Horizontal Array Research Articles

3D Reconstruction of Slug Flow in Mini-Channels with a Simple and Low-Cost Optical Sensor.

The present work provides a new approach for 3D image reconstruction of gas-liquid two-phase flow (GLF) in mini-channels based on a new optical sensor. The sensor consists of a vertical and a horizontal photodiode array. Firstly, with the optical signals obtained by the vertical array, a measurement model developed by Support Vector Regression (SVR) was used to determine the cross-sectional information. The determined information was further used to reconstruct cross-sectional 2D images. Then, the gas velocity was calculated according to the signals obtained by the horizontal array, and the spatial interval of the 2D images was determined. Finally, 3D images were reconstructed by piling up the 2D images. In this work, the cross-sectional gas-liquid interface was considered as circular, and high-speed visualization was utilized to provide the reference values. The image deformation caused by channel wall was also considered. Experiments of slug flow in a channel with an inner diameter of 4.0 mm were carried out. The results verify the feasibility of the proposed 3D reconstruction method. The proposed method has the advantages of simple construct, low cost, and easily multipliable. The reconstructed 3D images can provide detailed and undistorted information of flow structure, which could further improve the measurement accuracy of other important parameters of gas-liquid two-phase flow, such as void fraction, pressure drop, and flow pattern.

A Modal Intensity Distribution Estimation Algorithm Based on Horizontal Circular Array

In shallow-water waveguide, the normal mode information of acoustic signals plays an important role in localization research. In this paper, an extraction algorithm of modal intensity distribution based on horizontal circular array is proposed. By using the horizontal wavenumber of each mode, the modal domain beamforming is used to estimate the modal intensity distribution of the acoustic signal. The theoretical derivation, data simulation and experimental data are used to verify the feasibility of the algorithm based on circular array and the superiority compared with the line array extraction algorithm. At the last part of the paper, an application based on modal intensity distribution is proposed: water surface interference suppression, and the effectiveness of the interference suppression algorithm is verified from theoretical derivation and simulation experiments.

Growth of high-density horizontal SWNT arrays using multi-cycle in-situ loading catalysts

Density of horizontal single-walled carbon nanotube (SWNT) array is considered as one of most important index in SWNT-based integrated circuits. However, it is still a challenge to directly obtain horizontal SWNT arrays with ultra-high density on quartz. Herein, we developed multi-cycle in-situ loading catalysts method to directly grow horizontal SWNT arrays with high density on quartz substrate. In this method, Cu catalysts showed much higher efficiency to grow SWNT, which were in-situ loaded through depositing Cu vapor produced by hot copper mesh. Density and size of catalysts could be directly controlled by depositing temperature and time. Moreover, the high efficiency of in-situ loaded Cu catalysts can be maintained after multi-cycle loading, which leads to the linear increase of SWNTs density with loading times. Finally, further optimizing depositing temperature and time, horizontal SWNT arrays with the average density higher than 60 SWNTs/μm and area larger than 8 × 12 mm on quartz have been obtained. This method opens up an opportunity for obtaining SWNT arrays with any density, which shows great potential in the nanoelectronics application in the future.

Performance analysis of sparse and small arrays

Horizontal arrays are often used to detect/separate a weak signal and estimate its direction of arrival among many loud interfering sources and ambient noise. Conventional beamforming (CBF) is robust but suffers from fat beams and high level sidelobes. To improve performance, either high resolution beamforming is used, which has its own problems, or one needs to increase the array aperture, hence requiring more elements on the array. To reduce the cost, sparse and/or nested arrays have been proposed, such as the coprime arrays, to achieve approximately the same aperture, and hence the same beam resolution with a less number of elements. For sonar arrays, deconvolution is shown to yield an unique solution as opposed to, say, image processing. For coprime array, deconvolution algorithm is shown to yield a narrower beam width, lower sidelobe levels and higher array gain than the product or min processing, Deconvolution is shown to yield superdirectivity and supergain for a small array. This raises new research issues about optimal array configuration design.

