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The aim of this study was to investigate a possibility of synthesis of porous ceramics with controlled open porosity, which could be used as sorbents and catalyst supports. Two organic additives were used to obtain open porosity: polystyrene beads and cellulose fibers, which are mixed with kaolin clay powder and the appropriate water content. Samples were sintered at 1050 oC for 1 h. Characterization of the obtained products included X-ray powder diffraction analysis (XRPD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and elemental CHNS analysis. In addition, porosity was examined by quantification of visual information. The specific surface areas were determined by the Brunauer–Emmett–Teller (BET) method. Also, density and compressive strength of the obtained samples were assessed. It was determined that by sintering, the organic component completely leaves the system. For samples prepared with polystyrene beads and with cellulose fibers, satisfactory mechanical properties were obtained: compressive strengths were 1.42 and 1.56 MPa, respectively. It was noted that significantly higher open porosity was obtained by using polystyrene beads as a sacrificial template (porosity of ~56 %) instead of cellulose fibers (porosity of ~6 %).

U okviru ovoga rada dat je sistematski pregled uzroka intenzivnog povećanja sadržaja štetnih supstanci u masi papira i vodama kružnog toka u poslednjih dvadesetak godina i njihov negativan uticaj na proizvodnost papir mašina i kvalitet proizvedenog papira ili kartona. Ukratko su opisane metode određivanja sadržaja štetnih supstanci u masi papira i vodama kružnog toka, supstance koje se koriste za fiksiranje i pasiviranje štetnih supstanci, kao i procesi koji se koriste za uklanjanje štetnih supstanci iz mase papira i voda kružnog toka u cilju neometanog vođenja proizvodnje i dobijanje papira i kartona željenih svojstava., This work shows a systematic review of the cause for intensive increase of harmful substances in paper pulp and circular water streams during last twenty years, as well as their negative influence on productivity of paper machines and quality of produced paper or board. A brief description of methods for determining the content of harmful substances in paper pulp and circular water stream, substances used for fixation and deactivation of harmful substances, as well as processes used for removing harmful substances from paper pulp and circular water stream for the purpose of smooth production of paper and board with desired properties are given.

U radu su prikazani fenomeni prenosa toplote i mase u procesu sušenja papira i analiziraju se pojedine tehnološke celine u proizvodnji papira sa aspekta ispitivanja mogućnosti smanjenja specifične potrošnje toplotne i električne energije modernizacijom tehnologije. Prikazana su neka od rešenja primenjena na papir mašinama u svetu u cilju poboljšanja energetske efikasnosti. Teoretska i praktična saznanja iz ove oblasti su primenjena u Fabrici kartona UMKA, pa su i ovi rezultati prikazani u ovom radu., In this work, phenomena of heat and mass transfer in process of paper drying are given, certain technology units are analyzed, while possibility for decrease of specific heat and electric energy consumption by modernization of technology is examined. Some of the solutions applied on paper machines worldwide in order to improve energy efficiency are shown. Theoretic and practical discoveries in this area are applied in Board factory UMKA, and these results are shown in the work as well.

Radom se ukazuje na raspoložive svetske izvore energije. Razmatra se korišćenje energije u narednom periodu. Daje se pregled, upotreba i značaj alternativnih izvora energije. Potencira se neophodnost razvoja novih tehnologija i racionalizacija korišćenja energije. Navode se podaci o korišćenju energije (toplote i elektične) i vode u celulozno−papirnoj industriji., The available worldwide energy sources are presented. The applications of energy over the next period are considered in this study. The applications and the importance of alternative energy sources is reviewed. The emphasis is put on the necessity of developing new technologies and rationalization of energy use. The data regarding heat and electric energy, along with water applications in cellulose and paper industry are also given.

Biodiesel is defined as a fuel which may be used as pure biofuel or at high concentration in mineral oil derivatives, in accordance with specific quality standards for transport applications. The main raw material used for biodiesel production is rapeseed, which contains mono-unsaturated acids (about 60%) and also poly-unsaturated fatty acids (C 18:1 and C 18:3) in a lower quantity, as well as some undesired saturated fatty acids (palmitic and stearic acids). Other raw materials have also been used in research and the industrial production of biodiesel (palm oil, sunflower oil, soybean oil, waste plant oil, animal fats, etc). The historical background of biodiesel production, installed industrial capacities, as well as the Directive of the European Parliament and of the Council (May 2003) regarding the promotion of the use of biofuels or other renewable fuels for transport are discussed in the first part of this article. The second part focuses on some new concepts for the future development of technology for biodiesel production, based on the application of non-catalytic transesterification under supercritical conditions or the use of lipases as an alternative catalyst for this reaction., Biodizel je definisan kao gorivo koje se može kao čisto ili u mešavini sa dizelom mineralnog porekla koristiti za pokretanje dizel motora. Prefiks bio ukazuje da se dobija od sirovina biljnog porekla (repičino, suncokretovo, sojino, kukuruzno, pamučno, bademovo, palmino, laneno, kokosovo, ulje od kikirikija, kao i svih vrsta masti biljnog porekla) ali se može govoriti i o bio-dizelu (ili ani-dizelu) ako se kao polazna sirovina za proizvodnju mono-alkil estara masnih kiselina koriste masnoće (trigliceridi) životinjskog porekla. Za proizvodnju estara masnih kiselina, kao biološkog goriva, najprihvatljivije je repičino ulje. U prvom delu ovog rada se izlaže istorijski pregled početka proizvodnje biodizela u Svetu, analiziraju instalirani kapaciteti u Evropi za proizvodnju biodizela, njihovo iskorišćenje, zatim se u kratkim crtama predstavlja direktiva Evropske zajednice u pogledu supstitucije dizela mineralnog porekla dobijenog iz nafte sa bio-dizelom do 2010 godine koja je usvojena prošle godine, te na kraju daje pregled standarda koje su do sada usvojile neke države koji su najveći proizvođači biodizela. U drugom članku ove serije biće prikazan razvoj nekih novih tehnologija za proizvodnju biodizela koje se zasnivaju na direktnoj nekatalitičkoj konverziji triglicerida u odgovarajuće estre masnih kiselina u natkritčnim uslovima ili korišćenje lipaza kao katalizatora.

Biodiesel is defined as a fuel which may be used as pure biofuel or at high concentration in mineral oil derivatives, in accordance with specific quality standards for transport applications. The main raw material used for biodiesel production is rapeseed, which contains mono-unsaturated acids (about 60%) and also poly-unsaturated fatty acids (C 18:1 and C 18:3) in a lower quantity, as well as some undesired saturated fatty acids (palmitic and stearic acids). Other raw materials have also been used in research and the industrial production of biodiesel (palm oil, sunflower oil, soybean oil, waste plant oil, animal fats, etc). The historical background of biodiesel production, installed industrial capacities, as well as the Directive of the European Parliament and of the Council (May 2003) regarding the promotion of the use of biofuels or other renewable fuels for transport are discussed in the first part of this article. The second part focuses on some new concepts for the future development of technology for biodiesel production, based on the application of non-catalytic transesterification under supercritical conditions or the use of lipases as an alternative catalyst for this reaction., Biodizel je definisan kao gorivo koje se može kao čisto ili u mešavini sa dizelom mineralnog porekla koristiti za pokretanje dizel motora. Prefiks bio ukazuje da se dobija od sirovina biljnog porekla (repičino, suncokretovo, sojino, kukuruzno, pamučno, bademovo, palmino, laneno, kokosovo, ulje od kikirikija, kao i svih vrsta masti biljnog porekla) ali se može govoriti i o bio-dizelu (ili ani-dizelu) ako se kao polazna sirovina za proizvodnju mono-alkil estara masnih kiselina koriste masnoće (trigliceridi) životinjskog porekla. Za proizvodnju estara masnih kiselina, kao biološkog goriva, najprihvatljivije je repičino ulje. U prvom delu ovog rada se izlaže istorijski pregled početka proizvodnje biodizela u Svetu, analiziraju instalirani kapaciteti u Evropi za proizvodnju biodizela, njihovo iskorišćenje, zatim se u kratkim crtama predstavlja direktiva Evropske zajednice u pogledu supstitucije dizela mineralnog porekla dobijenog iz nafte sa bio-dizelom do 2010 godine koja je usvojena prošle godine, te na kraju daje pregled standarda koje su do sada usvojile neke države koji su najveći proizvođači biodizela. U drugom članku ove serije biće prikazan razvoj nekih novih tehnologija za proizvodnju biodizela koje se zasnivaju na direktnoj nekatalitičkoj konverziji triglicerida u odgovarajuće estre masnih kiselina u natkritčnim uslovima ili korišćenje lipaza kao katalizatora.

