- 标题
- 摘要
- 关键词
- 实验方案
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Iterative Adaptive Nonconvex Low-Rank Tensor Approximation to Image Restoration Based on ADMM
摘要： In this paper, in order to recover more ?ner details of the image and to avoid the loss of image structure information for image restoration problem, we develop an iterative adaptive weighted core tensor thresholding (IAWCTT) approach based on the alternating direction method of multipliers (ADMM). By observing the decoupling property of the ADMM algorithm, we ?rst propose that the key step to image restoration is to tackle the denoising subproblem ef?ciently using appropriate prior information. Secondly, by analyzing the properties of the core tensor, we propose that low-rank tensor approximation can be implemented by penalizing the core tensor itself, instead of penalizing the CP rank, Tucker rank or the multilinear rank and Tubal rank. The IAWCTT approach is proposed to solve the denoising subproblem in the ADMM framework, and we claim that such an adaptive weighted scheme is equivalent to a kind of nonconvex penalty for the core tensor; thus, it is unnecessary to use the nonconvex penalty term to induce strong sparse/low-rank solution in image restoration optimization problem, because the scheme that selecting appropriate weights to the convex penalty term can also lead to strong sparse/low-rank solution. Numerical experiments show that our proposed model and algorithm are comparable to other state-of-the-art models and methods.
关键词： Image restoration,Low-rank tensor approximation,ADMM,Nonconvex penalty
更新于2025-09-23 15:23:52
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Enhancing defects characterization in pulsed thermography by noise reduction
摘要： In the field of NDT techniques for aeronautic components of composite materials, the development of automatic and robust approaches for defect detection is largely desirable for both safety and economic reasons. This paper introduces a novel methodology for the automatic analysis of thermal signals resulting from the application of pulsed thermography. Input thermal decays are processed by a proper FIR filter designed to reduce the measurement noise, and then modeled to represent both sound regions and defective ones. Output signals are thus fitted on an exponential model, which approximates thermal contrasts with three robust parameters. These features feed a decision forest, trained to detect discontinuities and characterize their depths. Several experiments on actual sample laminates have proven the increase of the classification performance of the proposed approach with respect to related ones in terms of the reduction of missing predictions of defective classes.
关键词： FIR filter,Decision forest,Pulsed thermography,Model approximation
更新于2025-09-23 15:23:52
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Scaling Relations of Plasmon Resonance Peak in Au@Fe3O4 Core-Shell Nanohybrids Structure
摘要： In this paper, we study the absorption efficiency spectra of Au nanoparticles enveloped with Fe3O4 nanoshell by applying the discrete dipole approximation method. Three kinds of Au@Fe3O4 core-shell nanohybrids (NHs) structure, including the same core with different shell thickness, the same outer shell with different core radius, and the same size of total radius, have been discussed in detail. The simulation results show that the square of localized surface plasmon resonance (LSPR) peak wavelength of NHs is linearly proportional with the volume fraction of the shell, regardless of the outer shell material properties. Compared to the plasmon resonance peak of the Au nanoparticles, the LSPR shift of the NHs is dependent on both the total particles size and the outer Fe3O4 shell thickness. Our calculation results would provide some key guidances to design the structure variables of NHs for a broad range of plasmon applications.
关键词： Nanohybrids,Discrete dipole approximation,Absorption efficiency
更新于2025-09-23 15:23:52
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Thermal Fluctuations in the Phase Structure of the Excitonic Insulator Charge Density Wave State in the Extended Falicov–Kimball Model
摘要： Excitonic insulator (EI) instability accompanied by a charge density wave (CDW) state in the two-dimensional extended Falicov–Kimball model including electron–phonon interaction is investigated by applying the unrestricted Hartree–Fock approximation. Treating both the Coulomb attraction and the electron–phonon coupling on an equal footing, we have derived a set of self-consistent equations, which allows us to determine both the excitonic insulator order parameter and the lattice displacement. The phase structures show us that both the Coulomb interaction and the electron–phonon coupling act together in establishing the EI-CDW state, which typifies either a phononic-CDW or an excitonic-CDW state depending on the competition of the interactions. At a given low temperature, the EI-CDW state is found between two critical values of the Coulomb interaction. The window of the condensation state grows when increasing the electron–phonon coupling. Depending on the temperature and the Coulomb interaction the Bardeen–Cooper–Schrieffer–Bose–Einstein condensation (BCS–BEC) crossover of the EI-CDW state in the systems has been established. Under the effects of phonons, the BCS–BEC crossover deviates to a larger Coulomb interaction while the semimetal–semiconductor transition in the normal state remains.
