Search Results (821)

Floating offshore wind turbines (FOWTs) experience six-degree-of-freedom motions and related forces acting on their mooring systems. Under combined wind, wave, and current loading, platform motions and mooring line tensions are dynamically coupled. To support ballast control decisions without repeatedly running high-fidelity coupled simulations, this paper developed a specialized computational framework combining FAST-AQWA time-domain simulation, short-term mooring tension prediction, and ballast control optimization. Five predictive models were trained and evaluated using the same sliding window dataset. After training, the predicted mooring tension data were used for ballast control calculations. In this study, the bidirectional long short-term memory (BiLSTM) model showed the highest prediction accuracy for mooring tension and the Model Prediction Control (MPC) produced a smoother control action and significantly reduced the amplitude of low-frequency roll and pitch. The proposed framework provides a practical approach for combining short-term response prediction with ballast control and demonstrates that explicit mooring tension constraints must be incorporated into the design considerations of subsequent control systems. Full article

The stability of cemented backfill during secondary extraction depends on its response to coupled static and blast-induced loading, yet the required strength and dominant failure mechanisms remain uncertain. Using the Makeng Iron Mine as a case study, we combined mix-design tests, analytical strength assessment, split Hopkinson pressure bar (SHPB) tests, static and dynamic FLAC^3D simulations, and field monitoring. A slurry mass concentration of 78% and a binder-to-tailings ratio of 1:8 produced a 28-day uniaxial compressive strength of 2.69 MPa. Six self-supporting models yielded a conservative design strength of 2.45 MPa, slightly higher than the theoretically estimated blast-transmitted stress of 2.40 MPa. In the SHPB tests, the dynamic peak stress increased from 4.09 to 19.15 MPa as the average strain rate rose from 50 to 152 s⁻¹, while the dynamic increase factor increased from 1.52 to 7.12, demonstrating a pronounced rate-strengthening effect. Numerical simulations identified the orebody–backfill interfaces as the principal zones of stress-wave reflection, deformation incompatibility, and shear-dominated plastic deformation. Flexible mesh reinforcement reduced the maximum lateral displacement of the exposed backfill from 18.85 to 7.24 mm (61.60%) and reduced the extent of the shear-failure zone by approximately 39.72%. Field monitoring recorded a maximum lateral displacement of 8.97 mm, with no large-scale backfill instability observed. These findings provide a case-specific framework for selecting backfill strength and controlling interface instability under blasting disturbance. Full article

Portable Ocean Wave Energy Harvesters (POWEH) offer a potential approach for supplying autonomous low-power marine sensing systems; however, their long-term reliability, durability, and economic viability remain insufficiently demonstrated. But conventional wave energy converters are often big, expensive, and fixed to seabed structures, which makes it hard to use them in different places and makes it hard to sell them. People have been paying more attention to portable ocean wave energy harvesters in recent years. These are small, light systems that can be set up anywhere and do not need to be moored or anchored. These devices are meant to power autonomous ocean sensors, emergency buoys, and maritime applications that do not need to be connected to the grid. This review looks closely at the development trends, structural designs, and power take-off mechanisms of portable wave energy systems. We compare different types of harvesters, such as mechanical, electromagnetic, piezoelectric, and hybrid ones, based on their design principles, conversion efficiency, and scalability. Focus is directed towards the importance of symmetry in structural design, dynamic response, and energy conversion. The structure, whether symmetric or asymmetric, has a crucial role in determining mass distribution, stiffness traits, vibrational dynamics, hydrodynamic loading, and the capture of multi-directional wave energy, thereby influencing the overall performance, resilience, and stability of portable harvesters. The review goes on to talk about the main problems with dynamic stability, frequency tuning, environmental adaptability, and energy management when things are portable. Finally, new strategies like nonlinear dynamic designs, self-tuning mooring systems, and hybrid energy integration are suggested as ways to improve performance and reliability. The insights from this review are meant to help future innovations that will make it possible to use portable ocean wave energy technologies in a practical and long-lasting way. Full article

