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The intensity of coastal erosion is a measure of the strength of erosion processes affecting coastal areas. Traditionally, assessments of coastal erosion intensity have relied on singular indices, such as the rate of shoreline retreat or erosion, often prioritizing higher rates over lower ones. This approach, however, lacks comprehensive consideration and scientific rigor. In this study, we adopt a more holistic approach by examining the Qionghai-Wanning coast on the eastern side of Hainan Island. We selected four indices that reflect local conditions and influence coastal erosion strength: Annual rate of shoreline change (T1), Beach annual down-cutting rate (T2), Beach slope (T3), Average particle size of the beach (T4). These indices were used to comprehensively evaluate the erosion intensity of the Qionghai-Wanning coast. The evaluation results categorized the study area into six grades: serious erosion (3.45%), strong erosion (6.90%), erosion (20.69%), micro erosion (44.38%), stabilization (20.69%), and accretion (3.45%). The findings indicate that, under the broader environmental trends of global warming and rising sea levels, most sandy coasts exhibit micro-erosion intensity. Areas experiencing strong and serious erosion are predominantly influenced by human activities, such as those occurring in promenade bays, artificial islands, and harbors. To further understand the relationship between these factors and erosion intensity, we employed the Spearman correlation coefficient method. The analysis revealed that the T1 and the T2 are the primary factors influencing coastal erosion intensity, with the T4 serving as a secondary factor. These factors collectively impact the force and energy absorption of the coast through wave and tidal actions, ultimately determining the intensity of coastal erosion. The multi-index assessment method for coastal erosion intensity demonstrated an accuracy of 82.75%, providing a scientific basis for the management, protection, and restoration of coastal areas.

Regarding the issue of changes in the aerodynamic force of the bridge main beam under the action of wind-driven rain, this article explores the changes in air density caused by rainfall, the calculation theory of raindrop impact force and its simplified mass-weighted equivalent method (MWEM), and the calculation method of water accumulation thickness on the surface of the main beam. The calculation shows that the changes in air density caused by rainfall can be ignored, and the error of the MWEM increases with the increase in rainfall intensity; however, even at a rainfall intensity of 709 mm/h, the deviations in the MWEM value of the horizontal and vertical raindrop impact force is only about +5% and −4%, respectively. Then, based on the above analysis, a calculation model for the aerodynamic three-component forces of the main beam caused by rainfall under the action of wind-driven rain is provided. Finally, taking two typical main beam sections as an example, static three-component force tests are carried out on the main beam model under different rainfall intensities. The experimental results show that the drag coefficient variations obtained through the MWEM are in good agreement with experimental data, which proves the correctness of the theoretical model of the raindrop impact force. But for the lift and torque coefficient, the differences between theoretical and experimental values are much more significant than the drag coefficient, and it increases with the increase in rain intensity. It can be seen that the surface ponding model and influence of rainfall intensity need to be further explored. In summary, the theoretical calculation method for the additional aerodynamic force of wind-driven rain on the main beam proposed in this article is convenient and practical, and it can provide a certain reference for the rapid safety assessment of bridges under extreme meteorological conditions.

Recently, drilling wells have encountered rich gas hydrates in fine-grained sediments in the northern South China Sea. Gas hydrate in fine-grained sediments is very heterogeneous, and its physical properties are different from those of oil and gas reservoirs. The reliability of the classical logging saturation evaluation models established for diagenetic reservoirs is questionable. This study used four wells in GMGS3 and GMGS4 to evaluate the effects of the application of three typical methods for evaluating saturation with different principles in the unconsolidated fine-grained sediments: nuclear magnetic logging, sigma logging, and the Archie formula. It was found that the value of the lithologic capture cross-section in sigma logging and the rock’s electrical parameters in the Archie formula affect the accuracy of the model. Therefore, to obtain a reliable saturation value for fine-grained sediments, an innovative method for the calculation of resistivity and acoustic time is proposed to estimate gas hydrate saturation based on logging data, which is most consistent with the results of core analysis. The overall relative error of the verification well was 5.87%, whereas that of the density NMR logging method was 56%, showing that the accuracy of the newly proposed resistivity DT logging method’s saturation formula was significantly improved. Finally, a new model-based cross chart was developed, which can rapidly differentiate gas saturation during drilling.

