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- Broström, Stig, et al.
(författare)
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Preschool teachers' view on learning in preschool in Sweden and Denmark
- 2014
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Ingår i: European Early Childhood Education Research Journal. - 1350-293X .- 1752-1807. ; 22:5, s. 590-603
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to examine how preschool teachers in Sweden and Denmark perceive children's learning in preschool. The study aimed to answer the following questions: What is 'learning'? How do children learn? What are the best conditions for children's learning? What is the role of participation in children's learning? The results show that from the teacher's perspectives, children's learning is connected to children's social interaction and development in which the children's initiatives are crucial. Learning, to a great extent, results from children's active involvement. There are many similarities between how Danish and Swedish preschool teachers think of learning and participation. This supports earlier assumption about the coherence of Nordic preschool beliefs which unites education and care.
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- Karlsson, Jesper, et al.
(författare)
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An a posteriori error estimate for symplectic Euler approximation of optimal control problems
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This work focuses on numerical solutions of optimal control problems. A time discretization error representation is derived for the approximation of the associated value function. It concerns Symplectic Euler solutions of the Hamiltonian system connected with the optimal control problem. The error representation has a leading order term consisting of an error density that is computable from Symplectic Euler solutions. Under an assumption of the pathwise convergence of the approximate dual function as the maximum time step goes to zero, we prove that the remainder is of higher order than the leading error density part in the error representation. With the error representation, it is possible to perform adaptive time stepping. We apply an adaptive algorithm originally developed for ordinary differential equations. The performance is illustrated by numerical tests.
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- Steinvall, Ove, et al.
(författare)
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Laser dazzling impacts on car driver performance
- 2013
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Konferensbidrag (refereegranskat)abstract
- A growing problem for the Police and Security Forces has been to prevent potentially hostile individuals to pass a checkpoint, without using lethatl violence. Therefore the question has been if there is a laser or any other strong light source that could be used as a warning and dazzling device, without lethal or long term effects. To investigate the possibilities a field trial has been performed at a motor-racing track. A green CW laser with an irradiance on the eye of maximum 0.5 MPE, as defined by ICNIRP [1] and the ANZI standard [2], was used as a dazzle source. Ten drivers have been driving with dipped headlights through a course of three lines with orange cones. In every line there has been only one gate wide enough to pass without hitting the cones. The time through the course, the choice of gates and the number of cones hit have been measured. For every second trial drive through the track, the driver was exposed to the laser dazzler. The background illuminances ranged from a thousand lux in daylight to about ten millilux in darkness. The protective effect of the sun-visor of the car was investigated. The drives visual system was carefully examined before and after experimental driving and a few weeks after the experimental driving to verify that no pathological effects, that could potentially be induced by the laser exposure, pre-existed or occurred after the laser exposure. An analysis of variance for a within subjects design has been used for evaluation. It was found that green laser light can have an obvious warning effect in daylight. Dazzling does reduce the drivers ability to make judgments and manouver the car in twilight and darkness. A sun-visor can reduce the glare and give the driver an improved control, but that perception can be unjustified. No damage to the visual system was observed.
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| 9. |
- Yu, Zhaohua, 1983-, et al.
(författare)
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Green light laser exposure at 532nm near the exposure limit during a human volunteer vehicle driving task does not alter structure or function in the visual system
- 2014
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Ingår i: Journal of laser applications. - Melville : Laser Institute of America. - 1042-346X .- 1938-1387. ; 26:2, s. 022009-1-022009-7
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to verify nonexistence of clinically important pathological effects to the visual system after exposure to 532 nm green laser light close to the exposure limit. The present medical surveillance of vision and visual health reported in this paper is the conjunction with a study of driver performance in the presence of 532 nm laser induced glare. The driving time varied between 25 and 55 s, depending on background luminance. The laser was on during the complete test drive. The peak corneal irradiance typically was 3.5Wm2 in one test drive. Considering a typical test drive, the typical time integrated corneal radiant exposure for one test drive was estimated to be 53 J/m2. The number of test drives varied among drivers but was typically 50, thus resulting in a cumulative corneal exposure dose of approximately 2.7 kJ/m2. Altogether, ten subjects were recruited according to inclusion and exclusion criteria. All ten subjects were examined for visual acuity, intraocular pressure, contrast sensitivity, color vision, monocular reading speed, and eye structure with clinical slit-lamp microscopy examination and indirect retinoscopy. All subjects were examined before exposure, immediately after exposure, and finally within an interval between 1 week and 4 weeks after exposure. There was no significant change of visual acuity, intraocular pressure, contrast sensitivity, color vision, or monocular reading speed between before and after exposure. No abnormal ocular structure was detected after exposure. This study demonstrates that close to exposure limit, exposure to 532 nm green laser light during a vehicle driving task does not induce structural or functional damage to the human visual system as observed in the interval minutes to weeks after exposure.
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