The analytical modelling of the PbSb alloy resistance spot welding process has been developed on the basis of mathematical analysis of thermomechanical conservation laws. The numerical solution of partial differential equations, obtained by such modelling, has been achieved by the finite element method. Thermomechanical equilibrium equations are derived, including specific properties, typical for PbSb alloys. The paper utilizes the basic experimentally proven assumption, that the temperature fields govern all processes during welding. Full agreement is evident between the experimental and analytical data.

The main subject of this paper is the representation of the probabilistic technique for thermal power system reliability assessment. Exploitation research of the reliability of the fossil fuel power plant system has defined the function, or the probabilistic law, according to which the random variable behaves (occurrence of complete unplanned standstill). Based on these data, and by applying the reliability theory to this particular system, using simple and complex Weibull distribution, a hypothesis has been confirmed that the distribution of the observed random variable fully describes the behaviour of such a system in terms of reliability. Establishing a comprehensive insight in the field of probabilistic power system reliability assessment technique could serve as an input for further research and development in the area of power system planning and operation.

As a result of a very limited number of geometric and other input data, the temperature modeling of the river Ibar downstream of the lake Gazivode was started by analyzing one river reach between Pridvorica, secondary dam in the system Gazivode, and the city Kosovska Mitrovica. River reach was selected so that the numerical results can be compared with available measured temperature data. Water quality component of HEC-RAS one-dimensional hydraulic river model was used for temperature calculations.

The utilization of modern paraboloidal concentrators for conversion of solar radiation into heat energy requires the development and implementation of compact and efficient heat absorbers. Accurate estimation of geometry influence on absorption characteristics of receiver tubes is an important step in this process. This paper deals with absorption characteristics of heat absorber made of spirally coiled tubes with transverse circular corrugations. Detailed 3-D surface-to-surface Hemicube method was applied to compare radiation performances of corrugated and smooth curved tubes. The numerical results were obtained by varying the tube curvature ratio and incident radiant heat flux intensity. The details of absorption efficiency of corrugated tubes and the effect of curvature on absorption properties for both corrugated and smooth tubes were presented. The results may have significance to further analysis of highly efficient heat absorbers exposed to concentrated radiant heating. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 42006]

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