60 Technik
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A new iterative matrix algorithm has been applied to improve the precision of temperature and force decoupling in multi-parameter FBG sensing. For the first time, this evaluation technique allows the integration of nonlinearities in the sensor’s temperature characteristic and the temperature dependence of the sensor’s force sensitivity. Applied to a sensor cable consisting of two FBGs in fibers with 80 μm and 125 μm cladding diameter installed in a 7 m-long coiled PEEK capillary, this technique significantly reduced the uncertainties in friction-compensated temperature measurements. In the presence of high friction-induced forces of up to 1.6 N the uncertainties in temperature evaluation were reduced from several degrees Celsius if using a standard linear matrix approach to less than 0.5°C if using the iterative matrix approach in an extended temperature range between −35°C and 125°C.
Die operationelle Transferpfadanalyse (oTPA) bietet die Möglichkeit subjektive Fahrkomforteindrücke zu objektivieren. Hierbei werden die einzelnen Vibrationspfade im Bereich des primary ride und secondary ride comfort ermittelt. Hierfür muss ein geeigneter Messaufbau gewählt werden, bei dem alle Vibrationsquellen des Fahrwerks, des Aggregats sowie die Immissionsorte des Karosserieaufbaus (Sitze) mit Schwingungsaufnehmern versehen werden. Die Fahrkomfortmes-sungen werden im realen Betrieb auf verschiedenen Fahrbahnuntergründen durchgeführt. Die Ergebnisse helfen den Schwingungsbeitrag der einzelnen Quellen auf die Vibration am Fahrersitz zu quantifizieren. Ferner können Fahrzeuge objektiv bezüglich Fahrkomfort relevanter Kriterien miteinander verglichen werden.
The thesis aimed to clarify whether there are differences in the technical acceptance of students from Germany and Japan. If applicable, the thesis pointed out possible reasons for differences. To achieve this, it was necessary to conduct research in existing literature. A literature review also led to a model capable of observing the level of technical acceptance and factors connected to acceptance. While the effectivity of the model could not be completely confirmed, it became the basis for an online survey. The survey was distributed to students in Germany (mainly Munich) and Japan (mainly Tokyo) and accessible for about three weeks. The survey investigated the stance of the students towards the topics virtual reality, robotics and alternative means of payment. No strong, general correlation between the nationality of the students and their rate of technical acceptance was found. The results indicated differences for some items of robotics and alternative means of payment, but due to a small number of participants, the significance of the indications is low and requires a more thorough investigation on a bigger scale.
MEMS microphones must be further miniaturized for use in mobile devices. So we developed packaging technologies for MEMS microphones using flip chip technology instead of wire bonding. The first two generations have the sound hole in a ceramic interposer at the bottom side of the package. Now a new flip chip microphone package with the sound hole on the top side has been developed. The new package technology combines a large acoustic reference volume for good signal to noise ratio with small size. Compared to other microphone packages the sensitivity is improved by 3 dB. The front volume is small to avoid resonances in the acoustic frequency range.
Videobasierte Anleitungen in Form von How-To-Videos werden immer beliebter. Der Wunsch, sich audiovisuell über sein Produkt zu informieren, steigt stetig (vgl. Bitkom 2017, 27). Um diesen Umstand darzulegen, befasst sich diese Arbeit mit dem internen und externen Nutzen solcher Anleitungen für BMW Motorrad. Ziel ist es ein Konzept zur Erstellung von videobasierten Anleitungen anzufertigen. Zunächst wird anhand didaktischer Kriterien eine Checkliste erstellt. Durch diese ist es möglich, eine konsistente videobasierte Anleitung für die Veröffentlichung auf Youtube zu produzieren. Zur Überprüfung ob videobasierte Anleitungen einen Mehrwert aufweisen, werden sowohl Videos auf Youtube, als auch Handlungsanweisungen in der Betriebsanleitung von BMW Motorrad analysiert. Die Analyse erfolgt anhand eines Kriterienkatalogs. Da dieser sowohl qualitative als auch quantitative Aspekte umfasst wird auf die qualitative Inhaltsanalyse nach Mayring zurückgegriffen. Mithilfe dieser gewonnen Daten, werden Handlungsempfehlungen zur Erstellung von videobasierten Anleitungen für BMW Motorrad ausgesprochen. Diese Arbeit richtet sich an Technische Redakteure und Kommunikationswissenschaftler.
The AEgIS collaboration (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) at CERN has assigned itself the goal of directly measuring Earth's gravitational force on antimatter with a precision of 1% for the first time. Neutral antihydrogen atoms enable this measurement and are produced using the highly efficient charge exchange reaction of cold antiproton plasma with laser excited Rydberg-positronium. These atoms are then transported by Stark-acceleration towards a Moiré deflectometer which detects the displacement of the antihydrogen beam caused by gravity.
