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Interplay between intercalated oxygen superstructures and monolayerh-BN on Cu(100)
Ma, Chuanxu,Park, Jewook,Liu, Lei,Kim, Yong-Sung,Yoon, Mina,Baddorf, Arthur P.,Gu, Gong,Li, An-Ping American Physical Society 2016 Physical Review B Vol.94 No.6
<P>The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. Here we report the formation of ordered Cu(100) p(2 x 2) oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride (h-BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling h-BN and Cu, and disintegrating h-BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface or quasi-1D stripes of paired oxygen intercalated in the interface of h-BN and Cu predominantly oriented along the moire modulations. The oxygen superstructure is shown to etch the overlaying h-BN monolayer in a thermal annealing process. After extended annealing, the h-BN monolayer disintegrates into nanoislands with zigzag edges. We discuss the implications of these findings on the stability and oxidation resistance of h-BN and relate them to challenges in process integration and 2D heterostructures.</P>
Development and validation of reactor nuclear design code CORCA-3D
Ping An,Yongqiang Ma,Peng Xiao,Fengchen Guo,Wei Lu,Xiaoming Chai 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.7
The advanced node core code CORCA-3D is one of the independent developed codes of NPIC for the nuclear reactor core design. CORCA-3D code can calculate the few-group cross section, solve the 3D diffusion equations, consider the thermal-hydraulic feedback, reconstruct the pin-by-pin power. It has lots of functions such as changing core status calculation, critical searching, control rod value calculation, coefficient calculation and so on. The main theory and functions of CORCA-3D code are introduced and validated with a lot of reactor measured data and the SCIENCE system. Now, CORCA-3D code has been applied in ACP type reactor nuclear cores design.
Zhou Qixun,Ma Ping’an,Gong Hao,Wang Pei,Du Guanghui 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.5
To address the problem of high frequency torque pulsation in the zero-low-speed permanent magnet synchronous motor (PMSM) sensorless control by the high frequency square wave injection method, a torque pulsation suppression strategy based on the dual high frequency square wave injection method for the dual-winding permanent magnet synchronous motor (DW-PMSM) sensorless control is proposed. A high-frequency mathematical model of the PMSM is established, and the analytical relationship between the torque pulsation and the injection signal is analyzed. For a surface mounted DW-PMSM with two windings differing in γ electrical angle, the general form of the square wave signal that should be injected into the second winding is derived based on the position relationship between the two windings when the first winding is injected with a high-frequency square wave, with the objective of minimizing the equivalent high-frequency torque generated. The rotor position estimation error contained in the high-frequency signals of the two windings is extracted, and the rotor position estimation accuracy is improved by tracking the rotor position using a luenberger observer with the goal of minimizing the error. Simulation and experimental results show that the method is able to reduce torque pulsation by more than 50% and improve rotor position estimation accuracy by more than 4 times.
Spatio-Temporal Residual Networks for Slide Transition Detection in Lecture Videos
( Zhijin Liu ),( Kai Li ),( Liquan Shen ),( Ran Ma ),( Ping An ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.8
In this paper, we present an approach for detecting slide transitions in lecture videos by introducing the spatio-temporal residual networks. Given a lecture video which records the digital slides, the speaker, and the audience by multiple cameras, our goal is to find keyframes where slide content changes. Since temporal dependency among video frames is important for detecting slide changes, 3D Convolutional Networks has been regarded as an efficient approach to learn the spatio-temporal features in videos. However, 3D ConvNet will cost much training time and need lots of memory. Hence, we utilize ResNet to ease the training of network, which is easy to optimize. Consequently, we present a novel ConvNet architecture based on 3D ConvNet and ResNet for slide transition detection in lecture videos. Experimental results show that the proposed novel ConvNet architecture achieves the better accuracy than other slide progression detection approaches.