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Lightweight Al-Nb-Ti-V-Cr high entropy alloys with high hardness and enhanced mechanical properties via doping Co

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China Foundry 2025年

作者： Fang-dong Xu De-zhi chen Rui-run chen Bin Gan Jing-yue Yu National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of Technology Suzhou Laboratory

To develop high-hardness and high-strength lightweight high entropy alloys （LHEAs）,a series of CoxAlNbTiVCr alloys were *** phase constitution,distribution,and crystal structure of the Laves phase in alloys can be altered by adjusting the composition of HEAs,which in turn influences their mechanical *** Nb Ti VCr （x=0,0.5,1,1.5,and 2,atomic ratio percentage） LHEAs were designed and prepared to characterize the microstructure and tailor the mechanical *** introduction of Co changes the microstructure of LHEAs from a single B2 structure to a mixture dendrite structure,which consists of B2 phase,C14 and C15 Laves *** the C14 and C15 Laves phases exhibit coupled *** parameters including mixing enthalpy (ΔHmix),valence electron concentration （VEC）,atomic radius size （δ）,mixing entropy （ΔS）,and electronegativity difference （Δχ） are used to predict the formation of B2 and Laves phase in *** the Co content increases from 0 to 1.5at.%,Laves phase volume fraction gradually increases,which leads to an enhancement in the compressive strength from 1,520.8 MPa to 1,844.4 ***1.5Al Nb Ti VCr alloy exhibits the maximum Vickers hardness of 699.4 *** improvement of mechanical properties mainly originates from solid solution strengthening and second phase strengthening.

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新加坡的语言政策与国家安全

外语学刊 2025年第1期 113-118页

作者：陈志杰南京信息工程大学新加坡研究中心南京210044

新加坡的语言政策与国家身份建构息息相关,因而一直受到学界的关注。然而,国家安全是新加坡国家身份建构的前提。因此,本文从国家安全的视角出发,分析了语言政策在新加坡的国际政治安全、国内社会安全、经济安全和文化安全等方面所起的... 详细信息

新加坡的语言政策与国家身份建构息息相关,因而一直受到学界的关注。然而,国家安全是新加坡国家身份建构的前提。因此,本文从国家安全的视角出发,分析了语言政策在新加坡的国际政治安全、国内社会安全、经济安全和文化安全等方面所起的作用,指出新加坡的双语制制造了新加坡语言身份与文化身份的割裂,在一定程度上阻碍了新加坡文化安全的实现,可能最终威胁到新加坡的国家安全。

关键词：新加坡语言政策国家安全文化身份语言身份

Surface micro-arrays enhancing electromagnetic interference shielding of polydimethylsiloxane/multiwalled carbon nanotubes nanocomposites

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Nano Research 2025年第1期18卷 508-519页

作者： Ke Jiang zhi chen Ji Yu chen Zheng Shan Huang Ming Wang Chongqing Key Laboratory of Soft-Matter Material Manufacturing School of Chemistry and Chemical EngineeringSouthwest UniversityChongqing 400715China School of Mechanics Civil Engineering and ArchitecturesNorthwestern Polytechnical UniversityXi’an 710072China Jieyang Branch of Chemistry and Chemical Engineering Guangdong Laboratory(Rongjiang Laboratory) Jieyang 515200China

Herein,the electromagnetic shielding performance of surface concave-convex(SC)and zig-zag micro-arrays was studied by using a simulation prediction and a three-dimensional(3D)printing custom ***,surface stripe concaveconvex(SSC)and surface cylindrical concave-convex(SCC)micro-arrays with or without zig-zag micro-arrays are designed,and their shielding performance is simulated in multi-bands(C-,X-band).The multiwalled carbon nanotubes/polydimethylsiloxane composites(MWCNT/PDMS)with different SC structures and different electrical conductivity are molded in acrylonitrile-butadiene-styrene copolymer(ABS)molds which are printed by a 3D *** results show that the electromagnetic interference shielding effectiveness(EMI SE)of the samples can be enhanced by constructing the SC micro-arrays with zig-zag micro-arrays,and improving with the increase of conductivity and *** addition,the shielding mechanism of the SC-MWCNT/PDMS composites is investigated and discussed by an electromagnetic simulation.