Hydrogels are attractive materials for drug delivery applications due to biocompatible, porous structure with the possibility to load and deliver drugs in a controllable manner. In this paper, poly(methacrylic acid) (PMAA) hydrogels are described, which are synthesized by free-radical polymerization, using poly(ethylene glycol) diacrylate (PEGDA) as a crosslinker. Influence of the PEGDA content on hydrogel properties was investigated and compared to commonly used crosslinker - N,N’-methylenebisacrylamide (MBA). The increasing concentration of crosslinkers led to a higher degree of crosslinking, which was demonstrated by a higher degree of conversion, lower swelling capacity, and improved thermal stability and mechanical properties. Also, the PEGDA-crosslinked hydrogels demonstrated a higher degree of crosslinking than the corresponding MBA-crosslinked hydrogels. Potential application of the synthesized hydrogels for controlled drug delivery was investigated by using two model drugs - oxaprozin and ciprofloxacin. In vitro drug release tests indicated that the interactions between drug, polymer and medium have a key influence on the drug release behavior, rather than the swelling rate. Drug release tests in simulated gastrointestinal conditions indicated that PEGDA-crosslinked PMAA hydrogels are suitable for colon-targeted delivery of oxaprozin., Zbog svoje biokompatibilne, visoko-porozne strukture i mogućnosti da nose i kontrolisano otpuštaju lekove, hidrogelovi su našli široku primenu u biomedicini. U ovom radu, hidrogelovi na bazi poli(metakrilne kiseline) (PMK), umreženi pomoću poli(etilen-glikol) diakrilata (PEGDA), sintetisani su metodom toplotno-indukovane slobodno-radikalske polimerizacije. Ispitan je uticaj sadržaja PEGDA na svojstva hidrogelova i upoređen sa uticajem najčešće korišćenog umreživača – N,N' – metilenbisakrilamida (MBA). Povećanje količine oba umreživača dovelo je do većeg stepena umreženja, što je bilo manifestovano povećanjem stepena konverzije monomera, smanjenjem ravnotežnog stepena bubrenja i poboljšanim toplotnim i mehaničkim svojstvima. Takođe, hidrogelovi umreženi pomoću PEGDA pokazali su veći stepen umreženja u odnosu na odgovarajuće hidrogelove umrežene pomoću MBA. Mogućnost primene dobijenih hidrogelova za kontrolisano otpuštanje lekova, ispitivano je korišćenjem dva leka – oksaprozina i ciprofloksacina. In vitro testovi otpuštanja pokazali su da presudan uticaj na kinetiku otpuštanja imaju međusobne interakcije između leka, hidrogela i medijuma, a ne stepen i brzina bubrenja hidrogela. Prema tome, otpuštanje ciprofloksacina je bilo intenzivnije u kiseloj sredini, a oksaprozina u baznoj. Otpuštanje u simuliranim gastrointestinalnim uslovima pokazalo je da su PEGDA-umreženi hidrogelovi pogodni za kontrolisano otpuštanje oksaprozina u debelo crevo.

Hydrogels are attractive materials for drug delivery applications due to biocompatible, porous structure with the possibility to load and deliver drugs in a controllable manner. In this paper, poly(methacrylic acid) (PMAA) hydrogels are described, which are synthesized by free-radical polymerization, using poly(ethylene glycol) diacrylate (PEGDA) as a crosslinker. Influence of the PEGDA content on hydrogel properties was investigated and compared to commonly used crosslinker - N,N’-methylenebisacrylamide (MBA). The increasing concentration of crosslinkers led to a higher degree of crosslinking, which was demonstrated by a higher degree of conversion, lower swelling capacity, and improved thermal stability and mechanical properties. Also, the PEGDA-crosslinked hydrogels demonstrated a higher degree of crosslinking than the corresponding MBA-crosslinked hydrogels. Potential application of the synthesized hydrogels for controlled drug delivery was investigated by using two model drugs - oxaprozin and ciprofloxacin. In vitro drug release tests indicated that the interactions between drug, polymer and medium have a key influence on the drug release behavior, rather than the swelling rate. Drug release tests in simulated gastrointestinal conditions indicated that PEGDA-crosslinked PMAA hydrogels are suitable for colon-targeted delivery of oxaprozin., Zbog svoje biokompatibilne, visoko-porozne strukture i mogućnosti da nose i kontrolisano otpuštaju lekove, hidrogelovi su našli široku primenu u biomedicini. U ovom radu, hidrogelovi na bazi poli(metakrilne kiseline) (PMK), umreženi pomoću poli(etilen-glikol) diakrilata (PEGDA), sintetisani su metodom toplotno-indukovane slobodno-radikalske polimerizacije. Ispitan je uticaj sadržaja PEGDA na svojstva hidrogelova i upoređen sa uticajem najčešće korišćenog umreživača – N,N' – metilenbisakrilamida (MBA). Povećanje količine oba umreživača dovelo je do većeg stepena umreženja, što je bilo manifestovano povećanjem stepena konverzije monomera, smanjenjem ravnotežnog stepena bubrenja i poboljšanim toplotnim i mehaničkim svojstvima. Takođe, hidrogelovi umreženi pomoću PEGDA pokazali su veći stepen umreženja u odnosu na odgovarajuće hidrogelove umrežene pomoću MBA. Mogućnost primene dobijenih hidrogelova za kontrolisano otpuštanje lekova, ispitivano je korišćenjem dva leka – oksaprozina i ciprofloksacina. In vitro testovi otpuštanja pokazali su da presudan uticaj na kinetiku otpuštanja imaju međusobne interakcije između leka, hidrogela i medijuma, a ne stepen i brzina bubrenja hidrogela. Prema tome, otpuštanje ciprofloksacina je bilo intenzivnije u kiseloj sredini, a oksaprozina u baznoj. Otpuštanje u simuliranim gastrointestinalnim uslovima pokazalo je da su PEGDA-umreženi hidrogelovi pogodni za kontrolisano otpuštanje oksaprozina u debelo crevo.

Heat and mass transfer through textile fabrics play a crucial role in achieving optimal thermal comfort perception by a person. The governing properties of textile fabrics by which they influence heat and mass transfer from the human skin to the environment are thermal transport capacity, water vapor permeability, and air permeability. The transfer of liquid moisture through textiles is important for thermal comfort during frequent changes in physical activity or climate. Despite numerous studies on the transport properties of textile materials over the past years, investigation in this subject area is still needed. This special issue includes five articles that offer valuable information on the subject. Both commercial and specially designed textile structures were investigated within the presented studies with the ambitious goal of providing a new understanding of their transport properties. Within the first four papers presented, certain aspects of heat and mass transfer through textile materials were analyzed at the three scale levels: microscopic (fiber type), mesoscopic (yarn geometry and fineness), and macroscopic (fabric porosity) levels. The fifth article dealt with the influence of the seam type and the sewing thread fineness on the transport propert ies of the seamed structure., Sposobnost tekstilnih materijala da prenose toplotu i masu ima ključnu ulogu u obezbeđivanju optimalnog toplotnog komfora korisnika. Toplotna svojstva, propustljivost vazduha i vodene pare predstavljaju osnovne parametre tekstilnih materijala koji definišu njihovu sposobnost da prenose toplotu i masu. Često se kao četvrti parametar tekstilnih materijala ističe sposobnost prenosa tečnosti, koji uslovljava doživljaj toplotnog komfora pri čestim promenama nivoa fizičke aktivnosti i klimatskih uslova okruženja, kada dolazi do vremenskog zaostajanja u termoregulaciji ljudskog organizma. Uprkos brojnim istraživanjima transportnih svojstava tekstilnih materijala sprovedenih poslednjih godina, neophodna su dalja istraživanja u cilju uspostavljanja pouzdanih smernica inženjerskog dizajna odevnih tekstilnih materijala sa zadovoljavajućim svojstvima u pogledu toplotnog komfora. Stoga, ovo specijalno izdanje časopisa Hemijska industrija, koje obuhvata pet radova, ima za cilj da obezbedi dragocene informacije u ovoj oblasti. U okviru predstavljenih istraživanja, ispitivane su komercijalno dostupne ili posebno projektovane tekstilne strukture sa ambicioznim ciljem da se pruže nova saznanja o njihovim transportnim svojstvima. U okviru prva četiri rada razmatran je kompleksan uticaj hijerarhijske strukture tekstilnih materijala na njihova transportna svojstva, pri čemu su obuhvaćeni svi strukturni elementi: vlakna, pređe i tkanine (ili pletenine). Poslednji rad se odnosi na ispitivanje uticaja vrste šava i finoće šivaćeg konca na prenos toplote i mase kroz šavnu konstrukciju.

