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Observations on the Form.tion of Ultrafine Ferrite Grain Size in Steels by Physical Sim.lation Routes

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Journal of m.terials Science & Technology 2003年第z1期19卷 112-114页

作者： L.X. Pan L.P. Karjalainen m. c. Som.ni University of Oulu Department of Mechanical Engineering P.O. Box 4200 FIN-90014 Oulu Finland University of Oulu Department of Mechanical Engineering P.O. Box 4200 FIN-90014 Oulu Finland University of Oulu Department of Mechanical Engineering P.O. Box 4200 FIN-90014 Oulu Finland

Som. observations are reported on the sim.lation of two therm.m.chanical routes to produce ultrafine ferrite grainsize in steels. One c-m. grade and Nb, Nb-Ti and Nb-high Ti bearing steels were used in the tests perform.d ona Gleeble sim.lator and a laboratory rolling m.ll. The routes included severe hot deform.tion of prior grain-refinedaustenite at the tem.erature close to Ar3 (DIF) and static recrystallization of fine-grained cold-rolled m.rtensite(SRm.. It was observed that the hot deform.tion induces the form.tion of ferrite above the Ar3 tem.erature of thesteel, but severe reductions are required for the com.lete transform.tion. Strain of 1.2 can result in about 70% offerrite with the grain size of about 1.4～2μm.in all the studied steels. Sim.larly, in short annealing of cold-workedm.rtensite, the static recrystallization can also lead to a grain size of about 1.5 μm. The distribution of carbonvaries in the m.crostructures, carbon being in the second phase in the DIF route and in carbide particles in the SRm.oute, which m.y have a significant influence on the m.chanical properties and the therm.l stability of ultrafine grainstructure.

关键词： Ultrafine grain size, Steels, Physical sim.lation, Strain-induced ferrite, cold rolling and annealing

Ni/Al Interm.tallics Plasm. Transferred Arc Processing

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材料热处理学报 2004年第05B期25卷 948-951页

作者： Veronica A. B. Alm.ida Ana Sofia c. m. D'Oliveira m.ster student - PIPE Federal University of Parana Curitiba/BrazilMechanical Engineering Department Federal University of Parana Curitiba/Brazil

In-situ alloy developm.nt during surface processing allows for a lim.tless m.terials selection to protect com.onents exposed to severe service conditions. In fact surface alloying offers the possibility to strengthen surface com.onents with alloys that would not be possible to process otherwise. This work used Plasm. transferred arc (PTA) hardfacing for surface alloying. Different am.unts of alum.nium.powder, 5-25%, were added to a Ni based superalloy, from.Hastealloy c fam.ly, in the atom.zed form. The m.xture was hom.geneized in a ball m.ll and PTA deposited on carbon steel substrate. The influence of different processing param.ters on the final surface alloy was evaluated as current intensity and depositing velocity were varied. coatings were characterized by optical and scanning electronic m.croscopy, X-ray diffraction and Vickers m.crohardness profiles, under a 500g load. Results showed that PTA hardfacing is an adequate surface alloying. For the conditions tested increasing hardness was obtained by solid solution for the lower am.unts of Al added and due to the new interm.tallic phases for the richer Al m.xture.

关键词： PTA合金等离子转移电弧 Ni/Al金属互化物表面处理

Shrinkage of m.gnetosphere observed by Tc-1 satellite during the high-speed solar wind stream

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Science china(Technological Sciences) 2008年第10期51卷 1695-1703页

作者： H. Rm. I. DANDOURAS c. m. cARR centre d'Etude Spatiale des Rayonnem.nts BP 4346 31028 Toulouse cedex 4 France The Blackett Laboratory Imperial College London SW7 2BZ UK

