检索结果-南通市图书馆

Determining the moment of inertia of triaxial Mars with updated global gravity models

在线全文

学校读者我要写书评

暂无评论

Earth and Planetary Physics 2023年第6期7卷 615-619页

作者： changyi xu Yan Jiang Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China

The principal moments of inertia(PMIs)with the principal axes are usually taken as the dynamic figure parameters of Mars;they can be deduced from satellite-observed degree-two gravitational potentials in recent global gravity models and from the dynamic ellipticities resulting from precession *** PMIs are natural and significant for the geodetic,geophysical,and geodynamic problems of Mars,which are functions of internal density *** this study,a closed and concise formula for determining the PMIs of the entire planet and its core was developed based on the second invariants of gravity and a multipole *** deduced the polar oblateness J^(2)and the equatorial ellipticity J_(22)of Mars to be 1.9566×10^(−3)and 6.3106×10^(−5),*** preferred principal moments of inertia of Mars are A=2.66589×1036 kg·m^(2),B=2.66775×10^(36)kg·m^(2),and C=2.68125×10^(36)kg·m^(2).These values indicate that Mar is slightly *** equatorial principal moment of inertia of the Martian core is 1.46008×10^(35)kg·m^(2),accounting for~5.47%of the planet’s PMI;this result is critical for investigating the density and size of the core of Mars,and the planet’s free core nutation.

关键词： Mars principal moment of inertia dynamic ellipticity Chandler wobble core density and size

An overview and perspective of identifying lunar craters

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第5期67卷 1395-1416页

作者： Yan JIANG changyi xu Ling CHEN State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100029China Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100049China

The spatiotemporal evolution of lunar impact craters is crucial for investigating lunar interior structure,internal and external dynamic processes,and interplanetary impact *** in lunar crater identification are reviewed based on topography and gravity data,and the features and mechanisms of topographic or buried craters are analyzed regarding morphology,gravity anomalies,gravity gradients,and the underlying crust-mantle interface *** on the compiled crater catalog,the early lunar impact flux and thermal evolution are further discussed according to the basin ages and their interior *** some ancient impact basins,the crater size-frequency distribution measurements revealed age discrepancies from previous studies,suggesting that the lunar late heavy bombardment event started at~3.95 *** degraded bulge structures of the crust-mantle interface beneath mare basins reveal that these basins formed on the lunar crust surface under high-temperature conditions and underwent prolonged relaxation compared to highland ***,we reveal that the up-to-date identification of lunar buried craters remains inaccurate and incomplete,preventing us from accurately reconstructing lunar and interplanetary impact ***,we propose that a gravity model constructed using localized orthogonal basis functions can be useful for identifying lunar craters.

关键词： Moon Gravity field Craters Impact flux Early evolution

A general Boolean semantic modelling approach for complex and intelligent industrial systems in the framework of DES

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2024年第5期35卷 1219-1230页

作者： xu changyi WANG Yun DUAN Yiman ZHANG Chao Key Laboratory of Intelligent Control and Optimization for Industrial Equipment of Ministry of Education School of Control Science and EngineeringDalian University of TechnologyDalian 116024China State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310027China

Discrete event system(DES)models promote system engineering,including system design,verification,and *** advancement in manufacturing technology has endowed us to fabricate complex industrial ***,the adoption of advanced modeling methodologies adept at handling complexity and scalability is ***,industrial systems are no longer quiescent,thus the intelligent operations of the systems should be dynamically specified in the *** this paper,the composition of the subsystem behaviors is studied to generate the complexity and scalability of the global system model,and a Boolean semantic specifying algorithm is proposed for generating dynamic intelligent operations in the *** traditional modeling approaches,the change or addition of specifications always necessitates the complete resubmission of the system model,a resource-consuming and error-prone *** with traditional approaches,our approach has three remarkable advantages:(i)an established Boolean semantic can be fitful for all kinds of systems;(ii)there is no need to resubmit the system model whenever there is a change or addition of the operations;(iii)multiple specifying tasks can be easily achieved by continuously adding a new ***,this general modeling approach has wide potential for future complex and intelligent industrial systems.

