Compressive properties of pristine and SiC-Te-added MgB2 powders,green compacts and spark-plasma-sintered bulks

Pristine and (SiC+Te)-added MgB₂ powders, green and spark plasma sintered (SPS) compacts were investigated from the viewpoint of quasi-static and dynamic (Split-Hopkinson Pressure Bar, SHPB) compressive mechanical properties The amount of the additive (SiC+Te) was selected to be the optimum one for maximization of the superconducting functional parameters. Pristine and added MgB₂ show very similar compressive parameters (tan δ, fracture strength, Vickers hardness, others) and fragment size in the SHPB test. However, for the bulk SPSed samples the ratio of intergranular to transgranular fracturing changes, the first one being stronger in the added sample. This is reflected in the quasi-static K_IC that is higher for the added sample. Despite this result, sintered samples are brittle and have roughly similar fragmentation behavior as for brittle engineering ceramics. In the fragmentation process, the composite nature of our samples should be considered with a special focus on MgB₂ blocks (colonies) that show the major contribution to fracturing. The Glenn-Chudnovsky model of fracturing under dynamic load provides the closest values to our experimental fragment size data.     

Tree-Based Concurrency Control in Distributed Groupware

We present a novel algorithm, called dARB, forsolving the concurrency control problem indistributed collaborative applications. Themain issue of concurrency control is resolvingthe conflicts resulting from simultaneousactions of multiple users. The algorithmreduces the need for manual conflict resolutionby using a distributed arbitration scheme. Themain advantages of our approach are thesimplicity of use and good responsiveness, asthere are no lock mechanisms. Our algorithmrequires the applications to use a tree as theinternal data structure. This makes itapplication independent and suitable forgeneral collaborative applications. The treerequirement is reasonable since many newapplications use XML (extensible MarkupLanguage) for data representation and exchange,and parsing XML documents results in treestructures. Example applications of thealgorithm, a group text editor and acollaborative 3D virtual environment calledcWorld, are implemented and evaluated in theDISCIPLE collaboration framework. We alsointroduce awareness widgets that users avoidgenerating the conflicting events and help inmanual conflict resolution.     

Greedily computing associative aggregations on sliding windows

We present an algorithm for combining the elements of subsequences of a sequence with an associative operator. The subsequences are given by a sliding window of varying size. Our algorithm is greedy and computes the result with the minimal number of operator applications.     

Laser-Printed Plasmonic Metasurface Supporting Bound States in the Continuum Enhances and Shapes Infrared Spontaneous Emission of Coupled HgTe Quantum Dots

In order to advance the development of quantum emitter-based devices, it is essential to enhance light-matter interactions through coupling between semiconductor quantum dots with high quality factor resonators. Here, efficient tuning of the emission properties of HgTe quantum dots in the infrared spectral region is demonstrated by coupling them to a plasmonic metasurface that supports bound states in the continuum. The plasmonic metasurface, composed of an array of gold nanobumps, is fabricated using single-step direct laser printing, opening up new opportunities for creating exclusive 3D plasmonic nanostructures and advanced photonic devices in the infrared region. A 12-fold enhancement of the photoluminescence in the 900–1700 nm range is observed under optimal coupling conditions. By tuning the geometry of the plasmonic arrays, controllable shaping of the emission spectra is achieved, selectively enhancing specific wavelength ranges across the emission spectrum. The observed enhancement and shaping of the emission are attributed to the Purcell effect, as corroborated by systematic measurements of radiative lifetimes and optical simulations based on the numerical solution of Maxwell's equations. Moreover, coupling of the HgTe photoluminescence to high quality factor modes of the metasurface improves emission directivity, concentrating output within an ≈20° angle.     

