浅谈吐哈油田数字电视网络的建设

介绍吐哈油田有线数字电视前端、数字电视网络以及远距离传输的建设方案,网络共传输120套数字电视节目和18套广播节目,达到了数字整体平移的目的,分析数字化后存在的问题,为今后更好地发展数字电视提供了科学依据.     

双向HFC＋CM网络模式是西部地区县级广电运营商开展双向增值业务的最佳选择

本文以西部地区县级广电网络的现状为出发点,指出以双向HFC＋CM的网络模式是支持西部地区县级广电网络运营商开展双向增值业务、实现可持续发展的主要网络技术模式。     

宽带城域网的多种接入方式混合应用

本文着重分析了宽带城域网的多种接入方式类型和特点,并提出了多种接入方式混合应用的实例。     

Analysis based on EU Regulation No 517/2014 of new HFC/HFO mixtures as alternatives of high GWP refrigerants in refrigeration and HVAC systems

The EU Regulation No 517/2014 is going to phase-out most of the refrigerants commonly used in refrigeration and air conditioning systems (R134a, R404A and R410A) because of their extended use and their high GWP values. There are very different options to replace them; however, no refrigerant has yet imposed. In this paper we review and analyze the different mixtures proposed by the AHRI as alternative refrigerants to those employed currently. These mixtures are composed by HFC refrigerants: R32, R125, R152a and R134a; and HFO refrigerants: R1234yf and R1234ze(E). It is concluded, from the theoretical analysis, that most of the new HFO/HFC mixtures perform under the HFC analyzed (although some experimental studies show the contrary) and, in most cases, do not meet the GWP restrictions approved by the European normative. Furthermore, some of the mixtures proposed would have problems due to their flammability.     

基于分等级搜索的可持续进化算法研究

通过分析标准遗传算法在可持续性进化方面的缺陷，提出了HFC模型及其运算流程，井给出了详细的数学描述。HFC算法的分等级搜索方式改进了标准遗传算法的缺陷，是一种能实现可持续性进化的算法模型。HFC模型不仅能确保种群的多样性，而且保证了个体间的公平竞争。实例验证了HFC模型和标准遗传算法在相同问题上的不同效果。     

Tribochemical Effects on Tribological Properties of Self-Mated Zirconia Ceramic in HFC-134a Gas

Tribochemical effects on the tribological properties of self-mated zirconia ceramic in CF₃CH₂F (HFC-134a) were investigated using a ball-on-disk type environmental tribometer. The friction chamber of the tribometer was attached to a micro-spot X-ray Photoelectron Spectrometer (XPS) for ensuring that surface analysis be conducted without exposuring the frictional surfaces to air. It was found that HFC-134a gas was an effective lubricant for zirconia ceramic, especially at a pressure higher than 10³ Pa. The products of tribochemical reactions between zirconia and HFC-134a molecules were detected. The amount and chemical state of the tribochemical products seemed to control the tribological behaviors. Thus, the role of tribochemical products on the tribological properties of zirconia in HFC-134a gas at 10⁴ Pa was studied in detail under applied loads of 0.6–5.0 N and sliding speed of 0.04–0.35 m/s. It was found that severe tribochemical reactions occurred at low speeds and high loads. The formation of ZrF₄ accelerated the chemical wear of zirconia, and raised the friction. Zirconia ceramic is suitable for use at moderate load and sliding speed under a reactive environment.     

GPON+CMC接入方案在汕头广电HFC网改的规划与部署

根据汕头广电网络的实际情况,对广东广电汕头分公司的HFC(Hybrid Fiber Coaxial)双向网改中应用的GPON(Gigabit-Capable Passive Optical Networks)+CMC(Coax Media Converter,同轴电缆媒体转换器)接入方案的实施背景及方案选择、网改的规划设计、设备的安装部署及调测、系统网管及装维常见问题、网改效果和经济效益社会效益等方面作了详细地介绍。     

太阳能喷射制冷系统在中原地区的性能分析

通过建立系统性能分析模型,结合中原地区典型气象日的气象条件,了解了太阳能喷射制冷系统在中原地区的运行特性,计算并分析了发生温度、蒸发温度和冷凝温度改变时系统COP0的变化情况.研究表明,在研究参数范围内,喷射系统COP随发生温度和蒸发温度的增加而增加,随冷凝温度的增加而减小,系统综合COP0随时刻呈先上升后下降的趋势,最大可达0.33.进一步针对中原地区200m2的别墅,计算了当集热面积为40m2时的太阳能喷射系统的供冷情况,结果表明,在8:00～16:00之间,太阳能喷射系统可以为别墅提供80%以上的冷量.     

CATV网渐进升级为全业务接入网的技术

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。     

双向HFC网上行通道的噪声与干扰

以ＨＦＣ网上行通道的噪声干扰为主题,着重讨论了侵入噪声的来源及其特点,提出了其解决措施。