A Study on the Thermal Characteristics of the Epoxy Insulator in the Stop Joint Box of HTS Power Cable

AbstractThe HTS power cable is cooled by the circulation of liquid nitrogen. The cooling capacity of refrigerator increases with cable length. As the length of power cable increases, a joint box should be installed to reduce the cooling capacity and pressure drop for unit cooling system. The type of joint box can be divided into two groups. There are NJB(Normal Joint Box) and SJB(Stop Joint Box). Generally, SJB can separate each cooling system. In case of long distance DC cable, it is necessary to separate the cooling line in the regular distance of cooling system so SJB should be used. However, SJB, which has a difference from the insulation method of existing joint box, uses solid electrical insulation method. At the primary cooling time, thermal stress is generated by the temperature difference between the internal and external epoxy. So to prevent the damage stress analysis is required for the electrical insulation structure of SJB. In this paper, using the FEM analysis we study the cooling method and optimal shape of SJB to reduce the thermal stress result from temperature difference during the cooling time

WAVE: Popularity-based and collaborative in-network caching for content-oriented networks

Abstract—In content-oriented networking, content files are typically cached in network nodes, and hence how to cache content files is crucial for the efficient content delivery and cache storage utilization. In this paper, we propose a content caching scheme, WAVE, in which the number of chunks to be cached is adjusted based on the popularity of the content. In WAVE, an upstream node recommends the number of chunks to be cached at its downstream node, which is exponentially increased as the request count increases. Simulation results reveal that the average hop count of content delivery of WAVE is lower than other schemes, and the inter-ISP traffic volume of WAVE is the second lowest (CDN is the lowest). Also, WAVE achieves higher cache hit ratio and fewer frequent cache replacements than other on-demand caching strategies. Index Terms—Content chunk caching, caching strategy, content-oriented networks I

Decentralized and autonomous content overlay networking (DACON) with WiFi access points

Accessing contents from mobile devices becomes more and more proliferated and hence the need for the content dis-tribution in the pervasive environment is growing. How-ever, distributing contents in such environments taxes wire-less network operators substantially. To provide the content distribution service in a reasonable cost, we pay attention to user-deployable WiFi access points (APs). In this paper, we propose a decentralized and autonomous content overlay networking (DACON) architecture for the pervasive content distribution services, which is the overlay network architec-ture comprised of public WiFi APs. We identify and answer major challenges in realizing the content distribution ser-vice in the pervasive environment by exploiting the overlay network of public WiFi APs

Investigation of the over current characteristics of HTS tapes considering the application for HTS power devices

High temperature superconductor (HTS) is developed for applications in HTS power devices such as power transmission cable, transformers, superconducting fault current limiter (SFCL), motor, and generators. HTS power devices applied in power systems might undergo over current, such as over load, fault conditions, and unbalanced current. The electrical characteristic analyses of Bi2Ca2Sr2Cu3Ox (Bi-2223) HTS tapes and YBa2Cu3Ox (YBCO) tapes are very important for the application of HTS power devices. In this study, the transient phenomenon of HTS tapes was analyzed when the DC over current as well as the AC over current flow. Also, the experimental results of breakdown cycle, variation of temperature and resistance according to fault current in HTS tapes were analyzed. These results would be very significant data and give good information in order to design and fabricate HTS power devices. © 2008 IEEE