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https://www.readbyqxmd.com/read/27914306/a-contactless-ultrasonic-surface-wave-approach-to-characterize-distributed-cracking-damage-in-concrete
#1
Suyun Ham, Homin Song, Michael L Oelze, John S Popovics
We describe an approach that utilizes ultrasonic surface wave backscatter measurements to characterize the volume content of relatively small distributed defects (microcrack networks) in concrete. A simplified weak scattering model is used to demonstrate that the scattered wave field projected in the direction of the surface wave propagation is relatively insensitive to scatterers that are smaller than the propagating wavelength, while the scattered field projected in the opposite direction is more sensitive to sub-wavelength scatterers...
November 9, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27913901/3d-active-passive-response-of-human-knee-joint-in-gait-is-markedly-altered-when-simulated-as-a-planar-2d-joint
#2
H Marouane, A Shirazi-Adl, M Adouni
Musculoskeletal models of the lower extremity make a number of important assumptions when attempting to estimate muscle forces and tibiofemoral compartmental loads in activities such as gait. The knee is commonly idealized as a planar 2D joint in the sagittal plane with no consideration of motions and equilibrium in remaining planes. With muscle forces predicted, the static equilibrium in the frontal plane is then used to estimate compartmental loads neglecting also joint passive resistance and assuming condylar contact centers...
December 2, 2016: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/27913332/a-method-for-accurate-modeling-of-baw-filters-at-high-power-levels
#3
Andreas Tag, Vikrant Chauhan, Christian Huck, Bernhard Bader, Dominik Karolewski, F Maximilian Pitschi, Robert Weigel, Amelie Hagelauer
A novel approach for multiphysics modeling of bulk acoustic wave (BAW) filters is presented allowing accurate and at the same time efficient modeling of BAW filters at high power levels. The approach takes the different types of losses and their spatial distribution into account in order to provide the required input for thermal simulation. The temperature distribution determined by thermal simulation is used to modify the geometry and the layer stack of each single resonator of the filter. In this way, the required input for modeling of electromagnetic (EM) and acoustic behavior at high power level is generated...
December 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913329/2-d-ultrasound-sparse-arrays-multidepth-radiation-optimization-using-simulated-annealing-and-spiral-array-inspired-energy-functions
#4
Emmanuel Roux, Alessandro Ramalli, Piero Tortoli, Christian Cachard, Marc C Robini, Herve Liebgott
Full matrix arrays are excellent tools for 3-D ultrasound imaging, but the required number of active elements is too high to be individually controlled by an equal number of scanner channels. The number of active elements is significantly reduced by the sparse array techniques, but the position of the remaining elements must be carefully optimized. This issue is faced here by introducing novel energy functions in the simulated annealing (SA) algorithm. At each iteration step of the optimization process, one element is freely translated and the associated radiated pattern is simulated...
December 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/27913178/estimating-the-material-properties-of-heel-pad-sub-layers-using-inverse-finite-element-analysis
#5
Nafiseh Ahanchian, Christopher J Nester, David Howard, Lei Ren, Daniel Parker
Detailed information about the biomechanical behaviour of plantar heel pad tissue contributes to our understanding of load transfer when the foot impacts the ground. The objective of this work was to obtain the hyperelastic and viscoelastic material properties of heel pad sub-layers (skin, micro-chamber and macro-chamber layers) in-vivo. An anatomically detailed 3D Finite Element model of the human heel was used to derive the sub-layer material properties. A combined ultrasound imaging and motorised platform system was used to compress heel pad and to create input data for the Finite Element model...
November 29, 2016: Medical Engineering & Physics
https://www.readbyqxmd.com/read/27911473/enhancement-of-upconverted-fluorescence-by-interference-layers
#6
Janina Wirth, Kory K Green, Megan O'Connor, Shuang F Lim
Upconverting nanoparticles show potential applications in the field of photovoltaics and array-based detection devices. While fluorescence enhancement using interference of incident radiation is well known in Stokes-shift type systems such as fluorescent dyes; the effect of such interference geometry in nonlinear Anti-Stokes type emission, such as in upconversion rare earth photophysics is demonstrated for the first time. This work describes in detail the influence of the interference modulation on both the excitation (interion energy transfer) and radiative decay with nonradiative decay processes active between emissive levels...
