scholarly journals Imperfect maintenance in a generalized competing risks framework

2006 ◽  
Vol 43 (03) ◽  
pp. 825-839 ◽  
Author(s):  
Laurent Doyen ◽  
Olivier Gaudoin
Keyword(s):  
Competing Risks ◽  
Preventive Maintenance ◽  
General Framework ◽  
Imperfect Maintenance ◽  
Repairable Systems ◽  
New Class ◽  
Virtual Age ◽  
System A ◽  
Age Model ◽  
The One

In this paper we present a general framework for the modelling of the process of corrective and condition-based preventive maintenance actions for complex repairable systems. A new class of models is proposed, the generalized virtual age models. On the one hand, these models generalize Kijima's virtual age models to the case where both preventive and corrective maintenances are present. On the other hand, they generalize the usual competing risks models to imperfect maintenance actions which do not renew the system. A generalized virtual age model is defined by both a sequence of effective ages which characterizes the effects of both types of maintenance according to a classical virtual age model, and a usual competing risks model which characterizes the dependency between the two types of maintenance. Several particular cases of the general model are derived.

scholarly journals Imperfect maintenance in a generalized competing risks framework

2006 ◽  
Vol 43 (3) ◽  
pp. 825-839 ◽  
Author(s):  
Laurent Doyen ◽  
Olivier Gaudoin
Keyword(s):  
Competing Risks ◽  
Preventive Maintenance ◽  
General Framework ◽  
Imperfect Maintenance ◽  
Repairable Systems ◽  
New Class ◽  
Virtual Age ◽  
System A ◽  
Age Model ◽  
The One

In this paper we present a general framework for the modelling of the process of corrective and condition-based preventive maintenance actions for complex repairable systems. A new class of models is proposed, the generalized virtual age models. On the one hand, these models generalize Kijima's virtual age models to the case where both preventive and corrective maintenances are present. On the other hand, they generalize the usual competing risks models to imperfect maintenance actions which do not renew the system. A generalized virtual age model is defined by both a sequence of effective ages which characterizes the effects of both types of maintenance according to a classical virtual age model, and a usual competing risks model which characterizes the dependency between the two types of maintenance. Several particular cases of the general model are derived.

Some results for repairable systems with general repair

1989 ◽  
Vol 26 (1) ◽  
pp. 89-102 ◽  
Author(s):  
Masaaki Kijima
Keyword(s):  
Failure Time ◽  
Survival Function ◽  
Repairable Systems ◽  
Minimal Repair ◽  
Virtual Age ◽  
System A ◽  
A Value ◽  
Extremal Values ◽  
Repair Models ◽  
Age Process

In this paper, we develop general repair models for a repairable system by using the idea of the virtual age process of the system. If the system has the virtual age Vn –1 = y immediately after the (n – l)th repair, the nth failure-time Xn is assumed to have the survival function where is the survival function of the failure-time of a new system. A general repair is represented as a sequence of random variables An taking a value between 0 and 1, where An denotes the degree of the nth repair. For the extremal values 0 and 1, An = 1 means a minimal repair and An= 0 a perfect repair. Two models are constructed depending on how the repair affects the virtual age process: Vn = Vn– 1+ AnXn as Model 1 and Vn = An(Vn– 1 + Xn) as Model II. Various monotonicity properties of the process with respect to stochastic orderings of general repairs are obtained. Using a result, an upper bound for E[Sn] when a general repair is used is derived.

Repairable systems availability optimization under imperfect maintenance

2009 ◽  
Vol 57 (3) ◽  
pp. 249-256 ◽  
Author(s):  
S. Samet ◽  
A. Chelbi ◽  
F. Hmida
Keyword(s):  
Preventive Maintenance ◽  
Imperfect Maintenance ◽  
Repairable Systems ◽  
Renewal Function ◽  
Corrective Maintenance ◽  
Unit System ◽  
Periodic Preventive Maintenance ◽  
The Times ◽  
Imperfect Repairs ◽  
Random Failures

Repairable systems availability optimization under imperfect maintenanceThis paper deals with the modeling of a preventive maintenance strategy applied to a single-unit system subject to random failures. According to this policy, the system is subjected to imperfect periodic preventive maintenance restoring it to ‘as good as new’ with probability p and leaving it at state ‘as bad as old’ with probability q. Imperfect repairs are performed following failures occurring between consecutive preventive maintenance actions, i.e the times between failures follow a decreasing quasi-renewal process with parametera. Considering the average durations of the preventive and corrective maintenance actions as well as their respective efficiency extents, a mathematical model is developed in order to study the evolution of the system stationary availability and determine the optimal PM period which maximizes it. The modeling of the imperfection of the corrective maintenance actions requires the knowledge of the quasi-renewal function. A new expression approximating this function is proposed for systems whose times to first failure follow a Gamma distribution. Numerical results are obtained and discussed.

