Single-layer Structure Research Articles

A bearing fault diagnosis model with convolutional cross transformer and ResNet18

Abstract In the industrial field, malfunction of rotating machinery, especially bearings, can cause significant economic losses to enterprises. Addressing the limitations of traditional fault diagnosis methods, such as poor generalization performance and low noise resistance, this paper introduces a fault diagnosis model that parallels the cross convolutional transformer and ResNet18 (CCTAR). The proposed CCTAR utilizes two feature extraction channels, aimed at balancing the extraction of local and global features, and the specially designed convolutional cross-decoding layer has excellent noise resistance, surpassing traditional multi-layer Transformer encoding layers with a single-layer structure. CCTAR achieves commendable recognition accuracy across multiple datasets and maintains high accuracy in noisy environments. Furthermore, transfer learning experiments have demonstrated the proposed model’s capability to achieve superior fault diagnosis performance across different working conditions with a limited number of samples, highlighting its practical significance.

Study of the Dispersion Compensation Double-Layer Diffractive Optical Components Based on Metasurface and Grating, and Their Application in Augmented Reality Displays

We employed a double-layer coupled diffractive optical element, based on metasurfaces and diffraction gratings, which exhibits wavefront modulation and chromatic dispersion compensation. Utilizing this double-layer coupled diffractive optical element in the optical information transmission process of a diffractive waveguide allows for the transmission of color image information using a single-layer waveguide structure. Our results demonstrate that, under the conditions of a field of view of 47° × 47°, an entrance pupil size of 2.9 × 2.9 mm2, and an exit pupil extension size of 8.9 mm, the uniformity of the brightness for each monochromatic field reached 85%, while the uniformity of color transmission efficiency exceeded 95%.

Revisiting the human umbilical cord epithelium. An atypical epithelial sheath with distinctive features.

The umbilical cord epithelium (UCE) is the surface tissue that covers the umbilical cord (UC). It is widely considered a single-layered epithelium composed of squamous or cuboidal cells, which are in constant contact with amniotic fluid. The objective of this study was to elucidate the distinctive structural characteristics and abundance of specific proteins in this unique epithelium, many of which have not been previously demonstrated. Samples of the UC were obtained from term pregnancies (n = 12) and processed for examination using stereo, light, electron, and 3D high-resolution confocal microscopy. Sections displayed a range of stratification, ranging from a single squamous layer to 4-5 layers of round/cuboid cells, challenging the notion of considering it as a single-layered structure. Cells are located on a well-developed basement membrane (BM), as evidenced by the expression of BM-specific proteins and PAS staining. The cells possess distinctive cytoplasmic domains that are tightly bound to each other by desmosomes and interdigitating anchoring surfaces. Desquamations and limited organelles suggest that the cells have reached the final stages of differentiation and are no longer actively synthesizing proteins, despite maintaining stratification-specific expression levels of cytoskeletal, junctional, receptor, and stem cell proteins. Although definitive keratinization was not observed, the distribution of proteins and the distinctive structural organization of the single/multi-layered cells suggest that they exhibit plasticity, likely due to adaptive mechanisms in response to chemical and/or mechanical stimuli during fetal development. These structural alterations may facilitate the active transportation of soluble ingredients between the amniotic fluid and cord blood through an intercellular route.

Beam steerable MIMO antenna based on conformal passive reflective metasurface for 5G millimeter wave applications

A conformal reflective metasurface fed by a dual-band multiple-input multiple-output (MIMO) antenna is proposed for low-cost beam steering applications in 5G Millimeter-wave frequency bands. The beam steering is accomplished by selecting a specific port of MIMO antenna. Each MIMO port is associated with a beam that points in a different direction due to a conformal reflective metasurface. This novel conformal metasurface antenna design has the advantages of higher gain, lower cost, a simpler feeding source, and a lower profile when compared to traditional reflective metasurfaces using bulky horn antennas and phased arrays with complex feeding networks and phase shifters for beam steering. The proposed beam steering antenna consists of a compact five-element dual-band MIMO and a 32×32\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$32 \ imes 32$$\\end{document} unit-cell conformal dual-band reflective metasurface placed at the top of the MIMO antenna to obtain the beam steering capability as well as gain enhancement. The proposed reflective metasurface has a stable response under oblique incidence angles of up to 600\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$60^0$$\\end{document} at 24 GHz and 38 GHz and its symmetric, single-layer structure, ensures polarization insensitivity and stable response under conformal conditions. The presented MIMO antenna design is not only compact but also offers a wideband response effectively covering the desired 5G mm-wave frequency bands. The overall size of the MIMO antenna alone is 70 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 12 mm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {mm}^2$$\\end{document} with a maximum gain of 5.4 and 7.2 dB. It is further improved up to 13.1 and 14.2 dB at 24 and 38 GHz respectively, with a beam steering range of ś400\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$40^0$$\\end{document} by using a conformal reflective metasurface. Unlike the existing beam steering strategies, the suggested method is not only cost-effective but also increases the overall directivity and gain of the source MIMO antenna. The measured results agree with the simulated results, making it a potential candidate in the 5G and beyond beam steering applications.

