Daily reference evapotranspiration modeling by using genetic programming approach in the Basque Country (Northern Spain)     

Jalal Shiri  Özgur Kişi  Gorka Landeras  José Javier López  Amir Hossein Nazemi  Louis C.P.M. Stuyt 《Journal of Hydrology》2012

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Mass loss of the Greenland ice sheet from GRACE time-variable gravity measurements     

Gholamreza Joodaki  Hossein Nahavandchi 《Studia Geophysica et Geodaetica》2012,56(1):197-214

The Gravity Recovery and Climate Experiment (GRACE) satellite data is used to estimate the rate of ice mass variability over Greenland. To do this, monthly GRACE level 2 Release-04 (RL04) data from three different processing centers, Center for Space Research (CSR), German Research Center for Geosciences (GFZ) and Jet Propulsion Laboratories (JPL) were used during the period April 2002 to February 2010. It should be noted that some months are missing for all three data sets. Results of computations provide a mass decrease of −163 ± 20 Gigaton per year (Gt/yr) based on CSR-RL04 data, −161 ± 21 Gt/yr based on GFZ-RL04 data and −84 ± 26 Gt/yr based on JPL RL04.1. The results are derived by the application of a non-isotropic filter whose degree of smoothing corresponds to a Gaussian filter with a radius of 340 km. Striping effects in the GRACE data, C₂₀ effect, and leakage effects are taken into the consideration in the computations. There is some significant spread of the results among different processing centers of GRACE solutions; however, estimates achieved in this study are in agreement with the results obtained from alternative GRACE solutions.  相似文献   

Landform classification from a digital elevation model and satellite imagery   总被引：4，自引：0，他引：4  

Hossein Saadat  Robert Bonnell  Forood Sharifi  Guy Mehuys  Mohammad Namdar  Sasan Ale-Ebrahim 《Geomorphology》2008,100(3-4):453-464

The Iranian Soil and Water Research Institute has been involved in mapping the soils of Iran and classifying landforms for the last 60 years. However, the accuracy of traditional landform maps is very low (about 55%). To date, aerial photographs and topographic maps have been used for landform classification studies. The principal objective of this research is to propose a quantitative approach for landform classification based on a 10-m resolution digital elevation model (DEM) and some use of an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image. In order to extract and identify the various landforms, slope, elevation range, and stream network pattern were used as basic identifying parameters. These are extractable from a DEM. Further, ASTER images were required to identify the general outline shape of a landform type and the presence or absence of gravel. This study encompassed a relatively large watershed of 451 183 ha with a total elevation difference of 2445 m and a variety of landforms from flat River Alluvial Plains to steep mountains. Classification accuracy ranged from 91.8 to 99.6% with an average of 96.7% based upon extensive ground-truthing. Since similar digital and ASTER image information is available for Iran, an accurate landform map can now be produced for the whole country. The main advantages of this approach are accuracy, lower demands on time and funds for field work and ready availability of required data for many regions of the world.  相似文献   

Unification of vertical datums by GPS and gravimetric geoid models using modified stokes formula     

Hossein Nahavandchi  Lars E. Sjöberg 《Marine Geodesy》2013,36(4):261-273

In general, neighboring vertical datums can be compared directly at one or more common points on the border between the datums. This direct method requires leveling and gravity measurements. Such a direct connection is not possible if the datums are separated by an ocean or another body of water. Then a rigorous mathematical model, an indirect approach, may be useful. In order to connect regional vertical datums, a rigorous mathematical model is derived based on a method by Rummel and Teunissen. In this study, two vertical datums are connected indirectly by means of a combination of precise geocentric positions of tide gauge sites and their geoid heights in one geocentric coordinate system and their height values in the respective height datums. This method is used to connect the Swedish and the Finnish height systems. The difference between Swedish RH70 and the Finnish N60 height systems is estimated to —12.1±2.7 cm. The results are mostly in good agreement with those of the direct approach by Sjöberg and by Ekman and the indirect approach by Pan and Sjöberg.  相似文献   

Physical and numerical studies of stability of soil blocks reinforced by brittle shear pins     

Ukritchon  Boonchai  Ouch  Rithy  Pipatpongsa  Thirapong  Khosravi  Mohammad Hossein 《Acta Geotechnica》2019,14(6):2103-2122

In this paper, the stability and failure mechanism of soil blocks that were reinforced by brittle shear pins and rested on a low-interface friction plane were studied by means of physical and numerical models. The humid silica sand no. 6 was employed to build the physical models of soil blocks, while the Teflon sheet was employed as the low-interface friction plane. To study the effect of stabilizing piles on slopes, the soil blocks were reinforced by brittle shear pins using pencil leads with 2 mm in diameter. Three-dimensional finite element analyses were employed to analyze the stability of this problem. The effects of numbers and patterns of shear pins on the stability and failure mechanisms of physical and numerical models were compared and discussed.

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Nematode community structure in relation to metals in the southern of Caspian Sea     

Kazem Darvish Bastami  Mehrshad Taheri  Maryam Yazdani Foshtomi  Sarah Haghparast  Ali Hamzehpour  Hossein Bagheri  Marjan Esmaeilzadeh  Neda Molamohyeddin 《海洋学报(英文版)》2017,36(10):79-86

Spatial distribution and structure of nematode assemblages in coastal sediments of the southern part of the Caspian Sea were studied in relation to environmental factors. By considering metals, organic matter, Shannon diversity index(H), maturity index(MI) and trophic diversity(ITD), ecological quality status of sediment was also determined. Fifteen nematode species belonging to eleven genera were identified at the sampling sites. Average density of nematode inhabiting in sediment of the studied area was 139.78±98.91(ind. per 15.20 cm~2). According to redundancy analysis(RDA), there was high correlation between metals and some species. Based on biological indicators, the studied area had different environmental quality. Generally, chemical and biological indices showed different results while biological indices displayed similar results in more sites.  相似文献   

Studying Hygienic Status of Mechanized Long Wall Face from the Perspective of the Existing Dust Containing Silica in Tabas Coal Mine     

Hossein Arasteh  Gholamreza Saeedi 《Geotechnical and Geological Engineering》2017,35(1):213-224

In order to consider the quantity of the existing negative effect in mechanized longwall mining face in Tabas coal mine, the concentration of the available coal dust and amount of its toxicity in every part of the mining face and tail gate were investigated and compared with the permissible amount. After sampling and preparing dust, its concentration was determined by gravimetric method. Then, using Zetasizer, the particle size distributions were determined and also the available amount of silica in the samples was found using SEM and XRF device. The results of the elemental analysis of dust in the mine showed that the weight percentage of silica in dust was between 27.9 and 26.7 %. The correction of the permissible dust concentration from the perspective of silica was done and the result was reported as 0.36 mg/m³. Computational fluid dynamics can be used to determine dust accumulation zones and the zones with high dust concentration. Finally, D₅₀ of the samples showed that the existing toxicity in dust can be transferred to dozens of meters far from the source (shearer).  相似文献   

Monthly reservoir inflow forecasting using a new hybrid SARIMA genetic programming approach     

Hamid Moeeni  Hossein Bonakdari  Isa Ebtehaj 《Journal of Earth System Science》2017,126(2):18

Forecasting reservoir inflow is one of the most important components of water resources and hydroelectric systems operation management. Seasonal autoregressive integrated moving average (SARIMA) models have been frequently used for predicting river flow. SARIMA models are linear and do not consider the random component of statistical data. To overcome this shortcoming, monthly inflow is predicted in this study based on a combination of seasonal autoregressive integrated moving average (SARIMA) and gene expression programming (GEP) models, which is a new hybrid method (SARIMA–GEP). To this end, a four-step process is employed. First, the monthly inflow datasets are pre-processed. Second, the datasets are modelled linearly with SARIMA and in the third stage, the non-linearity of residual series caused by linear modelling is evaluated. After confirming the non-linearity, the residuals are modelled in the fourth step using a gene expression programming (GEP) method. The proposed hybrid model is employed to predict the monthly inflow to the Jamishan Dam in west Iran. Thirty years’ worth of site measurements of monthly reservoir dam inflow with extreme seasonal variations are used. The results of this hybrid model (SARIMA–GEP) are compared with SARIMA, GEP, artificial neural network (ANN) and SARIMA–ANN models. The results indicate that the SARIMA–GEP model (R ²=78.8, VAF =78.8, RMSE =0.89, MAPE =43.4, CRM =0.053) outperforms SARIMA and GEP and SARIMA–ANN (R ²=68.3, VAF =66.4, RMSE =1.12, MAPE =56.6, CRM =0.032) displays better performance than the SARIMA and ANN models. A comparison of the two hybrid models indicates the superiority of SARIMA–GEP over the SARIMA–ANN model.  相似文献   

Rock types of the Kangan Formation and the effects of pore-filling minerals on reservoir quality in a gas field,Persian Gulf,Iran     

Ali-Akbar Irajian  Kamaladdin Bazargani-Guilani  Rahim Mahari  Ali Solgi  Alireza Moshrefizadeh  Hossein Alnaghian 《Arabian Journal of Geosciences》2017,10(12):272

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Clear-water scour around semi-elliptical abutments with armored beds     

Jueyi SUI  Hossein AFZALIMEHR  Abdolreza Kabiri SAMANI  Mehrnoosh MAHERANI 《国际泥沙研究》2010,25(3):233-245

Experimental study has been carried out under a clear-water scour condition to explore the local scour around semi-elliptical model bridge abutments with armor-layer bed, compared with the local scour process around semi-circular abutment. Two types of model bridge abutments, namely semi-elliptical and semi-circular abutments have been used in this experimental study. The model abutments had a ratio of streamwise length of abutment to the length of abutment transverse to the flow of 2 for semi-circular abutments and 3 for semi-elliptical abutments. In total, 50 Experiments have been designed and conducted under different flow conditions such as bed shear velocities, flow depth, and dimensions of bridge abutment model, as well as grain size of the bed material. Based on these experiments, the scour process around bridge abutments has been assessed. The dependence of the equilibrium scour depth of the scour hole on hydraulic variables has been studied. Empirical equation describing the equilibrium scour depth of the scour hole around bridge abutments has been developed.  相似文献