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emission colour tuning in kLnF_(4):Yb^(3+),er^(3+)/Ho^(3+)phosphor

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Journal of Rare earths 2024年第1期42卷 57-65,I0002页

作者： Janani k Gayathri e Vijayatha V Ramasubramanian S Thiyagarajan P Department of Science and Humanities Nehru Institute of TechnologyKaliapuramThirumalayampalayamCoimbatoreIndia Department of Sciences Amrita School of Physical SciencesAmrita Vishwa VidyapeethamCoimbatoreIndia Department of Physics Anna UniversityChennaiIndia

kLnF_(4):Yb^(3+),er^(3+)/Ho^(3+)(Ln=Y,Yb,Gd)phosphors were prepared by solid-state reaction *** each of the Yb^(3+)/er^(3+)and Yb^(3+)/Ho^(3+)co-doped phosphors independently,phase confirmation and morphological examination were accomplished using the X-ray diffraction technique and scanning electron microscope analysis.X-ray photoelectron spectroscopy analysis shows the charge state and existence of lanthanides and *** luminescence emissions of green and red colour were detected for the synthesized *** changes in the upconverted emission intensities and colour output pertaining to the change of the lanthanide host matrix along with dopants were investigated for the prepared *** the upconversion luminescence,erbium-doped samples exhibit a predominance of red emission while holmium-doped samples display a prevalence of green *** rare-earth er/Ho doped kYbF4shows strong red emission compared to other ***_(4):Yb,er/Ho exhibits relatively significant green upconve rsion emissions,while Yb,er-doped kGdF_(4)host displays a 10-fold increase in green/red emission ratio with an increase in the input power of 20-780 *** photoluminescence studies and decay curve analysis were carried out using UV light excitation for the developed phosphors.A higher lifetime of 2.2 ms was measured for the downshifting red emission in the Ho doped kYbF_(4)*** study suggests a potential for colour tunability in the upconversion and downshifting emissions through host modifications to the fluoride phosphor.

关键词： Rare earths energy transfer upconversion Downshifting Colour coordinates

Semi-Relativistic Reflection and Transmission Coefficients for Two Spinless Particles Separated by a Rectangular-Shaped Potential Barrier

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Communications in Theoretical Physics 2016年第10期65卷 389-395页

作者： k.e.Thylwe O.J.Oluwadare k.J.Oyewumi kTH-Mechanics Royal institute of Technology Department of Physics Federal University Oye-Ekiti Theoretical Physics Section Department of PhysicsUniversity of Ilorin

A generalized Schr¨odinger approximation,due to Ikhdair & Sever,of the semi-relativistic two-body problem with a rectangular barrier in(1+1) dimensions is compared with exact *** and approximate transmission and reflection coefficients are obtained in terms of local wave *** approximate transmission and reflection coefficients turn out to be surprisingly accurate in an energy range |∈-V0| ere μ is the reduced mass,∈ the scattering energy,and V_0 the barrier top *** approximate wave numbers are less accurate.

关键词： two-body relativistic equation rectangular barrier transmission 1+1D relativistic scattering semi-relativistic approximation spinless Salpeter equation

Non-Relativistic Phase Shifts for Scattering on Generalized Radial Yukawa Potentials

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Communications in Theoretical Physics 2016年第4期65卷 434-440页

作者： O.J.Oluwadare k.e.Thylwe k.J.Oyewumi Department of Physics Federal University Oye-Ekiti kTH-Mechanics Royal institute of Technology Theoretical Physics Section Department of PhysicsUniversity of Ilorin

Non-relativistic phase shifts for a generalized Yukawa potential V(r) =-V_0( e^(-αr)/r)-V_1( e^(-2αr)/r^2) are studied by the amplitude-phase method and by a frequently used analytic method based on a Pekeris-type approximation of power-law potential *** variations of V_1 seem to have marginal effects on the effective potential and on exact phase ***,as pointed out in this study,a Pekeris-type approximation in scattering applications often implies serious distortions of both effective potentials and phase *** Pekeris-type based analytic approximation in this study seems to give low-quality scattering results for this model potential at low energies.

