Service-Learning stands out as a teaching approach that connects theory and practice by giving students the opportunity both to participate in a service that meets community needs and to reflect on ...the experience in class in order to gain a deeper understanding of the course content and an enhanced sense of civic engagement. The advantages of Service-Learning for inclusive education have recently been underpinned by studies, in which pre-service teachers are exposed to diverse population groups in schools or communities. Our study explores how Service-Learning is applied in teacher education in Austria. It is based on a series of semi-structured interviews with 13 teacher educators who apply this form of teaching in cooperative projects with schools. Our findings suggest that teacher educators distinguish between five orientations in Service-Learning (connecting theory and practice, engagement, community needs, job-related skills, learning outside the classroom), take on distinct expert and support roles, and see multiple benefits in Service-Learning. Our study underlines the importance of Service-Learning for inclusive education and the value of preparing pre-service teachers for dealing with diverse groups of pupils by allowing them to experience the real-world problems that confront schools.
Improving and clarifying a construction of Horowitz and Shelah, we show how to construct (in
$\mathsf {ZF}$
, i.e., without using the Axiom of Choice) maximal cofinitary groups. Among the groups we ...construct, one is definable by a formula in second-order arithmetic with only a few natural number quantifiers.
We show that there is an effectively closed maximal eventually different family in spaces of the form ∏nAn with each An countable and discrete (for example, Baire space) and give an exact criterion ...for when there exists an effectively compact such family. The proof generalizes and simplifies earlier proofs by Horowitz and Shelah, as well as by the present author.
Typically, polymeric materials experience material degradation and damage over time in harsh environments. Improved understanding of the physical and chemical processes associated with possible ...damage modes intended in high-pressure hydrogen gas exposed atmospheres will help to select and develop materials well suited for applications fulfilling future energy demands in hydrogen as an energy carrier. In high-pressure hydrogen gas exposure conditions, damage from rapid gas decompression (RGD) and from aging in elastomeric as well as thermoplastic material components is unavoidable. This review discusses the applications of polymeric materials in a multi-material approach in the realization of the "Hydrogen economy". It covers the limitations of existing polymeric components, the current knowledge on polymeric material testing and characterization, and the latest developments. Some improvements are suggested in terms of material development and testing procedures to fill in the gaps in existing knowledge in the literature.
The Ramsey property implies no mad families Schrittesser, David; Törnquist, Asger
Proceedings of the National Academy of Sciences - PNAS,
09/2019, Volume:
116, Issue:
38
Journal Article
Peer reviewed
Open access
We show that if all collections of infinite subsets of ℕ have the Ramsey property, then there are no infinite maximal almost disjoint (mad) families. The implication is proved in Zermelo–Fraenkel set ...theory with only weak choice principles. This gives a positive solution to a long-standing problem that goes back to Mathias A. R. D. Mathias, Ann. Math. Logic 12, 59–111 (1977). The proof exploits an idea which has its natural roots in ergodic theory, topological dynamics, and invariant descriptive set theory: We use that a certain function associated to a purported mad family is invariant under the equivalence relation E₀ and thus is constant on a “large” set. Furthermore, we announce a number of additional results about mad families relative to more complicated Borel ideals.
The observation that every two-person adversarial game is an affine transformation of a zero-sum game is traceable to Luce and Raiffa (1957) and made explicit in Aumann (1987). Recent work of Adler ...et al. (2009) and of Raimondo (2023) in increasing generality, proves what has so far remained a conjecture. We present two proofs of an even more general formulation: the first draws on multilinear utility theory developed by Fishburn and Roberts (1978); the second is a consequence of Adler et al.’s 2009 proof itself for a special case of a two-player game in which each player has a set of three actions.
