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Acta Mathematicae Applicatae Sinica 2023年第1期39卷 28-48页

作者： Ye-chi lIU Academy of Mathmatics and Systems Science Chinese Academy of SciencesBeijing 100190China

In this paper,it is proved that the weak solution to the Cauchy problem for the scalar viscous conservation law,with nonlinear viscosity,different far field states and periodic perturbations,not only exists globally in time,but also converges towards the viscous shock wave of the corresponding Riemann problem as time goes to ***,the decay rate is *** proof is given by a technical energy method.

关键词： viscous conservation law asymptotic behavior time decay rate viscous shock wave periodic perturbation

Transition control of Mach 6.5 hypersonic flat plate boundary layer

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Applied Mathematics and Mechanics(English Edition) 2019年第2期40卷 283-292页

作者： Yunchi ZHANG chi lI State Key laboratory for Turbulence and Complex Systems Peking University Department of Aeronautics and Astronautics College of EngineeringPeking University

An artificial disturbance is introduced into the boundary layer over a flat plate to investigate the effect on the transition process in the Mach 6.5 wind tunnel at Peking University. A linear stability theory(lST) is utilized to predict the evolution of the eigenmodes, and the frequency of the artificial disturbance is chosen according to the lST results. The artificial disturbance is generated by glowing discharge on the surface of the plate close to the leading edge. The Rayleigh-scattering visualization and particle image velocimetry(PIV) measurements are performed. By comparing the experimental results with artificial disturbances with those under the natural condition(without artificial disturbances), the present paper shows that the second-mode instability waves are significantly stimulated by the artificial disturbances, and the boundary layer transition is effectively triggered.

关键词： hypersonic boundary layer transition control glowing discharge

A NEW NEURAl NETWORK-BASED ADAPTIVE IlC fOR NONlINEAR DISCRETE-TIME SYSTEMS WITH DEAD ZONE SCHEME

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Journal of Systems Science & Complexity 2009年第3期22卷 435-445页

作者： Ronghu chi Zhongsheng HOU Institute of Autonomous Navigation and Intelligent Control School of Automation and Electrical EngineeringQingdao University of Science and Technology Qingdao 266042 China. Advanced Control Systems laboratory School of Electronics and Information Engineering Beijing JiaotongUniversity Beijing 100044 China.

By introducing a deadwzone scheme, a new neural network based adaptive iterative learning control （IlC）（NN-AIlC） scheme is presented for nonlinear discrete-time systems, where the NN weights are time-varying. The most distinct contribution of the proposed NN-AIlC is the relaxation of the identical conditions of initial state and reference trajectory, which are common requirements in traditional IlC problems. Convergence analysis indicates that the tracking error converges to a bounded ball, whose size is determined by the dead-zone nonlinearity. Computer simulations verify the theoretical results.

关键词： Adaptive control iterative learning control neural network non-identical initial condition,non-identical trajectory.

large scale current systems developed from substorm onset:Global MHD results

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Science china(Technological Sciences) 2018年第3期61卷 389-396页

作者： TANG BinBin WANG chi State Key laboratory of Space Weather National Space Science Center Chinese Academy of Sciences

We investigate the large-scale substorm current systems developed from its onset in an idealized substorm event simulated by global magnetohydrodynamic(MHD) models. Mainly three current systems(loops) are revealed:(1) the classical substorm current wedge, which is composed by the disputed cross-tail current in the magnetotail, the nightside westward electrojet in the high-latitude ionosphere and a pair of region 1 field-aligned currents(fAC);(2) the partial-ring current system, which is braced by two region 2 fACs; and(3) the meridional current system, which is formed by an equatorial radial current(outward/inward in the morning/evening sector), and region 1 and region 2 fACs at its two ends. The region 2 fAC connects with region 1 fAC by a latitudinal horizontal current at each morning/evening ionosphere to complete loops 2 and 3. A quantitative study shows the significant enhancement of these current systems during the substorm expansion phase, while loop 1 dominates, which can reach a magnitude of ~1 MA. Empirical relations among the ionospheric currents and the related magnetotail currents are established based on the simulation results, implying that the substonn current systems are not evolved locally or separately, but must be viewed from a global perspective. This knowledge of large-scale substorm current system would deepen our understanding of the substorm development and could be validated by observations in the future.

关键词： magnetospheric physics substorm current system magnetohydrodynamic(MHD) simulation

Hull form optimization of a cargo ship for reduced drag

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Journal of Hydrodynamics 2016年第2期28卷 173-183页

作者： fuxin HUANG chi YANG Department of Physics and Astronomy George Mason University

Hydrodynamic optimization of the hull forms can be realized through the implementation and integration of computational tools that consist of a hydrodynamic module, a hull surface representation and modification module, and an optimization module. In the present paper, a new bulbous bow generation and modification technique has been developed and integrated into the hull surface representation and modification module. A radial basis function based surrogate model is developed to approximate the objective functions and reduce the computing cost. A multi-objective artificial bee colony optimization algorithm is implemented and integra- ted into the optimization module. To illustrate the integrated hydrodynamic optimization tools, a cargo ship is optimized for reduced drag. The optimal hull forms obtained are then validated computationally and experimentally. Validation results show that the prese- nt tools can be used efficiently and effectively in the simulation based design of the hull forms for reduced drag.

