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U okviru doktorske disertacije izvedena su eksperimentalna istraživanja osnovnih hidrodinamičkih i maseno-prenosnih karakteristika airlift reaktora sa spoljnom recirkulacijom sa ugrađenom višekanalnom cevnom membranom u silaznu cev (ALSRM). ALSRM je radio na dva načina rada: bez mehurova u silaznoj cevi (način rada A) i sa mehurovima u silaznoj cevi (način rada B) u zavisnosti od nivoa tečnosti u gasnom separatoru. Ispitivani su uticaji prividne brzine gasa, površinskih osobina tečne faze, tipa distributora gasa i prisustva mehurova gasa u silaznoj cevi na sadržaj gasa, brzinu tečnosti u silaznoj cevi i zapreminski koeficijent prenosa mase u tečnoj fazi u ALSRM. Rezultati su poređeni sa vrednostima dobijenim u istom reaktoru ali bez membrane (ALSR). Sadržaj gasa u uzlaznoj i silaznoj cevi određivan je pomoću piezometarskih cevi merenjem hidrostatičkog pritiska na dnu i vrhu uzlazne i silazne cevi. Brzina tečnosti merena je pomoću konduktometrijskih elektroda dok je zapreminski koeficijent prenosa mase dobijen primenom dinamičke metode merenjem promene koncentracije kiseonika u vremenu optičkom elektrodom. Eksperimentalni rezultati pokazuju da sadržaj gasa, brzina tečnosti i zapreminski koeficijent prenosa mase zavise od prividne brzine gasa, vrste alkohola i tipa distributora gasa kod oba reaktora. Višekanalna cevna membrana u silaznoj cevi uzrokovala je povećanje ukupnog koeficijenta trenja za 90% i time dovela do smanjenja brzine tečnosti u silaznoj cevi do 50%. Smanjena brzina tečnosti u silaznoj cevi povećala je sadržaj gasa do 16%. Predložene neuronske mreže i empirijske korelacije odlično predviđaju vrednosti za sadržaj gasa, brzinu tečnosti i zapreminski koeficijent prenosa mase., An objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift membrane reactor (ELAMR). The ELAMR was operated in two modes: without (mode A), and with bubbles in the downcomer (mode B), depending on the liquid level in the gas separator. The influence of superficial gas velocity, gas distributor’s geometry and various diluted alcohol solutions on hydrodynamics and gas-liquid mass transfer coefficient of the ELAMR was studied. Results are commented with respect to the external loop airlift reactor of the same geometry but without membrane in the downcomer (ELAR). The gas holdup values in the riser and the downcomer were obtained by measuring the pressures at the bottom and the top of the riser and downcomer using piezometric tubes. The liquid velocity in the downcomer was determined by the tracer response method by two conductivity probes in the downcomer. The volumetric mass transfer coefficient was obtained by using the dynamic oxygenation method by dissolved oxygen probe. According to experimental results gas holdup, liquid velocity and gas-liquid mass transfer coefficient depend on superficial gas velocity, type of alcohol solution and gas distributor for both reactors. Due to the presence of the multichannel membrane in the downcomer, the overall hydrodynamic resistance increased up to 90%, the liquid velocity in the downcomer decreased up to 50%, while the gas holdup in the riser of the ELAMR increased maximally by 16%. The values of the gas holdup, the liquid velocity and the gas-liquid mass transfer coefficient predicted by the application of empirical power law correlations and feed forward back propagation neural network (ANN) are in very good agreement with experimental values.

U disertaciji je razvijen novi pristup optimizacije vulkanizacije koji omogućava određivanje optimalnih radnih parametara, vremena i temperature kalupa, kako bi se omogućilo dobijanje kvalitetnih homogenih proizvoda. Optimizacioni model je razvijen na primeru četiri sfere, različitih prečnika (2,5; 5; 10 i 20 cm). Dobijeni reometarski podaci vulkanizacije, komercijalno dostupne kaučukove smeše, fitovani su novim pristupom koji deli vulkanizacionu krivu na dva skupa fitovanja, umrežavanje i reverziju. Tačnost razvijenog pristupa fitovanja je potvrđena drugim tipom kaučukove smeše na bazi prirodnog kaučuka, sa različitim sadržajem biočađi kao punila i dobijena je visoka tačnost, gde vrednosti R2 nisu niže od 0,84,a MAPE vrednosti nisu više od 2,4 %. Kaučukova smeša sa biočađi kao punilom je detaljno ispitana različitim metodama kako bi se utvrdila mogućnost delimične zamene čađi sa biopunilom. Ustanovljeno je da komercijalno dostupna čađ može da se zameni za10 phr sa biočađi dobijenom od otpadne drvene biomase, bez značajne promene mehaničkih osobina konačnog gumenog proizvoda. Uveden je novi temperaturno zavisni parametar, nazvan stepen reverzije, koji omogućava određivanje najniže radne temperature (Tmin = 132,36 °C) na kojoj ne dolazi do reverzije i pregrevanja proizvoda. Određena je zavisnost optimalne temperature i vremena vulkanizacije od dimenzija gumenih