Simultaneous Signals Research Articles

In Stanisław Lem's Orbit

In Stanisław Lem's Orbit

Characteristics of a novel alkali flame ionization detector as an air sensor for volatile organo-nitrogen compounds

A novel alkali flame ionization detector (AFID) is introduced and characterized for use as an air sensor (i.e., without chromatographic separation) for organo-nitrogen compounds. Using a planar channeled quartz design, a simple, lightweight architecture for the portable device is presented, which yields sensitive and selective response toward nitrogen-containing analytes. For instance, the AFID sensor offers a detection limit of 30 pg N/s and a selectivity for nitrogen response over carbon of nearly two orders of magnitude. Further, nitrogen response is linear over the 1000-fold range of concentrations investigated. Relative to a flame photometric detector (FPD) device also used in a sensor mode, the AFID is observed to provide 100 times greater S/N values for nitrogen analytes with a nitrogen-to-carbon selectivity that is about 15 times larger. When using the AFID and FPD sensors in tandem, it is found that the response ratio of the simultaneous signals generated by each produces characteristic values that more clearly identify the presence or absence of nitrogen in unknown analytes. The AFID sensor was used to detect organo-nitrogen analytes in several samples, and results indicate that it could be a useful approach for portable air sensing of nitrogen compounds.

Overview and Recent Advances in Hyphenated Electrochemical Techniques for the Characterization of Electroactive Materials.

A hyphenated electrochemical technique consists of the combination of the coupling of an electrochemical technique with a non-electrochemical technique, such as spectroscopical and optical techniques, electrogravimetric techniques, and electromechanical techniques, among others. This review highlights the development of the use of this kind of technique to appreciate the useful information which can be extracted for the characterization of electroactive materials. The use of time derivatives and the acquisition of simultaneous signals from different techniques allow extra information from the crossed derivative functions in the dc-regime to be obtained. This strategy has also been effectively used in the ac-regime, reaching valuable information about the kinetics of the electrochemical processes taking place. Among others, molar masses of exchanged species or apparent molar absorptivities at different wavelengths have been estimated, increasing the knowledge of the mechanisms for different electrode processes.

Deep learning seismic damage assessment with embedded signal denoising considering three-dimensional time–frequency feature correlation

Fast and accurate seismic damage assessment is crucial for timely post-earthquake evaluation and rescue. In seismic damage assessment, the correlation between ground motions in three directions during the time–frequency transform and the appropriate denoising thresholds during signal data preprocessing pose challenges for traditional methods. We propose a novel deep learning framework, DRSNet (deep residual shrinkage network), which incorporates the CNN structure of ResNet and a soft-threshold denoising module for simultaneous seismic signal denoising and damage assessment. To consider the feature correlation in time–frequency transform of seismic signals, they are first decomposed synchronously with noise-assisted multivariate empirical mode decomposition (NAMEMD) into multi-dimensional intrinsic mode functions (MIMF), and MIMFs are then transformed into seismic time–frequency maps using a non-parametric time–frequency analysis with scalable time windows and the Duhamel integral form. The subsidence and the subsidence rate of the dam are computed with finite element analysis and considered to assess seismic damage. The time–frequency maps and the finite element analysis results are used as input and output data to train DRSNet with no need for preprocessing seismic signal noise. The proposed model has been applied to a large-scale hydropower dam and achieved an average precision of 94.52% for predicting the seismic damage levels, which outperforms ResNet and ResNeSt by 3.09% and 2.62%, respectively. Thorough comparison and analysis of the model demonstrate its potential for accurate and efficient seismic damage assessment.

Coverage Probability Analysis of Amplify and Forward Based Multi-user Hybrid Satellite Terrestrial Relay Network

This article examines coverage probability for a multi-user hybrid satellite terrestrial relay network (HSTRN) with opportunistic user scheme. Better quality information are gathered via HSTRN-based networks for users on the ground. Simultaneous satellite signals are amplified by relays and relayed to terrestrial users with the highest instantaneous signal-to-noise ratio (SNR) on an individual channel. Analytically approximate coverage probability is derived for fixed and variable gain relaying. The multi-user relay network is analyzed under Nakagami-m fading, and Rician shadowed fading. We perform simulation and analytical validation to validate our study and compare the performance of fixed and variable gain relaying.

