1. Region-based approach for machining time improvement in robot surface finishingTomaž Pušnik, Aleš Hace, 2024, original scientific article Abstract: Traditionally, in robotic surface finishing, the entire workpiece is processed at a uniform speed, predetermined by the operator, which does not account for variations in the machinability across different regions of the workpiece. This conventional approach often leads to inefficiencies, especially given the diverse geometrical characteristics of workpieces that could potentially allow for different machining speeds. Our study introduces a region-based approach, which improves surface finishing machining time by allowing variable speeds and directions tailored to each region’s specific characteristics. This method leverages a task-oriented strategy integrating robot kinematics and workpiece surface geometry, subdivided by the clustering algorithm. Subsequently, methods for optimization algorithms were developed to calculate each region’s optimal machining speeds and directions. The efficacy of this approach was validated through numerical results on two distinct workpieces, demonstrating significant improvements in machining times. The region-based approach yielded up to a 37% reduction in machining time compared to traditional single-direction machining. Further enhancements were achieved by optimizing the workpiece positioning, which, in our case, added up to an additional 16% improvement from the initial position. Validation processes were conducted to ensure the collaborative robot’s joint velocities remained within safe operational limits while executing the region-based surface finishing strategy. Keywords: robot surface finishing, collaborative robot, region-based machining, workpiece optimization, clustering, task-oriented machining, machining time optimization Published in DKUM: 25.11.2024; Views: 0; Downloads: 6 Full text (20,89 MB) |
2. A brief measure of disgust propensityAnne Schienle, Saša Zorjan, Albert Wabnegger, 2022, original scientific article Abstract: In the context of large-scale surveys, pre-screening or longitudinal studies, researchers may be faced with the choice of using a brief measure of disgust propensity (DP: the general tendency to respond with the emotion of disgust to any given situation) or using no measure at all. The goal of the present study was to develop and validate such a short scale based on the Questionnaire for the Assessment of Disgust Propensity (QADP); Schienle et al., 2002). The participants (n=1367; 80% female; mean age = 28 years) completed the QADP, and scales on disgust sensitivity and self-disgust. Brain structural data and disgust rating data were available for subsets of the total sample. Factor analysis revealed a five-factor structure of the QADP. A total of 10 items (two items for each factor) with the highest item-total correlations were selected. The resulting five-factor QADP (Cronbach's alpha =.76) covers a broad range of disgust domains. The short QADP is correlated with the original questionnaire (r=.90), disgust sensitivity, disgust ratings for gustatory, olfactory and visual disgust elicitors, and volume in the insular cortex (a brain region involved in disgust processing). For future investigations, the QADP_brief can be a useful tool for assessing DP with high time efficiency. Keywords: disgust propensity, short questionnaires, time-efficient assesments Published in DKUM: 18.11.2024; Views: 0; Downloads: 3 Full text (275,29 KB) This document has many files! More... |
3. Most influential feature form for supervised learning in voltage sag source localizationYounes Mohammadi, Boštjan Polajžer, Roberto Chouhy Leborgne, Davood Khodadad, 2024, original scientific article Keywords: voltage sag (dip), source localization, supervised and unsupervised learning, convolutional neural network, time-sample-based features Published in DKUM: 23.08.2024; Views: 65; Downloads: 5 Full text (15,94 MB) |
4. Quantifying power system frequency quality and extracting typical patterns within short time scales below one hourYounes Mohammadi, Boštjan Polajžer, Roberto Chouhy Leborgne, Davood Khodadad, 2024, original scientific article Keywords: quantifying power system frequency quality, statistical indices, pattern extracting, machine learning, short time scales, renewable energy sources Published in DKUM: 23.08.2024; Views: 50; Downloads: 5 Full text (12,67 MB) |
