Papers

O que diferencia o conhecimento científico do tradicional? Não é o facto deste último ser imutável, porque transmitido pelas gerações, não recorrer a procedimentos investigativos, não inovar, nem aprofundar informação. Inovação, mudança, procedimentos lógicos e investigativos definem ambos os tipos de conhecimento e tratam mais das suas semelhanças do que das diferenças.

A plataforma continental setentrional do Rio Grande do Norte caracteriza-se por apresentar uma variedade de feições de fundo marinho que variam desde 10 cm até quilômetros, sobretudo submersos nas porções mais rasas da plataforma e indicam processos de retrabalhamento. Além do caráter singular dos processos, formas efáceis de fundo diferenciados a qual esta plataforma está submetida, compreendese a importância do conhecimento da dinâmica das ondas, uma vez que estas são consideradas o agente forçador dominante na hidro e morfodinâmica costeira. O objetivo principal deste trabalho é caracterizar o clima de ondas por meio da modelagem numérica, através do modelo de ondas de superfície do mar, SWAN, e analisar sua interação com o fundo marinho raso da plataforma continentalsetentrional do Rio Grande do Norte. Foram realizadas várias medições de campo entre 2011 e 2012, com o objetivo de se obter os parâmetros de ondas: altura signifi cativa (HS), período médio (Tmed), direção (DIR) para servir de comparação e validação da modelagem.Os resultados apontam que o SWAN conseguiu, no geral, reproduzir adequadamente o clima de ondas para este litoral. Entretanto, ao analisar os resultados, confi rmou-se que as alturas signifi cativas apresentam resultados mais aceitáveis em relação aos demais parâmetros. A interação da onda com o fundo marinho revela alteração das alturas significativas e direções ao propagarem-se sobre as formas de fundos presentes, como as rochas praiais, os campos de dunas longitudinais, transversais e subaquáticos. Tais resultados mostram que nesta plataforma continental o mecanismo de dissipação dominante à propagação das ondas nestas águas rasas é o atrito de fundo.

A plataforma continental setentrional do Rio Grande do Norte caracteriza-se porapresentar uma variedade de feições de fundo marinho que variam desde 10 cm atéquilômetros, sobretudo submersos nas porções mais rasas da plataforma e indicamprocessos de retrabalhamento. Além do caráter singular dos processos, formas efáceis de fundo diferenciados a qual esta plataforma está submetida, compreendesea importância do conhecimento da dinâmica das ondas, uma vez que estas sãoconsideradas o agente forçador dominante na hidro e morfodinâmica costeira.O objetivo principal deste trabalho é caracterizar o clima de ondas por meio damodelagem numérica, através do modelo de ondas de superfície do mar, SWAN,e analisar sua interação com o fundo marinho raso da plataforma continentalsetentrional do Rio Grande do Norte. Foram realizadas várias medições de campoentre 2011 e 2012, com o objetivo de se obter os parâmetros de ondas: altura signifi cativa (HS), período médio (Tmed), direção (DIR) para servir de comparação e validação da modelagem.Os resultados apontam que o SWAN conseguiu, no geral, reproduzir adequadamente o clima de ondas para estelitoral. Entretanto, ao analisar os resultados, confi rmou-se que as alturas signifi cativas apresentam resultados maisaceitáveis em relação aos demais parâmetros. A interação da onda com o fundo marinho revela alteração das alturassignifi cativas e direções ao propagarem-se sobre as formas de fundos presentes, como as rochas praiais, os camposde dunas longitudinais, transversais e subaquáticos. Tais resultados mostram que nesta plataforma continental omecanismo de dissipação dominante à propagação das ondas nestas águas rasas é o atrito de fundo.

Os autores refletem sobre o risco de incêndio florestal nas interfaces entre os espaços urbanizados e florestados. Explora-se assim a organização e o uso do espaço das habitações na sua envolvente, e questionam-se perspetivas de abordagem teórica e possibilidades de investigação. Defende-se que o conteúdo jurídico das normas legais não é suficiente para abarcar a responsabilidade coletiva dos comportamentos individuais, a propósito dos usos da habitação e áreas adjacentes. É assim essencial, para uma melhor prevenção, o desenvolvimento de uma análise das vulnerabilidades aos incêndios florestais tendo em conta fatores de percepção social, de comportamento humano e das características das habitações e da própria organização do espaço.

Crash prediction models play a major role in highway safety analysis. These models can be used for various purposes, such as predicting the number of road crashes or establishing relationships between these crashes and different covariates. However, the appropriate choice for the functional form of these models is generally not discussed in research literature on road safety. In case of run-off-the-road crashes, empirical evidence and logical considerations lead to conclusion that the relationship between expected frequency and traffic flow is not monotonously increasing.

