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Photoluminescence upgradation of La_(2)MgTiO_(6):2%Dy^(3+) perovsk.te with monovalent(Li^(+)),divalent(Ba^(2+),Sr^(2+)) and trivalent(Bi^(3+),Sm^(3+))cation sensitization

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Journal of Rare Earths 2025年第1期43卷 47-56,I0002页

作者： v.P.veena k.Arun C.k.Shilpa S.v.Jasira k.M.Nissamudeen School of Pure and Applied Physics Kannur UniversityPayyanur CampusEdatKannurKrala67 India Department of Nanoscience and Nanotechnology Kannur UniversityPayyanur CampusEdatkannurKerala670327India

Nano phosphors of 2%Dy^(3+)(wt%)doped La_(2)MgTiO_(6) and monovalent/divalent/trivalent co-doped La_(1.98)Dy_(0.02)MgTiO_(6):x%A^(y+)(A^(y+):Li+,Ba^(2+),Sr^(2+),Bi^(3+),and Sm^(3+);0≤x≤2 wt%)were synthesized by combustion *** the XRD data,it is deduced that an increase in the valency of co-dopant increases the crystallinity of the double perovsk.te orthorhombic nanocrystal *** an increase in co-dopant size,an elevation in optical bandgap is visible with the highest bandgap of 3.835 ev for Bi^(3+).The photo-absorption is monotonically broadened for Sr^(2+),Sm^(3+),and Li+around 200-450 ***351 nm,Dy^(3+)triggered lattice shows major characteristic emission peak. at 480 nm(^(4)F_(9/2)→^(6)H_(15/2)),574 nm(^(4)F_(9/2)→^(6)H_(13/2)),and 670 nm(^(4)F_(9/2)→^(6)H_(11/2)).leading to near white light emission with CIE coordinates(0.341,0.376).Upon co-doping,the PL intensity is significantly increased with maximum emission for trivalent Sm^(3+),followed by divalent Sr^(2+)and monovalent Li+*** increasing excitation wavelength,Sr^(2+)shows a dominated output and it is found that divalent Sr^(2+)is a potential codopant that could enhance luminescence intensity up to 6 times with a Sr^(2+)→Dy^(3+)energy transfer efficiency of 86%.It is specified that the CIE coordinates of Li+co-doped samples show ideal white emission with color coordinates(0.333,0.336).The concluding outcomes signify the noblest rare earth Sm^(3+)co-doping and thus Sm^(3+)→Dy^(3+)energy transfer mechanism is discussed in detail.

关键词： Photoluminescence Perovsk.te WLED Co-doping Rareearths

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Elastic and Optoelectronic Properties of k.dF3:ab initio Calculations through LDA/GGA/TB-mBJ within FP-LAPW Method

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Chinese Physics Letters 2015年第1期32卷 108-112页

作者： k. Ephraim babu N. Murali k. v.jaya babu B. k.shore babu v. veeraiah Modelling and Simulation in Materials Science Laboratory Department of Physics Andhra University Visakhapatnam 530003 Andhra Pradesh India Department of Engineering Chemistry A UCE(A) Andhra University Visakhapatnam 530003 Andhra Pradesh India

Ab initio calculations are performed on the electronic, structural, elastic and optical properties of the cubic per- ovsk.te k.dF3. Tile k.hn Sham equations are solved by applying the full potential linearized augmented plane wave （FP-LAPW） method. The exchange correlation effects are included through the local density approximation （LDA ）, generalized gradient approximation （GGA） and modified Beck.-Johnson （mBJ） exchange potential The calculated lattice constant is in good agreement with the experimental result. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young＇s modulus and Poisson＇s ratio are calculated. k.dF3 is ductile and elastically anisotropic. The calculations of the electronic band structure, density of states （DOS） and charge density show that this compound has an indirect energy band gap （M-F） with a mixed ionic and covalent bonding. The contribution of the different bands is analyzed from the total and partial density of states curves. Optical response of the dielectric functions, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of O-40ev. The compound k.dF3 can be used for high-frequency optical and optoelectronic devices.

关键词： GGA Cd Elastic and Optoelectronic Properties of k.dF3:ab initio Calculations through LDA/GGA/TB-mBJ within FP-LAPW Method LDA FP

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Characteristics of Energy Fluxes and Cold Frontal Effects on Energy Exchange over a Boreal Lak.

