From field study to numerical modeling of hydrothermal dolomitization in Early Cretaceous platform carbonates (Cantabrian mountains,northern Spain)     

F.H. Nader  C. Dumont  M.M. Shah  D. Garcia  R. Swennen  J.-M. Daniel  O. Lerat  B. Doligez 《Journal of Geochemical Exploration》2009

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Cosmic energy equation for extended structures and its application to gravitational galaxy clustering     

Abdul Wahid  Ajaz Ahmad 《Astrophysics and Space Science》2012,341(2):611-616

Cosmic energy equation represents the law of conservation of energy in the region expanding with time as the universe expands. It gives the evolution of kinetic and correlation potential energy with time in a cluster expanding as the universe expands. To understand the clustering of galaxies under the influence of gravitational force, cosmic energy equation is of great help. We use cosmic energy equation for extended structures (galaxies with halos) to analyse the gravitational galaxy clustering in different ways. We try to understand the influence of expansion on the clustering by deriving the relation between correlation parameter b _V and scale factor R. We also derive the relation between the peculiar kinetic energy K and correlation parameter to know that when peculiar kinetic energy dominates over the kinetic energy of galaxies due to expansion. Besides, the evolution of specific heat and energy provides the information regarding the different states of clustering.  相似文献   

The structure and dynamics of young star clusters: King 16, NGC 1931, NGC 637 and NGC 189     

Priya Hasan  S. N. Hasan  Urmi Shah 《Astrophysics and Space Science》2008,318(1-2):25-33

In this paper, using 2MASS photometry, we study the structural and dynamical properties of four young star clusters viz. King 16, NGC 1931, NGC 637 and NGC 189. For the clusters King 16, NGC 1931, NGC 637 and NGC 189, we obtain the limiting radii of 7′, 12′, 6′ and 5′ which correspond to linear radii of 3.6 pc, 8.85 pc, 3.96 pc and 2.8 pc respectively. The reddening values E(B?V) obtained for the clusters are 0.85, 0.65–0.85, 0.6 and 0.53 and their true distances are 1786 pc, 3062 pc, 2270 pc and 912 pc respectively. Ages of the clusters are 6 Myr, 4 Myr, 4 Myr and 10 Myr respectively. We compare their structures, luminosity functions and mass functions (φ(M)=dN/dM ∝ M ^?(1+χ)) to the parameter τ=t _age /t _relax to study the star formation process and the dynamical evolution of these clusters. We find that, for our sample, mass seggregation is observed in clusters or their cores only when the ages of the clusters are comparable to their relaxation times (τ≥1). These results suggest mass seggregation due to dynamical effects. The values of χ, which characterize the overall mass functions for the clusters are 0.96±0.11, 1.16±0.18, 0.55±0.14 and 0.66±0.31 respectively. The change in χ as a function of radius is a good indicator of the dynamical state of clusters.  相似文献   

Household vulnerability and resilience in flood hazards from disaster-prone areas of Punjab,Pakistan     

Ahmad  Dilshad  Afzal  Muhammad 《Natural Hazards》2019,99(1):337-354

Natural Hazards - An environmental variation has caused Pakistan an alarming portrait of vulnerability in flood disasters. The government has focused on a number of realistic actions, heartening...  相似文献   

Building the Hindu Kush: monazite records of terrane accretion,plutonism and the evolution of the Himalaya–Karakoram–Tibet orogen     

Shah Faisal  Kyle P. Larson  John M. Cottle  Jaida Lamming 《地学学报》2014,26(5):395-401

In situ U‐Th/Pb (LA‐ICP‐MS) monazite ages from the Hindu Kush of NW Pakistan provide new petrochronologic constraints on the tectonic evolution of the Himalaya–Karakoram–Tibet orogen. Monazites from two adjacent garnet + staurolite schist specimens yield multiple age populations that record the major Mesozoic and Cenozoic deformational, magmatic and metamorphic events along the southern margin of Eurasia. These include the accretion of the Hindu Kush–SW Pamir to Eurasia during the Late Triassic, followed by the accretion of the Karakoram terrane in the Early Jurassic. Younger Jurassic and Cretaceous ages record the development of an Andean‐style volcanic arc along the southern Eurasian margin, which ended with the docking of the Kohistan island arc and the emplacement of the Kohistan–Ladakh batholith during the Late Cretaceous. The initial Eocene collision of India with Eurasia was followed by widespread high‐temperature metamorphism and anatexis associated with crustal thickening within the Himalaya system in the Late Oligocene and Early Miocene.  相似文献   

Integration of Cluster Analysis and Rock Physics for the Identification of Potential Hydrocarbon Reservoir     

Ali  Amjad  Sheng-Chang  Chen  Shah  Munawar 《Natural Resources Research》2021,30(2):1395-1409

Natural Resources Research - Rock physics has proven its credibility for the quantitative seismic interpretation of reservoir and reservoir characterization. In this study, we implemented K-means...  相似文献   

New urban map of Eurasia using MODIS and multi-source geospatial data     

Bayan Alsaaideh  Ryutaro Tateishi  Dong Xuan Phong  Nguyen Thanh Hoan  Ahmad Al-Hanbali  Bai Xiulian 《地球空间信息科学学报》2017,20(1):29-38

Urban areas are of paramount significance to both the individuals and communities at local and regional scales. However, the rapid growth of urban areas exerts effects on climate, biodiversity, hydrology, and natural ecosystems worldwide. Therefore, regular and up-to-date information related to urban extent is necessary to monitor the impacts of urban areas at local, regional, and potentially global scales. This study presents a new urban map of Eurasia at 500 m resolution using multi-source geospatial data, including Moderate Resolution Imaging Spectroradiometer (MODIS) data of 2013, population density of 2012, the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) nighttime lights of 2012, and constructed Impervious Surface Area (ISA) data of 2010. The Eurasian urban map was created using the threshold method for these data, combined with references of fine resolution Landsat and Google Earth imagery. The resultant map was compared with nine global urban maps and was validated using random sampling method. Results of the accuracy assessment showed high overall accuracy of the new urban map of 94%. This urban map is one product of the 20 land cover classes of the next version of Global Land Cover by National Mapping Organizations.  相似文献   

Photogrammetric Capabilities of the Kodak DC40, DCS420 and DCS460 Digital Cameras     

A. Ahmad  & J. H. Chandler 《The Photogrammetric Record》1999,16(94):601-615

The aim of this study is to assess the impact of sensor size and resolution of different digital camera sensors upon the accuracy and precision of three dimensional data derived by photogrammetry. Kodak DC40, DCS420 and DCS460 digital cameras were used to produce digital images of retroreflective targets in a 4 m three dimensional test field. The image locations of the targeted points were automatically measured using an off the shelf image processing software package. Two different sub-pixel measurement approaches were examined: centre of gravity and weighted mean. From the automated sub-pixel measurement of the targeted points, results indicate that the high resolution DCS460 camera produces optimum results using either the weighted mean or centre of gravity approaches. Although this was perhaps expected, the far lower resolution DC40 camera performed better than was originally anticipated, suggesting potential for the cheaper DC40 for many applications.  相似文献   

Urban steeplands in the tropics: an environment of accelerated erosion     

Avijit Gupta  Rafi Ahmad 《GeoJournal》1999,49(2):143-150

The developing countries at present have a high urban growth rate that is likely to continue for at least another quarter-century. In addition, many of these urban centres are located in the Neogene plate boundary zones and are subject to multiple earthquake and volcanic hazards. Slope failures and accelerated surface and channel erosion are particularly severe in cities near active plate margins, and in areas affected also by tropical cyclones. We discuss two extreme cases: Singapore and Kingston (Jamaica). Singapore is located in a stable environment and the urbanization related problems of flood and slope instability have been reduced by proper building and drainage practices at a considerable cost. In Kingston, the external disturbances are repetitive, large-scale, and very difficult to control. The fast-growing cities in the tropics need to be carefully monitored, especially when located in an unstable physical environment. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Regional bivariate modeling of droughts using L-comoments and copulas   总被引：1，自引：0，他引：1  

Amin?AbdiEmail author  Yousef?Hassanzadeh  Siamak?Talatahari  Ahmad?Fakheri-Fard  Rasoul?Mirabbasi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(5):1199-1210

The regional bivariate modeling of drought characteristics using the copulas provides valuable information for water resources management and drought risk assessment. The regional frequency analysis (RFA) can specify the similar sites within a region using L-comoments approach. One of the important steps in the RFA is estimating regional parameters of the copula function. In the present study, an optimization-based method along with the adjusted charged system search are introduced and applied to estimate the regional parameters of the copula models. The capability of the proposed methodology is illustrated by copula functions on drought events. Three commonly used copulas containing Clayton, Frank and Gumbel are employed to derive the joint distribution of drought severity and duration. The result of the new method are compared to the method of moments and after applying several goodness-of-fit tests, the results indicate that the new method provides higher accuracy than the classic one. Furthermore, the results of the upper tail dependence coefficient indicate that the Gumbel copula is the best-fitted copula among the other ones for modeling drought characteristics.  相似文献