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Decoration with Pd clusters increases the magnetic heating ability of cobalt ferrite (CFO) nanoparticles by a factor of two. The origin of this previous finding is unraveled by element-specific X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) combined with atomic multiplet simulations and density functional theory (DFT) calculations. While the comparison of XAS spectra with atomic multiplet simulations show that the inversion degree is not affected by Pd decoration and, thus, can be excluded as a reason for the improved heating performance, XMCD reveals two interrelated responsible sources: significantly larger Fe and Co magnetic moments verify an increased total magnetization which enhances the magnetic heating ability. This is accompanied by a remarkable change in the field-dependent magnetization particularly for Co ions which exhibit an increased low-field susceptibility and a reduced spin canting behavior in higher magnetic fields. Using DFT calculations, these findings are explained by reduced superexchange between ions on octahedral lattice sites via oxygen in close vicinity of Pd, which reinforces the dominating antiparallel superexchange interaction between ions on octahedral and tetrahedral lattice sites and thus reduces spin canting. The influence of the delocalized nature of Pd 4d electrons on the neighboring ions is discussed and the conclusions are illustrated with spin density isosurfaces of the involved ions. The presented results pave the way to design nanohybrids with tailored electronic structure and magnetic properties.
To segment complex and versatile image data from different modalities it is almost impossible to achieve satisfying results without the consideration of contextual information. In this approach, image segmentation is regarded as a high- dimensional optimization task, that can be solved by stochastical methods like evolutionary algorithms (EA). Initially, the iterative algorithm is provided with a set of good-quality sample segmentations. An efficient EA-based learning strategy generates a segmentation for a given target image from the provided samples. This two-level process consists of a global image-based optimization whose convergence is enhanced by locally operating pixel-based Boltzmann processes which restrict the search space to reasonable subsets. The stochastic reconstruction extracts the relevant information from the samples in order to adapt it onto the current segmentation problem, which results in a consistent labeling for the target image. The algorithm works unsupervised, because the range of possible labels and their contextual interpretation is provided implicitly by the sample segmentations. To prove the usefulness of the method experimental results based on both, reproducible phantom images and physiological NMR scans are presented. Moreover, an analysis of the basic segmentation and convergence properties is provided.
Es wird erläutert, warum man mit der Finite-Element-Methode (FEM) das elektrostatische Problem mit Grenzflächen und darauf befindlichen Flächenladungen prinzipiell nicht lösen kann. Es werden dann Verfahren entwickelt, dies näherungsweise zu tun. Anschließend wird eine Methode entwickelt, die es gestattet, aus den so erhaltenen Lösungen näherungsweise konsistent auf die Ausgangsgleichungen zurückzurechnen und so den Driftterm der Kontinuitätsgleichung für die hydrodynamische Modellierung einer Gasentladung zu ermitteln.
Nanocomposite films consisting of gold inclusions in the polytetrafluoroethylene (PTFE) matrix were obtained by thermal vacuum deposition. Annealing of the obtained films with different temperatures was used to measure varying of film morphologies. The dependence of optical properties of the films on their morphology was studied. It was established that absorption and profile of the nanocomposite film obtained by thermal vacuum deposition can be changed with annealing owing to the fact that different annealing temperatures lead to different average particle sizes. A method to calculate the optical properties of nanocomposite thin films with inclusions of different sizes was proposed. Thus, comparison of experimental optical spectra with the spectra obtained during the simulation enables estimating average sizes of inclusions. The calculations give the possibility of understanding morphological changes in the structures.
Why does Planck (1900), referring to Boltzmann’s 1877 probabilistic treatment, obtain his quantum distribution function while Boltzmann did not? To answer this question, both treatments are compared on the basis of Boltzmann’s 1868 three-level scheme (configuration—occupation—occupancy). Some calculations by Planck (1900, 1901, and 1913) and Einstein (1907) are also sketched. For obtaining a quantum distribution, it is crucial to stick with a discrete energy spectrum and to make the limit transitions to infinity at the right place. For correct state counting, the concept of interchangeability of particles is superior to that of indistinguishability.