Ground fissures pose a serious threat to the deformation stability and operational safety of high-speed railway embankments. In this study, a three-dimensional transient finite element model was developed to investigate the dynamic response of a double-track high-speed railway embankment crossing an active ground fissure. Natural and CFG pile–raft composite foundations were compared under different train speeds and single- and double-line operating conditions. The results show that the ground fissure causes abrupt changes in displacement, acceleration, and dynamic stress, accompanied by evident hanging-wall amplification and asymmetric deformation. Double-line operation intensifies wave interference and dynamic amplification near the fissure, while increasing train speed further aggravates these effects, particularly for acceleration. The CFG pile–raft composite foundation effectively reduces dynamic response amplitudes, limits downward disturbance propagation, and improves deformation compatibility across the fissure through raft bridging and pile–soil load transfer. The proposed evaluation indices further quantify response asymmetry, double-line interference, and speed-induced amplification. These findings provide a basis for the dynamic stability assessment and reinforcement design of high-speed railway embankments in ground-fissure regions. Full article

Fish–net contact is a practical concern for exposed offshore aquaculture platforms during severe waves, yet it is seldom assessed together with platform hydrodynamics and mooring response. This study compares two protection strategies for a semi-submersible truss aquaculture platform: add-on flow-guiding structures fitted with hoods and side baffles, and a deepened-netting configuration. Tests on a 1:50 physical model under severe regular waves measured fish-school-boundary displacement, platform surge, heave and pitch, and mooring-line tension. The maximum horizontal displacement of the upwave school boundary served as an engineering proxy for the school’s tendency to approach the netting. Frequency-domain ANSYS-AQWA calculations were also used to compare wave excitation, added mass, and radiation damping. The flow-guiding structures generally reduced school-boundary displacement, but they often increased surge and mooring demand, revealing a trade-off between reduced school-boundary approach and station keeping. Under the tested conditions, the deepened-netting configuration reduced school-boundary displacement, platform motion, and mooring tension. Its fish-school response cannot, however, be attributed to netting depth alone because culture volume increased while stocking density decreased. These results provide a joint assessment of fish-school response, platform motion, and mooring load for the proposed configurations. The findings are limited to the tested severe regular waves and require validation under irregular waves, combined waves and currents, and full-scale conditions. Full article

The Wavepiston modular energy collector is a string of vertical ‘sails’, each comprising several vertical ‘paddles’, that respond primarily in surge to incident wave excitation. In an early device development stage, the sails were designed to allow spacing between the vertical paddles to minimise hydrodynamic forces, in extreme conditions, to improve survivability. However, the benefit for survivability was at the cost of energy absorption performance as a result of a substantial decrease in the sail excitation force. Therefore, flexible paddles, which can deform in response to large surge wave loads, are considered a feasible design strategy to minimise the energy-capture–survivability trade-off. An experimental wave tank test campaign was undertaken to investigate the response of paddle materials, with different paddle flexibility and overlaps, to wave-induced and forced motion excitation. This paper explores how different configurations of these hydroelastic structures affect the wave-induced load experienced by a fixed sail and the wave energy absorption potential of the sail. Two metrics are proposed to assess how different paddle overlaps and material properties affect device performance and survivability at particular deployment locations. The sail response is characterised and depicted through these metrics for increasing excitation amplitudes to provide initial insights into how the sail configuration design choices and materials impact the device capacity factor. Full article

To address the limited endurance of unmanned underwater vehicles (UUVs) during long-duration missions, this study proposes a foldable and retractable wave energy converter (WEC) conformally integrated with the UUV hull. A two-degrees-of-freedom heave-coupled dynamic model of the float–UUV system is established, and parameter-matching relationships are derived using complex dynamic stiffness and impedance-matching theory. A bidirectionally coupled STAR-CCM+-AMESim co-simulation framework resolves the nonlinear viscous flow field, relative motion, and PTO dynamic response in closed loop. Under regular wave conditions defined based on a representative Bohai Sea state, the effects of the transmission ratio and spring stiffness on the coupled motion and equivalent resistive load power output are systematically investigated. Under the specified wave condition, average electrical power varies unimodally with both parameters, reaching 70.8 W at a transmission ratio of 15 and a spring stiffness of 4642 N/m; the corresponding peak power is 161.2 W. The system is more sensitive to increases than decreases in transmission ratio, suggesting a value slightly below the theoretical optimum for engineering design. The instantaneous power shows an asymmetric double-peak pattern, indicating a shift in dominance between direct float-driven generation and spring-mediated energy release. Agreement between theory and co-simulation provides numerical cross-validation and offers a theoretical basis and numerical methodology for designing and optimizing WECs on mobile UUV platforms. Full article

