Energy dissipation is of fundamental interest and crucial importance in quantum systems. However,whether energy dissipation can emerge without backscattering inside topological systems remains a question. As a hallmar...Energy dissipation is of fundamental interest and crucial importance in quantum systems. However,whether energy dissipation can emerge without backscattering inside topological systems remains a question. As a hallmark, we propose a microscopic picture that illustrates energy dissipation in the quantum Hall(QH) plateau regime of graphene. Despite the quantization of Hall, longitudinal, and two-probe resistances(dubbed as the quantum limit), we find that the energy dissipation emerges in the form of Joule heat. It is demonstrated that the non-equilibrium energy distribution of carriers plays much more essential roles than the resistance on energy dissipation. Eventually, we suggest probing the phenomenon by measuring local temperature increases in experiments and reconsidering the dissipation typically ignored in realistic topological circuits.展开更多
Friction stir welding （FSW） is a solid-state joining process, where joint properties largely depend on the amount of heat generation during the welding process. The objective of this paper was to develop a numerical...Friction stir welding （FSW） is a solid-state joining process, where joint properties largely depend on the amount of heat generation during the welding process. The objective of this paper was to develop a numerical thermomechanical model for FSW of aluminum--copper alloy AA2219 and analyze heat generation during the welding process. The thermomechanical model has been developed utilizing ANSYS APDL. The model was verified by comparing simulated temperature profile of three different weld schedules （i.e., different combinations of weld parameters in real weld situations） from simulation with experimental results. Furthermore, the verified model was used to analyze the effect of different weld parameters on heat generation. Among all the weld parameters, the effect of rotational speed on heat generation is the highest.展开更多
In this paper, flume experiments are focused on sediment transport inside and outside the surf zone. According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissi...In this paper, flume experiments are focused on sediment transport inside and outside the surf zone. According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump, formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves. Assuming that the sediment diffusion coefficient, which is related with energy dissipation, is proportional to water depth, formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves, and the prediction shows a good agreement with the measurement.展开更多
Compared with general trapeziform plunge pools, an arciform plunge pool has its advantages, e.g. less excavate quantity, higher stability, etc. In this paper, the hydrodynamic pressure distribution on the soleplate of...Compared with general trapeziform plunge pools, an arciform plunge pool has its advantages, e.g. less excavate quantity, higher stability, etc. In this paper, the hydrodynamic pressure distribution on the soleplate of the arciform plunge pool is measured under a relatively dangerous condition of operation. The result is helpful to the design of the arciform plunge pool. The result also shows that the difference between the maximum and the minimum pressures on the upward surface of the soleplate may cause an additional uplift force on the soleplate under certain condition and should be taken into consideration in the uplift force calculation of the soleplate. The scour experiment verifies the higher stability of the arciform plunge pool.展开更多
This paper reported the diurnal variations of photochemical efficiency of PSII, thermaldissipation rate and other physiology process in the low content chlorophyll mutant rice andits wild type under field conditions, ...This paper reported the diurnal variations of photochemical efficiency of PSII, thermaldissipation rate and other physiology process in the low content chlorophyll mutant rice andits wild type under field conditions, and analyzed the difference of absorbed light distributionbetween the two rice varieties in a day. The results showed that the mutant had poor absorbedlight because of its little light absorption coefficient, but higher electron transportg ratecould partly reduce the disadvantageous effect of deficient absorbed light in mutant. Comparedwith wild-type rice, the mutant had less excess excitation energy and the fraction of absorbedlight allocated to photochemical process was more.展开更多
We first propose fundamental solutions of wave propagation in dispersive chain subject to a localized initial perturbation in the displacement. Analytical solutions are obtained for both second order nonlinear dispers...We first propose fundamental solutions of wave propagation in dispersive chain subject to a localized initial perturbation in the displacement. Analytical solutions are obtained for both second order nonlinear dispersive chain and homogenous harmonic chain using stationary phase approximation. Solution is also compared with numerical results from molecular dynamics （MD） simulations. Locally dominant phonon modes （k-space） are introduced based on these solutions. These locally defined spatially and temporally varying phonon modes k（x, t） are critical to the concept of the local thermodynamic equilibrium （LTE）. Wave propagation accompanying with the nonequilibrium dynamics leads to the excitation of