A Linear Dependence between the Magnitude and the Logarithm of the Length of the Time the Quasars OJ287 and 3C345 Stay below this Magnitude     

Jin He  G.Z. Xie 《Astrophysics and Space Science》1997,254(2):223-232

We have studied the optical historical light curves of two Active Galactic Nuclei (AGNs): OJ287 and 3C345. We find a linear dependence between the magnitude and the logarithm of the length of the time the objects stay below this magnitude. The relation may originate from a fractal structure of the light curve. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The Magnetic Topological Structure and Energy of the 2B/X2 Flare in NOAA 8100     

Yihua Yan  Yang Liu  Maki Akioka  Fengsi Wei 《Solar physics》2001,201(2):337-355

In this paper, we reconstruct the finite energy force-free magnetic field of the active region NOAA 8100 on 4 November 1997 above the photosphere. In particular, the 3-D magnetic field structures before and after a 2B/X2 flare at 05:58 UT in this region are analyzed. The magnetic field lines were extrapolated in close coincidence with the Yohkoh soft X-ray (SXR) loops accordingly. It is found that the active region is composed of an emerging flux loop, a complex loop system with differential magnetic field shear, and large-scale, or open field lines. Similar magnetic connectivity has been obtained for both instants but apparent changes of the twisting situations of the calculated magnetic field lines can be observed that properly align with the corresponding SXR coronal loops. We conclude that this flare was triggered by the interaction of an emerging flux loop and a large loop system with differential magnetic field shear, as well as large-scale, or open field lines. The onset of the flare was at the common footpoints of several interacting magnetic loops and confined near the footpoints of the emerging flux loop. The sheared configuration remained even after the energetic flare, as demonstrated by calculated values of the twist for the loop system, which means that the active region was relaxed to a lower energy state but not completely to the minimum energy state (two days later another X-class flare occurred in this region).  相似文献   

紫阳滑坡治理工程实例分析     

刘满全 《地球科学与环境学报》1994,(2)

本文介绍紫阳骨坡治理工程中有关抗滑桩的设计与施工。文中详细地论述了设计中设计人员应根据工程的具体情况去灵活处理的一些技术问题，如确定有关参数的选择原则，计算上的条件简化和一些具体技术细节的处理方法等．  相似文献   

CSCO_3 CYCLES IN SALAWUSU RIVER BASINSINCE 150KA B.P.     

LUO Kai-li    LI Bao-sheng    ZHU Yi-zhi  JIN He-ling  ZHANG David Dian  YAN Man-cun  LI Hou-xin  YAO Chun-xia  ZHANG Yu-hongf . Department of Geography  South China Normal University  Guangzhou  P. R. China  . State Key Labor 《中国地理科学(英文版)》2001,11(4):336-342

About 70years ago，Frenc卜卜alaeohdoglst回LL sc卜dars al卜ome and a卜road卜ave successively con－HARD de Chardin P．et al．Initiated the Quaternary ducted large amount ofwork on the Later Quaternarygeologlcal research In the ＞alawusu River Basin of strata（TEILHARD，1924； YUAN，1978； LI，1987；desert region of Northern China and established th，ZHENG，1989； SUN et al，1996； LI et al，1993），Salawusu Formation门EILHARD，1924）．Sine，then，palaeobiology…  相似文献   

Numerical calculations in the orbital determination of an artificial satellite for a long arc     

Lin Liu  Xinhao Liao 《Celestial Mechanics and Dynamical Astronomy》1994,59(3):221-235

Numerical methods are usually used for the computation of ephemerides with perturbations for the precise orbital determination of an artificial satellite. But their numerical stability will be encountered in a long arc. In this case the use the improved Encke special perturbation methods has been suggested. The results of this paper show that Encke's method does indeed have a certain effectiveness, but cannot yet completely resolve the numerical stability, and the more efficient method is to use the energy integral or its variational relation to control the growth of the along-track error in general numerical calculations so that the aim of stabilization can be achieved.  相似文献   

FARMLAND AND URBAN AREA DYNAMICS MONITORING INCHINA USING REMOTE SENSING AND SPATIALSTATISTICS METHODOLOGY     

LIU Ming-liang  ZHUANG Da-fang  LIU Ji-yuan 《中国地理科学(英文版)》2001,11(1):42-49

1 INTRODUCTIONGlobal change research involves much geo-objectsand geo-process, such as climate and environmentalchange, substance and energy cycling, land-use/land-cover change (LUCC), interactivity between human and nature, etc.. So it need cooperation frommany research communities including international research programs groups such as IGBP (InternationalGeosphere-Biosphere Programme IPCC (Intergovemmental Panel on Climate Change), IHDP (InternationalHuman Dimension Program o…  相似文献   

黄河下游窄河道挖河疏浚是维持黄河健康生命的重要措施之一          下载免费PDF全文

刘景国  许考云 《山东国土资源》2005,21(9):21-23

黄河水利委员会提出了“维持黄河健康生命”的治河新理念，把维持黄河健康生命作为黄河开发与管理的终极目标。“堤防不决口，河道不断流，污染不超标，河床不抬高”是实现其终极目标的4个主要标志。河床不抬高就要通过综合措施解决泥沙问题，包括上中游拦减人黄泥沙，中下游采取人工调控水沙“关系”，在黄河下游挖河疏浚。在黄河下游窄河道特别是在河口地区挖河疏浚，减少其对下游河道的反馈影响，是维持黄河健康生命的重要措施之  相似文献   

陕西秦巴山区农业自然资源开发利用     

刘胤汉  陆立新 《山地学报》1990,(1)

农业自然资源据其在农业利用过程中的地位可分为两类:一类是生成农业自然资源的环境,另一类为可资直接利用的自然生成物(即狭义的农业自然资源)。陕西秦巴山区自然环境的主要特点是:复合山体高峻庞大,地跨暖温带和北亚热带,垂直分异明显。区内有:森林、草场、野生生物、林特产与农作物等多种农业自然资源。据此,提出了本区农业自然资源的开发利用途径。  相似文献   

现代天文选址中的视宁度（Ⅱ）     

仇朴章  刘忠 《天文学进展》1996,14(3):175-180

在文献」１「４ 基础上，根据近年文选址实践中提出的问题，先进一步讨论了大气相干直径和时间的的物理和意义，然后强调了自由大气湍流的天文成像效应及选址中进行研究和测量的重要性。最后对差分像运动方法测量视宁度的定标和系统误差等问题作了分析。  相似文献   

The nature of parallax microlensing events towards the Galactic bulge     

Martin C. Smith  Vasily Belokurov  N. Wyn Evans  Shude Mao  Jin H. An 《Monthly notices of the Royal Astronomical Society》2005,361(1):128-140

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