Daily Maersk’s impacts on shipper’s supply chain inventories and implications for the liner shipping industry

The liner shipping industry has long been characterized by a weekly sailing frequency and schedule unreliability. This research is motivated by the launch of the revolutionary “Daily Maersk” service in late 2011, which introduced daily departures and “absolute reliability” in the Asia–North Europe trade lane. This article analyzes Daily Maersk’s impacts on a shipper’s supply chain inventories and profound implications for the liner shipping industry as a game changer. The quantitative analyses show that the impact of more frequent sailings is most significant on a shipper’s cycle stock, while improving schedule reliability substantially reduces safety stock and pipeline stock. Daily Maersk is most valuable for products that have high value density, high inventory holding cost ratio, low demand variability, and high service level (SL) requirement. These findings imply that the trend of liner alliance/merger/acquisition is likely to continue or even accelerate as shipping lines consolidate fleet capacity to offer more frequent sailings. Rival carriers may step up their involvement in terminal operations to improve schedule reliability. They also need to rethink about their SL targets and clearly define their preferred customer segments.     

Seabed collision emergency decision-making of AUV based on safety domain model北大核心CSCD

［Objectives］To ensure safety and prevent seabed collisions in complex unknown underwater environments, this study proposes a seabed safety domain model and tiered emergency response strategies. ［Methods］A vertical motion simulation model is established and verified by surpassing the test results, then used to calculate the active and passive safety domain distance of an autonomous underwater vehicle (AUV), thereby establishing a seabed safety domain model. An AUV emergency control system and emergency strategies are then built on the basis of the dynamic safety domain model. The trim and distance from the seabed of the AUV are used to calculate the current and future risk factors. Based on the weighted sum, the comprehensive risk factor is employed to provide the AUV with emergency response strategies.［Results］Lake tests with the AUV sailing at a fixed depth and height show a strong dependency of the comprehensive risk coefficient on seabed height when it is close to the boundary of the AUV's active safety domain. In the opposite case, there is a weak dependency of the comprehensive risk coefficient on seabed height. The results show that the proposed AUV emergency control system can reduce emergency false alarms caused by frequently changing riverbed heights and sailing altitudes close to the seabed. In such cases, reasonable emergency strategies can be realized under complex rough terrain.［Conclusions］The AUV seabed safety domain model and tiered emergency response strategies based on vertical motion equations proposed herein can be applied to evaluate seabed collision risk in various cases. Finally, this paper provides emergency response strategies to avoid seabed collision accidents, which can enhance the safety of AUV navigation. © 2023 Chinese Journal of Ship Research. All rights reserved.     

Effects of the ‘Belt and Road’ initiative on the wine import logistics of China

China’s Belt and Road (BR) initiative is expected to facilitate international trade between the countries involved. In this study, we review the special requirements of wine logistics and the market growth potential of wine consumption in China. A model minimizing generalized logistical costs is developed and applied to wine imports in China, so that the best candidate cities in which to locate transport gateways and distribution centers can be identified. Our analysis suggests that the most preferred gateways are Shanghai, Tianjin, Guangzhou, and Hong Kong, which all have similar delivery costs. In comparison, Beijing and Chongqing have much higher delivery costs, mainly because they do not have good access to marine transport and/or efficient domestic distribution networks. For long-distance intercontinental transport of large volumes of wine, marine shipping remains the only viable delivery mode. However, wine distribution within China extensively uses air, road, and water transport. Therefore, cities with excellent multi-modal transport services are better positioned to become wine logistics gateways. Our study also highlights the importance of value-added services and good government support, which are important factors that influence distribution costs and quality.     

