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2799 items

  • Rietveld crystal structure refinement of a natural rhombohedral grossular-andradite garnet from Serbia

    Pavle Tančić, Aleksandar Kremenović (2022)
    Four macroscopically visible B–E (rim) zones, within a large natural ferric grossular garnet of Grs58–64Adr36–42 Sps2 composition, are described by means of Rietveld refinements of the crystal structures in a series of six space groups, followed by com parative analysis of the R-values, site occupancy factors, and bond lengths and angles. The garnet crystallized in the rhombohedral R63c space group. Various polyhedral distortions and structural or derdis or dervariations between the zones studied are also described and discussed. The ...
    Geology

  • Towards Automatic Definition Extraction for Serbian

    Ranka Stanković, Cvetana Krstev, Rada Stijović, Mirjana Gočanin, Mihailo Škorić (2021)
    U radu su prikazani preliminarni rezultati automatske ekstrakcije kandidata za definicije rečnika iz nestrukturiranih tekstova na srpskom jeziku u cilju ubrzanja razvoja rečnika. Definicije u rečniku Srpske akademije nauka i umetnosti (SANU) korišćene su za modelovanje različitih tipova definicija (opisnih, gramatičkih, referentnih i sinonimskih) koje imaju različite sintaksičke i leksičke karakteristike. Korpus istraživanja sastoji se od 61.213 definicija imenica, koje su analizirane korišćenjem morfoloških e-rečnika i lokalnih gramatika implementiranih kao pretvarači konačnih stanja u paketu za obradu korpusa otvorenog ...
    ... definitions from unstructured text by means of local grammars presented in the previous section, we created a corpus of 25 primary and secondary school textbook covering the following domains: biology, history, logic, music, computer science, physics and design and technology (technological education). ...
    ... evidenced by the statistics of definitions grouped by type. These models were used to retrieve noun definitions from a 1.4-million-word corpus containing 25 primary and secondary school textbooks covering various domains. The obtained results were thoroughly analysed, and guidelines were offered for ...
    ... from unstructured texts. To that end, we prepared a corpus consisting of primary and secondary school textbooks to which we applied the models developed for the SASA dictionary. While the rule-based approach is intuitive and has high precision, it suffers from the low recall issue. In order to overcome ...

  • Synthesis and characterization of high-pressure and high-temperature sphene (CaTiSiO5)

    Jelena Pantić, Vladimir Urbanovich, Vesna Poharc-Logar, Bojan Jokić, Marija Stojmenović, Aleksandar Kremenović, Branko Matović (2014)
    Sphene (CaTiSiO5), a calcium titanosilicate ceramic has been prepared from a powder mixture of CaCO3, TiO2 and SiO2 using vibro-milling for homogenization and activation of precursors. During the highpressure and high-temperature synthesis (HPS) process at 4 GPa and 1,200 °C, sphene undergoes into phase transition, from room-temperature phase P21/a to high-temperature phase A2/a. Evidence of that structural phase transition is given in this paper using infrared, Raman spectroscopy and X-ray powder diffraction. Rietveld refinement was employed to get the ...
    Sphene, Phase transition, Raman spectroscopy, X-ray diffraction, SEM, IR

  • Waste rocks and medieval slag as sources of environmental pollution in the area of the Pb-Zn Mine Rudnik (Serbia)

    Alena Zdravković, Vladica Cvetković, Kristina Šarić, Aleksandar Pačevski, Aleksandra Rosić, Suzana Erić (2020)
    The new geochemical and mineralogical data of soil and water from the Pb-Zn Rudnik Mine area (central Serbia) reveal that the areas close to the mining sites and those located remotely from them are both affected by significant pollution by toxic elements, especially As, Pb, Ni and Cr. We, therefore, propose that two main sources are generally responsible for the current state of pollution in this area. The first is the material from waste rock dumps (WRDs) in which ...
    распадање сулфида, микроелементи, пиротин, загађење земљишта, Рударска активност, распадање шљаке

  • Distribution of Uranium and Rare Elements in Radioactive Phosphate-Bearing Anomalies in Southeast Mongolia

