排序方式: 共有39条查询结果,搜索用时 15 毫秒
21.
Physically based modelling of sheet erosion (detachment and deposition processes) in complex hillslopes 总被引:1,自引:0,他引:1 下载免费PDF全文
Ali Talebi Rasoul Hajiabolghasemi Mohamad Reza Hadian Nosratollah Amanian 《水文研究》2016,30(12):1968-1977
A one‐dimensional uncoupled model governed by this research is a physics‐based modelling of the rainfall‐runoff induced erosion process. The presented model is composed of three parts of a three‐dimensional (3D) hillslope geometry, a nonlinear storage (kinematic wave) model for hillslope hydrological response, and an unsteady physically based surface erosion model. The 3D hillslope geometry model allows describing of the hillslope morphology by defining their plan shape and profile curvature. By changing these two topographic parameters, nine basic hillslope types are derived. The modelling of hillslope hydrological response is based on a flow continuity equation as the relation of discharge and flow depth is passed on kinematic wave approximation. The erosion model is based on a mass conservation equation for unsteady flow. The model assumes that suspended sediment does not affect flow dynamics. The model also accounts for the effect of flow depth plus loose soil depth on soil detachment. The presented model was run for two different precipitations, slope content, and length, and results were plotted for sediment detachment/deposition rate. Based on the obtained results, in hillslopes with convex and straight profile curvatures, sediment detachment only occurred in the whole length of the hillslope. However, in concave ones, sediment detachment and deposition only occurred together in hillslope. The hillslopes with straight profiles and convergent plans have the highest rate of detachment. Also, results show that most detachment rates occur in convex profile curvatures, which are about 15 times more than in straight profiles. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
22.
Rasoul Sorkhabi 《Geology Today》2020,36(4):140-145
In 2020, the coronavirus pandemic has overshadowed every affair of our society, and rightly so. Nevertheless, the world has also plunged into an economic crisis of enormous gravity on par with the Great Depression of the 1930s. The oil market crash is an alarming symptom of this weakened economy which hurts all people, whether affected by coronavirus or not. This article examines its causes, consequences and historical context. 相似文献
23.
Spatio-temporal analysis of daily,seasonal and annual precipitation concentration in Jharkhand state,India 总被引:1,自引:0,他引:1
Reza?ZamaniEmail author Rasoul?Mirabbasi Mohammad?Nazeri Sarita?Gajbhiye?Meshram Farshad?Ahmadi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(4):1085-1097
Nowadays, climate change and global warming have led to changes in the distribution of precipitation, which affect on the availability of water resources. Therefore, investigating the temporal and spatial variations of precipitation in the previous period is highly important in the future planning for flood control and local management of water resources. Considering the importance of this issue, in the present study, the precipitation concentration indices have been used for analysing precipitation changes at daily, seasonal, and annual time scales in the period of 1971 to 2011 over the Jharkhand state, India. Also, Modified Mann–Kendall test has used to study the trend of precipitation concentration indices in annual and seasonal time scales. The result shows a highly irregular and non-uniform distribution in the annual scale. For the seasonal scale an irregular and non-uniform distribution has been also observed, although the summer had a better situation than other seasons. For daily scale, none of the stations had a regular concentration and in the northeast and southern parts of the study area, there have been more irregularities. Furthermore, the results of investigating annual precipitation trend showed a combination of increasing and decreasing trend over the study area. The results of this study can be applied to manage water supplies, drainage projects, construct collection structures of urban flood, develop plans to prevent soil erosion, and designing appropriate plans to cope with drought conditions. 相似文献
24.
China Ocean Engineering - Multiple reflections of the waves between structure and wavemaker in hydraulic flumes could change the frequency content of the desired incident wave or result in... 相似文献
25.
Nanoparticles in natural systems I: The effective reactive surface area of the natural oxide fraction in field samples 总被引:1,自引:0,他引:1
Information on the particle size and reactive surface area of natural samples is essential for the application of surface complexation models (SCM) to predict bioavailability, toxicity, and transport of elements in the natural environment. In addition, this information will be of great help to enlighten views on the formation, stability, and structure of nanoparticle associations of natural organic matter (NOM) and natural oxide particles.Phosphate is proposed as a natively present probe ion to derive the effective reactive surface area of natural samples. In the suggested method, natural samples are equilibrated (?10 days) with 0.5 M NaHCO3 (pH = 8.5) at various solid-solution ratios. This matrix fixes the pH and ionic strength, suppresses the influence of Ca2+ and Mg2+ ions by precipitation these in solid carbonates, and removes NOM due to the addition of activated carbon in excess, collectively leading to the dominance of the PO4-CO3 interaction in the system. The data have been interpreted with the charge distribution (CD) model, calibrated for goethite, and the analysis results in an effective reactive surface area (SA) and a reversibly bound phosphate loading Γ for a series of top soils.The oxidic SA varies between about 3-30 m2/g sample for a large series of representative agricultural top soils. Scaling of our data to the total iron and aluminum oxide content (dithionite-citrate-bicarbonate extractable), results in the specific surface area between about 200-1200 m2/g oxide for most soils, i.e. the oxide particles are nano-sized with an equivalent diameter in the order of ∼1-10 nm if considered as non-porous spheres. For the top soils, the effective surface area and the soil organic carbon fraction are strongly correlated. The oxide particles are embedded in a matrix of organic carbon (OC), equivalent to ∼1.4 ± 0.2 mg OC/m2 oxide for many soils of the collection, forming a NOM-mineral nanoparticle association with an average NOM volume fraction of ∼80%. The average mass density of such a NOM-mineral association is ∼1700 ± 100 kg/m3 (i.e. high-density NOM). The amount of reversibly bound phosphate is rather close to the amount of phosphate that is extractable with oxalate. The phosphate loading varies remarkably (Γ ≈ 1-3 μmol/m2 oxide) in the samples. As discussed in part II of this paper series (Hiemstra et al., 2010), the phosphate loading (Γ) of field samples is suppressed by surface complexation of NOM, where hydrophilic, fulvic, and humic acids act as a competitor for (an)ions via site competition and electrostatic interaction. 相似文献
26.
