这项工作得到了海军研究办公室 (进货 N00014-15-1-0020) [Tkacik 和 Keanini] 的支持, 并在北卡罗莱纳大学在夏洛特的赛车研究实验室进行. 抛光介质由 Rosler 捐赠。

1. 振动系统的制备
<ol><li>
设置振动系统, 如图 1所示。这个系统由一个环形聚氨酯碗 (具有外径600毫米), 连接到一个单一的速度 (1740 rpm), 不平衡的马达, 后者产生的过程振动。这是附加到一个加权的基础, 并由一组八弹簧 (碗和加权基地被购买组装成一件)。将碗总成固定在它的支架上, 并用两个供应的橡皮钩连接。将蠕动泵放在靠近碗的桌子上, 并将泵出口软管连接到碗润滑入口点。
	<ol>
<li>将三轴加速度计附加到环形碗的内半径, 在低振幅条件下记录碗振动, 并将加速度计连接到传感器信号调理器。将信号调理装置放在远离振动系统的桌子上。加速度计/信号调理组合由标准计算机上安装的数据采集硬件/软件控制。</li>
	</ol>
</li>
	<li>
通过在水中洗涤和允许干燥来准备选择的介质。在各种实验中使用了几种类型的介质。对于本文, 使用陶瓷抛光介质直切三角形 (10 mm x 10 mm x 10 mm 三角形, 从前面和10毫米厚)。
	<ol>
<li>首先把一个空塑料袋放在实验室的天平上, 然后 taring, 确定介质的填料密度。用所选介质填充塑料袋 (不超过18.927 升 (5 加仑), 记录介质重量 (g 或千克)。对于这种类型的媒体和目前的实验设置, 重量是22.68 公斤 (50 磅)。<ol>
<li>把水桶放在一个大水槽里, 或者从其他设备外面的大楼里。装满水桶 (为这个设置, 一个18.927 升 (5 加仑) 桶被使用) 与水的满分, 并慢慢降低塑料袋充满媒体进入水桶。一旦媒体袋被完全淹没, 慢慢地从水中提袋, 以避免飞溅和放在一旁的麻袋。使用1000毫升的毕业气缸重新灌装桶, 以其原来的满分, 记录了总水量增加。添加的水量将为, 其中是介质的材料包装容积 (对于此设置, 13750 毫升的水被添加回桶中). <img alt="Equation 5" src="/files/ftp_upload/56632/56632eq5.jpg"> <img alt="Equation 5" src="/files/ftp_upload/56632/56632eq5.jpg">增加的水量将取决于所使用的介质类型。</li>
			<li>按以下公式计算介质的包装密度: <img alt="Equation 6" src="/files/ftp_upload/56632/56632eq6.jpg"> 其中是媒体的包装密度, 是媒体的质量 (对于此媒体, 密度被计算为 1649). <img alt="Equation 7" src="/files/ftp_upload/56632/56632eq7.jpg"> <img alt="Equation 8" src="/files/ftp_upload/56632/56632eq8.jpg"> <img alt="Equation 9" src="/files/ftp_upload/56632/56632eq9.jpg"> </img></li>
		</ol>
</li>
		<li>通过将振动系统插入到电源插座 (此模型有两个选项, 1) 插入到墙上或 2) 运行与定时器连接到站)。通过在用户编写的程序上按 "启动" 箭头并收集数据1分钟, 激活计算机上的数据采集软件。加速数据将同时显示, 以供立即审阅 (在时间域和频率域中), 并自动存储到. csv 文件中以进行潜在的后处理。从电源插座上拔下设备, 使振动系统停用。</li>
		<li>将介质添加到振动碗中。</li>
		<li>配制复合物, 由3880毫升水和120毫升的精加工化合物 (FC) (3% 体积) 溶液组成。将蠕动泵设置为1.9 升/小时 (旋转速度拨至27以达到此流速), 但不启动流量。这将确保解决方案不会再循环, 但足以使介质保持湿润。(本解决方案是一种常用的振动整理解决方案)。该溶液起到润滑剂的作用, 确保介质在过程中不粘在一起或磨损。</li>
		<li>通过将振动系统插入电源插座来激活它。收集步骤1.2.2 中指定的加速度计数据。从电源插座上拔下设备, 使振动系统停用。</li>
	</ol>
</li>
</ol>2. 高速成像
注: 对于颗粒速度场的测量, 通过对流动颗粒桩表面的一部分进行成像, 成像区, 对应于下面步骤2.2.4 中确定的视场 (视). <img alt="Equation 10" src="/files/ftp_upload/56632/56632eq10.jpg">通过选择一个小的、固定的子区域 () 在内, 可以获得时间变化、单个晶粒速度 (在桩表面) 的测量, 如下所述, 按单个晶粒的投影区域的顺序排列. <img alt="Equation 11" src="/files/ftp_upload/56632/56632eq11.jpg"> </img> <img alt="Equation 12" src="/files/ftp_upload/56632/56632eq12.jpg"> <img alt="Equation 11" src="/files/ftp_upload/56632/56632eq11.jpg">
<ol><li>
设置一个高速摄像头 (相机有 1504 x 1128 分辨率, 每秒1000帧 (fps)), 以捕捉图像, 无论是放置在三脚架上或建立一个刚性框架与镜头垂直的开放表面的振动系统 (当碗是振动婷), 如图 1所示。这个刚性的框架是独立于振动系统, 并确保从系统的振动不影响成像。
	<ol>
<li>为所需的表面集成区域和分辨率附上适当的透镜。对于当前设置, 使用 18-250 毫米变焦镜头和镜头比 1:3. 6-6.3。 将电源和 GPS 天线连接到摄像头。 使用 CAT5 电缆将照相机连接到计算机。 放置相机, 使镜头的末端是大约550毫米以上的媒体表面。 注意: 将照相机放在离介质太近的时候会导致边缘效果增加, 将相机放得太远会导致图像太暗而无法处理。在指定的距离, 由于边缘效应和测试区域的整体曲率的误差是 < 2%。</li>
		<li>取下镜头盖并启动摄像头软件。启动后, 单击 "照相机" 按钮, 然后单击 "确定"。当照相机列表填充时, 从列表中选择照相机, 然后单击 "打开"。</li>
