103,736 research outputs found

    Distributed LQG control of a water delivery canal with feedforward from measured consumptions

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    This work addresses the design of distributed LQG controllers for water delivery canals that include feedforward from local farmer water consumptions. The proposed architecture consists of a network of local control agents, each connected to one of the canal pools and sharing information with their neighbors in order to act in a coordinated way. In order to improve performance, the measurement of the outflows from each pool is used as a feedforward signal. Although the feedforward action is local. It propagates due to the coordinates procedure. The paper presents the distributed LQG algorithm with feedforward and experimental results in a large scale pilot water delivery canal

    A sacred landscape: an enquiry of the “Cubas” from the South of Portugal

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    Ponencia presentada a Session 9: Forma urbana y relaciones entre historia y proyecto: el medio ambiente como patrimonio / Urban form and relationships between design and history: environmental heritage, arquitecture and planningThe purpose of this paper is to study the cubas – small constructions known for their domes painted with whitewash – specifically those located in the “kĂ»ra” of Beja in Portugal. Although we can pinpoint the existence of many of these buildings in the Beja territorial area, many questions remain about them, such as: What was the purpose of the cubas? When were they built? What is their origin? In order to try and answer these questions, I will be following two methods of analysis. First, I will focus on the correlation that exists between these buildings and the landscape in which they are located. This can shed some light on the reason behind their construction and the purpose of this type of structures. Secondly, I will analyse the buildings themselves – with special attention given to the metric and constructive analysis – in order to clarify the period of construction and the origin of their architectural typology. With this project I also aim to raise awareness of both the academic community and the political decision-makers on the existence of these buildings and their importance for the understanding of Iberian-Islamic culture. And maybe this can eventually inspire political action that will lead to the forging of policies for the preservation of this important part of our architectural and cultural heritage

    Heritage Building Stones from Évora, Portugal

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    The city of Évora, a World Heritage Site recognized by UNESCO in 1986, also owes this recognition to the stones that built its monuments and preserve them until today. This work brings together the contributions that we have gathered over the past three decades and allow us to have a very complete idea, not only about the materials used in the hundreds of monuments and historic buildings but also about their provenance. If some materials are so emblematic that they allow an immediate identification with the naked eye, others needed more sophisticated and precise techniques so that there was no doubt about their origin. The igneous rocks and gneisses of granite composition are part of the “Massif of Évora” on which the city is built. Thus, and quite naturally they are by far the most represented group in monuments from all historical periods. Its function is essentially structural, but there are also functional, ornamental and decorative objects. For example, the oldest megalithic structures found in the vicinity of the city are made up of large granite blocks that often had to be transported to their locations. On the other hand, many gargoyles and statues that decorate the churches are also made up of these granite rocks. On these, the natural erosion of centuries of exposure to the environment has led to a state of alteration, sometimes very accentuated, which would justify its replacement by replicas sculpted in similar rocks. Provenance studies have made it possible to identify old quarries in the vicinity of the city where, on the one hand, the ancient rock extraction techniques can be observed and on the other hand, they allow the obtaining of the raw material necessary for these restoration and conservation works. In any case, they are places that need to be inventoried and protected, with the municipality already aware of their existence. As well as the monuments of the Roman Period, also the structures of the Medieval Period, such as the city walls, the Cathedral (started to be built in 1186 AD) and all the great churches, were also built with these granitoids. In addition to these rocks, many others of multiple varieties and origins are present. The marbles, especially the Estremoz Marbles (Global Heritage Stone Resource), are ubiquitous in the city, but there are also emblematic marbles from other places, some easily identifiable (ie Viana do Alentejo, Escoural, Trigaches, Serpa and Vila Verde de Ficalho, for presenting mineralogy, textures, colors and patterns which, together with more recent analytical techniques, have confirmed its provenance. Sedimentary rocks, with emphasis on Portuguese Mesozoic limestones, ie Lioz - GHSR and Brecha da Arrábida - GHSR candidate, among others more rare and with very specific use in ornamental details, are also present and contribute to enrich a heritage in stone that makes this city so special and very popular with tourists of all nationalities. Acknowledgments: the authors thank to FCT for funding the ICT (UID/GEO/04683/2019), as well as COMPETE POCI-01-0145-FEDER-007690

    The Geology as an indispensable tool for optimizing the exploration of dimension Stones

