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This paper discusses the predefined practical finite-time (PPFT) dynamic positioning (DP) control problem for DP vessels subject to internal/external uncertainties. Those heterogeneity uncertainties are handled by a separate-type treatment approach. The finite-time (FT) DP control is fulfilled by a predefined FT function on the basis of a time-based generator (TBG). Under the dynamic surface control together with the TBG design framework, the convergence time and control accuracy of the DP system can be determined by the designer offline. Meanwhile, the virtual derivation and computational burden problems are dissolved by using a first-order filter and virtual parameter learning technique. To reduce mechanical wear, an event-triggering protocol between the control law and the actuator is built to reduce the operating frequency of the actuator. An event-triggered neuroadaptive PPFT control scheme is presented for DP vessels. The stability of the closed-loop DP control systems is validated via the Lyapunov theorem. Approach efficiency is confirmed by numerical examples.

High-quality ship kinematic information (i.e., speed and heading) is important for Vessel Traffic Service (VTS) to assess traffic situation. Presently, the ship speed and heading are derived from the Automatic Identification System (AIS) and radar signal transmission in VTS. However, there are uncertainties on ship speed and heading estimation caused by the false echo in radar images and packet loss rate in AIS data transmission, which affects the supervision of ship navigation and its safety. To address the uncertainty on ship speed and heading estimation and enhance the supervision of the marine traffic system, this paper proposes a ship speed and heading estimation approach by using radar sequential images and AIS data fused. The proposed approach consists of three steps: 1) ship detection using radar sequential images, 2) ship tracking with inter-frame information, and 3) ship speed and heading fusion. The experimental results in selected radar sequential images of the Yangtze River show that the variance of ship speed and heading distribution at 10s sampling frequency reduce from 2.55 to 0.38, and 28.35 to 23.48, respectively. It is indicated that the proposed approach can reduce the uncertainty on ship speed and heading estimation and quantitatively describe the ship navigation status.

With the development of green tribology in the shipping industry, the application of water lubrication gradually replaces oil lubrication in stern bearings and thrust bearings. In terms of large-scale and high-speed ships, water-lubricated bearings with high performance are more strictly required. However, due to the lubricating medium, water-lubricated bearings have many problems such as friction, wear, vibration, noise, etc. This review focuses on the performance of marine water-lubricated bearings and their failure prevention mechanism. Furthermore, the research of marine water-lubricated bearings is reviewed by discussing its lubrication principle, test technology, friction and wear mechanism, and friction noise generation mechanism. The performance enhancement methods have been overviewed from structure optimization and material modification. Finally, the potential problems and the perspective of water-lubricated bearings are given in detail.

This paper proposes an approach to estimate ship dynamic features (i.e., speed and heading) using radar sequential images, which can be used to assess the ship-ship collision risk in vessel traffic service (VTS) center. The proposed approach estimates the ship speed and heading in three steps, including ship detection, tracking, and data fusion. First, the ship target, together with its center coordinate, is detected by introducing the background subtraction detector in each radar image. Second, the ship position in one frame is mapped to the consecutive frame, and ship trajectory distribution is established using the Kalman filter and Hungarian algorithms. Third, fuzzy logic is introduced to fuse data from radar and AIS. Specifically, input variables include two parameters, which are the ship speed/heading difference in consecutive frames using radar and AIS, respectively. The variance of ship speed distribution is 1.30 at 10s sampling frequency, and the variance of ship heading distribution is 26.53, the experimental results indicate that the proposed approach can accurately estimate ship speed and heading in the radar sequential images of the Yangtze River. The strength of the proposed approach is its capability to estimate the ship speed and heading quantitatively from radar sequential images, which is interactive and interpretable for VTS operators.

Printed circuit heat exchangers (PCHEs) are considered as the most promising heat exchangers for use of the supercritical carbon dioxide (S-CO2) Brayton cycle. As crucial components operating at high pressure and thermal load at the same time, PCHE structural integrity evaluations are essential. In this study, to assess the structural strength of PCHEs serving as recuperators and precoolers in the S-CO2Brayton cycle as a waste heat recovery system for marine engines, the finite element method (FEM) is used and compared with a currently used method from ASME codes. The effects of temperature and pressure on the hot and cold sides are studied in terms of the temperature and pressure differences between the two sides and the main factors affecting its strength discussed. Then, detailed stress intensities of a PCHE under design conditions are investigated, and the results indicate that the highest stress appears at the middle of the semicircular arc of the channel, except for a concentration near the channel tip regions. Stresses of the PCHE are mainly caused by both pressure and temperature differences, with the minimum effect from temperature. The synthesis of the temperature and pressure fields exhibits a complicated action on the total stress under the design conditions. FEM was a more comprehensive means for structural assessment than the method from ASME codes. Further structural optimization of PCHE is conducted to ensure a maximum life span. This research work can provide theoretical guidance for structural integrity assessment of PCHE for the S-CO2Brayton cycle.