		<li>在计算机上的摄像头软件中, 在 "实时" 选项卡下, 单击 "实时" 按钮 (蓝色箭头) 查看照相机的视。打开光源以照亮要成像的区域。这可以是任何明亮的光, 只要它照亮测试区均匀。图 1显示了与振动系统有关的相机和光源配置。</li>
		<li>若要确定 f 停止, 请从照相机中使用实时流查看计算机屏幕, 并将 f 停止调整为最小设置 (最大亮度)。如果 f 停止设置为 "低", 则结果为浅景深。如果 f 站设置为 "高", 则屏幕太暗。对于这个实验, f 站设置为3.6。</li>
		<li>调整镜头焦距以提供所需的视 (本例中为 210 mm x 160 mm)。对于这个实验, 设置焦距在180毫米与照相机设置550毫米在媒介表面之上。图 2a通过照相机显示视。</li>
		<li>使用相机软件对500X 放大倍数进行数字放大。调整镜头上的焦点环, 以最佳的光学焦点。将数字缩放返回到 100% (普通视图)。</li>
		<li>在计算机上的购置设置下, 单击 "速率 [Hz]", 并设置为每秒500帧。 注意: 为了解决粒度碰撞-时间尺度动态,, 必须至少大于所施加的振动频率的数量级, (此处, Hz) <img alt="Equation 14" src="/files/ftp_upload/56632/56632eq14.jpg"> </img> <img alt="Equation 15" src="/files/ftp_upload/56632/56632eq15.jpg"> <img alt="Equation 16" src="/files/ftp_upload/56632/56632eq16.jpg"></li>
		<li>在拍摄图像之前, 在视野中放置一个标尺;这为后续图像数据处理提供了长度刻度。在 "相机软件" 的 "获取设置" 下, 选择 "实时" 下的 "记录" 选项卡。将 "记录模式" 设置为 "循环", 并将帧设置为1。单击 "实时" 选项卡中的 "红色圆圈" 以记录图 2b中所示的单个图像。</li>
		<li>通过单击 "文件" 将获取的图像作为 TIFF 文件保存到一个方便的文件目录位置 (如外部硬盘驱动器), 然后单击 "保存购置"。将出现一个带有多个选项的对话框。在对话框的 "文件类型" 旁边, 从下拉菜单中选择. tiff。<ol>
<li>在对话框底部选择 "下载选项" 选项卡, 然后单击 "浏览"。在对话框的顶部, 添加测试的文件夹名称。在 "浏览" 对话框中, 搜索并选择所需的位置 (如外置硬盘驱动器) 和适当的文件夹。选定文件夹后, 单击 "确定" 然后 "保存"。将显示 "下载管理器" 框。文件将开始传输并保存在子文件夹001中指定的文件位置。一旦图像转移, "完成" 状态框将出现在屏幕上。</li>
			<li>单击 "红色删除" 按钮, 从照相机中删除图像。 注意: 协议可以在此处暂停。</li>
		</ol>
</li>
	</ol>
</li>
</ol>3. 收集数据
注意: 如果协议被暂停, 摄像机将需要重新启动。按照步骤3.1。如果协议未暂停, 请跳到步骤3.1.2。
<ol><li>
启动相机软件, 并按照步骤2中的规定打开照明。
	<ol>
<li>随着摄像头软件的激活, 检查光的条件和运行现场详细的步骤2.2.2。以确保适当的焦点。</li>
		<li>选择一个总的实验运行时间,<img alt="Equation 17" src="/files/ftp_upload/56632/56632eq17.jpg"> 注意: 必须满足两个相互竞争的要求: i) 必须足够长, 在统计上稳定的颗粒流条件和 ii) 不应长到产生大量的多余数据. <img alt="Equation 18" src="/files/ftp_upload/56632/56632eq18.jpg"> <img alt="Equation 18" src="/files/ftp_upload/56632/56632eq18.jpg">固定条件出现的时间尺度必须通过试验和误差来确定。各种方法, 不同的严谨性, 可以使用。例如, i) 确保在固定点或多个固定点上的时间平均晶粒速度达到名义上固定的大小或数量, 或 ii), 确保除了固定的方法外, 相应的方差也假设名义上固定程度.对于这个实验, 收集了 10.12 s 的数据, 对应于5060帧的获取。稳定的条件在五谷流动在大约 1 s 以后设置了。</li>
	</ol>
</li>
	<li>
激活振动碗。
	<ol>
<li>将150毫升的精加工/润滑化合物 (步骤 1.2.4) 均匀地涂在碗周围, 以提供初始润湿介质;然后将壶与剩余的化合物放在地板上, 用软管连接在蠕动泵上。激活蠕动泵 (如步骤 1.2.4), 将开关从 "off" 翻转到 "顺时针"。</li>
		<li>打开振动碗, 将其插入电源插座, 并等待至少一分钟, 以确保均匀润湿和稳定的流体运动在整个媒体 (稳态流体运动发生时, 流体从蠕动泵进入碗大约等于从碗里排出的液体流量。</li>
	</ol>
</li>
	<li>
捕获视频和收集数据。
	<ol>
<li>一旦流体达到稳定运动 (步骤 3.2.2), 通过单击计算机屏幕上的红色记录图标来触发照相机, 然后单击红色触发器复选标记以记录所选时间段的图像,. <img alt="Equation 18" src="/files/ftp_upload/56632/56632eq18.jpg"> </img>照相机将为指定的记录图像, 并将这些图像保存到其内部内存中. <img alt="Equation 18" src="/files/ftp_upload/56632/56632eq18.jpg">图 2a是从一组5060图像中取出的单个图像的示例。</li>
		<li>一旦收集到数据, 关闭振动系统, 从电源插座, 关掉蠕动泵通过翻转开关从 "顺时针" 到 "关闭"。 注意: 协议可以在此处暂停。</li>
	</ol>
</li>
</ol>4. 利用 PIV 技术处理视频数据
<ol><li>
准备高速摄像图像进行 PIV 处理。
	<ol>
<li>按照步骤2.1.9 中概述的步骤, 将获取的图像保存为 TIFF 文件。(在当前系统中, 在10.12 秒内收集的5060图像帧需要超过一小时才能传输)。一旦图像被转移, "完成" 状态框将出现在屏幕上。这些文件将保存在标识为002的子文件夹中的校准文件所在的目录中。从照相机中删除图像。</li>
