The Duane plot is a simple and widely used graphical technique in the analysis of repairable systems. The fitting of a straight line to points in that graph serves to determine the behavior of the system assuming a power law process. However, the classical least squares fitting suffer from lack of robustness and it is specially heavily affected by the more remote and perhaps least interesting points. In order to solve this drawback we propose a robust fit based on Least Median of Squares (LMS) or Least Trimmed Squares (LTS) regression estimators of [1] . This methodology has been applied in a project aimed to study the reliability, availability and maintainability of the aerial contact line of the Spanish railways.
In this article, a new methodology to determine the criticality of the components of the overhead contact line (OCL) system by means of a component criticality index is proposed. The methodology is based on classic failure mode and effects analysis (FMEA) but adapted to its application on this system, with characteristics far from industrial systems where FMEA was developed. The procedure is focused on the analysis of the system's operating history with the important advantage that the subjectivity of the usual procedures is reduced. This methodology has proved to be very useful when applied to decision-making and for establishing maintenance frequencies of the elements of the OCL of the Spanish railway network, and it could also be applied to other kind of large-scale distributed systems.
Smartphones may be seen as miniature toolboxes to perform Physics experiments. In this paper, we present three different “optics workbenches" mainly based on the light meter of a smartphone. One is aimed at the precise study of Malus law and other effects associated to linearly polarized light, the second allows quantifying the light intensity distribution of diffraction or interference patterns projected on a screen, and the third demonstrates the so-called inverse square law obeyed by the light from a point-like source. These experiments allow to quantitatively demonstrate three fundamental laws of optics using quite inexpensive equipment.