Mechanical and fracture investigation of magnesia refractories with acoustic emission-based method

In this study, the fracture behaviour of magnesia, magnesia chrome and magnesia spinel (MgAl₂O₄ and FeAl₂O₄) refractories under wedge splitting test are qualitatively and quantitatively investigated with the acoustic emission (AE) and digital image correlation (DIC). First of all, the concepts of characteristic widths are proposed for estimating the brittleness of refractory materials according to the shape of load-displacement curve and validated by their good correlation with the characteristic length. Besides, the AE data are analyzed with AE parameter-based approaches and offer new insight into the fracture behaviour of refractory materials, including the classification of the cracking events in grains and in matrix, the distinction between the tensile mode and shear mode damage, and the visualization of the fracture process zone development. It confirms that the pre-existing micro-crack networks in refractories are favourable for the brittleness reduction, which enhance their nonlinear fracture behaviour and thermal shock resistance.     

Estimating posterior inference quality of the relational infinite latent feature model for overlapping community detection

Overlapping community detection has become a very hot research topic in recent decades, and a plethora of methods have been proposed. But, a common challenge in many existing overlapping community detection approaches is that the number of communities K must be predefinedmanually. We propose a flexible nonparametric Bayesian generative model for count-value networks, which can allow K to increase as more and more data are encountered instead of to be fixed in advance. The Indian buffet process was used to model the community assignment matrix Z, and an uncollapsed Gibbs sampler has been derived.However, as the community assignment matrix Z is a structured multi-variable parameter, how to summarize the posterior inference results and estimate the inference quality about Z, is still a considerable challenge in the literature. In this paper, a graph convolutional neural network based graph classifier was utilized to help to summarize the results and to estimate the inference quality about Z. We conduct extensive experiments on synthetic data and real data, and find that empirically, the traditional posterior summarization strategy is reliable.     

有机膜精确调控传质的新型溶析结晶及过程强化

溶析结晶是一种环保、高效的结晶方法，在温敏性、低溶解度物系的晶体生产领域具有不可替代的重要作用。但是，传统溶析结晶过程中溶液过饱和度的时空均一性差，传质调控为微米级尺度，容易爆发成核，是亟待解决的关键问题。本文提出利用聚醚砜（PES）中空纤维膜，为溶析剂与结晶溶液之间的传质提供均匀稳定的界面，实现结晶溶液与溶析剂的精确混合和结晶过程强化，开发了一种新型的溶析结晶传质调控技术。溶析剂在压力差驱动下均匀渗透通过有机膜，在结晶溶液一侧的膜外表面形成溶析剂液膜层，通过表面液膜的不断更新，将传统溶析结晶的毫米级宏观混合转变为亚微米级尺度的微观混合，实现过饱和度的均匀分布。同时，这层液膜的存在，避免了结晶溶液直接接触膜表面，有效地解决了异相成核附着导致膜污染的问题。实验中，对壳程流速做出周期性改变后，渗透通量可即时发生一致的线性响应变化，证实有机膜调控传质过程的精确性和灵敏性。PES膜重复使用多次后，渗透通量仍可以保持稳定。相比传统的滴加式溶析结晶，在相同的溶析剂传质速率下，有机膜调控过程制备的晶体产品，形貌更加规整、粒径分布更集中。因此，在溶析剂精确传质和抗污染方面，有机膜调控的溶析结晶过程均表现出良好的性能，为药物、大分子结晶的高效工业化制备开拓了新的思路。     

一种液压摩擦焊机电液系统研究与试验

针对海上石油平台、海底输送管线维修的需要,提供了一种液压摩擦焊机液压和电器系统设计思路,通过参数计算、电液控制系统设计,研发了一种液压摩擦焊机,通过对DH38钢摩擦叠焊单元成型工艺试验,发现焊接接头拉伸强度达到了母材强度的76%以上,验证了液压摩擦焊机的可靠性能,通过该研究的应用,可对海上石油平台、海底输送管线的维修起到积极作用。     