proizvoda, a predloženi model ostvaruje visoki stepen tačnosti, gde su vrednosti R2 veće od od 0,8328 i MAPE manje od 2,3099 %. Jednačine prenosa toplote za odgovarajuću geometriju su rešavane istovremeno sa razvijenim kinetičkim modelom kako bi se izvršila simulacija vulkanizacije tri sfere različitih prečnika i dva gumena točka, od kojih je jedan komercijalni proizvod gumarske industrije. Predloženi model simulacije uključuje i hlađenje nakon vađenja proizvoda iz prese, jer se reakcije umrežavanja i dalje odvijaju zbog tople unutrašnjosti proizvoda. Kriterijum za vađenje proizvoda je vrednost srednjeg stepena vulkanizacije od 0,9, kako bi se obezbedilo dobijanje gumenih proizvoda odgovarajućih oblika. Optimizacija radnih parametara je izvršena na osnovu minimalne razlike maksimalnog i minimalnog stepena vulkanizacije, što omogućava efikasno izvođenje procesa za kraće vreme i dobijanje kvalitetnih homogenih proizvoda. Određeni su optimalni radni uslovi za sve gumene proizvode. Model veštačke neuronske mreže je razvijen za predviđanje reoloških podataka vulkanizacije komercijalno dostupne kaučukove smeše. Ispitivan je uticaj tri aktivacione funkcije i različit broj skrivenih slojeva i neurona u njma na tačnost predviđanja mreže, pri čemu neuronska mreža sa Softplus aktivacionom funkcijom i 20 neurona u dva skrivena sloja predviđa zavisnost obrtnog momenta od vremena sa visokom tačnošću, tako da su vrednosti MAPE i MSE niže od 2 % i 0,032 dN2m2, redom, a R2 više od 0,98. Razvijeni model veštačke neuronske mreže je potvrđen kaučukovom smešom sa biočađi kao punilom., A novel approach for the optimization of vulcanization process was developed, which enables the determination of optimal operating parameters, time exposure and mold temperature, in order to obtain a high-quality products. The spheres of different diameters (2.5, 5, 10 and 20 cm) were selected for development of optimization model. Obtained vulcanization rheometer data of commercially available rubber blend was fitted using a novel approach, which devide the vulcanization curve into two fitting sets, curing and reversion.The accuracy of the developed fitting approach was examined with another type of rubber mixture based on natural rubber, with different content of biochar as a filler. High accuracy was obtained, where R2 values were not lower than 0.84 and MAPE values were not higher of 2.4%. The rubber compound with biochar as a filler was thoroughly tested by different methods in order to determine the possibility of carbon black partial replacement with biofiller. Commercially available carbon black can be replaced by 10 phr of biochar obtained from hardwood waste biomass, without significantly changing the mechanical properties of the final rubber product. It was introduced a new temperature-dependent parameter, named the reversion degree, enabling the determination of the lowest vulcanization operating temperature(Tmin = 132.36 °C), ensuring that reversion and product overheating do not occur. The dependence of the optimal temperature and vulcanization time on the dimensions of rubber products was determined, and the proposed model achieves a high degree of accuracy, where R2 values were greater than 0.8328 and MAPE was less than 2.3099 %. The heat transfer equations for the appropriate geometry were solved simultaneously with the developed kinetic model for simulation the vulcanization process of three spheres of different diameters and two rubber wheels, where one is a commercial product of the rubber industry. The proposed simulation model includes cooling after removing the product from the mold, as the crosslinking reactions continue to take place due to the warm interior of the product. The criteria for extracting the product from mold was set to value 0,9 of the average vulcanization degree, ensuring obtaining the appropriate shapes of rubber products. The optimization of vulcanization was carried out with obtained the minimum difference between the maximum and minimum vulcanization degree, enabling efficient process and obtaining high-quality homogeneous products. The optimal process parameters for all rubber products have been determined. An artificial neural network model was developed to predict the vulcanization rheological data of a commercially available rubber compound. The influence of three activation functions and different number of hidden layers and neurons, on the neural network prediction accuracy was examined, where by the neural network with the Softplus activation function and 20 neurons in two hidden layers predicts the torque dependence on time with high accuracy, where the MAPE and MSE values were lower than 2% and 0.032 dN2m2, respectively, and R2 values were higher than 0.98. The developed artificial neural network model was validated with a rubber mixture with biochar as a filler.

