Union University of Serbia

Belgrade, Serbia

Union University of Serbia

Belgrade, Serbia
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Alghwail A.D.A.,Union University of Serbia
Scour and Erosion - Proceedings of the 8th International Conference on Scour and Erosion, ICSE 2016 | Year: 2016

In this paper, a reversed cross-jet flow is developed to dissipate the energy of flow over an ogee weir spillway. The problem is handled analytically and experimentally. Both measured and calculated data indicate a great effect on the forced hydraulic jump characteristics compared to those describing the characteristics of the free jump condition. The obtained results revealed that, the reversed flow, can speed up the transition from supercritical to subcritical flow by creating a forced perfect jump starting at the contracted section and consequently, shortening the protection length needed to counter the problem of scouring downstream of the channel, since the length of the perfect hydraulic jump was reduced by 19%, while reduction in the length of the stilling basin amounted to 79%, in comparison to the case without a dissipator. The efficiency of such energy dissipation methods can have a significant impact on the overall cost of hydraulic structures projects. © 2016 Taylor & Francis Group, London.

Mastilovic S.,Union University of Serbia
Latin American Journal of Solids and Structures | Year: 2017

Molecular dynamics simulations of the ballistic Taylor test are used to explore correlation between the largest fragment mass and the impact energy of a projectile as well as a set of selected state variables. Flat-ended, monocrystalline, nanoscale bars collide with a rigid wall with striking velocities ranging from 0.27 km/s to 60 km/s. The investigation emphasis is on two border regions of the emerging nonlinear phenomenological model identified with two transitions: the damage-fragmentation transition and the shattering transition. In between these two nonlinear regions, the maximum fragment mass is largely inversely proportional to the impact energy, and the maximum values of the pressure, temperature, and the square of the effective strain. A reverse-sigmoid phenomenological model is proposed to capture the unifying features of this nonlinear and saturable dependence. A crystallographic orientation dependence of the damage-fragmentation transition parameters is investigated. © 2017, Brazilian Association of Computational Mechanics. All rights reserved.

Babic D.,Union University of Serbia
2012 20th Telecommunications Forum, TELFOR 2012 - Proceedings | Year: 2012

This paper introduces a generalized design method for polynomial-based interpolation filters and Farrow structure. In this approach, the ideal continuous-time (CT) impulse response is truncated by using CT Kaiser window function. The obtained windowed impulse response is then approximated using the piecewise Taylor polynomial approximation. Length of the impulse response and degree of the approximating polynomial can be arbitrarily selected, and in this way the transition band width can be controlled. The stopband attenuation can be controlled by selecting the value of parameter of Kaiser window. © 2012 IEEE.

Jankovic R.,Union University of Serbia
Defence Science Journal | Year: 2011

Swarming is a tactical approach considered in modern armies combat activities conceptualisation. More intensive research of military application of swarming began after 2000, mostly in the areas of unmanned air, underwater, and ground vehicles, as well as in air force, navy and some special ground force units. In spite of relative inconveniences of contemporary main battle tanks to act as swarmers, some of initial results of the armoured mobile platforms swarming research have been presented. The motivation for the research is that adaptation of contemporary tanks for swarming could prolong their working life until the new generation comes, and could be the best investment in medium and smaller countries armies' modernisation. Brief survey of the till date research, description of the simulation model and the results of experiments simulating swarming of the battalion-sized group of armed mobile platforms, defending territory from superior adversary unit, have been considered in the paper. © 2011,DESIDOC.

Upper Hauterivian deposits in the Kurilovo area, Kamenica 1 section, NE of Niš, are described based of abundant and diverse orbitolinids. So far, the interval was assigned to the Barremian-Aptian on the geological map. Such a new age assignment results from the first detailed study carried out on the orbitolinid fauna contained in the Lower Cretaceous (upper Hauterivian) shallow-water limestones of eastern Serbia. The upper Hauterivian is documented on the basis of two key stratigraphic markers, specifically Valserina primitiva and Paleodictyoconus beckerae.In addition to these late Hauterivian index fossils, the studied section bears orbitolinids having a larger stratigraphic distribution: Cribellopsis neoelongata, Cribellopsis thieuloyi?, Montseciella glanensis, Orbitolinopsis debelmasi, Orbitolinopsis cf. debelmasi, Orbitolinopsis sp., Paleodictyoconus cuvillieri, Paleodictyoconus cf. cuvillieri, Paleodictyoconus cf. beckerae, Paleodictyoconus cf. actinostoma, Paleodictyoconus sp., Paracoskinolina? jourdanensis, Paracoskinolina cf. hispanica, Urgonina alpillensis, Valserina sp. The microfossil assemblage includes other foraminifers such as Charentia cuvillieri, Mayncina bulgarica, Nautiloculina cretacea, Pfenderina globosa, Pseudocyclammina cf. lituus, Pseudolituonella gavonensis, Ammobaculites sp., Bolivinopsis sp., abundant trocholinids, various miliolids, other foraminifers and sparse algae which will be presented separately. © 2013 Elsevier Ltd.

