Search the digital library catalog

Abstract: Water hammer phenomena in pipelines can induce significant transient pressure surges, leading to structural failures and operational inefficiencies. This study presents a comparative analyzis of two numerical approaches for simulating water hammer: a one-dimensional (1D) inviscid model with added friction based on the Euler equations and the method of characteristics, and a three-dimensional (3D) viscous model utilizing the Navier-Stokes equations in OpenFOAM. Benchmarking problems are solved first, then both methods are used to study a 3.4 km long DN400 pipeline subject to sudden pump failure by analyzing pressure surges, cavitation, and water column separation. The 1D model effectively predicts transient pressure waves and cavitation conditions with minimal computational cost, while the 3D model provides a detailed representation of multiphase flow dynamics, including cavitation bubble growth and collapse via the volume of fluid method. To mitigate adverse effects, a dynamic combination air valve is introduced, and its effectiveness in reducing pressure surges and cavitation is demonstrated. The results highlight the trade-offs between computational efficiency and accuracy in modelling water hammer events and underscore the importance of protective measures in pipeline systems.
Keywords: wood-based material, renewable resources, recycling, new materials
Published in DKUM: 09.12.2025; Views: 0; Downloads: 14
Full text (120,97 KB)
This document has many files! More...

Abstract: Strateške kovine, med katere spada tudi baker, predstavljajo ključne surovine v sodobni industriji, zlasti pri razvoju elektronskih in električnih naprav. Zaradi omejenih naravnih virov in naraščajočega povpraševanja postaja njihovo pridobivanje iz sekundarnih virov, kot so elektronski in električni odpadki (e-odpadki), vse pomembnejše. Ena izmed obetavnih metod na tem področju je magnetna nanohidrometalurgija (MNHM), ki združuje hidrometalurške postopke z nanotehnologijo in temelji na adsorpciji kovinskih ionov z uporabo funkcionaliziranih magnetnih nanodelcev. V magistrskem delu smo sintetizirali magnetne nanodelce (MNPs), funkcionalizirane z λ-karagenanom (λ-CARR), naravnim polisaharidom, z namenom učinkovite adsorpcije strateških kovin iz vodnih raztopin, kjer adsorpcijska mesta predstavljajo sulfatne skupine. Kristalno strukturo nanoadsorbenta smo okarakterizirali z rentgensko praškovno difrakcijo (XRD), njegovo morfologijo in velikost pa določili s transmisijsko elektronsko mikroskopijo (TEM). Površinsko kemijo magnetnih nanodelcev, prevlečenih z λ-CARR, smo kvalitativno analizirali s Fourierjevo transformacijsko infrardečo spektroskopijo (ATR-FTIR), ter podrobneje z rentgensko fotoelektronsko spektroskopijo (XPS). Z dinamičnim sipanjem svetlobe (DLS) in meritvami ζ-potenciala smo ovrednotili velikost delcev in njihov površinski naboj. Količino vezanega polisaharida na površini nanodelcev smo določili s termogravimetrično analizo (TGA), magnetne lastnosti pa preverili z vibracijskim vzorčnim magnetometrom (VSM). Razviti magnetni polisaharidni nanoadsorbent (MNPs@CARR) je pokazal potencial za odstranjevanje bakrovih ionov. Preučili smo vpliv različnih parametrov na adsorpcijsko učinkovitost, in sicer: maso adsorbenta, pH-vrednost raztopine, začetno koncentracijo Cu²⁺, kontaktni čas, temperaturo ter možnosti regeneracije in ponovne uporabe adsorbenta. Koncentracijo bakrovih ionov smo določali s kolorimetrično metodo s pomočjo fotometra. Kot optimalne pogoje za odstranjevanje Cu²⁺ z MNPs@CARR smo določili: γ (Cu2+) = 1,3 mg L−1, V= 20 mL, pH=6, T = 298 K, 20 mg adsorbenta, kontaktni čas=2 h, pri čemer smo dosegli 84,6 % učinkovitost odstranjevanja. Pri teh pogojih je MNPs@CARR po štirih ciklih regeneracije ohranil približno 60 % začetne adsorpcijske zmogljivosti. Rezultati nakazujejo, da je sintetiziran nanomaterial primeren za trajnostno obdelavo in predelavo strateških in kritičnih kovin (Al, Sr, B) iz sekundarnih virov, kot so tiskana vezja mobilnih telefonov.
Keywords: magnetni polisaharidni nanoadsorbent, strateške kovine, baker, predelava kovin, e-odpadki, magnetna nanohidrometalurgija, trajnostno ravnanje z viri
Published in DKUM: 02.10.2025; Views: 0; Downloads: 54
Full text (5,05 MB)

