High-fidelity, broadband stimulated-Brillouin-scattering-based slow light using fast noise modulation

We demonstrate a 5-GHz-broadband tunable slow-light device based on stimulated Brillouin scattering in a standard highly-nonlinear optical fiber pumped by a noise-current-modulated laser beam. The noise modulation waveform uses an optimized pseudo-random distribution of the laser drive voltage to obtain an optimal flat-topped gain profile, which minimizes the pulse distortion and maximizes pulse delay for a given pump power. Eye-diagram and signal-to-noise ratio (SNR) analysis show that this new broadband slow-light technique significantly increases the fidelity of a delayed data sequence, while maintaining the delay performance. A fractional delay of 0.81 with a SNR of 5.2 is achieved at the pump power of 350 mW using a 2-km-long highly nonlinear fiber with the fast noise-modulation method, demonstrating a 50% increase in eye-opening and a 36% increase in SNR compared to a previous slow-modulation method

Validation of EN 12354-1 prediction models by means of Intensity and Vibration measurement techniques in Spanish buildings involving flanking airborne sound transmission

Flanking transmission in building structures can be estimated using the Intensity technique according to the method described in the standard EN 15186-2 Annex C. This can also be done by using Vibration measurement technique. In situ conditions, the junctions of a room show different behaviours when compared to those obtained in laboratory. Measurements were performed to compare the results obtained by the pressure measurement procedure according to EN 140-4 and the prediction results obtained by the methods described in the standard EN 12354-1. Also the Intensity measurement technique was used to evaluate the contribution of each wall and flanking paths, which were compared with the results obtained by the Vibration measurements procedure. The main issue is to use the prediction models previously referred for validation to the particular Spanish buildings

Evaluation of flanking airborne sound transmission involving intensity and vibration measurement techniques for in situ conditions

Building structures can provide different flanking transmissions in situ condition compared to those in laboratory. Two different measurement techniques were used and compared for this paper. Both techniques measured the airborne sound insulation in buildings (between rooms) and evaluated the contribution of the partition wall and respective flanking walls. The Intensity measurement technique was used according to EN-15186-2. The Vibration measurement technique was used following some specifications of the EN-10848, this method is also evaluated as a procedure to be used instead of the Intensity technique. This paper reports the first results obtained by both techniques used in situ and estimates the overall flanking contribution for different types of junction in common Spanish buildings

Modulation instability-induced fading in phase-sensitive optical time-domain reflectometry

Phase-sensitive optical time-domain reflectometry (?OTDR) is a simple and effective tool allowing the distributed monitoring of vibrations along single-mode fibers. We show in this Letter that modulation instability (MI) can induce a position-dependent signal fading in long-range ?OTDR over conventional optical fibers. This fading leads to a complete masking of the interference signal recorded at certain positions and therefore to a sensitivity loss at these positions. We illustrate this effect both theoretically and experimentally. While this effect is detrimental in the context of distributed vibration analysis using ?OTDR, we also believe that the technique provides a clear and insightful way to evidence the Fermi?Pasta?Ulam recurrence associated with the MI process

A microdestructive capillary electrophoresis method for the analysis of blue-pen-ink strokes on office paper

This manuscript describes the development of a capillary electrophoresis (CE) method for the detection of acid and basic dyes and its application to real samples, blue-pen-ink strokes onoffice paper. First, a capillary zone electrophoresis (CZE) method was developed for the separation of basic and acid dyes, by studying the separation medium (buffer nature, pH andrelative amount of additive) and instrumental parameters (temperature, voltage and capillary dimensions). The method performance was evaluated in terms of selectivity, resolution (above 5 and 2 for acid dyes and basic dyes, respectively, except for two basic dye standards), LOD (lower than 0.4 mg/L) and precision as intraday and interday RSD values of peak migrationtimes (lower than 0.6 %). The developed method was then applied to 34 blue pens from different technologies (rollerball, ballpoint, markers) and with different ink composition (gel, 30 water-based, oil-based). A microdestructive sample treatment using a scalpel to scratch 0.3 mg of ink stroke was performed. The entire electropherogram profile allowed the visual discrimination between different types of ink and brands, being not necessary a statistical treatment. A 100% of discrimination was achieved between pen technologies, brands, and models, although non-reproducible zones in the electropherograms were found for blue gel pen samples. The two different batches of blue oil-based pens were also differentiated. Thus, this method provides a simple, microdestructive, and rapid analysis of different blue pentechnologies which may complement the current analysis of questioned documents performed by forensic laboratories

