The Experts below are selected from a list of 9222 Experts worldwide ranked by ideXlab platform
Lisa H Wei - One of the best experts on this subject based on the ideXlab platform.
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the state of the warm and Cold gas in the extreme starburst at the core of the phoenix galaxy cluster spt clj2344 4243
The Astrophysical Journal, 2014Co-Authors: Michael Mcdonald, Mark Swinbank, A C Edge, David J Wilner, Sylvain Veilleux, B A Benson, M T Hogan, D P Marrone, B R Mcnamara, Lisa H WeiAbstract:We present new optical integral field spectroscopy (Gemini South) and submillimeter spectroscopy (Submillimeter Array) of the central galaxy in the Phoenix cluster (SPT-CLJ2344-4243). This cluster was previously reported to have a massive starburst (~800 M ☉ yr–1) in the central, brightest cluster galaxy, most likely fueled by the rapidly cooling intracluster medium. These new data reveal a complex emission-line nebula, extending for >30 kpc from the central galaxy, detected at [O II]λλ3726, 3729, [O III]λλ4959, 5007, Hβ, Hγ, Hδ, [Ne III]λ3869, and He II λ4686. The total Hα luminosity, assuming Hα/Hβ = 2.85, is L Hα = 7.6 ± 0.4 ×1043 erg s–1, making this the most luminous emission-line nebula detected in the center of a cool core cluster. Overall, the relative fluxes of the low-ionization lines (e.g., [O II], Hβ) to the UV continuum are consistent with photoionization by young stars. In both the center of the galaxy and in a newly discovered highly ionized plume to the north of the galaxy, the ionization ratios are consistent with both shocks and active galactic nucleus (AGN) photoionization. We speculate that this extended plume may be a galactic wind, driven and partially photoionized by both the starburst and central AGN. Throughout the cluster we measure elevated high-ionization line ratios (e.g., He II/Hβ, [O III]/Hβ), coupled with an overall high-velocity width (FWHM gsim 500 km s–1), suggesting that shocks are likely important throughout the interstellar medium of the central galaxy. These shocks are most likely driven by a combination of stellar winds from massive young stars, core-collapse supernovae, and the central AGN. In addition to the warm, ionized gas, we detect a substantial amount of Cold, molecular gas via the CO(3-2) transition, coincident in position with the galaxy center. We infer a molecular gas mass of $M_{{\rm H_2}}$ = 2.2 ± 0.6 × 1010 M ☉, which implies that the starburst will consume its fuel in ~30 Myr if it is not replenished. The L IR/$M_{{\rm H_2}}$ that we measure for this cluster is consistent with the starburst limit of 500 L ☉/M ☉, above which radiation pressure is able to disperse the Cold Reservoir. The combination of the high level of turbulence in the warm phase and the high L IR/$M_{{\rm H_2}}$ ratio suggests that this violent starburst may be in the process of quenching itself. We propose that phases of rapid star formation may be common in the cores of galaxy clusters, but so short-lived that their signatures are quickly erased and appear only in a subsample of the most strongly cooling clusters.
Xuejiao Hu - One of the best experts on this subject based on the ideXlab platform.
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Thermal-driven flow inside graphene channels for water desalination
2D Materials, 2019Co-Authors: Bo Chen, Kang Liu, Haifeng Jiang, Huidong Liu, Xiang Liu, Xuejiao HuAbstract:A novel concept of membrane process in a thermal-driven system is proposed for water desalination. By means of molecular dynamics simulations, we show fast water transport through graphene galleries at a temperature gradient. Water molecules are driven to migrate through nanometer-wide graphene channels from Cold Reservoir to hot Reservoir by the effect of thermal creep flow. Reducing the interlayer spacing to 6.5 A, an abrupt escalation occurs in water permeation between angstrom-distance graphene slabs. A change from disordered bulklike water to quasi-square structure has been found under this extremely confined condition. This leads to a transition to subcontinuum transport. Water molecules perform collective diffusion behaviors inside graphene channels. The special transport processes with structure change convert thermal energy into motion without dissipation, resulting in unexpectedly high water permeability. The thermal-driven system reaches maximum flowrate at temperature variance of 80 K, corresponding to the quantity at pressure difference up to 105 bar in commercial reverse osmosis processes and 230 bar in pressure-driven slip flow. Our results also reveal the movement of saline ions influenced by thermophoretic effect, which complements the geometry limitation at greater layer spacing, enhancing the blockage of ions. This finding aims to provide an innovational idea of developing a high-efficiency desalination technology able to utilize various forms of energy.
