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Variation in the Flaring Potential of Different Sunspot Groups During Different Phases of Solar Cycles 23 and 24
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作者 Abha Singh Anurag Chaudhari +1 位作者 Gyaneshwar Sharma a.k.singh 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第2期144-153,共10页
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... 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 2019.During 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 only.We 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 surface.Here we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and 24.In 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 24.These 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. 展开更多
关键词 (Sun:)sunspots-Sun flares-Sun activity-Sun magnetic fields-Sun filaments-prominences
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Effect of induced magnetic field on natural convection in vertical concentric annuli 被引量:2
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作者 R.K.Singh a.k.singh 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2012年第2期315-323,共9页
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 pro... 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. 展开更多
关键词 Natural convection ISOTHERMAL Heat flux SKIN-FRICTION Induced magnetic field Magnetohydrody- namics
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Reflection of three-dimensional plane waves at the free surface of a rotating triclinic half-space under the context of generalized thermoelasticity 被引量:1
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作者 P.SINGH a.k.singh A.CHATTOPADHYAY 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2021年第9期1363-1378,共16页
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 anisotro... 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. 展开更多
关键词 REFLECTION energy ratio TRICLINIC THERMOELASTICITY ROTATION three-dimensional(3D)wave
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Tangential and Vertical Compact Torus Injection Experiments on the STOR-M Tokamak 被引量:1
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作者 肖持进 S.Livingstone +2 位作者 a.k.singh E.Zhang A.Hirose 《Plasma Science and Technology》 SCIE EI CAS CSCD 2005年第2期2701-2704,共4页
This paper describes the setup and results of compact torus (CT) injection experiments on the STOR-M tokamak. Tangential CT injection into STOR-M induced H-mode-like phenomena including doubling the electron density, ... This paper describes the setup and results of compact torus (CT) injection experiments on the STOR-M tokamak. Tangential CT injection into STOR-M induced H-mode-like phenomena including doubling the electron density, reduction in the Ha radiation level, suppression of the floating potential fluctuations, suppression of the m = 2 Mirnov oscillations, and increase in the global energy confinement time. Experimental setup, bench-test results, and some preliminary injection data for vertical CT injection experiments on STOR-M will be shown. In addition, numerical simulations of the CT trajectories in tokamak discharges for both tangential and vertical injection geometries will be discussed. 展开更多
关键词 compact torus TOKAMAK H-MODE
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从种子蛋白质谱带分析花生区组的系统发育关系 被引量:1
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作者 a.k.singh 周蓉 《花生科技》 北大核心 1993年第3期36-40,共5页
前言 种子蛋白质电泳谱带分析对于从分子水平上确定物种的遗传同源性及解决分类和系统发育问题已成为一项实用技术。在花生属的花生区组中,各个种之间的系统发育关系已从形态学、植物地理学及细胞遗传学等方面作过许多探索。这些研究主... 前言 种子蛋白质电泳谱带分析对于从分子水平上确定物种的遗传同源性及解决分类和系统发育问题已成为一项实用技术。在花生属的花生区组中,各个种之间的系统发育关系已从形态学、植物地理学及细胞遗传学等方面作过许多探索。这些研究主要揭示了大多数二倍体种都有一个共同的A染色体组,而A.atizocoi则有不同的染色体组即B染色体组。A、B染色体组都是同源的,并共同构成四倍体栽培种A.hypogaea。 展开更多
关键词 花生 系统发育 种子 蛋白
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Dispersion equation of magnetoelastic shear waves in irregular monoclinic layer
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作者 A.CHATTOPADHYAY S.GUPTA +1 位作者 S.A.SAHU a.k.singh 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2011年第5期571-586,共16页
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 mono... 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. 展开更多
关键词 shear wave MAGNETOELASTIC MONOCLINIC IRREGULARITY dispersion equation PERTURBATION
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MHD free convective flow past semi-infinite vertical permeable wall
