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Solidification microstructure formation in HK40 and HH40 alloys

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International Journal of Minerals,Metallurgy and Materials 2016年第4期23卷 442-448页

作者： xian-fei ding Dong-fang Liu Pei-liang Guo Yun-rong Zheng Qiang Feng National Center for Materials Service Safety University of Science and Technology Beijing Beijing Key Laboratory of Special Melting and Preparation of High-end Metal University of Science and Technology Beijing State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Melting and Casting Center Beijing Institute of Aeronautical Materials

The microstructure formation processes in HK40 and HH40 alloys were investigated through JmatP ro calculations and quenching performed during directional solidification. The phase transition routes of HK40 and HH40 alloys were determined as L → L ＋ γ→ L ＋ γ ＋ M_7C_3 →γ ＋ M_7C_3 →γ ＋ M_7C_3 ＋ M_（23）C_6→γ ＋ M_（23）C_6 and L → L ＋ δ→ L ＋ δ ＋ γ→ L ＋ δ ＋ γ ＋ M_（23）C_6→δ ＋ γ ＋ M_（23）C_6, respectively. The solidification mode was determined to be the austenitic mode（A mode） in HK40 alloy and the ferritic–austenitic solidification mode（FA mode） in HH40 alloy. In HK40 alloy, eutectic carbides directly precipitate in a liquid and coarsen during cooling. The primary γ dendrites grow at the 60° angle to each other. On the other hand, in HH40 alloy, residual δ forms because of the incomplete transformation from δ to γ. Cr_（23）C_6 carbide is produced in solid delta ferrite δ but not directly in liquid HH40 alloy. Because of carbide formation in the solid phase and no rapid growth of the dendrite in a non-preferential direction, HH40 alloy is more resistant to cast defect formation than HK40 alloy.

关键词： iron chromium nickel alloys solidification phase transitions carbides

Turning machining induced microstructural stability of a high Nb-containing TiAl alloy during high temperature exposure

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Rare Metals 2016年第1期35卷 77-84页

作者： Lu Fang Jun-Pin Lin Xiao-Chan Qiu Jin-Xiao Ou xian-fei ding State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing School of Architecture and Engineering Heilongjiang University National Center for Materials Service Safety University of Science and Technology Beijing

Turning machining induced microstructural instability was investigated in a fully lamellar Ti-45Al-8.5Nb-（W,B,Y） alloy during high temperature *** turning machining followed by thermal exposure at900 or 1000℃ for 100,300 and 500 h,a depth-dependent gradient microstructure with random orientations was produced in the region close to the machining *** typical layers,a fine-grained（FG） layer with equiaxed grains and a coarse-grained（CG） layer with elongated grains,are formed in this region in transversal *** thickness of the two layers is up to 120 urn after thermal exposure at 1000℃ for 500 h,which is less than the depth of the hardened region（200 μm） after turning *** of the new grains in FG and CG layers are constituted of γ single phase,while short α_2 segments and few B2 particles are precipitated at the γ/γ interface or inside the γ *** and phase boundary bulging are found to be the major mechanisms responsible for lamellar degradation in FG layer and CG layer,*** residual deformation energy stored is considered to be the main driving force of this process.

关键词： High Nb-containing TiAl alloy Residualdeformation energy Microstructural instability Recrystallization Phase transformation

Growth rate and composition of directionally solidified intermetallic TiAl–Nb alloys with different solidification conditions

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Rare Metals 2016年第1期35卷 54-64页

作者： Li-Wei Zhang Jun-Pin Lin xiang-Jun Xu Jian-Ping He xian-fei ding Xiao-Ou Jin State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Materials and Chemistry School Zhongyuan University of Technology National Center for Materials Service Safety University of Science and Technology Beijing School of Architecture and Engineering Heilongjiang University

