MOF‐Confined Sub‐2 nm Atomically Ordered Intermetallic PdZn Nanoparticles as High‐Performance Catalysts for Selective Hydrogenation of Acetylene

Controllable synthesis of ultrasmall atomically ordered intermetallic nanoparticles is a challenging task, owing to the high temperature commonly required for the formation of intermetallic phases. Here, a metal–organic framework (MOF)‐confined co‐reduction strategy is developed for the preparation of sub‐2 nm intermetallic PdZn nanoparticles, by employing the well‐defined porous structures of calcinated ZIF‐8 (ZIF‐8C) and an in situ co‐reduction therein. HAADF‐STEM, HRTEM, and EDS characterizations reveal the homogeneous dispersion of these sub‐2 nm intermetallic PdZn nanoparticles within the ZIF‐8C frameworks. XRD, XPS, and EXAFS measurements further confirm the atomically ordered intermetallic phase nature of these sub‐2 nm PdZn nanoparticles. Selective hydrogenation of acetylene evaluation results show the excellent catalytic properties of the sub‐2 nm intermetallic PdZn, which result from the energetically more favorable path for acetylene hydrogenation and ethylene desorption over the ultrasmall particles than over larger‐sized intermetallic PdZn as revealed by density functional theory (DFT) calculations. Moreover, this protocol is also extendable for the preparation of sub‐2 nm intermetallic PtZn nanoparticles and is expected to provide a novel methodology in synthesizing ultrasmall atomically ordered intermetallic nanomaterials by rationally functionalizing MOFs.     

土石坝防渗墙位置和深度对渗流量的影响

建在无限深透水地基上的土石坝坝基垂直防渗体位置和深度对渗流量的影响按现有的计算理论无法确定,本文根据边界元的特点和计算理论,建立适用于解决该问题的计算模型,编制相应的计算程序,并计算分析了防渗墙位置和深度对渗流量的影响,为今后的工程设计提供参考依据.     

基于温控参数折减有限元法的水库进水塔-地基结构稳定分析

针对边坡稳定分析中采用的强度折减有限元法,提出用温度场控制强度参数折减和变形参数调整的有限元法,对结构复杂的水库进水塔-地基3维结构进行稳定分析,较于传统的强度折减有限元法大大提高了计算效率。用考虑变形参数调整和不考虑变形参数调整的温控强度折减有限元法,分别对算例进行分析,并将其和水压超载法计算进行对比计算,综合不同部...     

可拼装式三维钢桁桥振动分析与试验

根据可拼装式三维钢桁桥的结构特点 ,可拼装式钢桁桥的拼装单元可被肢解成子结构。在空间杆系有限元法的基础上 ,利用模态综合技术对可拼装式钢桁桥进行振动分析。通过结构振动试验 ,验证了理论分析结果的正确性     

一种新的民用燃气表应用模式

介绍了一种称为“燃气表数据远程传输模式”的燃气表应用模式，利用开发的“燃气表集中读写控制器”，其内置读写牟器、主电路板、远传控制组件等，能同时连接8块燃气表，实现了读写卡器等设备的共享，节约了制造成本。经过一年多的应用，效果良好。     

Au/LaVO4 Nanocomposite: Preparation, characterization, and catalytic activity for CO oxidation

The size of the gold particles is a very important parameter to get active catalysts. This paper reports a novel colloidal deposition method to prepare Au/LaVO₄ nanocomposite catalyst with monodispersed Au colloids and uniform LaVO₄ nanoplates in nonpolar solvent. Monodispersed Au colloids with tunable size (such as 2, 5, 7, 11, 13, and 16 nm) and LaVO₄ nanocrystals with well-defi ned shapes were pre-synthesized assisted with oleic acid/amine. During the following immobilization process, the particle size and shape of Au and LaVO₄ were nearly preserved. As-prepared Au/LaVO₄ nanocomposite showed high catalytic activity for CO oxidation at room temperature. Since sizes of gold particles were well-defi ned before the immobilization process, size effect of gold particles was easy to be investigated and the results show that 5-nm Au/LaVO₄ nanocomposite has the highest activity for CO oxidation. This synthetic method can be extended further for the preparation of other composite nanomaterials.     

激光等离子体声波及应用

本文简要介绍了激光等离子体声波的产生机理、特性应用前景。     

成像技术在纺织品颜色测量中的应用进展

快速、准确、高效的纺织品颜色测量方法一直是纺织领域的研究热点,成像技术在纺织品颜色测量中的应用有较好的研究前景。为此,介绍了光电积分法和分光光度法的特点及其用于纺织品颜色测量存在的局限性。阐述了成像技术中数码摄像法、多光谱成像法、高光谱成像法的成像特点,分析了相机颜色特征化、光谱重建算法、图像分割法等对纺织品颜色测量的影响,并对不同成像技术在纺织品颜色测量应用中的研究现状进行总结。最后从纺织品颜色特点、纺织品颜色测量要求以及高光谱成像技术的优点等角度,展望了高光谱成像技术用于未来纺织品颜色测量的发展方向。     

圆中环沉沙排沙池流场三维数值模拟研究

针对新型二级泥沙处理设施—圆中环沉沙排沙池,采用RNG k-ε湍流模型结合自由水面追踪的VOF方法对其流场进行水气二相流三维数值模拟。计算得出流速分布特性,在数值模拟结果与模型试验结果吻合良好的基础上,揭示流场分布规律。研究结果表明:数值模拟可弥补物理模型试验不足,对类似工程基本可以代替模型试验,提高研究效率;计算显示"圆中环"径向速度在数值上大于轴向及切向速度,表层水体径向流速大小沿径向及垂向锐减,水体沿径向存在回流区。