Cylindrical Array Research Articles

Sparse Nested Cylindrical Sensor Networks for Internet of Mission Critical Things

In this paper, two new structures of sparse cylindrical sensor network are proposed, which are 1-D nested cylindrical sensor network (1-D NCSN) and 2-D NCSN. Considering the development of Internet of Mission Critical Things, numerous of devices need to be interconnected and sharing information. Sparse structures of sensor networks will not only reduce the cost of deployment, but also decrease the quantity of data. The reason of choosing cylindrical sensor network is that cylindrical array has been widely used in wireless communication and underwater target detection. According to the characteristic of cylindrical array, the 1-D and 2-D nested array is extended to build the 1-D and 2-D sparse cylindrical sensor networks, respectively. Comparing with the 1-D NCSN, the 2-D structure could save more elements, while it is hard to derive the beampattern expression of the 2-D NCSN. Simulation results show that the 1-D NCSN has a higher resolution than the uniform cylindrical sensor network (UCSN). In addition, through augmented matrix MUSIC approach, 2-D NCSN could detect all targets in the range, even if the number of targets is larger than the number of real elements in the network. However, both the UCSN and the 1-D NCSN could not find all the sources.

Iterative solutions of the array equations for rapid design and analysis of large projector arrays.

A fast computational method for modeling and simulation of large projector arrays is presented. The method is based on the array equations that account for the acoustic interaction among the projector elements as well as the individual characteristics of each projector. Unlike the existing solution method in which the acoustic interaction must be known a priori in the form of interaction impedance matrix Z, the present method seeks the solution of modified array equations through iterations without explicitly evaluating the Z matrix. This significantly speeds up the analysis of complex arrays with surrounding structures, where the evaluation of the Z matrix may require a large number of time-consuming finite element computations. The method is compared with the traditional Z-matrix method for the case of a cylindrical array of 72 × 8 Tonpilz transducers. For the same level of accuracy, the iterative method is shown to be up to 2 orders-of-magnitude faster than the Z-matrix method. The method can be used for rapid design and analysis of active sonar arrays and medical ultrasonic transducers, often made of hundreds and even thousands of elements.

Numerical analysis for source direction finding using a cylindrical array with scattered sound fields

Numerous studies on beamforming techniques have been done for source direction finding using various types of arrays. A circular array as well as a linear array is also widely used for its compact configuration and smaller angular dependency of beamforming performance. In underwater environments, a circular array faces high drag forces due to not only ocean current but also its moving platform. One of the solutions may be an array of hydrophones flush mounted on a cylindrical structure to reduce the drag. However this configuration causes sound scattering, which deteriorate the pressure distribution based on the free field condition. This talk deals with numerical approach for source localization techniques with scattered sound fields. Parametric study shows that beamforming performance is improved and relative high resolution can be achieved using an array of small-sized aperture. [This work was financially supported by the research project PES9410 funded by KRISO.]

Fabrication of high fill factor cylindrical microlens array with isolated thermal reflow.

We demonstrate a simple, controllable, and stable method for fabricating high fill factor cylindrical microlens array with a novel isolated thermal reflow process. In this method, microstripes with a very small gap were obtained via digital micromirror device-based lithography, then covered with polydimethylsiloxane (PDMS) solution. The prepared microstripes were isolated and were heated and reflowed to a cylindrical microlens array. During the reflow process, the semicross-linked PDMS can serve as a barrier to prevent the diameter change and the bonding of adjacent microlenses. By this special treatment, the fill factor of the cylindrical microlens array can be significantly improved. Moreover, the reflow time and temperature have very little effect on the microlens shape due to the surrounded semicross-linked PDMS. This will make our process stabler than traditional methods. The measured 3D profile is good and satisfactory, and excellent optical performance is demonstrated with the fabricated cylindrical microlens arrays. The proposed method may offer a viable route for fabrication of high fill factor microlens arrays in a very simple and stable way.

Comparison of X-ray-Mammography and Planar UWB Microwave Imaging of the Breast: First Results from a Patient Study.

