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Journal of Materials Science & Technology 2014年第7期30卷 649-655页

作者： z.Y.liu B.l.Xiao W.G.Wang z.Y.Ma Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences Dalian University of Technology liaoning Shihua University

A route combining powder metallurgy and subsequent friction stir processing was utilized to fabricate carbon nanotube （CNT） reinforced AI （CNT/AI） and 6061AI （CNT/6061AI） composites. Microstructural observations indicated that CNTs were uniformly dispersed in the matrix in both CNT/AI and CNT/6061AI composites. Mg and Si elements tended to segregate at CNT-AI interfaces in the CNT/6061AI composite during artificial aging treatment. The tensile properties of both the AI and 6061AI were increased by CNT incorporation. The electrical conductivity of CNT/AI was decreased by CNT addition, while CNT/6061AI exhibited an increase in electrical conductivity due to the Mg and Si segregation.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Electrical properties Friction stir processing

INFlUENCE OF lOCAl BRITTlE zONE ON THE FRACTURETOUGHNESS OF HIGH-STRENGTH lOW-AllOYEDMUlTIPASS WElD METAlS

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Acta Metallurgica Sinica(English letters) 1998年第2期11卷 87-92页

作者： z.l.zhou S.H.liu Dalian Railway Inst Dalian China

In this paper, toughness properties and microstructurc of low-alloyed multipass welds with yield strength above 700MPa have 6een studied using the weld thermal simulation and throughout thickness CTOD fracture mechanics tests. Impact testing of thermal simulated specimens showed that the primary weld metal and the fine gmmed weld metal had good toughness, while the coarse grained weld metal had the lowest toughness value as the local brittle zone (lBz) in multipass weld metals. Cleavage fracture in CTOD testing of thick multipass weld metals was initiated from martensite-austenite (MA) phases in the lBz. MA phases were distributed at the prior austenite grain boundaries and around ferrite grains. As the size of the local brittle zone along the fatigue crack front increases, CTOD frncture toughness of multipass weld metals decreases. The weakest link theory was used to evaluate effect of the local brittle zone on fracture toughness of thick multipass weld metals. The estimated curves agree well with the eaperimental data.

关键词： multipass weld metal local brittle zone weld thermal simulation CTOD fracture toughness

Drag reducing nose fairings for existing freight train locomotives

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Advances in Aerodynamics 2022年第1期4卷 780-797页

作者： Chad l.Stucki daniel Maynes Corvid Technologies MooresvilleNC28115USA Department of Mechanical Engineering Brigham Young UniversityProvoUT84602USA

At cruising speed,one of the most significant contributing factors to train fuel consumption is aerodynamic drag,and the leading locomotive experiences much more drag than any other car in the *** work reports on the drag reduction that can be realized by the use of add-on nose fairings that are deployed on leading locomotives in a train *** types of fairing shapes were considered and all fairing walls are *** is anticipated that the fairing shapes would result from the deployment of easily stowed panels in an origami inspired *** of the fairing shapes has the appearance of a wedge and the other fairing is also wedge shaped,but with flow directing side wall *** each general fairing shape,the important dimensions were parametrically varied in a systematic manner to identify the dimensions that yield maximum drag *** the first shape,45 different scenarios were considered;for the second shape,15 were considered.A steady commercial computational fluid dynamic solver was employed to solve the flow field and locomotive drag for each of the *** best performing wedge-shaped fairing reduced the leading locomotive drag by nominally 14%and the best performing fairing shape with the side walls reduced the drag by 17%.

关键词： Drag reduction Front-fairing Origami locomotive

A NOVEl METHOD FOR EVAlUATING PlANE STRESS DYNAMIC FRACTURE TOUGHNESS OF 0Cr18Ni10Ti STAINlESS STEEl WElDED JOINTS

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Acta Metallurgica Sinica(English letters) 2008年第4期21卷 303-312页

作者： z.J. Xu Y.l. li School of Aeronautics Northwestern Polytechnical University Xi＇an 710072 China

A novel method was proposed for the evaluation of Mode I dynamic fracture toughness （DFT） under plane stress and small scale yielding conditions for welded joints of stainless steel （SS）, 0Cr18Ni10Ti. In a hybrid experimental-numerical approach, the experiments were carried out on the Hopkinson pressure bar apparatus, and three dimensional （3D） transient numerical simulations were performed by a finite element （FE） computer program. Macroscopical plastic deformation was observed at the loading and supporting points, on the specimens, after the test, which could cause a large error if omitted in the numerical simulation. Therefore, elustic-viscoplustic analysis was performed on the specimen by adopting the Johnson-Cook （J-C） model to describe the rate-dependent plastic flow behavior of the material. The material heterogeneity in the mismatched welded joints, induced by the difference in the base metal （BM） and the weld metal （WM） in yield stress, has also been taken into consideration by using the J-C models separately. Good accordance was obtained between the experimental and the computational results by the present approach. The relationship between plane stress DFT and loading rate was also obtained on the order of 108 MPa.m^1/2.s^-1.

