319,733 research outputs found
Microstructures and strengthening mechanisms of Cu/Ni/W nanolayered composites
No full textCu/Ni/W nanolayered composites with individual layer thickness ranging from 5nm to 300nm were prepared by a magnetron sputtering system. Microstructures and strength of the nanolayered composites were investigated by using the nanoindentation method combined with theoretical analysis. Microstructure characterization revealed that the Cu/Ni/W composite consists of a typical Cu/Ni coherent interface and Cu/W and Ni/W incoherent interfaces. Cu/Ni/W composites have an ultrahigh strength and a large strengthening ability compared with bi-constituent Cu–X(X¼Ni, W, Au, Ag, Cr, Nb, etc.) nanolayered composites. Summarizing the present results and those reported in the literature, we systematically analyze the origin of the ultrahigh strength and its length scale dependence by taking into account the constituent layer properties, layer scales and heterogeneous layer/layer interface characteristics, including lattice and modulus mismatch as well as interface structure
Estudo das ligas Fe-Ni produzidas por métodos não convencionais
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas.Na primeira parte deste trabalho, preparamos e estudamos as ligas Fe65Ni35 e Fe22Ni78 na forma de partículas ultra finas. Elas foram produzidas por precipitação auto-catalítica catastrófica a partir de soluções aquosas em temperatura de 80 °C, pH=12 e utilizando Hidrazina como agente redutor. As análises da estequiometria Fe65Ni35 revelaram uma segregação de fases. Através dos espectros Mössbauer e dos difratogramas de raios-X da amostra identificamos a presença de uma fase austenítica paramagnética (g1), de um fase taenita (g2) e de uma fase kamacita (a). Para a liga Fe22Ni78, as análises demonstraram se tratar de uma amostra desordenada química e estruturalmente. A liga foi caracterizada como a awaruita. Na segunda parte, fizemos um estudo de difusão em grãos micrométricos de ferro recobertos por uma camada de níquel nanométrico depositado por electroless. Mostramos que, utilizando do artifício de oxidar/reduzir ciclicamente a amostra, podemos provocar um agigantamento significativo do processo de difusão, o que torna possível a formação da fase Fe50Ni50 ordenada (tetrataenita) e, também, de uma fase desordenada g-Fe-Ni ferromagnética. Estas fases foram formadas em temperaturas tão baixas quanto 300 e 350 °C
Impact of metalloporphyrin-based porous coordination polymers on catalytic activities for the oxidation of alkylbenzene
No full textSeven metalloporphyrin-based porous coordination polymers: Feш (TZP)Poly (CP1), CoII (TZP)Poly (CP2), NiII (TZP)Poly (CP3), CuII (TZP)Poly (CP4), ZnII (TZP)Poly (CP5), MnII (TZP)Poly (CP6), PbII (TZP)Poly (CP7) (TZP = 5,10,15,20- tetrakis[4-(2,3,4,5-tetrazolylphenyl)] porphyrin) were prepared and characterized. CP1−CP7 are amorphous aggregation supported with lower crystallinity by scanning electron microscopy, Brunauer−Emmett−Teller and powder X-ray diffraction. These coordination polymers exhibit effective dye scavenging and catalytic activities toward the oxidation of alkylbenzene to ketones and can be reused by filtration with a slight decreasing of catalytic activities. Metal atoms metalloporphyrin polymers have a great influence on the catalytic activities of metalloporphyrin polymers
Study on the characteristic laws of urban road traffic flow under rainstorm and waterlogging: Calibration results of car-following models
No full textAn experiment based on a high-fidelity driving simulator is conducted to collect the drivers’ behavior data in the scenario of rainfall and waterlogging where totally 30 groups of scenarios with different levels of rainfall intensity and water depth are included. Different car following models are calibrated in the light of the drivers’ behavior database from the experiment and the best one is chosen to simulate the traffic flow on urban road sections.
As to the study, see our published paper for more details: Ni X, Huang H, Chen A, et al. Effect of heavy rainstorm and rain-induced waterlogging on traffic flow on urban road sections – an integrated experiment and simulation study[J]. Journal of Transportation Engineering, Part A: Systems. DOI: 10.1061/JTEPBS.0000557.
