The Experts below are selected from a list of 1242 Experts worldwide ranked by ideXlab platform
Paul Wellington - One of the best experts on this subject based on the ideXlab platform.
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Bessel smoothing Filter for spectral-element mesh
Geophysical Journal International, 2017Co-Authors: P.t. Trinh, Jean Virieux, Romain Brossier, Ludovic Métivier, Paul WellingtonAbstract:Smoothing Filters are extremely important tools in seismic imaging and inversion, such as for traveltime tomography, migration and waveform inversion. For efficiency, and as they can be used a number of times during inversion, it is important that these Filters can easily incorporate prior information on the geological structure of the investigated medium, through variable coherent lengths and orientation. In this study, we promote the use of the Bessel Filter to achieve these purposes. Instead of considering the direct application of the Filter, we demonstrate that we can rely on the equation associated with its inverse Filter, which amounts to the solution of an elliptic partial differential equation. This enhances the efficiency of the Filter application, and also its flexibility. We apply this strategy within a spectral-element-based elastic full waveform inversion framework. Taking advantage of this formulation, we apply the Bessel Filter by solving the associated partial differential equation directly on the spectral-element mesh through the standard weak formulation. This avoids cumbersome projection operators between the spectral-element mesh and a regular Cartesian grid, or expensive explicit windowed convolution on the finite-element mesh, which is often used for applying smoothing operators. The associated linear system is solved efficiently through a parallel conjugate gradient algorithm, in which the matrix vector product is factorized and highly optimized with vectorized computation. Significant scaling behaviour is obtained when comparing this strategy with the explicit convolution method. The theoretical numerical complexity of this approach increases linearly with the coherent length, whereas a sublinear relationship is observed practically. Numerical illustrations are provided here for schematic examples, and for a more realistic elastic full waveform inversion gradient smoothing on the SEAM II benchmark model. These examples illustrate well the efficiency and flexibility of the approach proposed.
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Structure-Smoothing Bessel Filter for Finite Element Mesh - Application on 3D Elastic FWI
79th EAGE Conference and Exhibition 2017, 2017Co-Authors: P.t. Trinh, Jean Virieux, Romain Brossier, Ludovic Métivier, Paul WellingtonAbstract:Smoothing Filters are extremely important tools in seismic imaging and especially in full waveform inversion. For complex geological structures with variable heterogeneities, these Filters should be able to incorporate efficiently geological prior information of the target medium, through coherent lengths and 3D orientation, which are expected to vary in space. In this study, we introduce a novel smoothing strategy based on the Bessel Filter, for which we are able to design a highly efficient implementation. Its application is performed by solving the elliptic partial differential equation associated to its sparse inverse operator. The development of this equation in any discretization method naturally yields a symmetric and well-conditioned linear system. We develop this smoothing strategy within an elastic spectral-element-based full-waveform-inversion framework. The associated linear system can be solved efficiently through a parallel conjugate-gradient algorithm, in which the matrix-vector product is factorized and optimized in a similar way as the one used for solving the elastodynamic system. By doing so, we avoid expensive explicit-windowed-convolution over the finite element mesh. The efficiency and the flexibility of the proposed smoothing method are illustrated through various schematic examples, and on a more realistic elastic full waveform inversion problem on the SEAM II benchmark model.
P.t. Trinh - One of the best experts on this subject based on the ideXlab platform.
