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RESEARCH ON AS-CAST GRAIN REFINING TECHNOlOGy By INOCUlATING ClEAN STEEl WITH TITANIUM OXIDE

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Acta Metallurgica Sinica(English letters) 2003年第5期16卷 379-384页

作者： G.G.Cheng M.l.Wang X.E.yang y.l.li y.G.Wang l.y.Wang P.Zhao UniversityofScienceandTechnologyBeijing Beijing100083China CentralironandSteelResearchInstitute Beiiing100081China

Precipitation condition and nucleation of Ti2O3 during solidification of clean steel have been studied. The behavior of Ti2O3 during solidification as well as possibility of using Ti2O3 to refine as-cast grains as heterogeneous nucleation sites is discussed. It is shown that Ti2O3 can be formed provided that the steelmaking and solidification process is controlled strictly. And inoculating clean steel with Ti2O3 is an effective way to refine as-cast grains.

关键词： clean steel solidification Ti2O3 precipitation

The effects of fabrication atmosphere condition on the microstructural and mechanical properties of laser direct manufactured stainless steel 17-4 PH

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Journal of Materials Science & Technology 2019年第7期35卷 1315-1322页

作者： D.Wang C.T.Chi W.Q.Wang y.l.li M.S.Wang X.G.Chen Z.H.Chen X.P.Cheng y.J.Xie Institute of Applied Physics Jiangxi Academy of SciencesNanchang 330029China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Mechanical and Electrical Engineering Nanchang UniversityNanchang 330029China Jiangxi Reman Additive Technology Co. ltd Nanchang 330096China

The effects of atmosphere conditions on microstructural and mechanical properties of stainless steel 17-4PH components fabricated by laser direct manufacturing (lDM) were investigated through mea-surements on phase constitution, porosity, tensile strength, fracture morphology, hardness and evolution of substrate temperature. Results showed that the samples produced in air atmosphere condition pos-sessed higher tensile strength and hardness for both as-deposited and heat-treated states than that in Ar chamber condition, due to dispersion strengthening effect of amorphous oxide particles and nitrogen solution strengthening as a result of higher content of oxygen and nitrogen. The temperature of substrate heat accumulation was higher in Ar chamber condition, leading to dramatically lower porosity and more reverse austenite, which also contributed to the lower strength and hardness.

关键词： Additive manufacturing laser direct manufacturing 17-4 PH stainless steel Fabrication atmosphere Mechanical properties

Experimental methods for determination of mechanical behaviors of materials at high temperatures via the split Hopkinson bars

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Acta Mechanica Sinica 2020年第6期36卷 1275-1293,I0003页

作者： Q.B.Dou K.R.Wu T.Suo C.Zhang X.Guo y.Z.Guo W.G.Guo y.l.li School of Aeronautics Northwestern Polytechnical UniversityXi’an710072China Joint International Research laboratory of Impact Dynamics and its Engineering Application Xi’an710072China Shaanxi Key laboratory of Impact Dynamics and its Engineering Application Xi’an710072China State Key laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an710049China

Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure design and safety *** efforts have been made for abilities of operation the split Hopkinson bars,the most popular technique for experimental determination of mechanical behaviors of materials over the strain rates from 10^2 to 10^4 s^−1 over the past 70 years,at high temperatures since 1960s.A review of experiment work is presented in this paper to give an overview of the development of experimental techniques at high temperatures based on Hopkinson bar *** principles of the split Hopkinson bar requires the loading bars avoiding temperature gradient or keeping relatively low temperature when performing high temperature *** such as performing temperature gradient corrections,rapid heating or using special designed automatically assembled systems were proposed by researchers to enable the operation of the split Hopkinson bars at temperature as high as ***,to the application of high speed photographic technique for capturing the dynamic deformation process of the specimen in high temperature Hopkinson bar testing,some key issues of eliminating the strong thermal radiation induced lights oversaturation and de-blurring of images due to insufficient exposure at high temperature and high strain rate condition,as well as fabrication of high contrast speckle pattern for high temperature digital image correlation measurement were also *** technique can now enable the split Hopkinson bar testing to be performed at high temperature up to 1873 K under the loading conditions of compression or tension with the in situ observation and full field measurement of deformation as *** paper concludes with summaries of the most important achievements and highlighting of the prospects,trends and remaining challenge

