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491.
The variables affecting the nucleation and crystallization of biological hydroxy carbonate apatite (HCA) on porous gel-silica substrates are examined. Texture is the critical variable with the rate of HCA formation increasing as pore size and pore volume increase, with pore sizes >2 nm required to achieve rapid kinetics (4–6 days) of fully crystallized HCA. The concentration of silanol groups on the silica surface does not control the rate of HCA formation although metastable surface defects, such as trisiloxane rings, may be involved in HCA nucleation. 相似文献
492.
Ce0.65Zr0.35O2 solid solution was prepared by co-precipitation method and characterized by X-ray diffraction (XRD), Raman spectra, BET, oxygen storage capacity (OSC) and temperature-programmed reduction measurements (H2-TPR) after calcination at 100 ℃, 300 ℃, 600 ℃, and 1 000 ℃. The results showed that the precipitation was a crystalline of fluorite structure, and in the process of the precipitation transformation into Ce0.65Zr0.35O2 solid solution, the fluorite structure of the precipitation kept unchanged. The samples had different BET surface areas and OSC at different temperatures, but they held the performance of stable structure. After 1 000 ℃, there didn′t appear the other crystalline phase. So the samples prepared by co-precipitation method had excellent texture and higher thermal stability. 相似文献
493.
Swanhild Bernstein Helmut Schaeben 《Mathematical Methods in the Applied Sciences》2005,28(11):1269-1289
We consider a one‐dimensional Radon transform on the group SO (3), which is motivated by texture goniometry. In particular, we will derive several inversion formulae and compare them with the inversion of the one‐dimensional spherical Radon transform on ??3 for even functions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
494.
The influence of the high-energy heavy ion irradiation on the short range order and magnetic texture in amorphous FeNiSiB alloys are studied by Mössbauer spectroscopy. The rf-Mössbauer measurements reveal clear changes of the local structure induced due to high electronic energy deposition and related to the anisotropic growth effect. In the substantial volume fraction of irradiated samples the spins change their orientation from the in-plane to the perpendicular one.
相似文献495.
The surface structure and surface mechanical properties of low‐ and high‐density polyethylene were characterized by atomic force microscopy (AFM) as the polymers were stretched. The surfaces of both materials roughened as they were stretched. The roughening effect is attributed to deformation of nodular structures, related to bulk spherulites, at the surface. The surface‐roughening effect is completely reversible at tensile strains in the elastic regime and partially reversible at tensile strains in the plastic regime until the polymers are irreversibly drawn into fibers. AFM force versus distance interaction curves, used to measure changes in the stiffness of the surface and the surface elastic modulus as a function of elongation, show that the surfaces become softer as the polymers are drawn into fibers at high strains. At low elastic strains, however, the surface elastic modulus of HDPE increases—attributed to elastic energy stored by the amorphous regions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2263–2274, 2001 相似文献
496.
497.
On the optimization of surface textures for lubricated contacts 总被引:1,自引:0,他引:1
Gustavo C. Buscaglia 《Journal of Mathematical Analysis and Applications》2007,335(2):1309-1327
The pressure field that develops inside a lubricated contact obeys an elliptic equation known as Reynolds equation, with coefficients that depend on the shape of the contacting surfaces. The load-carrying capacity of a contact, defined as the integral of the pressure field, is an important performance indicator that should be as high as possible to avoid wear and damage of the surfaces. In this article, the effect of arbitrary uniform periodic textures on the load-carrying capacity of lubricated devices known as thrust bearings is investigated theoretically by means of homogenization techniques and first-order perturbation analysis. It is shown that the untextured shape is a local optimum for the load-carrying capacity of the homogenized pressure field. This is proved for bearings of general shape and considering both incompressible and compressible models for the lubricant. The homogenization technique however implies an error. Suitable bounds for the effect of this error are provided in a simplified case. 相似文献
498.
The formation of banded texture both in a semiflexible thermotropic liquid-crystalline polyester (SBH 112, synthesized from
sebacic acid, 4,4′-dihydroxybiphenyl and 4-hydroxybenzoic acid, from Eniricerche, Milan) and in a blend of SBH with graft
copolymers, consisting of a polyolefin (polyethylene or polypropylene) backbone and SBH grafts (COPPE, COPPP) has been studied
by polarization microscopy and by scanning electron microscopy. The influence of the preparation conditions upon the perfection,
characteristics and thermal stability of the banded texture has been investigated. The results show that the banded texture
formed in SBH sheared films possesses greater perfection, smaller band width and larger angle of deviation, and higher thermal
stability than the banded texture formed in COPPE and COPPP prepared under similar conditions. It has been assumed that the
chain rigidity of the macromolecules of the system is mainly responsible for the formation and perfection of the banded texture.
Received: 17 March 2000 Accepted: 26 July 2000 相似文献
499.
500.
表面织构对刀具切削性能及前刀面摩擦特性的影响 总被引:2,自引:1,他引:1
为了研究刀具表面织构对切削性能的影响,通过控制前刀面上微凹坑的直径、深度和面积占有率等参数制备了两组表面高度算术平均值Sa相同的织构刀具.使用Talysurf CCI Lite非接触式三维光学轮廓仪对织构表面进行测量,采用ISO25178参数对测量表面进行表征;通过SL200KS接触角测量仪测量织构刀具前刀面湿润性的变化;随后在CA6140车床上进行45钢切削试验,研究不同织构对切削力、前刀面摩擦特性、工件表面粗糙度和切屑形变的影响.结果表明:合理的表面织构能够改善刀具的切削性能;切削液在前刀面铺展较快的织构刀具获得了较好的切削性能;凹坑直径、深度和面积占有率的协同作用对改善刀具切削性能至关重要,为了协调这三个织构参数,进一步研究三维表征参数Sku、Ssk、Sv、Vvv、Vvc、Sdv、Sda、Spd与刀具切削性能的关联性,为刀具表面设计提供了基础. 相似文献