关键词： industrial complex system operation specifying Boolean semantic discrete event system(DES)theory intelligent operation

Implicit expansion rate of the Earth in global plate motions

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2019年第3期10卷 228-234页

作者： changyi xu Xiao Yu Dongping Wei Institute of Earthquake Forecasting China Earthquake AdministrationBeijingChina Institute of Earth Sciences Academia SinicaTaipeiTaiwan Key Laboratory of Computational Geodynamics University of Chinese Academy of SciencesBeijingChina

Based on eight published plate motion models, we separately estimated the net area changes of tectonic plates and the area change of the solid Earth surface over geological time using the Euler vectors of plates with determined boundaries. Then, under the context of a currently expanding Earth, we inferred the change rate of the Earth’s mean radius from the estimated net area changes. The results show that the total increases and decreases in the areas of different plates cannot be compensated. Specifically, the area of the Northern Hemisphere decreases while that of the Southern Hemisphere increases, but the net area of the solid Earth surface slightly increases in th computing period(0.01 Ma). For the latest NNRMORVEL56 plate motion model, the area of the Southern Hemisphere increases by 7802 km2 while the area of the Northern Hemisphere decreases by 7711 km^2. This indicates a net area increase of 91 km2 in the solid Earth surface corresponding to an expansion rate of 0.06 mm/a for the Earths mean *** result coincides with the slow rate of expansion derived from geodetic measurements and geophysical modeling.

关键词： Plate motion model Area change of plate boundary Earth expansion

Micro-Newton scale variable thrust control technique and its noise problem for drag-free satellite platforms:a review

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第10期24卷 841-858页

作者： changyi xu Wenya LI xuhui LIU Yong LI Chao ZHANG School of Control Science and Engineering Dalian University of TechnologyDalian 116024China Beijing Institute of Control Engineering Beijing 100190China State Key Laboratory of Fluid Power&Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310058China

High-precision detection in fundamental space physics,such as space gravitational wave detection,high-precision earth gravity field measurement,and reference frame drag effect measurement,is the key to achieving important breakthroughs in the scientific study of fundamental space *** high-precision measurements requires high-performance satellite platforms to achieve“drag-free control”in a near“pure gravity”flight *** critical technology for drag-free control is variable thrust control at the micro-Newton *** noise is the most important technical indicator for achieving drag-free ***,there is no literature about the current status and future prospects of variable thrust control based on thrust ***,the micro-Newton variable thrust control technology and the thrust noise of the drag-free satellite platform are reviewed in this ***,the research status of micro-Newton scale variable thrust control technology and its applications to drag-free satellite platforms are ***,the noise problem is analyzed in detail and its solution is theoretically investigated in three aspects:“cross-basin flow problem,”“control problem,”and“system instability and multiple-coupled problem.”Finally,a systematic overview is presented and the corresponding suggested directions of research are *** work provides detailed understanding and support for realizing low-noise variable thrust control in the next generation of drag-free satellites.

关键词： Space physics detection Satellite platforms Drag-free control Micro-Newton scale variable thrust Thrust noise

Co-seismic Earth's rotation caused by the 2012 Sumatra earthquake

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2012年第4期3卷 28-31页

作者： xu changyi Sun Wenke Key Laboratory of Computational Geodynamics University of Chinese Academy of Sciences

Earthquakes heavily deform the crust in the vicinity of the fault, which leads to mass redistribution in the earth interior. Then it will produce the change of the Earth＇s rotation （ polar motion and length of day） due to the change of Earth inertial moment. This paper adopts the elastic dislocation to compute the co-seismic polar motion and variation in length of day （LOD） caused by the 2011 Sumatra earthquake. The Earth＇s rota- tional axis shifted about 1 mas and this earthquake decreased the length of day of 1 p,s, indicating the tendency of earthquakes make the Earth rounder and to pull the mass toward the centre of the Earth. The result of varia- tion in length of day is one order of magnitude smaller than the observed results that are available. We also compared the results of three fault models and find the co-seismic change is depended on the fault model.

