Luleå University of Technology Publications
Not a member yet
39356 research outputs found
Sort by
Assessment of self-reported heart rate-increasing physical activity and perceived stress levels among students at Luleå university of technology : A survey study
No full textBakgrund: Stress är ett växande folkhälsoproblem och förekommer i hög grad bland universitetsstudenter. Tidigare forskning visar att studenter ofta rapporterar högre nivåer av stress, oro och ångest jämfört med jämnåriga yrkesverksamma. Långvarig stress kan ge negativa konsekvenser för både den psykiska och fysiska hälsan. Pulshöjande fysisk aktivitet har visat sig fungera som en skyddsfaktor mot stress. Syfte: Syftet med studien var att undersöka självskattad pulshöjande fysisk aktivitet och upplevd stress hos studenter vid Luleå tekniska universitet (LTU), samt att analysera skillnader avseende kön, ålder och utbildningsår. Metod: Studien var en observationsstudie. Data samlades in genom en egenkonstruerad anonym enkät som besvarades av 84 studenter vid LTU. Enkäten mätte självskattad fysisk aktivitetsnivå, upplevd stress samt hur dessa upplevdes påverka hälsan. Data analyserades genom deskriptiv statistik, Spearmans rangkorrelation och Mann-Whitney U-test. Resultat: Ett svagt men statistiskt signifikant negativt samband identifierades mellan pulshöjande fysisk aktivitet och upplevd stress (rho = −0,23, p <0,05). Inga signifikanta skillnader i stressnivå eller aktivitetsnivå observerades mellan män och kvinnor, och inga signifikanta samband påvisades mellan stress- och aktivitetsnivå i relation till ålder eller utbildningsår. Majoriteten av deltagarna uppgav att fysisk aktivitet förbättrade deras psykiska mående och minskade stressnivån efter träningspass. Konklusion: Resultaten indikerar att regelbunden pulshöjande fysisk aktivitet kan bidra till minskad upplevd stress och förbättrat psykiskt välbefinnande hos universitetsstudenter, även om sambandet är svagt. Fysisk aktivitet bör därför ses som en relevant strategi inom stressförebyggande arbete i studentmiljöer.Background: Stress is a growing public health problem and is highly prevalent among university students. Previous research shows that students often report high levels of stress and anxiety. Prolonged stress can lead to negative consequences for both physical and mental health. Physical activity has been shown to function as a protective factor against stress. Aim: The aim of this study was to investigate self-reported heart rate–increasing physical activity and perceived stress among students at LTU, and analyze differences between gender, age, and year of study. Method: An observational study design was used. Data was collected through a self-developed anonymous questionnaire completed by 84 students. The questionnaire measured selfreported physical activity level, perceived stress, and how these affected the perceived health. Data was analyzed using descriptive statistics, Spearman’s rank correlation, and the Mann– Whitney U test. Results: A weak but statistically significant negative correlation was identified between heart rate– increasing physical activity and perceived stress (rho = −0.23, p < 0.05). No significant differences in stress level or physical activity level were observed between genders, and no significant associations were found between stress or activity in relation to age or year of study. Most participants reported that physical activity improved their psychological health and reduced stress. Conclusion: These results indicate that regular heart rate–increasing physical activity may contribute to reduced stress and improve mental well-being among university students, although the association is weak. Physical activity should be considered a relevant strategy in stresspreventive efforts within university settings
Sustainable Ventures And External Financing:Empirical Insights On The Financing Access Gap
No full textReaching sustainable development is one of the most pressing concerns of our time. From an industry perspective, this calls for a sustainable industrial transformation, including a foundational shift in long-standing practices and social norms that currently set unsustainable industry trajectories. High expectations have redirected the focus to sustainable ventures with the potential to address sustainability challenges as entrepreneurial opportunities while integrating sustainability goals into their core values. These ventures not only have the potential to challenge but also to surpass incumbent firms in contributing to radical innovations and sustainability solutions, positioning them as key catalysts and entrepreneurial pioneers in the forthcoming sustainable industrial transformation. However, a key factor in enabling these ventures to succeed lies in their ability to secure financing to sustain and grow their businesses. Despite the rapid growth of sustainable financial markets and a growing interest among financial actors in leading the industrial transition, the actual financing reaching sustainable ventures remains scarce. Sustainable ventures tend to misalign with current sustainable finance frameworks and deviate from the type of investment that financiers typically prefer. These circumstances represent a critical shortcoming and a significant impediment for sustainable ventures seeking to realize their full potential in generating