| 1. |
- 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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| 2. |
- 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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| 3. |
- Nilsson, Elin, 1984-
(författare)
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Where to shop? : understanding consumers' choices of grocery stores
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For the last couple of decades consumer decision-making has been of increasing interest for retail as well as for consumer behaviour research. Food shopping constitutes a unique type of shopping behaviour. In comparison to other types of shopping, food is essential to life, and not often are there as many choices to be made in a short period of time as when shopping groceries.The purpose of this dissertation was to advance the knowledge of what influences consumers’ choices of grocery stores. More specifically, the main focus has been on how different situations (e.g., type of shopping) influence choices of grocery stores. Five papers, which build on three surveys on how consumers choose grocery stores in Sweden, are included in this dissertation.In the first paper a comprehensive set of ten aggregated attributes that determine store choices were developed. The second paper brought forward five consumer segments (Planning Suburbans, Social Shoppers, Pedestrians, City Dwellers, and Flexibles) based on where and how they shop. In the third paper it was shown that accessibility attributes (e.g., accessibility by car, availability) and attractiveness attributes (e.g., price, service) have different impacts on satisfaction, depending on consumer characteristics and shopping behaviour in supermarkets compared to convenience stores. In the fourth paper the result showed that satisfaction is affected by type of grocery shopping (major versus fill-in shopping) in conjunction with time pressure and which store attributes that are important for satisfaction. It was also shown that the effect of time pressure and type of shopping on satisfaction varied in different consumer segments. In the final paper it was shown that a store has to be more attractive in terms of attributes for a consumer to switch from the grocery store they usually patronage, even if the new store is situated right beside or closer than the consumer’s regular grocery store. The view of a “good location” is further developed in this dissertation, arguing that consumers’ mental distance to a store – their cognitive proximity – is much more important than the physical place of the store.In sum, this dissertation revealed that the situation is more important than previous research has shown. Depending on the situation, consumers will face different outcomes (different stores) and value different store attributes. Hence, stores need to manage different store attributes depending on which consumer groups the stores want to attract and what situation the consumers are facing. Therefore, consumers’ choices of grocery stores are situation-based choices.
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| 4. |
- Spühler, Jeannette Hiromi, 1981-
(författare)
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Patient-Specific Finite Element Modeling of the Blood Flow in the Left Ventricle of a Human Heart
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heart disease is the leading cause of death in the world. Therefore, numerous studies are undertaken to identify indicators which can be applied to discover cardiac dysfunctions at an early age. Among others, the fluid dynamics of the blood flow (hemodymanics) is considered to contain relevant information related to abnormal performance of the heart.This thesis presents a robust framework for numerical simulation of the fluid dynamics of the blood flow in the left ventricle of a human heart and the fluid-structure interaction of the blood and the aortic leaflets.We first describe a patient-specific model for simulating the intraventricular blood flow. The motion of the endocardial wall is extracted from data acquired with medical imaging and we use the incompressible Navier-Stokes equations to model the hemodynamics within the chamber. We set boundary conditions to model the opening and closing of the mitral and aortic valves respectively, and we apply a stabilized Arbitrary Lagrangian-Eulerian (ALE) space-time finite element method to simulate the blood flow. Even though it is difficult to collect in-vivo data for validation, the available data and results from other simulation models indicate that our approach possesses the potential and capability to provide relevant information about the intraventricular blood flow.To further demonstrate the robustness and clinical feasibility of our model, a semi-automatic pathway from 4D cardiac ultrasound imaging to patient-specific simulation of the blood flow in the left ventricle is developed. The outcome is promising and further simulations and analysis of large data sets are planned.In order to enhance our solver by introducing