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Forecast daily indices of solar activity, F10.7, using support vector regression method

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Research in Astronomy and Astrophysics 2009年第6期9卷 694-702页

作者： Cong Huang Dan-Dan Liu Jing-Song Wang national center For {2. {3. CMA Beijing 100081 China

The 10.7 cm solar radio flux （F10.7）, the value of the solar radio emission flux density at a wavelength of 10.7 cm, is a useful index of solar activity as a proxy for solar extreme ultraviolet radiation. It is meaningful and important to predict F10.7 values accurately for both long-term （months-years） and short-term （days） forecasting, which are often used as inputs in space weather models. This study applies a novel neural network technique, support vector regression （SVR）, to forecasting daily values of F10.7. The aim of this study is to examine the feasibility of SVR in short-term F10.7 forecasting. The approach, based on SVR, reduces the dimension of feature space in the training process by using a kernel-based learning algorithm. Thus, the complexity of the calculation becomes lower and a small amount of training data will be sufficient. The time series of F10.7 from 2.02.to 2.06 are employed as the data sets. The performance of the approach is estimated by calculating the norm mean square error and mean absolute percentage error. It is shown that our approach can perform well by using fewer training data points than the traditional neural network.

关键词： methods data analysis -- Sun activity -- Sun radio radiation

Interaction between electromagnetic waves and energetic particles by a realistic density model

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Science china(Technological Sciences) 2010年第9期53卷 2552-2557页

作者： HE YiHua1,2.CHEN LiangXu1,XIAO FuLiang1 & YANG Chang1 1 School of Physics and Electronic Sciences,Changsha University of Science and Technology,Changsha 410004,china 2.State Key Laboratory of space {2.,Chinese Academy of Sciences,Beijing 100190,china 1. School of Physics and Electronic Sciences Changsha University of Science and Technology Changsha 410004 China2. State Key Laboratory of Space Weather Chinese Academy of Sciences Beijing 100190 China

Using a realistic density model,we present a first study on the interactions between electromagnetic waves and energetic particles in the inner *** calculations show that as the latitude λ increases,the number density ne increases,and resonant frequency range moves to lower pitch *** L-mode/electron and L-mode/proton interactions,the pitch angle diffusion dominates over the momentum *** indicates that L-mode waves are primarily responsible for pitch angle *** R-mode/electron interaction,the momentum diffusion is found to be comparable to the pitch angle diffusion,implying that R-mode waves can play an important role in both pitch angle scattering and stochastic acceleration of *** R-mode/proton interaction,diffusion coefficients locate primarily below pitch angle 60° and increase as kinetic energy increases,suggesting that R-mode waves have potential for pitch angle scattering of highly energetic (~1 MeV) protons but cannot efficiently accelerate protons.

关键词： wave-particle interaction energetic particles resonant frequency pitch angle and momentum diffusion density model

Experimental realization of quantum cryptography communication in free space

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Science china(Physics,Mechanics & Astronomy) 2005年第2期48卷 237-246页

作者： WANG Chuan1, ZHANG Jingfu1, WANG Pingxiao1, DENG Fuguo1, AI Qing1 & LONG Guilu1,2.1. Department of Physics, Key Laboratory for Quantum Information and Measurements, Tsinghua Univer- sity, Beijing 100084, china 2. center for Atomic and Molecular NanoSciences, Tsinghua University, Beijing 100084, china Department of Physics Key Laboratory for Quantum Information and Measurements Tsinghua University Beijing 100084 China Atomic and Molecular NanoSciences Tsinghua University Beijing 100084 China

Utilizing linear optical devices, the principle of B92.quantum key distribution (QKD) protocol is demonstrated in free space with a distance of transmission of 2.2.meters. The faint laser pulses with 650 nm wavelength are used as the single photon sources. The experimental results show that the eavesdropping behavior in the signal transmission can be detected. We also discuss the problems and solutions in using the quantum cryptography communication practically. It is pointed out that one of the approaches to increasing the distance of the quantum communication is to overcome the attenuation of the single photon in transmission. This could not be solved by the use of single photon source, and new quantum communication protocols are needed to solve these problems.

关键词： quantum key distribution, free space, linear optics, faint pulses.

