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Zhang, H.*; 梅原 裕太郎*; 吉田 啓之; 森 昌司*
International Journal of Heat and Mass Transfer, 211, p.124253_1 - 124253_13, 2023/09
被引用回数：2 パーセンタイル：59.37(Thermodynamics)In this study, the characteristics of disturbance waves, including velocity, longitudinal size, and frequency, are comprehensively investigated by conducting gas-liquid upward annular flow experiments in a 5 mm tube through the constant electric current method (CECM). The film thickness time trace is recorded concerning time, and the information on disturbance waves is subsequently extracted. The effect of liquid and gas flow rate, density ratio, and surface tension on the disturbance wave is quantitatively analyzed. A predictive model of the wave velocity based on the shear stress balance of the liquid film is proposed. A physical model for wave frequency prediction is derived on the basis of the mass conservation equation. A simple empirical model with good prediction accuracy of wave frequency is also derived. Compared with existing correlations available in the literature, the newly derived models show better performance under a wide range of flow conditions.
O近藤 洋介*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; 馬場 秀忠*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
被引用回数：5 パーセンタイル：92.64(Multidisciplinary Sciences)非常に中性子が過剰な原子核Oは、陽子、中性子ともに魔法数であることから古くからその性質に興味が持たれていたが、酸素の最後の束縛核
Oよりも中性子が4個も多いため、これまで観測されてこなかった。この論文では、理化学研究所RIBFにて
Fからの1陽子ノックアウト反応によってOを生成し、そこから放出される中性子を測定することによって初めてその観測に成功した。核構造の観点からは、Oでは二重閉殻が保たれているか興味が持たれていたが、実験で得られた分光学的因子が殻模型計算で予言されて程度の大きいことから、閉殻構造をもたない可能性が高いことがわかった。
Ne at the transition into the island of inversion; Detailed structure study of NeWang, H.*; 安田 昌弘*; 近藤 洋介*; 中村 隆司*; Tostevin, J. A.*; 緒方 一介*; 大塚 孝治*; Poves, A.*; 清水 則孝*; 吉田 数貴; et al.
Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08
被引用回数：2 パーセンタイル：68.16(Astronomy & Astrophysics)Neからの1中性子除去反応を用いて、Neの詳細な
線分光を行った。平行運動量分布の解析に基づき、Neの準位構造とスピンパリティを決定し、初めて負のパリティ状態を同定した。測定された断面積と運動量分布から、N=20とN=28のシェルギャップの消失の証拠となる有意なintruder p-wave強度が明らかになった。束縛状態については、弱いf-waveの可能性のある強度が観測された。いくつかの有効相互作用を用いた大規模殻模型計算では、実験的に観測された大きなp-wave強度と小さなf-wave強度は再現されず、Ne同位体に沿った反転の島への遷移の完全な理論的記述への挑戦が続いていることを示している。
Zhang, H.*; 森 昌司*; 久野 努*; 吉田 啓之
International Journal of Multiphase Flow, 159, p.104342_1 - 104342_15, 2023/02
被引用回数：5 パーセンタイル：65.31(Mechanics)At the gas-liquid interface, disturbance waves with various heights commonly arise. Because the thin liquid film between two successive disturbance waves leads to the dryout on the heating surface and limits the performance of the heating components, complete knowledge of the film thickness and disturbance waves is crucial. However, most existing experimental data and analysis are limited to near atmospheric conditions, and the liquid gas density ratio is much higher than in practical nuclear applications. In this study, we use nitrogen gas and water under the system pressures of 0.2 and 0.4 MPa and HFC134a gas and water under the system pressure of 0.7 MPa. The density ratio can be varied between 32 and 434. Based on experimental results, two models are proposed to predict the averaged film thickness and wave height, which are then compared with previous data.
Xu, X.*; 大平 拓実*; Xu, S.*; 平田 研二*; 大森 俊洋*; 植木 洸輔*; 上田 恭介*; 成島 尚之*; 長迫 実*; 貝沼 亮介*; et al.
Advanced Materials & Processes, 180(7), p.35 - 37, 2022/10
Metallic biomaterials are widely used to replace or support failing hard tissues due to excellent mechanical properties and high wear resistance, with demand increasing as the global population continues to age. It is widely accepted that successful metallic biomaterials should have good biocompatibility, high corrosion resistance, and strong wear resistance. In addition, a low Young's modulus similar to human bone is now recognized as another important factor, in order to avoid bone atrophy due to the stress shielding effect. While the Young's modulus of stainless steels and conventional fcc CoCr alloys is as high as 190-240 GPa, for 
-type Ti-base alloys it is generally in the range of 50-80 GPa. Young's modulus values are as low as 35 GPa for Ti-Nb-Ta-Zr, close to that of human bone at approximately 10-30 GPa. However, Ti-base alloys come with the compromise of low wear resistance. In fact, alloys that feature a low Young's modulus along with high wear resistance have been difficult to realize. This article explores the recently developed bcc CoCr-base alloy Co-Cr-Al-Si as a potential solution to these issues, i.e., the difficulty in combining a low Young's modulus with high wear resistance, and the challenge of realizing large superelastic strains.
