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Microstructure, thermophysical property and ablation behavior of high thermal conductivity carbon/carbon composites after heat-treatment

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Chinese Journal of Aeronautics 2020年第5期33卷 1541-1548页

作者： xue-song LIU Qian-Gang FU Hui WANG Qiang song State Key Laboratory of Solidification Processing Shannxi Province Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an 710072PR China

Uni-directional carbon/carbon composites with high thermal conductivity are suitable to supply continuous thermal protection for future reentry vehicles since they could reduce surface temperature and ablation rates simultaneously in harsh *** this work,the high thermal conductivity carbon/carbon composites were prepared by chemical vapor *** heat-treatment,both their open porosity and internal friction increase due to the fiber/matrix thermal expansion mismatch;while their thermal conductive performance become better due to more complete carbon *** raising heat-treatment temperature from 1800℃to 2450℃,the mass and linear ablation rates of C/C composites with fibers vertical to the oxyacetylene torch for 60 s decrease from 0.66 mg/s and 2.95μm/s to 0.51 mg/s and 2.05μm/s *** improved ablation resistance is resulted from the increased thermal conductivity from 282 to 508 W/(m·K)and more carbon fibers exposed to the flame during ablation,which have better oxidation resistance than those of carbon *** such ablation rates become larger for composites with fibers parallel to the flame,from 1.02 mg/s and 3.73μm/s to 1.28 mg/s and 5.0μm/s respectively since the ablation occurred more easily through gaps at the fiber/matrix interfaces,which become larger and are always exposed to the flame for this case.

关键词： Ablation Carbon/carbon composites Fiber orientation Heat treatment Thermal conductivity

Ta-Doped Sb2Te Allows Ultrafast Phase-Change Memory with Excellent High-Temperature Operation Characteristics

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Nano-Micro Letters 2021年第2期13卷 221-231页

作者： Yuan xue Shuai Yan Shilong Lv Sannian song Zhitang song State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information TechnologyChinese Academy of SciencesShanghai 200050People’s Republic of China

Phase-change memory(PCM)has considerable promise for new applications based on von Neumann and emerging neuromorphic computing ***,a key challenge in harnessing the advantages of PCM devices is achieving high-speed operation of these devices at elevated temperatures,which is critical for the efficient processing and reliable storage of data at full ***,we report a novel PCM device based on Ta-doped antimony telluride(Sb2Te),which exhibits both high-speed characteristics and excellent high-temperature characteristics,with an operation speed of 2 ns,endurance of >106 cycles,and reversible switching at 140℃.The high coordination number of Ta and the strong bonds between Ta and Sb/Te atoms contribute to the robustness of the amorphous structure,which improves the thermal ***,the small grains in the three-dimensional limit lead to an increased energy efficiency and a reduced risk of layer segregation,reducing the power consumption and improving the long-term *** findings for this new Ta-Sb2Te material system can facilitate the development of PCMs with improved performance and novel applications.

关键词： Phase-change memory High speed Ta High-temperature operation

Spatial-temporal pattern and formation mechanism of county urbanization on the Chinese Loess Plateau

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Journal of Mountain Science 2021年第4期18卷 1093-1111页

作者： song Yong-yong MA Bei-bei DAI Lan-hai xue Dong-Qian XIA Si-you WANG Peng-tao School of Geography and Tourism Shaanxi Normal UniversityXi'an 710119China College of History Culture and TourismHexi UniversityZhangye 734000China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China School of Tourism&Research Institute of Human Geography Xi'an International Studies UniversityXi'an 710128China

