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Spacecraft potential variations of the Swarm satellites at low Earth orbital altitudes

Earth and Planetary Physics 2023年第4期7卷 421-435页

作者： HaiCheng Jiang Chao Xiong fan Yin YuHao Zheng ZiYuan Zhu Rui Yan Yi Wen liu Department of Space Physics Electronic Information SchoolWuhan UniversityWuhan 430072China Hubei Luojia Laboratory Wuhan 430079China National Institute of Natural Hazards the Ministry of Emergency Management of ChinaBeijing 100085China School of Physics and Electronic Information Shangrao Normal UniversityShangrao 334001China

In this study, we provide the first detailed analysis of variations in the spacecraft potential (Vs) of the three Swarm satellites, which are flying at about 400-500 km. Unlike previous studies that have investigated extreme charging events, usually with spacecraft potentials as negative as −100 V, this study is focused on variations of Swarm Vs readings, which fall within a few negative volts. The Swarm observations show that spacecraft at low Earth orbital (LEO) altitudes are charged only slightly negatively, varying between −7 V and 0 V, with the majority of recorded potentials at these altitudes clustering close to −2 V. However, a second peak of Vs data is found at −5.5 V, though the event numbers for these more-negative observations are less, by an order of magnitude, than for incidents near the −2 V peak. These two distinct Vs peaks suggest two different causes. We have thus divided the Swarm spacecraft Vs data into two categories: less-negatively charged (−5 < Vs < 0 V) and more-negatively-charged (−6.5 < Vs < −5 V). These two Vs categories exhibit different spatial and temporal distributions. The Vs observations in the first category remain relatively closer to 0 V above the magnetic equator, but become much more negative at low and middle latitudes on the day side;at high latitudes, these first-category Vs readings are relatively more-negative during local summer. Second-category Vs events cluster into two bands at the middle latitudes (between ±20°-50° magnetic latitude), but with slightly more negative readings at the South Atlantic Anomaly (SAA) region;at high latitudes, these rarer but more-negative second-category Vs events exhibit relatively more-negative values during local winter, which is opposite to the seasonal pattern seen in the first category. By comparing Vs data to the distributions of background plasma density at Swarm altitudes, we find for the first category that more-negative Vs readings are recorded at regions with higher background pl

关键词： spacecraft potentia low Earth orbit satellites Swarm mission particle precipitation

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P wave velocity structure of upper and middle crust beneath the Three Gorges reservoir dam and adjacent regions

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Science China Earth Sciences 2009年第4期52卷 567-578页

作者： LI Qiang zhao Xu CAI JinAn liu RuiFeng LONG GuiHua AN YanRu National Earthquake Infrastructure Service China Earthquake AdministrationBeijing 100037China China Earthquake Network Center China Earthquake AdministrationBeijing 100045China Institute of Earthquake Science China Earthquake AdministrationBeijing 100036China Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China

The three-dimensional P wave velocity structures of upper and middle crust beneath the Three Gorges reservoir dam and adjacent regions were reconstructed by means of the seismic tomography, using the absolute P-arrivals from the events observed by the Three Gorges seismic network. Our preliminary study of the deep structure shows: (1) the lithology of the Huangling anticline, integral and highly so-lidified, exhibits a uniformity. Down to a depth of 20 km, the Huangling anticline still shows high- velocity anomalies. Note that the characteristics of the velocity images with the different depths are not the same; (2) the depth of the sedimentary rocks beneath the entire Zigui basin is not constant, which is less than 6 km; (3) the top boundary of the crystalline basement varies from 0 to 7 km, whereas the bottom one between 14 and 16 km; (4) the partially molten substances of the upper mantle are located in the Badong-Zigui and its adjacent regions as well as nearby Peishi area. The development and evo-lution of the current tectonics are associated with the cooling and solidifying process of the molten substances within the upper mantle; (5) the different velocity structures of the deep crust in both east and west side of the Jiuwanxi fault are to be investigated in order to understand the origin of gravita-tional gradient zone in the Three Gorge areas; and (6) the velocities within the upper crust would be affected by reservoir water permeability.

