| 1. |
- Adman, Per, et al.
(författare)
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171 forskare: ”Vi vuxna bör också klimatprotestera”
- 2019
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Ingår i: Dagens nyheter (DN debatt). - Stockholm. - 1101-2447.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DN DEBATT 26/9. Vuxna bör följa uppmaningen från ungdomarna i Fridays for future-rörelsen och protestera eftersom det politiska ledarskapet är otillräckligt. Omfattande och långvariga påtryckningar från hela samhället behövs för att få de politiskt ansvariga att utöva det ledarskap som klimatkrisen kräver, skriver 171 forskare i samhällsvetenskap och humaniora.
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| 2. |
- Hedberg Larsson, Emma, 1976-
(författare)
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Source-Receptor Modeling of Air Pollution : Assessment of Source Contributions: Source Characterization and Chemometric Applications
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Particles released to the atmosphere from anthropogenic sources affect the Earth’s climate as well as the health of the population. Anthropogenic sources of atmospheric particles are e.g. the combustion of biomass and fossil fuels, road, brake and tire wear and various industrial activities. There is great interest to find the importance of different sources to the particle concentrations in the atmosphere to minimize their impact on climate and health. This work investigates how well particle sources are assessed when using source-receptor models. The main focus of this work lies in retrieving the uncertainties and difficulties of using these models on sampled particulate data. Comparison is made with other methods, e.g. a meteorological air pollution dispersion model and a tracer method.Depending on the source origin, the uncertainties of the source profiles are different and require different approaches to be quantified. Conclusions drawn from this thesis are:• assessment of point-sources which affect the sampling site less frequently, requires longer periods of sampling. • at a sampling site impacted by many different sources the time resolution of the samples has to be high in order to enable a differentiation between the sources. • natural sources, or area sources that impact the sampling site frequently, requires fewer samples and can be assessed even when the time resolution of the samples is as low as 3-4 days. This is further stressed by the fact that the natural sources are well characterized in terms of inorganic compounds.Using levoglucosan as sole quantitative tracer for domestic wood burning was shown to be associated with large uncertainties. In contrast to the unique tracer method for source assessment, the multivariate methods will also point at uncertainties in the data model, when the model cannot give a good estimate from the sampled data.
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| 3. |
- Asami-Johansson, Yukiko
(författare)
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Designing Mathematics Lessons Using Japanese Problem Solving Oriented Lesson Structure : A Swedish case study
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis is concerned with applying the Japanese problem solving oriented (PSO) teaching approach to Swedish mathematics classrooms. The overall aim of my research project is to describe and investigate the viability of PSO as design tool for teaching mathematics. The PSO approach is a variation of a more general Japanese teaching paradigm referred to as “structured problem solving”. These teaching methods aim to stimulate the process of students’ mathematical thinking and have their focus on enhancing the students’ attitudes towards engaging in mathematical activities. The empirical data are collected using interviews, observations and video recordings over a period of nine months, following two Swedish lower secondary school classes. Chevallard’s anthropological framework is used to analyse which mathematical knowledge is exposed in the original Japanese lesson plans and in the lessons observed in the classrooms. In addition, Brousseau’s framework of learning mathematics is applied to analyse the perception of individual students and particular situations in the classroom.The results show that the PSO based lesson plans induce a complex body of mathematical knowledge, where different areas of mathematics are linked. It is found that the discrepancy between the Japanese and Swedish curriculum cause some limitations for the adaptation of the lesson plans, especially in the area of Geometry. Four distinct aspects of the PSO approach supporting the teaching of mathematics are presented.
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| 4. |
- Eriksson, Robert
(författare)
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High-temperature degradation of plasma sprayed thermal barrier coating systems
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermal barrier coating systems (TBCs) are used in gas turbines to prevent high-temperature degradation of metallic materials in the combustor and turbine. One of the main concerns regarding TBCs is poor reliability, and accurate life prediction models are necessary in order to fully utilise the beneficial effects of TBCs. This research project aims at developing deeper understanding of the degradation and failure mechanisms acting on TBCs during high temperature exposure, and to use this knowledge to improve life assessments of TBCs. The present work includes a study on the influence of coating interface morphology on the fatigue life of TBCs and a study on the influence of some different heat treatments on the adhesive properties of TBCs.The influence of coating interface morphology on fatigue life has been studied both experimentally and by modelling. Large interface roughness has been found experimentally to increase fatigue life of TBCs. The modelling work do, to some extent, capture this behaviour. It is evident, from the study, that interface morphology has a large impact on fatigue life of TBCs.Three thermal testing methods, that degrade TBCs, have been investigated: isothermal oxidation, furnace cycling and burner rig test. The degraded TBCs have been evaluated by adhesion tests and microscopy. The adhesion of TBCs has been found to depend on heat treatment type and length. Cyclic heat treatments, (furnace cycling and burner rig test), lower the adhesion of TBCs while isothermal oxidation increases adhesion. The fracture surfaces from the adhesion tests reveal that failure strongly depends on the pre-existing defects in the TBC.
