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The inversion of the real kinematic properties of coronal mass ejections by forward modeling

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Research in astronomy and astrophysics 2011年第2期11卷 237-244页

作者： You Wu 1 and Peng-Fei Chen 1,2 1 Department of astronomy,Nanjing University,Nanjing 210093,china 2.key Lab of modern Astron.and Astrophys.,ministry of education,Nanjing 210093,china Department of astronomy Nanjing University Nanjing 210093 China key Lab of modern Astron. and Astrophys. Ministry of Education Nanjing 210093 China

Kinematic properties of coronal mass ejections （CMEs） suffer from projection effects,and it is expected that the real velocity should be larger and the real angular width should be smaller than the apparent *** attempts have been taken to correct the projection effects,which however led to an inflated average velocity probably due to the biased choice of CME *** order to estimate the overall influence of the projection effects on the kinematic properties of the CMEs,we perform a forward modeling of real distributions of CME properties,such as the velocity,the angular width,and the latitude,by requiring their projected distributions to best match *** a matching is conducted by Monte Carlo *** to the derived real distributions,we found that （1） the average real velocity of all non-full-halo CMEs is about 514 km s-1,and the average real angular width is about 33°,in contrast to the corresponding apparent values of 418 km s-1 and 42.7° in observations;（2） For the CMEs with the angular width in the range of 20°-120°,the average real velocity is 510 km s-1 and the average real angular width is 43.4°,in contrast to the corresponding apparent values of 392 km s-1 and 52° in observations.

关键词： Sun: coronal mass ejections (CMEs) -- methods: statistical -- methods:numerical

The frequencies of high frequency quasi-periodic oscillations in two different frames in black hole LMXBs

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Research in astronomy and astrophysics 2011年第11期11卷 1327-1335页

作者： Chang-Sheng Shi College of Material Science and Chemical Engineering,Hainan University,Hainan 570228,china key laboratory of modern astronomy and astrophysics,Nanjing University,Nanjing 210093,china College of Material Science and Chemical Engineering Hainan University Hainan 570228 China key laboratory of modern astronomy and astrophysics Nanjing University Nanjing 210093 China

We discuss the modes of the Alfvén waves in the accretion disk with a toroidal magnetic field in black hole low mass X-ray binaries in a rotating frame. By solving the perturbed general relativistic magnetohydrodynamic equations in the rotating frame, we find two stable modes of the Alfvén wave which are the same as those in the fiducial observer frame. This gives a feasible way to transform between the two different frames, which validates the possible Alfvén wave modes in the accreting celestial bodies with a toroidal magnetic field.

关键词： accretion accretion disks-magnetohydrodynamics-relativity

Sediment transport capacity of hyperconcentrated flow

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Science china(Physics,Mechanics & astronomy) 2008年第8期51卷 961-975页

作者： SHU AnPing1,2 & FEI XiangJun2 1 School of Environment & key laboratory of Water and Sediment Sciences,ministry of education,Beijing Normal University,Beijing 100875,china 2 State key laboratory of Hydroscience and Engineering,Tsinghua University,Beijing 100084,china School of Environment & key laboratory of Water and Sediment Sciences Ministry of Education Beijing Normal University Beijing China State key laboratory of Hydroscience and Engineering Tsinghua University Beijing China

As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data,which were obtained through two kinds of sediment transport experiments in the state of equilibrium,in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow,the main parameters in the structural expression of sediment transport capacity were calibrated,and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River,Wuding River,and Yangtze River,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.

