Development of a new wavelet-based hybrid model to forecast multi-scalar SPEI drought index (case study: Zanjan city,Iran)     

Karbasi  Masoud  Karbasi  Maryam  Jamei  Mehdi  Malik  Anurag  Azamathulla  Hazi Mohammad 《Theoretical and Applied Climatology》2022,147(1-2):499-522

Theoretical and Applied Climatology - Drought forecasting plays a vital role in managing drought and reducing its effects on agricultural systems and water resources. In the present study, three...  相似文献   

Soil genesis and clay mineralogy on Aliabbas River Alluvial Fan, Kerman Province     

Mohammad Hady Farpoor  Mehdi Irannejad 《Arabian Journal of Geosciences》2013,6(3):921-928

Alluvial fan is among the important geomorphic positions in arid and semi-arid environments, and the history of settlement in central parts of Iran plateau has significantly been related to this landform. Soil properties are also related to the stability and the position of geomorphic surfaces. To study and compare clay mineralogy and soil physicochemical responses to geomorphic positions, 11 representative pedons on stable and unstable alluvial fan surfaces and plain geomorphic position in a transect from Sarcheshmeh Mountains toward Rafsanjan Plain were studied. Soil moisture and temperature regimes of the area were aridic and mesic, respectively. Smectite, kaolinite, chlorite, illite, and palygorskite clay minerals were found in almost all the studied soils. More salinity was investigated in stable alluvial fan surfaces than unstable positions. Evidence of a more humid paleoclimate shown by buried Bt horizons in plain surface was observed. Transformation of palygorskite to smectite in surface horizon of unstable alluvial fan position and preservation of palygorskite associated by gypsum crystals in By horizon of stable fan surfaces were among the important findings of the research. There was a significant and mutual relationship between geomorphology and physicochemical and mineralogical properties of soils under study.  相似文献   

Electron transport and precipitation at Mercury during the MESSENGER flybys: Implications for electron-stimulated desorption     

David Schriver  Pavel Trávní?ek  Maha Ashour-Abdalla  Robert L. Richard  Petr Hellinger  James A. Slavin  Brian J. Anderson  Daniel N. Baker  Mehdi Benna  Scott A. Boardsen  Robert E. Gold  George C. Ho  Haje Korth  Stamatios M. Krimigis  William E. McClintock  Jason L. McLain  Thomas M. Orlando  Menelaos Sarantos  Ann L. Sprague  Richard D. Starr 《Planetary and Space Science》2011,59(15):2026-2036

To examine electron transport, energization, and precipitation in Mercury's magnetosphere, a hybrid simulation study has been carried out that follows electron trajectories within the global magnetospheric electric and magnetic field configuration of Mercury. We report analysis for two solar-wind parameter conditions corresponding to the first two MESSENGER Mercury flybys on January 14, 2008, and October 6, 2008, which occurred for similar solar wind speed and density but contrasting interplanetary magnetic field (IMF) directions. During the first flyby the IMF had a northward component, while during the second flyby the IMF was southward. Electron trajectories are traced in the fields of global hybrid simulations for the two flybys. Some solar wind electrons follow complex trajectories at or near where dayside reconnection occurs and enter the magnetosphere at these locations. The entry locations depend on the IMF orientation (north or south). As the electrons move through the entry regions they can be energized as they execute non-adiabatic (demagnetized) motion. Some electrons become magnetically trapped and drift around the planet with energies on the order of 1–10 keV. The highest energy of electrons anywhere in the magnetosphere is about 25 keV, consistent with the absence of high-energy (>35 keV) electrons observed during either MESSENGER flyby. Once within the magnetosphere, a fraction of the electrons precipitates at the planetary surface with fluxes on the order of 10⁹ cm⁻² s⁻¹ and with energies of hundreds of eV. This finding has important implications for the viability of electron-stimulated desorption (ESD) as a mechanism for contributing to the formation of the exosphere and heavy ion cloud around Mercury. From laboratory estimates of ESD ion yields, a calculated ion production rate due to ESD at Mercury is found to be on par with ion sputtering yields.  相似文献   

Effect of soil cohesion and friction angles on reverse faults     

Mehdi Ghafari  Haslinda Nahazanan  Zainuddin Md Yusoff  Vahed Ghiasi 《地震工程与工程振动(英文版)》2021,20(2):329-334

