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111.
Weathering features are described from an arid coastal area in northern Morocco which are indicative of invasive chasmolithic and endolithic microbial communities. Active weathering of marine terraces and karst development is associated with endolithic and epilithic algae responsible for boring, disintegration of matrix and mineral fabrics, solution and biomineralization that undermines the marine carbonate platform. Evidence of a range of biological weathering agents remains preserved, speci?cally calci?ed ?laments and sporangial material. An abundance of ?laments and spores representative of a consortium of algae, fungi, cyanobacteria and lichens is associated with the most denuded outcrops. The array of microbes contributes to the formation of the stromatolites to depths of 0·5 m within the limestone substrate. The preservation of stromatolites is supported by calci?cation of spores and ?laments, with trapping and binding of carbonate held in suspension by vadose waters. The pervasive weathering on this sector of coastline has important practical implications for coastal planning and development authorities in Morocco. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
112.
An academic geophysical research as a regional gravity survey was made during 1994 in the Western White Nile to infer the shallow crustal structures in the area. The result of the survey was compiled as a Bouguer anomaly map with a contour interval of 2 ×10-5m/s2. It is found that the negative residual anomalies are related to the Upper Cretaceous sediments (Nubian Sandstone Formation) filling all depressions in the Basement complex surface while the positive residual anomalies are attributed to the relatively shallow or outcropping Basement rocks and the steep gravity gradients are resulting from the sharp contacts between the sedimentary infill and the Basement rocks. To define the geological structures in the area, 9 profiles were studied. For each of the profiles, measured and computed Bouguer gravity anomalies, crustal density model, subsurface geology evaluation were performed. A G-model computer program was applied in the gravity modeling, which is based on the line-integral method of gravity computation. A geological/structural map was proposed showing inferred sedimentary basins, faulting troughs and uplifted Basement block and tectonic trends. The basins are believed to be fault-controlled which developed by extensional tectonics (pull-apart mechanism). As for the mechanism and cause of faulting, the area is considered as a part of the Central Sudan rift system which had been subjected to several tectonic events since Early Cambrian to Tertiary times which resulted in the formation of several fracture systems associated with block subsidence, rifting and basin formation. 相似文献
113.
Mohammed Jaffal Azzouz Kchikach Jean-Pierre Lefort Lahoucine Hanich 《Comptes Rendus Geoscience》2002,334(4):229-234
A large number of seismic reflection lines and boreholes have been carried out in the Essaouira Basin by the oil industry. The present study concentrates on the reinterpretation of these data in the restricted area of Khemis Meskala, in order to better characterise the structure of the Cretaceous aquiferous system. The reflector corresponding to the bottom of the Vraconian formation has been identified on the different seismic sections. This horizon, which marks the base of the aquiferous system, was first digitised on time migration sections and then converted to depth sections using a suitable linear velocity law. The isobath map of the bottom of the Vraconian resulting from this study images the 3D geometrical structure of this horizon and shows that it is slightly folded in domes and basins. This document will be useful for rationalising the future hydrogeological researches that will be undertaken in the Khemis Meskala area. To cite this article: M. Jaffal et al., C. R. Geoscience 334 (2002) 229–234. 相似文献
114.
Lahcen Zouhri Christian Gorini Christian Lamouroux Daniel Vachard Mohammed Dakki 《Comptes Rendus Geoscience》2003,335(3):319-326
The aquifer of the Rharb Basin is constituted by heterogeneous material. The seismic reflexion interpretation carried out in this area, highlighted a permeable device compartmentalized in raised and subsided blocks. Depressions identified in the northern and southernmost zones are characterized by Plio-Quaternary fillings that are favourable to the hydrogeological exploitation. Two mechanisms contribute to structure the Plio-Quaternary aquifer: the Hercynian reactivation in the southernmost part, and the gravitational mechanism of the Pre-Rifean nappe. The groundwater flow and the aquifer thickening are controlled by this reactivation. 相似文献
115.
Mohammed A. A. Al-qaness 《地球空间信息科学学报》2019,22(2):128-137
ABSTRACTHuman activity tracking plays a vital role in human–computer interaction. Traditional human activity recognition (HAR) methods adopt special devices, such as cameras and sensors, to track both macro- and micro-activities. Recently, wireless signals have been exploited to track human motion and activities in indoor environments without additional equipment. This study proposes a device-free WiFi-based micro-activity recognition method that leverages the channel state information (CSI) of wireless signals. Different from existed CSI-based micro-activity recognition methods, the proposed method extracts both amplitude and phase information from CSI, thereby providing more information and increasing detection accuracy. The proposed method harnesses an effective signal processing technique to reveal the unique patterns of each activity. We applied a machine learning algorithm to recognize the proposed micro-activities. The proposed method has been evaluated in both line of sight (LOS) and none line of sight (NLOS) scenarios, and the empirical results demonstrate the effectiveness of the proposed method with several users. 相似文献
116.
