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Journal of Rare Earths 2024年第10期42卷 1995-2002页

作者： Minakshi koundal Chhaya Sharma a.k.singh Department of Applied Science and Engineering Indian Institute of Technology RoorkeeSaharanpur Campus Department of Pulp and Paper Technology Indian Institute of Technology Roorkee Saharanpur Campus

Cerium tartrate（CeTar）,produced in this study by precipitating cerium nitrate with potassium sodium tartrate（kNaTar）,was examined as a corrosion *** loss tests show inhibition efficiency of 71.7% with Ce（NO3）3and 88.7% with CeTar inhibitor for one-month exposure to mild steel in 7 g/L NaCl *** inhibition efficiency drops to 28.6% with the fo rmer and remains around 8 7% with the latter inhibitor after six months of *** results from electrochemical testing indicate that the inhibition efficiency decreases by adding cerium ***,the cerium tartrate inhibitor demonstrates a nearly constant inhibition efficiency for up to 30 d,i.e.,≈90%.Electrochemical impedance spectroscopy（EIS） performed in these cases shows the following results:（ⅰ） with cerium nitrate,a film of iron and cerium oxide,which on prolonged exposure diminishes,and（ⅱ） with cerium tartrate,the formation of a bimetallic film（Fe-tartrate-Ce） and a mixture of cerium hydroxide and iro n oxide that protects steel for a longer *** inferences are based on the analyses of scanning electron microscopy/energydispersive X-ray analysis（SEM/EDAX）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron（XPS）,and Raman spectroscopy results.

关键词： Cerium nitrate Cerium tartrate Corrosion inhibition Inhibitor film characterization Mild steel Rare earths

Variation in the Flaring Potential of Different Sunspot Groups During Different Phases of Solar Cycles 23 and 24

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Research in Astronomy and Astrophysics 2024年第2期24卷 144-153页

作者： Abha singh Anurag Chaudhari Gyaneshwar Sharma a.k.singh Department of Physics T.D.P.G.College Jaunpur-222002India Department of Physics Banaras Hindu UniversityVaranasi-221005India

In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration of 24 yr from 1996 to *** this,we observed a total of 15015 flares(8417 in SC-23 and 6598 in SC-24)emitted from a total of 33780 active regions(21746 in SC-23 and 12034 in SC-24)with sunspot *** defined the flaring potential or flare-production potential as the ratio of the total number of flares produced from a particular type of SSG to the total number of the same-class SSGs observed on the solar *** we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and *** addition,we investigated yearly variations in the potential of producing flares by different SSGs(A,B,C,D,E,F,and H)during different phases(ascending,maximum,descending,and minimum)of SC-23 and *** are our findings:(1)D,E,and F SSGs have the potential of producing flares≥8 times greater than A,B,C and H SSGs;(2)The larger and more complex D,E,and F SSGs produced nearly 80%of flares in SC-23 and 24;(3)The A,B,C and H SSGs,which are smaller and simpler,produced only 20%of flares in SC-23 and 24;(4)The biggest and most complex SSGs of F-class have flaring potential 1.996 and 3.443 per SSG in SC-23 and 24,respectively.(5)The potential for producing flares in each SSG is higher in SC-24 than in SC-23,although SC-24 is a weaker cycle than SC-23.(6)The alterations in the number of flares(C+M+X)show different time profiles than the alterations in sunspot numbers during SC-23 and 24,with several peaks.(7)The SSGs of C,D,E,and H-class have the highest flaring potential in the descending phase of both SC-23 and 24.(8)F-class SSGs have the highest flaring potential in the descending phase of SC-23 but also in the maximum phase of SC-24.

关键词： (Sun:)sunspots-Sun flares-Sun activity-Sun magnetic fields-Sun filaments-prominences

MHD free convective flow past semi-infinite vertical permeable wall

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Applied Mathematics and Mechanics(English Edition) 2012年第9期33卷 1207-1222页

作者： R.k.singh a.k.singh Department of Mathematics Banaras Hindu University

In this paper, the basic equations governing the flow and heat transfer of an incompressible viscous and electrically conducting fluid past a semi-infinite vertical per- meable plate in the form of partial differential equations are reduced to a set of non-linear ordinary differential equations by applying a suitable similarity transformation. Approx- imate solutions of the transformed equations are obtained by employing the perturbation method for two cases, i.e., small and large values of the suction parameter. From the numerical evaluations of the solution, it can be seen that the velocity field at any point decreases as the values of the magnetic and suction parameters increase. The effect of the magnetic parameter is to increase the thermM boundary layer. It is also found that the velocity and temperature fields decrease with the increase in the sink parameter.