sustainability impacts. In complement to traditional entrepreneurial finance, which regularly explains financing gaps through agency-based reasoning and information asymmetric problems, this thesis argues for the need to further investigate the social underpinnings of this financing gap, suggesting that current theorizing may not fully explain the financing access gap faced by sustainable ventures. From a socialized perspective, information may not be missing but rather contested. Drawing on the sustainable entrepreneurship and entrepreneurial finance literature, the theoretical framework of this thesis integrates perspectives from organizational identity theory, reference points theory, and the dynamic capabilities view, with the purpose of advancing understanding of access to external financing in sustainable ventures. More specifically, this thesis seeks to understand how sustainable ventures' organizational identity, performance reference points, and dynamic capabilities relate to access to external financing. This thesis adopts a qualitative research approach implemented through a multiple case study strategy. 53 case companies representing finance-seeking sustainable ventures, and their associated financers were selected based on theoretical sampling. Data were mainly collected from 109 semi-structured interviews, supplemented by secondary data. Data were analyzed following a stepwise and iterative coding process to identify emerging codes, themes, and overarching categories, inspired by the method of Gioia et al., (2013). To ensure a comprehensive analysis, the cases were considered holistically rather than in isolation. This thesis integrates the findings of four appended studies into a framework for understanding the finance access gap and the (mis)alignment between sustainable ventures and external financiers in financial exchange situations. As a theoretical lens, organizational identity theory[1] is used to analyse the study’s findings as a coherent set of values (hybrid identity), practices (performance reference points), and routines (dynamic capabilities) that tends to shape the self-defining identity of sustainable ventures and, furthermore, to inform the identity interpretations made by external financiers. The framework reveals an almost dichotomous misalignment between the ventures' self-defining identities and the identity interpretations of private debt and equity financiers. This identity misalignment tends to negatively influence funding decisions, expressed as pending or declined funding. Conversely, the framework identifies a strong identity alignment between the ventures' self-defining identity and the identity interpretations of corporate debt and equity financiers. This alignment thus tends to positively influence funding decisions, leading to pending or accepted funding, although the funding is associated with a significant risk of losing ownership and control. Moreover, the potentially contradictory identity interpretations of financiers tend to trigger critical identity work in sustainable ventures, who seek to balance the financier's conflicting identity expectations and identity change demands while strengthening their self-defining identity, including maintaining sustainability-driven values and aspirations. From a socialized perspective, the sustainability-driven identity of sustainable ventures seem to significantly constrain their access to external financing, primarily because they are interpreted as misaligned with private debt and equity financiers’ perception of a financially viable funding prospect. Furthermore, they are categorized as outside the scope of conventional financing frameworks and practice. Specifically, these financiers expect ventures to display conventional industry practice or "business as usual" to increase fundability. This represents a serious shortcoming because such expectations conflict with the very values, practices, and routines that define the venture's self-defining identity and that are held to be vital to achieve measurable and positive sustainability outcomes beyond the principles of “reducing harm”. This thesis contributes to the emerging literature on sustainable entrepreneurship by proposing a framework for understanding the financing access gap, which seems to prevent sustainable ventures from growing and expanding. Moreover, this thesis contributes to organizational identity theory, reference points theory, and the dynamic capability view by demonstrating how sustainable ventures' hybrid identity, multiple reference points, and sustainability-oriented dynamic capabilities tend to be associated with access to external financing in adverse ways. In addition, the findings carry novel implications for both policy and practice and offer empirical insights that may enhance the development of better metrics and models to support the advancement of sustainable venturing and the leverage of potentially transformative sustainability innovations. [1] (see Albert & Whetten; 1985; Corely et al., 2006; Pratt 2018; Whetten, 2006)
Analysis of RUL dynamics and uncertainty via time transformation
