8639 research outputs found
Sort by
Assesment of measurement uncertainty when determining heavy metal content in fly ash samples
No full textМетрологија представља науку о мерењу, али и основни елемент инфраструктуре квалитета. Њена основна улога је да обезбеди одговарајућу тачност, прецизност и поузданост мерења. Мерење је активност која се спроводи од давнина, а резултати овог процеса у великој мери могу утицати на квалитет живота. Мендељејев је говорио да наука почиње тамо где започну мерења, међутим свако мерење подразумева и одговарајућу мерну несигурност. Овај проблем препознат је од стране међународне организације за стандардизацију (ISO) и међународне електротехничке комисије (IEC) приликом развоја и доношења стандарда SRPS ISO/IEC 17025:2017, који се користи за акредитацију лабораторија. Процена мерне несигурности обезбеђује повећано поверење у добијане резултате, посебно приликом поређења добијених вредности са законском регулативом. У оквиру овог рада приказан је процес одређивања комбиноване мерне несигурности (u), као и проширене мерне несигурности (U), приликом испитивања садржаја тешких метала присутних у узорцима летећег пепела, методом „одоздо на горе“. Идентификација процеса при којима може настати мерна несигурност одређена је применом алата квалитета, дијаграма тока и дијаграма узрок-последица. Резултати добијени у овом раду показали су да процес калибрације највећим делом утиче на мерну несигурност, као и да је мерна несигурност приликом одређивања никла највећа, док је најмања приликом одређивања кадмијума.Metrology is a science dealing with measurement but also a basic constituent of quality infrastructure. Its main role is to ensure the appropriate accuracy, precision and reliability of measurement. Measurement is an activity that has been carried out since ancient times, and the results of this process may impact the quality of life to a large extent. According to Mendeleev, science begins where measurements begin. However, each measurement is loaded with corresponding measurement uncertainty. This problem is recognized by the international standardization organization (ISO), as well as by the International Electrotechnical Commission (IEC) in adopting the SRPS ISO/IEC 17025:2017 standard, which is used for accreditation of testing laboratories. The assessment of measurement uncertainty ensures an increased confidence in the obtained results, especially when comparing the obtained values with legal regulations. This paper presents the process of determining combined uncertainty (u), as well as extended uncertainty (U) when examining the amount of heavy metals present in fly ash samples, using the bottom-up method. The identification of the processes in which measurement uncertainty arises has been determined using quality tools: flowcharts and cause-effect diagrams. The results obtained in this work showed that the calibration process mostly affects the measurement uncertainty. Moreover, the measurement uncertainty is highest when determining nickel, while it is lowest when determining cadmium
Chemometric Approach to Modeling the Extraction Method Parameters for Toxic and Strategic Elements from Fly Ash Samples
No full textThe modern development of industry brings with it an increasing energy demand. In Serbia, a significant portion of electricity is generated by burning coal in thermal power plants, which results in the production of large amounts of industrial waste: fly ash, bottom ash, and slag. These waste materials can contain both toxic and strategically important elements. By determining the quantity of toxic elements present, proper handling of this hazardous waste can be ensured. Additionally, extracting strategic elements from waste materials could offer an ecological alternative to mining.
In this study, a comparison of two digestion methods was conducted: HNO3/HCl/HF and HNO3/H2SO4 with V2O5. Additionally, modeling of microwave digestion parameters was performed, including temperature, time, catalyst, and type of mineral acids. The investigations were carried out on seven different fly ash samples.
The obtained results were processed using advanced techniques of multivariate chemometric analysis: artificial neural networks (ANN), cluster analysis (CA) and principal component analysis (PCA). The results indicated that lower temperatures and the method HNO3/H2SO4 with V2O5 are more suitable for volatile toxic and some strategic elements, whereas higher temperatures and the method HNO3/HCl/HF are more suitable for other elements, including most of the strategic elements
Razvoj novog proizvoda – funkcionalni sladoled u prahu
No full textSladoled je omiljena poslastica u kojoj uživaju potrošači svih starosnih grupa, zbog
jedinstvenih teksturalnih svojstava. On nema značajnu nutritivnu vrednost a doprinosi
prekomernom unosu masti i "praznih" kalorija, jer obiluje šećerima i mastima.
12
Poboljšanje nutritivnog profila sladoleda funkcionalnim sastojcima moglo bi imati dubok
uticaj i na poboljšanje ishrane celokupne populacije. Nutritivna i senzorska svojstva
sladoleda obogaćenog funkcionalnim sastojcima treba da zadovolje očekivanja potrošača.
