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Optimizing smart manufacturing systems using digital twin
Robert 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: 171; Prenosov: 9
.pdf Celotno besedilo (1,28 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: 480; Prenosov: 18
.pdf Celotno besedilo (3,38 MB)

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: 323; Prenosov: 25
.pdf Celotno besedilo (2,91 MB)
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Industry 4.0 and the new simulation modelling paradigm
Blaž Rodič, 2017, izvirni znanstveni članek

Opis: Background and Purpose: The aim of this paper is to present the influence of Industry 4.0 on the development of the new simulation modelling paradigm, embodied by the Digital Twin concept, and examine the adoption of the new paradigm via a multiple case study involving real-life R&D cases involving academia and industry. Design: We introduce the Industry 4.0 paradigm, presents its background, current state of development and its influence on the development of the simulation modelling paradigm. Further, we present the multiple case study methodology and examine several research and development projects involving automated industrial process modelling, presented in recent scientific publications and conclude with lessons learned. Results: We present the research problems and main results from five individual cases of adoption of the new simulation modelling paradigm. Main lesson learned is that while the new simulation modelling paradigm is being adopted by big companies and SMEs, there are significant differences depending on company size in problems that they face, and the methodologies and technologies they use to overcome the issues. Conclusion: While the examined cases indicate the acceptance of the new simulation modelling paradigm in the industrial and scientific communities, its adoption in academic environment requires close cooperation with industry partners and diversification of knowledge of researchers in order to build integrated, multi-level models of cyber-physical systems. As shown by the presented cases, lack of tools is not a problem, as the current generation of general purpose simulation modelling tools offers adequate integration options.
Ključne besede: simulation, modelling, automated modelling, Industry 4.0, Digital Twin, SME, multiple-case study
Objavljeno v DKUM: 30.11.2017; Ogledov: 1488; Prenosov: 478
.pdf Celotno besedilo (1,07 MB)
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A statistical model for shutdowns due to air quality control for a copper production decision support system
Khalid Aboura, 2015, izvirni znanstveni članek

Opis: Background: In the mid-1990s, a decision support system for copper production was developed for one of the largest mining companies in Australia. The research was conducted by scientists from the largest Australian research center and involved the use of simulation to analyze options to increase production of a copper production facility. Objectives: We describe a statistical model for shutdowns due to air quality control and some of the data analysis conducted during the simulation project. We point to the fact that the simulation was a sophisticated exercise that consisted of many modules and the statistical model for shutdowns was essential for valid simulation runs. Method: The statistical model made use of a full year of data on daily downtimes and used a combination of techniques to generate replications of the data. Results: The study was conducted with a high level of cooperation between the scientists and the mining company. This contributed to the development of accurate estimates for input into a support system with an EXCEL based interface. Conclusion: The environmental conditions affected greatly the operations of the production facility. A good statistical model was essential for the successful simulation and the high budget expansion decision that ensued.
Ključne besede: decision support system, simulation, statistical modelling
Objavljeno v DKUM: 28.11.2017; Ogledov: 1226; Prenosov: 326
.pdf Celotno besedilo (339,98 KB)
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Roundabout arm capacity determined by microsimulation and discrete functions technique
Tomaž Tollazzi, Matjaž Šraml, Tone Lerher, 2008, izvirni znanstveni članek

Opis: The paper demonstrates the influence of the multi-channel pedestrian flow on the actual capacity of a one-lane roundabout, using micro-simulation and discrete functions. The proposed model is based on the theory of the expected time gap between the units of pedestrian traffic flow, which have the priority when crossing the arm of the roundabout. The proposed model represents an upgrade of the previous research in the field of modelling traffic flows in the one-lane roundabout.Apart from the multi-channel pedestrian flow the disturbances caused by the circular traffic flow of motorised vehicles at the roundabout are also considered. In this way the model can better illustrate the real conditions in traffic. A simulation analysis has been performed on the roundabout arm at Koroška Street in Maribor. The results of the analysis have indicated a relatively high reserve of the actual throughput capacity for the main motorized traffic flow in the analysed roundabout arm. The presented model represents a practicable and adaptable tool for planning the roundabout capacity in practice and for the sensitivity analysis of individual variables on the throughput capacity of the roundabout.
Ključne besede: roundabouts, traffic flow analysis, micro-simulation modelling, capacity analysis
Objavljeno v DKUM: 05.06.2017; Ogledov: 1518; Prenosov: 158
.pdf Celotno besedilo (4,50 MB)
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Simulation analysis of economic burden in hypertension and myocardial infarction treatment with beta blockers
Maja Atanasijević-Kunc, Jože Drinovec, Barbara Guštin, Aleš Mrhar, 2012, izvirni znanstveni članek

