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Search Results (187)

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Keywords = shape of the supply current

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36 pages, 856 KiB  
Systematic Review
Is Blockchain the Future of AI Alignment? Developing a Framework and a Research Agenda Based on a Systematic Literature Review
by Alexander Neulinger, Lukas Sparer, Maryam Roshanaei, Dragutin Ostojić, Jainil Kakka and Dušan Ramljak
J. Cybersecur. Priv. 2025, 5(3), 50; https://doi.org/10.3390/jcp5030050 - 29 Jul 2025
Viewed by 381
Abstract
Artificial intelligence (AI) agents are increasingly shaping vital sectors of society, including healthcare, education, supply chains, and finance. As their influence grows, AI alignment research plays a pivotal role in ensuring these systems are trustworthy, transparent, and aligned with human values. Leveraging blockchain [...] Read more.
Artificial intelligence (AI) agents are increasingly shaping vital sectors of society, including healthcare, education, supply chains, and finance. As their influence grows, AI alignment research plays a pivotal role in ensuring these systems are trustworthy, transparent, and aligned with human values. Leveraging blockchain technology, proven over the past decade in enabling transparent, tamper-resistant distributed systems, offers significant potential to strengthen AI alignment. However, despite its potential, the current AI alignment literature has yet to systematically explore the effectiveness of blockchain in facilitating secure and ethical behavior in AI agents. While existing systematic literature reviews (SLRs) in AI alignment address various aspects of AI safety and AI alignment, this SLR specifically examines the gap at the intersection of AI alignment, blockchain, and ethics. To address this gap, this SLR explores how blockchain technology can overcome the limitations of existing AI alignment approaches. We searched for studies containing keywords from AI, blockchain, and ethics domains in the Scopus database, identifying 7110 initial records on 28 May 2024. We excluded studies which did not answer our research questions and did not discuss the thematic intersection between AI, blockchain, and ethics to a sufficient extent. The quality of the selected studies was assessed on the basis of their methodology, clarity, completeness, and transparency, resulting in a final number of 46 included studies, the majority of which were journal articles. Results were synthesized through quantitative topic analysis and qualitative analysis to identify key themes and patterns. The contributions of this paper include the following: (i) presentation of the results of an SLR conducted to identify, extract, evaluate, and synthesize studies on the symbiosis of AI alignment, blockchain, and ethics; (ii) summary and categorization of the existing benefits and challenges in incorporating blockchain for AI alignment within the context of ethics; (iii) development of a framework that will facilitate new research activities; and (iv) establishment of the state of evidence with in-depth assessment. The proposed blockchain-based AI alignment framework in this study demonstrates that integrating blockchain with AI alignment can substantially enhance robustness, promote public trust, and facilitate ethical compliance in AI systems. Full article
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11 pages, 2924 KiB  
Article
Liquid Resistive Switching Devices with Printable Electrodes
by Viet Cuong Nguyen
Micromachines 2025, 16(8), 863; https://doi.org/10.3390/mi16080863 - 26 Jul 2025
Viewed by 207
Abstract
In this work, research on liquid-based resistive switching devices is carried out, using bottom printable electrodes fabricated from Silver (Ag) paste and silver nitrate (AgNO3) solution. The self-crossing I-V curves are observed and repeatedly shown by applying 100 sweep cycles, demonstrating [...] Read more.
In this work, research on liquid-based resistive switching devices is carried out, using bottom printable electrodes fabricated from Silver (Ag) paste and silver nitrate (AgNO3) solution. The self-crossing I-V curves are observed and repeatedly shown by applying 100 sweep cycles, demonstrating repeatability and stability. This liquid device can be refreshed by adding extra droplets of AgNO3 so that self-crossing I-V hysteresis with up to 493 dual sweeps can be obtained. The ability to be refreshed by supplying a new liquid solution demonstrates an advantage of liquid-based memristive devices, in comparison to their solid counterparts, where the switching layer is fixed after fabrication. The switching mechanism is attributed to Ag migration in the liquid, which narrows the gap between electrodes, giving rise to the observed phenomenon. The devices further show some synaptic properties including excitatory post-synaptic current (EPSC) and potentiation-depression, presenting opportunities to utilize the devices in mimicking some functions of biological neurons. The simplicity and cost-effectiveness of these devices may advance research into fluidic memristors, in which devices with versatile forms and shapes could be fabricated. Full article
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27 pages, 516 KiB  
Article
How Does Migrant Workers’ Return Affect Land Transfer Prices? An Investigation Based on Factor Supply–Demand Theory
by Mengfei Gao, Rui Pan and Yueqing Ji
Land 2025, 14(8), 1528; https://doi.org/10.3390/land14081528 - 24 Jul 2025
Viewed by 248
Abstract
Given the significant shifts in rural labor mobility patterns and their continuous influence on the transformation of the land factor market, it is crucial to understand the relationship between labor factor prices and land factor prices. This understanding is essential to keep land [...] Read more.
