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Nenad Grujovic Dejan Divac Miroslav Zivkovic Radovan Slavkovic Nikola Milivojevic Vladimir Milivojevic Dragan Rakic 《Acta Geotechnica》2013,8(3):265-278
The mechanical behaviour of a rock mass is described in this paper using a method that combines experimental and numerical techniques. A new discontinuity (joint) constitutive model is proposed based on the non-associative yield law. Constitutive relationships for an anisotropic rock mass are determined by introducing an interaction between sets of discontinuities and the monolith in which they occur. The model is based on the concept that deformation of the monolith and its associated sets of discontinuities are coupled. An experimental investigation of the concrete foundations of the Bogovina Dam on the Crni Timok River in Serbia has been used to verify the presented numerical model. The tests included discontinuity and monolith sample investigations and large-scale field tests. 相似文献
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Dejan Pavlic 《Urban geography》2013,34(3):378-401
Spatially referenced quantitative research that attempts systematically to assess inner suburban decline in Canadian metropolitan areas is almost completely missing from the literature. This paper aims to fill this gap and examine whether inner suburban decline is occurring in Canada. Aggregated census tract level data are used to assess all zones for decline based on relative prosperity changes in median household income, average dwelling values, and average gross rent. The results indicate that inner suburbs in Canadian cities experienced a decline in median household income, average dwelling value, and prosperity factors between 1986 and 2006. While a few possible explanations and policy approaches are offered, more research is necessary to explore the implications of these trends. 相似文献
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Seismic stratigraphy based chronostratigraphic (SSBC) analysis of the Serbian Banat region allows the delineation of the spatial and stratigraphic relationships of the generally regressive and shallowing upward Neogene depositional fill of a tectonically unstable central portion of the Pannonian Basin. When geometrically restored in time and space, the sediment dispersal directions, sediment source directions, types of sedimentation breaks and the tectonic events influencing basin evolution can be delineated. For such an analysis the time-transgressive lithostratigraphic units used in the neighbouring Hungarian part of the Pannonian Basin are conveniently introduced based upon their characteristic seismic facies and constrained borehole log records as mappable seismic stratigraphic sequence units, termed “seismic operational sequences”. The respective Neogene stage and operational sequence equivalents (Hungarian lithostratigraphic units or formations) are the Middle Miocene (Badenian, Sarmatian), Upper Miocene-Lower Pliocene (Pannonian-Endrod and Szolnok Formations; Pontian- Algyo and Ujfalu Formations and Lower Pliocene- Zagyva Formation) and Upper Pliocene-Quaternary (Nagyalfold Formation). SSBC analysis greatly assists in the geological constraint or “geovalidation” of interpreted seismic stratigraphic relationships and provides potentially critical insight into stratigraphic and structural problems of non-unique interpretations. In the specific case, using such an approach on previously unpublished regional seismic lines, SSBC analysis reveals that the Banat region has undergone structural inversion. This may be related to changes in local stress directions along strike slip faults, which initiated in earliest Late Miocene (Endrod Formation), culminating in the reverse tilting and incipient shortening of the western graben. Therefore during the time interval that the Badenian through Endrod sediments were deposited in the graben, autocyclic progradation initiated from the Kikinda Szeged High in the East followed by Szolnok, Algyo, Ujfalu and younger units prograding from the West as the central high uplifted relative to the graben. Such tectonic inversion has substantial hydrocarbon potential implications for exploration in the region. 相似文献
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Cüneyt Akal Cahit Helvacı Dejan Prelević Paul van den Bogaard 《International Journal of Earth Sciences》2013,102(2):435-453
