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microstructure and mechanical Properties of a Dissimilar Friction Stir Weld between Austenitic Stainless Steel and Low Carbon Steel

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journal of materials Science & Technology 2013年第4期29卷 367-372页

作者： m jafarzadegan A.Abdollah-zadeh A.h.Feng T.Saeid j.Shen h.Assadi Department of materials Eng. Tarbiat Modares UniversityP.O.Box 14115-143TehranIran School of materials Science and Eng. Harbin Institute of TechnologyP.O.Box 150001HarbinChina Advanced materials Research Center Sahand University of TechnologyP.O.Box 51335-1996TabrizIran

Dissimilar fusion welding of austenitic stainless steels to carbon steels has some metallurgical and technical problems. It was suggested that the solid-state nature of friction stir welding （FSW） can overcome these problems and produce a sound weld with reliable mechanical properties. In this study, plates of 304 stainless steel and st37 steel were welded together by FSW at tool rotational speed of 600 r/rain and welding speed of 50 ram/rain. In the stir zone （SZ） of 304 stainless steel, the results showed a refined grain structure with some features of metadynamic recrystallization. In the SZ of st37 steel, the hot deformation of material in the austenite region produced small austenite grains. These grains transformed to fine ferrite and pearlite by cooling the material after FSW. The production of fine grains increased the hardness and tensile strength in the SZ of both sides with respect to their base metals （Bms）.

关键词： Friction stir welding microstructure mechanical properties Stainless steel Low carbon steel

Plasma density measurement and downstream etching of silicon and silicon oxide in Ar/NF3 mixture remote plasma source

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Plasma Science and Technology 2019年第6期21卷 52-57页

作者： h j YEOm D h ChOI Y S LEE j h KIm D j SEONG S j YOU h C LEE Korea Research Institute of Standards and Science(KRISS) Daejeon 34113 Republic of Korea Department of Physics Chungnam National University Daejeon 34134 Republic of Korea

In this study,plasma density measurements were performed near the plume region of the remote plasma source (RPS) in Ar/NF3 gas mixtures using a microwave cutoff *** measured plasma density is in the range of 1010-1011 cm-3 in the discharge conditions with RPS powers of 2-4 kW and gas pressures of 0.87-4 *** plasma density decreased with increasing gas pressures and RPS powers under various Ar/NF3 mixing *** decrease in the plasma density measured at the fixed measurement position (plume region) can be understood by the reduction of the electron energy relaxation length with increases in the gas pressures and mixing ratio of NF3/(Ar/NF3).We also performed downstream etching of silicon and silicon oxide films in this *** etch rate of the silicon films significantly increases while the silicon oxide is slightly etched with the gas pressures and *** was also found that the etch rate strongly depends on the wafer position on the processing chamber electrode,and that the etch selectivity reached 96-131 in the discharge conditions of RF powers (3730-4180 W) and gas pressures (3.6-4 Torr).

关键词： remote plasma source electron density cutoff probe downstream etch

The effect of swelling agent on the pore characteristics of mesoporous hydroxyapatite nanoparticles

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Progress in Natural Science:materials International 2015年第3期25卷 185-190页

作者： L.Bakhtiari j.javadpour h.R.Rezaie m.Erfan m.A.Shokrgozar School of metallurgical and materials Engineering Iran University of Science and Technology School of Pharmacy Shahid Beheshti University of Medical Sciences National Cell Bank of Iran Pasteur Institute of Iran

The effect of swelling agent on the physicochemical properties of mesoporous hydroxyapatite particles synthesized by self-assembly process has been investigated. Cetyl trimethylammonium bromide(CTAB) and 1-dodecanethiol were used as soft template and swelling agent respectively. The results of the field emission scanning electron microscopy(FESEm), X-ray diffraction(XRD), simultaneous thermal analysis(STA), Brunauer-Emmett-Teller(BET) surface area, small-angle X-ray diffraction and Fourier transform infrared spectroscopy(FTIR)assessments revealed that in the case of low concentration, 1-dodecanethiol performed as swelling agent and caused an increase in the pore size. however, at higher concentrations it led to the formation of microemulsion and foamy structures. The optimum swelling agent: surfactant mass ratio in synthesis of mesoporous hydroxyapatite particles with high pore volume was determined to be around 2.1 in this study.

