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Statistical study of magnetic holes in the upstream region of Mercury’s bow shock

Earth and Planetary Physics 2024年第2期8卷 326-337页

作者： GuoQiang Wang SuDong Xiao mingyu wu YuanQiang Chen TieLong Zhang Institute of Space Science and Applied Technology Harbin Institute of TechnologyShenzhen 518055China Shenzhen Key Laboratory of Numerical Prediction for Space Storm Harbin Institute of TechnologyShenzhen 518055China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences Center for Excellence in Comparative Planetology Hefei 230026China Space Research Institute Austrian Academy of SciencesGrazAustria

Magnetic holes are magnetic depression structures that exist widely in many plasma environments.The magnetic holes with durations of>1 s in the solar wind at Mercury’s orbit have drawn much attention,but the properties of the magnetic holes with shorter durations are still unclear.Here,we investigate the magnetic holes with durations of 0.1-100 s in the upstream region of Mercury’s bow shock based on observations by the MESSENGER(MErcury Surface,Space ENvironment,GEochemistry,and Ranging)spacecraft.They can be divided into two groups according to the distribution of their duration:small-duration magnetic holes(SDMHs,0.6 s).The duration of each group approximately obeys a log-normal distribution with a median of~0.25 s and 3 s,respectively.Approximately 1.7%(32.6%)of the SDMHs(LDMHs)reduce the magnetic field strength by more than 50%.For both groups,some structures have a linear or quasi-linear polarization,whereas others have an elliptical polarization.The magnetic hole events in both groups tend to have a higher rate of occurrence when the interplanetary magnetic field strength is weaker.Their occurrence rates are also affected by Mercury’s foreshock,which can increase(decrease)the occurrence rate of the SDMHs(LDMHs).This finding suggests that Mercury’s foreshock might be one source of the SDMHs and that the foreshock can destroy some LDMHs.These observations suggest that a new group of magnetic holes with durations of<0.6 s exist in the upstream region of Mercury’s bow shock.

关键词： magnetic hole solar wind Mercury foreshock

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Two-dimensional semiconductor heterostructures for photocatalytic CO2 conversion

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Science China Chemistry 2024年第8期 2434-2447页

作者： Yang wu mingyu wu Yongfu Sun Yi Xie Hefei National Research Center for Physical Sciences at Microscale University of Science and Technology of China

The CO2reduction into carbon-contained fuel via solar energy offers the powerful tools to realize the zero-emission carbon cycle. Owing to the intriguing features of the two-dimensional（2D） heterostructures, it is susceptible to modulate the electronic structure as well as the surface geometry for optimizing the photocatalytic CO2reactivity. From this perspective, we surveyed the fundamental insights of 2D semiconductor heterostructures, involving the fabrication strategies and classification of the 2D semiconductor heterostructure. Also, we have detailly discussed the overview of 2D semiconductor heterostructure for optimizing CO2photocatalytic influenced factors, including the solar energy utilization, photogenerated carriers separation, and redox reaction kinetics. Afterwards, we showed the significant advantages of 2D heterostructures in elevating CO2photoreduction performance, focusing on activity, selectivity and photostability. By analyzing the limitations and developments, we ended by putting forward insights into the further researches about the CO2photocatalysts and reactor design, even industrial applications.

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The Regularity of Solutions to Mixed Boundary Value Problems of Second-Order Elliptic Equations with Small Angles

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Journal of Applied Mathematics and Physics 2024年第4期12卷 1043-1049页

作者： mingyu wu School of Mathematics East China University of Science and Technology Shanghai China

This paper considers the regularity of solutions to mixed boundary value problems in small-angle regions for elliptic equations. By constructing a specific barrier function, we proved that under the assumption of sufficient regularity of boundary conditions and coefficients, as long as the angle is sufficiently small, the regularity of the solution to the mixed boundary value problem of the second-order elliptic equation can reach any order.

关键词： Mixed Boundary Value Problems for Elliptic Equations Small-Angle Boundary Value Problems Regularity of Solutions to Elliptic Equations

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High-rate CH_(4)-to-C_(2)H_(6) photoconversion enabled by Au/ZnO porous nanosheets under oxygen-free system

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Science China Chemistry 2024年第3期67卷 869-875页

作者： Kai Zheng Xiaojing Zhang Jun Hu Chengbin Xu Juncheng Zhu Jing Li mingyu wu Shan Zhu Li Li Shumin Wang Yumei Lv Xin He Ming Zuo Chengyuan Liu Yang Pan Junfa Zhu Yongfu Sun Yi Xie Hefei National Laboratory for Physical Sciences at Microscale National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei 230026China Key Laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China State Grid Anhui Electric Power Research Institute Hefei 230601China

