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The availability of freely available moderate-to-high spatial resolution (10–30 m) satellite imagery received a major boost with the recent launch of the Sentinel-2 sensor by the European Space Agency. Together with Landsat, these sensors provide the scientific community with a wide range of spatial, spectral, and temporal properties. This study compared and explored the synergistic use of Landsat-8 and Sentinel-2 data in mapping land use and land cover (LULC) in rural Burkina Faso. Specifically, contribution of the red-edge bands of Sentinel-2 in improving LULC mapping was examined. Three machine-learning algorithms – random forest, stochastic gradient boosting, and support vector machines – were employed to classify different data configurations. Classification of all Sentinel-2 bands as well as Sentinel-2 bands common to Landsat-8 produced an overall accuracy, that is 5% and 4% better than Landsat-8. The combination of Landsat-8 and Sentinel-2 red-edge bands resulted in a 4% accuracy improvement over that of Landsat-8. It was found that classification of the Sentinel-2 red-edge bands alone produced better and comparable results to Landsat-8 and the other Sentinel-2 bands, respectively. Results of this study demonstrate the added value of the Sentinel-2 red-edge bands and encourage multi-sensoral approaches to LULC mapping in West Africa. 相似文献
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Several significant parameters that could affect interaction in a dam-foundation system are discussed. These parameters are: (1) Fundamental periods of the dam and the foundation layer. (2) Lateral extent of the dam. (3) The material properties of the dam and the foundation layer. Five cases are analysed to illustrate the influence of these parameters on interaction. An interaction ratio, R1, relating the response of the dam-foundation system at the base of the dam to the free field response is introduced and interaction effects are expressed in terms of this ratio; the smaller this ratio, the less are the interaction effects. For very small values of R1, it is shown that the dam-foundation system could be decoupled The results of the studies presented in the paper suggest that the interaction effects cannot be uniquely related to either the ratio of the period of the dam to the period of the foundation layer, or to the material properties of the dam and foundation layer. However, for the limited number of cases investigated, the interaction effects were found to be uniquely related to the ratio D/B, where D is the depth of the foundation layer and B is the width of the dam section. For values of D/B less than unity, strong interaction effects were obtained and the dam-foundation system could only be analysed as a coupled system. For values of D/B greater than unity, the interaction appeared negligible and the dam and its foundation layer could be decoupled. It should be noted, however, that for very small values of D/B the interaction effects would decrease becaase as D approaches zero, there would be no interaction The use of the interaction ratio, R1, and the parameter D/B should aid in assessing the need for analysing the response of the dam-foundation as a coupled or as a decoupled system. 相似文献
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克里雅河下游及圆沙古城脊椎动物考察记录 总被引：1，自引：0，他引：1
克里雅河发源于昆仑山脉,位置在新疆的南部。2001年10月18-11月22日,中法联合考察队对克里雅河下游进行了深入的调查。根据标本采集与资料统计,克里雅河流域的野生脊椎动物约有98种（包括已绝迹的几种）,隶属于5纲,24目,48科。其中,鱼类约4种;两柄类1种;爬行类约4种;鸟类70种;兽类约19种。有一些动物的遗骸发掘自圆沙古城及附近的古墓地。本文探讨了物种绝迹的原因。 相似文献
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Hajo Idriss Isam Salih Abdulaziz S. Alaamer M. A. AL-Rajhi Alshfia Osman Tahir Elamin Adreani M. Y. Abdelgalil Nagi I. Ali 《Acta Geophysica》2018,66(4):673-681
This study shows the assessment of radiation hazard parameters due to terrestrial radionuclides in the soil around artisanal gold mining for addressing the issue of natural radioactivity in mining areas. Hence, the levels 238U, 232Th, 40K and 226Ra in soil (using gamma spectrometry), 222Rn in soil and 222Rn in air were determined. Radiation hazard parameters were then computed. These include absorbed dose D, annual effective dose E, radium equivalent activity Raeq, external hazard Hex, annual gonadal dose equivalent hazard index AGDE and excess lifetime cancer risk ELCR due to the inhalation of radon (222Rn) and consumption of radium (226Ra) in vegetation. Uranium (238U), thorium (232Th) and potassium (40K) averages were, respectively, 26, 36 and 685 