Search Results (205)

The replacement of fishmeal (FM) in aquafeeds for carnivorous fish remains challenging due to reduced palatability and adverse effects on liver health and intestinal microbiota. Marine by-products-based additives containing fish protein hydrolysates and seaweed polysaccharides have shown potential to overcome these limitations. This study evaluated the effects of graded supplementation of Haiweisu (HWS), a multi-marine by-product formulated with squid viscera hydrolysate, small-molecule components from fish protein hydrolysate, seaweed polysaccharides, and seaweed residue as a carrier, in a FM-free diet for juvenile largemouth bass. Four isonitrogenous and isolipidic diets were prepared: a FM-free control diet (CON) and three diets supplemented with 10, 20, or 30 g/kg HWS (designated S10, S20, and S30, respectively). Each diet was fed to triplicate groups of fish (29.26 ± 2.61 g) for 56 days. Results showed that HWS supplementation linearly increased final body weight, weight gain rate, and feed intake, while significantly reducing the feed conversion ratio (p < 0.05). All HWS-supplemented groups exhibited markedly lower hepatic lipid accumulation and plasma total cholesterol levels compared with the CON group, accompanied by alleviated hepatocellular steatosis and inflammatory infiltration as revealed by Oil Red O and H&E staining. Moreover, HWS significantly enhanced intestinal microbiota alpha diversity (Ace, Chao, Sobs, and Shannon indices), decreased the relative abundance of the dominant genus Mesomycoplasma, and enriched potentially beneficial genera including Methylobacterium, Delftia, and Sphingomonas (p < 0.05). In conclusion, dietary HWS supplementation effectively improved growth performance, alleviated hepatic steatosis and inflammation, and beneficially reshaped the intestinal microbiota in juvenile largemouth bass fed a FM-free diet. These findings support HWS as a promising functional additive for sustainable FM-free aquafeeds in carnivorous fish species. Full article

Offshore wind turbine blades are chronically exposed to complex marine environments with high humidity, salt spray, strong wind, waves, and intense radiation. Under such conditions, blade defects often exhibit small sizes, weak visual features, and heterogeneous visible infrared manifestations. Conventional single-sensor monitoring and empirically weighted fusion methods are insufficient for reliable defect diagnosis and risk grading. To address this problem, this paper proposes a cross-sensor consistency-guided dual-spectrum fusion framework, termed CG-DSF, for offshore wind turbine blade defect diagnosis and risk assessment. First, visible-light images and infrared thermal images are acquired by UAV-mounted imaging sensors, and sensor-specific branches are constructed to extract surface structural features and thermal anomaly responses. Second, visible and infrared features are aligned at the feature token level, and cross-sensor evidence is evaluated for spatial consistency, diagnostic semantic consistency, and anomaly consistency. A reliability-aware fusion strategy is then used to suppress low-quality or conflicting observations and construct a unified defect representation. Finally, a series of representative simulation case studies are carried out to comprehensively assess the overall performance and practical applicability of the constructed model. Experimental results reveal that the proposed framework possesses evident advantages in blade defect identification for offshore wind turbines, offering a feasible solution for advancing proactive and intelligent condition-based operation and maintenance of offshore wind assets in complex marine environments. Full article

Aquatic environments that support tourism, including coasts, lakes, reservoirs, and estuaries, are experiencing accelerating eutrophication worldwide. This trend increases the frequency and intensity of algal blooms. These blooms undermine ecosystem services and weaken the socio-economic performance of destination areas. Despite these challenges, existing research remains fragmented. Aquatic sciences mainly examine nutrient enrichment and bloom dynamics. In contrast, tourism studies often treat blooms as episodic disturbances and rarely integrate exposure pathways, risk communication, or feedback to destination governance. This review synthesizes evidence across freshwater and marine systems to develop a coupled tourism–water ecosystem perspective. We link eutrophication drivers and bloom typologies to three dimensions. These are the degradation of tourism-supporting ecosystem services, compound health stressors, and communication filters. The first includes losses of water clarity and aesthetic value. The second involves multi-route exposure through contact, inhalation, and seafood ingestion. The third shapes perceived safety, trust, and behavioral adaptation. We further connect perceived health risks to observable tourist behaviors, including cancellation, destination substitution, and activity avoidance. These micro-level responses can aggregate into market-level demand contractions and consumption reallocation. They can also trigger regional economic cascades, including public management costs, employment impacts, and long-term reputational damage. Crucially, tourism is not merely a victim of blooms. It can also act as a reinforcing anthropogenic driver through wastewater burdens, infrastructure expansion, and pulse pressures. These pressures lower ecological resilience, especially under warming and hydrological stabilization. Finally, we identify governance leverage points. These include early-warning systems, threshold-based graded interventions, transparent risk communication, and integrated social–ecological modeling. These strategies can reduce uncertainty-driven losses and support adaptive destination management. Overall, this review reframes algal blooms as systemic social–ecological risks. It provides a structured basis for future empirical attribution and policy design in tourism-dependent waters under climate stress. Full article

