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61.
Fuquan LI Chunqing WANG Yanhong TIAN 《材料科学技术学报》2006,22(3):392-396
The interracial phenomena of the Sn-Pb solder droplet on and needle-like AuSn4 are formed at the interface after Au/Ni/Cu pad are investigated. A continuous AuSn2 the liquid state reaction (soldering). The interracial reaction between the solder and Au layer continues during solid state aging with AuSn4 breaking off from the interface and felling into the solder. The kinetics of Au layer dissolution and diffusion into the solder during soldering and aging is analyzed to elucidate intermetallic formation mechanism at the solder/Au pad interface. The concentration of Au near the solder/pad interface is identified to increase and reach the solubility limit during the period of liquid state reaction. During solid state reaction, the thickening of Au-Sn compound is mainly controlled by element diffusion. 相似文献
62.
Xiang Ren Jingyuan Sun Zhengliang Huang Yao Yang Sihang Tian Jingdai Wang Yongrong Yang 《American Institute of Chemical Engineers》2020,66(5):e16909
Nowadays, the droplet–particle collision characteristics in the gas-phase ethylene polymerization process are still unclear. The high-speed photography and a quasi-circle imaging approach are employed to study the collision interaction characteristics between liquid droplets and polyethylene particles. The liquid film evolution is studied through variations of the film thickness on the particle north pole, the dynamic contact angle, center angle and film thickness at the maximum extension. Results have found that for n-hexane the threshold temperature of the recoil happening increases with increasing initial Weber number, but for 1-hexene it is stable. Over 70°C evaporation and splash occurs immediately. Under low Weber numbers, the water droplet stays for damping oscillations, the reference stable height of which is linearly related to temperatures. Moreover, three regimes of film thickness variation with time are identified and mathematically described, while Regime 3 characteristics are found strongly dependent on the liquid species, Weber number, and particle temperature. 相似文献
63.
Zhenyu Wu Jinjin Cai Zhonghui Liu Lihang Wu Xiaojiang Liang Qinglong Xie Meizhen Lu Fengwen Yu Yong Nie Jianbing Ji 《American Institute of Chemical Engineers》2020,66(5):e16914
The hydrodynamic cavitation multiphase reactor (HCMR) is emerging as a promising alternative for the intensification of liquid–liquid heterogeneous reactions, but research on HCMR modeling is lacking. In this article, an HCMR model was developed using Prileschajew epoxidation as the model system. First, based on experimental measurements of oil/water two-phase flow downstream of hydrodynamic cavitation devices, semiempirical correlations were proposed to describe the droplet size and droplet size distribution (DSD) as functions of flow conditions and geometry parameters. Then, with boundary conditions calculated by the DSD correlation, a droplet dynamics simulation in a reaction tank was performed by computational fluid dynamics coupled with population balance model to obtain the two-phase interfacial area. Finally, the acquired reactor model was substituted into an overall kinetic model, to simulate the epoxidation reaction in HCMR. Model predictions were verified by experimental results measured on an industrial scale HCMR. 相似文献
64.
This work aims to investigate the unsteady conjugate interphase mass transfer between a stationary deformed drop and the modest extensional flow in a cross-intersected 2D channel. It is very difficult to accurately quantify the transient mass transfer rate of solute in such a geometry. Therefore, we established a mathematical model on the basic of the Stokes equation and solved it by the boundary element method, which could deal precisely with a two-phase flow system with a deformable interface; meanwhile, the convection-diffusion equation was solved by the finite difference method to calculate the unsteady conjugate interphase mass transfer. The simulation results showed that the mass transfer rate, analyzed and characterized in terms of mean concentration variation and Sherwood number Sh, was affected by capillary number Ca, Peclet number Pe, viscosity ratio λ , interior-to-exterior diffusivity ratio K, distribution coefficient m, and wall effect factor W. 相似文献
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66.
为解决某矿破碎筛分车间粉尘污染问题,采用喷嘴雾化理论设计喷嘴雾化降尘实验,并根据实验结果在该矿破碎筛分车间应用了超声雾化降尘技术。实验及应用结果表明:超声雾化发生器的液体雾化装置,气体辅助雾化装置和雾束形成器的几何结构影响喷雾的雾化参数与流量特性,液体雾化器与气体辅助雾化装置影响液体初次破碎与雾化,雾束形成器影响雾滴的二次破碎与约束液束形态;超声雾化发生器的气液比与气液压力比存在幂函数关系,幂指数为-1.09;雾滴粒径越小,雾滴的降尘效率越高,当雾滴D50为23 μm时,雾滴的降尘效率在94%以上;在破碎筛分车间振动筛给料皮带和筛上皮带受料点布置超声雾化发生器,超声雾化发生器开启后,车间内粉尘浓度降低至586~10.54 mg/m3,降尘效率在71.38%以上。 相似文献
67.
液滴特性是影响雾化溶液除湿系统性能的关键因素,但目前适用于该类除湿系统的最佳液滴特性尚不明确。为此,本文基于雾化溶液除湿过程所遵循的质量、能量平衡,借助数值模拟及正交设计,以超声波雾化溶液除湿系统(UADS)为例,对除湿剂液滴在各典型粒径、温度、质量分数等特性组合下的除湿性能进行研究。结果表明:随着液滴粒径的减小、溶液质量分数的增加以及液滴温度的降低,雾化除湿系统性能虽均有所提升,但其改善作用依次减弱;通过正交设计优化液滴特性组合,可显著提升雾化除湿系统性能。与液滴优化前相比,UADS系统在本文所得最适液滴特性下的性能,比传统典型性能(除湿速率为7.5g/s,除湿效率为48.5%)大幅提升,除湿速率提升31.04%,除湿效率改善达24.63%。研究可为雾化溶液除湿系统液滴特性的合理优选,并进一步提高系统的除湿性能及经济性提供积极参考。 相似文献
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69.
Emine Kaplanoglu Igor Kolotilin Rima Menassa Cam Donly 《International journal of molecular sciences》2022,23(7)
Plant-mediated RNA interference (RNAi) holds great promise for insect pest control, as plants can be transformed to produce double-stranded RNA (dsRNA) to selectively down-regulate insect genes essential for survival. For optimum potency, dsRNA can be produced in plant plastids, enabling the accumulation of unprocessed dsRNAs. However, the relative effectiveness of this strategy in inducing an RNAi response in insects using different feeding mechanisms is understudied. To investigate this, we first tested an in vitro-synthesized 189 bp dsRNA matching a highly conserved region of the v-ATPaseA gene from cotton mealybug (Phenacoccus solenopsis) on three insect species from two different orders that use leaf-chewing, lacerate-and-flush, or sap-sucking mechanisms to feed, and showed that the dsRNA significantly down-regulated the target gene. We then developed transplastomic Micro-tom tomato plants to produce the dsRNA in plant plastids and showed that the dsRNA is produced in leaf, flower, green fruit, red fruit, and roots, with the highest dsRNA levels found in the leaf. The plastid-produced dsRNA induced a significant gene down-regulation in insects using leaf-chewing and lacerate-and-flush feeding mechanisms, while sap-sucking insects were unaffected. Our results suggest that plastid-produced dsRNA can be used to control leaf-chewing and lacerate-and-flush feeding insects, but may not be useful for sap-sucking insects. 相似文献
70.