Search Results (80)

Quantitative sustainability assessments in the EU rarely differentiate between the roles of governments, businesses, and the population, making it difficult to empirically test theories of socio-technical transitions, stakeholder governance, and convergence/club convergence. To address this gap, the study constructs four stakeholder-specific indices: the Government Sustainability Index (GSI), Environmental Sustainability Index (ESI), Population Sustainability Index (PSI), and Business Sustainability Index (BSI) alongside a Composite Sustainability Index (CSI). The indices are built from harmonised Eurostat, European Environment Agency, and SDG Index data using min–max normalisation, covering all 27 EU Member States over the period of 2015–2024 (270 country–year observations). The empirical analysis applies K-means clustering, compound annual growth rates (CAGRs), and correlation analysis, complemented by a robustness module testing alternative weighting schemes, z-score normalisation, and ±10% indicator perturbations. The results identify four relatively stable sustainability tiers with limited inter-tier mobility, an S-curve-type relationship between initial performance levels and subsequent growth, a consistent hierarchy of stakeholder response speeds (ESI > GSI > PSI), and a structural slowdown after 2019. These patterns are robust across alternative specifications and imply that EU sustainability transitions follow multiple, tier-structured trajectories shaped by institutional lock-in rather than converging toward a single equilibrium. The framework offers a basis for tier-differentiated and stakeholder-sensitive policy strategies. Full article

The Ieodo plume is a distinctive suspended sediment plume near the Ieodo Ocean Research Station (I-ORS), located in the middle of the northern East China Sea. Because the Ieodo plume exhibits multiple different spatial scales, this study conducted an integrated remote sensing observation using satellites and unmanned aerial vehicles (UAVs) to observe its development and dispersion. Sentinel-2 and Geostationary Ocean Color Imager-II (GOCI-II) data were used to determine the plume’s spatial characteristics, broad-scale behavior, hourly variability, and turbidity characteristics. Also, TPXO model outputs were employed to evaluate the relationship between plume occurrence and tides, together with satellite imagery. Plume was repeatedly observed near the top of the Ieodo Seamount, with an affected extent of 11.4 ± 3.2 km in the east–west direction and 14.3 ± 4.1 km in the north–south direction. Moreover, hourly variations observed using GOCI-II showed that the Ieodo plume rotated clockwise with shifting tidal currents, forming a counterclockwise curved band or a ring-shaped structure. Total suspended solids (TSSs) in the plume reached their maximum when the southward component of the TPXO tidal current was dominant. Based on UAV optical surveys at the I-ORS, fine-scale morphology at the early stage of plume development was revealed, and it was confirmed that the Ieodo plume can occur even when it is not detected by satellite imagery. Furthermore, the u- and v-velocity vectors of the propagating Ieodo plume were derived by applying large-scale particle image velocimetry (LSPIV) to geometrically corrected sequential UAV imagery obtained in I-ORS. Plume speed was greatest near the source during the initial stage (0.81 ± 0.30 m s⁻¹) and gradually decreased to 0.34 ± 0.29 m s⁻¹ over distance. Based on the results above, we propose that the Ieodo plume is primarily generated by a pressure reduction associated with tidally accelerated currents over topography, driven by the Bernoulli effect. This study shows that an integrated satellite and UAV observation framework can effectively monitor rapidly evolving suspended sediment plumes. It can further help improve our understanding of dynamically driven submesoscale marine events. Full article

The Arctic Puffin Optimization (APO) Algorithm is a recently proposed metaheuristic algorithm that has been widely applied to solve optimization problems in continuous spaces. However, it cannot be directly used to solve combinatorial optimization problems in discrete spaces. To address these limitations, a Binary Arctic Puffin Optimization (BAPO) Algorithm is proposed, focusing on developing transfer functions to convert the algorithm’s continuous solutions into discrete binary solutions. Two primary transfer function types, S-shaped and V-shaped, are commonly employed. Experimental analysis identifies optimal functions for different algorithmic stages. These are then integrated with a conversion factor to propose a hybrid transfer function for the binarization of the Puffin Optimization Algorithm. To address the issue of slow particle convergence in the later stages of the exploration phase and the tendency to overlook high-quality solutions during the exploitation phase in the binary algorithm, logarithmic inertia weight and the golden sine strategy are incorporated, respectively, for improvement. Simulation experiments were conducted to solve both single-dimensional and multidimensional 0–1 knapsack problems. Experimental data and convergence curves, including mean values and standard deviations, were analyzed. The results demonstrate that the binary Arctic puffin optimization algorithm exhibits excellent convergence, stability, and fast search speed. Full article