关键词： simulation based design ship hull form optimization drag reduction radial basis function surrogate model,Neumann-Michell theory

Sin1-mTORC2 signaling drives glycolysis of devetoping thymocytes

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Journal of Molecular Cell Biology 2019年第2期11卷 91-92页

作者： Hongbo chi Department of Immunology St. Jude Children's Research Hospital Memphis TN 38105 USA

Emerging studies highlight the import-ance of metabolic reprogramming in T cell development and function, although how these processes are regulated remains to be fully understood. Recent advances in dissecting the roles of Sinl-m T0RC2 signaling in early thymocyte development provide new in sight into the dynamic in terplay between immune signaling and cell metabolism, as well as the crucial role in directi ng thymocyte pro life ration and development.

关键词： Sin1-mTORC2 thymocytes glycolysis

Influence of South china Sea SST and the ENSO on Winter Rainfall over South china

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Advances in Atmospheric Sciences 2010年第4期27卷 832-844页

作者：周连童 chi-Yung TAM 周文 Johnny C. l. CHAN Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of Sciences CityU-IAP laboratory for Atmospheric Sciences City University of Hong Kong Guy Carpenter Asia-Pacific Climate Impact Centre School of Energy and EnvironmentCity University of Hong Kong

The present study investigates the influence of South china Sea （SCS） SST and ENSO on winter （January-february-March; JfM） rainfall over South china and its dynamic processes by using station observations for the period 1951-2003, Met Office Hadley Center SST data for the period 1900-2008, and ERA-40 reanalysis data for the period 1958-2002. It is found that JfM rainfall over South china has a sig- nificant correlation with Nio-3 and SCS SST. Analyses show that in El Nio or positive SCS SST anomaly years, southwesterly anomalies at 700 hPa dominate over the South china Sea, which in turn transports more moisture into South china and favors increased rainfall. A partial regression analysis indicates that the independent ENSO influence on winter rainfall occurs mainly over South china, whereas SCS SST has a larger independent influence on winter rainfall in northern part of South china. The temperature over South china shows an obvious decrease at 300 hPa and an increase near the surface, with the former induced by Nio-3 and the latter SCS SST anomalies. This enhances the convective instability and weakens the potential vorticity （PV）, which explains the strengthening of ascending motion and the increase of JfM rainfall over South china.

关键词： ENSO South china Sea SST rainfall convective instability potential vorticity

An overview of simulation-based hydrodynamic design of ship hull forms

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Journal of Hydrodynamics 2016年第6期28卷 947-960页

作者： chi YANG fuxin HUANG Center for Computational fluid Dynamics George Mason University

This review paper presents an overview of simulation-based hydrodynamic design optimization of ship hull forms. A computational tool that is aimed to accomplishing early-stage simulation-based design in terms of hydrodynamic performance is discussed in detail. The main components of this computational tool consist of a hydrodynamic module, a hull surface modeling module, and an optimization module. The hydrodynamic module includes both design-oriented simple CfD tools and high-fidelity CfD tools. These integrated CfD tools are used for evaluating hydrodynamic performances at different design stages. The hull sur- face modeling module includes various techniques for ship hull surface representation and modification. This module is used to automatically produce hull forms or modify existing hull forms in terms of hydrodynamic performance and design constraints. The optimization module includes various optimization algorithms and surrogate models, which are used to determine optimal designs in terms of given hydrodynamic performance. As an illustration of the computational tool, a Series 60 hull is optimized for reduced drag using three different modification strategies to outline the specific procedure for conducting simulation-based hydrodynamic design of ship hull forms using the present tool. Numerical results show that the present tool is well suited for the hull form design optimization at early design stage because it can produce effective optimal designs within a short period of time.

关键词： simulation based design ship hull form optimization radial basis function NURBS hydrodynamics

Analysis on residual strain of Zipingpu Concrete faced Rockfill Dam after Wenchuan earthquake

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Earthquake Engineering and Engineering Vibration 2013年第2期12卷 221-228页

作者： liu Zhenping chi Shichun Institute of Earthquake Engineering School of Hydraulic EngineeringDalian University of Technology

The Zipingpu Concrete faced Rockfill Dam （CfRD） was subjected to significant local damage in the ＂5.12＂ Wenchuan earthquake. It is the first rockfill dam of more than one hundred meters high to encounter a strong earthquake anywhere in the world. Based on the finite element smoothing method, the residual strains at a typical cross-section and a downstream slope of the dam were obtained by processing the dam monitored displacement data. The position of and reason for the dam settlement and deformation ofrockfill dilatancy in the earthquake were analyzed according to the section residual strain. The results show that the maximum settlement ratio on the dam body approximately occurs at 2/3 of the dam height; dilatancy occurs from the dam crest to 25-30 m in the upstream and downstream slope; the immediate cause of the face slabs horizontal construction joint dislocation is excessive residual shear strain. Meanwhile, the position of and reason for the dam fissure in the earthquake were analyzed according to the dam slope residual strain.

关键词： Zipingpu CfRD Wenchuan earthquake fEM data smooth residual strain damage mechanism

Effect of glow discharge on hypersonic flat plate boundary layer

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Applied Mathematics and Mechanics(English Edition) 2019年第2期40卷 249-260页

作者： chi lI Yunchi ZHANG State Key laboratory for Turbulence and Complex Systems Peking University Department of Aeronautics and Astronautics College of EngineeringPeking University

Glow discharge is introduced as an artificial disturbance to investigate the evolution of first-and second-mode instabilities in a hypersonic flat plate boundary *** are conducted in a Mach 6.5 quiet wind tunnel using Rayleigh scattering visualization and particle image velocimetry(PIV). Detailed analysis of the experimental observations is provided. It is found that the artificially introduced 17 kHz disturbance,which belongs to the first-mode frequency band, can effectively enhance first-mode ***, it can enhance second-mode waves even more intensely. Possible mechanisms to explain this phenomenon are discussed.

关键词： glow discharge hypersonic particle image velocimetry(PIV)