Monitoring the performance of any structure requires real-time measurements of the change of position of critical points. Different techniques can be used for this purpose, each one offering advantages and disadvantag...Monitoring the performance of any structure requires real-time measurements of the change of position of critical points. Different techniques can be used for this purpose, each one offering advantages and disadvantages. The technique based on satellite positioning systems （GPS, GLONASS and the future GALILEO） seems to be very promising at least for long period structures. The GPS in particular provides sampling rates that are able to track dynamic displacements with high accuracy. Its service ability is independent of atmospheric conditions, temperature variations and visibility of the monitored object. This paper investigates the reliability and accuracy of the measurements of dual frequency GPS receivers. A linear electromagnetic motor moves an object along a given direction. The changes of position are compared witb their estimates as recorded by a GPS receiver, whose antenna is located on the reference object. The comparison is based on sufficiently long records.展开更多
The number of clients that receive high-quality streaming video from a source is greatly limited by the application requirements, such as the high bandwidth and reliability. In this work, a method was de-veloped to co...The number of clients that receive high-quality streaming video from a source is greatly limited by the application requirements, such as the high bandwidth and reliability. In this work, a method was de-veloped to construct a color overlay, which enables clients to receive data across multiple paths, based on the forward error correction technique. The color overlay enlarges system capacity by reducing the bottle-necks and extending the bandwidth, improves reliability against node failure, and is more resilient to fluctua-tions of network metrics. A light-weight protocol for building the overlay is also presented. Extensive simula-tions were conducted and the results clearly support the claimed advantages.展开更多
文摘Monitoring the performance of any structure requires real-time measurements of the change of position of critical points. Different techniques can be used for this purpose, each one offering advantages and disadvantages. The technique based on satellite positioning systems （GPS, GLONASS and the future GALILEO） seems to be very promising at least for long period structures. The GPS in particular provides sampling rates that are able to track dynamic displacements with high accuracy. Its service ability is independent of atmospheric conditions, temperature variations and visibility of the monitored object. This paper investigates the reliability and accuracy of the measurements of dual frequency GPS receivers. A linear electromagnetic motor moves an object along a given direction. The changes of position are compared witb their estimates as recorded by a GPS receiver, whose antenna is located on the reference object. The comparison is based on sufficiently long records.
基金the National Natural Science Foundation of China (No. 60273008) and the Major Research Project of the National Key Basic Research and Development (973) Program of China (No. G1999032704)
文摘The number of clients that receive high-quality streaming video from a source is greatly limited by the application requirements, such as the high bandwidth and reliability. In this work, a method was de-veloped to construct a color overlay, which enables clients to receive data across multiple paths, based on the forward error correction technique. The color overlay enlarges system capacity by reducing the bottle-necks and extending the bandwidth, improves reliability against node failure, and is more resilient to fluctua-tions of network metrics. A light-weight protocol for building the overlay is also presented. Extensive simula-tions were conducted and the results clearly support the claimed advantages.