关键词： Mechanical behaviors Split Hopkinson bar High strain rate High temperature

POlAR NANOREGION IN RElAXOR FERROElECTRICS STUDIED By ANAlyTICAl ElECTRON MICROSCOPy

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Journal of Advanced Dielectrics 2012年第2期2卷 119-120页

作者： y.l.li l.XIE J.ZHU Beijing National Center for Electron Microscopy Tsinghua University Beijing 100084P.R.China Department of Materials Science and Engineering The State Key laboratory of New Ceramics Fine Processing laboratory of Advanced Materials Tsinghua University Beijing 100084P.R.China

Relaxor ferroelectrics have different properties from that of the normal ferroelectrics,such as dielectric properties with diffuse phase transition and frequency dispersion,specific heat,birefringence,elastic constants and Raman scattering,*** is considered that the different properties are related with the polar nanoregions in *** this work we briefly introduce how we use the high spatial resolution analytical electron microscopy and high resolution electron microscopy methods to investigate the polar nanoregion in Pb(Mg_(1/3)Nb_(2/3))O_(3)(PMN),Pb(Mg_(1/3)Nb_(2/3))O_(3)PbTiO_(3)(PMNPT)and Ba(Ti_(1-x)Sn_(x))O_(3)(BTSn).The main experimental results110 are as mentioned in next three parts.

关键词： Relaxor polar nanoregion analytical transmission electron microscopy

Dynamic mechanical Response of two fiber-reinforced composites

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Dynamic mechanical Response of two fiber-reinforced composit...

The 16th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics 2012、The 1st Mainland-Hong Kong youth Forum on Mechanics 2012、The 8th Shanghai-Hong Kong Forum on Mechanics and Its Application 2012

作者： y.Z.Guo X.Chen Z.Zeng y.l.li School of Aeronautics Northwestern Polytechnical University

The mechanical behavior of two fiber-reinforced composites,i.e.,CF3031/Qy8911 and EW100A/BA9916,under dynamic loadings were carefully studied by using split Hopkinson pressure bar(SHPB) *** results show that most of the stress strain curves of both of the two composites are not monotonous but exhibite double-peak shape. The deformation as well as fracture characteristics of the composites under dynamic loadings were captured by using high speed *** photoes indicate that two different failure mechanisms work during dynamic fracture *** first one is the overall shear,which occurs along the path 45°to the loading *** second one is the cleavage between the fiber and the matrix(see figure 1).The competition between these two mechanisms determines the deformation behavior of the *** the overall shear dominates,the stress increase monotonously with increasing strain until ***,if the cleavage mechanism dominates,the double peak character shows itself in the stress-strain curves.

关键词： Dynamic mechanical Response of two fiber-reinforced composites

Inertia Effect on the Impact Successive Crushing of Aluminium Honeycombs

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Inertia Effect on the Impact Successive Crushing of Aluminiu...

作者： B.Hou H.Zhao S.Pattofatto y.l.li School of Aeronautics Northwestern Polytechnical University laboratoire de Mecanique et Technologie ENS-Cachan/CNRS-UMR8535/Universite Paris 661 avenue du president Wilson94235 Cachan cedexFrance

Cellular materials have attracted much of the engineers' interests due to their excellent energy absorbing capabilities in vehicle or aircraft crashworthness *** application as energy absorber necessitates the knowledge of the behavior under dynamic *** the reported studies, an enhancement of loading capacity under dynamic condition has been found for several of these *** up till now,the available experimental data is still a great lack and argument also remains for the potential reason of this phenomenon of dynamic enhancement. This paper studied experimentally the out-of-plane compressive behavior for a series of aluminium honeycombs of different sizes(relative densities varying from 1.78%to 4.72%) and base materials (3003 and 5052 aluminum alloys) under moderate impact *** same testing procedures using large diameter Nylon Split Hopkinson bar were applied in a range of impact speed from 10m/s to 30m/*** accuracy of such a Nylon SHPB system is proved to be enough to obtain reliable testing results for such soft *** testing results confirmed that there do exist a strength enhancement from 10% to 60% for different alloys,even though the 3003 alloy and 5052 alloy have both very limited rate sensitivities around 10%.A comprehensive numerical investigation with rate insensitive constitutive laws is afterwards performed to reproduce the experimental results for different cell size/wall thickness/base materials,which proves that honeycomb impact strength enhancement should be due to a structural effect. A possible explanation of this strength enhancement under moderate impact velocities is that this enhancement is due to the lateral inertia in the successive folding of *** basic idea lies in the fact that the buckling of an elastic-plastic column under compressive impact occurs at a larger strain(than under quasi-static loading) because of lateral inertia,so that the critical buckling force is higher than in the s

关键词： Inertia Effect on the Impact Successive Crushing of Aluminium Honeycombs

An experimental research on coal gasification for hydrogen production in supercritical water

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An experimental research on coal gasification for hydrogen p...

