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Elimination of Anti-spiral Waves by Local Inhomogeneity in Oscillatory Systems

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Chinese Journal of Chemical Physics 2008年第6期21卷 575-580页

作者： Fu-cheng Liu xiao-fei Wang College of Physics Science & Technology Hebei University Baoding 071002 China

Anti-spiral waves are controlled in an oscillatory system by using a local inhomogeneity. The inhomogeneity acts as a wave source, and gives rise to the propagating plane waves, tt is found that there is a critical pacemaking domain size below which no wave will be created at all. Two types of ordered waves （target waves and traveling waves） are created depending on the geometry of the local inhomogeneity. The competition between the anti-spiral waves and the ordered waves is discussed. Two different competition mechanisms were observed, which are related to the ordered waves obtained from different local inhomogeneities. It is found that traveling waves with either lower frequency or higher frequency can both eliminate the anti-spiral waves, while only the target waves with lower absolute value of frequency can eliminate the anti-spiral waves. This method also applies to outwardly rotating spiral waves. The control mechanism is intuitively explained and the control method is easily operative.

关键词： Anti-spiral wave Traveling wave Inhomogeneity Oscillatory system

Symplectic system based analytical solution for bending of rectangular orthotropic plates on Winkler elastic foundation

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Acta Mechanica Sinica 2011年第6期27卷 929-937页

作者： Wei-An Yao xiao-fei Hu Feng xiao State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology 116024 Dalian China Department of Computer Science Dalian Medical University 116044 Dalian China

This paper analyses the bending of rectangular orthotropic plates on a Winkler elastic *** definition of symplectic inner product and symplectic space formed by generalized displacements establish dual variables and dual equations in the symplectic *** operator matrix of the equation set is proven to be a Hamilton operator *** of variables and eigenfunction expansion creates a basis for analyzing the bending of rectangular orthotropic plates on Winkler elastic foundation and obtaining solutions for plates having any boundary *** is discussion of symplectic eigenvalue problems of orthotropic plates under two typical boundary conditions,with opposite sides simply supported and opposite sides *** equations of eigenvalues and symplectic eigenvectors in analytical form *** solutions using two examples are presented to show the use of the new methods described in this *** verify the accuracy and convergence,a fully simply supported plate that is fully and simply supported under uniformly distributed load is used to compare the classical Navier method,the Levy method and the new *** show that the new technique has good accuracy and better convergence speed than other methods,especially in relation to internal forces.A fully clamped rectangular plate on Winkler foundation is solved to validate application of the new methods,with solutions compared to those produced by the Galerkin method.

关键词： Orthotropic plate Symplectic space Winklerelastic foundation Analytical solution

Ultrathin self-assembly MXene/Co-based bimetallic oxide heterostructures as superior and modulated microwave absorber

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Journal of Materials Science & Technology 2023年第3期134卷 132-141页

作者： Hui-Ya Wang xiao-Bo Sun Yue Xin Shu-Hao Yang Peng-fei Hu Guang-sheng Wang School of Chemistry Beihang UniversityBeijing 102206China Research Institute of Aero-Engine Beihang UniversityBeijing 102206China

Lightweight and high-efficiency absorbing materials equipped with tunable electromagnetic properties are the foremost important factors for driving applications of 5 G smart era and military ***-ulated by the remarkable merits of heterogeneous interface engineering,a series of unique flower-like Co-based multiphases nanostructures were successfully synthesized through identical hydrothermal method,and subsequently anchored on the Ti_(3)C_(2)T_(x)*** suitable metal ion modulation is feasible to regulate the components,heterogeneous interfaces and defects for tailoring the electromag-netic parameters and microwave absorption(MA)***,the permittivity decreases of CMOT(CoO/MCo_(2)O_(4)/Ti_(3)C_(2)T_(x),M=Fe,Cu,Zn)composites proceed gradually in the order of Fe^(2+),Cu^(2+),Zn^(2+),while the MA performance with tunable absorption peak could be modulated *** asobtained CFOT-12(10 wt%),CCOT-15(10 wt%)and CZOT-15(15 wt%)exhibit excellent MA capacity with a minimum reflection loss(RL_(min))of-41.06,-52.67,-52.52 dB and corresponding effective absorption bandwidth(EAB)of 3.68,4.48,3.92 GHz at 2.10,1.90,1.80 mm,*** work expands a novel approach to construct multicomponent heterostructure for tuning the EM parameters and absorbing property,as well as realize the high efficient and light weight.

