Multiple Arrays Research Articles

Closed-Form Rectilinear Emitters Localization With Multiple Sensor Arrays: Phase Alignment and Optimal Weighted Least-Square Method

Position determination algorithms of rectilinear emitters (also called strictly second-order noncircular emitters) with multiple sensor arrays (SAs) allow for higher localization accuracy and more achievable degrees of freedom compared to the conventional version with circular emitters. However, it also brings additional computational complexity and noise. In this article, we develop a position determination algorithm of rectilinear emitters in closed-form on the basis of phase alignment and optimal weighted least square (OWLS), which is termed the PAOWLS method. First, we utilize the polynomial root-finding method to obtain the angle of arrival (AOA) and estimate rectilinear phases to align AOA. Then, we construct a least-square (LS) constraint to estimate the positions of emitters directly (termed the PALS method). Finally, we construct a weighted LS constraint and deduce the optimal weight to compensate for the position estimation bias. Extensive numerical results verify the outstanding performance of the proposed algorithm in terms of localization accuracy, resolution capability, and computational complexity.

Optimizing electrode positions on forearm to increase SNR and myoelectric pattern recognition performance

With the advances in electromyography-based human–computer interaction, particularly in myoelectric prosthetic hands, the position of electromyography electrodes has gained less attention from researchers. However, the performance of hand movement recognition significantly varies with the change of electrode position around the forearm muscles and along the length of the forearm muscles. To find the robust position on the forearm, this study performs a comprehensive and systematic investigation of the feasibility of hand movement recognition using electromyogram (EMG) signals concurrently recorded for sixteen electrode arrays on the forearm. The obtained results indicate that the electrode array placed on the middle of the extensor digitorum communis and extensor digiti minimi performs better than other electrode positions around the forearm. In addition, multiple electrode arrays placed near to elbow joint achieve a significantly higher signal to noise ratio and signal to movement artifact ratio. In addition to improved EMG signal quality, the recommended positions on the forearm significantly overperform in hand movement recognition and it is validated with five well-known feature extraction methods, various window sizes, and three classification algorithms. In this study, the electrode arrays near to elbow joint on the forearm achieve an F1 score of 98.28% to 98.80% with a linear discriminant analysis classifier. Therefore, this study clearly demonstrates the feasibility of recommended forearm positions for hand movement recognition. As these electrode positions are near to elbow joint, so, it is expected that these positions will be available in most amputees and utilized for improved hand movement recognition.

Abdominal MR elastography with multiple driver arrays: performance and repeatability.

To evaluate the performance and repeatability assessing liver, spleen, and kidney stiffness with magnetic resonance elastography (MRE), using arrays of pneumatic passive drivers. An array of four flexible, pneumatically activated passive drivers for abdominal MRE were developed and tested in this study. Multiple MRE acquisitions were performed prospectively in a series of eleven volunteers, with activation of all combinations of the four drivers, individually and simultaneously. MRE exams were repeated three times to study within-day and between-day test-retest repeatability. Semi-quantitative evaluation of wave propagation and penetration, and quantitative assessment of tissue stiffness was conducted for liver, spleen, and kidneys. When driver location and amplitude were sufficient to achieve necessary shear wave illumination in any given region of interest, the results showed excellent test-retest repeatability in abdominal organ stiffness with both single and multiple driver configurations. The results confirmed that multiple driver arrays provided suitable shear wave illumination over a larger region of the abdomen, allowing more reliable stiffness measurements in multiple organs. MRE assessment of the spleen was found to be prone to effects of excessive shear wave amplitude, however. A multiple driver array provides shear wave illumination over a larger region of the abdomen than obtained with a single driver, for MRE assessment of multiple abdominal organs, providing excellent test-retest repeatability in stiffness measurements. However, careful tuning of the location and amplitude of each driver is essential to achieve consistent results.

Electrophysiological Activity of Primary Cortical Neuron-Glia Mixed Cultures.

