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| 2. |
- Liu, Dongming, 1987-
(author)
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Polyethylene – metal oxide particle nanocomposites for future HVDC cable insulation : From interface tailoring to designed performance
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Low-density polyethylene (LDPE) nanocomposites containing metal oxide nanoparticles are considered as promising candidates for insulating materials in future high-voltage direct-current (HVDC) cables. The significant improvement in dielectric properties compared with unfilled polymer is attributed to the large and active interface between the nanoparticles and the polymer. The nanoparticles may also initiate cavitation under stress and potential accelerated aging risks due to the adsorption and inactivation of the protecting antioxidants. This study is focused on the possibilities of achieving well-balanced performances of the polyethylene nanocomposites for HVDC insulation via tailoring the particle interface in the nanocomposites.A facile and versatile surface coating method for metal oxide particles was developed based on silane chemistry. The developed method was successfully applied to 8.5 nm Fe3O4, 25 nm ZnO and 50 nm Al2O3 particles, with the aim to develop uniform coatings that universally could be applied on individual particles rather than aggregates of particles. The surface properties of the coatings were further tailored by applying silanes with terminal alkyl groups of different lengths, including methyl (C1-), octyl (C8-) and octadecyl (C18-) units. Transmission electron microscopy, infrared spectroscopy and thermal gravimetric analysis confirmed the presence of uniform coatings on the particle surface and importantly the coatings were found to be highly porous.The capacity of metal oxide particles to adsorb relevant polar species (e.g. moisture, acetophenone, cumyl alcohol and phenolic antioxidant) was further assessed due to its potential impact on electrical conductivity and long-term stability of the nanocomposites. The oxidative stability of the nanocomposites was affected by the adsorption of phenolic antioxidants on particles and transfer of catalytic impurities (ionic species) from metal oxide particles to polymer matrix. It was found that carefully coated metal oxide particles had much less tendency to adsorb antioxidants. They could, however, adsorb moisture, acetophenone and cumyl alcohol. The coated particles did not emit any destabilizing ionic species into the polymer matrix. The inter-particle distance of the nanocomposites based on C8-coated nanoparticles showed only a small deviation from the ideal, theoretical value, indicating a good particle dispersion in the polymer. Scanning electron microscopy of strained nanocomposite samples suggested the cavitation mainly occurred at the polymer/nanoparticles interface. The microstructural changes at polymer/nanoparticle interface were studied by small-angle X-ray scattering coupled with tensile testing. The polymer/nanoparticle interface was fractal before deformation due to the existence of the bound polymers at the nanoparticle surface. Extensive de-bonding of particles and cavitation were observed when the nanocomposites were stretched beyond a critical strain. It was found that the composites based on carefully coated particles showed higher strain at cavitation than the composites based on uncoated particles. The composites based on C8-coated nanoparticles showed the largest decrease in electrical conductivity and the lowest temperature coefficient of the electrical conductivity among the composite samples studied.
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| 3. |
- Chéramy, Mikael
(author)
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Characteristics of GADA in Type 1 Diabetes following Immunomodulation with GAD65
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Type 1 diabetes (T1D) is a serious autoimmune disease which increases worldwide and affects children at a young age, but there still is no cure available. Clinical intervention trials in recent onset T1D patients are therefore very important, since even a modest preservation of β-cell function has proven to reduce end-organ complications. Glutamic acid decarboxylase 65 (GAD65) is one of the major antigens in T1D, to which autoantibodies (GADA) are formed. Immunomodulation with aluminum-formulated GAD65 (GAD-alum) has been considered both in the prevention and intervention of T1D. In a phase II trial using GADalum we showed clinical benefits in C-peptide preservation, but unfortunately a following larger European phase III trial failed to reach primary end-point. The general aim of this thesis was to study the characteristics and phenotypes of GADA following immunomodulation with GAD-alum in T1D patients during a phase II and III trial.In the phase II trial, a transient increase of the GADA IgG3 and IgG4 subclasses, and a decrease in IgG1 was detected as part of the treatment-induced GADA levels after 2 GADalum doses, a result interpreted to be T helper (Th) 2-associated. This Th2-associated immune response was also observed, in parallel to increased GADA levels, during the following phase III trial including a larger group of patients. However, enhanced Th2-like IgG subclass distribution, reflected as increased IgG4 frequency, was in contrast only observed in the group treated with 4 doses of GAD-alum. In addition, the GADA fold-change was associated with in vitro GAD65-stimulated cytokine secretion, but only in patients receiving 2 GAD-alum doses. Furthermore, a 4-year follow-up of the phase II trial showed that the effect of GAD-alum treatment was long-lasting as GADA titers remained elevated. Even though the phase III trial did not reach primary end-point, and was closed after 15 months, preservation of β-cell function was observed in the small sub-group of Swedish patients receiving 2 GAD-alum doses that completed the 30 months trial-period. During the trials, concerns were raised whether the elevated GADA titers might induce Stiff person syndrome (SPS), a disease affecting the nervous system, but in vitro analysis of GADA phenotypes showed that the GAD65-enzyme activity and GADA epitope distribution differed from that detected in SPS patients.Continued research to clarify how immunomodulation with autoantigens affects immune responses and also to identify which patients are suitable for treatment, is crucial for optimizing future T1D intervention- and prevention trials.
