排序方式: 共有33条查询结果,搜索用时 15 毫秒
11.
AbstractThe main objective of this study is to assess the relative contribution of the state-of-the-art topo-hydrological factor, known as height above the nearest drainage (HAND), to landslide susceptibility modellling using three novel statistical models: weights-of-evidence (WofE), index of entropy and certainty factor. In total, 12 landslide conditioning factors that affect the landslide incidence were used as input to the models in the Ziarat Watershed, Golestan Province, Iran. Landslide inventory was randomly divided into a ratio of 70:30 for training and validating the results of the models. The optimum combination of conditioning factors was identified using the principal components analysis (PCA) method. The results demonstrated that HAND is the defining factor among hydrological and topographical factors in the study area. Additionally, the WofE model had the highest prediction capability (AUPRC = 74.31%). Therefore, HAND was found to be a promising factor for landslide susceptibility mapping. 相似文献
12.
Khalil Sarkarinejad Abdolreza Partabian Ali Faghih Timothy M. Kusky 《Geological Journal》2012,47(1):99-110
3D finite strain analyses and kinematic vorticity measurements were carried out on the Loghon Anticline within the HP‐LT Sanandaj–Sirjan metamorphic belt (Neyriz area, SW Iran). Rƒ/φ and Fry methods were used on the strain markers (e.g. deformed fossils) to interpret geometric relationships between the fold axis, strain ellipsoid axes and shear zone boundaries. The results indicate the predominance of prolate strain in the anticline. Quantitative kinematic analyses show that the Wk parameter is 0. 67 ± 0. 06 (i.e. pure‐shear dominated non‐coaxial flow). This study quantitatively supports the establishment of a dextral transpressive system, which is responsible for the development of the large‐scale right‐lateral shear zones that strike sub‐parallel to the major folds. Flexural shear combined with regional dextral‐shear is suggested to be the most common mechanism of folding in this area. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
13.
14.
Finite element analysis of damage and failure of reinforced concrete members under earthquake loading
下载免费PDF全文
![点击此处可从《地震工程与结构动力学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper presents a three‐dimensional analysis framework, based on the explicit finite element method, for the simulation of reinforced concrete components under cyclic static and dynamic loading. A recently developed triaxial constitutive model for concrete is combined with a material model for reinforcing steel which can account for rupture due to low‐cycle fatigue. The reinforcing bars are represented with geometrically nonlinear beam elements to account for buckling of the reinforcement. The strain penetration effect is also accounted for in the models. The modeling scheme is used in a commercial finite element program and validated with the results of experimental static and dynamic tests on reinforced concrete columns and walls. The analyses are supplemented with a parametric study to investigate the impact of several modeling assumptions on the obtained results. 相似文献
15.
In this study, the Maastrichtian-Danian boundary was measured and sampled in two stratigraphic sections, the north and south flanks of the Dehnow anticline in Coastal Fars, Southern Iran. This boundary was also investigated in the drilled exploratory well-1 in the same region. The lithology of the Maastrichtian-Danian deposits consists of glauconitic, phosphatic argillaceous limestones and marlstones. 30 genera and 77 species of planktonic foraminifera have been determined. The recognized biozones are the Gansserina gansseri Interval Zone, and the Contusotruncana contusa Interval Zone, which indicates latest Campanian to middle Maastrichtian age for the upper part of the Gurpi Formation. In addition, the Eoglobigerina edita (P1) Partial Range Zone, Praemurica uncinata (P2) Lowest Occurrence Zone, Morozovella angulata (P3) Lowest Occurrence Zone and Globanomalina psudomenardii (P4) Taxon Range Zone represent a Danian to Thanetian age for the lower part of the Pabdeh Formation. From the absence of the Abathomphalus mayaroensis Interval Zone, Pseudoguembelina hariaensis Interval Zone, Pseudotextularia elegans Interval Zone, Plummerita hantkeninoides Interval Zone, Guembelitria cretacea (P0) Partial Range Zone and Parvularugoglobigerina eugubina (Pα) Total Range Zone, it can be deduced that there is a paraconformity across the Maastrichtian–Danian boundary in the studied area, this hiatus encompassing the late Maastrichtian and the earliest Danian. Danian deposits from the study area contain reworked glauconitized macrofossils, planktonic and benthic foraminifera of the Cretaceous. The obtained surface gamma-ray spectrometry logs resemble the exploratory well-1 gamma-ray wireline log. 相似文献
16.
