| 41. |
- Bäckström, Magnus
(författare)
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Grassed swales for urban storm drainage
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigates the environmental, economic and functional aspects of using grassed swales for the conveyance and treatment of stormwater. A grassed swale is a shallow, grass-lined channel. The environmental aspects relate to the transport and retention of stormwater pollutants in grassed swales and the utilisation of natural resources for the construction and operation of different stormwater transport systems (e.g. grassed swales). The economic aspects considered are the costs needed to construct and operate stormwater transport systems. The investigated functional aspects of grassed swales relate to conveyance and infiltration. Two full-scale studies were performed: 1) a study of sediment removal in a 70-m long grassed swale (Gammelstad, Luleå) and 2) a study of the transport and retention of suspended solids and heavy metals in a 110-m roadside grassed swale (Södra Hamnleden, Luleå). Particle trapping and flow conditions in different grassed swales were analysed using a standardised runoff event simulation procedure where water and road sediment were mixed in a 1-m3 tank and then pumped into a swale. The utilisation of resources of a pipe system and a swale system was analysed. It was suggested that the use of physical resources (in terms of exergy) could be one indicator on environmental sustainability and that a cost analysis would measure how society (human beings) valued these resources. Grassed swales with fully developed turfs and mild bottom slopes (<7%) provide high flow resistance. Grassed swales require lower amounts of natural resources, in terms of exergy, than a comparable stormwater pipe system. A grassed swale is more cost-efficient than a pipe system in areas with low land prices and good topsoil. The variations in pollutant removal efficiency of a grassed swale could be explained by the variations in influent pollutant concentrations. In general, grassed swales may be regarded as facilities that even out the peaks in pollutant loads without being capable of producing consistent high removal rates. Low to moderate removal efficiencies could be expected for heavy metals, especially metals in solution (i.e. the dissolved phase). Pollutant load reductions in grassed swales may be considerable over an extended time period with several successive rain events. This thesis shows that there are exponential relationships between grassed swale sediment removal potential and mean hydraulic detention time. Furthermore, surface loading or specific swale area (i.e. the ratio between swale area and contributing impervious drainage area) might be used as design parameters when constructing grassed swales for pollution control.
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| 42. |
- Carlander, Carl
(författare)
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Installation effects and self diagnostics for ultrasonic flow measurement
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the district heating industry, heat meters, consisting among other things of a flow meter, are used for billing purpose. The district heating industry desires accurate and low cost flow measurements. There are mainly two reasons. An under estimation of the flow rate leads to a loss of income for the district heating industry. Further, the total cost for measuring, including the cost for the heat meter, the reading and the maintenance, represents a relatively large part of the total energy cost. Therefore a project concerning measurement quality assurance in district heating systems is in progress at Luleå University of Technology. As a part of this project the possibility of self diagnostic techniques for flow meters is investigated. It is well known that installation effects greatly impair the flow measurement involved in heat metering. Thus this thesis focus on self diagnostics of different installation effects. The basic assumption is that the flow meter noise level is correlated to turbulence intensity. Since the turbulence intensity is effected by installation effects, the noise level can be used to detect conditions for which the flow meter shows erroneous results. In district heating applications the use of ultrasonic flow meters are becoming more and more frequent. The self diagnostic approach has therefore been investigated for a small size prototype ultrasonic flow meter. Single and double elbow pipe bends and pipe diameter reductions mounted in front of the meter and pulsating flow give rise to small but reproducible errors. The magnitude of the maximum errors were in the range of 2 to 4% of flow rate. At low flow rates with pulsating flow the errors were larger. Also small commercial ultrasonic flow meters were investigated. These commercial meters are commonly used in heat meters in small district heating subscriber stations. The results demonstrate that both temperature changes and installation effects introduce errors in the flow measurements. By studying the noise level of the signal from the prototype ultrasonic flow meter it is clear that all installation effects tested caused a clear increase in the flow signal noise level. It is clear that no tested disturbance causing measurement errors, larger than 1% of the flow rate, will pass undetected. Neither will normal conditions with a varying flow rate or single measurement outliers cause false alarms. It is anticipated that this increase in the future can be detected on-line by the flow meter itself giving it a self diagnostic capability.
