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Finite elements analysis

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https://www.readbyqxmd.com/read/28917984/multi-objective-optimization-of-asymmetric-acoustic-transmission-with-periodical-structure
#1
Jiu-Jiu Chen, Jian-Cheng Zhang, Shao-Yong Huo
Asymmetric acoustic wave propagation is important for control and manipulation of the acoustic wave signals in various devices. However, previous approach to find optimal asymmetric acoustic transmission (AAT) is through repeatedly adjusting the geometrical parameters, thus causing time-consuming. Here we propose a study on the multi-objective optimization of the AAT, aiming to achieve the widest working frequency range (fr) and the highest transmittance peak (η) with regard to the design variables. For this purpose, the Radial Basis Function (RBF) neural work and finite element (FE) method are applied to obtain the valuable data in the procedure...
September 8, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28917130/bending-behaviors-of-fully-covered-biodegradable-polydioxanone-biliary-stent-for-human-body-by-finite-element-method
#2
Yanhui Liu, Guoqing Zhu, Huazhe Yang, Conger Wang, Peihua Zhang, Guangting Han
This paper presents a study of the bending flexibility of fully covered biodegradable polydioxanone biliary stents (FCBPBs) developed for human body. To investigate the relationship between the bending load and structure parameter (monofilament diameter and braid-pin number), biodegradable polydioxanone biliary stents derived from braiding method were covered with membrane prepared via electrospinning method, and nine FCBPBSs were then obtained for bending test to evaluate the bending flexibility. In addition, by the finite element method, nine numerical models based on actual biliary stent were established and the bending load was calculated through the finite element method...
August 24, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28916110/a-fast-and-accurate-langmuir-type-polymer-microtensiometer
#3
REVIEW
Pieter Gijsenbergh, Robert Puers
A semi-flexible polymer microtensiometer for local surface pressure measurements of Langmuir monolayers is presented. The current device geometry and read-out method via image analysis result in a theoretical accuracy of ±0.02mN⋅m(-1) for a dynamic range between 0 and 75mN⋅m(-1). The tensiometer sensitivity and dynamic range are easily tunable as they are solely based on the tensiometer spring dimensions. Finite element simulations are used to determine the response time of 20ms for a subphase viscosity of 1mPa⋅s...
September 5, 2017: Advances in Colloid and Interface Science
https://www.readbyqxmd.com/read/28915352/all-atom-simulations-reveal-protein-charge-decoration-in-the-folded-and-unfolded-ensemble-is-key-in-thermophilic-adaptation
#4
Lucas Sawle, Jonathan Huihui, Kingshuk Ghosh
Thermophilic proteins denature at much higher temperature compared to their mesophilic homologues, in spite of high structural and sequential similarity. Computational approaches to understand this puzzle faces three major challenges: i) unfolded ensembles are usually neglected, ii) simulation studies of the folded states are often too short and iii) majority of investigations focus on a few protein pairs, obscuring the prevalence of different strategies across multiple protein systems. We address these concerns by carrying out all-atom simulations to characterize physicochemical properties of both the folded and disordered ensemble in multiple (12) thermophilic-mesophilic homologous protein pairs...
September 15, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28911284/effect-of-nicotine-replacement-therapy-on-mortality-delirium-and-duration-of-therapy-in-critically-ill-smokers-a-systematic-review-and-meta-analysis
#5
K T Ng, M Gillies, D M Griffith
Nicotine replacement therapy is widely used in critically ill smokers and its effect on delirium, mortality and duration of intensive care unit (ICU) admission is unknown. The aims of this review were to determine whether the management of nicotine withdrawal with nicotine replacement therapy reduces delirium, mortality or length of stay in critically ill smokers in ICU. The primary outcome was incidence of author-defined ICU delirium. Secondary outcomes were ICU or hospital mortality, ICU-free days at day 28, and ICU or hospital length of stay...
