Oscillating water column (OWC) breakwaters have become promising in recent years for their wave energy conversion and wave protection functions. However, the changes in structural hydrodynamic performance induced by the multi-chamber design still require further in-depth investigation. In this study, a two-dimensional numerical wave tank based on the Smoothed Particle Hydrodynamics (SPH) method is first established and validated using a box-type floating breakwater case and a fixed OWC simulation. Subsequently, three OWC structures with varying chamber numbers are simulated under seven incident wave periods. The effects of chamber number on hydrodynamic performance, including wave transmission coefficient and three-degree-of-freedom motion responses, are analyzed. Results show that in low periods, the single-chamber structure exhibits the lowest transmission coefficient, the two-chamber the highest, and the three-chamber intermediate. Motion responses generally show a monotonic upward trend with increasing period, but sway and pitch reach peaks under medium wave periods in some cases.
Beam-truss coupled inflatable structures, such as marine evacuation slides, show pressure-dependent bending governed by beam deformation, truss axial feedback, and nodal compatibility. This study develops a mechanics-based reduced-order model for efficient global deformation prediction. The load-transfer mechanism is first clarified. A pressure-stiffened inflatable-beam bending model is derived from the virtual work principle, and a tensile-compressive asymmetric axial model is introduced for inclined inflatable truss members. The coupled equilibrium is formulated as a nodal force residual and solved by constrained optimization. Full-scale bending tests and Abaqus simulations are conducted at 25, 30, and 35 kPa under 500, 1000, and 1500 N. The model captures the overall deformation trend and nodal displacement distribution, with an average error of 7.96%, demonstrating its applicability for preliminary prediction and rapid assessment of beam-truss coupled inflatable structures.
The present study examines the effectiveness of multiple finite-width porous structures in mitigating wave impact on the shorelines featuring trench-type bottom seabed. Wave propagation through thick porous structures is represented using the Sollitt and Cross model, utilizing the principles of small-amplitude water wave theory. The boundary value problem is converted into a system of linear algebraic equations through the eigenfunction expansion method, which is then solved numerically. The findings indicate that increasing the number of porous structures and trenches enhances wave reflection while reducing wave transmission. Analysis of the reflection coefficient's variation with wavenumber for various numbers of trenches and porous structures shows that wave reflection exhibits harmonic peaks followed by subharmonic peaks, with the amplitude of these peaks increasing up to certain wavenumbers before diminishing for higher wavenumbers. The scattering coefficients exhibit oscillatory and periodic patterns in response to changes in the spacing between trenches, porous structures, and the distance from the last trench to the first porous structure. Additionally, oscillatory and periodic patterns are observed in scattering coefficients as a function of trench width. In contrast, as the width of the porous structures increases, the wave reflection exhibits an oscillatory increasing pattern before eventually stabilizing at larger widths. Meanwhile, the transmission coefficient decreases and ultimately becomes zero. Furthermore, higher frictional coefficients result in an increased wave reflection and decreased wave transmission. However, a lower free surface elevation in the lee-side region Rt compared to the region R1 occurs due to multiple porous structures and trenches. With three trenches and four porous structures, the transmission coefficient is reduced to less than 3% , leading to a negligible free surface elevation in Rt . Notably, as the number of porous structures increases, the free surface elevation on the lee-side continues to decrease, even when the quantity of rubble mounds remains constant. This study underscores the potential of multiple porous structures in combination with trench-type bottoms for effective coastal protection.
Traditional Intrusion Detection Systems (IDS) have the disadvantage of being centrally controlled, having high false alarm rates, and being inflexible to changes in cyber threats. To solve these problems, this paper presents SLBAQ-Sec, a blockchain-based and AI-assisted intrusion detection framework that combines SHAP-LIME-based recursive feature optimization (SLRFO), an attentive spatio-temporal intrusion detection network (AST-IDNet), and adaptive deep Q-learning-based smart contract security (ADQ-Sec). Distributed IDS nodes operate within a network and share validated intrusion alerts via a permissioned blockchain, ensuring tamper-proof logging and eliminating single points of failure. AST-IDNet is a hybrid CNN, BiLSTM, and attention-based model that learns spatial and temporal attack patterns, and ADQ-Sec enables adaptive threat mitigation. Experiments on the CIC-IDS-2017 dataset show the proposed framework achieves 0.95 accuracy, 0.94 precision, and 0.93 recall, outperforming CNN, RNN, BiLSTM, and transformer-based IDS models. These results highlight the effectiveness of combining blockchain and deep learning for real-time cyber defense.
