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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - A Dimension-Reduced Modal Space Detector in Deep-Sea Environment
摘要： The matched correlation detector (MCD), combining the received data with the sound transfer function (namely the replica field) is theoretically optimal for underwater passive detection. However, it suffers from the model mismatch problem caused by environmental uncertainties. And furthermore, when applied to the deep-sea environment, it encounters the large search range problem. In this paper, we focus on the source detection problem in deep-sea environment. To overcome the disadvantages of MCD, we choose the modal space detector (MSD) which uses a vertical linear array (VLA). We derive the expression of the deep-sea MSD and further, to improve the signal-to-noise ratio (SNR) of the test statistic, we propose a dimension-reduced form of MSD, which is termed as DR-MSD for short. By numerical simulation, we discuss that how source frequency, array depth and array aperture influence the dimension reduction. And we point out that the dimension-reduced number in DR-MSD decreases when the source frequency and the VLA aperture increase. The numerical results also indicate that DR-MSD can alleviate the search burden and obtain a better detection performance when compared to traditional MSD.
关键词： underwater acoustic,passive source detection,Deep-sea environment,dimension reduction,MSD
更新于2025-09-23 15:22:29
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Enhanced Solar Conversion of CO <sub/>2</sub> to CO Using Mn-doped TiO <sub/>2</sub> Based on Photo-thermochemical Cycle
摘要： Photo-thermochemical cycle (PTC) is a promising method to converting CO2 to solar fuels. To study the mechanism of CO2 reduction based on PTC, sol-gel synthesized titanium dioxide (ST) and Mn-doped TiO2 (MT) films were produced and applied to the PTC under simulated solar light irradiation. Commercial P25 (PT) was used as a reference. Experiments show that Mn-doped TiO2 produced more CO than undoped TiO2 and P25. The average CO production of 1.0 wt% MT by the PTC was 32.19 μmol?m?2?h?1, 4.36 times than that of ST and 3.63 times that of PT. Various characterization methods were conducted to investigated the effect of Mn ions doping on the photo-response and charge transfer of samples. Density functional theory (DFT) calculations were also performed to verify the analysis and enhance the PTC mechanism. In conclusion, several key factors that Mn ions promote CO2 conversion have been clarified.
关键词： Oxygen vacancy,Mn doping,DFT calculation,CO2 reduction,Photo-thermochemical cycle
更新于2025-09-23 15:22:29
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Exact analysis of imperfect angle-ply laminated panels with surface-bonded piezoelectric layers
摘要： The electromechanical behavior of an angle-ply laminated plate in cylindrical bending with surface-bonded piezoelectric layers is investigated. The interlaminar bonding of this smart laminate is described by a Kelvin–Voigt viscoelastic model. Besides, a matrix reduction method is employed to construct the transfer relations between the piezoelectric layer and the elastic strip. Based on the state-space approach, a state differential equation of the interfacial sliding displacements with respect to time variable is derived, from which the exact solutions are obtained in the time domain. Comparison with the existing techniques validates the high efficiency and excellent accuracy of the present analysis. Furthermore, the numerical results indicate that the intelligent laminate may lose partly or completely the load-bearing capacity and the function of sensor/actuators with time elapsing because of the viscoelastic interfaces.
关键词： Angle-ply laminate,Matrix reduction method,Viscoelastic interface,Exact analysis,State-space formulation
更新于2025-09-23 15:22:29
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Pulsed light treatment for the reduction of Salmonella Typhimurium and Yersinia enterocolitica on pork skin and pork loin
摘要： The aim of the presented study was to investigate the impact of pulsed light on the reduction of Salmonella Typhimurium and Yersinia enterocolitica on pork skin and loin. Fluences of 0.52 to 19.11 J/cm2 were applied to the pathogen-inoculated products to perform microbiological studies, as well as analyses of color, temperature, lipid peroxidation and odor. Reductions on pork skin ranged from 1.73 to 3.16 log for Salmonella and from 1.48 to 4.37 log for Yersinia. Microbial reduction was significantly lower on pork loin, varying between a minimum of 0.4 and a maximum of 1.7 log for both pathogens. Treatments ≥7.36 J/cm2 modified the color parameters of pork skin and fluences ≥9.66 J/cm2 rendered pork loin samples less red. All studies with pulsed light resulted in odor changes, except for the experiment on pork skin at 0.52 J/cm2. Despite significant microbiological reduction on pork skin, further studies should be carried out to optimize this promising technology.
