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  • 62901.
    Åström, Hans
    Luleå tekniska universitet.
    Svetsparametrarnas inverkan på smältbadsgeometri, stelningsstruktur och varmsprickbildningskänslighet vid pulverbågsvetsning av C-Mn-stål1977Report (Other academic)
  • 62902. Åström, Helena
    Den vinnande formeln: Om Stieg Larssons framgångskoncept i Män som hatar kvinnor2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 62903.
    Åström, Henrik
    Luleå tekniska universitet.
    Grease in elastohydrodynamic lubrication1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The rheology of soap thickened greases has been investigated in a cone and plate rheometer and a model that includes base oil viscosity and temperature has been suggested and fitted to the results. With the use of a bouncing ball apparatus, the pressure coefficient of the limiting shear stress of the greases was determined. It is related to friction in EHL and the results verified the friction reducing properties of the soap thickeners of the grease. Film thickness in EHL of a grease lubricated point contact was measured in a ball and disc apparatus. The initial film thickness was thicker than the film thickness given by the base oil. After some seconds of running the film thickness dropped far below the base oil film thickness, because of insufficient replenishment. Replenishment was studied by looking at the distribution and flow of lubricant around the contact in the ball and disc apparatus. Primary reservoirs and primary bands close to the track of the contact, on the ball and the disc, contained small amounts of grease that constituted a potential supply of lubricant to the inlet of the contact. The majority of the grease was pushed away from the contact initially and seemed no to participate in the lubrication. Soap thickener formations were observed entering the contact in the ball and disc apparatus and cause a local increase in the film thickness that disturbed the normally horseshoe-shaped film thickness map. For lithium greases, the amount and size of the film disturbances were found to be connected with the manufacturing process of the grease and the soap thickener content. A method to evaluate the pressure fluctuations induced by the film thickness disturbances was proposed. The method was verified by comparing film thickness measurements from an oil lubricated contact and the pressure profile calculated from that, with the results from a fully numerical solution. Good agreement was found. The method was applied to a grease lubricated contact and showed significant variations in the pressure, caused by the soap thickener formations.

  • 62904.
    Åström, Henrik
    Luleå tekniska universitet.
    Rheological and elastohydrodynamic properties of lithium, lithium complex and sodium soap greases1991Licentiate thesis, monograph (Other academic)
  • 62905.
    Åström, Henrik
    et al.
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Inverkan av smörjfetters reologi och smörjförmåga på energiförluster i maskiner1991Report (Other academic)
  • 62906.
    Åström, Henrik
    et al.
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Rheological properties of six greases and their two base oils1990Report (Other academic)
  • 62907.
    Åström, Henrik
    et al.
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Viewpoints on noise in grease lubricated bearings1994In: N L G I Spokesman, ISSN 0027-6782, Vol. 58, no 4Article in journal (Other academic)
    Abstract [en]

    The noise level of a rolling element bearing is normally low, compared to the noise from the machine in which the bearing operates. Under certain circumstances, though, the noise caused by the bearing can be crucial and might influence the operation, for example, of very sensitive equipment. When lubricating rolling element bearings with grease, the noise level will depend upon the type of grease used. The relationship between structure and composition of lithium greases, and the noise they cause in rolling element bearings, is the subject of this paper. Different lithium greases have been studied in a model of the contact between ball and race in a bearing, using a ball and disc machine, as well as optical interferometry. The bearing noise levels have also been measured, using the same greases, and their microscopic structure studied, with the bearing noise level. Normal lithium greases cause disturbances in the model contact and also noise in a ball bearing. The noise level and the amount of disturbance is connected, with formations found in the microscopic grease structure. This technical paper can be obtained from the ELGI Office; see page 38 for ELGI address

  • 62908.
    Åström, Henrik
    et al.
    Luleå tekniska universitet.
    Isaksson, Ove
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Video recordings of an EHD point contact lubricated with grease1991In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 24, no 3, p. 179-184Article in journal (Refereed)
    Abstract [en]

    Optical interferometry has been used to study the film thickness of an EHD point contact lubricated with grease. The greases used were two lithium, two lithium complex and two sodium greases, all with NLGI grade two, the most common grade. They were based on one mineral oil of naphthenic type and one synthetic polyalphaolefin. The contact was lubricated without a continuous supply of grease and thus the film thickness decreased with time as the grease was gradually squeezed away from the contact area. The film thickness fluctuated during the measurement. To overcome this problem, the contact point was recorded with a video camera and the results evaluated after the tests. The video camera proved to be a powerful help in this evaluation. The tests were run at 20°C and under pure rolling conditions at a rolling velocity of 0.055 m s-1. The results from all greases showed a decreasing film thickness that tended to stabilize on about 0.2 μm after 40 cycles. The lithium and lithium complex greases showed strong local film thickness variations inside the lubricated contact, deviating from the normally horseshoe-shaped contact, during the first 20 to 40 cycles.