Becquerel per kilogram (Bq kg?1). Soil radon (4671 Bq m?3) and radon in air (14.77 Bq m?3) were found to be less than worldwide data. Nevertheless, the average 40K concentration was 685 Bq kg?1. This is slightly higher than the United Nations Scientific Committee on the Effects of Atomic Radiation average value of 412 Bq kg?1. The obtained result indicates that some of the radiation hazard parameters seem unsavory. The mean value of absorbed dose rate (62.49 nGy h?1) was slightly higher than average value of 57 nGy h?1 (~?45% from 40K), and that of AGDE (444 μSv year?1) was higher than worldwide average reported value (300 μSv year?1). This study highlights the necessity to launch extensive nationwide radiation protection program in the mining areas for regulatory control. 相似文献
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Christophe Nkem Kamel Hammami Idriss Yacoub Halalaw Luc Calvin Owono Owono Nejm-Eddine Jaidane 《Astrophysics and Space Science》2014,349(1):171-179
We report on ab initio coupled-cluster calculations of the interaction potential energy surface for the HCNH+–He complex. The aug-cc-pVTZ Gaussian basis, to which is added a set of bond functions placed at mid-distance between HCNH+ center of mass and He atom is used. The HCNH+ bonds length are set to their values at the equilibrium geometry, i.e., r e [HC]=1.0780 Å, r e [CN]=1.1339 Å and r e [NH]=1.0126 Å. The interaction energy presents a global minimum located $266.9~\mathrm{cm^{-1}}$ below the HCNH+–He dissociation limit. Using the interaction potential obtained, we have computed rotational excitation cross sections in the close-coupling approach and downward rate coefficients at low temperature (T≤120 K). It is expected that the data worked out in this study may be beneficial for further astrophysical investigations as well as laboratory experiments. 相似文献
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Semi-empirical procedures for evaluating the liquefaction potential of saturated cohesionless soils during earthquakes are re-examined and revised relations for use in practice are recommended. The stress reduction factor (rd), earthquake magnitude scaling factor for cyclic stress ratios (MSF), overburden correction factor for cyclic stress ratios (Kσ), and the overburden normalization factor for penetration resistances (CN) are discussed and recently modified relations are presented. These modified relations are used in re-evaluations of the SPT and CPT case history databases. Based on these re-evaluations, revised SPT- and CPT-based liquefaction correlations are recommended for use in practice. In addition, shear wave velocity based procedures are briefly discussed. 相似文献
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An economical approach was developed to examine the effect of radiation damping on earthquake response of pilesupported offshore platforms. Parameteric studies were conducted to evaluate the effects of radiation damping on response. Various features of this effect were found for pile head stiffnesses, and responses of platforms subjected to harmonic and earthquake excitations. 相似文献
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Ashok S. Patwardhan I. M. Idriss John M. Hobgood Ram B. Kulkarni K. Sadigh 《Marine Georesources & Geotechnology》2013,31(3):243-267
Abstract The characterization of earthquake sources in the Gulf of Alaska and the relative significance of earthquake sources for establishing seismic design inputs at a typical site for engineering purposes are discussed. Earthquake sources in the complex tectonic environment can be divided into two groups: (a) a subduction zone that underlies the entire region (maximum magnitude M = 8.5); and (b) individual thrust and strike‐slip faults associated with the plate motions (maximum magnitude M = 6 to 7.5). The sources of either group and individual earthquake events can be represented as planar surfaces for consistency with the physical process and a mathematically tractable computational scheme. Although the area is very active seismically, the degree of activity of individual sources varies significantly. Therefore, even for sources with the same maximum earthquakes, different magnitudes may apply for a selected design return period. The area is considered to be a “seismic gap.”; No great earthquakes have occurred in nearly 80 years. Estimates based on a temporally varying seismic function such as the semi‐Markov model indicate that the probability of occurrence of a great earthquake in the near future is significantly