Masahiko Machida
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View article: High-resolution imaging by superconducting delay-line detector using 30ps operating readout circuit
High-resolution imaging by superconducting delay-line detector using 30ps operating readout circuit Open
A current-biased kinetic inductance detector CB-KID was proposed to observe an image of hot spots produced local stimuli on the orthogonal XY meanderlines. Under pulsed neutrons, the CB-KID system has two functions, i.e., not only as a del…
View article: Specific Heat Anomalies and Local Symmetry Breaking in (Anti-)Fluorite Materials: A Machine Learning Molecular Dynamics Study
Specific Heat Anomalies and Local Symmetry Breaking in (Anti-)Fluorite Materials: A Machine Learning Molecular Dynamics Study Open
Understanding the high-temperature properties of materials with (anti-)fluorite structures is crucial for their application in nuclear reactors. In this study, we employ machine learning molecular dynamics (MLMD) simulations to investigate…
View article: Neutron transmission imaging system with a superconducting kinetic inductance detector
Neutron transmission imaging system with a superconducting kinetic inductance detector Open
We optimized the design and operating conditions of our superconducting neutron detector to improve spatial resolution. We obtained the best spatial resolution of 10 μm when a Gd Siemens star pattern was mounted in close contact with the d…
View article: Selection method for observation points using Bayesian LASSO at estimating radiation source distribution from air dose rates
Selection method for observation points using Bayesian LASSO at estimating radiation source distribution from air dose rates Open
When we decommission a reactor building, it is essential to identify the radiation source distribution for safety. It has been reported that the source distribution can be predicted from the measured air dose rates at appropriate observati…
View article: Superconducting neutron transmission imaging for investigating a sequential change in phase separations of low-melting Wood’s metal
Superconducting neutron transmission imaging for investigating a sequential change in phase separations of low-melting Wood’s metal Open
We built a new cryostat system for a current-biased kinetic inductance detector (CB-KID) to be able to place a sample at room temperature for conducting the neutron transmission imaging experiments with pulsed neutrons. A Wood’s metal allo…
View article: Simulation study on 3H behavior in the Fukushima coastal region: Comparison of influences of discharges from the Fukushima Daiichi and rivers
Simulation study on 3H behavior in the Fukushima coastal region: Comparison of influences of discharges from the Fukushima Daiichi and rivers Open
The release of tritium (3H) to the ocean is planned on the coastal environment in the Fukushima coastal region from Spring or Summer of 2023. Before its release, we evaluate the effect of 3H discharges from the port of Fukushima Daiichi an…
View article: Promotive Effects of Siltfence on Deposition of Suspended Particles: Evaluations of Diffusion Suppression of Radionuclides in Rectangular Open Channel via Numerical Simulations
Promotive Effects of Siltfence on Deposition of Suspended Particles: Evaluations of Diffusion Suppression of Radionuclides in Rectangular Open Channel via Numerical Simulations Open
A siltfence is installed to prevent the spread of suspended sediments generated by engineering construction works in rivers and on the coast. Thus, the siltfence is regarded to be a tool to prevent radioactive materials adsorbed on suspend…
View article: Estimation of Temporal Variation of Discharged Inventory of Radioactive Strontium <sup>90</sup>Sr (<sup>89</sup>Sr) from Port of Fukushima Daiichi Nuclear Power Plant
Estimation of Temporal Variation of Discharged Inventory of Radioactive Strontium <sup>90</sup>Sr (<sup>89</sup>Sr) from Port of Fukushima Daiichi Nuclear Power Plant Open
We estimate the monthly discharged inventory of 90Sr from the port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2022 by the Voronoi tessellation method inside the port, following the monitoring of 90Sr seawater radi…
View article: Survey of Air Dose Rate Distribution Inside and Outside of Wooden Houses in Fukushima Prefecture: Actual Condition of Dose Reduction Factor
Survey of Air Dose Rate Distribution Inside and Outside of Wooden Houses in Fukushima Prefecture: Actual Condition of Dose Reduction Factor Open
Dose reduction factors of Japanese houses are important for estimating the levels of external exposure of returning residents. In 2019, a total of 19 wooden houses were surveyed in Iitate Village and Namie Town using a gamma plotter that c…
View article: Tritium Inventory and Its Temporal Variation in Fukushima Front Sea Area
Tritium Inventory and Its Temporal Variation in Fukushima Front Sea Area Open
We estimate the inventory of tritium in two sea areas corresponding to coastal and offshore ones around Fukushima Daiichi Nuclear Power Plant (1F) on the basis of the measured seawater tritium concentrations monitored constantly from 2013 …
View article: Spectrum prediction in X-ray fluorescence analysis using Bayesian estimation
Spectrum prediction in X-ray fluorescence analysis using Bayesian estimation Open
Reducing the measurement time is important in X-ray fluorescence (XRF) analysis. Micro-XRF and confocal-micro XRF analyses have been used to obtain elemental distributions. Because these techniques are performed in the scanning mode, reduc…
View article: Narrow-area Bragg-edge transmission of iron samples using superconducting neutron sensor
