Search Results (444)

The construction industry is responsible for 39% of global CO₂ emissions related to energy use, with cement responsible for 5–8% of it. Limestone calcined clay cement (LC³), a ternary blended binder system, offers a low-carbon alternative by partially substituting clinker with calcined clay and limestone. This study investigated the use of waste clay brick powder (WBP), a waste material, as a source of calcined clay in LC³ formulations, addressing both environmental concerns and SCM scarcity. Two LC³ mixtures containing 15% limestone, 5% gypsum, and either 15% or 30% WBP, corresponding to clinker contents of 65% (LC³-65) or 50% (LC³-50), were evaluated against general purpose (GP) cement mortar. Tests included setting time, flowability, soundness, compressive and flexural strengths, drying shrinkage, isothermal calorimetry, and scanning electron microscopy (SEM). Isothermal calorimetry showed peak heat flow reductions of 26% and 49% for LC³-65 and LC³-50, respectively, indicating a slower reactivity of LC³. The initial and final setting times of the LC³ mixtures were 10–30 min and 30–60 min longer, respectively, due to the slower hydration kinetics caused by the reduced clinker content. Flowability increased in LC³-50, which is attributed to the lower clinker content and higher water availability. At 7 days, LC³-65 retained 98% of the control’s compressive strength, while LC³-50 showed a 47% reduction. At 28 days, the compressive strengths of mixtures LC³-65 and LC³-50 were 7% and 46% lower than the control, with flexural strength reductions being 8% and 40%, respectively. The porosity calculated from the SEM images was found to be 7%, 11%, and 15% in the control, LC³-65, and LC³-50, respectively. Thus, the reduction in strength is attributed to the slower reaction rate and increased porosity associated with the reduced clinker content in LC³ mixtures. However, the results indicate that the performance of LC³-65 was close to that of the control mix, supporting the viability of WBP as a low-carbon partial replacement of clinker in LC³. Full article

Based on a comprehensive review of the current research status of ecological compensation both domestically and internationally, combined with field survey data, this study delves into the issue of multi-stakeholder participation in the ecological compensation mechanisms of the Xin’an River Basin. This research reveals that the joint participation of multiple stakeholders is crucial to achieving the goals of ecological compensation in river basins. The government plays a significant role in macro-guidance, financial support, policy guarantees, supervision, and management. It promotes the comprehensive implementation of ecological environmental protection by formulating relevant laws and regulations, guiding the public to participate in ecological conservation, and supervising and punishing pollution behaviors. The public, serving as the main force, forms strong awareness and behavioral habits of ecological protection through active participation in environmental protection, monitoring, and feedback. As participants, enterprises contribute to industrial transformation and green development by improving resource utilization efficiency, reducing pollution emissions, promoting green industries, and participating in ecological restoration projects. Scientific research institutions, as technology enablers, have effectively enhanced governance efficiency through technological research and innovation, ecosystem value accounting to provide decision-making support, and public education. Social organizations, as facilitators, have injected vitality and innovation into watershed governance by extensively mobilizing social forces and building multi-party collaboration platforms. Communities, as supporters, have transformed ecological value into economic benefits by developing characteristic industries such as eco-agriculture and eco-tourism. Based on the above findings, further recommendations are proposed to mobilize the enthusiasm of upstream communities and encourage their participation in ecological compensation, promote the market-oriented operation of ecological compensation mechanisms, strengthen cross-regional cooperation to establish joint mechanisms, enhance supervision and evaluation, and establish a sound benefit-sharing mechanism. These recommendations provide theoretical support and practical references for ecological compensation worldwide. Full article

The accelerating integration of electric vehicles (EVs) into contemporary transportation infrastructure has underscored significant limitations in traditional charging paradigms, particularly in accommodating heterogeneous user requirements within dynamic operational environments. This study presents a differentiated optimization framework for EV charging strategies through the systematic classification of user types. A multidimensional decision-making environment is established for three representative user categories—residential, commercial, and industrial—by synthesizing time-variant electricity pricing models with dynamic carbon emission pricing mechanisms. A bi-level optimization architecture is subsequently formulated, leveraging deep reinforcement learning (DRL) to capture user-specific demand characteristics through customized reward functions and adaptive constraint structures. Validation is conducted within a high-fidelity simulation environment featuring 90 autonomous EV charging agents operating in a metropolitan parking facility. Empirical results indicate that the proposed typology-driven approach yields a 32.6% average cost reduction across user groups relative to baseline charging protocols, with statistically significant improvements in expenditure optimization (p < 0.01). Further interpretability analysis employing gradient-weighted class activation mapping (Grad-CAM) demonstrates that the model’s attention mechanisms are well aligned with theoretically anticipated demand prioritization patterns across the distinct user types, thereby confirming the decision-theoretic soundness of the framework. Full article

