University of the Aegean

About: University of the Aegean is a education organization based out in Mytilene, Greece. It is known for research contribution in the topics: Population & Tourism. The organization has 2818 authors who have published 8100 publications receiving 179275 citations. The organization is also known as: UAEG.

The evaluation of information technology projects: a fuzzy multicriteria decision-making approach

Abstract: This paper presents a fuzzy set-based approach to the evaluation of information technology (IT) projects. We assume a multi-criteria decision-making framework, where sets of general and domain-specific criteria are used to judge the relative performance of alternative technologies. The methodology was originally developed for DIAS.net, an EU project aiming at the development of the Information Society in insular and isolated regions of Europe. In this paper, we present many aspects of our evaluation framework, including the synthesis of evaluation teams, the assessment of the importance of criteria, the evaluation of the performance of the alternatives and the final ranking and selection of projects. The methodology presented has the innovative feature of embodying techniques of fuzzy sets theory into the classical multi-criteria decision analysis. This combination enables us to handle efficiently the subjectiveness that often characterizes expert judgements on a decision problem. Fuzzy linguistic terms, such as "poor," "fair," "very important," etc. are proposed for assessing the relative merit of alternatives and criteria. The paper concludes by exploring the potentiality of the above methodology in providing a flexible and robust IT evaluation framework.

Solutions of matrix NLS systems and their discretizations: a unified treatment

Abstract: Using a bidifferential graded algebra approach to 'integrable' partial differential or difference equations, a unified treatment of continuous, semi-discrete (Ablowitz?Ladik) and fully discrete matrix NLS systems is presented. These equations originate from a universal equation within this framework, by specifying a representation of the bidifferential graded algebra and imposing a reduction. By application of a general result, corresponding families of exact solutions are obtained that in particular comprise the matrix soliton solutions in the focusing NLS case. The solutions are parametrized in terms of constant matrix data subject to a Sylvester equation (which previously appeared as a rank condition in the integrable systems literature). These data exhibit a certain redundancy, which we diminish to a large extent. More precisely, we first consider more general AKNS-type systems from which two different matrix NLS systems emerge via reductions. In the continuous case, the familiar Hermitian conjugation reduction leads to a continuous matrix (including vector) NLS equation, but it is well known that this does not work as well in the discrete cases. On the other hand, there is a complex conjugation reduction, which apparently has not been studied previously. It leads to square matrix NLS systems, but works in all three cases (continuous, semi- and fully discrete). A large part of this work is devoted to an exploration of the corresponding solutions, in particular regularity and asymptotic behaviour of matrix soliton solutions.

Spatio-temporal variability in human and natural sounds in a rural landscape

Abstract: The study of landscape structure and functions, including the underlying ecological and anthropogenic processes has traditionally relied on visual aspects without considering information of non-visionary cues, e.g. auditory. In this work we applied a complementary approach for the study of landscapes using qualitative information for the sonic environment. In particular we studied the qualitative linkages between landscape structure and functions and daily sound patterns. The main objectives were the investigation of the spatial and temporal variability in sound perception, and the identification of the dominant sound categories (anthropogenic, biological, geophysical originated sounds) in relation to landscape characteristics. Our results showed significant spatio-temporal variability in the intensity of different sound categories, which reflects distinct soundscape patterns. Temporal sound variability reflected the daily cycle of anthropogenic activities and biological processes, whereas the spatial sound viability was mainly shaped by landscape attributes. The combination of the visual landscape information and its emergent acoustic profile enhances our perception and understanding of nature and this integrated approach may have many practical applications in landscape management, monitoring and planning.

The day of the week effect patterns on stock market return and volatility: Evidence for the Athens Stock Exchange

Abstract: This paper investigates the day of the week effect on return and volatility for major Athens Stock Exchange (ASE) indexes. Using a conditional variance framework, which extends previous work on the Greek stock market, we find that the day of the week effect in both the return and volatility equations is present for the emerging ASE over the period 1995-2000. However, this stock market anomaly seems to loose its strength and significance after the Greek entry to the Euro-Zone and the market upgrade to the developed ones (period 2001-2005). We suggest that this is a consequence of the competitive transformation and the institutional reforms introduced in the ASE.