In the paper a novel mathematical model of electromechanical actuator is presented. It is based on application of Hamiltonian equations in the description of electro-mechanical energy conversion. It results in employment of flux linkages as state variables in the state space equations. For simplicity only a 3-phase wye connected stator winding without a neutral wire is considered in detail. The procedure can be generalised to any number of phases. Topology-based approach is used in the model implementation. Procedures for evaluation of all quantities (currents, energy/coenergy, electro-magnetic torque) present in model equations are described. Eddy currents and hysteresis phenolmenon are neglected in formulation of the model to enable application of state-space description.

The main topic of this study is the mathematical modelling of bubble size distributions in an aerated stirred tank using the population balance method. The air-water system consisted of a fully baffled vessel with a diameter of 0.29 m, which was equipped with a six-bladed Rushton turbine. The secondary phase was introduced through a ring sparger situated under the impeller. Calculations were performed with the CFD software CFX 14.5. The turbulent quantities were predicted using the standard k-ε turbulence model. Coalescence and breakup of bubbles were modelled using the MUSIG method with 24 bubble size groups. For the bubble size distribution modelling, the breakup model by Luo and Svendsen (1996) typically has been used in the past. However, this breakup model was thoroughly reviewed and its practical applicability was questioned. Therefore, three different breakup models by Martínez-Bazán et al. (1999a, b), Lehr et al. (2002) and Alopaeus et al. (2002) were implemented in the CFD solver and applied to the system. The resulting Sauter mean diameters and local bubble size distributions were compared with experimental data.

In the southern Spitsbergen area, thermal and mineral waters are primarily

associated with subpermafrost deep circulation, being mixed with shallow circulation and

glacial waters. Four thermal springs, located in the region of Stormbukta (Sørkappland),

were studied and analyzed. In the thermal waters, the main cation is sodium, while the

main anions are chloride and bicarbonate. The temperatures of the mineral and thermal

waters range from 3.4 to 15.1°C. The pH values are between 7.43 and 8.41. The total

dissolved solids (TDS) content of the geothermal waters is in the range of 346–4031 mg/l

and the Olsok thermal spring has the highest TDS values. Based on the variation in

physicochemical characteristics, two thermal water types were distinguished in the study

area. The first type is associated with thermal waters originating from deep circulation

waters. The second type is associated with the thermal and mineral waters originating

from the mixture of subpermfrost hot brines with glacial waters.