关键词： Three Gorges reservoir upper and middle crust three-dimensional velocity structure

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Central projections and connections of lumbar primary afferent fibers in adult rats:effectively revealed using Texas red-dextran amine tracing

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Neural Regeneration Research 2017年第10期12卷 1695-1702页

作者： Shi-de Lin Tao Tang Ting-bao zhao Shao-jun liu State Key Laboratory of Proteomics Department of NeurobiologyBeijing Institute of Basic Medical Sciences Department of Spinal Cord Injury the General Hospital of Jinan Military Command

Signals from lumbar primary afferent fibers are important for modulating locomotion of the ***,silver impregnation techniques,autoradiography,wheat germ agglutinin-horseradish peroxidase and cholera toxin B subunit-horseradish peroxidase cannot image the central projections and connections of the dorsal root in ***,we injected 3-k Da Texas red-dextran amine into the proximal trunks of L4 dorsal roots in adult *** microscopy results revealed that numerous labeled arborizations and varicosities extended to the dorsal horn from T12–S4,to Clarke＇s column from T10–L2,and to the ventral horn from L1–*** labeled varicosities at the L4 cord level were very dense,particularly in laminae I–Ⅲ,and the density decreased gradually in more rostral and caudal *** addition,they were predominately distributed in laminae I–IV,moderately in laminae V–VⅡ and sparsely in laminae VⅢ–***,direct contacts of lumbar afferent fibers with propriospinal neurons were widespread in gray *** conclusion,the projection and connection patterns of L4 afferents were illustrated in detail by Texas red-dextran amine-dorsal root tracing.

关键词： nerve regeneration spinal cord injury dorsal root central projection connection Texas red-dextran amine neural regeneration

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Line profile analysis of an astronomical spectrograph with a laser frequency comb

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Research in Astronomy and Astrophysics 2014年第8期14卷 1037-1045页

作者： Fei zhao Gang zhao Gaspare Lo Curto Hui-Juan Wang Yu-Juan liu Liang Wang Wei Wang Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of Sciences University of Chinese Academy of Sciences Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and PhysicsShandong University European Southern Observatory Karl-Schwarzschild-Str. 285748 GarchingGermany

We present a study of the spectral line shape associated with a High Resolution Spectrograph on the 2.16 m telescope at the Xinglong Observing Station of National Astronomical Observatories, Chinese Academy of Sciences. This measurement is based on modeling the instrumental line shape obtained by unresolved modes from a Yb-fiber mode-locked laser frequency comb. With the current repetition rate of 250 MHz and 26 GHz mode spacing on the spectrograph, we find the absolute variation of the line center, 0.0597 pixel in the direction of the CCDs, and 0.00275 pixel （～3 m s^-1） for relative variation in successive exposures on a short timescale. A novel double-Gaussian model is presented to improve the quality of the fit by a factor of 2.47 in a typical single exposure. We also use analysis with raw moments and central moments to characterize the change in line shape across the detector. A trend in charge transfer efficiency can be found on the E2V 4096 ×4096 CCD that provides a correction for wavelength calibration aiming to reach a level of precision for radial velocity below 1 m s^- 1.

关键词： techniques radial velocities -- instrumentation laser frequency comb

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Microstructures and mechanical properties of homogenization and isothermal aging Mg–Gd–Er–Zn–Zr alloy

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Rare Metals 2016年第6期35卷 443-449页

作者： Kai Wen Wen-Bo Du Ke liu zhao-Hui Wang Shu-Bo Li College of Materials Science and Engineering Beijing University of Technology