Intermetallic Ti-xAl-8Nb（x = 41,43,45,47,49;at%） alloys were solidified unidirectionally upwards with a constant temperature gradient of G=3.8 K·mm^（-1）at wide range of growth rates of v=10-400 μm·s^（-1）using a Bridgman directional solidification（DS） *** parameters including the primary dendrite arm spacing（λ_1）,secondary dendrite arm spacing（λ_2）,dendrite tip radius（R） and mushy zone depth（d） were measured *** values of λ_1,λ_2,R and d decrease as the growth rate increases for a given composition（x）.The values of λ_1,λ_2,R and v increase with the increase in x value,while the value of d firstly increases and then decreases with the increase in x value for a given *** relationships between λ_1,λ_2 and R were analyzed by the linear *** average growth rate exponent of λ_1 is 0.29,which is in accordance with the previous experimental observations,and that of λ_2 is close to the previous experimental results,while those of R and d are lower than the results in other alloy *** addition,theoretical models for λ_1,λ_2 and R were compared with the experimental observations,and a comparison of the present experimental results with the theoretical models and previous experimental results was also made.

关键词： TiAl-Nb alloys Intermetallic Directionalsolidification Microstructural parameters Soluteconcentration

Effect of low high-density lipoprotein levels on mortality of septic patients: A systematic review and meta-analysis of cohort studies

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World Journal of Emergency Medicine 2020年第2期11卷 109-116页

作者： Shao-hua Liu Huo-yan Liang Hong-yi Li xian-fei ding Tong-wen Sun Jing Wang General ICU the First Affi liated Hospital of Zhengzhou UniversityHenan Key Laboratory of Critical Care MedicineZhengzhou 450052China Department of Respiratory Critical Care Medicine the First Affi liated Hospital of Zhengzhou UniversityZhengzhou 450052China

BACKGROUND:An increase in high-density lipoprotein(HDL)is well associated with a decreased cardiovascular risk,especially *** studies suggest that lower levels of HDL may also be associated with an increased risk of sepsis and an increased rate of mortality in septic ***,this conclusion remains ***:MEDLINE,EMBASE,and CENTRAL databases were searched from inception to September 30,*** studies were conducted to evaluate the correlation of lipoprotein levels and the risk and outcomes of sepsis in adult *** primary outcomes were the risk and mortality of ***:Seven studies comprising 791 patients were *** levels of HDL had no marked relevance with the risk of sepsis(odds radio[OR]for each 1 mg/dL increase,0.94;95%CI 0.86–1.02;P=0.078),whereas lower HDL levels were related to an increased mortality rate in septic patients(OR for below about median HDL levels,2.00;95%CI 1.23–3.24;P=0.005).CONCLUSION:This meta-analysis did not reveal a signifi cant association between lower HDL levels and an increase in the risk of sepsis,whereas it showed that lower HDL levels are associated with a higher mortality rate in septic adult *** findings suggest that HDL may be considered as a promising factor for the prevention and treatment of sepsis in the future.

关键词： High-density lipoprotein Sepsis Mortality Meta-analysis

Chemical composition analysis on industrial scale ingots and castings of TiAl alloys

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China Foundry 2020年第6期17卷 441-446页

作者： xian-fei ding Yi-qun Zhao Jia-bin Zuo Xin Feng Hai Nan Yong-feng Liang Yan-qing Su Cast Titanium Alloy R&D Center Beijing Institute of Aeronautical MaterialsBeijing 100095China Beijing Engineering Research Center of Advanced Titanium Alloy Precision Forming Technology Beijing 100095China BAIMTEC Material Co. Ltd.Beijing 100094China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of Technology HarbinHarbin150001China

The chemical composition variation of the TiAl-4722 alloys was examined in a batch of the industrial scale master ingots,and in the corresponding castings prepared by conventional vacuum arc remelting(VAR)combined with induction skull melting(ISM)and investment casting *** content changes of major elements and interstitial elements were evaluated based on the chemical analysis at the top and bottom of the ingots and *** show that the contents of C,N,H,Fe and Si have almost no change in the ingots and castings,suggesting that the chemical analysis on these elements can be based on the batch *** O content keeps almost the same in different ingots,but exhibits relatively large differences in castings,which was probably influenced by the reaction between the shell mold and the molten alloy,and the spalling of face coat of the shell mold during *** the major elements of Al,Nb and Cr,the composition difference between the top and the bottom of the ingots is less than that of the *** for the O element,the trend is different,especially for the castings,suggesting that the investment casting is a homogenization process for Cr and Nb,but a differentiation process for *** contents of major elements in castings fluctuate mainly in the same range as that in the ingots,indicating that the contents of the major elements are controllable during investment casting.