关键词： mesopore hydroxyapatite Nanoparticle Swelling agent Pore characteristics

A numerical study on the influence of grain boundary oxides on dwell fatigue crack growth of a nickel-based superalloy

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journal of materials Science & Technology 2022年第9期104卷 224-235页

作者： C.Z.Fang h.C.Basoalto m.j.Anderson h.Y.Li S.j.Williams P.Bowen Department of materials Science and Engineering University of SheffieldMappin StSheffield S13JDUK School of metallurgy and materials University of BirminghamEdgbastonBirmingham B152TTUK Institute of Structural materials Swansea UniversitySwansea SA18ENUK

A theoretical treatment on the oxide-controlled dwell fatigue crack growth of aγ'strengthened nickelbased superalloys is *** particular,this study investigates the influence of an externally applied load and variations in theγ'dispersion on the grain boundary oxide growth kinetics.A dislocation-based viscoplastic constitutive description for high temperature deformation is used to simulate the stress state evolution in the vicinity of a crack at elevated *** viscoplastic model explicitly accounts for multimodalγ'particle size distributions.A multicomponent mass transport formulation is used to simulate the formation/evolution of an oxide wedge ahead of the crack tip,where stress-assisted vacancy diffusion is assumed to *** resulting set of constitutive and mass transport equations have been implemented within a finite element *** of predicted compositional fields across the matrix/oxide interface are compared with experiments and shown to be in good *** indicate that the presence of a fineγ'size distribution has a strong influence on the predicted ow stress of the material and consequently on the relaxation in the vicinity of the crack-tip/oxide *** is shown that a unimodal dispersion leads to reduced oxide growth rates(parabolic behavior)when compared to a bimodal *** conditions for oxide formation are investigated and is associated with the prediction of compressive stresses within the oxide layer just ahead of the crack tip,which become progressively negative as the oxide wedge ***,mechanical equilibrium requirements induce tensile stresses at the tip of the oxide wedge,where failure of the oxide is *** time taken to reach this critical stress for oxide failure has been calculated,from which dwell crack growth rates are computationally *** predicted rates are shown to be in good agreement with available experimental data.

关键词： Nickel based superalloy Dwell crack growth Gamma prime Creep Oxidation Dislocation-based modeling multicomponent diffusion Finite element method

Effects of concurrent grain boundary and surface segregation on the final stage of sintering: the case of Lanthanum doped yttriastabilized zirconia

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journal of materials Science & Technology 2017年第3期33卷 251-260页

作者： m.m.Gong S.Dey L.j.Wu C.h.Chang h.Li R.h.R.Castro F.Liu State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China Department of materials Science ＆ Engineering University of California Davis CA 95616 USA

Dopants play a critical role in tailoring the microstructure during sintering of compacts. These dopants may form solid solution within the bulk, and/or segregate to the grain boundaries（GBs） and the solidvapor interfaces（free surfaces）, each causing a distinct energetic scenario governing mass transports during densification and grain growth. In this work, the forces controlling the dopant distribution, in particular the possibility of concurrent segregation at both surfaces and GBs, are discussed based on the respective enthalpy of segregation. An equation is derived based on the minimum Gibbs energy of the system to determine enthalpy of segregation from experimental interface energy data, and the results applied to depict the role of La as a dopant on the interface energetics of yttria stabilized zirconia during its final stage of sintering. It is shown that La substantially decreases both GB and surface energies（differently）as sintering progresses, dynamically affecting its driving forces, and consequent grain growth and densification in this stage.

关键词： Grain boundary(GB) segregation Surface segregation Enthalpy of segregation GB energy Surface energy

h∞ synchronization of chaotic neural networks with time-varying delays

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Chinese Physics B 2013年第11期22卷 244-252页

作者： O. m. Kwon m. j. Park ju h. Park S. m. Lee E. j. Cha School of Electrical Engineering Chungbuk National University Department of Electrical Engineering Yeungnam University School of Electronic Engineering Daegu University Department of Biomedical Engineering School of Medicine Chungbuk National University

In this paper, we investigate the problem of h∞ synchronization for chaotic neural networks with time-varying delays. A new model of the networks with disturbances in both master and slave systems is presented. By constructing a suitable Lyapunov–Krasovskii functional and using a reciprocally convex approach, a novel h∞ synchronization criterion for the networks concerned is established in terms of linear matrix inequalities （LmIs） which can be easily solved by various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed method.

关键词： chaotic neural networks time-varying delays h∞ synchronization Lyapunov method

Plant phosphatidylinositol-specific phospholipase C at the center of plant innate immunity

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journal of Integrative Plant Biology 2017年第3期59卷 164-179页

作者： Ahmed m.Abd-El-haliem matthieu h.A.j.joosten Laboratory of Phytopathology Wageningen University Droevendaalsesteeg 1 6708 PB Wageningen The Netherlands Plant Physiology Swammerdam Institute for Life Sciences University of Amsterdam Science Park 904 1098 XH Amsterdam The Netherlands

Understanding plant resistance to pathogenic microbes requires detailed information on the molecular mechanisms controlling the execution of plant innate immune responses. A growing body of evidence places phosphoinositide-specific phospholipase C （PI-PLC） en- zymes immediately downstream of activated immune receptors, well upstream of the initiation of early defense responses. An increase of the cytoplasmic levels of free Ca2＋, lowering of the intercellular ph and the oxidative burst are a few examples of such responses and these areregulated by PI-PLCs. Consequently, PI-PLC activation represents an early primary signaling switch between elicitation and response involving the controlled hydrolysis of essential signaling phospholipids, thereby simulta- neously generating lipid and non-lipid second messenger molecules required for a swift cellular defense response. here, we elaborate on the signals generated by PI-PLCs and their respective downstream effects, while providing an inventory of different types of evidence describing the involvement of PI-PLCs in various aspects of plant immunity. We project the discussed information into a model describing the cellular events occurring after the activation of plant immune receptors. With this review we aim to provide new insights supporting future research on plant PI-PLCs and the development of plants with improved resistance.

