| 1. |
- Fredriksson, Håkan, et al.
(author)
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Gyro feedback of a hydraulic steering system
- 2011
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In: International Journal of Vehicle Autonomous Systems. - 1471-0226 .- 1741-5306. ; 9:3/4, s. 189-202
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Journal article (peer-reviewed)abstract
- We study the problem to steer, teleoperated as well as autonomously, a tractor that is to operate on a rough and slippery surface. The main idea is to control the effective steering angle of the vehicle. A benefit with this approach is that the vehicle will strive to move in a predefined way irrespective of the surface conditions. To test if the approach is usable we implemented a straight forward p-controller in combination with an estimator of the effective steering angle of the tractor. Our tests indicates that the approach can be useful. Future work would include studies on more advanced control strategies and estimators to reduce some of the problems that we address.
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| 2. |
- Fredriksson, Håkan, et al.
(author)
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Track loader kinematics
- 2010
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In: Preprints. - Timisoara : Ed. Politehnica. ; , s. 139-142
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Conference paper (peer-reviewed)abstract
- We study the problem to teleoperate a Caterpillar 973c track loader. The track loader and a system for teleoperation are described. A tested and working kinematic model used for dead reckoning is also presented. Track speed sensors combined with a rate gyro are used as input to the model. The model shows good results when tested and compared to a GPS navigation system.
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| 3. |
- Bergström, Lena, et al.
(author)
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Fish community responses to restoration of a eutrophic coastal bay
- 2024
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In: Ambio. - 0044-7447 .- 1654-7209. ; 53, s. 109-125
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Journal article (peer-reviewed)abstract
- Interest in coastal restoration measures is increasing, but information about subsequent ecosystem recovery processes is limited. In Bjornofjarden on the Baltic Sea coast, Stockholm archipelago, a pioneering case study to reduce coastal eutrophication led to improvements and initially halved phosphorus levels. Here, we evaluate the effects of the restoration on the local fish assemblage over one decade after the measures. The study gives a unique possibility to evaluate responses of coastal fish to nutrient variables and abatement in a controlled natural setting. Cyprinid abundance decreased and perch partially increased with decreasing turbidity levels, while mean trophic level increased over time in the restored area. Responses were overall weak, likely attributed to an attenuation of the eutrophication abatement effect over time. The results suggest that nutrient reduction gives slow responses in fish compared to alternative measures such as fishing closures.
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| 4. |
- Deakin Crick, Ruth, et al.
(author)
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Developing an instrument to measure learning to learn : Paper presented at the Association for Educational Assessment Europe 8th Annual Conference in Stockholm in November 2007
- 2007
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Conference paper (peer-reviewed)abstract
- There is a growing interest in learning to learn in a European context. European Union initiatives have resulted in describing the competence of learning to learn in the framework for competencies for lifelong learning. Related to this has also been a wish to find ways to measure learning to learn. An Expert Group initiated by the European Commission developed a proposal to organise a pilot project on learning to learn. The group identified three interesting research projects which could be used in the further work to develop a European pilot study on learning to learn: an instrument to test learning to learn developed by the University of Helsinki, the Effective Lifelong Learning Inventory developed by the University of Bristol and the tests on cross-curricular skills developed by the University of Amsterdam. The Expert Group also proposed a framework on learning to learn. The framework was based on the assumption, proposed in the definition on learning to learn decided by the Education Council and the European Parliament, that this key competence can be defined as containing two dimensions; a cognitive and an affective (or belief) part. Under each dimension a number of subscales, based on existing subscales in the tests which have been developed in the research project mentioned above, were developed. A working group containing the authors of this paper was asked by the Expert Group to develop a test on learning to learn. This group has developed a draft instrument. The instrument has been constructed to correspond to the earlier developed framework. This paper describes how the work to construct this instrument has proceeded.
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| 5. |
- Fredriksson Möller, Björn, et al.
(author)
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CO2-free power generation - A study of three conceptually different plant layouts
- 2003
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In: American Society of Mechanical Engineers, International Gas Turbine Institute, Turbo Expo (Publication) IGTI. ; 3, s. 255-262
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Conference paper (peer-reviewed)abstract
- Ever since the release of the Kyoto protocol the demand for CO2-free processes have been increasing. In this paper three different concepts with no or a very small release of CO2 to the atmosphere are evaluated and compared concerning plant efficiency and investment cost. A novel approach to biomass gasification is proposed to provide fuel for a combined gas turbine cycle, where the biomass is considered to be a renewable fuel with zero impact regarding CO2 in the exhaust gases. The gasification concept used is a Dual Pressurised Fluidised Bed Gasifier (DPFBG) system, using steam and recycled product gas as fluidising agent in the gasification reactor. In the separate combustion reactor air is used as fluidising agent. The second cycle is a hybrid fuelled Humid Air Turbine (HAT) cycle with post-combustion CO 2-separation. Steam used for regenerating the amines in the separation plant is produced using a biomass boiler, and natural gas is used as fuel for the humid air turbine. With this fuel mix the net release of CO 2 can even be less than zero if the exhaust gas from the steam generator is mixed and cleaned together with the main exhaust gas flow. The third cycle proposed is a combined cycle with postcombustion CO 2-separation and the steam generation for the CO 2-separation integrated in the bottoming steam cycle. All power cycles have been modelled in IPSEpro [trademark] (tm), a heat and mass balance software, using advanced component models developed by the authors. An equilibrium model is employed both for the gasification and the separation of CO2 from exhaust gases. All three power cycles show efficiencies around 45%, which is high for a biomass gasification cycle. The HAT and the combined cycle show efficiency drops of about 8 percentage points, due to the post-combustion treatment of exhaust gases.
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