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Primal-dual algorithms for total variation based image restoration under Poisson noise Dedicated to Professor Lin Qun on the Occasion of his 80th Birthday

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Science China Mathematics 2016年第1期59卷 141-160页

作者： wen youwei CHAN Raymond Honfu ZENG TieYong Faculty of Science Kunming University of Science and TechnologyKunming 650093China Department of Mathematics The Chinese University of Hong KongShatinHong KongChina Department of Mathematics Hong Kong Baptist UniversityKowloonHong KongChina

We consider the problem of restoring images corrupted by Poisson noise. Under the framework of maximum a posteriori estimator, the problem can be converted into a minimization problem where the objective function is composed of a Kullback-Leibler(KL)-divergence term for the Poisson noise and a total variation(TV) regularization term. Due to the logarithm function in the KL-divergence term, the non-differentiability of TV term and the positivity constraint on the images, it is not easy to design stable and efficiency algorithm for the problem. Recently, many researchers proposed to solve the problem by alternating direction method of multipliers(ADMM). Since the approach introduces some auxiliary variables and requires the solution of some linear systems, the iterative procedure can be complicated. Here we formulate the problem as two new constrained minimax problems and solve them by Chambolle-Pock's first order primal-dual approach. The convergence of our approach is guaranteed by their theory. Comparing with ADMM approaches, our approach requires about half of the auxiliary variables and is matrix-inversion free. Numerical results show that our proposed algorithms are efficient and outperform the ADMM approach.

关键词： image restoration Poisson noise total variation (TV) alternating direction method of multipliers (ADMM) primal-dual minimax problem

A Total Variation Based Method for Multivariate Time Series Segmentation

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Advances in Applied Mathematics and Mechanics 2023年第2期15卷 300-321页

作者： Min Li Yumei Huang youwei wen School of Mathematics and Statistics Center for Data ScienceLanzhou UniversityLanzhouGansu 730000China School of Mathematics and Statistics Hunan Normal UniversityChangshaHunan 410081China and Key Laboratory of Computing and Stochastic Mathematics(LCSM)Ministry of Education of China

Multivariate time series segmentation is an important problem in data mining and it has arisen in more and more practical applications in recent *** task of time series segmentation is to partition a time series into segments by detecting the abrupt changes or anomalies in the time *** time series segmentation can provide meaningful information for further data analysis,prediction and policy decision.A time series can be considered as a piecewise continuous function,it is natural to take its total variation norm as a prior information of this time *** this paper,by minimizing the negative log-likelihood function of a time series,we propose a total variation based model for multivariate time series *** iterative process is applied to solve the proposed model and a search combined the dynamic programming method is designed to determine the *** experimental results show that the proposed method is efficient for multivariate time series segmentation and it is competitive to the existing methods for multivariate time series segmentation.

关键词： Multivariate time series segmentation total variation dynamic programming

Thermodynamic theory of flotation for a complex multiphase solid -liquid system and high-entropy flotation

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International Journal of Minerals,Metallurgy and Materials 2024年第6期31卷 1177-1197页

作者： Shuming wen State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization Faculty of Land Resource EngineeringKunming University of Science and TechnologyKunming 650093China

The flotation of complex solid–liquid multiphase systems involve interactions among multiple components,the core problem facing flotation ***,the combined use of multicomponent flotation reagents to improve mineral flotation has become an important issue in studies on the efficient use of refractory mineral ***,studying the flotation of complex solid–liquid systems is extremely difficult,and no systematic theory has been developed to *** addition,the physical mechanism associated with combining reagents to improve the flotation effect has not been unified,which limits the development of flotation theory and the progress of flotation *** this study,we applied theoretical thermodynamics to a solid–liquid flotation system and used changes in the entropy and Gibbs free energy of the reagents adsorbed on the mineral surface to establish thermodynamic equilibrium equations that de-scribe interactions among various material components while also introducing adsorption equilibrium constants for the flotation reagents adsorbed on the mineral *** homogenization effect on the mineral surface in pulp solution was determined using the chemical potentials of the material components of the various mineral surfaces required to maintain *** flotation effect can be improved through synergy among multicomponent flotation reagents;its physical essence is the thermodynamic law that as the number of compon-ents of flotation reagents on the mineral surface increases,the surface adsorption entropy change increases,and the Gibbs free energy change of adsorption *** to the results obtained using flotation thermodynamics theory,we established high-entropy flotation theory and a technical method in which increasing the types of flotation reagents adsorbed on the mineral surface,increasing the adsorption entropy change of the flotation reagents,decreasing the Gibbs free energy change,and improving the adsorption efficiency

