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- Lü, Bo, 1986-
(författare)
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Nano- and mesoscale morphology evolution of metal films on weakly-interacting surfaces
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thin films are structures consisting of one or several nanoscale atomic layers of material that are used to either functionalize a surface or constitute components in more complex devices. Many properties of a film are closely related to its microstructure, which allows films to be tailored to meet specific technological requirements. Atom-by-atom film growth from the vapor phase involves a multitude of atomic processes that may not be easily studied experimentally in real-time because they occur in small length- (≤ Å) and timescales (≤ ns). Therefore, different types of computer simulation methods have been developed in order to test theoretical models of thin film growth and unravel what experiments cannot show. In order to compare simulated and experimental results, the simulations must be able to model events on experimental time-scales, i.e. on the order of microseconds to seconds. This is achievable with the kinetic Monte Carlo (kMC) method.In this work, the initial growth stages of metal deposition on weakly-interacting substrates is studied using both kMC simulations as well as experiments whereby growth was monitored using in situ probes. Such film/substrate material combinations are widely encountered in technological applications including low-emissivity window coatings to parts of microelectronics components. In the first part of this work, a kMC algorithm was developed to model the growth processes of island nucleation, growth and coalescence when these are functions of deposition parameters such as the vapor deposition rate and substrate temperature. The dynamic interplay between these growth processes was studied in terms of the scaling behavior of the film thickness at the elongation transition, for both continuous and pulsed deposition fluxes, and revealed in both cases two distinct growth regimes in which coalescence is either active or frozen out during deposition. These growth regimes were subsequently confirmed in growth experiments of Ag on SiO2, again for both pulsed and continuous deposition, by measuring the percolation thickness as well as the continuous film formation thickness. However, quantitative agreement with regards to scaling exponents in the two growth regimes was not found between simulations and experiments, and this prompted the development of a method to determine the elongation transition thickness experimentally. Using this method, the elongation transition of Ag on SiO2 was measured, with scaling exponents found in much better agreement with the simulation results. Further, these measurement data also allowed the calculation of surface properties such as the terrace diffusion barrier of Ag on SiO2 and the average island coalescence rate.In the second part of this thesis, pioneering work is done to develop a fully atomistic, on-lattice model which describes the growth of Ag on weakly-interacting substrates. Simulations performed using this model revealed several key atomic-scale processes occurring at the film/substrate interface and on islands which govern island shape evolution, thereby contributing to a better understanding of how 3D island growth occurs at the atomic scale for a wide class of materials. The latter provides insights into the directed growth of metal nanostructures with controlled shapes on weakly-interacting substrates, including twodimensional crystals for use in catalytic and nano-electronic applications.
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| 2. |
- Borghei, Benny Behbood, 1980-
(författare)
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Incumbent Actors in Sectoral Transformations Towards Sustainability : A sociotechnical study of the European heavy commercial vehicles sector
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Industrial sectors need to be transformed in response to the increasing demands for environmental sustainability as one of the greatest challenges in the modern times. In social science research, extensive efforts have been made over the recent decades to formulate comprehensive theories about transformation of various sectors such as energy, manufacturing, agriculture, food and transportation. Accordingly, ‘sustainability transitions’ have emerged as a research field dedicated to the study of far-reaching sociotechnical transformations.Understanding sectoral transformations and how different actors can get involved in sustainability transitions are in the heart of these efforts. Of particular importance is the involvement of industry incumbents that hold established positions and considerable amounts of knowledge, resources, and technological competence built upon vigorous structures of the existing industrial setup. This in turn calls for more attention to the role of incumbents to actively participate in the transformation of established sectors towards sustainability.However, despite the potentials to get involved in processes of transformative change, incumbents are often neglected in transition theories, and their role is predetermined to resist the change. Incumbents are widely black-boxed as a homogenous group of actors to the extent that they are conceived as a