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Characterization of Anomalous Forces in Dielectric Rotors 介电转子异常力的表征
Pub Date : 2020-09-22 DOI: 10.1139/CJP-2020-0570
E. Porcelli, V. S. Filho
We performed several measurements of anomalous forces on a dielectric rotor in operation, subjected to high voltage. The device operated under constant and intense angular velocity for each high voltage applied. The measurements were made in the similar way than an analogue magnetic gyroscope, by considering clockwise and counterclockwise rotations. We found that there are significant weight reduction on the device in the clockwise case, with one order of magnitude higher than the magnetic case. In addition, we detected a similar asymmetry in the observation of the effect, that is, there are smaller results for the anomalous forces in counterclockwise rotation. We also propose a theoretical model to explain the quantitative effect based on average values of macroscopic observables of the device rotation and concluded that it is consistent with the experimental results.
在高压下,我们对电介质转子的异常力进行了几次测量。每次施加高电压时,该装置都在恒定而强烈的角速度下工作。通过考虑顺时针和逆时针旋转,测量方法与模拟磁陀螺仪相似。我们发现,顺时针表壳下的设备重量明显减轻,比磁性表壳高一个数量级。此外,我们在对效应的观察中发现了类似的不对称性,即逆时针旋转的异常力的结果较小。我们还提出了一个基于器件旋转宏观观测值平均值的理论模型来解释定量效应,并得出了与实验结果一致的结论。
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引用次数: 0
Surface adhesion of back-illuminated ultrafast laser-treated polymers 背照超快激光处理聚合物的表面附着力
Pub Date : 2020-09-22 DOI: 10.1103/PhysRevMaterials.5.045201
D. Kallepalli, Alan T. K. Godfrey, Jesse Ratté, A. Staudte, Chunmei Zhang, P. Corkum
We report a decreased surface wettability when polymer films on a glass substrate are treated by ultra-fast laser pulses in a back-illumination geometry. We propose that back-illumination through the substrate confines chemical changes beneath the surface of polymer films, leaving the surface blistered but chemically intact. To confirm this hypothesis, we measure the phase contrast of the polymer when observed with a focused ion beam. We observe a void at the polymer-quartz interface that results from the expansion of an ultrafast laser-induced plasma. A modified polymer layer surrounds the void, but otherwise the film seems unmodified. We also use X-ray photoelectron spectroscopy to confirm that there is no chemical change to the surface. When patterned with partially overlapping blisters, our polymer surface shows increased hydrophobicity. The increased hydrophobicity of back-illuminated surfaces can only result from the morphological change. This contrasts with the combined chemical and morphological changes of the polymer surface caused by a front-illumination geometry.
我们报告了当在玻璃基板上的聚合物薄膜在背光几何中被超快激光脉冲处理时,表面润湿性降低。我们建议通过衬底的反向照明限制聚合物薄膜表面下的化学变化,使表面起泡,但化学完整。为了证实这一假设,我们测量了用聚焦离子束观察聚合物时的相位差。我们在聚合物-石英界面上观察到一个空洞,这是由超快激光诱导等离子体膨胀引起的。一层修饰的聚合物层包围着空隙,但除此之外,薄膜似乎没有修饰。我们还使用x射线光电子能谱来确认表面没有化学变化。当图案与部分重叠的水泡,我们的聚合物表面显示出增加的疏水性。背照表面疏水性的增加只能由形态变化引起。这与由前照射几何形状引起的聚合物表面的化学和形态变化形成对比。
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引用次数: 0
A numerical fitting routine for frequency-domain thermoreflectance measurements of nanoscale material systems having arbitrary geometries 具有任意几何形状的纳米级材料系统的频域热反射测量的数值拟合程序
Pub Date : 2020-09-21 DOI: 10.1063/5.0030168
R. Warzoha, Adam A. Wilson, Brian F. Donovan, A. Smith, N. Vu, Trent Perry, Longnan Li, N. Miljkovic, E. Getto
In this work, we develop a numerical fitting routine to extract multiple thermal parameters using frequency-domain thermoreflectance (FDTR) for materials having non-standard, non-semi-infinite geometries. The numerical fitting routine is predicated on either a 2-D or 3-D finite element analysis that permits the inclusion of non semi-infinite boundary conditions, which can not be considered in the analytical solution to the heat diffusion equation in the frequency domain. We validate the fitting routine by comparing it to the analytical solution to the heat diffusion equation used within the wider literature for FDTR and known values of thermal conductivity for semi-infinite substrates (SiO2, Al2O3 and Si). We then demonstrate its capacity to extract the thermal properties of Si when etched into micropillars that have radii on the order of the pump beam. Experimental measurements of Si micropillars with circular cross-sections are provided and fit using the numerical fitting routine established as part of this work. Likewise, we show that the analytical solution is unsuitable for the extraction of thermal properties when the geometry deviates significantly from the standard semi-infinite case. This work is critical for measuring the thermal properties of materials having arbitrary geometries, including ultra-drawn glass fibers and laser gain media.
