Rapid disappearance of useful seaweeds and seagrasses in the coastal area of Japan is called isoyake, i. e., rocky-shore denudation. Feeding damage by plant eating fishes and sea urchins is considered to be the main cause of the isoyake. A recent increase in the feeding damage is closely related to sea water temperature rise due to global warming. As the seaweeds and seagrasses can absorb and fix great amount of CO₂ through photosynthesis, the so-called blue carbon is significantly decreased by the isoyake and, hence, the global warming is further accelerated. The current situation and some solution methods of the isoyake are briefly reviewed in this article.

Most of rice husks are disposed as industrial waste because utilization of rice husk is minimal and burning is prohibited in many prefectures in Japan. This study aimed to evaluate the mechanical and physical properties of particleboard formed from rice husk particles by hot pressing with a polyvinyl alcohol (PVA) binder. A preform was prepared using mixed rice husk particles, PVA powder, and purified water. The rice husk particleboard was fabricated by hot pressing with the preform. Some mechanical (flexural strength and flexural modulus) properties and physical (thickness swelling and water absorption) properties of the resulting particleboard were evaluated. Results showed that mainly, the water absorption decreased with increasing the density of the rice husk particleboard. However, the thickness swelling increased with increasing the density of the rice husk particleboard. The flexural strength and flexural modulus of dried rice husk particleboard increased with increasing the density. On the other hand, in the case of wetted rice husk particleboard, the flexural properties decreased significantly over the density of 0.8 g/cm³.

In the context of the need to improve the performance of rechargeable batteries, attention was paid to magnesium, which is promising in terms of energy density, safety, and procurement costs, and anode materials were prepared. Anode ribbons were produced using the single-roll rapid solidification method. This method is less expensive to produce than rolling and has a weaker orientation to the basal (0001) plane, resulting in better electrochemical activity. In this study, constant current charge-discharge tests were carried out on AZ31, AZ61, and AZ91 to investigate the influence of aluminum content on their electrochemical properties. The results showed that in the discharge reaction, the overvoltage increased with increasing aluminum content, while in the charge reaction, the voltage slope tended to increase significantly. In other words, the electrochemical properties were degraded. It is suggested that the cause is the change in lattice constant and increased basal orientation with increasing aluminum content.

Hydrogen-based ironmaking is one of the most promising technologies that does not emit CO₂ to achieve carbon neutrality in the ironmaking process. On the other hand, high-grade hematite iron ore with low gangue content has depleted. Magnetite iron ore can improve its grade by crushing, grinding, and magnetic separation. It is expected to be used as the primary iron source for hydrogen-based ironmaking by reducing its fine ore with hydrogen. In this study, magnetite concentrate was reduced with H₂-N₂ gas at 1173 K and the reduction rate was investigated. The time required to reduce fine iron ore to a fixed fractional reduction increased linearly concerning the ratio of iron ore mass to the flow rate of the reducing gas. The reduction rate, independent of the gas flow rate, was obtained from the results. It was found that the reduction rate of the magnetic particles in the fine iron ore was smaller than that of the non-magnetic particles and became significantly small at the reduction stage from Fe_1-yO to Fe. This difference is caused by pores forming only in the non-magnetic particles associated with the progress of gaseous reduction.

Recycling Al scraps is extremely important to achieve carbon neutrality. To produce wrought Al alloy, alloying elements must be controlled to a low concentration. However, Al scraps recovered from the society contain Cu, which is difficult to remove once dissolved in molten Al alloy. Fe, Si, and Mn can be removed from molten Al through the precipitation of intermetallic compounds by adding Mg. In this study, this method was applied to remove Cu from molten Al. Molten Al-Mg-10mass%Cu alloy was equilibrated with Mg₃₂(Al,Cu)₄₉ at 723 and 733 K, and Cu content of molten Al-Mg alloy was investigated. It was found that Mg₃₂(Al,Cu)₄₉ precipitated in molten Al-Mg-Cu alloy and the Cu content of molten Al-Mg alloy decreased from the initial content. The residual Cu content was higher at higher Mg content and lower temperature. The Cu removal from molten Al-Mg alloy through the precipitation of Mg₃₂(Al,Cu)₄₉ was thermodynamically discussed. The results revealed that the activity coefficient of Cu decreased at higher Mg content due to the attractive interaction between Mg and Cu although Mg₃₂(Al,Cu)₄₉ become more stable. Therefore, Cu content of molten Al-Mg alloy can be decreased at higher Mg content.

In a steel refining process, droplets of various sizes are usually generated in the atmosphere above the bath of a top-blown converter. There are two generation mechanisms of droplets which are called splash (made of large droplets) and spitting (made of fine droplets), respectively. In the top-blown converter, molten slag (low density) is placed on the molten metal (high density) so that the metal droplets generated can contain the slag in itself. The amount of molten metal contained in the droplets is responsible for metal loss and refining efficiency. It is therefore of practical importance to predict the amounts of molten metal and slag contained in the droplets which are generated by the splash and the spitting. This study proposes the prediction method of slag concentration in droplets generated in the top-blown converter based on water-model experiment.

Irradiation damage is one of the main factors determining the lifetime of the mercury target vessel for spallation neutron source in J-PARC. In order to understand material degradation of the used vessels, it is planned to conduct an evaluation using inverse analyses with indentation tests on the structural materials of the used vessels and numerical experiments. This evaluation technique was applied to two kinds of ion-irradiated materials with different displacement damage doses, in which the irradiation condition was simulated. It could be confirmed that the ultimate strength increased, and the total elongation decreased with increasing irradiation. These trends are similar to the material degradation behaviors which have been reported by using small specimen’s tensile tests as taking the scatters into account. Furthermore, the decrease in the total elongation with increasing temperature and the fatigue strength of the irradiated materials are discussed because the vessels are subjected to repeated thermal load, and the temperature of the vessel is estimated to be over 140 °C at the rated maximum beam power.

The purpose of this study is to discuss vibration extraction of a bridge pier from processed video by a commercial digital camera. The proposed method transforms the video images into the frequency domain and reconstructs them by enlarging the designated frequency bands. Vibration patterns of the target structure are extracted from the magnified video, and vibration characteristics are estimated using statistical methods. To investigate the feasibility of the proposed method, the acceleration of an integrated column by multi steel pipes was measured. Vibration characteristics obtained from the video images are compared with those identified from accelerometers to verify the accuracy of the identification by video images. As a result, it was confirmed that the dominant frequencies identified from the measured accelerations and the frequencies emphasized by the proposed method from the video images are almost identical.