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Microstructure evolution and mechanical properties of brazing joint for ultra-thin-walled Inconel 718 considering grain size effect and brazing temperature

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Chinese Journal of Aeronautics 2024年第2期37卷 541-556页

作者： Rui ZHAO Yueshuai sONG Hui kang Min WAN school of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Jiangxi Research Institute of Beihang University Jiangxi 330000China

The systematic investigation of the mechanical properties and microstructure evolution process of ultra-thin-walled Inconel 718 capillary brazing joints is of great significance because of the exceptionally high demands on its *** achieve this objective,this study investigates the impact of three distinct brazing temperatures and five typical grain sizes on the brazed joints’mechanical properties and microstructure evolution *** evolution analysis was conducted based on Electron Back scatter Diffraction(EBsD),scanning Electron Microscopy(sEM),X-Ray Diffraction(XRD),High-Resolution Transmission Electron Microscopy(HRTEM),and Focused Ion Beam(FIB).Besides,the mechanical properties and fracture behavior were studied based on the uniaxial tension tests and in-situ tension *** findings reveal that the brazing joint’s strength is higher for the fine-grain capillary than the coarse-grain one,primarily due to the formation of a dense branch structure composed of G-phase in the brazing *** effects of grain size,such as pinning and splitting,are amplified at higher brazing ***,micro-cracks initiate around brittle intermetallic compounds and propagate through the eutectic zone,leading to a cleavage fracture *** fracture stress of fine-grain specimens is higher than that of coarse-grain due to the complex micro-crack ***,this study contributes significantly to the literature by highlighting the crucial impact of grain size on the brazing properties of ultra-thin-walled Inconel 718 structures.

关键词： EYWORDs Ultra-thin-walled structure Brazing Inconel 718 Grain size effect Brazing temperature

Health-oriented strategies are needed to optimize China’s 2025 clean air action plan

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science Bulletin 2024年第13期69卷 2007-2008页

作者： Tao Xue Ning kang Wei Wan Tong Zhu Institute of Reproductive and Child Health/National Health Commission key Laboratory of Reproductive Health and Department of Epidemiology and Biostatistics/Ministry of Education key Laboratory of Epidemiology of Major Diseases(PkU) School of Public HealthPeking University Health Science CentreBeijing 100191China state Environmental Protection key Laboratory of Atmospheric Exposure and Health Risk Management Center for Environment and HealthPeking UniversityBeijing 100871China Advanced Institute of Information Technology Peking UniversityHangzhou 311215China Clean Air Asia Beijing 100600China College of Environmental sciences and Engineering Peking UniversityBeijing 100871China

Recently,China’s state Council issued the Continuous Improvement of Air Quality Action Plan(hereafter,the third action plan),which follows the Air Pollution Prevention and Control Action Plan(2013–2017)(hereafter,the first action plan)and the Three-Year Action Plan for Winning the Blue sky Defense Battle(2018–2020)(hereafter the second action plan).The first two action plans yielded nationwide health benefits[1–3],from improving lung function[4]to saving medical expenditures[5].Based on our previous estimates[6],due to reductions in the fine particulate matter(PM2.5)level,implementation of the first and second action plans was expected to increase life expectancy by 2.11 and 3.68 months.

关键词： action hereafter nationwide

Development of EPDM composites reinforced by CNTs@siO_(2)for thermal protection systems of aerospace propulsion:significant improvement in oxidation and ablation resistance properties

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Chinese Journal of Aeronautics 2024年第2期37卷 471-481页

作者： Li WANG Jiang LI kang LI Yiwei WANG Chenyang MA science and Technology on Combustion Internal Flow and Thermal-Structure LaboratoryNorthwestern Polytechnical UniversityXi’an 710072China

