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- Rudsberg, Karin, 1973-
(författare)
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Elevers lärande i argumentativa diskussioner om hållbar utveckling
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall ambition with this thesis is to develop knowledge about students’ learning, especially with regard to process and content, when they participate in argumentation. Students’ learning is investigated through in situ studies of classroom practices. The theoretical point of departure is a pragmatic perspective in which learning is understood and investigated in terms of concrete actions. The empirical material consists of video recorded lessons at secondary and upper secondary schools in Sweden. The content of the lessons is argumentative discussions about sustainable development and socioscientific issues. In the first study, the functions that teachers’ actions have for students’ learning processes are investigated using Epistemological Move Analysis. In the second study, an approach is developed and illustrated that facilitates investigations into students’ learning processes in terms of knowledge content and argument construction in argumentation. The method, called Transactional Argumentation Analysis, combines a pragmatic perspective of learning with an argument analysis based on Toulmin’s Argument Pattern. In the third study, the functions that knowledge have when used by students in argumentative discussions are examined. The fourth study investigates the role of peers for students’ learning and how students influence the argumentation at a collective level. Here Transactional Argumentation Analysis is developed further in order to facilitate investigations of the dynamic interplay between the intra-personal and the inter-personal dimensions of learning and the result of this interplay in terms of the knowledge content and arguments that are constructed. The thesis shows how students’ learning can be investigated through in situ studies of educational practices. The methodological contribution of the thesis consists of the development and further elaboration of Transactional Argumentation Analysis. The thesis also contributes with substantial knowledge about students’ learning processes with regard to knowledge content and argument construction when participating in argumentation. Another contribution concerns the functions of knowledge when used by students in argumentation. Finally, the studies show how peers and teachers influence students’ learning, and how students contribute to the shared argumentation in the classroom.
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| 2. |
- Öhman, Johan, 1991-
(författare)
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3D localization in digital holography from scattered light from micrometer-sized particles
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When a particle is illuminated by a beam of light it will scatter and redistribute the light in all directions. How it scatters depends on the size, shape and refractive index of the particle. Additionally, it depends on the wavelength and polarization of the illuminating beam. The direction and distance to the observer relative the particle also needs to be considered. A digital holographic imaging system is used to collect parts of the scattered light from micrometer-sized particles. By utilizing digital holography a three-dimensional reconstruction of the imaged scene is possible. Traditionally, particles are localized based on the intensity in the holographic reconstructions. In this licentiate thesis, the phase response of the scattered light is investigated and utilized. An alternative method for locating spherical particles is presented. The method locate particles based on a simple feature of a propagating wave, namely the fact that the wavefront curvature changes from converging to diverging at the axial location of the particle. The wavefront curvature is estimated using two different methods. The first method estimates the lateral phase-gradients using a finite-difference method. The second method uses a three-dimensional parametric model based on a Chebyshev polynomial expansion. The methods are demonstrated using both simulations and experimental measurements. The simulations are based on the Lorenz-Mie scattering theory for spherical particles and are combined with an imaging system model. Experiments are performed using an off-axis polarization sensitive digital holographic system with a coherent Nd:YAG laser. Measurements of stationary particles are made to validate and evaluate the proposed method. It is found that these methods estimate the true axial position and does not have the offset that is associated with intensity-based methods. Additionally, it is possible to exclude noise that shows up as false particles since noise does not have the same phase response as a real particle. The second method, that uses a parametric model, also improves the standard deviation in the positioning.
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