| 51. |
- Drugge, Lars
(författare)
-
Modelling and simulation of pantograph-catenary dynamics
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis considers theoretical and experimental investigations of the dynamic behaviour of pantograph-catenary systems for trains and its relation to simulation driven product development. The pantograph and catenary form an oscillating system that is coupled via the contact force between the pantograph head and the contact wire. Too large contact force variation can lead to loss of contact, arcing and wear as well as damage to the system. Thus, the dynamic behaviour plays a decisive role for high-speed trains from the power collecting point of view. It is therefore a need for enhanced possibilities to predict the dynamic behaviour of this type of system. To accomplish this, modelling, simulation and experiments have been used. In this work, different models for catenary systems and pantographs are developed, ranging from simple lumped mass models to full three-dimensional models. The dynamic behaviour is also studied using full-scale and laboratory-scale experiments. Modelling of different aspects are covered, such as for example the damping in the catenary system that is important for multiple pantograph operation. Non-linear phenomena in the dynamic behaviour of the current collector suspension and dynamic effects caused by parameter variations due to wear of pantographs are also investigated. A simulation tool is developed to increase the actual use of computational support in the product development process. Depending on the specific questions to be answered, available information, skill of engineers, available software etc. models of different detail are appropriate. To handle this problem, the structuring of an advanced simulation tool for simulation driven product development is proposed.
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| 52. |
- Ecke, Frauke
(författare)
-
Effects of landscape patterns on small mammal abundance
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Several studies indicate a long-term decline in the numbers of voles in northern Fennoscandia. Altered land use and forest management practices have been proposed as possible causes of the decline. This doctorial thesis aimed to identify, on different spatial scales, landscape patterns that are important for the abundance of small mammals and that might be related to the decline. General trends and aspects of spatial habitat modelling were reviewed. Trapping data from three large extent monitoring programs were related to habitat factors on different spatial scales. For these analyses, a broad range of statistical and GIS (geographic information system) related methods was applied. On the microscale (trapping station, extent <= 10 m) and mesoscale (transect, length 90 m), structural habitat factors such as coarse and fine woody debris, umbrella vegetation and structural complexity of the forest floor were identified as important factors influencing small mammal abundance. Small mammal densities were related to the percentage landcover of vegetation types on the micro-, meso-, macro- (subarea/landscape, 1 x 1, 2.5 x 2.5 and 2 x 5 km) and regional scale (overall study area, 20 x 20 - 80 x 80 km). The spatial continuity (non- fragmentation) of old-growth pine forest patches on the landscape scale was positively related to the abundance of C. rufocanus, the species that showed the most pronounced long-term decline in numbers. The results of this thesis strongly suggest that altered land use might indeed be involved in the decline in numbers of voles in managed forest areas in northern Fennoscandia. To reveal and test responses of small mammals to changes in landscape patterns in more detail, this work proposes further application of large scale approaches. These approaches, e.g. the GIS-based prediction of the areas with currently high abundance of C. rufocanus can be tested by field sampling of the type applied in this thesis. Such approaches should consider the key aspects identified in the reviews on GIS-based habitat modelling, e.g. reconciling the scale of the population dynamics of small mammals with the scale (resolution and extent) of the input data, the application of different modelling approaches and the performance of sensitivity analysis.
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| 53. |
- Ecke, Holger
(författare)
-
Carbonation for fixation of metals in municipal solid waste incineration (MSWI) fly ash
- 2001
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The waste management is in need of a reliable and economical treatment method for metals in fly ashes from municipal solid waste incineration (MSWI). However, no state-of-the-art technique has gained wide acceptance yet. This Doctoral Thesis aimed at assessing the possibilities and limitations of carbonation as a stabilization method. Factors that were studied are the partial pressure of carbon dioxide, the addition of water, the temperature, and the reaction time. Laboratory experiments were performed applying methods such as factorial experimental design, thermal analysis, scanning electron microscopy (SEM), x-ray diffraction (XRD), and leaching assays including titration at static pH and sequential extraction. Leaching data were verified and complemented using chemical equilibrium calculations. Data evaluation was performed by means of multivariate statistics such as multiple linear regression, principal component analysis (PCA), and partial least squares (PLS) modeling. It was found that carbonation is a good prospect for a stabilization technique especially with respect to the major pollutants lead (Pb) and zink (Zn). However, a mobilization of cadmium (Cd) was observed, which requires further research on possible countermeasures such as e.g. metal demobilization through enhanced silicate formation.