Continuous monitoring of gas-induced changes in coal is important for carbon dioxide storage, coalbed methane recovery, and underground mine safety. Conventional ultrasonic monitoring primarily relies on direct-wave velocities, which may exhibit limited sensitivity to subtle, distributed changes within the coal microstructure. This study evaluates coda wave interferometry (CWI) for monitoring the response of an anthracite coal specimen to helium (He) and carbon dioxide (CO₂) injection under controlled triaxial loading with an axial-to-confining stress ratio of 2:1, with confining stress held 1.0 MPa above the gas pressure in every test so that the effective confining stress was constant at 1.0 MPa and the stages differ only in the gas present. Gas was introduced at nominal injection pressures of 2.5, 5.5, and 12.5 MPa. Ultrasonic waveforms were recorded continuously for 5 h during the CO₂ experiments and 7 h during the He experiments. P- and S-wave velocities, and their fractional changes (dv/v), were calculated from Akaike Information Criterion-based arrival picks, while coda-derived relative velocity changes (δv/v) were estimated by the CWI stretching method over a 300–600 µs coda window. All six gas–pressure conditions were imposed sequentially on a single specimen, which was vented, degassed, and reconditioned between successive runs. CO₂ exhibited slower upstream-pressure dissipation than He, a response consistent with sorptive retention and adsorption-induced modification of the coal pore structure. Direct-wave velocities captured pronounced mechanical changes at low and intermediate injection pressures but showed limited sensitivity during the 12.5 MPa CO₂ experiment. In contrast, CWI detected a persistent negative δv/v trend at 5.5 MPa and a progressive negative trend at 12.5 MPa. Although adsorption was not measured independently, the contrasting He and CO₂ responses demonstrate that CWI can complement direct-wave analysis by detecting subtle, distributed changes associated with coupled mechanical and gas–coal interactions. Full article

Direct-drive wave power generation systems based on permanent magnet linear generators (PMLGs) produce fluctuating electromagnetic power under irregular wave excitation, which may affect DC-bus voltage stability and load-side power quality. To smooth the fluctuating output power, this paper develops an empirical mode decomposition (EMD)-based power allocation strategy for a battery–supercapacitor hybrid energy storage system (HESS). In the proposed strategy, EMD is used to decompose the fluctuating electromagnetic power into low-frequency and high-frequency components according to their time-scale characteristics. The low-frequency component is assigned to the battery for energy buffering, while the high-frequency component is assigned to the supercapacitor for transient power compensation. Finite-control-set model predictive current control (FCS-MPCC) is adopted on the generator side to improve the current response of the PMLG, and an MPC-based HESS controller is designed to track the assigned power commands and regulate the DC-bus voltage. Simulation results show a battery power-tracking error of 3.93 W and a DC-bus voltage standard deviation of 0.108 V; compared with LPF, EMD reduced the load-step voltage deviation by 11.94%. Experiments confirm that the PMLG back-EMF follows the translator velocity, the storage currents track their references, and the DC-bus voltage remains within ±2 V of its reference. Full article

