687 research outputs found

    Facilitating argumentative knowledge construction with computer-supported collaboration scripts

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    Online discussions provide opportunities for learners to engage in argumentative debate, but learners rarely formulate well-grounded arguments or benefit individually from participating in online discussions. Learners often do not explicitly warrant their arguments and fail to construct counterarguments (incomplete formal argumentation structure), which is hypothesized to impede individual knowledge acquisition. Computer-supported scripts have been found to support learners during online discussions. Such scripts can support specific discourse activities, such as the construction of single arguments, by supporting learners in explicitly warranting their claims or in constructing specific argumentation sequences, e.g., argument–counterargument sequences, during online discussions. Participation in argumentative discourse is seen to promote both knowledge on argumentation and domain-specific knowledge. However, there have been few empirical investigations regarding the extent to which computer-supported collaboration scripts can foster the formal quality of argumentation and thereby facilitate the individual acquisition of knowledge. One hundred and twenty (120) students of Educational Science participated in the study with a 2×2-factorial design (with vs. without script for the construction of single arguments and with vs. without script for the construction of argumentation sequences) and were randomly divided into groups of three. Results indicated that the collaboration scripts could improve the formal quality of single arguments and the formal quality of argumentation sequences in online discussions. Scripts also facilitated the acquisition of knowledge on argumentation, without affecting the acquisition of domainspecific knowledge

    Vertrauen und Sozialkapital

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    Amnesie und Antizipation

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    In modern postwar orders (and disorders) the concept of democratic peace prescribes that losing parties remember defeat and accept blame in order to redeem themselves and receive amnesty. In addition, the winning side’s position is to be accepted as rightful, morally just, and inherently peaceable. However, the historian Reinhart Koselleck remarks that throughout history succeeding postwar transitions were creatively framed through three alternatives: first, noting down what really has happened (documentation); second, embedding war experience into larger historical frameworks in order to integrate and minimize the defeat (contextualization); and, third, denying the defeat by rewriting it (annihilation/reinterpretation). But groups who are likely to be defeated are already able to anticipate the modern constrictions on these alternatives during wartime. Our thesis is that the recent limiting of options for postwar arrangements is one key factor for both the emerging permanence of asymmetric, or so-called ‘new wars’, and the multitude of notoriously unstable postwar architectures

    Intra- and intercellular fluctuations in Min-protein dynamics decrease with cell length

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    Self-organization of proteins in space and time is of crucial importance for the functioning of cellular processes. Often, this organization takes place in the presence of strong random fluctuations due to the small number of molecules involved. We report on stochastic switching of the Min-protein distributions between the two cell halves in short Escherichia coli cells. A computational model provides strong evidence that the macroscopic switching is rooted in microscopic noise on the molecular scale. In longer bacteria, the switching turns into regular oscillations that are required for positioning of the division plane. As the pattern becomes more regular, cell-to-cell variability also lessens, indicating cell length-dependent regulation of Min-protein activity.Comment: Article and Supplementary Information: 26 pages, 12 figure

    Knowledge convergence in collaborative learning

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    In collaborative learning the question has been raised as to how learners in small groups influence one another and converge or diverge with respect to knowledge. Knowledge convergence can be conceptualised as knowledge equivalence and as shared knowledge prior to, during, and subsequent to collaborative learning. Knowledge equivalence refers to learners becoming more similar to their learning partners with regard to the extent of their individual knowledge. Shared knowledge means that learners have knowledge on the very same concepts as their learning partners. In this article, we provide measures for assessing both, knowledge equivalence and shared knowledge

    Entwicklung einer verbundoptimierten ProzessfĂŒhrung im variothermen Pressverfahren

