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Alireza Owji Isa Esfandiarpour Boroujeni Ardavan Kamali Seyed Javad Hosseinifard Mohsen Bagheri Bodaghabadi 《Arabian Journal of Geosciences》2014,7(4):1491-1499
Soil texture is an important physical soil property that may contribute to variations in many soil functions as well as nutrient storage and availability, water retention, and soil erosion. Although several methods for determining the texture classes of soil particles have been proposed, differences among hydrometer reading times have presented challenges in determining the precise soil texture classes. Therefore, this study was conducted to evaluate the effects of hydrometer reading time on the spatial variability of soil textures in the Rafsanjan area, southeast Iran. To accomplish this, 77 soil samples were collected on a 500-m square sampling grid from depths of 0–40, 40–80, and 80–120 cm, and their particle sizes were determined through analysis for 40 s, 2 h, 6.5 h, and 8 h using the Bouyoucos hydrometer method. The results showed a strong spatial correlation in the soil particles among sampling soil layers and across the study area. Moreover, the differences among hydrometer reading times did not have a significant impact on determination of coarse soil texture classes, although they did influence determination of the finer classes. Although the 8 h reading time provided the most accurate response with respect to mechanical analysis of a soil, after 6.5 h the hydrometer could also largely (more than 80.0 %, on average) achieve this goal. Additionally, the 2 h hydrometer reading time could also be useful for the initial assessment or general overview of the soil texture in a certain region; however, it is not recommended for precision agriculture or site-specific management. 相似文献
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Asghar Siahmansouri Javad Gholamnejad Mohammad Fatehi Marji 《Arabian Journal of Geosciences》2014,7(3):1059-1066
Twin tunnels can be used for many applications. Interaction between two tunnels is an important problem in tunnel engineering that should be studied specially. Numerical investigations are well adapted to field data and numerical methods can be used in design of rock pillar of twin circular tunnels. So far, no relationship has been provided to estimate the minimum stable rock pillar width. In this paper, the interaction between twin circular tunnels has been studied using 2D finite element analysis. To do this, a great number of twin tunnels were modeled in Phase2 software with different conditions of rock mass (RMR value) and depth of tunnel. Models were analyzed and minimum stable rock pillar width was determined. This process was repeated for three different ratios of K (ratio of horizontal stress to vertical stress, 0.5, 1, and 1.5). Finally, according to the linear and nonlinear regression methods, the best merit function was fitted to result of numerical analysis. Then, new approximate formula was proposed to estimate the minimum rock pillar width according to RMR value and depth of twin circular tunnels with different K values. The formulae are very accurate (coefficient of correlation equals to minimum 0.96) that can be used for estimating the minimum rock pillar width of twin circular tunnels. 相似文献
33.
Kalaee Mohammad Javad Memarian Mohammad Hossein Nekoie Zahra 《Geomagnetism and Aeronomy》2021,61(8):1240-1250
Geomagnetism and Aeronomy - The global TEC (Total Electron Content) behavior has been studied for several decades, but some properties of this behavior have not been understood well, such as the... 相似文献
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In this experimental study,the effect of suspended sediment concentration on the characteristics of a submerged hydraulic jump in a rectangular channel has been investigated,based on the sediment conce... 相似文献
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A multi-technique approach for characterizing the SVN49 signal anomaly, part 1: receiver tracking and IQ constellation 总被引:3,自引:1,他引:2
André Hauschild Oliver Montenbruck Steffen Thoelert Stefan Erker Michael Meurer Javad Ashjaee 《GPS Solutions》2012,16(1):19-28
A characterization of the signal anomaly of SVN49 is presented. A mathematical model is developed to relate the observed multipath
to the internal signal reflection. The analyses provided are based on measurements, which have been collected during a dedicated
tracking campaign with a 30-m dish antenna. Data on the L1 and L2 frequency have been collected with four different receivers.
In addition, IQ samples have been recorded directly with a spectrum analyzer. The multipath combination of the receiver measurements
on L1 and L2 is analyzed to demonstrate the effect of the signal reflections on different correlator spacing. The capability
to suppress the signal reflection with receiver multipath mitigation methods is demonstrated. Finally, preliminary estimates
of the attenuation, delay, and phase shift over elevation are obtained from an IQ sample analysis. 相似文献
37.
Evolution of Multipath Error Reduction with Signal Processing 总被引:1,自引:0,他引:1
GPS Solutions - The described method of code and carrier multipath error reduction is a refinement of the strobe method of pseudo random noise (PRN) signal processing. This method utilizes as a... 相似文献
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The Bam Earthquake of 26 December 2003 总被引:3,自引:0,他引:3
Farrokh?NadimEmail author Masoud?Moghtaderi-Zadeh Conrad?Lindholm Arild?Andresen Svein?Remseth Mohammad?Javad?Bolourchi Mohammad?Mokhtari Eirik?Tvedt 《Bulletin of Earthquake Engineering》2004,2(2):119-153
The devastating earthquake of 26 December 2003 claimed more than 26,000 lives in the city of Bam and surrounding towns and villages in Southeast Iran, and left the majority of the Bam population homeless. The reason for this tragedy was an unfortunate combination of geological, social and human circumstances. The causative fault practically traversed the city of Bam and the earthquake occurred at a shallow depth. The residential buildings were completely inappropriate for a seismic region, being extremely vulnerable to earthquake shaking, and the earthquake occurred early in the morning when most people were still sleeping. The damage pattern was nearly symmetric about a line 3 km to the west of the surface expression of the Bam fault, and the damage attenuated rapidly with distance from this line. The industrial facilities and the lifelines performed relatively well and experienced slight to moderate damage, but this might have been due to their distance from the earthquake epicentre. However, many of the qanat (traditional subterranean irrigation channels) chains that served the twin cities of Bam and Baravat collapsed. Emergency facilities (hospitals, police and fire stations), schools and the university were destroyed and/or heavily damaged during the earthquake. The geotechnical effects of the earthquake were not significant. There was little evidence that site response effects played a major role in the damage pattern in the city. There were no reports of liquefaction and only minor sliding activity took place during the event. A unique set of strong motion acceleration recordings were obtained at the Bam accelerograph station. The highest peak ground acceleration (nearly 1g) was recorded for the vertical component of the motion. However, the longitudinal component (fault-parallel motion in N–S direction) clearly had the largest energy flux, as well as the largest maximum velocity and displacement. 相似文献
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