Space Very Long Baseline Interferometry(S-VLBI) is an aperture synthesis technique utilizing an array of radio telescopes including ground telescopes and space orbiting telescopes.It can achieve much higher spatial re...Space Very Long Baseline Interferometry(S-VLBI) is an aperture synthesis technique utilizing an array of radio telescopes including ground telescopes and space orbiting telescopes.It can achieve much higher spatial resolution than that from the ground-only VLBI.In this paper,a new concept of twin spacecraft S-VLBI has been proposed,which utilizes the space-space baselines formed by two satellites to obtain larger and uniform uv coverage without atmospheric influence and hence achieve high quality images with higher angular resolution.The orbit selections of the two satellites are investigated.The imaging performance and actual launch conditions are all taken into account in orbit designing of the twin spacecraft S-VLBI.Three schemes of orbit design using traditional elliptical orbits and circular orbits are presented.These design results can be used for different scientific goals.Furthermore,these designing ideas can provide useful references for the future Chinese millimeter-wave S-VLBI mission.展开更多
The Solar Polar ORbit Telescope(SPORT) project for space weather mission has been under intensive scientific and engineering background studies since it was incorporated into the Chinese Space Science Strategic Pionee...The Solar Polar ORbit Telescope(SPORT) project for space weather mission has been under intensive scientific and engineering background studies since it was incorporated into the Chinese Space Science Strategic Pioneer Project in 2011.SPORT is designed to carry a suite of remote-sensing and in-situ instruments to observe Coronal Mass Ejections(CMEs),energetic particles,solar high-latitude magnetism,and the fast solar wind from a polar orbit around the Sun.The first extended view of the polar regions of the Sun and the ecliptic enabled by SPORT will provide a unique opportunity to study CME propagation through the inner heliosphere,and the solar high-latitude magnetism giving rise to eruptions and the fast solar wind.Coordinated observations between SPORT and other spaceborne/ground-based facilities within the International Living With a Star(ILWS) framework can significantly enhance scientific output.SPORT is now competing for official selection and implementation during China's 13 th Five-Year Plan period of 2016-2020.展开更多
To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on ...To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on the upper atmosphere has been developed by a Japanese inter-university project called the Inter-university Upper atmosphere Global Observation Network （1UGONET）. The objective of this paper is to describe the infrastructure and tools developed by IUGONET. We focus on the data analysis software. It is written in Interactive Data Language （IDL） and is a plug-in for the THEMIS Data Analysis Software suite （TDAS）, which is a set of IDL libraries used to visualize and analyze satellite- and ground-based data. We present plots of upper atmospheric data provided by IUGONET as examples of applications, and verify the usefulness of the software in the study of polar science. We discuss IUGONET＇s new and unique developments, i.e., an executable file of TDAS that can run on the IDL Virtual Machine, IDL routines to retrieve metadata from the IUGONET database, and an archive of 3-D simulation data that uses the Common Data Format so that it can easily be used with TDAS.展开更多
In this paper,technological progress for China's microwave remote sensing is intro-duced.New developments of the microwave remote sensing instruments for meteorological satellite FY-3,ocean dynamic measurement sat...In this paper,technological progress for China's microwave remote sensing is intro-duced.New developments of the microwave remote sensing instruments for meteorological satellite FY-3,ocean dynamic measurement satellite(HY-2),environment small SAR satellite(HJ-1C) and China's lunar exploration satellite(Chang'E-1),geostationary orbit meteorological satellite FY-4M,are reported.展开更多
In this presentation, technological progress for China's microwave remote sensing is introduced. New developments of the microwave remote sensing instruments formeteorological satellite FY-3, ocean dynamic measure...In this presentation, technological progress for China's microwave remote sensing is introduced. New developments of the microwave remote sensing instruments formeteorological satellite FY-3, ocean dynamic measurement satellite (HY-2), environment small SAR satellite (H J-1C) and China's lunar exploration satellite (Chang'E-1), are reported.展开更多
