Résumé: In this paper the queues are used as a method to improve maintenance performance. The information collected by vibration analysis is used to check the system status and see whether a maintenance operation is to be organized. Thus, for a precise decision, the improvement of accelerometer parameters is required. In order to solve this issue, the piezoresistive accelerometer step and impulse responses are enhanced by using appropriate parameters (damping rate and frequency range). Computer simulation tests were conducted to con¯rm this approach. The obtained results have shown the di®erence between the accelerometer with the proposed parameters and the accelerometer used in the experiment. It can be concluded that the proposed parameters provide stable and accurate accelerometer.

Résumé: This paper addresses the problem of bond graph methodology as a graphical approach for modeling fuel cell systems. The system consists of a Proton Exchange Membrane Fuel Cell (PEMFC) stack, an interleaved boost converter, battery pack connected via a buck converter. Simulation results illustrate the simplified system response obtained using implementation of the governing equations in MATLAB/Simulink and is compared with a bond graph implementation in the simulation program 20-sim. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights

Résumé: This paper addresses the problem of bond graph methodology as a graphical approach for modeling fuel cell systems. The system consists of a Proton Exchange Membrane Fuel Cell (PEMFC) stack, an interleaved boost converter. Simulation results illustrate the simplified system response obtained using implementation of the governing equations in MATLAB/Simulink or a bond graph implementation in the simulation program 20- sim.

Résumé: The industry world uses machines and plants that are increasingly powerful and complex. The requirements of high safety, the reduction of the exploitation costs, and the control of the equipment availability give to maintenance a dominating role. The industrialists attach a great importance to the conditional maintenance of the revolving machines that use primarily the vibrations of their rotors. The temperature measurements in the stages can bring additional information to vibrations. In conditional preventive maintenance, the diagnosis of failures of the industrial systems, if it is carried out with effectiveness, represents one of the means to gain points of productivity. It consists in observing the symptoms of a failure and then identifying the cause using a logical reasoning founded on observations, that is, to dismount a deterministic mechanism between the cause and its effect. This research presents and discusses the decision making that is practically exerted with each stage in the procedure of industrial diagnosis and tool of assistance to the decision making. The approach used is Bayesian theory to reveal a defect masked by another in the low frequency (combined defect). The turbo compressor as an object of research, vibratory analyses, and thermography are the techniques used in this work. Copyright © 2011 John Wiley & Sons, Ltd.

Résumé: Abstract Several methodologies for risk analysis have been developed to manage major industrial risks. All of these developed scientific methodologies represent the discipline of operational system safety. In the industrial activities, it is often difficult to choose and to find the best and the most appropriate methodology for a given situation which allows us to obtain the most complete and benefic results. In this article, 35 methods were identified to be studied that will allow us to choose and eventually develop the most appropriate methodology in a given situation. We found that these methods are either empirical, statistical or both at the same time and in any case they may be either qualitative or quantitative. The review of all input and output data used permits us to divide them into different classes. To understand the usefulness and role of each methodology links were developed between different classes of input data and different types of methodologies, on the one hand, and on the other hand, links between the different classes of output data and methodologies. This work shows the judicious way to choose or develop the methodology for risk analysis the most appropriate depending on the situation to be analyzed, the availability of the basic input data and the type of results needed.

Résumé: In accordance constant movement of the Earth, the fixed photovoltaic panels intercept less sunlight far than they could. Consequently, they produce much less power than the possible maximum. These panels could be directed in variable degrees for follow-up the sun and that will increase their production of the power "it is the solar pursuit", the systems of solar pursuit does not cease evolving/moving, using several types of structures and increasingly powerful orders, because the profit of power reaches values maximum. Present research is intended for the presentation and the study of the various types of solar system of pursuit by highlighting the type of order used. This present work energetically will discover the role of a tracker by tangible results