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Le Touquet – Paris-Plage, France

Walker G.C.,University of Reading | Bowen J.W.,University of Reading | Matthews W.,University of Reading | Roychowdhury S.,University of Reading | And 5 more authors.
Optics Express | Year: 2013

Pulsed terahertz imaging is being developed as a technique to image obscured mural paintings. Due to significant advances in terahertz technology, portable systems are now capable of operating in unregulated environments and this has prompted their use on archaeological excavations. August 2011 saw the first use of pulsed terahertz imaging at the archaeological site of Catalhöyük, Turkey, where mural paintings dating from the Neolithic period are continuously being uncovered by archaeologists. In these particular paintings the paint is applied onto an uneven surface, and then covered by an equally uneven surface. Traditional terahertz data analysis has proven unsuccessful at sub-surface imaging of these paintings due to the effect of these uneven surfaces. For the first time, an image processing technique is presented, based around Gaussian beammode coupling, which enables the visualization of the obscured painting. © 2013 Optical Society of America. Source

Patole-Edoumba E.,C2RMF | Pawlik A.F.,University of the Philippines at Diliman | Mijares A.S.,University of the Philippines at Diliman
Comptes Rendus - Palevol | Year: 2012

During the past ten years, our knowledge of Paleolithic industries in the Philippines has grown thanks to new excavations and discoveries of stone implements, but also thanks to new studies on older collections. The study of knapped stones in the Philippines dates back to the 1920s. At this time, stone tools were used as type fossils to propose an initial chronology of prehistoric cultures. Later, taxonomies and functional analyses were used to assess lithic assemblages until the end of the 1990s. Current functional technology and traceological methods allow us to propose new hypotheses about prehistoric behavior during the Pleistocene, and also technological developments across the archipelago during the Paleolithic. © 2011 Académie des sciences. Source

Serna C.G.,Hubert Curien Laboratory | Pillay R.,C2RMF | Tremeau A.,Hubert Curien Laboratory
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

In this paper we present a semi-automatic 2D-3D local registration pipeline capable of coloring 3D models obtained from 3D scanners by using uncalibrated images. The proposed pipeline exploits the Structure from Motion (SfM) technique in order to reconstruct a sparse representation of the 3D object and obtain the camera parameters from image feature matches. We then coarsely register the reconstructed 3D model to the scanned one through the Scale Iterative Closest Point (SICP) algorithm. SICP provides the global scale, rotation and translation parameters, using minimal manual user intervention. In the final processing stage, a local registration refinement algorithm optimizes the color projection of the aligned photos on the 3D object removing the blurring/ghosting artefacts introduced due to small inaccuracies during the registration. The proposed pipeline is capable of handling real world cases with a range of characteristics from objects with low level geometric features to complex ones. © Springer International Publishing Switzerland 2015. Source

Castillo-Rodriguez M.,University of the Basque Country | Gallardo-Lopez A.,University of Seville | Munoz A.,University of Seville | Castaing J.,C2RMF | And 2 more authors.
Philosophical Magazine | Year: 2013

The influence of dislocation core extension on plastic properties is discussed. Dislocation dissociation has been studied in ceramics. Such investigation has been carried out for the past decades, but in spite of new results, there are still pending questions. Here, we review cases of glide and climb dissociation. The former has been found in 4H-SiC with implications not only on the plasticity but also on the crystal structure changes. The latter has been found in several oxides (sapphire, spinel, strontium titanate, etc.). It is, sometimes, associated with a maximum in the critical resolved shear stress (CRSS) dependence on temperature. We discuss the reasons for such effects, emphasising factors that can reduce the mobility of dislocations to justify why dissociation can influence plasticity and, sometimes, has negligible effects. © 2013 Copyright Taylor and Francis Group, LLC. Source

Walker G.C.,University of Reading | Bowen J.W.,University of Reading | Labaune J.,Ecole Polytechnique - Palaiseau | Jackson J.-B.,Ecole Polytechnique - Palaiseau | And 4 more authors.
Optics Express | Year: 2012

The ability to retrieve information from different layers within a stratified sample using terahertz pulsed reflection imaging and spectroscopy has traditionally been resolution limited by the pulse width available. In this paper, a deconvolution algorithm is presented which circumvents this resolution limit, enabling deep sub-wavelength and sub-pulse width depth resolution. The algorithm is explained through theoretical investigation, and demonstrated by reconstructing signals reflected from boundaries in stratified materials that cannot be resolved directly from the unprocessed time-domain reflection signal. Furthermore, the deconvolution technique has been used to recreate sub-surface images from a stratified sample: imaging the reverse side of a piece of paper. © 2012 Optical Society of America. Source

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