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Synthesis of poly(thiourethane-alt-thioester) by alternating ring-opening copolymerization of N-thiocarboxyanhydrides and episulfides

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Science China Chemistry 2024年第9期67卷 3091-3097页

作者： Wei Xiong Tianjun Yue Haiwang Lai Chunyan Lyu Weimin Ren Hua Lu Beijing National Laboratory for Molecular Sciences Center for Soft Matter Science and Engineering Key Laboratory of Polymer Chemistry and Physics of Ministry of Education College of Chemistry and Molecular Engineering Peking University State Key Laboratory of Fine Chemicals Dalian University of Technology

Polythiourethanes(PTU) and polythioesters(PTE) derived from renewable sources are emerging sustainable polymers for their excellent degradability and recyclability. However, P(TU-alt-TE) copolymers have been rare and challenging to ***, we report the efficient synthesis of novel P(TU-alt-TE) copolymers via the alternating copolymerization of N-thiocarboxyanhydrides(NTA)/episufides(ES) and provide mechanistic insight into the alternating chain propagation process via density functional theory(DFT) calculation. The incorporation of ESs into traditional peptide backbone is capable of adjusting the glass transition temperature below thermal decomposition temperature, which confers better thermal processability by regulating the rigidity of the backbone and the hydrogen bond interaction among the polymer chains. Crosslinked PTUs with tailored properties are accessible by altering the feeding ratio of NTAs and(bifunctional) ESs. Moreover, the thiourethane in the backbone can endow interesting underwater adhesion properties to the materials. Considering the broad scope of NTA and ES monomers, this method is expected to provide a promising and general route to a wide range of P(TU-alt-TE) copolymers with diverse properties.

关键词： poly(thiourethane-alt-thioester) alternating ring-opening copolymerization N-thiocarboxyanhydrides episulfides

alternating Direction Method of Multipliers for l_(1)-l_(2)-Regularized Logistic Regression Model

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Journal of the Operations Research Society of China 2016年第2期4卷 243-253页

作者： Yan-Qin Bai Kai-Ji Shen Department of Mathematics Shanghai UniversityShanghai 200444China

Logistic regression has been proved as a promising method for machine learning,which focuses on the problem of *** this paper,we present anl_(1)-l_(2)-regularized logistic regression model,where thel1-norm is responsible for yielding a sparse logistic regression classifier and thel_(2)-norm for keeping betlter classification *** solve thel_(1)-l_(2)-regularized logistic regression model,we develop an alternating direction method of multipliers with embedding limitedlBroyden-Fletcher-Goldfarb-Shanno(L-BFGS)***,we implement our model for binary classification problems by using real data examples selected from the University of California,Irvine Machines Learning Repository(UCI Repository).We compare our numerical results with those obtained by the well-known LIBSVM and SVM-Light *** numerical results show that ourl_(1)-l_(2)-regularized logisltic regression model achieves better classification and less CPU Time.

关键词： Classification problems Logistic regression model Sparsity alternating direction method of multipliers

Reduction in Microsegregation in Al-Cu Alloy by alternating Magnetic Field

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Acta Metallurgica Sinica(English Letters) 2020年第2期33卷 267-274页

作者： Sheng-Ya He Chuan-Jun Li Tong-Jun Zhan Wei-Dong Xuan Jiang Wang Zhong-Ming Ren State Key Laboratory of Advanced Special Steel and School of Materials Science and Engineering Shanghai UniversityShanghai 200444China Helmholtz-Zentrum Dresden-Rossendorf(HZDR) 01328 DresdenGermany

The microsegregation behavior of the Al-4.5 wt%Cu alloy solidified at different cooling rates under the alternating magnetic field(AMF) was *** experimental results showed that the amount of non-equilibrium eutectics in the interdendritic region decreased upon applying the AMF at the same cooling *** change in microsegregation could be explained quantificationally by the modifications of dendritic coarsening,solid-state back diffusion and convection in the *** enhanced diffusivity in the solid owing to the AMF was beneficial for the improvement in microsegregation compared to the cases without an *** contrast,the enhanced dendritic coarsening and forced convection in the AMF were found to aggravate the microsegregation *** the contributions of the changes in above factors,an increase in solid diffusivity was found to be primarily responsible for the reduced microsegregation in the *** addition,the microsegregation in the AMF was modeled using the analytical model developed by *** calculated and experimental results were in reasonable agreement.