Dynamic evolution of outer radiation belt electrons driven by superluminous R-X mode waves

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Science china(Technological Sciences) 2010年第10期53卷 2734-2738页

作者： XIAO FuLiang1,2. CHEN LiangXu1, HE YiHua1 & YANG Chang1 1 School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha 410004, china 2.State Key Laboratory of space {2., Chinese Academy of Sciences, Beijing 100190, china 1. School of Physics and Electronic Sciences Changsha University of Science and Technology Changsha 410004 China2. State Key Laboratory of Space Weather Chinese Academy of Sciences Beijing 100190 China

We present initial results on the temporal evolution of the phase space density (PSD) of the outer radiation belt energetic electrons driven by the superluminous R-X mode waves. We calculate diffusion rates in pitch angle and momentum assuming the standard Gaussian distributions in both wave frequency and wave normal angle at the location L=6.5. We solve a 2. momentum-pitch-angle Fokker-Planck equation using those diffusion rates as inputs. Numerical results show that R-X mode can produce significant acceleration of relativistic electrons around geostationary orbit,supporting previous findings that superluminous waves potentially contribute to dramatic variation in the outer radiation belt electron dynamics.

关键词： wave-particle interaction superluminous R-X waves phase space density evolution radiation belt electrons

Application analysis of empirical mode decomposition and phase space reconstruction in dam time-varying characteristic

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Science china(Technological Sciences) 2010年第6期53卷 1711-1716页

作者： ZHANG ZhiJun1,2.3.GU ChongShi1,2.BAO TengFei1,2.ZHANG Lan1,2.& YU Hong1,2.1 State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University,Nanjing 2.0098,china 2.{2. Engineering Research {2. of Water Resources Efficient Utilization and Engineering Safety,Hohai University,Nanjing 2.0098,china 3.Department of Civil,Environmental and Geomatic Engineering,Swiss Federal Institute of Technology,Zurich 8093.Switzerland 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing 210098 China2. National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Hohai University Nanjing 210098 China3. Department of Civil Environmental and Geomatic Engineering Swiss Federal Institute of Technology Zurich 8093 Switzerland

In view of some courses of the time-varying characteristics processing in the analysis of dam deformation,the paper proposes a new method to analyze the dam time-varying characteristic based on the empirical mode decomposition and phase space reconstruction *** of all,to reduce the influences on the traditional statistical model from human factors and assure the analysis accuracy,response variables of the time-varying characteristic are obtained by the way of the empirical mode decomposition;and then,a phase plane of those variables is reconstructed to investigate their processing *** methods have already been applied to an actual project and the results showed that data interpretation with the assists of empirical mode decomposition and phase space reconstruction is effective in analyzing the perturbations of response variables,explicit in reflecting the entire development process,and valid for obtaining the evolution rules of the time-varying *** methodology is a powerful technical support for people to further master the rules of dam operation.

关键词： dam safety monitoring dam time-varying characteristic empirical mode decomposition phase space reconstruction

Improving the accuracy of image-based forest fire recognition and spatial positioning

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Science china(Technological Sciences) 2010年第S1期53卷 184-190页

作者： JIANG LiLi 1,QI QingWen 1,ZHANG An 1,GUO ChaoHui 2.& CHENG Xi 1,3.1 Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing 100101,china 2.2. {2. for Resources Satellite Data and Applications,Beijing 100094,china 3.raduate University of Chinese Academy of Sciences,Beijing 100049,china Chinese Acad Sci Inst Geog Sci & Nat Resources Res Beijing 100101 Peoples R China china Ctr Resources Satellite Data & Applicat Beijing 100094 Peoples R China Chinese Acad Sci Grad Univ Beijing 100049 Peoples R China

Forest fires are frequent natural *** is necessary to explore advanced means to monitor,recognize and locate forest fires so as to establish a scientific system for the early detection,real-time positioning and quick fighting of forest *** paper mainly expounds methods and algorithms for improving accuracy and removing uncertainty in image-based forest fire recognition and spatial ***,we discuss a method of forest fire recognition in visible-light *** are four aspects to improve accuracy and remove uncertainty in fire recognition:(1)eliminating factors of interference such as road and sky with high brightness,red leaves,other colored objects and objects that are lit up at night,(2.excluding imaging for specific periods and azimuth angles for which interference phenomena repeatedly occur,(3.improving the thresholding method for determining the flame border in image processing by adjusting the threshold to the season,weather and region,and (4)integrating the visible-light image method with infrared image ***,we examine infrared-image-based methods and approaches of improving the accuracy of forest fire recognition by combining the spectrum threshold with an object feature value such as the normalized difference vegetation index and excluding factors of disturbance such as interference signals,extreme weather and high-temperature ***,a method of visible analysis to enhance the accuracy of forest fire positioning is examined and realized;the method includes decreasing the visual angle,selecting central points,selecting the largest spots,and judging the selection of fire spots according to the central *** studies are examined and the results are found to be satisfactory.

