| 1. |
- Bergman, Filip, 1992-
(författare)
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Sustainability performance of multi-utility tunnels : Sustainability assessments for furthering knowledge and understanding
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The multi-utility tunnel has received increased attention as an alternative method for the installation of subsurface infrastructure for the distribution of electricity, water, sewage and district heating. In previous research, the multi-utility tunnel (MUT) has been described as a more sustainable technology compared to the conventionally used technique where the cables and pipes are placed with open-cut excavation (OCE), especially when the entire life cycle is taken into account. This thesis aims to contribute to an improved understanding of MUT's sustainability performance in relation to conventional installation using open-cut excavation. This is done by using literature study, interview study and quantitative sustainability assessments to gain an understanding of the current state of knowledge. Furthermore, this thesis also focuses on how knowledge can be deepened with the help of quantitative sustainability assessments and the challenges of conducting this type of assessment. This thesis shows that the state of knowledge regarding MUT's sustainability performance is low and scattered, with a lack of a holistic approach. Direct economic performance has gained the most attention, followed by indirect and social impact, and the environmental impact has so far barely been assessed. The sustainability performance depends to a large extent on the conditions of the specific case, and these should be considered when assessing the technology. Quantitative assessments have the potential to help deepen the knowledge of the sustainability implications of using MUT. The characteristics of MUT have some similarities with other types of physical infrastructure. Similarities are that the systems are long-lived, have project conditions that affect sustainability performance, and impact a broad spectrum of actors. One difference to typical infrastructure systems is that the owner and management structure of MUT is, by design, more complex as several types of utility systems are in use. The characteristics of MUT give some practical considerations that need to be addressed: data availability, including practitioners; detailed data; transparency; and flexibility. This thesis highlights the complexity of assessing MUT´s sustainability performance and advocates that future studies should have a learning-oriented approach so that the knowledge level can collectively and gradually improve over time rather than focusing on decision-oriented studies.
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| 2. |
- Schmuck, Stefan, 1980-
(författare)
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Bayesian Inference for Microwave Diagnostics at Joint European Torus
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The major goal of this thesis is to perform Bayesian inference jointly for electron kinetic profiles, a toroidal magnetic field correction, diagnostic sensitivities, and wall reflection properties given noisy measurements of four microwave diagnostics at the tokamak JET. Besides the measurements, this kind of inference considers prior knowledge, like profile length-scales, to update objectively the information about the physics parameters. Such a probabilistic update, i.e. a posterior probability distribution or posterior, states the plausibility of parameter combinations and captures parameter uncertainties and correlations. The already existing Bayesian framework Minerva was used to carry out the inference.Contrary to standard approaches, plasma physics and diagnostic models and physics parameters are used to make predictions which are compared objectively with the data provided by one reflectometer and three electron cyclotron emission (ECE) diagnostics; two broadband Martin-Puplett interferometers and one heterodyne radiometer. In addition, these models represent reality more closely, for instance: (i) the smoothnesses of temperature and density profiles are modelled and estimated by length-scale parameters, (ii) the models SPECE and ECEPT, predicting each broadband ECE spectra, take into account relativistic and density effects like the finite optical thickness, (iii) the working principle and measurement uncertainty of each diagnostic are considered. As an example for the latter point, the two interferometers supply convoluted ECE spectra over several harmonic ranges up to 500 GHz and in mainly ordinary and extra-ordinary wave mode polarisations. The uncertainties on these spectra originate mostly from absolute calibrations for which a dedicated, robust and reliable procedure had to be established during this thesis.Further intermediate achievements of this thesis are for example: (i) the analytical derivation of the generalised square-exponential covariance function, enabling the estimation of multiple length-scales for electron temperature and density profiles in the plasma core and edge domains, (ii) the already existing ray-tracer SPECE, which predicts accurately but slowly ECE spectra, was parallelised successfully by a client-server approach, (iii) the derivation of the model ECEPT to predict quickly and sufficiently accurately broadband ECE spectra for an Ohmically heated plasma, and (iv) the extension of the multi-reflection model to allow different properties for the high-field and low-field side walls of a fusion device, affecting substantially the predictions of ECE spectra at frequencies for which the plasma has a low optical thickness.For a low temperature and low density plasma, the joint inference of more than 200 parameters was carried out for a given flux surface geometry, using either SPECE or ECEPT as predictor for the measured ECE spectra from 50 GHz to 280 GHz (first three harmonic ranges at least) with contributions from the ordinary and extra-ordinary wave-modes. For the ECEPT case, the shape of the joint posterior could be explored numerically. Related findings are, for example, smooth electron temperature and density profiles with