The formation of suspensions of fibre-optic submarine cables on the seabed in great depths of water is inevitable due to the “bending stiffness” of the cables combined with the complexity of the seabed topography, especially in areas of trench or seamount terrain. Abyssal currents can cause cable suspensions to oscillate and drag thereby abrading the cable’s outer polyethylene sheath at the points that touch the seabed. If the polyethylene wears through to the copper conductor, the submarine cable system will fail with an insulation fault and the network will shut down until a repair can be made. Technologically advanced societies and industries supported by the global submarine network may be deeply affected by such system downtime. For situations where suspended cables are subjected to sea currents, the submarine cable system is dependent on the abrasion resistance of its outer sheath throughout the commercial life of the system. This study aims to provide a system of installing cable systems that will reduce the number and span length of cable suspensions and increase the system’s mechanical stability.
Bisphenol A (BPA) is suspected of risk for ecological damage, but the risks are little known in Japan’s coastal areas. A major goal of this research is to identify the risk of bisphenol analogs (BPs) in Japan’s coastal areas. In this paper, ecological risk was first assessed in the Tama River towards understanding future ecological risk for Tokyo Bay. A total of 74 chronic toxicity datasets testing aquatic species resident in Japan were found in published literature. These were simulated using species sensitivity distribution (SSD) divided into reproductive and non-reproductive effects. Measured environmental concentration (MEC) obtained by actual field measurements (monitoring data) was used to represent exposure conditions. The risk of BPA in Tama River waters was assessed by hazard quotient (HQ) method. The 95th percentile concentrations were used to calculate HQ. The results showed that BPA was found at a concentration in the range of 0.008–0.083 μg/L in the Tama River. Predicted no-effect concentrations (PNEC) for reproductive and non-reproductive effects were 0.014 μg/L and 0.38 μg/L, respectively. Using these results, HQ was calculated to be 6.0 for reproductive effects and 0.2 for non-reproductive effects. Because reproductive endpoints are a risk concern, it is necessary to continue investigation in the future.
In this paper, a general outline of geotechnical engineering is explained briefly as one of the typical interdisciplinary subjects. Then, the focus is placed to a limited part of this broad engineering field, i.e. marine geotechnical engineering, which is related to seabed and seafloor. Education systems in the universities and prospective of recent research papers are examined to characterize this subject. Finally, some research works that the author has been involved in are introduced as typical examples of research projects in the relevant study.
Recently, in order to realize autonomous ships (MASS), researches and developments related to MASS are actively carried out in the world. Feasibility Studies using small crafts, ferries and Pure Car Carrier have been executed. On the other hand, business model using MASS and legal issues for MASS are still required more discussion. In this paper, the research and development project of zero-emission waterborne transit system, which is the research project of Tokyo University of Marine Science and Technology, is introduced. Technological properties of battery-powered boat, a hybrid boat and an autonomous boat are explained. Legal issues to realize autonomous ship are also explained.
A long-term osmotically pumped fluid sampler, OsmoSampler, consists mainly of an osmotic pump with a semipermeable membrane and sampling coil, which allows for sequential fluid sampling for years without an electric power supply. We reviewed the theoretical/technical properties of the OsmoSampler and three studies that analyzed fluids collected with the OsmoSampler system in marine environments: Juan de Fuca ridge (2656 mbsl [624 mbsf] at ~64°C for three years), Gulf of Mexico (540 mbsl at ~8°C for one year), and eastern margin of the Japan Sea (904 mbsl at ~0°C for one year). These studies reliably obtained continuous fluid samples and pointed to the time-series changes of fluid geochemistry due to the migration of deep hydrothermal fluid, the active fluid migration in near-seafloor methane-rich systems, and the oscillation of water/gas composition in response to gas hydrate formation/dissolution near the seafloor. The OsmoSampler could provide new insights for long-term monitoring of environmental changes in deep sea conditions.