902 research outputs found
Folding a 2-D powder diffraction image into a 1-D scan: a new procedure
A new procedure aiming at folding a powder diffraction 2-D into a 1-D scan is
presented. The technique consists of three steps: tracking the beam centre by
means of a Simulated Annealing (SA) of the diffraction rings along the same
axis, detector tilt and rotation determination by a Hankel Lanczos Singular
Value Decomposition (HLSVD) and intensity integration by an adaptive binning
algorithm. The X-ray powder diffraction (XRPD) intensity profile of the
standard NIST Si 640c sample is used to test the performances. Results show the
robustness of the method and its capability of efficiently tagging the pixels
in a 2-D readout system by matching the ideal geometry of the detector to the
real beam-sample-detector frame. The whole technique turns out in a versatile
and user-friendly tool for the scanning of 2-D XRPD profiles.Comment: 11 pages, 1 table, 2 figure
Signal Analysis Algorithms for Optimized Fitting of Nonresonant Laser Induced Thermal Acoustics Damped Sinusoids
This study seeks a numerical algorithm which optimizes frequency precision for the damped sinusoids generated by the nonresonant LITA technique. It compares computed frequencies, frequency errors, and fit errors obtained using five primary signal analysis methods. Using variations on different algorithms within each primary method, results from 73 fits are presented. Best results are obtained using an AutoRegressive method. Compared to previous results using Prony s method, single shot waveform frequencies are reduced approx.0.4% and frequency errors are reduced by a factor of approx.20 at 303K to approx. 0.1%. We explore the advantages of high waveform sample rates and potential for measurements in low density gases
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