The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Stéphane Holé - One of the best experts on this subject based on the ideXlab platform.
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Direct observation of electric charges at solid/liquid interfaces with the pressure-Wave-Propagation Method
Journal of Electrostatics, 2021Co-Authors: Assane Ndour, Stéphane Holé, P. Leblanc, Thierry PaillatAbstract:Abstract Development of intrinsic electric charges at solid/liquid interfaces is still not fully understood and may generate large industrial damages by electrostatic discharges due to flow electrification. The pressure-Wave-Propagation (PWP) Method is used to study solid/liquid interfaces in still and flowing conditions. Experimental results are shown with aluminum, brass, copper or pressboard in contact with demineralized water, salted water, glycerol or mineral oil. Salted water presents larger charge extent than expected. In still conditions with glycerol, copper gives more charges and pressboard has the largest charge extent. In flowing conditions, signal decrease seems attributed to physico-chemical time constant.
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Direct observation of charge effects at liquid-solid interface with the pressure-Wave-Propagation Method
2020 IEEE 3rd International Conference on Dielectrics (ICD), 2020Co-Authors: Assane Ndour, Stéphane Holé, P. Leblanc, Thierry PaillatAbstract:Charge transfer at interface between a solid and a liquid is a complex physico-chemical phenomenon. It is shown in this paper that pressure-Wave-Propagation (PWP) Method can be used to study the charges distribution at solidliquid interfaces both in still and flowing conditions.
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Erratum: Pressure Wave Propagation Method for space charge measurement in coaxial geometry
IEEE Transactions on Dielectrics and Electrical Insulation, 2018Co-Authors: Yali Sun, Yewen Zhang, Stéphane Holé, Zhien Zhu, Liming Yang, Cong Guo, Zhiyu Cao, Xinlong Zheng, Feihu ZhengAbstract:The existence and accumulation of space charge in the insulation of polyethylene cable has a significant influence on the conductivity, aging and breakdown of the cable. Therefore, it is of great importance to study the space charge distribution in high voltage polyethylene cable. This paper proposes a simplified approximate analysis of pressure Wave Propagation measurement Method in coaxial geometry. The experimental results show that, as in the case of planar sample, the peak of current in coaxial geometry obeys the simple model proposed.
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Physical model of measuring space charge distribution by Pressure Wave Propagation Method for high voltage cable
2016 International Conference on Condition Monitoring and Diagnosis (CMD), 2016Co-Authors: Yewen Zhang, Feihu Zheng, Stéphane Holé, Zhenlian AnAbstract:Based on theoretical analysis of pressure Wave Propagation Method for the space charge distribution measurement in the plate samples, this paper suggested the processing Method of space charge distribution data measured in coaxial samples such as high voltage power cable. In terms of Poisson Equation, considering variety of the sample's electric field, dielectric constant and density of space charge disturbed by pressure Waves, the influence on coaxial samples can be divided into two parts, sample deformation and particle displacement. Therefore, the voltage and current equations about the space charge distribution in the coaxial structure like high voltage cable were found. Comparing with the flat plate sample, the pressure Wave focusing effect and the radial electric field in coaxial cable structure will have the important action on the results of Pressure Wave Propagation Method (PWP).
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The pressure Wave Propagation Method for the study of interface electric field
2015 IEEE Electrical Insulation Conference (EIC), 2015Co-Authors: Basil Salame, Stéphane HoléAbstract:The spatial resolution of the measurement Methods used to estimate the microscopic distribution of charges in insulating materials is not sufficient to study the distribution at the interface of metals and semi-conductors. In this paper it is experimentally shown that applying the Pressure Wave Propagation (PWP) Method to an aluminum sample generates a signal corresponding to the charges distribution at the interface. This result is attributed to the difference between mechanical and/or electrical properties of the coupled materials that causes a non-symmetrical response of the charges on each side of the interface. Other results with different metal and silica samples show the influence of the metal work function.
Yewen Zhang - One of the best experts on this subject based on the ideXlab platform.