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| 43. |
- Carlson, Johan
(författare)
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Ultrasonic characterization of materials and multiphase flows
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with three different applications of ultrasound measurement technology. In process industries like the mining industry, the oil and gas industry, and the paper pulp industry, multiphase flows play an important role. It is of interest to measure several different parameters of these flows, such as the mass fractions and the mass fraction velocities of the different phases. There are currently no single technique available that can measure all of these properties, and commercial multiphase flow meters are in practice a combination of several flow meters that each measure different parameters. The long-term goal of the project presented in this thesis is to develop an ultrasonic technique that can measure all of these properties. The first focus of the work presented in this thesis has been to develop an ultrasonic method that can measure the mass fraction of particles in a solid/liquid multiphase flow. The technique is based on a sensor array that measures an entire cross section of the flow. The use of an array makes it possible to measure the particle distribution. This can then be used to detect static installation effects, thus enabling the use of single point sensor. The sensor array used is clamped on to the outside of the flow pipe which means the technique is completely non-invasive. The second focus is on imaging of opaque flows. While traditional optical techniques such as LDV, etc. does not work for opaque media, there is no such restriction on the ultrasonic method. The imaging technique, called ultrasonic speckle correlation velocimetry (USV) has been applied to image vortices in flows, and to measure particle velocity profiles in multiphase flows. The third and last contribution is in the field of non-destructive evaluation (NDE) of materials. In a biomaterial engineering project, the goal has been to develop an injectable bone cement that can be used to repair or replace fractured bone. During the setting reaction, the cement undergoes a series of phase changes, which have implications on how the cement can be used. The research is motivated by the lack of satisfying standards to measure the setting time. The existing methods are based on mechanical testing and visual examination, which makes them time-consuming and subjective. The ultrasonic technique presented in this thesis provides a non-destructive and objective way to determine both the setting time and some mechanical properties of the cement, during the entire setting process. The thesis consists of an introductory part and a collection of seven papers.
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| 44. |
- Carlsson, Erik
(författare)
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Sulphide-rich tailings remediated by soil cover : evaluation of cover efficiency and tailings geochemistry, Kristineberg, northern Sweden
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The efficiency of soil cover as a method of remediation of sulphide-rich tailings has been studied at an impoundment at the Kristineberg mine, Northern Sweden. Two variations of soil cover were used in the remediation. The major part of the impoundment was covered with a 1.0 m layer of till where the groundwater table was shallow. In combination with the removal of the water dividing ditches surrounding the impoundment, saturation of the tailings as well as the till cover was achieved. In areas with a deeper groundwater it was not possible to saturate the tailings by means of this method. Instead, a sealing layer consisting of a 0.3 m compacted clayey till, acting as an oxygen diffusion barrier, situated underneath a 1.5 m protective cover was used. Field studies at the impoundment cover pore-water extraction and solid-sample collection at five locations. Solid tailings were subject to sequential extractions in the laboratory. Open groundwater pipes for measuring groundwater levels as well as BAT® groundwater pipes for geochemical sampling of the groundwater were installed over the entire impoundment. At a location in the area with the sealing layer, tension lysimeters were installed in a profile in the vadose zone down to the unoxidised tailings. Nearby, one oxygen diffusion lysimeter and one water infiltration lysimeter were installed below 1.5, 1.0, and 0.3 m of protective till cover, respectively. The sealing layer has been investigated in the laboratory with respect to its susceptibility to the effects of freezing and thawing. The solid samples from the tailings revealed that in some areas, the sulphide oxidation prior to the remediation had been intense. In other areas, with a shallower pre-remediation groundwater table, the oxidation seemed to have ceased upon reaching it. In the area with water- saturated tailings increased pore water concentrations around and below the oxidation zone were visible, due to release of secondarily retained elements. Elements with peaks at this level were As, Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn. However, compared with pre-remediation data the concentrations are generally lowered, indicating that sulphide oxidation has slowed down. Sequential extraction of the solid tailings samples showed that a large part of the elements below the oxidation front, in the secondary enrichment layer, are relatively mobile and are released within the adsorbed, or the amorphous iron (oxy)hydroxide fractions. This was the case for elements such as Fe, As, Ba, Cd, Co, Cr, Cu, Ni, and Zn. The continuous measurements performed in the groundwater pipes show that elements released by raising the groundwater table are transported out of the impoundment, and that the overall water quality is constantly improving due to the inflow of uncontaminated groundwater from the adjacent hill slope. A model for the water transport has been developed and prediction of the future behaviour of the impoundment is proposed. The tension lysimeter measurements show that infiltrating water and diffusing oxygen cause remobilisation of metals around the oxidation front. However, most of these metals are retained again prior to reaching the groundwater table. The mass flow caused by this mobilisation is very small compared to that of the laterally flowing groundwater. Mobilised elements are Fe, S, Si, Al, Cd, Co, Hg, Mg, Mn, Mo, Ni, Pb, and Zn. The freeze/thaw laboratory experiments stress that the compaction degree is very important for achieving a hydraulic conductivity low enough for the requirements of a sealing layer. If a high enough compaction degree is obtained, the corresponding hydraulic conductivity is very low, approximately 5x10-10 m/s with the clayey till used at the study site. The freeze/thaw experiments also revealed that when properly compacted the clayey till is sensitive to frost penetration, leading to an increase of hydraulic conductivity, up to ~10-8 m/s. Oxygen diffusion measurements indicate that the effective diffusion through the sealing layer is low for all three different protective till-cover thicknesses, and so is the water infiltration. However, during the field measurements, no frost penetration into the sealing layer was monitored.
