This research was made possible through funding from the U.S. Office of Naval Research under Grant No. N000141210337, Deborah Nalchajian and Ronald Joslin.

1.实验准备<ol><li>选择合适的麦克风来构建RMP。感兴趣的频率范围内使用的麦克风的频率范围。 注意:在这个实验中，100和10000赫兹之间的压力波动的兴趣。所选麦克风的测量频率范围是从100到10000赫兹。麦克风的尺寸应尽可能小，虽然有对大小没有具体标准。 </li><li>估计使用附录中描述的分析方法中的制冷剂管理系统的灵敏度和频率响应。调整通过改变管和结构的尺寸的RMP的灵敏度和频率响应。 </li><li>使用的Dremel到0.5 mm内口径不锈钢管切成5.25厘米长的片。 </li><li>用剪刀，剪1.25毫米内径软管到4.75米长的一块。 </li><li>使用铣床一块有机玻璃切成长方体。的长度，宽度，和长方体的高度应2.54厘米，1.27厘米，和1.27厘米，分别。 </li><li>钻孔以0.81 2，2.56，并在有机玻璃支架0.76毫米直径， 如图2所示。 </li><li>用针钻头以使树脂玻璃底座的锥部， 如图2。 </li><li>仰视麦克风灵敏度由制造商提供的说明书中，或使用由黄18介绍的方法校准麦克风。 </li><li>座位麦克风入有机玻璃支架， 如图2，并用环氧树脂固定的麦克风。 </li><li>在不锈钢管和软管连接到有机玻璃底座，并用环氧树脂修复。 </li><li>钻一个直径0.81毫米垂直于模型表面处测量的位置的孔。 </li></ol> 2.实验设置<ol><li>嵌入式安装的主要不锈钢管RMP传感器到模型表面，并添加环氧树脂的不锈钢管固定到相对的模型表面， 如图2。 </li><li>包围声学泡沫的制冷剂管理，以防止寄生噪声污染的系统。 </li><li>路由所有的电线出隧道试验段。 </li><li>路线软消声管出隧道试验段。 </li><li>软消声管的端部连接到压力换能器，以便与不稳定压力同时获得的平均静压的测量。 </li><li>制冷剂管理连接到低噪声放大器和数据采集系统。 </li><li>放大器的增益因子设定为10。注意，可以从壳体改为情况下，增益因子的值。 </li></ol> 3.校准<ol><li>选择一个参考麦克风是高质量和具有频率无关的灵敏度。 </li><li>连接参考微电话到放大器的输入端和所述放大器的输出连接到数据采集系统。 </li><li>同时设置输入增益和放大器至10dB的输出增益。需要注意的是，增益因子可以在不同的测量条件下进行改变。 </li><li>插入基准传声器成活塞发声，如图补充图。 </li><li>打开活塞发声。 </li><li>采集频率为4000赫兹。 </li><li>设定的样本数240,000。 </li><li>获取和保存从参考麦克风输出电压。 </li><li>计算的基准传声器的校准常数。校准常数，C REF，是活塞式制作声压到基准麦克风的电压输出的标准偏差的标准偏差的比率。 </li><li>重复校准处理（步骤3.8和3.9）数次。使用平均值，C REF，作为校准常数。 </li> &lt;li&gt;将参考麦克风垂直于在其上的压力波动被测量， 如图1中的固体表面上。 </li><li>对准RMP自来水参考麦克风的中心。使用参考麦克风和1毫米的RMP抽头之间的距离。 </li><li>放置在靠近测试模型扬声器。使用扬声器和2.5米对于这些测量的麦克风之间的距离。 </li><li>扬声器连接到函数发生器并打开函数发生器。 </li><li>使用该函数发生器的"白噪声"选项，以提供需要的声音信号，并设置均方根电压，V 有效值 ，至0.4V。 </li><li>调整扬声器到最小的体积。 </li><li>打开扬声器。 </li><li>调整扬声器放大器尽可能高的体积而不损坏扬声器。请注意，大多数发言者有一个指示灯警告日E用户如果输出振幅高于扬声器范围。 </li><li>获得和使用40000 Hz的扫描频率为60秒，从两个参考麦克风和RMP的电压输出保存的时间序列数据。 </li><li>计算的声压波动，这是由扬声器和功能发生器产生和由基准麦克风测量的时间序列的值。