December 2, 2016: Small
https://www.readbyqxmd.com/read/27911025/effect-of-balloon-expandable-transcatheter-aortic-valve-replacement-positioning-a-patient-specific-numerical-model
#7
Matteo Bianchi, Gil Marom, Ram P Ghosh, Harold A Fernandez, James R Taylor, Marvin J Slepian, Danny Bluestein
Transcatheter aortic valve replacement (TAVR) has emerged as a life-saving and effective alternative to surgical valve replacement in high-risk, elderly patients with severe calcific aortic stenosis. Despite its early promise, certain limitations and adverse events, such as suboptimal placement and valve migration, have been reported. In the present study, it was aimed to evaluate the effect of various TAVR deployment locations on the procedural outcome by assessing the risk for valve migration. The deployment of a balloon-expandable Edwards SAPIEN valve was simulated via finite element analysis in a patient-specific calcified aortic root, which was reconstructed from CT scans of a retrospective case of valve migration...
December 2016: Artificial Organs
https://www.readbyqxmd.com/read/27910661/spider-beam-dump-as-diagnostic-of-the-particle-beam
#8
M Zaupa, M Dalla Palma, E Sartori, M Brombin, R Pasqualotto
The beam power produced by the negative ion source for the production of ion of deuterium extracted from RF plasma is mainly absorbed by the beam dump component which has been designed also for measuring the temperatures on the dumping panels for beam diagnostics. A finite element code has been developed to characterize, by thermo-hydraulic analysis, the sensitivity of the beam dump to the different beam parameters. The results prove the capability of diagnosing the beam divergence and the horizontal misalignment, while the entity of the halo fraction appears hardly detectable without considering the other foreseen diagnostics like tomography and beam emission spectroscopy...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910650/full-wave-feasibility-study-of-anti-radar-diagnostic-of-magnetic-field-based-on-o-x-mode-conversion-and-oblique-reflectometry-imaging
#9
Orso Meneghini, Francesco A Volpe
An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contains information on the magnetic field vector B at the cutoff layer. Probing the plasma with different wave frequencies provides the radial profile of B...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910556/thermal-analysis-of-the-in-vessel-components-of-the-iter-plasma-position-reflectometry
#10
P B Quental, H Policarpo, R Luís, P Varela
The ITER plasma position reflectometry system measures the edge electron density profile of the plasma, providing real-time supplementary contribution to the magnetic measurements of the plasma-wall distance. Some of the system components will be in direct sight of the plasma and therefore subject to plasma and stray radiation, which may cause excessive temperatures and stresses. In this work, thermal finite element analysis of the antenna and adjacent waveguides is conducted with ANSYS V17 (ANSYS® Academic Research, Release 17...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910484/design-analysis-and-testing-of-kinematic-mount-for-astronomical-observation-instrument-used-in-space-camera
#11
Mingxin An, Lihao Zhang, Shuyan Xu, Jihong Dong
A statically determinate kinematic mount structure is designed for an astronomical observation instrument. The basic principle of the proposed kinematic mount is introduced in detail, including the design principle, its structure, and its degrees of freedom. The compliance equations for the single-axis right circle flexure hinge are deduced, and mathematical models of the compliances of the bipod in the X-axis and Z-axis directions are established. Based on the index requirements, the range of one design parameter (the hinge groove depth, R) for the kinematic mount is determined...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910463/design-and-experiments-of-a-linear-piezoelectric-motor-driven-by-a-single-mode
#12
Zhen Liu, Zhiyuan Yao, Xiang Li, Qianwei Fu
In this contribution, we propose a novel linear piezoelectric motor with a compact stator that is driven by a single mode. The linear piezoelectric motor can realize bidirectional motion by changing the vibration modes of the stator. Finite element analysis is performed to determine the required vibration mode of the stator and obtain the optimal stator structure and dimensions. Furthermore, the trajectories of the driving foot are analyzed with and without consideration of the mechanical contact with the slider...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910461/a-novel-microgripper-hybrid-driven-by-a-piezoelectric-stack-actuator-and-piezoelectric-cantilever-actuators
#13
Weilin Chen, Xianmin Zhang, Sergej Fatikow
For the piezo-driven microgripper, one issue is to enlarge the grasping stroke and realize parallel grasping movement in the compact design. Piezoelectric stack actuator (PSA) and piezoelectric cantilever actuator (PCA) are two kinds of typical piezoelectric actuators. In this study, a novel microgripper hybrid driven by a PSA and two PCAs is proposed, which can be a better solution for the issue, compared with the previous microgripper using PSA-driven multi-stages displacement amplification mechanism (DAM) or using longer and narrower PCAs...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910368/airfoil-based-electromagnetic-energy-harvester-containing-parallel-array-motion-between-moving-coil-and-multi-pole-magnets-towards-enhanced-power-density
#14
Chung Ming Leung, Ya Wang, Wusi Chen