Towards a neighborhood simplification of tile systems: From Moore to quasi-linear dependencies

Self-assembly is the process by which objects aggregate independently and form complex structures. One of the theoretical frameworks in which the process of self-assembly can be embedded and formally studied is that of tile systems. A Wang tile is a square unit, with glues on its edges, attaching to other tiles which have matching glues, and forming larger and larger structures. In this paper we concentrate over two basic, but essential, self-assembling structures done by Wang tiles. The first one, called ribbon, is a non-self-crossing wire-like structure, in which successive tiles are adjacent along an edge, and where tiles are glued to their predecessor and successor by use of matching glues. The second one, called zipper, is a similar contiguous structure, only that here, all touching tiles must have matching glues on their abutting edges, independently of their position in the structure. In case of Wang tiles, it has been shown that these two structures are equivalent. Here we generalize this result for the case when the tiles have eight glues, four on their edges and four on their corners. Thus we show that an eight neighborhood dependency, namely the Moore neighborhood, can be simulated by a quasi-linear dependency.     

Modeling the effect of node synchronization times in ultra-wideband wireless networks

Ultra-wideband wireless (UWB) can provide the physical layer for high-throughput personal area networks. When UWB is used for communication between many nodes, relatively long acquisition times are needed when dropping and re-establishing wireless links between the nodes. This paper describes the development and use of mathematical and simulation models to investigate the impact of dropping and reacquiring links between nodes on average packet delay; we also consider the performance of the alternative strategy of forwarding packets through intermediate nodes without breaking the established wireless links. The work presented here assumes that no specific MAC layer protocol, such as WiMedia UWB MAC, is in operation. The paper describes the models, explains the selection of modeling parameters used, compares the average packet delay for a network of three simple UWB nodes and for a ring of ten UWB nodes and explains the use of these results for network design engineers.     

Die mikroskopische Untersuchung von Fleisch- und Wurstwaren

Zusammenfassung Die Ergebnisse der chemischen Untersuchung von Fleisch- und Wurstwaren sind als ausschließliche Grundlage für ihre Beurteilung durchaus ungenügend; denn wir können noch nicht annähernd sämtliche chemischen Einzelbestandteile des Fleisches und der Wurstwaren mittels der im praktischen Laboratorium anwend aren Methoden nachweisen und noch viel weniger diese Einzelbestandteile quantitativ ermitteln. Es läßt sich aber auch im allgemeinen durch die chemische Untersuchung allein nicht feststellen, ob eine unter bestimmten Namen in den Handel gebrachte Ware die in diesem Namen zum Ausdruck gebrachten Fleischbestandteile tatsächlich enthält, wie z. B., ob Leberwurst Leber enthält, ferner ob minderwertige oder verbotene Organund Gewebeteile beigemischt sind oder nicht.Daher ist die mikroskopische Untersuchung, besonders in gerichtlichen Fällen, unerläßlich.Die nur auf mikroskopischem Wege erreichbare Kenntnis der in Fleisch und Wurstwaren enthaltenen Gewebe und Organe erleichtert bezw. ermöglicht die Beurteilung von Fleisch- und Wurstwaren nicht nur in vorgenannter Richtung, sondern sie erleichtert auch sehr wesentlich die Beurteilung ihres Gesamtwertes. Dieser ist verschieden je nach dem Vorhandensein der mikroskopisch nachzuweisenden Gewebe bezw. Organe und nach deren Wassergehalt. Letzterer wiederum ist z. B. bei Muskelfleisch konstanter und liegt in engeren Grenzen als bei den drüsigen Organen; im elastischen Bindegewebe ist er bedeutend niedriger als im kollagenen Bindegewebe oder im Muskelfleisch.In der vorliegenden Arbeit ist der Versuch gemacht, die mikroskopischen Schnitte der wichtigsten in Betracht kommenden Gewebe und Organe in gekochtem Zustande so zu charakterisieren, daß sie in Gemischen einwandfrei identifiziert werden können.Die Technik der mikroskopischen Untersuchung von Fleisch- und Wurstwaren ist unter Angabe bewährter Verfahren eingehend dargestellt.