剪切稀化流体中微粒子聚集行为研究

在化工过程、生物工程等领域中,实现颗粒分离至关重要。通过整合微流控技术、高速显微图像采集技术和数字图像处理技术,探究微粒尺寸、通道流量和液相流变特性对微粒聚集的影响规律。结果表明,在剪切稀化流体羧甲基纤维素钠(CMC)水溶液中,随着通道流量和颗粒粒径增大,微颗粒聚集位置逐渐向剪切速率较高的一侧偏移;随着CMC质量分数增加,聚集位置不断向剪切速率较低的一侧偏移。利用求解的幂律型剪切稀化流体速度和剪切速率方程,结合对微颗粒的受力分析,证明稠度系数越大,聚集位置越偏向剪切速率较低处;剪切稀化特性越强,聚集位置越偏向剪切速率较高处,说明在幂律型剪切稀化流体中的黏度变化是微颗粒发生特殊迁移聚集行为的一个重要原因。     

IMPELLER CLEARANCE EFFECT ON OFF BOTTOM PARTICLE SUSPENSION IN AGITATED VESSELS

The effect of impeller off bottom clearance on the power input requirement for off bottom solid suspension was examined for 45° pitched blade impellers in flat and round bottom fully baffled agitated vessels. Results showed a similar dependence as obtained for radial flow impellers when similar flow patterns were observed. The dependence appears to be independent of the impeller diameter to tank diameter ratio and vessel shape.     

膨胀石墨烟幕发生装置烟流颗粒运动规律与试验研究

针对膨胀石墨设计了一种简易烟幕发生装置,该装置利用烟火药燃烧时释放出的热量使可膨胀石墨膨化并分散于空中,形成膨胀石墨干扰烟幕。基于该装置建立了烟流颗粒(膨胀石墨颗粒)扩散规律的理论计算模型,对烟幕发生剂反应参数与烟流颗粒运动规律进行计算,得到烟流颗粒的运动方程。同时,对该装置进行了试验研究,并通过高速摄影记录烟流颗粒运动规律,试验结果表明烟流颗粒理论运动规律与试验结果相符,能够描述烟流颗粒的运动规律。     

Underlying reasons for waxy rice flours having different pasting properties

The underlying reasons for three waxy rice varieties, Yang-fu-nuo (Y), Su-yu-nuo (S), and Guang-ling-xiang-nuo (G), having different flour pasting properties were examined. The pasting properties of the isolated waxy rice starches did not correlate with those of the corresponding waxy rice flours. Examining the pasting properties of the flours in 0.5 mM AgNO₃ solution, treated with dithiothreitol and protease, suggested that rice protein and amylase activity were the main causes of the pasting property differences among the rice starches and flours. Starch isolated from Y flour had a larger proportion of A and B₁ chains, longer average chain length and longer exterior chain length, which explained its higher gelatinisation temperature, higher pasting consistency, greater extent of retrogradation, and the firm texture of cooked Y rice.     

精糖生产过程中的脱色研究

选用二种脱色剂和三种絮凝剂，结合气浮提纯分离技术，运用正交试验方法，对精糖生产过程糖汁的脱色进行了对比研究，以达到优化工艺参数和指标的目的。结果表明，选用TR型脱色剂和TALODURA型絮凝剂对脱色和降低混浊度效果最好，清汁脱色率可达到65．74％，混浊度降低率可达到72．05％。     

PVC dust removal from the air by a new dynamical scrubber

Removal of the poly vinyl chloride (PVC) dust particles by a new dynamical scrubber in a PVC manufacturing plant is presented in this work. The effects of inlet air flow rate (containing PVC particles) and water flow rate (the physical absorber of particles) on the PVC dust removal efficiency were investigated. The size of the PVC particles which have been treated in this study was ranging from 0.5 up to 20 μm. The experimental results showed approximately 100% removal efficiency for particles larger than 1 μm and 73% for 0.5 μm particles while employing low water flow rates. The results of these experimental tests indicate a good performance of the scrubber in a short residence time (about 2 s) which is also completely economic for removing fine particles.     

高速精密轧辊磨头液体止推轴承油膜性能的数值分析

高速精密轧辊磨头止推轴承的性能是影响轧辊磨床加工稳定性和精度的重要因素。Roynolds方程是滑动轴承油膜压力计算的基础,文中基于有限差分法,对Roynolds方程进行量纲一化处理,并借助MATLAB软件强大的符号运算、数值计算及图形可视化处理功能,进行编程计算,求解了高速精密轧辊磨头止推轴承油膜的完整二维流动Roynolds方程。求解结果表明:液体静压止推轴承具有很高的承载能力和较高的油膜刚性,保证了磨头主轴的旋转精度和运动精度。研究结果对于高速轧辊磨床的整体设计具有一定的参考价值。     

高速切削机床主轴轴承的研究与发展

基于高速切削中高速机床主轴用轴承的运动机理，本文着重从润滑、密封、预紧等方面阐述了滚动轴承的研究与发展，并明确了其与工程应用的关系。     

Synthesis of CeO2 nanoparticles by rapid thermal decomposition using microwave heating

Abstract

This article describes the synthesis of a CeO₂ fine powder by thermal decomposition of cerium oxalate and cerium nitrate powders using a microwave furnace. Plate-like crystalline CeO₂ particles were obtained using the cerium oxalate precursor powder. Using the cerium nitrate powder as a precursor, spherical crystalline CeO₂ particles were obtained with a primary particle diameter of 30?nm and secondary particle size of 550?nm.     

无机超细粒子表面改性技术研究进展

综述了无机超细粒子表面改性技术研究现状;重点介绍了局部化学反应改性和表面包覆改性.其中局部化学反应改性又包括偶联剂处理改性、与脂肪酸或醇反应改性和表面接枝聚合改性等.