Abstract
The Porto settlement (Northwest Portugal, Iberian Peninsula) was originally built in the twelfth century and has been developed on granitic hill slopes of the Douro riverside, being one of the oldest cities in Europe. In the urban area of Porto, the second most important city of the Portuguese mainland, there is a population of about 216,000 inhabitants. This study highlights the importance of urban speleological mapping applied to groundwater and geo-engineering studies. All the water that flows from the so-called Paranhos or Arca D'Agua springs is captured by catchwork galleries and their utilization date back around 1120 AD. Paranhos spring galleries catchworks (c. 3,3 km extension and a -21m below ground level) was one of the main water supplies to Porto City for more than six centuries and, nowadays, these waters are still appropriate for irrigation uses. Topographical, geological, geophysical and hydrogeological data were collected and interpreted, allowing the definition of a hydrogeotechnical zoning. All these features were mapped and overlaid using GIS mapping techniques. This multidisciplinary approach offers a good potential for reliable urban speleological and geo-engineering studies of Arca D'Agua site.

Abstract
A new approach to gas leakage detection in high pressure distribution networks is proposed, where the pipeline is modelled as a Linear Parameter Varying (LPV) System driven by the source node mass flow with the pressure as the scheduling parameter, and the system output as the mass flow at the offtake. Using a recently proposed successive approximations LPV system subspace identification algorithm, the pipeline is thus identified from operational data. The leak is detected using a Kalman filter where the fault is treated as an augmented state. The effectiveness of this method is illustrated with an example with a mixture of real and simulated data.

Abstract
The fitting of physical dynamical models to stimulus-response data such as the chemical concentration measured after a gas has been released to the environment, or the plasma concentration measured after an intravenous or oral input of a drug, are important problems in the area of system identification. Using models of different structures, one can obtain relevant statistical information on the parameters of the model from an array of software packages available in the literature. A meaningful interpretation of these parameters requires that in the presence of error-free data and an error-free model structure, a unique solution for the model parameters is guaranteed. This problem is known as a priori identifiability. Once the model is deemed identifiable, the parameters are then obtained, usually via a nonlinear least squares technique. In addition to identifiability, there is the problem of convergence of the parameters to the true values. It is a known fact that nonlinear parameter estimation algorithms do not always converge to the true parameter set. This is due to the fact that estimating the parameters of a nonlinear model can at times be an ill-conditioned problem. In this paper we use the same state space analysis techniques used to determine identifiability, to estimate the model parameters in a linear fashion. We approach the problem from a system identification point of view and then take advantage of the similarity transformation between the physical model and the identified model. We formulate the similarity relations and then transform them into a null space problem whose solution leads to the physical parameters. The novelty of our approach is in the use of a state space system identification algorithm to identify a black-box system, followed by a physical parameter extraction step using robust numerical tools such as the singular value decomposition.

Abstract
In this paper a lumped transfer function (TF) model is derived for High Pressure Natural Gas Pipelines. Departing from a nonlinear partial differential equation (PDE) model a high order continuous state space (SS) linear model is obtained using a finite difference method. An infinite order TF is calculated from the SS representation and finally is approximated by a compact non-rational function. This model is compared with SIMONE(R), a commercial simulator of gas transport and distribution, using a case study, and both exhibit a similar accuracy.

Abstract
The Lagoa da Apulia is a unique feature in the NW coastal zone of Portugal, a remaining form from a lagoon complex system that, during the Late Holocene, was dominant in the region. This system was mainly neotectonically controlled, occupying a depressed area bounded by faults on a Palaeozoic rocky lower platform, today observable on beaches at low tide. With the intention of knowing the main architecture of the palaeo-lagoon, geophysical prospecting with GPR and resistivity was carried out. Accordingly, six cores were taken and the sedimentary and mineralogical facies, and diatom and foraminifer contents were analysed, and five rich organic layers were dated by radiocarbon analysis. With the data, an evolutionary environment reconstruction model was created for this palaeo-lagoon and the main structural features of the neighbouring area.

Abstract
This article describes the concept, design, fabrication and experimental results of a touchscreen based on acoustic pulse recognition. It uses piezoelectric transducers fabricated from the piezoelectric polymer poly(vinylidene fluoride), PVDF, in its beta phase. The transducers are located at the edges of the panel in order to receive the acoustic pulses generated by the touches. Each transducer is connected to a readout electronic circuit composed by a differential charge amplifier and a comparator, whose output signal is attached to a microcontroller. The microcontroller uses an algorithm to determine the location of the touch, based on the time differences of the transducer signals. The touchscreen itself is made of ordinary glass, providing good durability and optical transparency. The experimental results obtained with the first prototype demonstrate the effectiveness of the method.