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- Otero, Jaime, et al.
(författare)
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Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar)
- 2014
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 20:1, s. 61-75
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Tidskriftsartikel (refereegranskat)abstract
- Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater ('parr') stage to the migratory stage where they descend streams and enter salt water ('smolt') is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes.
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- Grip, Carl Erik, et al.
(författare)
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Numerical prediction and experimental verification of thermal stratification during holding in pilot plant and production ladles
- 1999
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 39:7, s. 715-721
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Tidskriftsartikel (refereegranskat)abstract
- A 3-dimensional CFD-model has been developed to simulate the natural convection flow in ladles. Qualified measurements of temperature and velocities in 107 and 7 tonne ladles have been made to verify the model. The downward convection flow at the ladle wall has been studied using radioactive isotopes and the thermal stratification has been studied by means of continuous temperature measurements. The experimental techniques are complex and additional numerical simulations have been carried out to study the effect of the measurement technique on the measurement error. The result indicates that the measurements are of sufficient accuracy for the validation. The measurements are compared to predictions from the numerical model. The main conclusion is that the theoretical CFD model gives a very accurate estimation of the temperature distribution during holding.
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- Grip, Carl-Erik, et al.
(författare)
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Theoretical and practical study of thermal stratification and drainage in ladles of different geometry
- 2000
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 29:1, s. 30-38
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Tidskriftsartikel (refereegranskat)abstract
- SSAB Lulea, SSAB Oxelosund, MEFOS and Lulea University of Technology have cooperated in developing theoretical models for prediction of thermal stratification and drainage in steel ladles. Predicted results have been verified by measurements done in production ladles with heat weighs of 105 and 200 tonne as well as in a 7-tonne pilot plant ladle. The thermal stratification was measured by thermocouples at different depths. The drainage flow was studied by means of tracer experiments. Numerical simulation models of the steel flow were developed for 7, 105 and 200 tonne steel ladles. The agreement between predictions and measurements was found to be good. The conclusion is that CFD simulation gives a good prediction of stratification and drainage flows in production ladles.
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- Andersson, Jan, 1973-
(författare)
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Laborativt arbete i fysikundervisningen : Något som behöver diskuteras!
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BaksidestextI gymnasieskolans kursplaner för ämnet fysik framhålls det undersökande arbetssättet genom att betona att eleverna ska ges förutsättningar att utveckla förmågan att söka svar på frågor, planera, genomföra, tolka och redovisa experiment. Eleverna ska dessutom ges möjligheter att använda sina kunskaper i fysik för att kommunicera, argumentera och presentera slutsatser. Utgångspunkten i den här avhandlingen är att laborationsmomentet skapar en speciell diskurs där eleverna blir aktörer och läraren iträder rollen som observatör. I en sådan miljö skapas förutsättningar för att eleverna på ett naturligt sätt får möjlighet att prata och diskutera fysik, utifrån sina egna förutsättningar. Syftet med denna avhandling är att genom praktikbaserade studier tydliggöra hur fysiklaborationens utformning påverkar elevernas kommunikation och vidare hur eleverna använder språket vid laborationstillfället för att skapa förståelse. Detta bidrar till debatten om fysiklaborationens effektivitet, sett både ur ett undervisnings- och inlärningsperspektiv. Resultaten visar att olika laborationsformer är uppbyggda av liknande aktiviteter, men varierar i tid som ägnas åt de olika aktiviteterna. Aktiviteterna i sin tur skapar samtal av olika karaktär. Olika samtalsformer används för skilda syften. Ett analytiskt ramverk har skapats för att ingående kunna studera hur och vad eleverna talar om både på en lingvistisk och kognitiv nivå.
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