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Sensitivity analysis of surface ozone to emission controls in Beijing and its neighboring area during the 2008 Olympic Games

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Journal of Environmental Sciences 2012年第1期24卷 50-61页

作者： yi gao Meigen Zhang State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

The regional air quality modeling system RAMS （Regional Atmospheric Modeling System）-CMAQ （Community Multi-scale Air Quality modeling system） is applied to analyze temporal and spatial variations in surface ozone concentration over Beijing and its surrounding region from July to October *** of simulated and observed meteorological elements and concentration of nitrogen oxides （NOx） and ozone at one urban site and three rural sites during Olympic Games show that model can generally reproduce the main observed feature of wind,temperature and ozone,but NOx concentration is *** ozone concentration decreased during Olympics,high ozone episodes occurred on 24 July and 24 August with concentration of 360 and 245 μg/m 3 at Aoyuncun site,*** analysis of sensitive test,with and without emission controls,shows that emission controls could reduce ozone concentration in the afternoon when ozone concentration was highest but increase it at night and in the *** evolution of the weather system during the ozone episodes （24 July and 24 August） indicates that hot and dry air and a stable weak pressure field intensified the production of ozone and allowed it to *** analysis at the urban site and rural site shows that under favorable weather condition on 24 August,horizontal transport was the main contributor of the rural place and the pollution from the higher layer would be transported to the surface *** 24 July,as the wind velocity was smaller,the impact of transport on the rural place was not obvious.

关键词： chemical smoke tropospheric ozone emission control CMAQ process analysis

Random Weighting Estimation Method for Dynamic Navigation Positioning

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Chinese Journal of Aeronautics 2011年第3期24卷 318-323页

作者： gao Shesheng gao yi ZHONG Yongmin WEI Wenhui School of Automation Northwestern Polytechnical University Xi 'an 710072 China Department of Mechanical Engineering Curtin University WA6845 Australia

This paper presents a new random weighting estimation method for dynamic navigation positioning. This method adopts the concept of random weighting estimation to estimate the covariance matrices of system state noises and observation noises for controlling the disturbances of singular observations and the kinematic model errors. It satisfies the practical requirements of the residual vector and innovation vector to sufficiently utilize observation information, thus weakening the disturbing effect of the kinematic model error and observation model error on the state parameter estimation. Theories and algorithms of random weighting estimation are established for estimating the covariance matrices of observation residual vectors and innovation vec- tors. This random weighting estimation method provides an effective solution for improving the positioning accuracy in dynamic navigation. Experimental results show that compared with the Kalman filtering, the extended Kalman filtering and the adaptive windowing filtering, the proposed method can adaptively determine the covariance matrices of observation error and state error, effectively resist the disturbances caused by system error and observation error, and significantly improve the positioning accu- racy for dynamic navigation.

关键词： estimation navigation error random weighting estimation dynamic navigation positioning covariance matrix kinematic model error observation model error

Influence of the Acoustic Liner in Large Eddy Simulation of Longitudinal Thermoacoustic Instability in a Model Annular Combustor

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Journal of Thermal Science 2024年第2期33卷 710-724页

作者： MENG Sheng ZHANG Man gao yi AECC Commercial Aircraft Engine Co. Ltd.Shanghai200241China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai200240China

Although extensive efforts have been made to dampen the thermoacoustic instability,successfully controlling the pressure oscillations in modern gas turbines or aeroengines remains *** influence of the acoustic liner on the longitudinal thermoacoustic mode in a model annular combustor is investigated by Large Eddy Simulation(LES) in this *** result of the self-excited longitudinal thermoacoustic instability without the liner agrees well with the frequency and acoustic analysis of the pressure mode based on experimental *** different bias flow velocities of the liner located downstream of the combustor are then *** results reveal that the existence of the liner influences not only the acoustic field but also the flow *** the bias velocity is large,it leads to intense turbulence-induced fluctuations,and the pressure oscillation is modulated *** shows that the weak coupling between flow and pressure oscillations plays a significant role in the onset of the intermittency of a thermoacoustic *** on the dynamic analysis of the thermoacoustic system with the acoustic liner,this intermittency is caused by the influence of the flow field on the flame-acoustic ***,a low-order modeling method based on Van der Pol(VdP) oscillator with additive stochastic forcing is conducted to reproduce the evolving dynamics of the thermoacoustic *** the numerical cases demonstrated in this work are relatively simpler than those in a practical combustion system,the results are helpful for us to understand the effect of the acoustic liner and show the attractive potential to apply this device to suppress thermoacoustic instability.

