This study investigates how foldable container (FLD) design features, specifically the number of tiers bundled (NT) and the wait time (WT) for collecting empty containers, affect vehicle operations for repositioning empty containers. Repositioning empty containers efficiently is crucial to minimise unproductive transport, as it consumes substantial resources similar to those required for moving laden containers, without generating direct revenue. We employ a simulation model to assess the potential reduction in vehicle usage through the use of FLDs within a basic container reuse network. Numerical experiments reveal a trade-off between WT and the number of vehicles, with the fixed-quantity departure method proving more efficient than the fixed-interval departure method. However, its efficiency depends on the frequency of empty container arrivals. These findings offer valuable insights for optimising FLD utilisation and enhancing empty container repositioning operations.

The main purpose of using bottom paint is to maintain the speed and hull condition of the vessel by preventing marine life from attaching to the bottom of the vessel.

When a ship is at sea for a long time, marine organisms are attached to vessel hull below the water line. The problem with removing the paint is that it takes a lot of time and effort, as the attached marine organisms must be removed manually with a spatula or similar tool. The purpose of this research is to improve the efficiency of peeling work by proposing the use of layered paints with different adhesive strengths as ship bottom paint. Adjusting the adhesive strength reduces the effort required for peeling work when docking. First, we confirmed that the proposed paint thickness could be used for multiple coatings. The t-test was performed for each coating thickness group, and it was confirmed that the coating could be applied in different thicknesses based on significant differences. Next, the cross-cut method was used to check the relative adhesion strength, and since most of the adhesion strength was rated 0, it was possible to demonstrate that the adhesion strength was suitable for practical applications.

A pull-off method was performed to investigate the adhesion of the proposed coating method in more detail. From the relationship between the measured adhesion and film thickness, it was found that sufficient adhesion can be obtained when the undercoat/topcoat film thickness is 0.5. In preparation for future practical use, we plan to examine resistance to sunlight and seawater.

The Kanmon sea area is a marine traffic congested area and a rich fishing ground in Japanese coastal sea area. Authors have investigated opinions of 94 fishermen, 29 pilots, 388 navigational watch keepers of the domestic vessel regarding reduction of conflict between fishing boats and vessels in this area through a questionnaire. This study has been analyzed each opinion of fishermen, pilots and watch keepers of domestic vessel. And these objective analyses revealed any difference of opinions between fishermen, pilots and watch keepers of domestic vessel. In these analyses, about 80% of fishermen have opinion about cooperative avoiding vessels. However, any fishermen have admitted minimum distance between fishing boat and vessel less than limitation of minimum distance between fishing boat and vessel that about 80% of pilots and watch keepers of domestic vessel have been aware. And, about 50% of watch keepers of domestic vessel have expected to reduction of conflict between fishing boats and vessels when fishermen operate AIS and VHF radio equipment. But then, over 60% of pilots have negative opinion about reduction of conflict between fishing boats and vessels when fishermen operate AIS and VHF radio equipment.

For preparing the emergency operations against earthquake and tsunami disasters, we conducted a questionnaire survey to understand the present ship mooring situation of small and medium size ships, such as training ships and a ship which operates during mainly day time without cargo handling operations. It has been clarified that instant correspondences against tsunami occurred by an earthquake, such as the emergency ship evacuation from the ports, cannot be operated due to a lack of the number of crew members aboard and shortage of the time for the evacuation.

In recent years, ships equipped with marine propellers made of CFRP (Carbon Fiber Reinforced Plastic: hereinafter "CFRP") have been introduced, and the Nagasaki Maru, a fisheries training ship of the Faculty of Fisheries of Nagasaki University, was also replaced with a CFRP propeller during the January 2023 dock. However, there has been little verification of the effects for changing propeller material on an actual ship, so in this study, we compared effects of changing propeller material between metal and CFRP on an actual ship in terms of underwater radiated noise, onboard noise and vibration environment, and fuel consumption. Of these, underwater radiated noise was measured with a small memory hydrophone at a depth of 20 m, and noise and vibration were simultaneously measured at seven locations on board. In addition, fuel consumption was compared in terms of cruising distance per liter. The results showed as follows, ①underwater noise was reduced by an average of 2 dB, ②onboard noise was below the standard value of the IMO Shipboard Code before the conversion, still more noise was further reduced, ③vibration was clearly decreased in the 100-150 Hz, and ④compared in cruising distance per liter of oil of up to more than 40% at research mode.

Ensuring sufficient stability is crucial for the safe operation of a ship, while stability can decrease during a voyage. One method for real-time estimation of stability magnitude is through the rolling period. Being aware of the natural period is beneficial in preventing synchronous and parametric rolling, phenomena linked to significant cargo damage. In this study, we installed Inertial Measurement Unit (IMU) on a full-scale ship and collected motion data. In addition to an industrial-grade Micro-Electro-Mechanical Systems (MEMS)-IMU, we also utilized a smartphone in which a consumer-grade MEMS-IMU is embedded. The IMU consists of gyro and acceleration sensors, and we compared the performance of these two sensors. We applied time-frequency analysis to the motion data to compute the rolling frequency/period. We assessed the accuracy of the estimated GM from the rolling period against the one obtained from condition calculations. Our findings indicate that the gyro sensor is better suited for measuring the rolling period. Although it observed that a ship does not always roll at the same period; by considering the most frequently occurring period as the natural period, GM can be estimated with an error of less than 10%.