values at the centre of 1.5 keV and 1.75x1e19 m^-3 and at the separatrix of 80 eV and 2x1e18 m^-3 with uncertainties of the order of 10 eV and few 1e17 m^-3. Furthermore, the smoothness of each core and edge profile originates in the inferred length-scale. These results were confirmed by the most likely parameter combination of the posterior when the more accurate predictor SPECE is used. The only exceptions are the correction to the magnetic field, which increased from 1.4% to 2%, and the reflectivity of the ITER-like wall, which elevated from 0.72 to 0.92.With ECEPT in use, multiple posterior correlation features could be revealed of which many could be explained. For instance, each profile smoothness, due to the estimated length-scale, implies considerable correlationsbetween nearby locations. In addition, a global correlation feature is evidentfor edge and core density profiles, likely caused by the measurement principle of the reflectometer.The second part of this thesis focusses on Bayesian inference about spectra in the field of Fourier transform spectroscopy. An example application has been carried out for the calibration data measured with one of the Martin-Puplett interferometers at JET. Compared to standard analysis techniques, more information could be extracted about the spectra from the so-called double-, single- and zero-sided data domains. The spectra have been modelled as Brownian bridge processes a priori, by which the global trend of the data located in double- and single-sided domains is modelled. This enables the estimation of the posterior uncertainties of the spectra due to non-probed data domains, especially the zero-sided domain. Such consideration is not made in any form by conventional techniques, because no method has been developed to estimate the seemingly lost information contained in the zero-sided domain. The lower and upper limits of the spectra have been estimated by (33+/-1.7) GHz and (913+/-2.9) GHz. These limits are rated to be more likely by a factor of 1e277 than the limits at 0 GHz and 3747 GHz (Nyquist frequency) assumed by conventional analysis approaches but never checked for plausibility.
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| 3. |
- Svensson, Torbjörn, Adjunkt, 1969-
(författare)
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From games to news : Creating an engagement model for digital local news
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The transition of local news from the analog, printed format to a digital format, fit for our increasingly digitized media technology society, has not been as straight-forward as was imagined at the dawning of the World Wide Web. Newspapers, in particular local newspapers, were quite fast in trying to adapt to the new technology platform and put their content on the web. User experiences of reading news have certainly evolved since 1995, with the introduction, for example, of the smartphone and proprietary news apps. However, there has been no deep or consistent commitment to understanding more specifically how the digital format can provide a means of interactivity for users and support a range of content and means to engage it. The digital news format does enable interaction between readers and news staff, and, not least, between users in real-time. However, many features for engagement are currently under-explored. Other media, for example computer games, have developed new ways to engage their audience of players both in terms of how the media is distributed and also how the content is personally adaptive, for example, to the unique skill level of players, or by offering them freedom of action to explore content, and/or by enabling increasing communication among player groups.The main knowledge contribution of this research is a novel model for reader engagement in digital local news. The model is constructed by transferring features for user needs satisfaction and engagement in digital games to the realm of digital local news. Self Determination Theory, which establishes ways of describing user engagement in general, and when applied to computer games specifically, forms the basis of the research. Additionally detailed knowledge about user types counters a traditional ‘one to many’ broadcast logic and supports greater understanding of heterogeneity within reader groups. The model also defines the digital maturity of the different features across a spectrum, from substitution via modification to disruption (Su-Mo-Di). For example, some digital features replicate those from the analog printed version II of the newspaper (substitution), while some are impossible to implement in a paper format (disruption).The aim of the research is to outline a unique model of engagement and illustrate how to apply the varied and detailed features when applied to digital local news. This usage of game engagement transferred to digital news contexts also allows alternative ways to interpret the term gamification. Classically gamification has been defined as using game design elements in non-game contexts, where typical game features like points, leaderboards, and badges have been introduced into a significant variation of media and forms, often to increase effectiveness or output from processes. This research contests that view and suggests that gamification can be used to engage mechanisms from games on a higher or more abstract level than actual game mechanics.The method for transferring this form of game engagement to digital local news engagement is built on a process where the more detailed strategies for making computer games engaging are abstracted and re-applied to the field of digital local news. These strategies form the basis for the unique engagement model illustrated within the thesis. These engagement aspects drawn from the model are further elaborated and used to examine specific examples and two prototypes focused on digital local news. The conclusions demonstrate that a focus on engagement through many varied applications can offer a rich method to increase and to analyze user experiences and to design novel features specific to enhancing digital local news.
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