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Simulation of flow conditions in nuclear power plant reactor pressure vessel lower plenum experimental facility
Blaž Kamenik, 2019, magistrsko delo

Opis: The flow conditions during the experiment LIVE2D on reactor core melt behaviour in the lower plenum of a reactor pressure vessel, performed at the Karlsruhe Institute of Technology (Germany), were simulated with a Computational Fluid Dynamics computer code. In this hypothetical severe accident scenario in a pressurized water reactor nuclear power plant, the melt is divided into an oxidic layer and a metallic layer on top of it, and the oxidic layer is volumetrically heated due to decay heat. In the experiment, oil and salt were used as simulant materials for metallic and oxidic melt, respectively. The main goal of performed simulations was to investigate the so-called “focusing effect”, where a thin layer of the reactor vessel steel wall is exposed to high heat flux. Due to the length of experiment, which exceeds 100 hours, only intervals of the melt behaviour were simulated. Four cases were simulated. The first case investigated different boundary conditions for the oil layer behaviour for layer thickness 35 mm. The second case investigated the same conditions with added modelling of the reactor vessel steel wall and salt crust from the lower layer. The third case used similar modelling as the second case to investigate the oil layer behaviour for layer thickness 75 mm. The fourth case investigated both salt and oil layers for oil layer thickness 75 mm. Different analytical and numerical calculations were performed to determine heat losses from simulant liquids to the surroundings, which played an important part in the experiment.
Ključne besede: nuclear power plant, severe accident, reactor core melt, lower plenum, heat flux focusing effect
Objavljeno: 17.09.2019; Ogledov: 478; Prenosov: 81
.pdf Celotno besedilo (6,83 MB)

Razvoj in optimizacija motorja s feritnimi magneti za centralni pogon
Nejc Smolar, 2018, magistrsko delo

Opis: Magistrska naloga se osredotoča na delovanje in konstruiranje električnega motorja. Poudarek je predvsem na modeliranju in optimizaciji motorja, ki deluje po principu preklapljanja magnetnega pretoka (flux switching machine), s feritnimi magneti na rotorju. V prvem delu je razložen postopek modeliranja v programu Flux. Opisani so problemi, ki se lahko pojavijo in naše rešitve za izpostavljene probleme. V drugem delu je prikazan postopek optimizacije motorja, njegovi parametri in izračuni modelov.
Ključne besede: Električni motor, električni pogon, centralni pogon, sinhronski stroj, flux switching machine, FSM, motor s feritnimi magneti, metoda končnih elementov, MKE, modeliranje električnega motorja, Flux
Objavljeno: 23.08.2018; Ogledov: 527; Prenosov: 80
.pdf Celotno besedilo (5,36 MB)

Modeliranje elektromagnetnega aktuatorja in izračun sile na pomični del
Tadej Sel, 2017, delo diplomskega projekta/projektno delo

Opis: V projektnem delu smo opisali delovanje linearnega elektromagnetnega aktuatorja, v nadaljevanju pa smo predstavili postopek računalniškega modeliranja dejanskega aktuatorja v programskem paketu Flux 3D. Opravili smo simulacijske izračune v šestih pozicijah armature aktuatorja. Rezultati numeričnega izračuna so grafično prikazani s smermi gostote magnetnega pretoka v 3D modelu in z barvnim prikazom porazdelitve gostote magnetnega pretoka v 2D prerezu. Preverili smo obremenjenost materiala in izračunali silo, s katero armatura aktuatorja v različnih pozicijah deluje na strojni element.
Ključne besede: računalniško modeliranje, elektromagnetni aktuator, Flux 3D
Objavljeno: 02.10.2017; Ogledov: 1128; Prenosov: 105
.pdf Celotno besedilo (2,25 MB)

Rate-dependent extensions of the parametric magneto-dynamic model with magnetic hysteresis
Simon Steentjes, Martin Petrun, G. Glehn, Drago Dolinar, Kay Hameyer, 2017, izvirni znanstveni članek