关键词： Pulsed broad spectrum light,Lipid peroxidation,Microbial reduction,Pork,Sensory analysis
更新于2025-09-23 15:22:29
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Submillisievert CT angiography for carotid arteries using wide array CT scanner and latest iterative reconstruction algorithm in comparison with previous generations technologies: Feasibility and diagnostic accuracy
摘要： Objectives: To assess evaluability and diagnostic accuracy of a low dose CT angiography (CTA) protocol for carotid arteries using latest Iterative Reconstruction (IR) algorithm in comparison with standard 100 kVp protocol using previous generation CT and IR. Materials and Methods: 105 patients, referred for CTA of the carotid arteries were prospectively enrolled in our study and underwent CTA with 80 kVp and latest IR algorithm (group 1). Data were retrospectively compared with 100 consecutive patients with similar examination indications that had previously undergone CTA of carotid arteries with a standard 100 kVp protocol and a first generation IR algorithm (group 2). Image quality was evaluated with a 4-point Likert-scale. For each exam CT number, image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) at level of common carotid artery (CCA), internal carotid artery (ICA) and at level of Circle of Willis and Effective Dose (ED) were evaluated. 62 Group 1 patients underwent a clinically indicated DSA and results were compared with CTA. Results: No exams reported as not diagnostic. The overall mean CT number value of all arterial segments was above 450 HU in both groups. Significant lower noise, and higher SNR and CNR values were found in group 1 in comparison with group 2 despite the use of 80 kVp. In 62-group 1 patients studied by DSA, CTA showed in a segment-based analysis a sensitivity, negative predictive value and accuracy of 100%, 100% and 99% respectively. Mean ED in group 1 was 0.54±0.1 mSv with a dose reduction up to 86%. Conclusions: CTA for carotid arteries using latest IR algorithm allows to perform exams with submillisievert radiation exposure maintaining good image quality, overall evaluability and diagnostic accuracy.
关键词： atherosclerosis,Carotid arteries,Computed Tomography Angiography,Iterative reconstruction algorithm.,dose reduction
更新于2025-09-23 15:22:29
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Two-dimensional-related catalytic materials for solar-driven conversion of CO <sub/>x</sub> into valuable chemical feedstocks
摘要： The discovery of improved chemical processes for CO and CO2 hydrogenation to valuable hydrocarbon fuels and alcohols is of paramount importance for the chemical industry. Such technologies have the potential to reduce anthropogenic CO2 emissions by adding value to a waste stream, whilst also reducing our consumption of fossil fuels. Current thermal catalytic technologies available for CO and CO2 hydrogenation are demanding in terms of energy input. Various alternative technologies are now being developed for COx hydrogenation, with solar-driven processes over two-dimensional (2D) and 2D-related composite materials being particularly attractive due to the abundance of solar energy on Earth and also the high selectivity of defect-engineered 2D materials towards specific valuable products under very mild reaction conditions. This review showcases recent advances in the solar-driven COx reduction to hydrocarbons over 2D-based materials. Optimization of 2D catalyst performance demands interdisciplinary research that embraces catalyst electronic structure manipulation and morphology control, surface/interface engineering, reactor engineering and density functional theory modelling studies. Through improved understanding of the structure–performance relationships in 2D-related catalysts which is achievable through the application of modern in situ characterization techniques, practical photo/photothermal/photoelectrochemical technologies for CO and CO2 reduction to high-valuable products such as olefins could be realized in the not-too-distant future.
关键词： hydrocarbons,feedstocks,two-dimensional materials,solar-driven conversion,catalysis,COx reduction
更新于2025-09-23 15:22:29
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Lightweight Ultra-Wideband RCS Reduction Structure using Double-Layer Metasurfaces
摘要： In this paper, we propose the design of a lightweight RCS reduction structure using double-layer metasurfaces. The structure is composed of two layers of metasurfaces spaced by PMI foams. To extend the bandwidth, two unit structures are firstly designed to operating in two respective bands for circularly polarized (CP) waves, which are then combined to act as the unit structure of the double-layer metasurface. The metasurface is expected to operate in two continuous bands. Nevertheless, due to the couplings between the two unit structures, there is Fano resonance that prohibits merging of the two bands. To solve this problem, we tune the resonant frequency of the bottom unit structure to suppress the Fano resonance and obtain a merged band. The combined unit structure is employed as the element of chessboard configuration, which can reduce RCS by more than 10dB in an ultra-wideband (4.5-16.5GHz). We designed, fabricated and measured a lightweight prototype (the aerial density is 726g/m2). Both the simulation and experiment result verify the design. This work provides an effective method of extending the operation band of RCS reduction without sacrificing the efficiency.