Iako je tržište funkcionalnog sladoleda u svetu u ranoj fazi razvoja, očekuje se njegov brzi
rast u narednih 5 godina. S obzirom na široku potrošnju ovog proizvoda, brojne grupe
potrošača, poput dijabetičara, osoba sa kardiovaskularnim oboljenjima i onih sa
prekomernom težinom, novi funkcionalni proizvod bi mogle sa sigurnošću da uključe u svoju
ishranu bez ugrožavanja zdravlja.
Suština predloženog tehničkog rešenja je proizvodnja funkcionalnog sladoleda u prahu uz
smanjenje energetske vrednosti, uz dodatak hidrolizata proteina surutke poboljšanih
funkcionalnih svojstava, pre svega antioksidativnog kapaciteta u odnosu na nehidrolizovane
proteine surutke. Kontrolisana enzimska hidroliza proteina je metoda koja se koristi za
“oslobađanje” bioaktivnih peptida iz dugih lanaca proteina. Ovom metodom moguće je
značajno povećati bioaktivna svojstva proteina.
U okviru tehničkog rešenja izvršeno je ispitivanje mogućnosti kombinovanja tradicionalnih
komponenti sladoleda u prahu sa hidrolizatom proteina surutke i određenom količinom
vlakana (inulina), uz mogućnost primene nutritivnih i zdravstvenih izjava za ovaj proizvod.
U cilju dobijanja takvog proizvoda najpre je ispitivan uticaj uslova hidrolize proteina surutke
na antioksidativni kapacitet i tehnološka svojstva (stvaranje pene i emulgovanje). Korišćenje
komponenti koje nisu deo standardne recepture sladoleda, može izazvati pogoršanja
osetljivih reoloških, odnosno teksturalnih svojstva sladoleda. Zbog toga su u uzorcima
ispitana topivost i senzorska svojstva. Reološke osobine sladoleda se ogledaju u njegovoj
teksturi. Od teksture sladoleda će zavisiti prihvatljivost i održivost proizvoda na tržištu od
strane potrošača. Rezultati su upoređeni sa kontrolnim uzorkom, sladoledom sa ukusom
vanile koji Aleva d.o.o. trenutno proizvodi.
Cilj tehničkog rešenja je da se dobije funkcionalni sladoled u prahu, dobrih senzorskih
svojstava, topivosti i antioksidativnih svojstava, uz poboljšanje nutritivnog sastava sladoleda
u prahu. Ukoliko se sladoledu u prahu, nakon obogaćenja proteinima i peptidima surutke i
vlaknima, ne naruši konzistencija, a poboljša nutritivna vrednost, potrebno je predložiti
nutritivne i zdravstvene izjave prema uslovima iz Pravilnika o prehrambenim i zdravstvenim
izjavama koje se navode na deklaraciji hrane ( Sl. Gl. RS, 51/2018, 103/2018 i 110/2023),
odnosno EU Regulativi 1924/2006.Tehničko rešenje kategorije M8
OPTIMIZACIJA PROCESA OBRADE MEDICINSKIH TKANINA KOLOIDNIM RASTVOROM SREBRA I ISPITIVANJE ANTIMIKROBNE AKTIVNOSTI DOBIJENOG PROIZVODA
No full textPredloženo novo tehničko rešenje odnosi se na optimizaciju procesa obrade medicinskih tkanina koloidnim rastvorom srebra i ispitivanje antimikrobne aktivnosti dobijenog proizvoda. Cilj ovog tehničkog rešenja je da se proizvede novi proizvod baziran na medicinskoj tekstilnoj tkanini obrađen rastvorom srebra koji će posedovati antimikrobna svojstva. Ovim medicinskim proizvodom bi se preventivno uticalo na sprečavanje kao i na širenje već postojećih infekcija izazvanih patogenim mikroorganizmima.
Predloženo tehničko rešenje razvijano je u saradnji sa frimom Koloid d.o.o. i NIVA d.o.o. tokom 2022 godine. Za ova ispitivanja korišćen je već postojeći proizvod firme Koloid a to je koloidni rastvor srebra kako bi se njime obradile gaze, tuferi, komprese, zavoji, vate i ulošci firme NIVA i tako dobili poboljšani tesktilni proizvodi sa antimikrobnim karakteristikama. Obrada medicinskog tekstila je vršena u Laboratoriji za radijacionu hemiju i fiziku, Instituta za nuklearne nauke „Vinča“, dok je utvrđivanje koncentracije srebra na tekstilu određeno u akreditovanoj laboratoriji Anahem. Ispitivanje antimikrobne aktivnosti obrađenih tekstilnih materijala vršeno je u laboratoriji Tehnološko-metalurškog fakulteta u Beogradu.