Jianhui Wang - One of the best experts on this subject based on the ideXlab platform.
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efficiency at maximum power output of quantum heat engines under finite time operation
Physical Review E, 2012Co-Authors: Jianhui WangAbstract:We study the efficiency at maximum power, ${\ensuremath{\eta}}_{m}$, of irreversible quantum Carnot engines (QCEs) that perform finite-time cycles between a hot and a Cold Reservoir at temperatures ${T}_{h}$ and ${T}_{c}$, respectively. For QCEs in the reversible limit (long cycle period, zero dissipation), ${\ensuremath{\eta}}_{m}$ becomes identical to the Carnot efficiency ${\ensuremath{\eta}}_{{}_{C}}=1\ensuremath{-}{T}_{c}/{T}_{h}$. For QCE cycles in which nonadiabatic dissipation and the time spent on two adiabats are included, the efficiency ${\ensuremath{\eta}}_{m}$ at maximum power output is bounded from above by ${\ensuremath{\eta}}_{{}_{C}}/(2\ensuremath{-}{\ensuremath{\eta}}_{{}_{C}})$ and from below by ${\ensuremath{\eta}}_{{}_{C}}/2$. In the case of symmetric dissipation, the Curzon-Ahlborn efficiency ${\ensuremath{\eta}}_{{}_{\mathit{CA}}}=1\ensuremath{-}\sqrt{{T}_{c}/{T}_{h}}$ is recovered under the condition that the time allocation between the adiabats and the contact time with the Reservoir satisfy a certain relation.
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efficiency at maximum power output of quantum heat engines under finite time operation
Physical Review E, 2012Co-Authors: Jianhui Wang, Jizhou He, Zhaoqi WuAbstract:: We study the efficiency at maximum power, η(m), of irreversible quantum Carnot engines (QCEs) that perform finite-time cycles between a hot and a Cold Reservoir at temperatures T(h) and T(c), respectively. For QCEs in the reversible limit (long cycle period, zero dissipation), η(m) becomes identical to the Carnot efficiency η(C)=1-T(c)/T(h). For QCE cycles in which nonadiabatic dissipation and the time spent on two adiabats are included, the efficiency η(m) at maximum power output is bounded from above by η(C)/(2-η(C)) and from below by η(C)/2. In the case of symmetric dissipation, the Curzon-Ahlborn efficiency η(CA)=1-√(T(c)/T(h)) is recovered under the condition that the time allocation between the adiabats and the contact time with the Reservoir satisfy a certain relation.
Bo Chen - One of the best experts on this subject based on the ideXlab platform.
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Thermal-driven flow inside graphene channels for water desalination
2D Materials, 2019Co-Authors: Bo Chen, Kang Liu, Haifeng Jiang, Huidong Liu, Xiang Liu, Xuejiao HuAbstract:A novel concept of membrane process in a thermal-driven system is proposed for water desalination. By means of molecular dynamics simulations, we show fast water transport through graphene galleries at a temperature gradient. Water molecules are driven to migrate through nanometer-wide graphene channels from Cold Reservoir to hot Reservoir by the effect of thermal creep flow. Reducing the interlayer spacing to 6.5 A, an abrupt escalation occurs in water permeation between angstrom-distance graphene slabs. A change from disordered bulklike water to quasi-square structure has been found under this extremely confined condition. This leads to a transition to subcontinuum transport. Water molecules perform collective diffusion behaviors inside graphene channels. The special transport processes with structure change convert thermal energy into motion without dissipation, resulting in unexpectedly high water permeability. The thermal-driven system reaches maximum flowrate at temperature variance of 80 K, corresponding to the quantity at pressure difference up to 105 bar in commercial reverse osmosis processes and 230 bar in pressure-driven slip flow. Our results also reveal the movement of saline ions influenced by thermophoretic effect, which complements the geometry limitation at greater layer spacing, enhancing the blockage of ions. This finding aims to provide an innovational idea of developing a high-efficiency desalination technology able to utilize various forms of energy.
