排序方式： 共有89条查询结果，搜索用时 46 毫秒
41.
Davoud Agha‐Aligol Mohammad Lamehi‐Rachti Parvin Oliaiy Farah Shokouhi Mohammad Farmahini Farahani Mahmoud Moradi Fatemeh Farshi Jalali 《Geoarchaeology》2015,30(3):261-270
It had long been thought that obsidian found in Iranian sites originated from Anatolia and Armenia, but new research has challenged this assumption. In this study, 68 samples of obsidian obtained from an archaeological survey of Nader‐Tepe Aslanduz were analyzed by Proton Induced X‐ray Emission (PIXE). Nader‐Tepe Aslanduz is a tell site west of the city of Aslanduz in the Parsabad county of the Ardebil province in northern Iran. The site was inhabited from the first millennium B.C. to A.D. 17, and its history may extend back to the third or fourth millennium B.C. Our chemical composition results have been combined with obsidian composition data from Turkey and Armenia and subjected to Principal Component Analysis (PCA). This analysis shows that obsidian from each location can be grouped into distinctive classes—the obsidian from Nader‐Tepe Aslanduz is therefore probably derived from volcanic outcrops of the Sahand and Sabalan region. This study has been unable to assign a known source from Anatolia and Armenia for the obsidian of Nader‐Tepe Aslanduz. 相似文献
42.
Application of weights-of-evidence and certainty factor models and their comparison in landslide susceptibility mapping at Haraz watershed, Iran 总被引：10，自引：1，他引：9
Hamid Reza Pourghasemi Biswajeet Pradhan Candan Gokceoglu Majid Mohammadi Hamid Reza Moradi 《Arabian Journal of Geosciences》2013,6(7):2351-2365
The main goal of this study was to investigate the application of the weights-of-evidence and certainty factor approaches for producing landslide susceptibility maps of a landslide-prone area (Haraz) in Iran. For this purpose, the input layers of the landslide conditioning factors were prepared in the first stage. The landslide conditioning factors considered for the study area were slope gradient, slope aspect, altitude, lithology, land use, distance from streams, distance from roads, distance from faults, topographic wetness index, stream power index, stream transport index and plan curvature. For validation of the produced landslide susceptibility maps, the results of the analyses were compared with the field-verified landslide locations. Additionally, the receiver operating characteristic curves for all the landslide susceptibility models were constructed and the areas under the curves were calculated. The landslide locations were used to validate results of the landslide susceptibility maps. The verification results showed that the weights-of-evidence model (79.87%) performed better than certainty factor (72.02%) model with a standard error of 0.0663 and 0.0756, respectively. According to the results of the area under curve evaluation, the map produced by weights-of-evidence exhibits satisfactory properties. 相似文献
43.
Isaac Moradi Richard Mueller Richard Perez 《Theoretical and Applied Climatology》2014,116(3-4):661-669
Solar radiation is an important variable for studies related to solar energy applications, meteorology, climatology, hydrology, and agricultural meteorology. However, solar radiation is not routinely measured at meteorological stations; therefore, it is often required to estimate it using other techniques such as retrieving from satellite data or estimating using other geophysical variables. Over the years, many models have been developed to estimate solar radiation from other geophysical variables such as temperature, rainfall, and sunshine duration. The aim of this study was to evaluate six of these models using data measured at four independent worldwide networks. The dataset included 13 stations from Australia, 25 stations from Germany, 12 stations from Saudi Arabia, and 48 stations from the USA. The models require either sunshine duration hours (Ångstrom) or daily range of air temperature (Bristow and Campbell, Donatelli and Bellocchi, Donatelli and Campbell, Hargreaves, and Hargreaves and Samani) as input. According to the statistical parameters, Ångstrom and Bristow and Campbell indicated a better performance than the other models. The bias and root mean square error for the Ångstrom model were less than 0.25 MJ m2 day?1 and 2.25 MJ m2 day?1, respectively, and the correlation coefficient was always greater than 95 %. Statistical analysis using Student’s t test indicated that the residuals for Ångstrom, Bristow and Campbell, Hargreaves, and Hargreaves and Samani are not statistically significant at the 5 % level. In other words, the estimated values by these models are statistically consistent with the measured data. Overall, given the simplicity and performance, the Ångstrom model is the best choice for estimating solar radiation when sunshine duration measurements are available; otherwise, Bristow and Campbell can be used to estimate solar radiation using daily range of air temperature. 相似文献
44.
Fatemeh Sadeghi Mohammad Reza Mehrnia Ramin Nabizadeh Mohammad Hossein Sarrafzadeh 《洁净——土壤、空气、水》2012,40(4):416-421
The objective of this study was to investigate the effect of salt concentration on performance of a membrane bioreactor (MBR) for treating an olefin plant wastewater. For this purpose, a lab‐scale submerged MBR with a flat‐sheet ultrafiltration membrane was used for treatment of synthetic wastewater according to oxidation and neutralization unit of olefin plant. The synthetic wastewater was adjusted to have 500 mg/L chemical oxygen demand (COD). Trials on different concentrations of sodium sulfate (Na2SO4) (0–20 000 ppm) in the feed were conducted under aerobic conditions in the MBR. The results showed that increasing the salt concentrations causes an increase in the effluent COD, phenol, and oil concentrations. These results are due to reduction of the membrane filtration efficiency and also decline in the microbial activity that it is indicated by decreasing the sOUR in MBR. But in all the trials, the effluent COD and oil concentration was well within the local discharge limit of 100 and 10 mg/L, respectively. These results indicate that the MBR system is highly efficient for treating the olefin plant wastewater, and although high salt concentrations decreased organic contaminant removal rates in the MBR, the effluent still met the discharge limits for treating the olefin plant wastewater. 相似文献
45.
