Diagenesis of Holocene beachrocks: a comparative study between the Arabian Gulf and the Gulf of Aqaba,Saudi Arabia     

Khalid Al-Ramadan 《Arabian Journal of Geosciences》2014,7(11):4933-4942

Beachrocks occur in present-day intertidal zones of the Arabian Gulf and the Gulf of Aqaba, on the eastern and northwestern coasts, respectively, of Saudi Arabia. The beachrocks occur as linear patches within beach deposits, which have variable grain size and detrital compositions. The Arabian Gulf beachrocks are composed of sand-sized bioclasts and siliciclastic grains, whereas the Gulf of Aqaba beachrocks are composed of sand- to pebble-size grains, which are dominated by igneous rock fragments and small amounts of skeletal carbonate grains. The cement includes micritic high-magnesian calcite and isopachous acicular/bladed aragonite. In addition to cements, intergranular pores are locally filled by a lime–mud matrix. Radiocarbon dating of beachrock samples from the Arabian Gulf yielded ages from ca. 655 to 2185 year bp, whereas the Gulf of Aqaba samples range in age between 2745 and 5075 year bp.  相似文献   

Exploring disaster preparedness of students at university in Bangladesh     

Hasan  Md. Khalid  Moriom  Masuma  Shuprio  Shariaj Ibna Mizan  Younos  Tahmina Bintay  Chowdhury  Md. Arif 《Natural Hazards》2022,111(1):817-849

Natural Hazards - Adequate and effective disaster preparedness in each sector is indispensable to abate disaster impacts and intensify disaster resilience in Bangladesh for achieving sustainable...  相似文献   

Integrating core and wireline log data to evaluate porosity of Jurassic formations of Injra-1 and Nuryal-2 wells,Western Potwar,Pakistan     

Perveiz Khalid  Qamar Yasin  Gmd Sohail  Jam Muhammad Kashif 《Journal of the Geological Society of India》2015,86(5):553-562

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Statistical significance of modal parameters of bridge systems identified from strong motion data     

Yalin Arici  Khalid M. Mosalam 《地震工程与结构动力学》2005,34(10):1323-1341

Modal parameters of structural systems have commonly been determined using system identification (SI) methods for damage detection and health monitoring. For determining the deterioration of the integrity of structural systems correctly, modal parameters of a healthy structure have to be obtained with adequate certainty so that these parameters can be used as reliable references for the healthy system to compare with those of the damaged system. In this study, the statistical significance of modal parameters identified using strong motion time histories recorded on two bridge structures is assessed. The confidence intervals of identified modal frequencies and damping ratios are obtained using Monte Carlo simulations and sensitivity analyses in conjunction with eigenrealization algorithm. The dependence of the statistical bounds on model parameters is examined. The effect of using different number of sensors on the statistical significance is evaluated using simulated time history data from a validated finite element model of a bridge. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Erratum     

Khalid J. Fahmi 《Natural Hazards》1984,2(2):199

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Optimal and sustainable extraction of groundwater in coastal aquifers   总被引：1，自引：0，他引：1  

Khalid Qahman  Abdelkader Larabi  Driss Ouazar  Ahmed Naji  Alexander H. -D. Cheng 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(2):99-110

Four examples are investigated for the optimal and sustainable extraction of groundwater from a coastal aquifer under the threat of seawater intrusion. The objectives and constraints of these management scenarios include maximizing the total volume of water pumped, maximizing the profit of selling water, minimizing the operational and water treatment costs, minimizing the salt concentration of the pumped water, and controlling the drawdown limits. The physical model is based on the density-dependent advective-dispersive solute transport model. Genetic algorithm is used as the optimization tool. The models are tested on a hypothetical confined aquifer with four pumping wells located at various depths. These solutions establish the feasibility of simulating various management scenarios under complex three-dimensional flow and transport processes in coastal aquifers for the optimal and sustainable use of groundwater.  相似文献   

Preliminary study on PAH degradation by bacteria from contaminated sediments in Xiamen Western Sea,Fujian, China   总被引：1，自引：0，他引：1  

哈里德郑天凌  洪华生俞志明  袁建军胡忠 《中国海洋湖沼学报》2004,22(4):431-435

In order to estimate the biodegradation of three polycyclic aromatic hydrocarbons (PAHs) compounds, bacterial strains were isolated from marine sediments in three heavily contaminated sites (Yuandang Lake, Dongdu Port and Aquacultural zones in Maluan Bay) in Xiamen Western Sea. The results show three bacterial strains, which used pyrene as the sole carbon source, were identified as strains of Aureobacterium sp.,Arthrobacter sp., Rhodococcus sp. The PAH-degrading bacteria isolated had a strong ability to degrade phenanhrene, fluoranthene and pyrene at different degradation rates. The highest degradation rate was observed when three PAH compounds were mixed with an individual strain in the medium. The three PAHs were degraded after one week with a degradation rate of 89.94 % for phenanthrene and 93.4 % for both of fluoranthene and pyrene.In addition, after 25 days of incubation, the degradation rate was 99.98 % for phenanthrene and 99.97 % for both of fluoranthene and pyrene. Optical density was measured to estimate bacterial growth during the degradation of PAHs. Highest levels of bacterial growth were observed with a three PAH mixture in the culture, suggesting that the concentration of PAHs influenced bacterial growth and the highest levels of degradation for most series were detected after one week of incubation.  相似文献   

