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Zhen Liu - One of the best experts on this subject based on the ideXlab platform.
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using molecular dynamics to unravel phase Composition behavior of nano size pores in frozen soils does young laplace equation apply in low temperature range
Canadian Geotechnical Journal, 2018Co-Authors: Chao Zhang, Zhen Liu, Peng DengAbstract:The phase Composition Curve of frozen soils is a fundamental relationship in understanding permafrost and seasonally frozen soils. However, due to the complex interplay between adsorption and capillarity, a clear physically based understanding of the phase Composition Curve in the low temperature range, i.e., <265 K, is still absent. Especially, it is unclear whether the Young–Laplace equation corresponding to capillarity still holds in nano-size pores where adsorption could dominate. In this paper, a framework based on molecular dynamics was developed to investigate the phase transition behavior of water confined in nano-size pores. A series of simulations was conducted to unravel the effects of the pore size and wettability on the freezing and melting of pore water. This is the first time that the phase Composition behavior of frozen soils is analyzed using molecular dynamics. It is found that the Young–Laplace equation may not apply in the low temperature range.
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Predicting the phase Composition Curve in frozen soils using index properties: A physico-empirical approach
Cold Regions Science and Technology, 2014Co-Authors: Zhen Liu, Xiong YuAbstract:The relationship between unfrozen water content and temperature in frozen soils, which is referred to as the phase Composition Curve (PCC), is a fundamental relationship in cold regions engineering. In a previous study, the authors succeeded in developing a physical description and a physically-based equation for the PCC, which overcomes the limitations of the existing empirical approaches. Here, the authors propose a physico-empirical approach to predict the parameters in this equation to facilitate the calculation of the PCC in practice. An accurate prediction of the PCC will only need simple soil index properties and one measured data point for constraint. In this approach, the four parameters in the PCC equation are first calculated from soil index properties using accepted formulas. Two selected parameters are then adjusted by a Curve fitting process using the measured data point. A criterion was suggested for obtaining the best point. This new approach was implemented using a computer program to automate the process. Validations with data from several soils indicated that the approach offers consistent and accurate predictions of PCCs when used with Zapata's model for plastic soils and with the Mechanistic-Empirical Pavement Design Guide (MEPDG) model for non-plastic soils. This study thus bridges an important gap between the theory and application of PCCs.
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predicting the phase Composition Curve in frozen soils using index properties a physico empirical approach
Transportation Research Board 93rd Annual MeetingTransportation Research Board, 2014Co-Authors: Zhen LiuAbstract:The relationship between unfrozen water content and temperature in frozen soils, which is referred to as the Phase Composition Curve (PCC), is a fundamental relationship in cold regions engineering. In a previous study, the authors succeeded in developing a physical description and a physically-based equation for the PCC, which overcomes the limitations of the existing empirical approaches. This study proposes a physico-empirical approach to predict the parameters in this equation to facilitate the applications of the PCC. An accurate prediction of the PCC will only need simple soil index properties and one measured data point. In this method, the four parameters in the PCC equation are first calculated from soil index properties using accepted formulas. Two selected parameters are then adjusted by a Curve fitting process using a measured data point. A criterion was suggested for obtaining the one point measurement. This new approach was implemented using a computer program to automate the process. Validations with measured results indicated that the approach offers consistent and accurate predictions of PCCs when used with Zapata's model for plastic soils and with the Mechanistic-Empirical Pavement Design Guide (MEPDG) model for non-plastic soils, respectively. This study thus bridges an important gap between the theory and applications of PCCs.
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physically based equation for phase Composition Curve of frozen soils
Transportation Research Record, 2013Co-Authors: Zhen LiuAbstract:The relationship between unfrozen water content (or saturation in freezing and thawing) and temperature, which is referred to as the phase Composition Curve in frozen soils, is a fundamental relationship in cold regions engineering. Because of the lack of a physical basis, there have been only empirical equations for this relationship. This study investigated the mechanisms underlying the phase Composition Curve. A detailed physical basis was established on the basis of the soil freezing characteristic Curve, the Clapeyron equation, and the bundle of cylindrical capillary model. From this physical basis, a closed-form equation was developed for the formulation and prediction of this Curve. This physically based equation quantifies the unique correlation between saturation and temperature in frozen soils and takes various factors into account, such as the soil saturation under unfrozen conditions and the lowest temperature used in experiments. The equation was validated with phase Composition data measured...
Keivan G Stassun - One of the best experts on this subject based on the ideXlab platform.
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
The Astrophysical Journal, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M-dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5-1.7 μm), high-resolution (R ∼ 22,500) spectra from the SDSS Apache Point Galactic Evolution Experiment survey. We determined precise atmospheric parameters T eff = 3231 ±100 K, log g = 4.96 ±0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03 ± 0.09 dex). The derived results were obtained via spectral synthesis (1D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicates that it lies below the pure-rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a subsolar Si abundance, and assuming the planet's Composition matches that of the host star, it likely has a larger core size relative to the Earth despite this producing a planet with a Si/Mg abundance ratio ∼34% greater than the Sun. The derived planetary parameters - insolation flux (S Earth = 1.79 ±0.26) and equilibrium temperature (T eq = 294 ±10 K) - support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone. (Less)
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5--1.7 \micron) high-resolution ($R$$\sim$22,500) spectra from the SDSS-APOGEE survey. We determined precise atmospheric parameters $T_{\rm eff}$=3231$\pm$100K, log$g$=4.96$\pm$0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03$\pm$0.09 dex). The derived results were obtained via spectral synthesis (1-D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicate that it lies below the pure rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a sub-solar Si/Mg ratio, and assuming the planet's Composition matches that of the host-star, it likely has a larger core size relative to the Earth. The derived planetary parameters -- insolation flux (S$_{\rm Earth}$=1.79$\pm$0.26) and equilibrium temperature ($T_{\rm eq}$=294$\pm$10K) -- support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone.
