检索结果-南通市图书馆

Pseudo-reconnection in MHD numerical simulation

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2000年第9期45卷 798-801页

作者： CHEN Pengfei FANG Cheng hu youqiu Department of Astronomy Nanjing UniversityNanjing 210093China Department of Space and Earth Sciences University of Science and Technology of ChinaHefei 230026China

A class of pseudo-reconnections caused by a shifted mesh in magnetohydrodynamics(MHD) simulations is reported. In terms of this mesh system, some non-physical results may be obtained in certain circumstances, e.g. mag... 详细信息

关键词： magnetohydrodynamics (MHD) numerical simulation magnetic reconnection.

Anisotropic propagation of flare-induced shocks

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1998年第5期43卷 402-404页

作者： hu youqiu University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China Chinese Academy of Sciences University of Science and Technology of China Hefei China

It is demonstrated that the fastest propagation direction of a flare-induced shock deviates eastwards by about 4° at 1 AU relative to the flare normal if the shock introduced at 0.1 AU propagates along the local magnetic field, whereas it deviates westwards by about 1° if the introduced shock propagates in the radial direction instead.

关键词： solar flare MHD shock interplanetary dynamics.

Magnetohydrodynamics (MHD) numerical simulations on the interaction of the solar wind with the magnetosphere: A review

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2013年第7期56卷 1141-1157页

作者： WANG Chi GUO XiaoCheng PENG Zhong TANG BinBin SUN TianRan LI WenYa hu youqiu State Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences School of Earth and Space Sciences University of Science and Technology of China

The magnetosphere is the outermost layer of the geospace, and the interaction of the solar wind with the magnetosphere is the key element of the space weather cause-and-effect chain process from the Sun to Earth, which is one of the most challenging scientific problems in the geospace weather study. The nonlinearity, multiple component, and time-dependent nature of the geospace make it very difficult to describe the physical process in geospace using traditional analytic analysis approach. Numerical simulations, a new research tool developed in recent decades, have a deep impact on the theory and application of the geospace. MHD simulations started at the end of the 1970s, and the initial study was limited to two-dimensional (2D) cases. Due to the intrinsic three-dimensional (3D) characteristics of the geospace, 3D MHD simulations emerged in the 1980s, in an attempt to model the large-scale structures and fundamental physical processes in the magnetosphere. They started to combine with the space exploration missions in the 1990s and make comparisons with observations. Physics-based space weather forecast models started to be developed in the 21st century. Currently only a few space-power countries such as USA and Japan have developed 3D magnetospheric MHD models. With the rapid advance of space science in China, we have developed a new global MHD model, namely PPMLR-MHD, which has high order spatial accuracy and low numerical dissipation. In this review, we will briefly introduce the global 3D MHD modeling, especially the PPMLR-MHD code, and summarize our recent work based on the PPMLR-MHD model, with an emphasis on the interaction of interplanetary shocks with the magnetosphere, large-scale current systems, reconnection voltage and transpolar potential drop, and Kelvin-Helmholtz (K-H) instability at the magnetopause.

关键词： solar wind magnetosphere MHD simulations

在线全文

学校读者我要写书评

暂无评论

部分开放多极磁场中的日冕磁绳灾变

空间科学学报 2005年第2期25卷 81-85页

作者：彭忠胡友秋中国科学技术大学地球与空间科学学院合肥230026

采用球坐标下二维三分量理想MHD模型,研究部分开放多极背景磁场中日冕磁绳的灾变现象.背景磁场由含3个闭合双极场的冕流和带赤道中性电流片的开放场构成,磁绳位于中心双极场的下方,其特性由环向磁通和轴向磁通表征.对给定的环向磁通,... 详细信息

采用球坐标下二维三分量理想MHD模型,研究部分开放多极背景磁场中日冕磁绳的灾变现象.背景磁场由含3个闭合双极场的冕流和带赤道中性电流片的开放场构成,磁绳位于中心双极场的下方,其特性由环向磁通和轴向磁通表征.对给定的环向磁通,存在轴向磁通的一个临界值;对给定的轴向磁通,也存在环向磁通的一个临界值.在该临界值以下,磁绳附着于太阳表面,系统处于平衡状态;该临界值一旦被超越,磁绳将脱离太阳表面向上喷发,说明部分开放多极背景磁场中的日冕磁绳系统存在灾变现象.本文算例表明,灾变点对应的磁能阈值超过对应部分开放场(中心双极场开放,两侧的双极场仍维持闭合)能量约15％,其超过部分可为日冕物质抛射一类太阳爆发提供能源.

