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[IEEE 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Shenzhen, China (2018.7.13-2018.7.15)] 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Image Correction Technology Supporting Power Device Monitoring
摘要： An automatically monitoring method of electrical device is proposed in this paper. Various visualization monitoring systems are built to save maintenance costs and improve operation efficiency. Limited to the working principle of ordinary camera lens, obtained image is easy to produce image deformity and aberration. In order to solve this problem, an image correction method based on phase-only correlation (POC) in power industry is suggested to get the image information of the actual situation of device. Experimental results show that proposed method can effectively save testing cost and achieve a high correction accuracy of device image.
关键词： Device monitoring,Image distortion,Image correction,Phase-only correlation
更新于2025-09-23 15:22:29
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Evaluating the Effect on Demodulation With a Comprehensive Model of Distortions of Fiber Bragg Grating Sensing Signals
摘要： Spectral distortions are complex and unpredictable in fiber Bragg grating (FBG) sensing applications. An inappropriate choice of FBG demodulation algorithm will lead to unacceptable results in practice. Although many demodulation algorithms have been developed for distorted spectra, they may be limited for some types of spectral distortion. Until now, no model of FBG spectral distortion has been proposed to test different demodulation algorithms. Here, we fulfill this aim by introducing a comprehensive model with asymmetrical distortion, multi-peaks distortion, interferometric noise, background noise, and random noise. Using numerical simulations, we evaluate the performance of eight most typical demodulation algorithms with this model. We show that different algorithms should be used within specific ranges of spectral distortions. Altogether, this study provides a guide map as useful reference for selecting an appropriate FBG demodulation algorithm for practical applications. Furthermore, our proposed model paves the way for developing more reliable FBG demodulation algorithms for different spectral distortions.
关键词： spectral distortion,fiber Bragg grating,Demodulation
更新于2025-09-23 15:22:29
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Valley engineering by strain in Kekulé-distorted graphene
摘要： A Kekulé bond texture in graphene modi?es the electronic band structure by folding the Brillouin zone and bringing the two inequivalent Dirac points to the center. This can result in the opening of a gap (Kek-O) or the locking of the valley degree of freedom with the direction of motion (Kek-Y). We analyze the effects of uniaxial strain on the band structure of Kekulé-distorted graphene for both textures. Using a tight-binding approach, we introduce strain by considering the hopping renormalization and corresponding geometrical modi?cations of the Brillouin zone. We numerically evaluate the dispersion relation and present analytical expressions for the low-energy limit. Our results indicate the emergence of a Zeeman-like term due to the coupling of the pseudospin with the pseudomagnetic strain potential which separates the valleys by moving them in opposite directions away from the center of the Brillouin zone. For the Kek-O phase, this results in a competition between the Kekulé parameter that opens a gap and the magnitude of strain which closes it, while for the Kek-Y phase, it results in a superposition of two shifted Dirac cones. As the Dirac cones are much closer in the superlattice reciprocal space than in pristine graphene, we propose strain as a control parameter for intervalley scattering.
关键词： Brillouin zone,tight-binding,strain,graphene,valley engineering,Kekulé distortion
更新于2025-09-23 15:22:29
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Oxygen Vacancy Induced Structural Distortions in Black Titania - A Unique Approach using Soft X-Ray EXAFS at the O K-Edge
摘要： Unknown changes in the crystalline order of regular TiO2 result in the formation of black titania, which has garnered significant interest as a photocatalytic material due to the accompanying electronic changes. Herein, we determine the nature of the lattice distortion caused by an oxygen vacancy that in turn results in the formation of mid-band gap states found in previous studies of black titania. We introduce an innovative technique using a state-of-the-art silicon drift detector, which can be used in conjunction with extended x-ray absorption fine structure (EXAFS) to measure bulk interatomic distances. We illustrate how the energy dispersive nature of such a detector can allow us an unimpeded signal, indefinitely in energy space, thereby sidestepping the hurdles of more conventional EXAFS, which is often impeded by other absorption edges.
关键词： black titania,EXAFS,black TiO2,structural distortion,photocatalytic
更新于2025-09-23 15:22:29
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Image defogging approach based on incident light frequency
摘要： Aiming at solving the problem of color distortion existing in the dark original pruning algorithm, an improved transmittance computation approach separated for each color channel is proposed. Firstly, the influence of the incident light frequency on the transmittance of each color channel is analyzed based on Beer-Lambert law. Meanwhile, the proportional relationship among the transmittance of each channel is deduced. Secondly, the image is resumed to improve the operation efficiency. After that, the image is pretreated to get the refined transmittance. Finally, the transmittance of all the color channels is obtained through the proportional relationship. And the corresponding transmittance is used to recover the image on each channel. Thus, the image defogging is realized. We evaluate the proposed algorithm qualitatively and quantitatively. From the subjective results, the proposed algorithm has better visual effect than that of the other algorithms, and our method has more details compared to the other two methods. While from the objective results, the proposed approach can achieve natural image color without high saturation, and reduce the running time by 4 to 10 times compared with several state-of-art algorithms. The proposed algorithm can obtain a higher color fidelity and a better image color in terms of e, r and H. The proposed method is obviously superior to those of the others in terms of no-reference quality evaluator in spatial domain and has the highest average PSNR value.
