排序方式: 共有36条查询结果,搜索用时 14 毫秒
11.
Extreme and/or prolonged rainfall events frequently cause landslides in many parts of the world. In this study, infiltration of rainfall into an unsaturated soil slope and triggering of landslides is studied through laboratory model (flume) tests, with the goal of obtaining the triggering rainfall intensity–duration (I–D) threshold. Flume tests with fine sand at two different relative densities (34 and 48%) and at slope angle of 56.5° are prepared, and rainfall (intensity in the range of 18 to 64 mm/h) is applied via a mist sprinkler system to trigger landslides. Soil water characteristic curve and hydraulic conductivity function of the fine sand are also presented. In flume tests, suction in the soil is measured with tensiometers, the progress of wetting front with time and deformations in the soil are also measured. Some of the findings of this study are: for the fine sand used in this study (a) the failure mechanism is infinite-slope type (mostly translational), and the failure surface is generally coincident with the wetting front or is in its vicinity, (b) the deformations leading to a landslide occurred abruptly, (c) both relatively high-intensity–short-duration rainfalls and relatively low-intensity–long duration rainfalls triggered landslides, (d) the shape of the I–D threshold is demonstrated to be a bilinear relation in log intensity–log duration plot, (e) below a certain rainfall intensity landslides are not triggered, (f) the effect of relative density of the soil on the I–D threshold is demonstrated by physical laboratory tests (as the relative density of the soil increases, the triggering rainfall intensity–duration threshold moves to larger rainfall events). The results of this study could be useful for accurate numerical modeling of rainfall-triggered landslides. 相似文献
12.
T. Nasrabadi G. R. Nabi Bidhendi A. R. Karbassi H. Hoveidi I. Nasrabadi H. Pezeshk F. Rashidinejad 《Environmental Geology》2009,58(4):693-700
Sungun mine is the largest open-cast copper mine in northwest of Iran and is in the primary stages of extraction. The influence
of mining activity on the quality of regional groundwater has been taken in to consideration in this study. Accordingly, sampling
was done from 22 springs in the study area. The concentrations of major anions and cations as well as Al, Cu, Cd, Cr, Fe,
Mn, and Zn were determined for all 22 spring samples in mid-August 2005. The results showed that the concentrations of most
of these elements were below the USA Environmental Protection Agency (EPA) limits; however, Al and Fe concentrations are considered
to be more than limits in a couple of samples. Despite the fact that geological formations are highly weathered and fractured,
the dissolution of minerals within the study area is low. This may be justified by the relatively high alkalinity of local
underground water which keeps metals in solid phase and does not let them enter dissolved phase. Additionally, this may be
attributed to the high velocity of groundwater flows, which do not give enough time for minerals to dissolve. Correlation
coefficients among water chemistry components were determined and the weighted-pair group method was chosen for cluster analysis.
Accordingly, high correlation among Al, Fe and Cr, Cd ,and Cu, sodium absorption ratio (SAR) and Na as well as total hardness
(TH), Ca, and Mg were observed. The chemical characteristics of water compositions on the basis of major ion concentrations
were evaluated on a Schoeller and Piper diagram. Accordingly, the dominant type of water in the region is considered to be
Ca-HCO3 (calcium-bicarbonate type). However, this type of water is also rich in Na, K, and especially Mg. Regarding Schoeller diagram,
the current status of local underground water is good for drinking purposes. By commencing mining excavation with designed
capacity in near future, the minerals will come into contact with air and water resulting in dissolution, especially in ponds,
which, in turn, will increase the concentration of toxic metals in groundwater. Considering future uses of this water including
for drinking, irrigation, industrial purposes, etc., precautions must be taken in to consideration. 相似文献
13.
Evaluation of spatial and seasonal variations in surface water quality using multivariate statistical techniques 总被引:6,自引:1,他引:5
A. H. Pejman M.Sc. G. R. Nabi Bidhendi Ph.D A. R. Karbassi Ph.D N. Mehrdadi Ph.D M. Esmaeili Bidhendi M.Sc. 《International Journal of Environmental Science and Technology》2009,6(3):467-476
In this study, spatial and seasonal variations of water quality in Haraz River Basin were evaluated using multivariate statistical techniques, such as cluster analysis, principal component analysis and factor analysis. Water quality data collected from 8 sampling stations in river during 4 seasons (Summer and Autumn of 2007, Winter and Spring of 2008) were analyzed for 10 parameters (dissolved oxygen, Fecal Coliform, pH, water temperature, biochemical oxygen demand, nitrate, total phosphate, turbidity, total solid and discharge). Cluster analysis grouped eight sampling stations into three clusters of similar water quality features and thereupon the whole river basin may be categorized into three zones, i.e. low, moderate and high pollution. The principle component analysis/factor analysis assisted to extract and recognize the factors or origins responsible for water quality variations in four seasons of the year. The natural parameters (temperature and discharge), the inorganic parameter (total solid) and the organic nutrients (nitrate) were the most significant parameters contributing to water quality variations for all seasons. Result of principal component analysis and factor analysis evinced that, a parameter that can be significant in contribution to water quality variations in river for one season, may less or not be significant for another one. 相似文献
14.
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
15.
Jameel-Un Nabi 《Astrophysics and Space Science》2012,339(2):305-315
Electron capture and positron decay rates are calculated for neutron-deficient Kr and Sr waiting point nuclei in stellar matter.