No full textThis work introduces a novel analytical method to analyze the dynamics of remaining useful life (RUL) and quantify uncertainty in its estimation. The approach employs a time transformation that makes the mean residual life (MRL) a linear function of transformed time, enabling the derivation of explicit RUL confidence bounds. Once mapped back to physical space, the bounds quantify aleatoric (stochastic) uncertainty in RUL and yield asymmetrical confidence intervals for both parametric and non-parametric lifetime distributions. The approach leverages a key feature of reliability distributions: the average RUL loss rate, , in transformed time, facilitating a direct derivation of confidence bounds. In parametric cases, is uniquely defined by the reliability distribution parameters, while for non-parametric distributions, it is derived from data by estimating the coefficient of variation. Higher slopes indicate faster degradation, leading to narrower confidence intervals and lower RUL variance. The method’s applicability to stochastic processes and robustness under different data volumes are also investigated and discussed. The novel approach reveals heretofore unknown insights into classical reliability distributions. It is demonstrated through real-world applications, including LED reliability assessment, parallel system RUL estimation, and turbofan lifespan prediction using NASA N-CMAPSS data, offering a new perspective on the evolving dynamics of mean residual life and remaining useful life.Validerad;2025;Nivå 2;2025-10-14 (u4);Full text licens: CC BY</p
Enabling dependable flexibility in industrial automation with formal methods integrated to development toolchains
No full textEnabling dependable flexibility in industrial automation requires architectures that can adapt to evolving system requirements without compromising safety, reliability, or performance. One of the major challenges in this context is balancing dependability with flexibility. As systems evolve, rapid revalidation becomes essential. Automatic testing plays a crucial role in addressing this by enabling quick verification after changes. However, in safety-critical systems, automatic testing alone is insufficient. To ensure correctness and reliability, formal verification techniques are required. Closed-loop verification helps mitigate state-space explosion by integrating plant models with the control logic, allowing for more rigorous analysis. Another key challenge lies in obtaining appropriate models of the physical plant for verification. One practical solution is to leverage existing simulation models, discretize them, and inject non-determinism to represent execution uncertainties. Process mining techniques facilitate the construction of plant models by analyzing event logs from digital twins, providing an accurate representation of system behavior. This approach ensures robust validation, verifying system performance under diverse conditions and operational uncertainties. Within this context, IEC 61499 provides a modular and event-driven framework for designing control systems, enabling distributed control through function blocks (FBs). This architecture enhances reusability, interoperability, and scalability, making it well-suited for cyber-physical automation systems and reconfigurable manufacturing. Blockchain based traceability enhances security and ensures verification in flexible production system. AI-driven automation further optimizes industrial control by enabling intelligent decision-making, real-time adjustments, and process adaptation. AI agents, leveraging large language models (LLMs) and knowledge graphs (KGs), enhance human-machine collaboration by analyzing tasks and executing actions via OPC UA. These agents can interpret operator instructions, generate and validate execution sequences, and ensure conformance with specified requirements to support reliable and adaptive industrial automation.
Low Back Pain in Golfers; A Comparison Between Elite and Amateur Golfers
No full textBakgrund: Ländryggssmärta är ett vanligt problem bland golfare och uppstår ofta till följd av repetitiva, asymmetriska rörelser och hög mekanisk belastning på ryggraden vid golfsvingar. Skillnader i teknik, träningsvolym och biomekaniska mönster gör att elit- och amatörgolfare kan påverkas på olika sätt.Trots omfattande forskning kring golfrelaterade skador finns begränsad kunskap om hur ländryggssmärta skiljer sig mellan elit- och amatörspelare. Syfte: Syftet med studien är att undersöka ländryggssmärta hos golfare samt jämföra skillnader mellan elit- och amatörnivå gällande smärtfrekvens, varaktighet, påverkan på spel och förebyggande åtgärder. Metod: Studien är en kvantitativ tvärsnittsstudie som genomförts med ett webbaserat enkätformulär distribuerat via golfgrupp på Facebook. Enkäten omfattade frågor om duration, intensitet funktionspåverkan och förebyggande insatser. Data analyserades i JASP genom olika tabeller, figurer och jämförelser för att identifiera likheter, skillnader och betydande faktorer. Resultat: Totalt deltog 225 golfare i åldern 18 – 70, varav 10% klassificerades som elitspelare (handikapp ≤ 5, tävlingsaktiv eller PGA-utbildad) och 90% som amatörer. Majoriteten av deltagarna (82 %) hade upplevt ländryggssmärta under det senaste året, utan signifikant skillnad mellan elit- och amatörnivå. Smärtfrekvens och varaktighet var liknande mellan grupperna, där de flesta uppgav att smärtepisoderna varade mindre än en vecka. Elitspelare rapporterade något högre smärtintensitet, men skillnaden var inte statistiskt signifikant. Förebyggande åtgärder som