关键词： Heterogeneous interface Modulation MXene High-efficiency absorbing materials Lightweight

Comparative Studies on Properties of Polymers with Bulky Side Groups Synthesized by Cyclopolymerization of α,ω-Dienes and α,ω-Diynes

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Chinese Journal of Polymer Science 2019年第2期37卷 149-156页

作者： Shao-fei Song xiao-Yu Liu Hao Zhang Zhi-sheng Fu Jun-Ting Xu Zhi-Qiang Fan Ministry of Education Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University

Four polymers containing five-membered rings in the main chain, with or without conjugation structure along the backbone and with or without conjugated pendent groups, were designed and synthesized by metathesis cyclopolymerization of functionalized α,ω-diynes, and cyclopolymerization of functionalized α,ω-dienes catalyzed by the α-diimine palladium-based catalyst, respectively. High to moderate monomer conversions were achieved. Chain structure, molecular weight, and molecular weight distribution(MWD) of the cyclopolymerization products were characterized by ~1 H-, ^(13) C-NMR, FTIR, and GPC. The polymers showed regular main chain structures,moderately high molecular weight, and narrow MWD. Thermal properties and chain stacking behaviors of the polymers were investigated by differential scanning calorimetry(DSC) and X-ray diffraction(XRD) as well as atomic force microscopy(AFM). The polymer with conjugation system in both the backbone and the pendent groups exhibited UV-Vis absorption at a much longer wavelength than those with the conjugation only in the backbone or only in the side groups. The polymers with conjugated backbone need more space for chain stacking, and the conjugated backbone causes enhanced size of polymer particles assembled from solution. The results showed that primary microstructures of the polymer exerted significant influences on the physical properties.

关键词： Cyclopolymerization α,ω-Diene α,ω-Diyne Conjugation system Properties

Research on feed-pulse collaborative control method in micro-electrical discharge machining

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Advances in Manufacturing 2024年第2期12卷 270-287页

作者： Qiang Gao Ya-Ou Zhang Xue-Cheng Xi Yuan-Ding Wang xiao-fei Chen Wan-sheng Zhao School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240People’s Republic of China State Key Laboratory of Mechanical System and Vibration Shanghai200240People’s Republic of China Shanghai Institute of Space Propulsion Shanghai201112People’s Republic of China

Reducing the short-circuit rate and increasing the effective discharge rate are important targets for improving the servo control effect of micro-electrical discharge machining(micro-EDM),as these two indicators are closely related to the machining efficiency and *** this study,a feed-pulse collaborative control(FPCC)method is proposed for micro-EDM based on two dimensions(space and time).In the spatial dimension,a feed control strategy with a discharge holding process is ***,in the time dimension,a forward-looking pulse control strategy is adopted,in which the pulse interval is adjusted based on a sequence analysis of feed commands and discharge *** experiments are carried out to determine the key parameters used in this method,including the discharge holding threshold and pulse interval adjustment value(T_(off_(adj))).The feed smoothness and discharge sufficiency analyses of the experimental results show that compared to the traditional double threshold average voltage method,the FPCC method reduces the number of long-distance retreats by 64%and improves the effective discharge time by 40%.

关键词： Micro-electrical discharge machining(micro-EDM) Electrode feed control Discharge pulse control Machining surface quality

Synthesis, Characterization and Thermal Stability of Novel Carborane- Containing Epoxy Novolacs

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Chinese Journal of Polymer Science 2016年第9期34卷 1103-1116页

作者： guo han zhen yang xiao-xue yang 张孝阿 sheng-ling jiang ya-fei lu Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education College of Materials Science and EngineeringBeijing University of Chemical TechnologyBeijing 100029China

Carborane bisphenol novolacs （3 and 4） were synthesized in the presence of acid catalyst from carborane bisphenols （5 and 6） and formaldehyde. Further epoxidization of carborane bisphenol novolacs with epichlorohydrin gave carborane bisphenol epoxy novolacs （1 and 2）. The molecular weight and epoxy value of obtained resins were determined using the molecular weight of their precursors. The epoxy values of 1 and 2 were 0.48 and 0.52 respectively, higher than the maximum theoretical epoxy value （0.45） of difunctional carborane bisphenol epoxy resins. FTIR and NMR were utilized to characterize 1 and 2. The curing behaviors were also studied by DSC and the optimized curing conditions were obtained. TGA analysis indicated that carborane moiety could shield its adjacent organic structures against initial decomposition. On the other hand, B--H on carborane cage could react with oxygen to form a three-dimensional network linked by B--O--B and B--C bonds, which further blocked the movement of formed radicals and thus the degradation process was inhibited.

