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finite-element method modeling in 4 and 16 sensors electric-charge tomography systems for particles moving in pipeline

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FLOW MEASUREMENT AND INSTRUMENTATION 2014年 38卷 9-20页

作者： Thuku, Iliya Tizhe Rahmat, Mohd Fua'ad Univ Teknol Malaysia Fac Elect Engn Dept Control & Mechatron Engn Skudai Johor Bahru 81310 Malaysia

Tomography determines the distribution of materials by the use of sensors that captures information on the materials in regions of interests such as cross-section of pipelines or process vessels. In this paper, system equation for the 4 and 16 sensor systems is derived based on the Cartesian coordinate system, the elements' technique of the finite-element method, Gauss's and Coulomb's theories. The derived equation relates the electric charge distribution in a pipeline cross-section and the installed sensors at the periphery of the pipeline. From the developed system equation, sensitivity matrices for the two systems resulting from the assumed spatial electric-charge distribution on the pipeline cross-section were made. The developed sensitivity matrices of the two systems were in turn used for the reconstruction of the tomography images or concentration profiles of the moving particles across the pipeline cross-section. This research is carried out in order to explore the possibilities of reducing the 8 to 32 electrodynamic sensor systems that are normally used in electric charge tomography systems. A comparison between the reconstructed images of the 4 and 16 sensor systems was made, and the results show that the 16 sensor system produced more accurate images than the 4 sensor system. Nevertheless, the 4 sensors' system could be used in quantitative applications. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： finite-element method Sensitivity matrix Pro-rata distribution Cartesian coordinates Electric charge tomography Landweber's iteration

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Development, calibration and validation of impact-specific cervical spine models: A novel approach using hybrid multibody and finite-element methods

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COMPUTER methodS AND PROGRAMS IN BIOMEDICINE 2024年 257卷 108430-108430页

作者： Holzinger, Thomas Cazzola, Dario Sagl, Benedikt Med Univ Vienna Univ Clin Dent Competence Ctr Artificial Intelligence Snsengasse 2A A-1090 Vienna Austria Med Univ Vienna Univ Clin Dent Clin Res Ctr A-1090 Vienna Austria Univ Bath Dept Hlth Bath BA2 7AY England Univ Bath Ctr Anal Mot Entertainment Res & Applicat Bath BA2 7AY England Univ Bath Ctr Hlth & Injury & Illness Prevent Sport Bath BA2 7AY England

Background and Objective: Spinal cord injuries can have a severe impact on athletes' or patients' lives. High axial impact scenarios like tackling and scrummaging can cause hyperflexion and buckling of the cervical spine, which is often connected with bilateral facet dislocation. Typically, finite-element (FE) or musculoskeletal models are applied to investigate these scenarios, however, they have the drawbacks of high computational cost and lack of soft tissue information, respectively. Moreover, material properties of the involved tissues are commonly tested in quasi-static conditions, which do not accurately capture the mechanical behavior during impact scenarios. Thus, the aim of this study was to develop, calibrate and validate an approach for the creation of impact-specific hybrid, rigid body- finite-element spine models for high-dynamic axial impact scenarios. methods: Five porcine cervical spine models were used to replicate in-vitro experiments to calibrate stiffness and damping parameters of the intervertebral joints by matching the kinematics of the in-vitro with the in-silico experiments. Afterwards, a five-fold cross-validation was conducted. Additionally, the von Mises stress of the lumped FE-discs was investigated during impact. Results: The results of the calibration and validation of our hybrid approach agree well with the in-vitro experiments. The stress maps of the lumped FE-discs showed that the highest stress of the most superior lumped disc was located anterior while the remaining lumped discs had their maximum in the posterior portion. Conclusion: Our hybrid method demonstrated the importance of impact-specific modeling. Overall, our hybrid modeling approach enhances the possibilities of identifying spine injury mechanisms by facilitating dynamic, impact-specific computational models.

关键词： Musculoskeletal modeling finite-element method Hybrid modeling Impact-specific Cervical spine Injury biomechanics

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Hybridization of finite-element method and Support Vector Machine to Determine Scour Bridge Safety Level

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JOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIES 2015年第3期29卷 04014079-04014079页

作者： Feng, Chung-Wei Huang, Hsun-Yi Natl Cheng Kung Univ Dept Civil Engn Tainan 70101 Taiwan

Bridge failure as a result of scour may cause a serious disaster because it tends to occur suddenly and without prior warning. Although the scour depth around a bridge pier is an important index to evaluate the condition of the bridge, it is difficult to measure directly because the bridge foundation is under water. In addition, the safety level of the bridge could be arbitrary, depending on the environment and bridge. In this study, an approach that combines a finite-element simulation and support vector machine (SVM) is used to determine the scour safety level of a bridge through the variation in the natural frequency of the bridge structure. A series of finite-element simulations is implemented with different environmental scenarios to obtain bridge natural frequencies. Moreover, SVM is used to classify the data and provide a safety level for a bridge scour prewarning. At the same time, a five-fold cross-validation and two-step grid search technique are introduced to optimize the SVM parameters. Finally, the examination results are presented that show the high performance of the SVM classification.

