Search Results (135)

The recent integration of Unmanned Ground Vehicles (UGVs) into human activities represents a significant scientific advancement and technological development, with substantial impacts across various fields, not limited to mechanical engineering, including agriculture, defense, and civil construction. Therefore, this study aims to provide a practical methodological framework, developed through a historical and systematic literature review, to emphasize the general criteria and the main interactions that an engineer should consider in the initial design phase of a UGV, thereby subsequently proceeding with its computer-aided modeling and simulation. To this end, a systematic literature review is conducted to identify current research interests in this field and pinpoint potential research gaps. Following the systematic literature review presented in this study, the focus of the present investigation shifts to classifying UGVs by analyzing their characteristics based on specific criteria, including weight, type of steering system, and wheel and track configurations. Additionally, the differences between wheels and tracks are further examined by comparing these two solutions and highlighting their advantages and limitations. This review paper also addresses power systems, hardware components, and navigation challenges. Subsequently, the primary sectors and applications where these vehicles are widely utilized are thoroughly analyzed. Finally, a specific section of the manuscript is dedicated to illustrating the preliminary mechanical design of a typical unmanned ground vehicle, thereby highlighting its functional requirements and selecting the most suitable locomotion system. For this purpose, preliminary evaluations and simple calculations are introduced to determine the motor performance required for the proposed design example. In conclusion, the literature survey on UGVs presented in this paper, rooted in the common perspective of kinematic and dynamic analysis of multibody mechanical systems, clearly highlights the importance of this topic in modern engineering applications. Full article

Leader–member relationships shape public sector performance, yet how leader–member exchange (LMX) operates through capability and motivation pathways remains underexplored. Drawing on social information processing and career construction theories, this study examines how LMX quality influences civil servant performance through career adaptability and perceived social impact. Moderated mediation analyses of survey data from 363 civil servants in Province A, China, reveal that higher-quality LMX enhances career adaptability and perceived social impact, which, in turn, predict higher task performance and organizational citizenship behavior. However, LMX differentiation weakens these positive effects when perceived as high. In practice, public agencies should prioritize high-quality, low-differentiation LMX systems that enhance civil servants’ performance. Full article

The main aim of this study is to propose a series of recommendations to public administrations for the development of economic policies that promote the contribution of the construction and civil engineering sectors to the design and implementation of sustainable cities. The study was conducted on the island of Tenerife. Documentary research and in-depth interviews with key agents were used as qualitative techniques. The recommendations are described in a portfolio of action policies grouped into three action areas: macroeconomic demand policies, regulation and reform policies, promotion and support policies, and governance and collaboration policies. Among other results, it is worth mentioning that there is a European support framework for economic policies to promote this transformation, but it is necessary to apply them whilst taking into account the environment where they are applied. Existing measures need to be evaluated to improve them and/or replace them with those mentioned by the key agents, all within an action plan that facilitates their implementation. Building sustainable cities requires public–private collaboration, institutional efficiency, and the socio-environmentally responsible performance of companies in the sector. Full article

This systematic review applies the PRISMA methodology (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) to evaluate the use of recycled sand, obtained from construction and demolition waste (CDW), in mortars for civil construction. A total of 24 studies published between 2020 and 2025 were analyzed, retrieved from the Scopus and Web of Science databases. The main objective is to assess the technical feasibility and environmental benefits of recycled sand in mortars, while addressing research gaps such as the lack of standardized methodologies and the limited understanding of durability at higher replacement levels. Given the significant resource consumption and waste generation in the construction sector, the study highlights emerging trends in adopting recycled sand as a sustainable alternative to natural aggregates. Findings indicate that optimal replacement levels range between 30 and 50% in ordinary Portland cement (OPC) mortars, and up to 100% in geopolymer mixtures when appropriate processing and activation methods are applied, without compromising mechanical performance. Reported benefits include cost reduction, lower carbon footprint, and enhanced compactness. However, challenges such as higher porosity and the need for optimized mix designs, and high heterogeneity of CDW sources and processing methods remain. Overall, the review confirms that recycled sand is a technically viable and environmentally beneficial material for mortar production, though future research must focus on harmonizing test protocols and long-term performance evaluation. In addition, a bibliometric analysis was conducted to map scientific output on this topic, identifying key countries, journals, and publication trends. Full article