在这项工作中,我们开发了一个数值拟合程序,用于提取具有非标准,非半无限几何形状的材料的多个热参数,使用频域热反射(FDTR)。数值拟合程序基于二维或三维有限元分析,允许包含非半无限边界条件,而非半无限边界条件在频域热扩散方程的解析解中不能考虑。我们通过将其与广泛文献中用于FDTR和半无限基材(SiO2, Al2O3和Si)导热系数的已知值的热扩散方程的解析解进行比较来验证拟合程序。然后,我们展示了它在蚀刻成具有泵浦光束半径的微柱时提取Si热特性的能力。具有圆形截面的硅微柱的实验测量提供和拟合使用数值拟合程序建立作为这项工作的一部分。同样地,我们表明,当几何形状明显偏离标准半无限情况时,解析解不适用于热性质的提取。这项工作对于测量具有任意几何形状的材料的热性能至关重要,包括超拉伸玻璃纤维和激光增益介质。
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引用次数: 2
Shape-shifting panel from 3D printed undulated ribbon lattice 由3D打印起伏带晶格制成的可变形面板
Pub Date : 2020-09-21 DOI: 10.1016/J.EML.2020.101089
Filippo Agnelli, M. Tricarico, A. Constantinescu
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引用次数: 5
Fully printed, all-carbon, recyclable electronics 全印刷,全碳,可回收的电子产品
Pub Date : 2020-09-21 DOI: 10.21203/rs.3.rs-74355/v1
Nicholas X. Williams, George Bullard, N. Brooke, M. Therien, A. Franklin
The rapid growth of electronic waste must be curtailed to prevent accumulation of environmentally and biologically toxic materials, which are essential to traditional electronics1. The recent proliferation of transient electronics has focused predominantly on biocompatibility(2,3), and studies reporting material recapture have only demonstrated reuse of conducting materials(4–6). Meanwhile, the ideal solution to the electronic waste epidemic — recapture and reuse of all materials — has been largely neglected. Here we show complete recyclability of all materials in printed, all-carbon electronics using paper substrates, semiconducting carbon nanotubes, conducting graphene, and insulating crystalline nanocellulose. The addition of mobile ions to the dielectric produced significant improvements in switching speed, subthreshold swing, and among the highest on-current for printed transistors. These devices evinced superlative stability over 6 months, after which they are shown to be controllably decomposed for complete recycling of materials and re-printing of devices with similar performance to baseline devices. The printing of all-carbon, recyclable electronics presents a new path toward green electronics with potential to mitigate the environmental impact of electronic waste. We anticipate all-carbon, recyclable electronics to be a watershed, facilitating internet-of-everything applications, such as ubiquitous sensors for continuous monitoring of diseases or environmental conditions, while preserving carbon neutrality in the device lifecycle.
