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. Tumor immune microenvironment in pancreatic ductal adenocarcinoma revisited - Exploring the "Space"Konstantin Bräutigam, Kristijan Skok, Krzysztof Szymonski, Charlotte Vestrup Rift, Eva Karamitopoulou, 2025, review article Abstract: Pancreatic ductal adenocarcinoma (PDAC) remains one of the most deadly malignancies with a highly immunosuppressive tumor immune microenvironment (TIME) that hinders effective therapy. PDAC is characterized by significant heterogeneity in immune cell composition, spatial distribution and activation states, which impacts tumor progression and treatment response. Tumour-infiltrating lymphocytes (TILs), including CD4+ T-helper cells, CD8+ cytotoxic T-cells and FOXP3+ regulatory T-cells, play a key role in immune regulation, yet PDAC is largely an immunologically "cold" tumour with limited effector T-cell infiltration. The surrounding cellular microenvironment, particularly Cancer Associated Fibroblasts (CAFs) and macrophages, contributes to immune evasion by promoting a fibrotic and desmoplastic barrier that limits TIL infiltration. The prognostic significance of TILs is increasingly recognized, with higher densities correlating with improved survival, whereas regulatory T-cell infiltration and immunosuppressive stromal interactions are associated with poor outcomes. Emerging therapeutic strategies targeting the TIME (e.g., CAFs), immune checkpoint inhibitors, and TIL-based therapies offer the potential to overcome resistance. Future research must focus on optimizing immunotherapy strategies and unravelling the complex stromal-immune interactions to improve clinical translation.
Keywords: immune system, pancreatic adenocarcinoma (PDAC), spatial analysis, tumor immune microenvironment (TIME), tumor infiltrating lymphocytes (TILs)
Published in DKUM: 18.08.2025; Views: 0; Downloads: 1
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3. 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 Abstract: This paper addresses the lack of consideration of short time scales, below one hour, such as sub-15-min and sub1-hr, in grid codes for frequency quality analysis. These time scales are becoming increasingly important due to
the flexible market-based operation of power systems as well as the rising penetration of renewable energy
sources and battery energy storage systems. For this, firstly, a set of frequency-quality indices is considered,
complementing established statistical indices commonly used in power-quality standards. These indices provide
valuable insights for quantifying variations, events, fluctuations, and outliers specific to the discussed time
scales. Among all the implemented indices, the proposed indices are based on over/under frequency events (6
indices), fast frequency rise/drop events (6 indices), and summation of positive and negative peaks (1 index), of
which the 5 with the lowest thresholds are identified as the most dominant. Secondly, k-means and k-medoids
clustering methods in a learning scheme are employed to identify typical patterns within the discussed time
windows, in which the number of clusters is determined based on prior knowledge linked to reality. In order to
clarify the frequency variations and patterns, three frequency case studies are analyzed: case 1 (sub-15-min scale,
10-s values, 6 months), case 2 (sub-1-hr scale, 10-s values, 6 months), and case 3 (sub-1-hr, 3-min values, the
year 2021). Results obtained from the indices and learning methods demonstrate a full picture of the information
within the windows. The maximum value of the highest frequency value minus the lowest one over the windows
is about 0.35 Hz for cases 1 and 2 and 0.25 Hz for case 3. Over-frequency values (with a typical 0.1% threshold)
slightly dominates under-frequency values in cases 1 and 2, while the opposite is observed in case 3. Medium
fluctuations occur in 35% of windows for cases 1 and 2 and 41% for case 3. Outlier values are detected using the
quartile method in 70% of windows for case 2, surpassing the other two cases. About six or seven typical patterns
are also extracted using the presented learning scheme, revealing the frequency trends within the short time
windows. The proposed approaches offer a simpler alternative than tracking frequency single values and also
capture more comprehensive information than existing approaches that analyze the aggregated frequency values
at the end of the specific time windows without considering the frequency trends. In this way, the network
operators have the possibility to monitor the frequency quality and trends within short time scales using the most
dominant indices and typical patterns.
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: 17
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4. 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: 46
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5. A microfluidic, flow-through, liquid reagent fluorescence sensor applied to oxygen concentration measurementDominik Gril, Denis Đonlagić, 2023, original scientific article Keywords: microfluidic, microfluidic sensing systems, capillary-based fluorescent chemical sensor system, fluorescent sensors, oxygen sensing, fluorescent decay time measurements, on-line liquid analysis, optical fibers, capillaries, liquid reagent
Published in DKUM: 31.05.2023; Views: 550; Downloads: 84
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6. Financial system and agricultural growth in UkraineOlena Oliynyk, 2017, original scientific article Abstract: Background/Purpose: An effective financial system should increase the efficiency of economic activities. This study provides evidence regarding the importance of financial development for agricultural growth in Ukraine.
