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Nepheloid layer generation by gas eruption:unexpected experimental results

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Journal of Oceanology and Limnology 2023年第2期41卷 769-777页

作者： Chaoqi zhu Sanzhong LI Jiangxin CHEN Dawei WANG xiaoshuai SONG Zhenghui LI Bo CHEN Hongxian SHAN Yonggang JIA Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Key Lab of Submarine Geosciences and Prospecting TechniquesMinistry of Education(MOE)Ocean University of ChinaQingdao 266100China Laboratory for Marine Geology Qingdao National Laboratory for Marine Science and TechnologyQingdao 266061China Frontiers Science Center for Deep Ocean Multispheres and Earth System and College of Marine GeosciencesOcean University of ChinaQingdao 266100China Hainan Key Laboratory of Marine Geological Resources and Environment Haikou 570206China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and TechnologyQingdao 266061China Key Laboratory of Gas Hydrate Ministry of Natural ResourcesQingdao Institute of Marine GeologyQingdao 266061China Laboratory of Marine Geophysics and Georeource Institute of Deep-Sea Science and EngineeringChinese Academy of SciencesSanya 572000China

Knowledge of nepheloid layers is important to improve the understanding of physical,geological,and sedimentary processes from continental shelf to abyssal environments.We had not tried to study the nepheloid layers in a hydrate-associated tank until unexpected results occurred.Tank experimental results show that gas eruptions triggered intermediate nepheloid layers.Thus,we proposed a new mechanism of intermediate nepheloid layer generation by eruptions.The intermediate nepheloid layers were generated in uniform-density fluid,which indicated that stratified fluid is not a necessary condition for intermediate nepheloid layers.Sufficient space for advection and an oblique slope for detachment are the key ingredients for intermediate nepheloid layer generation by eruptions.Our experiments also offer a new experimental evidence for bottom nepheloid layer generation by earthquakes.Given the scale effects of laboratory experiment,it is important to determine whether submarine volcanic eruption or hydrate-associated venting causes intermediate nepheloid layer in the nature.

关键词： intermediate nepheloid layer gas eruption bottom nepheloid layer gas hydrate tank experiment seafloor instability

Change Ratios of Magnetic Helicity and Magnetic Free Energy During Major Solar Flares

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天文和天体物理学研究:英文版 2023年第9期23卷 309-321页

作者： Quan Wang Mei Zhang Shangbin Yang Xiao Yang xiaoshuai zhu National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China

Magnetic helicity is an important concept in solar physics,with a number of theoretical statements pointing out the important role of magnetic helicity in solar flares and coronal mass ejections(CMEs).Here we construct a sample of 47 solar flares,which contains 18 no-CME-associated confined flares and 29 CME-associated eruptive flares.We calculate the change ratios of magnetic helicity and magnetic free energy before and after these 47 flares.Our calculations show that the change ratios of magnetic helicity and magnetic free energy show distinct different distributions in confined flares and eruptive flares.The median value of the change ratios of magnetic helicity in confined flares is-0.8%,while this number is-14.5%for eruptive flares.For the magnetic free energy,the median value of the change ratios is-4.3%for confined flares,whereas this number is-14.6%for eruptive flares.This statistical result,using observational data,is well consistent with the theoretical understandings that magnetic helicity is approximately conserved in the magnetic reconnection,as shown by confined flares,and the CMEs take away magnetic helicity from the corona,as shown by eruptive flares.

关键词： Sun corona-Sun flares-Sun magnetic fields

Solar ultraviolet bursts in a coordinated observation of IRIS,Hinode and SDO

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Science China(Technological Sciences) 2019年第9期62卷 1555-1564页

作者： CHEN YaJie TIAN Hui ZHU XiaoShuai SAMANTA Tanmoy WANG LingHua HE JianSen School of Earth and Space Sciences Peking UniversityBeijing 100871China Max Planck Institute for Solar System Research Gottingen 37077Germany