    Boris Vakanjac, Neil Rutherford, Vesna Ristić Vakanjac, Tanita Đumić, Suzana Đorđević Milošević (2020)
    Soviet and Mongolian geologists initiated geological exploration of Mongolia for minerals after World War II (1945). These activities lasted until the breakup of the USSR in 1991. As part of this exploration systematic uranium and rare element exploration was undertaken across Mongolia. New exploration resumed in Mongolia at the beginning of the 21st century for a range of ore and mineral deposit styles including uranium, coal, base and precious metals and Fe-ore. This was generally undertaken by Western-based companies. This ...
    uran, radioaktivnost, kreda, retki elementi, fosfati, anomalije, Dornogobi

  • Determination of Mechanical Properties of Altered Dacite by Laboratory Methods

    Veljko Rupar, Vladimir Čebašek, Vladimir Milisavljević, Dejan Stevanović, Nikola Živanović (2021)
    This paper presents a methodology for determining the uniaxial and triaxial compressive strength of heterogeneous material composed of dacite (D) and altered dacite (AD). A zone of gradual transition from altered dacite to dacite was observed in the rock mass. The mechanical properties of the rock material in that zone were determined by laboratory tests of composite samples that consisted of rock material discs. However, the functional dependence on the strength parameter alteration of the rock material (UCS, intact ...
    Geology, Geotechnical Engineering, Engineering Geology
    ... the diameter of the specimen for UCS testing was 54 mm, whereas the height and diameter ratio of the specimen ranged from 2–2.5:1. This research, in addition to the UCS tests, also conducted triaxial tests. Therefore, specimens with a diameter of 54 mm with a ratio of height and diameter of 2:1 were formed ...
    ... (ASTM) with a height to diameter ratio of 2–2.5:1, and the duration of the experiment should be 2–15 min. ISRM [18] suggested that the diameter of the specimen should not be less than 54 mm (ISRM), while the ratio of height and diameter should be 2.5–3:1, with the duration of the experiment from 5–10 min ...
    ... base mass and phenocrysts of quartz, plagioclase, sanidine, biotite, and hornblende. The accessory ingredients are apatite, zircon, and metallic minerals, while the secondary minerals are calcite, sericite, chlorite, and iron oxides/hydroxides. Mineralogical-petrographic analysis of D and AD samples ...

  • Characterization of bituminite in Kimmeridge Clay by confocal laser scanning and atomic force microscopy

    Paul C. Hackley, Jolanta Kus, João Graciano Mendonça Filho, Andrew D. Czaja, Angeles G. Borrego, Dragana Životić, Brett J. Valentine, Javin J. Hatcheries (2022)
    This work investigates bituminite (amorphous sedimentary organic matter) in Upper Jurassic Kimmeridge Clay source rock via confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). These petrographic tools were used to provide better understanding of the nature of bituminite, which has been historically difficult to identify and differentiate from similar organic matter types in source rocks. As part of an International Committee for Coal and Organic Petrology (ICCP) working group, an immature (0.42% vitrinite reflectance), organic-rich (44.1 wt% ...
    Битуминит, Kонфокална ласерска скенирајућа микроскопија, Mикроскопија атомских сила, Органска петрологија, Термичка зрелост

  • Correlation Between Dynamic CBR and Compaction and Bearing Capacity of Pavement Foundation Layers

    Milan Bogdanović, Snežana Bogdanović, Dragoslav Rakić, Irena Basarić Ikodinović (2024)
    This paper presents a dynamic California Bearing Ratio (CBRd) device that can be used on a prepared pavement foundation layer to obtain a certain parameter of the tested material in the laboratory and in situ in a direct and fast way. For the selected natural material (gravel), it is shown that the laboratory CBRd can be used to estimate the compaction and bearing capacity, because it correlates well with the parameters of the standard and modifed Proctor compaction tests. ...
    korelacija parametara, donji slojevi saobraćajnica, laboratorijska i terenska ispitivanja, dinamički kalifornijski indeks nosivosti CBRd
    ... parameter, E,, -E,,, and Eyq. Conclusion The primary objective of this study was to establish reliable correlations between the selected param- eters of the gravel material so as to describe the compaction and bearing capacity of the substrate, and de- 32 velop a method of using and defining the values ...
    ... results of California Bearing Ratio (CBR) research on stat- ic (classic) and dynamic methods with ash samples in the unsaturated state has been presented [5], and the correlations of the parameters of the laboratory dynamic California Bearing Ratio (CBR, ) with the com- paction properties of sandy ...
    ... modulus: a) E,, and b) Ey,. The correlation coefficient is typically defined as a number, and provides an idea of how closely one variable is related to another [17]. The ratio of variables is reflected by the values of the determination co- efficient. The high coefficient of determination of Eqs. (3) ...

