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991.
992.
993.
T. L. Cheeks T. Sands R. E. Nahory J. P. Harbison H. L. Gilchrist V. G. Keramidas 《Journal of Electronic Materials》1991,20(7):881-884
Enhancement of the Schottky barrier height was obtained in MBE grown (CoAl or NiAl)/ AlAs/GaAs heterostructures by incorporating
ultra thin AlAs layers between the metal and GaAs. By varying the AlAs thickness from 0 to 10 nm the effective barrier height,
determined by current-voltage and capacitance-voltage measurements, could be tailored from 0.76 eV to 1.1 eV. Internal photoemission
measurements were performed to verify the 1.1 eV barrier height. The temperature dependence of the current-voltage characteristics
showed that thermionic emission was the dominant transport mechanism for all thicknesses of AlAs. The results were consistant
with transport through the X-band of AlAs. 相似文献
994.
Gödel's Incompleteness Theorems have the same scientific status as Einstein's principle of relativity, Heisenberg's uncertainty principle, and Watson and Crick's double helix model of DNA. Our aim is to discuss some new faces of the incompleteness phenomenon unveiled by an information-theoretic approach to randomness and recent developments in quantum computing. 相似文献
995.
振动沉模板墙技术是一项新的防渗技术。该技术在应用中出现了一些问题 ,本文针对具体工程 ,对这些问题产生的原因及解决方法进行了初步探讨 ,对今后更好的应用该技术提供了一个借鉴 相似文献
996.
In part III of this series of articles, we present the analysis of transient permeation through two‐layer reactive–passive (RP) film designs, the analysis extension to multilayer structures, and optimized design solutions for multilayer barriers incorporating immobile noncatalytic oxygen scavenger within one of the layers. The reduction of oxygen ingress into a package within a certain timeframe depends on two factors: extension of the scavenger exhaustion time and reduction of the transient transmission rate through the film during that time. The optimal design for the scavenger exhaustion time involves exposure of the reactive layer to the package contents and its protection from high levels of environmental oxygen by the best possible passive barrier layer. The film barrier properties can be further optimized by the selection of the matrix material to place the scavenger in. Reducing the initial transmission rate requires the placement of the scavenger within a layer with the lowest diffusivity of the matrix polymer. When one chooses between two layers with different material transport properties in which to put the scavenger, the optimal solution for the ingress depends on the desired time to provide an improved barrier. The lifetime of the scavenger in the RP film is shortened for design 1, when the diffusivity of the reactive layer is smaller than that of the passive layer, compared to RP design 2, with the layer matrix sequence reversed, but the transient transmission rate is greatly reduced on average for the former. If the desired time to provide a barrier does not exceed the scavenger exhaustion time for RP design 1, the lowest diffusivity material should be used as a matrix for the innermost layer loaded with the scavenger. Otherwise, the highest possible passive barrier should be placed into the film external layer to minimize the total ingress during longer times. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1966–1977, 2006 相似文献
997.
严文群 《水电自动化与大坝监测》1998,(2)
近年来美国的一些实验室,开始将流泵(flowpump)用于渗透仪,以代替传统的渗流试验装置。与达西渗透仪相比,用流泵测定土的渗透系数,不仅操作简便易行,试验时间大为节省,而且试验结果稳定可靠,精度高,试验的可重复性强。 相似文献
998.
999.
EPS材料在桥头软基处理中的技术经济分析 总被引:1,自引:0,他引:1
采用EPS超轻质材料填筑路堤,通过与其他处理方式比较,结果表明,EPS材料在深厚软土地基低填方路堤中具有良好经济性和处理效果。 相似文献
1000.
OSCAR T. F. DA COSTA† ANA CAROLINA E. PEDRETTI† ANKE SCHMITZ STEVEN F. PERRY & MARISA N. FERNANDES† 《Journal of microscopy》2007,225(1):1-9
Previous morphometric methods for estimation of the volume of components, surface area and thickness of the diffusion barrier in fish gills have taken advantage of the highly ordered structure of these organs for sampling and surface area estimations, whereas the thickness of the diffusion barrier has been measured orthogonally on perpendicularly sectioned material at subjectively selected sites. Although intuitively logical, these procedures do not have a demonstrated mathematical basis, do not involve random sampling and measurement techniques, and are not applicable to the gills of all fish. The present stereological methods apply the principles of surface area estimation in vertical uniform random sections to the gills of the Brazilian teleost Arapaima gigas. The tissue was taken from the entire gill apparatus of the right‐hand or left‐hand side (selected at random) of the fish by systematic random sampling and embedded in glycol methacrylate for light microscopy. Arches from the other side were embedded in Epoxy resin. Reference volume was estimated by the Cavalieri method in the same vertical sections that were used for surface density and volume density measurements. The harmonic mean barrier thickness of the water‐blood diffusion barrier was calculated from measurements taken along randomly selected orientation lines that were sine‐weighted relative to the vertical axis. The values thus obtained for the anatomical diffusion factor (surface area divided by barrier thickness) compare favourably with those obtained for other sluggish fish using existing methods. 相似文献