Simulation-Based Planning of Optimal Conditions for Industrial Computed Tomography

We present a method to optimise conditions for industrial computed tomography (CT). This optimisation is based on a deterministic simulation. Our algorithm finds task-specific CT equipment settings to achieve optimal exposure parameters by means of an STL-model of the specimen and a raytracing method. These parameters are positioning and orientation of the specimen, X-ray tube voltage and prefilter thickness

Методы измерения фазового сдвига с промежуточным преобразованием напряжение-частота

В статті розглянуті методи вимірювання фазового зсуву з проміжним перетворенням напруга-частота. Проаналізовано переваги й недоліки методів. Проведено оцінку похибки, обумовленої неточністю формування часових інтервалів.In article methods of measurement of phase shift with preliminary transformation a voltage-frequency are considered. Their merits and demerits are analyzed. The estimation of the error caused by discrepancy of formation of time intervals is made

Semiclassical theory of surface plasmons in spheroidal clusters

A microscopic theory of linear response based on the Vlasov equation is extended to systems having spheroidal equilibrium shape. The solution of the linearized Vlasov equation, which gives a semiclassical version of the random phase approximation, is studied for electrons moving in a deformed equilibrium mean field. The deformed field has been approximated by a cavity of spheroidal shape, both prolate and oblate. Contrary to spherical systems, there is now a coupling among excitations of different multipolarity induced by the interaction among constituents. Explicit calculations are performed for the dipole response of deformed clusters of different size. In all cases studied here the photoabsorption strength for prolate clusters always displays a typical double-peaked structure. For oblate clusters we find that the high--frequency component of the plasmon doublet can get fragmented in the medium size region ($N \sim 250$). This fragmentation is related to the presence of two kinds of three-dimensional electron orbits in oblate cavities. The possible scaling of our semiclassical equations with the valence electron number and density is investigated.Comment: 23 pages, 8 figures, revised version, includes discussion of scalin

Synchronous artefact reduction in industrial computed tomography

Computertomografie (CT) kann als Messmittel für das dimensionelle Messen genutzt werden. Um aussagekräftige Messergebnisse zu erhalten, ist es notwendig, im Rekonstruktionsvolumen entstehende Artefakte z. B. mit der IAR (Iterative Artefact Reduction) effektiv zu korrigieren. Die hier präsentierte Arbeit stellt mit der EAR eine Korrekturmethode vor, die auf der IAR aufbaut. Mit der EAR ist es möglich, die Korrekturkennlinie schon während der Datenaufnahme und damit deutlich schneller als noch bei der IAR zu erstellen. Die Korrekturmethode EAR benötigt ein CAD-Volumen des zu untersuchenden Bauteiles, welches während der Datenaufnahme registriert werden muss. Für diese Registrierung werden in dieser Arbeit Ähnlichkeitsmaße in Bezug auf ihre Registrierungseigenschaften verglichen

Koordinatenmessung mit industrieller Röntgen-Computertomografie

Industrial computed tomography (CT) has lately experienced a distinct development with respect to the coordinate measuring technique. Numerous measuring tasks can already be solved reasonably and in competition with other measuring techniques. This article describes - by means of a special test body and selected measurands and characteristics - the dimensional measuring properties of industrial CT systems. The possible influence of different physical effects on these dimensional measurands is demonstrated. In addition, a correction method to improve the accuracy of the geometric data determined by CT is presented

Monte Carlo X-ray Scattering Studies in the MeV Regime

A study is shown which is performed to enhance an existing deterministic X-ray simulation method for nondestructive testing applications by including the effect of pair production and annihilation. Therefore, a Monte Carlo simulation tool was used to perform parameter studies. Several materials from polyvinyl chloride to lead and of different lengths were simulated with 109 monoenergetic photons per simulation run. These were used to quantify and evaluate the radial distribution of scattered photons for each length, material and energy as a function of the scattering angle. The results indicate that the radiation originating from the electron-positronannihilation and thus from the pair generation is one major contributor to the total deposited energy only for certain angular ranges whereas for other angles Compton is by far the leading scattering effect. Furthermore, the results indicate that the electron-positron-annihilation radiation is negligible for most imaging tasks and thus unimportant for deterministic scattering simulations