WikiEdge:ArXiv速遞/2025-03-03
摘要
- 原文標題：Investigation of O interstitial diffusion in $β$-Ga$_2$O$_3$: direct approach via master diffusion equations
- 中文標題：$β$-Ga$_2$O$_3$中氧間隙擴散的研究：通過主擴散方程的直接方法
- 發佈日期：2025-03-03 16:54:55+00:00
- 作者：Grace McKnight, Channyung Lee, Elif Ertekin
- 分類：cond-mat.mtrl-sci, physics.app-ph, physics.comp-ph
- 原文連結：http://arxiv.org/abs/2503.01735v1
中文摘要：單斜晶系的$\beta$-Ga$_2$O$_3$是一種有前景的寬帶隙半導體材料，由於其低對稱性的晶體結構，表現出複雜的各向異性擴散特性和質量傳輸行為。通過第一性原理計算結合主擴散方程，我們確定了中性氧間隙（$\text{O}_{\text{i}}^{0}$）和帶2-電荷的氧間隙（$\text{O}_{\text{i}}^{2-}$）的三維擴散張量。通過對構型空間的系統探索，我們識別了這兩種主要電荷態的穩定構型及其相應的形成能。通過考慮間隙或間隙跳躍，連接每一對低能構型，我們構建了三維擴散網絡，並評估了網絡中所有過渡路徑的跳躍勢壘。結合（i）缺陷構型及其形成能和（ii）連接它們的跳躍勢壘，我們通過Onsager方法分別構建並求解了$\text{O}_{\text{i}}^{0}$和$\text{O}_{\text{i}}^{2-}$的主擴散方程，得到了相應的三維擴散張量D$_{\text{O}_{\text{i}}}^{0}$和D$_{\text{O}_{\text{i}}}^{2-}$。$\text{O}_{\text{i}}^{0}$和$\text{O}_{\text{i}}^{2-}$都表現出沿$b$軸的最快擴散，顯示出顯著的各向異性。沿[100]和[$\overline{2}01$]方向預測的自擴散係數與之前報道的同位素標記氧示蹤實驗值吻合良好，突出了該方法在捕捉複雜擴散機制方面的可靠性。
摘要
- 原文標題：Fire danger likely overestimated in future climate projections
- 中文標題：未來氣候預測中火災危險可能被高估
- 發佈日期：2025-03-03 18:42:50+00:00
- 作者：Aurora Matteo, Ginés Garnés-Morales, Alberto Moreno, Ribeiro Andreia, César Azorín-Molina, Joaquín Bedia, Francesca Di Giuseppe, Robert J. H. Dunn, Sixto Herrera, Antonello Provenzale, Yann Quilcaille, Miguel Ángel Torres Vázquez, Marco Turco
- 分類：physics.ao-ph
- 原文連結：http://arxiv.org/abs/2503.01818v1
原文摘要：The Canadian Fire Weather Index (FWI) is widely used to assess wildfire danger and relies on meteorological data at local noon. However, climate models often provide only daily aggregated data, which poses a challenge for accurate FWI calculations in climate change studies. Here, we examine how using daily approximations for FWI95d -- the annual count of extreme fire weather days exceeding the 95th percentile of local daily FWI values -- compares to the standard noon-based approach for the period 1980--2023. Our findings reveal that FWI95d calculated with noon-specific data increased globally by approximately 65\%, corresponding to 11.66 additional extreme fire weather days over 44 years. In contrast, daily approximations tend to overestimate these trends by 5--10\%, with combinations involving minimum relative humidity showing the largest divergences. Globally, up to 15 million km$^2$, particularly in the western United States, southern Africa, and parts of Asia, exhibit significant overestimations. Among our daily approximation methods, the least biased proxy is the one that uses daily mean data for all variables. We recommend (i) prioritizing the inclusion of sub-daily meteorological data in future climate model intercomparison projects to enhance FWI accuracy, and (ii) adopting daily mean approximations as the least-biased alternative if noon-specific data are unavailable. 中文摘要：加拿大火災天氣指數（FWI）被廣泛用於評估野火風險，並依賴於當地中午的氣象數據。然而，氣候模型通常僅提供每日匯總數據，這為氣候變化研究中的準確FWI計算帶來了挑戰。本文研究了在1980年至2023年期間，使用每日近似值計算FWI95d（即超過當地每日FWI值第95百分位數的極端火災天氣日數的年計數）與標準基於中午的方法的比較。 我們的研究結果表明，使用中午特定數據計算的FWI95d在全球範圍內增加了約65%，相當於44年內增加了11.66個極端火災天氣日。相比之下，每日近似值往往會高估這些趨勢5-10%，其中涉及最低相對濕度的組合顯示出最大的差異。在全球範圍內，多達1500萬平方公里的地區，特別是美國西部、南部非洲和亞洲部分地區，顯示出顯著的高估。在我們的每日近似方法中，偏差最小的代理是使用所有變量的每日平均值的方法。 我們建議：（i）在未來的氣候模型比較項目中優先納入次每日氣象數據，以提高FWI的準確性；（ii）如果無法獲得中午特定數據，則採用每日平均值近似作為偏差最小的替代方案。