第九届全国氢能学术会议

作者： y.l.li,l.J.Guo,X.M.Zhang,H.Jin,y.J.lu Xi''an Jiaotong University,China

＜正＞The main problem in hydrogen produciton from coal gasification in supercritical water is the stable and continuous operation of high concentration of coal *** work in this paper aims at hydrogen production by gasification of high concentration coal in supercritical *** experiment of gasification of high concentration coal in supercritical water was

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On B(5,20)2-Groups

Algebra Colloquium 2024年第3期31卷 429-440页

作者： E.A.Alhassan y.l.Tan y.li School of Mathematical Sciences Jiangsu UniversityZhenjiangJiangsu 212013China Department of Mathematics Brock UniversitySt.CatharinesOntario L2S 3A1Canada

A finite group G is said to be a B(n,k)group if for any n-element subset[a_(1),…,a_(n)]of G,|{a_(i)a_(j)|1≤i,j≤n}|≤*** is of interest to characterize the structure of B(n,k)groups for n(n+1)/2≤k≤n^(2)-*** B(5,k)groups for 15≤k≤19 have been investigated by several *** this paper,we give a complete characterization of B(5,20)2-groups by showing there are five classes of such groups which are nontrivial and nonabelian.

关键词： B(n,k)groups small squaring property central extension GAP

Intestinal microbiota and oral administration of Enterococus faecium associated with the growth performance of newborn piglets

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Intestinal microbiota and oral administration of Enterococus...

中国畜牧兽医学会动物微生态学分会第五届第十二次全国学术研讨会

作者： y.B.Wang W.Du A.K.Fu X.P.Zhang y.Huang K.H.lee K.yu W.F.li y.l.li College of Animal Science Zhejiang University National Engineering laboratory of Bio Feed Safety and pollution prevention Key Laboratory of Molecular Animal NutritionMinistry of EducationKey Laboratory of Animal Nutrition and Feed Science in East ChinaMOA College of Biosystems Engineering and Food Science Zhejiang University College of Animal Science and Technology Guangxi University Faculty of Medicine Dentistry and Health ScienceThe University of Western Australia

The oral administration of Enterococus faecium(EFl) to newborn suckling and weaned piglets along with their growth performances and intestinal microbiota was investigate in this study..Twenty-four newborn piglets were initially divided into 2 *** treatment or probiotics group receiving 2 ml of 10%sterilized skim milk by oral gavage was supplemented with viable Enterococcus faecium EF1(6×10 CFU/ml) at the first,the third and the fifth day after birth,while the control group was made of 2 ml of 10%sterilized skim milk without probiotic at the same *** showed that oral administration of Enterococcus faecium EF1 was associated with a remarkable increaseon the body weight of piglets for both suckling and weaning periods,by 30.73%(Plso decreased the diarrhea rate,by 43.21%(Pyrosequencing analysis revealed that there was no significant difference in the intestinal microbial diversity of the suckling piglets between the two groups,nevertheless,when compared to the control group,the relative abundance of Firmicutes in the probiotics group substantially augmentedy,while the relative abundance of Proteobacteria,Bacteroidetes and Fusobacteria ***,result indicated that oral administration of Enterococus faecium EF1 did not have any influence on the relative abundance of Firmicutes in weaned piglets rather than increasing the relative abundance of Bacteroidetes and decreasing the relative abundance of ***,at level of Firmicutes phylum,the relative abundance of lactobacillales in theprobiotic group increased *** findings suggest that oral administration of *** EF1 to newborn piglets could improve the growth performance and intestinal microbiota of piglets for both suckling and weaning periods.

关键词： Enterococus faecium EF1 piglets growth performance microbiota