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A new strategy for corrosion protection of porous stainless steel using polypyrrole films

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Journal of Materials Science & Technology 2020年第2期37卷 85-95页

作者： c.Garcia-cabezon c.Garcia-Hernandez M.L.Rodriguez-Mendez f.Martin-Pedrosa Materials Engineering E.I.I.Universidad de Valladolid47011 ValladolidSpain UVASENS E.I.I.Universidad de Valladolid47011 ValladolidSpain

In this work,a method to improve the protection against corrosion of porous sintered stainless steel is *** is based on the electrodeposition of polypyrrole(PPy)layers doped with a large size counterion such as dodecylbenzenesulphonic acid(DBSA),a conducting polymer with high corrosion resistance and good *** efficacy of PPy coating depends on the adequate adhesion between the metal substrate and the coating *** protection against corrosion has been tested using 316 L stainless steel(SS)powder sintered at different conditions to evaluate the effect of the sintering atmosphere(nitrogen and vacuum)and cooling rates(furnace and water)on corrosion resistance,while wrought 316 L SS has been used as reference *** addition,two electrochemical deposition techniques have been tested to select the most *** circuit potential evolution,anodic polarization measurements and electrochemical impedance spectra have been used to evaluate corrosion protection in phosphate buffer saline *** has been evidenced that a more homogeneous and stable coating was obtained in the case of porous stainless *** corrosion potential shifted to nobler values and the anodic polarization branch became more *** porous samples have a good passivation performance with a lower stable passive current density and a higher breakdown *** transfer electronic resistance and the impedance module increase more than one order of ***,the porosity of sintered stainless steel is seen as an advantage for the improvement of the adherence of the PPy *** best corrosion protection is found for samples sintered in nitrogen and water-cooled.

关键词： Stainless steel Powder metallurgy Protection corrosion Electrodeposited films Polymer coatings

Zinc-oxide/PDMS-clad tapered fiber saturable absorber for passively mode-locked erbium-doped fiber laser

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chinese Physics B 2021年第5期30卷 384-389页

作者： f D Muhammad S A S Husin E K Ng K Y Lau c A c Abdullah M A Mahdi Department of Physics Faculty of ScienceUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Wireless and Photonics Networks Research centre Faculty of EngineeringUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Department of Electronics and Nanoengineering Tietotie 3Aalto University02150 EspooFinland

We propose and demonstrate a passively mode-locked erbium-doped fiber laser(EDfL)based on zinc-oxide/polydimethylsiloxane(ZnO/PDMS)saturable absorber(SA)that evanescently interacts with the light on a tapered *** ZnO/PDMS composite is coated on the whole surface of the tapered fiber to guarantee the maximum efficiency of the SA device,with a measured insertion loss of 0.87 dB and a modulation depth of 6.4%.The proposed laser can generate soliton mode-locking operation at a threshold power of 33.07 *** generated output pulse yields a repetition rate and pulse width of 9.77 MHz and 1.03 ps,*** results indicate that the proposed ZnO/PDMS-clad tapered fiber could be useful as an efficient,compatible,and low-cost SA device for ultrafast laser applications.

关键词： zinc-oxide saturable absorber tapered fiber mode-locked fiber laser

Analysis of Turbulent Heat Transfer and fluid flow in channels with Various Ribbed Internal Surfaces

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Journal of Thermal Science 2011年第3期20卷 260-267页

作者： smith Eiamsa-ard Wayo changcharoen Department of Mechanical Engineering Faculty of Engineering Mahanakorn University of Technology Bangkok 10530 Thailand

This paper presents results of a numerical investigation of heat transfer and flow pattern characteristics of a channel with repeated ribs on one broad wall. Numerical computations are performed for seven ribs placed on the bottom wall of a channel for Reynolds numbers ranging from 10,000 to 30,000. The newly modified ribs (the ones with convex pointing upstream/downstream rib, wedge pointing upstream/downstream rib, concave pointing upstream/downstream rib and also concave-concave rib as well as convex-concave rib), are proposed for simulation with prospect to reduce flow separation and extend reattachment area compared to the unmodified square rib. The numerical results are reported in forms of flow structure, temperature field, turbulent kinetic energy, Nusselt number, friction factor and thermal enhancement factor. The results indicate the rib with concave-concave surfaces efficiently suppresses flow separation bubble in the corner of the rib and induces large recirculation zone over those of the others, hence giving the highest Nusselt number and friction factor. On the other hand, the one with convex-concave surface provides the lowest friction factor with moderate Nusselt number. Due to the prominent effect of its low friction factor, the rib with convex-concave surface offers the highest thermal enhancement factor of 1.19.