关键词： Microsegregation Solidification alternating magnetic field Diffusion Coarsening Convection

Rapid determination of thiabendazole in orange extract using excitation-emission matrix fluorescence and second-order calibration based on alternating trilinear decomposition/alternating normalization-weighted error algorithms

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Science China Chemistry 2008年第8期51卷 729-735页

作者： WANG XueMei WU HaiLong NIE JinFang LI YuanNa YU YongJie YU RuQin State Key Laboratory of Chemo/Biosensing and Chemometrics Hunan UniversityChangsha 410082China

A novel approach is proposed for direct quantitative analysis of thiabendazole in the orange extract by using excitation-emission matrix fluorescence coupled with second-order calibration methods based on the alternating trilinear decomposition(ATLD) and the alternating normalization-weighted error(ANWE) algorithms,respectively. The average recoveries of thiabendazole in the orange extract by using ATLD and ANWE with an estimated component number of two were 99.7 ± 3.3% and 103.5 ± 4.1%,respectively. Furthermore,the accuracy of the two algorithms was also evaluated through elliptical joint confidence region(EJCR) tests as well as figures of merit,such as sensitivity(SEN),selectivity(SEL) and limit of detection(LOD). The experimental results demonstrate that both algorithms have been satisfactorily applied to the determination of thiabendazole in orange extract,and the perform-ance of ANWE is slightly better than that of ATLD.

关键词： excitation-emission matrix fluorescence alternating trilinear decomposition alternating normalization-weighted error orange extract thiabendazole

Magnetoelastic combined resonance and stability analysis of a ferromagnetic circular plate in alternating magnetic field

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Applied Mathematics and Mechanics(English Edition) 2019年第7期40卷 925-942页

作者： Yuda HU Bingbing MA School of Civil Engineering and Mechanics Yanshan University Qinhuangdao 066004 Hebei Province China Hebei Key Laboratory of Mechanical Reliability for Heavy Equipment and Large Structures Yanshan University Qinhuangdao 066004 Hebei Province China

The nonlinear combined resonance problem of a ferromagnetic circular plate in a transverse alternating magnetic field is investigated. On the basis of the deformation potential energy, the strain potential energy, and the kinetic energy of the circular plate, the Hamilton principle is used to induce the magnetoelastic coupling transverse vibration dynamical equation of the ferromagnetic circular plate. Based on the basic electromagnetic theory, the expressions of the magnet force and the Lorenz force of the circular plate are presented. A displacement function satisfying clamped-edge combined with the Galerkin method is used to derive the Duffing vibration differential equation of the circular plate. The amplitude-frequency response equations of the system under various combined resonance forms are obtained by means of the multi-scale method, and the stability of the steady-state solutions is analyzed according to the Lyapunov theory. Through examples, the amplitude-frequency characteristic curves with different parameters, the amplitude of resonance varying with magnetic field intensity and excitation force, and the time-course response diagram, phase diagram, Poincar′e diagram of the system vibration are plotted, respectively. The effects of different parameters on the amplitude and stability of the system are discussed. The results show that the electromagnetic parameters have a significant effect on the multi-valued attribute and stability of the resonance solutions, and the system may exhibit complex nonlinear dynamical behavior including multi-period and quasi-periodic motion.

