inert medium is found to be an effective solution for joining with improved mechanical properties compared to without inert bobbin tool as well as conventional tool friction stir welding.

关键词： Mg FSW Bobbin tool process parameters Mechanical properties Fractography Microstructural characterization

Variability of waste copper slag concrete and its effect on the seismic safety of reinforced concrete building: A case study

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Frontiers of Structural and Civil Engineering 2022年第1期16卷 117-130页

作者： Swetapadma pANDA nikhil p.ZADE pradip SARKAR Robin DAVIS Department of Civil Engineering Institute of Technical Education and ResearchOdisha 751030India Department of Civil Engineering National Institute of Technology RourkelaOdisha 769008India Department of Civil Engineering National Institute of Technology CalicutKerala 673601India

proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built *** numerous studies on waste copper slag concrete can be found in the published literature,no research has focused on the structural application of this type of *** particular,the variability in the strength properties of waste copper slag concrete,which is required for various structural applications,such as limit state design formulation,reliability-based structural analysis,etc.,has so far not attracted the attention of *** paper quantifies the uncertainty associated with the compressive-,flexural-and split tensile strength of hardened concrete with different dosages of waste copper slag as fine ***-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory *** addition,the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building,considering the proposed distribution *** results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand.

关键词： waste copper slag quantification of variability goodness-of-fit test seismic risk assessment pSDM

Structural and luminescence enhancement properties of Eu^(3+)/Ag nanocrystallites doped SiO_2-TiO_2 matrices

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Journal of Rare Earths 2013年第5期31卷 441-448页

作者： Arun Kumar K V Revathy K p prathibha vasudevan Sunil Thomas Biju p R Unnikrishnan N V School of pure & Applied physics Mahatma Gandhi University

We reported here the structural and optical characterisation of silver nanocrystallites/Eu3＋：SiO2-TiO2 matrices synthesised through sol-gel route. Structural characterisations were done by using energy dispersive spectroscopy （EDX）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, atomic force microscope （AFM） and transmission electron microscopy （TEM） measurements and optical characterisations were performed by absorption and emission spectroscopy. The TEM and XRD measurements confirmed the presence of nanocrystals. A broad absorption band was observed due to surface plasmon resonance of silver nanocrystals. The effect of silver nanocrystals on the emission spectrum of Eu3＋ doped SiO2-TiO2 matrices was discussed. An attempt was made to explain this fluorescence enhancement by invoking phenomena such as energy transfer, asymmetry ratio, surface plasmon, surface roughness, crystallinity and grain boundary. Our analysis, based on the experimental results, suggested that all the phenomena except crystallinity and grain boundary had favourable effects on fluorescence enhancement. We also estimated the relevant parameters associated with the phenomena that affected the fluorescence emission from the Eu3＋ ions in the matrix. It was seen that the theoretical estimate of fluorescence enhancement agreed well with the experimental estimate.

关键词： sol-gel luminescence SiO2-TiO2 silver nanoparticles rare earths

Hydrothermal synthesis of Zn-Mg-based layered double hydroxide coatings for the corrosion protection of copper in chloride and hydroxide media

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International Journal of Minerals,Metallurgy and Materials 2021年第12期28卷 1991-2000页

作者： nikhil Gopal Ji Rajiv prakash School of Materials Science and Technology Indian Institute of Technology(BHU)VaranasiVaranasi-221005Uttar PradeshIndia Centre for advanced studies Dr.APJAKTU LucknowU.P.-226031India

Layered double hydroxides(LDHs)hinder corrosive elements by forming a double layer and locking them between its ***,LDHs are interesting materials in corrosion *** this work,Zn-Mg-based LDHs are grown over a copper substrate by using a hydrothermal *** types of Zn-Mg-based LDH coating are prepared based on hydrothermal reaction *** types are characterized through Fourier transform infrared spectroscopy,Raman spectroscopy,high-resolution scanning electron microscopy,energy dispersive X-ray analysis,atomic force microscopy,and X-ray *** show that the two types of LDH coating are successfully grown on copper;however,they differ in thickness and structural *** testing of the LDH coatings is executed in 0.1 M Na Cl and 0.1 M Na OH through alternating current impedance measurements and Tafel polarization *** show that L48 gives more than 90%protection to copper,which is higher than the protection provided by ***,both LDH coatings(L24 and L48)are more effective corrosion inhibitors in Na Cl than in Na OH,suggesting that the LDH coatings can more efficiently exchange Cl ions than OH ions.