U toku ovog istraživanja, optimizovan je način obrade tkanine (metoda raspršivanja) koloidnim rastvorom srebra dve koncentracije (10 i 30 ppm) ispitivanjem dobijenih materijala na antimikrobna svojstva prema bakteriji E. coli kao referentnoj kulturi. Dalja ispitivanja su rađena na materijalima koji su obrađeni raspršivanjem koloidnog rastvora srebra koncentracije 30 ppm. Ispitana je količina srebra na tkanini koja se zadržala nakon obrade i rezultati su pokazali da se na tkaninama nalazi 15-20 µg srebra/gtkanine.
Antimikrobno ispitivanje obrađenih materijala je rađeno kontaktnom metodom (2 h i 24 h) prema patogenim mikroorganizama, Gram-negativnim bakterijama Escherichia coli, Pseudomonas aeruginosa, Gram-pozitivnim bakterijama Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis i gljivici Candida albicans. Svi ispitivani uzorci (gaza, tufer, uložak, vata i zavoj) obrađeni koloidom koncentracije 30 ppm pokazali su zadovoljavajuća, a u nekim slučajevima i odlična antimikrobna svojstva prema svim ispitivanim sojevima mikroorganizama (tufer. Antimikrobna efikasnost ispitivanih materijala (uložak, vata, tufer, zavoj) prema Gram-negativnim bakterijama E. coli i P .aeruginosa je već posle 2 h kontakta gotovo maksimalna za E. coli preko 98%, dok je za P. aeruginosa maksimalna i iznosi preko 99% (svi ispitivani tekstilni materijali). Već posle 24 h kontakta bakterija i materijala, gotovo da nema rasta mikroorganizama i možemo smatrati da je efikasnost maksimalna. Kod Gram-pozitivnih bakterija S. aureus, B.subtilis i E. faecalis potrebno je duže vreme za kompletnu redukciju bakterija (24 h, preko 99%), osim kod B. subtilis, gde je dovoljno 2 h kontakta za maksimalnu redukciju početnog broja bakterija za sve ispitivane uzorke obrađenih tekstilnih materijala (najizraženija redukcija je kod tufera). Kod S. aureus posle 2 h kontakta imamo zadovoljavajuću redukciju broja bakterija kod svih ispitivanih tekstilnh tkanina izuzev zavoja, dok je nakon 24 h kontakta redukcija mikroorganizam već maksimalna za sve ispitivane uzorke obrađenih tesktilnih materijala. Za E. faecalis je potrebno duže vreme kontakta od 24h da se postigne maksimalna redukcija broja ćelija (96-99%). Ispitivanje antifungalne aktivnosti prema gljivici C. albicans dalo je umerene rezultate antifungalne aktivnosti. Nakon 24 h postoji određena redukcija broja mikroorganizama 65-96.50% pri čemu je redukcija najizraženija kod tufera.Tehničko rešenje kategorije M82 - Novo tehničko
rešenje (metoda) primenjeno na nacionalnom nivo
The impact of disposed petrochemical waste on the environment - the case of acid tar
No full textAcid tar (AT) is a specific hazardous waste from the petrochemical industry generated in the
processes of white oil production, benzole refining, and oil re-refining. AT represents a black,
viscous emulsion of organic matter, sulfuric acid, and water, similar to bitumen, with a strong,
acrid odor. For decades, the common practice worldwide has been to dump AT into open pits
near refineries, called acid tar lagoons, causing significant pollution of the local environment.
