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A new class of symmetric periodic solutions of the spatial elliptic restricted three-body problem

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science china(Physics,Mechanics & Astronomy) 2009年第9期52卷 1404-1413页

作者： XU XingBo1,2 & FU YanNing1 1 Purple Mountain Observatory, chinese academy of s.iences, Nanjing 210008, china 2 graduate university of chinese academy of s.iences, beijing 100039, china Purple Mountain Observatory Chinese Academy of Sciences Nanjing China graduate university of chinese academy of s.iences Beijing China

We show that there exists a new class of symmetric periodic solutions of the spatial elliptic restricted three-body problem. In such a solution, the infinitesimal body is confined to the vicinity of a primary and moves on a nearly circular orbit. This orbit is almost perpendicular to the orbital plane of the primaries, where the line of symmetry of the orbit lies. The existence is shown by applying a corollary of Arenstorf's fixed point theorem to a periodicity equation system of the problem. And this existence doesn't require any restriction on the mass ratio of the primaries, nor on the eccentricity of their relative elliptic orbit. Potential relevance of this new class of periodic solutions to real celestial body systems and the follow-up studies in this respect are also discussed.

关键词： periodic orbits spatial restricted three-body problem symmetric orbits averaging

The deep thermal characteristic of continental margin of the northern south china sea

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chinese science Bulletin 2000年第18期45卷 1717-1722页

作者： ZHANG Jian & WANG Jiyang1. graduate school, university of science and Technology of china, chinese academy of s.iences, beijing 100039, china 2. Institute of Geology, chinese academy of s.iences, beijing 100029, china graduate school University of Science and Technology of China Chinese Academy of Sciences Beijing China Institute of Geology Chinese Academy of Sciences Beijing China

Heat flow plays an important role in the study ot thermal structure and thermal evolutionof continental margin of the northern south china sea. The analysis of heat flow value shows that margin heat flow in the northern south china sea is relatively high setting, but the percentage of crustal heat flow is lower than 35% in terrestrial heat flow. The terrestrial heat flow exhibited a current of rise from the Northern Continental Margin to the southern Central Basin. However, the proportion of crustal heat flow in terrestrial heat flow slowly dropped down in the same direction. It is suggested that the main factor causing high heat flow setting is the moving up of hot material from asthenosphere.

关键词： margin of northern south china sea terrestrial heat flow thermal structures.

Observation results of relativistic electrons detected by Fengyun-1 satellite and analysis of relativistic electron enhancement (REE) events

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science china(Physics,Mechanics & Astronomy) 2008年第12期51卷 1947-1956页

作者： YANG XiaoChao1,2↑ & WANG shiJin1 1 Center for space science and Applied Research, chinese academy of s.iences, beijing 100190, china 2 graduate university of chinese academy of s.iences, beijing 100049, china Center for space science and Applied Research Chinese Academy of Sciences Beijing China graduate university of chinese academy of s.iences Beijing China

The space particle component detector on Fengyun-1 satellite which works at the sun-synchronous orbit of about 870 km altitude has detected relativistic electrons for a long time. In comparison with the sAMPEX satellite observations during 1999–2004, the relativistic electron data from Fengyun-1 satellite from June 1999 to 2005 are used to analyze the relativistic electron enhancement (REE) events at the low earth orbit, and the possible correlation among REE events at the low earth orbit, high-speed solar wind and geomagnetic storms is discussed. The statistical result presents that 45 REE events are found in total during this time period, and the strong REE events with the maximum daily average flux > 400 cm?2·srt-1·s?1 occur mostly during the transition period from solar maximum to solar minimum. Among these 45 REE events, four strong REE events last a longer time period from 26-to 51-day and correlate closely with high speed solar wind and strong geomagnetic storms. Meanwhile, several strong geomagnetic storms occur continuously before these REE events, and these continuous geomagnetic storms would be an important factor causing these long-lasting strong REE events. The correlation analysis for overall 45 events indicates that the strength of the REE events correlates with the solar wind speed and the strength of the geomagnetic storm, and the correlation for strong REE events is much stronger than that for weak REE events.

