Variations in the redox state of As and Fe measured by X-ray absorption spectroscopy in aquifers of Bangladesh and their effect on As adsorption     

Takaaki Itai  Yoshio Takahashi  Ashraf Ali Seddique  Teruyuki Maruoka  Muneki Mitamura 《Applied Geochemistry》2010

  相似文献   

Nonlinear finite element modeling of beams on two-parameter foundations     

Ravi Mullapudi  Ashraf Ayoub 《Computers and Geotechnics》2010

This paper presents an inelastic element for the analysis of beams resting on two-parameter foundations. The element is derived from a two field mixed formulation with independent approximation of forces and displacements. The values for the two parameters of the foundation are derived through an iterative technique that is based on an assumption of plane strain for the soil medium. This iterative behavior is repeated at each time step of the nonlinear solution algorithm. The nonlinear response of structures resting on this improved two-parameter foundation model is analyzed following both a Vlasov and a Pasternak approach. Numerical examples that clarify the advantage of the newly developed model are conducted. These studies confirmed the importance of accounting for the foundation second parameter, and the efficiency and accuracy of the proposed model.  相似文献   

Minimizing the impacts of contaminant intrusion in small water distribution networks through booster chlorination optimization     

Nilufar?Islam  Manuel?J.?Rodriguez  Ashraf?Farahat  Rehan?SadiqEmail author 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(7):1759-1775

Contaminant intrusion in a water distribution network (DN) has three basic pre-conditions: source of contaminant (e.g., leaky sewer), a pathway (e.g., water main leaks), and a driving force (e.g., negative pressure). The impact of intrusion can be catastrophic if residual disinfectant (chlorine) is not present. To avoid microbiological water quality failure, higher levels of secondary chlorination doses can be a possible solution, but they can produce disinfectant by-products which lead to taste and odour complaints. This study presents a methodology to identify potential intrusion points in a DN and optimize booster chlorination based on trade-offs among microbiological risk, chemical risk and life-cycle cost for booster chlorination. A point-scoring scheme was developed to identify the potential intrusion points within a DN. It utilized factors such as pollutant source (e.g., sewer characteristics), pollution pathway (water main diameter, length, age, and surrounding soil properties, etc.), consequence of contamination (e.g., population, and land use), and operational factors (e.g., water pressure) integrated through a geographical information system using advanced ArcMap 10 operations. The contaminant intrusion was modelled for E. Coli O156: H7 (a microbiological indicator) using the EPANET-MSX programmer’s toolkit. The quantitative microbial risk assessment and chemical (human health) risk assessment frameworks were adapted to estimate risk potentials. Booster chlorination locations and dosages were selected using a multi-objective genetic algorithm. The methodology was illustrated through a case study on a portion of a municipal DN.  相似文献   

Dietary effects of A zolla pinnata combined with exogenous digestive enzyme(Digestin~(TM)) on growth and nutrients utilization of freshwater prawn,Macrobrachium rosenbergii(de Man 1879)     

GODA Ashraf  SAAD Amal  HANAFY Mohamed  SHARAWY Zaki  EL-HAROUN Ehab 《中国海洋湖沼学报》2018,(4)

The present study was conducted to evaluate the effect of either individual or combined wheat bran(WB) replacement with Azolla pinnata supplemented with Digestin~(TM) in the diet of freshwater prawn, Macrobrachium rosenbergii Postlarvae(PL) on growth performance, nutrient utilization, chemical body composition and survival(%). Experimental diets were a wheat bran-soybean based diet with no Azolla and Digestin~(TM)(control, T_1), and diets containing 17% Azolla supplemented with Digestin~(TM) 0%(T_2), 1%(T_3), 2%(T_4) and 3%(T 5). Each experimental diet was allocated into three tanks(6 m~3/tank) fed for 12 wks. Each tank was subdivided into three equal pens by nets(2 m~3) and stoked with 84 PL/m~2. The experimental diets were readily consumed by prawns PLs where both high growth and good feed efficiency were achieved for all diets. The results showed that the diets containing A. pinnata supplemented with Digestin? at the level up to 3% have the higher growth and better nutrient utilization than the control diet. No differences were observed for moisture and protein content among the experimental diets. However, the highest protein content was observed on prawns fed on diets T_1 and T 5 respectively, while the lowest value was recorded for T_4 diet. The results also show that prawn PLs fed the diets contain A. pinnata and supplemented with Digestin~(TM) recorded the highest values of body lipid content compared to the control diet. Feed efficiency and economic conversion rate(ECR) values show that economic performance and the cost-effectiveness of the A. pinnata supplemented with up to 3% Digestin~(TM) recorded the highest net return, and therefore it is recommended for prawn, M. rosenbergii PL's. These results are clearly indicating that A. pinnata have a good potential for use in prawn diets at reasonable levels than other conventional diets.  相似文献   

Cretaceous Environments of Afghanistan:A Synthesis Based on Selected Sections     

Abdul Rahman Ashraf  Ashok Sahni 《世界地质(英文版)》2003,6(1)

