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HISTORICAL DESERTIFICATION PROCESS IN HEXI CORRIDOR,CHINA

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Chinese Geographical Science 2005年第3期15卷 245-253页

作者： Wang Nai-ang z.ang chun-hui LI Gang CHENG Hong-yi College of Earth and Environment Sciences Lanzhou University Lanzhou 730000P. R. China

Over the last 2000 years, approximately 38 ancient cities were abandoned through desertification in Hexi Corridor, Northwest China. Among them, 21.05% were abandoned during the Northern and Southern Dynasties, 21.05% during the end of the Tang Dynasty and the Five Dynasties, and 57.9% during the Ming and Qing dynasties. At the same time, main lakes were shrinking rapidly from the 5th Century to the 6th Century and the end of the Qing Dynasty. The climate in these periods was relatively arid and cold with frequent dusts. The phase of these changes indicated that there were three periods of desertification enlargement in the northern China. They were Northern and Southern Dynasties, the end of Tang Dynasty and Five Dynasties, the Ming and Qing dynasties. The macro-process of desertification in the study area was controlled mainly by the climatic changes. But from the facts that the population density in the middle of Qing Dynasty had exceeded the critical index of population pressure in arid area and the usage rate of water resources had exceeded 40% in Hexi Corridor, this paper also suggests that human activities have played an important role in desertification processes of the study area mainly during the recent 300 years.

关键词： historical desertification climate change human activities Hexi Corridor

Preliminary safety analysis for heavy water-moderated molten salt reactor

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Nuclear Science and Techniques 2024年第6期35卷 202-217页

作者： Gao-ang Wen Jian-Hui Wu chun-Yan zou Xiang-zhou Cai Jin-Gen Chen Man Bao College of Science University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The heavy water-moderated molten salt reactor(HWMSR)is a newly proposed reactor concept,in which heavy water is adopted as the moderator and molten salt dissolved with fissile and fertile elements is used as the *** arising from graphite in traditional molten salt reactors,including the positive temperature coefficient and management of highly radio-active spent graphite waste,can be addressed using the *** now,research on the HWMSR has been centered on the core design and nuclear fuel cycle to explore the viability of the HWMSR and its advantages in fuel ***,the core safety of the HWMSR has not been extensively ***,we evaluate typical accidents in a small modular HWMSR,including fuel salt inlet temperature overcooling and overheating accidents,fuel salt inlet flow rate decrease,heavy water inlet temperature overcooling accidents,and heavy water inlet mass flow rate decrease accidents,based on a neutronics and thermal-hydraulics coupled *** results demonstrated that the core maintained safety during the investigated accidents.

关键词： Heavy water-moderated molten salt reactor Neutronics and thermal-hydraulics coupling Transient analysis Accident analysis

Symmetry-driven half-integer conductance quantization in Cobalt–fulvalene sandwich nanowire

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npj Computational Materials 2023年第1期9卷 314-321页

作者： zhuoling Jiang Kah-Meng Yam Yee Sin ang Na Guo Yongjie z.ang Hao Wang chun z.ang Department of Physics and Centre for Advanced 2D Materials National University of SingaporeSingapore 117551Singapore Science Mathematics and Technology(SMT)ClusterSingapore University of Technology and DesignSingapore 487372Singapore Department of Chemistry National University of SingaporeSingapore 117543Singapore National University of Singapore Chongqing Research Institute 401123 ChongqingChina

Precise manipulation and monitoring spin transport in one-dimensional (1D) systems is a long-sought goal in the field of nano-spintronics. Based on first-principles calculations, we report the observation of half-integer conductance quantization in the Cobalt-fulvalene sandwich nanowire. Compared with a pure monatomic Cobalt wire, the introduction of fulvalene molecules leads to threeimportant features: Firstly, the strong coupling between the fulvalene and the Cobalt prevents the contamination of the ambientair, ensuring both chemical and physical stabilities;Secondly, the fulvalene symmetry-selectively filters out most of the d-typeorbitals of the Cobalt while leaving a single d-type orbital to form an open spin channel around the Fermi level, which offers amechanism to achieve the observed half-integer conductance;Thirdly, it maintains a superexchange coupling between adjacent Coatoms to achieve a high Curie temperature. Spin transport calculations show that this half-metallic nanowire can serve as a perfectspin filter or a spin valve device, thus revealing the potential of Cobalt-fulvalene sandwich nanowire as a promising building blockof high-performance spintronics technology.

