激光诱发荧光漂白测速技术的发展与应用(特邀)

微纳尺度流动现象广泛存在于生命科学、界面科学、微纳芯片技术以及材料科学等领域,微纳流体测速技术是研究微纳尺度流动现象及其应用的基础。本文首先介绍了几种主要的微流体测速技术,包括显微粒子图像速度计、粒子追踪速度计、分子标记速度计、光学相干层析技术、磁共振成像测速技术等。然后,详细介绍一种新型的光学微纳流体速度测量技术——激光诱发荧光漂白测速技术,该技术同时具有非侵入性、远场测速、纳米级高时空分辨率等优点,适应目前微纳流控实际研究中对高时间分辨率和高空间分辨率的迫切需求;重点介绍了基于该技术所取得的一些研究成果,包括对微流体电动力湍流和非线性交流电渗流等非稳态、非线性流动等现象和规律的最新研究成果。最后,对该技术进一步的发展进行了展望。

点焊接头剪切拉伸试验试件临界宽度

通过对比发现电阻点焊剪切拉伸试验关于试样尺寸的标准并不统一.以普通的Q235镀锌钢为材料进行电阻点焊接头的剪切拉伸试验,检测了点焊接头抗拉载荷及其对应的引伸计位移量(抗拉位移)和失效吸收能随试件宽度的变化趋势,并从力学角度解释了产生这种变化趋势的原因.结果表明,这3个检测量趋于恒定时宽度对应着一致的临界值.如果试样宽度不足,试件变形使熔核旋转过量产生正向拉伸的分力,导致测量结果小于接头实际抗剪拉伸强度.

Efficient Thickness of Solid Oxide Fuel Cell Composite Electrode

The efficient thickness of a composite electrode for solid oxide fuel cells was directly calculated by developing a physical model taking into account of the charge transfer process, the oxygen ion and electron transportation, and the microstructure characteristics of the electrode. The efficient thickness, which is defined as the electrode thickness corresponding to the minimum electrode polarization resistance, is formulated as a function of charge transfer resistivity, effective resistivity to ion and electron transport, and three-phase boundary length per unit volume. The model prediction is compared with the experimental reports to check the validity. Simulation is performed to show the effect of microstructure, intrinsic material properties, and electrode reaction mechanism on the efficient thickness. The results suggest that when an electrode is fabricated, its thickness should be controlled regarding its composition, particle size of its components, the intrinsic ionic and electronic conductivities,and its reaction mechanisms as well as the expected operation temperatures. The sensitivity of electrode polarization resistance to its thickness is also discussed.