Discrete Array Research Articles

Three-Terminal Superconducting Digital Transistor

Discrete array of small Josephson junctions can exhibit flux-flow behavior, which is drastically different from that of long Josephson junctions. In particular, the flux-flow voltage does not monotonically increase with magnetic field; rather, it decreases after a threshold until it reaches zero. Here, using simulation and experimental results, we show that the flux-flow voltage switches abruptly to zero if a magnetic field larger than the threshold is applied to a part of the array. This provides for a digital NOT gate in which the flux-flow voltage corresponds to digital state 1 and zero voltage denotes digital state 0. For a device size of 230 μm, a switching frequency of 15 GHz is evaluated, which can be improved by downsizing the device. Since this device provides gain, its input and output are isolated and has unlimited fan-out, designing and implementing various digital systems is easily accomplished.

Exploring the sensing behavior in the detection of nitroaromatics using coordination complexes based on 4,4′-(1,3-phenylenedioxy)-dianiline ligand

The aromatic ligand 4,4′-(1,3-phenylenedioxy)-dianiline (L), has been used to explore its coordination chemistry behaviour and nitroaromatic sensing ability by crystallizing it with a variety of transition metals. The supramolecular structures [CuCl2(L)] (1), [Mn(H2O)2Cl2(L)2] (2), [Ni(H2O)2 (L)2] Cl2 (3) and [Co(H2O)2 (L)2] Cl2 (4) have been characterized by single crystal X-ray diffraction (SC-XRD) and X-ray powder diffraction (XRPD) analysis. While 1 and 2 do not form polymeric structures but discrete (0D) arrays, 3 and 4 resulted in extended isostructural 2D coordination polymers. The solid-state fluorescence properties of the reported crystals have been investigated. Interestingly, coordination polymers 3 and 4 showed a better solid-state fluorescence emission compared to that of complexes 1 and 2. Coordination polymer 3 has been successfully used as a sensor for the detection of trace amounts of nitrobenzene, 2-nitrotoluene and 3-nitrotoluene with a high quenching efficiency of 96% for 3-nitrotoluene. The quenching efficiency of 3 is better than that of the free ligand L. The polymeric nature of 3 is maintained after the sensing experiment and thus can be used in a recyclable manner. Due to the fact that 3 is a nonporous and its structure does not change in the presence of the quenchers, the quenching effect occurs in the surface of the solids when is in a suspension.

Effect of Thermal Conductivity on Cooling of Square Heat Source Array under Natural Convection in a Vertical Channel

This article presents experimental and numerical investigation on natural convection air-cooling of discrete square heat source array in a vertical channel. Conjugate heat transfer for three-dimensional laminar developing flows over an array of square heat sources representing integrated circuit components for electronic cooling has been studied. Experiments are conducted using three-substrate board materials viz. FR4, Bakelite, and copper clad board having thermal conductivities of 0.3, 1.4, and 8.8 W/m K to study the effects of substrate thermal conductivity on fluid flow and heat transfer. A finite element-based software is used to solve the coupling between heat transfer in solids and fluid region. Incompressible flow over discrete square heat sources is modeled using Navier–Stokes equations under Boussinesq approximation. Air-cooling of circuit boards populated with heat sources is modeled and simulated to present heat transport in combination with the fluid flow resulting from the natural air circulation at constant heat fluxes of 1,000, 2,000, and 3,000 W/m2. Multilayer copper clad board of thermal conductivity of 40.5 W/m K have been studied numerically. The results show that single sided copper clad board is the preferred candidate. Experiments indicate a deviation of under 5% with simulations.

Generalized Friis Transmission Equation for Orbital Angular Momentum Radios

Generalization of a Friis transmission equation for orbital angular momentum (OAM) radios is rigorously formulated using the Lorentz reciprocity theorem and a near-and-far-field convolution integral (NFCI). Based on the discretization of NFCIs, we computed the generalized Friis transmission equation to obtain the power-receiving behaviors of practical helicoidal parabolic reflector antennas (HPRAs) with continuously deformed surfaces. A simplified Friis equation is also used for computing the link budget and approximate Rayleigh length of discrete uniform circular arrays (UCAs) composed of $2\times 2$ dipole antennas. The transmission coefficients for the given OAM modes, represented by our equations for the HPRA and UCA, agree very well with commercial numerical simulators. In addition, an $m$ th-order NFCI, which is an orthogonal convolution integral for the $m$ th OAM mode, is proposed to define a figure of merit for the OAM mode purity of transmitting and receiving antennas.

