1. Konstruiranje testne priprave za pbc sklope s pomočjo analize mke : diplomsko deloMitja Dšuban, 2024, undergraduate thesis Abstract: V diplomskem delu so opisane različne vrste testnih priprav, ki se uporabljajo v proizvodnji elektronik. Diplomsko delo govori o konstrukciji testne priprave za določeno elektroniko, na kateri je potrebno preveriti funkcionalnost elektronike. Po končani konstrukciji se s pomočjo MKE analize preveri, ali je elektronika med samim testiranjem preobremenjena. Po uspešni analizi je potrebno sprogramirati programe za elemente testne priprave, ki bodo izdelani na CNC rezkalnem stroju. Za elemente, ki so bili izdelani na klasičnem rezkalnem stroju ali univerzalni stružnici, se pripravijo delavniške risbe. Za lažjo sestavo testne priprave so se izdelale sestavne risbe, s katerimi si je sestavljalec pomagal.
Keywords: testna priprava, elektronika, simulacija, CNC, programiranje, risbe
Published in DKUM: 11.04.2025; Views: 0; Downloads: 6
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2. Hydrothermal decomposition of virgin and waste polylactic acid with subcritical water under N[sub]2 and air atmospheresMaja Čolnik, Mihael Irgolič, Mojca Škerget, 2025, original scientific article Abstract: This study addresses the inherent shortcomings of poly (lactic acid) (PLA), a biodegradable polymer widely used in industries such as packaging and biomedical applications. The principal challenge of PLA resides in its low crystallinity, which detrimentally affects its mechanical properties and thermal stability. Additionally, PLA is prone to water and hydrolysis, which compromises its chemical resistance and can lead to degradation over time. To overcome surmount these limitations, the study focuses on the development of hybrid films through the blending of PLA with poly (l-lactide-co-ethylene adipate) (pLEA) block copolymers. The objective is to augment the crystallinity, mechanical performance, and chemical resistance of the resulting materials. The study employs a range of analytical techniques, including Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Polarised Light Microscopy (PLM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA), to thoroughly characterize the copolymers and blend films. By systematically selecting blending ratios and processing methodologies, the study demonstrates enhancements in the properties of the resultant hybrid films compared to neat PLA. Specifically, the structure of films significantly changed from amorphous to crystalline in a short duration - 5 min, of annealing., leading to better tensile strength, modulus and reduced wettability, which are crucial for applications requiring durability and resistance to environmental factors. Films made from 30 wt% of pLEA 97.5/2.5 with 70 % of PLA by fast cooling exhibited outstanding mechanical properties, with a tensile strength 20 MPa higher than that of neat PLA films. Additionally, the chemical resistance may be improved, as evidenced by a decrease in wettability by approximately 15° and a reduction in the polar component of the surface free energy by about 7 mN/m. Hydrophobic, water-repellent materials resist penetration by water and other polar solvents, reducing exposure to corrosive substances and enhancing chemical resistance through barrier protection. Overall, this research addresses the limitations of PLA through innovative copolymerization and blending strategies, offering valuable insights into optimizing the material's properties for various practical applications.
Keywords: biopolymers recycling, polylactic acid, subcritical water, lactic acid, carboxylic acids, gaseous products
Published in DKUM: 01.04.2025; Views: 0; Downloads: 1
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3. Functional coatings with ethyl cellulose-calcium carbonate alkaline nanoparticles for deacidification and mechanical reinforcement of paper artifactsMatej Bračič, Jasna Malešič, Mihael Brunčko, Doris Bračič, Alenka Ojstršek, Tea Kapun, Sašo Gyergyek, Karin Stana-Kleinschek, Tamilselvan Mohan, 2025, original scientific article Abstract: Paper artifacts susceptible to acid hydrolysis and mechanical stress require effective conservation methods to ensure their longevity. In this study, a novel approach for the deacidification of acidic paper using calcium carbonate (CaCO3) [1,2]-ethylcellulose nanoparticles (CaCO3-EC NPs) dispersed in a non-aqueous ethyl acetate solution is presented. The dispersions were carefully prepared and applied to model acidic paper samples using a dipcoating method and then analyzed for their effectiveness. Transmission electron microscopy showed the formation of agglomerates containing quadrangular alkaline nanoparticles with diameters of 40 to 100 nm and a total agglomerate size of 250 nm. Hydrodynamic analyzes indicate the presence of a swollen ethyl cellulose coating on these agglomerates, which facilitates their dispersion. The results show the effectiveness of the CaCO3-EC NPs system in neutralizing acidic components (change of paper pH from 4.3 to 7) due to the homogeneous distribution within the paper substrates, effectively arresting the degradation processes. Acid-base titration showed a linear correlation between the concentration of alkaline nanoparticles and the alkaline reserve, emphasizing the role of ethylcellulose in facilitating particle transport within the paper matrix. In addition, ethylcellulose was found to improve the mechanical properties of the treated paper, as demonstrated by the standard mechanical tests. Importantly, the optical properties remained unchanged after treatment, as no adverse changes in color were observed. These results underline the effectiveness of the developed deacidification dispersions for the treatment of acidic paper and potentially other cellulose-based cultural heritage documents prone to acidic degradation. This approach offers promising implications for preserving and restoring valuable historical materials.
