Urban Noise Modelling in Boka Kotorska Bay

Traffic is the most significant noise source in urban areas. The village of Kamenari in Boka Kotorska Bay is a site where, in a relatively small area, road traffic and sea (ferry) traffic take place at the same time. Due to the specificity of the location, i.e. very rare synergy of sound effects of road and sea traffic in the urban area, as well as the expressed need for assessment of noise level in a simple and quick way, a research was conducted, using empirical methods and statistical analysis methods, which led to the creation of acoustic model for the assessment of equivalent noise level (Leq). The developed model for noise assessment in the Village of Kamenari in Boka Kotorska Bay quite realistically provides data on possible noise levels at the observed site, with very little deviations in relation to empirically obtained values.</p

The influence of the polarizability in some bremsstrahlung processes

We consider the general results of the theory of the polarizational bremsstrahlung (BrS) and we present the results of recent calculations of the cross sections in the conditions when the radiation of atomic electrons dominates in the total spectrum. For example, we investigated the case when the frequency of the emitted photon is comparable with the energy of the great dipole or plasmon resonance in a cluster (fullerene).Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Chemometric characterization of the hydrogen bonding complexes of secondary amides and aromatic hydrocarbons

The paper reports the results of the study of hydrogen bonding complexes between secondary amides and various aromatic hydrocarbons. The possibility of using chemometric methods was investigated in order to characterize N-H•••π hydrogen bonded complexes. Hierarchical clustering and Principal Component Analysis (PCA) have been applied on infrared spectroscopic and Taft parameters of 43 N-substituted amide complexes with different aromatic hydrocarbons. Results obtained in this report are in good agreement with conclusions of other spectroscopic and thermodynamic analysis

PEST Analysis of Serbia

The main purpose of this paper is to examine the impact of the current Serbian macro-environment on the businesses through the implementation of PEST analysis as a framework for assessing general or macro environment in which companies are operating. The authors argue the elements in presented PEST analysis indicate that the current macro-environment is characterized by the dominance of threats and weaknesses with few opportunities and strengths. Consequently, there is a strong need for faster implementation of structural changes in order to eliminate or minimize the impact of weaknesses and threats of the current macro-environment and create more favorable business climate that would enable companies to formulate effective strategies and to raise their business performances

Influence of world crisis on Western Balkans countries: undertaken measures and expected effects

This paper has attempted to analyse certain influence aspects the global crisis has had on the Western Balkans countries, above all on Serbia, Croatia, Bosnia and Herzegovina, Macedonia and Montenegro. Our analysis focuses on events on stock exchanges, for which we have applied comparative analysis method and noticed that indexes at Western Balkans countries stock exchanges have significantly more fallen (from -46,09% to -73,86%) for the same period of time from 1 January 2008 until 20 August 2009 than indexes at leading world stock exchanges, which have fallen in the ratio of -25,00% to -35,59%. In addition, we have discovered that reinforcement of the global crisis has led to a notable capital withdraw in Western Balkans countries; investors have lost trust in banking and financial system, as well as to a number of other negative occurrences. The world crisis has proven to have had a rather strong influence on countries in this part of Europe, which is an additional issue for governments of certain countries in finalising transition process and quicker accession to the European Union (EU). Different countries have reacted in different ways and this paper aims at underlining some of the most important undertaken measures, as well as at assessing their potential effects. The paper consists of five parts. The introduction reviews global crisis phenomenon, emphasizing a great number of issues open to debate and dilemmas it has brought about, trying to discover answers to some of them within this paper. The second part has been devoted to the crisis cause influence and its development phases, not only in developed countries, but in Western Balkans countries as well. The third part analyses empiric data on indexes fluctuation at stock exchanges of developed and Western Balkans countries. Following the review of negative effects of the global crisis, the forth part deals with a short analysis of measures that governments of the respective Western Balkans countries have undertaken in fighting the crisis, so that we are able to sum up in the fifth part and try to draw the most important conclusions