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| 54. |
- Ekenberg, Lilly
(författare)
-
The meaning of physiotherapy : experiences of parents of young adults with impairment
- 2000
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis is to increase the understanding of the meaning of physiotherapy when fathering and mothering a child with impairment. The research has been focused on parents’ experiences of their participation in physiotherapy training of their child. The research focus and research methods have gradually changed from a more quantitative approach to a more qualitative approach as the understanding and knowledge progressed. The first two studies were questionnaires sent to parents of 49 and 105 parents respectively of children with impairment, all with contacts with physiotherapists. The third investigation comprised semi-structured qualitative interviews with strategically selected parents of 22 children, interviews that were analysed in a descriptive way. These interviews were then reanalysed, applying a hermeneutic-phenomenological method to three papers, evolving and proceeding step-by-step, from the first paper with a case analysis, in the second paper with the focus on parents of 17 young adults with experiences of Vojta physiotherapy, and finally in the third paper, with the focus on the experiences of physiotherapy of fathers’ and mothers’ of 22 young adults. The findings indicated that both fathers and mothers participated in physiotherapy. The Vojta physiotherapy was experienced as hard work but could also create a sense of hope. The meaning of physiotherapy was understood through three relations: (1) the fathers’ and mothers’ relation to the child, (2) the fathers’ and mothers’ relation to physiotherapists and (3) the fathers’ and mothers’ relation to the practice of physiotherapy. There is a need to consider whether movement or merely a body perspective should be the ontological base for clinical practice in physiotherapy for persons with impairment.
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| 55. |
- Ekenberg, Stefan
(författare)
-
The power of recognition : the limitation of indigenous peoples
- 2000
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the thesis is to investigate the relationship between power and indigenous peoples and to find a relevant method with which to study this relationship. It is the condition of power or the lack of power that allows an ethnic group, a ‘tribe’, an ‘indigenous people’ or a ‘people, to become a ‘nation’. Power has thus a significant affect on ethnicity and in recognising ethnic groups as nations. I argue that indigenous peoples have to be understood as self-defined ethnic minorities which include the dynamic character of identities. This subjective definition will focus on the constitution process of identities, rather than objective attributes. It also highlights the power aspects of identification. However, the subjective definition also creates a crucial problem. The three traditional views of power cannot combine identity with power. Either there is simply power and no identity, or there is identity but no power. We thus need a fourth view of power. Usually, power is a force that presses on the subject from the outside, as what subordinates, sets underneath, and relegates to a lower order. This is, of course, a fair description of what power does. However, in the fourth view of power subjection is a form of power. We must understand power as forming the subject as well as providing the very condition of its existence. Power is not simply what we oppose but also what we depend on for our existence. The thesis shows that all identities are relational and causes ordination, that is it always constitutes a hierarchy. One identity cannot exist in isolation. As soon as a relationship occurs power is involved. Power is productive, that is, it constitutes, reconstitutes and legitimises categories and norms connected to them. No one is in charge of this power, all actors are vehicles of the power that continuously constitutes their reality. Identification is ordination and thus produces its own norms, discipline and resistance. Resistance, self-discipline and self-subjection are thus power techniques that strengthen a given discourse and the power relationship it upholds. Thus, there are no theories on identity, indigenous or ethnic, only theories of history encompassing indigenousness capable of explaining the empirical production of identities. There is no identity without power and there is no power without identity. To understand indigenous peoples’ political situation one must analyse how they are constituted by a sophisticated interplay between internal and external power techniques. Members of indigenous peoples, as well as members of other group identities, must question their own foundation of identification in order to uncover future alternatives. This may change present discourses and categories and the power relationships they constitute, reproduce and legitimise.