single entity whose predefined role is to act as the guardians of the existing structures and defenders of the status-quo. While there are legitimate concerns about the power of incumbent firms, such one-sided views do not offer an inclusive approach in formulating multi-actor processes for sustainability transitions. Therefore, the purpose of this thesis is to contribute to a more comprehensive theorization on the role of incumbent actors in sectoral transformations. The main research question is formulated as follows: how can incumbents act to facilitate sectoral transformations towards environmental sustainability?In answering this research question, the thesis offers an alternative perspective to the dominant view about incumbents in sustainability transition theories. It challenges prevailing assumptions by providing empirical evidence from the heavy commercial vehicles sector in Europe. The research findings show that incumbents are able to adopt various technological strategies ranging from incremental innovations with highly coordinated actions for reducing emission levels based on the established technologies, to the adoption of radical technological choices for introducing alternative propulsion technologies in the market. In fact, the strong position of incumbents can sometimes enable them to introduce radical innovations in established markets. The research findings also indicate that incumbents can act as learning agents or knowledge repositories to overcome the problem of isolation for new technological innovations by transferring knowledge and technologies over the boundaries of time and space. Moreover, incumbents can facilitate diffusion of radical innovations and ramp up the adoption of new technologies through standardization at the industry level. In addition, incumbents from a range of different sectors have been recognized as integrators for the development of new technological solutions that span over traditional boundaries. Hence, new industrial sectors can emerge through the integration of knowledge and technologies from various established sectors, and incumbents are at the heart of the integration processes due to their knowledge and familiarity of the established sectors.Finally, the theoretical implications from the thesis invite transition scholars to reconsider the role of incumbent actors in sustainability transitions, while the practical implications suggest that policy-makers need to pay more attention to the diversity of technology strategies of incumbent firms and their alignments for sectoral transformations towards sustainability.
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| 3. |
- Hol, Jeroen D., 1981-
(författare)
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Sensor Fusion and Calibration of Inertial Sensors, Vision, Ultra-Wideband and GPS
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The usage of inertial sensors has traditionally been confined primarily to the aviation and marine industry due to their associated cost and bulkiness. During the last decade, however, inertial sensors have undergone a rather dramatic reduction in both size and cost with the introduction of MEMS technology. As a result of this trend, inertial sensors have become commonplace for many applications and can even be found in many consumer products, for instance smart phones, cameras and game consoles. Due to the drift inherent in inertial technology, inertial sensors are typically used in combination with aiding sensors to stabilize andimprove the estimates. The need for aiding sensors becomes even more apparent due to the reduced accuracy of MEMS inertial sensors.This thesis discusses two problems related to using inertial sensors in combination with aiding sensors. The first is the problem of sensor fusion: how to combine the information obtained from the different sensors and obtain a good estimate of position and orientation. The second problem, a prerequisite for sensor fusion, is that of calibration: the sensors themselves have to be calibrated and provide measurement in known units. Furthermore, whenever multiple sensors are combined additional calibration issues arise, since the measurements are seldom acquired in the same physical location and expressed in a common coordinate frame. Sensor fusion and calibration are discussed for the combination of inertial sensors with cameras, UWB or GPS.Two setups for estimating position and orientation in real-time are presented in this thesis. The first uses inertial sensors in combination with a camera; the second combines inertial sensors with UWB. Tightly coupled sensor fusion algorithms and experiments with performance evaluation are provided. Furthermore, this thesis contains ideas on using an optimization based sensor fusion method for a multi-segment inertial tracking system used for human motion capture as well as a sensor fusion method for combining inertial sensors with a dual GPS receiver.The above sensor fusion applications give rise to a number of calibration problems. Novel and easy-to-use calibration algorithms have been developed and tested to determine the following parameters: the magnetic field distortion when an IMU containing magnetometers is mounted close to a ferro-magnetic object, the relative position and orientation of a rigidly connected camera and IMU, as well as the clock parameters and receiver positions of an indoor UWB positioning system.