关键词： magnetohydrodynamics (MHD) suction source/sink Prandtl number permeability boundary layer

Effect of induced magnetic field on natural convection in vertical concentric annuli

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Acta Mechanica Sinica 2012年第2期28卷 315-323页

作者： R.k.singh a.k.singh Department of Mathematics Central University of BiharPatnaIndia Department of Mathematics Banaras Hindu UniversityVaranasiIndia

In the present paper, we have considered the steady fully developed laminar natural convective flow in open ended vertical concentric annuli in the presence of a ra- dial magnetic field. The induced magnetic field produced by the motion of an electrically conducting fluid is taken into account. The transport equations concerned with the con- sidered model are first recast in the non-dimensional form and then unified analytical solutions for the velocity, induced magnetic field and temperature field are obtained for the cases of isothermal and constant heat flux on the inner cylin- der of concentric annuli. The effects of the various phys- ical parameters appearing into the model are demonstrated through graphs and tables. It is found that the magnitude of maximum value of the fluid velocity as well as induced magnetic field is greater in the case of isothermal condition compared with the constant heat flux case when the gap be- tween the cylinders is less or equal to 1.70 times the radius of inner cylinder, while reverse trend occurs when the gap between the cylinders is greater than 1.71 times the radius of inner cylinder. These fields are almost the same when the gap between the cylinders is equal to 1.71 times the radius of inner cylinder for both the cases. It is also found that as the Hartmann number increases, there is a flattening ten- dency for both the velocity and the induced magnetic field. The influence of the induced magnetic field is to increase the velocity profiles.

关键词： Natural convection Isothermal Heat flux Skin-friction Induced magnetic field Magnetohydrody- namics

Reflection of three-dimensional plane waves at the free surface of a rotating triclinic half-space under the context of generalized thermoelasticity

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Applied Mathematics and Mechanics(English Edition) 2021年第9期42卷 1363-1378页

作者： P.singh a.k.singh A.CHATTOPADHYAY Department of Mathematics and Computing Indian Institute of Technology(ISM)Dhanbad-826004JharkhandIndia

The reflection of three-dimensional(3D) plane waves in a highly anisotropic(triclinic) medium under the context of generalized thermoelasticity is studied. The thermoelastic nature of the 3D plane waves in an anisotropic medium is investigated in the perspective of the three-phase-lag(TPL), dual-phase-lag(DPL), Green-Naghdi-III(GNIII), Lord-Shulman(LS), and classical coupled(CL) theories. The reflection coefficients and energy ratios for all the reflected waves are obtained in a mathematical form. The rotational effects on the reflection characteristics of the 3D waves are discussed under the context of generalized thermoelasticity. Comparative analyses for the reflection coefficients of the waves among these generalized thermoelastic theories are performed. The energy ratios for each of the reflected waves establish the energy conservation law in the reflection phenomena of the plane waves. The highly anisotropic materials along with the rotation may have a significant role in the phenomenon of the reflection behavior of the 3D waves. Numerical computations are performed for the graphical representation of the study.

关键词： reflection energy ratio triclinic thermoelasticity rotation three-dimensional(3D)wave

Rayleigh-type wave propagation in incompressible visco-elastic media under initial stress

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Applied Mathematics and Mechanics(English Edition) 2018年第3期39卷 317-334页

作者： P.singh A.CHATTOPADHYAY a.k.singh Department of Applied Mathematics Indian Institute of Technology (ISM)

Propagation of Rayleigh-type surface waves in an incompressible visco-elastic material over incompressible visco-elastic semi-infinite media under the effect of initial stresses is discussed. The dispersion equation is determined to study the effect of differ- ent types of parameters such as inhomogeneity, initial stress, wave number, phase velocity, damping factor, visco-elasticity, and incompressibility on the Rayleigh-type wave prop- agation. It is found that the affecting parameters have a significant effect on the wave propagation. Cardano＇s and Ferrari＇s methods are deployed to estimate the roots of dif- ferential equations associated with layer and semi-infinite media. The MATHEMATICA software is applied to explicate the effect of these parameters graphically.

关键词： Rayleigh-type wave inhomogeneity initial stress visco-elasticity incom-pressible

Rayleigh-type wave propagation through liquid layer over corrugated substrate

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Applied Mathematics and Mechanics(English Edition) 2017年第6期38卷 851-866页

作者： a.k.singh A.DAS A.RAY Department of Applied Mathematics Indian Institute of Technology(ISM)

The propagation of the Rayleigh-type wave in a fluid layer overlying a corrugated substrate is studied. The corrugated substrate is considered as a fluid satu- rated poroelastic substrate and a quadratically heterogeneous isotropic elastic substrate in Case I and Case II, respectively. Closed form expressions of dispersion relation for Case I and Case II ave obtained. The influence of corrugation, porosity, and hetero- geneity on the phase velocity of Rayleigh-type wave, for both cases, is highlighted and demonstrated through numerical computation and graphical discussion. Neglecting cor- rugation at the common interface, expressions of phase velocity of the Rayleigh-type wave for both cases ave derived in a closed form as a special case of the problem. Comparison between the presence and the absence of both heterogeneity and poroelasticity in the substrate of the composite structure is a key in the present study.

