联合群稀疏和代表系数双向空间光谱全变分的高光谱图像去噪

高光谱图像去噪是遥感领域的一个基本问题,也是预处理的重要步骤。基于代表系数全变分的去噪方法在高光谱图像(HSI)去噪中有着广泛的应用。代表系数矩阵U继承了干净HSI的先验信息,能够实现全局低秩并降低计算复杂度,但由于一阶全变分的引入,该类方法在去噪过程中产生了很强的阶梯效应并且忽略了不同波段间的共同特征,因此去噪效果很差。针对此问题,提出了一种新的联合群稀疏和代表系数双向空间光谱全变分(RCBGS)的正则化去噪模型。高阶全变分的引入缓解了阶梯效应,并在子空间的差分上引入加权l_(2,1)范数,充分挖掘不同波段除全局低秩外的共同特征,提高了HSI的内在群稀疏性和整体光滑性。最后,通过交替方向乘子法(ADMM)给出了所提方法的迭代规则,且所提方法的评价指标峰值信噪比相对于对比方法平均提升了8.79%。在模拟和真实数据集上的实验表明,所提方法在视觉质量和定量评估方面都优于相关方法。

Generalized Bi quasi variational Inequalities in Locally Convex Topological Vector Spaces

In this paper we investigate generalized bi quasi variational inequalities in locally convex topological vector spaces. Motivated and inspired by the recent research work in this field,we establish several existence theorems of solutions for generalized bi quasi variational inequalities,which are the extension and improvements of the earlier and recent results obtained previously by many authors including Sun and Ding [18],Chang and Zhang [23] and Zhang [24].

Estimations of directional Hlder regularity by shearlets

This paper studies directional Hlder regularity of two-variable functions by their shearlet coefficients, where the shearlets are defined by Guo and Labate(2013). We provide necessary conditions for a function possessing some directional H¨older regularity and the corresponding sufficient conditions, motivated by the work of Sampo and Sumetkijakan(2009) and Lakhonchai et al.(2010).

Hierarchical control for parallel bidirectional power converters of a grid-connected DC mlcrogrnd

The DC microgrid is connected to the AC utility by parallel bidirectional power converters （BPCs） to import/export large power, whose control directly affects the performance of the grid-connected DC microgrid. Much work has focused on the hierarchical control of the DC, AC, and hybrid microgrids, but little has considered the hierarchical control of multiple parallel BPCs that directly connect the DC microgrid to the AC utility. In this paper, we propose a hierarchical control for parallel BPCs of a grid-connected DC mierogrid. To suppress the potential zero-sequence circulating cm-cent in the AC side among the parallel BPCs and realize feedback linearization of the voltage control, a d-q-O control scheme instead of a conventional d-q control scheme is proposed in the inner current loop, and the square of the DC voltage is adopted in the inner voltage loop. DC side droop control is applied to realize DC current sharing among multiple BPCs at the primary control level, and this induces DC bus voltage deviation. The quantified relationship between the current sharing error and DC voltage deviation is derived, indicating that there is a trade-off between the DC voltage deviation and current sharing error. To eliminate the current sharing error and DC voltage deviation simultaneously, slope-adjusting and voltage-shifting approaches are adopted at the secondary control level. The pro- posed tertiary control realizes precise active and reactive power exchange through parallel BPCs for economical operation. The proposed hierarchical control is applied for parallel BPCs of a grid-connected DC microgrid and can operate coordinately with the control for controllable/uncontrollable distributional generation. The effectiveness of the proposed control method is verified by corresponding simulation tests based on Matlab/Simulink, and the performance of the hierarchical control is evaluated for prac- tical applications.

On the hyperbolicity of flows

Let X be a C1 vector field on a compact boundaryless Riemannian manifold M（dim M≥2）,and A a compact invariant set of X.Suppose that A has a hyperbolic splitting,i.e.,T∧M = Es Eu with Es uniformly contracting and Eu uniformly expanding.We prove that if,in addition,A is chain transitive,then the hyperbolic splitting is continuous,i.e.,A is a hyperbolic set.In general,when A is not necessarily chain transitive,the chain recurrent part is a hyperbolic set.Furthermore,we show that if the whole manifold M admits a hyperbolic splitting,then X has no singularity,and the flow is Anosov.