这项工作得到了以色列科学基金会306/15 号赠款的支持。

1. 系统准备
<ol><li>用自来水将水箱装满20厘米深, 以满足深水条件;清洗任何可能影响表面张力的污染物的水面。</li>
	<li>在所需的提取处放置仪表托架。<ol>
<li>装入托管管并将其放置在测试部分气流部分的中心。</li>
		<li>在计算机控制的垂直舞台上安装波形测量仪, 以实现其静态校准。</li>
	</ol>
</li>
	<li>将汉莎组件放置在所需的提取位置, 并在7厘米的横向距离上从波形表中定位, 以消除波规组件与光路的干扰。 注: 建议使用不透明窗帘, 以防止 PSD 暴露于周围光线, 以及保护环境不受激光束的虚假反射。<ol>
<li>将激光定位在水箱下方, 使光束垂直定向, 并聚焦光束。</li>
		<li>将菲涅耳透镜放置在试验区内尽可能高的水面上, 以尽量减少透镜对气流的扰动。</li>
		<li>确保偏转激光束击中透镜在其中心部分的极端风条件下计划在实验阶段。</li>
		<li>将扩散屏幕完全安装在透镜的焦点平面上, 然后检查透镜和屏幕的水平和垂直对准。</li>
		<li>确保当水面静止时, 任何两个平行的垂直激光光束在中心上完全击中扩散屏。 注意: 这可以用两个相同的激光器进行测试, 它们位于一定距离。</li>
		<li>定位 PSD, 确保扩散屏的整个区域位于探测器的有效区域内。通过将透镜设置调整为透镜与屏幕之间的实际距离来执行 PSD 透镜的聚焦。</li>
	</ol>
</li>
</ol>2. 传感器的校准和操作
<ol><li>
测波仪的标定
	<ol>
<li>对每个测量位置和实验运行中预期的最大风速进行波形校准。<ol>
<li>设置传感器的垂直位置, 使平均水位近似于传感线长度的中间。</li>
			<li>将风机速度设置为所需值, 并允许风平稳地吹过足够长的时间 (2-3 分钟)。</li>
			<li>使用示波器, 手动调整波形测量器的灵敏度、增益和偏移量, 使用调理单元, 以确保在波形场中, 与最高波峰和最低槽相对应的电压值在 a/d 范围内。转换器 (+/-10 V)。</li>
			<li>关闭鼓风机几分钟, 直到水的表面变得完全不受干扰。</li>
			<li>通过垂直移动波形表 , 验证浸没长度是否在预期的最峰和槽值内。</li>
			<li>使用自定义的常规在静止水中自动校准波形测量仪在一定深度下淹没测量器, 并在5秒内记录每深度的平均电压输出。</li>
			<li>将二次校准多项式与记录的数据相匹配, 以获得依赖h (V), 其中h是沉没深度 (对应于瞬时表面高程), 作为测量输出电压V的函数。</li>
			<li>直观地验证安装的校准多项式的质量 (图 3)。</li>
		</ol>
</li>
	</ol>
</li>
</ol><img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56480/56480fig3.jpg"> 图3。测波仪的标定曲线。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56480/56480fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<ol start="2"><li>
汉莎的标定与调整
	<ol>
<li>验证传感器组件每次位移后汉莎的性能。<ol>
<li>使用在水平玻璃板上放置的光学楔形棱镜, 将激光光束与模拟已知水面坡度的光轴偏移。</li>
			<li>使用示波器或自定义的数据采集程序, 在扩散屏幕上采样偏激光光斑的 PSD 输出。</li>
			<li>从实测坐标激光光斑坐标计算光束偏转角和斜率;将结果与已知的楔形角进行比较。</li>
			<li>使用一个或多个棱镜对多个偏转角重复该过程。 注: 采用从2.5°到17.5°的偏转角楔形棱镜;如果由于 psd 与扩散屏的不协调性而导致测试失败, 请手动调整 psd, 以纠正不对齐。此过程使用2D 水平平移阶段和级别手动执行, 非常耗时。</li>
		</ol>
</li>
		<li>
PSD 线性度校验与标定程序
		<ol>
<li>将已打印在扩散屏幕上的透明工作表上的相同间距的网格放在一起, 使其坐标轴、 x和y分别与向下和交叉风向对齐 (图 4)。 注: 网格方便准确地将激光光束定向到扩散屏幕上所需的位置, 或者使用一组棱镜或沿风向和风向方向将激光移动到扩散屏下。</li>
			<li>使用棱镜集, 偏转垂直激光束, 在扩散屏上获得激光光斑的多个径向位置, 同时保持恒定的方位角。 注: 分辨率为1厘米, 最大半径为7厘米, 用于9个方位角。</li>
			<li>将激光光斑移动到x方向中的多个位置, 同时保持y坐标常量, 然后将移动的方向更改为y, 并保持x常量。 注意: 所用的范围和分辨率与上一节中的相同。</li>
			<li>每次校准时, 在网格上收集大约50点。 注: 激光光斑坐标由 psd 获取, 并使用连接到 psd 的标准双通道示波器进行评估。<ol>
<li>对于每个方向, 使用数据的线性拟合来产生校准系数, 将 PSD 传感器上的激光束的坐标转换为扩散屏幕上相应的坐标。 注意: 在图5中绘制了 PSD 校准的一个示例, 其中列出了沿测试部分中线所采取的一组点。当扩散屏和传感器的轴线正确对准时, 传感器的响应和校准系数在各个方向上几乎是相同的。网格方便了校准程序, 允许在扩散屏幕上轻松地确定激光斜率坐标。</li>
			</ol>
</li>
		</ol>
</li>
	</ol>
</li>
</ol><img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56480/56480fig4.jpg"> 图4。扩散屏幕网格.网格方便准确地将激光光束定向到扩散屏幕上所需的位置, 无论是使用一组棱镜, 还是沿风向和风向方向将激光移动到扩散屏下方<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56480/56480fig4large.jpg" target="_blank">请单击此处以查看此图的较大版本.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56480/56480fig5.jpg"> 图5。PSD 校准曲线.该图表明, 将 PSD 输出电压转换为坐标将产生足够的结果。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56480/56480fig5large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
3. 实验程序和数据采集
注意: 有关以下步骤中使用的用户界面, 请参见辅助图 1 。
<ol><li>使用自定义生成的程序用户界面设置鼓风机频率。 注: 在最初未受干扰的水面上, 几乎逐步增加风速, 其次是在规定的持续时间 (120s) 内稳定的气流速率, 以及风机的近脉冲关闭。</li>
	<li>确定不同的稳定风速和所需风机设置的数量。</li>
	<li>调整压力传感器设置, 以预期的范围内的动态压力变化检测到的皮托管。</li>
	<li>确保在每一个实现的开始, 没有风和水面不受干扰 (镜面平滑)。与鼓风机的操作同步启动数据采集。</li>
	<li>记录瞬时表面高程、沿横风向方向的表面斜率分量、托管管输出监测平均风速U和按规定采样速率从鼓风机控制器发出的电压变化 (300 Hz 或渠道使用了)。 注: 由程序获取的波形测量器的电压自动转换为表面高程, 使用图 3中显示的校准系数。</li>
	<li>继续取样, 以便在鼓风机关闭后记录衰减波场的足够时间。</li>
	<li>取样完成后, 确保自动实验程序允许有足够的时间 (取决于系统) 在启动下一次运行之前使水表面处于未受干扰的状态。</li>
	<li>保存所有记录的数据以供后续处理。</li>
	<li>执行规定的认识的数字 (通常100独立奔跑被发现足够)。</li>
	<li>计算记录数据的集合平均参数, 作为鼓风机启动后所经过的时间的函数。</li>
	<li>对测试部分中对应于选定目标风速的鼓风机下一设置重复整个过程。</li>
</ol>

