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A computational particle fluid-dynamics simulation of hydrodynamics in a three-dimensional full-loop circulating fluidized bed: Effects of particle-size distribution

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Particuology 2020年第2期18卷 134-145页

作者： hang zhang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

A computational particle fluid-dynamics model coupled with an energy-minimization multi-scale(EMMS)drag model was applied to investigate the influence of particle-size distribution on the hydrodynamics of a three-dimensional full-loop circulating fluidized *** particle systems,including one monodisperse and two polydisperse cases,were *** numerical model was validated by comparing its results with the experimental axial voidage distribution and solid mass *** EMMS drag model had a high accuracy in the computational particle fluid-dynamics simulation of the three-dimensional full-loop circulating fluidized *** total number of parcels in the system(Np)influenced the axial voidage distribution in the riser,especially at the lower part of the *** numerical simulation results showed that axial segregation by size was predicted in the two polydisperse cases and the segregation size increased with an increase in the number of size *** axial voidage distribution at the lower portion of the riser was significantly influenced by particle-size ***,radial segregation could only be correctly predicted in the upper region of the riser in the polydisperse case of three solid species.

关键词： Circulating fluidized bed Computational particle fluid dynamics Particle-size distribution Energy-minimization multiscale model Three-dimensional full-loop simulation

Effects of Monovacancy on Thermal Properties of Bilayer Graphene Nanoribbons by Molecular Dynamics Simulations

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Journal of Thermal Science 2021年第6期30卷 1917-1924页

作者： YANG Ming zhang Xingli zhang hang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China College of Mechanical and Electrical Engineering Northeast Forestry UniversityHarbin 150040China Department of Mechanical Engineering University of ColoradoBoulderCO80309USA

The monovacancy defect effect on thermal conductivity of bilayer graphene nanoribbons(BGNs)was investigated using non-equilibrium molecular dynamics(NEMD)simulations in this *** results demonstrate that the presence of monovacancy defect in BGNs reduces their thermal transport properties *** major finding of this work shows that the calculated thermal conductivity reduces approximately linearly with the raise of monovacancy *** contrast to the temperature-dependent thermal conductivity in perfect BGNs,the thermal conductivity of defected BGNs first increases and then decreases with the increasing *** addition,when the difference in the monovacancy density between two layers is larger,the thermal conductivity of BGNs is *** also calculated the phonon density of states,phonon relaxation time and participation ratio to provide a deeper understanding of the simulation *** investigation confirms that the BGNs-based nano-devices could be applied in thermal management by defect engineering.

关键词： monovacancy thermal conductivity molecular dynamics graphene nanoribbons

Mechanical properties and failure behavior of 3D printed thermoplastic composites using continuous basalt fiber under high-volume fraction

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Defence Technology（防务技术） 2023年第9期27卷 237-250页

作者： hang zhang Wei-fu Sun State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing401120China Explosion Protection and Emergency Disposal Technology Engineering Research Center of the Ministry of Education Beijing10081China

Continuous basalt fiber(CBF)is an outstanding inorganic fiber produced from nature,which has a wide range of applications in the field of armor protection of national defense ***,the mechanical response and failure mechanism of 3D printed CBF reinforced components are still not well ***,the 3D printing thermoplastic composites with high volume fraction CBF have been successfully prepared by fused deposition modelling(FDM)*** effects of fiber printing direction and polymer matrix type on the tensile and flexural properties of the 3D printed composites have been explored,and the detailed failure morphology has been characterized using scanning electron microscopy and optical *** was found that under high fiber volume fraction,3D printed CBF reinforced polyamides(PA)composites have the best ability to maintain material integrity of the composites,followed by acrylonitrile butadiene styrene(ABS)and high impact polystyrene(HIPS).Besides,the results from rule of mixtures can accurately predict the longitudinal Young’s modulus of the 3D printed specimens,but there exists a large discrepancy for the prediction of the tensile *** microstructure analysis shows that the failure modes of 3D printed composites mainly include fiber debonding,fiber pull-out,stress whitening and matrix cracking.

关键词： Additive manufacturing Continuous basalt fiber Failure behavior Mechanical properties Thermoplastic composites

Transition control of a tail-sitter unmanned aerial vehicle with L1 neural network adaptive control

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Chinese Journal of Aeronautics 2023年第7期36卷 460-475页

作者： Jingyang ZHONG Chen WANG hang zhang School of Construction Machinery Chang’an UniversityXi’an 710061China

The main task of this work is to design a control system for a small tail-sitter Unmanned Aerial Vehicle(UAV)during the transition *** reasonable control performance can be obtained through a well-tuned single PID or cascade PID control architecture under nominal conditions,large or fast time-varying disturbances and a wide range of changes in the equilibrium point bring nonlinear characteristics to the transition control during the transition process,which leads to control precision ***,the PID controller’s tuning method relies on engineering experiences to a certain extent and the controller parameters need to be retuned under different working conditions,which limits the rapid deployment and preliminary *** on the above issues,a novel control architecture of L1 neural network adaptive control associated with PID control is proposed to improve the compensation ability during the transition process and guarantee the security *** L1 neural network adaptive control is revised to solve the multi-input and multi-output problem of the tail-sitter UAV system in this ***,the transition characteristics of the time setting difference between the desired transition speed and the desired transition pitch angle are analyzed.