Methodology: We used non-integrated and integral indicators, time series and regression analysis to investigate the link between the financial development and agricultural growth.
Results: The results based on integral indicators shows that the financial development does not affect agricultural growth in Ukraine. The study based on non-integrated indicators, which characterizes various aspects of the financial system’s banking component and agricultural growth, provided a significant link between the financial system and agriculture growth. The regression models revealed if bank deposits to GDP (%) increases the value added per worker in agriculture increases exponentially. The results of the study indicate that, agriculture is more sensitive to lending changes than the vast majority of other sectors of the economy. The increasing lending of one UAH (Ukrainian hryvnia) resulted in retail turnover growth of 1.62 UAH, while agricultural gross output, growth was UAH 5.06.
Conclusion: Our results reveal a positive relationship between financial system’s banking component and agriculture growth in Ukraine. The results indicate the necessity for continued research into further developing universal methodological approaches of appraising the nexus of the financial system’s banking component on agriculture growth in general as well separate farm groups. The results of our study has important implications on policy making authorities efforts to stimulate agricultural growth by improving the efficiency of the financial system’s banking component.
Keywords: agricultural growth, the integral indicator of the agricultural growth, the integral indicator of the financial development, time series analysis, regression analysis, financial system
Published in DKUM: 04.05.2018; Views: 1477; Downloads: 417
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8. OPTIMIRANJE DOBAVNE VERIGE V PODJETJU B/S/H HIŠNI APARATI, D.O.O., NAZARJERomana Markelj, 2009, undergraduate thesis Abstract: V diplomskem delu sem predstavila optimiranje dobavne verige v podjetju EUREL Poljčane. Prvi del diplomskega dela predstavlja teoretična izhodišča, ki se nanašajo na uvajanje t.i. vitke proizvodnje, metode za uvajanje vitke proizvodnje ter principe vitkih podjetij. Opisala in opredelila sem pojem upravljanje dobavne verige, vrste dobavnih verig, globalne dobavne verige, optimiranje dobavne verige, model integracije dobavne verige, ovire pri njihovi integraciji, ključne procese v njej ter opredelila bodoče trende in usmeritve na področju optimiranja dobavnih verig.
V empiričnem delu sem predstavila podjetje B/S/H Hišni aparati, osnovne podatke o podjetju, kratek zgodovinski oris podjetja, proizvodni program ter politiko in strategijo podjetja.
Praktični del diplomskega dela se nanaša na optimiranje dobavne verige v podjetju EUREL Poljčane. Ta del je pravzaprav raziskovalno delo, saj je bil projekt izveden pilotno in je predstavljal osnovo za izvedbo nadaljnjih projektov optimiranja dobavnih verig vseh dobaviteljev v žarišču. Pri projektu so sodelovali tudi zunanji strokovnjaki, ki so nas usmerjali pri izvajanju različnih analiz: mapa/zemljevid vrednostnega toka, analiza vrednostnega toka, design vrednostnega toka. Izdelane analize so nam služile kot osnova za izdelavo akcijskega načrta, plana implementacije ter za dejansko implementacijo bodočega stanja. Zadnji korak optimiranja dobavne verige zajema kontrolno fazo, ki je namenjena prikazu in ovrednotenju rezultatov. Rezultati oz. koristi, ki izhajajo iz implementiranih izboljšav, se partnersko delijo med ključne udeležence dobavne verige.
Keywords: Upravljanje dobavne verige, vitka proizvodnja, mapa vrednostnega toka, analiza vrednostnega toka, design vrednostnega toka, Toyotin proizvodni sistem, Just in Time, Jidoka (neodvisen, samoupraven, avtonomen), Kaizen (aktivnosti nenehnega izboljševanja), tok proizvodnje, Pull-System (material je "povlečen" na delovno mesto), Outsourcing (zunanje izvajanje dejavnosti), Lead Time (časovna perioda med prejemom naročila odjemalca in dobavo končnega proizvoda odjemalcu), MRP-Material Requirements Planning (p
Published in DKUM: 25.05.2010; Views: 6328; Downloads: 570
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