Optimal Periodic Inspection Policy for a Parallel System Subject to Continuous Bi-Levels Degradation

2021 ◽  
pp. 2150037
Author(s):  
Bachir Cherfaoui ◽  
Radouane Laggoune
Keyword(s):  
Main Idea ◽  
Parallel System ◽  
Initial State ◽  
Maintenance Costs ◽  
Periodic Inspection ◽  
Failure State ◽  
Global Cost ◽  
Intermediate States ◽  
Inspection Policy ◽  
Component Parallel

Each system goes through several intermediate states between its initial state and the failure state, which are called degradation states. In addition, knowing these intermediate states allows us the building of an effective maintenance plan for the system under consideration. In this paper, we have considered a two-component parallel system where each component is subjected to two levels of degradation. Our first objective is to identify the mathematical (probabilistic) model associated with this system and this when the hypothesis of periodic inspection of the system is retained. Then, the main idea is to build the economic model encompassing the different average costs (inspection costs, preventive maintenance costs and corrective maintenance costs) spent during a renewal cycle. The latter will allow us to determine the optimal “inspection interval” while minimizing the average global-cost spent. Finally, in order to illustrate and analyze the sensitivity of the optimal inspection policy to the various maintenance costs, numerical examples are presented.

Availability of Systems Subject to Multiple Failure Modes Under Calendar-based Inspection

2020 ◽  
pp. 2150022
Author(s):  
Himani Pant ◽  
S. B. Singh ◽  
Neelam Chantola
Keyword(s):  
Wind Turbine ◽  
Failure Mode ◽  
Functional State ◽  
Failure Modes ◽  
Failure Time ◽  
Random Time ◽  
Multiple Failure Modes ◽  
Periodic Inspection ◽  
Wind Turbine System ◽  
Inspection Policy

The availability of a maintained system subject to multiple failure modes undergoing periodic inspection is studied in this paper. Calendar-based inspection policy is being incorporated. Explicitly, a system with a functional state and [Formula: see text] failure modes is taken into account. Failure time of each failure mode is random. As the [Formula: see text]th ([Formula: see text]) failure occurs, the respective corrective repair taking a random time [Formula: see text] [Formula: see text] is carried out. Some theorems on the point availability and limiting average availability are obtained in this study. The application of the derived result is explained through an example of wind turbine system.

Nonuniqueness in a Single-Column Model for Moist Convection

2019 ◽  
Vol 77 (3) ◽  
pp. 1001-1018
Author(s):  
M. R. Turner ◽  
J. Norbury
Keyword(s):  
Climate Models ◽  
Global Maximum ◽  
Moist Convection ◽  
Initial State ◽  
Vertical Column ◽  
Cost Functional ◽  
Atmospheric Column ◽  
Global Cost ◽  
Convective Adjustment ◽  
Convection Model

Abstract We investigate a moist atmospheric column convection model by considering the atmosphere as a single vertical column of air parcels, each of which contains water vapor. The moist convective adjustment of both air and water mass in the column is considered from an (unstable) initial state to a statically stable final configuration of parcels. Two variations of an algorithm based upon swapping neighboring parcels are compared: after swapping, no parcels remain supersaturated. The results of these algorithms are compared directly with those of the adjustment algorithm of Cheng et al., which adjusts an atmospheric column to achieve the global maximum of a relevant cost functional. Two examples are considered: in the first, the algorithms adjust to similar arrangements, showing that the global maximum of the functional is the dynamically preferred state, while in the second, the algorithms adjust to significantly different states. Thus, we identify a nonuniqueness to the solution to the adjustment problem in terms of local and global cost functional maximizers. We then discuss the relevance of this nonuniqueness to numerical prediction in weather and climate models.

Availability of periodically inspected systems subject to Markovian degradation

2002 ◽  
Vol 39 (4) ◽  
pp. 700-711 ◽  
Author(s):  
Peter C. Kiessler ◽  
Georgia-Ann Klutke ◽  
Yoonjung Yang
Keyword(s):  
Markov Chain ◽  
Lifetime Distribution ◽  
Periodic Inspection ◽  
Inspection Policy

This paper studies inspected systems with non-self-announcing failures where the rate of deterioration is governed by a Markov chain. We compute the lifetime distribution and availability when the system is inspected according to a periodic inspection policy. In doing so, we expose the role of certain transient distributions of the environment.

Scheduling spares with exponential lifetimes in a two-component parallel system

1980 ◽  
Vol 17 (4) ◽  
pp. 1025-1032 ◽  
Author(s):  
Michael Pinedo
Keyword(s):  
Parallel System ◽  
Two Component ◽  
System Breakdown ◽  
Component Parallel

Consider a two-component parallel system. There is a stockpile of n spares, spare i having lifetime Xi, exponentially distributed with rate µi. The system breaks down when neither component functions. Every time a spare expires it has to be replaced, to avoid system breakdown. We investigate the policies which maximize the expected lifetime of the system using these n spares.

Cirrus Mark III.

1929 ◽  
Vol 33 (221) ◽  
pp. 386-391
Author(s):  
A. N. Caple
Keyword(s):  
Main Idea ◽  
Maintenance Costs

It may be of interest to give a resume of the Cirrus engine from the time of its conception up to the present period. The main idea actuating the designer was to produce an engine whose features would be reliability, low maintenance costs, and capacity to run for long periods with little more attention than a motorist gives to his car engine, and also so constructed that the average owner driver or motor mechanic could readily understand it and maintain it in perfect running order. The first Cirrus type engine was completed in May, 1925, and was submitted to the 100-hour Air Ministry type tests. These tests were successfully passed. The series of tests laid down by the Air Ministry Form A. P. 840 are of a most exacting nature.

Unitarity and the real world: applications of direct phasing to electron diffraction data

1995 ◽  
Vol 53 ◽  
pp. 156-157
Author(s):  
W. F. Tivol
Keyword(s):  
Electron Diffraction ◽  
Scattering Amplitude ◽  
Direct Methods ◽  
Quantitative Relationship ◽  
Electron Diffraction Data ◽  
Initial State ◽  
Final State ◽  
Intermediate States ◽  
Complete Set ◽  
Image Position

The Sayre equation can be derived as a special case of unitarity, and recently it was shown that the derivation applies to dynamical scattering and electron diffraction. Since both the triplet formula and the tangent formula can be derived from the Sayre equation, use of these direct methods to find the phases for electron diffraction amplitudes is fully justified.The most transparent form of the unitary equation iswhere  is the scattering amplitude operator, f is the final state, i the initial state, and n is a complete set of intermediate states; the sum over these states becomes an integral where the intermediate states form a continuum.If there is Friedel symmetry, the form of the Sayre equation derived from equation (1) isThe prime on the sum means K ≠ 0. If Friedel symmetry is violated, Σ' | A(K) |2 becomesThis equation is a quantitative relationship which not only has an essentially unique solution for the phases, but which also constrains the magnitudes of the intensities.

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