  • 62909.
    Åström, Henrik
    et al.
    Luleå tekniska universitet.
    Östensen, Jan Ove
    Luleå tekniska universitet.
    Höglund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Lubricating grease replenishment in an elastohydrodynamic point contact1993In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 115, no 3, p. 501-506Article in journal (Refereed)
    Abstract [en]

    A ball and disk apparatus was used to investigate the lubricant replenishment of an elastohydrodynamically lubricated point contact. This replenishment of the contact is crucial for building up a lubricating film. Whereas lubricating oil manages to achieve replenishment, lubricating grease appears not to achieve this, with lubricant starvation and a dramatic decrease in film thickness as a result. The distribution of grease around the contact was studied using normal and high-speed video. The movements of grease in the vicinity of the contact could be seen by adding molybdenum disulfide particles to the grease. A recording was then made, using high-speed video recording. The overall cavitation regions were studied using an ordinary video camera and grease without particles. On the basis of the results, possible lubricating grease replenishment mechanisms are discussed. The resulting film thickness was also compared with theoretical predictions using the Hamrock and Dowson starvation criterion, assuming negligible replenishment. The measured film thickness was larger than the predicted, which indicated that some replenishment occurs. In the case of an ordinary thrust ball bearing, replenishment was found to rely on the spin motion of the balls.

  • 62910. Åström, Håkan
    Kommunalt inköpsbeteende av missbrukarvård2001Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 62911.
    Åström, Jan A.
    et al.
    Centre for Scientific Computing, Esbo.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Linna, R.P.
    Department of Physics, University of Jyväskylä.
    Timonen, J.
    Department of Physics, University of Jyväskylä.
    Universal dynamic fragmentation in D dimensions2004In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 92, no 24, p. 245506-Article in journal (Refereed)
    Abstract [en]

    A generic model is introduced for brittle fragmentation in D dimensions, and this model is shown to lead to a fragment-size distribution with two distinct components. In the small fragment-size limit a scale-invariant size distribution results from a crack branching-merging process. At larger sizes the distribution becomes exponential as a result of a Poisson process, which introduces a large-scale cutoff. Numerical simulations are used to demonstrate the validity of the distribution for D = 2. Data from laboratory-scale experiments and large-scale quarry blastings of granitic gneiss confirm its validity for D = 3. In the experiments the nonzero grain size of rock causes deviation from the ideal model distribution in the small-size limit. The size of the cutoff seems to diverge at the minimum energy sufficient for fragmentation to occur, but the scaling exponent is not universal.

  • 62912. Åström, Jennie
    CFD-simulering av flöde i inloppstub och spiral2005Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62913. Åström, Jenny
    Strategier kring rekryteringsbehovet i Luleå kommun: en kvalitativ studie om strategier för att säkra chefsförsörjningen2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 62914. Åström, John
    et al.
    Måttgård, David
    Key account relationships: selling to the public sector2004Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Key Account Management has become more and more important because of the need to retain and develop relationships with large and global businesses. Key Account Management is about managing a journey that commences at the first contact with the client and then goes through a series of stages and then develops into a complex relationship based on trust and mutual interest. There are many factors influencing the journey along the way and the responsibility to coordinate the supplier’s activities and bring added value to the relationship is the function of the key account manager. In this thesis we discuss the area of key account relationships from the selling company’s perspective. We have chosen to focus on how a company identify/select and characterize a key account, the development of a key account relationship and finally the work of a key account manager. In order to reach the purpose of the thesis we have conducted two interviews with a company that has employed Key Account Management for many years. The study shows that sales volume is the single most important criterion when a company identifies/selects key accounts. Furthermore, the findings imply that trust building activities are essential from a relationship development perspective. Finally, the role of the key account manager is to coordinate the activities of the Key Account Management team.