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作者没有什么可透露的。

本实验协议的目的是在不稳定的风强迫下, 在时间和空间上演化的波场进行定量表征。由于风浪本质上是随机的和三维的, 因此在时间和空间上变化很快, 在时间依赖的风力强迫下, 一个不断增长的风浪场个体认识的记录只能提供对治理的定性估计。波形参数。为了实现该协议的目标, 获得统计上可靠的时间和提取相关波特性, 需要应用具有相同风变化模式的大量实验运行的时间分辨集合平均。由于?...

自古以来, 众所周知, 水面上的波浪被风所激发。目前对控制这一进程的物理机制的理解远非令人满意。许多试图描述风力发电的理论在过去几年中提出了1,2,3,4, 但他们的可靠的实验验证还没有可用。在海洋中随机风浪的测量是极具挑战性的, 因为不可预知的风可能会在方向上和震级上变化得很快。实验室实验的优点是可控制的条件, 使长期和可重复的测量。
在实验室环境的恒定风强迫下, 风浪在空间中演化。几十年前在稳态强迫下进行的波浪的早期实验室实验仅限于瞬时表面高程测量5,6,7,8。最近的研究还使用各种光学技术来测量瞬时水表面倾角, 如汉莎9,10。这些测量允许得到一些有限的质量信息的三维结构的风波场。当风强迫是不稳定的, 因为它是在野外试验中, 引入额外的复杂性, 以风的激励问题, 因为产生的波场的统计参数不仅在空间, 但时间也不一样。到目前为止的尝试, 以定性和定量地描述波浪演变模式在时间依赖强迫下仅部份地成功了11,12,13,14,15,16. 不同似然的物理机制的相对贡献可能导致激发和波浪的增长由于风作用仍然是未知数。
我们的实验设施的目的是为了能够积累准确和多样的统计信息的变化的风波场特征在稳定或不稳定的风强迫。两个主要因素有助于进行这些详细的研究。首先, 该设施的适度规模导致了相对较短的特征演化尺度的时间和空间。第二, 整个实验由计算机完全控制, 从而使实验运行在不同实验条件下的性能能够自动、实际地实现, 无需人工干预。这些特性的实验设置是非常重要的, 在进行实验的波浪兴奋从休息的冲动风。
本文研究了风波在稳定强迫下的空间生长, 为风速17。根据植物19所提出的里程18理论, 将结果与增长率估计进行了比较。对比表明, 实验结果与理论预测有显著差异。在17中还获得了其他重要参数, 例如测试部分中的平均压降, 以及特征静压波动的绝对值和相位。在空气-水界面上的剪切应力对于描述风与波浪之间的动量和能量传递是必不可少的17,19。因此, 在大量的提取和风速下, 进行了对数边界层的详细测量, 并对水波上的湍流波动进行了分析, 结果为20。本文所确定的空气-水界面的摩擦速度u*的值用于获取在我们的设施21中测量到的风浪的无量纲统计参数。将这些值与大型实验装置和野外试验中获得的相应无量纲参数进行了比较。以前的21表明, 在适当的尺度下, 小规模设施所获得的风波场的重要特征与较大实验室积累的相应数据没有显著差异。安装和露天测量。这些参数包括具有代表性的波浪高度和波长的空间增长, 表面高程的频谱的形状, 以及较高统计矩的值。
随后在我们的设施中进行的研究22,23表明, 风波本质上是随机的和三维的。为了更好地了解风波的3D 结构, 我们尝试使用立体视频成像22对扩展区域的水面高程进行定量的时间依赖性测量。由于现有的计算机电源不足, 而且处理算法还不够有效, 这些尝试被证明只是部分成功。结果表明, 采用传统的电容式波规和汉莎, 可为风浪的空间结构提供有价值的信息。同时应用这两种仪器, 可以独立测量瞬时表面高程和瞬时表面斜率的两个分量的高时间分辨率23。这些测量允许估计波浪的主导频率和主要波浪长度, 并且提供对波浪结构的洞察在正常风向的方向。一种可由计算机控制的马达垂直移动的托管管, 它补充了传感器的集合, 用于测量风速。
所有这些研究表明, 随机和三维的风波导致测量参数的显著变化, 即使在稳定的风强迫和单一测量位置。因此, 需要长时间的测量与实测波场的特征时间尺度相称, 以积累足够的信息来提取可靠的统计量。为了获得有价值的物理洞察力的机制, 控制波场的空间变化, 必须在许多地点进行测量, 并尽可能多的价值的风速尽可能在测试部分。为了实现这一目标, 最好采用自动化的实验程序。
