Browsing by Issue Date, starting with "2019-08-16"
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- Visual analytics for spatiotemporal eventsPublication . Silva, Ricardo Almeida; Moura Pires, João; Datia, Nuno; Santos, Maribel Yasmina; Martins, Bruno; Birra, FernandoCrimes, forest fires, accidents, infectious diseases, or human interactions with mobile devices (e.g., tweets) are being logged as spatiotemporal events. For each event, its geographic location, time and related attributes are known with high levels of detail (LoDs). The LoD plays a crucial role when analyzing data, as it can highlight useful patterns or insights and enhance the user’ perception of phenomena. For this reason, modeling phenomena at different LoDs is needed to increase the analytical value of the data, as there is no exclusive LOD at which the data can be analyzed. Current practices work mainly on a single LoD of the phenomena, driven by the analysts’ perception, ignoring that identifying the suitable LoDs is a key issue for pointing relevant patterns. This article presents a Visual Analytics approach called VAST, that allows users to simultaneously inspect a phenomenon at different LoDs, helping them to see in what LoDs do interesting patterns emerge, or in what LoDs the perception of the phenomenon is different. In this way, the analysis of vast amounts of spatiotemporal events is assisted, guiding the user in this process. The use of several synthetic and real datasets supported the evaluation and validation of VAST, suggesting LoDs with different interesting spatiotemporal patterns and pointing the type of expected patterns.
- 3-D scale model study of wave run-up, overtopping and damage in a rubble-mound breakwater subject to oblique extreme wave conditionsPublication . Santos, João Alfredo; Pedro, Francisco; Coimbra, Mário; Figuero, Andrés; Fortes, Conceição Juana; Sande, José; Körner, Moritz; Lemos, Rute; Bornschein, Antje; Weimper, Julius; van den Bos, Jeroen; Dost, Bastian; Hofland, Bas; Carvalho, Rita F.; Alvarellos, Alberto; Peña, Enrique; Pohl, Reinhard; Kerpen, Nils B.; Reis, Maria TeresaA set of scale-model tests carried out to enlarge the range of wave steepness values analysed in run-up, overtopping and armour layer stability studies, focusing on oblique extreme wave conditions and on their effects on a gentler slope breakwater’s trunk armour and roundhead, is presented in this paper. A stretch of a rubble mound breakwater (head and part of the adjoining trunk, with a slope of 1(V):2(H)) was built in a wave basin at the Leibniz University Hannover to assess, under extreme wave conditions (wave steepness of 0.055) with different incident wave angles (from 40º to 90º), the structure behaviour in what concerns wave run-up, wave overtopping and damage progression of the armour layer. Two types of armour elements (rock and Antifer cubes) were tested. Non-intrusive methodologies including a new application of laser scanning technique for the assessment of both armour layer damage and wave run-up and overtopping were used. It is expected that such work will contribute also with data to improve empirical formulas as well as to validate complex numerical model for wave-structure interaction.
- Physical modelling of motions and forces on a moored ship at the Leixões portPublication . Santos, João Alfredo; Pinheiro, Liliana; Abdelwahab, Hossam S.; Fortes, Conceição; Pedro, Francisco G. L.; Capitão, Rui P.; Hinostroza, Miguel; Soares, Carlos GuedesThis paper describes the physical model, experimental setup and tests performed at the Portuguese Civil Engineering Laboratory (LNEC), to study the motions and forces of a moored ship at the Leixões port, for different sea states in irregular waves. The tests were carried out at one of the wave tanks of LNEC, where the Leixões port layout was implemented at scale 1:80 with the detailed model similar to the prototype bathymetry and surrounding structures. The moored ship is a 3.43 m long scale model of the well-known “Esso Osaka” tanker and is moored to the pier A of the oil terminal at 0.135 m draft. Several types of measurements were recorded in this study. The freesurface elevation and wave direction were measured with a set of resistive wave gauges. The wave velocities at the entrance of the harbour were measured with an acoustic Doppler velocimeter. Motions of the moored ship were measured with the OptiTrack™ motion capture system whereas forces on fenders and mooring lines were measured with load cells attached to a complex spring system developed at LNEC. Several tests were carried out for a number of incident sea states characterized by a JONSWAP spectrum, with different significant wave heights and peak periods. The measurement, analysis and results obtained for the incident wave conditions characterized by a significant wave height of 6 m and a peak wave period of 14 s are presented and discussed in this paper.