The Space Environment Prediction Center (SEPC) of the Center for Space Science and Applied Research of the Chinese Academy of Sciences (CSSAR, CAS)took on the mission of offering the space environment parameters which...The Space Environment Prediction Center (SEPC) of the Center for Space Science and Applied Research of the Chinese Academy of Sciences (CSSAR, CAS)took on the mission of offering the space environment parameters which may be of use to the safety of manned spacecraft. In order to complete the space environment safety guarantee mission for SZ-4 and SZ-5, SEPC improved the space environment monitoring system, database system, prediction result display system, prediction implementation system, etc. For guaranteeing the safety of the airship and cosmonaut in the first manned SZ-5, flying experiment mission,SEPC developed the software for analyzing radiation dose and early-warning software for large debris collision with SZ-5. Three months before the flights of SZ-4 and SZ-5, SEPC began to predict the safe launch period in view of the space environment, and offered timely and valid reference opinions for selecting the safety period. Especially during the mission of SZ-5, SEPC analyzed the space high-energy environment in a pre-arranged orbit and abnormal orbit andevaluated the radiation dose which cosmonauts may encounter in space. The evaluation offered an important reference for cosmonaut safety and decisionmaking in the SZ-5 mission. The calculation of the distribution of large debris and the collision risk assessment at different orbit entry times for SZ-5 provided an important base for the superior department to make flight decisions.展开更多
Learning incorporates a broad range of complex procedures. Machine learning（ML） is a subdivision of artificial intelligence based on the biological learning process. The ML approach deals with the design of algorith...Learning incorporates a broad range of complex procedures. Machine learning（ML） is a subdivision of artificial intelligence based on the biological learning process. The ML approach deals with the design of algorithms to learn from machine readable data. ML covers main domains such as data mining, difficultto-program applications, and software applications. It is a collection of a variety of algorithms（e.g. neural networks, support vector machines, self-organizing map, decision trees, random forests, case-based reasoning, genetic programming, etc.） that can provide multivariate, nonlinear, nonparametric regression or classification. The modeling capabilities of the ML-based methods have resulted in their extensive applications in science and engineering. Herein, the role of ML as an effective approach for solving problems in geosciences and remote sensing will be highlighted. The unique features of some of the ML techniques will be outlined with a specific attention to genetic programming paradigm. Furthermore,nonparametric regression and classification illustrative examples are presented to demonstrate the efficiency of ML for tackling the geosciences and remote sensing problems.展开更多
We analyse the WIND data of an interplanetary magnetic cloud （MC） on 2 November 2001, and find new evidences for magnetic reconnection in the tail of this MC. In the MC tail, the largely dip and the large change of ...We analyse the WIND data of an interplanetary magnetic cloud （MC） on 2 November 2001, and find new evidences for magnetic reconnection in the tail of this MC. In the MC tail, the largely dip and the large change of the orientation of the magnetic field occurred simultaneously, △θ≈45° and △φ changed from 90° to 320°. Correspondingly, the number density of ions increased, and the superthermal electrons were heated and accelerated, however its number density decreased. Meanwhile, inverse jets and Hall term were observed. The pitch-angle distributions of the electrons with lower energy and higher energy showed strong turbulence and bi-direction flow, respectively. The plasma wave activity enhanced near the electron plasma frequency, fpe and 2fpe. These important physical characteristics are new evidences for magnetic reconnection existing in interplanetary space.展开更多
Chang'E-1 is the first lunar mission in China,which was successfully launched on Oct.24th,2007.It was guided to crash on the Moon on March 1,2009,at 52.36°E,1.50°S,in the north of Mare Fecunditatis.The t...Chang'E-1 is the first lunar mission in China,which was successfully launched on Oct.24th,2007.It was guided to crash on the Moon on March 1,2009,at 52.36°E,1.50°S,in the north of Mare Fecunditatis.The total mission lasted 495 days,exceeding the designed life-span about four months.1.37Terabytes raw data was received from Chang'E-1.It was then processed into 4Terabytes science data at different levels.A series of science results have been achieved by analyzing and applicating these data,especially "global image of the Moon of China's first lunar exploration mission".Four scientific goals of Chang'E-1 have been achieved.It provides abundant materials for the research of lunar sciences and cosmochemistry.Meanwhile these results will serve for China's future lunar missions.展开更多
