Grain refinement of dual phase steel maximizes deformation ability of martensite, leading to simultaneous enhancement of strength and ductility

Park, M.-H.*; 柴田 曉伸*; Harjo, S.; 辻 伸泰*

Acta Materialia, 292, p.121061_1 - 121061_13, 2025/06

https://doi.org/10.1016/j.actamat.2025.121061

Dual-phase (DP) steel, composed of soft ferrite and hard martensite, offers excellent strength-ductility balance and low cost. This study found that refining the DP microstructure enhanced both yield strength and strain hardening, improving strength and ductility. Digital image correlation (DIC) revealed strain localization in ferrite, but refinement reduced strain differences between ferrite and martensite, suppressing crack initiation. More ferrite/martensite interfaces promoted plasticity in martensite via enhanced deformation constraint. neutron diffraction showed martensite bore higher phase stress, which increased with refinement. By combining -DIC and neutron data, individual stress-strain curves for ferrite and martensite were constructed for the first time, explaining the strength-ductility synergy through interphase constraint. These findings offer guidance for designing heterostructured materials to overcome the strength-ductility trade-off.

Accelerating the adoption of advanced manufacturing technologies for Gen IV nuclear reactors through international collaboration

Van Rooyen, I. J.*; Ivan, L.*; Messner, M.*; Edwards, L.*; Abonneau, E.*; 上地 優; Lowe, S.*; Nilsson, K.-F.*; 岡島 智史; Pouchon, M.*; et al.

Proceedings of 4th International Conference on Generation IV and Small Reactors (G4SR-4), p.2 - 12, 2022/10

Developments in advanced manufacturing (AM) are occurring faster than the ability to introduce new materials and methods into design codes. Qualifying new AM technologies for use with nuclear design codes can be a long and complex process. The Generation IV International Forum (GIF) Advanced Manufacturing Materials Engineering Task Force (AMME-TF), focuses on how collaborative AM R&D could be used to decrease time to deployment of Gen-IV reactors. This paper provides a critical review of 2019 and 2021 surveys sampling nuclear reactor vendors, supply chain specialists, regulators, and other experts in GIF member countries. Both surveys confirmed that many AM technologies were considered opportunities by potential end users, although 90% of respondents identified the creation and approval of codes and standards as the greatest obstacle to their adoption. Industry prioritization on AM technologies, components and materials changed significantly during the three-year timespan. Additionally, the paper summarizes a 2021 modeling & simulation workshop that developed ideas on how to accelerate the qualification of AM and synthesizes the survey results and workshop conclusions into a review of critical research gaps and paths to address these gaps, particularly through international collaboration.

Search for the dark photon in , , , and decays at Belle

Park, S.-H.*; 谷田 聖; Belle Collaboration*; 他217名*

Journal of High Energy Physics (Internet), 2021(4), p.191_1 - 191_15, 2021/04

https://doi.org/10.1007/JHEP04(2021)191

We present a search for the dark photon in the decays, where subsequently decays to , , and . The search is performed by analyzing events collected by the Belle detector at the KEKB energy-asymmetric collider at the resonance. No signal is found in the dark photon mass range , and we set upper limits of the branching fraction of at the 90% confidence level. The products of branching fractions, and , have limits of the order of depending on the mass. Furthermore, considering decay rate to each pair of charged particles, the upper limits of are of the order of -. From the upper limits of , we obtain the Higgs portal coupling for each assumed dark photon and dark Higgs mass. The Higgs portal couplings are of the order of - at and - at .

Signatures of the vortical quark-gluon plasma in hadron yields

田屋 英俊*; Park, A.*; Cho, S.*; Gubler, P.; 服部 恒一*; Hong, J.*; Huang, X.-G.*; Lee, S. H.*; 門内 明彦*; 大西 明*; et al.

