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The Influence of the Sun and Moon on the Observation of Very High Energy Gamma-ray Sources Using EAS Arrays

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Research in Astronomy and Astrophysics 2024年第6期24卷 245-252页

作者： Tao wen Songzhan chen Benzhong Dai school of Physics and Astronomy Yunnan UniversityKunming 650091China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Tianfu Cosmic Ray Research Center Chengdu 610000China

With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the ***,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous *** this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is *** tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some *** absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are *** main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray *** influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.

关键词： astroparticle physics Sun:general methods:observational Sun:UV radiation

Robust fixed-time flight controller for a dual-system convertible UAV in the cruise mode

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Defence Technology（防务技术） 2024年第9期39卷 53-66页

作者： Lulu chen Zhenbao Liu Qingqing Dang wen Zhao wenyu chen school of Civil Aviation Northwestern Polytechnical UniversityXi'an 710072China Shenzhen Research Institute of Northwestern Polytechnical university Shenzhen 518057China Air and Missile Defense College Air Force Engineering UniversityXi'an 710051China

This paper investigates the attitude tracking control problem for the cruise mode of a dual-system convertible unmanned aerial vehicle(UAV)in the presence of parameter uncertainties,unmodeled uncertainties and wind ***,a fixed-time disturbance observer(FXDO)based on the bi-limit homogeneity theory is designed to estimate the lumped disturbance of the convertible UAV ***,a fixed-time integral sliding mode control(FXISMC)is combined with the FXDO to achieve strong robustness and chattering ***-limit homogeneity theory and Lyapunov theory are applied to provide detailed proof of the fixed-time ***,numerical simulation experimental results verify the robustness of the proposed algorithm to model parameter uncertainties and wind *** addition,the proposed algorithm is deployed in a open-source UAV autopilot and its effectiveness is further demonstrated by hardware-in-the-loop experimental results.

关键词： Convertible UAV Flight control Disturbance observer Fixed-time control

Process-driven susceptibility assessment of glacial lake outburst debris flow in the Himalayas under climate change

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Advances in Climate Change Research 2024年第3期15卷 500-514页

作者： Bin ZHOU Qiang ZOU Hu JIANG Tao yang wen-Tao ZHOU Si-Yu {2. Hong-Kun YAO Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China university of Chinese Academy of Sciences Beijing 100049China school of Environment and Resource Southwest University of Science and TechnologyMianyang 621010China

Global warming is causing glaciers to retreat and glacial lakes to expand in the Himalayas,which amplifies the risk of glacial lake outburst debris flows(GLODFs)and poses a significant threat to downstream lives and ***,the complex interplay between GLODF occurrences and associated indicators,coupled with the lack of a comprehensive susceptibility indicator system that considers the entire GLODF process,presents a substantial challenge in assessing GLODF susceptibility in the *** study proposes a process-driven GLODF susceptibility assessment indicator system responding to climate change that considers the complete process of GLODF formation,incorporating relevant parameters about upstream,themselves,and downstream of glacial ***,to mitigate subjective factors associated with traditional evaluation methods,we developed three novel hybrid machine-learning models by integrating classic machine-learning algorithms with the whale optimization algorithm(WOA)to delineate the distribution of GLODF susceptibility in the *** the hybrid models effectively predicted the GLODFs occurrence,with the WOA-SVC model demonstrating the highest prediction *** 34%of the catchments exhibit high and very high susceptibility levels,primarily concentrated along the north and south sides of the Himalayan ridge,particularly in the eastern and central *** capturing the physical formation process of hazards,such as topographic potential(highest relative importance value of 40%),can precisely identify GLODF.A total of 12. catchments pose potential transboundary threats,with 2. classified as having a very high susceptibility level and 2. as having a high susceptibility ***,the border region between china and Nepal is a prominent hotspot for transboundary threats of *** findings can provide valuable clues for disaster prevention,mitigation,and cross-border coordination in the Himalayas.

