Search Results (265)

Over the past 20 years, laser beam–electric arc hybrid welding has gained popularity, enabling high quality and efficiency standards needed for steel welds in structures subjected to severe working conditions. This process enables single-pass welding of thick components, overcoming issues concerning the individual use of traditional processes based on an electric arc or laser beam. Therefore, thorough knowledge of both processes is necessary to combine them optimally in terms of efficiency, reduced presence of defects, corrosion resistance, and mechanical and metallurgical features of the welds. This article aims to review the technical and metallurgical aspects of hybrid welding reported in the scientific literature mainly of the last decade, outlining possible choices for system configuration, the inter-distance between the two heat sources, as well as the key process parameters, considering their effects on the weld characteristics and also taking into account the consequences for solidification modes and weld composition. Finally, a specific section has been reserved for hybrid welding of clad steel plates. Full article

Against the backdrop of increasingly depleted global non-renewable resources, research on renewable energy has become urgently critical. As a significant marine clean energy source, tidal current energy has attracted growing scholarly interest, effectively addressing global energy shortages and fossil fuel pollution. Semi-enclosed bay straits, with their geographically advantageous topography, offer substantial potential for tidal energy exploitation. China’s Bohai Strait exemplifies such a geomorphological feature. This study focuses on the Bohai Strait, employing the Delft3D model to establish a three-dimensional numerical simulation of tidal currents in the region. Combined with the Flux tidal energy assessment method, the tidal energy resources are evaluated, and exploitation recommendations are proposed. The results demonstrate that the Laotieshan Channel, particularly its northern section, contains the most abundant tidal energy reserves in the Bohai Strait. The Laotieshan Channel has an average power flux density of 50.83 W/m², with a tidal energy potential of approximately 81,266.5 kW, of which about 12,189.97 kW is technically exploitable. Particularly in its northern section, favorable flow conditions exist—peak current speeds can reach 2 m/s, and the area offers substantial effective power generation hours. Annual durations with flow velocities exceeding 0.5 m/s total around 4500 h, making this zone highly suitable for deploying tidal turbines. To maximize the utilization of tidal energy resources, installation within the upper 20 m of the water layer is recommended. This study not only advances tidal energy research in semi-enclosed bay straits but also provides a critical reference for future studies, while establishing a foundational framework for practical tidal energy development in the Bohai Strait region. Full article

The West Africa Power Pool (WAPP) Interconnected Transmission System (WAPPITS) has faced challenges with frequency control due to limited primary frequency control reserves (PFRs). Battery Energy Storage Systems (BESSs) have been identified as a possible solution to address frequency control challenges and to support growing levels of variable renewable energy in the WAPPITS. This paper uses a dynamic PSS/E grid simulation to evaluate the effectiveness of BESSs and conventional power plants for the maximum N-1 contingency scenario in WAPPITS—the loss of 400 MW of generation. BESSs outperform conventional power plants in fast frequency response; a BESS-only PFR mix produces the best technical performance for the metrics analyzed. However, this approach does not have the best marginal cost; a balanced mix of BESSs and conventional reserves achieves adequate performance on all metrics to meet grid requirements. This hybrid approach combines BESSs’ rapid power injection with the lower cost of conventional units, resulting in improved nadir frequencies (e.g., 49.70–49.76 Hz), faster settling times (1.00–2.20 s), and cost efficiency. The study indicates that an optimal approach to frequency control should include a combination of regulatory reforms and coordinated reserve procurement that includes BESS assets. Regulatory reforms should require or incentivize conventional plant to provide PFRs, possibly through creation of a (new to WAPPITS) market for ancillary services. While not a comprehensive analysis of all variables, these findings provide critical insights for policymakers and system operators. Full article

