Aiming at the problems of poor real-time detection, low accuracy, and false detection and omission of pavement disease detection including hole and crack, an improved algorithm based on YOLOv9 was proposed to resolve the problem. Firstly, AKConv (alterable kernel convolution) was introduced into the backbone network to replace the convolution module in RepNCSPELAN4, which improves the feature extraction ability of the network for different diseases and effectively solve the problem that road disease is difficult to distinguish from background environment features. Secondly, selective image attention mechanism (SimAM) and DySample sampling modules were introduced to focus on the key information in the detection head, and the capability to extract information features was enhanced more efficiently. Finally, the inner-IOU function was used to optimize the weight parameters of the model to improve the learning ability of mixed samples. The experimental comparison between YOLOv9-c and our model showed that the accuracy, recall rate and MAP of the improved model are increased by 40.17%, 15.99% and 20.95% respectively. The performance has been significantly improved, and the detection effect is more accurately and efficiently, and the accuracy and generalization ability of pavement disease detection algorithm are improved.

When tunnels with extra-large cross-sections pass through layered rock formations, given the unique structural characteristics of these layers, suitable control strategies must be implemented to mitigate any adverse impacts. Based on the extra-large section tunnel project of Chongqing Guobo Center Station passing through layered rock, numerical simulations, and field monitoring are adopted in this study to compare the mechanical differences between balanced and unbalanced anchor cable supports during tunneling. The results show that compared with the balanced anchor cable support, the influence of the unbalanced anchor cable support on the control difference of displacement and plastic zone of surrounding rock is not significant. However, the unbalanced anchor cable supportcould significantly affect the bending moment distribution range of the vault of lining structure, while having little influence on the peak bending moment and the distribution and magnitude of axial force, with the differences between them being 8% and 11.2% respectively. The reduction in the safety redundancy of the lining structure under the unbalanced anchor cable support is less, and the stability of the tunnel in layered rock could still be maintained. From the perspectives of economy and construction convenience, the amount of anchor cable could be saved by 51%, and the economic advantages are more prominent, which is more advantageous in the construction of tunnels with large sections in layered rock. The effectiveness of the unbalanced support in maintaining tunnel stability is confirmed by field monitoring. The discrepancy between the numerical simulation and field monitoring results is merely 2 mm, demonstrating high consistency and validating the accuracy of the calculations. Critical insights for the design and construction of future similar tunnels in layered rock are provided.

The cornering stiffness of automobile tires is closely linked to the vehicle’s handling characteristics, and accurately estimating the tire cornering stiffness in real time is of significant importance for enhancing the stability of vehicle handling. Addressing the challenge of direct measurement of cornering stiffness, a real-time identification method based on the estimation of tire lateral force and slip angle was proposed. Firstly, considering the influence of longitudinal force on lateral force, a tire lateral force estimator was designed based on the yaw dynamics model and sliding mode observer algorithm, followed by the design of a slip angle feedback estimator based on the estimation error of lateral force. Secondly, a nonlinear tire force model that describes the relationship among tire lateral force, slip angle, and cornering stiffness was established. Taking the real-time estimated lateral force and slip angle as inputs, a recursive least squares online identification algorithm with limited memory was designed to address the issue of estimation error due to “data saturation” and improve identification accuracy. Finally, joint simulation experiments using Simulink and CarSim were conducted. The experimental results indicate that the estimation error of tire lateral force is approximately 4.153 9% on average, while the estimation error of tire slip angle is 3.285 2% on average. The identification model based on the recursive least squares method is robust to changes in road conditions, demonstrating good tracking accuracy and stability under both high and low adhesion conditions, with an average estimation accuracy of tire cornering stiffness of approximately 98.379 3%.

Aiming at the U-turn scenario of autonomous vehicles in two-way single lanes, a safety decision-making method was proposed by fuzzy reasoning, and a U-turn mathematical model was established based on the spatial distribution relationship of vehicles, seven key control points were determined, the search strategy of particle swarm optimization was improved, and an efficient and comfortable U-turn trajectory planning method was proposed. The safety decision-making method firstly establishes a membership relationship between the relative distance between the vehicle and the vehicle on the target lane and the minimum safety distance during steering when making a U-turn, and selects the time with higher safety to make a U-turn. The trajectory planning method combines the spatial distribution characteristics of vehicles, improves the constraints of particle swarm optimization, and proposes a new search strategy, which can quickly converge to the optimal extreme value and plan the optimal path of U-turn. The results show that the proposed decision-making and trajectory planning methods can complete the U-turn safely and efficiently.

To explore the impact of the community built environment on the walking time of elderly people, and considering gender differences among the elderly group, a CatBoost model was constructed and the SHAP (Shapley additive explanations) explanation method was integrated. The relative importance and nonlinear relationships of the community built environment features with the walking time of elderly people of different genders were comparatively analyzed. The study findings indicate that the community built environment variables have a more significant influence on the walking time of the elderly compared to personal socioeconomic attributes. However, the impact varies between genders. Compared to elderly males, elderly females pay more attention to built environment variables closely related to social needs, such as NDVI and population density. In contrast, the walking time of elderly males is more closely associated with personal socioeconomic attributes, often linked to transportation convenience and travel efficiency.

