Luleå University of Technology Publications
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Crustal structure of the central Norwegian Caledonides and underlying basement with the Atnsjø tectonic window, inferred from magnetotelluric data
No full textMuch of the Norwegian upper crust was shaped by Caledonian thrusting and post-orogenic extension. We investigate the electrical conductivity structure of the crust and associated thrusts and detachments using magnetotellurics to obtain a better understanding Paleozoic tectonics. New magnetotelluric data were collected over an area of c. 60 × 70 km that includes the Gudbrandsdalen Antiform and Atnsjø tectonic window in central Norway.The final 3D electrical conductivity model reveals a highly resistive crustal block, extending E–W along the Gudbrandsdalen Antiform and from the surface to several tens of kilometres depths, imaging the parautochthonous Precambrian basement. No major thrust or detachment has been mapped under the Atnsjø tectonic window, which is therefore considered to most likely represent autochthonous or parautochthonous Baltica basement. Several conductors are imaged along the edge of the magnetotelluric survey, which can be correlated with a major Caledonian thrust and structures in the Precambrian basement.Full text license: CC BY 4.0;Funder: Norwegian Geological Survey;</p
Digital Twins for Asset Management of Civil Structures : Perceived Potential and Practical Applications
No full textThe Engineering and Construction (E&C) industry has vast potential to leverage technology for solving current asset management issues, with significant environmental and financial benefits. This study investigates the use of Digital Twins (DTs) for asset management of civil structures, identifying a gap between the perceived potential of DTs and practical applications due to misconceptions, industry fragmentation, and lack of standardizations. To address this, a literature review and experimental programs were conducted, leading to the development and validation of a proof-of-concept DT platform applied to two case studies. The study concludes with a purpose-driven DT roadmap to address the gap between potential and practical applications in the E&C industry. Background: the integration of Building Information Modeling (BIM) and DTs for asset management in construction offers a promising solution to improve current processes, which are often time-consuming or inefficient. With technology rapidly advancing and the advent of Industry 4.0, there is a growing belief in the transformative potential of DTs to address longstanding challenges within the industry. By leveraging these innovative tools, stakeholders aim to enhance operational efficiency, optimize maintenance practices, and ultimately revolutionize infrastructure asset management. Aims and objectives: this study aims to investigate the use of DTs to improve asset management processes within the E&C industry. The objectives include a thorough investigation of DTs, establishing their purpose within the industry, proposing a replicable DT methodology, demonstrating the methodology through case studies, and addressing the gap between potential and practical applications to promote DT dissemination. Methodological approach: i. Identify problem: thorough literature review and DT investigation (Paper I). ii. Define solution: understand the purpose of DT applications in E&C (Paper II). iii. Methodology and Demonstration: propose and demonstrate a replicable DT methodology through experimental work, digital modelling, and case studies (Papers III, IV, and V). iv. Evaluation: propose a purpose-driven DT roadmap to evaluate the impact of applications, address the gap between potential and applications, and promote widespread DT adoption (Paper VI). Results: the main results include a deep DT investigation, experimental work with a reinforced concrete beam, snow galleries and a trough bridge, digital models using BIM and finite elements, a scalable DT platform methodology demonstrated in two case studies, and a roadmap from conclusions and lessons learned to promote DT adoption in the industry. Conclusions: given the particularities of the E&C industry and its assets, DTs can primarily benefit asset management and maintenance processes by enabling real-time monitoring, predictive maintenance, and data integration for improved safety and efficiency. To address the gap between potential and practical applications, two paradigm shifts are proposed: shifting the perception of DTs from a digital model to integrated technology tools, and adopting a generalizable, purpose-focused approach instead of context-specific frameworks
Public clients creating lead markets for innovation towards sustainability transitions: Market-shaping in the Swedish construction sector
