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A Second-Order Image Denoising Model for Contrast Preservation

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Communications on Applied Mathematics and Computation 2024年第2期6卷 1406-1427页

作者： Wei zhu Department of Mathematics University of AlabamaBox 870350TuscaloosaAL35487USA

In this work,we propose a second-order model for image denoising by employing a novel potential function recently developed in zhu(j Sci Comput 88:46,2021)for the design of a regularization *** to this new second-order derivative based regularizer,the model is able to alleviate the staircase effect and preserve image *** augmented Lagrangian method(ALM)is utilized to minimize the associated functional and convergence analysis is established for the proposed *** experiments are presented to demonstrate the features of the proposed model.

关键词： Image denoising Variational model Image contrast Augmented Lagrangian method(ALM)

Optimal Operation Strategy Analysis with Scenario Generation Method Based on Principal Component Analysis,Density Canopy,and K-medoids for Integrated Energy Systems

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journal of Modern Power Systems and Clean Energy 2024年第1期12卷 89-100页

作者： Bingtuan Gao Yunyu zhu Yuanmei Li School of Electrical Engineering Southeast UniversityNanjingChina

The operation of integrated energy systems(IESs)is confronted with great challenges for increasing penetration rate of renewable energy and growing complexity of energy *** generation is one of ordinary methods to alleviate the system uncertainties by extracting several typical scenarios to represent the original high-dimensional *** paper proposes a novel representative scenario generation method based on the feature extraction of panel *** original high-dimensional data are represented by an aggregated indicator matrix using principal component analysis to preserve temporal ***,the aggregated indicator matrix is clustered by an algorithm combining density canopy and *** with the proposed scenario generation method,an optimal operation model of IES is established,where the objective is to minimize the annual operation costs considering carbon trading ***,case studies based on the data of Aachen,Germany in 2019 are *** results indicate that the adjusted rand index(ARI)and silhouette coefficient(SC)of the proposed method are 0.6153 and 0.6770,respectively,both higher than the traditional methods,namely K-medoids,K-means++,and density-based spatial clustering of applications with noise(DBSCAn),which means the proposed method has better *** error between optimal operation results of the IES obtained by the proposed method and all-year time series benchmark value is 0.1%,while the calculation time is reduced from 11029 s to 188 s,which verifies that the proposed method can be used to optimize operation strategy of IES with high efficiency without loss of accuracy.

关键词： Scenario generation principal component analysis(PCA) density canopy K-medoids integrated energy system

2-local unstable homotopy groups of indecomposable A3～2-complexes

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Science China Mathematics 2024年第3期67卷 607-626页

作者： Zhongjian zhu jianzhong Pan College of Mathematics and Physics Wenzhou University Hua Loo-Keng Key Laboratory of Mathematics Institute of MathematicsAcademy of Mathematics and Systems ScienceChinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of Sciences

In this paper,we calculate the 2-local unstable homotopy groups of indecomposable A3～*** main technique used is analysing the homotopy property of j（A,X）,defined by Gray（1973） for a CW-pair（X,A）,which is homoto... 详细信息

关键词： homotopy groups A 2 n -complexes fibration sequence relative james construction 55P15

Partial Collapsing Degeneration of Floer Trajectories and Adiabatic Gluing

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Acta Mathematica Sinica,English Series 2024年第1期40卷 161-249页

作者： Yong-Geun OH Ke zhu Center for Geometry and Physics Institute for Basic Science(IBS)79 Jigok-ro 127beon-gilNam-guPohang-siGyeongsangbuk-doKorea 37673&POSTECHGyeongsangbuk doKorea Department of Mathematics and Statistics Minnesota State UniversityMankatoMN 56001USA

In the present paper,we study partial collapsing degeneration of Hamiltonian-perturbed Floer trajectories for an adiabatic ε-family and its reversal adiabatic gluing,as the prototype of the partial collapsing degeneration of 2-dimensional(perturbed)j-holomorphic maps to 1-dimensional gradient *** consider the case when the Floer equations are S^(1)-invariant on parts of their domains whose adiabatic limit has positive length as ε→0,which we call thimble-flow-thimble *** main gluing theorem we prove also applies to the case with Lagrangian boundaries such as in the problem of recovering holomorphic disks out of pearly *** particular,our gluing theorem gives rise to a new direct proof of the chain isomorphism property between the Morse-Bott version of Lagrangian intersection Floer complex of L by Fukaya-Oh-Ohta-Ono and the pearly complex of L Lalonde and *** also provides another proof of the present authors’earlier proof of the isomorphism property of the PSS map without involving the target rescaling and the scale-dependent gluing.

