• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 12
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 30
  • 30
  • 11
  • 10
  • 7
  • 7
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

A One-line Numerical Model For Shoreline Evolution Under The Interaction Of Wind Waves And Offshore Breakwaters

Artagan, Salih Serkan 01 July 2006 (has links) (PDF)
A numerical model based on one-line theory is developed to evaluate the wind wave driven longshore sediment transport rate and shoreline change. Model performs wave transformation from deep water through the surf zone and computes the breaking parameters. The formula of longshore sediment transport rate used in the numerical model is selected as a result of comparative studies with the similar expressions and the field measurements. Offshore breakwater module of the numerical model is developed to compute the change of shoreline behind single or multiple offshore breakwaters. The validity of the numerical model was confirmed by comparing model results with the shoreline change given within the sheltered zone behind the offshore breakwaters. A series of offshore breakwaters are hypothetically proposed for a case study where a series of groins were constructed whose numerical model results qualitatively matched well with the field measurements. The results of the influences of offshore breakwaters on the shoreline predicted by the model are discussed comparatively with the case study.
12

Numerical Modeling Of Wind Wave Induced Longshore Sediment Transport

Safak, Ilgar 01 July 2006 (has links) (PDF)
In this study, a numerical model is developed to determine shoreline changes due to wind wave induced longshore sediment transport, by solving sediment continuity equation and taking one line theory as a base, in existence of seawalls, groins, T-groins, offshore breakwaters and beach nourishment projects, whose dimensions and locations may be given arbitrarily. The model computes the transformation of deep water wave characteristics up to the surf zone and eventually gives the result of shoreline changes with user-friendly visual outputs. A method of representative wave input as annual average wave characteristics is presented. Compatibility of the currently developed tool is tested by a case study and it is shown that the results, obtained from the model, are in good agreement qualitatively with field measurements. In the scope of this study, input manner of long term annual wave data into model in miscellaneous ways is also discussed.
13

Assessing Saudi Arabia's Vision 2030: Economic Diversification, Social Inclusion, and Environmental Preservation through the Triple Bottom Line Lens

Salman, Zara January 2024 (has links)
This essay critically analyzes the implementation of Saudi Arabia's Vision 2030 initiative through a detailed descriptive case study as the methodological framework, employing the Triple Bottom Line (TBL) model as the theoretical basis. The essay delves into the alignment of Vision 2030 with TBL principles, particularly in its influence on economic diversification, social inclusivity, and environmental conservation.  The study incorporated the three dimensions, concluding that Vision 2030 has successfully taken substantial steps in steering the Saudi economy away from its conventional reliance on oil. Socially, Vision 2030 places a significant emphasis on enhancing the quality of life for all Saudi citizens by investing in education, healthcare, and social welfare programs. On the environmental front, Vision 2030 demonstrates a steadfast commitment to sustainability through initiatives that promote renewable energy and environmentally friendly practices. The TBL framework serves as a valuable perspective for assessing the intricate impact of Vision 2030. Through an evaluation of the initiative's advancements in economic diversification, social inclusivity, and environmental preservation, it becomes evident that Vision 2030 is facilitating a more balanced and sustainable developmental trajectory for Saudi Arabia. / <p>My deepest gratitude extends to the individuals who have played a pivotal role in the success of this essay, particularly my unwavering family and cherished friends. Their unwavering support, encouragement, and constructive feedback have been instrumental in shaping my thoughts and refining the essay's content. I am particularly indebted to my esteemed advisor, Abdulelah Al Mutairi, whose guidance, expertise, and unwavering belief in my potential have been invaluable. His insightful suggestions and meticulous attention to detail have elevated the essay to a level I could not have achieved on my own. I am truly grateful for the collective support and encouragement that has made this endeavor possible.</p>
14

Contribution à l'étude du rayonnement des conducteurs filaires / Contribution to the study of the radiation from thin-wire structures

