检索结果-南通市图书馆

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

在线全文

学校读者我要写书评

暂无评论

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 {2., beijing 100190, China 2.{4. university of chinese academy of {2., beijing 100049, China Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China graduate university of {2. academy of {4. 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 1999–2.04. the relativistic electron data from Fengyun-1 satellite from June 1999 to 2.05 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 4. REE events are found in total during this time period, and the strong REE events with the maximum daily average flux > 4.0 cm?2.srt-1·s?1 occur mostly during the transition period from solar maximum to solar minimum. Among these 4. REE events, four strong REE events last a longer time period from 2.-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 4. 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

Applications of URANS on predicting unsteady turbulent separated flows

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第3期25卷 319-324页

作者： Jinglei Xu Huiyang Ma Department of Physics, graduate university of the {2. academy of {4., 100049 beijing, China Department of Physics Graduate University of the Chinese Academy of Sciences Beijing China

Accurate prediction of unsteady separated turbulent flows remains one of the toughest tasks and a practi cal challenge for turbulence modeling. In this paper, a 2. flow past a circular cylinder at Reynolds number 3,900 is numerically investigated by using the technique of unsteady RANS （URANS）. Some typical linear and nonlinear eddy viscosity turbulence models （LEVM and NLEVM） and a quadratic explicit algebraic stress model （EASM） are evaluated. Numerical results have shown that a high-performance cubic NLEVM, such as CLS, are superior to the others in simulating turbulent separated flows with unsteady vortex shedding.

关键词： URANS Nonlinear eddy viscosity turbulencemodel ,Separated flows Circular cylinder

The identity of some taxa of Schizophragma (Saxifragaceae)

在线全文

学校读者我要写书评

暂无评论

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

作者： 1,2.ei LIU 1Xiang-Yun ZHU 1(Institute of Botany,chinese academy of {2.,beijing 100093,China) 2.{4. university of chinese academy of {2.,beijing 100049,China) Institute of Botany Chinese Academy of Sciences Beijing 100093 China graduate university of {2. academy of {4. 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

Ionization state of cosmic hydrogen by early stars and quasars

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

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 {2., beijing 100012. China 2.{4. university of chinese academy of {2., beijing 100049, China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China graduate university of {2. academy of {4. 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 2. 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 4.0% 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

Modeling and verifying Web services driven by requirements:An ontology-based approach

在线全文

学校读者我要写书评

暂无评论

Science in China(Series F) 2006年第6期49卷 792-820页

作者： HOU Lishan1,3,JIN ZHi1,2.& WU Budan1,4.1. academy of Mathematics and Systems Science, {2. academy of sciences, {4. 100080, China 2. Institute of Computing Technology, {2. academy of sciences, {4. 100080, China 3. Institute of Software, {2. academy of sciences, {4. 100080, China 4. graduate university of chinese academy of sciences,{14., China academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China Institute of Software Chinese Academy of Sciences Beijing China Institute of Computing Technology Chinese Academy of Sciences Bejing China graduate university of {2. academy of {4. Beijing China

Automatic discovery and composition of Web services is an important research area in Web service technology, in which the specification of Web services is a key issue. This paper presents a Web service capability description framework based on the environment ontology. This framework depicts Web services capability in two aspects： the operable environment and the environment changes resulting from behaviors of the Web service. On the basis of the framework, a requirement-driven Web service composition model has been constructed. This paper brings forward the formalization of Web service interactions with π calculus. And an automatic mechanism converting conceptual capability description to the formal process expression has been built. This kind of formal specification assists in verifying whether the composite Web service model matches the requirement.

关键词： Web service environment ontology automatic composition π calculus formal verification.

Analysis and application of automatic deformation monitoring data for buildings and structures of mining area

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2011年第S3期21卷 516-522页

作者： XIAO Jie1, 2. 3, ZHANG Jin4.1. Institute of Geodesy and Geophysics, chinese {2. of {2., Wuhan 4.0077, China 2. Key Laboratory of Dynamic Geodesy, Institute of Geodesy and Geophysics, chinese {2. of {2., Wuhan 4.0077, China 3. graduate School of chinese {2. of {2., beijing 100049, China 4. Department of Surveying and Mapping, Taiyuan university of Technology, Taiyuan 03002.0} China Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Key Laboratory of Dynamic Geodesy Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China graduate School of chinese {2. of sciences Beijing 100049 China Department of Surveying and Mapping Taiyuan University of Technology Taiyuan 030024 China

The buildings and structures of mines were monitored automatically using modern surveying technology. Through the analysis of the monitoring data, the deformation characteristics were found out from three aspects containing points, lines and regions, which play an important role in understanding the stable state of buildings and structures. The stability and deformation of monitoring points were analysed, and time-series data of monitoring points were denoised with wavelet analysis and Kalman filtering, and exponent function and periodic function were used to get the ideal deformation trend model of monitoring points. Through calculating the monitoring data obtained, analyzing the deformation trend, and cognizing the deformation regularity, it can better service mine safety production and decision-making.