Given the significant shifts in rural labor mobility patterns and their continuous influence on the transformation of the land factor market, it is crucial to understand the relationship between labor factor prices and land factor prices. This understanding is essential to keep land factor prices within a reasonable range. This study establishes a theoretical framework to investigate how migrant workers’ return shapes land price formation mechanisms. Using 2023 micro-level survey data from eight counties in Jiangsu Province, China, this study empirically examines how migrant workers’ return affects land transfer prices and its underlying mechanisms through OLS regression and instrumental variable approaches. The findings show that under the current pattern of labor mobility, the outflow factor alone is no longer sufficient to exert substantial downward pressure on land transfer prices. Instead, the localized return of labor has emerged as a key driver behind the rise in land transfer prices. This upward mechanism is primarily realized through the following pathways. First, factor substitution effect: this effect lowers labor prices and increases the relative marginal output value of land factors. Second, supply–demand effect: migrant workers’ return simultaneously increases land demand and reduces supply, intensifying market shortages and driving up transfer prices. Lastly, the results demonstrate that enhancing the stability of land tenure security or increasing local non-agricultural employment opportunities can mitigate the effect of rising land transfer prices caused by the migrant workers’ return. According to the study’s findings, stabilizing land factor prices depends on full non-agricultural employment for migrant workers. This underscores the significance of policies that encourage employment for returning rural labor. Full article
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17 pages, 4255 KiB  
Article
Exploring the Global and Regional Factors Influencing the Density of Trachurus japonicus in the South China Sea
by Mingshuai Sun, Yaquan Li, Zuozhi Chen, Youwei Xu, Yutao Yang, Yan Zhang, Yalan Peng and Haoda Zhou
Biology 2025, 14(7), 895; https://doi.org/10.3390/biology14070895 - 21 Jul 2025
Viewed by 200
Abstract
In this cross-disciplinary investigation, we uncover a suite of previously unexamined factors and their intricate interplay that hold causal relationships with the distribution of Trachurus japonicus in the northern reaches of the South China Sea, thereby extending the existing research paradigms. Leveraging advanced [...] Read more.
In this cross-disciplinary investigation, we uncover a suite of previously unexamined factors and their intricate interplay that hold causal relationships with the distribution of Trachurus japonicus in the northern reaches of the South China Sea, thereby extending the existing research paradigms. Leveraging advanced machine learning algorithms and causal inference, our robust experimental design uncovered nine key global and regional factors affecting the distribution of T. japonicus density. A robust experimental design identified nine key factors significantly influencing this density: mean sea-level pressure (msl-0, msl-4), surface pressure (sp-0, sp-4), Summit ozone concentration (Ozone_sum), F10.7 solar flux index (F10.7_index), nitrate concentration at 20 m depth (N3M20), sonar-detected effective vertical range beneath the surface (Height), and survey month (Month). Crucially, stable causal relationships were identified among Ozone_sum, F10.7_index, Height, and N3M20. Variations in Ozone_sum likely impact surface UV radiation levels, influencing plankton dynamics (a primary food source) and potentially larval/juvenile fish survival. The F10.7_index, reflecting solar activity, may affect geomagnetic fields, potentially influencing the migration and orientation behavior of T. japonicus. N3M20 directly modulates primary productivity by limiting phytoplankton growth, thereby shaping the availability and distribution of prey organisms throughout the food web. Height defines the vertical habitat range acoustically detectable, intrinsically linking directly to the vertical distribution and availability of the fish stock itself. Surface pressures (msl-0/sp-0) and their lagged effects (msl-4/sp-4) significantly influence sea surface temperature profiles, ocean currents, and stratification, all critical determinants of suitable habitats and prey aggregation. The strong influence of Month predominantly reflects seasonal changes in water temperature, reproductive cycles, and associated shifts in nutrient supply and plankton blooms. Rigorous robustness checks (Data Subset and Random Common Cause Refutation) confirmed the reliability and consistency of these causal findings. This elucidation of the distinct biological and physical pathways linking these diverse factors leading to T. japonicus density provides a significantly improved foundation for predicting distribution patterns globally and offers concrete scientific insights for sustainable fishery management strategies. Full article
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27 pages, 2692 KiB  
Article
Spatiotemporal Evolution Characteristics of Green Logistics Level: Evidence from 51 Countries
by Song Wang, Xiaowan Liu and Yige Liu
Sustainability 2025, 17(14), 6418; https://doi.org/10.3390/su17146418 - 14 Jul 2025
Viewed by 352
Abstract
With the current acceleration of climate change, there is a global demand for sustainable development and carbon emission reduction. As a major link in the global supply chain, the logistics industry’s green and low-carbon transformation has become a critical breakthrough in achieving the [...] Read more.