这仅仅是从基准传声器输出的时间序列电压的乘积， <img alt="公式3" src="/files/ftp_upload/53627/53627eq3.jpg" />和它的校准常数， <img alt="公式4" src="/files/ftp_upload/53627/53627eq4.jpg" /> ; <img alt="公式5" src="/files/ftp_upload/53627/53627eq5.jpg" /> 。注意，该时间序列的声压， <img alt="公式6" src="/files/ftp_upload/53627/53627eq6.jpg" /> ，也是在RMP的自来水压力波动。 </li><li>计算由麦克风在RMP一个测得的时间系列的声压波动<html> S中的时间序列电压输出的产品从贼法牧， <img alt="公式7" src="/files/ftp_upload/53627/53627eq7.jpg" />和麦克风的灵敏度， <img alt="式（8）" src="/files/ftp_upload/53627/53627eq8.jpg" /> ; <img alt="公式9" src="/files/ftp_upload/53627/53627eq9.jpg" /> 。注意，麦克风的灵敏度， <img alt="式（8）" src="/files/ftp_upload/53627/53627eq8.jpg" /> ，应该由制造商提供。 </li><li>计算自动谱密度<img alt="10式" src="/files/ftp_upload/53627/53627eq10.jpg" />的<img alt="11式" src="/files/ftp_upload/53627/53627eq11.jpg" /> 。计算自动谱密度<img alt="12式" src="/files/ftp_upload/53627/53627eq12.jpg" />的<img alt="13式" src="/files/ftp_upload/53627/53627eq13.jpg" /> 。计算交叉谱密度， <img alt="14式" src="/files/ftp_upload/53627/53627eq14.jpg" />之间，.JPG"/&gt;和<img alt="11式" src="/files/ftp_upload/53627/53627eq11.jpg" /> 。自动谱密度和交叉谱密度被Bendat和皮索尔19限定。 </li><li>计算作为传输函数<img alt="15式" src="/files/ftp_upload/53627/53627eq15.jpg" /> 。 </li><li>计算的一致性功能<img alt="16式" src="/files/ftp_upload/53627/53627eq16.jpg" /> ，其中星号表示复共轭。 </li><li>取出参考麦克风。 </li><li>关闭扬声器和函数发生器。 </li><li>卸下扬声器。 </li></ol> 4.数据采集<ol><li>打开风洞。 </li><li>记录时间系列电压输出， <img alt="17式" src="/files/ftp_upload/53627/53627eq17.jpg" /> ，与数据采集系统中的贼法牧。使用40000赫兹的扫描频率。使用采集64秒的持续时间。 </li><li>关闭风洞。 </li></ol><ol><li>计算的声压波动， <img alt="18式" src="/files/ftp_upload/53627/53627eq18.jpg" /> ，通过在RMP麦克风测得<img alt="19式" src="/files/ftp_upload/53627/53627eq19.jpg" /> 。 </li><li>计算自动谱密度<img alt="20式" src="/files/ftp_upload/53627/53627eq20.jpg" />中，表面压力波动作为<img alt="21式" src="/files/ftp_upload/53627/53627eq21.jpg" /> ，其中<img alt="式（22）" src="/files/ftp_upload/53627/53627eq22.jpg" />在声压波动的自谱密度通过在RMP麦克风测量<img alt="18式" src="/files/ftp_upload/53627/53627eq18.jpg" /> 。 </li></ol>