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Bessel smoothing Filter for spectral-element mesh
Geophysical Journal International, 2017Co-Authors: P.t. Trinh, Jean Virieux, Romain Brossier, Ludovic Métivier, Paul WellingtonAbstract:Smoothing Filters are extremely important tools in seismic imaging and inversion, such as for traveltime tomography, migration and waveform inversion. For efficiency, and as they can be used a number of times during inversion, it is important that these Filters can easily incorporate prior information on the geological structure of the investigated medium, through variable coherent lengths and orientation. In this study, we promote the use of the Bessel Filter to achieve these purposes. Instead of considering the direct application of the Filter, we demonstrate that we can rely on the equation associated with its inverse Filter, which amounts to the solution of an elliptic partial differential equation. This enhances the efficiency of the Filter application, and also its flexibility. We apply this strategy within a spectral-element-based elastic full waveform inversion framework. Taking advantage of this formulation, we apply the Bessel Filter by solving the associated partial differential equation directly on the spectral-element mesh through the standard weak formulation. This avoids cumbersome projection operators between the spectral-element mesh and a regular Cartesian grid, or expensive explicit windowed convolution on the finite-element mesh, which is often used for applying smoothing operators. The associated linear system is solved efficiently through a parallel conjugate gradient algorithm, in which the matrix vector product is factorized and highly optimized with vectorized computation. Significant scaling behaviour is obtained when comparing this strategy with the explicit convolution method. The theoretical numerical complexity of this approach increases linearly with the coherent length, whereas a sublinear relationship is observed practically. Numerical illustrations are provided here for schematic examples, and for a more realistic elastic full waveform inversion gradient smoothing on the SEAM II benchmark model. These examples illustrate well the efficiency and flexibility of the approach proposed.
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Structure-Smoothing Bessel Filter for Finite Element Mesh - Application on 3D Elastic FWI
79th EAGE Conference and Exhibition 2017, 2017Co-Authors: P.t. Trinh, Jean Virieux, Romain Brossier, Ludovic Métivier, Paul WellingtonAbstract:Smoothing Filters are extremely important tools in seismic imaging and especially in full waveform inversion. For complex geological structures with variable heterogeneities, these Filters should be able to incorporate efficiently geological prior information of the target medium, through coherent lengths and 3D orientation, which are expected to vary in space. In this study, we introduce a novel smoothing strategy based on the Bessel Filter, for which we are able to design a highly efficient implementation. Its application is performed by solving the elliptic partial differential equation associated to its sparse inverse operator. The development of this equation in any discretization method naturally yields a symmetric and well-conditioned linear system. We develop this smoothing strategy within an elastic spectral-element-based full-waveform-inversion framework. The associated linear system can be solved efficiently through a parallel conjugate-gradient algorithm, in which the matrix-vector product is factorized and optimized in a similar way as the one used for solving the elastodynamic system. By doing so, we avoid expensive explicit-windowed-convolution over the finite element mesh. The efficiency and the flexibility of the proposed smoothing method are illustrated through various schematic examples, and on a more realistic elastic full waveform inversion problem on the SEAM II benchmark model.
Anju Nandakumar - One of the best experts on this subject based on the ideXlab platform.
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frequency analysis of memristor based low pass Bessel Filter
International Conference on Computing and Network Communications, 2018Co-Authors: Alex Pappachen James, Yerniyaz Tolegen, Anju NandakumarAbstract:Bessel Filter is a type of linear form Filter, which is widely used for applications where constant group delay response is required. Such implementation allows to avoid linear distortion. It is believed that recent realization of memristor element can significantly affect Filter's performance by being able to adjust Filter gain and cut-off frequency. Therefore, this paper presents a memristor based active low pass Bessel Filter, where resistor elements were replaced by memristors. The circuit is analysed by on frequency response. Memristor resistances are to be adjusted by means of tuning circuits. Overall, memristive circuit resulted in slight deviation from the original circuit with the same power consumption and verified adjustability of several Filter characteristics.
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notice of retraction frequency analysis of memristor based low pass Bessel Filter
International Conference on Computing and Network Communications, 2018Co-Authors: Alex Pappachen James, Yerniyaz Tolegen, Anju NandakumarAbstract:Bessel Filter is a type of linear form Filter, which is widely used for applications where constant group delay response is required. Such implementation allows to avoid linear distortion. It is believed that recent realization of memristor element can significantly affect Filter's performance by being able to adjust Filter gain and cut-off frequency. Therefore, this paper presents a memristor based active low pass Bessel Filter, where resistor elements were replaced by memristors. The circuit is analysed by on frequency response. Memristor resistances are to be adjusted by means of tuning circuits. Overall, memristive circuit resulted in slight deviation from the original circuit with the same power consumption and verified adjustability of several Filter characteristics.
