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| 2. |
- Outomuro, David, et al.
(författare)
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Preference for supernormal stimuli tends to override initially learned associations for conspicuous prey traits : implications from a laboratory study
- 2020
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Ingår i: Journal of ethology. - : SPRINGER JAPAN KK. - 0289-0771 .- 1439-5444. ; 38:3, s. 365-371
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Tidskriftsartikel (refereegranskat)abstract
- How predators select on conspicuous prey traits is not well understood. We used a laboratory setup to investigate the role of learning in predator choice of conspicuous visual traits. We used a generalist predator, the great tit, and coloured wings of males of two species of damselflies as prey. Wing pigmentation differs between the species in colour (green vs. blue) and size (large vs. small). Wing pigmentation is a sexually selected trait that experiences negative selection by avian predators. Inexperienced great tits showed no preference for the colour or the size of wing pigmentation. Great tits were then repeatedly exposed to rewarded wings with either large or small wing patch size. When these experienced birds were exposed to both wing patch sizes for the first time, they tended to prefer the wings with the large patch, irrespective of their previous experience. Our results suggest that the choice of the predator was based on an initial association of the trait to a reward followed by a preference for a supernormal stimulus, probably due to a larger sensory stimulation. We discuss the implications of our laboratory results in the light of previous estimates of damselfly predation risk under field conditions.
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| 3. |
- Reidhav, Charlotte, 1977
(författare)
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Sparse district heating and flexible district heating pipes
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to describe sparse district heating conditions and explore how to improve them. Few sparse areas are heated by district heat, which reflects the economic competitiveness. A method that could be used by the district heating companies to identify the boundaries of profitable district heat is presented. Important key figures are identified when investigating the boundaries of competitive district heat. This method was identified using data gained from research on sparse areas in Göteborg, Sweden and demonstrates what to focus on in order to improve competitiveness. It is concluded that distribution heat losses must decrease in future connected sparse areas to be an efficient and competitive heating alternative. The insulation properties of flexible district heating pipes, widely used when connecting sparse areas, are an important issue when improving the energy efficiency. The long term insulation properties of flexible district heating pipes are experimentally investigated by studying the cell gas transport in semi-flexible polyurethane foams. The results show that the insulation properties are impaired more rapidly than for traditional straight pipes. The flexibility of the material is partly achieved at the cost of faster gas transport. An effective diffusion barrier hindering this gas transport is thus important. A new method to determine the temperature-dependent thermal conductivity of flexible district heating pipes is presented. The method is based on the fact that the temperature decline of hot water in a district heating pipe placed in cool water depends on the thermal conductivity of the polyurethane foam. The temperature decline of the water inside the service pipe is measured and modelled numerically. The difference between measured and calculated temperatures is used to determine the temperature-dependent thermal conductivity and the specific heat by fitting. The method is based on simple measurements of the temperature decline of the service pipe water, and it is applied on single and twin pipes. A single experiment gives the thermal conductivity for a large temperature span.
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| 4. |
- Stroeven, Arjen P., et al.
(författare)
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Importance of sampling across an assemblage of glacial landforms for interpreting cosmogenic ages of deglaciation
- 2011
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 76:1, s. 148-156
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Tidskriftsartikel (refereegranskat)abstract
- Deglaciation chronologies for some sectors of former ice sheets are relatively poorly constrained because of the paucity of features or materials traditionally used to constrain the timing of deglaciation. In areas without good deglaciation varve chronologies and/or without widespread occurrence of material that indicates the start of earliest organic radiocarbon accumulations suitable for radiocarbon dating, typically only general patterns and chronologies of deglaciation have been deduced. However, mid-latitude ice sheets that had warm-based conditions close to their margins often produced distinctive deglaciation landform assemblages, including eskers, deltas, meltwater channels and aligned lineation systems. Because these features were formed or significantly altered during the last glaciation, boulder or bedrock samples from them have the potential to yield reliable deglaciation ages using terrestrial cosmogenic nuclides (TCN) for exposure age dating. Here we present the results of a methodological study designed to examine the consistency of TCN-based deglaciation ages from a range of deglaciation landforms at a site in northern Norway. The strong coherence between exposure ages across several landforms indicates great potential for using TCN techniques on features such as eskers, deltas and meltwater channels to enhance the temporal resolution of ice-sheet deglaciation chronologies over a range of spatial scales.
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| 5. |
- Vedder, Benjamin, 1987-, et al.
(författare)
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Automated Testing of Ultra-Wideband Positioning for Autonomous Driving
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Autonomous vehicles need accurate and dependable positioning, and these systems need to be tested extensively. We have evaluated positioning based on Ultra-Wide Band (UWB) ranging with our self-driving model car using a highly automated approach. Random drivable trajectories were generated, while the UWB position was compared against the Real-Time Kinematic Satellite Navigation (RTK-SN) positioning system that our model car also is equipped with. Fault injection was used to study the fault tolerance of the UWB positioning system. Addressed challenges are: automatically generating test cases for real-time hardware, restore the state between tests and to maintain safety by preventing collisions. We were able to automatically generate and carry out hundreds of experiments on the model car in real time, and re-run them consistently with and without fault injection enabled. Thereby we demonstrate one novel approach to perform automated testing on complex real-time hardware.
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