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- Kao-Walter, Sharon, et al.
(författare)
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Fracture Toughness of a Laminated Composite
- 2003
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Ingår i: Fracture of Polymers, Composites and Adhesives II. ; , s. 355-364
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Konferensbidrag (refereegranskat)abstract
- The fracture toughness of a polymer-metal laminate composite is obtained by mechanical testing of a specimen containing a pre-crack. The laminate is a material used for packaging. It consists of a thin aluminium foil and a polymer coating. A centre cracked panel test geometry is used. Each of the layers forming the laminate is also tested separately. The result is compared with the measured fracture strength of the individual layers. It is observed that the load carrying capacity increases dramatically for the laminate. At the strain when peak load is reached for the laminate only aluminium is expected to carry any substantial load because of the low stiffness of the LDPE. However, the strength of the laminate is almost twice the strength of the aluminium foil. The reason seems to be that the aluminium forces the polymer to absorb large quantities of energy at mmall nominal strain. The toughness compares well with the accumulated toughness of all involved layers. Possible fracture of the interface between the layers is discussed.
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| 3. |
- Fagerström, Martin, 1979, et al.
(författare)
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MODELLING AND TESTING THE CRASH BEHAVIOUR OF COMPOSITE VEHICLES COMPONENTS
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the current contribution we will present the latest developments in the project “Modelling crash behaviour in future lightweight composite vehicles – Step 2”, involving 11 Swedish partners. On the material modelling side, a fully three-dimensional model to describe fibre kinking has recently been developed. The model is physically based and considers the fibre rotation during kink-band formation under large deformations. The FE implementation of the model is straightforward which allows for easy implementation. The validation of the model for stiffness and strength shows good correlation with the experiments. The influence of initial misalignments on the stiffness is well captured, the strength defined at the onset of unstable fibre rotation, is well predicted, and, in addition, the crushing response shows very good agreement with experimental results in terms of morphology in the crushing zone, as well as in the load response. To allow for computational efficiency, we have also developed and implemented (as a user element in LS-DYNA) an adaptive modelling strategy which allows for laminates to be initially modelled with only one element over the thickness.The user element kinematics can be adaptively enriched by introducing new degrees of freedom during the simulation to allow for more accurate stress predictions in critical regions by introducing discrete material interfaces, and for the modelling of delamination crack growth by introducing discrete crack surfaces interconnected with a cohesive zone law. In this work, special care has been taken to develop a robust method for explicit crash analysis. In the element, we also able to consider the correct intralaminar fracture toughness regularisation for various spatial discretisations. To assess and validate the models developed in the project, we have also conducted a series of bending and crushing experiments on component level. Three-point bending tests (in total 45 beams) have been conducted for three different carbon-epoxy material systems (pre-preg and vacuum infused), two different span lengths and two different lay-ups at several impact speeds. Similarly, crushing tests have been conducted for the same material systems by crushing tubes (in total 35 tubes) at various angles, with two different lay-ups and at two different loading speeds (quasi-static and dynamic). We believe that these tests serve as a very strong basis for any crash model validation.
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| 5. |
- Bonaldi, Carlotta, et al.
(författare)
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Recurrence, fidelity and proximity to previously visited sites throughout the annual cycle in a trans-Saharan migrant, the common cuckoo
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Ingår i: Journal of Avian Biology. - 0908-8857.
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Tidskriftsartikel (refereegranskat)abstract
- Most migratory birds return every year to the same breeding sites and some species show a similarly high fidelity to wintering grounds as well. Fidelity to stopover sites during migration has been much less studied and is usually found to be lower. Here, we investigate site fidelity and distance to previously visited sites throughout the annual cycle in the common cuckoo, a nocturnal trans-Saharan migrant, based on satellite-tracking data from repeated annual migrations of thirteen adult males. All birds (100%) returned to the same breeding grounds, with a median shortest distance of only 1 km from the locations in previous year. This was in strong contrast to a much lower and much less precise site fidelity at non-breeding sites during the annual cycle: In only 18% of the possible cases in all non-breeding regions combined, did the cuckoos return to within 50 km of a previously visited non-breeding site, with no significant differences among the main staging regions (Europe in autumn, Sahel in autumn, wintering in Central Africa, West Africa in spring, Europe in spring). The shortest distance to a previously visited non-breeding site differed among the staging regions with median shortest distances for the longest stopovers of 131 km [2;1223] (median [min;max]) in Europe, 207 km [1;2222] in Sahel in autumn and 110 km [0;628] in Central Africa. The distance to a previously visited staging site decreased with the time spent at the stopover in a previous year. Understanding the drivers of recurrence and site selection in migratory birds are important for guiding conservation efforts in this group but further studies are needed to establish whether the patterns observed in cuckoos are general among terrestrial migrants with continuous distribution of habitat.
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| 8. |
- Nieto Piña, Luis, 1988, et al.
(författare)
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Training Word Sense Embeddings With Lexicon-based Regularization
- 2017
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Ingår i: Proceedings of the Eighth International Joint Conference on Natural Language Processing (Volume 1: Long Papers), Taipei, Taiwan, November 27 – December 1, 2017. - : Asian Federation of Natural Language Processing. - 9781948087001
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Konferensbidrag (refereegranskat)abstract
- We propose to improve word sense embeddings by enriching an automatic corpus-based method with lexicographic data. Information from a lexicon is introduced into the learning algorithm’s objective function through a regularizer. The incorporation of lexicographic data yields embeddings that are able to reflect expertdefined word senses, while retaining the robustness, high quality, and coverage of automatic corpus-based methods. These properties are observed in a manual inspection of the semantic clusters that different degrees of regularizer strength create in the vector space. Moreover, we evaluate the sense embeddings in two downstream applications: word sense disambiguation and semantic frame prediction, where they outperform simpler approaches. Our results show that a corpusbased model balanced with lexicographic data learns better representations and improve their performance in downstream tasks
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| 10. |
- Braco, Veletanlic, et al.
(författare)
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Flipped classroom approach and its implementation in an online course
- 2016
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Ingår i: Lärarlärdom 2016. - Högskolan Kristianstad : Kristianstad University Press.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Active learning is the process where students learn beyond passively listening to an instructor's lecture. In this way students are engaged in their learning activities. It has been accepted that active learning leads to deeper understanding and better learning outcomes.The term flipped classroom has been widely used to describe a new pedagogical approach in which traditional lecture and homework elements of a course are reversed so that the initial exposure to the learning content takes place outside of the classroom. This approach frees up class time, promotes active learning and engagement in learning and facilitates student-centered learning.In this study we experimented with flipped classroom approach in the online course Programming in C during the autumn term 2015. The purpose of the experiment was to determine whether flipped classroom can serve as an appropriate method to use in an online course and to find out to what extent flipped classroom can stimulate active learning in an online setting. Based on known concept of flipped classroom approach and literature review, we systematically reviewed YouTube videos and selected 52 video clips to use as companion course materials. We also compiled and produced 212 quiz questions to use as formative assessment. In order to promote interaction among the students, we experimented with peer-review as a part of the laboratory work process. We also provided scheduled online sessions in the form of chat rooms. Short video clips were positively received by the students. Even the peer-review approach was positively received but the students gave up this activity at the end of the course, due to the work load. Flipped classroom has potential to be used in online settings but distinction between "classroom" and "outside classroom" is not always clear.More work is needed to make this distinction visible and to make the transition between these two learning environments smooth.
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