Performance decay of stern bearing based on lubrication numerical model and state parameters北大核心CSCD

[目的]为了实现对船舶艉轴承润滑状态的监测和评估,提出一种结合润滑性能衰变模型和支持向量机(SVM)算法的艉轴承润滑性能评估方法。[方法]针对船舶艉轴承润滑状态难以监测和识别的问题,建立轴承润滑衰变数值模型,并运用实验数据对该模型进行验证,研究载荷、粗糙度和半径间隙对润滑状态衰变机理的影响。基于SVM算法,构建润滑状态分类器,通过网格搜索算法优化超参数,利用不同润滑状态的数据集进行训练,最后实现对艉轴承润滑状态的评估。[结果]结果显示,随着外部载荷、粗糙度和半径间隙的增大,轴承润滑状态恶化的临界速度增大,动压润滑工作范围减小,混合润滑工作范围增大;由仿真数据集对润滑状态识别模型的验证表明,所提的润滑状态识别方法准确率达96.88%。[结论]所提方法能监测轴承的润滑性能特征,有效识别轴承的润滑状态。     

Analysis of students’ perceptions of seafaring career in China based on artificial neural network and genetic programming

Research indicates that the worldwide shortage of qualified seafarers has been due to the rapidly increasing world merchant fleet on the one hand and the difficulty of attracting and retaining people in the industry on the other. The paper argues that in the context of the Chinese shipping industry, the high “wastage” is one of the major contributors to the shortage. The aims of the research are to examine the motives of students studying nautical courses; identify the key factors affecting nautical students to choose seafaring career, and to predict students’ career choice behavior. The research finds that (a) those who had a clear sense of their future career when enrolled in the nautical studies tend to choose a seafaring career and remain active for a longer period of time; (b) high wage is the most important factor affecting students’ decisions to choose seafaring as a career; (c) prolonged separation from family, job opportunities ashore, and concern about children’s growth and education are among the top three factors for students not to choose a seafaring career or to quit it early; and (d) nautical students’ career choice behaviors can be predicted through the use of artificial neural network (ANN) and genetic programming (GP) with five rules being generated. This novel methodological approach, a combination of ANN and GP, has been proven to be effective in analyzing complex variables and in generating rules.     

Application of analytical model in the prediction of dynamic responses and fatigue damage of flexible risers: Part I – Improvement of analytical model considering shear deformation and varying tension effects

Flexible risers have been widely utilized for the transfer of oil and gas products from a well to production units. The components of flexible risers, unlike steel risers, experience complex contact phenomena during bending. The contact between helical wires and adjacent layers especially causes a significant level of bending nonlinearity, making it hard to estimate the structural responses. Accordingly, a large-scale dynamic analysis of flexible risers usually involves an analytical model that predicts the bending moment and axial stress of helical wires based on theoretical approaches. The analytical model consists of an axis-symmetrical model and a bending model. Among them, the bending model plays a critical role in the prediction of the bending responses of flexible risers. The conventional bending models usually neglect the shear deformation of internal layers and continuity of sliding force, which leads to a significant error of analysis. Furthermore, the previous bending models assume that the contact pressure on helical wires is constant during bending. In real operating conditions, however, most flexible risers experience a considerable change of tension that governs the slip of helical wires. Hence, the current study presents a new dynamic analysis method for flexible risers. The suggested analytical model improves the bending model based on an accurate estimation of the internal strain field considering the shear deformation and continuous sliding force. Also, this study proposes a stiffness update method to reflect the effect of varying tension in the dynamic analysis. The presented method updates the bending property of flexible risers considering the continuous change of the contact pressure from varying tension. For the validation of suggested method, the current study carries out numerical simulations with a pure bending and varying tension for the internal diameter 7 inches flexible risers. It is identified that the suggested analytical model provides accurate analysis results. Moreover, it is found that the effect of varying tension gives a significant impact on the bending behavior of flexible risers by changing the slip condition of helical wires. Part I of this series of papers describes the detailed formulation method for the analytical model and with some verification examples. The suggested analytical model is expanded to the large-scale dynamic analysis in Part II for the investigation of the effect of shear deformation and varying tension.     