关键词： magnetoelasticity ferromagnetic circular plate combined resonance multi- scale method alternating magnetic field

O(1/t) complexity analysis of the generalized alternating direction method of multipliers

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Science China Mathematics 2019年第4期62卷 795-808页

作者： Xingju Cai Deren Han School of Mathematical Sciences and Key Laboratory for Numerical Simulation of Large Scale Complex Systems of Jiangsu Province Nanjing Normal University

Owing to its efficiency in solving some types of large-scale separable optimization problems with linear constraints, the convergence rate of the alternating direction method of multipliers(ADMM for short) has recently attracted significant attention. In this paper, we consider the generalized ADMM(G-ADMM), which incorporates an acceleration factor and is more efficient. Instead of using a solution measure that depends on a bounded set and cannot be easily estimated, we propose using the original ?-optimal solution measure, under which we prove that the G-ADMM converges at a rate of O(1/t). The new bound depends on the penalty parameter and the distance between the initial point and the solution set, which is more reasonable than the previous bound.

关键词： generalized alternating direction method of multipliers separable convex optimization iteration complexity sublinear convergence rate

Spline Fictitious Boundary Element alternating Method for Edge Crack Problems with Mixed Boundary Conditions

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Computer Modeling in Engineering & Sciences 2018年第9期116卷 407-431页

作者： Z.Xu M.Chen X.M.Fan School of Civil Engineering and Transportation South China University of TechnologyGuangzhouChina State Key Laboratory of Subtropical Building Science South China University of TechnologyGuangzhouChina

The alternating method based on the fundamental solutions of the infinite domain containing a crack,namely Muskhelishvili’s solutions,divides the complex structure with a crack into a simple model without crack which can be solved by traditional numerical methods and an infinite domain with a crack which can be solved by Muskhelishvili’s ***,this alternating method cannot be directly applied to the edge crack problems since partial crack surface of Muskhelishvili’s solutions is located outside the computational *** this paper,an improved alternating method,the spline fictitious boundary element alternating method(SFBEAM),based on infinite domain with the combination of spline fictitious boundary element method(SFBEM)and Muskhelishvili’s solutions is proposed to solve the edge crack *** the SFBEM and Muskhelishvili’s solutions are obtained in the framework of infinite domain,no special treatment is needed for solving the problem of edge *** mixed boundary conditions edge crack problems with varies of computational parameters are given to certify the high precision,efficiency and applicability of the proposed method compared with other alternating methods and extend finite element method.

关键词： Spline fictitious boundary element alternating method mixed boundary conditions edge crack problem Muskhelishvili’s solutions stress intensity factor

A Class of alternating Linearization Algorithms for Nonsmooth Convex Optimization

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Acta Mathematicae Applicatae Sinica 2019年第2期35卷 435-443页

作者： Dan LI Jie SHEN Yuan LU Li-Ping PANG Zun-Quan XIA Information and Engineering College Dalian University School of Mathematics Liaoning Normal University Normal College Shenyang University School of Mathematical Sciences Dalian University of Technology

We consider the problems of minimizing the sum of a continuously differentiable convex function and a nonsmooth convex function in this paper. These problems arise in many applications of practical interest.A class of alternating linearization methods is presented for solving these problems. The global convergence rate is also obtained under certain mild conditions. Numerical experiments validate the theoretical convergence analysis and verify the implementation of the proposed algorithm.

关键词： alternating linearization method proximal point convex programming nonsmooth optimization

Total curvature(TC) model and its alternating direction method of multipliers algorithm for noise removal

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Optoelectronics Letters 2019年第3期15卷 217-223页

作者：牟云平黄宝香王誉熹王明磊薛超 School of Computer Science Qingdao University

This paper develops a variational model for image noise removal using total curvature(TC), which is a high-order regularizer. The TC has the advantage of preserving image feature. Unfortunately, it also has the characteristics of nonlinear, non-convex and non-smooth. Consequently, the numerical computation with the curvature regularization is difficult. In order to conquer the computation problem, the proposed model is transformed into an alternating optimization problem by importing auxiliary variables. Furthermore, based on alternating direction method of multipliers, we design a fast numerical approximation iterative scheme for proposed model. Finally, numerous experiments are implemented to indicate the advantages of the proposed model in image edge preserving, image contrast and corners preserving. Meanwhile, the high computational efficiency of the designed model is verified by comparing with traditional models, including the total variation(TV) and total Laplace(TL) model.

关键词： Total curvature model and its alternating direction method of multipliers algorithm for noise removal TC TV