Tom 17 (2016): Zeszyt 3 (September 2016)

The orthogonal frequency division multiplexing (OFDM) aggregate signal energy characteristics are studied based on the OFDM signal simulation model. The information reliability of OFDM signal is explored for different sets of OFDM subcarrier numbers and varied multiposition keying types (MPK) on OFDM subcarriers. The conditions for optimal gain factor for OFDM signal are described analytically based on the simulation modeling results. The effect and value from using an optimal gain factor for OFDM signal is shown in this paper.

Synchronous motors and their modifications (ac converter-fed motor, etc.) enable to develop low-noise, reliable and economically efficient electric drive systems. The construction of up-to-date systems based on the synchronous machines is impossible without development of the computing software incorporating mathematical and computing simulation. In its turn, modelling of the synchronous machines as a rule is based on the equations by Park-Gorev, application of which requires adoption of a series of allowances. These allowances in a number of cases do not permit to obtain adequate results of the simulation coinciding with the results of field experiments of the systems under review. Moreover, while applying the system of equations by Park-Gorev to research the systems including interaction of synchronous machines with semiconducting converters of electric energy it is necessary simulate the process of formation their controlling signals in the sphere of frequency. If the states of converter’s keys are defined not only by controlling impulses but also by the state of currents in the synchronous machines flowing through them, such approach is not reasonable.

Recently in-vehicle route guidance and information systems are rapidly developing. Such systems are expected to reduce congestion in an urban traffic area. This social benefit is believed to be reached by imposing the route choices on the network users that lead to the system optimum traffic assignment. However, guidance service could be offered by different competitive business companies. Then route choices of different mutually independent groups of users may reject traffic assignment from the system optimum state. In this paper, a game theoretic approach is shown to be very efficient to formalize competitive traffic assignment problem with various groups of users in the form of non-cooperative network game with the Nash equilibrium search. The relationships between the Wardrop’s system optimum associated with the traffic assignment problem and the Nash equilibrium associated with the competitive traffic assignment problem are investigated. Moreover, some related aspects of the Nash equilibrium and the Wardrop’s user equilibrium assignments are also discussed.

The article deals with the optimizing the postal transportation network with two different optimizing methods. The research adopted in this article uses allocation models within graph theory to obtain results for addressed optimization problem. The article presents and compares two types of these models: p-median and uncapacitated fixed charge facility location model. The aim of p-median model is to find the location of P facilities in network, serving all demands in a way ensuring the average transport cost to be minimal. Fixed charge location model approach the issue of facility location based on minimizing the overall costs of implementation of selected variants. The latter this two models are subsequently applied on the postal network to determine the optimal location of postal facilities. These two models are adopted in the condition of large country with area above 300 000 km². The Italy was chosen as a typical country that fits this condition. The underlying infrastructure of Italy is represented by simplified model of a postal network, abstracted by a graph G = (V, E, c, w).

The results can serve as a basis for modification of the used models for the simulation of networks in the postal sector and as a key that compares the opportunities and results of application of these two models in the conditions large countries.

This paper introduces a multi-stakeholder multi-criteria evaluation framework, which can be used for the assessment of the last mile distribution performance of urban freight terminals. To this end, a comparative analysis is conducted addressing two Greek urban intermodal freight terminals located at the port of Thessaloniki (ThPA) and Kuehne+Nagel (K+N)’s premises. The assessment of the terminals’ performance relies on a tailored multi-criteria Key Performance Indicator (KPI)-based evaluation framework, whereas the selection and significance of the incorporated criteria and KPIs is predetermined by the relevant responsible stakeholders, who imposed their viewpoint through an analytic hierarchy process. Results showed that ThPA was ranked first according to its performance pertaining to the role of an intermodal interchange; still, K+N’s performance index was only 8.5% lower than ThPA’s, while in specific KPIs it seems that it performs in a better way.

This paper describes a systematic calibration process of a Vissim model, based on data derived from BT detectors. It also provides instructions how to calibrate and validate a highway network model based upon a case study and establishes an example for practitioners that are interested in designing highway networks with micro simulation tools. Within this case study, a 94,5 % proper calibration to all segments was achieved First, an overview of the systematic calibration approach that will be followed is presented. A description of the given datasets follows. Finally, model’s systematic calibration and validation based on BT data from segments under free flow conditions is thoroughly explained. The delivered calibrated Vissim model acts as a test bed, which in combination with other analysis tools can be used for potential future exploitation regarding transportation related purposes.