- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Effect of Secondary Emission Yield and Initial Charge of Dielectric Material on Multipactor in Parallel-Plate Dielectric-Loaded Waveguide
摘要： We present a theoretical analysis and comparison of the effect of (cid:2)1 versus (cid:2)2 regularization for the resolution of ill-posed linear inverse and/or compressed sensing problems. Our formulation covers the most general setting where the solution is speci?ed as the minimizer of a convex cost functional. We derive a series of representer theorems that give the generic form of the solution depending on the type of regularization. We start with the analysis of the problem in ?nite dimensions and then extend our results to the in?nite-dimensional spaces (cid:2)2(Z) and (cid:2)1(Z). We also consider the use of linear transformations in the form of dictionaries or regularization operators. In particular, we show that the (cid:2)2 solution is forced to live in a prede?ned subspace that is intrinsically smooth and tied to the measurement operator. The (cid:2)1 solution, on the other hand, is formed by adaptively selecting a subset of atoms in a dictionary that is speci?ed by the regularization operator. Beside the proof that (cid:2)1 solutions are intrinsically sparse, the main outcome of our investigation is that the use of (cid:2)1 regularization is much more favorable for injecting prior knowledge: it results in a functional form that is independent of the system matrix, while this is not so in the (cid:2)2 scenario.
关键词： linear inverse problems,compressed sensing,regularization,Sparsity,total variation,(cid:2)1-norm minimization
更新于2025-09-23 15:19:57
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Scalable Bayesian Uncertainty Quantification in Imaging Inverse Problems via Convex Optimization
摘要： We propose a Bayesian uncertainty quanti?cation method for large-scale imaging inverse problems. Our method applies to all Bayesian models that are log-concave, where maximum a posteriori (MAP) estimation is a convex optimization problem. The method is a framework to analyze the con?dence in speci?c structures observed in MAP estimates (e.g., lesions in medical imaging, celestial sources in astronomical imaging), to enable using them as evidence to inform decisions and conclusions. Precisely, following Bayesian decision theory, we seek to assert the structures under scrutiny by performing a Bayesian hypothesis test that proceeds as follows: ?rst, it postulates that the structures are not present in the true image, and then seeks to use the data and prior knowledge to reject this null hypothesis with high probability. Computing such tests for imaging problems is generally very di?cult because of the high dimensionality involved. A main feature of this work is to leverage probability concentration phenomena and the underlying convex geometry to formulate the Bayesian hypothesis test as a convex problem, which we then e?ciently solve by using scalable optimization algorithms. This allows scaling to high-resolution and high-sensitivity imaging problems that are computationally una?ordable for other Bayesian computation approaches. We illustrate our methodology, dubbed BUQO (Bayesian Uncertainty Quanti?cation by Optimization), on a range of challenging Fourier imaging problems arising in astronomy and medicine. MATLAB code for the proposed uncertainty quanti?cation method is available on GitHub.
关键词： Bayesian inference,inverse problems,image processing,hypothesis testing,uncertainty quanti?cation,convex optimization
更新于2025-09-19 17:15:36
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Characterization of a vertical crack using Laser Spot Thermography
摘要： This paper deals with the solution of an inverse problem for the heat equation aimed at nondestructive evaluation of fractures, emerging on the accessible surface of a slab, by means of Active Thermography. In real life, this surface is heated with a laser and its temperature is measured for a time interval by means of an infrared camera. A fundamental step in iterative inversion methods is the numerical solution of the underlying direct mathematical model. Usually, this step requires specific techniques in order to limit an abnormal use of memory resources and computing time due to excessively fine meshes necessary to follow a very thin fracture in the domain. Our contribution to this problem consists in decomposing the temperature of the damaged specimen as a sum of a term (with known analytical form) due to an infinite virtual fracture and the solution of an initial boundary value problem for the heat equation on one side of the fracture (i.e. on a rectangular domain). The depth of the fracture is a variable parameter in the boundary conditions that must be estimated from additional data (usually, measurements of the surface temperature). We apply our method to the detection of simulated cracks in concrete and steel specimens.
关键词： finite elements,heat equation,crack,Inverse problems,active thermography
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE International Conference on Consumer Electronics - Asia (ICCE-Asia) - Bangkok, Thailand (2019.6.12-2019.6.14)] 2019 IEEE International Conference on Consumer Electronics - Asia (ICCE-Asia) - Development of Automated LED Light Compensation System for Lycopersicon Esculentum
摘要： The cells in an organism emit different amounts of proteins according to their clinical state (healthy/pathological, for instance). The resulting proteomic pro?le can be used for early detection, diagnosis, and therapy planning. In this paper, we study the classi?cation of a proteomic sample from the point of view of an inverse problem with a joint Bayesian solution, called inversion-classi?cation. We propose a hierarchical physical forward model and present encouraging results from both simulation and clinical data.
关键词： proteins,classi?cation algorithms,proteomics,Statistical signal processing,probability,liquid chromatography,mass spectrometry,selective reaction monitoring,inverse problems,mathematical modelling
更新于2025-09-19 17:13:59
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Techniques for Evaluating the Depth of a Crack by Means of Laser Spot Thermography
摘要： Laser Spot Thermography is a useful tool in nondestructive crack detection. Our goal is to estimate the depth of a fracture from external thermal measurements. First we transform a set of real 3D data in a 2D effective one. Then we use the 2D data set as input in different methods for solving an inverse problems for the heat equation. Our guiding idea is that an effort in the direction of the mathematical analysis of the problem, rewards us in term of computational costs.
