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Three Dimensional Structures of NiO Nanoporous/ZnO Nanoarray Film for Enhanced Electrochromic Performance
摘要： An electrochromic device using the as-obtained NiO nanoporous/ZnO nanoarray working electrode was constructed and assembled. NiO nanoporous/ZnO nanoarray three dimensional structures was prepared on ITO glass substrate by a two-step route which combined chemical bath deposition method with hydrothermal method. NiO nanoporous/ZnO nanoarray electrode reveals noticeable improvement of electrochromism compared to unitary NiO nanoporous, including larger optical modulation (81%), higher coloration efficiency (78.5 cm2/C), faster response times (2.6 s and 9.7 s for coloring and bleaching), and favourable durability performance. Such enhancement is mainly attributed to the three dimensional structures of NiO nanoporous coated on ZnO nanoarray. Namely, (1) uniform hexagonal ZnO nanoarray loaded more amount of NiO nanoporous, (2) NiO nanoporous cross-linked with ZnO nanorods provided a loose interspace morphology, (3) stronger adhesion between ZnO nanorods and ITO rested with ZnO seed, (4) core-shell and cross-linked structures promoted electrolyte infiltration, and (5) appropriate bandgap improved the charges transfer.
关键词： NiO nanoporous,ZnO nanorod array,electrochromic,three dimensional
更新于2025-09-23 15:23:52
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Optical Properties of Nanohole Arrays with Various Depths
摘要： Studies to imitate structural colors have been conducted with various methods, most of which are disadvantageous for mechanical stability and economic feasibility because of complexity or lack of reproducibility. Numerous alternatives to overcome these shortcomings have been proposed. One such method is the anodic oxidation of aluminum, which requires relatively simple equipment and techniques. The present study used the aluminum anodic oxidation process to fabricate nanohole arrays of various sizes. Furthermore, using the finding that the structure color is the most strongly influenced by the nanohole depth based on the Bragg's Law, this study fabricated nanoholes of various depths to identify the structural colors arising from varied depths. This study further identified the colors from the same color series occurring periodically at each interval of 250 nm using the CIE 1931 color coordinate system. Moreover, nanohole arrays with two different depths were fabricated on a single substrate to confirm the coexistence of different colors and their capacity for deformation into various shapes.
关键词： Nanohole array,Structural color,Bragg's law,Anodic aluminum oxidation,Thin film effect
更新于2025-09-23 15:23:52
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Hybrid Camera Array-Based UAV Auto-Landing on Moving UGV in GPS-Denied Environment
摘要： With the rapid development of Unmanned Aerial Vehicle (UAV) systems, the autonomous landing of a UAV on a moving Unmanned Ground Vehicle (UGV) has received extensive attention as a key technology. At present, this technology is confronted with such problems as operating in GPS-denied environments, a low accuracy of target location, the poor precision of the relative motion estimation, delayed control responses, slow processing speeds, and poor stability. To address these issues, we present a hybrid camera array-based autonomous landing UAV that can land on a moving UGV in a GPS-denied environment. We first built a UAV autonomous landing system with a hybrid camera array comprising a fisheye lens camera and a stereo camera. Then, we integrated a wide Field of View (FOV) and depth imaging for locating the UGV accurately. In addition, we employed a state estimation algorithm based on motion compensation for establishing the motion state of the ground moving UGV, including its actual motion direction and speed. Thereafter, according to the characteristics of the designed system, we derived a nonlinear controller based on the UGV motion state to ensure that the UGV and UAV maintain the same motion state, which allows autonomous landing. Finally, to evaluate the performance of the proposed system, we carried out a large number of simulations in AirSim and conducted real-world experiments. Through the qualitative and quantitative analyses of the experimental results, as well as the analysis of the time performance, we verified that the autonomous landing performance of the system in the GPS-denied environment is effective and robust.