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Erratum: Pressure Wave Propagation Method for space charge measurement in coaxial geometry
IEEE Transactions on Dielectrics and Electrical Insulation, 2018Co-Authors: Yali Sun, Yewen Zhang, Stéphane Holé, Zhien Zhu, Liming Yang, Cong Guo, Zhiyu Cao, Xinlong Zheng, Feihu ZhengAbstract:The existence and accumulation of space charge in the insulation of polyethylene cable has a significant influence on the conductivity, aging and breakdown of the cable. Therefore, it is of great importance to study the space charge distribution in high voltage polyethylene cable. This paper proposes a simplified approximate analysis of pressure Wave Propagation measurement Method in coaxial geometry. The experimental results show that, as in the case of planar sample, the peak of current in coaxial geometry obeys the simple model proposed.
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Physical model of measuring space charge distribution by Pressure Wave Propagation Method for high voltage cable
2016 International Conference on Condition Monitoring and Diagnosis (CMD), 2016Co-Authors: Yewen Zhang, Feihu Zheng, Stéphane Holé, Zhenlian AnAbstract:Based on theoretical analysis of pressure Wave Propagation Method for the space charge distribution measurement in the plate samples, this paper suggested the processing Method of space charge distribution data measured in coaxial samples such as high voltage power cable. In terms of Poisson Equation, considering variety of the sample's electric field, dielectric constant and density of space charge disturbed by pressure Waves, the influence on coaxial samples can be divided into two parts, sample deformation and particle displacement. Therefore, the voltage and current equations about the space charge distribution in the coaxial structure like high voltage cable were found. Comparing with the flat plate sample, the pressure Wave focusing effect and the radial electric field in coaxial cable structure will have the important action on the results of Pressure Wave Propagation Method (PWP).
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Significant suppression of space charge injection into linear low density polyethylene by surface oxyfluorination
Journal of Applied Physics, 2009Co-Authors: Zhenlian An, Chen Xie, Yue Jiang, Feihu Zheng, Yewen ZhangAbstract:Surface oxyfluorination of linear low density polyethylene (LLDPE) was performed to suppress space charge injection and accumulation under direct current high voltage. Significant suppression effect that there is almost no space charge inside LLDPE was obtained, as observed by space charge measurements based on the pressure Wave Propagation Method. Oxyfluorination led to the substantial variation in chemical composition, forming the various polar groups in surface layer, as indicated by attenuated total reflection infrared analyses. The suppression mechanisms are mainly attributed to the charge trap change and the remarkable increase in permittivity of the oxyfluorinated surface layer, as investigated by open-circuit thermally stimulated discharge current measure-ments and surface energy calculations, respectively.
James A. Rossmanith - One of the best experts on this subject based on the ideXlab platform.
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A Wave Propagation Method for hyperbolic systems on the sphere
Journal of Computational Physics, 2006Co-Authors: James A. RossmanithAbstract:Presented in this work is an explicit finite volume Method for solving general hyperbolic systems on the surface of a sphere. Applications where such systems arise include passive tracer advection in the atmosphere, shallow water models of the ocean and atmosphere, and shallow water magnetohydrodynamic models of the solar tachocline. The Method is based on the curved manifold Wave Propagation algorithm of Rossmanith, Bale, and LeVeque [A Wave Propagation algorithm for hyperbolic systems on curved manifolds, J. Comput. Phys. 199 (2004) 631-662], which makes use of parallel transport to approximate geometric source terms and orthonormal Riemann solvers to carry out characteristic decompositions. This approach employs TVD Wave limiters, which allows the Method to be accurate for both smooth solutions and solutions in which large gradients or discontinuities can occur in the form of material interfaces or shock Waves. The numerical grid used in this work is the cubed sphere grid of Ronchi, Iacono, and Paolucci [The 'cubed sphere': a new Method for the solution of partial differential equations in spherical geometry, J. Comput. Phys. 124 (1996) 93-114], which covers the sphere with nearly uniform resolution using six identical grid patches with grid lines lying on great circles. Boundary conditions across grid patches are applied either through direct copying from neighboring grid cells in the case of scalar equations or 1D interpolation along great circles in the case of more complicated systems. The resulting numerical Method is applied to several test problems for the advection equation, the shallow water equations, and the shallow water magnetohydrodynamic (SMHD) equations. For the SMHD equations, we make use of an unstaggered constrained transport Method to maintain a discrete divergence-free magnetic field.
