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https://www.readbyqxmd.com/read/28253676/time-reversal-focusing-of-elastic-waves-in-plates-for-an-educational-demonstration
#1
Christopher Heaton, Brian E Anderson, Sarah M Young
The purpose of this research is to develop a visual demonstration of time reversal focusing of vibrations in a thin plate. Various plate materials are tested to provide optimal conditions for time reversal focusing. Specifically, the reverberation time in each plate and the vibration coupling efficiency from a shaker to the plate are quantified to illustrate why a given plate provides the best spatially confined focus as well as the highest focal amplitude possible. A single vibration speaker and a scanning laser Doppler vibrometer (SLDV) are used to provide the time reversal focusing...
February 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28252394/development-of-an-acoustic-levitation-linear-transportation-system-based-on-a-ring-type-structure
#2
Gilles Thomas, Marco Aurelio Andrade, Julio Adamowski, Emilio Silva
A linear acoustic levitation transportation system based on a ring-type vibrator is presented. The system is composed by two 21 kHz Langevin transducers connected to a ring-shaped structure formed by two semicircular sections and two flat plates. In this system, a flexural standing wave is generated along the ring structure, producing an acoustic standing wave between the vibrating ring and a plane reflector located at a distance of approximately a half wavelength from the ring. The acoustic standing wave in air has a series of pressure nodes, where small particles can be levitated and transported...
February 23, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/28249528/low-vibration-laboratory-with-a-single-stage-vibration-isolation-for-microscopy-applications
#3
Bert Voigtländer, Peter Coenen, Vasily Cherepanov, Peter Borgens, Thomas Duden, F Stefan Tautz
The construction and the vibrational performance of a low vibration laboratory for microscopy applications comprising a 100 ton floating foundation supported by passive pneumatic isolators (air springs), which rest themselves on a 200 ton solid base plate, are discussed. The optimization of the air spring system leads to a vibration level on the floating floor below that induced by an acceleration of 10 ng for most frequencies. Additional acoustic and electromagnetic isolation is accomplished by a room-in-room concept...
February 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28248509/young-s-equation-for-a-two-liquid-system-on-the-nanometer-scale
#4
J-C Fernandez-Toledano, T D Blake, J De Coninck
We use large-scale molecular dynamics simulations to study the Lennard-Jones forces acting at the various interfaces of a liquid bridge (liquid 1) between two realistic solid plates on the scale of few nanometers when the two free surfaces are in contact with a second immiscible liquid (liquid 2) with an interfacial tension of γ12. Each plate comprises a regular square planar lattice of atoms arranged in three atomic layers. To maintain rigidity while allowing momentum exchange with the liquid, solid atoms are allowed to vibrate thermally around their initial positions by a strong harmonic potential...
March 8, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28237824/damage-detection-of-fatigue-cracks-under-nonlinear-boundary-condition-using-subharmonic-resonance
#5
Mengyang Zhang, Li Xiao, Wenzhong Qu, Ye Lu
In recent years, the nonlinear ultrasonic technique has been widely utilized for detecting fatigue crack, one of the most common forms of damage. However, one of limitations associated with this technique is that nonlinearities can be produced not only by damage but also by various intrinsic effects such as boundary conditions. The objective of this paper is to demonstrate the application of a nonlinear ultrasonic subharmonic method for detecting fatigue cracks with nonlinear boundary conditions. The fatigue crack was qualitatively modeled as two elastic, frictionless half spaces that enter into contact during vibration and where the contact obeys the basic Hertz contact law...
February 4, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28222002/friction-reduction-through-ultrasonic-vibration-part-1-modelling-intermittent-contact
#6
Eric Vezzoli, Zlatko Virdih, Vincenzo Giamundo, Betty Lemaire-Semail, Frederic Giraud, Tomaz Rodic, Djordje Peric, Michael Adams
Ultrasonic vibration is employed to modify the friction of a finger pad in way that induces haptic sensations. A combination of intermittent contact and squeeze film levitation has been previously proposed as the most probable mechanism. In this paper, in order to understand the underlying principles that govern friction modulation by intermittent contact, numerical models based on finite element (FE) analysis and also a spring-Coulombic slider are developed. The physical input parameters for the FE model are optimised by measuring the contact phase shift between a finger pad and a vibrating plate...
February 17, 2017: IEEE Transactions on Haptics
https://www.readbyqxmd.com/read/28222001/friction-reduction-through-ultrasonic-vibration-part-2-experimental-evaluation-of-intermittent-contact-and-squeeze-film-levitation
#7
Thomas Sednaoui, Eric Vezzoli, Brygida Maria Dzidek, Betty Lemaire-Semail, Cedrick Chappaz, Michael Adams
In part 1 of the current study of haptic displays, a finite element (FE) model of a finger exploring a plate vibrating out-of-plane at ultrasonic frequencies was developed as well as a spring-frictional slider model. It was concluded that the reduction in friction induced by the vibrations could be ascribed to ratchet mechanism as a result of intermittent contact. The relative reduction in friction calculated using the FE model could be superimposed onto an exponential function of a dimensionless group defined from relevant parameters...
February 17, 2017: IEEE Transactions on Haptics
https://www.readbyqxmd.com/read/28130556/the-new-vestibular-stimuli-sound-and-vibration-anatomical-physiological-and-clinical-evidence
#8
REVIEW
Ian S Curthoys
The classical view of the otoliths-as flat plates of fairly uniform receptors activated by linear acceleration dragging on otoconia and so deflecting the receptor hair bundles-has been replaced by new anatomical and physiological evidence which shows that the maculae are much more complex. There is anatomical spatial differentiation across the macula in terms of receptor types, hair bundle heights, stiffness and attachment to the overlying otolithic membrane. This anatomical spatial differentiation corresponds to the neural spatial differentiation of response dynamics from the receptors and afferents from different regions of the otolithic maculae...
April 2017: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
https://www.readbyqxmd.com/read/28125270/response-to-tendon-vibration-questions-the-underlying-rationale-of-proprioceptive-training
#9
Anat Vilnai Lubetzky, Sarah Westcott McCoy, Robert Price, Deborah Kartin
CONTEXT: Proprioceptive training on compliant surfaces is used to rehabilitate and prevent ankle sprains. The ability to improve proprioceptive function via such training has been questioned. Achilles tendon vibration is used in motor-control research as a form of proprioceptive stimulus. Using measures of postural steadiness with nonlinear measures to elucidate control mechanisms, tendon vibration can be applied to investigate the underlying rationale of proprioceptive training. OBJECTIVE: To test whether the effect of vibration on young adults' postural control depended on the support surface...
February 2017: Journal of Athletic Training
https://www.readbyqxmd.com/read/28117740/a-low-frequency-fbg-accelerometer-with-symmetrical-bended-spring-plates
#10
Fufei Liu, Yutang Dai, Joseph Muna Karanja, Minghong Yang
To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating) accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed...
January 22, 2017: Sensors
https://www.readbyqxmd.com/read/28113602/vibrotactile-compliance-feedback-for-tangential-force-interaction
#11
Seongkook Heo, Geehyuk Lee
This paper presents a method to generate a haptic illusion of compliance using a vibrotactile actuator when a tangential force is applied to a rigid surface. The novel method builds on a conceptual compliance model where a physical object moves on a textured surface in response to a tangential force. The method plays vibration patterns simulating friction-induced vibrations as an applied tangential force changes. We built a prototype consisting of a two-dimensional tangential force sensor and a surface transducer to test the effectiveness of the model...
August 30, 2016: IEEE Transactions on Haptics
https://www.readbyqxmd.com/read/28102524/heat-transfer-capability-of-ethylene-glycol-water-based-nanofluids-containing-graphene-nanoplatelets-design-and-thermophysical-profile
#12
D Cabaleiro, L Colla, S Barison, L Lugo, L Fedele, S Bobbo
This research aims at studying the stability and thermophysical properties of nanofluids designed as dispersions of sulfonic acid-functionalized graphene nanoplatelets in an (ethylene glycol + water) mixture at (10:90)% mass ratio. Nanofluid preparation conditions were defined through a stability analysis based on zeta potential and dynamic light scattering (DLS) measurements. Thermal conductivity, dynamic viscosity, and density were experimentally measured in the temperature range from 283.15 to 343.15 K and nanoparticle mass concentrations of up to 0...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28057352/sigmoid-sinus-cortical-plate-dehiscence-induces-pulsatile-tinnitus-through-amplifying-sigmoid-sinus-venous-sound
#13
Shan Tian, Lizhen Wang, Jiemeng Yang, Rui Mao, Zhaohui Liu, Yubo Fan
Sigmoid sinus cortical plate dehiscence (SSCPD) is common in pulsatile tinnitus (PT) patients, and is treated through SSCPD resurfacing surgery in clinic, but the bio-mechanism is not clear as so far. This study aimed to clarify the bio-mechanism of PT sensation induced by SSCPD, and quantify the relationship of cortical plate (CP) thickness and PT sensation intensity. It was hypothesized that SSCPD would induce PT through significantly amplifying sigmoid sinus (SS) venous sound in this study. Finite element (FE) analysis based on radiology data of typical patient was used to verify this hypothesis, and was validated with clinical reports...
February 8, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28012413/long-thickness-extensional-waves-in-thin-film-bulk-acoustic-wave-filters-affected-by-interdigital-electrodes
#14
Jing Liu, Jianke Du, Ji Wang, Jiashi Yang
We studied free vibrations of thin-film bulk acoustic wave filters with interdigital electrodes theoretically using the scalar differential equations by Tiersten and Stevens. The filters are made from AlN or ZnO films on Si substrates with ground and driving electrodes. They operate with thickness-extensional modes. The basic vibration characteristics including resonant frequencies and mode shapes were obtained. Their dependence on various geometric parameters was examined. It was found that for properly design filters there exist trapped modes whose vibrations are strong in regions with a driving electrode and decay away from the electrode edges...