Glass ionomer cements (GICs) are bioactive restorative materials valued for their sustained ion release and remineralisation capacity. However, their long-term interactions with sound enamel and dentine remain underexplored. This 12-month in vitro study aimed to evaluate microstructural and compositional changes in sound dental tissues adjacent to four GICs—Ketac Universal, Fuji IX and Equia Forte Fil (conventional GICs) and the advanced Glass Carbomer (incorporating hydroxyapatite nanoparticles)—using field-emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Glass Carbomer uniquely formed hydroxyapatite nanoparticles and mineralised regions indicative of active biomineralisation—features not observed with conventional GICs. It also demonstrated greater fluoride uptake into dentine and higher silicon incorporation in both enamel and dentine. Conventional GICs exhibited filler particle dissolution and mineral deposition within the matrix over time; among them, Equia Forte released the most fluoride while Fuji IX released the most strontium. Notably, ion uptake was consistently higher in dentine than in enamel for all materials. These findings indicate that Glass Carbomer possesses superior bioactivity and mineralising potential which may contribute to the reinforcement of sound dental tissues and the prevention of demineralisation. However, further in vivo studies are required to confirm these effects under physiological conditions. Full article

Ammonia (NH₃), as a vital component of the nitrogen cycle, exerts significant influence on the biosphere, air quality, and climate by contributing to secondary aerosol formation through its reactions with sulfur dioxide (SO₂) and nitrogen oxides (NO_x). Despite its critical environmental role, NH₃’s transient atmospheric lifetime and the variability in spatial and temporal distributions pose challenges for effective global monitoring and comprehensive impact assessment. Recognizing the inadequacies in current in situ measurement capabilities, this study embarked on an extensive analysis of NH₃’s temporal and spatial characteristics over East Asia, using the Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp-B satellite from 2013 to 2024. The atmospheric NH₃ concentrations exhibit clear seasonality, beginning to rise in spring, peaking in summer, and then decreasing in winter. Overall, atmospheric NH₃ shows an annual increasing trend, with significant increases particularly evident in Eastern China, especially in June. The regional NH₃ trends within China have varied, with steady increases across most regions, while the Northeastern China Plain remained stable until a recent rapid rise. South Korea continues to show consistent and accelerating growth. East Asia demonstrates similar NH₃ emission characteristics, driven by farmland and livestock. The spatial and temporal inconsistencies between satellite data and global chemical transport models underscore the importance of establishing accurate NH₃ emission inventories in East Asia. Full article

In recent decades, environmental requirements for reducing the toxic components emitted from vehicle exhausts have decreased drastically. Technologies for after-treatment of diesel vehicle emissions are being improved continuously in order to meet increasingly stringent regulations. Passenger cars are a significant source of air pollution, especially in urban areas. The EU has decided to phase out internal combustion engines. Stricter Real Driving Emissions (RDE) testing procedures have also been introduced, aiming to assess the emissions of nitrogen oxides (NO_x) and particle number (PN). The present work investigates the interaction between performance and smoke emissions of a diesel vehicle on a pre-established route in an urban environment with an everyday (normal) driving style. The results showed that when the vehicle is technically sound and meets its technical specifications, smoke emissions are within normal limits. Full article

Battery electric vehicles (BEVs) are seeing widespread adoption globally due to technological improvements, lower manufacturing costs, and supportive policies aimed at reducing greenhouse gas emissions. Governments have introduced incentives such as purchase subsidies and investments in charging infrastructure, while automakers continue to broaden their electric vehicle portfolios. Although BEVs show high overall safety performance comparable to internal combustion engine vehicles (ICEVs), they also raise distinct safety challenges that merit policy attention. This review synthesizes the current literature on safety concerns associated with BEVs, with particular attention to fire risks, vehicle weight, low-speed noise levels, and unique driving characteristics. Fire safety remains a significant issue, as lithium-ion battery fires, although less frequent than those in ICEVs, tend to be more severe and difficult to manage. Strategies such as improved thermal management, fire enclosures, and standardized response protocols are essential. BEVs are typically heavier than ICEVs, affecting crash outcomes and braking performance. These risks are especially important for interactions with pedestrians and smaller vehicles. Quiet operation at low speeds can also reduce pedestrian awareness, prompting regulations for vehicle sound alerts. Together, these issues highlight the need for policies that address both emerging safety risks and the evolving nature of BEV technology. Full article