ABSTRACTIn recent years, the inland river shipping industry in China has been facing the pressure to comply with ‘low carbon shipping’ policies. Solar energy as one of the most widely used new energy sources has attracted more and more attention in the shipping industry. In 2015, the researchers from Wuhan University of Technology have successfully applied solar energy in an inland river 800PCC (Pure Car Carrier) – ‘Anji204’. The present article described the photovoltaic (PV) generation system which was installed on board the ship and reported the results of actual navigation trials on the testing leg, Yangtze River. On the basis of the collected data, the main research purpose is to evaluate the greenhouse gas (GHG) emission and fuel consumption after introduced solar energy into ship energy system by using Energy Efficiency Design Index (EEDI) analysis. The results show that the ship EEDI reduced from 55.09 g_CO2/ton·nmile to 52.02 g_CO2/ton·nmile, decreased by about 5.57%. In addition, it can reduce the fuel consumption by an average about 16 tons per year. Therefore, the utilisation of solar energy in ships can help the inland river shipping industry to meet the ‘low carbon shipping’ policies.

Energy efficiency management is becoming increasingly important in the trend towards decarbonisation and intelligentisation of future ships. Establishing a verified energy efficiency model is essential in realising reliable assessment of various energy efficiency strategies. Based on a 53,000-tonne bulk carrier, modelling and verification of a ship’s energy efficiency with consideration of multiple factors is carried out. First, the existing ship’s energy efficiency regulation and its evaluation methods are introduced. Second, the onboard data collection system is introduced with the features of the measured data detailed. A ship energy efficiency model is developed from four main aspects, namely ship energy efficiency operational indicator, ship fuel consumption, ship main engine power, and ship resistance characteristics. Based on the Monte Carlo simulation method and utilising Matlab/Simulink, the energy efficiency model for the selected ship is simulated and measured fuel consumption data is used to verify the model. Finally, the simulation results are presented and discussed. The research results show that the devised model provides good enough accuracy to simulate ship energy efficiency with consideration to cargo loading, ship speed and the random impact of multiple natural environmental parameters. This study not only helps the ship manager assess the projected energy efficiency, but can also provide decision support for the optimisation of ship energy efficiency.

A Bayesian network–based risk analysis approach is proposed to analyse the risk factors influencing maritime transport accidents. Comparing with previous studies in the relevant literature, it reveals new features including (1) new primary data directly derived from maritime accident records by two major databanks Marine Accident Investigation Branch and Transportation Safety Board of Canada from 2012 to 2017, (2) rational classification of the factors with respect to each of the major types of maritime accidents for effective prevention, and (3) quantification of the extent to which different combinations of the factors influence each accident type. The network modelling the interdependency among the risk factors is constructed by using a naïve Bayesian network and validated by sensitivity analysis. The results reveal that the common risk factors among different types of accidents are ship operation, voyage segment, ship type, gross tonnage, hull type, and information. Scenario analysis is conducted to predict the occurrence likelihood of different types of accidents under various situations. The findings provide transport authorities and ship owners with useful insights for maritime accident prevention.

Collision is a major type of accident in maritime transportation, which in the downstream of Yangtze River is even more pronounced due to specific features that have significant impact on the collision consequence, including a special lane for small-sized ships, traffic intensity variation with the tide period, many restricted areas, and emergency resources spread along the river. This article models the collision consequences in the downstream of Yangtze River using Bayesian Networks, considering the causation factors and including a novel approach for the emergency management of maritime accidents. The graphical structure lies on domain experts and on previous works, while the conditional probability tables are developed from historical data. Both the graphical structure and parameters are validated using the well-known methods, which reflects that the developed model is reasonable. The merits of the proposed consequence estimation model that considers emergency management includes (1) a detailed description of the collision accident development and (2) consequence estimation result with good accuracy.

Three-dimensional (3D) porous hosts play pivotal roles in realizing dendrite-free lithium metal anodes (LMAs) owing to their high specific area. However, uneven local electric field and lack of lithiophilic sites on the reactive interface cause nonuniform lithium ion (Li+) deposition, leading to Li dendrite growth and parasitic reactions. These issues will inevitably incur short cycling life and severe safety hazards of lithium metal batteries. Herein, a 3D self-supporting host composed of hollow carbon nanofibers incorporated with silicon (Si) nanoparticles inside (Si-HCF) is constructed as Li metal host by a scalable coaxial electrospinning technique. During the first cycle, the Si nanoparticles is alloyed with Li+to form lithiophilic Li-Si alloy, contributing to deliver a low nucleation overpotential and homogeneous surface potential confirmed by Kelvin probe force microscopy, finally guiding Li+flux homogeneously throughout the fibrous mat. As expected, the Li metal can percolate through Si-HCF host reversibly without uncontrollable Li dendrites and the Si-HCF exhibits a stable cycle life of Li plating/stripping over 1400h. Additionally, the full cell combined with LiFePO4cathodes presents steady cycling over 400 cycles with a high average coulombic efficiency of 99.4%. This work provides new insights for the synthesis of 3D hosts with controllable nucleation sites to homogenize Li+deposition in LMAs.

