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CODEPOsITION OF ALUMINUM AND sILICON ON PURE MOLYBDENUM sUBsTRATE UsING HALIDE ACTIVATED PACK CEMENTATION TREATMENTs

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Acta Metallurgica sinica(English Letters) 2002年第2期15卷 167-171页

作者： J.L. Xu, F.s. liu, C.G. Zhou, s.K. Gong and H.B. Xu Department of Material science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China Department of Material science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

A multi-component diffusion coating has been developed to protect Mo-based alloys from high temperature environmental attack. Aluminum addition was made during the coating process to improve the oxidation resistance by developing hexagonal Mo(si, Al)2 through the development of the halide activated pack cementation coating process on pure Mo substrate. The results show that Mo(si, Al)2 formed as a main phase on the surface and a little amount of Mo5si3 also formed. The total thickness of coating is tens ofμm at 1373K. During the cyclic oxidation test at high temperature(at about 1323K in air), mullite (3Al2O3.2siO2) and some siO2 formed. The addition of Al is beneficial for Mosi2 coating and the Al-doped coating exhibited only a small weight gain and protected the Mo substrate, while the Mosi2 coating without Al suffered a significant weight loss, indicating a loss of volatile MoO3 after cycles.

关键词： multi-component coating Mo(si A1)2 halide activated pack cementation 3Al2 O3. 2siO2 oxidation resistance

Microstructure and Mechanical Property of Hot-Rolled Mg-2Ag Alloy Prepared with Multi-pass Rolling

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Acta Metallurgica sinica(English Letters) 2023年第2期36卷 335-342页

作者： H.Zhang H.L.Hao G.Y.Fu B.s.liu R.G.Li R.Z.Wu H.C.Pan school of Mechanical and Power Engineering Shenyang University of Chemical TechnologyShenyang110142China Key Laboratory of superlight Materials and surface Technology Ministry of EducationCollege of Materials Science and Chemical EngineeringHarbin Engineering UniversityHarbin150001China Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) Northeastern UniversityShenyang110819China

A conventional multi-pass rolling is designed to form different microstructures in a Mg-2Ag *** relationship between microstructure and mechanical property is *** result shows that twin-induced nucleation plays a prominent role for the dynamic recrystallization(DRX)behavior of the rolled Mg-2Ag *** DRXed grains distributed around elongated grains have random orientations but gradually turn to the concentrated orientation with strong basal texture when the rolling pass *** yield strength and ultimate tensile strength of rolled Mg-2Ag alloy gradually increase with increasing rolling *** elongation of rolled sample is gradually improved when the rolling pass increases from one to three,while a significant drop of elongation shows in the four-pass rolling *** strong basal texture,refined grains,high-density dislocations,and Ag segregation along grain boundaries are suggested to play a prominent role for enhancing the strength of Mg-Ag alloys,while the low-density dislocations,homogeneously fine-grained microstructure,and weak texture are critical for improving the ductility.

关键词： Magnesium alloy Conventional rolling Twinning Dynamic recrystallization Texture

sTUDY OF ANODIC OVERVOLTAGE IN NEODYMIUM ELECTROLYsIs

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Acta Metallurgica sinica(English Letters) 2003年第5期16卷 355-359页

作者： K.R. liu, J.s. Chen, Q. Han and X.J. Weischool of Materials and Metallurgy, Northeastern University, shenyang 110004, China school of Materials and Metallurgy Northeastern University Shenyang 110004 China

The anodic overvoltage of neodymium electrolysis was determined by slow scanning oscillograrn. The effects of some factors, i.e. the temperature, the anodic current density, the concentration of Nd2O3 and the components of the electrolyte were investigated and the approaches to decrease the anodic overvoltage were also discussed. The results show that the anodic overvoltage increases with the anodic current density and decreases with the increasing temperature. The linear relation between the anodic overvoltage and the current density corresponding to Tafel equation is determined to some extent. The anodic overvoltage decreases with the increasing concentrations of LiF and NdF3. It also decreases by controlling the anodic current density properly, increasing the temperature or the concentrations of LiF and NdF3 and the reducing polar distance.

