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- 摘要
- 关键词
- 实验方案
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[IEEE 2018 New Generation of CAS (NGCAS) - Valletta, Malta (2018.11.20-2018.11.23)] 2018 New Generation of CAS (NGCAS) - High-Resolution ADCs for Biomedical Imaging Systems
摘要： With the rapid development of biomedical imaging systems, the requirement of the accuracy of an Analog-to-Digital Converter (ADC) becomes more and more critical. Traditional Nyquist-rate analog to digital data converters cannot meet the requirement any more. Sigma-Delta analog to digital data converter, which makes a trade-off between speed and accuracy, can achieve an ideal accuracy by employing the oversampling and noise-shaping technology. In this work, a Verilog-AMS model for sigma-delta modulator is built, including the topologic, the order of stage, oversampling rate, system parameters, etc. On the basic of theoretical analysis and scienti?c ?ow path, ?nally, a third-order 1-bit sigma-delta modulator is designed and optimized, whose performance agrees well with the theoretical module.
关键词： Analog-to-Digital Converter,Σ? ADC,Successive Approximation Register(SAR) ADC,Oversampling,Biomedical Imaging Systems
更新于2025-09-23 15:19:57
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[Communications in Computer and Information Science] Advances in Signal Processing and Intelligent Recognition Systems Volume 968 (4th International Symposium SIRS 2018, Bangalore, India, September 19–22, 2018, Revised Selected Papers) || Pre-processed Hyperspectral Image Analysis Using Tensor Decomposition Techniques
摘要： Hyperspectral remote sensing image analysis has always been a challenging task and hence there are several techniques employed for exploring the images. Recent approaches include visualizing hyperspectral images as third order tensors and processing using various tensor decomposition methods. This paper focuses on behavioural analysis of hyperspectral images processed with various decompositions. The experiments includes processing raw hyperspectral image and pre-processed hyperspectral image with tensor decomposition methods such as, Multilinear Singular Value Decomposition and Low Multilinear Rank Approximation technique. The results are projected based on relative reconstruction error, classification and pixel reflectance spectrums. The analysis provides correlated experimental results, which emphasizes the need of pre-processing for hyperspectral images and the trend followed by the tensor decomposition methods.
关键词： Low Multilinear Rank Approximation,Remote sensing image,Pixel reflectance spectrums,Multilinear Singular Value Decomposition,Relative reconstruction error,Tensor decomposition
更新于2025-09-19 17:15:36
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Light Field Super-Resolution using a Low-Rank Prior and Deep Convolutional Neural Networks
摘要： Light ?eld imaging has recently known a regain of interest due to the availability of practical light ?eld capturing systems that offer a wide range of applications in the ?eld of computer vision. However, capturing high-resolution light ?elds remains technologically challenging since the increase in angular resolution is often accompanied by a signi?cant reduction in spatial resolution. This paper describes a learning-based spatial light ?eld super-resolution method that allows the restoration of the entire light ?eld with consistency across all angular views. The algorithm ?rst uses optical ?ow to align the light ?eld and then reduces its angular dimension using low-rank approximation. We then consider the linearly independent columns of the resulting low-rank model as an embedding, which is restored using a deep convolutional neural network (DCNN). The super-resolved embedding is then used to reconstruct the remaining views. The original disparities are restored using inverse warping where missing pixels are approximated using a novel light ?eld inpainting algorithm. Experimental results show that the proposed method outperforms existing light ?eld super-resolution algorithms, achieving PSNR gains of 0.23 dB over the second best performing method. The performance is shown to be further improved using iterative back-projection as a post-processing step.
关键词： Low-Rank Matrix Approximation,Super-Resolution,Light Field,Deep Convolutional Neural Networks
更新于2025-09-19 17:15:36
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Markov Chain Investigation of Discretization Schemes and Computational Cost Reduction in Modeling Photon Multiple Scattering
摘要： Establishing fast and reversible photon multiple scattering algorithms remains a modeling challenge for optical diagnostics and noise reduction purposes, especially when the scattering happens within the intermediate scattering regime. Previous work has proposed and verified a Markov chain approach for modeling photon multiple scattering phenomena through turbid slabs. The fidelity of the Markov chain method has been verified through detailed comparison with Monte Carlo models. However, further improvement to the Markov chain method is still required to improve its performance in studying multiple scattering. The present research discussed the efficacy of non-uniform discretization schemes and analyzed errors induced by different schemes. The current work also proposed an iterative approach as an alternative to directly carrying out matrix inversion manipulations, which would significantly reduce the computational costs. The benefits of utilizing non-uniform discretization schemes and the iterative approach were confirmed and verified by comparing the results to a Monte Carlo simulation.
关键词： computational cost reduction,markov chain approximation,discretization schemes,multiple scattering
更新于2025-09-19 17:15:36
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Direct prediction of bidirectional reflectance by dense particulate deposits
摘要： To observe and study the effects of the volume packing density on polarimetric scattering by deposited particulate materials, a comparison is made between the vector radiative transport equation (VRTE) and the plane wave plane parallel (PWPP) models for the polarized bidirectional reflectance and transmittance from plane parallel layers of randomly distributed, wavelength–sized particles. Calculations have been performed on ice and mineral materials with refractive indices of m = 1.31 and m = 1.5 + 0.01i respectively. In these simulations, particle volume fraction ranges from around 0.05–0.3 for deposits consisting of spherical particles with size parameters of one and two. It is found that the PWPP model results converge to those predicted by the VRTE at small (～5% or less) particle volume fractions. At higher volume fractions, the difference between the PWPP and VRTE results depends strongly on the particle size and refractive index, yet not so much on the optical thickness (equivalently, volume of particles per unit area of layer). PWPP simulation results of coherent backscattering effects – brightness opposition and polarization opposition effects – for ice and mineral particles are also represented. Their dependency on the particle volume fraction and particle size has been discussed.
