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1.
Aiming at the performance degradation of the existing presentation attack detection methods due to the illumination variation, a two-stream vision transformers framework (TSViT) based on transfer learning in two complementary spaces is proposed in this paper. The face images of RGB color space and multi-scale retinex with color restoration (MSRCR) space are fed to TSViT to learn the distinguishing features of presentation attack detection. To effectively fuse features from two sources (RGB color space images and MSRCR images), a feature fusion method based on self-attention is built, which can effectively capture the complementarity of two features. Experiments and analysis on Oulu-NPU, CASIA-MFSD, and Replay-Attack databases show that it outperforms most existing methods in intra-database testing and achieves good generalization performance in cross-database testing. 相似文献
2.
针对高帧频、全局曝光和光谱平坦等成像应用需求,设计了一款高光谱成像用CMOS图像传感器。其光敏元采用PN型光电二极管,读出电路采用5T像素结构。采用列读出电路以及高速多通道模拟信号并行读出的设计方案来获得低像素固定图像噪声(FPN)和非均匀性抑制。芯片采用ASMC 0.35μm三层金属两层多晶硅标准CMOS工艺流片,为了抑制光电二极管的光谱干涉效应,后续进行了光谱平坦化VAE特殊工艺,并对器件的光电性能进行了测试评估。电路测试结果符合理论设计预期,成像效果良好,像素具备积分可调和全局快门功能,最终实现的像素规模为512×256,像元尺寸为30μm×30μm,最大满阱电子为400 ke^(-),FPN小于0.2%,动态范围为72 dB,帧频为450 f/s,相邻10 nm波段范围内量子效率相差小于10%,可满足高光谱成像系统对CMOS成像器件的要求。 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(12):8145-8154
High-quality p-type semiconducting Co3O4 with mixed morphology of nanoparticles/nanorods are synthesized using a hydrothermal route for high response and selective hydrogen sulphide (H2S) sensor application. XRD and Raman studies revealed the crystal structure and molecular bonding for obtained Co3O4, respectively. The nanoparticles/nanorods-like structures were confirmed for Co3O4 using FESEM and TEM analysis. The EDS and XPS spectra analysis were carried out for elemental composition and chemical atomic states of Co3O4. The Co3O4 sensor is investigated for gas sensing properties in dynamic conditions. The sensor exhibited the highest selectivity towards H2S among various hydrogen-contained gases at 225 °C. The sensor revealed a high response of 357% and 44% for 100 and 10 ppm H2S gas concentrations, respectively. The Co3O4 sensor exhibited a systematic dynamic resistance response for 100–10 ppm range H2S gas. The excellent dynamic resistance repeatability of the sensor was shown towards 25 ppm H2S gas. The response of Co3O4 sensor was investigated at different operating temperatures and H2S concentrations. The sensor stability and H2S sensing mechanism for the Co3O4 sensor have been reported. Highly uniform and mixed nanostructures of Co3O4 can be the potential sensor material for real-time high-performance H2S sensor application. 相似文献
4.
《Ceramics International》2022,48(11):15043-15055
This work reports magnetic permeability and ammonia gas sensing characteristics of La3+ substituted Co–Zn nano ferrites possessing chemical formula Co0.7Zn0.3LaxFe2-2xO4 (x = 0–0.1) synthesized by a sol-gel route. Refinement of X-ray diffraction (XRD) patterns of the ferrite powders by the Rietveld technique has revealed the creation of single-phase spinel structure. The tenancy of constituent cations at tetrahedral/octahedral sites was obtained from the refinement of XRD. The crystallite sizes calculated from the W–H method vary from 20 to 24 nm. The scanning electron microscope (SEM) profiles of the ferrite samples were analyzed for the morphological details. The energy dispersive X-ray analysis (EDAX) patterns of the samples were obtained to test the elemental purity of the ferrites within their stoichiometry. The transmission electron microscope (TEM) image of the ferrite (x = 0.1) exhibits the spherical and oval shaped particles with a mean size of 20 nm. Fourier transform infra-red (FTIR) spectra were analyzed to confirm the superseding of La3+ cations at octahedral sites. The Brunauer-Emmett-Teller (BET) analysis of nitrogen adsorption-desorption isotherms of the ferrites was performed to investigate the porous structure and to determine the surface area of the nanocrystalline ferrites. The oxidation states of the constituent ions were confirmed by means of X-ray photoelectron spectroscopy (XPS). The complex permeability as a function of frequency was studied to explore the effects of structural parameters on the magnetic behaviour of the ferrites. Analysis of gas sensing properties of the ferrites have proved that the Co–Zn–La ferrite with controlled La composition can be utilized as an effective ammonia gas sensing material in commercial gas sensors. 相似文献
5.
Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔECMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns. 相似文献
6.
《中国稀土学报(英文版)》2022,40(11):1691-1698
White light-emitting diodes (WLEDs) fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting. The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor. Here, we report a high quality white light-emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ with spectral distribution covering whole visible region. Blue light emission originates from Ce3+ ions occupying preferentially Ba2+ site by controlling synthesis conditions. Green and red lights are obtained from Eu2+ occupying Ba2+ (and Ca2+) site and Mn2+ occupying Ca2+ site, respectively. In this triple-doped phosphor, strong red emission with a low concentration of Mn2+ is realized by the efficient energy transfer from Ce3+ and Eu2+ to Mn2+. Furthermore, high quality white light is accomplished by properly tuning the relative doping amount of Ce3+(K+)/Eu2+/Mn2+ based on efficient simultaneous energy transfer. The results indicate that Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ is a promising white light-emitting phosphor in WLEDs application. 相似文献
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9.
The wearable intelligent electronic product similar to electronic skin has a great application prospect. However, flexible electronic with high performance pressure sensing functions are still facing great challenges. In this paper, the highly sensitive flexible electronic skin (FES) based on the PVDF/rGO/BaTiO3 composite thin film was fabricated using the near-field electrohydrodynamic direct-writing (NFEDW) method. The PVDF/rGO/BaTiO3 composite solution was directly written on flexible substrate by the NFEDW method to fabricate FES with micro/nano fiber structure, which has the function of sensing pressure with high sensitivity and fast response. The surface morphology and microstructure were characterized by SEM, AFM, and optical microscope in detail. The fabricated FES has high sensitivity (59 kPa−1) and faster response time (130 ms). FES has been successfully applied to the detection of human motion and subtle physiological signals. The experimental results show that FES has good stability and reliability. FES can recognize human motion, and it has a broad application prospect in the field of wearable devices. 相似文献
10.
随着海洋资源勘探和海洋污染物监控工作的开展,水文数据的监测和采集等已经成为重要的研究方向。其中,水下无线传感器网络在水文数据采集过程中起着举足轻重的作用。本文研究的是水下无线传感器二维监测网络模型中,传感器节点数据采集的问题,其设计方法是通过自组织映射(Self-organizing mapping,SOM)对传感器节点进行路径最优化处理,结合优化的路径图形和K-means算法找到路径内部聚合点,利用聚合点和传感器的节点得到传感器通信半径内的数据采集点,最后通过SOM得到水下机器人(Autonomous underwater vehicle,AUV)到各个数据采集点采集数据的最优路径。经过实验验证,在水下1 200 m × 1 750 ![]()
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m范围内布置52个传感器节点的情景下,数据采集点相比于传感器节点路径规划采用相同的采集顺序得到的路径优化了6.7%;对数据采集点重新进行自组织路径规划得到的路径比传感器结点路径的最优解提高了12.2%。增加传感器节点的数量,其结果也大致相同,因此采用该方法可以提高水下机器人采集数据的效率。 相似文献