1. Integrating Multi-Physics Modeling within Multi-Objective Optimization to Enhance the Performance and Efficiency of Permanent Magnet Synchronous Machines : doktorska disertacijaMitja Garmut, 2025, doktorska disertacija Opis: This Dissertation focuses on the optimization of an Interior Permanent Magnet (IPM) machine for handheld battery-powered tools, aiming to enhance performance and efficiency.
The research integrates multi-physics modeling, including electromagnetic Finite Element Method (FEM) and thermal models, to evaluate machine performance under various operating conditions. The performance is evaluated according to selected Key Performance Indicators (KPIs). Further, different control methods, such as Field Oriented Control and Square-Wave Control, impact the performance significantly and are incorporated into the optimization process.
Due to the computational challenges of FEM-based performance evaluations in Multi-Objective Optimization (MOO), this work utilizes Artificial Neural Network (ANN)-based meta-models, to accelerate the optimization process while preserving accuracy.
The developed meta-models capture nonlinear machine characteristics from the FEM model. These meta-models are then used to evaluate machine performance through a combination of analytical and numerical post-processing methods.
Four MOO scenarios are presented, each aimed at optimizing the cross-sectional design of IPM machines, to enhance performance and efficiency while reducing mass and cost. Additionally, these scenarios modify the machine’s electromagnetic behavior, to ensure better alignment with the selected control method.
By comparing the optimization process of Scenario 1, which uses direct FEM-based evaluation without time reduction measures, to the approach incorporating Artificial Neural Network based meta-models, the total number of individual FEM evaluations decreased from 2.35×10^9 to 2.03×10^5, without almost any loss of accuracy. This reduced the computation time from 297 years to 9.07 days on our standard desktop computer. The obtained ANN-base meta-models can be used further for other optimizations without the need for additional FEM evaluations.
In all four optimization scenarios, the use of meta-models enabled the generation of a Pareto front of the optimal solutions, leading to improved KPIs compared to the reference design. The highest relative improvement occurred in Scenario 1, where the selected optimized machine design achieved a 30% increase in power density compared to the reference design.
Ključne besede: Interior Permanent Magnet (IPM) Machine, Artificial Neural Network (ANN), Meta-Modeling, Multi-Objective Optimization (MOO), Finite Element Method (FEM), Multi-Physics Modeling, Field Oriented Control (FOC), Square-Wave Control (SWC)
Objavljeno v DKUM: 15.05.2025; Ogledov: 0; Prenosov: 12
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2. A novel system for quasi-continuous THz signal transmission and receptionAndrej Sarjaš, Blaž Pongrac, Dušan Gleich, 2022, izvirni znanstveni članek Opis: This paper presents a novel system for generating and receiving quasi-continuous (QC)
TeraHertz (THz) waves. A system design and theoretical foundation for QC-THz signal generation
are presented. The proposed QC-THz system consists of commercially available photo-conductive
antennas used for transmission and reception of THz waves and a custom-designed QC optical
signal generator, which is based on a fast optical frequency sweep of a single telecom distributedfeedback laser diode and unbalanced optical fiber Michelson interferometer used for a high-frequency
modulation. The theoretical model for the proposed system is presented and experimentally evaluated. The experimental results were compared to the state-of-the-art continuous-wave THz system. The comparison between the continuous-wave THz system and the proposed QC-THz system
showed the ability to transmit and receive QC-THz waves up to 300 GHz. The upper-frequency limit
is bounded by the length of the used Michelson interferometer. The presented design of THz signal
generation has a potential for industrial application because it is cost-efficient and can be built using
commercially available components.