摘要
- 原文標題：A COMSOL framework for predicting hydrogen embrittlement -- Part II: phase field fracture
- 中文標題：用於預測氫脆的COMSOL框架——第二部分：相場斷裂
- 發佈日期：2025-03-03 17:39:02+00:00
- 作者：A. Díaz, J. M. Alegre, I. I. Cuesta, E. Martínez-Pañeda
- 分類：cs.CE, physics.app-ph, physics.chem-ph
- 原文連結：http://arxiv.org/abs/2503.01765v1
原文摘要：Prediction of hydrogen embrittlement requires a robust modelling approach and this will foster the safe adoption of hydrogen as a clean energy vector. A generalised computational model for hydrogen embrittlement is here presented, based on a phase field description of fracture. In combination with Part I of this work, which describes the process of hydrogen uptake and transport, this allows simulating a wide range of hydrogen transport and embrittlement phenomena. The material toughness is defined as a function of the hydrogen content and both elastic and elastic-plastic material behaviour are incorporated, enabling to capture both ductile and brittle fractures, and the transition from one to the other. The accumulation of hydrogen near a crack tip and subsequent embrittlement is numerically evaluated in a single-edge cracked plate, a boundary layer model and a 3D vessel case study, demonstrating the potential of the framework. Emphasis is placed on the numerical implementation, which is carried out in the finite element package COMSOL Multiphysics, and the models are made freely available. 中文摘要：預測氫脆需要一種穩健的建模方法，這將促進氫作為清潔能源載體的安全採用。本文提出了一種基於斷裂相場描述的氫脆通用計算模型。結合本工作的第一部分，該部分描述了氫的吸收和傳輸過程，這使得模擬廣泛的氫傳輸和氫脆現象成為可能。材料韌性被定義為氫含量的函數，並且結合了彈性和彈塑性材料行為，從而能夠捕捉到韌性斷裂和脆性斷裂以及兩者之間的轉變。在單邊裂紋板、邊界層模型和三維容器案例研究中，數值評估了裂紋尖端附近氫的積累和隨後的氫脆，展示了該框架的潛力。重點放在數值實現上，該實現是在有限元軟件COMSOL Multiphysics中進行的，並且模型是免費提供的。
摘要
- 原文標題：Improved sensitivity in the search for rare decays of Gd isotopes
- 中文標題：改進的Gd同位素稀有衰變搜索靈敏度
- 發佈日期：2025-03-03 15:20:27+00:00
- 作者：B. Lehnert, S. S. Nagorny, M. Thiesse, F. Ferella, M. Laubenstein, E. Meehan, S. Nisi, P. R. Scovell
- 分類：nucl-ex, hep-ex
- 原文連結：http://arxiv.org/abs/2503.01641v1
原文摘要：Gadolinium is widely used in multiple low-background experiments, making its isotopes accessible for rare decay searches both in-situ and through radiopurity screening data. This study presents an improved search for rare alpha and double-beta decay modes in $^{152}$Gd, $^{154}$Gd, and $^{160}$Gd isotopes using ultra-low background HPGe detectors at the Boulby Underground Screening (BUGS) facility. A total exposure of 6.7 kg$\cdot$yr of natural gadolinium was achieved using gadolinium sulfate octahydrate $(\text{Gd}_2(\text{SO}_4)_3 \cdot 8\text{H}_2\text{O})$ samples, originally screened for radiopurity prior to their deployment in the