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Microstructure and microtexture evolution characteristics of a powder metallurgy Ni-based superalloy during static recrystallization

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JOURNAL OF IRON AND STEEL RESEARCH INTERNATIONAL 2024年第9期31卷 2308-2325页

作者： Li, Zhi-qiang Wang, De-cheng zhai, yue-wen Jiang, Chao Zhou, Le-yu Zhou, Zhi-guang Wang, Hui-zhen Zhang, Zi-bo Yan, Lin Wang, Li-ping Yu, Guang Tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China Beijing Res Inst Mech & Elect Technol Co Ltd CAM Beijing 100083 Peoples R China China Acad Machinery Sci & Technol Grp Beijing 100044 Peoples R China Beijing Univ Technol Inst Adv Mfg & Intelligent Technol Beijing 100124 Peoples R China

Static recrystallization (SRX) characteristics of a powder metallurgy superalloy were investigated by isothermal compression at 1080-1170 degrees C under strain rates of 0.01-0.1 s(-1), strains of 0.1, 0.22, or 0.5, and holding time of 0-300 s. The impacts of temperature, strain rate, holding time, and strain on the SRXed grain size, volume fraction, and microtexture were explored by electron backscatter diffraction technique. It was found that temperature played a key role in these processes. As SRX progressed, the fiber parallel to the axis compression direction gradually weakened and was replaced by the fiber because was the preferred recrystallization orientation and grain growth direction for the Ni-based superalloy. Moreover, high temperatures and low strain rates promoted the formation of the fiber. Three nucleation mechanisms during SRX process were found: grain boundary bulging, primary twin assistance, and subgrain coalescence. Grain boundary bulging occurred under all process conditions; however, at low temperatures and high strain rates, the latter two mechanisms could provide additional nucleation modes. In addition, SRX size and volume fraction models were established.

关键词： Powder metallurgy Ni-based superalloy Static recrystallization Microtexture evolution Recrystallization mechanism Prediction model NICKEL-BASED SUPERALLOY DYNAMIC RECRYSTALLIZATION HOT DEFORMATION DISSOLUTION BEHAVIOR GRAIN-GROWTH MECHANISMS ALUMINUM TEXTURE STEEL TWINS

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On Some Sums Involving Small Arithmetic Functions

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Acta Mathematica Sinica,English Series 2024年第10期40卷 2497-2518页

作者： wen Guang zhai Department of Mathematics China University of Mining and Technology

Let f be any arithmetic function and define S_f（x）:=Σn≤xf （[x/n]）.If the function f is small,namely,f （n）﹤﹤ nε,then the error term E_f（x） in the asymptotic formula of S_f（x） has the form O(x1/2+ε).In this paper,we shall study the mean square of E_f（x） and establish some new results of E_f（x） for some special functions.

关键词： 11L07 11N37 asymptotic formula exponential sum Small arithmetic function

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On the global smooth solutions of 3D incompressible Hall-MHD equations

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Applied Mathematics(A Journal of Chinese Universities) 2024年第2期39卷 319-327页

作者： yue Gao-cheng SUN wen-da School of Mathematics Nanjing University of Aeronautics and AstronauticsNanjing 211106China

The present paper is devoted to the well-posedness issue for the 3D incompressible Hall-MHD system obtained from kinetic models. Our analysis strongly relies on the use of the Fourier analysis. We establish the global existence of smooth solutions for a class of large initial data, this result implies the initial velocity and magnetic field can be arbitrarily large.