Siavash Kazemirad - One of the best experts on this subject based on the ideXlab platform.
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Lamb Wave Propagation Method for nondestructive characterization of the elastic properties of wood
Applied Acoustics, 2021Co-Authors: Hamidreza Fathi, Siavash Kazemirad, Vahid NasirAbstract:Abstract Nondestructive evaluation (NDE) of the mechanical properties of structural wood is of great importance for quality control purposes in wood industries and construction applications. The currently used ultrasonic and stress Wave Methods fail to accurately estimate the elastic properties of wood. The present study aimed to propose an NDE Method for accurate characterization of the elastic properties of wood using the Lamb Wave Propagation Method. Lamb Wave Propagation and mechanical three-point-bending tests were performed on the green poplar wood specimens with different moisture content (MC) levels. The fundamental antisymmetric Lamb Wave mode was propagated in specimens using an ultrasonic actuator, and an ultrasonic sensor was used to acquire the Wave signal at different locations of the specimens along the Propagation direction. The Lamb Wave velocity was measured for the wood specimens with different MC and found to be in very good agreement with those from semi-analytically obtained dispersion curves. Afterwards, the corresponding inverse Lamb Wave Propagation problem was solved and the modulus of elasticity (MOE) of the specimens was estimated. The maximum difference between the MOE calculated by the proposed Lamb Wave Propagation Method and that measured from the three-point bending test was less than 2%, proving the validity of the proposed Method for nondestructive characterization of wood.
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A nondestructive guided Wave Propagation Method for the characterization of moisture-dependent viscoelastic properties of wood materials
Materials and Structures, 2020Co-Authors: Hamidreza Fathi, Siavash Kazemirad, Vahid NasirAbstract:The in-situ monitoring and characterization of the mechanical properties of wood and timber materials is of great importance due to their broad structural applications. The purpose of this study was to propose a nondestructive Method to assess the moisture-dependent viscoelastic behavior of structural wood using the guided Lamb Wave Propagation. Twelve green poplar wood specimens with different moisture content (MC) underwent the Lamb Wave Propagation tests and the Wave characteristics were acquired. The viscoelastic properties of the wood specimens, including the shear storage and shear loss moduli and the loss factor, were then estimated through the solution of the corresponding inverse Lamb Wave Propagation problem using the experimentally measured Lamb Wave characteristics. The structural stiffness and damping of wood specimens were affected by their MC, as the Lamb Wave amplitude and velocity significantly decreased with MC. While the shear storage modulus decreased with MC, the shear loss modulus and loss factor increased with MC, resulting in a higher viscoelastic behavior. The loss factor of the wood specimens was estimated to be between 5.88% and 8.49% for different classes of MC, showing an increase of 44% with MC. The Lamb Wave Propagation Method offers a strong tool for nondestructive characterization of the viscoelastic properties of wood materials and structures over a broad MC range. Wood materials show a significant viscoelastic behavior which is highly impacted by their MC. The loss factor can play an important role in the characterization and classification of structural wood and timber with different MC.
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Ultrasound viscoelasticity assessment using an adaptive torsional shear Wave Propagation Method.
Medical physics, 2016Co-Authors: Abderrahmane Ouared, Siavash Kazemirad, Emmanuel Montagnon, Guy CloutierAbstract:Purpose: Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear Wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite element Method (FEM) models. In this study, a new Method is proposed for the quantification of both shear storage and loss moduli of confined lesions, in the context of breast imaging, using adaptive torsional shear Waves (ATSWs) generated remotely with radiation pressure. Methods: A FEM model was developed to solve the inverse Wave Propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness to noise and geometric constraints was evaluated. The proposed model was validated in vitro with two independent rheology Methods on several homogeneous and heterogeneous breast tissue-mimicking phantoms over a broad range of frequencies (up to 400 Hz). Results: Viscoelastic properties matched benchmark rheology Methods with discrepancies of 8%–38% for the shear modulus G′ and 9%–67% for the loss modulus G″. The robustness study indicated good estimations of storage and loss moduli (maximum mean errors of 19% on G′ and 32% on G″) for signal-to-noise ratios between 19.5 and 8.5 dB. Larger errors were noticed in the case of biases in lesion dimension and position. Conclusions: The ATSW Method revealed that it is possible to estimate the viscoelasticity of biological tissues with torsional shear Waves when small biases in lesion geometry exist.
