Tidal stream generators, current state and potential opportunities for condition monitoring

Tidal power industry has made significant progress towards commercialization over the past decade. Significant investments from sector leaders, strong technical progress and positive media coverage have established the credibility of this specific renewable energy source. However, its progress is being retarded by operation and maintenance problems, which results in very low operational availability times, as low as 25 %. This paper presents a literature review of the current state of tidal device operators as well as some commercial tidal turbine condition monitoring solutions. Furthermore, an overview is given of the global tidal activity status (tidal energy market size and geography), the key industry activity and the regulations-standards related with tidal energy industry. Therefore, the main goal of this paper is to provide a bird’s view of the current status of the tidal power industry to serve as a roadmap for the academia regarding the real needs of the tidal power industry

Thermographic non-destructive evaluation for natural fiber-reinforced composite laminates

Natural fibers, including mineral and plant fibers, are increasingly used for polymer composite materials due to their low environmental impact. In this paper, thermographic non-destructive inspection techniques were used to evaluate and characterize basalt, jute/hemp and bagasse fibers composite panels. Different defects were analyzed in terms of impact damage, delaminations and resin abnormalities. Of particular interest, homogeneous particleboards of sugarcane bagasse, a new plant fiber material, were studied. Pulsed phase thermography and principal component thermography were used as the post-processing methods. In addition, ultrasonic C-scan and continuous wave terahertz imaging were also carried out on the mineral fiber laminates for comparative purposes. Finally, an analytical comparison of different methods was give

Application of NDT thermographic imaging of aerospace structures

This work aims to address the effectiveness and challenges of Non-Destructive Testing (NDT) inspection and improve the detection of defects without causing damage to the material or operator. It focuses on two types of NDT methods; pulsed thermography and vibrothermography. The paper also explores the possibility of performing automated aerial inspection using an unmanned aerial vehicle (UAV) provided with a thermographic imaging system. The concept of active thermography is discussed for inspecting aircraft CFRP panels along with the proposal for performing aerial inspection using the UAV for real time inspection. Static NDT results and the further UAV research indicate that the UAV inspection approach could significantly reduce the inspection time, cost, and workload, whilst potentially increasing the probability of detection

Autonomous systems thermographic NDT of composite structures

Transient thermography is a method used successfully in the evaluation of composite materials and aerospace structures. It has the capacity to deliver both qualitative and quantitative results about hidden defects or features in a composite structure. Aircraft must undergo routine maintenance – inspection to check for any critical damage and thus to ensure its safety. This work aims to address the challenge of NDT automated inspection and improve the defects’ detection by suggesting an autonomous thermographic imaging approach using a UAV (Unmanned Aerial Vehicle) active thermographic system. The concept of active thermography is discussed and presented in the inspection of aircraft CFRP panels along with the mission planning for aerial inspection using the UAV for real time inspection. Results indicate that the suggested approach could significantly reduce the inspection time, cost, and workload, whilst potentially increase the probability of detection of defects on aircraft composites

The role of cooperation in rural development

L'apparition tardive et le développement de la coopération en Grècesont liés à l'évolution économique, sociale et politique du pays. Sonretard est dû au sous-développement économique et aux rapports deproduction féodaux qui prévalaient encore dans l’économie agrairebien des décennies après l'Indépendance du pays. C’est seulementaprès l'abolition des rapports féodaux dans l'agriculture, avec ladistribution des terres aux paysans, que naissent les conditionsnécessaires au développement du mouvement coopératif.En dépit de son extension dans l'après-guerre, le mouvementcoopératif présente des retards dans les domaines tant de l'organisa­tion ou du fonctionnement que de l'activité, a cause essentiellementde la législation anachronique sur les coopératives, de l'interventiondes services publics, de l’absence d’aide économique et d'assistance dela part de l’État, de l'absence de capitaux et de formation.Aujourd'hui, surtout avec l'entrée de la Grèce dans le Marché com­mun, la coopération peutjouer un rôle important pour la réorganisa­tion de l'agriculture et sonajustement aux conditions de la CEE, pourla croissance du revenu agricole, pour la réduction du sous-emploi etde l'exode rural, pour le développement culturel au village, pour ledéveloppement général des campagnes.The late emergence and the development of cooperatives in Greeceare linked to the economic social and political evolution of the coun­try. This is owing to the economic under development and the feudalnature of production relations which were still prevailing in theagrarian economy many decades after the country become indepen­dent. The necessary conditions for the cooperative movement to develop only appeared when feudal relations in agriculture were abolished and land was distributed to the peasants.Though it spread in the post-war period, the cooperative move­ment is behind the times both in its organization and functioning, aswell as in its operations, mainly because of the anachronistic legislation on cooperatives, the interventions of public services, the lack ofeconomic help and assistance from the State and the absence ofcapital and training.Especially with' the entry of Greece into the Common Market,cooperatives can play today an important role in helping toreorganize agriculture and adjust it to the EEC requirements, in­crease the agricultural income, reduce under employment and ruraldepopulation. It can also take part in the cultural development ofvillages and the general development of the countryside

Theoretical assessment of different ultrasonic configurations for defects detection in composite components

It is well known that structures’ safety is crucial and of great importance. Part of their maintenance procedure is structural inspection, which is currently performed with the aid of Non Destructive Testing techniques, aiming to detect structural defects in damaged or flawed components and prevent a catastrophic failure by substituting or repairing them. The objective of this work is the theoretical assessment of different ultrasonic configurations that could maximize delamination defect detection in composite components. Modeling study was performed using simulation software, where physical models representative of laminated Carbon Fiber Reinforced Polymer composites, consisting of a variety of artificial delamination defect modes (different sizes and depth), were numerically tested. Different ultrasonic configurations on both the positioning and the firing of the probe's elements including Phased Array delay timings and sampled array techniques were investigated and are presented in this paper. The potential of Full Matrix Capture data acquisition technique, modelled here, along with the post processing Total Focusing Method reconstruction approach is also assessed in terms of their ability to enhance defect detectability and visualization

Thermography methodologies for detecting energy related building defects

Thermography is becoming more widely used amongst construction professionals for energy related defect detection in buildings. Until quite recently, most of the research and practical use of building thermography has centred on employing a building walk-around or walk-through methodology to detect sources of unacceptable energy use. However, thermographers are now creating new building thermography methodologies that seek to address some of the known limitations, such as camera spatial resolution, transient climatic conditions and differences in material properties. Often such limitations are misunderstood and sometimes ignored. This study presents a review of the existing literature, covering both well-established and emerging building thermography methodologies. By critically appraising techniques and observing methodology applications for specific energy related defects, a much clearer picture has been formed that will help thermographic researchers and thermographers to decide upon the best methodology for performing building thermography investigations and for the invention of new approaches. Whilst this paper shows that many of the different passive building thermography methodologies seek to address particular building issues such as defects and energy use, it has also demonstrated a lack of correlation between the different methodology types, where one methodology is often chosen over another for a particular reason, rather than making use of several methodologies to better understand building performance. Therefore this paper has identified the potential for using several passive building thermography methodologies together in a phased approach to building surveying using thermography. For example, a less costly and faster survey could be conducted to quickly identify certain defects before enabling more time consuming and expensive surveys to hone in on these with greater detail and spatial resolution if deemed necessary. © 2014 Elsevier Ltd