A new numerical scheme of 3rd order Weighted Essentially Non-Oscillatory (WENO) type for 2.5D mixed GLM-MHD in Cartesian coordinates is proposed. The MHD equations are modified by combining the arguments as by Dellar ...A new numerical scheme of 3rd order Weighted Essentially Non-Oscillatory (WENO) type for 2.5D mixed GLM-MHD in Cartesian coordinates is proposed. The MHD equations are modified by combining the arguments as by Dellar and Dedner et al to couple the divergence constraint with the evolution equations using a Generalized Lagrange Multiplier (GLM). Moreover, the magnetohydrodynamic part of the GLM-MHD system is still in conservation form. Meanwhile, this method is very easy to add to an existing code since the underlying MHD solver does not have to be modified. To show the validation and capacity of its application to MHD problem modelling, interaction between a magnetosonic shock and a denser cloud and magnetic reconnection problems are used to verify this new MHD code. The numerical tests for 2D Orszag and Tang's MHD vortex, interaction between a magnetosonic shock and a denser cloud and magnetic reconnection problems show that the third order WENO MHD solvers are robust and yield reliable results by the new mixed GLM or the mixed EGLM correction here even if it can not be shown that how the divergence errors are transported as well as damped as done for one dimensional ideal MHD by Dedner et al.展开更多
This paper gives a brief introduction of YingHuo-1(YH-1),a Chinese Martian Space Environment Exploration Orbiter.YH-1 is a micro-satellite developed by Chinese Aerospace Industry,and will be launched together with Rus...This paper gives a brief introduction of YingHuo-1(YH-1),a Chinese Martian Space Environment Exploration Orbiter.YH-1 is a micro-satellite developed by Chinese Aerospace Industry,and will be launched together with Russian spacecraft,Phobos-Grunt,to orbit Mars in September,2009.Four payloads are selected for the mission,plasma package,including of electron analyzer,ion energy and mass analyzer;sat-sat occultation receiver;flux-gate magnetometer;and optical monitor.YH-1 mission focus on the investigation of the characteristics and its evolution of the Martian space Environment,and identifying major plasma processes,which provide channels for Martian volatiles escaping.展开更多
The Meridian Project is a ground- based network program to monitor solar-terrestrial space environment, which consists of a chain of ground-based observatories with multiple instruments including magnetometers, ionoso...The Meridian Project is a ground- based network program to monitor solar-terrestrial space environment, which consists of a chain of ground-based observatories with multiple instruments including magnetometers, ionosondes, HF and VHF radar, Lidar, IPS monitors, sounding rockets etc. The chain is mainly located in the neighborhood of 120°E meridian, and is thus named the Meridian Project. It has officially been approved by the Chinese government and will be finished by 2009. This talk will give an overview of the Meridian Project and the proposed International Space Weather Meridian Circle Program.展开更多
The European Space Agency will launch the first salinity satellite for remotely sensing the global soil moisture and ocean salinity (SMOS) at a sun-synchronous orbit in 2009. One of the payloads on the satellite is a ...The European Space Agency will launch the first salinity satellite for remotely sensing the global soil moisture and ocean salinity (SMOS) at a sun-synchronous orbit in 2009. One of the payloads on the satellite is a synthetic aperture microwave radiometer (MIRAS), which is an innovative instrument designed as a two-dimensional (2D) interferometer for acquiring brightness temperature (TB) at L-band (1.4 GHz). MIRAS allows measuring TB at a series of incidences for full polarizations. As the satellite travels, a given location within the 2D field of view is observed from different incidence angles. The authors develop a new scheme to retrieve the sea-surface salinity (SSS) from SMOS's TB at multi-incidence angles in a pixel, utilizing the properties of emissivity changing with incidence angles. All measurements of a given Stokes parameter in a pixel are first fitted to incidence angles in three order polynomial, and then the smoothed data are used for retrieving the SSS. The procedure will remove the random noise in TB greatly. Furthermore, the new method shows that the error in retrieved SSS is very sensitive to the system biases in the calibrated TB of the sensor, but the error in the retrieval is also a system bias, which can be corrected by post-launch validation. Therefore, this method may also serve as a means to evaluate the calibration precision in TB.展开更多