关键词： L1 adaptive control Neural network Transition control Tail-sitter UAV Transition strategy

FIR system identification with set-valued and precise observations from multiple sensors

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Science China(Information Sciences) 2019年第5期62卷 179-194页

作者： hang zhang Ting WANG Yanlong ZHAO Key Laboratory of Systems and Control Academy of Mathematics and Systems ScienceChinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of Sciences

This paper considers the system identification problem for FIR(finite impulse response) systems with set-valued and precise observations received from multiple sensors. A fusion estimation algorithm based on some suitable identification algorithms for different types of observations is proposed. In particular, least square method is chosen for FIR systems with precise observations, while empirical measure method and EM algorithm are chosen for FIR systems with set-valued observations in the cases of periodic and general system inputs, respectively. Then, the quasi-convex combination estimator(QCCE) fusing the two different estimators by a linear combination with appropriate weights is constructed. Furthermore, the convergence properties are theoretically analyzed in terms of strong consistency and asymptotic efficiency. The fused estimator QCCE is proved to achieve the Cram′er-Rao(CR) lower bound asymptotically under periodic inputs. Extensive numerical simulations validate the superiority of the fusion estimation algorithm under both periodic and general inputs.

关键词： system identification FIR system set-valued precise fusion estimation quasi-convex combination estimator

Splitting positive sets

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Science China Mathematics 2023年第11期66卷 2457-2470页

作者： hang zhang Jialiang He Shuguo zhang School of Mathematics Southwest Jiaotong UniversityChengdu 610756China College of Mathematics Sichuan UniversityChengdu 610064China

We introduce a class of cardinal invariants sI for ideals I onωwhich arise naturally from the FinBW property introduced by Filipów et al.(2007).Let I be an ideal onω.Define sI=min{|X|:X■[ω]ω,B∈I+,?x∈X(Bx,B∩x... 详细信息

关键词： cardinal invariant forcing ideal convergence

多功能一体化装备高灵敏度侦察的虚假频率抑制技术研究

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电子信息对抗技术 2025年第1期40卷 11-15页

作者：陈善涛张伟张航王刚中国电子科技集团公司第二十九研究所成都610036

高灵敏度侦察系统由于侦察灵敏度高,当侦察环境中出现大功率信号时,会给系统引入工作带宽内的虚假频率。而在一体化装备中,系统本身就会产生大功率信号,对侦察造成了无意干扰并引入虚假频率。当大功率信号频率在带外时,使用宽开接收机... 详细信息

高灵敏度侦察系统由于侦察灵敏度高,当侦察环境中出现大功率信号时,会给系统引入工作带宽内的虚假频率。而在一体化装备中,系统本身就会产生大功率信号,对侦察造成了无意干扰并引入虚假频率。当大功率信号频率在带外时,使用宽开接收机侦收大功率信号,将侦收到的脉冲引入到窄带高灵敏度系统,在窄带接收机中,通过比较脉冲的时序关系,将大功率信号的频率作为参考频率写入到窄带接收机产生的脉冲描述字参数中。当大功率信号频率在带内时,直接比较带内产生的脉冲的时序关系进行参考频率打标。对具有参考频率的脉冲描述字,使用基于统计的脉冲串虚假频率抑制方法,在信号级对虚假频率进行滤除,能够有效地抑制一体化装备中高灵敏侦察面临的虚假频率问题。

关键词：高灵敏度侦察谐波虚假交调互调虚假虚假频率抑制

Density-Functional Theories for Polyelectrolyte Systems

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Chinese Journal of Polymer Science 2024年第9期42卷 1302-1312,I0006页

作者： Jia-Wei zhang Yu-hang zhang Bao-Hui Li Qiang Wang School of Physics Nankai UniversityTianjin90001China Department of Chemical and Biological Engineering Colorado State University1370 Campus DeliveryFort CollinsCO80523-1370USA

Polymer density-functional theories(PDFTs)have distinct advantages in the study of polyelectrolyte(PE)systems over experiments and molecular *** we give an introductory review of some PDFTs recently developed for PE *** start with a general formalism of PDFTs and its relation to the widely used polymer self-consistent field theory(SCFT),then explain the various correlations that are neglected in SCFT but can be accounted for in PDFTs,including those due to the excluded-volume interaction and chain connectivity of uncharged polymers,the electrostatic correlations of small ions,and the chain correlations in *** also list some applications of PDFTs for PE systems,and finally give some perspectives on future *** hope that our review can attract more researchers to apply and further develop PDFTs as a promising class of theoretical and computational tools.

关键词： Polymer density-functional theories Polyelectrolytes Correlations

Carbon quantum dots: An innovative additive for water lubrication

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Science China(Technological Sciences) 2019年第4期62卷 587-596页

作者： XIAO HuaPing LIU ShuHai XU Quan zhang hang College of Mechanical and Transportation Engineering China University of Petroleum-Beijing Institute of New Energy China University of Petroleum-Beijing

Water soluble carbon quantum dots(CQDs) were prepared and used as lubricant additives in deionized(DI) water. The impacts of CQDs on the tribological properties of water were evaluated for both Si_3N_4-on-steel and Si_3N_4-on-Si_3N_4 contacts. Experimental results show that the coefficient of friction(COF) reduced in the two types of tribopairs after the addition of *** reductions in COF were found to be 30% and 14% for the Si_3N_4-steel and Si_3N_4-Si_3N_4 contacts, respectively. In terms of wear behaviors, the CQDs notably improved tribofilm formation on the Si_3N_4 disk surface for the Si_3N_4-Si_3N_4 contacts,confirming that the nanoparticles increase friction while providing better protection from wear. This research will help to expand the application of CQDs as promising additives in water-based lubricants.

关键词： carbon quantum dot water lubrication lubricant additives ceramic tribopairs