Irradiation embrittlement occurs in the cladding materials of fusion reactors during irradiation. Determining the ductile–brittle transition temperature via Charpy impact testing is the primary method for evaluating irradiation embrittlement. Standard-sized V-shaped Charpy impact specimens (CVN) are too large in size and have high induced radioactivity. Small-sized specimens (KLST) can solve these problems, but the performance data measured from small-sized specimens are different from those of standard specimens. In other words, there is a size effect in impact performance. The notch size and hammer impact speed of KLST specimens are different from those of CVN specimens. The influence of these factors on impact performance requires further study. In response to these issues, on the basis of the previous experiments conducted by the research group, GTN damage models of CVN specimens and KLST specimens are constructed using the inverse operation method. Numerical simulation of the impact on the upper platform area is carried out for KLST specimens and variable-sized KLST specimens. Compared with the test results, the numerical simulation results are in good agreement, verifying the accuracy and reliability of the model. The results show that the notch angle and radius have little influence on the plastic zone. The cross-sectional area of the notch has a significant impact on the plastic zone. The impact velocity within the range of 3.8 m/s to 5.24 m/s affects the impact response process, but does not affect the load–displacement curve, the length of the non-plastic deformation zone, or the volume of the plastic zone. Full article

The locomotion of fish provides inspiration for designing efficient and agile underwater robots. Potamotrygon motoro propels itself by generating traveling waves along its pectoral fins. Inspired by its graceful swimming stroke, we design and fabricate a robotic fish, where the snap-through instability of elastic curved rods is exploited to produce the undulatory fin motion. In this design, the rotary input of two motors is transformed smoothly and continuously to controllable wave-like fin deformation. By changing the initial fin shape, motor speed, and friction at the releasing end, the propulsion performance and the maneuverability of the robotic fish can be significantly improved. The physical prototype of the robotic fish is fabricated, and its swimming performance is measured. Its maximum swimming speed reaches 0.76 BL/s, and it can achieve small-radius turns with a maximum angular speed of 1.25 rad/s. In contrast to the multi-actuator systems, the proposed dual-motor, elastic-snapping–driven design is featured by simple structural construction, low energy consumption, excellent maneuverability, and superb adaptation to environments. Our robotic fish holds promising applications in such areas as environmental monitoring, underwater inspection, and ocean exploration. The propulsion strategy presented in this work may pave a new way for the design of shape-morphing robots as well as other soft machines at multiple length scales. Full article

In the article “New Technological Approach to Cable Car Boarding”, the authors attempted to correctly design the curve geometrically along which the rope moves through the station during the deceleration of cabins with attaching platforms in a central position, primarily intended for mass public transport. Since the suspension continuously connects the cabin and the rope during cabin deceleration, the rope moves at a constant speed along a special curve that enables the cabin to stop in the central position. This curve is symmetric with respect to the longitudinal axis of the station. However, the authors found that in the previous article presenting this cable car system, an error was made in the geometric design of the rope path curve, which the original authors were not aware of at the time. They determined that, in the presented example, a suspension length of 8 m was too short for the combination of rope speed of 5 m/s (cable car speed) and cabin deceleration of 0.5 m/s². This article revisits this geometric problem in greater detail. The study shows that not every combination of rope speed, suspension length, and cabin deceleration in the central position functions correctly. First, the boundary conditions and spatial constraints of the rope path curve were defined. Based on the upper bound and lower bound rope path lengths, the optimal or correct shape of the rope path curve was determined geometrically. The study concludes that for a given combination of rope speed (cable car speed) and cabin deceleration, only one suspension length is suitable. In the case of a rope speed of 5 m/s and cabin deceleration of 0.5 m/s², the correct suspension length is 16.85 m. The authors also found that the result depends on the time interval used in constructing the curve. Full article

