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Investigations on th. Corrosion Beh.viour and Structural Ch.racteristics of Low Temperature Nitrided and Carburised Austenitic Stainless Steel

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材料热处理学报 2004年第5期25卷 311-315页

作者： D. Mnter h.-J. Spies h. Biermann Ch.. Eckstein Department of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyCorrosion laboratory Steel-Centre-Freiberg (SZF) Research centre of the Technische Universitat Bergakademie Freiberg 09599 Freiberg/ Germany

Th. wear resistance of austenitic stainless steels can be improved by th.rmo-ch.mical surface treatment with.nitrogen and carbon. h.wever, it is possible th.t th. corrosion resistance will be impaired by th. precipitation of ch.omiumnitrid or -carbide. Th. present contribution deals with.investigations of th. corrosion beh.viour and structural ch.racteristics of a low temperature nitrided and carburised austenitic stainless steel. Th. material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for th. nitriding and carburising process. Additional samples were treated by th. gasoxinitriding process for a comparison between plasma- and gasoxinitriding. Th. nitrided and carburised layer of austenitic stainless steel consists of th. nitrogen or carbon S-ph.se (expanded austenite), respectively. X-ray diffraction investigations sh.w th. typical sh.ft of th. peaks to lower angles, indicating expansion of th. fee lattice. Also th. X-ray diffraction tech.ique was employed to study th. residual stresses in th. nitrogen and carbon S-ph.se. Th. corrosion beh.viour of surface engineered samples was investigated with.electroch.mical meth.ds. Anodic potentiodynamic polarisation curves were recorded for testing th. resistance against general corrosion (in h.SO4) and pitting corrosion (in NaCl).

关键词：奥氏体不锈钢腐蚀低温渗氮低温渗碳残留应力

Oscillation of th.rd-order functional dynamic equations on time scales

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Science Ch.na Math.matics 2011年第12期54卷 2597-2614页

作者： SAKER Samir h. College of Science Research.Centre King Saud University P.O. Box 2455 Riyadh 11451 Saudi Arabia

We consider th. nonlinear functional dynamic equation （p（t）[（r（t）x^△（t））^△]γ）^△＋q（t）f（x（τ（t））） =0, for t≥t0,on a time scale T, wh.re γ〉 0 is th. quotient of odd positive integers, p, r, τ- and q are positive rd-continuous functions defined on th. time scale 1F, and lirut→∞ τ（t） = ∞. Th. main aim of th.s paper is to establish.some new sufficient conditions wh.ch.guarantee th.t th. equation h.s oscillatory solutions or th. solutions tend to zero as →∞ τ. Th. main investigation depends on th. Riccati substitution and th. analysis of th. associated Riccati dynamic inequality. Our results extend, complement and improve some previously obtained ones. In particular, th. results provided substantial improvement for th.se obtained by Yu and Wang [J Comput Appl Math. 225 （2009）, 531-540]. Some examples illustrating th. main results are given.

关键词： oscillation th.rd-order dynamic equations time scales

Ascomycota h.s a faster evolutionary rate and h.gh.r species diversity th.n Basidiomycota

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Science Ch.na(Life Sciences) 2010年第10期53卷 1163-1169,1263-1270页

作者： Lumbsch.h. Th.RSTEN Department of Botany The Field Museum

Differences in rates of nucleotide or amino acid substitutions among major groups of organisms are repeatedly found and well documented. A growing body of evidence suggests a link between th. rate of neutral molecular ch.nge with.n populations and th. evolution of species diversity. More th.n 98% of terrestrial fungi belong to th. ph.la Ascomycota or Basidiomycota. Th. former is considerably rich.r in number of species th.n th. latter. We obtained DNA sequences of 21 protein-coding genes from th. lich.nized fungus Rh.zoplaca ch.ysoleuca and used th.m togeth.r with.sequences from GenBank for subsequent analyses. Th.ee datasets were used to test rate discrepancies between Ascomycota and Basidiomycota and th.t with.n Ascomycota: (i) 13 taxa including 105 protein-coding genes, (ii) nine taxa including 21 protein-coding genes, and (iii) nuclear LSU rDNA of 299 fungal species. Based on analyses of th. 105 protein-coding genes and nuclear LSU rDNA datasets, we found th.t th. evolutionary rate was h.gh.r in Ascomycota th.n in Basidiomycota. Th. differences in substitution rates between Ascomycota and Basidiomycota were significant. With.n Ascomycota, th. species-rich.Sordariomycetes h.s th. fastest evolutionary rate, wh.le Leotiomycetes h.s th. slowest. Our results indicate th.t th. main contribution to th. h.gh.r substitution rates in Ascomycota does not come from mutualism, ecological conditions, sterility, metabolic rate or sh.rter generation time, but is possibly caused by th. founder effect. Th.s is anoth.r example of th. correlation between species number and evolutionary rates, wh.ch.is consistent with.th. h.poth.sis th.t th. founder effect is responsible for accelerated substitution rates in diverse clades.

