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Nanosized complex fluorides based on Eu^(3+) doped sr_2LnF_7(Ln=La, Gd)

Journal of Rare Earths 2014年第3期32卷 242-247页

作者： m.Runowski s.Balabhadra s.Lis Department of Rare Earths Faculty of Chemistry Adam Mickiewicz University

A simple co-precipitation approach taking place between Ln3＋, sr2＋ cations and F anions, led to the formation of nanocrystalline Eu3＋ doped sr2LnF7 （Ln-La and Gd） complex fluorides. The reaction was carried out in the presence of polyeth- ylene glycol, PEG 6000 as a surfactant/surface modifier, providing small size and homogeneity of the products. The synthesized compounds were composed of small nanoparticles with an average size of 15 nm. All obtained Eu3＋ doped compounds exhibited an intensive red luminescence. In the case of gadolinium based compounds, the energy transfer phenomena could be observed from Gd3＋ ions to Eu3＋ ions. In order to study the structure and morphology of the synthesized fluorides, powder X-ray diffraction （XRD） and transmission electron microscopy （TEm） measurements were performed. Also FT-IR spectra of the products were re- corded, revealing the presence of PEG molecules on the nanoparticles suN＇ace. A spectrofluorometry technique was applied to examine optical properties of the synthesized nanoparticles. Excitation and emission spectra as well as luminescence decay curves were measured and analysed. The performed analysis revealed a red luminescence, typical for the Eu3＋ ion situated in the inorganic, highly symmetric matrix. Concentration quenching phenomena and lifetimes shortening, together with an increasing of the Eu3＋ doping level, were observed and discussed. Judd-Ofelt analysis was also performed for all doped samples, in order to support the registered spectroscopic data and examine in details structural and optoelectronic properties of the synthesized nanomaterials.

关键词： luminescence Eu3+ doping complex strontium lanthanide fluorides nanoparticles sr2LnF7 sr0.69La0.31F2.31 rare earths

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Interactions of ion acoustic multi-soliton and rogue wave with Bohm quantum potential in degenerate plasma

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Chinese Physics B 2017年第9期26卷 301-309页

作者： m s Alam m G Hafez m R Talukder m Hossain Ali Department of Applied mathematics University of RajshahiRajshahi-6205Bangladesh Plasma science and Technology Lab Department of Applied Physics and Electronic EngineeringUniversity of RajshahiRajshahi-6205Bangladesh Department of mathematics Chittagong University of Engineering and TechnologyChittagong-4349Bangladesh

This work investigates the interactions among solitons and their consequences in the production of rogue waves in an unmagnetized plasmas composing non-relativistic as well as relativistic degenerate electrons and positrons, and inertial non-relativistic helium ions. The extended Poincare′–Lighthill–Kuo（PLK） method is employed to derive the two-sided Korteweg–de Vries（KdV） equations with their corresponding phase shifts. The nonlinear schrodinger equation（NLsE） is obtained from the modified Kd V（mKdV） equation, which allows one to study the properties of the rogue waves. It is found that the Fermi temperature and quantum mechanical effects become pronounced due to the quantum diffraction of electrons and positrons in the plasmas. The densities and temperatures of the helium ions, degenerate electrons and positrons, and quantum parameters strongly modify the electrostatic ion acoustic resonances and their corresponding phase shifts due to the interactions among solitons and produce rogue waves in the plasma.

关键词： wave-wave interaction rogue waves degenerate plasmas Bohm potential

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Thermal bleaching of optical absorption and photoluminescence spectra of γ-irradiated CaF_2:Dy:Pb:Na single crystals

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Journal of Rare Earths 2010年第4期28卷 493-497页

作者： s.m. moses Kennedy Department of Physics S.S.N. College of Engineering Rajiv Gandhi Salai Kalavakkam-603 110 Chennai Tamil Nadu India

The variation of the optical absorption (OA) and photoluminescence (PL) spectra with temperature was studied on γ-irradiated CaF2:Dy:Pb:Na single crystals. The OA spectrum showed bands around 2.05, 3.20, 3.82 and 6.20 eV which could be attributed to different sodium associated (sA) colour centres (CCs) such as mNa and RA+ . Heating the crystal indicated the annihilation and formation of different sACCs. The excitation spectrum for the characteristic Dy3+ emission at 2.14 eV immediately after irradiation was...