关键词： corrosion coating copper

A New Design Approach for Nearly Linear phase Stable IIR Filter using Fractional Derivative

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IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 527-538页

作者： nikhil Agrawal Anil Kumar Varun Bajaj Department of Electronics and Communication Engineering PDPM Indian Institute of Information TechnologyDesign and Manufacturing JabalpurMadhya Pradesh 482005India

In this paper,a new design method for digital infinite impulse response(IIR)filters with nearly linear-phase response is presented using fractional derivative constraints(FDCs).In the proposed method,design problem of an IIR frlter is constructed as the minimization of phase error between the desired and designed phase response of an allpass filter(ApF)such that the designed lowpass filter(LpF)or highpass frlter(HpF)yields less passband(ep),and stopband errors(es)with optimal stopband attenuation(As).In order to have accurate passband(pb)response,FDCs are imposed on appropriate reference frequency,where the optimality of these FDCs are ensured by using a new greedy based sorting *** simulated results reflect the efficiency of the proposed method in term of improved passband response along with better transition ***,small reduction in^is observed within the allowable limit,when compared to noin-fractional design approach,but the designed filter remains immune to wordlength(WL)effect.

关键词： Fractional derivative constraint(FDC) infinite impulse response(IIR)filter least squared linear phase quantization

Factors influencing IOp changes in postmenopausal women

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Family Medicine and Community Health 2018年第3期6卷 97-103页

作者： Chin p.Siuw Suresh vasudevan Mushawiathi Mustapha Ophthalmology Department Sultanah Aminah HospitalJohor BahruJohorMalaysia Ophthalmology Department Pusat Perubatan UniversityKebangsaanJalan Yaacob LatifBandar Tun RazakWilayah Persekutuan Kuala LumpurMalaysia

Objective:Intraocular pressure(IOp)is essential in maintaining normal function of the *** IOp is associated with *** physiological factors,including age and hormones,can cause variation in *** study was designed to investigate IOp changes in postmenopausal women and the associated factors,which included sex hormones and body mass index(BMI).Methods:This was a cross-sectional ***-eight women were recruited:49 premenopausal women and 49 postmenopausal *** between the two groups were *** influence of estradiol,progesterone,testosterone,and BMI on IOp was analyzed by a multivariate method.ppremenopausal group was 47.14±3.93 years and that of the postmenopausal group was 52.10±3.04 *** other factors in both groups,which included BMI,blood pressure,and central cornea thickness,were not significantly *** mean IOp in the postmenopausal group was significantly higher than the mean IOp in the premenopausal group(15.26±2.96 mm Hg vs.14.07±2.65 mm Hg,p=0.04).BMI had a weak positive correlation with IOp in premenopausal women(r=0.31,p=0.03).Estradiol was less likely to influence IOp changes in the postmenopausal group as compared with the premenopausal group(B=−0.021,p=0.002).IOp was not significantly related to progesterone and testosterone ***:Menopausal status has a significant effect on IOp,with a significant increase in IOp seen in postmenopausal women as shown by our *** was shown to be a protective factor in reducing IOp among postmenopausal *** understanding of the influence of postmenopausal status and sex hormones on IOp,glaucoma management may be improved and the target group for disease screening may be more specific.

关键词： Intraocular pressure postmenopausal hormones body mass index

Estimation of citrus canker lesion size using hyperspectral reflectance imaging

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International Journal of Agricultural and Biological Engineering 2013年第3期6卷 41-51页

作者： nikhil p.Niphadkar Thomas F.Burks Jianwei Qin Mark A.Ritenour ATW Automation Inc. DaytonOH 45402USA Department of Agricultural and Biological Engineering University of FloridaGainesvilleFL 32611USA U.S.Department of Agriculture BeltsvilleMD 20705USA Department of Horticultural Sciences University of FloridaGainesvilleFL 34945USA