Background: Lateral elbow tendinopathy (LET) is a common upper-limb musculoskeletal disorder causing pain during gripping activities, reduced work capacity, and functional limitation. LET is currently considered a predominantly degenerative condition characterized by collagen disorganization, extracellular matrix changes, neovascularization, and impaired tendon healing. Objective: To evaluate short-term clinical and functional outcomes of a multimodal protocol including focused extracorporeal shock wave therapy (f-ESWT), ultrasound-guided intralesional injection of low-molecular-weight peptides (LWPs) derived from hydrolyzed bovine collagen and therapeutic exercise in patients with chronic LET unresponsive to standardized conservative therapy. Methods: This retrospective observational study included 11 screened patients; 10 completed follow-up. Eligibility required age ≥ 18 years, symptoms ≥ 3 months, positive provocation tests, ultrasound-confirmed common extensor tendon pathology, and incomplete response to prior treatment. All patients received f-ESWT before ultrasound-guided LWPs injection and performed progressive loading exercises. Outcomes included Patient-Rated Tennis Elbow Evaluation (PRTEE), grip strength, and clinical provocation tests at baseline (T0; Day 0) and at T1 (Day 51, 30 days after injection). Results: PRTEE pain improved by 31.2 points (95% CI 22.2–40.2; Cohen’s d_z = 2.48) and PRTEE function by 32.6 points (95% CI 26.7–38.5; d_z = 3.95). Mean maximal strength and maximal strength improved by 4.61 kg (95% CI 2.89–6.32) and 4.02 kg (95% CI 2.36–5.68), respectively. Clinical test severity decreased by an estimated 2.5 points (95% CI 2.0–3.0). No adverse events were reported. Conclusions: Patients showed clinically meaningful short-term improvements in pain, function, and strength following the sequential multimodal management strategy. However, the retrospective design, small sample, lack of control group, and short follow-up preclude causal attribution and require confirmation in prospective controlled studies. Full article

This study aims to investigate the influence of non-local elasticity on the coupled optoelectronic photo-thermoelastic response of an anisotropic fiber-reinforced silicon half-space subjected to optical carrier excitation. A coupled analytical model is developed by incorporating non-local elasticity into a fiber-reinforced anisotropic semiconductor framework, where the thermal, carrier-density, displacement, and stress fields are fully coupled. After introducing the appropriate non-dimensional variables, the governing equations are transformed using the normal-mode technique into a system of ordinary differential equations and solved analytically through an eigenvalue-based vector–matrix approach. The novelty of the present work lies in examining the influence of the non-local parameter within a fiber-reinforced anisotropic semiconductor and performing a systematic comparison between fiber-reinforced and non-reinforced configurations under identical photothermal loading conditions. The numerical results demonstrate that increasing the non-local parameter produces pronounced changes in the mechanical response, including displacement amplitudes, stress distributions, and wave attenuation characteristics, whereas the temperature and carrier-density fields exhibit only slight variations within the investigated parameter range. Fiber reinforcement further influences the mechanical response by enhancing the structural stability and directional stiffness of the medium. The proposed analytical framework provides physical insight into the coupled effects of nonlocality and fiber reinforcement, with potential relevance to the analysis and design of semiconductor devices, optoelectronic and photonic structures, MEMS/NEMS, and smart fiber-reinforced composite materials operating under coupled thermo-mechanical and optical excitations. Full article

As marine development extends into deep and far-offshore waters, fixed breakwaters become increasingly costly and difficult to construct and may have greater environmental impacts. Floating breakwaters (FBs) offer flexible deployment across a wide range of water depths and have therefore received growing attention. Yet the dominant wave attenuation mechanisms and key hydrodynamic responses differ among FB configurations, making it difficult to compare their performance and select suitable analysis methods. This review examines advances in FB configurations, analysis methods, and hydrodynamic characteristics. It summarizes structural types and shows that FB design has evolved from reliance on principal dimensions and wave reflection toward the combined use of multiple attenuation mechanisms. The applicability and limitations of empirical methods, potential flow methods, computational fluid dynamics, and experimental methods are compared. Structural optimization, mooring system design, wave attenuation mechanisms, and fluid–structure interaction are also reviewed, with attention paid to motions, loads, and local flows. Key unresolved challenges include broadband attenuation of long-period waves, safety under extreme sea states, performance trade-offs in multifunctional systems, and scale effects and prototype validation. By linking FB configuration characteristics with dominant wave attenuation mechanisms, key hydrodynamic responses, and the applicability of different analysis methods, this review provides an integrated comparative framework for evaluating FB performance, selecting appropriate analysis methods, and supporting engineering assessment in deep and far-offshore waters. Full article