The response of an aircraft engine to bird strikes has the fan blade as its primary component, and the flight safety of the aircraft is directly impacted by the dynamic damage caused by stress changes. A three-dimensional model of a near-real bird body was established in this paper based on the structural features of the “bar-headed goose”. The dynamic damage of the blade was studied in consideration of the take-off-climb and approach-landing stages where bird strike accidents are most likely to occur for aircraft, with the effects of different impact speeds, fan blade speeds, and bird impact attitudes being taken into account. It is indicated by the results that the axial damage and deformation of fan blades tend to be increased monotonically with the increasing of aero-engine speed and relative velocity of bird strike blades. Additionally, as the fan blade speed is increased, the stress peak value after a bird strike shows a V-shaped trend, with the smallest stress peak value being occurred at 2 005 r/min. Furthermore, as the contact area between the bird body and fan blade at the initial collision moment is increased, both the stress and damage degree of the blade are gradually increased across different postures. When impacted at a 90° posture, the axial damage deformation of the blade is reached to 60.887 mm. Valuable reference for anti-bird strike design considerations for aero-engine fan blades is provided by these research findings.

The perforated walls of transonic wind tunnels with different parameters have a considerable influence on the flow field quality of the test section, therefore, the characterization of the perforated wall parameters is extremely essential for the design of the test section of transonic wind tunnels. The relationship between the characteristic parameters near the perforated wall of three-dimensional and two-dimensional perforated wall models was studied using the single straight perforated hole of the FL-3 wind tunnel. The mass and velocity distributions of the two-dimensional and three-dimensional perforated wall show obvious linear characteristics under different pressure difference coefficients. It is proposed that the two-dimensional perforated wall can be equivalent to the flow characteristic parameters of the three-dimensional perforated wall by the corresponding coefficient transformation under the same incoming flow Mach number when the wall pressure difference coefficient and the boundary layer displacement thickness are satisfied. A two-dimensional calculation model of the transonic wind tunnel was established, and the effects of perforated wall parameters and free stream Mach number on the flow field and flow characteristic parameters near the wall in the test section were analyzed by numerical method. When l / d = 1, the increase in perforated wall size makes the wall pressure difference coefficient increase, otherwise, the relative area of flow in the perforated wall decreases. As d = 2 mm, the flow field was proposed. When l / d > 2, ΔC_p tends to be stable. When l / d = 3, m' and S / d are the maximum values, in the Ma = 0.8 ~ 0.9 range, m' is positively correlated with the incoming Mach number, but ΔC_p changes little. The pressure difference coefficient and velocity component obtained under different perforated wall parameters have certain guiding significance for understanding the perforated wall flow and adjusting the perforated wall of the test section.

The extremely short-term prediction of seaplane motion can provide the rocking motion posture over the next few seconds, which is considered essential for ensuring safety during take-off and landing phases under adverse wind and wave conditions. Although some research has been conducted on extremely short-term prediction methods for seaplane motion, limited attention has been given to analyzing differences in the applicability of various methods. In this context, the NACA TN 2929 aircraft was taken as an example, and the three degree of freedom motion simulation data under typical working conditions were calculated based on potential flow theory. To compare the forecasting performance under different forecasting conditions, three typical extremely short-term prediction of seaplane motion models, namely AR (auto-regressive), LSTM (long short term memory), and TCN (temporal convolutional network), were constructed. The results show that compared to the AR model, the LSTM and TCN neural network models exhibit superior forecasting accuracy for longer prediction durations, effectively enabling accurate predictions of the heave, roll, and pitch motions of the seaplane at the ten-second level, providing a valuable theoretical reference for the selection of seaplane motion prediction algorithms.

To determine the presence of sulfhydryl groups on natural aquatic biofilms and their adsorption characteristics for typical heavy metals, a method for sulfhydryl masking in the biofilms based on a specific masking agent was established in this study. Based on this method, surface concentration of sulfhydryl group in natural biofilms and their adsorption characteristics for typical heavy metals, including Cu, Pb, and Cd, at different pH were investigated. The results indicate that the established masking method can effectively mask sulfhydryl groups and has little effect on microorganisms in biofilms. There are relatively low concentrations of sulfhydryl groups on the surface of natural biofilms, with a concentration of (5.8 ± 0.6) μmol/g, accounting for 5.7% of the total site concentration on the biofilms. Despite the low concentration of sulfhydryl groups, their stronger metal binding capacity makes them significantly contribute to metal adsorption when the metal concentration is low (the theoretical loading of heavy metals by the biofilm is less than 1.0 μmol/g). This pattern is essentially unaffected by the pH of the adsorption system and the type of heavy metal. This proves that sulfhydryl groups in biofilms also have an important impact on the behavior and risk of heavy metals in natural aquatic environments with low metal content, further highlighting the environmental significance of natural biofilms.

The Chishui River Basin has been recognized as an important ecological security barrier in the upstream of the Yangtze River Basin. Research on the ecosystem service value of the Chishui River Basin under different future development scenarios is of great significance to carry out the environmental protection policies and the environmental protection measures. Therefore, Chishui River Basin has been selected as the research area and the FLUS (future land use simulation) model and InVEST (integrated valuation of ecosystem services and trade off) model were functioned to predict the ecosystem services, including water yield, soil conservation, and water purification, under three scenarios, such as natural development, environmental protection, and economic development in 2040. The high ecosystem services functions in all three scenarios are identified as the key protected areas. The results show as follows. There are significant changes in agriculture area and urban area under different scenarios, especially, the agriculture area under the economic development scenario has increased 510.55 km² and 1 475.76 km² compared to the natural development and environmental protection scenarios, respectively. In the environmental protection scenario, the areas with high water yield (>700 mm) and high soil conservation function (>2 000 t/hm²) account for approximately 36.81% and 47.15% of the Chishui River basin area, respectively. The proportion of key protected areas for ecosystem services functions in the Zunyi City account for approximately 62.65%. The results of this study aim to provide certain support for identifying key protected areas in the Chishui River Basin and promoting the implementation of spatial refinement protection and management.