A central sustainability question is how the digital economy helps societies decarbonize at lower cost. We develop a carbon-market-consistent framework to show how digitalization can strengthen market governance, reduce regional carbon-abatement costs, and accelerate green transformation. Using data for 30 Chinese provinces from 2011–2022, we estimate panel fixed-effects models and conduct numerical simulations to test the digital economy’s dynamic, inverted-U-shaped effect on abatement costs, accounting for internal and external drivers. The digital development shifts the abatement–cost curve downward and leftward by speeding the transition from internal mitigation costs to external trading costs, enabling regions to reach the cost-reduction stage earlier and at lower overall cost. Mechanism evidence indicates two channels: externally, digitalization enhances carbon-market sophistication (liquidity, price discovery, and compliance efficiency); internally, it promotes technological progress and energy-efficiency improvements that raise emission-reduction productivity. In the short run, emissions trading provides external incentives that buffer production-cost pressures from digital-capital investment; in the long run, digital growth accelerates the energy transition and structurally increases abatement efficiency. Heterogeneity analysis shows a more pronounced inverted-U in central and western provinces, while eastern provinces have largely entered a sustained cost-decline phase. By lowering the social cost of achieving emissions targets, the digital economy directly supports sustainable development and China’s green, low-carbon transition. Full article

The increasing penetration of renewable energy, such as photovoltaic generation, makes it essential to enhance power system dynamic performance through improved grid-forming control strategies. In the grid-forming control system, the virtual synchronous generator control (VSG) is currently widely used. However, the inertia (J) and damping (D) in the traditional VSG are fixed values, which can result in large overshoots and long adjustment times when dealing with disturbances such as load switching. To address these issues, this paper proposes an adaptive virtual synchronous generator (VSG) control strategy for grid-side inverters, which is accomplished by adaptively adjusting the VSG’s inertia and damping. Firstly, we established a photovoltaic-storage VSG grid-forming system; here, the photovoltaic power is boosted through a DC-DC converter, and the energy storage is connected to the common DC bus through a bidirectional DC-DC converter. We analyzed how J and D shape the system’s output characteristics. Based on the power-angle characteristic curve, the tanh function was introduced to design the control function, and a JD collaborative adaptive control (ACL) strategy was proposed. Finally, simulation experiments were conducted under common working conditions, such as load switching and grid-side voltage disturbance, to verify the results. From the results shown, the proposed strategy can effectively improve the response speed of the system, suppress system overshoot and oscillation, and, to a certain extent, improve the dynamic performance of the system. Full article

Mixing hydrogen into natural gas pipelines for transportation is an effective solution to the imbalance between the supply and demand of hydrogen energy. Studying the influence of bent pipes in hydrogen-mixed natural gas explosion accidents can enhance the safety of hydrogen energy storage and transportation. Through experiments and LES, the influence of pipe spacing configuration on the vented explosion of this mixed gas in pipes with a large length-to-diameter ratio was analyzed. The maximum explosion pressure (Pmax) of the straight pipe is 21.7 kPa and the maximum pressure rise rate ((dp/dt)max) is 1.8 MPa/s. After adding the double elbow, Pmax increased to 65.2 kPa and (dp/dt)max increased to 3.7 MPa/s. By increasing the distance (D1) from bent pipe-1 to the ignition source, the flame shape changes from “finger-shaped” to “concave-shaped” to “wrinkled-shaped.” When D1 is at its minimum, the explosion reaction is the most intense. However, as D1 increases, each characteristic parameter decreases linearly and the flame propagation speed significantly reduces, the flame area decays more severely, and the flame acceleration effect is also suppressed. When the distance between the two bent pipes (D2) was gradually increased, the flame transformed from “finger-shaped” to “tongue-shaped” to “wrinkled-shaped”. The flame area curve exhibited a unique evolutionary process of “hitting bottom” to “rebounding” to “large-scale flame backflow”. This paper explores the development process of various characteristic parameters, which is of great reference value for preventing explosions in hydrogen-blended natural gas pipelines in underground pipe galleries. Full article