Narrow-area Bragg-edge transmission of iron samples using superconducting neutron sensor Open
This study investigates a current-biased kinetic inductance detector (CB-KID) performance by investigating Bragg-edge spectra from the restricted-area neuron transmission of materials. Iron samples with a size of 5 × 5 ×2 mm 3 were used as…
View article: Estimation of temporal variation of tritium inventory discharged from the port of Fukushima Dai-ichi Nuclear Power Plant:analysis of the temporal variation and comparison with released tritium inventories from Japan and world major nuclear facilities
Estimation of temporal variation of tritium inventory discharged from the port of Fukushima Dai-ichi Nuclear Power Plant:analysis of the temporal variation and comparison with released tritium inventories from Japan and world major nuclear facilities Open
We estimate monthly discharge inventory of tritium from the port of Fukushima Dai-ichi Nuclear Power Plant (1 F) from April 2011 to March 2020, using the Voronoi tessellation based on monitoring inside 1 F port and other techniques utilizi…
View article: Accumulation mechanisms of radiocaesium within lichen thallus tissues determined by means of in situ microscale localisation observation
Accumulation mechanisms of radiocaesium within lichen thallus tissues determined by means of in situ microscale localisation observation Open
Many lichens are well known to accumulate radiocaesium and, thus acting as biomonitors of contamination levels. However, the actual localisation and chemical forms of radiocaesium in contaminated lichens have not yet been elucidated becaus…
View article: Supercomputing Frontiers
Supercomputing Frontiers Open
As the share of supercomputers in Asia continues to increase, the relevance of supercomputing merits a supercomputing conference for Asia.Supercomputing Asia 2022 (SCA22) was an umbrella of notable supercomputing events that promoted a vib…
View article: High Performance Parallel LOBPCG Method for Large Hamiltonian Derived from Hubbard Model on Multi-GPU Systems
High Performance Parallel LOBPCG Method for Large Hamiltonian Derived from Hubbard Model on Multi-GPU Systems Open
The physical property of the Hubbard model can be understood by solving the eigenvalue problem for the Hamiltonian derived from the model. Since the Hamiltonian is a large sparse matrix, an iteration method is usually utilized for solving …
View article: Estimation of Temporal Variation of Discharged Tritium from Port of Fukushima Dai-ichi Nuclear Power Plant: Analysis of the Temporal Variation and Comparison with released Tritium from Japan and Major Nuclear Facilities Worldwide
Estimation of Temporal Variation of Discharged Tritium from Port of Fukushima Dai-ichi Nuclear Power Plant: Analysis of the Temporal Variation and Comparison with released Tritium from Japan and Major Nuclear Facilities Worldwide Open
We estimate the monthly discharge inventory of tritium from the port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2020 using the Voronoi tessellation scheme, following the tritium monitoring inside the port that sta…
View article: A modeling approach to estimate 3H discharge from rivers: Comparison of discharge from the Fukushima Dai-ichi and inventory in seawater in the Fukushima coastal region
A modeling approach to estimate 3H discharge from rivers: Comparison of discharge from the Fukushima Dai-ichi and inventory in seawater in the Fukushima coastal region Open
Estimation of 3H discharge from river catchments is important to evaluate the effect of Fukushima Dai-ichi discharge and future planned 3H release to the ocean on the coastal environment. Using a previously developed model based on the tan…
View article: Hydration structures of barium ions: Ab initio molecular dynamics simulations using the SCAN meta-GGA density functional and EXAFS spectroscopy studies
Hydration structures of barium ions: Ab initio molecular dynamics simulations using the SCAN meta-GGA density functional and EXAFS spectroscopy studies Open
Hydration structures of barium ion (Ba2+) were studied by ab initio molecular dynamics using the strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation (GGA) exchange-correlation (XC) functional and ex…
View article: Practical tests of neutron transmission imaging with a superconducting kinetic-inductance sensor
Practical tests of neutron transmission imaging with a superconducting kinetic-inductance sensor Open
Samples were examined using a superconducting (Nb) neutron imaging system employing a delay-line technique which in previous studies was shown to have high spatial resolution. We found excellent correspondence between neutron transmission …
View article: Evaluation of distributions on radioactive materials around the port of Fukushima Daiichi Nuclear Power Plant through both monitoring and numerical simulations on seawater flow
Evaluation of distributions on radioactive materials around the port of Fukushima Daiichi Nuclear Power Plant through both monitoring and numerical simulations on seawater flow Open
<p>A large amount of radionuclides has been released into the environment by the accident of Fukushima Daiichi Nuclear Power Plant (1F). About 10 years have passed since the accident, and the effects have significantly decreased. How…
View article: Machine learning potentials for tobermorite minerals
Machine learning potentials for tobermorite minerals Open
Molecular dynamics (MD) simulation is an important tool to understand the physical and chemical properties of cement hydrates at the atomic level. MD with the machine learning potential (MLP) is considered a promising approach for accurate…