1. Simulation study of different OPM-MEG measurement componentsUrban Marhl, Tilmann Sander, Vojko Jazbinšek, 2022, izvirni znanstveni članek Opis: Magnetoencephalography (MEG) is a neuroimaging technique that measures the magnetic fields of the brain outside of the head. In the past, the most suitable magnetometer for MEG was the superconducting quantum interference device (SQUID), but in recent years, a new type has also been used, the optically pumped magnetometer (OPM). OPMs can be configured to measure multiple directions of magnetic field simultaneously. This work explored whether combining multiple directions of the magnetic field lowers the source localization error of brain sources under various conditions of noise. We simulated dipolar-like sources for multiple configurations of both SQUID- and OPM-MEG systems. To test the performance of a given layout, we calculated the average signal-to-noise ratio and the root mean square of the simulated magnetic field; furthermore, we evaluated the performance of the dipole fit. The results showed that the field direction normal to the scalp yields a higher signal-to-noise ratio and that ambient noise has a much lower impact on its localization error; therefore, this is the optimal choice for source localization when only one direction of magnetic field can be measured. For a low number of OPMs, combining multiple field directions greatly improves the source localization results. Lastly, we showed that MEG sensors that can be placed closer to the brain are more suitable for localizing deeper sources.
Ključne besede: magnetoencephalography, optically pumped magnetometers, superconducting quantum interference device, volume conductor, boundary element method, equivalent current dipole, source localization, ambient noise, spontaneous brain noise
Objavljeno v DKUM: 16.12.2024; Ogledov: 0; Prenosov: 2
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2. Fonološka zmožnost bosansko govorečih priseljenk in priseljencevJana Lovrec Srša, Gjoko Nikolovski, 2024, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Opis: Od vseh jezikovnih ravnin, ki se obravnavajo pri poučevanju nekega jezika kot neprvega, je najmanj zastopana fonetično-fonološka raven. Razlog za to je dejstvo, da je sporazumevanje možno tudi takrat, ko izgovorjava ni povsem pravilna. Uporaba komunikacijskega pristopa pri poučevanju tujih jezikov tudi vpliva na »zanemarjanje« fonetično-fonološke ravni, saj se tako učenci kot tudi učitelji zavedajo, da je sporazumevanje kljub nepravilni/neustrezni izgovorjavi možno. Prispevek obravnava fonološko zmožnost neslovensko govorečih priseljenk in priseljencev iz Bosne in Hercegovine, ki živijo v Mariboru in se za uspešno integracijo v slovensko okolje učijo slovenščino kot neprvi jezik. Za potrebe prispevka je analiziran korpus njihovih govorjenih besedil, v katerih so obravnavane in definirane glasoslovne težave, s katerimi se soočajo pri učenju slovenščine. Analiza temelji na posnetkih njihovih govorjenih besedil ter registrira sledeče težave: izgovor polglasnika, izgovor vzglasnega v- pred (ne)zvenečim soglasnikom, izgovor izglasnega -v v položaju za samoglasnikom ali r, izgovor predloga v, izgovor morfemskega -ol- za nekdanji zvočniški glas v položaju pred soglasnikom, izgovor izglasnega -l v položaju za samoglasnikom, izgovor -l- v položaju za samoglasnikom in pred soglasnikom, težave z naglasnim mestom, težave s kakovostjo samoglasnikov idr.
Ključne besede: glasoslovne težave, izgovorjava, slovenščina kot drugi jezik, jezikovne interference, jezikovna integracija
Objavljeno v DKUM: 13.08.2024; Ogledov: 78; Prenosov: 12
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3. Transforming and comparing data between standard SQUID and OPM-MEG systemsUrban Marhl, Anna Jodko-Wladzinska, Rüdiger Brühl, Tilmann Sander, Vojko Jazbinšek, 2022, izvirni znanstveni članek Opis: Optically pumped magnetometers (OPMs) have recently become so sensitive that they are suitable for use in magnetoencephalography (MEG). These sensors solve operational problems of the current standard MEG, where superconducting quantum interference device (SQUID) gradiometers and magnetometers are being used. The main advantage of OPMs is that they do not require cryogenics for cooling. Therefore, they can be placed closer to the scalp and are much easier to use. Here, we measured auditory evoked fields (AEFs) with both SQUID- and OPM-based MEG systems for a group of subjects to better understand the usage of a limited sensor count OPM-MEG. We present a theoretical framework that transforms the within subject data and equivalent simulation data from one MEG system to the other. This approach works on the principle of solving the inverse problem with one system, and then using the forward model to calculate the magnetic fields expected for the other system. For the source reconstruction, we used a minimum norm estimate (MNE) of the current distribution. Two different volume conductor models were compared: the homogeneous conducting sphere and the three-shell model of the head. The transformation results are characterized by a relative error and cross-correlation between the measured and the estimated magnetic field maps of the AEFs. The results for both models are encouraging. Since some commercial OPMs measure multiple components of the magnetic field simultaneously, we additionally analyzed the effect of tangential field components. Overall, our dual-axis OPM-MEG with 15 sensors yields similar information to a 62-channel SQUID-MEG with its field of view restricted to the right hemisphere.
