Dragan V. Petrović

An analytical approach to the uniqueness problem of hot-wire probes to measure simultaneously three velocity components

The uniqueness range of hot-wire probes to simultaneously measure all three velocity components is analysed analytically. Expressions defining the uniqueness cone half-angle are presented for triple as well as for quadruple sensor configurations. Using these expressions the influence of the main probe parameters on the uniqueness cone, i.e. the number of sensors and their orientation, the effective angle and the pitch and yaw coefficients, are analysed. Different types of probes are compared and optimum parameters are proposed. The same analysis is valid for complex vorticity probes configured as combinations of triple and quadruple sensor arrays.

Optimal utilization of the terminal for bulk cargo unloading

This paper analyses the capacity of a bulk cargo unloading river terminal, i.e. the existing terminal configuration with two unloading devices (operation without a help strategy and under a complete help strategy between unloading devices) and the predicted future terminal configuration with three unloading devices operating under a partial help strategy. The optimization procedure to determine unloading terminal optimal utilization, for each terminal configuration and operation strategy (existing and future situation) is also shown, due to the fact that ports (terminals) operation under an optimal capacity provides prompt accommodation of vessels with the minimum port waiting time and maximum use of berth facilities. For the purpose of a comprehensive analysis, three different river terminal simulation models have been developed due to the number of unloading devices and their operation strategy. Some of the obtained results have been applied and verified on the existing system.

Enlarging the uniqueness cone of the nine-sensor, T-configuration probe to measure the velocity vector and the velocity gradient tensor

The original concept of a nine-sensor T-configuration hot-wire probe to simultaneously measure three velocity and three vorticity components, as well as other velocity gradient-based turbulence properties, assumes three T-arrays, each with three sensors inclined at 45° to the probe axis. It is shown in this paper that probes having sensors asymmetrically arranged with respect to the probe axis, at specific but different geometrical angles, provide larger angular uniqueness domains in comparison to the original probe. To date it was believed that orthogonal arrays in which three sensors are mounted at 54.74° to the probe axis, as well as their vorticity counterparts, have the largest uniqueness domain of all triple-array-based probes. However, the proposed modified design of the T-array provides uniqueness cone half-angles similar to those that can be achieved by the orthogonal triple-array. In more extreme cases (i.e. at larger departures of the sensor angles from 45°), the uniqueness range of the modified T-array can be made even larger in comparison to the orthogonal array.

Jednodimenzijska difuzijska jednadžba za raspodjelu veličine čestica granulacije perlita za pročišćavanje

Preliminary communication Many filtration systems employing perlite granulations have been designed so far. Size distribution of perlite particles directly influences the retention properties of filter media. The information on the size distribution of perlite particles, used in each specific dead-end filtration process (the flow of fluid being filtered is perpendicular to the surface of filter medium), is crucial for the adequate design of filter medium. In order to facilitate the design of filter systems possessing filter media of this kind, a new and particular mathematical model has been developed for this present study. It is based on an appropriate partial differential equation and additional mathematical conditions, whose solution is an exponential function describing the probability density distribution of perlite particle sizes. The formulated model was experimentally verified by measuring the particle sizes of a perlite granulation using the morphometric method, based on the application of a standard light microscope and digital image analysis software. The fitting procedure of experimental data gave acceptable values of accuracy parameters high R-square factor (R = 0,905) and small value of the root-mean square error (MSE = 0,490).

Analysis of the Labor Market in the Republic of Srpska

Abstract We are witnessing that the labor market indicators of the Republic of Srpska have been deteriorating for years. Unemployment rates are up to three times higher than the already high European average, with no prospect of changing the situation in the near future. Deterioration in the labor market with respect to people younger than 30 years of age bears particular significance. There is a notable gap between the reduction of unemployment rate and the increase of employed people from this population group. The question is: Where (and whether) are the young (educated) people disappearing from the labor market of the Republic of Srpska? The authors provide an analysis of the main indicators of the Republic of Srpska’slabor market, with the aim of recognizing the main tendencies and problems existing at the market, as well as the need to define adequate measures for their resolution.