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Evaluation of the impact and fracture toughness of a nanostructured bainitic steel with low retained austenite content
Mihael Brunčko, Peter Kirbiš, Ivan Anžel, Leo Gusel, Darja Feizpour, Tomaž Irgolič, Tomaž Vuherer, 2023, izvirni znanstveni članek

Opis: The impact and fracture toughness of a nanostructured, kinetically activated bainitic steel was determined using Standard methods. Prior to testing, the steel was quenched in oil and aged naturally for a period of 10 days in order to obtain a fully bainitic microstructure with a retained austenite content below 1%, resulting in a high hardness of 62HRC. The high hardness originated from the very fine microstructure of bainitic ferrite plates formed at low temperatures. It was determined that the impact toughness of the steel in the fully aged condition improved remarkably, whereas the fracture toughness was in line with expectations based on the extrapolated data available in the literature. This suggests that a very fine microstructure is most beneficial to rapid loading conditions, whereas material flaws such as coarse nitrides and non-metallic inclusions are the major limitation for obtaining a high fracture toughness.
Ključne besede: evaluation of fracture toughness, impact toughness, nanostructured bainite, natural aging, low retained austenite content, kinetically activated bainite KAB
Objavljeno v DKUM: 16.02.2024; Ogledov: 305; Prenosov: 19
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Cotton woven fabrics as protective polymer materials against solar radiation in the range of 210–1200 nm
Polona Dobnik-Dubrovski, Darinka Fakin, Alenka Ojstršek, 2023, izvirni znanstveni članek

Opis: The proposed paper describes the influence of woven fabric constructional parameters (type of weave, relative fabric density) and colouration (obtained by eco-friendly dyeing) on the solar transmittance of cotton woven fabrics in the range of 210-1200 nm. The cotton woven fabrics in their raw state were prepared according to Kienbaum's setting theory, at three levels of relative fabric density and three levels of the weave factor, and then exposed to the dyeing process with natural dyestuffs (beetroot, walnut leaves). After ultraviolet/visible/near-infrared (UV/VIS/IRA) solar transmittance and reflection in the range of 210-1200 nm were recorded, the influence of the fabric construction and colouration were analysed. The guidelines for fabric constructor were proposed. The results show that the walnut-coloured satin samples at the third level of relative fabric density provide the best solar protection in the whole solar spectrum. All the tested eco-friendly dyed fabrics offer good solar protection, while only raw satin fabric at the third level of relative fabric density can be classified as solar protective material with even better protection in IRA region than some coloured samples.
Ključne besede: fabric engineering, solar protection, woven fabric structure, natural dyeing of polymer material, testing
Objavljeno v DKUM: 15.02.2024; Ogledov: 226; Prenosov: 4
.pdf Celotno besedilo (1,93 MB)
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Use of mobile technologies in tourism : natural health resorts study
Boštjan Brumen, Peter Planinc, Tomi Špindler, Mitja Gorenak, Tanja Lešnik Štuhec, 2020, izvirni znanstveni članek

Opis: Mobile technologies have drastically changed the way people do everyday activities. Tasks previously reserved for desktop environments have moved to mobile devices, and nowadays, half of the internet traffic is stemming from mobile devices. The tourism industry is no exempt from the shift from desktop to mobile. In our research, we check to what extent natural health resorts have adapted and integrated mobile solutions to their websites. We collected data about the friendliness of selected websites using automated online tools and carried out a heuristic evaluation. The results were statistically analyzed and compared. Only roughly half of natural health resorts have optimized their websites for mobile devices. There are no statistically significant differences when comparing purely technical aspects. However, an in-depth heuristic evaluation has shown that some web sites are significantly more mobile-friendly than others and offer better technical conditions for enhanced user experience. Our study is the first technical and contentual evaluation of website mobile devices' friendliness in the natural health resort sector. It warns management, their marketing consultants, and web site developers about the opportunities they are missing by not supporting mobile users sufficiently. Further, it outlines deficiencies and provides suggestions and instructions for optimizing websites to enhance user-friendliness on mobile devices.
Ključne besede: mobile technology, mobile device, mobile Internet, health tourism, spa, natural health resort, web page, evaluation, heuristics
Objavljeno v DKUM: 26.01.2024; Ogledov: 202; Prenosov: 7
.pdf Celotno besedilo (632,73 KB)
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Natural disasters and tourism : Are the risks taken into account?
Aleš Semeja, 2022, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Opis: The tourism sector can be severely affected by unforeseen events, such as natural disasters, which are characterized as events with low probability but high impact. The COVID-19 pandemic came as an unprecedented shock to the tourism sector, with numerous reports appearing in many media outlets showing industry experts and directors calling for outside help to avoid worst-case scenarios for their businesses, even in the early days of the pandemic. We therefore wonder whether the approach of tourism companies to risk was inappropriate. Given the number of natural disasters that have occurred over the past few decades, we cannot argue that there have not been enough warning signs to encourage tourism companies to prepare for unforeseen events. A comprehensive review of natural disasters in recent years can be a valuable tool for tourism companies to assess such risks and develop strategies and action plans to increase resilience and sustainability. The latter should become key components of regular business.
Ključne besede: natural disasters, tourism, risk, resilience, sustainability
Objavljeno v DKUM: 17.01.2024; Ogledov: 264; Prenosov: 12
.pdf Celotno besedilo (19,75 MB)
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Preparation of Synthetic and Natural Porous Polymers via Multiphase Media : doctoral dissertation
Stanko Kramer, 2023, doktorska disertacija