On 10 March 2001 the active region NOAA 9368 produced an unusually impulsive solar flare in close proximity to the solar limb. This flare has previously been studied in great detail, with observations classifying it as a type 1 white-light flare with a very hard spectrum in hard X-rays. The flare was also associated with a type II radio burst and coronal mass ejection. The flare emission characteristics appeared to closely correspond to previous instances of seismic emission from acoustically active flares. Using standard local helioseismic methods, we identified the seismic signatures produced by the flare that, to date, is the least energetic (in soft X-rays) of the flares known to have generated a detectable acoustic transient. Holographic analysis of the flare shows a compact acoustic source strongly correlated with the impulsive hard X-rays, visible continuum, and radio emission. Time?–?distance diagrams of the seismic waves emanating from the flare region also show faint signatures, mainly in the eastern sector of the active region. The strong spatial coincidence between the seismic source and the impulsive visible continuum emission reinforces the theory that a substantial component of the seismic emission seen is a result of sudden heating of the low photosphere associated with the observed visible continuum emission. Furthermore, the low-altitude magnetic loop structure inferred from potential-field extrapolations in the flaring region suggests that there is a significant anti-correlation between the seismicity of a flare and the height of the magnetic loops that conduct the particle beams from the corona. 相似文献
46.
47.
Marine fine-grained soils are well known for their compressibility, which is typically measured and reported in terms of compression index, Cc. The difficulties associated with measuring Cc have resulted in growing research interest in statistics-based estimates (i.e., correlation equations). Although many empirical and semiempirical correlations exist for estimating Cc, most available correlations are based on either data from nonmarine soils or data collected from Japanese and Korean marine clays. Thus, there are few correlations for marine clays from other parts of the world. In the present study, two independent databases which contain a total of 1,000 data points from 170 different sites worldwide are used to build and validate statistically significant correlations for estimating compression index of marine soils. The results of this study suggest that (1) the proposed correlation equations provide quite good estimates of Cc for marine soils with different stress histories and sensitivities and (2) most of the existing models have unacceptable performance when they are applied to marine soils. 相似文献
48.
Aquifer vulnerability assessment techniques have been developed to predict which areas are more likely than others to become
contaminated as a result of activities at or near the land surface. This research focuses on the evaluation of groundwater
vulnerability to pollution in an urban area. Among several assessment methods, DRASTIC has been selected for this study. ArcGIS
has been used to overlay and calculate different layers and obtain the vulnerability map. In order to show the importance
of fuzzy algorithms in classification, both Boolean and fuzzy algorithms were used and compared. The fuzzy algorithm could
recognize the areas with low and negligible vulnerability potentials whereas the Boolean model classified them as moderate.
Two sensitivity tests, the map removal sensitivity analyses and single-parameter sensitivity analysis, were performed to show
the importance of each parameter in the index calculation. 相似文献
49.
Pre-processing data using wavelet transform and PCA based on support vector regression and gene expression programming for river flow simulation 总被引：1，自引：0，他引：1
Abazar Solgi Amir Pourhaghi Ramin Bahmani Heidar Zarei 《Journal of Earth System Science》2017,126(5):65
An accurate estimation of flow using different models is an issue for water resource researchers. In this study, support vector regression (SVR) and gene expression programming (GEP) models in daily and monthly scale were used in order to simulate Gamasiyab River flow in Nahavand, Iran. The results showed that although the performance of models in daily scale was acceptable and the result of SVR model was a little better, their performance in the daily scale was really better than the monthly scale. Therefore, wavelet transform was used and the main signal of every input was decomposed. Then, by using principal component analysis method, important sub-signals were recognized and used as inputs for the SVR and GEP models to produce wavelet-support vector regression (WSVR) and wavelet-gene expression programming. The results showed that the performance of WSVR was better than the SVR in such a way that the combination of SVR with wavelet could improve the determination coefficient of the model up to 3% and 18% for daily and monthly scales, respectively. Totally, it can be said that the combination of wavelet with SVR is a suitable tool for the prediction of Gamasiyab River flow in both daily and monthly scales. 相似文献
50.
Land Surface Temperature (LST) is considered important in monitoring the energy flux between the land surface and atmosphere. Due to the diversity of topography in Iran and its effect on the climate diversity, we decided to study the effect of topography on the LST variations. To this end, the LST digital data derived from the observations of the MODIS Terra and Aqua were used. The results indicated that, during the daytime, from sea level up to a height of 400 meters, the LST increased, and then the temperature decreased with increasing altitude, and up to a height of 3000 meters, there was a strong correlation between the two. LST lapse rate was more during the daytime compared with that of the night time and it was more during the winter compared with the summer. LST lapse rate showed larger variability in diurnal cycle, but its monthly patterns were similar in different aspects. The aspect had substantial effect on LST inversion elevation. Furthermore, the inverse relationship between LST and slope was strong in slopes up to 20°. 相似文献