Individual horizontal array elements as windows to estimating ship radiated noise signature lobing patterns

A horizontal hydrophone array is typically beamformed to produce the directivity required to produce array gain and determine bearing to a contact of interest. For ships passing near an array each omnidirectional hydrophone also provides a number of discrete “look windows” at the ship from a range of received angles. By assembling similar look window angles and applying a propagation model to estimate transmission loss, a partial lobing pattern for the ship's radiated noise signature can be estimated. A 48-element bottom-mounted hydrophone array in the Canadian Arctic provides an opportunity to test this approach in a low ambient noise environment with a variety of passing ships.

Short-range propagation characteristics of airgun pulses during marine seismic reflection surveys.

Marine seismic reflection surveys use airguns to generate repetitive high energy sound signals to image the structure of the seafloor. To better mitigate against the impact of airgun pulses on marine mammals, safety criteria are defined to ensure marine mammals are not exposed to high levels of acoustic energy. Accurate prediction of the sound received levels away from the airguns is required for conducting effective marine mammal monitoring. In this study, measurements by a horizontal hydrophone array towed by the R/V Marcus G. Langseth behind a seismic source array have been used to characterize short-range propagation of airgun pulses and predict the acoustic energy radiated from a seismic source. Data from the Cascadia Open-Access Seismic Transects seismic reflection survey are used to train a linear regression (LR) and a random forest (RF) model to estimate sound exposure levels (SELs) in short ranges from the airguns. Results show that the LR model does not account for all the variance in data. However, the RF model is able to estimate the SELs with a high coefficient of determination and a low mean squared error. Results from the LR model show that the rate at which SELs decrease in deep water does not match either of the cylindrical or spherical spreading models. Simulations are undertaken to understand this inconsistency as well as the effect of hydrophone group-averaging on data recorded by a seismic hydrophone array.

Growth of Single-Walled Carbon Nanotubes with Different Chirality on Same Solid Cobalt Catalysts at Low Temperature.

Currently, designing solid catalysts at high temperature is the main strategy to realize single-walled carbon nanotubes (SWNTs) with specific chirality, meaning it is very hard and challenging to create new catalysts or faces to fit new chirality. However, low temperatures make most catalysts solid, and developing solid catalysts at low temperature is desired to realize chirality control of SWNTs. A rational approach to grow SWNTs array with different chiralities on same solid Co catalysts at low temperature (650 °C) is herein put forward. Using solid Co catalysts, near-armchair (10, 9) tubes horizontal array with ≈75% selectivity and (12, 6) tubes array with ≈82% are realized by adopting a small amount of ethanol and large amount of CO respectively. (10, 9) tubes are enriched for thermodynamic stability and (12, 6) tubes for kinetics growth rate. Both kinds of tubes show a similar symmetry to the Co (1 1 1) face with threefold symmetry for the symmetry matching nucleation mechanism proposed earlier. This method provides a new strategy to study the nucleation mechanism and more possibilities for preparing new solid catalysts to control the structure of SWNTs.

Development of a kinematic GNSS-Acoustic positioning method based on a state-space model