With China’s high-speed rail network undergoing rapid expansion, turnouts constitute critical elements whose safety and stability are essential to railway operation. At present, the efficiency of wheel–rail force safety monitoring conducted in the small hours reserved for the construction and maintenance of operating lines without marking train operation lines is relatively low. To enhance the efficiency of turnout safety monitoring, in this study, a three-dimensional BIM model of the No. 42 turnout was established and a corresponding wheel–rail force monitoring scheme was devised. Collision detection for monitoring equipment placement and construction process simulation was conducted using Navisworks, such that the rationality of cable routing and the precision of construction sequence alignment were improved. A train wheel–rail force analysis program was developed in MATLAB R2022b to perform signal filtering, and static calibration was applied to calculate key safety evaluation indices—namely, the coefficient of derailment and the rate of wheel load reduction—which were subsequently analyzed. The safety of the No. 42 turnout and the effectiveness of the proposed monitoring scheme were validated, theoretical support was provided for train operational safety and turnout maintenance, and technical guidance was offered for whole-life-cycle management and green, sustainable development of railway infrastructure. Full article

This paper is concerned with the choice of data granularity for the application of the Mack chain ladder model to forecast a loss reserve. It is a sequel to a related paper by Taylor, which considers the same question for the EDF chain ladder model. As in the earlier paper, it considers the question as to whether a decrease in the time unit leads to an increase or decrease in the variance of the loss reserve estimate. The question of whether a Mack chain ladder that is valid for one time unit (here called mesh size) remains so for another is investigated. The conditions under which the model does remain valid are established. There are various ways in which the mesh size of a data triangle may be varied, two of them of particular interest. The paper examines one of these, namely that in which development periods are preserved. Two versions of this are investigated: 1. the aggregation of development periods without change to accident periods; 2. the aggregation of accident periods without change to development periods. Taylor found that, in the case of the Poisson chain ladder, an increase in mesh size always increases the variance of the loss reserve estimate (subject to mild technical conditions). The case of the Mack chain ladder is more nuanced in that an increase in variance is not always guaranteed. Whether or not an increase or decrease occurs depends on the numerical values of certain of the age-to-age factors actually observed. The threshold values of the age-to-age factors at which an increase transitions to a decrease in variance are calculated. In the case of a change in the mesh of development periods, but with no change to accident periods, these values are computed for one particular data set, where it is found that variance always increases. It is conjectured that data sets in which this does not happen would be relatively rare. The situation is somewhat different when changes in mesh size over accident periods are considered. Here, the question of an increase or decrease in variance is more complex, and, in general terms, the occurrence of an increase in variance with increased mesh size is less likely. Full article

The natural history of focal non-infected lesions of the abdominal aorta (fl-AA) remains unclear and largely depends on their aetiology. These lesions often involve a focal “tear” or partial disruption of the arterial wall. Penetrating aortic ulcers (PAUs) and intramural hematomas (IMHs) are examples of focal tears in the aortic wall that can either progress to dilatation (saccular aneurysm) or fail to fully propagate through the medial layers, potentially leading to aortic dissection. These conditions typically exhibit a morphology consistent with eccentric saccular aneurysms. The management of focal non-infected pathologies of the abdominal aorta remains a subject of debate. Unlike fusiform abdominal aortic aneurysms, the inconsistent definitions and limited information regarding the natural history of saccular aneurysms (sa-AAAs) have prevented the establishment of universally accepted practice guidelines for their management. As emphasized in the latest 2024 ESVS guidelines, the focal nature of these diseases makes them ideal candidates for endovascular repair (class of evidence IIa—level C). Moreover, the Society for Vascular Surgery just referred to aneurysm diameter as an indication for treatment suggesting using a smaller diameter compared to fusiform aneurysms. Consequently, the management of saccular aneurysms is likely heterogeneous amongst different centres and different operators. Endovascular repair using tube stent grafts offers benefits like reduced recovery times but carries risks of migration and endoleak due to graft rigidity. These complications can influence long-term success. In this context, the use of endovascular bifurcated grafts may provide a more effective solution for treating these focal aortic pathologies. It is essential to achieve optimal sealing regions through anatomical studies of aortic morphology. Additionally, understanding the anatomical characteristics of focal lesions in challenging necks or para-visceral locations is indeed crucial in device choice. Off-the-shelf devices are favoured for their time and cost efficiency, but new endovascular technologies like fenestrated endovascular aneurysm repair (FEVAR) and custom-made devices enhance treatment success and patient safety. These innovations provide stent grafts in various lengths and diameters, accommodating different aortic anatomies and reducing the risk of type III endoleaks. Although complicated PAUs and focal saccular aneurysms rarely arise in the para-visceral aorta, the consequences of rupture in this segment might be extremely severe. Experience borrowed from complex abdominal and thoracoabdominal aneurysm repair demonstrates that fenestrated and branched devices can be deployed safely when anatomical criteria are respected. Elective patients derive the greatest benefit from a fenestrated graft, while urgent cases can be treated confidently with off-the-shelf multibranch systems, reserving other types of repairs for emergent or bail-out cases. While early outcomes of these interventions are promising, it is crucial to acknowledge that limited aortic coverage can still impede effective symptom relief and lead to complications such as aneurysm expansion or rupture. Therefore, further long-term studies are essential to consolidate the technical results and evaluate the durability of various graft options. Full article

