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排序方式: 共有6033条查询结果,搜索用时 15 毫秒
31.
WEN Lingjuan LU Huayu & QIANG Xiaoke State Key Laboratory of Loess Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an China 《中国科学D辑(英文版)》2005,48(9):1452-1462
In recent years, the Red Clay deposits underlying Quaternary loess on the Chinese Loess Plateau (north China) have attracted more attention because they show a direct and continuous record of past atmos- pheric circulation and palaeoclimatic change. Investiga- tions on Red Clay deposits through multidisciplinary methods have demonstrated an aeolian origin for the Red Clay, like the overlying Quaternary loess. The Red Clay formed during the Miocene and Pliocene[1―13]. However, the type o… 相似文献
32.
Wan Zheng 《地震工程与工程振动(英文版)》2015,14(2):229-238
A simple cyclic elastoplastic constitutive model for sand is proposed based on the UH model for overconsolidated clay. The proposed model has the following features. First, in order to describe the stress-induced anisotropy in sand, a rotational hardening rule is introduced for the evolution of the yield surface axis with development of plastic deviatoric strain in the principal stress space. Second, the relationship between the rotational axis and stress-induced anisotropy is modeled by introducing the slope of rotational axis into the yield function. The fl atness of the yield surface can be determined by the slope of rotational axis. Finally, a revised unifi ed hardening parameter is proposed to incorporate the stress-induced anisotropy. The model capability in describing the cyclic response of sand is verifi ed by comparing the simulations with available test results. 相似文献
33.
Marwan?KaturjiEmail author Andrew?Sturman Peyman?Zawar-Reza 《Boundary-Layer Meteorology》2011,139(1):143-160
An investigation into high Reynolds number turbulent flow over a ridge top in New Zealand is described based on high-resolution
in-situ measurements, using ultrasonic anemometers for two separate locations on the same ridge with differing upwind terrain
complexity. Twelve 5-h periods during neutrally stratified and weakly stable atmospheric conditions with strong wind speeds
were sampled at 20 Hz. Large (and small) turbulent length scales were recorded for both vertical and longitudinal velocity
components in the range of 7–23 m (0.7–3.3 m) for the vertical direction and 628–1111 m (10.5–14.5 m) for the longitudinal
direction. Large-scale eddy sizes scaled to the WRF (Weather Research and Forecasting) numerical model simulated boundary-layer
thickness for both sites, while small-scale turbulent features were a function of the complexity of the upwind terrain. Evidence
of a multi-scale turbulent structure was obtained at the more complex terrain site, while an assessment of the three-dimensional
isotropy assumption in the inertial subrange of the spectrum showed anisotropic turbulence at the less complex site and evidence
of isotropic turbulence at the more complex site, with a spectral ratio convergence deviating from the 4/3 or unity values
suggested by previous theory and practice. Existing neutral spectral models can represent locations along the ridge top with
simple upwind complexity, especially for the vertical wind spectra, but sites with more orographic complexity and strong vertical
wind speeds are often poorly represented using these models. Measured spectra for the two sites exhibited no significant diurnal
variation and very similar large-scale and small-scale turbulent length scales for each site, but the turbulence energy measured
by the variances revealed a strong diurnal difference. 相似文献
34.
A remote sensing model for monitoring soil evaporation based on differential thermal inertia and its validation 总被引:2,自引:0,他引:2
To develop geosciences quantification and multi-dimensional researches will be an inevitable trend in the 21st century. The interaction between the land surface and the atmosphere not only serves as an important component in geosciences quantification, bu… 相似文献
35.