关键词： relativistic electron enhancement low earth orbit high-speed solar wind geomagnetic storm

A novel operation mode for spaceborne polarimetric sAR

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science china(Information s.iences) 2011年第4期54卷 884-897页

作者： QI WeiKong 1,2 & YU WeiDong 1 1 Institute of Electronics,chinese academy of s.iences,beijing 100190,china 2 graduate school of chinese academy of s.iences,beijing 100039,china Institute of Electronics Chinese Academy of Sciences Beijing China graduate school of chinese academy of s.iences Beijing China

A novel operation mode for spaceborne polarimetric sAR,named polarization space-division adding polarization code-division (PsD-PCD) operation mode,is proposed in this paper through combining polarimetric sAR with elevation digital beam-forming (DBF) on *** a pulse repetition interval the up-chirp LFM sub-pulse is transmitted with horizontal polarization antenna,and with some delay the down-chip LFM subpulse is transmitted with vertical polarization antenna to realize code *** every sub-aperture receives returns from ground,sAR system uses range DBF to separate echoes relative to different sub-pulses in order to realize space *** system PRF is equal to that of single-polarization sAR,and elevation DBF help reduce range ambiguity ***,the main system parameters,including PRF,delay between two sub-pulses,radar equation and ambiguity are analyzed and compared with those of single-polarization *** results demonstrate the feasibility and validity of PsD-PCD operation mode.

关键词： spaceborne synthetic aperture radar (sAR) polarimetry digital beamforming (DBF) operation mode ambiguity ratio polarization space-division polarization code-division

Ionization state of cosmic hydrogen by early stars and quasars

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Research in Astronomy and Astrophysics 2009年第6期9卷 665-681页

作者： Xiao-Chun Mao1,2 1 National Astronomical Observatories, chinese academy of s.iences, beijing 100012, china 2 graduate university of chinese academy of s.iences, beijing 100049, china National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China graduate university of chinese academy of s.iences Beijing 100049 China

Cosmic hydrogen is reionized and maintained in its highly ionized state by the ultraviolet emission attributed to an early generation of stars and quasars. The Lyα opacity observed in absorption spectra of high-redshift quasars permits more stringent constraints on the ionization state of cosmic hydrogen. Based on density perturbation and structure formation theory, we develop an analytic model to trace the evolution of the ionization state in the post-overlap epoch of reionization, in which the bias factor is taken into account. For quasars, we represent an improved luminosity function by utilizing a hybrid approach for the halo formation rate that is in reasonable agreement with the published measurements at 2 ≤ z ≤ 6. Comparison with the classic Press-schechter mass function of dark matter halos, we demonstrate that the biased mass distribution indeed enhances star formation efficiency in the overdense environment by more than 25 per cent following the overlap of ionized bubbles. In addition, an alternative way is introduced to derive robust estimates of the mean free path for ionizing photons. In our model, star-forming galaxies are likely to dominate the ionizing background radiation beyond z = 3, and quasars contribute equally above a redshift of z ～ 2.5. From 5 ≤ z ≤ 6, the lack of evolution in photoionization rate can thus be explained by the relatively flat evolution in star formation efficiency, although the mean free path of ionizing photons increases rapidly. Moreover, in the redshift interval z ～ 2 - 6, the expected mean free path and Gunn-Peterson optical depth obviously evolve by a factor of ～ 500 and ～50 respectively. We find that the relative values of critical overdensities for hydrogen ionization and collapse could be 430% at z ≈2 and 2% at z ≈6, suggesting a rapid overlap process in the overdense regions around instant quasars following reionization. We further illustrate that the absolute estimates of the fraction of neutral hydrogen computed fr

关键词： cosmology theory -- formation galaxies -- quasars general -- diffuse radiation -- intergalactic medium

The identity of some taxa of schizophragma (saxifragaceae)

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Journal of systematics and Evolution 2009年第2期47卷 151-161页

作者： 1,2Wei LIU 1Xiang-Yun ZHU 1(Institute of Botany,chinese academy of s.iences,beijing 100093,china) 2(graduate university of chinese academy of s.iences,beijing 100049,china) Institute of Botany Chinese Academy of Sciences Beijing 100093 China graduate university of chinese academy of s.iences Beijing 100049 China

After examining a large number of type and authoritative specimens of schizophragma siebold & Zucc.,*** *** and *** *** Rehder were reduced to synonyms of *** Rehder and *** *** *** was reduced to synonym of *** *** crassum *** *** was treated as the correct name of *** ***(Chun) *** name *** *** Rehder is *** taxonomic treat-ment is supported by leaf epidermal characters.

