The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
D A B Miller - One of the best experts on this subject based on the ideXlab platform.
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Characteristic Impedance model for plasmonic metal slot waveguides
IEEE Journal of Selected Topics in Quantum Electronics, 2008Co-Authors: Danysebastien Lygagnon, Sukru Ekin Kocabas, D A B MillerAbstract:We investigate the transmission properties of a subwavelength plasmonic slot waveguide. We show that the transmission can be accurately calculated using the Characteristic Impedance of the propagating mode. Using such a model, we show that it is possible to design devices without extensive 3-D finite-difference time-domain (FDTD) computer simulations. We illustrate the approach with calculations of an asymmetric Fabry-Perot germanium photodetector based on the slot waveguide geometry, showing predicted detector efficiencies as high as 69% despite metallic losses.
E. Mousseaux - One of the best experts on this subject based on the ideXlab platform.
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How to estimate aortic Characteristic Impedance from magnetic resonance and applanation tonometry data?
Journal of Hypertension, 2015Co-Authors: E. Bollache, N. Kachenoura, I. Bargiotas, A. Giron, A. De Cesare, M. Bensalah, D Lucor, A. Redheuil, E. MousseauxAbstract:Objectives: Compare seven previous methods for the estimation of aortic Characteristic Impedance, which contributes to left ventricle pulsatile load, from phase-contrast cardiovascular magnetic resonance (CMR) and applanation tonometry data. Methods: We studied 77 healthy (43 ± 16 years) individuals and 16 hypertensive (61 ± 9 years) patients, who consecutively underwent ascending aorta CMR and carotid tonometry, resulting in flow and pressure waveforms, respectively. Characteristic Impedance was semi-automatically estimated in time domain from these latter waveforms, using seven methods. The methods were based on the following: methods 1-4, magnitudes at specific times; method 5, early-systolic up-slope; method 6, time-derivatives peak; and method 7, pressure-flow loop early-systolic slope. Results: Aortic Characteristic Impedance was significantly increased in hypertensive patients when compared to elderly controls (n = 32) with a similar mean age of (59 ± 8 years) when using methods based on 95% of peak flow, up-slopes, and derivatives peaks (P < 0.05). When considering healthy individuals, Impedance indices were significantly correlated to central pulse pressure for all methods (P < 0.005). Finally, Characteristic Impedance was correlated to the frequency-domain reference values (r > 0.65, P < 0.0001), with a slight superiority for the same three methods as above (r > 0.82, P < 0.0001). Conclusions: This is the first study demonstrating phase-contrast CMR and tonometry usefulness in aortic Characteristic Impedance temporal estimation. Methods based on 95% of peak flow, as well as those based on derivative peaks and up-slopes, which are fast and independent of curve preprocessing, were slightly superior. They can be easily integrated in a clinical workflow and may help to understand the complementarity of this pulsatile index with other CMR aortic geometry and stiffness measures in the setting of left ventricle-aortic coupling.
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how to estimate aortic Characteristic Impedance from magnetic resonance and applanation tonometry data
Journal of Hypertension, 2015Co-Authors: E. Bollache, N. Kachenoura, I. Bargiotas, A. Giron, A. De Cesare, M. Bensalah, D Lucor, A. Redheuil, E. MousseauxAbstract:Objectives: Compare seven previous methods for the estimation of aortic Characteristic Impedance, which contributes to left ventricle pulsatile load, from phase-contrast cardiovascular magnetic resonance (CMR) and applanation tonometry data. Methods: We studied 77 healthy (43 ± 16 years) individuals and 16 hypertensive (61 ± 9 years) patients, who consecutively underwent ascending aorta CMR and carotid tonometry, resulting in flow and pressure waveforms, respectively. Characteristic Impedance was semi-automatically estimated in time domain from these latter waveforms, using seven methods. The methods were based on the following: methods 1–4, magnitudes at specific times; method 5, early-systolic up-slope; method 6, time-derivatives peak; and method 7, pressure-flow loop early-systolic slope. Results: Aortic Characteristic Impedance was significantly increased in hypertensive patients when compared to elderly controls (n = 32) with a similar mean age of (59 ± 8 years) when using methods based on 95% of peak flow, up-slopes, and derivatives peaks (P 0.65, P 0.82, P Conclusions: This is the first study demonstrating phase-contrast CMR and tonometry usefulness in aortic Characteristic Impedance temporal estimation. Methods based on 95% of peak flow, as well as those based on derivative peaks and up-slopes, which are fast and independent of curve preprocessing, were slightly superior. They can be easily integrated in a clinical workflow and may help to understand the complementarity of this pulsatile index with other CMR aortic geometry and stiffness measures in the setting of left ventricle-aortic coupling.
Zhichun Yang - One of the best experts on this subject based on the ideXlab platform.
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Network Model Approach for Investigation of Regenerator on Characteristic Impedance in Thermoacoustic Engine
Digital Manufacturing and Automation (ICDMA), 2010 International Conference on, 2010Co-Authors: Zhichun Yang, Feng Wu, Jun WangAbstract:Characteristic Impedances of regenerator in thermo acoustic engine are analyzed by network model. The effects of system frequency, working gas and temperature on Characteristic Impedance of regenerator are studied. If the size of regenerator fixed, the change law of Characteristic Impedances with frequency is complicated. If the ratio of spacing between two plates to thermal penetration depth is fixed, the absolute value of Characteristic Impedance increases with frequency increases. The absolute value of Characteristic Impedance when using Nitrogen as working gas is always higher than using Helium, and the absolute value of Characteristic Impedance decreases with temperature increases.