This article has been published under the category Technical paper instead of Original scientific paper by mistake made by the Editorial Office of the journal Hemijska industrija during the proofreading process. Apologies are offered to authors and readers of the journal Hemijska industrija.

This article has been published under the category Technical paper instead of Original scientific paper by mistake made by the Editorial Office of the journal Hemijska industrija during the proofreading process. Apologies are offered to authors and readers of the journal Hemijska industrija.

This paper presents the results of experiments performed to determine how the quantity of the binder (bentonite) and the parameters of the laboratory roll press affect the quality of the briquettes obtained from limestone powder. These experiments aim to examine the conditions in which limestone briquettes are formed and to determine their use for agricultural purposes. During the experiments various mass fractions of bentonite was added to limestone (from 1 to 10 %), while the force of roll press drums ranged from 2 to 25 kN. The briquettes have been tested by applying scanning electron microscopy (SEM), differential thermal and thermo-gravimetric (DTA/TG) analyses, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Bentonite distribution was found to be uniform within the compact briquette structure. Formation of new compounds was not evidenced. The experiments also demonstrated that during briquetting, limestone properties remain unchanged, the changes are only physical, water solubility is not reduced, mechanical properties (impact resistance, compressive strength and abrasion resistance) are satisfactory by the transport and storage terms if the binder mass fraction is over 5% and the briquetting force exceeds 10kN and finally there is no loss due to wind dispersal during application. The only downside of the "green" briquettes obtained is the time required for their complete disintegration if totally immersed in water.

A perfect dielectric model was incorporated into the OpenFOAM® software and used for investigation and, possibly, improvements of electrohydrodynamic calculations. Two different sets of numerical simulations were analyzed, in which two different fluids were present. The first set was one-dimensional, while in the second, a drop of one fluid was surrounded by the other fluid. It is shown that oscillations and possibly artificial generation of a curl of the electric field strength can be observed at applying certain expressions or calculation strategies, which can be thus abandoned. Usage of dynamic meshes, at least those present in the used software, and of limiters for the gradient of the electric field strength can lead to large numerical errors. It is also shown that usage of certain cell face values could improve the results. An electric Courant number was derived by dimensional analysis, and it could be suggested for future calculations. Conclusions made in this paper are expected to be transferable to other more complicated models., Model idealnog dielektrika je uključen u programski paket OpenFOAM® (OpenFOAM Foundation, UK) i korišćen za ispitivanje i moguće poboljšavanje elektrohidrodinamičkih proračuna. Analizirana su dva različita seta numeričkih simulacija, u kojima su bila modelovana dva različita fluida. Prvi set je bio jednodimenzionalan dok je u drugom setu kap jednog fluida bila okružena drugim fluidom. U radu je pokazano da se određeni izrazi ili strategije izračunavanja mogu odbaciti usled pojave oscilacija i mogućeg veštačkog stvaranja rotora jačine električnog polja. Korišćenje pokretnih mreža, barem onih prisutnih u programskom paketu OpenFOAM®, i limitera za gradijent jačine električnog polja mogu dovesti do velikih numeričkih grešaka. Takođe je pokazano da bi korišćenje određenih vrednosti sa površi ćelija moglo poboljšati rezultate. Izraz za električni Kuronov broj je izveden dimenzionom analizom i mogao bi se preporučiti za buduće proračune. Očekuje se da su zaključci iz ovog rada prenosivi na druge, komplikovanije modele.

A perfect dielectric model was incorporated into the OpenFOAM® software and used for investigation and, possibly, improvements of electrohydrodynamic calculations. Two different sets of numerical simulations were analyzed, in which two different fluids were present. The first set was one-dimensional, while in the second, a drop of one fluid was surrounded by the other fluid. It is shown that oscillations and possibly artificial generation of a curl of the electric field strength can be observed at applying certain expressions or calculation strategies, which can be thus abandoned. Usage of dynamic meshes, at least those present in the used software, and of limiters for the gradient of the electric field strength can lead to large numerical errors. It is also shown that usage of certain cell face values could improve the results. An electric Courant number was derived by dimensional analysis, and it could be suggested for future calculations. Conclusions made in this paper are expected to be transferable to other more complicated models., Model idealnog dielektrika je uključen u programski paket OpenFOAM® (OpenFOAM Foundation, UK) i korišćen za ispitivanje i moguće poboljšavanje elektrohidrodinamičkih proračuna. Analizirana su dva različita seta numeričkih simulacija, u kojima su bila modelovana dva različita fluida. Prvi set je bio jednodimenzionalan dok je u drugom setu kap jednog fluida bila okružena drugim fluidom. U radu je pokazano da se određeni izrazi ili strategije izračunavanja mogu odbaciti usled pojave oscilacija i mogućeg veštačkog stvaranja rotora jačine električnog polja. Korišćenje pokretnih mreža, barem onih prisutnih u programskom paketu OpenFOAM®, i limitera za gradijent jačine električnog polja mogu dovesti do velikih numeričkih grešaka. Takođe je pokazano da bi korišćenje određenih vrednosti sa površi ćelija moglo poboljšati rezultate. Izraz za električni Kuronov broj je izveden dimenzionom analizom i mogao bi se preporučiti za buduće proračune. Očekuje se da su zaključci iz ovog rada prenosivi na druge, komplikovanije modele.

This paper utilizes a stochastic optimization approach using genetic algorithms, for conducting rigorous pipe size sensitivity assessments onto the design of pressure relief networks. By sampling high performance candidates, only the finest options can survive. The pressure relief network system that was investigated in this work was previously reported in literature. The problem is constrained and involves minimizing a cost objective function that evaluates the overall network performance, in which the best pipe size combination should be selected for each segment within the network. The overall goal of this paper was to seek cost-effective designs for the pressure relief piping system by exploring different ranges of pipe diameters that are available for each segment in the network and comparing how the overall design of the system is affected, when the number of pipe size options to select from is varied.

This paper utilizes a stochastic optimization approach using genetic algorithms, for conducting rigorous pipe size sensitivity assessments onto the design of pressure relief networks. By sampling high performance candidates, only the finest options can survive. The pressure relief network system that was investigated in this work was previously reported in literature. The problem is constrained and involves minimizing a cost objective function that evaluates the overall network performance, in which the best pipe size combination should be selected for each segment within the network. The overall goal of this paper was to seek cost-effective designs for the pressure relief piping system by exploring different ranges of pipe diameters that are available for each segment in the network and comparing how the overall design of the system is affected, when the number of pipe size options to select from is varied.

This paper presents microstructural properties and damage behaviour of a vacuum mixed poly(methyl metacrylate) (PMMA) bone cement, during the sliding contact with AISI 316L stainless steel, under micro-loads. Influence of the Ringer's solution on the wear was analysed in comparison to dry contact. The variation of load did not produce any significant change of the wear factor while the increase in the sliding speed induced significant increases in the wear factor, more pronounced in the case of dry sliding. The obtained wear factors were in average higher for the sliding in Ringer's solution than those obtained under dry conditions. Significant fragmentation of the worn tracks, of irregular shapes with broken edges, was observed, slightly more pronounced for the dry contact. Many cavities and voids were formed on the wear track surface, but they did not extend into the bulk material. Higher loads produced more uniform and less fragmented wear tracks. Abrasive, adhesive wear and plastic deformation grooves were observed, as well as fatigue and erosive wear. Fatigue cracks developed in the direction normal to sliding. Network of fine craze cracks was exhibited on the surface of wear tracks, especially pronounced in the case of dry sliding. These results are important since they contribute to understanding the sites of crack initiation, and development mechanisms on the surface of PMMA bone cements, also including synergistic effects of physiological environments pertaining to the non-steady crack and craze behaviour and crack pattern development in PMMA.

