Search Results (1,802)

The durability of coral concrete in marine tidal zones is a critical concern due to the coupling effects of impact loads and aggressive ion erosion. This study investigates the dynamic mechanical degradation of Sisal Fiber-Reinforced Coral Aggregate Concrete (SFCAC) under a semi-submerged environment, focusing on the interplay between fiber bridging and corrosion evolution. Split Hopkinson Pressure Bar (SHPB) tests were conducted on specimens with varying fiber dosages (0–6 kg/m³) and erosion durations (0–120 days). Quantitative results indicate that while the addition of sisal fibers had a limited effect on increasing the peak impact-compression strength, it significantly modified the failure characteristics. The dynamic compressive strength exhibited a non-linear trend, peaking at 30 days due to pore filling. However, after 120 days, the strength of the Plain Coral Concrete (SF0) deteriorated to 70.84 MPa, while the 6 kg/m³ fiber-reinforced group (SF6) maintained a higher residual strength of 77.63 MPa. Crucially, although the 6 kg/m³ specimens still suffered crushing failure under high strain rates, the fibers effectively mitigated catastrophic shattering by holding the fragments together, exhibiting superior post-peak energy absorption compared to the pulverized plain matrix. Microscopic analysis (SEM) revealed that although the hydrophilic nature of sisal fibers accelerated ion transport (leading to Friedel’s salt and gypsum formation), their physical bridging effect counteracted the corrosion-induced brittleness. Collectively, these findings provide a theoretical basis for the durability design of SFCAC structures in severe marine splash zones and offer new insights into utilizing sustainable, locally sourced materials for island engineering. Full article

Cardiovascular disease (CVD) continues to be the primary cause of morbidity and mortality worldwide, underscoring the urgent need for novel therapeutic alternatives. In recent years, marine ecosystems have garnered increasing attention as a promising source of bioactive compounds with unique structural and pharmacological properties. Marine-derived toxins and venoms, including tetrodotoxin, ω-conotoxins, anthopleurins, palytoxin, brevetoxin, aplysiatoxin, and asterosaponins, exert cardioprotective effects through diverse mechanisms such as modulation of ion channels, inhibition of sympathetic overactivity, antioxidative actions, and enhancement of myocardial contractility. These properties make them potential candidates for addressing various CVD manifestations, including arrhythmia, hypertension, ischemia–reperfusion injury, and heart failure. However, despite their therapeutic promise, the clinical application of these marine compounds remains limited due to poor tissue selectivity, narrow therapeutic indices, proinflammatory activity, and limited metabolic stability. Structural modifications, advanced drug delivery platforms, and in vivo validation studies are crucial for overcoming these challenges. This review highlights the pharmacological actions, molecular targets, and cardiovascular relevance of selected marine toxins and venoms while also addressing key translational barriers. Advances in biotechnology and peptide engineering are enabling the safer and more targeted use of these compounds. Collectively, marine-derived toxins and venoms represent a largely untapped but highly promising frontier in cardiovascular drug discovery. Strategic research focused on elucidating mechanisms, optimizing delivery, and translating clinical applications will be critical to unlocking their full therapeutic potential. Full article

Polypropylene microplastics (PP-MPs) represent a persistent class of marine pollutants due to their hydrophobicity, high crystallinity, and resistance to environmental degradation. This review summarizes recent advances in understanding the environmental behavior, physicochemical aging, and ecotoxicological risks of PP-MPs, with emphasis on microbial degradation pathways involving bacteria, fungi, algae, and filter-feeding invertebrates. The biodegradation of PP-MPs is jointly regulated by environmental conditions, polymer properties, and the structure and function of plastisphere communities. Although photo-oxidation and mechanical abrasion enhance microbial colonization by increasing surface roughness and introducing oxygenated functional groups, overall degradation rates remain low in marine environments. Emerging mitigation strategies include biodegradable polymer alternatives, multifunctional catalytic and adsorptive materials, engineered microbial consortia, and integrated photo–biodegradation systems. Key research priorities include elucidating molecular degradation mechanisms, designing programmable degradable materials, and establishing AI-based monitoring frameworks. This review provides a concise foundation for developing ecologically safe and scalable approaches to PP-MP reduction and sustainable marine pollution management. Full article

To address the significant deterioration in the performance of traditional drilling slurries due to seawater intrusion, this study developed a novel salt-tolerant polymer slurry (MXC) utilizing grafting modification techniques. The performance of MXC was systematically evaluated and compared with two commercial slurries, PAC and Flowz, through simulated formation filtration experiments. The results indicate that the MXC slurry exhibited the lowest filtration loss and was capable of forming a thinner, denser filter cake, thereby providing optimal wall protection. Mechanistic analysis revealed that grafting modification optimized the hydrophobic interactions between polymer molecules, constructing a dynamic physical cross-linking network and a rigid double-helical structure within the solution. This significantly enhanced the system’s viscosity and resistance to ionic interference, ultimately resulting in the formation of a dense network structure during the filtration process. This study offers a novel material solution and theoretical foundation for the development of high-performance salt-tolerant slurries in marine engineering. Full article

