Edge-Weighted L1 Norm Minimization in Undersampled MRI Reconstruction

MRI作为一种重要的成像工具，已在临床诊断中得到了广泛应用，但其仍面临数据采集慢的挑战。欠采MRI稀疏重建是减少采样时间的一种有效方法。然而，对k空间进行欠采违背了奈奎斯特采样定理，将在重建图像中引入伪影，造成MRI图像的边缘特征模糊。但边缘特征通常包含丰富的对病理诊断极为重要的结构信息，因此如何提高重建图像边缘的能力成为一个重要问题。本文在常见的求解L1范数最优化方法的基础上，设计了不同的加权矩阵，提出提高MRI图像边缘重建的新方法。本论文的主要成果如下： 一、简要介绍了MRI空间编码的原理及与欠采MRI稀疏重建有关的基本数学理论，结合欠采MRI稀疏重建的最新发展现状，总结目前欠采MRI稀...Although MRI has been widely used in clinical applications as an important imaging tool, it is still burdened by the long acquisition time. Undersampling k-space is an effective way to solve the long acquisition time problem. However, undersampling violates the Nyquist-Shannon sampling theorem and introduces aliasing artifacts in the reconstruction, which blur the edge features that usually contai...学位：工学硕士院系专业：物理与机电工程学院物理学系_电磁场与微波技术学号：1982009115250

Effects of Municipal Domestic Sewage Effluents on the Growth of Calendula officinalis

用三种稀释倍数的城市生活污水[污水∶清水(v/v)为1﹕0、1﹕0.5、1﹕1]处理金盏菊种子及盆花,结果表明,污灌处理不仅显著地降低种子的萌发率,还增加萌发后幼苗病害的发生率;未经稀释的原生污水显著抑制金盏菊幼苗的生长,而稀释后抑制作用降低,当稀释至适当浓度时,则对幼苗生长起促进作用;对于金盏菊成年植株,污灌处理(不论稀释与否)显著地增加其茎、叶和根的鲜重,分别较对照增加161.63%～215.12%、86.77%～109.23%和23.89%～34.13%。综合分析表明,原生污水经过适当稀释后用于草花污灌,可以使污水中的营养盐得到回用,提高草花的观赏性。The seeds and potted plants of Calendula officinalis were treated with municipal domestic sewage effluents. The treatments were divided into 4 groups according to effluents : tap water(v/v): I, 1 : 0; II, 1 : 0.5; III, 1 : 1; control, 0 : 1. Compared with the control, sewage irrigation treatments (I, II and III) obviously reduced the rate of seed germination and increased the disease incidence of seedlings. The undiluted raw sewage could remarkably restrain the seedling growth, and the retarding effect could be relaxed by diluting with tap water. Furthermore, the diluted sewage of proper concentration could improve the seedlings growth. Compared to the control, sewage irrigation treatments increased the fresh weight of the stem, leave and root of full-grown C. officinalis plant by 161.63 %～215.12 %, 86.77 %～109.23 % and 23.89 %～34.13 %, respectively. The results of this study showed that the diluted sewage could be reused in irrigation and the nutrient elements in the sewage effluents could increase the ornamental value of herbage flowers

混凝土中钢筋腐蚀早期过程宏观腐蚀电池与微观腐蚀电池相互作用

建立一种阵列电极技术,通过测量不同时空的微电极腐蚀电位、电偶电流及其动态变化,研究了在腐蚀介质作用下,混凝土中钢筋腐蚀发生、发展早期过程阳极区和阴极区分布特征,探讨了钢筋腐蚀过程宏观腐蚀电池与微观腐蚀电池的相互作用机制.结果表明,伴随着点腐蚀的发生、发展过程,在钢筋/混凝土界面宏观腐蚀电池的作用明显,宏观腐蚀电池电流分布与腐蚀电位有密切的对应关系.混凝土中钢筋腐蚀过程总是存在着宏观腐蚀电池和微观腐蚀电池,二者密切相关、相互作用,对钢筋局部腐蚀的发生、发展过程有重要影响.国家自然科学基金重点项目(批准号:50731004);国家科技支撑计划项目(批准号:2007BAB27B04)资

Combined sparsifying transforms for compressed sensing MRI

In traditional compressed sensing MRI methods, single sparsifying transform limits the reconstruction quality because it cannot sparsely represent all types of image features. Based on the principle of basis pursuit, a method that combines sparsifying transforms to improve the sparsity of images is proposed. Simulation results demonstrate that the proposed method can well recover different types of image features and can be easily associated with total variation.This work was partially supported by NNSF of China under Grants (10774125 and 10605019)

Magnetic resonance image reconstruction using trained geometric directions in 2D redundant wavelets domain and non-convex optimization

