4,375 research outputs found
DropIn: Making Reservoir Computing Neural Networks Robust to Missing Inputs by Dropout
The paper presents a novel, principled approach to train recurrent neural
networks from the Reservoir Computing family that are robust to missing part of
the input features at prediction time. By building on the ensembling properties
of Dropout regularization, we propose a methodology, named DropIn, which
efficiently trains a neural model as a committee machine of subnetworks, each
capable of predicting with a subset of the original input features. We discuss
the application of the DropIn methodology in the context of Reservoir Computing
models and targeting applications characterized by input sources that are
unreliable or prone to be disconnected, such as in pervasive wireless sensor
networks and ambient intelligence. We provide an experimental assessment using
real-world data from such application domains, showing how the Dropin
methodology allows to maintain predictive performances comparable to those of a
model without missing features, even when 20\%-50\% of the inputs are not
available
Concentric ESN: Assessing the Effect of Modularity in Cycle Reservoirs
The paper introduces concentric Echo State Network, an approach to design
reservoir topologies that tries to bridge the gap between deterministically
constructed simple cycle models and deep reservoir computing approaches. We
show how to modularize the reservoir into simple unidirectional and concentric
cycles with pairwise bidirectional jump connections between adjacent loops. We
provide a preliminary experimental assessment showing how concentric reservoirs
yield to superior predictive accuracy and memory capacity with respect to
single cycle reservoirs and deep reservoir models
Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer
During the first steps of photosynthesis, the energy of impinging solar photons is transformed into electronic excitation energy of the light-harvesting biomolecular complexes. The subsequent energy transfer to the reaction center is commonly rationalized in terms of excitons moving on a grid of biomolecular chromophores on typical timescales [Formula: see text]100 fs. Today's understanding of the energy transfer includes the fact that the excitons are delocalized over a few neighboring sites, but the role of quantum coherence is considered as irrelevant for the transfer dynamics because it typically decays within a few tens of femtoseconds. This orthodox picture of incoherent energy transfer between clusters of a few pigments sharing delocalized excitons has been challenged by ultrafast optical spectroscopy experiments with the Fenna-Matthews-Olson protein, in which interference oscillatory signals up to 1.5 ps were reported and interpreted as direct evidence of exceptionally long-lived electronic quantum coherence. Here, we show that the optical 2D photon echo spectra of this complex at ambient temperature in aqueous solution do not provide evidence of any long-lived electronic quantum coherence, but confirm the orthodox view of rapidly decaying electronic quantum coherence on a timescale of 60 fs. Our results can be considered as generic and give no hint that electronic quantum coherence plays any biofunctional role in real photoactive biomolecular complexes. Because in this structurally well-defined protein the distances between bacteriochlorophylls are comparable to those of other light-harvesting complexes, we anticipate that this finding is general and directly applies to even larger photoactive biomolecular complexes
Human activity recognition using multisensor data fusion based on Reservoir Computing
Activity recognition plays a key role in providing activity assistance and care for users in smart homes. In this work, we present an activity recognition system that classifies in the near real-time a set of common daily activities exploiting both the data sampled by sensors embedded in a smartphone carried out by the user and the reciprocal Received Signal Strength (RSS) values coming from worn wireless sensor devices and from sensors deployed in the environment. In order to achieve an effective and responsive classification, a decision tree based on multisensor data-stream is applied fusing data coming from embedded sensors on the smartphone and environmental sensors before processing the RSS stream. To this end, we model the RSS stream, obtained from a Wireless Sensor Network (WSN), using Recurrent Neural Networks (RNNs) implemented as efficient Echo State Networks (ESNs), within the Reservoir Computing (RC) paradigm. We targeted the system for the EvAAL scenario, an international competition that aims at establishing benchmarks and evaluation metrics for comparing Ambient Assisted Living (AAL) solutions. In this paper, the performance of the proposed activity recognition system is assessed on a purposely collected real-world dataset, taking also into account a competitive neural network approach for performance comparison. Our results show that, with an appropriate configuration of the information fusion chain, the proposed system reaches a very good accuracy with a low deployment cost
Sparsity in Reservoir Computing Neural Networks
Reservoir Computing (RC) is a well-known strategy for designing Recurrent
Neural Networks featured by striking efficiency of training. The crucial aspect
of RC is to properly instantiate the hidden recurrent layer that serves as
dynamical memory to the system. In this respect, the common recipe is to create
a pool of randomly and sparsely connected recurrent neurons. While the aspect
of sparsity in the design of RC systems has been debated in the literature, it
is nowadays understood mainly as a way to enhance the efficiency of
computation, exploiting sparse matrix operations. In this paper, we empirically
investigate the role of sparsity in RC network design under the perspective of
the richness of the developed temporal representations. We analyze both
sparsity in the recurrent connections, and in the connections from the input to
the reservoir. Our results point out that sparsity, in particular in
input-reservoir connections, has a major role in developing internal temporal
representations that have a longer short-term memory of past inputs and a
higher dimension.Comment: This paper is currently under revie
Radar Sensing in Assisted Living: An Overview
This paper gives an overview of trends in radar sensing for assisted living. It focuses on signal processing and classification, looking at conventional approaches, deep learning and fusion techniques. The last section shows examples of classification in human activity recognition and medical applications, e.g. breathing disorder and sleep stages recognition
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