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Senast inlagda
Investigation of linear correlations between soil indicators
(2025) Westergren, Sofia
The soil is an important part of the world that contributes to ecosystem services
such as food production, water purification, and protection from climate changes.
Despite that, knowledge and understanding of the structure and functions of the soil
system is deficient. The world faces challenges related to crop production and food
consumption. These challenges are predicted to become even greater in the future.
An increased understanding, will contribute to the work to assess the status of soils
and preserve or regain the functions from soil. The aim of this study is to increase
the understanding of how soil indicators can be used to describe soil and specifically
to investigate the existence of linear correlations between soil indicators. The investigation
includes calculation of biological soil indicators based on environmental
DNA from The Land Use/Cover Area frame statistical Survey (LUCAS). The calculated
biological soil indicators are the ratio of gram-positive and gram-negative
bacteria, diversity index and presence of actinomycetes bacteria, mycorrhiza forming
fungi, and saprotrophic fungi. The data analysis includes regression analysis and
principal component analysis between the biological soil indicators and characteristic
soil indicators (see Table 4.5). The results indicate that there may be no linear
correlations between the chosen biological soil indicators and the characteristic soil
indicators.
Evaluation of system strength in a converterdominated power system
(2025) Rosengren, Malte
The steady increase in power electronic-interfaced generation, driven by the continued growth of renewable energy sources, is altering the dynamic behavior of modern power systems. While traditional system dynamics have been dictated by the characteristics of synchronous generators, the increasing penetration of Converter-Based Resources (CBRs) is contributing to a gradual transition toward converter dominated power systems. This transition introduces new challenges to power system stability and raises questions regarding the applicability of conventional system strength metrics, particularly the Short Circuit Ratio (SCR), which has historically been used to assessgrid strength. The aim of this thesis is to evaluate the limitations of the SCR metric in grid strength assessment for converter-dominated power systems and to assess alternative system strength metrics that may be more suitable under these changing conditions. Furthermore, the alternative system strength metrics need to be applicable during grid planning and is therefore restricted to the data available at this stage. The study was structured into three phases: (1) an initial review of the traditional grid strength metric, SCR, supported by Electromagnetic Transient (EMT) simulations; (2) initial evaluation and selection of alternative system strength metrics through comparative evaluation using small-scale case study with EMT simulations; and (3) implementation and evaluation in PSS®E, of the most promising metrics selected in (2), followed by validation of PSS®E results through detailed EMT simulations to determine the most reliable metric for system strength assessment.
The results indicate that traditional SCR metric consistently overestimates system strength in systems with high CBR penetration. The preliminary grid strength asessment conducted in phase 2 identified the Available Fault Level (AFL), Equivalent Short Circuit Ratio (EqSCR), and Site-Dependent Short Circuit Ratio (SDSCR) as the most appropriate alternative metrics for evaluating grid strength. While the AFL demonstrated promise in the initial small-scale review, it exhibited inconsistencies in the estimation of system strength during the validation process in phase 3. The results obtained from the EqSCR and SDSCR metrics were closely aligned. This outcome is expected, as both methods are fundamentally similar, differing primarily
in the specific computational approaches they employ. For both small-scale (phase 2) and more complex system models (phase 3), the two metrics consistently identified the point of instability. System weakness and instability were observed at EqSCR values ranging from 1.1 to 1.3, and SDSCR values between 1.2 and 1.4. Given their comparable performance, EqSCR was identified as the more suitable metric due to its greater computational efficiency. Based on these findings, this thesis recommends the use of EqSCR for system strength screening in converter dominated power systems.
Enabling a Broader Use of Time-Coupled Building Information Modeling: Understanding current barriers and investigating takt planning as a catalyst for implementation
(2025) Hjelmqvist, Axel; Sandros, Ronja
Time-coupled Building Information Modeling (BIM) is a powerful tool for integrat ing BIM and production planning. This paper reviews the literature and interviews
conducted with practitioners in the construction industry to test the benefits men tioned in the literature. The interviews showed that StreamBIM has the potential
to integrate BIM into existing workflows and tools. It also enables the development
of automated methods for this integration. In addition, the interviews show that
BIM’s flexibility and ability to visualize 3D for production planning can be improved
by combining BIM with a takt-time plan. The results from the interviews suggest
that iterative and continuous usage of time-coupled BIM needs to be done to make
on-boarding easier for both clients, designers, and contractors.
Optimization of estimating intrinsic parameters of a camera using a robot arm
(2025) Sudhir, Shilpa
Eye-tracking technology is applied across industries such as automotive, aerospace,
and human-computer interaction, where precise gaze estimation relies on the accurate
calibration of eye-tracking cameras. In this work, a robot arm is used to perform
the intrinsic calibration of eye tracking cameras. The motivation behind using a
robotic arm for the intrinsic calibration of an eye-tracking camera instead of a manual
procedure stems from several key advantages related to precision, repeatability,
and efficiency. Control over the camera poses in front of the checkerboard leads to a
more accurate and efficient calibration process. This eliminates the challenges and
inconsistencies associated with manual camera movements and opens the door for
automating and scaling the calibration process with minimal human involvement.
The robotic arm ensures a level of consistency and reliability that would be hard to
achieve manually, making it a compelling choice for eye-tracking camera calibration,
especially in high-precision applications.
The Design and Performance Evaluation of a Double-three-phase Inverter - DC-Link Thermal Evaluation and Lifetime Estimation
(2025) Yodwong, Jedsada
This thesis presents the design, implementation, and experimental evaluation of a double–three–phase traction inverter based on silicon carbide (SiC) power modules for heavyduty
electric vehicle applications. The work focuses on achieving high power density and robust thermal performance through co-design of the DC-link capacitor bank and laminated busbar structure. Two alternative DC-link layouts were investigated: Case I, with capacitors mounted above the busbar, and Case II, with capacitors in direct contact with the housing.
A comprehensive methodology combining analytical modeling, MATLAB/Simulink simulations, and laboratory testing was employed. Open-loop SVPWM tests validated inverter
functionality, while thermal performance was assessed under RMS ripple currents of 156 Arms and 300 Arms at 10 kHz under 2 thermal conditions: with and without liquid cooling.
Results show that liquid cooling significantly reduces busbar temperatures (up to 67% in Case I), whereas capacitor hot-spot remain dominated by internal thermal paths, limiting
improvements to 18–21%. Lifetime analysis, based on datasheet models, experimental data, and MATLAB/Simulink model, indicates that capacitor lifetime is highly sensitive to temperature. Under ideal assumptions, the lifetime at 55 ◦C ambient was estimated at 24.8 years, whereas experimentally adjusted scenarios ranged from 8.7 to 13.1 years. Liquid cooling improved lifetime by up to 50% at high ripple currents compared to the worst case, emphasizing the importance of accurate thermal modeling and integrated cooling strategies for next-generation traction inverters. The findings underscore the importance of integrated electro–thermal design for reliability in high-power SiC-based traction inverters. Future work includes closed-loop control implementation, and EMI/EMC characterization.