Methanol is a promising alternative marine fuel due to its favorable combustion characteristics and potential to reduce exhaust emissions under increasingly stringent International Maritime Organization (IMO) regulations. This study presents a three-dimensional computational fluid dynamics (CFD) analysis of a four-stroke, medium-speed marine engine operating in methanol–diesel dual-fuel (DF) mode. Simulations were performed using AVL FIRE for a MAN B&W 6H35DF engine, covering the in-cylinder process from intake valve closing to exhaust valve opening. Nine operating cases were investigated, including seven methanol–diesel DF cases with equivalence ratios (Φ) from 0.18 to 0.30, one methane–diesel DF case (Φ = 0.22), and one pure diesel baseline. A power-matched condition (IMEP ≈ 20 bar) enabled consistent comparison among fueling strategies. The results show that methanol–diesel DF operation reduces peak in-cylinder pressure, heat-release rate, turbulent kinetic energy, and wall heat losses compared with diesel operation. At low to moderate Φ, methanol DF combustion significantly suppresses nitric oxide (NO), soot, and carbon monoxide (CO emissions), while carbon dioxide (CO₂) emissions increase with Φ and approach diesel levels under power-matched conditions. These results highlight methanol’s potential as a viable low-carbon fuel for marine engines. Full article

Reverse engineering (RE) has been increasingly adopted in metal manufacturing to digitize legacy parts, connect “as-is” geometry to mechanical performance, and enable agile repair and remanufacturing. This review consolidates scan-to-simulation workflows that transform 3D measurement data (optical/laser scanning and X-ray computed tomography) into simulation-ready models for structural assessment and manufacturing decisions, with an explicit focus on sustainability. Key steps are reviewed, from acquisition planning and metrological error sources to point-cloud/mesh processing, CAD/feature reconstruction, and geometry preparation for finite-element analysis (watertightness, defeaturing, meshing strategies, and boundary condition transfer). Special attention is given to uncertainty quantification and the propagation of geometric deviations into stress, stiffness, and fatigue predictions, enabling robust accept/reject and repair/replace choices. Sustainability is addressed through a lightweight reporting framework covering material losses, energy use, rework, and lead time across the scan–model–simulate–manufacture chain, clarifying when digitalization reduces scrap and over-processing. Industrial use cases are discussed for high-value metal components (e.g., molds, turbine blades, and marine/energy parts) where scan-informed simulation supports faster and more reliable decision making. Open challenges are summarized, including benchmark datasets, standardized reporting, automation of feature recognition, and integration with repair process simulation (DED/WAAM) and life-cycle metrics. A checklist is proposed to improve reproducibility and comparability across RE studies. Full article

Ocean current energy, owing to its predictability and stability, is regarded as an ideal power source for distributed marine observation networks and underwater intelligent equipment. However, conventional ocean current energy devices that rely on rigid turbines and electromagnetic generators generally suffer from high cut-in flow velocity, bulky size, high maintenance costs, and significant environmental disturbance, making them unsuitable for deep-sea, miniaturized, and long-duration power supply scenarios. These limitations highlight the urgent need for flexible and low-speed energy harvesters capable of autonomous, long-term operation. In recent years, nanogenerator technology has provided new opportunities for distributed and low-power ocean current energy harvesting. PENGs and TENGs can directly convert weak mechanical energy into electricity, enabling energy harvesting in small-scale and low-velocity flow fields. PENGs offer high durability and mechanical robustness, whereas TENGs exhibit superior output performance in low-speed and intermittent flows. This paper provides a comprehensive review of structural designs, material innovations, interface engineering, hybrid energy-conversion architectures, and power-management strategies for PENG- and TENG-based ocean current energy harvesters. Overall, future progress will rely on the integration of intelligent materials, multi-field coupling mechanisms, and system-level engineering strategies to achieve durable, scalable, and autonomous ocean current energy harvesting for distributed marine systems. Full article