In this paper,we present an innovative method of double balanced differential configuration,in which two adjacent single photon avalanche diodes(SPADs)from the same wafer are configured as the first balanced structure...In this paper,we present an innovative method of double balanced differential configuration,in which two adjacent single photon avalanche diodes(SPADs)from the same wafer are configured as the first balanced structure,and the output signal from the first balanced stage is subtracted by the attenuated gate driving signal as the second balanced stage.The compact device is cooled down to 236 K to be characterized.At a gate repetition rate of 400 MHz and a1 550 nm laser repetition rate of 10 MHz,the maximum photon detection efficiency of 13.5%can be achieved.The dark count rate is about 10-4 ns-1 at photon detection efficiency of 10%.The afterpulsing probability decreases with time exponentially.It is shown that this configuration is effective to discriminate the ultra-weak avalanche signal in high speed gating rates.展开更多
As friction, intrinsic steady-state nonlinearity poses a challenging dilemma to the control system of 3-DOF （three degree of freedom） flight simulator, a novel hybrid control strategy of nonlinear PID （proportional...As friction, intrinsic steady-state nonlinearity poses a challenging dilemma to the control system of 3-DOF （three degree of freedom） flight simulator, a novel hybrid control strategy of nonlinear PID （proportionalintegral-derivative） with additional FFC （feed-forward controller） is proposed, and the hardware-in-the-loop simulation results are also given. Based on the description of 3-DOF flight simulator, a novel nonlinear PID theory is well introduced. Then a nonlinear PID controller with additional FFC is designed. Subsequently, the loop structure of 3-DOF flight simulator is also designed. Finally, a series of hardware-in-the-loop simulation experiments are undertaken to verify the feasibility and effectiveness of the proposed nonlinear PID controller with additional FFC for 3-DOF flight simulator.展开更多
We present a new hybrid numerical scheme for two-dimensional(2D)ideal magnetohydrodynamic(MHD)equations.A simple conservation element and solution element(CESE)method is used to calculate the flow variables,and the un...We present a new hybrid numerical scheme for two-dimensional(2D)ideal magnetohydrodynamic(MHD)equations.A simple conservation element and solution element(CESE)method is used to calculate the flow variables,and the unknown first-order spatial derivatives involved in the CESE method are computed with a finite volume scheme that uses the solution of the derivative Riemann problem with limited reconstruction to evaluate the numerical flux at cell interface position.To show the validation and capacity of its application to 2D MHD problems,we study several benchmark problems.Numerical results verify that the hybrid scheme not only performs well,but also can retain the solution quality even if the Courant number ranges from close to 1 to less than 0.01.展开更多
46 magnetosheath crossing events from the two years (2001.2-2003.1) of Cluster magnetic field measurements are identified and used to investigate the characters of the magnetic field fluctuations in the regions of und...46 magnetosheath crossing events from the two years (2001.2-2003.1) of Cluster magnetic field measurements are identified and used to investigate the characters of the magnetic field fluctuations in the regions of undisturbed solar wind, foreshock, magnetosheath. The preliminary results indicate the properties of the plasma turbulence in the magnetosheath are strongly controlled by IMF orientation with respect to the bow shock normal. The amplitude of the magnetic field magnitude and direction variations behind quasiparallel bow shock are larger than those behind quasi-perpendicular bow shock. Almost purely compressional waves are found in quasi-perpendicular magnetosheath.展开更多
A new hybrid numerical scheme of combining an E-CUSP(Energy-Convective Upwind and Split Pressure) method for the fluid part and the Constrained Transport(CT) for the magnetic induction part is proposed.In order to avo...A new hybrid numerical scheme of combining an E-CUSP(Energy-Convective Upwind and Split Pressure) method for the fluid part and the Constrained Transport(CT) for the magnetic induction part is proposed.In order to avoid the occurrence of negative pressure in the reconstructed profiles and its updated value,a positivity preserving method is provided.Furthermore,the MHD equations are solved at each physical time step by advancing in pseudo time.The use of dual time stepping is beneficial in the computation since the use of dual time stepping allows the physical time step not to be limited by the corresponding values in the smallest cell and to be selected based on the numerical accuracy criterion.This newly established hybrid scheme combined with positivity preserving method and dual time technique has demonstrated the accurateness and robustness through numerical experiments of benchmark problems such as the 2D Orszag-Tang vortex problem and the3 D shock-cloud interaction problem.展开更多
