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Sattam Almadani Elkhedr Ibrahim Mahfooz Hafez Hussain Alfaifi Talal Alharbi Kamal Abdelrahman Essam Abdel-Motaal 《Arabian Journal of Geosciences》2018,11(2):33
In the present study, the existence of cavities, voids, and fractures was verified at the site of the El-Elb Dam, which is located to the northwest of Riyadh City across Wadi Hanifa, using 2D electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) techniques. For this purpose, four ERT profiles were measured on the downstream side of the El-Elb Dam using the Syscal Pro Switch-72 resistivity meter. In addition, a GPR survey using a 400-MHz antenna and a SIR-3000 instrument was conducted along five profiles above the stilling basins on the downstream side of the dam and one radar profile was measured outside the stilling basins area across the course of the wadi. The resultant geophysical data were interpreted with the aid of information from a field-based structural and stratigraphic evaluation of the outcropped bedrock on the banks of the wadi course. The analysis of the inverted ERT and filtered radar sections revealed several resistivity and electromagnetic reflection anomalies that are identified laterally and vertically across the measured sections. These anomalies indicate the presence of fractures and karst features affected the limestone bedrock in the dam site. These near-surface karstified and fractured strata represent a critical hazard to the structural safety of the dam. 相似文献
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Ahmed Mohamed Tawfiek Guanzheng TAN Ali G. Hafez Abdullah Al-Amri Nassir Alarif Kamal Abdelrahman 《Arabian Journal of Geosciences》2016,9(11):580
Despite the popularity of using the Haar wavelet filter in many applications, it sometimes introduces fake patterns into the multi resolution analysis (MRA) of seismic data. In this work, we compared different wavelet filters to demonstrate that these patterns are fake and not part of the original waveforms and to show that they are a result of using the Haar wavelet filter as a short-width wavelet. To achieve this, many seismic waveforms from two different sources: the Egyptian National Seismic Network (ENSN) and the High Sensitivity Seismograph Network Japan (Hi-net) are used with different wavelet filters. We propose an algorithm based on an autoregressive (AR) model to detect these patterns automatically and fully. 相似文献
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Stefano Urbini Iacopo Nicolosi Antonio Zeoli Sami El Khrepy Ahmed Lethy Mahfooz Hafez Mohamed El Gabry Ahmed El Barkooky Aly Barakat Mahomoud GOMAA Ali M. Radwan Mohamed El Sharkawi Massimo D’orazio Luigi Folco 《Meteoritics & planetary science》2012,47(11):1842-1868
Abstract– We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small‐scale hypervelocity impact craters. It is an exceptionally well‐preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth‐to‐diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45°. Newly identified asymmetries, including the off‐center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well‐preserved craters. Geomagnetic data reveal no buried individual impactor masses >100 kg and suggest that the total mass of the buried shrapnel >100 g is approximately 1050–1700 kg. Based on this mass value plus that of shrapnel >10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t. 相似文献
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Ramin Vaghei Farzad Hejazi Hafez Taheri Mohd Saleh Jaafar Farah Nora Aznieta Abdul Aziz 《地震工程与工程振动(英文版)》2017,16(1):97-117
The Industrialized Building System (IBS) was recently introduced to minimize the time and cost of project construction. Accordingly, ensuring the integration of the connection of precast components in IBS structures is an important factor that ensures stability of buildings subjected to dynamic loads from earthquakes, vehicles, and machineries. However, structural engineers still lack knowledge on the proper connection and detailed joints of IBS structure construction. Therefore, this study proposes a special precast concrete wall-to-wall connection system for dynamic loads that resists multidirectional imposed loads and reduces vibration effects (PI2014701723). This system is designed to connect two adjacent precast wall panels by using two steel U-shaped channels (i.e., male and female joints). During casting, each joint is adapted for incorporation into a respective wall panel after considering the following conditions: one side of the steel channel opens into the thickness face of the panel; a U-shaped rubber is implemented between the two channels to dissipate the vibration effect; and bolts and nuts are used to create an extension between the two U-shaped male and female steel channels. The developed finite element model of the precast wall is subjected to cyclic loads to evaluate the performance of the proposed connection during an imposed dynamic load. Connection performance is then compared with conventional connections based on the energy dissipation, stress, deformation, and concrete damage in the plastic range. The proposed precast connection is capable of exceeding the energy absorption of precast walls subjected to dynamic load, thereby improving its resistance behavior in all principal directions. 相似文献
