Self-organized criticality in a model of collective bank bankruptcies

The question we address here is of whether phenomena of collective bankruptcies are related to self-organized criticality. In order to answer it we propose a simple model of banking networks based on the random directed percolation. We study effects of one bank failure on the nucleation of contagion phase in a financial market. We recognize the power law distribution of contagion sizes in 3d- and 4d-networks as an indicator of SOC behavior. The SOC dynamics was not detected in 2d-lattices. The difference between 2d- and 3d- or 4d-systems is explained due to the percolation theory.Comment: For Int. J. Mod. Phys. C 13, No. 3, six pages including four figure

Vectorcardiographic changes during extended space flight

To assess the effects of space flight on cardiac electrical properties, vectorcardiograms were taken on the 9 Skylab astronauts during the flights of 28, 59, and 84 days. The Frank lead system was used and observations were made at rest; during 25%, 50% and 75% of maximum exercise; during a short pulse of exercise (150 watts, 2 minutes); and after exercise. Data from 131 in-flight tests were analyzed by computer and compared to preflight and postflight values. Statistically significant increase in QRS vector magnitude (six of nine crewmen); T vector magnitude (five of nine crewmen); and resting PR interval duration (six of nine crewmen) occurred. During exercise the PR interval did not differ from preflight. Exercise heart rates inflight were the same as preflight, but increased in the immediate postflight period. With the exception of the arrhythmias, no deleterious vectorcardiographic changes were observed during the Skylab missions

Model-based prototyping of a controller for MR actuators

Magnetorheological (MR) actuators are semi-active devices that leverage the smart properties of the MR fluids whose rheology can be controlled by an external magnetic field. Within the presence of an external magnetic field, the magnetic domains of the MR fluid align with the external field, which results in the yield stress induced in the fluid, thus undergoing a transition from a fluid to a semi-solid. Thus, the control challenge for MR actuators is in controlling the rheology of the material by magnetic flux. Typically the control system is based on the coil’s current feedback. However, this approach based purely on the current control is not optimal since it is the magnetic stimuli that directly controls the material’s yield stress and not the current. Thus, this work investigates the capability of a flux controller in handling the non-linearities of the actuator, including magnetic hysteresis. A model of an MR actuator that incorporates the magnetic hysteresis and the control coil dynamics is developed. The flux controller is tuned to handle the addition of the hysteresis effect. The obtained results show that the chosen control topology is very effective for the considered flux commands inputs.info:eu-repo/semantics/publishedVersio