1. Analytical model and swapping policy assessment of a vertical lift module – buffer integrated storage systemJakob Marolt, Fabio Sgarbossa, Jesus A. Jimenez, Abhimanyu Sharotry, Tone Lerher, 2024, original scientific article Abstract: To meet the rising demands of global trade and e-commerce, efficient warehousing relies on inte-grated and cooperative material handling systems. This paper investigates the extension of VerticalLift Module (VLM) storage capability with a Buffer System and assesses the impact of this integra-tion on performance. We developed an analytical model to calculate the expected dual commandcycles, forming the basis for evaluating the VLM – Buffer integrated storage system’s performance.Our research emphasises minimising unnecessary swaps between the VLM and the Buffer Systemto enhance throughput performance. We introduce the Look Ahead Strategy (LAS) to minimiseinter-system swaps and develop a Binary Integer Program (BIP) to benchmark its performance. Theresults indicate that LAS performs on par with BIP, due to its ability to consider product popular-ity during the final selection of the outbound swapping tote. Through a comprehensive analysisof the analytical model with an empirical correction, utilising Pareto-based order sequences, theresults show deviations of less than 1% on average, affirming the analytical model’s accuracy. Ourresearch provides insights on using the VLM-Buffer integrated storage system, emphasising efficienttote swapping policies like LAS for enhanced warehouse operations, and allows managers to assesssystem performance through scenario-based analyses.
Keywords: automated warehouses, vertical lift module, toteswapping, analytical and numerical modelling, performance evaluation
Published in DKUM: 11.10.2024; Views: 0; Downloads: 0
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2. Control model for ground crew scheduling problem at small airports : case of SerbiaLena Đorđević Milutinović, Dragana Makajić-Nikolić, Slobodan Antić, Marija Živić, Andrej Lisec, 2021, original scientific article Abstract: Present-day airline industry is quite a competitive field and crew scheduling represents one of the crucial problems due to significant impact on the airline's cost. The crew scheduling problem is based on the assignment of crew members to operate different tasks of route. The main goal of this paper is to provide an analysis and a solution to one of the biggest problems detected on a small airport in the Serbia - the problem of ground crew scheduling. The paper presents the main characteristics, goals and limitations of a real-life problem identified at this small airport. In order to solve the problem, we developed a dynamic discrete simulation model. The model is developed in a spreadsheet environment of Microsoft Excel. Some of the main limitations found in the development of the model are strong constraints and multiple goals. The model presented in the paper is designed as a useful management tool for smaller airports and is aimed at the improvement of operative processes.
Keywords: crew scheduling problem, modelling, air transport, small airport, management, spreadsheets
Published in DKUM: 01.10.2024; Views: 0; Downloads: 1
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3. Personalizing human–robot workplace parameters in human-centered manufacturingRobert Ojsteršek, Borut Buchmeister, Aljaž Javernik, 2024, original scientific article Abstract: This study investigates the relationship between collaborative robot (CR) parameters and worker utilization and system performance in human–robot collaboration (HRC) environments. We investigated whether optimized parameters increase workplace efficiency and whether adapting these parameters to the individual worker improves workplace outcomes. Three experimental scenarios with different CR parameters were analyzed in terms of the setup time, assembly time, finished products, work in process, and worker utilization. The main results show that personalized CR parameters significantly improve efficiency and productivity. The scenario in which CR parameters were tailored to individual workers, balanced the workload, and minimized worker stress, resulting in higher productivity compared to non-people-centric settings. The study shows that personalization reduces cognitive and physical stress, promotes worker well-being, and is consistent with the principles of human-centered manufacturing. Overall, our research supports the adoption of personalized, collaborative workplace parameters, supported by the mathematical model, to optimize employee efficiency and health, contributing to human-centered and efficient HRC environments.
Keywords: human–robot workplace, collaborative workplace, human-centered manufacturing, stress index, modelling, efficiencxy
Published in DKUM: 03.09.2024; Views: 38; Downloads: 6
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4. Numerical analysis of low-enthalpy deep geothermal energy extraction using a novel gravity heat pipe designUrban Gselman, Vid Peršak, Darko Goričanec, 2024, original scientific article Abstract: Geothermal energy, derived from the Earth’s internal heat, can be harnessed due to the
geothermal gradient between the Earth’s interior and its surface. This heat, sustained by radiogenic
decay, varies across regions, and is highest near volcanic areas. In 2020, 108 countries utilised
geothermal energy, with an installed capacity of 15,950 MWe for electricity and 107,727 MWt for
direct use in 2019. Low-enthalpy sources require binary systems for power production. Open-loop
systems face issues like scaling, difficult water treatment, and potential seismicity, while closed-loop
systems, using abandoned petroleum or gas wells, reduce costs and environmental impacts greatly.
