A nodeless variable element method with the fluxbased formulation is developed to analyze two-dimensional thermal-structural problems. The nodeless variable formula- tion provides accurate temperature distributions to...A nodeless variable element method with the fluxbased formulation is developed to analyze two-dimensional thermal-structural problems. The nodeless variable formula- tion provides accurate temperature distributions to yield more accurate thermal stress solutions. The flux-based formulation is used to reduce the complexity in deriving the finite element equations as compared to the conventional finite element method. The solution accuracy is further improved by implementing an adaptive meshing technique to generate finite element meshes that can adapt and move along with the transient solution behavior. A version of a nearly optimal element size determination is proposed to provide high convergence rate of the predicted solutions. The combined procedure is evaluated by solving several thermal, structural, and thermal stress problems.展开更多
Eu2＋ and Dy3＋ codoped （Ca, Sr）7（SiO3）6C12 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction （...Eu2＋ and Dy3＋ codoped （Ca, Sr）7（SiO3）6C12 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2＋ single-doped phosphor, while located at 548 544 nm for the Eu2＋, Dy3＋ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3＋ was doped into the （Ca,Sr）7（SiO3）6C12：Eu2＋ system. The composition-optimized sample with 3 mol.% of Dy3＋ and constant 10 tool.% of Eu2＋ exhibited a 220% PL enhancement compared to the phosphor with 10 tool.% Eu2＋ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely （Ca,Sr）7（SiO3）6Cl2：3 tool.% Dy3＋ 10 mol.% Euz＋ could get up to 24.6%. The synthesized yellow-emitting （Ca,Sr）7（SiO3）6C12：Dy3＋,Eu2＋ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.展开更多
文摘A nodeless variable element method with the fluxbased formulation is developed to analyze two-dimensional thermal-structural problems. The nodeless variable formula- tion provides accurate temperature distributions to yield more accurate thermal stress solutions. The flux-based formulation is used to reduce the complexity in deriving the finite element equations as compared to the conventional finite element method. The solution accuracy is further improved by implementing an adaptive meshing technique to generate finite element meshes that can adapt and move along with the transient solution behavior. A version of a nearly optimal element size determination is proposed to provide high convergence rate of the predicted solutions. The combined procedure is evaluated by solving several thermal, structural, and thermal stress problems.
基金Project supported by Shanghai Education Committee Research Project(08YZ166,11YZ222)Shanghai Science and Technology Committee Project(09530500800)National Natural Science Foundation of China(51002096)
文摘Eu2＋ and Dy3＋ codoped （Ca, Sr）7（SiO3）6C12 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2＋ single-doped phosphor, while located at 548 544 nm for the Eu2＋, Dy3＋ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3＋ was doped into the （Ca,Sr）7（SiO3）6C12：Eu2＋ system. The composition-optimized sample with 3 mol.% of Dy3＋ and constant 10 tool.% of Eu2＋ exhibited a 220% PL enhancement compared to the phosphor with 10 tool.% Eu2＋ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely （Ca,Sr）7（SiO3）6Cl2：3 tool.% Dy3＋ 10 mol.% Euz＋ could get up to 24.6%. The synthesized yellow-emitting （Ca,Sr）7（SiO3）6C12：Dy3＋,Eu2＋ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.
