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This paper presents a case study in the use of ultrasonic NDE/SHM techniques for detecting and locating damage in a real (but small) wind turbine blade.Two techniques are considered: (1) non-linear acoustics, and (2) guided-wave "pitch-catch" SHM. While the non-linear acoustics approach proved disappointingly insensitive to damage induced experimentally in the blade, the guided-wave approach not only detected the damage but also proved capable of locating it, using a "network of novelty detectors" methodology. A first, slightly ill-conceived, programme of guided-wave tests actually provided valuable insight into attenuation of waves in the structure of interest and supported the idea that actuator-sensor networks of a feasible density could be used for wind turbine blade SHM. KEYWORDS guided wave-based SHM, non-linear acoustics, structural health monitoring (SHM), wind turbine blades Strain. 2018;54:e12290.wileyonlinelibrary.com/journal/str of the total electricity costs from a wind turbine. One effective way forward is to reduce the life cycle costs and to extend the life of the wind turbine structure by the application of SHM.The second reason for the choice of structure here relates to a serious issue in the application of ultrasonic wave-based SHM to WT blades. WT blades are very large structures, with current generations of blades approaching 100 m in length. Furthermore, blades are typically manufactured from composite materials, which are known to have high levels of attenuation for ultrasonic waves. Clearly, a limitation of the use of guided-wave SHM is the density of the sensor/actuator network needed; if too high a sensor/actuator density is needed, then ultrasonic SHM is infeasible. This project allowed an investigation into the degree of attenuation experienced by a guided-wave SHM system implemented on a structure manufactured from realistic material.Another difference in the current study was the damage mechanism investigated. In Yang et al., [2,3] single fatigue cracks were initiated and propagated in the glass and composite plates under fairly ideal laboratory fatigue test conditions. In the current study, it was decided to generate the damage via a more realistic mechanism. It is widely accepted that fibre-reinforced polymer-based wind turbine blades are susceptible to low velocity impact damage, e.g., from hail or birdstrike. The low velocity impact often causes internal damage and is usually barely detectable by eye. This damage although small may propagate to more severe damage and eventually cause failure of the structure without warning. The damage in the WT blade of this study was generated using a hammer impact.In summary, this paper presents damage detection on an wind turbine blade exposed to impact, by using modal analysis, non-linear acoustics, and guided-wave SHM. The layout of the paper is as follows. Section 2 presents the results of an experimental modal analysis of the WT blade; this provided useful information in designing the subsequent programme of SHM activity. Section 3 prese...

The foveal cone mosaic can be directly visualized using adaptive optics scanning light ophthalmoscopy (AOSLO). Previous studies in individuals with normal vision report wide variability in the topography of the foveal cone mosaic, especially the value of peak cone density (PCD). While these studies often involve a human grader, there have been no studies examining intergrader reproducibility of foveal cone mosaic metrics. Here we re-analyzed published AOSLO foveal cone images from 44 individuals to assess the relationship between the cone density centroid (CDC) location and the location of PCD. Across 5 graders with variable experience, we found a measurement error of 11.7% in PCD estimates and higher intergrader reproducibility of CDC location compared to PCD location (p < 0.0001). These estimates of measurement error can be used in future studies of the foveal cone mosaic, and our results support use of the CDC location as a more reproducible anchor for cross-modality analyses.

In this study, we aimed at constructing polycaprolactone (PCL) reinforced keratin/bioactive glass composite scaffolds with a double cross-linking network structure for potential bone repair application. Thus, the PCL-keratin-BG composite scaffold was prepared by using keratin extracted from wool as main organic component and bioactive glass (BG) as main inorganic component, through both cross-linking systems, such as the thiol-ene click reaction between abundant sulfhydryl groups of keratin and the unsaturated double bond of 3-methacryloxy propyltrimethoxy silane (MPTS), and the amino-epoxy reaction between amino groups of keratin and the epoxy group in (3-glycidoxymethyl) methyldiethoxysilane (GPTMS) molecule, along with introduction of PCL as a reinforcing agent. The success of the thiol-ene reaction was verified by the FTIR and 1H-NMR analyses. And the structure of keratin-BG and PCL-keratin-BG composite scaffolds were studied and compared by the FTIR and XRD characterization, which indicated the successful preparation of the PCL-keratin-BG composite scaffold. In addition, the SEM observation, and contact angle and water absorption rate measurements demonstrated that the PCL-keratin-BG composite scaffold has interconnected porous structure, appropriate pore size and good hydrophilicity, which is helpful to cell adhesion, differentiation and proliferation. Importantly, compression experiments showed that, when compared with the keratin-BG composite scaffold, the PCL-keratin-BG composite scaffold increased greatly from 0.91 ± 0.06 MPa and 7.25 ± 1.7 MPa to 1.58 ± 0.21 MPa and 14.14 ± 1.95 MPa, respectively, which suggesting the strong reinforcement of polycaprolactone. In addition, the biomineralization experiment and MTT assay indicated that the PCL-keratin-BG scaffold has good mineralization ability and no-cytotoxicity, which can promote cell adhesion, proliferation and growth. Therefore, the results suggested that the PCL-keratin-BG composite scaffold has the potential as a candidate for application in bone regeneration field. Graphical Abstract