Floating offshore wind turbines (FOWTs) constitute a pivotal offshore renewable energy technology, offering a sustainable and eco-friendly solution for large-scale marine power generation. Their low-carbon emission characteristics are highly aligned with global sustainable development goals, playing a crucial role in promoting energy structure transformation and reducing reliance on fossil fuels. This paper presents a numerical study on the coupled dynamic behavior of a semi-submersible FOWT during its mooring system installation. The proposed methodology incorporates environmental loads from incident waves, wind, and currents. Those forces act on not only the floating platform but also on the three tugboats employed throughout the installation procedure. Detailed evaluations of forces and motion responses are conducted across successive stages of the operation. The findings demonstrated the feasibility of the proposed mooring installation process for FOWTs while offering critical insights into suitable installation weather windows and motion responses of both the platform and tugboats. Furthermore, the novel installation scheme presented herein offers practical guidance for future engineering applications. Full article

The collision dynamics of binary seawater droplets are pivotal in marine engineering applications, like spray desalination and engine cooling. While high-fidelity simulations can resolve these dynamics, they are computationally prohibitive for rapid design and analysis. This study introduces the first interpretable machine learning (ML) framework to predict and elucidate the collision outcomes of head-on binary seawater droplets. A high-fidelity numerical dataset, generated via Modified Coupled Level Set-VOF (M-CLSVOF) simulations across a broad Weber number (We) range, serves as the foundation for training multiple classifiers. Among the tested algorithms, the Random Forest model achieved superior performance with 96.2% accuracy. The model’s predictions precisely identified the critical Weber number for the transition from coalescence to reflexive separation at We ≈ 22.3 for seawater. Moving beyond black-box prediction, we employed SHapley Additive exPlanations (SHAP) to quantitatively deconstruct the model’s decision-making process. SHAP analysis confirmed the dominance of the Weber number (75% contribution) and revealed the context-dependent role of the Reynolds number (25% contribution) in modulating the collision outcome. Furthermore, a comparative analysis with freshwater droplets quantified a 6% elevation in the critical Weber number for seawater, attributed to salinity-induced modifications in fluid properties. Finally, a machine-learned regime map in the We-Ohnesorge space was constructed, delineating the coalescence and separation boundaries. This work establishes ML as a powerful, interpretable surrogate model that not only delivers rapid, accurate predictions but also extracts fundamental physical insights, offering a valuable paradigm for optimizing marine spray systems. Full article

Shipping is a high-energy-intensive sector and a major source of climate-relevant and harmful air pollutant emissions. In response to growing environmental concerns, the sector has been subject to increasingly stringent regulations, promoting the uptake of alternative fuels and emission control technologies. Accurate and diverse emission factors (EFs) are critical for quantifying shipping’s contribution to current emission inventories and projecting future developments under different policy scenarios. This study advances the development of load-dependent EFs for ships by incorporating alternative fuels, biofuels and emission control technologies. The methodology combines statistical analysis of data from an extensive literature review with newly acquired on-board emission measurements, including two-stroke propulsion engines and four-stroke auxiliary units. To ensure broad applicability, the updated EFs are expressed as functions of engine load and are categorized by engine and fuel type, covering conventional marine fuels, liquified natural gas, methanol, ammonia and biofuels. The results provide improved resolution of shipping emissions and insights into the role of emission control technologies, supporting robust, up-to-date emission models and inventories. This work contributes to the development of effective strategies for sustainable maritime transport and supports both policymakers and industry stakeholders in their decarbonization efforts. Full article

The Soft Yoke Mooring (SYM) system is a critical single-point mooring method for Floating Production Storage and Offloading systems (FPSOs) in shallow waters. Its articulated thrust roller bearing operates long-term in harsh marine environments, making it prone to failure and difficult to diagnose. To address the issues of non-stationary signals and fault features submerged in strong noise caused by the bearing’s non-rotational oscillatory motion, this paper proposes an adaptive improved diagnosis scheme based on Minimum Entropy Deconvolution (MED). By optimizing Finite Impulse Response (FIR) filter parameters to adapt to the oscillatory operating conditions and combining joint analysis of time-domain indicators and envelope spectra, precise identification of bearing faults is achieved. Research shows that this method effectively enhances fault impact components. After MED processing, the kurtosis value of the fault signal can be significantly increased from approximately 2.6 to over 8.6. Its effectiveness in noisy environments was verified through simulation. Experiments conducted on a 1:10 scale soft yoke model demonstrated that the MED denoising and filtering signal analysis method can effectively identify damage in the thrust roller bearing of the SYM system under marine conditions characterized by high noise and complex frequencies. This study provides an efficient and reliable method for fault diagnosis of non-rotational oscillatory bearings in complex marine environments, holding significant engineering application value. Full article

