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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, doktorska disertacija

Opis: 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.
Ključne besede: 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
Objavljeno: 02.06.2011; Ogledov: 3610; Prenosov: 252
.pdf Celotno besedilo (13,21 MB)

2.
The use of micro-simulation in determining the capacity of a roundabout with a multi-channel pedestrian flow
Tomaž Tollazzi, Tone Lerher, Matjaž Šraml, 2008, izvirni znanstveni članek

Opis: The main purpose of this paper is to analyse the influence of the multi-channel pedestrian flow on the capacity of the one-lane roundabout, using discrete simulation methods. The proposed model is based on the theory of the expected time void 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. While the previous model of the pedestrian crossing is handled as the single-channel system in which the pedestrians arrive randomly from one side of the pedestrian crossing only, the proposed model deals with the multi-channel system in which the pedestrians arrive randomly from both sides of the pedestrian crossing. In thi sway the mathematical model can better illustrate the real conditions. The previous model considers only the disturbances of entry traffic flow of motorised vehicles caused by the pedestrian flow crossing the roundabout arm. The proposed model considers the disturbances caused by the circular traffic flow of motorised vehicles as well. A simulation analysis has been conducted on the roundabout at Koroška Street in Maribor, in which the counting of the motorised traffic flow and the pedestrian flow has been performed in the morning peek hour. The results of the analysis have indicated a high reserve of the capacity for pedestrians who arrive from the left and right sides of the roundabout with regard to motorised vehicles in the analysed arm of the roundabout. The real reserve of the capacity would otherwise be smaller in case of enlargement of the motorised vehicle flow in the future. Nevertheless it would be high enough for an undisturbed traffic flow of motorised vehicles through the roundabout to be possible. The presented methodology 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: roundabout, pedestrian flow, traffic flow modeling, simulation models
Objavljeno: 31.05.2012; Ogledov: 1285; Prenosov: 27
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3.
Modeling distributed real-time applications with specification PEARL
Roman Gumzej, Shourong Lu, 2007, izvirni znanstveni članek

Opis: The methodology of hardware/software co-design of embedded control systems with Specification PEARL is presented. Hardware and software are modeled with the language Specification PEARL, which has its origins in standard Multiprocessor PEARL. Its usefulness is enhanced for modeling hierarchical and asymmetrical multiprocessor systems, and by additional parameters for schedulability analysis. Graphical symbols are introduced for its constructs to enable graphical modeling while maintaining the semantical background. It is meant to be a superlayer for programs, based on the PEARL programming model. To model program tasks, Timed State Transition Diagrams have been defined. The model of a co-designed system is verified for feasibility with co-simulation. The resulting information should be used when considering changes in a current design with the goal of producing a temporally feasible model. To support dynamic re-configurations, configuration management is introduced into the models. Since UML is becoming a de facto standard also for designing embedded control systems, and since Timed State Transition Diagrams and State Chart Diagrams share great similarity, an interface of the methodology to UML 2 is defined, using UML's extension mechanisms.
Ključne besede: specification language, application modeling, co-design, co-simulation, configuration management, PEARL, UML
Objavljeno: 01.06.2012; Ogledov: 950; Prenosov: 54
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4.
A Multi-criteria decision analysis framework tool for the selection of farm business models on organic mountain farms
Karmen Pažek, Črtomir Rozman, Franc Bavec, Andreja Borec, Martina Bavec, 2010, izvirni znanstveni članek

Opis: Mountain regions are important producers of organic food. For them, reliable decision making regarding business planning necessitates different critical support methods. KARSIM 1.0 (DSM) is a methodology based on an integrated deterministic simulation system application for decision-making support, consisting of 74 deterministic production simulation models. DSM enables different types of cost and financial feasibility calculations for organic production and food processing. KARSIM 1.0 was used to simulate three specific business alternatives for mountain organic farms. (Alternative 1: spelt grain, fruit cider, wine and brandy, plum brandy, calves meat and sheep-soft cheese production, Alternative 2: spelt flour, pear and apple juice, plum brandy, veal and sheep's milk, Alternative 3: spelt grain, dried fruit, calves, soft and hard sheep cheese). Simulation model results were compared using two multi-objective analysis methods: the analytical hierarchical process (Expert Choice Decision Support System software) and DEX-i method. the results showed the bigest multi-objective decision evaluation for alternative 2 (Expert Choice = 0.361 and DEX-i evaluation = excellent). We can conclude that the combination of a deterministic cost simulation model and multi-criteria decision analysis present an acceptable decision support tool for mountain organic farms; however, further research is desirable.
Ključne besede: simulation modeling, KARSIM 1.0, MCDA, DEXži, analytical hierarchical process, mountain organic farms
Objavljeno: 05.06.2012; Ogledov: 1378; Prenosov: 70
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5.
The Decision support system for supplementary activies on organic farms
Karmen Pažek, Črtomir Rozman, 2007, izvirni znanstveni članek

