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Search Results: 1 - 10 of 144816 matches for " Pejovi? Branko B. "
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Determination of the number of radicals in the initial chain reactions by mathematical methods
PejoviBranko B.,Jotanovi? Milovan B.,Mi?i? Vladan 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.
A model for reliability analysis and calculation applied in an example from chemical industry
PejoviBranko B.,Tadi? Goran S.,Jotanovi? Milovan B.,Tomi? Milorad V.
Hemijska Industrija , 2010, DOI: 10.2298/hemind091105002p
Abstract: The subject of the paper is reliability design in polymerization processes that occur in reactors of a chemical industry. The designed model is used to determine the characteristics and indicators of reliability, which enabled the determination of basic factors that result in a poor development of a process. This would reduce the anticipated losses through the ability to control them, as well as enabling the improvement of the quality of production, which is the major goal of the paper. The reliability analysis and calculation uses the deductive method based on designing of a scheme for fault tree analysis of a system based on inductive conclusions. It involves the use standard logical symbols and rules of Boolean algebra and mathematical logic. The paper eventually gives the results of the work in the form of quantitative and qualitative reliability analysis of the observed process, which served to obtain complete information on the probability of top event in the process, as well as objective decision making and alternative solutions.
Graphic constructions of characteristic diagrams in chemical engineering and the application of differential geometry
PejoviBranko B.,Mi?i? Vladan 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 stoichiometric coefficients by the matrix method
Tadi? Goran S.,PejoviBranko В.,Gligori? Miladin J.,Mi?i? Vladan 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.
Radiation-sensitive field effect transistor response to gamma-ray irradiation
Pejovi? Mili? M.,Pejovi? Mom?ilo M.,Jak?i? Aleksandar B.
Nuclear Technology and Radiation Protection , 2011, DOI: 10.2298/ntrp1101025p
Abstract: The influence of gate bias during gamma-ray irradiation on the threshold voltage shift of radiation sensitive p-channel MOSFETs determined on the basis of transfer characteristics in saturation has been investigated. It has been shown that for the gate bias during the irradiation of 5 V and 10 V the sensitivity of these transistors can be presented as the threshold voltage shift and the absorbed irradiation dose ratio. On the bases of the subthreshold characteristics and transfer characteristics in saturation using the midgap technique we have determined the densities of radiation induced oxide traps and interface traps responsible for the threshold voltage shift. In addition, the charge pumping technique was used to determine the energy density of true interface traps. It has been shown that radiation-induced oxide traps have dominant role on threshold voltage shift, especially for gate biases during the irradiation of 5 V and 10 V.
Successive gamma-ray irradiation and corresponding post-irradiation annealing of pMOS dosimeters
Pejovi? Mili? M.,Pejovi? Mom?ilo M.,Jak?i? Aleksandar B.,Stankovi? Koviljka ?.
Nuclear Technology and Radiation Protection , 2012, DOI: 10.2298/ntrp1204341p
Abstract: The paper investigates a possibility of pMOS dosimeter re-use for the measurement of gamma-ray irradiation. The dosimeters were irradiated to the dose of 35 Gy, annealed at room and elevated temperatures, after which they were irradiated again to the same dose value. Changes in the threshold voltage shift during those processes were followed, and it was shown that their re-use depends on a gate polarization during irradiation. For the gate polarization of 5 V during irradiation the pMOS dosimeters can be re-used for measurements of the irradiation dose after annealing without prior calibration. The pMOS dosimeters with the gate polarization during irradiation of 2.5 V can also be re-used for irradiation dose measurements but they require calibration. It is shown that for their re-use it is necessary to anneal the pMOS dosimeter so that the fading is higher than 50%. [Projekat Ministarstva nauke Republike Srbije, br. 171007]
The uneven results of institutional changes in Central and Eastern Europe: The role of culture
Pejovi? Svetozar
Economic Annals , 2004, DOI: 10.2298/eka0463007p
Abstract: It has been widely observed that the same formal rules, enacted in the parliaments in the form of written laws, give vastly different results in different social and cultural environments. This phenomenon came to be particularly pronounced in the process of transition of the formerly communist countries to market economies and politically pluralized societies. Highly similar and occasionally identical institutional changes turned out to be unequally accepted by the societies under consideration and produced widely different results in the material restructuring of the economies. It became clear that the notion of institutions had to be widened so as to encompass the informal rules: the customs, the traditions, cultural values and national myths. Informal rules define the constraints for implementing the formal ones and, on the other hand, determine the actual effects of the latter once they are implemented. Forcing the formal rules upon the transition societies cannot be successful unless preceding and/or contemporaneous changes of informal rules are provided for. The paper ends with a design of the strategy for the decisively important changes in values and other components of informal rules.
Pironaea buseri n. sp. from olistostromal breccia of Paleocene flysch by Anhovo
Desanka Pejovi
Geologija , 1996,
Abstract:
Musical instruments depicted in medieval Serbian art under oriental and western influences
Pejovi? Roksanda
Muzikologija , 2005, DOI: 10.2298/muz0505015p
Abstract: Researching musical instruments on frescoes, miniatures, icons and sculptural decorations of mediaeval Serbian art, painted and sculptured in the manner of Byzantine art, we discover Oriental and Western influences. Musical instruments arriving from the Orient were unchanged for centuries and those from West Europe were mainly used in the Middle Ages or the Renaissance. Oriental and Western influences can be observed on instruments of all families-idiophones, membranophones, bowed and string instruments, as well as on aero phones. The same form of some crotales and cymbals can be found both in Oriental and Western art, the majority of membranophones are of Oriental origin, but the tambourine on Bodani frescoes originated in West Europe. Lyres and angular harps are close to Antique tradition. Some bowed instruments, psalteries, lutes, harps, short horns, business and shawms have Oriental patterns and other instruments of these families accepted Western shapes. There are, as well, same kinds of bowed instruments and S-trumpets peculiar for both continents.
Simulation of Power Electronic Converters Using Quasi Steady State Approximation
Predrag Pejovi
Electronics , 2012,
Abstract: A new method to compute voltage and current waveforms of power electronic converters is proposed in the paper. The method relies on simulation result of averaged circuit model, and superimposes the ripple of the inductor currents to the obtained average values, assuming that the linear ripple approximation applies. To determine the amplitude of the switching ripple, a quasi steady state approximation is proposed. After the inductor currents are obtained, currents of switching components are computed by multiplying them with appropriate switching functions. The algorithmprovides an efficient tool to generate the converter waveforms in order to compute their spectra, mean and RMS values, which are of interest in designing filters and estimating converter losses.
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