基金Supported by the Natural Science Foundation of China(40701100,40801136)the Strategic Priority Program on Space Science of the Chinese Academy of Sciences(XDA04060803)
文摘Space Very Long Baseline Interferometry(S-VLBI) is an aperture synthesis technique utilizing an array of radio telescopes including ground telescopes and space orbiting telescopes.It can achieve much higher spatial resolution than that from the ground-only VLBI.In this paper,a new concept of twin spacecraft S-VLBI has been proposed,which utilizes the space-space baselines formed by two satellites to obtain larger and uniform uv coverage without atmospheric influence and hence achieve high quality images with higher angular resolution.The orbit selections of the two satellites are investigated.The imaging performance and actual launch conditions are all taken into account in orbit designing of the twin spacecraft S-VLBI.Three schemes of orbit design using traditional elliptical orbits and circular orbits are presented.These design results can be used for different scientific goals.Furthermore,these designing ideas can provide useful references for the future Chinese millimeter-wave S-VLBI mission.
基金Supported by the Strategic Priority Research Program on Space Science(XDA04060801,XDA04060802,XDA04060803,XDA04060804)of Chinese Academy of Sciencesthe Specialized Research Fund for State Key Laboratory of China+1 种基金the Chinese National Science Foundation(41374175,41204129)the CAS/SAFEA international Partnership Program for Creative Research Teams
文摘The Solar Polar ORbit Telescope(SPORT) project for space weather mission has been under intensive scientific and engineering background studies since it was incorporated into the Chinese Space Science Strategic Pioneer Project in 2011.SPORT is designed to carry a suite of remote-sensing and in-situ instruments to observe Coronal Mass Ejections(CMEs),energetic particles,solar high-latitude magnetism,and the fast solar wind from a polar orbit around the Sun.The first extended view of the polar regions of the Sun and the ecliptic enabled by SPORT will provide a unique opportunity to study CME propagation through the inner heliosphere,and the solar high-latitude magnetism giving rise to eruptions and the fast solar wind.Coordinated observations between SPORT and other spaceborne/ground-based facilities within the International Living With a Star(ILWS) framework can significantly enhance scientific output.SPORT is now competing for official selection and implementation during China's 13 th Five-Year Plan period of 2016-2020.
基金supported by the Special Edu-cational Research Budget(Research Promotion)[FY2009]the Special Budget(Project)[FY2010 and later years]from the Ministry of Education,Culture,Sports,Science and Technology(MEXT),Japansupported by the GRENE Arctic Climate Change Research Project,Japan
文摘To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on the upper atmosphere has been developed by a Japanese inter-university project called the Inter-university Upper atmosphere Global Observation Network （1UGONET）. The objective of this paper is to describe the infrastructure and tools developed by IUGONET. We focus on the data analysis software. It is written in Interactive Data Language （IDL） and is a plug-in for the THEMIS Data Analysis Software suite （TDAS）, which is a set of IDL libraries used to visualize and analyze satellite- and ground-based data. We present plots of upper atmospheric data provided by IUGONET as examples of applications, and verify the usefulness of the software in the study of polar science. We discuss IUGONET＇s new and unique developments, i.e., an executable file of TDAS that can run on the IDL Virtual Machine, IDL routines to retrieve metadata from the IUGONET database, and an archive of 3-D simulation data that uses the Common Data Format so that it can easily be used with TDAS.
文摘In this paper,technological progress for China's microwave remote sensing is intro-duced.New developments of the microwave remote sensing instruments for meteorological satellite FY-3,ocean dynamic measurement satellite(HY-2),environment small SAR satellite(HJ-1C) and China's lunar exploration satellite(Chang'E-1),geostationary orbit meteorological satellite FY-4M,are reported.
