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M. Bahmanabadi A. Anvari G. Rastegarzadeh J. Samimi M. Lamehi Rachti 《Experimental Astronomy》1998,8(3):211-229
We have carried out a series of measurements with twenty-one light enclosures of different geometry and inside finishes to compare their performance for use in extensive air shower experiments. It is found that for light enclosures with white inside finish there is an inherent induced uncertainty in time measurement, in addition to the uncertainty arising from the uncertain transit location of the shower particle in a large area scintillator. Both of these uncertainties which can not be improved with better electronics limit the angular resolution of EAS arrays. 相似文献
2.
M. Bahmanabadi A. Anvari M. Khakian Ghomi D. Purmohammad J. Samimi M. Lamehi Rachti 《Experimental Astronomy》2002,13(1):39-57
We have studied Extensive Air Showers (EAS) with two small arraysof 1 m2 scintillation detectors inTehran, 1200 m above sea level.The distribution of air showersin zenith and azimuth angles has been studied and a cosnΘdistribution with n = 7.2±0.2 was obtained for zenith angledistribution. An asymmetry has been observed in the azimuthaldistribution of EAS of cosmic rays because of magnetic field ofthe Earth. Amplitudes of the first and the second harmonics ofobserved distribution depend on zenith angle as A
I ≈ (0.02 + 0.35 sin2Θ)±0.02, and A
II ≈ (0.03 + 0.42 sin4Θ)±0.03. Meanwhile, the uncertainties arising from the instrument, transit location of shower particles in the scintillator and fluctuations in the shower front have been calculated. 相似文献
3.
At the end of the western part of Bagharan Kuh Mountain in the northeast of Iran, mountain growth has been stopped toward the west because of the stress having been consumed by the thrusting movements and region rising instead of shear movement. Chahkand fault zone is situated at the western part of this mountain; this fault zone includes several thrust sheets that caused upper cretaceous ophiolite rocks up to younger units, peridotite exposure and fault related fold developing in the surface. In transverse perpendicular to the mountain toward the north, reduction in the parameters like faults dip, amount of deformation, peridotite outcrops show faults growth sequence and thrust sheets growth from mountain to plain, thus structural vergence is toward the northeast in this fault zone. Deformation in the east part of the region caused fault propagation fold with axial trend of WNW-ESE that is compatible with trending of fault plane. In the middle part, two types of folds is observed; in the first type, folding occurred before faulting and folds was cut by back thrust activity; in the second type, faults activity caused fault related folds with N60-90W axial trend. In order to hanging wall strain balance, back thrusts have been developed in the middle and western part which caused popup and fault bend folds with N20-70E trend. Back thrusts activity formed footwall synclines, micro folds, foliations, and uplift in this part of the region. Kinematic analysis of faults show stress axis σ1 = N201.6, 7, σ2 = N292.6, 7.1, σ3 = N64.8, 79.5; stress axis obtained by fold analysis confirm that minimum stress (σ3) is close to vertical so it is compatible with fault analysis. Based on the results, deformation in this region is controlled by compressional stress regime. This stress state is consistent with the direction of convergence between the Arabian and Eurasian plates. Also study of transposition, folded veins, different movements on the fault planes and back thrusts confirm the progressive deformation is dominant in this region that it increases from the east to the west. 相似文献
4.