This Master's thesis is based on AEgIS' goal and focuses on the positron system which is an essential component of the overall experiment. Two main objectives are dealt with. Firstly, the systematical optimization of the positron apparatus consisting of a source, two Surko-type buffer gas Penning-Malmberg traps with rotating walls and a transfer line to the AEgIS antihydrogen apparatus or to a test chamber for sample examination. Secondly, two positron/positronium converter targets are investigated for the first time at AEGIS using single-shot positron annihilation lifetime spectroscopy. Regarding the first objective, a large enhancement of the total positron yield (ten times higher) is achieved which results in a higher positronium output and thus satisfies the needs of a high antihydrogen yield. This is realized by applying horizontal and vertical magnetic correction fields in one of the traps; optimizing the frequency and amplitude of the rotating wall; shielding critical parts with µ-metal sheets from environmental magnetic fields and by adjusting the potentials in the traps and the transfer line. After this, a positron bunch with 20 ns time-spread containing up to 5.7 · 107 positrons within a reasonable accumulation time of ten minutes can be provided for further measurements. The two investigated converter targets for the positronium production are an aerogel target from NASA and a nanochannel converter produced by the University of Trento. The annihilation radiation of the incident positron bunch is detected with a PbF2- Cherenkov detector which shows a slow decreasing signal for tens of nanoseconds for both targets which proves the emission of positronium. The nanochannel converter is slightly more effective and has a positronium lifetime of (90 ± 2) ns, whereas the yield with the aerogel target is smaller and only a lifetime of (59 ± 2) ns is found. These results indicate that the nanochannel converter is best suited for AEgIS but also that additional and more precise measurements will help to improve the positronium yield in the future.
Designing mechanical structures exposed to random vibration loading compromises the central challenges of defining comprehensive load assumptions and of processing these efficiently in a fatigue assessment. For this matter of statistical load description, frequency-domain methods withhold major advantages. They describe random vibration loading by its power spectral density, which allows drastic data reduction, to conduct efficient response analyses and to derive a statistical description of resulting load spectra. Nevertheless, this procedure is limited to stationary Gaussian loading. Thus, this paper proposes an extension of the frequency-domain approach to a special class of non-stationary loading – amplitude-modulated processes. These consist of a unique vibration state that varies in intensity, which is represented by a modulating signal. This paper develops a methodology to test for amplitude-modulated processes, to derive efficient measures for the intensity variation and to include this behavior in a fatigue assessment carried out in frequency-domain. The full methodology is presented via a set of simulated data.
Enthält
Vortrag 1: Generic loss minimization in synchronous machines / Christoph Hackl
Vortrag 2: Smooth transition between optimal operation strategies considering iron losses / Niklas Monzen
Vortrag 3: Generische Maschinenidentifikation und effizienzoptimierte Momentensteuerung für Asynchronmaschinen (in englischer Sprache) / Julian Kullick
Vortrag 4: Optimized pulse patterns for the control of a 2-Level VSI feeding a PMSM with high magnetic anisotropy / Athina Birda
Vortrag 5: Open Loop Control with Analytic Equations for High Power DC-DC Converters in Design and Operation / Daniel Goldmann
In forest ecology, a snag refers to a standing, partly or completely dead tree, often missing a top or most of the smaller branches. The accurate estimation of live and dead biomass in forested ecosystems is important for studies of carbon dynamics, biodiversity, and forest management. Therefore, an understanding of its availability and spatial distribution is required. So far, LiDAR remote sensing has been successfully used to assess live trees and their biomass, but studies focusing on dead trees are rare. The paper develops a methodology for retrieving individual dead trees in a mixed mountain forest using features that are derived from small-footprint airborne full waveform LIDAR data. First, 3D coordinates of the laser beam reflections, the pulse intensity and width are extracted by waveform decomposition. Secondly, 3D single trees are detected by an integrated approach, which delineates both dominate tree crowns and understory small trees in the canopy height model (CHM) using the watershed algorithm followed by applying normalized cuts segmentation to merged watershed areas. Thus, single trees can be obtained as 3D point segments associated with waveform-specific features per point. Furthermore, the tree segments are delivered to feature definition process to derive geometric and reflectional features at single tree level, e.g. volume and maximal diameter of crown, mean intensity, gap fraction, etc. Finally, the spanned feature space for the tree segments is forwarded to a binary classifier using support vector machine (SVM) in order to discriminate dead trees from the living ones. The methodology is applied to datasets that have been captured with the Riegl LMSQ560 laser scanner at a point density of 25 points/m2 in the Bavarian Forest National Park, Germany, respectively under leaf-on and leaf-off conditions for Norway spruces, European beeches and Sycamore maples. The classification experiments lead in the best case to an overall accuracy of 73% in a leaf-on situation and 71% in a leaf-off situation, if we assess the classification results using 5-fold cross-validation method with the help of reference data acquired by the field surveying.
In this paper, we present an integrated strategy to comprehensively evaluate the feature relevance of point cloud and image data for classification of trees and vehicles in urban scenes. First of all, point cloud and image data are co-registered by backprojection with available orientation parameters if necessary. After that, all data points are grid-fitted into the raster format in order to facilitate acquiring spatial context information per pixel/point. Then, various spatial-statistical and radiometric features can be extracted using a cylindrical volume neighborhood. Classification results as labeled pixels can be acquired from the classifier, and after appropriate refinements we obtain the objects of trees and vehicles. Compared to other methods which have assessed the classification and relevance simultaneously using a single classifier, we first introduce AdaBoost classifier combined with contribution ratio to provide both classification results and measures of feature relevance, and then utilize Random Forest classifier to evaluate and compare the feature relevance from a more independent viewpoint. In order to confirm the accuracy and reliability of classification and feature relevance results, we consider not only characteristics of the classifiers itself, but also errors of data co-registration and alterable parameters. We apply the procedure to two different datasets. In the dataset requiring co-registration a-priori, the AdaBoost classifier even achieves a great accuracy of 96.99% for trees and 83.45% for vehicles. The quantitative results of feature relevance assessment highlight the most important features for classification of tree covers and vehicles, such as NDVI, LiDAR intensity, planarity and entropy. By comparative analysis of the two independent approaches, the reliable and consistent feature selection for classification of trees and vehicles from LiDAR and image data could be validated and achieved, being unrelated to the classifiers.