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1.
Using neural networks in the process of calibrating the microsimulation models in the analysis and design of roundabouts in urban areas
Irena 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: 02.06.2011; Views: 3648; Downloads: 257
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2.
Investigation into the effect of different fuels on ignition delay of M-type diesel combustion process
Dževad Bibić, Ivan Filipovič, Aleš Hribernik, Boran Pikula, 2008, original scientific article

Abstract: An ignition delay is a very complex process which depends on a great number of parameters. In practice, definition of the ignition delay is based on the use of correlation expressions. However, the correlation expressions have very often limited application field. This paper presents a new correlation which has been developed during the research project on the direct injection M-type diesel engine using both the diesel and biodiesel fuel, as well as different values of a static injection timing. A dynamic start of injection, as well as the ignition delay, is defined in two ways. The first approach is based on measurement of a needle lift, while the second is based on measurement of a fuel pressure before the injector. The latter approach requires calculation of pressure signals delay through the fuel injection system and the variation of a static advance injection angle changing. The start of a combustion and the end of the ignition delay is defined on the basis of measurements of an in-cylinder pressure and its point of separation from a skip-fire pressure trace. The developed correlation gives better prediction of the ignition delay definition for the M-type direct injection diesel engine in the case of diesel and biodiesel fuel use when compared with the classic expression by the other authors available in the literature.
Keywords: ignition delay, diesel engine, M-type, biodiesel
Published: 31.05.2012; Views: 1015; Downloads: 198
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3.
Modeling the large scale disruptions of an airline network
Milan 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: 05.06.2012; Views: 879; Downloads: 64
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Impact of hybrid queing disciplines on the VoIP traffic delay
Saša Klampfer, Jože Mohorko, Žarko Čučej, 2009, original scientific article

Abstract: Impact of hybrid queuing disciplines on the VoIP traffic delay
Keywords: hibridne metode, načini uvrščanja, VoIP, zakasnitev, ožičeno omrežje, hybrid methods, queuing disciplines, VoIP, delay, wired network
Published: 10.07.2015; Views: 516; Downloads: 5
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8.
Quasipolynomial approach to simultaneous robust control of time-delay systems
Nikolaj Semenič, Andrej Sarjaš, Amor Chowdhury, Rajko Svečko, original scientific article

Abstract: A control law for retarded time-delay systems is considered, concerning infinite closed-loop spectrum assignment. An algebraic method for spectrum assignment is presented with a unique optimization algorithm for minimization of spectral abscissa and effective shaping of the chains of infinitely many closed-loop poles. Uncertainty of plant delays of a certain structure is considered in a sense of a robust simultaneous stabilization. Robust performance is achieved using mixed sensitivity design, which is incorporated into the addressed control law.
Keywords: time-delay systems, simultaneous robust control, algorithm
Published: 15.06.2017; Views: 273; Downloads: 200
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9.
Dimensioning of signalized intersections in realistic urban environment
Matej Dobovšek, Drago Sever, 2005, review article

Abstract: It is very complex to assure the dynamics of traffic networkin urban environment because of the intensity of traffic flowsand the limited space in the urban area. Signalized intersectionsare undoubtedly very important and frequent element inroad traffic network in urban regions, which greatly influencesthe traffic flow dynamics on each section as in the whole trafficnetwork. The time (delay) a vehicle needs to drive through anintersection directly influences the travel comfort, fuel consumption,traffic pollution and so on. There are many methodsfor dimensioning signalized intersections in the world literature.One of the most applied methods is the HIGHWAY CAPACI1YMANUAL (HCM) 2000 which is based on competentinput traffic flows and other characteristics of traffic signalregulations. The intention of this paper is to establish whetherwe can use the HCM 2000 method directly in the Slovenian realenvironment. Based on the established methodology of researchand limited number of delay measurement in real environmentintersections, there have been some deviations. Thecompletion of the level of service criterion for signalized intersectionshas been proposed, with the intention for more suitabilityestimation in the realistic environment.
Keywords: road traffic, intersections, signallization, control delay measurement, level of service
Published: 02.06.2017; Views: 354; Downloads: 39
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10.
Synchronous bursts on scale-free neuronal networks with attractive and repulsive coupling
Qingyun Wang, Guanrong Chen, Matjaž Perc, 2011, original scientific article

Abstract: This paper investigates the dependence of synchronization transitions of bursting oscillations on the information transmission delay over scale-free neuronal networks with attractive and repulsive coupling. It is shown that for both types of coupling, the delay always plays a subtle role in either promoting or impairing synchronization. In particular, depending on the inherent oscillation period of individual neurons, regions of irregular and regular propagating excitatory fronts appear intermittently as the delay increases. These delay-induced synchronization transitions are manifested as well-expressed minima in the measure for spatiotemporal synchrony. For attractive coupling, the minima appear at every integer multiple of the average oscillation period, while for the repulsive coupling, they appear at every odd multiple of the half of the average oscillation period. The obtained results are robust to the variations of the dynamics of individual neurons, the system size, and the neuronal firing type. Hence, they can be used to characterize attractively or repulsively coupled scale-free neuronal networks with delays.
Keywords: synchronization, neuronal networks, noise, stochastic processes, scale-free networks, information transmission delay
Published: 19.06.2017; Views: 360; Downloads: 186
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