The reliability of the electro-power equipment of electrical power transmission systems is essential in ensuring an uninterrupted power supply with the necessary voltage and frequency stability. This is especially important when performing lengthy procedures requiring the serviceability of the electrical equipment used, such as those related to foundries and metallurgical processes, or with the processes of testing complex means for the remote control of electromagnetic radiation within the implementation of the Sustainable development of the Competence Center “Quantum Communication, Intelligent Security Systems and Risk Management” (QUASAR) Project, funded with the participation of the EU under the “Research, Innovation and Digitalization for Smart Transformation” Program 2021.2027 according to procedure BG16RFPR002-1.014. One of the main issues in this case is related to the availability of information regarding the technical condition of the deployed or reserve energy resources. In this connection, this study proposes methods for determining the quantity of operational equipment that is either in use or in storage, based on the reliability testing of a representative sample of it. Full article

Rural tourism plays a crucial role in promoting industrial revitalization in mountainous regions. Drawing inspiration from the site selection mechanisms of nature reserves, this study constructs a gap analysis framework tailored to rural tourism destinations, aiming to provide technical support for their spatial layout and systematic planning. By integrating a potential evaluation system based on tourism resources, market demand, and synergistic factors, the study identifies rural tourism priority zones and proposes a development typology and spatial optimization strategy across five provinces in Southwest China. The findings reveal: (1) First- and second-priority zones are primarily located in the core and periphery of provincial capitals and prefecture-level cities, while third-priority zones are concentrated in resource-rich areas of Yunnan and Guizhou and market-oriented areas of Sichuan, Chongqing, and Guangxi. (2) The Chengdu Plain emerges as the core region for rural tourism development, with hotspots clustered around Chengdu, northern and western Guizhou, central Chongqing, eastern Guangxi, and northwestern Yunnan, whereas cold spots are mainly situated in the western Sichuan Plateau and the Leshan–Liangshan–Zhaotong–Panzhihua–Chuxiong–Pu’er belt. (3) The alignment between tourism resources and rural tourism destinations is highest in Yunnan and Guizhou, while Chongqing exhibits the strongest match between destinations and tourism market potential and synergistic development conditions. Overall, 79.35% of rural tourism destinations in the region are situated within identified priority zones, with Chongqing, Guizhou, and Sichuan exhibiting the highest proportions. Based on the spatial mismatch between potential and existing destinations, the study delineates four development types—maintenance and enhancement, supplementation and upgrading, expansion, and reserve development—and offers regionally tailored planning recommendations. The proposed framework provides a replicable approach for spatial planning of rural tourism destinations in complex mountainous settings. Full article

