While detecting link breaks is crucial in AODV, the manner of dealing with link breaks is equally important in mobile networks. Basically, AODV introduces two approaches in dealing with link breakage. In the first approach, when link breakage is detected, the affected node will send a Route Error (RERR) message downwards to the source node. Upon receiving the RERR message, the source node will initiate a new route discovery process. This approach is referred to as source repair; as the name suggests, a source node will initiate a route repair and discovery process.
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The second approach involves searching from the affected node itself. The affected node can set off an upstream search for the alternative route, rather than sending an RERR message back to the source. This process is called local route repairs. The affected node will initiate the discovery of a route process to the targeted node, via the RREQ message broadcast. During this process, the affected node will buffer all data projected for the destination, within the discovery period. The affected node will hold on, within the discovery period, for the route replies (RREP) message from the destination itself or any other node that has a route to the destination. Once the affected node received the RREP message, the local repair process could be considered successful, and the communication can be resumed. In AODV, the extent of the RREQ message on local repair is limited by the Time To Leave (TTL) setting. In the case of failed local repair, where no RREP message is received, the affected node will slip back to the source node for source-initiated repairs.
The objective of this survey is to compare these two pedestrian crossing configurations in terms of driver behavior at the approach to the conflict point with a pedestrian that crosses the road. The starting point of the observation is set at 70 meters from the pedestrian crossings (Figure 2). It is worth noting that, in the first configuration (as Figure 2(a)), a second pedestrian crossing is placed into the observation section. For sake of comparability, the data surveys have been considered valid only when this second pedestrian crossing was clear.
Furthermore, the analysis of yielding behavior with respect to the vehicle dynamics constraints has highlighted that drivers in approaching to the red and white zebra crossing have experienced more opportunities to yield in terms of kinematic vehicle condition.
The Feature Paper can be either an original research article, a substantial novel research study that often involvesseveral techniques or approaches, or a comprehensive review paper with concise and precise updates on the latestprogress in the field that systematically reviews the most exciting advances in scientific literature. This type ofpaper provides an outlook on future directions of research or possible applications.
Abstract:Satellite data offer the opportunity for monitoring the temporal flooding dynamics of seasonal wetlands, a parameter that is essential for the ecosystem services these areas provide. This study introduces an unsupervised approach to estimate the extent of flooded areas in a satellite image relying on the physics of light interaction with water, vegetation and their combination. The approach detects automatically thresholds on the Short-Wave Infrared (SWIR) band and on a Modified-Normalized Difference Vegetation Index (MNDVI), derived from radiometrically-corrected Sentinel-2 data. Then, it combines them in a meaningful way based on a knowledge base coming out of an iterative trial and error process. Classes of interest concern water and non-water areas. The water class is comprised of the open-water and water-vegetation subclasses. In parallel, a supervised approach is implemented mainly for performance comparison reasons. The latter approach performs a random forest classification on a set of bands and indices extracted from Sentinel-2 data. The approaches are able to discriminate the water class in different types of wetlands (marshland, rice-paddies and temporary ponds) existing in the Doñana Biosphere Reserve study area, located in southwest Spain. Both unsupervised and supervised approaches are examined against validation data derived from Landsat satellite inundation time series maps, generated by the local administration and offered as an online service since 1983. Accuracy assessment metrics show that both approaches have similarly high classification performance (e.g., the combined kappa coefficient of the unsupervised and the supervised approach is 0.8827 and 0.9477, and the combined overall accuracy is 97.71% and 98.95, respectively). The unsupervised approach can be used by non-trained personnel with a potential for transferability to sites of, at least, similar characteristics.Keywords: inundation mapping; automatic thresholding; Sentinel-2; marshland; rice-paddies; temporary ponds 2ff7e9595c
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