关键词： 0Cr18Ni10Ti Welded joint High strain rate Dynamic fracture Plane stress

NUMERICAl SIMUlATION OF SUCCINONITRITE DENDRITIC GROWTH IN A FORCED FlOW

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Acta Metallurgica Sinica(English letters) 2008年第6期21卷 444-450页

作者： z. Chen C.l. Chen l.M. Hao School of Science Department of Applied Physics Shaanxi Key Laboratory of Condensed Matter Structures and Properties Northwestern Polytechnical University Xi＇an 710072 China School of Science Xi＇an University of Science ＆ Technology Xi＇an 710054 China

Numerical simulation based on phase field method is performed to describe solidification process of pure material in a free or forced flow. The evolution of the interface is showed, and the effects of mesh grid and flow velocity on succinonitrite shape are studied. These results indicate that crystal grows into an equiaxial dendrite in a free flow and into an asymmetrical dendritic in a forced flow. With increasing flow velocity, the upstream dendritic arm tip grows faster and the downstream arm grows slower. However, the evolution of the perpendicular tip has no significant change. In addition, mesh grid has no influence on dendritic growth shape when mesh grid is above 300×300.

关键词： Phase field method Forced flow Dendritic Succinonitrite Tip velocity

Ab initio STUDIES ON MAGNETISM OF 3d TRANSITION METAl DIMERS

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Acta Metallurgica Sinica(English letters) 2007年第5期20卷 341-346页

作者： J.H. Gu z.l. zhu School of Physical Engineering and Material Physics laboratory Zhengzhou University Zhengzhou 450052 China

Ab initio calculations with the self-consistent full-potential linearized augmented-plane-wave method （FlAPW）, under generalized gradient approximation, have been carried out to describe the electronic and magnetic properties of 3d transition metal dimers. It predicted the antiferromagneticity of Cr2 and ferromagneticity of other species. The Mn2 dimer was shown to be ferromagnetic coupling with a local magnetic moment of 5μB. retaining the value of its free atom state. The V2 and Ni2 exhibited low spin-polarization with local magnetic moment of only 1μB per atom. On the other hand, Fe2 and Co2 were highly spin-polarized with local magnetic moments of 3 and 2μB.

关键词： magnetism 3d transition metal dimer ab initio calculation

Design of 16S rRNA gene primers for 454 pyrosequencing of the human foregut microbiome

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World Journal of Gastroenterology 2010年第33期16卷 4135-4144页

作者： Carlos W Nossa William E Oberdorf Jφrn A Aas Bruce J Paster Todd z DeSantis Eoin l Brodie daniel Malamud Michael A Poles zhiheng Pei Department of Medicine New York University School of Medicine Department of Molecular Genetics The Forsyth Institute Faculty of Dentistry University of Oslo Harvard School of Dental Medicine lawrence Berkeley National laboratory Center for Environmental Biotechnology New York University College of Dentistry Depar tment of Pa thology and Medicine New York University School of MedicineNew YorkNY 10016United States Department of Veterans Affairs New York Harbor Health SystemNewYorkNY 10010United States

AIM:To design and validate broad-range 16S rRNA primers for use in high throughput sequencing to classify bacteria isolated from the human foregut ***:A foregut microbiome dataset was constructed using 16S rRNA gene sequences obtained from oral,esophageal,and gastric microbiomes produced by Sanger sequencing in previous studies represented by 219 bacterial *** primers evaluated were from the European rRNA *** assess the effect of sequence length on accuracy of classification,16S rRNA genes of various lengths were created by trimming the full length *** spanning various hypervariable regions were selected to simulate the amplicons that would be obtained using possible primer *** sequences were compared with full length 16S rRNA genes for accuracy in taxonomic classification using online software at the Ribosomal Database Project (RDP).The universality of the primer set was evaluated using the RDP 16S rRNA database which is comprised of 433 306 16S rRNA genes,represented by 36 ***:Truncation to 100 nucleotides(nt)downstream from the position corresponding to base 28 in the Escherichia coli 16S rRNA gene caused misclassification of 87(39.7%)of the 219 sequences,compared with misclassification of only 29(13.2%)sequences with truncation to 350 *** 350-nt sequence reads within various regions of the 16S rRNA gene,the reverse read of an amplicon generated using the 343F/798R primers had the least(8.2%)effect on *** comparison,truncation to 900 nt mimicking single pass Sanger reads misclassified 5.0%of the 219 *** 343F/798R amplicon accurately assigned 91.8%of the 219 sequences at the species *** by abundance of the species in the esophageal dataset,the 343F/798R amplicon yielded similar classification accuracy without a significant loss in species coverage(92%).Modification of the 343F/798R primers to 347F/803R increased their universality among foregut ***