关键词： forest fire monitoring spatial positioning accuracy improvement

Observation constraints of the hard X-ray modulation telescope HXMT

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Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 31-35页

作者： LU Yu1,2.ZHANG WenZhao3.QU JinLu1,SONG LiMing1,GAO Jian3.ZHANG HongMei4 & OU Ge4 1 Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,{2. 2.Graduate University of Chinese Academy of Sciences,Beijing 100049,{2. 3.Department of Astronomy,Beijing Normal University,Beijing 100875,{2. 4 Computing {3.,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,{2. 1. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China 2. Graduate University of Chinese Academy of Sciences Beijing 100049 China 3. Department of Astronomy Beijing Normal University Beijing 100875 China 4. Computing center Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China

The hard X-ray modulation telescope HXMT is a low orbit X-ray space telescope whose main science goals are to accomplish a hard X-ray all sky survey and to study timing and spectral characteristics of X-ray *** has three kinds of science instruments:the high energy X-ray detector(HE),the medium energy X-ray detector(ME) and the low energy X-ray detector(LE).The observation schedule of HXMT is a key to achieving the science goal of HXMT,and the analysis of the observation constraints is one of the first tasks in making the observation *** paper analyzes how the observation constraints influence the sky visibility and the visible time distribution of X-ray sources and discusses the schedule strategy with regard to the observation constraints.

关键词： HXMT observation constraints sky visibility

Approximate Solution of the Nonlinear Parallel Diffusion Theory of Charged Particles

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Approximate Solution of the Nonlinear Parallel Diffusion The...

Electron surfing acceleration in a current sheet of flares

第十四届全国日地空间物理学术研讨会

作者： Yu-Ting Zhu1 Gang Qin2.Gui Ming Le3.(1 Chinese Academy of Meteorological Science, Beijing 100081 ) (2.national {2. Science {2., Beijing 100190 ) (3.national {2. for {2. weather, china Meteorological Administration, Beijing 100081 )

Charged particles’ diffusion mechanism is one of outstanding problem in the astrophysics. Recently, Matthaeus et al. （ApJ 2.03. developed a nonlinear guiding center theory （NLGC） of perpendicular diffusion of charged energetic particles with parallel diffusion coefficient as an input, which agrees with numerical simulations. In addition, Qin （ApJ 2.07） developed a nonlinear parallel diffusion theory （NLPA） which if combined with NLGC could be used to solve parallel and perpendicular diffusion simultaneously. However, both of the NLGC and NLPA are in the forms of integral equation and not easy to be adopted in cosmic ray transport models. So that Zank et al. （JGR 2.04） provided an approximate solution of NLGC. The solution agrees with the exact solution of the NLGC results very well. In this work we will adopt the similar method from Zank et al. （2.04）to approximately solve the NLPA （Qin 2.07） so that the solution of both parallel and perpendicular nonlinear diffusion coefficients can be included in numerical codes for cosmic rays transport simultaneously.

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来源： cnki会议评论

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Science china(Physics,Mechanics & Astronomy) 2009年第11期52卷 1810-1812页

作者： WANG DeYu1 & LU QuanMing2.1 Purple Mountain Observatory, Nanjing 2.0008, china 2.School of Earth and space Sciences, University of Science and Technology of china, Hefei 2.3}02., china Purple Mountain Observatory Nanjing 210008 China School of Earth and space Sciences University of Science and Technology of China Hefei 230026 China

A model of electron acceleration in a current sheet of flares is studied by the analytical approximation solution and the test particle simulation. The electron can be trapped in a potential of propagating electrostatic wave. The trapped electron moving with the phase velocity v p of wave may be effectively accelerated by ev p/c × B z force along the outflow direction in the current sheet, if a criterion condition K > 0 for electron surfing acceleration is satisfied. The electron will be accelerated continuously until the electron de-trap from the wave potential at the turning point S.

关键词： electron acceleration electrostatic wave current sheet