Improved photoluminescence and multi-mode optical thermometry of Er3+/Yb3+ co-doped (Ba,Sr)3Lu4O9 phosphors

Contactless optical thermometers have attracted extensive attentions for applications in scientific research and technological fields due to their apparent advantages. Herein, a novel sequence of Ba_3-xSr_xLu₄O₉ (B_3-xS_xLO):Er³⁺/Yb³⁺ phosphors were successfully prepared to investigate the temperature sensing property. By establishing energy transfer from Yb³⁺ to Er³⁺ and regulating the local lattice environment, up-conversion luminescence of Er³⁺ is dramatically improved when excited by 980 nm laser. This can effectively promote signal-noise ratio and reduce the errors in temperature detection. Furthermore, a multi-mode optical thermometry, which includes the fluorescence intensity ratio (FIR) from two thermally coupled levels of ²H_11/2/⁴S_3/2, FIR based on non-thermally coupled system of ²H_11/2/⁴F_9/2 and fluorescence lifetime of ⁴S_3/2 state of Er³⁺, was explored systematically. The fabricated samples exhibit the superior temperature measurement performances containing wide temperature-sensing range, superior signal discriminability, high sensitivity and favorable repeatability, indicative of the enormous utilization prospects of B_3-xS_xLO:Er³⁺/Yb³⁺ for thermometry.     

Tuning the electronic and thermal transport behaviors of metal-dispersed Ti2O3 composites derived by metal–insulator transition

Thermal management requires an understanding of the relations among the thermal energy transfer, electronic properties, and structures of thermoconductive materials. Here, we enhanced the metal–insulator transition (MIT)-induced effect on the thermal conductivities of microstructure-controlled Ti₂O₃ composites containing W as a thermal conductive filler at approximately 450 K. To change the electronic and thermal transport properties, we varied the particle radii of the conductive phases in the raw material. The change in the calculated electronic thermal conductivity relative to the electrical conductivity of the W_x(Ti₂O₃)_1?x composite was enhanced by compounding the material. When x was reduced from 50 vol% to 20 vol% and the W particle diameter was reduced from 150 μm to 5 μm, the variation in the estimated electronic thermal conductivity of the W_x(Ti₂O₃)_1?x composite was increased by a factor of 2.01. The total thermal conductivity was also changed by the MIT. At x = 50 vol% and a W particle diameter of 5 μm, the maximum thermal conductivity change was 6.34 times larger than that of pure Ti₂O₃. The detailed relation between the MIT-induced changes in thermal transport and the microstructure were elucidated in classical effective medium approximations.     

BiLaWO6: Er3+/Tm3+/Yb3+ phosphor: Study of multiple fluorescence intensity ratiometric thermometry at cryogenic temperatures

Highly thermally stable Er³⁺/Tm³⁺/Yb³⁺ tri-doped bismuth lanthanum tungstate phosphors were prepared by high temperature solid-state reaction method. The structural and morphological properties of the prepared phosphors were analysed by X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM) coupled with energy dispersion spectrum (EDS). Visible upconversion (UC) luminescence was measured by exciting the phosphors with 980 nm laser radiation. The dependence of the UC intensity of each emission band of Er³⁺ and Tm³⁺ ions as a function of temperature in the range from 30 to 300 K was monitored. Fluorescence intensity ratios (FIR) of thermally coupled levels (TCL) and non-thermally coupled levels (NTCL) were analysed and verified with appropriate theoretical validation. The absolute (S_A) and relative sensitivities (S_R) were estimated and compared with the reported systems. In the present case of BiLaWO₆: Er³⁺/Tm³⁺/Yb³⁺, S_R (0.43 % K^?1) related to TCL of Er³⁺ UC is found to have maximum sensitivity compared to any of the NTCL combinations at 300 K. From this study we inferred that the S_R values estimated from NTCL are smaller than that of TCL involved in BLW: Er³⁺/Tm³⁺/Yb³⁺ phosphor. The temperature dependent CIE color coordinates were also evaluated in the cryogenic temperature region.     

KH 560改性水泥砂浆的防水性能研究

向水泥砂浆中添加γ-(2,3-环氧丙氧)丙基三甲氧基硅烷(KH 560)制得改性水泥砂浆,并与未添加KH 560的水泥砂浆行了性能对比,研究了KH 560对水泥砂浆试件折压比、水接触角、吸水率、抗渗压力的影响,并探讨了KH 560改性水泥砂浆的防水机理.结果表明,添加适量KH 560能够提高水泥砂浆的防水性能.当KH ...     

结构强度储备的评估及结构维修过程的跟踪决策

本文提出了已建成结构在服役过程中构件的强度储备比和结构整体的强度储备比的概念和定义,它们都是随结构使用和维修过程而变化的时间的函数。我们建议以实际的强度储备比作为构件和结构服役安全度的表达方式,给出了构件和结构强度储备比的具体评定方法,并以结构整体的强度储备比作为控制参数决策结构的维修过程,以求得结构全寿命维修的优化控制。本文所提出的方法适用于具有良好的结构重分析程序和精密细致的检测手段的工程。一般重要的结构工程,例如核电站、海上结构、航空航天设备等均具备上述条件。因而本文所提的方法非常实用,可以立即应用于重要的工程项目,具有重大的经济和社会效益。     

高重合度直齿渐开线圆柱齿轮传动承载能力与优化设计研究

本文系统地研究了高重合度齿轮齿副的变形与刚度、同时啮合齿对之间的载荷分配、胶合承载能力、弯曲强度、接触强度、参数优化设计.     

利萨如图周边切点与频率比的研究

由利萨如图形与周边切点数,来确定参与合振动的两个相互垂直方向上的振动频率。     

悬挑梁对结构受力特性影响分析

当梁对客运站的悬挑长度为0.9 m时,分别应用高层建筑结构空间有限元分析软件（SATWE）和结构分析软件（SAP2000）进行结构计算。在风荷载、多遇地震作用下,利用SAP2000的反应谱分析和SATWE弹性分析方法,分析结构的整体稳定性,水平层间最大位移、周期比、位移比,A、B轴两榀框架的轴压比。分析表明:不同软件建模分析结果存在差异;结构增加悬挑梁后,周期比增大,X方向上的层间位移和轴压比变化较小,但Y方向上层间位移变化较大。悬挑梁对建筑结构稳定性存在一定影响。     

不同基质配比对银毛野牡丹扦插的影响

银毛野牡丹是优良的园林观赏性植物,但是繁殖有性结实率低。通过为期30天的扦插试验,对比不同基质（原土、草炭土、蛭石、珍珠岩）配比对银毛野牡丹插穗生长的影响,分析插穗生根时间、生根数目、最长根长、生根率、生长状态以及基质变化,找出适合其生长发育的优良基质,为银毛野牡丹的繁殖提供技术支撑。研究表明：试验组T8（原土：细沙：草炭土：蛭石：珍珠岩=1：1：2：1：1）的插穗生根率、最长根长、插穗长势为最佳,试验组T2（草炭土）效果次之,在条件有限的情况下可以作为备用方案以供生产所需。     

配筋UHPC柱的抗震性能及影响因素分析

为研究配筋超高性能混凝土(ultra-high performance concrete,UHPC)柱抗震性能及影响因素,以碳纤维增强树脂(carbon fiber reinforced polymer,CFRP)布缠绕、钢筋强度和剪跨比为参变量,对1根普通钢筋UHPC柱、1根CFRP布缠绕的普通钢筋UHPC柱和3根高...