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  • 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.
61

Metodologia para desenvolvimento e aplicação de um emulador de redes elétricas inteligentes em ambiente controlado. / Methodology for developing and application of a Smart Grid emulator in a controlled environment.

Rosa, Luiz Henrique Leite 25 June 2018 (has links)
O presente trabalho visa propor uma metodologia para desenvolvimento e aplicação de um inovador emulador de redes elétricas inteligentes (REIs) para testes sistêmicos de funcionalidades de Smart Grids envolvendo dispositivos inteligentes (hardware) e sistemas de tecnologia da informação (software) em ambiente laboratorial. Além de dar uma dimensão da importância dos laboratórios de redes elétricas inteligentes para a pesquisa do tema, o levantamento bibliográfico apresentado neste trabalho permite concluir que as pesquisas envolvendo hardware-in-the-loop (HIL) tendem a concentrar suas análises nos equipamentos de hardware testados, como dispositivos de medição, equipamentos de potência (inversores de frequência e outros), dispositivos de controle e seus algoritmos e não em estudos que envolvam análises mais sistêmicas e interações dos dispositivos com sistemas de TI normalmente presentes nos Centros de Operação da Distribuição (COD), os quais cumprem papéis cada vez mais importantes nas funcionalidades de Redes Inteligentes. A metodologia proposta parte da premissa de que um ambiente para testes de funcionalidades de Smart Grids deve permitir análises sistêmicas, não apenas focadas nos dispositivos de controle de uma porção particular da rede ou sistemas de automação específicos, mas devem envolver a maior porção de rede possível e necessária para a correta representação das redes elétricas inteligentes. Neste sentido, a metodologia define e caracteriza os principais módulos e etapas de desenvolvimento de um emulador de redes elétricas inteligentes, ao mesmo tempo em que propõe soluções para os desafios de integração destes módulos, aplicando conceitos de hardware-in-the-loop, software-in-the-loop (SIL), e simulação com sincronização orientada a evento, além de propor soluções com simulação de sistemas de potência em regime permanente e hardware de baixo custo que permitiram o desenvolvimento do emulador de redes em laboratório de Smart Grid. As principais características do emulador de REIs desenvolvido e implementado no laboratório de Smart Grid, conforme a metodologia proposta, também são descritas neste trabalho. Por fim, são apresentados os casos teste, mais especificamente provas de conceito, envolvendo redes de teste IEEE/PES e redes reais das concessionárias do grupo EDP, financiador do projeto de implantação do laboratório no âmbito do Programa de P&D ANEEL, os quais serviram de base para a avaliação do desempenho do emulador e discussões finais sobre as contribuições da metodologia de desenvolvimento proposta neste trabalho. / This work aims to proposing a methodology for the development and application of an innovative Smart Grid emulator for systemic testing of Smart Grids functionalities involving intelligent devices and information technology systems in a laboratory environment. Besides demonstrating the importance of the Smart Grid for the subject research, the literature review clarifies that the research involving hardware-in-the-loop (HIL) tends to concentrate its analyses in the equipment under test, such as power devices, control devices and their algorithms. Instead, it should consider systemic studies involving the interaction of these devices with Operation Centre IT systems, so relevant to the Smart Grid functionalities. The proposed methodology is based on the premise that an environment for testing Smart Grids functionalities should allow systemic analysis instead of focusing only on control devices of a specific area or specific automation systems. Instead, it should involve a more detailed representation of the network that is necessary for the correct representation of the Smart Grid. In this direction, the methodology defines and characterizes the development stages and main modules of a Smart Grid emulator and proposes solutions for integration issues. It applies concepts of hardware-in-the-loop, software-in-the-loop (SIL), simulation with event-driven synchronization, besides steady-state power simulation and low-cost hardware solutions that enabled the development of the Power grid emulator at a Smart Grid laboratory. The main features of the Smart Grid emulator developed and implemented at the Smart Grid laboratory, according to the proposed methodology, are also described in this work. Finally, the description of the Smart Grid laboratory, test cases and proofs of concepts involving IEEE/PES test feeders and real networks of the EDP utility, sponsor of the project for laboratory implementation under the ANEEL R&D Program, are presented to prove the Emulator performance and to discuss the contribution of the methodology herein proposed.
62

