Mechanical characterization of adobe bricks in existing constructions in Aveiro Region, Portugal

In Portugal it is common to find earth constructions all over the country, being predominant in the centre and south. In the past, earth was massified as a construction material, used with different typologies and applications. Adobe construction is confined mainly to the central part of the country and more viewed in the west coast (gandaresa region). Aveiro, an Atlantic sea line city is an excellent example of a place with several ancient adobe constructions, some with architectural and historical relevance like some art-noveau houses. Just a few ones have been preserved with the passing years. The majority are in the threshold of ruin and structurally weak needing an urgent solution for their furtherance as buildings. Preservation and rehabilitation of those constructions was simply forgotten, carrying to the actual situation. In this context, becomes urgent, and absolutely necessary, to advance with rehabilitation and strengthening of these constructions. A great difficulty for technicians working on the rehabilitation relies on the lack of knowledge on adobe’s mechanical behaviour. In fact, in order to properly describe the structural behaviour of those constructions, there’s a need to investigate the mechanical properties of adobe. Hence, this paper presents a study which intended to characterise the behaviour of adobe brick units. Specimens were prepared from selected representative Aveiro’s constructions. The prepared specimens were tested in order to evaluate their mechanical behaviour in compression and tension. Usually, adobe blocks were made from clay soils. A basic characterization was also performed by the adobes’ granulometric analysis

Invariants of Welded Virtual Knots Via Crossed Module Invariants of Knotted Surfaces

We define an invariant of welded virtual knots from each finite crossed module by considering crossed module invariants of ribbon knotted surfaces which are naturally associated with them. We elucidate that the invariants obtained are non trivial by calculating explicit examples. We define welded virtual graphs and consider invariants of them defined in a similar way.Comment: New results. A perfected version will appear in Compositio Mathematic

Probability distribution of the order parameter

The probability distribution of the order parameter is exploited in order to obtain the criticality of magnetic systems. Monte Carlo simulations have been employed by using single spin flip Metropolis algorithm aided by finite-size scaling and histogram reweighting techniques. A method is proposed to obtain this probability distribution even when the transition temperature of the model is unknown. A test is performed on the two-dimensional spin-1/2 and spin-1 Ising model and the results show that the present procedure can be quite efficient and accurate to describe the criticality of the system.Comment: 5 pages, 7 figures, to appear in Braz. J. Phys. 34, June 200

Spectroscopic direct detection of reflected light from extra-solar planets

At optical wavelengths, an exoplanet's signature is essentially reflected light from the host star - several orders of magnitude fainter. Since it is superimposed on the star spectrum its detection has been a difficult observational challenge. However, the development of a new generation of instruments like ESPRESSO and next generation telescopes like the E-ELT put us in a privileged position to detect these planets' reflected light as we will have access to extremely high signal-to-noise ratio spectra. With this work, we propose an alternative approach for the direct detection of the reflected light of an exoplanet. We simulated observations with ESPRESSO@VLT and HIRES@E-ELT of several star+planet systems, encompassing 10h of the most favourable orbital phases. To the simulated spectra we applied the Cross Correlation Function to operate in a much higher signal-to-noise ratio domain than when compared with the spectra. The use of the Cross-Correlation Function permitted us to recover the simulated the planet signals at a level above 3 \sigma_{noise} significance on several prototypical (e.g., Neptune type planet with a 2 days orbit with the VLT at 4.4 \sigma_{noise} significance) and real planetary systems (e.g., 55 Cnc e with the E-ELT at 4.9 \sigma_{noise} significance). Even by using a more pessimistic approach to the noise level estimation, where systematics in the spectra increase the noise 2-3 times, the detection of the reflected light from large close-orbit planets is possible. We have also shown that this kind of study is currently within reach of current instruments and telescopes (e.g., 51 Peg b with the VLT at 5.2 \sigma_{noise} significance), although at the limit of their capabilities.Comment: Accepted for Publication on MNRAS: 2013 August 29; Online Article: http://mnras.oxfordjournals.org/content/early/2013/09/27/mnras.stt1642; 5 Figures, 11 page