these locally defined phonon modes. It is found that the system energy is gradually redistributed among these excited phonons modes （k-space）. This redistribution process is only possible with nonlinear dispersion and requires a finite amount of time to achieve a steady state distribution. This time scale is dependent on the spatial distribution （or frequency content） of the initial perturbation and the dispersion relation. Sharper and more concentrated perturbation leads to a faster energy redistribution and dissipation. This energy redistribution generates localized phonons with various frequencies that can be important for phonon-phonon interaction and energy dissipation in nonlinear systems. Depending on the initial perturbation and temperature, the time scale associated with this energy distribution can be critical for energy dissipation compared to the Umklapp scattering process. Ballistic type of heat transport along the harmonic chain reveals that at any given position, the lowest mode （k = O） is excited first and gradually expanding to the highest mode （km^（x,t））, where km^（x,t） can only asymptotically approach the maximum mode kB of the first Brillouin zone （kmax（x,t） --~ kB）. NO energy distributed into modes with k_max（x,t） 〈 k 〈 k^B demonstrates that th展开更多
Breaking wave is a complex physical phenomenon that takes place at the gas fluid interface which is the chief reason for the generation of two phase turbulence wave energy dissipation and mass transfer between air and...Breaking wave is a complex physical phenomenon that takes place at the gas fluid interface which is the chief reason for the generation of two phase turbulence wave energy dissipation and mass transfer between air and water. For marine hydrodynamics the breaking bow wave of high speed vessels induces the bubble mixed flow travelling around the ship eventually developing to be the turbulent wake which is easy to be detected by photoelectric equipment. Besides the flow induced noise stemming from wave plunging may weaken the acoustic stealth of water surface craft. In the oceanographic physics context wave breaking accounts for the energy and mass exchange of the ocean atmosphere system which has a great effect on the weather forecasts and global climate predictions. Due to multi scale properties of multiphase turbulent flows a wide range of time and length scales should be resolved making it rather complicated for experimental and numerical investigations. In early reviews[1-4] general mechanisms related to wave breaking problems are well described. However previous emphasis lies on the phenomenological characteristics of breaking wave. Thus this review summarizes the recent experimental and numerical advances of the studies of air entrainment bubble distribution energy dissipation capillary effect and so on.展开更多
基金supported by National Natural Science Foundation of China(61304256)Zhejiang Provincial Natural Science Foundation of China(LQ13F030013)+4 种基金Project of the Education Department of Zhejiang Province(Y201327006)Young Researchers Foundation of Zhejiang Provincial Top Key Academic Discipline of Mechanical Engineering and Zhejiang Sci-Tech University Key Laboratory(ZSTUME01B15)New Century 151 Talent Project of Zhejiang Province521 Talent Project of Zhejiang Sci-Tech UniversityYoung and Middle-aged Talents Foundation of Zhejiang Provincial Top Key Academic Discipline of Mechanical Engineering
基金supported by the National Key R&D Program of China (2019YFA0308403, and 2022YFA1403700)the Innovation Program for Quantum Science and Technology (2021ZD0302400)+2 种基金the National Natural Science Foundation of China (12350401, 12304052, 12374034, and 11921005)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB28000000)funded by China Postdoctoral Science Foundation (BX20220005)。
文摘Energy dissipation is of fundamental interest and crucial importance in quantum systems. However,whether energy dissipation can emerge without backscattering inside topological systems remains a question. As a hallmark, we propose a microscopic picture that illustrates energy dissipation in the quantum Hall(QH) plateau regime of graphene. Despite the quantization of Hall, longitudinal, and two-probe resistances(dubbed as the quantum limit), we find that the energy dissipation emerges in the form of Joule heat. It is demonstrated that the non-equilibrium energy distribution of carriers plays much more essential roles than the resistance on energy dissipation. Eventually, we suggest probing the phenomenon by measuring local temperature increases in experiments and reconsidering the dissipation typically ignored in realistic topological circuits.
基金financial support received from the Louisiana Economic Development Assistantship (EDA) program
文摘Friction stir welding （FSW） is a solid-state joining process, where joint properties largely depend on the amount of heat generation during the welding process. The objective of this paper was to develop a numerical thermomechanical model for FSW of aluminum--copper alloy AA2219 and analyze heat generation during the welding process. The thermomechanical model has been developed utilizing ANSYS APDL. The model was verified by comparing simulated temperature profile of three different weld schedules （i.e., different combinations of weld parameters in real weld situations） from simulation with experimental results. Furthermore, the verified model was used to analyze the effect of different weld parameters on heat generation. Among all the weld parameters, the effect of rotational speed on heat generation is the highest.