Opis: PolyHIPEs are highly porous polymers with an interconnecting porous structure. They have found usage in the removal of pollutants, water clean-up, oil spill removal, catalysis, controlled release of active compounds, wound dressing and tissue engineering. The wide applicability of polyHIPEs is possible through their inherent porosity and chemical diversity. The aim of this dissertation was to increase the chemical diversity of polyHIPEs, develop an efficient method for the synthesis of polyHIPE beads and to use natural resources for the synthesis of polyHIPEs, subsequently, paving the pathway to more sustainable synthetic procedures. PolyHIPEs tend to have poor mechanical properties, therefore, it was crucial to investigate the influence of the internal phase volume, initation type (photo vs thermal) and monomer functionality on the mechanical and morphological properties of thiol-ene polyHIPEs. The results show that the main factors influencing the morphological and mechanical properties are the monomer structure and the internal phase volume. Besides the inherent porosity and chemical versatility typical of polyHIPEs, they can also be produced in various shapes, e.g., monoliths, membranes and beads. Therefore, the dissertation also focuses on the synthesis of polyHIPE beads. The polyHIPE beads were produced through the usage of water-in-oil-in-water (W/O/W) multiple emulsions. To enable the synthesise of open porous polyHIPE beads, thiol-ene polymerisation was combined with photopolymerisation to guarantee a rapid polymerisation prior the break-down of the multiple emulsion. Consequently, it was possible to synthesise polyHIPE beads. The first study showed that by altering the thiol to acrylate ratio in favour of the acrylate the degradation rate of the synthesised polyHIPE beads gets reduced. Additionally, it was demonstrated that the beads can be readily functionalised with allyl amine and used for the adsorption of methylene blue (12.0 mg/g in 24 hours). The next study combined polyHIPE beads with magnetic nanoparticles (MNPs) to produce magnetic polyHIPE beads which were used for the removal of Pb2+. To produce the magnetic polyHIPE beads, magnetic nanoparticles (MNPs) were added to the organic phase. The MNPs get incorporated into the polymer-network after the polymerisation, therefore, forming magnetic polyHIPE beads. The MNPs were shown to influence the morphology and the size of the beads. Additionally, the polyHIPE beads were shown to remove up to 97.0 % of Pb2+ after 24 hours from a 2.9 mg/L solution of Pb2+. In the last study related to the synthesis of polyHIPE beads, functional polyHIPE beads were produced and then functionalised to enable the binding of the enzyme invertase. These beads were then utilised for the hydrolysis of sucrose. The conversion of sucrose to glucose and fructose was 100% after 60 minutes for the polyHIPE beads, while the conversion for non-porous beads was only 6.5%. The last part of the thesis focused on more sustainable/natural approaches to polyHIPE synthesis. The first study utilised limonene as a replacement to conventional solvents (e.g., cyclohexane) in the production of O/W HIPEs and the polymerisation thereof into polyHIPEs. It was shown that limonene can be used as an efficient replacement in the production of polyHIPEs. The next study used natural resources (terpenoids) which were modified to contain polymerisable units, which were used for the synthesis of terpenoid-based polyHIPEs. The synthesised monomers were then crosslinked with 5 and 10 mol. % TMPTA to form polyHIPEs, consequently producing porous polymers. The last study in this thesis used the terpenes limonene, carvone and myrcene to produce bio-based polyHIPEs by utilising multifunctional acrylates (PETA and TMPTA) as the comonomers. This study demonstrates that it is possible to prepare polyHIPEs from commercially available terpenes, therefore, moving the field of polyHIPEs into a more sustainable direction.
Ključne besede: HIPE, PolyHIPE, Multiple Emulsions, Functional polyHIPEs, Natural Polymers, Terpenes
Objavljeno v DKUM: 08.12.2023; Ogledov: 369; Prenosov: 63
.pdf Celotno besedilo (8,08 MB)

