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61.
This paper further illustrates the applicability of multiple internal reflectance infrared spectroscopy to the analysis of near-surface photooxidation. The results are compared with transmission infrared spectra to evaluate compositional gradients resulting from photooxidation and the influence of oxygen diffusion. The sample was a solvent-cast film of atactic, narrow distribution polystyrene, Mw of 100,000, that had been drawn to a ratio of 3.0 at 110°C by solid state coextrusion. Irradiation of these thin films, ~25μm thickness, was performed on exposure to air at 35°C for periods of up to 6 h using a mercury source emitting at 254 nm. On photooxidation, a board peak appears at 3200–3500 cm?1, attributable to hydroperoxide formation. The most dramatic increase in the infrared spectra is found for a carbonyl band at 1730 cm?1. It appears to result from an aromatic acid group since it is shifted to 1660 cm?1 on immersion of the oxidized polystyrene films in aqueous ammonium hydroxide. It is confirmed that the photooxidation of polystyrene occurs preferentially at the surface and that this reaction rate is greatly reduced in the drawn polystyrene film. 相似文献
62.
The determination of the diffusion coefficient for water in various porosity cellulose acetate membranes by a gravimetric method, using a humidified carrier gas, is described. It was found to be impossible to obtain meaningful results for very porous membranes, although dense membranes gave limiting values of diffusion coefficient at high carrier gas velocities. This phenomenon is explained in terms of the dissipation of the heat of sorption by the forced convection provided by the carrier gas. The variation of diffusion coefficient with concentration of water in dense cellulose acetate is explained in terms of clustering of water molecules in the polymer at high concentration. 相似文献
63.
64.
Barbara Porter 《计算机与网络》2014,(15):77-77
<正>长期以来,Emulex I/O解决方案的价值一直为全球电信公司所公认。如今,Emulex宣布推出计划中的高级功能,使用这些功能,电信公司能够更快速地开发优质网络服务提供给客户。新增功能包括增强了Emulex OneConnect OCe14000系列10Gb和40Gb以太网(10/40GbE)网络以及融合网络适配器(CNA)的数据包处理并提高了可编程性。使用这些新增功能,电信设备制造商(TEM)和电信运营商可以加快网络功能虚拟化(NFV)解决方案的部署。Emulex已经与6WIND建立合作伙伴关系,共同开发了Emulex轮询模式驱动程序(PMD),以增强数据平面开发工具包 相似文献
65.
The development of crystalline and mesophase structure on drawing of poly(ethylene terephthalate) (PET) has been studied. The uniaxial drawing has been done by solid-state coextrusion from 50 to 90°C. The unit-cell parameters of stress-induced crystallites in extrudates have been determined as a function of extrusion draw ratio (EDR) up to 4.4 and at an extrusion temperature (ET) above Tg, at 70 and 90°C. The higher the EDR, the longer the c-axis chain direction, the shorter the a and b axes and the smaller the unit-cell volume. In comparison with the conventional lattice parameters obtained by Bunn and Fisher, the highest elongation of the c axis is near 10%. These features imply that the lattice of stress-induced crystallites is far from the closest packing. Coextrudates made below the Tg of PET differ markedly from those made above Tg. Wide-angle X-ray diffraction (WAXD) patterns of PET extruded at 50°C (below Tg) even at high draw ratio exhibit small and/or imperfect crystallites. They appear much as a mesophase. The distance between macromolecular chains ranges from 3.2 to 5.4 Å. The shortest value in the mesophase approaches the interplanar crystal distance of 3.4 Å for the (100) crystal face, on which the benzene rings lie. The crystalline peak separation of the PET, WAXD curve has been evaluated to obtain absolute crystallinities and the content of mesophase and amorphous phase. 相似文献
66.