5. Derivation of analytical expressions for fast calculation of resistance spot welding system currentsRobert Brezovnik, Jožef Ritonja, 2024, original scientific article Abstract: 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. Keywords: 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 Published in DKUM: 08.08.2024; Views: 77; Downloads: 17 Full text (6,72 MB) |
6. Swarmalators under competitive time-varying phase interactionsGourab Kumar Sar, Sayantan Nag Chowdhury, Matjaž Perc, Dibakar Ghosh, 2022, original scientific article Abstract: Swarmalators are entities with the simultaneous presence of swarming and synchronization that reveal emergent collective behavior due to the fascinating bidirectional interplay between phase and spatial dynamics. Although different coupling topologies have already been considered, here we introduce time-varying competitive phase interaction among swarmalators where the underlying connectivity for attractive and repulsive coupling varies depending on the vision (sensing) radius. Apart from investigating some fundamental properties like conservation of center of position and collision avoidance, we also scrutinize the cases of extreme limits of vision radius. The concurrence of attractive–repulsive competitive phase coupling allows the exploration of diverse asymptotic states, like static π, and mixed phase wave states, and we explore the feasible routes of those states through a detailed numerical analysis. In sole presence of attractive local coupling, we reveal the occurrence of static cluster synchronization where the number of clusters depends crucially on the initial distribution of positions and phases of each swarmalator. In addition, we analytically calculate the sufficient condition for the emergence of the static synchronization state. We further report the appearance of the static ring phase wave state and evaluate its radius theoretically. Finally, we validate our findings using Stuart–Landau oscillators to describe the phase dynamics of swarmalators subject to attractive local coupling. Keywords: swarmalators, time-varying couplings, synchronization, competitive phase coupling Published in DKUM: 16.07.2024; Views: 87; Downloads: 12 Full text (3,26 MB) This document has many files! More... |
7. Associations between physical activity and academic competence : a cross-sectional study among Slovenian primary school studentsJoca Zurc, Jurij Planinšec, 2022, original scientific article Abstract: Physical activity has beneficial effects on overall academic performance in children. However, there is a lack of evidence regarding how the individual characteristics of physical activity interact with other confounding variables of academic competence. Leisure-time physical activity with potential confounders—such as developmental, behavioral, family, and school factors, predicting overall, mathematical, and reading academic competence—was studied in a random sample of 1520 Slovenian primary school students in grades 4–6 (51.9% female; mean age = 10.4 years; SD = 0.93). A structured self-reported questionnaire was used to gather data on the children’s leisuretime physical activity and social-demographic variables, while academic competence was measured by teachers using the SSRS Academic Competence Evaluation Scale. The findings showed that children engage in physical activity most days a week, with moderate-intensity and unorganized activities. It was predicted that engaging in physical activity would lead to an increase in academic performance by 4.2% in males (p = 0.002) and 3.2% in females (p = 0.024), but after fully adjusting the model for controlling confounding variables, the prediction increased to 81.1% in females and 84.1% in males (p < 0.001). The frequency and intensity of physical activity, the absence of digital games, and attending sports clubs seem to have the most beneficial effects in terms of academic competence in school children, among other relevant confounders mediating in this complex relationship. Keywords: physical activity, leisure time, sports, academic competences, late childhood, multiple regression analyses Published in DKUM: 12.07.2024; Views: 94; Downloads: 10 Full text (394,49 KB) This document has many files! More... |