Among the test-methods for evaluation of aggregates reactivity towards alkali-silica reaction (ASR), linear dilatation of mortar bars or concrete prisms is often used in several tests under various conditions, criteria and procedures of measuring and accelerating the reaction. As reactivity is an essentially kinetic property, the expansion limits in such tests, or even tests results for the same aggregate, should be kinetically inter-related. This paper presents a proposal of a kinetic relationship for critical reaction rates, evaluated from criteria of standard test-methods NF P 18-590, ASTM C 1260 and ASTM C 1293 . To do so, the critical expansion rate of these tests were corrected for a reference 1M alkalinity and depicted as Arrhenius plot. The high correlation of the regression line shows linearity of the plotted data, which was assumed as a criterion of kinetic compatibility between the said tests. The discussion includes a comparison with other tests and literature comments on their evaluation. The main interest of this study concernong the potential for ASR, is to discuss and compare methods aiming to improve the service life of concrete structures, by: i) selection of good materials; ii) decisions on the appropriate concrete formulation; iii) foreseeing possible problems allowing to plan monitoring and/or the need for adequate intervention as well as the possibility of test improvements. The extension of service life allows savings in raw materials and energy, improvement of the investment economics and, in the long term, lower investment requirements.

A new laboratory test, named the flow limitation erosion test (FLET), has been designed anddeveloped to study upstream flow limitation during the phase of progression of internalerosion in the embankment of zoned dams. Upstream flow limitation may occur because ofthe presence of the shell or a transition zone upstream of a cracked core. In the FLET, thesoil specimen is composed of core and upstream shell materials. These are compactedinside a test apparatus made up of several pieces assembled in steps. Then the soilspecimen is subjected to water flow through a predrilled hole in the core material tosimulate a concentrated leak, initiated, for example, by large differential settlement orhydraulic fracture. In most tests, the hole is also drilled in the upstream material to simulatethe scenario in which the mechanism causing the flaw in the core is also likely to affect theupstream zone. Combinations of the same core material and several types of coarse-grainedupstream materials (broadly graded and gap-graded soils) are tested for a range ofcompaction conditions and hydraulic loads. It is shown that FLET is capable of assessingwhether there is upstream flow limitation and whether the internal erosion process stops,shows a trend of slowing down, or progresses. Upstream flow limitation is shown to bedependent on the fines and gravel content, fines plasticity, and compaction water content ofthe upstream material. In the particular case of the tested gap-graded soils, it is shown to bealso dependent on the initial gradient along the upstream material.

Here, we investigated the potential of laser removal of iron-rich dark films from weathered granite substrates, which represents a very difficult conservation problem because of the polymineralic nature of the stone and of its complex deterioration mechanisms. As often occurs, biotite was the most critical component because of its high optical absorption, low melting temperature, and pronounced cleavage, which required a careful control of the photothermal and photomechanical effects to optimize the selective ablation of the mentioned unwanted dark film. Different pulse durations and wavelengths Nd:YAG lasers were tested and optimal irradiation conditions were determined through thorough analytical characterisations. Besides addressing a specific conservation problem, the present work provides information of general valence in laser uncovering of encrusted granite.

This paper presents the design and compares the performance of linear, decoupled and direct power controllers for three-phase matrix converters operating as Unified Power Flow Controllers (lIPFC). A simplified steady-state model of the matrix converter based UPFC (MC-UPFC) fitted with a modified Venturini high frequency PWI\I modulator is first used to design the linear controllers for the transmission line active (P) and reactive (Q) power. ln order to minimize the resulting cross-coupling between P and Q power control, decoupled linear controllers (DLC) are synthesized using inverse dynamics linearization. Direct power controllers (DPC) are then developed using sliding mode control techniques, in order to guarantee both robustness and decoupled control. The designed P and Q power controllers are compared using simulations and experimental results. Linear controllers show acceptable steady-state behavior but still exhibit coupling between P and Q powers in transient operation. DLC are free from cross-coupling but are parameter sensitive. Results obtained by DPC show decoupled power control with zero error tracking and guarantee faster responses with no overshoot and no steady-state error. Ali the designed controllers were implemented using the sarne digital signal processing (DSP) hardware.

This paper presents the reaction behavior of lime and metakaolin (MK) pastes submitted to long term aging at ambient temperature and relative humidity of 95 ± 5%. The results presented are the basis for an extensive research pointing towards the formulation of lime based mortars for conservation of historic buildings, namely in humid environments. MK, when mixed with calcium hydroxide, in the presence of water, originates a set of major hydrated compounds, specifically, stratlingite, monocarboaluminate and calcium aluminate hydrate. The type of hydrated compounds formed is dependent on the lime/MK ratio, being some of them unstable over time. This instability can compromise the mechanical properties of lime–MK mortars. From this work different reaction kinetics with aging were perceived, being the best results in terms of the pozzolanic reaction obtained with 50% MK content. Pastes with less than 25% of MK also present reliable stability.