| 1. |
- Nybacka, Mikael, et al.
(författare)
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Project: CASTT - Centre for Automotive Systems Technologies and Testing
- 2007
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Annan publikation (populärvet., debatt m.m.)abstract
- Through the Centre for Automotive Systems Technologies and Testing, Luleå University of Technology aims to first of all support automotive winter testing in Northern Sweden. This means to support the local automotive test entrepreneurs and through them their customers: the car manufacturers and their suppliers. To succeed in this task, the center relies on the university's areas of leading research and most importantly on the cooperation between those areas.
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| 2. |
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| 3. |
- Ehnberg, Jimmy, 1976, et al.
(författare)
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Reliability of a small power system using solar power and hydro
- 2005
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Ingår i: Electric Power Systems Research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 74:1, s. 119-127
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the availability of the electricity supply when the sources consist of a combination of solar energy and a small hydro installation. Instead of flow-of-river, a small reservoir is used. By not using the hydro energy during sunny periods, the natural flow-of-river fills up the reservoir for later use. A model for global solar radiation is proposed with an astronomical part (deterministic) and a meteorological part (stochastic). The meteorological part is based on a Markov model of the cloud coverage. The solar model does not require solar radiation measurements, just cloud observations. A case study has been performed for Timbuktu (16.75degreesN, 0.07degreesW) in which generation availability is simulated for four different cases: solar power only; solar power with storage; solar and hydro power and solar and hydro, power with storage. To be able to use exclusively renewable energy sources, a combination of sources is needed to secure the reliability of the supply. Using solar cells in combination with a small reservoir is favorable. Even with a weak flow the affect of the flow on the day time reliability is minor, but great benefits can be found for reliability during low load hours (night time).
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| 4. |
- Bollen, Math, et al.
(författare)
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Classification of Underlying Causes of Power Quality Disturbances: Deterministic versus Statistical Methods
- 2007
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Ingår i: Eurasip Journal on Applied Signal Processing. - : Springer Science and Business Media LLC. - 1110-8657 .- 1687-0433. ; 2007, s. 17 pages (Article ID 79747)-
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the two main types of classification methods for power quality disturbances based on underlying causes: deterministic classification, giving an expert system as an example, and statistical classification, with support vector machines as an example. An expert system is suitable when one has limited amount of data and sufficient power system expert knowledge, however its application requires a set of threshold values. Statistical methods are suitable when large amount of data is available for training. Two important issues to guarantee the effectiveness of a classifier, data segmentation and featureextraction, are discussed. Segmentation of a sequence of data recording is pre-processing to partition the datainto segments each representing a duration containing either an event or transition between two events. Extraction of features is applied to each segment individually. Some useful features and their effectiveness are then discussed. Some experimental results are included for demonstrating theeffectiveness of both systems. Finally, conclusions are given together with the discussion of some future research directions.
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| 5. |
- Cervantes, Michel, et al.
(författare)
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Porjus U9A full-scale hydropower research facility
- 2008
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Ingår i: Hydro technology and the evironment for the new century. - Foz do Iguassu.
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Konferensbidrag (refereegranskat)abstract
- Hydropower still faces complex scientific and technical challenges in order to secure the availability and reliability of the power plants despite more than a century of development. The main challenge is due to new market constrains such as electrical market deregulation and introduction of renewable sources of energy. The major problem is related to the dynamic of the rotor involving several fields: hydraulics, power engineering and mechanics. On the other side, the large and growing hydropower world market represents an opportunity for technically advanced companies offering better efficiency. The difficulty to scale rigorously any technical advance makes full-scale experiment a necessity. World unique facilities are available at Porjus, Sweden, for this purpose. The Porjus Hydropower Centre is composed of a Francis (U8) and a Kaplan (U9) turbine of 10 MW, each exclusively dedicated to education, research and development. In order to further investigate specific issues related to availability and reliability, a project was initiated in 2006. The main objective is to make U9 a full-scale hydropower laboratory able firstly to furnish the necessary data for the development of rotor-dynamic models but also turbines and bearings. To this purposes more than 200 sensors have been installed to measure displacements, forces, pressure, film thickness, strains... The work presents an overview of the newly upgrade facility as well as some of the problems faced during the instrumentation of the machine.
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| 6. |
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| 7. |
- Fransson, Lennart, et al.