The elliptic pipe jet screech is explored at a pressure ratio from 2 to 6. The pipe length to diameter ratio is 5. The fundamental screech frequency and magnitude are obtained from the sound pressure level spectrum. The screech frequency decreases as the pressure ratio increases. The minor plane has more tones than the major plane at an emission angle of 75 degrees from the jet axis. The amplitude of the screech differs among the planes. The amplitude is higher at lower emission angles from 45 to 75 degrees and lower at a sideline angle of 90 degrees. Full article

The decommissioning of offshore oil rigs presents complex environmental challenges and opportunities, particularly in the context of energy transition goals and marine ecosystem protection. This study applies a Life Cycle Assessment (LCA) approach to evaluate the energy and environmental impacts associated with two different decommissioning approaches: full removal and partial removal. The analysis considers greenhouse gas emissions, energy consumption, material recovery, and long-term waste management. The study demonstrates important energy savings through the recovery and recycling of steel, which offsets energy-intensive operations such as cutting and marine transport. In addition, the analysis underscores the potential of integrating decommissioned infrastructure into offshore renewable energy systems, highlighting synergies with circular economy principles and the decarbonization of offshore operations. The findings highlight the importance of site-specific assessments and integrated policy frameworks to guide environmentally sound decommissioning decisions in offshore energy infrastructure. The analysis shows that full removal results in 14,300 kg CO₂ eq emissions during cutting and transport, compared to 3090 kg CO₂ eq for partial removal. Meanwhile, steel recycling generates environmental benefits of −3.80 × 10⁶ kg CO₂ eq for full removal and −1.17 × 10⁶ kg CO₂ eq for partial removal. Full article

Lighthill’s theory of sound generation was developed to calculate acoustic radiation from a narrow region of turbulent flow embedded in an infinite homogeneous fluid. The theory is extended to include a simple model of non-isothermal fluid that allows finding analytical solutions. The effects of one specific temperature gradient on the wave generation and propagation are studied. It is shown that the presence of the temperature gradient in the region of wave generation leads to monopole and dipole sources of acoustic emission and that the efficiency of these two sources may be higher than Lighthill’s quadrupoles. In addition, the wave propagation far from the source is different than in Lighthill’s original work because of the presence of the acoustic cutoff frequency resulting from the temperature gradient. Full article

The accurate quantification of urban anthropogenic CO₂ emissions is of paramount importance for comprehending regional carbon fluxes and supporting climate change mitigation strategies. This study explores the applicability of a cost-effective unmanned aerial vehicle (UAV)-based mass balance method for independent urban-scale emission assessments. An integrated air–ground–satellite observation framework was established by combining UAV-based vertical CO₂ profiles, ground-based observations, and ERA5 reanalysis data, and applied to quantify CO₂ emissions in Chengdu, a major city in southwestern China. The UAV-derived CO₂ concentration profiles were coupled with meteorological parameters to compute cross-sectional fluxes, yielding an annual emission estimate of 48.4 MtCO₂, which aligns well with census-based estimations. The primary uncertainty, approximately 23.61%, stems from meteorological parameter variations, highlighting the need for improved data resolution and extended observation periods. This study demonstrates that UAV-based mass balance observations can serve as an independent and verifiable approach for urban emission estimation. Beyond supplementing existing inventories, it provides a robust reference for cross-validation, contributing to the development of more accurate and adaptive emission monitoring systems for urban climate governance. Full article

