Luleå University of Technology Publications
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"Sittplatser, blommor och sånt" : En studie om planering, drift och nyttjande av Luleås parker
No full textParker och grönområden utgör viktiga inslag i städer. De bidrar till rekreation, hälsa, möten och trygghet. Samtidigt finns studier för att kvinnor och män kan uppleva det offentliga rummet i allmänhet, och parker i synnerhet olika - särskilt vad gäller trygghet och användbarhet. Mot denna bakgrund fokuserar studien på att ta reda på hur parker fungerar för olika grupper, och hur planering, utformning och drift samspelar med att främja en jämställd stad. Studien bygger på litteraturstudier, fältstudier och observationer där studiens tre frågeställningar lyder: 1. Vilka förväntningar har parkbesökare i Luleå? 2. Hur används parkerna och av vilka grupper? 3. Vilka utmaningar finns i planering, drift och underhåll ur ett jämställdhetsperspektiv? Studien belyser hur demografi, lokalisering, gångavstånd och målpunkter spelar stor roll för parkens användning, vilket också stärks i tidigare studier. Forskning visar att en park sällan besöks om den upplevs som otrygg, oavsett närhet till hemmet. Det är därför relevant att undersöka hur trygghetsrelaterade kvaliteter – såsom belysning, skötsel och orienterbarhet – samverkar med användningen av parkerna.Studien lyfter fram olika verktyg för att analysera det offentliga rummet. Observationer i fem centrumnära parker i Luleå visar bland annat att användningen varierar betydligt mellan parkerna, och att de parker med flest antal besökare också var de parker med flest antal uppfyllda kriterier enligt checklistan i En plats att leva på – Handbok för samskapande, inkludering och attraktiva livsmiljöer. Intervjuer visar samtidigt att kvinnor och män har liknande förväntningar på parker, samtidigt som begreppet park uppfattas snävare av användare än av forskningen, särskilt vad gäller möjligt nyttjande även på andra månader än under sommarhalvåret. Samtidigt pekar observationer på att parkmiljöer kan nyttjas även vintertid trots att många användare uppger att de inte besöker parker under vintern, vilket väcker frågor om förväntningar kontra faktisk användning och om hur skötsel, tillgänglighet och väder påverkar parkdeltagandet.
Coping, escapism, and fantasy motives and depression symptoms mediate the relationship between emotion dysregulation and gaming disorder
No full textBackground Studies have shown that emotion dysregulation, depression symptoms, and escapism motives are associated with Gaming Disorder (GD) symptoms. Findings indicate a discrepancy between the World Health Organization (WHO) and the American Psychiatric Association (APA) GD symptoms frameworks. Objective The current study aimed to investigate the serial mediating effect of depression symptoms and coping, escapism and fantasy motives on the relationship between emotion dysregulation and GD symptoms and compare the WHO and APA frameworks. Methods Data was collected through an online survey utilizing validated self-reported measures. The final convenience sample consisted of 678 video game players (68.44 % men [n = 464], 29.65 % women [n = 201], and 1.92 % reported ’other’ as gender identification [n = 13]) with an average age of 29.50 years (SD = 8.92). Structural equation modeling (SEM) was used to analyze the mediating effects. Results The results showed that depression symptoms and a composite measure of coping, escapism, and fantasy motivations, in sequence, fully mediated the relationship between emotion dysregulation and GD symptoms within the WHO framework and partially mediated it within the APA framework. Conclusions The results indicate that individuals with emotion dysregulation and higher levels of depression symptoms may use video games as an emotion regulation strategy. Managing emotion dysregulation and coping in the context of video games may aid in the clinical course for gaming disorder and co-occurring depression. Future research should utilize longitudinal designs to investigate study variables.Fulltext license: CC BY,This article has previously appeared as a manuscript in a thesis.</p
Hydrogen embrittlement mitigation by surface modification: A review on current advances and future perspectives
No full textHydrogen is emerging as a sustainable energy source that can reduce fossil fuel reliance and associated environmental impact. However, it poses embrittlement challenges for storage and transport materials that affect the widespread deployment of the hydrogen economy. Surface modification of materials by employing coatings, thermochemical, mechanical treatments, and others modifies surface chemistry, microstructure, stress states, and enhances surface integrity. These surface modification methods form physical or chemical barriers that impede hydrogen permeation and lower hydrogen-induced degradation. Though an unfavorable combination of thermodynamic properties, hydrogen solubility, and hydrogen diffusivity of the modified surfaces promotes hydrogen embrittlement mechanisms. This review focuses on a comprehensive overview of various surface modification techniques applied to base materials to counter their hydrogen embrittlement susceptibility. This work emphasizes the relationship between the surface modification methods and their effects on microstructural and mechanical properties, and their contribution to hydrogen storage and transport solutions. Additionally, limitations, challenges, and research gaps related to these surface modification techniques for materials in hydrogen infrastructure are discussed.Full text: CC BY license;</p
Sliding-speed effects on self-lubricating marine composites: A comparative assessment of tribological, mechanical, and thermal performance