In this letter, the airfoil-based electromagnetic energy harvester containing parallel array motion between moving coil and trajectory matching multi-pole magnets was investigated. The magnets were aligned in an alternatively magnetized formation of 6 magnets to explore enhanced power density. In particular, the magnet array was positioned in parallel to the trajectory of the tip coil within its tip deflection span. The finite element simulations of the magnetic flux density and induced voltages at an open circuit condition were studied to find the maximum number of alternatively magnetized magnets that was required for the proposed energy harvester...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910366/the-rectangular-array-of-magnetic-probes-on-j-text-tokamak
#15
Zhipeng Chen, Fuming Li, Ge Zhuang, Xiang Jian, Lizhi Zhu
The rectangular array of magnetic probes system was newly designed and installed in the torus on J-TEXT tokamak to measure the local magnetic fields outside the last closed flux surface at a single toroidal angle. In the implementation, the experimental results agree well with the theoretical results based on the Spool model and three-dimensional numerical finite element model when the vertical field was applied. Furthermore, the measurements were successfully used as the input of EFIT code to conduct the plasma equilibrium reconstruction...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910335/detailed-characterization-of-the-llnl-imaging-proton-spectrometer
#16
A M Rasmus, A U Hazi, M J-E Manuel, C C Kuranz, S R Klein, P X Belancourt, J R Fein, M J MacDonald, R P Drake, B B Pollock, J Park, G J Williams, H Chen
Ultra-intense short pulse lasers incident on solid targets (e.g., thin Au foils) produce well collimated, broad-spectrum proton beams. These proton beams can be used to characterize magnetic fields, electric fields, and density gradients in high energy-density systems. The LLNL-Imaging Proton Spectrometer (L-IPS) was designed and built [H. Chen et al., Rev. Sci. Instrum. 81, 10D314 (2010)] for use with such laser produced proton beams. The L-IPS has an energy range of 50 keV-40 MeV with a resolving power (E/dE) of about 275 at 1 MeV and 21 at 20 MeV, as well as a single spatial imaging axis...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27909833/verification-of-a-virtual-fields-method-to-extract-the-mechanical-properties-of-human-optic-nerve-head-tissues-in-vivo
#17
Liang Zhang, Sri Gowtham Thakku, Meghna R Beotra, Mani Baskaran, Tin Aung, James C H Goh, Nicholas G Strouthidis, Michael J A Girard
We aimed to verify a custom virtual fields method (VFM) to estimate the patient-specific biomechanical properties of human optic nerve head (ONH) tissues, given their full-field deformations induced by intraocular pressure (IOP). To verify the accuracy of VFM, we first generated 'artificial' ONH displacements from predetermined (known) ONH tissue biomechanical properties using finite element analysis. Using such deformations, if we are able to match back the known biomechanical properties, it would indicate that our VFM technique is accurate...
December 1, 2016: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/27908486/an-inverse-method-to-determine-arterial-stiffness-with-guided-axial-waves
#18
Guo-Yang Li, Qiong He, Lin Jia, Ping He, Jianwen Luo, Yanping Cao
Many cardiovascular diseases can alter arterial stiffness; therefore, measurement of arterial wall stiffness can provide valuable information for both diagnosis of such diseases in the clinic and evaluation of the effectiveness of relevant drugs. However, quantitative assessment of the in vivo elastic properties of arterial walls in a non-invasive manner remains a great challenge. In this study, we found that the elastic modulus of the arterial wall can be extracted from the dispersion curve of the guided axial wave (GAW) measured using the ultrasound elastography method...
November 28, 2016: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/27908055/acoustic-modeling-of-a-three-dimensional-rectangular-opened-enclosure-coupled-with-a-semi-infinite-exterior-field-at-the-baffled-opening
#19
Guoyong Jin, Shuangxia Shi, Zhigang Liu
A modeling method is proposed for the acoustic analysis of a three-dimensional (3D) rectangular opened enclosure coupled with a semi-infinite exterior field by a rectangular opening of arbitrary size, and with general wall impedance. In contrast to existing modeling methods that solve the differential equations, the energy principle in combination with a 3D modified Fourier cosine series is employed in the present method for the modeling of this system. Under this theoretical framework, the effect of an opening in the wall of a rectangular enclosure is taken into account via the work done by the sound pressure acting on the opening between the finite enclosure and exterior domain...
November 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27908040/modeling-and-design-of-two-dimensional-membrane-type-active-acoustic-metamaterials-with-tunable-anisotropic-density
#20
Ahmed Allam, Adel Elsabbagh, Wael Akl
A two-dimensional active acoustic metamaterial with controllable anisotropic density is introduced. The material consists of composite lead-lead zirconate titanate plates clamped to an aluminum structure with air as the background fluid. The effective anisotropic density of the material is controlled, independently for two orthogonal directions, by means of an external static electric voltage signal. The material is used in the construction of a reconfigurable waveguide capable of controlling the direction of the acoustic waves propagating through it...
November 2016: Journal of the Acoustical Society of America
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