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作者 R.K.SINGH a.k.singh 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2012年第9期1207-1222,共16页
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 differentia... 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. 展开更多
关键词 magnetohydrodynamics (MHD) SUCTION source/sink Prandtl number permeability boundary layer
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Dielectric relaxation and conduction mechanism in Aurivillius ceramic Bi_(5)Ti_(3)FeO_(15)
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作者 Rasmita Jena K.Chandrakanta +3 位作者 P.Pal Md.F.Abdullah S.D.Kaushik a.k.singh 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2021年第6期1063-1071,共9页
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 ... 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 impurities.The surface morphology of the prepared sample was observed to contain microstructural grains approximately 0.2–2μm in size.The 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 behavior.Our results indicate that both the resistance and capacitance of the grain boundaries are more prominent than those of the grains.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 mechanism.The 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. 展开更多
关键词 Nyquist plot impedance spectroscopy activation energy ac conductivity HOPPING
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Rayleigh-type wave propagation in incompressible visco-elastic media under initial stress
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作者 P.SINGH A.CHATTOPADHYAY a.k.singh 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第3期317-334,共18页
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 i... 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. 展开更多
关键词 Rayleigh-type wave INHOMOGENEITY initial stress VISCO-ELASTICITY incom-pressible
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澳大利亚新兴市场实体的尾部风险
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作者 D.E.Allen A.R.Kramadibrata +3 位作者 R.J.Powell a.k.singh 吕少飒 黄梅波 《经济资料译丛》 2012年第4期64-70,共7页
在全球金融危机期间,澳大利亚经济被广泛地认为较之全球其他经济体表现良好,尽管如此,该国金融市场仍然经历了极端的波动。为了理解澳大利亚新兴经济实体较之成熟经济实体受到此类极端事件影响的程度,本文运用4个风险衡量指标,将新兴企... 在全球金融危机期间,澳大利亚经济被广泛地认为较之全球其他经济体表现良好,尽管如此,该国金融市场仍然经历了极端的波动。为了理解澳大利亚新兴经济实体较之成熟经济实体受到此类极端事件影响的程度,本文运用4个风险衡量指标,将新兴企业指数(EMCOX)涵盖范围内的新兴实体和标准普尔/澳大利亚证券交易所200指数涵盖范围内的成熟实体进行了比较。四个风险指标中的前两者是市场及信用风险的传统衡量指标——风险价值(VaR)及违约距离(DD);后两者则关注分布尾部的极端风险,包括条件风险价值(CVaR)和条件违约距离(CDD),其中条件违约距离(CDD)是本文作者独创的,可将条件风险价值技术应用到违约风险的度量中。将这些指标应用于全球金融危机发生之前及危机阶段,便可以发现:所采用的一切指标对于新兴市场股份都显示出更高的风险,在危机阶段新兴企业和成熟企业投资组合之间的价差缩小,违约风险价差在分布尾部处达到最大。这一信息对于投资者和贷款人在极端经济环境下决定其股票或贷款投资组合都具有重要意义。 展开更多
关键词 条件风险价值 条件违约距离 澳大利亚新兴市场
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Rayleigh-type wave propagation through liquid layer over corrugated substrate
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作者 a.k.singh A.DAS A.RAY 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2017年第6期851-866,共16页
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 heterogen... 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. 展开更多
关键词 Rayleigh-type wave POROSITY HETEROGENEITY CORRUGATION
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Effect of Co substitution on the structural,dielectric and optical properties of KBiFe_(2)O_(5)
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作者 K.Chandrakanta R.Jena +3 位作者 P.Pal Md.F.Abdullah S.D.Kaushik a.k.singh 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2021年第11期1861-1867,共7页
Cobalt(Co)-modified brownmillerite KBiFe_(2)O_(5)(KBFO;[KBiFe_(2(1−x))Co_(2x)O_(5)(x=0,0.05)])polycrystalline is synthesized following the solid-state reaction route.Rietveld refinement of X-ray diffraction data confi... Cobalt(Co)-modified brownmillerite KBiFe_(2)O_(5)(KBFO;[KBiFe_(2(1−x))Co_(2x)O_(5)(x=0,0.05)])polycrystalline is synthesized following the solid-state reaction route.Rietveld refinement of X-ray diffraction data confirmed the phase purity of KBFO and KBiFe_(1.9)Co_(0.1)O_(5)(KBFCO).The optical bandgap energy(Eg)of KBFO decreased from 1.59 to 1.51 eV because of Co substitution.The decrease in bandgap can be attributed to the tilting of the Fe–O tetrahedral structure of KBFCO.The observed room-temperature Raman peaks of KBFCO shifted by 3 cm^(−1) toward a lower wavenumber than that of KBFO.The shift in Raman active modes can be attributed to the change in the bond angles and bond lengths of the Fe–O tetrahedral structure and modification in response to oxygen deficiency in KBFO because of Co doping.Compared with that of KBFO,the frequency-dependent dielectric constant and dielectric loss of KBFCO decrease at room temperature,which is a consequence of the reduction in oxygen migration and modification in response to vibrational modes present in the sample. 展开更多