关键词： neodymium electrolysis anodic overvoltage deposition voltage fluoride

Cross-scale mechanical softening of Marcellus shale induced by CO_(2)-water-rock interactions using nanoindentation and accurate grain-based modeling

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Underground space 2024年第6期19卷 26-46页

作者： Yiwei liu Quansheng liu Zhijun Wu shimin liu Yong Kang Xuhai Tang school of Civil Engineering Wuhan UniversityWuhan 430072China Department of Energy and Mineral Engineering G3 Center and EMS Energy InstituteThe Pennsylvania State UniversityUniversity ParkPA 16802USA school of Power and Mechanical Engineering Wuhan UniversityWuhan 430072China

Mechanical softening behaviors of shale in CO_(2)-water–rock interaction are critical for shale gas exploitation and CO_(2)*** work investigated the cross-scale mechanical softening of shale triggered by CO_(2)-water–rock ***,the mechanical softening of shale following 30 d of exposure to CO_(2)and water was assessed at the rock-forming mineral scale using *** mechanical alterations of rock-forming minerals,including quartz,muscovite,chlorite,and kaolinite,were analyzed and ***,an accurate grain-based modeling(AGBM)was proposed to upscale the nanoindentation *** models were generated based on the real microstructure of shale derived from TEsCAN integrated minerals analyzer(TIMA)digital *** parameters of shale minerals determined by nanoindentation served as input material properties for ***,numerical simulations of uniaxial compression tests were conducted to investigate the impact of mineral softening on the macroscopic Young’s modulus and uniaxial compressive strength(UCs)of *** results present direct evidence of shale mineral softening during CO_(2)-water–rock interaction and explore its influence on the upscale mechanical properties of *** paper offers a microscopic perspective for comprehending CO_(2)-water-shale interactions and contributes to the development of a cross-scale mechanical model for shale.

关键词： shale Cross-scale modeling Nanoindentation CO_(2)-water-rock interaction Mechanical softening

Design and synthesis of thiol-terminated imidothioether oligomer as thermally latent hardener and modifier for high-performance epoxy/thiol thermosets

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science China Chemistry 2024年第2期67卷 632-641页

作者： Xing liu Jianjun Zhou shumei liu Jianqing Zhao school of Materials science and Engineering South China University of TechnologyGuangzhou510640China Key Lab Guangdong High Property&Functional Polymer Materials Key Laboratory of Polymer Processing EngineeringMinistry of EducationGuangzhou510640China

Conventional base-catalyzed epoxy/aliphatic thiol systems have a poor storage stability,and are impossible to be one-pot systems.A widely accepted solution is to use the latent catalysts,which are usually insoluble anionic initiators sensitive to impurities and moisture,and have many limitations in practical *** this work,a soluble thiol-terminated imidothioether oligomer(TPI) was synthesized and used as a latent hardener and modifier to prepare one-pot epoxy/thiol systems without the latent *** latent behavior and curing mechanism of epoxy systems(EP/TPI series),consisted of bisphenol A diglycidyl ether(DGEBA),pentaerythritol tetrakis(mercaptoacetate)(PETMP) and TPI,were *** thiol exchange reaction between TPI and PETMP preceded the curing reaction of DGEBA,and produced aromatic thiols,which were unreactive at ambient conditions and reacted with DGEBA to form the thermosets at temperatures above 130 ℃.At the loading of 24.4 wt%TPI,the epoxy system(EP/TPI-3) had a shelf life of 13 days and was completely cured within 20 min at 180 ℃.Meanwhile,the catalyst-free curing process of EP/TPI-3 system was insensitive to impurities and ***,the thermal and mechanical properties of EP/TPI-3 thermoset were simultaneously improved,thereinto,the glass transition temperature,Young's modulus and ultimate tensile strength were increased by 16.7 ℃,12.9%,and 13.6%,respectively,compared with those of the commercial DGEBA/PETMP *** work shows that TPI has the potential to be a powerful alternative to commercial latent catalysts,and EP/TPI thermosets with high performance have broad application prospects.

关键词： thiol-terminated imidothioether oligomer epoxy systems thiol exchange reaction thermal latency high performance

An interpretable model for large-scale smart contract vulnerability detection

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Blockchain(Research and Applications) 2024年第3期5卷 130-139页

作者： Xia Feng Haiyang liu Liangmin Wang Huijuan Zhu Victor s.sheng City University of Macao Macao 999078China Jiangsu University Zhenjiang 212013China southeast University Nanjing 211189China Texas Tech University Lubbock 79409USA

smart contracts hold billions of dollars in digital currency,and their security vulnerabilities have drawn a lot of attention in recent *** methods for detecting smart contract vulnerabilities rely primarily on symbol execution,which makes them time-consuming with high false positive ***,deep learning approaches have alleviated these issues but still face several major limitations,such as lack of interpretability and susceptibility to evasion *** this paper,we propose a feature selection method for uplifting *** fundamental concept of this method is a feature selection algorithm,utilizing interpretation outcomes to select critical features,thereby reducing the scales of *** learning process could be accelerated significantly because of the reduction of the feature *** experiment shows that our proposed model performs well in six types of vulnerability *** accuracy of each type is higher than 93%and the average detection time of each smart contract is less than 1 ***,through our proposed feature selection algorithm,the training time of each type of vulnerability is reduced by nearly 80%compared with that of its original.

