arXiv subjects

Ella Gale

Publications and source records attributed to Ella Gale.

27 records · Page 2Linked to original sources

arXiv2014

Boolean Logic Gates From A Single Memristor Via Low-Level Sequential Logic

By using the memristor's memory to both store a bit and perform an operation with a second input bit, simple Boolean logic gates have been built with a single memristor. The operation makes use of the interaction of current spikes (occasionally called current transients) found in both memristors and other devices. The sequential time-based logic methodology allows two logical input bits to be used on a one-port by sending the bits separated in time. The resulting logic gate is faster than one relying on memristor's state switching, low power and requires only one memristor. We experimentally demonstrate working OR and XOR gates made with a single flexible Titanium dioxide sol-gel memristor.

cs.ET↗

arXiv2013

The effect of changing electrode metal on solution-processed flexible titanium dioxide memristors

Flexible solution processed memristors show different behaviour dependent on the choice of electrode material. Use of gold for both electrodes leads to switchable WORM (Write Once Read Many times) resistive devices. Use of aluminium for both electrodes increases the richness of behaviour allowing both curved and triangular memristive switching resistance memories. A comparison device with an aluminium bottom electrode and gold top electrode only exhibited significant memristive resistance switching when the aluminium electrode was the cathode, suggesting that the electrode is acting as a source/sink of oxygen anions. When the gold electrode was the cathode this electrode was deformed by oxygen evolution. These results demonstrate that aluminium is helpful for stabilising and promoting memristive behaviour in sol-gel TiO$_2$ devices and that changing electrodes from aluminium to gold creates fundamentally different device characteristics.

cond-mat.mtrl-sci↗

arXiv2013

Beyond Markov Chains, Towards Adaptive Memristor Network-based Music Generation

We undertook a study of the use of a memristor network for music generation, making use of the memristor's memory to go beyond the Markov hypothesis. Seed transition matrices are created and populated using memristor equations, and which are shown to generate musical melodies and change in style over time as a result of feedback into the transition matrix. The spiking properties of simple memristor networks are demonstrated and discussed with reference to applications of music making. The limitations of simulating composing memristor networks in von Neumann hardware is discussed and a hardware solution based on physical memristor properties is presented.

cs.ET↗

arXiv2013

Comparison of Ant-Inspired Gatherer Allocation Approaches using Memristor-Based Environmental Models

Memristors are used to compare three gathering techniques in an already-mapped environment where resource locations are known. The All Site model, which apportions gatherers based on the modeled memristance of that path, proves to be good at increasing overall efficiency and decreasing time to fully deplete an environment, however it only works well when the resources are of similar quality. The Leaf Cutter method, based on Leaf Cutter Ant behaviour, assigns all gatherers first to the best resource, and once depleted, uses the All Site model to spread them out amongst the rest. The Leaf Cutter model is better at increasing resource influx in the short-term and vastly out-performs the All Site model in a more varied environments. It is demonstrated that memristor based abstractions of gatherer models provide potential methods for both the comparison and implementation of agent controls.

cs.NE↗

arXiv2013

Observation, Characterization and Modeling of Memristor Current Spikes

Memristors have been compared to neurons (usually specifically the synapses) since 1976 but no experimental evidence has been offered for support for this position. Here we highlight that memristors naturally form fast-response, highly reproducible and repeatable current spikes which can be used in voltage-driven neuromorphic architecture. Ease of fitting current spikes with memristor theories both suggests that the spikes are part of the memristive effect and provides modeling capability for the design of neuromorphic circuits.

cond-mat.mtrl-sci↗

arXiv2013

Drop-coated Titanium Dioxide Memristors

The fabrication of memristors by drop-coating sol-gel Ti(OH)$_4$ solution onto either aluminium foil or sputter-coated aluminium on plastic is presented. The gel layer is thick, 37$μ$m, but both devices exhibit good memristance I-V profiles. The drop coated aluminium foil memristors compare favourably with the sputter-coated ones, demonstrating an expansion in the accessibility of memristor fabrication. A comparison between aluminium and gold for use as the sputter-coated electrodes shows that aluminium is the better choice as using gold leads to device failure. The devices do not require a forming step.

cond-mat.mtrl-sci↗

arXiv2012

Evolution of Plastic Learning in Spiking Networks via Memristive Connections

This article presents a spiking neuroevolutionary system which implements memristors as plastic connections, i.e. whose weights can vary during a trial. The evolutionary design process exploits parameter self-adaptation and variable topologies, allowing the number of neurons, connection weights, and inter-neural connectivity pattern to emerge. By comparing two phenomenological real-world memristor implementations with networks comprised of (i) linear resistors (ii) constant-valued connections, we demonstrate that this approach allows the evolution of networks of appropriate complexity to emerge whilst exploiting the memristive properties of the connections to reduce learning time. We extend this approach to allow for heterogeneous mixtures of memristors within the networks; our approach provides an in-depth analysis of network structure. Our networks are evaluated on simulated robotic navigation tasks; results demonstrate that memristive plasticity enables higher performance than constant-weighted connections in both static and dynamic reward scenarios, and that mixtures of memristive elements provide performance advantages when compared to homogeneous memristive networks.

cs.ET↗

arXiv2012

Filamentary Extension of the Mem-Con theory of Memristance and its Application to Titanium Dioxide Sol-Gel Memristors

Titanium dioxide sol-gel memristors have two different modes of operation, believed to be dependent on whether there is bulk memristance, i.e. memristance throughout the whole volume or filamentary memristance, i.e. memristance caused by the connection of conducting filaments. The mem-con theory of memristance is based on the drift of oxygen vacancies rather than that of conducting electrons and has been previously used to describe bulk memristance in several devices. Here, the mem-con theory is extended to model memristance caused by small filaments of low resistance titanium dioxide and it compares favorably to experimental results for filamentary memristance in sol-gel devices.

cond-mat.mtrl-sci↗

arXiv2012

The Effect of Electrode Size on Memristor Properties: An Experimental and Theoretical Study

The width of the electrodes is not included in the current phenomenological models of memristance, but is included in the memory-conservation (mem-con) theory of memristance. An experimental study of the effect of changing the top electrode width was performed on titanium dioxide sol-gel memristors. It was demonstrated that both the on resistance, Ron, and the off resistance, Roff, decreased with increasing electrode size. The memory function part of the mem-con model could fit the relationship between Ron and electrode size. Similarly, the conservation function fits the change in Roff. The experimentally measured hysteresis did not fit the phenomenological model's predictions. Instead the size of the hysteresis increased with increasing electrode size, and correlated well to decreasing Ron.

cond-mat.mtrl-sci↗