| 1. |
- Lundberg, Mattias, 1985-
(författare)
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Residual stresses, fatigue and deformation in cast iron
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The complex geometry of cylinder heads in heavy-duty diesel engines makes grey iron or compact graphite iron a preferred material choice due to its price, castability, thermal conductivity and damping capacity. Today’s strict emission laws have increased the demands on engine performance and engine efficiency. This means that material properties such as fatigue resistance need to be improved. Shot peening is often used to improve the fatigue resistance of components and the benefits of shot peening are associated with the induced compressive surface stresses and surface hardening. How different shot peening parameters can affect fatigue strength of grey and compact graphite iron has been investigated within the project underlying this thesis. To do this, X-ray diffraction (XRD) was utilized for residual stress measurements, scanning electron microscopy (SEM) for microstructural characterizations and mechanical fatigue testing for mechanical quantifications. The ultimate aim of this work has been to increase the fatigue resistance of cast iron by residual stress optimization.XRD measurements and SEM examinations revealed that the shot peening parameters shot size and peening intensity significantly influence residual stresses and surface deformation. Residual stress profiles, similar to the one general considered to improve the fatigue strength in steels, were obtained for both grey and compact graphite iron. Uniaxial push-pull fatigue testing on grey iron with these shot peening parameters reduced the fatigue strength with 15–20 %. The negative effect is likely related to surface damage associated with over peening and relatively high subsurface tensile residual stresses. With very gentle shot peening parameters, the uniaxial fatigue strength were unaltered from the base material but when subjected to bending fatigue an increase in fatigue strength were observed. An alternative way to increase the fatigue strength was to conduct a 30 min annealing heat treatment at 285 XC which increased the fatigue strength by almost 10 % in uniaxial loading. The improvement could be an effect of favourable precipitates forming during the annealing, which could hinder dislocation movement during fatigue.Measuring residual stresses using XRD and the sin2 -method demands accurate X-ray elastic constants (XEC) for meticulous stress analysis. The XEC referred to as 1~2s2 should therefore always be calibrated for the specific material used. The experiments conducted revealed that the XEC value is independent of the testing method used in this work. A small correction from the theoretical value should be applied when the material contains small amounts of residual stresses. The amount of residual stresses has a great impact on the XEC and thus on the stress analysis. Concluding that proper analysis of residual stresses in cast iron is not straight forward.
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| 2. |
- Calmunger, Mattias, 1986-
(författare)
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On High-Temperature Behaviours of Heat Resistant Austenitic Alloys
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Advanced heat resistant materials are important to achieve the transition to long term sustainable power generation. The global increase in energy consumption and the global warming from greenhouse gas emissions create the need for more sustainable power generation processes. Biomass-fired power plants with higher efficiency could generate more power but also reduce the emission of greenhouse gases, e.g. CO2. Biomass offers no net contribution of CO2 to the atmosphere. To obtain greater efficiency of power plants, one option is to increase the temperature and the pressure in the boiler section of the power plant. This requires improved material properties, such as higher yield strength, creep strength and high-temperature corrosion resistance, as well as structural integrity and safety.Today, some austenitic stainless steels are design to withstand temperatures up to 650 °C in tough environments. Nickel-based alloys are designed to withstand even higher temperatures. Austenitic stainless steels are more cost effective than nickel-based alloys due to a lower amount of expensive alloying elements. However, the performance of austenitic stainless steels at the elevated temperatures of future operation conditions in biomass-red power plants is not yet fully understood.This thesis presents research on the influence of long term high-temperature ageing on mechanical properties, the influence of very slow deformation rates at high-temperature on deformation, damage and fracture, and the influence of high-temperature environment and cyclic operation conditions on the material behaviour. Mechanical and thermal testing have been performed followed by subsequent studies of the microstructure, using scanning electron microscopy, to investigate the material behaviours.Results shows that long term ageing at high temperatures leads to the precipitation of intermetallic phases. These intermetallic phases are brittle at room temperature and become detrimental for the impact toughness of some of the austenitic stainless steels. During slow strain rate tensile deformation at elevated temperature time dependent deformation and recovery mechanisms are pronounced. The creep-fatigue interaction behaviour of an austenitic stainless steel show that dwell time gives shorter life at a lower strain range, but has none or small effect on the life at a higher strain range.Finally, this research results in an increased knowledge of the structural, mechanical and chemical behaviour as well as a deeper understanding of the deformation, damage and fracture mechanisms that occur in heat resistant austenitic alloys at high-temperature environments. It is believed that in the long term, this can contribute to material development achieving the transition to more sustainable power generation in biomass-red power plants.
