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51.
Wan-Li He Fei-Fei Wang Ping Song Ke-Xuan Li Hang-Jun Ding Zhou Yang 《Liquid crystals》2017,44(3):582-592
A wide pitch gradient covering the near infrared region (750.0–2500.0 nm) were facilely obtained by simple controlling temperature difference to LC mixtures with a twist grain boundary (TGB)–N* phase transition. After the pitch gradient formed, the structure of broad reflective bandwidth was fixed through polymerisation of monomers in mixtures by UV irradiation. It was found that the temperature difference between the up and down side of the samples was critical to form wide-pitch gradient distribution. Additionally, the reflection wavelength and bandwidth of films could be adjusted by the applied temperature difference with the widest bandwidth up to 1750 nm. This simple method for the preparation of broad reflective films was expected to be used in the fields like architectural energy conservation or infrared shield. 相似文献
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A variety of studies have focused on the effect of competition in broadband markets on increasing broadband penetration rates. Few studies however have focused on the extent to which competition also results in innovation in the marketplace, as demonstrated by increased broadband speeds, and other improvements that provide value to broadband users. This paper considers the effectiveness of market competition as a means of encouraging broadband providers to offer innovative services that meet citizens’ increasing needs for affordable high quality and high speed broadband connectivity. The study focuses on the provision of broadband services in Canada, a country where consumers were early adopters of broadband and where the policy environment has encouraged competition in the broadband market from its inception. Drawing on data from the OECD and the Canadian Radio-television and Telecommunications Commission (CRTC), the paper demonstrates that Canada’s regulatory regime does not appear to be sufficient to enable a competitive marketplace that results in the provision of innovative broadband services. 相似文献
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Nanoporous ZnO/SiO2 bilayer coatings were prepared on the surface of glass substrates via sol-gel dip-coating process. The structural, morphological and optical properties of the coatings were characterized. The refractive indices of ZnO layer and SiO2 layer are 1.34 and 1.21 at 550 nm, respectively. The transmittance and reflectance spectra of the coatings were investigated and the broadband antireflection performance of the bilayer structure was determined over the solar spectrum. The solar transmittances in the range of 300-1200 nm and 1200-2500 nm are increased by 6.5% and 6.2%, respectively. The improvement of transmittance is attributed to the destructive interference of light reflected from interfaces between the different refractive-index layers with an optimized thickness. Such antireflection coatings of ZnO/SiO2 provide a promising route for solar energy applications. 相似文献
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异步转移模式(ATM)正在以前所未有的速度向前发展,ATM交换成为未来宽带ISDN的关键。本文分析了ATM的产生背景,介绍了其基本概念和原理,讨论了ATM网络的演进和应用,并概述了它在国内外的发展。 相似文献
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本文就CATV网向宽带全业务网升级的策略和技术进行了讨论。首称要将现有CATV网改造为双向传输网。在此基础上,建成CATV广播网和计算机网并行的网络。在计算机网中,应用Cable modem实现数据双向传播,或在CATV网中应用暂时富裕的光纤构成独立计算机网。 相似文献
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由于金属间化合物的生成,会使金铝键合的接触电性能受到影响.从金属间化合物生成这一单一失效机理出发,以失效物理为理论基础,通过恒定高温加速和高温步进加速试验,针对不同温度下的金铝键合寿命做出评价,并给出键合寿命评价流程. 相似文献