Xu, S.*; 大平 拓実*; 佐藤 駿介*; Xu, X.*; 大森 俊洋*; Harjo, S.; 川崎 卓郎; Seiner, H.*; Zoubkov
, K.*; 村上 恭和*; et al.
Nature Communications (Internet), 13, p.5307_1 - 5307_8, 2022/09
被引用回数：8 パーセンタイル：66.14(Multidisciplinary Sciences)Crystalline metals can have large theoretical elastic strain limits. However, a macroscopic block of conventional crystalline metals practically suffers a very limited elastic deformation of 
0.5% with a linear stress-strain relationship obeying Hooke's law. Here, we report on the experimental observation of a large tensile elastic deformation with an elastic strain of 
4.3% in a Cu-based single crystalline alloy at its bulk scale at room temperature. The large macroscopic elastic strain that originates from the reversible lattice strain of a single phase is demonstrated by in situ microstructure and neutron diffraction observations. Furthermore, the elastic reversible deformation, which is nonhysteretic and quasilinear, is associated with a pronounced elastic softening phenomenon. The increase in the stress gives rise to a reduced Young's modulus, unlike the traditional Hooke's law behaviour. The experimental discovery of a non-Hookean large elastic deformation offers the potential for the development of bulk crystalline metals as high-performance mechanical springs or for new applications via "elastic strain engineering."
Yakushev, A.*; Lens, L.*; D
llmann, Ch. E.*; Khuyagbaatar, J.*; J
ger, E.*; Krier, J.*; Runke, J.*; Albers, H. M.*; 浅井 雅人; Block, M.*; et al.
Frontiers in Chemistry (Internet), 10, p.976635_1 - 976635_11, 2022/08
被引用回数：9 パーセンタイル：79.28(Chemistry, Multidisciplinary)114番元素フレロビウム(Fl)は現在その化学的性質が研究されている最も重い元素である。Flに関する最初の化学実験では、Flは貴ガス的な性質を持つ元素であると報告された。一方、2番目の研究では、Flは揮発性金属の性質を示すと報告された。より信頼性の高い結論を得るため、我々は更なる実験的研究を行い、二酸化ケイ素と金表面におけるFlの吸着挙動を調べた。その結果、Flは揮発性金属の水銀よりも高い揮発性と低い反応性を示し、一方、貴ガスのラドンよりは反応性が高いことを明らかにした。
大平 拓実*; Xu, S.*; 平田 研二*; Xu, X.*; 大森 俊洋*; 植木 洸輔*; 上田 恭介*; 成島 尚之*; 長迫 実*; Harjo, S.; et al.
Advanced Materials, 34(27), p.2202305_1 - 2202305_11, 2022/07
被引用回数：12 パーセンタイル：87.73(Chemistry, Multidisciplinary)The demand for biomaterials has been increasing along with the increase in the population of elderly people worldwide. The mechanical properties and high wear resistance of metallic biomaterials makes them well-suited for use as substitutes or as support for damaged hard tissues. However, unless these biomaterials also have a low Young's modulus similar to that of human bones, bone atrophy inevitably occurs. Because a low Young's modulus is typically associated with poor wear resistance, it is difficult to realize a low Young's modulus and high wear resistance simultaneously. Also, the superelastic property of shape memory alloys makes them suitable for biomedical applications, like vascular stents and guide wires. However, due to the low recoverable strain of conventional biocompatible shape memory alloys, the demand for a new alloy system is high. The novel body-center-cubic cobalt-chromium-based alloys in this paper provide a solution to both of these problems. We believe our novel alloys are promising candidates for biomedical applications.
K
(Zn
Mn
)
As studied by X-ray magnetic circular dichroism and resonant inelastic X-ray scattering鈴木 博人*; Zhao, G.*; 岡本 淳*; 坂本 祥哉*; Chen, Z.-Y.*; 野中 洋亮*; 芝田 悟朗; Zhao, K.*; Chen, B.*; Wu, W.-B.*; et al.
