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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.

Cross-layer modeling and optimization of next-generation internet networks

Pedrola Escribà, Oscar 30 November 2012 (has links)
Scaling traditional telecommunication networks so that they are able to cope with the volume of future traffic demands and the stringent European Commission (EC) regulations on emissions would entail unaffordable investments. For this very reason, the design of an innovative ultra-high bandwidth power-efficient network architecture is nowadays a bold topic within the research community. So far, the independent evolution of network layers has resulted in isolated, and hence, far-from-optimal contributions, which have eventually led to the issues today's networks are facing such as inefficient energy strategy, limited network scalability and flexibility, reduced network manageability and increased overall network and customer services costs. Consequently, there is currently large consensus among network operators and the research community that cross-layer interaction and coordination is fundamental for the proper architectural design of next-generation Internet networks. This thesis actively contributes to the this goal by addressing the modeling, optimization and performance analysis of a set of potential technologies to be deployed in future cross-layer network architectures. By applying a transversal design approach (i.e., joint consideration of several network layers), we aim for achieving the maximization of the integration of the different network layers involved in each specific problem. To this end, Part I provides a comprehensive evaluation of optical transport networks (OTNs) based on layer 2 (L2) sub-wavelength switching (SWS) technologies, also taking into consideration the impact of physical layer impairments (PLIs) (L0 phenomena). Indeed, the recent and relevant advances in optical technologies have dramatically increased the impact that PLIs have on the optical signal quality, particularly in the context of SWS networks. Then, in Part II of the thesis, we present a set of case studies where it is shown that the application of operations research (OR) methodologies in the desing/planning stage of future cross-layer Internet network architectures leads to the successful joint optimization of key network performance indicators (KPIs) such as cost (i.e., CAPEX/OPEX), resources usage and energy consumption. OR can definitely play an important role by allowing network designers/architects to obtain good near-optimal solutions to real-sized problems within practical running times.

The notion of specialization in the i*framework

López Cuesta, Lidia 16 May 2013 (has links)
This thesis provides a formal proposal for the specialization relationship in the i* framework that allows its use in a well-defined manner. I root my proposal over existing works in different areas that are interested in representing knowledge: knowledge representation from Artificial Intelligence and conceptual modeling and object-oriented programming languages from Software Development. Also, I use the results of a survey conducted in the i* community that provides some insights about what i* modelers expect from specialization. As a consequence of this twofold analysis, I identify three specialization operations: extension, refinement and redefinition. For each of them, I: - motivate its need and provide some rationale; - distinguish the several cases that can occur in each operation; - define the elements involved in each of these cases and the correctness conditions that must be fulfilled; - demonstrate by induction the fulfilment of the conditions identified for preserving satisfaction; - provide some illustrative examples in the context of an exemplar about travel agencies and travelers. The specialization relationship is offered by the i* framework through the is-a construct defined over actors (a subactor is-a superactor) since it was first released. Although the overall meaning of this construct is highly intuitive, its effects at the level of intentional elements and dependencies are not always clear, hampering seriously its appropriate use. In order to be able to reason about correctness and satisfaction, I define previously the conditions that must be preserved when a specialization takes place. In addition, I provide a methodology with well-defined steps that contextualize the formal aspects of this thesis in a development process. As a conclusion, this thesis is making possible the use of the specialization relationship in i* in a precise, non-ambiguous manner.