Pipes conveying fluids are important fluid–structure interaction systems encountered in aerospace, energy, marine, and industrial applications. Their dynamic behavior is strongly influenced by the interaction between structural motion and internal or external flow, leading to complex phenomena such as divergence, flutter, and flow-induced vibration. This review presents a comprehensive assessment of the dynamics and stability of pipes conveying fluids by integrating classical theories with recent developments in modeling, computation, materials, and control. The review covers mathematical formulations based on Euler–Bernoulli, Rayleigh, Timoshenko, and shell theories, together with analytical and numerical solution methods used for stability and vibration analysis. The effects of geometry, boundary conditions, flow configuration, damping, and material properties on dynamic response and instability thresholds are discussed. Special attention is given to composite, viscoelastic, functionally graded, and smart materials, as well as micro- and nanoscale pipe systems. Recent advances in vibration suppression, reduced-order modeling, machine learning, and physics-informed computational approaches are also reviewed. Finally, the paper identifies current challenges and future research directions, including multiphysics coupling, experimental validation, digital twins, and AI-assisted predictive modeling for fluid-conveying pipe systems. Full article

This paper analyzes the vibrational characteristics of a novel sandwich plate configuration composed of an auxetic honeycomb (AH) core and laminated functionally graded carbon nanotube-reinforced composite (FG-CNTRC) face sheets, hereafter referred to as the SD-AuCNT plate. Based on Reddy’s third-order shear deformation theory (SDT), which accurately accounts for transverse shear effects without requiring shear correction factors, the equations of motion are derived using Hamilton’s principle and subsequently solved using a pb-2 Ritz formulation combined with the Newmark time integration scheme for dynamic response analysis. By combining an auxetic core with negative Poisson’s ratio characteristics and laminated FG-CNTRC face sheets featuring tailored CNT distribution patterns and orientations, the hybrid SD-AuCNT plate can improve structural stiffness, energy absorption, and dynamic performance; however, it has not been thoroughly investigated in the existing literature. After verifying the accuracy of the proposed computational procedure, the effects of auxetic core geometry, CNT distribution patterns, thickness ratios, and boundary conditions on the natural frequencies and transient responses of the plate are comprehensively investigated. The results provide new insights into the dynamic behavior of advanced sandwich plates and offer practical guidance for the design of high-performance lightweight structures in aerospace, marine, defense, and other engineering applications. Full article

Chinese Traditional Concrete (CTC), known as “San-he-tu,” has ensured the long-term durability of ancient coastal structures, yet its underlying material design logic remains insufficiently understood. This study investigates the Chongwu Ancient City Wall (Quanzhou, China), a Ming Dynasty granite fortification exposed to over 600 years of marine weathering, to elucidate the structure–property–function relationships of CTC across three functional layers: the horse-track surface, wall core backfill, and masonry bonding layer. A multi-technique analytical framework (XRF, XRD, TG, and SEM) was employed to characterize chemical composition, mineral phases, thermal behavior, and microstructure. Results reveal a deliberate “functional adaptability” material design. The surface layer adopts a rigid protective formulation with high quartz (76.9%) and CaO (17.06%), forming a dense, low-porosity matrix resistant to abrasion and weathering. The wall core exhibits a flexible filling strategy with high porosity (35.44%), enabling moisture dissipation and deformation accommodation. The bonding layer, enriched in kaolinite (~29.8%) and reactive Al–Fe components, promotes pozzolanic reactions that generate hydraulic gels, ensuring durable interfacial adhesion under humid coastal conditions. These findings demonstrate that ancient builders engineered zone-specific material compositions to meet distinct structural and environmental demands, forming a functionally graded system analogous to modern material design concepts. This study provides a scientific basis for adopting partitioned, differentiated restoration strategies in coastal heritage conservation. Full article

