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Through-thickness heterogeneity in creep properties of friction stir welding 7B50-T7451 aluminum alloy thick plate joint:Experiments and modeling

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Chinese Journal of Aeronautics 2023年第6期36卷 378-389页

作者： huan WANG Weifeng xu Hongjian LU Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi'an 710072China

Through-thickness heterogeneity in creep properties of 7B50-T7451 aluminum alloy Friction Stir Welding(FSW)joints was investigated.Creep tests for three slices of the FSW joint were conducted at the temperature of 150-200℃ and applied stress of 60-225 MPa.The theta projection method was used to predict creep curves and minimum creep rate.The results show that the minimum creep rate increases and creep rupture life decreases with the increase of creep temperature and applied stress.Creep properties of the FSW joint deteriorate along the thickness direction from the top to the bottom.The threshold stress of all three slices of the FSW joint decreases with the increase of creep temperature and even disappears at 200℃ for the bottom slice.Creep activation energy approaches the activation energy of the lattice self-diffusion of aluminum.The value of true stress exponent for different slices is approximately equal to three.The predominant creep mechanism of the FSW joint is dislocation viscous glide by lattice self-diffusion.What is more,a constitutive model is established based on the theta method to accurately describe creep behavior ofdifferent slices of the FSW joint.

关键词： 7B50 high strength aluminum alloy Creep mechanism Creep modeling Friction stir welding Theta projection method Through-thickness heterogeneity

Clinical factors in predicting extreme preterm birth after cerclage

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Chinese Medical Journal 2023年第3期136卷 370-372页

作者： xuping Ye Yuezhou Yang Jun Li Kaikai Chang Huan Xu Department of Obstetrics Obstetrics and Gynecology Hospital affiliated to Fudan UniversityShanghai 200011China ShanghaiJiai Genetics and IVF Center Obstetrics and Gynecology Hospital affiliated to Fudan UniversityShanghai 200011China

To the Editor:Cerclage reduces the rate of preterm birth and improves perinatal outcomes in patients with cervical insufficiency.However,previous findings on this subject are discordant.Many clinical factors affect the outcome of cerclage.The morbidity rate of neonates born after 32 weeks of gestation is reported to be significantly reduced.[1]Therefore,the use of a gestational age of<32 weeks at delivery as the main efficacy measure for cerclage is of practical significance.

关键词： insufficiency cervical clinical

Prediction of Listed Company Innovation Ability Based on Attention Mechanism

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Journal of the Operations Research Society of China 2023年第1期11卷 177-187页

作者： huan-Yu Ma Yan xu Yu-Long Liu Department of Information and Computer Science University of Science and Technology BeijingBeijing100083China No.15 Research Institute China Electronics Technology Group CorporationBeijing100083China

Innovation is the center of the enterprise development, which is the main driving force of enterprises’ competitiveness. To evaluate the enterprises’ innovation ability, we firstly establish an index system which aims at analyzing the enterprise innovation ability. We also retrieve the data of the listed companies in Wind database from 2015 to 2019 and label them using factor analysis method. Then, a new deep learning classificational framework with attention mechanism and LSTM is established. The results show that when attention mechanism and LSTM are added into the convolutional neural network(CNN), the model’s prediction performance is better improved, and the accuracy, recall, precision and F-score are 0.914, 0.914, 0.916 and 0.915, respectively. This indicates the strong generalization ability of our new model. Finally, we also find that patents and R &D expenditures are the most important factor affecting the corporate innovation ability through SHapley Additive exPlanations(SHAP). Companies with more patents and R &D expenditures are generally considered to be more innovative.

关键词： Corporate innovation ability convolutional neural network Attention mechanism long short-term memory

Recent Advances of Single-atom Catalysts for Electro-catalysis

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Chemical Research in Chinese Universities 2022年第5期38卷 1146-1150页

作者： xu Guangyuan LIU Qin YAN huan Department of Chemical Physics University of Science and Technology of ChinaHefei 230026P.R.China

Single-atom catalysis is the“hot spot”in the field of catalysis due to the special geometries,electronic states,and their unique catalytic performance.Single-atom catalysts(SACs),isolated metal atoms dispersed on the support,show the highest atom efficiency,cutting down the potential cost in the industrial process.Consequently,this“homo-hetero”catalyst could be a promising candidate for the next-generation catalysts.The applications for the SACs are widely reported,like gas-solid reactions,organic reactions,and electro-catalysis.In this mini-review,we will focus on the recent work of SACs on electro-catalysis,including hydrogen evolution reaction(HER),oxygen reduction reaction(ORR),oxygen evolution reaction(OER),CO_(2) reduction reaction(CO_(2) RR),and nitrogen reduction reaction(NRR).