The Citrus industry has need for effective approaches to remove fruit with canker before they are shipped to selective international market such as the European *** research aims to determine the detectable size limit for cankerous lesions using hyperspectral imaging *** developed multispectral algorithms using visible to near-infrared wavelengths,were used to segregate cankerous citrus fruits from other peel conditions(normal,greasy spot,insect damage,melanose,scab and wind scar).However,this previous work did not consider lesion size.A two-band ratio method with a simple threshold based classifier(ratio of reflectance at wavelengths 834 nm and 729 nm),which gave maximum overall classification accuracy of 95.7%,was selected for lesion size estimation in this *** smallest size of cankerous lesion detected in terms of equivalent diameter was 1.66 *** effect of variation of threshold values and number of erosion cycles(applying morphological erosion multiple times to the image)on estimation of smallest detectable lesion was *** was found that small threshold values gave better canker classification accuracies,while exhibiting a lower overall classification ***,higher threshold values portrayed the opposite *** threshold value of 1.275 gave the optimum tradeoff between canker classification accuracy,overall classification accuracy and minimal lesion size *** the number of erosion cycles reduced detection rates of smaller canker lesions,leading to the conclusion that a single erosion cycle gave the best size estimation *** erosion kernel of the size 3 mm×3 mm was used during the exploration.

关键词： citrus canker lesion size disease detection hyperspectral reflectance imaging image classification multispectral algorithm size detection limit

probing atomic-scale symmetry breaking by rotationally invariant machine learning of multidimensional electron scattering

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npj Computational Materials 2021年第1期7卷 595-600页

作者： Mark p.Oxley Maxim Ziatdinov Ondrej Dyck Andrew R.Lupini Rama vasudevan Sergei V.Kalinin Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTNUSA Computational Sciences and Engineering Division Oak Ridge National LaboratoryOak RidgeTNUSA

The 4D scanning transmission electron microscopy(STEM)method maps the structure and functionality of solids on the atomic scale,yielding information-rich data sets describing the interatomic electric and magnetic fields,structural and electronic order parameters,and other symmetry breaking distortions.A critical bottleneck is the dearth of analytical tools that can reduce complex 4D-STEM data to physically relevant *** propose an approach for the systematic exploration of 4D-STEM data using rotationally invariant variational autoencoders(rrVAE),which disentangle the general rotation of the object from other latent *** implementation of purely rotational rrVAE is discussed as are applications to simulated data for graphene and zincblende *** rrVAE analysis of experimental 4D-STEM data of defects in graphene is illustrated and compared to the classical center-of-mass *** approach is universal for probing symmetry-breaking phenomena in complex systems and can be implemented for a broad range of diffraction methods.

关键词： symmetry breaking rotational

Learning the right channel in multimodal imaging: automated experiment in piezoresponse force microscopy

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npj Computational Materials 2023年第1期9卷 2008-2015页

作者： Yongtao Liu Rama K.vasudevan Kyle p.Kelley Hiroshi Funakubo Maxim Ziatdinov Sergei V.Kalinin Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTN 37923USA Department of Materials Science and Engineering Tokyo Institute of TechnologyYokohama 226-8502Japan Computational Sciences and Engineering Division Oak Ridge National LaboratoryOak RidgeTN 37923USA Department of Materials Science and Engineering University of TennesseeKnoxvilleTN 37996USA

We report the development and experimental implementation of the automated experiment workflows for the identification of thebest predictive channel for a phenomenon of interest in spectroscopic measurements. The approach is based on the combinationof ensembled deep kernel learning for probabilistic predictions and a basic reinforcement learning policy for channel selection. Itallows the identification of which of the available observational channels, sampled sequentially, are most predictive of selectedbehaviors, and hence have the strongest correlations. We implement this approach for multimodal imaging in piezoresponse forcemicroscopy (pFM), with the behaviors of interest manifesting in piezoresponse spectroscopy. We illustrate the best predictivechannel for polarization-voltage hysteresis loop and frequency-voltage hysteresis loop areas is amplitude in the model samples. Thesame workflow and code are applicable for any multimodal imaging and local characterization methods.

关键词： automated policy modal

Influence of quenching medium on the dendrite morphology,hardness,and tribological behaviour of cast Cu-Ni-Sn spinodal alloy for defence application

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Defence Technology（防务技术） 2023年第12期30卷 83-100页

作者： Bipin Sankar Karthik V Shankar Vamu Sunil Hemanth Kashyap S nikhil Nair Adarsh A.Nair Abhinav p M Department of Mechanical Engineering Amrita Vishwa VidyapeethamAmritapuriIndia

Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and *** paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)*** analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values *** analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze *** hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal ***,the grain size was approximately 30%finer for spinodal bronze when compared with regular *** the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal *** was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze *** results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.

关键词： Quenching Water Brine SAE 40 oil Grain size Hardness Wear rate Spinodal decomposition CuSn Spinodal alloy CuNiSn