Roger Flage
& Terje Aven
EXPRESSING AND
COMMUNICATING UNCERTAINTY IN RELATION TO QUANTITATIVE RISK
ANALYSIS
A
quantitative risk analysis (QRA) should provide a broad,
informative and balanced picture of risk, in order to
support decisions. To achieve this, a proper treatment
of uncertainty is a prerequisite. Most approaches to
treatment of uncertainty in QRA seem to be based on the
thinking that uncertainty relates to the calculated
probabilities and expected values. This causes
difficulties when it comes to communicating what the
analysis results mean, and could easily lead to weakened
conclusions if large uncertainties are involved. An
alternative approach is to hold uncertainty, not
probability, as a main component of risk, and regard
probabilities purely as epistemic-based expressions of
uncertainty. In the paper the latter view is taken, and
we describe what should be the main components of a risk
description when following this approach. We also
indicate how this approach relates to decision-making.
An important issue addressed is how to communicate the
shortcomings and limitations of probabilities and
expected values. Sensitivity analysis plays a key role
in this regard. Examples are included to illustrate
ideas and findings.
A. Blokus-Roszkowska, K. Kołowrocki
MODELLING ENVIRONMENT
AND INFRASTRUCTURE OF SHIPYARD TRANSPORTATION SYSTEMS AND
PROCESSES
In the
paper an analytical model of port transportation systems
environment and infrastructure influence on their
operation processes is constructed and presented in an
example of shipyard rope transportation systems in Naval
Shipyard in Gdynia. A general semi-markov model of a
system operation process is proposed and the methods of
its parameters statistical identification are presented.
Further, the shipyard rope transportation system and the
ship rope elevator operation processes are analyzed and
their operation states are defined. A preliminary
collection of statistical data necessary to the ship
transportation systems’ operation processes
identification is included.
P. Baraldi, E. Zio, M. Compare
IMPORTANCE MEASURES
IN PRESENCE OF UNCERTAINTIES
This
paper presents a work on the study of importance
measures in presence of uncertainties originating from
the lack of knowledge and information on the system
(epistemic uncertainties). A criterion is proposed for
ranking the risk contributors in presence of
uncertainties described by probability density
functions.
L. Gucma, M. Schoeneich
MONTE CARLO METHOD OF
SHIP’S UNDERKEEL CLEARANCE EVALUATION FOR SAFETY OF FERRY
APPROACHING
TO YSTAD PORT DETERMINATION
The
paper is concerned with the analysis of simulation
research results of newly design Piast ferry entering to
modernized Ystad Port. The ship simulation model is
described. After execution of real time simulations the
Monte Carlo method of underkeel clearance evaluation is
applied to asses the probability of ferry touching the
bottom. The results could be used in risk assessment of
ships entering to the ports.
L. Gucma
METHODS OF
SHIP-BRIDGE COLLISION SAFETY EVALUATION
The paper presents methods and models
used nowadays for risk assessment of ship-bridge
collisions.
R. Guo, D. Guo
DEAR THEORY IN SYSTEM
DYNAMIC ANALYSIS
In this paper, we introduce our newly
created DEAR (an abbreviation of Differential Equation
Associated Regression) theory, which merges differential
equation theory, regression theory and random fuzzy
variable theory into a new rigorous small sample based
inferential theoretical foundation. We first explain the
underlying idea of DEAR modelling, its classification,
and then the M-estimation of DEAR model. Furthermore, we
explore the applicability of DEAR theory in the analysis
in system dynamics, for example, repairable system
analysis, quality dynamics analysis, stock market
analysis, and ecosystem analysis, etc.
S. Guze
RELIABILITY ANALYSIS
OF TWO-STATE SERIES-CONSECUTIVE “M OUT OF K: F” SYSTEMS
A non-stationary approach to reliability
analysis of two-state series and consecutive “m out of
k: F” systems is presented. Further, the
series-consecutive “m out of k: F” system is defined and
the recurrent formulae for its reliability function
evaluation are proposed. Moreover, the application of
the proposed formulae to reliability evaluation of the
radar system composed of two-state components is
illustrated.
