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991.
992.
In this paper the authors present the main problem of operating video tape recorders for television production, viz. picture degradations through multiple generations, which could be cancelled by using digital machines. Efficient error protection is mandatory. Burst error statistics are given as collected on a laboratory digital recorder as well as a physical interpretation. Different protection methods are used for luminance and colour differences, which results in sharing the available redundancy between two distinct coding systems. Adequate codes are selected through the use of two bounds stated as theorems. The main parameters of a possible system are presented. They are likely to be improved when further information is available to make an operating system practical. 相似文献
993.
The economy of telecommunications is presently characterized by differentiation of services. This paper explores this differentiation in different institutionnal situations starting from very simple but realistic assumptions. It is established that the most efficient situation should associate a technical monopoly of the network with a competitive supply of services. 相似文献
994.
Jean-Louis Besson Dominique Billieres Tanguy Rouxel Paul Goursat Robert Flynn Stuart Hampshire 《Journal of the American Ceramic Society》1993,76(8):2103-2105
Glasses have been prepared in the Si -Y-Al O-N system by melting mixtures of silica, alumina, yttria, and silicon nitride. One particular glass containing 17 equiv% N has been investigated to Observe the crystallization at temperatures in the range 1050o -1300o C. The major crystalline phase observed is Y2 Si2 O7 , existing as the α form below 1200o C and the β form above this temperature. Properties of the glass-ceramic, including thermal expansion coefficient, hardness, electrical resistivity, and creep have been assessed. 相似文献
995.
Stephane Marais Yuichi Hirata Dominique Langevin Corinne Chappey Trong Q. Nguyen Michel Metayer 《Materials Research Innovations》2002,6(2):79-88
The transport of water and gases (pure oxygen and carbon dioxide) through poly(ethylene-co-vinyl acetate) (EVA) films of different
VA contents and through a low density polyethylene LDPE (used as reference with 0 wt.% VA), was analysed by permeation and
sorption measurements.
In the case of water, for EVA of 70 wt.% VA, a plasticization effect on the material was observed. For EVA of 19 wt.% VA,
there was no plasticization, while for EVA of 4.5 wt.% VA and for LDPE, the water diffusion coefficient decreases with increasing
water. An empirical law was then found to account for the reduction of the water diffusivity. A negative plasticization effect
was attributed to the formation of water clusters in these rather non polar polymers. This latter result was confirmed by
sorption measurements and infra-red spectroscopy. The increase in water sorption extent with the VA content leads to a steady
increase in the water permeability in the EVA copolymers.
In the case of gas permeation, both for O2 and CO2 and whatever the VA content of the copolymer used, the experimental curves are characterized by a constant diffusion coefficient.
This is confirmed by sorption experiments. In terms of gas permeability, EVA copolymers are characterized by low coefficients
especially for oxygen. In the EVA rubbery copolymers, The O2 solubility coefficient does not increase with the VA content due to the lack of polar interactions, while the CO2 one increases due to the overall interactions between CO2 induced dipoles and the polar the VA carbonyl groups. For these copolymers, the H2O/CO2 and H2O/O2 selectivities are very high. The experimental values of the selectivities indicate that these EVA copolymers appear as good
candidates for applications using high perm-selectivity properties.
Electronic Publication 相似文献
996.
Abstracts of invited papers 相似文献
997.
Nicolas Dupré Jean-Frédéric Martin Dominique Guyomard Atsuo Yamada Ryoji Kanno 《Journal of power sources》2009
7Li MAS NMR, usually a bulk characterization technique, is used here to analyze the positive electrode/electrolyte interphase. The sharpening of the NMR spectra line shape as the amount of surface species increases shows that the observed signal is clearly the sum of signals due to the distribution of lithium ions in the interphase in terms of distance from the bulk of electrode active material. This technique is then used to compare characteristics of the interphase coming from the contact with LiPF6-based electrolyte in the case of storage or electrochemical cycling. A clear influence of the change of potential on the interphase configuration and in particular on its intimacy with the bulk of active material is deduced from the change in NMR spectra lineshape. This information is hardly obtained by other characterization technique, making NMR a powerful tool for the study of interphases and passivation layers in lithium batteries materials. 相似文献
998.
Céline Teintenier-Cousin Catherine Lefranc-Millot Gianni Froidevaux Marie-Christine Slomianny Didier Guillochon Dominique Vercaigne-Marko 《International Dairy Journal》2009,19(5):286-294
A strategy was developed for the preparation of a latent transforming growth factor-β2 (latent TGF-β2) rich fraction from bovine colostrum. Different conventional chromatography techniques were tested to investigate some physicochemical properties of latent TGF-β2 complexes to optimize their recovery. Three latent TGF-β2 forms were detected by gel filtration (600, 150–250 and 65–150 kDa). Cation exchange chromatography showed that the pI of latent TGF-β2 was above pH 7; hydrophobic interaction chromatography showed that the hydrophobicity of latent TGF-β2 was much higher than that of other whey proteins. Affinity chromatography on Cibacron Blue 3G was used to separate latent TGF-β2 and immunoglobulin G from the most immunogenic proteins, α-lactalbumin, β-lactoglobulin and albumin. Optimum conditions were determined: preparation of a fraction 26 times richer in TGF-β2 than in serocolostrum was obtained with a good yield (up to 70%) of TGF-β2, 80% of which was in the latent form. 相似文献
999.
Anthony Thuault Sylvain Marinel Etienne Savary Romain Heuguet Sébastien Saunier Dominique Goeuriot Dinesh Agrawal 《Ceramics International》2013,39(2):1215-1219
In this study, the reaction sintering of boron carbide, which consists in doing reactive infiltration of molten silicon throughout a porous sample made of B4C and carbon graphite was investigated. Thus, it has been shown that a single-mode microwave cavity can be successfully used to produce reaction-bonded B4C–SiC composite. A specific package, consisting of a SiC based susceptor and a boron nitride based insulating container, was used to heat up the B4C–Si system using a single-mode microwaves cavity under an Ar–H2 atmosphere. Pore-free B4C–SiC composite successfully produced consists of a mixture of B4C and polygonal shaped β-SiC within a residual silicon matrix. The indentation technique permits to determine mechanical properties of the samples which are compared to those obtained conventionally. It appears that the average hardness (H≈22 GPa) value is quite constant all along the sample thickness which highlights good homogeneity of the samples obtained. Some aspects of the microstructure are also discussed and compared to those of samples conventionally obtained. 相似文献
1000.
Titanium Oxide Fibers: Original Electrospun Core–Shell Nanostructured Magnéli Titanium Oxide Fibers and their Electrical Properties (Adv. Mater. 17/2014)
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