Analysis and computation of (n,N): Strategies for maintenance of a two-component system

Computer Science;produktieleer/ produktieplanning

Optimal maintenance of multi-component systems: a review

In this article we give an overview of the literature on multi-component maintenance optimization. We focus on work appearing since the 1991 survey "A survey of maintenance models for multi-unit systems" by Cho and Parlar. This paper builds forth on the review article by Dekker et al. (1996), which focusses on economic dependence, and the survey of maintenance policies by Wang (2002), in which some group maintenance and some opportunistic maintenance policies are considered. Our classification scheme is primarily based on the dependence between components (stochastic, structural or economic). Next, we also classify the papers on the basis of the planning aspect (short-term vs long-term), the grouping of maintenance activities (either grouping preventive or corrective maintenance, or opportunistic grouping) and the optimization approach used (heuristic, policy classes or exact algorithms). Finally, we pay attention to the applications of the models.literature review;economic dependence;failure interaction;maintenance policies;grouping maintenance;multi-component systems;opportunistic maintenance;maintencance optimization;structural dependence

Maintenance optimization of a production system with buffercapacity

Marketing;Optimization;produktieleer/ produktieplanning

Life is short. The impact of power states on base station lifetime

We study the impact of power state transitions on the lifetime of base stations (BSs) in mobile networks. In particular, we propose a model to estimate the lifetime decrease/increase as a consequence of the application of power state changes. The model takes into account both hardware (HW) parameters, which depend on the materials used to build the device, and power state parameters, that instead depend on how and when power state transitions take place. More in depth, we consider the impact of different power states when a BS is active, and one sleep mode state when a BS is powered off. When a BS reduces the power consumption, its lifetime tends to increase. However, when a BS changes the power state, its lifetime tends to be decreased. Thus, there is a tradeoff between these two effects. Our results, obtained over universal mobile telecommunication system (UMTS) and long term evolution (LTE) case studies, indicate the need of a careful management of the power state transitions in order to not deteriorate the BS lifetime, and consequently to not increase the associated reparation/replacement costs

The Introduction of a Private Wealth Module in CAPP_DYN: an Overview

Household saving rate in Italy declined over the last two decades.This trend still persists despite three pension reforms have been enacted since the beginning of the nineties. In this paper we search further evidence of general macroeconomic effects through the analysis of households behaviour. In the first part of the paper we use data from five surveys of the Bank of Italy Surveys of Household Income and Wealth (SHIW) to estimate the lifetime profiles of saving and wealth accumulation. Estimates show that the age profile of the propensity to save has been influenced more by cohort effects than by general trend effects; whereas the age profile of the ratios of financial assets to disposable income has been subject to relevant trend effects. In the second part of the paper we analyse the effects of pension reforms on saving behaviour of Italian Households. Firstly we use a difference-in-difference estimator in order to test whether the groups more severely hit by the reforms actually increased their saving rate relative to the other groups. Then we estimate the Social Security Net Wealth (SSWN) for each individual in the SHIW in the analysed period (1989-2000). Finally we estimate the substitution coefficient between SSWN and private wealth taking into account that the reaction of saving to a change in SSWN depends also on age of the individual. Our results show that the reduction of SSWN is unequally distributed across individuals. The cut is stronger for self employed, young workers and women. Most of the groups more severely hit by the reforms did not increase their saving rate relative to the control group: younger households, in particular, did not increase the saving rate. On the whole a reduction of one Euro in SSWN seems to induce, on the average, a compensating increase in private wealth by about fifty cents. The substitution coefficient between private and social security wealth is higher for the richest and oldest part of the sample. Finally when we split the sample observations by year we find that the more dramatised is the impact of the reform, the higher is the substitution coefficient.Pension reform; household saving; social security wealth; difference-in-difference