A trust-driven privacy architecture for vehicular ad-hoc networks

Serna-Olvera, Jetzabel Maritza 08 January 2013 (has links)
Vehicular Ad-Hoc NETworks (VANETs) are an emerging technology which aims to improve road safety by preventing and reducing traffic accidents. While VANETs offer a great variety of promising applications, such as, safety-related and infotainment applications, they remain a number of security and privacy related research challenges that must be addressed. A common approach to security issues widely adopted in VANETs is the use of Public Key Infrastructures (PKI) and digital certificates in order to enable authentication, authorization and confidentiality. These approaches usually rely on a large set of regional Certification Authorities (CAs). Despite the advantages of PKI-based approaches, there are two main problems that arise, i) the secure interoperability among the different and usually unknown- issuing CAs, and ii) the sole use of PKI in a VANET environment cannot prevent privacy related attacks, such as, linking a vehicle with an identifier, tracking vehicles ¿big brother scenario" and user profiling. Additionally, since vehicles in VANETs will be able to store great amounts of information including private information, unauthorized access to such information should be carefully considered. This thesis addresses authentication and interoperability issues in vehicular communications, considering an inter-regional scenario where mutual authentication between nodes is needed. To provide interoperability between vehicles and services among different domains, an Inter-domain Authentication System (AS) is proposed. The AS supplies vehicles with a trusted set of authentication credentials by implementing a near real-time certificate status service. The proposed AS also implements a mechanism to quantitatively evaluate the trust level of a CA, in order to decide on-the-y if an interoperability relationship can be created. This research work also contributes with a Privacy Enhancing Model (PEM) to deal with important privacy issues in VANETs. The PEM consists of two PKI-based privacy protocols: i) the Attribute-Based Privacy (ABP) protocol, and ii) the Anonymous Information Retrieval (AIR) protocol. The ABP introduces Attribute-Based Credentials (ABC) to provide conditional anonymity and minimal information disclosure, which overcome with the privacy issues related to linkability (linking a vehicle with an identifier) and vehicle tracking (big brother scenario). The AIR protocol addresses user profiling when querying Service Providers (SPs), by relying in a user collaboration privacy protocol based on query forgery and permutation; and assuming that neither participant nodes nor SPs could be completely trusted. Finally, the Trust Validation Model (TVM) is proposed. The TVM supports decision making by evaluating entities trust based on context information, in order to provide i) access control to driver and vehicle's private information, and ii) public information trust validation.

A filtering engine for large conceptual schemas

Villegas Niño, Antonio 29 January 2013 (has links)
No description available.

Voice Interactive Classroom, a service-oriented software architecture to enable cross-platform multi-channel access to Internet-based learning