Severe faults have caused many earthquakes around the world throughout history.More recently,earthquakes have occurred in Taiwan,China(Chi-Chi fault),and elsewhere,causing loss of lives and destroying many buildings and structures.These tectonic movements have gained attention from engineers,and in the past 15 years,the focus has been on faulting mechanisms.In this study,a physical model(1 g)was fabricated and used to evaluate the impact of a reverse fault in a field with a tunnel.In the 1 g model,researchers installed additional gauges on the tunnel,so that all the displacements could be adjusted,and all the responses could be monitored during faulting.An experimental study of various soil properties(cohesion and friction angles)in reverse faults on the tunnel lining were carried out and are described herein.A comparison of results for different levels of soil cohesion revealed that it can dramatically reduce the displacement by as much as 40%,and that friction angles of 27ocan record approximately 60%more displacements than at 37o.Furthermore,a comparison of fault angles of 30oand 60oindicates that the displacements can be different by more than 43%in cohesionless soil and about 64%for a friction angle of 27o.  相似文献   

Interference of Human Impacts in Urban Growth Modelling with Transition Rules of Cellular Automata, GIS and Multi-Temporal Satellite Imagery: A Case Study of Maraghe, Iran     

Mehdi Azari  Mohsen Ahadnejad Reveshty 《Journal of the Indian Society of Remote Sensing》2013,41(4):993-1008

Urban growth is the result of physical and human impacts. In this study Cellular Automata (CA) has been used to analyze physical suitability and human forces in urban growth modelling of Maraghe. The multi-temporal satellite imagery, physical suitability and human impacts Layers have been applied to the modelling. In order to evaluate the accuracy of the image classification methods, Fuzzy ARTMAP is compared with Maximum Likelihood Classification (MLC) and Minimum Distance Classification (MDC) methods. The image classification results showed an overall accuracy of 93 %. Therefore, it is employed for classification of multi-temporal satellite imagery. In order to weight physical suitability and human impacts layers or geographical transition rules in the modelling, regression analysis, the correlation coefficient, trial-and-error method and visual comparison used. The statistical methods are presented to validate neighbourhood scales in the urban growth modelling. The calibration of the model is in fact to the estimate value of the physical suitability and human impacts layer (combinatory layer of demand for urban land and the government facilities) in the modelling. The results obtained from the model calibration showed that human impacts have the highest influence in the urban growth among other factors. Also a small neighbourhood scale (25:5?×?5 cells) is more realistic in the modeling. The accuracy of final validation is 83 % and the final scenario is based on this validation. A fuzzy CA has been used in urban growth modeling of Maraghe. The final scenario shows that Maraghe will growth on the east side, where the land demand for built up area and government facilities plays the significant role.  相似文献   

On regularized time varying gravity field models based on grace data and their comparison with hydrological models     

Mehdi Eshagh  Jean-Michel Lemoine  Pascal Gegout  Richard Biancale 《Acta Geophysica》2013,61(1):1-17

Determination of spherical harmonic coefficients of the Earth’s gravity field is often an ill-posed problem and leads to solving an ill-conditioned system of equations. Inversion of such a system is critical, as small errors of data will yield large variations in the result. Regularization is a method to solve such an unstable system of equations. In this study, direct methods of Tikhonov, truncated and damped singular value decomposition and iterative methods of ν, algebraic reconstruction technique, range restricted generalized minimum residual and conjugate gradient are used to solve the normal equations constructed based on range rate data of the gravity field and climate experiment (GRACE) for specific periods. Numerical studies show that the Tikhonov regularization and damped singular value decomposition methods for which the regularization parameter is estimated using quasioptimal criterion deliver the smoothest solutions. Each regularized solution is compared to the global land data assimilation system (GLDAS) hydrological model. The Tikhonov regularization with L-curve delivers a solution with high correlation with this model and a relatively small standard deviation over oceans. Among iterative methods, conjugate gradient is the most suited one for the same reasons and it has the shortest computation time.  相似文献   

“Phasic” metropolitan settlers: a phase-based model for the distribution of households in US metropolitan regions     

Hossein Estiri  Andy Krause  Mehdi P. Heris 《Urban geography》2013,34(5):777-794

In this article, we develop a model for explaining spatial patterns in the distribution of households across metropolitan regions in the United States. First, we use housing consumption and residential mobility theories to construct a hypothetical probability distribution function for the consumption of housing services across three phases of household life span. We then hypothesize a second probability distribution function for the offering of housing services based on the distance from city center(s) at the metropolitan scale. Intersecting the two hypothetical probability functions, we develop a phase-based model for the distribution of households in US metropolitan regions. We argue that phase one households (young adults) are more likely to reside in central city locations, whereas phase two and three households are more likely to select suburban locations, due to their respective housing consumption behaviors. We provide empirical validation of our theoretical model with the data from the 2010 US Census for 35 large metropolitan regions.  相似文献   

