我们要感谢国家科学基金会资助CMMI＃1126862资助的设备和开发的合成孔径算法在杨百翰大学，在内部实验室的独立研究（伊利尔·）的资金（监测博士托尼Ruffa），为的设备提供资金和发展NUWC纽波特和美国国立卫生研究院/ NIDCD的授予R01DC009616为SLT，DJD和JRN资金和相关的数据声带实验和埃尔兰根大学的研究生院在先进光学技术（SAOT）SLT部分支持。最后，落基山美国宇航局太空格兰特财团的资金JRN。

1。三维光场的成像设置<ol><li>首先通过确定的测量体积的大小以及调查正在研究流体流动实验所需的时间和空间分辨率。 </li><li>估计的光学密度，这将是本实验中，以确定，以产生良好的信号-噪声比（SNR）1，2（ 例如用于PIV 1应计算每个像素的粒子）的重新聚焦的图像所需的摄像机的数量。对于与本文提出的合成声带的的3D SAPIV实验中，我们使用8个摄像头，并期望实现接种密度为0.05-0.1颗粒每像素（的ppp）。此数目增加，越来越多的收益递减的摄像头，达到了约13台摄像机的信噪比迅速降低，低于5相机。 </li><li>挂载相机以阵列配置的框架上，使得每个相​​机可以查看从不同视点的测量体积。</li><li>将摄像机一台中央计算机数据采集和查看。 </li><li>选择适合所需的放大倍数和光学工作距离与焦距的镜头。通常，相同类型的固定焦距镜头被安装到每个摄像机，在每个图像中，以产生类似的放大倍率。 </li><li>放置一个可视目标（如校准网格）中的测量体积的中心。 </li><li>使用该图像从作为参考的阵列的中心相机，移动的整个相机阵列帧更近或更远的测量体积，以达到所需的倍率。 </li><li>接着，数组中分离剩余的相机。间距彼此分开更远的相机在总解析的深度为1的成本，提高了空间分辨率的深度维度中。注意：我们使用深度指于Z的尺寸，这是正朝向照相机（参见图1）。深度的比率在- 图面的分辨率的约<img alt="式（1）" fo:src="/files/ftp_upload/4325/4325eq1highres.jpg" src="/files/ftp_upload/4325/4325eq1.jpg" /> ， 其中 Z是在卷中的深度，S O是摄像机的距离的前方的体积，和D的摄像机间距的比率是S O。 </li><li>角度，使得可视目标的测量体积的中心在大约集中在每个摄像机图像的所有摄像机。 </li><li>孔完全开放的每个镜头，每个相机对焦的视觉目标。 </li><li>将在后面的测量体积的校准目标。确保目标是在视图中的每个摄像机;如果它不是，则相机和测量体积和/或相机间距需要调节（步骤1.7-1.8）之间的距离。 </li><li>关闭每个摄像机的光圈，直到目标是在每个相机对焦。 </li><li>重复步骤1.11-1.12的目标在t他前面的测量体积。校准目标应该出现类似于图2的每个摄像机后调整。 </li></ol> 2。音量照明设置<ol><li>确定照亮被施加到的流场的具体的测量方法的基础上的测量体积的适当的方法。对于粒子图像测速（PIV）的激光量。 </li><li>选择激光的脉冲率，可以实现所需的时间分辨率的测量。激光可以单时间分辨脉冲或双脉冲帧跨越3。 </li><li>使用光学透镜，以形成激光束到一个光量，涵盖了测量体积。 </li><li>种子量的示踪粒子，适用于PIV测量3。流体中的颗粒的浓度应足够大，以达到所需的空间分辨率，但也不能太大，以减少的SNRSA重新调整图像低于可接受的水平。参考文献1实现的接种密度，包含了深入研究，但作为一个经验法则的0.05-0.15的颗粒每像素的图像密度（ppp的）是合适的具有8个或更多个摄像机的大部分实验。对于一个固定的摄像机数量，每像素的粒子的体积较大，深度尺寸减小。 </li></ol> 3。摄像机阵列校准<ol><li>校准需要在每个摄像机拍摄的一系列图像的校准目标（ 例如棋盘格，参见图2）在整个测量体积的多个位置。首先，选择两种类型的校准：要么多摄像机自标定方法或成像校准目标，通过精确地移动领域的兴趣。 </li><li>建立一个参考坐标系中的测量体积。通常，此坐标系中选择的方式是有关f或实验（ 例如，与气缸的轴线对齐，原在前缘处的平板等）。在这里，我们选择了我们的格点放置在XY平面内沿Z轴（ 图1）的点上对齐。 </li><li>如果使用多相机自校准算法4，5的校准目标的位置可以是随机的，除了在参考坐标系中的一个位置，精确地定位。在此精确定位的目标必须是已知的校准点的位置，精度高。