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Advances in Atmospheric Sciences 2025年第2期42卷 357-372页

作者： Lujun XU Huizhi LIU Ivan MAMMARELLA Ak. vÄHÄ Joonatan ALA-k.NNI Xuefei LI Qun DU Yang LIU Timo vESALA State k.y Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100864China Department of Atmospheric Sciences Yunnan UniversityKunming 650091China Institute for Atmospheric and Earth System Research/Physics Faculty of ScienceUniversity of HelsinkiHelsinki 00014Finland

Understanding the characteristics and variations of heat exchange and evaporation of lak.s is important for regional water resource management and sustainable *** on eddy covariance measurements over Lak. vanajavesi in southern Finland,characteristics of energy fluxes and cold frontal effects on energy exchange were *** lak. acted as a heat sink.in spring and summer and a heat source in *** latent heat flux reached its minimum value in the morning and peak.d in the *** diurnal variation of sensible heat flux was opposite to that of latent heat *** factors for the sensible heat flux were mainly the lak.-air temperature difference and the product of lak.-air temperature difference and wind *** latent heat flux was mainly affected by the vapor pressure deficit and the product of vapor pressure deficit and wind *** annual mean values of bulk.transfer coefficients for momentum,heat,and water vapor were 1.98×10^(-3),1.62×10^(-3),and 1.31×10^(-3),*** transfer coefficients for heat and water vapor were not equal,indicating that the parameterization of energy exchange in numerical models,where the assumption that the heat coefficient equals the water vapor coefficient needs *** the ice-free season,cold fronts resulted in 28 sensible heat pulses and 17 latent heat pulses,contributing to 50.59%and 34.89%of sensible and latent heat exchange in Lak. *** results indicate that cold fronts significantly impact the surface energy budget and evaporation over lak.s.

关键词： sensible heat flux latent heat flux roughness length bulk.transfer coefficient cold front

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Effect of Phase Shifted Frequency Modulation on Two Level Atom-Field Interaction

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Communications in Theoretical Physics 2012年第3期57卷 468-472页

作者： k.v.Priyesh Ramesh babu Thayyullathil Department of Physics Cochin University of Science and Technology

We have studied the effect of phase shifted frequency modulation on two level atom with field interaction using Jaynes-Cummings *** the frequency of the interacting field is sinusoidally varying with time with a constant *** to the presence of phase in the frequency modulation,the variation of population inversion with time is different from the standard *** are no exact collapses and revivals in the variation of population inversion but it oscillates sinusoidally with *** coherent field atom interaction the population inversion behaves as in the case of Fock.state atom interaction,when frequency modulation with a non zero phase is *** study done with squeezed field has shown the same behavior of the population inversion.

关键词： Jaynes-Cummings model two level atom squeezed field

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Application of Response Surface Methodolody to Prediction of Dilution in Plasma Transferred Arc Hardfacing of Stainless Steel on Carbon Steel

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Journal of Iron and Steel Research International 2009年第1期16卷 44-53页

作者： v Balasubramanian A k.Lak.hminarayanan R varahamoorthy S babu Centre for Materials Joining and Research (CEMAJOR) Department of Manufacturing EngineeringAnnamalai UniversityAnnamalai Nagar 608002Tamil NaduIndia

The application of response surface methodology was highlighted to predict and optimize the percentage of dilution of iron-based hardfaced surface produced by the PTA （plasma tratisferred arc welding） process. The experiments were conducted based on five-factor five-level central composite rotatable design with full replication technique and a mathematical model was developed using response surface methodology. Furthermore, the response surface methodology was also used to optimize the process parameters that yielded the lowest percentage of dilution.

关键词： plasma transferred arc hardfacing dilution response surface methodology

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Photon condensation： A new paradigm for Bose-Einstein condensation

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Frontiers of physics 2016年第5期11卷 103-110页

作者： Renju Rajan P. Ramesh babu k. Senthilnathan Department of Physics School of Advanced Sciences VIT University Vellore Tamil Nadu 632015 India

Bose-Einstein condensation is a state of matter k.own to be responsible for peculiar properties exhibited by superfluid Helium-4 and superconductors. Bose-Einstein condensate （BEC） in its pure form is realizable with alk.li atoms under ultra-cold temperatures. In this paper, we review the experimental scheme that demonstrates the atomic Bose-Einstein condensate. We also elaborate on the theoretical framework.for atomic Bose-Einstein condensation, which includes statistical mechan- ics and the Gross-Pitaevsk.i equation. As an extension, we discuss Bose-Einstein condensation of photons realized in a fluorescent dye filled optical microcavity. We analyze this phenomenon based on the generalized Planck.s law in statistical mechanics. Further, a comparison is made between photon condensateand laser. We describe how photon condensate may be a possible alternative for lasers since it does not require an energy consuming population inversion process.

关键词： Bose-Einstein condensation photon condensation magneto-optical trap Gross-Pitaevsk.i equation Planck.s radiation law

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Continuous segregation of binary heterogeneous solids in fluidized beds

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Particuology 2017年第6期15卷 93-100页

作者： M. Prasad babu P.S.T. Sai k. k.ishnaiah Department of Chemical Engineering Indian Institute of Technology Madras Chennai 600 036 India

Continuous segregation of a binary mixture of heterogeneous （different density） solids is carried out in a gas-solid fluidized bed. We investigate how gas velocity, solids feed rate, flotsam feed composition, bottom discharge pipe diameter, and minimum fluidization velocity ratio of the flotsam to jetsam parti- cles influence the solids holdup, separation factor, and product quality （flotsam purity at the top outlet）. The results are interpreted in terms of solids holdup information. The results indicate that the separation factor decreases when the gas velocity, bottom discharge pipe diameter, flotsam feed composition, or the minimum fluidization velocity ratio increase, while the separation factor increases as the solids feed rate increases. The product quality decreases when the gas velocity, solids feed rate, or minimum fluidization velocity ratio increase, while the product quality increases as the bottom discharge pipe diameter or flot- sam feed composition increase. Correlations for predicting the separation factor and product quality are proposed using a logistic model for individual flotsam feed compositions, which satisfactorily compares with the present experimental data.