基金supported by special fund for important and large scientific and technical projects from the Ministry of Communications (Grant No. 201132874660)funds from Nanjing Hydraulic Research Institute (Grant No. Y210001)
文摘In this paper, flume experiments are focused on sediment transport inside and outside the surf zone. According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump, formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves. Assuming that the sediment diffusion coefficient, which is related with energy dissipation, is proportional to water depth, formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves, and the prediction shows a good agreement with the measurement.
文摘Compared with general trapeziform plunge pools, an arciform plunge pool has its advantages, e.g. less excavate quantity, higher stability, etc. In this paper, the hydrodynamic pressure distribution on the soleplate of the arciform plunge pool is measured under a relatively dangerous condition of operation. The result is helpful to the design of the arciform plunge pool. The result also shows that the difference between the maximum and the minimum pressures on the upward surface of the soleplate may cause an additional uplift force on the soleplate under certain condition and should be taken into consideration in the uplift force calculation of the soleplate. The scour experiment verifies the higher stability of the arciform plunge pool.
基金supported by the National Natural Science Foundation of China(30300217).
文摘This paper reported the diurnal variations of photochemical efficiency of PSII, thermaldissipation rate and other physiology process in the low content chlorophyll mutant rice andits wild type under field conditions, and analyzed the difference of absorbed light distributionbetween the two rice varieties in a day. The results showed that the mutant had poor absorbedlight because of its little light absorption coefficient, but higher electron transportg ratecould partly reduce the disadvantageous effect of deficient absorbed light in mutant. Comparedwith wild-type rice, the mutant had less excess excitation energy and the fraction of absorbedlight allocated to photochemical process was more.
文摘We first propose fundamental solutions of wave propagation in dispersive chain subject to a localized initial perturbation in the displacement. Analytical solutions are obtained for both second order nonlinear dispersive chain and homogenous harmonic chain using stationary phase approximation. Solution is also compared with numerical results from molecular dynamics （MD） simulations. Locally dominant phonon modes （k-space） are introduced based on these solutions. These locally defined spatially and temporally varying phonon modes k（x, t） are critical to the concept of the local thermodynamic equilibrium （LTE）. Wave propagation accompanying with the nonequilibrium dynamics leads to the excitation of these locally defined phonon modes. It is found that the system energy is gradually redistributed among these excited phonons modes （k-space）. This redistribution process is only possible with nonlinear dispersion and requires a finite amount of time to achieve a steady state distribution. This time scale is dependent on the spatial distribution （or frequency content） of the initial perturbation and the dispersion relation. Sharper and more concentrated perturbation leads to a faster energy redistribution and dissipation. This energy redistribution generates localized phonons with various frequencies that can be important for phonon-phonon interaction and energy dissipation in nonlinear systems. Depending on the initial perturbation and temperature, the time scale associated with this energy distribution can be critical for energy dissipation compared to the Umklapp scattering process. Ballistic type of heat transport along the harmonic chain reveals that at any given position, the lowest mode （k = O） is excited first and gradually expanding to the highest mode （km^（x,t））, where km^（x,t） can only asymptotically approach the maximum mode kB of the first Brillouin zone （kmax（x,t） --~ kB）. NO energy distributed into modes with k_max（x,t） 〈 k 〈 k^B demonstrates that th
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51879159,51490675,11432009,and 51579145)the Chang Jiang Scholars Program(Grant No.T2014099)+2 种基金the Shanghai Excellent Academic Leaders Program(Grant No.17XD1402300)the Program for Professor of Special Appointment(Eastern Scholar)at the Shanghai Institutions of Higher Learning(Grant No.2013022)the Innovative Special Project of Numerical Tank of Ministry of Industry and Information Technology of China(2016-23/09)
文摘Breaking wave is a complex physical phenomenon that takes place at the gas fluid interface which is the chief reason for the generation of two phase turbulence wave energy dissipation and mass transfer between air and water. For marine hydrodynamics the breaking bow wave of high speed vessels induces the bubble mixed flow travelling around the ship eventually developing to be the turbulent wake which is easy to be detected by photoelectric equipment. Besides the flow induced noise stemming from wave plunging may weaken the acoustic stealth of water surface craft. In the oceanographic physics context wave breaking accounts for the energy and mass exchange of the ocean atmosphere system which has a great effect on the weather forecasts and global climate predictions. Due to multi scale properties of multiphase turbulent flows a wide range of time and length scales should be resolved making it rather complicated for experimental and numerical investigations. In early reviews[1-4] general mechanisms related to wave breaking problems are well described. However previous emphasis lies on the phenomenological characteristics of breaking wave. Thus this review summarizes the recent experimental and numerical advances of the studies of air entrainment bubble distribution energy dissipation capillary effect and so on.