Hybrid heat exchangers (H2Xs) can be used for heat exchange equipment between high-temperature exhaust gas from ships and high-pressure supercritical carbon dioxide (S-CO2) from the S-CO2 power cycle. We investigate structural stress intensity characteristics of the H2Xs based on thermal-hydraulic performance. Air and S-CO2 are employed as the working fluids and the Stainless Steel 316 (SS316) as the solid substrate. The thermal-hydraulic performance and structural stress intensity characteristics of the H2Xs are conducted by Ansys Fluent and Mechanical, respectively. The results show the mechanical stress induced by pressure loading and the thermal stress induced by temperature gradient are found to be equally important sources of stress intensity. At the inlet and outlet of the H2Xs, the total stress intensity along all paths is not smooth and continuous, and there will be a significant change due to the change in the temperature gradient. The mechanical stress caused by the fluid pressure loss is almost negligible. The change in inlet mass flowrate and temperature mainly affects the stress intensity distribution of the left and right walls on the fin channel. The pressure variation of the diesel engine has little effect on the total stress intensity. Importantly, the total stress intensity of the H2X is mainly affected by the change in S-CO2 fluid pressure.

A numerical three-dimensional computational fluid dynamics-fluid structure interaction (CFD-FSI) model including lining deformation and cavitation is developed to evaluate the effect of perturbation amplitudes on stiffness coefficients of hydrodynamic water-lubricated plain journal bearings. Three types of bearing with rubber, polymer and steel lining materials are compared in terms of stiffness coefficients, load-carrying capacity and journal center equilibrium position under different eccentricity (ɛ) conditions. The simulation results indicate that perturbation amplitudes have great influence on the four stiffness coefficients of water film of hard lining bearings at large ɛ. However, when ɛ≤ 0.5 and the perturbation varies within 2.9% of the bearing radial clearance, the effect is less than 10% regardless the lining materials. For the rubber lining bearing, the effect of perturbation amplitudes on the stiffness coefficients is negligible due to the rubber deformation, even at ɛ= 1.9 and the perturbation amplitudes up to 7% of the radial clearance. Lining deformation also affects the attitude angle of the journal and the stiffness of water film. The calculation results demonstrate that the lining deformation and journal perturbation amplitudes are two important factors which cannot be ignored in the calculation of bearing stiffness in case of the journal at large eccentricity ratios.

This paper aims to identify the major risk factors influencing the safety and security of maritime container supply chains (MCSCs) to aid the effective management of the associated risks. A novel risk classification framework, incorporating a Delphi survey and a risk matrix approach, is proposed to identify the major risk factors of significant safety concerns from five perspectives, including society, natural environment, management, infrastructure and technology, and operations. Relevant data for the assessment of all identified risk factors are collected through a large-scale questionnaire survey, and the identified risk factors are quantitatively evaluated regarding their occurrence likelihood and consequence severity. This paper extends the risk analysis from the segment level (e.g., nodes and links) to a supply chain level, and realises the hazard identification and risk evaluation of different MCSC segments on the same plate so that they can be better understood and managed from a systematic perspective.

ABSTRACTThe constant development of electronic inverter technology has played a key role in promoting the exploration and development of solar ships. For the large-scale ocean-going ship platform, the critical issue of applying solar photovoltaic (PV) system is integrating PV equipment into the ship power system (SPS) without changing its original structure. This paper compares the existent technical differences for applying the off-grid and grid-connected PV system in the SPS and proposes the basic design principles for marine integration applications. The 5000 PCTC ro-ro ship is set as the application object, on which a hybrid PV system with large-capacity lithium battery storage device is designed and installed as an independent subsystem. The typical feature of this hybrid PV system is that it can implement operation mode switching between off-grid and grid-connected, according to the evaluation on solar radiation resource, power load requirement and state of charge in the lithium battery. The test results show that this PV system has a stable operation characteristic under different operation modes. In addition, this ship-based PV power system has automatic and reliable operation management capability, which could effectively reduce manual control frequency and maintenance workload of a marine engineer.

The so-called “green ship” is being regarded as a potential solution to the problems that the shipping industry faces, such as energy conservation and environmental protection. Some new features, such as integrated renewable energy application, biomimetic materials, and antifriction and wear resistant coating have been accepted as the typical characteristics of a green ship, but the tribology problems involved in these domains have not been precisely redefined yet. Further, the related research work is generally focused on the technology or material itself, but not on the integration of the applicable object or green ship, marine environment, and tribological systematical analysis from the viewpoint of the energy efficiency design index (EEDI) and ship energy efficiency management plan (SEEMP) improvements. Aiming at the tribology problems of the green ship, this paper reviews the research status of this issue from three specific domains, which are the tribology problems of the renewable energy system, tribological research for hull resistance reduction, and energy efficiency enhancement. Some typical tribological problems in the sail‐auxiliary system are discussed, along with the solar photovoltaic system and hull drag reduction in traditional marine mechanical equipment. Correspondingly, four domains that should be further considered for the future development target of the green ship are prospected.

