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Search Results: 1 - 10 of 460010 matches for " Mi?i? Vladan M. "
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Graphic constructions of characteristic diagrams in chemical engineering and the application of differential geometry
Pejovi? Branko B.,MiiVladan M.,Tomi? Milorad V.,Tadi? Goran S.
Hemijska Industrija , 2012, DOI: 10.2298/hemind110721067p
Abstract: Starting from the experimental concentration-time ( cA,t diagram this work gives the construction of the rate of reaction-time (rA,t diagram using the pure graphic method. The diagram was constructed based on the constructed tangents in arbitrary points of the starting diagram by drawing lines parallel to them in the predetermined pole. The evidence of the construction was derived using differential geometry, i.e. the main theorem of differential calculus. Differential properties between the observed values were used in the method. Starting from the analytic relations rA = rA(t) and cA = cA(t), which can be very complex (polynomes of the n-th order), and, eliminating time t in order to give a full description of the process, we obtain the analytical relation rA = rA(cA), which is then graphically represented. Hoewever, this elimination of time can also be done graphically, in a relatively simple way. After that, through the use of the integral calculus, it was shown that concentration increase in a time interval is proportional to the (rA,t) diagram surface area. Using a similar procedure, further in the paper, it was shown that the time increase is proportional to the (1/rA, cA) diagram surface area. In order for the method to be applicable in practice, we have derived relations for appropriate coefficients of proportionality. Verification of the method is illustrated by the two characteristic examples from chemical kinetics at different monotonies of the starting experimental functions.
Determination of the number of radicals in the initial chain reactions by mathematical methods
Pejovi? Branko B.,Jotanovi? Milovan B.,MiiVladan M.,Tomi? Milorad V.
Hemijska Industrija , 2009, DOI: 10.2298/hemind0902121p
Abstract: Starting from the fact that the real mechanism in a chemical equation takes places through a certain number of radicals which participate in simultaneous reactions and initiate chain reactions according to a particular pattern, the aim of this study is to determine their number in the first couple of steps of the reaction. Based on this, the numbers of radicals were determined in the general case, in the form of linear difference equations, which, by certain mathematical transformations, were reduced to one equation that satisfies a particular numeric series, entirely defined if its first members are known. The equation obtained was solved by a common method developed in the theory of numeric series, in which its solutions represent the number of radicals in an arbitrary step of the reaction observed, in the analytical form. In the final part of the study, the method was tested and verified using two characteristic examples from general chemistry. The study also gives a suggestion of a more efficient procedure by reducing the difference equation to a lower order.
Determination of stoichiometric coefficients by the matrix method
Tadi? Goran S.,Pejovi? Branko В.,Gligori? Miladin J.,MiiVladan M.
Hemijska Industrija , 2007, DOI: 10.2298/hemind0701018t
Abstract: The problem of calculating stoichiometric coefficients in a chemical equation can be solved by standard methods and the method of multidimensional vector space, but good knowledge of vector algebra is required. In this paper, the authors proposed a matrix method and other treatment of the problem was given as the authors' own interpretation. A matrix was formed in the form of base using all the elements which take place in a chemical reaction, after which the matrixes of all the chemical compounds were determined based on numerical indexes and element symbols. This approach enables the setting of a principal matrix equation based on a mathematical approach. The solutions of this matrix equation are the desired stoichiometric coefficients that form a balanced equation. A new approach to tabular solving is presented. This method, compared to existing standard methods, is faster, simpler, and more effective, especially for complex chemical equations. The method was tasted on examples from inorganic chemistry and metallurgy.
Smart grids concept in electrical distribution system
Popovi? ?eljko N.,Radmilovi? Bratislava B.,Ga?iVladan M.
Thermal Science , 2012, DOI: 10.2298/tsci120124072p
Abstract: This paper defines key business processes in electrical distribution systems and key elements and priority components that should be (re)defined in these processes in order to enable the goals of smart grids concept to be fulfilled in the cost effective way. Activities undertaken in the Power Distribution Company of “Elektrovojvodina” (Serbia), which provide the basis for fulfilling the Smart Grids goals and thus enable full implementation of smart grids concept are presented in details.
Streamlines based visualization of air flow in clouds
Kova?evi? Marko M.,Mihajlovi? Vladan T.,Ran?i? Dejan D.
Serbian Journal of Electrical Engineering , 2012, DOI: 10.2298/sjee1201043k
Abstract: The most important functionality of the hail suppression information system in Serbia is to enable timely and reliable detection of the formation of hail-containing clouds. Improvement of this functionality can be achieved by adequate visualization of air flow (wind) inside the cloud system. This was the motivation for implementing a 2D steady vector field visualization method, based on the streamlines method. The choice of this method is dictated by the requirements for the given appliance: efficiency (a crucial requirement in hail suppression systems), generality of use, an accurate and easily understandable display. By implementing algorithms for streamlines seeding strategy and streamlines points distance control, the infinite loop problem that occurs due to the existence of field vortices is eliminated and evenly spaced streamlines are obtained. For analyzing the influence of the implemented method’s parameters on performance and image quality, a framework for visualization is developed. The implemented method is successfully applied for visualization of data obtained from meteorological radars.
