- 标题
- 摘要
- 关键词
- 实验方案
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Local spatial correlation-based stripe non-uniformity correction algorithm for single infrared images
摘要： Stripe non-uniformity typically exists in infrared images and affects the visual effect; thus, eliminating stripe non-uniformity is essential to improve image quality. In this paper, a correction model with higher accuracy is developed. Unlike some other stripe non-uniformity correction methods using the same gain coefficient and offset parameters for the pixels of each column, different deviations of the correction parameters in the same column resulted by unsatisfactory preliminary non-uniformity correction are considered and are thought to be small and still relevant in space. The proposed method calculates the correction parameters for each pixel respectively based on the intrinsic spatial correlation between adjacent pixels in a column. What is more, an edge detection method is included. The experimental results indicate that the proposed algorithm effectively eliminates stripe noise of images of different scenes and it also works well in terms of preserving details. Furthermore, the algorithm exhibits high real-time performance.
关键词： De-striping,Spatial correlation,Non-uniformity correction,Stripe noise,Infrared imaging
更新于2025-09-23 15:23:52
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Estimating $c$-level partial correlation graphs with application to brain imaging
摘要： Alzheimer’s disease (AD) is a chronic neurodegenerative disease that changes the functional connectivity of the brain. The alteration of the strong connections between different brain regions is of particular interest to researchers. In this article, we use partial correlations to model the brain connectivity network and propose a data-driven procedure to recover a c-level partial correlation graph based on PET data, which is the graph of the absolute partial correlations larger than a pre-speci?ed constant c. The proposed procedure is adaptive to the “large p, small n” scenario commonly seen in whole brain studies, and it incorporates the variation of the estimated partial correlations, which results in higher power compared to the existing methods. A case study on the FDG-PET images from AD and normal control (NC) subjects discovers new brain regions, Sup Frontal and Mid Frontal in the frontal lobe, which have different brain functional connectivity between AD and NC.
关键词： Partial correlation,High dimensionality,Alzheimer’s Disease,Brain connectivity
更新于2025-09-23 15:23:52
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Proof-of-principle demonstration of vertical-gravity-gradient measurement using a single-proof-mass double-loop atom interferometer
摘要： We demonstrate a proof-of-principle of direct Earth gravity-gradient measurement with an atom interferometer-based gravity gradiometer using a single proof mass of cold 87Rb atoms. The atomic gradiometer is implemented in the so-called double-loop configuration, hence providing a direct gravity-gradient dependent phase shift insensitive to dc acceleration and constant rotation rate. The atom interferometer (AI) can be either operated as a gravimeter or a gradiometer by simply adding an extra Raman π pulse. We demonstrate gravity-gradient measurements first using a vibration isolation platform and second without seismic isolation using the correlation between the AI signal and the vibration signal measured by an auxiliary classical accelerometer allowing one to bypass the absence of common-mode vibration noise rejection in a double-loop geometry. The simplicity of the experimental setup (a single atomic source and unique detection) and the immunity of the AI to rotation-induced contrast loss make it a possible candidate for onboard gravity-gradient measurements.
关键词： gradiometer,gravity gradient,vibration isolation,atom interferometer,correlation technique
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Communication and Signal Processing (ICCSP) - Chennai (2018.4.3-2018.4.5)] 2018 International Conference on Communication and Signal Processing (ICCSP) - Envelope Modification of the Hyperbolic Frequency Modulated Signal with LC-Filters in order to have a Better Range Resolution in Radar Systems
摘要： The theme of this paper is to realize a continuous time domain window similar to the Hamming window. Windowing is used in signal processing to smooth the spectral content and for reducing the spectral leakage as well. Long time duration windows with narrow spectral content can provide much better smoothing compared with short duration windows with broad spectral content. The other advantage of the windowing in the time domain is the reduction of sidelobe levels in the output of the matched filter (MF). In radar systems which use the MF, this reduction in the relative sidelobe level improves the resolution of the system. Radar systems use the hyperbolic frequency modulated (HFM) signals to have the better range and velocity resolutions since these waveforms are Doppler invariant. To further improve the range resolution, the envelope of the HFM signal has been modified using a continuous time domain Hamming window and its Doppler invariant property has been observed. In order to realize the practical circuit that implements the analogous continuous time domain Hamming window for the HFM signal, Butterworth notch filter, and Butterworth highpass filters (HPF) has been considered and it is observed that HPF is approximating the characteristics of the Hamming window.
