Miloš Tanasijević

Risk assessment model of mining equipment failure based on fuzzy logic

Abstract The systematic maintenance of mining machinery and equipment is the crucial factor for the proper functioning of a mine without production process interruption. For high-quality maintenance of the technical systems in mining, it is necessary to conduct a thorough analysis of machinery and accompanying elements in order to determine the critical elements in the system which are prone to failures. The risk assessment of the failures of system parts leads to obtaining precise indicators of failures which are also excellent guidelines for maintenance services. This paper presents a model of the risk assessment of technical systems failure based on the fuzzy sets theory, fuzzy logic and min–max composition. The risk indicators, severity, occurrence and detectability are analyzed. The risk indicators are given as linguistic variables. The model presented was applied for assessing the risk level of belt conveyor elements failure which works in severe conditions in a coal mine. Moreover, this paper shows the advantages of this model when compared to a standard procedure of RPN calculating – in the FMEA method of risk assessment.

Effectiveness assessment of agricultural machinery based on fuzzy sets theory

Highlights? The concept of effectiveness - exact indicator of the quality of service of machine. ? New structure of max-min composition - outcomes as represent of If-Then rules. ? Evaluation of tractors - on the base of expertise judgment. The quality of service of agricultural machinery represents one of the basic factors for successful agricultural production. In this sense, there is a clear need for defining the exact indicator of the quality of these machines, according to which it could be possible to determine which machine is optimal for different working conditions. The concept of effectiveness represents one of synthesis indicators of the quality of service of the technical systems. In this paper the effectiveness is defined using the fuzzy set theory, and reliability, maintainability and functionality are used as influence indicators of the effectiveness. In that sense the model for assessing the effectiveness of tractor as a typical representative of agro machinery has been formed. The model is based on integration of linguistic description of the above mentioned influence indicators using fuzzy set theory and max-min composition. The model was tested on the example of three tractors of the same category, which are exploited in climatic and soil conditions in the wider Belgrade (Serbia) area. Even if the conditions in this experiment were approximately equal, the difference of the achieved effects was attained and very significant, compared to other operation parameters.

The state and perspective of the natural gas sector in Serbia

ABSTRACT The strategy of long-term energy development of Serbia identifies an increase of share of natural gas in final energy consumption as one of the main aims. Serbia has signed a strategic agreement with the Russian Federation on cooperation in the oil and gas sector, within which the project South Stream pipeline is planned to be realized. In addition, the Republic of Serbia has signed the Treaty that establishes the Energy Community and accepted the obligation to implement the Energy Community acquis. In the natural gas sector it is related to establishing a fully liberated national and regional natural gas market. Overview and analysis of the current state concerning indigenous production, infrastructure, and consumption structure are presented as the basis for projections of the possible Serbian natural gas sector development. Three possible scenarios for future natural gas consumption, considering different influential parameters, have been developed by the Long-range Energy Alternatives Planning System (LEAP) software. Scenarios characterized by different levels and structures of consumption are analyzed in detail.

Energy resources in the Republic of Serbia: Development policy

ABSTRACT By joining the Energy Community and obtaining candidate status for accession to the European Union (EU), Serbia has committed to harmonize its energy policy to the legislation of the EU. The backbone of this policy is the power sector, which will continue to be the foundation of future development. In fact, the power sector is probably the closest to EU standards. This paper presents the energy resources in Serbia and the potentials that can be used to define the power sector policy. It is expected that lignite and large hydropower plants (HPPs) will become the basis of the energy system in the future, but with a significant increase in the share of renewable sources, primarily wind energy and biomass. One of the main objectives is to reach a 50:50 ratio of electricity produced from renewable and non-renewable sources in the period 2020–2030.

Study of Dependability Evaluation for Multi-hierarchical Systems Based on Max–Min Composition

This article presents the model for calculating the performance of dependability for complex technical systems. According to ISO-IEC 300, dependability is an overall indicator for the quality of service and considers simultaneously reliability, maintainability, and maintenance support. For a proper understanding of the quality of service for any technical system, it is important to define dependability performance at the level of single component as well as at the upper levels—levels of subsystems and entire system. As dependability indicators (reliability, maintainability, and maintenance support) have been defined as linguistic variables, the fuzzy max–min composition has been used for the dependability determination and integration of its indicators. A procedure for the synthesis of single components dependability performance to upper levels in complex technical system is proposed. Max–min composition is again used as a tool for fuzzy synthesis because it enables obtaining the comprehensive and synergetic effect in a process of dependability evaluation. A practical engineering example (mechanical systems at bucket wheel excavator) has been used to demonstrate the proposed dependability synthesis model. Copyright