Implémentation de méthodes d'intelligence artificielle pour le contrôle du procédé de projection thermique / Implementing artificial intelligence methods for controlling the thermal spraying process

Liu, Taikai 09 December 2013 (has links)
Depuis sa création, la projection thermique ne cesse d’étendre son champ d’application en raison de ses potentialités à projeter des matériaux bien différents (métallique, céramique, plastique,...) sous des formes bien différentes aussi (poudre, fil, suspension, solution,...). Plusieurs types de procédés ont été développés afin de satisfaire les applications industrielles, par exemple, le procédé HVOF (High Velocity Oxygen Fuel), le procédé APS (Atmospheric Plasma Spraying), le procédé VLPPS (Very Low Pressure Plasma Spray). Parmi ces procédés, le procédé APS est aujourd’hui bien implanté dans l’industrie et en laboratoire réussissant à élaborer des revêtements de bonne qualité à coût intéressant. Néanmoins, cette technologie pâtit des incidences des instabilités du procédé sur la qualité du produit obtenu et souffre d’un manque de compréhension des relations entre les paramètres opératoires et les caractéristiques des particules en vol.Pour rappel, pendant la projection APS, les phénomènes d’instabilité du pied d’arc, d’érosion des électrodes, d’instabilité des paramètres opératoires ne peuvent pas être complètement éliminés. Et, il est encore aujourd’hui difficile de mesurer et de bien contrôler ces paramètres.Compte tenu des progrès réalisés sur les moyens de diagnostic qui peuvent être utilisés en milieu hostile (comme dans le cas de la projection APS), un contrôle efficace de ce procédé en boucle fermée peut être maintenant envisagé et requiert le développement d’un système expert qui se compose des réseaux de neurones artificiels et de logique floue. Les réseaux de neurones artificiels sont développés dans plusieurs domaines d’application et aussi maintenant au cas de la projection thermique. La logique floue quant à elle est une extension de la logique booléenne basée sur la théorie mathématique des ensembles flous. Nous nous sommes intéressés dans ce travail à bâtir le modèle de contrôle en ligne du procédé de projection basé sur des éléments d’Intelligence Artificielle et à construire un émulateur qui reproduise aussi fidèlement que possible le comportement dynamique du procédé. / Since its creation, the thermal spraying continuously expands its application scope because of its potential to project very different materials (metal, ceramic, plastic ...) as well as different forms (powder, wire, suspension, solution ...). Several types of methods have been developed to meet industrial applications, for example, the process HVOF (High Velocity Oxygen Fuel), the process APS (Atmospheric Plasma Spraying), the process VLPPS (Very Low Pressure Plasma Spray). Among these methods, the APS process is now well established in the industry and laboratory for successfully developing coatings with good quality but low cost. However, this technology suffers from the instability effect of the process on the obtained product quality and endures a lack of understanding of the relationship between the operating parameters and the characteristics of in-flight particles.As a reminder, during the projection APS, the arc foot instability phenomena, the electrode erosion, the instability of the operating parameters cannot be completely eliminated. Further, it is still difficult to measure and control these parameters well. With the developing technology of diagnostic tools that can be used in a hostile environment (as in the case of APS process), an effective control of APS process in closed-loop can be considered and requires the development of an expert system consisting of artificial neural networks and fuzzy logic controlling. The artificial neural networks have been developed in several application fields and now also to plasma spraying process. Fuzzy logic controlling is an extension of Boolean logic based on the mathematical theory of fuzzy sets.We are interested in this work to build an on-line control model for the APS process based on the elements of artificial intelligence and to build an emulator that replicates as closely as possible the dynamic behavior of the process. Further, the artificial neural networks will be combined with the emulator for constituting a big system who can monitor the process and also can automatically carry out modification action. The system then will be tested off-line, the time response will be discussed.
63

