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Finite elements analysis

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https://www.readbyqxmd.com/read/27913178/estimating-the-material-properties-of-heel-pad-sub-layers-using-inverse-finite-element-analysis
#1
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/27911025/effect-of-balloon-expandable-transcatheter-aortic-valve-replacement-positioning-a-patient-specific-numerical-model
#2
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
#3
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/27910556/thermal-analysis-of-the-in-vessel-components-of-the-iter-plasma-position-reflectometry
#4
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
#5
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
#6
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
#7
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/27910335/detailed-characterization-of-the-llnl-imaging-proton-spectrometer
#8
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
#9
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
#10
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
#11
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/27903785/microstructure-and-mechanics-of-healthy-and-aneurysmatic-abdominal-aortas-experimental-analysis-and-modelling
#12
Justyna A Niestrawska, Christian Viertler, Peter Regitnig, Tina U Cohnert, Gerhard Sommer, Gerhard A Holzapfel
Soft biological tissues such as aortic walls can be viewed as fibrous composites assembled by a ground matrix and embedded families of collagen fibres. Changes in the structural components of aortic walls such as the ground matrix and the embedded families of collagen fibres have been shown to play a significant role in the pathogenesis of aortic degeneration. Hence, there is a need to develop a deeper understanding of the microstructure and the related mechanics of aortic walls. In this study, tissue samples from 17 human abdominal aortas (AA) and from 11 abdominal aortic aneurysms (AAA) are systematically analysed and compared with respect to their structural and mechanical differences...
November 2016: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/27903534/high-structural-stress-and-presence-of-intraluminal-thrombus-predict-abdominal-aortic-aneurysm-18f-fdg-uptake-insights-from-biomechanics
#13
Yuan Huang, Zhongzhao Teng, Maysoon Elkhawad, Jason M Tarkin, Nikhil Joshi, Jonathan R Boyle, John R Buscombe, Timothy D Fryer, Yongxue Zhang, Ah Yeon Park, Ian B Wilkinson, David E Newby, Jonathan H Gillard, James H F Rudd
BACKGROUND: Abdominal aortic aneurysm (AAA) wall inflammation and mechanical structural stress may influence AAA expansion and lead to rupture. We hypothesized a positive correlation between structural stress and fluorine-18-labeled 2-deoxy-2-fluoro-d-glucose ((18)F-FDG) positron emission tomography-defined inflammation. We also explored the influence of computed tomography-derived aneurysm morphology and composition, including intraluminal thrombus, on both variables. METHODS AND RESULTS: Twenty-one patients (19 males) with AAAs below surgical threshold (AAA size was 4...
November 2016: Circulation. Cardiovascular Imaging
https://www.readbyqxmd.com/read/27898599/influence-of-sacral-slope-on-the-loading-of-pedicle-screws-in-postoperative-l5-s1-isthmic-spondylolisthesis-patient-a-finite-element-analysis
#14
Liang Chen, Yu Feng, Chun-Qing Che, Yong Gu, Ling-Jun Wang, Hui-Lin Yang
STUDY DESIGN: A finite element analysis. OBJECTIVE: To evaluate the influence of sacral slope (SS) on the loading of pedicle screws in postoperative isthmic spondylolisthesis (IS). SUMMARY OF BACKGROUND DATA: The spinopelvic anatomy was important for the biomechanics in spondylolisthesis. To our knowledge, no study concentrated on the postoperative biomechanics of the IS with the different SS. METHODS: Based on the computed tomography images, a finite model of L5/S1 IS was constructed...
December 1, 2016: Spine
https://www.readbyqxmd.com/read/27898383/influence-of-anatomical-detail-and-tissue-conductivity-variations-in-simulations-of-multi-contact-nerve-cuff-recordings
#15
Purbasha Garai, Ryan G L Koh, Martin Schuettler, Thomas Stieglitz, Jose Zariffa
Accurate simulations of peripheral nerve recordings are needed to develop improved neuroprostheses. Previous models of peripheral nerves contained simplifications whose effects have not been investigated. We created a novel detailed finite element (FE) model of a peripheral nerve, and used it to carry out a sensitivity analysis of several model parameters. To construct the model, in vivo recordings were obtained in a rat sciatic nerve using an 8-channel nerve cuff electrode, after which the nerve was imaged using magnetic resonance imaging (MRI)...
