Fault tolerant and integrated token ring network

This thesis is a study of communication protocols (token ring, FDDI, and ISDN), microcontrollers (68HC 1EVB), and fault tolerance schemes. One of the major weaknesses of the token ring network is that if a single station fails, the entire system fails. A scheme involving a combination of hardware and timer interrupts in the software has been designed and implemented which deals with this risk. Software and protocols have been designed and applied to the network to reduce the chance of bit faults in communications. ISDN frame format proved to be exceptional in its capacity to carry echoed data and a large variety of tokens which could be used by the stations to test the data. By its very nature, the token ring supplied another major fault detection device by allowing the data to be returned and tested at its source. The resulting network was successful

Parallel hierarchical radiosity rendering

The radiosity equation is examined, and is found to contain a previously unexploited symmetry. This symmetry is formalized, and a solution method previously unusable in the field of computer graphics (conjugate gradients) is shown to be superior to all methods currently in use. A detailed analysis of all solution techniques previously applied to the radiosity problem is conducted, and results presented;So-called hierarchical methods have reduced the operational complexity of the N-body problem from O(N[superscript]2) to O(N log N) assuming a pre-set error tolerance. An algorithm following the same basic tenets has been applied to radiosity rendering by other researchers, and has reduced the operational complexity from O(N[superscript]2) to (arguably) O(N);Shortcomings in the state-of-the-art hierarchical radiosity method are pointed out, and enhancements are offered. A consistent treatment of various types of error is found to be absent from present methods. Catastrophic error is possible in the visibility assessment between two polygons. A self-consistency check is possible during the solution process, but never exploited;Until now, supercomputer-class computers have not been used to solve radiosity problems at a production-quality level even though realistic image synthesis has always been a prodigious consumer of computer time. A state-of-the-art hierarchical radiosity code is implemented on an nCUBE-2 parallel computer, and discussed in detail. The algorithm is found to have ample sources of parallelism, in both data- and operational modes. Its performance is analyzed in detail;The hierarchical method has only been applied to realistic image synthesis since 1991. Not surprisingly, many avenues of further research are open. Some are pointed out, and include: analytic determination of coupling factors, quantifying discretization error, incorporating specular light reflection modes into the hierarchical treatment, and exploring what other important physical problems might benefit from the hierarchical approach

System Architectures for Cooperative Teams of Unmanned Aerial Vehicles Interacting Physically with the Environment

Unmanned Aerial Vehicles (UAVs) have become quite a useful tool for a wide range of applications, from inspection & maintenance to search & rescue, among others. The capabilities of a single UAV can be extended or complemented by the deployment of more UAVs, so multi-UAV cooperative teams are becoming a trend. In that case, as di erent autopilots, heterogeneous platforms, and application-dependent software components have to be integrated, multi-UAV system architectures that are fexible and can adapt to the team's needs are required. In this thesis, we develop system architectures for cooperative teams of UAVs, paying special attention to applications that require physical interaction with the environment, which is typically unstructured. First, we implement some layers to abstract the high-level components from the hardware speci cs. Then we propose increasingly advanced architectures, from a single-UAV hierarchical navigation architecture to an architecture for a cooperative team of heterogeneous UAVs. All this work has been thoroughly tested in both simulation and eld experiments in di erent challenging scenarios through research projects and robotics competitions. Most of the applications required physical interaction with the environment, mainly in unstructured outdoors scenarios. All the know-how and lessons learned throughout the process are shared in this thesis, and all relevant code is publicly available.Los vehículos aéreos no tripulados (UAVs, del inglés Unmanned Aerial Vehicles) se han convertido en herramientas muy valiosas para un amplio espectro de aplicaciones, como inspección y mantenimiento, u operaciones de rescate, entre otras. Las capacidades de un único UAV pueden verse extendidas o complementadas al utilizar varios de estos vehículos simultáneamente, por lo que la tendencia actual es el uso de equipos cooperativos con múltiples UAVs. Para ello, es fundamental la integración de diferentes autopilotos, plataformas heterogéneas, y componentes software -que dependen de la aplicación-, por lo que se requieren arquitecturas multi-UAV que sean flexibles y adaptables a las necesidades del equipo. En esta tesis, se desarrollan arquitecturas para equipos cooperativos de UAVs, prestando una especial atención a aplicaciones que requieran de interacción física con el entorno, cuya naturaleza es típicamente no estructurada. Primero se proponen capas para abstraer a los componentes de alto nivel de las particularidades del hardware. Luego se desarrollan arquitecturas cada vez más avanzadas, desde una arquitectura de navegación para un único UAV, hasta una para un equipo cooperativo de UAVs heterogéneos. Todo el trabajo ha sido minuciosamente probado, tanto en simulación como en experimentos reales, en diferentes y complejos escenarios motivados por proyectos de investigación y competiciones de robótica. En la mayoría de las aplicaciones se requería de interacción física con el entorno, que es normalmente un escenario en exteriores no estructurado. A lo largo de la tesis, se comparten todo el conocimiento adquirido y las lecciones aprendidas en el proceso, y el código relevante está publicado como open-source

