Relationship between magnetic field evolution and flaring sites in AR 6659 in June 1991   总被引：2，自引：0，他引：2  

B. Schmieder  M. J. Hagyard  Guoxiang Ai  Hongqi Zhang  B. Kalmán  L. Györi  B. Rompolt  P. Démoulin  M. E. Machado 《Solar physics》1994,150(1-2):199-219

During the international campaign of June 1991, the active region AR 6659 produced six very large, long-duration flares (X10/12) during its passage across the solar disk. We present the characteristics of four of them (June 4, 6, 9, 15). Precise measurements of the spot motions from Debrecen and Tokyo white-light pictures are used to understand the fragmentation of the main sunspot group with time. This fragmentation leads to a continuous restructuring of the magnetic field pattern while rapid changes are evidenced due to fast new flux emergence (magnetograms of MFSC, Huairou). The first process leads to a shearing of the field lines along which there is energy storage; the second one is the trigger which causes the release of energy by creating a complex topology. We conjecture that these two processes with different time scales are relevant to the production of flares.  相似文献   

Observations of vector magnetic fields in flaring active regions     

Jimin Chen  Haimin Wang  Harold Zirin  Guoxiang Ai 《Solar physics》1994,154(2):261-273

We present vector magnetograph data of 6 active regions, all of which produced major flares. Of the 20 M-class (or above) flares, 7 satisfy the flare conditions prescribed by Hagyard (high shear and strong transverse fields). Strong photospheric shear, however, is not necessarily a condition for a flare. We find an increase in the shear for two flares, a 6-deg shear increase along the neutral line after a X-2 flare and a 13-deg increase after a M-1.9 flare. For other flares, we did not detect substantial shear changes.Visiting Associate from Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, China.  相似文献   

AN EXPLANATION OF TRANSIENT BRIGHTENINGS BY MAGNETIC RECONNECTION THEORY     

Bi-Qiang  Li  Xiao-Qing  Li  Guo-Xiang  Ai 《Solar physics》1997,173(1):103-109

It has been discovered that active regions commonly have numerous flare-like transient loop brightenings. We use a magnetic reconnection theory driven by a ponderamotive force with transverse plasmons on account of the basic properties of a transient brightening: lifetime a few minutes and total energy 10 25–10 29 ergs. The numerical results are consistent with the observations.  相似文献   

峰峰第五煤矿电厂供水方案优化选择     

吴爱君 《河南国土资源》2001,(4)

在目前市场经济条件下 ,峰峰第五煤矿由原先单纯治水向综合利用水方向过渡 ,提出了建电厂 ,以矿井废水作为电厂冷却用水。本文关于建电厂的三个供水方案优化选择 ,采用系统理论、权重分析 ,对方案进行优化选择 ,供决策者参考  相似文献   

EVOLUTION OF MAGNETIC HELICITY IN MAGNETIC RECONNECTION   总被引：1，自引：0，他引：1  

Hu  Y. Q.  Xia  L. D.  Li  X.  Wang  J. X.  Ai  G. X. 《Solar physics》1997,170(2):283-298

This paper presents a definition of magnetic helicity specifically for two-dimensional magnetic fields and derives the associated helicity equation. The newly defined helicity is closely related to its three-dimensional counterpart and serves as a measure of the shear of magnetic field. Based on this, a numerical simulation is carried out on magnetic reconnection occurring in the lower solar atmosphere. It is found that the helicity dissipation due to magnetic reconnection is very small. A large amount of helicity is transferred upward and escapes from the domain of the solution, and the total helicity is approximately conserved during the magnetic reconnection and helicity transfer. This is in support of the applicability of a postulate, which was proposed by Taylor (1974, 1986) concerning the approximate conservation of magnetic helicity in the presence of resistive dissipation and magnetic reconnection in a highly conductive laboratory plasma, to the solar atmosphere.  相似文献   

Arctic glacier movement monitoring with GPS method on 2005     

艾松涛  鄂栋臣阎明 任贾文 《极地研究(英文版)》2006,17(1):61-68

During the 2005 Arctic Yellow River Station expedition, the research on monitoring the movement and mass balance of two glaciers around Ny-Alesund, Austrelovenbreen and Pedersenbreen, which were selected in the 2004 Yellow River Station expedition were conducted. This paper analyzes the feasibility and advantage in using GPS method to monitor the Arctic glaciers＇movement, estimates the precision of first time measured GPS data and discusses the relevant problems in surveying on the Arctic Glaciers with GPS.  相似文献   

