Formal safety assessment based on relative risks model in ship navigation

Formal safety assessment (FSA) is a structured and systematic methodology aiming at enhancing maritime safety. It has been gradually and broadly used in the shipping industry nowadays around the world. On the basis of analysis and conclusion of FSA approach, this paper discusses quantitative risk assessment and generic risk model in FSA, especially frequency and severity criteria in ship navigation. Then it puts forward a new model based on relative risk assessment (MRRA). The model presents a risk-assessment approach based on fuzzy functions and takes five factors into account, including detailed information about accident characteristics. It has already been used for the assessment of pilotage safety in Shanghai harbor, China. Consequently, it can be proved that MRRA is a useful method to solve the problems in the risk assessment of ship navigation safety in practice

A Hybrid Probabilistic Risk Analytical Approach to Ship Pilotage Risk Resonance with FRAM

Collision risk in ship pilotage process has complex characteristics that are dynamic, uncertain, and emergent. To reveal collision risk resonance during ship pilotage process, a hybrid probabilistic risk analysis approach is proposed, which integrates the Functional Resonance Analysis Method (FRAM), Dempster–Shafer (D–S) evidence theory, and Monte Carlo (MC) simulation. First, FRAM is used to qualitatively describe the coupling relationship and operation mechanism among the functions of the pilotage operation system. Then, the D–S evidence theory is used to determine the probability distribution of the function output in the specified pilotage scenario after quantitatively expressing the function variability, coupling effect, and the influence of operation conditions through rating scales. Finally, MC simulation is used to calculate the aggregated coupling variability between functions, and the critical couplings and risk resonance paths under different scenarios are identified by setting the threshold and confidence level. The results show that ship collision risk transmission is caused by function resonance in the pilotage system, and the function resonance paths vary with pilotage scenarios. The critical coupling ‘F2-F7(I)’ emerges as a consistent factor in both scenarios, emphasizing the significance of maintaining a proper lookout. The hybrid probabilistic risk analytical approach to ship pilotage risk resonance with FRAM can be a useful method for analysing the causative mechanism of ship operational risk

Dynamics Simulation for Process Risk Evolution on the Bunker Operation of an LNG-fueled Vessel with Catastrophe Mathematical Models

Liquefied nature gas (LNG) is a green energy. LNG-fueled vessels are extremely complex engineering systems. In view of the inherent hazardous properties of LNG fuel, LNG fueling is not only an important part, but it is also full of high risks in the operation of LNG-fueled vessels (LNGFVs). Therefore, it is necessary to study the risk factors, and the intrinsic relationship among them between the LNG and the vessel, and to simulate the system dynamics in the process of LNGFV operation. During the process of fueling of LNGFV, at every moment the vessel interacts with the energy and information of the surrounding environment. First, the impact of the three interactions of the fueling operation process, ship factors, and environmental factors were analyzed on the risk of fueling operation, and a complete node system was proposed as to the complex system dynamics mode. Second, by analyzing the boundary conditions of the system, the relationship of factors was established via the tools of system dynamics (SD). Based on the catastrophe theory (CA), the dynamics model for the fueling of LNG is set up to study the system’s risk mutation phenomenon. Third, combined with the simulation results of the case analysis, the risk evolution mode of the LNGFV during the fueling process was obtained, and constructive opinions were put forward for improving the safe fueling of the LNGFV. Application examples show that formal description of risk emergence and transition is a prerequisite for the quantitative analysis of the risk evolution mode. In order to prevent accidents, the coupling synchronization of risk emergence should be weakened, and meanwhile risk control should be implemented

Path Analysis of Causal Factors Influencing Marine Traffic Accident via Structural Equation Numerical Modeling

Many causal factors to marine traffic accidents (MTAs) influence each other and have associated effects. It is necessary to quantify the correlation path mode of these factors to improve accident prevention measures and their effects. In the application of human factors to accident mechanisms, the complex structural chains on causes to MTA systems were analyzed by combining the human failure analysis and classification system (HFACS) with theoretical structural equation modeling (SEM). First, the accident causation model was established as a human error analysis classification in sight of a MTA, and the constituent elements of the causes of the accident were conducted. Second, a hypothetical model of human factors classification was proposed by applying the practice of the structural model. Third, with the data resources from ship accident cases, this hypothetical model was discussed and simulated, and as a result, the relationship path dependency mode between the latent independent variable of the accident was quantitatively analyzed based on the observed dependent variable of human behavior. Application examples show that relationships in the HFACS are verified and in line with the path developing mode, and resource management factors have a pronounced influence and a strong relevance to the causal chain of the accidents. Appropriate algorithms for the theoretical model can be used to numerically understand the safety performance of marine traffic systems under different parameters through mathematical analysis. Hierarchical assumptions in the HFACS model are quantitatively verified

Interfacial Growth of TiO₂‑rGO Composite by Pickering Emulsion for Photocatalytic Degradation

A 2D sandwich-like TiO₂-rGO composite was fabricated by the Pickering emulsion approach to improve the photocatalytic efficiency. Through an in situ growth of antase-TiO₂ nanoparticles on the interface of O/W type GO Pickering emulsion, TiO₂ nanoparticles were closely and densely packed on the surface of well-exfoliated rGO sheets; meanwhile, many mesoporous voids acting as the adsorption chamber and microreactor were produced. Evaluated by methylene blue (MB) degradation, its photocatalytic activity was prominent compared with the common TiO₂-based photocatalyst, with the rate constants 5 and 3.1 times higher under visible light and xenon lamp, respectively. When we applied it in the photocatalytic degradation of tetracycline hydrochloride (TCH, such as 10 ppm) under the visible light without adding any oxidants, the total removal efficiency was as high as 94% after 40 min. The mechanism of this good photocatalytic efficiency was illustrated by the scavenger trapping tests, which showed that this unique structure of TiO₂-rGO composite induced by the Pickering emulsion can significantly enhance the light absorption ability, accelerate the separation rate of electron–hole pairs, increase the adsorption capacity of organic pollutants, and hence improve the photocatalytic efficiency

Interfacial Growth of Metal Organic Framework/Graphite Oxide Composites through Pickering Emulsion and Their CO₂ Capture Performance in the Presence of Humidity

We proposed an in situ interfacial growth method induced by the Pickering emulsion strategy to produce metal organic framework (MOF)/graphite oxide (GO) composites of Cu₃(BTC)₂/GO, in which GO was demonstrated to be a promising stabilizer for producing the Pickering emulsion and provided a large interfacial area for the in situ growth of Cu₃(BTC)₂ nanoparticles. When Cu₃(BTC)₂/GO composites were used as adsorbents for CO₂ capture from the simulated humid flue gas, they showed both significantly improved thermodynamic and dynamic properties. Because most of the H₂O molecules were adsorbed on the highly exfoliated GO sheets in Cu₃(BTC)₂/GO-m, CO₂ uptake reached 3.30 mmol/g after exposure to the simulated flue gas for 60 min and remained unchanged for up to 120 min. This highlighted its potential application for real CO₂ capture. More importantly, the in situ interfacial growth of nanoparticles induced by Pickering emulsions would be a promising strategy for designing and fabricating nanocomposites