1. Optimal bus stops' allocation : a school bus routing problem with respect to terrain elevationKlemen Prah, Abolfazl Keshavarzsaleh, Tomaž Kramberger, Borut Jereb, Dejan Dragan, 2018, izvirni znanstveni članek Opis: The paper addresses the optimal bus stops allocation in the Laško municipality. The goal is to achieve a cost reduction by proper re-designing of a mandatory pupils' transportation to their schools. The proposed heuristic optimization algorithm relies on data clustering and Monte Carlo simulation. The number of bus stops should be minimal possible that still assure a maximal service area, while keeping the minimal walking distances children have to go from their homes to the nearest bus stop. The working mechanism of the proposed algorithm is explained. The latter is driven by three-dimensional GIS data to take into account as much realistic dynamic properties of terrain as possible. The results show that the proposed algorithm achieves an optimal solution with only 37 optimal bus stops covering 94.6 % of all treated pupils despite the diversity and wideness of municipality, as well as the problematic characteristics of terrains' elevation. The calculated bus stops will represent important guidelines to their actual physical implementation.
Ključne besede: logistics, maximal covering problems, optimization, data clustering, Monte Carlo simulation, geographic information system (GIS), reduction of transportation costs, Laško, Slovenia
Objavljeno v DKUM: 22.08.2024; Ogledov: 26; Prenosov: 3
 Celotno besedilo (2,40 MB)
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2. Implementation of the digital sales channel in the coatings industryEva Krhač Andrašec, Marjan Senegačnik, Benjamin Urh, Tomaž Kern, 2021, izvirni znanstveni članek Opis: The development process in the coatings industry can be shortened by digital transformation, and its costs can be reduced using a technical enabler. However, formulators need up-to-date and comprehensive data on existing and potential ingredients to develop the formulation. We were curious about how to supply formulators with data. The idea was that suppliers of ingredients provide data using the “common enabling technology”. We hypothesize that direct data entry compensates suppliers because they can shorten the sales process and increase sales. We used a survey to select key sales channels in the industry. Detailed process models were designed using structured interviews. We analyzed models using structural and operational indicators. Finally, we formed a new digital sales process and verified it. The results show that the digitally formatted sales process can be shortened by up to 32%. Simultaneously, more potential customers can be accessed using the common technology. Existing sales channels would not be closed down. Nevertheless, the digital sales channel is expected to prove its worth over time and gradually increase its share. The suppliers of ingredients can thus avoid a radical process transformation and the immediate integration of additional information technology into the company information system in such an evolutionary way.
Ključne besede: digital sales channel, process analyses and improvement, digital transformation, technical enabler, coatings industry, process simulation
Objavljeno v DKUM: 06.08.2024; Ogledov: 85; Prenosov: 4
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3. Road freight transport forecasting : a fuzzy Monte-Carlo simulation-based model selection approachDejan Dragan, Simona Šinko, Abolfazl Keshavarzsaleh, Maja Rosi, 2022, izvirni znanstveni članek Opis: As important as the classical approaches such as Akaike's AIC information and Bayesian BIC criterion in model-selection mechanism are, they have limitations. As an alternative, a novel modeling design encompasses a two-stage approach that integrates Fuzzy logic and Monte Carlo simulations (MCSs). In the first stage, an entire family of ARIMA model candidates with the corresponding information-based, residual-based, and statistical criteria is identified. In the second stage, the Mamdani fuzzy model (MFM) is used to uncover interrelationships hidden among previously obtained models criteria. To access the best forecasting model, the MCSs are also used for different settings of weights loaded on the fuzzy rules. The obtained model is developed to predict the road freight transport in Slovenia in the context of choosing the most appropriate electronic toll system. Results show that the mechanism works well when searching for the best model that provides a well-fit to the real data.
