The Experts below are selected from a list of 68727 Experts worldwide ranked by ideXlab platform
Shihyuin Lin - One of the best experts on this subject based on the ideXlab platform.
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fluctuation dissipation and correlation propagation relations from the nonEquilibrium dynamics of detector quantum field systems
Physical Review D, 2019Co-Authors: Jen Tsung Hsiang, Shihyuin LinAbstract:We consider $N$ uniformly-accelerating Unruh-DeWitt detectors whose internal degrees of freedom are coupled to a massless scalar field in $(1+1)$D Minkowski space. We use the influence functional formalism to derive the Langevin equations governing the nonEquilibrium dynamics of the internal degrees of freedom and show explicitly that the system relaxes in time and equilibrates. We also show that once the Equilibrium Condition is established a set of fluctuation-dissipation relations (FDR) and correlation-propagation relations (CPR) emerges for the detectors, extending earlier results of [1] which discovered these relations for the quantum field. Although similar in form to the FDRs commonly known from linear response theory, which assumes an Equilibrium Condition a priori, their physical connotations are dissimilar from that of a nonEquilibrium origin. We show explicitly that both sets of relations are needed to guarantee the balance of energy flow in and out of the system in dynamical Equilibrium with the field. These results are helpful to investigations of quantum information and communications of detectors in space experiments and inquiries of theoretical issues in black holes and cosmology.
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fluctuation dissipation and correlation propagation relations from the nonEquilibrium dynamics of detector quantum field systems
Physical Review D, 2019Co-Authors: Jen Tsung Hsiang, Shihyuin LinAbstract:We consider $N$ uniformly accelerating Unruh-DeWitt detectors whose internal degrees of freedom are coupled to a massless scalar field in $(1+1)\mathrm{D}$ Minkowski space. We use the influence functional formalism to derive the Langevin equations governing the nonEquilibrium dynamics of the internal degrees of freedom and show explicitly that the system relaxes in time and equilibrates. We also show that once the Equilibrium Condition is established a set of fluctuation-dissipation relations (FDRs) and correlation-propagation relations emerges for the detectors, extending earlier results of Raval, Hu, and Anglin [Stochastic theory of accelerated detectors in quantum fields, Phys. Rev. D 53, 7003 (1996)] which discovered these relations for the quantum field. Although similar in form to the FDRs commonly known from linear response theory, which assumes an Equilibrium Condition a priori, their physical connotations are dissimilar from that of a nonEquilibrium origin. We show explicitly that both sets of relations are needed to guarantee the balance of energy flow in and out of the system in dynamical Equilibrium with the field. These results are helpful to investigations of quantum information and communications of detectors in space experiments and inquiries of theoretical issues in black holes and cosmology.
Keyong Wang - One of the best experts on this subject based on the ideXlab platform.
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forced convection gaseous slip flow in a porous circular microtube an exact solution
International Journal of Thermal Sciences, 2015Co-Authors: Fatmeh Tavakkoli, Keyong Wang, Shujuan Wang, Kambiz VafaiAbstract:Rarefied phenomena can occur when a gas flows through a microchannel. However, most available convective solutions were obtained under the local thermal Equilibrium Condition. In this study, gaseous slip flow in a circular microtube filled with a porous medium is analytically investigated under the local thermal non-Equilibrium Condition. The first-order velocity slip and temperature jump Conditions at the tube wall are invoked in order to account for the rarefaction effects. Rigorous analytical solutions are obtained for the velocity and temperature distributions as well as the average Nusselt number. Theoretical predictions are then compared to those of existing limiting cases in the literature. Results indicate that the degree of rarefaction, represented by the Knudsen number ranging from 10−3 to 10−1, has a significant effect on the velocity, temperature, pressure drop and heat transport within the microtube for various combinations of pertinent parameters such as the porosity, effective thermal conductivity ratio, Biot number and porous media shape factor.
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analysis of gaseous slip flow in a porous micro annulus under local thermal non Equilibrium Condition an exact solution
International Journal of Heat and Mass Transfer, 2015Co-Authors: Fatemeh Tavakkoli, Keyong Wang, Kambiz VafaiAbstract:Abstract The phenomenon of rarefaction in a micro-annulus filled with a porous medium is analyzed in the slip-flow regime. A local thermal non-Equilibrium (LTNE) model is utilized to represent the energy transport within the porous medium. Exact solutions are derived for both the fluid and solid temperature distributions within the annulus. Two distinct cases of the thermal boundary Conditions are considered, namely a constant heat flux at the outer wall and adiabatic inner wall (Case I) and vice versa (Case II). By eliminating the temperature difference between the fluid and solid phases, the local thermal Equilibrium (LTE) model is theoretically proved to be a special case of the LTNE counterpart. Analytical predictions indicate that although the rarefaction leads to a reduction in the heat transfer, the effects of other thermophysical parameters such as the Biot number, the effective thermal conductivity ratio, the porous media shape factor and the annulus aspect ratio also play an important role. The results suggest that the configuration of Case II is superior to that of Case I from the heat transfer point of view.