Ključne besede: optically pumped magnetometer, magnetoencephalography, superconducting quantum interference device, magnetic field map
Objavljeno v DKUM: 26.06.2024; Ogledov: 153; Prenosov: 16
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5. Don't leave your heart at work : profiles of work-life interference and cardiometabolic riskKatja Kerman, Sara Tement, Christian Korunka, 2021, izvirni znanstveni članek Opis: The present study adopts an exploratory, person-oriented approach to investigate possible patterns of work-life interference. We examine work–life interference from a cognitive (i.e., thinking about work), behavioral (i.e., engaging in work-related behavior), and performance perspective (i.e., reduced functionality in private life, or work–life conflict) in order to identify profiles of employees that could potentially remain uncovered with variable-oriented research. Furthermore, as work–life interference relates to well-being and health, we were interested in exploring possible differences between profiles in emotional exhaustion, cardiometabolic risk, and health-related behavior. Self-report data on work–life interference and well-being, as well as objective health data, were collected from a heterogeneous sample of 289 employees.
Four profiles with different patterns of work–life interference were identified. Out of the four profiles, two profiles reported moderate and high work–life interference (the Moderate Interference and High Interference profiles). The other two profiles revealed distinct combinations of moderate and low performance and behavioral interference (the Low Performance Interference and Low Behavioral Interference profiles). The High Interference and Low Behavioral Interference profiles were identified as risk groups in terms of cardiometabolic health, while the Low Performance Interference and Moderate Interference profiles
showed low to no risk. Regarding work-related well-being, the High Interference profile showed the highest risk of emotional exhaustion.
Ključne besede: work-life interference, person-oriented approach, latent profile analysis, well-being, cardiometabolic risk
Objavljeno v DKUM: 12.04.2024; Ogledov: 236; Prenosov: 18
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6. Work-Home conflict and strain: the role of work-related smartphone use, job insecurity and segmentation preferencesTjaša Srnko, 2018, magistrsko delo Opis: Nowadays, through organisational and technological changes, organizations expect availability and work from their employees not just during working hours, but also in their free time. Work can be done from anywhere and at any time, also with the help of smartphones, which is one of the main constructs of the current research. If the employee is working from home on their smartphone, this can have an important contribution to managing work and private life, and also to strain. The individual’s preference of whether to segment his or her work from home also plays an important role in experiencing internal conflicts. As the motivation for work-related smartphone use is not fully clear, job insecurity was additionally explored as a potential predictor. In an online study, conducted in Austria, we collected data from 454 participants of different ages, gender and working backgrounds. For the analysis, multiple moderated regression and mediation analyses were used. Results showed significant relations between work-home interference and strain but no significant results between those constructs while adding work-related smartphone use. Segmentation preferences did not have an influence on the relationship between work-home interference and strain. Job insecurity was revealed to be related to work-related smartphone use and smartphone use to work-home interference. Smartphone use was also found to partially mediate the path from job insecurity to work-home interference. Finally, to prevent negative outcomes of strain, work-home interference and job insecurity, organizations should focus on: providing culture that fits their employees, try to plan availability free time and provide a clear communication.
Ključne besede: Smartphone use, work-home interference, strain, stress, job insecurity, segmentation preferences
Objavljeno v DKUM: 14.01.2019; Ogledov: 1847; Prenosov: 138
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7. The "magnet effect" - a powerful source of L1 dialect interference in the pronunciation of English as a foreign languageKlementina Penelope Jurančič, 2014, izvirni znanstveni članek Opis: Wieden and Nemser (1991) carried out a study investigating the development of pronunciation of English as a foreign language in Austria. One of the main issues in this research was L1 dialect interference. Individual studies have proven that the pronunciation of a second (L2) or foreign language (FL) is not influenced only by the standard variety of the first language (L1), but also by the L1 dialect of the speaker's place of origin (Karpf et al. 1980). Wieden and Nemser's study wished to prove this on a larger scale. A similar study was carried out also for Slovenia (Jurančič Petek 2007). Contrastive analysis (CA) of the Slovene Standard pronunciation and English was performed as well as that of the sound systems of individual Slovene dialects and the English one. Error analysis (EA) of the obtained results showed that L1 dialect interference did not occur in the instances predicted by contrastive analysis; however the study in itself did prove the existence of such influence ("magnet effect" in vowels).