Journal of the Physical Society of Japan, 91(6), p.064710_1 - 064710_5, 2022/06
被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)The magnetic properties and the electronic excitations of the new diluted magnetic semiconductor BaK(ZnMn)As have been studied by X-ray magnetic circular dichroism (XMCD) and resonant inelastic X-ray scattering (RIXS). The sum rule analysis of the XMCD spectra indicates that the Mn atoms are in the high-spin configurations of 
, whereas the presence of competing ferromagnetic and antiferromagnetic interactions between the Mn ions reduces the net spin moment. Based on a comparison of the RIXS line shapes with those of GaMnAs, it is concluded that the ground state of Mn in BaK(ZnMn)As consists of both the 
and 
electron configurations.
Zhao, Y.*; Suzuki, T.*; Iimori, T.*; Kim, H.-W.*; Ahn, J. R.*; 堀尾 眞史*; 佐藤 祐輔*; 深谷 有喜; Kanai, T.*; Okazaki, K.*; et al.
Physical Review B, 105(11), p.115304_1 - 115304_8, 2022/03
被引用回数：1 パーセンタイル：17.38(Materials Science, Multidisciplinary)本研究では、時間・角度分解光電子分光を用いて、SiC基板上に作製したグラフェン層におけるキャリアダイナミクスについて調べた。光ポンピング後の準結晶グラフェンのディラックバンドでは、電子ドーピングに層依存性が観測された。また、光誘起キャリア輸送量は基板からの距離に依存することがわかった。フラット基板及びステップ基板上の単層グラフェンの結果から、キャリアの生成源は界面のステップ状態に由来することがわかった。本メカニズムは、密度汎関数計算による電子構造を基にした動的モデルにより記述できる。
Yao, Y.*; Cai, R.*; Yang, S.-H.*; Xing, W.*; Ma, Y.*; 森 道康; Ji, Y.*; 前川 禎通; Xie, X.-C.*; Han, W.*
Physical Review B, 104(10), p.104414_1 - 104414_6, 2021/09
被引用回数：2 パーセンタイル：7.92(Materials Science, Multidisciplinary)We report the experimental observation of half-integer Shapiro steps in the strong ferromagnetic Josephson junction (Nb-NiFe-Nb) by investigating the current-phase relation under radio-frequency microwave excitation. The half-integer Shapiro steps are robust in a wide temperature range from T = 4 to 7 K. The half-integer Shapiro steps could be attributed to co-existence of 0- and 
-states in the strong ferromagnetic NiFe Josephson junctions with the spatial variation of the NiFe thickness. This scenario is also supported by the high-resolution transmission electron microscopy characterization of the Nb/NiFe/Nb junction.
山中 謙太*; 黒田 あす美*; 伊藤 美優*; 森 真奈美*; Bian, H.*; 菖蒲 敬久; 佐藤 茂男*; 千葉 明彦*
Additive Manufacturing, 37, p.101678_1 - 101678_12, 2021/01
被引用回数：23 パーセンタイル：86.72(Engineering, Manufacturing)Ti-6Al-4V alloy is widely used in aerospace and biomedical industries, and its preparation using additive manufacturing techniques has recently attracted considerable attention. Herein, the dislocation structures developed during electron beam and laser beam powder-bed fusion (EB-PBF and LB-PBF, respectively) of the Ti-6Al-4V alloy were quantitatively examined via XRD line profile analysis. Accordingly, a higher dislocation density and finer crystallite size were observed at the top cross-section from the XRD line profile analysis, suggesting that the extent of phase decomposition depended on the duration of the exposure to the elevated temperature. Nonetheless, the saturated dislocation density was as high as 10
m
, where dislocation strengthening affected the overall strength of the EB-PBF specimen. Diffraction peaks of sufficient intensity that enabled the analysis of the dislocation structures in both the 
(')-matrix and the nanosized beta-phase precipitates at the (')-laths were obtained under high-energy synchrotron radiation; this revealed that the beta-phase had a much higher dislocation density than the surrounding (')-matrix. The enhanced dislocation accumulation in the nanosized -phase precipitates probably reflects the elemental partitioning that occurred during post-solidification cooling. The valuable insights provided in this study are expected to promote further development of alloy preparation using additive manufacturing processes.
