Mooring systems for marine energy converters

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.This paper discusses several new technologies for mooring floating marine energy converter (MEC) devices, such as wave energy generators, tidal current turbines and floating wind turbines. The principal mooring component is a special nylon fiber rope which provides cyclic tension fatigue endurance much superior to that of conventional nylon ropes. The nylon fiber is treated with a new proprietary coating which has excellent wet yarn abrasion properties. The parallel-subrope type rope construction further reduces internal abrasion. Extensive laboratory testing was carried out on this new nylon rope design. Cyclic tension fatigue tests were conducted at mean loads and load amplitudes typical of actual service conditions and at higher mean loads and amplitudes. These tests demonstrate that the special nylon rope has essentially the same, desirable stretch characteristics as conventional nylon rope and has much better endurance performance. The mooring connection to the floating MEC device consists of a high-modulus fiber rope pendant which passes through a low-friction bell-mouth nylon fairlead on the MEC device. This eliminates the use of heavy, unreliable chain in this critical connection. A unique bag anchor system would be used on sand, clay, rock and other sea beds in which conventional drag embedment anchors and driven piles are impractical. The bag anchor consists of a large abrasion resistant carcass with lifting straps and top closure. The bag is transported to site in a collapsed form and is filled with local sand or aggregate to provide ballast weight. Several or many such bags are enclosed within a fiber rope net for deployment and are grouped together for connection to the mooring line. The paper will be of particular interest to designers of moorings for MEC systems in shallow water and severe wave environments. It will also be of interest for other mooring applications.This work would not have been possible without the funding and support of the Scottish Government, the Carbon Trust and Innovate UK.   The project was funded under the Marine Renewables Commercialization Fund (MRCF) and Marine Energy Supporting Array Technologies (MESAT).   Other partners who contributed to this project include Lloyd’s Register, DNV‐GL, TenCate, Orion Energy Centre, Nylacast, and offshore wind developer IDEOL.    Input and encouragement was provided by tidal power developer partner Bluewater, and wave energy developers AWS Ocean Energy and Pelamis.

Effective connectivity reveals strategy differences in an expert calculator

Mathematical reasoning is a core component of cognition and the study of experts defines the upper limits of human cognitive abilities, which is why we are fascinated by peak performers, such as chess masters and mental calculators. Here, we investigated the neural bases of calendrical skills, i.e. the ability to rapidly identify the weekday of a particular date, in a gifted mental calculator who does not fall in the autistic spectrum, using functional MRI. Graph-based mapping of effective connectivity, but not univariate analysis, revealed distinct anatomical location of “cortical hubs” supporting the processing of well-practiced close dates and less-practiced remote dates: the former engaged predominantly occipital and medial temporal areas, whereas the latter were associated mainly with prefrontal, orbitofrontal and anterior cingulate connectivity. These results point to the effect of extensive practice on the development of expertise and long term working memory, and demonstrate the role of frontal networks in supporting performance on less practiced calculations, which incur additional processing demands. Through the example of calendrical skills, our results demonstrate that the ability to perform complex calculations is initially supported by extensive attentional and strategic resources, which, as expertise develops, are gradually replaced by access to long term working memory for familiar material