Πλοήγηση ανά Συγγραφέα "Sahalos, John N."
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Τεκμήριο Seasonal decomposition and forecasting of telecommunication data: A comparative case study(2006-06) Hilas, Constantinos S.; Goudos, Sotirios K.; Sahalos, John N.In this paper, forecasting models for the monthly outgoing telephone calls in a University Campus are presented. The data have been separated in the categories of international and national calls as well as calls to mobile phones. The total number of calls has also been analyzed. Three different methods, namely the Seasonal Decomposition, Exponential Smoothing Method and SARIMA Method, have been used. Forecasts with 95% confidence intervals were calculated for each method and compared with the actual data. The outcome of this work can be used to predict future demands for the telecommunications network of the University.Τεκμήριο User Profiling for Fraud Detection in Telecommunication Networks(2005) Hilas, Constantinos S.; Sahalos, John N.Telecommunications fraud is increasing dramatically each year resulting in loss of a large amount of euros worldwide. A statistical machine learning method is presented that constructs user profiles for the detection of fraudulent activities in telecommunications networks. The approach presented here can be used for the detection of superimposed or hacking fraud, works well for mid-term decisions and cannot be used for on-line account comparison.