National Repository of Grey Literature 3 records found  Search took 0.00 seconds. 
Analysis of Baroque sculpture based on X-ray fluorescence imaging and X-ray\ncomputed tomography data fusion
Vavřík, Daniel ; Kumpová, Ivana ; Vopálenský, Michal ; Lauterkranc, J.
It is advantageous to combine information about geometry and the inner structure of historical artifacts with information about the elemental composition of decorative layers, typically covering historical wooden sculptures. X-ray computed tomography describing artifact structure is quite common and easy. Standard X-ray fluorescence (XRF) analysis of decorative layers is typically done for several selected spots of the artifact’s surface utilizing single pad detector. XRF imaging fully describing the surface’s elemental composition is commonly done for flat objects, while time consuming XRF tomography is applied to relatively small objects. It will be shown in this work that an effective fusion combination of XRF imaging and X-ray tomography describing the whole object can be realized even when using a limited number of XRF images.
Three-dimensional characterization of polymer foams using X-ray dark-field imaging
Senck, S. ; Plank, B. ; Gusenbauer, C. ; Salaberger, D. ; Vavřík, Daniel ; Santer, W. ; Kastner, J.
Due to the low cost, the ease of processing, and excellent material properties, polymer foams are used in various applications, e.g. packaging, building and construction, furnitures and bedding, and the automotive and aerospace sector. The mechanical response of polymer foams is primarily influenced by density and morphology. While foam density can be determined with high precision, cell morphology is more difficult to determine since the size distribution of foam cells differs in three dimensions. However, using conventional methods, e.g. optical light microscopy or scanning electron microscopy, it is very difficult to obtain three-dimensional information and to differentiate between the strut system and cell walls. An alternative for the three-dimensional characterization of foam morphology is micro-computed tomography (XCT). But even non-destructive techniques like XCT are not able to characterize anisotropic foams if the thickness of single struts and cell walls is below the physcial resolution of the respective XCT system. In this contribution we therefore investigate different polymeric foam samples using a Talbot-Lau grating interferometer XCT (TLGI-XCT) system. We show that the obtained darkfield contrast images show a high contrast and a strong signal at struts and cell walls, facilitating the segmentation of foam cells in various examples.
Optimization of acquisition parameters in radiography and tomography
Vopálenský, Michal ; Vavřík, Daniel ; Kumpová, Ivana
Contrast in radiographic images is one of the most important parameters both in radiography and tomography. This paper investigates the possibility of adjusting the radiographic parameters, in particular the accelerating voltage of the X-ray tube, in order to maximize the difference in the detected intensity in response to the change in the thickness of the investigated object. Simplified model is used that allows finding the optimal operating point for the given material and thickness without an apriory knowledge about the X-ray spectra, detector response and the material composition. It is shown that in case of small changes of thickness, the optimum is met when the detected intensity behind the object of certain thickness is at approx. 37 % of the full range (i.e., of the value that would be measured under the same conditions in the absence of the object). In spite of simplifications made, the theoretical model shows a very good correspondence with the experimental data. A brief consideration is made on the case of a general difference in thicknesses.

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