关键词： GPS-denied environment,moving UGV,UAV autonomous landing,hybrid camera array,motion compensation
更新于2025-09-23 15:23:52
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Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals
摘要： The main aim of this work is to provide a method to retrieve the intrinsic spatial resolution of a gamma-ray detector block based on monolithic crystals within an assembled scanner. This method consists on a discrimination of the data using a software collimation process. The results are compared with an alternative method of separating two detector blocks far enough to produce a "virtual" source collimation due to the geometric constraints on the allowed coincidence event angles. A theoretical model has been deduced to fit the measured light distribution profiles, allowing estimating the detector intrinsic spatial resolution. The detector intrinsic spatial resolution is expected to follow a Gaussian distribution and the positron-emitter source shape, given the small size of a 22Na source with 0.25 mm in diameter, can be assumed to follow a Lorentzian profile. However, the collimation of the data modifies the source shape that is no longer a pure Lorentzian distribution. Therefore, the model is based on the convolution of a Gaussian shaped distribution (contribution of the detector) and a modified Lorentzian distribution (contribution of the collimated source profile) that takes into account the collimation effect. Three LYSO crystals geometries have been studied in the present work, namely a 10 mm thick trapezoidal monolithic block, and two rectangular monolithic blocks with thicknesses of 15 mm and 20 mm, respectively. All the blocks have size dimensions of 50 mm × 50 mm. The experimental results yielded an intrinsic detector spatial resolution of 0.64 ± 0.02 mm, 0.82 ± 0.02 and 1.07 ± 0.03 mm, for the 10 mm, 15 mm and 20 mm thick blocks, respectively, when the source was placed at the center of the detector. The detector intrinsic spatial resolution was moreover evaluated across one of the axis of each crystal. These values worsen to an average value of 0.68 ± 0.04 mm, 0.90 ± 0.14 and 1.29 ± 0.19 mm, respectively, when the whole crystal size is considered, as expected. These tests show an accurate method to determine the intrinsic spatial resolution of monolithic-based detector blocks, once assembled in the PET system.
关键词： Intrinsic spatial resolution,SiPM array,Monolithic blocks,Positron Emission Tomography,Gamma ray detectors
更新于2025-09-23 15:23:52
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A compact leaky-wave antenna using a planar spoof surface plasmon polariton structure
摘要： This article presents and validates a leaky-wave antenna by using the spoof surface plasmon polariton (SSPP) technique. By properly designing the proposed SSPP unit, the SSPP wave can be switched between the confinement and radiation modes. A large radiation efficiency can be achieved by properly designing the modulation depth, which ensures that a compact SSPP leaky-wave array can be realized by using a small number of SSPP radiation units. To verify the design, a prototype which consists of a SSPP feeding network and a 4 by 4 SSPP radiation units has been fabricated by using a low cost FR-4 substrate. A good agreement between simulated and measured results has been obtained. The proposed array antenna shows the promising capability of the SSPP technique for leaky-wave antenna applications.
关键词： dispersion curve,the spoof surface plasmon polariton (SSPP),SSPP antenna array,SSPP power divider
更新于2025-09-23 15:23:52
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Spectral-optical-tweezer-assisted fluorescence multiplexing system for QDs-encoded bead-array bioassay
摘要： As an efficient tool in the multiplexed detection of biomolecules, bead-array could achieve separation-free detection to multiple targets, making it suitable to analyze valuable and scarce samples like antigen and antibody from living organism. Herein, we propose a spectral-optical-tweezer-assisted fluorescence multiplexing system to analyze biomolecule-conjugated bead-array. Using optical tweezer, we trapped and locked beads at the focus to accept stimulation, offering a stable and optimized analysis condition. Moving the system focus and scanning the sample slide, we achieved emissions collection to QDs-encoded bead-array after the multiplexed detection. The emission spectra of fluorescence were collected and recorded by the spectrometer. By recognizing locations of decoding peaks and counting the intensities of label signals of emission spectra, we achieved qualitative and quantitative detection to targets. As proof-of-concept studies, we use this system to carry out multiplexed detection to various types of anti-IgG in the single sample and the detection limit reaches 1.52 pM with a linear range from 0.31 to 10 nM. Through further optimization of experimental conditions, we achieved specific detection to target IgG with sandwich method in human serum and the detection limit reaches as low as 0.23 pM with a linear range from 0.88 to 28 pM, validating the practical application of this method in real samples.