  • 62915. Åström, Jörgen
    Användbarhetsteoriers inverkan vid utveckling av ledningssystems datorstöd2007Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 62916.
    Åström, Kalle
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Automatisk inmätning av reflektorpositioner med SGV1990Report (Other academic)
  • 62917.
    Åström, Kalle
    et al.
    Centre for Mathematical Sciences, Lund University.
    Persson, Lars-ErikLuleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.Silvestrov, Sergei D.Division of Applied Mathematics, Mälardalen University.
    Analysis for science, engineering and beyond: the tribute workshop in honour of Gunnar Sparr held in Lund, May 8-9, 20082012Collection (editor) (Other academic)
  • 62918. Åström, Lina
    Energikartläggning för Bureåbostäder AB: Med investeringskalkyl för installation av bergvärme2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    During this work, an energy survey of six apartment building, (in the report termed as house 29, 32, 61, 62, GK and PZ), has been executed for Bureåbostäder AB. Input energy in the form of pellets- and electric heating has been inventoried to show the heat demand for each apartment building. Based on the heat demand investment calculations for the installation of geothermal heating have been made for each house. The calculation resulted in a lower pellets energy consumption for heating of every house in the survey. The results of the thesis are: •The net calorific value of the pellets was determined to be 4900 kWh per tonne.•System efficiencies for the boilers at Bureåbostäder have been set to 71% for pellet boilers and 75% for the modified oil boilers. •Inventory of tonnes of consumed pellets gives a mean value in tonnes per year for each house. The consumption of pellets ranged from 13 tonnes to 38 tonnes per year for the different properties. •After deductions of major electricity consumers such as washing machines and engine warmers were made on the property electricity, a mean value of the heating supplied by electricity was given for each property. The electrical energy input ranged from 4 000 kWh to 21 000 kWh per year for the different properties.•A mean value of the total heat demand was then calculated for each house, in kWh per year:oHus 61 & 62 – 152 000 kWh/yearoHus 29 – 56 000 kWh/yearoHus 32 – 53 000 kWh/yearoHus GK – 54 000 kWh/yearoHus PZ – 82 000kWh/year•An investment calculation for drilling and the purchase of ground source heat pump (GSHP) for each house was then calculated, whereas 70 % of the total heat demand is accounted for by ground source heating. For house 61 & 62 two options of heat pumps are available. A break-even time was made by counting investment cost subtracted with the savings for every following year:oHouse 61 & 62 with GSHP, 30 kW: 6 years, more than 4 monthsoHouse 61 & 62 with GSHP, 40 kW: 6 years, around 2 monthsoHouse 29 with GSHP, 4-16 kW: 6 years, more than 7 monthsoHouse 32 with GSHP, 4-16 kW: 6 years, around 9 monthsoHouse GK with GSHP, 4-16 kW: 7 years, around 1 month oHouse PZ with GSHP, 24 kW: 5 years, more than 9 months•The differences in costs between each property, and each ground source heat pump, with today’s costs have then been calculated to see if geothermal heating is a viable investment. oHouse 61 & 62 with GSHP, 30 kW: 53 000 kroHouse 61 & 62 with GSHP, 40 kW: 57 000 kroHouse 29 with GSHP, 4-16 kW: 22 800 kroHouse 32 with GSHP, 4-16 kW: 21 000 kroHouse GK with GSHP, 4-16 kW: 20 000 kroHouse PZ with GSHP, 24 kW: 29 000 kr

  • 62919. Åström, Lina
    Standardisering av emballage2007Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62920. Åström, Linn
    Konsumentskydd enligt KköpL 16 §: Säljarens felansvar2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 62921. Åström, Lisa
    En modellstudie av ett dammsystem hos SSAB Tunnplåt AB2006Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62922.
    Åström, Lisbeth
    et al.
    Luleå tekniska universitet.
    Medin-Olsson, Inger
    Undersköterskerollen i förändring: en undersökning av konverteringar inom Norrbottens läns landsting1994Report (Other academic)
  • 62923. Åström, Magnus
    Buller från godståg: detaljerad kartläggning av buller från godståg samt utvärdering av skärmar2003Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62924.
    Åström, Magnus
    Luleå tekniska universitet.
    Implementing artificial neural networks in microsimulation2001Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This licentiate thesis presents a work focused on investigating the possibility of using "artificial methods" such as artificial neural networks (ANN) as an analytical alternative to the conventional technique of regression. The work has been concentrated towards two different modules in the SVERIGE microsimulation model, an earnings module used for predicting individual earnings and a property value module used for predicting real estate prices. The results from this work, shows that the use of artificial neural networks can improve the performance (degree of explanation), and reduce the time needed to develop the individual modules. But it also shows that replacing regression equations with artificial neural networks have drawbacks, e.g. that the modules become less transparent. Another example is that the difficulties in analysing each variable's importance increases since a neural net does not easily provide any coefficient estimates.