Method of the best available technology and low carbon future of a combined heat and power plant
Dušan Strušnik, Marko Agrež, 2022, izvirni znanstveni članek

Opis: The low-carbon development strategy and ecological awareness of a combined heat and power (CHP) plant is the key factor that enables further development of such systems. CHP plants are subject to rigid European ecological guidelines, which dictate the pace of development of global thermal power engineering. For this purpose, the European Union issued a special Directive for the promotion of heat and power cogeneration, and is established with the best available technology (BAT) method. Even though the production of electricity using carbon-free technologies is on the rise, the production of electricity by fossil fuel combustion cannot be avoided completely. The meaning of the operation of the CHP plant is reflected particularly in the provision of tertiary services to the electric power system, regulation of the network frequency, particularly in winter months, when electricity production using carbon-free technologies is limited. In CHP systems, the low-carbon future is linked intricately to high investment costs and these impacts the final price of energy. Using the BAT method, the article presents the advantages of energy production in a combined heat and power plant, an example of the restructuring of a larger CHP system into a low-carbon plant and guidelines for further development.
Ključne besede: alternative facilities, best available technology, combined plant, heat recovery, hydrogen, low-carbon, methanisation, natural gas, steam recovery
Objavljeno v DKUM: 26.10.2023; Ogledov: 269; Prenosov: 3
.pdf Celotno besedilo (1,47 MB)
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Seasonal changes in chemical profile and antioxidant activity of Padina pavonica extracts and their application in the development of bioactive chitosan/PLA bilayer film
Martina Čagalj, Lidija Fras Zemljič, Tjaša Kraševac Glaser, Eva Mežnar, Meta Sterniša, Sonja Smole Možina, María del Carmen Razola-Díaz, Vida Šimat, 2022, izvirni znanstveni članek

Opis: Seaweeds are a potentially sustainable source of natural antioxidants that can be used in the food industry and possibly for the development of new sustainable packaging materials with the ability to extend the shelf-life of foods and reduce oxidation. With this in mind, the seasonal variations in the chemical composition and antioxidant activity of brown seaweed (Padina pavonica) extracts were investigated. The highest total phenolic content (TPC) and antioxidant activity (measured by ferric reducing/antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, and oxygen radical absorbance capacity (ORAC)) were found for P. pavonica June extract. The TPC of 26.69 ± 1.86 mg gallic acid equivalent/g, FRAP of 352.82 ± 15.41 µmole Trolox equivalent (TE)/L, DPPH of 52.51 ± 2.81% inhibition, and ORAC of 76.45 ± 1.47 µmole TE/L were detected. Therefore, this extract was chosen for the development of bioactive PLA bilayer film, along with chitosan. Primary or quaternary chitosan was used as the first layer on polylactic acid (PLA) films. A suspension of chitosan particles with entrapped P. pavonica extract was used as the second layer. X-ray photoelectron spectroscopy confirmed the presence of layers on the material surface. The highest recorded antioxidant activity of the newly developed films was 63.82% inhibition. The developed functional films exhibited antifogging and antioxidant properties, showing the potential for application in the food industry.
Ključne besede: functional PLA films, seaweed and chitosan bilayer, sustainable natural antioxidants, microwave-assisted extraction
Objavljeno v DKUM: 23.08.2023; Ogledov: 331; Prenosov: 17
.pdf Celotno besedilo (3,28 MB)
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Design and development of sustainable capsule collection : magistrsko delo
Lucie Görlichová, 2023, magistrsko delo

Opis: The current fast fashion system has a negative impact on the environment, exploits natural resources, and violates workers' rights. The aim of this master's thesis is to design and develop a sustainable capsule collection of versatile and timeless garments that can be worn in different ways over a long period of time. The thesis includes theoretical and practical research on sustainability, sustainable materials, collection development and sustainable design methods. Final collection is made of natural and eco-friendly materials and implements various sustainable approaches. The concept of the collection proves that garments can be made in harmony with nature and still be modern and fashionable.
Ključne besede: capsule collection, sustainable development, sustainable fashion, natural fabrics
Objavljeno v DKUM: 17.04.2023; Ogledov: 396; Prenosov: 55
.pdf Celotno besedilo (7,73 MB)

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