Enabling collaboration in virtual reality navigators

In this paper we characterize a feature superset for Collaborative Virtual Reality Environments (CVRE), and derive a component framework to transform stand-alone VR navigators into full-fledged multithreaded collaborative environments. The contributions of our approach rely on a cost-effective and extensible technique for loading software components into separate POSIX threads for rendering, user interaction and network communications, and adding a top layer for managing session collaboration. The framework recasts a VR navigator under a distributed peer-to-peer topology for scene and object sharing, using callback hooks for broadcasting remote events and multicamera perspective sharing with avatar interaction. We validate the framework by applying it to our own ALICE VR Navigator. Experimental results show that our approach has good performance in the collaborative inspection of complex models.Postprint (published version

La ecuación hipergeométrica de Gauss

En este trabajo se estudiarán las ecuaciones diferenciales lineales de orden superior a 1 con coeficientes holomorfos en la esfera de Riemann, en especial la ecuación hipergeométrica de Gauss. En la primera parte se compararán los teoremas de existencia y unicidad para ecuaciones diferenciales no lineales y ecuaciones diferenciales lineales donde los coeficientes son funciones holomorfas, abordando también la prolongación analítica de las soluciones a lo largo de curvas y el teorema de monodromía. En la segunda parte clasificaremos las singularidades de las ecuaciones diferenciales lineales en singularidades de primer y segundo tipo, regulares e irregulares; y se hará un estudio más exhaustivo de las ecuaciones de orden 2 con coeficientes funciones racionales. En la tercera parte se estudiará como caso particular la ecuación hipergeométrica de Gauss y finalmente se darán aplicaciones prácticas de las ecuaciones diferenciales lineales, así como ideas sobre su implementación computacional.Grado en Matemática

The wrong subordination of territorial planning to the planning of transport infrastructure: the catalan case, 2006-2010

En base a unas reflexiones metodológicas de carácter general (apartados 1, 2 y 3) y la exposición de ocho casos de estudio catalanes (apartado 4), el artículo argumenta que el planeamiento territorial aprobado en Cataluña en el periodo 2006-2010 contiene un grave error: la supeditación del modelo territorial a las determinaciones del plan sectorial de infraestructuras de transporte aprobado en 2006. El artículo contiene también un apartado propositivo (apartado 5), donde se esboza una metodología para abordar las diferentes debilidades expuestas en los apartados anteriores. Finalmente se concluye con un epílogo sobre el coste de oportunidad de las infraestructuras.En base a unes reflexions metodològiques de caràcter general (apartats 1, 2 i 3) i l’exposició de vuit casos d’estudi catalans (apartat 4), l’article argumenta que el planejament territorial aprovat a Catalunya en el període 2006-2010 conté un greu error: la supeditació del model territorial a les determinacions del pla sectorial d’infraestructures de transport aprovat l’any 2006. L’article conté també un apartat propositiu (apartat 5), on s’esbossa una metodologia per abordar les diferents debilitats exposades als apartats anteriors. Finalment es conclou amb un epíleg sobre el cost d’oportunitat de les infraestructures.Based on a general methodological reflections (paragraphs 1, 2 and 3) and the exposure of eight Catalonian study cases (section 4), the paper argues that the approved territorial planning in Catalonia in the period 2006-2010 contains a serious error: the subordination of the territorial model to the determinations of the sectorial plan of transportation infrastructure approved in 2006. The article also contains a purposing section (paragraph 5), which outlines a methodology to address the various weaknesses exposed in the previous sections. Finally it concludes with an epilogue on the opportunity cost of infrastructures.Peer Reviewe

Prado Vargas y la variabilidad tecnológica a finales del Paleolítico Medio en la meseta norte

Los asentamientos del EIO 3 del Occidente europeo presentan unas cadenas operativas en donde los clásicos sistemas de explotación musterienses se intercambian, dando lugar, según nuestro método de análisis, a decenas de categorías diferentes. Estos núcleos, bien sobre lasca, bien sobre canto, originan morfotipos en gran variedad de soportes. En la Meseta norte hay al menos tres asentamientos que comparten estas características, Prado Vargas, Millán y Hundidero. Trataremos de conocer a través del registro de estos sitios, a qué se debe el aprovechamiento terminal de la materia prima y la forma de gestionarla.Els assentaments de l'EIO 3 de l'Occident europeu presenten unes cadenes operatives on els clàssics sistemes d'explotació musterians s'intercanvien donant lloc, segons el nostre mètode d'anàlisi, a desenes de categories diferents. Aquests nuclis, ja sigui sobre ascla o sobre còdol, originen morfotipus sobre gran varietat de suports. A la Meseta nord hi ha almenys tres assentaments que comparteixen aquestes característiques, Prado Vargas, Millán i Hundidero. A través del registre d'aquests jaciments tractarem de saber a què és degut l'aprofitament terminal de la matèria primera i la manera de gestionar-la.Les sites du EIO 3, en Europe occidentale, présentent des chaînes opératoires où les systèmes classiques d'exploitation moustérienne s'échangent donnant, selon notre méthode d'analyse, des dizaines de catégories différentes. Ces nucléus taillés sur éclats ou sur des galets, donnent des morphotypes sur une grande variété de supports. Dans les plateaux de nord, il y a au moins 3 sites qui partagent ces mêmes caractéristiques, Prado Vargas, Millán et Hundidero. On essayera de connaître, grâce au registre de ces sites, les raisons du profitement terminal de la matière première et la façon dont elle a été gestionnée.OIS3 sites in Western Europe show chaines operatoires in which there is a combination of classic Mousterian exploitation systems, leading to a wide range of knapping methods. Cores, either on cobble or on flakes, give place to morphotypes made on a variety of blanks. These features can be traced in at least three sites in the Northern Plateau, Prado Vargas, Millán and Hundidero. This paper investigates the exhaustion of raw materials and how they were exploited