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| 56. |
- Eklund, Monica
(författare)
-
Interkulturellt lärande : intentioner och realiteter i svensk grundskola sedan 1960-talets början
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I avhandlingen studeras interkulturellt lärande dels utifrån statens intentioner avseende den formella socialisationens mål och innehåll, dels utifrån lärandet hos eleverna, det vill säga som realitet. Det övergripande målet var att analysera om den offentliga socialisationen inom grundskolan ger barn och ungdomar redskap att hantera kulturell mångfald. Det interkulturella lärandet studeras inom ramen för två delstudier, en som utifrån ett samhällsvetenskapligt/läroplansteoretiskt perspektiv fokuserar statens intentioner och en som utifrån ett socialisationsteoretiskt perspektiv fokuserar det uppfattade och upplevda interkulturella lärandet hos och mellan elever i skolår nio. I dokumentstudien analyseras förutsättningarna för interkulturellt lärande i dokument från början av 1960-talet till slutet av 1990-talet. Tidsperioden är indelad i tre faser: initierings-, utvärderings- och omformuleringsfasen. I elevstudien analyseras de interkulturella socialisationsprocesserna utifrån intervjuer med elever i skolår 9. Av dokumentstudien framkommer det att i de tidigaste formella läroplanerna under initieringsfasen är ingen mångkulturalitet synlig. Perspektivet är internationellt snarare än interkulturellt. Fram till hemspråksreformen 1977 ses undervisning i modersmålet och i svenska som stödundervisning. Ett embryo till interkulturellt synsätt finns i läroplanssupplement från mitten av 1970-talet. Förespråkade arbetssätt främjar inte interkulturellt lärande. Under utvärderingsfasen är mångkulturaliteten ett faktum, men elever med annan bakgrund än etniskt svensk ses som representanter för andra kulturer. Sverige. Skolan skall aktivt tillvarata alla elevers kulturarv och kommunen är skyldig att erbjuda hemspråksundervisning. Att lära sig svenska börjar ses som en skyldighet. Tvåspråkighet lyfts fram som ett mål i läroplanen. Förespråkade arbetssätt ger förutsättningar för interkulturellt lärande. Efter riksdagsbeslutet om interkulturellt synsätt i all undervisning framkommer detta perspektiv tydligare i olika kommentarmaterial, men Lgr 80 ändras inte. Mångkulturaliteten är ett faktum under omformuleringsfasen, men omnämns nu som mångfald. Perioden präglas av genomgripande förändringar, vilket bl.a. ledde fram till en ny typ av läroplaner där endast målen kommer till uttryck och inga specifika arbetssätt föreskrivs. Det interkulturella synsättet kommer främst till uttryck i läroplanens ”värdegrund” och i strävansmål som inte ligger till grund för betygssättning. Tvåspråkighet är inte längre ett mål inskrivet i läroplanen och för flertalet elever med annat modersmål än svenska inskränks rätten till modersmålsundervisning. Svenska som andraspråk blir under perioden ett eget ämne som ger full behörighet för vidare studier. Detta kan ses som ett erkännande av de svårigheter som det innebär att lära sig ett andraspråk. De tidigaste målen för undervisning av elever med annan språklig eller kulturell bakgrund formulerades inom