Papers by Keyword: X-Ray Imaging

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Authors: Peter J. Wellmann, Z.G. Herro, Sakwe Aloysius Sakwe, Pierre M. Masri, M.V. Bogdanov, S.Yu. Karpov, A.V. Kulik, M.S. Ramm, Yuri N. Makarov
Authors: H.J. Jung, Nathalie Mangelinck-Noël, Henri Nguyen-Thi, Nathalie Bergeon, Bernard Billia, Adeline Buffet, J. Baruchel
Abstract: The columnar to equiaxed transition (CET) has been widely studied for many years [1] because this phenomenon is observed in metallurgical applications like castings. In non refined alloys, detachment of dendrite fragments is the most probable mechanism responsible for the formation of an equiaxed microstructure [1]. In this frame, melt convection influences the grain structure evolution by playing a role in the fragmentation phenomena [2].
Authors: Min Kook Cho, Ho Kyung Kim, Thorsten Graeve, Jung Min Kim
Abstract: In order to develop a cost-effective digital X-ray imaging system, we considered a CMOS (complementary metal-oxide-semiconductor) photodiode array in conjunction with a scintillation screen. Imaging performance was evaluated in terms of MTF (modulation-transfer function), NPS (noise-power spectrum) and DQE (detective quantum efficiency). The presampled MTF was measured using a slanted-slit method. The NPS was determined by 2-dimensional Fourier analysis. Both the measured MTF and NPS, and a self-developed computational model for the X-ray spectral analysis were used to determine the spatial frequency-dependent DQE. From the measured MTF, the spatial resolution was found to be about 10.5 line pairs per millimeter (lp/mm). For a 45-kVp tungsten spectrum, the measured DQE around zero spatial frequency was about 40%.
Authors: Bernd Hasse, Mustafa Koçak, Walter Reimers
Abstract: The non-destructive and phase selective determination of residual stresses caused by material processing (such as welding) in polycrystalline samples is usually performed by diffraction methods. In order to obtain information about stress fields at high spatial resolution with conventional methods, for example with micro beam techniques, the sample needs to be scanned in a very time consuming manner. A much faster method is the simultaneous investigation of a larger area using position sensitive diffractometry. This method was used for the analysis of the residual stress distribution in laser beam welded thin (2 mm and 3 mm) magnesium sheets.
Authors: Sergei Stuchebrov, Dan Verigin, Yelena Lukyanenko, Maria Siniagina, Alexander Wagner
Abstract: In the work digital x-ray apparatus on the basis of the gas-discharge linear detector is considered. X-ray images of laboratory rats are presented. Application prospects of gas-discharge detectors as a solution of the up-to-date radiographic problems are deduced.
Authors: Peter J. Wellmann, Matthias Bickermann, Dieter Hofmann, L. Kadinski, M. Selder, Thomas L. Straubinger, Albrecht Winnacker
Authors: Wolfgang Ludwig, S.F. Nielsen, Henning Friis Poulsen, Daniel Bellet
Authors: Jörn Donges, André Rothkirch, Thomas Wroblewski, Aniouar Bjeoumikhov, Oliver Scharf, Ivan Ordavo, Sebastian Ihle
Abstract: Position resolved structural information from polycrystalline materials is usually obtained via micro beam techniques illuminating only a single spot of the specimen. Multiplexing in reciprocal space is achieved either by the use of an area detector or an energy dispersive device. Alternatively spatial information may be obtained simultaneously from a large part of the sample by using an array of parallel collimators between the sample and a position sensitive detector which suppresses crossfire of radiation scattered at different positions in the sample. With the introduction of an X-ray camera based on an energy resolving area detector (pnCCD) we could combine this with multiplexing in reciprocal space.
Authors: Bernd Hasse, Helene Rahn, Stefan Odenbach, Felix Beckmann, Walter Reimers
Abstract: At the HARWI II beamline at the GKSS outstation at DESY a new experiment for position sensitive diffractometry and tomography called DITO was built and commissioned this year. Due to the available high energy synchrotron radiation with photon energies up to 100 keV it is possible to investigate the bulk of metallic samples of a few mm thickness with both methods. The diffractometry detector allows the investigation of the phase composition as well as phase sensitive determination of residual stresses with a spatial resolution of 6 μm while the tomography detector can either measure a whole tomogram in high resolution mode with a spatial resolution of 2 μm within 3 to 4 hours or in high speed mode recording a whole tomogram within 15 seconds with a spatial resolution of 40 μm.
Authors: Peter J. Wellmann, Dieter Hofmann, L. Kadinski, M. Selder, Thomas L. Straubinger, Albrecht Winnacker
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