The Experts below are selected from a list of 79647 Experts worldwide ranked by ideXlab platform
Nuh Gedik - One of the best experts on this subject based on the ideXlab platform.
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measurement of intrinsic dirac fermion cooling on the surface of the topological insulator bi 2 se 3 using time resolved and angle resolved photoemission spectroscopy
Physical Review Letters, 2012Co-Authors: Yang Wang, D Hsieh, Edbert J Sie, Hadar Steinberg, Dillon Gardner, Y S Lee, Pablo Jarilloherrero, Nuh GedikAbstract:We perform time- and angle-resolved photoemission spectroscopy of a prototypical topological insulator (TI) Bi_2Se_3 to study the ultrafast dynamics of surface and bulk electrons after photoexcitation. By analyzing the evolution of surface states and bulk band spectra, we obtain their electronic Temperature and chemical potential relaxation dynamics separately. These dynamics reveal strong phonon-assisted surface-bulk coupling at high lattice Temperature and total suppression of inelastic scattering between the surface and the bulk at low lattice Temperature. In this low Temperature regime, the unique cooling of Dirac fermions in TI by acoustic phonons is manifested through a power law dependence of the surface Temperature Decay rate on carrier density.
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measurement of intrinsic dirac fermion cooling on the surface of the topological insulator bi2se3 using time resolved and angle resolved photoemission spectroscopy
Physical Review Letters, 2012Co-Authors: D Hsieh, Edbert J Sie, Hadar Steinberg, Dillon Gardner, Y S Lee, Pablo Jarilloherrero, Yihua Wang, Nuh GedikAbstract:We perform time- and angle-resolved photoemission spectroscopy of a prototypical topological insulator (TI) Bi_2Se_3 to study the ultrafast dynamics of surface and bulk electrons after photoexcitation. By analyzing the evolution of surface states and bulk band spectra, we obtain their electronic Temperature and chemical potential relaxation dynamics separately. These dynamics reveal strong phonon-assisted surface-bulk coupling at high lattice Temperature and total suppression of inelastic scattering between the surface and the bulk at low lattice Temperature. In this low Temperature regime, the unique cooling of Dirac fermions in TI by acoustic phonons is manifested through a power law dependence of the surface Temperature Decay rate on carrier density.
Yihua Wang - One of the best experts on this subject based on the ideXlab platform.
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measurement of intrinsic dirac fermion cooling on the surface of the topological insulator bi2se3 using time resolved and angle resolved photoemission spectroscopy
Physical Review Letters, 2012Co-Authors: D Hsieh, Edbert J Sie, Hadar Steinberg, Dillon Gardner, Y S Lee, Pablo Jarilloherrero, Yihua Wang, Nuh GedikAbstract:We perform time- and angle-resolved photoemission spectroscopy of a prototypical topological insulator (TI) Bi_2Se_3 to study the ultrafast dynamics of surface and bulk electrons after photoexcitation. By analyzing the evolution of surface states and bulk band spectra, we obtain their electronic Temperature and chemical potential relaxation dynamics separately. These dynamics reveal strong phonon-assisted surface-bulk coupling at high lattice Temperature and total suppression of inelastic scattering between the surface and the bulk at low lattice Temperature. In this low Temperature regime, the unique cooling of Dirac fermions in TI by acoustic phonons is manifested through a power law dependence of the surface Temperature Decay rate on carrier density.
Yang Wang - One of the best experts on this subject based on the ideXlab platform.
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measurement of intrinsic dirac fermion cooling on the surface of the topological insulator bi 2 se 3 using time resolved and angle resolved photoemission spectroscopy
Physical Review Letters, 2012Co-Authors: Yang Wang, D Hsieh, Edbert J Sie, Hadar Steinberg, Dillon Gardner, Y S Lee, Pablo Jarilloherrero, Nuh GedikAbstract:We perform time- and angle-resolved photoemission spectroscopy of a prototypical topological insulator (TI) Bi_2Se_3 to study the ultrafast dynamics of surface and bulk electrons after photoexcitation. By analyzing the evolution of surface states and bulk band spectra, we obtain their electronic Temperature and chemical potential relaxation dynamics separately. These dynamics reveal strong phonon-assisted surface-bulk coupling at high lattice Temperature and total suppression of inelastic scattering between the surface and the bulk at low lattice Temperature. In this low Temperature regime, the unique cooling of Dirac fermions in TI by acoustic phonons is manifested through a power law dependence of the surface Temperature Decay rate on carrier density.
Fei Tang - One of the best experts on this subject based on the ideXlab platform.
