The Development of Cable Data Communications Standards

Commercially successful application of data communications technology to coaxial cable distribution networks requires the creation of systems useful to large numbers of subscribers sharing common communications procedures. Furthermore, it is desirable, particularly in entertainment CATV networks, that subscriber ownership of some or all terminal equipment and peripheral attachments be possible since such ownership enables the sharing of capital costs between the network operator and the subscriber. Systems designers are led inescapably to the need for standard interfaces and protocols. The paper describes some of the major types of cable data systems currently under development for both institutional and entertainment network applications. Common to both is the concept of a local interface unit to act as a link between the subscriber's terminal equipment and the cable drop. The design of the drop-side interface of this unit raises some major standardization issues. Another important issue is that of compatibility between data and video channels where both types of services are offered on the same cable television plant. The major thrust of present standardization activity has been founded upon the open systems interconnection (OSI) reference model and has taken place within a joint CVCC/EIA committee on teletext and within the IEEE Project 802.6 subcommittee on metropolitan area networks. The paper reviews this activity and explains the principal issues to be resolved.     

Desalination: the State of the Art

Desalination technology is applied in many areas of the world to provide fresh water from brackish or seawater sources. The paper reviews the technology which is available and discusses both distillation and membrane processes. Indications of capital and operating costs are provided.     

金川全尾砂新型充填胶凝材料激发剂配比与力学特性研究

针对金川全尾砂充填料,采用石灰、脱硫灰渣、芒硝和NaOH复合激发矿渣微粉,开展全尾砂新型充填胶凝材料试验。首先进行全尾砂物化特性分析,然后开展胶结充填体强度正交试验,最后以试验数据为学习样本,利用神经网络模型进行胶凝材料激发剂配比学习,获得充填胶凝材料激发剂配比的隐含知识。在此基础上,进行不同激发配比胶结充填体强度预测分析,由此揭示充填体强度和激发剂的关系,获得了激发剂最优配比。结果表明,在相同条件下,全尾砂充填胶凝材料胶结充填体强度是32.5R水泥强度的2倍以上,而成本仅为水泥的2/3。但金川矿山采用下向分层胶结充填法开采,全尾砂充填胶凝材料仍不能满足充填体1.5MPa的3d设计强度,有待于进一步开展其早强特性试验研究。     

竹笋脚料再利用探讨

竹笋是竹子的嫩茎,含糖为2%~4%,脂肪类物质为0．2%~0．3%,蛋白质为2．5%~3．0%。蛋白质等营养成份含量虽低于白菜、菠菜等植物类蔬菜,但味道鲜美,促进肠胃健康,降低人体脂肪积累等作用。我国长江以南各省均有竹笋罐头食品厂,每年春季将大量竹笋加工成各种罐头,畅销东南亚诸国及西欧国家。     

微生物驱油过程中配气对菌群结构及驱油效果的影响

为揭示油藏条件下微生物驱油过程中配注空气对菌群结构及驱油效果的影响规律,通过岩心驱替模拟实验研究了配气量对微生物驱驱油效率的影响,并通过显微镜、高通量测序仪和气相色谱分析了产出液中的菌群和小分子酸的动态变化。结果表明,微生物驱油过程中,配注空气量对菌群结构及驱油效果的影响显著。配注不同体积的空气激活微生物作用后产生了明显的驱替效果,并且随着配气量的增加驱替效率升高并逐渐稳定,液气比为1∶5时的驱替效率最高(8.77%)。随配气量增加产出液中菌数升高,不同类型的功能微生物被激活,其中4类主要优势功能菌占整个菌群比例的67%,功能微生物主要以产表面活性剂和乳化剂的芽孢杆菌和假单胞菌为主。配气量为液气比1∶5时微生物群落shannon多样性指数最高,代谢产生的小分子酸浓度较高,微生物代谢活性最佳。液气比1∶5可以作为现场实际配气的选择依据。图3表3参19