| 1. |
- Abrahamsson, Lena
(författare)
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Att återställa ordningen : könsmönster och förändring i arbetsorganisationer
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Avhandlingen är en könsteoretisk studie av organisationsförändringar i industrin - med fokus på kvinnor som arbetar med produktionsarbete. Avhandlingen beskriver vad som händer med organisationsstrukturen och med genusordningen i organisationen när företaget försöker införa en platt integrerad arbetsorganisation. Empirin omfattar åtta svenska industriföretag: fem massa- och papper, ett tvätteri, ett charkuteri och ett elektronikföretag. Resultaten visar att återställare och dämpande krafter ute i lokala arbetsorganisationer drar organisationen tillbaka till sitt ursprungliga utseende. Många av återställarna har koppling till "kön" och genusordningen. De lokala organisationernas utgångsläge inför organisationsförändringarna bygger ofta på en struktur som ger olika villkor för kvinnor och för män. Denna könsordning är en förklaring till många återställare och det är dessutom ofta just den som återställs. Genusordningens segregerande och hierakiserande krafter gör att människor lätt återskapar gamla könsmönster i nya organisationer. Detta innebär att de nya organisationsmodellernas strävan efter integrering, tillplattning, kompetensutveckling och flexibilitet riskerar att motarbetas. En stark och omfattande könsmärkning och könsuppdelning i utgångsläget inför organisationsförändringen innebär många återställare och därmed svårare att införa den platta integrerade arbetsorganisationen.
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| 2. |
- Aidanpää, Jan-Olov
(författare)
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Dynamics of some vibro-impacting systems with amplitude constraints
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the dynamics of some vibro-impacting systems with fixed or moving amplitude constraints. It is based on and includes five papers, marked A to E. Simple models of three different vibro-impacting systems with applications in the fields of impact hammers, granular flow and disk brakes in vehicles are analysed. A 2-DOF (two-degree-of-freedom) model of a threshold-limited impact hammer is studied (Paper A). The stability of a class of periodic motions is analysed. For some parameter values these periodic motions are found to be qualitatively similar to the ones observed for a corresponding 1-DOF system. At other parameter combinations, however, new kinds of periodic or chaotic motions can be observed. For low damping, phenomena resembling antiresonance for linear systems can also be observed. Granular shear flows show a transitional behaviour in the rapid flow regime as the shear speed or the concentration of the grains is varied. The motion can, for example, change from smooth and orderly to erratic and turbulent. Some aspects of this transitional behaviour in granular shear flow are studied numerically, analytically and experimentally (Papers B, C and D). Simple vibro-impacting models are suggested to get some analytical insight into the dynamics of shear layers. Results from a 1-DOF model show that for high forcing frequencies, which correspond to high shear speeds, periodic as well as chaotic motions can exist, whereas, for low forcing frequencies the vibrations are completely damped out to a stationary state (Paper B). Stability of this stationary state is studied analytically (Paper C), and experimentally (Paper D), where the motions of granular particles in a transparent shear cell are followed by using video techniques. For low shear speeds a single shear layer adjacent to the bottom boundary of the shear cell is observed. As the shear speed is increased, a transition to a random like state involving many layers is found to occur. In order to understand the phenomenon of squeal in disk brakes, a 3-DOF model is suggested to simulate the dynamics of a brake pad. The region of contact between the brake pad and the disk is described by using a coefficient of friction and distributed stiffness. The brake pad is allowed to have adjustable support locations and possibilities of impacts with its surroundings. The equilibrium state of the pad is determined by using a static analysis. The assumption is that the instability of this stationary state is a possible explanation of squeal, therefore, the stability is analysed in detail. Examples of different kinds of pad motions are presented. A rich variety of motions are found to exist including periodic, seemingly chaotic, stationary behaviour in slip, vibrations with full contact with the disk, stick-slip and impacts.