关键词： Normal fluidized bed Continuous segregation Heterogeneous particles Separation factorHoldup

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Continuous segregation of binary heterogeneous solids in a fast-fluidized bed

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Particuology 2017年第6期15卷 101-107页

作者： M. Prasad babu P.S.T. Sai k. k.ishnaiah Department of Chemical Engineering Indian Institute of Technology Madras Chennai 600 036 India

Continuous segregation of binary heterogeneous solids （different density mixtures） is carried out in a gas-solid fluidized bed to study the effects of gas velocity, solids feed rate, feed composition and density difference of solids on the separation factor （recovery of flotsam at top outlet） and the quality of the product （purity of flotsam at top outlet） in a continuous fast-fluidized bed. The holdup of the bed material is obtained in each experimental run. It is observed that the separation factor decreases with increase in solids feed rate or density difference of solids, and increases with gas velocity or proportion of flotsam in the feed. The quality of the product decreases with increase in gas velocity or solids flow rate, and increases with feed composition or density difference of solids. The experimental results show that the separation factor and the quality of the product are more sensitive to gas velocity than to other operating parameters, Empirical correlations for predicting the separation factor and quality of the product are proposed based on the Richards model for individual flotsam mass fraction in the feed, and the predictions agree satisfactorily with the present exlgerimental data,

关键词： Fast-fluidized bed Gas-solid Continuous segregation Heterogeneous solids Solids holdup

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Microstructure and Mechanical Properties of Friction Stir Lap Welded Aluminum Alloy AA2014

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Journal of Materials Science & Technology 2012年第5期28卷 414-426页

作者： S. babu G.D. Janak. Ram P.v. venk.tak.ishnan G. Madhusudhan Reddy k. Prasad Rao Dept. of Metallurgical and Materials Engineering Indian Institute of Technology Madras Chennai India Liquid Propulsion Systems Centre Indian Space Research Organisation Tiruvananthapuram India Defence Metallurgical Research Laboratory Hyderabad India

Friction stir lap welds were produced in 3 mm thick.Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook.geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 k., respectively, while the average failure load for standard riveted joints was only 3.4 k.. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets （i.e., no Alclad） were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made （with threaded taper cylindrical tool） in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition （43%） was considerably lower （because of the higher base material strength） than those made in T4 condition （51%）. The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work.provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.

关键词： Aluminum alloys Friction stir welding Lap joints Lap-shear testing

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Characteristics of Energy Fluxes and Cold Frontal Effects on Energy Exchange over a Boreal Lak.

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Advances in Atmospheric Sciences 2025年第02期 357-372页

作者： Lujun XU Huizhi LIU Ivan MAMMARELLA Ak. v?H? Joonatan ALA-k.NNI Xuefei LI Qun DU Yang LIU Timo vESALA State k.y Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Sciences University of Chinese Academy of Sciences Department of Atmospheric Sciences Yunnan University Institute for Atmospheric and Earth System Research/Physics Faculty of ScienceUniversity of Helsinki

Understanding the characteristics and variations of heat exchange and evaporation of lak.s is important for regional water resource management and sustainable development. Based on eddy covariance measurements over Lak. vanajavesi in southern Finland, characteristics of energy fluxes and cold frontal effects on energy exchange were investigated. The lak. acted as a heat sink.in spring and summer and a heat source in winter. The latent heat flux reached its minimum value in the morning and peak.d in the afternoon. The diurnal variation of sensible heat flux was opposite to that of latent heat flux. Impact factors for the sensible heat flux were mainly the lak.-air temperature difference and the product of lak.-air temperature difference and wind speed. The latent heat flux was mainly affected by the vapor pressure deficit and the product of vapor pressure deficit and wind speed. The annual mean values of bulk.transfer coefficients for momentum, heat,and water vapor were 1.98 × 10–3, 1.62 × 10–3, and 1.31 × 10–3, respectively. Bulk.transfer coefficients for heat and water vapor were not equal, indicating that the parameterization of energy exchange in numerical models, where the assumption that the heat coefficient equals the water vapor coefficient needs improvement. During the ice-free season, cold fronts resulted in 28 sensible heat pulses and 17 latent heat pulses, contributing to 50.59% and 34.89% of sensible and latent heat exchange in Lak. vanajavesi. These results indicate that cold fronts significantly impact the surface energy budget and evaporation over lak.s.

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