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Modelling of unit differential reversal curves in the G2E hysteresis model
Ermin Rahmanović, Martin Petrun, 2024, izvirni znanstveni članek

Opis: Iron losses represent a crucial factor in the design process of electrical machines. For this reason, it is important to consider adequate hysteresis behavior within models which predict iron losses. A promising hysteresis description is the static hysteresis model developed by the G2Elab research group. It proposes a unique approach of modelling magnetization curves inside the major loop based on the so-called unit differential reversal curves (uDRCs). This work focuses on modelling of the uDRCs. We analyzed the accuracy and identification approaches of several uDRC models, where we compared the established model with simplified solutions with less parameters. Further, we analyzed the impact of individual models regarding identification convergence. Finally, we highlighted which simplified models give the best trade-off between the ease and stability of identification process of parameters, and the accuracy of the hysteresis model.
Ključne besede: static hysteresis model, iron loss, loss surface model, magnetic material, mathematical modelling
Objavljeno v DKUM: 26.01.2024; Ogledov: 79; Prenosov: 11
.htm Celotno besedilo (154,34 KB)

Most prominent topics in wellness tourism research : topic modelling analysis
Mila Zečević, Milica Rančić Demir, 2022, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Opis: This paper presents a brief overview of the development of the wellness tourism literature. In addition, an analysis and presentation of the topics that appear within this literature field are given. The purpose of this research was to point out the relevant topics that have attracted research efforts over time. In order to detect these topics, we have selected wellness tourism literature articles from Web of Science. Our analysis used topic modelling tools using a machine learning algorithm in Python. The results imply the distinction between two main research topics within wellness tourism literature – wellness and health and medical research. Such differentiation also matches the development of the wellness tourism research field itself.
Ključne besede: wellness tourism, literature, topic modelling, health, medical
Objavljeno v DKUM: 17.01.2024; Ogledov: 67; Prenosov: 3
.pdf Celotno besedilo (19,75 MB)
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Barriers to applying last-mile logistics in the Egyptian market : an extension of the technology acceptance model
Mohamed Amr Sultan, Tomaž Kramberger, Mahmoud Barakat, Ahmed Hussein Ali, 2023, izvirni znanstveni članek

Opis: Drawing on the Technology Acceptance Model (TAM), this research aims to investigate the impact of social, environmental, and technological barriers on adopting the last-mile logistics application. This research used a self-administrative questionnaire to collect 1060 respondents from the Egyptian market and analysed it using partial least square structural equation modeling. The findings revealed that some elements could obstruct the implementation of last-mile delivery technologies, namely complexity, collaboration efforts between users and application developers and the impact of technical knowledge and expertise on the potentially involved users. The sharing economy helps organisations reduce contaminants, emissions and carbon footprints, and last-mile logistics is one of the tools of the sharing economy that can enhance the productivity and competitiveness of logistics and boost consumer fulfillment. This research will help enhance organisations’ performance in Egypt as a developing country and push towards applying environmental sustainability practices, as it introduces a tool to enhance customer satisfaction and reduce emissions by illustrating how last-mile logistics can be implemented. This is particularly important as last-mile logistics face some implementation barriers, especially in developing countries. In addition, it will help in extending the theory through conceptualising its abstract ideas with the research variables and applying it in a different context.
Ključne besede: technology acceptance model, technology implementation barrier, last-mile delivery, sustainability, sharing economy, structural equation modelling
Objavljeno v DKUM: 15.12.2023; Ogledov: 234; Prenosov: 8
.pdf Celotno besedilo (1,04 MB)
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Managing the complexity of empty container movements through repositioning strategies and routing practices under certain demand and supply : doctoral dissertation
Alaa 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: 260; Prenosov: 13
.pdf Celotno besedilo (3,38 MB)

NARX Deep Convolutional Fuzzy System for Modelling Nonlinear Dynamic Processes
Marjan Golob, 2023, izvirni znanstveni članek

Opis: This paper presents a new approach for modelling nonlinear dynamic processes (NDP). It is based on a nonlinear autoregressive with exogenous (NARX) inputs model structure and a deep convolutional fuzzy system (DCFS). The DCFS is a hierarchical fuzzy structure, which can overcome the deficiency of general fuzzy systems when facing high dimensional data. For relieving the curse of dimensionality, as well as improving approximation performance of fuzzy models, we propose combining the NARX with the DCFS to provide a good approximation of the complex nonlinear dynamic behavior and a fast-training algorithm with ensured convergence. There are three NARX DCFS structures proposed, and the appropriate training algorithm is adapted. Evaluations were performed on a popular benchmark—Box and Jenkin’s gas furnace data set and the four nonlinear dynamic test systems. The experiments show that the proposed NARX DCFS method can be successfully used to identify nonlinear dynamic systems based on external dynamics structures and nonlinear static approximators.
Ključne besede: process identification, input-output modelling, NARX model, decomposed fuzzy system, hierarchical fuzzy system, deep convolutional fuzzy system
Objavljeno v DKUM: 30.11.2023; Ogledov: 199; Prenosov: 8
.pdf Celotno besedilo (5,86 MB)
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Geometry design and analysis of an electric bus for the interior ther-mal modelling
Costica Nituca, Gabriel Chiriac, Georgel Gabor, Ilie Nucǎ, Vadim Cazac, Marcel Burduniuc, 2021, izvirni znanstveni članek