		<li>将彩色图像转换为灰度图像, 以便通过 PIV 软件进行处理。使用 "imread ()" 函数将图像上传到数据分析软件中。使用 "rgb2gray ()" 函数转换图像的副本, 并使用 "imwrite ()" 函数将这些新图像保存/写入新的文件夹中。 注: 此过程/数据分析功能可用于多种类型的数据分析软件, 并由研究员编写完整的程序。图 2c是在图像被转换为灰度并经过 PIV 处理后放大的一个示例。</li>
	</ol>
</li>
	<li>
使用 PIV 软件计算速度场。
	<ol>
<li>使用导入向导将灰度图像集作为单个帧图像导入到 PIV 软件环境中。通过单击 "文件" 开始导入, 然后选择 "导入" 和 "导入图像"。 将显示 "图像导入向导" 对话框。 从菜单中选择 "单帧" 导入选项, 然后单击 "添加图像" 按钮。 选择校准图像并单击 "打开", 这会将图像添加到 "要导入的图像" 对话框列表中。 导入图像时, 首先添加校准图像 (步骤 2.1.9), 使其成为导入列表中的顶部图像。 再次单击 "添加图像" 按钮并突出显示所有数据图像, 然后单击 "打开", 将它们添加到 "要导入的图像" 对话框中。 选择所有需要的图像后, 单击 "下一步"。输入相机设置使用, 包括帧率和像素间距在对话框。单击 "下一步" 和 "完成" 以完成导入过程。</li>
		<li>将校准图像与图像集和输入长度刻度参数分离到 PIV 软件中。<ol>
<li>如果内容列表尚未显示, 请右键单击导入的图像集, 并在数据基树的屏幕左侧选择 "显示内容列表"。假设校准图像是第一个导入的图像, 右键单击列表中的第二个图像, 然后选择 "从这里拆分合奏"。将新创建的图像集 (仅包含校准图像) 拖放到标有 "新校准" 的屏幕左侧的位置。</li>
			<li>右键单击新放置的校准图像集, 然后选择 "测量比例因子"。当校准图像出现在屏幕上时, 将 "a" 和 "B" 标记放在图像标尺上 (或者如果没有使用标尺, 则将 "已知大小的其他对象") 定位到 "绝对距离" 文本框中的标记之间的距离。单击 "测量比例因子" 对话框中的 "确定", 它将保存校准设置并关闭对话框和校准图像。</li>
		</ol>
</li>
		<li>通过选择导入的图像集创建一组图像对, 然后单击 "分析"。接下来从可用分析方法列表中选择 "制作双帧"。选择 "(1-2、2-3、3-4,.。。(N-1) 双图像) "样式选项。<ol>
<li>打开图像集中的任何图像 (校准图像除外), 然后右击图像并选择 "粒子密度"。屏幕上会出现一个显示识别粒子的对话框。它将显示一个放大的视野中的探测区域。单击此对话框上的 "设置" 选项卡, 并更改 "探头大小区域", 直到探头区域中始终看到至少3粒子。 此探测区域大小将是在步骤4.2.5 中输入的审讯区域大小。</li>
		</ol>
</li>
		<li>使用所选图像集的 "分析" 命令选择 PIV 处理算法和相关参数。选择 "自适应相关" 方法, 并定义将用于在步长4.2.5 中定义空间向量的像素区域。(此过程将图像划分为 n x n 像素 "审讯区域" 的网格)</li>
		<li>通过定位 "审讯区域" 选项卡设置审讯区大小, 并在最小8像素和最大256像素之间选择任何可用的审讯区域大小 (对于此方法, 使用32像素32像素)。输入在步骤4.2.3.1 中确定的值。<ol>
<li>若要增加所创建的向量的密度, 请通过从下拉菜单中选择0%、25%、50% 或75% 重叠来增加审讯区域的 "重叠" 百分比。</li>
		</ol>
</li>
		<li>通过在 "自适应相关" 对话框中选择 "OK", 对测量的晶粒速度场进行分析。系统将开始分析。 当系统处理数据时, 第一个矢量映射将出现在屏幕上。检查前几个速度字段, 以确定它们是否在图 2c中看到的估计速度和方向是否满意。如果 "速度" 字段不符合实际, 请取消分析会话, 重复步骤 4.2.4, 并更改分析设置。(分析完成后, 将为集合中的每个图像对 (步骤 4.2.3) 创建一个矢量场, 跨越视。图 2c显示了在灰度图像上覆盖的分析过程中的一个满意向量场示例。 注: 对于每个 n 个像素的审讯区, PIV 软件比较了在审讯区内的子粒级亮点的模式, 以对应于下一幅图像中捕获的相应模式。从这个比较, PIV 软件确定一个区域平均位移向量,, 最后, 除以的时间增量之间的帧,, 区域平均速度, 的地方是指<img alt="Equation 21" src="/files/ftp_upload/56632/56632eq21.jpg"> </img> <img alt="Equation 21" src="/files/ftp_upload/56632/56632eq21.jpg"> <img alt="Equation 22" src="/files/ftp_upload/56632/56632eq22.jpg"> </img> <img alt="Equation 23" src="/files/ftp_upload/56632/56632eq23.jpg"> <img alt="Equation 24" src="/files/ftp_upload/56632/56632eq24.jpg">审讯区域. <img alt="Equation 24" src="/files/ftp_upload/56632/56632eq24.jpg"> </img>在当前的实验中, 每个审讯区域由 n x n = 32 x 32 象素组成;审讯区的总数细分每210毫米 x 160 毫米视因而是 47 x 35, 对应于 1504 x 1128 个映像点。</li>
	</ol>
</li>
</ol>5. 处理振动数据
注: 如果使用不同的计算机系统或分析软件, 请在步骤4中同时执行步骤5月5日。
<ol><li>
开放式数据分析软件和使用 "负载 ()" 功能, 带来的加速度计的数据, 是获得时, 振动碗是空的 (步骤 1.2.2)。使用 "fft ()" 函数对数据进行快速傅立叶变换。使用 "绘图" 函数创建数据的图形。重复所获得的数据时, 振动碗有媒体存在 (步骤 1.2.5)。 注: 此过程/数据分析功能可用于多种类型的数据分析软件, 并由研究员编写完整的程序。<ol>
<li>为了研究分子流体动力学过程, 通常需要一些数据处理操作。有关主要加工程序概述, 见代表性成果和讨论部分;见 Keanini, et al。(2017)12有关如何测量 PIV 数据以提取分子流体动力学系统的动态信息的细节。</li>
	</ol>
</li>
</ol>