Deciphering the piezoelectric and conductive mechanisms of Nb-doped Bi3Ti1.5W0.5O9 high-temperature piezoelectric ceramics

The study utilizes Bi3Ti(1.5-x)NbxW0.5O9 (BTW-xNb, x=0.00, 0.01, 0.02, 0.04, 0.06) bismuth layered piezoelectric ceramics synthesized via a conventional solid-phase reaction process. This is the study to investigate the impact of B-site Nb ion doping on the structural and electrical properties of BTW-xNb ceramic. The results show that all ceramics have a single bismuth layer structure, with reduced lattice distortion according to Rietveld refinement findings. The presence of oxygen vacancies in the ceramic is the main factor that affects the high temperature conductivity of the samples. The XPS results, the increase in the activation energy of AC and DC conductivity confirm that doping with Nb5+ ions reduces oxygen vacancy concentration. The ceramics with the highest overall electrical performance are the BTW-0.02 Nb ceramics. Notably, the DC resistivity at 500 °C was enhanced from 9.16 × 105 Ω·cm (x = 0.00) to 8.24 × 106 Ω·cm. The TC was enhanced from 730 °C(undoped) to 743 °C. At 500 °C, tanδ decreases from 21.1 % to 8.2 %. The ceramic's increased resistivity increases the polarization voltage, resulting in more complete polarization. The d33 is increased from 7.5 pC/N (undoped) to 13 pC/N. Furthermore, the piezoelectric properties remain stable up to 700°C, suggesting that the material has considerable potential for use at elevated temperatures.

Estimation of random incidence sound transmission loss of panels based on normal incidence sound transmission loss measurements

The performance of building sound insulation is an important parameter for evaluating the quality of construction projects. So far, the sound insulation performance testing of building walls requires the installation of large-dimensioned wall samples in specialized sound insulation laboratories, which is time-consuming and costly. If small-dimensioned components of the wall panels can be applied and quickly tested at the project site, it could significantly improve efficiency and reduce costs. To address this issue, this paper investigates a method for estimating the random incidence sound transmission loss of wall panels based on the measurement of the normal incidence sound transmission loss of corresponding small samples. Initially, the sound transmission loss of single-layer and composite structures is theoretically analyzed based on the theories of Equivalent Single Layer method and Layer-Wise method. Subsequently, the random incidence sound transmission loss is estimated by the normal incidence sound transmission loss. The methodology for estimating the random incidence sound transmission loss of wall panels proposed in this study offers both a practical approach and theoretical support for the rapid assessment of the sound insulation performance of building walls. This study is of great significance for improving the quality of construction projects and inspection efficiency.

LONGITUDINAL-RADIAL VIBRATIONS OF A VISCOELASTIC CYLINDRICAL THREE-LAYER STRUCTURE

The paper considers a cylindrical three-layer structure of arbitrary thickness made of viscoelastic material. It consists of two external bearing layers and a middle layer, the materials of which are generally different. The problem of nonstationary longitudinal-radial vibrations of such a structure is formulated. Based on the exact solutions in transformations of the three-dimensional problem of the linear theory of viscoelasticity for a circular cylindrical three-layer body, a mathematical model of its nonstationary longitudinal-radial vibrations is developed. Equations are derived that allow, based on the results of solving the vibration equations, to determine the stress-strain state of a cylindrical structure and its layers in arbitrary sections. The results obtained allow for special cases of transition into cylindrical viscoelastic and elastic two-layer structures, as well as into homogeneous single-layer cylindrical structures and round rods.