The effects of homogenization and isothermal aging treatment on the mechanical properties of Mg-12Gd- 2Er-1Zn-0.6Zr （wt%） alloy were investigated. The precipitated long-period stacking order （LPSO） structure and the aging precipitation sequence of the conditioned alloys were observed and analyzed, respectively. The results indicate that the 14H-LPSO structure occurs after the homogenization treatment and the 131 phase forms after the isothermal aging process. These two independent processes could be controlled by the precipitation temperature range. The significant increase in the elongation of the as-cast alloy after homogenization treatment is attributed to the disappearance of the coarse primary Mgs（Gd, Er, Zn） phase and the presence of the 14H-LPSO structure. The precipitation sequence of the investigated alloy is α-Mg（SSS）/β″（D019）/β′（cbco）/β. Furthermore, the yield tensile strength （YTS） and ultimate tensile strength （UTS） values of the isothermal aging alloy have a great improvement, which could be attributed to the high density of the precipitated β′ phase.

关键词： Magnesium alloys Isothermal aging Mechanical properties Mg-Gd-Er-Zn(Zr) Microstructures

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Three-dimensional path following control system for net cage inspection using bionic robotic fish

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Information Processing in Agriculture 2022年第1期9卷 100-111页

作者： Yuanrong Chen Jingfen Qiao Jincun liu Ran zhao Dong An Yaoguang Wei College of Information and Electrical Engineering China Agricultural UniversityBeijing 100083China National Innovation Centre for Digital Fishery China Agricultural UniversityBeijing 100083China Beijing Engineering and Technology Research Centre for Internet of Things in Agriculture Beijing 100083China Key Laboratory of Agricultural Information Acquisition Technology Ministry of AgricultureBeijing 100083China School of Computing The Australian National UniversityCanberra2601Australia

With the increasing impacts of overfishing and environmental pollution,the deep-sea cage culture of marine fishes has become an important direction of *** this paper,a tuna-like robotic fish with a three-dimensional helix path-following control system is designed for deep-sea net cage *** mimic the flexibility of the fish’s movement,the kinematic model of the robotic fish adopts a tuna-like double-joint design with an addi-tional thruster device at the *** the descending interval control plays a critical role in deep-sea net cage inspection,the control system utilizes the proportion integration differ-entiation(PID)based fuzzy logic control method to control the descending interval and yaw angle during the helix path movement.A polar coordinate path definition method is also proposed to simplify the reference path definition during net cage *** experi-mental results demonstrates that the proposed three-dimensional path-following model can conduct net inspection task in an interferential environment and move along prede-fined reference path.

关键词： Net cage inspection Bionic robotic fish Path following Three-dimensional motion control

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Monitoring the Status of Multi-Wave Omicron Variant Outbreaks-71 Countries,2021–2023

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China CDC weekly 2024年第41期6卷 1054-1058页

作者： Chuanqing Xu Lianjiao Dai Songbai Guo Xiaoyu zhao Xiaoling liu School of Science Beijing University of Civil Engineering and ArchitectureBeijingChina School of Mathematics Shandong UniversityJinan CityShandong ProvinceChina Hanshan Normal University Chaozhou CityGuangdong ProvinceChina.

What is already known about this topic?Analyzing the characteristics of epidemic development after the emergence of the severe acute respiratory syndrome virus 2 Omicron variants with its subvariants and the impact of income level inequalities on the coronavirus disease 2019(COVID-19)case-fatality ratio helps to better understand the spread of novel coronavirus *** is added by this report?The median time interval between the first and second waves of Omicron sub-variants was 70 days(interquartile spacing:43.75–91),and between the second and third waves was 87.5 days(interquartile spacing:49–119),which obeyed a lognormal *** case-fatality ratio of the first wave was significantly higher than that of the second and third *** the initial epidemic period,there was no significant geographic differences in the case-fatality ratio of the first wave,while the case-fatality ratio in countries with high income levels was significantly lower than in countries with other income *** are the implications for public health practice?We still need to pay attention to the COVID-19 pandemic,as inequalities in income levels have an impact on the case-fatality ratio during the early stages of Omicron *** most countries,strains of the virus are likely to move from low to high population prevalence after 2–4 months.

