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Coverage Analyses on Directional Transmissions Ultra-Dense Networks with Imperfect Beam Alignment

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China Communications 2022年第5期19卷 318-328页

作者： Yining Xu sheng zhou Beijing National Research Center for Information Science and Technology Department of Electronic EngineeringTsinghua UniversityBeijing 100084China

Blockage and imperfect beam alignment are two principal difficulties in high-frequency bands directional *** this paper,the coverage performance of downlink directional transmissions in ultra-dense networks is analyzed,with the consideration of beam alignment error and link blockage through stochastic *** experiments demonstrate that narrower beam leads to higher coverage probability with perfect beam alignment,but it is not the case with imperfect beam ***,the optimal beamwidth that maximize the coverage probability is characterized and a closed-form approximation of the optimal beamwidth is derived under imperfect beam alignment,***,the optimal beamwidth is a monotonically increasing function of the standard deviation of the beam alignment error,and a monotonically decreasing function of the beamwidth of correspondent communication end,indicating that the beamwidth of the communication pairs ought to be jointly designed.

关键词： imperfect beam alignment directional transmission ultra-dense networks stochastic geometry

Analytical solution for the stress field of hierarchical defects:multiscale framework and applications

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Applied Mathematics and Mechanics(English Edition) 2021年第2期42卷 183-208页

作者： Baijian WU sheng zhou Zhaoxia LI Jiangsu Key Laboratory of Engineering Mechanics Southeast UniversityNanjing 210096China Department of Engineering Mechanics Southeast UniversityNanjing 210096China

Hierarchical defects are defined as adjacent defects at different length *** are the two scales where the stress field distribution is *** on the complex variable method and conformal mapping,a multiscale framework for solving the problems of hierarchical defects is *** separated representations of mapping function,the governing equations of potentials,and the stress field are subsequently *** proposed multiscale framework can be used to solve a variety of simplified engineering *** case in point is the analytical solution of a macroscopic elliptic hole with a microscopic circular edge *** results indicate that the microscopic defect aggregates the stress concentration on the macroscopic defect and likely leads to global propagation and *** micro-defects have interactive effects on the distribution of the stress *** level of stress concentration may be reduced by the coalescence of *** work provides a unified method to analytically investigate the influence of edge micro-defects within the scope of multiscale *** formulated multiscale approach can also be potentially applied to materials with hierarchical defects,such as additive manufacturing and bio-inspired materials.

关键词： hierarchical defect stress field multiscale framework scale separation complex variable method elliptic crack edge defect

Resource Allocation for Channel Estimation in Reconfigurable Intelligent Surface-Aided Multi-Cell Networks

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Journal of Communications and Information Networks 2024年第1期9卷 64-79页

作者： Yining Xu sheng zhou Department of Electronic Engineering Beijing National Research Center for Information Science and TechnologyTsinghua UniversityBeijing 100084China

Reconfigurable intelligent surface(RIS)is a promising solution to deal with the blockage-sensitivity of millimeter wave band and reduce the high energy consumption caused by network densification. However, deploying large scale RISs may not bring expected performance gain due to significant channel estimation overhead and non-negligible reflected *** this paper,we derive the analytical expressions of the coverage probability, area spectrum efficiency(ASE)and energy efficiency (EE)of a downlink RIS-aided multi-cell *** order to optimize the network performance, we investigate the conditions for the optimal number of training symbols of each antenna-to-antenna and antenna-to-element path (referred to as the optimal unit training overhead) in channel *** study shows that:1)RIS deployment is not“the more, the better”, only when blockage objects are dense should one deploy more RISs;2) the coverage probability is maximized when the unit training overhead is designed as large as possible;3)however,the ASE-and-EE-optimal unit training overhead exists. It is a monotonically increasing function of the frame length and a monotonically decreasing function of the average signal-to-noise-ratio (in the high signal-to-noise-ratio region). Additionally,the optimal unit training overhead is smaller when communication nodes deploy particularly few or many antennas.