In this paper, the chemical composition of an AT sample from a fifty-year-old lagoon was
compared with values for fresh acid tar samples found in the literature. The differences in
chemical composition were analyzed in order to assess the impact of disposed acid tar on the
environment. The results show significant emission of water-soluble components (sulfuric acid
and heavy metals salts) into the surrounding soil, and that AT retains hazardous waste
characteristics even decades after its creation. The paper also discusses possible processes for
the treatment of this type of waste with a special focus on the solidification/stabilization
process
Doxorubicin and quercetin combined effect on SAOS-2 cells grown in 2D and 3D model systems
No full textOsteosarcoma (OS) is a highly aggressive primary malignant bone tumor that most commonly affects children, adolescents, and young adults. The standard treatment for OS consists of surgical resection and chemotherapy, whereas radiation therapy is recommended for the unresectable tumor. Due to its easy metastasis and recurrence, the 5-year overall survival rate is only 66.5 %. Thus, there is a critical need to recognize the molecular mechanisms underlying OS development and pathogenesis. Traditionally, two-dimensional (2D) cells are widely used in cancer biology and pre-clinical studies. However, 2D models are unable to mimic cell–cell and cell-extracellular matrix interactions which are crucial for adequate cellular function. Three-dimensional (3D) model systems are able to recapitulate key features of human cancer and are recognized as a promising platform for fundamental and translational research. In the present work, we established an osteosarcoma 3D model based on alginate microbeads and studied the effect of combined treatment with doxorubicin (Doxo), widely used chemotherapeutic, and quercetin (Quer), a plant pigment with anticancer properties, on OS model systems.ExcellMater Conference 2024: Innovative Biomaterials for Novel Medical Devices, Belgrade, Serbia, April 10-12, 202
Influence of pretreatments and drying method on element content in red “paprika” pepper (Capsicum Annuum)
No full textCrvena paprika koja se koristi u proizvodnji začinske paprike je izvor značajnih vitamina i
esencijalnih elemenata. Sušenjem paprike dobijaju se različiti proizvodi (sušena paprika, sušene
ljuspice ili mlevena paprika). Pre samog procesa sušenja često se primjenjuju fizički i hemijski
predtretmani, kao i njihove kombinacije. Cilj predtretmana je postizanje boljeg kvaliteta proizvoda,
skraćivanje vremena sušenja, a samim tim i smanjenje troškova proizvodnje. Iako predtretmani imaju
brojne prednosti, tokom ovih procesa često dolazi do gubitka određenih nutrijenata. Cilj ovog
istraživanja je bio da se utvrdi kao različiti hemijski predtretmani, ultrazvuk i metode sušenja utiču
na sadržaj elemenata u začinskoj paprici. Eksperimenti su postavljeni korištenjem frakcionog
faktorijskog eksperimentalnog dizajna. Parametri su bili temperatura predtretmana (20, 50, 80 ℃),
vreme (1, 3, 5 min), ultrazvuk (off/on), 0,25% aditiv (limunska kiselina, K2S2O5, limunska kiselina/
K2S2O5), pH vrednost (3, 6.5, 10), masa tretiranog uzorka (30, 100 i 170 g u 1L rastvora za
predtretman) i metoda sušenja (sušenje u tunelskoj sušati i liofilizacija). Najveći uticaj na sadržaj
elemenata imala je metoda sušenja. Klasično sušenje je doprinelo boljem očuvanju K, Ca, Na, P, Fe,
Zn, Cu, Co i Cr. Vrsta primenjenog aditiva je uticala na sadržaj Fe, K, Na i Mo. Veći sadržaj Fe, K
i Mo postiže se sa K2S2O5, dok je smeša limunska kiselina/K2S2O5 (NaOH je upotrebljen za regulaciju
pH) bila efikasnija za veći sadržaj Na. Više temperature dovele su do većih gubitaka svih elemenata,
posebno Cr, K i P. Duže vreme predtretmana je doprinelo višem izluživanju većine elemenata. Veća
masa tretiranog uzorka obezbedila je manji gubitak većine elemenata, posebno Cr, Co i Fe.The red peppers used in the production of paprika are a source of valuable vitamins and essential elements. By drying peppers, various products are obtained (dried peppers, dried flakes, or
ground paprika). Before the actual drying process, physical and chemical pre-treatments, as well as their combinations, are frequently applied. The goal of pre-treatment is to achieve better product
quality, shorten drying time, and consequently reduce production costs. Although pre-treatments
have numerous advantages, during these processes, there is often a loss of certain nutrients. This
study aimed to investigate how different chemical pre-treatments, ultrasound, and drying methods
influence element content in red peppers. The experiments were set using fractional factorial experimental design. Parameters were pre-treatment temperature (20, 50, 80 ℃), time (1, 3, 5 min), ultrasound (off/on), 0.25% additive (citric acid, K2S2O5, citric acid/K2S2O5), pH value (3, 6.5, 10), mass
of treated sample (30, 100 and 170 g in 1L pre-treatment solution) and drying method (hot air drying
and freeze drying). The drying method had the greatest impact on the elemental content. Classic