Ključne besede: forecasting road transport, electronic toll system, Monte Carlo simulation, ARIMA models, logistics
Objavljeno v DKUM: 11.06.2024; Ogledov: 119; Prenosov: 5
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6. Optimizing smart manufacturing systems using digital twinRobert Ojsteršek, Aljaž Javernik, Borut Buchmeister, 2023, izvirni znanstveni članek Opis: Presented paper investigates the application of digital twins for the optimisation of intelligent manufacturing systems and focuses on the comparison between simulation modelling results and real-world production conditions. A digital twin was created in the Simio software environment using a data-driven simulation model derived from a real-world production system. Running the digital twin in real time, which was displayed graphically, facilitated the analysis of key parameters, including the number of finished products, average flow time, workstation utilization and product quality. The discrepancies were attributed to the use of random distributions of input data in the dynamic digital twin, as opposed to the long-term measurements and averages in the real-world system. Despite the limitations in the case study, the results underline the financial justification and predictive capabilities of digital twins for optimising production systems. Real-time operation enables continuous evaluation and tracking of parameters and offers high benefits for intelligent production systems. The study emphasises the importance of accurate selection of input data and warns that even small deviations can lead to inaccurate results. Finally, the paper high-lights the role of digital twins in optimising production systems and argues for careful consideration of input data. It highlights the importance of analysing real-world production systems and creating efficient simulation models as a basis for digital twin solutions. The results encourage extending the research to different types of production, from job shop to mass production, in order to obtain a comprehensive optimisation perspective.
Ključne besede: smart manufacturing, digital twin, optimisation, simulation modelling, Simio, case study
Objavljeno v DKUM: 25.03.2024; Ogledov: 253; Prenosov: 10
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7. Obtaining the synthetic fuels from waste plastic and their effect on cavitation formation in a common-rail diesel injectorLuka Kevorkijan, Amalia Palomar-Torres, Eloisa Torres Jiménez, Carmen Mata, Ignacijo Biluš, Luka Lešnik, 2023, izvirni znanstveni članek Opis: The presented paper addresses two significant issues of the present time. In general, the studies of the effect of synthetic fuels on cavitation formation and cavitation erosion prediction in the nozzle tip of common-rail diesel injectors were addressed. The first problem is plastic waste, which can have a significant negative environmental impact if not treated properly. Most plastic waste has high energy value, so it represents valuable material that can be used in resource recovery to produce various materials. One possible product is synthetic fuel, which can be produced using thermal and catalytic pyrolysis processes. The first issue addressed in the presented paper is the determination of fuel properties since they highly influence the fuel injection process, spray development, combustion, etc. The second is the prediction of cavitation development and cavitation erosion in a common-rail diesel injector when using pyrolytic oils from waste plastic. At first, pyrolytic oils from waste high- and low-density polyethylene were obtained using thermal and catalytic pyrolysis processes. Then, the obtained oils were further characterised. Finally, the properties of the obtained oils were implemented in the ANSYS FLUENT computational program and used in the study of the cavitation phenomena inside an injection nozzle hole. The cavitating flow in FLUENT was calculated using the Mixture Model and Zwart-Gerber-Belamri cavitation model. For the modelling of turbulence, a realisable k–ε model with Enhanced Wall Treatment was used, and an erosion risk indicator was chosen to compare predicted locations of cavitation erosion. The results indicate that the properties of the obtained pyrolytic oils have slightly lower density, surface tension and kinematic viscosity compared to conventional diesel fuel, but these minor differences influence the cavitation phenomenon inside the injection hole. The occurrence of cavitation is advanced when pyrolytic oils are used, and the length of cavitation structures is greater. This further influences the shift of the area of cavitation erosion prediction closer to the nozzle exit and increases its magnitude up to 26% compared to diesel fuel. All these differences have the potential to further influence the spray break-up process, combustion process and emission formation inside the combustion chamber.