关键词： wavelet analysis Kalman filtering deformation monitoring data analysis mine

Strong decays of N~*(1535) in an extended chiral quark model

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2009年第10期52卷 1452-1457页

作者： AN ChunSheng1,2.3 & ZOU BingSong1,2.3 1 Institute of High Energy Physics,chinese academy of {2.,beijing {4.,China 2.Theoretical Physics Center for Science Facilities,chinese academy of {2.,beijing {4.,China 3 graduate university of chinese academy of {2.,beijing {4.,China Institute of High Energy Physics Chinese Academy of Sciences Beijing China Theoretical Physics Center for Science Facilities Chinese Academy of Sciences Beijing China graduate university of {2. academy of {4. Beijing China

The strong decays of the N*(1535) resonance are investigated in an extended chiral quark model by including the low-lying $ qqqq\bar q $ components in addition to the qqq component. The results show that these five-quark components in N*(1535) contribute significantly to the N*(1535) → Nπ and N*(1535) → Nη decays. The contributions to the Nη decay come from both the lowest energy and the next-tolowest energy five-quarks components, while the contributions to the Nπ decay come from only the latter one. Taking these contributions into account, the description for the strong decays of N*(1535) is improved, especially for the puzzling large ratio of the decays to Nη and Nπ.

关键词： N*(1535) strong decays five-quark components

Genetic structure and phylogeography of a relict tree fern,Sphaeropteris brunoniana (Cyatheaceae) from China and Laos inferred from cpDNA sequence variations:Implications for conservation

在线全文

学校读者我要写书评

暂无评论

Journal of Systematics and Evolution 2011年第1期49卷 72-79页

作者： 1,2.Zi-Juan WANG 1 Kai-Yun GUAN 1 (Kunming Institute of Botany, chinese academy of {2., Kunming 6502.4. China) 2.(graduate {4. of chinese academy of {2., beijing 100049, China) (Kunming Institute of Botany Chinese Academy of Sciences Kunming 650204 China) (graduate university of {2. academy of {4. Beijing 100049 China)

In this study, we analyzed the genetic structure and phylogeography of Sphaeropteris brunoniana from China and Laos. Combining cpDNA trnL-trnF and atpB-rbcL sequence variations, five haplotypes were identi- fied from the 10 investigated populations. Moderate haplotype diversity (h = 0.66580) and low nucleotide diver- sity (π = 0.2. × 10 ?3 ) were detected. The S. brunoniana in Yunnan region had much higher genetic diversity (h = 0.60195, π = 0.35 × 10 ?3 ) than that of Hainan–Laos (h = 0.00000, π = 0.00). A high level of genetic differentiation (94.74.) between the two regions was revealed by AMOVA. Nested clade analysis identified two major clusters of the five haplotypes, one clade in the Yunnan region and the other in Hainan–Laos. The analysis indicated that restricted gene flow with isolation by distance and allopatric fragmentation were likely the major processes that shaped the spatial distribution of the haplotypes. The isolated distribution of clades implied the emergence of independent refugia of this species in each region during Quaternary glaciations. The Yunnan populations frequently contained an ancestral haplotype, and most of them harbored other descendent haplotypes. Based on the distribution pattern of haplotypes and the nested clade analysis results, the Yunnan region potentially had several refugia of this species during glacial periods, whereas the Hainan populations were probable new colonizations.

关键词： atpB-rbcL Hainan–Laos phylogeography Sphaeropteris brunoniana trnL-trnF Yunnan.

Infrared Galaxies in the Nearby Universe

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2008年第6期8卷 643-652页

作者： Jian-Ling Wang 1 National Astronomical Observatories,chinese academy of {2.,beijing 100012.China 2.{4. School of chinese academy of {2.,beijing 100049,China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China graduate School of chinese {2. of sciences Beijing 100049 China

We used the Sloan Digital Sky Survey （SDSS） Data Release 5 （DR5） to study the morphological properties of 1137 nearby infrared （IR） galaxies, most of which are brighter than 15.9 mag in r-band. This sample was drawn from a cross-correlation of the Infra-Red Astronomical Satellite （IRAS） point source catalog redshift survey with DR5 at z ≤ 0.08. Based on this IR galaxy sample, we constructed five volume-limited sub-samples with IR luminosity ranging from 10^9.5 L⊙ to 10^12.⊙. By deriving the IR luminosity functions （LF） for different morphological types, we found that normal spiral galaxies are the dominant population below LIR ~ 8 ~ 10^10 L⊙; while the fraction of barred spiral galaxies increases with increasing IR luminosity and becomes dominant in spiral galaxies beyond LIR ≈ 5 × 10^10L⊙. As the IR luminosity decreases, the IR galaxies become more compact and have lower stellar masses. The analysis also shows that normal spiral galaxies give the dominant contribution to the total comoving IR energy density in the nearby universe, while, in contrast, the contribution from peculiar galaxies is only 39%.

关键词： galaxies evolution galaxies interactions galaxies starburst infrared galaxies galaxies luminosity function