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thermal driven flow inside graphene channels for water desalination
arXiv: Soft Condensed Matter, 2018Co-Authors: Bo Chen, Kang Liu, Haifeng Jiang, Huidong Liu, Xiang LiuAbstract:A novel concept of membrane process in thermal-driven system is proposed for water desalination. By means of molecular dynamics simulations, we show fast water transport through graphene galleries at a temperature gradient. Water molecules are driven to migrate through nanometer-wide graphene channels from Cold Reservoir to hot Reservoir by the effect of thermal creep flow. Reducing the interlayer spacing to 6.5 {\AA}, an abrupt escalation occurs in water permeation between angstrom-distance graphene slabs. The change from disordered bulklike water to quasi-square structure have been found under this extremely confined condition. This leads to a transition to subcontinuum transport. Water molecules perform collective diffusion behaviors inside graphene channels. The special transport processes with structure change convert thermal energy into motion without dissipation, resulting in unexpected high water permeability. The thermal-driven system reaches maximum flowrate at temperature variance of 80 K, corresponding to the quantity at pressure difference up to 10^5 bar in commercial reverse osmosis processes and 230 bar in pressure-driven slip flow. Our results also reveal the movement of saline ions influenced by thermophoretic effect, which complement the geometry limitation at greater layer spacing, enhancing the blockage of ions. This finding aims to provide an innovational idea of developing a high-efficiency desalination technology able to utilize various forms of energy.
Michael Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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the state of the warm and Cold gas in the extreme starburst at the core of the phoenix galaxy cluster spt clj2344 4243
The Astrophysical Journal, 2014Co-Authors: Michael Mcdonald, Mark Swinbank, A C Edge, David J Wilner, Sylvain Veilleux, B A Benson, M T Hogan, D P Marrone, B R Mcnamara, Lisa H WeiAbstract:We present new optical integral field spectroscopy (Gemini South) and submillimeter spectroscopy (Submillimeter Array) of the central galaxy in the Phoenix cluster (SPT-CLJ2344-4243). This cluster was previously reported to have a massive starburst (~800 M ☉ yr–1) in the central, brightest cluster galaxy, most likely fueled by the rapidly cooling intracluster medium. These new data reveal a complex emission-line nebula, extending for >30 kpc from the central galaxy, detected at [O II]λλ3726, 3729, [O III]λλ4959, 5007, Hβ, Hγ, Hδ, [Ne III]λ3869, and He II λ4686. The total Hα luminosity, assuming Hα/Hβ = 2.85, is L Hα = 7.6 ± 0.4 ×1043 erg s–1, making this the most luminous emission-line nebula detected in the center of a cool core cluster. Overall, the relative fluxes of the low-ionization lines (e.g., [O II], Hβ) to the UV continuum are consistent with photoionization by young stars. In both the center of the galaxy and in a newly discovered highly ionized plume to the north of the galaxy, the ionization ratios are consistent with both shocks and active galactic nucleus (AGN) photoionization. We speculate that this extended plume may be a galactic wind, driven and partially photoionized by both the starburst and central AGN. Throughout the cluster we measure elevated high-ionization line ratios (e.g., He II/Hβ, [O III]/Hβ), coupled with an overall high-velocity width (FWHM gsim 500 km s–1), suggesting that shocks are likely important throughout the interstellar medium of the central galaxy. These shocks are most likely driven by a combination of stellar winds from massive young stars, core-collapse supernovae, and the central AGN. In addition to the warm, ionized gas, we detect a substantial amount of Cold, molecular gas via the CO(3-2) transition, coincident in position with the galaxy center. We infer a molecular gas mass of $M_{{\rm H_2}}$ = 2.2 ± 0.6 × 1010 M ☉, which implies that the starburst will consume its fuel in ~30 Myr if it is not replenished. The L IR/$M_{{\rm H_2}}$ that we measure for this cluster is consistent with the starburst limit of 500 L ☉/M ☉, above which radiation pressure is able to disperse the Cold Reservoir. The combination of the high level of turbulence in the warm phase and the high L IR/$M_{{\rm H_2}}$ ratio suggests that this violent starburst may be in the process of quenching itself. We propose that phases of rapid star formation may be common in the cores of galaxy clusters, but so short-lived that their signatures are quickly erased and appear only in a subsample of the most strongly cooling clusters.