Mn
As via soft X-ray magnetic circular dichroism竹田 幸治; 大矢 忍*; Pham, N. H.*; 小林 正起*; 斎藤 祐児; 山上 浩志; 田中 雅明*; 藤森 淳*
Journal of Applied Physics, 128(21), p.213902_1 - 213902_11, 2020/12
被引用回数：8 パーセンタイル：44.34(Physics, Applied)In order to understand the mechanism of the ferromagnetism in GaMnAs ((Ga,Mn)As), we have investigated the magnetic behavior on a microscopic level through systematic temperature (
) and magnetic-field (
) dependent soft X-ray magnetic circular dichroism (XMCD) experiments at the Mn 
absorption edges. The and dependences of XMCD intensities have been analyzed using a model consisting of the ferromagnetic (FM), paramagnetic, and superparamagnetic (SPM) components. Intriguingly, we have found a common behavior for the ferromagnetic ordering process in (Ga,Mn)As samples with different Mn concentrations and different Curie temperature (
) values. In particular, the SPM component develops well above , indicating that local FM regions are formed well above . The present findings indicate that the onset of ferromagnetic ordering is triggered by local electronic states around the substitutional Mn ions. Insight into the most representative ferromagnetic semiconductor, (Ga,Mn)As, will be an important step in understanding the mechanism of ferromagnetic ordering in various ferromagnetic semiconductor families.
-based materials; A View on valence-fluctuating EuIrSiUsachov, D. Yu*; Tarasov, A. V.*; Schulz, S.*; Bokai, K. A.*; Tupitsyn, I. I.*; Poelchen, G.*; Seiro, S.*; Caroca-Canales, N.*; Kliemt, K.*; Mende, M.*; et al.
Physical Review B, 102(20), p.205102_1 - 205102_11, 2020/11
被引用回数：9 パーセンタイル：53.43(Materials Science, Multidisciplinary)Using photoelectron diffraction (PED) and magnetic dichroism measurements, we explore the electronic and magnetic properties of the near-surface region of the valence-fluctuating material EuIrSi. We present and discuss the methodology for modeling of the 4 photoemission spectra, PED patterns and magnetic dichroism for rare-earth-based materials. For the Eu-terminated surface we found that the topmost Eu layer is divalent and exhibits a ferromagnetic order below 10 K. The valency of the next Eu layer, that is the 5th atomic layer, is about 2.8 at low temperature that is close to the valency in the bulk. The properties of the Si-terminated surface are drastically different. The first subsurface Eu layer (4th atomic layer below the surface) behaves divalently and orders ferromagnetically at much higher temperature. Experimental data indicate, however, that there is an admixture of trivalent Eu in this layer, resulting in its valency of about 2.1. The next deeper lying Eu layer (8th atomic layer below the surface) behaves mixed-valently, but the estimated valency of 2.4 is notably lower than the value in the bulk. The obtained results create a background for further studies of exotic surface properties of 4-based materials, and allow to derive information related to valency and magnetism of individual rare-earth layers in a rather extended area near the surface.
Al
GaO
scintillators by gamma-ray-induced positron annihilation lifetime spectroscopy藤森 公佑*; 北浦 守*; 平 義隆*; 藤本 將輝*; Zen, H.*; 渡邊 真太*; 鎌田 圭*; 岡野 泰彬*; 加藤 政博*; 保坂 将人*; et al.
Applied Physics Express, 13(8), p.085505_1 - 085505_4, 2020/08
被引用回数：5 パーセンタイル：33.01(Physics, Applied)CeドープGdAlGaO(Ce:GAGG)シンチレーターにおける陽イオン空孔の存在を明らかにするために、ガンマ線誘起陽電子消滅寿命測定(GiPALS)法による測定を行った。GAGGおよびCe:GAGGのGiPALSスペクトルに現れる成分は、バルク中と欠陥に捕獲された状態の陽電子消滅であり、その結果2つの指数減衰成分で構成されている。Ce:YAl
Oに関する研究から、欠陥に関連する構造はAl/Ga-Oの複空孔に起因するものであることが示唆された。この成分は、Ce, Mg:GAGGの方が小さくなり、その傾向はリン光の原因である浅い電子トラップの抑制と相関していた。酸素空孔は、Al/Ga空孔の電荷を補う役割をしている。欠陥に関連した構造における寿命は、Mg共ドーピングによって大幅に変化し、これは、酸素空孔とともに、Al/GaサイトでのMg
イオンとの集合体を考慮することで理解され、その結果、空孔クラスターが形成された。
Parker, J. D.*; 原田 正英; 林田 洋寿*; 廣井 孝介; 甲斐 哲也; 松本 吉弘*; 中谷 健; 及川 健一; 瀬川 麻里子; 篠原 武尚; et al.