Ključne besede: English language, magnet effect, monophthongs, dialect interference, pronunciation, L1 dialect interference, pronunciation of English
Objavljeno v DKUM: 16.05.2017; Ogledov: 1155; Prenosov: 214
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8. ERROR PROBABILITY MODEL FOR IEEE 802.15.4 WIRELESS TRANSMISSION WITH CO-CHANNEL INTERFERENCE AND BACKGROUND NOISEUroš Pešović, 2016, doktorska disertacija Opis: Data transmission sent through wireless channel is usually affected by background noise, multipath fading and interference which cause data errors. Influence of such disturbances is the most commonly expressed in a form of error probability statistics. Effects of these disturbances on IEEE 802.15.4 wireless transmissions are previously studied, except influence of co-channel interference (CCI) which originates from collision between IEEE 802.15.4 devices which perform simultaneous radio transmission. Our thesis puts forward the assumption that it is possible to derive more accurate analytical error probability model for higher data level error probability parameters without the idealization of PN spreading sequences. Additionally, thesis is that is possible to derive an accurate analytical error probability model in the case of CCI influenced by background noise by consideration of constellation diagram. IEEE 802.15.4 standard uses CSMA/CA (Carrier Sense Multiple Access with Collision Detection) channel access mechanism to prevent collisions between devices, but this mechanism doesn't provide protection from hidden node problem which is primary source of co-channel interference. Using Monte Carlo simulations we determined frequency of hidden node collisions, which shown that co-channel interference frequently occur in parts of the network with high traffic load. Some prior works in this field tend to idealize these non-ideal spreading sequences in order to simplify calculations for error probability parameters. Our doctor thesis presents analytical model of data level error probability parameters (symbol, bit and packet) for IEEE 802.15.4, which uses original non-ideal spreading sequences without their idealization. Proposed error probability model consists of mutually dependent chip, symbol, bit and packet error probability models. Derived error probability models are linked together, so each of error probability parameters can be determined using error probability parameter from the previous stage. Error probability model for IEEE 802.15.4 wireless communication could be used in network simulation tools in order to accurately simulate energy efficient medium access protocols in realistic scenarios. Presented theoretical results are tested by independent numerical simulation of IEEE 802.15.4 transmission according to Monte Carlo method. Simulation results shows that derived models for error probability parameters were matched by two simulation scenarios in background noise, for multipath fading and co-channel interface, respectively Furthermore, the accuracy of derived mathematical models was tested in real-world experiment using IEEE 802.15.4 compliant wireless transceivers for creating co-channel interference. Packets were received by software defined radio platform, which enabled realization of coherent receiver in which all error probability statistics could be collected. The results of the experiment show consistency with proposed analytical error probability models, but some deviations are caused by poor preamble synchronization under low SNR (Signal to Noise Ratio) value. The thesis was proved with Monte Carlo simulations of the physical level of the IEEE 802.15.4 communication and experimental measurements on a real physical communication system.
Ključne besede: IEEE 802.15.4 standard, error probability model, co-channel interference, Rician fading channel, additive white Gaussian noise, wireless transmission, wireless sensor networks, numerical simulations, software defined radio
Objavljeno v DKUM: 14.10.2016; Ogledov: 2502; Prenosov: 141
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9. Karakterizacija in uporaba optičnih senzorjev za on - line in in - situ merjenje plinov v biotehnoloških procesihPolonca Brglez, 2013, doktorska disertacija Opis: Doktorska disertacija je razdeljena na več sklopov, v katerih smo poskušali poglobiti dosedanje raziskave na področju optičnega senzorja kisika na osnovi 4,7 - difenil - 1,10 - fenantrolin rutenijevega(II) diklorid kompleksa - (Ru(dpp)3). Namen doktorskega dela je bila izboljšava optičnih lastnosti in odziva senzorjev na osnovi Ru(dpp)3. Lastnosti senzorja smo dodatno raziskali s poudarkom na preučevanju različnih tehnik izdelave senzorjev, spreminjanja koncentracij barvila, aplikacije različnih polimernih nosilcev, vpliva potencialnih interferenčnih plinov in vključevanja nanodelcev.
Izdelali smo tankoslojne optične senzorje kisika s pomočjo različnih tehnik nanosa senzorskih raztopin (»spin coating« tehnike, s pomočjo naprave za tanke nanose in s pomočjo mehanskega nanosa). Namen je bil pripraviti najbolj homogen nanos senzorske raztopine in tako dobiti najbolj optimalne lastnosti senzorjev.
