检索结果-南通市图书馆

Degree One Loading by Pressure Variations at the CMB

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2013年第5期24卷 736-749页

作者： Ming Fang Bradford H Hager weijia kuang Department of Earth Atmospheric & Planetary Sciences Massachusetts Institute of Technology Planetary Geodynamics Laboratory NASA Goddard Space Flight Center

Hemispherical asymmetry in core dynamics induces degree-1 pressure variations at the core mantle boundary （CMB）, which in turn deforms the overlaying elastic mantle, at the same time keeps center of mass of the whole Earth stationary in space. We develop a systematic procedure to deal with the degree-1 CMB pressure loading. We find by direct calculation a surprisingly negative load Love number h1=-1.425 for vertical displacement. Further analysis indicates that the negative hi corre- sponds to thickening above the positive load that defies intuition that pressure inflation pushes over- laying material up and thins the enveloping shell. We also redefine the pressure load Love numbers in general to enable comparison between the surface mass load and the CMB pressure load for the whole spectrum of harmonic degrees. We find that the gravitational perturbations from the two kinds of loads at degrees n〉l are very similar in amplitude but opposite in sign. In particular, if the CMB pressure variation at degree 2 is at the level of -1 hpa/yr （1 cm water height per year）, it would perturb the variation of Earth＇s oblateness, known as the J2, at the observed level.

关键词： Degree One Loading by Pressure Variations at the CMB MRSP

Numerical simulations on origin of Galilean moons' magnetic anomalies

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2011年第12期54卷 1754-1760页

作者： JIAO LiGuo kuang weijia MA ShiZhuang Laboratory of Computational Geodynamics College of Earth Sciences Graduate University of Chinese Academy of Sciences Beijing 100049 China NASA Goddard Space Flight Center Greenbelt MD 20771 USA

Galileo mission detected the magnetic anomalies originated from Galilean *** anomalies are likely generated in the moons' interiors,under the influence of a strong ambient Jovian *** various possible generation mechanisms of the anomalies,we focus on magneto-convection and dynamos in the interiors via numerical *** mimic the electromagnetic environment of the moons,we introduce in our numerical model an external uniform magnetic field B0 with a fixed orientation but varying field *** results show that a finite B0 can substantially alter the dynamo processes inside the *** the ambient field strength B0 increases to approximately 40% of the field generated by the pure dynamo action,the convective state in the core changes significantly:the convective flow decreases by 80% in magnitude,but the differential rotation becomes stronger in much of the fluid layer,leading to a stronger field generated in the *** field morphologies inside the core tend to align with the ambient field,while the flow patterns show the symmetry-breaking effect under the influence of ***,the generated field tends to be temporally more stable.

关键词： Galilean moons magnetic fields magneto-convection dynamo

Reassessment of electromagnetic core-mantle coupling and its implications to the Earth’s decadal polar motion

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2019年第5期10卷 356-362页

作者： weijia kuang Benjamin F.Chao Jianli Chen Geodesy and Geophysics Laboratory NASA Goddard Space Flight CenterGreenbeltMD20771USA Institute of Earth Sciences Academia SinicaTaipeiTaiwanROC Center for Space Research University of TexasAustinUSA

The observed Earth’s polar motion on decadal time scales has long been conjectured to be excited by the exchange of equatorial angular momentum between the solid mantle and the fluid outer core,via the mechanism of electromagnetic(EM)core-mantle ***,past estimations of the EM coupling torque from surface geomagnetic observations is too weak to account for the observed decadal polar *** recent estimations from numerical geodynamo simulations have shown the *** this paper,we re-examine in detail the EM coupling mechanism and the properties of the magnetic field in the electrically conducting lower mantle(characterized by a thin D '-layer at the base of the mantle).Our simulations find that the toroidal field in the D'-layer from the induction and convection of the toroidal field in the outer core could be potentially much stronger than that from the advection of the poloidal field in the outer *** former,however,cannot be inferred from geomagnetic observations at the Earth’s surface,and is missing in previous EM torque estimated from geomagnetic *** deduction suggests further that this field could make the actual EM coupling torque sufficiently strong,at approximately 5×1019 Nm,to excite,and hence explain,the decadal polar motion to magnitude of approximately 10 mas.

关键词： Polar motion Electromagnetic core-mantle coupling Geomagnetic field Geodynamo

MoSST−DAS:The First Generation Geomagnetic DataAssimilation Framework

在线全文

学校读者我要写书评

暂无评论

Communications in Computational Physics 2008年第1期3卷 85-108页

作者： weijia kuang Andrew Tangborn Weiyuan Jiang Don Liu Zhibin Sun Jeremy Bloxham Zigang Wei Planetary Geodynamics Laboratory NASA Goddard Space Flight CenterGreenbeltMDUSA Joint Center for Earth Systems Technology University ofMaryland-Baltimore CountyBaltimoreMDUSA Department of Mathematics and Statistics University of Maryland-Baltimore CountyBaltimoreMDUSA Department of Earth and Planetary Science Harvard UniversityCambridgeMAUSA.

