Luleå University of Technology Publications
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Pressure-driven flow in thin straight tubes of non-uniform cross-section
No full textWe analyze stationary Stokes flow of a Navier–Stokes fluid in a thin tube with a variable cross-section. The objective is to derive a simplified model by examining the asymptotic behavior as the tube's thickness approaches zero. The flow is driven by a pressure gradient between the inlet and outlet, which is modeled by prescribing the normal component of the stress tensor at the tube's ends. Using multiple-scale asymptotic expansions, we first obtain an approximate solution. This inner approximation is accurate for thin tubes, except in thin boundary layers near the inlet and outlet. To address this, we refine the approximation by introducing boundary layer correctors. Finally, we rigorously prove an error estimate for the difference between the exact solution and the improved approximate solution.Validerad;2025;Nivå 2;2025-10-10 (u5);Full text license: CC BY-NC-ND</p
Modelling the spread of infectious diseases in public transport systems under varying demand patterns and capacity constraints
No full textUnderstanding the dynamics of passenger interactions and their epidemiological impact across public transportation systems is crucial for both service efficiency and public health. High passenger density and close physical proximity have been shown to accelerate the spread of infectious diseases. During the COVID-19 pandemic, many public transportation companies took measures to slow down and minimize the spread of the disease. One of these measures was introducing spacing and capacity constraints on public transit vehicles. Our objective is to explore the effects of changes in demand and transportation measures from an epidemiological point of view, offering alternative measures to public transportation companies to keep the system operational while minimizing the epidemiological risk as much as possible. Our findings show that restricting vehicle capacity can significantly reduce the spread of infections, while demand-related measures have an even stronger effect. Combining these approaches offers the best solutions for balancing public health and operability.Validerad;2025;Nivå 2;2025-10-10 (u5);Funder: National Center of Science (DEC-2020/39/I/HS4/03533); Slovenian Research and Innovation Agency (N1-0223); Austrian Science Fund (I 5443-N); CogniCom (0013103);Fulltext license: CC BYBioLOG projec
Reduction Behavior of Biochar-in-Plant Fines Briquettes for CO2-Reduced Ironmaking
No full textBlast furnace (BF) ironmaking remains one of the most efficient countercurrent processes; however, achieving further CO2 emission reductions through conventional methods is increasingly challenging. Currently, BF ironmaking emits approximately 2.33 tonnes of fossil-derived CO2 per tonne of crude steel cast. Integrating briquettes composed of biochar and in-plant fines into the BF process offers a promising short- to medium-term strategy for lowering emissions. This approach enables efficient recycling of fine residues and the substitution of fossil reductants with bio-based alternatives, thereby improving productivity while reducing energy and carbon intensity. This study investigates the reduction behavior of (i) biochar mixed with pellet fines, (ii) various in-plant residues individually, and (iii) briquettes composed of biochar and in-plant fines. The reduction rate of biochar–pellet fine mixtures was found to depend on biochar type, with pyrolyzed pine sawdust exhibiting the highest reactivity, and pyrolyzed contorta wood chips the lowest. A correlation between reduction rate and the alkali index of each char was established, although other factors such as char origin and physical properties also influenced reactivity. The effect of biochar addition (0, 5, and 10 wt.%) on the reduction of steelmaking residues was also studied. In general, biochar enhanced the reduction degree and shifted the reaction onset to lower temperatures. The produced briquettes maintained high mechanical integrity during and after reduction, regardless of biochar origin. Thermogravimetric and XRD analyses revealed that mass loss initiates with the dehydroxylation of cement phases and release of volatiles, followed by carbonate decomposition and reduction of higher oxides above 500 °C. At temperatures ≥ 850 °C, the remaining iron oxides were further reduced to metallic iron.Validerad;2025;Nivå 2;2025-10-20 (u4);Fulltext license: CC BYReduced CO2 Emission through Designed Bio-Coal in the Residue Briquette for the Blast Furnace—MIC
Exploring Carcinogenic Risk and Life Cycle Analysis of Printed Circuit Board Bioleaching
