RT&A 2012, # 2(25) Vol.7

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Igor Ushakov

SENSITIVITY ANALYSIS  OF OPTIMAL REDUNDANCY SOLUTIONS

Solving practical optimal redundancy problems, one can ponder: what is the sense of optimizing if input data are taken “from the ceiling”? Indeed, statistical data are so unreliable (especially in reliability problems that such doubts have a very good ground. Not found any sources after searching the answer for this question, the author decided to make some investigation of optimal solutions sensitivity under influence of data scattering. Thus, one can notice that input parameters variation may influence enough significantly enough on probability of failure-free operation and the total system cost from run to run  of Monte Carlo simulation though optimal solution remains more or less stable.

Shubinsky Igor B., Zamyshlyaev Alexey M.

TOPOLOGICAL SEMI-MARKOV METHOD FOR CALCULATION OF STATIONARY PARAMETERS OF RELIABILITY AND FUNCTIONAL SAFETY OF TECHNICAL SYSTEMS

The paper offers the method for calculation of reliability parameters and functional safety of technical systems, differing from known methods by an opportunity of obtaining strict formula expressions of stationary parameters directly from a system state graph. The method is suitable for solution of both Markov, and semi-Markov models of reliability and safety. In addition the paper presents some examples of determining safety and availability factors, as well as time parameters of safety and reliability of the two-channel safety related device.

G. Tsitsiashvili, M. Osipova

RECURRENT SEQUENCE OF PARALLEL-SERIAL CONNECTIONS

In this paper a sequence of parallel-serial connections is considered. In this sequence next connection is obtained by parallel or serial linking of new arc to obtained connection. Distributions of random numbers of connectivity components are analyzed. These distributions are considered intensively now. Central limit theorem is proved for these distributions and parameters (mean and variance) of normal limit distribution are calculated.

Igor Ushakov

UNIVERSAL GENERATING FUNCTION & OPTIMAL REDUNDANCY PROBLEMS

The Method of U-functions, or the Method of the Universal Generating Function (UGF), was introduced in [(1986) Ushakov, (1987)  Ushakov] and later developed in [(1988)  Ushakov;  (1995)  Gnedenkon& Ushakov]. Actually this is a generalization and “algebraic” formalization of the well-known Kettelle’s Algorithm [(1962) Kettelle].  In turn, Kettelle’s Algorithm, is a form of presentation of convolution of  discrete random variables. The method of U-functions is very convenient for computerized calculations.  Last years, this method was significantly developed by G. Levitin and A. Lisnianski

Alexander V. Bochkov, Valery V. Lesnykh, Nikolay N. Zhigirev

DYNAMIC MULTI-CRITERIA DECISION MAKING METHOD FOR SUSTAINABILITY RISK ANALYSIS OF STRUCTURALLY COMPLEX TECHNO-ECONOMIC SYSTEMS

The paper considers the characteristics of the functioning and sustainability of the structurally complex techno-economic systems (SCTES) in terms of different types of risk. The validity of the application to describe the behavior of this class of systems of semi-empirical mathematical models, which are based on a vector description of the system states, using the criteria approach for assessing the quality of its functioning, is demonstrated. Under discussion is conceptual model for the interaction of the object and its environment, allowing to estimate the "optimal" allocation ratio between the productive system and its development potential. The concept of non-formalizable threats for the sustainable functioning of this systems class was introduced. Expert procedure to account non-formalizable threats in case of risk assessment was proposed. For the construction of indicators for assessing the status the methods of quantitative analysis based on the theory and multi-criteria utility was used. Multi-criteria utility as an indicator of sustainability in the form of dimensionless complex hierarchy of indicators was proposed. Computing for through the convolution of the primary indicators. The hierarchical model proposed to calculate the integral index of multi-criteria preference of one embodiment of the system over the other. Some results of case study are discussed.

Fedol Ghazi, Pr: Hamouine Abdelmadjid, Dr: Zouaoui Chikr el Mezouar

BEAM BEHAVIOUR UNDER MONOTONIC LOADS

In this work we interest to study the beam behavior under monotonic loads in four point, to improve the mechanical properties of a concrete beam fiber and establish an identification card of the new concrete beams were comparing these beams witnesses.

G. Tsitsiashvili, M. Osipova

BASIS OF CONTINUUM APPROXIMATION IN MODELS OF GROWING RANDOM NETWORKS

Accuracy asymptotics for differences between prelimit and limit distributions of nodes powers in models of random growing networks are constructed. A rate of a convergence in these relations is power. Obtained formulas allow to ground the continuum approximations for considered models.

A. Blokus-Roszkowska, L. Smolarek

COLLISION RISK ESTIMATION FOR MOTORWAYS OF THE SEA

The Motorways of the Sea is rather a new concept and, thus, is still in the process of development by the European Commission and in the Baltic Sea Region. The Baltic Sea Region is one of the most dynamic growth areas. Due to this fact the new ideas and technologies are needed to optimize the sea transport system. In the paper the simulation model for the system safety state evaluation is presented. The simulation program can constitute a base for decision-support tool, on the level of safety management, especially to optimally plan the safety transport system.

Kumar Pardeep, Chaturvedi D.K., Pahuja G.L.

A HEURISTIC METHOD FOR RELIABILITY REDUNDANCY OPTIMIZATION OF FLOW NETWORKS

In flow networks, from the quality and service management point of view, measurement of the transmission ability of a network to meet the customers demand is very important.  To meet the ultra high reliable requirements of such networks, a heuristic method for reliability redundancy optimization of flow networks using composite performance measure (CPM) integrating reliability and capacity has been proposed. The method is based upon the selection of main flow paths and backup paths and then optimizing main paths on priority basis. Thus, the reduced computation work makes the proposed algorithm suitable for designing of large, reliable telecommunications networks.

A.N.  Patowary, J. Hazarika and G. L. Sriwastav

ESTIMATION OF RELIABILITY IN INTERFERENCE MODELS USING MONTE CARLO SIMULATION

This paper presents estimation of reliability of a system, for the cases when its strength (X) and stress (Y) follow exponential, normal or gamma distributions, using Monte Carlo simulation (MCS). First the parameters of strength and / stress are estimated and substituting them in the reliability expressions, in different cases, the estimates of reliability are obtained. Normal distribution is fitted to various sets of estimated reliability , generated by MCS. The goodness of fit is tested using Kolmogorov-Smirnov one sample test.

V. M. Chacko, M. Manoharan

MULTISTATE COHERENT SYSTEMS WITH MULTIPLE STATE TRANSITIONS AT A TIME

A key requirement in defining a multistate coherent system (MCS) is the relevance condition of its components. A new class of MCSs is introduced with a new component relevance condition. Also we introduce a more general relevance condition. They are compared with some existing component relevance conditions. Based on the two new relevance conditions, two component importance measures for MCSs are defined. They are most appropriate for comparing components when certain type of system improvement is sought. We introduce new joint importance measures for two or more components with respect to the proposed relevance conditions. The new MCS classes include several existing MCSs as special case. An illustrative example of the proposed MCSs is also provided.