关键词： multicomponent flotation reagent adsorption entropy change equations of thermodynamic equilibrium adsorption equilibri-um constant high-entropy flotation

Goal-Oriented Control Systems(GOCS):From HOW to WHAT

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 816-819页

作者： wen-Hua Chen the Department of Aeronautical and Automotive Engineering Loughborough UniversityLeicestershireLE113TUU.K.

Brief:New control theory is required to underpin safe design and deployment of future highly automated systems to deal with uncertain environments and complicated tasks,enabled by AI and other advanced ***-Oriented Control Systems offer potential to transform the control system design from currently instructing a control system how to perform a task to specifying what is to be achieved.

关键词： automated instru system

Observation of gapless corner modes of photonic crystal slabs in synthetic translation dimensions

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Photonics Research 2024年第3期12卷 444-455页

作者： wen-JIN ZHANG HAO-CHANG MO wen-JIE CHEN XIAO-DONG CHEN JIAN-wen DONG School of Physics&State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-sen UniversityGuangzhou 510275China

Second-order topological photonic crystals support localized corner modes that deviate from the conventional bulk-edge ***,the frequency shift of corner modes spanning the photonic band gap has not been experimentally ***,we observe the gapless corner modes of photonic crystal slabs within a parameter space by considering translation as an additional synthetic *** corner modes,protected by topological pumping in synthetic translation dimensions,are found to exist independently of the specific corner *** gapless corner modes are experimentally imaged via the near-field scanning measurement and validated numerically by full-wave *** propose a topological rainbow with gradient translation,demonstrating the ability to extract and separate specific frequency components of light into different spatial *** work contributes to the advancement of topological photonics and provides valuable insights into the exploration of gapless corner modes in synthetic dimensions.

关键词： translation dimensions corner

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全变差噪声消除问题的半光滑牛顿法

激光技术 2017年第2期41卷 289-295页

作者：王满文有为陈智斌昆明理工大学理学院数学系昆明650500 湖南师范大学数学与计算机科学学院长沙410006

为了达到全变差噪声消除的图像去噪目的,将去噪问题转换为优化问题。采用了结合广义最小残差法的半光滑牛顿法来解决相关优化问题,求解非对称线性方程组,进行了理论分析和实验验证,取得了将该方法与其它方法应用于1维信号、2维图像去噪... 详细信息

为了达到全变差噪声消除的图像去噪目的,将去噪问题转换为优化问题。采用了结合广义最小残差法的半光滑牛顿法来解决相关优化问题,求解非对称线性方程组,进行了理论分析和实验验证,取得了将该方法与其它方法应用于1维信号、2维图像去噪实验的大量可行数据。结果表明,结合广义最小残差法的半光滑牛顿法的收敛速度比结合预处理共轭梯度法的半光滑牛顿法和交替方向乘子法更快,而且能够有效地消除噪声。

关键词：图像处理全变差半光滑牛顿法广义最小残差法交替方向乘子法

Flow characteristics and bubble statistics during the fragmentation process of the ingested main cavity in plunging breaking waves

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Journal of Hydrodynamics 2024年第3期36卷 546-555页

作者： wen-bin Zhang Wei-wen Zhao De-cheng Wan Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