Opis: This paper extends the parametric magneto-dynamic model of soft magnetic steel sheets to account for the phase shift between local magnetic flux density and magnetic field strength. This phase shift originates from the damped motion of domain walls and is strongly dependent on the microstructure of the material. In this regard, two different approaches to include the rate-dependent effects are investigated: a purely phenomenological, mathematical approach and a physical-based one.
Ključne besede: magnetic hysteresis, eddies, magnetic flux, viscosity, magnetic fields, magneto-dynamic models, parametric
Objavljeno: 03.08.2017; Ogledov: 604; Prenosov: 327
.pdf Celotno besedilo (567,72 KB)
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The influence of electric arc activation on the speed of heating and the structure of metal in welds
Oleksandr Savytsky, Mychailo Savytsky, Darko Bajić, Yuriy Shkrabalyuk, Tomaž Vuherer, 2016, izvirni znanstveni članek

Opis: This paper presents the results of a research related to the impact of electric arc activation onto drive welding energy and metal weld heating speed. It is confirmed that ATIG and AMIG methods, depending on metal thickness, single pass weldability and chemical composition of activating flux, enable the reduction of welding energy by 2-6 times when compared to conventional welding methods. Additionally, these procedures create conditions to increase metal weld heating speed up to 1,500-5,500 °C/s-1. Steel which can be rapidly heated, allows for a hardened structure to form (with carbon content up to 0.4%), together with a released martensitic structure or a mixture of bainitic-martensitic structures. Results of the research of effectiveness of ATIG and AMIG welding showed that increase in the penetration capability of electric arc, which increases welding productivity, is the visible side of ATIG and AMIG welding capabilities.
Ključne besede: arc welding, active flux, penetration, heating speed, driving energy
Objavljeno: 07.07.2017; Ogledov: 547; Prenosov: 279
.pdf Celotno besedilo (592,40 KB)
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Elliptic fibrations with rank three Mordell-Weilgroup
Mirjam Cvetič, Denis Klevers, Hernan Piragua, Peng Song, 2014, izvirni znanstveni članek

Opis: We analyze general F-theory compactifications with U(1)xU(1)xU(1) Abelian gauge symmetry by constructing the general elliptically fibered Calabi-Yau manifolds with a rank three Mordell-Weil group of rational sections. The general elliptic fiber is shown to be a complete intersection of two non-generic quadrics in P-3 and resolved elliptic fibrations are obtained by embedding the fiber as the generic Calabi-Yau complete intersection into Bl(3)P(3), the blow-up of P-3 at three points. For a fixed base B, there are finitely many Calabi-Yau elliptic fibrations. Thus, F-theory compactifications on these Calabi-Yau manifolds are shown to be labeled by integral points in reflexive polytopes constructed from the nef-partition of Bl(3)P(3). We determine all 14 massless matter representations to six and four dimensions by an explicit study of the codimension two singularities of the elliptic fibration. We obtain three matter representations charged under all three U(1)-factors, most notably a tri-fundamental representation. The existence of these representations, which are not present in generic perturbative Type II compactifications, signifies an intriguing universal structure of codimension two singularities of the elliptic fibrations with higher rank Mordell-Weil groups. We also compute explicitly the corresponding 14 multiplicities of massless hypermultiplets of a six-dimensional F-theory compactification for a general base B.
Ključne besede: flux compactifications, F-theory, superstring vacua, D-branes
Objavljeno: 27.06.2017; Ogledov: 583; Prenosov: 110
.pdf Celotno besedilo (840,88 KB)
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Chiral four-dimensional F-theory compactifications with SU(5) and multiple U(1)-factors
Mirjam Cvetič, Antonella Grassi, Denis Klevers, Hernan Piragua, 2014, izvirni znanstveni članek