Printed soft skin electrodes for seamless bio-impedance measurements

Bio-impedance measurements are widely used to assess various physiological parameters. Contemporary skin electrodes for bio-impedance measurements are cumbersome and novel electrode designs are needed to allow fast and easy placement, long-term stability and user comfort. This investigation introduces dry, printed, bio-compatible electrode arrays, made of screen-printed carbon and inkjet-printed PEDOT:PSS that measure bio-impedance non-invasively and stably. Two contact impedance measurements yield the lowest normalized values of soft electrodes reported to date. Four contact bio-impedance measurements from the radial, ulnar, common carotid and superficial temporal arteries were performed, demonstrating the ability to capture blood pulsation in different areas with small form factor. Owing to the unique properties of the printed electrodes reported here, we were able to demonstrate for the first time blood pulsation in the face, continuous blood pulsation measurement during simultaneous muscle activation and signal stability over many hours.

Customizable self-powered pressure sensor based on piezo-transmittance of tilted structures

In the era of the Internet of Things, there is an increasing demand for specialized self-powered sensors owing to extensive applications involving an enormous number of distributed devices in numerous fields. However, realizing self-powered sensors with excellent predictability and designability to accommodate diverse application requirements remains a significant challenge because of the randomness of the nanomaterials or micro/nano-porous structures used. This report describes the development of a customizable and designable self-powered pressure sensor based on the piezo-transmittance of opaque tilted structures. The light transmittance decreases with increasing pressure owing to the deformation of tilted structures. Piezo-transmittance sensors with various linear ranges were customized by rationally designing Young’s moduli and structural parameters and optimizing cross-sectional architectures of tilted structures. The pressure sensor was fabricated by molding on 3D-printed master patterns comprising various tilted structures. Each customized sensor exhibits excellent static and dynamic responses, and responses are unaffected by light intensity, ambient temperature, and humidity. Finally, the piezo-transmittance sensors were applied to a self-powered wireless breath monitoring system that integrated flexible solar cell and Bluetooth Low Energy, an all-weather wind detection system with simultaneous signal processing and energy harvesting, and a real-time control system for teleoperated a robotic manipulation.

Relationship between vortex shedding noise and remotely-sensed surface pressure fluctuations of a structured porous-coated cylinder

Tonal noise suppression of a cylinder placed in uniform flow has been achieved, to some extent, by coating it with a structured porous material as a form of passive flow and noise control. A previously studied structured porous-coated cylinder is investigated in an anechoic wind tunnel to determine the relationship between the far-field vortex shedding noise and the pressure recorded on the outer porous surface. To date, no experimental studies have been conducted on the surface pressure of any type of porous-coated cylinder. Acoustic measurements are obtained using an equispaced microphone arc array and simultaneously unsteady surface pressure fluctuations are obtained around the cylinder mid-span circumference using remote-sensing techniques. By obtaining simultaneous time-dependent signals, more light is shed on the underlying noise-reduction mechanism of the structured porous-coated cylinder. In this paper, strong relationships between surface pressures and acoustic signals are revealed at the vortex shedding frequency. A spatio-temporal relationship between surface pressure and vortex shedding phenomena is also presented that helps explain the role of the structured porous media in passive flow and noise control.