关键词： laser-spot thermography,cracks,inverse problems
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Solving the Inverse Problem in OCT using Full-Wave Adjoint Models
摘要： We explore the use of full-wave (Maxwell’s Equations-based) forward and adjoint solvers to approach the inverse problem in Optical Coherence Tomography. We demonstrate that oscillatory artifacts in the electric susceptibility arise in the inversion process due to the intrinsic wave-nature of the forward and adjoint models. These methods however still perform well in reproducing measured data sets.
关键词： Microscopy,Inverse Problems,Optical Coherence Tomography
更新于2025-09-11 14:15:04
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Contrast enhanced tomographic reconstruction of vascular blood flow with first order and second order adjoint methods
摘要： In this work, we study the reconstruction of blood velocity with contrast enhanced computed tomography with a tomographic projections perpendicular to the main flow field direction. The inverse problem is regularized with a convection-diffusion partial differential equation. The velocity field is reconstructed with first order and second order adjoint methods with a receding optimal control method and tested on simple phantoms.
关键词： optimal control,tomography,X-ray imaging,Inverse problems
更新于2025-09-11 14:15:04
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[Studies in Computational Intelligence] Advances in Neural Computation, Machine Learning, and Cognitive Research II Volume 799 (Selected Papers from the XX International Conference on Neuroinformatics, October 8-12, 2018, Moscow, Russia) || Artificial Neural Networks for Diagnostics of Water-Ethanol Solutions by Raman Spectra
摘要： The present paper is devoted to an elaboration of a method of diagnosis of alcoholic beverages using artificial neural networks: the inverse problem of spectroscopy – determination of concentrations of ethanol, methanol, fusel oil, ethyl acetate in water-ethanol solutions – was solved using Raman spectra. We obtained the following accuracies of concentration determination: 0.25% vol. for ethanol, 0.19% vol. for fusel oil, 0.35% vol. for methanol, and 0.29% vol. for ethyl acetate. The obtained results demonstrate the prospects of using Raman spectroscopy in combination with modern data processing methods (artificial neural networks) for the elaboration of an express non-contact method of detection of harmful and dangerous impurities in alcoholic beverages, as well as for the detection of counterfeit and low-quality beverages.
关键词： Neural networks,Raman spectroscopy,Inverse problems,Water-ethanol solutions
更新于2025-09-10 09:29:36
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Solving Inverse Computational Imaging Problems using Deep Pixel-level Prior
摘要： Signal reconstruction is a challenging aspect of computational imaging as it often involves solving ill-posed inverse problems. Recently, deep feed-forward neural networks have led to state-of-the-art results in solving various inverse imaging problems. However, being task specific, these networks have to be learned for each inverse problem. On the other hand, a more flexible approach would be to learn a deep generative model once and then use it as a signal prior for solving various inverse problems. We show that among the various state of the art deep generative models, autoregressive models are especially suitable for our purpose for the following reasons. First, they explicitly model the pixel level dependencies and hence are capable of reconstructing low-level details such as texture patterns and edges better. Second, they provide an explicit expression for the image prior which can then be used for MAP based inference along with the forward model. Third, they can model long range dependencies in images which make them ideal for handling global multiplexing as encountered in various compressive imaging systems. We demonstrate the efficacy of our proposed approach in solving three computational imaging problems: Single Pixel Camera (SPC), LiSens and FlatCam. For both real and simulated cases, we obtain better reconstructions than the state-of-the-art methods in terms of perceptual and quantitative metrics.
关键词： lensless image reconstruction,MAP inference,Inverse problems,compressive image recovery,autoregressive models,deep generative models
更新于2025-09-10 09:29:36
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[Institution of Engineering and Technology 2015 IET International Conference on Biomedical Image and Signal Processing (ICBISP 2015) - Beijing, China (19 Nov. 2015)] 2015 IET International Conference on Biomedical Image and Signal Processing (ICBISP 2015) - Iterative reconstruction for bioluminescence tomography based on an adaptive region shrinking strategy
摘要： The main challenge of bioluminescence tomography (BLT) is the ill-posed, non-unique nature of the inverse problem. To get reliable reconstruction, permissible source region is a commonly used a priori knowledge in the inverse procedure. In this paper, to accurately reveal 3D distribution of bioluminescent sources from limited boundary measurement, we propose an iterative reconstruction method incorporating adaptive algebraic reconstruction technique (AART) and adaptively shrinking permissible source region. AART algorithm is applied to get the solution without permissible region. Base on the distribution of the solution, we calculate the expectation and the covariance matrix and then derive the parameters for determining a cuboid-shaped region. Simulation experiments on a 3D digital mouse and an in vivo experiment are conducted to validate the feasibility and evaluate the performance of the proposed reconstruction method. The reconstructed results demonstrate the shrinking strategy is helpful for improving the stability of inverse algorithm.
关键词： iterative reconstruction method,finite element method,inverse problems,bioluminescence tomography
更新于2025-09-10 09:29:36