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- 2018
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- classification
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- Brno University of Technology
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- Mohammed V University in Rabat
- Southern Taiwan University of Science and Technology
- Institut National Polytechnique Felix Houphou?t-Boigny Yamoussoukro
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Hyperspectral image classification using a spectral–spatial random walker method
摘要： This article proposes a spectral–spatial method for classification of hyperspectral images (HSIs) by modifying traditional random walker (RW). The proposed method consists of suggesting two main modifications. First, to construct a spatial edge weighting function, low-frequency edge weighting function is proposed. In this function, the detail weights are removed. Second, to enhance the classification accuracy, a fusion of spectral and spatial Laplacian matrix in RW is suggested. This fusion can improve the classification performances compared to traditional RW using only spatial Laplacian matrix. In comparison with some of the state-of-the-art RW and spectral–spatial classifier methods, the experimental results of the proposed method (spectral–spatial RW) show that the proposed method significantly increases the classification accuracy of HSI.
关键词： spectral–spatial random walker,edge weighting function,Hyperspectral image classification,Laplacian matrix
更新于2025-09-09 09:28:46
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Dual Energy Spectral CT Imaging in the assessment of Gastric Cancer and cell proliferation: A Preliminary Study
摘要： Gastric cancer is one of the main diseases leading to cancer-related death. The recently introduced dual-energy spectral CT (DEsCT), allows to obtain many quantitative measurements from iodine-based material decomposition (MD) images, which contribute to improve the accuracy of staging of GC comparing to multidetector spiral CT. And Ki-67 is a well-recognized nuclear antigen-specific biomarker reflecting cellular proliferation for estimating growth fractions of various tumor types. In the present study we analyzed the features of quantitative measurements (the curve slope (λHU), IC, normalized iodine concentrations (NIC)) obtained from DEsCT and levels of Ki-67 protein expression. We demonstrated that the values between advanced gastric cancer (AGC) and early gastric cancer (EGC) were significantly different both in venous phase (VP) and delayed phase (DP). The values of different level of Ki-67 expression grade were significantly different both in VP and DP. The rank correlation analysis between Ki-67 grade and IC, NIC and λHU values showed significantly positive correlation in VP and DP. These results suggested that quantitative parameters (IC, NIC and λHU) in dual-energy CT imaging can be used to differentiate EGC from AGC, and have significantly positive correlation with Ki-67 antigen expression levels in gastric cancer for indicating tumor cellular proliferation.
关键词： Gastric cancer,dual-energy spectral CT,Ki-67,iodine concentration,cellular proliferation
更新于2025-09-09 09:28:46
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Difference-based target detection using Mahalanobis distance and spectral angle
摘要： Two difference-based target detection methods are proposed in this work. In contrast to many target detectors which only calculate the distance between the testing pixel to the target spectrum, the proposed methods calculate the distance of the testing pixel to both of target and of background spectra. In other words, they utilize the difference between target and background computed distances. The first proposed method uses the Mahalanobis distance and benefits the valuable information contained in the statistics of targets and background. The second proposed method uses the kernel-based spectral angle mapper to benefit the advantages of spectral angle and kernel trick to separate targets from background, especially in non-linear cases. The experiments done on three real hyperspectral images indicate the high detection probability of the proposed methods compared to several target detectors.
关键词： hyperspectral imaging,Mahalanobis distance,target detection,spectral angle
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Combination of Band Selection and Weighted Spatial-Spectral Method for Hyperspectral Image Classification
摘要： In this paper we propose a new method for land cover classification in hyperspectral remote sensing images by combining band selection with weighted spatial-spectral feature fusion. Spectral information for each pixel is represented by a spectral curve over all the bands. Spatial information is represented by a Bag of visual Words model within a small region around each pixel. A cluster-based band selection method is used before spatial feature extraction to reduce the computation complexity. Then spectral and spatial feature weights are learnt under a Support Vector Machine framework, obtaining a balance between the two basis features for each class. Classification results on three popular hyperspectral remote sensing images demonstrate that the proposed method can yield a higher accuracy and a lower false alarm rate compared with the other similar classifiers.
关键词： bag of words,Hyperspectral image,spatial-spectral,classification,band select
更新于2025-09-09 09:28:46
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The study of undulator radiation of transversal oscillator
摘要： We study the radiation intensity for a charged transversal oscillator moving around a dielectric cylinder. Similar to the case of coaxial circular motion, under certain conditions for the parameters of the trajectory and dielectric cylinder, strong narrow peaks appear in the angular distribution of the radiation intensity in the exterior medium for a given harmonic. Comparing to the case of a uniform coaxial circular motion, for a transversal oscillator new peaks may appear. The oscillations serve as a mechanism for the control of the spectral-angular characteristics of the radiation intensity.
关键词： spectral-angular characteristics,transversal oscillator,dielectric cylinder,undulator radiation
更新于2025-09-09 09:28:46
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Full-Vector Gradient for Multi-spectral or Multivariate Images
摘要： Gradient extraction is important for a lot of metrological applications such as Control Quality by Vision. In this work, we propose a full-vector gradient for multi-spectral sensors. The full-vector gradient extends Di Zenzo expression to take into account the non-orthogonality of the acquisition channels thanks to a Gram matrix. This expression is generic and independent from channel count. Results are provided for a color and a multi-spectral snapshot sensor. Then, we show the accuracy improvement of the gradient calculation by creating a dedicated objective test and from real images.