Rasoul B. Sorkhabi Arvind K. Jain Tetsumaru Itaya Shiro Fukui Nand Lal Ashok Kumar 《Journal of Earth System Science》1997,106(3):169-179
The cooling and tectonic history of the Higher Himalayan Crystallines (HHC) in southwest Zanskar (along the Kishtwar-Padam
traverse) is constrained by K-Ar biotite and fission-track (FT) apatite and zircon ages. A total of nine biotite samples yields
ages in the range of 14–24 Ma, indicating the post-metamorphic cooling of these rocks through ∼ 300°C in the Miocene. Overall,
the ages become younger away from the Zanskar Shear Zone (ZSZ), which marks the basement-cover detachment fault between the
HHC and the Tethyan sedimentary zone, towards the core of the HHC. The same pattern is also observed for the FT apatite ages,
which record the cooling of the rocks through ∼ 120°C. The apatite ages range from 11 Ma in the vicinity of the ZSZ to 4 Ma
at the granitic core of the HHC. This pattern of discordant cooling ages across the HHC in southwest Zanskar reveals an inversion
of isotherms due to fast uplift-denudation (hence cooling) of the HHC core, which is, in turn, related to domal uplift within
the HHC. The Chisoti granite gneiss is the exposed domal structure along the studied traverse. Cooling history of two granite
gneisses at the core of the HHC is also quantified with the help of the biotite, zircon and apatite ages; the time-temperatures
thus obtained indicate a rapid pulse of cooling at ∼ 6 Ma, related to accelerated uplift-denudation of the HHC core at this
time. Long-term denudation rates of 0.5–0.7 mm/yr are estimated for the high-grade rocks of the Higher Himalaya in southwest
Zanskar over the past 4.0–5.5 m.yr. 相似文献
27.
S. Mehdi Saghebian M. Taghi Sattari Rasoul Mirabbasi Mahesh Pal 《Arabian Journal of Geosciences》2014,7(11):4767-4777
A decision tree-based approach is proposed to predict ground water quality based on the United States Salinity Laboratory (USSL) diagram using the data from aquifers in agricultural lands of Ardebil province, northwest of Iran. Several combinations of hydro chemical parameters of groundwater and monthly precipitation with different lag time were considered to find an accurate and economical alternative for groundwater quality classification. The performance evaluation was based on the number of correctly classified instances (CCI) and kappa statistics. The results suggested the suitability of decision tree-based classification approach for the used data sets. The overall average of CCI and kappa statistic for the prediction of groundwater quality classes based on the USSL diagram was 0.88 and 0.83 %, respectively. Principal component analysis (PCA) was also used to determine the important parameters for groundwater quality classification. The results showed that groundwater quality classification by decision tree is more precise and efficient in comparison with PCA. The best alternative could evaluate groundwater quality class with only two parameters: electrical conductivity and cumulative precipitation of 11 months earlier. The developed model is able to predict water quality class by only two variables and this lead to a reduction in the number of variables analyzed on a routine basis, resulting in a significant reduction in laboratory costs and latency times between the sampling moment and the outcome of the laboratory analyses. 相似文献
28.
The prediction of the probability of cavitation occurrence to prevent serious damages in the spillways is the major concern for hydraulic engineers. In this research, the three-dimensional model of Shahid Madani Dam’s spillway was simulated with the Flow 3D software and by the comparison of numerical model results with the experi-mental data, the probability of occurrence of the cavitation phenomenon has been investigated. The flow parameters including pressure, velocity, and water depth were calculated for three different flow rates of 495 m3/s, 705 m3/s and 2 205 m3/s respectively. The Renormalization Group (RNG) turbulence model was used to simulate current turbulence. Comparison of simulation results for pressure, velocity and water depth with the results of the experimental model with two statistical indices Root Mean Square Error (RMSE) and Coefficient of Determination (R2) showed that the numerical simulation results are in good consistency with experimental model. However, simulation results indicated that at any flow rates with a return period of 1 000 years, probable maximum flood and designed flow rates, the cavitation number is not lower than the critical cavitation number; Therefore, it is predicted that the cavitation phenomenon in Shahid Madani Dam’s spillway will not happen. 相似文献
29.
30.