非恒定风强迫下的波浪实验引入了一个额外的复杂程度。在这类研究中, 必须将瞬时测量参数与风速的瞬时水平联系起来。考虑以近脉冲风强迫作为一个重要例子, 从静止的波浪中激发的实验。在这种情况下, 需要许多独立的测量, 在风的作用下演变的风波场, 在不同的时间根据相同的规定模式24。有意义的统计参数, 表示为自空气流动开始以来所经过的时间函数, 然后通过平均从独立认识积累的集合中提取的数据来计算。这项工作可能涉及连续抽样的十个和上百个小时。完成这样一项雄心勃勃的任务所需的实验课程总持续时间, 除非实验完全自动化, 否则整个方法是行不通的。直到最近, 在风浪设施中没有这样的完全计算机化的实验程序。这是在非恒定强迫下缺乏可靠的风浪统计数据的主要原因之一。
由于该实验所用的设施不是从商用的现成硬件构造的, 所以这里提供了其主要部件的简要描述。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56480/56480fig1.jpg"> 图1。示意图 (不缩放) 实验设施的视图.1-鼓风机;2流入沉降室;3-流出沉降室;4-消音器盒;5试验段;6滩;7-换热器;8蜂窝;9喷嘴;10-板式;11瓣;12-仪器运输;13波计由步进电机驱动;14-由步进电机驱动的托管管。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56480/56480fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
实验设施包括一个封闭环风洞安装在一个波坦克 (示意图视图显示在图 1)。测试部分为5米长, 0.4 米宽, 0.5 米深。壁和地板由6毫米厚的玻璃板组成, 并被封闭在一个由铝型材制成的框架内。一个40厘米长的襟翼提供平滑的扩展气流剖面从喷嘴到水面。波浪能吸收的海滩由多孔的包装材料制成位于坦克的末端。计算机控制的鼓风机允许在测试区段达到平均气流速度在15米/秒。
该定制电容式100毫米长波测量仪由阳极氧化钽制成。0.3 毫米线安装在一个垂直的阶段, 由 PC 控制的步进电机驱动, 为波规校准设计。一个直径为3毫米的托管管, 用于测量测试部分中央气流部分的动态压力。
测量瞬时2D 水表面斜率的汉莎安装在与测试部分分离的框架上, 可以定位在罐体上的任意位置 (图 2)。汉莎由四主要部分组成: 激光二极管、菲涅尔透镜、扩散屏和位置传感探测器 (PSD) 组件。激光二极管产生 650 nm (红色), 200 兆瓦可获得焦点激光束直径约0.5 毫米。26.4 厘米直径的菲涅尔透镜, 焦距为22.86 厘米, 将传入的激光光束定向到位于透镜后焦平面上的 25 x 25 厘米2扩散屏幕。
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56480/56480fig2.jpg"> 图2。激光斜率计 (汉莎) 的示意图.1-激光二极管;2-菲涅尔透镜;3-扩散屏幕;4位传感器检测器 (PSD)。<a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56480/56480fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
该协议描述了允许执行实验的过程, 在这种情况下, 在时间依赖的风力强迫下, 测量非恒定波的许多参数。考虑到实验设施的技术局限性, 可以根据所需风速的时间来调整程序。本议定书具体描述了在每一个实现中, 风开始几乎在最初平静的水的冲动的实验。稳定的风强迫, 然后持续足够长的风波场在测试段各处达到准稳态状态。风最后被关闭, 再几乎冲动。在各个阶段, 记录了多个波形参数。该程序允许计算出许多统计代表性的集合-平均数量表征瞬时局部风波场是新颖的, 并在最近在我们的设施进行的实验过程中发展22,23,24。

