The accessibility of a network: The great lakes corridor passenger as an example     

Dr. Abdullah R. Al.-Kandari 《GeoJournal》1986,12(3):255-266

  相似文献   

Sheet flow and suspension of sand in oscillatory boundary layers   总被引：1，自引：0，他引：1  

Jan S. Ribberink  Abdullah A. Al-Salem 《Coastal Engineering》1995,25(3-4)

after revisionTime-dependent measurements of flow velocities and sediment concentrations were conducted in a large oscillating water tunnel. The measurements were aimed at the flow and sediment dynamics in and above an oscillatory boundary layer in plane bed and sheet-flow conditions. Two asymmetric waves and one sinusoidal wave were imposed using quartz sand with D₅₀ = 0.21 mm. A new electro-resistance probe with a large resolving power was developed for the measurement of the large sediment concentrations in the sheet-flow layer. The measurements revealed a three layer transport system consisting of a pick-up/deposition layer, an upper sheet flow layer and a suspension layer.In the asymmetric wave cases the total net transport was directed “onshore” and was mainly concentrated in the thin sheet flow layer (< 0.5 cm) at the bed. A small net sediment flux was directed “offhore” in the upper suspension layer. The measured flow velocities, sediment concentrations and sedimenl fluxes showed a good qualitative agreement with the results of a (numerical) 1DV boundary-layer flow and transport model. Although the model did not describe all the observed processes in the sheet-flow and suspension layer, the computational results showed a reasonable agreement with measured net transport rates in a wide range of asymmetric wave conditions.  相似文献   

Hydrogeology and hydrochemistry of a shallow alluvial aquifer,western Saudi Arabia   总被引：2，自引：0，他引：2  

Abdulaziz M. Al-Shaibani 《Hydrogeology Journal》2008,16(1):155-165

A hydrogeological and hydrochemical study was conducted on a shallow alluvial aquifer, Wadi Wajj, in western Saudi Arabia to assess the influence of protection measures on groundwater quality. The hydrochemistry was assessed up-gradient and down-gradient from potential contamination sources in the main city in dry and wet seasons prior to and after the installation of major drainage and wastewater facilities. Wadi Wajj is an unconfined aquifer where water is stored and transmitted through fractured and weathered bedrock and the overlying alluvial sediments. Natural recharge to the aquifer is about 5% of rainfall-runoff. Hydrochemistry of the aquifer shows temporal and seasonal changes as influenced by protection measures and rainfall runoff. Both groundwater and runoff showed similar chemical signature, which is mostly of chloride-sulfate-bicarbonate and sodium-calcium type. Groundwater downstream of the city, though of poorer quality than upstream, showed significant improvement after the installation of a concrete runoff tunnel and a wastewater treatment plant. Concentrations of many of the groundwater quality indicators (e.g., TDS, coliform bacteria, and nitrate) exceed US Environmental Protection Agency drinking-water standards. Heavy metal content is, however, within allowable limits by local and international standards. The chemical analyses also suggest the strong influence of stream runoff and sewage water on the groundwater quality.

---

Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.