关键词： Blockchain Vulnerability detection smart contract

How to Construct a Lower Risk FOF Based on Correlation Network? The Method of Principal Component Risk Parity Asset Allocation

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Journal of systems science & Complexity 2024年第3期37卷 1052-1079页

作者： BAI Wei ZHANG Junting liu Haifei liu Kai school of Management and Engineering Nanjing UniversityNanjing 210093China Postdoctoral Workstation of Bank of Jiangsu Co. LtdNanjing 210006China College of Finance Nanjing Agricultural UniversityNanjing 210095China University of Prince Edward Island 550 University AveCharlottetownPE C1A4P3Canada

In order to build a low-risk Fund of Funds(FOF), from the perspective of correlation, the principal component factor is used to improve the traditional risk parity model. Principal component analysis is used to decompose the underlying assets and generate unrelated principal component factors,and then the authors can construct a principal component risk parity portfolio. The proposed empirical results based on China’s mutual fund market show that the performance of principal component risk parity portfolio(PCRPP) is better than that of equal weight portfolio(EWP) and traditional risk parity portfolio(RPP). That is to say, not only the PCRPP in this paper has much lower risk than EWP and RPP, but also slightly better than EWP and RPP in terms of average return. Moreover, the study of dividing the underlying assets shows that the PCRPP in this paper is not sensitive to the underlying assets. The PCRPP in this paper is better than EWP and RPP for both the better performing funds and the worse performing funds. In addition, the empirical results on dynamic portfolio adjustments show that it is not appropriate to adjust asset allocation too frequently when the expected rate of return is calculated using the arithmetic mean.

关键词： Fund of funds(FOF) mutual funds portfolio risk principal component analysis risk parity portfolio

China’s　environmental　scientific　research　and　technology　development:review　and　envisage

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Journal of Environmental sciences 1997年第3期9卷 123-131页

作者： liu Jian Bureau of s & T for Resources and Environment, Chinese Academy of sciences, Beijing 100864, China

The topic was concentrated on environmental technology development in China within the context of China's economic acceleration and reform. Firstly, cleaner technology should be adopted where possible in industrial production; secondly, eco agricultural technological system, especially biological technology, should be developed in agricultural production; thirdly, end of pipe solution should focus on waste utilization or recycling technology where appropriate clean technology does not exist; lastly but not the least, existing technologies to minimize eco environmental deterioration such as soil erosion, salinization, desertification and deforestation should also be extended and developed. The mentioned ways of environmental technology development can only be realized on the condition that a resource conservation based production system and life style could be established and appropriate policy secured.

关键词： China environment research technology development.

Real-World Evidence of Multiple Air Pollutants and Mortality:A Prospective Cohort study in an Oldest-Old Population

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Environment & Health 2024年第1期2卷 23-33页

作者： Linxin liu Yi Zeng John s.Ji Vanke school of Public Health and school of Medicine Tsinghua UniversityBeijingChina 100084 Center for the study of Aging and Human Development School of MedicineDuke UniversityDurhamNorth Carolina 27710United States Center for Healthy Aging and Development studies National School of DevelopmentPeking UniversityBeijingChina 100091 Vanke school of Public Health Tsinghua UniversityBeijingChina 100084

We aimed to report real-world longitudinal ambient air pollutants levels compared to WHO Air Quality Guidelines(AQG)and analyze multiple air pollutants’joint effect on longevity,and the modification and confounding from the climate and urbanization with a focus on the *** study included 13,207 old participants with 73.3%aged 80 and beyond,followed up from 2008 to 2018 in 23 Chinese *** used the Cox-proportional hazards model and quantile-based g-computation model to measure separate and joint effects of the multiple *** adjusted for climate and area economic factors based on a directed acyclic *** 2018,no participants met the WHO AQG for PM_(2.5) and O_(3),and about one-third met the AQG for NO_(2).The hazard ratio(HR)for mortality was 1.07(95%confidence interval-CI:1.05,1.09)per decile increase in all three pollutants,with PM_(2.5) being the dominant contributor according to the quantile-based g-computation *** the three-pollutant model,the HRs(95%CI)for PM_(2.5) and NO_(2) were 1.27(1.25,1.3)and 1.08(1.05,1.12)per 10μg/m3 increase,*** oldest-old experienced a much lower mortality risk from air pollution compared to the *** mortality risk of PM_(2.5) was higher in areas with higher annual average *** adjustment of road density considerably intensified the association between NO_(2) and *** ambient PM_(2.5) and O_(3) levels in China exceeded the WHO AQG target *** pollutants coexposure,confounding,and modification of the district economic and climate factors should not be ignored in the association between air pollution and mortality.

关键词： air quality multiple exposures climate district economic health equity