<table>
	<tbody>
		<tr>
			<td>PSD</td>
			<td>THORLABS</td>
			<td>PDP90A</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Diode</td>
			<td></td>
			<td></td>
			<td>any laser pointer &#8804; 200 mW</td>
		</tr>
		<tr>
			<td>Aspheric Fresnel Lens</td>
			<td>EDMUND OPTICS</td>
			<td>#46-390</td>
			<td>Diameter 10.4&#39;&#39;, Focal length 9&#39;&#39;</td>
		</tr>
		<tr>
			<td>Wave-gauge</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>Pressure Transducer</td>
			<td>MAMAC SYSTEMS</td>
			<td>PR-274-R2-VDC</td>
			<td></td>
		</tr>
		<tr>
			<td>Signal Conditioner</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>Diffusive screen</td>
			<td>EDMUND OPTICS</td>
			<td>#02-147</td>
			<td></td>
		</tr>
		<tr>
			<td>Water tank</td>
			<td></td>
			<td></td>
			<td>custome made</td>
		</tr>
		<tr>
			<td>A/D card PCI-6221</td>
			<td>National Instruments</td>
			<td>779066-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Pitot tube</td>
			<td>KIMO Instruments</td>
			<td>12971</td>
			<td></td>
		</tr>
		<tr>
			<td>15&#176; Nom. VIS-NIR Coated, Wedge Prism</td>
			<td>EDMUND OPTICS</td>
			<td>#47-624</td>
			<td></td>
		</tr>
		<tr>
			<td>10&#176; Nom. VIS 0&#176; Coated, Wedge Prism</td>
			<td>EDMUND OPTICS</td>
			<td>#49-444</td>
			<td></td>
		</tr>
		<tr>
			<td>2.5&#176; Nom. Fused Silica Wedge Prism Uncoated</td>
			<td>EDMUND OPTICS</td>
			<td>#84-863</td>
			<td></td>
		</tr>
		<tr>
			<td>4&#176; Nom. Uncoated, Wedge Prism</td>
			<td>EDMUND OPTICS</td>
			<td>#43-650</td>
			<td></td>
		</tr>
		<tr>
			<td>5.0&#176; Nom. Fused Silica Wedge Prism Uncoated</td>
			<td>EDMUND OPTICS</td>
			<td>#84-865</td>
			<td></td>
		</tr>
		<tr>
			<td>LabView Full Development System</td>
			<td>National Instruments</td>
			<td>776670-35</td>
			<td></td>
		</tr>
	</tbody>
</table>