<ol>
	<li>Berne, B. J., Pecora, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Dynamic Light Scattering. , (1976).</li><li>Boon, J. P., Yip, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Hydrodynamics. , (1980).</li><li>Brown, J. C., Pusey, P. N., Goodwin, J. W., Ottewill, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+scattering+study+of+dynamic+and+time-averaged+correlations+in+dispersions+of+charged+particles.">Light scattering study of dynamic and time-averaged correlations in dispersions of charged particles.</a> J. Phys. A: Math Gen. 5 (8), 664-682 (1975).</li><li>Wainwright, T. E., Alder, B. J., Gass, D. 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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-time+behavior+of+the+velocity+autocorrelation+function+for+a+fluid+of+soft+repulsive+particles.">Long-time behavior of the velocity autocorrelation function for a fluid of soft repulsive particles.</a> Phys. Rev. Lett. 33, 277-280 (1970).</li><li>Lovesey, S. W., Lovesey, S. W., Springer, 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> Dynamics of solids and liquids by neutron scattering. , (1977).</li><li>Forster, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Hydrodynamic fluctuations, broken symmetry, and correlation functions. , (1990).</li><li>Mountain, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generalized+hydrodynamics.">Generalized hydrodynamics.</a> Adv. Mol. Relax. Processes. 9, 225-291 (1977).</li><li>Zwanzig, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-correlation+functions+and+transport+coefficients+in+statistical+mechanics.">Time-correlation functions and transport coefficients in statistical mechanics.</a> Ann. Rev. Phys. Chem. 16, 67-102 (1965).</li><li>Keanini, R. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macroscopic+liquid-state+molecular+hydrodynamics.">Macroscopic liquid-state molecular hydrodynamics.</a> Sci. Rep. 7, 41658 (2017).</li><li>Kushick, J., Berne, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+attractive+forces+in+self-diffusion+in+dense+Lennard-Jones+fluids.">Role of attractive forces in self-diffusion in dense Lennard-Jones fluids.</a> J. Chem. Phys. 59 (7), 3732-3736 (1973).</li><li>Mullany, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+application+of+computational+fluid+dynamics+to+vibratory+finishing+processes.">The application of computational fluid dynamics to vibratory finishing processes.</a> CIRP Annals. , (2017).</li><li>Fleischhauer, E., Azimi, F., Tkacik, P. T., Keanini, R. G., Mullany, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+particle+imaging+velocimetry+(PIV)+to+vibrational+finishing.">Application of particle imaging velocimetry (PIV) to vibrational finishing.</a> J. Mater. Process. Technol. 229, 322-328 (2016).</li><li>Navare, 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> Experimental and computational evaluation of a vibratory finishing process. , (2017).</li><li>Bolmatov, V., Brazhkin, V., Trachenko, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+phonon+theory+of+liquid+thermodynamics.">The phonon theory of liquid thermodynamics.</a> Sci. Rep. 2, 421 (2012).</li><li>Elton, D. C., Fernandez-Serra, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hydrogen-bond+network+of+water+supports+propagating+optical+phonon-like+modes.">The hydrogen-bond network of water supports propagating optical phonon-like modes.</a> Nat. Commun. 7, 10193 (2016).</li><li>Pathria, R. K., Beale, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical mechanics. , (2011).</li><li>Gibbs, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Elementary principles in statistical mechanics. , (1902).</li><li>Toda, M., Kubo, R., Saito, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical physics I. , (1992).</li><li>Kubo, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+mechanical+theory+of+irreversible+processes.">Statistical mechanical theory of irreversible processes.</a> I. J. Phys. Soc. Japan. 12, 570-586 (1957).</li><li>Kubo, R., Toda, M., Hashitsume, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical physics II: nonequilibrium statistical mechanics. , (1991).</li></ol>

