University of Piraeus

About: University of Piraeus is a education organization based out in Piraeus, Attiki, Greece. It is known for research contribution in the topics: Context (language use) & Computer science. The organization has 1731 authors who have published 6209 publications receiving 106699 citations.

UAV-to-Ground Communications: Channel Modeling and UAV Selection

Abstract: Unmanned aerial vehicle (UAV)-enabled communications have been proposed as a critical part of the beyond fifth-generation (5G) cellular networks. This type of communications is frequently characterized by line-of-sight (LoS) and dynamic propagation conditions. However, in various scenarios, the presence of large obstacles in the LoS path is unavoidable, resulting in shadowed fading environments. In this paper, a new channel model is proposed, in which the effects of mobility and shadowing are simultaneously considered. In particular, the performance of a UAV-based communication system operating in a shadowed double-scattering channel is analyzed. The new channel model is generic, since it models various fading/shadowing conditions, while it is in terms of easy-to-evaluate mathematical functions. Moreover, a low complexity UAV selection policy is proposed, which exploits shadowing-related information. The proposed scheme offers a reduction of the signal processing complexity, without any important degradation on the performance, as compared to alternatives approaches. In this context, a new analytical framework has been developed for investigating the performance of the new strategy. Finally, the main outcomes of this paper are also validated by empirical data, collected in an air-to-ground measurement campaign.

The economic viability of container mega-ships

Abstract: In this study, we analyze the container mega-ship viability by considering competitive circumstances. We adopt a non-zero sum two-person game with two specific strategies based on different service network configurations for different ship sizes: hub-and-spoke for mega-ship and multi-port calling for conventional ship size. A shipping characteristic for each route is approximately optimized to set up pay-off (or profit) matrixes for both players. Throughout model applications for Asia–Europe and Asia–North America trades, the mega-ship is competitive in all scenarios for Asia–Europe, while it is viable for Asia–North America only when the freight rate and feeder costs are low.

The Relationship Between Corruption and Income Inequality in U.S. states: Evidence From a Panel Cointegration and Error Correction Model

Abstract: We investigate the causality between corruption and income inequality within a multivariate framework using a panel data set of all 50 U.S. states over the period 1980 to 2004. The heterogeneous panel cointegration test by Pedroni (Oxf. Bull. Econ. Stat. 61:653–670, 1999; Econom. Theory 20:597–627, 2004) indicates that in the long run corruption and the unemployment rate have a positive and statistically significant impact on income inequality while a negative impact is found for real personal income per capita, education, and unionization rate. The Granger-causality results associated with a panel vector error correction model indicate both short-run and long-run bidirectional causality between corruption and income inequality.

Towards a holistic knowledge management model

Abstract: Knowledge management (KM) has been gradually established as a strong methodology to support business viability, competitiveness and growth; however, the lack of maturity is obvious, as evidenced by divergent points of view in critical sub‐domains of the related theory and practice, such as the spectrum of processes and the clusters of tactics scheduled to underpin them. The systems thinking logic, the discipline for seeing structures underlying complex phenomena, is perceived as a promising direction for consolidating the various approaches and developing a holistic KM paradigm. Through the integration of the fragmented landscape of knowledge management on a transparent and concrete framework based on cause‐effect relationships, not only the underlying theoretical assumptions are clarified and subjected to further analysis at a strategic level, but also practical issues concerning planning and decision making become less complicated, increasing effectiveness.