  • 62925. Åström, Magnus
    Provtryckningsutrustning till härdlinje 3 och 4 på Gestamp Hardtech2007Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62926. Åström, Maria
    Rice Husk Ash as an Additive in Concrete Reinforced with Natural Fibers1998Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An additive is needed in order to be able to produce durable, low cost, corrugated roof sheets of concrete reinforced with natural fibres (as e.g. sisal and jute). In this report rice husk ash is tested as such an additive as an alternative to condensed silica fume. A literature study has been carried out and short time tests have been performed where the properties of concrete with rice husk ash (RHS) have been compared to concrete with condensed silica fume (CSF). The rice husk ash showed good properties especially in combination with long jute fibres treated with aluminium sulphate.

  • 62927. Åström, Markus
    et al.
    Ögren Lindfors, Fredrik
    Undersökning hur man ska mäta salthalt samt reglera denna2002Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 62928. Åström, Martin
    Hyttsten som ersättning för 0-8 mm gjutgrus i betong: Målet med detta examensarbete har varit att ta reda på vilken inverkan hyttsten har som ersättningsballast vid betongtillverkning2014Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [en]

    The aim of this study was to determine the impact air cooled blast furnace slag has as replacement for aggregate in concrete production. By sifting of material samples to ensure grain size distribution, literature studies and interviews data were collected cab stone. Evaluation and analysis of data from screening, strength tests, as well as measurements carried out by Martin Åström.The ASR analysis was conducted by Envix Nord AB Umeå. The results from the ASR test resulted in the following conclusions:•Short-term and long-term tests with air cooled blast furnace slag in the concrete show that there is no negative expansion caused by the ASR reaction.•From the analysis (ASTM 1260) it becomes clear that investigated the nature of aggregates is more expansive than the air cooled blast furnace slag.•Durability is approved under the requirements of C25/30.•Pozzolan (silica) increases the strength of the specimens. Whether it is economically viable to set up pozzolan is uncertain.•Use of the air cooled blast furnace slag as substitutes for natural materials may prove to be cost effective.

  • 62929.
    Åström, Mats E.
    et al.
    Linnaeus University, School of Natural Sciences.
    Österholm, Peter
    Abo Akademi University, Department of Geology.
    Gustafsson, Jon Petter
    Royal Institute of Technology, Department of Land and Water Resources Engineering.
    Nystrand, Miriam
    Abo Akademi University, Department of Geology.
    Peltola, Pasi
    Linnaeus University, School of Natural Sciences.
    Nordmyr, Linda
    Linnaeus University, School of Natural Sciences.
    Boman, Anton
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Attenuation of rare earth elements in a boreal estuary2012In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 96, p. 105-119Article in journal (Refereed)
    Abstract [en]

    This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6 ‰). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the <1kDa pool became depleted in the middle REE and the colloidal (0.45 μm (1kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (<0.45 μm) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.

  • 62930. Åström, Mattias
    Designförslag till nästa generation effektpedaler2009Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62931.
    Åström, M.E.
    et al.
    Kalmar University, School of Natural Sciences.
    Boman, Anton
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Fröjdö, S.
    Abo Akademi University, Department of Geology.
    Fast iron sulfide oxidation in a region of land uplift and artificial drainage2011Conference paper (Other academic)
  • 62932. Åström, Mikael
    Utbud och efterfrågan av silvermarknaden: En ekonometrisk analys2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study investigates the determinant factors of supply and demand of silver. The study covers the time period 1973 to 2011, the factors that is being investigated is US industrial production index, US dollar index, US adjusted monetary base, US real interest rate, oil price, silver price, base metal prices and a time trend variable representing technological change. In order to examine how these variables affects supply and demand of silver, two models, one for supply and one for demand are developed and regressed by two-stage least squares regression techniques. The result of the demand regression shows that price of silver, US industrial production index, US adjusted monetary base and US dollar index and technology where statistically significant, where US industrial production had the largest impact on demand. The result of the supply regression shows that price of oil, US real interest rate and technology where statistically significant, with price of oil as the most important determinant factor for supply.

