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https://www.readbyqxmd.com/read/27914423/measurement-of-the-low-wavenumber-component-within-a-turbulent-wall-pressure-by-an-inverse-problem-of-vibration
#1
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
#2
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
#3
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...
November 16, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27893474/hypertrophy-and-explosive-reactive-functioning-in-sedentary-men-following-10-weeks-of-whole-body-vibration
#4
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
#5
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
https://www.readbyqxmd.com/read/27857683/in-vitro-magnetic-stimulation-a-simple-stimulation-device-to-deliver-defined-low-intensity-electromagnetic-fields
#6
Stephanie Grehl, David Martina, Catherine Goyenvalle, Zhi-De Deng, Jennifer Rodger, Rachel M Sherrard
Non-invasive brain stimulation (NIBS) by electromagnetic fields appears to benefit human neurological and psychiatric conditions, although the optimal stimulation parameters and underlying mechanisms remain unclear. Although, in vitro studies have begun to elucidate cellular mechanisms, stimulation is delivered by a range of coils (from commercially available human stimulation coils to laboratory-built circuits) so that the electromagnetic fields induced within the tissue to produce the reported effects are ill-defined...
2016: Frontiers in Neural Circuits
https://www.readbyqxmd.com/read/27794334/motion-of-the-cello-bridge
#7
Ailin Zhang, Jim Woodhouse, George Stoppani
This paper presents an experimental investigation of the motion of the bridge of a cello, in the frequency range up to 2 kHz. Vibration measurements were carried out on three different cellos, and the results used to determine the position of the Instantaneous Centre of rotation of the bridge, treated as a rigid body. The assumption of rigid body rotation is shown to give a good approximation up to at least 1 kHz. The instantaneous centre moves from the sound-post side of the bridge at the lowest frequencies towards the bass-bar side at higher frequencies, remaining close to the surface of the top plate of the instrument...
October 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27794327/vibration-energy-analysis-of-a-plate-for-defect-imaging-with-a-scanning-laser-source-technique
#8
Takahiro Hayashi, Misaki Fukuyama
Vibration energies generated by laser irradiation to a plate with a crack were calculated by the semi-analytical finite element method to elucidate the principle of defect imaging using a scanning laser source. For normal incidence in the ablation regime, the incident energy increases when the incident source is located in the vicinity of the crack, owing to the effect of the non-propagating A1 modes. For dipole loading in the thermoelastic regime, the vibration energies are completely different, depending on the position of the crack opening...
October 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27794294/sound-radiation-from-a-fluid-loaded-plate-with-periodic-inhomogeneities-of-finite-width
#9
Yanni Zhang, Hai Huang, Jie Pan
This paper focuses on the frequency-filtering behavior of the structural vibration and sound radiation of a fluid-loaded plate with periodic inhomogeneities of finite width. The passbands of the flexural waves in the plate and the frequency bands of effective sound radiation from the plate are examined for air and water loading conditions. The mechanisms that generate the differences in these two bands are explained by analyzing the dispersion curves of the waves in the plate and the sound radiation behavior of supersonic wavenumber components in the plate vibration...
October 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27787468/effect-of-direct-whole-body-vibration-on-upper-body-muscular-power-in-recreational-resistance-trained-men
#10
Margaret T Jones, Joel Martin, Andrew R Jagim, Jonathan M Oliver
To determine the acute effect of whole body vibration (WBV) on upper body power, 15 men (mean ± SD; age 21.5 ± 2.3 years; height 173.1 ± 6.5 cm; weight 77.2 ± 13.8 kg) with ≥ 1 year resistance training experience and a bench press (BP): body mass ratio ≥ 1.25 participated in a repeated measures crossover design. Session 1 included body composition ((BodPod) 15.76 ± 6.7 % body fat), 3-repetition maximum BP, and familiarization with: seated medicine ball throw (SMBT), plyometric push-up on a force plate (PPU), and vertical WBV platform...
