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1.
Two-dimensional velocity-vorticity based LES for the solution of natural convection in a differentially heated enclosure by wavelet transform based BEM and FEM
Jure Ravnik, Leopold Škerget, Matjaž Hriberšek, 2006, izvirni znanstveni članek

Opis: A wavelet transform based boundary element method (BEM) numerical scheme is proposed for the solution of the kinematics equation of the velocity-vorticityformulation of Navier-Stokes equations. FEM is used to solve the kinetics equations. The proposed numerical approach is used to perform two-dimensional vorticity transfer based large eddy simulation on grids with 105 nodes. Turbulent natural convection in a differentially heated enclosure of aspect ratio 4 for Rayleigh number values Ra=107-109 is simulated. Unstable boundary layer leads to the formation of eddies in the downstream parts of both vertical walls. At the lowest Rayleigh number value an oscillatory flow regime is observed, while the flow becomes increasingly irregular, non-repeating, unsymmetric and chaotic at higher Rayleigh number values. The transition to turbulence is studied with time series plots, temperature-vorticity phase diagrams and with power spectra. The enclosure is found to be only partially turbulent, what is qualitatively shown with second order statistics-Reynolds stresses, turbulent kinetic energy, turbulent heat fluxes and temperature variance. Heat transfer is studied via the average Nusselt number value, its time series and its relationship to the Rayleigh number value.
Ključne besede: numerical modelling, boundary element method, discrete wavelet transform, large eddy simulation, velocity-vertocity formulation, natural convection
Objavljeno: 31.05.2012; Ogledov: 1401; Prenosov: 21
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2.
Advanced modelling and simulation methods for communication networks
Jože Mohorko, Matjaž Fras, Saša Klampfer, 2008, izvirni znanstveni članek

Opis: This paper contains a brief overview of suitable simulation tools available for education and research on network technologies and protocols. Among the mentioned tools we present advanced methods for network simulations using the OPNET modeler simulation tool. This is one of the most widespread simulation tools for network simulations, appropriate for both for teaching and also for the researching procedures of new internet devices and protocols. The basic package is intended for simulating communication networks and for protocols and devices development. There are also additional specific modules, such as a module assigned to the simulation of wireless networks, an ACE module for application analyzing, 3DNV module for visualizing networks on virtual terrain and the "System in the loop" module for simulating networks with real communication equipment in the loop, in real-time.
Ključne besede: network simulation, simulation tools, modelling, communication networks, OPNET
Objavljeno: 31.05.2012; Ogledov: 956; Prenosov: 25
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Traffic modelling and performance evaluation in the Kotor cruise port
Davorin Kofjač, Maja Škurić, Branislav Dragović, Andrej Škraba, 2013, izvirni znanstveni članek

Opis: Simulation modelling of traffic in the Kotor cruise port is used for performance evaluation and optimization of the operational policy. During the summer, the traffic intensity of the cruise shipsŽ arrivals is higher than in other periods of the year. The increased traffic intensity causes congestion at anchorages, which can lead to significant dissatisfaction of the cruise ship operators and passengers. The simulation model, based on the port callingfrequency statistics and port tariff charges, is developed. First, the simulation model is validated against the real data. Second, several simulations are performed, where the scenarios of an extended main berth and of increased traffic intensity are evaluated in order to minimize congestion and to maximize revenue. Simulation results indicate significant queue reductions and a higher revenue, thus justifying the intention in the main berth extension.
Ključne besede: traffic modelling, port revenue, operational policy, simulation, model validation, Kotor cruise port
Objavljeno: 30.12.2015; Ogledov: 528; Prenosov: 20
URL Povezava na celotno besedilo

6.
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: 28.03.2017; Ogledov: 228; Prenosov: 42
.pdf Celotno besedilo (1,10 MB)
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7.
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: 28.03.2017; Ogledov: 276; Prenosov: 18
.pdf Celotno besedilo (809,50 KB)
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8.
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: 05.06.2017; Ogledov: 433; Prenosov: 38
.pdf Celotno besedilo (4,50 MB)
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9.
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: 28.11.2017; Ogledov: 126; Prenosov: 52
.pdf Celotno besedilo (339,98 KB)
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10.
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: 30.11.2017; Ogledov: 253; Prenosov: 107
.pdf Celotno besedilo (1,07 MB)
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