- 标题
- 摘要
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- 实验方案
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Speckle Noise Reduction of Medical Imaging via Logistic Density in Redundant Wavelet Domain
摘要： In the digital world, artificial intelligence tools and machine learning algorithms are widely applied in analysis of medical images for identifying diseases and make diagnoses; for example, to make recognition and classification. Speckle noises affect all medical imaging systems. Therefore, reduction in corrupting speckle noises is very important, since it deteriorates the quality of the medical images and makes tasks such as recognition and classification difficult. Most existing denoising algorithms have been developed for the additive white Gaussian noise (AWGN). However, AWGN is not a speckle noise. Therefore, this work presents a novel speckle noise removal algorithm within the framework of Bayesian estimation and wavelet analysis. This research focuses on noise reduction by the Bayesian with wavelet-based method because it provides good efficiency in noise reduction and spends short time in processing. The subband decomposition of a logarithmically transformed image is best described by a family of heavy-tailed densities such as Logistic distribution. Then, this research proposes the maximum a posteriori (MAP) estimator assuming Logistic random vectors for each parent-child wavelet coefficient of noise-free log-transformed data and log-normal density for speckle noises. Moreover, a redundant wavelet transform, i.e., the cycle-spinning method, is applied in our proposed methods. In our experiments, our proposed methods give promising denoising results.
关键词： wavelet transforms.,Bayesian estimation,speckle noise,non-Gaussian model
更新于2025-09-23 15:22:29
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An Efficient and Robust Iris Segmentation Algorithm Using Deep Learning
摘要： Iris segmentation is a critical step in the entire iris recognition procedure. Most of the state-of-the-art iris segmentation algorithms are based on edge information. However, a large number of noisy edge points detected by a normal edge-based detector in an image with specular reflection or other obstacles will mislead the pupillary boundary and limbus boundary localization. In this paper, we present a combination method of learning-based and edge-based algorithms for iris segmentation. A well-designed Faster R-CNN with only six layers is built to locate and classify the eye. With the bounding box found by Faster R-CNN, the pupillary region is located using a Gaussian mixture model. Then, the circular boundary of the pupillary region is fit according to five key boundary points. A boundary point selection algorithm is used to find the boundary points of the limbus, and the circular boundary of the limbus is constructed using these boundary points. Experimental results showed that the proposed iris segmentation method achieved 95.49% accuracy on the challenging CASIA-Iris-Thousand database.
关键词： Iris segmentation,Faster R-CNN,Gaussian mixture model,Boundary point selection,Deep learning
更新于2025-09-23 15:22:29
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Quantification of uncertainty in aerosol optical thickness retrieval arising from aerosol microphysical model and other sources, applied to Ozone Monitoring Instrument (OMI) measurements
摘要： Satellite instruments are nowadays successfully utilised for measuring atmospheric aerosol in many applications as well as in research. Therefore, there is a growing need for rigorous error characterisation of the measurements. Here, we introduce a methodology for quantifying the uncertainty in the retrieval of aerosol optical thickness (AOT). In particular, we concentrate on two aspects: uncertainty due to aerosol microphysical model selection and uncertainty due to imperfect forward modelling. We apply the introduced methodology for aerosol optical thickness retrieval of the Ozone Monitoring Instrument (OMI) on board NASA's Earth Observing System (EOS) Aura satellite, launched in 2004. We apply statistical methodologies that improve the uncertainty estimates of the aerosol optical thickness retrieval by propagating aerosol microphysical model selection and forward model error more realistically. For the microphysical model selection problem, we utilise Bayesian model selection and model averaging methods. Gaussian processes are utilised to characterise the smooth systematic discrepancies between the measured and modelled reflectances (i.e. residuals). The spectral correlation is composed empirically by exploring a set of residuals. The operational OMI multi-wavelength aerosol retrieval algorithm OMAERO is used for cloud-free, over-land pixels of the OMI instrument with the additional Bayesian model selection and model discrepancy techniques introduced here. The method and improved uncertainty characterisation is demonstrated by several examples with different aerosol properties: weakly absorbing aerosols, forest fires over Greece and Russia, and Sahara desert dust. The statistical methodology presented is general; it is not restricted to this particular satellite retrieval application.
