作者非常感谢支持由美国国家科学基金会，CBET0846359，授予显示器霍斯特·亨宁冬季。

1。创建一个可测流量<ol><li> EPIV验证测量将被证明在管内流动的甘油水溶液（甘油50％ - 50％的水）。是图1中所示的实验装置的示意图。 </li><li>已加入空心玻璃球，其标称直径为10μm处的流体的浓度为约17重量份每百万。空心玻璃球作为超声造影剂，和它们的大小和密度的选择，使得它们被动跟随流体流动10 </li><li>一个固定的电压被供给到泵引入公知的流量。 U &lt;&lt;ΔX/δt的 ， 其中 U是在管道中的平均流速，ΔX是的EPIV测量体积的线性长度，δt是图像之间的时间步长， 即 ，流速是这样选择的需要的话，则流程“慢”相比fps的超声系统，干。 </li></ol> 2。校准超声<ol><li>安装超声探头的外管壁。一种水性外用凝胶剂被施加到的超声波探头，探头面和管壁之间的超声波束的传输，以减少损失。 </li><li>对超声机的电源。超声图像的实时流后自动开始所有的系统负载。 </li><li>设置的图像的深度，使用深度的超声波机的控制面板上的控制旋钮。 </li><li>设置总的影像增益的超声波机的控制面板上的使用的二维增益旋钮。 </li><li>调整的时间增益补偿（TGC）滑块，以削弱分散管壁和深度相关的超声信号的衰减补偿。 </li><li> 图像的宽度，重点，探头工作频率和帧速率 ，使用分配的控制旋钮进行调整。这些四个旋钮，位于左上方的控制面板上，根据不同的模式，在该模式下，在系统运行。在2D模式下（如目前所用的），由左到右旋钮对应的宽度，焦点，频率 ，和帧速率 ，分别。需要注意的是，由于9超声成像的基本原则，这四个参数本质上是耦合。因此，对于一个给定的超声图像扫描（ 即 ，EPIV实验）有一个空间和时间分辨率之间进行权衡。 </li><li>请参阅图2为代表的超声图像与10微米空心玻璃球管流接种。请注意，由于有限的横向分辨率，在横向方向上有污点的玻璃球和作为椭球图像中出现。 </li></ol> 3。数据采集<ol><li>按新的考试按钮在超声控制面板上的开始新的实验。 </li><li>创建一个新的“病人”输入姓氏和名字和今天的日期，测试病人ID管流。 </li><li>超声波扫描开始创作的“病人”，直到1000-1500之间的图像达到预设的最大值，之后，一个新的扫描循环开始。按两次在超声控制面板上的“ 冻结 ”按钮将重新启动在日前任何时间，以达到最大预设数量的影像扫描。 </li><li>一旦已取得良好的超声图像（ 即尖锐的的种子颗粒图像和足够的种子颗粒密度），按在超声控制面板上的“冻结”按钮，停止图像采集。 </li><li>按电影回放按钮在超声控制面板上的。选择一组的超声图像进行分析， 第一周期旋钮在超声控制面板上的选择集合中的第一个图像，而最后一个周期旋钮选择集合中的最后一个图像。 </li><li>按的超声控制面板上的图像存储按钮保存选定的一组超声图像。 </li><li>按“ 存档 ”按钮的超声控制面板，并使用鼠标光标选择结束考试 。这将提示用户选择图像或cineloops，将其保存到本地硬盘驱动器。选择感兴趣的电影回放（S），然后退出考试。 </li><li>按“ 存档 ”按钮的超声控制面板上，并使用鼠标光标移动到第一个选择“ 更多”，然后选择“ 磁盘管理”。 “磁盘管理”将转移保存的电影回放（S）的PC运行的PIV软件。 </li></ol> 4。转换文件格式<ol><li>超声波图像被存储为一个数字成像在医药（DICOM）的超声波机器上的文件类型的通信。为了被打开和读出的PIV软件，DICOM文件必须被转换为图片文件。目前，一个Matlab运行的脚本DICOM2JPG.m使用联合图像专家组（JPEG）文件类型转换为DICOM文件。 </li><li> JPEG超声图像进行分析，然后使用DaVis软件LaVision。 </li></ol> 5。计算位移场，D（X，Y），使用戴维斯<ol><li>在电脑上双击鼠标点击的戴维斯图标上。选择“ 新建项目”。选择PIV。 </li><li>在工具栏上选择“ 导入图像 ，并通过编号的文件中选择” 导入“。在下拉菜单中，找到存储JPEG超声图像的文件夹，然后双击第一个图像的设置。这将导入所有的超声图像，在此编号的集合。 </li><li>通常情况下的图像的掩模将被定义为在以被处理的超声波图像中的感兴趣区域（ROI）的隔离。管流中，掩模被用来定义之间的配管的壁（ 即 ，流体）的ROI。 </li><li>戴维斯在主控制面板，选择当前项目中导入的图像“选项卡下，选择标签的批量处理 。这使得向量处理窗口戴维斯的进口超声图像进行批量处理。 </li><li>从操作列表中，使用PIV时间序列的树，选择矢量计算参数 ，并选择要使用的参数向量处理。如果使用口罩，检查数据范围框，在的矢量计算参数 “菜单中使用屏蔽的区域 。需要注意的是矢量计算参数的最佳选择是依赖于流动几何，流动性能，图像分辨率，示踪粒子密度，所需的定量流动分析。 对于管道的流量测量，通常已取得了最好的结果的参数是随着审讯大小为32 x 32像素的2至8×的多路径8像素2中 ，与50％的重叠。相对矢量范围的限制被设置为± 所有（窗口大小/ 2）和绝对矢量范围的限制被设置为±5个像素。最后，一个3×3pixel的2位数过滤器是用来抑制噪声，平滑的矢量场。 </li><li>在左侧的“ 批处理”屏幕上，选择要处理的图像的总量，并选择启动处理 。这将计算的位移字段， 二维（x，y）的 ，连续的超声图像之间，使用互相关算法。 </li></ol> 6。分析向量场<ol><li>后处理和数据分析，EPIV向量场戴维斯导出为txt文件。这是通过选择项目屏幕中的JPEG图像分支下的矢量位移分支。在工具栏中，选择“ 导出 ”选项卡，选择“文件类型”ASCII 文件 ，选择/创建一个导出文件夹，d选择“ 导出”。 </li><li>导出矢量场被命名为Bxxxxx.txt，其中00001≤XXXXX≤99999， 用 B表示缓冲。每个文件都包含四个数据列：（1）的X位置的图像中的载体，（2）γ-位置的图像中的矢量，（3）的x分量的位移（ 即位移）的流向，（4）位移的y分量（ 即 ，正常的壁位移）。 Bxxxxx.txt文件打开和处理在MATLAB中首先计算速度场，通过知道图像对之间的时间步长ΔT[秒]，以及图像的放大倍率，M [米/像素]， 即u（的x，Ŷ ）=（MD的x，y）/ΔT。图像之间的时间步长ΔT= 1/fps + D（的x，y）/ B，其中 B [像素/ s]是所花费的时间为超声波探头扫过的图像宽度。在本研究中，M = 77 [μm/像素]，帧率= 49.5 [1 /秒]， 和 B = 25047 [像素/秒]。接下来，ensem表平均速度矢量场，壁正常的平均流速剖面，在其他流量计算。 （参见第代表性的结果。） </li></ol>