  • 62933. Åström, Mikaela
    Kvalitetssäkring av leveransprocesser för IT-system2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The development is constantly moving forward and it applies to continue to deliver and produce competitive products. Today the IT-systems are integrated to each other and they are often composed in different packages, compared with 20 years ago when the systems were more isolated. The integration and the communication between systems and functions is making the demand handling more difficult which is making a larger need of supply-chains with quality assurance. The customers decides which quality is needed and also contributes to the evolution of factors and aims regarding quality of supplies, this according to the need of customers, expectations and wishes. The guarantee of quality is a link to reduce delay and unnecessary problems. Instead you want to create effective supply-chains which support and could be measured trough good documentation. The study has research an company’s supply-chain for an specific IT-system with focus on quality assurance. Observations and interviews has been conducted with employees and customers, the study investigate how the process, the collaboration and communication looks like in the supply-chain. In the qualitative study has there been two research questions. How does todays supply-chains executes and which deficiency could there be? How can the supply-chain be changed so good quality, delivery and customer’s satisfaction is accomplished? The empirical material indicates that work with quality is not given priority to and there are many possible potential improvements to create an quality assurance supply-chain. Today the process is described in different ways with different parts and content, both by the employees and the customers. It makes it unclear both in and outside the company. Further it can be established that today there are many deliveries delayed which creates disaffection instead of customer satisfaction.

  • 62934. Åström, Monica
    Produktutveckling av ett hyllsystem i trä: fördjupning i svenska träslags egenskaper2005Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 62935. Åström, Niklas
    Radiostyrd underhållsport2002Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 62936. Åström, Ossian
    Evaluation and modeling of trace elements from drillcore analysis at Kankberg Au-Te mine, Skellefte District, Sweden2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Information derived from 498 drill holes encompassing over 2,6 million sampling points taken from the Kankberg Au-Te mine located in the Skellefte District were used in order to model and evaluate the trace element distribution and association in and around the mine. The modeling software Leapfrog Geo was used, revealing the samples to mainly be confined within the western part of the deposit. A zonation of Al, K, Mg and Fe could be seen possibly representing the andalusite, sericite and chlorite-biotite alteration respectively. By constructing a correlation matrix several element associations could be seen showing elements sharing similar chemical properties or related to minerals known to occur in the deposit. Au was shown to correlate moderately with Ag and slightly with Te, Bi, Sb, Th, La, U and P. The trace elements found within monazite (Ce, La and Th) could be found in the vicinity of Au in the model suggesting a possible genetic link. Immobile-incompatible and immobile-compatible elements were used to determine the precursor lithology in the Kankberg deposit which consisted mainly of dacite but also of rhyolite, andesite and sparse mafic rocks. Mass change calculations were made, using least altered dacite from Maurliden and Petiknäs VMS-deposits, revealing mass losses in Y, Nb and Sc, elements traditionally thought to be immobile. However, these can be mobile under certain conditions like extensive alteration which is known to have occurred in the Kankberg deposit. The losses could also have been enabled by transport of fluoride complexes in the hydrothermal fluid as evident by topaz that can be found in the deposit. A link between element loss in mass and abundance in the model could be observed when comparing to the Petiknäs deposit, with Y and Nb having lost more mass than Sc and subsequently occurring less abundant in the model.

  • 62937.
    Åström, Patrik
    Luleå University of Technology, Department of Arts, Communication and Education, Education, Language, and Teaching.
    Myten om Vadstena-stilen2010In: Arkiv för nordisk filologi, ISSN 0066-7668, Vol. 215, p. 99-126Article in journal (Refereed)
    Abstract [en]

    There has existed a dominating idea among palaeographers that the Latin script in Western Europe in the late Middle Ages was divided into a number of national variants. This idea has been confronted in later years, above all by Albert Derolez in his The palaeography of gothic manuscript books (2003). When it comes to Sweden, Nils Dverstorp has followed his predecessor, and nvincingly shown that what has been known as “Vadstenastilen”, the Swedish national script, has few if any characteristics that separates it from the general Western uropean script. I here follow up the arguments presented by Dverstorp, and scrutinize the foundations of the idea of the “Vadstenastil”. I show that the basic articles in which the idea is presented holds a low standard from a methodological, scientific viewpoint. I show this, among other things, by a number of digitally constructed alphabets from the examples pointed out in the articles, and thus pointing at the necessity for palaeographers to use digital tools.