Constraining numerical geodynamo models with surface geomagnetic observationsis very important in many respects:it directly helps to improve numericalgeodynamo models,and expands their geophysical applications beyond geomagnetism.A successful approach to integrate observations with numerical models isdata assimilation,in which Bayesian algorithms are used to combine observationaldata with model outputs,so that the modified solutions can then be used as initialconditions for forecasts of future physical *** this paper,we present the firstgeomagnetic data assimilation framework,which comprises the MoSST core dynamicsmodel,a newly developed data assimilation component(based on ensemble covarianceestimation and optimal interpolation),and geomagnetic field models basedon paleo,archeo,historical and modern geomagnetic *** overall architecture,mathematical formulation,numerical algorithms and computational techniques of theframework are *** results with 100-year geomagnetic data assimilationand with synthetic data assimilation are presented to demonstrate the operation of thesystem.

关键词： Geomagnetism geodynamo data assimilation ensemble forecasting.

Assessment of the effect of three-dimensional mantle density heterogeneity on Earth rotation in tidal frequencies

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2016年第6期7卷 396-405页

作者： Lanbo Liu Benjamin F.Chao Wenke Sun weijia kuang Center for Integrative Geosciences University of Connecticut Institute of Earth Sciences Academia Sinica School of Earth Sciences University of Chinese Academy of Sciences Goddard Space Flight Center NASAGreenbelt

In this paper, we report the assessment of the effect of the three-dimensional （3D） density heterogeneity in the mantle on Earth orientation parameters （EOP）（i.e., the polar motion, or PM, and the length of day, or LOD） in the tidal frequencies. The 3D mantle density model is estimated based upon a global S-wave velocity tomography model （S16U6LS） and the mineralogical knowledge derived from laboratory experiment. The lateral density variation is referenced against the preliminary reference earth model （PREM）. Using this approach the effects of the heterogeneous manHe density variation in all three tidal frequencies （zonal long periods, tesseral diurnal, and sectorial semidiurnal） are estimated in both PM and LOD. When compared with mass or density perturbations originated on the Earth＇s surface such as the oceanic and barometric changes, the het- erogeneous mantle contributes less than 10% of the total variation in PM and LOD in tidal frequencies. However, this is the gap that has not been explained to close the gap of the observation and modeling in PM and LOD. By computing the PM and LOD caused by 3D heterogeneity of the mantle during the period of continuous space geodetic measure- ment campaigns （e.g., CONT94） and the contribution from ocean tides as predicted by tide models derived from satellite altimetry observations （e.g., TOPEX/Poseidon} in the same period, we got the lump-sum values of PM and LOD. The computed total effects and the observed PM and LOD are generally agree with each other. In another word, the difference of the observed PM and LOD and the model only considering ocean tides, at all tidal frequencies （long periods, diurnals, and semidiurnals） contains the contributions of the lateral density heterogeneity of the mantle. Study of the effect of mantle densityheterogeneity effect on torque-free Earth rotation may provide useful constraints to construct the reference earth model （REM）, which is the next major objective in global geophysics resea

关键词： Polar motionLength of dayTidal frequencyMantle densityLateral heterogeneitySeismic tomography

在线全文

学校读者我要写书评

暂无评论

数值模拟火星古发电机湮灭前磁场特征

中国科学：地球科学 2013年第8期43卷 155-162页

作者：王天媛 ZiGang WEI WeiYuan JIANG weijia kuang 马石庄云南大学资源环境与地球科学学院昆明650091 Joint Center for Earth Systems Technology University of MarylandBaltimore CountyBaltimoreMarylandUSA SGT at Planetary Geodynamics Laboratory NASA Goddard Space Flight CenterGreenbeltMDUSA Planetary Geodynamics Laboratory NASA Goddard Space Flight CenterGreenbeltMarylandUSA 中国科学院研究生院计算动力学实验室北京100049

火星地壳磁场观测结果表明,该行星目前已经丧失了由其内部发电机作用产生的行星尺度的本征磁场,只在其表面残留不对称分布的剩余磁场.通过MoSST行星液核发电机动力学模式的前期模拟工作发现,在火星古发电机"死亡"之前,很可能处于亚临界... 详细信息

火星地壳磁场观测结果表明,该行星目前已经丧失了由其内部发电机作用产生的行星尺度的本征磁场,只在其表面残留不对称分布的剩余磁场.通过MoSST行星液核发电机动力学模式的前期模拟工作发现,在火星古发电机"死亡"之前,很可能处于亚临界发电机状态(此时维持发电机所需能量小于激发发电机所需能量).为了解火星发电机湮灭前的磁场特征,本文选取该亚临界发电机区间内,Rayleigh数(表征驱动发电机能量的无量纲参数)=2480时的火星表面磁场数据,采用自然经验正交函数对其分析,结果表明:在火星古发电机湮灭过程中的亚临界发电机状态下,火星表面磁场形态是非轴向偶极子占优的;并频繁出现磁极倒转和漂移现象,该过程中其磁偶极距随时间呈非单调形态的衰减.

