The kinematics of the large western knot in the halo of the young planetary nebula NGC 6543     

Deborah L. Mitchell  M. Bryce  J. Meaburn  J. A. López  M. P. Redman  D. Harman  M. G. Richer  H. Riesgo 《Monthly notices of the Royal Astronomical Society》2005,362(4):1286-1294

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Photometric distances to nine dark globules     

G. Maheswar  H. C. Bhatt 《Monthly notices of the Royal Astronomical Society》2006,369(4):1822-1836

Distances to nine dark globules are determined by a method using optical ( VRI ) and near-infrared (near-IR) ( JHK ) photometry of stars projected towards the field containing the globules. In this method, we compute intrinsic colour indices of stars projected towards the direction of the globule by dereddening the observed colour indices using various trial values of extinction   A _V   and a standard extinction law. These computed intrinsic colour indices for each star are then compared with the intrinsic colour indices of normal main-sequence stars and a spectral type is assigned to the star for which the computed colour indices best match with the standard intrinsic colour indices. Distances ( d ) to the stars are determined using the   A _V   and absolute magnitude  ( M_V )  corresponding to the spectral types thus obtained. A distance versus extinction plot is made and the distance at which   A _V   undergoes a sharp rise is taken to be the distance to the globule. All the clouds studied in this work are in the distance range 160–400 pc. The estimated distances to dark globules LDN 544, LDN 549, LDN 567, LDN 543, LDN 1113, LDN 1031, LDN 1225, LDN 1252 and LDN 1257 are  180 ± 35, 200 ± 40, 180 ± 35, 160 ± 30, 350 ± 70, 200 ± 40, 400 ± 80, 250 ± 50  and 250 ± 50 pc, respectively. Using the distances determined, we have estimated the masses of the globules and the far-IR luminosity of the IRAS sources associated with them. The mass of the clouds studied are in the range  10–200 M_⊙  .  相似文献   

Method for evaluating the degrees of land use sustainability of mountainous county and its application in Yunnan Province,China   总被引：4，自引：1，他引：3  

Zisheng Yang  Yansui Liu  Wenxing Tao  Jingjing Xu  Qiaogui Zhao 《山地科学学报》2008,5(2):98-112

The evaluation of sustainable land use is the key issue in the field of studying the sustainable land utilization. In general analysis, the sustainable land use is evaluated respectively from its ecological sustainability, economic sustainability and social sustainability in China and other countries in recent years. Although this evaluation is an important work, it seems insufficient and hard to comprehensively reflect the whole degree of land use sustainability. Thus, to make up this deficiency, this paper brings forward the evaluation indexes, which make it possible to quantitatively reflect the whole degree of land use sustainability, namely, the concept of ＂degrees of overall land use sustainability＂ （Dos）, and research and measurement development of the method of and calculation in Dos. Taking the evaluation of the degree of land use sustainability in county regions of Yunnan Province as the actual example for analysis, results are basically as follows：
1） The degree of land use sustainability （Dos） is the ration index to organically and systematically integrate the degree of ecological friendliness （DeF）, the degree of economic viability （Dev） and the degree of social acceptability （Dsa）, able to comprehensively reflect the whole sustainability degree of regional land use
2） Based on the value of Dos, the grading system and standard for the sustainability of land use may be established and totally divided into five grades, namely, the high-degree sustainability, middle-degree sustainability, low-degree sustainability, conditional sustainability and non-sustainability. Meanwhile, the standard for distinguishing sustainability grades has also been confirmed so as to determine the nature of sustainability degrees in different grades. This makes the possibility for the combination of nature determination with ration in research result and provides with the scientific guideline and decision-making gist for better implementation of sustainable land use strategy.
3） The pract  相似文献   

胶辽鲁西徐淮地区新元古代地层多重划分对比          下载免费PDF全文

许克民  王来明  刘桂玲  张增奇  汪又平  胡艳蕾 《山东国土资源》2004,20(5):26-31,36

依据岩性组合、古生物特征及地震事件层研究，对胶辽鲁西徐淮地区新元古代地层可作如下多重划分对比：鲁西黑山官组、二青山组分别与辽东的钓鱼台组，南芬组相当，胶东豹山口组可与南芬组对比，它们同属青白口系。辽东南关岭组下部、鲁西石旺庄组下部、苏皖北部贾园组、淮南九里桥组皆为一套砂灰岩组合，都发育第一期地震事件层，并开始含有后生动物化石，为等时地层单位，与其以上各前寒武岩石地层单位同属灯影峡阶，鲁西的佟家庄组、浮来山组可分别与辽东桥头组、长岭子组、胶东辅子夼组、南庄组、苏皖北部兰陵组一城山组、淮南伍山组一四十里长山组对比，归属《中国区域年代地层(地质年代)表》新划分的陡山陀阶。  相似文献   

Tanlu Fault Zone and Gold Ore Metallogenesis     

SHEN Yuanchao  ZENG Qingdong  LIU Tiebing 《东北亚地学研究》2002,(1)

