ΚΑΘΟΡΙΣΜΟΣ ΤΗΣ ΔΙΑΝΟΜΗΣ ΤΩΝ ΠΕΔΙΑΚΩΝ ΜΕΓΕΘΩΝ ΣΕ ΣΥΣΤΗΜΑ ΑΓΩΓΙΜΩΝ ΠΛΑΚΩΝ ΑΠΟ ΔΙΕΓΕΡΣΗ ΓΕΝΙΚΕΥΜΕΝΗΣ ΜΟΡΦΗΣ ΜΕ ΕΦΑΡΜΟΓΗ ΤΟΥ ΑΛΓΟΡΙΘΜΟΥ FFT

THE PRESENT THESIS IS DIVIDED IN TWO PARTS. IN THE FIRST PART THE PROBLEM OF CALCULATING THE DISCRETE FOURIER TRANSFORM (DFT) OR THE INVERSE DISCRETE FOURIER TRANSFORM (IDFT) OF FUNCTIONS THAT ARE NOT DURATION LIMITED AND NOT BAND LIMITED IS CONSIDERED. FOR THIS CATEGORY OF FUNCTIONS TWO KINDS OF ERRORS ARE INTRODUCED, BY THE USE OF DFT OR IDFT. THESE ERRORS ARE THE TRUNCATION ERROR (TE)AND THE ALIASING ERROR (AE). THESE ERRORS ARE INFLUENCED BY THREE PARAMETERS WHICH ARE THE KIND AND THE WIDTH OF THE WINDOW FUNCTION AND THE NUMBER OF SAMPLES. SINCE THERE WAS NOT ANY AVAILABLE METHOD RELATING THE ABOVE PARAMETERS TO THE TE AND AE WE FACED A PROBLEM WHICH WE SHOULD OVERCOME. FOR THIS REASON WE HAVE DEVELOPED A METHOD (CHAPTER II) WHICH WE HAVE CALLED "THE BEST DC VALUEMETHOD". THIS METHOD FIRST ESTABLISHES A SUITABLE TRUNCATION INTERVAL SO THATTHE TE WILL BE WITHIN ACCEPTABLE LIMITS AND THEN MINIMIZES THE AE. WE HAVE ALSO OBSERVED THAT FOR THE DC (ZERO FREQUENCY) TERM AND FOR CONSTANT NUMBER OF SAMPLES THERE EXIST A TRUNCATION INTERVAL FOR WHICH TE AND AE CANCEL EACH OTHER. THIS IS A VERY INTERESTING RESULT AND CAN BE USED AS A BASIS FOR A SEPARATEMATHEMATICAL ANALYSIS. THE METHOD WE HAVE INTRODUCED CAN BE USED FOR THE CALCULATION OF GENERALIZED INTEGRALS AND FOR THE CALCULATION OF DFT AND IDFT OF GENERAL FUNCTIONS. IN THE SECOND PART OF THE THESIS, WHICH CONSISTS OF CHAPTER IV TO CHAPTER V WE HAVE APPLIED THE BEST DC VALUE METHOD FOR THE SOLUTION OF CERTAIN ELECTROMAGNETIC PROBLEMS. SO WE HAVE CALCULATED THE EDDY CURRENT DENSITYWITH AND WITHOUT THE DISPLACEMENT CURRENT FOR DIFFERENT KINDS OF EXCITATIONS FOR ONE CONDUCTING SLAB AND FOR A SYSTEM OF TWO CONDUCTING SLABS. WE HAVE ALSO CALCULATED THE MAGNETIC FLUX DENSITY FOR THE REGIONS OUTSIDE THE SLAB(S). THE EXCITATION WAS A CURRENT DISTRIBUTION OF THE GENERAL FORM: (TYPE). THE EXCITATION WAS PLACED ABOVE AND PARALLEL TO THE SLAB(S) AT A DISTANCE Y=B. WE HAVE EXAMINED THE CASES WHERE I(X,T) WAS A LINE CURRENT SHEET OF FINITE WIDTH AND OF CONSTANT DENSITY, AND A CURRENT SHEET OF FINITE WIDTH AND OF SINUSOIDAL VARIATION WITH RESPECT TO X. THE PENETRATION DEPTH AS WELL AS THE SHIELDING EFFECTWHICH IS INTRODUCED IN THE CASE OF TWO SLABS WAS EXAMINED WITH VERY INTERESTING RESULTS. IN THE VI CHAPTER AN ANALYTICAL APPROACH TO THE CALCULATION OF EDDY CURRENT DENSITY AND MAGNETIC FLUX DENSITY WITH THE EXCITATION BEING A SYSTEM OF TWO CONDUCTORS CARRYING DC CURRENT AND TRAVELLING WITH CONSTANT VELOCITY ABOVE THE CONDUCTING SLAB WAS INTRODUCED. WE MUST MENTION THAT THE RESULTS AGREE WITH THOSE OBTAINED WITH OTHER METHODS (WHERE RESULTS EXIST). OUR APPROACH IS VERY POWERFULL AND CAN BE USED FOR THE SOLUTION OF LINEAR PARTIAL DIFFERENTIAL EQUATIONS OF TWO DIMENSIONS. FOR THE CALCULATION OF THE DFT THE FAST FOURIER TRANSFORM ALGORITHM WAS USED.

Grantor dc:publisher

Aristotle University Of Thessaloniki (AUTH)

Year dc:date

1983

Authors dc:creator

• Panas, Stavros
• Πάνας, Σταύρος

• Δινορρεύματα
• Επεξεργασία σήματος
• Ηλεκτρομαγνητική θωράκιση
• Ηλεκτρομαγνητικό πεδίο
• Ταχύς μετασχηματισμός Fourier
• EDDY CURRENTS
• Electromagnetic fields
• FAST FOURIER TRANSFORM FFT
• HM SHIELDING
• Signal processing
• Επιστήμες Μηχανικού και Τεχνολογία
• Επιστήμη Ηλεκτρολόγου Μηχανικού, Ηλεκτρονικού Μηχανικού, Μηχανικού Η/Υ
• Engineering and Technology
• Electrical Engineering, Electronic Engineering, Information Engineering

Language dc:language

gre

Identifier

10.12681/eadd/0247

OAI identifier oai:identifier

oai:10442/0247