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Structure stability and configuration evolution of Al_n(n=3, 4, 6, 13, 19) clusters

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Science China(Technological Sciences) 2006年第4期49卷 385-392页

作者： PENG Ping LI Guifa ZHENG Caixing han Shaochang liu Rangsu School of Materials Science and Engineering Hunan University Changsha 410082 China School of Materials Science and Engineering Hunan University Changsha 410082 China School of Materials Science and Engineering Hunan University Changsha 410082 China School of Materials Science and Engineering Hunan University Changsha 410082 China School of Materials Science and Engineering Hunan University Changsha 410082 China

Using a first-principles pseudo-potential plane wave method, the geometrical and electronic structures of Aln (n=3, 4, 6, 13, 19) clusters with different configurations have been calculated. Several parameters such as the binding energy Eb and the HOMO-LUMO energy gap ?EH-L have been adopted to characterize and analyze the structure stability of these clusters, and their configuration evolutions are also investigated by linear synchronous transit (LST) method. It is demonstrated that the stable configura- tions of Al3, Al4, Al6, Al13, Al19 clusters are triangle, rhombus, octahedron, icosahedron and double icosahedron, respectively. For Al6 and Al19 clusters there are metastable structures of parallelogram and octahedron, respectively, whereas in the Al3, Al4 and Al13 clusters, no metastable configuration is validated. There exist a large energy gap and a low energy barrier between the octahedron and the parallelogram of the Al6 cluster, so the transfor- mation from its metastable to stable structures is rather easy. By contrast, a small energy gap and a high energy barrier between the stable and metastable structures of Al19 cluster mean its configuration evolution from the octahedron to the double icosahedron occurs hardly, therefore the metastable octahedron configuration of Al19 cluster can be extensively detected in experiments and simulations.

关键词： first-principles calculation, Al cluster, configuration evolution.

Influence of principal stress rotation of unequal tensile and compressive stress amplitudes on characteristics of soft clay

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Journal of Mountain Science 2017年第2期14卷 369-381页

作者： SHEN Yang WANG Xin liu han-long DU Wen-han WANG Bao-guang XU Hai-dong Key Laboratory of Geomechanics and Embankment Engineering of Ministry of Education Hohai UniversityNanjing 210098China Jinan Rail Transit Group Co. LtdJinan 250100China School of Civil Engineering Chongqing UniversityChongqing 400044China

Soil behavior can reflect the characteristics of principal stress rotation under dynamic wave and traffic loads. Unequal amplitudes of tensile and compressive stresses applied to soils have complex effects on foundation soils in comparison with the pure principal stress rotation path. A series of undrained cyclic hollow torsional shear tests were performed on typical remolded soft clay from the Hexi area of Nanjing, China. The main control parameters were the tensile and compressive stress amplitude ratio(α) and the cyclic dynamic stress ratio(η). It was found that the critical η tended to remain constant at 0.13, when the value of the compressive stress amplitude was higher than the tensile stress amplitude. However, the influence of the tensile stress was limited by the dynamic stress level when α= *** obvious structural change in the soil, the corresponding numbers of cyclic vibration cycles were found to be independent of α at low stress levels and were only related to η. Finally, a new method for evaluating the failure of remolded soft clay was presented. It considers the influence of the tensile and compressive stresses which caused by complex stress paths of the principal stress rotation. This criterion can distinguish stable, critical, and destructive states based on the pore-water-pressure-strain coupling curve while also providing a range of failure strain and vibration cycles. These results provide the theoretical support for systematic studies of principal stress rotation using constitutive models.