<ol>
	<li>White, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fluid Mechanics. , (1994).</li><li>Hak, M. G. a. d. -. e. l. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Flow Control: Passive, Active, and Reactive Flow Management. , (2000).</li><li>Kim, B. H., Hertzberg, J. R., Shandas, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+validation+of+echo+PIV.">Development and validation of echo PIV.</a> Exp. Fluids. 36, 455-462 (2004).</li><li>Zheng, H., Liu, L., Williams, L., Hertzberg, J. R., Lanning, C., Shandas, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real+time+multicomponent+echo+particle+image+velocimetry+technique+for+opaque+flow+imaging.">Real time multicomponent echo particle image velocimetry technique for opaque flow imaging.</a> Appl. Phys. Lett. 88, 261915 (2006).</li><li>Beulen, B., Bijnens, N., Rutten, M., Brands, P., van de Vosse, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perpendicular+ultrasound+velocity+measurement+by+2D+cross+correlation+of+RF+data.+Part+A:+validation+in+a+straight+tube.">Perpendicular ultrasound velocity measurement by 2D cross correlation of RF data. Part A: validation in a straight tube.</a> Exp. Fluids. 49, 1177-1186 (2010).</li><li>Poelma, C., Mari, J. M., Foin, N., Tang, M. -. X., Krams, R., Caro, C. G., Weinberg, P. D., Westerweel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+Flow+reconstruction+using+ultrasound+PIV.">3D Flow reconstruction using ultrasound PIV.</a> Exp. Fluids. 50, 777-785 (2011).</li><li>GE VINGMED ULTRASOUND A/A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Vivid 7/Vivid 7 PRO Userâ€™s Manual. , (1988).</li><li>Szabo, 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> Diagnostic Ultrasound Imaging: Inside Out. , (2004).</li><li>Raffel, M., Willert, C., Wereley, S., Kompenhans, 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></ol>