必须遏制电子废物的迅速增长,以防止对环境和生物有毒物质的积累,这些物质对传统电子产品至关重要。最近瞬态电子学的扩散主要集中在生物相容性上(2,3),而报告材料回收的研究只证明了导电材料的再利用(4-6)。与此同时,电子垃圾泛滥的理想解决方案——所有材料的回收和再利用——在很大程度上被忽视了。在这里,我们展示了印刷中所有材料的完全可回收性,全碳电子产品使用纸质衬底,半导体碳纳米管,导电石墨烯和绝缘晶体纳米纤维素。在电介质中加入可移动离子,在开关速度、亚阈值摆幅和印刷晶体管的最高导通电流方面产生了显著的改进。这些设备在6个月内表现出最高的稳定性,之后它们被证明可以可控地分解,以完全回收材料并重新打印具有与基线设备相似性能的设备。全碳、可回收电子产品的印刷为绿色电子产品提供了一条新的道路,有可能减轻电子废物对环境的影响。我们预计全碳、可回收的电子产品将成为一个分水岭,促进万物互联应用,比如无处不在的传感器,用于持续监测疾病或环境条件,同时在设备生命周期中保持碳中和。
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引用次数: 1
Assessment of Physical Properties of Water Repellent Soils 拒水土壤物理特性的评价
Pub Date : 2020-09-20 DOI: 10.1061/(ASCE)GT.1943-5606.0002604
M. Movasat, I. Tomac
This note presents a comprehensive characterization of physical and mechanical properties of water repellent (hydrophobic) soil collected from Cleveland National Forest in California immediately after the Holy Fire, 2018, and delineates comparisons with chemically induced hydrophobic sand in the laboratory. Hydrophobicity is a particle surface characteristic that governs different levels of attraction between water molecules and solid particles. Wildfires can cause different levels of hydrophobicity in shallow soil layers based on fire severity, vegetation, and chemical structure of the soil. Natural and chemically induced regular and hydrophobic sands are characterized by grain size distribution, water retention curve, water contact angle and electron microscopic imaging, including the relationship between water entry value and the drop contact angle in hydrophobic soil. Comparative knowledge of natural and chemically induced hydrophobic soil properties will help future research to better predict soil behavior and improve insights into post-wildfire soil erosion and mudflow mechanisms. This note contributes to a database of wildfire-induced hydrophobic soil with detailed properties and assesses the applicability of laboratory made hydrophobic soils for studying mudflows by comparison to the natural water repellent soil collected from the burned site.
本文介绍了2018年圣火之后从加州克利夫兰国家森林收集的疏水(疏水)土壤的物理和机械特性的综合特征,并与实验室中化学诱导的疏水砂进行了比较。疏水性是粒子表面的一种特性,它决定了水分子和固体粒子之间不同程度的吸引力。野火会在浅层土壤中造成不同程度的疏水性,这取决于火灾的严重程度、植被和土壤的化学结构。天然砂和化学诱导的规则砂和疏水砂的粒度分布、保水曲线、水接触角和电镜成像特征,包括疏水土中水进入值与水滴接触角的关系。自然和化学诱导疏水土壤特性的比较知识将有助于未来的研究更好地预测土壤行为,并提高对野火后土壤侵蚀和泥石流机制的认识。该笔记有助于建立具有详细特性的野火疏水性土壤数据库,并通过与从燃烧地点收集的天然疏水性土壤进行比较,评估实验室制备的疏水性土壤在研究泥石流方面的适用性。
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引用次数: 6
Microwave Photonic Ising Machine 微波光子成像机
Pub Date : 2020-09-19 DOI: 10.21203/rs.3.rs-79539/v1
Qizhuang Cen, Tengfei Hao, Hao Ding, Shanhong Guan, Zhiqiang Qin, Kun Xu, Yitang Dai, Ming Li
Ising machines based on analog systems have the potential of acceleration in solving ubiquitous combinatorial optimization problems. Although some artificial spins to support large-scale Ising machine is reported, e.g. superconducting qubits in quantum annealers and short optical pulses in coherent Ising machines, the spin coherence is fragile due to the ultra-low equivalent temperature or optical phase sensitivity. In this paper, we propose to use short microwave pulses generated from an optoelectronic parametric oscillator as the spins to implement the Ising machine with large scale and also high coherence under room temperature. The proposed machine supports 10,000 spins, and the high coherence leads to accurate computation. Moreover, the Ising machine is highly compatible with high-speed electronic devices for programmability, paving a low-cost, accurate, and easy-to-implement way toward to solve real-world optimization problems.