Greenhouse gas emission and subsequent global warming have attracted more and more attention all over the world. As one of the biggest emission sources, shipping industry is suffering great emission reduction pressure from the public. Although shipping industry can improve the energy efficiency by exploring new strategies to reduce the fuel cost and the emission to air, some deficiencies may be discovered in practice due to lack of a comprehensive consideration of other significant factors, such as safety factors. Therefore, energy efficiency management strategies that consider both safety and economy factors have more practical significance for enhancing the ship energy efficiency. In this article, a power supply model considering economy, emission reduction and safety was established, and a multi-objective optimization problem to keep the system working at a high safety level, a low CO2emission and a moderate fuel consumption was proposed. Furthermore, the particle swarm optimization algorithm was adopted to solve the multi-objective optimization problem, and the obtained non-inferior solutions could help officers on duty to select the optimum main engine speed by weighing the economy and the safety of the ship. The results show that the proposed method of energy efficiency management could reduce the greenhouse gas emission and the energy efficiency operation index (EEOI) of the ship effectively. The trade-off between ship economy, emission and robustness of the power supply system was studied, which is meaningful to the energy efficiency improvement and the CO2emission reduction under the safety requirement of power supply.

ABSTRACTIn this study, a remote collecting system for ship operation energy efficiency was designed by using a tourist ship. According to measured data, the navigation environment factors of the ship were analysed statistically. The Gray correlation analysis was used to study the correlation degree among wind, water depth, water velocity and ship operation energy efficiency. On this basis, the Wuhan–Nanjing section of Yangtze River (upstream and downstream) was selected to analyse the law of wind speed effect on the energy efficiency of ship operation. The data analysis demonstrates that in different navigation environments, the ship energy efficiency can be significantly improved by optimising the main engine speed.

This article examines the distribution characteristics of the navigational environment in the Yangtze River trunk line using several information collection sensors installed on ships that navigate in this line. Through experiments on these ships, data of energy consumption and the navigational environment are collected. Water flow and waterway depth are proved to be the main influencing factors on the ship energy consumption via Spearman’s correlation analysis. Next, data of water velocity and waterway depth that cover the entire trunk line are graded using the k-means clustering algorithm. To build an evaluation matrix of navigational environment, the frequency distribution of each grade in different Yangtze River legs is counted statistically, and on this basis, similar legs are clustered using the hierarchical clustering algorithm. In this way, the waterway partition in the Yangtze River trunk line is completed. Furthermore, the distribution of the energy consumption of ships in different legs is also calculated. The study results indicate that not only the navigational environment of the Yangtze River trunk line but also the energy consumption level of ships have distinctive regional differences. Finally, the laws of the Yangtze River navigational environment are analyzed, and the corresponding energy-saving navigation strategies are proposed, which are useful for crews to operate their ships in energy-efficient and safe conditions.

A good ship traffic scheduling mode can enhance traffic efficiency to a large degree, especially in restricted waterways such as approach channel of ports and straits. A ship scheduling model for restricted two-way waterways is proposed in this article. The assumption is made in the model that two-way transportation is not allowed for cases in which there is at least one large ship. Based on this assumption, a mathematical model is proposed to minimize the weighted average of the mean and the maximum waiting time given several safety restrictions. A sequential scheduling algorithm is proposed to solve such problem, in which the ships are divided into rounds. The ships in each round are scheduled simultaneously to enhance traffic efficiency by the trade-off between the priorities of small and large ships. Experiments are carried out by comparing sequential scheduling method with first-come-first-serve model. The results indicate that the proposed algorithm can reduce ships’ waiting time, whereas a lot of ships need to wait for long time with first come first serve. The distinctions are more evident with a higher proportion of large ships, and the proposed algorithm can keep ships’ waiting time to an acceptable level.

The parameter value chosen to measure driving performance affects the accuracy of the estimated fatigue level. Methods to analyze the sensitivity of these parameter values were proposed. Standard deviation of lane position (SDLP) and steering reversal rate (SRR) were considered to assess fatigue, and the sensitivity of these parameters was analyzed from the time domain and value domain. Thirty-six male drivers participated in a field test. Lane position, steering wheel angle data, and self-reported fatigue level (scored on the Karolinska sleepiness scale) were recorded. SDLP results indicate that the maximum average coefficient with fatigue level reached .11, with a unified statistical interval of 202 s when the consecutive analysis method was used; the maximum average coefficient was .12 with a unified interval of 120 s when the maximum analysis method was used. SRR results indicate that a steering angle difference of 6° was the most sensitive threshold for driver fatigue level and has an average correlation coefficient of .42, which demonstrated that SRR was more reliable than SDLP for monitoring fatigue level. With the use of the optimal parameter value, the variation results of SDLP and SRR at each fatigue level were examined, and results indicate that driving ability was impaired as fatigue level increased. The methods and results can be applied to analyses of fatigued or drowsy driving.

Maritime safety has been one of the top concerns for inland waterway transportation, and safety assessment based on historic accident data is one of the most effective ways to evaluate navigation risk and take steps to enhance safety. Maritime safety is usually affected by many cost/benefit indicators, and it can be treated as multi-criteria decision making problem. An extended technique for order preference by similarity to ideal solution is proposed in this article at first. The model not only facilitates the comparison between fuzzy numbers with the same expected value but also makes it possible for the fuzzy number with lower expected value but higher reliability to outperform that with higher expected value but lower reliability. A variance matrix is adapted to measure the degree of uncertainty of an alternative. The proposed method is then applied to an inland waterway transportation safety assessment, which is regarded as a multi-criteria decision making. The results indicate that the safety situation has been improved a lot over the last 21 years with some local fluctuations, and an evident improvement can be seen from the year of 2003. In addition, the extended model is proved to provide more flexibility for the ranking of alternatives with similar expected values.