A microwave/millimeter-wave triple-band shared-aperture antenna integrating differentially-fed patch and transmitarray

This paper presents a microwave (MW)/millimeter-wave (MMW) triple-band shared-aperture antenna. It is implemented by integrating a differentially-fed patch (3.6 GHz) and a dual-band transmitarray (TA) (26 GHz and 39 GHz) through structure reuse. To realize an efficient integration, the patch antenna is evolved from a single-layer structure to a multi-layer one, with an extended ring-shaped patch added in each layer to obtain a proper transmitting surface (TS) size. For the TA, it adopts a unit cell (UC) consisting of two interleaved slots. By adjusting the lengths of the slots, independent dynamic phase shifts covering 360∘ can be attained for the 26 GHz and 39 GHz bands, respectively. To achieve an appropriate focal-to-diameter ratio (F/D) for the TA, a frequency selective surface (FSS) is employed to replace the ground plane of the patch antenna. Thanks to the spatial feeding architecture of the TA, the proposed antenna eliminates the need of complicated feeding network and features low feeding loss and high gain in the MMW bands. To validate the design idea, a prototype is fabricated and measured. The experimental results demonstrate that the proposed antenna can successfully operate in the three bands with peak gain of 7.6 dBi, 19.3 dBi and 19.5 dBi, respectively. In the 26 GHz and 39 GHz bands, beam scanning ranges of ±25∘ and ±13∘ can be obtained, respectively. The proposed antenna can be a promising candidate for 5G multi-band applications.

Self-adaptive radiation recuperator with double phase transition temperature switches based on VO2 intelligent films

Developing renewable energy for heating and cooling to achieve carbon neutrality and environmental protection is of great significance. The combination of photothermal (PT) and radiative cooling (RC) technology to continuously obtain energy throughout the day is gradually attracting interest, in which vanadium dioxide (VO2) intelligent phase transition film serves as a bridge between the daytime PT mode and the nighttime RC mode. The high phase transition temperature of VO2 poses a challenge to environmental adaptability and dynamic switching in practical applications. In this work, a novel self-adaptive radiation recuperator with double phase transition temperature (37 °C and 68 °C) switches is proposed to exchange energy from the sun and outer space by radiation. Compared with VO2 and W-doped VO2 single-layer structure, this method has a higher self-adaptability to easily achieve the phase transition temperature of mode switching. The absorptivity of the radiation recuperator is 0.75 in the solar band (0.3–2.5 μm), and the emissivity switching capability is present from 0.3 to 0.86 in the atmospheric window band (8–14 μm). The transition mode generated by the presence of double phase transition temperature improves temperature self-adaptability and improves energy collection efficiency in dynamic environments.

Study of the Nature of the Destruction of Coatings Based on the ZrN System Deposited on a Titanium Alloy Substrate

The fracture strength was compared in a scratch test of coatings based on the ZrN system with the introduction of Ti, Nb and Hf, which were deposited on a titanium alloy substrate. The coatings were deposited using Controlled Accelerated Arc (CAA-PVD) technology. In coatings that simultaneously include Zr and Ti, a nanolayer structure is formed, while in coatings without Ti, the formation of a monolithic single-layer structure is observed. The comparison was carried out according to two parameters: adhesion strength to the substrate and overall coating strength. The (Zr,Hf)N coating showed better resistance to destruction, but had worse adhesion to the substrate. As a result, although the coating is retained directly in the scribing groove, a large area of delamination and destruction is formed around the groove. The (Ti,Zr,Nb)N coating, with its somewhat lower strength, has a high adhesion to the substrate; no noticeable delamination is observed along the groove boundary. In this paper, not only is the fracture resistance of various coatings deposited on a titanium alloy substrate compared, but the nature of this fracture is also investigated depending on the composition of the coatings.

MS-UNet: Multi-Scale Nested UNet for Medical Image Segmentation with Few Training Data Based on an ELoss and Adaptive Denoising Method

Traditional U-shape segmentation models can achieve excellent performance with an elegant structure. However, the single-layer decoder structure of U-Net or SwinUnet is too “thin” to exploit enough information, resulting in large semantic differences between the encoder and decoder parts. Things get worse in the field of medical image processing, where annotated data are more difficult to obtain than other tasks. Based on this observation, we propose a U-like model named MS-UNet with a plug-and-play adaptive denoising module and ELoss for the medical image segmentation task in this study. Instead of the single-layer U-Net decoder structure used in Swin-UNet and TransUNet, we specifically designed a multi-scale nested decoder based on the Swin Transformer for U-Net. The proposed multi-scale nested decoder structure allows for the feature mapping between the decoder and encoder to be semantically closer, thus enabling the network to learn more detailed features. In addition, ELoss could improve the attention of the model to the segmentation edges, and the plug-and-play adaptive denoising module could prevent the model from learning the wrong features without losing detailed information. The experimental results show that MS-UNet could effectively improve network performance with more efficient feature learning capability and exhibit more advanced performance, especially in the extreme case with a small amount of training data. Furthermore, the proposed ELoss and denoising module not only significantly enhance the segmentation performance of MS-UNet but can also be applied individually to other models.