Neuroinflammation plays a central role in many neurological disorders, ranging from traumatic brain injuries to neurodegeneration. Electrophysiological activity is an essential measure of neuronal function, which is influenced by neuroinflammation. In order to study neuroinflammation and its electrophysiological fingerprints, there is a need for in vitro models that accurately capture the in vivo phenomena. In this study, we employed a new tri-culture of primary rat neurons, astrocytes, and microglia in combination with extracellular electrophysiological recording techniques using multiple electrode arrays (MEAs) to determine the effect of microglia on neural function and the response to neuroinflammatory stimuli. Specifically, we established the tri-culture and its corresponding neuron-astrocyte co-culture (lacking microglia) counterpart on custom MEAs and monitored their electrophysiological activity for 21 days to assess culture maturation and network formation. As a complementary assessment, we quantified synaptic puncta and averaged spike waveforms to determine the difference in excitatory to inhibitory neuron ratio (E/I ratio) of the neurons. The results demonstrate that the microglia in the tri-culture do not disrupt neural network formation and stability and may be a better representation of the in vivo rat cortex due to its more similar E/I ratio as compared to more traditional isolated neuron and neuron-astrocyte co-cultures. In addition, only the tri-culture displayed a significant decrease in both the number of active channels and spike frequency following pro-inflammatory lipopolysaccharide exposure, highlighting the critical role of microglia in capturing electrophysiological manifestations of a representative neuroinflammatory insult. We expect the demonstrated technology to assist in studying various brain disease mechanisms.

The test-retest reproducibility of the multiple array probe Leiden in men with lower urinary tract symptoms.

We aimed to study the test-retest reliability of the Multiple Array Probe Leiden (MAPLe), a multiple electrode probe designed to acquire and discriminate electromyography signals in the pelvic floor muscles, in men with lower urinary tract symptoms (LUTS). Adult male patients with LUTS with sufficient knowledge of Dutch language, but without complications (e.g., urinary tract infection), or previous urologic cancer and/or urologic surgery were enrolled. In the initial study, next to physical examination and uroflowmetry, all men underwent MAPLe assessment at baseline and after 6 weeks. Second, participants were reinvited for a new assessment using a stricter protocol. A time interval of 2 h (M2) and 1 week (M3) after baseline (M1) allowed the calculation of the intraday agreement (M1 vs. M2), and the interday agreement (M1 vs. M3) for all 13 MAPLe variables. The outcomes of the initial study in 21 men suggested a poor test-retest reliability. The second study in 23 men showed a good test-retest reliability with intraclass correlations ranging from 0.61 (0.12-0.86) to 0.91 (0.81-0.96). The agreement was generally higher for the intraday determinations than for the interday determinations. This study revealed a good test-retest reliability of the MAPLe device in men with LUTS, when using a strict protocol. With a less strict protocol, the test-retest reliability of MAPLe was poor in this sample. To make valid interpretations of this device in a clinical or research setting, a strict protocol is needed.

Correlating shipping noise on multiple beams

There has been much interest in using transiting surface ships as sources of opportunity for tomography and geo acoustic inversion. In tomography, it would be valuable to increase the ranges at which ship signatures can be processed by measuring times of arrival at the output of beamforming processes, which provide spatial processing gain. This additional gain may enable fainter multipath arrivals to be identified and exploited as additional paths to sample the ocean water column. This seems readily achievable when cross-correlating multiple vertical beams formed on a single vertical line array for example. However, cross-correlating beams from multiple arrays, vertical or horizontal, raises questions. In both cases, different beams may have different Doppler, which is manageable with a correlation process that includes Doppler compensation. But obeserving a ship from different vantage points may be problematic, if the ship signature is due to horizontally displaced noise sources distributed around the ship. We will present results of processing surface ships observed on single and multiple arrays and assess the use of such processing in ambient noise tomography.

