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Structural and optical properties of green emitting Y_(2)SiO_(5):Tb^(3+) and Gd_(2)SiO_(5):Tb^(3+) nanoparticles for modern lighting applications

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Rare Metals 2021年第11期40卷 3289-3298页

作者： Sitender singh devender singh Department of Chemistry Maharshi Dayanand UniversityRohtak 124001India

The optical and structural properties of Tb^(3+)-doped yttrium and gadolinium oxyorthosilicate(Y_(2)SiO_(5) and Gd_(2)SiO_(5)) phosphors were *** samples were synthesized via sol-gel combustion method using organic *** phase purity and structural properties of the samples were determined via combined approach of powder X-ray diffraction,Fourier transformation infrared(FTIR) and transmission electron microscopy(TEM).X-ray measurements revel monoclinic crystal lattice with P_(21/c) symmetry for both M_(2)SiO_(5)(pure host) and M_(2)SiO_(5):Tb^(3+)(doped) silicates,irrespective of the nature of metal(Y or Gd),presence or absence of Tb^(3+)in lattice and change in calcination temperature up to 1050℃.FTIR analysis was applied to confirm the bonding of prepared *** appearance of bands corresponding to SiO_(4) tetrahedra(880-1020 cm^(-1)) suggest the layered structure and support the diffraction *** micrographs confirm the synthesis of spherical nanoparticles with filled morphology,narrow size distribution and slightly agglomerated crystallites of the *** elemental composition of prepared materials was determined using energy dispersive X-ray *** spectra show peaks only for elements assimilated within the host *** photoluminescence(PL) emission spectra of Tb^(3+)-doped samples show ^(5)D_(4)→^(7)F_(J)(J=3-6) transitions under 254 *** dominant peak at 544 nm for ^(5)D_(4)→^(7)F_(5) transition is responsible for the emission of green light on ultraviolet-visible excitation in both the Tb^(3+)-doped host *** to advantageous properties like intense PL and high crystallinity,these nanophosphors could possess potential applications in the mercury free lighting sources and optoelectronic devices.

关键词： Structural Optical Silicates Luminescence Optoelectronic

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Synthesis and spectroscopic investigations of trivalent europium- doped Z_(2)Si_(3)O_(8)(Z = Mg, Ca and Sr) nanophosphors for display applications

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Rare Metals 2021年第9期40卷 2610-2617页

作者： Suman Sheoran Kuldeep singh Vijeta Tanwar Sitender singh Anura Samantilleke devender singh Department of Chemistry Maharshi Dayanand UniversityRohtak 124001India Centro de Fisica Universidade of MinhoBraga 4710057Portugal

To explore the silicate lattice-based nanophosphors, a series of Eu3+-doped Z_(2)Si_(3)O_(8)(Z = Mg, Ca and Sr) materials were prepared by sol–gel procedure. The metal nitrates and silica powder were used as precursor components for the synthesis of these luminescent materials. Photoluminescence(PL) emission spectra, powder X-ray diffraction(PXRD), energy-dispersive X-ray spectroscopy(EDS), Fourier transform infrared spectroscopy(FTIR) and transmission electron microscopy(TEM)spectroscopic techniques were applied for the characterization of the fabricated materials. Three peaks were observed at 589, 613 and 650–652 nm corresponding to ^(5)D_(0)→^(7)F_(1-3) transition in PL emission spectra. Upon395 nm excitation and at 0.03 mol Eu3+, these nanophosphors displayed optimum photoluminescence with the most intense peak analogous to ^(5)D_(0)→^(7)F_(2)transition of dopant ion. The as-prepared phosphor materials were re-heated at1050 and 1150 ℃ to observe the consequences of higher temperatures on the emission intensity and crystal *** analysis confirmed that all the synthesized materials were of crystalline nature, and the crystallinity was observed to be improved by increasing the temperature. In the FTIR spectrum, peaks at 483 and 610 cm^(-1) proved the existence of SiO_(4)group in Ca_(2)Si_(3)O_(8), and the peak centered at 417 cm^(-1) confirmed the presence of MgO6 octahedral in Mg_(2)Si_(3)O_(8) materials. TEM images were used to determine the particle size(13–35 nm) and to study the threedimensional structure of nanophosphor materials. The experimental studies indicate that these materials may be promising as red-emitting nanophosphors for white lightemitting diodes.

关键词： Z_(2)Si_(3)O_(8) Nanophosphors Sol–gel Photoluminescence Crystalline

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Down-conversion characteristics of Eu3+ doped M2Y2Si2O9(M=Ba, Ca, Mg and Sr) nanomaterials for innovative solar panels

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Progress in Natural Science:Materials International 2019年第4期29卷 457-465页

作者： Suman Sheoran Vachan singh Sitender singh Sonika Kadyan Jasbir singh devender singh Department of Chemistry Maharshi Dayanand University Department of Physics Government College

Down-conversion properties of Eu3+doped M2Y2Si2O9(M=Ba,Ca,Mg,Sr) phosphors have been investigated in *** phosphors were synthesized via the simple,fast and cost-effective sol-gel technique at a temperature of 950℃.Color coordinates and emission color can be altered by the varying concentration of dopant ion in *** luminescence intensity was obtained when doping 0.03 mol of Eu3+*** the excitation wavelength of 395 nm,these silicates showed strong red color,pure and sharp spectral peaks in visible region due to ~5 D0→F1-3transitions of Eu3+present in the *** of reaction temperature on luminescence was also analyzed for these *** sharp peaks in the X-ray diffraction pattern indicated the high crystallinity of prepared ***2Y2Si2O9has shown an orthorhombic crystal *** FTIR results confirmed the metal-oxygen vibrational modes available in the range of 400-1600 *** electron microscopy images have revealed that the variation of alkaline earth metal provided a very different crystal *** down conversion response of these phosphor materials can provide a great significance in the application of the coming solar devices.

