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Eksperimentalna analiza atmosferske korozije čelika S235JR u industrijskoj sredini
No full textThe aim of this study was evaluation of atmospheric corrosion of structural steel S235JR in an industrial environment. General corrosion testing was carried out for six months in the field, at selected atmospheric corrosion stations, near the Sulphuric acid plant, in the Electrolytic refining plant and next to the automatic air quality monitoring station in the city of Bor, Serbia. The results were compared with the standard specimens stored in the laboratory. The steel S235JR specimens were characterized regarding mechanical characteristics by tensile testing. With the aim of assessing the mutual effect of corrosion and polluted industrial environment meteorological parameters were also determined, as well as pollutants in the atmosphere (mainly SO2). The X-ray diffraction method was used to identify the composition of corrosion products. Research within this work enabled a better understanding of the behavior of structural steel S235JR in which there was a reduction in load capacity due to corrosion. The corrosion rates obtained under each tested exposure condition showed noticeable differences. It was found that depending on the content of pollutants in the atmosphere and the location of the steel specimen, the corrosion products represented different compounds and solid phases.U ovom radu ispitana je atmosferska korozija konstrukcionog čelika S235JR u industrijskoj sredini. Opšta ispitivanja korozije vršena su u blizini fabrike sumporne kiseline, u postrojenju za elektrolitičku rafinaciju i pored automatske stanice za praćenje kvaliteta vazduha u Boru u periodu od 6 meseci. Za ispitivanje međusobnog dejstva korozije i zagađenja industrijske sredine, korišćen je čelik S235JR, a njegove mehaničke karakteristike su dobijene ispitivanjem zatezanjem. Određeni su i meteorološki parametri, kao i zagađujuće materije u atmosferi (uglavnom SO2). Rendgenska difrakciona analiza (engl. X-ray diffraction, XRD) je korišćena za identifikaciju minerološkog sastava produkata korozije. XRD analiza može ukazati na vezu između gubitka nosivosti i vrste sredine u kojoj se korozija razvija. Na osnovu dobijenih rezultata vrši se dalje predviđanje degradacije materijala usled korozije u industrijski agresivnoj sredini. Istraživanja u okviru ovog rada su omogućila bolje razumevanje ponašanja konstrukcionog čelika S235JR u kom je došlo do redukcije nosivosti usled korozije. Utvrđeno je da su produkti korozije različita jedinjenja u zavisnosti od sadržaja zagađujućih materija u atmosferi i lokacije čeličnih elemenata
Immobilization of crude laccase onto chitosan beads to enhance its thermal and pH stability
No full textLaccases are essential enzymes in various industrial applications, playing a vital role in
numerous industrial processes. When immobilized, laccases demonstrate enhanced resistance to
environmental changes and offer the added benefit of being easily recoverable and recyclable,
which makes them superior to their free forms. Immobilization primarily protects the enzymes
from harsh conditions, such as high temperatures and extreme pH levels, significantly improving
their stability and lifespan. In this study, we explored the impact of immobilization of crude
laccase, isolated from Ganoderma sp., on its thermal and pH stability. The crude laccase was
immobilized onto chitosan beads that were pre-activated with 0.5% glutaraldehyde. The study
focused on determining the effects of crosslinking and immobilization time on the relative activity
of the immobilized enzyme. The thermal and pH stability of both free and immobilized laccase
were evaluated over an 8-hour incubation period, across a pH range of 4-8 and temperatures
between 20°C and 50°C. The optimal crosslinking time was found to be 2h, which resulted in a
relative activity of 34.04% for the immobilized enzyme with a corresponding immobilization time
of 2 h. Further optimization of the immobilization time yielded the highest relative activity of
51.31% when the crosslinking time was 2h and the immobilization time was extended to 3 h. In
contrast, the lowest relative activity was observed when the crosslinking time was 4 h and the
immobilization time was 2h. Both free and immobilized laccases exhibited maximum stability at
pH 5 and 20°C. However, immobilized laccase showed superior stability compared to the free
form. After an 8-hour incubation at 4°C and pH 5, the immobilized laccase retained 68.25% of its
initial activity, whereas the free laccase showed 59.64% of the residual activity. For thermal
stability, after 8 h at pH 5 and 20°C, the immobilized laccase demonstrated a residual activity of
58.89%, outperforming the free laccase, which retained 53.29% of the activity. These results
underscore the importance of optimizing the immobilization process to enhance the stability of
laccases, demonstrating that immobilization significantly improves both thermal and pH stability
Image analysis method combined with machine learning for the prediction of soil and air quality
No full textThe pressing need for rapid, cost-effective, in-situ and non-destructive methods for assessing soil and air quality
is driven by increasing environmental concerns and the limitations of traditional laboratory-based analyses.
