Publikationer från Linköpings universitet
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Exploring the Roles of Swedish Actors in the Internationalization of the Nordic Biogas Model
No full textThis thesis investigates the roles that Swedish actors can play in the internationalization of the Nordic Biogas Model (NBM), and how they can contribute to its adaptation to overcome the existing the barriers in diverse international contexts. The main problem is that the misalignment between the Swedish actors is hindering the export process of the Nordic biogas model. The NBM is a waste-based approach to biogas that integrates energy production, waste management, and nutrient recycling within a circular economy framework. Using a qualitative case study method, the research draws on nine semi-structured interviews with key stakeholders, including government agencies, technology providers, consultants, financiers, and intermediary actors. The analysis is guided by stakeholder theory, symbiotic internationalization theory, and export promotion theory, and is structured through thematic coding. Findings reveal that Swedish actors are capable of fulfilling a range of complementary roles from system integrators and reference cases to policy ambassadors and project orchestrators. However, the current export landscape is hindered by fragmented responsibilities, feasibility study misalignment, and a lack of long-term project ownership. Successful internationalization of the NBM requires greater coordination, stakeholder alignment, and flexible system packaging. Swedish actors contribute most effectively when they engage in long-term, locally embedded partnerships and co-create context-specific solutions rather than exporting standardized models. The study concludes that a more coherent and adaptive export strategy is essential for realizing Sweden’s global potential in biogas systems
En jämförelse av Embedded Template Library prestanda med libstdc++ i ESP-IDF
No full textThe ESP32 family of microcontrollers by Espressif Systems is widely used in IoT applications due to its built-in WiFi and Bluetooth. Its official SDK, ESP-IDF, provides a C/C++-based API and uses the Two-Level-Segregated-Fit (TLSF) allocator for dynamic memory management. While C++ is popular in embedded development for its C compatibility,and low runtime overhead, parts of the standard library are often avoided due to their reliance on heap allocation. This paper compares the performance of common C++ standardlibrary containers with their statically allocated counterparts from the Embedded Template Library (ETL) on the ESP32-S3. CPU cycle counts and long-term memory behaviourare evaluated in a small weather-station simulation. ETL containers showed better performance and predictable memory use. However, responsible use of standard containerscaused no severe heap fragmentation, indicating they remain viable under ESP-IDF with care
Energy Harvesting - Rotational Sensor
No full textIt is costly for industrial companies to run power supply cables through a rotating head of a milling machine. The objective of this thesis is to investigate the possibility of harvesting energy from a rotating milling machine and power a wireless sensor network with that energy. The report investigates three different methods for harvesting energy: kinetic energy, radiation energy, and thermal energy. In the early part of the study, it is demonstrated that kinetic and radiation energy are not suitable methods for this purpose. Thermal energy is identified as the most appropriate method and is therefore examined through laboratory tests in Gävle. The report concludes that thermoelectric elements can be used as a method to power a wireless sensor network if the temperature gradient is sufficient. The thesis was performed in collaboration with Syntronic in Linköping with the supervisor located in Gävle, Sweden
Utnyttjande av diffusionsmodeller och Gaussian Splatting för kontextuellt sammanhängande utökningar av 3D scener
No full textThere have been significant advances in high resolution 3D reconstruction with the use of Gaussian Splatting. With this technique multi-view high resolution images can be reconstructed into high resolution 3D scenes by first building up a point cloud and optimizing 3D Gaussians projected on the point cloud, minimizing the difference between images and the rendered scene. Recent research has delved into using generative models to modify reconstructions created with Gaussian Splatting. Previous work is either limited in the scale of which scenes can be generated or focused on editing parts of existing reconstructions. To address the limitations, we propose a framework of iterative scene generation with the purpose of extending 3D reconstructions created using Gaussian Splatting. The framework extends a baseline reconstruction by adding new information created through inpainting and estimating point clouds in the missing areas of the reconstruction. In efforts to automate this process, functions for identifying poor reconstruction and a dynamic weighting loss are presented. The results show that it is possible to extend existing reconstructions without a significant loss in 3D representation.Gaussian Splatting har gett upphov till signifikanta framsteg i högupplösta 3D rekonstruktioner. Tekniken möjliggör att bilder från flera vyer rekonstrueras i 3D genom att bygga upp ett punktmoln och optimera 3D Gaussians projekterade på punktmolnet genom att minimera skillnaden mellan bilderna och renderade 3D Gaussians. Ny forskning har undersökt användningen av generativa modeller för att modifiera rekonstruktioner skapade genom Gaussian Splatting. Tidigare forskning är begränsad i den storlek av scener som kan genereras eller fokuserar på att modifiera befintliga rekonstruktioner. Vi föreslår ett ramverk av iterativ scen utökning för att hantera de tidigare begränsningar med ändamålet att utöka 3D rekonstrueringar skapade med Gaussian Splatting. Ramverket utökar en existerande rekonstruktion genom att lägga till ny information genom inpainting och estimering av punktmoln i delar av rekonstruktionen som saknar information. I strävan mot att automatisera processen presenteras funktioner för att identifiera felrekonstruerade områden och en dynamisk viktningsförlust. Resultaten visar att det går att utöka existerande rekonstrueringar genom ramverket utan en signifikant förlust i 3D representation