关键词： Radiative transfer theory,Densely packed media,Coherent backscattering and polarization opposition effects,Plane parallel media,Adding and doubling,Periodic discrete dipole approximation,Multiple scattering
更新于2025-09-19 17:15:36
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Geometric phase transferred from photonic mode to atomic BEC
摘要： A process of geometric phase generation in a composite matter-field system is considered. Two atomic modes correspond to different localizations of a single Bose–Einstein condensate (BEC). One of the trapping localizations is formed by a photonic mode of a ring cavity. The photonic mode is governed by an external harmonic field source, by dissipation and by the number of localized atoms due to their non-resonant interaction with photons. This interaction gives rise to entanglement between the BEC and the photonic mode. By varying the intensity and frequency of the external source, it is possible to create a geometric phase for the optical mode. Because of the entanglement between the state of atomic and photonic modes, geometric phase acquired by the latter causes modification of the BEC state. This modification can be revealed by studying the tunneling between the atomic localizations.
关键词： Bose–Einstein condensate,Geometric phase,Two-mode approximation
更新于2025-09-19 17:15:36
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Inconsistency between linearized Thomas–Fermi approximation and electron-ionized impurity scattering rate in the first Born approximation
摘要： We show that by computing the electron-impurity scattering rate at the first order via Fermi’s golden rule, and assuming that the localized impurity potential is of Yukawa form, one obtains a wave vector transfer distribution which is inconsistent with the finite temperature linearized Thomas–Fermi approximation for n-type semiconductors. Our previous findings show that this is not the case for the carrier nondegenerate dynamics, because the average wave vector transferred being in general negligible in this regime. Moreover, we examine the behavior of the electron-impurity differential cross-sections in the first Born approximation for relevant values of the wave vector transfer. We find that in the majority of collisions, the scattering probabilities differ at the most by 1% from the estimates computed by means of the impurity potential at random phase approximation level.
关键词： Born approximation,electron-impurity scattering,Thomas–Fermi screening
更新于2025-09-19 17:15:36
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Excitonic states in spherical layered quantum dots
摘要： The properties of excitons formed in spherical quantum dots are studied using the ?? ? ?? method within the Hartree approximation. The spherical quantum dots considered have a central core and several concentric layers of different semiconductor materials that are modeled as a succession of potential wells and barriers. The ?? ? ?? Hamiltonian and the Coulomb equations for the electron–hole pair are solved using a self-consistent iterative method. The calculation of the spectrum of the empty quantum dot and the electron–hole pair is performed by means of a very accurate numerical approximation. It is found that the exciton binding energy as a function of the core radius of the quantum dot shows a strong non-linear behavior. In particular, for quantum dots with two potential wells, the binding energy presents a large steep change. This last behavior is explained in terms of the polarization charges at the interfaces between different materials and the matching conditions for the eigenfunctions.
关键词： Spherical quantum dots,Hartree approximation,Excitons
更新于2025-09-19 17:13:59
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Plasmonic coupling in closed-packed ordered gallium nanoparticles
摘要： plasmonic gallium (Ga) nanoparticles (nps) are well known to exhibit good performance in numerous applications such as surface enhanced fluorescence and Raman spectroscopy or biosensing. However, to reach the optimal optical performance, the strength of the localized surface plasmon resonances (LSPRs) must be enhanced particularly by suitable narrowing the NP size distribution among other factors. With this purpose, our last work demonstrated the production of hexagonal ordered arrays of Ga NPs by using templates of aluminium (Al) shallow pit arrays, whose LSPRs were observed in the VIS region. The quantitative analysis of the optical properties by spectroscopic ellipsometry confirmed an outstanding improvement of the LSPR intensity and full width at half maximum (FWHM) due to the imposed ordering. Here, by engineering the template dimensions, and therefore by tuning Ga NPs size, we expand the LSPRs of the Ga NPs to cover a wider range of the electromagnetic spectrum from the UV to the IR regions. More interestingly, the factors that cause this optical performance improvement are studied with the universal plasmon ruler equation, supported with discrete dipole approximation simulations. the results allow us to conclude that the plasmonic coupling between nps originated in the ordered systems is the main cause for the optimized optical response.
关键词： plasmonic coupling,gallium nanoparticles,spectroscopic ellipsometry,discrete dipole approximation,localized surface plasmon resonances
更新于2025-09-19 17:13:59
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Influence of the polarization of a multielectron atom in a strong laser field on high-order harmonic generation
摘要： We study the ionization and high-order harmonic generation (HHG) in argon by short linearly polarized laser pulses. We compare the populations of atomic orbitals and HHG spectra in a wide range of laser-pulse parameters, taking into account the dynamics of all orbitals based on the time-dependent density-functional theory (TDDFT) and only the most active orbital within the single-active electron (SAE) approximation. At high intensities of laser pulses, the atom polarization leads to suppression in the bound-state depletion due to the screening of the external field. The significant increase in the HHG yield is observed for the TDDFT calculations in comparison with the SAE calculations. The contribution of different orbitals in the TDDFT calculations of HHG spectra is discussed.
关键词： ionization,high-order harmonic generation,atom polarization,argon,TDDFT,laser pulses,SAE approximation
更新于2025-09-19 17:13:59