With the current acceleration of climate change, there is a global demand for sustainable development and carbon emission reduction. As a major link in the global supply chain, the logistics industry’s green and low-carbon transformation has become a critical breakthrough in achieving the objective of reducing carbon emissions. This study develops a multidimensional assessment index method for the green logistics level. The study selects 51 major economies worldwide from 2000 to 2022 as research subjects. The cloud model–entropy value–TOPSIS method is applied to measure the green logistics level. The results of the green logistics level are analyzed from the perspectives of developed and developing countries, and their spatiotemporal evolution characteristics are explored. The study shows that (1) the green logistics level in developed countries is relatively high, mainly due to policy-driven, core technology advantages. However, they continue to encounter issues, such as regional imbalance and excessive green costs. (2) The green logistics level in developing countries is in the middle to lower level, limited by technological dependence, outdated infrastructure, and so on. They are generally caught in a “high-carbon lock-in” situation. (3) From the perspective of time, the global level of green logistics shows a rising trend year by year. The peak of the kernel density curve of the green logistics level is characterized by an “I” shape. There is a significant disparity in each country’s green logistics level, although it is narrowing every year. (4) From the spatial perspective, the green logistics level in each country shows a rising trend year by year vertically, while the horizontal disparity between countries is enormous. The development of the green logistics level between continents is unbalanced. The study presents several recommendations, including boosting technology transfer, giving financial support, strengthening international cooperation, and developing green infrastructure, to promote the global logistics industry’s green and low-carbon transformation to accomplish sustainable development goals. Full article
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28 pages, 6036 KiB  
Article
Supply–Demand Assessment of Cultural Ecosystem Services in Urban Parks of Plateau River Valley City: A Case Study of Lhasa
by Shouhang Zhao, Yuqi Li, Ziqian Nie and Yunyuan Li
Land 2025, 14(6), 1301; https://doi.org/10.3390/land14061301 - 18 Jun 2025
Viewed by 512
Abstract
Cultural ecosystem services (CES) in urban parks, as a vital component of urban ecosystem services (ES), are increasingly recognized as an important tool for advancing urban sustainability and implementing nature-based solutions (NbS). The supply–demand relationship of CES in urban parks is strongly shaped [...] Read more.
Cultural ecosystem services (CES) in urban parks, as a vital component of urban ecosystem services (ES), are increasingly recognized as an important tool for advancing urban sustainability and implementing nature-based solutions (NbS). The supply–demand relationship of CES in urban parks is strongly shaped by sociocultural and spatial geographic factors, playing a crucial role in optimizing urban landscape structures and enhancing residents’ well-being. However, current research generally lacks adaptive evaluation frameworks and quantitative methods, particularly for cities with significant spatial and cultural diversity. To address this gap, this study examines the central district of Lhasa as a case study to develop a CES supply–demand evaluation framework suitable for plateau river valley cities. The study adopts the spatial integration analysis method to establish an indicator system centered on “recreational potential–recreational opportunities” and “social needs–material needs,” mapping the spatial distribution and matching characteristics of supply and demand at the community scale. The results reveal that: (1) in terms of supply–demand balance, 25.67% of communities experience undersupply, predominantly in the old city cluster, while 16.22% experience oversupply, mainly in key development zones, indicating a notable supply–demand imbalance; (2) in terms of supply–demand coupling coordination, 55.11% and 38.14% of communities are in declining and transitional stages, respectively. These communities are primarily distributed in near-mountainous and peripheral urban areas. Based on these findings, four urban landscape optimization strategies are proposed: culturally driven urban park development, demand-oriented park planning, expanding countryside parks along mountain ridges, and revitalizing existing parks. These results provide theoretical support and decision-making guidance for optimizing urban park green space systems in plateau river valley cities. Full article
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17 pages, 1253 KiB  
Article
The Intangible Value of Brisbane’s Urban Megaprojects: A Property Market Analysis
by Maximilian Neuger and Connie Susilawati
Buildings 2025, 15(12), 2011; https://doi.org/10.3390/buildings15122011 - 11 Jun 2025
Viewed by 426
Abstract
This study investigated the intangible value transferred from urban megaprojects to surrounding residential property markets, focusing on Brisbane’s transformative urban regeneration projects currently in the development pipeline. The research objectives were twofold: first, to empirically investigate the dynamics of property markets influenced by [...] Read more.