关键词： Bridge scour Natural frequency finite-element method Support vector machine

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Implicit inverse force identification method for vibroacoustic finite element model

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JOURNAL OF SOUND AND VIBRATION 2023年第1期556卷

作者： Oh, Seungin Ahn, Chang-uk Ahn, Kwanghyun Kim, Jin-Gyun Kyung Hee Univ Dept Mech Engn Integrated Engn 1732 Deogyeong Daero Yongin 17104 Gyeonggi Do South Korea Korea Atom Energy Res Inst 111 Daedeok Daero 989beon Gil Daejeon South Korea

The two-field vibroacoustic finite-element (FE) model requires a relatively large number of degrees of freedom compared to the monophysics model, and the conventional force identifi-cation method for structural vibration can be adjusted for multiphysics problems. In this study, an effective inverse force identification method for an FE vibroacoustic interaction model of an interior fluid-structure system was proposed. The method consists of: (1) implicit inverse force identification based on the Newmark-fl time integration algorithm for stability and efficiency, (2) second-order ordinary differential formulation by avoiding the state-space form causing large degrees of freedom, (3) projection-based multiphysics reduced-order modeling for further reduction of degrees of freedom, and (4) Tikhonov regularization to alleviate the measurement noise. The proposed method can accurately identify the unmeasured applied forces on the in situ application and concurrently reconstruct the response fields. The accuracy, stability, and computational efficiency of the proposed method were evaluated using numerical models and an experimental testbed. A comparative study with the augmented Kalman filter method was performed to evaluate its relative performance.

关键词： Inverse force identification Inverse dynamics finite-element method Reduced-order modeling Virtual sensing Vibroacoustics

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Simulating Stresses Associated with the Bending of Wood Using a finite element method

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BIORESOURCES 2015年第2期10卷 2009-2019页

作者： Gaff, Milan Gasparik, Miroslav Boruvka, Vlastimil Babiak, Marian Czech Univ Life Sci Prague Dept Wood Proc Prague 16521 6 Czech Republic

This article examines the stress-strain curves of various thicknesses of soft and hard wood when bent during three-point loading. The finite element method was used to simulate the course of stresses that occurred during the bending of these materials. Reference curves obtained by bending real specimens offered a basis for simulation. The results showed that with increasing material thickness, deflection values decreased and the proportionality limit increased;eventually, the bendability coefficient value decreased and the loading force necessary for bending increased. Moreover, it was apparent when bending hard materials that higher loading forces were necessary for different materials of the same thickness. It is possible to determine the stress-strain curves without having to perform experiments (except for indispensable reference ones) under real conditions.

关键词： Layered wood material finite-element method Stress simulation Bending Stress-strain curve Bendability coefficient

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Optimal Remediation Design of Unconfined Contaminated Aquifers Based on the finite element method and a Modified Firefly Algorithm

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WATER RESOURCES MANAGEMENT 2015年第8期29卷 2895-2912页

作者： Kazemzadeh-Parsi, Mohammad Javad Daneshmand, Farhang Ahmadfard, Mohammad Amin Adamowski, Jan Islamic Azad Univ Shiraz Branch Dept Mech Engn Shiraz Iran McGill Univ Dept Mech Engn Montreal PQ H3A 0C3 Canada McGill Univ Dept Bioresource Engn Montreal PQ H9X 3V9 Canada Shiraz Univ Sch Mech Engn Shiraz Iran

Remediation of contaminated sites requires an optimal decision making system to develop remediation techniques in a cost-effective and efficient manner. A coupled simulation-optimization solution approach, based on the finite element method (FEM) and a modified firefly algorithm (MFA), is developed in this study for optimal contaminated groundwater remediation design. A new modified firefly optimization algorithm is proposed by modifying the traditional firefly algorithm in three ways: (i) adding memory, (ii) preventing premature convergence to local optima and thus accelerating the optimization process, and (iii) proposing a new updating formula. Modifications performed in the present study improved the applicability and efficiency of the traditional metaheuristic firefly optimization algorithm, and led the MFA to outperform both its predecessor and conventional optimization methods (e.g., genetic algorithm). A hypothetical, unconfined contaminated field is considered and remediated by considering pump and treat and flushing methods. Pumping rates are considered as design variables while the number of pumps and pump locations, as well as the pumping period, are initially assumed. The coupled simulation-optimization model (FEM-MFA) proposed in this study constitutes an effective way to determine an optimal remediation design for a contaminated aquifer. The results of the present investigation will contribute to improve groundwater management in contaminated aquifers.

