The Influences of Iron Ore Tailings as Fine Aggregate on the Strength of Ultra-High Performance Concrete

The present study looks for the feasibility of preparing UHPC with iron ore tailings (IOT for short) as fine aggregate. To enhance outstanding high performances, some influences on UHPC mortars were investigated such as different kinds of sands, different mix ratio of sands, and different largest particle size of fine aggregate. The results show that IOT have negligible poorer aggregate performance than silica sands but better than river sands. The strength of UHPC reaches the highest point when silica sands were instead 60% by IOT. As the largest particle size of fine aggregate is decreasing, the strength and frost resistance of UHPC were improved, but the liquidity was decreased. Micropowder of IOT affects the strength and the optimal content was 4%

Experimental Study of Broadcatching in BitTorrent

Abstract—Broadcatching is a promising mechanism to improve the experience of BitTorrent users by automatically downloading files advertised through RSS feeds. However, though widely used, the mechanism itself has not been well studied. In this paper, we conducted extensive experiments on PlanetLab to evaluate the performance of Broadcatching under different typical scenarios. The results demonstrated the effectiveness of the Broadcatching: it reduces the average completion time and downloading failure ratio. It also improves the overall fairness of the system: the subscribers are encouraged to share more while downloading faster, which results in the increased share ratio. Our study is the first work to systematically evaluate the benefit of Broadcatching and sheds lights on how to improve performance of BitTorrrent by manipulating peer’s behavior like Broadcatching. I

NC-APT: An Efficient and Scalable Download Mirror Selecting System

Abstract—When large files are offered by many mirrors for clients to download, selecting the proper download mirrors is necessary in speeding up the clients ’ download. The existing method, which measures all the Round Trip Time (RTT) between clients and all mirrors, costs much time and Internet traffic. In this paper, we propose NC-APT, an efficient and scalable download mirror selecting system, which is capable to provide clients an efficient method to select quick download mirror. NC-APT is scalable because it only requires the mirrors to response to ICMP ping instead of keeping running an NC software program. Our experimental results show that NC-APT significantly improves the clients ’ download rates with slight cost of time and Internet traffic. I