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Recent progress of solar physics research in china

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Research in astronomy and astrophysics 2011年第12期11卷 1377-1402页

作者： Cheng Fang 1 School of astronomy and Space Science,nanjing university,nanjing 210093,china 2 key laboratory of modern astronomy and astrophysics(nanjing university),Ministry of Education,china School of astronomy and Space Science Nanjing University Nanjing 210093 China key laboratory of modern astronomy and astrophysics (nanjing university) Ministry of Education China

Owing to the largely improved facilities and working conditions, solar physics research in china has recently shown marked development. This paper reports on the recent progress of solar physics research in china's Mainland, mainly focusing on several hot issues, including instrumentations, magnetic field observations and research, solar flares, filaments and their eruptions, coronal mass ejections and related processes, as well as active regions and the corona, small-scale phenomena, solar activity and its predictions. A vision of the future is also described.

关键词： Sun: general -- Sun: coronal mass ejections (CMEs) -- solar physics:recent progress

A new frequency scale of Chinese whispered speech in the application of speaker identification

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Progress in Natural Science:Materials International 2006年第10期16卷 1072-1078页

作者： LIN Wei, YANG Lili and XU Boling (Institute of Acoustics & key laboratory of modern Acoustics, nanjing university, nanjing 210093, china) Institute of Acoustics and key laboratory of modern Acoustics Nanjing University Nanjing 210093 China

In this paper, the frequency characteristics of Chinese whispered speech were investigated by a filter bank analysis. It was shown that the first and the third formants were more important than the other formants in the speaker identification of Chinese whispered speech. The experiment showed that the 800-1200 Hz and 2800-3200 Hz ranges were the most significant frequency ranges in discriminating the speaker. Based on this result, a new feature scale named whisper sensitive scale (WSS) was proposed to replace the common scale, Mel scale, and to extract the cepstral coefficient from whispered speech signal. Furthermore, a speaker identification system in whispered speech was presented based on the modified Hidden Markov Models integrating advantages of WSCC (the whisper sensitive cepstral coefficient) and LPCC. And the new system performed better in solving the problem of speaker identification of Chinese whispered speech than the traditional method.

关键词： speaker identification Chinese whispered speech whisper sensitive scale.

An effective absorbing boundary algorithm for acoustical wave propagator

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Progress in Natural Science:Materials International 2007年第9期17卷 1012-1017页

作者： Lin Zhibin ,Lu Jing and Xu Boling(key laboratory of modern Acoustics,Institute of Acoustics,nanjing university,nanjing 210093,china) key laboratory of modern Acoustics Institute of Acoustics Nanjing University Nanjing 210093 China

In this paper,Berenger’s perfectly matched layer(PML)absorbing boundary condition for electromagnetic waves is introduced as the truncation area of the computational domain to absorb one-dimensional acoustic wave for the scheme of acoustical wave propagator(AWP).To guarantee the efficiency of the AWP algorithm,a regulated propagator matrix is derived in the PML *** simulations of a Gaussian wave packet propagating in one-dimensional duct are carried out to illustrate the efficiency of the combination of PML and *** with the traditional smoothing truncation windows technique of AWP,this scheme shows high computational accuracy in absorbing acoustic wave when the acoustical wave arrives at the computational *** coefficients of the PML configurations are also discussed.

关键词： acoustical wave propagator perfectly matched layer absorbing boundary conditions(ABC).

A self-steering close-talking microphone array

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Progress in Natural Science:Materials International 2005年第11期15卷 1044-1049页

作者： PENG Ke, YANG Xinfeng and XU Boling (State key laboratory of modern Acoustics, Institute of Acoustics, nanjing university, nanjing 210093, china) State key laboratory of modern Acoustics Institute of Acoustics Nanjing University Nanjing 210093 China

For communication in extremely noisy environments, close-talking microphone arrays are useful. Differential microphone array systems possessing excellent nearfield directivity and strong farfield-noise reduction capability are very suitable for close-talking situations. In order to improve the focusing effect at the desired bearing in the nearfield, we propose a novel self-steering system of close-talking arrays with the first-order differential sub-arrays in this paper. Calculations of directivity patterns and directivity factors show that when a kind of optimized beamforming technique is adopted even small arrays with a focusing configuration will exhibit a satisfactory nearfield directivity which is electronically steerable within a specific range. The superiority of the proposed array system is verified by experiments with real acoustic data.