Investigating the Impact of Process Parameters on Bead Geometry in Laser Wire-Feed Metal Additive Manufacturing

Laser wire-feed metal additive manufacturing (LWAM) is an innovative technology that shows many advantages compared with traditional manufacturing approaches. Despite these advantages, its industrial adoption is limited by complex parameter management and inconsistent process quality. To address these issues and improve geometric accuracy, this study explores how process parameters influence bead geometry. We conducted a parameter study varying laser power, wire feed rate, traverse speed, and welding angle. Using a full factorial design with a central composite design methodology, we assessed bead height and width. This allowed us to develop a model to estimate ideal process parameters. The findings offer a detailed analysis of parameter interactions and their effects on bead geometry, aiming to enhance geometric accuracy and process stability in LWAM. Moreover, we have evaluated the proposed process parameters from our developed model, which showed a significant enhancement to the overall quality. This was validated via printing a single layer and multi-layer structures. The quality of the final predicted sample using the proposed method was improved by 40% compared to the best sample produced for the Design of Experiment trials.

A closely spaced dual band polarization insensitive FSS for 5G applications

This study presents a novel single layer Frequency Selective Surface (FSS) for fifth generation (5G) applications with a polarization independent closely spaced dual band response. The proposed design consists of four split ring apertures etched on a square patch printed on a RT5880 dielectric substrate. The FSS has two stop-bands at 24.78 GHz and 28 GHz center frequencies with attenuations around 55 dB. The S21<−10 dB bandwidths (BW) of these bands are 14.48 % and 9.25 %, respectively and these closely spaced bands succeed 1.13 frequency ratio. It shows a stable frequency response for both TE and TM polarizations. Furthermore, the FSS represents a single layered and quite thin (thickness 0.042λl) structure with its unit cell size (0.70λl × 0.70λl, where λl is the free-space wavelength at lower frequency). The novelty of the presented FSS is not only achieving a small closely spaced band ratio in the mmWave band and exhibiting polarization insensitivity but also providing these features with a simple geometry and, uncomplicated single layer structure. The simulation results were confirmed by well accordant measurement results. All these results make the presented FSS a good candidate for 5G electromagnetic interference (EMI) shielding applications.

Thermal concentrating efficiency enhanced for multilayer circular thermal concentrators with gradient structures

The thermal concentrating efficiency of a thermal concentrator is determined by the ratio of its interior to exterior temperature gradients, serving as a crucial indicator influenced by the interaction of geometrical and thermal conductivity parameters. Finding simpler and more effective ways to improve thermal concentrating efficiency has been a key concern in this field. In our study, we present a method to enhance the concentrating efficiency of an isotropic multilayer circular thermal concentrator by introducing gradient-distributed thermal conductivities or layer thicknesses within the multilayer circular structure. Our goal is to identify the optimal structural setup parameters for achieving enhanced thermal concentrating efficiency using an optimization approach that combines stepwise refinement search with machine-learning predictions. Initial investigations explore the impacts of different gradient schemes on thermal concentration performance. The gradient distribution function with high thermal concentrating efficiency is established through the stepwise refinement search strategy and the machine-learning model. Subsequently, a detailed search process is carried out in small increments, followed by finite element simulations to validate the thermal concentrating efficiency and ascertain the optimal design parameters of the thermal concentrator. Our findings reveal that the optimally designed gradient thermal concentrator showcases an 8.56 % increase in thermal concentrating efficiency compared to a single-layer structure without gradients. Moreover, applying the gradient function to the outer and inner rings elucidates the inherent influence of the inner and outer layered ring structures on thermal concentrating efficiency. The optimization methodology, combining stepwise refinement search and machine-learning predictions, succeeds in improving the efficiency with easy, fast and efficient operation. This approach can be extended to advance the development of various other thermal metastructured devices.

BiFeO3/SrTiO3 superlattice-like based ferroelectric memristors with pronounced artificial synaptic plasticity

Memristors are attracting widespread attention for their multilevel storage capacity and synaptic learning ability. Ferroelectric memristors, with resistance switching based on polarization reversal, offer uniform threshold voltage and analog resistance modulation. By preparing superlattice-like ferroelectric films, the ferroelectric properties can be significantly enhanced, thereby improving the memristive characteristics. In this study, the constructed BiFeO3/SrTiO3 (BFO/STO) superlattice-like structure increases the remanent polarization by approximately 200 % compared to a single-layer BFO structure, as well as the dramatically enhanced resistance switching performance. Notably, the Pt/(BFO/STO)2/NSTO device shows superior storage performance, with extended endurance (1000 cycles), reliable retention (10000 seconds) and fundamental synaptic behaviors being demonstrated. Finally, simulations for handwritten digit recognition classification, involving modulation of conductance to vary synaptic weights, achieve an impressive accuracy of 87.46 %, showing great promising for applications in information storage and neuromorphic computing.