Area-Efficient Parallel Multiplication Units for CNN Accelerators With Output Channel Parallelization

Many existing studies on accelerating convolutional neural networks (CNNs) use parallel data operation schemes to increase the throughput. This study proposes area-efficient parallel multiplication unit (PMU) designs for a CNN accelerator that uses parallelization on the output channels of a CNN layer, which parallel multiplies a common feature map pixel with multiple CNN kernel weights. First, tailored PMU designs are proposed for CNNs with specific low-precision 3-to-8-bit weights. Second, the proposed 5-to-8-bit PMU designs are extended with two-clock-cycle operations to develop PMUs for weight precision scalable to 10/12/14/16 bits. Compared to 16-path PMUs directly using carry-save-adder array multipliers, our PMU designs can achieve the area reductions of 28.19%−56.09% and 22.10%−30.71% for 3–8 bit and 10-/12-/14-/ 16-bit weights, respectively. Moreover, a resultant 16-path 16-bit weight PMU is verified through the system-on-chip (SoC) field-programmable gate array (FPGA) implementation to demonstrate the CNN inference.

State-Of-The-Art On Reversible Multiplier Architectures and Its Comparison for Future Quantum Computing

Multiplication is the key crucial operation in realizing digital signal processing (DSP) functions. It is accomplished by using diverse multiplier architectures. Multiplication operation is furthermost basic and normally used action in the central processing unit (CPU). The multiplication operation is the most fundamental and commonly performed activity in the central processing unit (CPU). An efficient multiplier design should have a high speed, small area, and a low power consumption. Compact, efficient multipliers with minimal power dissipation are needed. The proposed paper provides a thorough inspection of multipliers such as the Array multiplier, Booth multiplier, column bypass multiplier, Baugh-Wooley multiplier, and Vedic multiplier based on their operational activities and working, as well as their benefits and limits. A comparison of these multipliers' performance parameters such as speed, area, power consumption, quantum cost, garbage generation and circuit complexity.

Imaging ocean water columns by acoustic contrast reflection signals in existing marine seismic data

Marine seismic surveys conducted for oil and gas exploration use a source-receiver system consisting of airgun sources and hydrophone receiver arrays. The collected data were commonly used to image subsurface beneath the seafloor. The surveys had also collected signals of acoustic reflections from ocean water columns due to acoustic impedance contrast by temperature and salinity. These signals can be processed to provide high-resolution images of the water-column structures such as eddies and internal waves, forming a discipline termed as seismic oceanography in the literature. Acoustic contrast reflection signals in a three-dimensional seismic survey, collected by multiple parallel receiver arrays, can even be used to explore movements of water columns {see our recent study in [Zou,etal., Ocean Sci. 17(4), 1053–1066 (2021)]}. Nevertheless, because of the low acoustic impedance contrast in oceans, these water-column reflection signals are extremely weak, e.g., about 2–3 orders weaker than the seafloor reflections. Meanwhile, these signals consist of acoustic multipath features that require an appropriate filtering of the signals (see our recent study in the study by Zou and Zhang [JASA 150(5), 3852–3860 (2021)]. Understanding of the signal features and appropriate applications of acoustic signal processing methods are inspired to improve the imaging quality.

3-D Coherent Multi-Transducer Ultrasound Imaging with Sparse Spiral Arrays.

Coherent multi-transducer ultrasound (CoMTUS) creates an extended effective aperture through the coherent combination of multiple arrays, which results in images with enhanced resolution, extended field-of-view, and higher sensitivity. The subwavelength localization accuracy of the multiple transducers required to coherently beamform the data is achieved by using the echoes backscattered from targeted points. In this study, CoMTUS is implemented and demonstrated for the first time in 3-D imaging using a pair of 256-element 2-D sparse spiral arrays, which keep the channel count low and limit the amount of data to be processed. The imaging performance of the method was investigated using both simulations and phantom tests. The feasibility of free-hand operation is also experimentally demonstrated. Results show that, in comparison to a single dense array system using the same total number of active elements, the proposed CoMTUS system improves spatial resolution (up to 10 times) in the direction where both arrays are aligned, contrast-to-noise-ratio (CNR, up to 46%), and generalized CNR (up to 15%). Overall, CoMTUS shows a narrower main lobe and higher contrast-to-noise ratio, which results in an increased dynamic range and better target detectability.

