Albeanu Grigore, Duda Gheorghe
Recent soft computing methods in software reliability engineering
This paper presents recent approaches in soft computing to manage imprecision and uncertainty which appear
in software reliability engineering. Firstly, recent approaches like imprecise probabilities, generalized
intervals, fuzzy sets and intuitionistic-fuzzy sets are shortly described, and the usage of intuitionistic fuzzy
numbers for system reliability computation is shown. Intuitionistic-fuzzy approaches for software reliability
growth models are proposed and experimental results are given.[full text]

Babczyński Tomasz, Kowalski Marcin, Łukowicz Mirosław, Magott Jan, Skrobanek Paweł
Safety and reliability models of time-dependent systems
The paper concerns models with time dependencies that can be used in modelling dynamic reliability and
complex maintenance processes. Emphasis is put on models that have been elaborated with authors
participation. The following models are presented: fault trees with time dependencies, probabilistic fault trees
with time dependencies, reliability enhanced activity diagrams. The above models are illustrated by examples.
Both types of fault trees are used in modelling the time coordination of distance protections in high voltage
transmission line. Then reliability enhanced activity diagrams that express the maintenance process of
computer system with redundant components. Components are submitted to failures and repairs. [full text]

Berg Heinz-Peter, Hauschild Jan
Assessing external explosions and their probabilities
External hazards such as explosions can be safety significant contributors to the risk in case of operation of
industrial plants. The procedure to assess external hazard explosion pressure waves within probabilistic safety
assessment starts with a screening procedure in order to determine scope and content of the assessment. The
second step is to choose an appropriate approach in case that a full scope analysis has to be performed. Several
methods can be applied to evaluate the probability of occurrence of an external explosion event. The presented
results indicate that the probability of occurrence of external explosion pressure waves can be successfully
assessed by means of the Monte Carlo simulation, in particular in difficult site-specific conditions.[full text]

Briš Radim, Praks Pavel, Janurová Kateřina, Martínek Lubomír
Survival analysis on data of different surgery techniques to evaluate
risk of postoperative complications
Medical survival censored data of about 850 patients are evaluated to compare two basic surgery techniques.
Data comes from patients who underwent colectomy in the University Hospital of Ostrava. The data has been
screened into three general groups: all patients (data from both rectum and colon operations), data from rectum
operations, data from colon operations. Two basic surgery techniques are used for the colectomy: either
classical (open) or laparoscopic operation. Basic question which arises at the colectomy operation is which
type of operation to choose to guarantee longer overall survival time. Two methodological approaches have
been used to answer this relevant question. First is the non-parametric approach which results from Kaplan-
Meier estimates of the survival function. For each data group two survival curves are constructed, i.e. for both
open and laparoscopic type of operation. Final survival curves are compared and evaluated using advanced
methods of statistical inference (e.g. log-rank test). Second is parametric approach which results from
modelling of survival time. It is based on Maximum Likelihood Estimation method to estimate parameters of
probability distribution of overall survival time. Moreover, two Weibull models are used to compare the two
surgery techniques. Mean survival times assigned to particular types of operation are compared. [full text]

Frank P.A. Coolen
Nonparametric predictive inference in reliability and risk:
recent developments
During the last two decades, statistical methods using lower and upper probabilities have become increasingly
popular. One such method is Nonparametric Predictive Inference (NPI), which makes relatively few
modelling assumptions. Due to the speci c nature of many reliability and risk scenarios, NPI provides
attractive new solutions to many problems in these elds. This paper provides an introductory overview
to this area, including examples on competing risks, system reliability and prediction of unobserved or
even unknown failure modes. [full text]

Cui Yanhong, Guo Renkuan
Nash-lambda algorithm with applications in safety and reliability
In this paper, a new algorithm, named as Nash-lambda algorithm by merging Nash equilibrium solution and
the lambda algorithm, is proposed. The lambda algorithm, a new global optimization algorithm, is created by
imitating ancient Chinese human body system model, which has already demonstrated its simplicity in
searching scheme, codes and efficiency in computation comparing to the genetic algorithm. The noncorporative
game environments determine the optimization problems which are different from those of the
traditional safety and reliability optimizations because of the engagement of the Nash equilibrium for seeking
the best strategy. The lambda algorithm serves the searching the Nash equilibrium solution efficiently. In other
worlds, the Nash-lambda algorithm is just developed to address the optimization problems of the multiple
objective functions representing non-corporative players’ interests. [full text]