Golic K.,Union University of Serbia | Kosoric V.,SEEEA D.o.o. | Furundzic A.K.,University of Belgrade
Renewable and Sustainable Energy Reviews | Year: 2011

The building sector, which accounts for about 40% of total energy consumption in Europe, offers various possibilities for achieving higher energy efficiency by introducing distributed RES. As 20% of total energy consumption in this sector is used for water heating, it follows that 8% of total energy in Europe is consumed for water heating purposes, which provides great opportunities for energy savings. Solar water heating systems (SWHSs) are a suitable technology for renewable energy source (RES) exploitation to be applied in residential building refurbishment that generate both fossil fuel savings and reductions in CO2 emissions. Due to its complexity, SWHS integration requires a comprehensive approach including consideration of the functional and aesthetic, energy performance, and economic and ecological aspects from conceptual design through to design realization. This article defines a general model of SWHS integration in residential building refurbishment. The model is divided into several basic phases in order to facilitate problem-solving and to enable the individual optimization processes for variant design. The phases are systematically analyzed and a proper procedure and/or methods are established to solve them. At the very beginning of the suggested problem-solving procedure, the measures 'Building Potential', P̃B, and 'Degree of Feasibility', pB, are first introduced in order to estimate the suitability of SWHS integration. A Multi-Criteria compromise ranking method, is recommended for a comprehensive evaluation of design variants and for the selection of the optimal SWHS integration Design Variant. The proposed general model is also applied for solving a real problem - namely, the integration of SWHS through the refurbishment of residential buildings in the suburb of "Konjarnik" in Belgrade, Serbia, which is one of the many that were built in Belgrade after the Second World War. © 2010 Elsevier Ltd.

Mastilovic S.,Union University of Serbia
Continuum Mechanics and Thermodynamics | Year: 2013

An idealized brittle microscale system is subjected to dynamic uniaxial tension in the medium-to-high strain-rate range (•∈ ε [100s -1,1 × 107 s-1]) to investigate its mechanical response under constrained spatial and temporal scales. The setup of dynamic simulations is designed to ensure practically identical in-plane stress conditions on a system of continuum particles forming a two-dimensional, geometrically and structurally disordered, lattice. The rate sensitivity of size effects is observed as well as the ordering effect of kinetic energy. A simple phenomenological expression is developed to account for the tensile strength sensitivity of the small-sized brittle systems to the strain-rate and extrinsic size effects, which may serve as a guideline for formulation of constitutive relations in the MEMS design. The representative sample is defined as a square lattice size for which the tensile strength becomes rate-insensitive and an expression is proposed to model its evolution between two asymptotes corresponding to the limiting loading rates. The dynamics of damage accumulation is analyzed as a function of sample size and loading rate. © 2012 Springer-Verlag.

Mastilovic S.,Union University of Serbia
International Journal of Damage Mechanics | Year: 2011

This article illuminates some general features and provides elementary interpretations of the deformation, damage, and failure of brittle solids characterized by very low fracture energy. The dynamic response of these materials is determined to a large extent by stochastic and random factors. The investigation emphasis is on the moderate-to-extremely high rate range (10 s-1, 1 × 109 s-1), explored under practically identical in-plane stress conditions. The statistical approach is based on repeated particle dynamics simulations for different physical realizations of micromechanical disorder of a 2D brittle discrete system. The proposed strategy is computationally intensive, which necessitates simplicity of the laws governing the interparticular interaction. Based on the simulation results, an expression is proposed to model the mean tensile strength dependence on the strain rate. The linearity of the rate dependence of the stress-peak macroscopic response parameters is observed and discussed. © The Author(s), 2010.

Radivojevic M.,Union University of Serbia
Photonic Network Communications | Year: 2010

Ethernet passive optical networks (EPONs) have been considered as the one of the most promising candidates for next-generation access networks. However, the EPON architecture although cost effective is bandwidth limited and quality of service (QoS) support is still a major concern. In this paper, we propose a cost-efficient wavelength division multiplexing (WDM) EPON architecture. We present two wavelength and bandwidth allocation algorithms with full QoS support to fulfill all requirements of new application and services in a converged triple play network. We analyze and compare the presented models and algorithms in terms of delay, jitter, queue occupancy, throughput and overall system performance. We conduct detailed simulation experiments to study the performance and validate the effectiveness of the proposed architecture and algorithms. © Springer Science+Business Media, LLC 2010.

Babic D.,Union University of Serbia
Circuits, Systems, and Signal Processing | Year: 2013

An efficient implementation for finding digitally the interpolated samples is the Farrow structure. It mimics digitally a hybrid system where a continuous-time (CT) signal is reconstructed using an analog reconstruction filter having a piecewise-polynomial impulse response. The interpolated samples are obtained by sampling reconstructed signal. This paper introduces a generalized design method for polynomial-based interpolation filters and Farrow structure. The proposed method also can be used to calculate the coefficients of Selva interpolator. In this approach, the ideal CT impulse response is truncated by using CT window functions. The obtained windowed impulse response is then approximated using the piecewise Taylor polynomial approximation. Length of the impulse response and degree of the approximating polynomial can be arbitrarily selected, and in this way the transition band width can be controlled. However, if CT fixed-window functions are used, the stopband attenuation is determined by window type and remains approximately constant with increase of length and order of the impulse response. The stopband attenuation can be controlled by using CT dynamic windows such as Kaiser window. The presented windowing design method is an effective tool for calculation of the Farrow structure coefficients, with filter performance that is comparable to the frequency domain design. © 2012 Springer Science+Business Media, LLC.

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