Recent advances in capillary electrophoresis instrumentation for the analysis of explosives

Capillary electrophoresis (CE) is a well-established analytical separation technique. Owing to its high versatility, major advancements have been made with regard to the instrumental set-ups during the last years. New strategies have been proposed to develop high-sensitive methods, portable CE or miniaturized devices. These techniques are of great interest in the analysis of explosives, which generally requires a highly selective approach. This review provides a recent perspective (from the beginning of 2008 to March 2015) on the use of CE for the analysis of explosives. First, a general description of explosives is made, emphasizing the role of separation techniques and specifically CE. Next, the most recent works focused on the analysis of explosives by using conventional CE, portable CE and microchip CE are compared and critically discussed. Besides, other emerging techniques for the analysis of explosives are referred and compared to CE results. Finally, future perspectives for the analysis of explosives by CE are proposed

Sidelobe apodization in optical pulse compression reflectometry for fiber optic distributed acoustic sensing

We demonstrate a technique to reduce the sidelobes in optical pulse compression reflectometry for distributed acoustic sensing. The technique is based on using a Gaussian probe pulse with linear frequency modulation. This is shown to improve the sidelobe suppression by 13 dB compared to the use of square pulses without any significant penalty in terms of spatial resolution. In addition, a 2.25 dB enhancement in signal-to-noise ratio is calculated compared to the use of receiver-side windowing. The method is tested by measuring 700 Hz vibrations with a 140 nϵ amplitude at the end of a 50 km fiber sensing link with 34 cm spatial resolution, giving a record 147,058 spatially resolved points.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri

BED: A new dataset for EEG-based biometrics

Various recent research works have focused on the use of electroencephalography (EEG) signals in the field of biometrics. However, advances in this area have somehow been limited by the absence of a common testbed that would make it possible to easily compare the performance of different proposals. In this work, we present a dataset that has been specifically designed to allow researchers to attempt new biometric approaches that use EEG signals captured by using relatively inexpensive consumer-grade devices. The proposed dataset has been made publicly accessible and can be downloaded from https://doi.org/10.5281/zenodo.4309471. It contains EEG recordings and responses from 21 individuals, captured under 12 different stimuli across three sessions. The selected stimuli included traditional approaches, as well as stimuli that aim to elicit concrete affective states, in order to facilitate future studies related to the influence of emotions on the EEG signals in the context of biometrics. The captured data were checked for consistency and a performance study was also carried out in order to establish a baseline for the tasks of subject verification and identification

EEG-based biometrics: Effects of template ageing

This chapter discusses the effects of template ageing in EEG-based biometrics. The chapter also serves as an introduction to general biometrics and its main tasks: Identification and verification. To do so, we investigate different characterisations of EEG signals and examine the difference of performance in subject identification between single session and cross-session identification experiments. In order to do this, EEG signals are characterised with common state-of-the-art features, i.e. Mel Frequency Cepstral Coefficients (MFCC), Autoregression Coefficients, and Power Spectral Density-derived features. The samples were later classified using various classifiers, including Support Vector Machines and k-Nearest Neighbours with different parametrisations. Results show that performance tends to be worse for crosssession identification compared to single session identification. This finding suggests that temporal permanence of EEG signals is limited and thus more sophisticated methods are needed in order to characterise EEG signals for the task of subject identificatio

Phase-measuring time-gated BOCDA

We demonstrate a simple scheme that allows performing distributed Brillouin phase spectrum (BPS) measurements with very high spatial resolution (~7 cm) over long (~4.7 km) optical fibers. This is achieved by inserting a Sagnac interferometer (SI) in a Brillouin optical correlation domain analysis (BOCDA) configuration. Over its already-presented time-domain equivalent (SI-BOTDA), this approach reduces the main source of noise (coherent backscatter noise) thanks to the low-coherence nature of the used signals. On the other hand, over the most usual schemes used for distributed BPS measurements, this implementation presents the key advantage of not requiring high-bandwidth detection or complex modulation while reaching unprecedented values of spatial resolution and number of resolved points for this type of measurement. Thanks to the linear dependence of the BPS feature around the Brillouin frequency shift, this scheme could also have the advantage of requiring shorter scanning ranges than amplitude-based configurations.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri