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Integration of Talum's roll-bond heat exchanger for different applications
Janko Ferčec, Rajko Habjanič, 2019, original scientific article

Abstract: This article presents the integration of heat exchangers made using the roll-bond technology of Talum d.d., Kidričevo, Slovenia, to applications in refrigeration and heating technology. Talum has more than 30 years of tradition in the production of evaporators for cooling technology and heat exchangers for various purposes, such as absorbers and condensers. The heat exchangers produced in Talum are made of aluminium or aluminium alloys and are categorized as flat heat exchangers. Aluminium and aluminium alloys can be completely recycled after they reach the final phase of their life cycle, which is an essential feature in terms of sustainable construction. The roll-bond technology enables the manufacture of heat exchangers with a complex geometry of channels, which enables them to be used for various applications. Enabled through roll-bond technology, all of these features give the roll-bond heat exchanger a very useful and functional value. In this article, we focused only on some implemented and potential applications of heat exchangers made with using the roll-bond technology.
Keywords: talum, roll-bond, heat exchanger, evaporator, absorber
Published in DKUM: 05.12.2023; Views: 192; Downloads: 5
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Thermal analysis and application of roll bond solar absorbers for heating and cooling in residential buildings
Jurij Avsec, Daniel Brandl, Helmut Schober, Urška Novosel, Janko Ferčec, 2019, original scientific article

Abstract: The use of renewable energy sources will have to be increased significantly over the coming decades. The potential of solar energy in Slovenia represents the largest share of renewable energy sources. This article shows the use of roll bond solar absorbers for the heating and cooling of houses. For this purpose, we performed a numerical simulation of solar absorbers and theoretical calculations.
Keywords: roll bond technology, STAF panel, solar technology, heat pump
Published in DKUM: 05.12.2023; Views: 238; Downloads: 4
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Production, thermal analysis and application of roll bond solar absorbers for heating and cooling in residential buildings
Jurij Avsec, Daniel Brandl, Helmut Schober, Urška Novosel, Janko Ferčec, 2019, published scientific conference contribution

Abstract: The effects of global warming are a crucial issue in the near future. The combination of renewable energy sources (RES) and the use of alternative energy technology such as heat pumps and hydrogen technology could solve major ecological problems. In Central Europe, the energy demand for heating and cooling in residential buildings is clearly higher than for generation of electricity or energy for trucking e.g. In this paper, a new solar thermal absorber has been analysed which is produced by using the so called "roll bond" technology (ABS Network, 2018). The focus of this study lies on the determination of the energy efficiency by combining this solar thermal absorber with heat pumps and biomass or geothermal systems in the region of Central Europe.
Keywords: roll bond solar absorbers, thermal analysis, solar systems, heat pump systems, heating and cooling in residential buildings
Published in DKUM: 04.12.2023; Views: 261; Downloads: 14
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Force measurements on teeth using fixed orthodontic systems
Rebeka Rudolf, Janko Ferčec, 2013, review article

Abstract: The fixed orthodontic appliance consists of brackets that are bonded to the teeth. When the wire is engaged in the slot of the brackets, it generates forces for orthodontic tooth movement. The change in periodontal blood supply provides a biological response which leads to remodelling of the alveolar bone and the orthodontic tooth movement. Many variables influencing orthodontic treatment cannot be controlled fully, such as growth and tissue response to appliances. However, the force placed on the tooth should be a controllable variable, and a careful study of the physics underlying clinical applications can help in reducing undesirable side effects. The properties of orthodontic wires such as: strength, stiffness, elasticity and spring-back define their clinical usefulness. The ideal orthodontic wire should exhibit the following properties: large spring-back, low stiffness, good formability, high stored energy, biocompatibility and environmental stability, low surface friction, and the capability of being welded or soldered to auxiliaries. The ideal arch wire has not been introduced yet. Once the wire is activated or bent, it is the unloading or deactivating forces that produce the orthodontic tooth movement. For these reasons, it is necessary to know the force level caused by each individual wire used in orthodontic treatment. Finally, the purpose of this paper is a presentation of force measurements which are generated by different super-elasticity NiTi wires.
Keywords: force measurements, orhodontic system, teeth, NiTi alloys
Published in DKUM: 09.08.2017; Views: 1245; Downloads: 342
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The correlation between pain perception among patients with six different orthodontic archwires and the degree of dental crowding
Evgenija Marković, Janko Ferčec, Ivana Ščepan, Branislav Glišić, Nenad Nedeljković, Jovana Juloski, Rebeka Rudolf, 2015, original scientific article

Abstract: Introduction: Forces generated in orthodontic treatment with fixed appliances create tension and compression zones in the periodontal ligament resulting in a painful experience for patients. In the first phase of orthodontic treatment, when leveling of teeth is needed, nickel-titanium (NiTi) archwires can be completely engaged in brackets, even in the cases of extreme crowding, exerting small forces. There is a great individual variation in the pain perception related to the application of orthodontic forces. Objective: The aim of this study was to investigate the pain perception among patients with dental crowding after insertion of six different NiTi orthodontic archwires as a part of fixed appliances in the first stage of orthodontic treatment. Methods: The study was conducted on a sample of 189 orthodontic patients receiving one of six different either superelastic or heat activated NiTi archwires, in the first phase of orthodontic treatment. Pain perception was evaluated in groups of patients with different degree of crowding. The modified McGill Pain Questionnaire with Visual Analogue Scale was used to evaluate the quality and intensity of pain. Statistical analysis was performed using simple descriptive statistics, and Pearson`s chi-square test with statistical significance of p<0.05. Results: Majority of patients reported pain as discomfort or pressure of moderate intensity caused by chewing or biting, started within 12 hours, carried on for 3-4 days, and decreased over time without self-medication. Conclusion: No correlation was found between pain perception among patients with different types of NiTi archwires and the degree of crowding.
Keywords: nickel-titanium archwires, pain, dental crowding, orthodontics
Published in DKUM: 04.08.2017; Views: 1211; Downloads: 334
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Microstructure of NiTi orthodontic wires observations using transmission electron microscopy
Janko Ferčec, Darja Feizpour, Borut Buchmeister, Franc Rojko, Bojan Budič, Borut Kosec, Rebeka Rudolf, 2014, original scientific article

Abstract: This work presents the results of the microstructure observation of six different types of NiTi orthodontic wires by using Transmission Electron Microscopy (TEM). Within these analyses the chemical compositions of each wire were observed in different places by applying the EDS detector. Namely, the chemical composition in the orthodontic wires is very important because it shows the dependence between the phase temperatures and mechanical properties. Micro- structure observations showed that orthodontic wires consist of nano-sized grains containing precipitates of Ti2Ni and/or TiC. The first precipitated Ti2Ni are rich in Ti, while the precipitated TiC is rich in C. Further investigation showed that there was a difference in average grain size in the NiTi matrix. The sizes of grains in orthodontic wires are in the range from approximately 50 to 160 nm and the sizes of precipitate are in the range from 0,3 μm to 5 μm.
Keywords: orthodontic wires, nickel-titanium orthodontic wire, NiTi wire, shape memory alloys, SMA wires, microstructure, transmission electron microscopy, TEM, average grain size
Published in DKUM: 03.07.2017; Views: 1420; Downloads: 120
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Pressing of partially oxide-dispersion-strengthened Copper using the ECAP process
Matija Kos, Janko Ferčec, Mihael Brunčko, Rebeka Rudolf, Ivan Anžel, 2014, original scientific article

Abstract: A combination of internal oxidation (IO) and equal channel angular pressing (ECAP) was used to explore the possibility of uniting the mechanisms of dispersion and deformation strengthening to improve the properties of a Cu-Al alloy with 0.4 % Al. The IO of Cu-Al billets served in the first step of the experiment as a means for dispersion, strengthening the mantle of the billets with a fine dispersion of nanosized oxide particles. The experimental procedure continued with deformation strengthening performed by ECAP, which allowed an intense plastic strain through simple shear. Material flow in a partly internally oxidized Cu-0.4 % Al billet and in a homogenous reference sample made of modelling mass was also studied to analyse, on the macroscale, the influence of the internal oxidation zone (IOZ) on the material flow behaviour during the ECAP process. The analysis was performed with the aim of revealing the uniformity of the strain distribution and to obtain information about the deformation strengthening across the volume of the billet. We found that the oxide particles have a minor influence on the material flow on the macroscopic scale during the ECAP process. However, the degree of deformation strengthening in the IOZ was much lower than in the unoxidized core region. The combination of IO and ECAP allows us to produce a Cu composite composed of a hardened oxidized mantle region with good electrical and thermal conductivity and a high- hardened core region. This combination represents a new technological route for the production of high-hardness Cu composites, which could also be used at higher temperatures.
Keywords: ECAP, Cu-Al alloys, strengthening mechanisms, internal oxidation
Published in DKUM: 17.03.2017; Views: 1376; Downloads: 90
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Comparison of NiTi orthodontic archwires and a determination of the charasteristic properties
Janko Ferčec, Matija Kos, Mihael Brunčko, Ivan Anžel, Branislav Glišić, Evgenija Marković, Rebeka Rudolf, 2014, original scientific article