Opis: We develop geometric techniques to determine the spectrum and the chiral indices of matter multiplets for four-dimensional F-theory compactifications on elliptic Calabi-Yau fourfolds with rank two Mordell-Weil group. The general elliptic fiber is the Calabi-Yau onefold in dP(2). We classify its resolved elliptic fibrations over a general base B. The study of singularities of these fibrations leads to explicit matter representations, that we determine both for U(1) xU(1) and SU(5) x U(1) x U(1) constructions. We determine for the first time certain matter curves and surfaces using techniques involving prime ideals. The vertical cohomology ring of these fourfolds is calculated for both cases and general formulas for the Euler numbers are derived. Explicit calculations are presented for a specific base B = P-3. We determine the general G(4)-flux that belongs to H-V((2,2)) of the resolved Calabi-Yau fourfolds. As a by-product, we derive for the first time all conditions on G(4)-flux in general F-theory compactifications with a non-holomorphic zero section. These conditions have to be formulated after a circle reduction in terms of Chern-Simons terms on the 3D Coulomb branch and invoke M-theory/F-theory duality. New ChernSimons terms are generated by Kaluza-Klein states of the circle compactification. We explicitly perform the relevant field theory computations, that yield non-vanishing results precisely for fourfolds with a non-holomorphic zero section. Taking into account the new Chern-Simons terms, all 4D matter chiralities are determined via 3D M-theory/F-theory duality. We independently check these chiralities using the subset of matter surfaces we determined. The presented techniques are general and do not rely on toric data.
Ključne besede: flux compactifications, F-theory
Objavljeno: 27.06.2017; Ogledov: 551; Prenosov: 428
.pdf Celotno besedilo (1,75 MB)
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Modeliranje univerzalnega motorja in izračun vrtilnega momenta
Sandra Iljaš, 2016, delo diplomskega projekta/projektno delo

Opis: V projektnem delu smo najprej predstavili univerzalni motor, ter njegove specifikacije. Njegovo konstrukcijo smo nato načrtovali v programu AutoCAD. Končana modela rotorja in statorja smo prenesli v program Flux z namenom, da izračunamo vrtilni moment in prikažemo potek in gostoto magnetnega polja pri različnih položajih rotorja. Rezultati magnetnega polja so prikazani slikovno, vrednosti vrtilnega momenta pa so prikazane grafično in tabelarično. Izvedena je tudi primerjava vrednosti maksimalnega vrtilnega momenta pri maksimalnem in polovičnem nazivnem toku.
Ključne besede: univerzalni motorji, vrtilni moment, AutoCAD, Flux
Objavljeno: 12.05.2017; Ogledov: 1466; Prenosov: 153
.pdf Celotno besedilo (2,51 MB)

Modeliranje transformatorja z metodo končnih elementov
Marko Volčič, 2016, diplomsko delo

Opis: Diplomska naloga temelji na modeliranju transformatorja s programom Cedrat Flux 3D, verzija 12. Najprej smo spoznali osnovno teorijo in obratovalna stanja transformatorja, sledilo je spoznavanje obravnavanega transformatorja, katerega smo uporabili za model. Nato smo v programu Flux 3D sestavili model in simulirali obratovalna stanja transformatorja in rezultate primerjali z izmerjenimi.
Ključne besede: Transformator, program Flux, obratovalna stanja transformatorja
Objavljeno: 28.09.2016; Ogledov: 690; Prenosov: 101
.pdf Celotno besedilo (5,95 MB)

Contribution of non-troglobiotic terrestrial invertebrates to carbon input in hypogean habitats
Tone Novak, Franc Janžekovič, Saška Lipovšek Delakorda, 2013, izvirni znanstveni članek

Opis: Eleven of the most important terrestrial invertebrate species in Slovenian caves were analyzed for differences in their fresh and dry biomass, energy content and carbon bulk during winter. These data were combined with the species abundance in 54 caves and adits in order to estimate their organic carbon bulk and carbon input into these habitats. In Central European caves, Troglophilus cavicola, T. neglectus, Faustina illyrica, Amilenus aurantiacus and Scoliopteryx libatrix are the most important vectors of carbon between the epigean and hypogean habitats. In contrast to the general assumption, carbon total contribution to caves via dead bodies is only 0.15% of total migratory biomass, and it is not directly available to troglobionts because of infection with entomopathogenic fungi. In winter, together with predated migratory specimens, carbon input does not exceed 0.3% of the total migratory biomass. This situation should be carefully examined in every karstic region inhabited by distinctive fauna.
Ključne besede: biomass, carbon flux, caves, non-troglobiotic species, organic carbon, respiration
Objavljeno: 21.12.2015; Ogledov: 866; Prenosov: 71
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