文摘In this presentation, technological progress for China's microwave remote sensing is introduced. New developments of the microwave remote sensing instruments formeteorological satellite FY-3, ocean dynamic measurement satellite (HY-2), environment small SAR satellite (H J-1C) and China's lunar exploration satellite (Chang'E-1), are reported.
文摘The Space Environment Prediction Center (SEPC) of the Center for Space Science and Applied Research of the Chinese Academy of Sciences (CSSAR, CAS)took on the mission of offering the space environment parameters which may be of use to the safety of manned spacecraft. In order to complete the space environment safety guarantee mission for SZ-4 and SZ-5, SEPC improved the space environment monitoring system, database system, prediction result display system, prediction implementation system, etc. For guaranteeing the safety of the airship and cosmonaut in the first manned SZ-5, flying experiment mission,SEPC developed the software for analyzing radiation dose and early-warning software for large debris collision with SZ-5. Three months before the flights of SZ-4 and SZ-5, SEPC began to predict the safe launch period in view of the space environment, and offered timely and valid reference opinions for selecting the safety period. Especially during the mission of SZ-5, SEPC analyzed the space high-energy environment in a pre-arranged orbit and abnormal orbit andevaluated the radiation dose which cosmonauts may encounter in space. The evaluation offered an important reference for cosmonaut safety and decisionmaking in the SZ-5 mission. The calculation of the distribution of large debris and the collision risk assessment at different orbit entry times for SZ-5 provided an important base for the superior department to make flight decisions.
文摘Learning incorporates a broad range of complex procedures. Machine learning（ML） is a subdivision of artificial intelligence based on the biological learning process. The ML approach deals with the design of algorithms to learn from machine readable data. ML covers main domains such as data mining, difficultto-program applications, and software applications. It is a collection of a variety of algorithms（e.g. neural networks, support vector machines, self-organizing map, decision trees, random forests, case-based reasoning, genetic programming, etc.） that can provide multivariate, nonlinear, nonparametric regression or classification. The modeling capabilities of the ML-based methods have resulted in their extensive applications in science and engineering. Herein, the role of ML as an effective approach for solving problems in geosciences and remote sensing will be highlighted. The unique features of some of the ML techniques will be outlined with a specific attention to genetic programming paradigm. Furthermore,nonparametric regression and classification illustrative examples are presented to demonstrate the efficiency of ML for tackling the geosciences and remote sensing problems.
基金Supported by National Natural Science Foundation of P.R.China(50275150)National Research Foundation for the Doctoral Program of Higher Education of P.R.China(20040533035)
基金Supported by the National Natural Science Foundation of China under Grant Nos G200078405, 40336053 and 40274052, and the International Collaboration Research Team Program of the Chinese Academy of Sciences.
文摘We analyse the WIND data of an interplanetary magnetic cloud （MC） on 2 November 2001, and find new evidences for magnetic reconnection in the tail of this MC. In the MC tail, the largely dip and the large change of the orientation of the magnetic field occurred simultaneously, △θ≈45° and △φ changed from 90° to 320°. Correspondingly, the number density of ions increased, and the superthermal electrons were heated and accelerated, however its number density decreased. Meanwhile, inverse jets and Hall term were observed. The pitch-angle distributions of the electrons with lower energy and higher energy showed strong turbulence and bi-direction flow, respectively. The plasma wave activity enhanced near the electron plasma frequency, fpe and 2fpe. These important physical characteristics are new evidences for magnetic reconnection existing in interplanetary space.
文摘Chang'E-1 is the first lunar mission in China,which was successfully launched on Oct.24th,2007.It was guided to crash on the Moon on March 1,2009,at 52.36°E,1.50°S,in the north of Mare Fecunditatis.The total mission lasted 495 days,exceeding the designed life-span about four months.1.37Terabytes raw data was received from Chang'E-1.It was then processed into 4Terabytes science data at different levels.A series of science results have been achieved by analyzing and applicating these data,especially "global image of the Moon of China's first lunar exploration mission".Four scientific goals of Chang'E-1 have been achieved.It provides abundant materials for the research of lunar sciences and cosmochemistry.Meanwhile these results will serve for China's future lunar missions.
