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- Fredin, Ola, 1972-
(författare)
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Mountain centered icefields in northern Scandinavia
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mountain centered glaciers have played a major role throughout the last three million years in the Scandinavian mountains. The climatic extremes, like the present warm interglacial or cold glacial maxima, are very short-lived compared to the periods of intermediate climate conditions, characterized by the persistence of mountain based glaciers and ice fields of regional size. These have persisted in the Scandinavian mountains for about 65% of the Quaternary. Mountain based glaciers thus had a profound impact on large-scale geomorphology, which is manifested in large-scale glacial landforms such as fjords, glacial lakes and U-shaped valleys in and close to the mountain range.Through a mapping of glacial landforms in the northern Scandinavian mountain range, in particular a striking set of lateral moraines, this thesis offers new insights into Weichselian stages predating the last glacial maximum. The aerial photograph mapping and field evidence yield evidence that these lateral moraines were overridden by glacier ice subsequent to their formation. The lateral moraines were dated using terrestrial cosmogenic nuclide techniques. Although the terrestrial cosmogenic nuclide signature of the moraines is inconclusive, an early Weichselian age is tentatively suggested through correlations with other landforms and stratigraphical archives in the region. The abundance and coherent spatial pattern of the lateral moraines also allow a spatial reconstruction of this ice field. The ice field was controlled by topography and had nunataks protruding also where it was thickest close to the elevation axis of the Scandinavian mountain range. Outlet glaciers discharged into the Norwegian fjords and major valleys in Sweden.The process by which mountain based glaciers grow into an ice sheet is a matter of debate. In this thesis, a feedback mechanism between debris on the ice surface and ice sheet growth is presented. In essence, the growth of glaciers and ice sheets may be accelerated by an abundance of debris in their ablation areas. This may occur when the debris cover on the glacier surface inhibits ablation, effectively increasing the glaciers mass balance. It is thus possible that a dirty ablation area may cause the glacier to advance further than a clean glacier under similar conditions. An ice free period of significant length allows soil production through weathering, frost shattering, and slope processes. As glaciers advance through this assemblage of sediments, significant amounts of debris end up on the surface due to both mass wastage and subglacial entrainment. Evidence that this chain of events may occur, is given by large expanses of hummocky moraine (local name Veiki moraine) in the northern Swedish lowlands. Because the Veiki moraine has been correlated with the first Weichselian advance following the Eemian, it implies a heavily debris charged ice sheet emanating from the mountain range and terminating in a stagnant fashion in the lowlands.
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| 2. |
- Förstberg, Johan, et al.
(författare)
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Simulatorer för spårburen trafik : kompletterande förstudie angående behov av och möjligheterna att realisera en körsimulator för spårburen trafik
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta notat motsvarar i princip dokumentationen från den kompletterade förstudie som skickades in till VINNOVA och Banverket september/oktober 2002, inför deras respektive beslut om finansiering av en körsimulator för spårburen trafik (SST). En viss redaktionell översyn av texten har gjorts, och budget och finansiering av simulatorn har tagits bort ur detta notat. Notatet bygger på Anders Janssons analys av behoven av forskning, utveckling av ny teknik och utbildning med hjälp av en simulator, på Johan Förstbergs förstudie, vilken är redovisad i VTI notat 5-2002 samt på möjligheterna för de deltagande organisationerna/företagen att deltaga i denna innovations- och utvecklingsprocess av en ny simulator. Antalet körsimulatorer, som är tillgängliga för forskning i järnvägs- och spårvägsmiljö, är få. De flesta simulatorer som finns är utvecklade och används för utbildning och träning av förare och ägs därför av olika järnvägsföretag/operatörer. Det är viktigt att kunna samverka i existerande och kommande europeiska forskningsprojekt, dvs. i kommande nätverk och projekt inom sjätte ramprogammet. Ett exempel på sådan samverkan är EU-projektet European Drivers Desk (EUDD) inom femte ramprogrammet. En simulator skulle kunna förbättra/vidga möjligheterna att utvärdera de förslag till förarbord för höghastighetståg och godståg som utvecklas inom EUDD. Ävenledes är en samverkan med existerande forskningsmiljöer, Lex. hos SNCF i Lille, viktig för att nå en god forskningsnivå på denna kommande simulator.
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| 3. |
- Gustafsson, Fredrik, et al.
(författare)
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Particle Filters for Positioning, Navigation and Tracking
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A framework for positioning, navigation and tracking problems using particle filters (sequential Monte Carlo methods) is developed. It consists of a class of motion models and a general non-linear measurement equation in position. A general algorithm is presented, which is parsimonious with the particle dimension. It is based on marginalization, enabling a Kalman filter to estimate all position derivatives, and the particle filter becomes low-dimensional. This is of utmost importance for high-performance real-time applications. Automotive and airborne applications illustrate numerically the advantage over classical Kalman filter based algorithms. Here the use of non-linear models and non-Gaussian noise is the main explanation for the improvement in accuracy. More specifically, we describe how the technique of map matching is used to match an aircraft's elevation profile to a digital elevation map, and a car's horizontal driven path to a street map. In both cases, real-time implementations are available, and tests have shown that the accuracy in both cases is comparable to satellite navigation (as GPS), but with higher integrity. Based on simulations, we also argue how the particle filter can be used for positioning based on cellular phone measurements, for integrated navigation in aircraft, and for target tracking in aircraft and cars. Finally, the particle filter enables a promising solution to the combined task of navigation and tracking, with possible application to airborne hunting and collision avoidance systems in cars.
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