September 2017: Anaesthesia and Intensive Care
https://www.readbyqxmd.com/read/28910701/biomechanical-analysis-of-lumbar-decompression-surgery-in-relation-to-degenerative-changes-in-the-lumbar-spine-validated-finite-element-analysis
#6
Quan You Li, Ho-Joong Kim, Juhyun Son, Kyoung-Tak Kang, Bong-Soon Chang, Choon-Ki Lee, Hyun Sik Seok, Jin S Yeom
BACKGROUND: There are no studies about the biomechanical analysis of lumbar decompression surgery in relation to degenerative changes of the lumbar spine. Therefore, the purpose of this study was to compare, by using finite element (FE) analysis, the biomechanical changes of the lumbar spine in terms of annulus stress and nucleus pressure after two different kinds of lumbar decompression surgery in relation to disc degenerative changes. METHODS: The validated intact and degenerated FE models (L2-5) were used in this study...
September 6, 2017: Computers in Biology and Medicine
https://www.readbyqxmd.com/read/28910537/analysis-of-mechanics-of-side-impact-test-defined-in-un-ece-regulation-129
#7
Pawel Baranowski, Krzysztof Damaziak, Lukasz Mazurkiewicz, Jerzy Malachowski, Artur Muszynski, Dario Vangi
OBJECTIVE: This article discusses differences between a side impact procedure described in UN/ECE Regulation 129 and scenarios observed in real world cases. METHODS: Numerical simulations of side impact tests utilizing different boundary conditions are used to compare the severity of the Regulation 129 test and the other tests with different kinematics of child resistant systems (CRS). In the simulations, the authors use a validated finite element (FE) model of real world CRS together with a fully deformable numerical model of the Q3 anthropomorphic test device (ATD) by Humanetics Innovative Solution, Inc...
September 14, 2017: Traffic Injury Prevention
https://www.readbyqxmd.com/read/28906447/material-viscoelasticity-induced-drift-of-micro-accelerometers
#8
Wu Zhou, Peng Peng, Huijun Yu, Bei Peng, Xiaoping He
Polymer-based materials are commonly used as an adhesion layer for bonding die chip and substrate in micro-system packaging. Their properties exhibit significant impact on the stability and reliability of micro-devices. The viscoelasticity, one of most important attributes of adhesive materials, is investigated for the first time in this paper to evaluate the long-term drift of micro-accelerometers. The accelerometer was modeled by a finite element (FE) method to emulate the structure deformation and stress development induced by change of adhesive property...
September 14, 2017: Materials
https://www.readbyqxmd.com/read/28905122/static-and-free-vibration-analyses-of-dental-prosthesis-and-atherosclerotic-human-artery-by-refined-finite-element-models
#9
E Carrera, D Guarnera, A Pagani
Static and modal responses of representative biomechanical structures are investigated in this paper by employing higher-order theories of structures and finite element approximations. Refined models are implemented in the domain of the Carrera unified formulation (CUF), according to which low- to high-order kinematics can be postulated as arbitrary and, eventually, hierarchical expansions of the generalized displacement unknowns. By using CUF along with the principle of virtual work, the governing equations are expressed in terms of fundamental nuclei of finite element arrays...
September 13, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28901188/engineered-microvasculature-in-pdms-networks-using-endothelial-cells-derived-from-human-induced-pluripotent-stem-cells
#10
Amogh Sivarapatna, Mahboobe Ghaedi, Yang Xiao, Edward Han, Binod Aryal, Jing Zhou, Carlos Fernandez-Hernando, Yibing Qyang, Karen K Hirschi, Laura E Niklason
In this study, we used a polydimethylsiloxane (PDMS)-based platform for the generation of intact, perfusion-competent microvascular networks in vitro. COMSOL Multiphysics, a finite-element analysis and simulation software package, was used to obtain simulated velocity, pressure, and shear stress profiles. Transgene-free human induced pluripotent stem cells (hiPSCs) were differentiated into partially arterialized endothelial cells (hiPSC-ECs) in 5 d under completely chemically defined conditions, using the small molecule glycogen synthase kinase 3β inhibitor CHIR99021 and were thoroughly characterized for functionality and arterial-like marker expression...