基金Supported by the National Natural Science Foundation of China (40374056, 40536029, 40574068)the International Collaboration Research Team Program of the Chinese Academy of Sciences
文摘A new numerical scheme of 3rd order Weighted Essentially Non-Oscillatory (WENO) type for 2.5D mixed GLM-MHD in Cartesian coordinates is proposed. The MHD equations are modified by combining the arguments as by Dellar and Dedner et al to couple the divergence constraint with the evolution equations using a Generalized Lagrange Multiplier (GLM). Moreover, the magnetohydrodynamic part of the GLM-MHD system is still in conservation form. Meanwhile, this method is very easy to add to an existing code since the underlying MHD solver does not have to be modified. To show the validation and capacity of its application to MHD problem modelling, interaction between a magnetosonic shock and a denser cloud and magnetic reconnection problems are used to verify this new MHD code. The numerical tests for 2D Orszag and Tang's MHD vortex, interaction between a magnetosonic shock and a denser cloud and magnetic reconnection problems show that the third order WENO MHD solvers are robust and yield reliable results by the new mixed GLM or the mixed EGLM correction here even if it can not be shown that how the divergence errors are transported as well as damped as done for one dimensional ideal MHD by Dedner et al.
文摘This paper gives a brief introduction of YingHuo-1(YH-1),a Chinese Martian Space Environment Exploration Orbiter.YH-1 is a micro-satellite developed by Chinese Aerospace Industry,and will be launched together with Russian spacecraft,Phobos-Grunt,to orbit Mars in September,2009.Four payloads are selected for the mission,plasma package,including of electron analyzer,ion energy and mass analyzer;sat-sat occultation receiver;flux-gate magnetometer;and optical monitor.YH-1 mission focus on the investigation of the characteristics and its evolution of the Martian space Environment,and identifying major plasma processes,which provide channels for Martian volatiles escaping.
基金Supported by the National Natural Science Foundation of China (40325010, 40574068)
文摘The Meridian Project is a ground- based network program to monitor solar-terrestrial space environment, which consists of a chain of ground-based observatories with multiple instruments including magnetometers, ionosondes, HF and VHF radar, Lidar, IPS monitors, sounding rockets etc. The chain is mainly located in the neighborhood of 120°E meridian, and is thus named the Meridian Project. It has officially been approved by the Chinese government and will be finished by 2009. This talk will give an overview of the Meridian Project and the proposed International Space Weather Meridian Circle Program.
文摘The European Space Agency will launch the first salinity satellite for remotely sensing the global soil moisture and ocean salinity (SMOS) at a sun-synchronous orbit in 2009. One of the payloads on the satellite is a synthetic aperture microwave radiometer (MIRAS), which is an innovative instrument designed as a two-dimensional (2D) interferometer for acquiring brightness temperature (TB) at L-band (1.4 GHz). MIRAS allows measuring TB at a series of incidences for full polarizations. As the satellite travels, a given location within the 2D field of view is observed from different incidence angles. The authors develop a new scheme to retrieve the sea-surface salinity (SSS) from SMOS's TB at multi-incidence angles in a pixel, utilizing the properties of emissivity changing with incidence angles. All measurements of a given Stokes parameter in a pixel are first fitted to incidence angles in three order polynomial, and then the smoothed data are used for retrieving the SSS. The procedure will remove the random noise in TB greatly. Furthermore, the new method shows that the error in retrieved SSS is very sensitive to the system biases in the calibrated TB of the sensor, but the error in the retrieval is also a system bias, which can be corrected by post-launch validation. Therefore, this method may also serve as a means to evaluate the calibration precision in TB.
基金supported by the National Key Scientific Instrument and Equipment Development Project of China(No.2013YQ030595)the National High Technology Research and Development Program of China(No.2013AA122902)+1 种基金the National Natural Science Foundation of China(No.61274024)National Natural Science Foundation of China for the Youth(No.40804032)
文摘In this paper,we present an innovative method of double balanced differential configuration,in which two adjacent single photon avalanche diodes(SPADs)from the same wafer are configured as the first balanced structure,and the output signal from the first balanced stage is subtracted by the attenuated gate driving signal as the second balanced stage.The compact device is cooled down to 236 K to be characterized.At a gate repetition rate of 400 MHz and a1 550 nm laser repetition rate of 10 MHz,the maximum photon detection efficiency of 13.5%can be achieved.The dark count rate is about 10-4 ns-1 at photon detection efficiency of 10%.The afterpulsing probability decreases with time exponentially.It is shown that this configuration is effective to discriminate the ultra-weak avalanche signal in high speed gating rates.