Multi-scale structural design of multilayer magnetic composite materials for ultra-wideband microwave absorption

Broadband microwave absorbing (MA) materials have important applications in reducing electromagnetic radiation pollution and realizing low scattering characteristics. However, current MA materials with single-layer structure generally cannot meet this requirement due to the difficulty in achieving good impedance matching. Here, we design a multilayer-structured MA material, which consists of a wave transmitting layer, a carbon-magnetic material composite absorbing layer, a strong magnetic absorbing layer and a reflector layer. Hollow Co/CoFe@C composite particles prepared using CoCoPBA as templates are used as fillers to design carbon-magnetic material composite absorbing layer. The Co/CoFe bimagnetic phases enhance permeability while the hollow structure optimizes permittivity, which endows this absorbing layer with strong microwave absorption ability with a reflection loss of −47.18 dB. The introduction of a strong magnetic absorbing layer that combines FeSiAl with high permeability and SmFeB with high coercivity further significantly improves the overall impedance matching of the material. Benefitting from the multi-scale structural design, the obtained multilayer MA material achieves strong microwave absorption in both low and high frequency ranges, and the effective absorption bandwidth reaches 12.85 GHz, far superior to the traditional single-layer MA material.

Multifunctional seamless meta-sandwich composite as lightweight, load-bearing, and broadband-electromagnetic-wave-absorbing structure

Engineered porous geometries composed of low-density lossy materials are promising as broadband absorbers due to their tunable structural attenuation that can selectively manipulate electromagnetic (EM) waves. However, the exposed cellular architectures require mechanical reinforcement and additional packaging. Here, we present a multifunctional meta-sandwich structure as one seamlessly integrated component composed of functional faceplates and dielectric lossy material-based octet-truss geometries toward a lightweight, load-bearing, and high-performance broadband EM wave absorber. EM responses are explored in the 4–18 GHz range by varying material combinations and multilayers of the upper-lower faceplates and the octet-truss core, elucidating the absorbing mechanisms of meta-sandwich structures. Multi-material 3D printing that streamlines the production of the seamless meta-sandwich composite into a single step implements the devised design that simultaneously excel in EM wave absorption and mechanical functionalities. The fabricated composite in a thin, single-layer structure comprising a transmitting upper faceplate, a dielectric lossy core, and a reflecting lower faceplate, achieves an average absorption rate of 95.0 % and a broadband reflection loss (≤-10 dB) over the entire measured bandwidth. Furthermore, flexural testing confirms superior bending resistance compared to conventional honeycomb structures. The multi-materials meta-sandwich design will inspire versatile multifunctionalities enabled by rationally combining mechanical metamaterials and functional housing.

Improved electron transport in planar perovskite solar cells using TiO2, SnO2 and WO3 ultra-thin layers: a comparison on all single layer and bilayer structures

Improved electron transport in planar perovskite solar cells using TiO2, SnO2 and WO3 ultra-thin layers: a comparison on all single layer and bilayer structures

A Single Layer Low Axial Ratio Circularly Polarized Planar Wide-Angle Scanning Phased Array

This paper proposes a circularly polarized planar wide-angle scanning phased array radar. The structure of the proposed array element is a windmill-type patch with an octagon-shaped series power divider. The proposed array exhibits a low axial ratio because the element has a wide 3-dB axial ratio beamwidth and the array topology uses the sequential rotation technique. Test results show that the proposed 8 × 8 uniform planar array can realize two-dimensional circularly polarized scanning from −60° to +60° in the working band of 3.43–3.48 GHz. The coverage gains of θ = ±60° are about 3 dB lower than the gain when the main beam points at θ = 0°. Moreover, in the scanning mentioned above airspace, the scanning beam axial ratio is below 0.5 dB in the xz-plane (φ = 0°) and yz-plane (φ = 90°) and below 1.4 dB in the D-plane (φ = 45°). Another notable feature is the single-layer structure, and its profile is only 0.08λ0 at the center wavelength. This good low- axial ratio and low-profile characteristics make the proposed array potentially applicable to low-orbit satellite communications.

Polarization insensitive and wideband terahertz absorber using high-impedance resistive material of RuO2

This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band.