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Senast inlagda

Lessons from Using Indicators to Evaluate a Municipal Climate Action Plan: A Case Study of the City of Gothenburg
(2025) Kieksi, Carl; Svensson, Johan
This thesis aimed to investigate the monitoring and evaluation processes of the City of Gothenburg’s ECP, with a particular focus on indicators. Monitoring and evaluation are processes that often fall short, with common challenges being the selection of appropriate indicators or a lack of structures to support their use. The employed methodologies included a literature review, interviews with employees at the Environmental Administration and a thematic analysis, and an evaluation of the indicators, the indicator system and the data through the use of two frameworks and select data quality criteria. The first main finding concerns the indicators’ limited identification of distributional effects across space and groups. Second, no unified framework for indicator development was identified, and it instead relies on a few guiding principles, for example quantitative measurability and the possibility to follow up indicators over time. The third finding are the challenges and opportunities of indicator use and data structures in the evaluation process of the ECP, as a result of operating as a large organization. Lastly, public participation could be utilized in future iterations of the ECP to ensure that the indicators align with public concerns and values. To tackle these issues, recommendations include the adoption of a formalized framework grounded in the guiding principles, developing a shared data system for better management and collection of data, and increasing public participation by engaging in citizen dialogue.
Optimisation of plasma enhanced chemical vapour deposition for silicon nitride photonics using optimal design of experiments
(2025) Buchmayr, Mia
There have been many advances in silicon nitride based integrated photonics, enabling a variety of interesting applications. The deposition of high quality and low loss silicon nitride (SiN) during the fabrication of waveguides is essential for creating useful devices. Low temperature alternatives to low pressure chemical vapour deposition (LPCVD) such as plasma enhanced chemical vapour deposition (PECVD) are required to enable back-end-of-line (BEOL) integration. The difficulty with optimising PECVD deposition of silicon nitride is that it includes many process parameters that affect the deposition and resulting properties of the film. Thus, optimisation of the PECVD recipe requires a strategic approach to the experimental design. In this work, a technique called optimal design of experiments (DoE) is used to obtain an overview of the PECVD factor’s influence on silicon nitride properties, and to predict the optimal PECVD recipe. With the help of the statistical software JMP the optimal DoE for PECVD deposition of SiN created, significant factors and correlations identified, and optimal PECVD factor combinations predicted. Ellipsometry measurements provide data regarding the responses of interest, namely thickness uniformity, refractive index, and extinction coefficient of the SiN film. It is found that the refractive index is correlated with the ammonia gas flow rate and the extinction coefficient. Most PECVD factors appear to be relevant, in particular the ammonia gas flow rate for the refractive index and the extinction coefficient, and the frequency mode for the thickness uniformity. In addition, two-factor interaction effects are present in the PECVD process and affect the relationship between process parameters and responses. Furthermore, in terms of stoichiometry, silicon nitride films with a refractive index close to two are found to be silicon rich. The testing of predicted recipes shows that the three responses, i.e. refractive index, extinction coefficient and thickness uniformity, cannot be optimised simultaneously to the desired outcome. However, when considering a stoichiometric Si/N ratio instead of the refractive index, predicted recipes result in improved and equally good responses compared to default PECVD and LPCVD recipes, respectively. This approach of optimal DoE shows promising potential and could be interesting to explore further, especially regarding the optimisation of other relevant fabrication steps affecting the propagation losses in waveguides.
Comparison of time domain simulation methods for ship mooring arrangements
(2025) Pengattukunnel Thomas, Basil; Borges, José
Safe and effective mooring of ships at berth is a critical aspect of port operations, affecting crew safety and vessel integrity as well as operational cost and efficiency. It has become a common practice to plan ships mooring arrangements in advance using ship dynamics prediction tools. This study employs two prediction tools, one based on a fully nonlinear potential flow method and the other on a semi-empirical method, for simulating the dynamic behaviour of a moored ship in time domain. The simulations are carried out for a barge with a simple geometry, subjected to the primary environmental factors in ship mooring problems, namely wind, current and waves. The isolated and combined effects of these environmental factors on the ship dynamics are investigated by analysing the ship motions as well as mooring lines tensions. Overall, the results obtained from the employed tools were comparable, while the semiempirical method offered substantially faster calculations (lower computational costs) than the potential flow method. However, the study reveals that the lack of suitable models to account for quay wall effects on the moored ship within the semi-empirical method can adversely affect the dynamic behaviour predictions, hence significantly impact the assessment of mooring line arrangement performance.
Synthesis and Characterization of Metal Oxide Energy Storage Materials
Dahlberg, Hamus; Hult, Waldemar
In this study, procedures for the solid state and sol-gel synthesis of metal oxides were developed for the purpose of thermochemical energy storage materials. The metal oxides or (blends of them) were suggested by Joakim Brorsson et al., in at the time of writing, unpublished research where he mines databases that fits the desired thermodynamical properties for thermochemical energy storage. Magnesium chro mate, lithium aluminate, lithium chromate and calcium chromate where successfully synthesised by either one or both methods of synthesis, confirmed by X-ray powder diffraction. Barium Oxide had to be purchased from Sigma-Aldrich. Utilising thermogravimetric analysis, a reference from was cuprous oxide was pro duced to compare observations on the metal oxide systems oxidation and reduction reactions. This data was utilised to calculate the systems conversion yield. Rough estimations of reaction kinetics of the systems where also utilised in comparison to the cuprous oxide reference. Calcium chromate and barium oxide where found to be good candidates for the application of thermochemical energy storage as the chalcium chromates, made through solid state synthesis, weight changed by 8%, and the barium oxides’ weight changed by 10%.