Super-Kamiokande neutrino experiment. Due to the detection methodology, only decays into excited states accompanied by gamma-ray emission were accessible. A Bayesian analysis incorporating prior experimental results was employed, leading to new lower half-life limits in the range of $10^{19} - 10^{21}$ years - an improvement of approximately two orders of magnitude over previous constraints. No statistically significant decay signals were observed. These results demonstrate the effectiveness of repurposing large-scale radiopurity screening campaigns for fundamental physics research. 中文摘要：釓被廣泛應用於多種低本底實驗中，使其同位素在原位和通過放射性純度篩選數據中進行稀有衰變搜索成為可能。本研究利用Boulby地下篩選設施（BUGS）的超低本底高純鍺探測器，對$^{152}$Gd、$^{154}$Gd和$^{160}$Gd同位素的稀有α衰變和雙β衰變模式進行了改進的搜索。使用硫酸釓八水合物$(\text{Gd}_2(\text{SO}_4)_3 \cdot 8\text{H}_2\text{O})$樣品，實現了總計6.7 kg$\cdot$年的天然釓暴露量，這些樣品最初在部署到超級神岡中微子實驗之前進行了放射性純度篩選。由於檢測方法的原因，只有伴隨γ射線發射的激發態衰變是可檢測的。採用了結合先前實驗結果的貝葉斯分析，得出了$10^{19} - 10^{21}$年範圍內的新下限半衰期——比之前的限制提高了大約兩個數量級。未觀察到統計上顯著的衰變信號。這些結果證明了將大規模放射性純度篩選活動重新用於基礎物理研究的有效性。
摘要
- 原文標題：A COMSOL framework for predicting hydrogen embrittlement -- Part I: coupled hydrogen transport
- 中文標題：用於預測氫脆的COMSOL框架——第一部分：耦合氫傳輸
- 發佈日期：2025-03-03 16:57:26+00:00
- 作者：A. Díaz, J. M. Alegre, I. I. Cuesta, E. Martínez-Pañeda
- 分類：cs.CE, physics.app-ph, physics.chem-ph
- 原文連結：http://arxiv.org/abs/2503.01736v1
原文摘要：Hydrogen threatens the structural integrity of metals and thus predicting hydrogen-material interactions is key to unlocking the role of hydrogen in the energy transition. Quantifying the interplay between material deformation and hydrogen diffusion ahead of cracks and other stress concentrators is key to the prediction and prevention of hydrogen-assisted failures. In this work, a generalised theoretical and computational framework is presented that for the first time encompasses: (i) stress-assisted diffusion, (ii) hydrogen trapping due to multiple trap types, rigorously accounting for the rate of creation of dislocation trap sites, (iii) hydrogen transport through dislocations, (iv) equilibrium (Oriani) and non-equilibrium (McNabb-Foster) trapping kinetics, (v) hydrogen-induced softening, and (vi) hydrogen uptake, considering the role of hydrostatic stresses and local electrochemistry. Particular emphasis is placed on the numerical implementation in COMSOL Multiphysics, releasing the relevant models and discussing stability, discretisation and solver details. Each of the elements of the framework is independently benchmarked against results from the literature and implications for the prediction of hydrogen-assisted fractures are discussed. The second part of this work (Part II) shows how these crack tip predictions can be combined with crack growth simulations. 中文摘要：氫對金屬的結構完整性構成威脅，因此預測氫與材料的相互作用是揭示氫在能源轉型中作用的關鍵。量化裂紋和其他應力集中點前材料變形與氫擴散之間的相互作用是預測和預防氫輔助失效的關鍵。在這項工作中，提出了一個廣義的理論和計算框架，首次涵蓋了：(i) 應力輔助擴散，(ii) 由於多種陷阱類型導致的氫捕獲，嚴格考慮了位錯陷阱位點的生成速率，(iii) 通過位錯的氫傳輸，(iv) 平衡（Oriani）和非平衡（McNabb-Foster）捕獲動力學，(v) 氫誘導軟化，以及 (vi) 氫吸收，考慮了靜水應力和局部電化學的作用。特別強調了在 COMSOL Multiphysics 中的數值實現，發佈了相關模型並討論了穩定性、離散化和求解器細節。框架的每個元素都與文獻中的結果進行了獨立基準測試，並討論了其對氫輔助斷裂預測的影響。本工作的第二部分（第二部分）展示了如何將這些裂紋尖端預測與裂紋擴展模擬相結合。