No full textNet-zero by 2050 demands scalable renewables. Ocean wave/tidal energy, though denser than solar and wind, remains at low TRL. A pivotal barrier is the material durability and performance of ocean (hydraulic) rod linear bearings that remain key components of WECs including point absorbers. This study presents a comparative mechanical, thermal, and tribological evaluation of eight commercial and newly developed self-lubricating bearing materials, including thermoplastics, thermosets, elastomers, and a bronze-based alloy, under unlubricated conditions. The materials incorporate diverse reinforcement architectures, including short fibers, woven and continuous fiber fabrics, and solid lubricant particulate fillers. Tribological testing was conducted under an 18 hrs long-duration dry reciprocating pin-on-flat configuration at 0.02–0.1 m/s under 250 N load. Friction behavior, wear rates, and surface degradation were recorded. Post-test analyses using SEM, FTIR, and 3D surface profilometry revealed distinct wear mechanisms and transfer film behavior. Wear maps integrating friction, wear rate, and a normalized multi-parameter performance index reveal sliding-speed-dependent tribological transitions and enable ranking of marine composites. The findings establish a foundational understanding for bearing failure mechanisms, predictive design and material selection in ocean tribological systems.Full text: CC BY license;Funder: Slovenian Research Agency ARIS under the Research Core Funding Programme No. P2–0231; Marie-Sklodowska Curie COFUND - Seal of Excellence No. 5100–237/2023–7;</p
Investigating flexibility contracts in electricity markets considering single-price and 15-minute imbalance settlement
No full textFlexibility Contracts (FlexCons), in the context of power and energy systems, aim to address challenges arising from uncertainties in electricity consumption and variable renewable generation using a bilateral short-term instrument. Through such contracts, electricity retailers (RETs) and variable renewable energy producers (VREPs) agree to provide power flexibility to one another to reduce the impact of imbalances on their respective decision-making processes. In this paper, two four-stage decision-making problems are developed for RETs and VREPs to analyze their participation in FlexCons alongside the day-ahead market (DAM), intraday market (IDM), and balancing market (BLM). The proposed models incorporate uncertainties in market prices, electricity consumption, and renewable generation through scenario sets and a stochastic decision-making approach. Additionally, the framework includes single-price and 15-minute imbalance settlement, as well as location-specific considerations within the system. Subsequently, the outcomes of these decision-making problems are integrated into the market-clearing processes of DAM, IDM, and BLM to assess the positive and negative impacts of such bilateral transactions. A two-bus illustrative example and the IEEE 24-bus RTS system are used for simulations. The results indicate higher profit for FlexCons’ participants by 1.6%, lower flexibility prices in the BLM by 6.8%, and an overall reduction in system costs by 4% when FlexCons are used.Full text license: CC BY</p
Influence of salt on total and dissolved metal treatment in bioretention: A Field study
No full textUrban areas are affected by anthropogenic activities that cause pollutant load on receiving water bodies. Stormwater bioretention are popular and effective in removing pollutants. The main water quality treatment processes are filtration and adsorption in the top layer (0-10 cm) of the filters. So far, few in-field studies have evaluated effects of cold climate and de-icing salt on bioretention for treating metals. Thus, a comprehensive study of total and dissolved metal removal (Cd, Cr, Cu, Ni, Pb and Zn) in a bioretention system for management of road runoff from the European highway E4 was carried out. Three different filter configurations were examined: a sand filter (SF), a vegetated sand filter (BF) and a vegetated sand filter with chalk additive (BFC). The results show a general trend of significant metal removal in all three filters, BFC, BF and SF, both under impact of high (Cl− > 210 mg/l) and low (Cl− ≤ 98.2 mg/l) chloride concentrations. For total metal concentrations, the results show that removal was most efficient in filter BFC, then BF and least efficient in filter SF. For metals such as Cu, Ni and Pb, this may indicate that better removal could be achieved using vegetated filters with chalk additives that affect pH. For dissolved metals, there is a tendence of Cr, Cu, Ni, Pb and Zn removal in filter BFC when lower chloride impact. With higher chlorides concentrations, there tended to be a release of metals from the filters.Full text license: CC BY 4.0;</p
Eco-friendly alcohol-based frothers used in plastic and mineral flotation separation: Performance, recent advances, and future directions
