Analysis of vibration time histories in the time domain for propulsion systems of selected engineering objects

This paper presents the results of research carried out on the basis of vibration analysis for propulsion systems of ships used on the same basin. Six propulsion systems, identical in terms of mechanics, placed on three seagoing vessels, have been analyzed. The considered files have been divided into catalogues, separately for each measurement point, each direction, each rotational speed, and separately for usable and unusable shaft lines. Thus, it was possible to obtain vibration time histories of particular shaft lines for every combination point/direction/rotational speed. The mean value and standard deviation have been calculated separately for usable and unusable shaft lines and for each combination and each calculated characteristic. Next, a characteristic of time histories were calculated in the time domain: integral, mean value, energy, mean power (rms squared), simple moment of I order, simple moment of II order, central moment of I order, central moment of II order, normalized simple moment of I order, normalized simple moment of II order, normalized central moment of I order, normalized central moment of II order, an abscissa of the signal square gravity center, variance of the signal square, the signal equivalent diameter. It has been established that the characteristic is of concentrated type for standard deviation lower than 15 % of the mean value. On this basis the abscissa of the signal square gravity center, variance of the signal square and the value of normalized correlation function have been determined. A module and the sum of standard deviations have been calculated from the difference of mean values for usable and unusable objects have been calculated for each combination and characteristic. Basing on this it has been determined whether a given characteristic is reliable, that is, whether the module from the difference in mean values is higher than the sum of standard deviations

Rotating systems misalignment identification using fuzzy clustering method

In the phase of operation, a technical system accomplishes goals which were the reason of the system designing and creation. The execution of operation tasks by the system causes changes in the system state. The changes in the dynamic state of rotating systems can be early identified by means of vibrations measurement. Therefore, the operational tests were performed in order to register time histories of vibrations. Next, characteristics of the collected vibration signals were recorded and the most significant of them were taken as an input for further studies. The studies were performed to formulate a method of identifying the rotating systems misalignment with high reliability. The method consists in fuzzy clustering implementation. According to the method the input signals were used to formulate the fuzzy clusters of the ability and inability states of the system. Thanks to the method, it is possible to identify the operation position of the system on base of the vibration signals analysis. In the paper the proposed method was described. The results of the method application for a gas turbine engine as an example of a rotating system are also presented. It should be emphasized that the reliability of the described operation state identification is higher than other methods implemented by the authors previously

Environmental and socio-economic determinants of infant mortality in Poland : an ecological study

BACKGROUND: Health status of infants is related to the general state of health of women of child-bearing age; however, women's occupational environment and socio-economic conditions also seem to play an important role. The aim of the present ecological study was to assess the relationship between occupational environment, industrial pollution, socio-economic status and infant mortality in Poland. METHODS: Data on infant mortality and environmental and socio-economic characteristics for the 66 sub-regions of Poland for the years 2005–2011 were used in the analysis. Factor analysis was used to extract the most important factors explaining total variance among the 23 studied exposures. Generalized Estimating Equations model was used to evaluate the link between infant mortality and the studied extracted factors. RESULTS: Marked variation for infant mortality and the characteristics of industrialization was observed among the 66 sub-regions of Poland. Four extracted factors: “poor working environment”, “urbanization and employment in the service sector”, “industrial pollution”, “economic wealth” accounted for 77.3 % of cumulative variance between the studied exposures. In the multivariate regression analysis, an increase in factor “poor working environment” of 1 SD was related to an increase in infant mortality of 40 (95 % CI: 28–53) per 100,000 live births. Additionally, an increase in factor “industrial pollution” of 1 SD was associated with an increase in infant mortality of 16 (95 % CI: 2–30) per 100,000 live births. The factors “urbanization and employment in the service sector” and “economic wealth” were not significantly related to infant mortality. CONCLUSION: The study findings suggested that, at the population level, infant mortality was associated with an industrial environment. Strategies to improve working conditions and reduce industrial pollution might contribute to a reduction in infant mortality in Poland. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12940-015-0048-1) contains supplementary material, which is available to authorized users