Abstract: The aim of this paper was to analyse the characteristic properties of six different, commercially available nickel-titaniumorthodontic wires with a diameter of 0.305 mm (0.014"). The characteristic properties were determined by usingsemi-quantitative EDX analyses, DSC analyses for a determination of the phase temperatures, and a tensile test to obtain themechanical properties of the wires. The investigation of the chemical composition showed an equiatomic NiTi alloy. Analysesof phase temperatures showed that the nickel-titanium orthodontic wires were, in an austenitic microstructure, exhibiting asuperelastic effect in the oral environment. The uniaxial tensile stressstrain curves showed different values for the beginningand the end of the transformation range during the loading.
Keywords: shape-memory alloy, phase transformation, thermal analysis, tensile test
Published in DKUM: 21.12.2015; Views: 1477; Downloads: 106
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Determination of stresses and forces on the orthodontic system by using numerical simulation of the finite elements method
Janko Ferčec, Branislav Glišić, I. Šćepan, Evgenija Marković, Dragoslav Stamenković, Ivan Anžel, Jože Flašker, Rebeka Rudolf, 2012, original scientific article

Abstract: This study was addressed to use knowledge about the orthodontic system with numerical simulation of the nite elements method. For the rst time we simulated the stresses on the orthodontic system and, in this manner, calculated the orthodontic force on the tooth. A 3D orthodontic model or orthodontic system was designed resembling moderate crowding in the dental arch with all supporting structures. CATIA V5 computer software was used to set up a model for the orthodontic system and ABAQUS was used for simulation of the stresses on the orthodontic system. Our attention was focused on the stresses on the tooth lateral incisor and its periodontal ligament. The results of the numerical simulation showed complex stresses on the tooth lateral incisor and its periodontal ligament. In this paper is presented a calculation of the orthodontic force acting on the tooth lateral incisor due to the orthodontic wire. This orthodontic force was calculated from the stresses on the bracket. The calculated orthodontic force was in the area which is considered as the optimal orthodontic force for movement of the tooth.
Keywords: okluzija, ortodontski sistem, metoda končnih elementov, ortodonske sile, zobje, malocclusion, orthodontic system, finite elements method, orthodontic force, tooth
Published in DKUM: 10.07.2015; Views: 1298; Downloads: 104
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Janko Ferčec, 2014, doctoral dissertation

Abstract: V doktorski disertaciji je obravnavan problem vpliva večosnega napetostnega stanja na začetek in potek superelastičnega področja pri spominski zlitini Ni-Ti. Za raziskovalno delo je bila uporabljena komercialno dostopna ortodontska žica Ni-Ti z vsebnostjo 50,6 at.%Ni. V prvem delu raziskav smo izvedli karakterizacijo izbranega materiala. Določili smo transformacijske temperature Ms, Mf, As, Af, module elastičnosti, napetosti in deformacije na začetku in koncu superlastičnega področja ter analizirali mikrostrukturo v izhodnem nedeformiranem stanju. Z in-situ merjenjem električnega upora med obremenjevanjem pri enoosnem nategu na napravi za simulacijo enoosnega napetostnega stanja smo potrdili uporabnost te metode za določitev prehoda v superelastično stanje oziroma za spremljanje napetostno inducirane martenzitne fazne transformacije. Na osnovi teh rezultatov smo v drugem delu raziskav razvili napravo za simulacijo večosnega napetostnega stanja z možnostjo in situ merjenja električne upornosti in mikrotrdote. Z upogibom, torzijo ter kombinacijo torzije in upogiba smo simulirali obremenitve, ki so prisotne pri ortodontskem zdravljenju. S sočasnim merjenjem električnega upora smo za ta večosna napetostna stanja določili prehod v superelastično področje. Z analizo mikrostruktur pred in po obremenitvah smo identificirali spremembe in postavili modele razvoja mikrostrukture za različna napetostna stanja.
Keywords: spominska zlitina NiTi, ortodontska žica, fazna transformacija, mikrostruktura
Published in DKUM: 24.04.2014; Views: 2174; Downloads: 331
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