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排序方式: 共有187条查询结果,搜索用时 15 毫秒
21.
János Kovács Szabolcs Á. Fábián Gábor Varga Karoly Németh Corina Risso Francisco Nullo Gabor Kereszturi Titusz Bugya Szabolcs Á. Fábián Noémi L. Görcs István P. Kovács Bertalan Radvánszky Gabriella Barta Rudolf Musil Alice Ghiselli Marzio Merazzi Andrea Strini Roberto Margutti Michele Mercuriali Rauf Gardashov Daria Gushchina Boris Dewitte Martin Michálek Marián Putiš Christoph A. Hauzenberger Jindřich Šancer Martin Štrejbar Aneta Maleňáková George Migiros George D. Bathrellos Hariklia D. Skilodimou Theodoros Karamousalis 《Central European Journal of Geosciences》2011,3(2):229-229
22.
Jean-Denis Taupin Gaëlle Gaultier Guillaume Favreau Christian Leduc Christelle Marlin 《Comptes Rendus Geoscience》2002,334(1):43-50
The isotopic content of rainfall was measured in Niamey (Niger) over a period of eight years (1992–1999). Seasonal distribution of rainy events depends on the monsoon movement over the region. At the beginning and at the end of the rainy season, low rainfall, high temperatures and low relative humidity favour isotopic enrichment. In the middle of the rainy season, heavy rainfall, low temperatures and relative humidity close to saturation lead to isotopically depleted contents because of the mass effect; moreover, in the case of low rainfall, marked vertical convective development favours high altitude condensation. How far the Intertropical Front moves north, determines the quality of the rainy season and influences the isotopic contents. Thus the isotopic contents of rainfall are good climatic indicators. To cite this article: J.-D. Taupin et al., C. R. Geoscience 334 (2002) 43–50 相似文献
23.
水位下降是导致滑坡的重要原因之一,而土钉是加固土坡的有效手段。进行离心模型试验,再现了水位下降时土钉加固土坡的变形和破坏过程,测量了土坡的位移变化。试验结果表明,水位下降条件下土钉加固土坡的破坏模式以绕钉破坏为主,滑裂面从坡顶逐渐向下发展至坡面;土钉加固土坡的破坏过程与变形局部化过程表现出显著的耦合变化;土钉加固机制主要表现为通过土钉与坡体的相互作用,减小土坡的变形和变形局部化程度,从而提高土坡的稳定性。增加土钉长度使得滑裂面向坡内部移动,显著减小土坡的变形及变形局部化程度,从而提高了土坡安全性。 相似文献
24.
Benjamin R. K. Runkle Christian Wille Michal Gažovič Lars Kutzbach 《Boundary-Layer Meteorology》2012,142(3):401-423
Evapotranspiration is a source of water vapour to the atmosphere, and as a crucial indicator of landscape behaviour its accurate
measurement has widespread implications. Here we investigate errors that are prevalent and systematic in the closed-path eddy-covariance
measurement of latent heat flux: the attenuation of fluxes through dampened cospectral power at high frequencies. This process
is especially pronounced during periods of high relative humidity through the adsorption and desorption of water vapour along
the tube walls. These effects are additionally amplified during lower air temperature conditions. Here, we quantify the underestimation
of evapotranspiration by a closed-path system by comparing its flux estimate to simultaneous and adjacent measurements from
an open-path sensor. We apply models relating flux loss to relative humidity itself, to the lag time of the cross-correlation
peak between the water vapour and vertical wind velocity signals, and to models of cospectral attenuation relative to the
cospectral power of simultaneous sensible heat-flux measurements. We find that including the role of temperature in modifying
the attenuation–humidity relationship is essential for unbiased flux correction, and that physically based cospectral attenuation
methods are effective characterizers of closed-path instrument signal loss relative to the unattenuated flux value. 相似文献
25.
Yann Marcon Heiko Sahling Anne‐Gaëlle Allais Gerhard Bohrmann Karine Olu 《Marine Ecology》2014,35(1):77-95
The Regab pockmark is a large cold seep area located 10 km north of the Congo deep sea channel at about 3160 m water depth. The associated ecosystem hosts abundant fauna, dominated by chemosynthetic species such as the mussel Bathymodiolus aff. boomerang, vestimentiferan tubeworm Escarpia southwardae, and vesicomyid clams Laubiericoncha chuni and Christineconcha regab. The pockmark was visited during the West African Cold Seeps (WACS) cruise with RV Pourquoi Pas? in February 2011, and a 14,000‐m2 high‐resolution videomosaic was constructed to map the most populated area and to describe the distribution of the dominant megafauna (mussels, tubeworms and clams). The results are compared with previous published works, which also included a videomosaic in the same area of the pockmark, based on images of the BIOZAIRE cruise in 2001. The 10‐year variation of the faunal distribution is described and reveals that the visible abundance and distribution of the dominant megafaunal populations at Regab have not changed significantly, suggesting that the overall methane and sulfide fluxes that reach the faunal communities have been stable. Nevertheless, small and localized distribution changes in the clam community indicate that it is exposed to more transient fluxes than the other communities. Observations suggest that the main megafaunal aggregations at Regab are distributed around focused zones of high flux of methane‐enriched fluids likely related to distinct smaller pockmark structures that compose the larger Regab pockmark. Although most results are consistent with the existing successional models for seep communities, some observations in the distribution of the Regab mussel population do not entirely fit into these models. This is likely due to the high heterogeneity of this site formed by the coalescence of several pockmarks. We hypothesize that the mussel distribution at Regab could also be controlled by the occurrence of zones of both intense methane fluxes and reduced efficiency of the anaerobic oxidation of methane possibly limiting tubeworm colonization. 相似文献
26.