November 24, 2016: IEEE Transactions on Neural Systems and Rehabilitation Engineering
https://www.readbyqxmd.com/read/27898303/effect-of-acoustic-softening-on-the-thermal-mechanical-process-of-ultrasonic-welding
#16
Kunkun Chen, Yansong Zhang, Hongze Wang
Application of ultrasonic energy can reduce the static stress necessary for plastic deformation of metallic materials to reduce forming load and energy, namely acoustic softening effect (ASE). Ultrasonic welding (USW) is a rapid joining process utilizing ultrasonic energy to form a solid state joint between two or more pieces of metals. Quantitative characterization of ASE and its influence on specimen deformation and heat generation is essential to clarify the thermal-mechanical process of ultrasonic welding...
November 10, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27898302/a-novel-sandwich-type-traveling-wave-piezoelectric-tracked-mobile-system
#17
Liang Wang, Chengyou Shu, Quan Zhang, Jiamei Jin
In this paper, a novel sandwich-type traveling wave piezoelectric tracked mobile system was proposed, designed, fabricated and experimentally investigated. The proposed system exhibits the advantages of simple structure, high mechanical integration, lack of electromagnetic interference, and lack of lubrication requirement, and hence shows potential application to robotic rovers for planetary exploration. The tracked mobile system is comprised of a sandwich actuating mechanism and a metal track. The actuating mechanism includes a sandwich piezoelectric transducer and two annular parts symmetrically placed at either end of the transducer, while the metal track is tensioned along the outer surfaces of the annular parts...
November 15, 2016: Ultrasonics
https://www.readbyqxmd.com/read/27896687/evaluation-of-the-influences-of-various-force-magnitudes-and-configurations-on-scoliotic-curve-correction-using-finite-element-analysis
#18
Mohammad Taghi Karimi, Mohammad Hossein Ebrahimi, Ali Mohammadi, Anthony McGarry
Scoliosis is a lateral curvature in the normally straight vertical line of the spine, and the curvature can be moderate to severe. Different treatment can be used based on severity and age of subjects, but most common treatment for this disease is using orthosis. To design orthosis types of force arrangement can be varied, from transverse loads to vertical loads or combination of them. But it is not well introduced how orthoses control scoliotic curve and how to achieve the maximum correction based on force configurations and magnitude...
November 28, 2016: Australasian Physical & Engineering Sciences in Medicine
https://www.readbyqxmd.com/read/27893561/finite-element-evaluation-of-different-osteosynthesis-variations-that-used-after-segmental-mandibular-resection
#19
Koray Onur Şanal, Bora Özden, Burcu Baş
PURPOSE: The purpose of this study was to evaluate the effect of different reconstruction plates and screw combinations on stress distribution of segmental resected mandibles using finite element analysis. METHODS: Lateral (L) and lateral-central (LC) defects were simulated by a computer aided design modeling. The straight (s) and angular (a) titanium locking reconstruction plates of 2.5 mm (12 holes for L defects and 16 holes for LC defects) were modeled. Each screw was 2...
November 23, 2016: Journal of Craniofacial Surgery
https://www.readbyqxmd.com/read/27893440/a-3d-reconstruction-algorithm-for-magneto-acoustic-tomography-with-magnetic-induction-based-on-ultrasound-transducer-characteristics
#20
Ren Ma, Xiaoqing Zhou, Shunqi Zhang, Tao Yin, Zhipeng Liu
In this study we present a three-dimensional (3D) reconstruction algorithm for magneto-acoustic tomography with magnetic induction (MAT-MI) based on the characteristics of the ultrasound transducer. The algorithm is investigated to solve the blur problem of the MAT-MI acoustic source image, which is caused by the ultrasound transducer and the scanning geometry. First, we established a transducer model matrix using measured data from the real transducer. With reference to the S-L model used in the computed tomography algorithm, a 3D phantom model of electrical conductivity is set up...
December 21, 2016: Physics in Medicine and Biology
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