Cui Yanhong, Guo Renkuan, Guo Danni
Lambda algorithm and maximum likelihood estimation
In this paper, a new global optimization algorithm by imitating ancient Chinese human body system model,
named as lambda algorithm, is introduced. The lambda algorithm utilizes five-element multi-segment string to
represent the n-dimensional Euclidean point and hence the string based operation rules for expansion,
comparison and sorting candidate strings. The algorithm enjoys the simplest mathematical operations but
generates highest searching speed and accuracy. We furthermore explore to merge the lambda algorithm with
maximum likelihood procedure for creating a non-derivative scheme – likelihood- lambda procedure. A
illustrative example is given[full text]

Dagkinis Ioannis, Lilas Theodoros, Nikitakos Nikitas
Apply FMEA modeling to a floating ecological desalination unit
Water scarcity in small Aegean islands is considered a major problem for their development. On the other
hand high potential renewable energy sources are available. Therefore a floating desalination unit was
developed in order to treat the problem in an ecological manner. The floating unit has been operating for four
years at sea close to a small island. Marine environment and autonomous remote operation led to a more
complex design with several sensors and safety mechanisms. This paper illustrates and applies Failure Modes
and Effects Analysis (FMEA) modeling to Floating Ecological Desalination Unit. FMEA is based on
monitoring data and also taking into account failure dependencies between components during the assessment
of desalination system reliability. Then two systems, one with safety mechanisms and one without are
analyzed by Reliability Block Diagrams (RBD) and the reliability of each system is computed. The
comparison between a simple system and the remote autonomous system illustrates the implications of the
additional monitoring mechanisms and the impact of these mechanisms to reliability and risk assessment on
the floating wind powered offshore desalination unit. [full text]

Eid Mohamed
Time-dependant modelling of systems: some open questions
Time dependent modelling of complex system is one of the important topics in system reliability engineering.
Although system complexity is increasing, the existing models are numerically satisfactory. However, some
formal development is still lacking in reliability theory. A full system time-dependency modelling and analysis
is not possible without some formal answers on critical transitions and related issues. This is still one of the
open questions in system reliability theory. Some promising development relative to critical states is given in
this paper with an application case. [full text]

Eid Mohamed
Monitoring/detection systems: reliability based performance
Monitoring & Detection (M&D) systems are introduced in almost all daily life aspects. Today, it is unlikely
to find out a system that is not equipped with a sort of M&D apparatus, even the most ordinary and uncritical
systems. Objective assessments of the performances of M&D systems are increasingly needed. Performance
assessment may be motivated by commercial interests or by certification concerns if the application field is
ordinary or uncritical. While, if the application filed is critical, safety and security aspects may become the
major focus. The paper classifies in three classes the models that are the most-frequently used to describe
M&D systems. The author proposes for each class a suitable indicator of performance based on M&Dsystems
reliability targets. [full text]

Grabski Franciszek
Semi-Markov model of system damage process
The reliability characteristics and parameters of multi-state systems modelled by the finite states regress
characteristics and parameters of multi-state systems modelled by the finite states regress semi-Markov
processes are investigated in the paper. Presented here models deal with un-repairable systems. The essential
concepts of discrete states and continuous time semi-Markov process theory deliver. Mathematical apparatus
for models constructions and analysis. Multi-state reliability functions and corresponding expectations, second
moments and standard deviations are calculated for the presented systems. [full text]

Gucma Lucjan, Schoeneich Marta
Navigational risk management with under-keel clearance consideration
The paper presents idea of the safety management system established for safety UKC (under-keel clearance) for
ships entering to ports. System consists of three components which can be used for navigational risk
management during decision making in port. Application of newly system was presented for example research
which carried out by Marine Traffic Engineering team for Ystad port. [full text]

Guo Renkuan, Thiart Christrien, Cui Yanhong, Guo Danni
Lifetime distributions with wave-like bathtub hazard
In this paper, we argue the necessity of dealing with lifetime distributions with wave-like bathtub hazard
function. Four classes of wave-like bathtub hazards are investigated. For preparing maximum likelihood
estimation of the hazard parameters, the first-order and second-order partial derivatives are derived. [full text]

Guze Sambor, Smolarek Leszek
Methods for risk minimizing in the process of decision-making under
The sources of the uncertainty in the maritime transport system are described. Furthermore, the two models for
human factor reliability are presented. The possibilities of mixed these two methods as the estimators for the
probability of correct performance of the navigator are given. The analysis of decision-making process under
uncertainty has been done. Finally, the optimization task and his possible solution are shown. [full text]