additional features, the fluid solver is extended by embedding different geometrical prototypes of both a native and a mechanical aortic valve in the outflow area of the left ventricle.Both, the contact as well as the fluid-structure interaction, are modeled as a unified continuum problem using conservation laws for mass and momentum. To use this ansatz for simulating the valvular dynamics is unique and has the expedient properties that the whole problem can be described with partial different equations and the same numerical methods for discretization are applicable.All algorithms are implemented in the high performance computing branch of Unicorn, which is part of the open source software framework FEniCS-HPC. The strong advantage of implementing the solvers in an open source software is the accessibility and reproducibility of the results which enhance the prospects of developing a method with clinical relevance.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Fredén Jansson, Karl-Johan, 1988
(författare)
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The Balanced Electromagnetic Separation Transducer for Bone Conduction Audiometry and Hearing Rehabilitation
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hearing via air conduction (AC) and bone conduction (BC) are attributed to bethe natural ways of conducting sound to the cochlea. With AC hearing, air pressurevariations are transmitted to the cochlea via the ear canal, whereas with BChearing, sound vibrations are transmitted through the skull bone to the cochlea.Patients with a hearing loss in the cochlea or auditory nerve are commonly rehabilitatedwith conventional AC hearing aids in the ear canal, but also using cochlearimplants. If the pathway for AC sound to reach the cochlea is obstructed, patientscan often benet from bone conduction devices (BCDs). In order to determinethe type and degree of hearing loss, the BC hearing thresholds are measured usinga bone conduction vibrator, and then analyzed together with the AC hearingthresholds for the diagnosis and to suggest an appropriate rehabilitation alternative.The motor unit in conventional BCDs and bone vibrators are known togenerate high amount of distortion at low frequencies where the Balanced ElectromagneticSeparation Transducer (BEST) principle may oer a new era in BChearing rehabilitation and audiometry.This thesis combines two BC hearing related topics, where the rst topic is anevaluation of a new audiometric bone vibrator, Radioear B81, which is assumedto oer more accurate BC hearing threshold measurements. The second topic isrelated to a new type of active transcutaneous BCD, called the Bone ConductionImplant (BCI), which leaves the skin intact by using a wireless solution thatdoes not require a permanent skin penetration. Even though the applications aredierent, both devices use the BEST principle as motor unit in their design.The audiometric bone vibrator Radioear B81 was found to have an improvedperformance at low frequencies where it can produce higher output levels with lessharmonic distortion than the conventional Radioear B71. In a clinical study of therst six patients, the BCI was found as ecient as already commercially availableBCDs, and with the advantage of not needing a skin penetration. In a technicalevaluation of the BCI, it was shown to be a mechanically robust design and totolerate magnetic resonance imaging at 1.5 Tesla.
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| 8. |
- Hinchcliffe Voglio, Gabriela, 1981-
(författare)
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Jaget, laget, Dotterbolaget : En studie av feministiskt nätverkande och rummets betydelse
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This research explores how entrepreneurship interacts with feministic political commitments and praxis. It shows that this interaction is intimately shaped by its spatial setting, in this case Möllevången in the city of Malmö, Sweden. For a long time, the independent comics industry in Sweden has had men in leading positions and the medium has had masculinist connotations. My thesis shows that for women and transgender persons working in such a male-dominated industry, networking and collaborating are crucial for succeeding and staying in business. The particular network studied here is Dotterbolaget, a women and transgender separatist comic’s network based in Malmö.Dotterbolaget practices a feministic approach. The thesis analyses firstly its work practices and secondly the motives animating their adoption. Avoiding competition and promoting collaboration are important factors. So too is finding a means of motivation other than monetary, such as having fun and creating a professional environment for one another. The analysis also considers the spatial setting of the network, showing the deep significance of physical place. Finally, the non-hierarchal form of the network is considered. What does it mean to work as a comic’s artist without hierarchies in an individualised society? What tensions and strengths does such an organisational form give rise to?