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rayleigh Wave Propagation Method for the characterization of a thin layer of biomaterials
Journal of the Acoustical Society of America, 2013Co-Authors: Siavash Kazemirad, Luc MongeauAbstract:An experimental Method based on Rayleigh Wave Propagation was developed for quantifying the frequency-dependent viscoelastic properties of a small volume of expensive biomaterials over a broad frequency range. Synthetic silicone rubber and gelatin materials were fabricated and tested to evaluate the proposed Method. Planar harmonic Rayleigh Waves at different frequencies, from 80 to 4000 Hz, were launched on the surface of a sample composed of a substrate with known material properties coated with a thin layer of the soft material to be characterized. A transfer function Method was used to obtain the complex Rayleigh Wavenumber. An inverse Wave Propagation problem was solved and a complex nonlinear dispersion equation was obtained. The complex shear and elastic moduli of the sample materials were then calculated through the numerical solution of the obtained dispersion equation using the measured Wavenumbers. The results were in good agreement with those of a previous independent study. The proposed Method was found to be reliable and cost effective for the measurement of viscoelastic properties of a thin layer of expensive biomaterials, such as phonosurgical biomaterials, over a wide frequency range.
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Rayleigh Wave Propagation Method for the characterization of viscoelastic properties of biomaterials
The Journal of the Acoustical Society of America, 2012Co-Authors: Siavash Kazemirad, Luc MongeauAbstract:The frequency-dependent viscoelastic properties of injectable biomaterials used for vocal fold augmentation and repair must be characterized to ensure the integrity with the vibrating tissue throughout the frequency range of vocalization. Experimental Methods for quantifying the frequency-dependent viscoelastic properties of biomaterials over a broad frequency range (i.e., up to 4 kHz) using Rayleigh Wave Propagations were investigated. Appropriate models for Rayleigh Wave Propagations in single and layered media were developed. Different silicone rubber samples were made and tested to evaluate the proposed Methods. Rayleigh Waves at different frequencies were launched on the surface of different samples; i.e., single layer samples and samples composed of a substrate with known material properties coated with a thin layer of the soft material that is to be characterized. The input vibrations of the actuator and the motion of the sample surface were measured using an accelerometer and a laser Doppler vibrometer, respectively. A transfer function Method was used to obtain the complex Rayleigh Wavenumbers. Finally, the complex shear and elastic moduli and the loss factor of samples were calculated through the proper modelling using the measured Wavenumbers. The results were compared and shown to be in good agreement with those obtained from other measurement Methods.
Guy Cloutier - One of the best experts on this subject based on the ideXlab platform.
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Ultrasound viscoelasticity assessment using an adaptive torsional shear Wave Propagation Method.
Medical physics, 2016Co-Authors: Abderrahmane Ouared, Siavash Kazemirad, Emmanuel Montagnon, Guy CloutierAbstract:Purpose: Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear Wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite element Method (FEM) models. In this study, a new Method is proposed for the quantification of both shear storage and loss moduli of confined lesions, in the context of breast imaging, using adaptive torsional shear Waves (ATSWs) generated remotely with radiation pressure. Methods: A FEM model was developed to solve the inverse Wave Propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness to noise and geometric constraints was evaluated. The proposed model was validated in vitro with two independent rheology Methods on several homogeneous and heterogeneous breast tissue-mimicking phantoms over a broad range of frequencies (up to 400 Hz). Results: Viscoelastic properties matched benchmark rheology Methods with discrepancies of 8%–38% for the shear modulus G′ and 9%–67% for the loss modulus G″. The robustness study indicated good estimations of storage and loss moduli (maximum mean errors of 19% on G′ and 32% on G″) for signal-to-noise ratios between 19.5 and 8.5 dB. Larger errors were noticed in the case of biases in lesion dimension and position. Conclusions: The ATSW Method revealed that it is possible to estimate the viscoelasticity of biological tissues with torsional shear Waves when small biases in lesion geometry exist.