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| 45. |
- Carolin, Anders
(författare)
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Carbon fibre reinforced polymers for strengthening of structural elements
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is a large need for strengthening of concrete structures all around the world. There can be many reasons for strengthening, increased loads, design and construction faults, change of structural system, and so on. The need exists for both strengthening in flexure as well as in shear. Plate bonding with Carbon Fibre Reinforced Polymers, CFRPs has shown to be a competitive method for upgrading existing structures load bearing capacity. When applying composites for increased shear capacity, special concerns need to be taken for design with truss model. A limitation factor of approximately 0.6 must be used due to linear elastic behaviour. When limitation on maximum strain in concrete is applies, the allowable strain in the composite will be even lower due to anisotropy and divergence in fibre and principal strain direction. By bonding CFRP to a structure in sawn grooves some advantages compared to traditional plate bonding may be achieved. It is also found that a structure may be strengthened with live loads during strengthening process. CFRP plate bonding may further be used for strengthening for increased buckling load bearing capacity for steel members subjected to compression and a design proposal is presented. Suggestions for further research are identified and presented.
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| 46. |
- Cervantes, Michel
(författare)
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Effects of boundary conditions and unsteadiness on draft tube flow
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present research focuses on flow properties of the elbow draft tube. This element has a major function in low head turbines, since up to half of the losses may arise there at part load. The use of computational fluid dynamic (CFD) to redisign a draft tube necessitates detailed knowledged of the boundary conditions. They are generally not available and qualified guesses must be made. This applies in particular to the radial velocity at the inlet. A method to estimate this component in swirling flow from experimental values of the axial and tangential velocities is derived. The method uses a two dimensional non- viscous description of the flow, the Squire-Long formulation. It is tested against swirling flow in a diffuser and applied to the Turbine-99 draft tube flow. As several other boundary conditions are difficult to estimate and many input parameters are available to perform a simulation, the use of factorial design is proposed as an alternative to design simulations in a systematic, objective and quantitative way. The method allows the deternmination of the main and joint effects of input parameters on the numerical simulation. The input parameters may be experimental uncertainty on boundary conditions, unknown boundary conditions, grid and turbulence models. The method is applied to the Turbine-99 test case, where the radial velocity, the surface roughness, the turbulence length scale and the grid were the factors investigated. The inlet radial velocity is found to have a major effect on the pressure recovery. The flow in water turbines is highly unsteady due to the runner blade rotation, guide vanes and stay vanes. Unsteady pressure measurements on a Kaplan prototype point out unsteadiness in the high and low pressure regions of the turbine. Since model and prototype are not running in dynamically similar conditions, the influence of unsteadiness on the losses is of interest. The derivation of the variation of the mechanical energy for the mean, oscillating and turbulent fields point out the contribution of unsteadiness to the losses and the turbulent production. Application to turbulent channel flow reveals that the contribution is a function of the amplitude of the oscillation, the frequency and the friction velocity. Turbulent pulsating flow in a generic model of the rectangular diffuser found at the end of elbow draft tube is studied in detail with laser Doppler anemometry (LDA). Three frequencies, corresponding to the quasi-steady, relaxation and quasi-laminar regimes with an amplitude of about 10% are investigated. The results indicate no alteration of the mean flow by the excitation of a single frequency. Furthermore. the existence of the different regimes, as found in turbulent pulsating turbulent pipe and channel flows, is confirmed.
