Volume 2, 2026
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Impact-echo for different level cracks detection in concrete with artificial intelligence based on un/supervised deep learning
Aging concrete infrastructure such as bridges and tunnels requires effective inspection to ensure safety and durability, particularly for detecting invisible internal cracks subjected to structural integrity. Impact-echo, which is one of non-destructive testing methods, is widely used but costly and time-consuming with relying on skilled and experienced analysis. This study integrates AI with impact-echo data to improve crack detection. Supervised deep learning using FFT-transformed signals enables accurate classification of multiple crack levels, including intact condition of concrete. However, data labeling for each existing structures is impractical, so an unsupervised approach using an auto-encoder is proposed to identify internal crack levels through anomaly-based indices without labeled data.
Jeero Pandum, Katsufumi Hashimoto, Takafumi Sugiyama, Wanchai Yodsudjai
Effect of flow residence time on the flame-retardant performance of fluorine-based flame retardant: Comparison of blowoff limits of CH₂F₂ and CH₄
The article investigates the combustion characteristics of hydrofluorocarbon (HFC) and hydrocarbon (HC) fuels to understand the increased flammability of fluoropolymers like ETFE under microgravity. Key findings: CH₂F₂ exhibits minimal sensitivity of blowoff limit to oxygen, unlike CH₄. CH₂F₂ flames have lower temperatures and suppressed H and OH radical formation, due to dominant HF-producing pathways inhibiting radical chain reactions. Despite susceptibility to blowoff, CH₂F₂ maintains high adiabatic flame temperature, allowing combustion at low oxygen if sufficient residence time is provided.
Yusuke Konno, Ayuto Ota, Nozomu Hashimoto, and Osamu Fujita
Solid-phase fluorescence excitation-emission matrix spectroscopy of soil, fulvic acid fractions, and clay mineral complexes: Evidence from red shift of fluorescence maxima associated with aggregation
Most of the analysis of natural organic matter (humic substances) in soil is carried out in a solution state by an alkali extraction operation. However, this approach addresses concerns regarding the potential alteration of humic substances during alkaline extraction, which may cause these substances to lose their original structure. In this study, as a non-extraction and non-destructive method, solid-phase fluorescence (excitation-emission matrix) spectroscopy (SPF-EEM) was applied for the first time to a standard humic substance and its complex with clay. It was found that the excitation-emission wavelength could shift according to the state of solution, complex, aggregate, etc.
Yuki Nakaya, Takashi Hirose, Ryuichi Tamori, Nobuhide Fujitake, Satoru Nakashima, Hiroshi Yamamura, and Hisashi Satoh
Development of hydrogen production technology using plasma-assisted water electrolysis
In “contact glow discharge,” an electrolytic reaction where plasma and water come into contact, phenomena where the Faraday efficiency exceeds 1 have been reported, but the reaction mechanism remains unclear. We aim to develop a plasma-driven electrolysis method that generates stable direct-current plasma in water, elucidate the mechanism behind the phenomenon where hydrogen production increases significantly compared to conventional electrolysis, and establish a highly efficient hydrogen production technology.
Grant-in-Aid for Challenging Research (Pioneering) 2025.6.27～2029.3.31
Green Conversion of Palm Oil Wastes into Bio-Compressed Natural Gas (Bio-CNG) for Renewable Energy Diversification in Malaysia
This collaborative research aims to enhance the production and upgrading of bio-compressed natural gas (Bio-CNG) by effectively utilizing two major byproducts generated from Malaysia’s palm oil industry: palm oil mill effluent (POME) and empty fruit bunches (EFB). Specifically, the Japanese team will develop and support the operation of anaerobic digestion processes, conduct microbial community analyses, and apply machine-learning-based data-driven modelling to improve process stability and enable rapid and precise optimization of CO2 adsorbent performance. The Malaysian team will optimize pretreatment and fermentation conditions for EFB and lead the development and evaluation of gas separation technologies using EFB-derived biochar. Through collaborative research between the two countries, the project is expected to contribute to establishing a renewable energy technology platform that supports Malaysia’s transition toward a decarbonized energy society
Mamoru Oshiki, and Adeline Seak May CHUA
Networked Exchange, United Strength for Stronger Partnerships between Japan and ASEAN (NEXUS) 2026.1〜2028.12
Evaluation of Phosphorus Release from Lake Sediments Using Passive Sampling and Phosphate Oxygen Isotope Analysis
In eutrophic lakes, the persistent high phosphorus concentration in lake water poses a significant problem. This study employs passive sampling techniques and phosphorus oxygen isotope analysis to identify the sources supplying phosphorus to the lake water. This approach will also reveal contributions from lake sediments, which have not been evaluated previously. This research is expected to contribute to the assessment and conservation of lake water environments.
Akira Hafuka, Takuya Ishida, and Kazuto Sano
The Sumitomo Foundation, Grant for Environmental Research Projects 2025.11.01～2026.11.30
Development of Ethical Mining Technologies to Achieve Responsible Mineral Sourcing: The Future of Mining Development Enabled by Blockchain
Assistant Professor Okada of Hokkaido University, with support from the JST Sakura Science Program, will invite eight faculty members and students from Aksum University in Ethiopia. Using blockchain and GIS, they will examine new technological frameworks for ensuring transparency in responsible mineral sourcing and for environmentally conscious resource development through joint research, practical exercises, and presentations of results.
Sakura Science Exchange Program 2026.2.4~2026.2.18
Characterizing the Settlement of Activated Sludge Based on AI-Assisted Analysis of Moving and Still Images
In the final process of wastewater treatment, the settleability of activated sludge, a mass of microorganisms responsible for the adsorption and decomposition of pollutants, is important. In order to contribute to the improvement of the efficiency of wastewater treatment plants in rural areas and developing countries, which have problems in terms of economical human resources, this study proposed a low-cost settleability diagnosis method that uses AI-based technology to analyze still images of activated sludge using inexpensive digital microscopes and moving images of activated sludge settling using smartphone camera functions.
Yuki Nakaya, Kai Sugino, Shota Ishizaki, Reiko Hirano, Shuhei Noda, Shinobu Moniwa, Yukio Hiraoka, and Hisashi Satoh
Protium enrichment by polymer electrolyte fuel cell with hydrogen gas circulation
A polymer electrolyte fuel cell (PEFC) equipped with a gas recirculation system was employed for deuterium separation. Incorporating a hydrogen gas tank into the gas recirculation line achieved significant hydrogen concentration. During fuel cell operation, hydrogen concentration in the gas increased, yielding a high separation factor. This improvement in separation efficiency is thought to result from enhanced separation efficiency via gas-phase chemical exchange reactions.
Toranosuke Nago, Mikito Ueda, and Hisayoshi Matsushima
SH wave scattering in Eringen’s nonlocal elastic solid using the method of fundamental solutions
Eringen’s nonlocal elastic solid is a mechanical model that enables the analysis of phenomena difficult to describe using classical elasticity. This study analyzed wave scattering in nonlocal elastic solids using the method of fundamental solutions, a meshfree numerical method. An analytical representation of the traction operator specific to nonlocal elasticity was derived, and scattering characteristics relevant to ultrasonic nondestructive testing were evaluated.
Akira Furukawa, Taizo Maruyama, Takahiro Saitoh, Sohichi Hirose, Davinder Kumar, Dilbag Singh, and Sushil K. Tomar