Abstract: The rapid growth in wearable technology has recently stimulated the development of conductive textiles for broad application purposes, i.e., wearable electronics, heat generators, sensors, electromagnetic interference (EMI) shielding, optoelectronic and photonics. Textile material, which was always considered just as the interface between the wearer and the environment, now plays a more active role in different sectors, such as sport, healthcare, security, entertainment, military, and technical sectors, etc. This expansion in applied development of e-textiles is governed by a vast amount of research work conducted by increasingly interdisciplinary teams and presented systematic review highlights and assesses, in a comprehensive manner, recent research in the field of conductive textiles and their potential application for wearable electronics (so called e-textiles), as well as development of advanced application techniques to obtain conductivity, with emphasis on metal-containing coatings. Furthermore, an overview of protective compounds was provided, which are suitable for the protection of metallized textile surfaces against corrosion, mechanical forces, abrasion, and other external factors, influencing negatively on the adhesion and durability of the conductive layers during textiles’ lifetime (wear and care). The challenges, drawbacks and further opportunities in these fields are also discussed critically.
Keywords: metallization, conductive textiles, e-textiles, coatings techniques, protective coatings, durability
Published in DKUM: 16.06.2025; Views: 0; Downloads: 5
Full text (10,68 MB)
This document has many files! More...

Abstract: The presented review summarizes recent studies in the field of electro conductive textiles as an essential part of lightweight and flexible textile-based electronics (so called e-textiles), with the main focus on a relatively simple and low-cost dip-coating technique that can easily be integrated into an existing textile finishing plant. Herein, numerous electro conductive compounds are discussed, including intrinsically conductive polymers, carbon-based materials, metal, and metal-based nanomaterials, as well as their combinations, with their advantages and drawbacks in contributing to the sectors of healthcare, military, security, fitness, entertainment, environmental, and fashion, for applications such as energy harvesting, energy storage, real-time health and human motion monitoring, personal thermal management, Electromagnetic Interference (EMI) shielding, wireless communication, light emitting, tracking, etc. The greatest challenge is related to the wash and wear durability of the conductive compounds and their unreduced performance during the textiles’ lifetimes, which includes the action of water, high temperature, detergents, mechanical forces, repeated bending, rubbing, sweat, etc. Besides electrical conductivity, the applied compounds also influence the physical-mechanical, optical, morphological, and comfort properties of textiles, depending on the type and concentration of the compound, the number of applied layers, the process parameters, as well as additional protective coatings. Finally, the sustainability and end-of-life of e-textiles are critically discussed in terms of the circular economy and eco-design, since these aspects are mainly neglected, although e-textile’ waste could become a huge problem in the future when their mass production starts.
Keywords: electro conductive textiles, dip-coating, characterization, functional features, durability, sustainability, recyclability
Published in DKUM: 27.03.2025; Views: 0; Downloads: 9
Full text (3,34 MB)
This document has many files! More...

Abstract: The outbreak of the worrisome coronavirus disease in 2019 has caused great concern among the global public, especially regarding the need for personal protective equipment with applied antiviral agents to reduce the spread and transmission of the virus. Thus, in our research, chitosan-based bioactive polymers as potential antiviral agents were first evaluated as colloidal macromolecular solutions by elemental analysis and charge. Three different types of low and high molecular weight chitosan (LMW Ch, HMW Ch) and a LMW Ch derivative, i.e., quaternary chitosan (quart-LMW Ch), were used. To explore their antiviral activity for subsequent use in the form of coatings, the macromolecular Chs dispersions were incubated with the model virus phi6 (surrogate for SARS-CoV-2), and the success of virus inactivation was determined. Inactivation of phi6 with some chitosan-based compounds was very successful (>6 log), and the mechanisms behind this were explored. The changes in viral morphology after incubation were observed and the changes in infrared bands position were determined. In addition, dynamic and electrophoretic light scattering studies were performed to better understand the interaction between Chs and phi6. The results allowed us to better understand the antiviral mode of action of Chs agents as a function of their physicochemical properties.
Keywords: bacteriophage phi6, bioactive polysaccharide biomaterials, chitosans, antiviral activity, dynamic and electrokinetic light scattering, charge, biointerfaces
Published in DKUM: 26.03.2025; Views: 0; Downloads: 5
Full text (4,27 MB)
This document has many files! More...