This paper aims to study the mechanism of avoiding the S-shaped region (S-shaped region, SFR) during the startup of pumped storage units (pumped storage units, PSUs). Firstly, the state space model of the PSU in frequency mode is built using the transfer coefficient of the pump turbine. Then, according to the characteristics of the SFR, the accurate range of the SFR is determined in the full characteristic curve. Finally, combined with a specific power station, this paper proposes a novel geometric perspective method to reveal the underlying mechanism for avoiding the SFR during the startup of PSUs. The core innovation lies in establishing, for the first time, the precise spatial relationship (positioning and distance) between the no-load operating point and the upper boundary of the SFR, thereby identifying two critical necessary and sufficient conditions for successful startup avoiding instability. Based on this mechanism, the critical state of PSUs entering the SFR and the influence of operation points on the startup stability that the PSU is putting into PID control are analyzed using the Hopf bifurcation principle. The results show that two conditions need to be met when the PSU starts up to avoid the SFR. One is that the system operation point is in the stable region, and the other is that the speed overshoot is less than the critical speed overshoot. The speed overshoot is the direct cause of the unit entering the SFR, leading to startup failure. When the PSU is started up and put into proportional–integral–derivative (proportional–integral–derivative, PID) control, a certain margin of flow and guide vane opening will help reduce the speed overshoot and prevent the unit from entering the SFR. Full article

Under cyclic moving load action, tensile-dominant structures are prone to crack initiation due to cumulative damage effects. The presence of cracks leads to structural stiffness degradation and nonlinear redistribution of dynamic characteristics, thereby compromising str18uctural integrity and service performance. The current research on the dynamic behavior of cracked structures predominantly focuses on transient analysis through high-fidelity finite element models. However, the existing methodologies encounter two critical limitations: computational inefficiency and a trade-off between model fidelity and practicality. Thus, this study presents an innovative analytical framework to investigate the dynamic response of cracked simply supported beams subjected to moving loads. The proposed methodology conceptualizes the cracked beam as a system composed of multiple interconnected sub-beams, each governed by the Euler–Bernoulli beam theory. At crack locations, massless rotational springs are employed to accurately capture the local flexibility induced by these defects. The transfer matrix method is utilized to derive explicit eigenfunctions for the cracked beam system, thereby facilitating the formulation of coupled vehicle–bridge vibration equations through modal superposition. Subsequently, dynamic response analysis is conducted using the Runge–Kutta numerical integration scheme. Extensive numerical simulations reveal the influence of critical parameters—particularly crack depth and location—on the coupled dynamic behavior of the structure subjected to moving loads. The results indicate that at a constant speed, neither crack depth nor position alters the shape of the beam’s vibration curve. The maximum deflection of beams with a 30% crack in the middle span increases by 14.96% compared to those without cracks. Furthermore, crack migration toward the mid-span results in increased mid-span displacement without changing vibration curve topology. For a constant crack depth ratio (γ_i = 0.3), the progressive migration of the crack position from 0.05 L to 0.5 L leads to a 26.4% increase in the mid-span displacement (from 5.3 mm to 6.7 mm). These findings highlight the efficacy of the proposed method in capturing the complex interactions between moving loads and cracked concrete structures, offering valuable insights for structural health monitoring and assessment. Full article

The agricultural production process contributes to the global issue of pesticide pollution. Based on the static toxicity test of diuron (DCMU) on Daphnia magna (D. magna) for EC₅₀-48 h, a concentration range of 0.2 to 1 mg/L was set as sublethal concentrations, while lethal concentrations were set at 2 mg/L and 4 mg/L. This study analyzes the toxic response patterns of the swimming behavior indicators of D. magna exposed to different concentrations of DCMU. The results showed that the average speed (V) of D. magna decreased step by step with exposure time, regardless of exposure to sublethal concentration or lethal concentration. However, during the same short-term exposure period, the V of D. magna at lethal concentration was higher than that at sublethal concentration, which indicates that the swimming behavior of D. magna exposed to DCMU may be stimulated and accelerated. Compared to the control group, there is a statistically significant difference in the V of D. magna after short-term exposure, especially showing an extremely significant difference after 5 min of exposure. Evidently, compared to the traditional 48 h static toxicity testing method, the swimming behavior indicators of D. magna show a more sensitive response to DCMU after 5 min of exposure, making it more suitable for rapid toxicity detection. By expanding the range of exposure concentrations, it was found that the V indicator of D. magna responded significantly to a DCMU concentration of 0.05 mg/L after only 5 min of exposure, and a high degree of correlation was observed between the indicator and the exposure concentration. Through nonlinear fitting, the relationship between V and the dose–effect of DCMU toxicity presents an S-shaped curve, with R² > 0.9. Consequently, it becomes possible to study the dose–effect relationship between the changes in the swimming behavior indicators of D. magna and the stress concentration based on this theory. This further establishes a foundation for the development of comprehensive aquatic toxicity rapid detection technology based on the toxic response of swimming behavior indicators. Full article