关键词： calcium fluoride optical absorption photoluminescence colour centres dysprosium lead sodium rare earths

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Linear Precoder Design for Correlated Rician Fading Channel Under Imperfect CsI

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China Communications 2023年第9期20卷 160-170页

作者： s.B.m.Priya school of Electrical and Electronics Engineering SASTRA Deemed UniversityThanjavur 613401India

In this paper,we have modeled a linear precoder for indoor multiuser multiple input multiple output(mU-mImO)system with imperfect channel state information(CsI)at *** Rician channel is presumed to be mutually coupled and spatially,temporarily *** imperfection with CsI is primarily due to the channel estimation error at receiver and feedback delay amidst the receiver and transmitter in CsI *** with,the insufficient spacing between the antenna at transmitter and receiver persuades mutual coupling(mC)among the array *** addition,the mImO channel is presumed to be jointly correlated(Weichselberger correlation model).When we look back on the existing precoder design,it considered spatial correlation alone disregarding joint correlation of antenna array *** all above assumption,we have designed a linear precoder which minimizes mean squared error(msE)subjected to total transmit power constraint for mUmImO *** simulation results proven that proposed precoder shows substantial enhancement in bit error rate(BER)performance in comparison with the existing *** mathematical analysis corroborates the simulation results.

关键词： channel estimation error feedback delay mmsE linear precoder mutual coupling spatial cor-relation Weichselberger correlation model

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Orderly decorated nanostructural photoelectrodes with uniform spherical TiO2 particles for dye-sensitized solar cells

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Frontiers of Chemical science and Engineering 2015年第4期9卷 532-540页

作者： A.m. Bakhshayesh s.s. Azadfar Department of Research and Development SUN Nanotechnologists Company Tehran 13488-96394 Iran

This study presents a novel nanostructural electrode made of 20-nm-diameter nanoparticles, which orderly decorated with 2-μm TiO2 particles, deposited by a new gel process. The decorated electrode （DE） is better than the non-decorated electrode （NE） in both light scattering and light harvesting, as confirmed by diffuse reflectance spectroscopy. X-ray diffraction reveals that both electrodes have a mixture of anatase and rutile phases. The dye-sensitized solar cell based on the decorated electrode shows the highest power conversion efficiency of 7.80% as a result of less recombination demonstrated by electrochemical impedance spectroscopy. From internal power conversion efficiency measurement, the external quantum efficiency of DE cell at 530 nm is 89%, which is higher than that of NE cell （77%）.

关键词： dye-sensitized solar cell uniform particles,TiO2 gel process light harvesting

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Performance study of jute-epoxy composites/sandwiches under normal ballistic impact

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Defence Technology（防务技术） 2020年第4期16卷 947-955页

作者： sangamesh Rajole K.s.Ravishankar s.m.Kulkarni Department of mechanical Engineering National Institute of Technology KarnatakaSurathkalMangalore 575025India Department of metallurgical and materials Engineering National Institute of Technology KarnatakaSurathkalMangalore 575025India

This study is undertaken to explore the use of natural fiber Jute-epoxy(JE),Jute-epoxy-rubber(JRE)sandwich composite for ballistic energy *** absorbed and residual velocities for these composites are evaluated analytically and through Finite Element Analysis(FEA).FE analysis of JE plates is carried out for different thicknesses(3,5,10 and 15 mm).JE plates and JRE sandwiches having the same thickness(15 mm) are fabricated and tested to measure residual velocity and energy *** analytical results are found to agree well with the results of FE analysis with a maximum error of 9%.The study on JE composite plate reveals that thickness influences the energy *** and FE analysis study showed that JRE sandwiches have better energy absorption than JE *** absorption of a JRE sandwich is about 71% greater than JE *** obtained from FEA and testing are in good agreement,sEm analysis confirms composites failed by fiber rupture and fragmentation.

