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This paper exposes the existing problems for optimal industrial preventive maintenance intervals when decisions are made with right-censored data obtained from a network of sensors or other sources. A methodology based on the use of the z transform and a semi-Markovian approach is presented to solve these problems and obtain a much more consistent mathematical solution. This methodology is applied to a real case study of the maintenance of large marine engines of vessels dedicated to coastal surveillance in Spain to illustrate its usefulness. It is shown that the use of right-censored failure data significantly decreases the value of the optimal preventive interval calculated by the model. In addition, that optimal preventive interval increases as we consider older failure data. In sum, applying the proposed methodology, the maintenance manager can modify the preventive maintenance interval, obtaining a noticeable economic improvement. The results obtained are relevant, regardless of the number of data considered, provided that data are available with a duration of at least 75% of the value of the preventive interval. [ABSTRACT FROM AUTHOR]

Are food price elasticities different across city sizes? The aim of this article is to estimate expenditure and own-price elasticities for 10 aggregated food product groups using the Spanish Household Budget Survey for the year 2010. These products are the ones for which the survey provides information regarding prices and quantities, thus allowing the application of an Almost Ideal Demand System (AIDS) model with censored data. The estimation procedure allows not only  comparisons to be made among households with different levels of income, but also the contribution of residence characteristics to variations in demand. The results confirm that the size of the city in which the household resides has a similar significant and relevant effect on consumption patterns as family income level. This is especially clear with own-price elasticities. In Spain, large central cities show a greater response to price changes than smaller cities or rural peripheral areas. [ABSTRACT FROM PUBLISHER]