关键词：火星剩余磁场亚临界发电机偶极子

Towards advanced zinc anodes by interfacial modification strategies for efficient aqueous zinc metal batteries

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2024年第6期93卷 79-110,I0003页

作者： Changchun Fan weijia Meng Jiaye Ye Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology Ministry of EducationSchool of ChemistryBeihang UniversityBeijing 100191China Shaanxi Key Laboratory of New Transportation Energy and Automotive Energy Saving School of Energy and Electrical EngineeringChang’an UniversityXi’an 710061ShaanxiChina School of Chemistry and Physics Faculty of ScienceQueensland University of TechnologyBrisbaneQLD 4001Australia Centre for Materials Science Queensland University of TechnologyBrisbaneQLD 4001Australia

Developing sustainable and clean energy sources(e.g.,solar,wind,and tide energy)is essential to achieve the goal of carbon *** to the discontinuous and inco nsistent nature of common clean energy sources,high-performance energy storage technologies are a critical part of achieving this *** zinc metal batteries(AZMBs)with inherent safety,low cost,and competitive performance are regarded as one of the promising candidates for grid-scale energy ***,zinc metal anodes(ZMAs)with irreversible problems of dendrite growth,hydrogen evolution reaction,self-corrosio n,and other side reactions have seriously hindered the development and commercialization of *** increasing number of researchers are focusing on the stability of ZMAs,so assessing the effectiveness of existing research strategies is critical to the development of *** review aims to provide a comprehensive overview of the fundamentals and challenges of *** rch strategies for interfacial modification of ZMAs are systematically *** features of artificial interfacial coating and in-situ interfacial coating of ZMAs are compared and discussed in detail,as well as the effect of modified interfacial ZMA on the full-battery ***,perspectives are provided on the problems and challenges of *** review is expected to offer a constructive reference for the further development and commercialization of AZMBs.

关键词： Aqueous zinc metal batteries Zinc metal anode Interfacial modification Artificial interfacial coating In-situ interfacial coating

Multi-instance partial-label learning: towards exploiting dual inexact supervision

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第3期67卷 48-61页

作者： Wei TANG weijia ZHANG Min-Ling ZHANG School of Computer Science and Engineering Southeast University Key Laboratory of Computer Network and Information Integration (Southeast University) Ministry of Education School of Information and Physical Sciences The University of Newcastle

Weakly supervised machine learning algorithms are able to learn from ambiguous samples or labels, e.g., multi-instance learning or partial-label learning. However, in some real-world tasks, each training sample is associated with not only multiple instances but also a candidate label set that contains one groundtruth label and some false positive labels. Specifically, at least one instance pertains to the ground-truth label while no instance belongs to the false positive labels. In this paper, we formalize such problems as multi-instance partial-label learning(MIPL). Existing multi-instance learning algorithms and partial-label learning algorithms are suboptimal for solving MIPL problems since the former fails to disambiguate a candidate label set, and the latter cannot handle a multi-instance bag. To address these issues, a tailored algorithm named MIPLGP, i.e., multi-instance partial-label learning with Gaussian processes, is *** first assigns each instance with a candidate label set in an augmented label space, then transforms the candidate label set into a logarithmic space to yield the disambiguated and continuous labels via an exclusive disambiguation strategy, and last induces a model based on the Gaussian processes. Experimental results on various datasets validate that MIPLGP is superior to well-established multi-instance learning and partial-label learning algorithms for solving MIPL problems.

关键词： machine learning multi-instance partial-label learning multi-instance learning partial-label learning Gaussian processes

Power and rate adaption in wireless communication systems with energy harvesting-based on soft decision decoding

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2024年第4期31卷 70-82页

作者： Lei weijia Yu Shunhong Liu Meiding School of Communications and Information Engineering Chongqing University of Posts and TelecommunicationsChongqing 400065China Chongqing Key Lab of Mobile Communication Technology Chongqing 400065China

In this paper,the online power control and rate adaptation for a wireless communication system with energy harvesting(EH)are investigated,in which soft decision decoding is adopted by the *** efficiently utilize the harvested energy and maximize the actual achievable transmission rate under the constraints of the available channel codes and modulation schemes,the transmit power,code rate and modulation order are jointly *** Lyapunov framework is used to transform the long-term optimization problem into a per time slot optimization *** there is no theoretical formula for the error rate of soft decision decoding,the optimization problem cannot be solved analytically.A table to find the optimal modulation order and code rate under the different values of signal-to-noise ratio(SNR)is built first,and then a numerical algorithm to find the solution to the optimization problem is *** feasibility and performance of the proposed algorithm are demonstrated by *** simulation results show that compared with the algorithms to maximize the theoretical channel capacity,the proposed algorithm can achieve a higher actual transmission rate.

关键词： energy harvesting power control rate adaption soft decision decoding Lyapunov framework