In aerospace, flow control techniques have improved the separation flow characteristics around airfoils by various means. In this paper, the delayed detached eddy simulation (DDES) technique is used to simulate the detailed flow field around the NACA0021 airfoil with two different flow control methods (Gurney flaps and leading- and trailing-edge flaps) applied at an angle of attack of 20°. The aerodynamic characteristics around the airfoil under these two flow control methods are investigated, and the results show that both flow control methods lead to a significant increase in the pressure on the suction surface of the airfoil, which contributes to an increase in lift. The aeroacoustic characteristics of the original airfoil, the Gurney flapped airfoil and the airfoil with leading-edge and trailing-edge flaps are then analyzed using a combination of DDES and FW-H acoustic analog equations. The results show that the total sound pressure level of the Gurney flap airfoil and the leading-edge and trailing-edge flap airfoil are improved in most azimuthal angles of the acoustic pointing distribution, among which the degree of improvement of the leading-edge and trailing-edge flap airfoil is greater than that of the Gurney flap airfoil near the trailing edge, and the total sound pressure level of the band leading- and trailing-edge flap airfoil decreases in the azimuthal angles near the leading edge. Compared with the original airfoil, the noise value is thus reduced by up to 4.13 dB. The results of pressure pulsation cloud map, sound pressure level cloud map on the airfoil surface and vortex cloud map distribution show that the two flow controls increase the pressure pulsation near the trailing edge, the range and peak value of sound emission on the airfoil surface increase, and the trailing vortex becomes more finely grained, which leads to an increase in noise. Full article

Electric ducted fans are gaining prominence in aviation due to their compact size, low noise, and zero emissions compared to conventional gas turbines. This study presents an experimental test system for a 390 mm electric Ducted Propulsion Fan developed by the Aerospace Propulsion Systems group at Hanoi University of Science and Technology. The carbon fiber composite thruster, driven by a centrally located BLDC motor, was mounted on a test stand equipped with force and rotational speed (rpm) sensors. Power was supplied through two battery configurations, eight-pack and nine-pack, with voltage and current monitored and controlled via an ESC module. Experiments conducted from 2000 to 7000 rpm explored the relationship between electrical inputs and aero-propulsive outputs. The results revealed that input power, current, and sound pressure level (SPL) amplified meaningfully with rpm, while the voltage slightly declined. The maximum rpm reached 6500 rpm for the eight-pack and 7000 rpm for the nine-pack configurations. When greater than 6000 rpm, the SPL reaches close to 120 dB. The eight-pack configuration provided higher thrust per volt, whereas the nine-pack offered better thrust per ampere and improved starting power. Although dimensionless indices, including power coefficient (CP), thrust coefficient (CT), and figure of merit (FM), reduced with rpm, the FM remained between 0.7 and 0.75 at medium speeds, demonstrating effective energy conversion. Full article

Motion of dislocations is a common mechanism of plasticity in many materials. Acoustic emissions and stress bursts turned out to be integral parts of this mechanism. An adequate description of these processes is an important goal of the Materials Theory, which aims to describe the mechanical properties of materials and their reliability in service. In this article, a novel approach to dislocation plasticity capable of describing emission events and stress bursts is introduced, and computational experiments intended to model the processes of compressive creep and shock compression in samples of various makeup and sizes are discussed. It turns out that the emission events self-organize into dislocation avalanches, which propagate at a speed determined by the conditions of loading. In the compressive creep experiments, the avalanches arrange into slow-moving slip bands, while in the shock compression experiments the avalanches move faster than sound. Full article

To utilize a huge amount of oil palm trunk (Elaeis guineensis) biomass as wall insulation, its dimensional stability and insulation properties need to be improved. Thermal modification (TM) (without compression or densification) is one of the efficient methods widely used for improving insulation properties and dimensional stability of wood material, but such an existing method requires a complex system. In this work, the TM of oil palm wood with an initial density of 219 ± 34 kg/m³ was performed at 200 °C using a hot press machine. The optimum heat-treatment durations (2 h, 4 h, and 6 h) for their potential for insulation wall applications were explored. TM improved dimensional stability, sound-absorption coefficient, and thermal conductivity by approximately 66.7%, 26.7%, and 24.6%, respectively, but increased volatile organic compound (VOCs) emission compared with the control. Heat-treatment duration notably affected mass loss, density, and thermal conductivity. Compared with available natural material-based insulation walls, TM oil palm showed better insulation performance for all treatment durations. Thus, the heat-treatment duration of 2 h is suggested to save the energy consumption in the heat-treatment process while still achieving the same level of sound absorption, dimensional stability, and VOC emission performance as that of the long heat-treatment duration. Full article