| 1. |
- Jansson, Johan
(författare)
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Multiscale Constitutive Modeling of Heterogeneous Engineering Materials
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work deals with different methods used to determine heterogeneous constitutive model parameters for macro-scale finite element models, based on microstructural variations, caused by the manufacturing process. These methods could be applied to decrease modeling errors associated with the material behavior, improving the predictive capabilities of structural analyses in simulation-driven industrial product development. By providing engineers with more sophisticated tools and methods which lets them consider the complex relationships between the manufacturing process, the resulting microstructure and the final properties, manufactured components have the potential to be further optimized with respect to both weight and performance, reducing their cost and environmental impact.An empirical approach for cast components is presented in Papers I & II, where material testing is used as a basis for constitutive model parameter extraction via optimization. Linear models were created for both thermo-mechanical and thermo-physical material properties, by characterizing specimens extracted from different regions in a lamellar graphite cast iron cylinder head. These models were used to generate heterogeneous constitutive model parameters for the cylinder head, based on the solidification time as predicted by casting process simulations. The influence of several commonly made casting-specific engineering simplifications were investigated, and it was shown that non-trivial errors of a potentially large magnitude are introduced by not considering e.g. the compressive behavior of the material, residual stresses from the casting process, the temperature dependency of the material, or the process-induced heterogeneity.Paper III describes a statistical homogenization-based method, for modeling of anisotropic fiber reinforced materials. A non-linear anisotropic constitutive model was developed and implemented in commercial finite element codes, which is able to consider heterogeneous fiber orientations using only one material definition. The anisotropic elastic constitutive tensor is determined from fiber-matrix homogenization, and orientation averaging using second- and fourth order fiber orientation tensors provided by injection molding simulations. The plastic constitutive parameters are determined by optimization against experimental tensile tests using specimens with different fiber orientations. The method was demonstrated using a injection molded 50 wt.% short glass fiber reinforced plastic.A pixel/voxel-based method is presented in Papers IV (2D) & V (3D), for simple and efficient generation of reduced numerical microstructure models using imaging data as input. The input micrograph or image stack is split into subdomains, which are evaluated individually using numerical or semi-analytical homogenization. The constitutive tensor of each subdomain is mapped to a new, reduced numerical model. The purpose of this approach was to support component level analyses, by representing process-induced microstructural imperfections like e.g. porosity on the macro-scale, in a computationally efficient way. The geometrical description of the microstructure can be retrieved from experimental imaging methods like Scanning Electron Microscopy (SEM) or X-ray based Computed Tomography (CT). Alternatively, it can be approximated from phase field or manufacturing process simulations. The method was demonstrated by reducing a 2D aluminium micrograph by 99.89%, with material property errors of less than 0.5% in Paper IV. Also, in paper V by reducing a complex high-resolution 3D aluminum shrinkage porosity by 99.2%, with a material property error of approximately 1%. The method significantly reduces the complexity of building finite element models of complex microstructures, where the pre-processing step is replaced by image segmentation.
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| 2. |
- Brydges, Taylor
(författare)
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Made in Canada : The strategies, spaces and working lives of independent designers in the Canadian fashion system
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Drawing on 87 interviews with independent fashion designers and key informants, this thesis is a collection of papers which aim to explore the strategies, spatial dynamics and working lives of independent fashion designers in the Canadian fashion industry. The majority of fashion design firms in Canada are small independent businesses, typically run by an individual or pair of designers, with few employees. Independent fashion designers create unique small businesses, produce high quality garments defined by the label ‘made in Canada,’ strategically mobilize physical and virtual spaces within the national system, and yet, the long-term viability of these businesses is far from certain. The Canadian fashion industry is facing a number of systemic challenges relating to wider institutional and policy weaknesses that make it difficult to grow a long-term domestic or international fashion business. However, the findings also suggest that a key strength of the Canadian fashion system is that it offers a variety of spaces for designers of different sizes, scales, and motivations. Throughout this thesis lies the tension between the quest for independence and creative freedom, which often comes at the cost of highly precarious entrepreneurial and labouring conditions. This thesis contributes to our understanding of the dynamics of ‘second tier’ fashion cities and regional systems, the entrepreneurial motivations and working lives of independent fashion designers, the locational choice decisions and the mobility of patterns of creative workers in the digital age, and the evolving nature of intermediation and value creation within the fashion industry.