关键词： reconfigurable intelligent surface multi-cell network directional transmissions channel estimation resource allocation stochastic geometry

Importance-Aware Data Pre-Processing and Device Scheduling for Multi-Channel Edge Learning

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Journal of Communications and Information Networks 2022年第4期7卷 394-407页

作者： Xiufeng Huang sheng zhou Beijing National Research Center for Information Science and Technology Department of Electronic EngineeringTsinghua UniversityBeijing 100084China

The large-scale deployment of intelligent Internet of things(IoT)devices have brought increasing needs for computation support in wireless access *** machine learning(ML)algorithms at the network edge,i.e.,edge learning,requires efficient training,in order to adapt themselves to the varying ***,the transmission of the training data collected by devices requires huge wireless *** address this issue,we exploit the fact that data samples have different importance for training,and use an influence function to represent the *** on the importance metric,we propose a data pre-processing scheme combining data filtering that reduces the size of dataset and data compression that removes redundant *** a result,the number of data samples as well as the size of every data sample to be transmitted can be substantially reduced while keeping the training ***,we propose device scheduling policies,including rate-based and Monte-Carlo-based policies,for multi-device multi-channel systems,maximizing the summation of data importance of scheduled *** show that the proposed device scheduling policies bring more than 2%improvement in training accuracy.

关键词： edge computing ML data importance resource allocation

Frequency Analyses for Mechanism Research of Unsteady Flow Inside Three Dimensional Compressor Cascade

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Journal of Thermal Science 2004年第3期13卷 207-212页

作者： sheng zhou Hongbin Wu Xinqian Zheng Beijing Univ Aeronaut & Astronaut Natl Key Lab Aircraft Engine Beijing 100083 Peoples R China

Numerical simulations are carried out for unsteady flow field of certain kind of 3D compressor cascade. Emphasis is laid on vortex shedding and frequency analysis in a compressor cascade. Numerical simulations using unsteady Reynolds-averaged viscous turbulent equations are carried out. The results show that the flows in separated areas and wake areas are characterized as periodic or quasi-periodic vortex shedding and the frequencies of vortex shedding vary with incidences and Mach number. At the same Mach number, the frequency of vortex shedding will decrease as the incidence increases. Yet, the frequency will increase as the Mach number increases at the same incidence. In the same computation case, the frequency of vortex shedding will vary along the span of blade. The frequency is smaller at the middle of the span than that at the hub.

关键词： axial flow compressor cascade unsteady flow separated flow frequency of vortex shedding.

Influence of double-inlet design on the flow-head characteristics of axial-flow pump

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Journal of Hydrodynamics 2021年第4期33卷 763-772页

作者： Yong-sheng zhou Hua Zhang Bin Chen School of Mechanical Engineering Hefei University of TechnologyHefei230009China College of Hydraulic Science and Engineering Yangzhou UniversityYangzhou225127China School of Environmental Science and Engineering Nanjing University of Information Science and TechnologyNanjing210044China

The internal flow field of an axial-flow pump under low flow rate conditions is extremely turbulent. The unstable flow region is formed due to the tip leakage and the rotating stall, and is distinguished by a saddle patterned zone in its flow-head curve that demonstrates restrictions in its workable flow range. It is therefore important to understand and improve the operational characteristics of an axial-flow pump under low flow rate conditions. In this study, experiments are performed for the performances of an axial-flow pump at the flow rate in a range between 0.8Qd and 1.2Qd, with the internal flow field measured by the particle image velocimetry (PIV), and with the pump performances and the internal flow field simulated by the Ansys CFX. The simulation results agree well with the experimental results. From the predicted heads at the flow rate in the range between 0.1Qd and 0.7Qd by the numerical simulation, the complete flow-head curves are obtained. The streamlines and the velocity contours in the region in front of the impeller leading edge under different flow conditions are analyzed. By adopting the double-inlet structures, the flow-head characteristics are studied by varying the values of δ and σ respectively, where δ denotes the gap between the inner cylinder end and the impeller leading edge, and σ denotes the gap between the inner cylinder and the outer cylinder. The findings indicate that with the double-inlet design, the velocity distribution can be effectively improved in the region in front of the impeller leading edge, as well as the head performance under the low flow rate conditions, and the positive slope value of the head curve is reduced in the unstable flow range. The optimal δ and σ values are determined.