The civil construction sector is crucial to global economic development, influencing GDP and driving innovation with Industry 4.0 technologies such as BIM and IoT. However, how these technologies can be effectively aligned with the principles of Sustainability 4.0 within the framework of Construction 4.0 remains unclear. This paper aims to identify the barriers and drivers related to the impact of adopting Industry 4.0 enabling technologies on Sustainability 4.0 in the construction sector. To achieve this, we conducted a Systematic Literature Review (SLR) using articles from the Web of Science and Scopus databases, focusing on the period from 2021 to 2025. The methodology applied enabled a comprehensive analysis of 50 articles, highlighting challenges, barriers, and potential facilitators in the adoption of Sustainability 4.0 practices. Among the key findings, advanced technologies such as BIM and IoT have shown positive impacts on sustainability dimensions, like reducing energy consumption; yet, practical implementation still encounters significant barriers, including high costs and insufficient public policies. Only 30% of the reviewed articles discuss adoption in less developed regions, indicating geographical disparity in the application of these technologies. The paper provides valuable insights for managers and policymakers on overcoming existing barriers, emphasizing the importance of innovative business models and the need for cultural and educational adaptation. The study suggests that, with a collaborative approach and adequate support policies, Industry 4.0 technologies can transform sustainable practices in civil construction, fostering a more balanced and environmentally responsible economy. Full article

In the context of growing challenges related to the safety and durability of civil infrastructure, the demand for concrete composites capable of withstanding dynamic and impact loading is steadily increasing. Conventional concrete, owing to its brittle nature and limited energy absorption capacity, does not always meet the performance requirements imposed on protective structures. The construction sector’s substantial contribution to CO₂ emissions further underscores the need for environmentally responsible solutions. This study therefore explores the effects of partially replacing natural aggregate with waste-derived constituents such as SBR rubber granulate, copper slag, polypropylene and glass granulate on the mechanical properties and impact resistance of concrete. Scanning electron microscopy (SEM) and stereoscopic microscopy were used to characterize the additives’ geometry and interfacial bond quality, providing deeper insight into cement paste–aggregate interactions. Compressive testing confirmed that introducing the recycled components does not preclude meeting essential strength criteria, whereas impact experiments revealed pronounced differences in failure mode, crack propagation, and the specimen’s ability to dissipate kinetic energy. The experimental program was complemented by a life cycle assessment (LCA) that quantitatively estimated the CO₂ emissions associated with producing each mixture. The findings demonstrate that judiciously selected waste materials can reduce the consumption of virgin resources, enhance concrete functionality, and improve their protective performance, thereby advancing the principles of a circular economy. Full article

Accurate cost estimation during the conceptual and feasibility phase of highway projects is essential for informed decision making by public contracting authorities. Existing approaches often rely on pavement cross-section descriptors, general project classifications, or quantity estimates of major work categories that are not reliably available at the early planning stage, while focusing on one or more key asset categories such as roadworks, bridges or tunnels. This study makes a novel contribution to both scientific literature and practice by proposing the first early-stage highway construction cost estimation model that explicitly incorporates roadworks, interchanges, tunnels and bridges, using only readily available or easily derived geometric characteristics. A comprehensive and practical approach was adopted by developing and comparing models across multiple machine learning (ML) methods, including Multilayer Perceptron-Artificial Neural Network (MLP-ANN), Radial Basis Function-Artificial Neural Network (RBF-ANN), Multiple Linear Regression (MLR), Random Forests (RF), Support Vector Regression (SVR), XGBoost Technique, and K-Nearest Neighbors (KNN). Results demonstrate that the MLR model based on six independent variables—mainline length, service road length, number of interchanges, total area of structures, tunnel length, and number of culverts—consistently outperformed more complex alternatives. The full MLR model, including its coefficients and standardized parameters, is provided, enabling direct replication and immediate use by contracting authorities, hence supporting more informed decisions on project funding and procurement. Full article