关键词： Sing-atom catalyst Hydrogen evolution reaction Oxygen reduction reaction Oxygen evolution reaction CO_(2)reduction reaction Nitrogen reduction reaction

Year-round changes in tropospheric nitrogen dioxide caused by COVID-19 in China using satellite observation

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Journal of Environmental Sciences 2023年第10期132卷 162-168页

作者： Zhenyu Luo Hailian xu Zhining Zhang Songxin Zheng huan Liu State Key Joint Laboratory of ESPC State Environmental Protection Key Laboratory of Sources and Control of Air Pollution ComplexSchool of EnvironmentTsinghua UniversityBeijing 100084China

The lockdown policy deals a severe blow to the economy and greatly reduces the nitrogen oxides(NOx)emission in China when the coronavirus 2019 spreads widely in early 2020.Here we use satellite observations from Tropospheric Monitoring Instrument to study the year-round variation of the nitrogen dioxide(NO_(2))tropospheric vertical column density(TVCD)in 2020.The NO_(2)TVCD reveals a sharp drop,followed by small fluctuations and then a strong rebound when compared to 2019.By the end of 2020,the annual average NO_(2)TVCD declines by only 3.4%in Chinamainland,much less than the reduction of 24.1%in the lockdown period.On the basis of quantitative analysis,we find the rebound of NO_(2)TVCD is mainly caused by the rapid recovery of economy especially in the fourth quarter,when contribution of industry and power plant on NO_(2)TVCD continues to rise.This revenge bounce of NO_(2)indicates the emission reduction of NOx in lockdown period is basically offset by the recovery of economy,revealing the fact that China’s economic development and NOx emissions are still not decoupled.More efforts are still required to stimulate low-pollution development.

关键词： COVID-19 Tropospheric NO2 TROPOMI Economy recovery Environment sustainability

Detection of digestive malignancies and post-gastrectomy complications via gastrointestinal fluid examination

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Frontiers of Medicine 2017年第1期11卷 20-31页

作者： Lei huan Aman xu Department of Gastrointestinal Surgery the First Affiliated Hospital of Anhui Medical University Hefei 230022 China German Cancer Research Center (DKFZ) Heidelberg Germany Department of General Surgery the Fourth Affiliated Hospital of Anhui Medical University Hefei 230022 China

To date, gastric carcinoma （GC） is one of the common and fatal digestive malignancies worldwide. The prognosis of GC is not always satisfactory because of late diagnosis. Scholars are keen on discovering novel accurate and economical biomarkers in body liquids for GC screening to detect and evaluate the lesion before the results of imaging techniques are obtained. While traditional serum assays have limited sensitivity and specificity, gastrointestinal juice may provide relevant specific biomarkers because of its close contact with the tumor. Herein, the current progress in the relationship between gastrointestinal fluid analyses and GC is systematically and comprehensively reviewed. The detection of gastric juice pH, fluorescence spectrum, cytology, Helicobacterpylori- associated markers, nitrosamines, conventional tumor markers, amino acids, proteomics, microRNAs, long noncoding RNAs, protein-coding genes, vitamin C, etc., and combination tests of different category markers could provide important diagnostic and prognostic clues for gastrointestinal diseases. Particularly, early GC may be efficiently screened using gastric juice. Gastrointestinal fluid examination could also predict the adverse effects of postgastrectomy, such as pancreatic leakage, fistula, and abscess. Gastric fluid markers should be further studied to reveal the early predicators of malignancy and complications. The methods for obtaining the samples of gastrointestinal juice with minimum incision should also be comprehensively investigated.