Bayesian Uncertainty Quantification for Large Scale Spatial Inverse Problems

Mondal, Anirban 2011 August 1900 (has links)
We considered a Bayesian approach to nonlinear inverse problems in which the unknown quantity is a high dimension spatial field. The Bayesian approach contains a natural mechanism for regularization in the form of prior information, can incorporate information from heterogeneous sources and provides a quantitative assessment of uncertainty in the inverse solution. The Bayesian setting casts the inverse solution as a posterior probability distribution over the model parameters. Karhunen-Lo'eve expansion and Discrete Cosine transform were used for dimension reduction of the random spatial field. Furthermore, we used a hierarchical Bayes model to inject multiscale data in the modeling framework. In this Bayesian framework, we have shown that this inverse problem is well-posed by proving that the posterior measure is Lipschitz continuous with respect to the data in total variation norm. The need for multiple evaluations of the forward model on a high dimension spatial field (e.g. in the context of MCMC) together with the high dimensionality of the posterior, results in many computation challenges. We developed two-stage reversible jump MCMC method which has the ability to screen the bad proposals in the first inexpensive stage. Channelized spatial fields were represented by facies boundaries and variogram-based spatial fields within each facies. Using level-set based approach, the shape of the channel boundaries was updated with dynamic data using a Bayesian hierarchical model where the number of points representing the channel boundaries is assumed to be unknown. Statistical emulators on a large scale spatial field were introduced to avoid the expensive likelihood calculation, which contains the forward simulator, at each iteration of the MCMC step. To build the emulator, the original spatial field was represented by a low dimensional parameterization using Discrete Cosine Transform (DCT), then the Bayesian approach to multivariate adaptive regression spline (BMARS) was used to emulate the simulator. Various numerical results were presented by analyzing simulated as well as real data.
64

Emulação dos regimes permante e transitório das turbinas de eixo horizontal incluindo o modelo estático da turbina magnus / Emulation of the static and dynamic characteristics of horizontal axis wind turbines including the steady-state representation of a magnus turbine

Corrêa, Leonardo Candido 24 January 2014 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The lodgment of wind sites is in a visible growing demand not only in Brazil, but all over the world. The wind energy, even though consolidated, still hosts many scientific researches and industrial development in several areas such as control, power converter topologies and stability of grid connected wind turbines (WT). Due to the remarkable development of this technology in the market and the wind seasonality characteristics, it is difficult to study this power source in its operation field. Thus, a controlled environment for testing is desirable. This dissertation presents a topology of horizontal axis wind turbines (HAWT) emulator using a DC motor to provide an electrical generator the same torque that it would if it was driven by a typical WT. In addition to the static model, represented by the pitch angle and power coefficient, a dynamic model of HAWT is proposed in order to improve the representation of real turbines in the field, which allows characterizing the effect of wind shear, towering shadowing and turbine yaw. Furthermore, it permits emulating large inertia machines through smaller engines, by changing the torque imposed on the generator. The appealing motivation in this thesis is that the Magnus turbine emulation includes a relative new type of wind machine that possesses rotating cylinders instead of the traditional propeller blades in traditional HAWT. It is shown how these cylinders increase the available torque, then producing useful power even at lower wind speeds. Simulated and experimental results to evaluate the performance of the wind turbine emulator are presented. Both turbines are analyzed with and without MPPT. Finally the conclusions of this work are presented as well as new proposals for future works. / A instalação de parques eólicos tem se expandido não só no mundo, mas também no Brasil. A energia eólica, apesar de ser já bastante consolidada, ainda é palco para muitos trabalhos científicos e pesquisas na indústria nas áreas de controle, topologias de conversores de potência e estabilidade na conexão de aerogeradores com a rede. Devido a este fato junto com a sazonalidade do vento, torna-se difícil estudar esse tipo de fonte em seu âmbito de operação, sendo assim desejável um ambiente controlado para testes. Esta dissertação apresenta uma topologia para emulação de turbinas de eixo horizontal (HAWT) utilizando um motor de corrente contínua para acionar geradores com o mesmo torque que haveria caso estivessem acoplados a uma turbina real. Para melhor verossimilhança com as turbinas em campo, além do modelo estático composto pelo ângulo de passo das pás e o coeficiente de potência, propõe-se um modelo dinâmico para representar o efeito cortante do vento, o sombreamento da torre e o direcionamento da turbina em relação ao vento. Além do mais, o modelo proposto permite também a emulação de máquinas de grande inércia usando motores de menor porte, pela simples alteração do torque imposto ao gerador. O diferencial nesta dissertação consiste na possibilidade de emulação da turbina Magnus, que é um aerogerador que possui cilindros girantes no lugar das tradicionais pás presentes nas HAWT, que aumentam o torque disponível. Com isto, pode-se mostrar como a turbina Magnus pode gerar maior potência em baixas velocidades vento. São apresentados então os resultados simulados e experimentais avaliando o comportamento completo do emulador de turbinas eólicas. Ambas as turbinas são analisadas com e sem MPPT. Finalmente, são mostradas as conclusões do trabalho e as propostas para futuros trabalhos.
65

