| 1. |
- Cai, Yongqing, et al.
(författare)
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Impact of wave breaking on upper-ocean turbulence
- 2017
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Ingår i: Journal of Geophysical Research - Oceans. - 2169-9275 .- 2169-9291. ; 122:2, s. 1513-1528
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have demonstrated that surface wave breaking can impact upper-ocean turbulence through wave-breaking-induced turbulence kinetic energy (TKE) flux and momentum flux. Wave-breaking-induced momentum flux decays approximately exponentially with depth, and the decay exponent depends on both the wind speed and wave age. With increasing wave age, the decay speed of wave-breaking-induced momentum flux first decreases, reaching a minimum around a wave age of 16, and then increases. In this study, a wave-breaking-induced momentum flux parameterization was proposed based on wave age and wind-speed dependence. The new proposed parameterization was introduced into a one-dimensional (1-D) ocean model along with a wave-age-dependent wave-breaking-induced TKE flux parameterization. The simulation results showed that the wave-breaking impact on the ocean mainly affected the upper-ocean layer. Adding the wave-age impact to the wave-breaking-induced TKE flux and momentum flux improved the 1-D model performance concerning the sea temperature. Moreover, the wave-breaking-induced momentum flux had a larger impact on the simulation results than the wave-breaking-induced TKE flux.
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| 2. |
- Huang, Hongxun, et al.
(författare)
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Identification and detection of high NOx emitting inland ships using multi-source shore-based monitoring data
- 2024
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Ingår i: Environmental Research Letters. - : Institute of Physics Publishing (IOPP). - 1748-9326. ; 19:4
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Tidskriftsartikel (refereegranskat)abstract
- In urban areas situated along busy waterways like the Yangtze River, the diesel engines of inland navigation ships emerge as significant contributors to air pollution. Among these vessels, certain high-emission ships exhibit considerably higher levels of nitrogen oxides (NOx) emissions compared to others. To effectively identify such ships, this study employed a cost-effective ship emission monitoring sensor platform, comprising high-precision gas sensors, automatic identification system (AIS) receiver, and sensitive meteorological sensors, along the Yangtze River in Wuhan City. By combining multi-source shore-based monitoring data, we identified ship emission signals and proposed a high-emission ship detection method using inverse modelling. Using this method, we successfully detected inland high-emission ships based on two months of monitoring data. Furthermore, the relationship between different ship types, sizes, speeds, and ship NOx emission rates were investigated. The results of this study are beneficial for strengthening the regulation of high-emission vessels in inland waterways, thereby reducing the adverse impact of ship emissions on the environment and climate. It also encourages the inland shipping industry to adopt more environmentally friendly technologies and fuels, as advocated by the International Maritime Organization.
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| 3. |
- Peng, Xin, et al.
(författare)
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A sampling method for calculating regional ship emission inventories
- 2020
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Ingår i: Transportation Research Part D. - : Elsevier BV. - 1361-9209 .- 1879-2340. ; 89
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we propose a sampling method for calculating ship exhaust emission inventories, which reduces the uncertainties induced by missing ship static data in traditional methods. The stratified random sampling method is utilized to take sample ships based on the ship density, ship type, and main engine power. The exhaust emissions from sample ship are calculated using an activity-based method with 1Â s temporal resolution AIS (Automatic Identification System) data. Then the regional ship exhaust emissions are estimated based on the sampling relationship. Sensitivity experiments show that the relative error of the proposed method decreases quickly with the sampling ratio (the ratio between the number of sampled ships and total ships) and it is less than 3.5% when the sampling ratio is higher than 10%. The method is used to estimate the inventories of ship exhaust emissions in the Yangtze river, which can improve the computational accuracy of ship emissions.
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| 4. |
- Peng, Xin, et al.