No full textWaste from electronic and electrical components, or WEEE, is an ever-growing and important waste stream in Europe. Biochemical leaching is a new technology that can be used as a cleaner environmental option for metallic recovery from waste electronics. This study first compiles past research on microorganisms that have been tested and studied for use in the bioleaching process. From this, a hypothetical PCB leaching plant using a pre-treatment facility and a two-stage bioreactor will be simulated to find environmental impact and carcinogenic risk from its operation in Northern Sweden. This will be done with HSC, OpenLCA CML-2001, and Argo open-source tools. Chromium(VI) and Lead will be the key elements of study for an LCA analysis and Monte Carlo risk assessment. It is found through LCA simulation that there is a reasonable risk of future marine and freshwater ecotoxicity due to the waste outputs of the bioleaching facility regarding Pb and Cr(VI). After 100 years of simulation, concentrations of lead and chromium in aquatic environments may be higher than acceptable concentrations in both sediment and water. When studying carcinogenic risk, a landfill that houses e-waste is simulated and used as a comparison to the bioleaching process. Compared to landfilling, the health risk for cancer effects over a lifetime is 77.9% lower when bioleaching. Non-cancer risk is also found to be 44% higher than bioleaching when taking into account the 90th percentile of people. From the results, statistically, 5 in every 100,000 may get cancer from the bioleaching process, but 3 in every 10,000 may be effected if it is a landfill. It is also found that children have a higher risk of non-cancer health effects than adults due to the neurotoxic properties of lead. Bioleaching can be considered for cold climates as it requires less energy and has lower operation costs in long term. There exist some forms of microorganism that performs at colder temperatures that may be substituted to further aid this goal of arctic operation. Considering an end-of-life solution for one of Europe’s largest growing waste streams must be made in a cold climate area, in almost all regards. In that case, it is better to use bioleaching compared to landfilling when considering the local environment and people in the region of operation
Biomass gasification for hydrogen production : IEA Bioenergy: Task 33
No full textLow emission hydrogen produced with non-fossil fuels is expected to be key in the efforts de-fossilizing hard-to-abate sectors. Water electrolysis based on fossil-free electricity is regarded as the most promising technology to fulfil the anticipated exponentially growing demand for low emissions hydrogen, however securing the power supply for production of electrolytic hydrogen could in many world-regions be challenging, mainly coupled to the required large expansion of power production and distribution. Production of hydrogen via biomass gasification currently receives less attention but could be an important complement to electrolysis in many regions with available biomass resources. Biomass gasification possesses several beneficial characteristics such non-intermittent and fossil-free hydrogen production in a wide capacity range. The technology leads to many process integration opportunities, for example with water electrolysers since electrolysers generate significant amounts of oxygen, which potentially can be used as gasification media. Also, low temperature excess heat from electrolysers can be utilized for feedstock drying etc. This paves the way for more cost-efficient hydrogen production systems. One of the most prominent technology features is that the CO2 separation process is an integral part of the gasification system, which means that negative CO2-emissions can be obtained if carbon storage (CCS) is applied. LCA-studies show that combined with CCS, the greenhouse gas emission for hydrogen produced via biomass gasification may be as low as in the range of -15 to -22 kg CO2eq per kg produced hydrogen. The main aim of this report is to describe different biomass gasification technologies suitable for hydrogen production and to provide information of on-going commercial initiatives. The report also aims at identifying potential techno-economic opportunities and challenges as well as knowledge gaps to better understand its potential future role and need of further development. The hydrogen yield from biomass gasification varies depending on feedstock and process conditions, but an approximate value is about 100 kg of hydrogen per ton dry biomass. The energy efficiency also varies depending on process design but is normally in the range of 40-70% (based on the lower heating value). The Technology Readiness Level (TRL) of biomass gasification for hydrogen production is estimated to be in the 5 to 7 range depending on assessment methodology. All the main sub-processes of the conversion have a high