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| 4. |
- Moradi, Fatemeh, 1985-
(author)
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Working out work : from personal informatics to redesigning work
- 2016
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Doctoral thesis (other academic/artistic)abstract
- "Personal Informatics" (PI) and "Quantified Self" (QS) are two contemporary notions in the field of Human–Computer Interaction. Such hardware and software systems gather personalized quantified data and visualize them for the purpose of supporting self-reflection. Many of these systems focus on breaking the habit of prolonged sitting and increasing physical activity in our daily lives. The problems associated with the sedentary lifestyle and prolonged hours of sitting have been noted in many studies. In fact, stationary behavior is a risk factor for cardiovascular disease, diabetes and certain types of type of cancer. Nowadays we, as adults, spend more than 8 hours a day on work and work-related activities. As a consequence, the time spent sitting in office workspaces contributes to the majority of stationary behavior in our daily lives. Throughout history, designers and technocrats have constantly redesigned workspaces in attempts to increase work productivity and efficiency. Thus "modern" office work configuration includes desks and stationary computers and so office workers have become accustomed to prolonged sitting in their workplaces. In relation to this research problem, I have worked on my PhD thesis within the context of a four-year cross disciplinary research project in which we have been exploring ways of increasing physical activity and breaking the habit of prolonged sitting among office workers. This is a thesis in informatics and closely allied to medicine and it focuses on studying how contemporary office work affects the body and how to redesign this context. For this thesis, I conducted three empirical studies and designed and developed two prototypes - the "NEAT Lamp" and the "Talking Tree". The "Sport Co." study was the first quantitative study, and was followed by two qualitative observational ethnographic studies – the "Housing Co." study and the "Health Co." study. The research process adopted during the work can be described as an intertwined process consisting of three methodological approaches: observational ethnographic studies, concept development and prototyping. These three came together to form a coherent contextual design process for tackling the research question, "How can we approach the design of work in today's offices in order to make office workers more physically active in their workspaces?" This process resulted in five papers presenting various aspects and results of the research conducted. The results cover the role of bodies at work by considering the history of work design, knowledge about the local movement and mobility patterns of office workers in modern office spaces and eventually the design and evaluation of the two prototypes introduced in this thesis. Finally, I conclude this thesis by highlighting my overall contributions. The first contribution targets designers willing to design for increasing physical activity and breaking the habit of prolonged sitting in workspaces. In relation to this I introduce a design space as a tool for understanding the design of work in relation to worker’s bodies. The second contribution highlights how observational ethnographic studies, concept development, and prototyping can be combined when exploring the context of physical activity in office environments and it shows how contextual design might be a suitable approach for such studies. In addition, it emphasizes ways for how we can redesign work and expand our contextual knowledge. This, by examining and evaluating interactive prototypes in real office settings.
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| 5. |
- Nilsson, Maria, 1984-
(author)
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Tribology in Metal Working
- 2012
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Licentiate thesis (other academic/artistic)abstract
- This thesis focuses on the tribological performance of tool surfaces in two steel working operations, namely wire drawing and hot rolling. In all forming operations dimensions and surface finish of the products are of utmost importance. Forming basically includes three parts – forming conditions excluded – that may be changed; work material, tool and (possibly) lubricant. In the interface between work material and tool, the conditions are very aggressive with – generally or locally – high temperatures and pressures. The surfaces will be worn in various ways and this will change the conditions in the process. Consequently, the surface finish as well as the dimensions of the formed product may change and in the end, the product will not fulfil the requirements of the customer. Therefore, research and development in regard to wear, and consequently tribology, of the forming tools is of great interest.The investigations of wire drawing dies focus on coating adhesion/cohesion, surface characteristics and material transfer onto the coated steel both in laboratory scale as well as in the wire drawing process. Results show that it in wire drawing is possible to enhance the tribological performance of drawing dies by using a lubricant together with a steel substrate coated by a polished, dual-layer coating containing both hard and friction-lowering layers.The investigations of hot rolling work rolls focus on microstructure and hardness as well as cracking- and surface characteristics in both laboratory scale and in the hot strip mill. Results show that an ideal hot work roll material should be made up of a matrix with high hardness and a large amount of complex, hard carbides evenly distributed in the microstructure. The surface failure mechanisms of work rolls are very complex involving plastic deformation, abrasive wear, adhesive wear, mechanical and thermal induced cracking, material transfer and oxidation.This knowledge may be used to develop new tools with higher wear resistance giving better performance, lower costs and lower environmental impact.