关键词： sandwich coupling transport

Fabrication of nanoreactors based on polyoxoperoxometalates and enhancement of their catalytic activity

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Chinese Chemical Letters 2011年第7期22卷 875-878页

作者： Mei Jie Wei chun Li z.ang Cong Liang Sun ang Li Xiao Hong Wang Key Lab of Polyoxometalate Science of Ministry of Education Faculty of Chemistry Northeast Normal University Changchun 130024 China

The nanoreactors were fabricated by reacting amphiphilic quaternary ammoniums and polyoxoperoxometalates Kn[PW12-xTix. O40-x（O2）x] （x = 1, 2 and 3; n =5, 7 and 9）（K5[PW11TiO39（O2）], KT[PWloTi2038（O2）2] and K9[PW9Ti3O37（O2）3]）. Fourier transform infrared spectroscopy （FT-IR）, transmission electron microscopy （TEM） were used to characterize the resulting samples. This kind of nanocatalysts could promote NH4SCN＇ degradation into simple inorganic compounds such as SO4^2-, HCO3^- and NO3^- only using oxygen as an oxidant under room conditions.

关键词： Catalytic wet air oxidation Thiocyanate Polyoxometalate Nanocatalysts

Surface deformation-dependent mechanical properties of bending nanowires:an ab initio core-shell model

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Applied Mathematics and Mechanics(English Edition) 2022年第2期43卷 219-232页

作者： Ye XIAO J.SHang L.z.KOU chun LI School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an710072China School of Mechanical Medical and Process EngineeringQueensland University of TechnologyBrisbaneQLD4000Australia

An ab initio core-shell model is proposed to evaluate the surface effect in bending nanowires,in which the elastic modulus depends on the surface relaxation and deformation induced by external *** using first-principles calculations based on the density functional theory(DFT),the surface and bulk properties are calculated for Ag,Pb,and Si *** obtained theoretical predictions of the effective Young’s modulus of nanowires agree well with the experimental data,which shows that the fixed-fixed nanowire is stiffened and the cantilevered nanowire is softened as the characteristic size of the cross section ***,the contrastive analysis on the two kinds of nanowires demonstrates that increasing the nanowire aspect ratio would enhance the surface *** present results could be helpful for understanding the size effect in nanowires and designing nanobeam-based devices in nanoelectromechanical systems(NEMSs).

关键词： surface effect density functional theory(DFT) surface relaxation surface stress nanowire

Gas metal arc welding of high nitrogen stainless steel with AreN_(2)-O_(2)ternary shielding gas

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Defence Technology（防务技术） 2021年第3期17卷 923-931页

作者： zeng Liu Cheng-lei Fan zhu Ming Chao Chen ang Liu chun-li Yang San-bao Lin Lang-ping Wang State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin150001China Inner Mongolia Metal Material Research Institute BaotouChina

High nitrogen stainless steel with nitrogen content of 0.75%was welded by gas metal arc welding with Ar-N_(2)-O_(2)ternary shielding *** effect of the ternary shielding gas on the retention and improvement of nitrogen content in the weld was *** test was conducted first to compare the ability of O_(2)and CO_(2)in prompting nitrogen *** nitrogen content of the surfacing metal with O_(2)is slightly higher than CO_(2).And then AreN_(2)-O_(2)shielding gas was applied to weld high nitrogen stainless *** using N_(2)-containing shielding gas,the nitrogen content of the weld was improved by 0.1 wt%.As N_(2)continued to increase,the increment of nitrogen content was not obvious,but the ferrite decreased from the top to the *** the proportion of N_(2)reached 20%,a full austenitic weld was obtained and the tensile strength was improved by 8.7%.Combined with the results of surfacing test and welding test,it is concluded that the main effect of N_(2)is to inhibit the escape of nitrogen and suppress the nitrogen diffusion from bottom to the top in the molten pool.