关键词： Floer trajectory equation partial collapsing degeneration thimble-flow-thimble moduli space adiabatic gluing exponential decay estimates three-interval method

Association of daily sitting time and leisure-time physical activity with body fat among ***

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journal of Sport and Health Science 2024年第2期13卷 195-203页

作者： jingwen Liao Min Hu Kellie Imm Clifton j.Holmes jie zhu Chao Cao Lin Yang Guangdong Provincial Key Laboratory of Physical Activity and Health Promotion Guangzhou Sport UniversityGuangzhou 510500China Scientific Research Center Guangzhou Sport UniversityGuangzhou 510500China Division of Epidemiology&Genetics Department of Population and Public Health SciencesKeck School of Medicine of the University of Southern CaliforniaLos AngelesCA 90033USA Program in Physical Therapy Washington University School of MedicineSt.LouisMO 63110USA Center for Human nutrition Washington University School of MedicineSt.LouisMO 63110USA Department of Plastic and Reconstructive Surgery Shanghai East HospitalTongji UniversityShanghai 200070China Department of Cancer Epidemiology and Prevention Research Alberta Health ServicesCalgary T2S 3C3Canada Department of Oncology and Community Health Sciences University of CalgaryCalgary T2N 1N4Canada

Background:Prolonged sitting and reduced physical activity lead to low energy ***,little is known about the joint impact of daily sitting time and physical activity on body fat *** investigated the independent and joint associations of daily sitting time and physical activity with body fat among ***:This was a cross-sectional analysis of *** representative data from the national Health and nutrition Examination Survey2011-2018 among adults aged 20 years or *** sitting time and leisure-time physical activity(LTPA)were self-reported using the Global Physical Activity *** fat(total and trunk fat percentage)was determined via dual X-ray ***:Among 10,808 adults,about 54.6%spent 6 h/day or more sitting;more than one-half reported no LTPA(inactive)or less than 150 min/week LTPA(insufficiently active)with only 43.3%reported 150 min/week or more LTPA(active)in the past *** fully adjusting for sociodemographic data,lifestyle behaviors,and chronic conditions,prolonged sitting time and low levels of LTPA were associated with higher total and trunk fat percentages in both *** stratifying by LTPA,the association between daily sitting time and body fat appeared to be stronger in those who were inactive/insuufficiently *** the joint analyses,inactive/insuufficiently active adults who reported sitting more than 8 h/day had the highest total(female:3.99%(95%confidence interval(95%CI):3.09%-4.88%);male:3.79%(95%CI:2.75%-4.82%))and trunk body fat percentages(female:4.21%(95%CI:3.09%-5.32%);male:4.07%(95%CI:2.95%-5.19%))when compared with those who were active and sitting less than 4 h/***:Prolonged daily sitting time was associated with increased body fat among *** higher body fat associated with 6 h/day sitting may not be offset by achieving recommended levels of physical activity.

关键词： Adults Body fat distribution Physical activity Sitting time

Dirac-harmonic maps with the trivial index

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Science China Mathematics 2024年

作者： jürgen jost Linlin Sun jingyong zhu Max Planck Institute for Mathematics in the Sciences School of Mathematics and Statistics Guangxi Normal University School of Mathematics Sichuan University

For a homotopy class [u] of maps between a closed Riemannian manifold M and a general manifold n, we want to find a Dirac-harmonic map with the map component in the given homotopy class. Most known results require the index to be nontrivial. When the index is trivial, the few known results are all constructive and produce uncoupled solutions. In this paper, we define a new quantity. As a byproduct of proving the homotopy invariance of this new quantity, we find a new simple proof for the fact that all the Dirac-harmonic spheres in surfaces are uncoupled. More importantly, by using the homotopy invariance of this new quantity,we prove the existence of Dirac-harmonic maps from manifolds in the trivial index case. In particular, when the domain is a closed Riemann surface, we prove the short-time existence of the α-Dirac-harmonic map flow in the trivial index case. Together with the density of the minimal kernel, we get an existence result for Dirac-harmonic maps from closed Riemann surfaces to K¨ahler manifolds, which extends the previous result of the first and third authors. This establishes a general existence theory for Dirac-harmonic maps in the context of the trivial index.