The Cretaceous of Afghanistan is marked by great facies diversity. The evolution of Cretaceous basins is part of a complex accretionary history involving three distinct tectonic units namely the Asian (Russian) Block separated from the Indian plate by a rather well defined transcurrent fault (Chaman-Nuski). The southwestern component is representedby the Iran-Afghanistan plate. The Lower Cretaceous of the Asian Block is represented by the Red-Grit Series which isconformable to the underlying Upper Jurassic sequences. The transition is marked by evaporitic facies dominated by salt,gypsum and marl deposits. In south Afghanistan volcanic rocks occur at Farah, with the emplacement of plutonics inwest-central Afghanistan. The Upper Cretaceous of north Afghanistan is marked by richly fossiliferous, lime stone-dominated sequences. The Upper Cretaceous of southern Afghanistan is marked by strong ophiolitic magrmatism.  相似文献   

Avoiding high concentrations of arsenic, manganese and salinity in deep tubewells in Munshiganj District, Bangladesh   总被引：1，自引：0，他引：1  

Stephan J. Hug  Dominique GaertnerLinda C. Roberts  Mario SchirmerThomas Ruettimann  Thomas M. RosenbergA.B.M. Badruzzaman  M. Ashraf Ali 《Applied Geochemistry》2011,26(7):1077-1085

  相似文献   

Gypsum and dolomite biomineralization in endoevaporitic microbial niche,EMISAL, Fayium,Egypt     

Mohamed W. Ali-Bik  Hussein I. M. Metwally  Mohamed G. Kamel  Ashraf M. A. Wali 《Environmental Earth Sciences》2011,62(1):151-159

Biogenic gypsum in the form of microbialite and potential domal stromatolite as well as endoevaporitic dolomite are deposited in a perennial saline basin characterized by microbial bloom. Deposition environment, mode of occurrence, and microscopic investigation including SEM of these precipitates are discussed in conjunction with XRD, XRF, and FTIR data. Combined effects of salinity gradient and the wind action on the maturity of gypsum outcrop are evident. A characteristic multi-color vertical gypsum profile reflects steep gradient of oxi-anoxic microenvironments and encodes diverse seasonal microbial communities. Direct impact of microbial signature in gypsum crystal habit is conspicuous. Endoevaporitic authigenic dolomite is recorded in specific horizons in interstices of selenite layers.  相似文献   

Continuous velocity fields for the T‐bar problem     

Assaf Klar  Ashraf S. Osman 《国际地质力学数值与分析法杂志》2008,32(8):949-963

This paper deals with the problem of T‐bar penetration. New kinematically admissible velocity fields are derived from elastic solutions of incompressible material using Airy stress function. These velocity fields are used to obtain upper bounds to collapse loads. Two particular solutions are presented, one for a rough contact surface between the T‐bar and soil and the other for a smooth contact surface. The merit of the solutions is that within the boundaries of the velocity field, the soil is required to shear compatibly and continuously. Therefore, these solutions can easily be combined with the strain path method to estimate rate and softening effects. Analysis including consideration of strain rate effect showed that the new mechanisms predict, under certain conditions, lower values than previously published upper bound solutions. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Vegetation and Climate Reconstruction of the Planalto in Rio Grande do Sul, South Brazil (Late Glacial and Holocene)     

M.Herrmann  A.R.Ashraf  V.Mosbrugger  M.M.Toigo 《世界地质(英文版)》2003,6(2)

A 405 cm long core was drilled in the Aparados da Serra National Park (Rio Grande do Sul, Brazil) at the end of 1999, and in all, 23 samples were taken for palynological investigation. The cores′ age is estimated at 27 000 a BP based on three radiocarbon dates taken from different depths of the core. Palynological methods were used to reconglacial conditions mainly influenced by the South Pole throughout several transition stages to today's humid warm climate, mainly being influenced by the Brazil stream.  相似文献   

Sedimentary facies of Maastrichtian to Danian deposits in Amur River area, Russian Far East     

ShigeyukiSuzuki AbdulR.Ashraf HakuyuOkada 《东北亚地学研究》2004,7(2):149-155

Sedimentary facies of the Tsagayan Formation is distributed in the eastern Zeya-Bureya Basin has been analyzed. The formation is of the Maastrichtian to Danian in age and characterized by the cyclicity of the fining-upwards successions. Analysis of environmental changes during the K/T boundary is the focus of this study. Five facies have been identified: Facies A, thick and laterally extensive coarse-grained to medium-gained sandstone units, interpreted as channelfill deposits; Facies B, parallel-laminated to massive mudstone units interpreted as interchannel lakes and flood plain deposits; Facies C, sheet-like medium-grained to fine-grained sandstones interpreted as crevasse splay deposits; Facies D, coal to coaly mudstone beds interpreted as deposits of peatlands; Facies E, very poorly sorted sandy mudstone beds interpreted as debris flow deposits. Fluvial environments with the low-relief fiat topography was inferred. A channel transported large volumes of clasts, and a flood basin with interchannel lakes and peatlands was deciphered. Any distinct change of sedimentary environments has not been identified throughout the Tsagayan Formation (including the K/T boundary). However, two beds of debris flow deposits were identified. The one occurs at the uppermost part of the lower Tsagayan Subformation and contains dinosaur fossils. The other is intercalated in the upper Tsagayan Subformation.  相似文献