styrketräning, stretching och fysioterapi användes oftare av elitspelare, medan amatörer i större utsträckning avstod från förebyggande insatser. Konklusion: Studien visar att ländryggssmärta är vanligt bland golfare, oavsett spelnivå. Träningsmängd, teknik och belastning kan påverka smärtfrekvensen, vilket understryker behovet av förebyggande insatser genom utbildning, teknikträning och belastningshantering. Background: Low back pain in a common problem among golfers and often occurs as a result of repetitive, asymmetrical movements and high mechanical load on the spine during the golf swing. Difference in technique, training volume, and biomechanical patterns may cause elite and amateur golfers to be affected in different ways. Despite extensive research on golf-related injuries, there is limited knowledge regarding how low back pain differs between these levels. Aim: The aim of this study is to investigate the prevalence of low back pain among golfers and to compare the difference between elite and amateur levels regarding pain frequency, duration, impact on play and preventive measures. Method: The study is a quantitative cross-sectional design conducted through a web-based questionnaire via a Facebook golf group. A total of 225 golfers aged 18 – 70 participated, of which 10% were classified as elite players (handicap ≤ 5, competitive level or PGA-certified) and 90% as amateurs. The questionnaire included items on the pain occurrence, duration, intensity, functional impact and preventive strategies. Data were analyzed using JASP through different tables, figures and comparisons to identify differences, similarities, and meaningful factors. Results: The majority of participants (82%) had experienced low back pain in the past year, with no significant difference between elite and amateur levels. Pain frequency and duration were similar between groups, with most reporting episodes lasting less than a week. Elite players reported slightly higher pain intensity, but the difference was not statistically significant. Preventive measures such as strength training, stretching and physiotherapy were used more frequently by elite players, while amateurs were more likely to refrain from preventive measures. Conclusion: The study shows that low back pain is common among golfers, regardless of playing level. Training volume, technique and load may influence pain frequency, highlighting the importance of prevention through education, technique training, and load management.
Knowledge Distillation in Object Detection: A Survey from CNN to Transformer
No full textDeep learning models, especially for object detection have gained immense popularity in computer vision. These models have demonstrated remarkable accuracy and performance, driving advancements across various applications. However, the high computational complexity and large storage requirements of state-of-the-art object detection models pose significant challenges for deployment on resource-constrained devices like mobile phones and embedded systems. Knowledge Distillation (KD) has emerged as a prominent solution to these challenges, effectively compressing large, complex teacher models into smaller, efficient student models. This technique maintains good accuracy while significantly reducing model size and computational demands, making object detection models more practical for real-world applications. This survey provides a comprehensive review of KD-based object detection models developed in recent years. It offers an in-depth analysis of existing techniques, highlighting their novelty and limitations, and explores future research directions. The survey covers the different distillation algorithms used in object detection. It also examines extended applications of knowledge distillation in object detection, such as improvements for lightweight models, addressing catastrophic forgetting in incremental learning, and enhancing small object detection. Furthermore, the survey also delves into the application of knowledge distillation in other domains such as image classification, semantic segmentation, 3D reconstruction, and document analysis.Full text license: CC BY 4.0;Funder: AIRISE (101092312)</p
Laminated Partially-Composite Plate Theory (LPCPT)—An extension of the classical laminated plate theory for flexible n-layer plates with partial interlayer interaction
No full textThis paper introduces the Laminated Partial-Composite Plate Theory (LPCPT), as an extension of the classical laminated plate theory (CLPT), incorporating the effects of partial-interaction imperfection at the constituting layers’ interfaces. The interlayer interaction effects are modelled through out-of-plane shear stresses based on a shear spring model in terms of the relative displacements/slips at the interfaces. The proposed LPCPT extends a recently developed model for multilayer composite beam/column elements with interlayer partial-interaction imperfection. The model’s governing equations, as well as the extended classical boundary conditions, are formulated. Analytical solution schemes are introduced for free vibrations and buckling of partial-composite plates. The analytical solutions can flexibly capture any number of constituent layers. The validity and high accuracy of the established approach are demonstrated via comparative numerical results based on 3-D finite element analysis (FEA). It is shown how the buckling loads and natural vibration frequencies degrade from those predicted based on CLPT with perfect-bonding ideal assumptions, considering different levels of interlayer interaction. For a special case where the interlayer interaction modulus is set to the equivalent layers’ transverse shear modulus, the results of the present model are shown to match those of thick integrated plates based on higher-order shear deformation theory (HSDT).Full text license: CC BY</p
