Wave Energy Converter Array Optimization: A Genetic Algorithm Approach and Minimum Separation Distance Study

With the need to integrate renewable energy sources into the current energy portfolio and the proximity of power consumers to ocean coastlines, it is important to evaluate marine energy systems, specifically wave energy converters (WECs), as potential solutions for meeting electricity needs. The ability to model these systems computationally is vital to their eventual deployment. The power development, economics, grid integration requirements, operations and maintenance requirements, and ecological impacts must be understood before these devices are physically installed. However, the research area of WEC array optimization is young, and the few available results of previously implemented optimization methods are preliminary. The purpose of this work is to introduce a new WEC array optimization framework to explore systems-level concerns, specifically WEC layout and device spacing. A genetic algorithm approach that utilizes an analytical hydrodynamic model and includes an array cost model is presented, and the resulting optimal layouts for a preliminary test case are discussed. This initial work is integral in providing an understanding of device layout and spacing and is a foundational starting point for subsequent and more advanced WEC array optimization research

Optimal sampling design for spatial capture-recapture

Spatial capture-recapture (SCR) has emerged as the industry standard for estimating population density by leveraging information from spatial locations of repeat encounters of individuals. The precision of density estimates depends fundamentally on the number and spatial configuration of traps. Despite this knowledge, existing sampling design recommendations are heuristic and their performance remains untested for most practical applications. To address this issue, we propose a genetic algorithm that minimizes any sensible, criteria-based objective function to produce near-optimal sampling designs. To motivate the idea of optimality, we compare the performance of designs optimized using three model-based criteria related to the probability of capture. We use simulation to show that these designs out-perform those based on existing recommendations in terms of bias, precision, and accuracy in the estimation of population size. Our approach, available as a function in the R package oSCR, allows conservation practitioners and researchers to generate customized and improved sampling designs for wildlife monitoring.Publisher PDFPeer reviewe

Array Modeling and Testing of Fixed OWC Type Wave Energy Converters

If wave energy technology is to mature to commercial success, array optimization could play a key role in that process. This paper outlines physical and numerical modeling of an array of five oscillating water column wave energy converters. Numerical model simulations are compared with experimental tank test data for a non-optimal and optimal array layout. Results show a max increase of 12% in average power for regular waves, and 7% for irregular waves between the non-optimized and optimized layouts. The numerical model matches well under many conditions; however, improvement is needed to adjust for phase errors. This paper outlines the process of numerical and physical array testing, providing methodology and results helpful for researchers and developers working with wave energy converter arrays

Injury risk factors, screening tests and preventative strategies: A systematic review of the evidence that underpins the perceptions and practices of 44 football (soccer) teams from various premier leagues

Purpose: To systematically review the scientific level of evidence for the ‘Top 3’ risk factors, screening tests and preventative exercises identified by a previously published survey of 44 premier league football (soccer) teams. Also, to provide an overall scientific level of evidence and graded recommendation based on the current research literature. Methods: A systematic literature search (Pubmed [MEDLINE], SportDiscus, PEDRO and Cochrane databases). The quality of the articles was assessed and a level of evidence (1++ to 4) was assigned. Level 1++ corresponded to the highest level of evidence available and 4, the lowest. A graded recommendation (A: strong, B: moderate, C: weak, D: insufficient evidence to assign a specific recommendation) for use in the practical setting was given. Results: Fourteen studies were analysed. The overall level of evidence for the risk factors previous injury, fatigue and muscle imbalance were 2++, 4 and ‘inconclusive’, respectively. The graded recommendation for functional movement screen, psychological questionnaire and isokinetic muscle testing were all ‘D’. Hamstring eccentric had a weak graded ‘C’ recommendation, and eccentric exercise for other body parts was ‘D’. Balance/proprioception exercise to reduce ankle and knee sprain injury was assigned a graded recommendation ‘D’. Conclusions: The majority of perceptions and practices of premier league teams have a low level of evidence and low graded recommendation. This does not imply that these perceptions and practices are not important or not valid, as it may simply be that they are yet to be sufficiently validated or refuted by research