关键词： Foregut Microbiome 16S 454 sequencing Primer

Influencing mechanism of pre-existing nanoscale Al5Fe2 phase on Mg-Fe interface in friction stir spot welded Al-free zK60-Q235 joint

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Journal of Materials Science & Technology 2020年第7期42卷 220-228页

作者： R.z.Xu Q.Yang D.R.Ni B.l.Xiao C.z.liu z.Y.Ma Institute of Metal Research Chinese Academy of SciencesShenyang110016China College of Material Science and Engineering Shenyang Aerospace UniversityShenyang110136China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign1304 W Green StUrbanaIL61801United States Fredrick Seitz Materials Research laboratory University of Illinois at Urbana-Champaign104 S Goodwin AveUrbanaIL61801United States

Al-free zK60 magnesium (Mg) alloy sheet was selected as substrate material of Mg-steel pinless friction stir spot welding (FSSW), avoiding the effect of the Al element in the substrate on the alloying reaction of Mg-iron (Fe) interface. The sound FSSW joint of zK60 Mg alloy and Q235 steel with a hot-dipped aluminum (Al)-containing zinc (zn) coating was successfully realized. The detailed microstructural examinations proved that Al5Fe2 phase at the Mg-Fe interface came from the pre-existing Al5Fe2 phase in the coating and acted as the transition layer for promoting the metallurgical bonding of Mg and Fe. The interfaces with well-matched lattice sites among Fe, Al5Fe2 and Mg were formed during FSSW. A low energy interface with good match of lattice sites ((002)Al5Fe2//(110)Fe, [110]Al5Fe2//[113]Fe) between Al5Fe2 and Fe was identified. For the interface between Al5Fe2 and Mg, an orientation relationship of (622)Al5Fe2//(3112)Mgand[158]Al5Fe2//[2423]Mg was observed. The tensile-shear load of the zK60-steel joint could reach 4.6 kN. Moreover, the joint fracture occurred at the interface between the Al5Fe2 layer and the Mg alloy substrate, suggesting the brittle fracture characteristic.

关键词： Dissimilar welding Friction stir spot welding Magnesium alloys Steels zinc coating

Deformation behaviors of Cu bicrystals with an inclined twin boundary at multiple scales

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Journal of Materials Science & Technology 2017年第7期33卷 698-702页

作者： l.l.li z.J.zhang P.zhang J.Tan J.B.Yang z.F.zhang Shenyaag National laboratory for Materials Science lastitute of Metal Research Chinese Academy of Sciences Shenyaag 110016 China

Cu bicrystals of different sizes with a sole twin boundary（TB） inclined at 45？with respect to the loading direction were deformed under unidirectional and cyclic loading, respectively. It is found that the slip bands（SBs） parallel to the TB can be activated near the TB at all scales without obeying the Schmid＇s *** is concerned with the local stress enhancement in the macroscale while it is more closely related to the scarce dislocation sources in the microscale. Moreover, a wedge-shaped zone formed near the TB in the microscale ascribed to the limited specimen size.

关键词： Bicrystal Micropillar Twin boundary Schmid factors Size effect

What artifice can and cannot tell us aboutanimal behavior

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Current zoology 2017年第1期63卷 21-26页

作者： daniel l. POWEll Gil G. ROSENTHAl Department of Biology Texas A&M University College Station TX 77843 USA Centro de InvestigacionesCientfficas de las Huastecas Aguazarca 43230 Calnali Hidalgo Mexico

Artifice--the manipulation of social and environmental stimuli--is fundamental to research in ani-mal behavior. State-of-the-art techniques have been developed to generate and present complexvisual stimuli. These techniques have unique strengths and limitations. However, many of theissues with synthetic animation and virtual reality are common to playback experiments in general,including those using unmanipulated video or auditory stimuli. Playback experiments, in turn, fallinto the broader category of experiments that artificially manipulate the array of stimuli experi-enced by a subject. We argue that the challenges of designing and interpreting experiments usingvirtual reality or synthetic animations are largely comparable to those of studies using oldertechnologies or addressing other modalities, and that technology alone is unlikely to solve thesechallenges. We suggest that appropriate experimental designs are the key to validating behavioralresponses to artificial stimuli and to interpreting all studies using artifice, including those that pre-sent complex visual displays.

关键词： animation, animal communication, artifice, experimental design, mate choice, playback.