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| 3. |
- Carlsson, Petra, 1974-
(författare)
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Theology beyond Representation : Foucault, Deleuze and the Phantasms of Theological Thinking
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Theology beyond Representation explores the theological opportunities embedded in Michel Foucault’s and Gilles Deleuze’s critique of Christian thinking and of what they regard as a Christian and oppressive logic of representation. Foucault’s and Deleuze’s thoughts on representation are currently discussed in many fields neighbouring theology (e.g. by feminist Karen Barad, Literary theorist Claire Colebrook), but despite the fact that Foucault and Deleuze address some of the most frequently debated issues in contemporary theology, their thoughts on representation have not yet been fully examined in theology.This study offers such an exploration by searching out what new perspectives, forces and notions are brought to light when the critique of representation and the post-representational perspectives in Foucault and Deleuze are allowed to work within theology. It enacts encounters, for example, with the theological contributions of British Radical Orthodox theologian Graham Ward and North American radical theologian Thomas Altizer.The book finally suggests that contemporary theology should perhaps not leave its metaphysics behind but understand its task differently. From a post-representational perspective, the Christian God and inherited Christian dogma may be considered actual, affecting our world in reality – our account of meaning as well as our bodies, actions and politics – yet they are actual and real because they are repeated as such and used as such. The Christian truths are, in short, regarded as phantasms. In consequence, a “post-representational theology” would note the force of form, dogma, truths, authorities, eternal gestures and church buildings, but it would not believe in their final power. It would believe in representation, in its effects and its force, but it would also believe in the possibility of moving beyond its expressions, while also believing that expression already moves beyond representation.Such a perspective, the book argues, could open up a playful yet serious form of post-Christian resistance: To repeat, parody and play with whatever comes to the fore as eternal, or as the truth of concrete experience – both when reading and when doing theology – in order to make room negatively for those realities, actual but unknown, unthinkable yet possible, that no language could ever capture.
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| 4. |
- Haraldsson, Mattias, 1972-
(författare)
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Essays on Transport Economics
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Essay 1: The wear and tear of an extra vehicle that uses a road results in advancementof future repavements. This increases the present value cost of these repavements, which is interpreted as the marginal cost. Using a large data set covering all pavement renewals on the Swedish national road network since the 1950s, deterioration elasticities that express the relation between traffic intensity and the pavement lifetime are estimated and are then used to compute marginal costs. The elasticities for heavy goods vehicles and passenger cars are found to be small and marginal costs are accordingly low. Essay 2: Using observational data covering the whole Swedish national road network for the period 1998-2002, this essay estimates a set of maintenance and operation cost functions.It is found that costs for all operation and maintenance measures increase with traffic intensity, with two exceptions; total operation and winter operation measures are fixed cost activities. All other operation and maintenance measures have short run elasticities in the range 0.25-0.60. The impact of an additional vehicle is generally manifested in extra maintenance and operation costs, not only while the vehicle is using the road, but later on as well. Point estimates of long run cost elasticities are higher than one in general. Essay 3: This essay estimates the long run effects of distance work on various aspects of the activity-travel pattern. Estimations are made using econometric matching on a data material from the Swedish travel survey, RES, a travel diary collected in the period 1999-2001. The activity-travel pattern of men seems to be irresponsive to distance work, while some aspects of the activity-travel pattern of women change due to distance work. For instance, it is found that distance-working women adopt a more “local” lifestyle where purchases and child care are moved closer to home.
