Silmäile
Hakuohje

Osuva

Osuva on Vaasan yliopiston avoin julkaisuarkisto. Osuva sisältää Vaasan yliopiston omat julkaisut, opinnäytteet ja tieteellisten artikkeleiden rinnakkaistallenteet. Osuvaan sisältyy julkaisujen viitetietoja, tiivistelmiä ja kokotekstejä. Sähköisten arkistokokoelmien sisältö ei ole luettavissa verkossa.

Kokoelmat Osuvassa

Viimeksi tallennetut

  • Attribution of Responsibility for Short-Duration Voltage Variations in Power Distribution Systems via QGIS, OpenDSS, and Python Language
    de Souza, Arthur Gomes; Passatuto, Luiz Arthur Tarralo; Bernardes, Wellington Maycon Santos; Freitas, Luiz Carlos Gomes; Resende, Enio Costa (IEEE, 2025)
    Artikkeli
    Short-Duration Voltage Variations (SDVVs) are phenomena that significantly impact power quality. Although they typically last no longer than three minutes, such events can disrupt load operations and cause substantial production losses. This study presents an enhanced methodology for determining whether an SDVV event originates upstream or downstream of the point of common coupling between two agents interconnected through a transformer. Building upon the work of Ferreira et al., whose original approach was applied to a circuit using MATLAB/Simulink, this research advances the methodology by applying it to both real and benchmark distribution systems using open-source tools, namely QGIS, OpenDSS, and Python™. The well-known IEEE 34-Bus Test System has been used to verify the methodology’s generalizability. The method was also further validated through tests conducted on two actual Brazilian distribution feeders in Uberlândia, Minas Gerais: one supplying large industrial consumers such as a rice mill and a carbonated beverages factory, and the other serving a municipal wastewater treatment plant and a large photovoltaic plant. By using real, detailed and georeferenced data, the approach ensures an accurate representation of both the network topology and the installed equipment. The results confirm that the proposed methodology reliably identifies the origin of SDVV events. A key contribution of this study is that the attribution of responsibility remains robust regardless of variations in transformer winding configurations, fault resistance, circuit topology, load characteristics, or the presence of distributed generation. These findings demonstrate the accessibility, robustness and practical applicability, offering a valuable tool for utilities and researchers aiming to enhance power quality and accountability in distribution networks.
  • A comparative study of the modified high voltage olivine-phosphate LiMPO4 (M = Fe, Mn, Co, Ni) as promising cathode materials for next-generation rechargeable batteries
    Manfo, Theodore Azemtsop; Laaksonen, Hannu (Elsevier, 2026)
    Artikkeli
    The growing demand for energy storage has driven extensive research into advanced cathode materials for lithium-ion batteries (LIBs), where cathode chemistry critically governs safety, cost, and electrochemical performance. Olivine lithium metal phosphates (LiMPO4) are promising cathode candidates due to their structural robustness and thermal stability. Rietveld refinement confirms an orthorhombic olivine structure (Pnma), with lithium occupying octahedral sites and Mn2+ and Co2+ substituting for Fe2+. Cell parameters and unit-cell volume increase with Mn substitution; while LiFePO4 (LFP) exhibits favorable electrochemical stability, LiMnPO4 (LMP) offers higher operating potential but suffers from sluggish lithium intercalation kinetics. Recent studies demonstrate that partial substitution with Co and Ni can significantly enhance electrochemical performance by modifying lithium diffusion pathways and energetics within the olivine framework. This paper summarizes recent progress on olivine cathodes, including LiCoPO4 (LCP) and LiNiPO4 (LNPO), which exhibit operating potentials exceeding 5.0 V versus Li+/Li. Strategies to overcome intrinsic limitations, such as particle size reduction, surface modification, and cation doping, are critically discussed, highlighting clear correlations between structure and electrochemical behavior. Key material descriptors, including cohesive energy, lithium intercalation energetics, and electrochemical stability, are examined. Finally, emerging opportunities and remaining challenges for olivine phosphates in solid-state and aqueous energy storage systems are outlined, providing a forward-looking perspective for next-generation LIB development.
