The paper presents a conception of power electronics voltage controlled current source (VCCS) which is able much more precise mapping of its an output current in a reference signal, compared to a typical converter solution. It can be achieved by means of such interconnection of two separate converters that one of them corrects a total output current towards a reference signal. An output power of auxiliary converter is much smaller than an output power of main one. Thanks to continuous work of this converter also pulse modulation components in this current are minimized. These benefits are paid for by a relatively small increase in the complexity and the cost of the system. This conception of a converter has been called the double-converter topology (DCT). In the author opinion presented solution of the system can find application in many power electronics equipment and, therefore, will be developed. In the paper DCT basics, simulation experiments, and possible practical arrangement of the DCT are presented.

In marine seismic wide−angle profiling the recorded wave field is dominated by waves propagating in the water. These strong direct and multiple water waves are generally treated as noise, and considerable processing efforts are employed in order minimize their influences. In this paper we demonstrate how the water arrivals can be used to determine the water velocity beneath the seismic wide−angle profile acquired in the Northern Atlantic. The pattern of water multiples generated by air−guns and recorded by Ocean Bottom Seismometers (OBS) changes with ocean depth and allows determination of 2D model of velocity. Along the profile, the water velocity is found to change from about 1450 to approximately 1490 m/s. In the uppermost 400 m the velocities are in the range of 1455–1475 m/s, corresponding to the oceanic thermocline. In the deep ocean there is a velocity decrease with depth, and a minimum velocity of about 1450 m/s is reached at about 1.5 km depth. Be − low that, the velocity increases to about 1495 m/s at approximately 2.5 km depth. Our model compares well with estimates from CTD (Conductivity, Temperature, Depth) data collected nearby, suggesting that the modelling of water multiples from OBS data might be − come an important oceanographic tool.