measurements of waves in a wind-wave tank under steady and time-varying wind forcing

这篇手稿描述了一个实验程序, 它允许获得不同的定量信息的时间和空间演化的水波兴奋的时候依赖和稳定的风强迫。利用电容式波浪测量仪和激光斜率计 (汉莎) 测量了风波装置试验段沿线多个位置的瞬时水面高程和瞬时面斜率的两个分量。计算机控制的鼓风机在水箱的水中提供气流, 其速率可能会随时间而变化。在目前的实验中, 测试部分的风速最初从静止到设定值快速增加。它然后保持恒定为规定的期间;最后, 气流被关闭。在每次实验运行的开始, 水面是平静的, 没有风。鼓风机的操作是同时启动的, 并获得由计算机提供的所有传感器的数据;数据采集一直持续到坦克中的波浪完全衰减。在相同的强迫条件下进行的多个独立运行允许确定统计可靠的集合平均特征参数, 以定量地描述在初始开发阶段的风浪变化时间, 作为提取功能。该程序还允许描述在稳定的风力强迫下的波浪场的空间演化, 以及当风被关闭后, 随着海浪的衰减, 作为提取的函数。

在图 6、图 7和图 8中绘制了代表性的集合平均结果。瞬时曲面高程的 RMS 值的变化 <η2>1/2的特征是随机风波振幅的特点, 如图 6所示, 作为时间流逝的函数, 因为鼓风机的启动。显示的结果与板式、 x和三目标风速 ( U. ) 的距离为3。</...

Watch this Scientific Journal Video about Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing at JoVE.com

Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing

这篇手稿描述了一个完全计算机控制的程序, 允许获得可靠的统计参数, 从实验的水波的稳定和不稳定的风强迫在一个小规模的设施。

稳定时变风强迫下风浪罐中波浪的测量

This manuscript describes an experimental procedure that allows obtaining diverse quantitative information on temporal and spatial evolution of water ...

measurements-waves-wind-wave-tank-under-steady-time-varying-wind

Research

Education

JoVE Journal

JoVE Core

Engineering

Physics

Electrical Engineering

Unit 1

First and Second-Order Circuits

Waves

SCIENTISTS IN ACTION

8.6K 次观看.  Tel-Aviv University. 这篇手稿描述了一个完全计算机控制的程序, 允许获得可靠的统计参数, 从实验的水波的稳定和不稳定的风强迫在一个小规模的设施。

视频: Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.