In this paper, fabrication of silicon microchannels with integrated obstacles by using 25 wt.% tetramethylammonium hydroxide (TMAH) aqueous solution at the temperature of 80 C is presented and analysed. We studied basic island patterns, which present union of two symmetrical parallelograms with the sides along predetermined crystallographic directions (2. Acute angles of the parallelograms were smaller than 45o. We have derived analytical relations for determining dimensions of the integrated obstacles. The developed etching technique provides reduction of the distance between the obstacles. Before the experiments, we performed simulations of pattern etching based on the level set method and presented evolution of the etched basic patterns for the predetermined crystallographic directions . Combination of basic patterns with sides along the <610> and <100> crystallographic directions is used to fabricate a matrix of two row of silicon obstacles in a microchannel. We obtained a good agreement between the experimental results and simulations. Our results enable simple and cost-effective fabrication of various complex microfluidic silicon platforms with integrated obstacles., U ovom radu je prezentovana i analizirana izrada silicijumskih mikrokanala sa integrisanim preprekama u vodenom rastvoru 25 mas.% tetrametilamonijum hidroksida (TMAH) na temperaturi od 80 oC. Proučavani su osnovni oblici maski koji predstavljaju uniju dva simetrična ostrva u obliku paralelograma čije su stranice duž unapred određenih kristalografskih pravaca (2. Oštri uglovi paralelograma su manji od 45˚. Izvedene su formule za izračunavanje dimenzija integrisanih prepreka. Razvijena je tehnika nagrizanja koja smanjuje rastojanje između prepreka. Pre eksperimenata izvršene su simulacije osnovnih oblika koje se baziraju na metodi implicitno definisanih nivoa (engl. level set method). Prezentovan je razvoj nagrizanih osnovnih oblika maski za unapred određene kristalografske pravce . Kombinacija osnovnih oblika maski čije su stranice duž kristalografskih pravaca <610> i <100> je iskorišćena za izradu dva reda matrice silicijumskih prepreka u mikrokanalu. Dobijeno je dobro slaganje između eksperimenata i simulacija. Dobijeni rezultati omogućavaju jednostavnu i jeftinu izradu različitih kompleksnih mikrofluidnih silicijumskih platformi sa integrisanim preprekama.

In recent decades, probiotic products have been increasingly used to prevent certain gastrointestinal and urogenital disorders, to improve the general condition of the body and as a supplement to pharmacological therapy. They are most often registered as dietary supplements, and less often as drugs in the form of capsules, powders, and solutions. Optimization of technological processes of production and packaging of these products aims to maintain probiotic characteristics while adhering to all criteria during production that ensure quality, bioavailability and optimal therapeutic effects. In this paper, the importance of choosing primary and secondary packaging materials was explored with the aim of preserving the viability of probiotic cells in capsules for two years, i.e. during the shelf life. By comparing the applications of polyvinyl chloride (PVC) and PVC/polyvinylidene chloride/polyethylene blister foils, better protection of probiotic cells was observed by applying the multilayer foil. In addition, in this research, further improvements of probiotic cell protection were achieved by applying a secondary packing-flow pack bag with inert gas for storing multilayered blisters., Probiotski proizvodi se poslednjih decenija sve više koriste za prevenciju određenih gastrointestinalnih i urogenitalnih poremećaja, za poboljšanje opšteg stanja organi-zma i kao dopuna farmakološke terapije. Najčešće su registrovani kao dijetetski suple-menti, a ređe kao lekovi u obliku kapsula, praškova i rastvora. Optimizacija tehnoloških procesa proizvodnje i pakovanje ovih proizvoda ima za cilj održavanje probiotskih karakteristika uz istovremeno pridržavanje svih kriterijuma u toku proizvodnje koji osiguravaju kvalitet, biološku raspoloživost i optimalno terapijsko dejstvo U ovom radu razmatran je značaj izbora primarnog i sekundarnog materijala za pakovanje sa ciljem očuvanja vijabilnost probiotskih ćelija u kapsulama tokom dve godine tj. tokom roka upotrebe. Poređenjem primene PVC (polivinil hlorid) i PVC/poliviniliden hlorid/poli-etilen (PVC/PVdC/PE) blister folija uočena je bolja zaštita probotskih ćelija od kiseonika i vlage primenom višeslojene folije. Dodatne efekte zaštite probiotskih ćelija u ovom radu potvrdjene su primenom dodatne zaštite blistera upotrebom sekundarnog pakovanja (engl. flow pack) kesice sa inertni gasom.

In this paper, fabrication of silicon microchannels with integrated obstacles by using 25 wt.% tetramethylammonium hydroxide (TMAH) aqueous solution at the temperature of 80 C is presented and analysed. We studied basic island patterns, which present union of two symmetrical parallelograms with the sides along predetermined crystallographic directions (2. Acute angles of the parallelograms were smaller than 45o. We have derived analytical relations for determining dimensions of the integrated obstacles. The developed etching technique provides reduction of the distance between the obstacles. Before the experiments, we performed simulations of pattern etching based on the level set method and presented evolution of the etched basic patterns for the predetermined crystallographic directions . Combination of basic patterns with sides along the <610> and <100> crystallographic directions is used to fabricate a matrix of two row of silicon obstacles in a microchannel. We obtained a good agreement between the experimental results and simulations. Our results enable simple and cost-effective fabrication of various complex microfluidic silicon platforms with integrated obstacles., U ovom radu je prezentovana i analizirana izrada silicijumskih mikrokanala sa integrisanim preprekama u vodenom rastvoru 25 mas.% tetrametilamonijum hidroksida (TMAH) na temperaturi od 80 oC. Proučavani su osnovni oblici maski koji predstavljaju uniju dva simetrična ostrva u obliku paralelograma čije su stranice duž unapred određenih kristalografskih pravaca (2. Oštri uglovi paralelograma su manji od 45˚. Izvedene su formule za izračunavanje dimenzija integrisanih prepreka. Razvijena je tehnika nagrizanja koja smanjuje rastojanje između prepreka. Pre eksperimenata izvršene su simulacije osnovnih oblika koje se baziraju na metodi implicitno definisanih nivoa (engl. level set method). Prezentovan je razvoj nagrizanih osnovnih oblika maski za unapred određene kristalografske pravce . Kombinacija osnovnih oblika maski čije su stranice duž kristalografskih pravaca <610> i <100> je iskorišćena za izradu dva reda matrice silicijumskih prepreka u mikrokanalu. Dobijeno je dobro slaganje između eksperimenata i simulacija. Dobijeni rezultati omogućavaju jednostavnu i jeftinu izradu različitih kompleksnih mikrofluidnih silicijumskih platformi sa integrisanim preprekama.

The aim of this paper is to present image analysis as a useful technique for fast, reliable and non-destructive detection of dimensional and structural changes in polymers. The possibility of applying image analysis was demonstrated in the case of solvent-induced crystallization of poly(ethylene terephthalate) (PET) containers filled with commonly used organic solvents: chlorobenzene, isophorone, xylene, Espesol, Shellsol A 100, Solvesso 150, propylene glycol, glycerin and water and subjected to the storage stability test at 54 degrees C for 14 days (CIPAC 1-MT 46.1.3). In addition, the obtained results were analyzed using one-step analysis of variance (ANOVA) combined with the Duncan's statistical test (p lt 0.05). According to the achieved results, three main impacts of the presented paper could be distinguished: 1) dimensional and transparency changes could be precisely followed by image analysis in both following cases: for small changes in water, as well as for significant ones in chlorobenzene; 2) a correlation between the changes in the degree of crystallinity and transparency could be obtained without the continuous material testing by DSC; 3) image analysis is potentially applicable for assessment of other crystalline polymers.

The aim of this paper is to present image analysis as a useful technique for fast, reliable and non-destructive detection of dimensional and structural changes in polymers. The possibility of applying image analysis was demonstrated in the case of solvent-induced crystallization of poly(ethylene terephthalate) (PET) containers filled with commonly used organic solvents: chlorobenzene, isophorone, xylene, Espesol, Shellsol A 100, Solvesso 150, propylene glycol, glycerin and water and subjected to the storage stability test at 54 degrees C for 14 days (CIPAC 1-MT 46.1.3). In addition, the obtained results were analyzed using one-step analysis of variance (ANOVA) combined with the Duncan's statistical test (p lt 0.05). According to the achieved results, three main impacts of the presented paper could be distinguished: 1) dimensional and transparency changes could be precisely followed by image analysis in both following cases: for small changes in water, as well as for significant ones in chlorobenzene; 2) a correlation between the changes in the degree of crystallinity and transparency could be obtained without the continuous material testing by DSC; 3) image analysis is potentially applicable for assessment of other crystalline polymers.

The aim of this paper is to present image analysis as a useful technique for fast, reliable and non-destructive detection of dimensional and structural changes in polymers. The possibility of applying image analysis was demonstrated in the case of solvent-induced crystallization of poly(ethylene terephthalate) (PET) containers filled with commonly used organic solvents: chlorobenzene, isophorone, xylene, Espesol, Shellsol A 100, Solvesso 150, propylene glycol, glycerin and water and subjected to the storage stability test at 54 degrees C for 14 days (CIPAC 1-MT 46.1.3). In addition, the obtained results were analyzed using one-step analysis of variance (ANOVA) combined with the Duncan's statistical test (p lt 0.05). According to the achieved results, three main impacts of the presented paper could be distinguished: 1) dimensional and transparency changes could be precisely followed by image analysis in both following cases: for small changes in water, as well as for significant ones in chlorobenzene; 2) a correlation between the changes in the degree of crystallinity and transparency could be obtained without the continuous material testing by DSC; 3) image analysis is potentially applicable for assessment of other crystalline polymers.