关键词： Complex stress path Principal stress rotation Train loads Amplitude ratio Cyclic dynamic stress ratio Failure criterion

Effect of texture on deformation behavior of heterogeneous Mg-13Gd alloy with strength-ductility synergy

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Journal of Materials Science & Technology 2022年第18期113卷 271-286页

作者： Shuaishuai liu han liu Xiang Chen Guangsheng Huang Qin Zou Aitao Tang Bin Jiang Yuntian Zhu Fusheng Pan State Key Laboratory of Mechanical Transmission College of Materials Science and EngineeringChongqing UniversityChongqing 400044China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing400044China Department of Materials Science and Engineering City University of Hong KongHong Kong999077China Nano and Heterogeneous Material Center Nanjing University of Science and TechnologyNanjing210094China

Heterostructure metals as a new class of materials can effectively break the traditional strength–ductility trade-off dilemma. In this study, the extruded sheet with the small extrusion ratio(ER) of 3.9(ER3.9)presented a heterogeneous lamella structure(HLS) and texture, where the fine dynamical recrystallized(DRXed) grains formed a random texture and coarse un-DRXed grains exhibited a strong basal *** ER3.9 sample presented an excellent combination of strength and ductility. The texture strengthening in coarse grains and hetero-deformation induced(HDI) strengthening contributed to the enhanced strength of the ER3.9 sample besides grain refinement. The improving ductility mainly stems from the weakened texture in fine grains. Interestingly, in coarse grains, the strong basal texture, the occurrence of cross slip, low stacking fault energy(SFE), and dislocation pinned by precipitates weaken the HDI hardening effect. While the traditional dislocation hardening mainly generated by fine grains dominates overall strain hardening. Meanwhile, the activation of non-basal slips, especially pyramidal slip,and the generation of cross slips in fine grains benefit for coordinating plastic deformation. The ability for coordinate plastic deformation in fine grains is higher than that of coarse grains, which was confirmed by the digital image correlation technology. This work will promote the development of the heterogeneous theory in textured Mg alloys.

关键词： Mg-Gd alloy Recrystallization Heterogeneous texture Mechanical properties HDI hardening

Response of atmospheric carbon dioxide to the secular variation of weakening geomagnetic field in whole atmosphere simulations

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Earth and Planetary Physics 2021年第4期5卷 327-336页

作者： Xu Zhou XinAn Yue han-Li liu Yong Wei YongXin Pan Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China Beijing National Observatory of Space Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China High Altitude Observatory National Center for Atmospheric ResearchBoulderCOUSA

Responses of atmospheric carbon dioxide(CO_(2))density to geomagnetic secular variation are investigated using the Whole Atmosphere Community Climate Model-eXtended(WACCM-X).Our ensemble simulations show that CO_(2) volume mixing ratios(VMRs)increase at high latitudes and decrease at mid and low latitudes by several ppmv in response to a 50%weakening of the geomagnetic *** significant changes in CO_(2) are mainly found above~90 km altitude and primarily redetermine the energy budget at~100-110 *** analysis of transformed Eulerian mean(TEM)circulation found that CO_(2) change is caused by enhanced upwelling at high latitudes and downwelling at mid and low latitudes as a result of increased Joule *** further analyzed the atmospheric CO_(2) response to realistic geomagnetic weakening between 1978 and 2013,and found increasing(decreasing)CO_(2) VMRs at high latitudes(mid and low latitudes)*** the first time,our simulation results demonstrate that the impact of geomagnetic variation on atmospheric CO_(2) distribution is noticeable on a time scale of decades.

关键词： atmospheric carbon dioxide geomagnetic fields whole atmosphere simulation upper atmosphere

Controllable synthesis of argentum decorated CuO_(x)@CeO_(2) catalyst and its highly efficient performance for soot oxidation

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Journal of Rare Earths 2022年第10期40卷 1546-1553页

作者： Jie Wan Yanjun liu Yuanyuan Zhou han liu Gongde Wu Jianfei Kan Min Li Duan Weng Xiaodong Wu Energy Research Institute Nanjing Institute of TechnologyNanjing 211167China Key Laboratory of Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua UniversityBejing 100084China School of Civil Engineering Southeast UniversityNanjing 211189China State Key Laboratory of Digital Household Appliances Haier Group Technique R&D CenterQingdao 266100China