Opis: In this paper we present the decision support system for ranking food processing projects on organic farms. The system is based on simulation modeling and multi criteria decision analysis. The deterministic simulation system KARSIM EKO 1.0 (DSM) consists out of deterministic production simulation models that enable different types of costs calculations for organic production and on farm food processing in the framework of supplementary activities. Simulation models results were further evaluated using a qualitative multi-attribute modeling methodology, supported by the software tool DEX-i and quantitative analytical hierarchical process - AHP, supported by Expert Choice 2000 TM software. The analysis showed that by using current model input parameter the combination of apple cider, apple vinegar and plum brandy (business alternative 1) results with the best multicriteria evaluation (EC=0,413 and DEX-i evaluation = very good).
Ključne besede: simulation modeling, KARSIM EKO 1.0, expert choice (AHP), DEX-i, organic farming, suplementary activities
Objavljeno: 10.07.2015; Ogledov: 523; Prenosov: 21
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6.
A system dynamics model for improving primary education enrollment in a developing country
Chandra Sekhar Pedamallu, Linet Ozdamar, LS Ganesh, Gerhard-Wilhelm Weber, Erik Kropat, 2010, izvirni znanstveni članek

Opis: The system dynamics approach is a holistic way of solving problems in real-time scenarios. This is a powerful methodology and computer simulation modeling technique for framing, analyzing, and discussing complex issues and problems. System dynamics modeling is often the background of a systemic thinking approach and has become a management and organizational development paradigm. This paper proposes a system dynamics approach for studying the importance of infrastructure facilities on the quality of primary education system in a developing nation. The model is built using the Cross Impact Analysis (CIA) method of relating entities and attributes relevant to the primary education system in any given community. The CIA model enables us to predict the effects of infrastructural facilities on the community's access of primary education. This may support policy makers to take more effective actions in campaigns that attempt to improve literacy.
Ključne besede: developing countries, system modeling, cross impact analysis, simulation, system dynamics, primary education
Objavljeno: 28.11.2017; Ogledov: 255; Prenosov: 123
.pdf Celotno besedilo (1,03 MB)
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7.
Editorial
Mirjana Kljajić Borštnar, Davorin Kofjač, Andrej Škraba, Gerhard-Wilhelm Weber, Andreja Pucihar, 2017, predgovor, spremna beseda

Ključne besede: simulation, modeling, system dynamics, decision making
Objavljeno: 29.11.2017; Ogledov: 259; Prenosov: 38
.pdf Celotno besedilo (187,28 KB)
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8.
New trends in rock mass characterisation for designing geotechnical structures
Drago Ocepek, 2005, izvirni znanstveni članek

Opis: The investigation on designing supporting measures for geotechnical structures consists of the proper selection of the input data for the stress – strain analysis of the excavation process and the selection of retaining measures. In the preliminary phase of investigation the area must be geologically mapped in detail, and discontinuities precisely measured, boreholes and their “in situ” tests listed and samples for laboratory examinations taken. The new method allows rock mass classification for different rock quality, from soft rocks to mixed rock masses, as well as determination of the geological strength index GSI. The limits for using the suggested method are persistent discontinuities in rock mass which lead to translation or rotation failure mechanisms, either in a single plane or as a wedge. In all cases where discontinuities play a significant role, the rock mass structure must be considered and kinematical analyses performed. In other circumstances, a rock may be uniform and reasonably isotropic due to the geometry of discontinuities and their mutual intersections. The value range of GSI is first determined in the beginning of investigation and later in the excavation phase by considering the disturbance factor D, which expresses disturbances caused by excavation methods and rock mass relaxation. The strength and deformability parameters of rocks of different quality are determined by the generalized Hoek-Brown failure criterion and applied to shallow and deep tunnels or slopes. Before the start of excavations work and after establishing the retaining measures, the analysis results are checked by monitoring. New methods include the determination of post peak strength parameters of rock mass after relaxation, and routine measurements. The newest measurement system however allows direct readings of displacements of the rock mass in both the elastic and post-peak states. With back analyses we determine the softening behavior of the rock mass and a possible need for increasing retaining measures. Such a design method enables the optimization of retaining measures and the reduction of investment costs.
Ključne besede: geological strength index – GSI, simulation of a triaxial large scale »in situ« test, numerical modeling, retaining measures, rock reinforcement, monitoring, back analyses, strain softening, rock mass relaxation
Objavljeno: 16.05.2018; Ogledov: 261; Prenosov: 15
.pdf Celotno besedilo (1,05 MB)
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