October 13, 2016: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/27773288/effect-of-ultrasonic-vibration-time-on-the-cu-sn-ag-cu-cu-joint-soldered-by-low-power-high-frequency-ultrasonic-assisted-reflow-soldering
#11
Ai Ting Tan, Ai Wen Tan, Farazila Yusof
Techniques to improve solder joint reliability have been the recent research focus in the electronic packaging industry. In this study, Cu/SAC305/Cu solder joints were fabricated using a low-power high-frequency ultrasonic-assisted reflow soldering approach where non-ultrasonic-treated samples were served as control sample. The effect of ultrasonic vibration (USV) time (within 6s) on the solder joint properties was characterized systematically. Results showed that the solder matrix microstructure was refined at 1...
January 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/27767198/hydrothermal-preparation-of-perovskite-structures-dycro3-and-hocro3
#12
Shan Wang, Changmin Hou, Long Yuan, Mingyang Qu, Bo Zou, Dayong Lu
Perovskite structured rare-earth chromites are one of the most promising families of functional materials in solid oxide fuel cells, multiferroic materials, and sensors. Here, we report a mild hydrothermal method to synthesize DyCrO3 and HoCrO3 monodispersed single crystals. The synthesis conditions, crystal structure, Raman spectra and temperature- and field-dependent magnetic properties were studied. The two samples are indexed to the Pbnm space group. The shapes of the crystals are plates with a narrow particle size distribution in the range of 4-5 μm...
October 21, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/27718512/feasibility-and-tolerability-of-low-intensity-whole-body-vibration-and-its-effects-on-muscle-function-and-bone-in-patients-with-dystrophinopathies-a-pilot-study
#13
Anna Petryk, Lynda E Polgreen, Molly Grames, Dawn A Lowe, James S Hodges, Peter Karachunski
INTRODUCTION: Dystrophinopathies are X-linked muscle degenerative disorders that result in progressive muscle weakness complicated by bone loss. This study's goal was to evaluate feasibility and tolerability of whole body low intensity vibration (WBLIV) and its potential effects on muscle and bone in patients with Duchenne or Becker muscular dystrophy. METHODS: This 12-month pilot study included 5 patients (age 5.9-21.7 years) who used a low-intensity Marodyne LivMD plate vibrating at 30-90 Hz for 10 minutes/day for the first 6 months...
October 8, 2016: Muscle & Nerve
https://www.readbyqxmd.com/read/27661364/dual-wavelength-common-path-digital-holographic-microscopy-for-quantitative-phase-imaging-based-on-lateral-shearing-interferometry
#14
Jianglei Di, Ying Li, Min Xie, Jiwei Zhang, Chaojie Ma, Teli Xi, Enpu Li, Jianlin Zhao
A dual-wavelength common-path digital holographic microscopy based on a single parallel glass plate is presented to achieve quantitative phase imaging, which combines the dual-wavelength technique with lateral shearing interferometry. Two illumination laser beams with different wavelengths (λ<sub>1</sub>=532  nm and λ<sub>2</sub>=632.8  nm) are reflected by the front and back surfaces of the parallel glass plate to create the lateral shear and form the digital hologram, and then the hologram is reconstructed to obtain the phase distribution with a synthetic wavelength Λ=3339...
September 10, 2016: Applied Optics
https://www.readbyqxmd.com/read/27632854/does-the-acute-and-short-term-effect-of-whole-body-vibration-is-the-same-on-the-h-reflex-recruitment-curve-and-agility
#15
Morteza Ahmadi, Giti Torkaman, Sedigheh Kahrizi, Mojdeh Ghabaee, Leila Dadashi Arani
CONTEXT: Despite the widespread use of whole body vibration (WBV), especially in recent years, its neurophysiological mechanism is still unclear and it is yet to be determined whether acute and short term WBV exposure produce neurogenic enhancement for agility. OBJECTIVE: To compare the acute and short-term effects of WBV, on the H-reflex recruitment curve and agility . DESIGN: Cross over study. SETTING: Clinical electrophysiology lab...