No full textPublic demand is emphasized as a major driving force for environmental innovation addressing societal transitions. In 2007, the European Commission adopted the ‘lead market initiative’ to tackle grand societal challenges across several industrial sectors, of which construction has the greatest sustainability impact. To study how public clients can create lead markets for environmental innovation in construction, we build on recent advancements emphasizing market-shaping strategies as critical for societal transitions. The paper investigates how public construction clients proactively use and combine market-shaping strategies to create lead markets for environmental innovations. Our empirical findings, from a multiple-case study of three public construction clients in Sweden, illustrate how the clients use and combine a broad range of market-shaping strategies related to seven groups of lead market advantages. We contribute to theory by cross-fertilizing market-shaping and lead market literatures and showing how market-shaping strategies interplay in achieving combinatory effects, which incentivize creation of lead markets for environmental innovation towards sustainability transitions.Validerad;2025;Nivå 2;2025-10-01 (u5);Full text license: CC BY 4.0;</p
Analysis of high flux membranes for desalination in waste-heat driven vacuum membrane distillation plants: Experimental validation and techno-economic analysis
No full textVacuum membrane distillation is a promising technology for seawater desalination, as it enables high recovery ratios, with reasonable thermal and minimal electric consumption. Ceramic membranes can offer notable advantages over polymeric membranes, mainly due to their robust thermal and mechanical stability, yet they have limited representation in the literature. Accordingly, this work investigates ceramic membranes and their techno-economic performance for large scale desalination plants, with target recovery ratios above 85 %. First, a one-dimensional model for multilayered membranes was developed in MATLAB, validated against experimental data of water fluxes with different membrane materials, including ceramic ones, specifically collected within this work. This also enabled the fitting of the membrane characteristic parameters with the collected experimental data. With the aim of reducing the thermal consumption, a full-scale plant layout was defined with various stages in cascade and a sensible waste heat source at 90 °C. Results demonstrate that thermal consumption level in the 180–250 kWh/m3 range is possible, with average water fluxes around 20 kg/(m2·h). With reasonable assumptions on capital costs and plant availability, the levelized cost of water was found to be between 3 and $8/m3.Validerad;2025;Nivå 2;2025-12-02 (u4);Fulltext license: CC BY-NC-ND</p
Solvent extraction using crown ethers: Selective recovery of potassium from synthetic K-feldspar leachate
No full textThe present study focuses on the selective extraction of potassium from a hydrochloric acid-based feldspar leachate using solvent extraction with crown ethers, CE (dibenzo-18-crown-6 and 12-crown-4). The effects of hydrochloric acid concentration, extractant type, diluent, extractant concentration, and organic-to-aqueous phase ratio on potassium extraction efficiency have been examined. Dibenzo-18-crown-6 diluted in m-cresol was shown to preferentially extract potassium (≈85 %) from highly acidic hydrochloric acid solutions (2 to 6 M), with minimal co-extraction of impurities, such as aluminum and sodium, in a single extraction step. Aluminum, however, was shown to be extracted efficiently (≈99 %) at lower acidities (<0.1 M). The extraction mechanisms were explored using various analyses, such as slope analysis, nuclear magnetic resonance, and scanning electron microscopy showing that dibenzo-18-crown-6 forms a highly stable complex with potassium at 1:1 M ratio, (KCl)(CE), driven by the size compatibility between potassium ions and the crown ether cavity. For aluminum, the extraction mechanism likely involves the formation of a cooperative complex where aluminum ions are associated with the potassium-crown ether complex (AlKCl4)(CE). Increasing the concentration of hydrochloric acid increased potassium ion activity, chloride ion activity, and ionic strength in the solution. These changes would enhance selective potassium extraction over the formation and extraction of the aluminum‑potassium cooperative complex.Validerad;2025;Nivå 2;2025-11-12 (u2);Full text: CC BY license;POTASSIA
Investigation of internal density variation in Scots pine using X-Ray computed tomography and image analysis
No full textResinwood formation in Scots pine (Pinus sylvestris) resulting from Cronartium pini infection represents a critical quality defect that substantially reduces timber value and complicates industrial processing decisions in the Nordic Forest industry. Current timber grading protocols rely exclusively on visual surface inspection, which cannot detect internal resin accumulation patterns essential for optimal sawmill operations and volume yields. This knowledge gap generates cascading economic inefficiencies throughout timber processing, as sawmills cannot optimise cutting patterns without comprehensive internal defect information. This doctoral research addresses these fundamental limitations by developing and validating non-destructive methods for detecting and segmentation of internal resinwood distribution using X-ray computed tomography (CT) imaging. The pathophysiological basis for this approach stems from the host defence mechanism whereby C. pini infection