  • 62938. Åström, Per
    et al.
    Hultman, Nils
    High speed network adapters2003Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 62939. Åström, Per
    et al.
    Lindkvist, Rickard
    Kopplingsmanövrering2000Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62940. Åström, Peter
    Simulation methodologies within virtual manufacturing applied on mechanical cutting2001Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Virtual manufacturing, that is, simulation of welding, heat treatment, cutting and other manufacturing processes is becoming more and more used as a tool for prediction of material- and mechanical properties in modern industry. By simulations we refer in this case to FE-simulations of the thermo-mechanical effect of the manufacturing process on the component in question. Despite the fact that simulations are becoming more widely used, there is a lack of integration of simulations of manufacturing processes in the sense that most work focuses on an individual process being simulated. It is only when a complete chain of manufacturing processes can be simulated the real benefits, of using virtual manufacturing as a tool within product- and process development, will become evident. The thesis focuses on simulation methodologies within virtual manufacturing, and specifically methodologies for cutting simulations. Simulation of mechanical cutting has been identified as a key area where computational difficulties arise when attempting to simulate a sequence of manufacturing processes involving some form of cutting operation. A distortion problem during manufacture of a shaft front to a RM12 engine has been analysed. At one time, distortions aroused during the later stages of the cutting sequences involved in the manufacture of the shaft front. The cooling from solution heat treatment temperature and the cutting sequence was to be simulated. The result from the cooling sequence however show that the cooling does not cause residual stresses that in turn cause distortions in subsequent cutting sequences, and hence only results from the cooling procedure is presented. A test case was constructed to ensure that residual stresses would be present causing distortions during subsequent cutting. The experimental set- up with both a forming operation and subsequent cutting is used as a validation tool for the simulation of cutting using an element deactivation technique. The results show that the technique developed can be a useful tool for simulation of mechanical cutting when interested in distortions on component level. Another necessity when performing analyses of a sequence of manufacturing processes is a system for exchange of Engineering Analysis Data (EAD) between each of the simulations. Further, a system for handling the increasing amount of EAD in the product- and process development process is also needed. Most engineering software is today used to solve engineering problems within a single, limited domain. Efforts have been made to develop standardised formats such as IGES and STEP for EAD exchange both within and across domains. However, by limited implementation in commercial software the user is often forced to either program translation routines that enables data sharing or even recreate meshes, boundary conditions etc. A system has been developed that supports the management of computer-based simulation information. The paper describes how information modelling and database technologies can bring new dimensions to the effective use of engineering simulations in product- and process development.

  • 62941. Åström, Peter
    Simulation of manufacturing processes in product development2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the manufacture of aero engine components, three key manufacturing processes can be identified. These are welding, heat treatment and mechanical cutting. Depending on what is required in terms of mechanical- and geometrical properties in the final product these processes are typically combined in a certain sequence. It is consistently these three processes, and the modelling and simulation of them using the finite element method, that are of concern to the work presented in this thesis. Product development phases such as the detailed design phase and the process planning phase are typically simulation intensive in aerospace industry. Normally, both more extensive component and manufacturing process data are available at these stages compared to in the previous concept development phase. It is however becoming increasingly important to enable predictions of manufacturability to be made early in the product development process. Changes made in the manufacturing process chart after a product offer is released will result in an increase in cost and a decrease in profit of that component. The aim of the work presented here is thus to develop strategies and computational technologies suitable for simulation of manufacturing processes in early stages of product development. An example of a computational technology developed in this work is the method of element deactivation used to simulate distortion effects of mechanical cutting. Within the area of simulation of manufacturing processes most research work and most publications focus on one individual process being simulated. This has been of great importance for the evolution of computational methods and analysis tools used both in industry and academia. However, when the focus of using simulations often is to determine process parameters in order to obtain desired product properties in the final product, it is essential to include the entire manufacturing process sequence in these simulations. In order to enable a sequence of manufacturing processes to be simulated, engineering information data need to be transferred between simulations of the individual processes. A system for engineering information data exchange in the context of manufacturing simulations is presented in this work. An approach commonly used for concept generation is knowledge based engineering (KBE). In KBE-systems, rules are implemented that embodies the enterprises’ product- and process knowledge. In this thesis, an integrated system where mechanical cutting simulations are performed within a knowledge based engineering software framework is presented. The thesis also deals with friction modelling in the rotary friction welding process and what is appropriate, in terms of computational matters, when attempting to simulate friction welding in a concept development context. The main theme in the thesis is thus to develop strategies, methods and computational technologies suitable for simulation of manufacturing processes such as rotary friction welding and mechanical cutting in early stages of product development.