FASTM: a log-based hardware transactional memory with fast abort recovery

Version management, one of the key design dimensions of Hardware Transactional Memory (HTM) systems, defines where and how transactional modifications are stored. Current HTM systems use either eager or lazy version management. Eager systems that keep new values in-place while they hold old values in a software log, suffer long delays when aborts are frequent because the pre-transactional state is recovered by software. Lazy systems that buffer new values in specialized hardware offer complex and inefficient solutions to handle hardware overflows, which are common in applications with coarse-grain transactions. In this paper, we present FASTM, an eager log-based HTM that takes advantage of the processor’s cache hierarchy to provide fast abort recovery. FASTM uses a novel coherence protocol to buffer the transactional modifications in the first level cache and to keep the non-speculative values in the higher levels of the memory hierarchy. This mechanism allows fast abort recovery of transactions that do not overflow the first level cache resources. Contrary to lazy HTM systems, committing transactions do not have to perform any actions in order to make their results visible to the rest of the system. FASTM keeps the pre-transactional state in a software-managed log as well, which permits the eviction of speculative values and enables transparent execution even in the case of cache overflow. This approach simplifies eviction policies without degrading performance, because it only falls back to a software abort recovery for transactions whose modified state has overflowed the cache. Simulation results show that FASTM achieves a speed-up of 43% compared to LogTM-SE, improving the scalability of applications with coarse-grain transactions and obtaining similar performance to an ideal eager HTM with zero-cost abort recovery.Peer ReviewedPostprint (published version

Hybrid model for vascular tree structures

This paper proposes a new representation scheme of the cerebral blood vessels. This model provides information on the semantics of the vascular structure: the topological relationships between vessels and the labeling of vascular accidents such as aneurysms and stenoses. In addition, the model keeps information of the inner surface geometry as well as of the vascular map volume properties, i.e. the tissue density, the blood flow velocity and the vessel wall elasticity. The model can be constructed automatically in a pre-process from a set of segmented MRA images. Its memory requirements are optimized on the basis of the sparseness of the vascular structure. It allows fast queries and efficient traversals and navigations. The visualizations of the vessel surface can be performed at different levels of detail. The direct rendering of the volume is fast because the model provides a natural way to skip over empty data. The paper analyzes the memory requirements of the model along with the costs of the most important operations on it.Postprint (published version

La Congestió viària i la mobilitat sostenible

El paradigma de la sostenibilitat, introduït recentment al marc legal català (Llei d'urbanisme 1/2005, Llei de la mobilitat 9/2003), obliga a redefinir objectius i metodologies en la planificació territorial, en general, i en la planificació de la mobilitat, en particular. En aquest sentit, l'article pretén aportar elements per tal d'abordar el fenomen de la congestió viària sota aquest nou prisma, justificant la necessitat de frenar la construcció de nova xarxa viària i posant l'èmfasi en la gestió de la demanda i en estratègies que minimitzin la inducció de nou trànsit de vehicles privats.El paradigma de la sostenibilidad, introducido recientemente en el marco legal catalán (Ley de urbanismo 1/2005, Ley de la movilidad 9/2003), obliga a redefinir objetivos y metodologías en la planificación territorial, en general, y en la planificación de la movilidad, en particular. En este sentido, el artículo pretende aportar elementos para abordar el fenómeno de la congestión vial bajo este nuevo prisma, justificando la necesidad de frenar la construcción de nueva red vial y poniendo el énfasis en la gestión de la demanda y en estrategias que minimicen la inducción de nuevo tráfico de vehículos privados.The sustainable paradigm, introduced recently into the legal Catalan system (Law of urban planning 1/2005, Law of mobility 9/2003), forces to redefine objectives and methodologies in territorial planning and more also in mobility planning. In this sense this paper brings new elements in order to face the road congestion phenomenon. We justify the need to stop the expansion of new road networks and support the management of the demand fostering strategies that diminish the stimulation of more traffic of private vehicles

Ring oscillator clocks and margins

How much margin do we have to add to the delay lines of a bundled-data circuit? This paper is an attempt to give a methodical answer to this question, taking into account all sources of variability and the existing EDA machinery for timing analysis and sign-off. The paper is based on the study of the margins of a ring oscillator that substitutes a PLL as clock generator. A timing model is proposed that shows that a 12% margin for delay lines can be sufficient to cover variability in a 65nm technology. In a typical scenario, performance and energy improvements between 15% and 35% can be obtained by using a ring oscillator instead of a PLL. The paper concludes that a synchronous circuit with a ring oscillator clock shows similar benefits in performance and energy as those of bundled-data asynchronous circuits.Peer ReviewedPostprint (author's final draft

Geometric transformations in octrees using shears

Existent algorithms to perform geometric transformations on octrees can be classified in two families: inverse transformation and address computation ones. Those in the inverse transformation family essentially resample the target octree from the source one, and are able to cope with all the affine transformations. Those in the address computation family only deal with translations, but are commonly accepted as faster than the former ones for they do no intersection tests, but directly calculate the transformed address of each black node in the source tree. This work introduces a new translation algorithm that shows to perform better than previous one when very small displacements are involved. This property is particularly useful in applications such as simulation, robotics or computer animation.Postprint (published version