This study investigated the intangible value transferred from urban megaprojects to surrounding residential property markets, focusing on Brisbane’s transformative urban regeneration projects currently in the development pipeline. The research objectives were twofold: first, to empirically investigate the dynamics of property markets influenced by urban megaprojects and second, to assess the impact of a specific case study on these markets through a longitudinal analysis of residential sales data. Drawing from environmental economics, the concept of willingness to pay (WTP) is used to quantify externalities associated with urban megaprojects. The research constructs a comprehensive dataset integrating geospatial and property-specific data. Through revealed preference methods, the intangible value transferred from mixed-use developments is identified and quantified via residential transaction prices. Utilising hedonic price modelling, this study systematically analysed residential transaction data to estimate implicit prices associated with spatial proximity to megaprojects. A comprehensive dataset integrating property-specific attributes, geospatial proximity measures, and temporal dynamics of project development phases underpins this analysis. This research and its findings advance the existing literature in several important dimensions. That is, this research represents the first microeconomic assessment of the property market’s impacts resulting from mixed-use megaprojects in Brisbane, offering novel empirical insights for both academic and practical applications, how urban megaprojects shape residential property values, and informing stakeholders involved in urban planning, policymaking, and real estate investment decisions. Practitioners and policymakers can leverage these insights to inform policy frameworks and strategic decisions. At the governmental level, the results offer applicable insights for urban revitalisation strategies, particularly relevant to central business districts undergoing similar developments. Private sector stakeholders can utilise these outcomes to anticipate market adjustments, managing supply and demand fluctuations more effectively. Full article
(This article belongs to the Section Architectural Design, Urban Science, and Real Estate)
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24 pages, 5757 KiB  
Article
Mapping Urban Divides: Analyzing Residential Segregation and Housing Types in a Medium-Sized Romanian City
by Cristiana Vîlcea and Liliana Popescu
ISPRS Int. J. Geo-Inf. 2025, 14(5), 203; https://doi.org/10.3390/ijgi14050203 - 17 May 2025
Viewed by 1101
Abstract
This study investigates residential segregation and housing types in Craiova, Romania, with a particular focus on the disparities shaped by historical and contemporary urban developments. Using collected data from former hostels built for young workers during the communist era, this research maps and [...] Read more.
This study investigates residential segregation and housing types in Craiova, Romania, with a particular focus on the disparities shaped by historical and contemporary urban developments. Using collected data from former hostels built for young workers during the communist era, this research maps and analyzes the spatial distribution and living conditions of these housing types at a neighborhood level. Key metrics such as the number of inhabitants, the surface area of rooms, the current occupancy rates, and the number of unoccupied rooms were collected. Additionally, residential segregation is measured using indices of dissimilarity, isolation, exposure, concentration, and centralization, providing a comprehensive view of the socio-spatial divides within the city. The findings indicate significant disparities between these buildings with unsuitable living conditions and the newer residential developments, revealing a clear urban divide. No differences have been identified in terms of access to urban services like education, health, green areas, banks, or supermarkets, despite the appropriate location differences being noted in access to water and gas supply, and internet services. This study contributes to the understanding of how housing types and access to services in Craiova shape patterns of residential segregation, and it suggests policy interventions aimed at mitigating the negative impacts of these urban divides. Full article
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27 pages, 6774 KiB  
Article
Stakeholder Perspectives on District Heating and Cooling for Climate-Neutral and Smart Cities: A Romanian Analysis
by Timea Farkas, Paula Veronica Unguresan, Andrei Ceclan and Dan D. Micu
Sustainability 2025, 17(9), 3889; https://doi.org/10.3390/su17093889 - 25 Apr 2025
Viewed by 798
Abstract
District heating and cooling systems represent a great pillar of European cities aiming to achieve climate neutrality. This study investigates stakeholders’ perspectives on district heating and cooling to analyze the challenges, barriers, and potential accelerators of a sustainable low-carbon energy transition in urban [...] Read more.
