| 1. |
- Björklund, Glenn, 1972-, et al.
(författare)
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Låt underlaget bestämma löpsteget
- 2014
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Ingår i: Svensk Idrottsforskning. - 1103-4629. ; :4, s. 8-11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
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| 3. |
- Brandberg, August, 1990-, et al.
(författare)
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Characterization and impact of fiber size variability on the mechanical properties of fiber networks with an application to paper materials
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose fibers exhibit a wide range of shapes and sizes. This variation influences the mechanical performance of paper and paperboard by affecting the stress distribution inside the network and the degree of fiber-to-fiber bonding which is possible at a given density. However, the methods used to characterize the distribution of fiber sizes in the pulp neglect that the characteristic features of a fiber are generally not independent. Here, we resolve this shortcoming by fitting the fiber population to a multivariate distribution without enforcing normality or independence between the properties. The high-dimensional multivariate function is recast as a set of univariate distribution functions and a series of bivariate distributions connected by a canonical vine. Using a micro-mechanical model of a paper sheet the influence of this improved characterization is investigated. Reasonable margins and a description of the dependency is shown to be superior to assuming independence even for perfectly preserved marginal distributions. This result demonstrates that micro-mechanical models of paper and paperboard cannot by assumption neglect the influence of the interdependence between the characteristic features of fibers.
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| 4. |
- Filipovic, Mirjana
(författare)
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Evolution of artificial defects during shape rolling
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Very often defects are present in rolled products. For wire rods, defects are very deleterious since the wire rods are generally used directly in various applications. For this reason, the market nowadays requires wire rods to be completely defect-free. Any wire with defects must be rejected as scrap which is very costly for the production mill. Thus, it is very important to study the formation and evolution of defects during wire rod rolling in order to better understand and minimize the problem, at the same time improving quality of the wire rods and reducing production costs. The present work is focused on the evolution of artificial defects during rolling. Longitudinal surface defects are studied during shape rolling of an AISI M2 high speed steel and a longitudinal central inner defect is studied in an AISI 304L austenitic stainless steel during ultra-high-speed wire rod rolling. Experimental studies are carried out by rolling short rods prepared with arteficial defects. The evolution of the defects is characterised and compared to numerical analyses. The comparison shows that surface defects generally reduce quicker in the experiments than predicted by the simulations whereas a good agreement is generally obtained for the central defect.
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| 5. |
- Granbom, Ylva
(författare)
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Structure and mechanical properties of dual phase steels : An experimental and theoretical analysis
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The key to the understanding of the mechanical behavior of dual phase (DP) steels is to a large extent to be found in the microstructure. The microstructure is in its turn a result of the chemical composition and the process parameters during its production. In this thesis the connection between microstructure and mechanical properties is studied, with focus on the microstructure development during annealing in a continuous annealing line. In-line trials as well as the lab simulations have been carried out in order to investigate the impact of alloying elements and process parameters on the microstructure. Further, a dislocation model has been developed in order to analyze the work hardening behavior of DP steels during plastic deformation. From the in-line trials it was concluded that there is an inheritance from the hot rolling process both on the microstructure and properties of the cold rolled and annealed product. Despite large cold rolling reductions, recrystallization and phase transformations, the final dual phase steel is still effected by process parameters far back in the production chain, such as the coiling temperature following the hot rolling. Lab simulations showed that the microstructure and consequently the mechanical properties are impacted not only by the chemical composition of the steel but also by a large number of process parameters such as soaking temperature, cooling rate prior to quenching, quench and temper annealing temperature.