Jodejko-Pietruczuk Anna, Plewa Marcin
The model of reusability of series system product
The main goal of this paper is to create the reverse logistics model that uses reliability theory to describe
reusability of product parts with assumption that recovered components are used in production process but
they aren’t as good as new ones. The model allows to estimate the potential profits of the reusing policy in a
production and gives the base to optimize some of the process parameters: the threshold work time of returns
or the warranty period for products containing reused elements. [full text]

Kuráňová Pavlína
Logistic regression as a relevant statistical tool for medical data
investigation and evaluation
This paper presents the usage of logistic regression for predicting the classification of patients into one of the
two groups. Our data come from patients who underwent Phadiatop test examinations and patients who
underwent colectomy in the University Hospital of Ostrava. As the predictor variables were chosen personal
and family anamneses for Phadiatop test and the physiological and operative scores for colectomy. For
Phadiatop test, both of these anamneses were divided into four categories according to severity ranked by
doctors. Scores for morbidity were based on the POSSUM system. The psychological score comprises 12
factors and the operative score comprises 6. The categorical dependent variable which we want to predict was
Phadiatop test (respectively morbidity). The model for Phadiatop test was tested with the use of a medical
database of 1027 clients and morbidity was tested upon a medical database of 364 clients. The developed
models predict the right results with 75% probability for Phadiatop test and 70% probability for morbidity in
surgery. [full text]

Mazurkiewicz Jacek
Dependability of discrete transport system – model, simulation, measures
The paper proposes a method of reliability and functional analysis related to discrete transport systems. The proposed analysis is based on modelling and simulating of the system behaviour. Monte Carlo simulation is used for proper reliability and functional parameters calculation. The simulator is built using Scalable Simulation Framework (SSF). No restriction on the system structure and on a kind of distribution is the main advantage of the method. The paper presents some exemplar system modelling. The authors stress the problem of influence of the reliability parameters for final functional measures (required time of delivery) – the key value to calculate the availability of the system. They also propose to measure the economic quality of discrete transport system by “profit function”. The presented problem is practically essential for defining an organization of vehicle maintenance and transportation system logistics. [full text]

Michalska Katarzyna
Modelling of computer systems – an approach for functional and
dependability analysis
The paper presents a method of analyzing dependability aspects of service oriented information systems
based on functional and dependability modelling. Analysis approach is based on integrating different
computer system models into one coherent model suitable for simulation. To simplify integration of the
models author propose an automatic solution that is integrated with the tools chosen for system analysis.
Analysis is done with a usage of open-source simulation environment that can be easily modified and
extended for farther work. Based on the simulation results, with respect to defined dependability and
functionality metrics, some alternatives can be chosen in case of system or service failure.
The paper presents developed software which implements described methodology and results of analysis for
an exemplary business service oriented complex information system. [full text]

Piljugin Ewgenij, Herb Joachim, Röwekamp Marina, Berg Heinz-Peter
Methods to assess effects of cable failures caused by fire
It is state-of-the-art that a Level 1 PSA also includes a fire PSA for all plant operational states. In performing
Fire PSA not only the malfunction of the components has to be assessed but also all supply systems and cables
have to be traced for a given component. In the past it was assumed in the case of a fire in a compartment that
all components and cables in that compartment are not functional anymore. However, this is in many cases a
too conservative approach and could lead to overestimated fire induced core damage frequencies. Therefore, a
method is necessary to assess in a more realistic manner the effects of cables failures caused by fire. Such a
procedure requires a sound data base on equipment, list of cables and their properties as well as cable routing.
Two methods are described which are currently developed. One of them is a cable failure mode and effect
analysis which is easier to apply in practice.[full text]

Rabasová Marcela
Risk of morbidity in colorectal surgery
This study examines the risk of morbidity for colorectal surgery undergoing patients. The main aim was to
identify important risk factors that influence post-operative complications – morbidity, and to create a model to
predict possible complications for a patient before surgery. The source data file contains information about
1177 patients who underwent colorectal surgery between 2001 and 2009 at the University Hospital Ostrava,
Czech Republic. According to the surgeons’ judgment the following seven independent variables were
included in the analysis: Gender, BMI, American Society of Anaesthesiology (ASA) Classification, Stage of
Disease, Number of Previous Operations, Surgical Technique and Operation Severity. Discriminant analysis
was used for the data evaluation; statistical software SPSS 18 and NCSS 2004 were used for the calculations. [full text]