District heating and cooling systems represent a great pillar of European cities aiming to achieve climate neutrality. This study investigates stakeholders’ perspectives on district heating and cooling to analyze the challenges, barriers, and potential accelerators of a sustainable low-carbon energy transition in urban areas. This study was performed via a survey-based approach, targeting multi-level stakeholders, both from the supply and demand side. This study employed a structural methodology involving customized surveys tailored to different stakeholder groups, aiming to understand challenges, advancement, and opportunities in Romania’s district heating systems. The results highlighted the diverse interests of stakeholders, emphasizing the need for financial support to reduce reliance on fossil fuels from the supply side while addressing concerns about infrastructure and current operations from the demand side. This study laid the groundwork for shaping national and regional policies and promoting local partnerships to reduce fossil energy demand and support the transition to renewable energy sources. Using a multi-stakeholder, cross-sectorial approach, and SWOT analysis in Romania, it systematically addresses technical, financial, and regulatory challenges for the greater sustainability of these systems in the urban environment. Full article
(This article belongs to the Special Issue Sustainable Urban Development Prospective for Smart Cities)
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36 pages, 22177 KiB  
Article
How to Promote the Formation of Market-Based Mechanisms for Mine Water Recycling and Utilization in China? A Four-Party Evolutionary Game Analysis
by Bing Wang, Jiwei Zhu, Jiancang Xie and Liu Yang
Sustainability 2025, 17(9), 3861; https://doi.org/10.3390/su17093861 - 24 Apr 2025
Viewed by 388
Abstract
Mine water is both wastewater and a valuable unconventional water resource, and its recycling is crucial for the sustainable development of coal-resource-based cities. In response to the complex interactions among multiple stakeholders in the process of mine water recycling, this study innovatively develops [...] Read more.
Mine water is both wastewater and a valuable unconventional water resource, and its recycling is crucial for the sustainable development of coal-resource-based cities. In response to the complex interactions among multiple stakeholders in the process of mine water recycling, this study innovatively develops a four-party evolutionary game model involving local government, coal mining enterprises, mine water operators, and water users. For the first time, key variables—mine water pricing, water volume, water rights trading, water resource taxation, and objective utility of water resources—are systematically integrated into a multi-agent game framework, extending the analysis beyond conventional policies, such as penalties and subsidies, to explore their impact on recycling behavior. The results show the following: (1) There are 10 possible evolutionary stabilization strategies in the system. The current optimal strategy includes supply, input, use, active support, while the ideal strategy under the market mechanism includes supply, input, use, passive support. (2) Local governments play a leading role in collaborative governance. The decisions of coal mining enterprises and mine water operators are highly interdependent, and these upstream actors significantly influence the water users’ strategies. (3) Government subsidies exhibit an inverted U-shaped effect, while punitive measures are more effective than incentives. The tax differential between recycled and discharged mine water incentivizes coal enterprises to adopt proactive measures, and water rights trading significantly enhances the users’ willingness. (4) Mine water should be priced significantly lower than fresh water and reasonably balanced between stakeholders. Industries with lower objective utility of water tend to prioritize its use. This study provides theoretical support for policy optimization and a market-based resource utilization of mine water. Full article
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18 pages, 2236 KiB  
Review
IoT-Enabled Biosensors in Food Packaging: A Breakthrough in Food Safety for Monitoring Risks in Real Time
by Abdus Sobhan, Abul Hossain, Lin Wei, Kasiviswanathan Muthukumarappan and Maruf Ahmed
Foods 2025, 14(8), 1403; https://doi.org/10.3390/foods14081403 - 18 Apr 2025
Cited by 3 | Viewed by 2626
Abstract
The integration of biosensors and the Internet of Things (IoT) in food packaging is gaining significant interest in rapidly enhancing food safety and traceability worldwide. Currently, the IoT is one of the most intriguing topics in the digital and virtual world. Biosensors can [...] Read more.