Given the increasing concern around greenhouse gas emissions and the decline in the availability of fossil fuels, there is increasing global demand to develop alternate fuels for maritime transportation that are sustainable and which have lower greenhouse gas emissions. Methanol is one such alternative fuel that has garnered considerable attention given its potential to be produced by more sustainable processes and its more favorable greenhouse gas emission profile in comparison with current fossil fuels. Understanding the physical and chemical properties of methanol under a range of conditions is essential for its development as a marine fuel. In this study, we seek to define physical and chemical properties of different methanol samples to simulate real-world storage conditions as these data are lacking in the literature. Several methanol samples were evaluated: nearly pure methanol; International Organization for Standardization (ISO) marine methanol (MM) grades A, B, and C; and methanol plus higher alcohols. We first evaluated all methanol samples for impurities, acetic acid content, density, and distillation range. We then characterized the effects of water absorption and found that methanol can easily absorb unacceptable water content from humid air within hours, necessitating storage conditions that prevent this process. In eight-week aging experiments at 20 °C and 40 °C in ambient air, we did not observe significant oxidation for any of the methanol samples; however, we did observe increases in acid number. We assessed the impact of contamination of methanol with water, marine gas oil (MGO), and an MGO–biodiesel mixture on density, viscosity, distillation range, and lubricity. Finally, we show that MGO contamination of methanol results in a slight increase in sooting tendency. In aggregate, our results provide an in-depth analysis of physical and chemical properties of methanol as well as the impacts of storage conditions and impurities on the properties of fuel methanol. Full article

With the growing demand for strategic metals and the gradual depletion of traditional metal ore deposits, coal and coal-bearing strata are regarded as potential sources of rare metals; consequently, research into the characteristics of associated elements in coal-bearing strata has become one of the primary avenues of searching for new alternative resources. To investigate the sedimentary environmental characteristics and controlling factors of the coal-bearing strata along the southern margin of the Junggar Basin, coal seams 9–15 of the Xishanyao Formation in Sulphur Gully (Early Middle Jurassic) were selected as the subject of this study. This study employed analytical techniques including industrial analysis, total sulphur analysis, X-ray powder diffraction (XRD), X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) to determine the mineralogical and elemental geochemical characteristics of coal samples from Seylangou mining area, specifically from coal seams 9–15 and their overlying and underlying strata. Based on analyses of elemental ratios such as Al₂O₃/TiO₂, Sr/Ba, Rb/Sr, Ni/Co and V/(Ni + V), the source of material during the deposition of this deposit was identified, and the characteristics of the depositional environment, as indicated by palaeosalinity, palaeoclimate and redox conditions, were revealed. The results indicate that the macroscopic coal-rock types of coal seams 9–15 at the Sulphur Gully Coal Mine on the southern margin of the Junggar Basin are predominantly semi-dull to dull, with small amounts of filamentous coal and lustrous coal. The average proportion of the vitrinite group in the coal is 42.75%, the inertinite group is 51.40%, and the liptinite is 2.25%. The average content of inorganic matter in the coal is 3.60%, and the average maximum reflectance of the vitrinite group is 0.651%. The coal represents a transitional stage from low-rank to medium-rank coal, corresponding to a metamorphic stage of Grade I–II. The coal is classified as a bituminous coal with medium total moisture, very low ash, medium-volatile matter, medium-to-high fixed carbon and very low sulphur. The minerals in the coal seam are predominantly kaolinite, calcite and quartz. The major elements in the ceiling of the coal seam are dominated by SiO₂, followed by Al₂O₃; the coal itself is dominated by CaO, SiO₂ and Al₂O₃; and the base plate of the coal seam is dominated by Al₂O₃. The trace elements Cs and Bi are relatively enriched in the coal seam ceiling; Sr is relatively enriched in the coal; whilst Li, Cr and other elements are highly enriched in the coal seam base plate. The source rocks of the coal and the roof consist of deposits of felsic igneous rock (dacite), whilst the source rocks of the floor consist of deposits of intermediate igneous rock (andesite). The depositional environment ranges from marine brackish water at the base to transitional slightly brackish water and then to terrestrial freshwater at the top; the depositional climate was cold and arid, and the depositional environment was oxidising. This study provides valuable insights for further research into the elemental geochemical characteristics, sediment sources and depositional environments of the Xishanyao Formation coal seams in Liuhuangou, Xinjiang. Full article