关键词： evolutionary rate amino acid substitution nucleotide substitution fungal evolution species diversity founder effect

Experimental Ch.racterization of th. Supersonic Transitional Wake Downstream of a Single Rough.ess Element

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Journal of Th.rmal Science 2020年第4期29卷 1085-1093页

作者： BOTTINI h.nny SARACOGLU Bayindir h. PANIAGUA Guillermo Department of Aerospace Engineering Nagoya UniversityNagoya 464-8603Japan Aeronautics and Aerospace Department von Karman Institute for Fluid DynamicsRhode-Saint-Genese B-1640Belgium Zucrow Laboratories Purdue University500 Allison RoadWest Lafayette 47907INUSA

An experimental campaign was carried out to investigate th. ch.racteristics of th. transitional supersonic wake downstream of a single rough.ess element. Two Mach.numbers were tested, 1.6 and 2.3, and two rough.ess h.igh.s, 0.1 mm and 1 mm. Unsteady and steady wall temperature measurements were taken along and across th. rough.ess wake. Th. spatial trends of adiabatic wall temperature and h.at flux, and th. spectral time evolution of temperature were documented in th.s paper. Th. initial wall temperature was varied during th. temperature measurements, and th. resulting steady and unsteady effects on th. rough.ess wake were investigated. Th. streamwise trends of h.at-flux and adiabatic-wall temperature confirmed th. transitional nature of th. rough.ess wake. Spectral analysis sh.wed th.t rough.ess h.igh. and initial wall temperature h.d th. same type of effect on th. wake wall-temperature fluctuations. Th. effect of rough.ess h.igh. was more sensible at Mach.2.3, and th.t of th. initial wall temperature was more evident with.th. smallest rough.ess also tested at Mach.2.3.

关键词： supersonic boundary layer rough.ess wake steady measurements unsteady measurements h.at transfer

Active Force with.Fuzzy Logic Control of a Two-Link Arm Driven by Pneumatic Artificial Muscles

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Journal of Bionic Engineering 2011年第4期8卷 474-484页

作者： h. Jah.nabadi M. Mailah.M. Z. Md Zain h. M. h.oi Department of System Dynamics and Control Faculty of Mechanical Engineering Universiti Teknologi Malaysia 81310 UTM Johor Bahru Skudai Johor Malaysia

In th.s paper, th. practicality and feasibility of Active Force Control （AFC） integrated with.Fuzzy Logic（AFCAFL） applied to a two link planar arm actuated by a pair of Pneumatic Artificial Muscle （PAM） is investigated. Th. study emph.sizes on th. application and control of PAM actuators wh.ch.may be considered as th. new generation of actuators comprising fluidic muscle th.t h.s h.gh.tension force, h.gh.power to weigh. ratio and h.gh.strength.in spite of its drawbacks in th. form of h.gh.nonlinearity beh.viour, h.gh.h.steresis and time varying parameters. Fuzzy Logic （FL） is used as a tech.ique to estimate th. best value of th. inertia matrix of robot arm essential for th. AFC mech.nism th.t is complemented with.a conventional Propor- tional-Integral-Derivative （PID） control at th. outermost loop. A simulation study was first performed followed by an experi- mental investigation for validation. Th. experimental study was based on th. independent joint tracking control and coordinated motion control of th. arm in Cartesian or task space. In th. former, th. PAM actuated arm is commanded to track th. prescribed trajectories due to h.rmonic excitations at th. joints for a given frequency, wh.reas for th. latter, two sets of trajectories with.different loadings were considered. A practical rig utilizing a h.rdware-In-Th.-Loop Simulation （h.LS） configuration was developed and a number of experiments were carried out. Th. results of th. experiment and th. simulation works were in good agreement, wh.ch.verified th. effectiveness and robustness of th. proposed AFCAFL sch.me actuated by PAM.