Photocatalytic CH_(4) coupling into high-valued C_(2)H_(6) is highly attractive,whereas the photosynthetic rate,especially under oxygen-free system,is still unsatisfying.Here,we designed the negatively charged metal supported on metal oxide nanosheets to activate the inert C-H bond in CH_(4)and hence accelerate CH_(4) coupling performance.As an example,the synthetic Au/ZnO porous nanosheets exhibit the C_(2)H_(6) photosynthetic rate of 1,121.6μmol g^(-1)_(cat)h^(-1)and the CH_(4) conversion rate of 2,374.6μmol g^(-1)_(cat)h^(-1) under oxygen-free system,2 orders of magnitude higher than those of previously reported photocatalysts.By virtue of several in situ spectroscopic techniques,it is established that the generated Au^(δ-)and O^-species together polarized the C-H bond,while the Au^(δ-)and O^-species jointly stabilized the CH_(3) intermediates,which favored the coupling of CH_(3) intermediate to photosynthesize C_(2)H_(6) instead of overoxidation into CO_(x).Thus,the design of dual active species is beneficial for achieving high-efficient CH_(4)-to-C_(2)H_(6) photoconversion.

关键词： dual surface-active sites selective methane coupling ethane room temperature

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钛铝金属间化合物激光点火燃烧行为及机理

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材料工程 2024年第5期52卷 1-16页

作者：吴明宇弭光宝李培杰隋楠董富礼中国航发北京航空材料研究院先进钛合金航空科技重点实验室北京100095 清华大学新材料国际研发中心北京100084

采用激光氧浓度实验方法结合超高温红外测温仪和高速摄像机原位观察、扫描电子显微分析和X射线衍射分析等方法,对钛铝金属间化合物(TiAl合金)的点火燃烧行为进行研究,揭示燃烧过程熔体的形成与运动规律、氧化物类型和结构特征,进而探讨... 详细信息

采用激光氧浓度实验方法结合超高温红外测温仪和高速摄像机原位观察、扫描电子显微分析和X射线衍射分析等方法,对钛铝金属间化合物(TiAl合金)的点火燃烧行为进行研究,揭示燃烧过程熔体的形成与运动规律、氧化物类型和结构特征,进而探讨燃烧机理。结果表明:TiAl合金发生起燃及持续燃烧的激光功率和氧浓度临界条件分别遵循抛物线规律和抛物线+直线规律,且显著高于近α型高温钛合金,即具有更好的阻燃性能;TiAl合金的起燃温度高于基体相熔点,起燃时基体部分熔化,导致Al元素由内氧化机制转变为外氧化机制;扩展燃烧阶段形成的氧化物由内侧到燃烧表面依次为Al_(2)O_(3),Al_(2)Ti_7O_(15),Al_(2)TiO_(5)和Al_(6)Ti_(2)O_(13)相,其中熔凝区内形成的连续网状Al_(2)O_(3)层能够阻碍熔体运动,燃烧区内形成的Ti-Al-O三元相通过降低内层Al_(2)O_(3)的分解压提升Al_(2)O_(3)保护层的稳定性,使TiAl合金具有良好的阻燃性能。

关键词： TiAl合金激光点火氧化燃烧产物燃烧机理起燃温度

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Electrostatic Structure of the Electron Phase-space Holes Generated by the Electron Two-stream Instability with a Finite Width

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空间科学学报 2017年第5期37卷 517-523页

作者： SANG Longlong wu mingyu LU Quanming CAS Key Laboratory of Geospace Environment School of Earth and Space Sciences University of Science and Technology of China

Space satellite observations in an electron phase-space hole(electron hole) have shown that bipolar structures are discovered at the parallel cut of parallel electric field, while unipolar structures spring from the parallel cut of perpendicular electric field. Particle-in-cell(PIC) simulations have demonstrated that the electron bi-stream instability induces several electron holes during its nonlinear evolution. However, how the unipolar structure of the parallel cut of the perpendicular electric field formed in these electron holes is still an unsolved problem,especially in a strongly magnetized plasma(Ω_e >ω_(pe), where Ω_e is defined as electron gyrofrequency and ω_(pe) is defined as plasma frequency, respectively). In this paper, with two-dimensional(2D) electrostatic PIC simulations, the evolution of the electron two-stream instability with a finite width in strongly magnetized plasma is investigated. Initially, those conditions lead to monochromatic electrostatic waves, and these waves coalesce with each other during their nonlinear evolution. At last, a solitary electrostatic structure is formed. In such an electron hole, a bipolar structure is formed in the parallel cut. of parallel electric field, while a unipolar structure presents in the parallel cut of perpendicular electric field.

