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JPSRA 2011 Volume 2, Number 1

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 specic 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 assessment |

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 uncertainty |

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 activities |

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] |