<ol>
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The authors have nothing to disclose.

The measurement of USP in wind tunnel experiments is needed for many applications related to aeroacoustics and flow-induced vibrations. Compared to existing methods, such as flush-mounted imbedded sensors, PSP, or vibrated membranes, the method described here allows for accurate measurements with a high sensitivity to large-magnitude fluctuation over a wide range of frequencies. More importantly, it also provides a method for USP measurements using a small sensing area that minimizes the spatial averaging effects describ...

物体表面的流体流动通常会导致不稳定和动荡是导致不稳定的表面压力（USP）。流引起的响声和振动往往这个不稳定的直接结果。由散热风扇，螺旋桨，和风力涡轮机产生的辐射声是由相关的USP 1来源为主。的美国专利中湍流的空间和时间特性的测定一般都需要以预测的辐射声音。 美国专利的统计特性中的自动谱密度的形式一般是给定，二点交叉谱密度，和空间相关函数2,3。可以根据不同的应用而变化所需要的频率响应。在许多风洞应用，10kHz至20kHz的响应是足够的。湍流运动的小尺度通常需要感测区域和传感器间距小于1毫米。 EXTEnsive实验研究，以获得湍流诱发压力波动已进行。一个直接的方法是使用嵌入式安装嵌入式传感器。这种方法通常采用的麦克风大型阵列，因为每个传感器只能测量在一个离散点的压力波动。在该方法中使用的典型的传感器是压电换能器，通过高奇4建议。压电式传感器的阵列可以是昂贵的，和测量的频率范围通常是小于10千赫兹。 直接表面安装的麦克风通常用作便宜的USP传感器5。麦克风具有高灵敏度，这是低速流动的显着的益处。然而，这也导致了传感器饱和的风险时的压力大振幅的波动都存在。这种方法是不适合用于大曲率的不连续性，或几何形状过于薄，以包含整个传感器表面。 6。的时间和空间依赖性振动运动进行测量，然后转换为表面用膜的已知机械性能的压力的统计信息。此方法需要仔细的设计，实施和膜的动态响应的精确校准。另外，该振动测量设备，如激光多普勒振动计，是昂贵的。最后，这种方法只能适用于平面。 压敏涂料（PSP）是可用于测量不稳定的表面压力的另一种技术。这种技术需要在透明聚合物粘合剂，这将导致内的分子，因为它们是由特定波长的光照射被激发到更高的能态到待涂覆的表面。随着分子进行氧淬火，能量再在成比例的氧分压的速率，导致发光是成反比的表面压力7租用光。相比麦克风时到PSP方法的主要缺点是在测量的相对低的灵敏度。这限制了PSP相对高速流动的应用。 本通信描述了美国专利，它使用一个远程麦克风探针（RMP）的方法。这种方法首先由英格伦和Richards 8所述。的概念使用连接到表面压力抽头具有中空管的标准微型麦克风。在模型表面上的不稳定压力将行进到在声波的形式油管。管用作"波导"，以允许麦克风，其垂直地安装在管道，以测量声波。波浪然后继续到另一个管足够长，以消除大振幅声řeflections。 英格伦和Richards通过应用和贝赫9 Tijdeman概述确定RMP的动态响应的分析方法。 Perrenes和罗杰·10利用的RMP来衡量过度高扬程设备二维机翼表面的压力。他们开发了一种探针与被连接到一个27厘米长的刚性管经由两个单独的步骤的变化从0.7毫米膨胀至2.5mm表面的直径为0.5mm的毛细管。每一步的变化引起所述管的声阻抗相对大的变化。勒克莱尔和Bohineust 11研究湍流边界层下的墙壁压场。他们使用了一种直径恒定的贼法牧，由弗兰佐尼和Elliott 12的建议。然而，动态响应是只在一个有限的频率范围内足够高。 Arguillat 等人 13设计的制冷剂管理学习发送到车厢内部的噪声。他们测试各个管进行压力变动的麦克风。 Yang等人 14通过使用管道传递函数的方法，它类似于本报告中介绍的方法校正油管失真。 Hoarau 等 15研究了分离区下游的墙压迹。他们设计的RMP有恒定的内径和油管是完全非刚性。 根据先前的研究中，表面压力测量用的RMP获得的精确度主要依赖于该涉及的表面压力到麦克风压力探针的频率依赖传递函数的确定。下面的章节将描述一个贼法牧的几何形状，既简单又有效。实验和分析方法将被引入并为了准确​​地确定制冷剂管理的动态响应验证。该分析模型允许一个贼法牧为Optimized在设计阶段对潜在的广泛的应用范围。 的RMP可以用于在宽的频率范围内测量压力的波动。相对较高的空间分辨率可以提供在空间上分布的不稳定压力场16的特性的详细信息。作为探针小，制冷剂管理可以用来测量在复杂几何形状，如大曲率或有限间距17压力波动。此外，连接表面抽头和麦克风传感器管可以在麦克风减小感应压力波动的幅度。因此，RMP传感器的几何形状和参数的合理设计产生获得相对于嵌入式安装，直接将话筒模型表面时有显著较少限制USP特征的方法。 制冷剂管理的RMPThe一般结构的结构图1中示出</strong&gt;的信息。制冷剂管理由一个管从模型表面导致的膨胀部，并从该扩大部分延伸到第二管的"摇篮"。然后，第三管被连接到充当消声终止。摇篮是用于房屋麦克风和管连接的机械加工的塑料部件。制冷剂管理结构的细节可以为各种实验条件进行调整。第二，大径管的目的是允许的相对笨重的麦克风和支架进一步来自USP测量点被放置而不显著降低测量灵敏度。如果它不是必要该第二管可被消除，并扩大部分可以建在摇篮。消声终止制成的软塑料，这是大约2到3米的长度。 对于本演示中，贼法牧的设计是为表面压力波动的测量浊度下优化ulent 如图2所示边界层没有流向压力梯度，该第二管被淘汰了。观察到所述第一管的两种不同长度的影响。第一管从不锈钢制成具有0.5mm的内径和0.81毫米的外径。第一管的长度分别为5.35和10.40厘米分别。扩大部分，将其掺入支架的入口的内径，为0.5mm，和出口的内径为1.25毫米，这是相同的耗散终止的内径。扩大部分的角为7°。有在直径1.25毫米托架为了平稳地展开部与消声终止连接的孔。传感区域通过一个垂直0.75毫米孔连接到1.25毫米的孔。