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studies on ceiling maximum thermal smoke Temperature and longitudinal Decay in a tunnel fire with different transverse gas burner locations
Applied Thermal Engineering, 2017Co-Authors: Fei Tang, Lianjian Li, Wenkang Chen, Zhi ZhanAbstract:Abstract A series of experiments are conducted to analyze and discuss ceiling maximum thermal smoke Temperature and longitudinal Decay along the centerline of the tunnel with different transverse fire source locations. The size of scale model tunnel is 72 m (length) × 1.5 m (width) × 1.3 m (height). Three transverse gas burner locations were considered, such as Location A (close to the wall), Location B (near the wall), Location C (centerline of the tunnel), the corresponding distance between the centerline of the gas burner and the tunnel wall are 0.2 m, 0.475 m and 0.75 m, respectively. It was found that Li model underestimates the maximum thermal smoke Temperature beneath the ceiling with different transverse fire source locations. Thus a dimensionless coefficient λ is put forward to consider the effect of different horizontal fire source location on thermal smoke Temperature profile. The predictions by the modified model of this work agree well with the measured data in the maximum thermal smoke considering different transverse fire source locations. The revised thermal smoke Temperature Decay formula along the centerline of the tunnel is introduced, and the deduced values of coefficient K c down are correlated linearly with transverse fire location.
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longitudinal distributions of co concentration and Temperature in buoyant tunnel fire smoke flow in a reduced pressure atmosphere with lower air entrainment at high altitude
International Journal of Heat and Mass Transfer, 2014Co-Authors: Lizhong Yang, Longhua Hu, Fei Tang, Xiaochun ZhangAbstract:Abstract Smoke Temperature and CO (carbon monoxide) concentration are two most important parameters concerning human safety in case of a tunnel fire. Their longitudinal distributions in the smoke flow along the tunnel are both closely related to fresh air entrainment from the surroundings; meanwhile heat loss process also contributes to the Temperature Decay but not to the CO concentration dilution at the same time. However, previous researches are all considering in default the condition with normal pressure, which is needed to be extended for condition at reduced pressure atmosphere such as at high altitude (for example, Tibet). This paper reports new findings for the distributions of these two parameters in a reduced pressure atmosphere with lower air density and thus lower air entrainment. The longitudinal distributions of smoke flow Temperature and CO concentration for a tunnel fire near sea level (1 atm) and at high altitude (0.64 atm) have been correspondingly computed and compared by Fire Dynamics Simulator (FDS). It is found that the longitudinal Decay profiles of CO concentration are similar in these two pressures, as both the air entrainment mass flow rate during the smoke flow traveling (contributing to the dilution) and the air entrainment of the fire plume (dominating the initial mass flow rate of the smoke flow) are proportional to ambient pressure thus their ratio is independent of pressure. However, the longitudinal Decay of the smoke flow Temperature is faster with distance along the tunnel in the reduced pressure atmosphere, as the air entrainment of the fire plume (dominating the initial mass flow rate of the smoke flow) is lower in the reduced pressure atmosphere, meanwhile the heat loss term is independent of pressure giving their ratio (heat loss to initial mass flow rate) is larger in the reduce pressure. Therefore, the difference between normalized longitudinal profiles of CO concentration and smoke Temperature in a tunnel fire is larger, as indicated by a higher λ coefficient value, in the reduced pressure atmosphere at higher altitude than that in the normal pressure atmosphere, although their values of λ for both these two atmospheric pressure can be well correlated by a reciprocal function with longitudinal air flow speed.
Jie Wang - One of the best experts on this subject based on the ideXlab platform.
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experiment investigation on the influence of low pressure on ceiling Temperature profile in aircraft cargo compartment fires
Applied Thermal Engineering, 2015Co-Authors: Jie Wang, Yu Guan, Heping ZhangAbstract:Abstract The objective of the present study is to evaluate the low pressure effects on ceiling Temperature profile in aircraft cargo compartment fires, which will affect the activation of fire detectors. A Series of fire tests were carried out in a full scale simulated aircraft cargo compartment at four atmospheric pressures (100 kPa, 90 kPa, 80 kPa and 70 kPa) corresponding to the pressure within an actual aircraft cargo compartment from the sea level to the cruising altitude (about 10,000 m). Results show that the maximum ceiling Temperature increases and the ceiling Temperature Decays faster as ambient pressure reduces. The air entrainment ratio Cα is proposed in the correlation to predict the maximum ceiling Temperature based on previous plume theory, considering the low pressure effect and entrainment coefficient. Meanwhile, modified by the air entrainment ratio Cα, the previous classic correlations established by Alpert, Heskestad and Delichatsios for the ceiling Temperature Decay profile are further extended to low pressure conditions. The results based on Heskestad and Delichatsios method are more accurate than that of Alpert method in the experiments. All these findings would provide theoretical basis for the design of fire detection system in the aircraft cargo compartment.