One of the important tasks of evaluating the integrity of mechanical process elements and structures is to determine the local mechanical properties. In this paper, experimental and numerical analyses of the mechanical behavior of an output inter-heater tube, made of 12H1MF heat-resistant steel, was performed after 200,000 h of exploitation. During exploitation, the tube was exposed to various mechanisms of damage including gas corrosion. The tube was cut from a pipe system during reparations of a thermal power plant, and then cold-deformed by bending to obtain a U-bend tube, which was then used in the experiment. For this purpose, a specimen holder made of structural steel S235 was specifically designed to test such a sample. The U-bend tube was then exposed to the external compressive load during the experiment. Experimental research was based on the application of the 3D digital image correlation (DIC), while a finite element method (FEM) was applied in numerical simulation performed by using the Abaqus software package. The 3D DIC is an optical and contactless experimental method that allows measurements of displacement fields and deformations of geometrically complex structures. The Aramis system was used for the experimental analysis as well as for verification of the numerical model. During the experiment, the von Mises strain field was measured at the top of the U-bend tube, in the tightening zone, as it represents a critical place for crack initiation and propagation during the work of an inter-heater. Based on the obtained results and a comparative analysis of experimental and numerical values of the von Mises strain field at the U-bend tube, deviation of the model predictions of about 18 % was determined. The FEM predicted smaller values of the von Mises strain field compared to the DIC method. This is the result of an incomplete geometry applied in the model due to deformation that occurred in the bend zone of the U-bend tube, loss of material and the tu

Development of drugs is a complex, time- and cost-consuming process due to the lack of standardized and reliable characterization techniques and models. Traditionally, drug screening is based on in vitro analysis using two-dimensional (2D) cell cultures followed by in vivo animal testing. Unfortunately, application of the obtained results to humans in about 90 % of cases fails. Therefore, it is important to develop and improve cell-based systems that can mimic the in vivo-like conditions to provide more reliable results. In this paper, we present development and validation of a novel, user-friendly perfusion bioreactor system for single use aimed for cancer research, drug screening, anti-cancer drug response studies, biomaterial characterization, and tissue engineering. Simple design of the perfusion bioreactor provides direct medium flow at physiological velocities (100-250 mu m s(-1)) through samples of different sizes and shapes. Biocompatibility of the bioreactor was confirmed in short term cultivation studies of cervical carcinoma SiHa cells immobilized in alginate microfibers under continuous medium flow. The results have shown preserved cell viability indicating that the perfusion bioreactor in conjunction with alginate hydrogels as cell carriers could be potentially used as a tool for controlled anti-cancer drug screening in a 3D environment.

The paper presents static and dynamic tests of carbon/epoxy composite materials with fiber orientation at 0 degrees/90 degrees and +/- 45 degrees. The main tensile properties were determined as a basis for subsequent dynamic tests, in which permanent dynamic strength, crack growth, and crack growth rate in the material due to the action of fatigue load were assessed. Comparisons were made regarding the structure of the tested specimens. Samples were obtained from prepregs with a specific density of 1600 kg/m(3). The tests were performed at room temperature. Scanning electron microscopy (SEM) was used to analyze the damage in the material during these tests, the mechanisms of their further damage progression and, the impact on the growth and growth rate of the initial crack in the material. The analysis of numerical results and micromechanical analysis confirmed the dominant role of the reinforcing structural element in the material in all performed tests. The obtained results are of great importance in the application of composite materials of such structures under different operating conditions and load regimes.

One of the important tasks of evaluating the integrity of mechanical process elements and structures is to determine the local mechanical properties. In this paper, experimental and numerical analyses of the mechanical behavior of an output inter-heater tube, made of 12H1MF heat-resistant steel, was performed after 200,000 h of exploitation. During exploitation, the tube was exposed to various mechanisms of damage including gas corrosion. The tube was cut from a pipe system during reparations of a thermal power plant, and then cold-deformed by bending to obtain a U-bend tube, which was then used in the experiment. For this purpose, a specimen holder made of structural steel S235 was specifically designed to test such a sample. The U-bend tube was then exposed to the external compressive load during the experiment. Experimental research was based on the application of the 3D digital image correlation (DIC), while a finite element method (FEM) was applied in numerical simulation performed by using the Abaqus software package. The 3D DIC is an optical and contactless experimental method that allows measurements of displacement fields and deformations of geometrically complex structures. The Aramis system was used for the experimental analysis as well as for verification of the numerical model. During the experiment, the von Mises strain field was measured at the top of the U-bend tube, in the tightening zone, as it represents a critical place for crack initiation and propagation during the work of an inter-heater. Based on the obtained results and a comparative analysis of experimental and numerical values of the von Mises strain field at the U-bend tube, deviation of the model predictions of about 18 % was determined. The FEM predicted smaller values of the von Mises strain field compared to the DIC method. This is the result of an incomplete geometry applied in the model due to deformation that occurred in the bend zone of the U-bend tube, loss of material and the tu, Jedan od važnih zadataka procene integriteta mašinskih elemenata i konstrukcija je određivanje lokalnih mehaničkih svojstava. U ovom radu izvršeno je eksperimentalno i numeričko ispitivanje mehaničkih svojstava cevi, izlaznog međupregrejača pare, izrađenog od toplotnopostojanog čelika 12H1MF, nakon 200.000 h rada. Cev izlaznog međupregrejača pare je isečena iz cevnog sistema tokom remonta termoelektrane, a potom hladno deformisana savijanjem, u cilju dobijanja cevnog luka, za potrebe eksperimenta. Namenski je konstruisan držač za ispitivanje takvog uzorka. Eksperimentalno istraživanje je bazirano na primeni 3D metode korelacije digitalnih slika, dok je metoda konačnih elemenata primenjena u numeričkoj simulaciji. Metoda 3D korelacije digitalnih slika predstavlja optičku i beskontaktnu eksperimentalnu metodu koja omogućava merenje polja pomeranja i deformacija geometrijski kompleksnih struktura. Za eksperimentalnu analizu kao i verifikaciju numeričkog modela korišćen je sistem Aramis, baziran na metodi korelacije digitalnih slika. Na osnovu dobijenih rezultata i uporedne analize eksperimentalnih i numeričkih vrednosti, koje se odnose na fon Mizesove deformacije na temenu cevnog luka, javlja se odstupanje od oko 18%. Ovo odstupanje nastaje kao rezultat korišćenih metoda koje imaju bitne razlike u njihovim početnim uslovima ispitivanja.

Oxidized starch, an additive used in paper manufacturing and products for construction industry, is usually produced using harmful oxidant, such as hypochlorites or periodates. In this study, a simple and efficient eco-friendly laboratory and industrial procedures for starch oxidation were developed. The procedure involves application of small amounts of more environmentally friendly oxidant, hydrogen peroxide, a novel special metal complex catalyst such as copper(II) citrate and copper(II) ricinoleate and biobased plasticizers. Optimization procedure, with respect to the quantity of hydrogen peroxide and temperature in the presence of iron(II) sulphate catalyst, was performed by using the response surface methodology. Comparative analysis of the use of the other catalysts that is copper(II) sulphate, copper(II) citrate and copper(II) ricinoleate, indicated copper(II) citrate as the catalyst of choice. Improvement of starch is achieved using three plasticizers: ricinoleic acid (RA), diisopropyl tartarate, as well as epoxidized soybean, linseed and sunflower oils. The effects of hydrogen peroxide and catalyst concentrations, as well as the reaction temperature in the presence of naturally based plasticizers on the physicochemical, thermal and morphological properties of oxidized starch are presented. According to the results obtained in initial experiments, the optimal industrial process is based on the use of copper(II) citrate (0.1 %) as a catalyst and RA (3 %) as a plasticizer.

Adsorption processes are widely used in different technological areas and industry sectors, thus continuously attracting attention in the scientific research and publications. Design and scale-up of these processes are essentially based on the knowledge and understanding of the adsorption kinetics and mechanism. Adsorption kinetics is usually modeled by using several well-known models including the pseudo-first and pseudo-second order models, the Elovich equation, and the intra-particle diffusion based models. However, in the scientific literature there are a significant number of cases with the inappropriate use of these models, utilization of erroneous expressions, and incorrect interpretation of the obtained results. This paper is especially focused on applications of the pseudo-second order, intra-particle diffusion and the Weber-Morris models, which are illustrated with typical examples. Finally, general recommendations for selection of the appropriate kinetic model and model assumptions, data regression analysis, and evaluation and presentation of the obtained results are outlined.

