微管道气体流动的蒙特卡洛直接模拟

采用蒙特卡洛直接模拟(DSMC)方法,数值模拟了微管道中压力驱动的气体流动,结果表明固壁边界存在速度滑移,稀薄气体效应明显;整个流场温度变化很小,流动马赫数很小,密度、压力流向变化非常大而横向几乎不变;可压缩性导致压力随流向的非线性分布,但这种效应随Knudsen数增大而减弱.     

Erratum to “Simultaneous effects of magnetic field and space porosity on compressible Maxwell fluid transport induced by a surface acoustic wave in a microchannel”

We would like to acknowledge the misprinted terms in our published paper “Simultaneous effects of magnetic field and space porosity on compressible Maxwell fluid transport induced by a surface acoustic wave in a microchannel” [Chin. Phys. B 22 124702 (2013)]. Since only two misprints exist and the main results of the published paper are correct, we present the correct equations in this erratum.     

微通道板玻璃的电阻率

叙述微通道板玻璃的电阻率和其氢原处理后的表面电阻率以及表面电阻率的影响因素。按照玻璃钢络结构观点并就微通道板制造工艺中出现的电阻率差异进行了分析。最后，给出了改进措施。     

A position- and time-sensitive particle detector with subnanosecond time resolution

A microchannel plate/CCD-camera particle detector is described that utilises gold strips deposited upon the surface of a MCP to provide particle arrival time information. The uncertainty in the timing is assessed to be ∼500 ps (FWHM) for a measured time interval between adjacent strips. The main contribution of which is the result of the slow response time of the CFD compared to the signal. The application of timing measurement is shown to be of particular benefit in the accurate determination of product state branching ratios from the dissociative recombination of diatomic ions. Finally, the possibilities of such a detector are assessed. This revised version was published online in July 2006 with corrections to the Cover Date.     

微槽内二元混合液体的流动沸腾

1引言微型结构由于其巨大的应用潜力，作为热控制和冷却的有效手段已被引入电子集成电路、生物医学、航天、高效紧凑式与微型换热器、材料加工等现代高新技术领域。由于相交换热能传递更多的热量，微结构中的流动沸腾受到了日益重视。但微通道中流体流动和换热的特性当然与所用工质有关。微通道内液体混合物的流动沸腾至今极少见到公开报道［‘］。彭和王等人l‘－‘］报道了对微通道和微槽结构内单组元液体流动沸腾的研究，发现起始沸腾点所需壁面过热度比常规尺度槽道内的低得多，没有明显的部分核沸腾现象，同时发现微槽尺寸对流动沸腾的…     

国外图像光子计数系统的现状及发展

本文重点叙述国外图像光子计数探测系统的发展现状和未来趋势，以及高增益微通道板（ＭＣＰ）的最新进展。     

长微直管内气体低速流动的亚堵塞现象

长微直管道内多流态并存的流动特性研究不仅有理论意义，而且在太空飞行器的控制系统中有着重要的应用价值.采用实验研究和理论模型近似分析相结合的方法研究了长微直管道内的气体流动特性.实验中，以空气为工作介质，进口压力分别设定为130，250，320kPa，出口压力变化范围为9—100?kPa.沿程分布有五个测压点，进出口设有温度传感器，测量出口流量的同时可以得到沿程压力分布.近似理论模型采用二维平板近似模型.研究发现，在保持进口压力不变、不断降低出口压力的条件下，当进出口压比低于5.3左右时，质量流量随压比增加 关键词： 长微直管道 亚堵塞 表面积与体积比 多流态并存 临界压比     

混合微通道中不稳定的广义Couette流

在一个平行板通道中,部分充满了均匀的多孔介质,部分为纯流体的流动区,对其微通道中完全发展的不稳定层流进行了数值分析,流动由其中一块板的运动和压力梯度所引起.多孔介质区域的流动,采用扩展的Brinkman模型,即Darcy模型,纯净流动区域的流动,采用Stokes方程.还对稳定的完全发展流进行了理论分析,给出了分界面速度、边界板处的速度和表面摩擦的闭式解.通过数值计算发现,稳定完全发展流的闭式解,和不稳定流动的数值解,在所有时间点上得到很好地吻合.     

Flexible particle flow‐focusing in microchannel driven by droplet‐directed induced‐charge electroosmosis

We report herein a novel microfluidic particle concentrator that utilizes constriction microchannels to enhance the flow‐focusing performance of induced‐charge electroosmosis (ICEO), where viscous hemi‐spherical oil droplets are embedded within the mainchannel to form deformable converging‐diverging constriction structures. The constriction region between symmetric oil droplets partially coated on the electrode strips can improve the focusing performance by inducing a granular wake flow area at the diverging channel, which makes almost all of the scattered sample particles trapped within a narrow stream on the floating electrode. Another asymmetric droplet pair arranged near the outlets can further direct the trajectory of focused particle stream to one specified outlet port depending on the symmetry breaking in the shape of opposing phase interfaces. By fully exploiting rectification properties of induced‐charge electrokinetic phenomena at immiscible water/oil interfaces of tunable geometry, the expected function of continuous and switchable flow‐focusing is demonstrated by preconcentrating both inorganic silica particles and biological yeast cells. Physical mechanisms responsible for particle focusing and locus deflection in the droplet‐assisted concentrentor are analyzed in detail, and simulation results are in good accordance with experimental observations. Our work provides new routes to construct flexible electrokinetic framework for preprocessing on‐chip biological samples before performing subsequent analysis.     

矩形微通道中环状冷凝的数值模拟

建立了一套恒热流边界条件下矩形微通道内环状冷凝过程的一维稳态模型,进行了数值计算,并将数值模拟结果与正三角形中的冷凝过程进行了比较.研究显示,在不同截面的微通道中,液相毛细半径和流速的沿程变化趋势都是相似的.同条件下,矩形通道的冷凝段长度大于正三角形通道.在矩形微通道中,通道入口蒸气压力和水力直径越大或者接触角越小,则冷凝段长度越长.