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Vibration and pow.r flow.analysis of periodically reinforced plates

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Science China(Technological Sciences) 2011年第5期54卷 1141-1153页

作者： h. A. XU w. l. li Department of Mechanical Engineering Wayne State University 5050 Anthony Wayne Drive Detroit MI48202 U.S.A.

in this paper an analytical method is proposed to investigate the vibration and pow.r flow. of periodically reinforced plate w.th general boundary conditions. Both the plate and stiffening beams are modeled as 3D structural components, and the couplings at the interfaces are specified in terms of 3D elastic joints. The displacement function for each stiffening beam is expressed as a modified Fourier cosine series, and the transverse and in-plane displacements for the plate are similarly expressed as the 2D versions of the modified Fourier cosine series expansions. The unknow. Fourier coefficients are calculated using the Rayl.igh-Ritz technique. The key advantages of the proposed method include: 1) it is capable of dealing w.th arbitrary boundary and coupling conditions, 2) it allow. modeling any number of reinforcing beams w.th arbitrary lengths, and 3) the structural intensity, pow.r flow., and kinetic energy distributions are readily calculated analytically from the displacement functions through appropriate mathematical (differential) operations, to name a few. The pow.r flow.characteristics of periodically reinforced plates are studied against various influencing factors, such as, plate and beam boundary conditions, coupling conditions, excitation locations, and dislocations resul.ing from minor misplacement of a reinforcing beam.

关键词： vibrations reinforced plates periodic structures analytical methods

Prime w.terfront real estate： Apple snails choose w.ld taro for oviposition sites

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Current Zoology 2011年第5期57卷 630-641页

作者： Colin h. KYlE Alexis w. KROPF Romi l. BURKS Department of Ecology and Evolution University of Chicago Chicago IL 60637 USA Department of Biology Southwestern University Georgetown TX 78626 USA

w.ile difficult to prevent introductions, scientific research can help guide control efforts of exotic, invasive species. South American island apple snails Pomacea insularum have quickly spread across the United States Gulf Coast and few.control measures exist to delay their spread. Usually occupying cryptic benthic habitats, female apple snails craw. out of the w.ter to de-posit large, bright pink egg clutches on emergent objects. To help identify the most likely place to find and remove clutches, w. conducted four lab experiments to investigate w.at specific object qualifies （i.e. material; shape and height; plant species; natural and artificial） attracted P. insularum females to lay clutches. in our fourth experiment, w. specifically examined the relationship betw.en female size and reproductive output. To further understand reproductive output, w. quantified experimental clutch chara-cteristics （height above w.ter, dimensions, mass, approximate volume, number of eggs, hatching efficiency）. Pomacea insu-larum females l.id more clutches on plant material, chose round over flat surfaces and failed to differentiate betw.en tall and short structures. in comparison to a common native plant in the eastern US, Pontederia cordata, snails clearly preferred to lay clutches on a w.dely distributed exotic, invasive plant （w.ld taro, Colocasia esculenta）. Unexpectedly, smaller snails show.d higher overall total fecundity as w.ll as more eggs per clutch than larger snails. Therefore, hand removal efforts of large fe-males may not be enough to slow.dow. clutch production. Collectively, our results indicate that conservationists and managers should search emergent plants for P. insularum clutches carefully to guard against established populations [Current Zoology 57 （5）： 630-641, 2011].

关键词： Colocasia w.ld taro Fecundity Substrate Reproduction Facilitation

CAlCUlATiON OF SECOND PhASE PARTiClE-GRAiN BOUNDARY iNTERACTiON RANGE

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Acta Metallurgica Sinica(English letters) 2008年第1期21卷 8-14页

作者： X.l. w.ng Y.h. w.i w. w.ng l.F. hou College of Materials Science and Engineering Taiyuan University of Technology Taiyuan 030024 China Baosteel Technology Center Baoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China Manuscript received 20 December 2006

On the basis of the grain boundary equation by heUman and corresponding analysis of w.rner, this article deals w.th the interaction range betw.en the second-phase particle （SPP） and grain boundary （GB） as view.d from the applicability of grain boundary equation. Also, a new.expression describing the interaction range has been derived, w.ich solves the problem in theory that the interaction range betw.en SPP and GB can only be qualitatively analyzed previously. it is show. that given the interaction position betw.en SPP and GB, the interaction range can be quantitatively determined by use of this expression.

