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Ultra-broadband metamaterial absorber with graphene composites fabricated by 3D printing
摘要： An ultra-broadband electromagnetic (EM) absorber composed of composite metamaterials was designed, fabricated and characterized. Polylactic-acid/reduced graphene oxide (PLA/RGO) composites with different amounts of RGO were prepared as a primary material collection. To provide good impedance matching and efficient wave attenuation, the multilayer absorbers were designed with a gradient index (GRIN) of characteristic impedance by manipulating the RGO content and the geometric parameters of the unit cell. The absorbers with different numbers of layers were fabricated by a material extrusion process, and then the reflection loss (RL) of the prepared samples was measured. Results showed that the methodology for designing a metamaterial absorber with gradient impedance and fabricating through a 3D printing process was effective in producing ultra-broadband absorbers. The seven-layer absorber achieved an absorption above 90% in a broad bandwidth of 4.5–40 GHz. This work could provide inspiration for upgrading the performance of some conventional absorbing composites through a rational design of the composite proportion and structure.
关键词： Microwave absorption,Multilayer structure,3D printing,Composite materials,Metamaterials
更新于2025-09-23 15:23:52
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Performance improvement in photosensitive organic field effect transistor by using multi-layer structure
摘要： In this study, a new approach was introduced for Photo-OFETs as a multi-layer structure. Poly(3-hexylthiophene-2,5-diyl) regioregular (P3HT) and Copper(II) phthalocyanine (CuPc) thin films were used as two different active photo-absorber layers in the same device structure. Poly(methyl methacrylate) (PMMA) was used as a dielectric layer and all devices were fabricated with a top-gate bottom-contact configuration. In order to investigate the effect of the location of each layer on the Photoresponsive organic field-effect transistors (Photo-OFET) performance, five different devices in various structures were produced and analyzed. Surface properties of active layers have been investigated via Atomic Force Microscopy (AFM) and effects of surface roughness on device performance have been discussed. P3HT/CuPc/P3HT multi-layered structure exhibited the best performance in terms of photoresposivity(as 45 mA/W) and photosensitivity (~ 2x103). Photo-OFET based on a multi-layer structure demonstrated superior performance with wider absorbance spectrum region compared to conventional single component devices of P3HT or CuPc. The proposed multi-layer structure can be a model to improve the realization of high performance Photo-OFETs.
关键词： Photoresponsive organic field-effect transistors,Organic field effect transistors,Multilayer structure,Poly(3-hexylthiophene),Photosensitivity,Poly(methyl methacrylate)
更新于2025-09-23 15:23:52
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Piezoelectric properties of a near strain-free lead zirconate titanate thin films deposited on a Si substrate
摘要： Chemical solution deposition (CSD)-derived near strain-free lead zirconate titanate (PZT) thin films on a Si substrate were prepared by designing a buffer layer structure. Strain-free PZT thin films with different compositions ranging from Zr/Ti = 50/50 to 58/42 were obtained to demonstrate lattice strain effects on piezoelectric properties. Results show that a near strain-free condition was attained with a SrRuO3 (SRO: 160 nm)/(La0.5,Sr0.5)CoO3 (LSCO: 90 nm)/LaNiO3 (LNO: 120 nm)/stacking structure, even on a Si substrate. The highest effective d33 value of the near strain-free PZT thin film was observed at 53/47 composition, which is the same as bulk materials, although the highest effective d33 value was obtained from 58/42 composition under the compressive lattice strain condition.
关键词： Chemical solution deposition,Piezoelectricity,Thin films,Multilayer structure,Lattice strain,Sol-gel preparation
更新于2025-09-23 15:22:29
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Effect of Laser Power on Gradient Microstructure of Low-Alloy Steel Built by Laser Melting Deposition
摘要： In this paper low-alloy steel samples were fabricated by laser melting deposition at different laser power of 1500 W, 2000 W and 2500 W. The results show that the microstructure is gradient with a mixture of lower bainite and martensite on surface and tempered martensite in interior of each sample, and the morphology of microstructure both on surface and in interior develop with change of laser power, the develop of microstructures result in difference in mechanical properties. The hardness, ultimate tensile strength and plasticity of both surface and interior of the samples were studied, as well as the depth of the surface layer. This paper provides a reference for the evolution and control of gradient microstructure of LMD low-alloy samples.
关键词： multilayer structure,low-alloy steel,laser power,microstructure,deposition
更新于2025-09-11 14:15:04
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Hyperspectral unmixing using double-constrained multilayer NMF
摘要： Hyperspectral unmixing (HU) refers to the process decomposing the entire hyperspectral image into a set of endmembers and the corresponding abundance fractions. Nonnegative matrix factorization (NMF) has been widely used in HU due to its simplicity and effectiveness. Many extensions of NMF have been also developed since traditional NMF has a large solution space. On the other hand, the multilayer structure has shown great advantages in learning data representation. Inspired by these considerations, we added sparsity and geometric structure constraints to the multilayer NMF structure and proposed a double-constrained multilayer NMF (DCMLNMF) method for HU in this paper. The multilayer NMF structure was obtained by iteratively decomposing the target matrix into a number of layers. To improve the unmixing performance, a sparsity constraint term on the abundance matrix and a graph regularization term were both incorporated to each layer. Besides, a layer-wise optimization method based on Nesterov’s optimal gradient method was further proposed to solve the multi-factor NMF problem. Experimental results based on both synthetic data and real data demonstrate that the proposed method outperforms several other state-of-art approaches.
关键词： sparsity constraint,Hyperspectral unmixing,graph regularization,multilayer structure,nonnegative matrix factorization
更新于2025-09-10 09:29:36
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[IEEE 2018 48th European Microwave Conference (EuMC) - Madrid, Spain (2018.9.23-2018.9.27)] 2018 48th European Microwave Conference (EuMC) - Design of a Wideband Multilayer Meander-Line Polarizer (6 – 18 GHz) using a Semi-Analytical Method
摘要： A semi-analytical method to design multilayer meander-line polarizers is described in this paper. The proposed procedure consists of a combination of the transmission line equivalent circuit and a Simulated Annealing Algorithm to estimate the best values of the dimensions of the polarizer. A wideband four layers’ meander-line polarizer [6 – 18 GHz] is studied. Patch antenna resonating at different frequencies is associated to the polarizer to validate it. The results verify that the proposed multilayer meander-line polarizer convert the Linear wave to Circular one.
关键词： Simulated Annealing Algorithm,Transmission-Line Equivalent Circuit,Meander-line Polarizer,Linear polarization,Wideband Polarizer,Multilayer Structure,Circular polarization
更新于2025-09-09 09:28:46