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Riemann boundary value problems and reflection of shock for the Chaplygin gas

Science china mathematics 2012年第4期55卷 671-685页

作者： CHEN ShuXing 1,& QU AiFang 2 1 School of Mathematical sciences,Fudan University,Shanghai 200433,china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan 430071,china 1. School of Mathematical sciences Fudan University Shanghai 200433 China2. Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences Wuhan 430071 China

In this paper,we study two-dimensional Riemann boundary value problems of Euler system for the isentropic and irrotational Chaplygin gas with initial data being two constant states given in two sectors respectively,where one sector is a quadrant and the other one has an acute vertex *** prove that the Riemann boundary value problem admits a global self-similar solution,if either the initial states are close,or the smaller sector is also near a *** result can be applied to solving the problem of shock reflection by a ramp.

关键词： Riemann boundary value problem reflection of shock Chaplygin gas wave interaction Eulersystem

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TIME-IGGCAS model validation:Comparisons with empirical models and observations

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Science china Technological sciences 2008年第3期51卷 308-322页

作者： YUE XinAn1,2,3, WAN WeiXing1, LIU LiBo1, NING BaiQi1, ZHAO BiQiang1 & ZHANG ManLian1 1 institute of Geology and Geophysics, chinese academy of sciences, Beijing 100029, china 2 wuhan institute of physics and mathematics, chinese academy of sciences, wuhan 430071, china 3 Graduate University, chinese academy of sciences, Beijing 100049, china 1. institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China 2. wuhan institute of physics and mathematics Chinese Academy of Sciences Wuhan 430071 China 3. chinese academy of sciences Graduate University Beijing 100049 China

The TIME-IGGCAS (Theoretical Ionospheric Model of the Earth in institute of Ge- ology and Geophysics, chinese academy of sciences) has been developed re- cently on the basis of previous works. To test its validity, we have made compari- sons of model results with other typical empirical ionospheric models (IRI, NeQuick-ITUR, and TItheridge temperature models) and multi-observations (GPS, Ionosondes, Topex, DMSP, FORMOSAT, and CHAMP) in this paper. Several conclu- sions are obtained from our comparisons. The modeled electron density and elec- tron and ion temperatures are quantitatively in good agreement with those of em- pirical models and observations. TIME-IGGCAS can model the electron density variations versus several factors such as local time, latitude, and season very well and can reproduce most anomalistic features of ionosphere including equatorial anomaly, winter anomaly, and semiannual anomaly. These results imply a good base for the development of ionospheric data assimilation model in the future. TIME-IGGCAS underestimates electron temperature and overestimates ion tem- perature in comparison with either empirical models or observations. The model results have relatively large deviations near sunrise time and sunset time and at the low altitudes. These results give us a reference to improve the model and enhance its performance in the future.

关键词： ionosphere theoretical model empirical model satellite observation relative deviation

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An empirical model of ionospheric foE over wuhan

An empirical model of ionospheric foE over Wuhan

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中国科学院地质与地球物理研究所2006学术年会

作者： Xinan Yue~(1,2,3),Weixing Wan~1,Libo Liu~1,and Baiqi Ning~1 1 institute of Geology and Geophysics,chinese academy of sciences,Beijing 100029,china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan 430071,china 3 Graduate School of chinese academy of sciences,Beijing,china

Daytime half-hourly values of the critical frequency of the ionospheric E-layer,f oE, obtained at wuhan Ionospheric Observatory(geographic 114.4°E,30.6°N;45.2°dip),china, during the whole interval of 1957-1991 and 1999-2004 have been used to develop an empirical *** model,including variations with local time,day number and solar cycle,is in agreement with the observations.A comparison between our model and IRI and Titheridge’s model has also been ***,our model gives a better performance than IRI and Titheridge’s model because data set is obtained with our own *** the IRI and Titheridge’s model overestimate f oE especially in May to September *** with past investigations,we suggest that overestimation of ionospheric parameters by IRI may be a common feature in East *** result is very helpful for both the correction of IRI in East Asia and the development of chinese Reference Ionosphere(CRI) model.

关键词： Ionosphere model foE

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Studying the shape of the topside electron density profile using Arecibo and Millstone Hill incoherent scatter radar measurements

Studying the shape of the topside electron density profile u...