Tiny Machine Learning (TinyML): Research trends and future application opportunities
No full textTiny Machine Learning (TinyML) enables artificial intelligence on low-power edge devices, yet a quantitative understanding of TinyML research remains limited. This study addresses this gap through a comprehensive bibliometric analysis of 392 peer-reviewed publications (2020–2024) from the Web of Science, using Biblioshiny and VOSviewer. This article contributes by mapping the first bibliometric structure of TinyML, identifying major trends (exponential publication growth, strong international collaboration, core research themes, key contributors, etc.) and proposing future directions (such as sustainable hardware, federated learning, ethical frameworks, etc.). The findings provide a scholarly foundation and strategic roadmap for advancing scalable, energy-efficient, and privacy-preserving TinyML applications.Full text: CC BY license;</p
Magnetic-flotation: a sustainable solution for the flotation recycling of batteries’ blackmass
No full textRising interest in lithium-ion batteries as a key energy-storage option underscores the pressing need to develop recycling approaches that are both environmentally responsible and high-performing, especially for black mass rich in recoverable graphite and cathode active materials (CAMs). Froth flotation is the well-known technique for separating ultrafine CAM particles from graphite. Flotation beneficiation operates on the principle of surface properties, while binders in the batteries complicate the separation process. This study introduces magnetic-assisted flotation (MAGFLO) as a novel and environmentally friendly approach to enhance the flotation-based recycling of blackmass for nickel-manganese-cobalt (NMC) batteries. The MAGFLO leverages CAMs' magnetic susceptibility and hydrophilicity to improve their separation from non-magnetic and hydrophobic graphite, thereby reducing dependence on thermal/chemical surface modifications. The MAGFLO system was implemented as a retrofit setup, and experiments were conducted using an electromagnet with different setups (voltage: 10, 20, or 30) across various flotation cells (steel and stainless-steel) and configurations. Flotation results indicated that the magnetic properties of CAM particles could enhance their separation from graphite. SEM analysis revealed that fine CAM particles adhered to graphite particles, potentially influencing process efficiency. However, particle entrapment could be minimized by using magnetic field pulsation (the “on/off interval” mode of the electromagnet). The steel cell generally showed a higher separation efficiency with over 90 % CAM recovery. Overall, MAGFLO demonstrated strong potential as a sustainable and scalable approach for future industrial recycling applications.Full text license: CC BY 4.0;Funder: Centre of Advanced Mining and Metallurgy (CAMM) and CAMM-CRM</p
Phthalates and pharmaceuticals in soil, groundwater, and surface water downgradient of a wastewater soil infiltration system
No full textThis study investigates the occurrence, attenuation, and ecological risks of phthalates and pharmaceuticals in a long-operating wastewater soil infiltration system in northern Sweden. Concentrations of 15 phthalates, 67 pharmaceuticals, caffeine, and acesulfame K were measured in influent wastewater, groundwater, soil, and a downgradient pond across multiple seasons. Results showed that most micropollutant removal occurred in the unsaturated soil zone prior to groundwater recharge, possibly due to processes such as biodegradation and sorption. Substantial reductions were observed for caffeine (>99 %), carbamazepine (>96 %), losartan (>99 %), and phthalates (51 ± 72 % and 92 ± 5 %), with the higher attenuation for phthalates comparable to conventional activated sludge treatment. In contrast, compounds such as metoprolol exhibited moderate reductions (>71 %), while others showed low or even negative attenuation, including diclofenac (46 % and −180 %) and ibuprofen (33 % and −11 %). After groundwater recharge, only ibuprofen showed attenuation beyond dilution, although the mechanisms for this remains unknown. Several pharmaceuticals, including metoprolol, irbesartan, and metformin, were detected in soil samples, though it is unclear whether they were sorbed to the soil matrix or present in porewater. In downgradient surface water, diclofenac and ibuprofen exceeded risk quotient thresholds, while oxazepam surpassed the lowest predicted no-effect concentration (PNEC) in one sample, indicating ecological risks. Overall, the findings highlight both the strengths and limitations of soil infiltration systems in mitigating micropollutant contamination, emphasizing the importance of vadose zone processes while underscoring uncertainties in sorption and degradation mechanismsFull text: CC BY license;</p