摘要
- 原文標題：Entropic learning enables skilful forecasts of ENSO phase at up to two years lead time
- 中文標題：熵學習能夠在長達兩年的提前時間內對ENSO相位進行熟練預測
- 發佈日期：2025-03-03 11:06:10+00:00
- 作者：Michael Groom, Davide Bassetti, Illia Horenko, Terence J. O'Kane
- 分類：physics.comp-ph, physics.ao-ph
- 原文連結：http://arxiv.org/abs/2503.01412v1
原文摘要：This paper builds on previous work in applying the entropy-optimal Sparse Probabilistic Approximation (eSPA) machine learning algorithm to the task of classifying the phase of ENSO, as determined by the Ni\~no3.4 index (Groom et al., Artif. Intell. Earth Syst., 2024). In this study, only observations and reanalyses from the satellite era are employed when training and validating the entropic learning models, and a full set of hindcasts are performed over the period from 2012 to 2022 (with a maximum lead time of 24 months) in order to determine out-of-sample skill. The features used for prediction are the leading principal components from a delay-embedded EOF analysis of global sea surface temperature, the vertical derivative of temperature at the equator in the tropical Pacific (a proxy for thermocline variability) and the zonal and meridional wind stresses in the tropical Pacific. Despite the limited number of data instances available for training (ranging from 350 monthly averages for the earliest hindcast to 520 as of December 2024), eSPA is shown to avoid overfitting in this small data regime and produces probabilistic forecasts with comparable skill to the combined (model-based) probabilistic forecasts produced from the International Research Institute for Climate and Society (IRI) ENSO prediction plume. At lead times longer than those available from the IRI plume, eSPA maintains skill out to 23 months in terms of the ranked probability skill score and 24 months in terms of the area under the ROC curve, all at a small fraction of the computational cost of running a dynamical ensemble prediction system. Furthermore, eSPA is shown to successfully forecast the 2015/16 and 2018/19 El Ni\~no events at 24 months lead time, the 2016/17, 2017/18 and 2020/21 La Ni\~na events at 24 months lead time and the 2021/22 and 2022/23 La Ni\~na events at 12 and 9 months lead time. 中文摘要：本文基於先前的工作，將熵最優稀疏概率近似（eSPA）機器學習算法應用於ENSO相位的分類任務，該任務由Niño3.4指數確定（Groom等人，Artif. Intell. Earth Syst., 2024）。在本研究中，訓練和驗證熵學習模型時僅使用了衛星時代的觀測和再分析數據，並在2012年至2022年期間進行了一整套後報（最大提前期為24個月），以確定樣本外技能。用於預測的特徵包括全球海表溫度的延遲嵌入EOF分析中的主要主成分、熱帶太平洋赤道處溫度的垂直導數（作為溫躍層變化的代理）以及熱帶太平洋的緯向和經向風應力。儘管可用於訓練的數據實例數量有限（從最早的後報的350個月平均值到截至2024年12月的520個月平均值），eSPA在這種小數據情況下避免了過擬合，並生成了與國際氣候與社會研究所（IRI）ENSO預測羽流生成的組合（基於模型的）概率預測具有可比技能的概率預測。在比IRI羽流更長的提前期下，eSPA在排名概率技能評分方面保持了23個月的技能，在ROC曲線下面積方面保持了24個月的技能，且計算成本僅為運行動態集合預測系統的一小部分。此外，eSPA成功預測了2015/16和2018/19年厄爾尼諾事件（提前24個月）、2016/17、2017/18和2020/21年拉尼娜事件（提前24個月）以及2021/22和2022/23年拉尼娜事件（提前12和9個月）。