The Kapitza resistance is of fundamental importance for the thermal stability of the interface between the ceramic top coat and the thermal growth oxide layer in the thermal barrier coating structure,which is widely u...The Kapitza resistance is of fundamental importance for the thermal stability of the interface between the ceramic top coat and the thermal growth oxide layer in the thermal barrier coating structure,which is widely used to protect high-temperature components in current gas turbine engines.The top coat typically consists of the ZrO_(2)partially stabilized by 8%Y2O3(YSZ),and the main component of the thermal growth oxide isα-Al_(2)O_(3).In this work,the Kapitza resistance is found to be a small value of 0.69 m^(2)K/GW for the YSZ/α-Al_(2)O_(3)interface based on the heat dissipation simulation method.It indicates that the localization of thermal energy is rather weak,which is beneficial for the thermal stability of the YSZ/α-Al_(2)O_(3)interface.This Kapitza resistance can be further reduced to 0.50 m^(2)K/GW by a mechanical or thermal compressive strain of 8%.To explore the underlying mechanism for this strain effect,we analyze the phonon vibration and the microscopic deformation in the interface region.It is revealed that the interface becomes denser through the compression-induced twisting of some Al-O_(zr)and A1-O_(Al)chemical bonds in the interface region,which is responsible for the reduction in the Kapitza resistance.The temperature effect and crystal size effect on the Kapitza resistance of the YSZ/α-Al_(2)O_(3)interface are also systematically studied.These findings shall provide valuable information for further understanding of the thermal conductivity and thermal stability of the thermal barrier coating structures.展开更多
By applying a nonperturbative quantum electrodynamic theory, we study ponderomotive resonances when an electron beam is scattered by a standing photon wave. Our study shows that the pondero- motive parameter Up, the p...By applying a nonperturbative quantum electrodynamic theory, we study ponderomotive resonances when an electron beam is scattered by a standing photon wave. Our study shows that the pondero- motive parameter Up, the ponderomotive energy per laser-photon energy, for each of the two traveling laser modes possesses a minimum valuehω/（mec2）. Ponderomotive resonances occur only when the ratio of the laser photon energy to the electron rest-mass energy is a fraction, where the denomina- tor is twice the square of a positive integer and the numerator is the total ponderomotive number, which is also a positive integer.展开更多
We theoretically analyse a multi-modes atomic interferometer consisting of a sequence of Kapitza-Dirac pulses (KD) applied to cold atoms trapped in a harmonic trap. The pulses spatially split the atomic wave-functions...We theoretically analyse a multi-modes atomic interferometer consisting of a sequence of Kapitza-Dirac pulses (KD) applied to cold atoms trapped in a harmonic trap. The pulses spatially split the atomic wave-functions while the harmonic trap coherently recombines all modes by acting as a coherent spatial mirror. The phase shifts accumulated among different KD pulses are estimated by measuring the number of atoms in each output mode or by fitting the density profile. The sensitivity is rigorously calculated by the Fisher information and the Cramér-Rao lower bound. We predict, with typical experimental parameters, a temperature independent sensitivity which, in the case of the measurement of the gravitational constant g can significantly exceed the sensitivity of current atomic interferometers.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11822206 and 12072182)Innovation Program of the Shanghai Municipal Education Commission(Grant No.2017-01-07-00-09-E00019)。
文摘The Kapitza resistance is of fundamental importance for the thermal stability of the interface between the ceramic top coat and the thermal growth oxide layer in the thermal barrier coating structure,which is widely used to protect high-temperature components in current gas turbine engines.The top coat typically consists of the ZrO_(2)partially stabilized by 8%Y2O3(YSZ),and the main component of the thermal growth oxide isα-Al_(2)O_(3).In this work,the Kapitza resistance is found to be a small value of 0.69 m^(2)K/GW for the YSZ/α-Al_(2)O_(3)interface based on the heat dissipation simulation method.It indicates that the localization of thermal energy is rather weak,which is beneficial for the thermal stability of the YSZ/α-Al_(2)O_(3)interface.This Kapitza resistance can be further reduced to 0.50 m^(2)K/GW by a mechanical or thermal compressive strain of 8%.To explore the underlying mechanism for this strain effect,we analyze the phonon vibration and the microscopic deformation in the interface region.It is revealed that the interface becomes denser through the compression-induced twisting of some Al-O_(zr)and A1-O_(Al)chemical bonds in the interface region,which is responsible for the reduction in the Kapitza resistance.The temperature effect and crystal size effect on the Kapitza resistance of the YSZ/α-Al_(2)O_(3)interface are also systematically studied.These findings shall provide valuable information for further understanding of the thermal conductivity and thermal stability of the thermal barrier coating structures.
基金This work was partly supported by the Na- tional Natural Science Foundation of China （Grant Nos. 11004060, 11027403, and 51132004）.
文摘By applying a nonperturbative quantum electrodynamic theory, we study ponderomotive resonances when an electron beam is scattered by a standing photon wave. Our study shows that the pondero- motive parameter Up, the ponderomotive energy per laser-photon energy, for each of the two traveling laser modes possesses a minimum valuehω/（mec2）. Ponderomotive resonances occur only when the ratio of the laser photon energy to the electron rest-mass energy is a fraction, where the denomina- tor is twice the square of a positive integer and the numerator is the total ponderomotive number, which is also a positive integer.
文摘We theoretically analyse a multi-modes atomic interferometer consisting of a sequence of Kapitza-Dirac pulses (KD) applied to cold atoms trapped in a harmonic trap. The pulses spatially split the atomic wave-functions while the harmonic trap coherently recombines all modes by acting as a coherent spatial mirror. The phase shifts accumulated among different KD pulses are estimated by measuring the number of atoms in each output mode or by fitting the density profile. The sensitivity is rigorously calculated by the Fisher information and the Cramér-Rao lower bound. We predict, with typical experimental parameters, a temperature independent sensitivity which, in the case of the measurement of the gravitational constant g can significantly exceed the sensitivity of current atomic interferometers.