Projeto de um sistema emulador de escoamentos e vaso de separa??o prim?ria

Vieira, Pl?nio Alto? Costa 02 September 2009 (has links)
Made available in DSpace on 2014-12-17T14:55:38Z (GMT). No. of bitstreams: 1 PlinioACV.pdf: 2673165 bytes, checksum: 041961f375616fef1afc4244b3a44c02 (MD5) Previous issue date: 2009-09-02 / The purpose of this study was to develop a pilot plant which the main goal is to emulate a flow peak pressure in a separation vessel. Effect similar that is caused by the production in a slug flow in production wells equipped with the artificial lift method plunger lift. The motivation for its development was the need to test in a plant on a smaller scale, a new technique developed to estimate the gas flow in production wells equipped with plunger lift. To develop it, studies about multiphase flow effects, operation methods of artificial lift in plunger lift wells, industrial instrumentation elements, control valves, vessel sizing separators and measurement systems were done. The methodology used was the definition of process flowcharts, its parameters and how the effects needed would be generated for the success of the experiments. Therefore, control valves, the design and construction of vessels and the acquisition of other equipment used were defined. One of the vessels works as a tank of compressed air that is connected to the separation vessel and generates pulses of gas controlled by a on/off valve. With the emulator system ready, several control experiments were made, being the control of peak flow pressure generation and the flow meter the main experiments, this way, it was confirmed the efficiency of the plant usage in the problem that motivated it. It was concluded that the system is capable of generate effects of flow with peak pressure in a primary separation vessel. Studies such as the estimation of gas flow at the exit of the vessel and several academic studies can be done and tested on a smaller scale and then applied in real plants, avoiding waste of time and money. / A proposta desse trabalho foi desenvolver uma planta-piloto com o objetivo principal de emular picos de press?o de escoamentos num vaso de separa??o. Efeito semelhante ao provocado pela produ??o em forma de golfadas em po?os de produ??o equipados com o m?todo de eleva??o artificial plunger lift. A motiva??o para o desenvolvimento do mesmo foi a necessidade de se testar, numa planta em escala menor, uma nova t?cnica desenvolvida para a estima??o da vaz?o de g?s em po?os produtores equipados com plunger lift. Para seu desenvolvimento foram realizados estudos sobre efeitos dos escoamentos multif?sicos, funcionamento de m?todos de eleva??o artificial em po?os de plunger lift, dos elementos de instrumenta??o industrial, v?lvulas de controle, dimensionamento de vasos separadores e sistemas de medi??o. A metodologia utilizada foi a defini??o dos fluxogramas do processo, seus par?metros e como seriam gerados os efeitos necess?rios para o sucesso dos experimentos. Assim, foram definidas as v?lvulas de controle, o dimensionamento e constru??o dos vasos e a aquisi??o dos demais equipamentos utilizados. Um dos vasos funciona como reservat?rio de ar comprimido que, conectado ao vaso de separa??o, gera pulsos de g?s controlados por uma v?lvula on/off. Com o sistema emulador pronto, foram realizadas diversas experi?ncias de controle, sendo o controle de press?o com gera??o de picos e medi??o de vaz?o a principal experi?ncia, onde se comprovou a efici?ncia da utiliza??o da planta no problema que a motivou. Concluiu-se que o sistema ? capaz de gerar efeitos de escoamentos com picos de press?o num vaso de separa??o prim?ria. Estudos como a estima??o de vaz?o de g?s na saida do vaso e diversos estudos acad?micos poder?o ser feitos e testados numa escala menor sendo aplicados em seguida nas plantas reais, evitando perda de tempo e dinheiro
66

Emulation of a manufacturing process : Focusing on maintenance and operator training