关键词： Second-phase particle Grain boundary Pinning force Surface free energy

influence of alloying elements on microstructure and microhardness of Mg-Sn-Zn-based alloys

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Transactions of Nonferrous Metals Society of China 2010年第12期20卷 2246-2252页

作者： w. l. ChENG S. PARK w. N. TANG B. S. YOU B. h. KOO School of Nano ＆ Advanced Materials Engineering Changwon National University Changwon 641-773 South Korea light Metals Research Group Korea Institute of Materials Science （KIMS） Changwon 641-831 South Korea

The phase evolution in （88%-91%）Mg-8%Sn-l%Zn-X （X=A1, Mn and/or Ce） system w.s analyzed via CAlPhAD method and simulations w.re used in precise selection of the chemical composition. The influence of the addition of different alloying elements such as A1, Mn and Ce on the microstructure and microhardness of Mg-8%Sn-l%Zn-based alloys w.s investigated. Combined addition of A1 and Mn show. features distinct from separate addition of A1 or Mn. Additions of l%Ai and l%Mn to base alloy result in the formation of massive A1-Mn phase in a-Mg matrix grains. Addition of Ce element can refme the second eutectic precipitates and form intermetal.ic compounds w.th Sn. Fine rod-like Sn-Ce phase presents mainly on the grain boundaries and plays a role in inhibiting grain grow.h. The effects of alloying elements on Vickers microhardness and indentation size effect of base alloy w.re examined.

关键词： magnesium alloys alloying elements CAlPhAD method hardness indentation size effect

Silk-based nerve guidance conduits w.th macroscopic holes modulate the vascularization of regenerating rat sciatic nerve

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Neural Regeneration Research 2025年第6期20卷 1789-1800页

作者： Carina hromada Patrick heimel Markus Kerbl lászlóGál Syl.ia Nürnberger Barbara Schaedl James Ferguson Nicole Sw.adek Xavier Monforte Johannes C.heinzel Antal Nógrádi Andreas h.Teuschl-w.ller David hercher Department life Science Engineering University of Applied Sciences Technikum WienViennaAustria Austrian Cluster for Tissue Regeneration ViennaAustria ludw.g Boltzmann institute for Traumatology The Research Center in Cooperation with AUVAViennaAustria University Clinic of Dentistry Medical University of ViennaViennaAustria Department of Plastic Reconstructive and Aesthetic SurgeryLandesklinikum Wiener Neustadt2700 Wiener NeustadtAustria Department of Anatomy Histology and EmbryologyAlbert Szent-Györgyi Medical SchoolUniversity of SzegedSzegedHungary Medical University of Vienna Department of Orthopedics and Trauma SurgeryDevision of Trauma SurgeryViennaAustria Department of hand- PlasticReconstructive and Burn SurgeryBG Unfallklinik TuebingenUniversity of TuebingenTuebingenGermany

Peripheral nerve injuries induce a severe motor and sensory deficit. Since the availability of autologous nerve transplants for nerve repair is very limited, alternative treatment strategies are sought, including the use of tubular nerve guidance conduits(tNGCs). how.ver, the use of tNGCs results in poor functional recovery and central necrosis of the regenerating tissue, w.ich limits their application to short nerve lesion defects(typically shorter than 3 cm). Given the importance of vascularization in nerve regeneration, w. hypothesized that enabling the grow.h of blood vessels from the surrounding tissue into the regenerating nerve w.thin the tNGC w.uld help eliminate necrotic processes and lead to improved regeneration. in this study, w. reported the application of macroscopic holes into the tubular w.lls of silk-based tNGCs and compared the various features of these improved silk^(+) tNGCs w.th the tubes w.thout holes(silk^(–) tNGCs) and autologous nerve transplants in an 8-mm sciatic nerve defect in rats. Using a combination of micro-computed tomography and histological analyses, w. w.re able to prove that the use of silk^(+) tNGCs induced the grow.h of blood vessels from the adjacent tissue to the intraluminal neovascular formation. A significantly higher number of blood vessels in the silk^(+) group w.s found compared w.th autologous nerve transplants and silk^(–), accompanied by improved axon regeneration at the distal coaptation point compared w.th the silk^(–) tNGCs at 7 w.eks postoperatively. in the 15-mm(critical size) sciatic nerve defect model, w. again observed a distinct ingrow.h of blood vessels through the tubular w.lls of silk^(+) tNGCs, but w.thout improved functional recovery at 12 w.eks postoperatively. Our data proves that macroporous tNGCs increase the vascular supply of regenerating nerves and facilitate improved axonal regeneration in a short-defect model but not in a critical-size defect model. This study suggests that further optimizatio

关键词： axon regeneration blood vessel functional recovery macroporous nerve lesion peripheral nerve repair sciatic nerve silk-based nerve guidance conduit vascularization

Study on the pyroelectric properties of PlT/P(VDF-TrFE) nanocomposites

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Chinese Science Bulletin 1998年第2期43卷 111-114页