(författare)
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Ice loads for wind-power foundations in the Gulf of Bothnia
- 2009
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Ingår i: Proceedings of the 20th International Conference on Port and Ocean Engineering under Arctic Conditions. ; June 9-12, 2009, s. 12-19
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Konferensbidrag (refereegranskat)abstract
- Ice loads measured on lighthouses in the Gulf of Bothnia can serve as guidance for design of foundations for wind-power generators. At some locations in the sea these structures must withstand high pressure from solid land fast ice as well as from ridges or other compacted ice masses that are drifting. Recommendations for design of offshore foundations around the Swedish coastline have recently been written by the authors. For the purpose of design, effective pressure as well as compressive strength is assumed to be independent of ice thickness. All structures should be designed for dynamic ice loads that are dependent on the natural frequency of the structure and the ice drift velocity. Increased effective pressure has earlier been indicated for high speed ice crushing both in field studies and compression tests. The presented results from ice load measurements on lighthouse Norströmsgrund support the suspicion that also design ice loads should increase with drift speed. This rate effect and other uncertainties about the worst case scenario for ice-induced vibrations suggest a more conservative design of wind-power foundations inside the dynamic ice zone.
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| 8. |
- Larsson, Linda, et al.
(författare)
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Microscopic 3-D Displacement Field Measurements using Digital Speckle Photography
- 2004
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Ingår i: Optics and Lasers in Engineering, 41, 767-777 (2004). ; 41:5, s. 767-777
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Tidskriftsartikel (refereegranskat)abstract
- A technique to measure object shape and 3-D displacement fields in micro-scale is offered by microscopic stereo digital speckle photography. The displacement of the random features that are often present on many engineering surfaces when viewed in a microscope is measured with the system, using image correlation. In this paper the equipment, physical model and calibration routines are described. The technique can be applied for sub-mm sized objects of arbitrary shape for small deformation fields. As a verifying experiment, an in-plane rotation of a flat calibration plate is presented. The expected in-plane errors are shown to be less than 0.1 ?m and the corresponding out-of-plane errors about three times larger. As a pilot experiment, micro-structural paper expansion is studied, when exposed to humidity. The scaling properties of the microscope as well as the sampling criteria and reliability of the system are discussed in detail
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| 9. |
- Marklund, Erik, et al.
(författare)
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Stiffness of aligned wood fiber composites: Effects of microstructure and phase properties
- 2008
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Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 42:22, s. 2377-2405
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Tidskriftsartikel (refereegranskat)abstract
- The effect of wood fiber anisotropy and their geometrical features on wood fiber composite stiffness is analyzed. An analytical model for an N-phase composite with orthotropic properties of constituents is developed and used. This model is a straightforward generalization of Hashin's concentric cylinder assembly model and Christensen's generalized self-consistent approach. It was found that most macro-properties are governed by only one property of the cell wall which is very important in attempts to back-calculate the fiber properties. The role of lumen (whether it filled by resin or not) has a very large effect on the composite shear properties. It is shown that several of the unknown anisotropic constants characterizing wood fiber are not affecting the stiffness significantly and rough assumptions regarding their value would suffice. The errors introduced by application of the Hashin's model and neglecting the orthotropic nature of the material behavior in cylindrical axes are evaluated. The effect of geometrical deviations from circular cross-section, representing, for example, collapsed fibers, is analyzed using the finite element method (FEM) and the observed trends are discussed.
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| 10. |
- Engström, Niclas, et al.
(författare)
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Road grip test in Arjeplog
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Swedish road administration sees a need to improve the road grip estimation capacity for the Swedish road system. The challenge is to find methods to measure road grip fast and reliable. There where six different system types at the tests in Arjeplog, three continuous, two system measuring road grip through deceleration and one system based on GPS and accelerometers. Two system types used air craft runway tires. The other systems used either studded winter tires or friction winter tires. Test runs where performed and road grip where recorded for three different surface types, old system 2000 ice, polished ice and new system 2000 ice. Weather data was collected during the three days. It is clear that all systems can detect changes in road grip. It is clear that continuous systems hold an information advantage over the sequence oriented systems. For measurements of road grip on winter roads, we recommend that rubber compounds adapted for cold conditions are used, as the resolution of the road grip measurement where better. In extreme condition like on polished ice, studded winter tires increase the road grip significantly.
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