Solar ultraviolet(UV) bursts are small-scale compact brightenings in transition region images. The spectral profiles of transition region lines in these bursts are significantly enhanced and broadened, often with chromospheric absorption lines such as Ni ii 1335.203 and 1393.330 A superimposed. We investigate the properties of several UV bursts using a coordinated observation of the Interface Region Imaging Spectrograph(IRIS), Solar Dynamics Observatory(SDO), and Hinode on February 7, 2015. We have identified 12 UV bursts, and 11 of them reveal small blueshifts of the Ni ii absorption lines. However, the Ni ii lines in one UV burst exhibit obvious redshifts of ~20 km s^-1, which appear to be related to the cold plasma downflows observed in the IRIS slit-jaw images. We also examine the three-dimensional magnetic field topology using a magnetohydrostatic model, and find that some UV bursts are associated with magnetic null points or bald patches. In addition, we find that these UV bursts reveal no obvious coronal signatures from the observations of the Atmospheric Imaging Assembly(AIA) on board SDO and the EUV Imaging Spectrometer(EIS) on board Hinode.

关键词： Sun: chromosphere Sun: transition region Sun: UV radiation magnetic reconnection

A method of magnetosonic characteristics to correct the "rarefaction shocks" problem arising in ZEUS

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Science China(Physics,Mechanics & Astronomy) 2012年第9期55卷 1720-1726页

作者： ZHU XiaoShuai WANG HuaNing FAN YuLiang DU ZhanLe HE Han Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

ZEUS is a magnetohydrodynamics simulation code widely used in astrophysical research.However,it was recently found that the code may produce artificial shocks in the rarefaction region in some numerical tests since it is not upwinded in fast and slow waves.We propose a method of magnetosonic characteristics to evolve compressional waves.The tests indicate that this method cures the "rarefaction shocks" problem to a large extent and it also greatly reduces some post shock oscillations.

关键词：稀疏 ZEUS 声特性流体动力学模拟纠正数值试验天体物理学 Zeus

基于控保协同的环形直流微网电流式单端测距保护

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高电压技术 2022年第12期48卷 4959-4967页

作者：薛士敏朱晓帅王守相天津大学智能电网教育部重点实验室天津300072

目前,直流系统保护在故障限流、定位和隔离手段上仍存在不少技术难点。因此,以四端环形直流微网为研究对象,针对极间故障,兼顾选择性与经济性,提出了一种电流式单端测距保护技术。该方法从控保协同出发,仅利用单端电流值即可实现精准测... 详细信息

目前,直流系统保护在故障限流、定位和隔离手段上仍存在不少技术难点。因此,以四端环形直流微网为研究对象,针对极间故障,兼顾选择性与经济性,提出了一种电流式单端测距保护技术。该方法从控保协同出发,仅利用单端电流值即可实现精准测距,且原理上不受过渡电阻的影响。在系统发生极间故障后,对换流器以及外加的电力电子器件进行控制,实现拓扑变换,基于所提测距算法,实现精准故障定位。同时,无需直流断路器,仅通过所配置的快速隔离开关之间的配合即可实现故障隔离。最后,在PSCAD/EMTDC仿真平台上验证了所提保护原理的精确性。

关键词：直流微网控保协同单端故障测距快速隔离开关抗过渡电阻

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改进D^(*)算法下的无人机三维路径规划

西安工程大学学报 2023年第3期37卷 83-91页

作者：汪小帅朱其新朱永红苏州科技大学电子与信息工程学院江苏苏州215009 苏州科技大学机械工程学院/建筑智慧节能江苏省重点实验室/苏州市共融机器人技术重点实验室江苏苏州215009 景德镇陶瓷大学机电工程学院江西景德镇333001

针对无人机使用传统D^(*)算法进行三维路径自主规划过程中,存在算法效率低和路径拐点多且复杂等问题,给出一种改进的D^(*)算法。首先,使用变步长的方式扩展节点,加快算法在规划阶段遍历节点的速度;同时,使用切比雪夫距离和曼哈顿距离的... 详细信息

针对无人机使用传统D^(*)算法进行三维路径自主规划过程中,存在算法效率低和路径拐点多且复杂等问题,给出一种改进的D^(*)算法。首先,使用变步长的方式扩展节点,加快算法在规划阶段遍历节点的速度;同时,使用切比雪夫距离和曼哈顿距离的融合式作为代价值,改进代价函数,缩减算法计算量,克服算法效率低的问题;最后,将三维地图以及所得路径投影到二维平面上,选取关键节点,舍弃冗余节点,优化生成路径,所得路径的拐点数减少、复杂性降低。使用MATLAB进行仿真实验,仿真结果表明:改进后D^(*)算法可以有效利用于无人机在三维环境下的路径规划,在加快算法效率和提高路径质量方面取得了预期效果。

