Digitala Vetenskapliga Arkivet - Academic Archive On-line
Not a member yet
734120 research outputs found
Sort by
Mot cirkulär ekonomi för rymd: Satellitåteranvändningens roll
No full textDriven by innovation and cost reductions, the space industry is experiencing rapid growth. The proliferation of human-made objects launched into Earth orbits presents significant environmental challenges. If not properly addressed, continued growth at the current rate could lead to negative impacts both in space and on Earth. The space industry has begun exploring sustainable practices, though most efforts focus on addressing issues that are related to the space environment. This neglects the impact on Earth and its atmosphere. Progress has been made in reuse of rocket bodies, however the benefits of satellite reuse remain largely disregarded. For example, the environmental impact of satellite constellations that are currently designed with large amounts of single use satellites, is still underexplored. This underscores the critical research gap in understanding the fast-growing space industry’s impact on the environment and advancing knowledge related to satellite reuse. Therefore, the objective of this thesis is to explore satellite reuse and its contribution to space sustainability. The research starts by exploring how the fast-growing space industry impacts the environment and then examines if satellite reuse could help mitigate this impact. It ends with asking why satellite reuse is not yet widespread. The research in this thesis employs a mixed-method approach, starting with industry expert interviews to gain insight into the current state of practice for satellite reuse. Building upon these interviews, two scoping studies were conducted to further the understanding on how satellite reuse could be achieved. The findings emphasize the importance for the space industry to initiate an industrial transformation and develop sustainability-driven innovation rather than having a focus on mostly commercial gains. The absence of necessary practices and technologies for satellite reuse have been identified in three critical building blocks: (1) reverse logistics systems to retrieve and process satellites for reuse, (2) design practices that enable reuse, and (3) business models that ensure financial viability. Focusing on these three areas can advance sustainable practices in the space industry and could contribute to the mitigation of its negative environmental impact. The presented findings can provide valuable insights for policymakers and industry stakeholders, to rethink practices and to prioritize sustainability in space activities.Drivet av innovation och minskade kostnader upplever rymdindustrin en snabb tillväxt. Den ökande spridningen av mänskligt skapade objekt i omloppsbanor runt jorden medför betydande miljöutmaningar. Om detta inte hanteras kan den fortsatta tillväxten medföra betydande negativ miljöpåverkan, både i rymden och på jorden. Rymdindustrin har börjat arbeta med hållbarhet, men mestadels fokuseras frågor kopplade till rymdmiljön. Det innebär att miljömässig påverkan på jorden och atmosfären i stort sett bortses ifrån. Framsteg har gjorts inom återanvändning av raketdelar, men fördelarna med att återanvända satelliter har till stor del ignorerats. Exempelvis är miljöpåverkan från satellitkonstellationer, som idag ofta designas med stora mängder engångssatelliter, fortfarande ett relativt outforskat område. Detta framhäver ett kritiskt forskningsgap: en brist på förståelse för hur den snabbt växande rymdindustrin påverkar miljön och ett behov av fördjupad kunskap om återanvändning av satelliter. Syftet med denna avhandling är att utforska hur satellitåteranvändning kan bidra till rymdhållbarhet. Forskningen inleds med en undersökning av hur rymdindustrins tillväxt påverkar miljön och huruvida satellitåteranvändning kan mildra denna påverkan. Den avslutas med att undersöka varför återanvändning av satelliter ännu inte är utbrett.Studien använder en blandad forskningsmetodik, och inleddes med intervjuer av industriexperter för att få inblick om nuläget för satellitåteranvändning. Baserat på dessa intervjuer genomfördes två förstudier för att ytterligare förstå hur återanvändning av satelliter kan möjliggöras. Resultaten betonar vikten av att rymdindustrin genomgår en industriell omvandling och utvecklar hållbarhetsdriven innovation, i stället för att enbart fokusera på kommersiella mål. Tre viktiga områden identifierades som avgörande för att möjliggöra återanvändning av satelliter: (1) returlogistiksystem för att samla in och bearbeta satelliter för återanvändning, (2) designpraktik som möjliggör återanvändning, och (3) affärsmodeller som säkerställer ekonomisk bärkraft. Genom att prioritera dessa områden kan rymdindustrin främja hållbara metoder och minska sin miljöpåverkan. Resultaten kan ge värdefulla insikter för beslutsfattare och industrins aktörer, med möjlighet att förändra praxis och prioritera hållbarhet i rymdaktiviteter
Expression optimization in Pichia pastoris with Signal Peptide Shuffling and characterization of putative oxygenases and glucose oxidase
No full textOre extensions of abelian groups with operators
