Vol. 9 No. 2 (2019)

Open Access Original Scientific Paper

UNCONDITIONALLY POSITIVE FINITE DIFFERENCE AND STANDARD EXPLICIT FINITE DIFFERENCE SCHEMES FOR POWER FLOW EQUATION

by Branko Drljača, Svetislav Savović

Power flow equation for step-index glass optical fiber was solved using recently reported unconditionally-positive finite difference (UPFD) scheme. Solution obtained using UPFD scheme was compared with solution obtained using standard explicit finite difference (EFD) scheme. For accuracy testing both schemes were compared with analytical solution for steady state distribution of given fiber. The advantage of UPFD is reflected in stability of the scheme regardless of discretization step taken. Nevertheless EFD scheme has better concurrence with analytical solution than UPFD. This is due to the additional truncation-error terms in the approximations of the first and second derivatives with respect to θ.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-23312 Published: 30 Dec 2019

Open Access Original Scientific Paper

GENERALIZATION AND CHARTOMETRIC ANALYSIS OF THE SITNICA RIVER NETWORK SYSTEM

by Bojana Jandžiković

The basin of Sitnica river represents a good option for chartometric investigation. In modern hydrology, digital and GIS analyses play very important role today. In this research we were able to obtain the main properties of the river basin and river network with the help of digital line generalization. The results from the two kind of maps with two scales 1:25.000 and 1:50.000 showed differences in length of the main river Sitnica and its tributaries. These differences may be included into the analysis of the Sitnica river network. For the first time it was concluded that the Sitnica river has bi-polar dendritic parallel network. The 80% of right tributaries have angles between 2° and 5° degrees in direction of the Sitnica river. The left tributaries have angles between 1° and 2° degrees with the main water-course.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-24340 Published: 29 Dec 2019

Open Access Original Scientific Paper

MAPPING OF THE ENVIRONMENT USING MULTISPECTRAL SATELLITE IMAGERY

by Ivan Potić, Vanja Šimunić

Continuous environmental mapping has never been more necessary because of the fast-paced lifestyle, technology development, climate change. Monitoring changes in the environment has become one of the most important tasks todayto understand those changes and take the necessary measures to coordinate sustainable development with the emerging natural and socio-economic events. Remote sensing combined with cartography gives us the opportunity to obtain current information on the state of the environment and react suitablyin order to reduce damage to a minimum in accordance with sustainable development.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-24474 Published: 29 Dec 2019

Open Access Original Scientific Paper

OSCILLATION CRITERIA FOR SECOND ORDER HALF-LINEAR DIFFERENTIAL EQUATIONS WITH DELAY

by Radica Bojičić, Tanja Jovanović

The oscillation criteria of different types of differential equations are often the topic of numerous scientific papers, because their application in nuclear physics, fluid mechanics, relativistic mechanics, the study of chemical reactions in the system and in general are large in science. In this paper, the oscillation criteria using averaging functions of the half-linear differential equation are generalized to the half-linear differential equation with delay, under the appropriate assumptions for the delay function. Suitable examples illustrate the application of set oscillation criteria.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-22404 Published: 23 Sep 2019

Open Access Original Scientific Paper

EFFECT OF THE CASCADE NEUTRALIZATION ENERGY ON THE SURFACE MODIFICATION BY THE IMPACT OF SLOW HIGHLY CHARGED IONS

by Milena Majkic, Nataša Nedeljković, Marko Mirković

We consider the neutralization dynamics of slow highly charged ions in the interaction with a metal surface covered with a thin dielectric film from the standpoint of the surface modification. The quasi-resonant two-state vector model and the micro staircase model are used for the calculation of cascade neutralization energy for the ArZ+, KrZ+ and XeZ+ ions. The population of several ionic Rydberg states at each step of the neutralization cascade is demonstrated. The correlation between the neutralization and the potential energy is presented for moderate and very low ionic velocities and the relevance of this relation for the surface nanostructure formation is briefly discussed for a different angle of incidence and different dielectric materials.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-22085 Published: 08 Sep 2019

Open Access Original Scientific Paper

ISOMORPHIC TRANSFORMATION AND ITS APPLICATION TO THE MODULO (2^n+1) CHANNEL FOR RNS BASED FIR FILTER DESIGN

by Negovan Stamenković

In this paper, the implementation of a Finite Impulse Response (FIR) filter in the Residue Number System (RNS), is presented, in which a modulo multiplier based on the isomorphism technique is used to perform multiplication in the (2n+1) channel. An RNS modular multiplication in the Galois Field GF(2n+1) is presented in detail in this paper. The multiplication is based on the isomorphic mapping technique adapted to the residue arithmetic. The isomorphic encoder and decoder look-up tables in the GF(28+1) are given. An architecture for FIR filter design based on distributed arithmetic for multiplication and accumulation in mentioned (2n+1) channel is also presented. This architecture is discussed in details and compared with with architecture based on isomorphing technique.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-21821 Published: 25 Aug 2019

Open Access Original Scientific Paper

SYSTEM PERFORMANCES OF SC RECEPTION IN ASYMMETRIC MULTIPATH FADING ENVIRONMENTS

by Danijel Đošić, Časlav Stefanović, Dejan Milić, Mihajlo Stefanović

The paper takes into consideration dual-branch selection combining (SC) diversity reception technique in the presence of dissimilar fading at their branches. We efficiently obtained first and second order closed form statistics at the output of the considered model such as probability density function (PDF), cumulative distribution function (CDF) and average level crossing rate (aLCR). Moreover, obtained results are numerically presented for various sets of system model parameters and mainly confirmed by computer based MATLAB simulations.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-21769 Published: 23 Jun 2019