Multi-Input Physical Layer Network Coding in Two-Dimensional Wireless Multihop Networks

This paper proposes multi-input physical layer network coding (multi-input PLNC) for high speed wireless communication in two-dimensional wireless multihop networks. In the proposed PLNC, all the terminals send their packets simultaneously for the neighboring relays to maximize the network throughput in the first slot, and all the relays also do the same to the neighboring terminals in the second slot. Those simultaneous signal transmissions cause multiple signals to be received at the relays and the terminals. Signal reception in the multi-input PLNC uses multichannel filtering to mitigate the difficulties caused by the multiple signal reception, which enables the two-input PLNC to be applied. In addition, a non-linear precoding is proposed to reduce the computational complexity of the signal detection at the relays and the terminals. The proposed multi-input PLNC makes all the terminals exchange their packets with the neighboring terminals in only two time slots. The performance of the proposed multi-input PLNC is confirmed by computer simulation. The proposed multi-input physical layer network coding achieves much higher network throughput than conventional techniques in a two-dimensional multihop wireless network with 7 terminals. The proposed multi-input physical layer network coding attains superior transmission performance in wireless hexagonal multihop networks, as long as more than 6 antennas are placed on the terminals and the relays.

The ZuCo benchmark on cross-subject reading task classification with EEG and eye-tracking data.

We present a new machine learning benchmark for reading task classification with the goal of advancing EEG and eye-tracking research at the intersection between computational language processing and cognitive neuroscience. The benchmark task consists of a cross-subject classification to distinguish between two reading paradigms: normal reading and task-specific reading. The data for the benchmark is based on the Zurich Cognitive Language Processing Corpus (ZuCo 2.0), which provides simultaneous eye-tracking and EEG signals from natural reading of English sentences. The training dataset is publicly available, and we present a newly recorded hidden testset. We provide multiple solid baseline methods for this task and discuss future improvements. We release our code and provide an easy-to-use interface to evaluate new approaches with an accompanying public leaderboard: www.zuco-benchmark.com.

Passive noise suppression in Yb-doped fiber amplifier based on nonlinear amplifying loop mirror

We investigated the frequency-dependent transfer function of amplitude noise in an all-polarization-maintaining Yb-doped fiber amplifier based on nonlinear amplifying loop mirror (NALM). We generated artificially designed amplitude noise in laser by adding weak sinusoidal modulation into the seed pulses and pump. After transmitting through the NALM-based amplifier, we obtained the amplitude-frequency and phase-frequency responses of the amplitude noise at different gains. Systematic measurements indicate that pump power optimization in the NALM-based amplifier suppresses the amplitude noises from the signal pulses and amplification pump, achieving suppression ratios exceeding 12.7 and 23.0 dB, respectively, with a simultaneous signal amplification ratio reaching 10.0 dB. Moreover, the output noise characteristics confirm that the NALM-based amplifier exhibits broadband amplitude noise and phase noise suppression. Clarifying the mechanism and bandwidth of this amplifier is necessary for low-noise laser generation because it provides insight into the nonlinear laser dynamics of broadband passive noise suppression and signal amplification.

Scalability Improvement of IEEE 802.11ah IoT Networks

In this paper, we propose a non-orthogonal multiple access (NOMA) based grouping method for IEEE 802.11ah, a promising platform for the internet of things (IoT). The grouping method improves the scalability of IoT networks, by reducing collisions in the access points (APs). The proposed method puts those IoT devices (IoT-Ds) whose channel gains are far enough from each other, i.e., who satisfy NOMA constraints, in the same group. Therefore, using successive interference cancellation (SIC), the AP is able to decode the simultaneous signal transmissions from IoT-Ds in a group. To assign IoT-Ds into groups and determine their transmission power, we formulate a total throughput maximization problem as a joint optimal grouping and power allocation problem, which is a non-convex mixed-integer programming problem. We convert it to a convex problem using quadratic fractional programming, and then we solve it using augmented Lagrange multiplier (ALM) method. Moreover, to reduce the complexity of the solution, we propose a fast grouping method to allocate power to each group in parallel. Simulation results show that the proposed methods have outstanding performance compared to conventional association identifier (AID)-based grouping method; besides, scalability of the network in terms of throughput, power consumption and channel utilization improves dramatically because of the collision reduction of IoT-Ds, which is achieved by deploying NOMA and SIC. Furthermore, the fast grouping method decreases the computational complexity greatly at the expense of a small reduction in network performance.

