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 -