These conventional techniques are often time-consuming, resource-intensive, and may not provide the spatial
resolution required for comprehensive environmental monitoring. This work introduces a novel framework for
predicting soil and air quality parameters by leveraging the non-destructive power of image analysis coupled
with the predictive capabilities of neural network models. The study’s novelty lies in establishing a direct
relationship between readily obtainable pixel intensity data from images of soil and air filters and key environmental indicators such as humus, total organic carbon in soil, and deposited particulate matter in air. The
results showed a good relationship between the pixel intensity values obtained by image analysis and measured
concentrations of humus and total organic carbon in soil and deposited particulate matter from the air onto
filters. Furthermore, the developed neural network models demonstrate significantly enhanced predictive accuracy (99 % for soil TOC and 90 % for air particulate matter) compared to traditional linear regression approaches reported herein and in existing literature. The application of this methodology to predict metal ion
concentrations in air with moderate to high accuracy (64–83 %) also highlights the potential of this approach for
broader environmental monitoring applications
High pressure die casting simulation of aluminum mounting frame for recessed lighting
No full textHigh pressure die (HPD) casting is a widely y used practice in industry, especially when it comes to casting
metals such as aluminum, copper or bronze and their alloys. This paper discussed how variation of piston
speed and pressure influence casting errors such as shrinking. Using simulations for determining how
processing parameters effect the final casting product has been a more popular since it is made to save
money, resources and energy. The program used to simulate HPD casting is NOVACASTTM which uses
finite volume elements for calculation both metal flow and solidification. The model for simulation uses
500000 elements, with about 15mm of distance casting and the wall of the mold for the calculation box. The
casting temperature of EN AC-46000 (SS4250) alloy is 685 ºC. There are two cooling channels one on each
side of the casting inside the mold that use water as a coolant at 30 ºC. The heat transfer model used is
Surface heat transfer while for Shrinkage calculation High gravity influence is taken in account. For HPD
with filling chamber parameters the Chamber diameter is 80 mm, the Chamber length is 345 mm (5 mm are
given to the model for more precise gating placement), melt mass in chamber 3.5 kg and Metal filled into
casting cavity is 2.933 kg. The varying parameters are Piston velocity and Flow. Unfortunately the current
model for the casting had critical shrinkage regardless of the varying parameters therefore the simulation
must be further improved to correspond to the real life results
Bioceramic coatings electrodeposited on titanium surface aimed for medical applications
No full textAntibacterial bioceramic hydroxyapatite/chitosan/gentamicin (HAP/CS/Gent) and hydroxyapatite/chitosan/graphene/gentamicin (HAP/CS/Gr/Gent) coatings on titanium substrate, aimed at bone tissue implants, were produced by electrophoretic deposition (EPD) from aqueous suspensions. The formation and growth of the newly formed HAP layer on both HAP/CS/Gent and HAP/CS/Gr/Gent coatings surfaces were investigated in the simulated body fluid (SBF) at 37 °C using electrochemical impedance spectroscopy (EIS) and polarization measurements (PDS). The formation and growth of a new HAP layer were supported by results on the increase in coating impedance and coating pore resistance, as well as a decrease in coating capacitance and corrosion current density after 28-day immersion in SBF. The gentamicin release profiles were determined by high-performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) and were fitted by a novel two-compartment model with general fractional derivative (GFD) of distributed order, as well as Korsmeyer-Peppas, Makoid–Banakar, and Kopcha diffusion models. It has been proved that the proposed two-compartment model with general fractional derivative of distributed order exhibited significantly better fitting with the experimental release profile in respect to other models and enabled the determination of the gentamicin diffusion coefficient over the entire time period