Biomass estimation using Landsat-TM and -ETM+. Towards a regional model for Southern Africa? 总被引：1，自引：0，他引：1
Grazing and fire are major factors influencing the savanna ecosystems of Southern Africa. In both grazing and conservation
areas overgrazing is an important reason for degradation of vegetation and soil. Insufficient fire management can cause a
change in the species composition and may influence the soil negatively. For adequate planning purposes the knowledge of available
biomass is indispensable. High-resolution satellite systems can provide such knowledge on a large scale. Three study areas
in Southern Africa contributed to a first survey. Gutu District is situated in Zimbabwe. In its Communal Lands a high population
density leads to severe degradation of vegetation and soil. The South African test sites are located in Kruger National Park
and Madikwe Game Reserve. Therefore a wide ecological range from highly degraded to slightly disturbed savanna ecosystems
is included. Satellite images of both Landsat-5 (TM) and Landsat-7 (ETM+) were applied. After cross-calibration of the two
different satellite systems, indices applied to radiance and reflectance showed significant correlations with ground truth
data of grass and other foliage biomass. Including new data from Hluhluwe National Park (South Africa) into the regression
models improved the results, indicating that a regional model for savanna ecosystems in Southern Africa could be found.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Geotectonics - Geometry and kinematics of deformation across the Nehbandan Fault System (NFS) have been studied in the Bibimaryam and Damdameh areas in the Sistan Suture zone (SSZ). Nearly vertical... 相似文献
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A fully coupled element‐free Galerkin model for hydro‐mechanical analysis of advancement of fluid‐driven fractures in porous media 
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下载免费PDF全文 Hydraulic fracturing (HF) of underground formations has widely been used in different fields of engineering. Despite the technological advances in techniques of in situ HF, the industry uses semi‐analytical tools to design HF treatment. This is due to the complex interaction among various mechanisms involved in this process, so that for thorough simulations of HF operations a fully coupled numerical model is required. In this study, using element‐free Galerkin (EFG) mesh‐less method, a new formulation for numerical modeling of hydraulic fracture propagation in porous media is developed. This numerical approach, which is based on the simultaneous solution of equilibrium and continuity equations, considers the hydro‐mechanical coupling between the crack and its surrounding porous medium. Therefore, the developed EFG model is capable of simulating fluid leak‐off and fluid lag phenomena. To create the discrete equation system, the Galerkin technique is applied, and the essential boundary conditions are imposed via penalty method. Then, the resultant constrained integral equations are discretized in space using EFG shape functions. For temporal discretization, a fully implicit scheme is employed. The final set of algebraic equations that forms a non‐linear equation system is solved using the direct iterative procedure. Modeling of cracks is performed on the basis of linear elastic fracture mechanics, and for this purpose, the so‐called diffraction method is employed. For verification of the model, a number of problems are solved. According to the obtained results, the developed EFG computer program can successfully be applied for simulating the complex process of hydraulic fracture propagation in porous media. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
We have studied anisotropy of cosmic rays with an Extensive Air Shower(EAS) array in Tehran 1200 m above sea level. In analyzing
the data set, we have used appropriate techniques of analysis and considered environmental effects. An asymmetry has been
observed in the azimuthal distribution of EAS of cosmic rays because of magnetic field of the Earth. 相似文献
8.
Environmental impact assessment of open pit mining in Iran 总被引：2，自引：0，他引：2
Mining is widely regarded as having adverse effects on environment of both magnitude and diversity. Some of these effects
include erosion, formation of sinkhole, biodiversity loss and contamination of groundwater by chemical from the mining process
in general and open-pit mining in particular. As such, a repeatable process to evaluate these effects primarily aims to diminish
them. This paper applies Folchi method to evaluate the impact of open-pit mining in four Iranian mines that lacked previous
geo-environmental assessment. Having key geologic resources, these mines are: Mouteh gold mine, Gol-e-Gohar and Chogart iron
mines, and Sarcheshmeh copper mine. The environmental components can be defined as public health and safety, social relationships,
air and water quality, flora and fauna hence, various impacting factors from the mining activities were estimated for each
environmental component. For this purpose, each impacting factor was first given a magnitude, based solely on the range of
possible scenarios. Thereafter, a matrix of weighted factors was derived to systematically quantify and normalize the effects
of each impacting factor. The overall impact upon each individual environmental component was then calculated by summing the
weighted rates. Here, Folchi method was applied to evaluate those environmental conditions. Based on the acquired results,
the present paper finally concludes that amongst four case histories in Iran, Sarcheshmeh copper mine significantly affects
the environment, with critical level of air pollution there. 相似文献
9.
Natural Hazards - Advancement in technology has contributed to increment in complexity of systems and infrastructures. Furthermore, it has complicated the management of systems to deal with natural... 相似文献
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