The novel geothermal gravity heat pipe (GGHP) design eliminates parasitic power consumption by
using hydrostatic pressure for fluid circulation. Implemented in an abandoned well in north-east
(NE) Slovenia, the GGHP uses a numerical finite difference method to model heat flow. The system
vaporises the working fluid in the borehole, condenses it at the surface, and uses gravitational flow
for circulation, maintaining efficient heat extraction. The model predicts that continuous maximum
capacity extraction depletes usable heat rapidly. Future work will explore sustainable heat extraction
and potential discontinuous operation for improved efficiency.
Keywords: geothermal energy, geothermal gravity heat pipe, numerical modelling, single well closed-loop heat exchanger
Published in DKUM: 03.09.2024; Views: 41; Downloads: 3
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5. Revealing the spatial pattern of weather-related road traffic crashes in SloveniaDanijel Ivajnšič, Nina Zver, Igor Žiberna, Eva Konečnik Kotnik, Danijel Davidović, 2021, original scientific article Abstract: Despite an improvement in worldwide numbers, road traffic crashes still cause social, psychological, and financial damage and cost most countries 3% of their gross domestic product. However, none of the current commercial or open-source navigation systems contain spatial information about road traffic crash hot spots. By developing an algorithm that can adequately predict such spatial patterns, we can bridge these still existing gaps in road traffic safety. To that end, geographically weighted regression and regression tree models were fitted with five uncorrelated (environmental and socioeconomic) road traffic crash predictor variables. Significant regional differences in adverse weather conditions were identified; Slovenia lies at the conjunction of different climatic zones characterized by differences in weather phenomena, which further modify traffic safety. Thus, more attention to speed limits, safety distance, and other vehicles entering and leaving the system could be expected. In order to further improve road safety and better implement globally sustainable development goals, studies with applicative solutions are urgently needed. Modern vehicle-to-vehicle communication technologies could soon support drivers with real-time traffic data and thus potentially prevent road network crashes.
Keywords: GIS, hot spot analyses, traffic safety, spatial modelling, weather patterns
Published in DKUM: 20.08.2024; Views: 92; Downloads: 4
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6. The Lyme borreliosis spatial footprint in the 21st century : a key study of SloveniaDaša Donša, Jaša Veno Grujić, Nataša Pipenbaher, Danijel Ivajnšič, 2021, original scientific article Abstract: After mosquitoes, ticks are the most important vectors of infectious diseases. They play an important role in public health. In recent decades, we discovered new tick-borne diseases; additionally, those that are already known are spreading to new areas because of climate change. Slovenia is an endemic region for Lyme borreliosis and one of the countries with the highest incidence of this disease on a global scale. Thus, the spatial pattern of Slovenian Lyme borreliosis prevalence was modelled with 246 indicators and transformed into 24 uncorrelated predictor variables that were applied in geographically weighted regression and regression tree algorithms. The projected potential shifts in Lyme borreliosis foci by 2050 and 2070 were calculated according to the RCP8.5 climate scenario. These results were further applied to developing a Slovenian Lyme borreliosis infection risk map, which could be used as a preventive decision support system.
Keywords: CART, climate change, MGWR, Lyme disease, infection risk, spatial modelling
Published in DKUM: 12.08.2024; Views: 69; Downloads: 5
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7. The SEM model of better workers’ life in companiesMaja Rožman, Vesna Čančer, 2022, original scientific article Abstract: This paper seeks to build a model of the aging workers’ work-life quality and analyze the effect of its factors on the work engagement of elderly workers. Structural equation modeling was used to analyze the effects among seven constructs. The results show that the effect of the occupational stress of elderly workers on their work engagement and work satisfaction is negative, and the effects of the friendly working conditions, maintenance of work ability, and training programs on the work engagement of elderly workers are positive. The results show that the effect of health promotion in the workplace for elderly workers on their work satisfaction is positive, and so is the effect of work satisfaction on work engagement. The findings of this research can help employers better manage elderly workers and create a healthy and safe work environment for them. A better environment leads to higher work engagement of elderly workers.