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Artificially enhancing recharge rate into groundwater aquifer at specially designed facilities is an attractive option for increasing the storage capacity of potable water in arid and semi‐arid region such as Damascus basin (Syria). Two dug wells (I and II) for water injection and 24 wells for water extraction are available in Mazraha station for artificial recharge experiment. Chemical and stable isotopes (δ2H and δ18O) were used to evaluate artificial recharge efficiency. 400 to 500*103 m3 of spring water were injected annually into the ambient shallow groundwater in Mazraha station, which is used later for drinking purpose. Ambient groundwater and injected spring water are calcium bicarbonate type with EC about 880 ± 60 μS/cm and 300 ± 50 μS/cm, respectively. The injected water is under saturated versus calcite and the ambient groundwater is over saturated, while the recovered water is near equilibrium. It was observed that the injection process formed a chemical dilution plume that improves the groundwater quality. Results demonstrate that the hydraulic conductivity of the aquifer is estimated around 6.8*10?4 m/s. The effective diameter of artificial recharge is limited to about 250 m from the injection wells. Mixing rate of 30% is required in order to reduce nitrate concentration below 50 mg/l which is considered the maximum concentration limit for potable water. Deuterium and oxygen‐18 relationship demonstrates that mixing line between injected water and ambient groundwater has a slope of 6.1. Oxygen‐18 and Cl? plot indicates that groundwater salinity origin is from mixing process, and no dissolution and evaporation were observed. These results demonstrate the efficiency of the artificial recharge experiments to restore groundwater storage capacity and to improve the water quality. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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The chemical and isotopic composition of monthly composite rain samples collected at 13 meteoric stations in Syria during two hydrological cycles from 1991 to 1993 have been measured. The chemical analysis of the samples revealed at a number of stations pollution due to industry and sand storms. The temporal and spatial variation of the isotopic composition has been found to be comparable with one of the neighbouring countries such as Jordan and others. The average weighted oxygen‐18 and deuterium values are − 7·5 and − 39·11‰, respectively, and the deuterium excess is 21‰ . The individual isotope values can be divided into two groups. One group is represented by winter precipitation and fits closely the Mediterranean Meteorological Water Line (MMWL). Thus, for winter precipitation, condensation of Mediterranean water vapour appears to be the dominating isotope fractionation process. The other group represents spring precipitation and is spread along an evaporation line below the MMWL, thus indicating the influence of sub‐cloud evaporation. The d‐excess has been found to be lower in the north of Syria (19·9‰ at Tartous, 18·1‰ at Jarablous) than in the south of the country (23·4‰ at Sweida, 24·1‰ at Izra) where Mediterranean air mass dominates. The d‐excess of precipitation in neighbouring countries is also close to the average value of the eastern Mediterranean basin of 22‰ , e.g. for Jordan the value is 23‰ , which signifies that Mediterranean water vapour is, for all these countries, the dominant source of precipitation. The tritium content of precipitation was found to increase with distance from the coast (5·3 TU at coastal station Tartous, 8·8 TU at continental station Palmyra). Low tritium content and high d‐excess at coastal stations clearly indicate a Mediterranean air moisture source. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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The Eastern Mediterranean and the Middle East (EMME) is suffering from abnormal cooling of weather conditions and existence of an extreme weather phenomenon known as ice storm Alexa. The present paper investigates the weather conditions over Europe that causes this abnormal weather over the EMME through December of 2013. Daily data sets of several meteorological elements (temperature, precipitation, relative humidity, sea level pressure, and geopotential height at level 500 hPa, etc.) over the northern hemisphere, including Europe and EMME of December of 2013, have been used through the present work. In addition, to that, a time cross section analysis of the daily operational data for meteorological elements (mean surface temperature, temperature and geopotential height at level 500 hPa, relative humidity, precipitation rate, and sea surface pressure) was done over the EMME for December 2013. The methodology of anomaly and correlation coefficient techniques for the data sets has been used. The results uncovered that the EMME has abnormal and very cold weather conditions due to the inference of meridional blocking persisted over Europe and the existence of the extremely negative geopotential height anomaly aloft over Eastern Europe throughout this month. 相似文献
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