关键词： Glacial lake outburst debris flow Susceptibility assessment Climate change Himalayas

Notably Accelerated Nano-Bainite Transformation via Increasing Undissolved Carbides Content on GCr15Si1Mo Bearing Steel

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Acta Metallurgica Sinica(English Letters) 2024年第4期37卷 703-712页

作者： Yan-Hui Wang Hua-Qiang Sun wen-Jing Feng Lei-Jie Zhao Xiang chen Qing-An chen Hai-Tao Sun Jian-Jun Wang Zhi-Nan {2. Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province School of Mechanical and Equipment EngineeringHebei University of EngineeringHandan056038China Collaborative Innovation Center for Modern Equipment Manufacturing of Jinan New Area Hebei University of EngineeringHandan056038China school of Materials Science and Engineering Tsinghua UniversityBeijing100084China Avic Shang da Superalloys Company Limited Xingtai054800China National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan UniversityQinhuangdao066004China

In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bainite were analyzed. The results demonstrated that after prolonged austempering at low temperatures, the mixed microstructure composed of nano-bainite (NB), undissolved carbides (UC), and retained austenite (RA) was obtained in GCr15SiMo steel. When the experimental steel was austenitized at 900 ℃, the undissolved carbides gradually dissolved until reaching a stable state with increasing holding time. Furthermore, at the same austempering temperature, despite different volume fractions of undissolved carbides in the substrate, the volume fractions of nano-bainite in the final microstructures remained essentially the same. Moreover, the higher the content of undissolved carbides in steel, the faster the transformation rate of nano-bainite and the shorter the total transformation time.

关键词： Nano-bainite Undissolved carbides Bainitic transformation kinetics Carbon concentration

Asymmetric radical allylation of β-keto esters with vinyl cyclopropanes by dual photoredox/nickel catalysis

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Science china Chemistry 2024年第11期67卷 3807-3816页

作者： wen-Yuan Qu Xue-Song Zhou wen-Jing Xiao Jia-Rong {2. Engineering Research Center of Photoenergy Utilization for Pollution Control and Carbon Reduction Ministry of EducationCollege of Chemistry Central China Normal University Wuhan Institute of Photochemistry and Technology Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province Gannan Normal University

Radical-involved allylation reactions have emerged as a powerful platform for construction of carbon-carbon and carbonheteroatom bonds, facilitating the strategic incorporation of diverse allyl moieties. Nevertheless, this burgeoning field still faces ongoing challenges, including limitations of radical precursors and coupling partners, and difficulties in achieving enantiocontrol. Herein, we report for the first time a highly enantioselective radical allylation involving β-keto esters with vinyl cyclopropanes utilizing a synergistic dual photoredox/nickel catalysis under visible light irradiation. The mild and redox-neutral catalytic protocol demonstrates an extensive substrate compatibility and good functional tolerance, providing access to enantioenriched β-keto esters featuring quaternary α-stereocenter with good yields and high enantioselectivities. Preliminary mechanistic studies have uncovered that the success of the reaction hinges on the dual roles of nickel catalyst, including in situ formation of photoredox sensitive substrate/Ni complex and the ensuing asymmetric radical addition step.

关键词： asymmetric allylation photoredox catalysis radical addition nickel catalysis β-keto esters vinyl cyclopropanes

Deep insight of unique phase transition behaviors and mechanism in Zr_(2.Co-H isotope system with ultra-low equilibrium pressure

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Rare Metals 2024年第1期43卷 212-224页

作者： yang Liu Pan-Pan Zhou Xue-Zhang Xiao Jia-cheng Qi Jia-Peng Bi Tiao Ying Xing-{2. Feng Yan Shi {2.-Hua Luo Li-Xin chen State Key Laboratory of Silicon Materials School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027China Institute of Materials China Academy of Engineering PhysicsMianyang 621907China Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province Hangzhou 310013China