<table border="0" cellpadding="0" cellspacing="0" width="1651">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Microphone</td>
			<td style="width:513px;">ACO Pacific (http://www.acopacific.com/)</td>
			<td style="width:137px;">7016</td>
			<td style="width:739px;">Used to measure the sound pressure and calibrate the RMP as a reference.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Microphone</td>
			<td style="width:513px;">Knowles (http://www.knowles.com/eng)</td>
			<td style="width:137px;">FG-23629-C36</td>
			<td>Used to measure the pressure fluctuation as a part of the RMP.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Microbore Tubing</td>
			<td style="width:513px;">Saint-gobain (http://www.biopharm.saint-gobain.com/en/index.asp)</td>
			<td style="width:137px;">Tygon ND 100-80</td>
			<td>Used to dissipate the sound waves as a dissipation termination.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Hypodermic Tubing</td>
			<td style="width:513px;">MicroGroup (http://www.microgroup.com/)</td>
			<td style="width:137px;">304H21RW</td>
			<td>Used to connect the surface tap and allow the surface pressure fluctuation to convect to the microphone in the RMP in the form of sound.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Hypodermic Tubing</td>
			<td style="width:513px;">MicroGroup (http://www.microgroup.com/)</td>
			<td style="width:137px;">304H14H</td>
			<td>Used to reduce the dissipative effect and allow the surface pressure fluctuation to convect to the microphone in the RMP in the form of sound.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">plexiglass</td>
			<td style="width:513px;">Plaskolite (http://www.plaskolite.com/)</td>
			<td style="width:137px;">1X76204A</td>
			<td>Used to make cradles which can connect the tubing and the microphone for the RMP.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Data acquisition chassis</td>
			<td style="width:513px;">National Instruments (http://www.ni.com/)</td>
			<td style="width:137px;">PXI-1006</td>
			<td>For data acquisition.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Data acquisition channel</td>
			<td style="width:513px;">National Instruments (http://www.ni.com/)</td>
			<td style="width:137px;">PXI-4472</td>
			<td>For data acquisiton.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Function generator</td>
			<td style="width:513px;">thinkSRS (http://www.thinksrs.com/)</td>
			<td style="width:137px;">DS360</td>
			<td>To generate white noise signal.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Pistonphone</td>
			<td style="width:513px;">B&#38;K (http://www.bksv.com/)</td>
			<td style="width:137px;">4228</td>
			<td>To generate sine waves with constant frequency which will be used to calibrate the reference microphone.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">Loudspeaker</td>
			<td style="width:513px;">Mackie (http://www.mackie.com/index.html)</td>
			<td style="width:137px;">HD1531</td>
			<td>Used to convert the electrical white noise signal into sound. It is the sound source for calibrating the RMP.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">MatLab</td>
			<td style="width:513px;">Mathworks (http://www.mathworks.com/)</td>
			<td style="width:137px;"></td>
			<td>Used to process experimental data.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:263px;">LabVIEW</td>
			<td style="width:513px;">National Instruments (http://www.ni.com/)</td>
			<td style="width:137px;"></td>
			<td>Used control the hardware for data acquisition and record the data.</td>
		</tr>
	</tbody>
</table>