Keywords: ethylcellulose, calcium carbonate, functional coating, deacidification, strengthening, cultural heritage
Published in DKUM: 20.03.2025; Views: 0; Downloads: 1
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4. Oxidation behaviour of microstructurally highly metastable Ag-La alloyAndraž Jug, Mihael Brunčko, Rebeka Rudolf, Ivan Anžel, 2022, original scientific article Abstract: A new silver-based alloy with 2 wt.% of lanthanum (La) was studied as a potential candidate
for electric contact material. The alloy was prepared by rapid solidification, performed by the melt
spinning technique. Microstructural examination of the rapidly solidified ribbons revealed very fine
grains of αAg and intermetallic Ag5La particles, which appear in the volume of the grains, as well as
on the grain boundaries. Rapid solidification enabled high microstructural refinement and provided
a suitable starting microstructure for the subsequent internal oxidation, resulting in fine submicronsized La2O3 oxide nanoparticle formation throughout the volume of the silver matrix (αAg). The
resulting nanostructured Ag-La2O3 microstructure was characterised by high-resolution FESEM
and STEM, both equipped with EDX. High-temperature internal oxidation of the rapidly solidified
ribbons essentially changed the microstructure. Mostly homogeneously dispersed nano-sized La2O3
were formed within the grains, as well as on the grain boundaries. Three mechanisms of internal
oxidation were identified: (i) the oxidation of La from the solid solution; (ii) partial dissolution of
finer Ag5La particles before the internal oxidation front and oxidation of La from the solid solution;
and (iii) direct oxidation of coarser Ag5La intermetallic particles.
Keywords: Ag-La alloy, rapid solidification, metastable microstructure, internal oxidation, characterisation, formation mechanism
Published in DKUM: 20.03.2025; Views: 0; Downloads: 1
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5. Sistem za avtomatizirano testiranje prototipnih tiskanih vezijMihael Pajžlar, 2025, master's thesis Abstract: V magistrskem delu je obravnavano načrtovanje in implementacija sistema za avtomatsko testiranje tiskanih vezij na prototipih pred serijsko proizvodnjo. V nalogi so predstavljene ključne tehnologije in standardi, ki so pomembni za razvoj sistema. Strežniški del sistema je bil razvit s programskim jezikom Python in uporabo ogrodja FastAPI in Uvicorn. Odjemalni del sistema je prav tako razvit s programskim jezikom Python, vendar z uporabo okolja JupyterLab. Podatki in poročila se shranjujejo v oddaljeno podatkovno bazo MySQL. Sistem omogoča hitrejše izvajanje enakih testov v enakih pogojih, saj poročilo in priložena datoteka vsebujeta vse potrebne informacije za ponovno izvedbo testiranja. Cilj razvoja sistema je razbremenitev testerja pisanja poročila in s tem pospešitev izvajanja testov, pri čemer pa ne trpi kvaliteta izvajanja testa.
Keywords: programsko inženirstvo, RESTful spletne storitve, avtomatizacija, testiranje, poročilo
Published in DKUM: 04.03.2025; Views: 0; Downloads: 24
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6. Sodobni inženirski materialiIvan Anžel, Franc Zupanič, Mihael Brunčko, 2025, other educational material Abstract: Skripta, Sodobni inženirski materiali je kot temeljno študijsko gradivo namenjeno pervenstveno študentom 2. stopnje študijskih programov Strojništva, Gospodarskega inženirstva, Mehatronike in študentom Inženirsko oblikovanja izdelkov. Skripta je sestavljena iz treh poglavij: (i) Zgradba in izbira inženirskih materialov; (ii) Lastnosti inženirskih materialov; (iii) Primeri sodobnih inženirskih materialov. V prvem poglavju je obravnavana zgradba kovinskih, keramičnih, polimernih in kompozitnih materialov ter predstavljeni so kriteriji, ki omogočajo inženirjem glede na želeno kombinacijo lastnosti materialov, njihovo ustrezno izbiro za določeno aplikacijo. Drugo poglavje obravnava lastnosti sodobnih inženirskih materialov s poudarkom na poglobljenem študiju razlage korelacij med zgradbo, mikrostrukturo in lastnostmi. V zadnjem najobsežnejšem poglavju so predstavljeni izbrani primeri sodobnih inženirskih materialov, katerih uporaba e v industrijski praksi dandanes zelo aktualna. Če naštejemo samo najbolj zanimive: disperzijsko utrjeni materiali, spominske zlitine, konstrukcijska keramika, materiali za shranjevanje vodika, hitrostrjeni kovinski materiali, sodobne aluminijeve zlitine, biopolimeri in še mnogi drugi.