  • Selection of Artificial Lift Methods: A Brief Review and New Model Based on Fuzzy Logic

    Miroslav Crnogorac, Miloš Tanasijević, Dušan Danilović, Vesna Karović Maričić, Branko Leković (2020)
    Artificial lift methods have applications in oil wells where oil production is no longer possible due to natural reservoir energy, so this necessary energy is added by introducing lift methods. In order to achieve optimum production, the selection of an artificial lift method is very important. This paper uses fuzzy logic as a mathematical and conceptual model for selection of the optimal artificial lift method. The outcome or IF-THEN rules, as the central part of the model, is based ...
    mehaničke metode, proizvodnja nafte, fazi logika, donošenje odluka, optimizacija
    ... covered the topic of a gas-lift; Bill Capps described ESP; and Phil Wilson explained the HP [6]. As the main factors geographical and environmental restrictions were taken, the secondary factors were reservoir pressure, productivity index, the characteristics of reservoir fluids, and well productivity ...
    ... gas oil ratio—GOR, (C4) paraffin, and (C5) water cut. Figure 1 shows the conceptual model of an expert system for optimized selection of an artificial lift method evaluation on the base of fuzzy interferences of the input data. Energies 2020, 13, 1758 5 of 15 Energies 2020, 13, x 5 of 15 ...
    ... pressure at the bottom of the well, the deviation of the well, and characteristics of the reservoir. The second step further reduces the choice, based on secondary technical limitations, such as temperature limitations, operator training, availability of the main source of energy, fluid, surface ...

  • Mitigating hydrate formation in onshore gas wells: A case study on optimization techniques and prevention

    Milica Ješić, Bojan Martinović, Stefan Stančić, Miroslav Crnogorac, Dušan Danilović (2023)
    Gas wells, particularly those situated onshore, play a vital role in the global energy sector by supplying a significant portion of natural gas. However, operational challenges, notably gas hydrate formation, pose substantial issues, leading to complications such as flowline blockages and unexpected well shutdowns. Gas hydrates, crystalline structures resembling ice, ...
    Gas Well, Gas Hydrate Formation, Well Modeling, Well Performance Optimization, Choke Position Adjustments, Methanol Injection

  • Aлтерације перидотита контролисане карактером флуида на примеру харцбургита Рудника - Серпентинизација или талкизација?

    Стефан Петровић, Наталија Батоћанин (2020)
    У раду су приказани резултати испитивања серпентинисаних харцбургита Брђана (43°58'45.1" СГШ, 20°25'12.6" ИГД) и талкизираних харцбургита откривених у интервалу 429-559.8 m у истражној бушотини 330А/18 (44°07'33.2" СГШ, 20°30'28.5" ИГД) на Руднику. Узорци оба локалитета показују карактеристике резидуалних харцбургита из омотача, односно тектонита; лепидобластичне, бластозрнасте, или порфирокластичне структуре и масивне текстуре. Серпентинисани харцбургити и серпентинити Брђана су изграђени од серпентина, ретких реликата оливина и ортопироксена, акцесорног спинела, и веома ретког секундарног магнезита и магнетита. Најдоминантнији састојак (местимично гради и преко ...
    Рудник, Брђани, харцбургити, серпентинити, талк
    ... low-temperature lizardite (FAUST & FAHEY, 1962; MOODY, 1976). Low contents of secondary magnetite and magnesite (~ 5%) suggests on small percentage of fayalite component in primary olivine and on low CO2 mole fraction (<0.2) of the fluid (TROMMSDORF & EVANS, 1977). Serpentinization process is autom ...
    ... (hornfels and skarn), and acid and ultrabasic igneous rocks. Low-grade metamorphosed coarse-grained rocks include sandstones and conglomerates of preserved primary protolith textures. The alternation of skarn and hornfelses represents the most abundant lithology. It is cut by apophyses and a quartzlatite ...
    ... i.e. tectonites and lepidoblastic, blastogranular or porphyroclastic texture and massive structure. Serpentinized harzburgites and serpentinites from Brdjani consist of serpentine, scarce relics from olivine and orthopyroxene, accessory spinel and very seldom secondary magnesite and magnetite. The ...

