滴状模式下液桥形成及断裂的电流体动力学特性研究

对电场作用下微通道荷电液滴脱落过程中液桥形成及断裂的显微演变特征进行了可视化实验研究.借助时空分辨率较高的高速摄像技术精确捕捉了电场作用下液桥形成及断裂的界面演化过程,研究了液桥的界面结构变化及其断裂的动力学显微演变行为,获得了时间特征数、电邦德数及半月面形成角对液桥长度及断裂顺序的作用规律.实验结果显示,液桥断裂长度取决于黏度与表面张力之比,而受荷电弛豫时间的影响甚微,低电压工况下各实验介质液桥相对长度的变化并不明显,而在较高电压工况下相对液桥长度的增长速度加快.随着电邦德数的不断增加,液桥长度的变化在较高邦德数下更为明显且存在突变区,此时伴随着雾化模式的转变,表明液桥的突变恰恰是雾化模式过渡的信号.不同物性介质的射流过渡行为由于液桥上下游形成角的变化而存在较大差异.对于无水乙醇介质,电邦德数的增加使滴状模式首先过渡到纺锤模式,而对于生物柴油,滴状模式后会首先出现脉动模式而非纺锤模式.      

高速逆流色谱分离与鉴定鹿药中黄酮类化合物

采用高速逆流色谱(HSCCC)与其它色谱联用的方法分离纯化鹿药中的化学成分,得到5个黄酮类化合物: 5,7,3′,4′-四羟基-3-甲氧基-8-甲基黄酮(1)、 8-甲基木犀草素(2)、 3′-甲氧基木犀草素(3)、 木犀草素(4)和槲皮素(5),它们均为首次自该种及该属植物中分离得到.HSCCC以V(氯仿)∶ V(甲醇)∶ V(水)=4∶ 3∶ 2混合液为溶剂,上相为固定相,下相为流动相, 分离纯化得到3个分别含化合物1, 4和5的主要部分,经HPLC检验纯度分别为98.3%, 96.7%和95.3%;还有1个含有化合物2和3的较纯部分,通过Sephadex LH-20柱色谱,以V(甲醇)∶ V(水)=1∶ 1混合液洗脱将二者分离.通过理化性质及紫外、红外、质谱、核磁等波谱分析确定化合物结构.     

高速逆流制备分离中药黄柏中的生物碱

 利用高速逆流对传统中药黄柏中的生物碱类活性成分进行了制备分离。两相溶剂分离系统采用氯仿 甲醇 0 5mol/LHCl(体积比为 2∶1∶1) ,并对制备物进行了薄层分析。证实了生物碱成分 ,检出了小檗碱。     

高速开式离心泵内部的流动特性研究

基于N-S方程应用标准的k-ε湍流模型对高速开式离心泵进行三维湍流数值模拟,得到了流道内的压力场、速度场的变化规律,揭示了回流等流动现象,验证了液流冲击、流动不均匀和回流是开式叶轮效率低的主要原因;通过对蜗壳进口速度和压力沿周向分布的分析看出分布呈现明显的波动特征,验证了叶轮与蜗壳的干扰所造成的周向流动的不均匀性是非常强烈的。预测出其性能曲线,计算与试验结果吻合良好,证明该计算方法具有较高的可靠性。     

高速沉积微晶硅薄膜光发射谱的研究

采用PR650光谱光度计对高速沉积微晶硅薄膜的生长过程进行了在线监测研究,并对所对应的材料进行了Raman谱和红外吸收谱(FTIR)的测试.结果表明：能反映材料晶化程度的I_［SiH^*］/I_［Hβ^*］比值在沉积时间为100 s之内有下降的趋势,且反应气体总流量T_fl越小下降趋势越明显,这与拉曼散射光谱对材料的结构测试结果一致;沉积5 min时I 关键词： 高速沉积 微晶硅薄膜 电子温度     

Editorial for Focus Issue on Silicon Photonics

In recent years, ＂nanoscience＂, ＂nanotechnology＂, and ＂nanofabrication＂ have been the focus of the science and technology community in both academia and industry. This technological trend points to a general interest in ever smaller and more compact devices and products. Furthermore, as integrated circuit feature sizes continue to shrink and chip sizes continue to expand, conventional electrical interconnects and switching technologies are rapidly becoming critical issues in device and system integration. New devices, new interconnects, and new integration schemes must be developed to meet the demand for high-density data communication and high-speed data processing.     

High speed sub-micrometric microscopy using optical polymer microlens

We report the high speed scanning submicronic microscopy （SSM） using a low cost polymer microlens integrated at the extremity of an optical fiber. These microlenses are fabricated by a free-radical photopolymerization method. Using a polymer microlens with a radius of curvature of 250 nm, a sub-micrometric gold pattern is imaged experimentally by SSM. Different distances between the tip and the sample are used with a high scanning speed of 200 cm/s. In particular, metallic absorption contrasts are described with an optical spatial resolution of 250 nm at the wavelength of 532 nm. Moreover, finite-difference time-domain （FDTD） simulations concerning the focal lengths of microlenses with different geometries and heights support the experimental data.     

Theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains

One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions.This study conducts theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains.The quasistatic load series that corresponds to quasi-static deformation modes are identified according to the structural form and bearing conditions of high-speed train bogie frames.Moreover,a force-measuring frame is designed and manufactured based on the quasi-static load series.The load decoupling model of the quasi-static load series is then established via calibration tests.Quasi-static load–time histories,together with online tests and decoupling analysis,are obtained for the intermediate range of the Beijing—Shanghai dedicated passenger line.The damage consistency calibration of the quasi-static discrete load spectra is performed according to a damage consistency criterion and a genetic algorithm.The calibrated damage that corresponds with the quasi-static discrete load spectra satisfies the safety requirements of bogie frames.