The 4 February, 1986 flare and flare-filament current model     

Tang Yu-Hua  Yin Chun-Lin  Qiu Jiong 《Solar physics》1996,163(1):133-144

In this paper, the observational data in H, radio, soft X-ray, hard X-ray, and -ray emissions for the 3B/X3.0 solar flare on 4 February, 1986 are collected. This flare is studied in detail by using the flare-filament current model. The momentum equations and the energy equations of the filament current have been solved. The influence of the highly sheared background magnetic field on the motion of the filaments is studied through numerical calculation. The results show that the resistive tearing instability is a possible pre-heating mechanism in the preflare phase, and both the rotation of the spiral sunspots and the highly sheared background field are necessary for the energy storage of this flare. The high-energy data of the flare imply that the current-loop coalescence instability is a possible eruptive mechanism.  相似文献   

关于公元649年临汾地震的讨论   总被引：9，自引：3，他引：6  

丁国瑜 《中国地震》1998,14(3):38-42

唐贞观２３年８月癸酉（公元６４９年９月１２日）河东（黄河以东,今山西省境）地震,晋州（治临汾,今临汾市）尤甚。对此次地震事件的烈度等一直存在不同看法。  相似文献   

Geochemical studies on the intensity of chemical weathering in Luochuan loess-paleosol sequence, China   总被引：4，自引：0，他引：4  

Chen Jun  Ji Junfeng  Qiu Gang  Lu Huayu 《中国科学D辑(英文版)》1998,41(3):235-241

Major and trace element analyses of the Luochuan loess-paleosol sequence in China were performed in order to understand the cheniical weathering processes occurring on the I.oess Plateau during the last 600 ka. Results reveal that most elements in the loess remain immobile durlng chemical weathering. The typical stable elements are Al, K, Ti, Rb and REE, while the main mobile elements are Ca, Sr, P, Mg and Na. 120ess and paleosol experience the incipient stage of chemical weathering characterized by acid leaching and carbonate dissolution. Alteration of silicates in the sequence seems to be limited. Features of less chemical weathering of the loess and paleosol could he indicators for the dry-cold clinlate dominated on the Loess Plateau during the Quaternary. Project supported hy thc Nzitional Natural Science Foundation of China  相似文献   

RESEARCH ON REBUILDING OZONE DYNAMIC SYSTEM OF ZONAL AVERAGE OVER THE TROPIC ZONE     

王卫国  邱金桓  谢应齐  吴涧 《热带气象学报(英文版)》1998,4(2):172-180

The ozone data observed by TOMS in every 5°N are extended into the phase space to describe the characteristics of ozone with phase trace. First of all, the fractional dimension of the ozone layer is calculated. Then.the phase points are regarded as some discrete characteristics solution, and the parameters of mathematical model which describe the time variation of system state are retrieved, so that the nonlinear dynamic system which reflects the short-term variation of zonal average ozone layer over the tropics is rebuilt.  相似文献   

松嫩平原土地次生盐碱化研究   总被引：83，自引：7，他引：76  

李取生  裘善文 《地理科学》1998,18(3):268-272

松嫩平原是我国土地次生盐碱化最严重的地区之一。由于盲目开垦、过度放牧及一些水利工程带来的负效应,土地次生盐碱化迅速发展,每年增长速度达１％￣１．４％。到下世纪初将有４５％左右盐碱化土地退化为基本无利用价值的重盐碱地。主要防治措施有水田、芦苇开发和以藻代排的水利措施,改革草原经营机制、秸杆利用等草场改良和畜牧业发展措施,改土培肥、种植耐盐经济作物等农业技术措施。  相似文献   

花岗岩类源岩与深部地质作用关系研究的若干进展   总被引：1，自引：0，他引：1  

邱瑞照  彭松柏 《湖南地质》1998,17(4):276-279

花岗岩类源岩研究是成岩成矿物质演化过程研究的基础,各种各样花岗岩的存在归因于花岗岩源岩存在多样性,在不同层圈发生交代,熔融,同化,混染作用;同时,成矿元素亦存在不同深度层圈的多来源,在花岗岩成岩成矿过程中,岩石圈地幔起着重要作用。  相似文献   

云南天文台高分辨率斑点成像的新进展   总被引：2，自引：0，他引：2  

刘忠  邱耀辉 《天文学报》1998,39(2):217-224,T002

本文报道了对天文目标：双星ＡＤＳ１６８００、ＡＤＳ１６１７３,三星Ｈｕ６６（ＡＤＳ１１３４４）和Ｈｌｄ１７１（ＡＤＳ１６６４８）进行的斑点成像观测及测量结果。介绍了所用的二维光子计数斑点像探测系统的性能,分析了探测系统的光子噪声、附加噪声和其它更复杂的噪声对斑点图的平均功率谱和重谱的影响。在讨论了改正重谱中的噪声偏差项时提出了对重谱基底施加正性约束的算法。测量的结果表明,实现了高精度的微射受限天文  相似文献   