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| 47. |
- Chandler, John
(författare)
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Positioning our selves : work and the social (re)construction of the self in late modernity
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis returns to the individual that some postmodernists would leave behind, but not in the manner of individualising psychology. The individual in this thesis is a social individual, the self a social self. Self-hood is, as Mead (1934) and many others have recognised, a social creation, and the social self is imbued with agency in the act of positioning itself amongst others. But the individual is also positioned – within a social context or field of experience, within discursive practices, within social structures, within social institutions. Yet all is fluid – the self, the structures, the discourses, the institutions - and all are mutually conditioning. This thesis, then, makes a contribution to examining how individuals position themselves within particular sets of institutional and structural contexts, how they construct and re-construct themselves thereby and how they begin to construct and re-construct social identities, structures, institutions and discourses. It concentrates largely on ‘stress’ and ‘managerialism’, as aspects of emerging self-hoods, and reveals complexity and fluidity. Thus ‘stress’ is shown to position us as victims but it can also be used as a reason for resistance. The experience of ‘stress’ would seem to differ according to the institutional context in which we are positioned but it also constitutes a resource and a motive in the micropolitics of resistance to existing structures, institutions and discursive practices. Similarly managerialism may serve to position us as managers or as managerial subjects but individuals can embrace different kinds of managerialism, or resist managerialism altogether, and this has consequences for the nature of the organisations we inhabit and for the sort of people we, as individuals at work, become. Yet the examination of individuals, selves, institutions, discursive practices and social structure in this thesis is itself just one moment in a social process. This thesis is a self-reflexive act of positioning by a social individual who seeks to turn as well as return. A step in a dance - and by no means the last step - for this social individual.
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| 48. |
- Chiorescu, Sorin
(författare)
-
The forestry-wood chain : simulation technique, measurement accuracy, traceability concept
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A customer-oriented production philosophy, an integrated forestry-wood chain and the global vision of Precision Forestry are concepts that researchers and people involved in the forest and wood industry have to deal with in the beginning of this new millennium. Fulfilling the specific requirements for dimension, length, biological features and proof-of-origin that customers demand for the wood products entails the existence of advanced methods and tools for understanding and thus controlling the production process along the forestry-wood value chain. The two overall objectives of this thesis were a) to study the prerequisites of using the simulation technique together with advanced simulation tools in understanding the role of the measurement accuracy at different locations within the forestry-wood production chain and b) to study the prerequisites of developing a marking/reading free traceability system for sawlogs based on log measurement data as generated today at the sawmill site.
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| 49. |
- de Raadt, Veronica D.
(författare)
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A normative application of multi-modal systems thinking to a non-viable social system
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This research evaluates how multi-modal systems thinking, a normative approach to systems science, answers to the theoretical, practical and ethical demands emerging from research in sustainability and to systems scientists concerned with the norms of life and ethics. The thesis starts with a broad survey of sustainability literature and concludes that this multi-modal systems methodology, which has emerged during the last decade, has a significant contribution to make. This systems approach was applied to Rosvik, a small village in northern Sweden, which is undergoing instability and threats to its longterm viability. In particular, the multi-modal systems method and the software package, SmCube, especially developed to apply this method, proved useful tools. They pointed to issues and identified threats to the village that corresponded closely to those identified in the sustainability literature.
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| 50. |
- Drugge, Christina
(författare)
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Omsorgsinriktat lärande : en studie om lärande i hemtjänsten
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Studien är utförd i två norrlandskommuner i 6 olika hemtjänstgrupper. Syftet med studien har varit studera lärandets förutsättningar och villkor i hemtjänsten. Metoden som använts är en etnografisk fallstudie. Vad jag försökt visa i denna studie är att kunksap är en social process som förutsätter dialg, reflektion, småprat och berättande. De arbetslag som hade dialogiska ledare, en god sammanhållning och en inbyggd flexibilitet var också de arbetsgrupper som intog ett lärande förhållningssätt. Hemtjänstorganisationen domineras av en institutionalierad informalitet , en frizon som skapas av personalen själva. Genom den institutionaliserade informaliteten skapas möjligheter för ett lärande förhållningssätt där flexibilitet, fantasi och omdömesförmåga kan utvecklas.
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