Datenbasierte Generierung von situationsbezogenen Entscheidungsregeln für die Kraftwerksführung

Das Fuzzy{ROSA{Verfahren stellt ein Rahmenkonzept zur datenbasierten Generierung von Fuzzy-Systemen dar. Zur weiteren Ausgestaltung dieses Rahmens wird das Verfahren anhand des hoch komplexen Anwendungsproblems der datenbasierten Generierung von Entscheidungsregeln für die Kraftwerksführung erprobt. Es werden situationsbezogene Handlungsvorschläge von Prozessexperten hinsichtlich der Einstellung der Werte von drei ausgewählten Strategieparametern eines Kraftwerksführungssystems zur Verbesserung des Prozessverhaltens modelliert. Es zeigt sich, dass die Handlungsvorschläge bezüglich der Einstellung eines dieser drei Parameter mit dem Fuzzy-ROSA-Verfahren in seiner derzeitigen Form sehr gut modellierbar sind. Bei der Modellierung der Handlungsvorschläge für die anderen beiden Strategieparameter stößt das Verfahren jedoch auf Anwendungsgrenzen, die wesentlich damit zusammenhängen, dass die zugehörigen Daten ausgeprägte Widersprüchlichkeiten aufweisen. Von diesem Ergebnis ausgehend, werden neue methodische Ansätze zur weiteren Ausgestaltung des Fuzzy-ROSA-Verfahrens zur Beherrschung auch sehr widersprüchlicher Daten aufgezeigt

Effects of nonmagnetic disorder on the energy of Yu-Shiba-Rusinov states

We study the sensitivity of Yu-Shiba-Rusinov states, bound states that form around magnetic scatterers in superconductors, to the presence of nonmagnetic disorder in both two and three dimensional systems. We formulate a scattering approach to this problem and reduce the effects of disorder to two contributions: disorder-induced normal reflection and a random phase of the amplitude for Andreev reflection. We find that both of these are small even for moderate amounts of disorder. In the dirty limit in which the disorder- induced mean free path is smaller than the superconducting coherence length, the variance of the energy of the Yu-Shiba-Rusinov state remains small in the ratio of the Fermi wavelength and the mean free path. This effect is more pronounced in three dimensions, where only impurities within a few Fermi wavelengths of the magnetic scatterer contribute. In two dimensions the energy variance is larger by a logarithmic factor because impurities contribute up to a distance of the order of the superconducting coherence length

Proximity-induced gap in nanowires with a thin superconducting shell

Coupling a normal-metal wire to a superconductor induces an excitation gap Δind in the normal metal. In the absence of disorder, the induced excitation gap is strongly suppressed by finite-size effects if the thickness DS of the superconductor is much smaller than the thickness DN of the normal metal and the superconducting coherence length ξ. We show that the presence of disorder, either in the bulk or at the exposed surface of the superconductor, significantly enhances the magnitude of Δind, such that Δind approaches the superconducting gap Δ in the limit of strong disorder. We also discuss the shift of energy bands inside the normal-metal wire as a result of the coupling to the superconducting shell

Rekonstruktionsbasierte Selektion relevanter Einflussgrößen

In diesem Beitrag wird ein Verfahren vorgestellt,das im Rahmen einer Datenvoranalyse für eine nachgeschaltete datenbasierte Modellierung aus einer gegebenen Menge von potenziellen Einflussgrößen einen Satz relevanter und nichtredundanter Einflussgrößen selektiert.Hierdurch wird der Suchraum und somit auch die Komplexität für ein nachgeschaltetes Modellierungsverfahren erheblich reduziert. Im Gegensatz zu den meisten etablierten Selektionsverfahren bewertet das Verfahren nicht nur die Relevanz einzelner Einflussgrößen, sondern auch die von gesamten Sätzen von Einflussgrößen.Die Leistungsfähigkeit des Verfahrens wird an einem Demonstrationsbeispiel verdeutlicht. Des Weiteren wird exemplarisch die Auswirkung dieser Datenvoranalyse auf eine nachgeschaltete Fuzzy-Modellierung von bekannten Benchmarkbeispielen diskutiert

A scattering approach

Spin-polarized normal-metal wires coupled to a superconductor can host Majorana states at their ends. These decay into the bulk and are protected by a minigap in the spectrum. Previous studies have found that strong coupling between the superconductor and the normal-metal wire renormalizes the properties of this low-energy phase. Here, we develop a semiclassical scattering approach to explain these renormalization effects. We show that a renormalization of the propagation velocity in the normal wire originates from double Andreev reflection processes at the superconductor interface and that it continues to exist in the absence of a proximity-induced minigap in the normal-metal wire. We also show that the renormalization effects exist for arbitrary transparency of the normal-metal–superconductor interface, provided the superconductor coherence length is sufficiently long in comparison to the thickness of the normal metal

Powell-Sabin B-splines and unstructured standard T-splines for the solution of the Kirchhoff-Love plate theory exploiting Bézier extraction

The equations that govern Kirchhoff–Love plate theory are solved using quadratic Powell–Sabin B-splines and unstructured standard T-splines. Bézier extraction is exploited to make the formulation computationally efficient. Because quadratic Powell–Sabin B-splines result in inline image-continuous shape functions, they are of sufficiently high continuity to capture Kirchhoff–Love plate theory when cast in a weak form. Unlike non-uniform rational B-splines (NURBS), which are commonly used in isogeometric analysis, Powell–Sabin B-splines do not necessarily capture the geometry exactly. However, the fact that they are defined on triangles instead of on quadrilaterals increases their flexibility in meshing and can make them competitive with respect to NURBS, as no bending strip method for joined NURBS patches is needed. This paper further illustrates how unstructured T-splines can be modified such that they are inline image-continuous around extraordinary points, and that the blending functions fulfil the partition of unity property. The performance of quadratic NURBS, unstructured T-splines, Powell–Sabin B-splines and NURBS-to-NURPS (non-uniform rational Powell–Sabin B-splines, which are obtained by a transformation from a NURBS patch) is compared in a study of a circular plat

Flux penetration in slab shaped Type-I superconductors

We study the problem of flux penetration into type--I superconductors with high demagnetization factor (slab geometry).Assuming that the interface between the normal and superconducting regions is sharp, that flux diffuses rapidly in the normal regions, and that thermal effects are negligible, we analyze the process by which flux invades the sample as the applied field is increased slowly from zero.We find that flux does not penetrate gradually.Rather there is an instability in the process and the flux penetrates from the boundary in a series of bursts, accompanied by the formation of isolated droplets of the normal phase, leading to a multiply connected flux domain structure similar to that seen in experiments.Comment: 4 pages, 2 figures, Fig 2.(b) available upon request from the authors, email - [email protected]

Controlling toughness and strength of FDM 3D-printed PLA components through the raster layup

We investigate the influence of raster layup on the resulting material properties of FDM 3D-printed materials made of PLA. In particular, we investigate the resulting toughness, strength, and stiffness, with a special focus on toughness. We show that for standard layups with layer orientations alternating by 90°, stiffness and strength are almost isotropic, while a strong anisotropy is obtained for toughness. Moreover, we show that materials with such a layup can even switch their behavior from brittle to ductile depending on the loading direction. Finally, we propose a new layer stacking scheme which simultaneously provides increased toughness and increased strength compared to the standard approaches.publishedVersion© 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/)