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A novel geomagnetic satellite constellation:Science and applications

Earth and Planetary Physics 2023年第1期7卷 4-21页

作者： keke zhang State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyCNSA Macao Center for Space Exploration and ScienceMacaoChina

The European Space Agency(ESA)’s Swarm constellation of a trio of geomagnetic survey satellites in nearly circular polar orbits at altitude about 500 km was launched on 22 November 2013 and has been mapping the Earth’s global magnetic field in unprecedented details,helping scientists better understand how the geomagnetic field is generated and maintained inside the Earth’s fluid core and how the Earth’s external magnetic environment is *** review discusses a new novel constellation of the geomagnetic survey satellites that consists of at least four satellites:two satellites are in lower-latitude and nearly circular orbits at altitude about 450 km;two further satellites are marked by nearly polar but strongly eccentric orbits with perigee about 200 km and apogee about 5000 *** new geomagnetic satellites are equipped with highly stable optical benches,high-precision fluxgate magnetometers and scalar magnetometers which are capable of mapping the Earth’s three-dimensional magnetic field in unprecedented accuracies and *** new constellation will help elucidate different contributions to the measured geomagnetic field:the core dynamo field,the lithospheric magnetic field,the magnetic fields produced by currents in the ionosphere and the magnetosphere as well as by the currents coupling the ionosphere and magnetosphere,and the magnetic fields induced from the electrically conducting mantle,lithosphere and *** comparison to the Swarm mission,it will provide higher-accuracy,higher-resolution and higher-dimension measurements of the geomagnetic field required for shedding new insights into the core dynamo processes and the Earth’s space magnetic systems along with a wide range of important applications.

关键词： core dynamo geomagnetic field mantle ocean ionosphere magnetosphere

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Lower-order zonal gravitational coefficients caused by zonal circulations inside gaseous planets: Convective flows and numerical comparison between modeling approaches

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Earth and Planetary Physics 2020年第2期4卷 89-94页

作者： DaLi Kong keke zhang Key Laboratory of Planetary Sciences Shanghai Astronomical ObservatoryChinese Academy of Sciences80 Nandan RoadShanghai 200030China State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyTaipaMacao S.A.RChina Centre for Geophysical and Astrophysical Fluid Dynamics College of EngineeringMathematics and Physical SciencesUniversity of ExeterNorth Park RoadExeterEX44QFUK

To infer the internal equilibrium structure of a gaseous planet, especially the equation of state(EOS) and size of its inner core,requires accurate determination of lower-order zonal gravitational coefficients. Modeling of the gravitational signature associated with deep zonal circulation depends critically upon reliable subtraction of the dynamical components from totally derived gravitational coefficients. In the era of the Juno mission and the Grand Finale phase of the Cassini mission, it is timely and necessary to revisit and examine the so-called ‘Thermal Wind Equation(TWE)’, which has been extensively utilized to diagnose the dynamical parts of the gravitational fields measured by the two spacecrafts. TWE treats as negligible a few terms in the full equation of balance. However, the self-gravitational anomaly of the distorted fluid, unlike oblateness effects of solid-body rotation, is not a priori minor and thus should not be neglected in the name of approximation. Another equation, the ‘Thermal Gravitational Wind Equation(TGWE)’, includes this important additional term;we compare it with the TWE and show that physically the TGWE models a fundamentally different balance from the TWE and delivers numerical results considerably different from models based on the TWE. We conclude that the TWE balance cannot be relied upon to produce realistic convection models. Only after the TGWE balance is obtained can the relative importance of terms be *** calculations we report here are based on two types of zonal circulations that are produced by realistically possible convections inside planets, instead of being constructed or assumed.

关键词： gaseous planets gravitation zonal circulation

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The effect of model errors in ensemble sequential assimilation of geomagnetic field

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Earth and Planetary Physics 2023年第1期7卷 22-31页

作者： JinFeng Li YuFeng Lin keke zhang Department of Earth and Space Sciences Southern University of Science and TechnologyShenzhen 518055China State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyTaipaMacaoChina

Earth’s magnetic field is generated in the fluid outer core through the dynamo *** the last decade,data assimilation has been used to retrieve the core dynamics and predict the evolution of the geomagnetic *** presence of model errors in the geomagnetic data assimilation is inevitable because current numerical geodynamo models are still far from realistic core *** this paper,we investigate the effect of model errors in geomagnetic data assimilation based on ensemble Kalman filter(EnKF).We construct two dynamo models with different control parameters but exhibiting similar force balance and magnetic morphology at the core *** then use one dynamo model to generate synthetic observations and the other as the forward model in *** test experiments show that the EnKF approach with the pre-setting model errors can nevertheless recover large-scale core surface flow and make a rough short-term(5-year)***,the data assimilation in the presence of model errors cannot keep improving the core state even though new observations are *** by the planned Macao Science Satellite-1,which is expected to provide improved internal geomagnetic field model,we also perform a test experiment using synthetic observations up to spherical harmonic degree l=*** results indicate that high-resolution observations are crucial in reconstructing small scale flow.

