Selected Articles
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Study on long-term subsidence of soft clay due to Niigata-ken Chuetsu-oki earthquake of 2007
In the 2007 Niigata-ken Chuetsu-oki Earthquake, ground liquefaction was severe in sandy areas, but long-term settlement occurred in soft clay in Kashiwazaki’s Shinbashi district. Even without visible damage, the ground sank 71 mm over 14 years. We studied this by boring and testing soil samples, finding the clay to be soft and highly compressible. Using a specialized computer model (TS-CM), we successfully simulated the ground’s behavior, showing that this type of clay is prone to long-term sinking after earthquakes due to water pressure buildup and delayed consolidation. These findings help predict future ground behavior in similar soils.
Yazhou Jiang, Koichi Isobe, Satoru Ohtsuka, and Toshiyuki Takahara
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Seismic performance of a bridge pier integrated by multiple steel pipes with directly-connected piles using soil-water coupled with three-dimensional elasto-plastic finite element analysis
A new type of bridge support using connected steel pipes was tested to see if it performs as well as traditional designs during earthquakes. Small-scale shaking tests showed that it works just as well or even better. However, since only one type of shaking was tested, we are now using computer simulations to see how it reacts to different kinds of earthquake motions. This will help us better understand how safe and reliable this new bridge design is for the future.
Muhammad Mahmood Ul Hassan, Koichi Isobe, Yasumasa Soga, Yasuo Sawamura, Hiroki Sugiyama, and Masatsugu Shinohara
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Photoinduced Metal–Insulator Phase Separation Depending on the Conformational Order of Molecules in β-(BEDT-TTF)₂I₃
In this study, the role of the conformational order of organic molecules in photo-induced phase separation (PIPS), which forms the basis for ultrafast switching devices, is investigated. The results show that PIPS occurs below 150 K in the partially ordered phase and below 75 K in the homogeneously ordered phase. This result implies that conformational order plays a crucial role in determining the temperature at which PIPS occurs, providing significant insight for room-temperature operation, which is essential for the practical application of devices.
Kensho Nagata, Satoshi Tsuchiya, Koichi Nakagawa, Hiromi Taniguchi, and Yasunori Toda
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Mussel Adhesive Protein-Assisted Magnetic Recovery of Microplastics from Aquatic Environments
Mussel adhesive proteins can adhere to a wide range of materials, from iron (inorganic) to plastic (organic). By taking advantage of this adhesive property, we can form a composite of microplastics and magnetic microparticles, which can be magnetically recovered from an aqueous solution with an efficiency greater than 99%.
Anju Pilakka Veedu, Kazunori Nakashima,* Takahiro Sato, Ami Sasabe, Keita Suzuki, Chikara Takano, and Satoru Kawasaki
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Transport of radioactive elements in concrete due to utilization of recycled aggregate contaminated with nuclides
In the future, a huge amount of concrete waste will be generated in preparation for the demolition of nuclear power plants. From the perspective of rational processing and disposal, it is possible to reuse this waste, particularly waste with low levels of radioactivity, as recycled aggregate. Clarifying how radioactive materials migrate inside concrete is extremely important in building a safe and secure society.
Yingyao Tan, Takafumi Sugiyama, Katsufumi Hashimoto, and Junxiao Liu
Construction and Bulding Materials, Volume 471, 11 April 2025, 140689
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Nucleation probability of methane + propane mixed-gas hydrate depending on gas composition
Natural gas hydrate contains large amounts of natural gas and is attracting attention as one of the future domestic resources, or as its storage and transportation medium. For its industrial use, it is one of the problems that the nucleation process is difficult to control. This study has revealed that the nucleation probability of methane + propane mixed-gas hydrate, as a mimic of natural-gas hydrate, depends on the composition. This result will help develop technology for industrial use of gas hydrates.
Tsutomu Uchida, Masato Hayama, Motoi Oshima, and Kenji Yamazaki
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Spatiotemporal mode extraction for fluid–structure interaction using mode decomposition
We proposed a method to extract the spatiotemporal modes of structural deformation obtained from fluid-structure interaction analysis using Dynamic Mode Decomposition (DMD). By applying this method, it becomes possible to identify the dominant structural deformation modes in systems where fluid forces induce significant structural changes, such as flexible aeroshells.
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Effect of Wet−dry Cycles and Water-to-cement Ratios on Cement Paste Carbonation
Cement production consumes a significant amount of energy and releases CO₂ emissions, while concrete waste can potentially reabsorb CO₂. This study examined the effect of relative humidity (especially wet-dry cycles) on the carbonation of hardened cement pastes. Wet–dry cycles increased porosity and caused the decomposition of calcium silicate hydrate (C-S-H) through shrinkage and deformation during drying. As a result, the highest CO₂ absorption in the wet-dry cycle sample was twice that of the constant RH. Additionally, the amount of CO₂ captured during the 28-day wet-dry cycle accounted for about 17% of the annual CO₂ emissions from cement production.
Zhiwei Zhao, Dayoung Oh (researchmap.jp, researchgate.net, scholar.google.com), Ryoma Kitagaki, Tianlong Zheng, and Ippei Maruyama
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Unveiling the origin of diffusion suppression of hydrogen isotopes at the α-Al₂O₃(0001)/α-Cr₂O₃(0001) interfaces
Hydrogen in metallic materials causes degradation known as hydrogen embrittlement, which renders the materials brittle. Therefore, to promote the use of hydrogen energy in applications such as fuel cells and nuclear fusion reactors, strategies to prevent hydrogen permeation into structural materials are essential. In this study, we elucidated the mechanism by which coating multiple layers of different ceramic films on metal surfaces, which serve as hydrogen permeation barriers, can more effectively suppress hydrogen permeation than single-layer ceramic films. This research can contribute to extending the service life of metallic materials in a hydrogen environment.
Yuji Kunisada, Ryotaro Sano, and Norihito Sakaguchi
International Journal of Hydrogen Energy, Volume 97, Pages 1327-1334