No full textGiven a set A and an abelian group B with operators in A, in the sense of Krull and Noether, we introduce the Ore group extension B[x; σB, δB] as the additive group B[x], with A[x] as a set of operators. Here, the action of A[x] on B[x] is defined by mimicking the multiplication used in the classical case where A and B are the same ring. We derive generalizations of Vandermonde’s and Leibniz’s identities for this construction, and they are then used to establish associativity criteria. Additionally, we prove a version of Hilbert’s basis the oremfor this structure, under the assumption that the action of A on B is what we call weakly s-unital. Finally, we apply these results to the case where B is a left module over a ring A, and specifically to the case where A and B coincide with a non-associative ring which is left distributive but not necessarily right distributive.CC BY 4.0</p
Socialization, citizenship and the electoral integration of refugees: evidence from Sweden
No full textThis article seeks to fill a research gap by analysing refugees’ voting behavior, using Sweden (known for high refugee immigration, relatively liberal enfranchisement rules, and comprehensive electoral data) as a case study. Relying on register data on turnout from Swedish municipal elections, the article sheds new light on how the political integration of refugees varies. We test theories of resocialization and examine the extent to which a refugee’s political integration is affected by the surrounding environment, focusing on the political culture of the areas surrounding their neighborhoods. The results show that two major factors strongly affect refugee turnout rates: the acquisition of citizenship, and the degree of diversity of nationality in the districts in which refugees live, based on different experiences of “bonding” and “bridging” with the surrounding environment
To own or share e-scooters? : Factors in ownership and sharing of e-scooters
No full textThis paper aims to determine how consumer innovativeness, susceptibility to interpersonal influence, personal norms, and innovation attribute perceptions affect the consumer decision to use, share, and own an e-scooter. The decision to use encompasses traveling using an e-scooter, sharing means using an e-scooter on a demand basis, and owning means buying an e-scooter for personal use. Consequently, this paper contributes to understanding novel mobility modes that aim to decrease the environmental problems in transport. It also develops knowledge about green innovations that could be perceived as causing more environmental problems than their traditional counterparts. A survey was conducted in Sweden with 1002 participants, who were non-users, owners, and sharers of e-scooters. Structural equation modelling showed that susceptibility to interpersonal influence and perceived safety attributes of e-scooters consistently positively influence decisions to use and own. This paper increases the understanding of factors influencing e-scooter use, sharing, and ownership, which is valuable for e-scooter businesses and service providers, transport agencies, and policy-maker
Boundedness of weak solutions to degenerate Kolmogorov equations of hypoelliptic type in bounded domains
No full textWe establish the boundedness of weak subsolutions for a class of degenerate Kolmogorov equations of the hypoelliptic type, compatible with a homogeneous Lie group structure, within bounded product domains using the De Giorgi iteration. We employ the renormalization formula to handle boundary values and provide energy estimates. An – type embedding estimate derived from the fundamental solution is utilized to incorporate lower-order divergence terms. This work naturally extends the boundedness theory for uniformly parabolic equations, with matching exponents for the coefficients
From text to meaning : Semantic interpretation of non-standardized metadata in piping and instrumentation diagrams
No full textThe extraction of structured metadata from Piping and Instrumentation Diagrams (P&IDs) is a major bottleneck for digitalization in the process industries. Existing methods, based on Optical Character Recognition (OCR), stop at raw text extraction, failing to interpret critical engineering information encoded within variable-format identifiers like pipeline numbers. This paper bridges this semantic gap by introducing a system for the format-aware interpretation of P&ID pipeline metadata. Our hybrid system architecture integrates deep learning for text recognition with domain interpretation rules that allow the system to adapt to new project formats without model retraining. These rules perform validation, error correction, and semantic mapping of raw text to structured data. We validated our system on a challenging dataset of real-world P&IDs from four distinct industrial projects, each with a unique and complex pipeline number format. Our method achieved 91.1% end-to-end accuracy, demonstrating a significant leap in performance over standard OCR tools, which proved insufficient for the task. This work presents a robust solution that unlocks valuable data from non-standardized engineering documents, providing a practical pathway for creating reliable digital twins and supporting plant lifecycle management in the chemical engineering sector
Modeling System Dynamics in Computational Thinking Integration Using Causal Loop Diagrams