Keywords: elderly workers, work engagement of elderly workers, structural equation modelling
Published in DKUM: 03.07.2024; Views: 127; Downloads: 10
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8. Assessment of concept between rural development challenges and local food systems : A combination between Multi-criteria decision analysis and econometric modelling approachJernej Prišenk, Jernej Turk, 2022, original scientific article Abstract: This study investigates the influence of social, economic, and environmental impacts on the promotion and marketing systems of local food products from mountain areas in Slovenia. These impacts were assessed using an econometric modelling approach. Two econometric models were developed (one for production and one for marketing). The case studies of local food products were selected from Slovenian mountain regions, most of which were from less-favored areas (LFAs). A majority of the selected food commodities were of high quality, with or without protected designations. Data collection was carried out via interviews. Due to production limitation on mountain areas in Slovenia and other constraints in LFAs, the socio-economic and environmental impacts on success of production and marketing systems need to be clarified. These relations present a potential impact on the wider socio-economic development in the region. The empirical results, obtained using an econometric modelling approach, clearly show the importance of encouraging the socio-economic and environmental impacts in ensuring the marketing and production potentials of local food products. The result express good relationships, and cooperation between the actors in the food supply chains contributing to a successful marketing system and production system of local food products (small, average, large) is dependent on the available local labour in mountain rural areas.
Keywords: local food products, mountain areas, econometric modelling, socioeconomic impacts, evironmental impacts
Published in DKUM: 02.07.2024; Views: 117; Downloads: 8
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9. Small hydropower plants in Western Balkan countries : status, controversies and a proposed model for decision makingBarbara Pavlakovič Farrell, Andrea Okanovic, Bojana Vasić, Jelena Jesic, Polona Šprajc, 2022, original scientific article Abstract: Background: As the countries of the Western Balkans (WB) have committed to sustainable development, the process of regulatory and economic adjustment is underway. As part of the aforementioned fact, the WB countries have commenced exploitation of energy from renewable sources, among which hydropower is the most important. The main objective of the study is to analyse the status of renewable energy transition in the WB region, focusing on the construction and exploitation of small hydropower plants (SHPPs), as well as a proposal for an original model for decision making in this field, based on a multidimensional decision-making space. Namely, in most cases, there is resistance to the construction of SHPPs in the WB territory, as well as divided opinion among investors, companies, environmental movements, academia, and citizens on this issue. This shows that the entire decision-making process has to be reviewed and re-designed.
Results: The results of the study show that the construction of SHPPs caused damage to environmentally protected areas, living conditions of local communities, touristic and agricultural potential. All of the foregoing matters have led to mass protests by citizens and a high degree of mistrust so that the future of SHPPs in the WB is extremely uncertain. The assessment of the acceptability of existing SHPPs through the proposed model showed that 74% of SHPPs cannot be considered acceptable from the aspect of the location where they were built, and from the aspect of the impact on the quality of life of the local population. Accordingly, this paper provides suggestions for much-needed improvements.
Conclusions: The construction of SHPPs is causing numerous controversies, opposition, and resistance. To find the right solution, and contribute to sustainable energy and economic development, it is necessary to develop a fully transparent and objective policy system in this field, and to use contemporary models for decision making with emphasis on the involvement local communities in the decision-making process.
Keywords: sustainable energy transition, small hydropower plants, environmental awareness, modelling, decision making process, Western Balkans
Published in DKUM: 28.06.2024; Views: 420; Downloads: 5
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10. High strain rate hardening of metallic cellular metamaterialsNejc Novak, Matej Vesenjak, Zoran Ren, 2024, original scientific article Abstract: Strain rate hardening caused by the changed deformation mode is a fascinating phenomenon in cellular metamaterials where the material’s stiffness and energy absorption capabilities increase as the strain rate increases. This unique behaviour is attributed to a combination of micro-inertia effects, base material’s strain rate hardening and inertia effects. At high strain rates, the metamaterial’s inertia influences its deformation response, which changes to shock mode. This work briefly presents the geometry and fabrication of different metallic metamaterials. Then, it evaluates their mechanical response at different strain rates, ranging from quasi-static to intermediate dynamic and shock, determined by experimental and computational investigation. The three deformation modes can be separated into two critical loading velocities, unique for each metamaterial, which are also presented and compared in this work for various metamaterials. The investigations show that the deformation mode change in metallic metamaterials depends on their porosity. The critical velocities separating the deformation modes decrease with increasing porosity, i.e., decreased density of the metamaterial results in reduced critical loading velocities. The shock deformation mode in cellular metamaterials is thus attainable at much lower loading velocities than in homogeneous (nonporous) materials.
Keywords: metamaterials, cellular structures, high strain rate, experimental testing, computational modelling, compression loading, mechanical properties
Published in DKUM: 22.05.2024; Views: 204; Downloads: 12
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