关键词 BROWNMILLERITE rietveld refinement Raman spectroscopy bandgap
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Extreme ultraviolet and x-ray transition wavelengths in Rb XXIV
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作者 Indu Khatri Arun Goyal +2 位作者 Sunny Aggarwal a.k.singh Man Mohan 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第10期115-126,共12页
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 ... 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 levels.To 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. 展开更多
关键词 atomic data energy levels transition probability
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Perceiving the Trend of Terrestrial Climate Change during the Past 40 year(1978-2018)
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作者 Asheesh Bhargawa a.k.singh 《Journal of Atmospheric Science Research》 2021年第1期1-15,共15页
In past few decades,climate has manifested numerous shifts in its trend.Various natural and anthropogenic factors have influenced the dynamics and the trends of climate change at longer time scale.To understand the lo... In past few decades,climate has manifested numerous shifts in its trend.Various natural and anthropogenic factors have influenced the dynamics and the trends of climate change at longer time scale.To understand the long term climate fluctuations,we have analyzed forty years(1978-2018)data of ten climatic parameters that are responsible to influence the climate dynamics.The parameters involved in the present study are total solar irradiance(TSI),ultra violet(UV)index,cloud cover,carbon dioxide(CO2)abundances,multivariate(ENSO)index,volcanic explosivity index(VEI),global surface temperature(GST)anomaly,global sea ice extent,global mean sea level and global precipitation anomaly.Using the above mentioned climate entities;we have constructed a proxy index to study the quantitative measure of the climate change.In this process these indicators were aggregated to a single proxy index as global climate index(GCI)that has measured the strength of present climate change in semblance with the past natural variability.To construct GCI,the principal component analysis(PCA)has been used on yearly based data for the period 1978-2018.Actually PCA is a statistical tool with which we can reduce the dimensionality of the data and it retains most of the variation in the new data set.Further,we have confined our study to natural climate drivers and anthropogenic climate drivers.Our result has indicated that the strongest climate change has been occurred globally by the end of the year 2018 in comparison to late 1970’s natural variability. 展开更多
关键词 Principal component analysis Total solar irradiance(TSI) Cloud cover CO2 abundance Global surface temperature(GST)anomaly Global climate index(GCI)
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Effect of organic component(tartrate) addition on cerium nitrate's ability to inhibit corrosion of mild steel in NaCl solution
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作者 Minakshi Koundal Chhaya Sharma a.k.singh 《Journal of Rare Earths》 SCIE EI CAS CSCD 2024年第10期1995-2002,共8页
Cerium tartrate(CeTar),produced in this study by precipitating cerium nitrate with potassium sodium tartrate(KNaTar),was examined as a corrosion inhibitor.Weight loss tests show inhibition efficiency of 71.7% with Ce(... Cerium tartrate(CeTar),produced in this study by precipitating cerium nitrate with potassium sodium tartrate(KNaTar),was examined as a corrosion inhibitor.Weight loss tests show inhibition efficiency of 71.7% with Ce(NO_(3))_(3) and 88.7% with CeTar inhibitor for one-month exposure to mild steel in 7 g/L NaCl solution.The inhibition efficiency drops to 28.6% with the fo rmer and remains around 8 7% with the latter inhibitor after six months of exposure.Similar results from electrochemical testing indicate that the inhibition efficiency decreases by adding cerium nitrate.Still,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 duration.These 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. 展开更多
关键词 Cerium tartrate Cerium nitrate Corrosion inhibition Mild steel Inhibitor film characterization Rare earths
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