Physical Review C, 102(2), p.021901_1 - 021901_6, 2020/08

AA2020-0306.pdf:0.47MB

https://doi.org/10.1103/PhysRevC.102.021901

We investigate the hadron production from the vortical quark-gluon plasma created in heavy-ion collisions. Based on the quark-coalescence and statistical hadronization models, we show that total hadron yields summed over the spin components are enhanced by the local vorticity with quadratic dependence. The enhancement factor amounts to be a few percent and may be detectable within current experimental sensitivities. We also show that the effect is stronger for hadrons with larger spin, and thus propose a new signature of the local vorticity, which may be detected by the yield ratio of distinct hadron species having different spins such as and . The vorticity dependence of hadron yields seems robust, with consistent predictions in both of the hadron production mechanisms for reasonable values of the vorticity strength estimated for heavy-ion collisions.

Evaluation and modelling report of Task 9A based on comparisons and analyses of predictive modelling results for the REPRO WPDE experiments; Task 9 of SKB Task Force GWFTS - Increasing the realism in solute transport modelling based on the field experiments REPRO and LTDE-SD

Soler, J. M.*; Neretnieks, I.*; Moreno, L.*; Liu, L.*; Meng, S.*; Svensson, U.*; Trinchero, P.*; Iraola, A.*; Ebrahimi, H.*; Molinero, J.*; et al.

SKB R-17-10, 153 Pages, 2019/01

SKBタスクフォースは、亀裂性岩石中の地下水流動と物質移行のモデル化に関する国際フォーラムである。WPDE試験はフィンランドのオンカロ地下施設において実施された片麻岩中のマトリクス拡散試験である。複数の非収着性及び収着性のトレーサーを含む模擬地下水が試錐孔の試験区間に沿って注入された。タスク9Aは、WPDE試験で得られたトレーサー破過曲線に対する予測モデリングを行うことを目的とした。複数のチームが本タスクに参加し、異なるモデル化手法を用いた予測解析を行った。この予測解析の重要な結論は、試錐孔の開口部における地下水流動に関連する分散パラメータにモデル化結果が大きく影響されることである。マトリクス拡散及び収着に関連する破過曲線のテール部に着目すると、異なるチーム間の解析結果の差異は相対的に小さい結果となった。モデル化結果は、最終的に実測された破過曲線と比較された。

Assessment of operational space for long-pulse scenarios in ITER

Polevoi, A. R.*; Loarte, A.*; 林 伸彦; Kim, H. S.*; Kim, S. H.*; Koechl, F.*; Kukushkin, A. S.*; Leonov, V. M.*; Medvedev, S. Yu.*; 村上 匡且*; et al.

Nuclear Fusion, 55(6), p.063019_1 - 063019_8, 2015/06

https://doi.org/10.1088/0029-5515/55/6/063019

The operational space (-) for long pulse scenarios of ITER was assessed by 1.5D core transport modelling with pedestal parameters predicted by the EPED1 code. The analyses include the majority of transport models presently used for interpretation of experiments and ITER predictions. The EPED1 code was modified to take into account boundary conditions predicted by SOLPS for ITER. In contrast with standard EPED1 assumptions, EPED1 with the SOLPS boundary conditions predicts no degradation of the pedestal pressure as density is reduced. Lowering the plasma density to 5-6 10 m leads to an increased plasma temperature (similar pedestal pressure), which reduces the loop voltage and increases the duration of the burn phase to 1000 s with Q 5 for 13 MA at moderate normalised pressure ( 2). These ITER plasmas require the same level of additional heating power as the reference Q = 10 inductive scenario at 15 MA. However, unlike the "hybrid" scenarios considered previously, these H-mode plasmas do not require specially shaped q profiles nor improved confinement in the core for the transport models considered in this study. Thus, these medium density H-mode plasma scenarios with 13 MA present an attractive alternative to hybrid scenarios to achieve ITER's long pulse Q 5 and deserve further analysis and experimental demonstration in present tokamaks.

