We have numerically and experimentally investigated the flow modes of Taylor-Couette system consisting of coaxial two cylinders with vertical axes. The inner cylinder rotates and the outer cylinder and the bottom end ...We have numerically and experimentally investigated the flow modes of Taylor-Couette system consisting of coaxial two cylinders with vertical axes. The inner cylinder rotates and the outer cylinder and the bottom end of the cylinders remain stationary. The upper top boundary is the free surface of the working liquid between the inner and outer cylinders and it contacts with the air. While this flow appears in fluid machinery and chemical reactors and includes industrial interests, it also contains problems of fluid mechanics, which is about the behavior of the free surface in the rotating field. In this paper, we concretely show the developments of the one cell mode flow and the three cell mode flow at a small aspect ratio. We also represent the bifurcation diagram of the flow at the moderate aspect ratio about 5.5. In the numerical simulation, the flow is rest in the initial state, and the inner cylinder is linearly or suddenly accelerated to attain a flow with a prescribed Reynolds number. When the acceleration of the inner cylinder is high, an imperfect bifurcation occurs and the flows of the secondary modes emerge. At high Reynolds numbers, the flow first has many vortices and then some of the vortices collapse and the final stable flow arises. The loci of the normal five cell mode, the anomalous six cell mode and the secondary seven cell mode are determined.展开更多
In this paper,a W-band broadband vialess microstrip(MS)-to-MS vertical transition in multilayer liquid crystal polymer(LCP)substrate is presented,which consists of two MS lines in the top layer,a common ground plane a...In this paper,a W-band broadband vialess microstrip(MS)-to-MS vertical transition in multilayer liquid crystal polymer(LCP)substrate is presented,which consists of two MS lines in the top layer,a common ground plane and slotline resonators in the second layer,and a close-loop transmission-line in the third layer.To increase the passband of the vialess vertical transition,an H-shaped slotline resonator is introduced,which greatly improves the impedance performance of the slotline resonator,and the full-wave simulated results indicate that insertion loss(IL)is less than 2 dB and return loss(RL)is better than 10 dB at W-band.To verify this design,the broadband vertical transition is fabricated and measured.The measured results indicate that a broadband vertical transition with RL better than 10 dB and IL less than 5.67 dB can be obtained in the frequency range from 70.00 GHz to 104.09 GHz.Due to the fabrication error in the preparation process,the measured results are deteriorated compared to the simulated results,and the investigation indicates that the deviation is caused by the thickness error of the LCP substrate.展开更多
The electron and heavy hole energy levels of two vertically coupled In As hemispherical quantum dots/wetting layers embedded in a Ga As barrier are calculated numerically. As the radius increases, the electronic energ...The electron and heavy hole energy levels of two vertically coupled In As hemispherical quantum dots/wetting layers embedded in a Ga As barrier are calculated numerically. As the radius increases, the electronic energies increase for the small base radii and decrease for the larger ones. The energies decrease as the dot height increases. The intersubband and interband transitions of the system are also studied. For both, a spectral peak position shift to lower energies is seen due to the vertical coupling of dots. The interband transition energy decreases as the dot size increases, decreases for the dot shapes with larger heights, and reaches a minimum for coupled semisphere dots.展开更多
文摘We have numerically and experimentally investigated the flow modes of Taylor-Couette system consisting of coaxial two cylinders with vertical axes. The inner cylinder rotates and the outer cylinder and the bottom end of the cylinders remain stationary. The upper top boundary is the free surface of the working liquid between the inner and outer cylinders and it contacts with the air. While this flow appears in fluid machinery and chemical reactors and includes industrial interests, it also contains problems of fluid mechanics, which is about the behavior of the free surface in the rotating field. In this paper, we concretely show the developments of the one cell mode flow and the three cell mode flow at a small aspect ratio. We also represent the bifurcation diagram of the flow at the moderate aspect ratio about 5.5. In the numerical simulation, the flow is rest in the initial state, and the inner cylinder is linearly or suddenly accelerated to attain a flow with a prescribed Reynolds number. When the acceleration of the inner cylinder is high, an imperfect bifurcation occurs and the flows of the secondary modes emerge. At high Reynolds numbers, the flow first has many vortices and then some of the vortices collapse and the final stable flow arises. The loci of the normal five cell mode, the anomalous six cell mode and the secondary seven cell mode are determined.
基金Supported by the Shaanxi Provincial Innovation Team Project(2020TD-019)Xi'an Sciences Plan Project(21XJZZ0075)。
文摘In this paper,a W-band broadband vialess microstrip(MS)-to-MS vertical transition in multilayer liquid crystal polymer(LCP)substrate is presented,which consists of two MS lines in the top layer,a common ground plane and slotline resonators in the second layer,and a close-loop transmission-line in the third layer.To increase the passband of the vialess vertical transition,an H-shaped slotline resonator is introduced,which greatly improves the impedance performance of the slotline resonator,and the full-wave simulated results indicate that insertion loss(IL)is less than 2 dB and return loss(RL)is better than 10 dB at W-band.To verify this design,the broadband vertical transition is fabricated and measured.The measured results indicate that a broadband vertical transition with RL better than 10 dB and IL less than 5.67 dB can be obtained in the frequency range from 70.00 GHz to 104.09 GHz.Due to the fabrication error in the preparation process,the measured results are deteriorated compared to the simulated results,and the investigation indicates that the deviation is caused by the thickness error of the LCP substrate.
文摘The electron and heavy hole energy levels of two vertically coupled In As hemispherical quantum dots/wetting layers embedded in a Ga As barrier are calculated numerically. As the radius increases, the electronic energies increase for the small base radii and decrease for the larger ones. The energies decrease as the dot height increases. The intersubband and interband transitions of the system are also studied. For both, a spectral peak position shift to lower energies is seen due to the vertical coupling of dots. The interband transition energy decreases as the dot size increases, decreases for the dot shapes with larger heights, and reaches a minimum for coupled semisphere dots.