Sand is the backbone of modern civilization and faces heightened demand in the Anthropocene. The uncontrolled extraction of sand raises concerns regarding its irreversible ecological impact. The sand industry is not well understood, especially from the perspective of sustainability. To address this knowledge gap, this systematic review combines policy analysis with the use of material flow analysis (MFA) indicators, environmental externalities, and geopolitics to assess the overall sustainability of the sand industry. By utilizing trade data, this study identified the primary importers and exporters of sand within each continent and selected the top 3–4 countries for analysis. Based on these countries, relevant studies in the literature on the trade and domestic extraction of sand and that used the principles of MFA were found to assess the patterns of its consumption. Illicit sand mining adds a further challenge regarding data accuracy and verification. This study revealed that China’s consumption of sand surpasses that of all the other countries studied, at 17,700 million tonnes, and China has the highest mass of recycled aggregates in use. Using gross domestic product as a proxy for size of the economy, it was found that China consumed 0.001251 million tonnes of sand per million USD. European nations showed a striking balance in their sand industries by placing equal importance on using virgin sand and recycled aggregates, thus contributing to a circular economy. The use of MFA for future research can reveal hidden flows by positioning itself as a science–policy interface, enabling greater circularity within the lock-ins of the construction sector. Full article

Low-carbon development is closely linked to the concept of sustainability, which focuses on both economic growth and the targeted reduction of greenhouse gas (GHG) emissions, facilitating the transition to climate neutrality. This process involves the efficient use of resources and necessitates systemic transformations across various sectors of the economy. For Latvia to achieve its climate neutrality objectives, it is essential to adhere to the principles of the bioeconomy, with a particular emphasis on the use of timber in construction. This approach combines opportunities for economic development with environmental protection, as timber is a renewable resource that contributes to carbon sequestration. The utilisation of timber in construction enables carbon storage within buildings and substitutes traditional materials such as concrete and steel, the production of which is highly energy-intensive and generates substantial CO₂ emissions. Consequently, timber use also reduces indirect emissions associated with the construction sector. The objective of this study is to identify the main barriers hindering the broader application of timber construction materials in Latvia’s building sector and to propose solutions to overcome these obstacles. The research tasks include an analysis of climate neutrality and construction targets within the EU and Latvia; an examination of the current situation and influencing factors regarding Latvia’s forest resources, their harvesting, processing, use in construction, and trade balance; and the identification of critical problem areas and the delineation of possible solutions. For theoretical and situational analyses, the authors employ methods such as scientific literature review, policy content analysis, descriptive methodology, statistical data analysis, and interpretation of quantitative and qualitative data. The results are synthesised using PESTEL analysis, which serves as a continuation and elaboration of the initial SWOT analysis assessment and is visualised through graphical representation. The authors of this study participated in a national-level expert group whose members represented the Parliament of the Republic of Latvia, responsible ministries, forest managers, construction companies, wood product manufacturers, and representatives from higher education and research institutions. The following hypotheses are proposed and substantiated in this article: (1) Latvia possesses sufficient forest resources to increase the share of timber used in construction, (2) increasing the use of timber in construction would significantly contribute to both Latvia’s economic development and the achievement of climate neutrality targets, and (3) the expansion of timber use in the construction sector depends on a restructuring of national policy across multiple sectors. Suggested solutions include the improvement of regulatory frameworks for timber harvesting, processing, and utilisation in related sectors—agriculture and forestry, wood processing, and construction. The key challenges for policymakers include addressing the identified deficiencies in Latvia’s progress toward achieving its CO₂ targets, introducing qualitative changes in timber harvesting conditions, and amending regulations governing the forest management cycle accordingly. For timber processing companies, it is crucial to ensure stable conditions for their commercial activity. Promoting the use of timber in construction requires a broad set of changes in safety and financial regulations and procurement requirements. Timber construction is relevant not only in the building sector but also in civil engineering, and modifications and additions to educational programmes are necessary. The promotion of timber use among the wider public is of great importance. At all stages of timber processing—from harvesting to integration in buildings—access to financial resources should be facilitated. As numerous sectors of the national economy (agriculture, forestry, wood processing, construction, logistics, etc.) are involved in timber processing, interdisciplinary research is required to address complex challenges that demand expertise from multiple fields. Full article