关键词： TiAl alloys melting casting chemical composition casting ingot

Effi cacy and safety of low-dose corticosteroids for acute respiratory distress syndrome:A systematic review and meta-analysis

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World Journal of Emergency Medicine 2021年第3期12卷 207-213页

作者： Yu-qing Cui xian-fei ding Huo-yan Liang Dong Wang Xiao-juan Zhang Li-feng Li Quan-cheng Kan Le-xin Wang Tong-wen Sun General ICU the First Affi liated Hospital of Zhengzhou UniversityHenan Key Laboratory of Critical Care MedicineZhengzhou Key Laboratory of SepsisHenan Engineering Research Center for Critical Care MedicineZhengzhou 450052China Biotherapy Center the First Affi liated Hospital of Zhengzhou UniversityZhengzhou 450052China Department of Pharmacy the First Affi liated Hospital of Zhengzhou UniversityZhengzhou 450052China School of Biomedical Sciences Charles Sturt UniversityWagga Wagga 2650Australia

BACKGROUND:There are confl icting results regarding whether corticosteroids have better effi cacy than placebo in acute respiratory distress syndrome(ARDS)***,we aim to further evaluate the effi cacy and safety of corticosteroids in adult ARDS ***:The databases,including Medline,EMBASE,and Cochrane Central Register of Controlled Trials(CENTRAL)in the Cochrane Library,were searched from their inception to May 2,*** controlled trials(RCTs)and observational cohort studies were selected to assess the use of corticosteroids in adult ARDS *** quality of the results was judged by the Grading of Recommendations Assessment,Development,and Evaluation(GRADE)*** inverse-variance method with random or fixed effects modeling was used to compute pooled odds ratio(OR),standardized mean diff erence(SMD),and their 95%confi dence interval(CI).RESULTS:Eight eligible RCTs and six cohort studies were *** use of corticosteroids was associated with reduced mortality(OR 0.57,95%CI 0.43-0.76,I2=35.1%,P=0.148)in ARDS patients,and the result was confirmed in the included cohort studies(OR 0.51,95%CI 0.27-0.95,I2=66.7%,P=0.010).The subgroup analysis stratified by the initiation time and duration of corticosteroid use showed that early ARDS and prolonged corticosteroid use had signifi cant survival benefits in the *** low-dose corticosteroid use was also associated with significantly more ventilator-free days and a reduced rate of new infections in ARDS ***:The low-dose corticosteroid therapy may be safe and reduce mortality,especially in patients with prolonged treatment and early ARDS.

关键词： Low-dose Corticosteroid Acute respiratory distress syndrome Mortality Systematic review Meta-analysis

Microstructures and phase transformation in directionally solidified TiAl-Nb alloys

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China Foundry 2020年第6期17卷 402-408页

作者： Fu-qiang Zhang xian-fei ding Hai Nan Ru-yue You Qiang Wang Jian-ping He Yan-qing Su Yong-feng Liang Jun-pin Lin State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Cast Titanium Alloy R&D Center Beijing Institute of Aeronautical MaterialsBeijing 100095China AECC Hunan Aviation Powerplant Research Institute Harbin 150001China National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyZhuzhou 412002China

Intermetallic Ti-45Al-8Nb-(W,B,Y)(at.%)and Ti-46Al-5Nb alloys are directionally solidified at a constant growth rate of 30μm·s-1 using a Bridgman type *** quenched microstructures and lengths of different phase regions were observed and measured after various growing times of 0-30 *** show that the phase transformations in different phase regions are mainly depending on the high temperature microstructure and the supercooling degree during quenching *** isothermal holding,the primary phase grows into the liquid phase,the dendrites change from equiaxed to columnar grains,and the length of the L+βphase region,L+β+αphase region and mushy zone varies,indicating that the entire directional solidification process can be described by a static equilibrium-nonequilibrium-dynamic equilibrium evolution *** addition,the gap between the original growth interface and front interface shows that the actual crystal growth rate is not equal to the drawing velocity during directional solidification.