Tudero, Aitor, Azkue, Julen January 2017 (has links)
Having well-trained operators is a crucial need for Volvo Group Truck Operations (GTO). Mistakes from the factory staff may cause the production line to stop, and lead to economic losses. For this reason, Volvo GTO has decided to investigate the possibility of creating an emulation model from the production line and using it to train operators and maintenance personnel. The aim of this thesis is to develop an Operator Training Station (OTS) for the OP035 of the Volvo GTO Production Line 6. In the first part, a literature research was conducted, from which the authors gained insight into related fields such as emulation, virtual environments, and operator training. After that, an emulation model of theOP035 was created using some hardware from the factory. The real PLC program was analyzed and then modified in order to implement it to the emulation model. Then, communications were established between the different parts; emulation model and PLC program. Finally, a research of the common failures and problems of the production line was carried out, with the aim of being able to reproduce them in the Operator Training Station. Once the OTS was implemented, several tests had undergone to validate its behavior. These experiments verified that the emulation model was an accurate representation of the real system and validated its appropriateness for the operator training application
67

Emulátor 3.5“ disketové mechaniky pomocí RS232 a SD paměťové karty / Emulator of 3.5" diskette drive using RS232 and SD memory card

Sedláček, David January 2012 (has links)
This thesis deals with the design of the 3,5" floppy drive emulator with ATMEGA microprocessor unit. The emulator has been designed according to the principles of designing electronic devices, there is also object-control application and firmware for a microcontroller, which supports MFM coding. The thesis also lists all the formats of data stored or transmitted along with some flowcharts.
68

Doppler Wheel for Emulation of Automotive Radar Target

ALRimawi, Mohammed January 2019 (has links)
Automotive radar is an emerging field of research and development. Technological ‎advancements in this field will improve safety for vehicles, pedestrians, and ‎bicyclists, and enable the development of autonomous vehicles. Usage of the ‎Automotive radar is expanding ‎in car and road areas to reduce collisions and ‎accident. Automotive radar ‎developers face a problem to test their radar sensor in ‎the street since there are a lot of interferences ‎signals, noise and unpredicted ‎situations. This thesis provides a part of the solution for this problem by designing a ‎device can demonstrate a different speeds value. This device will help the developer ‎to test their radar sensor inside an anechoic chamber room that provides accurate ‎control of the environmental conditions. This report shows how to ‎build the ‎measuring setup device, step by step to demonstrate the people and vehicle’s speed ‎‎in the street by a Doppler emulator using the wheel for millimetre FWMC radar. ‎Linear speed system needs a large space for testing, but using the rotational wheel ‎allow the developer to test the radar sensor in a small area. It begins with the wheel ‎design specifications and the relation between the ‎rotational speed (RPM) of the ‎wheel and the Doppler frequency. The Doppler ‎frequency is changed by varying the ‎speed of the wheel. Control and power circuit ‎was carefully designed to control the ‎wheel speed accurately. All the measuring ‎setup device parts were assembled in one ‎box. Also, signal processing was done by ‎MATLAB to measure the Doppler frequency ‎using millimetre FMCW radar sensor. ‎The measuring setup device was tested in the ‎anechoic chamber room for different speeds. the ‎manual and automatic tests show ‎good results to measure the different wheel speeds ‎with high accuracy.‎ / Combined Radar-Based Communication and Interference Mitigation for Automotive Applications / EMC Hammer
69

Étude de l’impact des collectionneurs sur la préservation et la conservation du jeu vidéo

Lefloïc Lebel, Adam 09 1900 (has links)
No description available.
70

Μετάδοση δεδομένων υψηλών ταχυτήτων σε γραμμές χαμηλής τάσης εντός κτιρίων : χαρακτηρισμός επικοινωνιακού μέσου και αξιοποίηση διαθέσιμου ευρους ζώνης / High speed data transission using indoor power distribution circuits : communications media characterization and available bandwidth utilization