B. Kwiatuszewska-Sarnecka, K. Kołowrocki, J. Soszyńska
MODELLING OF
OPERATIONAL PROCESSES OF BULK CARGO TRANSPORTATION SYSTEM
A general analytical model of industrial
systems infrastructure influence on their operation
processes is constructed. Next, as its particular case a
detailed model of port infrastructure influence on port
transportation systems operation processes is obtained
to apply and test it to selected transportation systems
used in Gdynia Port.
D. Montoro-Cazorla
SHOCK MODELS UNDER
POLICY N
We
present the life distribution of a device subject to
shocks governed by phase-type distributions. The
probability of failures after shocks follows discrete
phase-type distribution. Lifetimes between shocks are
affected by the number of cumulated shocks and they
follow continuous phase-type distributions. The device
can support a maximum of N shocks. We calculate the
distribution of the lifetime of the device and
illustrate the calculations by means of a numerical
application. Computational aspects are introduced. This
model extends other previously considered in the
literature.
Joanna Soszynska
ASYMPTOTIC APPROACH
TO RELIABILITY EVALUATION OF LARGE “M OUT OF L”-SERIES
SYSTEM
IN VARIABLE OPERATION CONDITIONS
The semi-markov model of the system
operation process is proposed and its selected
parameters are defined. There are found reliability and
risk characteristics of the multi-state “m out of
l”-series system. Next, the joint model of the semi-markov
system operation process and the considered multi-state
system reliability and risk is constructed. The
asymptotic approach to reliability and risk evaluation
of this system in its operation process is proposed as
well.
C. Tanguy
ASYMPTOTIC DEPENDENCE
OF AVERAGE FAILURE RATE AND MTTF FOR A RECURSIVE, MESHED
NETWORK ARCHITECTURE
The paper is concerned with the exact and
asymptotic calculations of the availability, average
failure rate and MTTF (Mean Time To Failure) for a
recursive, meshed architecture proposed by Beichelt and
Spross. It shows that the asymptotic size dependences of
average failure rate and MTTF are different, but not
inverse of each other, as is unfortunately assumed too
frequently. Besides, the asymptotic limit is reached for
rather small networks.
D Valis
CONTRIBUTION TO
FAILURE DESCRIPTION
In our lives we meet many events which
have very diverse causes, mechanisms of development and
consequences. We frequently work with the events´
description besides other assessments in safety/risk
assessment. In pure technical applications these events
are related with the failure occurrence of equipment, a
device, a system or an item. The theory speaks about
failure itself, its mechanisms, circumstances of
occurrence, etc. but at the same time we need
appropriate terminology to describe these conditions.
Our basic approaches into observing, dealing and
handling failure may fall into two groups. We either
talk about a probabilistic approach or about a
deterministic (logic) approach. As we need to get some
information about a failure we need to find it or
transfer it from different sources. This contribution
can be a complex problem for the term “failure” and its
related characteristics. In the paper there are
mentioned functions of an object and their description,
classification of failures, main characteristics of
failure, possible causes of failure, mechanisms of
failure and consequences of failure and also other
contributions related with failure very closely.
D. Valis
CONTRIBUTION TO
AVAILABILITY ASSESSMENT OF COMPLEX SYSTEMS
As we use complex systems with one shot
items in many technical applications we need to know
basic characteristics of such system. Performance,
safety and other are as much important as dependability
measures. In real applications we have to take into
account a related distribution of an observed variable.
In terms of complex systems with one shot items it is a
discrete random variable related to one shot item. The
whole system and its failures (unexpected and
inadvertent events) may have two typical types of
distributions and their characteristics. We either
consider a continuous variable (such as time, mileage,
etc.) or a counting variable (such as number of cycles,
sequences, etc.) regarding to a failure occurrence. As
the one shot items is supposed to back up the main
system function the total reliability of the system
should be higher than. The main issue regarding the
system using one shot items in their construction is to
determine the probability of the task (mission) success.
The paper presents both theoretical approach and
practical example of the solution.
Mateusz Zajac, Tymoteusz Budny
ON DETERMINATION OF
SOME CHARACTERISTICS OF SEMI-MARKOV PROCESS
FOR DIFFERENT
DISTRIBUTIONS OF TRANSIENT PROBABILITIES
There is a model of transport system
presented in the paper. The possible semi - Markov
process definitions are included. The system is defined
by semi – Markov processes, while functions
distributions are assumed. There are attempts to assess
factors for other than exponential functions
distributions. The paper consist discussion on Weibull
and Gamma distribution in semi – Markov calculations. It
appears that some forms of distribution functions makes
computations extremely difficult.