关键词： hyperbolic frequency modulation,matched filter,notch filter,relative sidelobe level,Doppler invariance,Auto-correlation
更新于2025-09-23 15:23:52
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Low-rank Bayesian tensor factorization for hyperspectral image denoising
摘要： In this paper, we present a low-rank Bayesian tensor factorization approach for hyperspectral image (HSI) denoising problem, where zero-mean white and homogeneous Gaussian additive noise is removed from a given HSI. The approach is based on two intrinsic properties underlying a HSI, i.e., the global correlation along spectrum (GCS) and nonlocal self-similarity across space (NSS). We first adaptively construct the patch-based tensor representation for the HSI to extract the NSS knowledge while preserving the property of GCS. Then, we employ the low rank property in this representation to design a hierarchical probabilistic model based on Bayesian tensor factorization to capture the inherent spatial-spectral correlation of HSI, which can be effectively solved under the variational Bayesian framework. Furthermore, through incorporating these two procedures in an iterative manner, we build an effective HSI denoising model to recover HSI from its corruption. This leads to a state-of-the-art denoising performance, consistently surpassing recently published leading HSI denoising methods in terms of both comprehensive quantitative assessments and subjective visual quality.
关键词： Hyperspectral image denoising,Global correlation along spectrum,Full Bayesian CP factorization,Nonlocal self-similarity,Variational Bayesian inference,Tensor rank auto determination
更新于2025-09-23 15:23:52
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Photon bunching and N-photon interference in thermal light
摘要： We investigate the contribution of four-photon bunching term in fourth-order double-slit interference intensity correlation based on two different detection schemes with a pseudo-thermal light source. It is clearly demonstrated that the resolution of intensity correlation is significantly enhanced by using of double-slit in both fourth-order and third-order intensity correlation. Meanwhile, the visibility of fourth-order correlation can be dramatically improved in contrast to the third-order due to the four-photon bunching term by contributing in the visibility of fourth-order correlation. The position and full width at half maximum of interference peaks of fourth-order intensity correlation are same as third-order. We also use two different scanning approaches to change the resolution and visibility of interference intensity correlation. In the first detection scheme, we scan three reference detectors along the same orientation and speed. In second detection scheme we scan two of three reference detectors in the same orientation, and speed of one reference detector is twice that of the other, and simultaneously moving the other two reference detectors with opposite orientation but identical speed. Those investigations can also be promoted to high order intensity correlation of thermal light.
关键词： Correlation,Photon bunching,Photon interference,Fourier optics
更新于2025-09-23 15:23:52
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Effect of temperature on digital images of speckle patterns generated by a metallic rough surface
摘要： It is well known that roughness can be inferred from digital images of speckle patterns generated by illuminated rough surfaces, by analyzing parameters such as fractal dimension, lacunarity and correlation, to cite a few. In this article, we investigate the effect of temperature on the speckle pattern generated by the light scattered from a metallic rough surface. We show that fractal dimension is less sensitive to temperature changes than are lacunarity and correlation, and provide information about which method is more suitable for processing the speckle patterns produced by rough surfaces under temperature variation.