基于模拟系统的伊辛机器在解决泛在组合优化问题方面具有加速的潜力。虽然已经报道了一些支持大型Ising机器的人工自旋,例如量子退火中的超导量子比特和相干Ising机器中的短光脉冲,但由于超低的等效温度或光学相位灵敏度,自旋相干性是脆弱的。本文提出利用光电参量振荡器产生的微波短脉冲作为自旋,实现室温下大规模高相干的伊辛机。该机器支持10,000个自旋,并且高相干性导致精确的计算。此外,伊辛机器在可编程性方面与高速电子设备高度兼容,为解决现实世界的优化问题铺平了低成本、精确和易于实现的道路。
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引用次数: 9
Interference of co-propagating Rayleigh and Sezawa waves observed with micro-focused Brillouin light scattering spectroscopy 用微聚焦布里渊光散射光谱观察共传播瑞利波和塞泽波的干涉
Pub Date : 2020-09-10 DOI: 10.1063/5.0029308
M. Geilen, F. Kohl, A. Nicoloiu, A. Müller, B. Hillebrands, P. Pirro
We use micro-focussed Brillouin light scattering spectroscopy ($mu$BLS) to investigate surface acoustic waves (SAWs) in a GaN layer on a Si substrate at GHz frequencies. Furthermore, we discuss the concept of $mu$BLS for SAWs and show that the crucial parameters of SAW excitation and propagation can be measured. We investigate a broad range of excitation parameters and observe that Rayleigh and Sezawa waves are excited simultaneously at the same frequency. Spatially resolved measurements of these co-propagating waves show a periodic pattern, which proves their coherent interference. From the periodicity of the spatial phonon patterns, the wavevector difference between the two waves has been identified and compared to the dispersion relation. This concept of co-propagating phonons might be used to produce acoustic or magneto-elastic fields with a time-independent spatial variation similar to the situations realized using counter-propagating waves. However, co-propagating SAW have a well defined direction of the wave vector and thus, posses a finite phonon angular momentum which offers new opportunities, e.g. for angular momentum conversion experiments.
我们使用微聚焦布里渊光散射光谱($mu$BLS)来研究GHz频率下Si衬底上GaN层中的表面声波(saw)。此外,我们讨论了SAW的$mu$BLS的概念,并证明了SAW激发和传播的关键参数是可以测量的。我们研究了广泛的激励参数,并观察到瑞利波和Sezawa波以相同的频率同时被激发。对这些共传播波的空间分辨测量显示出周期模式,这证明了它们的相干干涉。从空间声子模式的周期性出发,确定了两波之间的波矢量差,并与色散关系进行了比较。这种共传播声子的概念可以用来产生与时间无关的空间变化的声场或磁弹性场,类似于使用反传播波实现的情况。然而,共传播声呐具有明确的波矢量方向,因此具有有限声子角动量,这为角动量转换实验提供了新的机会。
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引用次数: 4
Video: ON SECONDARY ATOMIZATION AND BLOCKAGE OF SURROGATE COUGH DROPLETS IN SINGLE AND MULTI-LAYER FACE MASKS 视频:单层和多层口罩中替代咳嗽飞沫的二次雾化和阻塞
Pub Date : 2020-09-04 DOI: 10.1103/aps.dfd.2020.gfm.v0059
Shubham Sharma, Roven Pinto, A. Saha, Swetaprovo Chaudhuri, S. Basu
By now it is well-understood that the usage of facemasks provides protection from transmission of viral loads through exhalation and inhalation of respiratory droplets. Therefore, during the current Covid-19 pandemic the usage of face masks is strongly recommended by health officials. Although three-layer masks are generally advised for usage, many commonly available or homemade masks contain only single and double layers. In this study, we show through detailed physics based analyses and high speed imaging that high momentum cough droplets on impingement on single- and double-layer masks can lead to significant partial penetration and more importantly atomization into numerous much smaller daughter droplets, thereby increasing the total population of the aerosol, which can remain suspended for a longer time. The possibility of secondary atomization of high momentum cough droplets due to impingement, hydrodynamic focusing and extrusion through the microscale pores in the fibrous network of the mask has not been explored before. However, this unique mode of aerosol generation poses a finite risk of infection as shown in this work. We also demonstrate that in single layer masks close to 70 % of a given droplet volume is atomized and only 30 % is trapped within the fibers. The entrapped volume is close to 90 % for double layer masks which still allows some atomization into smaller droplets. We however found that a triple-layer surgical mask permits negligible penetration and hence should be effective in preventing disease transmission.