the measurement of unsteady surface pressure using a remote microphone probe

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various characteristic length scales can result in pressure fluctuations over a wide frequency range. This property of turbulence requires sensing devices to have sufficient sensitivity over a wide range of frequencies. Furthermore, the small characteristic length scales of turbulent structures require small sensing areas and the ability to place the sensors in very close proximity to each other. The complex geometries of the solid bodies, often including large surface curvatures or discontinuities, require the probe to have the ability to be set up in very limited spaces. The development of a remote microphone probe, which is inexpensive, consistent, and repeatable, is described in the present communication. It allows for the measurement of pressure fluctuations with high spatial resolution and dynamic response over a wide range of frequencies. The probe is small enough to be placed within the interior of typical wind tunnel models. The remote microphone probe includes a small, rigid, and hollow tube that penetrates the model surface to form the sensing area. This tube is connected to a standard microphone, at some distance away from the surface, using a "T" junction. An experimental method is introduced to determine the dynamic response of the remote microphone probe. In addition, an analytical method for determining the dynamic response is described. The analytical method can be applied in the design stage to determine the dimensions and properties of the RMP components.

从两个有代表性的RMP设计标定结果显示在本节。第一个使用的5.35厘米主管，而第二个用于一个10.4厘米主管。耗散终端是4.75米长为制冷剂管理计划。 通过在RMP和由基准传声器的传声器测量的压力的波动之间的一致性示于图3。数据显示在一个宽的频率范围内的近统一相干值。在频率在10kHz以上，相干普遍居高不下，...

Watch this Scientific Journal Video about The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe at JoVE.com

The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe

Here, we present a protocol to measure, with high spatial resolution, the unsteady surface pressure in turbulent flows. This method demonstrates the construction of a remote microphone probe (RMP) and the determination of its frequency-dependent, complex transfer function. An analytical determination of the dynamic response is presented and validated.

非定常表面压力的使用远程麦克风探头测量

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various ...

the-measurement-unsteady-surface-pressure-using-remote-microphone

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Unit 1

Fluid Properties

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6.9K 次观看.  University of Notre Dame. Here, we present a protocol to measure, with high spatial resolution, the unsteady surface pressure in turbulent flows. This method demonstrates the construction of a remote microphone probe (RMP) and the determination of its frequency-dependent, complex transfer function. An analytical determination of the dynamic response is presented and validated.

视频: The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

在极端的压力和温度的合成和Microdiffraction

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

科研

工程学

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

扫描探针单电子电容谱

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Blast Quantification Using Hopkinson Pressure Bars

Near-field blast load measurement presents an issue to many sensor types as they must endure very aggressive environments and be able to measure pressures up to many hundreds of megapascals. In this respect the simplicity of the Hopkinson pressure bar has a major advantage in that while the measurement end of the Hopkinson bar can endure and be exposed to harsh conditions, the strain gauge mounted to the bar can be affixed some distance away. This allows protective housings to be utilized which protect the strain gauge but do not interfere with the measurement acquisition. The use of an array of pressure bars allows the pressure-time histories at discrete known points to be measured. This article also describes the interpolation routine used to derive pressure-time histories at un-instrumented locations on the plane of interest. Currently the technique has been used to measure loading from high explosives in free air and buried shallowly in various soils.

This protocol details the use of Hopkinson pressure bars to measure reflected blast loading from near-field explosive events. It is capable of interpolating a pressure-time history at any point on a reflective boundary and as such can be used to fully characterize the spatial and temporal variations in loading produced.

高炉利用定量霍普金森杆

Near-field blast load measurement presents an issue to many sensor types as they must endure very aggressive environments and be able to measure pressures ...

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

介电微粒的光阱装载在空气中

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

从微量炸药的擦拭取样测量收集效率的标准化方法

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

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

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

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

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

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

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

Safe Experimentation in Optical Levitation of Charged Droplets Using Remote Labs

The work presents an experiment that allows the study of many fundamental physical processes, such as photon pressure, diffraction of light or the motion of charged particles in electrical fields. In this experiment, a focused laser beam pointing upwards levitate liquid droplets. The droplets are levitated by the photon pressure of the focused laser beam which balances the gravitational force. The diffraction pattern created when illuminated with laser light can help measure the size of a trapped droplet. The charge of the trapped droplet can be determined by studying its motion when a vertically directed electrical field is applied. There are several reasons motivating this experiment to be remotely controlled. The investments required for the setup exceeds the amount normally available in undergraduate teaching laboratories. The experiment requires a laser of Class 4, which is harmful to both skin and eyes and the experiment uses voltages that are harmful.