关键词： thermoacoustic instability acoustic liner Large Eddy Simulation low-order modeling

Spin excitations in nickelate superconductors

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Science China(Physics,Mechanics & Astronomy) 2020年第8期63卷 114-122页

作者： Tao Zhou yi gao ZiDan Wang Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials Guangdong Provincial Engineering Technology Research Center for Quantum Precision MeasurementSchool of Physics and Telecommunication Engineeringand Frontier Research Institute for PhysicsSouth China Normal UniversityGuangzhou 510006China Department of Physics and Institute of Theoretical Physics Nanjing Normal UniversityNanjing 210023China Department of Physics and HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong The University of Hong KongHong Kong 999077China

Applying a three-band model and the random phase approximation,we theoretically study the spin excitations in nickelate superconductors,which have been newly *** spin excitations were found to be incommensurate in the low energy *** spin resonance phenomenon emerged as the excitation energy *** intensity can be maximized at the incommensurate or commensurate momentum,depending on the out-of-plane *** spin excitations reverted to incommensurate at higher *** also discuss the similarities and differences in the spin excitations of nickelate and cuprate *** predicted results can be later validated in inelastic neutron scattering experiments.

关键词： nickelates superconductivity d-wave pairing spin susceptibility

Liutex based new fluid kinematics

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Journal of Hydrodynamics 2022年第3期34卷 355-371页

作者： Chaoqun Liu yifei Yu yi-sheng gao Department of Mathematics University of Texas at ArlingtonArlingtonTexas76019USA College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016China

The traditional Cauchy-Stokes(C-S)decomposition states that the velocity gradient tensor can be decomposed into a symmetric tensor and an anti-symmetric tensor,namely the strain-rate tensor and the vorticity ***,there are two problems with the C-S *** is that the anti-symmetric(vorticity)tensor cannot represent the fluid rotation or *** is that the symmetric(strain-rate)tensor cannot distinguish the stretching/compression and *** vorticity cannot distinguish between the non-rotational shear and the rigid rotation,vorticity has been decomposed into a rigid rotation part called“Liutex”and an anti-symmetric shear in our previous work.A Liutex-based principal coordinate system has been proposed,and the corresponding velocity gradient tensor decomposition,called the principal decomposition,is presented in this principal coordinate system,which results in:(1)a Liutex tensor that represents rigid rotation,(2)a tensor that represents pure shear and(3)a tensor that represents stretching/***,each point has its own principal coordinate system,which implies that the principal decomposition is performed in different principal coordinate systems,not the original(global)coordinate *** address this issue,the principal decomposition in the original coordinate system is derived in this paper,and,therefore,provides a new kinematic approach to study the local rigid rotation,pure shear,and stretching/*** principal decomposition is unique,Galilean invariant and has clear physical *** new velocity gradient tensor decomposition could become a foundation for new fluid kinematics.

