排序方式： 共有12条查询结果，搜索用时 19 毫秒
1.
2.
3.
Frequency analysis of climate extreme events in Zanjan, Iran 总被引：2，自引：1，他引：1
Saeed Jahanbaksh Asl Ali Mohammad Khorshiddoust Yagob Dinpashoh Fatemeh Sarafrouzeh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(7):1637-1650
In this study, generalized extreme value distribution (GEV) and generalized Pareto distribution (GPD) were fitted to the maximum and minimum temperature, maximum wind speed, and maximum precipitation series of Zanjan. Maximum (minimum) daily and absolute annual observations of Zanjan station from 1961 to 2011 were used. The parameters of the distributions were estimated using the maximum likelihood estimation method. Quantiles corresponding to 2, 5, 10, 25, 50, and 100 years return periods were calculated. It was found that both candidate distributions fitted to extreme events series, were statistically reasonable. Most of the observations from 1961 to 2011 were found to fall within 1–10 years return period. Low extremal index (θ) values were found for excess maximum and minimum temperatures over a high threshold, indicating the occurrence of consecutively high peaks. For the purpose of filtering the dependent observations to obtain a set of approximately independent threshold excesses, a declustering method was performed, which separated the excesses into clusters, then the de-clustered peaks were fitted to the GPD. In both models, values of the shape parameters of extreme precipitation and extreme wind speed were close to zero. The shape parameter was less negative in the GPD than the GEV. This leads to significantly lower return period estimates for high extremes with the GPD model. 相似文献
4.
Aerosols emitted from volcanic activities and polluted mid-latitudes regions are efficiently transported over the Arctic during winter by the large-scale atmospheric circulation. These aerosols are highly acidic. The acid coating on ice nuclei, which are present among these aerosols, alters their ability to nucleate ice crystals. In this research, the effect of acid coating on deposition and contact ice nuclei on the Arctic cloud and radiation is evaluated for January 2007 using a regional climate model. Results show that the suppression of contact freezing by acid coating on ice nuclei leads to small changes of the cloud microstructure and has no significant effect on the cloud radiative forcing (CRF) at the top of the atmosphere when compared with the effect of the alteration of deposition ice nucleation by acid coating on deposition ice nuclei. There is a negative feedback by which the suppression of contact freezing leads to an increase of the ice crystal nucleation rate by deposition ice nucleation. As a result, the suppression of contact freezing leads to an increase of the cloud ice crystal concentration. Changes in the cloud liquid and ice water contents remain small and the CRF is not significantly modified. The alteration of deposition ice nucleation by acid coating on ice nuclei is dominant over the alteration of contact freezing. 相似文献
5.
A methodology for seismic microzonation and earthquake damage scenarios may be considered as composed of two stages. In the first stage, microzonation maps with respect to estimated earthquake characteristics on the ground surface are generated for an investigated urban area. The effects of local geological and geotechnical site conditions are taken into account based on site characterization with respect to representative soil profiles extending down to the engineering bedrock. 1D site response analyses are performed to calculate earthquake characteristics on the ground surface using as many as possible, hazard compatible real acceleration time histories. In the second stage, vulnerability of buildings and pipeline systems are estimated based on site-specific ground motion parameters. A pilot study is carried out to evaluate seismic damage in a district in Istanbul, Turkey. The results demonstrate the significance of site characterization and site response analysis in calculating the earthquake characteristics on the ground surface in comparison to simplified empirical procedures. 相似文献
6.
Naghizade Asl Fateme Asgari Hamid Reza Emami Hojat Jafari Mohammad 《Geotechnical and Geological Engineering》2021,39(5):3347-3360
Geotechnical and Geological Engineering - Mulching is fastest strategy to control sand dune movement in arid and semiarid areas. In the present study the effect of micro silica- cement mixture was... 相似文献
7.
Aslı Boz Alper Sezer Tuba Özdemir Gül Ece Hızal Özlem Azdeniz Dolmacı 《Arabian Journal of Geosciences》2018,11(6):122
In this paper, a comparative experimental study was carried out to evaluate the effect of inclusion of different fiber types on strength of lime-stabilized clay. In this scope, a series of unconfined compressive strength tests were carried out on specimens including basalt and polypropylene fiber compacted under Standard Proctor effort (i.e., 35% by weight of soil). The effects of curing period (1, 7, 28, and 90 days), fiber type (basalt and polypropylene), fiber content (0, 0.25, 0.5, 0.75, 1%), fiber length (6, 12, and 19 mm), and lime content (0 and 9%) on strength properties were investigated. The results revealed that both basalt and polypropylene fibers increased the strength without inclusion of lime. For specimens including lime, strength of polypropylene fiber-reinforced specimens was remarkably higher than that reinforced with basalt fiber for lime-stabilized clay. However, greatest strength improvement was obtained by use of 0.75% basalt fiber of 19 mm length with 9% lime content after 90-day curing. Additionally, results of strength tests on specimens including 3 and 6% lime and 12-mm basalt fiber after 1, 7, 28, and 90-day curing were presented. It is evident that the use of 6-mm basalt fiber and 12-mm polypropylene fiber were the best options; however, efficiency of fiber inclusion is subject to change by varying lime contents. It was also observed that the secant modulus was increased by use of lime; however, strength of the correlations among secant modulus and unconfined compressive strength values was decreased by increasing amount of lime for specimens including both basalt and polypropylene fibers. 相似文献
8.