•Theorem giving most general formulation of the Luce-Raiffa–Aumann conjecture to date•Novel proof adapting Fishburn & Roberts’s 1978 multilinear utility axiomatization•Alternative proof based on result for two-player game with three actions per player•Theorem entailing as corollaries results of Adler et al. 2009 and Raimondo 2023•Connection with developments of Moulin & Vial 1978 on strategically zero-sum games•Relevance for complexity of computing Nash equilibria á la Daskalakis et al. 2009
This research focuses on the investigation of endless fiber-reinforced elastomeric materials with special tailoring by different fiber orientations in the composite structure. Therefore, a modified ...testing device including a suitable specimen production was carried out and the comparability of tests conducted at different test scales (micro- to macro testing level) was proven. Two elastic matrix materials (silicone and polyurethane) and reinforcing fiber types (glass- and polyester fibers) were investigated in all combinations. Due to the important effect on the shear behavior during the deformation of textiles significantly influenced by the fiber orientations of the warp- and weft-yarns, a testing plan was established by using one material combination as a reference setting. Generally, the results reveal a good comparability between different testing levels for the same fiber-matrix combinations and the modified composite testing device has been proven. Furthermore, the significant influence of different fiber orientations on the shear stiffness was investigated.
Pre-service teachers often express a strong desire for more practical experience in teacher education, which requires teacher educators to consider new, meaningful opportunities for field ...experiences. This paper aims to bridge the gap between two 'practice worlds' - university teacher education and school practice - based on the example of the Austrian 'Partner School Programme' in order to overcome the theory-practice divide. In this conceptual paper, we explore how the 'Partner School Programme' has aimed at bridging the two 'practice worlds' by enhancing collaboration between universities and schools in different ways: pre-service teachers can take part in fieldwork in schools within the framework of a project (project-based learning), a research activity (community-based research) or an organised service (service-learning). The paper shows the relevance of developing integrated approaches for encouraging pre-service teachers' reflective practice as thorough preparation for their subsequent careers and provides teacher educators with new ideas for practical fieldwork.
This work provides a direct comparison of several experimental approaches used in the literature to measure fracture toughness of rubber of rubber using single edge notched in tension (SENT) ...specimens, with the final aim to provide guidelines for an optimal testing procedure. Digital image correlation measurements were used to get new insights into the fracture process. SENT is experimentally advantageous because of the simple preparation from laboratory plates and the small amount of material required. The most common experimental approaches to measure fracture toughness of rubber rely on the energy release rate, measured by the tearing energy or the J-integral parameters. This work points out the importance of experimental conditions and test procedures: long specimens and short notches are preferred, identification of fracture initiation from the front view is necessary, strain energy density should not be evaluated from un-notched specimens at the critical stretch level, rather alternative strategies are shown in this work.
•A standard procedure for fracture toughness testing of rubber still does not exist.•A comparison among different experimental approaches is shown here.•A simple specimen geometry, single edge notched in tension, SENT, is tested.•Digital image correlation measurements were used to get reference values.•From this work, optimal testing conditions are identified.
Concerning the still rising demand for oil and gas products, the development of new reliable materials to guarantee the facility safety at extreme operating conditions is an utmost necessity. The ...present study mainly deals with the influence of different carbon black (CB) filled hydrogenated nitrile butadiene rubber (HNBR), which is a material usually used in sealing applications, on the rapid gas decompression (RGD) resistance in harsh environments. Therefore, RGD component level tests were conducted in an autoclave. The supporting mechanical and dynamic mechanical property analysis, the microscopic level investigations on the material and failure analysis were conducted and are discussed in this work. Under the tested conditions, the samples filled with smaller CB primary particles showed a slightly lower volume increase during the compression and decompression phases; however, they steered to a significantly lower resistance to RGD. Transmission electron micrographs revealed that the samples filled with smaller CB particles formed larger structures as well as densified filler networks including larger agglomerates and as a consequence a decrease effective matrix component around the CB particles. Apparently, at higher loading conditions, which already deliver a certain level of mechanical stresses and strains, the densified filler network, and especially a lower amount of effective matrix material composition, adversely affect the RGD resistance. SEM-based fracture analysis did not identify any influence of the CB grades tested on the crack initiation site; however, it revealed that the cracks initiated from existing voids, hard particles, or low strength matrix sites and propagated to the outer surface.
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