作者没有透露。

操作协议回声粒子图像测速系统（EPIV）能够获得二维领域的速度，在不透光的液体或不透光的几何形状进行了描述。实际应用EPIV是非常适合于工业和生物流系统，其中不透明的流体的流动在很多应用程序发生的研究。这里介绍的特定的系统专门被建研究纤维素乙醇的生产中使用的液化生物量流体的流动性质。代表性的测量管流表现出的能力EPIV。特别是，平均值和均方根速度计算剖面从EPIV矢量场...

<table border="1"><tbody><tr><td>的试剂的名称</td><td>公司</td><td>目录编号</td><td>评论（可选） </td></tr><tr><td>超声波机</td><td>通用电器</td><td>生动的7专业版</td><td></td></tr><tr><td>线性超声阵列</td><td>通用电器</td><td> 10 L </td><td></td></tr><tr><td>直流水泵</td><td> KNF </td><td> NF 10 KPDC </td><td></td></tr><tr><td>向量处理软件</td><td> Lavision </td><td>戴维斯7.2 </td><td></td></tr><tr><td>后处理软件</td><td> Mathworks公司</td><td> MATLAB 7.12 </td><td></td></tr><tr><td>亚克力管</td><td>麦克马斯特车ŕ </td><td> 8486K531 </td><td></td></tr><tr><td>超声凝胶</td><td>帕克</td><td>使用Aquasonic 100 </td><td></td></tr></tbody></table>

echo particle image velocimetry

在流体流动的质量，动量和能量的运输最终确定的流体速度场的时空分布。因此，理解的先决条件，预测，控制流体流动的能力来衡量的速度场足够的空间和时间分辨率2速度测量不透光的液体或不透光的几何形状，回声颗粒图像测速（EPIV）的是一个有吸引力的诊断技术来产生“瞬间”二维领域的速度。3,4,5,6在此报告纸的经营协议的EPIV系统整合商业医疗超声机7台 PC上运行的商业粒子图像测速（PIV）软件8，验证测量在哈根泊肃叶流（ 即层流管） 。 对于EPIV措施MENTS，相控阵探头连接到医用超声机是用来产生一个二维超声波图像，通过在不同的时间脉冲的压电探针元件。每个探头元件的超声波脉冲发送到流体中，并在流体中的示踪粒子（无论是天然存在的或种子）回到探头它们被记录的位置反映超声回波。反射超声波和自己的时间延迟相对于传输的幅度被用来创建什么是被称为B-模式（亮度模式）二维超声图像。具体而言，延迟时间被用来确定在流体中的散射体的位置，并且振幅被用于分配的散射体的强度。所需的时间，以获得一个单一的B模式图像， 吨 ，确定所需要的时间，脉冲的相控阵探头的所有元素。用于获取多个B模式图像，帧速率中的系统帧每秒（fps）的= 1 /和deLTA吨。 （见9超声成像的评论。） 对于一个典型的EPIV实验，帧速率是20-60帧，根据流动性条件下，和（100-1000）的B模式图像的流中的示踪粒子的空间分布之间的获取。收购后，B型超声图像的传输通过以太网连接到PC上运行的PIV商业软件。使用PIV软件，示踪粒子位移字段，D（的x，y）[像素]，（其中x和y表示的超声波图像中的水平和垂直的空间位置，分别）获得互相关算法通过施加连续的超声B-模式的图像10的速度场，ü（的x，y）[米/秒]，确定从位移字段，知道图像对之间的时间步长，ΔT[秒]，以及图像的放大倍率，M [米/像素， 即u（x，y）= MD（X，Y）/ΔT。时间步骤between图像ΔT= 1/fps + D（的x，y）/ B，其中 B [像素/ s]是所花费的时间为超声波探头扫过的图像宽度。在本研究中，M = 77 [μm/像素]，帧率= 49.5 [1 /秒]， 和 B = 25047 [像素/秒]。收购后，速度场进行分析，以计算​​流量的利益。

