共查询到20条相似文献,搜索用时 171 毫秒
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ECT技术是多相流检测领域中的一项新技术,主要用于识别一个封闭管道内两相流/多相流系统中各个相成分分布问题。采用一种新的方法,通过电磁场有限元仿真软件COMSOL,对电容层析成像系统进行图像重建与仿真研究。构建了ECT的不同电极模型,分别对四种典型流型进行了图像重建;通过对离散介质场域的仿真研究,分析了电极数目、屏蔽罩、径向电极对重建图像质量的影响;对气液固三相流进行了图像重建,获得了满意的重建结果。 相似文献
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电容层析成像系统传感器场域新的剖分方法及图像重建 总被引:2,自引:0,他引:2
电容层析成像传感器的敏感场受多相流介质分布的影响,软场特性给图像重建带来很大困难,为了提高重建图像质量,对敏感场分布进行分析是非常必要的。本文采用有限元法,通过对敏感场场域采用两种不同剖分形式的比较,提出一种新的场域剖分形式,对敏感场分布进行计算机及仿真,依据敏感场计算的数据及测量结果,提出了基于遗传算法的图像重建算法。实验证明有限元模型是正确的,说明利用不等间距的剖分形式可以得到较好的仿真结果,重建的图像具有较高的精度。 相似文献
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在电阻层析成像系统中,激励模式和电极数目的设计直接影响到整个系统。为了提高重建图像质量,更好地指导ERT系统设计,对敏感场进行深入的分析是必要的。通过电磁场有限元仿真软件COMSOL,构建ERT的电极模型,通过对空场和离散介质场域的仿真研究,分析了各个因素对敏感场的影响,并对四种典型流型进行了图像重建。仿真实验表明,COMSOL图像重建效果满意,为图像重建的研究提供了新的思路。 相似文献
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采用一种可双峰分布的概率密度函数构建孔径分布模型,并与实验测量结果进行对比验证。建立了包含孔结构影响的气体扩散-反应数学模型,数值研究了多孔气体传感器内孔径分布形态对响应时间、灵敏度和选择性的影响规律。计算结果表明,双峰分布孔结构对提高传感器的气敏性能具有一定实际意义。孔结构变化时,孔内扩散阻力和比表面积呈相反变化趋势,共同影响传感器内被测气体的表面反应速率。多孔气体传感器对被测气体的80%响应时间随副峰概率的增大而逐渐缩短。多孔气体传感器的相对灵敏度则随副峰概率呈极值性变化,具有极大值。 相似文献
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Camera calibration is an essential issue in many computer vision tasks in which quantitative information of a scene is to be derived from its images. It is concerned with the determination of a set of parameters from the given images. In literature, it has been modeled as a nonlinear global optimization problem and has been solved using various optimization techniques. In this article, a recently developed variant of a very popular global optimization technique—the particle swarm optimization (PSO) algorithm—has been used for solving this problem for a stereo camera system modeled by pin-hole camera model. Extensive experiments have been performed on synthetic data to test the applicability of the technique to this problem. The simulation results, which have been compared with those obtained by a real coded genetic algorithm (RCGA) in literature, show that the proposed PSO performs a bit better than RCGA in terms of computational effort. 相似文献
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The segmentation of brain tumor plays an important role in diagnosis, treatment planning, and surgical simulation. The precise segmentation of brain tumor can help clinicians obtain its location, size, and shape information. We propose a fully automatic brain tumor segmentation method based on kernel sparse coding. It is validated with 3D multiple-modality magnetic resonance imaging (MRI). In this method, MRI images are pre-processed first to reduce the noise, and then kernel dictionary learning is used to extract the nonlinear features to construct five adaptive dictionaries for healthy tissues, necrosis, edema, non-enhancing tumor, and enhancing tumor tissues. Sparse coding is performed on the feature vectors extracted from the original MRI images, which are a patch of m×m×m around the voxel. A kernel-clustering algorithm based on dictionary learning is developed to code the voxels. In the end, morphological filtering is used to fill in the area among multiple connected components to improve the segmentation quality. To assess the segmentation performance, the segmentation results are uploaded to the online evaluation system where the evaluation metrics dice score, positive predictive value (PPV), sensitivity, and kappa are used. The results demonstrate that the proposed method has good performance on the complete tumor region (dice: 0.83; PPV: 0.84; sensitivity: 0.82), while slightly worse performance on the tumor core (dice: 0.69; PPV: 0.76; sensitivity: 0.80) and enhancing tumor (dice: 0.58; PPV: 0.60; sensitivity: 0.65). It is competitive to the other groups in the brain tumor segmentation challenge. Therefore, it is a potential method in differentiation of healthy and pathological tissues. 相似文献
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The dynamics of HIV spread: a computer simulation model 总被引:2,自引:0,他引:2
Mathematical modeling of the AIDS pandemic has been limited by the difficulty of satisfactorily representing the marked behavioral heterogeneity that characterizes the various populations at risk. We propose an approach which models the spread of infection as a discrete-event simulation using SIMSCRIPT, a powerful simulation language. The program developed provides sufficient flexibility to adequately represent and study a wide range of risk-group dynamics. Using this tool we have verified the May-Anderson prediction relating contact rate heterogeneity to the rate of HIV spread. We have also been able to assess the sensitivity of the model to the particular choice of distribution for contact rates, disease stage durations, and intercontact intervals. It is thought that this approach will permit the empirical testing of hypotheses which do not lend themselves to a purely mathematical treatment. 相似文献
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无边缘活动轮廓CV模型对于边界模糊以及背景灰度分布不均匀的图像缺乏良好的分割效果。基于此,对该模型进行了如下改进。对边界指示函数进行修改,将改进后的边界指示函数融入CV模型的长度项中。引用双阱势的距离正则项来避免水平集重新初始化,从而得到了一个梯度与区域信息相结合的水平集演化方程,并应用变分法中的有限差分法对方程进行求解。对木材虫眼、活节和死节图像进行了数值仿真模拟,仿真结果表明该模型对背景分布不均匀的图像具有良好的分割效果。 相似文献
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时空混沌系统有很好的密码学特性,常被用来设计伪随机数发生器。然而,时空混沌系统的概率密度分布不均匀,不利于保证伪随机数发生器的安全。针对此问题,提出一种新的基于时空混沌系统的伪随机发生器算法。该算法从提升时空混沌局部映射的密码学性能入手,将分段Logistic映射作为局部映射,并通过改变时空混沌系统的耦合参数来解决概率密度分布不均的问题。理论分析与仿真实验的结果表明,该算法产生的序列具有良好的初值敏感性和随机性,同时具有良好的执行效率,能够满足信息加密安全的需要。 相似文献