Demonstrating Advantages of Neuromorphic Computation: A Pilot Study

Neuromorphic devices represent an attempt to mimic aspects of the brain's architecture and dynamics with the aim of replicating its hallmark functional capabilities in terms of computational power, robust learning and energy efficiency. We employ a single-chip prototype of the BrainScaleS 2 neuromorphic system to implement a proof-of-concept demonstration of reward-modulated spike-timing-dependent plasticity in a spiking network that learns to play the Pong video game by smooth pursuit. This system combines an electronic mixed-signal substrate for emulating neuron and synapse dynamics with an embedded digital processor for on-chip learning, which in this work also serves to simulate the virtual environment and learning agent. The analog emulation of neuronal membrane dynamics enables a 1000-fold acceleration with respect to biological real-time, with the entire chip operating on a power budget of 57mW. Compared to an equivalent simulation using state-of-the-art software, the on-chip emulation is at least one order of magnitude faster and three orders of magnitude more energy-efficient. We demonstrate how on-chip learning can mitigate the effects of fixed-pattern noise, which is unavoidable in analog substrates, while making use of temporal variability for action exploration. Learning compensates imperfections of the physical substrate, as manifested in neuronal parameter variability, by adapting synaptic weights to match respective excitability of individual neurons.Comment: Added measurements with noise in NEST simulation, add notice about journal publication. Frontiers in Neuromorphic Engineering (2019

Transition between canted antiferromagnetic and spin-polarized ferromagnetic quantum Hall states in graphene on a ferrimagnetic insulator

In the quantum Hall regime of graphene, antiferromagnetic and spin-polarized ferromagnetic states at the zeroth Landau level compete, leading to a canted antiferromagnetic state depending on the direction and magnitude of an applied magnetic field. Here, we investigate this transition at 2.7 K in graphene Hall bars that are proximity coupled to the ferrimagnetic insulator Y3Fe5O12. From nonlocal transport measurements, we demonstrate an induced magnetic exchange field in graphene, which lowers the magnetic field required to modulate the magnetic state in graphene. These results show that a magnetic proximity effect in graphene is an important ingredient for the development of two-dimensional materials in which it is desirable for ordered states of matter to be tunable with relatively small applied magnetic fields (> 6 T)

Combining teaching and research: a BIP on geophysical and archaeological prospection of North Frisian medieval settlement patterns

We performed a research-oriented EU Erasmus+ Blended Intensive Program (BIP) with participants from four countries focused on North Frisian terp settlements from Roman Iron Age and medieval times. We show that the complex terp structure and environment can be efficiently prospected using combined magnetic and EMI mapping, and seismic and geoelectric profiling and drilling. We found evidence of multiple terp phases and a harbor at the Roman Iron Age terp of Tofting. In contrast, the medieval terp of Stolthusen is more simply constructed, probably uni-phase. The BIP proved to be a suitable tool for high-level hands-on education adding value to the research conducted in on-going projects

Combined Electrical Resistivity Tomography (ERT): Direct-Push Electrical Conductivity (DP-EC) Logging and Coring, A New Methodological Approach in Geoarchaeological Research

International audienc

Flax Fibre Yarn Coated with Lignin from Renewable Sources for Composites

The present experimental work analyses the potential of lignin as a matrix for materials made from renewable resources for composite components and the production of hybrid semi-finished products by coating a flax fibre yarn. Natural fibres, due to their low density, in combination with lignin can be a new renewable source for lightweight products. For this purpose, the extrusion process was adapted to lignin as a matrix material for bio-based composites and coating of natural fibre yarns. A commercial flax yarn is the basis for the lignin coating by extrusion. Subsequently, the coated flax yarn was characterised with regard to selected yarn properties. In order to produce composite plates, the lignin-coated flax yarn was used as warp yarn in a bidirectional fabric due to its insufficient flexibility transversely to the yarn axis. The commercial flax yarn was used as weft yarn to increase the fibre volume content. The tensile and flexural properties of the bio-based composite material were determined. There was a significant difference in the mechanical properties between the warp and weft directions. The results show that lignin can be used as matrix material for bio-based natural fibre composites and the coating of natural fibre yarns is an alternative to spun hybrid yarns