Model of Stress–Strain Dependence for Poly(Vinyl Alcohol)-Based Hydrogels
No full textThe poly(vinyl alcohol), poly(vinyl alcohol)/chitosan, and poly(vinyl alcohol)/chitosan/gentamicin hydrogels, aimed for wound dressing in medical treatment of deep wounds, were prepared by physical cross linking using freezing–thawing method in five cycles. In order to investigate the mechanical properties of synthesized hydrogels, tensile test was performed and values of modulus of elasticity have been calculated from the experimental dependence between stress and strain. The general fractional derivative model for the stress–strain relation was proposed and compared with experimental measurements. The values of modulus of elasticity calculated from the proposed model corresponded very well with the values determined from experimental curves, confirming the validity of the proposed mathematical model of stress–strain behavior of synthesized poly(vinyl alcohol)-based hydrogels. The new model was applied to the poly(vinyl alcohol)-based hydrogels tested in quasi-static extension. The final expression gives a new relation (Formula presented.) that is used to fit the experimental results. The least squares method was used to determine the optimal values of model parameters
Comprehensive analysis and risk assessment of fine road dust in Abbottabad city (Pakistan) with heavy traffic for potentially toxic elements
No full textHuman activities have far-reaching impact on natural ecosystems, causing increasing disturbances and disruptions to the delicate balance of the environment. Poor land use planning, urbanization, infrastructure development, and unplanned tourism exacerbate contamination and degradation in tourist destinations, yet the pollution of potentially toxic elements (PTEs) in these environments remains inadequately explored. To address this issue, we investigated the concentrations of acid-digested PTEs in road dust in Abbottabad city (Pakistan) with heavy traffic. The current study also evaluated PTE associated pollution, ecological and health risks, and potential sources of these elements. The average concentrations (in mg kg–1) of PTEs in road dust were highest for Fe (15540), followed by Mn (304), Zn (139), Cu (50.0), Pb (21.5), Cr (13.0), Ni (10.3), Co (6.66), and Cd (0.236). The levels of Co, Cr, Mn, Ni, and Fe were below the upper continental crust (UCC) averages, while Cd, Cu, Pb, and Zn exceeded them. Spatially, Cd, Cu, Pb, and Zn were found at higher levels near traffic hotspots, bus stands and automobile workshops. Road dust in Abbottabad exhibited unpolluted to moderate pollution levels (geo-accumulation index), with Cd, Cu, Zn, and Pb at 23 % of the sites. The enrichment factor results indicated a significant anthropogenic influence, with Cd being significantly enriched and Zn, Cu, and Pb moderately enriched. The contamination factor results revealed moderate contamination by (Cd: 2.62, Zn: 2.08, Cu: 1.79, Pb: 1.27). Single metal risk index showed that 61 % of the sites posed considerable to very high ecological risks due to Cd, which was highlighted as a significant concern. The absolute principal component scores-multiple linear regression model identified three factors contributing to PTE pollution: lithogenic (Co, Fe, Mn, Ni), traffic-related (Cd, Cu, Pb, Zn), and mixed sources (Cr), with contributions of 52.8 %, 35.8 %, and 11.4 %, respectively. The PTE hazard quotient and total hazard index values for children and adults were below the safe risk level of 1, indicating no non-carcinogenic health risks. The cumulative carcinogenic risk values to the residents were also within acceptable limits. However, children's susceptibility to non-carcinogenic risks is higher due to their behavior and lower body weight. This study highlights the accumulation of PTEs in Abbottabad's environment, which poses challenges to long-term sustainability, particularly amid unplanned tourism. Therefore, urgent measures are necessary to mitigate PTE pollution and preserve tourist spots and public health
Source-specific probabilistic exposure to PM2.5-bound trace elements in a school environment