到目前为止,人们都很清楚,使用口罩可以防止通过呼出和吸入呼吸道飞沫传播病毒载量。因此,在当前的Covid-19大流行期间,卫生官员强烈建议使用口罩。虽然一般建议使用三层口罩,但许多常见的或自制的口罩只有单层和双层。在这项研究中,我们通过详细的物理分析和高速成像显示,高动量咳嗽液滴撞击单层和双层口罩会导致明显的部分穿透,更重要的是会雾化成许多更小的子液滴,从而增加气溶胶的总数,这些微粒可以悬浮更长时间。高动量咳嗽液滴通过口罩纤维网络中的微孔撞击、流体动力聚焦和挤压产生二次雾化的可能性此前尚未被探索过。然而,正如这项工作所示,这种独特的气溶胶产生模式造成了有限的感染风险。我们还证明,在单层掩模中,给定液滴体积的近70%被雾化,只有30%被困在纤维中。双层掩模的捕获体积接近90%,这仍然允许一些雾化成更小的液滴。然而,我们发现三层外科口罩的穿透性可以忽略不计,因此应该有效地防止疾病传播。
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引用次数: 1
Thermal Effects in Spin-Torque Switching of Perpendicular Magnetic Tunnel Junctions at Cryogenic Temperatures 低温下垂直磁隧道结自旋转矩开关的热效应
Pub Date : 2020-09-03 DOI: 10.1103/PHYSREVAPPLIED.15.034088
L. Rehm, G. Wolf, B. Kardasz, Egecan Cogulu, Yizhang Chen, M. Pinarbasi, A. Kent
Temperature plays an important role in spin torque switching of magnetic tunnel junctions causing magnetization fluctuations that decrease the switching voltage but also introduce switching errors. Here we present a systematic study of the temperature dependence of the spin torque switching probability of state-of-the-art perpendicular magnetic tunnel junction nanopillars (40 to 60 nm in diameter) from room temperature down to 4 K, sampling up to a million switching events. The junction temperature at the switching voltage---obtained from the thermally assisted spin torque switching model---saturates at temperatures below about 75 K, showing that junction heating is significant below this temperature and that spin torque switching remains highly stochastic down to 4 K. A model of heat flow in a nanopillar junction shows this effect is associated with the reduced thermal conductivity and heat capacity of the metals in the junction.
温度在磁隧道结的自旋转矩开关中起着重要的作用,引起磁化波动,使开关电压降低,但也会引入开关误差。在这里,我们系统地研究了最先进的垂直磁隧道结纳米柱(直径40至60纳米)从室温到4 K的自旋转矩开关概率的温度依赖性,采样了多达一百万次的开关事件。从热辅助自旋转矩开关模型获得的开关电压下的结温在低于约75 K的温度下达到饱和,表明结加热在此温度以下是显著的,并且自旋转矩开关在4 K以下仍然是高度随机的。纳米柱结中的热流模型表明,这种效应与结中金属的热导率和热容的降低有关。
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引用次数: 3
期刊
arXiv: Applied Physics
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