On the topology of the inverse limit of a branched covering over a Riemann surface

We introduce the Plaque Topology on the inverse limit of a branched covering self-map of a Riemann surface of a finite degree greater than one. We present the notions of regular and irregular points in the setting of this Plaque Inverse Limit and study its local topological properties at the irregular points. We construct certain Boolean Algebra and certain sigma-lattice, derived from it, and use them to compute local topological invariants of the Plaque Inverse Limit. Finally, we obtain several results interrelating the dynamics of the forward iterations of the self-map and the topology of the Plaque Inverse Limit.Comment: 25 page

Characterization of the electrical behavior of a discontinuous hybrid yarn textile made of recycled carbon and PA6 fibers during Joule heating

The Joule heating of carbon fiber-based textiles enables an energy- and cost-efficient processing of carbon fiber reinforced thermoplastic parts. This article introduces a new method to pass direct current into a dry, not pre-consolidated hybrid yarn textile based on recycled carbon fibers and polyamide 6 fibers. The aim is to melt polyamide fibers, subsequently impregnate carbon fibers, and finally consolidate the material to form a composite part in a single process step. To increase the reliability of this technology, the electrical properties and the behavior of the material during the heating process must be thoroughly investigated. It will be addressed how the material is characterized during the process and how the changing resistivity of the textile affects the current flow between the electrodes to generate intrinsic heat. Moreover, a method to determine the effective material resistivity by finite element simulation on the fiber scale based on a CT scan is presented. Thus, a validated material model with respect to the temperature development in the textile based on ρ = ρ (T) was established

An Approach for Efficient Neural Architecture Search Space Definition

As we advance in the fast-growing era of Machine Learning, various new and more complex neural architectures are arising to tackle problem more efficiently. On the one hand their efficient usage requires advanced knowledge and expertise, which is most of the time difficult to find on the labor market. On the other hand, searching for an optimized neural architecture is a time-consuming task when it is performed manually using a trial and error approach. Hence, a method and a tool support is needed to assist users of neural architectures, leading to an eagerness in the field of Automatic Machine Learning (AutoML). When it comes to Deep Learning, an important part of AutoML is the Neural Architecture Search (NAS). In this paper, we propose a novel cell-based hierarchical search space, easy to comprehend and manipulate. The objectives of the proposed approach are to optimize the search-time and to be general enough to handle most of state of the art Convolutional Neural Networks (CNN) architectures.Comment: AAAI-22 Workshop: Learning Network Architecture During Training, Feb 2022, Online, United State

Surface Treatment of Carbon Fibers by Oxy-Fluorination

In this paper, the oxy-fluorination process and the influence of different concentrations of fluorine and oxygen in the gas phase on the physicochemical properties of polyacrylonitrile(PAN)-based carbon fibers are described. The properties of the treated carbon structures are determined by zeta potential and tensiometry measurements. In addition, changes in surface composition and morphology are investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Adhesion properties are characterized by the single fiber pull-out (SFPO) test. Furthermore, changes in intrinsic properties are described by means of tensile and density measurements. After a primary desizing effect by oxy-fluorination, an increased number of oxygen-containing surface functional groups could be detected, which led to more debonding work in SFPOs with an epoxy-based matrix. It was also shown that the polar surface energy grows with rising fluorine concentration in the reaction gas mixture. In addition, a minor increase of ~10% in the maximum strength of PAN-based carbon fibers is detected by single fiber tensile measurements after oxy-fluorination with a fluorine content of 5% in the reaction mixture

Optimale Beschaffungsentscheidungen für OP-Textilien: Ein Zusammenspiel von Hygiene, Textiltechnologie, Ökonomie und Ökologie