ramen för invandrarpolitiken. Ungefär samtidigt formulerades målen för grundskolereformen. Grundskolan som utmärktes av sitt mål om att vara en skola för alla – en mötesplats för alla barn och ungdomar oavsett bakgrund, hade föga till övers för att betona dessa barn och ungdomars språkliga eller kulturella bakgrund och göra den till något som särskilde elever. Invandrarpolitikens propåer under initierings- och utvärderingsfasen, om att möjliggöra kulturbevarande avseende invandrar- och minoritetselevers språk och kultur blev därför en anomali inom den svenska grundskolan. Det gick att bevara målet om en skola för alla, oberoende av bakgrund, men endast genom att låta den undervisning som tog fasta på annan kultur och annat språk utgöra en separerad undervisning. Under omformuleringsfasen är det inte integrationspolitiken som är överordnad utbildningspolitiken. Snarare är det målstyrningen som är överordnad såväl integrations- som utbildningspolitik. Även mångfald som paraplybeteckning blir överordnad inom båda politikområdena. Utifrån resultaten av elevstudien går det inte att verifiera tesen att värdegemenskap med den formella socialisationens interkulturella mål också innebär interkulturellt lärande hos eleverna. Tänkbara förklaringar till detta resultat är att socialisationsinnehållet är skilt från det tillämpade arbetssättet, en segregerande majoritetsläroplan, linjärt snarare än cirkulärt tänkande samt majoritetskulturella ramfaktorer och statens övergripande politik. Då dokumenten/intentionerna och empirin/realiteten studeras tillsammans framkommer diskrepans mellan intentionerna i den övergripande politiken och målen i läroplansdokumenten och inte minst i realiteten så som den kommer till uttryck i den av eleverna upplevda läroplanen. Eventuella orsaker till denna diskrepans är t.ex. att mål som formuleras på de högre läroplansnivåerna sällan följs av motsvarande resurser (ekonomiska, personella, intentionella) på de läroplansnivåer där målen skall implementeras. Inte heller prioriteras denna verksamhet, vilket även innebär att det är lätt att sortera bort det interkulturella innehållet. Vidare har man så att säga ”talat med kluven tunga”. Å ena sidan har man inom den övergripande politiken intentionellt gett uttryck för en sak, å andra sidan har man med andra beslut gett andra signaler. Ett exempel är att man i retoriken betonat vikten av modersmålsundervisning men i praktiken har man vare sig prioriterat utbildning av modersmålslärare eller gett denna yrkesgrupp med andra lärare likvärdiga arbetsvillkor. Inte heller har andra modersmål än svenska haft en självskriven plats inom skolans undervisning, utan istället har modersmålsundervisningen för elever med annat modersmål än svenska ständigt ifrågasatts. En slutsats är att det är rimligt att ställa frågan om det är möjligt att förena riksdagsbeslutet om interkulturellt synsätt i undervisningen med målstyrning och lokal läroplansuttolkning, det vill säga om målet kan skiljas från vägen dit. Den fortsatta forskningen bör inriktas mot den operationaliserade läroplansnivån, det vill säga, vad som faktiskt sker i skolans undervisning och övriga verksamhet. Nyckelgrupper här är lärare och skolledare.