关键词： 3D Hall-MHD well-posedness Fourier analysis

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Programmable silicon-photonic quantum simulator based on a linear combination of unitaries

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Photonics Research 2024年第8期12卷 1760-1767页

作者： yue YU YULIN CHI CHONGHAO zhai JIESHAN HUANG QIHUANG GONG JIANWEI WANG State Key Laboratory for Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871China Frontiers Science Center for Nano-optoelectronics&Collaborative Innovation Center of Quantum Matter Peking UniversityBeijing 100871China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China Yangtze Delta Institute of Optoelectronics Peking UniversityNantong 226010China Hefei National Laboratory Hefei 230088China Department of Electrical and Computer Engineering University of WashingtonSeattleWashington 98195USA China Mobile Research Institute Beijing 100053China

Simulating the dynamic evolution of physical and molecular systems in a quantum computer is of fundamental interest in many *** implementation of dynamics simulation requires efficient quantum *** Lie-Trotter-Suzuki approximation algorithm,also known as the Trotterization,is basic in Hamiltonian dynamics simulation.A multi-product algorithm that is a linear combination of multiple Trotterizations has been proposed to improve the approximation ***,implementing such multiproduct Trotterization in quantum computers remains challenging due to the requirements of highly controllable and precise quantum entangling operations with high success ***,we report a programmable integrated-photonic quantum simulator based on a linear combination of unitaries,which can be tailored for implementing the linearly combined multiple Trotterizations,and on the simulator we benchmark quantum simulation of Hamiltonian *** modify the multi-product algorithm by integrating it with oblivious amplitude amplification to simultaneously reach high simulation precision and high success *** quantum simulator is devised and fabricated on a large-scale silicon-photonic quantum chip,which allows the initialization,manipulation,and measurement of arbitrary four-qubit states and linearly combined unitary *** an example,the quantum simulator is reprogrammed to emulate the dynamics of an electron spin and nuclear spin coupled *** work promises the practical dynamics simulations of real-world physical and molecular systems in future large-scale quantum computers.

关键词： quantum Hamiltonian linearly

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Decadal Changes in Dry and Wet Heatwaves in Eastern China:Spatial Patterns and Risk Assessment

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Advances in Atmospheric Sciences 2024年第10期41卷 2011-2026页

作者： yue ZHANG wen ZHOU Ruhua ZHANG Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China CMA-FDU Joint Laboratory of Marine Meteorology Fudan UniversityShanghai 200438China Key Laboratory of Polar Atmosphere-ocean-ice System for Weather and Climate Ministry of EducationFudan UniversityShanghai 200438China

Under global warming,understanding the long-term variation in different types of heatwaves is vital for China’s preparedness against escalating heat *** study investigates dry and wet heatwave shifts in eastern China over recent *** trend analysis displays pronounced warming in inland midlatitudes and the Yangtze River Valley,with increased humidity in coastal *** results indicate intensifying dry heatwaves in northern China,while the Yangtze River Valley sees more frequent dry *** the other hand,Indochina and regions north of 25°N also experience intensified wet heatwaves,corresponding to regional humidity *** analysis is conducted based on different situations:strong,frequent dry or wet *** dry heatwaves are influenced by anticyclonic circulations over northern China,accompanied by warming SST anomalies around the coastal midlatitudes of the western North Pacific(WNP).Frequent dry heatwaves are related to strong subsidence along with a strengthened subtropical high over the *** and frequent wet heatwaves show an intensified Okhotsk high at higher latitudes in the lower troposphere,and a negative circumglobal teleconnection wave train pattern in the upper *** El Niño SST patterns are observed in two kinds of wet heatwave and frequent dry heatwave *** analysis indicates that El Niño events heighten the likelihood of these heatwaves in regions most at *** global warming continues,adapting and implementing mitigation strategies toward extreme heatwaves becomes crucial,especially for the aforementioned regions under significant heat stress.

关键词： decadal changes dry heatwave wet heatwave eastern China

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Pre-Cryogenian integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

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Science China Earth Sciences 2024年第4期67卷 899-918页

作者： Peiyuan HU Qingguo zhai Guochun ZHAO Peter A.CAWOOD yue TANG Yiming LIU Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China Department of Earth Sciences University of Hong KongPokfulam RoadHong Kong 999077China State Key Laboratory of Continental Dynamics Department of GeologyNorthwest UniversityXi’an 710069China School of Earth Atmosphere&EnvironmentMonash UniversityMelbourneVIC 3800Australia