近30年来西藏那曲地区湖泊变化对气候波动的响应 总被引:29,自引:4,他引:29
根据1975年地形图、20世纪80年代至2005年的TM、CBERS卫星遥感资料和近45年的气温、降水量、蒸发量、最大积雪深度和最大冻土深度等气候资料分析得出,西藏那曲地区东南部的巴木错、蓬错、东错、乃日平错等四个湖泊的水位面积在近30年来呈较显著的扩大趋势,2005年与1975年相比,分别增加了48.2 km2、38.2km2、19.8 km2 (比2004年)、26.0 km2,增长幅度分别为25.6%、28.2%、16.2%、37.6%。其主要原因与该地区近年来气温的上升、降水量的增加和蒸发量的减少、冻土退化等暖湿化的气候变化有很大关系。 相似文献
27.
28.
Jarrah Mohammed Ahmed Babiker Mustafa Mohammed Hariri Osman Abdullatif Gabor Korvin 《Arabian Journal of Geosciences》2017,10(6):146
This study evaluates the Late Ordovician glaciofluvial deposits of the Sarah Formation and equivalent outcroppings in north, central, and southwestern Saudi Arabia. The Sarah Formation also covers a wide area in the subsurface and is considered as an important target for unconventional tight gas reservoir. Defining the fracture types, nature, and distribution in outcrop scale might help to establish a successful fracture simulation model and behavior for the Sarah tight gas reservoir in the subsurface. This study investigates fracture characteristics for the Sarah Formation at Sarah paleochannel outcrops. The study revealed three sets of fractures, which have EW, NS, and SE-NW directions, and these fractures vary from open, resistive, and filled to resistive fractures. The closed fractures are filled with ferruginated iron oxides and gypsum. The filled fractures (the thrust boundary) are found in the study area at the SE-NW strike fracture set, while open and resistive fractures are found mainly at S-N and E-W fracture sets, respectively. The syn-depositional filled fractures (iron oxides) are considered as the younger fracture sets while the open and resistive fractures are post-depositional fractures which may have resulted from uplift or tectonic movement. A general model representing the fracture pattern and the thrusting boundaries due to glacial movement was constructed. It has been noticed that the systematic occurrence of filled fractures (thrust boundaries) described the boundaries between different glacial events, which act as a fluid barrier (filled fractures) and decrease the reservoir quality. The finding of this study might be utilized as a guide and lead for exploration in the subsurface Sarah glacial deposits. It will also help to understand and speculate the nature pattern and distribution of fractures with the Sarah Formation. 相似文献
29.
Gabor Korvin Klavdia Oleschko Abdulazeez Abdulraheem 《Arabian Journal of Geosciences》2014,7(3):1127-1138
A simple rock model is presented which reproduces the measured hydraulic and electric transport properties of sedimentary rocks and connects these properties with each other, as well as with the acoustic propagation velocities and elastic moduli. The model has four geometric parameters (average coordination number Z of the pores, average pore radius r, average distance between nearest pores d, and average throat radius δ) which can be directly determined from the measured porosity Φ, hydraulic permeability k, and cementation exponent m of the rock via simple analytic expressions. Inversion examples are presented for published sandstone data, and for cores taken from Saudi Arabian, Upper Jurassic and Permian carbonate reservoirs. For sandstone, the inversion works perfectly; for carbonates, the derived rock model shows order-of-magnitude agreement with the structure seen in thin sections. Inverting the equations, we express the transfer properties Φ, k, and m as functions of r, d, δ, and Z. Formulae are derived for the bulk density D b, formation factor F, and P-wave velocity in terms of the proposed geometrical parameters. 相似文献
30.
Marc Antoine Couillard Gilbert Cabana Jean François Dery Gaétan Daigle Julian John Dodson 《Estuaries and Coasts》2011,34(6):1234-1245
Tomcod (Microgadus tomcod) in the St. Lawrence estuarine transition zone (ETZ) undergo an ontogenetic habitat shift. Older age classes, characterised
by a male-dominated sex ratio, disperse downstream over the summer months to occupy the colder more saline waters of the estuary.
Significant differences in length and mass along the salinity gradient were observed in September with upstream fish of any
given age class generally exhibiting greater growth. These differences were not seen in early summer. Benthic amphipod δ
34S signatures were strongly correlated with salinity and served to demonstrate that tomcod δ
34S signatures were not in isotopic equilibrium in the more saline waters of the ETZ. Seasonal distributional patterns, growth
dynamics and isotopic disequilibrium all indicate that the observed habitat shift may occur on an annual basis, following
winter aggregation in warmer, less saline waters. Tomcod located in the downstream parts of the ETZ, predominantly males,
were significantly more sexually developed than upstream tomcod for a given age. On the other hand, greater growth early in
life is insured by occupying warmer, upstream waters during the summer months. 相似文献