Materials Research Proceedings, Vol.15, p.102 - 107, 2020/05
At the RADEN instrument, we take advantage of the accurate measurement of neutron energy by time-of-flight to perform energy-resolved neutron imaging using event-type neutron imaging detectors. We are continually working to improve these detectors for better spatial resolution and shorter measurement times and, as a user facility, to improve the ease-of-use of their control and analysis software. In particular, we are actively developing a 
He-based gaseous micropattern detector known as the Micro-pixel chamber based Neutron Imaging Detector (
NID). We have recently redesigned the NID control software to allow full integration into the automated experiment control system at RADEN, and we are carrying out optimization of the analysis algorithms for improved image quality and rate performance.
F from O
?Tang, T. L.*; 上坂 友洋*; 川瀬 頌一郎; Beaumel, D.*; 堂園 昌伯*; 藤井 俊彦*; 福田 直樹*; 福永 拓*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.
Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05
被引用回数：14 パーセンタイル：74.18(Physics, Multidisciplinary)中性子過剰核Fの構造が(
)反応で調査した。
軌道の分光学的因子は1.0
0.3と大きいが、一方で残留核であるOが基底状態である割合は約35%,励起状態は約0.65%であることが明らかになった。この結果は、Fのコア核Oは基底状態とは大きく異なり、Oの
軌道に陽子がひとつ加わることでOとFの中性子軌道が相当に変化していると推測される。これは酸素同位体ドリップライン異常のメカニズムである可能性がある。
and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCALens, L.*; Yakushev, A.*; Dllmann, Ch. E.*; 浅井 雅人; Ballof, J.*; Block, M.*; David, H. M.*; Despotopulos, J.*; Di Nitto, A.*; Eberhardt, K.*; et al.
Radiochimica Acta, 106(12), p.949 - 962, 2018/12
被引用回数：8 パーセンタイル：62.99(Chemistry, Inorganic & Nuclear)半減期4
49秒の短寿命同位体を用いて、水銀(Hg), タリウム(Tl), 鉛(Pb)の単一原子レベルでのSiO及びAu表面への固体吸着挙動をオンライン気相実験により調べた。超重元素Cn, Nh, Flの吸着エンタルピー測定のためのモデル実験として実施した。短寿命同位体はドイツ重イオン研究所の反跳核分離装置TASCAを用いて生成・分離した。生成核はヘリウムガス中に捕集された後、SiOあるいはAuで表面を覆われたSi検出器で作製されたガスクロマトグラフィーカラムへと導入した。短寿命Tl及びPb同位体は室温においてSiO表面に吸着し、Si検出器で測定することに成功した。一方、HgはSiO表面には吸着せず、Au表面に吸着した。この結果より、本実験のセットアップを用いることで短寿命Hg, Tl, Pb同位体の吸着特性を調べることができると証明され、この手法がCn, Nh, Flの実験にも適用できることが確認された。
末國 晃一郎*; Lee, C. H.*; 田中 博己*; 西堀 英治*; 中村 篤*; 笠井 秀隆*; 森 仁志*; 臼井 秀知*; 越智 正之*; 長谷川 巧*; et al.
Advanced Materials, 30(13), p.1706230_1 - 1706230_6, 2018/03
被引用回数：51 パーセンタイル：89.35(Chemistry, Multidisciplinary)高性能デバイスとしての熱電材料には、高い電気伝導度と低い熱伝導度という相反する要求を同時に満たす必要がある。本研究では、テトラへドライト(Cu,Zn)(Sb,As)
S
の結晶構造とフォノンダイナミクスを調べ、平面内に配位している銅原子のラットリング運動がフォノンを効率良く散乱することを見出した。これらの知見は、平面配位構造を有する高性能熱電材料の新たな開発指針を与えるものである。
田中 泰貴*; 成清 義博*; 森田 浩介*; 藤田 訓裕*; 加治 大哉*; 森本 幸司*; 山木 さやか*; 若林 泰生*; 田中 謙伍*; 武山 美麗*; et al.
Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01
被引用回数：18 パーセンタイル：74.47(Physics, Multidisciplinary)ガス充填型反跳生成核分離装置GARISを用いて
Ca + 
Pb, 
Ti + Pb, Ca + 
Cm反応系における準弾性散乱断面積の励起関数を測定した。これらのデータから融合障壁分布を導出し、チャンネル結合計算と比較した。Ca + Pb及びTi + Pb反応の障壁分布のピークエネルギーはそれらの反応系における2中性子蒸発断面積のピークエネルギーと良く一致し、一方Ca + Cm反応の障壁分布のピークエネルギーは4中性子蒸発断面積のピークエネルギーより少し下に現れることが判った。この結果は超重核合成の際の最適ビームエネルギーの予測に役立つ情報を与える。