关键词： hyperconcentrated flow turbulent energy equilibrium efficiency coefficient sediment transport capacity

Method of Green’s function of nonlinear vibration of corrugated shallow shells

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Science china(Physics,Mechanics & astronomy) 2008年第6期51卷 678-686页

作者： YUAN Hong key laboratory of Disaster Forecast and Control in Engineering, ministry of education of china, Institute of Applied Mechanics, Jinan University, Guangzhou 510632, china key laboratory of Disaster Forecast and Control in Engineering Ministry of Education of China Institute of Applied Mechanics Jinan University Guangzhou China

Based on the dynamic equations of nonlinear large deflection of axisymmetric shallow shells of revolution, the nonlinear free vibration and forced vibration of a corrugated shallow shell under concentrated load acting at the center have been investigated. The nonlinear partial differential equations of shallow shell were re-duced to the nonlinear integral-differential equations by using the method of Green’s function. To solve the integral-differential equations, the expansion method was used to obtain Green’s function. Then the integral-differential equations were reduced to the form with a degenerate core by expanding Green’s function as a series of characteristic function. Therefore, the integral-differential equations be-came nonlinear ordinary differential equations with regard to time. The ampli-tude-frequency relation, with respect to the natural frequency of the lowest order and the amplitude-frequency response under harmonic force, were obtained by considering single mode vibration. As a numerical example, nonlinear free and forced vibration phenomena of shallow spherical shells with sinusoidal corrugation were studied. The obtained solutions are available for reference to the design of corrugated shells.

关键词： corrugated shells spherical shells Green’s function integral equation nonlinear vibration

Magnetism induced by nonmagnetic dopants in zinc-blende SiC: First-principle calculations

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Science china(Physics,Mechanics & astronomy) 2010年第1期53卷 1-10页

作者： LIU ZhaoQing & NI Jun Department of Physics and key laboratory of Atomic and Molecular Nanoscience (ministry of education), Tsinghua University, Beijing 100084, china Department of Physics and key laboratory of Atomic and Molecular Nanoscience (ministry of education) Tsinghua University Beijing China

Magnetism induced by the nonmagnetic dopants in the zinc-blende SiC (3C-SiC) is investigated by first-principle calculations. The atoms of the first 20 elements in the periodic table except inert gas are used to replace either Si or C atoms as dopants. We find that some nonmagnetic substitutional dopants (mainly the Group IA, Group IIA, Group IIIB, and Group VIIB elements) prefer the spin-polarized ground states with local magnetic moments. In general, the condition for obtaining the local magnetic moments and the magnetic ground state requires that the dopants are p-type and have large electronegativity difference from the neighboring host atoms. The magnetic moments can be tuned over a range between 1 μ B and 3 μ B by doping with the nonmagnetic elements. The nearest-neighbor exchange couplings J 0 between the local magnetic moments are quite large and the codoping method is proposed to increase the dopant concentration. These imply that the nonmagnetic doping in SiC may exhibit collective magnetism. Moreover, the Group IIA Mg and Ca atoms substituting the preferred Si atoms favor the ferromagnetic ground states with the half-metallic electronic properties, which suggests that Mg or Ca substitutional doping on the Si sites in SiC could be a potential route to fabricating the diluted magnetic semiconductors.

关键词： nonmagnetic dopant magnetism SiC diluted magnetic semiconductor first-principle calculation

A study on odd-parity high-lying states of the Sm atom with three-color resonant excitation

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Science china(Physics,Mechanics & astronomy) 2011年第6期54卷 1124-1130页

作者： LI Ming 1,2,DAI ChangJian 1,2 & XIE Jun 1,2 1 key laboratory of Display Materials and Photoelectric Devices,ministry of education,Tianjin 300191,china 2 School of Science,Tianjin University of Technology,Tianjin 300384,china key laboratory of Display Materials and Photoelectric Devices Ministry of Education Tianjin China School of Science Tianjin University of Technology Tianjin China

The odd-parity high-lying states of the Sm atom are investigated systematically by a three-color resonant excitation scheme with two different excitation *** two intermediate states,4f 6 6s7s 7 F 0 and 4f 6 6s7s 7 F 1 are employed for paths I and II,***-seven bound states are detected with paths I and II in the energy range between 44188 and 45515 cm 1,while 64 autoionizing states are found in the energy range from 45528 to 45761 cm *** only the level energies of all observed states,but also the line widths of autoionizing states are *** possible impact of configuration interaction on the line shape of autoionizing states is also *** addition,the total angular momentum is assigned uniquely to most of the states,whereas the information about the relative line intensity of all states is also presented.