The integration of biosensors and the Internet of Things (IoT) in food packaging is gaining significant interest in rapidly enhancing food safety and traceability worldwide. Currently, the IoT is one of the most intriguing topics in the digital and virtual world. Biosensors can be integrated into food packaging to monitor, sense, and identify early signs of food spoilage or freshness. When coupled with the IoT, these biosensors can contribute to data transmission via IoT networks, providing real-time insights into food storage and transportation conditions for stakeholders across each stage of the food supply chain, facilitating proactive decision-making practices. The technologies of combining biosensors with IoT could leverage artificial intelligence (AI) to enhance food safety, quality, and security in food industries, compared to conventional existing food inspection technologies, which are limited to assessing weight, volume, color, and physical appearance. This review focused on highlighting the latest and existing advancements, identifying the knowledge gaps in the applications of biosensors and the IoT, and exploring their opportunities to shape future food packaging, particularly in the context of 21st-century food safety. The review also aims to investigate the role of the IoT in creating smart food ecosystems and examines how data transmitted from biosensors to IoT systems can be stored in cloud-based platforms, in addition to addressing upcoming research challenges. Concerns of data privacy, security, and regulatory compliance in implementing the IoT and biosensors for food packaging are also addressed, along with potential solutions to overcome these barriers. Full article
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39 pages, 1092 KiB  
Review
On the Interplay Between Behavior Dynamics, Environmental Impacts, and Fairness in the Digitalized Circular Economy with Associated Business Models and Supply Chain Management
by Shai Fernández, Ulf Bodin and Kåre Synnes
Sustainability 2025, 17(8), 3437; https://doi.org/10.3390/su17083437 - 12 Apr 2025
Viewed by 810
Abstract
In contemporary research, the digital transformation of industries and societies has increased the importance of interdisciplinary exploration, particularly when addressing the complex challenges faced by modern organizations and social systems. From the perspective of digitalization, this literature review examines the intricate interactions between [...] Read more.
In contemporary research, the digital transformation of industries and societies has increased the importance of interdisciplinary exploration, particularly when addressing the complex challenges faced by modern organizations and social systems. From the perspective of digitalization, this literature review examines the intricate interactions between three key research domains: behavior dynamics, environmental impact, and fairness. By reviewing a wide range of studies and methodologies, it reveals new insights, challenges, and opportunities that arise at the intersection and through the interdependencies of these areas within digital ecosystems. Through a structured approach covering preliminary background, state-of-the-art methods, and comprehensive analysis, this document seeks to reveal the synergies and divergences among these domains. Special emphasis is placed on their implications in the digitalization of modern circular economy, business models, and supply chain management contexts where these domains converge in meaningful ways. Additionally, through an extensive review of the existing literature, this document highlights the current state of research and identifies notable gaps. These include issues such as ensuring fairness in digitalized sustainable strategies, understanding the role of digital behavior dynamics in promoting environmental management, and managing environmental impacts in new digitally driven business models. By weaving together these diverse elements, this work offers a novel perspective, emphasizing the importance of collaborative and integrative research in shaping a sustainable and equitable digital future. Full article
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27 pages, 3758 KiB  
Review
Recycling or Sustainability: The Road of Electric Vehicles Toward Sustainable Economy via Blockchain
by Katarina Dimic-Misic, Shailesh Singh Chouhan, Vesna Spasojević Brkić, Milica Marceta-Kaninski and Michael Gasik
Recycling 2025, 10(2), 48; https://doi.org/10.3390/recycling10020048 - 19 Mar 2025
Cited by 1 | Viewed by 1199
Abstract
This semi-systematic review paper discusses four research questions based on findings from the last 10 years: What are the crucial issues in the ongoing debate on the development of the electric vehicle (EV) concept? Where are the major conflicting points and focuses between [...] Read more.
