旋转圆盘空蚀试验中的硅材料破坏过程研究

利用自制旋转圆盘空蚀试验装置,以流动自来水为介质,对磨片、化抛片、抛光片和刻蚀片等4种硅片进行连续8 h试验以及对磨片进行连续14 h跟踪观察试验,研究硅材料的微观破坏过程,并利用扫描电子显微镜、触针式表面形貌仪和原子力显微镜对其表面微观形貌进行分析.结果表明:经连续8 h空蚀试验后,磨片原始表面的片状层基本消失,表面破坏程度最严重,化抛片次之,其表面尖锐的边缘发生了钝化,抛光片和刻蚀片的表面变化不大;化抛片的表面粗糙度Ra值由227.79 nm降至173.31 nm,抛光片的Ra值由0.483 nm增加至3.455 nm,磨片在14 h试验后其Ra值由0.3304 μm降至0.1965 μm;一定尺度的表面微观形貌对硅材料产生显著影响.     

黑色电磁屏蔽织物的研制

本文应用电镀黑镍的方法在化学镀铜的涤纶织物上沉积一层均匀致密的黑镍层.借助正交实验,优化的工艺条件为,镀液组成为硫酸镍40g.L-1,硼酸30g.L-1,硫酸镍铵40g.L-1,硫酸锌50g.L-1,硫氰酸铵20g.L-1,pH=4,温度30℃.性能测试表明,这种黑色电磁屏蔽织物具有优异的导电性能功能,以及良好的耐磨、耐腐蚀性能和吸光性能,从而提高了它的装饰、保护、吸光等作用.     

治疗胃炎伴糜烂蒙药中多种微量元素的ICP-AES法测定

蒙药含有多种氨基酸和丰富的微量元素,特别是人体必需的微量元素含量相对高,而对人体有害的重金属元素含量相对低。采用微波消解ICP-AES法同时测定了治疗胃炎伴糜烂组合蒙药(1#:如达-6、2#:巴特日-7(Ⅱ))中Ca、Mg、Al、Fe、Mn、Sr、Cu、Zn、Pb等15种微量元素。加标回收率在94.9%~106.2%之间,相对标准偏差RSD≤3.2%,检出限在≤0.009μg/L。实验结果表明:1#、2#为不同类型的蒙药,其微量元素含量有所不同。     

A Semi-Empirical Model to Estimate Maximum Floc Size in a Turbulent Flow

The basic model for agglomerate breakage under the effect of hydrodynamic stress (d_max = C.G^−γ) is only applicable for low velocity gradients (<500 s⁻¹) and is often used for shear rates that are not representative of the global phenomenon. This paper presents a semi-empirical model that is able to predict mean floc size in a very broad shear range spanning from aggregation to floc fragmentation. Theoretical details and modifications relating to the orthokinetic flocculation output are also provided. Modelling changes in turbidity in relation to the velocity gradient with this model offer a mechanistic approach and provide kinetic agglomeration and breakage index k_a and k_b. The floc breakage mode is described by the relationship between the floc size and the Kolmogorov microscale. Shear-related floc restructuring is analysed by monitoring the fractal dimension. These models, as well as those used to determine floc porosity, density and volume fraction, are validated by the experimental results obtained from several flocculation operations conducted on ultrafine kaolin in a 4-litre reactor tank compliant with laws of geometric similarity. The velocity gradient range explored was from 60 to 6000 s⁻¹.     

Research on synergistic erosion by cavitation and sediment: A review

Sediment erosion frequently occurs in areas with high incidences of cavitation. The collaborative impact of abrasion and cavitation presents a host of challenges, threats, and damages to hydraulic engineering. However, little is known about the synergistic wear mechanism, and research conclusions remain inconsistent. In this work, relevant studies on synergistic erosion have been collected, classified, and analyzed. Presently, research on synergistic wear primarily operates at the macro and micro levels. The microscopic level enables the visualization and quantification of the process by which particles gain momentum from bubbles, the trajectory of particle acceleration, and the mechanism that triggers strong interactions between bubble-particle. At the macro level, erosion is understood as the summation of damage effects on the wall that is caused by the interaction between a plethora of bubbles of varying scales and numerous particles. The synergistic bubble-particle effect is reflected in the dual inhibiting or promoting mechanism. Furthermore, while numerical simulations could be realized by coupling cavitation, multiphase flow, and erosion models, their accuracy is not infallible. In the future, the dual role of particles, and particles driven by micro-jets or shock waves should be fully considered when establishing a combined erosion model. In addition, enhancing the influence of flow field and boundary parameters around bubbles and utilizing FSI would improve the predictive accuracy of erosion location and erosion rate. This work helps to elucidate the combined wear mechanism of hydraulic machinery components in sediment-laden flow environments and provides a theoretical basis for the design, manufacture, processing, and maintenance of hydraulic machinery.