| 1. |
- Bergsten, Christer, 1949-, et al.
(författare)
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Secondary school mathematics students exploring the connectedness of mathematics : The case of the parabola and its tangent in a dynamic geometry environment
- 2021
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Ingår i: The Mathematics Enthusiast. - Missoula, MT United States : University of Montana. - 1551-3440. ; 18:1-2, s. 183-209
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Tidskriftsartikel (refereegranskat)abstract
- Drawing on the Semiotic-cultural approach and the Anthropological theory of the didactic, this paper discusses how exploration of historically framed conceptualizations of mathematical objects can establish bridges between different mathematical areas such as calculus and Euclidean geometry. A classroom intervention study in two secondary mathematics classrooms involving dynamic geometry software tools to support the construction of a parabola and its tangent and aiming at the development of representational flexibility between algebraic/ functional and geometrical approaches, illustrates how students may benefit from participation in such explorations.
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| 2. |
- Bergsten, Christer, 1949-, et al.
(författare)
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Understanding the secondary-tertiary transition in mathematics education : Contribution of theories to interpreting empirical data
- 2019
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Ingår i: Proceedings of the Eleventh Congress of the European Society for Research in Mathematics Education. - Utrecht, Netherlands : Freudenthal Group & Freudenthal Institute, Utrecht University and ERME.
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Konferensbidrag (refereegranskat)abstract
- The paper reports a review of studies on the secondary-tertiary transition in mathematics. With an interest in the contribution of theories, it intends to explore what insights empirical studies using new theoretical lenses have added. While there is a move towards socio-cultural theorizing, some dimensions pertaining to issues of social (re)production still appear under-researched.
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| 3. |
- Rehan, Arbab
(författare)
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Microstructure and mechanical properties of a 5 wt.% Cr cold work tool steel : Influence of heat treatment procedure.
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demand for Advanced High Strength Steel (AHSS) in the automotive industry is increasing day by day. It is mainly motivated by the fact that AHSS can be used as thin sheets while having high strengths. It enables weight reduction of the automobiles which consequently increases the fuel efficiency and has proven to be less harmful to the environment. It is also expected that AHSS will have even higher strength in the near future. Cold work tools steels with 5 wt.% Cr are commonly used to process AHSS. Therefore, the tool steel must meet the challenges in the future, i.e. have even higher hardness, compressive strength and toughness. One way of increasing the mechanical properties of the tool steel is by improving the heat treatment parameters. However, it is not possible without a deeper understanding of the heat treatment process. Therefore, this work presents investigations related to phase transformations occurring in a 5 wt.% Cr cold work tool steel during heat treatment. Furthermore, the influence of austenitisation and tempering temperatures on the microstructure and mechanical properties were investigated. The studies revealed that a higher austenitisation temperature can be used to achieve a higher hardness, good compressive strength and adequate toughnessof the steel. However, too high austenitisation temperature may result inexcessive coarsening of prior austenite grains which reduced the impact toughness. It was also found that retained austenite can transform during tempering by two different mechanisms. Firstly, when tempering at 525°C, carbides precipitate in retained austenite lowering its stability and permitting a transformation to marten site on cooling. Secondly, when tempering at 600°Cfor extended holding time retained austenite isothermally transforms to ferrite and carbides. This occurs by precipitation of carbides in retained austenite followed by a final transformation to ferrite and carbides.These results were used to understand the standard tempering procedure of the 5 wt.% Cr cold work tool steel. Furthermore, alternative heat treatment procedures are discussed based on the important findings presented in this thesis.
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| 4. |
- Rehan, Arbab, et al.
(författare)
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Retained Austenite Transformation during Heat Treatment of a 5 Wt Pct Cr Cold Work Tool Steel
- 2017
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 48A:11, s. 5233-5243
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Tidskriftsartikel (refereegranskat)abstract
- Retained austenite transformation was studied for a 5 wt pct Cr cold work tool steel tempered at 798 K and 873 K (525 degrees C and 600 degrees C) followed by cooling to room temperature. Tempering cycles with variations in holding times were conducted to observe the mechanisms involved. Phase transformations were studied with dilatometry, and the resulting microstructures were characterized with X-ray diffraction and scanning electron microscopy. Tempering treatments at 798 K (525 degrees C) resulted in retained austenite transformation to martensite on cooling. The martensite start (M-s) and martensite finish (M-f) temperatures increased with longer holding times at tempering temperature. At the same time, the lattice parameter of retained austenite decreased. Calculations from the Ms temperatures and lattice parameters suggested that there was a decrease in carbon content of retained austenite as a result of precipitation of carbides prior to transformation. This was in agreement with the resulting microstructure and the contraction of the specimen during tempering, as observed by dilatometry. Tempering at 873 K (600 degrees C) resulted in precipitation of carbides in retained austenite followed by transformation to ferrite and carbides. This was further supported by the initial contraction and later expansion of the dilatometry specimen, the resulting microstructure, and the absence of any phase transformation on cooling from the tempering treatment. It was concluded that there are two mechanisms of retained austenite transformation occurring depending on tempering temperature and time. This was found useful in understanding the standard tempering treatment, and suggestions regarding alternative tempering treatments are discussed. (C) The Author(s) 2017.
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| 5. |
- Westergren, Ulrika H., 1974-
(författare)
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Partnership outsourcing evolution : The process of creating and maintaining a network of actors
- 2007
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Ingår i: Proceedings of the Fifteenth European Conference on Information Systems. ; , s. 1179-1189
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Konferensbidrag (refereegranskat)abstract
- This paper is an attempt to build on and extend existing outsourcing research by focusing on the process of managing an outsourcing partnership. Furthermore, it considers the role of information technology and the importance of establishing interorganizational trust in order to provide a deeper understanding of the partnership outsourcing phenomenon. The outsourcing partnership in focus in this paper is between Alpha Corp., a large minerals group, and RDC, its remote service provider. The paper shows that Alpha Corp.’s strategy for creating, maintaining and evolving the partnership with RDC occurs in three different stages: black-boxing of technology, establishing interorganizational trust, and performance based contracting. This study provides support for McFarlan and Nolan’s (1995, p. 22) claim that “What determines success or failure is managing the relationship less as a contract and more as a strategic alliance”. However, given the multiple roles information technology assumes in an outsourcing alliance, this paper also shows that understanding and managing the role of IT is just as crucial in maintaining a successful partnership. In addition, given the documented importance of information technology in outsourcing partnerships, there is a need to include trust in technology as yet another dimension in establishing interorganizational trust.
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