Efficient capture,safe storage and release of tritium from the international thermonuclear experimental reactor(ITER) reaction exhaust gas is a perplexing problem,and the development of an efficient tritium-getter material with ultra-low hydrogenation equilibrium pressure is considered as a reliable *** this work,Zr_(2.Co alloy was selected as a tritium-getter material and prepared through induction levitation *** performance test results show that Zr_(2.Co exhibits an ultra-low hydrogenation equilibrium pressure of 3.2. × 10^(-6) Pa at 2.℃ and excellent hydriding kinetics under a low hydrogen pressure of 0.005 ***,unique phase transition behaviors were presented in Zr_(2.Co-H ***,Zr_(2.CoH_(5) formed by Zr_(2.Co hydrogenated at room temperature is initially decomposed into ZrH_(2. and ZrCoH_(3) at2.0 ℃.With the temperature increasing to 350 ℃,ZrCoH_(3)is dehydrogenated to ZrCo,and then ZrCo further reacts with ZrH_(2. at 650 ℃ to reform Zr_(2.Co and *** the staged phase transition pathways during dehydrogenation,the decomposition of Zr_(2.CoH_(5) occurs preferentially,which is well accordance with both the smallest reaction energy barrier and the maximum reaction spontaneity that are determined respectively from kinetics activation energy and thermodynamics Gibbs free ***,first principles calculation results indicate that the stronger binding of hydrogen in interstitial environments of ZrCoH_(3)and ZrH_(2. triggers the hydrogen-stabilized phase transformation of Zr_(2.CoH_(5).The unique phase transition mechanisms in Zr_(2.Co-H system can shed light on the further exploration and regulation of analogous staged phase transition of hydrogen storage materials.

关键词： Zr_(2.Co alloy Tritium-getter materials Ultralow equilibrium hydrogen pressure Phase transition mechanism

Highly Sensitive Ammonia Gas Sensors at Room Temperature Based on the Catalytic Mechanism of N,C Coordinated Ni Single-Atom Active Center

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Nano-Micro Letters 2024年第12期16卷 515-531页

作者： wenjing Quan Jia Shi Min Zeng wen Lv Xiyu {2. Chao Fan Yongwei Zhang Zhou Liu Xiaolu Huang Jianhua yang Nantao Hu Tao Wang Zhi yang National Key Laboratory of Advanced Micro and Nano Manufacture Technology Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China Department of Micro/Nano Electronics School of Electronic Information and Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240People’s Republic of China Shanghai Key Laboratory of Intelligent Sensing and Detection Technology School of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237People’s Republic of China

Significant challenges are posed by the limitations of gas sensing mechanisms for trace-level detection of ammonia(NH3).In this study,we propose to exploit single-atom catalytic activation and targeted adsorption properties to achieve highly sensitive and selective NH3 gas ***,Ni singleatom active sites based on N,C coordination(Ni-N-C)were interfacially confined on the surface of two-dimensional(2.)MXene nanosheets(Ni-N-C/Ti_(3)C_(2.Tx),and a fully flexible gas sensor(MNPE-Ni-N-C/Ti_(3)C_(2.Tx)was *** sensor demonstrates a remarkable response value to 5 ppm NH3(2..3%),excellent selectivity for NH3,and a low theoretical detection limit of 12.1 *** analysis by density functional calculation reveals that the Ni single-atom center with N,C coordination exhibits specific targeted adsorption properties for ***,its catalytic activation effect effectively reduces the Gibbs free energy of the sensing elemental reaction,while its electronic structure promotes the spill-over effect of reactive oxygen species at the gas-solid *** sensor has a dual-channel sensing mechanism of both chemical and electronic sensitization,which facilitates efficient electron transfer to the 2. MXene conductive network,resulting in the formation of the NH3 gas molecule sensing ***,the passivation of MXene edge defects by a conjugated hydrogen bond network enhances the long-term stability of MXene-based electrodes under high humidity *** work achieves highly sensitive room-temperature NH3 gas detection based on the catalytic mechanism of Ni single-atom active center with N,C coordination,which provides a novel gas sensing mechanism for room-temperature trace gas detection research.