This dataset gives the calibration results of the potential car following models in the study
Preparation and temperature cycling reliability of electroless Ni(P) under bump metallization
No full textThe reliability of electroless Ni(P) under-bump metallization (UBM) was evaluated via temperature cycling and solder bump shear strength tests. Commercial diodes and dummy dies fabricated in-house were used as substrates for the electroless Ni(P) UBM deposition. Solder bumps were formed after reflowing eutectic 63Sn37Pb solder foils over the Ni(P) UBM. The solder bump shear strength was measured before and after different temperature cycling. The results from this study showed that the UBM thickness and dimension had important effects on the solder bump shear strength and reliability. Both the larger UBM dimension and larger UBM thickness tended to induce higher stress in the UBM, which resulted in the lower solder bump shear strength and lower temperature cycling reliability. A better UBM structure solution for high current electronic packaging application is indicated in this pape
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Documentation of a new hypotrich species in the family Amphisiellidae, Lamtostyla gui n. sp. (Protista, Ciliophora) using a multidisciplinary approach
No full textAn integrated approach considering both morphologic and molecular data is now required to improve biodiversity estimations and provide more robust systematics interpretations in hypotrichs, a highly differentiated group of ciliates. In present study, we document a new hypotrich species, Lamtostyla gui n. sp., collected from Chongming wetland, Shanghai, China, based on investigations using living observation, protargol staining, scanning and transmission electron microscopy, and gene sequencing. The new species is mainly recognized by having a short amphisiellid median cirral row composed of four cirri, three frontoventral cirri, three dorsal kinetids, four to eight macronuclear nodules, and small colorless cortical granules distributed as rosettes around dorsal bristles. Transmission electron microscope observation finds the associated microtubules of cirri and pharyngeal discs of L. gui are distinct from those in other hypotrichs. Morphogenesis of this species indicates that parental adoral membranelles retained intact or partial renewed is a potential feature to separate Lamtostyla granulifera-group and Lamtostyla lamottei-group. Phylogenetic analysis based on small subunit ribosomal RNA (rRNA) gene shows that this molecular marker is not useful to resolve phylogenetic relationships of the genus Lamtostyla, as well as many other hypotrichous taxa. We additionally characterize the internal transcribed spacers (ITS) region and the almost complete large subunit rRNA, which will be essential for future studies aimed at solving phylogenetic problems of Lamtostyla, or even the family Amphisiellidae. As a final remark, the critical screening of GenBank using ITS genes of our organism allows us to recognize a large amount of hypotrichous sequences have been misclassified as fungi. This observation suggests that hypotrichs could be frequently found in fungi-rich environment and overlooked by fungal specialists
Numerical modelling of plane strain tests on sands using a particulate approach
No full textThis paper describes the results of a series of numerical plane strain test simulations on a particulate material, carried out using the three-dimensional particle flow code PFC-3D. Samples comprised about 10 000 non-spherical particles, each formed by strongly bonding two spheres together. The simulations demonstrate the ability of such a model to capture the essential macro-features of soil behaviour as observed in laboratory tests, including the dependence of peak strengths on the initial void ratio relative to the critical. The development of strain localisations or shear bands associated with the use of rough loading platens, and the sensitivity of the model to the initial sample porosity, particle shape factor and interparticle friction angle, were also investigated.Cet exposé décrit les résultats d'une série de simulations numériques d'essais de déformation plane sur un maté-riau particulaire, essais effectués en utilisant le code de flux de particules en trois dimensions PFC-3D. Les échantillons étaient constitués d'environ 10 000 particules non sphériques, chacune ayant été formée en collant deux sphères ensemble. Les simulations démontrent la faculté d'un tel modèle à saisir les macro-caractéristiques essen-tielles du comportement du sol tel qu'il est observé dans les essais de laboratoire, y compris la dépendance des résistances de pointe sur le taux de pores initial par rapport au taux critique. Nous avons également étudié le développement des localisations de déformation ou de bandes de cisaillement associées à l'utilisation de plateaux de chargement grossiers, ainsi que la sensibilité du modèle à la porosité initiale de l'échantillon, le facteur forme de particule et l'angle de friction entre particules
Time-resolved polarization to extract coded information from early ballistic and snake signals through turbid media
No full textEffect of laser-induced nanocrystallisation on the properties of electroless Ni-P/Ni-W-P duplex coatings
No full textThis paper presents a comparative study of nanocrystallisation and the wear resistance of electroless plated Ni-P/Ni-W-P duplex coatings with a single Ni-W-P coating before and after high- power diode laser treatment. Effects of the laser operating parameters on microstructures, in terms of crystallisation, porosity formation, phase transformation and grain growth, were investigated using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and quantitatively X-ray Diffraction (XRD). Microhardness and wear behaviour of the coatings before and after laser treatment were evaluated by measurement of coating surface and cross-section hardness as well as un-lubricated friction and wear tests. The results revealed that in the case of laser treatment, the Ni-P/Ni-W-P duplex coatings offered better wear resistance than the single Ni-W-P coating, while the as-plated, single Ni-W-P coating showed better wear resistance than the Ni-P/Ni-W-P duplex coatings. Adhesive wear mechanism prevails in the laser-treated coatings when subjected to wear test against hardened steel material. The effects of microstructural characteristics in the coatings, in particularly the grain size of Ni 3P phase and the degree of crystallisation, on the adhesive wear behaviour have been investigated and found to be dominant besides the effect of hardness. This paper presents a comparative study of nanocrystallisation and the wear resistance of electroless plated Ni-P/Ni-W-P duplex coatings with a single Ni-W-P coating before and after high- power diode laser treatment. Effects of the laser operating parameters on microstructures, in terms of crystallisation, porosity formation, phase transformation and grain growth, were investigated using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and quantitatively X-ray Diffraction (XRD). Microhardness and wear behaviour of the coatings before and after laser treatment were evaluated by measurement of coating surface and cross-section hardness as well as un-lubricated friction and wear tests. The results revealed that in the case of laser treatment, the Ni-P/Ni-W-P duplex coatings offered better wear resistance than the single. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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