Controlling chaos in a Lorenz-like system using feedback

We demonstrate that the dynamics of an autonomous chaotic laser can be controlled to a periodic or steady state under self-synchronization. In general, past the chaos threshold the dependence of the laser output on feedback applied to the pump is submerged in the Lorenz-like chaotic pulsation. However there exist specific feedback delays that stabilize the chaos to periodic behavior or even steady state. The range of control depends critically on the feedback delay time and amplitude. Our experimental results are compared with the complex Lorenz equations which show good agreement

Transforming chaos to periodic oscillations

We demonstrate that the dynamics of an autonomous chaotic class C laser can be controlled to a periodic state via external modulation of the pump. In the absence of modulation, above the chaos threshold, the laser exhibits Lorenz-like chaotic pulsations. The average amplitude and frequency of these pulsations depend on the pump power. We find that there exist parameter windows where modulation of the pump power extinguishes the chaos in favor of simpler periodic behavior. Moreover we find a number of locking ratios between the pump and laser output follow the Farey sequence

Extreme geomorphological processes in the eastern part of the Polish Uplands – occurrence conditions and impact on the relief

The study presents the geomorphological effects of extreme hydroclimatic phenomena such as violent downpours, widespread rainfalls with a high sum of precipitation, and intensive snowmelt occurring in the eastern part of Polish Uplands between the Vistula and the Bug rivers. The intensity and impact of these phenomena on relief is exceptionally varied here due to the variety of natural conditions as well as the degree and type of land use. These conditions result in the various kinds, formation time and volume of surface runoff as well as the intensity and volume of erosion. The impact of extreme geomorphological processes is particularly pronounced in the case of agriculturally used loess-covered areas with strong relief that cover approx. 30% of the area. In morphological terms, the most effective are the processes of rill erosion in slopewash systems as well as gully erosion processes with the predominance of piping. These processes, along with tillage erosion, determine the development trends of contemporary slope relief in this part of the uplands. In slopewash systems, rainwater runoff causes the movement of material from slopes to valley bottoms that are dissected as a result of snowmelt runoff. In erosion systems (gully systems) during snowmelt, the edges of gullies are dissected (mainly through piping) and their bottoms are covered by sediments that, in turn, are dissected by rainwater runoff. In the valleys of rivers of a low hydrological order, extreme channel processes occur during torrential summer downpours. The bottoms of large valleys are intensively shaped primarily during high water stages caused by snowmelt and rainfall