English speaking contest for vocational colleges is held once a year.It' s not just a competition,but a chance to test contempo rary college students' English speaking ability,and a platform to show their ment...English speaking contest for vocational colleges is held once a year.It' s not just a competition,but a chance to test contempo rary college students' English speaking ability,and a platform to show their mental outlook.Many schools give high attention to this con test by spending much time tutoring students,but there are still many problems of the contestants.Through illustrating this competition in 2012,the writer raises some strategies for both training and competing in order to help competitors perform better.展开更多
The harmonic oscillator with time-dependent (indefinite and variable) mass subject to the force proportional to velocity is studied by extending Bateman’s dual Lagrangian and Hamiltonian formalism. To study the quant...The harmonic oscillator with time-dependent (indefinite and variable) mass subject to the force proportional to velocity is studied by extending Bateman’s dual Lagrangian and Hamiltonian formalism. To study the quantum analog of such a dissipative system, the Batemann-Morse-Feshback classical Hamiltonian of the damped harmonic oscillator with varying (time-dependent) mass is canonically quantized. In order to discuss the stability of the quantum dissipative system due to the influence of varying mass and the dissipative force, we derived a formula for the vacuum state of the dissipative system with the help of quantum field theoretical framework. It is shown that the formula based on this simple model could be used to study the influence of dissipation such as the instability due to the dissipative force and/or the variable mass. It is understood that the change in the oscillator mass corresponds to a control parameter in quantum dissipative systems.展开更多
This study focuses on flame hysteresis over a porous cylindrical burner. The hysteresis results from different operation procedure of the experiment. Gradually increasing inflow velocity can transform the envelope fla...This study focuses on flame hysteresis over a porous cylindrical burner. The hysteresis results from different operation procedure of the experiment. Gradually increasing inflow velocity can transform the envelope flame into a wake flame. The blow-off curve can be plotted by determining every critical inflow velocity that makes an envelope flame become a wake flame at different fuel-ejection velocities. In contrast, decreasing the inflow veiocity can transform the wake or lift-off flame into an envelope one. The reattachment curve can be obtained by the same method to explore the blow-off curve, but the intake process is reverse. However, these two curves are not coincident, except the origin. The discrepancy between them is termed as hysteresis, and it results from the difference between the burning velocities associated with both curves. At the lowest fuel-ejection velocity, no hysteresis exists between both curves owing to nearly no burning velocity difference there. Then, raising the fuel-ejection velocity enhances hysteresis and the discrepancy between the two curves. However, as fuel-ejection velocity exceeds a critical value, the intensity of hysteresis almost keeps constant and causes the two curves to be parallel to each other.展开更多
Solid oxide fuel cells(SOFCs)can directly convert renewable biogas into electricity with high efficiency at high temperature,however the long-term stability of SOFCs is significantly affected by the carbon deposition ...Solid oxide fuel cells(SOFCs)can directly convert renewable biogas into electricity with high efficiency at high temperature,however the long-term stability of SOFCs is significantly affected by the carbon deposition on the anode during cell operation.Herein,we report a novel carbon removal approach by high temperature infrared light driven photocatalytic oxidation.Upon the comparison of electrochemical performance of Ni-YSZ anode and TiO_(2)modified Ni-YSZ anode in the state-of-the-art single cell(Ni-YSZ/YSZ/LSCM),the modified anodes exhibit markedly improved peak powder density with simulated biogas fuel(70%CH_(4)+30%CO_(2))at 850℃with less coking after 40 h operation.The high activity and carbon deposition resistance of the modified anode is possibly attributed to the in situ generated hydroxyl radical from the reduced TiO_(x)powder under high temperature infrared light excitation,which is supported by detailed analysis of microstructural information of anodes and the powder-based thermo-photocatalytic experiments.展开更多
文摘English speaking contest for vocational colleges is held once a year.It' s not just a competition,but a chance to test contempo rary college students' English speaking ability,and a platform to show their mental outlook.Many schools give high attention to this con test by spending much time tutoring students,but there are still many problems of the contestants.Through illustrating this competition in 2012,the writer raises some strategies for both training and competing in order to help competitors perform better.
文摘The harmonic oscillator with time-dependent (indefinite and variable) mass subject to the force proportional to velocity is studied by extending Bateman’s dual Lagrangian and Hamiltonian formalism. To study the quantum analog of such a dissipative system, the Batemann-Morse-Feshback classical Hamiltonian of the damped harmonic oscillator with varying (time-dependent) mass is canonically quantized. In order to discuss the stability of the quantum dissipative system due to the influence of varying mass and the dissipative force, we derived a formula for the vacuum state of the dissipative system with the help of quantum field theoretical framework. It is shown that the formula based on this simple model could be used to study the influence of dissipation such as the instability due to the dissipative force and/or the variable mass. It is understood that the change in the oscillator mass corresponds to a control parameter in quantum dissipative systems.
文摘This study focuses on flame hysteresis over a porous cylindrical burner. The hysteresis results from different operation procedure of the experiment. Gradually increasing inflow velocity can transform the envelope flame into a wake flame. The blow-off curve can be plotted by determining every critical inflow velocity that makes an envelope flame become a wake flame at different fuel-ejection velocities. In contrast, decreasing the inflow veiocity can transform the wake or lift-off flame into an envelope one. The reattachment curve can be obtained by the same method to explore the blow-off curve, but the intake process is reverse. However, these two curves are not coincident, except the origin. The discrepancy between them is termed as hysteresis, and it results from the difference between the burning velocities associated with both curves. At the lowest fuel-ejection velocity, no hysteresis exists between both curves owing to nearly no burning velocity difference there. Then, raising the fuel-ejection velocity enhances hysteresis and the discrepancy between the two curves. However, as fuel-ejection velocity exceeds a critical value, the intensity of hysteresis almost keeps constant and causes the two curves to be parallel to each other.
基金supported by Shenzhen Science and Technology Innovation Commission(No.JCYJ20190813171403664)Basic research program of Guangdong Province(No.2018A030313851)+1 种基金Longgang District Technology Supporting Project(No.LGKCKJPT2019074)the Fundamental Research Funds for the Central Universities(No.HIT.NSRIF.2020074).
文摘Solid oxide fuel cells(SOFCs)can directly convert renewable biogas into electricity with high efficiency at high temperature,however the long-term stability of SOFCs is significantly affected by the carbon deposition on the anode during cell operation.Herein,we report a novel carbon removal approach by high temperature infrared light driven photocatalytic oxidation.Upon the comparison of electrochemical performance of Ni-YSZ anode and TiO_(2)modified Ni-YSZ anode in the state-of-the-art single cell(Ni-YSZ/YSZ/LSCM),the modified anodes exhibit markedly improved peak powder density with simulated biogas fuel(70%CH_(4)+30%CO_(2))at 850℃with less coking after 40 h operation.The high activity and carbon deposition resistance of the modified anode is possibly attributed to the in situ generated hydroxyl radical from the reduced TiO_(x)powder under high temperature infrared light excitation,which is supported by detailed analysis of microstructural information of anodes and the powder-based thermo-photocatalytic experiments.