Djilali Berkane Hakima Harichane Zamila Çelebi Erkan Elachachi Sidi Mohammed 《地震工程与工程振动(英文版)》2019,18(3):497-509
The goal of this study is to provide a stochastic method to investigate the effects of the randomness of soil properties due to their natural spatial variability on the response spectra spatial variation at sites with varying conditions. For this purpose, Monte Carlo Simulations are used to include the variability of both incident ground motion and soil parameters in the response spectra by mean of an appropriate coherency loss function and a site-dependent transfer function, respectively. The approach is built on the assumption of vertical propagation of SH type waves in soil strata with uncertain parameters. The response spectra are obtained by numerical integration of the governing equation of a single-degree-of-freedom(SDOF) system under non-stationary site-dependent and spatially varying ground motion accelerations simulated with non-uniform spectral densities and coherency loss functions. Numerical examples showed that randomness of soil properties significantly affects the amplitudes of the response spectra, indicating that as the heterogeneity induced by the randomness of the parameters of the medium increases, the spectral ordinates attenuate. 相似文献
117.
Stability is always the most important problem after high slope was excavated. The study analyzed the stress and strain inside the slope by Finite Element Method (FEM) and carried through stress distribution and failure zone, then analyzed the stability of the slope using three different methods and came to the conclusion that it is in unstable condition, so the designed retaining wall was put forward which makes the slope stable. 相似文献
118.
Alkali Mohammed 《东北亚地学研究》2008,(4)
This research studies the reliability of an activated carbon permeable reactive barrier in removing cadmium from a contaminated shallow aquifer.Laboratory tests have been performed to characterize the equilibrium and kinetic adsorption properties of the activated carbon in cadmium-containing aqueous solutions.A 2D numerical model has been used to describe pollutant transport within a groundwater and the pollutant adsorption on the permeable reactive barrier(PRB).In particular,it has been considered the case... 相似文献
119.
Pablo J Zarco-Tejada John R Miller Gina H Mohammed Thomas L Noland Paul H Sampson 《International Journal of Applied Earth Observation and Geoinformation》2001,3(4):321
This paper reports a series of laboratory and field measurements of spectral reflectance under artificial and natural light conditions which demonstrate that effects of natural chlorophyll fluorescence are observable in the reflectance red edge spectral region. These are results from the progress made to link physiologically-based indicators to optical indices from hyperspectral remote sensing in the Bioindicators of Forest Sustainability Project. This study is carried out on twelve sites of Acer saccharum M. in the Algoma Region, Ontario (Canada), where field measurements, laboratory-simulation experiments, and hyperspectral CASI imagery have been carried out in 1997, 1998, 1999 and 2000 campaigns. Leaf samples from the study sites have been used for reflectance and transmittance measurements with the Li-Cor Model 1800 integrating sphere apparatus coupled to an Ocean Optics Model ST1000 fibre spectrometer in which the same leaves are illuminated alternatively with and without fluorescence-exciting radiation. A study of the diurnal change in leaf reflectance spectra, combined with fluorescence measurements with the PAM-2000 Fluorometer show that the difference spectra are consistent with observed diurnal changes in steady-state fluorescence. Small canopies of Acer saccharum M. have been used for laboratory measurements with the CASI hyperspectral sensor, and under natural light conditions with a fibre spectrometer in diurnal trials, in which the variation of measured reflectance is shown experimentally to be consistent with a fluorescence signature imposed on the inherent leaf reflectance signature. Such reflectance changes due to CF are measurable under natural illumination conditions, although airborne experiments with the CASI hyperspectral sensor produced promising but less convincing results in two diurnal experiments carried out in 1999 and 2000, where small variations of reflectance due to the effect of CF were observed. 相似文献
120.
Abdessamad Najine Mohammed Jaffal Kamal El Khammari Tahar Aïfa Driss Khattach Mahjoub Himi Albert Casas Said Badrane Hicham Aqil 《Comptes Rendus Geoscience》2006,338(10):676-682
This study is based on the analysis and the interpretation of the gravity data of the Tadla basin. Its purpose is to increase the knowledge of this basin structure. A residual anomaly map was first calculated from the Bouguer anomaly data witch are strongly affected by a regional gradient. The computed map provides information on the ground density variation but it does not bring enough of new elements. Data filtering allows us to emphasize the structures affecting the basin. We chose the horizontal gradient coupled to the upward continuation techniques that permit to highlight news structures and to give information on their dip. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the Tadla basin. To cite this article: A. Najine et al., C. R. Geoscience 338 (2006). 相似文献