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| 3. |
- Nguyen, Van Dang, 1985-
(författare)
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High Performance Finite Element Methods with Application to Simulation of Vertical Axis Wind Turbines and Diffusion MRI
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Finite element methods have been developed over decades, and together with the growth of computer power, they become more and more important in dealing with large-scale simulations in science and industry.The objective of this thesis is to develop high-performance finite element methods, with two concrete applications: computational fluid dynamics (CFD) with simulation of turbulent flow past a vertical axis wind turbine (VAWT), and computational diffusion magnetic resonance imaging (CDMRI). The thesis presents contributions in the form of both new numerical methods for high-performance computing frameworks and efficient, tested software, published open source as part of the FEniCS/FEniCS-HPC platform. More specifically, we have four main contributions through the thesis work.First, we develop a DFS-ALE method which combines the Direct finite element simulation method (DFS) with the Arbitrary Lagrangian-Eulerian method (ALE) to solve the Navier-Stokes equations for a rotating turbine. This method is enhanced with dual-based a posteriori error control and automated mesh adaptation. Turbulent boundary layers are modeled by a slip boundary condition to avoid a full resolution which is impossible even with the most powerful computers available today. The method is validated against experimental data with a good agreement.Second, we propose a partition of unity finite element method to tackle interface problems. In CFD, it allows for imposing slip velocity boundary conditions on conforming internal interfaces for a fluid-structure interaction model. In CDMRI, it helps to overcome the difficulties that the standard approaches have when imposing the microscopic heterogeneity of the biological tissues and allows for efficient solutions of the Bloch-Torrey equation in heterogeneous domains. The method facilitates a straightforward implementation on the FEniCS/ FEniCS-HPC platform. The method is validated against reference solutions, and the implementation shows a strong parallel scalability.Third, we propose a finite element discretization on manifolds in order to efficiently simulate the diffusion MRI signal in domains that have a thin layer or a thin tube geometrical structure. The method helps to significantly reduce the required simulation time, computer memory, and difficulties associated with mesh generation, while maintaining the accuracy. Thus, it opens the possibility to simulate complicated structures at a low cost, for a better understanding of diffusion MRI in the brain.Finally, we propose an efficient portable simulation framework that integrates recent advanced techniques in both mathematics and computer science to enable the users to perform simulations with the Cloud computing technology. The simulation framework consists of Python, IPython and C++ solvers working either on a web browser with Google Colaboratory notebooks or on the Google Cloud Platform with MPI parallelization.
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| 4. |
- Degirmenci, Niyazi Cem, 1982-
(författare)
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Adaptive Finite Element Methods for Fluid Structure Interaction Problems with Applications to Human Phonation
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work presents a unified framework for numerical solution of Fluid Structure Interaction (FSI) and acoustics problems with focus on human phonation. The Finite Element Method is employed for numerical investigation of partial differential equations that model conservation of momentum and mass. Since the resulting system of equations is very large, an efficient open source high performance implementation is constructed and provided. In order to gain accuracy for the numerical solutions, an adaptive mesh refinement strategy is employed which reduces the computational cost in comparison to a uniform refinement. Adaptive refinement of the mesh relies on computable error indicators which appear as a combination of a computable residual and the solution of a so-called dual problem acting as weights on computed residuals. The first main achievement of this thesis is to apply this strategy to numerical simulations of a benchmark problem for FSI. This FSI model is further extended for contact handling and applied to a realistic vocal folds geometry where the glottic wave formation was captured in the numerical simulations. This is the second achievement in the presented work. The FSI model is further coupled to an acoustics model through an acoustic analogy, for vocal folds with flow induced oscillations for a domain constructed to create the vowel /i/. The comparisons of the obtained pressure signal at specified points with respect to results from literature for the same vowel is reported, which is the final main result presented.