关键词： geomagnetic field geodynamo data assimilation

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A NEW ADAPTIVE SUBSPACE MINIMIZATION THREE-TERM CONJUGATE GRADIENT ALGORITHM FOR UNCONSTRAINED OPTIMIZATION

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Journal of Computational Mathematics 2021年第2期39卷 159-177页

作者： keke zhang Hongwei Liu Zexian Liu School of Mathematics and Statistics Xidian UniversityXi’an 710126China State Key Laboratory of Scientific and Engineering Computing Institute of Computational Mathematics and Scientific/Engineering computingAMSSChinese Academy of SciencesBeijing 100190China

A new adaptive subspace minimization three-term conjugate gradient algorithm with nonmonotone line search is introduced and analyzed in this *** search directions are computed by minimizing a quadratic approximation of the objective function on special subspaces,and we also proposed an adaptive rule for choosing different searching directions at each *** obtain a significant conclusion that the each choice of the search directions satisfies the sufficient descent *** the used nonmonotone line search,we prove that the new algorithm is globally convergent for general nonlinear functions under some mild *** experiments show that the proposed algorithm is promising for the given test problem set.

关键词： Conjugate gradient method Nonmonotone line search Subspace minimization Sufficient descent condition Global convergence

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Solvates and polymorphs of clindamycin phosphate： Structural, thermal stability and moisture stability studies

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Frontiers of Chemical Science and Engineering 2017年第2期11卷 220-230页

作者： Junbo Gong Dejiang zhang Yuanyuan Ran keke zhang Shichao Do School of Chemical Engineering and Technology State Key Laboratory of Chemical Engineering Tianjin University Tianjin 300072 China Collaborative Innovation Center of Chemical Seience and Engineering (Tianjin) Tianjin University Tianjin 300072 China

Clindamycin phosphate （CP）, an antibacterial agent, has been reported to form several solid-state forms. The crystal structures of two CP solvates, a dimethyl sulfoxide （DMSO） solvate and a methanol/water solvate （solvate V）, have been determined by single crystal X-ray diffraction. The properties and transformations of these forms were characterized by powder X-ray diffraction, Single-crystal X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, hot-stage microscopy, and dynamic vapor sorption. Very different hydrogen bonding networks exist among the host-host and host-solvent molecules in the two crystal structures, resulting in different moisture stabilities. The thermal stabilities of the two solvates upon heating and desolvation were also studied. When the temperature was above the boiling point of methanol, solvate V converted to a polymorphic phase after a one step desolvation process, whereas the desolvation temperature of the DMSO solvate was below the boiling point of DMSO. At the relative humidity above 43%, the DMSO solvate transformed to a hydrate at 25 ℃. In contrast, solvate V did not transform at any of the humidities studied.

关键词： clindamycin phosphate solvate crystal structure thermal stability moisture stability

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Precise orbit determination for LEO satellites:single-receiver ambiguity resolution using GREAT products

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Geo-Spatial Information Science 2022年第1期25卷 63-73页

作者： Xingxing Li Yujie Qin keke zhang Jiaqi Wu Wei zhang Qian zhang Hongmin zhang School of Geodesy and Geomatics Wuhan UniversityWuhanHubeiChina Department of Geodesy and Remote Sensing of the German Research Centre for Geosciences(GFZ) PotsdamGermany

