The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
P. Von Paris - One of the best experts on this subject based on the ideXlab platform.
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The unstable CO2 feedback cycle on ocean planets
2015Co-Authors: D., Kitzmann, John Lee Grenfell, Heike Rauer, Y., Alibert, M., Godolt, K., Heng, B., Stracke, Beate, Patzer, P. Von ParisAbstract:Ocean planets are volatile rich planets, not present in our Solar System, which are dominated by deep, global oceans. Theoretical considerations and planet formation modeling studies suggest that extrasolar ocean planets should be a very common type of planet. One might therefore expect that low-mass ocean planets would be ideal candidates when searching for habitable exoplanets, since water is considered to be an essential requirement for life. However, a very large global ocean can also strongly influence the climate.The high pressure at the oceans bottom results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. In our study we, therefore, focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a Fundamental Quantity for assessing the potential habitability of the planet's surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree.In contrast to the stabilising carbonate-silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle on ocean planets is positive and has strong destabilising effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle is severely limiting the potential habitability of ocean planets.
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The unstable CO2 feedback cycle on ocean planets
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: D., Kitzmann, Y., Alibert, M., Godolt, J. L., Grenfell, K., Heng, A. B. C., Patzer, H., Rauer, B., Stracke, P. Von ParisAbstract:Ocean planets are volatile-rich planets, not present in our Solar system, which are thought to be dominated by deep, global oceans. This results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. Therefore, instead of a carbonate-silicate cycle like on the Earth, the atmospheric carbon dioxide concentration is governed by the capability of the ocean to dissolve carbon dioxide (CO2). In our study, we focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a Fundamental Quantity for assessing the potential habitability of the planet's surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree. In contrast to the stabilizing carbonate-silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle feedback on ocean planets is negative and has strong destabilizing effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle can severely limit the extension of the habitable zone for ocean planets.
Hugues Bodiguel - One of the best experts on this subject based on the ideXlab platform.
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X-ray radiography of viscous resuspension
Physics of Fluids, 2019Co-Authors: Brice Saint-michel, Sébastien Manneville, Steven Meeker, Guillaume Ovarlez, Hugues BodiguelAbstract:We use X-ray imaging to study viscous resuspension. In a Taylor-Couette geometry, we shear an initially settled layer of spherical glass particles immersed in a Newtonian fluid and measure the local volume fraction profiles. In this configuration, the steady-state profiles are simply related to the normal viscosity defined in the framework of the suspension balance model. These experiments allow us to examine this Fundamental Quantity over a wide range of volume fractions, in particular, in the semidilute regime where experimental data are sorely lacking. Our measurements strongly suggest that the particle stress is quadratic with respect to the volume fraction in the dilute limit. Strikingly, they also reveal a nonlinear dependence on the Shields number, in contrast with previous theoretical and experimental results. This likely points to shear-thinning particle stresses and to a non-Coulomb or velocity-weakening friction between the particles, as also evidenced from shear reversal experiments. I. INTRODUCTION
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X-ray Radiography of Viscous Resuspension
2019Co-Authors: Brice Saint-michel, Sébastien Manneville, Steven Meeker, Guillaume Ovarlez, Hugues BodiguelAbstract:We use X-ray imaging to study viscous resuspension. In a Taylor-Couette geometry, we shear an initially settled layer of spherical glass particles immersed in a Newtonian fluid and measure the local volume fraction profiles. In this configuration, the steady-state profiles are simply related to the normal viscosity defined in the framework of the Suspension Balance Model (SBM). These experiments allow us to examine this Fundamental Quantity over a wide range of volume fractions, in particular in the semi-dilute regime where experimental data are sorely lacking. Our measurements unambiguously show that the particle stress is quadratic with respect to the volume fraction in the dilute limit. Strikingly, they also reveal a nonlinear dependence on the Shields number, in contrast with previous theoretical and experimental results. This likely points to shear-thinning particle stresses and to a non-Coulomb or velocity-weakening friction between the particles, as also evidenced from shear reversal experiments.
D., Kitzmann - One of the best experts on this subject based on the ideXlab platform.