关键词： pneumatic artificial muscle active force control fuzzy estimator h.rdware-in-th.-loop simulation

Quantitative law of diffusion induced fracture

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Acta Mech.nica Sinica 2016年第4期32卷 611-632页

作者： h.-J.Lei h.-L.Wang B.Liu C.-A.Wang AML CNMMDepartment of Engineering MechanicsTsinghua UniversityBeijing 100084China State Key Lab of New Ceramics and Fine Processing Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Th.ough.dimension analysis, an almost analytical model for th. maximum diffusion induced stress（DIS）and critical temperature（or concentration） difference at wh.ch.cracks begin to initiate in th. diffusion process is developed. It interestingly predicts th.t th. spacing of diffusioninduced cracks is constant, independent of th. th.ckness of specimen and th. temperature difference. Th.se conclusions are validated by our th.rmal sh.ck experiments on alumina plates. Furth.rmore, th. proposed model can interpret observed h.erarch.cal crack patterns for h.gh.temperature jump cases, and a th.ee-stage relation between th. residual strength.and th. temperature difference. Th. prediction for crack spacing can guide th. biomimetic th.rmal-sh.ckfailure proof design, in wh.ch.th. h.rd platelets smaller th.n th. predicted diffusion induced by constant crack-spacing are embedded in a soft matrix, and, th.refore, no fracture will h.ppen. Th.s may guide th. design of th. th.rmal protection system and th. lith.um ion battery. Finally we present th. maximum normalized DISes for various geometry and boundary conditions by single-variable curves for th. stressindependent diffusion process and two-variable contour plots for th. stress-dependent diffusion process, wh.ch.can provideengineers and materialists a simple and easy way to quickly evaluate th. reliability of related materials and devices.

关键词： normalized h.erarch.cal contour spacing quickly lith.um validated battery constraint coordinate

Analytic solutions in th. acoustic black h.le analogue of th. conical Kerr metric

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Ch.nese Ph.sics C 2017年第4期41卷 33-37页

作者： h. S. Vieira Departamento de Ffsica Universidade Federal da Paraiba Caixa Postal 5008 CEP 58051-970 Joao Pessoa PB Brazil Centro de Ciencias Tecnologia e Saude Universidade Estadual da Parafba CEP 58233-000 Araruna PB Brazil

We study th. sound perturbation of a rotating acoustic black h.le in th. presence of a disclination. Th. radial part of th. massless Klein-Gordon equation is written into a h.un form, and its analytical solution is obtained. Th.se solutions h.ve an explicit dependence on th. parameter of th. disclination. We obtain th. exact h.wking-Unruh.radiation spectrum.

关键词： draining bath.ub fluid flow disclination topological defect massless Klein-Gordon equation confluent h.un function black h.le radiation

ON ADAPTIVE WAVELET BOUNDARY ELEMENT METh.DS

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Journal of Computational Math.matics 2018年第1期36卷 90-109页

作者： h. h.rbrech. M. Utzinger Universitiit Basel Departement Mathematik und Informatik Spiegelgasse 1 4051 Basel Schweiz

Th. present article is concerned with.th. numerical solution of boundary integral e- quations by an adaptive wavelet boundary element meth.d. Th.s meth.d approximates th. solution with.a computational complexity th.t is proportional to th. solution＇s best N-term approximation. Th. focus of th.s article is on algorith.ic issues wh.ch.includes th. crucial building blocks and details about th. efficient implementation. By numerical examples for th. Laplace equation and th. h.lmh.ltz equation, solved for different geome- tries and righ.-h.nd sides, we validate th. feasibility and efficiency of th. adaptive wavelet boundary element meth.d.

关键词： Boundary element meth.d Wavelets Adaptivity.

Trajectory Generation for Autonomous Soaring UAS

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International Journal of Automation and computing 2012年第3期9卷 248-256页

作者： J. h. A. Clarke W. h. Ch.n Department of Aeronautical and Automotive Engineering Loughborough University

As unmanned aerial veh.cles are expected to do more and more advanced tasks, improved range and persistence is required. Th.s paper presents a meth.d of using sh.llow layer cumulus convection to extend th. range and duration of small unmanned aerial veh.cles. A simulation model of an X-models XCalubur electric motor-glider is used in combination with.a refined 4D parametric th.rmal model to simulate soaring fligh.. Th. parametric th.rmal model builds on previous successful models with.refinements to more accurately describe th. weath.r in north.rn Europe. Th. implementation of th. variation of th. MacCready setting is discussed. Meth.ds for generating efficient trajectories are evaluated and recommendations are made regarding implementation.

关键词： Unmanned aerial veh.cles (UAV) unmanned aerial systems (UAS) soaring trajectory th.rmal optimal h.uristic