Abstract:The paper presents a method for processing acoustic signals which allows the extraction, from a very noisy signal, of components which contain diagnostically useful information on the increased valve clearance of a combustion engine. This method used two-stage denoising of the acoustic signal performed by means of a discrete wavelet transform. Afterwards, based on the signal cleaned-up in this manner, its entropy was calculated as a quantitative measure of qualitative changes caused by the excessive clearance. The testing and processing of the actual acoustic signal of a combustion engine enabled clear extraction of components which contain information on the valve clearance being diagnosed.

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Abstract. The description attempt of the system person-vehicleenvironment as an element of the system person-technical objectenvironment has been made. In the system analysis the reliability of the machine exploiter -a car driver has been taken into account. It has been pointed out that technical system operators (in this case -the drivers) have to be considered important in the structure of reliability of these systems. The operational and biological reliability characteristic of a human beingtechnical system operator has been carried out. The necessity for conducting different psychological tests for assessment of the quality of the human being -operator of each technical system -has been indicated.

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The purpose of this paper was to present a reliability comparison of two types of city transport buses. Case study on the example of the well-known brands of city buses: Solaris Urbino 12 and Mercedes-Benz 628 Conecto L used at Municipal Transport Company in Lublin was presented in details. A reliability index for the most failure parts and complex systems for the period of time failures was determined. The analysis covered damages of the following systems: engine, electrical system, pneumatic system, brake system, driving system, central heating and air-conditioning and doors. Reliability was analyzed based on Weibull model. It has been demonstrated, that during the operation significant reliability differences occur between the buses produced nowadays.