关键词： spacing inequalities wave

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Design and experiment of a subsoiling variable rate fertilization machine

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International Journal of Agricultural and Biological Engineering 2020年第4期13卷 118-124页

作者： Jiangtao Qi Xinliang Tian Yang Li Xuhui fan Hongfang Yuan Jiale zhao Honglei Jia Key Laboratory of Bionic Engineering Ministry of EducationJilin UniversityChangchun 130022China College of Biological and Agricultural Engineering Jilin UniversityChangchun 130022China Jilin Province Academy of Agricultural Machinery Changchun 130022China

In order to improve soil fertility and fertilizer utilization,a subsoiling variable rate fertilization machine based on conservation tillage and precision agriculture was designed and *** relationship between suspension parameters and penetrating distance was analyzed,and a matching model between fertilizing quantity and penetrating distance was *** variable rate fertilization control machine was developed based on an Advantech PCM-9363 industrial control *** machine operates under two patterns:DGPS-based positioning and straight-line path positioning based on a planar coordinate *** machine can perform on-demand fertilization according to the spatial differences in soil nutrients and the prescription maps pre-set before the *** experiments showed the machine has a subsoiling stability of 92.5%,a soil breaking rate of 61.1%,a maximum positioning relative error of 2.68%and a maximum variable rate fertilization error of 3.89%.The subsoiling performance and variable rate fertilization indices of this machine satisfy the requirements of GB/*** tested indices meet the national and industrial standards and satisfy the design *** findings of the research can be used as the structural design of the subsoiling variable rate fertilization machine.

关键词： agricultural machinery conservation tillage precision agriculture subsoiling variable rate fertilization

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Numerical and physical simulations of array laterolog in deviated anisotropic formation

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Petroleum Science 2022年第5期19卷 2107-2119页

作者： Yi-Zhi Wu Zhen-Guan Wu Yi-Ren fan Tao Xing Chao-liu Li Chao Yuan School of Geosciences China University of PetroleumQingdao266580ShandongChina Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and TechnologyQingdao266071ShandongChina CNPC Key Laboratory for Well Logging China University of PetroleumQingdao266580ShandongChina Research Institute of Petroleum Exploration and Development PetroChinaBeijing100083China

Due to the tremendous amount of high-resolution measurement information,array laterolog is widely used in evaluations of deviated anisotropic ***,the precision of a complementary numerical simulation should be improved as high as the core of fine-scale reservoir ***,the 3D finite element method(3D-FEM)is presented to simulate the array laterolog ***,a downscaled physical simulation system is introduced to validate and calibrate the precision of the ***,the size of the downscaled system is determined by ***,the surrounding and investigated beds are represented by a sodium chloride solution and planks soaked in solution,***,a half-space measurement scheme is presented to improve the experimental ***,the corresponding sensitivity function and separation factor are established to analyze the effects of the formation anisotro py and dipping angle on the array laterolog *** numerical and experimental results indicate that the half-space method is practical,and the mean relative error between the numerical and experimental results is less than 5%,which indicates that the numerical simulation is *** the proposed approach,the reversal angle of array laterolog response curves in anisotropic formations can be observed,and this range is determined to be 50°-62°.

关键词： Anisotropic formation Array laterolog Downscaled physical simulation Sensitivity function Reversal angle

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Switchable-multi-wavelength fiber laser based on dual-core all-solid photonic bandgap fiber

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Frontiers of Optoelectronics 2010年第3期3卷 283-288页

作者： Jiaqi zhao Zhi WANG Yange liu Bo liu Key Laboratory of Opto-Electronic Information and Technology Ministry of Education Institute of Modern Optics Nankai University

In this paper, we propose and demonstrate a switchable multi-wavelength fiber laser based on a dualcore all-solid photonic bandgap fiber(PBGF) comb-like filter. The transmission properties of the dual-core all-solid PBGF are theoretically and experimentally *** the fiber ring laser based on the PBGF is realized and its wavelength-selective mechanisms are studied. By adjusting the polarization controller(PC), the number and location of the laser wavelength can be tunable.

关键词： photonic crystal fiber all-solid photonic bandgap fiber multi-wavelength fiber laser

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