  • The final closure of the Vardar Ocean: paleomagnetic, AMS and structural results

    Emö Márton, Marinko Toljić, Vesna Lesić, Vesna Cvetkov (2020)
    ... westernand eastern sides, respectively and from the upper Cretaceous flysch deposited in the Sava zone. In the areas W and E of the Sava zone, respectively, the primary remanences of the igneous rockspoint to post-Oligocene CW rotation of about 30°. The sediments carry secondary magnetizations,imprinted during ...
    ... stress field outside of the zone. Acknowledgement. This work was financially supported by the National Development andInnovation Office of Hungary, project K 128625 and by the Ministry of Education and Science of theRepublic of Serbia, project 176015. Powered by TCPDF (www.tcpdf.org) http://www.tcpdf ...
    ... closure of the Vardar Ocean: paleomagnetic, AMS andstructural results Emö Márton, Marinko Toljić, Vesna Lesić, and Vesna Cvetkov Mining and Geological Survey of Hungary, Paleomagnetic Laboratory, Budapest, Hungary (paleo@mbfsz.gov.hu) The Vardar zone divides units of African affinity from units of the ...

  • Agates of the Lece Volcanic Complex (Serbia): Mineralogical and Geochemical Characteristics

    Zoran Miladinović, Vladimir Simić, Nenad Nikolić, Nataša Jović Orsini, Milena Rosić (2024)
    Agate veins and nodules occur in the Lece Volcanic Complex (Oligocene-Miocene) situated in the south of Serbia and occupying an area of 700 km2. This volcanic complex is composed predominantly of andesites, with sporadic occurrences of andesite-basalts, dacites and latites, and features agate formations that have been very little investigated. This study focuses on five selected agate occurrences within the Lece Volcanic Complex, employing optical microscopy, scanning electron microscopy (SEM), X-ray powder diffraction analysis, inductively coupled plasma mass spectrometry ...
    Lecki vulkanski kompleks, andeyit, kalcedon, kvarc, opal-CT, mikrostruktura, organska materija

  • Lower Berriasian ammonites from Dedina (Golubac Mountains, eastern Serbia) and their biostratigraphic implication

    Zdenek Vasícek , Dragoman Rabrenović, Petr Skupien, Barbara Radulović (2023)
    Ammonites, Taxonomy, Lower Berriasian, Getic, Northern Tethys, Serbia
    ... third shorter rib wedged between the primary ribs. With the exception of the ter- minal part, there are distinct lateral tubercles in the middle of the height of the whorl. Sometimes two or three clamped secondary ribs protrude from them. They are concave and proverse in the ventral region. The ...
    ... in two parts of the whorl. The initial part of the last whorl is covered by thin and dense ribs. They start as primary ribs on the line of coiling: without tubercles. They are distinctly proverse. Around the lower third of the height of the whorl, they bend with a knee shape and bifurcate in ...
    ... the umbilicus and approximately 33 secondary plus intacalar ribs. The specimen D5 has measurements, at Dmax, of D = 26.5 mm, H = 11.5 (0.43), and U = 7.8 (0.29). At this D by the umbilicus, there are approximately 18 ribs per half-whorl and 42 ribs on the ventral side. Remarks and relations. Adult ...

  • Late and post-collisional tectonic evolution of the Adria-Europe suture in the Vardar Zone

    Emő Márton, Marinko Toljić, Vesna Cvetkov (2022)
    The Vardar Zone is a product of the Triassic-Jurassic opening of the Neotethys, Jurassic obduction, Late Cretaceous/Paleogene consumption of the oceanic crust and continental collision. During the last process, the Eastern Vardar Zone was thrust over the Central and eventually both onto the Western Vardar Zone. The present paleomagnetic and structural study provided new results from the first two zones in the Belgrade area. The younger set of data, together with published ones from the third zone, provide firm ...
    Adria–Europe suture, Vardar Zone, Paleomagnetism, Thrusting, Vertical axis rotation

