The primary aim of our research is to complete physiological index to evaluate mental workload. We focus on salivary NO₃^- as an index, which is emitted to blood vessels from vascular endothelial cells when a human body receives mental workload. The development of a device to measure NO₃^- in vascular endothelial cells is thus required for the evaluation of mental workload. The device developed here is composed of field-effect transistors and ion-selective membranes. We have adopted a polymer for use with an ion-selective membrane. Two experiments were performed to verify the drift in the device characteristics and to validate the characteristics of the polymer as the ion-selective membrane. Verified experimental results indicated that the polymer was useful as ion-selective membrane material, which has less drift characteristics for a long time measurement. Validated experimental results indicated that NO₃^- device with new polymer KP-13 has the effectiveness of measurement of mental workload on the spot, compared with values from NO₃^- device with KP-13 and other physiological indices.

When looking back at the history of preventative regulations, 4 common principles can be seen within COLREGs. These principles form the basis for applying COLREGs to MASSs and for making the necessary amendments. Also, in terms of functionality, COLREGs can be broadly classified into the viewpoints of information collection and decision-making. When examining each provision of COLREGs, it is necessary to consider that their objectives are to prevent collisions and protect human life. This paper examines the navigation rules for each type of ship, look-out work, visibility restrictions, interpretation limitations of the ordinary practice of seamen, and the direction of regulation amendments, from the perspective of the above-mentioned principles and the objectives of COLREGs.

Facts of the storm surge in Fukae Harbor caused by Typhoon Jebi, T1821, on 4 September, 2018 were clarified by the recorded data. The maximum tidal level (TL) occurred between 14:16 and 14:18, and was estimated to be 305 cm. The maximum deviation of the TL from the predicted TL was 254 cm. The main factor in the storm surge was the wind effect of the southerly. The outside maximum water level in Fukae Harbor was 336 cm, and was 36 cm higher than the TL of the time due to wind waves generated by local winds. The flooding was produced not only by the overflow caused by the storm surge but also by waves overtopping. If the storm surge had occurred at the maximum TL of the year, flooding would have produced by the overflow alone. The hazard maps of inundation by flooding from rivers and of inundation inside levees very nearly express the inundation area resulting from the storm surge. Overlaying evaluation of hazard maps of similar disasters is important in a perspective of risk detection. As the present seawalls may not be able to prevent the greatest storm surge, both tsunamis and storm surges should be considered in coastal disaster prevention.

This study proposes a design method that can accurately estimate the scantling of spherical pressure shell to meet the ultimate strength requirements of structure. This pressure shell plays a crucial role in human occupied vehicles; therefore, it should be designed precisely and its ultimate strength should be analyzed. Several rules have been formulated for the design of spherical pressure shells. However, according to the results obtained herein and based on the consideration of various classification rules, the maximum deviation between the calculated and actual thickness values is approximately 30%.

This study uses five pressure shells as design targets and recalculates them using seven classification rules. Additionally, elastic–plastic buckling analysis was performed with the Riks method in ABAQUS to confirm the ultimate strength. It is demonstrated that the results calculated by LR rules are more stable and smaller deviations than other rules. Using the design correction curve of the British Standards Institution for the correction of the yield load shows that the thickness of the pressure shell is significantly lower than that of the original design. Despite the fact that the thickness is reduced, the structural strength can be maintained within a safe range that meets the design requirements.

In July 2017, the Marine Accident Investigation Branch of the United Kingdom reported an accident of a fishing vessel resulting in the fatalities of three seafarers. These seafarers were found in a face-down position, while they were wearing lifejackets certified in accordance with the International Conventions for the Safety of Life at Sea and the International Life-saving Appliance (LSA) Code, so-called “SOLAS lifejackets”. Following the research initiated by this accident, the European Commission submitted two documents, emphasizing the necessity of a new righting test method for lifejackets with clothing. The Maritime Safety Committee, at its 101st session, considered these documents and agreed to review the LSA Code and the Revised Recommendation on testing of life-saving appliances, in respect to the in-water performance of SOLAS lifejackets, taking into account that the current righting test of a SOLAS lifejacket is conducted only with a swimming costume.

In order to develop robust testing methods for the righting of lifejackets with clothing, the righting phenomenon of lifejackets with clothing should be examined. The purposes of our preliminary research are to evaluate the repeatability of righting tests with clothing and to obtain fundamental information on such tests. For these purposes, we conducted righting tests with clothing using three human test subjects under various conditions and compared the results of tests conducted just after entering the test basin with dry clothing in order to evaluate the repeatability of the tests. In addition, we repeated the righting tests using the same clothing without getting out of the test basin in order to obtain further information for reference. We further measured the forces required to dive into the water with and without clothing in order to roughly specify the buoyancy of clothing under lifejackets. The test results indicated that righting tests with clothing were sensitive to slight differences in clothing conditions, human actions and time elapsed. Our study showed that the righting test with clothing had poor repeatability and standardization of clothing could not solve the poor repeatability of the righting test with clothing.

In 2019, the authors proposed an industry-school education skill succession process, and used it to develop a learning system for self-study of skills1). In this study, we evaluated the appeal of the teaching materials in this system using the ARCS model from the perspective of learning motivation and searched for learning motivation factors. We used a teaching material evaluation sheet based on the ARCS motivation model to conduct a survey of instructors and students at a fisheries high school after using the skill succession system. From the results, we obtained many positive answers with all ARCS model factors and confirmed a high degree of usefulness for instructors and students. In addition, based on the results of the factor analysis, we confirmed that in this system, instructors focus on the factors of “Confidence” and “Attention,” and students on the factors of “Satisfaction” and “Relevance.” As such, we confirmed that learning motivation factors differ between instructors and students.

In this study, an autonomous surface vehicle was developed to support research on autonomous underwater vehicles. Surface vehicles are required to perform route-tracking of underwater vehicles. To improve the tracking control accuracy of the vehicle, its control gain must be optimized. Therefore, a tuning method that optimizes the proportional-integral-derivative control gain for tracking control is introduced in this study. First, the gain was obtained using a describing function method and Ziegler–Nichols’ ultimate gain method. Next, an evaluation function that focuses on the tracking control was created. Subsequently, the gains were optimized for tracking control using the evaluation function. A tank test using an actual surface vehicle was performed and the results demonstrate the effectiveness of the proposed method.