在每次摄像时，捕获的目标的图像，在每个位置，类似于图2。 </li><li>如果不使用多相机自校准算法，然后校准目标必须被精确地放置在多个位置中，使得在参考坐标系中的目标的方向是已知的以高准确度在测量体积。在每次摄像时，捕获的图像中的目标的每个位置。</li><li>确定在每个摄像机的每个图像对目标点。自校准，在所有摄像机的图像点的对应5，但只需要明确的引用到的图像点的对应点的精确定位目标。对于精确走过的校准方法，明确的参考图像点的对应所需要的所有相机中的所有点。 </li><li>应用所选择的校准所有的摄像机校准算法。在这里，我们选择了利用多摄像机自标定算法4，第5（开源<a href="http://cmp.felk.cvut.cz/~svoboda/SelfCal/" target="_blank">http://cmp.felk.cvut.cz/〜自由报/ SelfCal的/</a> ）和相机的相对位置对飞机的兴趣如图3中所示。 </li></ol> 4。定时，触发和数据采集<ol><li>定量，时间分辨光场成像要求所有的cameras和照明光源要精确地同步，往往到相关实验事件。 </li><li>外部脉冲发生器用于触发摄像机的暴露和照明序列。编程适当的定时脉冲序列的脉冲发生器上。对于声带实验中，我们使用的帧跨越的序列，从而使激光脉冲接近的一个相机的曝光结束，并开始下一个3附近。 </li><li>如果从一个实验性的事件触发时，确保一个适当的信号，生成并输入到脉冲发生器。 </li><li>如果手动触发，触发脉冲发生器的规定。 </li><li>开始实验数据的采集，通过选择触发方式启动摄像头的捕获和照明序列。 </li><li>虽然听起来微不足道，获取大量的数据与多相机的光场成像实验时，一个良好的命名约定是CRUCIAL。考虑数据将如何使用从捕捉到最后分析发展中的命名约定时，它是有帮助的。 </li></ol> 5。合成孔径归核化<ol><li>现在，我们将产生一个三维的焦点堆栈的图像产生一个综合的重新调整音量。首先，定义焦平面之间的间距和整体再聚焦深度，以在重新调整量的使用<img alt="式（1）" fo:src="/files/ftp_upload/4325/4325eq1highres.jpg" src="/files/ftp_upload/4325/4325eq1.jpg" /> 1，7。通常，焦平面间距被设置为一半的深度分辨率，总的再聚焦深度受该区域的所有相机视图重叠领域。的焦平面将垂直于Z轴的基准坐标系统。 </li><li>定义的规模后应用至图像重投影到测量体积。与原始图像的放大倍率的规模应该是一致的，为了避免显着的重投影图像的过采样或欠采样。 </li><li>建立每个摄像机的图像平面，每个合成焦平面之间的转换。 </li><li>执行图像的预处理，以消除背景噪音和适应图像，在强度之间的差异。 </li><li>重投影到合成焦平面的图像，应用的规模和重新采样的图像。一组内置在Matlab功能（图像处理工具箱）可以处理这些任务的平面，平面转换。 </li><li>在每个合成焦平面上，适用的加法或乘法SA重新定位算法1中，7。对于3D SAPIV应用，取得了很好的成功与添加剂SA（适用于声带）。乘法SA对于背光泡泡的图像，已经取得了骄人的业绩。作为检查应用的再聚焦到一个平面上的校准图像，看是否出现重建如预期。 </li&gt; </ol> 6。卷后处理<ol><li>为了估计原始物体上产生的光场的体积称为重建需要的处理步骤。一些算法存在从简单的强度阈值1基于梯度的重点指标，以更复杂的三维反褶积8。选择适合于应用程序将重构算法。对于PIV，我们已经成功地与强度阈值和三维反褶积。我们使用强度阈值，在这里形成一个焦点堆栈。从时间1（t 1）和时间2（t 2的 ）的两个焦点堆栈是互相关的，形成的矢量场。三维光场成像方法本身的对象，结果是细长的深度尺寸，这会影响PIV的精度，良好的重建算法试图减轻这种延伸。 </li><li>后重建的步骤，在该卷的功能可能需要或当然吸引到允许测量的大小，形状，等用于特征提取的算法是多种多样的，并依赖于应用程序7。要提取气泡，例如，需要化气泡的功能和定义它们的大小的一种手段。的PIV应用中，我们不显式提取颗粒和这一步可以跳过。 </li><li>对于3D SAPIV应用程序，解析重建审讯卷成更小的体积并施加适当的基于互相关的PIV算法测量的矢量场1，3。 </li></ol> 一个 maketform：构造一个平面的平面变换imtransform的：地图和重新采样图像的基础上的转换maketform。