D A Garciahernandez - One of the best experts on this subject based on the ideXlab platform.
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
The Astrophysical Journal, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M-dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5-1.7 μm), high-resolution (R ∼ 22,500) spectra from the SDSS Apache Point Galactic Evolution Experiment survey. We determined precise atmospheric parameters T eff = 3231 ±100 K, log g = 4.96 ±0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03 ± 0.09 dex). The derived results were obtained via spectral synthesis (1D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicates that it lies below the pure-rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a subsolar Si abundance, and assuming the planet's Composition matches that of the host star, it likely has a larger core size relative to the Earth despite this producing a planet with a Si/Mg abundance ratio ∼34% greater than the Sun. The derived planetary parameters - insolation flux (S Earth = 1.79 ±0.26) and equilibrium temperature (T eq = 294 ±10 K) - support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone. (Less)
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5--1.7 \micron) high-resolution ($R$$\sim$22,500) spectra from the SDSS-APOGEE survey. We determined precise atmospheric parameters $T_{\rm eff}$=3231$\pm$100K, log$g$=4.96$\pm$0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03$\pm$0.09 dex). The derived results were obtained via spectral synthesis (1-D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicate that it lies below the pure rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a sub-solar Si/Mg ratio, and assuming the planet's Composition matches that of the host-star, it likely has a larger core size relative to the Earth. The derived planetary parameters -- insolation flux (S$_{\rm Earth}$=1.79$\pm$0.26) and equilibrium temperature ($T_{\rm eq}$=294$\pm$10K) -- support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone.
Diogo Souto - One of the best experts on this subject based on the ideXlab platform.
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
The Astrophysical Journal, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M-dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5-1.7 μm), high-resolution (R ∼ 22,500) spectra from the SDSS Apache Point Galactic Evolution Experiment survey. We determined precise atmospheric parameters T eff = 3231 ±100 K, log g = 4.96 ±0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03 ± 0.09 dex). The derived results were obtained via spectral synthesis (1D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicates that it lies below the pure-rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a subsolar Si abundance, and assuming the planet's Composition matches that of the host star, it likely has a larger core size relative to the Earth despite this producing a planet with a Si/Mg abundance ratio ∼34% greater than the Sun. The derived planetary parameters - insolation flux (S Earth = 1.79 ±0.26) and equilibrium temperature (T eq = 294 ±10 K) - support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone. (Less)
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5--1.7 \micron) high-resolution ($R$$\sim$22,500) spectra from the SDSS-APOGEE survey. We determined precise atmospheric parameters $T_{\rm eff}$=3231$\pm$100K, log$g$=4.96$\pm$0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03$\pm$0.09 dex). The derived results were obtained via spectral synthesis (1-D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicate that it lies below the pure rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a sub-solar Si/Mg ratio, and assuming the planet's Composition matches that of the host-star, it likely has a larger core size relative to the Earth. The derived planetary parameters -- insolation flux (S$_{\rm Earth}$=1.79$\pm$0.26) and equilibrium temperature ($T_{\rm eq}$=294$\pm$10K) -- support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone.
Katia Cunha - One of the best experts on this subject based on the ideXlab platform.
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
The Astrophysical Journal, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M-dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5-1.7 μm), high-resolution (R ∼ 22,500) spectra from the SDSS Apache Point Galactic Evolution Experiment survey. We determined precise atmospheric parameters T eff = 3231 ±100 K, log g = 4.96 ±0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03 ± 0.09 dex). The derived results were obtained via spectral synthesis (1D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicates that it lies below the pure-rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a subsolar Si abundance, and assuming the planet's Composition matches that of the host star, it likely has a larger core size relative to the Earth despite this producing a planet with a Si/Mg abundance ratio ∼34% greater than the Sun. The derived planetary parameters - insolation flux (S Earth = 1.79 ±0.26) and equilibrium temperature (T eq = 294 ±10 K) - support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone. (Less)
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stellar and planetary characterization of the ross 128 exoplanetary system from apogee spectra
arXiv: Solar and Stellar Astrophysics, 2018Co-Authors: Diogo Souto, Katia Cunha, Verne V. Smith, D A Garciahernandez, Cayman T Unterborn, Johanna K Teske, Kevin R Covey, Barbara Rojasayala, Keivan G StassunAbstract:The first detailed chemical abundance analysis of the M dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5--1.7 \micron) high-resolution ($R$$\sim$22,500) spectra from the SDSS-APOGEE survey. We determined precise atmospheric parameters $T_{\rm eff}$=3231$\pm$100K, log$g$=4.96$\pm$0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03$\pm$0.09 dex). The derived results were obtained via spectral synthesis (1-D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicate that it lies below the pure rock Composition Curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a sub-solar Si/Mg ratio, and assuming the planet's Composition matches that of the host-star, it likely has a larger core size relative to the Earth. The derived planetary parameters -- insolation flux (S$_{\rm Earth}$=1.79$\pm$0.26) and equilibrium temperature ($T_{\rm eq}$=294$\pm$10K) -- support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone.