Recent glacier changes in the Kashmir Alpine Himalayas,India     

Khalid Omar Murtaza 《国际地球制图》2017,32(2):188-205

Using Landsat data at decadal interval (1980–2013), the glacier fluctuations (glacier area, equilibrium line altitude and specific mass balance) of nine benchmark glaciers in Kashmir Himalaya were estimated. The observed changes were related to topographic and climatic variables in order to understand their influence. From the data analysis, it was observed that the glaciers have shrunk by 17%, ELA has shifted upwards (80–300 m) and SMB shows variation in glacier mass loss from ?0.77 to ?0.16 m.w.e. Annual air temperature showed a significant increasing trend, and a slight but insignificant decrease in precipitation was observed during the period. It is evident that in the same climatic regime, varying topography plays a key role in determining the glacier changes. It is believed that the observed changes in the glacier geometry and dynamics, if continued, shall have adverse effect on the streamflows, water supplies and other dependent sectors in the region.  相似文献   

Geochemical characterization of zoned zircon from Wadi Abu Rusheid psammitic gneiss, south Eastern Desert, Egypt     

Sayed A. Omar  Hassan A. A. Shahin  Masoud S. Masoud 《Arabian Journal of Geosciences》2013,6(6):1807-1817

A unique zircon was studied in the gneiss samples collected from the Wadi Abu Rusheid psammitic gneiss using electron scanning microscope and electron probe microanalyses. This zircon can be categorized into two types according to the texture and trace element content: (l) magmatic zircon slightly enriched in HfO₂ with ordinary zone. (2) Overgrowths of zircon occur as two species, the first species being highly enriched in HfO₂ with irregular zoning. The second species is highly enriched in HfO₂ forming a rim around the second species with a very sharp thinner boundary. The first type shows a distinct oscillatory internal zoning pattern without change in shape of this zone and has conspicuous inclusion-free zircon overgrowths with distinct poor concentrations in Y, Hf, Th, U, Nb, and Ta in both rim and core. The second type shows two species, the first one displays distinct irregular interval zoning and irregular overgrowth with abrupt change in composition of these zones with distinct enrichment in Y, Hf, Th, U, Nb, and Ta in the rim relative to the core. The second species is forming a rim around the first species also with distinct enrichment in Y, Hf, Th, U, Nb, and Ta content. These indicate that two events (crystallization environment) have played an important role in the formation of this zircon and largely reflect differences in whole-rock trace element contents between the successive generations of this zircon. The first event is believed to be of magmatic origin giving rise to normal composition of magmatic zircon. The second event shows an intense successive process of metasomatic activity during the formation of the Abu Rusheid radioactive gneiss. Electron microprobe analysis indicates that oscillatory zoned zircon shows poor content of Y, Hf, Th, U, Nb, Ta, and rare earth elements (REE) in the rim and core, while overgrowths of zircon are slightly enriched by these elements. Also, these analyses indicate that the Abu Rusheid psammitic gneiss has been significantly enriched by the thorite mineral (Th content up to 54.72% ThO₂) and columbite-bearing minerals (Nb content up to 64.74% Nb₂O₅, Ta content up to 9.32% Ta2O₅). The poor content of REE in overgrowths of zircon indicates mobilization of REE during the metamorphism processes of gneiss.  相似文献   

Individual tree crown segmentation in tropical peat swamp forest using airborne hyperspectral data     

Sitinor Atikah Nordin  Hamdan Omar 《国际地球制图》2013,28(11):1218-1236

Abstract

Individual tree crown segmentation is important step for deriving various information for fine-scale analysis of ecological process. However, only several studies have applied tree crown segmentation in tropical forest ecosystems, especially in mixed peat swamp forests. In this study, hyperspectral data were used to detect changes in the biochemical and biophysical characteristics, which are important factors for tree crown segmentation. Principal Component Analysis method was performed to investigate its influence on crown segmentation. Visually Selected PCs, 160 PCs and 160 Spectral Bands image were used and two segmentation techniques; Watershed Transformation and Region Growing segmentation were applied on those images. The highest accuracy was achieved for the crown segmentation is using Region Growing segmentation, based on 1:1 measurement, D value and RMSE value. The results obtained from 160 PCs image using region growing algorithm shows better accuracy with D value of 0.2 (80% accuracy, 20% error) and RMSE of 9.9 m².  相似文献   

Kinetics of Methyldiethanolamine Mineralization by Using UV/H2O2 Process     

Sabtanti Harimurti  Anisa Ur Rahmah  Abdul Aziz Omar  Murugesan Thanapalan 《洁净——土壤、空气、水》2013,41(12):1165-1174

The UV/H₂O₂ is one of the popular techniques in the advanced oxidation processes (AOPs) and has been applied in the wastewater treatment during recent two decades. UV exposure on the H₂O₂ generate highly reactive hydroxyl radicals (OH^?), which are used to degrade organic contaminants through oxidation processes in wastewater. This present study involves the estimation of hydroxyl radical rate constants of methyldiethanolamine (MDEA) mineralization at different temperatures by using UV/H₂O₂ in aqueous solution. Laboratory experiments have been conducted and the profile of MDEA mineralization has been established. The hydroxyl radical rate constants and the activation energy of mineralization process have been calculated. The estimated hydroxyl rate constants and the activation energy are in good agreement with those reported in the literature.  相似文献   

Envelope instability in giant planet formation     

Omar G. Benvenuto  Adrián Brunini  Andrea Fortier 《Icarus》2007,191(1):394-396

We compute the growth of isolated gaseous giant planets for several values of the density of the protoplanetary disk, several distances from the central star and two values for the (fixed) radii of accreted planetesimals. Calculations were performed in the frame of the core instability mechanism and the solids accretion rate adopted is that corresponding to the oligarchic growth regime. We find that for massive disks and/or for protoplanets far from the star and/or for large planetesimals, the planetary growth occurs smoothly. However, notably, there are some cases for which we find an envelope instability in which the planet exchanges gas with the surrounding protoplanetary nebula. The timescale of this instability shows that it is associated with the process of planetesimals accretion. The presence of this instability makes it more difficult the formation of gaseous giant planets.  相似文献   

Discussion of ‘Soil creep effects on ground lateral deformation and pore water pressure under embankments’     

Gustav Grimstad  Mohammad Ali Haji Ashrafi  Samson Abate Degago  Arnfinn Emdal  Steinar Nordal 《Geomechanics and Geoengineering》2016,11(1):86-93

Settlement analysis of field cases is normally studied based on parameters interpreted from laboratory samples influenced by varying degrees of sample disturbance. Such disturbance is more pronounced in natural soft clays and could significantly affect the engineering properties of the soil, e.g. the over consolidation ratio (OCR) and compressibility index (C_c). Hence, it is vital to understand the role of sample quality in relation to soil characterisation for long-term settlement analyses. In this work, this is numerically illustrated by use of a simple creep model along with realistic parameter selection. This work takes its starting point on critical discussion of the work presented by Fatahi et al. (2013) and uses the opportunity to further clarify some important aspects of settlement/creep analyses in light of sample quality and parameter interpretation valid for the corresponding constitutive model.  相似文献   

Anisotropy of self-diffusion in forsterite grain boundaries derived from molecular dynamics simulations     

Johannes Wagner  Omar Adjaoud  Katharina Marquardt  Sandro Jahn 《Contributions to Mineralogy and Petrology》2016,171(12):98

  相似文献   

A comparison between karst development in two main zones of Iran: case study—Keyno anticline (Zagros Range) and Shotori anticline (Central Iran)     

Manouchehr Chitsazan  Hossein Karimi Vardanjani  Haji Karimi  Abbas Charchi 《Arabian Journal of Geosciences》2015,8(12):10833-10844

  相似文献   

An Overview of the Use of Rockbolts as Support Tools in Mining Operations     

Peter  Kolapo  Moshood  Onifade  Akinseye  Praise Oluwatomisin  Martha  Amwaama  Khadija  Said Omar  Abdulsalam  Jibril  Ismail  Lawal Abiodun  Emman  Aladejare Adeyemi 《Geotechnical and Geological Engineering》2022,40(4):1637-1661

Geotechnical and Geological Engineering - Historically, the idea of designing and installing rockbolts in rockmasses can be traced back to the construction of the Snowy Mountain hydroelectric...  相似文献   

Lahars risk at the Tacaná Volcano Complex (México–Guatemala) from numerical simulations and physical vulnerability analysis     

Cruz-Vázquez  Omar  Alatorre-Ibargüengoitia  Miguel A. 《Natural Hazards》2022,110(1):741-763

Natural Hazards - The Nile River provides Egypt with most of its water resources. Medium- and long-rage forecasts of Nile flows at Aswan have been recognized as of significant importance to allow...  相似文献