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Graphs Whose Critical Groups Have Larger Rank

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Acta Mathematica Sinica,English Series 2011年第9期27卷 1663-1670页

作者： Yao Ping hou wai Chee SHIU wai Hong CHAN Departement of Mathematics Hu'nan Normal University Changsha 410081 P. R. China Department of Mathematics Hong Kong Baptist University Kowloon Tong Hong Kong P. R. China

The critical group C（G） of a graph G is a refinement of the number of spanning trees of the graph and is closely connected with the Laplacian matrix. Let r（G） be the minimum number of generators （i.e., the rank） of the group C（G） and β（G） be the number of independent cycles of G. In this paper, some forbidden induced subgraphs axe given for r（G） = n - 3 and all graphs with r（G） = j3（G） = n - 3 are characterized

关键词： Critical group of a graph Laplacian matrix Smith normal form

Effect of radical scavenger on electrical tree in cross-linked polyethylene with large harmonic superimposed DC voltage

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High Voltage 2023年第4期8卷 739-748页

作者： Lewei Zhu Zhonglei Li kai hou Maritime College Tianjin Key Laboratory for Control Theory and Applications in Complicated Industry SystemsTianjin University of TechnologyTianjinChina Key Laboratory of Smart Grid of Ministry of Education School of Electrical and Information EngineeringTianjin UniversityTianjinChina

In this study,three kinds of radical scavenger Chimassorb 944,Tinuvin 622,and Tinuvin 770 are used to suppress the growth of electrical trees in cross-linked polyethylene(XLPE)with transient superimposed voltage under the temperature *** tree morphology,tree length,accumulated damage,and time to breakdown are used to investigate the effect of radical scavenger on the electrical treeing *** is found that under the temperature gradient caused by the temperature rise on the high voltage side,only Tinuvin 622 can always suppress the electrical tree as the temperature gradient *** the temperature gradient caused by the temperature rise on the ground side,the three radical scavengers can all suppress the electrical *** breakdown of electrical tree exhibits the strong DC polarity ***,energy levels of these three radical scavengers are calculated through quantum chemistry,and the results indicate that radical scavengers have greater electron affinity,smaller ionisation energy,and smaller energy gap than *** to the surface potential decay test results at 60℃,it is found that all three radical scavengers can introduce deep *** different performances of radical scavengers under different temperature gradients and voltages are determined by the trap distribution characteristics,the molecular structure and chemical reaction of the additives *** is concluded that Tinuvin 622 has potential for use in high voltage direct current XLPE cable application.

关键词： radical electrical harmonic

Dynamic Crushing Strength Analysis of Auxetic Honeycombs

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Acta Mechanica Solida Sinica 2016年第5期29卷 490-501页

作者： Xiuhui hou Zichen Deng kai Zhang School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical University State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology

The in-plane dynamic crushing behavior of re-entrant honeycomb is analyzed and compared with the conventional hexagon *** deformation modes along two orthogonal directions are examined,where a parametric study of the effect of impact velocity and cell wall aspect ratio is *** analytical formula of the dynamic crushing strength is then deduced based on the periodic collapse mechanism of cell *** with the finite element results validate the effectiveness of the proposed analytical *** results also reveal higher plateau stress of re-entrant honeycomb over conventional hexagon topology,implying better energy absorption *** underlying physical understanding of the results is emphasized,where the auxetic effect（negative Poisson＇s ratio） induced in the re-entrant topology is believed to be responsible for this superior impact resistance.