Opis: The heating, ventilation and air-conditioning (HVAC) system represents the main auxiliary load for any type of bus. Being the most significant energy-consuming auxiliary load for the electric bus, it must be given special attention in an electric bus system design. To study the heat transfer and thermal optimization for passenger comfort in the electric bus computer-aided design (CAD) is used. The geometry of an electric bus interior is designed considering the main components of the vehicle: passenger cabin, driver’s cabin, windows, walls, and seats. Materials of the same type as those used in the real bus are considered for the geometry model. Based on the heat transfer theory, a thermal model and simulations are made for the heat transfer inside the electric bus. The simulated data are compared with measurement data, and based on these, it can be concluded that the thermal model of the electric bus can be validated and used further for a wide variety of thermal simulation types.
Ključne besede: heat transfer, electric bus, passenger comfort, geometry design, thermal modelling
Objavljeno v DKUM: 13.11.2023; Ogledov: 135; Prenosov: 3
.pdf Celotno besedilo (1,04 MB)
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Energo-economics payback investment calculation modelling of gas-steam combined cycle power plant
Dušan Strušnik, Jurij Avsec, 2022, izvirni znanstveni članek

Opis: The paper deals with energo-economic payback calculation modelling of the combined gassteam cycle operation, demonstrating the basic characteristic properties of cycle behaviour in different operating regimes and calculating the payback period of the investment. The calculation of the payback period of the investment is based on the calculation of the net present value and with actual obtaining data sets from a recently built gas-steam combined cycle power plant. The results of the calculation modelling show that the gas-steam combined cycle power plant can achieve a useful efficiency of up to 88% in the back-pressure operation of the steam turbine. The useful efficiency of the gas turbine is up to 40%. The payback period of the investment depends on the investment costs, the quantity and market price of the consumed fuel, the quantity and market price of the generated electricity and thermal energy. The results show that with a price ratio fuel/electricity of 0.36, the payback period of the investment is 4 years, with a price ratio fuel/electricity of 0.54, the payback period of the investment is as much as 17 years.
Ključne besede: calculation, efficiency, investment, market, modelling, payback
Objavljeno v DKUM: 30.10.2023; Ogledov: 309; Prenosov: 3
.pdf Celotno besedilo (1,81 MB)
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Prediction of cavitation and particle erosion in a radial divergent test section
Luka Kevorkijan, Luka Lešnik, Ignacijo Biluš, 2022, izvirni znanstveni članek

Opis: The 3D unsteady, cavitating, particle-laden flow through a radial divergent test section was simulated with the homogeneous mixture model and Discrete Phase Model (DPM) within the commercial CFD code ANSYS Fluent. For turbulence, a RANS approach was adopted with the Reboud’s correction of turbulent viscosity in the k-ω SST model. Cavitation erosion was predicted with the Schenke-Melissaris-Terwisga (SMT) model, while particle erosion was predicted with the Det Norske Veritas (DNV) model. Two distinct erosion zones were identified, one for pure cavitation erosion and one for pure particle erosion. The occurrence of the pure particle erosion zone downstream of the cavitation erosion zone was analysed. By observing the streamlines downstream of the cavitation structures, it was found that vortices form in the flow and redirect the particles towards the wall, causing a pure particle erosion zone on the wall. Particles under consideration in this study were not found to alter the flow to the extent that the cavitation erosion zone would be significantly altered compared with the results without solid particles which are reported in the literature.
Ključne besede: cavitation, Particles ANSYS Fluent, erosion, CFD, modelling, DPM
Objavljeno v DKUM: 30.10.2023; Ogledov: 120; Prenosov: 7
.pdf Celotno besedilo (2,04 MB)
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Green walls : an eco-friendly system for achieving energy efficiency in buildings
Dejan Tasić, Amor Chowdhury, Dalibor Igrec, 2022, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: energy efficiency, green wall, heat losses, modelling
Objavljeno v DKUM: 27.10.2023; Ogledov: 133; Prenosov: 4
.pdf Celotno besedilo (14,78 MB)
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Simulated global empty containers repositioning using agent-based modelling
Alaa Abdelshafie, Bojan Rupnik, Tomaž Kramberger, 2023, izvirni znanstveni članek

Opis: 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. Empty containers accumulated at specific ports cannot only generate profit but also increase the environmental footprint. This research proposes a Maritime Empty Container Reposition Modelling Framework by integrating the agent-based modelling (ABM) paradigm to model the global movements of empty containers. An agent-based maritime logistic empty container redistribution model was developed to help minimize the total relevant costs for empty container movement in the planning horizon. In the system, ports, shipping companies, customers, and empty containers were identified as critical agents. Using simulated annealing (SA), shipping line agents were able to optimise empty container repositioning to determine the best sequence for moving containers. The model was applied to the Asia–Middle East region to simulate global empty containers repositioning in the region. The results comparison shows that the proposed optimised empty container repositioning framework can significantly reduce the shipping line’s costs and make full use of empty containers
Ključne besede: maritime industry, empty containers, repositioning, agent-based modelling, simulation, optimisation
Objavljeno v DKUM: 02.08.2023; Ogledov: 209; Prenosov: 20
.pdf Celotno besedilo (2,91 MB)
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