RELIABILITY of energy systems

Depending on the goals of studies, the object of studies may be either an energy complex as a whole, or individual energy systems it includes, or separate elements of the systems.

ERGODICITY OF FLUID SERVER QUEUEING SYSTEM IN RANDOM ENVIRONMENT

There are sufficient conditions of the ergodicity for queuing systems in a random environment. But as theoretically so practically it is very important to obtain a criterion of the ergodicity which defines an ability to handle customers of these systems and a possibility to analyze them in a regime of heavy traffic. Among queuing systems in the random environment there are systems with the hysteresis control which are very important in modern applications. In this paper the criterion of the ergodicity is obtained for one server queuing system in the random environment. This criterion is based on a reduction of this queuing system to classical Lindley chain. Some asymptotic formulas in the heavy traffic regime are obtained for this queuing system also.

RISK ANALISYS OF A SNOWBOARDER

Winter sports can be associated with risk of sustaining injuries. The risk reduction is possible as a result of an analysis, portraying the most dangerous incidents and undesired events. Decreasing the frequency of such events or reducing their consequences can limit the overall risk associated with snowboarding. First, a preliminary selection of undesired events was performed using the MIL-STD-882 matrix method. Then, a graph showing the most likely categories of body injuries that may occur during one day of snowboarding was developed. The graph allowed for determining events associated with the highest risk of injury.

MODELING SAFETY OF MULTISTATE SYSTEMS WITH APPLICATION TO MARITIME FERRY TECHNICAL SYSTEM

Basic notions of the ageing multistate systems safety analysis are introduced. The system components and the system safety functions are defined. The mean values and variances of the multistate system lifetimes in the safety state subsets and the mean values of its lifetimes in the particular safety states are defined. The notions of the multi-state system risk function and the moment of exceeding by the system the critical safety state are introduced. A series and a  parallel-series safety structures of the multistate systems with ageing components are defined and their safety function are determined. As a particular case, the safety functions of the considered multi-state systems composed of components having exponential safety functions are determined. An applications of the proposed multistate system safety models to the prediction of safety characteristics of a maritime ferry operating at winter conditions technical system is presented as well.

Wind hydropower system as a variant on diversification of distributed generation

Nowadays renewable energy sources attract attention of humanity because the depletion of conventional nonrenewable energy (coal, gas, oil, etc.) is getting increasingly obvious.  Wind energy is characterized by a considerable potential among the renewable resources. Human civilizations have harnessed wind since long ago. In the ancient times wind was used to propel boats. It is known that even 3000 years BC the citizens of Alexadria had used “wind wheels”.  In the 16th century the Netherlands had more than ten thousand wind-driven plants that were used to dry lakes for cultivation area. In 1888 the USA constructed a large wind power plant for electricity production. The multi-blade wind motors invented by the engineer Davydov appeared at the Russian Exhibition in Nizhny Novgorod in 1896. Wind mills found wide application. In the USSR the first 100 kV wind power plant was built in the Crimea in 1931 and was in operation until World War II. Currently wind energy is widely used in more than 60 countries of the world.  Today 10 leading countries account for about 86% of all wind power capacities installed in the world, of which more than 38% are situated in China  and the USA. In Europe wind energy is mostly used in Germany, Denmark, Spain, Portugal, and France. The total installed capacity in the world reached 194 GW  in 2011 and continues to soar.

CONNECTIVITY PROBABILITY OF RANDOM GRAPH GENERATED BY POINT POISSON FLOW

In different applications (for an example in the mining engineering) a problem of a definition of a set in two or three dimension spaces by a finite set of points origins. This problem consists of a determination in the finite set of some subset of points sufficiently close to each other. A solution of this problem consists of two parts. Primarily initial finite set of points is approximated by point Poisson flow in some area which is widely used in the stochastic geometry [1, sections 5, 6]. But a concept of a proximity is analyzed using methods of the random graph theory like a concept of maximal connectivity component [2] - [4]. This concept origins in a junction of the combinatory probability theory and of the graph theory. An analysis of these concepts and mathematical constructions leads to a generalization of the random graph theory theorems onto graphs generated by point Poisson flow in some area.

PRINCIPLES OF CLASSIFICATION RELIABILITY  STATISTICAL DATA OF THE ELECTRIC

EQUIPMENT OF POWER SUPPLY SYSTEMS

The result of comparison of criteria, which statistics characterize differing properties of random variables of sample, depends on the importance of these properties. In turn, the importance of properties can essentially change for modeled analogues of sample.

BLOCK INSPECTION POLICY MODEL WITH IMPERFECT INSPECTIONS FOR MULTI-UNIT SYSTEMS

In this paper, the authors’ research work is focused on imperfect inspection policy investigation, when not all defects are identified during inspection action performance and probability of defect identification is not a constant variable. They are interested in Block Inspection Policy performance for multi-unit systems, the maintenance policy which is one of the most commonly used in practice. As a result, at the beginning, few words about delay time modelling approach and a brief literature overview is given. Later, the model of Block-Inspection Policy is provided. The numerical example with the use of QNU Octave program is given. In the next Section, the sensitivity analysis of the developed model is characterized. The article ends up with summary and directions for further research.

APPLICATION OF GEOMETRIC PROCESS IN ACCELERATED LIFE TESTING ANALYSIS

WITH TYPE-I CENSORED WEIBULL FAILURE DATA

In Accelerated life testing (ALT), generally, the estimates of original parameters of the life distribution are obtained by using the log linear function between life and stress which is just a simple re-parameterization of the original parameter but from the statistical point of view, it is preferable to work with the original parameters instead of developing inferences for the parameters of the log-linear link function. By the use of geometric process one can easily deal with the original parameters of the life distribution in accelerated life testing. In this paper the geometric process is used in accelerated life testing to estimate the parameters of Weibull distribution with type-I censored data. The maximum likelihood estimates of the parameters are obtained by assuming that the lifetimes under increasing stress levels form a geometric process. In addition, asymptotic confidence interval estimates of the parameters using Fisher information matrix are also obtained. A Simulation study is also performed to check the statistical properties of estimates of the parameters and the confidence intervals.

SURVIVAL MODELS OF SOME POLITICAL PROCESSES

We extend the Probabilistic ideas from stochastic processes (queuing theory and reliability) on creation of some realistic models for studying several governing political formations, and find their survival characteristics. These models were presented at the Sixth and Seventh International Conferences on Mathematical Models in Reliability (Moscow 2009, and Beijing 2011). Our focus is on a “democracy” model, where the times of survival (existence at the political scene, duration of stay in leading coalition, governing survivability, life time distribution, longevity, etc.) can be derived from the model. Markovian models of spending time in certain sets of states are explored, and some discussion on statistical properties and evaluations are presented. We are confident that other political schemes also can be modeled using appropriate probabilistic tools.