Abstract Orbital angular momentum (OAM) provides a new physical dimension for enhancing the capacity of underwater acoustic communication. However, in complex propagation environments, acoustic OAM signals are often affected by factors such as multipath reflections, leading to distortion of their phase maps and increasing the difficulty of recognition. This paper proposes an Angular-Spectrum-Compensation Residual Network for intelligent and robust recognition of acoustic OAM in complex marine propagation environments. The method uses ResNet18 as its backbone. Based on the extraction of spatial texture features, it constructs a polar coordinate system centered on the prediction point, obtains angular harmonic spectral features via FFT, and finally compensates for the backbone recognition results using a residual correction approach. Furthermore, this study established a small-water-tank experimental platform to acquire experimental acoustic OAM phase data and developed a structured acoustic OAM simulator and a simulation-to-tank evaluation configuration to generate a more realistic simulation dataset. The experiments focused on 9 types of single-mode OAM and 28 types of composite OAM, and were compared with traditional neural network methods. The 28-class composite-OAM study is simulation-only.The results indicate that the proposed method exhibits faster convergence and higher validation accuracy; furthermore, it demonstrates stronger generalization capabilities. Additionally, the feature extraction capability of the angular-spectrum branch was validated through experiments. The research results show that this model can improve the accuracy and robustness of acoustic OAM pattern recognition under complex propagation conditions.
Abstract This study evaluated the biogas-production potential of anaerobic co-digestion (AcoD) of food waste (FW) and buffalo manure (BM) under mesophilic conditions (37±1 °C). Five FW/BM ratios were tested: 0:1, 1:3, 1:1, 3:1, and 1:0. The synergistic effects of FW/BM ratios were also evaluated by integrating experimental data and mathematical modelling. The results showed that the 3:1 FW/BM ratio achieved the highest cumulative biogas yield of 352.48 mL/g VS, along with the highest removal efficiencies for chemical oxygen demand (COD) (35.30%), volatile solids (VS) (37.35%), and total solids (TS) (34.18%). Moreover, the digestate with a 3:1 ratio of FW/BM showed the highest total nutrient content (TNPK) of about 4.80%. Furthermore, this study contributes to improving AcoD technology, promoting environmentally friendly waste management techniques, and facilitating the production of renewable energy on a commercial scale.
Abstract Commercial bivalve systems underpin coastal economies, food provision, and livelihoods, yet evidence on how environmental exposures translate into socio-economic vulnerability remains fragmented. This systematic map aimed to characterise the peer-reviewed evidence base on the socio-economic outcomes of environmental exposures in commercial bivalve systems. Following Collaboration for Environmental Evidence guidelines and ROSES reporting standards, searches were conducted in Web of Science Core Collection and Scopus, supported by citation chasing and organisational website searches. While initial screening sought out grey literature, only peer-reviewed articles met our empirical inclusion thresholds upon full-text review. Eligible studies were published in English from 2005 onwards and examined commercial bivalve systems, at least one environmental exposure, and at least one stakeholder-relevant socio-economic outcome. Included studies were coded for geography, bivalve type, system type, stakeholder group, exposure, outcome, and mitigation or adaptation response. Twenty-eight articles met the inclusion criteria. The evidence base was geographically concentrated, with the United States contributing the largest share of studies. Clams, mussels, and oysters were the most frequently represented bivalve groups. Temperature and ocean acidification were the dominant exposures, followed by storms, heatwaves, and pollution runoff. Revenue, cost, and yield or production were the most frequently reported socio-economic outcomes across stakeholder groups and exposure types, whereas labour, food security, health, and social outcomes were less commonly examined. Regulation, scenario planning, forecasting, and sustainable farming were the most frequently documented responses. Overall, the evidence base is strongest in documenting economic and production-related vulnerability to major climate stressors, but remains weaker on slower-onset exposures, broader wellbeing dimensions, underrepresented stakeholders, and diverse adaptation pathways.
Abstract Marine heatwaves (MHWs) are a rapidly growing threat to marine ecosystems. Historically, MHW monitoring has focused on the sea surface, but our understanding of how this translates to economically important subsurface ecosystems on shelf seas is limited. Here we assess the extent to which surface MHWs penetrate the water column and co-occur with those in deeper waters on the northwest European Shelf using a 1993-2023 hindcast, satellite data and in-situ observations. The rate at which surface and subsurface (>30m) MHWs co-occur varies dramatically across season and stratification regimes. Subsurface MHWs co-occur during almost 100% of surface MHWs in all waters during winter months and year-round in mixed waters as the excess heat is distributed throughout the whole water column. In contrast, in stratified waters during summer, surface and deep MHW regimes become almost totally disconnected with as little as of 10% surface MHWs co-occurring with subsurface (>30m) MHWs. This was confirmed by observational data that shows that deep water (>30m) temperature anomalies are almost identical inside and outside of surface MHWs in stratified waters. Mixed layer dynamics and temperature history were shown to act as key controls on the vertical extent of surface MHWs, with the penetration depth of surface MHWs being positive correlated with mixed layer depth, surface wind speed and medium-term air temperature history. Water-column stratification therefore acts as a strong barrier to the downward propagation of surface MHWs, which limits how much they penetrate the water column. MHW states at the sea surface can therefore provide limited and potentially misleading information on shelf seas when temperatures are at their most extreme. Marine heatwave monitoring should therefore extend routinely beyond the sea surface.
Abstract The ICOS atmospheric monitoring station at Saclay, southwest of Paris, continuously measures atmospheric CO₂, CH₄, and other trace gases for more than a decade, providing insight into processes acting from local to global scales. During winter under north-westerly winds, the station repeatedly records large methane enhancements that can be traced to the plume of a nearby complex of power plants located a few hundred metres from the site. The strong correlation between short-term CO₂ and CH₄ variations demonstrates that the methane is homogeneously mixed with CO2 within the emission plume from the plants. These large methane enhancements are observed only when the combined heat and power plant is operating. Methane emissions from power plants are generally neither regulated nor routinely monitored, unlike pollutants such as NOₓ. The observed CH₄-to-CO₂ enhancement ratio indicates that approximately 2 % of the gas supplied to the plant is emitted to the atmosphere without being combusted. Although only about 2 % of the natural gas escapes combustion, this methane slip increases the 20-year greenhouse-gas impact of the plant by nearly 60 %. The total methane emission is on the order of 20 kg per hour which is significant for local carbon budgets, but too small to be observed from space.