August 2017: Cell Transplantation
https://www.readbyqxmd.com/read/28900873/numerical-analysis-of-intracochlear-mechanical-auditory-stimulation-using-piezoelectric-bending-actuators
#11
Daniel Schurzig, Sebastian Schwarzendahl, Jörg Wallaschek, Wouter J van Drunen, Thomas S Rau, Thomas Lenarz, Omid Majdani
Cochlear implantation can restore a certain degree of auditory impression of patients suffering from profound hearing loss or deafness. Furthermore, studies have shown that in case of residual hearing, patients benefit from the use of a hearing aid in addition to the cochlear implant. The presented studies aim at the improvement of this electromechanical stimulation (EMS) approach by substituting the external hearing aid by an internal stimulus provided by miniaturized piezoelectric actuators. Finite element analyses are performed in order to derive fundamental guidelines for the actuator layout aiming at maximal mechanical stimuli...
September 13, 2017: Medical & Biological Engineering & Computing
https://www.readbyqxmd.com/read/28900622/biomechanical-measurement-error-can-be-caused-by-fujifilm-thickness-a-theoretical-experimental-and-computational-analysis
#12
Ahmed Sarwar, Simli Srivastava, Chris Chu, Alan Machin, Emil H Schemitsch, Habiba Bougherara, Zahra S Bagheri, Radovan Zdero
This is the first study to quantify the measurement error due to the physical thickness of Fujifilm for several material combinations relevant to orthopaedics. Theoretical and experimental analyses were conducted for cylinder-on-flat indentation over a series of forces (750 and 3000 N), cylinder diameters (0 to 80 mm), and material combinations (metal-on-metal, MOM; metal-on-polymer, MOP; metal-on-bone, MOB). For the scenario without Fujifilm, classic Hertzian theory predicted the true line-type contact width as WO = {(8FDcyl)/(πLcyl)[(1 - νcyl(2))/Ecyl + (1 - νflat(2))/Eflat]}(1/2), where F is compressive force, Dcyl is cylinder diameter, Lcyl is cylinder length, νcyl and νflat are cylinder and flat Poisson's ratios, and Ecyl and Eflat are cylinder and flat elastic moduli...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28893491/micro-finite-element-method-to-assess-elastic-properties-of-trabecular-bone-at-micro-and-macroscopic-level
#13
R Rieger, J C Auregan, T Hoc
OBJECTIVE OF THE STUDY: The objective of the present study is to assess the mechanical behavior of trabecular bone based on microCT imaging and micro-finite-element analysis. In this way two methods are detailed: (i) direct determination of macroscopic elastic property of trabecular bone; (ii) inverse approach to assess mechanical properties of trabecular bone tissue. PATIENTS: Thirty-five females and seven males (forty-two subjects) mean aged (±SD) 80±11.7 years from hospitals of Assistance publique-Hôpitaux de Paris (AP-HP) diagnosed with osteoporosis following a femoral neck fracture due to a fall from standing were included in this study...
September 8, 2017: Morphologie: Bulletin de L'Association des Anatomistes
https://www.readbyqxmd.com/read/28891108/tailoring-semiconductor-lateral-multijunctions-for-giant-photoconductivity-enhancement
#14
Yutsung Tsai, Zhaodong Chu, Yimo Han, Chih-Piao Chuu, Di Wu, Alex Johnson, Fei Cheng, Mei-Yin Chou, David A Muller, Xiaoqin Li, Keji Lai, Chih-Kang Shih
Semiconductor heterostructures have played a critical role as the enabler for new science and technology. The emergence of transition-metal dichalcogenides (TMDs) as atomically thin semiconductors has opened new frontiers in semiconductor heterostructures either by stacking different TMDs to form vertical heterojunctions or by stitching them laterally to form lateral heterojunctions via direct growth. In conventional semiconductor heterostructures, the design of multijunctions is critical to achieve carrier confinement...
September 11, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28890599/evaluation-of-structural-robustness-against-column-loss-methodology-and-application-to-rc-frame-buildings
#15
Yihai Bao, Joseph A Main, Sam-Young Noh
A computational methodology is presented for evaluating structural robustness against column loss. The methodology is illustrated through application to reinforced concrete (RC) frame buildings, using a reduced-order modeling approach for three-dimensional RC framing systems that includes the floor slabs. Comparisons with high-fidelity finite-element model results are presented to verify the approach. Pushdown analyses of prototype buildings under column loss scenarios are performed using the reduced-order modeling approach, and an energy-based procedure is employed to account for the dynamic effects associated with sudden column loss...