<ol>
	<li>Belden, J., Truscott, T. T., Axiak, M., Techet, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+synthetic+aperture+particle+imaging+velocimetry.">Three-dimensional synthetic aperture particle imaging velocimetry.</a> Measurement Science and Technology. 21 (12), 125403 (2010).</li><li>Wilburn, B., Joshi, N., Vaish, V., Talvala, E. -. V., Antunez, E., Barth, A., Adams, A., Horowitz, M., Levoy, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+performance+imaging+using+large+camera+arrays.">High performance imaging using large camera arrays.</a> ACM Trans. Graph. 24, 765-776 (2005).</li><li>Raffel, M., Willert, C., Wereley, S., Kompenhaus, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Particle image velocimetry - A Practical Guide. , (2007).</li><li>Belden, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Auto-Calibration+of+Multi-Camera+Systems+with+Refractive+Interfaces.">Auto-Calibration of Multi-Camera Systems with Refractive Interfaces.</a> Experiments in Fluids. , (2013).</li><li>Svoboda, T., Martinec, M., Pajdla, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+convenient+multi-camera+self-calibration+for+virtual+environments.">A convenient multi-camera self-calibration for virtual environments.</a> PRESENCE: Teleoperators and Virtual Environments. 14 (4), 407-422 (2005).</li><li>Vaish, V., Garg, G., Talvala, E., Antunez, E., Wilburn, B., Horowitz, M., Levoy, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthetic+aperture+focusing+using+a+shear-warp+factorization+of+the+viewing+transfor.">Synthetic aperture focusing using a shear-warp factorization of the viewing transfor.</a> 3, 129 (2005).</li><li>Belden, J., Ravela, S., Truscott, T. T., Techet, A. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-Dimensional+Bubble+Field+Resolution+Using+Synthetic+Aperture+Imaging:+Application+to+a+Plunging+Jet.">Three-Dimensional Bubble Field Resolution Using Synthetic Aperture Imaging: Application to a Plunging Jet.</a> Experiments in Fluids. , (2012).</li><li>Levoy, M., Ng, R., Adams, A., Footer, M., Horowitz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+field+microscopy.">Light field microscopy.</a> ACM Transactions on Graphics. 25 (3), (2006).</li><li>Triep, M., Br&#252;cker, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+nature+of+the+glottal+jet.">Three-dimensional nature of the glottal jet.</a> Journal of the Acoustical Society of America. 127, 1537-1547 (2008).</li><li>Elsinga, G., Scarano, F., Wieneke, B., van Oudheusden, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tomographic+particle+image+velocimetry.">Tomographic particle image velocimetry.</a> Experiments in Fluids. 41, 933-947 (2006).</li></ol>