  • 62942. Åström, Peter
    The effect of convective heat transfer coefficient on the residual stresses after cooling from solution heat treatment2001In: Simulation of Materials Processing: Theory, Methods and Applications: proceedings of the 7th International Conference on Numerical Methods in Industrial Forming Processes - NUMIFORM 2001, Toyohashi, Japan, 18 - 20 June 2001 / [ed] Ken-ichiro Mori, Lisse: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 2001Conference paper (Refereed)
  • 62943. Åström, Peter
    et al.
    Moini, Arash
    Parametrisering av selenfilter: för snabb variantframställning2000Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 62944. Åström, Peter
    et al.
    Näsström, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Friction model parameter optimization for friction welding simulation of Ti-62462006In: Trends in welding research: proceedings of the 7th international conference : May 16-20, 2005, Callaway Gardens Resort, Pine Mountain, Georgia, USA / [ed] Stan A. David, Materials Park, Ohio: ASM International, 2006, p. 849-854Conference paper (Refereed)
    Abstract [en]

    With regard to the rotary friction welding process as used for joining of large rotationally symmetric structures in the aerospace industry, the finite element software "MSC. Marc" coupled with the optimisation code INVSYS was used to simulate the friction welding of two cylindrical titanium alloy Ti 6246 specimens while optimising parameters in the friction model. The friction model took into account the friction coefficient variation as a function of normal pressure in the contact, temperature and relative sliding velocity. The unconstrained subspace searching simplex method was employed for optimisation. An objective function was formulated to minimise the error between calculated and measured torques, and a parameter set was identified that produced better flash geometry agreement with experiment.

  • 62945.
    Åström, Sanna
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences.
    Identitetsskapande och intrycksstyrning på sociala medier: En kvalitativ intervjustudie om hur identitet kan skapas på sociala medier2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this essay is to study individual’s experience of creating their own identity on social media. Eight people have been interviewed about their experience of how their use of social media can be a part of creating their own identity. The sociological problem is based on the awareness that images displayed on social media often are excessively perfect or positive. Despite this, people are experiencing pressure regarding achieving the perfect life, or at least give a sense of it on social media. The study results in three main themes, which are "identity", "control of impressions" and "requirements". These three themes contain quotes from the empirical material which are analyzed and linked to theory. The concepts discussed are essentially identity, individualization, self-reflexivity, impression management and standardized behavior. The results of the essay show that social media is a large part of the project candidates lives, and contributes to many impressions and experiences that shape the personality and identity. The project candidates can to some extent choose what impressions they want to get and thus choose, for example, what type of people they want to be influenced by. Contacting likeminded people through social media can also form the identity, and the project candidates feel influenced of what they see in social media to a degree when their own opinions become weaker. Regarding the possibility to choose what they want to share, the have the possibility to control what kind of impression the environment get. They do not always act in a way that is deliberately misleading, but regardless it leads to the surroundings getting an unrealistic picture of the project candidates lives. They experience a difference in their own actions on social media and beyond, and thus, a difference in identity is perceived. On social medias, the project candidates display an image that they are energetic and positive. The essence of the essay is the project candidate’s comparison with others, which can be experienced problematic with the impression control on social media. Actions on social media takes place according to a certain approach and within a certain framework where only certain events occur. In conclusion, it can be said that the framework for what belongs on social media is created and maintained by users, partly through impression control. This framework presented on social media is found to be a part of the individualization as well. The individual can fulfill her dreams with the freedom she has, and this fact can create a stressful situation and apply pressure on the project candidates.