关键词：三维路径规划 D^(*)算法无人机仿真建模

一种改进变步长LMS算法及其在系统辨识中的应用

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仪器仪表学报 2007年第7期28卷 1340-1344页

作者：李竹杨培林行小帅山西师范大学物理与信息工程学院临汾041004

在分析传统LMS算法及变步长LMS的基础上,本文提出了一种改进的变步长LMS算法并应用于系统辨识。新算法利用瞬时误差的四次方和遗忘因子共同来调整步长,进一步解决了收敛时间和稳态误差的矛盾。将新算法应用到系统辨识中时,与传统LMS算... 详细信息

在分析传统LMS算法及变步长LMS的基础上,本文提出了一种改进的变步长LMS算法并应用于系统辨识。新算法利用瞬时误差的四次方和遗忘因子共同来调整步长,进一步解决了收敛时间和稳态误差的矛盾。将新算法应用到系统辨识中时,与传统LMS算法和变步长LMS算法相比,仿真表明新算法有更快的收敛速率。

关键词： LMS算法变步长遗忘因子系统辨识

Fixed-time group consensus of second-order multi-agent systems based on event-triggered control

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Chinese Physics B 2023年第7期32卷 329-336页

作者：武肖帅孙凤兰朱伟 Jürgen Kurths College of Automation Chongqing University of Posts and TelecommunicationsChongqing 400065China School of Science Chongqing University of Posts and TelecommunicationsChongqing 400065China Department of Complexity Science Potsdam Institute for Climate Impact ResearchPotsdam 14473Germany Institute of Physics Humboldt University of BerlinBerlin 12489Germany

The problem of fixed-time group consensus for second-order multi-agent systems with disturbances is investigated.For cooperative-competitive network,two different control protocols,fixed-time group consensus and fixed-time eventtriggered group consensus,are designed.It is demonstrated that there is no Zeno behavior under the designed eventtriggered control.Meanwhile,it is proved that for an arbitrary initial state of the system,group consensus within the settling time could be obtained under the proposed control protocols by using matrix analysis and graph theory.Finally,a series of numerical examples are propounded to illustrate the performance of the proposed control protocol.

关键词： event-triggered control group consensus multi-agent system fixed-time

特高压输电用同步调相机端部涡流损耗及流固耦合传热研究

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中国电机工程学报 2022年第5期42卷 1968-1980页

作者：王立坤毕晓帅朱志佳孙玉田寇宝泉邢洪凯大型电机电气与传热技术国家地方联合工程研究中心(哈尔滨理工大学) 黑龙江省哈尔滨市150080 哈尔滨电机厂有限责任公司黑龙江省哈尔滨市150040 哈尔滨工业大学电气工程及自动化学院黑龙江省哈尔滨市150001

针对特高压输电用大型同步调相机端部复杂结构下漏磁、发热与冷却问题,结合调相机实际运行特点,建立三维瞬态电磁场数学模型,研究端部漏磁及各构件涡流损耗分布规律。通过构建调相机端部三维流固耦合传热模型,研究有限空间约束下端部通... 详细信息

针对特高压输电用大型同步调相机端部复杂结构下漏磁、发热与冷却问题,结合调相机实际运行特点,建立三维瞬态电磁场数学模型,研究端部漏磁及各构件涡流损耗分布规律。通过构建调相机端部三维流固耦合传热模型,研究有限空间约束下端部通风系统冷却介质导流规律及屏蔽外空间和屏蔽内狭小空间的传热规律;进一步,探究不同冷却介质对端部新型双阶铜屏蔽、凸形压圈等结构的热表征影响。为了验证该文数值分析模型的合理性及计算方法的有效性,对调相机端部铜屏蔽内缘温度进行实测,温度计算结果与温度实测结果相吻合,为提升调相机通风冷却系统散热效力,选择最优冷却介质,以及研发更大容量的特高压输电用调相机冷却系统提供理论基础。

关键词：同步调相机涡流损耗传热规律冷却介质通风冷却