Impact of major organophosphate pesticides used in agriculture to surface water and sediment quality (Southern Caspian Sea basin,Haraz River) 总被引:3,自引:3,他引:0
Touraj Nasrabadi Gholamreza Nabi Bidhendi Abdolreza Karbassi Peter Grathwohl Nasser Mehrdadi 《Environmental Earth Sciences》2011,63(4):873-883
Organophosphate pesticides are compounds that are not only toxic to both humans and wildlife but also difficult to degrade
under natural environmental conditions. In Iran, agricultural practices are strongly dependent on the use of pesticides due
to climatic and soil conditions, thus posing a potential risk to groundwater quality standards. Evaluating the concentration
of organophosphate pesticides namely diazinon, fenitrothion, dichlorvos, ethion, profenofos, malathion and azinphos methyl
in water samples in May (low precipitation rate), December (high precipitation rate) as well as the concentration in sediments
along the Haraz River is taken into consideration in this study. Generally the pesticides concentration in water samples are
relatively higher in May in comparison with that in December; this fact may be due to two major reasons: the first reason
is attributed to the prompt raining after the treatment period of most orchards and dry farming lands that will terminate
in more wash out of such pesticides towards the branches and main river channel, while the second reason may be considered
as the less river water dilution rate in May because of lower precipitation rate. Furthermore, the relatively higher concentrations
in downstream stations may be contributed to more intensified agricultural (specially rice paddies), urban and rural land
uses in this region in comparison with upstream areas which contain mainly dry farming, grazing lands and orchards with relatively
lower loads of pesticides. Additionally, as the Henry’s law constant of all pesticides considered in this study are relatively
low, volatilization may not be regarded as an important route of dissipation. Diazinon, azinphos methyl and dichlorvos showed
the highest water concentrations in comparison with other pesticides that may be justified by their extended use within the
basin during last decades. Based on the chemical properties as well as remarkably higher values in sediment samples in comparison
with water ones, it is concluded that the two pesticides, ethion and fenitrothion, persist in the environment due to non-degradable
tendencies. Although the concentration of mentioned pesticides is not so high in the water samples, more precautions must
be considered in their future use. Regarding the sorption coefficient variation alongside the river, the higher values in
upstream and central parts may be attributed to the higher potential of different types of erosion regarding deeper slopes
and also sand, gravel and carbonate mining activities at the banks and also river bed in such regions which is considered
as an anthropogenic disturbance. In case of central parts, in addition to mentioned reasons, the existence of coal outcrops
in the geologic texture of the study area may also be considered as a key role in augmentation of the sorption coefficient.
Finally, the dominant clayey and loamy soils containing more organics may be attributed as the major reason of sorption tendency
in downstream. 相似文献
17.
Experimental study has been carried out under a clear-water scour condition to explore the local scour around semi-elliptical model bridge abutments with armor-layer bed, compared with the local scour process around semi-circular abutment. Two types of model bridge abutments, namely semi-elliptical and semi-circular abutments have been used in this experimental study. The model abutments had a ratio of streamwise length of abutment to the length of abutment transverse to the flow of 2 for semi-circular abutments and 3 for semi-elliptical abutments. In total, 50 Experiments have been designed and conducted under different flow conditions such as bed shear velocities, flow depth, and dimensions of bridge abutment model, as well as grain size of the bed material. Based on these experiments, the scour process around bridge abutments has been assessed. The dependence of the equilibrium scour depth of the scour hole on hydraulic variables has been studied. Empirical equation describing the equilibrium scour depth of the scour hole around bridge abutments has been developed. 相似文献
18.
