Spatio-temporal effects of multimedia objects storage and delivery for video-on-demand systems

As the number of video streams to be supported by a digital video delivery system (DVDS) increases, an improved understanding of the necessity for reliable and cost-efficient support for a considerable number of video streams (in the magnitude of tens of thousands), and the dependency largely on software capabilities emerges. Even in the presence of an optimal hardware configuration, or model, and associated costs, using software to exploit the underlying hardware capabilities is of paramount importance. Although a number of DVDSs have become operational, their ability to deliver the required services mainly depends on the small number of streams supported and the hardware trade-offs. It is imperative that current software developments account for the eventual scalability of the number of video streams without commensurate increase in hardware. In this paper, we present strategies for the management of video streams in order to maintain and satisfy their space and time requirements. We use a DVDS architectural model with functionally dichotomized nodes: a single-node partition is responsible for data retrieval, while the remaining partition of nodes accepts user requests, determines object locations, and routes requests through the network that connects both partitions. We present a detailed analysis of the issues related to queuing I/O requests and data buffering. The discussion includes the requirements for arranging and scheduling I/O requests and data buffers, with the objective of guaranteeing the required data availability rates for continuous media display.     

多媒体通信：需求与对策

本文首先对网络环境下的多媒体应用程序进行了分类，介绍了多媒体通信所涉及的一些比较重要的基本概念，包括静态媒体和连续媒体概念、等时通信和异步通信概念等，讨论了连续媒体数据的基本特征。在此基础上，我们讨论了多媒体通信、特别是连续媒体通信对网络技术提出的要求和基本对策，最后得出结论     

博物馆建筑室内无障碍流线的评价

论文通过比较国内外无障碍设计规范的区别,指出能形成完整无障碍流线的建筑及其室内外环境是推动我国无障碍环境建设的最终目标,提出博物馆建筑室内公共空间的无障碍流线设计主要包括室内交通空间、室内功能空间和室内标示导向系统三个部分。在此基础上,运用GCAHP方法构建了博物馆建筑室内无障碍流线的评价体系,确定了各指标的评分办法。最后以南京博物院为案例进行实证分析,验证了该评级体系的可操作性,以提高我国公共建筑无障碍环境设计的水平。     

SIEMENS FM357多轴驱动模块在铸咀布流控制系统中的应用研究

本文介绍了SIEMENS FM357多轴驱动模块的特点及在超薄快速铸钇铸咀布流控制系统中的应用,并对FM357的参数调协、各功能模块及数据模块的应用做了阐述。     

同一问题的四次解答——南京邮电大学仙林校区图书馆的设计探索与反思

南京邮电大学仙林校区图书馆是新建校园中心区的标志性建筑,但建筑功能所需要的体量与其所处的特殊环境产生矛盾。面对这一问题,我们根据设计条件的变化提出了四种不同的解决问题的思路。     

Temporal variation of pharmaceuticals in an urban and agriculturally influenced stream

Pharmaceuticals have become ubiquitous in the aquatic environment. Previous studies consistently demonstrate the prevalence of pharmaceuticals in freshwater but we do not yet know how concentrations vary over time within a given system. Two sites in central Indiana with varying land use in the surrounding watershed (suburban and agricultural) were sampled monthly for pharmaceutical concentrations and stream physiochemical parameters. Sediment samples were also collected at each sampling event for measurement of δ¹⁵N natural abundance and sediment organic content. Across sites and sampling events, twelve pharmaceuticals were detected including acetaminophen, caffeine, carbamazepine, cotinine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, ibuprofen, sulfadimethoxine, sulfamethazine, sulfamethoxazole, triclosan, and trimethoprim. Sulfathiazole, lincomycin, and tylosin were not detected at either site at any time. The agriculturally-influenced site had comparable pharmaceutical concentrations to the urban-influenced site. In general, pharmaceutical concentrations increased during winter at both sites and decreased during spring and summer. Multiple regression analyses indicated that water column dissolved oxygen, the number of days since precipitation, and solar radiation influenced total pharmaceutical concentration in the urban-influenced site; whereas pH, chlorophyll a concentration, and total amount of rainfall in the previous 10 days influenced total pharmaceutical concentrations in the agriculturally-influenced site. Pharmaceutical concentrations were not correlated with sediment δ¹⁵N across or within sites. However, sediment in the urban-influenced site had higher mean δ¹⁵N signatures relative to sediment in the agriculturally-influenced site. These data indicate pharmaceuticals are persistent in aquatic ecosystems influenced by both agricultural and suburban activity. Pharmaceuticals are designed to have a physiological effect; therefore, it is likely that they may also influence aquatic organisms, potentially threatening freshwater ecosystem health.