Surface Crack Monitoring by Rayleigh Waves with a Piezoelectric-Polymer-Film Ultrasonic Transducer Array.

This paper presents a method for measuring surface cracks based on the analysis of Rayleigh waves in the frequency domain. The Rayleigh waves were detected by a Rayleigh wave receiver array made of a piezoelectric polyvinylidene fluoride (PVDF) film and enhanced by a delay-and-sum algorithm. This method employs the determined reflection factors of Rayleigh waves scattered at a surface fatigue crack to calculate the crack depth. In the frequency domain, the inverse scattering problem is solved by comparing the reflection factor of the Rayleigh waves between the measured and the theoretical curves. The experimental measurement results quantitatively matched the simulated surface crack depths. The advantages of using the low-profile Rayleigh wave receiver array made of a PVDF film for detecting the incident and reflected Rayleigh waves were analyzed in contrast with those of a Rayleigh wave receiver using a laser vibrometer and a conventional lead zirconate titanate (PZT) array. It was found that the Rayleigh waves propagating across the Rayleigh wave receiver array made of the PVDF film had a lower attenuation rate of 0.15 dB/mm compared to that of 0.30 dB/mm of the PZT array. Multiple Rayleigh wave receiver arrays made of the PVDF film were applied for monitoring surface fatigue crack initiation and propagation at welded joints under cyclic mechanical loading. Cracks with a depth range of 0.36-0.94 mm were successfully monitored.

The Use of AI and Algorithms for Decision-making in Workplace Recruitment Practices

The use of artificial intelligence (AI) and algorithms in human resource management systems has increased in recent years significantly due to the COVID-19 pandemic and the rise of remote work. Research has shown that implementing AI systems in different workplace scenarios increases efficiency, reduces worktime, production and labor costs and the need for human workers to perform the tasks that AI systems can perform. Within human resource management practices, AI systems have been employed to do a multiple array of tasks such as: screening candidates, performance evaluations, facial and voice analysis during candidate interviews, training, and development. Other recruitment practices that employ AI systems are considered to have implications that make employers liable for possible discrimination which could occur as an adverse effect of having these systems partake in the decision-making process for employee selection. Certain authors have recognized the lack of the human factor in this process as detrimental and increases the possibility of error and bias in selection of candidates.
 This study explored the use of these AI systems in the workplace and what regulations have been created to oversee how they can be employed for recruitment practices. It also aims to highlight the positive and negative impact of these AI supported practices. The results highlight the importance of regulating these practices as an effort to protect minority rights and privacy rights of people that are seeking employment. Identifying international and national legislation is necessary for adopting better regulated practices and guaranteeing worker’s rights.

FourierPIM: High-throughput in-memory Fast Fourier Transform and polynomial multiplication

The Discrete Fourier Transform (DFT) is essential for various applications ranging from signal processing to convolution and polynomial multiplication. The groundbreaking Fast Fourier Transform (FFT) algorithm reduces DFT time complexity from the naive O(n2) to O(nlogn), and recent works have sought further acceleration through parallel architectures such as GPUs. Unfortunately, accelerators such as GPUs cannot exploit their full computing capabilities since memory access becomes the bottleneck. Therefore, this paper accelerates the FFT algorithm using digital Processing-in-Memory (PIM) architectures that shift computation into the memory by exploiting physical devices capable of both storage and logic (e.g., memristors). We propose an O(logn) in-memory FFT algorithm that can also be performed in parallel across multiple arrays for high-throughput batched execution, supporting both fixed-point and floating-point numbers. Through the convolution theorem, we extend this algorithm to O(logn) polynomial multiplication – a fundamental task for applications such as cryptography. We evaluate FourierPIM on a publicly-available cycle-accurate simulator that verifies both correctness and performance, and demonstrate 5–15× throughput and 4–13× energy improvement over the NVIDIA cuFFT library on state-of-the-art GPUs for FFT and polynomial multiplication.