Expeditious Estimation of Angle-of-Arrival for Hybrid Butler Matrix Arrays

Arrays of Butler matrices provide a promising front-end design for massive MIMO transceivers with low cost and low complexity. However, this advanced design does not necessarily translate to effective applications, unless the angle-of-arrival (AoA) of signals avails to the Butler matrices. This paper presents an efficient approach to the unprecedented AoA estimation for the arrays of Butler matrices. Specifically, we design a new beam synthesis method to recursively narrow down and increasingly focus on the angular region of interest, and hence achieving robust estimation of the phase offset between Butler matrices. With the phase offset canceled in the received signals, we are able to identify the set of critical Butler beams with the dominating effect on the AoA estimation, and estimate the AoA accordingly with minimum signaling. The mean squared error of the proposed estimation is analyzed in the presence of non-negligible noises, with closed-form lower bounds derived. Validated by simulations, the proposed algorithm is able to indistinguishably approach the lower bounds, and significantly outperforms the state-of-the-art developed for discrete antenna arrays by orders of magnitude in terms of accuracy, especially in low signal-to-noise regimes.

Enhancing Image Quality of Photoacoustic Tomography Using Sub-Pitch Array Translation Approach: Simulation and Experimental Validation.

The purpose of this paper is to present a more convenient and practical alternate way of increasing the lateral discrete array sampling while using a typical λ pitch linear array transducer at receive for photoacoustic tomography (PAT) application. We have employed a linear translation-based approach, in which the array transducer is translated by sub-pitch amount to create an augmented RF frame data having denser lateral spatial sampling. The denser λ/2 and λ/4 pitch data were reconstructed and compared against conventional λ pitch reconstructed PAT image using simulation and tissue mimicking phantom experiments in terms of improvements in resolution and contrast. The results from experiments demonstrate a 34.48% improvement in lateral resolution (LR), measured in terms of full-width at half-maximum of the lateral profile of point spread function, and a maximum of 7-dB improvement in contrast is achieved while using a λ/2-pitch configuration when compared to the conventional λ-pitch configuration. It was demonstrated that λ/2- and λ/4-pitch configurations result in better LR and contrast than λ-pitch configuration. Based on the results obtained, the proposed method has the potential to serve as an easy-to-integrate and simple way of achieving better image quality without requiring to increase the system complexity with existing transducer array probe technology in regular clinical scanners.

Creating illusion of discrete source array by simultaneously allocating thermal and DC fields with homogeneous media

Highly efficient conversions and utilizations are long-standing topics of interest in energy field. Owing to the unique potentials of metamaterial in regulating thermal and electrical behaviors, classical research on efficient energy utilization has been further motivated. However, current investigations are mostly implemented with single basic transformation, which lead to the simple functions on single field. Hence, hybrid functions are of particular importance in achieving highly efficient devices for multiple energies. In this paper, the above concerns are addressed with hybrid maps to design a class of novel discrete source array, which significantly re-configures each field generated by an excited source into arrayed distributions. The expected energy collection and allocation are first exhibited only with one single source, and intense convergences/divergences are observed in tailored directions. Contrasts reveal that such designs robustly act as circular source arrays with multiple sources. The findings provide a novel function of efficiently manipulating and allocating energy generated by excited sources, which see potentials in conventional applications, such as extensive harvesting strategies with local energy focus, light routing on the sun-facing side of solar cells, and thermal-electric devices.