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| 5. |
- Holmström, Benny, 1974-
(författare)
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Early diagnosis and treatment of prostate cancer : observational studies in the National Prostate Cancer Register of Sweden and the Västerbotten Intervention Project
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Prostate-specific antigen (PSA) testing has caused a steep increase in the incidence of prostate cancer, especially the incidence of localised low risk disease. In order to decrease the overdiagnosis accompanied by PSA testing, analysis of inherited genetic variants have been suggested as potential tools for clinical assessment of disease risk. With the aim of minimizing overtreatment and postpone side-effects of curative treatment for low risk prostate cancer, active surveillance, a treatment strategy with initial surveillance and deferred radical prostatectomy at the time of progression has evolved. The aim of this thesis was to study the validity of PSA (paper I) and inherited genetic variants (paper II) for early diagnosis of prostate cancer, to assess the extent of PSA testing in Sweden (paper III), and to study the safety of deferred radical prostatectomy in localised low to intermediate risk prostate cancer (paper IV). The study designs were i) case-control studies nested within the Västerbotten intervention project (paper I and II), ii) observational study in the Cancer Register of Sweden (paper III), and iii) observational study in the NPCR Follow-up study (paper IV). PSA had a high validity in predicting a prostate cancer diagnosis with an area under the receiver operating characteristics (ROC) curve of 0.86 (95% CI, 0.84 to 0.88). A combined test, including PSA, the ratio of free to total PSA, and 33 single nucleotide polymorphisms (SNPs) in a genetic risk score, increased the area under curve to 0.87 (95% CI, 0.85 to 0.89). The estimated uptake of PSA testing among men aged 55 to 69 years increased from zero to 56% between 1997 and 2007 and there were large variations in the uptake of PSA testing between counties in Sweden. After a median follow-up time of eight years there was no significant difference in presence of any one or more adverse pathology features or prostate cancer specific mortality after primary compared to deferred radical prostatectomy in localised low to intermediate risk prostate cancer. Results from these studies indicate that PSA and the hitherto identified SNPs are not suitable biomarkers in single-test prostate cancer screening. It is possible to estimate the uptake of PSA testing on a population level. Initial surveillance and deferred radical prostatectomy represent a feasible treatment strategy in localised low to intermediate risk prostate cancer.
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| 6. |
- Höglund, Linda, 1974-
(författare)
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Growth and characterisation of InGaAs-based quantum dots-in-a-well infrared photodetectors
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents results from the development of quantum dot (QD) based infrared photodetectors (IPs). The studies include epitaxial growth of QDs, investigations of the structural, optical and electronic properties of QD-based material as well as characterisation of the resulting components.Metal-organic vapour phase epitaxy is used for growth of self-assembled indium arsenide (InAs) QDs on gallium arsenide (GaAs) substrates. Through characterisation by atomic force microscopy, the correlation between size distribution and density of quantum dots and different growth parameters, such as temperature, InAs deposition time and V/III-ratio (ratio between group V and group III species) is achieved. The V/III-ratio is identified as the most important parameter in finding the right growth conditions for QDs. A route towards optimisation of the dot size distribution through successive variations of the growth parameters is presented.The QD layers are inserted in In0.15Ga0.85As/GaAs quantum wells (QWs), forming so-called dots-in-a-well (DWELL) structures. These structures are used to fabricate IPs, primarily for detection in the long wavelength infrared region (LWIR, 8-14 μm).The electron energy level schemes of the DWELL structures are revealed by a combination of different experimental techniques. From Fourier transform photoluminescence (FTPL) and FTPL excitation (FTPLE) measurements the energy level schemes of the DWELL structures are deduced. Additional information on the energy level schemes is obtained from tunneling capacitance measurements and the polarization dependence studies of the interband transitions. From tunneling capacitance measurements, the QD electron energy level separation is confirmed to be 40-50 meV and from the polarization dependence measurements, the heavy hole character of the upper hole states are revealed.Further characterisation of the IPs, by interband and intersubband photocurrent measurements as well as dark current measurements, is performed. By comparing the deduced energy level scheme of the DWELL structure and the results of the intersubband photocurrent measurements, the origin of the photocurrent is determined. The main intersubband transition contributing to the photocurrent is identified as the QD ground state to a QW excited state transition. Optical pumping is employed to gain information on the origin of an additional photocurrent peak observed only at temperatures below 60 K. By pumping resonantly with transitions associated with certain quantum dot energy levels, this photocurrent peak is identified as an intersubband transition emanating from the quantum dot excited state. Furthermore, the detector response is increased by a factor of 10, when using simultaneous optical pumping into the quantum dots states, due to the increasing electron population created by the pumping. In this way, the potentially achievable responsivity of the detector is predicted to be 250 mA/W.Significant variations of photocurrent and dark currents are observed, when bias and temperature are used as variable parameters. The strong bias and temperature dependence of the photocurrent is attributed to the escape route from the final state in the QW, which is limited by tunneling through the triangular barrier. Also the significant bias and temperature dependence of the dark current could be explained in terms of the strong variation of the escape probability from different energy states in the DWELL structure, as revealed by interband photocurrent measurements. These results are important for the future optimisation of the DWELL IP.Tuning of the detection wavelength within the LWIR region is achieved by means of a varying bias across the DWELL structure. By positioning the InAs quantum dot layer asymmetrically in a 8 nm wide In0.15Ga0.85As/GaAs quantum well, a step-wise shift in the detection wavelength from 8.4 to 10.3 μm could be achieved by varying the magnitude and polarity of the applied bias. These tuning properties could be essential for applications such as odulators and dual-colour infrared detection.