关键词： finite-element method Modified firefly algorithm Pump and treat strategy Groundwater remediation

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A study of the efficiency of directional field-building methods for interpreting interferograms by the finite-element method

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RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING 2014年第6期50卷 369-375页

作者： Rozhkovskii, V. F. Sagan, N. V. Dnepropetrovsk Natl Univ UA-49000 Dnepropetrovsk Ukraine

Algorithms for interpreting (decoding) of interferograms plotted by the finite-element method are considered. Three directional field-building methods are used in them: the (i) complex averaging method, (ii) the projection-dispersion method, and (iii) the spectral method. The efficiency of the algorithms is checked on simulated and real interferograms.

关键词： interferogram directional field finite-element method

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SOLUTION OF THE PROBLEM OF THERMOPLASTICITY FOR A LAYERED SPHERE BY THE finite-element method

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MATERIALS SCIENCE 2014年第1期50卷 31-38页

作者： Mykhailyshyn, V. S. Ukrainian Natl Acad Sci Pidstryhach Inst Appl Problems Mech & Math Lvov Ukraine

We propose a new approach to the investigation of the thermomechanical states in layered plastically deformed heat-sensitive bodies of any geometric shape with arbitrary orientation of the interfaces between the layers. The proposed approach is based on the formulation of the nonstationary problem of heat conduction, problem of the theory of plastic nonisothermal flow, computational schemes of the finite-element method, and the corresponding software. We also study the thermomechanical behavior of a two-layer sphere under the conditions of rapid cooling from its initial uniform temperature.

关键词： layered bodies temperature stresses strains plastic deformation heat sensitivity hardening finite-element method

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Contact Temperature Prediction in Three-Phase Gas-Insulated Bus Bars With the finite-element method

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IEEE TRANSACTIONS ON MAGNETICS 2014年第2期50卷 277-280页

作者： Wu, Xiao Wen Shu, Nai Qiu Li, Hong Tao Li, Ling Wuhan Univ Sch Elect Engn Wuhan 430072 Peoples R China

Degradation of the electric contact in gas-insulated bus bars (GIBs) is closely related to the overheating phenomenon occurring at the contacts. This paper employs the finite-element method to solve the 3-D coupled eddy current, fluid, and thermal problems in a three-phase GIB. In the model, the contact resistance is measured and described as a resistor between the conductor and the contact. Computational fluid dynamics is used to predict the temperature rise of the components in the GIB. The temperature-dependent thermal properties of SF6 gas and air are considered in the thermal analysis. The developed methodology is implemented on a 126 kV three-phase GIB prototype and validated with the experimental temperature rise results.

关键词： Computational fluid dynamics condition monitoring contact resistance finite-element method

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Comparison of proportional-derivative and active-force controls on vibration of a flexible single-link manipulator using finite-element method

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ARTIFICIAL LIFE AND ROBOTICS 2014年第4期19卷 375-381页

作者： Muhammad, Abdul Kadir Okamoto, Shingo Lee, Jae Hoon Ehime Univ Grad Sch Sci & Engn Matsuyama Ehime Japan State Polytech Ujung Mech Engn Dept Padang Makassar Indonesia

The purposes of this research are to derive the equations of motion of a flexible single-link system by a finite-element method, to develop the computational codes in order to perform dynamics simulations with vibration control and to propose an effective control scheme of a flexible single-link manipulator using two control strategies, namely proportional-derivative (PD) and active-force (AF) controls. The flexible manipulator used in this paper consists of an aluminum beam as a flexible link, a clamp-part, a servo motor to rotate the link, and a piezoelectric actuator to control vibration. Computational codes on time history responses, FFT (Fast Fourier Transform) processing, and eigenvalues-eigenvectors analysis were developed to calculate the dynamic behavior of the link. Furthermore, the PD and AF control strategies were designed and compared their performances through the calculations. The calculated results show the superiority of the proposed AF control comparing the PD one to suppress the vibration of the flexible single-link manipulator.

关键词： Active-force control finite-element method Flexible manipulator Vibration control

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