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Controllable large-scale processing of temperature regulating sheath-core fibers with high-enthalpy for thermal management

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nano Materials Science 2024年第3期6卷 337-344页

作者： Ziye Chen Zexu Hu Shining Chen Senlong Yu Liping zhu Hengxue Xiang Meifang zhu Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai201620China College of Mechanical and Engineering Donghua UniversityShanghai201620China

Temperature regulating fibers(TRF_(s)) with high enthalpy and high form stability are the key factors for thermal management. However, the enthalpies of most TRFsare not high, and the preparation methods are still at the laboratory scale. It remains a great challenge to use industrial spinning equipment to achieve continuous processing of TRF_(s) with excellent thermal and mechanical properties. Here, polyamide 6(PA6) based TRF_(s) with a sheath-core structure were prepared by bicomponent melt-spinning. The sheath-core TRF(TRF_(sc)) are composed of PA6 as sheath and functional PA6 as core, which are filled with the shape stable phase change materials(ssPCM),dendritic silica@polyethylene glycol(SiO_(2)@PEG). With the aid of the sheath structure, the filling content of SiO_(2)@PEG can reach 30 %, so that the enthalpy of the TRF_(s) can be as high as 21.3 j/g. The ultra-high enthalpy guarantees the temperature regulation ability during the alternating process of cooling and heating. In hot environment, the temperature regulation time is 6.59 min, and the temperature difference is 12.93℃. In addition, the mechanical strength of the prepared TRF_(sc) reaches 2.26 cn/dtex, which can fully meet its application in the field of thermal management textiles and devices to manage the temperature regulation of the human body or precision equipment, etc.

关键词： Thermal management Hybrid fibers Polyamides Bicomponent melt spinning Temperature regulating fibers

Recent advances in graphene-based phase change composites for thermal energy storage and management

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nano Materials Science 2024年第2期6卷 115-138页

作者： Qiang zhu Pin jin Ong Si Hui Angela Goh Reuben j.Yeo Suxi Wang Zhiyuan Liu Xian jun Loh Institute of Materials Research and Engineering A*STAR(Agency for ScienceTechnology and Research)2 Fusionopolis WayInnovis#08-03138634Singapore Institute of Sustainability for Chemicals Energy and EnvironmentA*STAR(Agency for ScienceTechnology and Research)1 Pesek RoadJurong Island627833Singapore School of Chemistry Chemical Engineering and BiotechnologyNanyang Technological University21 Nanyang Link637371Singapore Shenzhen Institutes of Advanced Technology(SIAT) Chinese Academy of Sciences(CAS)1068 Xueyuan AvenueShenzhen518055China Department of Material Science and Engineering National University of Singapore9 Engineering Drive 1#03-09 EA117575Singapore

Energy storage and conservation are receiving increased attention due to rising global energy ***,the development of energy storage materials is *** energy storage(TES)systems based on phase change materials(PCMs)have increased in prominence over the past two decades,not only because of their outstanding heat storage capacities but also their superior thermal energy regulation ***,issues such as leakage and low thermal conductivity limit their applicability in a variety of ***-based materials such as graphene and its derivatives can be utilized to surmount these *** study examines the recent advancements in graphene-based phase change composites(PCCs),where graphene-based nanostructures such as graphene,graphene oxide(GO),functionalized graphene/GO,and graphene aerogel(GA)are incorporated into PCMs to substantially enhance their shape stability and thermal conductivity that could be translated to better storage capacity,durability,and temperature response,thus boosting their attractiveness for TES *** addition,the applications of these graphene-based PCCs in various TES disciplines,such as energy conservation in buildings,solar utilization,and battery thermal management,are discussed and summarized.

关键词： Phase change material nanocomposites Solar energy Sustainable energy Thermo-regulation

On the Trail of Self-Directed Online Learners

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ECnU Review of Education 2024年第2期7卷 406-419页

作者： Curtis j.Bonk 朱美娜 School of Education Indiana University201 N.Rose AvenueBloomingtonIN 4740lUSA Wayne State University

Purpose We describe a series of more than a dozen studies on self-directed online learning spanning over a ***/Approach/Methods We incorporated surveys,interviews,focus groups,and content analyses into these research studies,which initially targeted the goals,motivations,and challenges of learners using open educational resources and OpenCourseWare and then focused on learning from massive open online courses(MOOCs).This research accelerated after creating a database of over 3,000 MOOC instructors,through which we explored cultural sensitivity and personalization practices in MOOCs as well as instructional design considerations and challenges,MOOC instructor professional development and career development,instructor motivation and engagement,and student and instructor perceptions of self-directed *** This study reveals that self-directed online learners(SDOLs)seek learning environments offering freedom,choice,control,and a sense of autonomy and that both learners and instructors have intrinsic motivation for engaging in open online learning ***/Value Based on this research with both MOOC instructors and MOOC learners,we offer instructional design guidelines to address SDOLs’needs and assist in efforts to foster a new generation of SDOLs.

关键词： MOOCs motivation online learning self-directed learning self-management self-monitoring