我们什么都没有透露。

有几个步骤是正确执行的光场成像实验的关键。镜头选择和照相机的位置应慎重选择，测量体积内最大限度的决议。校准也许是最关键的一步，SA重新定位算法，将无法产生清晰的图像，而无需精确的校准。幸运的是，多摄像机自标定的努力与相对较低的水平，有利于精确的校准。均匀照明中的所有图像提供了良好的对象的兴趣和背景之间的对比度也是必要的，虽然图像处理可以在一定程度上正常化的图像。 SA的卷上有移动的物体时，时机也是很重要的。如果还没有触发每个相机拍摄图像，在相同的时间，图像重建显然将是不准确的。对于本文的实验中，我们利用时间序列s在图7 hown。 本文提出的三维光场成像应用涉及权衡的空间分辨率。例如，3D SAPIV可以从光密粒子图像重建颗粒量，但分布在一个潜在的大体积的粒子。对于二维PIV，粒子分布在薄的片材，从而具有相同的颗粒密度的图像对应到一个更大的测量体积密度。然而，的3D SAPIV方法允许更大的播种密度，其他的3D PIV方法1。另一个潜在的限制的考虑是比较大的计算强度与光场成像方法的计算复杂度是典型的基于图像的三维重建方法，如断层-PIV 10。 在这个实验中，我们使用了8 Photron SA3配备了适马105毫米微距镜头的相机和Quantron九，双达尔文的Nd：YLF激光（532纳米，200兆焦耳）。相机和激光同步时通过一个伯克利Nucleonics公司575 BNC数字延迟/脉冲发生器。接种的Expancel氦填充玻璃微球中的流体流动。的微球的平均直径为70μm，其密度为0.15克/立方厘米。本文所用的代码为学术界通过我们的网站<a href="http://www.3dsaimaging.com/" target="_blank">http://www.3dsaimaging.com/</a>我们提供的开源版本，我们鼓励用户向我们反馈和参与的改善和的定量光场社区提供有用的代码。

determining 3d flow fields via multi-camera light field imaging

在该领域的流体力学，计算计划的决议已经超过了实验方法和流体流动的预测和观察到的现象之间的差距扩大。因此，需要存在一个可访问的方法，其能够解决的问题的范围内的三维（3D）数据集。我们提出了一种新颖的用于许多类型的流场进行定量的三维成像的技术。 3D技术使复杂的速度场和泡状流的调查。这些类型的测量提出了各种仪器的挑战。比如，光密气泡多相流动不能很容易地由传统的，非侵入性的流量测量技术，由于阻断光接入感兴趣的体积的内部区域的气泡成像。我们能够通过利用光场成像，尽管每次实例，重建一个三维立体地图数组的摄像头捕捉到的图像进行重新参数化卷中的部分遮挡。该技术使得被称为合成孔径（SA）的再聚焦，由此所产生的多个摄像机的图像相结合的后捕捉1的3D焦点堆栈的算法的使用。光场成像可以捕捉的角度以及光线的空间信息，从而使3D场景重建。定量信息，然后可以提取从3D重建，使用各种不同的处理算法。特别是，我们已经开发了基于光场成像技术进行三维粒子图像测速（PIV），在3D领域中提取气泡和跟踪的边界闪烁的火焰的测量方法。我们提出的背景下，我们设置的气流经过合成声带的一组执行3DPIV的光场成像方法的基本原理，并显示出有代表性的一个的泡沫引气暴跌喷气技术的应用。