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| 5. |
- Drott, Carl Johan, 1984-
(författare)
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Influence of Islet-derived Factors in Islet Microcirculation and Endocrine Function
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diabetes mellitus is a disorder with complex pathology and is frequently associated with vascular complications. In the islet micro milieu locally generated factors may affect both the physiology and the morphology of the tissue. This thesis examines the impact of four different islet-derived factors; thrombospondin-1 (TSP-1), ghrelin, Cocaine and amphetamine regulated transcript (CART) and irisin, and how they influence the endocrine pancreas.TSP-1 is an angiogenesis inhibitor. Islets from TSP-1 deficient mice were hypervascular, but with normal endocrine mass. Beta-cell dysfunction was present in islets of TSP-1 deficient mice, both in vivo and in vitro. When trying to reconstitute TSP-1 in islets of TSP-1 deficient animals through a transplantation model, adult islets failed to recover, showing the importance of TSP-1 for glucose stimulated insulin secretion and thereby glucose homeostasis.Ghrelin inhibited glucose stimulated insulin secretion and decreased the islet blood flow, while the ghrelin receptor antagonist GHRP-6 in fasted, but not fed, rats increased the islet blood flow fourfold and improved the peak insulin response to glucose. The ghrelin receptor GHS-R1α was identified in the alpha cells and the islet arterioles.CART selectively reduced the islet blood flow in the pancreas, and this effect was unaltered by simultaneous administration of an endothelin-A receptor antagonist. CART administration did not affect insulin release, neither in insulin release from isolated islets or in an intravenous glucose tolerance test. Irisin was confirmed located within the pancreatic islets predominately in the alpha-cells. Irisin reduced islet and white adipose tissue blood flow. Irisin was secreted as a response to increased glucose concentrations in vivo. Irisin had no direct effect on insulin secretion.In conclusion, all factors investigated proved to have roles locally in the endocrine pancreas. TSP-1 deficiency caused vascular morphological alterations, and chronic β-cell dysfunction. Ghrelin, CART and irisin all decreased islet blood flow. Ghrelin acted directly through its receptor GHS-R1α in islet arterioles, thereby restricting the insulin response to hyperglycemia, whereas for CART and irisin the specific mechanism continues to be unknown, without identification of a receptor. In order to reach full physiological understanding, the receptors for CART and irisin need to be identified. All four islet-derived factors hold potential for the treatment of type 2 diabetes.
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| 6. |
- Berg, Su-Hyun, 1983-
(författare)
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Like a wave : Understanding the film and TV industries in Korea and Sweden
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral dissertation is concerned with the complex dynamics of knowledge in the South Korean film and TV industry and Swedish filmmaking from a spatiotemporal perspective. The film and TV industries are highly dependent on knowledge and innovation. Production in the film and TV industries usually takes place in the form of projects in which creative professionals form teams for a limited time period to complete creative tasks. Moreover, the film and TV industries are facing rapid and constant changes to work practices, technology, markets and demand. Therefore, the dynamics of knowledge and interactive learning can be an important source of competitive advantages and project success in the film and TV industries. The aim of this thesis is to enhance understanding of knowledge creation and diffusion processes, relationships with institutional settings and the systematic character of business in the film and TV industries. The focus of this thesis is on the production value chain in which many independent production firms are active. It is argued that 1) the film and TV industries and their institutional environments co-evolve; and 2) project-specific knowledge sourcing takes places through local-extra local linkages.The case of the Korean film and TV industry indicates that its evolution strongly depends on the setting of the respective institutions and regulations, and on the institutional environments. In addition, it is argued that diverse actors, factors and sectors are involved in the emergence and development of the Korean film and TV industry. The Swedish filmmaking case study examines production processes and ecologies and argues that production managers are the key players in them, and their roles – investigator, bridge builder and gatekeeper – in knowledge creation and diffusion processes are central to this part of the production of film and TV. Exploring two case studies with a focus on the key (f)actors of knowledge creation and diffusion processes has resulted in the view that knowledge-based competencies can be an important source of competitive advantage and project success in high-velocity environments.
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| 7. |
- Bernisson, Maud
(författare)
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The Public Interest in the Data Society : Deconstructing the Policy Network Imaginary of the GDPR
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When Facebook censored the Pulitzer Prize-winning photograph The Napalm Girl, it provoked a global outcry. It also showed digital media’s ability to redefine freedom of expression and information. Redefining fundamental rights and freedoms involves drawing limits upon other fundamental freedoms and rights like the right to privacy. It is therefore crucial to study the changing role of the public interest, which ensures conditions for all to exercise fundamental freedoms and rights, including the right to privacy. This thesis aims at analysing definitions and uses of the public interest during the policymaking process of the General Data Protection Regulation (GDPR). The policymaking process is approached through the policy network theory (Rhodes, 2007). Policy network theory permits researchers to study norms and beliefs that drive stakeholders’ strategies to construct knowledge during the policymaking process. The construction of knowledge is influenced by a shared imaginary (Ricœur, 1984), which frames shared knowledge at the societal level. Metaphors permit tracing imaginaries. The public interest, as a metaphor defined during the policymaking process of the GDPR, enables the reconstruction of the policy network imaginary of the GDPR. I use two methods, the assessment of the degree of preference attainment (DPA) and the discourse-historical approach (DHA), which belongs to the field of critical discourse studies. Assessing DPA allows a comparison of key definitions in the texts produced during the policymaking process by different groups of actors—like Google and the European Commission—with corresponding definitions in the GDPR. The DHA permits the contextualization of definitional changes, the identification of power games within the policy network, and the reconstruction of the policy network imaginary.Results show that the policy network imaginary corresponds to a techno-economic ideology. This ideology underlies a preconceived context, the data society, and frames societal phenomena to regulate through beliefs and norms. This ideology is taking over the public interest ideology. Technological and economic determinism drove the design of the GDPR, which limits capacities to regulate and aligns with the interest of the dominant tech and economic actors. The member states favoured specific topics related to the public interest, like security, to be implemented at the EU level, at the expense of other topics, such as freedom of expression and information, to be implemented at the national level.
