Deltas are threatened by erosion due to climate change and reduced sediment supply, but their response to these changes remains poorly quantified. We investigate the abandoned Yellow River delta that has transitioned from rapid growth to ongoing deterioration due to a river avulsion removing the sediment supply. Integrating bathymetric data, process observations, and sediment transport modeling, we find that while the subaerial delta was stabilized by engineering measures, the subaqueous delta continued to erode due to intensified storms, losing 39% of its mass deposited before the avulsion. Long-term observations show that winter storms initiate scouring of the subaqueous delta, contributing up to 70% of seabed erosion. We then analyze 108 global deltas to assess subaqueous delta erosion risks and identify 17 deltas facing similar situations of sediment decline and storm intensification during the past 40 years. Our findings suggest that subaqueous delta erosion must be integrated into delta sustainability evaluations.

The coupling mechanism between natural and anthropogenic noise in shallow marine areas is of great significance for maintaining the ecological safety of these regions. In this study, a section of Zhanjiang Bay’s entrance was selected as a typical research area, and environmental noise data at different depths were collected during the spring and autumn seasons. The spectral characteristics, sound pressure levels, and underwater noise frequency correlation matrices of environmental noise were analyzed to reveal the underwater noise characteristics of tidal channels in Zhanjiang Bay and their main influencing factors. The results show that underwater noise in this study area had a stable frequency band distribution. In the low-frequency range of 20–50 Hz, the main source of noise was the flow noise influenced by tides and topography, with a peak sound pressure level of approximately 97 dB. In the frequency range of 50 Hz to 500 Hz, the main noise sources were ships at sea, followed by wind-generated noise. At frequencies above 500 Hz, the noise intensity decreased. In addition, it was found that the sound pressure level in the low-frequency range had a significant correlation with the tidal level, increasing with the rise of the tide and decreasing during low tides. This study provides a research case on the impact that human noise activity has on environmental noise in shallow marine bays. These research findings can support the selection of sites and reduce construction noise from offshore wind farms, as well as ensure the acoustic ecological environment in the vicinity of marine ranches.

Pipeline defects such as aging, corrosion and cracks may result in the structural failure of industry pipelines, causing environmental pollution, energy waste and even catastrophic accidents of explosion. In-pipe inspection robots are regarded as an expected non-destructive testing tool of analyzing and evaluating in-pipe defects. This paper built a simple variable-diameter pipeline platform based on real pipeline environment. The movement of robots was analyzed to meet the functional requirements of variable diameter and obstacle-crossing. A design scheme of automated in-pipe robot with self-adaptive various diameter mechanism was developed, where a parallelogram connecting rod mechanism combining spring and feed screw nut pair was employed to adapt the diameter change of pipelines from 200mm to 250mm, actively and forcedly. Moreover, a digital camera device was equipped to perform on-line macro detections and in-pipe image acquirements. The results indicate that designed robot system has good various diameter properties. The work provides a reference for subsequent designs of in-pipe inspection robots.

In the BSC rules of the Chinese Society of Automotive Engineering, it is stipulated that the brake pedal should be designed to withstand a maximum brake pedal force of 450 LBF (2000 N). In order to ensure that the pedal design conforms to the rules of the event, it is necessary to use ANSYS finite element analysis software to conduct force analysis on the pedal design to ensure that it meets both the rules of the event and the safety design as well as the lightweight design. Therefore, through the finite element analysis of the pedal model in ANSYS environment, the structural stress and deformation data under the pedal force were obtained, and according to the stress and deformation cloud map, the pedal structure was optimized and the optimal material was selected, so as to obtain the brake pedal with high comprehensive performance and meet the competition rules.

Mangrove forests possess significant ecological and aesthetic values. Investigating the spatial distribution characteristics of beach sediments in mangrove habitats and their relationships with hydrodynamic conditions and vegetation dynamics is crucial for sustaining the health and sustainability of mangrove ecosystems. This study aims to explore the spatial distribution characteristics of sediments in the mangrove beach of Xiashan Sea-viewing Promenade, Zhanjiang, and their relationship with hydrodynamics and mangrove vegetation. A total of 59 surface sediment samples were collected from 6 transects in the study area. The elevation of the sampling points, as well as wave and current data during the sampling period, were measured. The sediment transport trends of the 6 transects were also analyzed. The results show that the average grain size of surface sediments in the study area ranges from -0.75 to 5.15 φ; the average sorting coefficient is 1.26, indicating poor sediment sorting; the average skewness is 0.19, with positively skewed and extremely positively skewed sediments widely distributed in the study area; the kurtosis values range from 0.36 to 2.31, with an average of 1.14, and narrow kurtosis is observed on the seaward side of the southern and northern parts of the study area. The significant wave height in the study area ranges from 0.05 to 0.17 m, the wave period ranges from 1.44 to 3.38 s, and the current velocity ranges from 1.44 to 7.44 cm·s⁻¹. The surface sediment types include gravel, sand, silt, and clay, with sand being the most abundant, followed by silt, while gravel and clay are present in small amounts, with gravel only found in small quantities near the shore in the northern part of the study area. The sand content decreases from the shore to the sea, while the spatial distribution of silt shows the opposite trend. The clay content is relatively low, with a higher concentration in the seaward area. The wave action in the study area is significantly stronger than the current action, with the strongest hydrodynamic forces occurring during the early flood tide and late ebb tide, leading to an onshore sediment transport trend. This process can increase beach elevation and stability, which is beneficial for the growth and development of mangroves.