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Oscilacije kompozitnih nanostruktura primenom teorija višeg reda
No full textIn this doctoral dissertation, the oscillatory characteristics of nanobeams and nanotubes were analyzed, considering the influence of various parameters on the change in the fundamental circular frequency, critical temperature, and critical fluid flow velocity. The dynamic equations were derived using Hamilton's principle, and analytical and numerical methods were applied to solve them. Special attention was given to structures made of functionally graded materials, which are significant due to their variable mechanical properties. Using Eringen's lower- and higher-order nonlocal theory, as well as strain gradient theory, mathematical models of the studied structures were presented. The change in the fundamental circular frequency with temperature variation was analyzed. Special emphasis was placed on the change in the fundamental circular frequency, critical temperature, and critical fluid flow velocity, with changes in the volume fraction exponent, lower- and higher-order nonlocal parameters, and the length scale parameter, allowing for a deeper understanding of nonlocal effects on the change in the fundamental circular frequency. It was demonstrated that the nonlocal parameter and length scale parameter affect material stiffness differently, and thus have different impacts on the change in the circular frequency of nanostructures. The influence of the geometric coefficient on the change in the circular frequency of a non-uniform nanotube was considered. In the case of the non-uniform nanotube, the fluid flow velocity is expressed as a function of the geometric coefficient, allowing for the analysis of the change in the critical fluid flow velocity through the non-uniform nanotube with the variation of the geometric coefficient
Short-circuit calculation in renewable energy resources-based microgrids
Get PDFУ дисертацији је обрађен проблем кратких спојева у микромрежама заснованим на обновљивим изворима енергије. Обрађени су такође, модели елемената, као и сам модел микромреже и предложена је једна ефикасна и робусна метода за прорачун кратких спојева. Верификација методе урађена је на примеру микромреже засноване на обновљивим изворима енергије, а тачност резултата је потрврђена помоћу „HIL” окружења. Извршена је и упоредна анализа резултата добијених предложеном методом и резултата добијених методом из међународног стандарда за прорачун кратких спојева.U disertaciji je obrađen problem kratkih spojeva u mikromrežama zasnovanim na obnovljivim izvorima energije. Obrađeni su takođe, modeli elemenata, kao i sam model mikromreže i predložena je jedna efikasna i robusna metoda za proračun kratkih spojeva. Verifikacija metode urađena je na primeru mikromreže zasnovane na obnovljivim izvorima energije, a tačnost rezultata je potrvrđena pomoću „HIL” okruženja. Izvršena je i uporedna analiza rezultata dobijenih predloženom metodom i rezultata dobijenih metodom iz međunarodnog standarda za proračun kratkih spojeva.The dissertation addresses the issue of short circuits in microgrids based on renewable energy sources. It also covers the modeling of all elements, as well as the microgrid model itself, and proposes an efficient and robust method for short circuit calculation. The method was verified using an example of microgrid based on renewable energy sources, with result accuracy confirmed through a "HIL" environment. A comparative analysis was also performed between the results obtained by the proposed method and those obtained using the method from the international standard for short circuit calculations
The model of shopping centres influence on traffic damand generation
Get PDFIstraživanje koje je sprovedeno u okviru disertacije poslužilo je za definisanje matematičkog modela koji se može primeniti za objektivnu procenu generisane saobraćajne potražnje za značajne promene namene zemljišta, kao što je izgradnja tržnih centara u gradovima srednje veličine. Analiza je pokazala da se broj posetilaca i vozila koja su privučena atrakcijom zone tržnog centra može utvrditi modelom koji je zasnovan na linearnoj regresionoj analizi. Verifikacija modela je izvršena u realnim uslovima saobraćajnog toka koji generiše tržni centar koji nije bio predmet analize pri formiranju modela prognoze. Razvijeni model se može primeniti u postupcima planiranja izgradnje novih tržnih