A comparison between observed and analytical velocity dispersion profiles of 20 nearby galaxy clusters     

Mohammad S. Khan  Mohamed H. Abdullah  Gamal B. Ali 《Astrophysics and Space Science》2014,351(1):289-297

We derive analytical expression for the velocity dispersion of galaxy clusters, using the statistical mechanical approach. We compare the observed velocity dispersion profiles for 20 nearby (z≤0.1) galaxy clusters with the analytical ones. It is interesting to find that the analytical results closely match with the observed velocity dispersion profiles only if the presence of the diffuse matter in clusters is taken into consideration. This takes us to introduce a new approach to detect the ratio of diffuse mass, M _diff , within a galaxy cluster. For the present sample, the ratio f=M _diff /M, where M the cluster’s total mass is found to has an average value of 45±12 %. This leads us to the result that nearly 45 % of the cluster mass is impeded outside the galaxies, while around 55 % of the cluster mass is settled in the galaxies.  相似文献   

A comparative study of support vector machines and artificial neural networks for predicting precipitation in Iran     

Omid Hamidi  Jalal Poorolajal  Majid Sadeghifar  Hamed Abbasi  Zohreh Maryanaji  Hamid Reza Faridi  Lily Tapak 《Theoretical and Applied Climatology》2015,119(3-4):723-731

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P–T–t evolution of granulite facies metamorphism and partial melting in the Winding Stair Gap,Central Blue Ridge,North Carolina,USA     

A. K. EL‐SHAZLY  C. LOEHN  R. J. TRACY 《Journal of Metamorphic Geology》2011,29(7):753-780

The Winding Stair Gap in the Central Blue Ridge province exposes granulite facies schists, gneisses, granofelses and migmatites characterized by the mineral assemblages: garnet–biotite–sillimanite–plagioclase–quartz, garnet–hornblende–biotite–plagioclase–quartz ± orthopyroxene ± clinopyroxene and orthopyroxene–biotite–quartz. Multiple textural populations of biotite, kyanite and sillimanite in pelitic schists support a polymetamorphic history characterized by an early clockwise P–T path in which dehydration melting of muscovite took place in the stability field of kyanite. Continued heating led to dehydration melting of biotite until peak conditions of 850 ± 30 °C, 9 ± 1 kbar were reached. After equilibrating at peak temperatures, the rocks underwent a stage of near isobaric cooling during which hydrous melt ± K‐feldspar were replaced by muscovite, and garnet by sillimanite + biotite + plagioclase. Most monazite crystals from a pelitic schist display patchy zoning for Th, Y and U, with some matrix crystals having as many as five compositional zones. A few monazite inclusions in garnet, as well as Y‐rich cores of some monazite matrix crystals, yield the oldest dates of c. 500 Ma, whereas a few homogeneous matrix monazites that grew in the main foliation plane yield dates of 370–330 Ma. Culling and analysis of individual spot dates for eight monazite grains yields three age populations of 509 ± 14 Ma, 438 ± 5 Ma and 360 ± 5 Ma. These data suggest that peak‐temperature metamorphism and partial melting in the central Blue Ridge occurred during the Salinic or Taconic orogeny. Following near isobaric cooling, a second weaker thermal pulse possibly related to intrusion of nearby igneous bodies resulted in growth of monazite c. 360 Ma, coinciding with the Neoacadian orogeny.  相似文献   

Principales caractéristiques des réservoirs du Sud-Ouest tunisien     

Moncef Chalbaoui  Hamed Ben Dhia 《Comptes Rendus Geoscience》2004,336(13):1191-1198

A study of the form and characteristics of the reservoirs and aquifers of southwestern Tunisia has been carried out from 62 petroleum explorations and hydrogeologic wells and structural maps. The evolution of basins can be deduced from the tectonic history. The Jurassic reservoirs are represented by the Upper Nara carbonates. The petrophysical characteristics and the fracturation affecting the Nara carbonates reveal the existence of very good reservoirs. Several reservoirs have also been identified in the Lower Cretaceous. These reservoirs are made of sandy levels, interbedded with shale, carbonates and dolomites. In addition, petroleum and hydrogeologic studies have revealed that potential aquifers may occur in two provinces (near the Chott Basin and east–west faults). Most of the geological formations in the South West of Tunisia are composed of sand, sandstone and limestone, with the existence of real aquifers. To cite this article: M. Chalbaoui, H. Ben Dhia, C. R. Geoscience 336 (2004).  相似文献   

Direct retrieval of exterior orientation parameters using a 2D projective transformation   总被引：3，自引：1，他引：2  

Gamal H.  Seedahmed 《The Photogrammetric Record》2006,21(115):211-231

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AERIAL RADIOMETRY OF EL ALAMEIN OILFIELD,EGYPT, U.A.R.*     

E. M. EL SHAZLY  W. M. MESHREF  K. M. FOUAD  A. A. AMMAR  M. L. MELEIK 《Geophysical Prospecting》1969,17(3):336-343

Total gamma airborne radiometric survey of El Alamein area in the Western Desert has been carried out by the Atomic Energy Establishment. The flight lines are directed north-south with 500 m spacing, while the ground clearance is about 50 m. Superimposition of the radioactivity profiles over El Alamein Oilfield shows a general decrease of gamma radiation in the central part of the structure framed by zones of relatively higher values. The aerial radioactivity of El Alamein Oilfield is described and it is correlated with some reported radiometric characteristics of other oil bearing structures. The distribution of aeroradiometric measurements over El Alamein Oilfield and its environment has been found to be lognormal.  相似文献   

Climatological analysis of Mediterranean cyclones using ECMWF data   总被引：2，自引：0，他引：2  

P. ALPERT  B. U. NEEMAN  Y. SHAY&#;EL 《地球，A辑:动力气象学与海洋学》1990,42(1):65-77

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Measuring the relationships between landscape aesthetics suitability and spatial patterns of urbanized lands: an informed modelling framework for developing urban growth scenarios     

Yousef Sakieh  Abdolrassoul Salmanmahiny  Seyed Hamed Mirkarimi  Sepideh Saeidi 《国际地球制图》2017,32(8):853-873

This study develops an informed modelling approach that follows a bottom-up planning strategy to define plausible urban growth scenarios. In this case, landscape aesthetics suitability of the area was first generated using multi-criteria evaluation method. Then, a buffer zone of 1 km was considered to extract the average values of aesthetics suitability scores surrounding urban patches with medium physical size (10–30 hectares). The averaged values were considered as the dependent variable. In the next step, landscape metrics of these urban patches, as explanatory variables, were also computed to measure compositional and configuration-based attributes of urban clusters. Bivariate associations (Pearson correlation analysis) and statistical relationships (linear regression algorithm) between landscape metrics and their associated aesthetics values were measured and modelled. According to the results, both composition and configuration values are significantly correlated to the dependent variable in which configuration-based attributes depicted a stronger explanatory power.  相似文献   

Trends of precipitation extreme indices over a subtropical semi-arid area using PERSIANN-CDR     

Pari-Sima?Katiraie-BoroujerdyEmail author  Hamed?Ashouri  Kuo-lin?Hsu  Soroosh?Sorooshian 《Theoretical and Applied Climatology》2017,130(1-2):249-260

In this study, satellite-based daily precipitation estimation data from precipitation estimation from remotely sensed information using artificial neural networks (PERSIANN)-climate data record (CDR) are being evaluated in Iran. This dataset (0.25°, daily), which covers over three decades of continuous observation beginning in 1983, is evaluated using rain-gauge data for the period of 1998–2007. In addition to categorical statistics and mean annual amount and number of rainy days, ten standard extreme indices were calculated to observe the behavior of daily extremes. The results show that PERSIANN-CDR exhibits reasonable performance associated with the probability of detection and false-alarm ratio, but it overestimates precipitation in the area. Although PERSIANN-CDR mostly underestimates extreme indices, it shows relatively high correlations (between 0.6316–0.7797) for intensity indices. PERSIANN-CDR data are also used to calculate the trend in annual amounts of precipitation, the number of rainy days, and precipitation extremes over Iran covering the period of 1983–2012. Our analysis shows that, although annual precipitation decreased in the western and eastern regions of Iran, the annual number of rainy days increased in the northern and northwestern areas. Statistically significant negative trends are identified in the 90th percentile daily precipitation, as well as the mean daily precipitation from wet days in the northern part of the study area. The positive trends of the maximum annual number of consecutive dry days in the eastern regions indicate that the dry periods became longer in these arid areas.  相似文献   

Modeling forest fire risk in the northeast of Iran using remote sensing and GIS techniques   总被引：3，自引：1，他引：2  

Hamed Adab  Kasturi Devi Kanniah  Karim Solaimani 《Natural Hazards》2013,65(3):1723-1743

Fire in forested areas can be regarded as an environmental disaster which is triggered by either natural forces or anthropogenic activities. Fires are one of the major hazards in forested and grassland areas in the north of Iran. Control of fire is difficult, but it is feasible to map fire risk by geospatial technologies and thereby minimize the frequency of fire occurrences and damages caused by fire. The fire risk models provide a suitable concept to understand characterization of fire risk. Some models are map based, and they combine effectively different forest fire–causing variables with remote sensing data in a GIS environment for identifying and mapping forest fire risk. In this study, Structural Fire Index, Fire Risk Index, and a new index called Hybrid Fire Index were used to delineate fire risk in northeastern Iran that is subjected to frequent forest fire. Vegetation moisture, slope, aspect, elevation, distance from roads, and vicinity to settlements were used as the factors influencing accidental fire starts. These indices were set up by assigning subjective weight values to the classes of the layers based on their sensitivity ratio to fire. Hot spots data derived from MODIS satellite sensor were used to validate the indices. Assessment of the indices with receiver operating characteristic (ROC) curves shows that 76.7 % accuracy of the HFI outperformed the other two indices. According to the Hybrid Fire Index, 57.5 % of the study area is located under high-risk zone, 33 % in medium-risk zone, and the remaining 9.5 % area is located in low-risk zone.  相似文献