CSO CO(2–1) and Spitzer IRAC observations of a bipolar outflow in high-mass star-forming region IRAS 22506+5944     

Ze-Qiang Xie  Ke-Ping Qiu 《天文和天体物理学研究(英文版)》2018,(2)

We present Caltech Submillimeter Observatory CO(2–1) and Spitzer IRAC observations toward IRAS 22506+5944, which is a 10~4 L_⊙massive star-forming region. The CO(2–1) maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 μm emission and are located at the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO(2–1) observations with previously published CO(1–0) data, we find that the CO(2–1)/(1–0) line ratio increases from low(~5 kms~(-1)) to moderate(~8–12 kms~(-1)) velocities, and then decreases at higher velocities. This is qualitatively consistent with the scenario that the molecular outflow is driven by multiple bow-shocks. We also revisit the position-velocity diagram of the CO(1–0) data, and find two spur structures along the outflow axis, which are further evidence for the presence of multiple jet bowshocks. Finally, power-law fittings to the mass spectrum of the outflow gives power law indexes more consistent with the jet bow-shock model than the wide-angle wind model.  相似文献   

Challenge of vegetation greening on water resources sustainability: Insights from a modeling‐based analysis in Northwest China          下载免费PDF全文

Fei Tian  Yi He Lü  Bo Jie Fu  Lu Zhang  Chuan fu Zang  Yong Hui Yang  Guo Yu Qiu 《水文研究》2017,31(7):1469-1478

Forest restoration policies are often implemented without the assessment of their full environmental impact. In this study, we investigated the challenges of vegetation greening resulted from forest restoration on water resource sustainability, using a model‐based simulation in northwestern China. Four different vegetation scenarios and 25 future climate scenarios were employed using the Soil and Water Assessment Tool model. Results suggest that (a) the mean annual evapotranspiration changes from only 7.2% in the barren case to 100% in the forest case; however, it produced a 35.2% reduction in average annual streamflow and a 157% increase in soil water storage. The upstream vegetation greening caused the enhancement of water retention, while also creating great challenges for future downstream water resource sustainability; (b) seasonal effect was significant in that 100% forest case increased evapotranspiration (+40%) but it also reduced the streamflow (?73%) compared to the barren case in growing season, which may exacerbate spring and summer drought; (c) changes of evapotranspiration and streamflow were only 0.3% and ?0.9% at T + 3.9 °C when compared to the historic scenario in barren cases, while for all forest cases, variations were 3% and ?21.8%, respectively; (d) vegetation greening induced more remarkable changes in hydrological components than those resulting from climate change. Our “what if” research provides new insights for promoting sustainable management of water resources and ecosystems in mountainous water source areas.  相似文献   

Analysis of dynamics and driving factors of wetland landscape in Zoige, Eastern Qinghai-Tibetan Plateau   总被引：3，自引：0，他引：3  

Pengfei Qiu  Ning Wu  Peng Luo  Zuyuan Wang  Maihe Li 《山地科学学报》2009,6(1):42-55

Zoige Wetland is one of the largest plateau wetlands in the world. This paper provides a dynamic analysis of spatial and temporal patterns of the wetland in Zoige, Eastern Qinghai-Tibetan Plateau, supported by ERDAS8.7 and ArcGIS9.0. It is the first comparative analysis of a system of rapidly changing wetland with landscape patterns in Zoige, using 3 classified landsat Thematic Mapper images of 1977, 1994 and 2001. The classified images were used to generate wetland distributing maps, and shape index （S）, diversity index （H）, dominance index （D）, evenness index （E）, fragmentation index （F） and fractal dimension （Fd） were calculated and analyzed spatiotemporally across pure grazing area in Zoige for each landscape type and in different periods （before 1977, during 1977-1994 and 1994-2001）, as well as the driving forces of natural and anthropogenic. The study shows that for a comprehensive understanding of the shapes and trajectories of the shrinking and desertificated land expansion of the wetland, a spatiotemporal landscape metrics analysis in different periods is an improvement than only with landscape changing rates. This type of analysis can also be used to infer underlying social, economic, and political processes that drive the observed wetland forms. The results indicate that wetland patterns can be changed over relatively short periods of time. The total area of lake reduced by 164.86 km^2, grassland extended by 141.74 km^2, semi-marsh extended by 105.94 km^2, marsh reduced by 86.00 km^2 the number of landscape patches reduced by 56, and their average area decreased by 2.68 km^2, the successions within lake, marsh, semi-marsh and grassland were found obviously. S decreased stepwise： D and F increased but H decreased： The changing rate after 1994 was 2.3 to 2.9 times greater than that before. The change of the wetland landscape patterns resulted in the interaction between socio-ceenomic and natural forces of positive and negative aspects; and natural factors affected as assistant aspect. Some important human activities in this period led to the change of the landscape patterns in this region directly. Some measurements made by government and NGO delayed the converting process partly.  相似文献