The civil construction and infrastructure sectors are known for their high environmental impact. Most of this impact is related to the carbon dioxide (CO₂) emissions from Portland cement. As a sustainable alternative, alkali-activated binders (AABs) are explored for their potential to replace traditional binders. This research focused on AAB formulations using steel industry byproducts, such as Baosteel’s slag short flow (BSSF), coke oven ash (CA), blast furnace sludge (BFS), and centrifuge sludge (CS), as well as fly ash (FA) from a thermoelectric plant. Byproducts were characterized through laser granulometry, Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), followed by the formulation of AABs with different precursor ratios. After 28 days, the compressive strength was obtained for each formulation. Based on the compressive strength tests, two binary mixtures were selected for microstructural and chemical analyses through XRF, FTIR, and SEM. CA demonstrated the greatest potential for use in binary AABs based on BSSF, as it presented a higher source of aluminosilicates and smaller particle sizes. The formulations containing BSSF and CA achieved compressive strengths of up to 9.8 MPa, while the formulations with BSSF and FA reached 23.5 MPa. SEM images revealed a denser, more cohesive matrix in the FA-based AAB, whereas CA-based AABs showed incomplete precursor dissolution and higher porosity, which contributed to the lower mechanical strength of CA-based AABs. These findings highlight the critical role of precursor selection in developing sustainable AABs from industrial byproducts and demonstrate how different formulations can be tailored for specific applications. Full article

This paper provides a comprehensive review of the development history, current status, and future trends of civil aviation meteorological services. With the rapid growth of global air traffic and the increasing complexity of operational environments, accurate and timely meteorological information has become indispensable for ensuring the efficiency and safety of civil aviation operations. Extreme weather events, in particular, have repeatedly demonstrated their potential to disrupt flight schedules, compromise passenger safety, and incur substantial economic losses, underscoring the critical need for robust meteorological service systems in the aviation sector. Against this backdrop, this paper first introduces the importance of civil aviation meteorological services in ensuring flight safety, improving flight regularity, and reducing operational costs. The development process is then detailed, from early infrastructure construction to the current modern and intelligent development, covering the evolution of observation equipment, forecasting technologies, and service models. When analyzing the current status, the paper discusses challenges such as the difficulty of accurate forecasting under complex weather conditions and multi-departmental collaboration issues, as well as improvement measures and achievements. Finally, it determines future trends, including the application of new technologies, such as artificial intelligence (AI) and big data, the expansion of service scope, and the strengthening of international cooperation, aiming to provide references for further improving the level of civil aviation meteorological services. Full article

As a new type of production factor, data possesses multidimensional application value, and its pivotal role is becoming increasingly prominent in the aviation sector. Data sharing can significantly enhance the utilization efficiency of data resources and serves as one of the key tasks in building smart civil aviation. However, currently, data silos are pervasive, with vast amounts of data only being utilized and analyzed within limited scopes, leaving their full potential untapped. The challenges in data sharing primarily stem from three aspects: (1) Data owners harbor concerns regarding data security and privacy. (2) The highly dynamic and real-time nature of aviation operations imposes stringent requirements on the timeliness, stability, and reliability of data sharing, thereby constraining its scope and extent. (3) The lack of reasonable incentive mechanisms results in insufficient motivation for data owners to share. Consequently, addressing the issue of aviation big data sharing holds significant importance. Since the release of the Bitcoin whitepaper in 2008, blockchain technology has achieved continuous breakthroughs in the fields of data security and collaborative computing. Its unique characteristics—decentralization, tamper-proofing, traceability, and scalability—lay the foundation for its integration with aviation. Blockchain can deeply integrate with air traffic management (ATM) operations, effectively resolving trust, efficiency, and collaboration challenges in distributed scenarios for ATM data. To address the heterogeneous data usage requirements of different ATM stakeholders, this paper constructs a blockchain-based multi-level data security sharing architecture, enabling fine-grained management and secure collaboration. Furthermore, to meet the stringent timeliness demands of aviation operations and the storage pressure posed by massive data, this paper optimizes blockchain storage deployment and consensus mechanisms, thereby enhancing system scalability and processing efficiency. Additionally, a dual-mode data-sharing solution combining raw data sharing and model sharing is proposed, offering a novel approach to aviation big data sharing. Security and formal analyses demonstrate that the proposed solution is both secure and effective. Full article