关键词： Energy absorption Composites Polymer composites Ballistic impact High velocity impact

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Y^(3+) substituting-adjusted mechanical,dielectric,and impedance properties of cobalt copper zinc nanoferrites for high frequency applications

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Journal of Rare Earths 2023年第10期41卷 1597-1605,I0005页

作者： s.F.mansour N.s.Al-Bassami m.Afifi m.A.Abdo Physics Department Faculty of ScienceZagazig UniversityZagazigEgypt General studies Department Jubail Industrial CollegeJubail Industrial CitySaudi Arabia Faculty of Nanotechnology for Postgraduate studies Cairo UniversityEl-Sheikh Zayed12588Egypt

Upgrading mechanical-dielectric features of ferrites through rare-earth yttrium(Y^(3+))doping provides feasibility to evolving high-frequency electronic *** paper reports the mechanical and dielectric properties of Co_(0.5)Cu_(0.25)Zn_(0.25)Y_(x)Fe_(2-x)O_(4)ferrite nanoparticles labeled as CCZYF#0,CCZYF#1,CCZYF#2,CCZYF#3,CCZYF#4 and CCZYF#5 for x=0.***.0.02,0.04,0.06,0.08,and 0.1,*** frequency and temperature dependence of dielectric parameters and co nductivity of all CCZYF nanoferrites are well *** nanoferrite CCZYF#5 has the highest dielectric constant(enhancing ratio 170%)and the highest conductivity(enhancing ratio 7125.81%)compared with the undoped *** plots of all CCZYF nano ferrites manifest two arcs;the main reasons for the dielectric process are the grain boundaries and bulk *** impedance parameters were determined,which showed the effective role of Y^(3+)ions on their *** nanoferrite CCZYF#5 has the highest grain boundaries capacitance(with enhancing ratio of 59.40%)and the highest grains capacitance(with enhancing ratio of 22.53%)with a relaxation time decrement efficiency of 62.51%.An ultrasonic flaw detector was utilized to determine the elastic moduli of all CCZYF *** nanoferrite CCZYF#5 has the highest longitudinal modulus(with enhancing ratio of 20.95%),the highest shear modulus(with enhancing ratio of48.72%),highest Young's modulus(with enhancing ratio of 88.47%),the highest bulk modulus(with enhancing ratio 13.27%)and the highest micro hardness(with enhancing ratio 77.77%).Hence,Y3+tuned Co-Cu-Zn nanoferrites possess new opportunities for high-frequency and storage applications.

关键词： Nanoferrites Rare arth ions mechanical properties Dielectric parameters Impedance spectroscopy

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Dual solutions of time-dependent magnetohydrodynamic stagnation point boundary layer micropolar nanofluid flow over shrinking/stretching surface

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Applied mathematics and mechanics(English Edition) 2021年第7期42卷 1013-1028页

作者： H.B.LANJWANI m.s.CHANDIO m.I.ANWAR s.A.sHEHZAD m.IZADI Department of mathematics University of SindhJamshoro 76080Pakistan Department of mathematics Engineering University SargodhaSargodha 40100Pakistan Department of mathematics COMSATS University IslamabadSahiwal 57000Pakistan Department of mechanical Engineering Faculty of EngineeringLorestan UniversityKhorramabad 68151-44316Iran