Civila insatspersoner 4(4)
No full textRapporten redogör för vilka nyttor/vinster och kostnader som är av betydelse för beslut och planering av verksamheten med Civila insatspersoner (CIP) från olika perspektiv samt ger förslag till vilka nyttor och kostnader som ska fokuseras på vid beslut och i vidare forskning.Nytta, vinster och kostnader avser såväl direkta som indirekta, statiska och dynamiska nyttor och kostnader för olika aktörer. Vid beräkning av nytta/vinst eller kostnader är det i första hand standardvinster och kostnader som är meningsfulla att beräkna.CIP:personer, räddningstjänstföreträdare och myndighetsföreträdare ansåg tidsvinst vid insats som en viktig nytta. CIP-företrädare framhöll vidare nyttan av att skapa gemenskap i lokalsamhället och att ha en egen gemenskap i CIP-grupperna, samt nytta med fler typer av uppdrag, exempelvis inom civilberedskap. Olika genomförande-strategier och organisering av CIP-verksamheten medför olika möjligheter och begränsningar vad gäller finansiering, olika typer av nytta/vinster eller kostnader och verksamhetsrisker. Den nationella samordningen möjliggör mer kraftfulla och uthålliga insatser vid behov och diversifierade resurser som samordnas möjliggör exempelvis att CIP kan bidra i såväl förebyggande som efterarbete efter insatser.Granskning:Har granskats av Jesper Bokvist, Brandskyddsföreningen.Finansiering:Brandskyddsföreningen och Centrum inom forskning - för respons och räddningssystem</p
Methodology for BRDF Measurements in Outdoor Conditions with Solar Illumination
No full textUnderstanding and modeling the reflectance properties of materials is essential in various fields, for example during the development and evaluation of camouflage materials. An important concept for this purpose is the Bidirectional Reflectance Distribution Function, BRDF, which describes how light is reflected from a surface as a function of both the incident and viewing angles. While BRDF is typically measured in indoor laboratories, there is significant value in developing methods for outdoor measurements under natural illumination, particularly for studying large or context specific samples. However, this introduces challenges in managing environmental variables. The aim of this project was to design a first useful methodology for measuring BRDF using the sun as the light source. A theoretical model was proposed to isolate the direct sunlight component by comparing radiometric measurements of both reference and sample materials under sunlit and shaded conditions. Measurements were performed with a high dynamic range camera sensitive to the visible spectrum, mounted onto an adjustable boom to alter the zenith angle. Images of the sample materials and the reference material were captured and the data was then used to calculate the BRDF of the different sample materials. Ingoing and outgoing angles were determined using a solar position algorithm program together with a mechanical angle measurement device on the boom. The results showed strong agreement between outdoor BRDF measurements and indoor laboratory measurements, performed with a 633 nm laser scatterometer, with only minor deviations. A limitation of the project was the boom that only allowed measurements within a fixed plane, which did not align with the incident plane of the sunlight. As a result, the measurement predominantly captured diffuse reflection, limiting characterization of specular materials. For future work, a drone based system flying in a hemispherical pattern could enable a broader angular sampling, allowing for detailed BRDF mapping of more specular or inhomogeneous materials in three dimensions
Fatigue Life of Lugs : A finite element-based model for fatigue life calculations of lugs with arbitrary geometry and load sequence
No full textLugs are commonly used in aircraft structures to transmit loads between parts through a bolt or pin connection. As a result, they are frequently subjected to cyclic loading and therefore susceptible to fatigue failure. The current lug fatigue life calculation method is based on fatigue test data of lugs, and is only applicable for straight lugs, subjected to a longitudinal load with constant amplitude. This makes the method limited and unnecessarily conservative, due to the assumption that the load is applied in a single direction. The aim has therefore been to expand the method with model, valid for any lug geometry and load sequence. The proposed model builds upon an existing method where the fatigue life of a lug is predicted based on the fatigue life of a tested reference lug, through scaling of geometrical and stress quantities. It further introduces a comparison between the stress concentration factors, enabling fatigue life predictions of lugs with arbitrary geometry and load angles by finite element calculations of the tangential stress in the lug. Additionally, damage theory has been applied to predict the fatigue of lugs subjected to arbitrary load sequences by calculating the cumulative damage in each point along the hole edge of the lug. The validity of the proposed model has been assessed by comparing the predicted fatigue life of lugs to test data, available for a few different lug geometries and different constant load angles. The calculation model showed a promising agreement between the predictions and test results. To validate the implementation of damage theory, tests with varying load angle and amplitude must be performed