Development of drugs is a complex, time- and cost-consuming process due to the lack of standardized and reliable characterization techniques and models. Traditionally, drug screening is based on in vitro analysis using two-dimensional (2D) cell cultures followed by in vivo animal testing. Unfortunately, application of the obtained results to humans in about 90 % of cases fails. Therefore, it is important to develop and improve cell-based systems that can mimic the in vivo-like conditions to provide more reliable results. In this paper, we present development and validation of a novel, user-friendly perfusion bioreactor system for single use aimed for cancer research, drug screening, anti-cancer drug response studies, biomaterial characterization, and tissue engineering. Simple design of the perfusion bioreactor provides direct medium flow at physiological velocities (100-250 mu m s(-1)) through samples of different sizes and shapes. Biocompatibility of the bioreactor was confirmed in short term cultivation studies of cervical carcinoma SiHa cells immobilized in alginate microfibers under continuous medium flow. The results have shown preserved cell viability indicating that the perfusion bioreactor in conjunction with alginate hydrogels as cell carriers could be potentially used as a tool for controlled anti-cancer drug screening in a 3D environment.

The paper presents static and dynamic tests of carbon/epoxy composite materials with fiber orientation at 0 degrees/90 degrees and +/- 45 degrees. The main tensile properties were determined as a basis for subsequent dynamic tests, in which permanent dynamic strength, crack growth, and crack growth rate in the material due to the action of fatigue load were assessed. Comparisons were made regarding the structure of the tested specimens. Samples were obtained from prepregs with a specific density of 1600 kg/m(3). The tests were performed at room temperature. Scanning electron microscopy (SEM) was used to analyze the damage in the material during these tests, the mechanisms of their further damage progression and, the impact on the growth and growth rate of the initial crack in the material. The analysis of numerical results and micromechanical analysis confirmed the dominant role of the reinforcing structural element in the material in all performed tests. The obtained results are of great importance in the application of composite materials of such structures under different operating conditions and load regimes.

The importance of biopharmaceutical considerations in pharmaceutical development and drug characterization has been well recognized both by pharmaceutical industry and regulatory authorities as a tool to establish predictive relationships between drug product quality attributes (in vitro data) and its clinical performance (in vivo data). In the present paper, contemporary biopharmaceutics toolkit including in vivo predictive dissolution testing, Biopharmaceutics Classification System, physiologically based pharmacokinetic and biopharmaceutics modeling and simulation, in vitro-in vivo correlation and biowaiver, are reviewed with regards to relevant general principles and applicability. The recently introduced innovative strategy for patient-centric drug development using an integrated systems approach grounded in fundamental biopharmaceutics concepts, clinical insights and therapeutic drug delivery targets, described as Biopharmaceutics Risk Assessment Roadmap (BioRAM) is also presented. Further development in the field will benefit from joint efforts and exchange of knowledge and experiences between pharmaceutical industry and regulatory authorities for the common goal to accelerate development of effective and safe drug products designed in accordance with patients’ needs and expectations., Značaj biofarmaceutskih razmatranja u razvoju i karakterizaciji lekova s ciljem uspostavljanja korelacije i mogućnosti predviđanja odnosa između in vitropodataka, odnosno karakteristika kvaliteta leka i njegovog in vivoponašanja/kliničkog učinka, prepoznata je kako od strane farmaceutske industrije, tako i od strane odgovarajućih regulatornih tela. U radu je dat pregled savremenih biofarmaceutskih alata,uključujući prediktivno ispitivanje brzine rastvaranja lekovite supstance iz farmaceutskog oblika leka, Biofarmaceutski sistem klasifikacije, fiziološki zasnovano farmakokinetičko i biofarmaceutsko modelovanje i simulacije, in vitro-in vivokorelaciju i mogućnost izostavljanja in vivostudija bioekvivalencije (engl. biowaiver) iz aspekta opštih principa i mogućnosti primene u razvoju i karakterizaciji lekova.Predstavljena je i nedavno osmišljena inovativna strategija za razvoj leka usmerena ka pacijentu, uz primenu integrisanog sistemskog pristupa zasnovanog na osnovnim biofarmaceutskim konceptima, uvidu u kliničku situaciju i definisanim terapijskim ciljevima označena kao Plan aktivnosti za procenu biofarmaceutskog rizika (engl. Biopharmaceutics Risk Assessment Roadmap, BioRAM). Očekuje se da će daljem razvoju u ovoj oblasti najviše doprineti združene aktivnosti i razmena znanja i iskustava između farmaceutskih kompanija i regulatornih agencija sa zajedničkim ciljem da se ubrza razvoj efikasnih i bezbednihlekova dizajniranih u skladu sa potrebama i očekivanjima pacijenata.

Development of drugs is a complex, time- and cost-consuming process due to the lack of standardized and reliable characterization techniques and models. Traditionally, drug screening is based on in vitro analysis using two-dimensional (2D) cell cultures followed by in vivo animal testing. Unfortunately, application of the obtained results to humans in about 90 % of cases fails. Therefore, it is important to develop and improve cell-based systems that can mimic the in vivo-like conditions to provide more reliable results. In this paper, we present development and validation of a novel, user-friendly perfusion bioreactor system for single use aimed for cancer research, drug screening, anti-cancer drug response studies, biomaterial characterization, and tissue engineering. Simple design of the perfusion bioreactor provides direct medium flow at physiological velocities (100-250 mu m s(-1)) through samples of different sizes and shapes. Biocompatibility of the bioreactor was confirmed in short term cultivation studies of cervical carcinoma SiHa cells immobilized in alginate microfibers under continuous medium flow. The results have shown preserved cell viability indicating that the perfusion bioreactor in conjunction with alginate hydrogels as cell carriers could be potentially used as a tool for controlled anti-cancer drug screening in a 3D environment.

Oxidized starch, an additive used in paper manufacturing and products for construction industry, is usually produced using harmful oxidant, such as hypochlorites or periodates. In this study, a simple and efficient eco-friendly laboratory and industrial procedures for starch oxidation were developed. The procedure involves application of small amounts of more environmentally friendly oxidant, hydrogen peroxide, a novel special metal complex catalyst such as copper(II) citrate and copper(II) ricinoleate and biobased plasticizers. Optimization procedure, with respect to the quantity of hydrogen peroxide and temperature in the presence of iron(II) sulphate catalyst, was performed by using the response surface methodology. Comparative analysis of the use of the other catalysts that is copper(II) sulphate, copper(II) citrate and copper(II) ricinoleate, indicated copper(II) citrate as the catalyst of choice. Improvement of starch is achieved using three plasticizers: ricinoleic acid (RA), diisopropyl tartarate, as well as epoxidized soybean, linseed and sunflower oils. The effects of hydrogen peroxide and catalyst concentrations, as well as the reaction temperature in the presence of naturally based plasticizers on the physicochemical, thermal and morphological properties of oxidized starch are presented. According to the results obtained in initial experiments, the optimal industrial process is based on the use of copper(II) citrate (0.1 %) as a catalyst and RA (3 %) as a plasticizer.

The paper presents static and dynamic tests of carbon/epoxy composite materials with fiber orientation at 0 degrees/90 degrees and +/- 45 degrees. The main tensile properties were determined as a basis for subsequent dynamic tests, in which permanent dynamic strength, crack growth, and crack growth rate in the material due to the action of fatigue load were assessed. Comparisons were made regarding the structure of the tested specimens. Samples were obtained from prepregs with a specific density of 1600 kg/m(3). The tests were performed at room temperature. Scanning electron microscopy (SEM) was used to analyze the damage in the material during these tests, the mechanisms of their further damage progression and, the impact on the growth and growth rate of the initial crack in the material. The analysis of numerical results and micromechanical analysis confirmed the dominant role of the reinforcing structural element in the material in all performed tests. The obtained results are of great importance in the application of composite materials of such structures under different operating conditions and load regimes.

Adsorption processes are widely used in different technological areas and industry sectors, thus continuously attracting attention in the scientific research and publications. Design and scale-up of these processes are essentially based on the knowledge and understanding of the adsorption kinetics and mechanism. Adsorption kinetics is usually modeled by using several well-known models including the pseudo-first and pseudo-second order models, the Elovich equation, and the intra-particle diffusion based models. However, in the scientific literature there are a significant number of cases with the inappropriate use of these models, utilization of erroneous expressions, and incorrect interpretation of the obtained results. This paper is especially focused on applications of the pseudo-second order, intra-particle diffusion and the Weber-Morris models, which are illustrated with typical examples. Finally, general recommendations for selection of the appropriate kinetic model and model assumptions, data regression analysis, and evaluation and presentation of the obtained results are outlined.

