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- 저자 : Zhiyuan Shi (검색결과 4 건)
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Channel Prediction Based on Non-Uniform Pilot Pattern for Mobile Massive MIMO Scenarios
Shi, Yi,Wang, Xianling,Jiang, Zhiyuan 한국통신학회 2023 Journal of communications and networks Vol.25 No.4
Massive multiple input multiple output (MIMO) isa broadly used technique that can provide numerous gains inspectral efficiency. However, the degradation of beamformingperformance due to outdated channel state information at thetransmitter side (CSIT) induced by the mobility of users hasbeen a significant problem waiting to be solved. It is reported thatsystem performance will decrease 50 percent even in a moderate30 km/h speed scenario. However, the CSI cannot be simplyreconstructed through interpolation in high mobility scenariosdue to the limitation of pilot density — the phenomenon is knownas “Doppler aliasing”. To address this, we propose a novel non-uniform pilot pattern that can provide more spectrum resolutioncompared with the uniform pilot currently used in most commu-nication protocols. Meanwhile, we maintain the density of pilotsin order not to sacrifice the payload resources. Based on the novelpilot setting, we propose two-channel prediction schemes withcompressive sensing and matrix completion methods. Simulationresults show our scheme can outperform deep learning-based andauto-regressive-based methods for about 15 percent in terms ofaverage throughput in the simulated channel generated from theCOST2100 channel model. To further verify the applicability,we apply our schemes in real channels measured from a channelsounding campaign, the proposed methods also achieve 5 percentgain which validates their superiority over conventional methods.
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Zhiyuan Hu,Guohua Xu,Yongjie Shi 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.4
Rotors with active flap control have considerable potential in reducing vibration and noise and improving aerodynamic performance. However, due to the movement of the flap, there are unavoidable gaps between the components that will lead to significant changes in the aerodynamic characteristics. Moreover, considering the difficulties in motion modeling and the accuracy of the simulation of the flow field in such a narrow gap, carrying out related research is challenging; thus, there has been inadequate targeted research, and that which does exist requires supplementation. To carry out this challenging flow field simulation, the overset assembly algorithm proposed by the author in previous research is adopted in the present study. It is used to successfully assemble the narrow gap, and the accuracy of the simulation is fully verified by comparing the results with the actual experimental results and a grid study. Furthermore, to compensate for the lack of research and experiments on the gap effect, cases considering a complete range of gap widths from an absence of a gap to a width of 10% of the chord length are set up and carried out under the following three case groups: steady cases with a fixed trailing-edge deflection angle, unsteady cases in which only the trailing-edge flap is flapping, and full-motion cases characterized by the periodic flap of the main airfoil and the trailing-edge flap. The results show that the gap increases the drag of the trailing-edge flap and decreases aerodynamic efficiency, especially at low speeds and high angles of attack. Nevertheless, when the gap is unavoidable, there is a range of the gap width that makes unapparent the decrease of aerodynamic efficiency. Moreover, the decrease of aerodynamic efficiency can be reduced as much as possible by a well-designed gap region geometry to ensure that the airfoil and the trailing-edge flap fit together when moving.
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CRISPR system for genome engineering: the application for autophagy study
( Jianzhou Cui ),( Shirley Jia Li Chew ),( Yin Shi ),( Zhiyuan Gong ),( Han-ming Shen ) 생화학분자생물학회(구 한국생화학분자생물학회) 2017 BMB Reports Vol.50 No.5
CRISPR/Cas9 is the latest tool introduced in the field of genome engineering and is so far the best genome-editing tool as compared to its precedents such as, meganucleases, zinc finger nucleases (ZFNs) and transcription activator-like effectors (TALENs). The simple design and assembly of the CRISPR/Cas9 system makes genome editing easy to perform as it uses small guide RNAs that correspond to their DNA targets for high efficiency editing. This has helped open the doors for multi-plexible genome targeting in many species that were intrac-table using old genetic perturbation techniques. Currently, The CRISPR system is revolutionizing the way biological researches are conducted and paves a bright future not only in research but also in medicine and biotechnology. In this review, we evaluated the history, types and structure, the mechanism of action of CRISPR/Cas System. In particular, we focused on the application of this powerful tool in autophagy research. [BMB Reports 2017; 50(5): 247-256]
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Preparation and Photoelectric Properties of Silver Nanowire/ZnO Thin Film Ultraviolet Detector
Zhenfeng Li,Wei Xiao,Hongzhi Zhou,Zhiyuan Shi,Rongqing Li,Jia Zhang,Yang Li,Peng He,Shuye Y. Zhang 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.5
Ultraviolet (UV) detectors have important applications in many fi elds. ZnO is an excellent semiconductor material for the preparation of UV detectors because of its large direct gap in forbidden bandwidth, its intrinsic response band in the UV region, and its high exciton binding energy. In this paper, high-performance ZnO thin fi lms with the optically advantageous nonpolar structure were prepared by using an atomic layer deposition, and the dominant crystal plane gradually changes from the amorphous phase to the (100) crystal plane. The conventional photoconductor structure ZnO UV detector was enhanced by the surface plasmon exciton eff ect of Ag nanostructure. When the operating voltage is 5 V and the response light is 350 nm, there is a maximum optical responsiveness of up to 131 A/W. The UV/visible rejection ratio can reach 1824 times. When the ZnO thin fi lm deposition thickness is 400 deposition cycles and about 72 nm, the ZnO thin fi lm UV detector obtains the highest responsiveness (5 V, 365 nm) of 365 A/W. Comparing the photovoltaic performance of the ZnO thin-fi lm detector with the enhanced ZnO thin-fi lm detector and its optimal response wavelength, it is found that the enhanced ZnO thin-fi lm detector increased the photoresponse value by about 100 times. The optimal response wavelength in the UV region is blueshifted, and the UV-visible rejection ratio and optical response rate are signifi cantly improved.
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