higher than the average probability inferred from a statistical analysis of historical seismicity data of the entire region. Separate attenuation relationships should be used for calculating ground motions due to earthquakes on the dipping subduction zone in the northern portion of the gulf. The dominant earthquake source for almost the entire Gulf of Alaska region is the subduction zone that contributes over 80 percent of the seismic exposure at a typical site. The dominant magnitude range is Ms = 6.5 to 7.5. “Gap filling”; earthquakes (Ms = 7.5 to 8.25) contribute a little over a third of the seismic exposure at a typical site. Deterministic assessments of ground motion values using the maximum earthquake on the subduction zone at the closest distance yield values significantly higher than those calculated for even 500‐year return periods. Estimated 100‐year return period accelerations in the area range from 180 to 340 cm/sec2. 相似文献
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Hajo Idriss Isam Salih Abdulaziz S. Alaamer M. Y. Abdelgalil Salih Ali Salih Amna M. Hasan Mohammed A. ELtahir Mustafa M. O. Ahamed 《Environmental Earth Sciences》2014,72(2):335-339
This study was conducted primarily to measure and map radon activity concentration in soil gas and to understand the effect of geology and lithology and meteorology on radon concentration. Portable radon meter has been used for the measurement of soil gas radon at 30 different locations around Uro and Korn area in eastern Nuba Mountain South Kordofan State. The results indicate that the activity concentrations of 222Rn in soil gas fall within the range of 20–1,359 Bq/m3 with geometric mean of 102.80 Bq/cm3. The obtained data show that samples around Uro have anomaly of 222Rn concentrations than the sample around Korn. The reason could be attributed to differences in the geological structure, lithology and climate parameters. GIS predicative map has shown that the elevated levels of radon concentration were measured in North study area. Upon comparing the results with global data, it was found that the obtained values are far below the reported range of India, Slovenia, Portugal and Syria. However, the range of 222Rn concentrations in the soil observed in this study is significantly high relative to similar data reported from Libya. The regression analysis has shown that no correlation was noted between radon concentrations, climatic parameters and trace element. 相似文献
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Abdellah Demdoum Mohamed Kamel Gueddouda Idriss Goual 《Geotechnical and Geological Engineering》2017,35(6):2677-2696
Compacted soil–bentonite liners, consisting of a sandy soil mixed with bentonite as backfill, are used extensively as engineered barriers for contaminant containment. This paper studies the valorization of local materials containing calcareous sand, tuff obtained from Laghouat region (in the South Algeria), to associate with bentonite in order to improve their hydraulic characteristics for use as landfill liner material. Firstly, a geotechnical characterization of mixtures chooses from a fixed percentage to 10% bentonite and different percentages of calcareous sand and tuff so that they are complementary to 90% by not 10%. Thereafter, the determination of saturated hydraulic conductivity at falling-head permeability (Kv) and oedometer (Kid, indirect Measure) tests of all compacted mixtures at Optimum Normal Proctor have been carried out using both permeates by tap water and a landfill leachate in order to simulate long-term conditions. The results showed that the saturated hydraulic conductivity of tap water is relatively lower than the one saturated by leachate in the falling-head test, unlike the oedometer test. The B10CS20T70 mixture has satisfied the hydraulic conductivity criterion of bottom barriers (i.e. water permeated: kv20° = 1.97 × 10?9 and kid from 7 × 10?9 to 1.83 × 10?10 < 10?9m/s; leachate permeated: kv20° = 2.91 × 10?9 and kid from 7 × 10?9 at 1.44 × 10?10 < 10?9 m/s). Finally, a comparison between direct measurements of the saturated hydraulic conductivity by triaxial (Kd) test and oedometer test (Kid) in the range of effective stress applied 100–800 kPa led to propose equations of correlations between these two methods. In conclusion, adopted formulation B10CS20T70 perfectly meets the regulatory requirements in force and constitutes an economic product based on available local materials for engineers barriers. 相似文献
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