Nanašanje senzorske raztopine s pomočjo mehanskega nanosa je enostavna in cenovno najbolj ugodna tehnika. Vendar se ta tehnika ni izkazala kot najprimernejša, saj je težko zagotoviti popolnoma homogen nanos po celotni senzorski površini.
Ugotovili smo, da je glavna prednost uporabe »spin coating-a« ta, da je tehnika hitra, enostavna za uporabo in primerna za nanos majhnih volumnov. Omogoča izdelavo več serij senzorjev z različnimi lastnostmi ob minimalni porabi reagentov. »Spin coating« se je izkazal kot učinkovita metoda za nanos senzorskih raztopin v laboratorijskem merilu, vendar je po celotni senzorski površini težko pripraviti popolnoma homogen nanos (150 µL senzorske raztopine, 80 mg Ru(dpp)3, kloroform, silikon E41, folija Dataline, program na »Spin coater-ju«: 1. korak: 750 obr. 3 s, 2. korak: 300 obr. 3 s in 3. korak: 150 obr. 3 s).
Kot najprimernejša tehnika za nanos senzorskih raztopin se je izkazala metoda nanosa senzorske raztopine s pomočjo naprave za tanke nanose, kjer smo nanašali senzorske raztopine v debelini: 10 µm, 15 µm, 20 µm, 25 µm, 30 µm, 40 µm in 50 µm. Ta način izdelave omogoča najbolj homogen nanos senzorske raztopine, postopek je hiter, enostaven in omogoča izdelavo večjih količin senzorjev s ponovljivimi lastnostmi.
Ugotovili smo, da so se z dodajanjem različnih kovinskih nanodelcev in Triton - X, karakteristike senzorjev izboljšale.
Pri uporabi senzorjev v realnih pogojih smo spremljali vsebnost kisika med postopkom biološke razgradnje, kjer imajo elektrokemijski senzorji omejitve. Elektrode iz plemenitih kovin, ki reagirajo s korozivnimi plini, zato niso primerne za tovrstne aplikacije. S pomočjo optičnega senzorja kisika na osnovi Ru(dpp)3 smo spremljali koncentracijo kisika pri razgradnji organskih odpadkov; le-ta je ključnega pomena pri proizvodnji komposta. Študirali smo tudi razgradnjo mešanih organskih odpadkov s pomočjo mikroorganizmov v avtomatskem kompostniku, ki je učinkovitejši način, v kolikor se odločimo za kompostiranje na domu. Za optimalno delovanje avtomatskega kompostnika so potrebne še dodatne študije, ki bodo vključevale drugačne pogoje kompostiranja (različne substrate in mešanice substratov, selekcionirane mikroorganizme, spremljanje nastanka plinov itd.).
Tretjo uporabnost razvitega senzorja smo preizkusili na področju meritev sestave bioplina. Merjenja, ki se lahko izvajajo on-line ali in-situ nam lahko povedo bistveno več o samem procesu in tako dajejo možnost vplivanja ter optimizacije procesa nastanka bioplina. Z merjenjem koncentracije kisika v pilotnem bioreaktorju smo dokazali, da je optični senzor kisika primeren tudi za merjenje kisika v bioplinu. Senzor ima sledeče prednosti: je enostaven za uporabo in omogoča meritve v vodi ali v plinskih fazi, je eksplozijsko varen in z njim lahko izvajamo meritve v vrtinah, kjer je podtlak ali nadtlak.
Ključne besede: 4, 7 - difenil-1, 10-fenantrolin rutenijev(II) diklorid kompleks, optični senzor kisika, spin coating, kisik, bioplin, interference, mešalna komora, kompost, mešanje plinov, nanodelci
Objavljeno v DKUM: 29.11.2013; Ogledov: 2937; Prenosov: 242
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10. Improved frequency characteristics of the randomized PWM boost rectifierFranc Mihalič, Miro Milanovič, Carlos Cuoto, 2003, izvirni znanstveni članek Opis: A randomized pulse width modulation (RPWM) algorithm is applied in the control unit of the boost rectifier to achieve improved frequency characteristics in the wide band. First, the introduction of the RPWM switching is reflected in a smaller increase of the total harmonic distortion (THD) factor in the input current. Nevertheless, decrease of the power factor is negligibly small. Second, the power spectrum density (PSD) of the input current is estimated and measured to evaluate the influence of randomization in the high-frequency range. This approach offers an effective and credible prediction method for reduction of conductive electromagnetic interference (EMI) by using the RPWM switching.
Ključne besede: rectifiers, boost rectifiers, randomized pulse width modulation, estimation methods, total harmonic distortion, power factor, conductive electromagnetic interference
Objavljeno v DKUM: 01.06.2012; Ogledov: 2357; Prenosov: 85
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