The composition and geological evolution of pre-Cryogenian material in the Tibetan Plateau and its surrounding areas have played an important role in studying the formation and evolution of early supercontinents on *** paper systematically summarizes the characteristics of pre-Cryogenian sedimentation,paleontology,magmatism,and metamorphism in the Tibetan Plateau and its surrounding *** on existing data,the records of pre-Cryogenian sedimentation and paleontology are mainly concentrated in the Meso-Neoproterozoic,with relatively few records from the Paleoproterozoic or *** oldest geological record is the Hadean detrital zircons in the metamorphosed sedimentary rocks of the Himalaya and Qamdo areas(ca.4.0 Ga).The Tibetan Plateau and surrounding areas preserve records related to the formation and evolution of the Kenor supercraton,and the Columbia,Rodinia,and Gondwana ***-Cryogenian basements can be divided into three types:Tarim-,Yangtze-,and *** Tarim-type basement has a paleogeographic affinity with the northern margins of the Australian and Indian continents and lacks detrital zircon age peaks and magmatic-metamorphic records related to the Rodinia assembly(ca.1.3-0.9 Ga).The Yangtze-type basement records volcanic activity related to global cooling in the latest pre-Cryogenian period and contains Meso-Neoproterozoic stromatolite and micropaleoflora fossils,as well as magmaticmetamorphic records related to Rodinia assembly(ca.1.1-1.0 Ga).The Lhasa-type basement is characterized by Neoproterozoic rift-related sediment records(ca.900 Ma)and high-pressure metamorphic events(ca.650 Ma),with a prominent peak of detrital zircon ages of ca.1.2-1.1 *** is likely to have a paleogeographic affinity with the African continent.

关键词： Tibetan Plateau Pre-Cryogenian Sedimentation Fossils Paleogeographic evolution

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Cascade electrolysis and thermocatalysis: a reliable system for upgrading C1 to C4 hydrocarbons

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Rare Metals 2024年第1期43卷 410-412页

作者： Chao-yue Sun wen Li Hai-Qing Wang Institute for Advanced Interdisciplinary Research(iAIR) College of Chemistry and Chemical EngineeringUniversity of JinanJinan 250022China

The carbon cycle is important for maintaining a stable climate and carbon balance on Earth. Renewable-electricitydriven upcycling of carbon dioxide (CO_(2)) into value-added multi-carbon molecules is a potentially sus... 详细信息

关键词： cycling hydrocarbons enable

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Human disturbance exacerbated erosion and deposition in the karst peak-cluster depressions during the Ming and Qing dynasties

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Science China Earth Sciences 2024年第11期67卷 3550-3561页

作者： Shuai YUAN yuemin yue Xinbao ZHANG Lu WANG Lu zhai Kelin WANG Key Laboratory for Agro-Ecological Processes in Subtropical Region Institute of Subtropical Agriculture Chinese Academy of Sciences Huanjiang Observation and Research Station for Karst Ecosystems Chinese Academy of Sciences University of Chinese Academy of Sciences Institute of Mountain Hazards and Environment Ministry of Water Resources Chinese Academy of Sciences State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences

Under the background of large-scale ecological restoration, China's southwestern karst region has become a hotspot of global vegetation cover “greening” in the past 20 years. However, because of geological constraints, it is difficult to restore the forest landscapes in some areas. It is urgent to understand the impacts of human disturbances during the historical period on the difficult-to-forestation rocky-desertification areas of the karst region in order to guide future afforestation. In this study, we quantified the changes of specific sediment yield in typical karst depressions over the past 500 years by using137Cs,210Pb, and14C dating methods in karst depressions, and identified the main human disturbances related to historical erosion and sedimentation by combining with historical data. The results showed that the erosion and sedimentation of the three depressions in 1921–1963 were significantly higher than that in 1963–2021, and the sedimentation rate(0.64–1.33 cm a-1) and the specific sediment yield(2.51–13.11 t ha-1a-1) during Ming and Qing dynasties（1504–1812） were higher than the sedimentation rate(0.26–0.95 cm a-1) and specific sediment yield(0.95–6.99 t ha-1a-1) in the recent century（1921–2021）. Reconstruction data and literature from the Ming and Qing dynasties show an empirical link between changes in population, arable land, food, forest area,and deforestation events during the same period. It was found that the population and arable land in Guangxi increased more than three-fold and the forest area decreased significantly in the 17th century after the migration of the Yao ethnic group and the introduction of maize to the region, which may be the main reason for intensifying the erosion of depressions. This study is of great significance to understanding the evolution history of rocky desertification in this region and to answer the potential of afforestation.