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| 4. |
- Ingo, Elisabeth, 1987-
(författare)
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Climbing up the hearing rehabilitation ladder
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hearing impairment is a major public health problem, affecting communication and participation, and is associated with a range of health problems. Most individuals with perceived hearing impairment do not seek help, do not opt for rehabilitation (hearing aids), and do not use prescribed hearing aids adequately. Reducing the impact of hearing impairment and supporting healthy aging are important public health goals. Motivation, access to hearing health care, and poor societal awareness about hearing impairment, consequences, and rehabilitation options influence help-seeking. Offering online hearing screening has been proposed to improve hearing help-seeking, access to hearing health care, and to increase public knowledge about hearing and hearing impairment. Applying theories from health psychology (i.e. the Stages of change model) could help audiologists and other hearing health care professionals understand the psychological barriers that prevent people with hearing problems to seek help and take up rehabilitation. The overarching aim of this thesis was to investigate behaviors related to hearing rehabilitation (help-seeking, hearing aid uptake, and hearing aid use) in adults who fail an online hearing screening. A second aim was to explore the usefulness of the Stages of change model in predicting hearing rehabilitation related behavior in a self-selected online hearing screening sample. Studies I–IV show tentative support for offering online hearing screening and for supplementary interventions for increasing help-seeking and provide tentative support for Stages of change as a useful classification tool to indicate individual needs for further information and guidance. Future studies should contemplate integrating screening for multiple health-related factors associated with hearing impairment and to provide a clear and tailored pathway for each participant (e.g. referral to adequate health care or equivalent online intervention).
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| 5. |
- Mukwaya, Anthony
(författare)
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Regulation of inflammation and angiogenesis in the cornea
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inflammation and angiogenesis, the growth of new blood vessels from pre-existing ones, are involved in tumor growth, ocular diseases and wound healing. In ocular angiogenesis, new pathological vessels grow into a specific eye tissue, leak fluid, and disrupt vision. The development of safe and effective therapies for ocular angiogenesis is of great importance for preventing blindness, given that current treatments have limited efficacy or are associated with undesirable side effects. The search for alternative treatment targets requires a deeper understanding of inflammation and how it can lead to angiogenesis in the eye in pathologic situations. This thesis provides new insights into the regulation of inflammation and angiogenesis, particularly at the gene expression and phenotypic levels, in different situations characterized by angiogenesis of the cornea, often called corneal neovascularization. For instance, specific genes and pathways are either endogenously activated or suppressed during active inflammation, wound healing, and during resolution of inflammation and angiogenesis, serving as potential targets to modulate the inflammatory and angiogenic response. In addition, as part of the healing response to restore corneal transparency, inflammation and angiogenesis subside with time in the cornea. In this context, LXR/RXR signaling was found to be activated in a time-dependent manner, to potentially regulate resolution of inflammation and angiogenesis. During regression of new angiogenic capillaries, ghost vessels and empty basement membrane sleeves are formed, which can persist in the cornea for a long time. Here, ghost vessels were found to facilitate subsequent revascularization of the cornea, while empty basement membrane sleeves did not revascularize. The revascularization response observed here was characterised by vasodilation, increased inflammatory cell infiltration and by sprouting at the front of the reperfused vessels. Importantly, reactive oxygen species and nitrous oxide signaling among other pro-inflammatory pathways were activated, and at the same time anti-inflammatory LXR/RXR signaling was inhibited. The interplay between activation and inhibition of these pathways highlights potential mechanisms that regulate corneal revascularization. When treating corneal neovascularization clinically, corticosteroids are in widespread use due to their effectiveness. To minimize the many undesirable side effects associated with corticosteroid use, however, identifying new and more selective agents is of great importance. Here, it was observed that corticosteroids not only suppressed pro-inflammatory chemokines and cytokines, but also activated the classical complement pathway. Classical complement may represent a candidate for further selective therapeutic manipulation to investigate its effect on treatment of corneal neovascularization.In summary, this thesis identifies genes, pathways, and phenotypic responses involved in sprouting and remodeling of corneal capillaries, highlights novel pathways and factors that may regulate inflammation and angiogenesis in the cornea, and provides insights into regulation of capillary regression and reactivation. Further investigation of these regulatory mechanisms may offer alternative and effective treatment targets for the treatment of corneal inflammation and angiogenesis.
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