采用高品质原材料的PIV图像中含有均匀分布的颗粒出现高反差的黑色背景（ 图4a）。为了弥补在图像中的非均匀的照明，影像前处理，可以进行删除明亮的区域，调整对比度和规范的强度直方图在所有的图像从所有的摄像机（ 图4b）。当实验接种到适当的密度，并进行精确的校准，SA重新聚焦的图像将显示在每个深度的平面（ 图5）上的焦点颗粒。如果测量体积过种子，将在重新调整的图像的信噪比低，使得难以重建的颗粒。 SA的重新调整保留每个深度的平面上的焦点颗粒，可以具有良好的信噪比的图像阈值， 图6示出了来自两个时间的步骤在Z = -10.6毫米深度平面的两个阈值处理的图像。阈值VOlume明然后解析成讯问的卷，其中包含有足够数量的颗粒用于执行PIV 3。施加3DPIV算法所解析的量的产生的流体的速度场， 图7中所示，在这种情况下，流场是诱导模型声带。以外的射流的流场的速度是非常小的，因此很少的载体，可以看出，在这个区域之外。在t = 0毫秒声带关闭，并在该领域是非常小的速度。在喷射的最大速度在t = 1毫秒在y的正方向上移动，并减少强度从t = 2至4毫秒。在t = 5毫秒的折叠闭合降低射流速度和周期重复。这些图像没有相同的平滑度，许多以前的作家谁目前100平均图像的每一个表示速度场的一个快照的时间。作为一个参照点，以前的模拟显示出典型的错误计算ð速度在每个速度分量，其中包括从PIV算法本身1的错误;为我们所使用的算法（MatPIV 11适于为3D）为5-10％的顺序上，该错误是已知的相比相对较大其他代码。 泡状流是另一个领域的科学兴趣，可以受益于光场成像的3D功能。可以类似地应用于对SA技术的多泡流场，其中激光与弥漫性白色背光，从而导致在图8a中所示，其中的气泡的边缘对白色背景上出现暗的图像，如替换。自校准后，乘法的SA算法的变体可以被应用于与清晰地聚焦于气泡的深度相对应的深度平面和模糊其它平面上从视图的气泡以产生焦点堆栈，如在图8b-D所示7。简单的阈值是不利用足够的泡沫，而不是一系列先进的特征提取算法提取方法详细7。 <img src="/files/ftp_upload/4325/4325fig1.jpg" alt="图1" /> 图1。摄像机的图像和标签的声带和坐标系。 <img src="/files/ftp_upload/4325/4325fig2.jpg" alt="图2" /> 图2：在Z = 0毫米。校准网格从所有8个摄像机。 <img src="/files/ftp_upload/4325/4325fig3.jpg" alt="图3" fo:content-width="2.5in" fo:src="/files/ftp_upload/4325/4325fig3highres.jpg"/> 图3。托普维尤的相机设置多摄像机自标定输出。相机1-8位数字和圆，与一般观看的directioŇ由一条线表示。原点附近的红色斑点实际上是从在每个Z深度绘制在3D相对于摄像机的校准网格的400 +点。 <img src="/files/ftp_upload/4325/4325fig4.jpg" alt="图4" /> 图4。信息从相机查看过的＃6在t 1和t 2（a和b）的粒子场的图像。相同的图像预处理后（C＆D）。 <img src="/files/ftp_upload/4325/4325fig5.jpg" alt="图5" /> 图5。从左至右依次为：原始的重新调整SAPIV图像深度（一）Z = -5.9毫米，（B）-10.6毫米-15.3毫米（C）。 <img src="/files/ftp_upload/4325/4325fig6.jpg" alt="图6" /> 图6。ThreshoLDED在时间的图像的步骤（A）T 1和（b）t 2的期间，在Z = -10.6毫米。 <img src="/files/ftp_upload/4325/4325fig7.jpg" alt="图7" fo:content-width="5.25in" fo:src="/files/ftp_upload/4325/4325fig7highres.jpg"/> 图7。创建的合成声带的6个时间步长的喷射流的三维矢量场。的左手侧示出的整个三维速度场的等轴测图。如上面指出的每一列，是通过中心的声带的xy平面和yz平面的削减。 <img src="/files/ftp_upload/4325/4325fig8.jpg" alt="图8" /> 图8。从左至右依次为：原始图像的气泡流场的摄像机阵列，并重新调整图像的深度（B）Z = -10毫米，（C）0毫米（D）10毫米。圈突出了泡沫，是Z = -10毫米深的平面，和从其他飞机上消失。气泡的详细实验，可以发现在4。

Watch this Scientific Journal Video about Determining 3D Flow Fields via Multi-camera Light Field Imaging at JoVE.com

Determining 3D Flow Fields via Multi-camera Light Field Imaging

提出的范围内的流体流动进行定量的三维（3D）成像的技术。光场成像领域的概念，我们从数组中的图像三维重建卷。我们的3D效果涵盖广泛，包括速度场和多阶段的气泡尺寸分布。

通过多摄像头的光场成像的三维流场测定

In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and ...

determining-3d-flow-fields-via-multi-camera-light-field-imaging

Research

Education

JoVE Core

JoVE Journal

Civil Engineering

Engineering

Unit 1

Differential Analysis of Fluid Flow

SCIENTISTS IN ACTION

16.5K 次观看.  Brigham Young University. 提出的范围内的流体流动进行定量的三维（3D）成像的技术。光场成像领域的概念，我们从数组中的图像三维重建卷。我们的3D效果涵盖广泛，包括速度场和多阶段的气泡尺寸分布。