关键词： semimetal–semiconductor transition,charge density wave,unrestricted Hartree–Fock approximation,Excitonic condensation
更新于2025-09-23 15:23:52
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Angular streaking of Auger-electrons by THz field
摘要： Rotational streaking by a circularly polarized THz field of Auger electrons generated by a short extreme ultraviolet (XUV) or X-ray pulse is theoretically investigated. The character of the streaking pattern depends on three main parameters: the duration of the XUV pulse, the Auger decay time-of-life and the period of the THz field. Different cases with various interrelations of these parameters are discussed. Examples of the patterns are calculated within the strong field approximation. Correspondence between the angular streaking of electrons in the processes of photoionization and Auger ionization is considered. Retrieval of the Auger decay parameters from circular streaking spectrum is discussed.
关键词： THz field,strong field approximation,Auger electrons,angular streaking,ultrafast processes
更新于2025-09-23 15:23:52
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Scattering of an Airy light-sheet by a non-spherical particle using discrete dipole approximation
摘要： The scattering of an Airy light-sheet by a non-spherical particle is investigated using the discrete dipole approximation (DDA). The internal and near-surface fields of the cube placed in an Airy light-sheet are calculated, and the effects of the transverse dimension factor w0, the attenuation factor a, and beam center z0 are mainly discussed. w0 can increase the number of side lobes incident on the target, thereby increase the wave jet energy. Increasing the attenuation coefficient a leads to less wave jet energy. By moving the light-sheet, the side lobe of the incident light-sheet increases, and the wave jet energy increases. Potential applications include optical manipulation of particles, particle sizing, optical imaging, etc.
关键词： Scattering,Airy light-sheet,Angular spectrum decomposition method,Discrete dipole approximation (DDA)
更新于2025-09-23 15:23:52
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Hyperspectral Mixed Denoising via Spectral Difference-Induced Total Variation and Low-Rank Approximation
摘要： Exploration of multiple priors on observed signals has been demonstrated to be one of the effective ways for recovering underlying signals. In this paper, a new spectral difference-induced total variation and low-rank approximation (termed SDTVLA) method is proposed for hyperspectral mixed denoising. Spectral difference transform, which projects data into spectral difference space (SDS), has been proven to be powerful at changing the structures of noises (especially for sparse noise with a specific pattern, e.g., stripes or dead lines present at the same position in a series of bands) in an original hyperspectral image (HSI), thus allowing low-rank techniques to get rid of mixed noises more efficiently without treating them as low-rank features. In addition, because the neighboring pixels are highly correlated and the spectra of homogeneous objects in a hyperspectral scene are always in the same low-dimensional manifold, we are inspired to combine total variation and the nuclear norm to simultaneously exploit the local piecewise smoothness and global low rankness in SDS for mixed noise reduction of HSI. Finally, the alternating direction methods of multipliers (ADMM) is employed to effectively solve the SDTVLA model. Extensive experiments on three simulated and two real HSI datasets demonstrate that, in terms of quantitative metrics (i.e., the mean peak signal-to-noise ratio (MPSNR), the mean structural similarity index (MSSIM) and the mean spectral angle (MSA)), the proposed SDTVLA method is, on average, 1.5 dB higher MPSNR values than the competitive methods as well as performing better in terms of visual effect.