GNSS-A (combination of Global Navigation Satellite System and Acoustic ranging) observations have provided important geophysical results, typically based on static GNSS-Acoustic positioning methods. Recently, continuous GNSS-Acoustic observations using a moored buoy have been attempted. Precise kinematic GNSS-Acoustic positioning is essential for these approaches. In this study, we developed a new kinematic GNSS-A positioning method using the extended Kalman filter (EKF). As for the observation model, parameters expressing underwater sound speed structure [nadir total delay (NTD) and underwater delay gradients] are defined in a similar manner to the satellite geodetic positioning. We then investigated the performance of the new method using both the synthetic and observational data. We also investigated the utility of a GNSS-Acoustic array geometry composed of multi-angled transponders for detection of vertical displacements. The synthetic tests successfully demonstrated that (1) the EKF-based GNSS-Acoustic positioning method can resolve the GNSS-Acoustic array displacements, as well as NTDs and underwater delay gradients, more precisely than those estimated by the conventional kinematic positioning methods and (2) precise detection of vertical displacements can be achieved using multi-angled transponders and EKF-based GNSS-Acoustic positioning. Analyses of the observational data also demonstrated superior performance of the EKF-based GNSS-Acoustic positioning method, when assuming a laterally stratified sound speed structure. Further, we found three superior aspects to the EKF-based array positioning method when using observational data: (1) robustness of the solutions when some transponders fail to respond, (2) precise detection for an abrupt vertical displacement, and (3) applicability to real-time positioning when sampling interval of the acoustic ranging is shorter than 30 min. The precision of the detection of abrupt steps, such as those caused by coseismic slips, is ~ 5 cm (1σ) using this method, an improvement on the precision of ~ 10 cm of conventional methods. Using the observational data, the underwater delay gradients and the horizontal array displacements could not be accurately solved even using the new method. This suggests that short-wavelength spatial heterogeneity exists in the actual ocean sound speed structure, which cannot be approximated using a simple horizontally graded sound speed structure.

Comparative Analysis of Horizontal Array Signal Processing in a Shallow-Water Channel with a Rough Windy Surface

The recent study [1] addressed how the characteristics of low-frequency acoustic signal propagation in a shallow-water channel under wind wave conditions affect the output performance of a horizontal phased array (PA) is further developed with the aim of comparative analysis of the efficiency of various array signal processing methods. The main focus is quantitative estimates of the additional array gain from optimal processing in comparison to the standard PA method compensated in the direction to the signal source, in dependence on the key parameters: direction and distance to the source, wind speed, and wave dimensions of the array. Numerical simulation is performed for a typical winter hydrological conditions of the Barents Sea, a signal frequency of 250 Hz, and a wide range of distances up to 500 km It is shown that the additional gain from optimizing the array processor can vary widely (from fractions of to a few dB), while the PA efficiency also varies widely and may have a nonmonotonic dependence on distance.

Robust estimation of DOA from array data at low SNR

We consider direction of arrival (DOA) estimation for a plane wave hidden in additive circularly symmetric noise at low signal to noise ratio. Starting point is the maximum-likelihood DOA estimator for a deterministic signal carried by a plane wave in noise with a Laplace-like distribution. This leads to the formulation of a DOA estimator based on the Least Absolute Deviation (LAD) criterion. The phase-only beamformer (which ignores the magnitude of the observed array data) turns out to be an approximation to the LAD-based DOA estimator. We show that the phase-only beamformer is a well performing DOA estimator at low SNR for additive homoscedastic and heteroscedastic Gaussian noise, as well as Laplace-like noise. We compare the root mean squared error of several different DOA estimators versus SNR in a simulation study: the conventional beamformer, the phase-only beamformer, and the weighted phase-only beamformer. The simulations indicate that the phase-only DOA estimator has desirable properties when the additive noise deviates from the Laplace-like assumption. The qualitative robustness of these DOA estimators is investigated by comparing the empirical influence functions. Finally, the estimators are applied to passive sonar measurements acquired with a horizontal array in the Baltic Sea.

Measurements of fast neutron scattering in plastic scintillator with energies from 20 to 200 MeV

Scattering of neutrons with energies ranging from 20 to 200 MeV was observed in an organic plastic scintillator array as a test for accuracy of simulation by two GEANT4-based models. The experiment was conducted at the LANSCE WNR facility at Los Alamos National Laboratory using a collimated neutron beam of well-defined energy and trajectory impinging on 16 BC-408 plastic scintillator detectors arranged in a horizontal array 2 detectors tall and 8 deep. Results from neutron scattering observations include hit-multiplicity distributions, beam attenuation depth, crosstalk events, scattering angle, attenuation depth between hits, and dark-scattering of neutrons from carbon nuclei, all as a function of the incident neutron energy. Measurement results are compared with predictions from two GEANT4-based Monte Carlo simulations, and agreement varies considerably over neutron energy, becoming poor at higher energies, pointing to needed improvement in simulation of neutrons in plastic scintillator.