Some results for repairable systems with general repair

1989 ◽  
Vol 26 (01) ◽  
pp. 89-102 ◽  
Author(s):  
Masaaki Kijima
Keyword(s):  
Failure Time ◽  
Survival Function ◽  
Repairable Systems ◽  
Minimal Repair ◽  
Virtual Age ◽  
System A ◽  
A Value ◽  
Extremal Values ◽  
Repair Models ◽  
Age Process

In this paper, we develop general repair models for a repairable system by using the idea of the virtual age process of the system. If the system has the virtual age Vn – 1 = y immediately after the (n – l)th repair, the nth failure-time Xn is assumed to have the survival function where is the survival function of the failure-time of a new system. A general repair is represented as a sequence of random variables An taking a value between 0 and 1, where An denotes the degree of the nth repair. For the extremal values 0 and 1, An = 1 means a minimal repair and An= 0 a perfect repair. Two models are constructed depending on how the repair affects the virtual age process: Vn = Vn – 1 + AnXn as Model 1 and Vn = An (Vn – 1 + Xn ) as Model II. Various monotonicity properties of the process with respect to stochastic orderings of general repairs are obtained. Using a result, an upper bound for E[Sn ] when a general repair is used is derived.

Purification of a Specific Placental Plasminogen Activator Inhibitor by Monoclonal Antibody and Its Complex Formation with Plasminogen Activator

1985 ◽  
Vol 53 (01) ◽  
pp. 122-125 ◽  
Author(s):  
B Åstedt ◽  
Ingegerd Lecander ◽  
T Brodin ◽  
A Lundblad ◽  
Karin Löw
Keyword(s):  
Monoclonal Antibody ◽  
Complex Formation ◽  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
System A ◽  
The One ◽  
Fast Acting ◽  
Chain Form ◽  
Activator Inhibitor

SummaryA monoclonal antibody of IgG2a-type was obtained against a specific fast acting plasminogen activator inhibitor found in placenta. The placental inhibitor was purified by affinity chromatography using the monoclonal antibody and additionally in a FPLC-system. A strong complex formation was found between the inhibitor and urokinase and also with the two-chain form of plasminogen activator of the tissue-type. A weaker complex was found between the placental inhibitor and the one- chain form of the tissue-type activator.

New Methods for Analyzing Water Pollutants

1982 ◽  
Vol 14 (4-5) ◽  
pp. 59-71 ◽  
Author(s):  
L H Keith ◽  
R C Hall ◽  
R C Hanisch ◽  
R G Landolt ◽  
J E Henderson
Keyword(s):  
Amino Acids ◽  
Gas Chromatography ◽  
Two Dimensional ◽  
Gas Chromatograph ◽  
New Class ◽  
New Methods ◽  
System A ◽  
Drinking Waters ◽  
Computer Controlled ◽  
Nitrogen Containing Compounds

Two new methods have been developed to analyze for organic pollutants in water. The first, two-dimensional gas chromatography, using post detector peak recycling (PDPR), involves the use of a computer-controlled gas Chromatograph to selectively trap compounds of interest and rechromatograph them on a second column, recycling them through the same detector again. The second employs a new detector system, a thermally modulated electron capture detector (TMECD). Both methods were used to demonstrate their utility by applying them to the analysis of a new class of potentially ubiquitous anthropoaqueous pollutants in drinking waters- -haloacetonitriles. These newly identified compounds are produced from certain amino acids and other nitrogen-containing compounds reacting with chlorine during the disinfection stage of treatment.

Chinese Historiography in the Age of Maturity, 960–1368

2018 ◽  
Author(s):  
Charles Hartman
Keyword(s):  
South China ◽  
Song Dynasty ◽  
Political Power ◽  
Examination System ◽  
Economic Expansion ◽  
New Class ◽  
The Song Dynasty ◽  
The North ◽  
System A ◽  
Age Of Maturity

This chapter looks at how the Song dynasty (960–1279) reconsolidated central power and eliminated the provincial regimes that had developed in the wake of Tang decentralization. During the first thirty years after 960, they fostered astute policies that promoted and took advantage of continuing economic expansion. To administer their new polity, the Song emperors recruited through the examination system a new class of bureaucratic elite that Western writings on China often call the ‘literati’. The aristocrats of Tang had given way to the merchants and bureaucrats of Song. However, although the Song expanded Chinese economic and political power into South China, it never completed the conquest of all the traditional Chinese lands in the north. The Song coexisted with a series of alien or conquest dynasties to its north and west.

Simple Systems

2017 ◽  
Author(s):  
Jochen Rau
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
General Framework ◽  
Gibbs State ◽  
Macroscopic System ◽  
Basic Model ◽  
System A ◽  
Paramagnetic Salt ◽  
High And Low Temperatures ◽  
Simple Systems

Even though the general framework of statistical mechanics is ultimately targeted at the description of macroscopic systems, it is illustrative to apply it first to some simple systems: a harmonic oscillator, a rotor, and a spin in a magnetic field. These applications serve to illustrate how a key function associated with the Gibbs state, the so-called partition function, is calculated in practice, how the entropy function is obtained via a Legendre transformation, and how such systems behave in the limits of high and low temperatures. After discussing these simple systems, this chapter considers a first example where multiple constituents are assembled into a macroscopic system: a basic model of a paramagnetic salt. It also investigates the size of energy fluctuations and how—in the case of the paramagnet—these fluctuations scale with the number of constituents.

Sign in / Sign up

Export Citation Format

Share Document