Ključne besede: quasi-continuous, terahertz, photoconductive antenna, wave emittance, wave detection
Objavljeno v DKUM: 01.04.2025; Ogledov: 0; Prenosov: 2
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3. Derivation of analytical expressions for fast calculation of resistance spot welding system currentsRobert Brezovnik, Jožef Ritonja, 2024, izvirni znanstveni članek Opis: The paper deals with the dynamics of a resistance spot welding system. At the core of this system is a transformer, which is powered on the primary side by a pulse-width modulated inverter and has a full-wave output rectifier on the secondary side that provides a direct welding current. The entire system is nonlinear, due to magnetic hysteresis and electronics. The electronics prevent the current from flowing in all parts of the welding transformer at separate time intervals during the voltage supply period; therefore, not all the parameters affect the dynamic of currents and voltages all the time so the system is also time-variant. To design a high-performance welding system and to predict the maximum possible welding current at a specific load, it is necessary to know the welding and primary currents. The leakage inductances of the system can reduce the maximum welding current significantly at higher frequencies and the same load. There are several methods to determine these currents, each with its drawbacks. Measurements are time-consuming, using professional software is expensive and requires time to learn and free open-source software has many limitations and does not guarantee the correctness of the results. The article presents a new, fourth option—a theoretical derivation of analytical expressions that facilitate straightforward and rapid calculation of the welding and primary currents of the resistance spot welding system with symmetrical secondary branches. The derivation of the mathematical expressions is based on the equivalent circuits that describe the system in different operating states. The results of the numerical simulations confirmed the derived expressions completely.
Ključne besede: DC–DC converters, pulse width modulation (PWM), welding transformers, center-tapped transformers, full-wave rectifier, resistance spot welding (RSW), leakage inductance, analytical modeling, time-variant system, equivalent circuit
Objavljeno v DKUM: 08.08.2024; Ogledov: 77; Prenosov: 42
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4. Confronting SARS-CoV-2 infection : patients’ experience in the first pandemic wave - cross-sectional studyMaja Sočan, Vanja Erčulj, 2022, izvirni znanstveni članek Opis: The aim of the study was to investigate the real-life experience of persons infected with SARS-CoV-2 in Slovenia in the first pandemic wave and how the buffering effect of social and informational support affected negative feelings. We used a self-administrated questionnaire. There were 1182 eligible notified cases with the response rate 64.9%. At least 62% of responders were able to follow the isolation rules, while 21.1% did not or could not organize their living separately from other household members. The main providers during the isolation period were close family members. The most prevalent emotion in our study was worry (70.3%) and fear (37.6%). Worry and fear during the illness were less probable for men than women, but more probable for older patients. Participants with strong emotional support had lower odds of being sad. Those who were exposed to a larger number of sources of information had higher odds of being worried. Those patients who used a higher number of more credible sources of information had higher odds of being afraid during illness. Pets did not play a special role in psychological well-being. The role of the media and public health communications should be explored further to achieve an improved response.
Ključne besede: COVID-19, first pandemic wave, isolation, information, social support, feelings, stigma
Objavljeno v DKUM: 04.07.2024; Ogledov: 147; Prenosov: 25
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5. Motor unit identification in the M waves recorded by high-density electromyMiloš Kalc, Jakob Škarabot, Matjaž Divjak, Filip Urh, Matej Kramberger, Matjaž Vogrin, Aleš Holobar, 2023, izvirni znanstveni članek Ključne besede: M wave, high-density surface EMG, firing identification, motor unit
Objavljeno v DKUM: 13.06.2024; Ogledov: 144; Prenosov: 15
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6. Quantum chaos in triangular billiardsČrt Lozej, Giulio Casati, Tomaž Prosen, 2022, izvirni znanstveni članek Opis: We present an extensive numerical study of spectral statistics and eigenfunctions of quantized triangular billiards. We compute two million consecutive eigenvalues for six representative cases of triangular billiards, three with generic angles with irrational ratios with π, whose classical dynamics is presumably mixing, and three with exactly one angle rational with π, which are presumably only weakly mixing or even nonergodic in case of right triangles. We find excellent agreement of short- and long-range spectral statistics with the Gaussian orthogonal ensemble of random matrix theory for the most irrational generic triangle, while the other cases show small but significant deviations which are attributed either to a scarring or superscarring mechanism. This result, which extends the quantum chaos conjecture to systems with dynamical mixing in the absence of hard (Lyapunov) chaos, has been corroborated by analyzing distributions of phase-space localization measures of eigenstates and inspecting the structure of characteristic typical and atypical eigenfunctions.