Analysis of cross effect on inherent deformation during the line heating process – Part 1 – Single crossed heating lines

This paper describes the effect of previous heating on inherent deformation by a subsequent heating line, more specifically, the case of two heating lines intersecting (crossing) each other. The paper has been divided into two parts. In the first part, the case of single crossed heating lines is studied in detail. The second part of the paper, discusses the case of more than one crossed heating lines. The novelty of the work lies in revealing the cross effect and how, factors such as, for example, the heating condition and the plate geometry, influence the resulting inherent deformation of crossed heating. In addition, relationships to easily get these influences are provided. The results are suitable for a wide range of heating conditions and plate thickness.     

The China State Shipbuilding Corporation(CSSC)offers warm congratulations on the opening of China Shenzhen Technology Fairl Wang Rongsheng Vice President of CSSC

Under the leadership of the State Council ofChina,CSSC was inaugurated in May,1982 andfunctions as an all-China shipbuilding corporationwith a framework intergrating production withtrade,military sector with civil sector,shipbuildingwith shiprepairing,and production with researchand development.It has under its jurisdiction 26shipyards and dockyards highlighting the reputedJiangnan and Hudong shipyards.It also has over60 marine equipment manufacturing plants andmore than 30 research and design institutes.Itstotal number of employees tops 300,000.     

An investigation of forecast horizon and observation fit’s influence on an econometric rate forecast model in the liner shipping industry

This paper evaluates the influence of forecast horizon and observation fit on the robustness and performance of a specific freight rate forecast model used in the liner shipping industry. In the first stage of the research, a forecast model used to predict container freight rate development is presented by exploring the relationship between individual company’s rates and aggregated market rates, and thus assists in dealing with uncertainty and market volatility for a given business situation. In the second stage, a design of experiment approach is applied to highlight the influence of the forecast horizon and observation fit and their interactions on the forecast model’s performance. The results underline the complicated nature of creating a suitable forecast model by balancing business needs, a desire to fit a good model and achieve high accuracy. There is strong empirical evidence from this study; that a robust model is preferable, that overfitting is a true danger, and that a balance must be achieved between forecast horizon and the number of observations used to fit the model. In addition, methodological guidance has also been provided on how to test, design, and choose the superior model for business needs.     

Application of analytical model in the prediction of dynamic responses and fatigue damage of flexible risers: Part II – Dynamic analysis of flexible risers in large-scale domain using a direct moment correction method

In recent years, the dynamic responses of flexible risers have been the focus of many researchers. Most flexible risers undergo a substantial level of irregular motion from environmental loadings, which involves a continuous slip of helical wires. The slip of helical wires especially leads to a hysteretic effect by reducing the bending stiffness, making it hard to predict the dynamic responses of flexible risers. The current study, as an extension to Part I, presents a new large-scale dynamic analysis method for flexible risers. The suggested method creates a large-scale model for the dynamic analysis that considers a geometric and bending nonlinearity of flexible risers. The kinematics of each beam element is formulated based on a Green-Lagrangian strain and the interaction with the seabed, providing a realistic analysis of flexible risers. In particular, the current study introduces a direct moment correction method that modifies the internal force vector using an improved analytical model. The improved analytical model is assigned at each node of the large-scale model and estimates an accurate bending hysteresis curve considering the effect of shear deformation and varying tension. The suggested method corrects the bending moment and shear force of all beam elements based on the bending hysteresis curves obtained from the improved analytical model, by which a complex bending behavior of flexible risers is reflected in a large-scale domain. As a result, this study achieves a more accurate prediction of the dynamic responses and fatigue damage of flexible risers. A new dynamic analysis program, called OPFLEX, is developed herein based on the suggested analysis method. Using the developed program, the current study conducts several numerical investigations to identify the effect of the shear deformation and varying tension. Consequently, it is confirmed that the shear deformation of internal layers reduces the fatigue damage of helical wires by delaying the increase of internal stress. It is also identified that the effect of varying tension deteriorates the fatigue life of flexible risers through a continuous change of contact pressure during bending.