Chaaban, Mohamed 31 May 2011 (has links)
Le travail de recherche proposé dans ce manuscrit consiste à modéliser le rayonnement électromagnétique de conducteurs filaires. En effet l’estimation du rayonnement est un enjeu majeur et l’utilisation de modèles exacts nous semble nécessaire. On propose donc dans ce mémoire une approche analytique qui permet de quantifier les niveaux de champs électromagnétiques rayonnés par les systèmes filaires. Dans un premier temps nous proposons un modèle analytique du calcul du champ électromagnétique rayonné par un système filaire basé sur un développement approfondi des équations de Maxwell. Ce formalisme est issu de la formulation intégrale du potentiel vecteur émis par une antenne filaire dont on supposera connu la distribution de courant. Le modèle analytique ainsi obtenu permet d’estimer aisément les champs sans avoir besoin de discrétiser ni le support de transmission ni l’espace d’observation. Pour enrichir notre modèle nous avons ensuite envisagé les cas où la distribution du courant le long des conducteurs était issu, soit de la théorie des lignes soit d’une simulation numérique basée sur la théorie des antennes, soit de mesures. Dans le cas où c’est la théorie des lignes qui est à la base de la détermination des courants distribués, nous proposons un formalisme analytique du champ électromagnétique rayonné basé uniquement sur la seule connaissance des courants et de leurs dérivées aux extrémités des conducteurs. Nous avons également montré que ce formalisme s’extrapole aisément au cas d’un réseau multifilaire. Dans le cas où la théorie des antennes ou des mesures sont à la base de la connaissance des courants distribués, on identifie ce courant par quelques pôles et résidus grâce à la méthode d’identification Matrix Pencil (MP). Le champ électromagnétique rayonné s’exprime alors par une série finie de termes intégrales. Ce formalisme reste analytique et présente l’avantage d’être adapté aux approches paramétriques et d’optimisations. Nos travaux de recherche ouvrent des perspectives de reconstruction de la distribution du courant par Matrix Pencil à partir de la connaissance du courant et de ses premières dérivées spatiales aux seules extrémités des conducteurs. Le champ électromagnétique rayonné sera alors déduit de notre modèle. / The research presented in this thesis is focused on the modelling of electromagnetic radiation from thin-wire configuration. The radiation assessment is one of the most important issues which strongly requires an accurate modelling. In this work, an analytic approach to evaluate electromagnetic field radiated from thin-wire structure sis proposed. In the first part, we propose an analytical model for calculation of the electromagnetic fields from wire structure derived from the Maxwell equations. This formalism arises from the integral formulation of the magnetic vector potential due to a known current distribution along a wire antenna. The analytical model enables one to readily calculate the fields without requirement of wire structure discretization or involving the propagation effect over the domain of interest. In order to improve the model, we subsequently analyze cases where the current distribution along the conductors is known, either obtained by using the transmission line theory, by numerical simulations based on the antenna theory, or by measurements. On the basis of the known current and its derivative at the ends of a two-wire configuration, obtained by using the transmission line theory, the proposed approach yields an analytical formalism for determination of the radiated electromagnetic field. This analytical formalism is readily extended to multiple wires structures, as well. Once the current distribution is determined by using the antenna theory, the proposed method extracts the corresponding poles and residues by using the Matrix Pencil Method (MPM). In this case, the radiated electromagnetic field is formulated just by few integral terms. The main advantage of the analytical formulation within the framework of the proposal approach is that the method is very suitable for parametric and optimisation studies. This research should be considered as an opener to the subject related to reconstruction of the current distribution by using the Matrix Pencil method (MPM) only based on the current and its first derivative at the wire structure ends. Consequently the radiated electromagnetic field may be subsequently readily calculated by using theproposed analytical model.
15

