Wyniki wyszukiwania - BazTech

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A method for obtaining the preventive maintenance interval in the absence of failure time data

Sánchez-Herguedas Antonio, Mena-Nieto Ángel, Rodrigo-Muñoz Francisco

Eksploatacja i Niezawodność

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2022

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Vol. 24, no. 3

564--573

EN

One of the ways to reduce greenhouse gas emissions and other polluting gases caused by ships is to improve their maintenance operations through their life cycle. The maintenance manager usually does not modify the preventive intervals that the equipment manufacturer has designed to reduce the failure. Conditions of use and maintenance often change from design conditions. In these cases, continuing using the manufacturer's preventive intervals can lead to non-optimal management situations. This article proposes a new method to calculate the preventive interval when the hours of failure of the assets are unavailable. Two scenarios were created to test the effectiveness and usefulness of this new method, one without the failure hours and the other with the failure hours corresponding to a bypass valve installed in the engine of a maritime transport surveillance vessel. In an easy and fast way, the proposed method allows the maintenance manager to calculate the preventive interval of equipment that does not have installed an instrument for measuring operating hours installed.

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The Role of Climatic Variables for Estimating Probability of Abundance of Tree Species

Antúnez P., Wehenkel C., López-Sánchez C. A., Hernández-Díaz J. C.

Polish Journal of Ecology

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2017

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Vol. 65, nr 3

324--338

EN

We analyzed the influence of climatic variables on the abundance of native tree species in 1,490 sampling plots systematically distributed in the Sierra Madre Occidental (state of Durango, Northwestern Mexico, 26°50′ and 22°17′N and 107°09′ and 102°30′W). We used the Weibull distribution and the finite Gaussian mixture model to study the climatic limits of 15 tree species in relation to seven variables thought to affect species abundance. We found that although they may occur in the same geographical region, some species display a wider range of ecological tolerance than others. Of the 15 species under study, only two (Quercus magnoliifolia and Q. arizonica) can be considered generalists in relation to some climatic variables, while the other 13 species behaved as specialists, implying a narrower range of distribution. The analytical techniques used enabled us to demarcate the zones in which the probability of abundance of each species is highest in relation to the climate variables considered. The findings could be used to help define climate for the 15 studied tree species of economic and ecological interest.

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The technical object reliability evaluation based on the parametric and momentary failures

Lindstedt P., Manerowski J., Borowczyk H.

Journal of KONES

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2016

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Vol. 23, No. 2

239--246

EN

The presented paper concerns with the technical object reliability evaluation based on the parametric and momentary failures during the process of object operating. The real world data observation shows that in the case of high quality technical objects the catastrophic failure events are too rare to the credible evaluation of the object’s reliability. For that reason, the parametric and momentary failures are in the centre of attention in this paper. The set of analysed failures was obtained with the classifiers of the field data provided by the monitoring system (the failure alarms) and the diagnostic system (the functional and technical condition parameters deviation). The changes of the functioning condition potential are used to determine the symptoms of momentary failures and the changes in the potential of the technical condition to determine the symptoms of parametric failures (non-total). The assumed reliability characteristics model has the form R(t) = f(_, Rb(t), Rc(t)), (where: Rb(t) and Rc(t) – the estimators of reliability for parametric and momentary failures, symbol ‘_’ denotes catastrophic failures not covered). For the identification of R (t) as an analytical function, the estimators are computed with the field data. The Weibull distribution function due to its flexibility is often used. Such is the case in this paper. Two parameters a and b known as the scale and the shape parameters are estimated with the computerized procedure realizing least-square method. The presented examples show good fit quality even for small set of data.