Tanlu Fault Zone (TFZ) is a large NE trending deep fracture system in East China and is about 2500 km long. It extends from the south of Lujiang to Tancheng, and passes through the Bohai Sea and continues to the north, where it branches into Yilan ?Shulan Fault and Dunhua ?Mishan Fault. TFZ is a long lasting huge deep - rooted lithospherical fault system with different characteristics in different parts and at different periods of its evolution. TFZ also controls the distribution and occur-rences of many superlarge, large, middle and small sized gold ore deposits, e. g. Jiapigou, Haigou, Xiaoxihancha and Ciwei-gou gold deposits in Northeast China; Linglong, Jiaojia, Sanshandao, Taishang, Xincheng, Rushan, and Pengjiakuang gold deposits in Jiaodong Peninsula of Shandong Province; and Guilaizhuang and Yinan in Western Shandong Province.  相似文献   

Is there a disc in the superluminal quasars?     

E. Rokaki  A. Lawrence  F. Economou  A. Mastichiadis 《Monthly notices of the Royal Astronomical Society》2003,340(4):1298-1308

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The intracluster iron distribution around 4C+55.16     

K. Iwasawa  A.C. Fabian  S.W. Allen  S. Ettori 《Monthly notices of the Royal Astronomical Society》2001,328(1):L5-L10

We report on the metal distribution in the intracluster medium around the radio galaxy 4C+55.16     observed with the Chandra X-ray Observatory . The radial metallicity profile shows a dramatic change at 10 arcsec (∼50 kpc) in radius from half solar to twice solar at inner radii. Also found was a plume-like feature located at ∼3 arcsec to the south-west of the centre of the galaxy, which is mostly accounted for by a strong enhancement of iron L emission. The X-ray spectrum of the plume is characterized by the metal abundance pattern of Type Ia supernovae (SNeIa), i.e. large ratios of Fe to α elements, with the iron metallicity being unusually high at     solar (90 per cent error). How the plume has been formed is not entirely clear. The inhomogeneous iron distribution suggested in this cluster provides important clues to understanding the metal enrichment process of the cluster medium.  相似文献   

Porous interstellar grains     

M. A. Iatì  C. Cecchi-Pestellini  D. A. Williams  F. Borghese  P. Denti  R. Saija  S. Aiello 《Monthly notices of the Royal Astronomical Society》2001,322(4):749-756

Recent observations of stellar composition suggest that elements in the Sun are significantly more abundant than in other stars. The reduction in the available element budget implies a drastic revision in current models of interstellar dust. Theoretical models are therefore exploring fluffy, porous physical structure for the grain material. Since a detailed exact treatment of extinction cross-sections is mandatory for a correct understanding of the nature of interstellar dust, we present a technique based on the multipole expansions of the electromagnetic field, which has proven to be general, flexible and powerful in treating scattering of light by porous, composite, arbitrarily shaped particles. The results of this study speak in favour of core–mantle structures characterized by the presence of porosities.  相似文献   

青海省沙柳河南区有色金属矿成矿物质来源及矿床成矿模式探讨     

马永铨  姜洪成 《青海国土经略》1994,(1)

本文简述了沙柳河南区有色金属矿床的基本特征。通过对成矿热液及成矿物质的来源与性质的研究,认为该矿床的成因类型为火山沉积—接触交代改造叠加型,进而探讨了该矿床的成矿模式。  相似文献   

A ROSAT WFC observation of SW UMa: the EUV behaviour of dwarf novae in superoutburst explained     

M.R. Burleigh  J.P. Pye  S.W. Poulton  K.B. Sohl  P.J. Wheatley  G.A. Wynn 《Monthly notices of the Royal Astronomical Society》2001,325(4):1458-1462

During re-processing and analysis of the entire ROSAT Wide Field Camera (WFC) pointed observations data base, we discovered a serendipitous, off-axis detection of the cataclysmic variable SW UMa at the onset of its 1997 October superoutburst. Although long outbursts in this SU UMa-type system are known to occur every ∼ 450 d, none had ever been previously observed in the extreme ultra-violet (EUV) by ROSAT . The WFC observations began just ≈13 hr after the optical rise was detected. With a peak count rate of ∼ 4.5 count s⁻¹ in the S1 filter, SW UMa was temporarily the third brightest object in the sky in this waveband. Over the next ≈19 hr the measured EUV flux dropped to < 2 count s⁻¹, while the optical brightness remained essentially static at m _v∼11 . Similar behaviour has also been recently reported in the EUV light curve of the related SU UMa-type binary OY Car during superoutburst, as reported by Mauche & Raymond. In contrast, U Gem-type dwarf novae show no such early EUV dip during normal outbursts. Therefore, this feature may be common in superoutbursts of SU UMa-like systems. We expand on ideas first put forward by Osaki and Mauche & Raymond and offer an explanation for this behaviour by examining the interplay between the thermal and tidal instabilities that affect the accretion discs in these systems.  相似文献