关键词： Liutex principal coordinates principal decomposition Helmholtz Cauchy-Stokes(C-S)

SOLVING SYMMETRIC MONOTONE LINEAR VARIATIONAL INEQUALITIES BY SOME MODIFIED LEVITIN-POLYAK PROJECTION METHODS

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Applied Mathematics(A Journal of Chinese Universities) 1998年第2期13卷 150-158页

作者： gao yi Department of Mathematics Nanjing University Nanjing

Abstract Some modified Levitin Polyak projection methods are proposed in this paper for solving monotone linear variational inequalityx∈Ω,(x′-x) T(Hx+c)≤0,\ x′∈Ω.It is pointed out that there are simil... 详细信息

关键词： Variational inequality projection mathod self-adaptive method

Painlevé analysis, auto-Bäcklund transformations, bilinear forms and soliton solutions for a(2+1)-dimensional variable-coefficient modified dispersive water-wave system in fluid mechanics

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Communications in Theoretical Physics 2023年第2期75卷 46-55页

作者： Fei-Yan Liu yi-Tian gao Ministry-of-Education Key Laboratory of Fluid Mechanics and National Laboratory for Computational Fluid Dynamics Beijing University of Aeronautics and AstronauticsBeijing 100191China

In this paper,we investigate a(2+1)-dimensional variable-coefficient modified dispersive waterwave system in fluid *** prove the Painlevéintegrability for that system via the Painlevé*** find some auto-B?cklund transformations for that system via the truncated Painlevé*** forms and N-soliton solutions are constructed,where N is a positive *** discuss the inelastic interactions,elastic interactions and soliton resonances for the two *** also graphically demonstrate that the velocities of the solitons are affected by the variable coefficient of that system.

关键词： fluid mechanics variable-coefficient modified dispersive water-wave system Painlevéanalysis bilinear forms soliton solutions auto-Bäcklund transformations

Theoretical advances of the structures and catalytic activities of small-sized gold nanoclusters

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Chinese Science Bulletin 2014年第3期59卷 239-246页

作者： Yadong Li yi gao Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology Shanghai Institute of Applied PhysicsChinese Academy of Sciences University of Chinese Academy of Sciences

Gold nanoclusters exhibit extraordinary catalytic activities,but the dominating factor is still unclear due to the complexity of the *** this review,we briefly summarized the recent theoretical progress on their structures and catalytic *** the experimental and theoretical efforts,the structures of small-sized gold clusters have been explored *** on the determined structures,factors that influence the catalytic capabilities of small-sized gold clusters(Au_(16)-Au_(35))are studied using CO oxidation asa *** preadsorption energies of CO and O_2are found strongly correlated with catalytic activities,which could be affected by the clusters'geometries,sizes,and charge *** addition,the presence of water could significantly lower the activation energy barrier of O_2 dissociation to enhance the clusters'catalytic activities.

关键词：催化活性金团簇小尺寸结构 CO氧化催化能力几何形状电荷分布

Explicit formula for the Liutex vector and physical meaning of vorticity based on the Liutex-Shear decomposition

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Journal of Hydrodynamics 2019年第3期31卷 464-474页

作者： yi-qian Wang yi-sheng gao Jian-ming Liu Chaoqun Liu School of Aerospace Engineering Tsinghua University Beijing 100084 China Department of Mathematics University of Texas at Arlington Arlington 76019 Texas USA School of Mathematics and Statistics Jiangsu Normal University Xuzhou 221116 China

In the present study, the physical meaning of vorticity is revisited based on the Liutex-Shear (RS) decomposition proposed by Liu et al. in the framework of Liutex (previously called Rortex), a vortex vector field with information of both rotation axis and swirling strength (Liu et al. 2018). It is demonstrated that the vorticity in the direction of rotational axis is twice the spatial mean angular velocity in the small neighborhood around the considered point while the imaginary part of the complex eigenvalue (2c.) of the velocity gradient tensor (if exist) is the pseudo-time average angular velocity of a trajectory moving circularly or spirally around the axis. In addition, an explicit expression of the Liutex vector in terms of the eigenvalues and eigenvectors of velocity gradient is obtained for the first time from above understanding, which can further, though mildly, accelerate the calculation and give more physical comprehension of the Liutex vector.

关键词： Vorticity Liutex Liutex-Shear(RS)decomposition explicit formula of Liutex