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| 3. |
- Alerby, Eva
(författare)
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Att fånga en tanke : en fenomenologisk studie av barns och ungdomars tänkande kring miljö
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis attempts to clarify the way in which young people think about our envíronment, based on their experiences as the starting point. The aim is to make the thinking of people available and to interpret the meaning of these thoughts, whose content comprises the environment. The theoretical roots of the study are to be found within the phenomenology of the lifeworld. I also use the phenomenological method as a type of analysis method to use as inspiration when analysing the empirical material. The children and young people who are included in the study are between the ages of 7 and 16. The data collection is based on two partial studies. In one partial study, empirical material is analysed consisting of the production of drawings by 105 children and young people with attached oral comments, and in the other partial study interviews which were conducted with 16 children and young people are analysed. These two studies are partially connected and partially dependent on one another. The drawing study is aimed at developing an understanding of the thinking of the children and young people and also forms the basis for the selection of subjects for the interview study. The interview study for its part is aimed at further deepening the understanding of the thinking process and the interviews took place on two occations with each person. In the drawing analysis four themes of thoughts were crystallised which focus on: the good world, the bad world, the dialectics between the good and bad world, and symbols and actions promoting the environment. In the interview analysis eight themes emerged of thoughts which focus on: pragmatic perspectives, emotional perspectives, future and visionary perspectives, philosophical perspectives, aesthetic perspectives and romantic perspectives. It can be stated that the results which emerged in the form of the thinking of the children and young people on the environment reflect their thinking as having many nuances. If these many-faceted thoughts are to be taken seriously it is necessary in the teaching and learning situation to take into account the thinking of young citizens. Teaching and learning situations should therefore create time and room for conversation and thinking. This is to stimulate the growing power which the experiences of young people have, experiences which are in turn requirements for thinking: thinking which is constituted by beeing-in-the-world.
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| 4. |
- Alm, Irma
(författare)
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Newspaper reports : do they influence remembering of the main session material?
- 1990
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis was aimed at investigating whether pre-exposure to biased newspaper reports influences remembering of the main session material. In general, the results show that remembering of the main session material varies as a function of the pre-exposure to the biased newspaper reports. It seems that pre-exposure to newspaper reports facilitates the accessibility of the main session items. However, recognition of the main session material in general seems to decrease when the participants are pre-exposed to newspaper reports written in order to discredit the defendant, whereas pre-exposure to newspaper reports written in favour of the defendant seem to facilitate recognition of the main session material. It Was suggested that the various schema activated on basis of the biased newspaper reports produced the effects obtained. Further, the ability to distinguish the various sources of information decreased when additional information (i.e., interference) was introduced. Some of the results obtained inquire previous views on expertise and prior knowledge and are discussed further. Moreover, the limits to generalizability are also discussed.
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| 5. |
- Almgren, Torgny
(författare)
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An approach to long range production and development planning with application to the Kiruna Mine, Sweden
- 1994
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The mining industry is increasingly oriented towards large scale mining and the planning concept of "Just in Time", which means activities starting and ending as late as possible without jeopardising production. The buffers, consisting of production blocks and development ahead of production, are then minimi. This, however, leads to a larger dependency on the quality of the output from the production systems. The Kiruna mine, Sweden, is a large scale mine and has a number of potential ore blocks with a content that varies in quality (Fe, P, K) and in quantity (ore tonnage). Ore production is restricted by operative and block sequencing constraints as well as by production requirements. A computerized planning model, based on operations research (multi period scheduling) has been developed to meet future demands on ore qualities and quantities. The model uses long range objectives, but can satisfy temporary short range demands without jeopardising the long range goals. A sub-optimal plan, made using the model, has been compared with a truly optimal plan. It is shown that, due to the unreliable information concerning the ore, the sub-optimal plan performs as well as the optimal one. The simulation process that was developed for this comparison is also used to estimate the need for production buffer blocks. Another buffer planning model is developed to determine when development work should take place in order to minimize the risk of additional costs, caused by an inability to start production on time. This algorithm considers the uncertainties in activity durations and is based on a Monte Carlo simulation using project networks and estimates the optimum development buffer.
