This study aims at evaluating the global geoid model for a regional shoreline fitting using advanced soft computing techniques and global navigation satellite system/leveling measurements. Artificial neural networks, fuzzy logic, and least square support vector machine models are developed and used to fit the global geoid model for the north coastal Egyptian line. In addition, a novel estimation geoid model is designed and evaluated based on the latest global geoid models. The results of the three estimation models show that they can be used to correct the shoreline geoid model, in terms of root mean square error that ranges from 1.7 to 8.5?cm. Moreover, it is found that the least square vector machine model is a competitive approach with certain advantage in solving complex problems represented by missing data. 相似文献
Storms, hurricanes, and earthquakes may cause seabed instability, especially if the seabed is weak. The seabed instability, manifested in movement of soil layers, exerts lateral forces that may cause large stresses in offshore foundations. The induced stresses may compromise the stability of the foundation and supported structure. The effect of seabed instability on a fixed offshore structure is examined in this study. The method used accounts for soil nonlinearity, dynamic soil resistance, and pile–soil–pile interaction within the stable soil layer. Dynamic p–y curves, dynamic t–z curves and q–z curves have been used to simulate the soil resistance in the lateral and axial directions. The effect of different parameters that influence the response of offshore structures to seabed instability is evaluated. The parameters considered include the value of soil movement, the sliding layer depth, the wave loading, the pile flexibility, the soil movement profile, and the axial loading at the pile head. The response predicted using the proposed analysis compared well with that calculated using a boundary element solution for a case history of a failed offshore platform. 相似文献
Scattering of SH waves in a half-space with simple overground structures is studied analytically. For two-dimensional structures, such as shells, shear walls and a slab-bridge over a river, the method of matched asymptotics is used for sinusoidal waves long compared to the thickness of the structures. Resonance features are deduced analytically and calculated numerically for various incidences and other parameters. 相似文献
Ore microscopic study was carried out on a great number of samples collected from four well-dated alkaline rock masses (ring complexes), namely Gabal Mishbeh, Gabal Nigrub El Fogani, Gabal Nigrub El Tahtani, and Gabal El Gezira located in the Eastern Desert of Egypt. These rings consist mainly of wide variety of rock types ranging from basic to acidic and from under saturated to quartz bearing. The opaques of the basic rocks consist mainly of various ilmenite–magnetite intergrowths and differ essentially from those of the acidic rocks where minor amount of titanomagnetite is present. Numerous exsolution, replacement, and deformational textures were described. The distribution of opaque minerals and their intergrowths in the four well-defined ring complexes is described. Systematic rock magnetic measurements such as natural remanent magnetization intensity and initial susceptibility, Curie point, saturation magnetization, and coercive force were carried out, and their results were discussed in the light of opaque mineralogical studies. 相似文献
In this paper, remote sensing and GIS have been used to assess the status of NO2 at the south west of Iran. 221 data about concentration of NO2 was extracted from Ozone Monitoring Instrument. Ordinary kriging and inverse distance weighting interpolation methods was used to interpolate data. Results showed that ordinary kriging method using cross-validation have had less error. North east of the study area has the highest concentration of NO2 (329 molecule/cm2) and the concentration of NO2 decreases from north east to South west of the study area. On the other hand, data trend results showed that the data seems to exhibit a fairly strong trend in the east west direction and a weaker one in the north–south direction. 相似文献
Natural Hazards - Landslides can cause extensive damage, particularly those triggered by earthquakes. The current study used back propagation of an artificial neural network (ANN) to conduct risk... 相似文献
This study integrates remote sensing data and geoelectrical dipole–dipole resistivity to delineate near-surface palaeochannels and shallow aquifer in the northern part of Abu Dhabi Emirate, United Arab Emirates. The shuttle imaging radar images and shuttle radar topographic mission DEM were used to delineate near-surface palaeochannels visually based on the contrast between bright and dark tone and automatically using the eight-direction flow model. The delineated palaeochannels were validated by comparing the textural features evident from advanced land observing satellite-phased array type L-band synthetic aperture radar images and determining whether these patterns were different. Field observation and geoelectrical dipole–dipole resistivity method was used to define the depth of palaeochannels and lithology of the shallow aquifer. The remote sensing and geophysical investigations in the UAE, including the study area, indicate the presence of buried palaeochannels with south-west and north-west flow directions from Oman Mountain. The study area can be of economic importance to the local population. 相似文献
This study has modified an approach based on fuzzy logic in a GIS and multi-criteria decision making (MCDM) for groundwater potentiality mapping in Al Fo’ah area, the United Arab Emirates. The proposed approach uses nine groundwater conditioning factors recognized by local hydrology experts. Each factor and class of each factor was given a weight and score based on its level of contributions to groundwater accumulation using analytical hierarchy process and MCDM. Our results revealed that the areas of very high harbouring groundwater are located at the foot of the Oman mountains and occupies an area of about 8.46 km2 (4%) of the study area. We validated our results using the Relative Operating Characteristics. The area under the curve showed a ratio of 0.8957 (of 89.57%). The modified approach is timely and economically effective and can be applied in semi-arid regions to help hydrologists. 相似文献
In this research, the spatial and temporal distribution of Mesoscale Convective Systems was assessed in the southwest of Iran using Global merged satellite IR brightness temperature (acquired from Meteosat, GOES, and GMS geostationary satellites) and synoptic station data. Event days were selected using a set of storm reports and precipitation criteria. The following criteria are used to determine the days with occurrence of convective systems: (1) at least one station reported 6-h precipitation exceeding 10 mm and (2) at least three stations reported phenomena related to convection (thunderstorm, lightning, and shower). MCSs were detected based on brightness temperature, maximum areal extent, and duration thresholds (228 K, 10,000 km2, and 3 h, respectively). An MCS occurrence classification system is developed based on mean sea level, 850 and 500 hPa pressure patterns.
The results indicated that the highest frequency of MCSs occurred in December and April. Assessment of MCSs spatial frequency showed that MCS occurrence is strongly correlated with topography in April and May unlike the cold months. In other words, the role of Zagros Mountains in developing MCSs varies based on the season so that its impact increases with enhancement of mean monthly temperature. In addition, the occurrence of MCSs depends closely on the configuration of the Sudan Low in the southwest of Iran.