560 research outputs found
Design of a self-adjusting antenna feed for a homologous designed tiltable 20m-radio-telescope
Radioteleskope sind verschiedenartigen UmwelteinflĂŒssen ausgesetzt. Dadurch hervorgerufene Verformungen der ReflektoroberflĂ€che verĂ€ndern deren geometrischen Eigenschaften und können die ursprĂŒngliche Position und Form des Brennpunkts verĂ€ndern. Eine Abweichung dieses Brennpunkt von der Lage der PrimĂ€rantenne beeinflusst die LeistungsfĂ€higkeit des Teleskops. Die vorliegende Arbeit zeigt eine Methode zur theoretischen AbschĂ€tzung der Verformung durch das Eigengewicht des Reflektors des INRAS RTâ20. Jene nach der Idee des homologen Designs von Hoerners konstruierten Teleskopen weisen eine StĂŒtzstruktur auf, die die ReflektorflĂ€che unabhĂ€ngig vom Elevationswinkel in einer der ursprĂŒnglichen Form Ă€hnlichen Gestalt halten. Somit kann die Verformung durch das NachfĂŒhren der PrimĂ€rantenne ausgeglichen werden. Grundlage der Untersuchung ist ein vorhandenes Strukturmodell des RTâ20âTeleskops. Zusammen mit den zugehörigen Geometriedaten und Materialparameten wird ein Finite-Element-Modell erstellt. FĂŒr dieses wird ein Belastungsfall mit dem Eigengewicht fĂŒr verschiedene Elevationswinkel simuliert. Um die deformierte ReflektorflĂ€che mathematisch zubeschreiben und den passenden Brennpunkt zu bestimmen wird eine parametrisierte Form eines Best-Fit-Paraboloids erörtert. FĂŒr die Ermittlung der Parameter werden drei Optimierungsalgorithmen in Matlab ausgefĂŒhrt und miteinander verglichen. Daraus wird die Verschiebung des Brennpunkts (Defokussierung) ermittelt und der Bedarf einer Korrekturbewegung fĂŒr die PrimĂ€rantenne abgeschĂ€tzt. In einem Entwurfsprozess werden nach den Ideen der VDI2221âNorm technische Prinzipe fĂŒr ein Aktuierungssystem entwickelt und bezĂŒglich ausgewĂ€hlter Kriterien gegeneinander abgewogen. Als Resultat dieses Bewertungsprozesses wird eines der Prinzipe erwĂ€hlt und spezifiziert. FĂŒr die spĂ€tere Umsetzung werden Komponenten vorgeschlagen, Bauteile vorbereitend konstruiert und in einer CADâSoftware zu einer funktionierenden Baugruppe zusammengefĂŒgt.Radio telescopes are exposed to various environmental conditions. These can produce
deformations of the reflector surface that will have impact on its paraboloidal
characteristics determining the position and shape of the focal point. A misalignment
between the reflector focal point and the radiationâreceiving primary antenna influences
the performance of the telescope. The actual work presents a method to estimate
theoretically the deadâweight induced deformation of the reflector surface for the INRAS
PUCP RTâ20 radio telescope. Such homologous designed telescopes consist of
a backing structure supporting the reflector surface to retain a shape familiar to the
original one and independent of the elevation angle. So it is possible to compensate
the deformation by the adjustment of the primary antenna. The analysis of the deformation
is done for an existing structural model of the RTâ20. This model is meshed
with the corresponding geometrical and material properties. In a finiteâelement software
the load situation due to the telescopeâs dead weight is simulated for different
elevation angles. To describe the deformed reflector surface in a mathematical way
an expression for a parametrized best-fitting paraboloid is derived. To determine the
fit-parameters for the discrete point set, three optimization algorithms are executed
in Matlab and their results compared. Based on this, the need of a re-alignment of
the primary antenna is demonstrated. Thereupon a design process for an actuation
system intended for the corrective movement is performed, following the ideas of the
VDI2221ânorm. Several mechanical concepts are presented and evaluated in relation
to their suitability for the main needs. Based on this assessment, a parallelâkinematic
mechanism is chosen as the most convenient concept. This is examined in more detail,
including a deviation for the inverse kinematics. For this concept, a preliminary
selection of specific components is done and assembled in a CADâprototype.Tesi
FrĂŒhdiagnose lokaler, struktureller SchĂ€den der GelenkoberflĂ€chen humaner Femurkondylen anhand fluoreszenzmikroskopisch-rĂ€umlicher Analysen
Die Diagnose frĂŒher struktureller VerĂ€nderungen im Gelenkknorpel ist nach wie vor ein klinisches Problem. In diesem Kontext ist die Organisation der Chondrozyten als bildbasierter Biomarker zur Feststellung frĂŒher struktureller und/oder degenerativer VerĂ€nderungen prinzipiell geeignet. Dieser Biomarker beruht bisher im Wesentlichen auf einer subjektiven Klassifizierung der Verteilungsmuster der oberflĂ€chennahen Chondrozyten. Mit dieser Arbeit sollten Fragen zur methodischen Weiterentwicklung der Verwendung der rĂ€umlichen Organisation der superfiziellen Chondrozyten als bildbasierter Biomarker beantwortet werden.
Hierzu wurden Proben (n=16) aus der KnorpeloberflĂ€che von humanen Femurcondylen zunĂ€chst makroskopisch-visuell nach SchĂ€digungsgrad klassifiziert und im Anschluss elektronen- und fluoreszenzmikroskopisch aufgearbeitet. Neben der Erfassung weiterer optisch-visueller Scores incl. des rĂ€umlichen Verteilungsmusters der oberflĂ€chlichen Chondrozyten erfolgt auch die Bestimmung von quantitativen Messparametern, wobei durch exakte Ăbereinanderlagerung der REM- und der fluoreszenzmikroskopischen Bilder, ein Vergleich sowohl global ĂŒber die ganze Probe hinweg, wie auch lokal in einzelnen kleinen Ausschnitten innerhalb der Probe zu ermöglicht wurde.
VerĂ€nderungen der rĂ€umlichen Organisation der superfiziellen Chondrozyten waren dabei bereits im visuell-makroskopisch- und rasterelektronenmikroskopisch intakten Knorpelproben zu finden. Eine lokale Betrachtungsweise der Proben schien dabei der globalen ĂŒberlegen. Es konnte ein Panel an quantitativen und qualitativen Messparametern der rĂ€umlichen Organisation superfizieller Chondrozyten bestimmt werden, das gegenĂŒber REM-Untersuchungen verlĂ€sslich dazu geeignet ist, SchĂ€den der KnorpeloberflĂ€che anzuzeigen. Dabei gingen relativ geringe Unterschiede in der Intaktheit der KnorpeloberflĂ€chen in der REM mit prominenten und deutlich diagnostifizierbaren VerĂ€nderungen in der rĂ€umlichen Organisation einher. Proben mit REM intakter KnorpeloberflĂ€che vs. REM-unebener OberflĂ€che mit Fibrillationen konnten durch Untersuchungen der rĂ€umlichen Organisation der superfiziellen Chondrozyten erstmalig statistisch erfolgreich voneinander unterschieden werden.
Damit könnte die visuelle Klassifikation der rĂ€umlichen Organisation der superfiziellen Chondrozyten ein besonders wichtiges Kriterium in der FrĂŒh-Diagnose von osteoarthrotischen VerĂ€nderungen von Gelenken sein, bestenfalls bereits im histologischen OARSI-Stadium I
THE H3/H4 HISTONE GENE CLUSTER OF LAND SNAILS (GASTROPODA: STYLOMMATOPHORA): TS/TV RATIO, GC3 DRIVE AND SIGNALS IN STYLOMMATOPHORAN PHYLOGENY
Histone gene primers were developed for land snails (Stylommatophora). The partial H3/H4 histone gene cluster was cloned and sequenced for 18 species. Transcription of the H3 and H4 genes was divergent (each gene is transcribed in the opposite direction) as has been found for other protostome and diploblast animals, with the exception of Mytilus. In the bivalve Mytilus transcription of both genes occurs in the same direction, i.e. land snails and bivalves seem to differ in their histone gene organization. The non-transcribed H3/H4 spacer varied in length between 279 and 691 basepairs. Nucleotide polymorphisms in this non-transcribed spacer might be of significance to study phylogenetics and systematics of closely related species and genera. As expected, the coding regions exhibited no amino acid substitution among land snail species. However, one amino acid substitution was found in comparison between land snails and Drosophila. The transition/transversion (TS/TV) ratio of H3 and H4 was predominately shaped by the third codon position and ranged in most cases from 1.0 to 2.0, indicating low nucleotide saturation. GC content was calculated for the third codon position (GC3 index at the âwobble' base position). The histone GC3 values were far lower in land snails than values currently available for other genomes (i.e. mammals). This indicates that H3/H4 histone wobble bases of land snails evolve without strong GC drive. Phylogenetic trees were reconstructed from the coding regions. We used Succinea putris (Elasmognatha) as outgroup. Trichia villosa (Helicoidea) showed six apomorphic nucleotide signals. Moreover, the nucleotide signals give evidence that the Cochlicopidae, Vertiginidae and Valloniidae are paraphyletic family categories. The paraphyletic status of cochlicopid, vertiginid and valloniid gastropods is also supported by our unpublished ribosomal DNA tree
A Proof Strategy Language and Proof Script Generation for Isabelle/HOL
We introduce a language, PSL, designed to capture high level proof strategies
in Isabelle/HOL. Given a strategy and a proof obligation, PSL's runtime system
generates and combines various tactics to explore a large search space with low
memory usage. Upon success, PSL generates an efficient proof script, which
bypasses a large part of the proof search. We also present PSL's monadic
interpreter to show that the underlying idea of PSL is transferable to other
ITPs.Comment: This paper has been submitted to CADE2
Is it COVID or a Cold? An Investigation of the Role of Social Presence, Trust, and Persuasiveness for Users\u27 Intention to Comply with COVID-19 Chatbots
The COVID-19 pandemic challenged the existing healthcare system by demanding potential patients to self-diagnose and self-test a potential virus contraction. In this process, some individuals need help and guidance. However, the previous modus-operandi to go to a physician is no longer viable because of the limited capacity and danger of spreading the virus. Hence, digital means had to be developed to help and inform individuals at home, such as conversational agents (CA). The human-like design and perceived social presence of such a CA are central to attaining usersâ compliance. Against this background, we surveyed 174 users of a commercial COVID-19 chatbot to investigate the role of perceived social presence. Our results provide support that the perceived social presence of chatbots leads to higher levels of trust, which are a driver of compliance. In contrast, perceived persuasiveness seems to have no significant effect
Applied Machine Learning: Reconstruction of Spectral Data for the Classification of Oil-Quality Levels
In modern complex systems and machines - e.g., automobiles or construction vehicles - different versions of a "Condition Based Service" (CBS) are deployed for maintenance and supervision. According to the current state of the art, CBS is focusing on monitoring of static factors and rules. In the area of agricultural machines, these are for example operating hours, kilometers driven or the number of engine starts. The decision to substitute hydraulic oil is determined on the basis of the factors listed. A data-driven procedure is proposed instead to leverage the decision-making process. Thus, this paper presents a method to support continuous oil monitoring with the emphasis on artificial intelligence using real-world spectral oil-data. The reconstruction of the spectral data is essential, as a complete spectral analysis for the ultraviolet and visible range is not available. Instead, a possibility of reconstruction by sparse supporting wavelengths through neural networks is proposed and benchmarked by standard interpolation methods. Furthermore, a classification via a feed-forward neural network with the conjunction of Dynamic Time Warping (DTW) algorithm for the production of labeled data was developed. Conclusively, the extent to which changes in hyper-parameters (number of hidden layers, number of neurons, weight initialization) affect the accuracy of the classification results have been investigated
Tragulidae and pecoran ruminants from the latest Middle Miocene (Sarmatian, late Astaracian) of Austria.
One of the richest and most complete European terrestrial vertebrate faunas of late Middle Miocene age (12.2¿12.0 Ma; Gross et al., in press) was found near Gratkorn, at the northeastern realm of the Styrian Basin (Austria). It is one of the rare localities from the Sarmatian sensu stricto (late Serravallian) in the Central Paratethys area with a vertebrate fauna, both high in quality as well as rich in quantity. So far, 62 taxa are recorded, including Euprox furcatus, Micromeryx flourensianus and Dorcatherium naui. This is one of the rare records of Dorcatherium naui older than Vallesian and the oldest finding of the species from the Paratethys realm so far. Up to now, Dorcatherium naui of pre-Vallesian ages have only been described from Przeworno (Poland; Glazek et al., 1971), and Abocador de Can Mata (Spain; Alba et al., 2011), which are of latest Middle Miocene age like Gratkorn. Therefore the latter does not only represent one of the oldest records of Dorcatherium naui but also supports the wide distribution of the taxon already at the latest Middle Miocene. In contrast to the site of Abocador de Can Mata, where Dorcatherium naui is an infrequent element (Alba et al., 2011), the species is abundant at the locality of Gratkorn. Apart from this the larger mammal fauna of Abocadar de Can Mata and Gratkorn is quite similar, except of proboscidean and bovid taxa. While in Abocador de Can Mata Gomphotherium, Deinotherium and bovids are present (Alba et al., 2009), in Gratkorn only Deinotherium giganteum was found until now. Bovids were found in contemporaneous sediments in the eastern Styrian Basin (Gross et al., in press), though. With the material of Gratkorn previous ideas on ecological adaptations in Dorcatherium (Rössner, 2004) are supported and the understanding of the ecological niche of the ¿forest-dweller¿ Dorcatherium is specified. Besides new ideas on dispersal, evolution and ecology of Dorcatherium the locality of Gratkorn also enables an in-depth evaluation of its species separation. The specimens from Gratkorn demonstrate, in comparison with other Material from the Paratethys area, a clear distinction between Dorcatherium crassum and Dorcatherium naui and underline the taxonomic separation of both species as accepted by several authors (e.g. Alba et al., 2011). REFERENCES Alba, D.M. et al. (2009). Middle Miocene vertebrate localities from Abocador de Can Mata (els Hostalets de Pierola, VallÚs PenedÚs Basin, Catalonia, Spain): An update after the 2006-2008 field campaigns. Paleolusitana, 1, 59¿73. Alba, D.M. et al. (2011). Middle Miocene tragulid remains from Abocador de Can Mata: the earliest record of Dorcatherium naui from Western Europe. Geobios, 44, 135-150. Glazek, J. et al. (1971). Miocene vertebrate faunas from Przeworno (Lower Silesia) and their geological setting. Acta Geologica Polonica, 21(3), 473-516. Gross, M. et al. (in press). Gratkorn ¿ A benchmark locality for the continental Sarmatian s. str. of the Central Paratethys. International Journal of Earth Sciences, doi: 10.1007/s00531-010-0615-1. Rössner, G.E. (2004). Community structure and regional patterns in late Early to Middle Miocene Ruminantia of Central Europe. Courier Forschungs-Institut Senckenberg, 249: 91-100.Peer Reviewe
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