关键词： ADMM,total variation,hyperspectral mixed denoising,low-rank approximation,spectral difference space
更新于2025-09-23 15:23:52
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Dynamical distortions of structural signatures in molecular high-order harmonic spectroscopy
摘要： We study the signature of two-center interferences in molecular high-order harmonic spectra, with an emphasis on the spectral phase. With the help of both ab initio computations based on the time-dependent Schr?dinger equation and the molecular strong-field approximation (SFA) as developed by Chiril? et al. [Phys. Rev. A 73, 023410 (2006)] and Faria [Phys. Rev. A 76, 043407 (2007)], we observe that the phase behavior is radically different for the short and the long trajectory contributions. By means of Taylor expansions of the molecular SFA, we link this effect to the dynamics of the electron in the continuum. More precisely, we find that the value of the electric field at recombination time plays a crucial role in the shape of the destructive interference phase jump.
关键词： molecular spectroscopy,spectral phase,strong-field approximation,two-center interferences,time-dependent Schr?dinger equation,high-order harmonic generation
更新于2025-09-23 15:23:52
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Nonreciprocal optical links based on time-modulated nanoantenna arrays: Full-duplex communication
摘要： Interference of transmitted and received signals hinders the simultaneous functionality of a conventional optical antenna as a transmitter and receiver which is required for full-duplex communication. The full-duplex communication schemes enabled by dense wavelength division multiplexed optical networks require distinct transmitter/receiver components operating at different wavelengths which increase the cost, complexity, and footprint of the physical layer. In this work, we demonstrate that an array of nanoantennas with leaky-wave architecture based on spatiotemporal modulation establishes nonreciprocal optical links which can reject the interference of transmitted and received signals by isolating the frequency of transmission and reception modes. For this purpose, we integrate indium-tin oxide into plasmonic nanodipoles which allows for realization of time-modulated nanoantennas in near-infrared frequency regime through electrical modulation of charge carrier density with radio-frequency signals. The radiation characteristics of individual nanoantennas and modal properties of nanoantenna arrays are rigorously studied through linking of charge transport and electromagnetic models. To this end, we extend the formulation of discrete dipole approximation as the standard modeling tool for electromagnetic scattering from nanoantenna arrays to treat realistic time-modulated structures with drastically different timescales between optical and modulation frequencies. The operation of spatiotemporally modulated array antennas in transmission and reception modes is investigated. Moreover, electrical beam-scanning functionality and dependence of antenna characteristics to modulation parameters and wavelength are demonstrated. It is rigorously established that such array antennas can operate as full transceivers by separating the transmitted and received signals propagating along the same direction through down conversion and up conversion of the frequency. Our results provide a route toward realization of optical antenna systems capable of full-duplex communication and real-time beam scanning which can increase the capacity and decrease the complexity of optical networks.
关键词： nonreciprocal optical links,indium-tin oxide,leaky-wave antenna,discrete dipole approximation,full-duplex communication,time-modulated nanoantenna arrays,spatiotemporal modulation
更新于2025-09-23 15:23:52
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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) - Modeling Reflection Loss of the Gaussian Rough Ocean Surface
摘要： Modeling the acoustic reflection loss at the rough ocean surface is a necessary component of a sonar transmission model when the scattering field is mainly forward scattering and focuses on the specular direction. To modeling the reflection loss at small angles is of great significance for acoustic field predictions at meduim-to-long ranges ,especially for shallow oceans or oceans with a surface duct. Firstly, based on the rough ocean surface of Gaussian spectrum, the validity of Ramsurf acoustic propagation model under rough surface conditions is demonstrated through comparison with the trial data in high state. Moreover, using the modified PE code—Ramsurf as a benchmark, Kirchhoff Approximation (KA) Reflection Loss (RL) model and Small Slope Approximation (SSA) RL model are compared and analyzed. The numerical simulation implies that the SSA model and results by Ramsurf match well.
关键词： rough sea surface,Small slope Approximation,reflection loss,Kirchhoff Approxiamtion,Gaussian spectrum
更新于2025-09-23 15:22:29