The parameter value chosen to measure driving performance affects the accuracy of the estimated fatigue level. Methods to analyze the sensitivity of these parameter values were proposed. Standard deviation of lane position (SDLP) and steering reversal rate (SRR) were considered to assess fatigue, and the sensitivity of these parameters was analyzed from the time domain and value domain. Thirty-six male drivers participated in a field test. Lane position, steering wheel angle data, and self-reported fatigue level (scored on the Karolinska sleepiness scale) were recorded. SDLP results indicate that the maximum average coefficient with fatigue level reached .11, with a unified statistical interval of 202 s when the consecutive analysis method was used; the maximum average coefficient was .12 with a unified interval of 120 s when the maximum analysis method was used. SRR results indicate that a steering angle difference of 6° was the most sensitive threshold for driver fatigue level and has an average correlation coefficient of .42, which demonstrated that SRR was more reliable than SDLP for monitoring fatigue level. With the use of the optimal parameter value, the variation results of SDLP and SRR at each fatigue level were examined, and results indicate that driving ability was impaired as fatigue level increased. The methods and results can be applied to analyses of fatigued or drowsy driving.

Due to heavy work load of marine diesel engines, the failure in their mechanical components may result in serious accidents. Existing condition monitoring methods for marine diesel engines usually adopt warning after the failure occurred. In order to predict potential faults, this work has put forward a remote intelligent monitoring system for marine diesel engines. The global system for mobile communication mode was employed to construct the basis of data remote transmission, and a new multi-kernel extreme learning machine algorithm was proposed to diagnose the early faults in an intelligent method. Experimental tests were carried out in the marine diesel engine fault diagnosis set-up. The analysis results show that the proposed remote intelligent monitoring system can accurately, timely and reliably detect the potential failures. Meanwhile, the proposed multi-kernel extreme learning machine was compared with the existing methods. The comparison indicates that the multi-kernel extreme learning machine outperforms its rivals in term of fault detection rate by an increase of 3.4%. Therefore, the proposed remote intelligent monitoring system has good prospects for engineering applications.

Reliability and safety issues on marine diesel engines have been received and still need considerable attentions. The literature review indicates that a large amount of failures are caused by abnormal wear of the diesel engine components. It is therefore essential to monitor the engine condition using the tribological information. To further promote the oil monitoring technology into industrial application, a new on-line condition monitoring and remote fault diagnosis system for marine diesel engines is proposed in this article. The new system consists of an on-line tribological signal acquisition model in the ship, a remote feature extraction model and a fault diagnosis model in the laboratory center. The third-generation telecommunication (3G/B3G) which is called wireless communication system is adopted to connect the remote ship with laboratory center. Nine wear characteristics are extracted to detect the engine faults. Experimental tests are implemented on a diesel engine in a real ship named “Changjing 2” to evaluate the performance of the proposed fault diagnosis system. The results show that index of particle covered area can be treated as the best feature for marine diesel engines fault detection. The results also reflect that the new system offers satisfactory on-line fault diagnosis ability and is effective for the diesel engine fault diagnosis in practice.

With the prosperity of global shipping industry, a variety of shipping-induced environmental problems and increasingly rigid emission restrictions have drawn more attention to an emerging marine fuel—liquefied natural gas (LNG), a clean and efficient energy that conforms to the essence of green shipping. Although with superiority using onboard, there are only fewer than 40 fully LNG-fueled ships in service worldwide by June 2013, and the quantity of LNG-fueled ships in operation is even much lower in China. Moreover, the majority of those in China are inland ships, which mainly navigate along the Yangtze River and canals. By using the SWOT (strengths, weaknesses, opportunities, and threats) analysis in combination with the analytic hierarchy process (AHP), this paper analyzes the development prospect of LNG-fueled ships in inland waterway transportation in China, aiming to fill the gaps of inadequate understanding of the new marine energy. This paper offers some insight on the prospects of the application of LNG in the Chinese shipping industry and simultaneously provides useful information to stakeholders and policy makers for decision-making on the development of LNG-fueled ships.

High effective management of civil aircraft spare parts is of significant importance for the economical operation of aircrafts. However, the stochastic characteristics of the aircraft spare parts make it difficult to find a reliable rule to precisely predict the future demand. In order to address this issue, this work presents a novel multi-components accumulation and high resolution analysis (MCAHR) method to improve the forecasting performance of aircraft spare parts. The MCAHR takes the advantages of high resolution of the wavelet transform to analyze the time series of spare part intermittent demand. The original time series were decomposed into several sub-bands along with the time axis of the wavelet. Then particle swarm optimized fuzzy neural networks were established for each sub-band to intelligently mine their intrinsic features. Accurate prediction result was hence obtained by the accumulation of the outputs of all fuzzy neural networks. Experimental tests using the historical data of A320 civil aircrafts were carried out in this work to evaluate the proposed MCAHR method. The analysis results have demonstrated a high efficiency of the MCAHR method and that its prediction performance is superior to existing methods. Hence, the proposed MCAHR method has practical importance in the civil aircraft spare part intermittent demand prediction and will provide a significant economic benefit to the industry through reasonable management of aircraft spare parts.