Carbon Nanotubes(CNTs)reinforced Polymer-Matrix Composites(PMCs)is widely used as insulation materials in thermal protection system of aerospace ***,CNTs are prone to oxidation and have high thermal conductivities,which makes it difficult to improve the ablation resistance of insulation materials that contain ***_(2)was encapsulated onto the surface of CNTs(CNTs@siO_(2)),which were then added to Ethylene Propylene Diene Monomer(EPDM)rubber to prepare the insulation *** analysis and ablation test were used to evaluate the resistance of the insulation materials to thermal oxidation and ***,scanning electron microscopy was performed to analyze their *** revealed that the addition of CNTs@siO_(2)could visibly reduce the effects of hot corrosion and ablation on insulation *** C-CNTs@siO_(2)-1 formulation had the best ablative ***,compared with the unencapsulated formulation(C-CNTs-10),the C-CNTs@siO_(2)-1 formulation reduced the line ablation rate by 51%to 0.0130 mm/s after oxygen-acetylene ***,the ablation mechanism was investigated based on the effects of the CNTs@siO_(2)additive on their ***,the improvement in ablation performance may be attributed to CNTs@siO_(2)-induced decreases in thermal conductivity,improvement in the hot corrosion resistance in the char layer,and changes in the microstructure.

关键词： Polymer-Matrix Composites(PMCs) Carbon Nanotubes(CNTs) Thermal properties Ablation Oxidation

socioeconomic inequalities in cancer incidence and mortality:An analysis of GLOBOCAN 2022

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Chinese Medical Journal 2024年第12期137卷 1407-1413页

作者： Wei Cao kang Qin Feng Li Wanqing Chen Office of Cancer screening National Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 100021China Hangzhou Center for Disease Control and Prevention HangzhouZhejiang 310021China The Third People’s Hospital of Xiaoshan HangzhouZhejiang 311251China

Background:Given the recent updates in cancer burden estimates by GLOBOCAN 2022,this study was undertaken to provide pertinent perspectives within the context of the Human Development Index(HDI)and major world ***:Datasets sourced from GLOBOCAN encompassed cancer cases and deaths across all cancer types in 2022,alongside projections up to *** incidences and deaths of the top 10 cancers within China and four distinct HDI-classified regions were compared using descriptive ***-standardized incidence rates(AsIRs)and mortality rates(AsMRs)worldwide for the most prevalent cancers in 2022 across ten largest economies and four-tier HDIs were *** top five cancer types concerning both incidence and mortality in China were delineated by sex and age ***:In males,prostate cancer predominated in countries with low,high(except China),and very high *** and liver cancers were prominent causes of death in countries with low *** females,breast and cervical cancers predominated in countries with low-to-medium *** and colorectal cancer incidence and deaths increased with high HDI for both *** and AsMRs for breast,prostate,lung,and colorectal cancers in the top 10 economies were higher than the global ***,liver,stomach,and cervical cancers in most Western countries exhibited lower *** China,hematologic malignancies(43%)were prevalent among children aged 0-14 years,whereas thyroid cancer led among adolescents and young adults aged 15-39 *** incidence and mortality,lung cancer predominated for individuals over 40 years,except for females aged 40-59 years,in whom breast cancer *** trends indicated substantial increases in new cancer cases(76.6%)and deaths(89.7%)over the next three ***:Infection-and poverty-related cancer burdens are offset by increased prostate,breast,colorectal,and lung cancer incidence associated with rapid societal and economic transi

关键词： Incidence Mortality Tumor burden China Human Development Index Hematologic neoplasms Lung neoplasms Breast neoplasms Colorectal neoplasms Thyroid neoplasms Liver neoplasms Prostatic neoplasms Early detection of cancer

Two Monte Carlo-based simulators for imaging-system modeling and projection simulation of flat-panel X-ray source

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Nuclear science and Techniques 2024年第7期35卷 31-46页

作者： Meng-ke Qi Ting He Yi-Wen Zhou Jing kang Zeng-Xiang Pan song kang Wang-Jiang Wu Jun Chen Ling-Hong Zhou Yuan Xu school of Biomedical Engineering Southern Medical UniversityGuangzhou510515China state key Laboratory of Optoelectronic Materials and Technologies Guangdong Province Key Laboratory of Display Material and TechnologySchool of Electronics and Information TechnologySun Yat-sen UniversityGuangzhou510275China Department of Radiotherapy Guangdong Provincial People’s Hospital(Guangdong Academy of Medical Sciences)Southern Medical UniversityGuangzhou510515China