PATTERN ANALYSIS OF THE RECEIVING-TRANSMITTING CIRCULAR ARRAY WITH LOW SIDE LOBE LEVEL

Context. A particular advantage of uniform circular arrays is the possibility of scanning the beam within 360° in azimuth withoutdistorting the characteristics of the directivity pattern only by changing the amplitude-phase distribution of the current on its elements.This feature, combined with modern beamforming techniques and digital methods of beamforming opens the prospect of usingcircular arrays in surveillance radars for military and civil purposes instead of antenna systems with mechanical rotation.Objective. Investigation of the possibility of reducing the sidelobe level of a uniform circular transmit-receive array using known amplitude distributions used for linear arrays.Methods. For the study, a phase-mode excitation technique is used in which an arbitrary excitation function of a uniform circular array is represented as a sum of phase excitation components (modes), and the circular array antenna pattern is a superposition of patterns produced by individual phase excitation modes. This technique makes it possible to apply for circular arrays the methods used to pattern synthesis and reduce the side lobe level in linear arrays due to the use of a special transformation matrix.Results. An imitation mathematical model of a discrete uniform circular array has been developed that provides an opportunity to study the efficiency of using amplitude distributions, known for linear arrays, to reduce its side lobe level.Conclusions. The computational experiments have confirmed the possibility of using the phase-mode excitation technique for a pattern synthesis with low sidelobe level in the uniform circular transmits-receive array. A variant of the practical application of the Dolph-Chebyshev amplitude distribution for the synthesis of a circular array pattern is shown.

Generation of Laguerre–Gaussian Modes by Aperture or Array Sources

This paper investigates the generation of Laguerre–Gaussian (LG) modes at radio frequencies (RFs) by utilizing either a continuous aperture or a discrete array. The mode generation can be performed with or without sidelobe control, and superdirectivity is avoided by properly selecting the system geometry and regularizing the associated inverse problem. For an individual mode, a continuous aperture source is first determined based on the singular value decomposition of the wave system. This continuous source is subsequently discretized following the construction of a 2-D quadrature rule, which, in the two extreme cases of no and maximum sidelobe suppression, results in an array grid that inherently requires a minimum number of antenna elements. A tradeoff can be made between the adopted array element number and the realized sidelobe level. A method to use a single array with a conserved number of elements to generate and multiplex multiple modes simultaneously is also developed. Full-wave simulations are used to demonstrate the application of the developed theories to arrays of realistic antennas with mutual coupling included. The study shows that, despite their origin in optics, LG modes can be accurately generated in the RF regime, and therefore still play a crucial role in orbital angular momentum (OAM)-based radio.

Divergent Linkage Reconfigurable Mould For Rapid Prototyping

Abstract Rapid prototyping (RP) is a manufacturing technology, where parts are built rapidly, without using traditional machining processes. Reconfigurable mould techniques are one of the rapid prototyping techniques for building parts. Mould cavity is created with the use of discrete array of movable pins. With the use of reconfigurable mould, mass customization of product can be done easily. In this article, we have discussed the basic set-up of reconfigurable mould, its mechanism, and limitations. One of the limitations of large screw size, and small pin size is discussed in detail. A proposed model of divergent linkage is discussed to solve this problem. With the use of this proposed model, pin size can be reduced for surface finish (high resolution) without reducing the lead screw size. Hence, divergent linkage is promising method to increase pin resolution and make it more valuable in industries rapid prototyping.

Local polynomial contrast binary patterns for face recognition

We propose a novel face representation model, called the polynomial contrast binary patterns (PCBP), based on the polynomial filters, for robust face recognition. It is assumed that the discrete array of pixel values comes about by sampling an underlying smooth surface in an image. The proposed method efficiently estimates the underlying local surface information, which is approximately represented as linear projection coefficients of the pixels in a local patch. The decomposition using polynomial filters can capture rich image information at multiple orientations and frequency bands. This guarantees its robustness to illumination and expression variations. The weighting scheme embeds different discriminative powers of each filter response image. We also propose to carry out a subsequent Fisher linear Discriminant (FLD) on each decomposed image for dimension reduction of features. Our extensive experiments on the public FERET and LFW databases demonstrate that the non-weighted Polynomial contrast binary patterns performs better than most of methods and the weighting scheme further improves the recognition rates. WPCBP+FLD(CD) and WPCBP+FLD(HI) can achieve much competitive or even better recognition performance compared with the state-of-the-art face recognition methods.

Quantifying Discretization Errors in Electrophoretically-Guided Micro Additive Manufacturing.