No full textSource-specific risks of fine particulate matter (PM2.5)-bound trace elements to student's health in a school located in an urban area were evaluated. The concentrations of the 29 elements in PM2.5 were analyzed indoors and outdoors at the school. PM2.5 concentrations ranged from 5.33 to 47.5 μg/m³ indoors to 8.22–83.1 μg/m³ outdoors. Besides Ca and Fe being the most abundant elements analyzed in PM2.5 both indoors and outdoors, the levels of Zn, Cr, Pb, Cu, Mn, and Ni were significant. The indoor/outdoor ratio of PM2.5 for most elements was below one. Positive matrix factorization (PMF) identified six primary sources with different loadings of PM2.5-bound toxic elements, whereas traffic and resuspended dust were the predominant element sources. The health risk assessment results indicated that the risks for students due to inhalation exposure to elements were within the safety threshold. Nickel, Cr, and Mn dominantly contributed to non-carcinogenic risks, whereas higher cancer risks were associated with Cr and, to a lesser extent, with As. The hazard index and total carcinogenic risk were within acceptable levels. The Monte Carlo simulations implied that vehicle-originated elements contributed the most to non-carcinogenic and carcinogenic health risks. These findings underscore the need to address air pollution in urban school environments more precisely, focusing on protecting young students from exposure to PM2.5-bound toxic elements
Analysis of the behavior of the mullite samples surface exposed to the cavitation using a statistical analysis approach
No full textCavitation erosion which occurs under specific fluid flow conditions in industrial processes, demands suitable materials. This study investigates the cavitation resistance of mullite by observing surface changes during exposure. A novel method focuses on morphological descriptors of defects caused by cavitation. Using image analysis (IA), surface degradation was quantified by selecting specific defect parameters, with datasets analyzed through principal component analysis (PCA) to identify key damage descriptors. This approach simplified the estimation of lifespan for exposed parts. The PCA of datasets obtained from IA indicated that the most informative descriptors of surface damage vary remarkably throughout the cavitation and per different periods of the cavitation curve. Among eleven selected parameters, PCA identified critical parameters Radiusmax, Perimeter, and Sizelength consistent throughout testing for monitoring mullite’s cavitation resistance. By combining traditional, non-destructive methods and statistical analysis, this study offers a new framework for tracking surface damage progression. This enables a deeper understanding of cavitation-induced material erosion, improving predictions of material performance and optimizing industrial applications
Fumaria officinalis Dust as a Source of Bioactives for Potential Dermal Application: Optimization of Extraction Procedures, Phytochemical Profiling, and Effects Related to Skin Health Benefits
No full textFumaria officinalis (fumitory), in the form of dust, was employed as a source of bioactive extracts whose chemical profile and biological potential were investigated. According to the results of the optimization of the extraction protocol, the extract with the highest polyphenol yield was prepared using fumitory dust under the optimal conditions determined using the statistical tool, 23 full factorial design: 50% ethanol and a 30:1 mL/g ratio during 120 s of microwave extraction (22.56 mg gallic acid equivalent/g of plant material). LC-MS and spectrophotometric/gravimetric analyses quantified the polyphenol, flavonoid, tannin, alkaloid, and protein contents. Caffeoylmalic acid, quercetin dihexoside, quercetin pentoside hexoside, rutin, and methylquercetin dihexoside were the most dominant compounds. The highest total flavonoid, condensed tannin, alkaloid, and protein yields were determined in the extract prepared using microwaves. In addition to the proven antioxidant potential, in the present study, the anti-inflammatory activity of fumitory extracts is also proven in the keratinocyte model, as well as a significant reduction of H2O2-induced reactive oxygen species production in cells and the absence of keratinocyte cytotoxicity. Thus, detailed chemical profiles and investigated biological effects related to skin health benefits encourage the potential application of fumitory dust extracts in dermo-cosmetic and pharmaceutical preparations for dermatological circumstances