Alvarez García, Víctor Manuel 17 February 2011 (has links)
Software technology is creating a ubiquitous context for human living and learning in which new modes of interaction are gradually being incorporated. At the same time, interaction with Internet-based learning systems has evolved from using the traditional access from a personal computer or laptop‟s web browser to more flexible access from mobile devices. However, in both cases, e-learning systems have created a context in which interaction with the user is carried out mainly by using visual perception. This situation restraints the number of scenarios in which students can make use of a learning management system. Audio-based software brings a new way of interacting with the Internet. Visual access to Internet resources can be complemented with audio interfaces to adapt e-learning systems to different educational settings and learning styles, but auditory access to web resources needs to be more broadly supported by software architectures. This dissertation proposes the use of a service-oriented approach, supported by the e-learning specifications IMS Abstract Framework and The Open Knowledge Initiative, to provide a complementary audio communication channel and enable the interoperability of audio features among the various e-learning platforms and components. In addition, the use of the W3C recommendations of VoiceXML, along with the methods and techniques of adaptive educational hypermedia, allows overcoming the limitations of using unusual or non-standard languages to describe voice dialogues and better adapt the on-line learning process to innovative e-learning scenarios. The components of this model have been mapped to a software architecture named “Voice Interactive Classroom” that serves as a starting point for the design of research case studies which aim to demonstrate the benefits of the proposed solution. The validation of this thesis has been achieved by setting up and following an active strategy for scientific outreach. Activities include planning, coordinating and supervising final year projects, master projects and master dissertations, presenting articles and communications in scientific meetings, and the publication of this research study in a prestigious scientific journal. / La tecnología software está creando un contexto ubicuo para la vida y el aprendizaje humano en el que gradualmente se incorporan nuevos modos de interacción. Además, la interacción con los sistemas de aprendizaje basados en Internet ha evolucionado desde el acceso tradicional a través del navegador web de un ordenador personal o portátil a accesos más flexibles desde dispositivos móviles. Sin embargo, en ambos casos, los sistemas de e-learning han creado un contexto en el cual la interacción con el usuario se realiza principalmente utilizando la percepción visual. Esta situación limita el número de escenarios en el que los estudiantes pueden hacer uso de los sistemas de gestión del aprendizaje. El software basado en audio proporciona una nueva manera de interaccionar con Internet. El acceso visual a los recursos de Internet puede ser complementado con interfaces de audio para adaptar los sistemas de e-learning existentes a diferentes entornos educativos y estilos de aprendizaje, pero el acceso auditivo a los recursos web necesita encontrar mayor soporte en las arquitecturas software. Esta tesis propone el uso de un enfoque orientado a servicios, apoyado en las especificaciones de e-learning IMS Abstract Framework y The Open Knowledge Initiative, para proporcionar un canal de comunicación complementario y auditivo, y permitir la interoperabilidad de las aplicaciones de audio con las plataformas y componentes de e-learning. Adicionalmente, el uso de las recomendaciones VoiceXML del W3C, junto con los métodos y técnicas de hipermedia adaptativa para sistemas educativos, permiten superar las limitaciones de usar lenguajes inusuales o no estándar para describir los diálogos de voz y adaptar mejor el proceso de aprendizaje en línea a escenarios de e-learning innovadores. Los componentes de este modelo han sido mapeados a una arquitectura software denominada “Aula de Voz Interactiva” que sirve como punto de partida en el diseño de casos de estudio que persiguen demostrar los beneficios de la solución propuesta. La validación de esta tesis se ha conseguido mediante el planteamiento y seguimiento de una estrategia de alcance científico. Las actividades incluyen la planificación, coordinación y dirección de proyectos fin de carrera y trabajos fin de máster, la presentación de artículos y comunicaciones en reuniones científicas y la publicación de esta investigación en una prestigiosa revista científica.

Grafos y digrafos asociados con teselaciones como modelos para redes de interconexión

Morillo Bosch, Paz 25 February 1987 (has links)
Formulación matemática de un método general para el diseño de redes y su aplicación para resolver problemas de optimización en algunas familias de redes conocidas así como para nuevas familias definidas.

Analytical models for the multiplexing of worst case traffic sources and their application to ATM traffic control.

Barceló Ordinas, José María 23 April 1998 (has links)
No description available.

Exploiting concurrency in a general-purpose one-instruction computer architecture

Emmons, Christopher Daniel January 2010 (has links)
Computer performance is suffering greatly from diminishing returns as the increasing cost of implementing complex hardware optimizations and of increasing clock frequency no longer yields the gains in computational ability and power efficiency consumers demand. Notable products including a generation of Intel Pentium 4 processors have been cancelled as a result. This sudden hiccup in an historically predictable performance road map has inspired research and industrial communities to investigate architectures, some rather unorthodox, that complete work more quickly and more efficiently. One such computer architecture under development, Fleet, exposes fine-grain instruction level concurrency, addresses the growing costs of on-chip communications, and promotes simplicity in the underlying hardware design. This one-instruction computer transports data using simple move operations. The globally-asynchronous architecture promotes high modularity allowing specialized configurations of the architecture to be generated quickly with low hardware and software complexity. The Armada architecture presented in this thesis expands on Fleet by introducing constructs that exploit thread-level concurrency. The proposals herein aim to increase the performance efficiency of Fleet and other communicationcentric architectures. Trade-offs between software and hardware complexity and between the static and dynamic division of labor are investigated through the implementation and study of an Armada microarchitecture and an Armada compiler created for this research. This thesis explores the merits and pitfalls of this unique architecture as the basis for general-purpose computers for the future.

