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Minjun Zhang,Fuyan Lyu,Shichen Fu,Xiuhang Cai,Kai Zong,Miao Wu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.10
The pitch angle of a roadheader is the key factor to ensure the quality during the formation of a roadway. Various control strategies have been employed to adjust the attitude angle of different cars or planes to achieve distinct goals for a roadheader. In this paper, we established a mathematical model of the pitch angle and adjustment actuator, as well as their transitive relation. The model was verified experimentally using a real roadheader. The accuracy in the adjustment of the pitch angle was analyzed using the model by designing and simulating the PID controller, fuzzy logic controller (FLC), and dynamic error elimination controller (DEEC). The performance of the controllers were tested by simulation and experiment using four types of input signal. The responses were compared with the expected results. The DEEC reduced the response time and overshoot but increased the robustness. Thus, this controller is better than the PID and FLC.
Zhang, Yuandong,Peng, Minjun,Xia, Genglei,Wang, Ge,Zhou, Cheng Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.9
The nuclear reactor coupled with supercritical carbon dioxide (S-CO<sub>2</sub>) Brayton cycle has good prospects in generation IV reactors. Turbomachineries (turbine and compressor) are important work equipment in circulatory system, whose performances are critical to the efficiency of the energy conversion system. However, the sharp variations of S-CO<sub>2</sub> thermophysical properties make turbomachinery performances more complex than that of traditional working fluids. Meanwhile, almost no systematic analysis has considered the effects of turbomachinery efficiency under different conditions. In this paper, an in-house code was developed to realize the geometric design and performance prediction of S-CO<sub>2</sub> turbomachinery, and was coupled with systematic code for Brayton cycle characteristics analysis. The models and methodology adopted in calculation code were validated by experimental data. The effects of recompressed fraction, pressure and temperature on S-CO<sub>2</sub> recompression Brayton cycle were studied based on detailed design of turbomachinery. The results demonstrate that the recompressed fraction affects the turbomachinery characteristic by changing the mass flow and effects the system performance eventually. By contrast, the turbomachinery efficiency is insensitive to variation in pressure and temperature due to almost constant mass flow. In addition, the S-CO<sub>2</sub> thermophysical properties and the position of minimum temperature difference are significant influential factors of cyclic performance.
Selective resolution of phonon modes in STM-IETS on clean and oxygen-adsorbed Cu(100) surfaces
Lee, Minjun,Oh, Myungchul,Jeon, Hoyeon,Yi, Sunwouk,Zoh, Inhae,Zhang, Chao,Chae, Jungseok,Kuk, Young Elsevier 2019 Surface science Vol.689 No.-
<P><B>Abstract</B></P> <P>The observation of surface phonon using scanning probe microscopy can provide important information related to local structural and electrical properties. In this study, surface phonon modes on a Cu(100) surface were measured using inelastic tunneling spectroscopy of scanning tunneling microscopy. One phonon mode was measured at 3.6 meV on a clean Cu(100) surface. On an oxygen-adsorbed Cu(100) surface, another phonon mode was measured at 13.5 meV. This phonon mode was considered to be enhanced by the symmetry created by Cu-missing rows. The spatially varying <I>d<SUP>2</SUP>I/dV<SUP>2</SUP> </I> map showed the effect of surface stress relaxation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We measured the surface phonon modes on a bare Cu(100) surface and two reconstructed oxidized Cu(100) surfaces. </LI> <LI> These measurements were performed with different selection rules owing to the structures of the surfaces and the probing tips. </LI> <LI> A geometrically sharp STM tip was an important factor for resolving many phonon mode peaks on the surface. </LI> <LI> The symmetry of the phonon modes was directly related to the STM-IETS signal strength. </LI> <LI> Broken symmetry due to surface stress relaxation can be another factor determining the STM-IETS signal. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
An advanced Parallel FPGA Architecture for Bi-directional Motion Estimation
Yangfan Huang,Minjun Deng,Donglian Li,Zhenzhen Li,Mingyan Yu,Cailan Zeng,Yu Zhang,Zhuo Chen,Pengcheng Cao,Ran Liu 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.9
Motion estimation (ME) and motion compensation (MC) are the key elements for frame rate up-conversion (FRUC) system. Fast and accurate motion estimation is the premise of high quality motion compensation. Unlike conventional unidirectional motion estimation which brings holes, overlaps and blocking artifacts, the bi-directional motion estimation does not produce any overlapped pixel or hole in the interpolated frames. As a result, the bi-directional motion estimation has better performance than conventional unidirectional motion estimation. This paper presents an efficient FPGA architecture targeting bi-directional motion estimation hardware implementation. This proposed architecture can achieve real-time processing for 1280x720@60Hz under 200MHz operating frequency. The design is described in Verilog HDL, verified in Virtex5 FPGA platform. Experimental results show that the proposed architecture has high performance and low cost for bi-directional motion estimation algorithm. This architecture can be used for video post-processing system.