Αναστασιάδου, Δέσποινα 25 June 2007 (has links)
Αντικείµενο της παρούσας διατριβής είναι η αξιοποίηση των γραµµών χαµηλής τάσης εντός κτιρίων για τη δηµιουργία ενός τοπικού δικτύου επικοινωνιών για µετάδοση δεδοµένων σε υψηλές ταχύτητες µε σκοπό την παροχή υπηρεσιών ευρείας ζώνης στον τελικό χρήστη. Η χρήση του δικτύου παροχής ηλεκτρικής ενέργειας ως επικοινωνιακό µέσο σε υψηλές συχνότητες εξαρτάται από την αντιµετώπιση των ιδιαίτερων χαρακτηριστικών της συµπεριφοράς του, που περιλαµβάνουν επιλεκτική εξασθένηση πλάτους συναρτήσει της συχνότητας, παραµόρφωση φάσης που εξαρτάται από τα µήκη των γραµµών, ισχυρό κρουστικό θόρυβο και παρεµβολές στενής ζώνης. Οι συνθήκες µετάδοσης επηρεάζονται επίσης δυσµενώς από την εξάρτηση των παραπάνω χαρακτηριστικών από το χρόνο, η οποία οφείλεται στη µεταβολή της φόρτισης του δικτύου. Η σύγχρονη αντιµετώπιση του επικοινωνιακού µέσου στηρίζεται σε εµπειρικά µοντέλα συµπεριφοράς, που πηγάζουν από µετρητικά δεδοµένα σε πειραµατικά δίκτυα και επιχειρεί να καλύψει αξιόπιστα µε κατάλληλες τεχνικές µετάδοσης τη ‘χειρότερη’ περίπτωση σε ότι αφορά τις συνθήκες του καναλιού, χωρίς να βοηθά στην κατανόηση των παραγόντων που επηρεάζουν τη συµπεριφορά του µέσου, ώστε να είναι εφικτή και η ουσιαστική αντιµετώπισή τους. Η παρούσα εργασία ακολουθεί µια διαφορετική προσέγγιση για την αξιοποίηση του µέσου, που στοχεύει στην ουσιαστική αντιµετώπιση της χρονικά µεταβαλλόµενης συµπεριφοράς του µέσου, προτείνοντας διαδικασίες και τεχνικές που προσαρµόζουν τη µετάδοση στο υφιστάµενο επικοινωνιακό περιβάλλον. Η ανάπτυξη των διαδικασιών αυτών στηρίχθηκε σε ένα πρότυπο περιβάλλον επικοινωνιών που καλείται pDSL (powerline Digital Subscriber Lines) και προτάθηκε για να αποτελέσει το πλαίσιο, σύµφωνα µε το οποίο αναπτύχθηκαν διαδικασίες ανίχνευσης και προσαρµογής της µετάδοσης στις συνθήκες του καναλιού. Στο pDSL περιβάλλον ορίζονται επικοινωνιακά κανάλια που ισοδυναµούν µε ‘σηµείο-προς-σηµείο’ ζεύξεις µεταξύ της pDSL πύλης (κεντρική µονάδα του δικτύου και µονάδα διασύνδεσης του τοπικού δικτύου µε άλλα δίκτυα) και των pDSL επικοινωνιακών συσκευών, όπως ονοµάζονται οι ηλεκτρονικές συσκευές που απαιτούν υπηρεσίες µετάδοσης δεδοµένων υψηλών ταχυτήτων. Η ανάπτυξη των τεχνικών µετάδοσης που αντιµετωπίζουν τις συνθήκες που επικρατούν στο επικοινωνιακό µέσο στηρίζεται στο χαρακτηρισµό της συµπεριφοράς του. Πρώτο βήµα της διαδικασίας αυτής αποτελεί η σύνδεση της απόκρισης του καναλιού µετάδοσης µε τα χαρακτηριστικά του δικτύου γραµµών. Για το σκοπό αυτό, αναπτύχθηκε και παρουσιάζεται ένας αλγόριθµος ανάλυσης της πολυοδικής µετάδοσης του σήµατος στο δίκτυο των γραµµών χαµηλής τάσης, ο οποίος προσδιορίζει µε αναλυτικό τρόπο τα προϊόντα της µετάδοσης που πραγµατοποιείται µέσω πολλαπλών διαδροµών στο δίκτυοκαι συνθέτει την κρουστική και φασµατική απόκρισή του. Ο αλγόριθµος βασίζεται στην