This paper presents process models for a new micro additive manufacturing process termed Electrophoretically-guided Micro Additive Manufacturing (EPμAM). In EPμAM, a planar microelectrode array generates the electric potential distributions which cause colloidal particles to agglomerate and deposit in desired regions. The discrete microelectrode array nature and the used pulse width modulation (PWM) technique for microelectrode actuation create unavoidable process errors—space and time discretization errors—that distort particle trajectories. To combat this, we developed finite element method (FEM) models to study trajectory deviations due to these errors. Mean square displacement (MSD) analysis of the computed particle trajectories is used to compare these deviations for several electrode geometries. The two top-performing electrode geometries evaluated by MSD were additionally investigated through separate case studies via geometry variation and MSD recomputation. Furthermore, separate time-discretization error simulations are also studied where electrode actuating waveforms were simulated. The mechanical impulse of the electromechanical force, generated from these waveforms is used as the basis for comparison. The obtained results show a moderate MSDs variability and significant differences in the computed mechanical impulses for the actuating waveforms. The observed limitations of the developed process model and of the error comparison technique are briefly discussed and future steps are recommended.

The coupled Hirota system as an example displaying discrete breathers: Rogue waves, modulation instability and varying cross-phase modulations

Discrete dynamical systems constitute an elegant branch of nonlinear science, where ingenious techniques provide penetrating insight for vibrations and wave motion on lattices. In terms of applications, such systems can model oscillators with hard quartic nonlinearities and switching of optical pulses on discrete arrays. A two-component Hirota system is investigated as an extension of the widely studied Ablowitz-Ladik equation by including discrete third order dispersion. Breathers (periodic pulsating modes) are derived analytically, and are used to establish conservation laws. Rogue waves (unexpectedly large displacements from equilibrium configurations) exhibit unusual features in undergoing oscillations above and below the mean level, and may even reverse polarity. Coupling produces new regimes of modulation instabilities for discrete evolution equations. The robustness of these novel rogue waves, in terms of sensitivity to initial conditions, is elucidated by numerical simulations. Self-phase modulations and cross-phase modulations of the same or opposite signs will generate nonlinear corrections of the frequency, due to the intensity of the wave train itself and the one in the accompanying waveguide respectively. Such effects have a crucial influence on the evolution of discrete and continuous multi-component dynamical systems.

Adaptive beamforming for uniformly-spaced linear hydrophone array using temporal convolutional neural networks

In oceanic remote sensing, large discrete linear hydrophone arrays are usually utilized to enhance the signal-to-noise ratio (SNR) by means of beamforming that attenuates noise coming from the directions outside the target direction. Although the widely adopted delay-and-sum (DS) and filter-and-sum (FS) beamforming techniques can improve the performance of linear hydrophone arrays in some scenarios, both DS and FS methods have limited adaptability to the changing oceanic environments especially with spatially correlated noise. Moreover, these beamforming techniques aims to optimize the SNR, which is not completely consistent with some objectives such as target recognition. In this work, a neural network adaptive beamforming framework for an uniformly-spaced linear hydrophone array is proposed to make use of the large-scale array signals and address the above issues. In particular, an architecture consists of temporal convolutional neural networks is designed to predict the beamforming filter coefficients in time domain by taking the raw multi-channel waveforms of sound pressure as the input. The filter prediction networks are also jointly trained with a convolutional neural network (CNN) based classification model with the purpose of increasing the target recognition accuracy. The proposed approach is validated by experiments carried out in the south coastal waters of China.

Radiation Beam Pattern Synthesis of Concentric Circular Antenna Arrays Using Hybrid Approach Based on Cuckoo Search

A novel hybrid approach to suppress the maximum sidelobe level (SLL) of large scale concentric circular antenna array (CCAA) is proposed. The approach includes an improved discrete cuckoo search algorithm (IDCSA) for thinning the CCAA and a cuckoo search-invasive weed algorithm (CSIWA) for further optimizing the thinned CCAA. IDCSA introduces the nest location coding discretization, the mapping method based on jumping path, and an improved egg elimination mechanism for optimizing the discrete sparse array synthesis problem. Moreover, CSIWA introduces the chaotic initialization and the invasive weed-based Levy flight method to solve the continuous excitation current optimization problem. Simulation results show that the thinning rate of CCAA obtained by IDCSA can reach more than 50%, resulting in significant cost savings. Moreover, both IDCSA and CSIWA can obtain a lower maximum SLL compared with other algorithms while achieving faster convergence rates. The stabilities of the proposed IDCSA and CSIWA are demonstrated by using multiple independent tests. In addition, the performance of the optimized designs obtained by the hybrid approach is also verified by electromagnetic simulations.