关键词： Gram matrix,Di Zenzo,color,Gradient,multivariate,multi-spectral
更新于2025-09-09 09:28:46
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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 - Feature-Level Loss for Multispectral Pan-Sharpening with Machine Learning
摘要： Multispectral pan-sharpening plays an important role in providing earth observation with both high-spatial and high-spectral resolutions, and recently pan-sharpening with machine learning has been attracting broad interest. However, these algorithms minimizing the pixel-wise mean squared error, generally suffer from over-smoothed results that lack of high-frequency details in both spatial and spectral dimensions. In this paper, we propose to tackle this problem by shifting the learning loss from pixel-wise error to a higher-level feature loss. The new loss function, formulated by spatial structure similarity and spectral angle mapping, pushes the model to generate results that have similar feature representations with ground truth, rather than match with pixel-wise accuracy. Consequently, more realistic fusion results can be produced. Visual and quantitative analysis both demonstrate that our approach achieves better performance in comparison with state-of-the-art algorithms. Furthermore, experiments on high-level remote sensing task further confirm the superiority of the proposed method in real applications.
关键词： Spectral Angle Mapping,Spatial Structure Similarity,Multispectral Pan-sharpening,Feature-Level Loss,Machine Learning
更新于2025-09-09 09:28:46
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A Novel Azimuth Cutoff Implementation to Retrieve Sea Surface Wind Speed From SAR Imagery
摘要： In this paper, the synthetic aperture radar (SAR) azimuth cutoff method is thoroughly revised and a new and general implementation is proposed. The key roles of the pixel spacing, the size of the image box, and the texture of the SAR scene are analyzed and optimized in terms of azimuth cutoff (λc) estimation. The reliability of the λc estimation is analyzed by measuring the distance between the measured and ?tted autocorrelation functions. This analysis shows that it is of paramount importance to ?lter unfeasible/unreliable λc values. To identify those values in an objective way, a criterion that is based on the χ2 test performed over a large data set of Sentinel-1 SAR imagery is de?ned and proven to be effective. The new robust implementation of the λc estimation at about 1-km grid spacing is then used to produce averaged λc at about 10-km grid spacing. The performance of the new estimation procedure, analyzed using a λc-to-wind-speed forward model, is shown to provide improved wind speed retrievals, with a root-mean-square error of 1.8–2 m/s when veri?ed against independent numerical weather prediction model output and scatterometer winds.
关键词： sea surface,spectral analysis,synthetic aperture radar,Cutoff frequency
更新于2025-09-09 09:28:46
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The development of lower-atmosphere turbulence early in a solar flare
摘要： We present the first observational study of the onset and evolution of solar flare turbulence in the lower solar atmosphere on an unprecedented time scale of 1.7 s using the Interface Region Imaging Spectrograph observing plasma at a temperature of 80,000 K. At this time resolution, nonthermal spectral line broadening, indicating turbulent velocity fluctuations, precedes the flare onset at this temperature and is coincident with net blue-shifts. The broadening decreases as the flare brightens and then oscillates with a period of ~10 s. These observations are consistent with turbulence in the lower solar atmosphere at the flare onset, heating that region as it dissipates. This challenges the current view of energy release and transport in the standard solar flare model, suggesting that turbulence partly heats the lower atmosphere.
关键词： Interface Region Imaging Spectrograph,nonthermal spectral line broadening,turbulence,lower solar atmosphere,solar flare
更新于2025-09-09 09:28:46
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The Effect of Relativistic Interactions on the Spectral Characteristics of the Ground State of Carbon Monoxide
摘要： Using high-precision nonempirical methods of modern quantum chemistry, the effect of the weak relativistic interactions on the potential energy and the permanent dipole moment of the ground electronic state of the CO molecule is studied. The relativistic energy is calculated by the following three optional methods: within the first-order perturbation theory using the Cowan–Griffin operator containing the sum of the mass-velocity and Darwin corrections, within the framework of the approximate Douglas–Kroll–Hess scalar Hamiltonian, and the most rigid “four-component” relativistic Dirac–Coulomb–Gaunt Hamiltonian. The relativistic correction obtained by different methods agrees within a few percents and equals about 55–60 cm–1 in the region of an equilibrium internuclear distance of 1.128 ?. The addition of the relativistic correction decreases the equilibrium bond length by about 0.0002 ?. The magnitude of the Lamb shift estimated by the semiempirical scaling of the one-electron Darwin’s term does not exceed several inverse centimeters near eR. The relativistic correction to the dipole moment function is in the range from –0.001 to +0.003 D, which does not exceed 1% of the nonrelativistic component of the dipole moment.
关键词： dipole moment,relativistic interactions,carbon monoxide,spectral characteristics,quantum chemistry
更新于2025-09-09 09:28:46