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| 7. |
- Jiangdong, Bao
(författare)
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Application of Statistical Methods on Occupational Health and Safety Management in the Mining Industry in Ezhou City, China
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chinaʹs mining enterprises are confronted with insufficient safety investments, insufficientsafety benefits, recurrent occupational diseases and accidents, low level of safety riskmanagement, and many employee complaints, that seriously affect the economicdevelopment and the sustainable development of the country. Selection of scientific, accurateand comprehensive evaluation methods of all aspects of occupational health and safetymanagement will directly affect the evaluation results and then the direction of improvement;which is greatly needed.The aim of this thesis is twofold: one aim is to test and analyze a set of evaluationmethods that provide different perspectives on how occupational health and safetymanagement really works in the mining industry in Ezhou City, China. The other aim is toexplore a set of comprehensive evaluation methods that are suitable for occupational healthand safety management in the industries as a whole.This thesis is based on the theory of Multi Objective Decision Making and Grey System,and is broken down into three phases including: The first phase of my study: to describe the applications of the methods in five aspects ofoccupational health and safety in the mining industry in Ezhou City, China. This isshown in five articles and Chapter 1‐5. The second phase: to present some suggestions of improvements for the development ofthe occupational health and safety in the mining industry in Ezhou City, China. This ispresented in Chapter 6 in my study. The third phase: to explore a set of comprehensive evaluation methods that are suitablefor the occupational health and safety management in the industries. This is also shownin Chapter 6 in my study.In this thesis I mainly used six methods to evaluate occupational health and safetymanagement and the suitability of them for this type of research as well as in other types inindustrial activity. The six methods included in my research are: entropy weight(EW), failuremode and effect analysis (FMEA), improved analytic hierarchy process (AHP), dataenvelopment analysis (DEA), grey relational analysis (GRA) and 2‐tuple linguisticinformation (2‐TLI). The results of the analysis showed that: EW can be well used to evaluate the multi indicators of occupational health and safetymanagement, and can be extended to other areas such as safety management evaluation,the quality of the project, project forecasting and other industrial activities; FMEA has been proved practical, simple and less costly in the perspective of riskmanagement, occupational health and safety management, identification and control ofenvironmental factors in enterprises, and quality key point preventive control in allindustrial activities; Improved AHP is practical, simple and less costly for multi objective and multi criteriadecision making problems in all industrial activities; DEA is special for production efficiency and can well estimate the effective productionfrontier by calculating the history data of the financial department, and embodies itsunique advantages in dealing with multi indicator inputs and multi indicator outputs inall industrial activities; GRA does not require too much sample size and any typical distribution regulation; thecalculated amount of data is relatively small, and the results would always be in goodagreement with the qualitative analysis, so it is quite suitable for measuring the degree ofassociation between factors for indicator evaluation according to their similarity ordissimilarity. GRA can cope with the types of problem associated with comparisonbetween evaluation objects and the comparison object in all industrial activities; 2‐TLI is special for language information and can provide the basis for multi‐attributedecision analysis in spite of large amounts of calculation in all industrial activities.On the whole, each method has its advantages and disadvantages, and the key to judgingwhether a method is most suitable is if it can withstand the validation of practice. Anyhow,the main contribution of this research is that it has systematically tested and verified a set ofstatistical methods applied in a mining industry in Ezhou, China, and explored a set ofstatistical methods utilized in occupational health and safety management in industrialactivities. Additionally, another contribution of this research is that it has provided a directionfor improvement of sustainable development.
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| 8. |
- Johansson, Elisabeth
(författare)
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Understanding Solution Quality
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The integration of services and products into solutions can open up new business opportunities for firms. This thesis concerns how firms can provide solutions that are perceived as high quality. Solutions are often provided over several years, which implies a changed customer relationship compared to product provisions. Since the solution aims to support the customer’s activities, firms face new challenges when introducing solutions. One challenge is to integrate all components and activities of the solution, and simultaneously support the customer’s activities. In addition, the firm must ensure that the solution and all of its parts are of high quality.Most of the existing research on quality is related to the management of a firm’s internal activities and the interaction during exchange. Within the research on quality, customer orientation means that a firm should manage the relevant product or service to meet customer requirements. When this is achieved, the product or service is of high quality. Since solutions are seen as services and products that are integrated as an outcome, as well as a customer relational process that aims to support the customer’s activities, firms have little to learn from previous research about the quality of solutions.The aim of this thesis is to increase knowledge about how to manage solution quality. The thesis combines insights from research on quality with research on solutions and servitization. Three research questions are answered. The first question concerns the content of solution quality; the second deals with how firms can, with support from interventions, meet the new challenges that arise from solution provision; and the third question concerns how customers can be involved to achieve solution quality. The research questions are answered through five papers based on literature studies and empirical data. The papers contribute to an increased knowledge of solution quality and how firms can work to achieve it.The results of the thesis suggest that solution quality is built on seven quality dimensions: reliability, communicability, internal consistency, empathy, approachability, tangibility, and adaptability. In addition, knowledge of processes and customer relationships are two prerequisites for the concept. These dimensions and prerequisites are supported by interventions that can provide a change. However, it has become evident that whatever intervention is used must be related to the dimensions that are supposed to be improved. Furthermore, customer involvement is argued to be an intervention to support the prerequisites for solution quality, especially during the solution development. The results of this thesis extend the research on quality by increasing the knowledge of the solution quality concept and by changing the view of customers and their involvement during solution development.