Ključne besede: quantum physics, quantum chaos, quantum scars, wave chaos, billiards, chaos and nonlinear dynamics, ergodic theory
Objavljeno v DKUM: 12.10.2023; Ogledov: 294; Prenosov: 44
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7. Optimizacija sestave in situ elektrode in metode za izboljšanje analitske učinkovitosti določanja kovin v sledovih : magistrsko deloKlara Jezernik, 2021, magistrsko delo Opis: Magistrsko delo prikazuje študijo delne validacije, določanje vpliva spremenljivk in optimizacijo analizne metode za elektrokemijsko določitev Zn(II), Cd(II) in Pb(II) v sledovih s tehniko ang. square wave anodne striping voltametrije. Vpliv spremenljivk smo določili v skladu z zasnovanim delnim dvonivojskim petfaktorskim eksperimentalnim načrtom. Optimizacijo smo izvedli z algoritmom Simpleks, pri čemer smo spreminjali čas in potencial elektrodepozicije ter masne koncentracije Bi(III), Sn(II) in Sb(III) ionov, ki so se uporabili za zasnovo modificirane in situ elektrode iz steklastega ogljika. V uporabljenem optimizacijskem kriteriju so bili združeni parametri, s katerimi se oceni analitska učinkovitost metode (širina linearnega koncentracijskega območja, LOQ, občutljivost, točnost in natančnost metode). Slednje je prav tako služilo kot odziv v eksperimentalnem načrtu.
Z eksperimentalnim načrtom smo določili vpliv spremenljivk na preiskovan eksperimentalni sistem in zagotovili zadostno število eksperimentov za pričetek optimizacije sistema. Na podlagi optimizacijskega kriterija smo pri optimizaciji Simpleks določili optimalno elektrodo pri potencialu elektrodepozicije –1,380 V vs Ag/AgCl in času elektrodepozicije 100 s ter masnih koncentracijah Bi(III) 1,00 mg/L, Sn(II) 0,60 mg/L in Sb(III) 0,34 mg/L. Pri enakih pogojih smo primerjali analitsko učinkovitost optimalne in situ elektrode s tremi elektrodami, pri katerih smo za zasnovo in situ elektrode uporabili le eno vrsto ionov kovine. Ugotovili smo, da je izmed teh elektrod optimalna in situ elektroda najbolj primerna za simultano določitev Zn(II), Cd(II) in Pb(II), zato smo jo uporabili za določitev Zn(II), Cd(II) in Pb(II) v realnem vzorcu pitne vode. Določili smo tudi vpliv različnih interferentov, ki so lahko prisotni v vzorcu pitne vode, pri čemer sta na določitev analitov najbolj vplivala Cu(II) in Fe(II).
Ključne besede: square wave anodna striping voltametrija, elektroanaliza težkih kovin, delna validacija analizne metode, eksperimentalni načrt, optimizacija Simpleks
Objavljeno v DKUM: 09.07.2021; Ogledov: 997; Prenosov: 173
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8. Elektronski vgrajeni sistem za določanje položaja sonca : diplomsko deloGregor Stavbar, 2019, diplomsko delo Opis: V diplomski nalogi je opisan postopek načrtovanja in izdelave elektronskega vgrajenega sistema za določanje položaja sonca. Predstavljeni so vsi elementi, ki so potrebni za izdelavo, in vsa teorija, povezana z napravo.
