TY - JOUR AB - Today, organizations must deal with a plethora of IT security threats and to ensure smooth and uninterrupted business operations, firms are challenged to predict the volume of IT security vulnerabilities and allocate resources for fixing them. This challenge requires decision makers to assess which system or software packages are prone to vulnerabilities, how many post-release vulnerabilities can be expected to occur during a certain period of time, and what impact exploits might have. Substantial research has been dedicated to techniques that analyze source code and detect security vulnerabilities. However, only limited research has focused on forecasting security vulnerabilities that are detected and reported after the release of software. To address this shortcoming, we apply established methodologies which are capable of forecasting events exhibiting specific time series characteristics of security vulnerabilities, i.e., rareness of occurrence, volatility, non-stationarity, and seasonality. Based on a dataset taken from the National Vulnerability Database (NVD), we use the Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) to measure the forecasting accuracy of single, double, and triple exponential smoothing methodologies, Croston's methodology, ARIMA, and a neural network-based approach. We analyze the impact of the applied forecasting methodology on the prediction accuracy with regard to its robustness along the dimensions of the examined system and software package "operating systems", "browsers" and "office solutions" and the applied metrics. To the best of our knowledge, this study is the first to analyze the effect of forecasting methodologies and to apply metrics that are suitable in this context. Our results show that the optimal forecasting methodology depends on the software or system package, as some methodologies perform poorly in the context of IT security vulnerabilities, that absolute metrics can cover the actual prediction error precisely, and that the prediction accuracy is robust within the two applied forecasting-error metrics. AU - Yasasin, Emrah AU - Prester, Julian AU - Wagner, Gerit AU - Schryen, Guido ID - 13175 IS - January JF - Computers & Security SN - 0167-4048 TI - Forecasting IT Security Vulnerabilities - An Empirical Analysis VL - 88 ER - TY - GEN AU - Bielak, Christian Roman AU - Böhnke, Max AU - Bobbert, Mathias AU - Meschut, Gerson ID - 20344 TI - Development of a numerical method for analyzing the robustness of clinching in versatile process chains ER - TY - JOUR AU - Atorf, Bernhard AU - Mühlenbernd, Holger AU - Zentgraf, Thomas AU - Kitzerow, Heinz-Siegfried ID - 16301 IS - 6 JF - Optics Express SN - 1094-4087 TI - All-optical switching of a dye-doped liquid crystal plasmonic metasurface VL - 28 ER - TY - CONF AB - At Paderborn University, a new 6th semester geometry-course for upper secondary student teachers has been designed and taught by the first author of this paper. To show links between academic mathematics and school mathematics we established so-called interface weeks. These are weeks during a course in which lecture, exercises and homework focus on topics that are related to the normal canon of content but specially chosen for their relevance in school contexts. In this article, we want to present our design for an interface week on the topic of congruence. In order to do so, we first illustrate how so-called interface aspects are used to systematize the mathematical background of the topic, thus giving future mathematics teachers the chance to act professionally. We then show examples of learning activities and first results of the accompanying research. AU - Hoffmann, Max AU - Biehler, Rolf ID - 31361 T2 - INDRUM 2020, Université de Carthage, Université de Montpellier, Sep 2020, Cyberspace (virtually from Bizerte), Tunisia TI - Designing a Geometry Capstone Course for Student Teachers: Bridging the gap between academic mathematics and school mathematics in the case of congruence ER - TY - JOUR AU - Weber, Jutta ID - 36263 JF - Wissenschaft & Frieden 2020-3: Der kranke Planet. Beilage