Boolean Dynamics with Random Couplings

This paper reviews a class of generic dissipative dynamical systems called N-K models. In these models, the dynamics of N elements, defined as Boolean variables, develop step by step, clocked by a discrete time variable. Each of the N Boolean elements at a given time is given a value which depends upon K elements in the previous time step. We review the work of many authors on the behavior of the models, looking particularly at the structure and lengths of their cycles, the sizes of their basins of attraction, and the flow of information through the systems. In the limit of infinite N, there is a phase transition between a chaotic and an ordered phase, with a critical phase in between. We argue that the behavior of this system depends significantly on the topology of the network connections. If the elements are placed upon a lattice with dimension d, the system shows correlations related to the standard percolation or directed percolation phase transition on such a lattice. On the other hand, a very different behavior is seen in the Kauffman net in which all spins are equally likely to be coupled to a given spin. In this situation, coupling loops are mostly suppressed, and the behavior of the system is much more like that of a mean field theory. We also describe possible applications of the models to, for example, genetic networks, cell differentiation, evolution, democracy in social systems and neural networks.Comment: 69 pages, 16 figures, Submitted to Springer Applied Mathematical Sciences Serie

Numerical simulation of random composite dielectrics. II. Simulations including dissipation

A simulation model presented earlier for the permittivity of a composite material has now been extended to include the dissipation of energy inside the medium. It is employed to calculate the complex dielectric function of so-called effective media, i.e. randomly distributed lossy particles in an insulating matrix. A general equation formulated before for lossless media proves to be valid also for the dissipative mixtures investigated. However, simulations and experimental data show that small deviations from random distribution can induce large deviations in the dielectric function. Experiments are reported that agree with the simulation results

Numerical simulation of random composite dielectrics

A novel computer simulation method is presented for the non-dissipative dielectric response of binary mixtures. It is based on the discretization of Maxwell's equations and thus takes into account all classical long-range interactions between different particles implicitly. The simulations performed yield a relationship between the dielectric functions of the two components, the volume fraction and the dielectric function of the mixture, which can be described by an exponential formula. It was found that the exponent in this formula depends on the volume fraction but not on the dielectric properties of each component. The mixture rule is in agreement with experimental data taken from literature

Guiding Soft Robots with Motor-Imagery Brain Signals and Impedance Control

Integrating Brain-Machine Interfaces into non-clinical applications like robot motion control remains difficult - despite remarkable advancements in clinical settings. Specifically, EEG-based motor imagery systems are still error-prone, posing safety risks when rigid robots operate near humans. This work presents an alternative pathway towards safe and effective operation by combining wearable EEG with physically embodied safety in soft robots. We introduce and test a pipeline that allows a user to move a soft robot's end effector in real time via brain waves that are measured by as few as three EEG channels. A robust motor imagery algorithm interprets the user's intentions to move the position of a virtual attractor to which the end effector is attracted, thanks to a new Cartesian impedance controller. We specifically focus here on planar soft robot-based architected metamaterials, which require the development of a novel control architecture to deal with the peculiar nonlinearities - e.g., non-affinity in control. We preliminarily but quantitatively evaluate the approach on the task of setpoint regulation. We observe that the user reaches the proximity of the setpoint in 66% of steps and that for successful steps, the average response time is 21.5s. We also demonstrate the execution of simple real-world tasks involving interaction with the environment, which would be extremely hard to perform if it were not for the robot's softness.Accepted Author ManuscriptLearning & Autonomous Contro

Auswahl und Abwicklung von Großprojekten

In der Öffentlichkeit entsteht aufgrund von Kostensteigerungen und Zeitverzügen oft der Eindruck, die hoch geschätzte Ingenieurskunst in Deutschland ginge verloren. Tatsächliche Ursachen für die Probleme sind aber oft Verzögerungen in den Phasen der strategischen Planung durch Abstimmungsprozesse mit Maximalforderungen, langwierige politische Grundsatzdebatten mit Blockaden notwendiger Entscheidungen oder Verzögerungen bei der Finanzierung und Mittelbereitstellung, der Projektplanung und deren rechtlichen Sicherung beziehungsweise Genehmigung. Darüber hinaus steht bei einigen eine grundsätzliche Skepsis gegenüber Großprojekten im Hintergrund, die manchmal mit einer partiellen Innovations-, Technik- und Veränderungsfeindlichkeit gepaart ist. Dabei sind sowohl überzogene Egoismen ("Nimby-Effekte") als auch tatsächlich hohe belastende Wirkungen für Betroffene zu beobachten. Ein weiterer Anlass für Kritik betrifft solche öffentliche Projekte, die oft aus lokalpolitischem Geltungsdrang und Prestigegründen oder mit deutlich überzogenen Nutzenerwartungen (Image, Standortmarketing, Wirtschaftsförderung) hoch subventioniert und ohne hinreichende Effizienznachweise politisch beschlossen und umgesetzt werden. Der Beitrag zeigt Problemursachen auf und beschreibt Möglichkeiten zur frühzeitigen Identifikation und Problembeseitigung. Dazu zählen klare Definitionen der Projektziele und des Zeitrahmens, der adäquate Umgang mit Unsicherheiten und Risiken, die Qualitätssicherung für Entscheidungen und Prozesse, die Bereitstellung ausreichender Ressourcen, die Vermeidung von Umplanungen während der Bauabwicklung, die Schaffung klarer Verantwortlichkeiten und Haftungsregelungen, die Verbesserung von Kommunikation und Partizipation sowie von Datengrundlagen und Instrumenten