关键词： close-talking array differential array self-steering directivity factor.

EIT waves and coronal magnetic field diagnostics

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Science china(Physics,Mechanics & astronomy) 2009年第11期52卷 1785-1789页

作者： CHEN PengFei Department of astronomy, nanjing university, nanjing 210093, china Department of astronomy Nanjing University Nanjing China

Magnetic field in the solar lower atmosphere can be measured by the use of the Zeeman and Hanle effects. By contrast, the coronal magnetic field well above the solar surface, which directly controls various eruptive phenomena, can not be precisely measured with the traditional techniques. Several attempts are being made to probe the coronal magnetic field, such as force-free extrapolation based on the photospheric magnetograms, gyroresonance radio emissions, and coronal seismology based on MHD waves in the corona. Compared to the waves trapped in the localized coronal loops, EIT waves are the only global-scale wave phenomenon, and thus are the ideal tool for the coronal global seismology. In this paper, we review the observations and modelings of EIT waves, and illustrate how they can be applied to probe the global magnetic field in the corona.

关键词： coronal mass ejections (CMEs) magnetic field diagnostics magnetohydrodynamics (MHD)

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

Differential AR algorithm for packet delay prediction

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Progress in Natural Science:Materials International 2006年第4期16卷 437-440页

作者： JIAO Liangbao, ZHANG De and BI Houjie Institute of Acoustics, State key laboratory of modern Acoustics, nanjing university, nanjing 210093, china Institute of Communication Technique, nanjing university, nanjing 210093, china Institute of Acoustics State Key Laboratory of Modern Acoustics Nanjing University Nanjing 210093 China Institute of Communication Technique Nanjing University Nanjing 210093 China

Different delay prediction algorithms have been applied in multimedia communication, among which linear prediction is attractive because of its low complexity. AR (auto regressive) algorithm is a traditional one with low computation cost, while NLMS (normalize least mean square) algorithm is more precise. In this paper, referring to ARIMA (auto regression integrated with moving averages) model, a differential AR algorithm (DIAR) is proposed based on the analyses of both AR and NLMS algorithms. The prediction precision of the new algorithm is about 5-10 db higher than that of the AR algorithm without increasing the computation complexity. Compared with NLMS algorithm, its precision slightly improves by 0.1 db on average, but the algorithm complexity reduces more than 90% . Our simulation and tests also demonstrate that this method improves the performance of the average end-to-end delay and packet loss ratio significantly.

关键词： AR algorithm NLMS algorithm differential AR algorithm ARIMA model.

On critical values concerning the evolution of the long period families

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Chinese Journal of astronomy and astrophysics 2009年第4期9卷 494-500页

作者： Xi-Yun Hou1,21 astronomy Department, nanjing university, nanjing 210093, china 2 Institute of Space Environment and Astronautics, nanjing university, nanjing 210093, china astronomy Department Nanjing University Nanjing 210093 China Institute of Space Environment and Astronautics Nanjing University Nanjing 210093 China

In a previous paper, we proposed another special critical value concerning the evolution of the long period family around the equilateral equilibrium points, besides the two values given by Henrard. Are there any other special critical values？ After studying the stability curves of the long period family carefully, we gave a negative answer. During the study, we found an interesting family of periodic orbits which we called the homo family. We studied the evolution of this family following the increase of μ. With these findings, we were able to explain the origin of the four branches of periodic families emanating from L4 and the stability results of the equilateral equilibrium points.

关键词： celestial mechanics

Effect of Conversion Efficiency on Gamma-Ray Burst Energy

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Chinese Journal of astronomy and astrophysics 2004年第3期4卷 267-274页

作者： Lei Xu Zi-Gao Dai Department of astronomy nanjing university nanjing 210093 Department of astronomy Nanjing University Nanjing 210093

Beaming effect makes it possible that gamma-ray bursts have a standardenergy, but the gamma-ray energy release is sensitive to some parameters. Our attention is focusedon the effect of the gamma ray conversion efficiency (η_γ), which may range between 0.01 and 0.9,and which probably has a random value for different GRBs under certain conditions. Making use of theafterglow data from the literature, we carried out a complete correction to the conical openingangle formula. Within the framework of the conical jet model, we ran a simple Monte Carlo simulationfor random values of η_γ, and found that the gamma-ray energy release is narrowly clustered,whether we use a constant value of η_γ or random values for different gamma-ray bursts.

关键词： gamma rays: bursts ISM: jets