关键词： Pradeep Kachroo University of Kentucky USA

Treating amyotrophic lateral sclerosis with allogeneic Schwann cell-derived exosomal vesicles: a case report

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Neural Regeneration Research 2025年第4期20卷 1207-1216页

作者： Pascal j.Goldschmidt-Clermont Aisha Khan George jimsheleishvili Patricia Graham Adriana Brooks Risset Silvera Alexander j.P.Goldschmidt Damien D.Pearse W.Dalton Dietrich Allan D.Levi james D.Guest miller School of medicine University of MiamiMiamiFLUSA Stem Cell Institute Miller School of MedicineUniversity of MiamiMiamiFLUSA The miami Project to Cure Paralysis Miller School of MedicineUniversity of MiamiMiamiFLUSA Alzady International LLC MiamiFLUSA Neurological Surgery Miller School of MedicineUniversity of MiamiMiamiFLUSA

Schwann cells are essential for the maintenance and function of motor neurons,axonal networks,and the neuromuscular *** amyotrophic lateral sclerosis,where motor neuron function is progressively lost,Schwann cell function may also be ***,important signaling and potential trophic activities of Schwann cell-derived exosomal vesicles have been *** case report describes the treatment of a patient with advanced amyotrophic lateral sclerosis using serial intravenous infusions of allogeneic Schwann cell-derived exosomal vesicles,marking,to our knowledge,the first instance of such *** 81-year-old male patient presented with a 1.5-year history of rapidly progressive amyotrophic lateral *** initial diagnosis,the patient underwent a combination of generic riluzole,sodium phenylbutyrate for the treatment of amyotrophic lateral sclerosis,and *** patient volunteered to participate in an FDA-approved single-patient expanded access treatment and received weekly intravenous infusions of allogeneic Schwann cell-derived exosomal vesicles to potentially restore impaired Schwann cell and motor neuron *** confirmed that cultured Schwann cells obtained from the amyotrophic lateral sclerosis patient via sural nerve biopsy appeared impaired(senescent)and that exposure of the patient’s Schwann cells to allogeneic Schwann cell-derived exosomal vesicles,cultured expanded from a cadaver donor improved their growth capacity in *** a period of observation lasting 10 weeks,during which amyotrophic lateral sclerosis Functional Rating Scale-Revised and pulmonary function were regularly monitored,the patient received weekly consecutive infusions of 1.54×1012(×2),and then consecutive infusions of 7.5×1012(×6)allogeneic Schwann cell-derived exosomal vesicles diluted in 40 mL of Dulbecco’s phosphate-buffered *** of the infusions were associated with adverse events such as infusion reactions(allergic or otherwise)or

关键词： allogeneic amyotrophic lateral sclerosis exosomes infusion neuromuscular junction Schwann cell

Semisolid joining of aluminum A356 alloy by partial remelting and mechanical stirring

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Transactions of Nonferrous metals Society of China 2010年第9期20卷 1792-1798页

作者： S.m.j.ALVANI h.AAShURI A.KOKABI R.BEYGI materials Science and Engineering Department Sharif University of Technology

A method to reach the globular weld structure of A356 aluminum alloy using stirring the localized semisolid zone during butt-joining is *** the heat conductivity of this alloy is very high, the accurate controlling of temperature during joining must be considered.A gas heating system was used to heat up the nitrogen gas up to the required temperature.A dried and free oxygen gas was prepared when a stream of nitrogen gas could pass closely around a hot *** and pure nitrogen gas flow through a precise ceramic nozzle was used to create a localized semisolid *** this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single uniform *** were moved in direction of joint line by a small trolley to avoid the deviation of nozzle from the joint line and its distance and angle from the substrate.A fixture system was used to hold two substrates together on the trolley.A narrow hot plate was located on the trolley to heat up the joint line due to high heat conductivity of *** of gas temperature was investigated on the microstructure and mechanical properties of weld *** showed that increase in temperature promoted the final welding properties, and also at liquid fractions less than 50% joining was not fully *** best mechanical properties were achieved with liquid fraction of about 70%.

关键词： semisolid joining A356 localized stirring shear punch semi-solid holding thermal treatment