Circadian rhythms, inherent in all humans, consist of 24-h biological patterns that affect a person's fatigue level. The effect of circadian rhythms on driving performance was explored in an on-road driving study. Fifteen middle-aged professional daytime drivers were recruited to participate in the experiment. Participants were classified into three groups: (a) a morning group that started driving at 09:00, (b) a noon group that started driving at 12:00, and (c) an evening group that started driving at 21:00. Each group completed a 6-h driving task. The self-reported Karolinska sleepiness scale score was recorded every 5 min, and data on driving performance parameters, such as steering and lane positioning, were also acquired. The results indicated that both circadian rhythms and driving duration had significant effects on self-reported fatigue levels and that the fatigue level increased faster in the evening group than the morning and noon groups. The results of the circadian rhythm analysis showed that a driver was most likely to feel tired between 14:00 and 16:00 and between 02:00 and 04:00, when the ability to stay within designated lane lines (lane maintenance) was significantly impaired for drivers in all three groups. The evening group drivers were the most at risk. The steering performance did not show a significant relationship with the self-reported fatigue level. The self-reported fatigue level is the result of the interactive effect of circadian rhythms and driving duration. The standard deviation of lane position was more correlated with circadian rhythms than with the steering reversal rate.

Inland waterway transportation is often claimed to be reliable, congestion-free, economic and environmentally friendly. However, inland waterway transport accidents such as groundings cause congestions that can easily reduce the navigational capability of the waterways with confined channel dimensions particularly during a dry season. An accident data–based approach is presented in this article to assess the congestion risk of inland waterways using a case of the Yangtze River. Through a correlation analysis of historical failure data, the safety critical factors of congestion are first identified and used to establish a Bayesian network for the analysis and prediction of the congestion risk in the Yangtze River. A Congestion Risk Index is then developed by taking into account both probability and consequence of congestion risks in order to evaluate the impacts of various safety critical factors (i.e. Visibility, Gross Tonnage, etc.) on the congestion of the Yangtze River. The outcomes of this work can be used to effectively diagnose and predict the congestion risks of inland waterways in general and the Yangtze River in specific.

Circadian rhythms, inherent in all humans, consist of 24-h biological patterns that affect a person's fatigue level. The effect of circadian rhythms on driving performance was explored in an on-road driving study. Fifteen middle-aged professional daytime drivers were recruited to participate in the experiment. Participants were classified into three groups: (a) a morning group that started driving at 09:00, (b) a noon group that started driving at 12:00, and (c) an evening group that started driving at 21:00. Each group completed a 6-h driving task. The self-reported Karolinska sleepiness scale score was recorded every 5 min, and data on driving performance parameters, such as steering and lane positioning, were also acquired. The results indicated that both circadian rhythms and driving duration had significant effects on self-reported fatigue levels and that the fatigue level increased faster in the evening group than the morning and noon groups. The results of the circadian rhythm analysis showed that a driver was most likely to feel tired between 14:00 and 16:00 and between 02:00 and 04:00, when the ability to stay within designated lane lines (lane maintenance) was significantly impaired for drivers in all three groups. The evening group drivers were the most at risk. The steering performance did not show a significant relationship with the self-reported fatigue level. The self-reported fatigue level is the result of the interactive effect of circadian rhythms and driving duration. The standard deviation of lane position was more correlated with circadian rhythms than with the steering reversal rate.

The tribological properties of ZrO2ceramic and 1Cr18Ni9Ti stainless steel rubbing pairs were investigated using a special tribotester under different concentrations of hydrogen peroxide (H2O2) solution. The comparison analyses of the friction coefficients, worn volume rates, worn particles and surface roughness were conducted under the tested conditions. There were significant differences of the tribological properties of the rubbing pairs in the different concentrations H2O2solution because of oxidation and corrosion. This research has revealed that the main wear mechanisms between the rubbing pairs are severe adhesive wear, abrasive wear and corrosive wear in the H2O2solution with different concentrations. A model has been established to assess the most suitable concentration of the H2O2solution for the tribological properties of the rubbing pairs. The result shows that 50% concentration of the H2O2solution is the most suitable. The assessment result is consistent with the experimental result. It is believed that the knowledge gained in this study is useful for the optimization of the friction pairs in the extreme condition.

Planned special events attract thousands of attendees from nearby cities or suburbia by car and transit. In most cases, the majority of attendees use personal automobiles, and a high parking demand results in a short time, with a consequent parking shortage. Parking guidance information systems can solve the problem by displaying information on parking lot availability to dynamically divert vehicles. This study focused on optimizing dynamic parking guidance information for automobile drivers at special events. An original multimode traffic network was converted to a novel network by considering parking lots as dummy links; therefore the shortest path and traffic assignment could be implemented in this extended network. A bilevel programming model based on quasi-dynamic route choice and linear programming was proposed to optimize the dynamic parking guidance information. On the basis of travelers' reaction to the guidance, stochastic dynamic user optimal route choice was employed within the lower-level model. The upper-level model was a linear program aimed at minimizing network total travel time. The solutions of the bilevel programming model were based on discrete particle swarm optimization and the method of successive average algorithms. Results of a case study implemented with a hypothetical network indicated that the optimization model could reduce the system total travel time by 4%.

