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arXiv 2020年

作者： Xu, Zigong Guo, Jingnan Wimmer-Schweingruber, Robert F. Freiherr von Forstner, Johan L. Wang, Yuming Dresing, Nina Lohf, Henning Zhang, Shenyi Heber, Bernd Yang, Mei Institute of Experimental and Applied Physics Kiel University KielD-24118 Germany CAS Key Laboratory of Geospace Environment University of Science and Technology of China Hefei230026 China CAS Center for Excellence in Comparative Planetology Hefei230026 China National Space Science Center Chinese Academy of Sciences Beijing China Beijing Key Laboratory of Space Environment Exploration Beijing China University of Chinese Academy of Science Beijing China Beijing Institute of Spacecraft System Engineering Beijing China

On May 6, 2019 the Lunar Lander Neutron & Dosimetry (LND) Experiment on board the Chang'E-4 lander on the far-side of the Moon detected its first solar energetic particle (SEP) event with proton energies up to 21 MeV. Combined proton energy spectra are studied based on the LND, SOHO/EPHIN and ACE/EPAM measurements which show that LND could provide a complementary dataset from a special location on the Moon, contributing to our existing observations and understanding of space environment. We applied velocity dispersion analysis (VDA) to the impulsive electron event and weak proton enhancement and show that electrons are released only 22 minutes after the flare onset and ∼15 minutes after the type II radio burst, while protons are released more than one hour after the electron release. The beam-like in-situ electrons and clear velocity dispersion indicate a good magnetic connection between the source and Earth. This is remarkable because stereoscopic remote-sensing observations from Earth and STEREO-A suggest that the Solar energetic particles (SEPs) are associated with an active region nearly 113◦ away from the magnetic footpoint of Earth. This suggests that these SEPs did not propagate along the nominal Parker spiral normally assumed for ballistic mapping and that the release and propagation mechanism of electrons and protons are likely to differ significantly for this event. Copyright © 2020, The Authors. All rights reserved.

关键词： Remote sensing

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A maneuvering penetration strategy via integrated flight/propulsion guidance and control method for air-breathing hypersonic vehicle

A maneuvering penetration strategy via integrated flight/pro...

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2018 IEEE CSAA Guidance, Navigation and Control Conference, CGNCC 2018

作者： Xue, Kong Guodong, Ning Ming, Yang Songyan, Wang Harbin Institute of Technology Control and Simulation Center and Science and Technology Complex System Control and Intelligent Agent Cooperation Laboratory China Beijing Electro-Mechanical Institute China Harbin Institute of Technology Control and Simulation Center China

ISBN: (纸本)9781538611715

Given a maneuvering control strategy for air-breathing hypersonic vehicle, which adopt the compound integrated flight/propulsion guidance and control method, further excavation the capability of scramjet to run stable and low fuel consumption, on this basis, implement accelerate snake maneuver, improve the survival probability of weapons, guarantee the practical application ability of the project. Take one certain type of air-breathing hypersonic vehicle as an example, on the basis of an accurate simulation model, several groups of simulation analysis are carried out, the simulation results show that the method is effective and reliable. © 2018 IEEE.

关键词： Hypersonic vehicles

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THE TROPICS

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BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY 2022年第8期103卷 S198-S255页

作者： Diamond, H. J. Schreck, C. J. NOAA/OAR Air Resources Laboratory College Park Maryland North Carolina State University North Carolina Institute for Climate Studies Cooperative Institute for Satellite Earth System Studies Asheville North Carolina NOAA/NWS Climate Prediction Center College Park Maryland University of Miami Rosenstiel School of Marine and Atmospheric Science Miami Florida NOAA/NWS National Hurricane Center Miami Florida NOAA/OAR/AOML Physical Oceanography Division Miami Florida Lamont-Doherty Earth Observatory Columbia University Palisades New York Institute for Climate and Application Research (ICAR)/KLME/ILCEC/CIC-FEMD Nanjing University of Information Science and Technology Nanjing China CPTEC/INPE Center for Weather Forecasts and Climate Studies National Institute for Space Research Cachoeira Paulista Brazil National Institute of Water and Atmospheric Research Ltd. Auckland New Zealand NOAA/OAR/AOML Hurricane Research Division Miami Florida Earth System Modeling Center Nanjing University of Information Science and Technology Nanjing China Department of Atmospheric Science Colorado State University Fort Collins Colorado NOAA/NESDIS Center for Satellite Applications and Research Fort Collins Colorado National Taiwan University Taipei Taiwan Centre for Water Climate and Land School of Environmental and Life Sciences University of Newcastle Callaghan NSW Australia Greater Wellington Regional Council Wellington New Zealand Australian Bureau of Meteorology Melbourne Victoria Australia WeatherTiger LLC Tallahassee Florida SOEST Department of Meteorology and IPRC University of Hawaii Honolulu Hawaii Department of Geosciences Mississippi State University Mississippi State Mississippi

