Luleå University of Technology Publications
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CO2 electrochemical reduction to CO with ionic liquids: evaluation and technology exploration
No full textElectrochemical CO2 reduction (CO2RR) is one of the most promising methods for decreasing the concentration of CO2, meanwhile, converting them into the high value-added chemicals, which has been more and more investigated and developed recently. Imidazolium ionic liquids (ILs) have been widely used as electrolytes in CO2RR and shown satisfactory performance. While the function of ILs is still unclear. Besides, the economic feasibility and potential of CO2RR with ILs-based electrolytes as well as the environmental effects are also unclear. Therefore, this work focuses on the technology evaluation and exploration for CO2RR-to-CO with ILs-based electrolyte. Firstly, a literature review about CO2RR to CO, CH4, CH3OH, and syngas (H2/CO=1:1 and 1:2) in ILs-based electrolytes was conducted. Then the processes to obtain these C1-products were analyzed from both economic and environmental aspects based on the state-of-the-art technology and the rationally hypothetical future cases. The results show that CO is the most valuable product considering both the economic benefits and environmental impact, which will be more lucrative in the future with the improvement of CO2RR performance. Then, based on 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), a series of imidazolium ILs with various proton in the group (-CH3, -CH3OH and -SH, noted as [BMMIM][PF6], [BMOHIM][PF6] and [BMSHIM][PF6], respectively) at C2 site of the imidazole ring were synthesized and used as electrolyte to perform CO2RR over a commercial Ag foil. As a result, the more inert the active proton, the more favorable for the production of CO. Notably, nearly 100% CO was obtained when [BMMIM][PF6] with the most inert proton. This confirms that the C2-H of the imidazole ring has an important influence on CO2RR performance and may be involved in the reaction. Finally, [BMMIM][PF6] and [BMIM][PF6] were selected as the electrolytes to conduct CO2RR over a bimetallic catalyst. As a result, the product from 99.69% HCOOH switched into 98.85% CO only via changing the electrolyte from [BMIM][PF6] into [BMMIM][PF6]. Mechanistic studies reveal that the CO2 adsorption configuration on the surface of the catalyst was altered when switching to another IL with a different CO2 active site, resulting in two distinct pathways for the generation of HCOOH and CO, respectively.
Log detection for autonomous forwarding using auto-annotated data from a real-time virtual environment
No full textObject detectors for autonomous forestry operations have previously been developed mainly by training on physical manually annotated data, which is both time-consuming and costly. Since the ground truth in the virtual model is known, the training data can be auto-annotated, enabling the creation of larger training datasets, while also improving time and cost efficiency. In this work, a virtual environment in Unity is used in co-simulation with a real-time digital twin of a physical forestry vehicle, to generate realistic auto-annotated training data, as captured by an onboard stereo camera. First, it is shown that a log detector trained on physical data can detect logs in the virtual environment. Second, new detectors are trained, using different shares of virtual and physical data. It is shown that a detector trained using only virtual data, can learn to detect logs in the physical world. Moreover, virtual pre-training is shown to improve the performance of physically trained and tested detectors, both at low availability of physical training data, and in terms of domain generalization. A detailed detector performance analysis also highlights further potential and opportunities for future improvements. Furthermore, the real-time capable virtual models enable future machine learning tasks utilizing different levels of Hardware-in-the-Loop. Validerad;2025;Nivå 2;2025-09-23 (u8);Funder: Skogstekniska Klustret (The Cluster of Forest Technology);Full text license: CC BYSustainable Autonomous Material Handling (SAMHand)AutoPlant
Status overview of the torrefaction technology, its limitations, and prospective solutions: A reactor design and performance viewpoint
No full textThe goal of torrefaction is to transform lignocellulosic biomass into a solid product with better characteristics than raw biomass. Torrefaction is especially helpful when converting biomass into a final energy carrier via thermochemical processes like gasification and direct combustion. However, even though torrefied biomass has demonstrated advantageous quality, the prevailing torrefaction methods are not yet considered sufficiently advanced to overcome certain operational difficulties such as finding the proper balance between salient independent variables like temperature, reaction time and particle size; hence, much of the torrefied products obtained exhibit inconsistent properties. The technique also lacks the ability to efficiently handle a wide range of biomass feedstocks and exhibits scale-up issues that could be linked to poor temperature control and non-uniform heat distribution. Many of the existing torrefaction systems have been developed and validated for use in the processing of wood-based materials. Studies performed with non-woody materials yielded unsatisfactory results due to their inclination to ignite and carbonize readily during torrefaction. This review, therefore, presents a status overview of torrefaction technology and discusses the limitations of the technique from a reactor design perspective, as well as identifies system-level research that could potentially help to address the technology’s constraints. The basic principles of torrefaction and the mechanisms that affect the quality of torrefied products, including key process variables and kinetics are also discussed. Other expounded aspects include reactor design concepts, process monitoring and control, and specific technological barriers thought to hamper the technology’s attempt to achieve commercial success.Validerad;2025;Nivå 2;2025-12-01 (u2);Full text license: CC BY</p