关键词： Speckle pattern,Fractal dimension,Correlation,Roughness,Lacunarity,Temperature
更新于2025-09-23 15:23:52
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Performance Evaluation of Hybrid FSO-SACOCDMA System under Different Weather Conditions
摘要： Spectral amplitude coding optical code division multiple access (SACOCDMA) is a multiplexing technique, which provides faster speed, efficiency, security and unlimited bandwidth. It is widely preferred because of its ability to eliminate multiple access interference (MAI). Free space optics (FSO) provides a wireless link to transmit data securely at higher rates for last mile access. In this work, a 100 Gb/s hybrid FSO-SACOCDMA is designed using direct detection. The performance of FSO using SACOCDMA utilizing NZCC (New Zero Cross Correlation) code is evaluated under different weather conditions (clear weather, haze and fog) for ten users where each user carries 10 Gb/s. The results indicate that in clear weather FSO distance can be extended up to 13 km. Moreover, after using pre-amplifier in clear weather, FSO enhances the maximum distance to 35 km with acceptable signal to noise ratio and bit error rate. Using an amplifier in the link not only makes the quality of the signal better but it also increases the communication range.
关键词： spectral amplitude coding optical code division multiple access (SACOCDMA),free space optics (FSO),direct detection (DD),new zero cross correlation (NZCC)
更新于2025-09-23 15:23:52
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High-Performance Chromatographic Characterization of Surface Chemical Heterogeneities of Fluorescent Organic–Inorganic Hybrid Core–Shell Silica Nanoparticles
摘要： In contrast to small-molar-mass compounds, detailed structural investigations of inorganic core–organic ligand shell hybrid nanoparticles remain challenging. The assessment of batch-reaction-induced heterogeneities of surface chemical properties and their correlation with particle size has been a particularly long-standing issue. Applying a combination of high-performance liquid chromatography (HPLC) and gel permeation chromatography (GPC) to ultra-small (<10 nm diameter) poly(ethylene glycol)-coated (PEGylated) fluorescent core–shell silica nanoparticles, we elucidate here previously unknown surface heterogeneities resulting from varying dye conjugation to nanoparticle silica cores and surfaces. Heterogeneities are predominantly governed by dye charge, as corroborated by molecular dynamics simulations. We demonstrate that this insight enables the development of synthesis protocols to achieve PEGylated and targeting ligand-functionalized PEGylated silica nanoparticles with dramatically improved surface chemical homogeneity, as evidenced by single-peak HPLC chromatograms. Because surface chemical properties are key to all nanoparticle interactions, we expect these methods and fundamental insights to become relevant to a number of systems for applications, including bioimaging and nanomedicine.
关键词： surface chemistry heterogeneity,high-performance liquid chromatography,nanoparticle characterization,nanoparticle surface functionalization,fluorescence correlation spectroscopy,molecular dynamics,nanoparticle heterogeneity
更新于2025-09-23 15:23:52
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Ultrafast data mining of molecular assemblies in multiplexed high-density super-resolution images
摘要： Multicolor single-molecule localization super-resolution microscopy has enabled visualization of ultrafine spatial organizations of molecular assemblies within cells. Despite many efforts, current approaches for distinguishing and quantifying such organizations remain limited, especially when these are contained within densely distributed super-resolution data. In theory, higher-order correlation such as the Triple-Correlation function is capable of obtaining the spatial configuration of individual molecular assemblies masked within seemingly discorded dense distributions. However, due to their enormous computational cost such analyses are impractical, even for high-end computers. Here, we developed a fast algorithm for Triple-Correlation analyses of high-content multiplexed super-resolution data. This algorithm computes the probability density of all geometric configurations formed by every triple-wise single-molecule localization from three different channels, circumventing impractical 4D Fourier Transforms of the entire megapixel image. This algorithm achieves 102-folds enhancement in computational speed, allowing for high-throughput Triple-Correlation analyses and robust quantification of molecular complexes in multiplexed super-resolution microscopy.
关键词： molecular assemblies,computational algorithm,multiplexed high-density super-resolution images,Triple-Correlation function,Ultrafast data mining
更新于2025-09-23 15:23:52