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语音、数据和视频业务的融合是不可质疑的发展趋势,文章首先给出了三重服务的定义,简要描述了该业务的分类和发展动力;接着从全球范围内的市场概况、运营模式和所面临的挑战三个方面阐述了Triple—play的发展状况,详细分析了运营商部署Triple—play的三个关键因素;最后,指出了国内运营商开展Triple—play服务需要做的网络准备。 相似文献
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高斯贝尔经过几年的努力,成功的开发和规模化生产了目前产品质量最高、规模化最大、性价比最合适、适合在中国大中城市数字电视整体平移中广泛应用的高性能、多功能、双向交互、标清基本型机顶盒。 相似文献
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Effect of radiation-induced mean wavelength shift in optical fibers on the scale factor of interferometric fiber optic gyroscope at a wavelength of 1300 nm 下载免费PDF全文
In order to analyze the effect of wavelength-dependent radiation-induced attenuation (RIA) on the mean transmission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes (IFOGs), three types of polarization-maintaining (PM) fibers is tested by using a 60Co γ -radiation source. The observed different mean wavelength shift (MWS) behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible range and total dose-dependent near infrared absorption bands. To evaluate the mean wavelength variation in fiber coil and the induced scale factor change for space-borne IFOG under low radiation dose in space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium (Ge) doped fibers and two germanium-phosphorus (Ge-P) codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmitting in fibers will shift to shorter wavelength in low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOG. 相似文献
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一般线性模型只能拟合一些特殊的资料,而广义线性模型则不一样,它具有较大的灵活性,运用也日趋广泛.基于此,运用广义估计方程证明了高维变量下Poisson分布相关阵的相合性. 相似文献
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1 引言
目前,我国一些农村和偏远地区还只能通过天线收看模拟电视,或者通过模拟MMDS无线覆盖看到电视。经过多年的使用,有些设施已经因年久失修或者老化等原因,电视质量已无法满足广大老百姓看上高质量电视的需求。 相似文献
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采用液压螺栓作为齿轮与轴及骨架与轴的联接形式,一方面实现轴向联接的作用,另一方面实现周向力矩传递的功能,改变了传统的力矩传递方式和联接形式,其结构简单,装拆无损坏,联接安全可靠。文中重点介绍了液压螺栓的工作原理和承载设计计算,为类似产品的设计提供经验指导。 相似文献