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Viliam Makis

Bio: Viliam Makis is an academic researcher from University of Toronto. The author has contributed to research in topics: Condition monitoring & Average cost. The author has an hindex of 36, co-authored 125 publications receiving 3796 citations.


Papers
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Journal ArticleDOI
01 Feb 1992-Infor
TL;DR: The form of the optimal replacement policy is found and an algorithm based on a recursive computational procedure is presented which can be used to obtain the optimal policy and the optimal expected average cost.
Abstract: In this paper, we examine a replacement problem for a system subject to stochastic deterioration. Upon failure the system must be replaced by a new one and a failure cost is incurred. If the systemis replaced before failure a smaller cost is incurred. The failure of the system depends both on its age and also on values of a diagnostic stochastic process observable at discrete points of time. Cox’s proportional hazards model is used to describe the failure rate of the system. We consider the problem of specifying a replacement rule which minimizes the long-run expected average cost per unit time. The form of the optimal replacement policy is found and an algorithm based on a recursive computational procedure is presented which can be used to obtain the optimal policy and the optimal expected average cost.

199 citations

Journal ArticleDOI
01 Feb 2001-Infor
TL;DR: The analysis of a preventive replacement policy of the control-limit type for a deteriorating system subject to inspections at discrete points of time is presented, using Cox’s PHM with a Weibull baseline hazard function and time dependent stochastic covariates.
Abstract: The focus of the paper is the optimization of condition-based maintenance decisions within the contexts of physical asset management. In particular, the analysis of a preventive replacement policy of the control-limit type for a deteriorating system subject to inspections at discrete points of time is presented. Cox’s PHM with a Weibull baseline hazard function and time dependent stochastic covariates is used to describe the failure rate of the system. The methods of estimating model parameters and the calculation of the optimal policy are given. The structure of the decision-making software EXAKT is presented. Experience with collecting, preprocessing and using real oil and vibration data is reported.

195 citations

Journal ArticleDOI
TL;DR: The Weibull proportional-hazards model is used to determine the optimal replacement policy for a critical item which is subject to vibration monitoring, and the policy is validated using data that arose from subsequent operation of the plant.
Abstract: This paper describes a case study in which the Weibull proportional-hazards model is used to determine the optimal replacement policy for a critical item which is subject to vibration monitoring. Such an approach has been used to date in the context of monitoring through oil debris analysis, and this approach is extended in this paper to the vibration monitoring context. The Weibull proportional-hazards model is reviewed along with the software EXAKT used for optimization. In particular the case considers condition-based maintenance for circulating pumps in a coal wash plant that is part of the SASOL petrochemical company. The condition-based maintenance policy recommended in this study is based on histories collected over a period of 2 years, and is compared with current practice. The policy is validated using data that arose from subsequent operation of the plant.

157 citations

Journal ArticleDOI
TL;DR: In this article, a fault growth parameter based on the amplitude of wavelet transform is proposed to evaluate gear fault advancement quantitatively, and the effectiveness of the proposed fault indicator is demonstrated using a full lifetime vibration data history obtained under sinusoidal varying load.

132 citations

Journal ArticleDOI
TL;DR: In this article, the condition classification is based on hidden Markov models (HMMs) processing information obtained from vibration signals, and the machinery condition is identified by selecting the HMM which maximises the probability of a given observation sequence.

130 citations


Cited by
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Journal ArticleDOI

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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Christopher M. Bishop1
01 Jan 2006
TL;DR: Probability distributions of linear models for regression and classification are given in this article, along with a discussion of combining models and combining models in the context of machine learning and classification.
Abstract: Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

10,141 citations

Journal ArticleDOI
TL;DR: This paper attempts to summarise and review the recent research and developments in diagnostics and prognostics of mechanical systems implementing CBM with emphasis on models, algorithms and technologies for data processing and maintenance decision-making.

3,848 citations

Journal ArticleDOI
TL;DR: This paper systematically reviews the recent modeling developments for estimating the RUL and focuses on statistical data driven approaches which rely only on available past observed data and statistical models.

1,667 citations

Journal ArticleDOI
Hongzhou Wang1
TL;DR: This survey summarizes, classifies, and compares various existing maintenance policies for both single-unit and multi-unit systems, with emphasis on single- unit systems.

1,507 citations