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| 57. |
- Ekman, Jonas
(författare)
-
Electromagnetic modeling using the partial element equivalent circuit method
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents contributions within the field of numerical simulations of electromagnetic properties using the Partial Element Equivalent Circuit (PEEC) method. Numerical simulations of electromagnetic properties are of high industrial interest. The two major fields of use are to ensure compliance with electromagnetic compatibility (EMC) regulations and to verify functionality in electronic designs. International EMC regulations bounds companies that develop or assemble electric products to market products that are electromagnetic compatible with other products in their environment. Failure to comply with regulations can result in products withdrawal and fines. To avoid incompatibility, numerical simulations can be used to improve EMC characteristics in the development and assembly stage in a cost efficient way. Functionality of today's compact high-performance electronic systems can be affected by unwanted internal electromagnetic effects. The result can be degradation of performance, malfunction, and product damage. Numerical simulations are used to predict electromagnetic effects at the design phase, thus minimizing the need for post-production actions delaying product releases and increasing product cost. At the Embedded Internet System Laboratory (EISLAB), Luleå University of Technology, a project concerning numerical simulations of electromagnetic properties in electric systems using the PEEC method is in progress. This thesis focuses on the development of the PEEC method for practical use, thus demanding optimal performance of the basic sections within a PEEC based electromagnetic solver in terms of speed and accuracy. In the PEEC method, the two most demanding sections are the partial element calculations and the solution of the final equation system. The latter problem is a pure mathematical problem with continuous progress while the partial coefficient calculations require further research. This thesis proposes several techniques for efficient partial element calculations. First, a discretization strategy is used for one-layer structures to enable the use of fast analytic formulas and the resulting simplified PEEC models are solved using a freeware version of SPICE, exemplifying the accessibility of the PEEC method. Second, a fast multi- function method is proposed in which different order of numerical integration is used, in the calculation of the partial elements, depending on a predefined coupling factor. Third, the fast multi-function method is further developed and compared to a fast multipole method applied to partial element calculations. Fourth, the calculation of the three- dimensional node coefficients of potential is addressed and three novel approaches are presented and evaluated in terms of speed and accuracy. The thesis includes a paper dealing with nonorthogonal PEEC models. This model extension allows the use of nonorthogonal volume and surface cells in the discretization of objects. This facilitates the modeling of realistic complex structures, improves accuracy by reducing the use of staircase- approximations, and reduces the number of cells in the PEEC model discretizations. The nonorthogonal formulation excludes the use of analytical formulas thus make topical the use of fast multi-function- and multipole-methods. The fundamentals of the PEEC method makes free-space radiation analysis computationally efficient. Radiated field characterization is important in EMC processes and therefore of great interest. One paper in this thesis explore different possibilities to use PEEC model simulations to determine the electric field emissions from objects.
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| 58. |
- Emami, Nazanin
(författare)
-
Variables affecting stress development and resin conversion in light-cured dental composites
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The general aim of this dissertation was to identify and investigate factors that can be used to minimize stress development in light cured dental resins without compromising the conversion level of the polymer. Modulus of elasticity, polymerization contraction strain, degree of conversion and shrinkage of light-cure dental composites were determined after curing with three different light power densities where total irradiated energy (J/cm2) kept constant. FT-Raman spectroscopy was employed to determine the degree of conversion. The cure kinetic of light cured resins was studied by use of photocalorimetry (photo-DSC). Dynamic mechanical thermal (DMTA) analysis was used to investigate how different light curing methods affected glass transition and tangent delta of light curable dental resins when the temperature changed from 0 to 200°C. Optical properties of dental composites were studied. Three different filler types, two different surface treatments and eight different filler fractions per filler type and surface treatment were investigated. Light transmission was measured for the different composite compositions at sample thicknesses of 1 to 5 mm by use of a universal power meter. As long as the total light energy remained the same, the modulus of elasticity remained constant for each composite, even though the power density differed. Composite thickness, irradiance time, composition of the light cure composite and irradiation value had significant impact on degree of conversion. The irradiance value did not significantly affect on the transition temperature value. Initiator, co-initiators and light irradiance value had all significant impact on cure behavior. Different filler types and filler surface treatments had significant effects on light absorption. In general, light absorption increased linearly with filler fraction and sample thickness of the cured composites. Conclusion: Low rather than high light irradiance values decrease stress levels in composites, and comparable conversion levels are reached as long as the total light energy value remains the same for low versus high irradiance. By increasing the composite thickness above 2 mm but not exceeding 6 mm, energy levels exceeding 30 J are needed to achieve acceptable levels of degree of conversion. Different irradiance values do not affect the final Tg of tested composites as long as the total light energy remains the same. By using appropriate photo initiator/co-initiator combination and soft-start curing it is possible to achieve slow curing and high DC within a 40 s. As expected, different filler particle properties have significant effects on light absorption during curing making it important to consider these differences when one tries to develop a general light curing strategy for light curable dental resins.
