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[Η προσέγγιση της αναπτυξιακής ψυχοπαθολογίας στην χρήση & κατάχρηση του διαδικτύου από εφήβους]
No full textΣτην παρούσα μελέτη προσεγγίζεται από την οπτική της αναπτυξιακής ψυχοπαθολογίας, η χρήση και η κατάχρηση διαδικτύου από εφήβους. Επιχειρήθηκε να γίνει καταγραφή των μεγεθών της κατάχρησης, προσδιορισμός ενός κατάλληλου κατωφλιού για το Ερωτηματολόγιο της Εξάρτησης από το Διαδίκτυο και να διερευνηθούν παράγοντές της, σε επίπεδο ατομικό, περιβαλλοντικό και διαδικτυακά περιβαλλοντικό. Έπειτα, εξετάστηκε η συσχέτιση της με την επίτευξη αναπτυξιακών στόχων. Τέλος, επιχειρήθηκε να συντεθούν τα επιμέρους ευρήματα σε ένα συνολικότερο μοντέλο κατανόησης
Integration of RES in AC grids
Get PDFThe power quality problems are generated by the deviation from the standard values of the amplitude and frequency of the supplied voltages and currents. The causes of these variations are different and can be generated by the utility or by the end users. In the present paper we deal with the generation current and voltage harmonics by the nonlinear loads and their cancellation techniques.
There are several methods for harmonic cancellation, the last and most efficient one being by direct injection of currents and/or voltages by the means of power electronic converters operating as current or voltage sources. A number of advanced solutions are presented in the present paper capable to minimize the overall harmonic distortion level. A special attention was given to weak systems harmonic cancellation for which the harmonic power flow direction has to be taken into account, as well as the use of multifrequency references and the prediction techniques for nonsinusoidal load currents
Stochastic prediction of hourly global solar radiation profiles
Get PDFA stochastic prediction model of the hourly profile of the I(h;nj) for any day nj at a site is outlined. It requires 1,2,or 3 measurements of the global solar radiation in a day nj, uses a D.B. and gives I(h;nj) for the rest hours. The model is validated against solar measurements. Conclusions are deducted for the predictive power of the model developed in MATLAB. It provides I(h;nj) profile predictions very close to the measured values and offers itself as a promising tool for a predictive on-line daily load management