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| 6. |
- Almqvist, Nils
(författare)
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Studies of plasma-facing materials and macromolecules using scanning probe microscopy
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main topic of this thesis is experimental analysis of material surfaces using scanning probe microscopies. These microscopes are used for characterization through high-resolution topographical imaging, but also for controlled modification of surfaces and molecules. The surface characterization includes evaluation and development of fractal methods for surface roughness determination. The term modification is used for manipulating the structures on a microscale by scraping them with a tiny tip. The major application of this technique in the present work is the analysis of effects induced by plasma-surface interactions. Such studies are fundamental in the understanding of erosion and deposition processes on the first wall in controlled fusion devices. In this work, scanning probe microscopes were for the first time used for studying such plasma-facing materials. Both the surface structure and composition have to be known in order to evaluate new wall-materials for fusion reactors. The materials studied here are graphites, SiC/Al coatings, graphite-silicon mixtures and various silicon carbide based composites. They were all exposed to plasmas, either to lowenergy deuterium plasmas and ions in laboratory experiments, or to the plasma in a socalled tokamak. The results show the usefulness of these high-resolution microscopes in the study of plasma-surface interaction. Several other surface sensitive techniques were also applied, at the home laboratories of our collaborators, the most important ones being Rutherford backscattering spectroscopy and nuclear reaction analysis. The scanning probe microscopy in combination with the ion-beam analysis made it possible to trace fine structural features on the surfaces and to measure the surface roughness. The main results are: (i) the detection of the initial stages of bubble/blister formation on CSi mixtures, SiC/AI coatings and graphites; (ii) the morphological changes and the physical properties of the silicon carbide composites; (iii) the distinction of radiation damages on different phases of multicomponent composites; (iv) the estimation of layer thickness with scanning probe microscopy; (v) the determination of the structure of codeposited layers formed during exposure in a tokamak; (vi) the uptake of deuterium by the materials. The atomic force microscope has also been used to study the human protein spectrin, and we managed to image free spectrins with molecular resolution in an almost natural environment. The elongated spectrin macromolecule was found to be 100 rim long and 5 nm broad. Indications of a substructure were observed. The force between the sensor tip and the molecules was crucial, both for sample movement, manipulation and image resolution. Therefore, the instrument was rebuilt to operate with so called tapping-mode in liquid. Preliminary results with this method on spectrin are presented.
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| 7. |
- Andersson, Annika
(författare)
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Frazil ice at water intakes
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To provide a better understanding of how frazil ice deposits on trash racks at water intakes, the phenomenon was video recorded at two hydropower plants and in a refrigerated laboratory flume. Initial accretion of frazil ice around a single bar and the motion of particles in the vicinity of an obstacle was simulated through numerical modelling and studied using plastic particles in a laboratory flume. Ice initially accumulates on the upstream face of the bars, and it progresses then to the upstream sides of the bars. Tha frazil ice layer grows in all directions, and it finally bridges over the spaces between bars. The ice blockage starts at the upper part of the rack and progresses downward. The head losses across each intake, which are observed continuously at the plants, illustrate the degree and importance of ice growth. Observations from laboratory experiments with a single bar in a flume, showed that frazil ice particles deposited on all bar surfaces. Separate flume tests were run with plastic particles simulating ice particles. The frequency of collision of these particles with the front face of a rectangular bar varied with the particle density and the fluid velocity. In a test with particles of various sizes, the smaller particles were more likely to enter the side wake than larger ones. A mathematical model can be used to predict patterns of ice deposition that correspond to the observed results. Such a model must include a hydrodynamic part for viscous flows and a particle trajectory model. Some models neglect the term for force due to pressure gradient in their calculations of a particle trajectory because the particles had larger density than the surrounding fluid. Ice particles have almost the same density as the water and simulated results showed that this term, caused by the pressure gradient, is the dominant force that counter the momentum of the particles when they move in the region close to the obstacle. The simulated results were affected by the particle size distribution, therefore the size distribution of frazil ice particles in a river is a factor in further studies. In tests in which no particles were allowed to deposit on the front part of the bar, in a simulation of a heated bar, lesser amounts deposited on the other parts of the bar. Knowledge of the way frazil ice accumulates on water intakes and the initial ice accretion on individual trash racks should be valuable in future work for finding methods to reduce the ice blockage and in the verification of more detailed model studies.