Three-dimensional ultrastructural and histomorphological analysis of the periodontal ligament with occlusal hypofunction via focused ion beam/scanning electron microscope tomography

The periodontal ligament (PDL) maintains the environment and function of the periodontium. The PDL has been remodelled in accordance with changes in mechanical loading. Three-dimensional (3D) structural data provide essential information regarding PDL function and dysfunction. However, changes in mechanical loading associated with structural changes in the PDL are poorly understood at the mesoscale. This study aimed to investigate 3D ultrastructural and histomorphometric changes in PDL cells and fibres associated with unloading condition (occlusal hypofunction), using focused ion beam/scanning electron microscope tomography, and to quantitatively analyse the structural properties of PDL cells and fibres. PDL cells formed cellular networks upon morphological changes induced via changes in mechanical loading condition. Drastic changes were observed in a horizontal array of cells, with a sparse and disorganised area of collagen bundles. Furthermore, collagen bundles tended to be thinner than those in the control group. FIB/SEM tomography enables easier acquisition of serial ultrastructural images and quantitative 3D data. This method is powerful for revealing 3D architecture in complex tissues. Our results may help elucidate architectural changes in the PDL microenvironment during changes in mechanical loading condition and regeneration, and advance a wide variety of treatments in dentistry.

An Advanced Multiple‐Layer Canopy Model in the WRF Model With Large‐Eddy Simulations to Simulate Canopy Flows and Scalar Transport Under Different Stability Conditions

AbstractForest canopies play a critical role in affecting momentum and scalar transfer. Although there have been recent advances in numerical simulations of turbulent flows and scalar transfer across plant canopies and the atmosphere interface, few models have incorporated all important physical and physiological processes in subcanopy layers. Here we describe and evaluate an advanced multiple‐layer canopy module (MCANOPY), which is developed based largely on the Community Land Model version 4.5 and then coupled with the Weather Research and Forecasting model with large‐eddy simulations (WRF‐LES). The MCANOPY includes a suite of subcanopy processes, including radiation transfer, photosynthesis, canopy layer energy balance, momentum drag, and heat, water vapor, and CO2 exchange between canopy layers and the canopy atmosphere. Numerical schemes for heat and water transport in soil, ground surface energy balance, and soil respiration are also included. Both the stand‐alone MCANOPY and the coupled system (the WRF‐LES‐MCANOPY) are evaluated against data measured in the Canopy Horizontal Array Turbulence Study field experiment. The MCANOPY performs reasonably well in reproducing vertical profiles of mean and turbulent flows as well as second‐order statistical quantities including heat and scalar fluxes within the canopy under unstable stability conditions. The coupled WRF‐LES‐MCANOPY captures major features of canopy edge flows under both neutral and unstable conditions. Limitations of the MCANOPY are discussed for our further work. Our results suggest that our model can be a promising modeling system for a variety of applications to study canopy flows and scalar transport (e.g., CO2).