technological maturity, but there is a need to demonstrate integrated operation of the complete hydrogen production chain in relevant scale to reach a higher TRL-score. Additional research is required to increase the knowledge on potential impurities, trace elements and their possible effects on for example fuel cells. This could serve as valuable inputs to updated ISO standards where biomass gasification-based hydrogen should be included. It is estimated that the current production cost for a large-scale gasification plant (200 MW) would be approximately 4 € per kg hydrogen at a biomass price of 20 € per MWh. With potential process improvements and utilisation of CCS, the production cost could reduce to below 3 € per kg hydrogen at the same biomass price. With the current price levels of fossil methane in Europe, these cost levels are comparable to hydrogen produced via steam methane reforming. It is also shown that the cost levels are competitive to future foreseen production cost of renewable hydrogen produced via solar- and wind-based electrolysis in many world regions. The report concludes that biomass gasification is an economical and environmentally beneficial technology well suited for producing climate-positive hydrogen. It is highly likely that negative carbon emissions will be essential to reach climate targets and hydrogen produced via biomass gasification is one of few hydrogen production pathways that can result in negative emissions. CH2ES
Design of Ferry Passenger Seats : With a Focus on Ergonomics and Comfort
No full textThis thesis was carried out in collaboration with the startup company Cstrider, with the aimof developing an ergonomic passenger seat adapted for ferry transportation. The project isbased on a user centered design process in which passenger needs were identified throughinterviews and translated into need statements. Based on these needs a target specificationwas established and a concept was developed with a focus on comfort, sustainability andCstriders design language. Currently Cstrider repurposes seats from buses that are no longer in use, the drawback ofthese seats is that they are not suitable for the marine environment. Through benchmarking,ergonomic reference values and user testing a new design proposal has been developed. The final concept is made of the biobased material Papershell featuring a reclined seating positionand has replaceable seat cushions to increase lifespan and flexibility. The result shows how industrial design, engineering and sustainable product development canbe combined to create functional, aesthetically appealing solutions for public transport at sea.Detta examensarbete har genomförts i samarbete med startup företaget Cstrider med syfte attutveckla ett ergonomiskt passagerarsäte anpassat för färjetrafik. Projektet grundar sig i enanvändarcentrerad designprocess där passagerares behov identifierats genom intervjuer ochtolkats till behov formuleringar. Med utgångspunkt i dessa behov har kravspecifikationerupprättats och ett koncept utvecklats med fokus på komfort, hållbarhet och formspråk. Idag återanvänder Cstrider säten från bussar som inte längre är i bruk, nackdelen med dessasäten är att de inte passar in i den marina miljön. Genom benchmarking, ergonomiskariktvärden och användartester har ett nytt designförslag tagits fram. Det färdiga konceptet ärtillverkat i det biobaserade materialet Paper Shell, har en bakåtlutad sittställning samtutbytbara sittdynor för ökad livslängd och flexibilitet. Resultatet visar hur industriell design, teknik och hållbar produktutveckling kan kombinerasför att skapa en funktionell, estetiskt tilltalande och användaranpassad lösning förkollektivtrafik till sjöss
Immobilized ionic liquids/deep eutectic solvents in carbon capture: current progress and future potential
No full textGlobal warming and the urgent need for net-zero emissions have intensified the search for efficient CO2 capture technologies. While the amine-based absorption technology has been widely used for CO2 capture, it faces high energy requirements for regeneration and degradation over time. Ionic liquids (ILs) and deep eutectic solvents (DESs) have emerged as promising alternatives due to their tunable properties and stability, but they also face challenges such as high viscosity and cost. One strategy to address these limitations is immobilizing ILs/DESs on a large surface, which not only reduces the required solvent volume but also enhances mass transfer rates. A variety of porous materials have been utilized for this purpose, including metal–organic frameworks, zeolitic imidazolate frameworks, zeolites, silica-based and carbon-based particles, polymeric particles, Al2O3, etc. However, there is a noticeable gap in comprehensive reviews on consolidating the reported data and analyzing the influence of key parameters, such as surface chemistry, pore size, pore volume, and surface area, on the CO2 capture performance. In this review, a detailed overview of all reported immobilized ILs/DESs composites for CO2 capture is provided, where the data are compiled and analyzed to offer an up-to-date resource for future research. The effects of structural properties and surface chemistry on the CO2 uptake are explored, with an investigation into whether a universal trend exists for enhancing the performance of the ILs/DESs-based composites.Validerad;2025;Nivå 2;2025-11-07 (u8);Full text license: CC BY </p
