Long-range acoustic communication is crucial to underwater applications such as collection of scientific data from benthic stations, ocean geology, and remote control of off-shore industrial ...activities. However, the transmission rate of acoustic communication is always limited by the narrow-frequency bandwidth of the acoustic waves because of the large attenuation for high-frequency sound in water. Here, we demonstrate a high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency. The topological charges of OAM provide intrinsically orthogonal channels, offering a unique ability to multiplex data transmission within a single acoustic beam generated by a transducer array, drastically increasing the information channels and capacity of acoustic communication. A high spectral efficiency of 8.0 ± 0.4 (bit/s)/Hz in acoustic communication has been achieved using topological charges between −4 and +4 without applying other communication modulation techniques. Such OAM is a completely independent degree of freedom which can be readily integrated with other state-of-the-art communication modulation techniques like quadrature amplitude modulation (QAM) and phase-shift keying (PSK). Information multiplexing through OAM opens a dimension for acoustic communication, providing a data transmission rate that is critical for underwater applications.
Zero index materials where sound propagates without phase variation, holds a great potential for wavefront and dispersion engineering. Recently explored electromagnetic double zero index ...metamaterials consist of periodic scatterers whose refractive index is significantly larger than that of the surrounding medium. This requirement is fundamentally challenging for airborne acoustics because the sound speed (inversely proportional to the refractive index) in air is among the slowest. Here, we report the first experimental realization of an impedance matched acoustic double zero refractive index metamaterial induced by a Dirac-like cone at the Brillouin zone centre. This is achieved in a two-dimensional waveguide with periodically varying air channel that modulates the effective phase velocity of a high-order waveguide mode. Using such a zero-index medium, we demonstrated acoustic wave collimation emitted from a point source. For the first time, we experimentally confirm the existence of the Dirac-like cone at the Brillouin zone centre.
Parity-time (PT) symmetric systems experience phase transition between PT exact and broken phases at exceptional point. These PT phase transitions contribute significantly to the design of single ...mode lasers, coherent perfect absorbers, isolators, and diodes. However, such exceptional points are extremely difficult to access in practice because of the dispersive behaviour of most loss and gain materials required in PT symmetric systems. Here we introduce a method to systematically tame these exceptional points and control PT phases. Our experimental demonstration hinges on an active acoustic element that realizes a complex-valued potential and simultaneously controls the multiple interference in the structure. The manipulation of exceptional points offers new routes to broaden applications for PT symmetric physics in acoustics, optics, microwaves and electronics, which are essential for sensing, communication and imaging.
The recent surge of interest towards deploying cyber systems in power grids exposes the resulted Smart Grids (SGs) to cyberattacks, and consequently resilience degradation. Among different possible ...remedies, i.e., prevention, mitigation, and recovery, developing a well-crafted recovery scheme following these cyberattacks can noticeably improve the system resilience. However, an appropriate resilience-based optimization problem with a metric to capture the system resilience during each step of recovery is needed to be solved and enhance it by the right decisions. To address such a concern, this paper proposes an innovative recovery framework based on a novel metric that captures the resilience posture of SGs against cyberattacks. The developed metric captures (i) Power-side Resilience (PsR) including load, available reserve capacity, available line capacity, and reliability, of which the last three are traditionally overlooked in resilience literature, and (ii) Cyber-side Resilience (CsR) considering the maximum possible implication of attacks on the power grid. PsR will calculate the physical side resilience based on immediate damage and CsR measure the cyber-side resilience e based on possible damage to the system. The SG is fully recovered from an attack when the proposed scheme brought back all the cyber and physical aspects to the proximity of the pre-disturbance conditions. For practical feasibility, we have incorporated different SG capabilities and limitations including generator Automatic Generation Control (AGC) capability and ramp rate, load variations during the recovery phase, transient stability, and multi-stage attacks. Moreover, an AC multi-island load flow is utilized to check the power balance, voltage boundaries, and transmission lines limitations in each recovery step. The proposed framework is evaluated on the 39-bus New England test system to demonstrate its effectiveness and also applied to the IEEE 30-bus test case to compare the results of the proposed approach with those of existing works. The comparisons show that the proposed approach can enhance the overall system resilience by 22% in comparison to existing works.