---

Résumé Une étude hydrogéologique et géochimique a été menée sur l’aquifère phréatique alluviale Wadi Wajj dans l’Ouest de l’Arabie Saoudite afin d’évaluer l’influence de mesures de protection sur la qualité de l’eau souterraine. L’hydrogéochimie de l’eau a été étudiée en amont et en aval de sources potentielles de contamination dans la ville principale, pendant les saisons sèches et humides, avant et après l’installation de réseaux majeurs de drainage et d’eaux usées. L’aquifère Wadi Wajj est libre, l’eau est stockée et s’écoule dans les sédiments alluviaux et dans le socle fracturé et altéré sous-jacent. La recharge naturelle de l’aquifère représente 5% des eaux de pluie et de ruissellement. L’hydrogéochimie de l’eau de l’aquifère montre que les changements saisonniers et temporaires sont influencés par les mesures de protection et par le ruissellement des eaux pluviales. L’eau souterraine et l’eau de ruissellement ont présenté le même faciès chimique, de type bicarbonatée-sulfatée-chlorée et calco-sodique. En aval de la ville, l’eau souterraine, bien que de moins bonne qualité qu’en amont, a présenté une nette amélioration après l’installation d’un système de récupération et d’une station de traitement des eaux usées. Les concentrations de plusieurs paramètres indicateurs de la qualité de l’eau (tels que la charge totale dissoute, les coliformes, et les nitrates) dépassent les normes de potabilité de l’eau de consommation de l’agence américaine de la protection de l’environnement. Les teneurs en métaux lourds en revanche n’excèdent pas les normes locales et internationales. Les analyses chimiques indiquent aussi l’influence importante de l’écoulement par ruissellement et des eaux usées sur la qualité de l’eau souterraine.

---

Resumen Un estudio hidrogeológico e hidroquímico fue hecho en un acuífero somero de Wadi Wajj, en Arabia Saudi oeste para evaluar la influecia de medidas de protección en la calidad del agua subterránea. La hidroquímica fue evaluada gradiente-arriba y gradiente-abajo de las fuentes potenciales de contaminación de la ciudad principal durante las estaciones seca y lluviosa, antes y después de la instalación de sistemas principales de drenaje y aguas servidas. Wadi Wajj es un acuífero no-confinado donde el agua es almacenada y transmitida a través de roca fracturada y meteorizada, y los sedimentos aluviales que le sobreyacen. La recarga natural del acuífero es de cerca del 5% de la precipitación-escorrentía. La hidroquímica del acuífero muestra cambios temporales y estacionales influenciados por las medidas de protección y la escorrentía de precipitación. Ambas, agua subterránea y escorrentía mostraron composición química similar, siendo mayoritariamente de tipos cloruro-sulfato-bicarbonato y sodio-calcio. El agua subterránea aguas arriba de la ciudad, aunque de calidad más pobre que aguas abajo, mostró significante mejoría después de la instalación de un tunel de concreto para escorrentía y una planta de tratamiento de aguas servidas. Las concentraciones de muchos de los indicadores de calidad de agua subterránea (e.g., STD, coliformes, y nitrato) exceden los estándares de la Agencia de Protección Ambiental USA para agua potable. El contenido de metales pesados está, sin embargo, dentro de los límites permisibles de los estándares locales e internacionales. Los análisis químicos también sugieren la fuerte influencia de la escorrentía y aguas residuales en la calidad del agua subterránea.

  相似文献   

Evaluation of three waterborne polymers as stabilizers for sandy soil     

Abdullah Al-Khanbashi  Shihab W. Abdalla 《Geotechnical and Geological Engineering》2006,24(6):1603-1625

This study reports on waterborne polymer emulsion systems that were used for structural modification of sandy soils. The first emulsion used was a styrene-acrylic, copolymer emulsion; the second and third were vinyl-acrylic, copolymer-based emulsions. Specimens were prepared by adding different polymer emulsions to the sand and water in prescribed amounts. The performance of the different emulsion systems as sand stabilizers was estimated through measurement of the hydraulic conductivity and compressive strength. Measurements of hydraulic conductivity were conducted in a flexible membrane test apparatus. The hydraulic conductivity for the three emulsions decreased at different rates, with an increase in polymer content up to 3 wt. (i.e., % by weight). Additional increase of polymer content did not introduce significant decrease in hydraulic conductivity, and, at 5 wt.%, the three emulsions had essentially the same effect. Measurements made on dry cylindrical specimens disclosed remarkable enhancement in the mechanical behavior of the system. The compressive strength and modulus of elasticity of the examined emulsions increased with a higher concentration of polymer. Scanning electron microscope (SEM) revealed that the reduction in the permeability and the improved mechanical properties can be attributed to three dominant structural changes: the development of interconnecting ties between the sand particles, the development of adhesion between neighboring sand particles in contact, and the covering of the sand particles with a thin polymer film.  相似文献   