Volcanic rocks of the Afyon province (eastern part of western Anatolia) make up a multistage potassic and ultrapotassic alkaline series dated from 14 to 12 Ma. The early-stage Si-oversaturated volcanic rocks around the Afyon city and further southward are trachyandesitic volcanic activity (14.23 ± 0.09 Ma). Late-stage Si-undersaturated volcanism in the southernmost part of the Afyon volcanic province took place in three episodes inferred from their stratigraphic relationships and ages. Melilite–leucitites (11.50 ± 0.03 Ma), spotted trachyandesites, tephryphonolites and lamproites (11.91 ± 0.13 Ma) formed in the first episode; trachyandesites in the second episode and finally phonotephrites, phonolite, basaltic trachyandesites and nosean-bearing trachyandesites during the last episode. The parameter Q [normative q-(ne + lc + kls + ol)] of western Anatolia volcanism clearly decreased southward with time becoming zero in the time interval 10–15 Ma. The magmatism experienced a sudden change in the extent of Si saturation after 14 Ma, during late-stage volcanic activity of Afyon volcanic province at around 12 Ma, though there was some coexistence of Si-oversaturated and Si-undersaturated magmas during the whole life of Afyon volcanic province. 相似文献
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Aaron Zimmerman Holly J. Stein Judith L. Hannah Dejan Koželj Kamen Bogdanov Tudor Berza 《Mineralium Deposita》2008,43(1):1-21
The Apuseni–Banat–Timok–Srednogorie magmatic–metallogenic belt (ABTS belt), forms a substantial metallogenic province in the
Balkan-South Carpathian system in southeastern Europe. The belt hosts porphyry, skarn, and epithermal deposits mined since
pre-Roman times. Generally, the deposits, prospects, and occurrences within the belt are linked to magmatic centers of calc-alkaline
affinity. Fifty-one rhenium-osmium (Re–Os) ages and Re concentration data for molybdenites define systematic geochronologic
trends and constrain the geochemical-metallogenic evolution of the belt in space and time. From these data and additional
existing geologic-geochemical data, a general tectonic history for the belt is proposed. Mineralization ages in Apuseni-Banat,
Timok, and Panagyurishte (the central district of the larger E–W Srednogorie Zone) range from 72–83, 81–88, and 87–92 Ma,
respectively, and clearly document increasing age from the northwestern districts to the southeastern districts. Further,
Re–Os ages suggest rapidly migrating pulses of Late Cretaceous magmatic–hydrothermal activity with construction of deposits
in ~1 m.y., districts in ~10 m.y., and the entire 1,500 km belt in ~20 m.y. Ages in both Timok and Panagyurishte show systematic
younging, while deposit ages in Banat and Apuseni are less systematic reflecting a restricted evolution of the tectonic system.
Systematic differences are also observed for molybdenite Re concentrations on the belt scale. Re concentrations generally
range from hundreds to thousands of parts per million, typical of subduction-related Cu–Au–Mo–(PGE) porphyry systems associated
with the generation of juvenile crust. The geochronologic and geochemical trends are compatible with proposed steepening of
subducting oceanic slab and relaxation of upper continental plate compression. Resulting influx of sub-continental mantle
lithosphere (SCML) and asthenosphere provide a fertile metal source and heat, while the subducting slab contributes connate
and mineral dehydration fluids, which facilitate partial melting and metal leaching of SCML and asthenosphere. Cu–Au–Mo–(PGE)
porphyry deposits may develop where melts are trapped at shallow crustal levels, often with associated volcanism and epithermal-style
deposits (South Banat, Timok, and Panagyurishte). Mo–Fe–Pb–Zn skarn deposits may develop where felsic melts are trapped adjacent
to Mesozoic limestones at moderate crustal levels (North Banat and Apuseni). Systematic spatial variations in deposit style,
commodity enrichment, Re–Os ages, and Re concentrations support specific tectonic processes that led to ore formation. In
a post-collisional setting, subduction of Vardar oceanic crust may have stalled, causing slab steepening and rollback. The
slab rollback relaxes compression, facilitating and enhancing orogenic collapse of previously thickened Balkan-South Carpathian
crust. The progression of coupled rollback-orogenic collapse is evidenced by the width of Late Cretaceous extensional basins
and northward younging of Re–Os ages, from Panagyurishte (~60 km; 92–87 Ma) to Timok (~20 km; 88–81 Ma) to Apuseni-Banat (~5 km;
83–72 Ma). Generation of a well-endowed mineral belt, such as the ABTS, requires a temporally and spatially restricted window
of magmatic–hydrothermal activity. This window is quickly opened as upper plate compression relaxes, thereby inducing melt