关键词：磁流体力学灾变现象 MHD数值模拟开放多极磁场

Predicting the strut forces of the steel supporting structure of deep excavation considering various factors by machine learning methods

在线全文

学校读者我要写书评

暂无评论

Underground Space 2024年第5期18卷 114-129页

作者： Haibo hu Xunjian hu Xiaonan Gong Research Center of Coastal and Urban Geotechnical Engineering Zhejiang UniversityHangzhou 310058China

The application of steel strut force servo systems in deep excavation engineering is not widespread,and there is a notable scarcity of in-situ measured *** presents a significant research gap in the *** this,our study introduces a valuable dataset and application scenarios,serving as a reference point for future *** main objective of this study is to use machine learning(ML)methods for accurately predicting strut forces in steel supporting structures,a crucial aspect for the safety and stability of deep excavation *** employed five different ML methods:radial basis function neural network(RBFNN),back propagation neural network(BPNN),K-Nearest Neighbor(KNN),support vector machine(SVM),and random forest(RF),utilizing a dataset of 2208 measured *** points included one output parameter(strut forces)and seven input parameters(vertical position of strut,plane position of strut,time,temperature,unit weight,cohesion,and internal frictional angle).The effectiveness of these methods was assessed using root mean square error(RMSE),correlation coefficient(R),and mean absolute error(MAE).Our findings indicate that the BPNN method outperforms others,with RMSE,R,and MAE values of 72.1 kN,0.9931,and 57.4 kN,respectively,on the testing *** study underscores the potential of ML methods in precisely predicting strut forces in deep excavation engineering,contributing to enhanced safety measures and project planning.

关键词： Deep excavation Steel supporting structure Strut forces Machine learning Time Temperature

The super-cycle of the global land-monsoon system

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

National Science Review 2024年第5期11卷 107-109页

作者： Yongyun hu Laboratory for Climate and Ocean-Atmosphere Studies Department of Atmospheric and Oceanic Sciences School of Physics Peking University

The modern monsoon system consists of six regional monsoons [1]. These regional monsoons demonstrate coherently annual variations of precipitation and atmospheric circulation patterns, although they have different characteristics. Therefore, these regional monsoons are unified in the context of the global monsoon [1,2], which reflects the dominant mode of coherent annual variations of precipitation and atmospheric circulations in the tropics and subtropics.

关键词：

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

磁通量消失所形成的中性电流片

Chinese Journal of Astronomy and Astrophysics 1984年第1期 14-24页

作者：胡友秋中国科学技术大学地球和空间科学系

在与太阳耀斑有关的活动区中,一般呈现各种复杂多变的磁场结构,其中特别是光球层表面局部地区磁通量的出现和消失.在无限电导率的假定下,上述两种现象都会在日冕中产生中性电流片;通常人们认为这正是耀斑前一种可能的贮能机制.Tur和Pri... 详细信息

在与太阳耀斑有关的活动区中,一般呈现各种复杂多变的磁场结构,其中特别是光球层表面局部地区磁通量的出现和消失.在无限电导率的假定下,上述两种现象都会在日冕中产生中性电流片;通常人们认为这正是耀斑前一种可能的贮能机制.Tur和Priest通过两个特例讨论了新磁通量的出现所形成的电流片的特征,这两个例子的背景磁场分别取为双极场和均匀场.本文采用同样的背景场,讨论磁通量消失所形成的电流片,并指出和纠正文[2]对第二个例子的分析中的一些原则错误.

关键词：电流片几何形式自由能电流分布热力学势热力学性质磁场冻结磁通量太阳耀斑偶极子场磁场位形末态日冕太阳大气

R-matrix for the 8-Dimensional Spin Representation of Uq(so7)

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2024年第2期40卷 485-497页

作者： Hong Mei hu Nai Hong hu School of Mathematical Sciences Suzhou University of Science and TechnologySuzhou 215009P.R.China School of Mathematical Sciences MOE Key Laboratory of Mathematics and Engineering Applications&Shanghai Key Laboratory of PMMPEast China Normal UniversityShanghai 200241P.R.China

The purpose of the paper is to describe the solution to the quantum Yang-Baxter equation associated with the 8-dimensional spin representation Tsp of Uq(so7).The self-duality of Tsp and the symmetry of the corresponding braiding matrix are ***,the minimal polynomial of the braiding R-matrix of Tsp is presented explicitly in an ingenious method by taking advantage of nice features of the spin representation Tsp.

关键词： Braiding R-matrix spin module minimal polynomial

Mapping out the reaction network of humin formation at the initial stage of fructose dehydration in water

在线全文

学校读者我要写书评

暂无评论

Green Energy & Environment 2024年第6期9卷 1016-1026页

作者： Xing Fu Yexin hu Ping hu hui Li Shuguang Xu Liangfang Zhu Changwei hu Key Laboratory of Green Chemistry and Technology Ministry of EducationCollege of ChemistrySichuan UniversityChengduSichuan610064China State Key Laboratory of Southwestern Chinese Medicine Resources Innovative Institute of Chinese Medicine and PharmacyChengdu University of Traditional Chinese MedicineChengduSichuan611137China

The formation of humins hampers the large-scale production of 5-hydroxymethylfurfural(HMF)in ***,a detailed reaction network of humin formation at the initial stage of fructose-to-HMF dehydration in water is delineated by combined experimental,spectroscopic,and theoretical *** bimolecular reaction pathways to build up soluble humins are *** is,the intermolecular etherification of β-furanose at room temperature initiates the C12 path,whereas the C-C cleavage of a-furanose at 130-150℃ leads to C11 path,and that of open-chain fructose at 180℃ to C11' *** successive intramolecular dehydrations and condensations of the as-formed bimolecular intermediates lead to three types of soluble *** show that the C12 path could be restrained by using HCl or AlCl_(3) catalyst,and both the C12 and C110 paths could be effectively inhibited by adding THF as a co-solvent or accelerating heating rate via microwave heating.

关键词： Carbohydrates 5-hydroxymethylfurfural Reaction network Soluble humins Tautomer