ABSTRACT:Spatio-temporal relations among movement events extracted from temporally varying trajectory data can provide useful information about the evolution of individual or collective movers, as well as their interactions with their spatial and temporal contexts. However, the pure statistical tools commonly used by analysts pose many difficulties, due to the large number of attributes embedded in multiscale and multi-semantic trajectory data. The need for models that operate at multiple scales to search for relations at different locations within time and space, as well as intuitively interpret what these relations mean, also presents challenges. Since analysts do not know where or when these relevant spatio-temporal relations might emerge, these models must compute statistical summaries of multiple attributes at different granularities. In this paper, we propose a multi-view approach to visualize the spatio-temporal relations among movement events. We describe a method for visualizing movement events and spatio-temporal relations that uses multiple displays. A visual interface is presented, and the user can interactively select or filter spatial and temporal extents to guide the knowledge discovery process. We also demonstrate how this approach can help analysts to derive and explain the spatiotemporal relations of movement events from taxi trajectory data.
Self-lubricating spherical plain bearings are widely used in some important mechanical moving parts. When used in the marine environment, bearing components may be sometimes immersed by seawater. The salinity changes with evaporation or addition of water. This paper discusses the effects of salinity on the friction properties of PTFE/Kevlar fabric composites. Four different salinities seawater were formulated. The friction test was carried out on MMU-5G friction and wear testing machine under seawater. The worn surface morphology was observed by Confocal Laser Scanning Microscopy (CLSM). The result shows that the salinity of seawater has an obvious influence on the friction and wear performance of PTFE/Kevlar fabric composites. The steady-state friction coefficient decreases with the salinity increasing under load 20 MPa, velocity 0.2 m/s. The wear rates increase with the slide velocity increasing. The suitable salinities range for PTFE/Kevlar fabric composites used in seawater is 3%~5%. The mechanoelectrochemical interactions and abrasive wear play an important role in the wear of PTFE/Kevlar fabric composites.
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