XJM-KS型浮选机矿化器负压产生机理研究

浮选机矿化器是用于浮选矿浆预处理的重要设备，其性能的优劣直接影响到浮选机的工作效果。文章通过流体力学仿真软件FLUENT对XJM-KS型浮选机矿化器的内部流场进行数值仿真，重点研究了聚焦式喷嘴布置所带来的流场特征。模拟结果表明，高速的矿浆射流能够在混合室内产生-2.43×10Pa的负压区，从而吸入大量的空气，实现空气与矿浆的有效混合与预矿化，与传统的机械搅拌式矿浆预处理装置相比，该矿化器能够大幅度提高预矿化效果。     

Atomistic insight into the hydration and proton conducting mechanisms of the cobalt doped Ruddlesden-Popper structure Sr3Fe2O7-δ

Sr₃Fe₂O_7-δ (SFO) with two-layer Ruddlesden-Popper (R–P) structure has recently been proved to be a promising material for the single phase cathode in proton conducting solid oxide fuel cells (P–SOFCs). To investigate the hydration reactions and proton conducting mechanisms of SFO and cobalt doped SFO (SFCO), both bulk and surface properties were calculated. We conclude that R–P structures have advantages in P–SOFCs. The unique Sr–O–M layer can facilitate the hydration process. Although in Sr–O–F and Sr–O–N layers, it is difficult for the formation and migration of oxygen vacancies, protons are most stable. Furthermore, cobalt doping can not only improve the electronic conductivity but also enhance surface properties of SFCO. The easily exposed Co–Fe–O surface can also facilitate the hydration reactions on the surface. Our work could give an informative insight into the relationships among the doped elements, the R–P structures, the hydration process and the proton conducting properties.     

MoS2-mesoporous LaFeO3 hybrid photocatalyst: Highly efficient visible-light driven photocatalyst

Perovskite type materials have high potential photocatalytic application towards both hydrogen energy generation and organic dye degradation due to their high stability and good reusability. Here, it is the first analysis of photocatalytic degradation of RhB and hydrogen energy evolution under visible light over MoS₂/LaFeO₃ nanocomposite. The physicochemical properties of the materials were characterized using a range of techniques such as XRD, TEM, XPS, FTIR, PL, photocurrent, etc. The optical properties of the nanocomposite show good absorption in UV-Vis spectra as compared to the bare LaFeO₃. In this study, MoS₂/LaFeO₃ nanocomposite was synthesized through single step in situ hydrothermal processes with a narrow bandgap, enhanced photocatalytic application under visible light. This novel MoS₂/LaFeO₃ nanocomposite is an efficient and promising photocatalyst for both hydrogen energy evolution and organic dye degradation.     

Magnetic field coupling microfluidic synthesis of Fe2Pt/C nanocatalysts for enhanced electrochemical catalytic oxidation of alcohol

The influence of magnetic field (MF) on electrochemical catalytic properties of carbon supported Fe₂Pt nanocatalysts is investigated. Nanocatalysts are produced through an external MF coupled microfluidic process. X-ray diffraction (XRD) measurements show that Fe₂Pt nanocrystals (NCs) with larger sizes are synthesized when an external MF of 1.4 T is applied. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) characterizations confirm that more Pt²⁺ reduces to Pt⁰ and NCs grow larger under magnetic fields (MFs) than those without MFs. The increased coercivity indicates that more surface unpaired electrons are present and the surface spin configuration changes under MFs. NCs synthesized under MFs show better catalytic performance in alcohol electrochemical catalytic oxidation reactions compared to samples synthesized without MFs. The mass activities significantly increase by 1.10 and 1.24 times and the specific activity increases up to 1.11 and 1.26 times for methanol and ethanol oxidation, respectively, compared to those without MFs.     

简析变压器油的生产工艺及质量

本文简要介绍了变压器油的运用价值,同时分析如何实现对变压器油生产工艺的优化,并从物理性能以及化学性能两个方面分析生产工艺改良后变压器油整体质量,以期为变压器油生产工作提供一定的参考与帮助。     

浅谈国际工程项目的技术标编制流程

本文将重点从阅读业主招标文件开始,以及参与业主组织的现场勘查和投标会议,成立投标组、会标、审标直至最后标书递交等各个阶段,并结合近几年参与国际工程项目投标的经验和体会去分析和探讨。