关键词： High nitrogen stainless steel AreN2-O2 shielding gas Action mechanism

Refining constitutive relation by integration of finite element simulations and Gleeble experiments

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Journal of Materials Science & Technology 2019年第6期35卷 1039-1043页

作者： D.J. Yu D.S. Xu H. W ang z.B. zhao G.z. Wei R. Yang College of Sciences Northeastern University Shenyang 110004 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Thermo-mechanical coupled finite element calculations were carried out to simulate the Gleeble compression of the samples of a titanium alloy(Ti60), and the results are analyzed and compared with the actual compression tests conducted on a Gleeble 3800 thermo-mechanical simulator. The changes in temperature, stress and strain distribution in the samples and the source of error on the constitutive relations from Gleeble hot compression test were analyzed in detail. Both simulations and experiments showed that the temperature distribution in the specimen is not uniform during hot compression, resulting in significant deformation inhomogeneity and non-ignorable error in the flow stress strain relation,invalidating the uniform strain assumption commonly assumed when extracting the constitutive relation from Gleeble tests. Based on the finite element simulations with iterative corrections, we propose a scheme to refine the constitutive relations from Gleeble tests.

关键词： Titanium alloy Constitutive relation Finite element Compression Temperature distribution

Magnetic,thermal stability and dynamic mechanical properties of beta isotactic polypropylene/natural rubber blends reinforced by Nizn ferrite nanoparticles

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Defence Technology（防务技术） 2019年第6期15卷 958-963页

作者： Lih-Jiun Yu Sahrim Hj Ahmad Ing Kong Mouad ATarawneh Shamsul Bahri Bin Abd Razak Elango Natarajan chun Kit ang Department of Mechanical Engineering Faculty of EngineeringTechnology and Built EnvironmentUCSI UniversityNo 1Jalan Menara GadingUCSI Heights(Taman Connaught)Cheras56000Kuala LumpurMalaysia School of Applied Physics Faculty of Science and TechnologyUniversity Kebangsaan Malaysia43600BangiSelangor Darul EhsanMalaysia School of Engineering and Mathematical Sciences La Trobe UniversityBundooraVIC3086Australia Department of Physics College of ScienceAl-Hussein Bin Talal UniversityP.O Box 20Ma'anJordan Department of Food Science and Technology University Malaysia TerengganuKuala NerusTerengganuMalaysia

The dispersion of magnetic nanoparticles in matrix is crucial to ensure optimum performance of the *** difficulty level of achieving good dispersion is further increase when a multi-phases of matrix is present.A pre-coating technique of magnetic nanoparticles with polypropylene using ball-mill prior to melt-blending process was employed to prepare a multi-phases thermoplastic natural rubber *** effect of filler loading(2 wt%-10 wt%) on morphology,structure,magnetic properties,thermal stability and dynamic mechanical properties of the composites were *** was found that the Nizn ferrite nanoparticles act as nucleating agent to form beta isostatic polypropylene thermoplastic *** composites’ magnetic properties are directly dependent on the filler *** dispersion of magnetic fillers in polymer matrix plays role in affecting the magnetic properties and thermal *** preference of filler to locate at amorphous phase has distorted the chain orientation of natural rubber and ***,the polymorphism and crystallinity of the matrix varied as the filler loading increased,affecting the dynamic mechanical *** was found that 8 wt% Nizn nanocomposite exhibits highest E’ and tanδ,indicating the dynamic mechanical properties of Nizn nanocomposite are affected by β-phase degree.

关键词： Magnetic Thermoplastic natural rubber Nanoparticles Composites

Rhodium-Catalyzed Direct C-H Alkenylation of Indoles with Alkenyl Borates

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Chinese Journal of Chemistry 2021年第10期39卷 2823-2828页

作者： ze-Tian Wang zi-ang zheng Peng-Jie Li chun-Ni zhou Shao-Jun Cai Biao Xiao Liang Wang Key Laboratory of Optoelectronic Chemical Materials and Devices Ministry of EducationSchool of Chemical and Environmental EngineeringJianghan University8 Sanjiaohu RoadWuhanHubei430056 China

Main observation and conclusion A new Rh(Ⅲ)-catalyzed direct C—H alkenylation of 2,3-unsubstitued indoles with alkenyl borates through C—H activation followed by transmetallation was *** protocol provides an efficient method for the synthesis of terminal C2-alkenylindoles under mild conditions,and also shows broad substrate scope and high functional group tolerance with respect to both ***,the C2-alkenylated indole can be easily transformed into carboline derivative,which is an important polycyclic indole moiety in natural products and drug molecules.

关键词： Rhodium C-H activation Terminal alkenylindoles Alkenyl borates Nitrogen heterocycles