F. Mirazizi A. Bahrami S. Soleimani Asl A. Zaribafan K. Haghbeen S. Aminzadeh 《International Journal of Environmental Science and Technology》2018,15(8):1679-1686
Tyrosinases, laccases, and peroxidases are three important groups of oxidative enzymes. A characteristic feature of these enzymes is their ability for the oxidation of aniline and phenolic compounds. Literature review reveals some overlap between the organic substrates of these enzymes, but how exactly they are different and how much they have in common from both substrate structure and rate of oxidation points of views. Can they complete functional efficiency of each other when co-immobilized in a multi-enzymes system? To address these questions, edible mushroom (Agaricus bisporus) tyrosinase, Neurospora crassa laccase, and horseradish peroxidase were examined for the oxidation of azo derivatives of anilines and phenols. These substances were selected because their enzymatic degradation is of interest to environmentalists and can be followed spectrophotometrically. Experiments showed that tyrosinase and laccase had limitations in oxidizing these substances, especially anilines, while peroxidase oxidized all the selected compounds. However, substrates carrying electron-withdrawing substituents had slower oxidation. Co-immobilization of tyrosinase and laccase would be effective against phenolic compounds, but phenols oxidation proceeds faster (between 100 and 500 times) if peroxidase and H2O2 are used. Combination of peroxidase and H2O2, instead of co-immobilization of tyrosinase, laccase, and peroxidase, seems to be more promising for the removal of organic pollutants from contaminated water resources. 相似文献
9.
Samira Mokhtari Asl Mohammadreza Jafari Reza Zarei Sahamiyeh Vahid Shahrokhi 《Arabian Journal of Geosciences》2015,8(9):7125-7139
Farsesh barite in the central part of Iranian Sanandaj-Sirjan zone is a sample of epigenetic hydrothermal mineralization in dolomitized limestone, which provides appropriate chemicophysical conditions making the passage of mineral-bearing fluids possible. Barite veins may range from a few centimeters to 2 m in thickness that increases downward. The microthermometry measurements obtained from more than 30 fluid inclusions show relative homogenization temperatures ranging from 125 to 200 °C with an average of 110 °C for Farsesh barite deposits. The mean salinity measured proves 16 times as much as weight percentage of NaCl for barite. Coexistence of liquid- and vapor-rich fluid inclusions in barite minerals may provide an evidence of boiling in ore veins. Moreover, occurrence of bladed calcite, high-grade ore zones, and presence of hydrothermal breccia are all consistent with boiling. Thermometric studies indicate that homogenization temperatures (Th) for primary and pseudosecondary fluid inclusions in barite range from 125 to 200 °C with an average of 1,100 °C. The δ34S values of barite also lie between 8.88 and 16.6 %. The relatively narrow spread in δ34S values may suggest uniform environmental conditions throughout the mineralization field. Thus, δ34S values are lower than those of contemporaneous seawater, which indicates a contribution of magmatic sulfur to the ore-forming solution. Barite is marked by total amounts of rare Earth elements (REEs) (6.25–17.39 ppm). Moreover, chondrite-normalized REE patterns of barite indicate a fractionation of light REEs (i.e., LREEs) from La to Sm, similar to those for barite from different origins. The LaCN/LuCN ratios and chondrite-normalized REE patterns reveal that barite in Farsesh deposit is enriched in LREEs compared with heavy rare Earth elements (HREEs). Similarity between Ce/La ratios in barite samples and those found in deep-sea barite supports its marine origin. Lanthanum and Gd exhibit positive anomalies, which are common features of chemical marine sediments. Cerium shows a negative anomaly in most samples inherited from the negative Ce anomaly of hydrothermal fluid that is mixed with seawater at barite precipitation. The available data including tectonic setting, host rock characteristics, REE geochemistry, and sulfur isotopic compositions may support a hydrothermal submarine origin for Farsesh barite deposit. 相似文献
10.
Asl? Kurtulu? 《Bulletin of Earthquake Engineering》2011,9(5):1443-1461
Geotechnical downhole arrays that record seismic ground response in near-surface layers are increasingly becoming one of the
best sources of information for developing, verifying, and calibrating engineering analyses and design methods. Recently,
three geotechnical downhole arrays have been installed in the European side of Istanbul, Turkey with efforts of Kandilli Observatory
and Earthquake Research Institute (KOERI). The existing high seismic activity of the region increases the scientific importance
of these downhole arrays. Each array is composed of one accelerometer on the ground surface and three or four borehole accelerometers
at various depths along the soil profile with the deepest sensor located at the engineering bedrock level (Vs > 750 m/s). The arrays also provide reference bedrock motion for Rapid Response Network composed of 55 surface instruments
operated by KOERI in the west European side of city. An important aspect of this paper is to introduce the recently-completed
test sites emphasizing on their potential to generate valuable data for scientific community. Preliminary analysis of the
recorded data provides evidence for significant site amplification of ground motion by the surface layers. Comparisons between
the recorded and modeled response indicate that Vs 30 alone is a poor indicator of the amplification potential emphasizing the importance of site-specific analyses in predicting
the ground response as opposed to empirical approaches. 相似文献