关键词： Gas sensor Single atom Catalytic activation Targeted adsorption End-sealing passivation

Effect of V on high-temperature mechanical properties of Al-5Cu-1.5Ni alloy

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Journal of Iron and Steel Research International 2024年第7期31卷 1792-1810页

作者： Jun-ge Cui Yong-bin chen Xiang-zhou Fu Hai-long yang Han-zhang Wang An-min Li Li-{2. Pan school of Resources Environment and MaterialsGuangxi UniversityNanning 530004GuangxiChina State Key Laboratory of Featured Metal Materials and Life-Cycle Safety for Composite Structures Nanning 530004GuangxiChina Guangxi Higher Education Key Laboratory of Advanced Materials Nanning 530004GuangxiChina

The effects of V on microstructure,room temperature,and high-temperature(350℃)mechanical properties of Al-5Cu-1.5Ni alloy were *** results show that Al-5Cu-1.5Ni-xV alloys mainly compriseα-Al,Al_(2.Cu,Al_(3)(Ni,Cu)_(2.,Al_(3)Ni,Al7Cu4Ni,and Al_(10)V *** addition of V can signally refineα-Al dendritic structure,which improves the mechanical properties of the as-cast alloys at room and high *** T6 heat treatment(540℃/12.h/WC+170℃/8 h/AC),α-Al,network skeleton structure Al_(3)(Ni,Cu)_(2.,and Al_(10)V phases all show coarsening,while the fine nano-θ'-Al_(2.Cu precipitated from the matrix and dispersed *** introduction of V promotes the quantity of precipitatedθ'-Al_(2.Cu *** ultimate tensile strength of the heat-treated alloys at room and high temperatures is greatly improved compared to that of the as-cast *** highest high-temperature ultimate tensile strength of the alloys with V is 111.8 MPa,2..5%higher than that of the base *** analysis shows that the improvement of high-temperature mechanical properties after heat treatment is mainly due to the introduction of V,increasing the precipitated quantity of nano-θ'-Al_(2.Cu particles and improving its thermal *** dispersion strengthening effect ofθ'-Al_(2.Cu particles exceeds the weakening effect of other adverse microstructures on the mechanical properties.

关键词： Al-Cu-Ni-V alloy θ'-Al_(2.Cu phase Heat treatment Microstructure Mechanical property

Regulated reaction pathway of CO_(2.photoreduction into CH_(4)by metal atom pair sites

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Rare Metals 2024年第9期43卷 4620-4627页

作者： Dong-Po He Guang-Bing Huang Jun Hu yang Wu Xiao-Dong Li Qing-Xia chen Shan Zhu {2.-Sheng Yan Jun-Fa Zhu yang Pan Xing-chen Jiao Key Laboratory of Synthetic and Biological Colloids Ministry of EducationSchool of Chemical and Material EngineeringJiangnan UniversityWuxi 214122China Hefei National Research Center for Physical Sciences at Microscale National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei 230026China Max Planck Institute of Microstructure Physics Weinberg 206120 HalleGermany State Grid Anhui Electric Power Research Institute Hefei 230601China

The carbon dioxide(CO_(2.)reduction process involves complex protonation,making the resulting product often *** achieve the desired product,it is crucial to manipulate the reaction ***,we build the metal atom pair sites for selective CO_(2.photoreduction into *** a prototype,Ni atom pair sites loaded on the Mo S_(2.nanosheets were synthesized and verified by highresolution transmission electron microscopy(HRTEM),X-ray photoelectron spectroscopy(XPS)and X-rayabsorption near edge structure spectra(XANES).In-situ Fourier transform infrared spectroscopy(FTIR)monitors the*CHO group,a crucial intermediate in CH_(4)production,during CO_(2.photoreduction on the Ni-Mo S_(2.nanosheets,whereas this monitoring is not observed for the Mo S_(2.***,theoretical calculations disclose that over the Ni-Mo S_(2.nanosheet slab,the formation energy of*CHO intermediates is determined to be lower(0.585 e V)than the desorption energy of*CO intermediates for CO production(0.64 e V),implying the higher selectivity of CH_(4)production.

关键词： steps dioxide desired