Istraņivanja u okviru ove doktorske disertacije bavila su se proizvodnjom novog bezglu-tenskog prehrambenog proizvoda na bazi pirinčanog brańna sa dodatkom korena cikorije na dvo-puņnom ekstruderu. U okviru ove studije prvi put je implementiran koren cikorije u flips pro-izvode kao potencijalno funcionalni dodatak. Koren cikorije je jedan od najbogatijih izvora inu-lina, prebiotske komponente poņeljne u ishrani osoba obolelih od dijabetesa, ali i mnogih drugih bioaktivnih komponenata (seskviterpenskih laktona, polifenolnih jedinjenja, masnih kiselina, amino kiselina, vitamina, minerala i dr). Ispitivanja u okviru doktorske disertacije definisana su u cilju odreĎivanja optimalnih uslova procesa ekstrudiranja neophodnih za ostvarivanje poņeljnih fizičkih, teksturnih, i funkcionalnih (sadrņaj inulina i drugih gorenavedenih sastojaka) karakte-ristika finalnog proizvoda.Proistekli rezultati daju uvid u zakonitosti koje vladaju izmeĎu zadatih procesnih parame-tara (sadrņaja vlage polazne smeńe, brzine obrtanja puņnice, i sadrņaja korena cikorije) i fizičkih, funkcionalnih, teksturnih, reolońkih i senzorskih karakteristika finalnih flips proizvoda. Pri-menom optimalnih uslova proizvodnje, koji su definisani uz pomoć genetskog algoritma (16,3 % vlage; brzina obrtanja puņnice od 700 o/min i 30% korena cikorije), uspeńno je proizveden hrs-kav flips proizvod prihvatljive boje, sa visokim sadrņajem prebiotika inulina (5,36%). Time je opravdana primena korena cikorije u razvoju novih funkcionalnih proizvoda prihvatljivih od strane potrońača.PredviĎanje vrednosti ispitivanih parametara ekstrudata vrńeno je primenom dva matema-tička modela čime se jasno pruņa uvid u njihovu primenjivost i učinkovitost kod ove vrste proizvoda. U tu svrhu primenjene su veńtačka neuronska mreņa (engl. Artificial neural network, ANN) i nova metodologija ubrzanog regresionog stabla (engl. Boosted regression trees, BRT), koja se po prvi put primenjuje kod procesa ekstrudiranja hrane.Jedan od ciljeva istraņivanja bio je obogaćnje ekstrudiranog proizvoda inulinom u literaturno preporučenim granicama. Stoga je posebna paņnja bila posvećena optimizaciji postup-ka ekstrakcije inulina, kao i razvoju i validaciji sofisticirane analitičke metode za njegovo kvan-titativno odreĎivanje primenom visokopritisne tečne hromatografije kuplovane sa detektorom ra-sipanja svetlosti na isparenom uzorku (engl. High performance liquid chromatography-Evapo-rative light scattering detector, HPLC-ELSD). Ova metoda primenjiva je na komercijalno do-stupnim proizvodima na teritorije Republike Srbije koji sadrņe inulin (flipsevi, kafe, dodaci ishrani sa inulinom).Inovativni prehrambeni funkcionalni proizvodi nastali u okviru ove disertacije mogu doprineti zdravijoj ishrani potrońača, obogatiti aktuelni trņińni asortiman flips proizvoda i pro-movisati implementaciju korena cikorije u prehrambene proizvode s obzirom na to da Srbija spada u 10 najvećih svetskih proizvoĎača ove sirovine., Research conducted within this doctoral thesis was focused on the production of a novel gluten-free food product based on rice flour with the addition of chicory root on a twin-screw extruder. As a part of this study, chicory root was implemented for the first time in snack puffed products as potential functional ingredient. Chicory root is one of the richest sources of inulin, a prebiotic component desirable in the diet of people with diabetes, but also many other bioactive components (sesquiterpene lactones, phenolic compounds, fatty acids, amino acids, vitamins, mi-nerals, etc.). The main goal of this doctoral thesis research was to define the optimal conditions of extrusion cooking process necessary to achieve the desired physical, textural, and potentially functional (inulin content and other bioactive compounds) characteristics of the final product.The results provide insight into the relationships that prevail between the set of process parameters (moisture content of the starting mixture, screw speed, and chicory root content) and physical, functional, textural, rheological and sensory characteristics of the final puffed snack products. Applying the optimal production conditions, which were defined using a genetic algo-rithm (16.3% moisture; 700 rpm and 30.0% chicory root), it was successfully generated a crispy snack product of attractive color, with a high content of inulin (5.36%). This justifies the use of chicory root in the development of new food products acceptable to consumers.Prediction of extrudates tested properties was performed using two mathematical models, which clearly provides insight into their applicability and effectiveness in this type of product. For this purpose, the Artificial neural network (ANN) was applied, as well as the new young methodology of Boosted regression trees (BRT), which is being used for the first time in food extrusion.One of the goals of the research was to develop a functional extruded snack product enriched with inulin within the literary recommended intake. Therefore, special attention was de-dicated to the optimization of the inulin extraction process, as well as for the development and validation of a sophisticated analytical method for its quantitative determination using high per-formance liquid chromatography coupled with evaporative light scattering detector (HPLC-ELSD). This method is applicable to commercially available products in the territory of the Re-public of Serbia that contain inulin (flips, coffee, dietary supplements with inulin).Innovative food products created within this dissertation can contribute to healthier consumer nutrition, enrich the current market range of snack products and promote the imple-mentation of chicory root in food products, considering that Serbia is one of the 10 largest world producers of this raw material.