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排序方式: 共有119条查询结果,搜索用时 17 毫秒
1.
Acta Geotechnica - In this study, an analytical model is developed to establish a framework for predicting the coefficient of lateral soil pressure in unsaturated soils. To this end, the disturbed... 相似文献
2.
Drought characterization: a probabilistic approach 总被引:4,自引:0,他引:4
A. K. Mishra V. P. Singh V. R. Desai 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(1):41-55
Using the alternative renewable process and run theory, this study investigates the distribution of drought interval time,
mean drought interarrival time, joint probability density function and transition probabilities of drought events in the Kansabati
River basin in India. The standardized precipitation index series is employed in the investigation. The time interval of SPI
is found to have a significant effect of the probabilistic characteristics of drought. 相似文献
3.
AbstractAn approach is presented for desktop-level environmental flow requirement (EFR) determination that is aligned with the Habitat Flow–Stressor Response (HFSR) method which evolved in South Africa over recent years. The HFSR method integrates hydrological, hydraulic and ecological habitat data, involves ecological and hydraulic specialists and is data-intensive and time-consuming. The revised desktop method integrates hydrological information with estimates of channel hydraulic cross-sectional characteristics to generate habitat-type frequencies under changing flow conditions. This information is used with the expected natural habitat requirements to determine acceptable habitat availability under different levels of ecological protection, which is then used with the hydraulic data to define flow regime characteristics that meet the ecological objectives. The paper describes the model components, discusses the assumptions, data requirements and limitations and presents some example results. The revised desktop approach uses approaches that are aligned with the more complex methods and generates results that are similar.
Editor D. Koutsoyiannis; Guest editor M. AcremanCitation Hughes, D.A., Desai, A.Y., Birkhead, A.L., and Louw, D., 2014. A new approach to rapid, desktop-level, environmental flow assessments for rivers in South Africa. Hydrological Sciences Journal, 59 (3–4), 673–687. 相似文献
4.
A generalized constitutive model is described with particular attention to determination of material constants, and its implementation. The model involves use of only a single function to characterize the complete range of plastic yielding, and employs a special function to describe plastic hardening. Laboratory behaviour of an artificial soil is used to iliustrate the determination of the constants and verification of the model. 相似文献
5.
The shallow marine sedimentary sequence of the Jaisalmer Basin exhibits one of the important and well-developed Tithonian sedimentary outcrops for western India. The ichnology and ichnofabric of the lower part of Bhadasar Formation (i.e., Kolar Dongar Member) belonging to Tithonian age are presented and discussed. The Kolar Dongar Member represents a shallow marine succession that contains 16 ichnotaxa: Ancorichnus ancorichnus, Conichnus conicus, Gyrochorte comosa, cf. Jamesonichnites heinbergi, Imponoglyphus kevadiensis, Laevicyclus mongraensis, Monocraterion tentaculatum, Ophiomorpha nodosa, Palaeophycus tubularis, P. bolbiterminus, Phycodes palmatus, Planolites beverleyensis, Rhizocorallium isp., Rosselia rotatus, R. socialis, and Teichichnus rectus. The ichnofabric analysis divulges five distinct ichnofabrics, each typifying distinct depositional environment within shallow marine conditions. The ichnofabric Ophiomorpha 1 with syn-sedimentary faulting exemplifies high energy conditions typical of lower shoreface environment, whereas the Ophiomorpha 2 ichnofabric typifies upper shoreface environment. The Ancorichnus ichnofabric reflects lower offshore condition of deposition. The high ichnodiversity Ancorichnus–Rosselia ichnofabric is indicative of inner shelf conditions, while low ichno-diversity Teichichnus ichnofabric indicates prevalence of low energy brackish bay environment. Thus, Tithonian Kolar Dongar Member indicates depositional environment ranging from shoreface to offshore to inner shelf and finally to brackish bay environment. 相似文献
6.