Application of Principal Component Analysis and Spectral Angle Mapper in the Mapping of Hydrothermal Alteration in the Jebal–Barez Area,Southeastern Iran     

Mehdi HONARMAND  Hojjatollah RANJBAR  Jamshid SHAHABPOUR 《Resource Geology》2012,62(2):119-139

The southeastern part of the central Iranian Cenozoic magmatic belt contains many areas with copper mineralization. In an analysis of this region, we used the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Enhanced Thematic Mapper plus (ETM⁺) images to map the distribution of hydrothermally altered rocks, based on their mineral assemblages. The spectral measurements, based on the field samples and satellite‐image‐derived spectra, show dominantly Al–OH (sericite and clays) and Fe–O absorption features in the visible–near infrared to shortwave infrared regions of the spectrum. Silica–bearing rocks, as well as silicic alteration, show an intense Si–O vibrational feature in the thermal infrared wavelength region. We analyzed ASTER/ETM⁺ images, performed a directed principal component analysis, and used spectral angle mapper to map areas of hydrothermal alteration and iron oxide/hydroxide minerals. The individual principal component images compiled by directed principal component analysis reveal the distribution of individual alteration minerals such as sericite, kaolinite, chlorite, epidote, and quartz. The best results, in terms of mapping the distribution of alteration, were obtained using the spectral angle mapper method. The altered areas were then sampled and the samples subjected to X–ray diffraction analysis, spectral analysis, and thin sections were observed under a microscope. Field observations reveal that more than 98% of the known copper mineralization occurs within the interpreted alteration areas. The present results indicate the great potential of ASTER and ETM⁺ data for mapping the distribution of alteration and exploring for copper mineralization in areas with a similar climate and geological setting to those of the present study.  相似文献   

The 27 August 2010 Mw 5.7 Kuh-Zar earthquake (Iran): field investigation and strong-motion evidence     

Mohammad P. Shahvar  Mehdi Zaré 《Natural Hazards》2013,66(2):689-706

In this study, seismological aspects and field observation of the 2010 Kuh-Zar earthquake has been investigated. The Kuh-Zar earthquake, of magnitude 5.7 (Mw), occurred in northeastern Iran on August 27, 2010. The area is surrounded by branches of the active faults which are coated by the quaternary alluvium. During the past several decades, this area has been struck by a number of earthquakes. This earthquake with a moderate magnitude caused a higher rate of damage contrasted with previous earthquakes of the same magnitude range in Iran. Fortunately, the source of the Kuh-Zar earthquake was in a sparsely populated area, and therefore, it caused a few loss of life with the highest observed intensity of shaking VII (modified Mercalli intensity) in the Kuh-Zar village. The shock killed 4 people, injured 40, and destroyed more than 12 villages. According to the field observation, the mechanism of this shock is defined as a left-lateral strike slip. We also checked out the properties of strong ground motions in this earthquake using the records availed by Iranian strong motion network. At KUZ station, about 7 km east of the epicenter, the recorded PGA and PGV in both horizontal and vertical components were remarkably large for an event of this size, and visual inspection of the velocity time history reveals a pulse-like shape. Unfortunately no other recording stations were located close enough to the fault to capture a directivity pulse. Finally, according to the strong-motion properties and observed information, ShakeMaps of the earthquake have been generated by the native intensity observations and the recorded strong motions.  相似文献   

Problematic Soft Soil Improvement with Both Polypropylene Fiber and Polyvinyl Acetate Resin     

Esmaeil Masoumi  Seyed Mehdi Abtahi Forooshani  Farzad Abdi Nian 《Geotechnical and Geological Engineering》2013,31(1):143-149

Several methods are used to improve mechanical properties of loose soils including rewetting, soil replacement, compaction control, chemical additives, moisture control, thermal methods, and more recently, discrete fibers. All the methods are applied to soft soil to increase load bearing capacity and to improve other properties such as prevention of erosion and dust generation. In the present study, a new method of soil improvement using both discrete polypropylene (PP) fibers and polyvinyl acetate (PVAc) is introduced. The method is applied to improve load bearing capacity of a problematic sandy soil in both dry and saturated states. Based on the results from CBR tests on various specimens, it has been revealed that the combination of PP fiber and PVAc resin with weight percentages of 0.1 and 0.6 %, respectively, had the optimum effect in increasing the CBR value in both saturated and dry soil specimens. It should be mentioned that this method has caused a great increase in the CBR value in the saturated soil.  相似文献