Plunging breaking waves play an important role in the exchange of heat,momentum,and mass between the atmosphere and *** this paper,a series of direct numerical simulations is conducted to investigate the fragmentation process of the ingested main cavity in plunging breaking *** two-phase Navier-Stokes equations are solved using the finite-volume method based on adaptive refinement *** free surface is captured using a geometrical volume of fluid *** 2-D,3-D simulations are *** flow fields at different stages of wave breaking are presented and quantitative analysis for bubbles is *** 2-D instantaneous vorticity field and local velocity field are visualized to discuss the general flow characteristics during the fragmentation *** a 2-D parametric study is conducted to investigate the differences in the flow characteristics during the fragmentation process under different wave parameters including initial wave steepness(ε),Bond number(Bo),and Reynolds number(Re).3-D vortex structures are shown to further investigate the mechanisms behind the differences in the flow *** bubble size distributions under two different initial wave steepness are also discussed with their relationship to the fragmentation process of the ingested main *** research offers a significant understanding of the distinct procedures and fundamental dynamics involved in wave breaking,enhancing our comprehension of this intricate event.

关键词： Plunging breaking waves multiphase flow bubble statistics

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基于交替迭代的均匀噪声消除算法

计算机工程 2018年第7期44卷 316-320页

作者：刘欣陈智斌文有为昆明理工大学理学院昆明650500 湖南师范大学数学与统计学院长沙410000

均匀噪声消除在数学上可以表示为一个带有无穷范数L∞约束的最小化问题,但无穷范数的不可微性会造成数值处理困难。为此,利用交替迭代算法求解该问题。引入一个凸示范性函数,根据变量分离的原则将原问题转化为2个具有解析解的最小化子... 详细信息

均匀噪声消除在数学上可以表示为一个带有无穷范数L∞约束的最小化问题,但无穷范数的不可微性会造成数值处理困难。为此,利用交替迭代算法求解该问题。引入一个凸示范性函数,根据变量分离的原则将原问题转化为2个具有解析解的最小化子问题。在此基础上,分别对不同的子问题进行求解,从而得到交替迭代公式。实验结果表明,对于一维逆热传导问题和二维逆源问题,交替迭代算法在精度和时间方面都有较好的性能提升效果。

关键词：均匀噪声无穷范数凸示范性函数交替迭代算法梯度投影算子

Isotopic insights on quantitative assessments of interaction of eco-hydrological processes in multi-scale karst watersheds

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International Soil and Water Conservation Research 2024年第1期12卷 156-170页

作者： Zhuo Hao Yang Gao Qingwen Zhang wen wen Agricultural Clean Watershed Research Group Institute of Environment and Sustainable Development in AgricultureCAASBeijing100081China Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchCASBeijing100101China School of Humanities and Social Sciences Beijing Institute of TechnologyBeijing100081China

The dynamics of hydrological processes and the storage mechanisms of karst water resources are the most important issues in karst *** impact of environmental changes on water quantity,and the evaluation and quantification of eco-hydrological processes remain poorly *** this study,high-frequency continuous monitoring in multi-scale karst watersheds in Southwest China combined the approaches of water isotopes and the hybrid single-particle lagrangian integrated trajectory(HYSPLIT)model to identify the recharge mechanisms between atmospheric vapor,rainfall,surface water,and groundwater,and to reveal the interaction of eco-hydrological *** dominant moisture sources in Puding(PD)County were the Indian Ocean(43-69%)and local moisture(24-33%).Theδ^(18)O and deuterium excess(d-excess)values showed a positive correlation indicating that secondary or sub-cloud evaporation was prominent in the wet *** water line-conditioned excess(lc-excess)indicated that karst water interacted with recent precipitation,groundwater,and evaporation across *** to its specific hydrogeological structure,surface water and rainwater have a higher contribution rate to groundwater *** Chenqi stream replenished the Houzhai River mainly in the form of groundwater,with percentages ranging from 38.1 to 93.5%in the wet season,and 47.8-80.1%in the dry *** the Houzhai outlet,surface water and groundwater interconverted frequently with a percentage of 45.6-49.1%.We believe this is the first systematic study to quantify the supply relationship between water vapor transport,rainfall,surface water and groundwater in the Chinese karst zone,making a significant move forward in the field of karst hydrological processes and improving the efficiency of water resource evaluation and management.

关键词： Stable isotope Moisture sources Water cycle Karst watersheds