关键词： Rib Turbulent flow Heat transfer Reattachment zone flow separation

combustion synthesis, characterization and luminescence properties of barium aluminate phosphor

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Journal of Rare Earths 2014年第9期32卷 806-811页

作者： A.H. Wako f.B Dejene H.c Swart Department of Physics University of the Free State (Qwaqwa Campus) Department of Physics University of the Free State

The blue-green emitting Eu2＋ and Nd3＋ doped polycrystalline barium aluminate （BaAI204：Eu2＋,Nd3＋） phosphor, was prepared by a solution-combustion method at 500 ℃without a post-annealing process. The characteristic variation in the structural and luminescence properties of the as-prepared samples was evaluated with regards to a change in the Ba/A1 molar ratio from 0.1：1 to 1.4：1. The morphologies and the phase structures of the products were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）, while the optical properties were investigated using ultra-violet （UV） and photoluminescence （PL） spectroscopy, respectively. The XRD and TEM results revealed that the average crystallite size of the BaAl2O4：Eu2＋,Nd3＋ phosphor was about 70 urn. The broad-band UV-excited luminescence of the phosphors was observed at 2max=500 um due to transitions from the 4f^65d1 to the 4f7 configuration of the Eu2＋ ion. The PL results indicated that the main peaks in the emission and excitation spectrum of phosphor particles slightly shifted to the short wavelength due to the changes in the crystal field due to the structure changes caused by the variation in the quantity of the Ba ions in the host lattice.

关键词： BaAl2O4:Eu2+,Nd3+ persistence luminescence Eu2+ and Nd3+ doping rare earths

Reduced formation of peroxide and radical species stabilises iron-based hybrid catalysts in polymer electrolyte membrane fuel cells

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Journal of Energy chemistry 2022年第2期31卷 433-438页

作者： Dongyoon Shin Sabita Bhandari Marc fTesch shannon ABonke frédéric Jaouen Sonia chabbra christoph Pratsch Alexander Schnegg Anna K.Mechler Max Planck Institute for chemical Energy conversion Stiftstr.34–3645470 Mülheim an der RuhrGermany IcGM Univ.MontpellierCNRSENSCMMontpellierFrance fritz Haber Institute of the Max Planck Society Department of Inorganic ChemistryFaradayweg 4-614195 BerlinGermany

The incorporation of Pt into an iron-nitrogen-carbon(fe Nc)catalyst for the oxygen reduction reaction(ORR)was recently shown to enhance catalyst stability without Pt directly contributing to the ORR ***,the mechanistic origin of this stabilisation remained *** is established herein with rotating ring disc experiments that the side product,H_(2)O_(2),which is known to damage feNc catalysts,is suppressed by the presence of *** formation of reactive oxygen species is additionally inhibited,independent of intrinsic H_(2)O_(2) formation,as determined by electron paramagnetic *** electron microscopy identifies an oxidised fe-rich layer covering the Pt particles,thus explaining the inactivity of the latter towards the *** insights develop understanding of fe Nc degradation mechanisms during ORR catalysis,and crucially establish the required properties of a precious metal free protective catalyst to improve fe Nc stability in acidic media.

关键词： Electrochemistry fuel cells Oxygen reduction reaction Non-precious metal catalyst Hybrid catalyst Stability

Stream-dwelling fungal decomposer communities along a gradient of eutrophication unraveled by 454 pyrosequencing

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fungal Diversity 2015年第1期70卷 127-148页

作者： S.Duarte f.Bärlocher J.Trabulo f.cássio c.Pascoal centre of Molecular and Environmental Biology(cBMA) Department of BiologyUniversity of MinhoCampus de Gualtar4710-057 BragaPortugal Department of Biology Mount Allison UniversitySackvilleNB E4L 1G7Canada

Microbial decomposers,especially a fungal group called aquatic hyphomycetes,play a critical role in processing plant litter in freshwaters by increasing its palatability to invertebrate ***,communities of aquatic hyphomycetes have been assessed through the identification of spores,which misses non-sporulating *** new technologies,454 pyrosequencing stands out as most promising for large-scale species ***,very few attempts have been made to validate its effectiveness for assessing the diversity of stream-dwelling fungal *** attempted to gain greater insight into the diversity of aquatic fungal communities in streams exposed to various degrees of eutrophication by using the 454 pyrosequencing technology.A total of 173,889 ITS2 pyrosequencing reads with hits for fungi were obtained from the 5 investigated *** majority of operational taxonomic units(OTUs)belonged to Ascomycota and the identification to the genus level was achieved for 169 *** the total,135,257 reads(ca.78%)showed close affinities to aquatic hyphomycete *** showed declining fungal diversity in the most eutrophic streams,which was congruent with a reduced diversity found through spore *** patterns revealed by connecting representative OTUs to ITS sequences from aquatic hyphomycetes were similar to those determined by traditional spore identification ***,454 pyrosequencing provided a more comprehensive view of fungal diversity;it captured almost twice as many taxa as spore *** study vali-dates the effectiveness of 454 pyrosequencing for surveying the diversity of stream-dwelling fungal decomposer *** application may accelerate the use of these communities for monitoring the integrity of freshwaters.