The aim of this study was to design and validate an automated 5 L prototype Stirred-Tank Photobioreactor (ST-PBR) dedicated to the two-stage cultivation of the microalga Haematococcus pluvialis. The classic limitations of stirred-tank reactors (such as high shear stress and suboptimal light penetration) were overcome through precise phase-controlled illumination (60 and 300 μmol m⁻² s⁻¹) and the implementation of an advanced embedded control system integrated with Keysight VEE Pro 9.33 software. The design features an innovative mixing system utilizing a dual marine impeller driven by a brushless motor—operating at a mathematically defined tip speed of 0.48 m/s to preserve cellular integrity—alongside a precise gas dosing strategy (pH-stat) employing medical-grade components. Process verification demonstrated highly stable operation, maintaining a dry biomass concentration of 1.315 g/L with no recorded sedimentation, while achieving a highly competitive astaxanthin biosynthesis yield of 4.12% dry weight (DW). Furthermore, enzymatic extraction facilitated the recovery of a product with high biological activity, as confirmed by an increase in equine adipocyte viability up to 128.1 ± 3.1% in in vitro MTS assays, highlighting its potential for veterinary nutraceutical applications. The developed solution represents a scalable, cost-effective, and viable alternative to advanced tubular photobioreactors. Full article

Copper-containing steel is widely used in ship plates and other marine engineering fields due to its excellent mechanical properties and good weldability. However, in hydrogen-containing media environments, ship plate steel is prone to hydrogen embrittlement during service. Existing research primarily focuses on steel grades with copper content below 3 wt.%, while the diffusion and trapping behavior of hydrogen in ultra-high-copper steel with copper content exceeding 3 wt.% remains unclear. Therefore, this study designed an ultra-high-copper-content steel with a copper content of 6.01% and investigated the diffusion behavior of hydrogen in the test steel under different hydrogen charging current densities through microstructure characterization, slow strain rate tensile testing, electrochemical hydrogen permeation, and internal friction tests. The results indicate that with an increase in hydrogen charging current density, accompanied by a slight degradation in mechanical properties, the irreversible hydrogen trap density increases by 50.7%. A large number of microstructures, such as phase boundaries, grain boundaries, and dislocations, have formed inside the material, which have reversible trapping effects on hydrogen, effectively suppressing the migration of hydrogen in the crystal structure and reducing the embrittlement phenomenon caused by hydrogen. This study expands the application potential of copper-containing steel in the field of ocean engineering, providing an important reference for the future development of high-strength, hydrogen embrittlement-resistant copper steel with ultra-high copper content. Full article

Titanium alloys exhibit exceptional strength-to-density ratios, high hardness, and outstanding resistance to elevated temperatures, making them indispensable structural materials in aerospace engineering, marine construction, and biomedical applications. In aerospace systems specifically, fatigue failure represents the predominant failure mode for titanium alloy components. This review systematically examines prevalent surface treatment techniques for titanium alloys—including shot peening, ultrasonic rolling treatment, hot isostatic pressing (HIP), physical vapor deposition (PVD), micro-arc oxidation (MAO), and thermal spray processes—and critically evaluates their respective effects on fatigue performance. The underlying mechanisms of each technique are concisely outlined, with emphasis on stress state evolution, near-surface microstructural refinement, and interfacial integrity. Building upon the characteristic surface-dominated fatigue fracture behavior of titanium alloys, this work focuses on how coating composition, architecture (e.g., graded, multilayer, or nanocomposite designs), and interfacial bonding strength govern fatigue resistance. A unified analysis is presented on the distinct yet complementary roles of substrate deformation strengthening (e.g., residual compression, grain refinement) and coating-mediated protection (e.g., barrier function, crack deflection, stress redistribution) during fatigue crack initiation and propagation. Key determinants of fatigue performance, including residual stress distribution, coating/substrate adhesion, thermal mismatch, and environmental degradation susceptibility, are rigorously assessed. Finally, emerging research frontiers are identified, including intelligent process–structure–property mapping, in situ monitoring of fatigue damage at coated interfaces, and design of multifunctional gradient coatings that synergistically enhance strength, wear resistance, and fatigue endurance of titanium alloy components. Full article

This article presents a proposed a new method for estimating the degree of dilution of lubricating oil with diesel oil, which can be applied to systems for ongoing monitoring of lubricating oil quality in an internal combustion engine. The test is performed for reference blends based on two commonly used single-season lubricating oils for marine and industrial engines. SAE 30 and SAE 40 viscosity grade base oils and ISO-F-DMX category diesel oil are used. For each base oil, reference blends are prepared with diesel oil content in the lubricating oil mixture equal to 0, 1, 2, 5, 10, 20, 30, 40, 50, 75, and 100% m/m. Concentration estimates are made for each mixture based on measured kinematic viscosity at different temperatures. Measurements are made for 40, 50, 60, 70, 80, 90, and 100 °C. The results are evaluated by determining the model’s fit to the empirical data and the maximum percentage absolute error in estimating the degree of dilution of the lubricating oil with diesel fuel. The results are contrasted with a previously used model based on the inverse Arrhenius equation for determining the viscosity of binary mixtures. The proposed new model for both base oils, for all tested reference concentrations and for all tested temperatures shows a much better fit to empirical data (R² > 0.999). Moreover, the maximum absolute error of the SATUFER estimation did not exceed the value of 1.5% m/m and, relative to the model based on the inverse Arrhenius equation, it is ~8.9 times higher for mixtures of SAE 30 grade base oil and ~10.3 for mixtures of SAE 40 grade base oil. Full article