centara u gradovima srednje veličine u Republici Srbiji i Bosni i Hercegovini, ali i šire u regionu Jugoistočne Evrope, radi procene obima generisane saobraćajne potražnje, odnosno njenog uticaja na uslove odvijanja saobraćaja na okolnoj saobraćajnoj mreži.The research conducted within the dissertation served to define a mathematical model that can be applied to objectively estimate the generated traffic demand for significant land use changes, such as the construction of shopping centers in medium-sized cities. The analysis showed that the number of visitors and vehicles attracted by the attraction of the shopping center zone can be determined by a model based on linear regression analysis. The verification of the model was carried out in the real conditions of the traffic flow generated by the shopping center, which was not the subject of analysis during the formation of the forecast model. The developed model can be applied in planning procedures for the construction of new shopping centers in medium-sized cities in the Republic of Serbia and Bosnia and Herzegovina, but also more widely in the region of Southeast Europe, in order to assess the volume of generated traffic demand, i.e. its impact on traffic conditions on the surrounding traffic network
The Influence of Socioeconomic Status and Parenting Styles on Depressiveness, Anxiety, Impulsivity and Hyperactivity in Youth
No full textOva studija ispituje uticaj socioekonomskog statusa i roditeljskih stilova na
mentalno zdravlje mladih, sa fokusom na depresivnost, anksioznost, impulsivnost i
hiperaktivnost. Uzorak je činilo 300 adolescenata i mladih uzrasta od 15 do 24 godine iz Novog
Pazara. Korišćeni su standardizovani instrumenti za procenu psiholoških simptoma, roditeljskih
stilova i socioekonomskog statusa. Rezultati pokazuju da je autoritativni stil roditeljstva
negativno povezan sa depresivnošću, anksioznošću i hiperaktivnošću, dok su autoritarni i
permisivni stilovi povezani sa višim nivoima ovih simptoma. Viši nivo obrazovanja majke
povezan je sa nižim stepenom anksioznosti, dok su niže obrazovanje oca, lošije materijalne
prilike povezani sa višim nivoom depresivnosti. Impulsivnost je povezana sa permisivnim
stilom, a hiperaktivnost je izraženija kod mlađih adolescentkinja. Nalazi ističu značaj
porodičnih i socioekonomskih faktora u prevenciji problema mentalnog zdravlja kod mladih
Cohomology algebra of Grassmann manifolds of oriented three-dimensional planes in euclidean space
No full textIspitivanje Grasmanovih mnogostrukosti, koje se prvi put pominju još
u 19. veku, je jedan od klasičnih problema algebarske topologije...The analysis of Grassmann manifolds, which were first introduced in the 19th century, is one of the classical problems in the algebraic topology..
Vertical ex vivo dermoscopy of pigmented skin lesions
No full textUvod: značaj vertikalne ex vivo dermoskopije u pružanju dijagnostičkih informacija
još uvek nije analizirana.
Ciljevi: definisati, opisati i utvrditi značaj struktura vidljivih vertikalnom ex vivo
dermoskopijom u dijagnostici i diferencijaciji pigmentnih benignih i svih malignih lezija
kože bez obzira na pigmentaciju, i utvrditi tačnost tehnike u proceni tumorskih margina.
Metod: prospektivno istraživanje sprovedeno je u dva univerzitetska centra. Digitalne
fotografije kompletno ekscidiranih lezija kože, fiksiranih u formalinu, pre dalje obrade,
dermoskopski su evaluirane analizom obrasca.
Rezultati: analizom 80 pigmentih benignih lezija, zapažen je značaj vertikalne ex vivo
dermoskopije u dijagnostici i/ili diferencijaciji plavog nevusa, seboroične keratoze i
hemangioma od drugih lezija kože. Među malignim lezijama, bazocelularni karcinomi (BCC)
su imali najraznovrsniju dermoskopsku prezentaciju na vertikalnom preseku, dok je većina
skvamocelularnih carcinoma (SCC) imala sličnu prezentaciju. Vertikalna ex vivo
dermoskopija svih tankih melanoma bila je skoro identična, za razliku od nodularnih
melanoma. Dermatološka procena tačnosti dubine invazije bila je 0,75 za BCC, 0,81 za SCC i
0,80 za melanom, dok je procena patologa iznosila 0,65, 0,75, odnosno 0,83.
Međuposmatračko slaganje iznosilo je 0,71 za BCC, 0,80 za SCC i 0,83 za melanom.
Dermatološka procena tačnosti širine bila je 0,82 za BCC, 0,87 za SCC i 1,00 za melanom.
Zaključci: vertikalna ex vivo dermoskopija može doprineti međusobnoj diferencijaciji
BCC-a, SCC-a i melanoma, kao i diferencijaciji pigmentnih benignih od malignih lezija kože.
