Papers by Keyword: Nonlinear Diffusion

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Authors: Michael Atzmon, E.W. Larsen
Authors: Sachin Patil, Shi Wei Zhou, Qing Li
Abstract: Despite significant success in developing various periodic composites, the challenge remains how to more efficiently design the base cell so that one or more physical properties can be attained. In this paper, the material design problem is formulated in a form of the least square of the difference between the targeted and designed values. By minimizing the objective subject to volume constraints and periodic boundary conditions, an optimal material distribution in base cell can be generated. Different from existing methods, this paper shows how to use the Evolutionary Structural Optimization (ESO) method to design composite material attaining to thermal conductivity defined by the Hashin-Strikman (H-S) bounds. The effectiveness of this method is demonstrated through several 2D examples, agreeing well with commonly known benchmarking microstructures.
Authors: Da Sheng Wu, Qing Qing Wen, Yu Ping Rao
Abstract: This article introduces the gradient fidelity term into the functional model of the image denoising to obtain a new denoising functional model and derive the relative nonlinear diffusion denoising model. The new model has been proved that the bounded variation function is integrable, which will get rid of the problem of edge leaking. According to the experimental results, the application of this model is to prevent the "ladder" effect, the result of piecewise smooth can be acquired with more natural visual effects, meanwhile, the method has been proved more stable for the value calculation and has higher computational efficiency.
Authors: Da Li Chen, Ding Yu Xue, Yang Quan Chen
Abstract: In this paper, five nonlinear diffusion models for fabric image denoising are introduced. The advantages and drawbacks of these five models are described through describing their implementation methods. Quantitative and perceptual comparison experiments are given to verify the performance of these methods. Finally some valuable conclusions about denoising performance of these five models are present which is helpful for choosing and using these models in fabric image denoising.
Authors: Yue Jing Qian, Yuan Fan
Abstract: Rice edge detection is the first step on obtaining rice image feature. In this paper, an improved Canny edge detection algorithm was represented to obtain thin and robust rice edges. Firstly, nonlinear diffusion filter was used to wipe of noise efficiently and kept the edge information of the image. Secondly, gradient calculation of pixel diagonal direction was considered in the calculation of neighborhood gradient amplitude which further repressed the impact of noise. Thirdly, using average interclass variance could self-adaptively calculate the double thresholds for different images. The results of the experiment indicate that the improved algorithm has a better accuracy and precision in the edge detection.
Authors: Shi Wei Zhou, Qing Li
Abstract: This study systemically presents an inverse homogenization method in the design of functional gradient materials, which gained substantial attention recently due to their layer-by-layer defined physical properties. Each layer of these materials is unilaterally constructed by periodically extended microstructural elements (namely base cells), whose effective properties can be decided by the homogenization theory in accordance with the material distribution within the base cell. The design objective is to minimize the summation of the least squares of the difference between corresponded entries in target and effective elasticity tensors. The method of moving asymptote drives the minimization of this positive objective function, which forces the effective values approach to the targets as closely as possible. The sensitivity of the effective elasticity tensors with respect to the design variables is derived from the adjoint variable method and it guides the minimization algorithm efficiently. To guarantee the connectivity between adjacent layers, non-design domains occupied by solid materials acting as connective bars are fixed in the design of base cells. Furthermore, nonlinear diffusion technique is introduced to avoid checkerboard patterns and blur boundaries in the microstructures. A series of two-dimensional examples targeted for the elasticity tensors with same extreme Poisson ratios but different densities in each layer are illustrated to highlight the computational material design procedure.
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