TI - Skynet oder Slaughterbots. Schwarmintelligenz in Militär, Politik und Populärkultur ER - TY - JOUR AU - Weber, Jutta ID - 36265 JF - Technosecurity Cultures, Sonderausgabe „Science as Culture“ (Hg.: Jutta Weber/Katrin M. Kämpf) TI - Introduction: Technosecurity Cultures VL - Vol. 29(1) ER - TY - JOUR AB - This paper presents the results of an interlaboratory study of the rheological properties of cement paste and ultrasound gel as reference substance. The goal was to quantify the comparability and reproducibility of measurements of the Bingham parameters yield stress and plastic viscosity when measured on one specific paste composition and one particular ultrasound gel in different laboratories using different rheometers and measurement geometries. The procedures for both in preparing the cement paste and carrying out the rheological measurements on cement paste and ultrasound gel were carefully defined for all of the study’s participants. Different conversion schemes for comparing the results obtained with the different measurement setups are presented here and critically discussed. The procedure proposed in this paper ensured a reasonable comparability of the results with a coefficient of variation for the yield stress of 27% and for the plastic viscosity of 24%, despite the individual measurement series’ having been performed in different labs with different rheometers and measurement geometries. AU - Haist, Michael AU - Link, Julian AU - Nicia, David AU - Leinitz, Sarah AU - Baumert, Christian AU - von Bronk, Tabea AU - Cotardo, Dario AU - Eslami Pirharati, Mahmoud AU - Fataei, Shirin AU - Garrecht, Harald AU - Gehlen, Christoph AU - Hauschildt, Inga AU - Ivanova, Irina AU - Jesinghausen, Steffen AU - Klein, Christopher AU - Krauss, Hans-W. AU - Lohaus, Ludger AU - Lowke, Dirk AU - Mazanec, Oliver AU - Pawelczyk, Sebastian AU - Pott, Ursula AU - Radebe, Nonkululeko W. AU - Riedmiller, Joachim Jürgen AU - Schmid, Hans-Joachim AU - Schmidt, Wolfram AU - Secrieru, Egor AU - Stephan, Dietmar AU - Thiedeitz, Mareike AU - Wilhelm, Manfred AU - Mechtcherine, Viktor ID - 21949 JF - Materials and Structures KW - Rheology KW - Wall Slip KW - Slip KW - apparent slip KW - suspension KW - cement KW - concrete SN - 1359-5997 TI - Interlaboratory study on rheological properties of cement pastes and reference substances: comparability of measurements performed with different rheometers and measurement geometries ER - TY - JOUR AB - Since suspensions (e.g., in food, cement, or cosmetics industries) tend to show wall slip, the application of structured measuring surfaces in rheometers is widespread. Usually, for parallel-plate geometries, the tip-to-tip distance is used for calculation of absolute rheological values, which implies that there is no flow behind this distance. However, several studies show that this is not true. Therefore, the measuring gap needs to be corrected by adding the effective gap extension δ to the prescribed gap height H in order to obtain absolute rheological properties. In this paper, we determine the effective gap extension δ for different structures and fluids (Newtonian, shear thinning, and model suspensions that can be adjusted to the behavior of real fluids) and compare the corrected values to reference data. We observe that for Newtonian fluids a gap- and material-independent correction function can be derived for every measuring system, which is also applicable to suspensions, but not to shear thinning fluids. Since this relation appears to be mainly dependent on the characteristics of flow behaviour, we show that the calibration of structured measuring systems is possible with Newtonian fluids and then can be transferred to suspensions up to a certain particle content. AU - Pawelczyk, Sebastian AU - Kniepkamp, Marieluise AU - Jesinghausen, Steffen AU - Schmid, Hans-Joachim ID - 21948 JF - Materials KW - wall slip prevention KW - effective gap height KW - parallel-plate system KW - structured surfaces KW - model suspensions KW - cement paste KW - fresh concrete SN - 1996-1944 TI - Absolute Rheological Measurements of Model