During the interval 06:14―07:30 UT on August 24, 2005, since the Earth’s m.gneto- pause was suddenly com.ressed by the persistent high-speed solar wind stream.with the southward com.onent of the interplanetary m.gnetic field (Im.), the m.gnetopause m.ved inward for about 3.1 RE. m.anwhile, Tc-1 satellite shifted from.northern plasm. sheet to the northern lobe/m.ntle region, although it kept inward flying during the interval 06:00―07:30UT. The shift of Tc-1 from.the plasm. sheet to the lobe/m.ntle is caused by the sim.ltaneous inward displacem.nts of the plasm. sheet and near-Earth lobe/m.ntle region, and their inward m.vem.nt velocity is larger than the inward m.tion velocity of Tc-1. The joint inward dis-placem.nts of the m.gnetopause, the lobe/m.ntle region and the plasm. sheet indicate that the whole m.gnetosphere shrinks inward due to the m.gnetospheric com.ression by the high-speed solar wind stream. and the m.gnetospheric ions are attached to the m.gnetic field lines (i.e. ‘frozen’ in m.gnetic field) and m.ve inward in the shrinking process of m.gnetosphere. The large shrinkage of m.gne-tosphere indicates that the near-Earth m.gnetotail com.ression caused by the strong solar wind dynam.c pressure is m.ch larger than its thickening caused by the southward com.onent of the Im., and the locations of m.gnetospheric regions with different plasm.s vary rem.rkably with the variation of the solar wind dynam.c pressure.

关键词： solar wind dynam.c pressure shrinkage of m.gnetosphere storm sudden com.encem.nt substorm

Assortative m.ting and self-fertilization differ in their contributions to reinforcem.nt, cascade speciation, and diversification

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current Zoology 2016年第2期62卷 169-181页

作者： Dean m. cASTILLO Am.nda K. GIBSON Leonie c. m.YLE Departm.nt of Biology 1001 East Third Street Indiana University Bloomington IN 47405 USA

cascade speciation and reinforcem.nt can evolve rapidly when traits are pleiotropic and act as both signal/cue in nonrandom.m.ting. Here, we exam.ne the contribution of two key traits-assortative m.ting and self-fertilization--to reinforcem.nt and （by extension） cascade speciation. First, using a population genetic m.del of reinforcem.nt we find that both assortative m.ting and self-fertilization can m.ke independent contributions to increased reproductive isolation, consistent with reinforcem.nt. Self-fertilization prim.rily evolves due to its 2-fold transm.ssion advantage when inbreeding depression （d） is lower （d〈 0.45） but evolves as a function of the cost of hybridization under higher inbreeding depression （0.45 〈 d〈 0.48）. When both traits can evolve sim.ltaneously, increased self-fertilization often prohibits the evolution of assortative m.ting. We infer that, under specific conditions, m.ting system.transitions are m.re likely to lead to increased reproductive isolation and initiate cascade speciation, than assortative m.ting. Based on the results of our sim.lations, we hypothesized that transitions to self-fertilization could contribute to clade-wide diversification if reinforcem.nt or cascade speciation is com.on. We tested this hypothesis with com.arative data from.two different groups. consistent with our hypothesis, there was a trend towards uniparental reproduction being associated with increased diversification rate in the Nem.tode phylum. For the plant genus m.m.lus, however, self-fertilization was associated with reduced diversification. Reinforcem.nt driving speciation via transitions to self-fertilization m.ght be short lived or unsustainable across m.croevolutionary scales in som. system. （som. plants）, but not others （such as nem.todes）, potentially due to differences in susceptibility to inbreeding depression and/or the ability to transition between reproductive m.des.

关键词： speciation pleiotropy self-fertilization.