关键词： honeycomb topology collapse plateau emphasized perfectly directions deduced validate Poisson

Preparation of Laser Cladding Coating Undercooling Cu-based Alloy and Co on Non-equilibrium Solidification Structure

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Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 463-472页

作者：田徐铭 CAO Shichao hou kai hou Xiaopeng WANG Hongfu 张煜 Department of Outpatient Xinzhou People’s HospitalXinzhou 034099China School of Mechanical Engineering North University of ChinaTaiyuan 030051China Department of Neurosurgery Xinzhou People’s HospitalXinzhou 034099China Department of Orthopedics Xinzhou People’s HospitalXinzhou 034099China

The effect of the gradient content of Co element on the solidification process of Cu-based alloy under deep under cooling conditions was *** non-equilibrium solidification structure of the under cooled alloy samples were *** is found that the rapidly solidified alloy has undergone twice grain refinement during the undercooling *** and significance of the maximum undercooling refinement structure of Cu60Ni35Co5 at T=253 K were ***-density defects were observed,such as dislocations,stacking faults networks,and twinning *** standard FCC diffraction pattern represents that it is still a single-phase *** on the metallographic diagram,EBSD and TEM data analysis,it is illustrated that the occurrence of grain refinement under high undercooling is due to stress induced *** addition,the laser cladding technology is used to coat Co-based alloy(Stellite12) coating on 304 stainless steel substrate;the microstructure of the coating cross-section was *** was found that the microstructure of the cross-section is presented as columnar crystals,planar crystals,and disordered growth direction,so that the coating has better hardness and wear *** electrochemical corrosion of the substrate and coating,it can be seen that the Co and Cr elements present in the coating are more likely to form a dense passivation film,which improved the corrosion resistance of the coating.

关键词： non-equilibrium solidification structure undercooling recrystallization laser cladding coating

Progress on High Voltage PEO-based Polymer Solid Electrolytes in Lithium Batteries

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Chemical Research in Chinese Universities 2022年第3期38卷 735-743页

作者： hou Wenhui OU Yu LIU kai Department of Chemical Engineering Tsinghua UniversityBeijing100084P.R.China

Polymer electrolytes have attracted great interest for next-generation lithium-based batteries on account of safety and high energy *** this review,we assess recent progress on the design of poly(ethylene oxide)(PEO)-based solid polymer electrolytes in high voltage lithium batteries and identify possible side reactions between PEO-based electrolytes and existing *** provide an overview of the ways to enhance high voltage resistance of PEO-based *** include components blend,molecular design and interface *** these efforts,we want to present new insights into rational design of PEO-based electrolytes to develop solid-state lithium batteries for advanced performance.

关键词： Poly(ethylene oxide) Lithium battery High voltage Molecular design Interface modification

Improve the Thermal and Mechanical Properties of Poly(L-lactide) by Forming Nanocomposites with Pristine Vermiculite

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Chinese Journal of Polymer Science 2016年第1期34卷 1-12页

作者：叶海木 kai hou Qiong Zhou Department of Materials Science and Engineering Beijing Key Laboratory of Failure Corrosion and Protection of Oil/Gas Facilities China University of Petroleum

Poly（L-lactide）（PLLA）/pristine vermiculite nanocomposites were prepared by melt blending in a twin-screw extruder, and the detailed information of vermiculite dispersion state and effect of vermiculite on thermal and mechanical properties were systematically studied. The results show that the dispersion of vermiculite in the matrix is quite well when the loading content does not exceed 3 wt%. Pristine vermiculite can obviously improve the melt-crystallization temperature during the nonisothermal crystallization. Both crystallization time span and spherulitic size of PLLA decrease with the increasing amount of vermiculite under isothermal crystallization condition by enhancing the primary nucleation of PLLA. And the adding vermiculite can also improve the tensile modulus and Izod impact strength of PLLA. The intrinsic mechanism for the nucleating effect of vermiculite on PLLA is proposed to be the epitaxial crystallization and specific interaction between vermiculite and PLLA.