(författare)
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Optimal site selection for the remote-monitoring sulfur content of ship fuels in ports
- 2022
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Ingår i: Ocean and Coastal Management. - : Elsevier. - 0964-5691 .- 1873-524X. ; 225
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Tidskriftsartikel (refereegranskat)abstract
- The remote monitoring method based on air-quality monitoring sensors is a common way to monitor the FSC (fuel sulfur content) of oils for ships. Considering the influences of geographical environments, atmospheric conditions, regional ship traffic flow, emission characteristics of ships, and height of monitoring sensors on the monitor station chosen, a new method was proposed to optimize the site selection for monitoring the FSC of fuel oils used by ships in waters of the port. SO2 numeric simulation and observation from sensors were integrated to estimate the FSCs. The proposed method was utilized to recommend the sites of the fixed sniffing monitoring stations in Yantian port, Shenzhen, China from June and July 2018. The results showed that the experimental stations could monitor FSCs, and the relative difference between the estimated and actual FSCs of ships was 16.34%. The proposed method for recommending sites of FSC monitoring sensors contributed to intelligently supervising air pollutants emitted from ships and fuel oils of ships in the emission control areas of China.
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| 5. |
- Peng, Xin, et al.
(författare)
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Remote detection sulfur content in fuel oil used by ships in emission control areas : A case study of the Yantian model in Shenzhen
- 2021
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Ingår i: Ocean Engineering. - : Elsevier. - 0029-8018 .- 1873-5258. ; 237
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Tidskriftsartikel (refereegranskat)abstract
- A method is proposed for remotely detecting sulfur content in fuel oil used by ships in emission control areas (ECAs) based on the direct collection of SO2 emission data from the plume of the ship and numerical simulation models. Assuming a ship in the ECA uses fuel oil with compliance fuel sulfur content (FSC), activity-based ship emission assessment model is firstly utilized to calculate the SO2 concentration emitted from the ship. Numerical simulation models are then used to estimate the theoretical SO2 diffusion concentration at the location of the monitoring equipment. The observed SO2 concentration at the same time can then be integrated to estimate the FSC of the ship. A sample of eleven ships was selected to verify the proposed method in Yantian port, Shenzhen, China in June 2018. The result illustrates that the method can remotely detect ships using fuel oil with the FSC greater than 0.146%m/m in the ECAs, the relative error is 46%.
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| 6. |
- Song, Rongxin, et al.
(författare)
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Semantic Modeling of Ship Behavior in Cognitive Space
- 2022
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Ingår i: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Ship behavior is the semantic expression of corresponding trajectory in spatial-temporal space. The intelligent identification of ship behavior is critical for safety supervision in the waterborne transport. In particular, the complicated behavior reflects the long-term intentions of a ship, but it is challenging to recognize it automatically for computers without a proper understanding. For this purpose, this study provides a method to model the behavior for computers from the perspective of knowledge modeling that is explainable. Based on our previous work, a semantic model for ship behavior representation is given considering the multi-scale features of ship behavior in cognitive space. Firstly, the multi-scale features of ship behavior are analyzed in spatial-temporal dimension and semantic dimension individually. Then, a method for multi-scale behaviors modeling from the perspective of semantics is determined, which divides the behavior scale into four sub-scales in cognitive space, considering spatial and temporal dimensions: action, activity, process, and event. Furthermore, an ontology model is introduced to construct the multi-scale semantic model for ship behavior, where behaviors with different semantic scales are expressed using the functions of ontology from a microscopic perspective to a macroscopic perspective consecutively. To validate the model, a case study is conducted in which ship behavior with different scales occurred in port water areas. Typical behaviors, which include leveraging the axioms expression and semantic web rule language (SWRL) of the ontology, are then deduced using a reasoner, such as Pellet. The results show that the model is reasonable and feasible to represent multi-scale ship behavior in various scenarios and provides the potential to construct a smart supervision network for maritime authorities.
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| 7. |
- Sui, Zhongyi, et al.