在图3中示出一种瞬时回波颗粒图像测速（EPIV）矢量场。向量图显示速度矢量，第四列和等高线图的背景色对应于速度的大小。系综平均的矢量绘图平均超过1000的瞬间EPIV向量图如图4所示。与管流一致，主要流向的方向的速度矢量，发生最大的速度在管道中心线，和在管道壁的速度减少到零。的根均方（rms）的速度大小波动是在图5中所示。由于在的Hagen-Poiseui...

Watch this Scientific Journal Video about Echo Particle Image Velocimetry at JoVE.com

Echo Particle Image Velocimetry

一个回声粒子图像测速系统（EPIV）能够取得两维领域的速度在不透光的液体或不透光的几何形状的描述和验证测量管流。

回声粒子图像测速技术

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 ...

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14.5K 次观看.  University of New Hampshire. 一个回声粒子图像测速系统（EPIV）能够取得两维领域的速度在不透光的液体或不透光的几何形状的描述和验证测量管流。

视频: Echo Particle Image Velocimetry

Gradient Echo Quantum Memory in Warm Atomic Vapor

Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain.

The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.

梯度回波量子存储在温暖的原子蒸气

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

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High-speed Particle Image Velocimetry Near Surfaces

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. 
Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (&gt; 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows.
A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included.

A procedure for studying transient flows near boundaries using high-resolution, high-speed particle image velocimetry (PIV) is described here. PIV is a non-intrusive measurement technique applicable to any optically accessible flow by optimizing several parameter constraints such as the image and recording properties, the laser sheet properties, and analysis algorithms.

表面附近的高速粒子图像测速

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

使用中子自旋回声解决放牧发生率散射调查有机太阳能电池材料

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model

Analysis of the size distribution of nanocrystals is a critical requirement for the processing and optimization of their size-dependent properties. The common techniques used for the size analysis are transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). These techniques, however, are not suitable for analyzing the nanocrystal size distribution in a fast, non-destructive and a reliable manner at the same time. Our aim in this work is to demonstrate that size distribution of semiconductor nanocrystals that are subject to size-dependent phonon confinement effects, can be quantitatively estimated in a non-destructive, fast and reliable manner using Raman spectroscopy. Moreover, mixed size distributions can be separately probed, and their respective volumetric ratios can be estimated using this technique. In order to analyze the size distribution, we have formulized an analytical expression of one-particle PCM and projected it onto a generic distribution function that will represent the size distribution of analyzed nanocrystal. As a model experiment, we have analyzed the size distribution of free-standing silicon nanocrystals (Si-NCs) with multi-modal size distributions. The estimated size distributions are in excellent agreement with TEM and PL results, revealing the reliability of our model.

We demonstrate how to determine the size distribution of semiconductor nanocrystals in a quantitative manner using Raman spectroscopy employing an analytically defined multi-particle phonon confinement model. Results obtained are in excellent agreement with the other size analysis techniques like transmission electron microscopy and photoluminescence spectroscopy.

使用拉曼光谱与多颗粒的声子坐月子型号纳米大小分布的特征

Analysis of the size distribution of nanocrystals is a critical requirement for the processing and optimization of their size-dependent properties. The ...

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

实验装置的研制归还系数在真空条件下测量

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

湍流应用三维粒子跟踪测速：一喷流病例

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

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 ...