关键词： high-lying states odd-parity the Sm atom resonant excitation

On the knee of Galactic cosmic rays in light of sub-TeV spectral hardenings

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Chinese Physics C 2018年第7期42卷 113-122页

作者： Yi-Qing Guo1 2 Qiang Yuan1 3 1. key laboratory of Dark Matter and Space astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 china 2. key laboratory of Particle astrophysics Institute of High Energy Physics key laboratory of Dark Matter and Space astronomy Purple Mountain ObservatoryChinese Academy of Sciences key laboratory of Particle astrophysics Institute of High Energy PhysicsChinese Academy of Sciences School of astronomy and Space Science University of Science and Technology of China

More than fifty years after the discovery of the knee in the cosmic ray （CR） spectra, its physical origin remains a mystery. This is partly due to the ambiguity of the energy spectra of individual components. Recently, direct measurements from several space experiments found significant spectral hardenings of CR nuclei at ~200 GV. A joint modeling of the direct and indirect measurements may help to understand the experimental systematics and the physics of the knee. In this work, we update the phenomenological ＂poly-gonato＂ model to include the spectral hardenings, with a changing spectral index of γ ＋ β·logE. This modification gives a reasonable description of the CR spectra in a wide energy range. However, the fits to different data sets give different results. We find that the fit to the AMS-02 and CREAM data slightly favors a relatively low energy knee of the light components. In such a case, the expected all-particle spectra under-shoot the data, which may require an extra component of CRs. The fits to AMS-02 data and the light component （H＋He） data from the Tibet ASγ/ARGO-YBJ/WFCTA and KASCADE experiments give consistent results with the all-particle spectra. We further propose a possible physical realization of such a ＂modified poly-gonato＂ model of spectral hardenings by means of spatially-dependent diffusion of CRs. We find reasonably good agreement between the model predictions and the data for CR spectra, the secondary-to-primary ratios, and the amplitude of anisotropies.

关键词： cosmic ray knee spectrum propagation

The reliability of the improved e^N method for the transition prediction of boundary layers on a flat plate

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Science china(Physics,Mechanics & astronomy) 2012年第5期55卷 837-843页

作者： SU CaiHong1,2 1 Department of Mechanics,Tianjin University,Tianjin 300072,china 2 Tianjin key laboratory of modern Engineering Mechanics,Tianjin 300072,china Department of Mechanics Tianjin University Tianjin China Tianjin key laboratory of modern Engineering Mechanics Tianjin China

The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1%-2% of the free stream velocity,while in the conventional eN method,the N factor is an empirical *** this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations(PSE).Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE *** from both methods agree fairly well with each other,implying that the transition criterion proposed in the improved eN method is reliable.

关键词： transition prediction boundary layer eN PSE

Two-dimensional thermoelasticity solution for functionally graded thick beams

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Science china(Physics,Mechanics & astronomy) 2006年第4期49卷 451-460页

作者： Lü Chaofeng1, CHEN Weiqiu1 & ZHONG Zheng2 1. Department of Civil Engineering, Zhejiang University, Hangzhou 310027, china 2. key laboratory of Solid Mechanics of ministry of education, School of Aerospace Engineering and Ap- plied Mechanics, Tongji University, Shanghai 200092, china Department of Civil Engineering Zhejiang University Hangzhou China key laboratory of Solid Mechanics of ministry of education School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai China

Two-dimensional thermoelasticity analysis of functionally graded thick beams is presented using the state space method coupled with the technique of differential quadrature. Material properties vary continuously and smoothly through the beam thickness, leading to variable coefficients in the state equation derived from the elasticity equations. Approximate laminate model is employed to translate the state equation into the one with constant coefficients in each layer. To avoid numerical instability, joint coupling matrices are introduced according to the continuity conditions at interfaces in the approximate model. The differential quadrature procedure is applied to discretizing the beam in the axial direction to make easy the treatment of arbitrary end conditions. A simply-supported beam with exponentially varying material properties is considered to validate the present method. Numerical examples are performed to investigate the influences of relative parameters.

关键词： state equation differential quadrature approximate laminate model joint coupling matrices thermal stresses.