  • Flyrock induced by blasting in surface mining

    Milanka Negovanović, Lazar Kričak, Snežana Ignjatović, Stefan Milanović, Jovan Marković, Nikola Simić, Rade Šarac (2022)
    Miniranje predstavlja i dalje najefikasniji i najjeftiniji način eksploatacije velikih količina čvrstih mineralnih sirovina na površinskim kopovima. Energija eksplozije se koristi za fragmentaciju čvrste stenske mase do zahtevane granulacije. Pored pozitivnih efekata miniranja, postoje i određeni neželjeni efekti svakog procesa miniranja koji se mogu javiti, a to su: potresi tla, razletanje komada stene, vazdušni udari, otrovni i zagušljivi gasovi i prašina. Razletanje komada stene je nekontrolisano izbacivanje fragmenata odminirane stenske mase i predstavlja jedan od glavnih izvora materijalne štete ...
    razletanje, bušenje, miniranje, površinska eksploatacija, bezbednost, nesreća

  • Laboratory testing of fly ash

    Miloš Šešlija, Aleksandra Rosić, Nebojša Radović, Milinko Vasić, Mitar Đogo, Milovan Jotić (2016)
    Fly ash is one of the most common waste materials created by burning of coal. It is composed of smaller particles, consisting mainly of aluminosilicate glass, mullite and quartz, which are collected by electrostatic separators (filter) of gaseous products arising from the combustion of coal. This paper presents the pozzolanic properties, mechanical properties, chemical and mineral composition of fly ash obtained in the combustion process in a power plant Nikola Tesla A (PPNT A) with the addition of a ...
    chemical composition, fly ash, mechanical properties, mineral properties, pozzolanic properties, X-ray diffraction
    ... in the content of the same binder amount in percentages, and in the addition of cement as the binder the deviation results are greater than those of the lime. Table 16 The modulus of elasticity after 112 days in the wet chamber Sample No. Modulus of elasticity in compression Ec / kPa Sample ...
    ... in the content of the same binder amount in percentages, and in the addition of cement as the binder the deviation results are very small, even negligible. Table 15 The modulus of elasticity after 28 days in the wet chamber Sample No. Modulus of elasticity in compression Ec / kPa Sample ...
    ... for wastewater treatment sludge from a primary copper smelter. // Journal of the Serbian Chemical Society. 78, (2013), pp. 725-739. DOI: 10.2298/JSC120716125I [4] SRPS B.H8.359. Methods of analysis of coal and coke - Determination of chemical composition of fuel ash - General requirements. // Belgrade ...

  • Early–Middle Jurassic brachiopods from Ponor Mountain, Western Balkan Mountains, Bulgaria; taxonomy, biostratigraphy and occurrence in the context of the early Toarcian Oceanic Anoxic Event

    Barbara V. Radulović, Lubomir S. Metodiev, Neda Motchurova-Dekova, Platon Tchoumatchenco (2023)
    Brachiopods, taxonomy, biostratigraphy, early Toarcian Anoxic Event, Bulgaria

  • Multihazard Exposure Assessment on the Valjevo City Road Network

    Miloš Marjanović, Biljana Abolmasov, Svetozar Milenković, Uroš Đurić, Jelka Krušić, Mileva Samardžić Petrović (2019)
    Prirodni hazardi, izloženost, klizišta, poplave, bujice, GIS, R

  • Investigating distant effects of the Moesian promontory: Brittle tectonics along the western boundary of the Getic unit (East Serbia)

    Ana Mladenović, Milorad D. Antić, Branislav Trivić, Vladica Cvetković (2019)
    In this study, we report evidence for brittle deformation in a part of the Carpatho–Balkan orogen, which is explained in terms of effects of the rigid Moesian promontory of the European plate on fault kinematics in East Serbia. We focus on the westernmost part of the Getic Unit of the East Serbian Carpatho–Balkanides, i.e. the Gornjak–Ravanica Unit, located between two main thrusts that were repeatedly activated from Early Cretaceous to recent times. We combine a new data set on ...
    Getikum, Mezijska jedinica, Karpato-balkanski orogen, krte deformacije, Gornjačko-ravanička jedinica