视频: Determining 3D Flow Fields via Multi-camera Light Field Imaging

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses triangulation between matching points in two views of the same scene at different angles to compute depth.&#160;However, unlike a stereo-based method, DFP uses a digital video projector to replace one of the cameras1. The projector rapidly projects a known sinusoidal pattern onto the subject, and the surface of the subject distorts these patterns in the camera&#8217;s field of view. Three distorted patterns (fringe images) from the camera can be used to compute the depth using triangulation.
Unlike other 3D measurement methods, DFP techniques lead to systems that tend to be faster, lower in equipment cost, more flexible, and easier to develop.&#160;DFP systems can also achieve the same measurement resolution as the camera.&#160;For this reason, DFP and other digital structured light techniques have recently been the focus of intense research (as summarized in1-5). Taking advantage of DFP, the graphics processing unit, and optimized algorithms, we have developed a system capable of 30&#160;Hz 3D video data acquisition, reconstruction, and display for over 300,000 measurement points per frame6,7.&#160;Binary defocusing DFP methods can achieve even greater speeds8.
Diverse applications can benefit from DFP techniques. Our collaborators have used our systems for facial function analysis9, facial animation10, cardiac mechanics studies11, and fluid surface measurements, but many other potential applications exist.&#160;This video will teach the fundamentals of DFP techniques and illustrate the design and operation of a binary defocusing DFP system.

This video describes the fundamentals of digital fringe projection techniques, which provide dense 3D measurements of dynamically changing surfaces.&#160;It also demonstrates the design and operation of a high-speed binary defocusing system based on these techniques.

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses ...

科研

工程学

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

The robust device design of fringing-field electrostatic MEMS actuators results in inherently low squeeze-film damping conditions and long settling times when performing switching operations using conventional step biasing. Real-time switching time improvement with DC-dynamic waveforms reduces the settling time of fringing-field MEMS actuators when transitioning between up-to-down and down-to-up states.

实时直流偏置的动态法切换时间改善严重欠阻尼边缘化场静电MEMS致动器

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input ...

Data Acquisition Protocol for Determining Embedded Sensitivity Functions

The effectiveness of many structural health monitoring techniques depends on the placement of sensors and the location of input forces. Algorithms for determining optimal sensor and forcing locations typically require data, either simulated or measured, from the damaged structure. Embedded sensitivity functions provide an approach for determining the best available sensor location to detect damage with only data from the healthy structure. In this video and manuscript, the data acquisition procedure and best practices for determining the embedded sensitivity functions of a structure is presented. The frequency response functions used in the calculation of the embedded sensitivity functions are acquired using modal impact testing. Data is acquired and representative results are shown for a residential scale wind turbine blade. Strategies for evaluating the quality of the data being acquired are provided during the demonstration of the data acquisition process.

The data acquisition procedure for determining embedded sensitivity functions is described. Data is acquired and representative results are shown for a residential scale wind turbine blade.

数据采集​​协议确定嵌入式灵敏度功能

The effectiveness of many structural health monitoring techniques depends on the placement of sensors and the location of input forces. Algorithms for ...

Hand Controlled Manipulation of Single Molecules via a Scanning Probe Microscope with a 3D Virtual Reality Interface

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building blocks in a bottom-up approach is still open. The scanning probe microscope (SPM) could be a tool of choice; however, SPM-based manipulation was until recently limited to two dimensions (2D). Binding the SPM tip to a molecule at a well-defined position opens an opportunity of controlled manipulation in 3D space. Unfortunately, 3D manipulation is largely incompatible with the typical 2D-paradigm of viewing and generating SPM data on a computer. For intuitive and efficient manipulation we therefore couple a low-temperature non-contact atomic force/scanning tunneling microscope (LT NC-AFM/STM) to a motion capture system and fully immersive virtual reality goggles. This setup permits &#34;hand controlled manipulation&#34; (HCM), in which the SPM tip is moved according to the motion of the experimenter&#39;s hand, while the tip trajectories as well as the response of the SPM junction are visualized in 3D. HCM paves the way to the development of complex manipulation protocols, potentially leading to a better fundamental understanding of nanoscale interactions acting between molecules on surfaces. Here we describe the setup and the steps needed to achieve successful hand-controlled molecular manipulation within the virtual reality environment.

We demonstrate the precise manipulation of individual organic molecules on a metal surface with the tip of a scanning probe microscope driven in 3D by the experimenter's hand using a motion capture system and fully immersive virtual reality goggles.

