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In the present study, the free vibration of functionally graded beams resting on two parameter elastic foundation was examined. The properties of the functionally graded materials were presumed to vary continuously along the thickness direction. The foundation medium was assumed to be linear, homogeneous, and isotropic, and it was modeled by the Winkler-Pasternak model with two parameters for describing the reaction of the elastic foundation on the beam. The functionally graded beam was modeled with classical beam theory. The governing equation including the effects of functionally graded material properties, Winkler-Pasternak elastic foundation was solved using separation of variables. The eigenvalues of yielding fundamental equation versus clamped-clamped, clamped-free, clamped-simply supported, and simply supported-simply supported boundary conditions were found. To corroborate the results, comparisons were carried out with available results for homogeneous and functionally graded beams. The effects of Winkler-Pasternak type elastic foundation and functionally graded material properties on the values of dimensionless frequency parameter of beams were discussed. Briefly, it was found that the dimensionless frequency parameters of beam change according to material properties, presence of elastic foundation, and boundary conditions; moreover, the separate effects of these quantities on each other are interesting. 相似文献
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Saeed Waleed Shouakar-Stash Orfan Unger André Wood Warren W. Parker Beth 《Hydrogeology Journal》2021,29(5):1939-1951
Hydrogeology Journal - Sabkha Matti is a potential discharge point for regional groundwater systems in the Rub’ al Khali topographic basin of Saudi Arabia. The hydrogeochemical evolution of... 相似文献
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Mohamed Metwaly Mohamed Ahmed Khalil El-Said Al-Sayed Abeer El-Kenawy 《Arabian Journal of Geosciences》2013,6(9):3527-3533
This study provides an evaluation of the subsurface oil contaminant flow in an oil production field at the Wadi Feiran fan, along the Gulf of Suez, Egypt. The 2D electrical resistivity tomography technique has been applied along four profiles surrounding the spill location of oil dump site. Theoretical soil resistivity response versus fluid resistivity for different cation exchange capacity values has been studied. Then, a physical model for the current situation of flowing the oil over the groundwater (sea invaded water) of saturated fluvial sediments has been introduced. It was supposed that the crude oil has higher resistivity values and turned to be conductive far away from the oil spill source under the effect of microbial biodegradation. Such conditions of contaminated distribution and its resistivity values have been considered during the inversion and interpretation of the acquired data sets. The processed 2D resistivity profiles reveal that oil plumes are accumulated in the seawater invasion direction, whereas it has low signatures along the profiles parallel to the shore line. 相似文献
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Prediction of the location of future rupture surfaces of a slowly moving loess landslide by electrical resistivity tomography 
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下载免费PDF全文 S. Szalai K. Szokoli M. Metwaly Z. Gribovszki E. Prácser 《Geophysical Prospecting》2017,65(2):596-616
A slowly moving loess landslide along the River Danube in South Hungary was studied using electrical resistivity tomography. Our aim was to determine the fracture system of the study site. Due to the homogeneous composition of the loess, it seems to be the only possibility to get information about the landslide and its further evolution. The applicability of the electrical resistivity tomography technique for such a supposedly dense fracture system was studied by numerical modelling, and the results have been verified in the field. The dip of the fractures could not always been observed, and they could not be explored deeply. However, it was possible to map their surface projection to get the desired information about the structure of the landslide. Fracture zones could have been especially well localized, enabling the prediction of the positions of future rupture surfaces and thus the delineation of the endangered zone. Although the area outside of the already subsided one is not endangered yet, the area which has already started to move is going to break into two. Parts of the about 5 m wide blocks at the front of the landslide may fall or slide down anytime. A large area was assumed to move as one unit. Most of our predictions have been verified by the mass movements that occurred about one and half years after the measurements. The electrical resistivity tomography method proved to be a good tool to characterize the fracture system of such a landslide area, enabling the prediction of future rupture surfaces and also delineation of the endangered area. Its use is therefore highly recommended to monitor landslides to provide early risk warnings to avoid damage to constructions or endangering human life. 相似文献