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| 9. |
- Johansson, Mattias Erik, 1980
(författare)
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Application of Passive DOAS for Studies of Megacity Air Pollution and Volcanic Gas Emissions
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Optical Remote Sensing Techniques offer the opportunity to, in real-time, obtain line averaged measurements of gases in the lower and upper atmosphere. These techniques easily offer themselves to automatization, which increases their usability for e.g. risk-assessment of remotely situated volcanoes and routine monitoring of air pollution levels in urban areas.This thesis deals with the application of two instruments based on passive Differential Optical Absorption Spectroscopy (DOAS) for studying air pollution in Megacities, applied to México City and Beijing, and for monitoring of emissions of volcanic gases. The mobile mini-DOAS instrument is designed for emission measurements from a mobile platform whereas the other instrument used, the scanning mini-DOAS instrument is designed to perform automatic measurements from a fixed point.Measurements have been performed to estimate the production of SO2 and NO2 in the city of Beijing. The first measurement of HCHO using mobile mini-DOAS has been performed in Mexico City. The measured outflow of NO2 and HCHO has been compared with the results of a chemical model showing good agreement flux but a disagreement in the spatial distributions. A technique has been developed to determine the speed and altitude of a gas plume using a modified standard instrument. The possibility to reconstruct the distribution of SO2 inside a gas plume by combination of data from two or more scanning instruments has been demonstrated. An algorithm for calculating the flux of a gas plume from measurements using the novel conical scanning mini-DOAS instrument has been developed and a partial error sensitivity of the instrument has been performed and compared to the flat scanning mini-DOAS instrument. Several algorithms have been developed with the purpose of making emission measurements using the scanning mini-DOAS instrument fully automatic. The newly developed routines have been implemented in software, the NovacProgram. This software is currently used for routine monitoring of volcanic gas emission on 17 volcanoes around the world.
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| 10. |
- Johansson, Mattias
(författare)
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Information Management for Manufacturing System Development
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the development of products the actual product design isnot an isolated occurrence solely providing the definitionalinformation needed to realise information into physicalproducts. There is also a need to develop and design themanufacturing process and manufacturing system that is to beused in the transformation of information into a physicalproduct. Integration of the design processes of products,processes and manufacturing systems has become important toeffectively transform knowledge into physical products. Thisdevelopment process is under a constant pressure to deliverhigher quality information in a shorter time than before. Thedrive for perfection has also forced industry to focus on thisspecific area of expertise and cooperate with partners in orderto have a complete coverage of all aspects in the productdevelopment.The last decade has shown a significant increased use ofcomputer applications within industry for an exact andefficient information creation. The use of computerapplications however, has not been as successful as intended.One major reason for this is due to problems in informationmanagement and communication issues were sharing of informationbetween computer applications has been a major obstacle.The research presented in this thesis focuses on the use ofstandardised information models as a base for an informationsystem supporting integrated design of products, processes andmanufacturing systems. The use of standardised informationmodels is key to communication and sharing of information amongcomputer applications. The development of these informationmodels has until now had a product design focus and theinformation concerned with the design of manufacturing systemshas not yet been addressed.In this thesis the design information of manufacturingsystems have been studied and used for the definition of aninformation model enabling communication of information amongcomputer applications used for manufacturing system design. Thedefinition of the information model has had a holistic approachwhere the integrated information management for design anddevelopment of products, processes and manufacturing systemshave been considered.This thesis has studied the ISO10303, STEP, standard anddefines the use of ISO10303-214 for the design information ofmanufacturing systems. This definition allows for therepresentation of integrated product, process and manufacturingsystem information through the use of one information model.This research has proposed changes to the ISO10303-214 standardin order to represent the integrated information from early todetailed design and had these changes accepted.
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