Numerical Modeling Of Wave Diffraction In One-dimensional Shoreline Change Model

Baykal, Cuneyt 01 January 2007 (has links) (PDF)
In this study, available coastal models are briefly discussed and under wind waves and a numerical shoreline change model for longshore sediment transport based on &ldquo / one-line&rdquo / theory is developed. In numerical model, wave diffraction phenomenon in one-dimensional modeling is extensively discussed and to represent the irregular wave diffraction in the sheltered zones of coastal structures a simpler approach based on the methodology introduced by Kamphuis (2000) is proposed. Furthermore, the numerical model results are compared with analytical solutions of accretion and erosion at a single groin. An application to a case study of a groin field constructed to the east side of Kizilirmak river mouth, at Bafra alluvial plain, is carried out by the numerical model. The results of comparisons show that the numerical model is in good agreement with the analytical solutions of shoreline changes at a groin. Similarly, numerical model results are compared with field data of Bafra and it is shown that they are in good agreement qualitatively. Therefore, the numerical model is accepted to be capable of representing of shoreline evolution qualitatively even for complex coastal regions.
16

An Implicit One-line Numerical Model On Longshore Sediment Transport

Esen, Mustafa 01 July 2007 (has links) (PDF)
In this study, a numerical model &ldquo / Modified Coast-Structure Interaction Numerical Model&rdquo / (CSIM) is developed with an implicit approach to determine the shoreline changes due to wind wave induced longshore sediment transport under the presence of groins, T-groins and offshore breakwaters by making modifications on the explicit numerical model &ldquo / Coast-Structure Interaction Numerical Model&rdquo / (CSI). Using representative wave data transformed to a chosen reference depth from deep water, numerical model (CSIM) simulates the shoreline changes considering structure interference. Breaking and diffraction within the sheltered zones of coastal structures defined for offshore breakwaters by using vectorial summation of the diffraction coefficients and as for T-groins shore-perpendicular part forms a boundary to define the shoreline changes seperately at two sides of the structure. Numerical model, CSIM is tested with a case study by applying in Bafra Delta, Kizilirmak river mouth at Black sea coast of Turkey. Numerical model simulations show that model results are in good agreement qualitatively with field measurements.
17

Χρήση ινοπλεγμάτων ανόργανης μήτρας για την ενίσχυση πλακών οπλισμένου σκυροδέματος δύο διευθύνσεων