Sugier Jarosław, Anders George J.
Probabilistic evaluation of deterioration processes with maintenance
Reliable operation of contemporary complex systems depends on selecting efficient maintenance policy,
which often must take into account not only the reliability, but also economic factors. In this work, we present
an approach which allows evaluation of various possible maintenance scenarios with respect to these two
areas. The method is based on the concept of a life curve and discounted cost used to study the effect of
equipment aging under different maintenance strategies. The deterioration process is first described by a
Markov model and then its various characteristics are used to develop the equipment life curve and to quantify
other reliability parameters. Based on these data, effects of various “what-if” maintenance scenarios can be
examined and their efficiency compared. Simple life curves are combined to model equipment deterioration
undergoing diverse maintenance actions, while computing other parameters of the model allows evaluation of
additional critical factors, such as probability of equipment failure. Additionally, the paper deals with the
problem of the model adjustment so that the computed frequencies are close to the historical values, which is
very important in practical applications of the method. [full text]

Tchórzewska-Cieślak Barbara, Rak Janusz Ryszard, Pietrucha Katarzyna
Failure risk analysis in the water supply sector management
The subject and main purpose of this study is to develop risk analytic model for the design and operation of
water supply sector. A water supply system belongs to the critical infrastructure of cities, and it should be a
priority task for waterworks and even for the local authorities to ensure the suitable level of its safety. A
water supply systems (WSS) ought to be high reliable continuous operating system. Failure factors in WSS
should be identified and prioritized, for example, the causing factors in the most frequent failures in waterpipe
network. Drinking water supply utilities are responsible for providing a safe and reliable supply of
potable water to their customers. Risk priority helps asset manager to target and refine maintenance plans,
capital expenditure plans, investigative activities, and deal with potential failure before it occurs. In this
paper, we present a review of classic risk analyses, risk management and new methodology for water supply
networks management. This paper presents a framework for the analysis of performance risk in water supply
that can be applied to the entire system or to individual subsystems. It is expecting that the methodology for
the water supply performance risk analysis would provide the city leadership for decision making support. [full text]

Walkowiak Tomasz
Simulation approach to Web system dependability analysis
The paper is concerned with the analysis of under-keel clearance of ships based on real data from Szczecin Maritime Office. Using probabilistic method for UKC assessment give it possibility to create the distribution of under-keel clearance in several ship’s passages and in further step to determine the probability of ship’s grounding accident during the port approach. The results of using this type of model could be used in risk assessment of ships entering to the ports, therefore it is possible to used probabilistic model in Maritime Office employees’ everyday decision making practice. Research results present verification of probabilistic model, based on data from Vessel Traffic Service database and probability of touching the bottom during ships’ passages on Swinoujscie – Szczecin waterway. Moreover there are presented examples of these situations when entering to the port for analysed ships is not allowed according to the model. [full text]

Walkowiak Tomasz, Mazurkiewicz Jacek
Critical situations and human resources in discrete transportation
systems analysis
The paper presents an approach to critical situations analysis related to discrete transportation systems (DTS).
The critical situation is understood as sudden shortage of some system recourses resulting in the
transportation system performance degradation. The analysis is realized based on availability calculation of
DTS. The system is described by the formal model, which includes reliability and functional parameters of
DTS as well as human resources – drivers and management system. The availability and average availability of
the system, defined in a functional way, is discussed as a function of different essential parameters of DTS.
The proposed analysis is based on the modelling and simulating of the system behaviour using Monte-Carlo
approach. The paper presents some exemplar systems – based on real Polish Post DTS – modelling and
results. [full text]

Zajac Mateusz, Kierzkowski Artur
Attempts at calculating chosen contributors with regard to the Semi-
Markov process and the Weibull function distribution
The main aim of this article is the presentation of the way of making calculation with the application of the
semi-Markov processes, with the continuous time t, where non-exponential distribution function is going to
be applied. These type of calculations were published but the time there was approaching infinity.
Engineering practice proves that the lack of solutions of this issue leads to obtainment of solutions that are
encumbered with errors. This article is the first attempt of the error analysis. [full text]

Zamojski Wojciech, Mazurkiewicz Jacek
From reliability to system dependability – theory and models
The paper presents a novel approach to system dependability problem. The analysed systems and networks –
characterised by different sets of features – are considered as a union of all their resources essential for the
predicted tasks realisation. The system dependability is discussed with respect to the occurrence of incidents
and treats that may cause to damage the system resources and – in consequence – to the collapse of the
executed tasks. The maintenance policy system is based on two main concepts: detection of unfriendly events
and system responses to them. The proposed analysis is realised from the user’s point of view, focusing on
functional features described by business services available in the system. [full text]