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| 6. |
- Olsson, Mikael, 1966-
(author)
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Ownership reform and corporate governance : The Slovak privatisation process in 1990-1996
- 1999
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Doctoral thesis (other academic/artistic)abstract
- Since 1989, there has been a period of rapid change of the economies of the former Eastern bloc. Within a few years, the majority of the formerly centrally administered economies had begun restructuring their economic systems, including the privatisation. of formerly state-owned enterprises. This process developed differently in different countries, depending among other things on their historical traditions and the momentum of their social, political and economic transformations. This doctoral dissertation examines the privatisation of large-scale industrial enterprises in Slovakia prior to 1997. In particular the thesis analyses the changing political and institutional framework governing the process and method of privatisation; and how the governance of firms was affected by the new markets and ownership- and control-structures that were established. Special attention is paid to the role played by investment funds andinvestment-companies established as a consequence of voucher privatisation. The research problem is approached both from an aggregate national level and from the enterprise level. The thesis includes a number of case studies of enterprises in Slovakia that underwent privatisation, and of investment funds that emerged to take part in the process. In addition, two panel-data sets were constructed for the sake of statistical analysis. The study points to the drastic changes in privatisation policy and its enactment, under different governments. It leads to the conclusion that privatisation is a highly political process, whose economic effects cannot be separated from its distributional effects. This politicised nature of ownership reform is shown to have some negative side-effects with regard to the development of well-functioning governance structures. It is, for example, pointed to that the capital market, as it developed during the period of study, was highly non-transparent,characterised by high transaction costs and insider-trading. The study also documents an increasingly concentrated ownership structure of the Slovak industry and relates it to the changes in privatisation policy. In the final analysis attention is drawn to a recurring theme in the study, namely the issues related to the relative stability and durability of the institutional set-up. In many cases an insecurity about "the rules of the game" led to short-term incentives and opportunism on behalf of the economic and political agents.
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| 7. |
- Pallon, Love, 1984-
(author)
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Polyethylene/metal oxide nanocomposites for electrical insulation in future HVDC-cables : probing properties from nano to macro
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Nanocomposites of polyethylene and metal oxide nanoparticles have shown to be a feasible approachto the next generation of insulation in high voltage direct current cables. In order to reach an operationvoltage of 1 MV new insulation materials with reduced conductivity and increased breakdown strengthas compared to modern low-density polyethylene (LDPE) is needed.In this work polyethylene MgO nanocomposites for electrical insulation has been produced andcharacterized both from an electrical and material perspective. The MgO nanoparticles weresynthesized into polycrystalline nanoparticles with a large specific surface area (167 m2 g–1). Meltprocessing by extrusion resulted in evenly dispersed MgO nanoparticles in LDPE for the silane surfacemodified MgO as compared to the unmodified MgO. All systems showed a reduction in conductivityby up to two orders of magnitude at low loading levels (1–3 wt.%), but where the surface modifiedsystems were able to retain reduced conductivity even at loading levels of 9 wt.%. A maximuminteraction radius to influence the conductivity of the MgO nanoparticles was theoretically determinedto ca. 800 nm. The interaction radius was in turn experimentally observed around Al2O3 nanoparticlesembedded in LDPE using Intermodulation electrostatic force microscopy. By applying a voltage on theAFM-tip charge injection and extraction around the Al2O3 nanoparticles was observed, visualizing theexistence of additional localized energy states on, and around, the nanoparticles. Ptychography wasused to reveal nanometre features in 3D of electrical trees formed under DC-conditions. Thevisualization showed that the electrical tree grows by pre-step voids in front of the propagatingchannels, facilitating further growth, much in analogy to mechanical crack propagation (Griffithconcept). An electromechanical effect was attributed as possible mechanism for the formation of the voids.