Elektronski vgrajen sistem je izdelan iz ploščice, na katero so pritrjeni vsi elementi, in nosilcev, na katere sta nameščena motorja za obračanje. Komunikacijski del naprave je modul Z-Wave, ki ima krmilnik za upravljanje delovanja naprave in komunikacijsko enoto. V začetku je opisana vsa teorija, ki je bila potrebna za to, da smo se lahko lotili izdelave sončnega sledilnika. Razloženi so vsi parametri, ki jih sledilnik meri, in vse naprave, ki so potrebne za njegovo delovanje. Predstavljen je celoten potek izdelave od načrtov do implementacije ter pisanja programske kode. Na koncu so predstavljene vse meritve, ki smo jih izvedli na prototipu.
Ključne besede: Z-wave, sončni sledilnik, krmilnik, motor, senzor
Objavljeno v DKUM: 26.11.2019; Ogledov: 1416; Prenosov: 104
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9. Koncept razvoja novega izdelka z metodo vitkega okvirjaTjaša Brdnik Zdolšek, 2018, magistrsko delo Opis: Magistrsko delo prikazuje analizo razvoja izdelka s pomočjo metode vitkega okvirja. V teoretičnem delu magistrskega dela je predstavljen razvoj izdelka od iskanja ideje, predstavitev invencij ter razčlenitev posameznih faz vitkega okvirja. V praktičnem delu je predstavljeno področje hišne avtomatizacije s fokusom na Z-Wave protokol, nato pa je s pomočjo vitkega okvirja analizirana smotrnost razvoja izdelka, predstavljene so posamezne komponente ter predvidena finančna struktura. Z omejitvami, sprejetimi v okviru magistrske naloge, je bilo ugotovljeno, da na trgu obstaja premajhna potreba za začetek razvoja navedenega izdelka, saj ugotovljena potreba po izdelku ni zadostna, da bi se projekt ekonomsko izplačal.
Ključne besede: Vitki okvir, koncept razvoja izdelka, kreiranje idej, hišna avtomatizacija, Z-Wave
Objavljeno v DKUM: 17.01.2019; Ogledov: 1298; Prenosov: 125
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10. Empirical correlation between the shear-wave velocity and the dynamic probing heavy test : case study, Varaždin, CroatiaStjepan Strelec, Davor Stanko, Mario Gazdek, 2016, izvirni znanstveni članek Opis: Varaždin is located in the north-western part of Croatia in shallow quaternary alluvial sediments of the Drava River basin. Local site effects due to the alluvial soft sediments can play a crucial role in the amplification of seismic-wave ground motions. The shear-wave velocity (VS) is one of the most important parameters for determining dynamic soil properties and ground-response analyses.
The seismic surface wave method (MASW) is the simplest and a very efficient way of measuring the shear-wave velocity in the field. The Dynamic Probing Heavy (DPH) test is suited to determining the soil strength and the soil deformation properties. However, there are a lack of correlations between the shear-wave velocity and the DPH tests (VS - NDPH) in the literature. In this paper we present empirical correlations between the shear-wave velocity VS and the soil penetration resistance NDPH with: a) raw (original) NDPH data: VS = 97.839·NDPH0.395, (R2 = 0.723); b) a groundwater correction NDPH data: VS = 92.998·NDPH0.363 (R2 = 0.815). From the measured DPH data, the shear-wave velocity (VS), the shear modulus (Go) and the Young’s modulus (Eo and Er) were estimated. Two different approaches (low vs. high strain) were compared, and the results were found to be in good agreement when the relative difference between the velocities is small and smooth.
Dynamic probing tests are good for studying a discrete point of interest in a large field area based on preliminary seismic tests. The suggested correlation VS - NDPH can be used for a rough estimation of VS from NDPH (they are site-specific, and so not applicable worldwide). In this way valuable information about dynamic soil properties can be extracted for ground-response analyses and the study of local site effects.
Ključne besede: shear-wave velocity, MASW, DPH, empirical correlations, dynamic elastic moduli, dynamic soil properties
Objavljeno v DKUM: 15.06.2018; Ogledov: 1850; Prenosov: 93
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