Summary A field measurement system for wind load based on a wireless sensor network was developed for large‐span roofs. The system achieves large‐area, long‐duration, synchronous data acquisition at a relatively high sampling rate. The custom wind pressure sensor was validated in a wind tunnel with an internal pressure test. The sensor matched the wind tunnel equipment well for both uniform and turbulent flows. The synchronization performance of the wireless system was evaluated with a custom device. The synchronization accuracy of the system was close to the accuracy of the electronic scanning valve in the wind tunnel. This system was validated on a roof with a span of 280 m. Continuous stable data acquisition from 48 nodes was achieved. The measurement system captured the wind pressure characteristics well, and the result was reasonable. The pressure results provide some useful conclusions, but more field measurements on roofing systems are required to obtain more reliable conclusions.

Abstract. Upload utilization is one of the most significant performance metrics in BitTorrent system, whereas there has been no accurate model which is suitable for it yet. For this reason, the delicate relation between some key parameters (maximum concurrent uploads, upload bandwidth, TFT round etc.) in BitTorrent is investigated, furthermore the piece diffusion model and the upload utilization model are proposed. Based on these models, we explore the effect of TFT round for the first time and find that the magnitude of TFT round has a significant influence on the transient stage as well as the end stage. Additionally, we show that when the seed's upload bandwidth is fully utilized, to achieve optimal performance, each peer's upload bandwidth should be proportional to its maximum concurrent uploads, and the file size should be large enough compared with the swarm size.

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