A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974: signature of an inner bar   总被引：1，自引：0，他引：1  

Eric Emsellem  Paul Goudfrooij  Pierre Ferruit 《Monthly notices of the Royal Astronomical Society》2003,345(4):1297-1312

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可持续发展进程中的政府能力建设     

芮国强 《广东海洋大学学报》2003,23(2):72-78

可持续发展作为现代化建设的两大战略之一 ,对我国政府的能力提出了挑战。可持续发展战略的实施 ,要求加强政府的作用 ,将政府建设成为强有力而又廉价的政府。为此 ,我国政府应从加强政府的财政汲取能力建设、强化中央政府协调地区发展的能力 ,加强政府调控能力建设、强化中央政府协调当前利益和长远利益、经济利益与生态效益的能力 ,并从根本上转变政府职能、精兵简政、建设廉价高效的政府等方面着手来提高我国政府推进和实施可持续发展战略的能力  相似文献   

An atlas of the optical spectrum of supernova 1987A in the large magellanic cloud     

V. J. Mclntyre  A. C. Gilmore  J. B. Hearnshaw 《Journal of Astrophysics and Astronomy》1990,11(1):81-123

Photographic spectra of SN1987A in the LMC have been obtained from 1987 February 25 to 1988 June 30. Microdensitometer tracings of these have been reduced to intensity and corrections for instrumental response have been applied to the spectra. This paper presents these data in an atlas format, discusses the reduction procedures in detail, and presents radial velocity measurements of selected lines in the spectra  相似文献   

Multiple longshore sand bars in the upper Chesapeake Bay     

Thomas J. Dolan  Robert G. Dean 《Estuarine, Coastal and Shelf Science》1985,21(5):727-743

In the upper Chesapeake Bay (Maryland, U.S.A.) field surveys were conducted at 18 multiple longshore sand bar sites. The multiple bar systems were found in water depths less than approximately 2 m (mean sea level), and exhibited mild bottom slopes of 0·0052 or less. The number of bars composing each system ranged from four to 17 and the spacing between the crests typically increased in the offshore direction, ranging from 12 to 70 m. Bar height also typically increased with distance offshore and ranged from 0·03 to 0·61 m. A grain size analysis of crest and trough sediment did not reveal any significant differences and the sediment was categorized as ‘fine sand’. A review of the literature data indicated that the Chesapeake Bay multiple bars possessed similar characteristics to those found in Gelding Bay (Baltic Sea); similarities in fetch, wave height and tidal range between the two bays may account for this finding. The surf-scaling parameter indicated that the multiple bar systems were extremely dissipative with regard to wave energy, and wave height appeared to be an important factor in controlling bar spacing and bar height. A multiple wave break point hypothesis was discussed as a possible mechanism for the formation of Chesapeake Bay multiple longshore bars, and limited observational evidence appeared to support such a mechanism.  相似文献   

Strain localization in sand: an overview of the experimental results obtained in Grenoble using stereophotogrammetry     

Jacques Desrues  Gioacchino Viggiani 《国际地质力学数值与分析法杂志》2004,28(4):279-321

Experimental results are presented from the extensive program of drained plane strain compression tests on sand carried out in Grenoble over the last two decades. Systematic analysis of photographs of the deforming specimen allowed for measuring deformations and determining strain fields throughout the test, that is: prior to, at, and after the onset of strain localization. The principles, details and accuracy of the procedure are described, as well as its suitability to properly depict the patterns of deformation. Findings concerning the occurrence and progression of strain localization are discussed. The issues of shear band orientation and thickness are addressed, as well as temporary and persistent complex localization patterns, and the volumetric behaviour inside a band after its formation. The influence of such variables as initial state of the sand (effective stress and relative density), specimen size and slenderness, as well as grain size, is discussed. Copyright © 2004 John Wiley & Sons, Ltd  相似文献   

CCD photometry inVRI bands of the galactic cluster NGC 2818     

R. Surendiranath  N. Kameswara Rao  Ram Sagar  J. S. Nathan  K. K. Ghosh 《Journal of Astrophysics and Astronomy》1990,11(2):151-166

bdAbstract The open cluster NGC 2818 containing a planetary nebula has been observed inVRI bands using the CCD system at prime focus of the 2.3-metre Vainu Bappu Telescope. The study extending to starsV ∼ 21 magnitude establishes the distance modulus as(m-M) ₀ = 12.9 ±0.1 for the cluster. Based on the fitting of theoretical isochrones computed for solar metallicity, an age of 5(±1) × 10₈ years has been assigned to the cluster. Association of the planetary nebula with the cluster indicates that the progenitor mass of the planetary nebula on the main sequence is ≥2.5M_⊙ Based on observations obtained with the Vainu Bappu Telescope.  相似文献   

北部湾北部海上油田发现历程     

钟铿  潘其云 《南方国土资源》1997,(2)

北部湾北部海上油田的开发工作始于５０年代，６０～７０年代作了大量地质工作。改革开放后，油气勘查取得突破性进展。累计发现油气构造６个，含油面积超过４０ｋｍ２，石油地质储量约４亿ｔ，已开发油田２个，揭开我国南方油气资源开发序幕  相似文献   

新疆阿尔泰哈巴河一带古生代火山岩的形成与演化     

Zhang Chuanling 《地球科学与环境学报》1997,(1)

文中详细地论述了新疆阿尔泰哈巴河一带古生代火山岩的地质、岩石化学、稀土元素地球化学特征。将其分为三个类型，认为火山岩是在陆缘裂陷槽的区域构造背景下发生和演化的。对各类型火山岩岩浆来源，上升模式也做了初步讨论。  相似文献   

西宁盆地泥石流类型及其防治意见     

洪文之  徐旭 《青海国土经略》1997,(1)

概略地叙述了西宁地区的泥石流形成条件和形成机理,并将西宁地区泥石流划分为稀性泥石流类及泥石质泥石流种类。在此基础上提出防治泥石流灾害的意见。  相似文献   

Towards a free–free template for CMB foregrounds     

C. Dickinson  R. D. Davies  R. J. Davis 《Monthly notices of the Royal Astronomical Society》2003,341(2):369-384

A full-sky template map of the Galactic free–free foreground emission component is increasingly important for high-sensitivity cosmic microwave background (CMB) experiments. We use the recently published Hα data of both the northern and southern skies as the basis for such a template.
The first step is to correct the Hα maps for dust absorption using the 100-μm dust maps of Schlegel, Finkbeiner & Davis. We show that for a range of longitudes, the Galactic latitude distribution of absorption suggests that it is 33 per cent of the full extragalactic absorption. A reliable absorption-corrected Hα map can be produced for ∼95 per cent of the sky; the area for which a template cannot be recovered is the Galactic plane area  | b | < 5°, l = 260°–0°–160°  and some isolated dense dust clouds at intermediate latitudes.
The second step is to convert the dust-corrected Hα data into a predicted radio surface brightness. The free–free emission formula is revised to give an accurate expression (1 per cent) for the radio emission covering the frequency range 100 MHz–100 GHz and the electron temperature range 3000–20 000 K. The main uncertainty when applying this expression is the variation of electron temperature across the sky. The emission formula is verified in several extended H  ii regions using data in the range 408–2326 MHz.
A full-sky free–free template map is presented at 30 GHz; the scaling to other frequencies is given. The Haslam et al. all-sky 408-MHz map of the sky can be corrected for this free–free component, which amounts to a  ≈6  per cent correction at intermediate and high latitudes, to provide a pure synchrotron all-sky template. The implications for CMB experiments are discussed.  相似文献