Browsing by Author "Sirakoulis, Georgios C."

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    1-D memristor-based cellular automaton for pseudo-random number generation
    (IEEE, 2017) Karamani, Rafailia Eleni; Ntinas, Vasileios; Vourkas, Ioannis; Sirakoulis, Georgios C.
    Cellular Automata (CAs) is a well-known parallel, bio-inspired, computational model. It is based on the capability of simpler, locally interacting units, i.e. the CAs cells, to evolve in time, giving rise to emergent computation, suitable to model physical system behavior, prediction of natural phenomena and multi-dimensional problem solutions. Moreover, at the same time CAs constitute a promising computing platform, beyond the von Neumann architecture. In this paper, a memristor device is considered to be the basic module of a CA cell circuit implementation, performing as a combined memory and processing element to implement CA-based circuits, able to model sufficiently systems and applications as mentioned above, targeting tentatively to a more energy efficient design compared to the conventional electronics. In particular and as a proof of concept, the results of elementary CAs modeling and simulation for the generation of pseudo-random numbers are presented using a 1-D memristor-based CAs array to illustrate the robustness and the efficacy of the proposed computing approach.
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    A Digital Memristor Emulator for FPGA-Based Artificial Neural Networks
    (IEEE, 2016) Vourkas, Ioannis; Abusleme Hoffman, Ángel Christian; Ntinas, Vasileios; Sirakoulis, Georgios C.; Rubio, Antonio
    FPGAs are reconfigurable electronic platforms, well-suited to implement complex artificial neural networks (ANNs). To this end, the compact hardware (HW) implementation of artificial synapses is an important step to obtain human brain-like functionalities at circuit-level. In this context, the memristor has been proposed as the electronic analogue of biological synapses, but the price of commercially available samples still remains high, hence motivating the development of HW emulators. In this work we present the first digital memristor emulator based upon a voltage-controlled threshold-type bipolar memristor model. We validate its functionality in low-cost yet powerful FPGA families. We test its suitability for complex memristive circuits and prove its synaptic properties in a small associative memory via a perceptron ANN.
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    Exploring the voltage divider approach for accurate memristor state tuning
    (IEEE, 2017) Vourkas, Ioannis; Gómez Luna, Jorge Antonio; Abusleme Hoffman, Ángel Christian; Vasileiadis, Nikolaos; Sirakoulis, Georgios C.; Rubio, Antonio
    The maximum exploitation of the favorable properties and the analog nature of memristor technology in future nonvolatile resistive memories, requires accurate multi-level programming. In this direction, we explore the voltage divider (VD) approach for highly controllable multi-state SET memristor tuning. We present the theoretical basis of operation, the main advantages and weaknesses. We finally propose an improved closed-loop VD SET scheme to tackle the variability effect and achieve <;1% tuning precision, on average 3x faster than another accurate tuning algorithm of the recent literature.