Pomološke osobine perspektivnih sejanaca maline sa žutom bojom ploda

From over a 100 seedlings obtained by open pollination of Meeker's yellow raspberry clone, 10 seedlings with yellow fruit were selected at the Experimental Station 'Radmilovac' of the Faculty of Agriculture, University of Belgrade. Phenological characteristics, as well as physical, chemical and sensorial fruit properties were investigated during the period 2007-2008 in selected seedlings and standard cultivar Meeker. Results showed that all examined seedlings expressed later flowering and maturing time than the standard cultivar. The best results of physical fruit properties had the standard cultivar, whereas for the majority of the chemical fruit characteristics selected seedlings showed much better results. Seedling 5 had the highest soluble solid content (15.3 %), while the highest vitamin C content was recorded in the fruits of seedlings 9 (51.04 mg/100g), 10 (51.92 mg/100g), and 17 (50.16 mg/100g). The highest values of the sensorial fruit quality achieved seedling 17 (18.9).Od preko 100 sejanaca dobijenih slobodnim oprašivanjem žutog klona sorte Miker izdvojeno je 10 sa žutom bojom ploda koji su kolekcionisani na Oglednom dobru 'Radmilovac' Poljoprivrednog Fakulteta, Univerziteta u Beogradu. U periodu 2007- 2008. godina kod izdvojenih sejanaca i standardne sorte Miker, pored fenoloških, ispitivane su fiziČke, hemijske i senzoricke osobine ploda. Rezultati istraživanja su pokazali da su svi ispitivani sejanci kasnije počinjali fenofaze cvetanja i zrenja u odnosu na sortu standard. Najbolje razultate fizičkih osobina ploda ispoljila je sorta standard, dok su prema većini hemijskih osobina izdvojeni sejanci bili daleko bolji od standardne sorte. Sejanac 5 se odlikuje najvišim sadržajem rastvorljive suve materije (15,3 %), a u pogledu sadržaja vitamina C najviše vrednosti su registrovane kod sejanaca 9 (51,04 mg/100g), 10 (51,92 mg/100g) i 17 (50,16 mg/100g). Najvišu senzoricku ocenu kvaliteta ploda imao je sejanac 17 (18,9)

Humic acids optical properties of rendzina soils in diverse environmental conditions of Serbia

This study examined the impact of climate, altitude and landforms on humic acids (HA) optical properties (E-4/E-6, Delta logK, RF indexes) in Serbian Rendzina soils. HA humification degree of calcareous and decarbonated Rendzinas under natural vegetation (forest and grassland, separately) decreased with altitude increasing. This particular rule was not manifested in arable Rendzinas. HA humification degree in Rendzinas on flat positions (hilltop and footslope) is significantly higher than in Rendzinas on slope sides. Humification degree of HA is the highest in Rendzinas in eastern Serbia (in the vicinity of Negotin), followed by central Serbia (Sumadija) and Srem, southeast and finally, southeast and southwest Serbia. With respect to the climate change foreseen for the end of this century, i.e. increase of precipitation and temperature variance among the regions in Serbia, also an increase in variance of quality of humic acids in Rendzinas on different altitudes and regions can be expected

Direct torque control of a current source inverter fed induction motor

U disеrtаciјi је prikаzаnа јеdnа nоvа strаtеgiја uprаvlјаnjа аsinhrоnim pоgоnоm sа struјnim prеtvаrаčеm učеstаnоsti zаsnоvаnа nа dirеktnој kоntrоli mоmеntа mоtоrа. Cilј је dа sе оvаkvоm pоgоnu оbеzbеdе bоlје dinаmičkе pеrfоrmаnsе оd оnih kоd еkvivаlеntnоg vеktоrski uprаvlјаnоg pоgоnа, а uz pојеdnоstаvlјеnjе uprаvlјаčkе strukturе i njеnu јеdnоstаvniјu implеmеntаciјu u mikrоprоcеsоrski sistеm. U tu svrhu su prvо dаtа tеоriјskа rаzmаtrаnjа dirеktnе kоntrоlе mоmеntа kоd аsinhrоnоg mоtоrа i prikаz rаzličitih pristupа zа rеаlizаciјu оvе uprаvlјаčkе strukturе. Nаkоn tоgа аnаlizirаnа је primеnа dirеktnе kоntrоlе mоmеntа kоd аsinhrоnоg pоgоnа sа struјnim prеtvаrаčеm učеstаnоsti pоmоću аdеkvаtnоg mаtеmаtičkоg mоdеlа pоgоnа. Pri tоmе је tеžištе stаvlјеnо nа spеcifičnоst tоpоlоgiје struјnоg prеtvаrаčа i nаčin nа kојi sе vrši trаnsfеr struје iz јеdnоsmеrnоg mеđukоlа u mоtоr. Rеzultаti istrаživаnjа su iskоrišćеni zа izrаdu uprаvlјаčkе strаtеgiје kоја pоrеd brzоg оdzivа mоmеntа kао kоd vеktоrskе kоntrоlе оbеzbеđuје јеdnоstаvniјi аlgоritаm uprаvlјаnjа bеz upоtrеbе оbrtnе trаnsfоrmаciје i zаhtеvа zа upоtrеbоm sеnzоrа brzinе nа vrаtilu mоtоrа. Zа rаzliku оd rеšеnjа dirеktnе kоntrоlе mоmеntа sа аsinhrоnim mоtоrоm nаpајаnim iz struјnоg invеrtоrа prеdlоžеnih u litеrаturi, dаtih bеz еkspеrimеntаlnе vеrifikаciје, аlgоritаm izlоžеn u disеrtаciјi је zаsnоvаn nа rаdu invеrtоrа sа kоnstаntnоm učеstаnоšću uz mоdifikаciјu оptimаlnе tаblicе аktivirаnjа prеkidаčа u invеrtоru. Оvim su izbеgnuti prоblеmi pri uprаvlјаnju dirеktnоm kоntrоlоm mоmеntа kоrišćеnjеm histеrеzisnоg rеgulаtоrа mоmеntа (znаčајnе pulsаciје mоmеntа, nеоphоdnоst filtrirаnjа еstimirаnоg signаlа mоmеntа, pоtrеbа аdаptаciје širinе histеrеzisа u zаvisnоsti оd brzinе mоtоrа). Аnаlizа pеrfоrmаnsi prеdlоžеnе strаtеgiје uprаvlјаnjа је izvršеnа simulаciјоm nа rаčunаru, а zаtim sе pristupilо rаzvојu uprаvlјаčkоg аlgоritmа u prоgrаmskоm јеziku C. Uprаvlјаčki аlgоritаm је implеmеntirаn i tеstirаn pоmоću mikrоprоcеsоrskоg sistеmа u оkviru rеаlizоvаnоg lаbоrаtоriјskоg prоtоtipа pоgоnа sа klаsičnim tiristоrskim prеtvаrаčеm učеstаnоsti. Svi pоstignuti rеzultаti, kаkо simulаciјоm tаkо i еkspеrimеntоm, pоtvrdili su isprаvnоst prеdlоžеnе uprаvlјаčkе strаtеgiје.The new control strategy based on direct torque control of CSI fed induction motor is presented. The goal of this work is to obtain better performances than exist in similar vector controlled drive, but with reduced control structure and its simpler implementation in the microprocessor system. For that purpose the theory of direct torque control (DTC) is given and different DTC-based strategies are described. Than, the analysis of DTC strategy in CSI fed induction motor drive is performed with adequate mathematical model. The aim of analysis were specific current converter topology and the way of current transfer from DC link to motor. Obtained results are used for developing such a control strategy that, besides a fast torque response as in vector control of the same drive, provide simpler control algorithm without necessity for coordinate transformation and speed sensor on the motor shaft. Contrary to the direct torque control of CSI drive presented in the known literature without experimental results, algorithm suggested in dissertation is based on constant-switching-frequency with modification of the inverter optimal switching table. With such a solution, problems detected under DTC using torque hysteresis controller are avoided (significant torque pulsations, requirement for filtering estimated torque and adaptation of hysteresis bandwidth in depend of motor speed). Performance analysis of recommended control strategy is completed on PC conmputer and than, the control algorithm is developed as software written in C programming language. Control algorithm is implemented and tested in the microprocessor system. This system is a part of the realized drive prototype with a standard thyristor type frequency converter. All results that are obtained by simulation and by experiment confirm the exactness of the proposed control strategy