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implementation of memristor in Bessel Filter with rlc components
arXiv: Signal Processing, 2018Co-Authors: Galymzhan Torebayev, Anju NandakumarAbstract:The Bessel Filters are optimized to collect competent transient response due to a linear phase in the passband. In other words, during the Filtering process, there will be comparatively impoverished frequency response with lower amplitude inequity. Memristor is asserted as a passive, two-terminal essential component of the circuit and the use of such element in schemes as an adjustable resistance allows the realization of the memory resistor based analog circuits, which achieve the wide range of specific parameters. The application of RLC circuit for Bessel Filter prototype is theoretically expected to behave in a positive way, however, the further simulations with software and analysis of the results will reveal the nature of the effect
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Implementation of Memristor in Bessel Filter with RLC components
2018 International Conference on Computing and Network Communications (CoCoNet), 2018Co-Authors: Galymzhan Torebayev, Anju NandakumarAbstract:The Bessel Filters are optimized to collect competent transient response due to a linear phase in the passband. In other words, during the Filtering process, there will be comparatively impoverished frequency response with lower amplitude inequity. Memristor is asserted as a passive, two-terminal essential component of the circuit and the use of such element in schemes as an adjustable resistance allows the realization of memory-resistor based analog circuits, which achieve the wide range of specific parameters. The application of RLC circuit for Bessel Filter prototype is theoretically expected to behave in a positive way, however, the further simulations with software and analysis of the results will reveal the nature of the effect.
David Gall - One of the best experts on this subject based on the ideXlab platform.
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The OpenPicoAmp-100k: an open-source high-performance amplifier for single channel recording in planar lipid bilayers
Pflügers Archiv - European Journal of Physiology, 2019Co-Authors: Vadim Shlyonsky, David GallAbstract:We propose an upgraded version of our previously designed open-source lipid bilayer amplifier. This improved amplifier is now suitable both for the use in introductory courses in biophysics and neurosciences at the undergraduate level and for scientific research. Similar to its predecessor, the OpenPicoAmp-100k is designed using the common lithographic printed circuit board fabrication process and off-the-shelf electronic components. It consists of the high-speed headstage, followed by voltage-gain amplifier with built-in 6-order Bessel Filter. The amplifier has a bandwidth of 100 kHz in the presence of 100-pF input membrane capacitance and is capable of measuring ion channel current with amplitudes from sub-pA and up to ± 4 nA. At the full bandwidth and with a 1 GΩ transimpedance gain, the amplifier shows 12 pA_rms noise with an open input and 112 pA_rms noise in the presence of 100-pF input capacitance, while at the 5-kHz bandwidth (typical in single-channel experiments), noise amounts to 0.45 pA_rms and 2.11 pA_rms, respectively. Using an optocoupler circuit producing TTL-controlled current impulses and using 50% threshold analysis, we show that at full bandwidth, the amplifier has deadtimes of 3.5 μs and 5 μs at signal-to-noise ratios (SNR) of 9 and 1.7, respectively. Near 100% of true current impulses longer than 5 μs and 6.6 μs are detected at these two respective SNRs, while false event detection rate remains acceptably low. The wide bandwidth of the amplifier was confirmed in bilayer experiments with alamethicin, for which open ion channel current events shorter that 10 μs could be resolved.