Suspensions: Influence and Correction of Wall Slip Prevention Measures ER - TY - GEN AU - Weber, Jutta AU - Nagenborg, Michael ED - Maasen, Sabine ED - Dickel, Sascha ED - Schneider, Christoph ID - 37505 T2 - TechnoScienceSociety. Technological Reconfigurations of Science and Society. Sociology of the Sciences Yearbook TI - TechnoSecuritySociety: Catastrophic Futures, Pre-emptive Security & Mass Surveillance ER - TY - GEN AU - Weber, Jutta AU - Pentenrieder, Annelie ED - Heßler, Martina ED - Liggieri, Kevin ID - 37507 T2 - Technikanthropologie. Handbuch für Wissenschaft und Studium TI - Lucy Suchman ER - TY - GEN AU - Weber, Jutta ED - Heßler, Martina ED - Liggieri, Kevin ID - 37506 T2 - Technikanthropologie. Handbuch für Wissenschaft und Studium TI - Donna Haraway ER - TY - GEN AU - Weber, Jutta ED - Heßler, Martina ED - Liggieri, Kevin ID - 37508 T2 - Technikanthropologie. Handbuch für Wissenschaft und Studium TI - MenschMaschine ER - TY - GEN ED - Weber, Jutta ED - Kämpf, Katrin ID - 37536 IS - 1 T2 - Science as Culture TI - Technosecurity Cultures. Special Issue of ‚Science as Culture‘. Vol. 29(1), März 2020 ER - TY - CONF AU - Krumme, Matthias AU - Webersen, Manuel AU - Claes, Leander AU - Webersen, Yvonne ID - 13943 T2 - Fortschritte der Akustik - DAGA 2020 TI - Analoge Klangsynthese zur Vermittlung von Grundkenntnissen der Signalverarbeitung an Studierende nicht-technischer Fachrichtungen ER - TY - JOUR AB - AbstractAs time-to-market is getting shorter, customer needs have to be identified as early as possible in product development. Correctly applied, corporate foresight can give a glimpse into the future to anticipate such needs and thus gain a competitive advantage. A support tool to choose the appropriate method of foresight is not available yet. Thus, a literature study on foresight methods in industry is performed and a novel decision support tool is proposed which avoids high entrepreneurial risks. Based on the findings, potentials for future work are identified for different types of methods. AU - Gräßler, Iris AU - Thiele, Henrik AU - Scholle, P. ID - 23436 JF - Proceedings of the DESIGN 2020 16th International Design Conference SN - 2633-7762 TI - ASSESSING THE FUTURE: METHODS AND CRITERIA VL - 1 ER - TY - JOUR AU - Thiele, Henrik AU - Weber, Sebastian AU - Reichwein, Jannik AU - Bartolo, Joseph A. AU - Tchana, Yvan AU - Jimenez, Lucas AU - Borg, Jonathan C. ID - 23490 JF - Proceedings of the DESIGN 2020 16th International Design Conference, 26. - 29. Okt. 2020 TI - A Scrum Agile Integrated Development Framework VL - 1 ER - TY - BOOK AU - Bonanati, Sabrina AU - Greiner, Christian AU - Gruchel, Nicole AU - Buhl, Heike M. ID - 32463 TI - Lesekompetenz fördern. Ein Manual für das LIFE-Programm zur Stärkung der Zusammenarbeit von Schule und Elternhaus ER - TY - JOUR AU - Gräßler, Iris AU - Scholle, Philipp AU - Thiele, Henrik ID - 23463 JF - Proceedings of the DESIGN 2020 16th International Design Conference; 26. - 29. Okt. 2020 TI - Improving scenario-technique by a semi-automatized consistency assessment based on pattern recognition by artificial neural networks VL - 1 ER - TY - THES AU - Gense, Alexander ID - 42068 TI - Mechatronischer Entwurf eines geregelten Federungssystems für mittelschwere gepanzerte Kettenfahrzeuge ER - TY - THES AU - Bertelsmeier, Fabian ID - 42067 TI - Produkttolerante Automation zellenbasierter Fertigungssysteme ER - TY - JOUR AU - Gharibian, Sevag AU - Aldi, Marco AU - de Beaudrap, Niel AU - Saeedi, Seyran ID - 16927 JF - Communications in Mathematical Physics TI - On efficiently solvable cases of Quantum k-SAT ER - TY - JOUR AU - Fuchs, Christian ID - 38144 IS - 3 JF - Journal for the Theory of Social Behaviour TI - Towards a Critical Theory of Communication as Renewal and Update of Marxist Humanism in the Age of Digital Capitalism VL - 50 ER - TY - JOUR AU - Fuchs, Christian ID - 38139 IS - 1 JF - tripleC: Communication, Capitalism & Critique TI - Communicative Socialism/Digital Socialism VL - 18 ER - TY - JOUR AU - Fuchs, Christian ID - 38163 IS - 1 JF - tripleC: Communication, Capitalism & Critique TI - Alltagsleben und Alltagskommunikation im Coronavirus-Kapitalismus VL - 18 ER - TY - JOUR AU - Fuchs, Christian ID - 38161 IS - 1 JF - tripleC: Communication TI - Everyday Life and Everyday Communication in Coronavirus Capitalism VL - 18 ER - TY - JOUR AU - Fuchs, Christian ID - 38140 IS - 1 JF - tripleC: Communication, Capitalism & Critique TI - The Utopian Internet, Computing, Communication, and Concrete Utopias VL - 18 ER - TY - JOUR AU - Fuchs, Christian ID - 38142 IS - 3 JF - Humanity & Society TI - Erich Fromm and the Critical Theory of Communication VL - 44 ER - TY - JOUR AU - Fuchs, Christian ID - 38137 IS - 2 JF - Journal of Media Ethics TI - The Ethics of the Digital Commons VL - 35 ER - TY - JOUR AU - Fuchs, Christian ID - 42486 IS - 2 JF - MATRIZes TI - Vida e comunicação cotidianas no capitalism da coronavirus VL - 14 ER - TY - JOUR AB - Thermally stabilized and subsequently carbonized nanofibers are a promising material for many technical applications in fields such as tissue engineering or energy storage. They can be obtained from a variety of different polymer precursors via electrospinning. While some methods have been tested for post-carbonization doping of nanofibers with the desired ingredients, very little is known about carbonization of blend nanofibers from two or more polymeric precursors. In this paper, we report on the preparation, thermal treatment and resulting properties of poly(acrylonitrile) (PAN)/poly(vinylidene fluoride) (PVDF) blend nanofibers produced by wire-based electrospinning of binary polymer solutions. Using a wide variety of spectroscopic, microscopic and thermal characterization methods, the chemical and morphological transition during oxidative stabilization (280 °C) and incipient carbonization (500 °C) was thoroughly investigated. Both PAN and PVDF precursor polymers were detected and analyzed qualitatively and quantitatively during all stages of thermal treatment. Compared to pure PAN nanofibers, the blend nanofibers showed increased fiber diameters, strong reduction of undesired morphological changes during oxidative stabilization and increased conductivity after carbonization. AU - Wortmann, Martin AU - Frese, Natalie AU - Mamun, Al AU - Trabelsi, Marah AU - Keil, Waldemar AU - Büker, Björn AU - Javed, Ali AU - Tiemann, Michael AU - Moritzer, Elmar AU - Ehrmann, Andrea AU - Hütten, Andreas AU - Schmidt, Claudia AU - Gölzhäuser, Armin AU - Hüsgen, Bruno AU - Sabantina, Lilia ID - 25901 JF - Nanomaterials SN - 2079-4991 TI - Chemical and Morphological Transition of Poly(acrylonitrile)/Poly(vinylidene Fluoride) Blend Nanofibers during Oxidative Stabilization and Incipient Carbonization ER - TY - JOUR AB - Large Co-MOF-74 crystals of a few hundred micrometers were prepared by solvothermal synthesis, and their structure and morphology were characterized by scanning electron microscopy (SEM), IR, and Raman spectroscopy. The hydrothermal stability of the material up to 60 °C at 93% relative humidity was verified by temperature-dependent XRD. Proton conductivity was studied by impedance spectroscopy, using a single crystal. By varying the relative humidity (70–95%), temperature (21–60 °C), and orientation of the crystal relative to the electrical potential, it was found that proton conduction occurs predominantly through the linear, unidirectional (1D) micropore channels of Co-MOF-74, and that water molecules inside the channels are responsible for the proton mobility by a Grotthuss-type mechanism. AU - Javed, Ali AU - Strauss, Ina AU - Bunzen, Hana AU - Caro, Jürgen AU - Tiemann, Michael ID - 25899 JF - Nanomaterials SN - 2079-4991 TI - Humidity-Mediated Anisotropic Proton Conductivity through the 1D Channels of Co-MOF-74 ER - TY - CONF AU - Hetkämper, Tim AU - Krumme, Matthias AU - Dreiling, Dmitrij AU - Claes, Leander ID - 19502 T2 - SEFI 48th Annual Conference Proceedings - Engaging Engineering Education TI - A modular, scalable open-hardware platform for project-based laboratory courses in electrical engineering studies ER - TY - GEN AB - Die Autor*innen werfen einen medienwissenschaftlichen Blick auf die Online-Lehre