Geochemical Prospectivity Mapping Through a Feature Extraction–Selection Classification Scheme     

Zekri  Hamid  Cohen  David R.  Mokhtari  Ahmad Reza  Esmaeili  Abbas 《Natural Resources Research》2019,28(3):849-865

Natural Resources Research - Machine learning (ML) schemes can enhance success in geochemical prospectivity mapping. This study has examined the effectiveness of several feature extraction or...  相似文献   

Heavy metal pollution and human health risk assessment for exposure to surface soil of mining area: a comprehensive study     

Abouian Jahromi  Mohammad  Jamshidi-Zanjani  Ahmad  Khodadadi Darban  Ahmad 《Environmental Earth Sciences》2020,79(14):1-11

Climate change projections indicate an increase in intense rainfall events with consequent river flooding, which could lead to devastating natural disaster  相似文献   

Prediction of copper content in waste dump of Sarcheshmeh copper mine using visible and near-infrared reflectance spectroscopy     

Khosravi  Vahid  Ardejani  Faramarz Doulati  Aryafar  Ahmad  Yousefi  Saeed  Karami  Shawgar 《Environmental Earth Sciences》2020,79(7):1-16

The pore structure characteristics of soil are closely related to soil engineering properties. For saline soil distributed in seasonally frozen areas, existing studies have focused on the influence of freeze–thaw cycles on pore structure, while the influence of soluble salt in the soil is not well understood. This study aims to explore the influence of salt content and salt type on the pore structure of freeze-thawed soil. Soil samples with different salt contents (0–2%) and types (bicarbonate salt and sulfate salt) were subjected to 10 freeze–thaw tests, and their pore size distributions (PSDs) were obtained by mercury intrusion porosimetry tests. In addition, the PSDs were quantitatively analyzed by fractal theory. For both salts, the PSDs of the tested soil samples were bimodal after the freeze–thaw cycles, and the porosity of saline soil samples increased with increasing salt content overall. However, the contents of various types of pores in soil samples with two salt types were quite different. The variation in bicarbonate salt content mainly affected the mesopore and macropore contents in the soil samples, and their change trends were opposite to each other. For soil samples with sulfate salt, the porosity and macropore content increased significantly when the salt content exceeded 1%. In addition, the pore structures in saline soil presented fractal characteristics after the freeze–thaw cycles, and the fractal dimension was positively correlated with macropore content. This study may provide references for understanding the engineering properties of saline soil in seasonally frozen areas at the microscale.  相似文献   

Socio-political and ecological stresses on traditional pastoral systems: A review     

Muhammad  Khurshid  Mohammad  Nafees  Abdullah  Khan  Mehmet  Somuncu  Ashfaq  Ahmad Khan  Wajid  Rashid 《地理学报(英文版)》2019,29(10):1758-1770

Journal of Geographical Sciences - Pastoralism is a viable socio-economic system-shaped by landless and agro-pastoral communities in many pastoral regions of the world. This system is mainly based...  相似文献   

Free Vibration Analysis of Symmetrically Laminated Composite Plates on Elastic Foundation and Coupled with Stationary Fluid     

Arash Shahbaztabar  Ahmad Rahbar-Ranji 《中国海洋工程》2018,32(3):266-277

Free vibration analysis of symmetrically laminated composite plates resting on Pasternak elastic support and coupled with an ideal, incompressible and inviscid fluid is the objective of the present work. The fluid domain is considered to be infinite in the length direction but bounded in the depth and width directions. In order to derive the eigenvalue equation, Rayleigh-Ritz method is applied for the fluid-plate-foundation system. The efficiency of the method is proved by comparison studies with those reported in the open literature. At the end, parametric studies are carried out to examine the impact of different parameters on the natural frequencies.  相似文献   

Effects of the geometry of two‐dimensional fractures on their hydraulic aperture and on the validity of the local cubic law          下载免费PDF全文

Ahmad Hajjar  Luc Scholtès  Constantin Oltéan  Michel Antoine Buès 《水文研究》2018,32(16):2510-2525