  • 62946.
    Åström, Sanna
    et al.
    Luleå University of Technology, Department of Health Sciences.
    Haglund, Malin
    Luleå University of Technology, Department of Health Sciences.
    Massage: En hälsofrämjande metod under arbetstid: En kvalitativ studie med öppna brev2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Introduction: At present there exists a great deal of research on how massage affects humans physiologically, for example lowering the stress hormone cortisol and reducing heart rate. To our knowledge only a few people have researched on how individuals experience the massage, especially at the workplace which this study focused on. Purpose: The aim of the study was to identify employees experience of massage as a health promotive method at the workplace. Method: A qualitative method with open letters was used, where the participants first had to take part in a 15 minute relaxing massage followed by a reflection on their experience of the massage. 27 participants who are employed at a health care facility in the northern part of Sweden contributed to the study. Results: The results showed that the massage gave the employees several benefits which they consider important to be able to perform as well as possible at work. These benefits formed 3 sub-themes: "Significant elements from the massage", "A contributed benefit that happens regularly" and "Experienced meaningfulness and gratitude" the sub-themes resulted in a main theme: "Beneficial massage creates a wholeness in the workplace". Conclusion: After the intervention the employees felt more recovered, gained more energy for their work tasks and wish they could be offered massage as a regular benefit in the workplace. Other professions that work within health promotion can be inspired by this study to improve the health of employees around the country in the health and social care profession.

  • 62947. Åström, Sara
    Överförmyndarens godkännande alternativt nekande av barnuttag.2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 62948. Åström, Thomas
    Partnering - inom husbyggnad2002Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 62949. Åström, Tove
    En god lärandemiljö: vad innebär det och hur skapas en sådan?2009Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 62950.
    Åström, Victor
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences.
    Vem ska jag tro på?: En netnografisk studie över synen på vaccin i sociala medier2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Under hösten 2009 vaccinerades mer än fem miljoner svenskar med vaccinet Pandemrix för att skyddas mot svininfluensan som då spreds som en löpeld. Tyvärr uppdagades det senare att vaccinet ökade risken för att utveckla den neurologiska sjukdomen narkolepsi, sjukdomsbilden innebär symptom som påtaglig sömnighet eller upplevelsen av att musklerna är kraftlösa. Detta är någonting som kommit att skapa en misstro mot vaccinationer rent generellt. I flertalet europeiska länder har dessutom de senaste åren utbrott av mässling förekommit, världshälsoorganisationen uttrycker i sammanhanget en oro över sjunkande vaccinationstäckningar och ett ökat motstånd mot vaccin överlag. Framväxten av internet har möjliggjort att information för de allra flesta är lättillgänglig, i fotspåren av denna utveckling skapades även Webb 2.0. Webb 2.0 utmärker sig i den benämning att den skapar möjligheter för användarna att interagera med varandra, de kan skapa, dela med sig och diskutera information. Inom ramen för denna studie är det av intresse att undersöka vilken roll de två sociala medierna Facebook och Twitter spelar i frågan om att diskutera och sprida information om vaccin. Studiens syfte är att undersöka hur information om vaccin skildras på sociala medier, samt hur dessa förhåller sig till myndigheters och experters information och rekommendationer rörande vaccin. Metoden som ligger till grund för genomförandet av studien är en netnografi, vilket som metod innebär att undersöka sociala och kulturella sammanhang över internet. I fallet för denna studie har det empiriska materialet samlats in från Facebook och Twitter för att sedan analyseras med utgångspunkt i Anthony Giddens teoretiska begrepp tillit och expertsystem samt Ulrich Beck och Giddens teoretisering av begreppet risk. 

    Studiens resultat pekar på att individer med en negativ inställning till vaccin tenderar att hysa en misstro mot den information och de råd som kommer från myndigheter och medicinska experter. Samtidigt råder ett motsatt förhållande när det kommer till individer som uttrycker en positiv inställning till vaccin, dessa individer finner informationen samt råden pålitlig och utgör i många fall en grund för argumentation i diskussion om potentiella risker med vaccin. I studien identifierades två huvudsakliga argument som framfördes i frågan varför föräldrar inte bör vaccinera sina barn. Det ena argumentet baserades på att läkemedelsföretag, läkare, myndigheter eller andra aktörer som på något vis kan gynnas ekonomiskt på den information och de råd som ges om vaccin inte går att lita på. Det andra huvudsakliga argumentet tog utgångspunkt i att vaccin innehåller gifter som skadar barnen, detta argument förstärkte användarna i många fall genom att sprida bilder eller filmklipp på sjuka barn tillsammans med en text där vaccin utgavs vara orsaken till sjukdomstillståndet.

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