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Publications

2025

Unlocking the potential of digital twins to achieve sustainability in seaports: the state of practice and future outlook

Authors
Homayouni, SM; de Sousa, JP; Marques, CM;

Publication
WMU JOURNAL OF MARITIME AFFAIRS

Abstract
This paper examines the role of digital twins (DTs) in promoting sustainability within seaport operations and logistics. DTs have emerged as promising tools for enhancing seaport performance. Despite the recognized potential of DTs in seaports, there is a paucity of research on their practical implementation and impact on seaport sustainability. Through a systematic literature review, this study seeks to elucidate how DTs contribute to the sustainability of seaports and to identify future research and practical applications. We reviewed and categorized 68 conceptual and practical digital applications into ten core areas that effectively support economic, social, and environmental objectives in seaports. Furthermore, this paper proposes five preliminary potential applications for DTs where practical implementations are currently lacking. The primary findings indicate that DTs can enhance seaport sustainability by facilitating real-time monitoring and decision-making, improving safety and security, optimizing resource utilization, enhancing collaboration and communication, and supporting the development of the seaport ecosystem. Additionally, this study addresses the challenges associated with DT implementation, including high costs, conflicting stakeholder priorities, data quality and availability, and model validation. The paper concludes with a discussion of the implications for seaport managers and policymakers.

2025

Development of a Variant Process-Planning Tool: A Case Study

Authors
Avila, P; Santos, B; Mota, A; Castro, H; Ferreira, LP; Bastos, J; Sá, JC; Moreira, J; Santos, AD; Santos, G;

Publication
QUALITY INNOVATION PROSPERITY-KVALITA INOVACIA PROSPERITA

Abstract
Purpose: This study addresses the development of a variant process planning tool, following the Knowledge-Based Variant Process Planning methodology, applied in a case study and presents the gains achieved. Methodology/Approach: Case study supported by six steps: (1) Feature Analysis, (2) Knowledge Retrieval, (3) Inference, (4) Plan Adaptation, (5) Knowledge Update, and (6) Plan Validation/Optimisation. Findings: The implementation of the Knowledge-Based Variant Process Planning tool led to significant improvements: planner time reduced by 70%, analyst workload by 90%, and process plan errors to 0%. Results show this approach significantly improves process planning in customised production. Research Limitation/Implication: The limitations are associated with the specificity of the case study problem-the electric engine production systems. Originality/Value of paper: This study helps fill the gap in case studies on the Variant Process Planning approach, specifically for electric engine production systems, paving the way for similar companies to adopt Knowledge-Based Variant Process Planning.

2025

Immersive Editing of 360° Video Experiences

Authors
Matos, T; Esteves, A; Rodrigues, R;

Publication
2025 INTERNATIONAL CONFERENCE ON GRAPHICS AND INTERACTION, ICGI

Abstract
Editing 360 degrees videos remains a challenge in the content creation process of immersive experiences, video editing tools are primarily presented as 2D desktop GUI applications. These interfaces provide limited capabilities for previewing content in a virtual reality (VR) headset or for manipulating the spherical video directly in an intuitive manner. As a result, editors must alternate between editing on the desktop and previewing in the headset, which may be tedious and interrupts the creative process. In this work, we present the conceptualization, implementation, and evaluation of an immersive 3D editor, built as an extension of an existing 2D editor, which allows for 360 degrees editing directly using a VR headset with controllers. The editor provides the main functionalities to create 360 degrees experiences augmented with visual annotations to provide information or guide users' attention during the viewing experience. The immersive editor was evaluated through a user study to assess its usability and intuitiveness. Participants performed several tasks in both the existing 2D editor and the developed immersive editor, and provided feedback on their experience. Results indicate that performing editing tasks in the immersive editor felt overall easier and more intuitive, while also identifying potential changes and improvements to be addressed as future work.

2025

The DDMRP Replenishment Model: An Assessment by Simulation

Authors
Fernandes, NO; Djabi, S; Thürer, M; Avila, P; Ferreira, LP; Carmo-Silva, S;

Publication
MATHEMATICS

Abstract
Demand-Driven Material Requirements Planning (DDMRP) has been proposed as a solution for managing uncertainty and variability in supply chains by combining decoupling, buffer management and demand-driven planning principles. A key element of DDMRP is its inventory replenishment model, which relies on dynamically adjusted inventory buffers rather than fixed stock levels. However, parameterization of these buffers often involves subjective choices, raising concerns about consistency and performance. This paper assesses the DDMRP replenishment model through discrete-event simulation of a multi-echelon, capacity-constrained production system. Two alternative formulations of the safety stock term in the red zone are compared: the original factor-based approach and a revised formula that incorporates measurable variability coefficients. While both safety stock formulations yield similar numerical results, the revised formula enhances transparency and reduces subjectivity. Assessing the impact of introducing a buffer for components in addition to a finished goods buffer further shows that the components buffer can reduce finished goods inventory requirements while maintaining service levels. These findings contribute to a better understanding of the DDMRP replenishment model, offering practical insights for parameter selection and supply chain design.

2025

RepliCo: Remote Collaboration over 3D Content in DeskVR through Miniature Replicas

Authors
Alves, N; Mendes, D; Rodrigues, R;

Publication
2025 INTERNATIONAL CONFERENCE ON GRAPHICS AND INTERACTION, ICGI

Abstract
Virtual Reality (VR) can be an excellent platform for collaborative work. However, standing in VR and gesturing in midair can be physically exhausting. We introduce RepliCo, a collaborative DeskVR approach focused on communication in the context of 3D content reviewing. Using an interactive surface and the world-in-miniature metaphor, it addresses common challenges in virtual collaboration, such as spatially referencing points of interest and user awareness. We conducted a user evaluation with 20 participants to assess the viability of our approach in both a large and a small environment. Results revealed that RepliCo efficiently allowed users to share points of interest in a user-friendly and physically undemanding manner. Although the larger model was identified as requiring more effort, there were few significant differences in task completion times, highlighting RepliCo's versatility.

2025

VR Training and Authoring Tool for Industrial Training Using Virtual Choreographies

Authors
Ferreira, A; Cassola, F;

Publication
Proceedings - 2025 IEEE International Symposium on Emerging Metaverse, ISEMV 2025

Abstract
Virtual Reality (VR) is a powerful tool for industrial training due to its capacity to simulate realistic, risk-free environments. However, creating VR training scenarios often requires significant technical expertise and large investments, limiting the technology's adoption. This paper presents a VR training platform that empowers trainers to author, test, and deliver immersive training procedures directly within a VR environment without writing code. It also gives trainees a place to practice and learn without consequences. A key feature is the integration of Virtual Choreographies, enabling trainers to define ordered procedures, record trainee attempts, more easily understand their actions, and automatically assess performance. A user study was conducted to evaluate usability, workflow clarity, and feature effectiveness. Results indicate strong usability and comprehension for non-expert users, and confirm the potential of Virtual Choreographies to guide and evaluate procedural training. The platform represents a step toward creating accessible, customizable VR training for industrial and educational settings. © 2025 IEEE.

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