近年来,银额盆地哈日凹陷的油气勘探呈现出良好的态势,但对于哈日凹陷油气成藏条件相关研究甚少,已不能满足目前油气勘探开发的需求。本研究基于钻录井、地球物理、分析化验等资料,系统分析哈日凹陷油气成藏的烃源岩、储层、圈闭等条件,总结油气成藏条件配置关系,以期为哈日凹陷的后续油气勘探及地质研究提供依据。哈日凹陷主要发育三套烃源岩,其中银根组烃源岩有机质丰度极高,成熟度较低,有机质类型为Ⅰ-Ⅱ1型;巴二段烃源岩有机质丰度较高,成熟-高成熟,有机质类型为Ⅱ1-Ⅱ2型;巴一段烃源岩有机质丰度中等,成熟-高成熟,有机质类型为Ⅱ1-Ⅱ2型。储层类型为砂(砾)岩常规储层、碳酸质泥岩非常规储层和火山岩储层,且均属于特低孔超低渗储层,其中砂、砾岩储层和灰质泥岩储层物性最好,白云岩储层和火成岩储层次之,目前主力油藏主要集中在砂、砾岩储层和灰质泥岩储层这两种类型中。哈日凹陷主要发育两套岩性圈闭,即巴一段砂岩岩性圈闭和巴二段泥岩岩性圈闭,形成了源内(准)连续成藏模式和近源不连续成藏模式。 相似文献
36.
LlPingxiang WANGZhijun 《地球空间信息科学学报》2003,6(2):31-34
On the basis of a thorough understanding of the physical characteristics of remote sensing image,this paper employs the theories of wavelet transform and signal sampling to develop a new image fusion algorithm.The algorithm has been successfully applied to the image fusion of SPOT PAN and TM of Guangdong province, China The experimental results show that a perfect image fusion can be built up by using the image analytical solution and reconstruction in the image frequency domain based on the physical characteristics of the image formation.The method has demonstrated that the results of the image fusion do not change spectral characteristics of the original image. 相似文献
37.
38.
Any human-induced terrestrial sink is susceptible to the effects of elevated atmospheric CO2 concentration, nitrogen deposition, climate variability and other natural or indirect human-induced factors. It has been suggested in climate negotiations that the effects of these factors should be excluded from estimates of carbon sequestration used to meet the emission reduction commitments under the Kyoto Protocol. This paper focuses on the methodologies for factoring out the effects of atmospheric and climate variability/change. We estimate the relative magnitude of the non-human induced effects by using two biosphere models and discuss possibilities for narrowing estimate uncertainty. 相似文献
39.
Jason?PatskoskiEmail authorView authors OrcID profile A.?Sankarasubramanian 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(4):1065-1083
Reservoir sizing is one of the most important aspects of water resources engineering as the storage in a reservoir must be sufficient to supply water during extended droughts. Typically, observed streamflow is used to stochastically generate multiple realizations of streamflow to estimate the required storage based on the Sequent Peak Algorithm (SQP). The main limitation in this approach is that the parameters of the stochastic model are purely derived from the observed record (limited to less than 80 years of data) which does not have information related to prehistoric droughts. Further, reservoir sizing is typically estimated to meet future increase in water demand, and there is no guarantee that future streamflow over the planning period will be representative of past streamflow records. In this context, reconstructed streamflow records, usually estimated based on tree ring chronologies, provide better estimates of prehistoric droughts, and future streamflow records over the planning period could be obtained from general circulation models (GCMs) which provide 30 year near-term climate change projections. In this study, we developed paleo streamflow records and future streamflow records for 30 years are obtained by forcing the projected precipitation and temperature from the GCMs over a lumped watershed model. We propose combining observed, reconstructed and projected streamflows to generate synthetic streamflow records using a Bayesian framework that provides the posterior distribution of reservoir storage estimates. The performance of the Bayesian framework is compared to a traditional stochastic streamflow generation approach. Findings based on the split-sample validation show that the Bayesian approach yielded generated streamflow traces more representative of future streamflow conditions than the traditional stochastic approach thereby, reducing uncertainty on storage estimates corresponding to higher reliabilities. Potential strategies for improving future streamflow projections and its utility in reservoir sizing and capacity expansion projects are also discussed. 相似文献
40.