Urbanization is a comprehensive and complex socioeconomic phenomenon that plays an influential role in promoting global socioeconomic *** Loess Plateau region is an important part of the China’s ecological security pattern,and occupies an important position in the implementation of China’s new-type urbanization strategy and the realization of the urban *** characteristics of the staged changes and regional differentiation of urbanization in the area from 1990 to 2018 were studied with focus on regions and subregions by selecting 341 county-level administrative units on the Chinese Loess Plateau as the research area,and employing partition analysis and geographic detector *** revealed the formation mechanism of the spatial differentiation pattern of urbanization on the Loess *** found that the urbanization of the Loess Plateau,previously in a slow growth phase,entered the accelerated development phase,presenting a macro pattern of high rates of urbanization in central and eastern areas and low rates in western *** formation of the regional differentiation patterns of urbanization on the Loess Plateau were the combined results of natural geographical and socioeconomic *** these factors,the interaction of any two factors had a stronger impact on regional urbanization patterns than a single factor,which was specifically manifested as nonlinear or bi-factor enhancement *** findings of this paper may provide a theoretical reference and scientific basis for the scientific promotion of healthy urbanization on the Chinese Loess Plateau and the ecologically fragile areas of developing countries around the world.

关键词： Urbanization Spatial-temporal pattern Influencing factors Driving mechanism Geographical detector Chinese Loess Plateau

Open-Shell Oligomers and Polymers: Theory, Characterization Methods, Molecular Design, and Applications

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Chinese Journal of Polymer Science 2024年第4期42卷 417-436页

作者： xue-Qing Wang Cheng song Ting Lei Key Laboratory of Polymer Chemistry and Physics(Ministry of Education) School of Materials Science and EngineeringPeking UniversityBeijing100871China

Open-shell oligomers and polymers have exhibited intriguing electronic and magnetic properties, making them highly desirable for a wide range of applications, including ambipolar organic field-effect transistors (OFETs), photodetectors, organic thermoelectrics, and spintronics. Although open-shell ground states have been observed in certain small molecules and doped organic semiconductors, the exploration of open-shell ground-state conjugated polymers is still limited, and the strategies for designing these polymers remain obscure. This review aims to briefly introduce the theory and characterization methods of open-shell conjugated polymers, along with an overview of recent progress and applications. The objective is to stimulate further advancements and investigations in this promising area by shedding light on the potential of open-shell conjugated polymers and the challenges that lie ahead.

关键词： Conjugated polymers Open-shell molecules High-spin ground state Donor-acceptor(D-A)polymers Optoelectronic and magnetic properties

Saturation phenomenon of Ce and Ti in the modification of Al–Zn–Si filler metal

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International Journal of Minerals,Metallurgy and Materials 2015年第2期22卷 184-189页

作者： Jin-long Yang song-bai xue Wei Dai Peng xue College of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Zhejiang Xinrui Welding Material Co. Ltd.

Cerium and titanium were added to an A1-42Zn-5.5Si brazing alloy, and the subsequent microstructures of the brazing alloy and the 6061 AI alloy brazing seam were investigated. The microstructures of filler metals and brazed joints were characterized by scanning elec- tron microscopy and X-ray energy dispersion spectrometry. A new Ce-Ti phase formed around the silicon phase in the modified filler metal and this saturation phenomenon was analyzed. Interestingly, following brazing of the 6061 alloy, there is no evidence of the Ce--Ti phase in the brazing seam. Because of the mutual solubility of the brazing alloy and base metal, the quantity of the solvent increases, and the solute Ce and Ti atoms assume an undersaturated state.

关键词： filler metals aluminum alloys brazing cerium titanium saturation

Tetravalent Terbium Chelates: Stability Enhancement and Property Tuning

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Precision Chemistry 2023年第10期1卷 583-591页

作者： Tianjiao xue you-song Ding xue-Lian Jiang Lizhi Tao Jun Li Zhiping Zheng Department of Chemistry Southern University of Science and TechnologyShenzhenGuangdong 518055China Key University Laboratory of Rare Earth Chemistry of Guangdong Southern University of Science and TechnologyShenzhenGuangdong 518055China Department of Chemistry and Engineering Research Center of Advanced Rare-Earth Materials of Ministry of Education Tsinghua UniversityBeijing 100084China

Coordination chemistry of rare-earth elements has been dominated by the+3 oxidation *** with higher-valence lanthanide ions are synthetically challenging but are of fundamental research interest and significance as advanced molecular ***,four tetravalent terbium complexes(2-5)of the common formula[Tb(OSiPh3)4L](L=ethylene glycol dimethyl ether(DME),2,2’-bipyridine(bpy),2,2’-bipyrimidine(bpym),and 1,10-phenanthroline(phen))are *** analyses reveal in each of these complexes a hexacoordinate Tb(IV)ion situated in a distorted octahedral coordination environment formed by four triphenylsi-loxido ligands and a bidentate chelating *** use of chelating ligands enhances the stability of the resulting complexes over their THF solvate *** significantly,the aromatic N-chelating ligands have been found to tune effectively the electronic structures of the complexes,as evidenced by the sizable potential shifts observed for the quasi-reversible redox Tb(IV/III)process and by the changes in their absorption *** experimental findings are augmented with quantum theoretical calculations in which the ligandπ-donation to the 5d orbitals of the Tb(IV)center is found to be primarily responsible for stability enhancement and the corresponding changes of physical properties *** measurements and results from electron paramagnetic resonance studies produced small absolute values of zero-field splittings of these complexes,ranging from 0.1071(22)to 1.1484(112)cm-1 and comparable to the values reported for analogous Tb(IV)complexes.

关键词： Tetravalent Terbium Ion Chelating Ligand Formal Potential Stability Magnetic Property

Some properties of the psi function and evaluations of γ

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Applied Mathematics(A Journal of Chinese Universities) 2016年第1期31卷 103-111页

作者： QIU song-liang ZHAO xue School of Science Zhejiang Sci-Tech University

In this paper, the authors show some monotonicity and concavity of the classical psi function, by which several known results are improved and some new asymptotically sharp estimates are obtained for this function. In addition, applying the new results to the psi function, the authors improve the well-known lower and upper bounds for the approximate evaluation of Euler＇s constant γ.

关键词： Psi function gamma function monotonicity concavity inequality Euler's constant.

Thoughts of Lao Tse and Chuang Tzu in Brecht＇ s Works

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学术界 2013年第9期 274-280页

作者： xue song School of Foreign Languages Chongqing University Chongqing 401331

Brecht once concentrated on the theories of Lao Tse and Chuang Tzu,which can be discovered in some works of *** in the turbulent times,Lao Tse and Chuang Tzu had dialectical observation of the troubled society,which evoked the critical thinking of Brecht,and he began to re-interpret the Chinese philosophy in his own *** the verfremdung,in which Brecht was expert,Brecht creatively combined the theories of Lao Tse and Chuang Tzu with the seemingly irrelative western thoughts to help him to further develop his theory *** philosophically rich stories helped him to achieve the verfremdungseffekt between the audience and the plot of the play.

关键词：庄子老子作品中国哲学批判性思维辩证观

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具有工作故障和附加服务的排队最优策略

应用数学 2025年第1期38卷 191-200页

作者：田瑞玲郝义博宋玉亭薛雅丹燕山大学理学院河北秦皇岛066004

为了拓展排队理论,本文研究了具有工作故障和附加服务的排队系统.运用概率母函数方法,推导出服务台的状态概率,进而得到稳态下系统的平均队长等性能指标.构建成本函数,采用粒子群优化技术寻找服务台处于不同状态的最优服务率和预期最小... 详细信息

为了拓展排队理论,本文研究了具有工作故障和附加服务的排队系统.运用概率母函数方法,推导出服务台的状态概率,进而得到稳态下系统的平均队长等性能指标.构建成本函数,采用粒子群优化技术寻找服务台处于不同状态的最优服务率和预期最小成本.通过数值分析考察系统参数对系统性能指标和最优服务率以及预期最小成本的影响.基于收入-支出结构,建立个体效用函数和社会收益函数.系统性能指标和收益函数的敏感性为现实生活中的排队问题提供理论支持.

关键词：排队系统均衡策略工作故障附加服务性能分析