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Abstract: The paper examines the impact of integration of macroeconomic indicators on the accuracy of container throughput time series forecasting model. For this purpose, a Dynamic factor analysis and AutoRegressive Integrated Moving-Average model with eXogenous inputs (ARIMAX) are used. Both methodologies are integrated into a novel four-stage heuristic procedure. Firstly, dynamic factors are extracted from external macroeconomic indicators influencing the observed throughput. Secondly, the family of ARIMAX models of different orders is generated based on the derived factors. In the third stage, the diagnostic and goodness-of-fit testing is applied, which includes statistical criteria such as fit performance, information criteria, and parsimony. Finally, the best model is heuristically selected and tested on the real data of the Port of Koper. The results show that by applying macroeconomic indicators into the forecasting model, more accurate future throughput forecasts can be achieved. The model is also used to produce future forecasts for the next four years indicating a more oscillatory behaviour in (2018-2020). Hence, care must be taken concerning any bigger investment decisions initiated from the management side. It is believed that the proposed model might be a useful reinforcement of the existing forecasting module in the observed port.
Keywords: container throughput forecasting, ARIMAX model, dynamic factor analysis, exogenous macroeconomic indicators, time series analysis
Published in DKUM: 12.12.2017; Views: 2198; Downloads: 432
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Abstract: Eno izmed temeljnih poslanstev televizije je, da zabava. To poslanstvo je tako del vsakdanje televizije, ki vključuje množico žanrov in medijskih platform. Televizija svojo nalogo opravlja s pomočjo razvedrilnih oddaj, vedno pogosteje pa v programske sheme vključuje svetovno prepoznavne televizijske formate. Te lahko pri nas spremljamo tako na javni televiziji kot tudi na komercialnih televizijah. Programi javne televizije se od komercialnih razlikujejo predvsem po tem, da so javni zapriseženi standardom kakovosti: »Ravnotežje med kvalitetnimi in kvantitetnimi prednostmi je nova naloga javnega servisa« (Žilič Fišer, 2007: 51). S prihodom komercialnih televizij se je konkurenca javni televiziji povečevala, sposobnost zabavati pa je postala ključna pri pridobivanju oz. ohranjanju gledalcev. Magistrsko delo predstavlja vpogled v oddaje razvedrilnega programa, ki so bile v zadnjih desetih letih predvajane v soboto ali nedeljo ob osmih zvečer. Gre za za t. i. prime time oddaje, to so oddaje, ki so umeščene v najbolj gledani termin in tako podvržene največji pozornosti ljudi, ki iščejo razvedrilo. V magistrskem delu uredniki pojasnijo svoje odločitve o ustvarjanju avtorske oddaje po eni strani ter nakupa licenčnega formata po drugi ter morebitne vzporednice med enimi in drugimi, ki vplivajo na proces ustvarjanja razvedrilnega programa.
Keywords: javna televizija, razvedrilni program, televizijski formati, televizijski žanri, prime time oddaje
Published in DKUM: 06.10.2017; Views: 1339; Downloads: 188
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Abstract: This master's thesis describes the support for modelling Voice over Internet Protocol (VoIP) applications in the INET Framework. First, it briefly presents the VoIP technology and factors responsible for the VoIP quality of service. Next, the thesis moves on to discuss the OMNeT++ environment and the INET Framework, their installation and usage. Following this, it examines all of the INET packages and modules available for VoIP modelling, with all VoIP-related INET examples then shortly described and tested. By using INET, our own network and application models are created and simulated using different parameters. Comparisons of the simulation results are carried out and some of the best-found parameters for the VoIP communications are presented. At last, the calculation of jitter by using the obtained simulation results and Excel program is described, because jitter is not shown in the simulation results in INET.
Keywords: voice over internet protocol, performance analysis, simulation, real-time transport protocol, user datagram protocol
Published in DKUM: 18.08.2017; Views: 1559; Downloads: 141
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Abstract: Microsimulation models are frequently used in traffic analysis. Various optimization methods are used in calibration, and the one method that has shown success is neural networks. This paper shows the responses of neural networks during calibration of a microsimulation traffic model. We analyzed two calibration methods by applying neural networks and comparing their neural network learning (according to their achieved correlation and the mean error of prediction) and their generalization ability (comparison of generalization results was analyzed in two steps). The best correlation between the microsimulation results and neural network prediction was 88.3%, achieved for the traveling time prediction, on which the first calibration method is based.
Keywords: microsimulation traffic models, calibration, response of neural networks, traveling time, queue parameters
Published in DKUM: 02.08.2017; Views: 1331; Downloads: 390
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Abstract: Optimal project scheduling under nonconvex time-cost relations represents a challenging problem in construction management. The nonconvex time-cost relations may appear in a construction project when several different duration options are available for its activities due to alternative technological processes enabled for their realization or wide accessibility of production resources. The source of nonconvexity of the project scheduling optimization problem can also be the project penalty- or bonus-duration relations arranged within the construction contract. The aim of this paper is to present the mixed-integer nonlinear programming (MINLP) based optimal time scheduling of construction projects under nonconvex costs. For this purpose, the MINLP model was developed and applied. A numerical example from literature and an example of construction project time-cost trade-off analysis under practical nonconvex penalty function are given in the paper to demonstrate advantages of MINLP optimization. The example from literature first presented the capability of the MINLP approach to obtain the optimal solution for difficult, highly combinatorial nonconvex discrete project scheduling problem. Thereupon, the following example revealed that the optimal project time-cost curve may take very nonuniform shape on account of discrete nature of activity direct cost options and nonconvex relation between project duration and total cost. In this way, the presented study intends to provide practitioners with new information from the field of optimization techniques for project scheduling as well as an alternative view on performance of total cost when project duration is changed.
Keywords: extreme environments, construction management, discrete optimization, mixed-integer nonlinear programming, nonconvex costs, time scheduling
Published in DKUM: 12.07.2017; Views: 1577; Downloads: 414
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