περιγραφή της τοπολογίας, των χαρακτηριστικών µετάδοσης των καλωδίων και των εµπεδήσεων των φορτίων τερµατισµού της. Η εργασία περιλαµβάνει επίσης την ανάπτυξη δύο πειραµατικών µεθοδολογιών µε τις οποίες πραγµατοποιείται η εκτίµηση των χαρακτηριστικών µετάδοσης των καλωδίων χαµηλής τάσης στις υψηλές συχνότητες και της εµπέδησης των ηλεκτρικών φορτίων που συνδέονται στα δίκτυα αυτά. Τα µεγέθη αυτά προκαλούν την εξάρτηση της συµπεριφοράς του µέσου µετάδοσης από τη συχνότητα και το χρόνο και ο προσδιορισµός τους είναι αναγκαίος για την εφαρµογή της ανάλυσης και της πρόβλεψης της συµπεριφοράς του καναλιού µε τη βοήθεια του αλγορίθµου ανάλυσης. Η αξιοπιστία των µεθόδων πιστοποιήθηκε µε τη σύγκριση της πειραµατικής και της θεωρητικής συνάρτησης µεταφοράς των καναλιών που σχηµατίζονται σε πειραµατικές τοπολογίες γραµµών χαµηλής τάσης, οι οποίες κατασκευάστηκαν για το σκοπό αυτό. Στην παρούσα εργασία, η ανάλυση της συµπεριφοράς του µέσου πλαισιώνεται µε τη σχεδίαση και την υλοποίηση ενός εξοµοιωτή πραγµατικού χρόνου του επικοινωνιακού καναλιού, ο οποίος εξοµοιώνει τη χρονικά µεταβαλλόµενη συµπεριφορά του µέσου µε βάση την τοπολογία και τη φόρτιση του. Ο εξοµοιωτής αυτός µπορεί να αποτελέσει πολύτιµο εργαλείο ελέγχου νέων τεχνικών µετάδοσης, κάτω από διαφορετικές συνθήκες επικοινωνίες. Τέλος, µε βάση το χαρακτηρισµό της συµπεριφοράς του επικοινωνιακού µέσου που προηγήθηκε επιχειρείται η ανάπτυξη διαδικασιών που αποσκοπούν στην ανίχνευση των συνθηκών που επικρατούν στο επικοινωνιακό κανάλι και στην προσαρµογή της τεχνικής µετάδοσης σε αυτές, στα πλαίσια της pDSL αρχιτεκτονικής επικοινωνιών. Για την ανίχνευση των συνθηκών µετάδοσης στις επικοινωνιακές ζεύξεις αναπτύχθηκαν δύο επιµέρους διαδικασίες: η ‘αρχική συνθηκοθέτηση’ του καναλιού, που πραγµατοποιείται κατά την αρχικοποίηση των επικοινωνιακών ζεύξεων και η ‘ενδιάµεση συνθηκοθέτηση’ που εκτελείται περιοδικά και επανεκτιµά τις συνθήκες του καναλιού κατά τη διάρκεια της µετάδοσης. Η δεύτερη διαδικασία, η οποία υπόκειται σε εξαιρετικά αυστηρούς χρονικούς περιορισµούς, πλαισιώθηκε από µια µέθοδο πρόβλεψης της συµπεριφοράς του µέσου που επιταχύνει και συµπληρώνει τη διαδικασία ‘ενδιάµεσης συνθηκοθέτησης’ και βασίζεται στη διαθέσιµη πληροφορία εκτίµησης του καναλιού και στον αλγόριθµο ανάλυσης της µετάδοσης στο κανάλι. Η προτεινόµενη διαδικασία προσαρµογής της µετάδοσης στις τρέχουσες συνθήκες που επικρατούν στο κανάλι στοχεύει στην κατάλληλη ανακατανοµή του διαθέσιµου εύρους ζώνης στις επικοινωνιακές ζεύξεις, Η διαδικασία αξιοποιεί την πληροφορία της εκτίµησης των συνθηκών στο µέσο και επιχειρεί να χαρακτηρίσει τα διαθέσιµα υπο-κανάλια ως προς την καταλληλότητα τους για µετάδοση δεδοµένων, ώστε να τα κατανείµει µε βέλτιστο τρόπο στις ζεύξεις, ανάλογα µε τις απαιτήσεις τους σε ρυθµό µετάδοσης.

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