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| 1 | Different structural origins for different sized surface pits observed on a-plane GaN film显示文摘A correlation study between the observed surface morphology using high-resolution scanning electron microscopy(HRSEM) and the observed structural imperfections using transmission electron microscopy(TEM) has been conducted for a-plane Ga N. There are three different sized asymmetric surface pits: large pit of 500 nm–2 ?m in side length, medium pit of 50 nm in side length, and small pit with side lengths of less than 5 nm, which originate from incomplete island coalescence, screw dislocation, and partial dislocation(PD), respectively. Both screw dislocation and PD can produce pits on the free surface because they have a perpendicular line tension to the surface, which must remain in balance with the surface tension. The two types of dislocation lead to distinctive pit sizes because the PD has a smaller Burgers vector component along the dislocation line than the pure screw dislocation. A pit that is produced in the island-coalescing process is much larger than those caused by dislocations because island coalescence is a kinetic process that involves large-scale mass transportation, whereas the dislocation mediates the surface in the local area. These three types of surface pits sometimes interact with one another in space. The coalescence of the island determines the surface morphology at large scales, whereas the defects affect the details. | GAO ZhiYuan LI JiangJiang XUE XiaoWei CUI BiFeng XING YanHui ZOU DeShu | 2016 | Science China(Technological Sciences)2016，59，1： | 1 |
| 2 | Modeling and flapping vibration suppression of a novel tailless flapping wing micro air vehicle显示文摘This paper establishes and analyzes a high-fidelity nonlinear time-periodic dynamic model and the corresponding state observer for flapping vibration suppression of a novel tailless Flapping Wing Micro Air Vehicle(FWMAV),named NPU-Tinybird.Firstly,a complete modeling of NPU-Tinybird is determined,including the aerodynamic model based on the quasi-steady method,the kinematic and dynamic model about the mechanism of flapping and attitude control,combined with the single rigid body dynamic model.Based on this,a linearized longitudinal pitch dynamic cycle-averaged model is obtained and analyzed through the methods of neural network fitting and system identification,preparing for the design of flapping vibration suppression observer.Flapping vibration is an inherent property of the tailless FWMAV,which arises from the influence of time-periodic aerodynamic forces and moments.It can be captured by attitude and position sensors on the plane,which impairs the flight performance and efficiency of flight controller and actuators.To deal with this problem,a novel state observer for flapping vibration suppression is designed.A robust optimal controller based on the linear quadratic theory is also designed to stabilize the closed-loop system.Simulation results are given to verify the performance of the observer,including the closed loop responses combined with robust optimal controller,the comparison of different parameters of observer and the comparison with several classic methods,such as Kalman filter,H-infinity filter and low-pass filter,which prove that the novel observer owns a fairly good suppression effect on flapping vibration and benefits for the improvement of flight performance and control efficiency. | Siqi WANG Bifeng SONG Ang CHEN Qiang FU Jin CUI | 2022 | Chinese Journal of Aeronautics2022，35，3： | 1 |
| 3 | End-to-end self-assembly and colorimetric characterization of gold nanorods and nanospheres via oligonucleotide hybridization显示文摘 | Bifeng Pan Limei Ao FengGao Hongye Tian Rong He Daxiang Cui | 2005 | Nanotechnology2005，16，： | 1 |
| 4 | The simulation of thermal characteristics of 980 nm vertical cavity surface emitting lasers显示文摘In order to design a single mode 980 nm vertical cavity surface emitting laser(VCSEL), a 2 μm output aperture is designed to guarantee the single mode output. The effects of different mesa sizes on the lattice temperature, the output power and the voltage are simulated under the condition of continuous working at room temperature, to obtain the optimum process parameters of mesa. It is obtained by results of the crosslight simulation software that the sizes of mesa radius are between 9.5 to 12.5 μm, which cannot only obtain the maximum output power, but also improve the heat dissipation of the device. | Tianxiao Fang Bifeng Cui Shuai Hao Yang Wang | 2018 | Journal of Semiconductors2018，39，2： | 0 |
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