Nanocomposite permanent magnetic materials Nd-Fe-B type: The influence of nanocomposite on magnetic properties
Talijan Nade?da M.,Staji?-Tro?i? Jasna,Gruji? Aleksandar,?osovi? Vladan
Journal of Mining and Metallurgy, Section B : Metallurgy , 2005, DOI: 10.2298/jmmb0501095t
Abstract: The influence on the magnetic properties of nanocristalline ribbons and powders has character of microstructure, between others – the grain size volume of hard and soft magnetic phases and their distribution. Magnetic properties of ribbons and powders depend mainly on their chemical composition and parameters of their heat treatment [1]. Technology of magnets from nanocristalline ribbon consists of the following process: preparing the Nd-Fe- B alloy, preparing the ribbon, powdering of the ribbon, heat treatment of the powder and finally preparing the magnets. Nanocomposite permanent magnet materials based on Nd-Fe- B alloy with Nd low content are a new type of permanent magnetic material. The microstructure of this nanocomposite permanent magnet is composed of a mixture of magnetically soft and hard phases which provide so called exchange coupling effect.
An overstoichiometric Nd–Fe–B hard magnetic material
Journal of the Serbian Chemical Society , 2010,
Abstract: A commercial Nd-rich Nd–Fe–B-based hard magnetic material was studied. The obtained results were compared before and after recording of the thermomagnetic curve up to 800 °C. The curve itself showed clearly besides Curie points of the Nd2Fe14B phase and α-Fe also another critical temperature. M ssbauer spectroscopic (MS) phase analysis and X-ray diffraction analysis (XRD) showed in addition to the commonly known phases Nd2Fe14B and NdFe4B4 also some paramagnetic and ferromagnetic iron atoms (MS) and Fe17Nd2 intermetallics (XRD). During the exerted thermal treatment, the content of the Nd2Fe14B and NdFe4B4 phases remained almost unchanged, while iron atoms from remnant minor phases built a separate α-Fe phase. The XRD pattern also showed the presence of some minor Nd phase. The results of Squid magnetic measurements suggest a nanocrystalline decoupled structure of the Nd-rich alloy in the optimized magnetic state. Measurement of the magnetization loop showed, in spite of small changes in the phase composition, that magnetic properties of the quality material deteriorated during the thermal treatment.
Data Sorting Using Graphics Processing Units
M. J. Mii,M. V. Toma?evi?
Telfor Journal , 2012,
Abstract: Graphics processing units (GPUs) have been increasingly used for general-purpose computation in recent years. The GPU accelerated applications are found in both scientific and commercial domains. Sorting is considered as one of the very important operations in many applications, so its efficient implementation is essential for the overall application performance. This paper represents an effort to analyze and evaluate the implementations of the representative sorting algorithms on the graphics processing units. Three sorting algorithms (Quicksort, Merge sort, and Radix sort) were evaluated on the Compute Unified Device Architecture (CUDA) platform that is used to execute applications on NVIDIA graphics processing units. Algorithms were tested and evaluated using an automated test environment with input datasets of different characteristics. Finally, the results of this analysis are briefly discussed.
Modern catalysis in the synthesis of some pharmaceuticals and fine chemicals
Petrovi? Slobodan D.,Mii?-Vukovi? Milica M.,Mijin Du?an ?.
Hemijska Industrija , 2002, DOI: 10.2298/hemind0201010p
Abstract: Catalysis in the synthesis of Pharmaceuticals and line chemicals nowadays becomes more and more important. Synthesis that minimizes wastes is important from the economical aspect, as well as from the environmental aspect. "Green chemistry" or "green technology" is an effort to protect the environment by increasing the efficiency of the overall synthetic processes in the chemical industry by minimizing or eliminating wasteful by-products. Modern catalytic methods in the synthesis of some Pharmaceuticals and fine chemicals are discussed such as phase-transfer catalysis, biocatalysis asymmetric catalysis and, generally, solid-phase chemistry.
Localization of-monoamine positive structures in the ovary and oviduct of developing rats
Radovanovi? Anita M.,Mii? Mileva,Gledi? Du?an S.
Acta Veterinaria , 2002, DOI: 10.2298/avb0204211r
Abstract: The aim of this study was to investigate the localization and distribution of sympathetic positive structures in the female gonads and oviducts of 15 30 and 60-day-oldAO rats. Histofluorescence and immunohistochemistry methods were used to determine their distribution in the ovary and oviduct, as well as for identification of dopamine and serotonin within sympathetic positive structures. Total monoamine positive structures (fibers and cells) were mainly localized under the surface epithelium, between follicles, especially surrounding groups of primary follicles and between secondary interstitial cells. The distribution of dopamine (DA) immunolabelled fibers and cells was in accordance with the distribution of total monoaminergic structures detected using histofluorescence. However, the density of structures labeled with DA antibodies was lower compared to total catecholamine positive structures detected by the fluorescence method. Delicate serotonin (5-HT) positive fibers were present mainly under the surface epithelium and in interstitial tissue between the cortex and medulla. In the hilum and medulla 5-HT positive cells were found perivascularly, while a dense population of 5-HT positive cells was found in the oviduct and mesovarium in 60-day-old animals. No corpus luteum cells were labelled using either of the two methods. Our findings corroborate observations that the monoamine supply of the ovary is not exclusively via extrinsic innervation and that intragonadal sources have an important role in their synthesis. Furthermore, the intraovarian localization of these elements suggests that monoamines exert direct or indirect effects on ovarian function.
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