Opis: Background: Hypertension has become a very frequent chronic disease worldwide and Slovenia is no exception. It is defined as a serious risk factor for developing different cardiovascular diseases. Several important studies proved that cardiovascular diseases are the main reason of deaths in more than 50 % of cases in the developed countries. All mentioned facts are indicating that treatment costs in patients with hypertension and cardiovascular diseases represent an important economic burden, which cannot be neglected. It may also be expected that in the next few decades the situation will become even worse. The reasons are the expected earlier disease development due to unhealthy life style and the fact that people live longer and populations are growing older. The mentioned facts have motivated the study, which would enable the estimation of patients’ number in the observed population and the evaluation of economic burden when using beta blockers, drugs which have become an important choice in antihypertensive treatment and are also used in patients with different cardiovascular complications. The projections indicating the expected trends of mentioned problems in the forthcoming decades would also be of interest. Methods: To answer some of the indicated questions, a simulation model was developed, which enabled the prediction of patients with hypertension and the influence of this disease to the development of myocardial infarction. Modeling was performed using the available statistical data and published studies. Main attention was devoted to the circumstances in Slovenia, but the results were also verified using the available data for some other countries. Combination of simulation results with demographic data enabled the estimation of the number of patients observed. In addition, expenses for the observed groups of patients were evaluated and, based on that, the economic burden was estimated. The mentioned expenses include hospitalizations, drugs required and the estimated mortality-related expenses. The developed model was accomplished with dynamical mathematical structure predicting the development of population number in Slovenia in the forthcoming decades, taking into account that the demographic properties remain unchanged. Also the observation of potential scenario regarding patients’ number and thus expected economic burden distribution among younger and older population is made possible. Results: In the paper simulation results are presented which enable the estimation of patients with hypertension and their connection with those who have experienced myocardial infarction. It is possible to observe the prevalence and the number of patients in Slovenia by age. In addition, economic burden associated with the observed groups of patients is calculated taking into account needed drugs, hospitalizations and patient mortality. In such circumstances it is possible to expect that in the group of one million people approximately 264,000 are patients with hypertension for whom, when healed optimally with beta blockers, over EUR 13 million is needed per year. In the same group of one million people are also patients with myocardial infarction. Among them 11 % experienced infarction within the current year. This amounts to more than 22,000 such patients and over EUR 22 million needed for them each year. In the case of unchanged statistical demographic characteristics in the future, it can be expected that in 50 years relative economic burden for active population would become twice as high as it is now. Conclusions: For optimal treatment, hospitalization and due to mortality more than EUR 35 million per year would be needed for patients with hypertension (around 260,000 patients) and for those who have experienced myocardial infarction (around 22,000) if observing the population of one million people. As the population is growing older, it can be expected that the relative economic burden will become significantly greater for active population in the forthcoming decades.
Ključne besede: hypertension, myocardial infarction, beta blockers, economic burden, modelling, simulation
Objavljeno v DKUM: 28.03.2017; Ogledov: 1029; Prenosov: 60
.pdf Celotno besedilo (809,50 KB)
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Modelling of the risk factors and chronic diseases that influence the development of serious health complications
Maja Atanasijević-Kunc, Jože Drinovec, Simona Ručigaj, Aleš Mrhar, 2008, izvirni znanstveni članek

Opis: Background: Some chronic diseases, like diabetes type 2 and hypertension, and risk factors, such as obesity, hypercholesterolemia, and smoking, are strongly correlated with the potential development of serious health complications that can threaten a patient's life or significantly influence the quality of life, while at the same time representing an enormous economic burden. Such complications include, for example, stroke, coronary heart disease, peripheralarterial vascular disease, end-stage renal disease and congestive heart failure. Methods: For a quantitative evaluation of the mentioned patient groups, the age distribution and an estimation of the treatment expenses a dynamic mathematical model was developed, where special attention was devoted to its structure, as it should enable the sequential construction and representation of different forms of data information. The model was realized in the Matlab program package with the Simulink Toolbox. Conclusions: A dynamic mathematical model is described that enables the observation of patients (in percentage terms) with diabetes type 2 and obesity, as well as those who smoke, have hypercholesterolemia and hypertension and all possible combinations of these problems, related to their age. Taking into account the Slovenian demographic data and annual treatment expenses, we were able to quantitatively evaluate these factors, not only in Slovenia but also in other developed regions where the demographic and economic situations are similar. It is also possible to extend the model to patients with serious complications, also taking into account the population dynamics, which is the goal of the next steps in our investigation. Regarding the presented results, it is estimated that from a group of a million people, those requiring treatment for diabetes type 2 cost as much as € 19.5 millions per year, since the treatment of one patient for one year is € 355. If all the sufferers requiring such treatment were located, as a consequence of more systematic medical examinations, an additional € 16 millions would be needed. In this group of one million people, as many as 40 % are expected to develop hypercholesterolemia, of which 26 % are diagnosed and treated adequately. The annual cost for the treatment of one patient is 313, which means that for a group of a million people the costs would be € 82 millions per year. An additional € 43.5 millions would be needed if all the sufferers with hypercholesterolemia were treated. Another chronic disease is hypertension. The annual cost for treating one patient is estimated to be € 271, and so for a group of a million people the treatment costs would be € 69.5 millions. If this were extended to include so far undiscovered sufferers with this chronic disease an additional € 14.5 millions would be needed.
Ključne besede: modelling, simulation, diabetes type 2, obesity, smoking, hypercholesterolemia, hypertension
Objavljeno v DKUM: 28.03.2017; Ogledov: 1075; Prenosov: 111
.pdf Celotno besedilo (1,10 MB)
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