关键词： Karst region 14C dating Peak-cluster depressions Ethnic minirity migration Specific sediment yield

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Rational design and energy catalytic application of high-loading single-atom catalysts

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Rare Metals 2024年第10期43卷 4844-4866页

作者： Zi-Wei Deng yue Liu Jie Lin wen-Xing Chen Energy and Catalysis Center School of Materials Science and EngineeringBeijing Institute of Technology Ningbo Institute of Materials Technology and Engineering Chinese Academy of Science

It is well known that single-atom catalysts(SACs)have become a hot topic in the field of catalysis due to their advantages such as 100% metal atom utilization efficiency,high catalytic activity and selectivity compared with conventional catalysts and nanocatalysts. However, the isolated metal atoms on SACs have thermodynamic instability and tend to agglomerate, which limit their catalytic ***, it is of great significance to synthesize stable and high-loading single-atom catalysts(HLSACs). In this paper,we review the research progress of HLSACs from two aspects:design and application. Firstly, we comprehensively introduce the synthesis strategies of HLSACs, namely, top-down and bottom-up methods. Secondly, we overview the application status of HLSACs in three fields: electrocatalysis, thermal catalysis and photocatalysis. Finally, we summarize the development prospects and challenges of HLSACs.

关键词： Design Electrocatalysis High-loading single-atom catalysts Photocatalysis Thermal catalysis

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Surface water resource attenuation attribution and patterns in Hai River Basin

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Science China Earth Sciences 2024年第5期67卷 1545-1560页

作者： Qingming WANG Yong ZHAO Hao WANG Jiaqi zhai yue ZHANG Fan HE Rong LIU Mengyang MA State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research(IWHR)Beijing 100038China Key Laboratory of Water Safety for Beijing-Tianjin-Hebei Region of Ministry of Water Resources Beijing 100038China General Institute of Water Resources and Hydropower Planning and Design Ministry of Water ResourcesBeijing 100120China

From 1956 to 2016,Hai River Basin suffered the most severe surface water resource attenuation among the 10 first-class river basins in *** on the surface water circulation process,and evolving characteristics of precipitation and underlying surface in Hai River Basin,this study attributed the causes of surface water resource attenuation to six primary impact factors,analyzed each factor's quantitative contribution,and revealed four patterns of surface water resource attenuation in Hai River *** pattern of the dominant factor:comparing the 1980–2000 period with the 1956–1979period,the variation of precipitation is the dominant factor of which contribution is 7 billion m^(3),accounting for 59%of total11.7 billion m^(3);comparing the 2001–2016 period with the 1956–1979 period,the increasing of vegetation cover in mountainous area is the dominant factor of which contribution is 2.78 billion m3,accounting for 51%of total 4.9 billion m^(3).The pattern of spatial distributions:comparing the 2001–2016 period with the 1956–1979 period,mountainous areas were more affected by increasing vegetation cover which for example contributed 42%in Luan River Basin mountainous;the plains were more impacted by farmland ridge interception which for example contributed 51%in Beisi River Basin *** pattern of attenuation trend:comparing the 2001–2016 period with the 1980–2000 period,surface water resources in mountainous areas continued to decline,owing to the increasing water consumption of large-scale vegetation restoration,while the influence of the underlying surface changes on surface water resources in plains areas tended to remain *** pattern of reversible change:among factors led to surface water resource attenuation,the human activity,including vegetation cover increase,farmland ridge interception,and urbanization expansion,contributed 36%of the attenuation,which resulted in the variation of precipitation-runoff *** study improved the traditiona

关键词： Hai River Basin Surface water resources Contribution decomposition Quantitative contribution Attenuation patterns

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