关键词： TiAl alloys directional solidification quenched microstructure phase transformation

Communication Resource-Efficient Vehicle Platooning Control With Various Spacing Policies

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IEEE/CAA Journal of Automatica Sinica 2024年第2期11卷 362-376页

作者： Xiaohua Ge Qing-Long Han xian-Ming Zhang Derui ding IEEE School of Science Computing and Engineering TechnologiesSwinburne University of TechnologyMelbourne VIC 3122Australia

Platooning represents one of the key features that connected automated vehicles may possess as it allows multiple automated vehicles to be maneuvered cooperatively with small headways on roads. However, a critical challenge in accomplishing automated vehicle platoons is to deal with the effects of intermittent and sporadic vehicle-to-vehicle data transmissions caused by limited wireless communication resources. This paper addresses the co-design problem of dynamic event-triggered communication scheduling and cooperative adaptive cruise control for a convoy of automated vehicles with diverse spacing policies. The central aim is to achieve automated vehicle platooning under various gap references with desired platoon stability and spacing performance requirements, while simultaneously improving communication efficiency. Toward this aim, a dynamic event-triggered scheduling mechanism is developed such that the intervehicle data transmissions are scheduled dynamically and efficiently over time. Then, a tractable co-design criterion on the existence of both the admissible event-driven cooperative adaptive cruise control law and the desired scheduling mechanism is derived. Finally, comparative simulation results are presented to substantiate the effectiveness and merits of the obtained results.

关键词： Automated vehicles constant time headway spacing constant spacing cooperative adaptive cruise control event-triggered communication vehicle platooning

Attention Markets of Blockchain-Based Decentralized Autonomous Organizations

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IEEE/CAA Journal of Automatica Sinica 2024年第6期11卷 1370-1380页

作者： Juanjuan Li Rui Qin Sangtian Guan Wenwen ding fei Lin fei-Yue Wang State Key Laboratory of Multimodal Artificial Intelligence Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China Faculty of Innovation Engineering Macao University of Science and TechnologyMacao 999078China State Key Laboratory for Management and Control of Complex Systems Chinese Academy of SciencesBeijing 100190 Faculty of Innovation Engineering Macao University of Science and TechnologyMacao 999078China IEEE

The attention is a scarce resource in decentralized autonomous organizations(DAOs),as their self-governance relies heavily on the attention-intensive decision-making process of“proposal and voting”.To prevent the negative effects of pro-posers’attention-capturing strategies that contribute to the“tragedy of the commons”and ensure an efficient distribution of attention among multiple proposals,it is necessary to establish a market-driven allocation scheme for DAOs’***,the Harberger tax-based attention markets are designed to facilitate its allocation via continuous and automated trading,where the individualized Harberger tax rate(HTR)determined by the pro-posers’reputation is ***,the Stackelberg game model is formulated in these markets,casting attention to owners in the role of leaders and other competitive proposers as *** equilibrium trading strategies are also discussed to unravel the intricate dynamics of attention ***,utilizing the single-round Stackelberg game as an illustrative example,the existence of Nash equilibrium trading strategies is ***,the impact of individualized HTR on trading strategies is investigated,and results suggest that it has a negative correlation with leaders’self-accessed prices and ownership duration,but its effect on their revenues varies under different *** study is expected to provide valuable insights into leveraging attention resources to improve DAOs’governance and decision-making process.

关键词： Attention decentralized autonomous organizations Harberger tax Stackelberg game.