1. Simulation-based study of structural changes in electrical time-series signalsLuka Živković, Željko Hederić, Tin Benšić, Goran Kurtović, Marinko Stojkov, 2025, original scientific article Abstract: his paper uses statistical indicators to address the detection of changes in electrical signals typical of industrial and power systems. A dedicated MATLAB algorithm was developed to identify change points by tracking shifts in signal behaviour and statistical properties. To evaluate the method, synthetic signals were generated through simulation to reproduce the common patterns observed in these systems, allowing testing under different operating conditions and varying noise levels. The results demonstrate that the algorithm detects change points reliably across multiple scenarios, showing flexibility and robustness. This study highlights the value of simulation-based signal generation as a controlled environment for testing detection methods. It provides a foundation for future applications to more complex real-world electrical signal analysis tasks.
Keywords: break points, energy system, noise, segmentation, signals, simulation, time series
Published in DKUM: 01.10.2025; Views: 0; Downloads: 1
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2. The influence of auditory dysfunction on ergonomic workplace design for aging employeesMatjaž Maletič, Albin Kotnik, Zvone Balantič, 2025, original scientific article Abstract: Background/Objectives: This research focuses on the increasing presence of older workers in the labor market, a group particularly vulnerable to hearing problems due to age-related changes and prolonged noise exposure. Methods: The research combines theoretical and empirical approaches to investigate the impact of noise on the workplaces of older employees. The empirical component is based on two primary methods: a survey and audiometric testing to assess participants’ hearing abilities. The study included a sample of 50 older workers, all with diagnosed hearing loss. Results: The results of the survey showed that most older workers are regularly exposed to noise at work, which has long-term negative effects on their hearing. This highlights the need to introduce appropriate protective measures such as personal protective equipment, insulation of noise sources, and raising awareness about the dangers of noise. In addition to the questionnaire survey, the analysis of hearing measurements revealed that all respondents had significant bilateral hearing loss, with sensorineural hearing loss being the most prevalent type. Conclusions: This study highlights the negative impact of chronic noise exposure in the workplace on the hearing, communication and productivity of older workers and emphasizes the importance of combining preventive measures, hearing protection and workplace adaptations to promote their well-being and performance.
Keywords: hearing dysfunction, older workers, noise exposure, ergonomics, audiometric assessments, workers’ perception
Published in DKUM: 04.09.2025; Views: 0; Downloads: 2
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3. Noise evaluation of S-polymer gearsBoštjan Trobentar, Matija Hriberšek, Simon Kulovec, Srečko Glodež, Aleš Belšak, 2022, original scientific article Abstract: In this study, an acoustic behaviour of S-polymer gears made of the material combination
POM/PA66 was investigated and compared to the standardised involute gears (E-gears). Basic
evaluating characteristics included noise during operation, which is of particular significance when
noise reduction is expected. The measured signals were analysed in time and frequency domains
and the levels of acoustic activity were compared. The experimental results have shown that the
sound pressure level of both E- and S-polymer gears are proportional to the torque. However, the
comprehensive noise evaluation has shown some advantages of S-polymer gears if compared to the
E-polymer gears. In that respect, S-polymer gears were found more appropriate for noise reduction
of gear drive systems in the case of normal loading and typical drive speed. Future studies in the
operating behaviour of S-polymer gears could also cover noise evaluation using new methods of
sound signal analysis at different temperatures of gears.
Keywords: polymers, S-gears, sound, noise analysis
Published in DKUM: 24.03.2025; Views: 0; Downloads: 13
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4. Simulation study of different OPM-MEG measurement componentsUrban Marhl, Tilmann Sander, Vojko Jazbinšek, 2022, original scientific article Abstract: 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.
