Introduction to the simulation disaster challenge of world robot summit harsh environment F-REI challenge pre-tournament event

Nakamura, Keita*; Suzuki, Kenta; Kaneko, Eiichiro*; Abe, Yoshitaka*; Shimizu, Masaru*; Ogane, Katsuji*

Journal of Robotics and Mechatronics, 38(1), p.192 - 201, 2026/02

https://doi.org/10.20965/jrm.2026.p0192

Structure of heavy quarkonia in a strong magnetic field

Arifi, A. J.; Suzuki, Kei

Physical Review D, 112(9), p.094013_1 - 094013_18, 2025/11

https://doi.org/10.1103/pwsl-xrq5

We investigate the structural modifications of heavy quarkonia in the presence of strong magnetic fields using a constituent quark model. By incorporating the effects of spin mixing and quark Landau levels, we employ a nonrelativistic Hamiltonian that captures the essential features of quark dynamics in a magnetic field. The two-body Schrodinger equation is solved using the cylindrical Gaussian expansion method, which respects the cylindrical symmetry induced by a magnetic field. We extract the corresponding light-front wave function (LFWF) densities and analyze their transverse and longitudinal structures, revealing characteristic features such as transverse momentum broadening. While the longitudinal structure is only slightly modified within the nonrelativistic Hamiltonian, we discuss some corrections that can significantly affect its longitudinal structure. Furthermore, we discuss the structure modifications of excited states and find notable changes in the LFWF densities, and state reshuffling near avoided crossings. These results demonstrate the sensitivity of hadron structure to external magnetic fields and help bridge our understanding to relativistic approaches.

Compliance measures at the Radioactive Waste Treatment Facilities at the Nuclear Science Research Institute; Aseismic reinforcement of the Radioactive Waste Treatment Facility No. 3, Waste Size Reduction and Storage Facility, and Waste Volume Reduction Facility

Iketani, Shotaro; Suzuki, Takeshi; Yokobori, Tomohiko; Sugawara, Satoshi; Yokota, Akira; Kikuchi, Genta; Muraguchi, Yoshinori; Kitahara, Masaru; Seya, Manato; Kurosawa, Tsuyoshi; et al.

JAEA-Technology 2025-001, 169 Pages, 2025/08

JAEA-Technology-2025-001.pdf:14.22MB

The radioactive waste treatment facilities at the Nuclear Science Research Institute includes the Radioactive Waste Treatment Facility No. 3, Waste Size Reduction and Storage Facility, and Waste Volume Reduction Facility. These three facilities come under the purview of the Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, and are included under Class C of the act based on the seismic requirements specified in the Act. We assessed the seismic capacity of these three radioactive waste treatment facilities based on the current Building Standards Act, to verify whether they comply with the new regulatory requirements enforced by the Nuclear Regulation Authority (NRA) in the aftermath of the 2011 nuclear accident at the Fukushima Daiichi Nuclear Power Station operated by the Tokyo Electric Power Company. We found that the allowable stress of a few structural members used in the construction of the facilities did not meet the regulatory requirements. After studying the approval granted by the NRA for the construction plans, including the design and construction methods (design and construction plans) of the three facilities on March 5, 2021, we made aseismic reinforcement at these facilities between 2021 and 2022. This report presents an overview of the seismic design of these facilities and an outline of the aseismic reinforcement conducted, management system existing, safety measures adopted, and the preoperational inspections conducted at these facilities.

Casimir effect at finite density

Fujii, Daisuke; Nakayama, Katsumasa*; Suzuki, Kei

International Journal of Modern Physics A, 40(10-11), p.2543020_1 - 2543020_8, 2025/04

https://doi.org/10.1142/S0217751X25430201

In this talk, I discuss the general features of the Casimir effect induced from quantum fields at finite chemical potential, particularly at finite density. Historically, the thermal Casimir effect has been well-established by the cooperation between theory and experiment, whereas its counterpart at finite chemical potential is still not. This is because it is usually difficult to control the chemical potential of photons in equilibrium experimentally. On the other hand, if one focuses on fermionic systems, their chemical potentials may be a tunable parameter for the Casimir effect. In addition, various quantum many-body phenomena realized at finite fermion density can modify the typical property of the Casimir effect. Within some theoretical frameworks, we evaluate the Casimir energy for Dirac fields at finite density and particularly show an oscillatory behavior as a function of the separation of boundary conditions or the chemical potential. As physical and realistic examples of the Casimir effect at finite chemical potential, I discuss applications to fermion fields inside thin dense quark matter in hadron physics and to Dirac/Weyl semimetal thin films in solid-state physics. Such materials will be platforms to examine the fermionic Casimir effect at finite chemical potential.