des Sommersemsters 2020. Dabei betrachten sie unter anderem den Unterschied von klassischen Hörsälen zu den neuen, virtuellen Lernräumen, die aber auch physische Elemente beinhalten. Dabei regen sie an, den Einsatz von Lehr-Lern-Plattformen kritisch zu diskutieren und insgesamt die Lehre mit andauernder Medienreflexion zu begleiten. Ein zentraler Punkt des Papiers ist das Aufzeigen von Inklusions- und Exklusionspotenzialen von Online-Lehre. Vermeintliche Selbstverständnisse spielen hier eine Schlüsselrolle. So wird zum Beispiel häufig eine gewisse technische Infrastruktur seitens der Studierenden vorausgesetzt, die nicht immer vorhanden ist. Andererseits entfallen physische Barrieren, die in Lehrgebäuden vorhanden wären. Die Autor*innen mahnen, bei der Konzeption von Online-Lehre zu vermeiden, nicht-behinderte Personen als die Norm anzunehmen und stattdessen von verschiedenen Körperlichkeiten her zu denken, um die positive Potenziale dieses Lehrmodus zu nutzen. Das Diskussionspapier widmet sich auch ausführlich dem Einsatz von (digitalen) Tools, die weniger als Werkzeuge, denn als Medien der Lehre verstanden werden. AU - Bohnenkamp, Björn AU - Burkhardt, Marcus AU - Grashöfer, Katja AU - Hlukhovych, Adrianna AU - Krewani, Angela AU - Matzner, Tobias AU - Missomelius, Petra AU - Raczkowski, Felix AU - Shnayien, Mary AU - Weich, Andreas AU - Wippich, Uwe ID - 35179 TI - Online-Lehre 2020 – Eine medienwissenschaftliche Perspektive. Diskussionspapier Nr. 10 ER - TY - JOUR AB - Die vorübergehende Umstellung der Lehre von Präsenz- auf alternative Formate (sowohl online als auch offline) ist nicht nur eine logistische Herausforderung, sondern hat auch eine medientheoretische und eine wissenschaftspolitische Dimension. Gerade als Medienwissenschaftler_innen sollten wir in dieser Hinsicht reflektiert vorgehen, denn wir haben es mit einer Frage der Übersetzbarkeit von Inhalten zwischen unterschiedlichen Medien zu tun. Der Versuch, Lehrinhalte vom Medium des Sprechens und Diskutierens vor Ort in das Medium etwa einer Konferenzschaltung oder einer kollaborativen schriftlichen Textkommentierung zu übersetzen, verändert diese Inhalte. Wenn wir neue Formate für die Lehre unter besonderen Bedingungen ausprobieren, sollten wir uns die medienwissenschaftliche Prämisse, dass das Medium die Botschaft ist, ständig vor Augen halten. Deshalb schlagen wir vor, diese Aufgabe als ein medienwissenschaftliches Experiment zu betrachten und dieses Experiment im kommenden Semester nicht nur zum Medium, sondern auch zum Inhalt unserer Seminare zu machen. AU - Heinke, Christian AU - Shnayien, Mary AU - Sprenger, Florian AU - Wippich, Uwe ID - 35180 JF - - TI - Lehre unter besonderen Bedingungen. Leitfaden zur temporären Umstellung der Lehre auf Online-Formate ER - TY - BOOK AB - Digital media are transformative: they (re)shape the ways of communicating, relating, doing, knowing, and living as much as they are themselves subject to continuous transformation. The contributions in this volume explore these contemporary shifts in and of digital cultures by analyzing a wide range of topics: from data, infrastructures, algorithms, logistics, economies, politics, identities, collectives […] It’s Open Access! Check it out! ED - Burkhardt, Marcus ED - Grashöfer, Katja ED - Shnayien, Mary ID - 35177 TI - Explorations in Digital Cultures ER - TY - JOUR AB - Jugend wird als eine eigenständige Lebens- und Entwicklungsphase betrachtet. Für junge Geflüchtete stellt sie eine besondere Herausforderung dar. Für sie geht es nicht nur um die Bewältigung alterstypischer Entwicklungsaufgaben, sondern auch um eine gelingende Integration in die Aufnahmegesellschaft. Dazu gehören u. a. das Kennenlernen und die Aneignung von Sprache, Kultur und Werten, genauso die Erschließung von Alltagsräumen und Lebenswelten, z. B. von Freizeitmöglichkeiten, Bildung und von beruflichen Erfahrungsräumen. Die Frage zur gelingenden Integration und Gestaltung von Lebenswelten junger Geflüchteter wurde im Kontext der wissenschaftlichen Begleitung des Projekts „angekommen in Deiner Stadt“ der Walter Blüchert Stiftung genauer