In recent years,the large Low Earth Orbit(LEO)constellations have become a hot topic due to their great potential to improve the Global Navigation Satellite Systems(GNSS)positioning *** of the important focus is how to obtain the accurate and reliable orbits for these constellations with dozens of LEO *** GNSS-based Precise Orbit Determination(POD)will be exclusively performed to achieve this goal,where the Integer Ambiguity Resolution(IAR)plays a key role in acquiring high-quality *** this study,we present a comprehensive analysis of the benefit of the single-receiver IAR in LEO POD and discuss its implication for the future LEO *** perform ambiguity-fixed LEO POD for four typical missions,including Gravity Recovery and Climate Experiment(GRACE)Follow-On(GRACE-FO),Swarm,Jason-3 and Sentinel-3,using the Uncalibrated Phase Delay(UPD)products generated by our GREAT(GNSS+REsearch,Application and Teaching)*** results show that the ambiguity fixing processing can significantly improve the accuracy of LEO *** are negligible differences between our UPD-based ambiguity-fixed orbits and those based on the Observable Signal Bias(OSB)and Integer Recovery Clock(IRC)products,indicating the good-quality of UPD products we *** to the float solution,the fixed solution presents a better consistency with the external precise science orbits and the largest accuracy improvement of 5 mm is achieved for GRACE-FO ***,the benefit can be observed in laser ranging residuals as well,with a Standard Deviation(STD)reduction of 3–4 mm on average for the fixed *** from the absolute orbits,the relative accuracy of the space baseline is also improved by 20–30%in the fixed *** result demonstrates the superior performance of the ambiguity-fixed LEO POD,which appears as a particularly promising technique for POD of future LEO constellations.

关键词： Precise orbit determination single-receiver ambiguity resolution onboard GPS observation LEO

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长期施肥下土壤氮素指标与小麦/玉米产量关系研究

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核农学报 2025年第1期39卷 157-169页

作者：丁世杰黄绍敏张水清郭斗斗宋晓张珂珂岳克郭腾飞河南省农业科学院植物营养与资源环境研究所河南郑州450002 信阳市农业科学院河南信阳464000

为明确施肥对典型潮土区土壤氮素指标的影响以及氮素指标与作物产量的量化关系,本研究利用长期定位施肥试验系统评估施肥对土壤全氮、碱解氮、酸解有机氮组分、微生物量氮含量的影响,并进一步定量分析氮素指标与小麦、玉米产量间的关系... 详细信息

为明确施肥对典型潮土区土壤氮素指标的影响以及氮素指标与作物产量的量化关系,本研究利用长期定位施肥试验系统评估施肥对土壤全氮、碱解氮、酸解有机氮组分、微生物量氮含量的影响,并进一步定量分析氮素指标与小麦、玉米产量间的关系。结果表明,与单施化肥或不施肥相比,长期化肥与秸秆或有机肥配施在显著提高土壤全氮含量的同时,对碱解氮、酸解总氮、酸解铵态氮、氨基酸态氮与微生物量氮含量的提高也有明显的促进作用。除土壤全氮外的其他氮素指标含量在高量化肥-有机肥配施、化肥-秸秆还田和常量化肥-有机肥配施处理间无显著差异。土壤全氮、微生物量氮和碱解氮含量是对作物产量影响程度相对较大的氮素指标。土壤全氮含量每增加0.1 g·kg^(−1),小麦和玉米分别增产822.7和968.2 kg·hm^(-2)。土微生物量氮与碱解氮含量每增加1 mg·kg^(−1),小麦增产195.2与58.1 kg·hm^(-2);玉米增产189.9与79.1 kg·hm^(-2)。酸解总氮与氨基酸态氮含量对小麦产量也有显著影响,酸解总氮与氨基酸态氮含量每增加1 mg·kg^(−1),小麦分别增产15.8与30.0 kg·hm^(-2)。综上所述,化肥与秸秆或有机肥配施可提高潮土氮素库容与供氮能力。小麦、玉米产量随土壤全氮、微生物量氮与碱解氮含量的提高呈线性增长,小麦产量与酸解总氮和氨基酸态氮含量呈显著正相关。本研究为典型潮土区地力培育与粮食丰产提供了理论依据和技术支撑。

关键词：长期定位试验施肥土壤氮素指标作物产量

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不同施肥模式对大豆生长季土壤有效氮供给的影响

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核农学报 2025年第2期39卷 391-403页

作者：丁世杰黄绍敏张水清郭斗斗宋晓张珂珂岳克郭腾飞河南省农业科学院植物营养与资源环境研究所河南郑州450002 信阳市农业科学院河南信阳464000

为探究施肥模式对潮土区大豆生长季土壤有效氮供给的影响,本研究基于33年长期定位施肥试验,选取4种处理:不施肥(CK)、施氮磷钾化肥(NPK)、氮磷钾化肥+秸秆还田(SNPK)与氮磷钾化肥+有机肥(MNPK),测定分析大豆生长季内土壤铵态氮(NH_(4)^(... 详细信息