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| 8. |
- Jansson, Johan
(författare)
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Process-Induced Local Material Variations in Finite Element Simulations of Cast and Fibre Reinforced Injection Moulded Components
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this thesis is to provide an overview of the methods used in the appended papers, in order to consider heterogeneous material properties in finite element simulations by using process simulations as input. The work deals with both injection moulded and cast components, and focuses on process-induced local material variations and their effect on component performance.The influence of heterogeneous properties originating from the casting process as well as some other common simplifications, which are made in finite element analyses, are evaluated for a cast iron component. It is found that commonly neglected properties such as compressive strength, residual stresses, temperature dependency and heterogeneous properties have a non-trivial and potentially large influence on the simulation results.Lastly, a computational method for fibre reinforced plastics is presented. The methodology enables designers to consider the non-linear anisotropic properties of fibre-reinforced polymers, due to the flow-induced fibre orientation predicted by injection moulding simulations. The method allows material data assignment in each integration-point of the structural mesh. The method is demonstrated to capture the behaviour of the full range of fibre orientations simultaneously with good accuracy.
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| 9. |
- Jansson, Johan, 1973-, et al.
(författare)
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Perspectives on sustainability in Sweden : stuck between two paradigms?
- 2020
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Ingår i: The future of the North - sustainability in Nordic countries. - Marburg : Metropolis Verlag für Ökonomie, Gesellscahft und Politik GmbH. - 9783731613640 ; , s. 167-216
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Bokkapitel (refereegranskat)abstract
- In this chapter we take a look at some, primarily, environmental sustainability issues in Sweden. Sweden is in many aspects a rich country with high social and economic welfare and it usually comes out as a country that has handled environmental challenges well. However, from a consumption perspective, Swedish consumers are among the world leaders when it comes to metrics such as ecological footprint and carbon dioxide emissions per capita. By using two paradigmatic views, the Dominant Social Paradigm (DSP) and the New Ecological Paradigm (NEP) we analyze sustainability in Sweden with a particular focus on energy use. We look at sustainability in the three broad areas of policies, corporate activities and consumption and in these areas we delve deeper into environmental sustainability issues concerning recycling and waste, energy efficiency, circular business models, sustainable consumer behaviors in relation to cars and transport, and responsible investments. We end the chapter by discussing implications for the future and the analytical framework and by developing a middle ground which we call ambiguous wavering.
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| 10. |
- Lind, Alexander, et al.
(författare)
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Anxiety, depression and quality of life in relation to SARS-CoV-2 antibodies in individuals living with diabetes during the second wave of COVID-19
- 2024
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Ingår i: Diabetes epidemiology and management. - : Elsevier. - 2666-9706. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Aims: The objective was to compare anxiety, depression, and quality of life (QoL) in individuals living with type 1 (T1D) and type 2 (T2D) diabetes with matched controls during the second wave of the COVID-19 pandemic.Methods: Via randomization, individuals living with diabetes T1D (n = 203) and T2D (n = 413), were identified during February-July 2021 through health-care registers. Population controls (n = 282) were matched for age, gender, and residential area. Questionnaires included self-assessment of anxiety, depression, QoL, and demographics in relation to SARS-CoV-2 exposure. Blood was collected through home-capillary sampling, and SARS-CoV-2 Nucleocapsid (NCP) and Spike antibodies (SC2_S1) were determined by multiplex Antibody Detection by Agglutination-PCR (ADAP) assays.Results: Younger age and health issues were related to anxiety, depression, and QoL, with no differences between the study groups. Female gender was associated with anxiety, while obesity was associated with lower QoL. The SARS-CoV-2 NCP seroprevalence was higher in T1D (8.9 %) compared to T2D (3.9 %) and controls (4.0 %), while the SARS-CoV-2 SC2_S1 seroprevalence was higher for controls (25.5 %) compared to T1D (16.8 %) and T2D (14.0 %).Conclusions: A higher SARS-CoV-2 infection rate in T1D may be explained by younger age and higher employment rate, and the associated increased risk for viral exposure.
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