通过手扫描探针显微镜用三维虚拟现实接口控制单分子的操作

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building ...

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. This paper proposes a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation. The polydimethylsiloxane (PDMS) chip was fabricated using the multi-layer soft lithography method. Hexadecane containing surfactant was used as the continuous phase, and PEGDA with the ultraviolet (UV) photo-initiator was the dispersed phase. Surfactants allowed the local surface tension to drop and formed a more cusped tip which promoted breaking into tiny micro-droplets. As the pressure of dispersed phase was constant, the size of droplets became smaller with increasing continuous phase pressure before dispersed phase flow was broken off. As a result, droplets with size variation from 1 &#181;m to 80 &#181;m in diameter could be selectively achieved by changing the pressure ratio in two inlet channels, and the average coefficient of variation was estimated to be below 7%. Furthermore, droplets could turn into micro-beads by UV exposure for photo-polymerization. Conjugating biomolecules on such micro-beads surface have many potential applications in the fields of biology and chemistry.

Generation of Size-controlled Poly ethylene Glycol Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Here, we present a protocol to illustrate the fabrication processes and verifying experiments of a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation.

Semi-3-Dimensional 流聚焦微流控装置产生尺寸控制的聚乙二醇二丙烯酸酯液滴

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. ...

Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods

It is well known that the flow field over a delta wing is dominated by a pair of counter rotating leading edge vortices (LEV). However, their mechanism is not well understood. The flow visualization technique is a promising non-intrusive method to illustrate the complex flow field spatially and temporally. A basic flow visualization setup consists of a high-powered laser and optic lenses to generate the laser sheet, a camera, a tracer particle generator, and a data processor. The wind tunnel setup, the specifications of devices involved, and the corresponding parameter settings are dependent on the flow features to be obtained.
Normal smoke wire flow visualization uses a smoke wire to demonstrate the flow streaklines. However, the performance of this method is limited by poor spatial resolution when it is conducted in a complex flow field. Therefore, an improved smoke flow visualization technique has been developed. This technique illustrates the large-scale global LEV flow field and the small-scale shear layer flow structure at the same time, providing a valuable reference for later detailed particle image velocimetry (PIV) measurement.
In this paper, the application of the improved smoke flow visualization and PIV measurement to study the unsteady flow phenomena over a delta wing is demonstrated. The procedure and cautions for conducting the experiment are listed, including wind tunnel setup, data acquisition, and data processing. The representative results show that these two flow visualization methods are effective techniques for investigating the three-dimensional flow field qualitatively and quantitatively.

Here, we present a protocol to observe unsteady vortical flows over a delta wing using a modified smoke flow visualization technique and investigate the mechanism responsible for the oscillations of the leading-edge vortex breakdown locations.

基于流动可视化方法的三角洲机翼流动结构实验研究

It is well known that the flow field over a delta wing is dominated by a pair of counter rotating leading edge vortices (LEV). However, their mechanism is ...

Synchrotron X-ray Microdiffraction and Fluorescence Imaging of Mineral and Rock Samples

In this report, we describe a detailed procedure for acquiring and processing&#160;x-ray microfluorescence (&#956;XRF), and Laue and powder microdiffraction two-dimensional (2D) maps at beamline 12.3.2 of the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory. Measurements can be performed on any sample that is less than 10 cm x 10 cm x 5 cm, with a flat exposed surface. The experimental geometry is calibrated using standard materials (elemental standards for XRF, and crystalline samples such as Si, quartz, or Al2O3 for diffraction). Samples are aligned to the focal point of the x-ray microbeam, and raster scans are performed, where each pixel of a map corresponds to one measurement, e.g., one XRF spectrum or one diffraction pattern. The data are then processed using the in-house developed software XMAS, which outputs text files, where each row corresponds to a pixel position. Representative data from moissanite and an olive snail shell are presented to demonstrate data quality, collection, and analysis strategies.

We describe a beamline setup meant to carry out rapid two-dimensional x-ray fluorescence and x-ray microdiffraction mapping of single crystal or powder samples using either Laue (polychromatic radiation) or powder (monochromatic radiation) diffraction. The resulting maps give information about strain, orientation, phase distribution, and plastic deformation.