Time-dependent,two-dimensional(2 D)magnetohydrodynamic(mHD)micropolar nanomaterial flow over a shrinking/stretching surface near the stagnant point is *** and heat transfer characteristics are incorporated in the problem.A model of the partial differential expressions is altered into the forms of the ordinary differential equations via similarity *** obtained equations are numerically solved by a shooting scheme in the mAPLE *** solutions are observed at different values of the specified physical *** stability of first and second solutions is examined through the stability analysis *** analysis interprets that the first solution is stabilized and physically feasible while the second one is un-stable and not ***,the natures of various physical factors on the drag force,skin-friction factor,and rate of mass and heat transfer are determined and *** micropolar nanofluid velocity declines with a rise in the suction and magnetic parameters,whereas it increases by increasing the unsteadiness *** temperature of the micropolar nanofluid rises with increase in the Brownian motion,radiation,thermophoresis,unsteady and magnetic parameters,but it decreases against an increment in the thermal slip constraint and Prandtl *** concentration of nanoparticles reduces against the augmented schmidt number and Brownian movement values but rises for incremented thermophoresis parameter values.

关键词： dual solution stability analysis micropolar nanofluid magnetic field stretching/shrinking surface

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Characterization and separation of pyrite from Abu Tartur black shale

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International Journal of mining science and Technology 2015年第4期25卷 565-571页

作者： Ibrahim s.s. El Kammar A.m. Guda A.m. Central metallurgical R&D Institute CMRDI Geology Dept. Faculty of Science National Research Astronomical & Geophysical Institute NRIAG

This work aimed for pyrite separation from Abu Tartur black shale as a source of sulfur to be an added economic value of Abu Tartur area. The considered samples in the present work were collected from a core drilled in Abu Tartur plateau representing the pyrite-rich black shale of the U. Cretaceous age, sample characterization was carried out using petrographic microscope, XRD, DTA/DTG, C/s and XRF techniques. Clay minerals, silt-sized quartz, calcite, and hematite were the main minerals associating pyr- ite （5.34g）. Liberation behavior of the sample was about 80% below 5 μm. sample processing was achieved through one-day soaking followed by classification using I inch mozley hydro-cyclone where about 35.5% by weight went to underflow and 64.5% went to overflow. The underflow product was subjected to an advanced gravity separation process using sB-40 Falcon Concentrator through a CCD statistical design prepared by Design-Expert 6.0 software proposed to opti- mize the separation process through a study for the effects of frequency （Hz） and water pressure （Psi） on both assay and recovery of the sulfur-rich heavy fraction. A heavy concentrate weighed 10.90% with inorganic sulfur content reached 11.37% （21.24% pyrite） with overall recovery （50.01%） was obtained after two cleaning at the optimum conditions.

关键词： Abu Tartur plateau Black shale Pyrite Falcon Concentrator

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A Tm-Bi Co-Doped Fiber Laser with Dual Pumping Operation

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Chinese Physics Letters 2013年第3期30卷 71-74页

作者： N.saidin s.W.Harun s.s.A.Damanhuri s.m.m.Ali H.Ahmad A.Halder m.C.Paul s.Das m.Pal s.K.Bhadra Department of Electrical Engineering Faculty of EngineeringUniversity of Malaya50603 Kuala LumpurMalaysia Photonics Research Centre University of Malaya50603 Kuala LumpurMalaysia Fiber Optics and Photonics Division CSIR-Central Glass&Ceramic Research InstituteKolkataIndia

We demonstrate an efficient fiber laser operating at 1901.6 nm using a newly developed thulium bismuth co-doped fiber(TBF)with dual pumping at 792 nm and 1552 *** fiber was fabricated using modified chemical vapor deposition and solution doping *** dopant concentrations(wt%)and compositions inside the core are 0.15 Bi_(2)O_(3),0.3 Tm_(2)O_(3),1.0 Al_(2)O_(3) and 12.0 GeO_(2).The TBF laser operates at 1901.6 nm with a lasing efficiency of 33.2%and pump power threshold of 85 mW using a 2-m-long TBF in a linear cavity with two fiber Bragg gratings(FBGs).The high efficiency is attributed to the use of additional 1552 nm pump to complement 792 nm *** maximum output power of 225 mW is achieved at the pump power of 820 mW with the optimum length of 2 m.

关键词： pump fiber pumping

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