Xuejing Zhao, Mitra Fouladirad, Christophe Bérenguer,
Laurent Bordes
MAINTENANCE POLICY
FOR DETERIORATING SYSTEM WITH EXPLANATORY VARIABLES
This paper discusses the problem of the
optimization of maintenance threshold and inspection
period for a continuously deteriorating system with the
influence of covariates. The deterioration is modeled by
an increasing stochastic process. The process of
covariates is assumed to be a temporally homogeneous
finite-state Markov chain. A model similar to the
proportional hazards model is used to represent the
influence of the covariates. Parametric estimators of
the unknown parameters are obtained by using Least
Square Method. The optimal maintenance threshold and the
optimal inspection interval are derived to minimize the
expected average cost. Comparisons of the expected
average costs under different conditions of covariates
and different maintenance policies are given by
numerical results of Monte Carlo simulation.
J. Okulewicz, T. Salamonowicz
PREVENTIVE
MAINTENANCE WITH IMPERFECT REPAIRS OF A SYSTEM WITH
REDUNDANT OBJECTS
An object ability to realise tasks may be
restored by repairing only failed components. This is
called imperfect repair as the object is not as good as
new after such a repair. Preventive replacement is an
example of imperfect repair as well. The advantage of
such maintenance is that it enables controlling a
reliability level of a system. Sets of objects’
components which should be replaced are derived on a
basis of statistical diagnosing with use of data about
components failures. The acceptable level of a failure
risk while executing transportation tasks has been taken
as a criterion of choosing elements to be replaced. An
algorithm of selecting components for preventive
replacement has been developed. It was shown that a
level of a system reliability can be controlled by
changing an order of a quantile function in coordination
and a number of redundant objects. A computer simulation
model of the system was used to illustrate derived
dependencies.
Jakub Nedbalek
RBF NETWORKS FOR
FUNCTION APPROXIMATION IN DYNAMIC MODELLING
The paper demonstrates the comparison of
Monte Carlo simulation algorithm with neural network
enhancement in the reliability case study. With regard
to process dynamics, we attempt to evaluate the tank
system unreliability related to the initiative input
parameters setting. The neural network is used in
equation coefficients calculation, which is executed in
each transient state. Due to the neural networks, for
some of the initial component settings we can achieve
the results of computation faster than in classical way
of coefficients calculating and substituting into the
equation.
M.F. Milazzo, G. Maschio, G. Uguccioni
FREQUENCY ASSESSMENT OF LOSS OF CONTAINMENT INCLUDING THE
EFFECTS OF MEASURES OF RISK PREVENTION
This paper presents a method for the
quantification of the effects of measures of risk
prevention of the frequency for rupture of pipework.
Some methodologies, given in the literature for this
purpose, assume that each plant under analysis is
characterized by the same combinations of causes of
failure and prevention mechanisms but this assumption is
not always true. The approach suggested here is based on
the methodology proposed in 1999 by Papazoglou for the
quantification of the effects of organizational and
managerial factors. Taking advantage of this methodology
the objective of the assessment of the influence of
measures of risk prevention in pipework has been
achieved through the definition of the links between the
causes of failure and the measures adopted by the
company in order to prevent and/or to mitigate them.
Krzysztof Kolowrocki, Joanna Soszynska
MODELLING ENVIRONMENT
AND INFRASTRUCTURE INFLUENCE ON RELIABILITYAND
OPERATION
PROCESSES OF PORT OIL TRANSPORTATION SYSTEM
In the paper a probabilistic model of
industrial systems environment and infrastructure
influence on their operation processes is proposed.
Semi-markov processes are used to construct a general
model of complex industrial systems’ operation
processes. Main characteristics of this model are
determined as well. In particular case, for a port oil
transportation system, its operation states are defined,
the relationships between them are fixed and particular
model of its operation process is constructed and its
main characteristics are determined. Further, the joint
model of the system operation process and the system
reliability is defined sand applied to the reliability
evaluation of the port oil transportation system.