矿物和岩石样品的同步辐射 x 射线 Microdiffraction 和荧光成像

In this report, we describe a detailed procedure for acquiring and processing&#160;x-ray microfluorescence (&#956;XRF), and Laue and powder ...

Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine micro-organisms, and/or sediments in the ocean, or fluidized bed reactors and combustion processes in engineered systems. In order to study the effect of turbulence on the kinematics of particles in such flows, simultaneous measurements of both the flow and particle kinematics are required. Non-intrusive, optical flow measurement techniques for measuring turbulence, or for tracking particles, exist but measuring both simultaneously can be challenging due to interference between the techniques. The method presented herein provides a low cost and relatively simple method to make simultaneous measurements of the flow and particle kinematics. A cross section of the flow is measured using a particle image velocimetry (PIV) technique, which provides two components of velocity in the measurement plane. This technique utilizes a pulsed-laser for illumination of the seeded flow field that is imaged by a digital camera. The particle kinematics are simultaneously imaged using a light emitting diode (LED) line light that illuminates a planar cross section of the flow that overlaps with the PIV field-of-view (FOV). The line light is of low enough power that it does not affect the PIV measurements, but powerful enough to illuminate the larger particles of interest imaged using the high-speed camera. High-speed images that contain the laser pulses from the PIV technique are easily filtered by examining the summed intensity level of each high-speed image. By making the frame rate of the high-speed camera incommensurate with that of the PIV camera frame rate, the number of contaminated frames in the high-speed time series can be minimized. The technique is suitable for mean flows that are predominantly two-dimensional, contain particles that are at least 5 times the mean diameter of the PIV seeding tracers, and are low in concentration.

The technique described herein offers a low cost and relatively simple method to simultaneously measure particle kinematics and turbulence in flows with low particle concentrations. The turbulence is measured using particle image velocimetry (PIV), and particle kinematics are calculated from images obtained with a high-speed camera in an overlapping field-of-view.

流成像技术同时测量湍流和粒子运动学

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine ...

Label-Free Imaging of Single Proteins Secreted from Living Cells via iSCAT Microscopy

We demonstrate interferometric scattering (iSCAT) microscopy, a method capable of detecting single unlabeled proteins secreted from individual living cells in real time. In this protocol, we cover the fundamental steps to realize an iSCAT microscope and complement it with additional imaging channels to monitor the viability of a cell under study. Following this, we use the method for real-time detection of single proteins as they are secreted from a living cell which we demonstrate with an immortalized B-cell line (Laz388). Necessary steps concerning the preparation of microscope and sample as well as the analysis of the recorded data are discussed. The video protocol demonstrates that iSCAT microscopy offers a straightforward method to study secretion at the single-molecule level.

We present a protocol for the real-time optical detection of single unlabeled proteins as they are secreted from living cells. This is based on interferometric scattering (iSCAT) microscopy, which can be applied to a variety of different biological systems and configurations.

通过 iscat 显微镜对活细胞分泌的单一蛋白质进行无标签成像

We demonstrate interferometric scattering (iSCAT) microscopy, a method capable of detecting single unlabeled proteins secreted from individual living ...

O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the prediction of the components in industrial processes. The ability to record spectra for solid and liquid samples without any pretreatment is advantageous and the method is widely used. However, the disadvantages of analyzing high-dimensional near-infrared spectral data include information redundancy and multicollinearity of the spectral data. Thus, we propose to use partial least squares regression method, which has traditionally been used to reduce the data dimensionality and eliminate the collinearity between the original features. We implement the method for predicting the o-cresol concentration during the production of polyphenylene ether. The proposed approach offers the following advantages over component regression prediction methods: 1) partial least squares regression solves the multicollinearity problem of the independent variables and effectively avoids overfitting, which occurs in a regression analysis due to the high correlation between the independent variables; 2) the use of the near-infrared spectra results in high accuracy because it is a non-destructive and non-polluting method to obtain information at microscopic and molecular scales.

The protocol describes a method of predicting o-cresol concentration during the production of polyphenylene ether using near-infrared spectroscopy and partial least squares regression. To describe the process more clearly and completely, an example of predicting the o-cresol concentration during the production of polyphenylene is used to clarify the steps.

O-cresol 浓度在线测量基于近红外光谱通过部分最小平方回归

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the ...