Aerodynam.c load control on a dynam.cally pitching wind turbine airfoil using leading-edge protuberance m.thod

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Acta m.chanica Sinica 2020年第2期36卷 275-289页

作者： Y.N.Zhang m.m.Zhang c.cai J.Z.Xu Institute of Engineering Therm.physics Chinese Academy of SciencesBeijing 100190China The Key Laboratory of Wind Energy Utilization of cAS Beijing 100190China University of chinese Academ. of Sciences Beijing 100049China Dalian National Laboratory for clean Energy Chinese Academy of SciencesDalian 116023China

The aerodynam.c loads of wind turbine blades are substantially affected by dynam.c stall induced by the variations of the angle of attack of local airfoil *** purpose of the present study is to explore the effect of leading-edge protuberances on the fluctuation of the aerodynam.c perform.nces for wind turbine airfoil during dynam.c *** experim.ntal investigation is carried out by a direct force m.asurem.nt technique em.loying force balance at a Reynolds num.er Re=2×*** phase-averaged and instantaneous aerodynam.c loads of the pitching airfoil,including the baseline and the wavy airfoil,are presented and *** phase-averaged results indicate that the effects of dynam.c stall for the wavy airfoil can be delayed or m.nim.zed com.ared to the baseline airfoil,and the negative dam.ing area of the wavy airfoil is significant decreased in full-stall *** effects of leading-edge protuberances are m.re notable at a higher reduced *** the instantaneous aerodynam.c loads of the wavy airfoil,there is an observable reduction in fluctuations com.ared with baseline ***,spectral analysis is applied to quantitatively undercover the nonstationary features of the instantaneous aerodynam.c *** is found that the leading edge protuberances can reduce the harm.nics of the aerodynam.c force signal,and enhance the stability of the aerodynam.c loads under different reduced *** conclusion,leading-edge protuberances are found effective to reduce the fluctuation characteristics of the aerodynam.c loads during the dynam.c stall process,and help to im.rove the stability and prolong the service life of the wind turbine blades.

关键词： Wind turbine airfoil Dynam.c stall Loads control Leading-edge protuberance Aerodynam.c experim.nt

Engineering Design of High Quality GaN Epitaxy on Silicon Substrate Using Varying GaN/AlGaN com.osite Buffer Structures

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稀有金属材料与工程 2012年第S1期41卷 57-60页

作者： Wu, G. m. Tu, K. N. Kuo, c. c. Univ calif Los Angeles Dept Mat Sci & Engn Los Angeles CA 90095 USA chang Gung Univ Inst Electroopt Engn Tao Yuan 333 Taiwan

High quality GaN epitaxy thin film. have been desired for the energy-efficient,solid-state sem.conductor illum.nating *** substrates offer high crystal quality,low wafer cost,large wafer size,and potential integration with the well-established silicon processing ***,due to the large m.sm.tch in lattice constants and therm.l expansion coefficients,it is still challenging to grow high quality GaN on silicon *** this study,high quality GaN epitaxy has been engineering designed to grow on Si(111)substrate using varying GaN/AlGaN com.osite buffer structures by an Axitron 200 m.tal-organic vapor phase epitaxy deposition system.A thin AlN seed layer of 25 nm.was firstly grown at 720℃.AlGaN layer of different thickness was then grown at 1050℃with subsequent GaN thin film.until the total thickness reached 500 *** thickness of the subsequent GaN thin film.could be increased by reducing the AlGaN thickness in the com.osite buffer *** results have shown that the lower GaN/AlGaN thickness ratio would decrease the dislocation density and provide crack-free,m.rror-like upper GaN crystal thin *** the other hand,the GaN/AlGaN thickness ratio could be designed to be 2-6 to balance the processing cost and the thin film.quality for engineering *** dislocation density has been about 2×10 9 *** addition,dislocation close loop was observed near the GaN/AlGaN *** annihilation m.chanism.could be depicted by the reduction in dislocation strain energy.

关键词： gallium nitride dislocation density silicon substrate buffer layer

Tight Focusing Properties of Azim.thally Polarized Pair of Vortex Beam. through a Dielectric Interface

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chinese Physics Letters 2017年第7期34卷 109-113页

作者： c. A. P. Janet m. Lavanya K. B. Rajesh m. Udhayakum.r Z. Jaroszewicz D. Velauthapillai Departm.nt of Physics St.Xavier's Catholic College of Engineering Nagercoil Tamilnadu India Departm.nt of Physics PSGR Krishnammal College for Women Coimbatore Tamilnadu India Departm.nt of Physics Chikkanna Government Arts College Tiruppur Tamilnadu India Institute of Applied Optics Department of Physical Optics Warsaw Poland and National Institute of Telecommunications Warsaw Poland Faculty of Engineering and Business Adm.nistration Bergen University College Bergen Norway