关键词： surface micro-arrays electrical properties electromagnetic interference(EMI)shielding three-dimensional(3D)printing

Europium anomalies in detrital zircons reveal the crustal thickness evolution of South China in Early Neoproterozoic

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Acta Geochimica 2023年第4期42卷 739-746页

作者： zhi chen Nanjing Institute of Geology and Palaeontology Chinese Academy of SciencesNanjingChina

The South China Block(SCB)is formed by the amalgamation of the Yangtze and Cathaysia blocks during the Early Neoproterozoic along the Jiangnan ***,the precise amalgamation time of these two blocks and the location of the united SCB in the Rodinia supercontinent remain highly *** tectonic models have been proposed and they may have different implications for the crustal thickness evolution of the central SCB in Early *** evaluate these models,this paper uses a recently calibrated Eu/Eu*-inzircon proxy to reconstruct crustal thickness evolution of the central SCB during Early Neoproterozoic.I compiled and screened U–Pb ages and trace elements of 900–700 Ma detrital zircons from the central SCB and then calculated the zircon Eu/Eu**** age-binned average zircon Eu/Eu*displays a decreasing trend from 870 to 790 Ma,and thus indicates no significant crustal thickening event occurred during this time *** finding seems to be inconsistent with tectonic models that the Yangtze and Cathaysia blocks amalgamated during this time ***,given that available coupled detrital zircon U–Pb and trace element datasets are very limited,additional studies are warranted to further evaluate this hypothesis.

关键词： South China Crustal thickness Neoproterozoic Detrital zircon Eu anomalies

An integrated optimization and simulation approach for air pollution control under uncertainty in open-pit metal mine

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Frontiers of Environmental Science & Engineering 2019年第5期13卷 101-114页

作者： Zunaira Asif zhi chen Institute of Environmental Engineering and Research University of Engineering and TechnologyLahorePakistan Concordia University Department of BuildingCivil and Environmental Engineering(BCEE)in MontrealQuebecCanada

Open-pit metal mines contribute toward air pollution and without effective control techniques manifests the risk of violation of environmental guidelines. This paper establishes a stochastic approach to conceptualize the air pollution control model to attain a sustainable solution. The model is formulated for decision makers to select the least costly treatment method using linear programming with a defined objective function and multi-constraints. Furthermore, an integrated fuzzy based risk assessment approach is applied to examine uncertainties and evaluate an ambient air quality systematically. The applicability of the optimized model is explored through an open-pit metal mine case study, in North America. This method also incorporates the meteorological data as input to accommodate the local conditions. The uncertainties in the inputs, and predicted concentration are accomplished by probabilistic analysis using Monte Carlo simulation method. The output results are obtained to select the cost-effective pollution control technologies for PM2.5, PM10, NOx, SO2 and greenhouse gases. The risk level is divided into three types (loose, medium and strict) using a triangular fuzzy membership approach based on different environmental guidelines. Fuzzy logic is then used to identify environmental risk through stochastic simulated cumulative distribution functions of pollutant concentration. Thus, an integrated modeling approach can be used as a decision tool for decision makers to select the cost-effective technology to control air pollution.

关键词： Air pollution Decision analysis Linear programming Mining Optimization Fuzzy Monte Carlo

Effect of Dy substitution on the microstructure and magnetic properties of nanograin Nd-Fe-B single-phase alloys

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 335-339页

作者： zhi-an chen Ji Luo zhi-meng Guo School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Nanocrystalline single-phase alloys with the nominal compositions （at%） of Nd12.3-xDyxFe79.7Zr0.8Nb0.8Cu0.4B6.0 （x=0, 0.5, 1.5, and 2.5） were prepared by melt-spinning and subsequent annealing. X-ray diffraction analysis shows that the as-spun ribbons were mainly com- posed of the amorphous phase. A slight content of Dy stabilizes the amorphous phase during annealing treatment. The grain size becomes smaller and the coercivity of the annealed ribbon is gradually improved with the increase of Dy content. Excessive Dy is harmful to the remanence. It is found that no intergramtlar phase exists between the grains by high-resolution transmission electron microscopy, and the grain boundaries are crystallographically coherent in the optimally annealed sample. The optimum magnetic properties of remanence （Jr=1.09 T）, coercivity （Hei=1048 kA/m）, and maximum magnetic energy product （（BH）m=169.5 kJ/m3） are obtained from the x=0.5 ribbon in a post heat-treated state （700℃, 10 min）.

