Eu3+-site occupation in CaTiO3 perovskite material at low temperature

In order to clarify the site occupancy of rare-earth ions in rare-earth doped perovskite materials, the un-doped pure CaTiO₃ and Eu³⁺-doped CaTiO₃ samples with a series of Ca/Ti ratio were synthesized via high-temperature solid-state reaction method. X-ray diffraction (XRD) powder patterns confirm that the crystal structure keeps invariant at various Ca/Ti ratios. Measurement results of unit-cell parameters and X-ray photoelectron spectroscopy (XPS) indicate that Eu³⁺ ions enter into the Ca²⁺ site. The high-resolution photoluminescence spectra of Eu³⁺ ions at 20 K in all samples did not witness a significant change under the excitation at different wavelength, implying that Eu³⁺ ions occupy only one type of site. Considering the small spectral splitting range of ⁵D₀ → ⁷F₂ transition and the large intensity ratio of ⁵D₀ → ⁷F₂/⁵D₀ → ⁷F₁, it can be concluded that Eu³⁺ occupies Ca²⁺ site with larger coordinate numbers rather than Ti⁴⁺ site.     

Effects of longitudinal fire source locations on the maximum temperature and longitudinal temperature decay in a mountain tunnel with vertical shaft: an experimental investigation and empirical model

Journal of Thermal Analysis and Calorimetry - Few investigations have focused on the influence of longitudinal fire source location on the temperature profile of smoke induced by fire in a tunnel...     

4~20 K 温区固体界面导热填料接触热阻实验研究

超导量子干涉仪、 超导光子探测器等深空探测器需要液氦温区制冷技术提供极低温温度, 固体界面接触热阻的存在会增大耦合界面温度差, 进而增加制冷机系统冷损. 为定量探究4~20 K 深低温区固体接触热阻, 采用GM 作为冷源, 设计了一台可同时调节压力和低温温度的固体界面接触热阻测试实验台. 利用感压纸进行接触界面压力校核, 并对温度重复性进行验证. 实验测试了不同导热介质填充情况下, 温度和压力变化时固体接触热阻的变化规律. 基于最小二乘法对实验数据进行半经验公式拟合, 获得4 ~20 K 温区不同压力加载条件下的接触热阻的定量参考.     

岩溶隧道突水灾害形成机理及发展趋势1）

岩溶隧道突水灾害具有“强突发、高水压、大流量、多类型”等显著特点,其灾变演化过程复杂、动力失稳规律尚不清楚.本文系统提出了不同类型突水灾害的发生条件、判据及安全厚度分析方法,剖析了近期研究进展及发展趋势.首先,给出了隧道突水灾害的概念、类型及构成三要素,从系统论角度分析了隧道突水的灾变过程;其次,总结了隧道突水灾害致灾机理、力学模型、失稳判据和最小安全厚度等方面的近期研究成果;最后,从构成三要素角度分析了隧道突水致灾机理方面的现状与问题,并提出了今后的发展趋势与方向,主要有：（1）灾害源固液气三相置换机制与释能模式,（2）突水通道多相物质迁移与流态演化规律,（3）隔水阻泥结构动力灾变演化机理,（4）突水通道破裂形成过程的模拟分析方法等.     

脉管制冷-90℃ 低温冰箱研究

基于真空绝热板(VIP)超低热导率的优点,开展了-90℃低温冰箱的设计和实验研究.分析了同轴型脉管制冷机的结构特点和制冷性能属性,研究了VIP和聚氨酯发泡层组成复合绝热层结构以及低温冰箱箱体的漏热损失计算方法,实验验证了容积为27.6L的低温冰箱良好的制冷效果和保温性能,在135 W的电功输入下可提供-90℃的低温环境.该研究为空间及商用长寿命深低温冰箱的研究提供一定的参考.     

Metal-Free Visible Light-Promoted Synthesis of 1,2,2-Triarylethanones and 2,2-Diarylethanones: Route Towards Tamoxifen

An efficient and straightforward methodology for the synthesis of 1,2,2-triarylethanones and 2,2-diarylethanones has been developed, via a visible light-promoted/Brønsted acid-catalyzed carbonyl-alkyne metathesis/transfer hydrogenation one-pot reaction of benzoquinone, arylalkyne, and Hantzsch ester. A series of synthetically useful triarylethanones and diarylethanones were achieved in excellent yield under mild reaction conditions. This protocol is operationally simple, photocatalyst-free, and scalable and has a broad substrate scope. Moreover, this reaction involves the formation of three chemical bonds, namely C=O, C−C, and C−H bonds. This feature enables de novo synthesis of 1,2,2-triarylethanones and 2,2-diarylethanones. Additionally, this protocol provides a convenient and practical synthetic route for tamoxifen.