关键词： Double-inlet particle image velocimetry(PIV) tip leakage numerical simulation axial-flow pump

Induction of membraneless organelles as a strategy for HIV-1 post-nuclear entry steps

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Journal of Molecular Cell Biology 2023年第2期15卷 1-2页

作者： sheng zhou Hongyu Deng CAS Key Laboratory of Infection and Immunity Institute of BiophysicsChinese Academy of SciencesBeĳing 100101China University of Chinese Academy of Sciences Beĳing 100049China CAS Center for Excellence in Biomacromolecules Institute of BiophysicsChinese Academy of SciencesBeĳing 100101China

As intracellular parasites,viruses must modulate the environment of host cells to facilitate viral genome replication and virion *** strategy is to establish specialized,membrane-associated subcellular structures to concentrate viral and cellular components and mediate viral replication *** strategy is utilized by many positive-strand RNA viruses such as coronaviruses,hepatitis C virus,and Zika virus,and they re-organize host endo-membranes to form double-membrane vesicles for viral genome replication(Wolff et al.,2020).

关键词： al. steps utilized

Solution of a sound field generated by the vibrating surface of a body moving at small Mach number

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Chinese Science Bulletin 1998年第1期43卷 75-78页

作者： Tongqing Wang sheng zhou Beijing Univ Aeronaut & Astronaut Aeroengine Aerodynam & Thermal Natl Lab Beijing 100083 Peoples R China

An approach to calculate the sound field generated by the Vibrating surface of a body with arbitrary shape moving at a small mach number has been developed by using acoustical analogy. A governing equation to calculate the sound pressure on the surface exited by its vibration has been derived on the basis of the united aerodynamics and aeroacoustics approach by Farassat and Long, and the sound field would be determinate. The cases relating to the sound sources of static sphere and moving compact pulsating sphere give a good check for the approach.

关键词： acoustic analogy aeroacoustics sound induced by vibration sound sources of sphere.

Overall optimization of Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines considering the cooling power consumption

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Science China(Technological Sciences) 2016年第2期59卷 309-321页

作者： YANG Can XIE Hui zhou sheng K State Key Laboratory of Engines Tianjin University

The Rankine cycle system for waste heat recovery of heavy-duty vehicle diesel engines has been regarded as a promising tech- nique to reduce fuel consumption. Its heat dissipation in the condensation process, however, should be take：l away in time, which is an energy-consuming process. A fan-assisted auxiliary water-cooling system is employed in this paper. Results at 1300 r/min and 50% load indicate that the cooling pump and cooling fan together consume 7.66% of the recovered power. What＇s worse for the heavy load, cooling accessories may deplete of all the recovered power of the Rankine cycle system. Af- terwards, effects of the condensing pressure and water feeding temperature are investigated, based on which a cooling power consumption model is established. Finally, an overall efficiency optimization is conducted to balance the electric power gener- ation and cooling power consumption, taking condensing pressure, pressure ratio and exhaust bypass valve as major variables. The research suggests that the priority is to increase condensing pressure and open exhaust bypass valve appropriately at high speed and heavy load to reduce the cooling power consumption, while at low speed and light load, a lower condensing pressure is favored and the exhaust bypass valve should be closed making the waste heat recovered as much as possible. Within the sub-critical region, a larger pressure ratio yields higher overall efficiency improvement at medium-low speed and load. But the effects taper off at high speed and heavy load. For a given vehicular heavy-duty diesel engine, the overall e：＇ficiency can be improved by 3.37% at 1300 r/min and 25% load using a Rankine cycle system to recover exhaust energy. The improvement becomes smaller as engine speed and load become higher.

关键词： vehicular diesel engines Rankine cycle system cooling power consumption waste heat recovery overalloptimization