untersucht. Der Beitrag referiert u. a. die Ergebnisse einer in diesem Kontext durchgeführten egozentrierten Netzwerkanalyse. Die Ergebnisse zeigen, dass die Angebote den Rahmen für den Aufbau und die Erweiterung kommunikativer, sozialer Netzwerke darstellen und lebensweltliche Zugänge öffnen. AU - Heisler, Dietmar AU - Schemmer, Susanne ID - 37014 JF - BWP@ Berufs- und Wirtschaftspädagogik - online KW - Jugend KW - Lebensweltorientierung KW - soziale Netzwerke KW - geflüchtete Jugendliche KW - Lebenslagen junger Geflüchteter und Zugewanderter TI - Lebenswelten und soziale Netzwerke von jungen Geflüchteten und Zugewanderten am Übergang in Ausbildung und Beruf. ER - TY - BOOK ED - Heisler, Dietmar ID - 36992 TI - Digitalisierung am Übergang Schule Beruf. Ansätze und Perspektiven in Arbeitsdomänen und beruflicher Förderung VL - 56 ER - TY - JOUR AB - Polarons in dielectric crystals play a crucial role for applications in integrated electronics and optoelectronics. In this work, we use density-functional theory and Green's function methods to explore the microscopic structure and spectroscopic signatures of electron polarons in lithium niobate (LiNbO3). Total-energy calculations and the comparison of calculated electron paramagnetic resonance data with available measurements reveal the formation of bound polarons at Nb_Li antisite defects with a quasi-Jahn-Teller distorted, tilted configuration. The defect-formation energies further indicate that (bi)polarons may form not only at Nb_Li antisites but also at structures where the antisite Nb atom moves into a neighboring empty oxygen octahedron. Based on these structure models, and on the calculated charge-transition levels and potential-energy barriers, we propose two mechanisms for the optical and thermal splitting of bipolarons, which provide a natural explanation for the reported two-path recombination of bipolarons. Optical-response calculations based on the Bethe-Salpeter equation, in combination with available experimental data and new measurements of the optical absorption spectrum, further corroborate the geometries proposed here for free and defect-bound (bi)polarons. AU - Schmidt, Falko AU - Kozub, Agnieszka L. AU - Biktagirov, Timur AU - Eigner, Christof AU - Silberhorn, Christine AU - Schindlmayr, Arno AU - Schmidt, Wolf Gero AU - Gerstmann, Uwe ID - 19190 IS - 4 JF - Physical Review Research TI - Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations VL - 2 ER - TY - JOUR AU - Fuchs, Christian ID - 41432 IS - 1 JF - tripleC: Communication, Capitalism & Critique TI - Communicative Socialism/Digital Socialism VL - 18 ER - TY - JOUR AU - Fuchs, Christian ID - 42485 IS - 2 JF - tripleC: Communication, Capitalism & Critique TI - Preface to Manfred Knoche’s Article “Science Communication and Open Access: The Critique of the Political Economy of Capitalist Academic Publishers as Ideology Critique” VL - 18 ER - TY - JOUR AB - Micropatterned nanoporous aluminum oxide arrays are prepared on silicon wafer substrates by using photopolymerized poly(dimethylacrylamide) hydrogels as porogenic matrices. Hydrogel micropatterns are fabricated by spreading the prepolymer mixture on the substrate, followed by UV photopolymerization through a micropatterned mask. The hydrogel is covalently bonded to the substrate surface. Al2O3 is produced by swelling the hydrogel in a saturated aluminum nitrate solution and subsequent thermal conversion/calcination. As a result, micropatterned porous Al2O3 microdots with heights in µm range and large specific surface areas up to 274 m2 g−1 are obtained. Hence, the hydrogel fulfills a dual templating function, namely micropatterning and nanoporosity generation. The impact of varying the photopolymerization time on the properties of the products is studied. Samples are characterized by light and confocal laser scanning microscopy, scanning electron microscopy, energy-dispersive x-ray spectrometry, and Kr physisorption analysis. AU - Chen, Zimei AU - Kuckling, Dirk AU - Tiemann, Michael ID - 23854 JF - Nanotechnology SN - 0957-4484 TI - Nanoporous aluminum oxide micropatterns