关键词： metasurface,ultra-wideband,Fano resonance,RCS reduction
更新于2025-09-23 15:22:29
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Laplacian Regularized Spatial-Aware Collaborative Graph for Discriminant Analysis of Hyperspectral Imagery
摘要： Dimensionality Reduction (DR) models are of signi?cance to extract low-dimensional features for Hyperspectral Images (HSIs) data analysis where there exist lots of noisy and redundant spectral features. Among many DR techniques, the Graph-Embedding Discriminant Analysis framework has demonstrated its effectiveness for HSI feature reduction. Based on this framework, many representation based models are developed to learn the similarity graphs, but most of these methods ignore the spatial information, resulting in unsatisfactory performance of DR models. In this paper, we ?rstly propose a novel supervised DR algorithm termed Spatial-aware Collaborative Graph for Discriminant Analysis (SaCGDA) by introducing a simple but ef?cient spatial constraint into Collaborative Graph-based Discriminate Analysis (CGDA) which is inspired by recently developed Spatial-aware Collaborative Representation (SaCR). In order to make the representation of samples on the data manifold smoother, i.e., similar pixels share similar representations, we further add the spectral Laplacian regularization and propose the Laplacian regularized SaCGDA (LapSaCGDA), where the two spectral and spatial constraints can exploit the intrinsic geometric structures embedded in HSIs ef?ciently. Experiments on three HSIs data sets verify that the proposed SaCGDA and LapSaCGDA outperform other state-of-the-art methods.
关键词： hyperspectral imagery,graph embedding,dimensionality reduction,collaborative representation,discriminant analysis
更新于2025-09-23 15:22:29
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Sustainable thermionic emission in CO2, helium and argon surroundings
摘要： Thermionic materials are commonly used in high vacuum (< 10?5 mbar). We measured thermionic emission of different doped metal-oxides cathodes – Zr doped Gd2O3 and Nb doped SrTiO3 (1 1 1) – in a CO2 surrounding, at T = 1300 °C and ～10?4 mbar ≤ p ≤ 300 mbar. Experimental setup validation and reference data were provided by measurements using cathodes made of CeB6, a commercial thermionic material, and by using either helium or argon as the surrounding gas. The study’s results could be used when examining enhancement of CO2 reduction to CO using vibration’s excitation. The thermionic emission of all cathodes decreased gradually as the pressure increased, as expected, but the exposure to CO2 did not cause a deterioration of the Zr doped Gd2O3 cathodes. They retained a reasonable emission, of ～60% and ～40% of the current in vacuum, at a CO2 pressure of 50 mbar and 300 mbar, respectively, over 20 operation hours. The data suggest that in the presence of significant gas pressure in the cathodes surrounding, the electric dipole of CO2 molecules and the cathode’s surface roughness may induce several mechanisms, which could affect the current emission.
关键词： Surface,CO2 helium argon,CO2 reduction,Thermionic emission
更新于2025-09-23 15:22:29
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Time–frequency-based non-harmonic analysis to reduce line-noise impact for LIGO observation system
摘要： Gravitational waves (GWs) are the subjects of a new type of space observation that is expected to reveal new information on the early universe, neutron stars, and black holes. To reduce the impact of the widely used notch filter on GW observations, we propose the use of non-harmonic analysis (NHA) for the high-accuracy visualization of GWs. A simulated signal is used to compare the results obtained using short-time Fourier transform, Hilbert spectrum analysis, Hilbert–Huang transformation, and NHA. We demonstrate that NHA exhibits superior performance. In addition, we verify the analytical precision of NHA using actual data measured by the Laser Interferometer Gravitational-Wave Observatory (LIGO). We found that the high time–frequency resolution of NHA and the small influence that the analysis window has on this technique facilitate effective quantitative analysis, even for LIGO signals containing mixing noise. In addition, we achieve GW visualization up to the noise limit without using a notch filter.
关键词： Noise reduction,Non-harmonic analysis,Gravitational wave
更新于2025-09-23 15:22:29