The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Dennis Stello - One of the best experts on this subject based on the ideXlab platform.
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oscillation mode lifetimes in xi hydrae will strong mode damping limit asteroseismology of red giant stars
Astronomy and Astrophysics, 2006Co-Authors: Dennis Stello, Hans Kjeldsen, Timothy R. Bedding, Derek L. BuzasiAbstract:We introduce a new method to measure Frequency Separations and mode lifetimes of stochastically excited and damped oscillations, so-called solar-like oscillations. Our method shows that velocity data of the red giant star ξ Hya (Frandsen et al. 2002) support a large Frequency Separation between modes of roughly 7 µ Hz. We also conclude that the data are consistent with a mode lifetime of 2 days, which is so short relative to its pulsation period that none of the observed frequencies are unambiguous. Hence, we argue that the maximum asteroseismic output that can be obtained from these data is an average large Frequency Separation, the oscillation amplitude and the average mode lifetime. However, the significant discrepancy between the theoretical calculations of the mode lifetime (Houdek & Gough 2002) and our result based on the observations of ξ Hya, implies that red giant stars can help us better understand the damping and driving mechanisms of solar-like p-modes by convection.
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Oscillation mode lifetimes in $\xi\,$Hydrae: will strong mode damping limit asteroseismology of red giant stars?
Astronomy & Astrophysics, 2006Co-Authors: Dennis Stello, Hans Kjeldsen, Timothy R. Bedding, Derek L. BuzasiAbstract:We introduce a new method to measure Frequency Separations and mode lifetimes of stochastically excited and damped oscillations, so-called solar-like oscillations. Our method shows that velocity data of the red giant star ξ Hya (Frandsen et al. 2002) support a large Frequency Separation between modes of roughly 7 µ Hz. We also conclude that the data are consistent with a mode lifetime of 2 days, which is so short relative to its pulsation period that none of the observed frequencies are unambiguous. Hence, we argue that the maximum asteroseismic output that can be obtained from these data is an average large Frequency Separation, the oscillation amplitude and the average mode lifetime. However, the significant discrepancy between the theoretical calculations of the mode lifetime (Houdek & Gough 2002) and our result based on the observations of ξ Hya, implies that red giant stars can help us better understand the damping and driving mechanisms of solar-like p-modes by convection.
Falk Lederer - One of the best experts on this subject based on the ideXlab platform.
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Influence of the interchannel Frequency Separation on the transmission capacity of a soliton-based WDM system
Optical Pulse and Beam Propagation III, 2001Co-Authors: Nicolae C. Panoiu, Christoph Etrich, Dumitru Mihalache, Falk LedererAbstract:We analyze the influence of the interchannel Frequency Separation on the transmission capacity of a soliton-based wavelength-division multiplexing (WDM) system. The input into the optical fiber is represented by a superposition of N single solitons with equal amplitudes and different frequencies. Two different cases are taken into account. In the first case, all solitons completely overlap but have different frequencies. It is found that there exists a critical Frequency Separation above which WDM is feasible. Furthermore, it is shown that this critical Frequency increases with the number of transmission channels. In the second case, there is a time shift between the overlapping solitons in adjacent channels. It is demonstrated that this combination of time- and wavelength-division multiplexing yields the largest transmission capacity. In addition, it is discussed the case in which the interchannel Frequency Separation is smaller than the critical Frequency. It is found that in this regime the soliton spectrum of the emerging optical field has a rich structure.
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Influence of the inter-channel Frequency Separation on the transmission capacity of a soliton based WDM system
2001Co-Authors: Nicolae C. Panoiu, Christoph Etrich, Dumitru Mihalache, Falk LedererAbstract:We analyze the influence of the interchannel Frequency Separation on the transmission capacity of a soliton-based wavelength-division multiplexing (WDM) system. The input into the optical fiber is represented by a superposition of N single solitons with equal amplitudes and different frequencies. Two different cases are taken into account. In the first case, all solitons completely overlap but have different frequencies. h is found that there exists a critical Frequency Separation above which WDM is: feasible. Furthermore, it is shown that this critical Frequency increases with the number of-transmission channels. In the second case, there is a time shift between the overlapping solitons in adjacent channels. It is demonstrated that this combination of time- and wavelength-division multiplexing yields the largest transmission capacity. In addition, it is discussed the case in which the interchannel Frequency Separation is smaller than the critical Frequency. It is found that in this regime the soliton spectrum of the emerging optical field has a rich structure.