Victory over Chaos? Constantinos A. Doxiadis and Ekistics 1945-1975

Constantinos A. Doxiadis (1913-1975) was an important figure in the realm of postwar urbanism, and yet his contribution has been largely neglected. This study reviews his trajectory and analyzes key projects related to different phases of his career: the housing programs of the Ministry of Reconstruction developed during the Greek Civil War and with Marshall Plan funds; the National Housing Program of Iraq in the context of the Third World modernization; and the Urban Detroit Area project developed against the suburbanization of the American city and Lyndon Johnson’s Great Society. Each one of these episodes is examined against the background of the opposing but interacting “processes” that characterized the forging of the postwar world: the efforts to internationalism and the schism of the Cold War. The first two projects reveal Doxiadis’ persistence on the importance of housing as a motor of economic development and his seminal contribution to aided self-help programs. In parallel, I examine his ideas on urban-regional development in relation to the modernization theory, namely the doctrine that advanced the development of Third World countries according to the paradigm of the West. Finally, his connections with the Ford Foundation and his participation in events organized by the Congress for Cultural Freedom offer an opportunity to examine his oeuvre in relation to the Cold War cultural policies. The second half of the thesis broadly coincides with the period 1960-1975 and focuses on ekistics, an action-oriented interdisciplinary approach to global urbanization problems that Doxiadis coined the science of human settlements. It examines the emergence of the ekistic movement, the establishment of the Athens Center of Ekistics as a hub in the European periphery “operating” between East and West, the intellectual forum of the Delos Symposia, and the journal Ekistics. In a parallel line, the analysis of the ekistic research programs aims to assess Doxiadis’ efforts to unite two different cultures of planning, that is, the sociological perspective with the calculative spirit of mathematics and statistics. The study of Doxiadis’ plan for Detroit reveals the flaws of his comprehensive approach and discusses the ekistic methodologies in reference to the systems approach to planning. Altogether, Doxiadis and ekistics epitomize the transition from the heroic modernism to the visionary approaches that explored the consequences of a world turning into a global village. Doxiadis, however, sought to plan the city of the future as part of a global urban system. In his eyes, facing the urban crisis was an attainable ideal. Eventually, the contradictions between his work and theory were the outcome of his commitment to plan an inevitable development and his anxiety to put order in the urban chaos.Constantinos A. Doxiadis (1913-1975) fue una figura importante en el ámbito de la planificación urbana de la posguerra, y sin embargo, su contribución ha sido descuidada en gran medida. El presente estudio repasa su trayectoria analizando los principales proyectos que corresponden a diferentes etapas de su carrera: la Reconstrucción de Europa, la modernización del Tercer Mundo, la suburbanización de la ciudad estadounidense y la Gran Sociedad de Lyndon Johnson. Cada uno de estos episodios está estrechamente vinculado a las transformaciones geopolíticas que se entienden como la Guerra Fría. Doxiadis comenzó su carrera en el sector público dirigiendo los programas de reconstrucción de Grecia. Su profesionalidad y la alineación ideológica con el intervencionismo estadounidense fueron fundamentales para su colaboración con las misiones de ayuda internacional y su posterior carrera. Despedido de su cargo, Doxiadis fundó Doxiadis Associates (DA) a principios de los años cincuenta. En pocos años, DA ha obtenido numerosos proyectos de vivienda en el mundo en desarrollo, convirtiéndose en una de las empresas más grandes de ingeniería y consultoría en el ámbito internacional. El punto de partida fue el Programa de Vivienda Nacional de Irak, contratado en 1955.El Plan Maestro de Bagdad vino después .El análisis de estos proyectos se centra en el modelo de planificación llamado Dynápolis - es decir, la respuesta de Doxiadis tanto al crecimiento urbano como a la conservación de la ciudad histórica - y la aplicación de la "comunidad humana”, una versión de la Unidad Vecinal. A mediados de 1960, Doxiadis fue encargado del proyecto Urban Detroit Area (UDA), un plan integral y exhaustivo que prácticamente examinó el desarrollo de la región de Michigan. Aunque no llegó a implementarse, el UDA fue uno de los mayores retos en la carrera de Doxiadis. En primer lugar, porque se desarrolló de acuerdo con su teoría y metodologías sistémicas. En segundo lugar, porque el avance del plan coincidió con el cambio de paradigma en la arquitectura moderna y el final de la década el desarrollo. En una línea paralela esta tesis examina ekistics, un enfoque holístico que contemplaba los problemas de urbanización global, y que Doxiadis nombró la ciencia de los asentamientos humanos .Ekistics fue concebido como un campo interdisciplinario que combinaba los conocimientos de otras áreas como la economía, la sociología, la estadística, la arquitectura y la geografía. Su objetivo era proporcionar un marco integral para planificar la ciudad del futuro, la llamada Ecumenópolis. Para desarrollar y difundir sus ideas, Doxiadis fundó el Athens Center of Ekistics (ACE) y puso en marcha diversas actividades institucionales. Las más importantes fueron la organización de los Simposios de Delos, y la publicación de la prestigiosa revista Ekistics. Esta tesis revisará el ACE como un centro de planificación en la periferia europea y los Simposios de Delos como un foro independiente entre el Este y el Oeste. Por otro lado, y para ofrecer una perspectiva crítica sobre los esfuerzos intelectuales de Doxiadis, la tesis analiza la "Ciudad del Futuro" y el proyecto de investigación de "la Comunidad Humana". Ambos apuntaban a la consolidación de ekistics ya la legitimación científica de los modelos de planificación y estrategias de diseño de Doxiadis. En total, la tesis utiliza el trabajo y la teoría de Doxiadis para revisar la redefinición de la planificación urbana y la arquitectura frente a los fenómenos y las transformaciones que marcaron las tres primeras décadas de la posguerra. Según Doxiadis los problemas de la ciudad contemporánea eran globales, mientras el futuro era urbano, universal e inevitable. Al final, su pensamiento estaba imbuido tanto con la ansiedad de enfrentar la crisis universal que con el optimismo de la década de desarrollo. Sin duda, Doxiadis fue uno de los últimos modernos.Postprint (published version