关键词： quantum mechanics scattering partial waves resonances

effect of gamification applications on success of dentistry students

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World Journal of Methodology 2025年第1期15卷 80-87页

作者： Hatice Ahsen Deniz elif Polat Balkan Burak İncebeyaz kıvanç kamburoğlu Department of Dentomaxillofacial Radiology Ankara University Faculty of DentistryAnkara 06500Türkiye

BACkGROUND Gamification,the use of game materials in education,has been used in several scientific fields,and studies have demonstrated its effectiveness in student *** To evaluate whether the success of 4th-and 5th-grade dentistry students increases when using the gamification applications kahoot!and *** An experimental design was used to measure the effect of gamification applications on students who were taught using the traditional *** this purpose,Mentimeter and kahoot!applications were used in this experimental *** groups of 4th-and 5th-grade students were formed:Mentimeter,kahoot!,and control *** effect of gamification applications on achievement was evaluated by administering a post-test to these groups after the instructional ***-way analysis of variance and t-tests were used for statistical *** A total of 35.5%of the students were in the Mentimeter group,29.8%in the kahoot!group,and 34.6%in the control *** the total number of students,54.8%were female and 45.2%were male,while 52.2%were 5th-grade students and 47.8%were 4th-grade *** overall grade point average was found to be 66.65(range,24-100).There was a statistically significant difference in average success scores between students of different groups(P=0.003es(P=0.036e average success score was the highest in the Mentimeter group(71.64)and the lowest in the kahoot!group(62.15).In the control group,this score was *** average success score was higher for students in the 5thgrade(68.16)and for female students(68.84).CONCLUSION Gamification has a great potential in the education of dentomaxillofacial radiology *** outperformed both the kahoot!and the traditional method in terms of average student success rates.

关键词： Gamification Mentimeter kahoot! education Dentistry

Mudcake effects on wellbore stress and fracture initiation pressure and implications for wellbore strengthening

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Petroleum Science 2018年第2期15卷 319-334页

作者： Yongcun Feng Xiaorong Li k.e.Gray The University of Texas at Austin AustinTXUSA

Although a large volume of mudcake filtration test data is available in the literature, effects of mudcake on wellbore strengthening cannot be quantified without incorporating the data into a stress-analysis model. Traditional models for determining fracture initiation pressure （FIP） either consider a wellbore with an impermeable mudcake or with no mudcake at all. An analytical model considering permeable mudcake is proposed in this paper. The model can predict pore pressure and stress profiles around the wellbore, and consequently the FIP, for different mudcake thickness, permeability, and strength. Numerical examples are provided to illustrate the effects of these mudcake parameters. The results show that a low-permeability mudcake enhances FIP, mainly through restricting fluid seepage and pore pressure increase in the near- wellbore region, rather than by mudcake strength. Fluid loss pressure （FLP） should be distinguished from FIP when a mudcake is present on the wellbore wall. Fracture may occur behind the mudcake at FIP without mudcake rupture. The small effect of mudcake strength on FIP does not mean its effect on FLP is small too. Mudcake strength may play an important role in maintaining integrity of the wellbore once a fracture has initiated behind the mudcake.

关键词： Mudcake Hoop stress Fracture initiation pressure Fluid loss pressure Wellbore strengthening

Lattice dynamical and thermodynamical properties of ReB_2,RuB_2,and OsB_2 compounds in the ReB_2 structure

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Chinese Physics B 2012年第10期21卷 355-361页

作者： e.Deligoz k.Colakoglu Y.O.Ciftci Department of Physics Aksaray University68100AksarayTurkey Department of Physics Gazi UniversityTeknikokullar06500AnkaraTurkey

Structural and lattice dynamical properties of ReB2,RuB2,and OsB2 in the ReB2 structure are studied in the framework of density functional theory within the generalized gradient *** present results show that these compounds are dynamically stable for the considered *** temperature-dependent behaviors of thermodynamical properties such as internal energy,free energy,entropy,and heat capacity are also *** obtained results are in good agreement with the available experimental and theoretical data.

关键词： ab initio calculations lattice dynamical properties thermodynamical properties diborides

Critical parameters near the ferromagnetic-paramagnetic phase transition in La_(0.67–x)Y_xBa_(0.23)Ca_(0.1)MnO_3 compounds(x=0.10 and x=0.15)

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Journal of Rare earths 2015年第3期33卷 263-270页

作者： Mounira Abassi N.Dhahri J.Dhahri k.Taibi e.k.Hlil Laboratory of Condensed Matter and Nanosciences University of Monastir 5019 Tunisia Institut Néel CNRS and Joseph Fourier university B.P.166 38042 Grenoble France Institut Néel CNRS et Université Joseph Fourier BP 166 F-38042 Grenoble cedex 9 France