No full textSystem dynamics provides a valuable framework for analyzing the complexities of a system over time. Using causal loop diagrams (CLDs), this study identifies two feedback mechanisms in the context of integrating computational thinking (CT) into education, focusing on leverage points such as coding-centric curricula and teacher competence development. The modeling shows how reinforcing and balancing feedback loops shape system behavior, demonstrating that interventions like coding-based approaches can deliver immediate benefits but risk hindering the long-term development of broader CT skills applicable to interdisciplinary problem-solving. The study enhances the analysis by uncovering patterns emerging from system dynamics, including the constraints limiting growth, reliance on symptomatic solutions, unintended consequences of quick fixes, and the prioritization of successful areas at the expense of others. These patterns highlight the importance of addressing foundational issues, such as teacher training and comprehensive curriculum design, to avoid overshadowing other critical goals of CT applications in interdisciplinary fields. By synthesizing CLDs, the study showcases the circular interactions between variables and the diverse dynamics influencing CT education, offering insights into potential scenarios and storylines for integrating CT into education systems
Numerical assessment of the high cycle fatigue behavior of high strength steels affected by shear-cutting operations
No full textShear-cutting processes are arguably among the most preferred technologies for performing material removal operations in the manufacturing of chassis components due to the combination of high production rate and cost-efficiency. Nevertheless, they may severely jeopardize the fatigue response of high strength metals, compromising the current trend of using this class of materials for weight reduction of automotive chassis parts. Thus, the generation of reliable data featuring the influence of these operations on the material fatigue behavior is essential to further support this lightweighting tendency. Commonly employed for this aim, traditional fatigue tests are usually time-consuming and rather expensive. In this context, numerical simulations arise as a viable alternative, providing not only material-related information but also assisting engineers in the design of new components. In this work, an isotropic damage-based high cycle fatigue model is employed to estimate the fatigue life of trimmed and punched specimens of two complex phase steels. The residual stresses obtained from each process simulation and the roughness measured on the cut surface are included in the model to account for the influence of these operations on the material fatigue strength. Furthermore, standard uniaxial tensile properties and S–N data resulting from fatigue tests on as-polished specimens are the only material information required. A good agreement is found between the numerical fatigue life predictions and the experimental measurements, remaining below an error factor of three for all the estimated cases. In addition to coupon specimens, the model is also readily extensible to component-level applications, enabling the fatigue assessment of metallic engineering structures featuring shear-cut surfaces.Validerad;2025;Nivå 2;2025-08-19 (u0);Full text license: CC BY</p
Designwise: Design principles for multimodal interfaces with augmented reality in internet of things-enabled smart regions
No full textTechnological developments, such as mobile augmented reality (MAR) and Internet of Things (IoT) devices, have expanded available data and interaction modalities for mobile applications. This development enables intuitive data presentation and provides real-time insights into the user’s context. Due to the proliferation of available IoT data sources, user interfaces (UIs) have become complex and diversified, while mobile devices have limited screen spaces. This state increases the necessity of design principles that help to secure sufficient user experience (UX). We found that studies of design principles for IoT-enabled MAR applications are limited. Therefore, we conducted a systematic literature review to identify existing design principles applicable to IoT-enabled MAR applications. From the state-of-the-art research, we compiled and categorized 26 existing design principles into seven categories. We analyzed the UIs of three IoT-enabled MAR applications with the identified design principles and user feedback gathered from each application’s evaluation to understand what design principles can be considered in designing these applications. Among the 26 principles, we find eight principles that are commonly identified as possible improvements for the applications based on their purposes. We demonstrate the practical use of the identified principles by redesigning the UIs, and we propose five new design principles derived from the application analysis. As a result, we summarized a total of 31 design principles, including the five new ones. We expect that our findings will give insight into the UX/UI design of IoT-enabled MAR applications for researchers, educators, and practitioners interested in UX/UI development.Validerad;2025;Nivå 2;2025-11-25 (u4);Funder: Korea Ministry of Science; ICT;Fulltext license: CC BY</p