为探究施肥模式对潮土区大豆生长季土壤有效氮供给的影响,本研究基于33年长期定位施肥试验,选取4种处理:不施肥(CK)、施氮磷钾化肥(NPK)、氮磷钾化肥+秸秆还田(SNPK)与氮磷钾化肥+有机肥(MNPK),测定分析大豆生长季内土壤铵态氮(NH_(4)^(+)-N)、硝态氮(NO_(3)^(-)-N)、微生物量氮、可溶性有机氮含量的变化动态,以及参与土壤氮素转化的有机氮矿化酶活性、氨化作用强度与硝化潜势。结果表明,化肥与秸秆或有机肥配施可提高土壤全氮、有机碳、微生物量碳和可溶性有机碳含量,这对土壤脲酶、酰胺酶、蛋白酶和N-乙酰-β-D-葡萄糖苷酶活性及氨化作用强度和硝化潜势的提升有不同程度的促进作用。土壤NH_(4)^(+)-N含量与脲酶和蛋白酶活性呈极显著正相关,与酰胺酶活性呈显著正相关;NO_(3)^(-)-N含量与氨化作用强度、硝化潜势呈极显著正相关。SNPK、MNPK处理下的土壤微生物量氮和可溶性有机氮含量均高于NPK、CK处理。潮土可溶性有机氮含量与大豆地上部氮素吸收呈极显著正相关,并最终影响大豆生长;成熟期SNPK、MNPK处理下的大豆地上部生物量均高于CK、NPK处理。综上所述,化肥与秸秆或有机肥配施可通过提高全氮、有机碳和活性有机碳含量正向调控土壤氮素转化微生物作用强度与酶活性,提高土壤有效氮供给能力,促进大豆生长。本试验结果可为潮土区合理施肥提供理论依据。

关键词：施肥模式有效氮有机氮矿化酶氨化作用强度硝化潜势

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Determination of global geodetic parameters using satellite laser ranging to Galileo,GLONASS,and BeiDou satellites

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Satellite Navigation 2024年第1期5卷 240-257页

作者： Xingxing Li Jiaqing Lou Yongqiang Yuan Jiaqi Wu keke zhang School of Geodesy and Geomatics Wuhan University129 Luoyu RoadWuhan430079HubeiChina

The new Global Navigation Satellite System(GNSS)satellites,including GLONASS,Galileo,and BeiDou system,are equipped with Laser Retroreflector Arrays(LRA)to support Satellite Laser Ranging(SLR)tracking,which contributes to the estimation of global geodetic *** this study,we estimate the global geodetic parameters using the SLR observations to GNSS satellites and also investigate the effects of different data processing strategies on the estimated Earth Rotation Parameters(ERP),geocenter motion,and terrestrial *** results indicate that setting range bias parameters for each satellite-station pair can effectively account for the satellite-specific biases induced by LRAs,leading to smaller Root Mean Square Errors(RMSE)of the post-fit SLR ***,estimating the range biases for each satellite-station pair improves the accuracy of the estimated station coordinates and *** also examine the impact of different arc lengths on the estimates of ERP,geocenter motion,and terrestrial *** results show that extending arc length can significantly reduce the formal error of *** 7-day strategy produces the smallest RMSEs of 473 microarcseconds and 495 microarcseconds for the estimated X-and Y-component of pole coordinates,and 52 microseconds for length-of-day,***,the estimated geocenter motion is less affected by the arc length,even the shortest 1-day arc strategy can capture the seasonal variations of geocenter motion in Z *** scale estimation,extending the arc length notably improves the accuracy of the estimated station coordinates and scale,but this advantage becomes less noticeable in longer *** 7-day solution also obtains the closet scale results compared to ITRF2014,with the RMSE of 2.10×10^(–9).

关键词： Satellite laser ranging GNSS Geodetic parameters Earth rotation parameters Geocenter motion Terrestrial scale

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Superplastic Solid-Phase Welding of 40 Cr-T10A Steel

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Journal of Materials Science & Technology 2001年第1期17卷 189-190页

作者： keke zhang Yunlin YANG Changsheng WANG Hongke LI Jin XUE Dept.of Material Engineering Luoyang institute of TechnologyLuoyang 471039China Dept.of Mechanical Engineering Xi’an Jiaotong UniversityXi’an 710049China

The microstructure of 40Cr and T10A steel sample and its surface to be welded is ultra-fined through salt-bath cyclic quenching and high frequency hardening, then the surface is cleaned. Under non-vacuum and no shielded gas, the welding parameter of isothermal superplastic solidphase welding and the effect of surface microstructure prior to pressure welding on the quality of joint are studied. At the temperature of 730~750℃ and at initial strain rate of (2~4) × 10-4 s-l, the strength of the joint is up to or close to that of 40Cr base metal in 3-5 min pressure welding

关键词： pressure welding welding parameter high frequency strength of strain rate welding on

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