Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session R23: Acoustics, Noise and Damping |
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Sponsoring Units: GIMS Room: BCEC 158 |
Thursday, March 7, 2019 8:00AM - 8:12AM |
R23.00001: Particulate dampers for absorption of structural vibrations at audible frequencies.
Hasson M. Tavossi, Ph.D., Savannah State University, Department of Engineering Technology,
3219 College St., Savannah, GA 31404. Hasson Tavossi Absorption of mechanical vibrations by particulate material versus frequency are investigated, with the goal of reduction of transmission of vibrations into building structures. Attenuation of vibration by particulates depend mainly on their mechanical properties, shape, size-distribution, and degree of compression. Structural vibrations can be damped by surrounding them with particulate materials. Experimental results show that, particulate dampers behave as band-pass filters for vibrations that pass through them. The frequencies outside their passband range are strongly absorbed. Some particulate materials have a frequency band-gap, where frequencies in the bandgap range are strongly attenuated by scattering, absorption, or localization of vibrational energy. Samples of uniform size are coupled to mechanical vibrations at different frequency and amplitude. Their vibration absorption versus frequency are determined. Effects of layer thickness, particulate size, orientation, at different frequencies, in the audible range, are measured. The goal is to determine optimal vibration dampers to mitigate the transmission of external mechanical vibrations into the buildings. |
Thursday, March 7, 2019 8:12AM - 8:24AM |
R23.00002: Cancelling Ambient Noise in Spectroscopic Images on a Scanning Tunneling Microscope Albert Chien, Bryce Primavera, Harris Pirie, Jenny Hoffman Scanning tunneling microscopy (STM), a technique to measure the electronic structure of condensed matter systems with atomic resolution, requires an extremely stable environment to operate. Modern ultra-quiet STMs typically employ a combination of pneumatic suspensions and massive inertial blocks to reduce ambient vibrations to the sub-nanometer scale. Yet the tip-sample junction still experiences picometer vibrations that limit the signal-to-noise ratio in the tunneling current. Here we demonstrate a measurement scheme and software algorithm that reduces the effects of residual sub-picometer vibrations by order 50% in both topographic and spectroscopic images. We first calibrate a transfer function between a sensitive geophone on the STM head, and the STM tip-sample distance itself. We then use the simultaneously measured geophone output and tunneling current to cancel the effects of vibrations in the STM data in a 300Hz bandwidth. |
Thursday, March 7, 2019 8:24AM - 8:36AM |
R23.00003: Design and Characterization of a Cylindrical Inertia Block for an Ultra-Low-Vibration Laboratory Wenjie Gong, Yu Liu, Joseph D. Gibbons, Jennifer Hoffman Typical low-vibration facilities employ a rectangular concrete inertia block supported on pneumatic isolators that damp vertical oscillation. However, it has been shown that when the inertia block sides are parallel to the surrounding room walls, acoustic standing waves can exert pressure on the parallel faces of the slab that causes measurable motion. To address this problem, we have designed a new low-vibration laboratory room housing a cylindrical inertia block, with no parallel faces. Here we simulate and measure the acoustic modes of the room and place limits on their coupling to the cylindrical inertia block. We further measure the transfer function from the building foundation to the inertia block. Finally, we drive the flexural resonance modes of the cylindrical inertia block and compare their frequencies to more traditional block shapes. |
Thursday, March 7, 2019 8:36AM - 8:48AM |
R23.00004: Imaging Sound Waves in Phononic Metamaterials William Fu, Nathan Drucker, Harris Pirie, Jennifer Wang, Wolfgang Rueckner, Jennifer Hoffman Phononic and photonic metamaterials have recently been proposed as analogs for topologically insulating structures, with a variety of potential applications. Most of these systems have been analyzed by simulation only (e.g. in COMSOL Multiphysics), but it has remained challenging to construct them experimentally and to measure their dynamics. Here we demonstrate two approaches to experimentally characterize real systems of topological phononic metamaterials using schlieren optics and a scanning microphone. In the schlieren setup, a mirror with long focal length is used to detect small changes in the refractive index of air using strobed light, which allows dynamic imaging of sound pressure [1]. Furthermore, we have developed a computer numerical control (CNC) scanning microphone with 6 degrees of freedom for dynamic imaging. Our sound wave imaging enables characterization of a topological phononic waveguide and other devices [2]. |
Thursday, March 7, 2019 8:48AM - 9:00AM |
R23.00005: Observation of GHz Modes in Quartz Circular Surface Acoustic Wave Resonator Joel Therrien, SaiSridevesh Kadambari A novel form of Surface Acoustic Wave (SAW) resonators functions by exciting SAW modes in a circular acoustic cavity formed on a ST-cut quartz substrate. The resonant and harmonic frequencies of these devices is dependent on the diameter of the cavity. Based on the acoustic properties of ST quartz, devices with dimension in the range of 100's of μm are expected to have resonant frequencies in the range of 10's to 100's of MHz. These modes are indeed observed, however additional modes with frequencies in the GHz range (between 1-8 GHz) have also been observed. These modes do not appear to be part of the harmonic series associated with the MHz range modes. Moreover, specific aspects of these modes are inconsistent with the known acoustic properties of ST-cut quartz. Progress on understanding these modes will be presented. |