Hemispherical and cylindrical antenna arrays are widely used in radar-based and tomography-based microwave breast imaging systems. Based on the dielectric contrast between healthy and malignant tissue, a three-dimensional image could be formed to locate the tumor. However, conventional X-ray mammography as the golden standard in breast cancer screening produces two-dimensional breast images so that a comparison between the 3D microwave image and the 2D mammogram could be difficult. In this paper, we present the design and realisation of a UWB breast imaging prototype for the frequency band from 1 to 9 GHz. We present a refined system design in light of the clinical usage by means of a planar scanning and compare microwave images with those obtained by X-ray mammography. Microwave transmission measurements were processed to create a two-dimensional image of the breast that can be compared directly with a two-dimensional mammogram. Preliminary results from a patient study are presented and discussed showing the ability of the proposed system to locate the tumor.

An analytic model for eddy current separation

Eddy current separation (ECS) is a process used throughout the scrap recycling industry for separating nonferrous metals from nonmetallic fluff. To date, however, the physical theory of ECS has generally been limited to empirical approximations and numerical simulations. We therefore introduce a simplified, two-dimensional model for ECS based on a cylindrical array of permanent, alternating magnets. The result is a Fourier-series expansion that describes the total magnetic field profile over all space. If the magnets are then rotated with constant angular velocity, the magnetic fields vary as a discrete series of sinusoidal harmonics, thereby inducing electrical eddy currents in nearby conductive particles. Force and torque calculations can then be used to predict the corresponding kinematic trajectories.

Multiscale array antireflective coatings for improving efficiencies of solar cells

Multiscale array (MSA) structures are present to reduce the front-side surface reflection loss of solar cells, which consists of nanostructure patterns spanned across the curved surface of micrometer-sized plano-concave cylindrical arrays. The MSAs are fabricated using flexible polydimethylsiloxane (PDMS) polymer by simple template replication together with surface modification technique and characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Optical characterization shows the MSA structure can reduce 3.85% integrated reflectivity of multicrystalline silicon solar cell encapsulated by the flat epoxy resin polymer (ERP) coating. Importantly, the MSA antireflective coating can improve the photovoltaic conversion efficiency of the ERP-encapsulated solar cell from 17.50% to 18.34% and can increase the contact angle of a 2 μL water droplet on the solar cell surface from 110.5° to 153.1°. These improvements have great significance for commercial Si solar cell devices.

Circularly Polarized Substrate-Integrated Cylindrical Dielectric Resonator Antenna Array for 60 GHz Applications

A 60 GHz circularly polarized (CP) substrate-integrated cylindrical dielectric resonator antenna (DRA) and its 2 × 2 array are studied. Each DRA element is excited in its HEM11δ mode by an aperture-coupled source. To obtain CP fields, each element is top-loaded by a patch, which has a pair of slits. For the array, a sequential-rotation feeding network is used to widen the bandwidth of the axial ratio. Reasonable agreement between the measured and simulated results is observed. It is found that the array can be used for the 60 GHz band (57–64 GHz), with a peak measured antenna gain of 11.43 dBic.

On the performance of three‐dimensionalantenna arrays in millimetre wave propagation environments

In order to reap the full scale of benefits of millimetre wave (mmWave) massive multiple-input multiple-output (MIMO) systems, the design of antenna arrays at the transmitter or receiver becomes more critical due to the propagation characteristic at mm-frequencies. In this study, the authors investigate the performance of two types of antenna array, namely uniform rectangular planar array (URPA) and uniform cylindrical array (UCYA). The channel behaviour is presented in full-dimensional mmWave propagation conditions by considering both the azimuth and elevation dimensions. The squared inner product and singular value spread are studied for URPA and UCYA configurations, these properties reveal the effective interference and channel's stability of antenna array. The authors also evaluate the achievable rate with the equal power allocation and water-pouring power allocation schemes. Simulation results show that under the same system configurations, the performance that includes the radiation pattern, the channel eigenvalue distribution, the effective interference, and the achievable rate, of UCYA configuration always outperforms that of URPA configuration. Therefore, it can be concluded that in three-dimensional propagation environments, the UCYA configuration is especially appealing for mmWave MIMO systems.