Since in-depth sensing indentation load–depth data of the entire loading–unloading cycle are available, more information than a single hardness value and an elastic modulus can be extracted from the experimental data. The conventional hardness H (h) = F (h)/Ac(h) and the differential hardness Hd(h)=dF/dAc are calculated as continuous functions of depth h and compared to each other in this paper (F: load, Ac: contact area). It turns out that Hd describes the momentary material resistance to deformation, whereas H integrates over deformation states from first tip–sample contact to current penetration h. This difference is particularly important for materials not homogeneous in depth (e.g. layer systems), and for situations where time-dependent external factors influence the momentary deformation resistance. Photoplasticity is considered as an example for the latter.
Integrated photonic devices have gained increasing research interests. Especially silicon photonics have become very attractive for various optical applications. Using silicon-on-insulator as a material platform provides the ability to fabricate photonic devices with electronic devices on a single chip. Driven by substantial research investments, the integration of photonic devices on silicon-on-insulator substrates has reached a degree of maturity that already permits industrial adoption. However, silicon has the disadvantage of linear electro-optical effects, and, therefore, advanced modulation formats are difficult to realize when using silicon-based high-speed modulators. Hence, a new approach was proposed: the silicon-organic hybrid technology. This technology is a viable extension of the silicon-on-insulator material system for efficient high-speed modulation. We herewith present our theoretical and experimental investigations of the silicon-organic hybrid slot-waveguide ring resonator. The advanced device design is described in detail, which allows using both, the efficient silicon-on-insulator strip-waveguides and the silicon-organic hybrid slot-waveguides in single ring resonator. For the first time, we report the transmission spectra of such a resonator covered with an electro-optical polymer.
Die CFD (Computational Fluid Dynamics)-Simulation hat mittlerweile in alle technischen Bereiche Einzug gehalten, in denen die Vorhersage strömungstechnischer Ereignisse relevant ist. Nach wie vor ist allerdings eine Validierung von Rechenergebnissen mit Messdaten unerlässlich, um zu vertrauenswürdigen Simulationsergebnissen zu kommen. Dies ist u. a. darauf zurückzuführen, dass die am Markt verfügbare CFD-Software darauf ausgerichtet ist, ein möglichst breites Anwendungsspektrum zu bedienen. Die implementierten Berechnungsmodelle müssen im Rahmen der Modellierung durch die Wahl geeigneter Randbedingungen an den zu untersuchenden Anwendungsfall angepasst werden.
Das ProInno-Projekt „Feinschleifen von Saphir“ (www.tfhwildau.de/mmueck) beschäftigt sich mit der Weiterentwicklung eines Verbundwerkstoffes für den Feinschleifprozess. Bei diesem Verbundwerkstoff handelt es sich um Diamantkörner, die in einer Kupfer-Zinn-Matrix eingebettet sind. In dem Projekt werden die Wirkungsmechanismen des neuartigen Verbundmaterials genauer untersucht. Mit diesen Erkenntnissen erfolgt eine Optimierung der einzelnen Komponenten und des Mischungsverhältnisses auf praxisbezogene Eigenschaften des Werkstoffes. Es ist geplant, hieraus ein marktfähiges Produkt zur Oberfl ächenbearbeitung harter Materialien zu entwickeln.
In diesem Artikel werden einige Elemente der Entwicklung eines Drucksensors auf der Basis eines neuen, zum Patent angemeldeten, optischen Prinzips dargestellt. Ausgangspunkt für die Entwicklung war die Forderung eines Medizingeräteherstellers nach einer Druckmessung in hochaggressiven Substanzen. Die Messung sollte vorzugsweise an einer leicht zu reinigenden Kunststoffmembran ohne Kavitäten erfolgen. Hinzu kam die Forderung nach Beständigkeit gegen hohe Medientemperaturen. Durchgeführte Recherchen und Untersuchungen gemeinsam mit Partnern ergaben theoretische Ansätze zur Gestaltung der Anordnung und ihrer Umsetzung in drei Hauptbaugruppen. Umfangreiche Entwicklungsarbeiten und Versuche bestätigten die Richtigkeit der Ansätze. Das Funktionsprinzip konnte nachgewiesen werden. Bevor im Einzelnen auf die Neuentwicklung Bezug genommen wird, soll kurz der Stand der Technik im Bereich Druckmessung/Drucksensorik dargestellt werden.