干湿交替下水分及氯离子在混凝土中传输的细观数值模拟   总被引：1，自引：0，他引：1       下载免费PDF全文

鲍玖文  王立成 《海洋工程》2014,32(1):68-74

氯离子侵蚀已成为影响海洋及近海环境中混凝土结构耐久性的主要因素。考虑材料组成的非匀质特性,将混凝土看作由粗骨料、硬化水泥砂浆及二者界面过渡区组成的三相复合材料的细观层次方法,是开展物质传输过程研究的新途径。建立非饱和混凝土中氯离子传输的一维非线性对流扩散方程,并利用伽略金加权余数法给出了该方程的有限元形式,采用适用于物质传输的细观格构网络模型开展了水分及氯离子在非饱和混凝土中传输过程及分布规律研究,分析了干湿循环周期和循环机制对水分及氯离子传输性能的影响规律。数值计算结果表明,干湿交替下,相同的干燥时间,非饱和混凝土内水分及氯离子的侵入深度主要取决于湿润时间,而干燥时间和循环周期数则影响混凝土表层氯离子含量,并在混凝土表层10 mm处有浓度集中现象。  相似文献   

盆地埋藏火山机构的地质-地球物理二维精细解剖——以松南腰英台地区营城组一段为例   总被引：2，自引：0，他引：2       下载免费PDF全文

衣健  单玄龙  唐华风  张洋洋  陈玉平 《地球物理学报》2011,54(2):588-596

腰英台地区营城组一段火山岩气藏为火山机构内幕型气藏,其储层分布受火山机构控制.本文以旋回作为时间格架进行火山机构的精细划分.首先通过钻井火山岩岩性、岩相、测井资料识别出的旋回间风化壳和沉积岩夹层等地质界面,地震剖面上全区发育的连续强反射同相轴等划分火山岩的旋回.然后,在旋回内部根据不同钻井岩性、岩相的变化以及火山机构的...  相似文献   

Life history, seasonal variation and production of Andesiops torrens (Lugo-Ortiz and McCafferty) and Andesiops peruvianus (Ulmer) (Ephemeroptera: Baetidae) in a headwater Patagonian stream     

Luis Beltrán Epele  María Laura MiserendinoPablo Pessacq 《Limnologica》2011,41(1):57-62

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松辽盆地白垩系营城组火山岩喷发旋回划分   总被引：3，自引：0，他引：3  

杨帝  王璞珺  梁江平  唐华风  黄玉龙  包丽 《地层学杂志》2011,(2):122-128

鉴于松辽盆地白垩纪营城组火山活动多中心、多旋回、火山物质运动方向多变、成分复杂等特征,依据火山旋回的三个基本要素,即共生序列、内在规律的外部结构表现、同源性,着重考虑对储层研究的指导作用,采用"组内划段-段内划旋回-旋回内划期次"的方案,定义火山旋回为火山活动强度由平静到强烈再到平静而构成的喷发周期内形成的一套火山岩组...  相似文献   

Decadal to millennial cyclicity in varves and turbidites from the Arabian Sea: hypothesis of tidal origin   总被引：1，自引：0，他引：1  

W. H. Berger  U. von Rad 《Global and Planetary Change》2002,34(3-4)

We have analyzed a Late Holocene record, almost 5000 years long, consisting of varved sediments deposited in the oxygen-minimum zone (OMZ) off Pakistan. We searched for cyclicity in the series of varve thickness (“varve” cycles), of unusually large excursions in varve thickness (“agitation” cycles), and of abundance of turbidites (“turbidite” cycles). We found the following high-frequency cycles (periods between 10 and 100 years) in one or several of the three types of series as follows: near 12.4, 14–15, 16.8, 18.6 (strong, agitation), 25–26 (strong, turbidite), 29–31 (strong, agitation), 39 (varve), 44 (strong, turbidite), 51–54 (strong, agitation), 56 (strong, varve), 64 (strong, turbidite), 69, 77 (strong, turbidite), 82 (very strong, agitation), and 95 years (strong, varve). Low-frequency cycles center around 99–115, 125 (very strong, varve), 164, 177, 202, 242–255 (strong, agitation and turbidite), 280 (strong, varve; doubled, turbidite), 340–370 and 460–490 years.Some cycles of varve thickness match the cyclicity of turbidite frequency (12.3, 14–15, 25–26, 245–255 years) but similarities between spectra are not striking. Taken as a whole, however, the sequence of cycles detected (by autocorrelation and standard Fourier analysis) seems to contain a large proportion of multiples of the basic tidal cycles 4.425 (lunar perigee cycle) and 9.3 years (lunar half-nodal cycle). This impression is supported by testing the three binned spectra for whole-number multiples and fractions as well as whole-number beat structure. We therefore propose that a large proportion of the cyclicity detected can be ascribed to tidal action. Our record also contains evidence for the presence of the 1470-year cycle previously reported from the glacial-age Greenland ice record. The main harmonics of this Greenland cycle can be tied to the pattern of periods seen in the varved sediments. We hypothesize that tidal action produces the cycle, and that the reason for its great length is the requirement that maximum tidal activity has to fall into a narrow seasonal window to be geologically effective.  相似文献   