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中国科学院地质与地球物理研究所2006学术年会

作者： Xiaoli Luan~(1,2,3),Libo Liu~1,Weixing Wan~1 and Jiuhou Lei~(1,2,3) 1 institute of Geology and Geophysics,chinese academy of sciences,Beijing 100029,china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan 430071,china 3 Graduate School of chinese academy of sciences

We have used over 90,000 ISR electron density profiles over Arecibo incoherent scatter radar(ISR) and more than 84,000 ISR electron density profiles over Millstone Hill ISR to fit the shape of the *** long-term incoherent scatter radar(ISR) observations are used to yield the equivalent shape factors of the assumed Chapman layer for the topside *** factors are firstly used to replace the constant factor of the Chapman alpha layer(f=0.5) or Chapman beta layer(f=1.0) and assuming that the scale height is equal to atomic oxygen scale *** results show that the averaged topside shape generally obeys the Chapman alpha layer except for some *** is also revealed that the shape factor depends apparently on local time, season,and solar activity in detail *** shape factor is also different at two ISR stations of Arecibo and Millstone *** of keeping a constant value of about 0.5 or 1.0 in the Chapman layer,the equivalent shape factor is mostly higher than 0.5 during daytime while close to 0.5 during night except for summer over Millstone Hill,and generally higher at solar maximum than solar *** value of the equivalent shape factor can be much larger than 0.5 by day and much smaller at *** solar maximum and during winter,the equivalent shape factor during daytime can reach a value over 0.74 over both stations,while at solar minimum and over Millstone Hill,it is no more than 0.35 during daytime in summer and can reach as low as about 0.3 during night in winter.

关键词： topside profile Chapman layer equivalent shape factor incoherent scatter radar

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TIME-IGGCAS model validation:Comparisons with empirical models and observations

TIME-IGGCAS model validation:Comparisons with empirical mode...

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中国科学院地质与地球物理研究所2008学术年会

作者： YUE XinAn~(1,2,3),WAN WeiXing~(1+),LIU LiBo~1,NING BaiQi~1,ZHAO BiQiang~1 & ZHANG ManLian~1 1 institute of Geology and Geophysics,chinese academy of sciences,Beijing 100029,china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan 430071,china 3 Graduate University,chinese academy of sciences,Beijing 100049,china

The TIME-IGGCAS(Theoretical Ionospheric Model of the Earth in institute of Geology and Geophysics,chinese academy of sciences) has been developed recently on the basis of previous *** test its validity,we have made comparisons of model results with other typical empirical ionospheric models(IRI, NeQuick-ITUR,and Tltheridge temperature models) and multi-observations(GPS, lonosondes,Topex,DMSP,FORMOSAT,and CHAMP) in this *** conclusions are obtained from our *** modeled electron density and electron and ion temperatures are quantitatively in good agreement with those of empirical models and ***-IGGCAS can model the electron density variations versus several factors such as local time,latitude,and season very well and can reproduce most anomalistic features of ionosphere including equatorial anomaly,winter anomaly,and semiannual *** results imply a good base for the development of ionospheric data assimilation model in the future. TIME-IGGCAS underestimates electron temperature and overestimates ion temperature in comparison with either empirical models or *** model results have relatively large deviations near sunrise time and sunset time and at the low *** results give us a reference to improve the model and enhance its performance in the future.

关键词： ionosphere theoretical model empirical model satellite observation relative deviation

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A theoretical model for mid-and low-latitude ionospheric electric fields in realistic geomagnetic fields

A theoretical model for mid-and low-latitude ionospheric ele...

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中国科学院地质与地球物理研究所2008学术年会

作者： REN ZhiPeng~(1,2,3),WAN WeiXing~(1+),WEI Yong~(1,2,3),LIU LiBo~1 & YU Tao~(1,4) 1 Beijing Observatory for Space Environment,institute of Geology and Geophysics,chinese academy of sciences,Beijing 100029, china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan 430071,china 3 Graduate School of chinese academy of sciences,Beijing 100049,china 4 National Center for Space Weather,china Meteorological Administration,Beijing 100081,china

The geomagnetic fields,which play important roles in the ionospheric dynamo,can greatly affect the global distribution of ionospheric electric fields,currents and other ionospheric electrodynamics *** the study of ionospheric electrodynamics phenomena,such as the longitudinal variations of ionospheric electric fields,the non-dipolar component of the geomagnetic fields must be taken into *** this paper,we deduce a theoretical electric field model for ionospheric dynamo at mid- and low-latitude which adopt a modified magnetic apex coordinates *** the new electric field model,the geomagnetic fields can be calculated from either the IGRF model or the dipole field model, and the neutral winds and conductivities are calculated based on empirical *** the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method,and the ionospheric electric fields and currents are derived from the calculated *** model can reproduce the main features of the ionospheric electrodynamics processes,so it will be a useful tool for the investigation of the upper atmosphere and ionosphere.

关键词： ionospheric dynamo ionospheric electric fields APEX coordinates

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Applying artificial neural network to derive long-term foF2 trends in the Asia/Pacific sector from ionosonde observations

Applying artificial neural network to derive long-term foF2 ...