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| 59. |
- Engström, T. Fredrik
(författare)
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Simulations and experiments of turbulent diffuser flow with hydropower applications
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Most hydropower plants in Sweden were built more than 50 years ago. The design tools were model tests and one-dimensional analytical methods. Since then the field of Computational Fluid Dynamics has evolved into an important engineering tool. To use CFD in a design or redesign stage of hydropower waterways would be very attractive due to its flexibility and cost-effectiveness. The hydropower plants operate under different circumstances today, since the electricity market has been deregulated and the nuclear power will be phased out. Turbines are thus run in a different manner than before with high power output during peak demand hours when the electricity price is high. Hence, efficiency improvements over a wide range of operating conditions are of interest. Predictions of runner flow have been established since long. Turbulence is of secondary importance which makes flow modeling relatively easy. The draft tube, however, is responsible for a large portion of the total hydraulic losses for low and medium head turbines and it is also the most challenging part of the waterways to predict numerically. The draft tube flow is characterized by the interaction of many complex flow features such as diffuser effects, unsteadiness, swirl, streamline curvature, separation and impingement. The Turbine-99 workshops assessed the ability of CFD to predict the flow features and engineering quantities of a model draft tube flow. It was found that many different problems contribute to the overall uncertainty in the results. The implementation of unknown boundary conditions and the post processing of the results were identified as error sources. The performance of the different turbulence models could not be evaluated, due to the numerical uncertainties. In the present work, factorial design was applied to investigate the sensitivity of the numerical solution to the unknown boundary conditions. It was shown to objectively give valuable information about the importance of different input parameters and to simplify the assessment of different turbulence models. To validate turbulence models for draft tubes, carefully selected validation cases need to be developed. This work presents two experimental validation cases that incorporates some of the complex phenomena in the draft tube, but in a well-controlled environment where detailed near-wall turbulence data can be measured by laser Doppler velocimetry. The effect of a 3-D straight asymmetric diffuser on a developing duct flow is investigated both for steady and pulsating flows. It was found that the average flow field is unaffected by the pulsation, while the oscillating turbulent quantities were influenced depending in their frequency.
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| 60. |
- Eriksson, Henrik
(författare)
-
Organisational value of participating in quality award processes
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Total Quality Management (TQM) is sometimes considered to be a continuously evolving management system consisting of values, methodologies and tools, the aim of which is to increase external and internal customer satisfaction with a reduced amount of resources. Whether TQM improves the performance of and strengthens values within organisations has been discussed for several years. One way of working with TQM and its values, methodologies and tools is to participate in a quality award process. The purpose of this thesis is to describe and explain the organisational value of participating in quality award processes. This thesis is limited to Swedish organisations, and consists of an extended summary and five appended papers on the subject, each with a different aim and methodology. The work described in one paper investigates the financial performance of quality award recipients compared with competitors and branch indices. Two of the papers illuminate participation in in-company quality award processes regarding experiences and organisational performance. Two of the papers describe the organisational value of participation in the Swedish Quality Award process. The main conclusion of the thesis, which is in agreement with earlier published results, is that, if companies successfully implement TQM, the financial performance is affected positively. Good examples are also identified of the application of methodologies and tools, based on participation in a quality award process, in order to improve organisational performance within a number of areas. The results of this thesis have not been able to show strong evidence proving that the organisational performance of company units which have worked with in-company quality awards, but have not yet successfully implemented TQM, are affected by this work. However, such units experience that working with in-company quality awards has positive effects on the customers as well as the employees. The same is also true of organisations participating in a national quality award process. In particular, the main value of participation in a national quality award process is improved customer orientation, process orientation and improvement work. On the other hand, the main drawbacks are the resource-demanding activities involved, in particular during the phase of description of activities, and the elaborate model used for participation in the quality award process.
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