Μπαλιούκος, Χρήστος 27 October 2008 (has links)
Στόχος της παρούσας διατριβής είναι η διερεύνηση της αποτελεσματικότητας της ενίσχυσης στοιχείων τύπου πλάκας μέσω ενός νέου σύνθετου υλικού. Το νέο αυτό σύνθετο υλικό συντίθενται από ινοπλέγματα δύο διευθύνσεων σε ανόργανη μήτρα. Τα ινοπλέγματα αποτελούνται από ίνες άνθρακα ή ίνες υάλου, ενώ η ανόργανη μήτρα αποτελείται από κονίαμα. Ο όρος που έχει προταθεί από συγγραφείς για το νέο αυτό υλικό είναι Textile Reinforced Concrete, που στην Ελληνική γλώσσα θα μπορούσε να αποδοθεί ως Ινοπλέγματα Ανόργανης Μήτρας (ΙΑΜ). Για τον λόγο αυτό, παρασκευάσθηκαν δοκίμια τύπου πλάκας επί τεσσάρων περιμετρικών δοκών. Συνολικά κατασκευάσθηκαν τέσσερα δοκίμια τύπου πλάκας, εκ των οποίων τρία ενισχύθηκαν μέσω ΙΑΜ και ένα ήταν το δοκίμιο αναφοράς. Τα δύο δοκίμια ενισχύθηκαν με μία και δύο στρώσεις πλεγμάτων συνεχών ινών από άνθρακα, ενώ το τρίτο ενισχύθηκε μέσω εφαρμογής τριών στρώσεων πλεγμάτων συνεχών ινών υάλου. Τονίζεται πως τρεις στρώσεις πλέγματος συνεχών ινών υάλου έχουν ισοδύναμη δυστένεια με μία στρώση πλέγματος συνεχών ινών από άνθρακα. Στο πρώτο κεφάλαιο παρουσιάζονται οι ιδιότητες των ινών και της ανόργανης μήτρας, καθώς επίσης και η μηχανική συμπεριφορά του σύνθετου υλικού. Τέλος, γίνεται μια ανασκόπηση της έρευνας που έχει διεξαχθεί στο Εργαστήριο Μηχανικής και Τεχνολογίας των Υλικών, γύρω από το πεδίο των ενισχύσεων μέσω ΙΑΜ στοιχείων από οπλισμένο σκυρόδεμα. Στο δεύτερο κεφάλαιο συνοψίζονται οι ήδη υπάρχουσες τεχνικές επισκευής και ενίσχυσης πλακών. Επίσης, αναφέρονται παραδείγματα ενισχύσεων στοιχείων τύπου πλάκας από την διεθνή βιβλιογραφία. Στο τρίτο κεφάλαιο περιγράφονται οι εργασίες που πραγματοποιηθήκαν προκειμένου να κατασκευασθούν τα δοκίμια. Το κεφάλαιο αυτό χωρίζεται σε τέσσερις βασικές ενότητες. Στην πρώτη ενότητα παρουσιάζονται οι μηχανικές ιδιότητες των υλικών που χρησιμοποιήθηκαν για την παρασκευή και ενίσχυση των δοκιμίων, καθώς και οι διαδικασίες μέσω των οποίων αυτές διακριβώθηκαν. Στην δεύτερη και τρίτη ενότητα, αναφέρονται οι εργασίες που διενεργήθηκαν κατά την φάση της σκυροδέτησης και της ενίσχυσης αντίστοιχα των δοκιμίων, ενώ στην τέταρτη ενότητα αναλύεται η πειραματική διαδικασία που ακολουθήθηκε. Στο τέταρτο κεφάλαιο παρουσιάζονται τα αποτελέσματα που προέκυψαν από την διεξαγωγή των πειραμάτων. Το κεφάλαιο αυτό χωρίζεται σε τρεις ενότητες. Στην πρώτη ενότητα περιγράφεται η συμπεριφορά κάθε δοκιμίου ξεχωριστά. Στην δεύτερη ενότητα γίνεται σύγκριση των αποτελεσμάτων που εξήχθησαν για όλα τα δοκίμια, ενώ στην τρίτη και τελευταία ενότητα παρουσιάζονται εν συντομία τα βασικότερα συμπεράσματα, που προέκυψαν από την πειραματική διαδικασία. Στο πέμπτο κεφάλαιο, παρουσιάζονται οι βασικές σχέσεις μέσω των οποίων μπορεί να εκτιμηθεί το φορτίο αστοχίας πλακών δύο διευθύνσεων ενισχυμένων μέσω ΙΑΜ. Για τον λόγο αυτό δίνονται προσομοιώματα και σχέσεις, ενώ στην συνέχεια συγκρίνεται το φορτίο αστοχίας εκ των προτεινόμενων σχέσεων με το καταγραφόμενο φορτίο αστοχίας. Το έκτο και τελευταίο κεφάλαιο, παραθέτει συνοπτικά τα βασικότερα αποτελέσματα της παρούσας Διατριβής Διπλώματος Ειδίκευσης. Γενικά η νέα τεχνική ενίσχυσης, είναι ιδιαίτερα αποτελεσματική, αφού αυξάνεται σημαντικά το φορτίο αστοχίας των ενισχυμένων δοκιμίων συγκριτικά με το δοκίμιο αναφοράς. Παράλληλα η συμπεριφορά του πλέγματος είναι άριστη, αφού μέχρι και την στιγμή της αστοχίας δεν παρατηρείται αποκόλλησή του από την επιφάνεια του σκυροδέματος. Αξίζει να σημειωθεί πως η αστοχία των δοκιμίων συνέβη λόγω διάτρησης. Στο τέλος του κεφαλαίου αναφέρονται προτάσεις για μελλοντική έρευνα. / The aim of the present thesis is to investigate the efficiency of a new composite material for the strengthening of two way slabs. This new material is called “Textile Reinforced Concrete - (TRC)”. It comprises textiles, that is fabric meshes made of long woven, knitted or even unwoven fiber rovings in at least two orthogonal directions, impregnated with inorganic binders such as cement based mortars. For the purposes of this study, four specimens of two way slabs were produced. Three of them were strengthened with TRC, and the remaining specimen was kept as control. Two specimens were strengthened with one and two layers of textile respectively, whose yarns consisted of carbon fibers. The third one was strengthened with three layers of textile whose yarns consisted of glass fibers. It is worth mentioning that three layers of textiles with glass fibers, are equivalent in terms of stiffness and strength with one layer of textile with carbon fiber. The first chapter analyses the properties of fibers, yarns, textiles, and those of the inorganic matrix. The principles of the bond behavior are also presented. Moreover, the work done in the area of strengthening of concrete members at the faculty of Civil Engineering of the University of Patras is discussed. The second chapter summarizes the existing techniques of enhancement in strength of two way slabs. The purpose of the third chapter is to describe the course of action towards the construction of the specimens. The test procedure and measurements are also included in this chapter. The results as derived from the testing procedure are discussed in the fourth chapter of this dissertation. Comparisons of the results for each specimen are also drawn. In the fifth chapter, several experimentally and analytically based expressions have been used to evaluate the two-way capacity of slabs. The sixth chapter recapitulates the findings of the present research. It has been generally shown that the suggested technique appears to be effective. Noteworthy is the fact that all specimens experienced punching shear failure.
18

