Rock avalanche on 14 July 2014 from Hillary Ridge,Aoraki/Mount Cook,New Zealand     

S. C. Cox  M. J. McSaveney  J. Spencer  S. K. Allen  S. Ashraf  G. T. Hancox  P. Sirguey  J. Salichon  B. G. Ferris 《Landslides》2015,12(2):395-402

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Nonlinear propagation of ion-acoustic waves in an electron-positron-ion plasma     

M. Ferdousi  S. Yasmin  S. Ashraf  A. A. Mamun 《Astrophysics and Space Science》2014,352(2):579-584

A theoretical investigation has been made of electrostatic solitary structures in an electron-positron-ion (e-p-i) plasma, taking nonextensive electrons and nonextensive positrons. By employing the reductive perturbation method, the basic characteristics of ion-acoustic (IA) solitary waves (SWs) in a three-component e-p-i plasma (consisting of negatively charged nonextensive electrons, positively charged nonextensive positrons, and ions) have been addressed. The Korteweg-de Vries (K-dV), modified K-dV (mK-dV), and Gardner equations are derived and their numerical solutions are obtained. It has been shown that the combined effects of electron nonextensivity, positron nonextensivity, and ions significantly modify the behavior of these electrostatic solitary structures that have been found to exist with positive and negative potential in this plasma model. The present analysis may be useful to understand and demonstrate the dynamical properties of IA SWs in different astrophysical and cosmological scenarios (viz. stellar polytropes, hadronic matter and quark-gluon plasma, protoneutron stars, dark-matter halos, etc.).  相似文献   

Primordial helium isotope signature from Plio–Quaternary alkaline basalts in Yemen     

Yuji Orihashi  Keisuke Nagao  Ashraf Al-Jailani  Barry B. Hanan 《Island Arc》2001,10(2):145-157

Abstract Isotopic compositions of He, Ne and Ar were measured on Plio–Quaternary alkaline basalts of Marib–Sirwah and Shuqra volcanic fields in Yemen, south-western Arabian Peninsula. Very high ³He/⁴He isotope ratios were found in olivine phenocrysts of some Quaternary alkaline basalts in both volcanic fields, located on the margin of the dispersed Afar mantle plume, compared with the Afar–Ethiopian province in the center of the mantle plume. This suggests that the Afar mantle plume source may consist of common component (C or focal zone (FOZO)) with variable primordial ³He/⁴He ratio rather than high μ mantle (HIMU) component. The three component mixing C as the Afar mantle plume, depleted mantle (DM) as upper mantle and lithospheric mantle with a hybrid enriched mantle I–II (EM I–EM II) characteristics may be adequate to explain He–Sr–Nd–Pb isotope variation for the Afar–Arabian Cenozoic volcanics. The occurrence of high ³He/⁴He ratios in the Marib–Sirwah volcanic field appears to show that the primitive basaltic magma, derived from the margin of the dispersed trous-like Afar mantle plume during 15–0 Ma, was not by contamination of lithospheric and upper mantle materials in comparison with that from the center of the Afar mantle plume as a result of relatively low thermal anomaly.  相似文献   

Cosmological Axially-Symmetric Viscous Fluid Interacting with the Gravitational Field     

L. Ibochouba Singh  Mohammed Ashraf Ali 《Astrophysics and Space Science》1998,260(3):291-297

The problem of cosmological axially-symmetric viscous fluid interacting with the gravitational field has been investigated. Exact solution have been obtained for the pressure and density of the fluid. Physical interpretation of the solutions regarding the expansion factor, acceleration components and reality condition have been made. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Arsenic release from biotite into a Holocene groundwater aquifer in Bangladesh   总被引：1，自引：0，他引：1  

Ashraf Ali Seddique  Harue Masuda  Muneki Mitamura  Keiji Shinoda  Toshiro Yamanaka  Takaaki Itai  Teruyuki Maruoka  Kenji Uesugi  Kazi Matin Ahmed  Dipak Kumar Biswas 《Applied Geochemistry》2008,23(8):2236-2248

Continuous core sediments (to a depth of 90.1 m) taken at a transitional area of Holocene and Pleistocene deposits in Sonargaon, Bangladesh were characterized for their mineralogy and chemistry. Among the sediments of the lower part of the Holocene aquifer (depth: 18–29 m), where most domestic wells are installed, As is mostly fixed in biotite and organic phases. A positive correlation of As concentration with those of Al and Fe but not that of total organic C clearly suggests that biotite is a primary source of As. Although microbial reduction–dissolution of As-containing Fe oxyhydroxides is thought to cause As-enriched groundwater in the Ganges–Brahmaputra–Meghna delta plain, the authors conclude that chemical weathering of biotite is the primary formation mechanism and prevailing reducing conditions contribute to the expansion of As-enriched groundwater in the study area.  相似文献   

Analyses of the impact of climate change on water resources components,drought and wheat yield in semiarid regions: Karkheh River Basin in Iran   总被引：2，自引：0，他引：2       下载免费PDF全文

S. Ashraf Vaghefi  S. J. Mousavi  K. C. Abbaspour  R. Srinivasan  H. Yang 《水文研究》2014,28(4):2018-2032

Water resources availability in the semiarid regions of Iran has experienced severe reduction because of increasing water use and lengthening of dry periods. To better manage this resource, we investigated the impact of climate change on water resources and wheat yield in the Karkheh River Basin (KRB) in the semiarid region of Iran. Future climate scenarios for 2020–2040 were generated from the Canadian Global Coupled Model for scenarios A1B, B1 and A2. We constructed a hydrological model of KRB using the Soil and Water Assessment Tool to project water resources availability. Blue and green water components were modeled with uncertainty ranges for both historic and future data. The Sequential Uncertainty Fitting Version 2 was used with parallel processing option to calibrate the model based on river discharge and wheat yield. Furthermore, a newly developed program called critical continuous day calculator was used to determine the frequency and length of critical periods for precipitation, maximum temperature and soil moisture. We found that in the northern part of KRB, freshwater availability will increase from 1716 to 2670 m³/capita/year despite an increase of 28% in the population in 2025 in the B1 scenario. In the southern part, where much of the agricultural lands are located, the freshwater availability will on the average decrease by 44%. The long‐term average irrigated wheat yield, however, will increase in the south by 1.2%–21% in different subbasins; but for rain‐fed wheat, this variation is from ?4% to 38%. The results of critical continuous day calculator showed an increase of up to 25% in both frequency and length of dry periods in south Karkheh, whereas increasing flood events could be expected in the northern and western parts of the region. In general, there is variability in the impact of climate change in the region where some areas will experience net negative whereas other areas will experience a net positive impact. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Considerations about the occurrence of pollen grains of the Valeriana eichleriana (C.A.Muller) Graebner, in sediments of the Upper Quaternary in the state of Rio Grande do Sul, Brazil     

Paulo C.P.Neves  Soraia G.Bauermann  Maria G.Rossoni  Jose R.R.Coiro  Marleni M.Toigo  Abdul R.Ashraf 《世界地质(英文版)》2004,7(1)

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Evaluation of code criteria for bridges with unequal pier heights     

Majid Tamanani  Yen Gian  Ashraf Ayoub 《Bulletin of Earthquake Engineering》2016,14(11):3151-3174

One of the challenges associated with Eurocode 8 and AASHTO-LRFD is predicting the failure of irregular bridges supported by piers of unequal heights. EC8 currently uses “moment demand-to-moment capacity” ratios to somewhat guarantee simultaneous failure of piers on bridges, while AASHTO-LRFD relies on the relative effective stiffness of the piers. These conditions are not entirely valid, in particular for piers with a relative height of 0.5 or less, where a possible combination of flexure and shear failure mode may occur. In this case, the shorter piers often result in brittle shear failure, while the longer piers are most likely to fail due to flexure, creating a combination of different failure modes experienced by the bridge. To evaluate the adequacy of EC8 design procedures for regular seismic behavior, various irregular bridges are simulated through a non-linear pushover analysis using shear-critical fiber-based beam-column elements. The paper investigates the behavior of irregular monolithic and bearing-type bridges experiencing different failure modes, and proposes different methods for regularizing the bridge performance to balance damage. The ultimate aim is to obtain a simultaneous or near-simultaneous failure of all piers irrespective of the different heights and failure mode experienced.  相似文献   

Response of the Dupi Tila aquifer to intensive pumping in Dhaka,Bangladesh     

Brian?L.?MorrisEmail author  Ashraf?Ali?Seddique  Kazi?Matin?Ahmed 《Hydrogeology Journal》2003,11(4):496-503

This paper focuses on the water-quantity issues facing Dhaka because of the rapid exploitation of the Dupi Tila aquifer. Dhaka is one of the world's largest groundwater-dependent cities, relying on water withdrawn from this underlying semiconfined sand aquifer. A meteoric rise in well construction in both the private and public sectors in recent years has produced an estimated 1,300 boreholes that tap the aquifer in urban and suburban parts of the city. Analysis of construction records for public-supply wells drilled between 1970 and 2000 shows that water levels are falling in several areas of the city despite apparently favorable recharge conditions. The productivity of boreholes as measured by specific capacity has also declined significantly. Even though the aquifer system is vital to the infrastructure of the city it remains a poorly quantified resource, and until this is resolved by investment in evaluation studies, attempts to efficiently manage the resource in a sustainable way will be frustrated.