Jamaica Bay studies III: Abiotic determinants of distribution and abundance of gulls (Larus)     

Joanna Burger 《Estuarine, Coastal and Shelf Science》1983,16(2):191-216

The distribution and abundance of gulls were examined at Jamaica Bay Wildlife Refuge (New York) from 31 May 1978 to 31 May 1979. Gulls were found to be affected by tidal, temporal and weather-related factors. The distribution of gulls was affected primarily by tidal factors on the bay, and by temporal (seasonal, circadian) and weather-related factors on the freshwater ponds. The most important weather-related factors were temperature, wind velocity and wind direction. Herring (L. argentatus), great black-backed (L. fuscus) and ring-billed gulls (L. delawarensis) fed on the bay at low tides, and used the ponds at high tide. Laughing gulls (L. atricilla) fed on the bay at low tide and on rising tides. Herring and great black-backed gulls were present all year, but were most abundant in the winter, ring-billed gulls were abundant in spring and early fall, and laughing gulls were present in the summer following the breeding season but were absent in winter. Gulls used the ponds during high velocity, north winds, when they usually rested or preened. Multiple regression models were used to determine the factors explaining the variability in the numbers of gulls. Temporal variables were important contributors to accounting for the variability in the numbers of great black-backed and herring gulls only; tidal variables were significant for great black-backed and herring gulls on the bay, and for ring-billed and laughing gulls on all areas; and weather variables were significant for all species.  相似文献   

Eddy viscosity and tidal cycles in a shallow sea     

D.G. Provis  G.W. Lennon 《Estuarine, Coastal and Shelf Science》1983,16(4):351-361

The very pronounced spring-neap tidal cycle in the South Australian Gulfs leads to an unusually large variation in the magnitude of the tidal currents. Measurements of the currents in these Gulfs show that the non-tidal circulation depends on the strength of the tidal currents and hence on the spring-neap cycle. A simple model is produced in which the vertical eddy viscosity is a function of both wind strength and tidal currents. Results from the model agree with the observations and suggest a means whereby variations in tidal mixing may be accounted for in hydrodynamic modelling of the circulation in shallow seas.  相似文献   

Disk wind in young binaries and the origin of the cyclic activity of young stars     

V. P. Grinin  L. V. Tambovtseva  N. Ya. Sotnikova 《Astronomy Letters》2004,30(10):694-706

We present the results of our numerical simulations of the cyclic brightness modulation in young binary systems with eccentric orbits and low-mass secondary components. We suggest that the binary components accrete matter from the remnants of the protostellar cloud, with the main accretor (according to current models) being the low-mass component. The brightness variations of the primary are attributable to the periodic extinction variations on the line of sight caused by the disk wind from the secondary and by the common envelope produced by this wind. The distribution of matter in the envelope was calculated in the ballistic approximation. When calculating the optical effects produced by the dust component of the disk wind, we adopted the dust-to-gas mass ratio of 1:100 characteristic of the interstellar medium and the optical parameters of the circumstellar dust typical of young stars. Our calculations show that the theoretical light curves for binaries with elliptical orbits exhibit a wider variety of shapes than those for binaries with circular orbits. In this case, the parameters of the photometric minima (their depth, duration, and shape of the light curve) depend not only on the disk-wind parameters and the orbital inclination of the binary to the line of sight, but also on the longitude of the periastron. We investigate the modulation of the scattered radiation from the common envelope with orbital phase in the single-scattering approximation. The modulation amplitude is shown to be at a maximum when the system is seen edge-on and to be also nonzero in binaries seen pole-on. We discuss possible applications of the theory to young stellar objects. In particular, several model light curves have been found to be similar to those of candidate FU Orionis stars (FUORs).  相似文献   