关键词： Carborane Epoxy novolacs Thermal stability.

Synthesis and Characterization of Carborane-containing Poly(hydroxy ethers) with Excellent Thermal Stability

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Chinese Journal of Polymer Science 2017年第12期35卷 1463-1473页

作者： Zhen Yang Ning Li xiao-xue Yang 张孝阿 sheng-ling Jiang Ya-fei Lyu Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education College of Materials Science and Engineering Beijing University of Chemical Technology School of Chemical Engineering and Technology Harbin Institute of Technology

o-Carborane-containing poly（hydroxy ethers）（P1, P2 and P3） were synthesized via ＂advancement reaction＂ of o-carborane-containing bisphenol（4） and diglycidyl ether of bisphenols（DGEBA and 1）. FTIR and 1^H^-, 13^C^-, and 11^ B-NMR were utilized to characterize the obtained polymers. TGA test was conducted under nitrogen and air. It is found that the shielding effect of carborane moiety on its adjacent aromatic structures contributes to high initial decomposition temperatures, while oxygen in air has an adverse effect on the initial decomposition temperature. The oxygen can combine with polymer chain to form peroxide and hydroperoxide groups, which are more reactive during the degradation process. Besides, o-carborane-containing poly（hydroxy ethers） have high char yield at elevated temperatures. The boron atom combines with oxygen from the polymer structure or/and from air, thus to form a three-dimensional network linked with B―O―B and B―C bonds, and retain the polymer weight to a large extent.

关键词： Carborane Poly(hydroxy ethers) Thermal stability

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关于数据结构中递归的教学探讨

山东建筑大学学报 2010年第6期25卷 656-661页

作者：牛小飞李盛恩张冬梅宋玲汤晓兵山东建筑大学计算机科学与技术学院山东济南250101

一个直接或间接调用自己的函数被称为递归函数,在程序设计中递归是一个非常重要且强有力的工具。在数据结构这门课程的教学过程中,学生对递归的理解和掌握将为以后学习二叉树、图和排序中的算法奠定坚实的基础。通过实例和图表对递归概... 详细信息

一个直接或间接调用自己的函数被称为递归函数,在程序设计中递归是一个非常重要且强有力的工具。在数据结构这门课程的教学过程中,学生对递归的理解和掌握将为以后学习二叉树、图和排序中的算法奠定坚实的基础。通过实例和图表对递归概念和递归执行过程这两方面进行了分析和探讨。在教学过程中采用该方法后,学生对递归的理解更加深刻,取得了更好的教学效果。

关键词：数据结构递归递归的执行过程

Efficient and Reliable Nanoindentation Simulation by Dislocation Loop Erasing Method

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Acta Mechanica Solida Sinica 2020年第5期33卷 586-599页

作者： fei Shuang Pan xiao Yilong Bai LNM Institute of MechanicsChinese Academy of SciencesBeijing100190China Department of Mechanical and Aerospace Engineering University of FloridaGainesvilleFL32611USA

Nanoindentation is a useful technique to measure material properties at microscopic ***,the intrinsically multiscale nature makes it challenging for large-scale simulations to be carried *** is shown that in molecular statics simulations of nanoindentation,the separated dislocation loops(SDLs)are trapped in simulation box which detrimentally affects the plastic behavior in the plastic zone(PZ);and the long-distance propagation of SDLs consumes much computational cost yet with little contribution to the variation of tip *** tackle the problem,the dislocation loop erasing(DLE)method is proposed in the work to alleviate the influence of artificial boundary conditions on the SDL–PZ interaction and improve simulation *** results indicate that the force–depth curves obtained from simulations with and without DLE are consistent with each other,while the method with DLE yields more reasonable results of microstructural evolution and shows better *** new method provides an alternative approach for large-scale molecular simulation of nanoindentation with reliable results and higher efficiency and also sheds lights on improving existing multiscale methods.

关键词： Nanoindentation Dislocation loops Boundary effects Molecular statics