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Network Model Approach for Investigation of Regenerator and Heat Exchanger on Characteristic Impedance in Thermoacoustic Engine
Power and Energy Engineering Conference (APPEEC), 2010 Asia-Pacific, 2010Co-Authors: Zhichun Yang, Wenjing Zou, Feng Wu, Kun WuAbstract:Characteristic Impedances of regenerator and heat exchanger in thermoacoustic engine are analyzed by network model. The effects of regenerator geometry on Characteristic Impedance of regenerator are studied. The Characteristic Impedances of regenerator and heat exchanger which have same structure are calculated, the result indicated that the absolute value of the Characteristic Impedance of regenerator is lower than heat exchanger because of thermoacoustic effects of regenerator.
Danysebastien Lygagnon - One of the best experts on this subject based on the ideXlab platform.
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Characteristic Impedance model for plasmonic metal slot waveguides
IEEE Journal of Selected Topics in Quantum Electronics, 2008Co-Authors: Danysebastien Lygagnon, Sukru Ekin Kocabas, D A B MillerAbstract:We investigate the transmission properties of a subwavelength plasmonic slot waveguide. We show that the transmission can be accurately calculated using the Characteristic Impedance of the propagating mode. Using such a model, we show that it is possible to design devices without extensive 3-D finite-difference time-domain (FDTD) computer simulations. We illustrate the approach with calculations of an asymmetric Fabry-Perot germanium photodetector based on the slot waveguide geometry, showing predicted detector efficiencies as high as 69% despite metallic losses.
E. Bollache - One of the best experts on this subject based on the ideXlab platform.
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How to estimate aortic Characteristic Impedance from magnetic resonance and applanation tonometry data?
Journal of Hypertension, 2015Co-Authors: E. Bollache, N. Kachenoura, I. Bargiotas, A. Giron, A. De Cesare, M. Bensalah, D Lucor, A. Redheuil, E. MousseauxAbstract:Objectives: Compare seven previous methods for the estimation of aortic Characteristic Impedance, which contributes to left ventricle pulsatile load, from phase-contrast cardiovascular magnetic resonance (CMR) and applanation tonometry data. Methods: We studied 77 healthy (43 ± 16 years) individuals and 16 hypertensive (61 ± 9 years) patients, who consecutively underwent ascending aorta CMR and carotid tonometry, resulting in flow and pressure waveforms, respectively. Characteristic Impedance was semi-automatically estimated in time domain from these latter waveforms, using seven methods. The methods were based on the following: methods 1-4, magnitudes at specific times; method 5, early-systolic up-slope; method 6, time-derivatives peak; and method 7, pressure-flow loop early-systolic slope. Results: Aortic Characteristic Impedance was significantly increased in hypertensive patients when compared to elderly controls (n = 32) with a similar mean age of (59 ± 8 years) when using methods based on 95% of peak flow, up-slopes, and derivatives peaks (P < 0.05). When considering healthy individuals, Impedance indices were significantly correlated to central pulse pressure for all methods (P < 0.005). Finally, Characteristic Impedance was correlated to the frequency-domain reference values (r > 0.65, P < 0.0001), with a slight superiority for the same three methods as above (r > 0.82, P < 0.0001). Conclusions: This is the first study demonstrating phase-contrast CMR and tonometry usefulness in aortic Characteristic Impedance temporal estimation. Methods based on 95% of peak flow, as well as those based on derivative peaks and up-slopes, which are fast and independent of curve preprocessing, were slightly superior. They can be easily integrated in a clinical workflow and may help to understand the complementarity of this pulsatile index with other CMR aortic geometry and stiffness measures in the setting of left ventricle-aortic coupling.
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how to estimate aortic Characteristic Impedance from magnetic resonance and applanation tonometry data
Journal of Hypertension, 2015Co-Authors: E. Bollache, N. Kachenoura, I. Bargiotas, A. Giron, A. De Cesare, M. Bensalah, D Lucor, A. Redheuil, E. MousseauxAbstract:Objectives: Compare seven previous methods for the estimation of aortic Characteristic Impedance, which contributes to left ventricle pulsatile load, from phase-contrast cardiovascular magnetic resonance (CMR) and applanation tonometry data. Methods: We studied 77 healthy (43 ± 16 years) individuals and 16 hypertensive (61 ± 9 years) patients, who consecutively underwent ascending aorta CMR and carotid tonometry, resulting in flow and pressure waveforms, respectively. Characteristic Impedance was semi-automatically estimated in time domain from these latter waveforms, using seven methods. The methods were based on the following: methods 1–4, magnitudes at specific times; method 5, early-systolic up-slope; method 6, time-derivatives peak; and method 7, pressure-flow loop early-systolic slope. Results: Aortic Characteristic Impedance was significantly increased in hypertensive patients when compared to elderly controls (n = 32) with a similar mean age of (59 ± 8 years) when using methods based on 95% of peak flow, up-slopes, and derivatives peaks (P 0.65, P 0.82, P Conclusions: This is the first study demonstrating phase-contrast CMR and tonometry usefulness in aortic Characteristic Impedance temporal estimation. Methods based on 95% of peak flow, as well as those based on derivative peaks and up-slopes, which are fast and independent of curve preprocessing, were slightly superior. They can be easily integrated in a clinical workflow and may help to understand the complementarity of this pulsatile index with other CMR aortic geometry and stiffness measures in the setting of left ventricle-aortic coupling.