Keywords: sodobni inženirski materiali, zgradba, izbira materialov, mikrostruktura, lastnosti
Published in DKUM: 27.02.2025; Views: 0; Downloads: 749
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7. Hydrolytic decomposition of corncobs to sugars and derivatives using subcritical waterMaja Čolnik, Mihael Irgolič, Amra Perva, Mojca Škerget, 2025, original scientific article Abstract: Corncobs are a widespread and renewable by-product of corn cultivation that are typically considered waste or low-value material. Corncobs contain hemicellulose, cellulose, and lignin, which can be converted into valuable products using suitable techniques. Subcritical water is increasingly used as a green medium for the extraction of valuable components from biomass, as it has many advantageous properties (high yield, pure extracts, shorter times) compared to other organic solvents. For this reason, subcritical water was used in this study to extract valuable components from corncobs at different temperatures (150–250 °C) and reaction times (10–60 min). During the decomposition of corncobs, numerous valuable products are formed in the aqueous phase depending on the temperature and reaction time. In addition to sugars and their derivatives, phenolic compounds were also formed, which are of great importance in numerous applications. It was found that at low temperatures (150–170 °C) the hemicellulose in the corncobs begins to decompose and, in particular, the sugars (glucose, xylose, arabinose, and galactose) are initially formed in the aqueous phase. Higher temperatures (200 and 250 °C) are more favorable for the decomposition of corncobs into valuable components. The yield of sugars increases with temperature due to the degradation of the cellulose content of the lignocellulosic biomass. At the same time, several new valuable products (furfural, 5-hydroxymethylfurfural (5-HMF), 1,3-dihydroxyacetone, levulinic acid, and formic acid as well as phenolic components) are formed through the degradation of lignin and the further degradation of sugars. The most important products are certainly the furfurals, which are central platform compounds. The highest furfural content was reached at 200 °C and 60 min and accounted for almost half of all components in the aqueous phase (472.01 ± 5.64 mg/g dry extract). These biomass-derived sugars and derivatives can be used in the production of fuels, pharmaceuticals, biodegradable polymers, and surfactants.
Keywords: corncobs, subcritical water, biomass, valuable compounds, sugar derivates
Published in DKUM: 07.02.2025; Views: 0; Downloads: 8
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9. Integrirani molekularni tkivni označevalci : matematični model v pristopu k oceni in predvidevanju raka prostate s tkivnimi molekularnimi označevalciMiha Munda, 2024, original scientific article Abstract: Standardni kriteriji za diagnozo raka prostate mnogokrat niso zadostni, da bi predvideli potek in izhod te pogoste bolezni. Vrednotenje molekularnih tkivnih označevalcev, še posebej tistih, ki označujejo apoptozo in proliferacijo, integrirani v matematični model, lahko pridonese k boljšemu razumevanju razvoja in patogeneze te bolezni; nadalje tudi k izboru oz. določitvi adekvatne terapije in bi odprlo tudi nove perspektive v iskanju novih terapij.
Keywords: matematični model, rak prostate, tkivni označevalec, p53, bcl-2, CD105, mathematical model, prostate cancer, tissue marker, p53, bcl-2, CD105
Published in DKUM: 28.01.2025; Views: 0; Downloads: 19
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10. Comparative analysis of a 3D printed polymer bonded magnet composed of a TPU-PA12 matrix and Nd-Fe-B atomised powder and melt spun flakes respectivelyGranit Hajra, Mihael Brunčko, Leo Gusel, Ivan Anžel, 2025, original scientific article Abstract: The present study reports the development of new polymer bonded magnet containing a Thermoplastic Polyurethane (TPU) – Nylon (PA12) blend as the matrix material and Nd-Fe-B magnetic particles. Two composite materials were explored: one using Nd-Fe-B atomised spherical powder (ASP) and another incorporating Nd-Fe-B melt-spun flakes (MSF). The filaments were formulated by blending TPU, PA12, and one of selected type of Nd-Fe-B particles using a mixing device. The ASP and the MSF were integrated into the matrix via a precise compounding process and 3D printing was used to produce the testing specimens. The preliminary findings indicate that both formulations exhibited promising magnetic properties while maintaining the mechanical characteristics of TPU and PA12. The atomised spherical powder formulation demonstrated worse magnetic behaviour compared to the melt-spun flake formulation. ASP particles enable better fluidity of the composite material during 3D printing. However, the close-packed arrangement of these particles is the cause of much higher porosity and consequently the poorer mechanical and magnetic properties. Optimization of the processing parameters showed significant influence on the final magnetic performance and structural integrity of the printed specimens.
Keywords: bonded magnets, Nd-Fe-B melt spun flakes, Nd-Fe-B atomised powders, material extrusion, additive manufacturing, fused specimen fabrication
Published in DKUM: 08.01.2025; Views: 0; Downloads: 9
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