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中国科学院地质与地球物理研究所2006学术年会

作者： Xinan Yue,~(1,2,3) Weixing Wan,~1 Libo Liu,~1 Baiqi Ning,~1 and Biqiang Zhao~(1,2,3) 1 institute of Geology and Geophysics,chinese academy of sciences,Beijing 100029,china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan,430071,china 3 Graduate School of chinese academy of sciences,Beijing,china

An artificial neural network(ANN) method is first used for deriving long-term trends of the F2-layer critical frequency(foF2) at 19 ionospheric stations in the Asia/Pacific *** is found that the ANN method can eliminate the geomagnetic activity effect on foF2 more effectively than usual regression *** the selected 19 stations,there are significant long-term trends corresponding to a confidence level 0%at 14 stations and 12 of these stations present negative *** average trend of .05%per year in the selected area can be obtained if the 12 stations with significant negative long-term trends be *** pronounced diurnal and latitudinal effects in trends and no uniform pattern of seasonal variation in most stations are *** long-term trends for low latitude and equatorial stations differ from other stations suggest that some special dynamical processes may take effects in the equatorial anomaly region. Many factors which can influence ionosphere,such as the greenhouse effect,solar and geomagnetic activity,and neutral background gas,might contribute to the trend.

关键词： Ionosphere model foE

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Modeling investigation of ionospheric storm effects over Millstone Hill during August 4-5,1992

Modeling investigation of ionospheric storm effects over Mil...

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中国科学院地质与地球物理研究所2004学术年会

作者： Jiuhou Lei~(1,2,3),Libo Liu~1,Weixing Wan~1,and Shun-Rong Zhang~4 1 institute of Geology and Geophysics.chinese academy of sciences,Beijing 100029,china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan 430071,china 3 Graduate School of the chinese academy of sciences,Beijing,china 4 Haystack Observatory,Massachusetts institute of Technology,Westford,Massachusetts,USA

We examine the physical mechanism of the negative and positive storm at middle latitude in August 1992, based on incoherent scatter radar(ISR) observations over Millstone Hill(42.6°N,288.5°E) and a first-principles ionospheric *** exospheric temperature T,thermospheric composition and neutral winds,inferred from the ion temperature T profile using the ion energy balance calculation(e.g.,Bauer et al.,1970;Oliver,1979) and from the electron density N profile using an ISR data assimilation method(Zhang et al.,2001,2002),are employed to investigate the storm *** derived thermospheric information shows that the negative phase on August 5 is attributed to both the large poleward wind and the reduced[O]/[N]and[O]/[O]ratio at *** the daytime positive storm on August 4,the thermospheric composition perturbation,in addition to the enhanced equatorward wind,plays a significant *** study also suggests that the data assimilation technique can provide useful information to understand some physical mechanisms of the ionospheric storm when direct experimental data are not available.

关键词： Ionospheric storm middle-latitude ionosphere incoherent scatter radar ion chemistry and composition modeling and forecasting data assimilation

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Development of a middle and low latitude theoretical ionospheric model and an observation system data assimilation experiment

Development of a middle and low latitude theoretical ionosph...

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中国科学院地质与地球物理研究所2008学术年会

作者： YUE XinAn~(1,2,3),WAN WeiXing~(1+),LIU LiBo~1,LE HuiJun~1,CHEN YiDing~1 & YU Tao~(4,1) 1 institute of Geology and Geophysics,chinese academy of sciences,Beijing 100029,china 2 wuhan institute of physics and mathematics,chinese academy of sciences,wuhan 430071,china 3 Graduate University of chinese academy of sciences,Beijing 100049,china 4 National Center for Spaceweather,CMA,Beijing 100081,china

On the basis of previous work,we develop a middle and low latitude theoretical ionospheric model in this paper,named Theoretical Ionospheric Model of the Earth in the institute of Geology and Geophysics, chinese academy of sciences(TIME-IGGCAS).TIME-IGGCAS solves the equations of mass continuity, motion and energy of electron and ions self-consistently and uses an eccentric dipole field approximation to the Earth’s magnetic *** combine the Eulerian and Lagrangian approaches in the model and take account of the plasma E×B drift *** results reveal that the model is steady and credible and can reproduce most large-scale features of *** using TIME-IGGCAS,we carried out an observation system data assimilation *** results show that the E×B drift velocity can be accurately estimated by ingesting the observed foF2 and hmF2 into the model applying nonlinear least-square fit *** suggest that this work is of great significance in the development of ionospheric data assimilation model to give better nowcast and forecast of ionosphere.

关键词： ionosphere theoretical model data assimilation nonlinear least-square fit method

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风险概念分析

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系统工程学报 2001年第5期16卷 402-406页

作者：丁义明方福康北京师范大学系统科学系北京师范大学非平衡系统研究所北京100875

分析了风险的概念 ,介绍了不确定性经济学、保险和金融三个领域中与风险有关的概念 (效用函数 ,风险厌恶 ,保险 ,金融风险 )和各自关心的主要问题 (如风险的衡量 ,保费的确定 ,资产价格波动 ) ,以及一些重要结论 (Pratt定理等 ) .

关键词：风险概念分析复杂系统金融

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