Investigation of the process and practice of animatronics

Issapour, Jahan January 2008 (has links)
Animatronics is a multi-disciplinary subject that embraces both art and. science It is acknowledged as a new discipline" and attracts a wide audience; In academia and discussion terms, this creates a problem as to where to place the subject, and how to define its key principles. This thesis sets out to investigate the practice and principles of animatronics design; to discover where it came from, what it encompasses and how it might develop. Early research establishes the definition of animatronics, which is developed by empirical research from industry. The structure and working practice of a major animatronics studio in the UK, Creature Shop, were examined and followed by an in-depth case study of the making of models for the BBC's 'Walking with Dinosaurs' production. The principles arising from the investigation have been tested by project, and the project brief was to make an animatronics model to explore the best methods for reproducing the correct facial movements to express fear, anger, sorrow, happiness, disgust and surprise. In this project the mouth and lip area was selected for the experiment, and both an art and engineering methodology were used and the results recorded. The value of the investigation is the platform it provides for process and practice, and the understanding this offers as a base line from which to move forward. It also presented an opportunity for the author to contribute to the animatronics design studio's working methods in a way that it acknowledged and is currently still using. The working title of the new role created was The Bridge, and the method used is a graphical movement design and navigation board. The thesis defines animatronics as an independent, interdisciplinary subject that draws diverse professionals together through its creative approach and its emphasis on visual communication methods. Because of the element of surprise or wonder that surrounds the technology, its future will rely on dramatic performance and the interactive area of artificial intelligence. Animatronics models require the 'wow factor' to maintain the public's interest, or to grow closer to new applications in biomechanics, robotics and amphibiotics.

Knowledge enhanced framework for the design and development of e-workflow systems

Ndeta, John January 2008 (has links)
For the last two hundred years the neo-classical cconomy has recogniscd only two factors of production: Labour and capital. With the advent of the Internet and e-business, the economy is now changing to knowledge and global economy in which information and knowledge are becoming the main factors and the primary wealth-crcating assets. Land, labour and capital - the economist's traditional factors of production - do not disappear, but they become secondary. This research work has focussed on the development of a new framework and methodologies to support the process of designing workflow management systems (e-workflow) adapted to the dynamic changes of the new business (e-business) environment in the new economy. Such framework and methodologies will support the automation and the dynamic changeso f e-businessp rocessest,h e integration of heterogeneousa pplication systems, and communications between intra and inter-organisational ebusiness processes. An initial literature review has found that traditional workflow metaphors are increasinglyi nadequatein the new e-businessc ra that is often characterisedb y an increasing pace of radical, discontinuous and unforeseen change in the business processes and e-business environment. The findings show that current workflow systems are less capable of dealing with the more dynamic situations encounteredin ad hoc and collaborative work processesin the new e-businesse nvironment.F urthermore,t raditional workflow developmentsf ail to characteriseth e information and knowledget hat flows in a workflow design process in such a manner as to promote its reuse. It has also showed that the traditional developments of workflow systems have ignored the human dimension of organisational knowledge creation. To address the above workflow development limitations, this research work has proposed the integration of a new knowledge perspective to the traditional framework for workflow design and development, which was limited to four perspectives i. e. organisational, behavioural, functional and informational perspectivesT. his new knowledgep erspectiveh as two main rolcs: monitoring the changes that are happening in the traditional workflow modelling perspectives and reflect the changes on the c-busincss processes, and enrich the framework with a knowledge repository. The knowledge repository is populated from two sources: the extraction or deduction of knowledge from the data and information flowing between the four perspectives and the memorisation of successful stories, best practices, previous cases which are organised as design patterns. These design patterns will be re-used to continuously evolve and provide flexibility of e-business processes to reflect immediate changes required in the new e-business environment. An evaluation of the proposed framework and methods was carried out through web-based survey and action research case study strategies.

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