关键词： M2Y2Si2O9:Eu3+ Phosphor Sol-gel Lattice Solar devices

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Moving Least Squares Interpolation Based A-Posteriori Error Technique in Finite Element Elastic Analysis

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Computer Modeling in Engineering & Sciences 2021年第10期129卷 167-189页

作者： Mohd Ahmed devender singh Saeed Al Qadhi Nguyen Viet Thanh Civil Engineering Department College of EngineeringKing Khalid UniversityAbha61421Saudi Arabia Ministry of Information Soochna BhavanCGO ComplexDelhi110003India Urban Transport&Coastal Engineering Department University of Transport and CommunicationsHanoi100000Vietnam

The performance of a-posteriori error methodology based on moving least squares(MLS)interpolation is explored in this paper by varying the finite element error recovery parameters,namely recovery points and field variable derivatives *** MLS interpolation based recovery technique uses the weighted least squares method on top of the finite element method’s field variable derivatives solution to build a continuous field variable derivatives *** boundary of the node support(mesh free patch of influenced nodes within a determined distance)is taken as circular,i.e.,circular support domain constructed using radial weights is *** field variable derivatives(stress and strains)are recovered at two kinds of points in the support domain,i.e.,Gauss points(super-convergent stress locations)and nodal *** errors are computed as the difference between the stress from the finite element results and projected stress from the post-processed energy norm at both elemental and global *** benchmark numerical tests using quadrilateral and triangular meshes measure the finite element errors in strain and stress *** numerical examples showed the support domain-based recovery technique’s capabilities for effective and efficient error estimation in the finite element analysis of elastic *** MLS interpolation based recovery technique performs better for stress extraction at Gauss points with the quadrilateral discretization of the problem *** is also shown that the behavior of the MLS interpolation based a-posteriori error technique in stress extraction is comparable to classical Zienkiewicz-Zhu(ZZ)a-posteriori error technique.

关键词： Recovery points field variable derivatives effectivity error recovery support domain error convergence

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Oxide ancillary ligand-based europium β-diketonate complexes and their enhanced luminosity

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Rare Metals 2021年第10期40卷 2873-2881页

作者： devender singh Shri Bhagwan Anuj Dalal Kapeesha Nehra Raman Kumar Saini Kapoor singh Anura Priyajith Simantilleke Sumit Kumar Ishwar singh Department of Chemistry Maharshi Dayanand UniversityRohtak 124001India Centre de Fisica Universidade of MinhoBraga 4710057Portugal Department of Chemistry DCR University of Science and TechnologyMurthal 131039India

Ternary materials of europium complex with2,2,6,6-tetramethyl-3,5-heptanedione(tmhd) ligand and aqua ligand as ancillary ligands have been prepared and characterized for various optoelectronic *** of hydrated complex [Eu(tmhd)_(3)(H_(2)O)_(2)] proceeded with triphenylphosphine oxide(TPPO) and pyridine-N-oxide(PNO) ancillary ligands were studied to develop novel complexes. The prepared complexes show good thermal stability. A comparative investigation of preparedmaterials[Eu(tmhd)_(3)(H_(2)O)_(2)],[Eu(tmhd)_(3)(TPPO)_(2)] and [Eu(tmhd)_(3)(PNO)_(2)] was conducted for their luminescent behaviors in order to obtain the role of ancillary ligand in the enhancement of illumination amount generated from europium(Eu^(3+)) ion. Color coordinates of prepared ternary complexes such as[Eu(tmhd)_(3)(H_(2)O)_(2)]with(x = 0.54,y = 0.32),[Eu(tmhd)_(3)(TPPO)_(2)] with(x = 0.56, y = 0.32) and[Eu(tmhd)_(3)(PNO)_(2)] with(x = 0.57, y = 0.33) indicated that these materials exhibited bright red emission in visible region spectrum. The complexes show a proficient energy transport pathway from the ligands to the innermost Eu^(3+)by means of an ancillary ligand-sensitized luminescence process. Interaction between the metal and ligand results in a distinguished effect on quantum efficiency(η) as well as on Judd–Ofelt intensity factor(Ω_(2)) of the prepared materials.

关键词： Ternary Eu^(3+)complexes Red emissive materials Photoluminescence Quantum efficiency Judd-Ofelt intensity Optoelectronic devices

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Supportive psychotherapy

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英国医学杂志中文版 2010年第1期13卷 49-49页

作者： devender singh Yadav specialty doctor in psychiatry department of psychiatry Princess of Wales Hospital

Dealing with a child with hyperpyrexia induced visual hallucinations is a terrifying *** 4 year old daughter woke up *** said that she could see worms coming out from her fingers,and she would then flick her *** was *** repeated that she could see worms on the bed and wouldn't sleep despite *** couldn't sit still and kept *** wife consoled her and held *** I had given my daughter paracetamol a few hours earlier for the symptoms of flu,I kept dreading the worst and called a paediatrician friend who tried to reassure *** though I'm a doctor,my wife and I ended up taking my daughter to the emergency department in case I'd missed *** paediatrician there was sympathetic,checked her,and reassured *** we got home my daughter was exhausted,but only fell sleep as dawn broke.

关键词：精神疗法心理疗法医学临床

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