Some studies on metamaterial transmission lines and their applications

Hu, Xin January 2009 (has links)
This thesis focuses mostly on investigating different potential applications of meta-transmission line (TL), particularly composite right/left handed (CRLH) TL, and analyzing some new phenomena and applications of meta-TL, mostly left-handed (LH) TL. Realization principle will also be studied.   First, the fundamental electromagnetic properties of propagation in the presence of left-handed material (LHM) are illustrated. The transmission line approach for LHM design is described together with a brief review of the transmission line theory. As a generalized model for LHM TL, CRLH TL provides very unique phase response, such as dual-band operation, bandwidth enhancement, nonlinear dispersion, and the existence of critical frequency with zero phase velocity. Based on these properties, some novel applications of the existing CRLH transmission lines are then given, including a notch filter, a diplexer, a broadband phase shifter, a broadband balun, and a dual band rat-ring coupler. In the design of notch filters and diplexers, CRLH TL shunt stub is utilized to provide high frequency selectivity due to the existence of critical frequency with zero phase velocity. The proposed wideband Wilkinson balun, which comprises of one section of conventional transmission lines and one section of CRLH-TL, is shown to have a 180°±10° bandwidth of 2.12 GHz centered at 1.5 GHz. In the analysis of the dual band rat-ring couplers, a generalized formulation of the requirements about impedances and electrical length of the branches are derived, and as an example, a compact dual-band rat-race coupler is designed utilizing the balanced CRLH TL. Furthermore, a low pass filter is also proposed and designed based on a single (epsilon) negative coplanar waveguide (CPW).Various principles to realize meta-transmission lines are investigated. The main conclusions are listed below:Ÿ         Dual composite right/left handed (D-CRLH) transmission line, which is the dual structure of conventional CRLH TL, shows opposite handedness in the high frequencies and low frequencies with CRLH TL. Meanwhile, in the practical implementation, D-CRLH TL always shows a sharp stopband. A notch filter and a dual-band balun are designed based on D-CRLH TL. Ÿ         The lattice type transmission line (LT-TL) shows the same magnitude response with the conventional right-handed (RH) TL, but a constant phase difference in the phase response over a wide frequency band. A wideband rat-race coupler is proposed as an application of the LT-TL. Ÿ         Finger-shorted interdigital capacitors (FSIDCs) are analyzed and it is shown that FSIDC alone can act as a left-handed transmission line. The value of the reactive elements (inductors and capacitors) in the equivalent circuit model is determined by the dimensions of FSIDC. The relationship between them is analyzed.Later, transmission line loaded with negative-impedance-converted inductors and capacitors is illustrated as the first non-dispersive LH transmission line. The design of a negative series impedance converter is given in detail and a wideband power divider is designed as a potential application of the newly proposed meta-transmission lines in is also given. The final part of the thesis focuses on the study of microstrip lines loaded with complementary split ring resonators (SRRs). An equivalent circuit is made for this structure. The circuit model is verified by the experimental results of cases with different periodic lengths. Thereafter, a meander line split ring resonator (MLSRR) is presented. It shows dual band property and the miniature prototypes of complementary MLSRR loaded transmission lines are fabricated. By comparing the resonance frequencies of complementary MLSRR and multiple SRR, it is shown that the complementary MLSRR is very compact. C-MLSRR is applied in rejecting unnecessary frequencies in the ultra wideband antennas. / QC 20100720
19