关键词： Rayleigh-type wave porosity heterogeneity corrugation

Extreme ultraviolet and x-ray transition wavelengths in Rb XXIV

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Chinese Physics B 2015年第10期24卷 115-126页

作者： Indu khatri Arun Goyal Sunny Aggarwal a.k.singh Man Mohan Department of Physics and Astrophysics University of Delhi Department of Physics Shyamlal CollegeUniversity of Delhi Department of Physics D.D.U.CollegeUniversity of Delhi

Energy levels, radiative rates, oscillator strengths and line strengths are reported for transitions among the lowest 97 levels of the（1s22s22p6） 3s23p2, 3s23p3 d, 3s3p3, 3p4, 3s3p23 d, and 3s23d2 configurations of Rb XXIV. A multiconfiguration Dirac-Fock（MCDF） method is adopted for the calculations. Radiative rates, oscillator strengths, and line strengths are provided for all electric dipole（E1）, magnetic dipole（M1）, electric quadrupole（E2）, and magnetic quadrupole（M2）transitions from the ground level to all 97 levels, although calculations are performed for a much larger number of *** achieve the accuracy of the data, comparisons are provided with similar data obtained from the Flexible Atomic Code（FAC） and also with the available theoretical and experimental results. Our energy levels are found to be accurate to better than 1.2%. Wavelengths calculated are found to lie in EUV（extreme ultraviolet） and x-ray regions. Additionally, lifetimes for all 97 levels are obtained for the first time.

关键词： atomic data energy levels transition probability

Dispersion equation of magnetoelastic shear waves in irregular monoclinic layer

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Applied Mathematics and Mechanics(English Edition) 2011年第5期32卷 571-586页

作者： A.CHATTOPADHYAY S.GUPTA S.A.SAHU a.k.singh Department of Applied Mathematics Indian School of Mines

This paper studies the propagation of horizontally polarized shear waves in an internal magnetoelastic monoclinic stratum with irregularity in lower interface. The stratum is sandwiched between two magnetoelastic monoclinic semi-infinite media. Dispersion equation is obtained in a closed form. In the absence of magnetic field and irregularity of the medium, the dispersion equation agrees with the equation of classical case in three layered media. The effects of magnetic field and size of irregularity on the phase velocity are depicted by means of graphs.

关键词： shear wave magnetoelastic monoclinic irregularity dispersion equation perturbation

Dielectric relaxation and conduction mechanism in Aurivillius ceramic Bi_(5)Ti_(3)FeO_(15)

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International Journal of Minerals,Metallurgy and Materials 2021年第6期28卷 1063-1071页

作者： Rasmita Jena k.Chandrakanta P.Pal Md.F.Abdullah S.D.kaushik a.k.singh Department of Physics and Astronomy National Institute of Technology RourkelaRourkela-769008OdishaIndia UGC-DAE Consortium for Scientific Research Mumbai Centre BARCMumbai-400085India

For this study,we synthesized Aurivillius Bi_(5)Ti_(3)FeO_(15) ceramic using the generic solid-state reaction route and then performed roomtemperature X-ray diffraction to confirm that the compound had a single phase with no *** surface morphology of the prepared sample was observed to contain microstructural grains approximately 0.2–2μm in *** dielectric properties of the sample were determined as a function of frequency in a range of approximately 100 Hz to 1 MHz at various temperatures(303 k≤T≤773 k).Nyquist plots of the impedance data were found to exhibit a semi-circular arc in the high-temperature region,which is explained by the equivalent electrical circuit(R_(1)C_(1))(R_(2)QC_(2)),where R_(1) and R_(2) represent the resistances associated with the grains and grain boundaries,respectively,C_(1) and C_(2) are the respective capacitances,and Q is the constant phase element(CPE),which accounts for non-Debye type of *** results indicate that both the resistance and capacitance of the grain boundaries are more prominent than those of the *** alternating current(ac)conductivity data were analyzed based on the Jonscher universal power law,which indicated that the conduction process is dominated by the hopping *** calculated activation energies of the relaxation and conduction processes were very similar(0.32 to 0.53 eV),from which we conclude that the same type of charge carriers are involved in both processes.

关键词： Nyquist plot impedance spectroscopy activation energy ac conductivity hopping