Vahid Toufigh Farnam Saeid Ahad Ouria Chandrakant S. Desai Hamid Saadatmanesh 《Geomechanics and Geoengineering》2014,9(3):208-214
Soil is a material which is weak in tension; however, different materials such as geotextiles are used to address this inadequacy. In recent years more than one million square metres of geotextiles were used for reinforcing soil. Nevertheless, there are several significant problems associated with geotextiles, such as creep, low modulus of elasticity and susceptibility to aggressive environments. Carbon fibre reinforced polymer (CFRP) was introduced over two decades ago to the field of structural engineering and it can also be used in geotechnical engineering. CFRP has all the benefits associated with geotextiles and it boasts a higher strength, higher modulus, no creep and reliability in aggressive environments. In this investigation, the interface properties of CFRP-sand and fine sand were investigated using the pull-out test. The pull-out test device was designed and assembled using a triaxial loading device and a direct shear device. In the pull-out test, the normal force applied by the triaxial loading and pull-out force is applied by a direct shear device. CFRP samples were prepared in the lab. Precast and cast-in-place samples were tested. The pull-out force and corresponding displacements of each of the materials were recorded and compared. 相似文献
7.
1 IntroductionHydrophobically modified water-soluble polymers,also known as hydrophobized polymers, are thosemodified by hydrophobic groups such as alkyl,arolkyl, and deoxycholic acid. In water, they canself-aggregate due to their intro- and/or intermolecularhydrophobic interaction. By this process, unique hy-drogel nanoparticles with hydrophobic core and hy-drophilic shell can be prepared, which is a new ap-proach to preparing the monodispersed hydrogelnanoparticles (Whitesides et al., 1991; … 相似文献
8.
Aurore E. Sibois Shailen D. Desai Willy Bertiger Bruce J. Haines 《Journal of Geodesy》2017,91(8):965-983
We present results from the generation of 10-year-long continuous time series of the Earth’s polar motion at 15-min temporal resolution using Global Positioning System ground data. From our results, we infer an overall noise level in our high-rate polar motion time series of 60 \(\upmu \hbox {as}\) (RMS). However, a spectral decomposition of our estimates indicates a noise floor of 4 \(\upmu \hbox {as}\) at periods shorter than 2 days, which enables recovery of diurnal and semidiurnal tidally induced polar motion. We deliberately place no constraints on retrograde diurnal polar motion despite its inherent ambiguity with long-period nutation. With this approach, we are able to resolve damped manifestations of the effects of the diurnal ocean tides on retrograde polar motion. As such, our approach is at least capable of discriminating between a historical background nutation model that excludes the effects of the diurnal ocean tides and modern models that include those effects. To assess the quality of our polar motion solution outside of the retrograde diurnal frequency band, we focus on its capability to recover tidally driven and non-tidal variations manifesting at the ultra-rapid (intra-daily) and rapid (characterized by periods ranging from 2 to 20 days) periods. We find that our best estimates of diurnal and semidiurnal tidally induced polar motion result from an approach that adopts, at the observation level, a reasonable background model of these effects. We also demonstrate that our high-rate polar motion estimates yield similar results to daily-resolved polar motion estimates, and therefore do not compromise the ability to resolve polar motion at periods of 2–20 days. 相似文献
9.
10.
K. P .Raju J. N. Desai T. Chandrasekhar N. M. Ashok 《Journal of Astrophysics and Astronomy》1991,12(4):311-317
The line intensity of the green coronal line and the continuum intensity are derived from the filter and white light photographs of the solar corona obtained during the 1980 total solar eclipse. Ratio of the line to continuum intensity is plotted against the radial distancer(=R/R0,R 0 is the solar radius), in various position angles. A simple model assuming an electron density dependence of the line and continuum intensities suggests a dominant collisional mechanism for the excitation of the line in the innermost regions (~ 1.4R 0). The measured line to continuum ratio tends to a constant value at different radial distances in different position angles. The constancy of the measured line to continuum ratio indicates significant radiative excitation beyond 1.4 R0, in some of the position angles. 相似文献