Oxidized starch, an additive used in paper manufacturing and products for construction industry, is usually produced using harmful oxidant, such as hypochlorites or periodates. In this study, a simple and efficient eco-friendly laboratory and industrial procedures for starch oxidation were developed. The procedure involves application of small amounts of more environmentally friendly oxidant, hydrogen peroxide, a novel special metal complex catalyst such as copper(II) citrate and copper(II) ricinoleate and biobased plasticizers. Optimization procedure, with respect to the quantity of hydrogen peroxide and temperature in the presence of iron(II) sulphate catalyst, was performed by using the response surface methodology. Comparative analysis of the use of the other catalysts that is copper(II) sulphate, copper(II) citrate and copper(II) ricinoleate, indicated copper(II) citrate as the catalyst of choice. Improvement of starch is achieved using three plasticizers: ricinoleic acid (RA), diisopropyl tartarate, as well as epoxidized soybean, linseed and sunflower oils. The effects of hydrogen peroxide and catalyst concentrations, as well as the reaction temperature in the presence of naturally based plasticizers on the physicochemical, thermal and morphological properties of oxidized starch are presented. According to the results obtained in initial experiments, the optimal industrial process is based on the use of copper(II) citrate (0.1 %) as a catalyst and RA (3 %) as a plasticizer.

Development of drugs is a complex, time- and cost-consuming process due to the lack of standardized and reliable characterization techniques and models. Traditionally, drug screening is based on in vitro analysis using two-dimensional (2D) cell cultures followed by in vivo animal testing. Unfortunately, application of the obtained results to humans in about 90 % of cases fails. Therefore, it is important to develop and improve cell-based systems that can mimic the in vivo-like conditions to provide more reliable results. In this paper, we present development and validation of a novel, user-friendly perfusion bioreactor system for single use aimed for cancer research, drug screening, anti-cancer drug response studies, biomaterial characterization, and tissue engineering. Simple design of the perfusion bioreactor provides direct medium flow at physiological velocities (100-250 mu m s(-1)) through samples of different sizes and shapes. Biocompatibility of the bioreactor was confirmed in short term cultivation studies of cervical carcinoma SiHa cells immobilized in alginate microfibers under continuous medium flow. The results have shown preserved cell viability indicating that the perfusion bioreactor in conjunction with alginate hydrogels as cell carriers could be potentially used as a tool for controlled anti-cancer drug screening in a 3D environment.

The paper presents static and dynamic tests of carbon/epoxy composite materials with fiber orientation at 0 degrees/90 degrees and +/- 45 degrees. The main tensile properties were determined as a basis for subsequent dynamic tests, in which permanent dynamic strength, crack growth, and crack growth rate in the material due to the action of fatigue load were assessed. Comparisons were made regarding the structure of the tested specimens. Samples were obtained from prepregs with a specific density of 1600 kg/m(3). The tests were performed at room temperature. Scanning electron microscopy (SEM) was used to analyze the damage in the material during these tests, the mechanisms of their further damage progression and, the impact on the growth and growth rate of the initial crack in the material. The analysis of numerical results and micromechanical analysis confirmed the dominant role of the reinforcing structural element in the material in all performed tests. The obtained results are of great importance in the application of composite materials of such structures under different operating conditions and load regimes.

One of the important tasks of evaluating the integrity of mechanical process elements and structures is to determine the local mechanical properties. In this paper, experimental and numerical analyses of the mechanical behavior of an output inter-heater tube, made of 12H1MF heat-resistant steel, was performed after 200,000 h of exploitation. During exploitation, the tube was exposed to various mechanisms of damage including gas corrosion. The tube was cut from a pipe system during reparations of a thermal power plant, and then cold-deformed by bending to obtain a U-bend tube, which was then used in the experiment. For this purpose, a specimen holder made of structural steel S235 was specifically designed to test such a sample. The U-bend tube was then exposed to the external compressive load during the experiment. Experimental research was based on the application of the 3D digital image correlation (DIC), while a finite element method (FEM) was applied in numerical simulation performed by using the Abaqus software package. The 3D DIC is an optical and contactless experimental method that allows measurements of displacement fields and deformations of geometrically complex structures. The Aramis system was used for the experimental analysis as well as for verification of the numerical model. During the experiment, the von Mises strain field was measured at the top of the U-bend tube, in the tightening zone, as it represents a critical place for crack initiation and propagation during the work of an inter-heater. Based on the obtained results and a comparative analysis of experimental and numerical values of the von Mises strain field at the U-bend tube, deviation of the model predictions of about 18 % was determined. The FEM predicted smaller values of the von Mises strain field compared to the DIC method. This is the result of an incomplete geometry applied in the model due to deformation that occurred in the bend zone of the U-bend tube, loss of material and the tu, Jedan od važnih zadataka procene integriteta mašinskih elemenata i konstrukcija je određivanje lokalnih mehaničkih svojstava. U ovom radu izvršeno je eksperimentalno i numeričko ispitivanje mehaničkih svojstava cevi, izlaznog međupregrejača pare, izrađenog od toplotnopostojanog čelika 12H1MF, nakon 200.000 h rada. Cev izlaznog međupregrejača pare je isečena iz cevnog sistema tokom remonta termoelektrane, a potom hladno deformisana savijanjem, u cilju dobijanja cevnog luka, za potrebe eksperimenta. Namenski je konstruisan držač za ispitivanje takvog uzorka. Eksperimentalno istraživanje je bazirano na primeni 3D metode korelacije digitalnih slika, dok je metoda konačnih elemenata primenjena u numeričkoj simulaciji. Metoda 3D korelacije digitalnih slika predstavlja optičku i beskontaktnu eksperimentalnu metodu koja omogućava merenje polja pomeranja i deformacija geometrijski kompleksnih struktura. Za eksperimentalnu analizu kao i verifikaciju numeričkog modela korišćen je sistem Aramis, baziran na metodi korelacije digitalnih slika. Na osnovu dobijenih rezultata i uporedne analize eksperimentalnih i numeričkih vrednosti, koje se odnose na fon Mizesove deformacije na temenu cevnog luka, javlja se odstupanje od oko 18%. Ovo odstupanje nastaje kao rezultat korišćenih metoda koje imaju bitne razlike u njihovim početnim uslovima ispitivanja.

The paper presents static and dynamic tests of carbon/epoxy composite materials with fiber orientation at 0 degrees/90 degrees and +/- 45 degrees. The main tensile properties were determined as a basis for subsequent dynamic tests, in which permanent dynamic strength, crack growth, and crack growth rate in the material due to the action of fatigue load were assessed. Comparisons were made regarding the structure of the tested specimens. Samples were obtained from prepregs with a specific density of 1600 kg/m(3). The tests were performed at room temperature. Scanning electron microscopy (SEM) was used to analyze the damage in the material during these tests, the mechanisms of their further damage progression and, the impact on the growth and growth rate of the initial crack in the material. The analysis of numerical results and micromechanical analysis confirmed the dominant role of the reinforcing structural element in the material in all performed tests. The obtained results are of great importance in the application of composite materials of such structures under different operating conditions and load regimes.

Complex structure experimental analysis has always been a huge challenge for researchers. Conventional experimental methods (e.g., strain gauges) give only limited data sets regarding measurement on critical areas with high geometrical discontinuities. A 3D Digital Image Correlation method is an optical method that overcomes the limitations of conventional methods and enables full-field displacement and strain measurement of geometrically complex structures. System Aramis, based on Digital Image Correlation method, is used for experimental analysis and numerical model verification in this paper. Investigated complex structure is sphere/cylinder junction on globe valve housing subjected to axial loading. The highest experimentally measured von Mises strain values around 0.15% are recorded on cylinder/sphere intersection. Von Mises strain values on cylindrical and spherical part are several times smaller than on intersection itself. It is important to emphasize that, to the authors' best knowledge, this is the first paper showing experimental results of 3D full and strain field of geometrically complex structure (sphere/cylinder intersection) on the intersection itself on pressure equipment. It is proven that 3D Digital Image Correlation method is fast and versatile method for recording strain during loading of complex structures.

Complex structure experimental analysis has always been a huge challenge for researchers. Conventional experimental methods (e.g., strain gauges) give only limited data sets regarding measurement on critical areas with high geometrical discontinuities. A 3D Digital Image Correlation method is an optical method that overcomes the limitations of conventional methods and enables full-field displacement and strain measurement of geometrically complex structures. System Aramis, based on Digital Image Correlation method, is used for experimental analysis and numerical model verification in this paper. Investigated complex structure is sphere/cylinder junction on globe valve housing subjected to axial loading. The highest experimentally measured von Mises strain values around 0.15% are recorded on cylinder/sphere intersection. Von Mises strain values on cylindrical and spherical part are several times smaller than on intersection itself. It is important to emphasize that, to the authors best knowledge, this is the first paper showing experimental results of 3D full and strain field of geometrically complex structure (sphere/cylinder intersection) on the intersection itself on pressure equipment. It is proven that 3D Digital Image Correlation method is fast and versatile method for recording strain during loading of complex structures.

