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Novel Multifunctional Reconfigurable Active Frequency Selective Surface
摘要： In this paper, a multifunctional active frequency selective surface (AFSS) is presented based on the switching responses of active components. The proposed structure comprises periodic arrays of metallic patterns imprinted on both sides of an FR4 substrate on which PIN diodes are embedded with parallel feed networks. The novelty of the design lies in its multifunctional characteristics with independent control of the biasing states (ON/OFF) of the diodes mounted on opposite layers. This leads to four different working states (dual-bandpass for OFF-OFF state, single-band absorber for OFF-ON state, single-bandpass for ON- OFF state, and reflector for ON-ON state) being facilitated by the proposed reconfigurable AFSS. Furthermore, the effects of the design parameters and active components on multifunctional responses are extensively analyzed by deriving equivalent circuit models. Even though the topology is polarization-sensitive, multiple dividable working functions (transmission, absorption and reflection) have been realized in single geometry unlike the earlier reported designs. The proposed structure has also been the measured responses show reasonable fabricated and agreement with the simulated results under normal incidence. A multifunctional AFSS with such diverse characteristics is an essential element for regulating electromagnetic wave propagation in manifold applications.
关键词： PIN diode,reconfigurable structure,Active frequency selective surface (AFSS),multifunctional AFSS (MAFSS)
更新于2025-09-04 15:30:14
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Distributed Fiber Optical Technology for Damage Identification of Engineering Structure
摘要： To conduct optical fiber monitoring rock slide model test and optical fiber monitoring of steel concrete interface slip model test, the large tri-axial shear test of geotechnical engineering was used. First, the data of sliding distance and optical loss and their dynamic range were obtained. Second, the slide distance and fiber loss relation curve and the fitting equation were worked out. Finally, the typical applications of optical fiber sensing technology in Rock Engineering (high slope engineering, rock foundation of Dam Engineering) slope stability and geological disaster monitoring were put forward. The results showed that optical fiber sensing was very sensitive, and the loss value was 30 to 50dB. The dynamic range of rock slide monitoring fiber was 3 to 3.5mm, and the dynamic range of the interface slip monitoring fiber was 1.6mm. Thus, the sensing system can detect the sliding process of the interface between the concrete and the steel plate. It provides some reference for the sliding monitoring of the composite materials.
关键词： Optical fiber sensing technology,engineering structure damage,sliding distance-fiber loss
更新于2025-09-04 15:30:14
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Impact of Low‐Frequency Vibrations on Charge Transport in High‐Mobility Organic Semiconductors
摘要： Despite decades of intensive studies of charge transport in organic semiconductors (OSs), understanding of mechanisms underpinning efficient charge transport in them remains elusive. Recently, it has been suggested that low-frequency (LF) vibrations are a limiting factor of charge transport in high-mobility OSs. Nevertheless, the relationship between the molecular structure, crystal packing, LF vibrations, and charge transport is still obscured. This hinders the focused search of high-mobility OSs so that researchers rely mainly on trial-and-error method. This review presents theoretical and experimental approaches to studying the LF vibrations and their role in charge transport with a focus on recent results. It is anticipated that tight cooperation between experimentalists and theorists will yield an advanced understanding of LF vibrations in OSs and their impact on charge transport. This will guide the design of novel high-mobility organic semiconductors for organic electronics.
关键词： structure–property relationship,organic electronics,Raman spectroscopy,electron–phonon interaction,charge mobility
更新于2025-09-04 15:30:14
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FABRICATION OF PYRAMIDAL CAVITY STRUCTURE WITH MICRON-SIZED TIP USING ANISOTROPIC KOH ETCHING OF SILICON (100)
摘要： Microelectromechanical System (MEMS) are systems of micron-sized structures and typically integrated with microelectronic components. Bulk micromachining using wet anisotropic etching is able to etch silicon substrates to a desired three-dimensional (3D) structure, depending on the silicon crystallographic orientation. To date, MEMS components i.e. thermal, pressure, mechanical, bio/chemical sensors have been fabricated with wet anisotropic etching of silicon. This paper presents the fabrication of a 3D pyramidal cavity structure with micron-sized tip of silicon (100) using anisotropic KOH etching of w/w 45 % at 80 oC temperature. Volume percent of 10 % IPA as a less polar diluent is added to the KOH etching solution in saturating the solution and controlling the etching selectivity and rate. Smooth etched silicon surface of hillock free is able to be achieved with IPA addition to the KOH etching solution. A characteristic V-shaped cavity with side angle of 54.8 degrees has successfully been formed and is almost identical to the theoretical structure model. Comparison of two different silicon nitride window masks on the micron-size tip formation is also investigated. Under etch, over etch and etching selectivity, as common problems effecting the micron-tip size variation, are also addressed in this work. In conclusion, anisotropic KOH etching as a simple, fast and inexpensive bulk micromachining technique, in fabricating 3D MEMS structure using silicon (100), is validated in this work.
关键词： pyramidal cavity structure,MEMS,KOH etching,anisotropic,crystallographic orientation
更新于2025-09-04 15:30:14
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Asymmetry of the Defect Structure of Semipolar GaN Grown on Si(001)
摘要： The defect structure of a thick (~15 μ m) semipolar gallium nitride (GaN) layer grown by hydride–chloride vapor phase epitaxy on a Si(001) substrate with buffer layers has been studied by transmission electron microscopy. The asymmetry of the defect structure of GaN epilayer has been revealed and analyzed. The influence of this asymmetry on the rate of decrease in the density of threading dislocations in the growing epitaxial layer is discussed.
关键词： transmission electron microscopy,semipolar GaN,threading dislocations,hydride–chloride vapor phase epitaxy,defect structure
更新于2025-09-04 15:30:14
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A Novel Multi-Exposure Image Fusion Method Based on Adaptive Patch Structure
摘要： Multi-exposure image fusion methods are often applied to the fusion of low-dynamic images that are taken from the same scene at different exposure levels. The fused images not only contain more color and detailed information, but also demonstrate the same real visual effects as the observation by the human eye. This paper proposes a novel multi-exposure image fusion (MEF) method based on adaptive patch structure. The proposed algorithm combines image cartoon-texture decomposition, image patch structure decomposition, and the structural similarity index to improve the local contrast of the image. Moreover, the proposed method can capture more detailed information of source images and produce more vivid high-dynamic-range (HDR) images. Speci?cally, image texture entropy values are used to evaluate image local information for adaptive selection of image patch size. The intermediate fused image is obtained by the proposed structure patch decomposition algorithm. Finally, the intermediate fused image is optimized by using the structural similarity index to obtain the ?nal fused HDR image. The results of comparative experiments show that the proposed method can obtain high-quality HDR images with better visual effects and more detailed information.
关键词： texture information entropy,adaptive selection,multi-exposure image fusion,patch structure decomposition
更新于2025-09-04 15:30:14