关键词： OMI,Gaussian processes,OMAERO,uncertainty quantification,Bayesian model selection,aerosol optical thickness
更新于2025-09-23 15:22:29
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All-optical regenerative technique for width-tunable ultra-wideband signal generation
摘要： We demonstrate all-optical generation of width-tunable mono-cycle pulses for ultra-wideband communication. It has been shown that the width of the mono-cycle pulses can be tuned dynamically by simply varying the power of the optical signal. We also investigate the regenerative property of the nonlinear medium-based technique for the generation of mono-cycle pulses. For the purpose of comparison, ultra-wideband mono-cycle pulses are also generated through the optical delay line-based technique. It has been demonstrated through numerical simulations that the nonlinear medium-based technique is highly resilient to amplified spontaneous emission noise that is induced over the optical signal. Furthermore, we have shown that the highly nonlinear fiber-based nonlinear medium performs better than the semiconductor optical amplifier-based medium. Bit error rate measurements are taken for different values of optical signal-to-noise ratios in order to elaborate our work.
关键词： Gaussian mono-cycle pulses,Ultra-wideband over fiber,Semiconductor optical amplifier,Pulse width tuning,Highly nonlinear fiber
更新于2025-09-23 15:22:29
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Tuning of non-paraxial effects of the Laguerre-Gaussian beam interacting with the two-component Bose–Einstein condensates
摘要： We present the theory of microscopic interaction of the spin-orbit coupled focused Laguerre-Gaussian beam with the two-component Bose–Einstein condensate, composed of two hyperfine states of 87Rb in a harmonic trap. We have shown that Raman Rabi frequency distributions over the inter-component coupling identify phase separation coupling strength. A significant enhancement of side-band transitions due to non-paraxial nature of vortex beam is observed for particular values of inter-component coupling around 1.25 and 0.64 in unit of 5.5 nm for 105 and 106 number of atoms, respectively. The uncertainty in the estimation of these coupling strengths is improved with the focusing angles of the beam. We discuss an experimental scheme to verify this non-paraxial effect on ultra-cold atoms.
关键词： Laguerre-Gaussian beam,Bose–Einstein condensate,non-paraxial effects
更新于2025-09-23 15:22:29
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AIP Conference Proceedings [Author(s) DAE SOLID STATE PHYSICS SYMPOSIUM 2017 - Mumbai, India (26–30 December 2017)] - First principles calculations for interaction of tyrosine with (ZnO)3 cluster
摘要： First Principles Calculations have been performed to study interactions of Phenol ring of Tyrosine (C6H5OH) with (ZnO)3 atomic cluster. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/C6H5OH have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations. The compatibility of the results with previous studies has been presented here.
关键词： (ZnO)3 cluster,Tyrosine,First Principles Calculations,Density Functional Theory,Gaussian basis set
更新于2025-09-23 15:21:21
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Majorization preservation of Gaussian bosonic channels
摘要： It is shown that phase-insensitive Gaussian bosonic channels are majorization-preserving over the set of passive states of the harmonic oscillator. This means that comparable passive states under majorization are transformed into equally comparable passive states by any phase-insensitive Gaussian bosonic channel. Our proof relies on a new preorder relation called Fock-majorization, which coincides with regular majorization for passive states but also induces another order relation in terms of mean boson number, thereby connecting the concepts of energy and disorder of a quantum state. The consequences of majorization preservation are discussed in the context of the broadcast communication capacity of Gaussian bosonic channels. Because most of our results are independent of the speci?c nature of the system under investigation, they could be generalized to other quantum systems and Hamiltonians, providing a new tool that may prove useful in quantum information theory and especially quantum thermodynamics.