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| 5. |
- Gustafsson, David, 1983-
(författare)
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Constitutive and fatigue crack propagation behaviour of Inconel 718
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this licentiate thesis the work done in the TURBO POWER project Influence of high temperature hold times on the fatigue life of nickel-based superalloys will be presented. The overall objective of this project is to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718. Firstly, the constitutive behaviour of the material has been been studied, where focus has been placed on trying to describe the mean stress relaxation and initial softening of the material under intermediate temperatures. Secondly, the fatigue crack propagation behaviour under high temperature hold times has been studied. Focus has here been placed on investigating the main fatigue crack propagation phenomena with the aim of setting up a basis for fatigue crack propagation modelling.This thesis is divided into two parts. The first part describes the general framework, including basic constitutive and fatigue crack propagation behaviour as well as a theoretical background for the constitutive modelling of mean stress relaxation. This framework is then used in the second part, which consists of the four included papers.
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| 6. |
- Gåsvaer, Daniel, 1984-
(författare)
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Towards radical improvement in production systems
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the speed of change is increasing, it’s of great importance that manufacturing companies strive to achieve not only incremental improvements, but also radical improvements within their production systems. Thus, more research has to be focused on how to realize radical improvement. In accordance, the objective of the licentiate thesis is to, through theoretical and empirical work, increase the understanding about radical improvement in production and identify what elements need to be considered when designing support on how to implement radical improvement in industrial production. Throughout the research process these issues has been addressed through theoretical and empirical studies. Three studies have been conducted in total, of which two are mainly of theoretical character and one of empirical character. Besides, a state-of-the-art theoretical review has been carried out as well, further framing the findings.The research results imply that radical improvement in production is a teamwork process that embraces the facilitation of creativity and innovation. The research further implies that there are a number of issues to consider when creating industry-applicable support on how to realize radical improvement in industrial production. For instance, what level of innovation is striven for must be decided, creativity must be facilitated throughout, the opposing cultures of incremental and radical innovation must be managed, and there is a need to apply a holistic perspective, thus embracing not only productivity results but organizational learning as well.As further work, creating industry-applicable support on how to realize radical improvement in industrial production is advocated, focusing not only on meeting the issues addressed above, but also how to make the support industry-applicable.
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| 7. |
- Johansson Kostenniemi, Urban, 1987-
(författare)
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Bacterial meningitis in children : clinical aspects and preventive effects of vaccinations
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bacterial meningitis, one of the most severe infections a child can contract, can be caused by several different strains of bacteria. Most commonly, Haemophilus influenzae type b (Hib), Streptococcus pneumoniae and Neisseria meningitidis. These colonize the upper respiratory tract, then either cause localized infections acting as primary foci or directly spread to the brain. As preventive measure, general infant Hib and pneumococcal vaccinations were introduced in Sweden in 1993 and in 2009, respectively. Although evaluated extensively elsewhere, their long-term effects in Arctic regions are less studied. For the individual child with bacterial meningitis, treatment involves many challenges starting with correctly identifying the condition, guiding treatment, and finally identifying both short-term and long-term disabilities.In this thesis, the overall aim was to study clinical aspects of bacterial meningitis and preventive effects of vaccinations in an Arctic region. We used two datasets in the Västerbotten Region to investigate incidence rates during the time-periods adjacent to vaccine introductions. This allowed us to study the preventive effects of general infant vaccinations on bacterial meningitis in one of the Swedish Arctic regions. More precisely, we investigated changes in incidence of bacterial meningitis and sepsis during the period of 1986-2015 and of respiratory tract infections during the period of 2005-2014, in the Västerbotten Region, Sweden. We also reviewed medical records of children being treated for bacterial meningitis in the Västerbotten Region to study clinical presentation, short-term outcome, and to develop a new predictive score for identifying adverse outcome and need of invasive procedures. Additionally, by reviewing medical records and child health records from discharge and onwards we assessed long-term disabilities and evaluated clinical guidelines’ follow-up recommendations.Following introduction of general infant Hib vaccination, incidence of all-cause bacterial meningitis and Haemophilus meningitis in children aged one month to four years declined by 82.3% and 95.3%, respectively. Likewise, all-cause bacterial meningitis and pneumococcal meningitis declined by 48.0% and 67.5%, respectively, following pneumococcal vaccination. In addition, incidence of sepsis caused by H. influenzae and by S. pneumonia also decreased in the same age group. Finally, respiratory tract infections in children under five years of age decreased following pneumococcal vaccination; by 41.5% for all-cause acute otitis media, by 80.7% for sinusitis and by 28.6% for pneumonia.At admission to the hospital, difference in clinical presentation mostly depended on age. Younger children were more ill at admission but also presented with more diffuse symptoms. When evaluating clinical decision rules for detecting bacterial meningitis, none reached 100% sensitivity. The predictive score developed by us could identify all children in need of invasive procedures to manage the intracerebral pressure and were graded as excellent in the ROC analysis at this task. However, neither this score nor any other could adequately predict complications or death. Finally, permanent disabilities affected more than half of surviving children with psychiatric disease being diagnosed in 30%, and another 5% had ongoing investigations for symptoms of psychiatric disease. Notably, psychiatric disabilities were detected late, in average 14 years after having had bacterial meningitis.From these findings, we concluded that vaccinations are excellent at protecting children against bacterial meningitis, also in the Arctic region, with the added bonus of providing protection against sepsis and less severe infections such as pneumonia and acute otitis media. Further, treating children with bacterial meningitis involves several challenges starting with correctly identifying this sever disease. For this task, no clinical decision rule is perfect. When making difficult treatment decisions such as deciding on invasive procedures to manage the intracerebral pressure, the predictive score developed and tested by us, the MeningiSSS, can be very helpful. Finally, permanent disabilities may be more common than previously thought. With more than one third of survivors being affected by psychiatric disabilities, specific long-term follow-up strategies are needed to reduce suffering caused by undetected psychiatric disabilities.