Stretch blow molding (SBM) is widely utilized in industrial applications, yet the deformation characteristics of materials during this process are intricate and challenging to precisely articulate. To accurately forecast the stress–strain response of polyethylene terephthalate (PET) in SBM, a hybrid Artificial Neural Network (ANN)-based constitutive model has been developed. The model has been created by combining a physical-based function for capturing the small-strain behavior in parallel with an ANN-based model for capturing the temperature-dependent large-strain nonlinear viscoelastic behavior. The architecture of the ANN has been designed to ensure stability in a load-controlled scenario, thus making it suitable for use in FEA simulations of stretch blow molding. Data for training the model have been generated by a new semi-automatic experimental rig which is able to produce 850 stress–strain curves over a wide range of process conditions (temperature range 95–115 °C and strain rates ranging from 1/s to 100/s) directly from blowing preforms using a combination of high-speed video, digital image correlation and sensors for pressure and force. The model has already been implemented in the commercial FEA package Abaqus via a VUMAT subroutine, with its performance validated by comparing the prediction of the evolution of preform shape during blowing vs. high-speed images. In conclusion, the developed hybrid ANN model, when integrated into Abaqus, offers a more accurate simulation of SBM processes, contributing to improved design efficiency and product quality. Full article

Acoustic temperature measurement (ATM) and sound source localization (SSL) are two important applications of acoustic sensors. The development of novel acoustic sensors capable of both ATM and SSL is an innovative research topic with great interest. In this work, an acoustic Fabry-Perot resonance detector (AFPRD) and its cross-shaped array were designed and fabricated, and the passive ATM function of the AFPRD and the SSL capability of the AFPRD array were simulated and experimentally verified. The AFPRD consists of an acoustic waveguide and a microphone with its head inserted into the waveguide, which can significantly enhance the microphone’s sensitivity via the FP resonance effect. As a result, the frequency response curve of AFPRD can be easily measured using weak ambient white noise. Based on the measured frequency response curve, the linear relationship between the resonant frequency and the resonant mode order of the AFPRD can be determined, the slope of which can be used to calculate the ambient sound velocity and air temperature. The AFPRD array was prepared by using four bent acoustic waveguides to expand the array aperture, which combined with the multiple signal classification (MUSIC) algorithm can be used for distant multi-target localization. The SSL accuracy can be improved by substituting the sound speed measured in real time into the MUSIC algorithm. The AFPRD’s passive ATM function was verified in an anechoic room with white noise as low as 17 dB, and the ATM accuracy reached 0.4 °C. The SSL function of the AFPRD array was demonstrated in the outdoor environment, and the SSL error of the acoustic target with a sound pressure of 35 mPa was less than 1.2°. The findings open up a new avenue for the development of multifunctional acoustic detection devices and systems. Full article

Piezoelectric-actuated machine tools (PAMTs) exhibit nanoscale motion capabilities, with their S-shaped curve trajectory further enabling smooth path execution and reduced terminal pulse. However, the speed changes inherent in multi-order trajectories introduce an additional non-uniform creep difference (NCD), which differs significantly from conventional hysteresis effects. Traditional models are inadequate for addressing this mixed shape nonlinearity. To overcome this limitation, this paper proposes a hybrid compensation method for the S-shaped curve trajectory of piezoelectric-actuated machine tools. The general deformation law is first established through a comprehensive mechanism analysis. The NCD and hysteresis, induced by speed changes and inherent properties, are decoupled and addressed using a pre-known phenomenon model and a clockwise operator model, respectively. Finally, a hybrid feedforward control strategy is developed to integrate these models for effective compensation. Experimental results demonstrate that the hybrid compensation method achieves a maximum relative error of 5.48% and a maximum mean square error of 0.28%, effectively mitigating the dual nonlinear factors arising from the piezoelectric-actuated machine tool’s trajectory in feedforward control. Full article