triggers systematic hyperproduction of oleoresin compounds that infiltrate wood tissues, generating distinguishable radiographic density variation, so the research work bridges this gap by integrating two approaches: Algorithm Development: An automated segmentation pipeline combining Gaussian Mixture Models (GMM), multi-directional ray-casting, and morphological refinement was developed to distinguish resinwood from healthy tissues in CT imagery. The method processes ~7,000 slices per log, achieving high sensitivity for sapwood (0.98) and heartwood (0.80) segmentation. Resinwood detection attained moderate precision (0.25), limited by density overlaps with heartwood and CT image artefacts.Qualitative Feature Identification: CT analysis of paired green- and dry- state specimens revealed three diagnostic resinwood signatures: (a) growth-ring distortions, (b) non-concentric cambial development, and (c) ground-glass opacity patterns. Resin extraction validated these features, confirming increase resin content in CT-identified zones (41% vs. control: 2%, p < 0.001).Key novel scientific contribution: Evaluated probabilistic framework for resinwood segmentation through industrial CT imaging.Dual-state (green/dry) CT scans enabling the utilisation of comparison imaging data for resinwood mapping in logs.Open-source implementation supporting model development in pilot testing for sawmill-related research and development.Challenges persist in distinguishing pathological resin accumulation from natural impregnation heartwood density gradients and moisture driven influenced false detections. Future work will integrate multi-threshold GMMs, more noise reduction, and spatial feature descriptors (e.g., resin morphology) to enhance specificity. This research establishes a foundation for data-driven defect detection and have potential to improve volume yield in production and processing optimisation in digitally assisted sawmilling.CT-Woo
From Wood to Advanced Materials: Multifunctional TEMPO-Oxidized Wood Nanofibril Networks as Wound Dressings and Energy Storage Device Separators
No full textThe overall aim of this thesis is to study (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation of wood particles from a structure-property relationship. Herein, the focus is on the characterization of materials after oxidation, fibrillation, and network formation from various wood species as raw materials, namely softwood- and hardwood particles. This thesis also compares the properties of corresponding nanofibrils, and networks produced through TEMPO-oxidation of raw wood and never dried softwood pulp (NDSP), as well as to commercial TEMPO-oxidized pulp, offering insights into the one-step delignification and oxidation process of wood. It further examines the applications of the nanofibril networks in liquid-absorbed state, in relation to their use as wound dressings and supercapacitor separators, while comparing their performance with commercial materials such as bacterial cellulose (BC) and polyolefin membranes. This thesis demonstrates that TEMPO-oxidation of wood provides a simplified and direct method to produce cellulose nanofibril (CNF) networks, eliminating separate pulping and bleaching processes prior to TEMPO-oxidation. The method streamlines the process by reducing the treatment and washing steps along with the time required, offering a straightforward route compared to traditional multi-step approaches, while utilizing cost-efficient by-products of wood processing as raw materials, such as sawdust. TEMPO-oxidized wood nanofibril networks are shown to be multifunctional materials with potential use for biomedical and electrochemical applications. They exhibit promising properties for use as advanced wound dressings, including high liquid absorption, wet mechanical integrity, thermal stability, transparency, and biocompatibility with skin cells, in relation to commercially available BC wound dressings. Furthermore, the thickness and fabrication methods, such as suspension casting and vacuum-assisted filtration, were found to significantly influence the interconnection of nanofibril layers and allow tunable design of network properties. The thesis also highlights the effect of wood specie on the chemical and mechanical properties of the TEMPO-oxidized wood nanofibril networks. Hardwood particles were found more prone to TEMPO-oxidation, and their nanofibrils exhibited higher carboxylate content than TEMPO-oxidized softwood nanofibrils (TO-SWNFs). However, TO-SWNFs displayed lower cytotoxicity with primary skin cells and their networks displayed better mechanical properties in wet state, making them a more suitable material for wound dressing applications. Furthermore, it has also been studied here that reducing the amount of TEMPO catalyst in the adapted method could be achieved without negative effects on the properties of the resulting hydrogel networks when advanced wound dressing applications are considered. Additionally, other application areas of TEMPO-oxidized wood nanofibril networks as supercapacitor separators were explored, with the addition of kraft lignin (KL) into developed networks, which improved the network uniformity while enhancing the electrochemical performance in coin-cell assemblies. An optimal KL content of 10 wt% provided the best balance of mechanical integrity and capacitance, with higher KL content leading to a decline in both material properties and electrochemical performance. In conclusion, this thesis establishes that TEMPO-oxidation of wood particles is a promising approach for production of CNFs that self-assembles to mechanically robust, transparent and cytocompatible hydrogel networks with tunable material properties for different potential applications, namely wound dressings and energy storage device separators as studied herein. Heali