关键词： freshwater ecosystems Plant litter decomposition Aquatic fungi ITS region

Effect of Hind Leg Morphology on Performance of a canine-inspired Quadrupedal Robot

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Journal of Bionic Engineering 2015年第3期12卷 339-351页

作者： James Andrew smith Jamil Jivraj Ryerson University 350 Victoria St. Toronto ON Canada

Biomimetic leg designs often appear to be arbitrarily chosen. To make a more objective choice regarding biomimetic leg configuration for small canine-inspired robots, we compare one hind leg to the same leg arranged in a different orientation, and show that the less biomimetic leg provides better performance. This differently-oriented leg design, which we call ＂transverse-mirrored＂ was more efficient and faster, both in simulation and experiment even though both leg configurations used the same passive and active components, rest angles, and monoartieular knee spring. In experiments the normal configuration had a maximum speed of 0.33 m·s^-1 and a specific resistance of 5.1. conversely, the less biomimetic transverse-mirrored configuration had a maximum speed of 0.4 m·s^-1 and specific resistance of 3.9. Therefore the transverse-mirrored leg＇s best performance yields a 21% increase in speed and 24% decrease in specific resistance when compared to the best performance achieved in the normal biomimetic leg. The major underlying reason is that the knee spring engages more readily in the transverse-mirrored configuration, resulting in this faster and more efficient locomotion. The conclusion is that simply copying from nature does not lead to optimal performance and that insight into the role played by passive design components on natural locomotory dynamics is important.

关键词： biomimetic legged robot quadruped leg design walking legged locomotion

Microstructure, Mechanical and corrosion Properties of AlcocrfeNi High-Entropy Alloy Prepared by Spark Plasma Sintering

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Acta Metallurgica Sinica(English Letters) 2020年第7期33卷 937-946页

作者： P.f.Zhou D.H.Xiao T.c.Yuan National Key Laboratory of Science and Technology for National Defence on High-strength Structural Materials Central South UniversityChangsha 410083China

AlcocrfeNi is one of the most widely studied alloy systems in the high-entropy alloy(HEA) area due to the interesting microstructure and mechanical *** this study,the AlcocrfeNi alloy was prepared using spark plasma sintering(SPS) with pre-alloy powders obtained through gas ***,the sintered samples were annealed at 700,800 and900℃,and the effect of annealing temperature on the microstructure,mechanical and corrosion properties was *** results show that phase formation takes place during annealing process with the new phase(σ) and some nano scale Bcc precipitates *** size and quantity of the nanoscale precipitates increase with increasing annealing *** twin is also observed after annealing at 900℃.The annealing temperature has an obvious effect on the mechanical properties and corrosion resistance of the spark plasma sintered AlcocrfeNi *** the annealing temperature is 700℃,the hardness,yield strength and fracture strength reach the maximum with the value of 545 HV,1430 MPa and 2230 MPa,*** compressive ratio reaches the maximum of 17.2%,with the annealing temperature increasing to 800℃.The corrosion resistance of the samples decreases with increasing the annealing temperature.

关键词： alloy corrosion microstructure

facultative social parasitism in the allodapine bee Macrogalea berentyensis

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Insect Science 2007年第1期14卷 65-69页

作者： JAcLYN A. smith School of Biological Sciences Flinders University Adelaide South Australia Australia

Previous research on social parasitism has largely ignored allodapine social parasites, which is surprising given the huge potential of these bees to provide a better understanding of social parasitism. Macrogalea berentyensis, a species that was previously suggested to be a social parasite, was collected in nests of M. ellioti, and also in nests consisting of only M. berentyensis. These f＇mdings, along with morphological and phylogenetic evidence, show that this species is a facultative social parasite. In the independently living M. berentyensis nests, brood were present that had been reared to an advanced stage, suggesting that：（i） these parasites may be effective at foraging and caring for their brood; or （ii） these nests may be colonies where all the hosts had died, and these parasites had yet to disperse. Macrogalea berentyensis is the closest relative of the facultative social parasite, M. antanosy, and both these species represent the most recent evolutionary origin of social parasitism within the allodapines. further behavioral research on both these parasitic species would therefore have important implications for the understanding of the evolution of social parasitism.

关键词： allodapine bee facultative social parasitism Macrogalea