The road construction sector urgently requires environmentally friendly, low-carbon, and high-performance base materials. Traditional materials exhibit issues of high energy consumption and carbon emissions, making it difficult for them to align with sustainable development requirements. While slag- and fly ash-based geopolymers demonstrate promising application potential in civil engineering, research on their application in road-stabilized soils remains insufficient. To address the high energy consumption and carbon emissions associated with conventional road base materials and to fill this research gap, this study investigated the utilization of industrial solid wastes through slag-based geopolymer and fly ash as stabilizers, systematically evaluating the pavement performance of two distinct soil types. Unconfined compressive strength tests and freeze–thaw cycling tests were conducted to elucidate the effects of stabilizer dosage, fly ash co-stabilization, and compaction degree on mechanical properties. The results demonstrated that the compressive strength of both stabilized soils increased significantly with higher slag-based geopolymer content, achieving peak values of 5.2 MPa (soil sample 1) and 4.5 MPa (soil sample 2), representing a 30% improvement over cement-stabilized soils with identical mix proportions. Fly ash co-stabilization exhibited more pronounced reinforcement effects on soil sample 2. At a 98% compaction degree, soil sample 1 maintained a stable 50% strength enhancement, whereas soil sample 2 displayed a dose-dependent exponential strength increase. Freeze–thaw resistance tests revealed the superior performance of soil sample 1, showing a loss of compressive strength (BDR) of 78% with 8% geopolymer stabilization alone, which improved to 90% after fly ash co-stabilization. For soil sample 2, the BDR increased from 64% to 80% through composite stabilization. This study confirms that slag/fly ash-based geopolymer-stabilized soils not only meet the strength requirements for heavy-traffic subbases and light-traffic base courses, but also demonstrates its great potential as a low-carbon and environmentally friendly material to replace traditional road base materials. Full article

Market-oriented ecological restoration is vital for advancing ecological civilization and promoting harmonious human–nature relationships. However, the precise implementation pathway remains unclear. Few studies specifically address challenges that arise during ecological restoration implementation. Ensuring the smooth and effective implementation and landing of ecological restoration projects harmonizes ecological and economic objectives at the regional scale and fosters sustainable development in the region. Based on the policies of market-oriented ecological restoration collected from various Chinese provinces, and through multi-level institutional analysis, the policy measures are categorized into three phases: early, middle, and late. For each phase, we summarize the challenges encountered in implementing market-oriented ecological restoration projects. Finally, by the method of constructing theoretical models, we propose sustainable countermeasures based on multiple theoretical models. The results show (1) China’s ecological restoration sector is experiencing rapid growth, and market-oriented policies in China, multiple Chinese provinces, and municipalities have enacted successive market-oriented ecological restoration policies, and the outlook for ecological restoration marketization in China remains highly promising. (2) The implementation process of current market-oriented ecological restoration projects confronts and encounters several challenges. These include the absence of project screening and evaluation mechanisms, limited investment and financing channels, ill-defined approval processes, ambiguous delineation of departmental responsibilities, insufficient industry incentives, and the absence of effective operational and management mechanisms. (3) To address the identified challenges, taking forest ecological restoration as an example, theoretical models should be developed encompassing six critical dimensions: the aspects of the mechanism, mode, approval process, management system, industrial chain, and platform. This aims to provide sustainable pathways for the effective implementation of market-oriented forest ecological restoration projects. Full article

The growing relevance of sustainable practices has driven organizations from various sectors to adapt their activities to current socio-environmental demands. In the construction sector, this demand is even more pronounced due to the high consumption of natural resources and the significant generation of solid waste. However, questions remain about the extent to which companies in this sector understand and incorporate sustainable practices into their routines. This study investigates the level of knowledge and the adoption of sustainable practices by residential building construction companies registered with the Civil Construction Industry Union of Mossoró/RN. A qualitative-quantitative approach was adopted, using questionnaires and photographic records collected during on-site visits. The data reveal an incipient adoption of Environmental Management Systems (EMSs) and limited knowledge about ESG principles, highlighting structural and cultural barriers to sustainability in the sector. Nevertheless, isolated initiatives related to waste reduction and the adoption of more efficient practices were observed. The study concludes that strengthening technical training, promoting management systems, and aligning with contemporary demands are relevant strategies to foster sustainability and competitiveness in the construction sector. Full article