Communicating Properties Using Salience-Induced Comparisons

A method for generating simple comparison sentences of the form A is like B is proposed. The postulated input to the generator consists of the name of an entity A, and a set of descriptors about A in the form of attribute:value pairs. The main source of knowledge that controls decision making is a probabilistic conception of salience of empirically observable properties among concrete objects. W e also use a salience heuristic based on the notion of property intrinsicness. The information-theoretic concept of redundancy is used to quantify salience in probabilistic contexts. Salience factors influencing selection decisions are modeled as utilities and costs, and the decision for selecting the best object of comparison is based on the maximization of net expected utility. The method proposed has been implemented in a generation system written in CProlog

Skipping unnecessary structural airframe maintenance using an on-board structural health monitoring system

International audienceStructural airframe maintenance is a subset of scheduled maintenance, and is performed at regular intervals to detect and repair cracks that would otherwise affect the safety of the airplane. It has been observed that only a fraction of airplanes undergo structural airframe maintenance at earlier scheduled maintenance times. But, intrusive inspection of all panels on the airplanes needs to be performed at the time of scheduled maintenance to ascertain the presence/absence of large cracks critical to the safety of the airplane. Recently, structural health monitoring techniques have been developed. They use on-board sensors and actuators to assess the current damage status of the airplane, and can be used as a tool to skip the structural airframe maintenance whenever deemed unnecessary. Two maintenance philosophies, scheduled structural health monitoring and condition-based maintenance skip, have been developed in this article to skip unnecessary structural airframe maintenances using the on-board structural health monitoring system. A cost model is developed to quantify the savings of these maintenance philosophies over scheduled maintenance

Aircraft Maintenance: Structural Health Monitoring Influence on Costs and Practices

The structural health monitoring (SHM) represents an evolution of the traditional way to design and maintain mechanical structures. SHM systems allow to continuously (or discretely) monitor the structural integrity of an asset, not waiting for the planned check. This result implies an important reduction of inspection time and guarantees an improvement of service life cost of the structural components, but how and how much this cost can be influenced is still an open issue. This research addresses the identification of previous studies that dealt with this topic. A systematic literature review (SLR) is carried out with the aim of investigating the current SHM state-of-the art in the aircraft industry in order to point out the main advantages deriving from the application of these technologies and the existing gaps and limitations. Three database (Scopus, Web of science and Google Scholar) are used for selecting peer-reviewed papers that address with evidence the changes in maintenance practices resulting from the use of SHM. The analysis proves the differences between the traditional programmed maintenance and the innovative predictive approach based on SHM information in terms of interval inspection policy and costs. Moreover, the technical limits that do not allow to totally exploit the potential strength of SHM are outlined