A shear cell is developed for small-angle neutron scattering measurements in the velocity-velocity gradient plane of shear and is used to characterize complex fluids. Spatially resolved measurements in the velocity gradient direction are possible for studying shear-banding materials. Applications include investigations of colloidal dispersions, polymer solutions, and self-assembled structures.

测量材料在微流使用1-2面流小角中子散射

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is ...

科研

工程学

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

互溶的测量准备和摩擦力显微镜，反对聚合物刷

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

Preparation and Evaluation of Hybrid Composites of Chemical Fuel and Multi-walled Carbon Nanotubes in the Study of Thermopower Waves

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs along the interface between the fuel and core materials. Simultaneously, dynamic changes in thermal and chemical potentials across the micro/nanostructured materials result in concomitant electrical energy generation induced by charge transfer in the form of a high-output voltage pulse. We demonstrate the entire procedure of a thermopower wave experiment, from synthesis to evaluation. Thermal chemical vapor deposition and the wet impregnation process are respectively employed for the synthesis of a multi-walled carbon nanotube array and a hybrid composite of picric acid/sodium azide/multi-walled carbon nanotubes. The prepared hybrid composites are used to fabricate a thermopower wave generator with connecting electrodes. The combustion of the hybrid composite is initiated by laser heating or Joule-heating, and the corresponding combustion propagation, direct electrical energy generation, and real-time temperature changes are measured using a high-speed microscopy system, an oscilloscope, and an optical pyrometer, respectively. Furthermore, the crucial strategies to be adopted in the synthesis of hybrid composite and initiation of their combustion that enhance the overall thermopower wave energy transfer are proposed.

A protocol for conducting thermopower wave experiments is presented. The synthesis of hybrid composites of a chemical fuel and micro/nanostructured material, manufacturing of a thermopower wave generator, and methods for measuring the corresponding physical phenomena are described.

化学燃料和多壁碳纳米管的混杂复合材料的热电波的研究准备和评估

When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs ...

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

The technique of diffusive gradients in thin films (DGT) is proposed for speciation studies of plutonium. This protocol describes diffusion experiments probing the behavior of Pu(IV) and Pu(V) in presence of organic matter. DGTs deployed in a karstic spring allow assessment of the bioavailability of Pu.

环境钚的薄膜弥散形态和生物利用度测量

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can ...

Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering, which is a fundamental element to the approach of nanosafety-by-design of nanostructured products for their durable development. This approach is basically a preemptive one in which the focus is put on minimizing the emission of engineered nanomaterials' aerosols during the usage phase of the product's life cycle. This can be attained by altering its material properties during its design phase without compromising with any of its added benefits. In this article, an experimental protocol is presented to investigate the nanosafety-by-design of three commercial nanostructured products with respect to their mechanical solicitation and environmental weathering. The means chosen for applying the mechanical solicitation is an abrasion process and for the environmental weathering, it is an accelerated UV exposure in the presence of humidity and heat. The eventual emission of engineered nanomaterials is studied in terms of their number concentration, size distribution, morphology and chemical composition. The purpose of the protocol is to study the emission for test samples and experimental conditions which are corresponding to real life situations. It was found that the application of the mechanical stresses alone emits the engineered nanomaterials' aerosols in which the engineered nanomaterial is always embedded inside the product matrix, thus, a representative product element. In such a case, the emitted aerosols comprise of both nanoparticles as well as microparticles. But if the mechanical stresses are coupled with the environmental weathering, the experimental protocol reveals then the eventual deterioration of the product, after a certain weathering duration, may lead to the emission of the free engineered nanomaterial aerosols too.

In this article, an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering is presented. Results on the emission of engineered nanomaterials, in the form of aerosols are presented. The specific experimental set-up is described in detail.