关键词： Incident light frequency,Image defogging,Transmittance,Dark primary color prior,Color distortion
更新于2025-09-23 15:22:29
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Precompensation and System Parameters Estimation for Low-Cost Nonlinear Tera-Hertz Transmitters in the Presence of I/Q Imbalance
摘要： Tera-Hertz (THz) transmission can offer several attractive applications, yet developing low-cost energy-efficient THz devices is at an early stage. The most promising low-cost THz transmitter architecture in the literature is the so-called frequency-multiplier-last architecture. However, it is incapable of transmitting quadrature amplitude modulation (QAM) due to the architecture's inherent nonlinear distortions. We study such nonlinear THz communication systems by incorporating the nonlinearity aspects of the low-cost THz devices and the inphase and quadrature (I/Q) imbalance effect into the signal model. Then, we propose a precompensation scheme to compensate the nonlinearity and I/Q imbalance effects, thus enabling the QAM-capable frequency-multiplier-last architecture for THz systems. The proposed precompensation scheme requires the knowledge of the system parameters. To estimate the system parameters, we propose a maximum-likelihood estimator and its practical implementation via an alternating estimation algorithm. We also derive closed-form expressions for the Cramér–Rao lower bounds (CRLBs) of the system parameters estimation, and design the pilot sequence used in estimating the system parameters. Numerical results show that the proposed precompensation schemes overcome the prominent problems experienced in the existing THz systems, namely severe nonlinear distortions of the modulation symbols as well as spectral spreading and/or large spectrum sidelobes, and mitigate the I/Q imbalance effect.
关键词： precompensation,estimation,QAM,I/Q imbalance,nonlinear distortion,Low-cost,Tera-Hertz
更新于2025-09-23 15:22:29
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Multiple Access With Polarity Division Sparse Code for Visible Light Communication
摘要： The increasing demand of mobile internet and Internet of Things poses challenging requirements for indoor wireless communication. Visible light communication (VLC) is a promising technology to alleviate the growing traffic problem. In addition, nonlinear distortion of light emitting diodes (LEDs) results in a poor link quality. In this paper, we propose multiple access with polarity division sparse code (PDSC) for VLC, which is based on nonorthogonal multiple access and spatial characteristic of LEDs. The experimental results indicate that the PDSC significantly enhances capacity and spectral efficiency of VLC network compared with orthogonal frequency division multiple access. We also demonstrate that the PDSC can optimize the problem of nonlinear distortion with polarity division. The experimental results reveal that PDSC is a promising multiple access scheme for the indoor VLC networks.
关键词： Nonorthogonal multiple access,visible light communication,PDSC,nonlinear distortion optimization
更新于2025-09-23 15:22:29
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Linearized Single Sideband Modulation Link with High SFDR Performance
摘要： A linearized fiber optic link without dispersion induced power fading is presented. It is based on using a dual-drive dual-polarization modulator to generate a single sideband RF modulated optical signal and an orthogonally linear polarized unmodulated optical signal. The link is linearized and consequently the third order spurious free dynamic range (SFDR3) is largely increased by designing the angle of a linear polarizer connected to the modulator output to suppress the third order intermodulation distortion. The two Mach Zehnder modulators inside the dual-polarization modulator are biased at the quadrature point. Hence there is no degradation in the link second order spurious free dynamic range (SFDR2) performance compared to the conventional quadrature-biased Mach Zehnder modulator link. Experimental results demonstrate a single sideband modulation link without dispersion induced power fading and a record measured SFDR3 of 121.4 dB?Hz4/5.
关键词： optical single sideband,intermodulation distortion,linearization techniques,dynamic range,Analog optical links
更新于2025-09-23 15:22:29
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Correcting geometric distortions in stereoscopic 3D imaging
摘要： Motion in a distorted virtual 3D space may cause visually induced motion sickness. Geometric distortions in stereoscopic 3D can result from mismatches among image capture, display, and viewing parameters. Three pairs of potential mismatches are considered, including 1) camera separation vs. eye separation, 2) camera field of view (FOV) vs. screen FOV, and 3) camera convergence distance (i.e., distance from the cameras to the point where the convergence axes intersect) vs. screen distance from the observer. The effect of the viewer’s head positions (i.e., head lateral offset from the screen center) is also considered. The geometric model is expressed as a function of camera convergence distance, the ratios of the three parameter-pairs, and the offset of the head position. We analyze the impacts of these five variables separately and their interactions on geometric distortions. This model facilitates insights into the various distortions and leads to methods whereby the user can minimize geometric distortions caused by some parameter-pair mismatches through adjusting of other parameter pairs. For example, in postproduction, viewers can correct for a mismatch between camera separation and eye separation by adjusting their distance from the real screen and changing the effective camera convergence distance.
关键词： display parameters,stereoscopic 3D,viewing parameters,geometric distortions,distortion correction,motion sickness,camera parameters
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Multistatic SAR Information Fusion Based on Image Registration and Fake Color Synthesis
摘要： Due to finite of information dimension of single bistatic synthetic aperture radar (SAR), to expand more information about ground objects we research multistatic SAR which can be decomposed into groups of bistatic SAR. It is known that scattering properties of the different viewing angles is different. In this paper, we focus on system of single transmitter and triple receivers and use polar format algorithm (PFA) to obtain images of ground objects for the triple receivers. A geometric distortion correction method is proposed due to elevation of ground objects. After the distortion correction, the three SAR images are registrated, then we put images into red, green, blue (RGB) channels respectively to realize fake color synthesis, and thus realize information fusion.
关键词： Multistatic SAR,geometric distortion,fake color,information fusion
更新于2025-09-23 15:22:29