The impact of short periods of match congestion on injury risk and patterns in an elite football club

Background: The effect of fixture congestion on injury rates and patterns has received scarce attention in elite football and existing investigations have not accounted for player rotation or examined the temporal distribution and potential cause of injuries. Aim: To prospectively investigate the epidemiology of injury during short periods of fixture congestion in a professional football club. Methods: Over a 6-season period, exposure time and injury data were compared in the same players (n=25 [14 individuals]) when participating in two frequently occurring short congested fixture cycles in comparison to match-play outside these cycles. 1) two successive matches separated by an interval totalling ≤3days calculated immediately from the end of play in match 1 to the beginning of play in match 2; 2) three successive matches separated by ≤4-day intervals commencing the day immediately after each match. Results: In 2-match congestion cycles, incidence rate ratios (IRR) showed there was a higher risk of injury in the final 15-minutes of play in the second match in comparison to match-play outside the cycles (IRR: 3.1 [95% CI 1.1 to 9.3], p=0.0400). A greater risk of injury overall (IRR: 2.0 [95% CI 1.1 to 3.8], p=0.0345) and in the 1st-half of play (2.6 [1.1 to 6,5], p=0.0386), and risk of ankle sprains (10.4 [95% CI 1.9 to 57.9], p=0.0068) and non-contact injuries due to a ‘change in direction’ (IRR: 7.8 [1.3 to 46.8], p=0.0243) was observed in the final match of 3-match congestion cycles in comparison to match-play outside the cycles. Conclusion: Injury rates and patterns were affected in the same elite football players when competing in short congested fixture cycles in comparison to match-play outside the cycles

Injury prevention strategies at the FIFA 2014 World Cup: perceptions and practices of the physicians from the 32 participating national teams

Purpose The available scientific research regarding injury prevention practices in international football is sparse. The purpose of this study was to quantify current practice with regard to (1) injury prevention of top-level footballers competing in an international tournament, and (2) determine the main challenges and issues faced by practitioners in these national teams. Methods A survey was administered to physicians of the 32 competing national teams at the FIFA 2014 World Cup. The survey included 4 sections regarding perceptions and practices concerning non-contact injuries: (1) risk factors, (2) screening tests and monitoring tools, (3) preventative strategies and (4) reflection on their experience at the World Cup. Results Following responses from all teams (100%), the present study revealed the most important intrinsic (previous injury, accumulated fatigue, agonist:antagonist muscle imbalance) and extrinsic (reduced recovery time, training load prior to and during World Cup, congested fixtures) risk factors during the FIFA 2014 World Cup. The 5 most commonly used tests for risk factors were: flexibility, fitness, joint mobility, balance and strength; monitoring tools commonly used were: medical screen, minutes/matches played, subjective and objective wellness, heart rate and biochemical markers. The 5 most important preventative exercises were: flexibility, core, combined contractions, balance and eccentric. Conclusions The present study showed that many of the National football (soccer) teams’ injury prevention perceptions and practices follow a coherent approach. There remains, however, a lack of consistent research findings to support some of these perceptions and practices

Can off-field ‘brains’ provide a competitive advantage in professional football?

‘Working-fast and working-slow’ in sport describes the concept that practice and research can be integrated to improve high-performance outcomes and enhance professional practice.1 ‘Working-fast’ is the task of the fast-thinking, intuitive practitioner operating on ‘the ground’ at a frenetic pace, interacting with coaches and athletes, and delivering the daily preparation programme. ‘Working-slow’ is key for the team's deliberate, focused researcher acting as the resident sceptic, operating behind the scenes on tasks that the ‘fast-practitioner’ may not have time and/or skills to undertake. Such hidden, but important, tasks include determining measurement noise/error in performance tests, establishing proof of concept for new ideas and ensuring validity of methods. Embedding research into the fast environment of high-performance football may provide a competitive advantage using ethical and evidence-based methods.