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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.
Grid planning by using a synthetic grid model - With the integration of EVs
(2025) Corneliusson, Anton
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%.