Natural Resources Research - Low salinity water (LSW) flooding alters rock surface wettability toward more water wetness, and consequently, oil recovery will be increased from a carbonate oil... 相似文献
19.
A new gravimetric, satellite altimetry, astronomical ellipsoidal boundary value problem for geoid computations has been developed and successfully tested. This boundary value problem has been constructed for gravity observables of the type (i) gravity potential, (ii) gravity intensity (i.e. modulus of gravity acceleration), (iii) astronomical longitude, (iv) astronomical latitude and (v) satellite altimetry observations. The ellipsoidal coordinates of the observation points have been considered as known quantities in the set-up of the problem in the light of availability of GPS coordinates. The developed boundary value problem is ellipsoidal by nature and as such takes advantage of high precision GPS observations in the set-up. The algorithmic steps of the solution of the boundary value problem are as follows:
- - Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and of the ellipsoidal centrifugal field for the removal of the effect of global gravity and the isostasy field from the gravity intensity and the astronomical observations at the surface of the Earth.
- - Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the gravity intensity and the astronomical observations at the surface of the Earth the effect of the residual masses at the radius of up to 55 km from the computational point.
- - Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and ellipsoidal centrifugal field for the removal from the geoidal undulations derived from satellite altimetry the effect of the global gravity and isostasy on the geoidal undulations.
- - Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the geoidal undulations derived from satellite altimetry the effect of the water masses outside the reference ellipsoid within a radius of 55 km around the computational point.
- - Least squares solution of the observation equations of the incremental quantities derived from aforementioned steps in order to obtain the incremental gravity potential at the surface of the reference ellipsoid.
- - The removed effects at the application points are restored on the surface of reference ellipsoid.
- - Application of the ellipsoidal Bruns’ formula for converting the potential values on the surface of the reference ellipsoid into the geoidal heights with respect to the reference ellipsoid.
- - Computation of the geoid of Iran has successfully tested this new methodology.
Keywords: Geoid computations; Ellipsoidal approximation; Ellipsoidal boundary value problem; Ellipsoidal Bruns’ formula; Satellite altimetry; Astronomical observations 相似文献
20.
Abdolreza Bahremand Sajad Ahmadyousefi Vahedberdi Sheikh Chooghi Bairam Komaki 《水文研究》2021,35(1):e13992
Hydrologic models are simplified representations of natural hydrologic systems. Since these models rely on assumptions and simplifications to capture some aspects of hydrological processes, calibration of parameters is unavoidable. However, utilizing the philosophy of a recent modelling framework proposed by Bahremand (2016), we show how calibration of most model parameters can be avoided by allocating or presetting these parameters utilizing knowledge gained from sensitivity analyses, field observations and a priori specifications as a part of a parameter allocation procedure. This paper details the simulation of daily river flow of the Shemshak-Roudak watershed performed using the Python version of the WetSpa model. The WetSpa-Python model is a distributed model of hydrological processes applied at the watershed scale. The model was applied to the Shemshak-Roudak watershed of Iran with parameter allocation. Model calibration involved only two parameters. Straightforward methods were proposed for allocating model parameters, including three baseflow-related parameters and the determination of maximum active groundwater storage using a mass curve technique. Also, the Budyko curve was used to constrain a correction factor for potential evapotranspiration. The WetSpa-Python model was extended to include the influence of snowmelt. A failure to include snow in the hydrological processes of the WetSpa-Python model creates a significant discrepancy between the observed and simulated hydrographs during the spring. The results of daily simulations for 12 years (2002–2014) are in good agreement with observations of discharge (Kling-Gupta Efficiency = 0.84). These results demonstrate that it is feasible to simulate hydrographs with limited calibration given a knowledge of hydrological processes and an understanding of relationships between catchment characteristics and model parameters. 相似文献