New general ships powered by electric propulsion always operate at low motor speeds. Popular sensorless vector control methods, including open loop and closed loop methods, are not reliable in this application. This is because the magnitude of back-electromotive force voltage is very small in the low speed region, and the performance of these methods is therefore significantly degraded. To overcome this problem, a high-frequency injection method is introduced in the control of the ship electric propulsion system. The injected periodic signal creates a high-frequency revolving field to act as a carrier. Then the desired information about the position angle of the motor can be retrieved. A simulation model of a ship electric propulsion system is established in Matlab/Simulink. The test results show that the newly proposed control system works stably with various ship operating conditions and robustly against speed variations. Its estimated position error is less than 0.3 rad. Moreover, the proposed sensorless vector control approach has been compared with the closed-loop-based model reference adaptive system. The comparison has demonstrated that the dynamic characteristics of the proposed control system are superior to the latter.

Marine intelligent anti-collision regulations have been a means of dealing with a particularly dangerous problem for many years. As the foundation for making anti-collision decisions, the International Regulations for Preventing Collisions at Sea formulated by the International Maritime Organization should always be considered. Based on the International Regulations for Preventing Collisions at Sea, the minimum distance required for anti-collision by only the give-way ship (under normal situations) and by both the give-way ship and the stand-on ship steering simultaneously (under critical situations) under all possible encounter situations are studied respectively. Rather than regarding ships as a point, a restricted area where no evasive action of other ships is allowed is introduced. Furthermore, the ship’s manoeuvrability is taken into account. The proposed model is also assessed by the traditional parameters used in anti-collision such as the closest point of approach, the distance to the closest point of approach and the time to the closest point of approach. The study shows that the results obtained in this paper are important and complement the above-mentioned regulations so that navigators can make wise decisions.

The aims of this study were to investigate how the dimples on a metallic counterface affect the wear rate of ultra-high molecular weight polyethylene (UHMWPE) in a multi-directional reciprocating pin-on-plate machine. The plates were high nitrogen stainless steel, representing the femoral head material. The pins used in this study were of ultra-high molecular weight polyethylene GUR 1120, which represents the material used in an acetabular cup. Three different cases were investigated: a smooth surface without dimples as a reference case, a surface with medium dimples with an average valley of 2.3 µm and a surface with large dimples with an average valley of 5.9 µm. It was found that all the dimples investigated did not improve the lubrication, but instead increased the surface roughness; consequently, the wear of UHWMPE was slightly increased.

Planned special events attract thousands of attendees from nearby cities or suburbia by car and transit. In most cases, the majority of attendees use personal automobiles, and a high parking demand results in a short time, with a consequent parking shortage. Parking guidance information systems can solve the problem by displaying information on parking lot availability to dynamically divert vehicles. This study focused on optimizing dynamic parking guidance information for automobile drivers at special events. An original multimode traffic network was converted to a novel network by considering parking lots as dummy links; therefore the shortest path and traffic assignment could be implemented in this extended network. A bilevel programming model based on quasi-dynamic route choice and linear programming was proposed to optimize the dynamic parking guidance information. On the basis of travelers' reaction to the guidance, stochastic dynamic user optimal route choice was employed within the lower-level model. The upper-level model was a linear program aimed at minimizing network total travel time. The solutions of the bilevel programming model were based on discrete particle swarm optimization and the method of successive average algorithms. Results of a case study implemented with a hypothetical network indicated that the optimization model could reduce the system total travel time by 4%.

Many studies have dealt with modeling crash occurrences on urban arterials. There is a dearth of research on urban arterials with mixed-traffic patterns in China, however, because of the large traffic flow volume of bicyclists and pedestrians in most Chinese cities. This study investigates the risk factors associated with severe crash occurrences on arterial roads in Beijing. Through use of the generalized estimating equations modeling technique with a negative binomial link function, statistical relationships were established to relate severe crashes to a variety of factors related to geometric design, traffic control, and other traffic-related characteristics. Crash records from 2004 to 2007 for 108 signalized intersections and 123.5 km of road segments were used to estimate the models. Results showed that arterial roads with heavier traffic volumes, more road lanes, and higher speed limits tended to have more severe crashes. Medians were helpful in reducing severe crash risk. Higher risks of severe crashes were generally associated with intersections having small angles and count-down signals and road segments having higher side-access densities and the presence of bus stops. With regard to nonmotorist protection facilities, results revealed that a combined use of crosswalks and overpasses was the most desired pedestrian-crossing facility for safety, especially at sites with heavy traffic or sites located in primarily residential areas. Barriers that separated bikeways from roadways on minor roads were found effective in significantly reducing severe crash risk at intersections.