Casimir effect on the lattice spacetime

Fujii, Daisuke; Nakayama, Katsumasa*; Suzuki, Kei

International Journal of Modern Physics A, 40(10-11), p.2543017_1 - 2543017_8, 2025/01

https://doi.org/10.1142/s0217751x25430171

We investigate the characteristics of Casimir energy within a lattice-regularized spacetime framework. Typically, Casimir energy requires a regularization procedure to remove divergences originating from vacuum fluctuations of quantum fields. In this work, we adopt lattice regularization, wherein discretization effects persist as long as the lattice spacing remains finite. We first detail how the Casimir energy is computed using both naive and Wilson fermion formulations. When discretization artifacts are limited to only a few lattice points, it becomes possible to recover the continuum Casimir energy by taking the continuum limit. To illustrate physical applications, we evaluate the Casimir energy for electron fields in Dirac/Weyl semimetals, where lattice effects are meaningfully retained, and for photon fields in axion electrodynamics, where the continuum limit is accurately reproduced.

Development of an electron spin resonance spectroscopy code for measuring carbonate radicals in tooth enamel and verification of its practicality using irradiated Japanese macaque teeth

Yamashita, Takuma*; Hayashi, Teppei*; Mitsuyasu, Yusuke*; Ono, Kenta*; Iwami, Satone*; Kino, Yasushi*; Sekine, Tsutomu*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; et al.

International Journal of Radiation Biology, 8 Pages, 2025/00

https://doi.org/10.1080/09553002.2025.2510676

no abstracts in English

Improved multicomponent analysis method for electron spin resonance spectra of gamma-irradiated tooth enamel

Yamashita, Takuma*; Iwami, Satone*; Mitsuyasu, Yusuke*; Ono, Kenta*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

KEK Proceedings 2024-6, p.85 - 90, 2024/12

https://lib-extopc.kek.jp/preprints/PDF/2024/2425/2425006.pdf

To clarify the radiation effects of the accident at the TEPCO's Fukushima Daiichi NPP on living organisms, it is important to accurately estimate the dose to each individual. We have developed a multi-component analysis program using random number optimization to extract only the components derived from carbonate radicals from the ESR spectra.

Biofilm formation on excavation damaged zone fractures in deep neogene sedimentary rock

Hirota, Akinari*; Kozuka, Mariko*; Fukuda, Akari*; Miyakawa, Kazuya; Sakuma, Keisuke; Ozaki, Yusuke; Ishii, Eiichi; Suzuki, Yohei*

Microbial Ecology, 87, p.132_1 - 132_15, 2024/10

https://doi.org/10.1007/s00248-024-02451-7

Deep underground galleries are used to access the deep biosphere in addition to mining and other engineering applications such as geological disposal of radioactive wastes. Fracture networks developed in the excavation damaged zone (EDZ) are concerned to accelerate mass transport, where microbial colonization might be possible due to the availability of space and nutrients. In this study, microbial biofilms at EDZ fractures were investigated by drilling from a 350-m deep gallery and subsequent borehole logging at the Horonobe underground research laboratory (URL). By using microscopic and spectroscopic techniques, the dense colonization of microbial cells was demonstrated at the surfaces of the EDZ fractures with high hydraulic conductivities. 16S rRNA gene sequence analysis revealed the dominance of gammaproteobacterial lineages, the cultivated members of which are aerobic methanotrophs. Near-complete Horonobe groundwater genomes affiliated within the methanotrophic lineages were fully equipped with genes involved in aerobic methanotrophy. Although the mediation of aerobic methanotrophy remains to be demonstrated, microbial O production was supported by the presence of genes in the near-complete genomes, such as catalase and superoxide dismutase that produce O from reactive oxygen species and a nitric oxide reductase gene with the substitutions of amino acids in motifs. It is concluded that the EDZ fractures provide energetically favorable subsurface habitats to microorganisms.

Long-term radiation effects on the genome structure and function, and energy metabolism

Hirose, Eri; Yokoya, Akinari*; Noguchi, Miho*; Huart, L.*; Suzuki, Keiji*

Hoshasen Seibutsu Kenkyu, 59(2), p.134 - 156, 2024/06

no abstracts in English

Degradation of a lithium cobalt oxide cathode under high voltage operation at an interface with an oxide solid electrolyte

Ito, Kotaro*; Tamura, Kazuhisa; Shimizu, Keisuke*; Yamada, Norifumi*; Watanabe, Kenta*; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*

RSC Applied Interfaces (Internet), 1(4), p.790 - 799, 2024/04

https://doi.org/10.1039/D3LF00251A

LiCoO is widely used as a cathode material in lithium-ion batteries. However, the reversible capacity of LiCoO at high voltage is not well known because of the oxidative degradation of the electrolyte. In this study, a thin-film all-solid-state battery was fabricated with epitaxially grown LiCoO cathode and LiPO solid electrolyte as a model battery that operates stably at high voltages, ranging up to 4.6 V, without drastic degradation. However, the charge-discharge capacities of the battery decreased with cycling at 4.7 V. synchrotron X-ray diffraction studies revealed that LiCoO was deactivated via a change in its crystal structure to O1 type, with narrow interlayer distances, at 4.7 V. The reduced distance between the interlayers in the O1 structure possibly prevents the re-intercalation of Li ions, leading to irreversibility.