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Resumen Este artículo trata de los aspectos cuantitativos relacionados con la sobreexplotación del acuífero de Dupi Tila, que suministra a la ciudad de Dhaka (Bangladesh). Ésta es una de las mayores ciudades del mundo con dependencia de las aguas subterráneas, y se abastece de un acuífero semiconfinado formado por arenas. El aumento meteórico en la construcción de pozos durante los últimos años, tanto en el sector público como en el privado, ha provocado que haya unas 1.300 captaciones del acuífero en las zonas urbana y suburbana de la ciudad. El análisis de los registros constructivos de pozos de abastecimiento público entre 1970 y 2000 muestra que los niveles piezométricos están descendiendo en diversas áreas de la ciudad, a pesar de la existencia de condiciones aparentemente favorables de recarga. La productividad de los pozos, determinada por su capacidad específica, también ha disminuido significativamente. Aunque el sistema acuífero es vital para la infraestructura de la ciudad, los recursos aún no han sido cuantificados adecuadamente. Hasta que este asunto no sea resuelto mediante la inversión en estudios de evaluación, los intentos por gestionar eficientemente los recursos de forma sustentable serán infructuosos.

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Résumé Cet article porte sur les pertes en quantité subies par Dacca du fait de l'exploitation rapide de l'aquifère de Dupi Tila. Dacca est l'une des villes dépendant de l'eau souterraine les plus importantes du monde, prélevant l'eau d'un aquifère sableux sous-jacent semi-captif. On estime à 1,300 forages l'accroissement des creusements de puits aussi bien dans le secteur privé que public dans ces dernières années; ils prélèvent dans l'aquifère dans la partie urbaine et à la périphérie de la ville. L'analyse des déclarations de creusement de puits pour l'AEP forés entre 1970 et 2000 montre que les niveaux d'eau ont chuté dans plusieurs zones de la ville malgré des conditions de recharge apparemment favorables. La productivité des puits mesurée par la capacité spécifique a également diminué significativement. Même si le système aquifère est vital pour l'infrastructure de la ville, il reste une ressource médiocrement quantifiée, et tant que ceci ne sera pas résolu par un investissement dans des études d'évaluation, les tentatives pour gérer efficacement la ressource de façon durable échoueront.

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CHEMICAL CHARACTERISTICS OF WETLAND＇S INFLOW DRY DIFFUSE DUST AND DIRT FROM IMPERVIOUS SURFACE     

Azam Khan　Saadat Ashraf 《湿地科学》2005,3(4):249-257

This paper presented chemical characteristics of wetland inflow diffuse dust and dirt. Single land use impervious areas (parking and roads) were observed and analyzed in commercial and residential areas for organic matters, phosphorus and heavy metals. The buildup data were collected for approximately six months from December to June. The frequency of monitoring was observed daily for the first two months, twice a week for the next two months and once a week for the last two months. The results indicated significant variations in the organic matters and heavy metals strength and total accumulation among the observed areas. High pollutants strength was associated with smaller dust and dirt (DD) particles. Concentrations of phosphorus varied between 5.1 μg/g and 8.3 μg/g in DD particle less than 75 μm and account for 35%-60% of the total phosphorus. The organic matter accumulation rate associated with particles less than 600 μm and greater than 600 μm was 0.1-1 g·(curb-m)-1·d-1 and 0.1-1.5 g·(curb-m)-1·d-1 , respectively. DD particles greater than 600 μm consist of 70%-90% of leaves and other plant residues. The strength of heavy metals was more at road compared to parking areas both in commercial and residential areas. Percentage of Zn, Cu and Pb attached with particles less than 200 μm were in the range of 50%-70% in parking, 45%-90% on smooth roads and 30%-80% on rough roads. All the dust and dirt exhibited rising trend with time. Dust and dirt buildup data follow a non-linear accumulation function and can be presented better either by an exponential or power function.  相似文献