作者没有什么可透露的。

为了将振动颗粒桩作为宏观的类似物用于研究分子流体动力学过程, 实验必须一方面学习和使用四基本测量, 另一方面, 掌握一些基本的平衡元素和非平衡统计力学。首先将重点放在实验测量上, 这些测量包括: i) 通过测量单粒子速度自相关函数的单个晶粒动力学, 二) 测量时间平均/长时间尺度的表面晶粒速度场, iii) 测量颗粒介质的有效粘度, iv) 测量介质碗的振动谱, 既空又充满介质。
<p class="jove...

分子流体力学研究的动力学和统计力学的个别分子和收集的分子在流体中。在研究分子水动力系统的许多实验技术中,1,2, 光散射1,2,3, 分子动态模拟4, 5、6、7以及在较小程度上, 非弹性中子散射8已被最常用。不幸的是, 后两种技术有很大的局限性。分子动力学 (MD) 模拟, 例如: i) 被限制到包含相对地少量分子的小空间和世俗域, ii) 需要使用近似的粒子间电位, iii) 通常引入周期性<img alt="Equation 1" src="/files/ftp_upload/56632/56632eq1.jpg"> <img alt="Equation 2" src="/files/ftp_upload/56632/56632eq2.jpg"> </img>边界条件, 在非平衡散流条件下无效, 和 iv) 目前不能回答的根本问题是如何分子尺度动力学, 涉及单一分子或分子集合, 受影响, 和夫妇回到, 散装, 非平衡流体流动。与中子散射有关的主要限制与获得有限数量的中子束源的困难有关。
为了为本文所提出的模拟实验技术提供背景, 我们着重介绍了光散射技术在简单稠密气体和液体状态流体中的应用。在典型的光散射实验中, 偏振激光光束被定向到含有固定流体样本的小审讯量。从样品中的分子中散射的光, 然后在相对于入射光束的固定角度检测。根据感兴趣的分子动力学机制, 散射光信号的检测和分析采用光滤波或光混合检测方法。正如伯尔尼和皮科拉1所概述的, 过滤技术, 它在时间尺度上探测流体状态分子动力学的短于, 引入了后向散射干涉仪或衍射光栅, 并允许扫描的频谱密度<img alt="Equation 3" src="/files/ftp_upload/56632/56632eq3.jpg">的散射光。光学混合技术, 用于慢时间尺度的动态, s, 相比之下, 合并后散射 autocorrelator 或频谱分析仪, 其中的散射信号的光谱内容从测量散射光提取<img alt="Equation 4" src="/files/ftp_upload/56632/56632eq4.jpg">强度.
一般而言, 激光探针, 至少在光谱的可见光范围内的探测器, 波长比液态态分子间的特征间距长得多。在这种情况下, 探头光束激发五集体, 慢时间尺度, 长波长度的水动力模式2,9,10 (相对于特征碰撞频率的慢速): 两个粘性阻尼, 反传播声波, 两个不耦合, 纯粹的扩散涡度模式, 和一个单一的扩散热 (熵) 模式。在入射光束的 (纵向) 方向上, 声模是兴奋的, 而涡模式在横向方向上是兴奋的。
考虑纯实验散射技术, 两个基本问题, 位于平衡的核心和非平衡统计力学的分子, 液体状态系统, 仍然超越光和中子散射测量: 1) 严格的参数9,11显示单个液态状态分子的随机、碰撞和次碰撞-时间尺度动力学, 无论是经典牛顿动力学还是量子动力学, 都可以在广义万方程 (GLE) 的形式。GLE 的, 反过来, 构成了一个中心的理论工具研究的非平衡的分子在稠密气体和液体的统计力学。不幸的是, 由于个体 (非大分子) 分子的动力学不能通过任何一种散射技术来解决, 目前还没有直接的方法, 除了 MD 模拟, 以测试 GLE 的有效性。 2) 一项基本假设位于宏观连续体流体动力学的核心, 以及微尺度分子流体力学, 假定在长度和时间尺度上相对于分子直径和碰撞时间大, 但相对于连续体小长度和时间尺度, 局部热力学平衡 (LTE) 盛行。在连续流和传热模型, 如 n-s-斯托克斯 (NS) 方程, LTE 假设是必需的9 , 以耦合本质上的非平衡, 连续尺度流和能量传输特征-像粘性剪应力和热传导-严格平衡热力学性质, 如温度和内部能量。同样, 虽然微尺度动量和能量传输本质上是非平衡过程, 反映了耦合的、微尺度的质量、动量和能量流的出现, 但这些微尺度过程的模型假设电流表示来自 LTE9的小扰动。再次, 据我们所知, 没有对 LTE 假设的直接实验测试。特别是, 似乎没有分子水动力学散射实验试图在稠密, 移动, 非平衡流体流动。
本文概述了用标准粒子成像测速仪 (PIV) 测量振动颗粒桩的宏观、单粒子和集体粒子动力学的模拟实验技术, 可用于间接预测,解释, 并暴露在稠密气体和液体的单和多分子流体力学。在我们的组12发布的最近一篇文章中, 介绍了启用该方法的物理和理论元素。实验上, 宏观系统必须表现: (一) 持续的趋势, 以局部, 宏观统计机械平衡, 和 (ii) 小, 线性偏离平衡, 模仿 (弱) 非平衡波动观察分子流体力学系统。从理论上讲: (一) 描述稠密、相互作用的 N 粒子系统的平衡和弱非平衡统计力学的经典微型模型必须以宏观形式进行重铸, (ii) 所产生的宏观模型必须可靠地预测单和多粒子动力学, 从短, 粒子碰撞-时间尺度到长, 连续流-时间尺度。
在这里, 我们提出了一个详细的实验协议, 以及代表性的结果得到了新的技术。与 MD 模拟和光和中子散射方法不同, 这项新技术首次允许对流动的、强烈的非平衡、稠密气体和液体中的分子流体力学过程进行详细研究。

<table><tbody><tr><td>Vibratory Polishing Bowl</td><td>Raytech</td><td>AV-75</td><td></td></tr><tr><td>Flow Meter</td><td>Peristaltic Pumps</td><td>913 Mity Flex</td><td></td></tr><tr><td>Scale</td><td>Pelouze</td><td>4040</td><td></td></tr><tr><td>Triaxial Accelerometer</td><td>PCB Piezotronics</td><td>PCB 356B11</td><td>Accelerometer with Sensor Signal Conditioner</td></tr><tr><td>Data Acquisition Computer</td><td>IBM</td><td>Thinkpad</td><td>Used with high speed camera</td></tr><tr><td>High Speed Camera</td><td>Redlake</td><td>Motionxtra HG-XR</td><td></td></tr><tr><td>Zoom Lens</td><td>Tamron</td><td>Model A18</td><td>18-250mm F/3.5-6.3&amp;nbsp;</td></tr><tr><td>High intensity Light</td><td>ARRI</td><td>EB 400/575 D</td><td></td></tr><tr><td>Data Processing Computer</td><td>Dell</td><td>Dell Precision Tower 7910</td><td></td></tr><tr><td>PIV Software&amp;nbsp;</td><td>Dantec Dynamics</td><td>Dynamic Studio 2013</td><td>version 3.41.38</td></tr><tr><td>Data Acquisition Hardware</td><td>National Instruments</td><td>SCXI</td><td>SCXI-1000 Chasis with SCXI 1100 Card and SCXI 1303 Adapter</td></tr><tr><td>Data Acquisition Software</td><td>National Instruments</td><td>LabVIEW 2012</td><td></td></tr><tr><td>Data Processing Software</td><td>MATHWORKS</td><td>MATLAB</td><td></td></tr><tr><td>Polishing Media</td><td>Rosler</td><td>RSG 10/10S</td><td>Multiple media types used (mixed, spherical, triangular)</td></tr><tr><td>Polishing Solution</td><td>Rosler</td><td>FC KFL (3%)</td><td>3% soap solution with water</td></tr><tr><td>Ruled Scale</td><td>Swiss Precision Instruments</td><td>13-911-3</td><td></td></tr><tr><td>Graduated Cylinder</td><td>Global Scientific</td><td>601082</td><td></td></tr></tbody></table>

an analog macroscopic technique for studying molecular hydrodynamic processes in dense gases and liquids