Paradigm and Framework of WUS-CLV Feedback Loop in Stem Cell Niche for SAM Maintenance and Cell Identity Transition

Shoot apical meristem (SAM) consists of stem cells that act as a reservoir for the aerial growth. It plays an important role in the differential architectural development in plants. SAM actively performs parallel functions by maintaining the pluripotent of stem cells and continuous organogenesis throughout the plant’s life cycle. Molecular mechanisms regulating the signaling networks of this dual function of the SAM have been progressively understood. In the SAM, the feedback loop of WUSCHEL (WUS)-CLAVATA (CLV) has been found to be the key regulator in stabilizing stem cell proliferation and differentiation. In general, WUS migrates into central zone (CZ) from organizing center (OC) and activates the expression of CLV3 by binding to the promoter elements. CLV3 acts as a ligand to interact with the CLV1, leucine rich repeats (LRR) receptor-like kinase (RLK) and LRR receptor-like protein CLV2, and protein kinase coryne (CRN) (CLV2/CRN) to restrict WUS transcription to the OC. Evolution of CLV3 is one of the main factors contributing to the transformation of two-dimensional (2D) to 3D plants. WUS-CLV loop is involved in several pathways and networks that integrate on meristem maintenance and cell identity transition. WUS-CLV maintains stem cells with simultaneous differentiation signals by the spatial-temporal signaling of the phytohormones. WUS-CLV loop has an interaction with reactive oxygen species (ROS), an important signaling molecules regulating cell proliferation and developmental transition. WUS also forms feedback loop with AGAMOUS (AG) for differentiation, proliferation, and termination of floral meristem. These loops might also involve in interaction with vernalization and its regulatory factors that oversees the precise timing of flowering after exposure to cold temperatures. In this review, we highlight the evolutionary and developmental importance of the WUS-CLV feedback loop on SAM maintenance and cell identity transition for inflorescence and floral meristem development.

Simultaneous distributed acoustic sensing and communication over a two-mode fiber.

We designed and tested a distributed acoustic sensing (DAS) that co-exists with optical communication over a two-mode fiber (TMF). In particular, we excited both linearly polarized (LP) modes, LP01 and LP11a, using a photonic lantern for simultaneous information signal transmission while collecting the backscattered Rayleigh light at the near end of the fiber to detect vibrations from a predetermined source. While transmitting data using on-off keying (OOK) or orthogonal frequency-division multiplexing (OFDM) modulation schemes, the optical fiber DAS offers high signal-to-noise ratio (SNR) values that are always larger than the minimum acceptable 2 dB SNR. In addition, as a proof-of-concept experiment, we report parallel sensing and OFDM transmission achieving a data rate of up to 4.2 Gb/s with a bit error rate (BER) of 3.2 × 10-3.

Visualizing Contralateral Suppression of Hearing Sensitivity via Acoustic and Electric Brainstem Audiometry in Bimodal Cochlear Implant Patients: A Feasibility Study

Introduction: The medial olivocochlear reflex (MOCR) is a part of the binaural processing strategies and influences the efferent auditory pathway in normal-hearing individuals. Patients with asymmetric hearing loss often benefit from a bimodal hearing solution with a cochlear implant (CI) and a hearing aid (HA). However, hearing performances may vary with some surprisingly high- or low-performing CI/HA users. A potential role of the MOCR among these patients warrants further investigation. Otoacustics emissions are an established method to visualize the reflex; however, this technique implies some disadvantages. To visualize the MOCR via auditory brainstem response (ABR) could be a promising alternative. Methods: Twenty-three bimodal CI/HA users were enrolled. Experimental setup was as follows: I. electrical ABR on the CI side was recorded with and without simultaneous contralateral noise signal at the HA side, II. acoustic ABR was recorded on the HA side with and without simultaneous contralateral noise at the CI side. Brainstem thresholds and amplitudes of waveforms I–V with and without contralateral noise were compared. Potential correlations of patient-related factors and hearing performances were analysed. Results: In four individuals, a reduction of brainstem audiometry thresholds could be observed at the acoustic brainstem audiometry. In these cases, results could be reproduced. Summarizing ABR measurements at the HA side of all individuals, no relevant changes of ABR thresholds (dB nHL) or waveform amplitude reductions (nV) could be observed irrespective of the presence or absence of a contralateral suppression signal. Conclusion: Threshold changes of acoustic ABR upon presentation of a contralateral suppression signal could not generally be measured in bimodal CI users. However, in a subgroup, a highly reproducible effect was demonstrated if a contralateral suppression signal was applied. A reactivated rather than rehabilitated MOCR may have accounted for this effect in this subgroup. One could speculate that in these patients, bimodal fitting could be affected by the MOCR efferents.