关键词： NdFeB magnets dysprosium nanocrystalline amorphous grain size magnetic properties

Modified constructions of binary sequences using multiplicative inverse

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Applied Mathematics(A Journal of Chinese Universities) 2008年第4期23卷 490-500页

作者： chen zhi-xiong LIN zhi-xing Key Laboratory of Applied Mathematics Putian University Putian 351100 China Key Laboratory of Network Security and Cryptology Fujian Normal University Fuzhou 350007China

Two new families of finite binary sequences are constructed using multiplicative inverse. The sequences are shown to have strong pseudorandom properties by using some estimates of certain exponential sums over finite fields. The constructions can be implemented fast since multiplicative inverse over finite fields can be computed in polynomial time.

关键词： stream cipher binary sequence multiplicative inverse pseudorandomness exponential sum

Soil Fertility Self-development Under Ecological Restoration in the Zhuxi Watershed in the Red Soil Hilly Region of China

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Journal of Mountain Science 2014年第5期11卷 1231-1241页

作者： BAI Li-yue chen zhi-qiang chen zhi-biao College of Geographical Sciences Fujian Normal University Institute of Agriculture Regional Planning of Fujian Province

Current methods that utilize simple data or models to judge whether soil fertility can selfdevelop are not sufficiently rigorous. A new framework has been set up using catastrophe theory, laboratory experiment, field work, and 3S(Geographic information system, Global positioning system, and Remote sensing) to explore soil fertility catastrophe under ecological restoration, discriminate whether soil fertility can self-develop, and propose adjustment of ecological restoration measures in the Zhuxi watershed of Changting County, Fujian Province, China, which is a typical representative of the red soil hilly region of China. The results show that: 1) the soil fertility is obviously improved through the four ecological restoration measures, which impels soil fertility catastrophe. Among 89 soil samples, catastrophic soil samples and stable soil samples account for 26(29.21%) and 63(70.79%) of the samples, respectively. The four ecological restoration measures are listed in the order lowquality forest improvement > arbor–bush–herb mixed plantation > orchard improvement > closing measures according to the proportions of catastrophic soil samples. A typical soil sample in Bashilihe that can self-develop is selected as the criterion to judge the upper lobe and lower lobe of soil fertility in the process surface of the Cusp catastrophe model. Twenty-six(29.21%) were in the middle lobe, 10(11.24%) were in the upper lobe, and 53(70.79%) were in the lower lobe. The catastrophic direction of 26 catastrophic soil samples is to the upper lobe according to soil and water loss change as well as fieldwork. There is a significant positive correlation of Δ with soil and water loss change, and the lower soil and water loss relates to higher catastrophic probability. 2) Soil fertility self-development could be regionalized as "Soil fertility can self-develop" whose area was 12.74 km2(28.33%) distributed mainly in the leftmost and rightmost parts, "Soil fertility tends to self-develop" who

关键词： Soil fertility Catastrophe Ecological restoration Red soil hilly region

Constructing quasi-random subsets of Z_N by using elliptic curves

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Applied Mathematics(A Journal of Chinese Universities) 2012年第1期27卷 105-113页

作者： LIN zhi-xing chen zhi-xiong Department of Mathematics Putian UniversityPutianFujian 351100China State Key Laboratory of Information Security Institute of SoftwareChinese Academy of SciencesBeijing 100049China

Let ε ： y^2 = x3 ＋ Ax ＋ B be an elliptic curve defined over the finite field Zp（p 〉 3） and G be a rational point of prime order N on ε. Define a subset of ZN, the residue class ring modulo N, asS：={n：n∈ZN,n≠0,（X（nG）/p）=1} where X（nG） denotes the x-axis of the rational points nC and （＊/P） is the Legendre symbol. Some explicit results on quasi-randomness of S are investigated. The construction depends on the intrinsic group structures of elliptic curves and character sums along elliptic curves play an important role in the proofs.

关键词： elliptic curve quasi-random subset quasi-randomness character sum Legendre symbol.