Gold is a vital strategic resource for many countries. The Laozhaiwan area is an important gold resource base in Yunnan Province and even nationwide. Conducting mineral resource exploration in this region to increase gold reserves is of great significance. The application of remote sensing technology in mineral resource exploration is a green and efficient technical approach, which has been widely utilized in the field of mineral resource prospecting. This study selects the Laozhaiwan area in the southeastern part of Yunnan Province as the research region. Linear and ring structures were extracted using the remote sensing visual interpretation method based on Sentinel-2A multispectral data. Additionally, Sentinel-2A, ASTER, and ZY1-02D data were used to extract iron-stained, hydroxyl, silicification, and limonite alteration information through Principal Component Analysis (PCA) and Spectral Angle Mapper (SAM) methods. Additionally, 50 linear structures and 12 ring structures were extracted. A comprehensive analysis of geological data reveals that alteration minerals and linear-ring structures are closely related to mineralization, providing valuable indicators for mineral resource exploration. By comprehensively analyzing the alteration information and remote sensing interpretation results of the linear-ring structures, two prospective areas for mineral exploration were delineated. Field investigations and petrographic studies confirmed the reliability of remote sensing technology in mineral exploration. The mineral exploration method based on multi-source remote sensing technology can clearly reflect various alteration information and linear-ring structural data. It provides remote sensing geological insights for geological survey work and has great application potential in the field of mineral resource exploration. Full article

Applying the resource-based view and dynamic capability theory, this study employs panel data analysis to examine how financial flexibility influences corporate innovation efficiency from an integrated resource-capability perspective. Analyzing data from Chinese A-share listed companies during 2013–2022, we discovered three key results. First, as an organizational liquidity buffer, financial flexibility reduces transaction costs, enhances incentives for technical talent retention, and better aligns executive compensation with innovation objectives. Second, as a manifestation of financial dynamic capabilities, financial flexibility significantly boosts a firm’s overall dynamic capabilities, thereby increasing innovation efficiency. Third, institutional investor engagement positively moderates this relationship through enhanced governance oversight. These investors strengthen governance oversight and reduce information asymmetry. Our findings advance the financial flexibility literature and offer actionable strategies to optimize innovation resource allocation and sustain R&D competitiveness. Companies should strategically build financial reserves to enhance innovation efficiency and achieve sustainable development. Full article

This paper presents a novel approach to economic dispatch (ED) optimization in power systems through the application of Proximal Policy Optimization (PPO), an advanced reinforcement learning algorithm. The economic dispatch problem, a fundamental challenge in power system operations, involves optimizing the generation output of multiple units to minimize operational costs while satisfying load demands and technical constraints. Traditional methods often struggle with the non-linear, non-convex nature of modern ED problems, especially with increasing penetration of renewable energy sources. Our PPO-based methodology transforms the ED problem into a reinforcement learning framework where an agent learns optimal generator scheduling policies through continuous interaction with a simulated power system environment. The proposed approach is validated on a 15-generator test system with varying load demands and operational constraints. Experimental results demonstrate that the PPO algorithm achieves superior performance compared to conventional techniques, with cost reductions of up to 7.3% and enhanced convergence stability. The algorithm successfully handles complex constraints including generator limits, ramp rates, and spinning reserve requirements, while maintaining power balance with negligible error margins. Furthermore, the computational efficiency of the PPO approach allows for real-time adjustments to rapidly changing system conditions, making it particularly suitable for modern power grids with high renewable energy penetration. Full article

Direct methanol fuel cells (DMFCs) represent a promising pathway for energy conversion, yet their reliance on platinum-group metal (PGM)-based anode catalysts poses critical sustainability challenges, which stem from finite mineral reserves, environmentally detrimental extraction processes, and prohibitive lifecycle costs. Current anode catalysts for DMFCs are dominated by platinum materials; therefore, this review systematically evaluates the following three emerging eco-efficient design paradigms using platinum materials as a starting point: (1) the atomic-level optimization of low-Pt alloy surfaces to maximize catalytic efficiency per metal atom, (2) Earth-abundant transition metal compounds (e.g., nitrides and sulfides) and coordination-tunable metal–organic frameworks as viable PGM-free alternatives, and (3) mechanically robust carbon architectures with engineered topological defects that enhance catalyst stability through covalent metal–carbon interactions. Through comparative analysis with pure Pt benchmarks, we critically examine how these strategic material innovations collectively mitigate CO intermediate poisoning risks and improve electrochemical durability. Such fundamental advances in catalyst design not only address immediate technical barriers, but also establish essential material foundations for the development of DMFC technologies compatible with circular economy frameworks and United Nations Sustainable Development Goal 7 targets. Full article

