The sowing density of wheat is important for expression of number of spikes per unit area, grain yield as well as other yield components. The aim of this work is investigation of variability of grain yield and number of spikes per unit area influenced by different sowing densities under different environmental conditions. Three wheat genotypes NS 40, Prima and Nova Bosanka were studied at seven different sowing densities (384, 424, 451, 504, 544, 588 and 604 seeds m-2) with four replications on experimental plot of one m2 on field experiment in agro‒ecological conditions of Banja Luka during two successive growing seasons. In all studied wheat cultivars, the lowest number of spikes m-2 and the lowest grain yield were found on variant of lowest sowing density (384 seeds m-2), while the highest number of spikes m-2 and the highest grain yield were found on variant of 588 seeds m-2 in both years. The wheat genotype NS 40S had the highest number of spikes m-2, while Nova Bosanka had the lowest at all variants of sowing densities in both years. Mainly, at all variants of sowing densities, the highest values of analyzed traits were expressed in first year of experimental investigation. Depending of year and variant of sowing density the highest grain yield were found in NS 40 and Prima, while the lowest grain yield had Nova Bosanka in both years of experiment. In general, the recommended wheat sowing rates should be confirmed in the specific area of production and for the specific genotype.

Aluminium and its alloys represent very important group of structural materials. They have many applications in mechanical and civil engineering, and welding is considered to be one of the most important joining techniques. However, welding of aluminium has several issues, like high thermal conductivity and easy formation of oxide layer with high melting temperature. Recently, solid state friction stir welding process has been developed to overcome such issues, but it is not easily applicable in every situation. Therefore, welding of aluminium still greatly relies on arc welding. Among commonly used TIG and MIG processes, pulsed MIG (and its variants) are developed to fulfil requests regarding heat input and oxide layer removal during welding. This paper gives brief general overview of technical and technological aspects of these processes, and then more details regarding welding of widely used aluminium 5754 alloy with thickness of 4 mm. Comparison of relevant costs is given as well. All welds were made using digitally controlled equipment, while voltage and current were additionally measured. Based on evaluation of welds and calculated costs, conclusion regarding feasibility of each process is given.

Pneumatic conveying involves the transportation powder, granular and piece of material and is based on the phenomenon that at the appropriate speed of air in the pipeline, the solid particles are brought in the desired direction. If inlet air velocity is too high the material flow rate may be reduced, the power requirements will be excessive, and operating problems will be severe. Considering the advantages that air-slide conveyors can offer in relation to pneumatic conveying systems especially in terms of low power consumption and operating problems associated with abrasive particles, such as erosive wear of system components and degradation of friable particles. In this paper is presented design calculation of airslide conveyor in the thermal power plant.

In this paper two parameter Same Slope Seasonality forecasting model was developed. Analytical expressions for determining optimal parameter values of the developed two parameter Same Slope Seasonality forecasting model were developed too. Furthermore, performance of Two Parameter Same Slope Seasonality model was compared with performance of Holt-Winters exponential model as well as with performance of Same Slope Seasonality model. All tests were performed on M2-Competition time series. To determine the parameters of Holt-Winters exponential model, nonlinear mathematical programming was used. Performed tests proved that Two Parameter Same Slope Seasonality model is more successful than Holt-Winters exponential model and Same Slope Seasonality model. Expressions developed for determination parameters of two parameter Same Slope Seasonality forecasting model give parameter values identical to the values obtained by using Solver in MS Excel, set to solve nonlinear programming model, in a way that the problem is set up to search the parameter values which minimizes the mean squared error of the model.

Inventory systems that use continuous review policy are under risk during lead time, when stock-out can occur. Therefore, system must have enough on-hand units to prevent such situations. Generally, in inventory control literature it can be found that lead time demand follows normal distribution and all other conclusions are derived from this assumption. However, in real life this does not have to be true, so it is of crucial importance to get better estimates of stochastic demand parameters over lead time. The objective of this research is to estimate the optimal (s, Q) continuous review inventory policy parameters that reduce risk of stock-out during lead time and to enhance robustness of such estimated parameters. This is done using approach we propose for demand modeling. Performances and adequacy of the proposed approach for lead time demand modeling, with various demand patterns, and its application in (s, Q) continuous inventory models are obtained by simulation and show very good results.