排序方式： 共有17条查询结果，搜索用时 15 毫秒
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N. N. Bursov Yu. N. Pariĭskiĭ E. K. Maĭorova M. G. Mingaliev A. B. Berlin N. A. Nizhel’skiĭ I. A. Glushkova T. A. Semenova 《Astronomy Reports》2007,51(3):197-214
A catalog of radio sources detected in a deep RATAN-600 survey is presented. The catalog was obtained in the region 0h ≤ RA2000.0 ≤ 24h, Dec2000.0 = 41°30′42″ ± 2′, at the declination of the bright radio source 3C 84. There were nine sessions of multi-wavelength observations at wavelengths λ = 1–55 cm, and more than 300 daily scans were accumulated at each wavelength. This is the first stage in the reduction of an extensive database accumulated by the Cosmological Gene Project. The RATAN-600 Zenith Field (RZF) catalog was obtained at the central wavelength of 7.6 cm, and contains 437 radio sources, virtually all of which have been identified with NVSS objects. Most of the flux densities for the catalog sources are above the 5σ level. Noise from faint (mainly new) background sources at a level of about 0.8 mJy has been detected. The minimum flux density of the catalog, 2.5 mJy, is comparable to the flux-density linit of the NVSS catalog. The catalog is more than 80% complete for sources with flux densities >3 mJy. 相似文献
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A. I. Kopylov W. M. Goss Yu. N. Pariĭskiĭ N. S. Soboleva O. V. Verkhodanov A. V. Temirova O. P. Zhelenkova 《Astronomy Letters》2006,32(7):433-438
A strong emission line at 6703 Å has been detected in the optical spectrum for the host galaxy (R = 23.1) of the radio source RC J0311+0507 (4C+04.11). This radio galaxy, with a spectral index of 1.31 in the frequency range 365–4850 MHz, is one of the ultrasteep-spectrum objects from the deep survey of a sky strip conducted with RATAN-600 in 1980–1981. We present arguments in favor of the identification of this line with Lyα at redshift z = 4.514. In this case, the object belongs to the group of extremely distant radio galaxies of ultrahigh radio luminosity (P 1400 = 1.3 × 1029 W Hz?1). Such power can be provided only by a fairly massive black hole (～109 M⊙) that formed in a time less than the age of the Universe at the observed z (1.3 Gyr) or had a primordial origin. 相似文献
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Morphology,structure and kinematics of a rainfall controlled slow‐moving Andean landslide,Peru 
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下载免费PDF全文 Swann Zerathe Pascal Lacroix Denis Jongmans Jersy Marino Edu Taipe Marc Wathelet Walter Pari Lionel Fidel Smoll Edmundo Norabuena Bertrand Guillier Lucile Tatard 《地球表面变化过程与地形》2016,41(11):1477-1493
The large slow‐moving landslide of Maca is located in the upper Colca valley (southern Peru), a region characterized by a well pronounced rainy period, and intense and recurrent sustained seismicity. The landslide, developed in deep lacustrine deposits, has recently accelerated, threatening the Maca village. This work aims at understanding the rupture mechanism and the causes of the recent landslide reactivation/acceleration. We present a multidisciplinary characterization of the Maca landslide that includes: (i) geological and morphological mapping in the field; (ii) remote sensing analysis using an historical aerial photograph of 1955 and the Pléiades satellite images (2013); (iii) global positioning system (GPS) including time‐series of surveys over 13 years, and continuous measurements over 14 months; (iv) a geophysical campaign with deep electrical resistivity tomography profiles acquired across the landslide mass. Our study shows that this 60 Mm3 landslide, which can be classified as a clay/silt compound landslide, moved by 15 m between 2001 and 2014 with a large inter‐annual velocity variation (up to a factor of 500) depending on the rainfall intensity. We suggest that these dramatic changes in velocity are the result of the combination of a threshold mechanism and the short intense rainy season in Peru. This study reveals three main driving factors acting at different timescales: (i) over several decades, the river course has significantly changed, causing the Maca landslide reactivation in the 1980s due to the erosion of its toe; (ii) at the year scale, a minimum amount of rainfall is required to trigger the motion and this amount controls the landslide velocity; (iii) transient changes in slide velocity may occur anytime due to earthquakes. This study particularly highlights the non‐linear behaviour of the motion with rainfall. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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The purpose of this paper is to examine the nature of particle saltation and movement over the beds of fixed roughness from flume experiments. A series of experiments are carried out to study the saltation of individual sand particles of different sizes over rough beds under different flow conditions. A 3‐D acoustic Doppler velocimeter is used to record the fluid velocity components; subsequently, under different flow conditions, the images of released sand particles are recorded using high‐speed video imaging technique. Systematic analysis is made with regard to the forces acting on the grains and the variation of their magnitudes along the saltation trajectories of the grains. Relations between the saltation parameters, flow intensity and bed roughness are developed. The distributions of the angle of orientations during a single saltation follows almost a Gaussian distribution. The shape of the Gaussian distribution depends on the particle size and bed roughness. Particle collisions with rough beds and the resulting coefficients of restitution are also discussed. A theoretical framework is developed to compute the mean particle velocity considering the spin in the energy balance equation. Results of the detailed analysis using the imaging technique are much better than in previously reported studies. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Nagapattinam, in the east coast of India, was severely affected during the deadliest Indian Ocean tsunami of December 26,
2004. The tsunami caused heavy damage to life and property, and the death toll was about 3,378 in Nagapattinam taluk. Certain
villages along the coast witnessed large inundation while adjacent villages were protected from the fury of the tsunami waves.
This study was carried out to examine the underlying causes for the vulnerability along Nagapattinam coast with the help of
field observations, remote sensing, and geographical information system as tools. Coastal areas with high sand dunes have
been protected from tsunami, and areas adjacent to backwaters were inundated. Realtime Kinematic Global Positioning System
and high-resolution satellite data were used to map the topographic information and maximum extent of inundation. Thematic
maps on land use, land cover, and coastal geomorphology were generated using remote sensing and field data. Using field data
as the primary source of information, tsunami hazard maps have been generated for Nagapattinam. 相似文献
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Adnan K. M. Mehedi Ying Liu Sarker Swati Anindita Yu Man Eliw Moataz Sultanuzzaman Md. Reza Huq Md. Enamul 《GeoJournal》2021,86(4):1981-1998
GeoJournal - Risk and uncertainty are distinctive features of agricultural cultivation, which significantly affect the production and income. Risk management is an important way for farmers to... 相似文献
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Assessment of the wave climate at near coast is vital for estimation of morphological changes, such as growth of sand spit
and associated siltation of tidal inlets. Vellar (bar-built) estuary is one of the prominent estuaries along the southeast
coast of India, located at 11°30′N and 79°46′E, less studied in terms of its morphological features. The inlet of Vellar is
exposed to high energetic waves, inducing large sediment transport rates and shoreline changes. Local wave characteristics
are not accurately defined and the available wave information at near coast is limited (point based observations). In the
present study, three decoupled numerical models are employed to derive the monthly nearshore wave climate at Vellar by transforming
waves from deep water to nearshore. These models are independently validated with buoy observations in deep water and wave
gauge data at nearshore. Based on the nearshore wave data, littoral drift along the coast was estimated and compared with
the spit growth at Vellar inlet. The estimated average littoral drift along this coast from February to October is 1.93 × 106 m3 toward north and from November to January it is 1.52 × 106 m3 toward south, resulting in a net northerly drift. Results indicated that increase in the wave energy during the period of
July to September is responsible for the maximum growth of the sand spit observed in the field. 相似文献