C10H16N6O19${\text{C}}_{10}{\text{H}}_{16}{\text{N}}_{6}{\text{O}}_{19}$, monoclinic, C2/c (no. 15), a = 29.980(5) Å, b = 8.4695(17) Å, c = 20.719(4) Å, β = 128.124(7)°, V = 4138.7(16) Å3, Z = 8, Rgt${R}_{gt}$(F) = 0.0587, wRref$w{R}_{ref}$(F2) = 0.1683, T = 170 K.

This paper proposes an ontology-based noise source identification method, establishes an ontology knowledge expression model in the field of noise, vibration, and harshness (NVH), and provides an extensible framework for sharing noise diagnosis knowledge in the field. Based on the key features extracted from the noise and vibration signals at different positions and the prior knowledge, mechanical engineers can construct an ontology rule and locate noise sources by identifying the intrinsic relationship between signal characteristics through ontology reasoning. A case study is conducted to demonstrate the effectiveness of the proposed method in resolving the problem of integrating multisource heterogeneous knowledge and exchanging noise diagnosis knowledge information in the field of NVH for agricultural machines. Thus, our study facilitates the sharing and reuse of knowledge and advances the development of intelligent noise diagnosis expert systems to a certain extent.

Submarine seismic ambient noise imaging combines current marine and on-land seismic detection technologies. Based on data from several broadband shallow-sea type ocean bottom seismometers (SOBSs) deployed in the Bohai Sea and north Yellow Sea, this paper analyzes the submarine seismic ambient noise characteristics. It explores the theory, technology, method and application of the submarine seismic ambient noise imaging using the single-point horizontal and vertical spectral ratio method (HVSR). The observations yield the following results: 1) Submarine seismic ambient noise has consistent and constant energy, making it an appropriate passive seismic source for submarine high-frequency surface wave investigation. 2) Using the HVSR approach, a single threecomponent OBS could differentiate between the basement and sediments. Array seismic observation could be utilized to extract the frequency dispersion curve and invert it to obtain the velocity structure for more accurate stratification. 3) The SOBS we use is suitable for submarine surface wave exploration. 4) Tomography results with greater resolution and deeper penetration could be obtained by combining active and passive sources in a simultaneous inversion of the HVSR and frequency dispersion curve. Seamless land-to-ocean seismic research can be accomplished with submarine seismic ambient noise imaging technologies. [ABSTRACT FROM AUTHOR]

Computational domain size is a key factor in the numerical simulation of complex terrain wind fields. However, present studies on the selection of computational domain size in the simulation process are scarce. The influence of computational domain size on calculation results also remains unclear. This study analyzed the length and height of calculation domain and established 11 numerical wind tunnel models with different lengths to determine the influence of calculation domain size on the simulation results of complex wind fields, this. Information about the average and fluctuating wind fields of the target location was obtained using large eddy simulation. A detailed analysis was conducted on an actual mountainous terrain wind field in Zhangjiajie, China. Results show that the stable position of wind speed in the height direction is 7 to 8 times the height of the highest mountain in the simulation of complex terrain wind field. In the horizontal direction, the complex mountain topography of several kilometers cannot sufficiently generate the average wind field, and fluctuating wind fields are consistent with the actual situation. The application of additional reasonable average wind speed and fluctuating wind speed at the inlet boundary is necessary for detailed analysis of complex terrain wind fields. This study can provide a reference for numerical simulation of complex terrain wind fields. [ABSTRACT FROM AUTHOR]

C10H16N6O19, monoclinic, C2/c (no. 15), a = 29.980(5) Å, b = 8.4695(17) Å, c = 20.719(4) Å, β = 128.124(7)°, V = 4138.7(16) Å3, Z = 8, Rgt (F) = 0.0587, wRref (F2) = 0.1683, T = 170 K. [ABSTRACT FROM AUTHOR]