The advantages of a flat-panel X-ray source(FPXs)make it a promising candidate for imaging *** imaging-system modeling and projection simulation are critical for analyzing imaging performance and resolving overlapping projection issues in *** conventional analytical ray-tracing approach is limited by the number of patterns and is not applicable to FPXs-projection ***,the computation time of Monte Carlo(MC)simulation is independent of the size of the patterned arrays in *** study proposes two high-efficiency MC projection simulators for FPXs:a graphics processing unit(GPU)-based phase-space sampling MC(gPsMC)simulator and GPU-based fluence sampling MC(gFsMC)*** two simulators comprise three components:imaging-system modeling,photon initialization,and physical-interaction simulations in the ***-system modeling was performed by modeling the FPXs,imaging geometry,and *** gPsMC simulator samples the initial photons from the phase space,whereas the gFsMC simulator performs photon initialization from the calculated energy spectrum and fluence *** entire process of photon interaction with the geometry and arrival at the detector was simulated in parallel using multiple GPU kernels,and projections based on the two simulators were *** accuracies of the two simulators were evaluated by comparing them with the conventional analytical ray-tracing approach and acquired projections,and the efficiencies were evaluated by comparing the computation *** results of simulated and realistic experiments illustrate the accuracy and efficiency of the proposed gPsMC and gFsMC simulators in the projection calculation of various phantoms.

关键词： Flat-panel X-ray source(FPXs) Imaging-system modeling Projection simulation Monte Carlo-based simulators

Emission wavelength selection via anomalous polarized fluorescence in ZnO-C nanowires

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Nano Research 2024年第5期17卷 4489-4497页

作者： Joon kiat kang kim Yong Lim Chorng Haur sow Department of Physics National University of SingaporeSingapore 117542Singapore

Defect fluorescence from high aspect ratio semiconductor nanowires typically displays a weak polarization parallel to the nanowire’s long axis due to dielectric mismatch in high aspect ratio ***,anomalous 2.2 eV defect fluorescence distinctly polarized perpendicular to the nanowire is observed and measured from carbon-incorporated zinc oxide *** observations are significant because polarized defect emissions with consistent polarization on a mesoscopic scale are *** a systematic study and comparison of experimental results with density functional theory calculations,an oriented defect complex comprising carbon substituting on an oxygen site and an oxygen vacancy(CO-VO)is deduced to be responsible for the anomalous yellow fluorescence,demonstrating a method for relating atomic-scale defect geometry to mesoscopic *** anomalous emission can appear in both green-and red-fluorescing nanowires grown with different carbon concentrations,verifying the independence and uniqueness of the 2.2 eV *** allows for polarization-dependent emission wavelength selection from a single nanowire.

关键词： anomalous polarization defects fluorescence zinc oxide carbon

Enhancement and Removal of PM_(2.5)by Cold and Warm Air Masses Accompanying Certain synoptic Weather systems across Hangzhou,China during 2014-2020

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Journal of Meteorological Research 2024年第3期38卷 620-634页

作者： Bu YU Feng CHEN Hanqing kang Bin ZHU Hongnian LIU Hangzhou Meteorological Bureau Hangzhou310051China Hangzhou International Urbanology Research Center for Urban Governance studies Hangzhou311121China Zhejiang Institute of Meteorological sciences Hangzhou310008China key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science&TechnologyNanjing210044China school of Atmospheric sciences Nanjing UniversityNanjing210023China