Direct tracking of noncircular sources for multiple arrays via improved unscented particle filter method

AbstractDirect tracking problem of moving noncircular sources for multiple arrays is investigated in this study. Here, we propose an improved unscented particle filter (I‐UPF) direct tracking method, which combines system proportional symmetry unscented particle filter and Markov Chain Monte Carlo (MCMC) algorithm. Noncircular sources can extend the dimension of sources matrix, and the direct tracking accuracy is improved. This method uses multiple arrays to receive sources. Firstly, set up a direct tracking model through consecutive time and Doppler information. Subsequently, based on the improved unscented particle filter algorithm, the proposed tracking model is to improve the direct tracking accuracy and reduce computational complexity. Simulation results show that the proposed improved unscented particle filter algorithm for noncircular sources has enhanced tracking accuracy than Markov Chain Monte Carlo unscented particle filter algorithm, Markov Chain Monte Carlo extended Kalman particle filter, and two‐step tracking method.

Melatonin and Health: Insights of Melatonin Action, Biological Functions, and Associated Disorders.

Melatonin is ubiquitous molecule with wide distribution in nature and is produced by many living organisms. In human beings, pineal gland is the major site for melatonin production and to lesser extent by retina, lymphocytes, bone marrow, gastrointestinal tract, and thymus. Melatonin as a neurohormone is released into circulation wherein it penetrates all tissues of the body. Melatonin synthesis and secretion is supressed by light and enhanced by dark. Melatonin mostly exerts its effect through different pathways with melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2) being the predominant type of receptor that are mainly expressed by many mammalian organs. Melatonin helps to regulate sleep patterns and circadian rhythms. In addition, melatonin acts as an antioxidant and scavenges excessive free radicals generated in the body by anti-excitatory and anti-inflammatory properties. A multiple array of other functions are displayed by melatonin that include oncostatic, hypnotic, immune regulation, reproduction, puberty timing, mood disorders, and transplantation. Deficiencies in the production or synthesis of melatonin have been found to be associated with onset of many disorders like breast cancer and neurodegenerative disorders. Melatonin could be used as potential analgesic drug in diseases associated with pain and it has quite promising role there. In the past century, a growing interest has been developed regarding the wide use of melatonin in treating various diseases like inflammatory, gastrointestinal, cancer, mood disorders, and others. Several melatonin agonists have been synthesized and are widely used in disease treatment. In this review, an effort has been made to describe the biochemistry of melatonin along with its therapeutic potential in various diseases of humans.

Assembly of the 81.6 Mb centromere of pea chromosome 6 elucidates the structure and evolution of metapolycentric chromosomes.

Centromeres in the legume genera Pisum and Lathyrus exhibit unique morphological characteristics, including extended primary constrictions and multiple separate domains of centromeric chromatin. These so-called metapolycentromeres resemble an intermediate form between monocentric and holocentric types, and therefore provide a great opportunity for studying the transitions between different types of centromere organizations. However, because of the exceedingly large and highly repetitive nature of metapolycentromeres, highly contiguous assemblies needed for these studies are lacking. Here, we report on the assembly and analysis of a 177.6 Mb region of pea (Pisum sativum) chromosome 6, including the 81.6 Mb centromere region (CEN6) and adjacent chromosome arms. Genes, DNA methylation profiles, and most of the repeats were uniformly distributed within the centromere, and their densities in CEN6 and chromosome arms were similar. The exception was an accumulation of satellite DNA in CEN6, where it formed multiple arrays up to 2 Mb in length. Centromeric chromatin, characterized by the presence of the CENH3 protein, was predominantly associated with arrays of three different satellite repeats; however, five other satellites present in CEN6 lacked CENH3. The presence of CENH3 chromatin was found to determine the spatial distribution of the respective satellites during the cell cycle. Finally, oligo-FISH painting experiments, performed using probes specifically designed to label the genomic regions corresponding to CEN6 in Pisum, Lathyrus, and Vicia species, revealed that metapolycentromeres evolved via the expansion of centromeric chromatin into neighboring chromosomal regions and the accumulation of novel satellite repeats. However, in some of these species, centromere evolution also involved chromosomal translocations and centromere repositioning.