•Proposing a cyber–physical resilience-based recovery scheme following cyberattacks.•Introducing a multi-aspect resilience-based recovery metric, known as CPARM.•Considering attacker’s capability, such as multi-stage attack, in recovery path.•Taking into consideration the practical power system limitations and characteristics.
The aim of the study is to assess whether a blue-enriched light intervention improves nocturnal alertness and daytime sleep of night workers.
Thirteen miners performing 12-hour night shifts for 12 ...consecutive nights were exposed to a baseline and a blue-enriched light condition. All subjects wore an actigraph and completed a Psychomotor Vigilance Task at the beginning and at the end of each shift. Data were analyzed with linear mixed models.
In the blue-enriched light condition, the daily increase in median reaction time (RT), mean RT, slowest 10% of RT, and fastest 10% of RT was lower than that observed in the baseline condition between day 1 and 12 ( P ≤ 0.05).
The addition of blue-enriched light during a long period of extended night shifts counteracts most of the daily decline in nocturnal alertness observed in the standard lighting condition, irrespectively of sleep duration and sleep efficiency.
The retina is recognized as an accessible part of the brain due to their common embryonic origin. The electroretinogram (ERG) has proven to be a valuable tool for detecting schizophrenia and ...bipolarity. We therefore investigated its ability to detect ADHD.
The cone and rod luminance response functions of the ERG were recorded in 26 ADHD subjects (17 women and 9 men) and 25 controls (16 women and 9 men).
No significant differences were found between the mixed groups, but sexual dysmorphia was observed in the significant results. In males, a significant prolonged cone a-wave latency was observed in the ADHD group. In females, we observed a significant decrease in the cone a- and b-wave amplitudes and a trend for a prolonged cone b-wave latency as well as a higher scotopic mixed rod-cone a-wave in the ADHD group.
The data obtained in this study show the potential of the ERG to detect ADHD, warranting further large-scale studies.
•Electroretinography appears to be a promising biomarker for ADHD.•ADHD men shown longer cones a-wave latency than controls.•ADHD women shown reduced amplitudes of the cones a- and b-waves than controls.•Electroretinography could help in the diagnosis of several psychiatric disorders.
Partial substitution of aluminium by scandium in the wurtzite structure of aluminium nitride (AlN) leads to a large increase of the piezoelectric response by more than a factor of 2. Therefore, ...aluminium scandium nitride (ASN) thin films attracted much attention to improve piezoelectric MEMS devices such as RF filters, sensors, micro actuators and energy harvesting devices. In this work, process-microstructure-property relationships of ASN thin films containing up to 42% Sc were investigated. Like AlN thin films, ASN films are sputter deposited at 300–350°C with pulsed DC powered magnetrons. The influence of the process parameters on the film structure, the intrinsic stress and the piezoelectric response was investigated in order to achieve optimal piezoelectric coefficients up to high Sc concentrations. X-Ray diffraction (XRD) and transmission electron microscopy (TEM) were used to analyse the quality of c-axis texture. The films showed exclusively (002) texture with rocking-curve widths in the range of 1.3–2° (FHWM). The films were further analysed by scanning electron microscopy (SEM). The Sc content was determined by energy-dispersive X-ray spectroscopy (EDX). A good compositional homogeneity in the range of 0.5–1at.% was achieved between border and centre of 200-mm wafers. So far, we obtained ASN films with transversal piezoelectric coefficients of up to e31,f=−2.77C/m2, which is a factor 2.6 higher than in pure AlN thin films.
•Aluminium scandium nitride thin films with 2.6 as large transversal piezoelectric coefficient e31,f than AlN•Largest achieved e31,f=−2.77C/m2 for 42% Sc films•Semiconductor compatible sputtering process for aluminium scandium nitride with high Sc content on industrial cluster tool•C-axis textured films confirmed by XRD and TEM for up to 42% Sc
Highlights • This is a systematic review on albumin administration for fluid resuscitation in burn patients. • Previous reviews suggest that albumin increases mortality in burn patients. • 4 trials ...involving 140 patients were included in our meta-analysis. • Albumin solutions were not associated with higher mortality in burn patients. • Changes in data extraction and included trials might explain differences in outcomes.
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