Flow through rough fractures is investigated numerically in order to assess the validity of the local cubic law for different fracture geometries. Two‐dimensional channels with sinusoidal walls having different geometrical properties defined by the aperture, the amplitude, and the wavelength of the walls' corrugations, the corrugations asymmetry, and the phase shift between the two walls are considered to represent different fracture geometries. First, it is analytically shown that the hydraulic aperture clearly deviates from the mean aperture when the walls' roughness, the phase shift, and/or the asymmetry between the fracture walls are relatively high. The continuity and the Navier–Stokes equations are then solved by means of the finite element method and the numerical solutions compared to the theoretical predictions of the local cubic law. Reynolds numbers ranging from 0.066 to 66.66 are investigated so as to focus more particularly on the effect of flow inertial effects on the validity of the local cubic law. For low Reynolds number, typically less than 15, the local cubic law properly describes the fracture flow, especially when the fracture walls have small corrugation amplitudes. For Reynolds numbers higher than 15, the local cubic law is valid under the conditions that the fracture presents a low aspect ratio, small corrugation amplitudes, and a moderate phase lag between its walls.  相似文献   

Yield Forecasting of Spring Maize Using Remote Sensing and Crop Modeling in Faisalabad-Punjab Pakistan     

Ishfaq Ahmad  Umer Saeed  Muhammad Fahad  Asmat Ullah  M. Habib ur Rahman  Ashfaq Ahmad  Jasmeet Judge 《Journal of the Indian Society of Remote Sensing》2018,46(10):1701-1711

Real time, accurate and reliable estimation of maize yield is valuable to policy makers in decision making. The current study was planned for yield estimation of spring maize using remote sensing and crop modeling. In crop modeling, the CERES-Maize model was calibrated and evaluated with the field experiment data and after calibration and evaluation, this model was used to forecast maize yield. A Field survey of 64 farm was also conducted in Faisalabad to collect data on initial field conditions and crop management data. These data were used to forecast maize yield using crop model at farmers’ field. While in remote sensing, peak season Landsat 8 images were classified for landcover classification using machine learning algorithm. After classification, time series normalized difference vegetation index (NDVI) and land surface temperature (LST) of the surveyed 64 farms were calculated. Principle component analysis were run to correlate the indicators with maize yield. The selected LSTs and NDVIs were used to develop yield forecasting equations using least absolute shrinkage and selection operator (LASSO) regression. Calibrated and evaluated results of CERES-Maize showed the mean absolute % error (MAPE) of 0.35–6.71% for all recorded variables. In remote sensing all machine learning algorithms showed the accuracy greater the 90%, however support vector machine (SVM-radial basis) showed the higher accuracy of 97%, that was used for classification of maize area. The accuracy of area estimated through SVM-radial basis was 91%, when validated with crop reporting service. Yield forecasting results of crop model were precise with RMSE of 255 kg ha^?1, while remote sensing showed the RMSE of 397 kg ha^?1. Overall strength of relationship between estimated and actual grain yields were good with R² of 0.94 in both techniques. For regional yield forecasting remote sensing could be used due greater advantages of less input dataset and if focus is to assess specific stress, and interaction of plant genetics to soil and environmental conditions than crop model is very useful tool.  相似文献   

The effect of traffic on levels,distribution and chemical partitioning of harmful metals in the street dust and surface soil from urban areas of Tehran,Iran     

Ahmad Jonidi Jafari  Majid Kermani  Roshanak Rezaei Kalantary  Hossein Arfaeinia 《Environmental Earth Sciences》2018,77(2):38

Due to the explosive industrialization and rapid expansion of the population in many parts of the world, heavy metals are released into the environment continuously and pose a great risk on human health. Street dust and surface soil samples from very heavy, heavy, medium and low traffic areas and a natural site in Tehran, Iran, were analyzed for some physicochemical features, total and chemical fractionating of selected metals (Zn, Al, Sr, Pb, Cu, Cr, Cd, Co, Ni and V) to investigate the influence of traffic on their mobility and accumulation in the environment. The pH, electrical conductivity (EC), carbonates and organic carbon contents were similar in soil and dust samples from the areas with same traffic. The traffic increases EC contents in dust/soil matrixes, but has no effect on concentrations of metals in soil samples. Rises in metal levels with traffic were found in dust samples. Moreover, the traffic increases the percentage of both acid-soluble and reducible fractions, which are related to Pb and Zn. The mobilization of Cu, Zn, Pb, Cr in dust samples was easier than in soil. The speciation of metals except Cd is mainly affected by physicochemical features in soil, though total metals affected the speciation in dust samples (except chromium and nickel).  相似文献   

Diagenetic evolution vis-a-vis reservoir characteristics of Dhosa sandstones,Ler dome,Kachchh, western India     

Asma A. Ghaznavi  Mohammad Masroor Alam  Zuhi Khan  A. H. M. Ahmad 《Arabian Journal of Geosciences》2018,11(14):387

The detrital mineralogy as well as diagenetic characters of the Dhosa Sandstone Member of Chari Formation exposed at the Lerdome, south of Bhuj was studied. In order to assess the potential of the Dhosa Sandstone as a reservoir, it is substantial to understand the diagenetic processes that are controlled largely by post-depositional cementation and compaction in addition to framework composition and original depositional textures. The petrologic analysis of 33 thin sections was carried out to discern primary composition and diagenetic features including primary and secondary porosity patterns. Monocrystalline quartz dominates the detrital mineralogy followed by polycrystalline quartz. Among the polycrystalline variety recrystallized metamorphic quartz surpasses stretched metamorphic quartz in terms of abundance. Feldspars comprise microcline and plagioclase where the former is dominant over the latter. Orthoclase too comprises a very small percentage. Mica, chert, rock fragments, and heavies form the remaining detrital constituent in descending order of their constituent percentage. The diagenetic precipitates are mainly carbonate (8.30%) and iron (7.80%) followed by clay (0.66%) and silica (0.88%) that are minor constituent of the total cementing material. The main paragenetic events identified are early cementation, mechanical compaction, late cementation, dissolution, and authigenesis of clays. The overall reservoir quality seems to be controlled by compaction and authigenic carbonate cementation. The minus cement porosity average 29.4%. The porosity loss due to compaction is 21.92% and by cementation is 29.71%. The loss of original porosity was due to early cementation followed by moderate mechanical compaction during shallow burial. Preservation of available miniscule primary porosity was ascribed to dissolution of carbonates and quartz overgrowth which resisted chemical compaction during deep burial. The studied sandstones may have low reservoir quality owing to existing porosity of less than 9%. More carbonate dissolution and its transformation in dolomite in sub-surface condition and macro-fracture porosity may result in enhanced secondary porosity and good diagenetic traps.  相似文献   

Eco-friendly smart hydrogels for soil conditioning and sustain release fertilizer     

J. Pushpamalar  S. J. Langford  M. B. Ahmad  Y. Y. Lim  K. Hashim 《International Journal of Environmental Science and Technology》2018,15(10):2059-2074

In the agricultural industry, biomass waste generated along with the production of food, is transformed into value-added products. Also, the demand for the slow or control release fertilizer is increasing to reduce the cost of maintaining the agricultural land. These issues are tackled by converting biomass waste to a slow fertilizer release vehicle and biodegradable water retention material that could reduce the cost for fertilizer application and simultaneously preserved the soil from dryness. A series of carboxymethyl sago pulp (CMSP) hydrogels were prepared by electron beam irradiation. Slow release systems were evaluated by loading potassium nitrate (KNO₃) and ammonium nitrate (NH₄NO₃) into the CMSP hydrogels. These CMSP hydrogels endow slow release property, biodegradability and a soil moisture preservation property that could find greener application in agricultural industries. The results indicate that CMSP hydrogels have a great potential as an agent for slow release of fertilizers.  相似文献