实验协议来调查产品的粒子雾化在耐磨和环境下风化

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental ...

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a new and inexpensive procedure to force mode locking in a pre-adjusted nonlinear polarization rotation fiber laser. This procedure is based on the detection of a sudden change in the output polarization state when mode locking occurs. This change is used to command the alignment of the intra-cavity polarization controller in order to find mode-locking conditions. More specifically, the value of the first Stokes parameter varies when the angle of the polarization controller is swept and, moreover, it undergoes an abrupt variation when the laser enters the mode-locked state. Monitoring this abrupt variation provides a practical easy-to-detect signal that can be used to command the alignment of the polarization controller and drive the laser towards mode locking. This monitoring is achieved by feeding a small portion of the signal to a polarization analyzer measuring the first Stokes parameter. A sudden change in the read out of this parameter from the analyzer will occur when the laser enters the mode-locked state. At this moment, the required angle of the polarization controller is kept fixed. The alignment is completed. This procedure provides an alternate way to existing automating procedures that use equipment such as an optical spectrum analyzer, an RF spectrum analyzer, a photodiode connected to an electronic pulse-counter or a nonlinear detecting scheme based on two-photon absorption or second harmonic generation. It is suitable for lasers mode locked by nonlinear polarization rotation. It is relatively easy to implement, it requires inexpensive means, especially at a wavelength of 1550 nm, and it lowers the production and operation costs incurred in comparison to the above-mentioned techniques.

A protocol to detect and automate mode locking in a pre-adjusted nonlinear polarization rotation fiber laser is presented. The detection of a sudden change in the output polarization state when mode locking occurs is used to command the alignment of an intra-cavity polarization controller in order to find mode-locking conditions.

锁模自动化的非线性偏振旋转光纤激光器通过输出偏振测量

When a laser is mode-locked, it emits a train of ultra-short pulses at a repetition rate determined by the laser cavity length. This article outlines a ...

Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly.

Acoustofluidic devices use ultrasonic waves within microfluidic channels to manipulate, concentrate and isolate suspended micro and nanoscopic entities. This protocol describes the fabrication and operation of such a device supporting bulk acoustic standing waves to focus particles in a central streamline without the aid of sheath fluids.

制造和Acoustofluidic设备的运营支撑体声波驻波的聚焦鞘颗粒

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must ...

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided.

We describe the use of micro-thermocouples to estimate local temperature gradients in steady laminar boundary layer diffusion flames. By extension of the Reynolds Analogy, local temperature gradients can be further used to estimate the local mass burning rates and heat fluxes in such flames with high accuracy.

在稳定层流边界层扩散火焰本地热通量和燃烧率的估计实验方法

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex ...

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to visualize the behavior of petroleum samples under process conditions. The experimental setup relies on a custom-built micro-reactor fitted with a sapphire window at the bottom, which is placed over the objective of an inverted microscope equipped with a cross-polarizer module. Using reflection microscopy enables the visualization of opaque samples, such as petroleum vacuum residues, or asphaltenes. The combination of the sapphire window from the micro-reactor with the cross-polarizer module of the microscope on the light path allows high-contrast imaging of isotropic and anisotropic media. While observations are carried out, the micro-reactor can be heated to the temperature range of cracking reactions (up to 450 &#176;C), can be subjected to H2 pressure relevant to hydroconversion reactions (up to 16 MPa), and can stir the sample by magnetic coupling. 
Observations are typically carried out by taking snapshots of the sample under cross-polarized light at regular time intervals. Image analyses may not only provide information on the temperature, pressure, and reactive conditions yielding phase separation, but may also give an estimate of the evolution of the chemical (absorption/reflection spectra) and physical (refractive index) properties of the sample before the onset of phase separation.

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

This article describes a setup and method for the in situ visualization of oil samples under a variety of temperature and pressure conditions that aim to emulate refining and upgrading processes. It is primarily used for studying isotropic and anisotropic media involved in the fouling behavior of petroleum feeds.

在油样品的相行为在炼油工艺条件的原位可视化

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

静态和扫描模式下中子伽马分析法测量土壤碳

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...