156 research outputs found
Surveying Position Based Routing Protocols for Wireless Sensor and Ad-hoc Networks
A focus of the scientific community is to design network oriented position-based routing protocols and this has resulted in a very high number of algorithms, different in approach and performance and each suited only to particular applications. However, though numerous, very few position-based algorithms have actually been adopted for commercial purposes. This article is a survey of almost 50 position-based routing protocols and it comes as an aid in the implementation of this type of routing in various applications which may need to consider the advantages and pitfalls of position-based routing. An emphasis is made on geographic routing, whose notion is clarified as a more restrictive and more efficient type of position-based routing. The protocols are therefore divided into geographic and non-geographic routing protocols and each is characterized according to a number of network design issues and presented in a comparative manner from multiple points of view. The main requirements of current general applications are also studied and, depending on these, the survey proposes a number of protocols for use in particular application areas. This aims to help both researchers and potential users assess and choose the protocol best suited to their interest
The general message ferry route (MFR∗) problem and the An-Improved-Route (AIR) scheme
In existing studies of message ferry (MF) schemes in wireless ad hoc networks, routes for message ferries are often adopted from the solutions of the Traveling Salesman Problem (TSP) and its variants. In such existing solutions, a message ferry route is often assumed to be a simple cycle which has no repeated vertices nor edges. In this paper, we consider a more general case, where the route is a closed walk. In doing so, we generalize the massage ferry route (MFR) problem as the MFR∗ problem, and propose the An-Improved-Route (AIR) scheme to construct routes for the ferry. Simulation proves that the AIR scheme effectively reduces the delay of the MF schemes. Moreover, our studies and schemes in this paper can easily be extended to operation research problems in other related fields, such as transportation and traffic coordination etc
The wrong Wright stuff : mapping human error in aviation
The Aviation Safety Reporting System (ASRS) was instituted to aid the Federal Aviation Administration in tracking trends in aviation incidents so that, ultimately, safety measures and training could be implemented to decrease the occurrence of accidents and incidents within the industry. The current system relies on hand coding of reports to recognize current trends and alert the proper parties. Although the filing party may enter some codified data describing the surrounding scenario (e.g., time of day, weather), there is no opportunity to specify a category if the problem is human error. Considering the prevalence of human error within these incidents (around 55% based on a report by Boeing, 2006), a greater understanding of the driving factors is needed. The current study was an investigation of the human error components of airline incident reports. Text analysis tools were applied to ASRS incident narrative reports to determine a classification based on human performance for commercial and general aviation. The results from the current study demonstrate that an empirically based approach can be used to uncover latent categories within the Flight Crew Human Performance\u27 classified reports. The combined approach of latent semantic analysis, k-means clustering, and keyword analysis were used successfully in developing a nine element classification of commercial aviation reports and twelve element classification of general aviation reports. The taxonomies suggested by the current study for both commercial and general aviation reveal categories beyond just human error elements. The classification scheme suggested for the commercial aviation reports most closely resembled the ACCERS taxonomy developed by Krokos and Baker (2005; see also Baker & Krokos, 2007), which was constructed to help in categorizing all incident reports. The classification suggested for general aviation reports did not closely resemble any existing classification scheme. Although the suggested taxonomy shared categories such as situational awareness and communication with classifications such as crew resource management (CRM) or single pilot resource management (SRM), the current classification also holds non-human elements such as weather and context. The taxonomies for both commercial and general aviation revealed a category for context, and the difficulty of flying into certain airports was apparent. These findings can be implemented to improve training programs by assisting in the creation of contextually based training scenarios. Furthermore, based on findings for general aviation in particular, pilots could benefit from increased training in situational awareness and monitoring of notices and airspace
Portland Daily Press: December 27,1880
https://digitalmaine.com/pdp_1880/1350/thumbnail.jp
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