本文介绍了一种研究稠密气体和液体中分子尺度流体力学过程的模拟、宏观方法。该技术适用于标准流体动态诊断, 粒子图像测速 (PIV), 以测量: i) 单个粒子 (晶粒) 的速度, 现存于短, 颗粒碰撞时间尺度, ii) 的速度系统的粒子, 在短碰撞时间-长, 连续流-时间尺度, iii) 在稠密分子流体中已知存在的集体水动力模式, 和 iv) 短期和长时间尺度的速度自相关函数, 中央了解粒子尺度动力学强相互作用, 稠密流体系统。基本系统由成像系统、光源、振动传感器、具有已知介质的振动系统以及 PIV 和分析软件组成。所需的实验测量和理论工具的概述, 当使用模拟技术来研究分子尺度的流体力学过程是突出的。该技术为传统用于分子流体力学研究的光子和中子束散射方法提供了一个相对简单的替代方案。

在介绍具有代表性的结果时, 我们指的是连续时间尺度过程, 它们是随着时间的推移而观察和预测的, 相对于特征粒碰撞时间刻度的来说, 是长期的, 和<img alt="Equation 25" src="/files/ftp_upload/56632/56632eq25.jpg"> <img alt="Equation 26" src="/files/ftp_upload/56632/56632eq26.jpg"> <img alt="Equation 27" src="/files/ftp_upload/56632/56632eq27.jpg"> 粒子时间尺度的进程, 如观察和预测的时间尺度,, 按顺序,...

Watch this Scientific Journal Video about An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids at JoVE.com

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

本文介绍了一种研究稠密流体分子流体力学过程的实验性模拟方法。该技术采用振动、高恢复力颗粒桩的粒子图像测速, 并允许对强相互作用、高密度气体和液体中已知和预测的动态过程进行直接、宏观的观察。

一种研究稠密气体和液体分子流体力学过程的模拟宏观技术

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a ...

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8.4K 次观看.  University of North Carolina at Charlotte. 本文介绍了一种研究稠密流体分子流体力学过程的实验性模拟方法。该技术采用振动、高恢复力颗粒桩的粒子图像测速, 并允许对强相互作用、高密度气体和液体中已知和预测的动态过程进行直接、宏观的观察。

视频: An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures

The behavior of confined colloidal suspensions with attractive interparticle interactions is critical to the rational design of materials for directed assembly1-3, drug delivery4, improved hydrocarbon recovery5-7, and flowable electrodes for energy storage8. Suspensions containing fluorescent colloids and non-adsorbing polymers are appealing model systems, as the ratio of the polymer radius of gyration to the particle radius&#160;and concentration of polymer control the range and strength of the interparticle attraction, respectively. By tuning the polymer properties and the volume fraction of the colloids, colloid fluids, fluids of clusters, gels, crystals, and glasses can be obtained9.&#160;Confocal microscopy, a variant of fluorescence microscopy, allows an optically transparent and fluorescent sample to be imaged with high spatial and temporal resolution in three dimensions. In this technique, a small pinhole or slit blocks the emitted fluorescent light from regions of the sample that are outside the focal volume of the microscope optical system. As a result, only a thin section of the sample in the focal plane is imaged. This technique is particularly well suited to probe the structure and dynamics in dense colloidal suspensions at the single-particle scale: the particles are large enough to be resolved using visible light and diffuse slowly enough to be captured at typical scan speeds of commercial confocal systems10. Improvements in scan speeds and analysis algorithms have also enabled quantitative confocal imaging of flowing suspensions11-16,37.&#160;In this paper, we demonstrate confocal microscopy experiments to probe the confined phase behavior and flow properties of colloid-polymer mixtures. We first prepare colloid-polymer mixtures that are density- and refractive-index matched. Next, we report a standard protocol for imaging quiescent dense colloid-polymer mixtures under varying confinement in thin wedge-shaped cells. Finally, we demonstrate a protocol for imaging colloid-polymer mixtures during microchannel flow.

Confocal microscopy is used to image quiescent and flowing colloid-polymer mixtures, which are studied as model systems for attractive suspensions. Image analysis algorithms are used to calculate structural and dynamic metrics for the colloidal particles that measure changes due to geometric confinement.

密闭静态和流动胶体聚合物混合物的共聚焦成像

The behavior of confined colloidal suspensions with attractive interparticle interactions is critical to the rational design of materials for directed ...

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化学

Fast Imaging Technique to Study Drop Impact Dynamics of Non-Newtonian Fluids

In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for detailed observation, scenarios that make it challenging to observe with conventional imaging systems. One of these is the drop impact of liquids, which usually happens within one tenth of millisecond. To tackle this challenge, a fast imaging technique is introduced that combines a high-speed camera (capable of up to one million frames per second) with a macro lens with long working distance to bring the spatial resolution of the image down to 10 &#181;m/pixel. The imaging technique enables precise measurement of relevant fluid dynamic quantities, such as the flow field, the spreading distance and the splashing speed, from analysis of the recorded video. To demonstrate the capabilities of this visualization system, the impact dynamics when droplets of non-Newtonian fluids impinge on a flat hard surface are characterized. Two situations are considered: for oxidized liquid metal droplets we focus on the spreading behavior, and for densely packed suspensions we determine the onset of splashing. More generally, the combination of high temporal and spatial imaging resolution introduced here offers advantages for studying fast dynamics across a wide range of microscale phenomena.