The global energy matrix needs to undergo considerable changes to achieve the clean and affordable energy target as per the Sustainable Development Goals determined by the United Nations (UN) by 2030. Hydrogen has stood out worldwide as a potential substitute for current non-renewable sources. Once thought to be minor, if not non-existent, natural hydrogen is now becoming a more significant alternative that is being explored. Natural hydrogen can be obtained from subsurface rocks by the generation process of serpentinization, radiolysis, rock fracturing, or magma degassing, using extraction technology similar to that already used in the oil and gas industries. Thus, the goal of this research was to perform a consistent technical–scientific and bibliometric review of natural hydrogen, presenting the Brazilian context. The results showed that from 2017 onwards, there has been an increase in research publications related to the topic. France is the country with the most publications. In Brazil, the potential of natural hydrogen sources has been studied in states such as Goias, Tocantins, Minas Gerais, Roraima, Bahia, and Ceará. It is still difficult to predict the potential cost of natural hydrogen production. However, estimates through the Hydroma company show a cost of 0.5 USD/kg, and Australia and Spain target price projects at approximately 1 USD/kg of natural decarbonization could be aided by natural hydrogen, which could supply the world’s energy needs for generations. Geological processes, reserve behavior, and the efficiency of extraction are among the unknowns, though. Brazil requires a strong regulatory framework and additional research. For exploration to be sustainable, cooperation between the government, businesses, and society is essential. Full article

This study investigates pressure relief mechanisms and gas migration control in gently inclined remote lower protective layer mining, using the Wu_8-31220 working face of Pingdingshan Tianan Coal Industry’s No. 1 Mine as a prototype. The integrated approach combining theoretical modeling with multidimensional monitoring systems yielded critical insights into pressure relief patterns. Analysis demonstrated dip-oriented pressure relief angles measuring 77° (intake side) and 83° (return side), collectively establishing a pressure relief zone spanning 160.5 m. Concurrently, horizontal pressure relief angles were determined to be 60° in both orientations, generating a pressure relief zone extending 1261 m. Mechanical monitoring revealed multistage “compression–expansion” responses in the Ding6 seam during protective seam extraction, achieving maximum expansion deformations of 9.89–13.55‰ within the boundary zone. By optimizing borehole spacing (20 m) and extraction duration (8 months), the Ding_6-32070 working face extracted 1.18 million m³ of gas (31.22% reserves), resolving spatial coupling challenges between gas recovery efficiency and pressure relief dimensions. This work advances understanding of pressure relief and permeability enhancement in gently inclined remote lower protective layer mining. The findings provide both theoretical foundations and technical benchmarks for safe deep coal mining operations and efficient gas control strategies. Full article

Ecological carrying capacity (ECC) is central to assessing the sustainability of ecosystems, aiming to quantify the limits of natural systems to support human activities while maintaining biodiversity and resource regeneration. To assess ECC, earlier studies typically used the analytic hierarchy process (AHP) method for modeling. In this study, we developed an AHP-EW method based on a combination of AHP and the entropy weight method, which considered important indicators including land use, vegetation, soil, location, topography, climate, and socio-economics, and constructed an ECC evaluation system. The new AHP-EW method was applied to analyze the spatiotemporal ECC patterns in Urumqi from 2000 to 2020. The results showed a general decreasing trend in ECC during the period 2000–2020. Among them, the ECC decreased significantly by 19.05% from 2000 to 2010. After 2010, the rate of decline in ECC slowed to 14.12% due to ecological conservation policies. In addition, Midong District, Dabancheng District, and Urumqi County had worse ECC. Still, in general, the distribution of ECC in each district and county showed a trend of decreasing in areas with low ECC and increasing in areas with high ECC. Cluster analysis showed that ECC improved in ecological reserve areas, while some built-up areas showed a decrease in ECC due to economic development and human activities. Driving factor analysis shows that NDVI, climate change, and land-use conversion are the key factors influencing the change in ECC in Urumqi. This study provides new ideas and technical support for ECC assessment in arid areas, which can help formulate more effective ecological protection strategies and promote the healthy and stable development of regional ecosystems. Full article