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Shoreline positions established from beach profile surveys combined with wave data are jointly analyzed, as a function of their contribution to coastal processes, to investigate the interaction between waves, shoreline orientation and coastal structures along the Nile delta promontories, Rosetta, Burullus and Damietta. Repeated beach profile surveys along the promontory sectors (64 km long in total) have been analyzed to determine rates of shoreline changes prior to construction (1971–1990) and after construction of protective structures (1990–2000). The behavior of coastline pre- and post-construction indicates that coastal erosion fronting protective structures has declined in the case of the seawalls at the tips of the Rosetta and Damietta promontories, or has been partially replaced by sand accumulation in the case of detached breakwaters at Baltim (east of Burullus promontory) and at Ras El Bar (west of the Damietta promontory). As a consequence, downdrift erosion has been initiated in local areas adjacent to these structures in the direction of longshore sediment transport. The 5-km-long seawall protecting the Rosetta promontory has stopped the dramatic erosion of this highly eroded area (formerly shoreward retreated 88 m/year), with adverse local erosion at its west and east ends, being 3 and 13 m/year, respectively. Similarly, the 6-km-long seawall built on the eastern tip of the Damietta Promontory, still under construction, has nearly stopped the severe erosion, which was formerly 10 m/year. The detached breakwaters at both Baltim and at Ras El Bar have accumulated sand at accretion rates of 37 and 14 m/year, respectively. This sand accumulation is associated with downdrift erosion of 25 and 13 m/year at Baltim and Ras El Bar, respectively. Results reaffirm that the original erosion/accretion patterns along the Nile delta promontories have been reshaped due to the massive protective structures built during the last decade. This reshaping along the examined promontories is generally controlled by the temporal variability in the intensity and reversibility of wave directions and associated longshore currents, coastline orientation and by the existing coastal protection structures. 相似文献
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Increasing the effectiveness of electrical resistivity tomography using γ11n configurations 下载免费PDF全文
下载免费PDF全文 I. Lemperger M. Metwaly Á. Kis V. Wesztergom K. Szokoli A. Novák 《Geophysical Prospecting》2015,63(2):508-524
A new array type, i.e., the γ11n arrays, is introduced in this paper, in which the sequence of the current (C) and potential (P) electrodes is CPCP, and the distance between the last two electrodes is n times the distance between the first two ones and that of the second one and the third one. These arrays are called quasinull arrays because they are—according to their array and behaviour—between the traditional and null arrays. It is shown by numerical modelling that, in detecting small‐effect inhomogeneity, these configurations may be more effective than the traditional ones, including the optimized Stummer configuration. Certain γ11n configurations—especially the γ112, γ113, and γ114—produced better results both in horizontal and vertical resolution investigations. Based on the numerical studies, the γ11n configurations seem to be very promising in problems where the anomalies are similar to the numerically investigated ones, i.e., they can detect and characterize, e.g., tunnels, caves, cables, tubes, abandoned riverbeds, or discontinuity, in a clay layer with greater efficacy than those of the traditional configurations. γ11n measurements need less data than traditional configurations; therefore, the time demand of electrical resistivity tomography measurements can be shortened by their use. 相似文献
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Much attention has recently been devoted to the fate and effects of pharmaceuticals in the water cycle. Removal of antibiotics in effluents by photo‐treatment or biodegradation is a topic currently under discussion. Degradation and removal efficiencies of sulfisomidine (SUI) by photodegradation and aerobic biodegradability were studied. SUI behavior was monitored during photolysis and photocatalysis (catalyst titanium dioxide) using 150‐W medium‐pressure Hg lamp. Also an aerobic bacterial degradation test from the OECD series (closed bottle test (CBT, OECD 301 D)) was performed. The primary elimination of SUI was monitored. Structures of photo‐degradation products were assessed by chromatographic separation on a C18 column with ultraviolet detection at 270 nm and ion trap MS. The results demonstrate that SUI is not readily biodegradable in CBT. Photo catalysis was more is effective than photolysis. SUI underwent photodegradation and several SUI photoproducts were identified. Accordingly, the photodegradation pathway of SUI was postulated. When reaching the aquatic environment, SUI and its photo products can constitute a risk to the environment. 相似文献
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Mohamed O.Soliman Waleed B.Suleiman Mohamed M.Roushdy Eman N.Elbatrawy Ahmed M.Gad 《海洋学报(英文版)》2022,41(3):86-93
Marine microorganisms were considered to be important sources of marine bioactive compounds. The major objective of the study was to isolate and characterize bacteria with antimicrobial activities from the various marine environment of Egypt. In this respect, thirty-five bacterial isolates were recovered from sediment samples collected from different spots along the Egyptian Red Sea coastline and Alexandria coastline during the summer season of 2017 and 2018. According to the morphological, phys... 相似文献