Knowledge ecosystem emergence: Organizing participation, identity, and actorhood to bridge the governance void
No full textMulti-organizational collaborations involving the industry, academia, and government have become prevalent in developing knowledge to address complex societal problems. These fluid and loosely coupled forms of collaboration, known as knowledge ecosystems, provide the necessary organizing elements for the search and creation of new knowledge. While the literature acknowledges the prevalence of knowledge ecosystems, it remains relatively silent on how their organization develops over time. This lacuna in our understanding is problematic, given the challenge of governance voids for cross-sectoral knowledge collaborations, which lead to difficulties in mobilizing action, securing resources, and ultimately achieving the knowledge-related goals of these collaborations. To address this gap, we theorize knowledge ecosystems as meta-organizations, examining how they gradually develop organizing elements that bridge the initial governance void. Empirically, we draw on an in-depth field case study of the High-Capacity Transport ecosystem in Sweden, demonstrating how three interrelated organizational elements—participation, identity, and actorhood—emerge through an iterative, yet broadly sequential process to resolve governance void challenges in resourcing, belonging, and collective action. Furthermore, we identify discursive and performative meta-organizational practices that enable the actors to collectively enact the aforementioned organizational elements and to engage in knowledge search. We further demonstrate how the organization of knowledge ecosystems is never ‘complete’ and the governance void remains only partially resolved, given the underdefined nature of new knowledge as the ecosystem's shared goal. Overall, our process model contributes to the theory, practice, and policy of knowledge ecosystem emergence and organizing. Validerad;2025;Nivå 2;2025-11-25 (u2);Full text: CC BY license;</p
Friction and wear behaviour of fully formulated water-based lubricants under rolling/sliding contacts
No full textThis study evaluates the tribological performance of fully formulated water-based lubricants (WBLs) under rolling/sliding conditions. The WBLs are composed of water-soluble glycols and glycerol with a functional proportion of water. They exhibited significantly lower friction across all lubrication regimes, with near superlubricity achieved under certain conditions. Unlike conventional oils, WBLs showed minimal shear heating effects and exhibited a low shear response with increasing slide-to-roll ratios. Long-duration tests confirmed consistently lower friction for the WBLs. Post-test analysis showed comparable wear between selected WBLs and the reference oil at 40 °C but greater surface modification for WBLs at higher temperatures. Observed wear mechanisms included abrasive and adhesive wear, with occasional instances of spalling after prolonged tests. X-ray photoelectron spectroscopy (XPS) analysis suggested the presence of chemical species on wear scars, attributed to additive-surface interactions. These findings highlight the potential of fully formulated WBLs in rolling/sliding contacts and their current state in comparison to a conventional gear oil.Full text: CC BY license;For funding information, see: https://doi.org/10.1016/j.triboint.2026.111669</p
Vibration reduction in cross-laminated timber panels using various lamination materials and integrated elastomer layers
No full textCross-laminated timber (CLT) is increasingly used for construction of multi-storey buildings. However, ensuring satisfactory vibro-acoustic performance, particularly in the low-frequency range (typically below 200 Hz), remains a significant challenge, often necessitating add-on solutions such as floating floors. In this study, the aim was to investigate how vibration levels for CLT panels can be reduced by using various lamination materials as well as integrated elastomer layers. Finite element (FE) models were developed, calibrated and validated based on experimental modal analysis of CLT panels with and without elastomer layers. Specifically, elastic moduli of spruce, birch and compressed spruce were calibrated to experimentally obtained eigenfrequencies and mode shapes. Moreover, calibrated FE models of selected panels were used to determine and calibrate a viscoelastic material model for the elastomer layer using frequency-dependent stiffnesses and damping. Using the material model for the numerical simulations, the deviations in accelerance root mean square values were less than 1 dB compared to the experimental data. Finally, it was shown that by using birch or compressed spruce instead of spruce the vibration response could be reduced by 30% and 50%, respectively, for a realistic floor panel size. By integrating a 12 mm elastomer layer into the panels, the vibration response could be reduced by an additional 40%, compared to a panel without an elastomer layer.Full text license: CC BY 4.0;Funder: Södra Foundation for Research, Development and Education;</p
Lightcurves, Rotation Periods, and Colors for Vera C. Rubin Observatory’s First Asteroid Discoveries