The tropics in 2021, in terms of the El Niño-Southern Oscillation (ENSO), featured La Niña episodes at both the beginning and end of the year. The year started with the continuation of a moderate strength La Niña (peak Oceanic Niño Index [ONI] value between −1.0° and −1.4°C is considered to be moderate strength) that had begun during July-September 2020 and ended during April-June 2021. The ONI then reflected a brief period of ENSO-neutral conditions May-July through June-August 2021, with the index increasing to −0.4°C, just greater than the minimum La Niña threshold of −0.5°C. Moderate La Niña conditions continued through the end of the year. © 2022 American Meteorological Society. All rights reserved.

关键词： Atmospheric pressure

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Topology Optimization Design of LEO Satellite Network

Topology Optimization Design of LEO Satellite Network

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第三十八届中国控制会议

作者： Jian Tai Junting Lv XiANDe Wu Ting Song Qiang Zhang Yanbing Xiang Jun Sun College of Aerospace and Civil Engineering Harbin Engineering University Shanghai Key Laboratory of Space Intelligent Control Technology Beijing Institute of Spacecraft System Engineering Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory

This paper establishes a satellite network topology optimization model based on satellite orbital dynamics, establishes constraints from two aspects of satellite geometric visibility and satellite elevation constraints in the concept of inter-satellite links, and finally solves the above optimization problems by using simulated annealing algorithm, and presents a time-varying satellite network topology optimization method. In the actual simulation, we give a satellite network with multiple satellites and optimize it. The optimal solution of the network configuration is obtained, and a shortest inter-satellite transmission path from signal start star to signal termination star based on time-varying is solved. For this inter-satellite link, the connectivity of inter-satellite link and the fault tolerance of satellite network are analyzed, which proves the feasibility and validity of the optimization method.

关键词： LEO satellite network topology optimization inter-satellite link simulated annealing algorithm

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Latitudinal variations in methane abundance, aerosol opacity and aerosol scattering efficiency in Neptune's atmosphere determined from VLT/MUSE

arXiv

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arXiv 2023年

作者： Irwin, Patrick G.J. Dobinson, Jack James, Arjuna Wong, Michael H. Fletcher, Leigh N. Roman, Michael T. Teanby, Nicholas A. Toledo, Daniel Orton, Glenn S. Pérez-Hoyos, Santiago Sánchez-Lavega, Agustin Simon, Amy Morales-Juberias, Raul de Pater, Imke Atmospheric Oceanic and Planetary Physics Department of Physics University of Oxford Parks Rd OxfordOX1 3PU United Kingdom Center for Integrative Planetary Science University of California BerkeleyCA94720-3411 United States School of Physics & Astronomy University of Leicester University Road LeicesterLE1 7RH United Kingdom School of Earth Sciences University of Bristol Wills Memorial Building Queens Road BristolBS8 1RJ United Kingdom Torrejón de Ardoz Madrid28850 Spain Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive PasadenaCA91109 United States University of the Basque Country UPV/EHU Bilbao48013 Spain Solar System Exploration Division/690 NASA Goddard Space Flight Center 8800 Greenbelt Rd Greenbelt MA20771 United States New Mexico Institute of Technology Soccoro NM United States Department of Astronomy Department of Earth and Planetary Science University of California BerkeleyCA94720 United States

Spectral observations of Neptune made in 2019 with the MUSE instrument at the Very Large Telescope in Chile have been analysed to determine the spatial variation of aerosol scattering properties and methane abundance in Neptune's atmosphere. The darkening of the South Polar Wave (SPW) at ∼ 60◦S, and dark spots such as the Voyager 2 Great Dark Spot is concluded to be due to a spectrally-dependent darkening (λ 2S ice. We also note a regular latitudinal variation of reflectivity at wavelengths of very low methane absorption longer than ∼ 650 nm, with bright zones latitudinally separated by ∼ 25◦. This feature, similar to the spectral characteristics of a discrete deep bright spot DBS-2019 found in our data, is found to be consistent with a brightening of the particles in the same ∼5-bar aerosol layer at λ > 650 nm. We find the properties of an overlying methane/haze aerosol layer at ∼ 2 bar are, to first-order, invariant with latitude, while variations in the opacity of an upper tropospheric haze layer reproduce the observed reflectivity at methane-absorbing wavelengths, with higher abundances found at the equator and also in a narrow 'zone' at 80◦S. Finally, we find the mean abundance of methane below its condensation level to be 6-7% at the equator reducing to ∼3% south of ∼25◦S, although the absolute abundances are model dependent. © 2023, CC BY.