Numerical Study on Heat Transfer Enhanced in a Microcombustor With Staggered Cylindrical Array for Micro-Thermophotovoltaic System

In consideration of high heat transfer efficiency and stable combustion, a new type of microplanar combustor for micro-thermophotovoltaic (micro-TPV) system is proposed, in which the heat transfer is enhanced by staggered cylindrical array. The numerical study results indicate that the temperature of radiation wall of cylindrical-array combustor is higher and more uniform comparing with the conventional-channel combustor, the application of cylindrical-array make the effective radiation of the combustor increase 34.55% and reach to 35.98 W. Moreover, with inlet velocity increase from 4 m/s to 16 m/s, the cylindrical-array combustor shows the better stability of combustion, which the position of the flame moves 4.8 mm in the cylindrical-array combustor and 9.1 mm in the conventional-channel combustor. However, the 0.5–4.5 equivalence ratio range for stable combustion is slightly narrower than 0.4–6.0 in the conventional-channel combustor. To extend the equivalence ratio range, one row of cylindrical array was canceled, and the distribution length of cylindrical array was reduced to 10 mm, After this improvement, the equivalence ratio range is extended to 0.3–5.5, and the negative effect on the flame stability of the cylindrical array is basically eliminated.

Impact of pillar configuration on the amphiphobicity of micro-patterned polymer surface

Hydrophobic surfaces are easily contaminated by oil owing to its lower surface tension, which significantly limits their potential applications. In this study, micro-patterned surfaces with cylindrical or square pillar arrays were fabricated on a polycarbonate substrate by the thermal imprinting process. The geometry and size of the pillars were varied to obtain different samples, whereas the height of the pillars was kept constant. The surface of each micro-patterned sample was fluorinated with perfluorooctanoic acid. With the aim of characterizing the wetting behavior of the samples, droplets of water and oily liquids with different surface tensions were employed to measure the contact angles. In addition, the applicability of the Wenzel and Cassie equations for explaining the wetting mechanisms of droplets on the surfaces of the micro-patterned samples was systematically investigated. The prediction obtained using the Wenzel equation was found to differ considerably from the experimental results, whereas the Cassie equation was found to be acceptable for satisfactorily explaining the wetting behaviors of liquids on the micro-patterned samples. The main factor influencing the surface wettability of the micro-patterned sample was not the pillar geometry, but rather the pillar configuration, e.g., the solid area fraction, groove fraction, and spacing between pillars.

Optogenetic entrainment of neural oscillations with hybrid fiber probes

Objective. Optogenetic modulation of neural activity is a ubiquitous tool for basic investigation of brain circuits. While the majority of optogenetic paradigms rely on short light pulses to evoke synchronized activity of optically sensitized cells, many neurobiological processes are associated with slow local field potential (LFP) oscillations. Therefore, we developed a hybrid fiber probe capable of simultaneous electrophysiological recording and optical stimulation and used it to investigate the utility of sinusoidal light stimulation for evoking oscillatory neural activity in vivo across a broad frequency range. Approach. We fabricated hybrid fiber probes comprising a hollow cylindrical array of 9 electrodes and a flexible optical waveguide integrated within the core. We implanted these probes in the hippocampus of transgenic Thy1-ChR2-YFP mice that broadly express the blue-light sensitive cation channel channelrhodopsin 2 (ChR2) in excitatory neurons across the brain. The effects of the sinusoidal light stimulation were characterized and contrasted with those corresponding to pulsed stimulation in the frequency range of physiological LFP rhythms (3–128 Hz). Main results. Within hybrid probes, metal electrode surfaces were vertically aligned with the waveguide tip, which minimized optical stimulation artifacts in neurophysiological recordings. Sinusoidal stimulation resulted in reliable and coherent entrainment of LFP oscillations up to 70 Hz, the cutoff frequency of ChR2, with response amplitudes inversely scaling with the stimulation frequencies. Effectiveness of the stimulation was maintained for two months following implantation. Significance. Alternative stimulation patterns complementing existing pulsed protocols, in particular sinusoidal light stimulation, are a prerequisite for investigating the physiological mechanisms underlying brain rhythms. So far, studies applying sinusoidal stimulation in vivo were limited to single stimulation frequencies. We show the feasibility of sinusoidal stimulation in vivo to induce coherent LFP oscillations across the entire frequency spectrum supported by the gating dynamics of ChR2 and introduce a hybrid fiber probe tailored to continuous light stimulation.