Machine-learning-based simultaneous detection and ranging of impulsive baleen whale vocalizations using a single hydrophone.

The low-frequency impulsive gunshot vocalizations of baleen whales exhibit dispersive propagation in shallow-water channels which is well-modeled by normal mode theory. Typically, underwater acoustic source range estimation requires multiple time-synchronized hydrophone arrays which can be difficult and expensive to achieve. However, single-hydrophone modal dispersion has been used to range baleen whale vocalizations and estimate shallow-water geoacoustic properties. Although convenient when compared to sensor arrays, these algorithms require preliminary signal detection and human labor to estimate the modal dispersion. In this paper, we apply a temporal convolutional network (TCN) to spectrograms from single-hydrophone acoustic data for simultaneous gunshot detection and ranging. The TCN learns ranging and detection jointly using gunshots simulated across multiple environments and ranges along with experimental noise. The synthetic data are informed by only the water column depth, sound speed, and density of the experimental environment, while other parameters span empirically observed bounds. The method is experimentally verified on North Pacific right whale gunshot data collected in the Bering Sea. To do so, 50 dispersive gunshots were manually ranged using the state-of-the-art time-warping inversion method. The TCN detected these gunshots among 50 noise-only examples with high precision and estimated ranges which closely matched those of the physics-based approach.

Curved Computer-Generated Integral Imaging Based on Backward Ray-Tracing Technique

In traditional computer-generated integral imaging (CGII) methods, the generated elemental image array (EIA) is flat, and it doesn't fit for curved integral imaging (II) systems. Here, a curved CGII method was proposed for curved II system. In the proposed method, multiple virtual camera arrays (VCAs) were built up to determine the origins and directions of the traced rays. Combined with the backward ray-tracing (BRT) technique, a curved EIA was generated, and the rendering time was the same as the BRT-CGII of flat II system. A curved II system consisting of a curved organic light emitting diode display screen, a curved lens array and a curved optical diffuser screen was built up in the experiment. The proposed curved CGII method generated correct curved EIA for the curved II system, and the system presented vivid 3D images with the viewing angle as wide as 80° × 50°.

The 2021 Mw 7.3 Madoi, China Earthquake: Transient Supershear Ruptures on a Presumed Immature Strike‐Slip Fault

AbstractWe used seismic data recorded at local and teleseismic distances to analyze the May 22, 2021 Mw 7.3 Madoi, China earthquake sequence, which occurred along a low‐slip‐rate (0.3–1.0 mm/yr) and small‐cumulative‐displacement (4–5 km) fault—the Kunlun Mountain Pass‐Jiangcuo Fault (KMPJF). We first restored the clipped waveforms recorded at local distances, and obtained more accurate phase arrivals for relocating the earthquake sequence. The relocated earthquakes illuminate a ∼170 km‐long complex northwest‐southeast (NW‐SE) striking ruptured fault with apparent bifurcated ends at both tips and variations in dip angles along strike. We further performed backprojection analyses to image the rupture process of the mainshock using seismic data recorded at four teleseismic arrays (Europe, Australia and Southeast Asia, Japan, and Alaska). The results show that the earthquake propagated bilaterally in the NW and SE directions with maximum rupture speeds of ∼4.0 km/s. This observation was further refined by multiple array backprojections onto the fault that was determined by the fine relocations of the earthquake sequence. Synthetic and realistic tests validated the resolutions of the backprojection analyses (within 5–20 km). The fast supershear rupture speeds were only transient but exhibited spatial correlation with the geometric complexities of the KMPJF. This suggests that the transient supershear ruptures are due to the varying geometry of the KMPJF, which is likely an immature fault. Our results suggest that the potential for supershear ruptures along immature strike‐slip faults should be emphasized in earthquake hazard assessment.

Coherent signal localization with multiple arrays: a successive perspective

Coherent signal localization with multiple arrays: a successive perspective