This report provides a multifaceted explanation of lithium-ion batteries （LIBs）, which are gaining popularity at a rapid rate, in four chapters: “Trends,” “Technology,” “Recycling,” and “Outlook”. Chapter 1, “Trends”, outlines the anticipated role of LIBs, their roadmap, and global trends. Chapter 2, “Technology”, covers the basic structure and manufacturing methods of LIBs, as well as the latest technologies such as all-solid-state batteries and dry processes, which have attracted particular attention in recent years. Chapter 3, “Recycling”, introduces the most common recycling methods and describes the author's own research. The final chapter, “Outlook”, discusses the author’s views on the future possibilities of LIBs.

The falling-film-type heat exchanger used in this study is expected to achieve high efficiency in heat exchange by utilizing the falling film. With this heat exchanger, the heating medium flows inside the heat exchanger tube and the falling liquid film flows on the outer surface of the heat exchanger tube to exchange heat. Our previous studies revealed the basic heat transfer characteristics of the falling-film-type heat exchanger; developed design equations applicable to a limited scope; demonstrated the possibility of improving performance by inserting a variety of shafts with screw blades into the heat exchanger tube; and clarified that the heat exchange performance can be improved by improving the liquid film flow condition on the outer surface of the heat exchanger tube. In this study, we investigate the relationship between the liquid film thickness and heat transfer characteristics for the falling-film-type heat exchangers of horizontal-tube-type, and consider the modification of dimensionless numbers that can uniformly evaluate the heat transfer coefficients on the liquid film side of this type and another type (vertical-plate-type in this study) of falling film heat exchangers. Furthermore, we attempt to derive a dimensionless equation for the liquid film side heat transfer coefficient using the Wilson plot method. As a result, the heat transfer characteristics of the falling-film-type heat exchangers of horizontal-tube-type were clarified to some extent, and a dimensionless equation for the heat transfer coefficient on the liquid film side using the modified Nusselt number was proposed.

This paper aims to clarify the growth of bubble nuclei in water flowing through the two-dimensional nozzle which is a model of diesel fuel injector nozzle. The nuclei growth is initiated due to tension induced by the sudden pressure drop at the sharp corner of the nozzle edge and it is investigated by means of experiment, CFD flow simulation and bubble dynamics. In the experiment, the observation section of the nozzle is around sharp corner to generate bubbles, and once cavitated, the water cannot return to the observation section. A single-phase water flow is simulated using LES-based CFD to obtain the velocity distribution at the sharp corner in the nozzle edge, flow separation, and vortex formation downstream of the separation point, pressure distribution before and after the sharp corner in the nozzle edge. The growth mechanism of bubble nuclei is clarified with Blake’s cavitation threshold theory and Rayleigh-Plesset equation in the CFD-flow field under experimental conditions. Finally, the bubble nuclei attain the critical radii a little downstream of the sharp corner in the nozzle and then explosively start growing in cases where Blake’s threshold is fulfilled.

Lattice structures are emerging due to the increasing demand for materials that are lightweight and can ensure safety, which is critical for sustainable development. This study aims to gain some knowledge on the characteristics of lattice structures with excellent energy absorption properties, and to contribute to the development of reusable energy-absorbing materials. Lattice structures with three types of unit cell topologies-body-centered cubic (BCC), Cruciform, and face-centered cubic (FCC)-were fabricated with acrylic polymer and subjected to multiple compression tests to investigate the strain recovery characteristics and changes in compressive and energy-absorbing properties. All structures exhibited significant strain recovery to 69-81% of their uncompressed height after sufficient time following compression. However, Young's modulus, plateau stress, and densification onset strain decreased after each cycle. Consequently, the specific energy absorption decreased significantly, especially after the first compression. The structure exhibiting strut buckling during plastic collapse (Cruciform and FCC) absorbed a large amount of energy during the first compression but showed a significant decrease during the second and subsequent compressions. On the other hand, the rate of decrease in specific energy absorption for the structure without strut buckling (BCC) was relatively small, suggesting that preventing strut buckling can suppress the decrease in specific energy absorption.