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| 8. |
- Sveen, Susanne
(author)
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Wear of coated and uncoated PCBN cutting tool used in turning and milling
- 2014
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Licentiate thesis (other academic/artistic)abstract
- This licentiate thesis has the main focus on evaluation of the wear of coated and uncoated polycrystalline cubic boron nitride cutting tool used in cutting operations against hardened steel. And to exam the surface finish and integrity of the work material used. Harder work material, higher cutting speed and cost reductions result in the development of harder and more wear resistance cutting tools. Although PCBN cutting tools have been used in over 30 years, little work have been done on PVD coated PCBN cutting tools. Therefore hard turning and hard milling experiments with PVD coated and uncoated cutting tools have been performed and evaluated. The coatings used in the present study are TiSiN and TiAlN. The wear scar and surface integrity have been examined with help of several different characterization techniques, for example scanning electron microscopy and Auger electron spectroscopy. The results showed that the PCBN cutting tools used displayed crater wear, flank wear and edge micro chipping. While the influence of the coating on the crater and flank wear was very small and the coating showed a high tendency to spalling. Scratch testing of coated PCBN showed that, the TiAlN coating resulted in major adhesive fractures. This displays the importance of understanding the effect of different types of lapping/grinding processes in the pre-treatment of hard and super hard substrate materials and the amount and type of damage that they can create. For the cutting tools used in turning, patches of a adhered layer, mainly consisting of FexOy were shown at both the crater and flank. And for the cutting tools used in milling a tribofilm consisting of SixOy covered the crater. A combination of tribochemical reactions, adhesive wear and mild abrasive wear is believed to control the flank and crater wear of the PCBN cutting tools. On a microscopic scale the difference phases of the PCBN cutting tool used in turning showed different wear characteristics. The machined surface of the work material showed a smooth surface with a Ra-value in the range of 100-200 nm for the turned surface and 100-150 nm for the milled surface. With increasing crater and flank wear in combination with edge chipping the machined surface becomes rougher and showed a higher Ra-value. For the cutting tools used in milling the tendency to micro edge chipping was significant higher when milling the tools steels showing a higher hard phase content and a lower heat conductivity resulting in higher mechanical and thermal stresses at the cutting edge.
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| 9. |
- W. Lindvall, Fredrik, 1980-
(author)
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Adhesive wear testing and modelling of tool steels sliding against sheet metals
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Sheet metal forming is a manufacturing method used because of its versatility. Sheets are plastically deformed by a tool to create a product. A tool is expected to last for several 100,000 forming operations and efforts are made to optimize the tools. A common type of wear referred to as galling is the adhesion of sheet material to the tools. This problem has become more prevalent as new high strength sheet materials have been developed at the same time as lubricants have become heavily regulated. This has forced the development of new tool steels with improved resistance to galling. There are many parameters influencing the response to galling. In this work the influence of surface preparation, contact geometry, material selection and lubrication has been investigated. The surface of the forming tools has a large influence on the tools effective life. To refurbish a forming tool is expensive and often requires special shops and hand polishing. The influence on galling of different surface preparations suited for sheet metal forming was investigated using a strip-reduction equipment. The contact conditions of a tool sliding against metal sheets were investigated using FE models. The contact conditions were calculated for a U-bending test and for a sliding-on-flat-surface wear tester. The results were compared to those found in literature. One model incorporated the surface roughness of a sheet as measured by optical profilometry. The strength of the interface between the tool and the sheet material determine if material can be transferred onto the tool. The interface between the tool and adhered sheet material was closely studied using transmission electron microscopy of thin lamellas produced by focused ion beam milling. This showed sheet material adhering to the tool without the formation of an interlayer. Finally, several different combinations of tool steels and sheet materials were tested with regards to their ability to withstand galling.
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| 10. |
- Wu, Qiong, 1987-
(author)
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Biofoams and Biocomposites based on Wheat Gluten Proteins
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Novel uses of wheat gluten (WG) proteins, obtained e.g. as a coproduct from bio-ethanol production, are presented in this thesis. A flame-retardant foam was prepared via in-situ polymerization of hydrolyzed tetraethyl orthosilicate (TEOS) in a denatured WG matrix (Paper I). The TEOS formed a well-dispersed silica phase in the walls of the foam. With silica contents ≥ 6.7 wt%, the foams showed excellent fire resistance. An aspect of the bio-based foams was their high sensitivity to fungi and bacterial growth. This was addressed in Paper II using a natural antimicrobial agent Lanasol. In the same paper, a swelling of 32 times its initial weight in water was observed for the pristine WG foam and both capillary effects and cell wall absorption contributed to the high uptake. In Paper III, conductive and flexible foams were obtained using carbon-based nanofillers and plasticizer. It was found that the electrical resistance of the carbon nanotubes and carbon black filled foams were strain-independent, which makes them suitable for applications in electromagnetic shielding (EMI) and electrostatic discharge protection (ESD). Paper IV describes a ‘water-welding’ method where larger pieces of WG foams were made by wetting the sides of the smaller cubes before being assembled together. The flexural strength of welded foams was ca. 7 times higher than that of the same size WG foam prepared in one piece. The technique provides a strategy for using freeze-dried WG foams in applications where larger foams are required.Despite the versatile functionalities of the WG-based materials, the mechanical properties are often limited due to the brittleness of the dry solid WG. WG/flax composites were developed for improved mechanical properties of WG (Paper V). The results revealed that WG, reinforced with 19 wt% flax fibres, had a strength that was ca. 8 times higher than that of the pure WG matrix. Furthermore, the crack-resistance was also significantly improved in the presence of the flax.
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