SYSTEM FOR AUTOMATIC GENERALIZATION OF TOPOGRAPHIC MAPS     

YAN Hao-wen LI Zhi-lin AI Ting-hua 《中国地理科学(英文版)》2006,16(2):165-170

1INTRODUCTION Map generalization may be defined as a procedure that generatessmallerscalemapsfromlargerscaleonesusing variousappropriateoperations (e.g.selection,combina- tion, displacement, simplification, etc.) under definite conditions (includingmap scale, purpose, etc.). The au- tomation of the generalization process has been a dream of cartographers for decades. For it is an indispensable wayto construct map databases from large-scale maps to small-scale ones, which can decrease repet…  相似文献   

P‐O‐rich sulfide phase in CM chondrites: Constraints on its origin on the CM parent body          下载免费PDF全文

Ai‐Cheng Zhang  Shoichi Itoh  Hisayoshi Yurimoto  Wei‐Biao Hsu  Ru‐Cheng Wang  Lawrence A. Taylor 《Meteoritics & planetary science》2016,51(1):56-69

CM chondrites are a group of primitive meteorites that have recorded the alteration history of the early solar system. We report the occurrence, chemistry, and oxygen isotopic compositions of P‐O‐rich sulfide phase in two CM chondrites (Grove Mountains [GRV] 021536 and Murchison). This P‐O‐rich sulfide is a polycrystalline aggregate of nanometer‐size grains. It occurs as isolated particles or aggregates in both CM chondrites. These grains, in the matrix and in type‐I chondrules from Murchison, were partially altered into tochilinite; however, grains enclosed by Ca‐carbonate are much less altered. This P‐O‐rich sulfide in Murchison is closely associated with magnetite, FeNi phosphide, brezinaite (Cr₃S₄), and eskolaite (Cr₂O₃). In addition to sulfur as the major component, this sulfide contains ~6.3 wt% O, ~5.4 wt% P, and minor amounts of hydrogen. Analyses of oxygen isotopes by SIMS resulted in an average δ¹⁸O value of ?22.5 ‰ and an average Δ¹⁷O value of 0.2 ± 9.2 ‰ (2σ). Limited variations in both chemical compositions and electron‐diffraction patterns imply that the P‐O‐rich sulfide may be a single phase rather than a polyphase mixture. Several features indicate that this P‐O‐rich sulfide phase formed at low temperature on the parent body, most likely through the alteration of FeNi metal (a) close association with other low‐temperature alteration products, (b) the presence of hydrogen, (c) high Δ¹⁷O values and the presence in altered mesostasis of type‐I chondrules and absence in type‐II chondrules. The textural relations of the P‐O‐rich sulfide and other low‐temperature minerals reveal at least three episodic‐alteration events on the parent body of CM chondrites (1) formation of P‐O‐rich sulfide during sulfur‐rich aqueous alteration of P‐rich FeNi metal, (2) formation of Ca‐carbonate during local carbonation, and (3) alteration of P‐O‐rich sulfide and formation of tochilinite during a period of late‐stage intensive aqueous alteration.  相似文献   

A map‐algebra‐based method for automatic change detection and spatial data updating across multiple scales          下载免费PDF全文

Min Yang  Tinghua Ai  Xiongfeng Yan  Yuanyuan Chen  Xiang Zhang 《Transactions in GIS》2018,22(2):435-454

The availability of geospatial data has increased significantly over recent decades. As a result, the question of how to update spatial data across different scales has become an attractive topic. One promising strategy is to use an updated larger‐scale dataset as a reference for detecting and updating changed objects represented in a to‐be‐updated smaller‐scale dataset. For such an update method, an understanding of the different types of changes that can occur is crucial. Using polygonal building data as an example, this study examines the various possible changes from different perspectives, such as the reasons for their occurrence, the forms in which they manifest, and their effects on output. Then, we apply map algebra theory to establish a cartographic model for updating polygonal building data. Supported by concepts of map algebra, an update procedure involving change detection, filtering, and fusion is implemented through a series of set operations. In addition to traditional polygon overlay functions, the constrained Delaunay triangulation model and knowledge of map generalization procedures are employed to construct set operations. The proposed method has been validated through tests using real‐world data. The experimental results show that our method is effective for updating 1:10k map data using 1:2k map data.  相似文献   

涡轮钻井技术在梨树断陷区块的应用          下载免费PDF全文

许爱 《探矿工程》2014,41(6):44-48,52

梨树断陷区块登娄库组、营城组、沙河子组、火石岭组地层可钻性差、岩性较致密、局部含砾严重,并且沙河子组局部层位岩石硬度达到7级,采用常规钻井技术,存在牙轮钻头效率低、寿命短等问题;各种型号PDC钻头试用后效果不理想。通过采用涡轮钻井技术,平均机械钻速提高了4倍,钻井周期缩短,钻井综合成本大大降低。实践证明,高速涡轮钻具＋孕镶金刚石钻井技术是高研磨性、高抗挤强度、高温地层深井钻进提速的有效技术。  相似文献