Local air pollution is strongly affected by synoptic weather systems,such as fronts,troughs,low-altitude vortices,or high-altitude ***,few studies have analyzed the meteorological properties of cold or warm air masses associated to these systems and their impact on local air *** this study,hourly observations of fine particulate matter(diameter of up to 2.5µm,i.e.,PM_(2.5)),wind(V),temperature(T),pressure(P),and precipitation(R),acquired in Hangzhou in 2014-2020,were *** this analysis,weather patterns were categorized into 27 types;89 and 94 cases illustrating the passage of warm and cold air masses over Hangzhou were identified,respectively;the influence of air mass temperature,wind speed,and wind direction on PM_(2.5) concentrations and local accumulation or removal was *** main results are as follows.(1)Pollution events occurred more frequently for cold than for warm air masses,but average pollutant concentration was lower for cold air masses;(2)48%of the cold air mass cases corresponded to PM_(2.5) decreases and 52%to PM_(2.5) increases,with strong cold air masses(ΔT_(24h)>4°C;∣V∣_(average)>4 m s^(−1))markedly reducing local pollution,but weak cold air masses(ΔT24hs^(−1))primarily inducing pollutant transport and accumulation;(3)for warm air masses,PM_(2.5)accumulation or removal occurred in 60%and 40%of the cases,respectively:warm air masses(ΔT24h>4°C)reduced the PM_(2.5) concentration whereas weaker winds(∣V∣_(average)s^(−1))increased it;and(4)PM_(2.5) concentration decreased sharply within 4 h after the passage of strong cold air masses,but more gradually within 14 h after the passage of strong warm air *** results considerably improve the current understanding of the influence of cold and warm air masses on local pollution patterns.

关键词： weather type air mass enhancement removal meteorological condition

Laser‑Induced and MOF‑Derived Metal Oxide/Carbon Composite for synergistically Improved Ethanol sensing at Room temperature

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Nano-Micro Letters 2024年第6期16卷 210-220页

作者： Hyeongtae Lim Hyeokjin kwon Hongki kang Jae Eun Jang Hyuk‑Jun kwon Department of Electrical Engineering and Computer science DGISTDaegu 42988South Korea Convergence Research Advanced Centre for Olfaction DGISTDaegu 42988South Korea

Advancements in sensor technology have significantly enhanced atmospheric ***,metal oxide and carbon(MO_(x)/C)hybrids have gained attention for their exceptional sensitivity and room-temperature sensing ***,previous methods of synthesizing MO_(x)/C composites suffer from problems,including inhomogeneity,aggregation,and challenges in ***,we introduce a refined method that employs a metal–organic framework(MOF)as a precursor combined with direct laser *** inherent structure of MOFs ensures a uniform distribution of metal ions and organic linkers,yielding homogeneous MO_(x)/C *** laser processing facilitates precise micropatterning(sensor rapidly detected ethanol gas even at room temperature(105 and 18 s for response and recovery,respectively),with a broad range of sensing performance from 170 to 3,400 ppm and a high response value of up to 3,500%.Additionally,this sensor exhibited enhanced stability and thermal resilience compared to previous MOF-based *** research opens up promising avenues for practical applications in MOF-derived sensing devices.

关键词： Metal-organic frameworks Metal oxide Carbon composite Laser Gas sensor

Transfer matrix method for free and forced vibrations of multi-level functionally graded material stepped beams with different boundary conditions

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Applied Mathematics and Mechanics(English Edition) 2024年第6期45卷 983-1000页

作者： Xiaoyang sU Tong HU Wei ZHANG Houjun kang Yunyue CONG Quan YUAN school of Civil Engineering and Architecture Guangxi UniversityNanning 530004China scientific Research Center of Engineering Mechanics Guangxi UniversityNanning 530004China state key Laboratory of Featured Metal Materials and Life-Cycle safety for Composite structures Guangxi UniversityNanning 530004China

Functionally graded materials(FGMs)are a novel class of composite materials that have attracted significant attention in the field of engineering due to their unique mechanical *** study aims to explore the dynamic behaviors of an FGM stepped beam with different boundary conditions based on an efficient solving *** the assumptions of the Euler-Bernoulli beam theory,the governing differential equations of an individual FGM beam are derived with Hamilton’s principle and decoupled via the separation-of-variable ***,the free and forced vibrations of the FGM stepped beam are solved with the transfer matrix method(TMM).Two models,i.e.,a three-level FGM stepped beam and a five-level FGM stepped beam,are considered,and their natural frequencies and mode shapes are *** demonstrate the validity of the method in this paper,the simulation results by ABAQUs are also *** this basis,the detailed parametric analyses on the frequencies and dynamic responses of the three-level FGM stepped beam are carried *** results show the accuracy and efficiency of the TMM.

关键词： transfer matrix method(TMM) free vibration forced vibration functionally graded material(FGM) stepped beam