Public transportation plays a key role in providing transport services for the public in most cities of China. Safety is a top priority for improving the level of services of public transportation. This study aims to identify crash risk factors associated with demographic characteristics, driving-related experiences, and aberrant driving behaviors of the drivers of public transportation vehicles as well as to establish the influence of risk perception, risk-taking attitudes, and risky driving behaviors. The data used for analyses were obtained from a self-reported questionnaire survey carried out among 248 taxi and bus drivers in Wuhan, China. The results showed that drivers who both reported more tendencies toward aggressive violations and ordinary violations and had previously been involved in crashes were at high risk of crash involvement. Moreover, through the use of a structural equation model, it was found that drivers' attitudes toward rule violations and speeding significantly affect risky driving behaviors. Two risk perception scales, likelihood of crash and concern, have indirect effects on risky driving behaviors through their influence on drivers' attitudes toward rule violations and speeding. The significant risk factors and influential paths identified in this study are expected to result in better planning of road safety campaigns aimed at the occupational drivers in public transportation.

To examine how the superior colliculus, the motor center of orientation and avoidance, could interact with postural reflexes, we investigated effects of unilateral and bilateral ablations on air-righting reflex movements in otherwise intact rats. Superior colliculus ablations variously modified righting movements: After falling from the supine position, the rats sometimes showed dorsiflexion instead of normal ventriflexion; the motor sequence of rotation from the fore- to the hindquarter was often modified to simultaneous rotation; lateral turn from supine to prone position was occasionally insufficient; body direction that was normally kept constant during falling was often changed; final posture sometimes deviated from the horizontal position. The first three abnormalities occurred almost twice in frequency as lesions increased from unilateral to bilateral ablation, and in unilaterally ablated rats, did so in righting contraversive to the lesions. Multiple influences of tectoreticular input to the air-righting reflex center are discussed.

Many studies have dealt with modeling crash occurrences on urban arterials. There is a dearth of research on urban arterials with mixed-traffic patterns in China, however, because of the large traffic flow volume of bicyclists and pedestrians in most Chinese cities. This study investigates the risk factors associated with severe crash occurrences on arterial roads in Beijing. Through use of the generalized estimating equations modeling technique with a negative binomial link function, statistical relationships were established to relate severe crashes to a variety of factors related to geometric design, traffic control, and other traffic-related characteristics. Crash records from 2004 to 2007 for 108 signalized intersections and 123.5 km of road segments were used to estimate the models. Results showed that arterial roads with heavier traffic volumes, more road lanes, and higher speed limits tended to have more severe crashes. Medians were helpful in reducing severe crash risk. Higher risks of severe crashes were generally associated with intersections having small angles and countdown signals and road segments having higher side-access densities and the presence of bus stops. With regard to nonmotorist protection facilities, results revealed that a combined use of crosswalks and overpasses was the most desired pedestrian-crossing facility for safety, especially at sites with heavy traffic or sites located in primarily residential areas. Barriers that separated bikeways from roadways on minor roads were found effective in significantly reducing severe crash risk at intersections.

Public transportation plays a key role in providing transport services for the public in most cities of China. Safety is a top priority for improving the level of services of public transportation. This study aims to identify crash risk factors associated with demographic characteristics, driving-related experiences, and aberrant driving behaviors of the drivers of public transportation vehicles as well as to establish the influence of risk perception, risk-taking attitudes, and risky driving behaviors. The data used for analyses were obtained from a self-reported questionnaire survey carried out among 248 taxi and bus drivers in Wuhan, China. The results showed that drivers who both reported more tendencies toward aggressive violations and ordinary violations and had previously been involved in crashes were at high risk of crash involvement. Moreover, through the use of a structural equation model, it was found that drivers’ attitudes toward rule violations and speeding significantly affect risky driving behaviors. Two risk perception scales, likelihood of crash and concern, have indirect effects on risky driving behaviors through their influence on drivers’ attitudes toward rule violations and speeding. The significant risk factors and influential paths identified in this study are expected to result in better planning of road safety campaigns aimed at the occupational drivers in public transportation.

Instantaneous angular speed of a diesel engine contains a lot of information about gas pressure in cylinders, which can be used to diagnose combustion-related faults and other faults affecting the gas pressure, such as fuel leakage in fuel system, valve leakage, etc. In this paper, a dynamic model for simulating the instantaneous angular speed is presented, and the instantaneous angular speed waveforms on a small four-cylinder diesel engine are simulated. The tangential forces induced by the gas pressure and the vertical imbalance inertial force are calculated and analysed based on the proposed dynamic model, respectively. It is concluded that the gas pressure and the vertical imbalance inertial force have a great influence on the instantaneous angular speed. The simulated results of the instantaneous angular speed fluctuation ratio based on the dynamic model are confirmed by the experimental results. The instantaneous angular speed waveforms both in the fuel leakage condition and in the normal condition are measured under various engine speeds and loads in laboratory condition. The characteristic parameters for detecting the faults relating to the gas pressure in the cylinder are obtained successfully. It is promising, therefore, to develop and to apply the diagnosis technique further using the instantaneous angular speeds to detect the faults relating to the gas pressure in the cylinder.