邻菲罗啉-硫氰酸钾-水体系液固分离钴(Ⅱ)

当分析元素含量极低时,往往要求在测定之前辅以化学分离预富集手段以纯化富集待测物和除去干扰基体。实验利用邻菲罗啉和硫氰酸钾作为微痕量Co²⁺的络合剂,建立了一种液固体系分离富集微痕量Co²⁺的新方法。分别考察了邻菲罗啉溶液用量、硫氰酸钾溶液用量、酸度对分离效率的影响。结果表明,当体系中Co²⁺含量为100 μg时,控制体系pH=2~6,加入1.00 mL 1.5 g/L邻菲罗啉溶液、1.00 mL 0.1 mol/L硫氰酸钾溶液、1.00 mL 10 g/L EDTA溶液、1.00 mL 40 g/L硫脲溶液,震荡静置后,Co²⁺与邻菲罗啉、硫氰酸钾反应生成的离子缔合物定量沉淀到溶液底部,而Cd²⁺、Fe³⁺、Zn²⁺、Ni²⁺、Cu²⁺、Pb²⁺、Al³⁺、Ag⁺等离子仍留在水相中,从而实现了Co²⁺与这些离子的定量分离。方法成功用于合成水样中微痕量Co²⁺的定量分离,富集率在97.2%～98.6%之间。     

循环冷却水系统无垢低腐蚀率的技术改进

泸天化公司大氮肥循环冷却水系统投用以来，经优选水稳剂配方、改进加氯方式、增设旁滤池、提高补充水质量等措施，年腐蚀率从0．3366mm降至0．0241mm，换热器运行一年无结垢现象。     

物联网环境下移动边缘计算安全问题

物联网时代多类型流量的接入与应用场景的多样性,从计算能力、存储和业务时延等多个方面对当前集中式云计算架构提出新的挑战.移动边缘计算(MEC)作为一种在网络边缘为用户提供服务的解决方案,能够满足物联网多样性的业务需求.针对移动边缘计算在物联网中的安全问题,对移动边缘计算的概念、应用场景和安全进程进行介绍,着重从数据传输安全、存储安全和计算安全3个方面阐述了移动边缘计算在物联网时代所面临的安全挑战.     

新型雨水径流计量用复合堰的设计及率定

针对其他流量计量方法不易监测雨水径流流量的问题,提出一种新型复合堰,用于测量雨水径流流量,新设计的堰由下部三角形堰和上部矩形堰复合而成。根据不同重现期下的雨水峰值流量,确定堰的量程和基本尺寸。通过率定试验,得出不同水头下的流量系数以及流量-水头关系曲线。新型复合堰不仅可以精确测量小流量,而且对大流量也可有效测量,具有较高的量程比和较大的泄流能力。     

Ultrahigh Energy Storage Capacitors Based on Freestanding Single-Crystalline Antiferroelectric Membrane/PVDF Composites

Inorganic/organic dielectric composites are very attractive for high energy density electrostatic capacitors. Usually, linear dielectric and ferroelectric materials are chosen as inorganic fillers to improve energy storage performance. Antiferroelectric (AFE) materials, especially single-crystalline AFE oxides, have relatively high efficiency and higher density than linear dielectrics or ferroelectrics. However, adding single-crystalline AFE oxides into polymers to construct composite with improved energy storage performance remains elusive. In this study, high-quality freestanding single-crystalline PbZrO₃ membranes are obtained by a water-soluble sacrificial layer method. They exhibit classic AFE behavior and then 2D–2D type PbZrO₃/PVDF composites with the different film thicknesses of PbZrO₃ (0.1-0.4 µm) is constructed. Their dielectric properties and polarization response improve significantly as compared to pure PVDF and are optimized in the PbZrO₃(0.3 µm)/PVDF composite. Consequently, a record-high energy density of 43.3 J cm⁻³ is achieved at a large breakdown strength of 750 MV m⁻¹. Phase-field simulation indicates that inserting PbZrO₃ membranes effectively reduces the breakdown path. Single-crystalline AFE oxide membranes will be useful fillers for composite-based high-power capacitors.     

Core–shell adsorbents by electrospun MOF-polymer composites with improved adsorption properties: Theory and experiments

A new class of core–shell adsorbents has been created by electrospun metal–organic framework (MOF) particles embedded in polymer nanofibers, which have provided many unique properties compared to the existing MOF coating technologies. For the first time, we demonstrate the improved adsorption selectivity of CO₂ over N₂ using electrospun polymer/ZIF-8 adsorbents in experiments. Furthermore, an analytical model based on the assumption that the diffusivity in core is 10 times higher than that in shell is developed to describe the theory of improved selectivity for core–shell adsorbents that is validated against a more accurate finite element model developed in COMSOL. Our model shows three regimes including exclusive shell uptake, linear core uptake, and asymptotic core uptake. These regimes are related to material properties and uptake times, which could be used as design criteria to balance core stability, maximum selectivity, and maximum uptake. An advanced HAADF STEM tomography (Movie S1 ) shows that the shell thickness in the case of polymer/ZIF-8 is on the order of 10 nm, allowing the regime of maximum selectivity to be realized. Kinetically limited adsorption tests at 45°C demonstrate that these composite fibers can perform in a regime of selectivity and uptake for the separation of CO₂ and N₂ that is unobtainable by either the MOF or fiber independently, showing a great potential for postcombustion CO₂ capture.     

中外土木工程专业高校教师本科教学投入对比分析

教学是高等院校实现教书育人目标的最重要手段。高校教师对教学的投入直接关系到人才培养的质量和高校教育的质量。文章阐述和分析了国内外土木工程专业高校教师在本科教学中的投入现状,提出了改进我国高校教师本科教学投入的政策措施和思想保障,为促进高校教师投入本科教学活动和人才培养工作提供了新思路。     

木材强度准则的研究进展

木材的强度准则是木结构理论分析和数值模拟的重要基础。根据国内外的研究进展,对木材单轴、双轴以及多轴应力状态下的强度准则进行系统地介绍,包括最大应力准则、最大应变准则、Hill屈服准则、Hill型强度理论、Tsai-Wu准则、van der Put强度理论和木材剪切强度理论。通过与文献中木材强度实测值的比较,验证木材斜纹强度公式的有效性。对比木材强度准则在多轴应力状态下的强度包络线,总结各强度准则间的差异和适用范围,并讨论张量系数对强度包络线的影响。通过综述木材强度准则在木结构数值模拟中的应用,简要分析各强度准则的优缺点。最后提出木材强度准则需要进一步研究的问题。     

高压断路器的操作振动现象

高压断路器操作过程伴随着一系列冲击振动,对应着内部构件的冲击或运动变化,利用这一点可以作内部状态、故障的外部监测诊断。实测了样品支架上的振动,加速度的幅值可达100g,信噪比高。监测时传感器位置与方位的选择要合适。