关键词： quantum channels,majorization theory,passive states,gaussian bosonic channels,quantum optics
更新于2025-09-23 15:21:21
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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 - Remote Compositional Pyroxene Estimates in the Reiner Gamma Formation Using Feature-Oriented Pca: New Insights Into Lunar Swirls
摘要： Moon, being the geological ‘Rosetta’ of the Earth, has its surface mainly composed of basalts and ferroan anorthosite rock suits whose intriguing elemental compositional variations outstands lunar geology. Pyroxene attributes to lunar sub-crustal evolution. The present work focuses on quantifying pyroxene-rich lithologies in the Reiner Gamma Formation (RGF) using an improved technique based on Feature-oriented Principal Component Analysis (FPCA). High resolution data from Moon Mineralogy Mapper (M3) facilitates spectral analysis of lunar soil. Optical Maturity (OMAT) has been operated revealing a more immature soil along the albedo trail of the RGF as compared to the surrounding. Further, FPCA-based band selection exhibited pyroxene-rich occurrences in the central RGF along with traces of olivine orthopyroxene lithology near wrinkled ridges. In support of this, spectra are compositionally analyzed using Modified Gaussian Model (MGM) portraying Mg-rich and moderate to high Ca bearing orthopyroxenes towards the eastern RGF attributing sub-crustal petrography.
关键词： Modified Gaussian Model,Moon Mineralogy Mapper,Pyroxene,Optical Maturity,FPCA
更新于2025-09-23 15:21:21
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Beam frame representation for ultra-wide-band radiation from volume source distributions: Frequency domain and time domain formulations
摘要： We present two novel beam summation (BS) schemes for radiation from time-harmonic or time-dependent volume source distributions, where the field is expanded using a discrete phase-space set of beam-wave propagators. The generic term “beams” is used here for both the frequency-domain and the time-domain formulations where the propagators are iso-diffracting Gaussian beam (ID-GB) or iso-diffracting pulsed beams (ID-PB), respectively. The formulations are structured upon the recently formulated “beam-frame” theorem that establishes these phase-space beam-sets as frame-sets everywhere in the propagation domain, and not only over the aperture plane as in previous formulations. The expansion coefficients are obtained by projecting the source distributions over the dual beam-frame sets that have essentially the same structure as the basic sets. As such, these formulations constitute local generalization to the conventional plane-waves or Green’s function formulations, and also reduce the overall degrees of freedom needed to describe the radiated field. As demonstrated by the numerical examples they resolve the local features of the source distributions in space-time, and hence provide a basis for a new local inverse scattering theory to be presented subsequently.
关键词： beam summation methods,pulsed beams,Gaussian beams,phase space representations,ultra wide band,time domain,Radiation theory
更新于2025-09-23 15:21:21
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An optimized space-time Gaussian beam migration method with dynamic parameter control
摘要： In the Gaussian beam (GB) method, initial beam parameters are principal factors influencing the accuracy and computational efficiency of seismic depth imaging. Various optimized beam parameter strategies for Gaussian beam migration (GBM) have been proposed to improve imaging quality as well as computational efficiency, while optimized space-time Gaussian beam schemes for seismic migration have still not been fully investigated. In this paper, an optimized space-time Gaussian beam approach with dynamic parameter control for seismic depth imaging is developed. We first provide an expression for dynamic beam parameter by taking in account the effect of velocity field variation on the beam forming. Based on dynamic beam parameters, the new space-time adaptive Gaussian beam generated by an arbitrary source wavelet is obtained, which can adaptively calculate the beam width to make the seismic beam energy better focused in the central ray neighborhood. Then, the forward wavefield is constructed in two-dimensional (2D) acoustic media by space-time adaptive Gaussian beam for the implementation of migration. Adhering to the framework of conventional space-time Gaussian beam method, we perform the up-going ray tracing from subsurface imaging points to the receiver surface to compute the asymptotic Green function for the construction of the backward wavefield. Numerical experiments demonstrate that the new presented approach has a superior accuracy for seismic depth imaging in both shallow and deep regions compared to the conventional space-time Gaussian beam migration scheme.
关键词： Space-time Gaussian beam,Green function,Up-going ray tracing,Dynamic beam parameter
更新于2025-09-23 15:21:21