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| 9. |
- Jansson, Daniel, 1986-
(författare)
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Identification Techniques for Mathematical Modeling of the Human Smooth Pursuit System
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis proposes nonlinear system identification techniques for the mathematical modeling of the human smooth pursuit system (SPS) with application to motor symptom quantification in Parkinson's disease (PD). The SPS refers to the complex neuromuscular system in humans that governs the smooth pursuit eye movements (SPEM). Insight into the SPS and its operation is of importance in a wide and steadily expanding array of application areas and research fields. The ultimate purpose of the work in this thesis is to attain a deeper understanding and quantification of the SPS dynamics and thus facilitate the continued development of novel commercial products and medical devices. The main contribution of this thesis is in the derivation and evaluation of several techniques for SPS characterization. While attempts to mathematically model the SPS have been made in the literature before, several key aspects of the problem have been previously overlooked.This work is the first one to devise dynamical models intended for extended-time experiments and also to consider systematic visual stimuli design in the context of SPS modeling. The result is a handful of parametric mathematical models outperforming current State-of-the-Art models in terms of prediction accuracy for rich input signals. As a complement to the parametric dynamical models, a non-parametric technique involving the construction of individual statistical models pertaining to specific gaze trajectories is suggested. Both the parametric and non-parametric models are demonstrated to successfully distinguish between individuals or groups of individuals based on eye movements.Furthermore, a novel approach to Wiener system identification using Volterra series is proposed and analyzed. It is exploited to confirm that the SPS in healthy individuals is indeed nonlinear, but that the nonlinearity of the system is significantly stronger in PD subjects. The nonlinearity in healthy individuals appears to be well-modeled by a static output function, whereas the nonlinear behavior introduced to the SPS by PD is dynamical.
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| 10. |
- Rezvani, Zeinab, 1981-
(författare)
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Drivers to and barriers against sustainable consumption : exploring the role of consumer anticipated emotions in the context of consumer adoption of alternative fuel vehicles
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the increasing environmental problems, sustainable consumption is an important consumer behavior. Therefore, it is important to investigate further the significant drivers to and barriers against sustainable consumption, in order to increase the share of sustainable consumption and understanding of consumer behavior. This dissertation identifies two gaps. The first is in understanding consumer positive and negative anticipated emotions as an important factor influencing high-involvement sustainable consumption. The second gap relates to the lack of understanding about the associations between anticipated emotions and personal moral norms in high-involvement sustainable consumption. Against this background, the aim is to contribute to the sustainable consumption literature by investigating the roles and relations of anticipated emotions, personal moral norms, and weighing costs and benefits as drivers to and barriers against consumer adoption of a high-involvement sustainable product. A literature review and two empirical studies were conducted. Consumer adoption of alternative fuel vehicles is the specific sustainable consumption. Using quantitative methods, this phenomenon is investigated in the empirical studies conducted in Sweden. It was shown that anticipated emotions have direct effects on consumers' intention to adopt alternative fuel vehicles. Moreover, positive anticipated emotions (e.g. pride, pleasure, happiness) are drivers of sustainable consumption, while negative anticipated emotions (e.g. regret, embarrassment) are barriers against the sustainable consumption. This dissertation suggests an extension to the norm activation model, and shows that moral norms, ascription of responsibility, and awareness of environmental problems influence consumers' intentions through consumers’ anticipated emotions. For people who perceive high social norms related to decreasing the environmental impacts of car driving, the influence of positive anticipated emotions and personal moral norms are stronger. This points toward the social aspect of sustainable consumption and suggests that targeting the consumers who perceive high social norms is an important step to promoting sustainable consumption. Findings would be of relevance to marketers, policymakers and environmental organizations. Creating awareness and communicating personal responsibilities and moral norms related to the environment and consumption are important drivers for consumer adoption of sustainable products. However, it is noteworthy that consumer anticipated emotions about high-involvement sustainable products (such as alternative fuel vehicle) have also important influence on the sustainable consumption. Thus, consumer anticipated emotions should be considered in designing promotion programs.
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