The calculation is performed within the framework of pn-QRPA model for rp-process conditions. Fine tuning of particle-particle,
particle-hole interaction parameters and a proper choice of the deformation parameter resulted in an accurate reproduction
of the measured half-lives. The same model parameters were used to calculate stellar rates. Inclusion of measured Gamow-Teller
strength distributions finally led to a reliable calculation of weak rates that reproduced the measured half-lives well under
limiting conditions. For the rp-process conditions, electron capture and positron decay rates on 72Kr and 76Sr are of comparable magnitude whereas electron capture rates on 78Sr and 74Kr are 1–2 orders of magnitude bigger than the corresponding positron decay rates. The pn-QRPA calculated electron capture
rates on 74Kr are bigger than previously calculated. The present calculation strongly suggests that, under rp-process conditions, electron
capture rates form an integral part of weak-interaction mediated rates and should not be neglected in nuclear reaction network
calculations as done previously. 相似文献
16.
Sami Hamed Abd El Nabi 《Arabian Journal of Geosciences》2012,5(6):1209-1221
The geothermal structure beneath of the Barramiya?CRed Sea coast area of the Central Eastern Desert of Egypt has been determined using Curie point depth (CPD), which is temperature-dependent. The CPD and the surface heat flow (q) maps of such area are estimated by analyzing aeromagnetic data. Such data are low-pass-filtered and analyzed to estimate the magnetic bottom using the centroid method. The heat flow map reflects the geothermic nature of the region. However, it is suggested that the shallow Curie point temperature depth pattern depends on the tectonic regime and morphology, which continues eastwards through the Red Sea. Particularly, the coastal regions are characterized by high heat flow (83.6?mW/m2) and shallow Curie depth (22.5?km), whereas the western portion of the studied area has a lower heat flow (<50?mW/m2) and deeper Curie depth (~40?km). In addition to its bordering to the Red Sea margin, such high heat flow anomaly is associated with the increased earthquake swarms activity in the Abu Dabbab area. El-Hady (1993) attributed the swarm activity to the geothermal evolution. Also, the heat flow pattern is correlatable by the numerous results of shallow borehole temperature measurements as reported by Morgan and Swanberg (1979). A significant low heat flow extending in the northeast?Csouthwest direction, which is associated with NE?CSW large areal extent negative Bouguer gravity anomaly and NE/SW-trending belt of the deep CPD region, seems to be directly related to the surface outcrops of Precambrian older granitoids of the mountainous range of that trend. 相似文献
17.
Jameel-Un Nabi 《Astrophysics and Space Science》2011,331(2):537-554
This paper reports on the microscopic calculation of ground and excited states Gamow-Teller (GT) strength distributions, both
in the electron capture and electron decay direction, for 54,55,56Fe. The associated electron and positron capture rates for these isotopes of iron are also calculated in stellar matter. These
calculations were recently introduced and this paper is a follow-up which discusses in detail the GT strength distributions
and stellar capture rates of key iron isotopes. The calculations are performed within the framework of the proton-neutron
quasiparticle random phase approximation (pn-QRPA) theory. The pn-QRPA theory allows a microscopic state-by-state calculation of GT strength functions and stellar capture rates which greatly increases the reliability of the results. For
the first time experimental deformation of nuclei are taken into account. In the core of massive stars isotopes of iron, 54,55,56Fe, are considered to be key players in decreasing the electron-to-baryon ratio (Y
e
) mainly via electron capture on these nuclide. The structure of the presupernova star is altered both by the changes in Y
e
and the entropy of the core material. Results are encouraging and are compared against measurements (where possible) and
other calculations. The calculated electron capture rates are in overall good agreement with the shell model results. During
the presupernova evolution of massive stars, from oxygen shell burning stages till around end of convective core silicon burning,
the calculated electron capture rates on 54Fe are around three times bigger than the corresponding shell model rates. The calculated positron capture rates, however,
are suppressed by two to five orders of magnitude. 相似文献
18.
Pharmaceutical compounds, widely produced and used all around the world, are partly responsible for the widespread water pollution in the environment. Carbamazepine (CBZ) is an antiepileptic drug that persists in the environment for many years. In the present study, we used the TiO2/UV, nanoparticulate zero‐valent iron (NZVI), and NZVI/H2O2 treatment processes to compare efficiency of CBZ removal from water. Influence of NZVI loading, H2O2 concentration, TiO2 loading, UV lamp power, and the matrix (distilled water and groundwater) on CBZ removal efficiency was evaluated using full factorial design. Results indicated that the NZVI/H2O2 process oxidized CBZ within 5 min. On the other hand, the NZVI process alone did not reduce CBZ concentration after 120 min of process time. The NZVI/H2O2 process was equally effective in CBZ removal from both distilled water and groundwater whereas the TiO2/UV process was less effective due to the presence of ions in groundwater. CBZ removal efficiency of the TiO2/UV process declined 30% when the matrix was changed from distilled water to groundwater. Negative divalent ions, i.e., and , were the main cause of reduction of CBZ removal efficiency from groundwater. It is likely that these two ions adsorb onto, and consequently prevent the superoxide anion and hydroxyl radical OH? from being generated on, the surface of the TiO2. 相似文献
19.
20.
Bakhadir Fayzullaevich Irgaziev Jameel-Un Nabi Abdul Kabir 《Astrophysics and Space Science》2018,363(7):148
Within the framework of potential cluster model, astrophysical S-factor of radiative capture reaction \(^{12}\mathrm{C} (\mathrm{p},\gamma)^{13}\mathrm{N}\) has been calculated in the two body cluster model for the energy range 0–1 MeV. The nuclear interaction in the initial and final states is described by the Woods–Saxon potential. The calculated astrophysical S-factor and rates are compared with known experimental results. 相似文献