98 research outputs found
Analyzing the impact of storage shortage on data availability in decentralized online social networks
Maintaining data availability is one of the biggest challenges in decentralized online social networks (DOSNs). The existing work often assumes that the friends of a user can always contribute to the sufficient storage capacity to store all data. However, this assumption is not always true in todayâs online social networks (OSNs) due to the fact that nowadays the users often use the smart mobile devices to access the OSNs. The limitation of the storage capacity in mobile devices may jeopardize the data availability. Therefore, it is desired to know the relation between the storage capacity contributed by the OSN users and the level of data availability that the OSNs can achieve. This paper addresses this issue. In this paper, the data availability model over storage capacity is established. Further, a novel method is proposed to predict the data availability on the fly. Extensive simulation experiments have been conducted to evaluate the effectiveness of the data availability model and the on-the-fly prediction
Testing of high current transformer by non-uniform equivalent magnetomotive force method
Peer Reviewe
Design of the Tsinghua Tabletop Kibble Balance
The Kibble balance is a precision instrument for realizing the mass unit, the
kilogram, in the new international system of units (SI). In recent years, an
important trend for Kibble balance experiments is to go tabletop, in which the
instrument's size is notably reduced while retaining a measurement accuracy of
. In this paper, we report a new design of a tabletop Kibble balance
to be built at Tsinghua University. The Tsinghua Kibble balance aims to deliver
a compact instrument for robust mass calibrations from 10 g to 1 kg with a
targeted measurement accuracy of 50 g or less. Some major features of the
Tsinghua Kibble balance system, including the design of a new magnet, one-mode
measurement scheme, the spring-compensated magnet moving mechanism, and
magnetic shielding considerations, are discussed.Comment: 8 pages, 9 figure
Multi-helical Lamb Wave Imaging for Pipe-like Structures Based on a Probabilistic Reconstruction Approach
The special form of pipe-like structure provides the helical route for ultrasonic guided wave. Considering the pipe as a flattened plate but with periodical replications, the helical wave becomes intuitional and a corresponding imaging algorithm can be constructed. This work proposes the multihelical Lamb wave imaging method by utilizing the multiple arrival wavepackets which are denoted as different orders. The helical wave signal model is presented and the constant group velocity point is illustrated. The probabilistic reconstruction algorithm is combined with the separation and fusion of different helical routes. To verify the proposed scheme, finite element simulations and corresponding experiments are conducted. The cases of single-defect simulation and two-defect simulation indicate the successful and robust implementation of the imaging algorithm. The test on actual pipe damage is also investigated to show its capability in imaging an irregular defect. The comparison with imaging results from only first arrival demonstrates the advantage of multihelical wave imaging, including the better imaging resolution and higher localization accuracy
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