Abstract
Airborne Wind Energy (AWE) systems represent an innovative method for capturing wind energy at high altitudes, where wind conditions are typically stronger and more consistent. These systems utilize flying devices tethered to a ground station to harness wind energy. An AWE system comprises a tether connecting the flying device to a base station, a control system for maneuvering the device, and a mechanism for converting kinetic energy into electricity. Researchers are exploring various materials, designs, and control methods to enhance the efficiency and reliability of AWE systems. Over the past decade, interest in AWE has surged, leading to a substantial increase in scholarly publications on the topic. This research conducts an in-depth bibliometric analysis. This analysis highlights emerging topics, allowing researchers to identify new trends and areas of interest within a field. By emphasizing these emerging topics, researchers and stakeholders can better align their efforts with the latest developments and opportunities in their area of study. Findings reveal that research on control techniques in AWE has grown at an average annual rate of 16% since 2013. Additionally, the study identifies the most influential aspects of the literature, including key topics, articles, authors, and keywords. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.

Abstract

Abstract
The Circular Economy, an alternative to the linear make-use-dispose system, promotes sustainable development through novel business models. Thus, Circular Business Models emerge as systems that minimize resource input and waste by slowing, closing, and narrowing material and energy loops. Circular Startups play a crucial role in the transition to a Circular Economy. Despite their significance, there is a research gap in how these companies scale. Moreover, the slow transition is attributed to the limited scalability of Circular Business Models, which leads to the need to scale current practices. The present study aims to fill this gap by defining a typology of scalability strategies employed by circular startups. A qualitative case studies methodology is adopted, using document analysis and semi-structured interviews conducted in the context of the European project SoTecIn Factory. This research identifies five scalability strategies used by Circular Startups-impact, commercial, ecosystem, institutional and cultural-with the commercial strategy being the main focus in terms of growth approach. The findings underline a strong commitment across the observed value chains to minimize environmental impact, enhance social welfare, and foster economic growth. Other key findings reveal the presence of R-imperatives across different value chains, leading to industry-specific approaches. In addition to the theoretical contribution, this research can support sustainable growth by practitioners in their scaling efforts, thus, accelerating the circular transformation. © 2025 The Authors.

Abstract
The concept of circular economy aims to extend the end-of-life of products by reducing or reusing products and materials, being Design a central part of a successful circular product. In line with the 6Rs strategy for circularity, Redesign (applied by eco-design practices) allows the creation of products that can be easily repaired, upgraded, or disassembled, extending their life, and fomenting a circular economy. For that reason, the aim of this research is to analyse the role of Redesign in the circularity of footwear products. Exploratory qualitative research was conducted, with five in-depth interviews with founders and R&D managers of prominent footwear organizations. Results demonstrate that most interviewed companies, which were born circular, considered Redesign practices from the definition of the product concept. In conclusion, looking at Redesign strategies holistically and through its specific sub-relationships have a major impact on the company's circularity practises.

Abstract
Industry 4.0 is transforming manufacturing environments, with robotics being a key technology that enhances various capabilities. The flexibility of Autonomous Mobile Robots has led to the rise of multi-robot systems in industrial settings. Considering the high cost of these robots, it is essential to determine the best fit of number and type before making any major investments. Simulation and modeling are valuable decision-support tools, allowing the simulation of different setups to address robot fleet sizing issues. This paper introduces a decision-support framework that combines a fleet manager software stack with the FlexSim simulator, helping decision-makers determine the most suitable mobile robots fleet size tailored to their needs. Unlike previous approaches, the developed solution integrates the same real robot coordination software in both simulation and actual deployment, ensuring that tested scenarios accurately reflect real-world conditions. A case study was conducted to evaluate the framework, involving multiple tasks of loading and unloading materials within a warehouse. Five different scenarios with varying fleet sizes were simulated, and their performances assessed. The analysis concluded that, for the case study under consideration, a fleet of three robots was the most suitable, considering relevant key performance indicators. The results confirmed that the developed solution is an effective alternative for addressing the problem and represents a novel technology with no prior state-of-the-art equivalents.

Abstract
Digital Twins are becoming an architectural and functional element in a variety of systems managing physical assets. From complex products to the interconnection of assets in complex processes, digital twins are becoming the overarching cognitive concept that operators interact with to design, manage, control and maintain those products and processes. Despite this evolution, there is still limited knowledge on how to design the human interaction and user experience with digital twin-based systems. In this paper, we review the scarce literature on this subject and identify the high-level requirements for designing user experience for both product and process digital twin-based systems. Finally, we instantiate the requirements for a product-process digital twin-based system, with the focus on circularity and sustainability. © 2025 IEEE.