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| 8. |
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| 9. |
- Andreasson, Patrik
(författare)
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A numerical investigation of energy conversions in geophysical boundary layers
- 1991
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The detailed energy conversions in turbulent geophysical boundary layers are examined and quantified. The governing transport equations are solved by utilizing turbulence modelling. Different turbulence closures have been adopted for the boundary layers examined. LowReynolds number modelling is required, since energy conversions are large in the near-wall region. The three examined boundary layers are: open channel flow, wind-induced countercurrent flow, and ice-covered channel flow. In addition, a generalized eddy-viscosity hypothesis is proposed. In the standard eddy-viscosity concept. zero shear stress coincides with zero shear. This is not realistic for many flows. such as wind-induced countercurrent Row. This limitation is relaxed in the new hypothesis, by recognizing the influence of gradients in the turbulent length scale and the shear. In open channel flow, energy is released to the kinetic energy of the mean flow by the lowering of the centre of mass. Between 20-70 % (depending on the Reynolds number) of the energy is dissipated by viscous forces working directly on the mean shear. The remaining portion is a source of turbulent kinetic energy, which is balanced by the dissipation. Eventually all of the energy will leave the domain as a boundary beat flux. In the modelling of open channel flow, a one-equation turbulence model and Reynolds analogy is used. In wind-induced countercurrent flow. energy is supplied to the mean flow by the wind acting on the free surface. Most of the mean kinetic energy is dissipated or transformed to turbulent kinetic energy in the surface drift current. Only about 5-10 % is supplied to the return flow underneath. As with open channel flow, 20-70 % of the mean kinetic energy is dissipated without entering the turbulent kinetic energy budget. The dissipated heat is considered to leave the domain through the free surface. A Reynolds stress model was adopted for the windinduced boundary layer, in conjunction with the "generalized gradient diffusion hypothesis" for beat flux. A detailed description is presented, of the spatial distribution and the depth-averaged features of energy conversions in the two boundary layers mentioned above. In the study of ice-covered channel flow, the analysis is focused on beat transfer characteristics. In water of a temperature close to 00C, the conversion from kinetic energy to heat may be of influence to the heat transfer in an ice-covered channel. In water of higher temperatures buoyancy effects may develop. In addition the melting ice-cover constitutes a moving boundary problem. These three effects are considered in the study, in which the predicted beat transfer characteristics are presented as Nusselt number relations. To make adequate predictions of the boundary layer flow beneath an ice-cover, a Reynolds stress and heat flux transport model is employed. Equations for the transport of temperature variance and its dissipation rate are also solved.
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| 10. |
- Antti, Lena
(författare)
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Heating and drying wood using microwave power
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The potentials for moisture flux in wood during microwave heating have been investigated experimentally and theoretically. The experiments were performed in three different kinds of microwave applicators. A computer model based on the finite difference method was developed to describe and predict the heat and mass transfer. The main conclusions are that microwave energy of 2.45 GHz frequency makes it possible to heat and dry pine and spruce 20 - 30 times faster than with conventional methods without any deterioration in drying quality. Some hardwoods are dried in approximately half the time compared to the softwoods. The drying method evokes unique results either with diminishing colour changes or with possibilities to create such during drying. However, to avoid unevenness in the electromagnetic field distribution and considering the limitation in power penetration depth the drying should be performed on line where wood components continuously are fed through a microwave field.
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