(författare)
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An improved approach for assessing marine traffic complexity based on Voronoi diagram and complex network
- 2022
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 266, s. 112884-
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Tidskriftsartikel (refereegranskat)abstract
- The shipping industry is constantly expanding, and maritime traffic is increasing in numerous navigable waters. For maritime traffic safety, improving Situation Awareness (SA) is critical. However, the majority of relevant research placed a greater emphasis on the risk of a collision between two ships, but failed to capture the complexity of the global traffic situation. In this paper, a framework for evaluating marine traffic complexity is developed. With the combination of the Voronoi diagram and complex network, an improved Marine Traffic Complex Network (MTSCN) is coming into being. The geometric features of Voronoi diagram are used to divide the water area into multiple cells, setting safe distances is avoided by treating ships as neighbors and other ships. The impact of neighbors on the situation awareness and the impact of other ships on the collision risk of own ship are considered. This method can more truly demonstrate the traffic complexity in the water area. Simulations are introduced to investigate the validity of the proposed method with two ships crossing situation, three ships crossing situation and four ships crossing situation. The proposed method is further demonstrated using actual AIS data in the Yangtze River, and the correlation between complexity and other indicators has been analyzed. The result shows that the improved MTSCN may give an intuitive and accessible measure to capture the essence of maritime traffic, which will be helpful in understanding, monitoring, and controlling maritime traffic safety in the future. Additionally, the complexity based on MTSCN could enhance the SA of VTSOs by supporting decision-making.
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| 8. |
- Wen, Yuanqiao, et al.
(författare)
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Green routing design in short seas
- 2017
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Ingår i: International Journal of Shipping and Transport Logistics. - : INDERSCIENCE ENTERPRISES LTD. - 1756-6517 .- 1756-6525. ; 9:3, s. 371-390
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, with the development of shipping industry, the mass of greenhouse gases (GHG) emissions originating from ships is also increasing rapidly. To reduce the GHG emissions from ships, designing the optimised routes with higher energy use efficiency is becoming more important for ships navigating in short seas. Based on the innovative application of energy efficiency operational index (EEOI), a route optimisation model is established. To solve the model, we divide one single voyage into several voyage segments and consider the variable speed across voyage segments. Then the navigation strategy is used to find out the sailing route of the minimum EEOI value, this sailing route is called as the green route. Finally, numerical experimental results show that the EEOI values of the experimental groups which used the optimised navigation method are 4.67%-16.95% lower than that of the control group. The results demonstrate that the green route designed in this paper can effectively improve the energy use efficiency of ships.
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| 9. |
- Wu, Lichuan, et al.
(författare)
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Modeling the Vulnerability of Waterway Networks
- 2014
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Ingår i: Journal of waterway, port, coastal, and ocean engineering. - 0733-950X .- 1943-5460. ; 140:4, s. 04014012-
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Tidskriftsartikel (refereegranskat)abstract
- In some areas, rivers and canals interweave into a network, making inland waterway transportation feasible. Significant losses will occur if a vulnerable waterway (where vulnerability is defined in terms of susceptibility to interference and difficulty in restoring the initial state) that is vital to a network is blocked. System vulnerabilities combined with hazard factors trigger disasters; therefore, reducing the vulnerability of a network system is a useful means of reducing major losses. In this paper, a model to calculate vulnerability based on inherent characteristics of waterways such as channel connectivity, transportation efficiency, and economic cost is developed. Three influence factors-importance, efficiency contribution, and loss-are used to build a vulnerability assessment model in which the relative vulnerabilities of various waterways can be assessed and the most vulnerable waterway can be found. Using this model, a simple waterway network is tested to identify vulnerable waterways. (C) 2014 American Society of Civil Engineers.
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| 10. |
- Zang, Shuo, et al.
(författare)
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Review of Different Propulsion Methods for Hybrid-Electric Propulsion Ship
- 2022
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Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; , s. 3727-3733
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Konferensbidrag (refereegranskat)abstract
- This paper reviews different hybrid-electric propulsion modes, i.e., series hybrid, parallel hybrid, and series-parallel hybrid. It then focuses on traditional propeller propulsion, shaftless rim propulsion, and pod propulsion. It mainly distinguishes and compares various propulsion methods, from advantages and disadvantages, power range, to technical issues, and analyzes the applicable ships and propulsion efficiencies for each type of propulsion method. Although shaftless rim propulsion and pod propulsion have various key technical challenges, their propulsion efficiencies are higher than traditional propeller propulsion. And they are promising to be used in hybrid power ships in the near future.
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