Intelligent Sensors and Signals
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Dieses Buch vermittelt sowohl Studenten, als auch Planern und Betreibern in Industrie und Wissenschaft das nötige umfangreiche Wissen, um Messungen an Motorenprüfständen durchführen zu können. Messtechnik und Prüfstände für Verbrennungsmotoren helfen, Kraftstoff einzusparen, Treibhausgase und Schadstoffe zu reduzieren, mit kleineren Motoren mehr Leistung abzugeben sowie Komponenten und Betriebsstoffe zu optimieren. Mit den Motoren und der Abgasgesetzgebung entwickelt sich auch die für die Entwicklung erforderliche mechanische, thermodynamische und Abgasmesstechnik weiter.
A wavelet-based sparse row-action method for image reconstruction in magnetic particle imaging
(2021)
Purpose
Magnetic particle imaging (MPI) is a preclinical imaging technique capable of visualizing the spatio-temporal distribution of magnetic nanoparticles. The image reconstruction of this fast and dynamic process relies on efficiently solving an ill-posed inverse problem. Current approaches to reconstruct the tracer concentration from its measurements are either adapted to image characteristics of MPI but suffer from higher computational complexity and slower convergence or are fast but lack in the image quality of the reconstructed images.
Methods
In this work we propose a novel MPI reconstruction method to combine the advantages of both approaches into a single algorithm. The underlying sparsity prior is based on an undecimated wavelet transform and is integrated into a fast row-action framework to solve the corresponding MPI minimization problem.
Results
Its performance is numerically evaluated against a classical FISTA (Fast Iterative Shrinkage-Thresholding Algorithm) approach on simulated and real MPI data. The experimental results show that the proposed method increases image quality with significantly reduced computation times.
Conclusions
In comparison to state-of-the-art MPI reconstruction methods, our approach shows better reconstruction results and at the same time accelerates the convergence rate of the underlying row-action algorithm.
Das Buch vermittelt die Grundlagen, um die Besonderheiten der Elektronik und Software im Kfz nicht nur zu kennen, sondern auch zu verstehen. Zusätzlich wird an Beispielen die Komplexität realer Systeme im Fahrzeug vorgeführt und gezeigt, welche Anwendungen durch die Elektronik erst möglich werden. Das Spannungsfeld zwischen Sicherheit, Zuverlässigkeit und Komplexität prägt in Verbindung mit branchenüblichen Abläufen das Vorgehen bei der Entwicklung, das ein in diesem Bereich tätiger Ingenieur verstehen muss.
Poster
We report on a comprehensive micromachining study of rotationally symmetric parts using femtosecond laser. A
laser turning process with tangential impingement of the laser radiation complemented by a trepanning optics is
implemented as to accomplish a true laser lathe micromachining approach. With the objective of optimized
ablation rate and reduced surface roughness, the influence of pulse energy, feed rate, trepanning diameter and
angular beam incidence, respectively, is investigated for processing stellite rods. We find the smallest feasible
feature sizes of 8.5 μm in diameter and smoothest surfaces with an arithmetic average of the roughness profile as
low as 0.18 μm. The surface roughness, however, appears to be limited by the occurrence of laser induced periodic
surface structures provoked by the femtosecond laser radiation. Furthermore, the variation of the fluence
in accordance to the incidence on a curved surface is discussed and the heat input into the material is examined
through a longitudinal cross section.
Laser turning with ultra-short laser pulses provides the possibility of manufacturing rotationally symmetric geometries, even of hard to machine materials as fused silica, down to a micrometer scale. In this laser micro machining approach, the laser beam is oriented perpendicularly to the rotational axis and tangentially to the material, whereas the target geometry is realized by moving the constantly rotating specimen according to the specified geometry under the focused laser spot. Due to the fric-tion-less laser ablation it is possible to realize a turning process in fused silica without the use of a contacting tool and therefore without causing mechanical tensions in the work piece. The processing head focuses the laser to a calculated spot size of 18 μm in diameter and the applied processing gas pressure assists in removing the ablated material. In this study, femto-second laser turning of fused silica with a diameter of 3.7 mm is investigated. The influence of the applied pulse energy is stated and the use of a trepanning optic during the turning process is characterized. Furthermore, compre-hensive parameter studies in order to optimize roughness and to find the maximum achievable abla-tion rate are shown. Limited by the mechanical speed of the rotational axis, the highest feasible abla-tion rate is 19.5 mm³/min. A roughness of Ra 0.65 μm are demonstrated.