关键词： Poly(L-lactide) Vermiculite Crystallization behavior Epitaxial crystallization Nucleating agent

Symplectic analysis for regulating wave propagation in a one-dimensional nonlinear graded metamaterial

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Applied Mathematics and Mechanics(English Edition) 2023年第5期44卷 745-758页

作者： Yunping ZHAO Xiuhui hou kai ZHANG Zichen DENG Department of Applied Mathematics Northwestern Polytechnical UniversityXi’an 710072China School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China Ministry of Industry and Information Technology Key Laboratory of Dynamics and Control of Complex SystemsNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China

An analytical method,called the symplectic mathematical method,is proposed to study the wave propagation in a spring-mass chain with gradient arranged local resonators and nonlinear ground *** with the linearized perturbation approach,the symplectic transform matrix for a unit cell of the weakly nonlinear graded metamaterial is derived,which only relies on the state *** results of the dispersion relation obtained with the symplectic mathematical method agree well with those achieved by the Bloch *** is shown that wider and lower frequency bandgaps are formed when the hardening nonlinearity and incident wave intensity ***,the displacement response and transmission performance of nonlinear graded metamaterials with finite length are *** dual tunable effects of nonlinearity and gradation on the wave propagation are explored under different excitation *** small excitation frequencies,the gradient parameter plays a dominant role compared with the *** reason is that the gradient tuning aims at the gradient arrangement of local resonators,which is limited by the critical value of the local resonator *** contrast,for larger excitation frequencies,the hardening nonlinearity is dominant and will contribute to the formation of a new bandgap.

关键词： symplectic mathematical method nonlinear graded metamaterial tunable bandgap

ST-Trader:A Spatial-Temporal Deep Neural Network for Modeling Stock Market Movement

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IEEE/CAA Journal of Automatica Sinica 2021年第5期8卷 1015-1024页

作者： Xiurui hou kai Wang Cheng Zhong Zhi Wei the Department of Computer Science New Jersey Institute of TechnologyNewarkNJ 07102 USA the School of Business Stevens Institute of TechnologyHobokenNJ 07030 USA

Stocks that are fundamentally connected with each other tend to move *** such common trends is believed to benefit stock movement forecasting ***,such signals are not trivial to model because the connections among stocks are not physically presented and need to be estimated from volatile *** by this observation,we propose a framework that incorporates the inter-connection of firms to forecast stock *** effectively utilize a large set of fundamental features,we further design a novel ***,we use variational autoencoder(VAE)to reduce the dimension of stock fundamental information and then cluster stocks into a graph structure(fundamentally clustering).Second,a hybrid model of graph convolutional network and long-short term memory network(GCN-LSTM)with an adjacency graph matrix(learnt from VAE)is proposed for graph-structured stock market *** on minute-level *** market data demonstrate that our model effectively captures both spatial and temporal signals and achieves superior improvement over baseline *** proposed model is promising for other applications in which there is a possible but hidden spatial dependency to improve time-series prediction.

关键词： Graph convolution network long-short term memory network stock market forecasting variational autoencoder(VAE)

Insights on advanced substrates for controllable fabrication of photoanodes toward efficient and stable photoelectrochemical water splitting

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Carbon Energy 2024年第4期6卷 164-221页

作者： Huilin hou Gang Shao Yang Wang wai‐Yeung Wong Weiyou Yang Institute of Micro/Nano Materials and Devices Ningbo University of TechnologyNingboChina School of Materials Science and Engineering Zhengzhou UniversityZhengzhouChina Department of Applied Biology and Chemical Technology and Research Institute for Smart Energy The Hong Kong Polytechnic UniversityHong KongChina

Conversion of solar energy into H_(2) by photoelectrochemical(PEC)water splitting is recognized as an ideal way to address the growing energy crisis and environmental *** a typical PEC cell,the construction of photoanodes is crucial to guarantee the high efficiency and stability of PEC reactions,which fundamentally rely on rationally designed semiconductors(as the active materials)and substrates(as the current collectors).In this review work,we start with a brief introduction of the roles of substrates in the PEC ***,we provide a systematic overview of representative strategies for the controlled fabrication of photoanodes on rationally designed substrates,including conductive glass,metal,sapphire,silicon,silicon carbide,and flexible ***,some prospects concerning the challenges and research directions in this area are proposed.

关键词： hydrogen photoanode photoelectrochemical substrates water splitting