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| 6. |
- Gustafsson, Marcus, 1987-
(författare)
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Energy efficient and economic renovation of residential buildings with low-temperature heating and air heat recovery
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the building sector accounting for around 40% of the total energy consumption in the EU, energy efficiency in buildings is and continues to be an important issue. Great progress has been made in reducing the energy consumption in new buildings, but the large stock of existing buildings with poor energy performance is probably an even more crucial area of focus. This thesis deals with energy efficiency measures that can be suitable for renovation of existing houses, particularly low-temperature heating systems and ventilation systems with heat recovery. The energy performance, environmental impact and costs are evaluated for a range of system combinations, for small and large houses with various heating demands and for different climates in Europe. The results were derived through simulation with energy calculation tools.Low-temperature heating and air heat recovery were both found to be promising with regard to increasing energy efficiency in European houses. These solutions proved particularly effective in Northern Europe as low-temperature heating and air heat recovery have a greater impact in cold climates and on houses with high heating demands. The performance of heat pumps, both with outdoor air and exhaust air, was seen to improve with low-temperature heating. The choice between an exhaust air heat pump and a ventilation system with heat recovery is likely to depend on case specific conditions, but both choices are more cost-effective and have a lower environmental impact than systems without heat recovery. The advantage of the heat pump is that it can be used all year round, given that it produces DHW.Economic and environmental aspects of energy efficiency measures do not always harmonize. On the one hand, lower costs can sometimes mean larger environmental impact; on the other hand there can be divergence between different environmental aspects. This makes it difficult to define financial subsidies to promote energy efficiency measures.
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| 7. |
- Gustafsson, Marcus
(författare)
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Energy Efficient Renovation Strategies for Swedish and Other European Residential and Office Buildings
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The high energy use in the European building stock is attributable to the large share of old buildings with poor energy performance. Energy renovation of buildings is therefore vital in the work towards energy efficiency and reduced environmental impact in the EU. Yet, the strategies and energy system implications of this work have not been made clear, and the rate of building renovation is currently very low.The aim of this thesis is to investigate the economic and environmental aspects of energy renovation strategies, with two main objectives:Renovation of Swedish district heated multi-family houses, including life-cycle cost and environmental analysis and impact on the local energy system;Renovation of European residential and office buildings, including life-cycle cost and environmental analysis and influence of climatic conditions.Buildings typical for the respective regions and the period of construction 1945-1970 were simulated, in order to determine the feasibility and energy saving potential of energy renovation measures in European climates. A variety of systems for heating, cooling and ventilation were studied, as well as solar energy systems, with focus on heat pumps, district heating, low-temperature heating systems and air heat recovery.Compared to normal building renovation, energy renovation can often reduce the life-cycle costs and environmental impact. In renovation of typical European office buildings, as well as Southern European multi-family houses, more ambitious renovation levels can also be more profitable.Exhaust air heat pumps can be cost-effective complements in district heated multi-family houses, while ventilation with heat recovery is more expensive but also more likely to reduce the primary energy use. From a system perspective, simple exhaust ventilation can reduce the primary energy use in the district-heating plant as much as an exhaust air heat pump, due to the lower electricity use.
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| 8. |
- Hedlund, Ann
(författare)
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Attraktivitetens dynamik : studier av förändringar i arbetets attraktivitet
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis takes a point of departure in the problems to recruit and retain personnel in woodworking companies. Companies, actors of society and researchers started with the ambition to create work which people, especially young ones, would like to have and where employees want to stay. The research has been carried out within the att…-project in collaboration between Dalarna University and National Institute for Working Life. The primary purpose was to create deeper understanding of characteristics of attractive work. A distinction has been made between on the one hand what makes work attractive, and on the other hand changes of the attractiveness. The empirical problem with recruitment was a starting point, followed by an interaction between theory and empiricism. The relation to practioners can be described as interactive with usefulness in focus. Questionnaires, group discussions and interviews, as well as informal conversations, have been used in five separate studies. The attractiveness of work depends on the individual’s estimation of the totality of work based upon her/his life situation. Characteristic for attractive work is that it is dynamic and comparative. Positive factors of work are related to other employments or to the idea of attractive work. A model of attractive work which represents an overall picture regarding what makes work attractive contains about 80 qualities in 22 dimensions. One finding is that changes in one dimension influences other dimensions. Another finding is that changed estimations of work depends both on changed valuation of the importance of different aspects of work, and on changed conception of the aspects. It is not enough to do a single effort aimed at retaining and recruiting personnel since the attractiveness of work is dynamic and comparisons are made with other employments. Companies must continuously do efforts for more attractive work. Existing attractive qualities that are hidden from applicants can be displayed. Other qualities can be realized and added to. Knowledge about what makes work attractive and about the dynamic of the attractiveness is valuable to create more attractive work.