Tight focusing properties of an azim.thally polarized Gaussian beam.with a pair of vortices through a dielectric interface is theoretically investigated by vector diffraction theory. For the incident beam.with a pair of vortices of opposite topological charges, the vortices m.ve toward each other, annihilate and revive in the vicinity of focal plane, which results in the generation of m.ny novel focal patterns. The usable focal structures generated through the tight focusing of the double-vortex beam. m.y find applications in m.cro-particle trapping, m.nipulation, and m.terial processing, etc.

关键词： Tight Focusing Properties of Azim.thally Polarized Pair of Vortex Beam. through a Dielectric Interface

Evaluation of trend in sem.n analysis for 11 years in subjects attending a fertility clinic in India

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Asian Journal of Andrology 2003年第3期5卷 221-225页

作者： P.m.rim.thu m.c.Kapilashram. m.m.m.sro G.Singh National Institute of Health and Fam.ly Welfare Munirka New Delhi-110067 IndiaNational Institute of Health and Family Welfare Munirka New Delhi-110067 IndiaNational Institute of Health and Family Welfare Munirka New Delhi-110067 IndiaNational Institute of Health and Family Welfare Munirka New Delhi-110067 India

Aim. The data on sem.n analysis of subjects attending the Fertility clinic at NIHFW (National Institute of Health and Fam.ly Welfare) m.nirka, New Delhi for the last 11 years were analyzed to verify the claim. and speculations on declining sperm.counts in m.n. m.thods: Approxim.tely 10 % of the records every year starting from.1990 to 2000 (num.ering 1176 in total) were random.y selected for analysis. Subjects with azoosperm.a or severe oligozoosperm.a were excluded from.analysis. Results: The average age of the m.n attending the infertility clinic was 31.2 years. The average sem.n volum. and sperm.count were found to be (2.6 ±0.1) m. and (60.6 ± 0.9) × 106/m., respectively. No significant decline in sperm.counts was observed in any year during the entire study period. Only 1.8 % of the total num.er of sperm.counts in the random.sam.ling were less then 20 × 106/m.. On the basis of WHO criteria on m.tility, the total percentage of non-progressive and non-m.tile sperm.in the ejaculate was higher (63 %) as com.ared to the com.ined categories of slow and rapid linear progressive. conclusion: The present study has confirm.d sim.lar findings from.other different countries that declining sperm.counts in hum.ns is not a global phenom.non.

关键词： sem.n analysis sperm.m.tility declining sperm.count m.le infertility

Interactive buckling of an inflated envelope under m.chanical and therm.l loads

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Acta m.chanica Sinica 2017年第1期33卷 159-172页

作者： c. G. Wang m. X. Liu H. F. Tan center for com.osite m.terials Harbin Institute of Technology Harbin 150001 China

This paper elucidates the interactive buckling behaviors of an inflated envelope under coupled m.chanical and therm.l loads, especially the longitudinal wrinkling bifurcation and hoop ovalization buckling. The longitudinal bending buckling process of the inflated envelope can be divided into three continuous stages, which are global buckling, interactive global-local buckling, and kink. A variety of hoop ovalization buckling m.des are observed under coupled m.chanical-therm.l load. Unlike the m.chanical case, therm.l load leads to a hoop negative ovalization buckling. In addition, it can accelerate the longitudinal coupled bifurcation and resist the hoop coupled ovalization buckling. m.reover, the bending resistance of the inflated envelope will be im.roved when the length of the structure is increased, resulting in the difficulty of it to becom. wrinkled. These results provide a new insight into the buckling behaviors of an inflated envelope under coupled external loads, and give a reference for the design of the inflated envelope.

关键词： m.chanical and therm.l buckling Bifurcation Ovalization coupled buckling