Repurposing decommissioned wind turbine blades provides a vital pathway to mitigate carbon emissions, yet the escalating volume of large-scale waste poses a severe environmental challenge. Recognizing the limitation that existing research focuses predominantly on small-scale legacy blades, this study addresses this gap by assessing the mechanical properties and microstructure of a 54-m (2.0 MW) blade decommissioned due to repowering after 10 years of service. GFRP samples extracted from the root, mid-span, and tip were investigated using X-ray computed tomography and a comprehensive suite of mechanical tests. The investigation confirmed a low internal porosity (~1.2%) without service-induced macroscopic interfacial cracking, alongside superior residual performance, exemplified by a tensile strength of 849.5 MPa at the root. Statistical analysis employing ANOVA revealed significant spatial variations, supporting a graded reuse strategy: roots with superior tensile strengths for critical members, mid-spans for axial compression, and tips as a reliable property baseline for general reuse, while Weibull analysis verified the statistical reliability required for structural design. Based on these superior residual properties, a raft-type wave energy converter utilizing repurposed blade segments was proposed. A comparative carbon footprint assessment revealed that this blade-repurposed WEC achieved a 71.5% reduction in carbon emissions and a 37.4% reduction in structural mass compared to conventional steel counterparts. These findings substantiate the viability of large-scale DWTBs as high-value resources for decarbonizing marine infrastructure within a circular economy. Full article

This work presents an experimental investigation into the fatigue and fracture behavior of explosion-welded aluminum–steel transition joints for marine applications. A commercial TriClad^® laminate (AA5086/AA1050/ASTM A516) was characterized by nanoindentation to assess local elastic–plastic properties across the interface. Fatigue tests revealed an endurance strength of approximately 20 MPa, with crack initiation predominantly occurring at or near the aluminum–steel interface. Fracture properties were determined using digital image correlation combined with an inverse analysis to estimate mixed-mode stress intensity factors. The results highlight the effectiveness of explosion welding in achieving a graded mechanical transition and provide guidance for the design of durable lightweight structures. In addition, results demonstrated that combining nanoindentation and full-field analysis is an effective pathway for assessing graded joints. Full article

Post-recycling plastic waste contamination in freshwater ecosystems represents an escalating environmental threat, while algal blooms continue to generate vast quantities of underutilized biomass. Addressing both challenges, this study investigated the co-hydrothermal liquefaction of Chlorella pyrenoidosa with representative post-recycling plastic wastes polypropylene, polyethylene terephthalate, and Nylon-6 as a dual-resource valorization strategy. Experiments were conducted in a 1000 mL high-pressure batch reactor at 350 °C for 30 min, with varying biomass-to-plastic feed ratios. Systematic product characterization, including functional group, elemental analysis, Van Krevelen diagrams, and heating value assessment, was employed to elucidate synergistic effects and evaluate product quality. Results revealed that co-processing with polyethylene terephthalate achieved the highest biocrude yield of 71.5%, with an enhanced higher heating value of 35.7 MJ kg⁻¹, surpassing the 62.4% yield from microalgae alone. Nylon-6 blends also improved oil yield to 69.6% while producing aqueous fractions enriched with ε-caprolactam, indicating the recovery of valuable nitrogenous monomers. In contrast, PP exhibited limited reactivity toward oil generation but produced carbon-rich biochar with a higher heating value up to 41.4 MJ kg⁻¹, comparable to high-grade solid fuels. Mechanistic analyses confirmed that plastics acted as hydrogen donors, promoting deoxygenation, radical stabilization, and selective depolymerization, thereby improving both liquid and solid fuel fractions. By employing ecologically relevant freshwater feedstocks from Thailand, this work advances beyond prior studies dominated by marine biomass or synthetic surrogates, providing realistic insights into resource integration within polluted inland waters. The co-hydrothermal liquefaction process simultaneously mitigates eutrophication-driven algal blooms and persistent plastic pollution while generating fuels and functional carbon materials, directly contributing to a circular bioeconomy. The demonstrated synergy between biological and synthetic wastes highlights a scalable, catalyst-free route to energy-dense biofuels and multifunctional biochar. These outcomes align strongly with SDG which offer a pragmatic framework for waste-to-energy transition in freshwater-dependent regions. Full article