关键词： Methane

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The Comparison of Different Visual Features for Visual Odometry

The Comparison of Different Visual Features for Visual Odome...

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2018 IEEE CSAA Guidance, Navigation and Control Conference, CGNCC 2018

作者： Jiang, Yuehan Wang, Qing Dong, Chaoyang Zhou, Min Zhong, Kewei Beihang University School of Automation Science and Electrical Engineering Beijing100191 China Science and Technology on Special System Simulation Laboratory Beijing Simulation Center Beijing100854 China Shanghai Aerospace Control Technology Institute Shanghai201100 China

ISBN: (纸本)9781538611715

For robots to work effectively, the availability of a map with detailed information surrounding the workspace is an important requirement for indoor and outdoor tasks. This is usually achieved with using visual odometry techniques with feature-based methods. In this paper, we compare the performance of three different feature extraction methods: Scale Invariant Feature Transform (SIFT), Speed Up Robust Features (SURF) and Oriented FAST Rotated BRIEF (ORB). This paper presents experimental results on standard evaluation datasets and all experiments use measurement of the number of image correspondences as well as the ratio of good matched for the evaluation purpose. The results of experiments demonstrate that the performances of three methods in processing time, matching capability and accuracy. SIFT presents its stability in most scenarios although it is very slow. SURF is faster than SIFT and outperform SIFT on some scenarios. ORB is the most efficient feature and shows strong performance. © 2018 IEEE.

关键词： Vision

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Compound Asynchronous Exploration and Exploitation

Compound Asynchronous Exploration and Exploitation

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2019 2nd International Conference on Mechanical,Electronic and Engineering technology(MEET 2019)

作者： Jie Bai Li Liu Yaobing Wang Haoyu Zhang Jianfei Li Beijing Key Laboratory of Intelligent Space Robotic Systems Technology and Applications Beijing Institute of Spacecraft System Engineering College of Engineering Peking University Science and Technology on Space Intelligent Control Laboratory Beijing Institute of Control Engineering

Data efficiency has always been a significant key topic for deep reinforcement learning. The main progress has been on sufficient exploration and effective exploitation. However, the two are often discussed separately. Profit from distributed systems, we propose an asynchronous approach to deep reinforcement learning by combining exploration and exploitation. We apply our framework to off-the-shelf deep reinforcement learning algorithms, and experimental results show that our algorithm is superior in final performance and efficiency.

关键词： Deep Reinforcement Learning Exploration and Exploitation Asynchronous Methods

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Finite-time stability analysis of linear time-varying systems: A numerical algorithm 15

Finite-time stability analysis of linear time-varying system...

引用

15th IEEE International Conference on Mechatronics and Automation, ICMA 2018

作者： Chen, Zhihua Xie, Yongchun Beijing Institute of Control Engineering China Science and Technology on Space Intelligent Control Laboratory Beijing China Tianjin Key Laboratory of Microgravity and Hypogravity Environment Simulation Technology Tianjin China

ISBN: (纸本)9781538660720

Under the perspective of numerical computation, this paper investigates the finite-time stability (FTS) of continuous linear time-varying (LTV) systems when all its initial values are confined within a given polyhedral set while all its states are confined within a given ellipsoidal set. First, by solving a certain function optimization problem, the paper proposes a necessary and sufficient condition to guarantee the FTS of continuous LTV systems. Then, by utilizing the Lipschitz continuity of a certain function, two sufficient conditions to verify the FTS and finite-time instability of continuous LTV systems are proposed under the perspective of numerical computation, respectively. Furthermore, a novel numerical algorithm for analyzing the FTS of continuous LTV systems is deigned by converting a certain function optimization problem into a corresponding quadratic programming. Finally, a numerical example is given to illustrate the effectiveness of the proposed algorithm. © 2018 IEEE.

