1. STEMI patients in the first and second waves of the COVID-19 pandemic in northeast Slovenia - a retrospective, single-center observational studyAndreja Sinkovič, Manja Kraševec, David Šuran, Martin Marinšek, 2022, original scientific article Abstract: The COVID-19 pandemic has affected the outcomes of ST-elevation myocardial infarction (STEMI) patients in most countries. We aimed to retrospectively assess the admissions, treatments, complications, and mortality of STEMI patients in the northeast of Slovenia during the first (March–May 2020) and second waves (October–December 2020) of the COVID-19 pandemic and to compare them with data from 2019 (March–October). Comparing 2019 and both waves of the COVID-19 pandemic, we observed nonsignificant differences in the number of STEMI admissions, baseline characteristics, use of primary percutaneous coronary intervention (PCI) within the first 3 (40.5%* vs. 38.7% vs. 25%*, *p = 0.074) or 6 h, TIMI III flow after primary PCI, and hospital complications, as well as significant increases in hospital heart failure (23.3% vs. 42%, p = 0.015) and mitral regurgitation in the second wave (10% vs. 26.9%, p = 0.008) of the pandemic and a nonsignificant increase in hospital mortality (8.9% vs. 9.4% vs. 13.6%) during both waves of the pandemic. We conclude that, due to the increased severity of the COVID-19 pandemic in the second wave, there were longer delays to primary PCI in STEMI patients, resulting in significantly increased hospital heart failure and non-significantly increased hospital mortality.
Keywords: ST-elevation myocardial infarction, COVID-19, time delay, primary percutaneous coronary intervention, heart failure, mortality, pandemic
Published in DKUM: 04.07.2024; Views: 134; Downloads: 20
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2. Time delays shape the eco‑evolutionary dynamics of cooperationSourav Roy, Sayantan Nag Chowdhury, Srilena Kundu, Gourab Kumar Sar, Jeet Banerjee, Biswambhar Rakshit, Prakash Chandra Mali, Matjaž Perc, Dibakar Ghosh, 2023, original scientific article Abstract: We study the intricate interplay between ecological and evolutionary processes through the lens of the prisoner’s dilemma game. But while previous studies on cooperation amongst selfsh individuals often assume instantaneous interactions, we take into consideration delays to investigate how these might afect the causes underlying prosocial behavior. Through analytical calculations and numerical simulations, we demonstrate that delays can lead to oscillations, and by incorporating also the ecological variable of altruistic free space and the evolutionary strategy of punishment, we explore how these factors impact population and community dynamics. Depending on the parameter values and the initial fraction of each strategy, the studied eco-evolutionary model can mimic a cyclic dominance system and even exhibit chaotic behavior, thereby highlighting the importance of complex dynamics for the efective management and conservation of ecological communities. Our research thus contributes to the broader understanding of group decision-making and the emergence of moral behavior in multidimensional social systems.
Keywords: cooperation, time delay, evolutionary dynamics, social dilemma, social physics
Published in DKUM: 04.04.2024; Views: 191; Downloads: 16
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4. Modeling the large scale disruptions of an airline networkMilan Janić, 2005, original scientific article Abstract: When the large-scale disruptions of airline networks occur, they can cause significant deterioration of the planned schedule. Such deterioration shows upin the form of long delays, rerouting and/or cancellation of flights. This paper presents a model for assessment of the economic consequences of large-scale disruptions of an airline single hub-and-spoke network. These consequences are expressed by the cost of delayed and cancelled complexes of flights. The model is based on the theory of queuing systems with the airline hub airport as a server and the complexes of flights as customers. The difference between the service time of the affected and planned complexes determine their delays caused by a given disruptive event. The cost of delays and revenues of the affected flights, and global airline mitigating strategies are used to determine the total airline cost of delayed and cancelled complexes. The model is applied to the disrupted hub-and-spoke network of a large European airline. The purpose is to illustrate the model's planning nature, complexity of the problem, influence of the relevant factors,and the magnitude of the economic consequences.
Keywords: air transportation, airlines, networks, delay time
Published in DKUM: 05.06.2012; Views: 1950; Downloads: 101
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5. Using neural networks in the process of calibrating the microsimulation models in the analysis and design of roundabouts in urban areasIrena Ištoka Otković, 2011, dissertation Abstract: The thesis researches the application of neural networks in computer program calibration of traffic micro-simulation models. The calibration process is designed on the basis of the VISSIM micro-simulation model of local urban roundabouts.
From the five analyzed methods of computer program calibration, Methods I, II and V were selected for a more detailed research. The three chosen calibration methods varied the number of outgoing traffic indicators predicted by neural networks and a number of neural networks in the computer program calibration procedure. Within the calibration program, the task of neural networks was to predict the output of VISSIM simulations for selected functional traffic parameters - traveling time between the measurement points and queue parameters (maximum queue and number of stopping at the roundabout entrance). The Databases for neural network training consisted of 1379 combinations of input parameters whereas the number of output indicators of VISSIM simulations was varied. The neural networks (176 of them) were trained and compared for the calibration process according to training and generalization criteria. The best neural network for each calibration method was chosen by using the two-phase validation of neural networks.
The Method I is the calibration method based on calibration of a traffic indicator -traveling time and it enables validation related to the second observed indicator – queue parameters. Methods II and V connect the previously described calibration and validation procedures in one calibration process which calibrates input parameters according to two traffic indicators.
Validation of the analyzed calibration methods was performed on three new sets of measured data - two sets at the same roundabout and one set on another location. The best results in validation of computer program calibration were achieved by the Method I which is the recommended method for computer program calibration.
The modeling results of selected traffic parameters obtained by calibrated VISSIM traffic model were compared with: values obtained by measurements in the field, the existing analysis methods of operational roundabouts characteristics (Lausanne method, Kimber-Hollis, HCM) and modeling by the uncalibrated VISSIM model. The calibrated model shows good correspondence with measured values in real traffic conditions. The efficiency of the calibration process was confirmed by comparing the measured and modeled values of delays, of an independent traffic indicator that was not used in the process of calibration and validation of traffic micro-simulation models.
There is also an example of using the calibrated model in the impact analysis of pedestrian flows on conflicting input and output flows of vehicles in the roundabout. Different traffic scenarios were analyzed in the real and anticipated traffic conditions.
Keywords: traffic models, traffic micro-simulation, calibration of the VISSIM model, computer program calibration method, neural networks in the calibration process, micro-simulation of roundabouts, traffic modeling parameters, driving time, queue parameters, delay
Published in DKUM: 02.06.2011; Views: 5471; Downloads: 385
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