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Limits for interchannel Frequency Separation in a soliton wavelength-division multiplexing system.
Physical Review E, 2000Co-Authors: Christoph Etrich, Nicolae C. Panoiu, Dumitru Mihalache, Falk LedererAbstract:We identify the required interchannel Frequency Separation of the input field for a soliton wavelength-division multiplexing (WDM) system. It is found that the critical Frequency Separation above which WDM with solitons is feasible increases with the number of transmission channels. Moreover, it is shown that a combination of time- and wavelength-division multiplexing yields the largest transmission capacity. Finally, the structure of the soliton spectra which correspond to the Frequency Separation smaller than the critical Frequency is discussed.
Derek L. Buzasi - One of the best experts on this subject based on the ideXlab platform.
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oscillation mode lifetimes in xi hydrae will strong mode damping limit asteroseismology of red giant stars
Astronomy and Astrophysics, 2006Co-Authors: Dennis Stello, Hans Kjeldsen, Timothy R. Bedding, Derek L. BuzasiAbstract:We introduce a new method to measure Frequency Separations and mode lifetimes of stochastically excited and damped oscillations, so-called solar-like oscillations. Our method shows that velocity data of the red giant star ξ Hya (Frandsen et al. 2002) support a large Frequency Separation between modes of roughly 7 µ Hz. We also conclude that the data are consistent with a mode lifetime of 2 days, which is so short relative to its pulsation period that none of the observed frequencies are unambiguous. Hence, we argue that the maximum asteroseismic output that can be obtained from these data is an average large Frequency Separation, the oscillation amplitude and the average mode lifetime. However, the significant discrepancy between the theoretical calculations of the mode lifetime (Houdek & Gough 2002) and our result based on the observations of ξ Hya, implies that red giant stars can help us better understand the damping and driving mechanisms of solar-like p-modes by convection.
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Oscillation mode lifetimes in $\xi\,$Hydrae: will strong mode damping limit asteroseismology of red giant stars?
Astronomy & Astrophysics, 2006Co-Authors: Dennis Stello, Hans Kjeldsen, Timothy R. Bedding, Derek L. BuzasiAbstract:We introduce a new method to measure Frequency Separations and mode lifetimes of stochastically excited and damped oscillations, so-called solar-like oscillations. Our method shows that velocity data of the red giant star ξ Hya (Frandsen et al. 2002) support a large Frequency Separation between modes of roughly 7 µ Hz. We also conclude that the data are consistent with a mode lifetime of 2 days, which is so short relative to its pulsation period that none of the observed frequencies are unambiguous. Hence, we argue that the maximum asteroseismic output that can be obtained from these data is an average large Frequency Separation, the oscillation amplitude and the average mode lifetime. However, the significant discrepancy between the theoretical calculations of the mode lifetime (Houdek & Gough 2002) and our result based on the observations of ξ Hya, implies that red giant stars can help us better understand the damping and driving mechanisms of solar-like p-modes by convection.
Karl Skretting - One of the best experts on this subject based on the ideXlab platform.
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AM-FM Image Analysis based on Sparse Coding Frequency Separation Approach
2020 28th European Signal Processing Conference (EUSIPCO), 2021Co-Authors: El Hadji S. Diop, Karl Skretting, Abdel-o. BoudraaAbstract:We propose here an extension to images of a sparse coding Frequency Separation method. The approach is based on a 2D multicomponent amplitude modulation (AM)-Frequency modulation (FM) image modeling, where the 2D monocomponent parts are obtained by sparse approximations that are solved with matching pursuits. For synthetic images, a separable dictionary is built, while a patch-based dictionary learning method is adopted for real images. In fact, the total variation (TV) norm is applied on patches to select the decomposition modes with highest TV-norm, doing so yields to an interesting image analysis tool that properly separates the image Frequency contents. The proposed approach turns out to share the same behaviors with the well known empirical mode decomposition (EMD) method. Obtained results are encouraging for feature and texture analysis, and for image denoising as well.