Complex structure experimental analysis has always been a huge challenge for researchers. Conventional experimental methods (e.g., strain gauges) give only limited data sets regarding measurement on critical areas with high geometrical discontinuities. A 3D Digital Image Correlation method is an optical method that overcomes the limitations of conventional methods and enables full-field displacement and strain measurement of geometrically complex structures. System Aramis, based on Digital Image Correlation method, is used for experimental analysis and numerical model verification in this paper. Investigated complex structure is sphere/cylinder junction on globe valve housing subjected to axial loading. The highest experimentally measured von Mises strain values around 0.15% are recorded on cylinder/sphere intersection. Von Mises strain values on cylindrical and spherical part are several times smaller than on intersection itself. It is important to emphasize that, to the authors best knowledge, this is the first paper showing experimental results of 3D full and strain field of geometrically complex structure (sphere/cylinder intersection) on the intersection itself on pressure equipment. It is proven that 3D Digital Image Correlation method is fast and versatile method for recording strain during loading of complex structures.

Industrial wastewater contains recalcitrant organic compounds with a very complex chemical structure, built of molecules with long chains of carbon atoms and attached different functional groups. Chemical or biological treatments used for removal of these compounds are being replaced with more efficient non-commercial wastewater treatments. Advanced oxidation processes overcome limitations of conventional methods regarding formation of by-products during degradation of recalcitrant organic compounds. The Fenton process, or use of the Fenton's reagent, has became one of the most utilized processes due to simplicity, economy and accessible amounts of ferrous iron and hydrogen-peroxide, which are used in the process. In specific, the Fenton's reagent is a catalytic-oxidative mixture of these two components. The ferrous iron Fe2+ initiates and catalyzes decomposition of H2O2, resulting in generation of hydroxyl radicals, which are the main radical species in the process able to detoxify several organic pollutants by oxidation. In addition, other mechanisms besides formation of hydroxyl radicals may occur during the Fenton process and participate in degradation of target pollutants. Generally, the treatment efficiency relies upon the physical and chemical properties of target pollutants and the process operating conditions. The main disadvantage of the Fenton process is production of sludge formed by iron hydroxide at certain pH values. An alternative solution for this problem is application of this process in fluidized bed reactors. This paper presents an overview of Fenton and photo-Fenton processes in dispersed systems for removal of different industrial wastewater pollutants. The most important process parameters, required for efficient degradation of recalcitrant organic compounds are also described, such as the catalyst type, pH value, temperature, H2O2 concentration and retention time. Strict control of Fenton process parameters in fluidized bed reactors at desire

This paper presents influence of the type of carbon nanotube functionalization on properties of poly(L-lactide) (PLLA) based nanocomposite materials. For this purpose surface modifications of multi-walled carbon nanotubes (MWCNTs) were performed by chemical and irradiation techniques, while thermo gravimetric analysis, UV-Visible and Fourier-transform infrared (FT-IR) spectroscopies confirmed successful covalent functionalization. Series of PLLA bionanocom-posites with different contents of functionalized MWCNTs (0.7; 1.6; 2.1 wt%), were synthesized via ring-opening solution polymerisation of L-lactide. FT-IR analysis confirmed that grafting of L-lactide, under controlled condition, is possible to perform starting from the surface of functionalized MWCNTs. From differential scanning calorimetry results it was concluded that even low contents of chemically and irradiation functionalized MWCNTs had a significant effect on thermal properties of the prepared nanocomposites, raising the values of melting and glass transition temperatures. Thermogravimetric analysis (TGA) has shown that the degradation onset temperature for composites with chemically functionalized MWCNTs, was much higher than that for the neat poly(L-lactide) sample and composites with irradiation functionalized MWCNTs. Morphology studies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that poly(L-lactide) covered surfaces and separated functionalized MWCNTs. Good dispersion of carbon nanotubes in polymer matrix enabled conductivity of synthesized materials, as determined by conductivity tests.

Dental cement materials have been developed with the aim to replace hard dental tissues. The first material used for pulp capping, root canal obturation, bifurcation perforation and apexification is calcium hydroxide (in 1920). A half century later, glass-ionomer cements began to suppress it as dentine substitutes. Finally, in the 1990s, calcium silicate (CS) material appeared in the dental research community as the most promising dentine substitute capable to adequately meet all clinical requirements. The aim of this paper is to present an overview of literature related to studies about CS materials taking into account their physical, chemical and biological properties and clinical applications. This review aims to discuss beneficial and adverse characteristics of CSs concerning interactions to the hard dentine and soft pulp/periodontal tissues. This review article deals with the literature data about currently commercially available CS concerning laboratory and clinical findings. 109 scientific articles were analyzed of which 62 references reported in vitro and 26 in vivo investigations while 21 references comprised reports, reviews and books dealing with both, in vitro and in vivo investigations. Although further data collection is necessary, CSs are promising materials that represent a gold standard for numerous dental clinical procedures. © 2019, Association of Chemists and Chemical Engineers of Serbia. All rights reserved.

In this paper, an innovative fluidized bed dryer with inert particles is presented. The system can be used for drying of solutions, suspensions and pastes in order to obtain a powdered product. The experiments were performed in a pilot-scale dryer with a cylindrical column 0.215 m in diameter and 1.2 mm height, with glass spheres as inert particles. The material used for drying was CuSO4 solution. The effects of operating conditions on the dryer throughput and product quality were investigated. Main performance criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, were quantified. Nearly isothermal conditions were found due to thorough mixing of the particles. The energy efficiency of the dryer was also assessed. Simple heat and mass balances predicted the dryer performance quite well., U ovom radu je predstavljen inovativni sušionik sa fluidizovanim slojem inertnih čestica. Prikazani sistem može da se koristi za sušenje rastvora, suspenzija i pasti u cilju dobijanja praškastog produkta. Eksperimenti su rađeni na pilot postrojenju čiji je centralni deo cilindrična kolona prečnika 215 mm i visine 1200 mm. Korišćene su staklene sfere kao inertne čestice. U radu je prikazano sušenje rastvora CuSO4. Ispitivan je uticaj operativnih uslova na performanse sistema za sušenje, kao i na kvalitet praškastog produkta. Kvantifikovani su glavni parametri koji opisuju performanse sušionika, kao što su specifična brzina isparavanja, specifična potrošnja toplote i specifična potrošnja vazduha. Usled intenzivnog mešanja u fluidizovanom sloju postižu se približno izotermni uslovi sušenja. Izvršena je procena energetske efikasnosti sušenja. Jednostavni bilansi prenosa mase i toplote adekvatno predviđaju radni režim sistema za sušenje.

In this paper, an innovative fluidized bed dryer with inert particles is presented. The system can be used for drying of solutions, suspensions and pastes in order to obtain a powdered product. The experiments were performed in a pilot-scale dryer with a cylindrical column 0.215 m in diameter and 1.2 mm height, with glass spheres as inert particles. The material used for drying was CuSO4 solution. The effects of operating conditions on the dryer throughput and product quality were investigated. Main performance criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, were quantified. Nearly isothermal conditions were found due to thorough mixing of the particles. The energy efficiency of the dryer was also assessed. Simple heat and mass balances predicted the dryer performance quite well.

Industrial wastewater contains recalcitrant organic compounds with a very complex chemical structure, built of molecules with long chains of carbon atoms and attached different functional groups. Chemical or biological treatments used for removal of these compounds are being replaced with more efficient non-commercial wastewater treatments. Advanced oxidation processes overcome limitations of conventional methods regarding formation of by-products during degradation of recalcitrant organic compounds. The Fenton process, or use of the Fenton's reagent, has became one of the most utilized processes due to simplicity, economy and accessible amounts of ferrous iron and hydrogen-peroxide, which are used in the process. In specific, the Fenton's reagent is a catalytic-oxidative mixture of these two components. The ferrous iron Fe2+ initiates and catalyzes decomposition of H2O2, resulting in generation of hydroxyl radicals, which are the main radical species in the process able to detoxify several organic pollutants by oxidation. In addition, other mechanisms besides formation of hydroxyl radicals may occur during the Fenton process and participate in degradation of target pollutants. Generally, the treatment efficiency relies upon the physical and chemical properties of target pollutants and the process operating conditions. The main disadvantage of the Fenton process is production of sludge formed by iron hydroxide at certain pH values. An alternative solution for this problem is application of this process in fluidized bed reactors. This paper presents an overview of Fenton and photo-Fenton processes in dispersed systems for removal of different industrial wastewater pollutants. The most important process parameters, required for efficient degradation of recalcitrant organic compounds are also described, such as the catalyst type, pH value, temperature, H2O2 concentration and retention time. Strict control of Fenton process parameters in fluidized bed reactors at desire