8. STEMI patients in the first and second waves of the COVID-19 pandemic in northeast Slovenia - a retrospective, single-center observational studyAndreja Sinkovič, Manja Kraševec, David Šuran, Martin Marinšek, 2022, original scientific article Abstract: The COVID-19 pandemic has affected the outcomes of ST-elevation myocardial infarction (STEMI) patients in most countries. We aimed to retrospectively assess the admissions, treatments, complications, and mortality of STEMI patients in the northeast of Slovenia during the first (March–May 2020) and second waves (October–December 2020) of the COVID-19 pandemic and to compare them with data from 2019 (March–October). Comparing 2019 and both waves of the COVID-19 pandemic, we observed nonsignificant differences in the number of STEMI admissions, baseline characteristics, use of primary percutaneous coronary intervention (PCI) within the first 3 (40.5%* vs. 38.7% vs. 25%*, *p = 0.074) or 6 h, TIMI III flow after primary PCI, and hospital complications, as well as significant increases in hospital heart failure (23.3% vs. 42%, p = 0.015) and mitral regurgitation in the second wave (10% vs. 26.9%, p = 0.008) of the pandemic and a nonsignificant increase in hospital mortality (8.9% vs. 9.4% vs. 13.6%) during both waves of the pandemic. We conclude that, due to the increased severity of the COVID-19 pandemic in the second wave, there were longer delays to primary PCI in STEMI patients, resulting in significantly increased hospital heart failure and non-significantly increased hospital mortality. Keywords: ST-elevation myocardial infarction, COVID-19, time delay, primary percutaneous coronary intervention, heart failure, mortality, pandemic Published in DKUM: 04.07.2024; Views: 134; Downloads: 20 Full text (1,04 MB) This document has many files! More... |
9. Advanced technologies in logistics engineering : automated storage systems with shuttles integrated with hoisted carriageTone Lerher, Primož Bencak, 2022, original scientific article Abstract: This paper presents automated storage systems with shuttles integrated with hoisted carriage for successful application in intralogistics. The first part of the paper presents classic and advanced AVS/RS along with specific intralogistics automation systems known as AutoStore from Swisslog and Skypod from Exotec. The second part of the paper focuses on an advanced system with shuttle vehicles capable of serving multiple tiers of the storage rack. An analytical model for the shuttle vehicles capable of serving multiple tiers of the storage rack is presented, which is based on (i) the sequences of acceleration, constant velocity and deceleration, and (ii) randomised assignment policy. Based on the presented model, the expected Single Command (SC) and Dual Command (DC) travel (cycle) time as well as the throughput performance of the shuttle vehicles capable of serving several tiers of warehouse, could be calculated. A programme code in MATLAB has been presented for the computation of throughput performances of automated storage systems with shuttles integrated with hoisted carriage capable of serving several tiers of the storage rack. Keywords: analytical and numerical model, automated vehicle-storage and retrieval systems AVS/RS, automated warehouses, cycle time and throughput performance, shuttles integrated with hoisted carriage Published in DKUM: 26.06.2024; Views: 162; Downloads: 16 Full text (609,91 KB) This document has many files! More... |
10. Evaluation of the eruption of permanent teeth and theirassociation with malocclusionAnita Fekonja, 2022, original scientific article Abstract: Objectives:This study was done to determine the timing of eruption of permanentteeth by sex and the number of permanent teeth erupted at different ages and toassess its association with malocclusion.
Material and Methods:The sample for this study consisted of 633 healthy subjects(317 boys and 316 girls) aged between 5.0 and 15.0 years. The subjects were dividedinto subgroups considering an age interval of 1 year.
Results:The mean eruption times were lower for girls compared with boys exceptfor the maxillary and mandibular second premolars and second molars, which werefound to erupt earlier in boys. All the permanent mandibular teeth, except thesecond premolars, tended to erupt earlier than their maxillary antagonists in bothsexes. The sequence of eruption differs between girls and boys in the maxillarycanine and maxillary second premolars. In Class III malocclusion, all the permanentmandibular teeth erupt earlier than their maxillary antagonists. In the entire sample,the correlation between the number of erupted teeth and age was strong (p< .05),but the differences between sexes were not significant.
Conclusions:It is important to know the normal eruption time of permanent teeth inthe population due to diagnosis and better treatment planning in pediatric dentistryand orthodontics. Keywords: eruption time, malocclusion, pediatric dentistry Published in DKUM: 11.06.2024; Views: 125; Downloads: 7 Full text (732,21 KB) This document has many files! More... |