关键词： Electron phase-space hole Two-stream instability PIC simulation

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基于RESYS程序的TOPAZ-Ⅱ反应堆系统模拟

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原子能科学技术 2024年第1期58卷 112-124页

作者：吴宗芸祁琳吴明宇李杨柳杨宏伟刘天才中国原子能科学研究院核工程设计研究所北京102413

本文使用C++语言开发了面向先进核反应堆的通用反应堆系统分析程序RESYS,在该程序的基础上建立了热离子核反应堆电源TOPAZ-Ⅱ的模型,并对其启动瞬态和稳态工况进行了模拟。建立的TOPAZ-Ⅱ反应堆系统模型包括反应堆堆芯热工模型、热离子... 详细信息

本文使用C++语言开发了面向先进核反应堆的通用反应堆系统分析程序RESYS,在该程序的基础上建立了热离子核反应堆电源TOPAZ-Ⅱ的模型,并对其启动瞬态和稳态工况进行了模拟。建立的TOPAZ-Ⅱ反应堆系统模型包括反应堆堆芯热工模型、热离子静态热电转换系统模型、热排放辐射散热器模型。铯热离子转换器电流密度使用Rasor模型,并使用6组缓发中子点堆动力学模型计算反应堆堆芯裂变功率随时间的变化,考虑各结构部件对反应性的影响。计算得到的稳态电功率输出与TITAM程序的计算结果较为一致,反应堆系统热电转换效率为5.04%。计算结果验证了所开发的RESYS程序以及建立的TOPAZ-Ⅱ系统模型的正确性。

关键词： TOPAZ-Ⅱ反应堆反应堆系统分析 RESYS程序热离子热电转换

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Effect of Ion Dynamics on the Evolution of Electron Phase-space Holes

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空间科学学报 2013年第4期33卷 413-417页

作者： WANG Peiran LU Quanming wu mingyu WANG Shui CAS Key Laboratory of Basic Plasma Physics Department of Geophysics and Planetary ScienceUniversity of Science and Technology of China

The evolution of two-dimensional（2D） electron phase-space holes（electron holes） has been previously investigated with electrostatic Particle-in-Cell（PIC） simulations,which neglect ion dynamics.The electron holes are found to be unstable to the transverse instability,and their evolution is determined by the combined action between the transverse instability and the stabilization by the background magnetic field.In this paper,the effect of ion dynamics on the evolution of an electron hole is studied.In weakly magnetized plasma(Ωeωpe),the electron hole is broken due to the lower hybrid waves, and its evolution is much faster.

关键词： Ion dynamics Electron holes Transverse instability Magnetized plasma

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基于复合动态采样的自动驾驶矿车节能路径规划方法

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汽车工程 2024年第4期46卷 588-595,642页

作者：丁志杰王亚飞章翼辰邬明宇王亦乐上海交通大学机械与动力工程学院上海200240 上海交通大学汽车动力与智能控制国家工程研究中心上海200240

近年来,考虑安全与效率的自动驾驶矿车路径规划方法已逐渐成熟,并在多种矿山场景落地应用。与此同时,产业界和学术界也开始关注如何利用路径规划提升矿车的燃油经济性。针对这一需求,本文提出了一种矿山场景下的自动驾驶矿车节能路径规... 详细信息

近年来,考虑安全与效率的自动驾驶矿车路径规划方法已逐渐成熟,并在多种矿山场景落地应用。与此同时,产业界和学术界也开始关注如何利用路径规划提升矿车的燃油经济性。针对这一需求,本文提出了一种矿山场景下的自动驾驶矿车节能路径规划方法,其主要特点是根据车速、道路坡度及障碍物进行S-L(进度-偏离)和S-T(进度-时间)的复合动态采样。针对矿山典型地形场景,建立了矿车燃油消耗指标,提出了安全性-运行效率-能耗综合路径评价模型;为了防止评价模型的各项权重陷入局部最优,设计了基于模拟退火策略的粒子群自适应优化方法。在矿山实际场景的测试中,本研究提出方法较现有方法在燃油经济性指标上平均提升了11.28%。

关键词：智能汽车自动驾驶燃油经济性局部路径规划

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Measurements of ^(134)Cs and ^(137)Cs in urine and estimation of the internal dose of an adult exposed to the Chernobyl Accident

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Nuclear Science and Techniques 2007年第2期18卷 115-117页

作者： ZHAO Shuquan HUANG Shibin LIU Shiming HU Heping wu mingyu XIANG Xiqiao ZHU Guoying Institute of Radiation Medicine Fudan University Shanghai 200032 China Shanghai Medical College Fudan University Shanghai 200032 China Jinan Maritime Safety Administration of China Jinan 250062 China

To estimate the internal dose of a Chinese visiting scholar internally contaminated because of the Cherno- byl Accident, the contents of 134Cs and 137Cs in urine were measured using a Ge(Li) γ-spectrometer. The internal doses were calculated based on data from the ICRP Publications. The effective doses from 134Cs and 137Cs were estimated to be 61 μSv and 98 μ Sv, respectively. The sum of 159 μSv was lower than the total effective dose (310 μSv), from the inhalation and ingestion of natural radionuclides. The dose of 131I was also reviewed referring to the UNSCEAR 2000 Report. The equivalent effective dose of 131I was estimated to be 2.9 mSv, 18 times more than the amount of 134Cs and 137Cs. Therefore, it is considered that the earlier estimation of internal doses of 131I is important in evaluating radiation injuries from a nuclear reactor accident.

关键词：切尔诺贝利核事故成年人内照射剂量估计尿液铯134 铯137 光谱测定

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