In this study, we investigated the risk of large vessels encountering strong winds during berthing and unberthing using wind direction and speed data from The Automated Meteorological Data Acquisition System (AMeDAS) observations by the Japan Meteorological Agency and grid point values from the Meso-Scale Numerical Weather Prediction Model (MSM-GPV, approximately 5km resolution). An investigation of the maximum instantaneous wind speed values at AMeDAS observation points in Kobe, Kobe Airport, and Kansai International Airport in Osaka Bay revealed that the risk of encountering strong winds varies significantly with the wind direction and speed from MSM grid point values. When the wind speed at the MSM grid points near the observation points is 7-10 m/s, the risk of encountering strong winds is higher at observation points close to the land compared to those offshore. For example, at the Kobe AMeDAS observation point, the probability of the maximum instantaneous wind speed exceeding 15 m/s reaches 58% with an ENE wind direction. At the AMeDAS observation points in Kobe Airport and Kansai International Airport, the risk of encountering strong winds is high with the SSW wind direction, therefore there is the need to take caution with the winds from the SSW.

Reducing GHG emissions is an urgent issue in the maritime industry. One of the effective measures is to increase the size of the ship. Here, such a ship is called a full ship. A full ship can reduce the fuel consumption per unit cargo, which subsequently can contribute to reducing the GHG emissions. However, the problem with full ships is their course instability. When maneuvering within a small range of rudder angle, a ship which has the course instability responds differently from the one that the helmsman intended. This significantly lowers the course-keeping ability, which may lead to inefficient maneuvering. Thus, in regard to GHG emissions reduction, it is important to consider the course instability of full ships. In this study, we analyzed the turning characteristics of a VLCC from the actual voyage data. We also conduct simulations based on MMG model to reproduce the turning characteristics of the ship.

Moreover, the effect of course instability during some course-changing tests in a real sea is also discussed.

Liquefied Natural Gas (LNG) carrier spot freight rates are shaped by numerous external factors, including global economic conditions and seasonal fluctuations, resulting in heightened volatility. To address this variability, we identified the key drivers of spot freight rates for LNG carriers using market data and applied a Long Short-Term Memory (LSTM) model, widely recognized for its effectiveness in time-series forecasting. The model was trained on multiple variables, including LNG stock levels in importing countries, LNG market prices, newbuilding costs, vessel operating speeds, number of port calls, and spot freight rates. Our analysis revealed that the most influential predictors of freight rate variability were LNG inventories, LNG prices, vessel speeds, and number of port calls. These factors were determined to be critical in shaping LNG carrier spot freight rates. In contrast, the ‘newbuilding costs’ variable, often assumed to correlate strongly with freight rates, proved to be insufficient for forecasting LNG spot freight rates due to its weak predictive performance. The findings from this study are anticipated to improve the accuracy and dependability of shipping freight rate predictions, thereby providing valuable insights for decision-making in the maritime industry.

This study adopted a data-driven approach using Tree Augmented Bayesian Networks (TAN) to analyze risk influencing factors for maritime accidents in congested waters in Japan. Specifically, data on 2,192 maritime accidents that occurred within the Tokyo Bay, Nagoya Port, Ise Bay, Osaka Bay, Bisan Seto, Kurushima Strait and Kanmon Strait during the period 2009-2022 were analyzed. In the analysis, 19 risk-influencing factors were extracted and the interactions between these factors were visualized and quantified using a Bayesian Networks (BN) structure. Particular focus was placed on seven factors with high mutual information values (human error, ship type, length, gross tonnage, number of crew, AIS on board, and total experience on board), and the impact of these factors on five accident types - collision, stranding, capsize/flooding, fire/explosion and inoperability - was analyzed in detail. In addition, a scenario analysis using the BN structure was used to assess the risk of maritime accidents under specific conditions. The analysis suggested the need for countermeasures against 'overconfidence' and 'pride' of experienced ship operators, maintaining vigilance under good navigational conditions, and risk management according to vessel characteristics.

In this study, a probabilistic risk assessment method was developed based on the Formal Safety Assessment Guidelines approved by the IMO, applying the Baysian Network to take human factors into account. And then, based on this risk assessment method, we estimated the contribution of safety measures to human factors and evaluated the effectiveness of Risk control option. As a practical example of application, we conducted a risk assessment of a collision accident involving a medium- to large-size vessel in the Seto Inland Sea, and examined the effectiveness of several risk control options that have been considered effective as safety measures.

The cargo transported by Pure Car and Truck Carriers (PCTC), including passenger vehicles, trucks, and construction machinery, has been increasing in size and weight in response to evolving market demands. The cargo decks of PCTC are designed with specific deck heights and strengths, making it crucial to assess the feasibility of stowage prior to loading. This evaluation is essential not only for maintaining the structural integrity of the PCTC but also for ensuring the safe transport of cargo entrusted by shippers. In this study, we focused on the recent rise in exports of construction machinery from Japan to international markets and examines the methods for determining stowage feasibility in relation to the design deck strength.