No full textThe role of frothers in flotation separation is pivotal because they generate stable bubbles and facilitate the transport of particles to the froth phase. Owing to increasing environmental concerns about hazardous plastic handling and stricter regulations in the mining industry, there is a growing need for less toxic, more environmentally friendly reagents. Frothers, which are typically synthetic, non-green, and unsustainable chemicals, have historically received less attention than other flotation reagents, including collectors and depressants. This is contrary to their significant role as the most critical reagent in plastic flotation separation. They also have a governing influence on ore separation, significantly affecting froth zone height and durability, consequently impacting selectivity and recovery. Alcohol-based frothers are a well-known group of frothers utilized in froth flotation. They are generally divided into aliphatic, aromatic, and cyclic alcohol categories. Several investigations have reported promising results from using natural and non-hazardous alcohol-based frothers, demonstrating enhanced flotation performance and reduced health risks. This comprehensive review focuses on natural alcohol-based frothers (eucalyptus oil, pine oil, and terpineol alcohol), providing an in-depth analysis of their structure, application, effectiveness in flotation separation, and comparison with conventional hazardous frothers. Despite promising results in flotation using alcohol-based frothers, substantial gaps remain, notably interactions and adsorption mechanisms with the particle surface and other flotation reagents, performance across various flotation systems, industrial scalability, etc. This robust review highlights the existing gaps, identifies challenges, and proposes future research directions to advance the adoption of natural alcohol-based frothers.Full text: CC BY license;</p
Innovative approaches for recycling of DRI fines in modern direct reduction processes
No full textTo maximize resource efficiency in the direct reduction ironmaking process, effectively recirculating DRI fines is essential. These fines, which account for 1–2% by weight of DRI production, are generated during handling, production, and transportation processes. The DRI fines, rich in iron and comprised of finer size fractions, present a significant opportunity for innovation; however, their effective recycling poses challenges without proper agglomeration. Briquetting emerges as a highly promising solution to this challenge. This research explores the application of both organic and inorganic binders in briquetting DRI fines, aiming to unlock their full potential. The H2-based reduction behavior of the resulting briquettes is analyzed, utilizing a reduction process powered by 100% H2. The impact of various binders on critical parameters such as mechanical strength, moisture content, and compaction pressure of the briquettes is explored. The optimized briquettes undergo rigorous hydrogen-based reduction through thermogravimetric analysis (TGA), followed by comprehensive characterization using XRD, and LECO methods. Impact of carbon addition on the mechanical strength of the briquettes was also investigated. Among the various binders tested, the optimal combination for enhancing the mechanical strength of DRI fines briquette was determined to be 2% polyacrylamide binder with 0.2–0.8% sodium silicate. Furthermore, the incorporation of 5% biocarbon into DRI fines effectively maintained mechanical integrity, emphasizing the critical role of binders in producing durable briquettes suitable for industrial processes. This research contributes to advancing sustainable practices in the industry and paves the way for a greener future in iron and steel manufacturing
Agro-food waste upcycling into mycelium insulation: Linking structure with mechanical and fire performance
No full textThis study presents a multiscale investigation of mycelium-based biocomposites produced via solid-state cultivation of Ganoderma lucidum on agro-food sidestreams. Three lignocellulosic residues, wheat bran (in two particle sizes), rice straw, and spent coffee grounds, were selected based on global availability and chemical diversity. The biocomposites were characterized to investigate how substrate composition and mycelial growth influence microstructure and macroscopic performance. Monosaccharide analysis and scanning electron microscopy (SEM) revealed that wheat bran supported enhanced mycelial growth. Fine wheat bran-based composites exhibited compressive strengths up to 449 kPa at 30 % strain and tensile moduli of 15–25 MPa, significantly higher than expanded polystyrene (EPS), a conventional insulator. All biocomposites showed intrinsic surface hydrophobicity (water contact angles of 106–120°). Thermal analyses, including thermogravimetric analysis (TGA) and hot-plate conductivity measurement, confirmed their suitability as porous insulation. Cone calorimetry demonstrated improved fire safety in wheat bran-based composites, with reduced peak heat release rates (112–115 kW/m2). Embodied energy and carbon footprint assessments indicated up to 89 % lower energy demand and 72 % lower CO2 emissions compared with EPS. Through multiscale characterization and direct benchmarking, this study shows how substrate selection and fungal-substrate interactions can be utilized to tailor performance. The findings provide insights into converting low-value biomass into scalable, fire-safer, and environmentally responsible insulation materials.Full text license: CC BY</p
Evaluating environmental effects of zero-discharge events in a regulated river in Northern Sweden using hydraulic modelling
No full textIncreasing periods of zero-discharge and large fluctuations in discharge are expected in future hydropower operations due to changes in the electricity system, including greater reliance on solar and wind power, as well as increased variability in precipitation driven by climate change. In this study, several types of zero-flow periods were analyzed in a regulated northern river in Sweden. The results highlight different mitigation measures that may be suitable for reducing ecological impacts associated with hydropeaking. The study also evaluates potential improvements that could be achieved by implementing a mean annual low flow instead of zero flow. Overall, the findings demonstrate the value of conducting detailed river-specific analyses to identify effective ecological restoration measures in regulated river systems.Full text license: CC BY 4.0;</p