In this paper,CuO_(x)@Ag/CeO_(2) catalysts were synthesized by simple wet-chemical method and equal volume impregnation *** obtained catalysts were subjected to soot temperature programmed oxidation(soot-TPO)activity tests and were further characterized by various techniques such as X-ray diffraction(XRD),transmission electron microscopy/high-resolution transmission electron microscopy(TEM/HR-TEM),N_(2) physisorption,X-ray photoelectron spectroscopy(XPS)and H_(2)-temperature programmed reduction(H_(2)-TPR).The results show that CuO_(x)@Ag/CeO_(2) synthesized presents well controlled core-shell structures,with nano-cube like Cu_(2)O as the core and Ag decorated polycrystalline CeO_(2) grafting layers as the *** core-shell structured CuO_(x)@Ag/CeO_(2) can successfully construct a secondary oxygen delivery channel(CuO_(x)→CeO_(2)→Ag)to effectively transfer bulk oxygen of the catalyst to the soot,resulting in its excellent soot oxidation activity compared to CuO_(x)@CeO_(2).The potential benefiting effect by Ag introduction over Cu@Ag/Ce can be concluded as:(ⅰ)pumping lattice oxygen and accelerating gaseous O_(2) dissociation to generate significantly increased active surface oxygen content;(ⅱ)modulating a moderate surface oxygen vacancies concentration to maintain more highly active O_(2) species.

关键词： Soot oxidation CuO_(x) Ag/CeO_(2) Controllable synthesis Active oxygen species Rare earths

Teaching of pathophysiology combined with clinical practice in the 21st century

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中国病理生理杂志 2009年第11期25卷 2249-2250页

作者： han Li- sha liu Jia Department of Pathophysiology Baotou Medical College Baotou 014060 China

Pathophysiology,dealing with the functional changes in the host with disease or particular syndrome,is regarded as a bridge to guide students from basic medicine to clinical medicine. However,the traditional way in teaching of pathophysiology is far from clinical practice,mainly focuses on the acquisition and mastery of theoretical knowledge. Moreover,it is difficult for students to master the basic theoretical knowledge specifically and effectively under the condition away from clinical patients. In order to enhance the association of basic course with clinic,to combine the lecture and learning knowledge and clinical skills,we try to perform the combination of teaching pathophysiology with clinical practice in the training program for teachers and teaching activities. 1. The object:(1)Based on typical clinical cases,students participate bed side teaching and study theoretical knowledge.(2)To create whole concept on association among organs and systems of human diseases.

关键词：病理生理学生理学教学临床实践临床医学基础医学传统方法综合征

High-strength Ti-Al-V-Zr cast alloys designed using α and β cluster formulas

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China Foundry 2023年第1期20卷 23-28页

作者： Zhi-hao Zhu Yu-han liu Zhi-peng Chen Tian-yu liu Shuang Zhang Dan-dan Dong Chuang Dong Key Laboratory for Materials Modification by Laser Ionand Electron Beams and School of Materials Science and EngineeringDalian University of TechnologyDalian 116024LiaoningChina State Key Laboratory of Light Alloy Casting Technology for High-end Equipment Shenyang Research Institute of Foundry Co.Ltd.Shenyang 110022China School of Materials Science and Engineering Dalian Jiaotong UniversityDalian 116028LiaoningChina College of Physical Science and Technology Dalian UniversityDalian 116622LiaoningChina

Ti-Al-V-Zr quaternary titanium alloys were designed followingα-{[Al-Ti12](AlTi2)}17-n+β-{[Al-Ti12Zr2](V3)}n,where n=1-7(the number ofβunits),on the basis of the dual-cluster formula of popular Ti-6Al-4V *** an alloying strategy aims at strengthening the alloy via Zr and V co-alloying in theβ-Ti unit,based on the originalβformula[Al-Ti14](V2Ti)of Ti-6Al-4V *** microstructures of the as-cast alloys by copper-mold suction-casting change from pureα(n=1)toα+α’martensite(n=7).When n is 6,Ti-5.6Al-6.8V-8.1Zr alloy reaches the highest ultimate tensile strength of 1,293 MPa and yield strength of 1,097 MPa,at the expense of a low elongation of 2%,mainly due to the presence of a large amount of acicularα’*** specific strength far exceeds that of Ti-6Al-4V alloy by 35%.