Evidence of early generation of liquid hydrocarbon from suberinite as visible under the microscope   总被引：1，自引：0，他引：1  

Wan Hasiah Abdullah   《Organic Geochemistry》1997,27(7-8)

The early generation of liquid hydrocarbons from suberinite can be clearly observed under the microscope. The generation of this oil-like material, mainly in the form of exsudatinite, from the maceral suberinite occurs at a maturity level of about 0.4% vitrinite reflectance. Hydrocarbons appear to be naturally expelled from coal initially through sweating and agglomeration of suberinite which subsequently forms exsudatinite. It is suggested that extensive expulsion of exsudatinite causes cracks to develop in vitrinite whereas limited expulsion of exsudatinite will only impregnate the vitrinite matrix. If cracks are formed, it is possible they could progressively develop to form an exsudatinite-crack network. The formation of such a network is believed to represent an effective way of hydrocarbon expulsion from coal source rocks.  相似文献   

Middle Paleolithic occupation on a Marine Isotope Stage 5 lakeshore in the Nefud Desert,Saudi Arabia     

Michael D. Petraglia  Abdullah M. Alsharekh  Rémy Crassard  Nick A. Drake  Huw Groucutt  Adrian G. Parker  Richard G. Roberts 《Quaternary Science Reviews》2011,30(13-14):1555-1559

Major hydrological variations associated with glacial and interglacial climates in North Africa and the Levant have been related to Middle Paleolithic occupations and dispersals, but suitable archaeological sites to explore such relationships are rare on the Arabian Peninsula. Here we report the discovery of Middle Paleolithic assemblages in the Nefud Desert of northern Arabia associated with stratified deposits dated to 75,000 years ago. The site is located in close proximity to a substantial relict lake and indicates that Middle Paleolithic hominins penetrated deeply into the Arabian Peninsula to inhabit landscapes vegetated by grasses and some trees. Our discovery supports the hypothesis of range expansion by Middle Paleolithic populations into Arabia during the final humid phase of Marine Isotope Stage 5, when environmental conditions were still favorable.  相似文献   

Evaluating İstanbul’s disaster resilience capacity by data envelopment analysis     

Abdullah Korkut Üstün 《Natural Hazards》2016,80(3):1603-1623

  相似文献   

Automatic identification of fake patterns caused by short-width wavelets in seismic data     

Ahmed Mohamed Tawfiek  Guanzheng TAN  Ali G. Hafez  Abdullah Al-Amri  Nassir Alarif  Kamal Abdelrahman 《Arabian Journal of Geosciences》2016,9(11):580

Despite the popularity of using the Haar wavelet filter in many applications, it sometimes introduces fake patterns into the multi resolution analysis (MRA) of seismic data. In this work, we compared different wavelet filters to demonstrate that these patterns are fake and not part of the original waveforms and to show that they are a result of using the Haar wavelet filter as a short-width wavelet. To achieve this, many seismic waveforms from two different sources: the Egyptian National Seismic Network (ENSN) and the High Sensitivity Seismograph Network Japan (Hi-net) are used with different wavelet filters. We propose an algorithm based on an autoregressive (AR) model to detect these patterns automatically and fully.  相似文献   

Relationship between finite strain and tectonic setting in the Ar-Ruwaydah area,eastern Arabian Shield,Saudi Arabia     

Osama M. K. Kassem  Abdullah L.A. Almutairi  Abdel Aziz M. Al Bassam  Hussain J. Al Faifi 《Arabian Journal of Geosciences》2016,9(19):728

  相似文献   

Assessment of toxic metals in coastal sediments of the Rosetta area,Mediterranean Sea,Egypt     

Abdelbaset S. El-Sorogy  Mohamed Tawfik  Sattam A. Almadani  Abdullah Attiah 《Environmental Earth Sciences》2016,75(5):398

  相似文献