To enhance the wear and corrosion resistance of Zr alloy components in marine engineering, this study investigated the influence of the applied voltage (ranging from 470 to 620 V) on the morphology, structure, and properties of ceramic coatings formed on a Zr alloy substrate by Micro-arc Oxidation (MAO) in a silicate–phosphate composite electrolyte. The results showed that with increasing voltage, the coating thickness increased (from 15.12 to 52.80 μm) and the surface roughness increased (from 1.12 to 4.89 μm), while both the surface and cross-sectional porosity first increased and then reached their minimum values at 620 V (1.61% and 5.75%, respectively). Phase analyses indicated that the coatings consisted mainly of monoclinic ZrO₂ (m-ZrO₂), along with minor amounts of SiO₂, ZrSiO₄, and Zr₃(PO₄)₄. The coating prepared at 620 V exhibited optimal performance: its hardness was 1.98 times that of the substrate, the wear volume decreased by approximately 87%, the self-corrosion potential shifted positively by 539 mV, the corrosion current density decreased by nearly two orders of magnitude, and the polarization resistance increased by approximately two orders of magnitude. These results demonstrate a substantial improvement in the service performance of Zr alloys for marine applications. Full article

The transfer of aircraft on deck relies on the traction system, which is easily affected by the offshore environment. Violent ship motion in the complex marine environment poses a great threat to the aircraft traction process, such as the tire sideslip, off-ground phenomena, the aircraft overturning, traction rod fatigue fracture, and so on. Therefore, it has merits in both academia and engineering practice to study the dynamic behaviors of the ship-borne aircraft towing system under high sea states. Considering the intricate coupling motions of the hull roll, pitch, and heave, the dynamic analysis of the towing system with rod are carried out based on the multibody dynamics theory. The influence of the sea state level and the traction speed on the dynamic characteristics of the towing system is investigated. The results indicate that noticeable tire sideslip occurs under sea state 3, with the peak lateral tire force increasing by approximately 250% compared with sea state 2. Under sea state 4, intermittent off-ground phenomena are observed, accompanied by a further increase of about 22% in lateral tire force. These findings provide quantitative insights into the dynamic characteristics and operational limits of rod-traction systems for ship-borne aircraft in rough marine environments. Full article

The valorization of dredged sediments represents a major environmental and logistical challenge, particularly in the context of forthcoming regulations restricting their marine disposal. This study investigates the potential of untreated dredged sediments as sustainable raw materials for geopolymer binder development, with the dual objective of sustainable sediment management and reduction in cement-related environmental impact. Dredged sediments from the Grand Port Maritime de Bordeaux (GPMB) were activated with sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃), both alone and in combination, with supplementary aluminosilicate and calcium-rich co-products, to assess their reactivity and effect on binder performance. A multi-scale experimental approach combining mechanical testing, calorimetry, porosity analysis, Scanning Electron Microscopy and Energy-Dispersive Spectroscopy (SEM–EDS), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), and solid-state Nuclear Magnetic Resonance (NMR) was employed to challenge the commonly assumed inert behavior of sediments within geopolymer matrices, to elucidate gel formation mechanisms, and to optimize binder formulation. The results show that untreated sediments actively participate in alkali activation, reaching compressive strengths of up to 5.16 MPa at 90 days without thermal pre-treatment. Calcium-poor systems exhibited progressive long-term strength development associated with the formation of homogeneous aluminosilicate gels and refined microporosity, whereas calcium-rich systems showed higher early age strength but more limited long-term performance, linked to heterogeneous gel coexistence and increased total porosity. These findings provide direct evidence of the intrinsic reactivity of untreated dredged sediments and highlight the critical role of gel chemistry and calcium content in controlling long-term performance. The proposed approach offers a viable pathway for low-impact, on-site sediment valorization in civil engineering applications. Full article

Subsea pipelines are critical lifelines for marine resource development, yet they face severe threats from accidental ship anchor impacts. This study addresses the scientific challenge of quantifying the “protection margin” of artificial rock-dumping layers, moving beyond traditional passive structural response to a “Critical Failure Intervention” logic. Based on the energy criteria of DNV-RP-F107, a critical velocity required to trigger Concrete Weight Coating (CWC) failure for a bare pipe was derived and established as the Safety Factor baseline (S = 1). Two groups of scaled model tests (1:15) were conducted using a Hall anchor to simulate impact scenarios, where impact forces were measured via force sensors beneath the pipeline under varying backfill thicknesses and configurations. Results show that artificial backfill provides a significant protective redundancy; a 10 cm coarse rock layer increases the safety factor to 3.69 relative to the H₀ baseline, while a multi-layer configuration (sand bedding plus coarse rock) elevates S to 27. Analysis reveals a non-linear relationship between backfill thickness and cushioning efficiency, characterized by diminishing marginal utility once a specific thickness threshold is reached. These findings indicate that while thickness is critical for extreme impacts, the protection efficiency optimizes at specific depths, providing a quantifiable framework to reduce small-particle layers in engineering projects without compromising safety. Full article