关键词： titanium alloy cluster-plus-glue-atom model composition design microstructure mechanical properties

Catalysts or Barriers?The Impacts of Natural Disasters on Internal Labor Migration in China

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China & World Economy 2024年第2期32卷 160-199页

作者： Xingyu Zhou liu han Jidong Chen Department of Political Science University of RochesterUS School of Finance Zhongnan University of Economics and LawChina School of Public Policy and Management Tsinghua UniversityChina

This paper discusses ways in which negative economic shocks captured by natural disasters can shape internal labor migration in *** impact of negative economic shocks on migration depends on the combination of two opposite driving forces:(i)negative economic shocks can make staying in the affected area less profitable,thus enhancing returns to migration;(ii)the shocks can make it more difficult to migrate out,thus inducing a higher fixed cost of *** on a nationwide dataset of China,this paper shows that when natural disasters were not severe,they caused migration out of rural *** sufficiently severe damage,however,the negative effect of natural disasters could be mitigated by villages'prior migrant ***,with a severe shock,only clan members were able to migrate in response to natural disasters and enjoyed the complementary effects of prior migrant networks,as they could receive more help from social capital.

关键词： family clans internal labor migration migrant networks natural disasters

Antioxidant activity of N-acetyl-glucosamine based thiazolidine derivative

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High Technology Letters 2007年第4期13卷 441-446页

作者：李春雷 Yang Yan han Baoqin liu Wanshun College of Marine Life Sciences Ocean University of China Qingdao 266003 P.R. China

N-acetyl-glucosamine, the monomer of chitin, was cyclo-condensed with L-cysteine to prepare thiazolidine derivative： 2-N-acetyl-glucosamine-thiazolidine-4（R）-carboxylic acid （GlcNAcCys）. The stability of GlcNAcCys was evaluated by high performance liquid chromatography （HPLC） measurement. The results showed that GlcNAcCys was more stable than other TCA derivatives, especially in alkaline condition. The direct in vitro antioxidative properties of GlcNAcCys were investigated by using UV radiation-induced lipid peroxidation （LPO） in mitochondria and nuclei and . OH-induced LPO in red blood cell （RBC） ghosts models. UV radiation caused dose-dependent LPO in both mitochondria and nuclei. This effect was catalyzed by addition of Fe^2 ＋ while prevented by co-incubation with GlcNAcCys. When nuclei and mitochondria was treated with 100μl, 300μl, 500μl of GlcNAcCys and co-incubated at 37℃ for 30min, LPO was decreased to 96%, 72%, 68% in nuclei and 95%, 72%, 68% in mitochondria when compared to the UV radiation group respectively. Hydroxyl radicals （. OH） generated by Fenton reaction induced LPO in RBC ghosts. Pretreatment of RBC ghosts with GlcNAcCys could induce antioxidant RBC ghosts and inhibit concentration-dependent malondialdehyde （MDA） formation in antioxidant RBC ghosts. Its inhibition percent was 14%, 35%, 36%, 42% at 10, 20, 30, 40mg/ml respectively. In a conclusion, the data suggest that GlcNAcCys has antioxidant ability and can significantly inhibit lipid peroxidation in biological samples tested in vitro.

关键词： thiazolidine-4(R)-carboxylic acid N-acetyl-glucosamine antioxidant lipid pemxidation