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    Die europĂ€ische Herausforderung, bis 2050 klimaneutral zu sein, fordert Industrie und Forschung gleichermaßen, neue Fertigungs- und Werkstoffkonzepte zu liefern und damit zum Erreichen dieses Ziels beizutragen. Die Kombination unterschiedlicher Werkstoffklassen zu einem hybriden Verbundsystem bietet ein neues und spannendes Werkstofffeld mit besonders hohem Potenzial. Die Arbeit fokussiert dabei ein Leichtbaukonzept aus faserverstĂ€rktem Kunststoffkern mit metallischen Deckschichten (fibre metal laminate, FML), hergestellt im einstufigen variothermen Fertigungsprozess. Ausgehend von einer Charakterisierung der Monomaterialien wird eine Analyse der Haftfestigkeiten zwischen Metall und Polymer im Heißpressprozess durchgefĂŒhrt. Die Optimierung der Haftungseigenschaften erfolgt einerseits durch Änderung der OberflĂ€chenmorphologie der metallischen Komponente. Untersucht werden der Einfluss thermischer Vorbehandlung (Tempern) und mechanischen Aufrauens. Andererseits werden sowohl die Druckstufen als auch das Temperaturprofil auf das Herstellungsverfahren des Dreischicht-Verbundsystems abgestimmt und ZusammenhĂ€nge charakterisiert. Die festgestellten Einflussfaktoren fließen in die Ermittlung des Prozessfensters fĂŒr den variothermen einstufigen UmformfĂŒgeprozess ein. Fokussiert wird in dieser Arbeit die Bestimmung eines Arbeitsfensters und dessen Einflusses auf den Kernwerkstoff des Dreischicht-Sandwichverbundes. Der Kernwerkstoff, glasfaserverstĂ€rktes Polyamid 6 (PA-GF), bringt in den komplexen Fertigungsprozess Besonderheiten ein, welche wĂ€hrend der Umformung beachtet werden mĂŒssen. Das Verhalten der textilen VerstĂ€rkung, aber auch das der polymeren Matrixkomponente, werden daher intensiv betrachtet. Die Formgebung der metallischen Deckschicht des Verbundes benötigt im hier vorgestellten Prozess verhĂ€ltnismĂ€ĂŸig hohe UmformkrĂ€fte, wohingegen der Kernwerkstoff, bedingt durch das schmelzflĂŒssige Polymer und das Scherdeformationsverhalten des Fasergewebes, geringe FormgebungskrĂ€fte benötigt. Ein Abstimmen der FĂŒgeparameter auf die gemeinsame Formgebung der Verbundpartner sowie das simultane Erzeugen einer Anbindung ist daher Kern dieser Abhandlung. Als BauteilprĂŒfung wird, in Anlehnung an automobile Strukturelemente (DachquertrĂ€ger, B-SĂ€ule oder StoßfĂ€nger) eine Hut-Profil Geometrie gewĂ€hlt. Diese Geometrie erlaubt die Identifikation der fertigungsbedingten Randbedingungen. Gleichzeitig erlaubt das Profil die Untersuchung der Übertragbarkeit des Fertigungsprozesses auf geĂ€nderte Sandwichzusammensetzungen. Untersucht wird der Einfluss der Kernschichtdicke sowie deren Faserorientierung (0°/90° und ± 45°), der Einfluss geĂ€nderter metallischer Deckschichten auf die Formbarkeit und das mechanische Bauteilverhalten bei quasistatischer 3-Punkt Biegung. Abschließend erfolgt die Charakterisierung der Feuchtigkeitsaufnahme anhand von ebenen FML-Proben, welche RĂŒckschlĂŒsse auf das Materialverhalten bei feuchter Lagerung/Nutzung, sowie RĂŒckschlĂŒsse auf das Verhalten einer lokalen Feuchtigkeitsaufnahme infolge einer BeschĂ€digung ermöglicht.The European commitment to be climate-neutral by 2050 requires industry and research to deliver new manufacturing and material concepts and thus contribute towards achieving this goal. The combination of different material classes into a hybrid composite system offers a new and exciting component with high potential. The work focuses on a lightweight construction concept consisting of a fibre-reinforced plastic core with metallic facesheets (fibre metal laminate, FML), produced in a single-stage variothermal manufacturing process. Beginning with a characterisation of the mono-materials, an analysis of the adhesive strengths in the hot pressing process is carried out. On one hand, the adhesion properties are optimised by changing the surface morphology of the metallic component. The influence of thermal pre-treatment (tempering) and mechanical surface preparation are investigated. On the other hand, both the pressure levels and the temperature profile are adapted and optimised to the manufacturing process of these three-layered composites. The determined influencing factors of the hot pressing process are integrated into the determination of the process window of the single-stage variothermal forming. This work focuses on the identification of a working window and its influence on the thermoplastic core material of the three-layer sandwich. The core material, glass fibre reinforced polyamide 6, brings special features into the complex manufacturing process, which must be taken into account during the forming. Therefore, the behaviour of the textile reinforcement, as well as that of the polymer matrix component, are investigated. The forming of the metallic facesheets of the composite requires relatively high forming loads in the process presented here, whereas the core material, due to the molten polymer and the shear characteristics of the textile structure requires lower loads. The focus of this experimental thesis is therefore the adjustment of the joining parameters to the forming of the composite components and their simultaneous adhesion. A hat-profile geometry is selected as the test component, based on automotive structural elements (roof cross member, B-pillar or bumper). This geometry allows the identification of the production-related boundary conditions. At the same time, the profile allows the investigation of the transferability of the manufacturing process to tailored sandwich compositions. The influence of the core layer thickness as well as its fibre orientation (0°/90° and ± 45°) and the influence of modified metallic cover layers on the component behaviour are also investigated. Finally, the moisture absorption is characterised on the basis of flat FML samples, which allows to draw conclusions about whether the material behaviour during bulk and localized moisture adsorption results in its failure
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