Methane mitigation is often evaluated by sector or by reactor performance, although deployment changes energy, food, waste, and wastewater systems beyond the point of treatment. This critical review evaluates prevention, recovery, destruction, and atmospheric removal within a common life-cycle framework. Evidence is screened by methane concentration, source controllability, recovery value, auxiliary demand, burden shifting, evidence maturity, governance fit, and net cost and incentives. Across sectors, prevention is considered first when methane generation or release can be avoided before dilution. Recovery is credible for concentrated streams only when collection losses are low and recovered products displace existing supply. Destruction is justified for controlled residual streams, but conversion efficiency alone does not establish net benefit. Atmospheric methane removal remains an early stage option. At a concentration of approximately 1.9 ppm, methane removal requires large volumes of air and may impose substantial energy, land, and material demands. Reported technology rankings are conditional on the counterfactual, system boundary, operating context, and evidence scale. The resulting stage-gated framework links production and consumption choices to intervention timing, life-cycle performance, and verification. Atmospheric removal is treated as a research contingency, not a substitute for source mitigation. The final gates specify the evidence required before an emerging approach can progress beyond controlled research.
Particle image velocimetry (PIV) was used to investigate the inlet flow and nozzle wake of a waterjet propulsor under bollard conditions. An ONR Model 5673 hull was converted to a single-waterjet configuration and tested in a transparent towing tank. Velocity fields and visible bubble transport were measured at four volume flow rates, and the plane-normal vorticity component was derived from the PIV data. Pump suction produced a fan-shaped converging flow beneath the hull inlet, with a high-speed core whose size and velocity magnitude increased with flow rate. The peak inlet velocity, however, increased nonlinearly. The near-surface nozzle wake consisted of a high-speed jet core and an outer entrainment layer. Increasing the flow rate strengthened jet shear, increased the magnitude of the measured plane-normal vorticity component near the shear layer, and promoted bubble entrainment. Bubble transport consequently changed from separated clusters to a more continuous banded wake. The results quantify how increasing flow rate modifies inlet suction, wake spreading and visible bubble transport under bollard operation.
Knowledge graphs offer a structured framework for organizing accident causation knowledge and supporting maritime safety decision-making. However, existing construction methods based on deep learning rely heavily on large-scale annotated corpora, resulting in high costs and limited scalability. This study proposes a novel knowledge graph construction method based on ontology-constrained prompt engineering for large language models, eliminating the need for model fine-tuning. A ship collision accident ontology comprising 10 entity types and 8 relation types is established to define semantic boundaries, and a two-stage extraction strategy is designed for entity-attribute identification and triplet construction. By embedding the ontology into structured prompts, the framework achieves high-precision conversion from unstructured accident reports to structured knowledge using few-shot prompting with lightweight human verification. Experiments on 318 official Chinese investigation reports demonstrate that entity recognition attains an F1 score of 94.7%, while most relation types exceed 96% F1. Ablation studies confirm that ontology constraints yield a 105.8% improvement over the baseline, primarily by anchoring extraction to the predefined ontology schema and improving coverage and standardization. The resulting knowledge graph reveals characteristic patterns including elevated accident frequency during early morning hours, human factor dominance, and a strong association between management deficiencies and severe accident outcomes. These findings provide a low-cost, scalable knowledge foundation for maritime accident causation analysis and safety governance.
Ion-exchangeable glass-ceramics (GCs) find wide applications due to their enhanced mechanical properties. The ion-exchange behavior of GCs is closely related to the microstructure, which can be adjusted by controlled crystallization. In this work, the effects of the nucleation process on crystallization and ion-exchange properties of the Na2O-MgO-Al2O3-SiO2 system were investigated. Results indicate that forsterite (Mg2SiO4) precipitates at relatively low temperatures or short durations, while nepheline forms at higher temperatures or prolonged durations. A single-step heat-treatment (without nucleation) produces large forsterite crystals and high nepheline content. However, a two-step schedule (with nucleation) reduces forsterite crystal size and suppresses nepheline growth. The crystallization of forsterite promotes K+ penetration, while nepheline crystallization inhibits it. Both crystallization and ion-exchange contribute to the increase in Vickers hardness, and ion-exchange does not affect the crystal structure but leads to the contraction of crystals. Results reported here provide valuable insights for controlled crystallization and ion-exchange properties of GCs.