August 2017: Journal of Structural Engineering (New York, N.Y.)
https://www.readbyqxmd.com/read/28890302/ulna-humerus-contact-mechanics-finite-element-analysis-and-experimental-measurements-using-a-tactile-pressure-sensor
#16
Mohsen Sharifi Renani, Munsur Rahman, Akin Cil, Antonis P Stylianou
Elbow articular cartilage withstands high compressive and shear forces while protecting the bone from excessive loading. Better understanding of elbow cartilage contact mechanics can provide insight into cartilage degeneration. In this study a tactile pressure sensor was used to measure the contact pressure distribution within the ulno-humeral joint of two cadaver specimens at 20° flexion angle across three different axial loads of 80 N, 110 N, and 140 N. Corresponding 3D finite element (FE) models were constructed from magnetic resonance imaging (MRI) and contact analysis was performed for each specimen with boundary and loading conditions identical to the experiment...
September 7, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28888931/biomechanical-testing-of-zirconium-dioxide-osteosynthesis-system-for-le-fort-i-advancement-osteotomy-fixation
#17
Lukas Hingsammer, Markus Grillenberger, Martin Schagerl, Malek Michael, Hunger Stefan
The following work is the first evaluating the applicability of 3D printed zirconium dioxide ceramic miniplates and screws to stabilize maxillary segments following a Le-Fort I advancement surgery. Conventionally used titanium and individual fabricated zirconium dioxide miniplates were biomechanically tested and compared under an occlusal load of 120N and 500N using 3D finite element analysis. The overall model consisted of 295,477 elements. Under an occlusal load of 500N a safety factor before plastic deformation respectively crack of 2...
September 5, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28888930/a-combined-experimental-modeling-and-computational-approach-to-interpret-the-viscoelastic-response-of-the-white-matter-brain-tissue-during-indentation
#18
Aref Samadi-Dooki, George Z Voyiadjis, Rhett W Stout
Viscoelastic properties of the white matter brain tissue are systematically studied in this paper utilizing indentation experiments, mathematical modeling, and finite element simulation. It is first demonstrated that the internal stiffness of the instrument needs to be thoroughly obtained and incorporated in the analysis as its contribution to the recorded mechanical response is significant for experiments on very compliant materials. The flat-punch monotonic indentation is then performed indirectly on sagittal plane slices with pushing a large rigid coverslip into the sample surface...
September 1, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28888789/modal-analysis-for-the-assessment-of-cementless-hip-stem-primary-stability-in-preoperative-tha-planning
#19
Andres Rondon, Elhadi Sariali, Quentin Vallet, Quentin Grimal
This numerical vibration finite element (FE) study introduces resonance three-dimensional planning (RP3D) to assess preoperatively the primary stability of a cementless stem for total hip arthroplasty. Based on a patient's CT-scan and a numerical model of a stem, RP3D aims at providing mechanical criteria indicative of the achievable primary stability. We investigate variations of the modal response of the stem to changes of area and apparent stiffness of the bone-implant interface. The model is computationally cheap as it does not include a mesh of the bone...
September 6, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28888758/large-area-alpha-sources-with-a-lip-integral-counting-and-spectral-distortions
#20
Lynne King, Ryan Fitzgerald, Ronald E Tosh
The detection efficiency for large area alpha sources with adjustable heights of a raised lip around the edge were measured by 2π gas-filled proportional counter. The variations in low-energy spectral shape were modeled using a Geant4 radiation and charge transport Monte Carlo simulation, to enable extrapolation of the spectrum to zero energy. COMSOL Multiphysics finite-element analysis was used to explore changes in the spectrum gain in the presence of a lip. It qualitatively reproduced an increase in peak height due to an increasing height of the source lip...
August 31, 2017: Applied Radiation and Isotopes
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