Evidence for a charge collective mode associated with superconductivity in copper oxides from neutron and X-ray scattering measurements of LaSrCuO

Park, S. R.*; 福田 竜生; Hamann, A.*; Lamago, D*; Pintschovius, L.*; 藤田 全基*; 山田 和芳*; Reznik, D.*

Physical Review B, 89(2), p.020506_1 - 020506_5, 2014/01

https://doi.org/10.1103/PhysRevB.89.020506

In superconducting copper oxides, some Cu-O bond-stretching phonons around 70 meV show anomalous giant softening and broadening of electronic origin, and electronic dispersions have large renormalization kinks near the same energy. These observations suggest that phonon broadening originates from quasiparticle excitations across the Fermi surface and the electronic dispersion kinks originate from coupling to anomalous phonons. We measured the phonon anomaly in underdoped ( = 0.05) and overdoped ( = 0.20 and 0.25) LaSrCuO by inelastic neutron and X-ray scattering with high resolution. Combining these and previously published data, we found that doping dependence of the magnitude of the giant phonon anomaly is very different from that of the ARPES kink, i.e., the two phenomena are not connected. We show that these results provide indirect evidence that the phonon anomaly originates from novel collective charge excitations as opposed to interactions with electron-hole pairs. Their amplitude follows the superconducting dome so these charge modes may be important for superconductivity.

Analysis of dismantling activities of rotary kiln for benchmark tests

立花 光夫; 出雲 沙理; 杉杖 典岳; Park, S.-K.*

DYNATOM (Internet), p.31 - 35, 2013/04

http://www.dynabondpowertech.com/images/stories/2013_DYNATOM_April/dynatom2013april.pdf

原子力機構(JAEA)は製錬転換施設を、KAERIはウラン転換施設を有している。これらの施設は、その役割を終え廃止措置を進めている。また、各組織は最適な廃止措置計画の作成及び効率的な解体作業を実施するために廃止措置エンジニアリングシステムの開発を進めている。そこで、双方の廃止措置エンジニアリンクシステムを検証するためにベンチマーク試験を開始した。本論文は、JAEA及びKAERIが有するロータリーキルンの解体作業について手順や実績データを比較した結果とJAEAによる管理データの計算結果について述べる。

Analysis of dismantling activities of rotary kiln for benchmark tests

立花 光夫; 出雲 沙理; 杉杖 典岳; Park, S.-K.*

Proceedings of American Nuclear Society Embedded Topical on Decommissioning, Decontamination and Reutilization and Technology Expo (DD&R 2012) (DVD-ROM), p.107 - 110, 2012/06

原子力機構は製錬転換施設を、KAERIはウラン転換施設を有している。これらの施設は、その役割を終え廃止措置を進めている。また、各組織は最適な廃止措置計画の作成及び効率的な解体作業を実施するために廃止措置エンジニアリングシステムの開発を進めている。そこで、双方の廃止措置エンジニアリンクシステムを検証するためにベンチマーク試験を開始した。本論文は、原子力機構及びKAERIが有するロータリーキルンの解体作業について手順や実績データを比較した結果と原子力機構による管理データの計算結果について述べる。

Study of ion-beam-induced damage and luminescence properties in terbium-implanted AlGaN

Park, J.-H.*; 若原 昭浩*; 岡田 浩*; 古川 雄三*; Kim, Y.-T.*; Chang, H.-J.*; Song, J.*; Shin, S.*; Lee, J.-H.*; 佐藤 真一郎; et al.

Japanese Journal of Applied Physics, 49(3), p.032401_1 - 032401_5, 2010/03

https://doi.org/10.1143/JJAP.49.032401

Terbium (Tb) ions were implanted into AlGaN epitaxial layers at room temperature to investigate ion-beam-induced damage and luminescence properties at various doses of - Tb/cm. Rutherford backscattering spectrometry/channeling (RBS/channeling) reveals that on-beam-induced damage level steeply increases and that the damage cannot be fully recovered even after rapid thermal annealing at 1100 C, when the dose exceeds Tb/cm. On the other hand, cathodoluminescence (CL) intensity related to Tb transitions increased initially and saturated above a dose of Tb/cm. The results suggest that Tb-related luminescence properties are much susceptible to defects and nonradiative defects, namely, Tb-defect complexes, are formed under low-dose conditions even at a very low structural defect density.