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the openpicoamp 100k an open source high performance amplifier for single channel recording in planar lipid bilayers
bioRxiv, 2019Co-Authors: Vadim Shlyonsky, David GallAbstract:We propose an upgraded version of our previously designed open-source lipid bilayer amplifier. This improved amplifier is now suitable both for the use in introductory courses in biophysics and neurosciences at the undergraduate level and for scientific research. Similar to its predecessor, the OpenPicoAmp-100k is designed using the common lithographic printed circuit board fabrication process and off-the-shelf electronic components. It consists of the high-speed headstage, followed by voltage-gain amplifier with built-in 6-order Bessel Filter. The amplifier has a bandwidth of 100 kHz in the presence of 100 pF input membrane capacitance and is capable of measuring ion channel current with amplitudes from sub-pA and up to {+/-}4 nA. At the full bandwidth and with a 1 G{Omega} transimpedance gain, the amplifier shows 12 pArms noise with an open input and 112 pArms noise in the presence of 100 pF input capacitance, while at the 5 kHz bandwidth (typical in single-channel experiments) noise amounts to 0.45 pArms and 2.11 pArms, respectively. Using an optocoupler circuit producing TTL-controlled current impulses and using 50% threshold analysis we show that at full bandwidth the amplifier has deadtimes of 3.5 {micro}s and 5 {micro}s at signal-to-noise ratios(SNR) of 9 and 1.7, respectively. Near 100% of true current impulses longer than 5 {micro}s and 6.6 {micro}s are detected at these two respective SNRs, while false event detection rate remains acceptably low. The wide bandwidth of the amplifier was confirmed in bilayer experiments with alamethicin, for which open ion channel current events shorter that 10 {micro}s could be resolved.
Jean Virieux - One of the best experts on this subject based on the ideXlab platform.
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Bessel smoothing Filter for spectral-element mesh
Geophysical Journal International, 2017Co-Authors: P.t. Trinh, Jean Virieux, Romain Brossier, Ludovic Métivier, Paul WellingtonAbstract:Smoothing Filters are extremely important tools in seismic imaging and inversion, such as for traveltime tomography, migration and waveform inversion. For efficiency, and as they can be used a number of times during inversion, it is important that these Filters can easily incorporate prior information on the geological structure of the investigated medium, through variable coherent lengths and orientation. In this study, we promote the use of the Bessel Filter to achieve these purposes. Instead of considering the direct application of the Filter, we demonstrate that we can rely on the equation associated with its inverse Filter, which amounts to the solution of an elliptic partial differential equation. This enhances the efficiency of the Filter application, and also its flexibility. We apply this strategy within a spectral-element-based elastic full waveform inversion framework. Taking advantage of this formulation, we apply the Bessel Filter by solving the associated partial differential equation directly on the spectral-element mesh through the standard weak formulation. This avoids cumbersome projection operators between the spectral-element mesh and a regular Cartesian grid, or expensive explicit windowed convolution on the finite-element mesh, which is often used for applying smoothing operators. The associated linear system is solved efficiently through a parallel conjugate gradient algorithm, in which the matrix vector product is factorized and highly optimized with vectorized computation. Significant scaling behaviour is obtained when comparing this strategy with the explicit convolution method. The theoretical numerical complexity of this approach increases linearly with the coherent length, whereas a sublinear relationship is observed practically. Numerical illustrations are provided here for schematic examples, and for a more realistic elastic full waveform inversion gradient smoothing on the SEAM II benchmark model. These examples illustrate well the efficiency and flexibility of the approach proposed.
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Structure-Smoothing Bessel Filter for Finite Element Mesh - Application on 3D Elastic FWI
79th EAGE Conference and Exhibition 2017, 2017Co-Authors: P.t. Trinh, Jean Virieux, Romain Brossier, Ludovic Métivier, Paul WellingtonAbstract:Smoothing Filters are extremely important tools in seismic imaging and especially in full waveform inversion. For complex geological structures with variable heterogeneities, these Filters should be able to incorporate efficiently geological prior information of the target medium, through coherent lengths and 3D orientation, which are expected to vary in space. In this study, we introduce a novel smoothing strategy based on the Bessel Filter, for which we are able to design a highly efficient implementation. Its application is performed by solving the elliptic partial differential equation associated to its sparse inverse operator. The development of this equation in any discretization method naturally yields a symmetric and well-conditioned linear system. We develop this smoothing strategy within an elastic spectral-element-based full-waveform-inversion framework. The associated linear system can be solved efficiently through a parallel conjugate-gradient algorithm, in which the matrix-vector product is factorized and optimized in a similar way as the one used for solving the elastodynamic system. By doing so, we avoid expensive explicit-windowed-convolution over the finite element mesh. The efficiency and the flexibility of the proposed smoothing method are illustrated through various schematic examples, and on a more realistic elastic full waveform inversion problem on the SEAM II benchmark model.