  • Harnessing wind energy: Can it become a strategic driver of national energy security and the global energy transition?
    Balcerzak, Adam P.; Igliński, Bartłomiej; Pietrzak, Michał Bernard; Dutta, Anupam; Uddin, Gazi Salah (Institute of Economic Research, 2026)
    Artikkeli
  • Just-in-Time & Just-in-Case toimintamallien yhdistäminen kokoonpanotuotannossa : Toimintamallien tehokas optimointi kokoonpanotuotannossa
    Mäensivu, Jani (2026-04-08)
    Kandidaatintutkielma
    Tämän tutkielman aiheena on Just-in-Time (JIT) ja Just-in-Case (JIC) -toimintamallien yhdistäminen kokoonpanoteollisuudessa. Työn tarkoituksena on tutkia, miten näiden kahden mallin synergiaa voidaan hyödyntää toimitusketjun hallinnan tehokkuuden ja resilienssin parantamiseksi. Erityistä huomiota kiinnitetään kriittisten komponenttien hallintaan ja toimintamallien strategiseen yhteensovittamiseen, jotka ovat keskeisiä kokoonpanoteollisuuden globaalissa liiketoimintaympäristössä. Tutkielma toteutetaan kirjallisuuskatsauksena, ja tutkimusaineisto koostuu vertaisarvioiduista tieteellisistä artikkeleista, alan julkaisuista ja empiirisistä tapaustutkimuksista. Näitä lähteitä analysoimalla pyritään selvittämään JIT- ja JIC-mallien vahvuudet ja heikkoudet sekä parhaita käytäntöjä niiden yhdistämiseen kokoonpanoteollisuudessa.The subject of this thesis is the integration of Just-in-Time (JIT) and Just-in-Case (JIC) operational models in the assembly industry. The purpose of this study is to examine how the synergy between these two models can be leveraged to improve the efficiency and resilience of supply chain management. Particular attention is paid to the management of critical components and the strategic coordination of operational models, which are central to the global business environment of the assembly industry. The study is conducted as a literature review, and the research material consists of peer-reviewed scientific articles, industry publications, and empirical case studies. By analyzing these sources, the study aims to identify the strengths and weaknesses of the JIT and JIC models, as well as best practices for combining them in the assembly industry.
  • Investigating the association between average hotel prices and international tourism
    Dutta, Anupam (Logos university international, 2024)
    Artikkeli
    Objective: The present study intends to examine the long- and short-run associations between average hotel prices and the international tourism demand in Singapore. Theoretical Framework: Employing Johansen Cointegration method and linear ARDL bound tests, we fail to capture the long-term linkage between average hotel prices and the number of visitors in Singapore. We then consider the application of non-linear ARDL (NARDL) models in order to explore whether the non-existence of the long-run connection is due to the non-linear structure of the variables. Method: We use monthly data which range from January 1995 to December 2022 yielding a total of 336 observations. All the data on average room rate and total tourist arrivals are retrieved from Thomson Reuters DataStream database. The starting period of the data used in our empirical analysis is dictated by data availability. Results and Discussion: The findings reveal that the NARDL model successfully detects the aforesaid association between the variables under consideration. Furthermore, adopting the Toda–Yamamoto test for Granger causality suggests a strong bidirectional short-run connection between these two variables. Research Implications: Policymakers could utilize these outcomes to implement appropriate strategies (e.g., stabilizing the hotel prices, rebranding the country as an attractive destination) for receiving significant attention from international tourists. Originality/Value: Although Singapore has been one of the major destinations for international tourists over the years, assessing the relationship between average hotel prices and the total number tourists visiting Singapore does not receive much attention in earlier studies. This study aims to extend such scarce literature.