Open Access Original Scientific Paper

EPIPHYTIC LICHENS IN THE TOWN OF ZVEČAN AND THEIR BIOINDICATIOR S VALUE

by Gordana Aleksić, Slaviša Stamenković, Svetlana Ristić, Marija Marković

This paper treats the long-term changes in area of the "lichen desert" of town Zvečan. Comparison of results obtained in 1926, when 67 lichen species where present, through the results in 1983 and 1988 when the "lichen desert", low or no lichen diversity was established because of the air pollution, with investigations carried out in 2014, 16 lichen species were identified. The "lichen desert" is no existing any more. The main reason that the lichens are present now is termination of operation of the "Trepča" company and cessation primary pollutants emissions. Using lichens as a bio-indicators in this investigation it was established the average air pollution, which is lichen "struggle zone",meaning increase air quality.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-19606 Published: 13 May 2019

Open Access

THE VENTRAL CRANIAL SIZE AND SHAPE VARIATION BETWEEN MALES AND FEMALES OF EUROPEAN BROWN FROGS: RANA DALMATINA, R. GRAECA AND R. TEMPORARIA (ANURA, AMPHIBIA)

by Jelena Krstičić Račković, Nataša Tomašević Kolarov, Tanja Vukov

Sexual size and shape dimorphism is a very common phenomenon widely studied in the field of evolutionary biology. The differences between sexes are related to their life strategies and driven by the two evolutionary processes, sexual and natural selection. In amphibians, females are larger sex due to high correlation with fecundity, while dimorphism in body shape is often related to intrasexual competition for opposite sex during the breeding season. The main aim of this study is to describe patterns of ventral cranial size and shape variation between males and females of three species of European brown frogs, Rana dalmatina, R. graeca, R. temporaria, from the Balkan Peninsula. Our results showed that species R. dalmatina and R. graeca are sexually dimorphic for the ventral cranial size while species R. graeca and R. temporaria for the ventral cranial shape. Sexual dimorphism in cranial size is most probably an indirect consequence of natural selection favoring larger body for higher fecundity in explosive breeders like brown frogs. Cranial shape variation is under a strong influence of size variation but without allometric scaling between sexes. Sexual shape differences of analyzed brown frog species were most pronounced in the level of connection between cranium and jaw which indicate that differential diet of males and females can be a factor affecting observed sexual dimorphism patterns. More detailed studies of males and females microhabitats are necessary to conclude if differences in intersexual ecology affect intersexual size and shape differences in the cranium.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-21223

Open Access

SYNTHESIS OF BIODEGRADABLE POLYESTER BASED ON RENEWABLE RESOURCES

by Vojislav Jovanović, Ivan Ristić, Aleksandra Miletić, Suzana Cakić, Jelena Tanasić, Jaroslava Budinski-Simendić

Due to the growing problem caused by waste plastics, academia and industry, invest great dials of efforts to solve this problem and enable the sustainability of polymeric materials. One way, which can successfully solve this problem, is certainly the synthesis of new polymeric materials based on renewable raw materials. Therefore, in this paper, synthesis of polyester based on ricinoleic acid (as well as the methyl ester of ricinoleic acid) is presented, in order to obtain the polyol of the desired molar masses. The polymerization of the ricinoleic acid was performed in the presence of diethylene glycol, as an initiator, and titanium isopropoxide, as a catalyst. By analyzing the molar masses of the obtained polyesters, it has been confirmed that the control of the molecular weight of the polyricinoleic acid can be successfully accomplished by the addition of a precisely determined amount of diethylene glycol, thus enabling in this way the synthesis of polyols of desired properties. The molecular structure of the synthesized polyols is confirmed by FTIR and NMR spectroscopy. The analysis of the thermal properties showed that the glass transition temperatures of the synthesized polyols range from -70 to -80ºC, which makes it possible to apply these materials in low-temperature applications. The slight increasment of thermal stability is observed, only with the increasment of molecular weight, which was confirmed by TG analysis. The viscosity measurement results confirmed that as the molar weight of synthesized polyester increases, the viscosity of the samples also increases.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-18120

Open Access

FIXED POINT RESULTS FOR WEAK S-CONTRACTIONS VIA C-CLASS FUNCTIONS

by Ljiljana Paunović, Müzeyyen Sangurlu Sezen, Arslan Hojat Ansari

In this paper, we prove some fixed point results for weak S-contraction mappings in partially ordered 2-metric spaces via C-class function. Our results are different and more general to the usual methods in the literature.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-21156

Open Access

A MINI-REVIEW OF ELECTROANALYTICAL METHODS FOR PESTICIDES QUANTIFICATION

by Sonja Jevtić, Dalibor Stanković, Anja Jokić, Branka Petković

This review paper shows the progress made in the last five years in electrochemical methods applied for the purpose of detection and quantification of pesticides - nowadays the most serious pollutants of the environment. Most pesticides can be successfully analyzed by chromatographic techniques, but because of high prices and immobility of the apparatus, the complexity of the method and the necessary special preparation of the samples, electrochemical methods have been recognized as an excellent alternative solution due to their advantages in speed, economy, simplicity and no exhaustive sample preparation. As the main limitation for use of this methods is electrochemical inactivity of many pesticides, this paper gives the essence of all elctroanalytical methods for pesticide quantification applied in last period, with an overview of the electrode materials and modifiers applied in a purpose to enhance analytical procedures application and characteristics of electrochemical sensors.

picture_as_pdf View Full-Text DOI 10.5937/univtho9-20130