The primary aim of this thesis is to fill important voids in the knowledge base regarding the accuracy and performance of fibre optic sensors adhered to the surface and embedded within advanced composite materials. Secondarily, the performance of the structure with embedded fibre optic sensors is also considered, with particular interest in the degradation of host strength and durability due to the embedment of optical fibre sensors. Towards this aim, a comprehensive investigation was conducted, ranging from small-scale materials to large-scale aerospace structures. Several types of fibre optic sensors were attached to structural surfaces and embedded in composites for a variety of configurations with respect to the structural fibre direction of adjacent composite plies. Such configurations were chosen because 1) practical implementation of this technology requires that sensors be embedded at arbitrary angles with respect to reinforcement fibre (i.e strain rosettes) and 2) the dearth of such studies available in the literature. Whatever studies were performed were in conflict in terms of accuracy reported. In addition, there are very few studies in which fibre optic sensors are either attached to the surface or embedded within realistically sized structures. Whenever these studies have been made found, fibre optic sensors have not been comprehensively validated according to a known standard. Fibre Bragg gratings (FBGs) and two types of Extrinsic Fabry Perot Interferometers (EFPI) are evaluated from the coupon level to large scale panels. Key questions identified in the literature are addressed. In general, FBGs are consistently 0-8% higher in magnitude, EFPI sensors from Fiso Technolgies are within 2-3%, and embedded EFPIs from Luna Innovations are ±3% compared with collocated strain gages. One of the most significant findings with this work, is that accurate measurements can be acquired with EFPI sensors embedded at a variety of configurations within composite structures. Overall, fibre optic sensor performance was determined to be a viable technology for a wide variety of structural health monitoring applications. No deleterious effects on the structural performance was observed in any of the tests conducted in this investigation.

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This project investigates the problem of automatically extracting and analysing astronomical spectra from large data sets. The . .. three core problems of spectral classification, physical parameterisation, and searching are examined, and a generalisable set of too established based on the techniques of artificial neural networks (ANNs), X2 minimisation, and principal components analysis (PCA). These tools are then applied to the archives of the Sloan Digital Sky Survey (SDSS) to automatically extract and analyse the spectra of hot subdwarf stars. Spectral classification is tackled by the versatile statisticalmachine learning method of ANNs. An ANN is trained to classify hot subdwarf spectra onto the classification system defined by Drilling (2006), obtaining global errors (arms) of -2 subtypes for spectral type, -1 subclass for luminosity class,' a'nd -4 subclasses for the helium class. These errors are in line with accuracies achieved by human classifiers. Physical parameters are obtained by fitting observations to grids of theoretical models using a X2 minimisation procedure. A new methodology has been developed for managing and indexing large grids of theoretical models in the '1.2 minimisatio.n code, SFIT. Concepts from the field of computational geometry are used to remove several limitations from this code, and pave the way for· its use in a distributed parallel computing environment. Searching for the spectra of a particular type of object in large, unknown data sets is accomplished using the multivariate statistical technique, PCA. The mechanics of this tool are outlined, and its use demonstrated by searching for hot subdwarf spectra in the SDSS. This solution provides a means to reduce unknown data sets to quantities suitable for visual inspection. 282 spectra of hot subdwarf candidates are obtained from the SDSS and analysed. The results evidence several unexplained p~enomena of extended horizontal branch stars, namely; 1) the existence of the second horizontal branch gap of Newell (1973); 2) two sdB nne -Teff sequences; 3) a high-Teff, log g == 5.0 sequence; and 4) a clustering of hot, helium rich stars along this sequence. These findings pose important questions for stellar evolution theory in the realms of the extended horizontal branch.