Suchergebnisse

Evaluation theories depicted as a five-branch tree reflect the assumptions of the post-positivist, constructivist, pragmatic, transformative, and Indigenous paradigms. A tree is useful because it provides a quick and clear way to show that different assumptions lead to different methodological assumptions. However, evaluation theory as a five-branch tree is limited because it does not show interrelationships between the paradigms. An ocean current visualization could accomplish that task, but it might not be a familiar concept for some populations. Evaluators need to check with stakeholders to ensure the visualizations that are used are viewed as useful to their purposes.

Abstract. Ocean-bottom seismometers (OBSs) are usually deployed for seismological investigations, but these objectives are impaired by noise resulting from the ocean environment. We split the OBS-recorded seismic noise into three bands: short periods, microseisms and long periods, also known as tilt noise. We show that bottom currents control the first and third bands, but these are not always a function of the tidal forcing. Instead, we suggest that the ocean bottom has a flow regime resulting from two possible contributions: the permanent low-frequency bottom current and the tidal current. The recorded noise displays the balance between these currents along the entire tidal cycle, between neap and spring tides. In the short-period noise band, the ocean current generates harmonic tremors corrupting seismic dataset records. We show that, in the investigated cases, the harmonic tremors result from the interaction between the ocean current and mechanical elements of the OBS that are not essential during the sea bottom recording and thus have no geological origin. The data from a new broadband OBS type, designed and built at Instituto Dom Luiz (IDL – University of Lisbon)/Centre of Engineering and Product Development (CEIIA), hiding non-essential components from the current flow, show how utmost harmonic noise can be eliminated.

This paper presents a comparative study of docking algorithms intended for non-holonomic autonomous underwater vehicles, docking in funnel-shaped docking stations, operating under the influence of ocean currents. While descriptive surveys have been already reported in the literature, our goal is to compare the most relevant algorithms through realistic Monte Carlo simulations to provide an insight into their performance. To this aim, a new numerical performance indicator is proposed, which, based on the geometry of the manoeuvre, is able to characterize a successful or unsuccessful docking, providing a metric for comparison. The experimental study is carried out using hardware-in-the-loop simulation by means of the Stonefish simulator, including the dynamic/hydrodynamic model of the Sparus II AUV, models of all internal and external sensors, and the collision geometry representing the docking station ; This work was supported by the European Union's Horizon 2020 Research and Innovation Program through the ATLANTIS ''The Atlantic Testing Platform for Maritime Robotics: New Frontiers for Inspection and Maintenance of Offshore Energy Infrastructures'' Project under Grant 871571

A spatial analysis was carried out to evaluate the compatibility of human activities and biophysical characteristics in the Mexican Caribbean Sea, in order to identify the most viable areas for energy generation from ocean currents and the areas where the population would most benefit from such energy projects. Of the study area, 82% have some form of protection legislation. Tourism is the main economic activity in the area and this is reflected in a wide range of activities and services that often overlap within the same spatial area. In the case study, the use of renewable ocean energies is seen as an important innovation to reduce fossil fuel dependency. These energies have the potential to meet the demands of the region. However, it is vital to seek for potential areas for this type of energy harvesting where the social, economic and environmental impacts would be minimal. The lack of marine policies and land-use planning processes in Mexico is a major obstacle in avoiding land use conflicts.