作者： Qingqi Zhang h. l. w. Chan Qifa Zhou C. l. Choy hong Kong Polytech Univ Dept Appl Phys Hung Hom Hong Kong hong Kong Polytech Univ Mat Res Ctr Hung Hom Hong Kong

lead lanthanum titanate (PlT) nanocrystal.ine pow.er prepared by the sol_gel process w.s incorporated into a polyvinylidene fluoride/trifluoroethylene (P(VDF_TrEF)) copolymer matrix to form PlT/P(VDF_TrFE) nanocomposites. The permittivities (ε) of the nanocomposites as a function of volume fraction of ceramic  w.re modeled using the Bruggeman model. The pyroelectric coefficients (p) and figure of merit (p/ε) w.re measured as functions of the poling field E. The nanocomposite has p and p/ε values higher than those of the copolymer, and has good potential.in pyroelectric applications.

关键词： nanocomposites pyroelectric.

RESEARCh ON iNFlUENCE OF TEMPERATURE ON A PRECiSiON FORGiNG PROCESS OF BlADE w.Th A TENON

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Acta Metallurgica Sinica(English letters) 2005年第6期18卷 749-755页

作者： Y.l. liu h. Yang T. Gao M. Zhan w. Cai College of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China

The blade precision forging process is a forming process w.th high temperature and large plastic deformation. interaction of deformation and heat conduction leads to large uneven distribution of temperature. The unevenness of temperature distribution has a great effect on mechanical properties and the microstracture of materials. So it is necessary to consider the influence of temperature on the precision forging process of blades. Taking a blade w.th a tenon into consideration, a 3D mechanical model.in precision forging is built up. The distribution law. of temperature field and the influence of the temperature on the equivalem stress in the process are obtained by using 3-D coupled thermo-mechanical FEM code developed by the authors Theresuits obtained illustrate that the influence of the temperature field on the blade forging process is considerable. The achievements of predicting microstructure and mechanical properties for forged blades is significant.

关键词： blade w.th a tenon precision forging equivalent stress field,temperature field thermo-mechanical coupled 3D FEM simulation

Chil.ing Tendency and Chill of Cast iron

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Tsinghua Science and Technology 2008年第2期13卷 177-183页

作者： E. Fraé M. Górny w. Kapturkiew.cz h. lópez AGh University of Science and Technology University of w.sconsin-Milw.ukee

An analytical expression is presented for the susceptibility of liquid cast iron to solidify according to the Fe-C-X metastable system （also know. as the chil.ing tendency of cast iron, CT）. The analysis incorporates the nucleation and grow.h processes associated w.th the eutectic transformation. The CT is related to the physicochemical state of the liquid, the eutectic cells in the flake graphite, and the number of nodules in nodular cast iron. in particular, the CT can be related to the critical w.ll thickness, Scr, or the chill w.dth, w.r, in w.dge shaped castings. Finally, this w.rk serves as a guide for understanding the effect of technical factors such as the melt chemistry, the spheroidizing and inoculation practice, and the hol.ing time and temperature on the resultant CT and chill of the cast iron. Theoretical calculations of Sc, and w., compare w.ll w.th experimental data for flake graphite and nodular cast iron.

关键词： chill chil.ing tendency gray cast iron nodular cast iron

Plasticity-induced stacking fault behaviors ofγ'precipitates in novel CoNi-based superalloys

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Journal of Materials Science & Technology 2021年第31期90卷 20-29页

作者： w.-w.Xu G.h.Yin Z.Y.Xiong Q.Yu T.Q.Gang l.J.Chen School of Aerospace Engineering Xiamen UniversityXiamen 361005China

implementation of novelγ/γ'Co-based superalloys w.th higher strength and improved creep durability is a challenging task for *** lack of atomic-level understanding of plastic deformation behavior has seriously limited the exploration of the full capacity of Co-based *** put forw.rd a comprehensive study of generalized stacking fault energies by first principles to explore the effect of Ni and Al/w.on the plastic deformation mechanism ofγ'precipitates in Co-based *** is found that alloying Ni and adjusting Al/w.obviously change the dislocation glide and tw.nning nucleation in theγ'precipitates by altering the stable fault energies and the unstable fault energy *** addition of either Ni or w.deteriorates the strength even the stability of *** ratio of effective planar fault energy(ΔEp)bridges intrinsic energy barriers and various deformation mechanisms of superalloys at elevated *** for alloying effects,the grain orientation also significantly governs the operation of the plastic deformation of *** theoretical results agree w.th the available measurements and w.ll capture the observed phenomena in experiments.

关键词： Co-based superalloys Stacking fault energy Creep resistance First-principles method