Ship-of-Opportunity Noise Inversions for Geoacoustic Profiles of a Layered Mud-Sand Seabed

This paper considers the use of broadband noise from a ship-of-opportunity in statistical inference for estimating geoacoustic parameters of a layered mud-sand seabed model via trans-dimensional (trans-D) Bayesian matched-field inversion, with applications to data collected with a bottom-moored horizontal array in the 2017 Seabed Characterization Experiment conducted on the New England Shelf. The trans-D approach applied here samples probabilistically over possible model parameterizations (different numbers of seabed layer interfaces), and provides quantitative uncertainty estimates of seabed geoacoustic profiles. Inversions are carried out for acoustic data sets collected both when the ship-of-opportunity (a container ship) was oriented with its bow and with its stern towards the array. A third inversion involved combining data from a series of segments along the ship track. Inversion results image an upper sediment layer 3–7 m thick with low-sound speed (close to the water sound speed) over higher speed sediment, with indication of a transition layer above the interface. Sediment parameter estimates from the inversions are in good agreement with direct measurements from sediment cores and other geophysical data collected in the experiment area.

A Miniaturized Broadband High-Impedance Surface With Flexible Circular Polarization Sense

This communication presents a miniaturized ( $0.084\lambda _{0} \times 0.044\lambda _{0}$ ) dual-layered broadband polarization-dependent high-impedance surface (PDHIS). The unit-cell (UC) structure consists of periodic narrow horizontal patch arrays and vertical meander lines on the top and bottom layers of a thin substrate ( $0.012\lambda _{0}$ ), respectively. Using this arrangement, the phase difference between the orthogonal polarization’s of the reflector is enhanced to 180° ± 30° over a wide range of frequencies. The UC of the proposed PDHIS is 88.7% smaller and the measured 3-dB axial-ratio bandwidth is 168.27% broader than a conventional anisotropic HIS. Also, the proposed PDHIS is polarization agile and the circular polarization sense can be easily controlled by changing the alignment of the reflector with respect to the incident plane wave. An equivalent circuit model of the dual-layered anisotropic HIS is presented and the proposed structure is validated using simulations and measurements.

Numerical validation of natural convection heat transfer with horizontal rectangular fin array using straight knurling patterns on fins—correlation for Nusselt number

AbstractNatural convection heat transfer from horizontal rectangular fin array with various knurling patterns has been studied experimentally by the present authors to investigate the effect of knurl‐produced surface roughness of fin on the heat transfer rate. The parameters like knurling height from base, knurling depth, fin spacing, and supply wattage were considered for parametric study. In the present paper, numerical method (CFD) is used to simulate natural convection phenomena with knurled fins and results are validated with the experimental data available from literature. The numerical results show similar trends compared with experimental data and one can use this method to study various fin configurations for knurling patterns. The flow patterns from experiments and numerical method are compared for different supply wattages and fin spacing to back up the conclusion. It is also observed that the variation in nondimensional roughness depth and spacing (D kn/H and S/H) have more effect on Nusselt number than roughness height parameter (H kn/H). Further, the method is extended to study numerically large number of fin configurations with knurling patterns to gather sufficient data for Nusselt number with respect to fin geometric parameters as above and establish correlation for heat transfer coefficient for such type of fins.

Plasmonic absorbing structure using horizontal bent-wire array for low-frequency absorption enhancement

In this paper, a miniaturized scheme of plasmonic absorbing structure (PAS) is proposed which bends straight wire array into horizontal bent-wire array, contributing to outstanding low-frequency absorption enhancement. Our investigation shows that the interval of adjacent absorptions in spectrum can be efficiently reduced when the resonator of straight wire is developed into horizontal bent-wire in metamaterial absorber (MA). On illumination, an improved PAS consisting of horizontal bent-wire array and vertical wire array is proposed which can make full use of dispersion engineering for broadband absorption enhancement by virtue of spoof surface plasmon polariton (SSPP). Simulation and experimental measurement show that the proposed improved PAS can achieve broadband absorption with the efficiency more than 90% in the frequency band of 5.3–29.0 GHz, which is 40.8% lower in figure of merit compared with the original PAS. Our strategy provides an effective way to enhance the low-frequency absorption in a wider frequency band with no increase of total thickness, and we expect a wide range of applications to emerge from the proposed scheme.