The Bushrangers: A play in five acts and other poems

https://commons.und.edu/settler-literature/1071/thumbnail.jp

Programming Languages and Systems

This open access book constitutes the proceedings of the 31st European Symposium on Programming, ESOP 2022, which was held during April 5-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 21 regular papers presented in this volume were carefully reviewed and selected from 64 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

Archaeological knowledge and its representation an inter-disciplinary study of the problems of knowledge representation

The thesis is a study of archaeology viewed from a perspective informed by (a) social constructionist theory and pragmatism; (b) techniques of Belief and Knowledge Representation developed by Artificial Intelligence research and (c) the conception of history and historical practice propounded by the philosopher, historian and archaeologist, R.G. Collingwood. It is argued that Gibsonian affordances and von Uexkull's notion of the Umwelt, recently discussed by Rom Harré, provide the basis for a description and understanding of human action and agency. Further, belief and knowledge representation techniques embodied in Expert Systems and Intelligent Tutoring Systems provide a means of implementing models of human action which may bridge intentionality and process and thereby provide a unifying learning environment in which the relationships of language, social action and material transformation of the physical world can be explored in a unified way. The central claim made by the thesis is that Collingwood's logic (dialectic) of Question & Answer developed in 1917 as a hermeneutic procedure, may be seen as a fore-runner of Newell and Simon's Heuristic Search, and thereby amenable to modem approaches to problem solving. Collingwood's own approach to History/ Archaeology is grounded on many shared ideas with pragmatism and a social constructionist conception of mind and is conducted within a problem solving framework. Collingwood is therefore seen as a three-way bridge between Social Psychology, Artificial Intelligence and Archaeology. The thesis concludes that Social Psychology, Artificial Intelligence and Archaeology can be integrated through the use of Intelligent Tutoring Systems informed by a Collingwoodian perspective on Archaeology, Mind and History - construed as Mind's self-knowledge

Programming Languages and Systems

This open access book constitutes the proceedings of the 31st European Symposium on Programming, ESOP 2022, which was held during April 5-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 21 regular papers presented in this volume were carefully reviewed and selected from 64 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