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The unstable CO2 feedback cycle on ocean planets
2015Co-Authors: D., Kitzmann, John Lee Grenfell, Heike Rauer, Y., Alibert, M., Godolt, K., Heng, B., Stracke, Beate, Patzer, P. Von ParisAbstract:Ocean planets are volatile rich planets, not present in our Solar System, which are dominated by deep, global oceans. Theoretical considerations and planet formation modeling studies suggest that extrasolar ocean planets should be a very common type of planet. One might therefore expect that low-mass ocean planets would be ideal candidates when searching for habitable exoplanets, since water is considered to be an essential requirement for life. However, a very large global ocean can also strongly influence the climate.The high pressure at the oceans bottom results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. In our study we, therefore, focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a Fundamental Quantity for assessing the potential habitability of the planet's surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree.In contrast to the stabilising carbonate-silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle on ocean planets is positive and has strong destabilising effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle is severely limiting the potential habitability of ocean planets.
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The unstable CO2 feedback cycle on ocean planets
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: D., Kitzmann, Y., Alibert, M., Godolt, J. L., Grenfell, K., Heng, A. B. C., Patzer, H., Rauer, B., Stracke, P. Von ParisAbstract:Ocean planets are volatile-rich planets, not present in our Solar system, which are thought to be dominated by deep, global oceans. This results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. Therefore, instead of a carbonate-silicate cycle like on the Earth, the atmospheric carbon dioxide concentration is governed by the capability of the ocean to dissolve carbon dioxide (CO2). In our study, we focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a Fundamental Quantity for assessing the potential habitability of the planet's surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree. In contrast to the stabilizing carbonate-silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle feedback on ocean planets is negative and has strong destabilizing effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle can severely limit the extension of the habitable zone for ocean planets.
Lorenzo Galleani - One of the best experts on this subject based on the ideXlab platform.
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The Transient Spectrum of a Random System
IEEE Transactions on Signal Processing, 2010Co-Authors: Lorenzo GalleaniAbstract:The frequency spectrum is a Fundamental Quantity for the analysis and design of a system. When a system is turned on or off, the frequency spectrum of its output changes with time. We define the transient spectrum as the time-frequency spectrum of the system output during the transient phase. We obtain the exact transient spectrum for a wide class of random systems, and we formulate it with respect to the classical power spectrum, which is reached for large times. We apply the developed method to the case of a harmonic oscillator and of a system with two resonances.
Brice Saint-michel - One of the best experts on this subject based on the ideXlab platform.
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X-ray radiography of viscous resuspension
Physics of Fluids, 2019Co-Authors: Brice Saint-michel, Sébastien Manneville, Steven Meeker, Guillaume Ovarlez, Hugues BodiguelAbstract:We use X-ray imaging to study viscous resuspension. In a Taylor-Couette geometry, we shear an initially settled layer of spherical glass particles immersed in a Newtonian fluid and measure the local volume fraction profiles. In this configuration, the steady-state profiles are simply related to the normal viscosity defined in the framework of the suspension balance model. These experiments allow us to examine this Fundamental Quantity over a wide range of volume fractions, in particular, in the semidilute regime where experimental data are sorely lacking. Our measurements strongly suggest that the particle stress is quadratic with respect to the volume fraction in the dilute limit. Strikingly, they also reveal a nonlinear dependence on the Shields number, in contrast with previous theoretical and experimental results. This likely points to shear-thinning particle stresses and to a non-Coulomb or velocity-weakening friction between the particles, as also evidenced from shear reversal experiments. I. INTRODUCTION
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X-ray Radiography of Viscous Resuspension
2019Co-Authors: Brice Saint-michel, Sébastien Manneville, Steven Meeker, Guillaume Ovarlez, Hugues BodiguelAbstract:We use X-ray imaging to study viscous resuspension. In a Taylor-Couette geometry, we shear an initially settled layer of spherical glass particles immersed in a Newtonian fluid and measure the local volume fraction profiles. In this configuration, the steady-state profiles are simply related to the normal viscosity defined in the framework of the Suspension Balance Model (SBM). These experiments allow us to examine this Fundamental Quantity over a wide range of volume fractions, in particular in the semi-dilute regime where experimental data are sorely lacking. Our measurements unambiguously show that the particle stress is quadratic with respect to the volume fraction in the dilute limit. Strikingly, they also reveal a nonlinear dependence on the Shields number, in contrast with previous theoretical and experimental results. This likely points to shear-thinning particle stresses and to a non-Coulomb or velocity-weakening friction between the particles, as also evidenced from shear reversal experiments.