BOOK REVIEWS     

《The Professional geographer》1983,35(4):488-524

Book Reviewed in this article: Main Street: Northeastern Oregon: The Founding and Development of Small Towns . Barbara Ruth Bailey . Food Politics: The Regional Conflict . David N. Balaam and Michael J. Carey , eds. The International Economy and Industrial Development: Trade and Investment in the Third World . R. Ballance , J. Ansari and H. Singer . Neighborhoods in Urban America . Ronald H. Bayor , ed. The English Heartland . By Robert Beckinsale and Monica Beckinsale . Regional Dimensions of Industrial Policy . Michael E. Bell and Paul S. Lande , eds. Tension Areas of the World . D. Gordon Bennett , ed. Latin America: an Introductory Survey . B. W. Blouet and O. M. Blouet , eds. Integration and Division: Geographical Perspectives on the Northern Ireland Problem . Frederick W. Boal and J. Neville H. Douglas , eds. Energy and Land Use . Robert W. Burchell and David Listokin , eds. Slopes and Weathering . Michael Clarke and John Small . Alaska's Rural Development . Peter G. Cornwall and Gerald Mc Beath , eds. The Politics of Park Design: A History of Urban Parks in America . Galen Cranz . World Congress on Land Policy, 1980, Proceedings . Matthew Cullen and Sharon Woolery , eds. Oregon Divided: A Regional Geography . Samuel N. Dicken and Emily F. Dicken . Urban Food Marketing and Third World Rural Development . T. Scarlett Epstein . South Africa: Spatial Frameworks for Development . T. J. D. Fair . Institutions and Geographical Patterns . Robin Flowerdew , ed. Industrialization of U.S. Agriculture, An Interpretive Atlas . Howard F. Gregor . Planning Theory: Prospects for the 1980s . Patsy Healy , Glen Mc Dougall and Michael J. Thomas , eds. Neighborhood Mobilization: Redevelopment and Response . Jeffrey R. Henig . The American Urban System: A Geographical Perspective . R. J. Johnston . Climate, History and the Modern World . Hubert H. Lamb . Climate and History: Studies in Past Climates and Their Impact on Man . T. M. L. Wigley , M. J. Ingram and G. Farmer . China: Railways and Agricultural Development, 1875–1935 . Ernest P. Liang . A Desirable Energy Future—A National Perspective . Robert S. Livingston , T. D. Anderson , T. M. Besmann , M. Olszewski , A. M. Perry , and C. D. West . Topothesia: Essays Presented to T. S. Ó Máille . B. S. Mac Aodha , ed. Transportation for the Poor: Research in Rural Mobility . Hal S. Maggied . Land Uses in American Cities . Harold M. Mayer and Charles R. Haves . Industrial Organisation and Location . Philip Mc Dermott and Michael Taylor . Human Adaptability: an Introduction to Ecological Anthropology . Emilio F. Moran . Regional Analysis and the New International Division of Labor . Frank Moulaert and Patricia W. Salinas , eds. The Nuclear War Atlas. Victoriaville, Quebec, Canada : Urbanization and Environmental Quality . Isao Orishimo . The Garden of Eden: The Botanic Garden and the Re-Creation of Paradise . John Prest . Earthfire, The Eruption of Mount St. Helens . Charles Rosenfeld and Robert Cooke . Contest for the South China Sea . Marwyn S. Samuels . The Future of the Wetlands: Assessing Visual-Cultural Values . Richard C. Smardon , ed. Tucson: the Life and Times of An American City. C. L. Sonnichsen . The Geography of Multinationals . Michael Taylor and Nigel Thrift , eds. Impact of Marine Pollution on Society . Virginia Tippie and Dana Kester . Reviving the Industrial City: the Politics of Urban Renewal in Lyon and Birmingham . Jerry A. Webman . Andean Reflections: Letters from Carl O. Sauer While on a South American Trip under a Grant from the Rockefeller Foundation, 1942 . Robert C. West , ed. Cartographic Drawing with Computers . P. Yoeli .  相似文献   

Seasonal changes in interstitial salinities and seasonal movements of subtidal benthic invertebrates in the Fraser River estuary,B.C.     

Peter M. Chapman  Ralph O. Brinkhurst 《Estuarine, Coastal and Shelf Science》1981,12(1):49-66

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