Monty A Hampton - One of the best experts on this subject based on the ideXlab platform.
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characteristics and dynamics of a large sub tidal sand wave field habitat for pacific sand lance ammodytes personatus salish sea washington usa
Geosciences, 2017Co-Authors: Gary H Greene, David A Cacchione, Monty A HamptonAbstract:Deep-water sand wave fields in the San Juan Archipelago of the Salish Sea and Pacific Northwest Washington, USA, have been found to harbor Pacific sand lance (PSL, Ammodytes personatus), a critical forage fish of the region. Little is known of the dynamics of these sand waves and the stability of the PSL sub-tidal habitats. Therefore, we have undertaken an initial investigation to determine the dynamic Conditions of a well-known PSL habitat in the San Juan Channel within the Archipelago using bottom sediment sampling, an acoustical doppler current profiling (ADCP) system, and multi-beam echo sounder (MBES) bathymetry. Our study indicates that the San Juan Channel sand wave field maintained its shape and bedforms geometry throughout the years it has been studied. Based on bed phase diagrams for channelized bedforms, the sand waves appear to be in a dynamic Equilibrium Condition. Sea level rise may change the current regime within the Archipelago and may alter some of the deep-water or sub-tidal PSL habitats mapped there. Our findings have global significance in that these dynamic bedforms that harbor PSL and sand-eels elsewhere along the west coast of North America and in the North Sea may also be in a marginally dynamic Equilibrium Condition and may be prone to alteration by sea level rise, indicating an urgency in locating and investigating these habitats in order to sustain the forage fish.
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Characteristics and Dynamics of a Large Sub-Tidal Sand Wave Field—Habitat for Pacific Sand Lance (Ammodytes personatus), Salish Sea, Washington, USA
MDPI AG, 2017Co-Authors: Gary H Greene, David A Cacchione, Monty A HamptonAbstract:Deep-water sand wave fields in the San Juan Archipelago of the Salish Sea and Pacific Northwest Washington, USA, have been found to harbor Pacific sand lance (PSL, Ammodytes personatus), a critical forage fish of the region. Little is known of the dynamics of these sand waves and the stability of the PSL sub-tidal habitats. Therefore, we have undertaken an initial investigation to determine the dynamic Conditions of a well-known PSL habitat in the San Juan Channel within the Archipelago using bottom sediment sampling, an acoustical doppler current profiling (ADCP) system, and multi-beam echo sounder (MBES) bathymetry. Our study indicates that the San Juan Channel sand wave field maintained its shape and bedforms geometry throughout the years it has been studied. Based on bed phase diagrams for channelized bedforms, the sand waves appear to be in a dynamic Equilibrium Condition. Sea level rise may change the current regime within the Archipelago and may alter some of the deep-water or sub-tidal PSL habitats mapped there. Our findings have global significance in that these dynamic bedforms that harbor PSL and sand-eels elsewhere along the west coast of North America and in the North Sea may also be in a marginally dynamic Equilibrium Condition and may be prone to alteration by sea level rise, indicating an urgency in locating and investigating these habitats in order to sustain the forage fish
Jen Tsung Hsiang - One of the best experts on this subject based on the ideXlab platform.
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fluctuation dissipation and correlation propagation relations from the nonEquilibrium dynamics of detector quantum field systems
Physical Review D, 2019Co-Authors: Jen Tsung Hsiang, Shihyuin LinAbstract:We consider $N$ uniformly-accelerating Unruh-DeWitt detectors whose internal degrees of freedom are coupled to a massless scalar field in $(1+1)$D Minkowski space. We use the influence functional formalism to derive the Langevin equations governing the nonEquilibrium dynamics of the internal degrees of freedom and show explicitly that the system relaxes in time and equilibrates. We also show that once the Equilibrium Condition is established a set of fluctuation-dissipation relations (FDR) and correlation-propagation relations (CPR) emerges for the detectors, extending earlier results of [1] which discovered these relations for the quantum field. Although similar in form to the FDRs commonly known from linear response theory, which assumes an Equilibrium Condition a priori, their physical connotations are dissimilar from that of a nonEquilibrium origin. We show explicitly that both sets of relations are needed to guarantee the balance of energy flow in and out of the system in dynamical Equilibrium with the field. These results are helpful to investigations of quantum information and communications of detectors in space experiments and inquiries of theoretical issues in black holes and cosmology.