关键词： gastrointestinal fluid gastric carcinoma biomarker diagnosis prognosis gastrectomy adverse events

合法的边缘性参与:小学新教师集体教研参与的个案研究

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基础教育 2023年第1期20卷 50-59页

作者：许环环华东师范大学教育学部上海200062

合法的边缘性参与是新教师参与集体教研活动所要遵循的实践框架,是新教师快速成长、提升专业能力的重要且有效的途径。本研究通过对十二位小学新教师参与区域和学校集体教研活动过程进行访谈,发现因教师个人、所在学校以及所获资源支持... 详细信息

合法的边缘性参与是新教师参与集体教研活动所要遵循的实践框架,是新教师快速成长、提升专业能力的重要且有效的途径。本研究通过对十二位小学新教师参与区域和学校集体教研活动过程进行访谈,发现因教师个人、所在学校以及所获资源支持的差异,新教师在集体教研活动中呈现出主动边缘化、被动边缘化、主动去边缘化、被动去边缘化、合法的边缘化五种不同的样态。在分析五种状态的表现及原因的基础上,提出了促进新教师走向合法的边缘性参与的有效建议。

关键词：新教师集体教研合法的边缘性参与

Uncertainty Analysis and Optimization of Quasi-Zero Stiffness Air Suspension Based on Polynomial Chaos Method

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Chinese Journal of Mechanical Engineering 2022年第4期35卷 284-302页

作者： Xing xu huan Liu Xinwei Jiang Akolbire Vincent Atindana Automotive Engineering Research Institute Jiangsu University

To improve the vibration isolation performance of suspensions, various new structural forms of suspensions have been proposed. However, there is uncertainty in these new structure suspensions, so the deterministic research cannot reflect the performance of the suspension under actual operating conditions. In this paper, a quasi-zero stiffness isolator is used in automotive suspensions to form a new suspensionquasi-zero stiffness air suspension(QZSAS). Due to the strong nonlinearity and structural complexity of quasi-zero stiffness suspensions, changes in structural parameters may cause dramatic changes in suspension performance, so it is of practical importance to study the effect of structural parameter uncertainty on the suspension performance. In order to solve this problem, three suspension structural parameters d0, L0and Pc0are selected as random variables, and the polynomial chaos expansion(PCE) theory is used to solve the suspension performance parameters. The sensitivity of the performance parameters to different structural parameters was discussed and analyzed in the frequency domain. Furthermore, a multi-objective optimization of the structural parameters d0, L0and Pc0of QZSAS was performed with the mean and variance of the root-mean-square(RMS) acceleration values as the optimization objectives. The optimization results show that there is an improvement of about 8%-10% in the mean value and about 40%-55% in the standard deviation of acceleration(RMS) values. This paper verifies the feasibility of the PCE method for solving the uncertainty problem of complex nonlinear systems, which provide a reference for the future structural design and optimization of such suspension systems.

关键词： Air suspension Quasi-zero stiffness Polynomial chaos Uncertainty analysis Optimization

Graphene-induced enhanced anticorrosion performance of waterborne epoxy resin coating

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Frontiers of Materials Science 2020年第2期14卷 211-220页

作者： huan-Yan xu Dan LU xu HAN School of Materials Science and Engineering Harbin University of Science and TechnologyHarbin 150040China

In this work,waterborne epoxy resin E44 and graphene were employed as the matrix and nanofiller,respectively,to construct composite coatings with enhanced anticorrosion performance.XRD pattern and TEM observation indicated that the obtained graphene had a stacked structure of few-layer graphitic sheets with numbers of wrinkles.SEM observations revealed that no defects or microcracks existed on the surface of graphene/epoxy coatings and the internal micropores and microcracks were filled by graphene.FTIR spectra displayed that all the characteristic absorption peaks were attributed to the epoxy resin cured with polyamide.The Tafel polarization curves showed that,as the graphene addition amount increased,the corrosive potential increased and the corrosive current decreased.ESI results proved that the addition of graphene into epoxy coatings could not only increase the impedance arc in Nyquist plots,but also increase the impedance modulus at low frequency.Finally,the enhanced anticorrosion mechanism was proposed and discussed.

关键词： graphene waterborne epoxy anticorrosion electrochemical property