关键词： bead-array,QDs encoding,optical tweezers,multiplexed biodetection
更新于2025-09-23 15:23:52
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Application of metasurfaces in the design of performance-enhanced low-profile antennas
摘要： This paper presents a review of metasurface-based antennas conducted at the Microwave Communication Laboratory (MCL) of Ajou University in the Republic of Korea. In this paper, pro?le miniaturization, bandwidth enhancement, multiband operation, and radiation pattern control of metasurface-based antennas are considered. The paper ?rst presents metasurface-based antennas implemented by placing various radiators on top of the metasurface. It then presents antennas implemented by placing the radiators below the metasurface with and without the ground plane. Metasurface-based antennas are not only able to achieve high ef?ciency with a low pro?le but they are also able to generate extra resonances from the metasurface structures, which signi?cantly enhances the overall performance of the antennas. These additional resonances were utilized in multiband and/or wideband operations. In addition, the design of a planar compact wide-gain-bandwidth metasurface-based antenna and its radiation characteristics are presented at a terahertz (THz) frequency range. The THz antennas were designed with metasurfaces and a planar leaky-wave feeding structure. Finally, the outlook on future research at the MCL for antenna-related work and their applications using metasurfaces is provided.
关键词： surface wave resonance,sequential rotation,crossed dipole,arti?cial magnetic conductor,metamaterial,wideband,circular polarization,leaky-wave,Antenna,array,metasurface
更新于2025-09-23 15:23:52
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Reduced order derivation of the two-dimensional band structure of a mixed-mode resonator array
摘要： In this paper, the 2D band structure of a mixed-mode metamaterial resonator array for in-plane waves is investigated. The band structure in the interior and on the boundary of the irreducible Brillouin zone and 1D dispersion diagrams for different propagation angles are calculated numerically and presented. Additionally, a reduced order analytical method is established to compare and approximate the band structure. The studied metamaterial, with a T-shaped cantilever beam as the resonator in its square array repeating unit cells, exhibits branches with mixed P and SV waves except at exactly one angle of propagation. This paper also reports on the occurrence of avoided level crossings, which are related to the existence of exceptional points in the complex domain. A reduced order analytical approach is used that can generate partial (low branches) band structure with relatively little computational effort. The reduced order model agrees well with the numerical results for these low branches and can provide support in mode identification and band sorting. With proper adjustments in parameters, this analytical method will be applicable to other metamaterials that have a similar unit cell structure.
关键词： band structure,reduced order model,resonator array,metamaterial,avoided level crossings,mixed-mode waves
更新于2025-09-23 15:23:52
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Passive cooling of building-integrated photovolatics in desert conditions: Experiment and modeling
摘要： The ef?ciency of photovoltaic modules depends mainly on the cell operating temperatures. Performance enhancement of building-integrated photovoltaic (BIPV) panels by passive cooling has been investigated both experimentally and with computational modeling. It has been shown that mounting the BIPV with a narrow channel can reduce the operating temperature of the photovoltaic panel. This enhancement in the heat transfer from the PV panel results in decreasing the average temperature of the PV panel from 5 to 10 (cid:1)C. Results show that having a 30 cm channel beneath the panel can increase the electrical output by 3e4%. This increase in PV output can translate into a signi?cant amount over the life cycle of a given PV module. Various channel aspect ratios have been tested in order to correlate the enhancement in performance to the cooling channel geometry. There is signi?cant consistency between the experimentally measured PV panel surface temperatures and those obtained from the computational model.
关键词： Building-integrated,Thermal performance,Passive cooling,Photovoltaic array
更新于2025-09-23 15:23:52
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Polarization Reconfigurable Corner Truncated Square Microstrip Array Antenna
摘要： In this paper, a simple 2 × 2 polarization reconfigurable planar microstrip array antenna is presented. It is based on electrical switching technology using PIN diodes. Each element of the array is excited with the aid of the corporate feed technique. Each element of the proposed structure consists of a corner truncated square patch connected to parasitic triangular conductors by means of PIN diodes. The array element is configured to facilitate linear polarization (LP), right-hand circular polarization (RHCP) or left-hand circular polarization (LHCP) by means of 4 independently biased PIN diodes. The proposed antenna is designed and simulated using electromagnetic simulation software CST Microwave Studio. In order to experimentally validate the design, a prototype is fabricated on a 1.6 mm thick RT Duroid substrate of relative permittivity εr = 2.2. The performance of the antenna is validated experimentally using 16 PIN diodes. The simulation and measured results for all the polarization states of the array antenna are found to be in good agreement. The measured results have established the polarization reconfigurable ability of the antenna for 5.7–6.0 GHz operating band. The proposed antenna is suitable for C-band point-to-point communication applications.
关键词： PIN diode switch,polarization reconfigurable,corporate feed network,reconfigurable antenna,Array antenna,circular polarization
更新于2025-09-23 15:23:52