This semi-systematic review paper discusses four research questions based on findings from the last 10 years: What are the crucial issues in the ongoing debate on the development of the electric vehicle (EV) concept? Where are the major conflicting points and focuses between sustainable economy and EVs? How does the mining of metals and minerals follow current zero-waste sustainability trends, and how does the prediction of the magnitude of the future demand for EV batteries guide strategic decision-making in policies throughout the globe? As it is not easy to currently predict how metals necessary for EV productions will be produced, this article suggests a strategy that is diverse regarding its approaches to shaping the sustainable mining and further development of EVs, along with the involvement of urban planning. Using broad literature and a published pool of prediction scenarios, we provide a comprehensive assessment of future EV battery raw materials development under a range of scenarios, accounting for factors such as developments in battery technology, variations in the EV fleet composition, sustainability aspects of development of second use and recycling technologies. Additionally, this paper demonstrates how blockchain technology is likely to force mineral and metal supply chains to become significantly more traceable and transparent. Full article
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19 pages, 8119 KiB  
Article
Monitoring Pipeline Leaks Using Fractal Analysis of Acoustic Signals
by Ayrat Zagretdinov, Shamil Ziganshin, Eugenia Izmailova, Yuri Vankov, Ilya Klyukin and Roman Alexandrov
Fractal Fract. 2025, 9(3), 178; https://doi.org/10.3390/fractalfract9030178 - 14 Mar 2025
Cited by 2 | Viewed by 728
Abstract
This paper proposes a method for searching for pipeline leaks by analyzing the Hurst exponent of acoustic signals. The investigations conducted on the laboratory setup and the current pipelines of the water supply system. During the experiments, through defects of the round shape-type [...] Read more.
This paper proposes a method for searching for pipeline leaks by analyzing the Hurst exponent of acoustic signals. The investigations conducted on the laboratory setup and the current pipelines of the water supply system. During the experiments, through defects of the round shape-type pipeline with diameters from 1 to 5 mm were modeled. For calculating Hurst exponent, rescaled range analysis (R/S analysis), and detrended fluctuation analysis (DFA) were used. The research results have shown that pipeline leaks are reliably detected by analyzing the Hurst exponent of acoustic signals. The signals of a defect-free pipeline are close to the level of a deterministic signal. When a leak occurs in a pipeline, the Hurst exponent decreases. Pipeline fluctuations are anti-persistent nature. It is shown that a change in the size of the through hole in the pipeline wall does not have a significant effect on the value of the Hurst exponent of acoustic signals. These results are explained by using spectral analysis and CFD modeling (Computational Fluid Dynamics modeling) methods in the Ansys Fluent software (v. 19.2). It has been established that the spectral components that contribute most to the fractal structure of signals are concentrated within the frequency range from 0 to 2 kHz. Full article
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20 pages, 9378 KiB  
Article
Ultra-Wideband Passive Polarization Conversion Metasurface for Radar Cross-Section Reduction Across C-, X-, Ku-, and K-Bands
by Xiaole Ren, Yunqing Liu, Zhonghang Ji, Qiong Zhang and Wei Cao
Micromachines 2025, 16(3), 292; https://doi.org/10.3390/mi16030292 - 28 Feb 2025
Viewed by 1139
Abstract
In this study, we present a novel ultra-wideband passive polarization conversion metasurface (PCM) that integrates double V-shaped patterns with circular split-ring resonators. Operating without any external power supply or active components, this design effectively manipulates the polarization state of incident electromagnetic waves. Numerical [...] Read more.
In this study, we present a novel ultra-wideband passive polarization conversion metasurface (PCM) that integrates double V-shaped patterns with circular split-ring resonators. Operating without any external power supply or active components, this design effectively manipulates the polarization state of incident electromagnetic waves. Numerical and experimental results demonstrate that the proposed PCM can convert incident linear polarization into orthogonal states across a wide frequency range of 7.1–22.3 GHz, encompassing the C-, X-, Ku-, and K-bands. A fabricated prototype confirms that the polarization conversion ratio (PCR) exceeds 90% throughout the specified band. Furthermore, we explore an additional application of this passive metasurface for electromagnetic stealth, wherein it achieves over 10 dB of monostatic radar cross-section (RCS) reduction from 7.6 to 21.5 GHz. This broad effectiveness is attributed to strong electromagnetic resonances between the top and bottom layers, as well as the Fabry–Pérot cavity effect, as evidenced by detailed analyses of the underlying physical mechanisms and induced surface currents. These findings confirm the effectiveness of the proposed design and highlight its potential for future technological applications, including 6G communications, radar imaging, anti-interference measures, and electromagnetic stealth. Full article
(This article belongs to the Special Issue Microwave Passive Components, 2nd Edition)
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