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51.
Lorenz B Persson BN Dieluweit S Tada T 《The European physical journal. E, Soft matter》2011,34(12):129-11
We have measured the friction force acting on a rubber block slid on a concrete surface. We used both unfilled and filled
(with carbon black) styrene butadiene (SB) rubber and have varied the temperature from −10 °C to 100 °C and the sliding velocity
from 1 μm/s to 1000 μm/s. We find that the experimental data at different temperatures can be shifted into a smooth master-curve, using the temperature-frequency
shifting factors obtained from measurements of the bulk viscoelastic modulus. The experimental data has been analyzed using
a theory which takes into account the contributions to the friction from both the substrate asperity-induced viscoelastic
deformations of the rubber, and from shearing the area of real contact. For filled SB rubber the frictional shear stress σf in the area of real contact results mainly from the energy dissipation at the opening crack on the exit side of the rubber-asperity
contact regions. For unfilled rubber we instead attribute σf to shearing of a thin rubber smear film, which is deposited on the concrete surface during run in. We observe very different
rubber wear processes for filled and unfilled SB rubber, which is consistent with the different frictional processes. Thus,
the wear of filled SB rubber results in micrometer-sized rubber particles which accumulate as dry dust, which is easily removed
by blowing air on the concrete surface. This wear process seams to occur at a steady rate. For unfilled rubber a smear film
forms on the concrete surface, which cannot be removed even using a high-pressure air stream. In this case the wear rate appears
to slow down after some run in time period. 相似文献
52.
53.
54.
Atsuko Nakamura 《Tetrahedron letters》2005,46(37):6373-6376
Xestobergsterol A, a potent inhibitor of histamine release, has been synthesized from dehydroepiandrosterone in a route that used introduction of a novel 15-oxygen functionality, side-chain construction via the orthoester Claisen rearrangement and TBAF-promoted epimerization-aldol condensation. 相似文献
55.
Atsuko Ito Keiko Iwai Chiyuki Oyama Setsu Morimoto Hiroaki Kato 《Hyperfine Interactions》1992,71(1-4):1371-1374
Magnetization and Mössbauer measurements have been made on a diluted antiferromagnets FexMg1?xTiO3 with x=0.2, 0.3 and 0.7. It has been demonstrated that this system exhibits a spin glass or a reentrant spin glass like behavior in the samples with x around the percolation concenrration xc≈0.25. It has been shown that various sizes of magnetic clusters are formed well above the transition temperatures determined by the magnetization measurements in the samples with x near xc. The behavior of Fe0.2Mg0.8TiO3 is discussed as a typical cluster glass. 相似文献
56.
In this paper, we introduce two iterative sequences for finding a common element of the set of fixed points of a nonexpansive
mapping and the set of solutions of an equilibrium problem in a Hilbert space. Then, we show that one of the sequences converges
strongly and the other converges weakly. 相似文献
57.
Dr. Tomoki Ogoshi Ryuta Sueto Kumiko Yoshikoshi Dr. Yoko Sakata Prof. Shigehisa Akine Prof. Tada‐aki Yamagishi 《Angewandte Chemie (International ed. in English)》2015,54(34):9849-9852
Activated perethylated pillar[5]arene crystals show an unexpected alkane‐shape‐ and ‐length‐selective gate‐opening behavior. Activated crystals were obtained upon removing solvents from perethylated pillar[5]arene crystals by heating. The activated crystals could quantitatively take up n‐alkanes with carbon chains containing more than five carbon atoms as a consequence of their gate‐opening pressure. As the chain length of the n‐alkanes increased, the gate pressure decreased. A transformation into a herringbone structure was induced when n‐hexane was used as a guest. By contrast, cyclic and branched alkanes were not taken up and could not induce a crystal transformation because they were too large to fit in the cavities of the pillar[5]arene. Alkane‐shape‐selective molecular recognition of pillar[5]arenes in the solution state was translated into the vapor/crystal state. 相似文献
58.
Fe K‐Edge X‐ray Absorption Fine Structure Determination of γ‐Al2O3‐Supported Iron‐Oxide Species
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Dr. Atsuko Tomita Dr. Takeshi Miki Takeru Tango Tatsuro Murakami Hideyuki Nakagawa Dr. Yutaka Tai 《Chemphyschem》2015,16(9):2015-2020
The structure of FeOx species supported on γ‐Al2O3 was investigated by using Fe K‐edge X‐ray absorption fine structure (XAFS) and X‐ray diffraction (XRD) measurements. The samples were prepared through the impregnation of iron nitrate on Al2O3 and co‐gelation of aluminum and iron sulfates. The dependence of the XRD patterns on Fe loading revealed the formation of α‐Fe2O3 particles at an Fe loading of above 10 wt %, whereas the formation of iron‐oxide crystals was not observed at Fe loadings of less than 9.0 wt %. The Fe K‐edge XAFS was characterized by a clear pre‐edge peak, which indicated that the Fe?O coordination structure deviates from central symmetry and that the degree of Fe?O?Fe bond formation is significantly lower than that in bulk samples at low Fe loading (<9.0 wt %). Fe K‐edge extended XAFS oscillations of the samples with low Fe loadings were explained by assuming an isolated iron‐oxide monomer on the γ‐Al2O3 surface. 相似文献
59.
Prof. Hiroshi Watanabe Ming-Long Yao Atsuko Yamagishi Kunihiro Osaki Toshiyuki Shitata Hirokazu Niwa Yotaro Morishima 《Rheologica Acta》1996,35(5):433-445
Linear and nonlinear viscoelastic properties were examined for a 50 wt% suspension of spherical silica particles (with radius of 40 nm) in a viscous medium, 2.27/1 (wt/wt) ethylene glycol/glycerol mixture. The effective volume fraction of the particles evaluated from zero-shear viscosities of the suspension and medium was 0.53. At a quiescent state the particles had a liquid-like, isotropic spatial distribution in the medium. Dynamic moduli G* obtained for small oscillatory strain (in the linear viscoelastic regime) exhibited a relaxation process that reflected the equilibrium Brownian motion of those particles. In the stress relaxation experiments, the linear relaxation modulus G(t) was obtained for small step strain (0.2) while the nonlinear relaxation modulus G(t, ) characterizing strong stress damping behavior was obtained for large (>0.2). G(t, ) obeyed the time-strain separability at long time scales, and the damping function h() (–G(t, )/G(t)) was determined. Steady flow measurements revealed shear-thinning of the steady state viscosity () for small shear rates (< –1; = linear viscoelastic relaxation time) and shear-thickening for larger (>–1). Corresponding changes were observed also for the viscosity growth and decay functions on start up and cessation of flow, + (t, ) and – (t, ). In the shear-thinning regime, the and dependence of +(t,) and –(t,) as well as the dependence of () were well described by a BKZ-type constitutive equation using the G(t) and h() data. On the other hand, this equation completely failed in describing the behavior in the shear-thickening regime. These applicabilities of the BKZ equation were utilized to discuss the shearthinning and shear-thickening mechanisms in relation to shear effects on the structure (spatial distribution) and motion of the suspended particles.Dedicated to the memory of Prof. Dale S. Parson 相似文献
60.