关键词： earthquake Earth rotation polar motion variation in LOD

Density anomaly and comparison with GRACE data after the 2011 Tohoku-Oki Earthquake

在线全文

学校读者我要写书评

暂无评论

Density anomaly and comparison with GRACE data after the 201...

Difference of reference frame between the spherical dislocation theory and space geodetic observations

2014年中国地球科学联合学术年会——专题3：地球重力场及其地学应用

作者： changyi xu Wenke Sun Key Laboratory of Computational Geodynamics Chinese Academy of Sciences

Earthquakes perturb the Earth’s gravitational field by vertical displacement of Earth’s layered density structure and by changing the densities of the crust and *** gravitational perturbations are visible from the satellite gravity data,such as the GRACE mission *** et al.(2006)discussed the gravity change due to the density change and compared with the GRACE gravity data based on a simple half-space

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Difference of reference frame between the spherical dislocat...

中国地球物理学会第二十九届年会

作者： changyi xu Benjamin F. Chao Wenke Sun Key Laboratory of Computational Geodynamics Chinese Academy of Sciences Institute of Earth Sciences Academia Sinica

＜正＞Earthquakes not only induce global deformations, but also change the internal gravity field. Space geodetic observations, such as GPS, SLR and GRACE, can detect coseismic deformations. Normal mode method and dis...

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

环渤海湾连续两条阵风锋的关联与成因分析

气象 2022年第6期48卷 729-745页

作者：许长义卜清军黄安宁天津市滨海新区气象局天津300457 南京大学大气科学学院南京210023

为加深对雷暴阵风锋多样性的认识,利用多普勒天气雷达、风廓线雷达、边界层气象铁塔、地面加密自动观测资料结合VDRAS系统分析场资料,对比分析了2016年6月10日渤海湾连续出现的两条阵风锋的差异及相互联系。结果表明:两条阵风锋的结构... 详细信息

为加深对雷暴阵风锋多样性的认识,利用多普勒天气雷达、风廓线雷达、边界层气象铁塔、地面加密自动观测资料结合VDRAS系统分析场资料,对比分析了2016年6月10日渤海湾连续出现的两条阵风锋的差异及相互联系。结果表明:两条阵风锋的结构存在明显差异,阵风锋1前沿强切变位置形成近地层γ中尺度涡旋,边界层和对流层低层的西南暖湿气流沿阵风锋1输送到雷暴母体;阵风锋2呈现两支强入流的典型动力结构,一支位于其后侧边界层内呈强东北入流,另一支位于前侧对流层低层呈强西南入流,两支入流分别构成阵风锋前侧反环流和后侧正环流圈。冷池与低层垂直风切变的配置对阵风锋的发展维持起到重要作用。阵风锋1后部冷池强度相对较弱,低层垂直风切变强于冷池传播速度,雷暴单体具有向冷区倾斜的层云结构,不利于系统的发展加强;阵风锋2后部冷池发展强盛,冷池传播速度强于低层垂直风切变,雷暴单体内的上升气流更加竖直,从而促进雷暴单体加强发展。阵风锋前沿γ中尺度涡旋和后部冷池存在相互影响及内在关联,近地层γ中尺度涡旋的碰撞,增强了两条阵风锋之间的辐合抬升,同时配合冷池的合并增强,加剧了低层不稳定,有利于维持上下层旋转,形成较强的水平涡度,从而导致对流风暴快速加强发展并演变为弓形回波。

关键词：阵风锋冷池低层垂直风切变 γ中尺度涡旋