Humus composition of rendzina soils in different environmental conditions of Serbia

This paper shows organic matter composition (humic acids, fulvic acids, humins) and fractions of humic (free and bounded with mobile R2O3 (HAI), bounded with Ca (HA2), and bounded with clay and stabile R2O3 (HA3)), and fulvo acids (free and bounded with mobile R2O3), bounded with HA1 bounded with HA2, and bounded with HA3), in Rendzina soils on different altitudes (151-1210 m), landforms (hilltop, flat or very gentle slope; foot slope, very gentle slope, south, southwest; slope 45-80 degrees, south, southeast, southwest; slope 20-60 degrees, north, northwest, northeast), and regions (Srem, west, central, east and southeast Serbia). Differences in temperature and water regimes of Rendzinas on various altitudes are not so prominent to have a significant impact on organic matter composition. Landform has more significant impact, with average higher content of HA on slopes, and FA on flat positions, which could be attributed to reduced wetting of soils on slopes. Exposition had no significant impact on humus composition. Differences in soil moisture among regions are more pronounced than differences in soil temperature. Differences in soil organic matter composition among Rendzinas from various regions are small and do not follow pattern of humidity change. Still, organic matter of Rendzina from most humid western region has the least favourable HA/FA ratio, while at the driest east and southeast regions content of humin is the greatest

Proposal of Simple and Accurate Two-Parametric Approximation for the Q

The approximations for the Q-function reported in the literature so far have mainly been developed to overcome not only the difficulties, but also the limitations, caused in different research areas, by the nonexistence of the closed form expression for the Q-function. Unlike the previous papers, we propose the novel approximation for the Q-function not for solving some particular problem. Instead, we analyze this problem in one general manner and we provide one general solution, which has wide applicability. Specifically, in this paper, we set two goals, which are somewhat contrary to each other. The one is the simplicity of the analytical form of Q-function approximation and the other is the relatively high accuracy of the approximation for a wide range of arguments. Since we propose a two-parametric approximation for the Q-function, by examining the effect of the parameters choice on the accuracy of the approximation, we manage to determine the most suitable parameters of approximation and to achieve these goals simultaneously. The simplicity of the analytical form of our approximation along with its relatively high accuracy, which is comparable to or even better than that of the previously proposed approximations of similar analytical form complexity, indicates its wide applicability