Invers reinforcement learning för utvärdering av ishockey : Inverse reinforcement learning in ice hockey
No full textThis study explores the application of machine learning through reinforcement learning techniques to assess individual player performance in ice hockey based on outcomes in the National Hockey League (NHL). The primary objective was to develop a value function trained using rewards linked to specific game outcomes, enabling a detailed analysis of player impact on the game. The methodology involved collecting game data, defining rewards based on match outcomes, and training a value function to understand and predict how individual player actions influence the possibility of winning. The results demonstrate that the trained value function effectively estimates player contributions and offers a nuanced view of their impact on game dynamics. This research confirms the potential of advanced analytical techniques in sports analytics, providing a foundation for future studies to refine player evaluation metrics and improve team strategy based on quantitative data
Autonomous Forklift Path Following Using Large Language Model Agents and Reinforcement Learning
No full textThis thesis explores the viability of utilising Large Language Models (LLMs) to iteratively tune automatic control parameters for an autonomous forklift truck performing a path-following task. Additionally, an established control policy learning method, Reinforcement Learning (RL), is implemented to perform the path-following task. The main objective is to evaluate the performance of each method, allowing for a comparison between them. Two systems are implemented to investigate the objective: a multi-agent LLM parameter tuning framework and a deep Q-network RL agent. The LLM framework focuses on tuning three control structures: Linear Quadratic (LQ), State Feedback, and Pure Pursuit, while examining the impact of different in-context learning prompt types, including zero-shot, zero-shot chain-of-thought, few-shot, and few-shot chain-of-thought prompting. The RL solution is trained in simulation to develop a policy that achieves desirable path-following performance. The results demonstrate the promising capability of the LLM-based framework to tune control parameters effectively using simulation feedback, achieving strong performance. Although the RL approach achieves good results when trained with a simplified system model, it struggles with policy transfer to the more realistic simulation environment. Both LLM and RL methods require significant time and effort to implement. The extensive in-context prompt design needed for consistent LLM tuning results is comparable in complexity to the reward function design and training required by the RL solution
En Systematisk Studie över Verklig Exploateringskomplexitet för Android Security Bulletins
No full textDespite its widespread use, prior research has shown that CVSS vulnerability severity evaluations can suffer from inconsistencies between its human evaluators and can fail to reflect contextual factors present in real-world systems. However, there has been limited research on how these inconsistencies manifest specifically in Android environments, especially in physical devices, instead mainly utilizing theoretical models or emulated environments. This thesis investigates that gap by experimentally testing on physical Android devices, and examining how well CVSS aligns with real-world, practical exploit complexity for vulnerabilities disclosed in the Android Security Bulletin. A custom tool was made where all CVEs (vulnerabilities) from the Android Security Bulletin were collected, and a targeted selection was made using a custom prioritization system designed to identify likely exploitable CVEs compatible with practical reproduction. Selected CVEs were then reproduced on real devices to evaluate how CVSS reflects exploitability in practical environments in terms of difficulty, behavior, and official scoring. The results revealed that a high percentage of the practically tested CVEs showed a discrepancy in the official scoring in real-world environments across multiple metrics, both in exploitability and impact as defined by CVSS. It also showed that discrepancies may stem from contextual factors like the granularity of privilege, the permission architecture of Android, and ambiguous metric interpretation. Where vulnerabilities saw justification in an adjusted score, most saw a decrease in severity. The trends showed an imbalance in the types of vulnerability and highlighted varying exploitability between them. In addition, other variables such as the neglect of auxiliary bug paths in CVSS scoring, inconsistent behavior between Android versions and devices, and a potential case of residual attack surface were discovered. These findings highlight the limitation of CVSS in capturing real-world risk in Android environments and the need for practical empirical testing. Without it, severity scores risk being misleading or lose precision, which can lead to worse patch prioritization and vulnerability management