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How big is an OMI pixel?
摘要： The Ozone Monitoring Instrument (OMI) is a push-broom imaging spectrometer, observing solar radiation backscattered by the Earth’s atmosphere and surface. The incoming radiation is detected using a static imaging CCD (charge-coupled device) detector array with no moving parts, as opposed to most of the previous satellite spectrometers, which used a moving mirror to scan the Earth in the across-track direction. The field of view (FoV) of detector pixels is the solid angle from which radiation is observed, averaged over the integration time of a measurement. The OMI FoV is not quadrangular, which is common for scanning instruments, but rather super-Gaussian shaped and overlapping with the FoV of neighbouring pixels. This has consequences for pixel-area-dependent applications, like cloud fraction products, and visualisation. The shapes and sizes of OMI FoVs were determined pre-flight by theoretical and experimental tests but never verified after launch. In this paper the OMI FoV is characterised using collocated MODerate resolution Imaging Spectroradiometer (MODIS) reflectance measurements. MODIS measurements have a much higher spatial resolution than OMI measurements and spectrally overlap at 469 nm. The OMI FoV was verified by finding the highest correlation between MODIS and OMI reflectances in cloud-free scenes, assuming a 2-D super-Gaussian function with varying size and shape to represent the OMI FoV. Our results show that the OMPIXCOR product 75FoV corner coordinates are accurate as the full width at half maximum (FWHM) of a super-Gaussian FoV model when this function is assumed. The softness of the function edges, modelled by the super-Gaussian exponents, is different in both directions and is view angle dependent. The optimal overlap function between OMI and MODIS reflectances is scene dependent and highly dependent on time differences between overpasses, especially with clouds in the scene. For partially clouded scenes, the optimal overlap function was represented by super-Gaussian exponents around 1 or smaller, which indicates that this function is unsuitable to represent the overlap sensitivity function in these cases. This was especially true for scenes before 2008, when the time differences between Aqua and Aura overpasses was about 15 min, instead of 8 min after 2008. During the time between overpasses, clouds change the scene reflectance, reducing the correlation and influencing the shape of the optimal overlap function.
关键词： OMI,correlation,MODIS,reflectance,super-Gaussian,FoV
更新于2025-09-09 09:28:46
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Universal Dissipationless Dynamics in Gaussian Continuous-Variable Open Systems
摘要： We investigate the universal dissipationless dynamics of Gaussian continuous-variable systems in the presence of a band-gapped bosonic environment. Our results show that environmental band gaps can induce localized modes, which give rise to the dissipationless dynamics where the system behaves as free oscillators instead of experiencing a full decay in the long-time limit. We present a complete characterization of localized modes and show the existence of the critical system-environment coupling. Beyond the critical values, localized modes can be produced, and the system dynamics become dissipationless. This novel dynamics can be utilized to overcome the environmental noises and protect the quantum resources in the continuous-variable quantum information.
关键词： dissipationless dynamics,Gaussian continuous-variable systems,quantum information,localized modes,band-gapped bosonic environment
更新于2025-09-09 09:28:46
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Tailoring Non-Gaussian Continuous-Variable Graph States
摘要： Graph states are the backbone of measurement-based continuous-variable quantum computation. However, experimental realizations of these states induce Gaussian measurement statistics for the field quadratures, which poses a barrier to obtain a genuine quantum advantage. In this Letter, we propose mode-selective photon addition and subtraction as viable and experimentally feasible pathways to introduce non-Gaussian features in such continuous-variable graph states. In particular, we investigate how the non-Gaussian properties spread among the vertices of the graph, which allows us to show the degree of control that is achievable in this approach.
关键词： photon subtraction,photon addition,graph states,continuous-variable quantum computation,non-Gaussian features
更新于2025-09-09 09:28:46
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Introduction of 12 Cores Optical Amplifiers in Optical Transport Network: Performance Study and Economic Impact
摘要： We investigate the techno-economic impact of the introduction of 12-core Multicore Erbium-Ytterbium doped fiber amplifiers (MC-EYDFA) in optical transport networks. We evaluate the CAPEX gain involved by their utilization as line amplifiers and the energy consumption reduction induced by the pump sharing between the 12 cores. We also evaluate the impact of the inter-core crosstalk in the MC-EYDFA on the quality of transmission through the use of the Gaussian noise model.
关键词： techno-economical study,multicore erbium-ytterbium fiber-doped amplifier (MC-EYDFA),Gaussian noise model,inter-core crosstalk
更新于2025-09-09 09:28:46
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Locally optimal control of continuous-variable entanglement
摘要： We consider a system of two bosonic modes each subject to the dynamics induced by a thermal Markovian environment and we identify instantaneous, local symplectic controls that minimize the loss of entanglement in the Gaussian regime. By minimizing the decrease of the logarithmic negativity at every instant in time, it will be shown that a nontrivial, finite amount of local squeezing helps to counter the effect of decoherence during the evolution. We also determine optimal control routines in the more restrictive scenario where the control operations are applied on only one of the two modes. We find that applying an instantaneous control only at the beginning of the dynamics, i.e., preparing an appropriate initial state, is the optimal strategy for states with symmetric correlations and when the dynamics is the same on both modes. More generally, even in asymmetric cases, the delayed decay of entanglement resulting from the optimal preparation of the initial state with no further action turns out to be always very close to the optimized control where multiple operations are applied during the evolution. Our study extends directly to “monosymmetric” systems of any number of modes, i.e., to systems that are invariant under any local permutation of the modes within any one partition, as they are locally equivalent to two-mode systems.