The critical properties of the mixed manganite La0.67–x Y x Ba0.23Ca0.1Mn O3 with x=0.10 and x=0.15 around the paramagnetic（PM）-ferromagnetic（FM） phase transition were investigated through various techniques. These involved modified Arrott plots, kouvel-Fisher method and Widom scaling relation. Magnetic data, analyzed in the critical region, using the above methods, yielded the critical exponents for（x=0.10） La0.57Y0.10Ba0.23Ca0.1Mn O3（β=0.312±0.002 and γ=1.147±0.003 at T C=299.23±0.05 k）. Moreover, the estimated critical exponents of（x=0.15） La0.52Y0.15Ba0.23Ca0.1Mn O3 were β=0.286±0.004 and γ=0.943±0.002 at T C=289.53±0.06 k. The critical exponents＇ values were close to the theoretical values of 3D-Ising model and tricritical mean-field model. These results suggested that the present composition should be close to a tricritical point in the La0.67–x Y x Ba0.23Ca0.1Mn O3 phase diagram. expressing the field dependence as ΔS M∝H n allowed us to establish a relationship between the exponent n and the critical exponents of the material and to propose a phenomenological universal curve for the field dependence of ΔS M.

关键词： perovskite manganites phase transition entropy critical properties rare earths

Influence of bismuth on magnetism and magnetocaloric properties of LaFe_(11.6)Si_(1.4) intermetallic compound

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Journal of Rare earths 2015年第7期33卷 740-745页

作者： A.Boutahar k.Zehani L.Bessais H.Lassri e.k.Hlil LPMMAT Hassan II University-Casablanca Faculty of Science Ain Chock BP 5366 Maarif-Casablanca Morocco ICMPe-CMTR UMR CNRS 7182 2-8 H. Dunant St 94320 Thiais France Néel Institue CNRS and Joseph Fourier University

Crystal structure, magnetic properties and magnetocaloric effects （MCe） of La1-xBixFe1 1.4Si1.6 （x=0.0 and 0.1） compounds were investigated by X-ray diffraction and magnetization measurements. The La1-xBixFe11.4Si1.6 compounds presented a cubic NaZnx3 type structure. First, the magnetization behavior and the magnetic transition were analyzed in terms of Landau theory. Then, Bi substitution for La in La1-xBixFe11.4Si1.6 compounds led to a decrease in magnetic entropy change （-△SM^max） but an increase in Curie temperature （Tc） significantly. The significant increase of Tc by Bi substitution from 202.5 to 256 k for x=0.0 and x=0.1 respectively was attributed to an increase in the Fe-Fe exchange interactions. Moreover, magnetocaloric effect was calculated in terms of isothermal magnetic entropy change. The maximum values of （-△SM^max ） of La1-xBixFe11.4Si1.6 for x=-0.0 and 0.1 compounds were found to be, respectively, 22.56 and 4.36 J/（kg.k） under an applied magnetic field change of 5 T. For the same applied magnetic field （μ0H=5 T）, the relative cooling power （RCP） values were found to vary between 487 and 296 J/kg.

关键词： NaZn13 itinerant-electron metamagnetic transition magnetocaloric effects rare earths

Optimal control of Hilfer fractional stochastic integrodifferential systems driven by Rosenblatt process and Poisson jumps

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Journal of Control and Decision 2023年第4期10卷 538-546页

作者： k.Ramkumar k.Ravikumar e.M.elsayed Department of Mathematics with CA PSG College of Arts&ScienceCoimbatoreIndia Department of Mathematics PSG College of Arts&ScienceCoimbatoreIndia Department of Mathematics Faculty of ScienceKing Abdulaziz UniversityJeddahSaudi Arabia Department of Mathematics Faculty of ScienceMansoura UniversityMansouraEgypt

In this work,the optimal control for a class of Hilfer fractional stochastic integrodifferential systems driven by Rosenblatt process and Poisson jumps has been discussed in infinite dimensional space involving the Hilfer fractional ***,we study the existence and uniqueness of mild solution results are proved by the virtue of fractional calculus,successive approximation method and stochastic analysis ***,the optimal control of the proposed problem is presented by using Balder’s ***,an example is demonstrated to illustrate the obtained theoretical results.

关键词： Hilfer fractional derivative stochastic integrodifferential systems Rosenblatt process Poisson jumps successive approximation optimal control