prepared by hydrogel templating VL - 31 ER - TY - JOUR AB - Metal oxide inverse opals are interesting for various applications. To achieve highly ordered inverse opal structures, one important issue during the colloidal crystal templating procedure is to form a stable precursor network before the template loses its structural integrity at high temperature. Using poly(methyl methacrylate), PMMA, colloidal crystal templates, it is essential to consider the physical and chemical changes of the precursors induced by the changes of PMMA during the thermal conversion. For a systematic investigation of this matter, we synthesized a variety of metal oxide inverse opals from the respective metal nitrates, including Cr2O3, Ga2O3, Fe2O3, In2O3, CuO, CeO2, and ZnO, to compare the effect of various modifications of precursors on the structural and optical properties. When the nitrate precursors have a lower thermal stability than the PMMA template, we have modified the metal nitrates by chelating or by polyacrylamide gelation to form more stable precursor networks. AU - Zhang, Xuyang AU - Weinberger, Christian AU - Amrehn, Sabrina AU - Wu, Xia AU - Tiemann, Michael AU - Wagner, Thorsten ID - 25898 JF - European Journal of Inorganic Chemistry SN - 1434-1948 TI - Synthesis of Metal Oxide Inverse Opals from Metal Nitrates by PMMA Colloidal Crystal Templating ER - TY - JOUR AB - The proton conduction properties of a phosphonato-sulfonate-based coordination polymer are studied by impedance spectroscopy using a single crystal specimen. Two distinct conduction mechanisms are identified. Water-mediated conductance along the crystal surface occurs by mass transport, as evidenced by a high activation energy (0.54 eV). In addition, intrinsic conduction by proton ′hopping′ through the interior of the crystal with a low activation energy (0.31 eV) is observed. This latter conduction is anisotropic with respect to the crystal structure and seems to occur through a channel along the c axis of the orthorhombic crystal. Proton conduction is assumed to be mediated by sulfonate groups and non-coordinating water molecules that are part of the crystal structure. AU - Javed, Ali AU - Wagner, Thorsten AU - Wöhlbrandt, Stephan AU - Stock, Norbert AU - Tiemann, Michael ID - 25900 JF - ChemPhysChem SN - 1439-4235 TI - Proton Conduction in a Single Crystal of a Phosphonato‐Sulfonate‐Based Coordination Polymer: Mechanistic Insight ER - TY - JOUR AB - This Special Issue on “Functional Nanoporous Materials” in the MDPI journal nanomaterials features seven original papers ... AU - Weinberger, Christian AU - Tiemann, Michael ID - 25902 JF - Nanomaterials SN - 2079-4991 TI - Functional Nanoporous Materials ER - TY - JOUR AB - Density-functional theory calculations of (TiO2)n clusters (n = 1–5) in the gas phase and adsorbed on pristine graphene as well as graphene quantum dots are presented. The cluster adsorption is found to be dominated by van der Waals forces. The electronic structure and in particular the excitation energies of the bare clusters and the TiO2/graphene composites are found to vary largely in dependence on the size of the respective constituents. This holds in particular for the energy and the spatial localization of the highest occupied and lowest unoccupied molecular orbitals. In addition to a substantial gap narrowing, a pronounced separation of photoexcited electrons and holes is predicted in some instances. This is expected to prolong the lifetime of photoexcited carriers. Altogether, TiO2/graphene composites are predicted to be promising photocatalysts with improved electronic and photocatalytic properties compared to bulk TiO2. AU - Badalov, Sabuhi AU - Wilhelm, René AU - Schmidt, Wolf Gero ID - 19189 JF - Journal of Computational Chemistry SN - 0192-8651 TI - Photocatalytic properties of graphene‐supported titania clusters from density‐functional theory ER - TY - JOUR AB - Vortices are topological objects representing the circular motion of a fluid. With their additional degree of freedom, the vorticity, they have been widely investigated in many physical systems and different