Reducing scanning time is significantly important for MRI. Compressed sensing has shown promising results by undersampling the k-space data to speed up imaging. Sparsity of an image plays an important role in compressed sensing MRI to reduce the image artifacts. Recently, the method of patch-based directional wavelets (PBDW) which trains geometric directions from undersampled data has been proposed. It has better performance in preserving image edges than conventional sparsifying transforms. However, obvious artifacts are presented in the smooth region when the data are highly undersampled. In addition, the original PBDW-based method does not hold obvious improvement for radial and fully 2D random sampling patterns. In this paper, the PBDW-based MRI reconstruction is improved from two aspects: 1) An efficient non-convex minimization algorithm is modified to enhance image quality; 2) PBDW are extended into shift-invariant discrete wavelet domain to enhance the ability of transform on sparsifying piecewise smooth image features. Numerical simulation results on vivo magnetic resonance images demonstrate that the proposed method outperforms the original PBDW in terms of removing artifacts and preserving edges

Image Fusion Algorithm Based On Orientation Information Motivated Pulse Coupled Neural Networks

Pulse Coupled Neural Networks (PCNN) is a visual cortex-inspired neural networks and characterized by the global coupling and pulse synchronization of neurons. It has been proven suitable for image processing and successfully employed in image fusion. However, in most PCNN-based fusion algorithms, only single pixel value is input to motivate PCNN neuron. This is not effective enough because humans are often sensitive to features, not only pixel value. In this paper, novel orientation information is considered as features to motivate PCNN. Visual observation and objective performance evaluation criteria demonstrate that the proposed algorithm outperforms typical wavelet-based, lapacian pyramid transform-based and PCNN-based fusion algorithms.This work is supported by Navigation Science Foundation of China under grant no. 05F07001 and National Natural Science Foundation of China under grant no. 60472081

中国物理海洋学研究70年：发展历程、学术成就概览

本文概略评述新中国成立70年来物理海洋学各分支研究领域的发展历程和若干学术成就。中国物理海洋学研究起步于海浪、潮汐、近海环流与水团,以及以风暴潮为主的海洋气象灾害的研究。随着国力的增强,研究领域不断拓展,涌现了大量具有广泛影响力的研究成果,其中包括:提出了被国际广泛采用的"普遍风浪谱"和"涌浪谱",发展了第三代海浪数值模式;提出了"准调和分析方法"和"潮汐潮流永久预报"等潮汐潮流的分析和预报方法;发现并命名了"棉兰老潜流",揭示了东海黑潮的多核结构及其多尺度变异机理等,系统描述了太平洋西边界流系;提出了印度尼西亚贯穿流的南海分支(或称南海贯穿流);不断完善了中国近海陆架环流系统,在南海环流、黑潮及其分支、台湾暖流、闽浙沿岸流、黄海冷水团环流、黄海暖流、渤海环流,以及陆架波方面均取得了深刻的认识;从大气桥和海洋桥两个方面对太平洋–印度洋–大西洋洋际相互作用进行了系统的总结;发展了浅海水团的研究方法,基本摸清了中国近海水团的分布和消长特征与机制,在大洋和极地水团分布及运动研究方面也做出了重要贡献;阐明了南海中尺度涡的宏观特征和生成机制,揭示了中尺度涡的三维结构,定量评估了其全球物质与能量输运能力;基本摸清了中国近海海洋锋的空间分布和季节变化特征,提出了地形、正压不稳定和斜压不稳定等锋面动力学机制;构建了"南海内波潜标观测网",实现了对内波生成–演变–消亡全过程机理的系统认识;发展了湍流的剪切不稳定理论,提出了海流"边缘不稳定"的概念,开发了海洋湍流模式,提出了湍流混合参数化的新方法等;在海洋内部混合机制和能量来源方面取得了新的认识,并阐述了混合对海洋深层环流、营养物质输运等过程的影响;研发了全球浪–潮–流耦合模式,推出一系列海洋与气候模式;发展了可同化主要海洋观测数据的海洋数据同化系统和用于ENSO预报的耦合同化系统;建立了达到国际水准的非地转(水槽/水池)和地转(旋转平台)物理模型实验平台;发展了ENSO预报的误差分析方法,建立了海洋和气候系统年代际变化的理论体系,揭示了中深层海洋对全球气候变化的响应;初步建成了中国近海海洋观测网;持续开展南北极调查研究;建立了台风、风暴潮、巨浪和海啸的业务化预报系统,为中国气象减灾提供保障;突破了国外的海洋技术封锁,研发了万米水深的深水水听器和海洋光学特性系列测量仪器;建立了溢油、危险化学品漂移扩散等预测模型,为伴随海洋资源开发所带来的风险事故的应急处理和预警预报提供科学支撑。文中引用的大量学术成果文献(每位第一作者优选不超过3篇)显示,经过70年的发展,中国物理海洋学研究培养了一支实力雄厚的科研队伍,这是最宝贵的成果。这支队伍必将成为中国物理海洋学研究攀登新高峰的主力军

Matlab Image Fusion Toolbox for Image Fusion Algorithm Based On Orientation Information Motivated Pulse Coupled Neural Networks

This toolbox contains Matlab files that implement the image fusion algorithm: orientation information motivated Pulse Coupled Neural Networks in the following paper: [1]Xiaobo Qu, Changwei Hu, Jingwen Yan, Image Fusion Algorithm Based On Orientation Information Motivated Pulse Coupled Neural Networks, The seventh World Congress on Intelligent Control and Automation-WCICA 2008，Chongqing, China,25-27 June 2008, pp.2437-244