Drop impact of non-Newtonian fluids is a complex process since different physical parameters influence the dynamics over a very short time (less than one tenth of a millisecond). A fast imaging technique is introduced in order to characterize the impact behaviors of different non-Newtonian fluids.

快速成像技术来研究非牛顿流体的跌落冲击动力学

In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for ...

工程学

Microfluidic Devices for Characterizing Pore-scale Event Processes in Porous Media for Oil Recovery Applications

Microfluidic devices are versatile tools for studying transport processes at a microscopic scale. A demand exists for microfluidic devices that are resistant to low molecular-weight oil components, unlike traditional polydimethylsiloxane (PDMS) devices. Here, we demonstrate a facile method for making a device with this property, and we use the product of this protocol for examining the pore-scale mechanisms by which foam recovers crude oil. A pattern is first designed using computer-aided design (CAD) software and printed on a transparency with a high-resolution printer. This pattern is then transferred to a photoresist via a lithography procedure. PDMS is cast on the pattern, cured in an oven, and removed to obtain a mold. A thiol-ene crosslinking polymer, commonly used as an optical adhesive (OA), is then poured onto the mold and cured under UV light. The PDMS mold is peeled away from the optical adhesive cast. A glass substrate is then prepared, and the two halves of the device are bonded together. Optical adhesive-based devices are more robust than traditional PDMS microfluidic devices. The epoxy structure is resistant to swelling by many organic solvents, which opens new possibilities for experiments involving light organic liquids. Additionally, the surface wettability behavior of these devices is more stable than that of PDMS. The construction of optical adhesive microfluidic devices is simple, yet requires incrementally more effort than the making of PDMS-based devices. Also, though optical adhesive devices are stable in organic liquids, they may exhibit reduced bond-strength after a long time. Optical adhesive microfluidic devices can be made in geometries that act as 2-D micromodels for porous media. These devices are applied in the study of oil displacement to improve our understanding of the pore-scale mechanisms involved in enhanced oil recovery and aquifer remediation.

The goal of this procedure is to easily and rapidly produce a microfluidic device with customizable geometry and resistance to swelling by organic fluids for oil recovery studies. A polydimethylsiloxane mold is first generated, and then used to cast the epoxy-based device. A representative displacement study is reported.

微流体器件用于表征多孔介质中的孔隙尺度事件过程, 用于采油应用

Microfluidic devices are versatile tools for studying transport processes at a microscopic scale. A demand exists for microfluidic devices that are ...

环境科学

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

This protocol describes the operation of a liquid flow specimen holder for scanning transmission electron microscopy of AuNPs in water, as used for the observation of nanoscale dynamic processes.

使用扫描透射电子显微镜研究纳米大小的物体的动态过程中的液体

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

The Diffusion of Passive Tracers in Laminar Shear Flow

A simple method to experimentally observe and measure the dispersion of a passive tracer in a laminar fluid flow is described. The method consists of first injecting fluorescent dye directly into a pipe filled with distilled water and allowing it to diffuse across the cross-section of the pipe to obtain a uniformly distributed initial condition. Following this period, the laminar flow is activated with a programmable syringe pump to observe the competition of advection and diffusion of the tracer through the pipe. Asymmetries in the tracer distribution are studied and correlations between the pipe cross-section and the shape of the distribution is shown: thin channels (aspect ratio &#60;&#60; 1) produce tracers arriving with sharp fronts and tapering tails (front-loaded distributions), while thick channels (aspect ratio ~1) present the opposite behavior (back-loaded distributions). The experimental procedure is applied to capillary tubes of various geometries and is particularly relevant to microfluidic applications by dynamical similarity.

A protocol for the study of the diffusion of passive tracers in laminar pressure-driven flow is presented. The procedure is applicable to various capillary pipe geometries.

无源示踪剂在层流剪切流中的扩散

A simple method to experimentally observe and measure the dispersion of a passive tracer in a laminar fluid flow is described. The method consists of ...

Combining Microfluidics and Microrheology to Determine Rheological Properties of Soft Matter during Repeated Phase Transitions

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement during previous phase changes and applied shear. To determine the extent of these changes, we have developed a microfluidic device that enables repeated phase transitions induced by exchange of the surrounding fluid and microrheological characterization while limiting shear on the sample. This technique is &#181;2rheology, the combination of microfluidics and microrheology. The microfluidic device is a two-layer design with symmetric inlet streams entering a sample chamber that traps the gel sample in place during fluid exchange. Suction can be applied far away from the sample chamber to pull fluids into the sample chamber. Material rheological properties are characterized using multiple particle tracking microrheology (MPT). In MPT, fluorescent probe particles are embedded into the material and the Brownian motion of the probes is recorded using video microscopy. The movement of the particles is tracked and the mean-squared displacement (MSD) is calculated. The MSD is related to macroscopic rheological properties, using the Generalized Stokes-Einstein Relation. The phase of the material is identified by comparison to the critical relaxation exponent, determined using time-cure superposition. Measurements of a fibrous colloidal gel illustrate the utility of the technique. This gel has a delicate structure that can be irreversibly changed when shear is applied. &#181;2rheology data shows that the material repeatedly equilibrates to the same rheological properties after each phase transition, indicating that phase transitions do not play a role in microstructural changes. To determine the role of shear, samples can be sheared prior to injection into our microfluidic device. &#181;2rheology is a widely applicable technique for the characterization of soft matter enabling the determination of rheological properties of delicate microstructures in a single sample during phase transitions in response to repeated changes in the surrounding environmental conditions.

We demonstrate the fabrication and use of a microfluidic device that enables multiple particle tracking microrheology measurements to study the rheological effects of repeated phase transitions on soft matter.

微流体和 Microrheology 相结合测定软物质在重复相变过程中的流变特性

The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement ...