No full textWe present lightcurves, rotation periods, and colors for the first asteroid discoveries made with the NSF-DOE Vera C. Rubin Observatory. These are the first science results derived from the 2103 asteroid discoveries released as part of the Rubin First Look (RFL) media event on 2025 June 23, in which the first LSST Camera commissioning images were released. The ∼340,000 observations in which the discoveries were made span nine nights between 2025 April 21 and May 5. With a limiting single-epoch 5σ depth of ∼23–25 mag and dense temporal sampling under an irregular, commissioning-driven cadence, the RFL observations provide an ideal test bed for determination of rotation periods, including sensitivity to rapid rotation. We model lightcurves and derive rotation periods and colors for the ∼2000 objects. We find 75 main-belt asteroids (MBAs) and one near-Earth object (NEO) with reliable rotation periods spanning 0.031–21.3 hr and a photometric precision in the range of 0.05–0.15 mag. We find 19 superfast rotators with periods shorter than the 2.2 hr spin barrier. Rubin-discovered MBA 2025 MN45 is the fastest-rotating d > 0.5 km known asteroid with a rotation period of 1.9 minutes; along with NEO 2025 MJ71 (1.9 minutes) and Rubin-discovered MBAs 2025 MK41 (3.8 minutes), 2025 MV71 (13 minutes), and 2025 MG56 (16 minutes), these five super- to ultrafast rotators join a couple of NEOs as the fastest-spinning subkilometer asteroids known. As this study demonstrates, even in early commissioning, Rubin is successfully probing a previously sparsely sampled region of the subkilometer size−spin rate regime for MBAs.Full text license: CC BY 4.0;For funding information, see: https://iopscience.iop.org/article/10.3847/2041-8213/ae2a30</p
Agentic TinyML for Intent-Aware Handover in 6G Wireless Networks
No full textAs sixth-generation (6G) wireless networks evolve into increasingly Artificial Intelligence (AI)-driven, user-centric ecosystems, traditional reactive handover mechanisms demonstrate limitations, especially in mobile edge computing and autonomous agent-based service scenarios. This manuscript introduces the Wireless AI Agent Network (WAAN), a cross-layer framework designed to enable intent-aware and proactive handovers in 6G networks. WAAN embeds lightweight Tiny Machine Learning (TinyML) agents as autonomous, negotiation-capable entities across heterogeneous edge nodes that contribute to intent propagation and network adaptation. To ensure continuity across mobility-induced disruptions, WAAN incorporates semi-stable Rendezvous Points (RPs) that serve as coordination anchors for context transfer and state preservation. The framework’s operational capabilities are demonstrated through a multimodal environmental control case study, highlighting its effectiveness in maintaining user experience under mobility. Finally, the article discusses key challenges and future opportunities associated with the deployment and evolution of WAAN.Funder: Research Council of Finland (369116); Business Finland through the Neural Pub/Sub Project (8754/31/2022); Digital Twinning of Personal Area Networks for Optimized Sensing and Communication Project (8782/31/2022);Full text license: CC BY</p
Klimatanpassad stadsutveckling i Norrbotten : En studie om hur blågröna strukturer kan implementeras för att stärka sociala värden i ett förändrat klimat.
No full textThis study examines how architectural solutions can contribute to climate adaptation in urban development in Norrbotten, with particular emphasis on human comfort in Luleå, Jokkmokk, and Kiruna. The conditions for spending time outdoors in subarctic cities vary substantially over the course of the year. Periods of both prolonged and limited daylight, as well as major variations in temperature and weather, are aspects that must be considered in the development of cities and the life between buildings. The focus of this study therefore concerns how climate adaptation measures can be integrated into urban development in order to create attractive and sustainable communities. The study is based on a literature review, with the aim of mapping existing material and recurring themes related to the subject and its development areas. On the basis of these insights, a digital conceptual model was developed to visualise selected climate adaptation methods identified in the literature review. The model was also complemented by a solar study, which was used to demonstrate variations in access to light and shade throughout the year. A digital workshop was conducted with representatives from the municipalities involved, in which the model, the solar study, and the themes of the literature review formed the basis for a discussion session with a semi structured format. The purpose of the workshop was to establish a clearer anchoring with the selected municipalities, while also supplementing the research based themes and models of the study with practical experience. The results show the significance of microclimate factors, such as wind and access to natural sunlight, for perceived outdoor comfort and thereby for the conditions that enable a pleasant urban life in Norrbotten. The study also demonstrates how blue and green elements can contribute to the pursuit of climate adapted cities, while simultaneously supporting and promoting social values by creating safe and inviting urban environments. In conclusion, the study as a whole indicates how the combination of academic research, visualisation methods, and municipal dialogue can make climate related issues more concrete and easier to discuss already within planning processes
Instantaneous thermally-driven erosion can explain dearth of dark near-Sun asteroids
No full textRecent models of the near-Earth asteroid population show that asteroids must be super-catastrophically destroyed when they evolve to orbits with perihelion passages well inside of Mercury’s orbit. The heliocentric distances at which the disruptions typically occur are tens of solar radii, which is too far from the Sun for asteroids to be destroyed by sublimation and tidal disruption. The typical disruption distance also appears to be larger for darker asteroids. Here, by carrying out irradiance experiments in vacuum that replicate the conditions in the near-Sun environment, we show that CI meteorite simulants are destroyed within minutes when exposed to the level of solar irradiance encountered at heliocentric distances of up to about 0.2 au. Our results provide an explanation for the scarcity of dark, carbonaceous asteroids with perihelion distances less than 0.2 au, and for the observed mass-loss rate of the asteroid-like object 322P/SOHO 1 assuming its composition is similar to CI carbonaceous chondrites.Full text license: CC BY</p