Optical levitation is a method for levitating micrometer-sized dielectric objects using laser light. Utilizing computers and automation systems, an experiment on optical levitation can be controlled remotely. Here, we present a remotely controlled optical levitation system that is used both for educational and research purposes.

远程实验室对带电液滴光学悬浮的安全实验

The work presents an experiment that allows the study of many fundamental physical processes, such as photon pressure, diffraction of light or the motion ...

Fabrication of Compressed Hosiery and Measurement of its Pressure Characteristic Exerted on the Lower Limbs

This article reports the pressure characteristic measurement of compressed hosiery via direct and indirect methods. In the direct method, an interface sensor is used to measure the pressure value exerted on the lower limbs. In the indirect method, the necessary parameters mentioned by the cone and cylinder model are tested to calculate the pressure value. The necessary parameters involve course density, wales density, circumference, length, thickness, tension, and deformation of the compressed hosiery. Compared with the results of the direct method, the cone model in the indirect method is more suitable for calculating the pressure value because the cone model considers the change in radius of the lower limb from the knee to the ankle. Based on this measurement, the relationship among fabrication, structure, and pressure is further investigated in this study. We find that graduation is the main influence that can change the wales density. On the other hand, elastic motors directly affect the course density and the circumference of the stockings. Our reported work provides the fabrication-structure-pressure relationship and a design guide for gradually compressed hosiery.

This article reports fabrication, structure and pressure measurement of compressed hosiery by employing direct and indirect methods.

压缩袜子的制造及其下肢压力特性测量

This article reports the pressure characteristic measurement of compressed hosiery via direct and indirect methods. In the direct method, an interface ...

In Situ Surface Temperature Measurement in a Conveyor Belt Furnace via Inline Infrared Thermography

Measuring the surface temperature of objects that are processed in conveyor belt furnaces is an important tool in process control and quality assurance. Currently, the surface temperature of objects processed in conveyor belt furnaces is typically measured via thermocouples. However, infrared (IR) thermography presents multiple advantages compared to thermocouple measurements, as it is a contactless, real-time, and spatially resolved method. Here, as a representative proof-of-concept example, an inline thermography system is successfully installed into an IR lamp powered solar firing furnace, which is used for the contact firing process of industrial Si solar cells. This protocol describes how to install an IR camera into a conveyor belt furnace, conduct a customer correction of a factory calibrated IR camera, and perform the evaluation of spatial surface temperature distribution on a target object.

This protocol describes how to install an infrared camera into a conveyor belt furnace, conduct a customer correction of a factory calibrated IR camera, and evaluate the spatial surface temperature distribution of an object of interest. The example objects are industrial silicon solar cells.

通过内联红外热成像在输送带炉中的原点表面温度测量

Measuring the surface temperature of objects that are processed in conveyor belt furnaces is an important tool in process control and quality assurance. ...

Measuring Sub-23 Nanometer Real Driving Particle Number Emissions Using the Portable DownToTen Sampling System

The current particle size threshold of the European Particle Number (PN) emission standards is 23 nm. This threshold could change because future combustion engine vehicle technology may emit large amounts of sub-23 nm particles. The Horizon 2020 funded project DownToTen (DTT) developed a sampling and measurement method to characterize particle emissions in this currently unregulated size range. A PN measurement system was developed based on an extensive review of the literature and laboratory experiments testing a variety of PN measurement and sampling approaches. The measurement system developed is characterized by high particle penetration and versatility, which enables the assessment of primary particles, delayed primary particles, and secondary aerosols, starting from a few nanometers in diameter. This paper provides instruction on how to install and operate this Portable Emission Measurement System (PEMS) for Real Drive Emissions (RDE) measurements and assess particle number emissions below the current legislative limit of 23 nm.

Presented here is the DownToTen (DTT) portable emission measurement system to assess real driving automotive emissions of sub-23 nm particles.