The dynamic bipolar electrode in polymer light-emitting electrochemical cells

The redox doping reactions in polymer light-emitting electrochemical cells (PLECs) have been analyzed to gain insight into a new type of bipolar electrode (BPE) formed within the cells. Planar (lateral) PLECs are constructed on a glass substrate with an exposed active polymer layer contacted by two aluminum (Al) driving electrodes at 11 mm apart. A horizontal array of 13 silver (Ag) microdiscus is deposited in-between the driving electrodes. When a 200 V bias is applied between the driving electrodes, the electrically floating Ag discs functioned as BPEs to induce redox p- and n-doping reactions in polymer layer that initially occur at the extremities of the BPEs. The doping reactions are visualized as strong photoluminescence quenching of the luminescent polymer. Over time, the doped regions grow in size, and the silver disc BPEs transform into dynamic, composite BPEs consisting of a p- and n-doped polymer conductor connected by the initial BPE disc. Unlike a homogenous BPE, the dynamic BPE is not a quasi-equipotential body under operation. Moreover, the n/p area ratios of all 13 BPEs in the array converge to a single value which is strongly affected by the composition of the PLEC layer. The n/p ratios ranging from 0.24 to 2.19 have been observed in PLECs made with Li, Na, and K triflate salts as well as two different luminescent polymers. The dynamic BPE array thus presents a novel essay to evaluate and screen the mixed luminescent conductor for device applications.

Experimental Study of Forced- Convection from Horizontal Rectangular Fins Array into Air Duct

In this work, an experimental study has been done to expect the heat characteristics and performance of the forced-convection from a heated horizontal rectangular fins array to air inside a rectangular cross-section duct. Three several configurations of rectangular fins array have been employed. One configuration without notches and perforations (solid) and two configurations with combination of rectangular-notches and circular-perforations for two various area removal percentages from fins namely 18% notches-9% perforations and 9% notches-18% perforations are utilized. The rectangular fins dimensions and fins number are kept constant. The fins array is heated electrically from the base plate with five different magnitudes of power-inputs. Five several air flow velocity into a duct are utilized. The influence of fin geometry, air flow velocity, Reynolds number and the surface heat flux on the heat-performance of forced heat convection have been simulated and studied experimentally. The experimental data indicates that the combination of 18% rectangular-notched and 9% circular-perforated rectangular fins array gave best forced heat performance in terms of average heat transfer coefficient about (25% - 45%) and (7% - 20%) compared than solid and 9% notches with18% perforations fins array respectively. Five empirical correlations to predict the average Nusselt number for the 18% notches with 9% perforations rectangular fins array at wide range of surface heat flux are deduced. The present data are compared with previous works and a good closeness in behavior is noticed.

Passive Source Depth Discrimination in Deep-Water

This paper addresses the problem of passive source depth discrimination in ocean acoustics using a horizontal line array (HLA). The scope is restricted to low-frequency sources (frequency $f Hz), broadband signals (bandwidth $B$ of a few Hz), deep-water environment (water depth $D>\text{1000}$ m), and distant sources (range $r$ greater than several kilometers) at the endfire position. In this context, the environment acts as a dispersive waveguide, and one should not use classical source localization methods based on plane waves or any other simplistic wave model. Instead, a method based on the modal behavior driving the propagation is proposed. It notably uses the concept of the waveguide invariant, a scalar that summarizes the waveguide dispersion. In deep water, the waveguide invariant largely depends on source depth, and thus is an interesting input for source depth discrimination. An algorithm is proposed to compute energy ratio in groups of modal interferences. The input data for the algorithm is a range-frequency intensity, as measured on a HLA. The modal interference groups are defined based on their respective waveguide invariant values which in turns depend on source depth. This idea is formalized to propose a source depth discrimination method, which is performed as a binary classification problem. As long as the sound speed profile features a surface thermocline, the algorithm does not require detailed knowledge about the environment and it allows the classification of sources under two hypotheses, above or under a user-chosen threshold depth.