Film Control to Study Contributions of Waves to Droplet Impact Dynamics on Thin Flowing Liquid Films

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous studies on flowing liquid films have neglected the contributions of spatial structures of waves to the impact outcome, while this has recently been shown to have a significant influence on the drop impact dynamics. In this report, we outline a step-by-step procedure to investigate the effect of periodic inlet forcing of a flowing liquid film leading to the production of spatiotemporally regular wave structures on drop impact dynamics. A function generator in connection with a solenoid valve is used to excite these spatiotemporally regular wave structures on the film surface while the impact dynamics of uniform-sized droplets are captured using a high-speed camera. Three distinct regions are then studied; viz. the capillary wave region preceding the large wave peak, the flat film region, and the wave hump region. The effects of important dimensionless quantities such as film Reynolds, drop Weber and Ohnesorge numbers parameterized by the film flow rate, drop speed, and drop size are also examined. Our results show interesting, hitherto undiscovered dynamics brought about by this application of film inlet forcing of the flowing film for both low and high inertia drops.

A protocol to study the contributions of waves to droplet impact dynamics on flowing liquid films is presented.

薄膜控制研究波浪对液滴冲击动力学的影响薄流动液体薄膜

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous ...

Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package

We have developed a Python-based open-source package to analyze the results stemming from ab initio molecular-dynamics simulations of fluids. The package is best suited for applications on natural systems, like silicate and oxide melts, water-based fluids, and various supercritical fluids. The package is a collection of Python scripts that include two major libraries dealing with file formats and with crystallography. All the scripts are run at the command line. We propose a simplified format to store the atomic trajectories and relevant thermodynamic information of the simulations, which is saved in UMD files, standing for Universal Molecular Dynamics. The UMD package allows the computation of a series of structural, transport and thermodynamic properties. Starting with the pair-distribution function it defines bond lengths, builds an interatomic connectivity matrix, and eventually determines the chemical speciation. Determining the lifetime of the chemical species allows running a full statistical analysis. Then dedicated scripts compute the mean-square displacements for the atoms as well as for the chemical species. The implemented self-correlation analysis of the atomic velocities yields the diffusion coefficients and the vibrational spectrum. The same analysis applied on the stresses yields the viscosity. The package is available via the GitHub website and via its own dedicated page of the ERC IMPACT project as open-access package.

Melts and fluids are ubiquitous vectors of mass transport in natural systems. We have developed an open-source package to analyze ab initio molecular-dynamics simulations of such systems. We compute structural (bonding, clusterization, chemical speciation), transport (diffusion, viscosity) and thermodynamic properties (vibrational spectrum).

使用 UMD 软件包分析 Ab Initio 分子动力学模拟中的熔体和流体

We have developed a Python-based open-source package to analyze the results stemming from ab initio molecular-dynamics simulations of fluids. The package ...

Microtensiometer for Confocal Microscopy Visualization of Dynamic Interfaces

Adsorption of surface-active molecules to fluid-fluid interfaces is ubiquitous in nature. Characterizing these interfaces requires measuring surfactant adsorption rates, evaluating equilibrium surface tensions as a function of bulk surfactant concentration, and relating how surface tension changes with changes in the interfacial area following equilibration. Simultaneous visualization of the interface using fluorescence imaging with a high-speed confocal microscope allows the direct evaluation of structure-function relationships. In the capillary pressure microtensiometer (CPM), a hemispherical air bubble is pinned at the end of the capillary in a 1 mL volume liquid reservoir. The capillary pressure across the bubble interface is controlled via a commercial microfluidic flow controller that allows for model-based pressure, bubble curvature, or bubble area control based on the Laplace equation. Compared to previous techniques such as the Langmuir trough and pendant drop, the measurement and control precision and response time are greatly enhanced; capillary pressure variations can be applied and controlled in milliseconds. The dynamic response of the bubble interface is visualized via a second optical lens as the bubble expands and contracts. The bubble contour is fit to a circular profile to determine the bubble curvature radius, R, as well as any deviations from circularity that would invalidate the results. The Laplace equation is used to determine the dynamic surface tension of the interface. Following equilibration, small pressure oscillations can be imposed by the computer-controlled microfluidic pump to oscillate the bubble radius (frequencies of 0.001-100 cycles/min) to determine the dilatational modulus The overall dimensions of the system are sufficiently small that the microtensiometer fits under the lens of a high-speed confocal microscope allowing fluorescently tagged chemical species to be quantitatively tracked with submicron lateral resolution.

This manuscript describes the design and operation of a microtensiometer/confocal microscope to do simultaneous measurements of interfacial tension and surface dilatational rheology while visualizing the interfacial morphology. This provides the real-time construction of structure-property relationships of interfaces important in technology and physiology.

用于动态界面共聚焦显微镜可视化的微量天体测量仪

Adsorption of surface-active molecules to fluid-fluid interfaces is ubiquitous in nature. Characterizing these interfaces requires measuring surfactant ...

A Microfluidic Approach for the Study of Ice and Clathrate Hydrate Crystallization

An accurate mechanistic description of water crystallization is challenging and requires a few key elements: superb temperature control to allow the formation of single microscopic crystals and a suitable microscopy system coupled to the cold stage. The method described herein adds another important feature that includes exchanging solutions around ice and clathrate hydrate crystals. The described system comprises a combination of unique and home-developed instruments, including microfluidics, high-resolution cold stages, and fluorescence microscopy. The cold stage was designed for microfluidic devices and allows for the formation of micron-sized ice/hydrate crystals inside microfluidic channels and the exchange of solutions around them. The temperature resolution and stability of the cold stage is one millikelvin, which is crucial for controlling the growth of these small crystals. This diverse system is used to study the different processes of ice and hydrate crystallization and the mechanism by which the growth of these crystals is inhibited. The protocol describes how to prepare microfluidic devices, how to grow and control microscopic crystals in the microfluidic channels, and how the utilization of the flow of liquids around ice/hydrate crystals affords new insights into the crystallization of water.

The present protocol describes the crystallization of microscopic ice crystals and clathrate hydrates in microfluidic devices, enabling liquid exchange around the formed crystals. This provides unparalleled possibilities to examine the crystallization process and binding mechanisms of the inhibitors.

一种用于研究冰和包合物水合物结晶的微流控方法

An accurate mechanistic description of water crystallization is challenging and requires a few key elements: superb temperature control to allow the ...