Från vision till handling : En studie av Luleå kommuns implementeringsprocess av ”Vision 2040” utifrån ett hållbarhetsperspektiv
No full textDenna studie undersöker Luleå kommuns implementeringsprocess av den strategiska planeringen ”Vision 2040” ur ett hållbarhetsperspektiv, med särskilt fokus på närbyråkraters roll. Med utgångspunkt i Lundquists implementeringsteori och Mikael Seväs vidareutveckling av Lipskys teori om närbyråkrati, analyseras hur kommunens tjänstepersoner upplever sin förmåga, vilja och förståelse för att uppnå de nio övergripande målen som visionen omfattar. Studien bygger på fem kvalitativa intervjuer med tjänstepersoner i Luleå kommun. Resultatet visar att det finns en stark förståelse för och vilja att arbeta mot målen, men att brist på resurser, byråkratiska processer och otydliga målformuleringar försvårar implementeringen. Framför allt är det målen kopplade till ekonomisk hållbarhet som förväntas uppnås, medan de sociala och ekologiska målen riskerar att hamna i skymundan. Detta tyder på en prioritering av tillväxt framför en helhetlig hållbar utveckling, vilket även tidigare forskning har pekat på. Studien drar slutsatsen att en lyckad implementering av ”Vision 2040” kräver tydligare styrning, mer resurser samt ökat handlingsutrymme och samordning inom kommunen.This study examines the implementation process of Luleå Municipality’s strategic framework “Vision 2040” through the lens of sustainability, focusing on the role of street-level bureaucrats. Based on Lundquist’s implementation theory and Sevä’s adaptation of Lipsky’s theory on street-level bureaucracy, the research investigates how public servants perceive their ability, willingness, and understanding to achieve the nine overarching goals outlined in the vision. The study is based on five qualitative interviews with key municipal employees. Findings show that while there is a strong understanding of and commitment to the vision among the staff, limited resources, bureaucratic inertia, and vague goal formulations hinder effective implementation. Notably, the goals related to economic sustainability are more likely to be achieved than those concerning social or ecological dimensions. This suggests a prioritization of economic growth over holistic sustainability, in line with previous research on implementation gaps and conflicts between growth and sustainable development. The thesis concludes that successful implementation of “Vision 2040” will require clearer policy guidance, increased resource allocation, and greater autonomy and coordination across municipal departments
Vinterdäcksinducerad kavitation - ett fenomen som bidrar till nedbrytning av våt vägbana
No full textSearch for top squarks in final states with many light-flavor jets and 0, 1, or 2 charged leptons in proton-proton collisions at √s = 13 TeV
No full textSeveral new physics models including versions of supersymmetry (SUSY) characterized by R-parity violation (RPV) or with additional hidden sectors predict the production of events with top quarks, low missing transverse momentum, and many additional quarks or gluons. The results of a search for top squarks decaying to two top quarks and six additional light-flavor quarks or gluons are reported. The search employs a novel machine learning method for background estimation from control samples in data using decorrelated discriminators. The search is performed using events with 0, 1, or 2 electrons or muons in conjunction with at least six jets. No requirement is placed on the magnitude of the missing transverse momentum. The result is based on a sample of proton-proton collisions at √s = 13 TeV corresponding to 138 fb−1 of integrated luminosity collected with the CMS detector at the LHC in 2016–2018. With no statistically significant excess of events observed beyond the expected contributions from the standard model, the data are used to determine upper limits on the top squark pair production cross section in the frameworks of RPV and stealth SUSY. Models with top squark masses less than 700 (930) GeV are excluded at 95% confidence level for RPV (stealth) SUSY scenarios.Godkänd;2025;Nivå 0;2025-11-21 (u2);Full text: CC BY license;For funding information, see: https://doi.org/10.1007/JHEP10(2025)236</p