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| 8. |
- Krecl, Patricia, 1968-
(författare)
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Impact of residential wood combustion on urban air quality
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wood combustion is mainly used in cold regions as a primary or supplemental space heating source in residential areas. In several industrialized countries, there is a renewed interest in residential wood combustion (RWC) as an alternative to fossil fuel and nuclear power consumption. The main objective of this thesis was to investigate the impact of RWC on the air quality in urban areas. To this end, a field campaign was conducted in Northern Sweden during wintertime to characterize atmospheric aerosol particles and polycyclic aromatic hydrocarbons (PAH) and to determine their source apportionment.A large day-to-day and hour-to-hour variability in aerosol concentrations was observed during the intensive field campaign. On average, total carbon contributed a substantial fraction of PM10 mass concentrations (46%) and aerosol particles were mostly in the fine fraction (PM1 accounted for 76% of PM10). Evening aerosol concentrations were significantly higher on weekends than on weekdays which could be associated to the use of wood burning for recreational purposes or higher space heat demand when inhabitants spend longer time at home. It has been shown that continuous aerosol particle number size distribution measurements successfully provided source apportionment of atmospheric aerosol with high temporal resolution. The first compound-specific radiocarbon analysis (CSRA) of atmospheric PAH demonstrated its potential to provide quantitative information on the RWC contribution to individual PAH. RWC accounted for a large fraction of particle number concentrations in the size range 25-606 nm (44-57%), PM10 (36-82%), PM1 (31-83%), light-absorbing carbon (40-76%) and individual PAH (71-87%) mass concentrations.These studies have demonstrated that the impact of RWC on air quality in an urban location can be very important and largely exceed the contribution of vehicle emissions during winter, particularly under very stable atmospheric conditions.
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| 9. |
- Pouransari, Zeinab, 1982-
(författare)
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Fundamental studies of non-premixed combustion in turbulent wall jets using direct numerical simulation
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis deals with the fundamental aspects of turbulent mixingand non-premixed combustion in wall-jet flows. Direct numerical simulations(DNS) of compressible turbulent flows are performed in a wall-jet configura-tion, which has a close resemblance to many industrial combustion applica-tions. The triple ”turbulence-chemistry-wall” interactions are also present inthis flow set-up. These interactions have been addressed by first focusing onturbulent flow effects on the isothermal reaction, including the near-wall issues.Then, by adding heat-release to the simulations, it has been concentrated onheat-release effects on various phenomena that occur in the reacting turbulentwall-jet flow. In the computational domain, fuel and oxidizer enter separatelyin a non-premixed manner and the flow is fully turbulent and subsonic in allsimulations. In the first phase of this study, the case of a turbulent wall-jetincluding an isothermal reaction without heat release is addressed in order toisolate the near-wall effects and the mixing characteristics of the flow and thekey statistics for combustion are studied in the absence of thermal effects. Adeeper insight into three-dimensional mixing and reaction characteristics in aturbulent wall-jet has been gained through investigation of the probability den-sity functions, higher order moments of velocities and reacting scalars and thescalar dissipation rates of different species. In the second phase, DNS of turbu-lent reacting wall-jets including heat release is performed, where a single-stepglobal exothermic reaction with an Arrhenius-type reaction rate is considered.The main target was to identify the heat-release effects on different mixingscales of turbulent wall-jet flow. The scalar dissipation rates, time scale ratios,two-point correlations, one and two-dimensional premultiplied spectra are usedto illustrate the heat release induced modifications. It is observed that heatrelease effects delay the transition process in the chemically reacting cases andenlarge the fluctuation intensities of density and pressure, but have a dampingeffect on all velocity fluctuation intensities. Finer small mixing scales were ob-served in the isothermal simulations and larger vortical structures formed afteradding significant amounts of heat-release. Simulations with different Damk ̈h- oler numbers, but comparable temperature-rise are performed and the expectedbehavior, a thinner flame with increasing Damk ̈hler number, is observed. Finally, some heat transfer related quantities are examined. The wall heat fluxand the corresponding Nusselt numbers are addressed. The near-wall reactioneffects on the skin friction coefficient are studied and further the reaction char-acteristics are investigated throughout the domain.
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