Class discovery from semi-structured EEG data for affective computing and personalisation

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Many approaches to recognising emotions from metrical data such as EEG signals rely on identifying a very small number of classes and to train a classifier. The interpretation of these classes varies from a single emotion such as stress [24] to features of emotional model such as valence-arousal [4]. There are two major issues here. First classification approach limits the analysis of the data within the selected classes and is also highly dependent on training data/cycles, all of which limits generalisation. Second issue is that it does not explore the inter-relationships between the data collected missing out on any correlations that could tell us interesting facts beyond emotional recognition. This second issue would be of particular interest to psychologists and medical professions. In this paper, we investigate the use of Self-Organizing Maps (SOM) in identifying clusters from EEG signals that could then be translated into classes. We start by training varying sizes of SOM with the EEG data provided in a public dataset (DEAP). The produced graphs showing Neighbour Distance, Sample Hits, Weight Position are analysed holistically to identify patterns in the structure. Following that, we have considered the ground- truth label provided in DEAP, in order to identify correlations between the label and the clustering produced by the SOM. The results show the potential of SOM for class discovery in this particular context. We conclude with a discussion on the implications of this work and the difficulties in evaluating the outcome

Slowing light in optical fibres sees fast progress

Slowing down light to produce optical delay lines for communication networks has advanced enormously in the last year. Luc Thévenaz and Miguel Gonzalez-Herraez chart this recent progress and describe the new challenges facing developers of practical device

Broad-bandwidth Brillouin slow light in optical fibers

We experimentally demonstrate that Brillouin slow light with an arbitrary large bandwidth can be readily obtained in conventional optical fibers using a simple and inexpensive pump spectral broadening techniqu

Real time dynamic strain monitoring of optical links using the backreflection of live PSK data.

A major cause of faults in optical communication links is related to unintentional third party intrusions (normally related to civil/agricultural works) causing fiber breaks or cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic strain recorded along the cable. In this work, a novel technique is proposed to implement real-time distributed strain sensing in parallel with an operating optical communication channel. The technique relies on monitoring the Rayleigh backscattered light from optical communication data transmitted using standard modulation formats. The system is treated as a phase-sensitive OTDR (ΦOTDR) using random and non-periodical non-return-to-zero (NRZ) phase-shift keying (PSK) pulse coding. An I/Q detection unit allows for a full (amplitude, phase and polarization) characterization of the backscattered optical signal, thus achieving a fully linear system in terms of ΦOTDR trace coding/decoding. The technique can be used with different modulation formats, and operation using 4 Gbaud single-polarization dual PSK and 4 Gbaud dual-polarization quadrature PSK is demonstrated. As a proof of concept, distributed sensing of dynamic strain with a sampling of 125 kHz and a spatial resolution of 2.5 cm (set by the bit size) over 500 m is demonstrated for applied sinusoidal strain signals of 500 Hz. The limitations and possibilities for improvement of the technique are also discussed.This work was supported by the European Research Council through Starting Grant UFINE (Grant no. 307441), the Spanish MINECO through project TEC2013-45265-R, PCIN-2015- 219, and the regional program SINFOTON-CM: S2013/MIT-2790. HFM acknowledges EU funding through the FP7 ITN ICONE program, gr. #608099. SML acknowledges funding from the Spanish MINECO through a “Ramon y Cajal” contract. UK EPSRC funding through project EP/J008842/1

The effect of organic matter management on the productivity of Eucalyptus globulus stands in Spain and Portugal: tree growth and harvest residue decomposition in relation to site and treatment

Sustainable management of forest resources, including nutrient retention and protection of the soil structure, is required to ensure long-term soil fertility and productivity of later rotations. Potential depletion of soil nutrients is particularly likely in production systems based on fast-growing trees, such as eucalypts. We have studied production of second rotation Eucalyptus globulus stands at two sites in northern Spain and two in central Portugal, after replanting or coppicing, under four treatments, in which plant residues from the ®rst crop were utilised. The residues were either removed from the sites (Treatment R), spread over the soil surface (Treatments S, uniform spreading, and W, in which the woody debris was con®ned to rows between the trees) or incorporated into the soil by harrowing to 15-cm depth (Treatment I). We measured tree height and girth at intervals over three growing seasons, and root biomass at the Portuguese sites. Decomposition of three residue components: leaves-plus-bark, twigs and branches, was measured in litter bags placed in the position corresponding to the placement of the organic residues. By the end of the experiment, tree height was signi®cantly greater in Treatment I than in Treatment R at both Spanish sites, if planted as seedlings, with intermediate growth in S and W. In Portugal, tree height was smaller in R, though not signi®cantly. DBH showed similar trends, although treatment differences were not signi®cant. Coppiced trees grew faster than seedling trees, but a signi®cant treatment effect on the growth was only observed at the inland Portuguese site, where it was better in Treatment I by the end of the experiment. The residues decomposed signi®cantly faster in I than S or W at the Portuguese sites, but not in Spain. Leaves-plus-bark decomposed faster than twigs, and twigs faster than branches. The results are discussed in relation to recommended management option

Chromatic dispersion mapping by sensing the power distribution of four-wave mixing along the fiber using Brillouin probing

A new method for chromatic dispersion mapping in optical fibers is presented. It is based on measuring the CW four-wave mixing distribution created by two beams along the fiber using a Brillouin-OTDA. Experimental results demonstrate the feasibility of the techniqu

Time-Expanded F-OTDR based on binary sequences

In this paper, the capabilities of time-expanded phase-sensitive optical time-domain reflectometry (TE F-OTDR) using binary sequences are demonstrated. We present a highly flexible and integrable TE F-OTDR approach that allows a customized distributed optical fiber sensor (range, spatial resolution, and acoustic sampling) by simply changing the length of the binary sequence and the reference clock frequencies of the binary sequence generators. The here presented architecture eliminates the need for the cumbersome arbitrary signal generators used to date to create the dual-comb spectra for interrogating the fiber. In this approach, the use of large binary sequences allows us to obtain dual combs in a simple and cost-effective way. Spatial resolution of ~1 cm is achieved, attaining ~15, 000 independent measurements points along the interrogated fiber, with a capability of sensing ~30, 000 measurements points

Providing Personalized Guidance in Arithmetic Problem Solving

Supervising a student's resolution of an arithmetic word problem is a cumbersome task. Di erent students may use di erent lines of reasoning to reach the nal solution, and the assistance provided should be consistent with the resolution path that the student has in mind. In addition, further learning gains can be achieved if the previous student's background is also considered in the process. In this paper, we outline a relatively simple method to adapt the hints given by an Intelligent Tutoring System to the line of reasoning that the student is currently following. We also outline possible extensions to build a model of the student's most relevant skills, by tracking user's actions