关键词： decoherence,local symplectic controls,logarithmic negativity,Gaussian regime,continuous-variable entanglement
更新于2025-09-09 09:28:46
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Hyperspectral Unmixing with Bandwise Generalized Bilinear Model
摘要： Generalized bilinear model (GBM) has received extensive attention in the field of hyperspectral nonlinear unmixing. Traditional GBM unmixing methods are usually assumed to be degraded only by additive white Gaussian noise (AWGN), and the intensity of AWGN in each band of hyperspectral image (HSI) is assumed to be the same. However, the real HSIs are usually degraded by mixture of various kinds of noise, which include Gaussian noise, impulse noise, dead pixels or lines, stripes, and so on. Besides, the intensity of AWGN is usually different for each band of HSI. To address the above mentioned issues, we propose a novel nonlinear unmixing method based on the bandwise generalized bilinear model (NU-BGBM), which can be adapted to the presence of complex mixed noise in real HSI. Besides, the alternative direction method of multipliers (ADMM) is adopted to solve the proposed NU-BGBM. Finally, extensive experiments are conducted to demonstrate the effectiveness of the proposed NU-BGBM compared with some other state-of-the-art unmixing methods.
关键词： alternative direction method of multipliers (ADMM),bandwise generalized bilinear model (BGBM),hyperspectral images (HSIs),additive white Gaussian noise (AWGN),mixed noise
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 20th International Conference on e-Health Networking, Applications and Services (Healthcom) - Ostrava (2018.9.17-2018.9.20)] 2018 IEEE 20th International Conference on e-Health Networking, Applications and Services (Healthcom) - Supervised Level Sets For Dermoscopic Image Segmentation
摘要： In this paper, we propose a novel segmentation method that has been used for segmenting lesions in dermoscopy images. This method uses the variational level sets formulation with a novel area term based on supervised learning that results in the global optimization of a cost function, that can potentially result in a robust segmentation of the images. This term uses a mixture of Gaussians that are trained from a set of training images, and evolves an active contour such that the difference between the learned models and the empirical distributions obtained from the evolving curve for both the lesion and the skin are minimized. In the end, our approach is validated on the publicly available PH2 dermoscopy imaging dataset and the results show that the proposed method outperforms the other state-of-the-art methods that have been considered in this paper.
关键词： Gaussian mixture models,Variational level sets,Segmentation,Skin cancer,Dermoscopy
更新于2025-09-09 09:28:46
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A Reduced-Reference Image Quality Assessment Model Based on Joint-Distribution of Neighboring LOG Signals
摘要： Previous work have validated that the output of retinal ganglion cells in human visual pathway, which can be modeled as an LOG (Laplacian of Gaussian) filtration, can whiten the power spectrum of not only the natural images, but also the distorted images, hence the first-order (average luminance) and the second-order (contrast) redundancies have been removed when applying the LOG filtration. Considering the fact that human vision system (HVS) always ignores the first-order and the second-order information when sensing image local structures, the LOG signals should be efficient features in IQA (image quality assessment) task and a lot of LOG based IQA models have been proposed. In this paper, we focus on an interesting question that has not been investigated carefully yet: what is an efficient way to represent image structure features that is perceptual quality aware based on relationship between the LOG signals. We examine the to represent neighboring LOG signals and propose relationship by computing the joint distribution of neighboring LOG signals, and thus propose a set of simple but efficient RR IQA feature and consequently yield an excellent RR IQA model. Experimental results on three large scale subjective IQA databases show that our proposed method works robustly across different databases and stay in the state-of-the-art RR IQA models.
关键词： Whiten,Reduced-Reference,Laplacian of Gaussian,Image Quality Assessment,Joint Distribution
更新于2025-09-09 09:28:46
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Wigner Function Reconstruction in Levitated Optomechanics
摘要： We demonstrate the reconstruction of the Wigner function from marginal distributions of the motion of a single trapped particle using homodyne detection. We show that it is possible to generate quantum states of levitated optomechanical systems even under the effect of continuous measurement by the trapping laser light. We describe the opto-mechanical coupling for the case of the particle trapped by a free-space focused laser beam, explicitly for the case without an optical cavity. We use the scheme to reconstruct the Wigner function of experimental data in perfect agreement with the expected Gaussian distribution of a thermal state of motion. This opens a route for quantum state preparation in levitated optomechanics.
关键词： Gaussian state,Wigner function,quantum state tomography,levitated optomechanics
更新于2025-09-09 09:28:46
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Theoretical investigation on spectral emissivity of thermal control coatings with optical-rough surface
摘要： A theoretical model for calculating the spectral emissivity of the thermal control coating with rough surfaces is proposed based on the Monte Carlo method in this paper. Instead of treating the surface of the coating as a smooth surface, a diffuse surface or a rough surface using an empirical formula, the model applies a Gaussian random rough surface to the spectral emissivity calculation of the coating. Firstly, the Gaussian rough surface is established, and its properties are mainly determined by two parameters: the root-mean-square roughness(δ) and the coherent length(l). Then the spectral emissivity model of the thermal control coating with the rough surface is established by Monte Carlo method. The directional spectral emissivity of the smooth surface and the rough surface with different roughness is compared. Finally, the reasons for their differences in spectral emissivity are explained.
关键词： Gaussian rough surface,Thermal control coating,Monte Carlo method,spectral emissivity
更新于2025-09-09 09:28:46