Partial discharge ultrasonic detection based on EULER‐MUSIC algorithm and conformal array sensor

A conformal array sensor suitable for partial discharge (PD) detection of electrical equipment was designed which displays multiple characteristics including compatibility with the surface of any carrier without affecting the performance of the carrier. Taking a cylindrical conformal array as an example, the simulation model was given and the array flow pattern of the cylindrical conformal array sensor was determined. Based on the Euler transform, the algorithm of multiple signal classification (MUSIC) was improved. An algorithm of array signal direction finding suitable for conformal array sensors was proposed and its performance under different signal-to-noise ratios and different array elements was simulated. The improved algorithm and conformal array sensor were used to simulate and test the PD signal. The results show that the algorithm and the conformal array sensor are suitable for PD detection of electrical equipment.

3-D Indoor Positioning for Millimeter-Wave Massive MIMO Systems

In this paper, a novel three-dimensional (3-D) indoor positioning scheme is proposed for millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems. Its operation is based upon a hybrid received signal strength and angle of arrival (RSS-AoA) positioning scheme, which employs only a single access point equipped with a large-scale uniform cylindrical array. To reduce the high computational complexity imposed by the large number of antennas used in mmWave massive MIMO (M3-MIMO) systems, we firstly propose a novel channel compression method. By proper quantization and selection of the received mmWave signals, which exhibit quasioptical and sparse multipath characteristics, the channel compression method reduces the dimension of the received signal space while maintaining the accuracy of the position estimation. Then, we propose a beamspace transformation approach to transform signal vectors in the element space to the beamspace, and thus the computational complexity of the angle estimation is significantly reduced. Finally, a novel hybrid RSS-AoA positioning scheme is designed for the computations of the 3-D coordinates of the target mobile terminal. Simulation results have shown that the proposed indoor positioning scheme is capable of achieving high accuracy as well as significantly lower computational complexity as compared to other previously known indoor positioning techniques.

Design of a Spatial RPR-2SS Valve Mechanism

This paper applies kinematic synthesis theory to obtain the dimensions of a constrained spatial serial chain for a valve mechanism that cleans and closes a soil conditioning port in a tunnel boring machine. The goal is a smooth movement that rotates a cylindrical array of studs into position and then translates it forward to clean and close the port. The movement of the valve is defined by six positions of the revolute-prismatic-revolute (RPR) serial chain. These six positions are used to compute the dimensions of the two spherical spherical (SS) dyads that constrain the RPR chain to obtain a one degree-of-freedom spatial mechanism. An example design of this valve mechanism is provided in detail.

Controllable long focal length microlens based on thermal expansion.

A novel method to fabricate a microlens array with a long focal length has been developed in this paper. It is based on the fabricating and heating of a microlens consisting of two materials with a great difference in coefficient of thermal expansion. A thermal expansion process leads to considerable deformation of the microlens surface and significant increase in focal length, which could be controlled by altering the processing temperature. Cylindrical polymeric microlens arrays with different focal lengths were successfully fabricated. By measuring the focal length and temperature dependence of the cylindrical microlens geometry, the formation mechanism was analyzed and validated. While the temperature is ranged from 20°C to 50°C, the focal length of the cylindrical microlens has been extended by 38.2% and the longest focal length was obtained up to 6.6mm for the microlens with a linewidth of 240μm.

