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

PauloC.P.Neves SoraiaG.Bauermann MariaG.Rossoni JoseR.R.Coiro MarleniM.Toigo AbdulR.Ashraf 《东北亚地学研究》2004,7(1):1-7

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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   

Efficient and accurate edge‐preserving smoothing for 3D hexagonally sampled seismic data          下载免费PDF全文

Haroon Ashraf  Wail A. Mousa  Saleh Al‐Dossary 《Geophysical Prospecting》2017,65(3):696-710

The automatic detection of geological features such as faults and channels is a challenging problem in today's seismic exploration industry. Edge detection filters are generally applied to locate features. It is desirable to reduce noise in the data before edge detection. The application of smoothing or low‐pass filters results in noise suppression, but this causes edge blurring as well. Edge‐preserving smoothing is a technique that results in simultaneous edge preservation and noise suppression. Until now, edge‐preserving smoothing has been carried out on rectangular sampled seismic data. In this paper, an attempt has been made to detect edges by applying edge‐preserving smoothing as a pre‐processing step in the hexagonally sampled seismic‐data spatial domain. A hexagonal approach is an efficient method of sampling and has greater symmetry than a rectangular approach. Here, spiral architecture has been employed to handle the hexagonally sampled seismic data. A comparison of edge‐preserving smoothing on both rectangular and hexagonally sampled seismic data is carried out. The data used were provided by Saudi Aramco. It is shown that hexagonal processing results in well‐defined edges with fewer computations.  相似文献   

Response-based damage assessment of structures     

A. Ghobarah  H. Abou-Elfath  Ashraf Biddah 《地震工程与结构动力学》1999,28(1):79-104

The structure's ability to survive an earthquake may be measured in terms of the expected state of damage of the structure after the earthquake. Damage may be quantified by using any of several damage indices defined as functions whose values can be related to particular structural damage states. A number of available response-based damage indices are discussed and critically evaluated for their applicability in seismic damage evaluation. A new rational approach for damage assessment is presented which provides a measure of the physical response characteristics of the structure and is better suited for non-linear structural analysis. A practical method based on the static pushover analysis is proposed to estimate the expected damage to structures when subjected to earthquakes of different intensities. Results of the analysis of ductile and non-ductile reinforced concrete buildings show that the proposed procedure for damage assessment gives a simple, consistent and rational damage indicator for structures. Copyright © 1999 John Wiley & Sons, Ltd.  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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