Predicting wave slamming pressures on bulbous bows is essential for ship structural safety. This study employs an overset-grid RANS-VOF framework to investigate viscous scale effects on bulbous bow slamming loads. Multi-scale simulations were conducted across four geometric scale ratios of 1:50, 1:20, 1:15, and 1:10 (α = 50, 20, 15, 10) under critical pitch-heave resonant head waves (λ/L_WL = 1.2). While global motion responses follow Froude similitude, local dynamic slamming pressures show notable scale disparities. Smaller physical models develop a relatively thicker viscous boundary layer that acts as a hydrodynamic cushion, reducing peak pressures while broadening pulse durations. Consequently, direct Froude scaling from small-scale models tends to underestimate full-scale impact loads. To account for these viscous scale effects, an engineering extrapolation approach based on multi-scale regression is proposed, which demonstrates a reasonable linear correlation across the investigated range (R² = 0.88–0.99) in the primary impact region. This study provides physical insights into the scaling behavior of bulbous bow slamming and offers a practical reference for full-scale load estimation. Full article

To address the issues of low mechanical rock-breaking efficiency and severe tool wear in hard rock, this study investigates the mechanical deterioration and abrasivity response of granite subjected to rapid flame-jet heating followed by liquid nitrogen cooling, with rock pre-treatment in thermal-assisted rock breaking as the background. Fine-grained granite specimens were heated by flame jet to temperatures ranging between 200 and 600 °C and then subjected to natural cooling or sudden liquid nitrogen cooling. Physical parameter measurements, uniaxial compression tests, Brazilian splitting tests, and CERCHAR abrasivity tests were conducted using national standards to investigate the evolution of thermal damage and the effect of cooling path. The results show that the damage degree of granite continuously increases with increasing heating temperature, and the damage induced by liquid nitrogen cooling is greater than that induced by natural cooling. Visible cracks begin to appear on the specimen surface after 300 °C, while crack propagation and structural deterioration become more pronounced at 500–600 °C. Among the measured physical parameters, P-wave velocity is the most sensitive to damage, with a maximum attenuation rate of 60.6%. The deterioration of the physical structure further reduces the load-bearing capacity and deformation performance of granite. After liquid nitrogen cooling at 600 °C, the uniaxial compressive strength, tensile strength, and elastic modulus decrease to 92.6 MPa, 1.42 MPa, and 17.4 GPa, respectively, corresponding to reductions of 56.0%, 87.7%, and 69.3% compared with the untreated specimens. The tensile strength is the most sensitive mechanical parameter to liquid nitrogen cooling. The CERCHAR abrasivity index decreases from 3.81 to 2.12. Liquid nitrogen cooling advances the transition of granite abrasivity from high to medium from 400–500 °C to 300–400 °C. The integrated analysis indicates that the non-uniform temperature field generated by rapid flame-jet heating and the differences in thermal deformation among minerals promote the initiation of initial cracks. The additional shrinkage stress induced by liquid nitrogen cooling further drives crack propagation and coalescence, eventually leading to the coupled reduction in the strength, stiffness, and abrasivity of granite. The results provide laboratory-scale evidence for evaluating granite pre-treatment under rapid flame-jet heating and liquid nitrogen cooling and offer a reference for thermal-assisted mechanical rock breaking and standardized abrasivity reduction. However, the relationship between CAI and actual tool wear still requires further verification. Full article

Triboelectric nanogenerators (TENGs) offer promising opportunities for distributed wind energy harvesting owing to their low-speed responsiveness, structural flexibility, and adaptability to non-stationary airflow. This review examines wind-driven TENGs from the perspective of realistic wind-field constraints, focusing on three representative scenarios: urban micro-winds, offshore wind–wave environments, and low-altitude complex flows. Scenario-specific advances in device architectures, materials and interfaces, environmental protection, power management, and system integration are systematically reviewed. Representative devices are further quantitatively compared in terms of wind-speed range, activation threshold, electrical output, power density, durability, and system-level energy delivery. Particular attention is given to inconsistent definitions of cut-in wind speed, output normalization, electrical loading, and validation conditions that limit cross-study comparison. Field-validation evidence is assessed from controlled laboratory tests to long-term field operation. Key challenges involving usable regulated energy, environmental reliability, lifetime prediction, array scaling, sustainability, and deployment economics are critically discussed. Finally, five grand challenges with actionable milestones are proposed to facilitate the transition of wind-driven TENGs from laboratory prototypes toward deployable distributed micro-energy systems. Full article