Development of Ordered, Porous (Sub-25 nm Dimensions) Surface Membrane Structures Using a Block Copolymer Approach

In an effort to develop block copolymer lithography to create high aspect vertical pore arrangements in a substrate surface we have used a microphase separated poly(ethylene oxide) -b- polystyrene (PEO-b-PS) block copolymer (BCP) thin film where (and most unusually) PS not PEO is the cylinder forming phase and PEO is the majority block. Compared to previous work, we can amplify etch contrast by inclusion of hard mask material into the matrix block allowing the cylinder polymer to be removed and the exposed substrate subject to deep etching thereby generating uniform, arranged, sub-25 nm cylindrical nanopore arrays. Briefly, selective metal ion inclusion into the PEO matrix and subsequent processing (etch/modification) was applied for creating iron oxide nanohole arrays. The oxide nanoholes (22 nm diameter) were cylindrical, uniform diameter and mimics the original BCP nanopatterns. The oxide nanohole network is demonstrated as a resistant mask to fabricate ultra dense, well ordered, good sidewall profile silicon nanopore arrays on substrate surface through the pattern transfer approach. The Si nanopores have uniform diameter and smooth sidewalls throughout their depth. The depth of the porous structure can be controlled via the etch process.

Application of millimeter-sized polymer cylindrical lens array concentrators in solar cells**Project supported by the Natural National Science Foundation of China (Grant No. 61377021).

A unique method is proposed to encapsulate solar cells and improve their power conversion efficiency by using a millimeter-sized cylindrical lens array concentrator. Millimeter-sized epoxy resin polymer (ERP) cylindrical lens array concentrators are fabricated by the soft imprint technique based on polydimethylsiloxane stamps. The photovoltaic measurements show that millimeter-sized ERP cylindrical lens array concentrators can considerably improve the power conversion efficiency of silicon solar cells. The validity of the proposed method is proved by the coupled optical and electrical simulations. The designed solar cell devices with the advantages of high-efficiency and convenient cleaning are very useful in practical applications.

The Application of an Ultrasound Tomography Algorithm in a Novel Ring 3D Ultrasound Imaging System.

Currently, breast cancer is one of the most common cancers in women all over the world. A novel 3D breast ultrasound imaging ring system using the linear array transducer is proposed to decrease costs, reduce processing difficulties, and improve patient comfort as compared to modern day breast screening systems. The 1 × 128 Piezoelectric Micromachined Ultrasonic Transducer (PMUT) linear array is placed 90 degrees cross-vertically. The transducer surrounds the mammary gland, which allows for non-contact detection. Once the experimental platform is built, the breast model is placed through the electric rotary table opening and into a water tank that is at a constant temperature of 32 °C. The electric rotary table performs a 360° scan either automatically or mechanically. Pulse echo signals are captured through a circular scanning method at discrete angles. Subsequently, an ultrasonic tomography algorithm is designed, and a horizontal slice imaging is realized. The experimental results indicate that the preliminary detection of mass is realized by using this ring system. Circular scanning imaging is obtained by using a rotatable linear array instead of a cylindrical array, which allows the size and location of the mass to be recognized. The resolution of breast imaging is improved through the adjustment of the angle interval (>0.05°) and multiple slices are gained through different transducer array elements (1 × 128). These results validate the feasibility of the system design as well as the algorithm, and encourage us to implement our concept with a clinical study in the future.

Optimal condition for employing an axicon-generated Bessel beam to fabricate cylindrical microlens arrays

A numerical algorithm, modelling the transformation from a Gaussian beam to a Bessel beam, is presented for the purpose to study the optimal condition for employing an axicon-generated Bessel beam to fabricate cylindrical microlens arrays (CMLAs). By applying the numerical algorithm to simulate the spatial intensity distribution behind the axicon under different defects of a rotund-apex and different diameter ratios of an incident beam to the axicon, we find that the diffraction effects formed by the axicon edge can be almost eliminated when the diameter ratio is less than 1:2, but the spatial intensity distribution is disturbed dramatically even a few tens of microns deviation of the apex, especially for the front part of the axicon-generated Bessel beam. Fortunately, the lateral intensity profile in the rear part still maintains a desirable Bessel curve. Therefore, the rear part of the Bessel area and the less than 1:2 diameter ratio are the optimal choice for employing an axicon-generated Bessel beam to implement surface microstructures fabrication. Furthermore, by applying the optimal conditions to direct writing microstructures on fused silica with a femtosecond (fs) laser, a large area close-packed CMLA is fabricated. The CMLA presents high quality and uniformity and its optical performance is also demonstrated.