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    Like any Geological Resource, the Dimension Stones can only be exploited where they occur. How they occur is a reflection of geological history that presided over its formation. Their nature determines the mode of deposit and therefore it’s potential to be exploited as ornamental stone. The geological setting of the Portuguese marbles became a key factor in the optimization of its exploitation, two ductile deformation phases must be consider, which originates the complex folded metamorphic layering. At least three fracturing systems are responsible for the high segmentation of the marbles in fragile deformation conditions and that must also be considered. Together these geological constraints lead to a really low production ratio (3% - 12%). These low efficiency productions emphasized the emergence of the geological knowledge of individual quarries in order to optimize is exploitation. Until recent years, with high prices for the Portuguese marbles the companies haven’t been concerned with the geological knowledge of its quarries, but now that an economic crisis is installed in the sector, basic geological studies in the quarries are mandatory and could save thousands of euros for each company

    FastM: Design and Evaluation of a Fast Mobility Mechanism for Wireless Mesh Networks

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    Although there is a large volume of work in the literature in terms of mobility approaches for Wireless Mesh Networks, usually these approaches introduce high latency in the handover process and do not support realtime services and applications. Moreover, mobility is decoupled from routing, which leads to inefficiency to both mobility and routing approaches with respect to mobility. In this paper we present a new extension to proactive routing protocols using a fast mobility extension, FastM, with the purpose of increasing handover performance in Wireless Mesh Networks. With this new extension, a new concept is created to integrate information between neighbor wireless mesh routers, managing locations of clients associated to wireless mesh routers in a certain neighborhood, and avoiding packet loss during handover. The proposed mobility approach is able to optimize the handover process without imposing any modifications to the current IEE 802.11 MAC protocol and use unmodified clients. Results show the improved efficiency of the proposed scheme: metrics such as disconnection time, throughput, packet loss and control overhead are largely improved when compared to previous approaches. Moreover, these conclusions apply to mobility scenarios, although mobility decreases the performance of the handover approach, as expected

    Car ownership and access to jobs in Spain

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    This study analyses the impact that job accessibility in public transport has on car ownership. An ordered probit explaining the number of cars per household is estimated as a function of head of household characteristics, household characteristics and job accessibility. The data used in the analysis come from the Microcensus of year 2001 of the Spanish Institute of Statistics for the areas of Barcelona and Madrid. Our results show a significant effect of accessibility on car ownership. Additionally, we carried out simulation exercises in which the expected number of vehicles decreases as accessibility improves. For instance, in the case of households living outside the central city, an improvement of accessibility up to the average level of the central city would offset the effect of the number of working adults on the expected number of vehicles.car ownership, job accessibility, public transport.

    Development of an electronic scholar notebook for students with special needs

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    Comunicação apresentada na DSAI - International Conference on Software Development for Enhancing Accessibility and Fighting Info-exclusion, Vila Real (Portugal), 8-9 Novembro 2007.The Salamanca Declaration promotes the integration of students with special needs in the regular education. To achieve this goal is fundamental to assist these students with different mechanisms some of which technology based. Students with motor difficulties face obstacles of diverse order like the execution of tasks that require handwriting (e.g. copies, dictations and worksheet resolution). Some of these students use portable computers equipped with text processors and rate enhancement systems that accelerate writing in the computer. However, our experience says that these tools are not enough. The management of the produced information has revealed itself a very challenging task for these children. Therefore we think that is of paramount importance the development of an application that helps students in the management of all produced information. This article reports the design of a digital scholar note book that can constitute an effective alternative to its traditional counterpart

    Asset Prices and Monetary Policy in the Euro Area: a tentative model

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    The nature of the relationship between asset price movements and monetary policy is a currently hotly debated topic in macroeconomics. This paper examines empirically if monetary policy in the euro-area, since 1987, has been influenced by high valuations of the equity and housing markets. A first aim of the paper is to assess the performance of Taylor-type rules and to evaluate whether alternative specifications, including asset prices, can better track the interest rate setting in the euro area. The general finding is that a Taylor-like rule, with an interest rate smoothing term but without including asset prices, seems to be helpful in describing monetary policy in the euro-area in the last fifteen years. Next, in the context of a simple macro model, extended with asset prices, we derive the optimal reaction function for the monetary authorities. Through a simple calibration of that model, we find that asset prices inclusion in the monetary authority’s reaction function implies a larger volatility for the interest rate and destabilizes the economy. That is, apart from demand shocks, the rule incorporating asset prices implies more volatility than a simple rule. The effect of the disturbances dies out after some periods, but the observed volatility in the variables is greater in the extended model.European Central Bank, Asset Prices, Monetary Policy, Inflation Targeting
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