Secure Energy Efficiency Maximization for Untrusted Wireless-Powered Full-Duplex Relay Networks Under Nonlinear Energy Harvesting

In this article, we raise the concern on secure energy efficiency (SEE) over the wireless-powered untrusted relay networks with nonlinear energy harvesting (EH). To achieve data confidentiality and secrecy performance enhancement concurrently, the untrusted relay can enable simultaneous energy signal reception and confidential information forwarding during the second phase, where no dedicated energy transmission phase or relaying signal splitting is needed for the energy supply. In particular, with the help of destination jamming, the relay can also harvest energy from source signal and jamming signal during the first phase, which is different from conventional relaying protocol that only harvests energy from source and recycled energy. Considering the nonlinear EH efficiency, our objective is to maximize the SEE through piecewise region selection and power allocation. To address this intractable nonconvex problem, a two-layer algorithm based on optimization decoupling, fractional programming, Lagrange dual decomposition and difference of convex functions (DC) programming is proposed. The core idea of the proposed algorithm is to convert the primary problem into simple subproblems by sequentially exploiting the above-mentioned optimization methods. Simulation results reveal the superior secrecy performance of the proposed scheme. The proposed algorithm achieves near-optimal solutions with faster convergence rate.

Thermal performance of a single loop pulsating heat pipe with asymmetric adiabatic channel

The thermal performance of an asymmetric single-turn closed-loop pulsating heat pipe (aCLPHP) has been investigated experimentally. In an asymmetric closed-loop, the working fluids may exhibit a consistent two-phase oscillatory-circulatory flow as a direct consequence of the capillary pressure difference. The adiabatic channels of different cross-sections will cause a pressure difference, boosting the flow of heated vapor and liquid. So, a novel aCLPHP of 208 mm with an evaporator of 35 mm length was fabricated from 2.4 and 3.4 mm inner diameter copper capillary tubes. The setup was subjected to gradual and abrupt heat loads (in vertical bottom heating mode) to find out the effects of inclination angles (0°, 30°, 60°, and 90°), working fluids, and filling ratios (FR) on the thermal performance. A constant supply of coolant in the condenser chamber through a bath assisted in dissipating the heat from the heat pipe. The simultaneous temperature and pressure signals at 10 Hz were recorded through a data acquisition system to analyze the thermal performance and flow characteristics. The average thermal resistance is mapped to different operating conditions to compare the conventional (uniform cross-section) and asymmetric adiabatic channel configurations. The pseudo-steady state operation was obtained up to 100 W power supply at 60% FR of pure water in the vertical orientation. Due to asymmetry, the heat carrying capacity was increased by 75% and 50% for working fluid water and acetone, respectively. The heat pipe was operating at lower inclination angles, except horizontal orientation only with pure water. Hence, introducing an asymmetric adiabatic section is a simple, reliable, and cost-effective approach to improve the capability of a single-turn CLPHP for the thermal management of various electronic components.

Intracellular Multicomponent Synchronous DNA-Walking Strategy for the Simultaneous Quantification of Tumor-Associated Proteins in a Single Cell.