March 2017: Ultrasonics
https://www.readbyqxmd.com/read/27973354/a-diffraction-correction-for-storage-and-loss-moduli-imaging-using-radiation-force-based-elastography
#15
Eliana Budelli, Javier Brum, Miguel Bernal, Thomas Deffieux, Mickaël Tanter, Patricia Lema, Carlos Negreira, Jean-Luc Gennisson
Noninvasive evaluation of the rheological behavior of soft tissues may provide an important diagnosis tool. Nowadays, available commercial ultrasound systems only provide shear elasticity estimation by shear wave speed assessment under the hypothesis of a purely elastic model. However, to fully characterize the rheological behavior of tissues, given by its storage (G') and loss (G″) moduli, it is necessary to estimate both: shear wave speed and shear wave attenuation. Most elastography techniques use the acoustic radiation force to generate shear waves...
January 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/27914423/measurement-of-the-low-wavenumber-component-within-a-turbulent-wall-pressure-by-an-inverse-problem-of-vibration
#16
Damien Lecoq, Charles Pézerat, Fabien Chevillotte, Rémi Bessis
An experimental validation is implemented for the measurement of a weak acoustic component within a turbulent wall pressure by an inverse problem of vibration. The turbulent flow is generated by a forward-facing step in a wind tunnel. In addition to the flow, an acoustic source with a low level excites the plate and plays the role of an additional acoustic component to be identified. The inverse methods called the force analysis technique and the corrected force analysis technique are used to compute the wall pressure fluctuations from the measurement of the plate vibration using an array of 13 accelerometers...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27900951/tuning-the-morphology-luminescence-and-magnetic-properties-of-hexagonal-phase-nagdf4-yb-er-nanocrystals-via-altering-the-addition-sequence-of-the-precursors
#17
Shuwen Zhao, Donglin Xia, Ruimin Zhao, Hao Zhu, Yiru Zhu, Yuda Xiong, Youfa Wang
Hexagonal-phase NaGdF4: Yb, Er upconversion nanocrystals (UCNCs) with tunable morphology and properties were successfully prepared via a thermal decomposition method. The influences of the adding sequence of the precursors on the morphology, chemical composition, luminescence and magnetic properties were investigated by transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectrometry (ICP-AES), upconversion (UC) spectroscopy, and a vibrating sample magnetometer (VSM). It was found that the resulting nanocrystals, with different sizes ranging from 24 to 224 nm, are in the shape of spheres,  hexagonal plates and flakes; moreover, the composition percentage of Yb(3+)-Er(3+) and Gd(3+) ions was found to vary in a regular pattern with the adding sequence...
January 6, 2017: Nanotechnology
https://www.readbyqxmd.com/read/27898300/a-new-topological-structure-for-the-langevin-type-ultrasonic-transducer
#18
Xiaolong Lu, Junhui Hu, Hanmin Peng, Yuan Wang
In this paper, a new topological structure for the Langevin-type ultrasonic transducer is proposed and investigated. The two cylindrical terminal blocks are conically shaped with four supporting plates each, and two cooling fins are disposed at the bottom of terminal blocks, adjacent to the piezoelectric rings. Experimental results show that it has larger vibration velocity, lower temperature rise and higher electroacoustic energy efficiency than the conventional Langevin transducer. The reasons for the phenomena can be well explained by the change of mass, heat dissipation surface and force factor of the transducer...
March 2017: Ultrasonics
https://www.readbyqxmd.com/read/27893474/hypertrophy-and-explosive-reactive-functioning-in-sedentary-men-following-10-weeks-of-whole-body-vibration
#19
Jens Ebing, Ulf Gast, Christoph Hauptmann, Dieter Felsenberg, Daniel L Belavý
The objective of this study was to determine the impact of vertical (Power-plate; POW) and side-alternating (Galileo; GAL) whole-body vibration exercise on muscle mass and lower-limb neuromuscular function. Forty-three sedentary male subjects (18-30yr) randomized into three groups underwent two upper-body exercise sessions per week for 10 weeks. Two groups of subjects underwent additional squat exercises on the GAL (N=15) or POW (N=14) devices. The third group was control. On magnetic resonance imaging, volume of the thigh muscles was measured...
November 16, 2016: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/27863340/solder-joint-failure-localization-of-welded-joint-based-on-acoustic-emission-beamforming
#20
Xiandong Liu, Denghong Xiao, Yingchun Shan, Qiang Pan, Tian He, Yong Gao
A localization approach of welded joint damage is proposed based on acoustic emission (AE) beamforming. In this method, a uniform line array is introduced to detect the AE signal of welded joints in specified area. In order to investigate the influence of fillet and crimping commonly existing in a welded plate structure during the AE wave propagation process, the finite element method (FEM) is applied to simulate the behavior of AE wave in the specimen. The simulation localization results indicate that the proposed localization approach can effectively localize AE sources although there exist the fillet and crimping, and it is also validated by the pencil-lead-broken test on rectangular steel tube with welded joints...
February 2017: Ultrasonics
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