Ključne besede: plastic waste, synthetic fuels, pyrolytic oils, common-rail, cavitation, erosion, transient simulation
Objavljeno v DKUM: 18.03.2024; Ogledov: 272; Prenosov: 14
Celotno besedilo (4,55 MB)
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8. Managing the complexity of empty container movements through repositioning strategies and routing practices under certain demand and supply : doctoral dissertationAlaa Abdelshafie, 2023, doktorska disertacija Opis: Over the past decades, container transportation management has become an important part of the global maritime industry. Due to an ever-increasing movement of containers across the globe in line with the economic boom, the trade imbalance and issues related to empty containers have become inevitable. The accumulation of empty containers in specific ports not only causes a waste of money but also increases the environmental footprint. Accordingly, the urgent need for empty container management has been gaining more attention than ever before, as the shipping companies recognized that more revenues are always derived from a good repositioning strategy. In this respect, this thesis described state-of-the-art of empty container management, focusing on the practices concerning the movement of empty containers that are varied between organizational policies, technical solutions, and optimization applications. With the development of computer-aided systems, the combination of optimization and simulation models has been proposed to tackle the maritime empty container problem. The thesis shows how the strengths of optimization-based simulation can be integrated to provide high-quality solutions with low computational costs. Agent-based modelling was developed to model the global movements of empty containers, providing realistic details of interactions among entities and characteristics of components within the system. The model was applied between ports in the Middle East and Asia for one of the biggest shipping lines worldwide. By using simulated annealing (SA), the best sequence for moving containers can be determined. The results comparison demonstrate that the proposed optimised repositioning strategy can significantly reduce the shipping line’s costs and make full use of empty containers in the planning horizon.
Ključne besede: shipping industry, container transportation management, empty container repositioning, simulation, optimization, agent-based modelling
Objavljeno v DKUM: 08.12.2023; Ogledov: 570; Prenosov: 22
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9. High strain-rate deformation analysis of open-cell aluminium foamAnja Mauko, Mustafa Sarıkaya, Mustafa Güden, Isabel Duarte, Matej Borovinšek, Matej Vesenjak, Zoran Ren, 2023, izvirni znanstveni članek Opis: This study investigated the high-strain rate mechanical properties of open-cell aluminium foam M-pore®. While previous research has examined the response of this type of foam under quasi-static and transitional dynamic loading conditions, there is a lack of knowledge about its behaviour under higher strain rates (transitional and shock loading regimes). To address this gap in understanding, cylindrical open-cell foam specimens were tested using a modified Direct Impact Hopkinson Bar (DIHB) apparatus over a wide range of strain rates, up to 93 m/s. The results showed a strong dependency of the foam's behaviour on the loading rate, with increased plateau stress and changes in deformation front formation and propagation at higher strain rates. The internal structure of the specimens was examined using X-ray micro-computed tomography (mCT). The mCT images were used to build simplified 3D numerical models of analysed aluminium foam specimens that were used in computational simulations of their behaviour under all experimentally tested loading regimes using LS-DYNA software. The overall agreement between the experimental and computational results was good enough to validate the built numerical models capable of correctly simulating the mechanical response of analysed aluminium foam at different loading rates.
Ključne besede: Open-cell aluminium foam, Micro-computed tomography, High-strain rate, Direct impact hopkinson bar, Digital image correlation, Computer simulation
Objavljeno v DKUM: 06.12.2023; Ogledov: 420; Prenosov: 30
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10. PSpice simulations for single-phase rectifiers for testing DC fusesAdrian Plesca, Costica Nituca, Gabriel Chiriac, Zhiyuan Liu, Yingsan Geng, 2019, izvirni znanstveni članek Opis: In this article, simulations were realized for different power rectifiers used for testing DC fuses. Using the OrCAD PSpice software, a single-phase uncontrolled bridge rectifier and a single-phase controlled bridge rectifier are simulated for different loads. From the data analysis, some important conclusions were realized regarding the form of the temperature waveforms in transient conditions and quasisteady state thermal conditions.
Ključne besede: Power Rectifiers, Simulation, PSpice, DC fuse
Objavljeno v DKUM: 05.12.2023; Ogledov: 326; Prenosov: 4
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