High order aberration calculations of a quadrupole–octupole corrector using a differential algebra method

A Differential algebraic method is of an effective technique in computer numerical analysis. It implements conveniently differentiation up to arbitrary high order, based on the nonstandard analysis. In this paper, the differential algebra (DA) method has been employed to compute the high order aberrations up to the fifth order of electron lenses with quadrupole and octupole corrector whose electric/magnetic fields are in the forms of discrete arrays, for example, the files computed by FEM or FDM method. The quadrupole and octupole electro-magnetic fields of arbitrary point are obtained by local analytic expressions, and then field potentials are transformed into new forms which can be operated in the DA calculation. The program has been developed and tested as well. The geometric and chromatic aberrations coefficients up to fifth order of electron lenses with quadrupole and octupole corrector are calculated by the developed program.

Design of an optical see-through light-field near-eye display using a discrete lenslet array

In this paper, we propose a novel method to construct an optical see-through light-field near-eye display (OST LF-NED) by using a discrete lenslet array (DLA). The DLA is used as a spatial light modulator (SLM) to generate dense light field of three-dimensional (3-D) scenes inside the user's eyebox of the system and provide correct focus cues to the user. A corresponding light-field image rendering method is also proposed and demonstrated. The light emitted from the real objects passes through the transparent region of the display panel and the planar area of the DLA successively without redirection, so the user can have a clear view of the real scene as well as the virtual information. The stray light that may degrade the image quality has been analyzed in detail. The experimental result shows that the proposed method is capable of obtaining a corrected depth perception of the virtual information in augmented reality (AR) applications.

Beam Selection for mmWave Massive MIMO Systems Under Hybrid Transceiver Architecture

Hybrid analog/digital precoding is a promising technology to cut down hardware cost in massive multi-input multi-output systems at millimeter wave frequencies. In this letter, we propose a joint beam selection scheme for analog domain precoding under discrete lens array. By considering channel correlation among users, the proposed scheme is able to avoid inter-user interference and maximize system sum rate. Moreover, a bio-inspired ant colony optimization-based algorithm is proposed to obtain a near-optimal solution with dramatically reduced computational complexity. Finally, simulations show the advantages of the proposed scheme in improving system sum rate.

High resolution, high efficiency liquid scintillator capillary array for gamma imaging.

We fabricated a liquid scintillator capillary array (LSCA) for gamma imaging with the aim of developing a one-dimensional detector system utilizing a streak camera for high temporal and spatial resolution pulsed gamma radiation detection. The detector's performance was studied in a simulation and via an experiment. The maximum efficiency of the LSCA's emission was at a wavelength of 420 nm. To establish a high fidelity representation of the detector's edge spread function and modulation transfer function (MTF), a slanted edge algorithm was introduced to calculate the edge spread function of the discrete sampling array's image screen. The simulation results showed that the spatial resolution of the LSCA was better for 14 MeV neutrons than for 1.25 MeV gamma radiation. The experimental results show that in comparison with a 6-mm-thick LaBr3 image plate, the LSCA had a higher temporal and spatial resolution when used as a gamma detector. The spatial resolution was 1.1 lp/mm (MTF = 0.1) for the LSCA. In addition, when an ultra-violet streak camera was coupled with the LSCA, it had a comparable sensitivity to that of a 6-mm-thick LaBr3 image plate.

Discrete EquiSpaced Unshaded Line Array method for target identification using side scan sonar imagery

Beam pattern resulting from Discrete Equispaced Unshaded Line Array method is to analyze the pattern of two-dimensional beam pivot at the angle of sound waves coming from the direction of origin on the axis of the received array, will affect the sound beam angle. This research was conducted in December 2016 in the Punggur Sea, Batam, Riau Islands-Indonesia, and its coordinate system is 104° 08.7102 E and 1° 03.2448 N until 1° 03.3977 N and 104° 08.8133 E, DEULA method in target 4 has the highest value in the directivity pattern is 21.08 dB. The results of the beam pattern model show that neither the central value at the incidence angle (°) of the directivity pattern (dB) were not at the 0 (zero) or the beam pattern central have been generated by the target 6 with incident angle -1.5° and 1.5°. In addition, it has declined by 40 dB. Highest result of line trace is target 1 with 191, 88 cm on target 1, and highest of time result is 13568 cm/second on target 4. Seismic figure of side scan sonar imagery have total line trace is 4479, time: 77.9547 cm/s, and gain: 0.00271091.