关键词： leaf epidermis new synonym reinstatement schizophragma

Cloning,expression and characterization of a nucleoside diphosphate kinase (NDPK) gene from tobacco

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Progress in Natural science:Materials International 2007年第8期17卷 906-912页

作者： Zhou Qiyun~(1,2**) Xie Zongming~(1**) Zhang Zhigang~1 Cao Yangrong~1 Zhang jinsong~(1***) Chen shouyi~(1***) (1.National Key Laboratory of Plant Genomics,Institute of Genetics and Developmental Biology,chinese academy of s.iences,beijing100101,china 2.graduate university of chinese academy of s.iences,beijing 100039,china) National Key Laboratory of Plant Genomics Institute of Genetics and Developmental Biology Chinese Acad. of Sci. Beijing 100101 China graduate university Chinese Acad. of Sci. Beijing 100039 China

Nucleoside diphosphate kinase (NDPK) is a housekeeping enzyme that maintains the intracellular levels of all (d)NTPs used in biosynthesis except *** we report that a full-length cDNA encoding nucleoside diphosphate kinase (NDPK) was cloned us- ing yeast two-hybrid approach.A tobacco NDPK gene was obtained and designated as ***1 is 704 bp in length and en- codes a putative 16.2 kD protein of 148 amino *** analysis showed that NtNDPK1 is highly homologous to other plant NDPK genes and identified as type I (NDPK1).RNA-gel blot analysis showed that there was no significant difference of NtNDPK1 ex- pression in roots,stems,leaves and *** expression of NtNDPK1 was induced by ABA and PEG and repressed by NaCl,but not significantly affected by Paraquat,wounding and low temperature (4℃) treatments,indicating that NtNDPK1 may play a certain role in response to abiotic *** vitro phosphorylation assay demonstrated that NtNDPK1 had autophosphoryLation activity.

关键词： abiotic stress autophosphorylation activity NtNDPK1 tobacco yeast two-hybrid

Recent advances in the data analysis method of functional magnetic resonance imaging and its applications in neuroimaging

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Progress in Natural science:Materials International 2006年第8期16卷 785-795页

作者： TIAN Jie, YANG Lei and HU Jin (Institute of Automation, chinese academy of s.iences, beijing 100080, china graduate school of chinese academy of s.iences, beijing 100039, china) Institute of Automation Chinese Academy of Sciences Beijing 100080 China graduate school of chinese academy of s.iences Beijing 100039 China

Functional magnetic resonance imaging (fMRI) has opened a new area to explore the human brain. The fMRI can reveal the deep insights of spatial and temporal changes underlying a broad range of brain function, such as motor, vision, memory and emotion, all of which are helpful in the clinical investigation. In this paper, we introduce some recent-developed algorithms for fMRI signal detection such as model-driven method (general linear model, deconvolution model, non-linear model, etc. ) and data-driven method (principle component analysis, independent component analysis, self-organization mapping, clustered constrained non-negative matrix factorization, etc. ). We also propose several important applications of neuroimaging and point out their shortcomings and future perspectives.

关键词： fMR1 data analysis neuroimaging.

Gasdynamic characteristics of toroidal shock and detonation wave converging

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science china(Physics,Mechanics & Astronomy) 2005年第6期48卷 739-749页

作者： TENG Honghui1,2 & JIANG Zonglin2 1. Key Laboratory of High Temperature Gas Dynamics, Institute of Mechanics, chinese academy of sci- ences, beijing 100080, china 2. graduate university of chinese academy of s.iences, beijing 100039, china Key Laboratory of High Temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences Beijing China graduate university of chinese academy of s.iences Beijing China

The modified CCW relation is applied to analyzing the shock, detonation wave converging and the role of chemical reactions in the process. Results indicate that the shock wave is strengthened faster than the detonation wave in the converging at the same initial Mach number. Euler equations implemented with a detailed chemical reaction model are solved to simulate toroidal shock and detonation wave converging. Gasdynamic characteristics of the converging are investigated, including wave interaction patterns, observable discrepancies and physical phenomena behind them. By comparing wave diffractions, converging processes and pressure evolutions in the focusing area, the different effects of chemical reactions on diffracting and converging processes are discussed and the analytic conclusion is demonstrated through the observation of numerical simulations.

关键词： converging, CCW relation, shock wave, detonation wave.