3D Printing - Evaluating Particle Emissions of a 3D Printing Pen

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament fabrication (FFF) is an inexpensive method used most frequently by consumers. Studies with 3D printers have shown that during the printing process particulate and volatile substances are released. Handheld 3D printing pens also use the FFF method but the consumer&#8217;s proximity to the 3D pens gives reason to higher exposure compared to a 3D printer. At the same time, 3D printing pens are often marketed for children who could be more sensitive to the printing emission. The aim of this study was to implement a low cost method to analyze the emissions of 3D printing pens. Polylactide (PLA) and acrylonitrile butadiene styrene (ABS) filaments of different colors were tested. In addition, filaments containing metal and carbon nanotubes (CNTs) were analyzed. An 18.5 L chamber and sampling close to the emission source was used to characterize emissions and concentrations near the breathing zone of the user.
Particle emissions and particle size distributions were measured and the potential release of metal particles and CNTs investigated. Particle number concentrations were found in a range of 105 - 106 particles/cm3, which is comparable to previous reports from 3D printers. Transmission electron microscopy (TEM) analysis showed nanoparticles of the different thermoplastic materials as well as of metal particles and CNTs. High contents of metal were observed by inductively coupled plasma mass spectrometry (ICP-MS).
These results call for a cautious use of 3D pens due to potential risk to the consumers.

This protocol presents a method to analyze the emission of 3D printing pens. Particle concentration and particle size distribution of the released particle is measured. Released particles are further analyzed with transmission electron microscopy (TEM). Metal content in filaments is quantified by inductively coupled plasma mass spectrometry (ICP-MS).

3D 打印 - 评估 3D 打印笔的粒子排放

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament ...

Study of Protein Dynamics via Neutron Spin Echo Spectroscopy

Most human body proteins' activity and functionality are related to configurational changes of entire subdomains within the protein crystal structure. The crystal structures build the basis for any calculation that describes the structure or dynamics of a protein, most of the time with strong geometrical restrictions. However, these restrictions from the crystal structure are not present in the solution. The structure of the proteins in the solution may differ from the crystal due to rearrangements of loops or subdomains on the pico to nanosecond time scale (i.e., the internal protein dynamics time regime). The present work describes how slow motions on timescales of several tens of nanoseconds can be accessed using neutron scattering. In particular, the dynamical characterization of two major human proteins, an intrinsically disordered protein that lacks a well-defined secondary structure and a classical antibody protein, is addressed by neutron spin echo spectroscopy (NSE) combined with a wide range of laboratory characterization methods. Further insights into protein domain dynamics were achieved using mathematical modeling to describe the experimental neutron data and determine the crossover between combined diffusive and internal protein motions. The extraction of the internal dynamic contribution to the intermediate scattering function obtained from NSE, including the timescale of the various movements, allows further vision into the mechanical properties of single proteins and the softness of proteins in their nearly natural environment in the crowded protein solution.

Study of Protein Dynamics via Neutron Spin Echo Spectroscopy

The present protocol describes methods for investigating the structure and dynamics of two model proteins that have an important role in human health. The technique combines bench-top biophysical characterization with neutron spin echo spectroscopy to access the dynamics at time and length scales relevant for protein interdomain motions.

通过中子自旋回声光谱研究蛋白质动力学

Most human body proteins' activity and functionality are related to configurational changes of entire subdomains within the protein crystal structure. The ...

Deep Neural Networks for Image-Based Dietary Assessment

Due to the issues and costs associated with manual dietary assessment approaches, automated solutions are required to ease and speed up the work and increase its quality. Today, automated solutions are able to record a person's dietary intake in a much simpler way, such as by taking an image with a smartphone camera. In this article, we will focus on such image-based approaches to dietary assessment. For the food image recognition problem, deep neural networks have achieved the state of the art in recent years, and we present our work in this field. In particular, we first describe the method for food and beverage image recognition using a deep neural network architecture, called NutriNet. This method, like most research done in the early days of deep learning-based food image recognition, is limited to one output per image, and therefore unsuitable for images with multiple food or beverage items. That is why approaches that perform food image segmentation are considerably more robust, as they are able to identify any number of food or beverage items in the image. We therefore also present two methods for food image segmentation - one is based on fully convolutional networks (FCNs), and the other on deep residual networks (ResNet).

The goal of the work presented in this article is to develop technology for automated recognition of food and beverage items from images taken by mobile devices. The technology comprises of two different approaches - the first one performs food image recognition while the second one performs food image segmentation.

基于图像的饮食评估深度神经网络

Due to the issues and costs associated with manual dietary assessment approaches, automated solutions are required to ease and speed up the work and ...