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| 9. |
- Heier, Johan
(författare)
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Energy Efficiency through Thermal Energy Storage : Possibilities for the Swedish Building Stock
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need for heating and cooling in buildings constitutes a considerable part of the total energy use in a country and reducing this need is of outmost importance in order to reach national and international goals for reducing energy use and emissions. One important way of reaching these goals is to increase the proportion of renewable energy used for heating and cooling of buildings. Perhaps the largest obstacle with this is the often occurring mismatch between the availability of renewable energy and the need for heating or cooling, hindering this energy to be used directly. This is one of the problems that can be solved by using thermal energy storage (TES) in order to save the heat or cold from when it is available to when it is needed.This thesis is focusing on the combination of TES techniques and buildings to achieve increased energy efficiency for heating and cooling. Various techniques used for TES as well as the combination of TES in buildings have been investigated and summarized through an extensive literature review. A survey of the Swedish building stock was also performed in order to define building types common in Sweden. Within the scope of this thesis, the survey resulted in the selection of three building types, two single family houses and one office building, out of which the two residential buildings were used in a simulation case study of passive TES with increased thermal mass (both sensible and latent). The second case study presented in the thesis is an evaluation of an existing seasonal borehole storage of solar heat for a residential community. In this case, real measurement data was used in the evaluation and in comparisons with earlier evaluations.The literature reviews showed that using TES opens up potential for reduced energy demand and reduced peak heating and cooling loads as well as possibilities for an increased share of renewable energy to cover the energy demand. By using passive storage through increased thermal mass of a building it is also possible to reduce variations in the indoor temperature and especially reduce excess temperatures during warm periods, which could result in avoiding active cooling in a building that would otherwise need it. The analysis of the combination of TES and building types confirmed that TES has a significant potential for increased energy efficiency in buildings but also highlighted the fact that there is still much research required before some of the technologies can become commercially available. In the simulation case study it was concluded that only a small reduction in heating demand is possible with increased thermal mass, but that the time with indoor temperatures above 24 °C can be reduced by up to 20%. The case study of the borehole storage system showed that although the storage system worked as planned, heat losses in the rest of the system as well as some problems with the system operation resulted in a lower solar fraction than projected.The work presented within this thesis has shown that TES is already used successfully for many building applications (e.g. domestic hot water stores and water tanks for storing solar heat) but that there still is much potential in further use of TES. There are, however, barriers such as a need for more research for some storage technologies as well as storage materials, especially phase change material storage and thermochemical storage.
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| 10. |
- Heier, Johan, et al.
(författare)
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Energy Efficiency through Thermal Energy Storage - Evaluation of the Possibilities for the Swedish Building Stock, Phase 1
- 2010
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Ingår i: Clima2010. - Antalya, Turkiet.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- As a first step in assessing the potential of thermal energy storage in Swedish buildings, the current situation of the Swedish building stock and different storage methods are discussed in this paper. Overall, many buildings are from the 1960’s or earlier having a relatively high energy demand, creating opportunities for large energy savings. The major means of heating are electricity for detached houses and district heating for multi dwelling houses and premises. Cooling needs are relatively low but steadily increasing, emphasizing the need to consider energy storage for both heat and cold. The thermal mass of a building is important for passive storage of thermal energy but this has not been considered much when constructing buildings in Sweden. Instead, common ways of storing thermal energy in Swedish buildings today is in water storage tanks or in the ground using boreholes, while latent thermal energy storage is still very uncommon.
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