Investigation of an aeroelastic model for a generic wing structure

Cilliers, M. E. 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Computational Aeroelasticity is a complex research field which combines structural and aerodynamic analyses to describe a vehicle in flight. This thesis investigates the feasibility of including such an analysis in the development of control systems for unmanned aerial vehicles within the Electronic Systems Laboratory at the Department of Electrical and Electronic Engineering at Stellenbosch University. This is done through the development of a structural analysis algorithm using the Finite Element Method, an aerodynamic algorithm for Prandtl’s Lifting Line Theory and experimental work. The experimental work was conducted at the Low-Speed Wind Tunnel at the Department of Mechanical and Mechatronic Engineering. The structural algorithm was applied to 20-noded hexahedral elements in a winglike structure. The wing was modelled as a cantilever beam, with a fixed and a free end. Natural frequencies and deflections were verified with the experimental model and commercial software. The aerodynamic algorithm was applied to a Clark-Y airfoil with a chord of 0:1m and a half-span of 0:5m. This profile was also used on the experimental model. Experimental data was captured using single axis accelerometers. All postprocessing of data is also discussed in this thesis. Results show good correlation between the structural algorithm and experimental data. / AFRIKAANSE OPSOMMING: Numeriese Aeroelastisiteit is ’n komplekse navorsingsveld waar ’n vlieënde voertuig deur ’n strukturele en ’n aerodinamiese analise beskryf word. Hierdie tesis ondersoek die toepaslikheid van hierdie tipe analise in die ontwerp van beheerstelsels vir onbemande voertuie binne die ESL groep van die Departement Elektriese en Elektroniese Ingenieurswese by Stellenbosch Universiteit. Die ondersoek bevat die ontwikkeling van ’n strukturele algoritme met die gebruik van die Eindige Element Methode, ’n aerodinamiese algoritme vir Prandtl se Heflynteorie en eksperimentele werk. Die eksperimentele werk is by die Department Meganiese en Megatroniese Ingensierswese toegepas in die Lae-Spoed Windtonnel. Die strukturele algoritme maak gebruik van ’n 20-nodus heksahedrale element om ’n vlerk-tipe struktuur op te bou. Die vlerk is vereenvouding na ’n kantelbalk met ’n vasgeklemde en ’n vrye ent. Natuurlike frekwensies en defleksies is met die eksperimentele werk en kommersiële sagteware geverifieer. Die aerodinamiese algoritme is op ’n Clark-Y profiel met 0:1m koord lengte en ’n halwe vlerk length van 0:5m geïmplementeer. Die profiel is ook in die eksperimentele model gebruik. Die eksperimentele data is met eendimensionele versnellingsmeters opgeneem. Al die verdere berekeninge wat op ekperimentele data gedoen is, word in die tesis beskryf. Resultate toon goeie korrelasie tussen die strukturele algoritme en die eksperimentele data.
20

A modified enhanced transmission line theory as a solution to wiring configurations inconsistent with the classical transmission line theory - Application to vehicle harnesses / Une théorie des lignes de transmission améliorée et modifiée comme solution à des configurations de câbles incompatibles avec la théorie des lignes de transmission classique - Application aux faisceaux de câbles automobiles