Natural silk is an important biopolymer with huge potential as it combines superb mechanical properties with environmentally sensitive production methods. Native silk dope taken straight from the gland can easily and without chemical assistance be drawn into strong fibres. Artificial silk fibres, on the other hand, rely on spinning dopes typically ‘reconstituted’ from natural silk fibres by strong chaotropic agents. Such fibres do not form readily, and often require chemical post-spin treatment for stabilisation. In addition these fibres tend to be brittle, and so far have been unable to match native fibres. Here we present novel rheometric data to argue that native and reconstituted silkworm silk dope differ in kind, not just in degree. While native silks behave like typical molten polymers, reconstituted silks do not. We conclude that rheology provides a powerful tool in the quest to learn from the Nature's polymer fibre technology. 相似文献
67.
Nuclear magnetic resonance spectroscopy has been used to study the dissociation and reaction of N,N′-(2-propyloximino)-4,4′-methylenebis(phenylcarbamate), as a crosslinking agent for polymers containing labile hydrogens. The crosslinking of poly(acrylic acid), polyacrylamide, and poly(vinyl alcohol) was found to result upon heating each to 150°C for 10 min with this component at 2–10 wt %. 相似文献
68.
W.Wade Adams Robert M. Briber Edward S. Sherman Roger S. Porter Edwin L. Thomas 《Polymer》1985,26(1):17-26
The microstructure of a series of solid state extruded polyethylene fibres was examined by wide- and small-angle X-ray scattering. By measuring absolute intensities using a two dimensional position sensitive detector, accurate values of the small-angle invariant for anisotropic samples were obtained. This measurement coupled with wide-angle X-ray scattering and d.s.c. permitted determination of the density of the noncrystalline component. The use of a two phase model for solid state extruded polyethylene is justified if consideration is given to the effective densities of the crystalline and noncrystalline phases, which change with deformation. The effective density of the crystalline phase decreases by 1% (0.999–0.990 g cm?3) from the unextruded billet compared to a 36 draw ratio extrudate, while the noncrystalline phase density increases by 6% (0.84–0.89 g cm?3). These changes lead to an overall decrease in the mean squared electron density fluctuation of 63%. The average axial crystallite length measured by wide-angle X-ray scattering increases with extrusion draw ratio while the SAXS long period decreases and weakens considerably. These observations and the electron microscopy results from the previous paper, (Polymer, 1982, 23, 1069), are fully consistent with the key features of the Peterlin model of fibre microstructure. 相似文献
69.
This paper describes a new multilayer TBC that incorporates a 10 μm-thick oxygen barrier layer of yttrium–aluminum garnet (YAG) into a typical YSZ TBC system. The thermal conductivity of as-sprayed YAG/YSZ coatings was reduced due to excessive porosity and amorphous areas in the YAG layer. After long-term heat treatments, the conductivity of the multilayer was unaffected by the presence of YAG. Sintering and recrystallization of the amorphous YAG regions occurred during high-temperature heat treatments. While YAG itself possesses excellent phase stability, its presence also improved the phase stability of zirconia near the YAG/YSZ interface, inhibiting the outward diffusion of yttrium from high-yttria t-ZrO2 The YAG layer reduced the NiCoCrAlY bond-coat oxidation rate by a factor of three during isothermalfurnace tests conducted at 1200° C. 相似文献
70.
Ben W. Morrison Mark W. Wiggins Glenn Porter 《International journal of human-computer interaction》2013,29(4):297-316
This study examined trainee crime-scene investigators' preference for, and accuracy in using, four different computer-based decision support interface designs, each of which incorporated a different reduced processing information acquisition strategy. The interfaces differed on the basis of the number of options that could be considered simultaneously and the level of control that could be exercised over the number and sequence in which feature values were accessed. Forty trainee investigators completed six decision scenarios in which they were asked to acquire information and formulate a decision by selecting one of three options. The study comprised two phases, the first of which involved familiarizing participants with each of the four interface designs and collecting performance and subjective data. The second phase involved trainees selecting one of the four interfaces to engage in a fifth and sixth decision scenario involving high or low levels of time-pressure. The results indicated that the “all options, full control” interface was the preferred option in the low time-pressure condition. Although the strategy remained the most frequently selected in the high time-pressure condition, this preference was not significant. It was concluded that the perceptions of difficulty and the degree of user control over information acquisition were more important than perceived efficiency in the selection of computer-based interface designs. The outcomes have implications for the design of decision support systems. 相似文献