Articles
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Self-organized luminous pattern formation observed above the anode surface of a DC glow discharge in pure He
To elucidate the mechanism of self-organization phenomena in luminescence observed on the anode surface during atmospheric pressure direct current glow discharge generation, we investigated luminescence patterns while varying pressure in a pure He environment. The results revealed that luminescence patterns appear when the product of pressure p and electrode distance d (pd) is high. Moving forward, we will connect this to reaction-diffusion systems, a method used in mathematics to obtain self-organization phenomena.
Toshiaki Miyazaki, Jan Kuhfeld, Koichi Sasaki, and Naoki Shirai
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
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
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
Mechanochemical activation of metallic lithium for the generation and application of organolithium compounds in air
Here we report a mechanochemical method for the direct generation of organolithium reagents from readily available organic halides and unactivated lithium metal (lithium wire) under bulk-solvent-free conditions. These reactions rapidly generate a diverse array of organolithium compounds at room temperature without special precautions against moisture and without temperature control.
Kondo Keisuke, Koji Kubota, and Hajime Ito
The Detail Matters: Unveiling Overlooked Parameters in the Mechanochemical Synthesis of Solid Electrolytes
“Simply mixing the reagents by hand for a short time in a mortar and pestle before mechanochemical synthesis dramatically improves the performance of the solid electrolyte.
Hand mixing changes the crystallization behavior, improving the ionic conductivity of the solid electrolyte by up to an order of magnitude.
This discovery will accelerate the search for efficient and logical new electrolyte materials, and ultimately the development of all-solid-state batteries.”Abdulkadir Kızılaslan, Mustafa Çelik, Yuta Fujii, Zheng Huang, Chikako Moriyoshi, Shogo Kawaguchi, Satoshi Hiroi, Koji Ohara, Mariko Ando, Kiyoharu Tadanaga, Saneyuki Ohno, and Akira Miura
Imaging valley-vortex edge modes in a phononic crystal at ultrahigh frequencies
We perform optical measurements and numerical simulations of guided phonon propagation in novel topological phononic crystal structures at ultrahigh frequencies. The structures support valley-polarized states that exhibit an energy vortex nature and propagate with high efficiency at domain boundaries because backscattering is suppressed due to conservation of time reversal symmetry. We extract frequency- and time-resolved spatial mode patterns and -space images, together with dispersion relations. We investigate the conditions required for robust propagation along interfaces and thereby observe very high efficiency waveguiding.
Paul H. Otsuka, Motonobu Tomoda, Daiki Hatanaka, Hiroshi Yamaguchi, Kenji Tsuruta, and Osamu Matsuda
Pore properties and CO₂ adsorption performance of activated carbon prepared from various carbonaceous materials
The production of activated carbon using biomass and coal as carbon sources, melamine as a nitrogen source, and K₂CO₃ as a chemical activator revealed that the lower carbon content and lower ash content of the carbon source resulted in better pore development, and that the surface area and micropore volume of activated carbon affected the CO₂ adsorption capacity. It was also shown that the optimal micropore size for CO₂ adsorption is 0.5 to 1.2 nm. These results are expected to lead to the establishment of production guidelines for activated carbon with high CO₂ adsorption capacity.
Yuuki Mochizuki, Javzandolgor Bud, Enkhsaruul Byambajav, and Naoto Tsubouchi