Peace-process infrastructure: constructing landscapes in-between Irelands

Over the course of 30 years ‘The Troubles’ in Northern Ireland led to the rupturing of physical sites from people’s everyday environment. In a post ‘Good Friday/Belfast Agreement’ era, this thesis considers the construction of common ground and the space of encounter as an instrument in peacemaking. I investigate how both the physical and the imagined landscape work together to form what I call peace-process infrastructure: landscapes that bolster a peaceprocess by being re-appropriated for civilian purposes and knit back into their surroundings. Under the practice strand of this study, I use movement as a tactic by choosing a series of traverses that were not possible to undertake as a civilian during the conflict: Divis Mountain next to Belfast City which changed hands from military zone to nature reserve; the now navigable Shannon-Erne Waterway; and the borderline hills between Ireland/European Union and Northern Ireland/United Kingdom where the watchtowers once stood. The garnered film footage works as testimony to a fragile peace-process, which in turn becomes an active archive that generates text. Specific tools that were used at each site to overcome topographical distance — limelight, lock and lens — are deployed once more to make what is considered remote and out of touch, close and tangible. At its heart, this project builds a multi-tiered rendering of particular landscapes — drawing on Hannah Arendt, Edmund Burke, amongst other political, landscape and feminism theorists — but it is motivated by the larger desire to contribute to a worldwide discussion about peace-process situations from a spatial perspective. People’s reactions to the constructed encounter in the world around them are a direct consequence to the architectural systems that command our surroundings. Landscapes hold the potential to deconstruct toxic territorial organisation leading to creative production. Revolutions are not just a protest but a creative process — a tool for remaking states and societies. In world terms the cultural Irish revolution preceded the political revolution galvanising world and Irish opinion towards independence for Ireland in 1916. About one hundred years later, this work creates a cultural milieu about the peace process that gathers strength for its advancement

Exploring Cognitive Processes with Virtual Environments

The scope of this thesis is the study of cognitive processes with, and within Virtual Environments (VEs). Specifically, the presented work has two main objectives: (1) to outline a framework for situating the applications of VEs to cognitive sciences, especially those interfacing with the medical domain; and (2) to empirically illustrate the potential of VEs for studying specific aspects of cognitive processes. As for the first objective, the sought framework has been built by proposing classifications and discussing several examples of VEs used for assessing and treating disorders of attention, memory, executive functions, visual-spatial skills, and language. Virtual Reality Exposure Therapy was briefly discussed as well, and applications to autism spectrum disorders, schizophrenia, and pain control were touched on. These applications in fact underscore prerogatives that may extend to non-medical applications to cognitive sciences. The second objective was sought by studying the time course of attention. Two experiments were undertaken, both relying on dual-target paradigms that cause an attentional blink (AB). The first experiment evaluated the effect of a 7-week Tibetan Yoga training on the performance of habitual meditators in an AB paradigm using letters as distractors, and single-digit numbers as targets. The results confirm the evidence that meditation improves the allocation of attentional resources, and extend this conclusion to Yoga, which incorporates also physical exercise. The second experiment compared the AB performance of adult participants using rapid serial presentations of road signs -- hence less abstract stimuli -- under three display conditions: as 2-D images on a computer screen, either with or without a concurrent auditory distraction, and appearing in a 3-D immersive virtual environment depicting a motorway junction. The results found a generally weak AB magnitude, which is maximal in the Virtual Environment, and minimal in the condition with the concurrent auditory distraction. However, no lag-1 sparing effect was observed. == La tesi attiene allo studio dei processi cognitivi in ambiente virtuale (AV). In particolare il lavoro presentato ha due obiettivi principali: (1) proporre un quadro di riferimento per le applicazioni degli AV nelle scienze cognitive, specialmente quando queste rientrano nel settore medico; e (2) illustrare empiricamente il potenziale degli AV per lo studio di specifici aspetti cognitivi. Il quadro di riferimento del primo obiettivo è stato costruito discutendo classificazioni ed esempi di AV usati per valutare e trattare disturbi dell'attenzione, della memoria, esecutivi, delle abilità visuo-spaziali e del linguaggio. Sono stati brevemente discussi anche esempi di applicazioni di Virtual Reality Exposure Therapy, e per i disturbi dello spettro autistico, la schizofrenia, e l'analgesia. Esse sono infatti rappresentative delle prerogative degli AV trasferibili ad aspetti non medici delle scienze cognitive. Per il secondo obiettivo del lavoro si è studiata l'attenzione nel dominio temporale. Sono stati realizzati due esperimenti, entrambi basati su un paradigma sperimentale di doppio-compito tale da indurre il fenomeno dell'attentional blink (AB). Il primo esperimento ha valutato l'effetto di 7 settimane di Yoga tibetano sull'AB di un gruppo di meditatori. La presentazione visiva seriale rapida comprendeva lettere come distrattori e numeri a una cifra come target. I risultati confermano che la meditazione riduce l'AB, ed estendono questa conclusione allo Yoga, che include anche l'esercizio fisico. Il secondo esperimento ha confrontato l'AB di un gruppo di adulti utilizzando presentazioni visive seriali rapide di segnali stradali -- dunque stimoli meno astratti -- in 3 condizioni: immagini 2-D sullo schermo di un computer, essendo simultaneamente presente o assente una distrazione uditiva, e presentazione 3-D in un AV immersivo che simula un incrocio autostradale. I risultati rilevano un AB lieve, che è massimo nell'AV, e minimo nella condizione 2-D con la distrazione uditiva. L'effetto lag-1 sparing non è presente