Abstract
An indirect downsampling approach for continuous-time input/output system identification is proposed. This modus operandi was introduced to system identification through a sub-space algorithm, where the input/output data set is partitioned into lower rate m subsets. Then, a state-space discrete-time model is identified by fusing the data subsets into a single one. In the present work the identification of the input/output downsampled model is performed by a least squares and a simplified refined instrumental variables (IV) procedures. In this approach, the inter-sample behaviour is preserved by the addition of fictitious inputs, leading to an increase of excitation requirements of the input signal. This over requirement is removed by directly estimating from the data the parameters of the transfer function numerator. The performance of the method is illustrated using the Rao-Garnier test system.

Abstract
This article the gas network is modelled as a repetitive process with smoothing and an explicit representation for its solution is presented. By an adequate choice of the inhomogeneity, the system is steered through boundary data control. We state explicit conditions for boundary control of the gas networks as well as observability criteria. Using these notions, some 2D criteria of stability are also applied to gas networks. To finalise, we use a 2D transfer function representation to withdraw a stability criterium suitable to being used in the practice with the use of a computer. © VDE VERLAG GMBH 2013.

Abstract
Student knowledge of Nature of Science (NOS) is an important and critical issue to their understanding of science, as well as to the development of scientific literacy. In the same way, the ability to use and generate models is central to scientific literacy and to the learning of science. Having this in mind, and recognizing that teachers' views and practices strongly influence students' learning, we intended to evaluate Portuguese prospective science teachers' (PPST) views of Nature of Science (NOS), models and earth structure models. A questionnaire, focused on those aspects, was applied to 19 prospective science teachers at the University of Porto. In general, the majority of the participants revealed correct perceptions about those issues. However, some inconsistences and alternative conceptions were found.

Abstract
Results of self-potential, seismic reflection and refraction, Infrared spectroscopy, ion chromatography and IR thermography survey performed over a Portuguese artistic tomb made of a porous limestone are presented. The tomb presents nowadays severe decay phenomena. The decay products associated to the decay patterns observed are mainly related with the presence of salts, namely nitrates and secondarily of chlorides. The self-potential and the thermography survey allowed verifying that moisture degrees change in different side walls of the tomb. The seismic methods showed there is no clear interface between undamaged and damaged stone material where the limestone is soft and the strength is slightly lower in the most humid zones.

Abstract
The result obtained from the investigation of Shear Waves Velocity (Vs) using Multichannel Analysis of Surface Waves for the geothecnical purposes in five study area of Aveiro gave an estimated Vs30 to develop the microzonation studies in this area. Copyright

Abstract
The measurement of shear wave velocity (Vs) is an established approach in contributing to earthquake site response. In situ dispersive wave measurements are one of the ways of determining Vs to a certain depth. Rayleigh type measurements have had a significant development in the past two decades. Since Spectral Analysis of Surface Waves measurements appeared, in the late 80s and early 90s, other approaches have developed. The later Multichannel Analysis of Surface Waves method (MASW), that took advantage of the engineering seismograph and the increasing number software routines that became available, greatly enhanced the confidence of this type of in situ results towards assessing the shear wave velocity profile of the near surface. Thus within this work we aim to show the results of 27 dispersive wave tests, made for 48 educational facilities located in 20 villages of the Chong-Alay district, Osh oblast, Kyrgyz Republic. The results of these seismic tests contributed towards the micro seismic wider hazard assessment study we performed.