August 24, 2016: Journal of Sport Rehabilitation
https://www.readbyqxmd.com/read/27623522/free-and-forced-vibrations-of-sc-cut-quartz-crystal-rectangular-plates-with-the-first-order-mindlin-plate-equations
#16
Rongxing Wu, Wenjun Wang, Guijia Chen, Hui Chen, Tingfeng Ma, Jianke Du, Ji Wang
Mindlin plate theory was used to provide accurate solutions to thickness-shear vibrations of plates, which have a much higher frequency than usual flexural vibrations and are the functioning modes of quartz crystal resonators. The vibration frequency solutions obtained with the Mindlin plate theory are proven being accurate along with mode shapes. In this paper, straight-crested wave solutions of free and forced vibrations of doubly rotated SC-cut of quartz crystal plates of rectangular shapes with four free edges are obtained with validated Mindlin plate equations...
September 4, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27611347/controlling-the-motion-of-multiple-objects-on-a-chladni-plate
#17
Quan Zhou, Veikko Sariola, Kourosh Latifi, Ville Liimatainen
The origin of the idea of moving objects by acoustic vibration can be traced back to 1787, when Ernst Chladni reported the first detailed studies on the aggregation of sand onto nodal lines of a vibrating plate. Since then and to this date, the prevailing view has been that the particle motion out of nodal lines is random, implying uncontrollability. But how random really is the out-of-nodal-lines motion on a Chladni plate? Here we show that the motion is sufficiently regular to be statistically modelled, predicted and controlled...
2016: Nature Communications
https://www.readbyqxmd.com/read/27597307/plate-type-elastic-metamaterials-for-low-frequency-broadband-elastic-wave-attenuation
#18
Yinggang Li, Ling Zhu, Tianning Chen
In this paper, we numerically and experimentally demonstrate the low-frequency broadband elastic wave attenuation and vibration suppression by using plate-type elastic metamaterial, which is constituted of periodic double-sides stepped resonators deposited on a two-dimensional phononic plate with steel matrix. The dispersion relations, the power transmission spectra, and the displacement fields of the eigenmodes are calculated by using the finite element method. In contrast to the typical phononic plates consisting of periodic stepped resonators deposited on a homogeneous steel plate, the proposed elastic metamaterial can yield large band gap in the low-frequency range, resulting in the low-frequency broadband elastic wave attenuation...
August 26, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27586764/directivity-pattern-of-the-sound-radiated-from-axisymmetric-stepped-plates
#19
Xiping He, Xiuli Yan, Na Li
For the purpose of optimal design and efficient utilization of the kind of stepped plate radiator in air, in this contribution, an approach for calculation of the directivity pattern of the sound radiated from a stepped plate in flexural vibration with a free edge is developed based on Kirchhoff-Love hypothesis and Rayleigh integral principle. Experimental tests of directivity pattern for a fabricated flat plate and two fabricated plates with one and two step radiators were carried out. It shows that the configuration of the measured directivity patterns by the proposed analytic approach is similar to those of the calculated approach...
August 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27586754/simulation-of-the-pressure-field-beneath-a-turbulent-boundary-layer-using-realizations-of-uncorrelated-wall-plane-waves
#20
Laurent Maxit
This paper investigates the modeling of a vibrating structure excited by a turbulent boundary layer (TBL). Although the wall pressure field (WPF) of the TBL constitutes a random excitation, the element-based methods generally used for describing complex mechanical structures consider deterministic loads. The response of such structures to a random excitation like TBL is generally deduced from calculations of numerous Frequency Response Functions. Consequently, the process is computationally expansive. To tackle this issue, an efficient process is proposed for generating realizations of the WPF corresponding to the TBL...
August 2016: Journal of the Acoustical Society of America
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