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Southwest regions of Iran, due to dry environmental and climatic conditions, have been identified as one of the five major regions in the world. In recent years, large parts of Iran have been affected by suspended particles from the dust storms. The studied area is located in foothills of the Zagros Mountain Range just north of Persian Gulf in southwest of Iran. Dust and other meteorological data were prepared in 3-hour intervals from 12 synoptic weather stations. For tracking dust storms, satellite images of MODIS were used. Atmospheric conditions during the occurrence of dust storms were determined using NCEP reanalysis data. According to the statistical calculations, most storms occurred in the spring and summer. The lowest number of dust events occurred in the fall and winter particularly in December and January, when there are high possibilities of rainfall occurrence and dynamical instability conditions in the north and west of the region. The results illustrated that the highest amounts of hourly dust occurred in the afternoon and the lowest amounts occurred at 00UTC (3.30 am local times). It seems that it is closely related to the heating surface and the occurrence of local dry instabilities. Analyses of data showed that dust amounts (or volumes) in all the stations have two climactic peaks, first between 1982 and 1990 and second between 2005 and 2008 periods. These peaks can be related to a variety of factors including anthropogenic factors such as war, agricultural activities, dam construction, and widespread droughts. 相似文献
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K. P. Sharma M.E. AMIS Utpal Miri M.E. 《Journal of the Indian Society of Remote Sensing》1975,3(1):29-35
Run-off is an important element of the hydrologic studies of any given basin. As such the estimation of the run-off factor of a catchment becomes imperative for determination of the total quantity of its surface run-off. The traditional ground survey methods of hydrologic studies of river basins are gradually getting replaced by more economical and reasonably accurate methods mostly based on aerial photographs. This paper deals with an experiment carried out on the Tons Catchment for determination of its run-off factor with the help of aerial photographs using the photo-interpretation and analysis techniques. The resultant values of the surface runoff have compared very well with the observed flow at Kisau gauging station. This indicates that a suitable methodology can be developed to estimate the discharge of the catchment of Indian rivers, where the run-off data is not available, with reasonable accuracy using the aerial photographs. 相似文献
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Natural Hazards - Dust storms are frequent in the Sistan region of south-eastern Iran and cause a wide range of problems, but few studies have assessed their negative impacts. This paper makes an... 相似文献
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The Havriliak-Negami model for dynamic viscoelastic material behavior and Biot＇s theory of poroelasticity are employed to develop an exact solution for three-dimensional scattering effect of harmonic plane P-SV waves from a circular cavity lined with a multilayered fluid-filled shell of infinite length containing viscoelastic damping materials and embedded within a fluid-saturated permeable surrounding soil medium. The analytical results are illustrated with numerical examples where the effects of liner/coating structural arrangement, viscoelastic material properties, liner-soil interface bonding condition, seismic excitation frequency, and angle of incidence on the induced dynamic stress concentrations are evaluated and discussed to obtain representative values of the parameters that characterize the system. It is demonstrated that incorporating viscoelastic damping materials with a low shear modulus in the constrained layer configuration is an efficient means of enhancing the overall seismic isolation performance, especially for near-normally incident seismic shear waves where the amplitudes of induced dynamic stresses may be reduced by up to one-third of those without isolation in a relatively wide frequency range. Some additional cases are considered and good agreements with solutions available in the literature are obtained. 相似文献
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Mirmohammad Miri Ali asghar Sepahi Farhad Aliani Mohammad Maanijou 《Arabian Journal of Geosciences》2016,9(13):619
Amphibolite layers of the Hamedan area (Sanandaj-Sirjan zone, west Iran) contain amphibole crystals with strong optical zoning. These amphibolites occur as interlayers in middle Jurassic, Buchan-type andalusite-garnet-staurolite and sillimanite-garnet-andalusite schist of the area that were intruded by late Jurassic magmatic bodies of the Alvand plutonic complex. Electron microprobe analyses results show that the zoned amphiboles have ferrohornblende cores that change to ferroedenite toward the rims. The core-to rim increase of Al, Fe, Na, and K and decrease of Si and Mg along with edenitic substitution in amphiboles is consistent with increase in metamorphic grade. Thermobarometry calculations based on amphibole composition and hornblende-plagioclase thermometry provided 492 to 508 o C and 4.3 to 4.9 kbar for the inner cores, 495 to 514 o C and 4.5 to 5.1 kbar for the outer cores, 538 to 564 o C and 5.3 to 5.8 kbar for the inner rims and 552 to 573 o C and 5.5 to 5.9 kbar for the outer rims, respectively. These results point to a nearly isobaric prograde P-T path for the Hamedan area amphibolites, compatible with a metamorphic evolution dominated by the thermal perturbation associated with the late Jurassic magmatism of the northern Sanandaj-Sirjan zone. 相似文献
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