Application of global snow model for the estimation of snow depth in the UK     

Mohsin Jamil Butt 《Meteorology and Atmospheric Physics》2009,105(3-4):181-190

Microwave imagery can be used successfully for mapping of snow and estimation of snow pack characteristics under almost all weather conditions. This research is a contribution to the field of space borne remote sensing of snow by means of passive microwave data imagery. The satellite data are acquired from the Special Sensor Microwave Imager (SSM/I). The SSM/I is a four frequency seven channels dual polarization (except 22 GHz which is only vertically polarized) scanning radiometer with channels located at 19, 22, 37, and 85 GHz frequencies. A radiative transfer theory based model is used to estimate the snow cover characteristics of different snow pack types in the UK. A revised form of the Chang et al. (Nord Hydrol 16:57–66, 1987) model is used for this purpose. The revised Chang model was calibrated for global snow monitoring and takes into account forest fractional coverage effects. Snow cover characteristics have significant effects on up-welling naturally emitted microwave radiation through the processes of forward scattering. The up-welling signal is more complex for snow covers that consist of free liquid water content. The aim of this study is to test the global snow depth model for the UK snow cover. The Chang model predicted snow depth bias results for January, February, and March 1995 are ?1.26, ?0.35, and ?0.63 cm, respectively. Similarly, the Chang model Mean Absolute Error (MAE) for January, February, and March 1995 have values 2.88, 2.38, and 1.91 cm, respectively. These results show that the Chang model underestimates the snow depth prediction for all the case studies. The results of this study led us to the conclusion that the global snow models (Chang model) when applied for the retrieval of local snow depth estimation (UK snow cover) underestimate snow depth.  相似文献   

Equivalent continuum strain calculations based on 3D particle kinematic measurements of sand          下载免费PDF全文

Siavash Amirrahmat  Khalid A. Alshibli  Maha F. Jarrar  Boning Zhang  Richard A. Regueiro 《国际地质力学数值与分析法杂志》2018,42(8):999-1015

Constitutive modeling of granular materials has been a subject of extensive research for many years. While the calculation of the Cauchy stress tensor using the discrete element method has been well established in the literature, the formulation and interpretation of the strain tensor are not as well documented. According to Bagi, 1 researchers mostly adopt well‐known continuum or discrete microstructural approaches to calculate strains within granular materials. However, neither of the 2 approaches can fully capture the behavior of granular materials. They are considered complementary to each other where each has its own strengths and limitations in solving granular‐mechanics problems. Zhang and Regueiro 2 proposed an equivalent continuum approach to calculating finite strain measures at the local level in granular materials subjected to large deformations. They used three‐dimensional discrete element method results to compare the proposed strains measures. This paper presents an experimental application of the Zhang and Regueiro 2 approach using three‐dimensional synchrotron microcomputed tomography images of a sheared Ottawa sand specimen. Invariant Eulerian finite strain measures were calculated for representative element volumes within the specimen. The spatial maps of Eulerian octahedral shear and volumetric strain were used to identify zones of intense shearing within the specimen and compared well with maps of incremental particle translation and rotation for the same specimen. The local Eulerian volumetric strain was compared to the global volumetric strains, which also can be considered as an averaging of all local Eulerian volumetric strains.  相似文献   

Collapsing loess-like soil in western Saudi Arabia     

Abbas A. Al-Harthi  Khalid A. Bankher 《Journal of Arid Environments》1999,41(4):383

Earth fissures have developed at Wadi Al-Yutamah, western Saudi Arabia. The fissues are associated with land subsidence which is considered to be due to both rapid draw down of the ground-water level and hydrocompaction of the wadi soil after flooding. This phenomenon is relatively recent in the area.The wadi soil was investigated and classified in the field, and disturbed and undisturbed samples were collected for laboratory testing and analysis. The engineering properties of the wadi soils were determined, including in situ field density, specific gravity, liquid limit, plastic limit, plasticity index, shrinkage limit, and consolidation characteristics such as total settlement and coefficient of subsidence (collapse).Four types of silty soil of different colours were identified, in addition to yellowish-brown sand (representing the dunes) which accumulated on the surface of the study area. The silty soils include yellowish-brown silty sand, yellowish-gray silt, pale brown silt and yellowish-brown clayey silt. The results of X-ray diffraction analysis indicated that the clay is mainly kaolinite and illite with minor smectite. The dominant soil type in the study area is silt of low plasticity, high void ratio and low density which decreased with depth. This soil was classified as loess-like materials.The studied soils are of a collapsing type, and settlement is greatly increased by excessive wetting under constant pressure. The calculated coefficients of subsidence (collapse) of the soils at different depths generally increased with decreasing soil density and ranged between 3·1% and 10·8%. The wadi soils are considered to pose a moderate problem when wetted.  相似文献