Chabane, Sofiane 10 June 2014 (has links)
Cette thèse présente, dans un premier temps, une nouvelle approche pour traiter les lignes de transmission, appelée la Théorie des Lignes de Transmission Améliorée et Modifiée (TLTAM). Cette extension du formalisme classique de la théorie des lignes de transmission est directement dérivée des équations de Maxwell et ne se limite pas à la seule prise en compte du mode transverse électromagnétique (TEM). Tout en conservant la simplicité du formalisme classique, cette extension aboutit à la définition de paramètres linéiques évolués et associés au mode antenne de la ligne de transmission. Cette solution présente l’avantage d’être compatible avec les noyaux de calcul existants, tout en palliant certaines limitations de la théorie des lignes de transmission (TLT) classique. LA TLTAM est tout d’abord définie pour le cas élémentaire d’une ligne de transmission à conducteur unique. Elle est ensuite généralisée au cas d’un nombre quelconque de conducteurs. Les matrices de paramètres linéiques correspondants sont alors définies. Les capacités de cette nouvelle théorie sont démontrées et validées au moyen de confrontations avec la solution directe des équations de Maxwell et de résultats de mesure. Dans un deuxième temps, le traitement d’une ligne de transmission multiconducteur située à distance d’un plan de référence conducteur est effectué au moyen d’une nouvelle approche désignée sous le nom de Théorie des Lignes de Transmission à Double Référence Intégrée (TLTDRI). Cette approche permet de simplifier l’évaluation des paramètres linéiques du faisceau en scindant le problème initial en deux sous-ensembles de lignes de transmission couplées. Le premier sous-ensemble est composé d'un fil conducteur du faisceau choisi arbitrairement et le plan de référence et constitue le sous-ensemble externe. Le deuxième sousensemble est composé uniquement des fils conducteurs du faisceau, en l’absence du plan de référence et constitue un sous-ensemble interne dont la référence locale est le fil choisi précédemment. On montre alors que seul le sous-ensemble externe nécessite le calcul de paramètres linéiques évolués associés à TLTAM. Le calcul des paramètres linéiques dans le système à référence unique constituée par le plan de référence, est reconstitué à partir de formules de passage permettant leur expression à partir des paramètres linéiques des deux sousensembles. Cette approche est validée et ses résultats sont en très bon accord avec ceux fournis par un calcul numérique direct des équations de Maxwell ainsi que ceux de la TLTAM. Elle permet une simplification très significative du traitement de l’interaction entre le faisceau de câble et la structure conductrice de référence. / This thesis presents, in a first step, a new approach to deal with transmission lines called the Modified Enhanced Transmission Line Theory (METLT). This extension of the classical formalism of the transmission line theory (TLT) is directly derived from Maxwell's equations without the restriction to the transverse electromagnetic (TEM) mode. This extension leads to the definition of enhanced per-unit-length (p.u.l.) parameters taking into account the antenna mode of the transmission line, while it keeps the simplicity of the classical formalism. This solution presents the advantage of being compatible with the existing TLT solvers while overcoming some limitations of the classical TLT. The METLT is firstly developed for the simple case of a single conductor transmission line. It is then generalized to the case of any number of conductors. The corresponding matrices of the p.u.l. parameters are then calculated. The capabilities of this new theory are demonstrated and validated by the means of comparisons with results obtained through a rigorous resolution of Maxwell's equations and measurements results. In a second step, a multi-conductor transmission line sufficiently far from the reference ground plane is assessed through a new approach called: Embedded Double Reference Transmission Line Theory (EDRTLT). This approach allows the simplification of the calculation of the harness p.u.l. parameters by splitting the first set of wires above a ground plane into two subsets of coupled transmission lines. The first subset consists in a conducting wire chosen arbitrarily and the reference ground plane and forms the external subset. The second subset consists only in the conducting wires of the harness, in the absence of the ground plane, and forms an internal subset which local reference is the wire chosen previously. We show that only the external subset requires the calculation of the enhanced p.u.l. parameters with the METLT. The calculation of the harness p.u.l. parameters in the system with a single reference, which is the ground plane only, is made through transformation formulae that allow their extraction from the p.u.l. parameters of the two subsets. This approach is validated and its results are in a very good agreement with those obtained by a rigorous resolution of Maxwell's equations and those of the METLT. It allows a great simplification to assess the interaction between the harness and the reference conducting structure.

Page generated in 0.0838 seconds