Thursday, March 7, 2019 9:00AM - 9:12AM |
R23.00006: Regenerative Acoustofluidic NanoFilters for Biomolecular Purification and Quantification Weiwei Cui, Shari Yosinski, Xuexin Duan, Mark A Reed Precise manipulation of target molecules is critical for microfluidic applications, such as molecular purification, target enrichment, and biosensing. Here, we report a microfluidic-based regenerable nanoscale filtration technique for purification and detection of target molecules from complex samples. By assembling specific functionalized nanoparticles (SFNPs) in an acoustofluidic vortex chip, an array of nanofilters is constructed. The acoustofluidic vortex is produced by a gigahertz bulk acoustic wave resonator, which allows for simple regeneration. Additionally, the acoustofluidic vortex increases SFNP–target interactions, overcoming diffusion limits. We demonstrate this nanofiltration method for rapid and effective purification of targets in both buffer and serum samples. We studied the molecular capturing dynamics using the biotin-SAv complex as a model, where we demonstrate a rapid (within 60 seconds) and accurate (with a detection limit of 170ng/mL) molecular quantification biosensor. The approach has the advantages of non-clogging high-throughput capability, as well as excellent flexibility, enabling wide biomedical applications. |
Thursday, March 7, 2019 9:12AM - 9:24AM |
R23.00007: Non-invasive, non-destructive characterization of subsurface weld defects via directed ultrasound John Greenhall, Alan Lyman Graham, Cristian Pantea, Dipen N Sinha Directed ultrasound is employed to identify defects in subsurface welded joints and to characterize the defects as either inclusions or voids. We scan over the welded joint with a single ultrasound transducer, which transmits an ultrasound burst, and then we measure the burst after it reflects from the subsurface weld defects. In contrast with existing ultrasound characterization techniques we do not require a mechanical connection between the ultrasound transducer and the welded specimen, which facilitates implementation in the field. We utilize a correlation envelope to identify and locate defects in the presence of noise, and we distinguish between voids and inclusions based on phase change in the measured burst after reflection from a weld defect. We demonstrate the directed ultrasound technique for identifying subsurface defects in a tungsten alloy with a square joint. In contrast with X-ray imaging techniques, which cannot penetrate tungsten alloys, we identify, locate, and characterize known defects at depths of >10 mm. This directed ultrasound technique enables non-invasive, non-destructive inspection of a wide range of materials, and finds application in numerous applications including welding, printed circuit board fabrication, and sintered 3D printing. |
Thursday, March 7, 2019 9:24AM - 9:36AM |
R23.00008: Ultrasonic Collimated Beams in Elastic Solids Vamshi Krishna Chillara, Cristian Pantea Ultrasonic collimated beams are directed beams that propagate in materials with very little angular spread. Generation of such beams in solids enable high resolution imaging of heterogeneous and attenuating materials like concrete and noninvasive materials characterization of anisotropic materials like composites. We present a simple approach to generating ultrasonic collimated beams that relies on a novel approach to generating Bessel beams using radial modes of piezoelectric disc transducers. We first discuss the resonance and vibration characteristics of radial modes of piezoelectric discs using numerical and experimental studies. Then, analytical and numerical results on ultrasonic Bessel beam generation in elastic solids will be presented. Finally, a technique for the reduction of side lobes in Bessel beams will be discussed and numerical results on ultrasonic collimated beam generation in elastic solids will be presented. |
Thursday, March 7, 2019 9:36AM - 9:48AM |
R23.00009: Multiscale porosity measurements of Shale rocks using multiple gas adsorption and mercury intrusion porosimetry Nicolas Chanut, Thibaut Divoux, Rénal Backov, Jeff Kenvin, Roland JM Pellenq Unconventional oil and gas production from shale has revolutionized the world energy landscape. Shale is a fine-grained sedimentary rock, composed of solid organic matter (OM) scattered in a mineral framework. The decomposition of this OM at high temperature leads to the generation of hydrocarbons during a process known as maturation. The resulting organic matter develops a nanoscale porosity that governs the ability of a shale petroleum reservoir to store and then to yield oil and gas. The mineral matrix also contributes to the overall porosity leading to a pore size distribution spanning from a few Å to the µm range. In this work, we have combined gas adsorption of multiple gases (CO2, H2, N2, and Ar) and mercury intrusion porosimetry to study the pore system of 5 samples from the Vaca Muerta formation that differ in maturities. Indeed, while gas adsorption allows probing the micro and mesoporosity (< 50nm), mercury intrusion allows for the characterization of the macroporosity (10nm to 500µm). Rather than using a fragmented approach of simple overlays from individual techniques, a unified approach that utilizes a kernel constructed from model isotherms and model intrusion curves is used to calculate the complete pore size distribution and the total pore volume of the material. |
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