关键词： Quadratic programming

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Transient Voltage Stability Assessment Method based on gcForest

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Journal of Physics: Conference Series 2021年第1期1914卷

作者： Sun Zhiyuan LI Mingpo Zhang Jie Hu Binjiang Qi Guo Zhu Yihua Guangxi Power Grid Electrical Power Research Institute Supported by the Science and Technology Project of Guangxi Power Grid (Contract No(***DL00006)). State Key Laboratory of HVDC Electric Power Research Institute CSG China Guangdong Provincial Key Laboratory of Intelligent Operation and Control for New Energy Power System CSG Key Laboratory of Power System Simulation

Aiming at the fact that the traditional method cannot quickly and accurately judge the power system transient voltage stability, and the deep neural network method needs many sample data sets and has a large number of hyperparameters, a power system transient voltage stability assessment method based on deep forest (gcForest) is proposed. gcForest effectively extracts features through ensemble learning, multi-layer feature transformation, and dynamically adjusting the number of model layers. Finally, this method is applied to transient voltage stability assessment of an electrolytic aluminium load-intensive area in Guangxi Power Grid. The results show that the method has high accuracy, the feasibility and effectiveness of this method are verified. This method can assist dispatchers to judge the transient voltage stability of the power grid.

关键词：

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THE TEMPO SURVEY II: science CASES LEVERAGED FROM A PROPOSED 30-DAY TIME DOMAIN SURVEY OF THE ORION NEBULA WITH THE NANCY GRACE ROMAN space TELESCOPE

arXiv

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arXiv 2024年

作者： Soares-Furtado, Melinda Limbach, Mary Anne Vanderburg, Andrew Bally, John Becker, Juliette Rosen, Anna L. Bouma, Luke G. Vos, Johanna M. Howell, Steve B. Beatty, Thomas G. Best, William M.J. Cody, Anne Marie Distler, Adam D’Onghia, Elena Heller, René Hensley, Brandon S. Hinkel, Natalie R. Jackson, Brian Kounkel, Marina Kraus, Adam Mann, Andrew W. Marston, Nicholas T. Robberto, Massimo Rodriguez, Joseph E. Steffen, Jason H. Teske, Johanna K. Townsend, Richard Yarza, Ricardo Youngblood, Allison Department of Astronomy University of Wisconsin-Madison 475 N. Charter St. MadisonWI53706 United States Department of Physics Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology CambridgeMA02139 United States Department of Astronomy University of Michigan Ann ArborMI48109 United States Center for Astrophysics and Space Astronomy Astrophysical and Planetary Sciences Department University of Colorado BoulderCO80389 United States Department of Astronomy San Diego State University San DiegoCA92182 United States Computational Science Research Center San Diego State University San DiegoCA92182 United States Department of Astronomy MC 249-17 California Institute of Technology PasadenaCA91125 United States School of Physics Trinity College Dublin The University of Dublin Dublin 2 Ireland NASA Ames Research Center Moffett FieldCA94035 United States Department of Astronomy The University of Texas at Austin AustinTX78712 United States SETI Institute 189 N. Bernardo Ave #200 Mountain ViewCA94043 United States Max Planck Institute for Solar System Research Justus-von-Liebig-Weg 3 Göttingen37077 Germany Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive PasadenaCA91109 United States Physics & Astronomy Department Louisiana State University Baton RougeLA70803 United States Department of Physics Boise State University BoiseID83725-1570 United States Department of Physics & Astronomy Vanderbilt University NashvilleTN37235 United States Department of Physics & Astronomy The University of North Carolina at Chapel Hill Chapel HillNC27599-3255 United States Space Telescope Science Institute 3700 San Martin Drive BaltimoreMD21218 United States Johns Hopkins University 3400 N. Charles St. BaltimoreMD21218 United States Center for Data Intensive and Time Domain Astronomy Department of Physics and Astronomy Michigan State University East LansingMI48824 United States Un

The TEMPO (Transiting Exosatellites, Moons, and Planets in Orion) Survey is a proposed 30-day observational campaign using the Nancy Grace Roman space Telescope. By providing deep, high-resolution, short-cadence infrared photometry of a dynamic star-forming region, TEMPO will investigate the demographics of exosatellites orbiting free-floating planets and brown dwarfs — a largely unexplored discovery space. Here, we present the simulated detection yields of three populations: extrasolar moon analogs orbiting free-floating planets, exosatellites orbiting brown dwarfs, and exoplanets orbiting young stars. Additionally, we outline a comprehensive range of anticipated scientific outcomes accompanying such a survey. These science drivers include: obtaining observational constraints to test prevailing theories of moon, planet, and star formation;directly detecting widely separated exoplanets orbiting young stars;investigating the variability of young stars and brown dwarfs;constraining the low-mass end of the stellar initial mass function;constructing the distribution of dust in the Orion Nebula and mapping evolution in the near-infrared extinction law;mapping emission features that trace the shocked gas in the region;constructing a dynamical map of Orion members using proper motions;and searching for extragalactic sources and transients via deep extragalactic observations reaching a limiting magnitude of mAB = 29.7 mag (F146 filter). © 2024, CC BY.

关键词： Orbits

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