Estimating the effect of cold forming and post processing on fatigue of high strength steels under component-related loading conditions
No full textStamping and shot peening of chassis components such as wheels and cross beams introduce residual stresses that affect the fatigue life. The tensile residual stresses from stamping are often found in the most critical areas for fatigue. These areas are commonly subject to bending stress states while smooth material fatigue data for steel sheets more commonly is obtained by uniaxial testing. Both the sensitivity to residual stresses and change in load condition are material dependent posing a challenge in fatigue life estimation of formed and shot-peened specimens. This paper aims to provide a convenient tool for high cycle fatigue life estimations in these conditions solely dependent on uniaxial tensile properties without parameter fitting. The underlying causes for the material dependency is discussed and reflected in the methodology. Uniaxial fatigue testing and fatigue testing of formed specimens with and without subsequent shot peening are performed for validation.Validerad;2025;Nivå 2;2025-11-24 (u4);Fulltext license: CC BY</p
Experimental and numerical evaluation of convective heat transfer correlations in a packed bed of iron ore pellets
No full textModeling heat transfer in packed bed processes such as iron ore pelletization is essential for optimizing process operation and furnace design. In these systems, materials like magnetite iron ore undergo thermal and chemical transformations, where heat and mass transfer are often coupled with heat effects from multiple processes — including both exothermic chemical reactions (e.g., oxidation) and endothermic physical changes (e.g., drying and sintering). As the industry moves towards fossil-free ironmaking, it becomes increasingly important to isolate pure heat transfer behavior, independent of chemical reactions, to support the development of sustainable process schemes. This study investigates convective heat transfer in a packed bed by evaluating several established correlations against the conventionally used modified Ranz–Marshall correlation. Pilot pot-scale experiments were performed by isothermally heating 120 kg of already indurated iron ore pellets at 300 °C to avoid chemical reactions, with additional experiments at 500 °C and 700 °C to assess performance at elevated temperatures typical of industrial pelletization. Results show that the modified Ranz–Marshall correlation underpredicts heat transfer rates under conditions isolating convective heat transfer, reinforcing the need for this investigation. The Wakao–Funazkri and Rowe–Claxton correlations provided the best agreement with experimental data, particularly at 300 °C. Minor deviations at higher temperatures suggest the influence of unaccounted variables, warranting further study. Sensitivity analysis identified gas velocity as the most significant parameter affecting heat transfer. The results suggest that adopting the Wakao–Funazkri and Rowe–Claxton correlations can provide a stronger basis for predictive pellet heat transfer modeling in future process design and simulation work.Funding: Swedish Mining Innovation;Fulltext license: CC BY</p
Innovativa Metoder för Brandgasventilation : En Studie av Tilluftsöppning i Taknivå
No full textDenna studie undersöker en alternativ utformning av termisk brandgasventilation. Utformningen bygger på att ersätta tilluftsöppningar i markplan med rökgasluckor i tak med hjälp av brandteknisk installation i form av rökgardin. Syftet med arbetet har varit att göra en jämförelse mellan denna hypotetiska utformning och traditionell brandgasventilation för att kunna utvärdera om samma effekt kan uppnås med de olika metoderna. Arbetet har utförts som en kombination av litteraturstudier och fallstudier med numeriska beräkningar utförda med Fire Dynamic Simulator (FDS). Genom att simulera olika scenarion med olika faktorer i fokus som till exempel placering av rökgardin samt vindpåverkan så har en analys av brandgasventilation varit möjlig. Analysen har visat att externa faktorer samt placeringen av tilluft har en påverkan på brandgasventileringen, men arbetet har ej kunnat säkerställa ett klart orsakssamband om varför denna påverkan sker. Resultatet visar att den utvecklade metoden har potential att ge en effektiv brandgasventilation jämfört med traditionell utformning. Slutsatsen är att det finns potential för den utvecklade metoden, men att vidare forskning, fler simuleringar och verkliga experiment anses nödvändiga för en användning av metoden i praktiken