Single-cell protein analysis is very important for understanding cellular heterogeneity and single-cell biology. However, owing to the extremely low levels of some tumor-associated proteins in individual cells, the absolute quantification of such tumor-associated proteins in a single cell remains a challenge. Herein, an intracellular multicomponent synchronous DNA-walking strategy is proposed for the simultaneous quantification of multiple tumor-associated proteins in a single cell. In this strategy, a nanoprobe based on a DNA walker was designed for the simultaneous signal amplification of nucleolin (NCL) and thymidine kinase 1 (TK1) in a single cell. NCL and TK1 in single cells were simultaneously detected on a microchip platform with detection limits of 1.0 and 0.8 pM, respectively. The results obtained from 20 liver cancer cells (HepG2) and 20 normal hepatocytes (HL-7702) indicated that NCL and TK1 were overexpressed in liver cancer cells. However, the levels of NCL and TK1 in normal hepatocytes are only about one-tenth to one-sixth of those in hepatic carcinoma. Using different nucleic acid aptamers, the proposed strategy can be applied for the analysis of other single-cell proteins and in the early diagnosis of cancer.

Double inversion recovery MRI versus contrast-enhanced MRI for evaluation of knee synovitis in juvenile idiopathic arthritis

BackgroundDouble inversion recovery (DIR) MRI has the potential to accentuate the synovium without using contrast agents, as it allows simultaneous signal suppression of fluid and fat. The purpose of this study was (1) to compare DIR MRI to conventional contrast-enhanced (CE) MRI for delineation of the synovium in the knee in children with juvenile idiopathic arthritis (JIA) and (2) to assess the agreement between DIR MRI and CE-MRI regarding maximal synovial thickness measurements.ResultsIn this prospective study, 26 children with JIA who consecutively underwent 3.0-T knee MRI between January 2018 and January 2021 were included (presence of knee arthritis: 13 [50%]; median age: 14 years [interquartile range [IQR]: 11–17]; 14 girls). Median confidence to depict the synovium (0–100 mm visual analogue scale; scored by 2 readers [consensus based]) was 88 (IQR: 79–97) for DIR MRI versus 100 (IQR: 100–100) for CE-MRI (p value = < .001). Maximal synovial thickness per child (millimeters; scored by 4 individual readers) on DIR MRI was greater (p value = < .001) in the children with knee arthritis (2.4 mm [IQR: 2.1–3.1]) than in those without knee arthritis (1.4 mm [IQR: 1.0–1.6]). Good inter-technique agreement for maximal synovial thickness per child was observed (rs = 0.93 [p value = < .001]; inter-reader reliability: ICC DIR MRI = 0.87 [p value = < .001], ICC CE-MRI = 0.90 [p value = < .001]).ConclusionDIR MRI adequately delineated the synovium in the knee of children with JIA and enabled synovial thickness measurement similar to that of CE-MRI. Our results demonstrate that DIR MRI should be considered as a child-friendly alternative to CE-MRI for evaluation of synovitis in children with (suspected) JIA.

Sampling Parallel SOA-MZIs Configuration for All-Optical Simultaneous Frequency Down-Conversion

In this paper, we expound a modulation concept to contrive simultaneous frequency down-conversion based on a three parallel Semiconductor Optical Amplifier Mach-Zehnder Interferometers (SOA-MZIs) link by using a band pass sampling method in a Virtual Photonics Inc. simulator. Each SOA-MZI is deployed to achieve a down-converted signal, which has ten replicas related to the first ten harmonic ranks of the sampling signal, at the SOA-MZI outer port. Then, the admixture of the three down-converted signals yields a sampled signal, which is called a simultaneous down-converted signal that contains thirty different replicas. The positive down-conversion gains with top values are reached with the sampling parallel SOA-MZIs link. Moreover, we evaluated the quality of the parallel SOA-MZIs transmission system over orthogonal frequency division multiplexing (OFDM) complex modulated signals using the error vector magnitude values as a performance index. The utmost bit rate attained is 2 Gbit/s for OFDM modulations.