Dieser Beitrag gibt, basierend auf einem BMBF-Verbundvorhaben, Einblicke in die umfassende Bewertung von OPTextilien. Ziel des Vorhabens ist es, Entscheidern in Krankenhäusern Anregungen und Know-how für ihren Berufsalltag und Produzenten von OP-Textilien Impulse für die Gestaltung ihrer Produkte zu geben. Es werden die hygienischen Anforderungen zur Vermeidung nosokomialer Infektionen, die die Schutzwirkung der Textilien garantierenden textiltechnologischen Voraussetzungen sowie die zur Erfüllung der Wirtschaftlichkeit und Umweltfreundlichkeit notwendigen Anforderungen an OP-Textilien dargestellt. Der Beitrag verdeutlicht, dass die Beachtung all dieser Kriterien und deren Zusammenführung für eine bewusste Entscheidung zum Einsatz von OP-Textilien notwendig ist.This article describes a holistic assessment approach for operating room (OR) textiles, based on a joint research project funded by the German Ministry of Education and Research. The objective of the project is to ease decision processes for decision makers in hospitals and OR textile manufacturers. The hygienic demands for protection against nosocominal infections, the technological requirements to guarantee textiles their protective properties, as well as the bases for an economically and environmentally optimum decision, are discussed. To permit a holistic procurement decision regarding OR textiles, it is necessary to consider all these criteria and their integration, as proposed in this article

Materialverhalten von AR-Glas- und Carbonfilamentgarnen unter Dauerlast- sowie unter Hochtemperatureinwirkung

In vielen technischen Anwendungen werden Faserverbundwerkstoffe mit Hochleistungsfasern aus Carbon und AR-Glas eingesetzt, die aufgrund ihrer physikalischen und chemischen Eigenschaften ein hohes Festigkeitspotential aufweisen. Damit eröffnen sich neue Anwendungsgebiete, z. B. als textile Bewehrungen für Betonbauteile. Die Garnmaterialien müssen hohe sicherheitstechnische Anforderungen erfüllen. Dazu gehören u. a. eine ausreichende Tragfähigkeit unter Dauerlastbeanspruchung und eine hohe Temperaturbeständigkeit im Brandfall. Zur Spezifizierung dieser Eigenschaften wurden experimentelle Untersuchungen durchgeführt, deren Ergebnisse nachfolgend vorgestellt werden.Due to their strong mechanical and chemical properties, fiber composite materials composed of high performance carbon and AR-glass fibers lend themselves to many technical applications. Potentially new and innovative application fields should be considered, such as textile reinforcements for concrete components. The yarn materials must meet high technical and safety standards, specifically sufficient load-bearing capabilities under long-term conditions and acceptable strength at high temperatures should fire occur. Research was conducted to document these characteristics. The results are presented in this paper

Textile Betonbewehrungen auf Basis der Multiaxial-Kettenwirktechnik

Dieser Beitrag bietet einen Überblick über die in zwölf Jahren Forschungsarbeit am Institut für Textilmaschinen und Textile Hochleistungswerkstofftechnik (ITM) erzielten Ergebnisse auf dem Gebiet textiler Betonbewehrungen unter Einsatz der Nähwirktechnik. Standen zunächst die Weiterentwicklung der Nähwirk- bzw. Multiaxial-Kettenwirktechnik und die Integration zusätzlicher Prozessschritte im Mittelpunkt, so wurde dies mit der Einführung neuer Faserwerkstoffe durch die Beantwortung grundlegender Fragen zum Materialverhalten von Glas- und Carbonfasern unter verschiedensten Belastungsszenarien ergänzt. Aufbauend auf den gewonnen Erkenntnissen stehen heute Multiaxialgelege als Bewehrung für Beton zur Verfügung, die ein weites Anforderungsspektrum abdecken können, mit hoher Qualität und Produktivität herstellbar sind und damit den praktischen Einsatz des Textilbetons auf breiter Basis ermöglichen.This paper provides an overview on the results of textile concrete achieved in twelve years of research at the Institute of Textile Machinery and High Performance Material Technology (ITM) in the field of textile reinforcements for concrete based on the multiaxial stitch-bonding technology. During the early years the research focused on the development of the textile manufacturing process and the integration of additional functions in stitch-bonding machines. With the introduction of new fiber materials this was shifted towards the description of the material behavior of glass and carbon fibers under different load scenarios. Based on the results of this research, multiaxial multi-ply fabrics are available now as reinforcements for concrete, covering a broad range of applications. These fabrics can be produced with high quality and productivity and enable the practical usage of textile reinforced concrete