drying was better for the preservation of K, Ca, Na, P, Fe, Zn, Cu, Co, and Cr. The type of applied
additive influenced the content of Fe, K, Na, and Mo. Higher Fe, K, and Mo content is achieved with
K2S2O5, while the mixture of citric acid/K2S2O5 (NaOH used for pH regulation) was more effective
for higher Na content. Higher temperatures led to greater losses of all elements, especially Cr, K,
and P. Longer pre-treatment resulted in increased leaching of most elements. Additionally, a larger
sample mass ensured better preservation of most elements, particularly Cr, Co, and Fe
Effect of section thickness on cavitation behaviour of selective laser sintered polyamide 12
No full textThe present study focuses on the results of cavitation resistance of samples obtained by the Selective Laser Sintering technology. All samples are made from Nylon 12 – Polyamide 12 powder, known as PA2200 in the industry, produced by EOS GmbH. The powder, which has been used for building of samples, represent mixture of 50% new powder and 50% of the recycled powder. In the work, samples with different section thicknesses (0.4; 0.8 and 1.0 mm) were subjected to the ultrasonically induced cavitation test method to investigate the effect of geometry on their cavitation behaviour. The change in mass loss during different cavitation times was measured on the tested samples. The morphology of cavitation damage was characterized using Scanning Electron Microscopy (SEM). Results obtained in this paper have shown that section thickness of the samples have a significant influence on the cavitation resistance. The highest cavitation resistance was obtained for the samples with 0.4 mm thickness
Utilization of Copper Flotation Tailings in Geopolymer Materials Based on Zeolite and Fly Ash
No full textCopper flotation tailings (FTs), resulting from the separation and beneficiation processes of ores, are a significant source of environmental pollution (acid mine drainage, toxic elements leaching, and dust generation). The most common disposal method for this industrial waste is dumping. However, due to their favorable physical and chemical properties—the high content of aluminosilicate minerals (60–90%)—flotation tailings can be effectively treated and reused through geopolymerization technology, thereby adding value to this waste. The objective of this study was to evaluate the potential of utilizing the geopolymerization of FTs to produce sustainable materials. Geopolymers based on natural zeolite (NZ), sodium-modified natural zeolite (NaZ), and fly ash (FA) were prepared using 20%, 35%, and 50% of FTs, activated with a 10 M NaOH solution. The study investigated the influence of Ca/Si, Si/Al, and Na/Al molar ratios on the structural, thermal, and mechanical properties (XRD, TG/DTG and unconfined compressive strength, UCS), and contaminant immobilization (TCLP method) of geopolymers. Geochemical modeling via the PHREEQC program was employed to interpret the results. The findings indicated that the UCS value decreased in zeolite-based geopolymers as the content of FT increased due to the inertness of the tailings and the low calcium content in the system (Ca/Si ≤ 0.3), in contrast to the FA-based geopolymer. The highest UCS of 44.3 MPa was recorded in an FA-based geopolymer containing 50% flotation tailings, with optimal molar ratios of 0.4 for Ca/Si, 3.0 for Si/Al, and 1.1 for Na/Al. In conclusion, the geopolymerization process has been determined to be a suitable technological approach for the sustainable treatment and reuse of FTs
Design and characterization of dynamic textiles with optimized ergonomic comfort for automotive seat upholstery
No full textAccording to recent studies, user comfort is one of the major challenges faced regarding the vehicle seating. The outer upholstery layer of the seat cover is the main factor contributing to overall user discomfort in the driving environment. This is related to the limitations of the conventional fabrics used. Therefore, alternative textile materials for seat covering are being increasingly sought out. In this work, we propose innovative shape memory-based seat covering fabrics offering improved comfort properties. Shape memory polyurethane (SMPU) multifilament yarns were combined with polyester (PES) yarns to produce three types of woven fabrics having the typical structures used in seat coverings (plain, twill 2/2 and derived twill) using a fixed warp and weft ratio of 3PES:1SMPU. The effects of SMPU yarns on the physical characteristics of the fabrics (thickness, areal weight, yarn density, and tightness) as well as on their mechanical behavior, shape memory effect, thermal comfort, and abrasion resistance under similar usage conditions in car seat covers were investigated. Improvement was observed in the ergonomic comfort with maintained thermal comfort in the presence of SMPU multifilament yarns, with this effect being more noticeable in the twill fabrics. The thermodynamic SMPU-based fabrics used in this study could be potential candidates for use in seat upholstery given the improvement in user comfort over extended use