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ICASSP - Frequency Separation Method Based on Sparse Coding
ICASSP 2019 - 2019 IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2019Co-Authors: El Hadji S. Diop, Karl SkrettingAbstract:The paper presents a sparse coding method that models a signal with amplitude modulation (AM) and Frequency modulation (FM) functions. Indeed, the proposed sparse coding Frequency Separation (SCFS) approach is based on a mutli-component AM-FM modeling where each monocomponent counterpart is obtained by sparse coding using orthogonal matching pursuits, and sorted from fine to coarse depending on its Frequency content. SCFS appears to be an efficient tool to properly separate the Frequency content of signals, and behaves like the empirical mode decomposition. Results show neat improvements in terms of Frequency Separation, tone Separation capability, and robustness against noise.
Christoph Etrich - One of the best experts on this subject based on the ideXlab platform.
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Influence of the interchannel Frequency Separation on the transmission capacity of a soliton-based WDM system
Optical Pulse and Beam Propagation III, 2001Co-Authors: Nicolae C. Panoiu, Christoph Etrich, Dumitru Mihalache, Falk LedererAbstract:We analyze the influence of the interchannel Frequency Separation on the transmission capacity of a soliton-based wavelength-division multiplexing (WDM) system. The input into the optical fiber is represented by a superposition of N single solitons with equal amplitudes and different frequencies. Two different cases are taken into account. In the first case, all solitons completely overlap but have different frequencies. It is found that there exists a critical Frequency Separation above which WDM is feasible. Furthermore, it is shown that this critical Frequency increases with the number of transmission channels. In the second case, there is a time shift between the overlapping solitons in adjacent channels. It is demonstrated that this combination of time- and wavelength-division multiplexing yields the largest transmission capacity. In addition, it is discussed the case in which the interchannel Frequency Separation is smaller than the critical Frequency. It is found that in this regime the soliton spectrum of the emerging optical field has a rich structure.
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Influence of the inter-channel Frequency Separation on the transmission capacity of a soliton based WDM system
2001Co-Authors: Nicolae C. Panoiu, Christoph Etrich, Dumitru Mihalache, Falk LedererAbstract:We analyze the influence of the interchannel Frequency Separation on the transmission capacity of a soliton-based wavelength-division multiplexing (WDM) system. The input into the optical fiber is represented by a superposition of N single solitons with equal amplitudes and different frequencies. Two different cases are taken into account. In the first case, all solitons completely overlap but have different frequencies. h is found that there exists a critical Frequency Separation above which WDM is: feasible. Furthermore, it is shown that this critical Frequency increases with the number of-transmission channels. In the second case, there is a time shift between the overlapping solitons in adjacent channels. It is demonstrated that this combination of time- and wavelength-division multiplexing yields the largest transmission capacity. In addition, it is discussed the case in which the interchannel Frequency Separation is smaller than the critical Frequency. It is found that in this regime the soliton spectrum of the emerging optical field has a rich structure.
-
Limits for interchannel Frequency Separation in a soliton wavelength-division multiplexing system.
Physical Review E, 2000Co-Authors: Christoph Etrich, Nicolae C. Panoiu, Dumitru Mihalache, Falk LedererAbstract:We identify the required interchannel Frequency Separation of the input field for a soliton wavelength-division multiplexing (WDM) system. It is found that the critical Frequency Separation above which WDM with solitons is feasible increases with the number of transmission channels. Moreover, it is shown that a combination of time- and wavelength-division multiplexing yields the largest transmission capacity. Finally, the structure of the soliton spectra which correspond to the Frequency Separation smaller than the critical Frequency is discussed.