materials for fundamental interest and for applications in data storage and information processing. Vortices have also been observed in non-equilibrium exciton-polariton condensates in planar semiconductor microcavities. There they appear spontaneously or can be created and pinned in space using ring-shaped optical excitation profiles. However, using the vortex state for information processing not only requires creation of a vortex but also efficient control over the vortex after its creation. Here we demonstrate a simple approach to control and switch a localized polariton vortex between opposite states. In our scheme, both the optical control of vorticity and its detection through the orbital angular momentum of the emitted light are implemented in a robust and practical manner. AU - Meier, Torsten AU - Ma, Xuekai AU - Berger, Bernd AU - Aßmann, Marc AU - Driben, Rodislav AU - Schneider, Christian AU - Höfling, Sven AU - Schumacher, Stefan ID - 43747 IS - 1 JF - Nature communications TI - Realization of all-optical vortex switching in exciton-polariton condensates VL - 11 ER - TY - JOUR AU - Martin, Sven AU - Camberg, Alan A. AU - Tröster, Thomas ID - 16859 JF - Procedia Manufacturing SN - 2351-9789 TI - Probability Distribution of Joint Point Loadings in Car Body Structures under Global Bending and Torsion ER - TY - JOUR AB - Abstract Safety-relevant components in automobiles require materials that combine high strength with sufficient residual ductility and high-energy absorption. A graded thermo-mechanical treatment of the press-hardening steel 22MnB5 with graded microstructure can provide a material with such properties. Different austenitization temperatures, cooling and forming conditions within a sheet part lead to the development of microstructures with mixed phase compositions. To determine the resulting phase contents in such graded processed parts, a large number of dilatometric tests are usually required. With a non-contact characterization method, it is possible to detect local phase transformations on an inhomogeneously treated flat steel specimen. For press-hardening steel after heat treatment and thermo-mechanical processing, correlations between austenitization temperature, hot deformation strain, microstructure, and hardness are established. AU - Reitz, Alexander AU - Grydin, Olexandr AU - Schaper, Mirko ID - 23797 JF - Metallurgical and Materials Transactions A SN - 1073-5623 TI - Characterization of Phase Transformations During Graded Thermo-Mechanical Processing of Press-Hardening Sheet Steel 22MnB5 ER - TY - JOUR AB - Al-Li based alloys are attractive materials for the aerospace industry. The twin-roll casting of such materials could provide properties not achievable by conventional direct-chill casting and downstream processing methods due to significantly higher solidification rates. An Al-Li-Cu-Mg-Zr alloy was twin-roll cast with the same alloy containing a small addition of Sc. The microstructure of as-cast materials and the influence of Sc on the behavior of the alloy at elevated temperatures were studied by means of light and electron microscopy and by resistivity measurements. A fine-grained structure was formed during twin-roll casting, but several surface and internal defects were found on the strips, which should be suppressed by a further adjustment of the casting conditions. The addition of Sc had a positive effect on grain size uniformity and microstructure stabilization at elevated temperatures, as shown by the precipitation of a fine dispersion of coherent Sc- and Zr-containing precipitates. AU - Grydin, Olexandr AU - Stolbchenko, Mykhailo AU - Schaper, Mirko AU - Belejová, Sára AU - Králík, Rostislav AU - Bajtošová, Lucia AU - Křivská, Barbora AU - Hájek, Michal AU - Cieslar, Miroslav ID - 24573 IS - 8 JF - Metals SN - 2075-4701 TI - New Twin-Roll Cast Al-Li Based Alloys for High-Strength Applications VL - 10 ER - TY - JOUR AU - Claes, Leander AU - Steidl, Carolin AU - Hetkämper, Tim AU - Henning, Bernd ID - 15489 JF - arXiv.org TI - Estimation of acoustic wave non-linearity in ultrasonic measurement systems ER -