Bez obzira na specijalnost lekara, vertikalna ex vivo dermoskopija omogućava precizniju
procenu dodatnih karakteristika tumora
Valorizacija uticaja i optimizacija pravila građenja u cilju unapređenja implementacije planskih dokumenata u Srbiji
No full textThe research focuses on the analysis of building regulations in Serbia within urban planning. Building regulations are integral parts of planning documents and are not just technically defined parameters, but elements that fit into broader social, economic, and environmental frameworks. However, issues often arise, such as the mismatch of building regulations with specific locations or the copying of regulations from different contexts, which reduces the effectiveness of planning and the implementation of plans. The research emphasizes the importance of adapting regulations to the existing conditions, needs, and specificities of the location, in order to achieve the integration of form and context. Therefore, building regulations should be viewed as components of a complex system that includes interdependent elements, where a change in one part can lead to effects in other parts. Planning in Serbia often relies on traditional practices and a lack of professional support, which causes inefficiency in the implementation of planning documents. The research also analyzes the shortcomings of the existing system and proposes a new model that integrates various aspects of urban planning, including building regulations, aiming to improve coordination and efficiency in planning
Klasifikacija motora automobila sa unutrašnjim sagorevanjem prema pogonskom gorivu na osnovu generisanog zvuka
No full textNoise pollution and exhaust emissions represent significant
environmental challenges, with vehicle classification based on the type of
fuel contributing to the reduction of air pollution and improvement of urban
space management. This research develops an original system for acquiring
engine sounds of passenger vehicles under real-world conditions, enabling
autonomous vehicle detection, minimal environmental impact, and
compatibility with future IoT systems. Key challenges included optimizing
the microphone position to avoid obstructing vehicle passage, as well as
selecting the engine operating mode that carries the most relevant acoustic
information. The system was tested on 350 vehicles, forming a database of
475 sound samples, along with the implementation of a method for
automatic extraction of acoustically relevant operating modes.
Two groups of audio features suitable for distinguishing fuel types
were identified: spectrogram representations (mel-spectrograms,
gammatonegrams) and psychoacoustic characteristics (loudness, roughness,
sharpness, crest factor). Classification was carried out using deep learning
methods (CNN) and unsupervised learning (SOM), with CNN achieving an F1
score of up to 97%, and SOM reaching 96.7% after eliminating technically
faulty vehicles.
The contribution of this research lies in the development of an
innovative acquisition system, the identification of key acoustic features,
and the demonstration of machine and deep learning applications in engine
sound analysis. The created sound sample database represents a valuable
resource for the scientific community and future research in noise analysis,
fuel type recognition, and fault detection. The results confirmed that it is
possible to successfully classify vehicles based on fuel type using sound,
opening opportunities for traffic monitoring, noise reduction, and the
development of standards for assessing engine sound quality
Prilog istraživanju uticaja histerezisa gume na koeficijenat trenja klizanja u kontaktu obuće
No full textThis dissertation investigates the influence of rubber hysteresis, used
for manufacturing shoe soles, on the coefficient of friction in contact
between footwear and floor. In addition to experimental testing,
numerical methods (regression and the Taguchi method) were
employed to analyze the results and define the influence of certain
parameters on the coefficient of friction. An artificial neural network
was also developed to predict the coefficient of friction between
footwear and the floor based on the hysteresis values of rubber and
other influencing parameters.
For the purpose of experimental determination of the coefficient of
friction, a special testing table was designed, capable of testing under
various conditions and with parameter variations (sliding speed,
normal load, different types of surfaces, surface conditions, roughness).
Experimental investigations included determining the hysteresis of the
rubber compounds used in the tests, measuring the hardness of the
rubber, and assessing the roughness of granite plates on which the
rubber samples were slid.
The experiments indicate that the influence of rubber hardness on the
coefficient of friction cannot be considered separately from hysteresis.
Larger variations in the coefficient of friction (up to 18 times) on
smooth plates suggest that hysteresis has a smaller influence due to the
dominant role of adhesion in determining the coefficient of friction. On
anti-slip plates, which are significantly rougher than smooth plates,
variations are smaller (up to 3 times) because hysteresis has a greater
impact on the coefficient of friction due to the deformations caused by
the movement of the rubber over the rough surface