基金the National Natural Science Foundation of China (60604009)Aeronautical Science Foundationof China(2006ZC51039)Beijing NOVA Program (2007A017).
文摘As friction, intrinsic steady-state nonlinearity poses a challenging dilemma to the control system of 3-DOF （three degree of freedom） flight simulator, a novel hybrid control strategy of nonlinear PID （proportionalintegral-derivative） with additional FFC （feed-forward controller） is proposed, and the hardware-in-the-loop simulation results are also given. Based on the description of 3-DOF flight simulator, a novel nonlinear PID theory is well introduced. Then a nonlinear PID controller with additional FFC is designed. Subsequently, the loop structure of 3-DOF flight simulator is also designed. Finally, a series of hardware-in-the-loop simulation experiments are undertaken to verify the feasibility and effectiveness of the proposed nonlinear PID controller with additional FFC for 3-DOF flight simulator.
基金Supported by the National Basic Research Program of China under Grant No 2012CB825601the National Natural Science Foundation of China under Grant Nos 40921063,41031066,40890162,40904050,41074121 and 41074122the Specialized Research Fund for State Key Laboratories.
文摘We present a new hybrid numerical scheme for two-dimensional(2D)ideal magnetohydrodynamic(MHD)equations.A simple conservation element and solution element(CESE)method is used to calculate the flow variables,and the unknown first-order spatial derivatives involved in the CESE method are computed with a finite volume scheme that uses the solution of the derivative Riemann problem with limited reconstruction to evaluate the numerical flux at cell interface position.To show the validation and capacity of its application to 2D MHD problems,we study several benchmark problems.Numerical results verify that the hybrid scheme not only performs well,but also can retain the solution quality even if the Courant number ranges from close to 1 to less than 0.01.
基金Supported by NNSFC (No. 40325010)RFBR-NSFC (2005-2006)the China-Russia Joint Research Center on Space Weather,Chinese Academy of Sciences
文摘46 magnetosheath crossing events from the two years (2001.2-2003.1) of Cluster magnetic field measurements are identified and used to investigate the characters of the magnetic field fluctuations in the regions of undisturbed solar wind, foreshock, magnetosheath. The preliminary results indicate the properties of the plasma turbulence in the magnetosheath are strongly controlled by IMF orientation with respect to the bow shock normal. The amplitude of the magnetic field magnitude and direction variations behind quasiparallel bow shock are larger than those behind quasi-perpendicular bow shock. Almost purely compressional waves are found in quasi-perpendicular magnetosheath.
基金Supported by the National Basic Research Program of China(2012CB825601)the National Natural Science Foundationof China(41031066,41231068,41274192,41074121,41204127)+1 种基金the Knowledge Innovation Program of the ChineseAcademy of Sciences(KZZD-EW-01-4)the Specialized Research Fund for State Key Laboratories
文摘A new hybrid numerical scheme of combining an E-CUSP(Energy-Convective Upwind and Split Pressure) method for the fluid part and the Constrained Transport(CT) for the magnetic induction part is proposed.In order to avoid the occurrence of negative pressure in the reconstructed profiles and its updated value,a positivity preserving method is provided.Furthermore,the MHD equations are solved at each physical time step by advancing in pseudo time.The use of dual time stepping is beneficial in the computation since the use of dual time stepping allows the physical time step not to be limited by the corresponding values in the smallest cell and to be selected based on the numerical accuracy criterion.This newly established hybrid scheme combined with positivity preserving method and dual time technique has demonstrated the accurateness and robustness through numerical experiments of benchmark problems such as the 2D Orszag-Tang vortex problem and the3 D shock-cloud interaction problem.