Keywords: magnetoencephalography, optically pumped magnetometers, superconducting quantum interference device, volume conductor, boundary element method, equivalent current dipole, source localization, ambient noise, spontaneous brain noise
Published in DKUM: 16.12.2024; Views: 0; Downloads: 6
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7. Pacemaker-driven stochastic resonance on diffusive and complex networks of bistable oscillatorsMatjaž Perc, Marko Gosak, 2008, original scientific article Abstract: We study the phenomenon of stochastic resonance on diffusive, small-world and scale-free networks consisting of bistable overdamped oscillators. Important thereby is the fact that the external subthreshold periodic forcing is introduced only to a single oscillator of the network. Hence, the forcing acts as a pacemaker trying to impose its rhythm on the whole network through the unit to which it is introduced. Without the addition of additive spatiotemporal noise, however, the whole network, including the unit that is directly exposed to the pacemaker, remains trapped forever in one of the two stable steady states of the local dynamics. We show that the correlation between the frequency of subthreshold pacemaker activity and the response of the network is resonantly dependent on the intensity of additive noise. The reported pacemaker-driven stochastic resonance depends most significantly on the coupling strength and the underlying network structure. Namely, the outreach of the pacemaker obeys the classic diffusion law in the case of nearest-neighbor interactions, thus being proportional to the square root of the coupling strength, whereas it becomes superdiffusive by an appropriate small-world or scale-free topology of the interaction network. In particular, the scale-free topology is identified as being optimal for the dissemination of localized rhythmic activity across the whole network. Also, we show that the ratio between the clustering coefficient and the characteristic path length is the crucial quantity defining the ability of a small-world network to facilitate the outreach of the pacemaker-emitted subthreshold rhythm. We additionally confirm these findings by using the FitzHugh-Nagumo excitable system as an alternative to the bistable overdamped oscillator.
Keywords: noise, bistable dynamics, stochastic simulations, complex networks
Published in DKUM: 03.07.2017; Views: 1498; Downloads: 481
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8. Synchronous bursts on scale-free neuronal networks with attractive and repulsive couplingQingyun Wang, Guanrong Chen, Matjaž Perc, 2011, original scientific article Abstract: This paper investigates the dependence of synchronization transitions of bursting oscillations on the information transmission delay over scale-free neuronal networks with attractive and repulsive coupling. It is shown that for both types of coupling, the delay always plays a subtle role in either promoting or impairing synchronization. In particular, depending on the inherent oscillation period of individual neurons, regions of irregular and regular propagating excitatory fronts appear intermittently as the delay increases. These delay-induced synchronization transitions are manifested as well-expressed minima in the measure for spatiotemporal synchrony. For attractive coupling, the minima appear at every integer multiple of the average oscillation period, while for the repulsive coupling, they appear at every odd multiple of the half of the average oscillation period. The obtained results are robust to the variations of the dynamics of individual neurons, the system size, and the neuronal firing type. Hence, they can be used to characterize attractively or repulsively coupled scale-free neuronal networks with delays.
Keywords: synchronization, neuronal networks, noise, stochastic processes, scale-free networks, information transmission delay
Published in DKUM: 19.06.2017; Views: 1218; Downloads: 393
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9. ERROR PROBABILITY MODEL FOR IEEE 802.15.4 WIRELESS TRANSMISSION WITH CO-CHANNEL INTERFERENCE AND BACKGROUND NOISEUroš Pešović, 2016, doctoral dissertation Abstract: 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.
Keywords: 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
Published in DKUM: 14.10.2016; Views: 2502; Downloads: 149
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10. Experimental analysis of the impact of particles on the cavitating flowBoštjan Gregorc, Andrej Predin, Drago Fabijan, Roman Klasinc, 2012, original scientific article Abstract: The purpose of this paper is to present an analysis of the impact of solid particles on the development of cavitating flow conditions around a hydrofoil. Experimental studies have been conducted in a cavitation tunnel with three different mixtures of particles and water. We used a particle-like properties, such as are found in river water, and with increasing mass concentration. We performed measurements of torque and the relative noise in the hydrofoil. The point in the formation of vapour phase on the hydrofoil and the pronounced frequency effect were determined by measuring the relative noise. Based on the analysis the results show that the particles increase the intensity and extent of cavitation.
Keywords: particles, cavitation, noise, measurements
Published in DKUM: 10.07.2015; Views: 6003; Downloads: 95
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