generation and ingress of melt to higher crustal levels. The window is just as quickly closed as upper plate compression is
reinstated. The transient tectonic state responsible for economic mineralization in the ABTS belt may be a paleo-analogue
to transient intervals in the present subduction tectonics of SE Asia where much mineral wealth has been created in the last
few million years. 相似文献
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Ju??KocijanEmail authorView author&#;s OrcID profile Dejan?Gradi?ar Martin?Stepan?i? Marija?Zlata?Bo?nar Bo?tjan?Gra?i? Primo??Mlakar 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(6):1759-1770
This paper highlights the problem of step-length selection for the one-step-ahead prediction of ozone called the data time interval. This is done using a case study-based comparison of two approaches for predicting the maximum daily values of tropospheric ozone. The first approach is the 1-day-ahead prediction and the second is the prediction of the maximum values based on a multi-step-ahead iteration of 1-h predictions. Gaussian process modelling is utilised for this comparison. In particular, evolving Gaussian-process models are used that update on-line with the incoming measurement data. These sorts of models have been successfully used in the past for the prediction of ozone pollution. This paper contributes an assessment of the way that the maximum ozone values are predicted. A comparison of the daily maximum ozone values forecasted by a model based on 1-day-ahead predictions with those obtained by iterated 1-h-ahead predictions of the ozone with predictions at predetermined hours of the day is given. The forecast results are in favour of the on-line model based on hourly predictions when approaching closer to the real maximum values of ozone, and in favour of the daily predictions when they are made on a daily basis. 相似文献
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Weather modification activities are performed predominantly by cloud seeding. Some operational projects have been performed for more than half a century and cover planetary scales. These activities lead to a large amount of deposited chemical materials (seeding agents) at the ground level during precipitation. These deposits depend on the amount of the seeding agent. In the future, increased amounts of seeding agent deposits could be a serious problem due to various negative effects on the human environment. Therefore, the main intent of this paper is to determine trends for the seeding agent amount over certain areas of Serbia. Four areas covered by the Hail Suppression Project in Serbia are considered: the target area in central Serbia and areas in western and central Serbia, which are well-known hailfall regions. The annual seeding agent amounts show a slow decreasing trend because fewer seedings were performed during the last decade of the last century, which was due to economic reasons. In contrast, the annual seeding agent amounts of the other analysed areas indicate an increasing trend induced by the transfer of rockets to these hailfall regions. The main difference among small areas is the mean agent amount and its maximum time position as a consequence of the high spatial and time variability of the hail. However, a sharp decreasing trend that is influenced by the implementation of new methodologies, seeding agents and delivery tools may also be a factor in the implementation of cloud seeding projects. The given method is not only strictly applicable locally and may be applied to any other cloud seeding scenario and seeding area. Dominantly increasing trends in the agent amount indicate that the importance of weather modifications in the future will be greater than ever and will have both positive and negative effects. 相似文献
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Dejan Urošević 《Astrophysics and Space Science》2003,283(1):75-86
This paper represents the updated empirical Galactic andextragalactic Σ-D relations (relations between the surface brightness Σ and the diameter D) for supernova remnants(SNRs), with checking the connection of the main Galactic radio loops (Loop I, II, III and IV) with
these relations. We present results which suggest, once again, that the radio loops may have an SNR origin. The updated relations
for old SNRs have been measured to have slopes, β ≈ 2 in log-log space. The best Σ-D relations for M31 and M33 galaxies were derived and these relations are shown to be flatter (β ≲2) than those for Galactic
SNRs alone. A Σ-D relation with168 reliable calibrators (both Galactic and extragalactic) is derived.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献