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RISS 인기검색어
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- 저자 : Guangxi Li (검색결과 6 건)
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SLNR-based User Scheduling in Multi-cell networks: from Multi-antenna to Large-Scale Antenna System
( Yanchun Li ),( Guangxi Zhu ),( Hua Chen ),( Minho Jo ),( Yingzhuang Liu ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.3
In this paper, we investigate the performance of Signal to Leakage and Noise Radio (SLNR) based user scheduling in uplink of multi-cell with large-scale antenna system. Large antenna array is desired to improve the performance in future system by providing better beamforming capability. However, some studies have found that the signal channel is `hardened` (becomes invariant) when the antenna number goes extremely large, which implies that the signal channel aware user scheduling may have no gain at all. With the mathematic tool of order statistics, we analyzed the signal and interference terms of SLNR in a homogeneous multicell network. The derived distribution function of signal and interference shows that the leakage channel`s variance is much more influential than the signal channel`s variance in large-scale antenna regime. So even though the signal channel is hardened, the SLNR-based scheduling can achieve remarkable multiuser diversity (MUD) gain due to the fluctuation of the uplink leakage channel. By providing the final SINR distribution, we verify that the SLNR-based scheduling can leverage MUD in a better way than the signal channel based scheduling. The Monte Carlo simulations show that the throughput gain of SLNR-based scheduling over signal channel based scheduling is significant.
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Design of Projection Optical System for Target Imaging Simulator with Long Exit Pupil Distance
Xueyuan Cao,Lingyun Wang,Guangxi Li,Ru Zheng 한국광학회 2023 Current Optics and Photonics Vol.7 No.6
In order to test the recognition ability and accuracy of a target imaging simulator under the irradiation of solar stray light in a laboratory environment, it needs to be fixed on a five-axis turntable during a hardware-in-the-loop simulation test, so the optical system of the simulator should have a long exit pupil distance. This article adopts a secondary imaging method to design a projection optical system suitable for thin-film-transistor liquid crystal displays. The exit pupil distance of the entire optical system is 1,000 mm, and the final optimization results in the 400 nm–850 nm band show that the modulation transfer function (MTF) of the optical system is greater than 0.8 at the cutoff frequency of 72 lp/mm, and the distortion of each field of view of the system is less than 0.04%. Combined with the design results of the optical system, TracePro software was used to model the optical system, and the simulation of the target imaging simulator at the magnitude of −1 to +6 Mv was analyzed and verified. The magnitude er-ror is less than 0.2 Mv, and the irradiance uniformity of the exit pupil surface is greater than 90%, which meets the requirements of the target imaging simulator.
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Analysis of the Influence of Atmospheric Turbulence on the Ground Calibration of a Star Sensor
Xian Ren,Lingyun Wang,Guangxi Li,Bo Cui 한국광학회 2024 Current Optics and Photonics Vol.8 No.1
Under the influence of atmospheric turbulence, a star’s point image will shake back and forth erratically, and after exposure the originally small star point will spread into a huge spot, which will affect the ground calibration of the star sensor. To analyze the impact of atmospheric turbulence on the positioning accuracy of the star’s center of mass, this paper simulates the atmospheric turbulence phase screen using a method based on a sparse spectrum. It is added to the static-star-simulation device to study the transmission characteristics of atmospheric turbulence in star-point simulation, and to analyze the changes in star points under different atmospheric refractive-index structural constants. The simulation results show that the structure function of the atmospheric turbulence phase screen simulated by the sparse spectral method has an average error of 6.8% compared to the theoretical value, while the classical Fourier-transform method can have an error of up to 23% at low frequencies. By including a simulation in which the phase screen would cause errors in the center-of-mass position of the star point, 100 consecutive images are selected and the average drift variance is obtained for each turbulence scenario;The stronger the turbulence, the larger the drift variance. This study can provide a basis for subsequent improvement of the ground-calibration accuracy of a star sensitizer, and for analyzing and evaluating the effect of atmospheric turbulence on the beam.
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Fan Chen,Guojian Mei,Bo Zhao,Wenbo Bie,Guangxi Li 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1
Three-dimensional (3D) ultrasonic vibration-assisted ELID grinding, which combines 3D ultrasonic vibration-assistance with electrolytic in-process grinding wheel dressing (ELID), is a compound process that is designed to achieve high-efficiency precision machining. A grinding force model of 3D ultrasonic vibration-assisted ELID grinding was first developed on the basis of the kinematics of a single grit particle and was verified through experimentation. The surface quality then was observed using white light interference profiling. It was demonstrated during the present investigation that the grinding force during 3D ultrasonic vibration-assisted ELID grinding was approximately 20 %~30 % lower than that of twodimensional (2D) ultrasonic vibration-assisted ELID grinding. In addition, the surface roughness (Ra) achieved during 3D ultrasonic vibration-assisted ELID grinding was approximately 40 %~50 % smoother than was achieved under 2D ultrasonic vibration-assisted ELID, and thus 3D ultrasonic vibration-assisted ELID grinding can achieve better surface quality.
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Ru Zheng,Bo Liu,Lingyun Wang,Yue Gao,Guangxi Li,Changyu Li 한국광학회 2021 Current Optics and Photonics Vol.5 No.3
To improve the measurement accuracy of a solar-radiation observer instrument, aiming at the problem of multiorder-stray-light interference caused by the diffraction of the flat-field concave grating in the spectroscopic system, straylight suppression methods for different forms of optical traps are studied. According to the grating surface-scattering distribution-function model, the bidirectional scattering distribution function (BSDF) of a dust-polluted surface and the flat-field concave grating’s transition area of the spectroscopic system is calculated, and a Lyot stop with blade baffle is designed to suppress this kind of stray light. For diffraction multiorder stray light, based on the theory of light-energy transmission, a design for precise positioning of the trench optical trap is proposed. The superiority of the method is verified through simulation and actual measurement. The simulation results show that in a spectroscopic system approximately 160 mm × 140 mm × 80 mm in size, the energy of the stray light is reduced by one order of magnitude by means of the trench optical trap and Lyot stop, and the number of beams is reduced from 5664 to 1040. The actual measurements show that the stray-light-suppression efficiency is about 69.4%, which is effective reduction of the amount of stray light.
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