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fluctuation dissipation and correlation propagation relations from the nonEquilibrium dynamics of detector quantum field systems
Physical Review D, 2019Co-Authors: Jen Tsung Hsiang, Shihyuin LinAbstract:We consider $N$ uniformly accelerating Unruh-DeWitt detectors whose internal degrees of freedom are coupled to a massless scalar field in $(1+1)\mathrm{D}$ Minkowski space. We use the influence functional formalism to derive the Langevin equations governing the nonEquilibrium dynamics of the internal degrees of freedom and show explicitly that the system relaxes in time and equilibrates. We also show that once the Equilibrium Condition is established a set of fluctuation-dissipation relations (FDRs) and correlation-propagation relations emerges for the detectors, extending earlier results of Raval, Hu, and Anglin [Stochastic theory of accelerated detectors in quantum fields, Phys. Rev. D 53, 7003 (1996)] which discovered these relations for the quantum field. Although similar in form to the FDRs commonly known from linear response theory, which assumes an Equilibrium Condition a priori, their physical connotations are dissimilar from that of a nonEquilibrium origin. We show explicitly that both sets of relations are needed to guarantee the balance of energy flow in and out of the system in dynamical Equilibrium with the field. These results are helpful to investigations of quantum information and communications of detectors in space experiments and inquiries of theoretical issues in black holes and cosmology.
Kambiz Vafai - One of the best experts on this subject based on the ideXlab platform.
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forced convection gaseous slip flow in a porous circular microtube an exact solution
International Journal of Thermal Sciences, 2015Co-Authors: Fatmeh Tavakkoli, Keyong Wang, Shujuan Wang, Kambiz VafaiAbstract:Rarefied phenomena can occur when a gas flows through a microchannel. However, most available convective solutions were obtained under the local thermal Equilibrium Condition. In this study, gaseous slip flow in a circular microtube filled with a porous medium is analytically investigated under the local thermal non-Equilibrium Condition. The first-order velocity slip and temperature jump Conditions at the tube wall are invoked in order to account for the rarefaction effects. Rigorous analytical solutions are obtained for the velocity and temperature distributions as well as the average Nusselt number. Theoretical predictions are then compared to those of existing limiting cases in the literature. Results indicate that the degree of rarefaction, represented by the Knudsen number ranging from 10−3 to 10−1, has a significant effect on the velocity, temperature, pressure drop and heat transport within the microtube for various combinations of pertinent parameters such as the porosity, effective thermal conductivity ratio, Biot number and porous media shape factor.
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analysis of gaseous slip flow in a porous micro annulus under local thermal non Equilibrium Condition an exact solution
International Journal of Heat and Mass Transfer, 2015Co-Authors: Fatemeh Tavakkoli, Keyong Wang, Kambiz VafaiAbstract:Abstract The phenomenon of rarefaction in a micro-annulus filled with a porous medium is analyzed in the slip-flow regime. A local thermal non-Equilibrium (LTNE) model is utilized to represent the energy transport within the porous medium. Exact solutions are derived for both the fluid and solid temperature distributions within the annulus. Two distinct cases of the thermal boundary Conditions are considered, namely a constant heat flux at the outer wall and adiabatic inner wall (Case I) and vice versa (Case II). By eliminating the temperature difference between the fluid and solid phases, the local thermal Equilibrium (LTE) model is theoretically proved to be a special case of the LTNE counterpart. Analytical predictions indicate that although the rarefaction leads to a reduction in the heat transfer, the effects of other thermophysical parameters such as the Biot number, the effective thermal conductivity ratio, the porous media shape factor and the annulus aspect ratio also play an important role. The results suggest that the configuration of Case II is superior to that of Case I from the heat transfer point of view.
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analysis of collimated irradiation under local thermal non Equilibrium Condition in a packed bed
International Journal of Heat and Mass Transfer, 2015Co-Authors: P Wang, Kambiz Vafai, C XuAbstract:Abstract Forced convective heat transfer in a packed bed in the presence of collimated irradiation and under local thermal non-Equilibrium is analyzed in this work. Both the collimated and diffusive radiative transfer processes are accounted for using the modified P-1 approximation. Two boundary Condition models considering different limiting Conditions at the wall which couple radiation and convection under LTNE were constructed. The effect of pertinent parameters such as the porosity φ, pore diameter dp, ratio of the solid to fluid thermal conductivities ζ; radiative properties including optical thickness τ, scattering albedo ω, and the wall emittance ɛw were analyzed. Also, their effects on the temperature and heat flux distributions in the incident direction were analyzed systematically and the limiting interactions between thermal radiation and conduction were revealed. The differences between the two boundary models with the effects of the cited parameters were analyzed. Our analysis demonstrated that an increase in either φ or dp enhances the transfer of radiative energy into the channel.