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A polynomial algorithm for finding (g,f)-colorings orthogonal to stars in bipartite graphs

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Science china Mathematics 2005年第3期48卷 322-332页

作者： LIU Guizhen & DENG Xiaotie department of Mathematics, Shandong university, Jinan 250100, china department of Computer Science, The city university of hong kong, hong kong, china 1. department of Mathematics Shandong University 250100 Jinan China 2. department of Computer Science The City University of Hong Kong Hong Kong China

Let G be a bipartite graph with vertex set V(G) and edge set E(G), and let g and f be two nonnegative integer-valued functions defined on V(G) such that g(x) ≤f(x)for every vertex x of V(G). A(g,f)-coloring of G is a generalized edge-coloring in which each color appears at each vertex x at least g(x) and at most f(x) times. In this paper a polynomial algorithm to find a(g, f)-coloring of a bipartite graph with some constraints using the minimum number of colors is given. Furthermore, we show that the results in this paper are best possible.

关键词： bipartite graph, (g, f)-coloring, (g, f)-factor, orthogonal coloring.

Does investor communication improve corporate social responsibility?A machine learning-based textual analysis

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china Journal of Accounting Research 2024年第3期17卷 25-49页

作者： Siyu Fan Dongmin kong Jie Lu honghai Yu School of Management and Engineering Nanjing UniversityNanjingChina department of Accountancy City University of Hong KongHong KongChina School of Economics Huazhong University of Science and TechnologyWuhanChina

In this study,we take a machine learning-based approach to measure institutional investor attention to corporate social responsibility(CSR)issues when communicating with firms during site *** find that institutional investors can effectively enhance CSR performance through CSR-related communica*** effect remains robust to various checks and is more pronounced for non-state-owned enterprises and firms with lower levels of institutional ownership and in periods following the issuance of Green Investment Guide*** also identify information asymmetry and financing constraints as the two mechanisms underlying this ***,our findings highlight the importance of private interactions between management and institutional investors in promoting CSR.

关键词： Corporate Social Responsibility Institutional Investors Site Visits Textual Analysis

Phase stability in high entropy alloys:Formation of solid-solution phase or amorphous phase

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Progress in Natural Science:Materials International 2011年第6期21卷 433-446页

作者： Sheng GUO,C.T.LIU Center of Advanced Structural Materials,MBE department, city university of hong kong,Kowloon,hong kong,china Center of Advanced Structural Materials MBE Department City University of Hong Kong Kowloon Hong Kong China

The alloy design for equiatomic multi-component alloys was rationalized by statistically analyzing the atomic size difference,mixing enthalpy,mixing entropy,electronegativity,valence electron concentration among constituent elements in solid solutions forming high entropy alloys and amorphous *** solution phases form and only form when the requirements of the atomic size difference,mixing enthalpy and mixing entropy are all *** most significant difference between the solid solution forming high entropy alloys and bulk metallic glasses lies in the atomic size *** rules provide valuable guidance for the future development of high entropy alloys and bulk metallic glasses.

关键词： high entropy alloys amorphous alloys bulk metallic glasses phase stability solid solution

Structural and electronic properties of single-walled carbon nanotubes adsorbed with 1-pyrenebutanoic acid,succinimidyl ester

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Science china Chemistry 2008年第12期51卷 1203-1210页

作者： FAN WenJie & ZHANG RuiQin Centre of Super-Diamond and Advanced Films (COSDAF) and department of Physics and Materials Science, city university of hong kong, hong kong SAR, china Centre of Super-Diamond and Advanced Films (COSDAF) and department of Physics and Materials Science City University of Hong Kong Hong Kong SAR China

The adsorption of a 1-pyrenebutanoic acid, succinimidyl ester (PSE) interacting with metallic armchair (n, n) carbon nanotubes (CNTs) (n= 3-13) was investigated by using a density-functional tight-binding method with an empirical van der Waals force correction. In this study of large systems involving weak interactions, our calculations showed that the pyrene ring of PSE could be spontaneously absorbed onto the CNTs surface through π-π stacking at the physisorption distances. Increasing of the CNTs diameter leads to a higher adsorption energy. After adsorption of PSE on its sidewall, the geometric and electronic structures of CNTs are basically undamaged. CNTs contribute to the main peak of the electron excitation procedure in the UV/vis spectrum, with a slight red shift after adsorption of PSE.

关键词： SWNTs PSE π-π stacking density-functional tight-binding method

Partitioning series-parallel multigraphs into υ*-excluding edge covers

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Science china Mathematics 2006年第8期49卷 1082-1093页

作者： LIU Guizhen, DENG Xiaotie & XU Changqing School of Mathematics and System Science, Shandong university, Jinan 250100, china department of Computer Science, city university of hong kong, Kowloon, hong kong, china department of Applied Mathematics, Hebei university of Technology, Tianjin 300130, china School of Mathematics and System Science Shandong University Jinan 250100 China department of Computer Science City University of Hong Kong Kowloon Hong Kong Hong Kong department of Applied Mathematics Hebei University of Technology Tianjin 300130 China

We prove that, for any given vertexν* in a series-parallel graph G, its edge set can be partitioned into k= min{k′(G) + 1,δ(G)} subsets such that each subset covers all the vertices of G possibly except forν*, whereδ(G) is the minimum degree of G and k′(G) is the edge-connectivity of G. In addition, we show that the results in this paper are best possible and a polynomial time algorithm can be obtained for actually finding such a partition by our proof.

关键词： series-parallel graph, edge-connectivity, edge cover coloring, min-max theorem.

Growth of HT-LiCoO2 thin films on Pt-metalized silicon substrates

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Rare Metals 2008年第3期27卷 266-272页

作者： ZHANG Yao~(a,b) CHUNG Chiyuen~b ZHU Min~a ~a School of Mechanical Engineering,South china university of Technology,Guangzhou 510640,china ~b department of Physics and Materials Science,city university of hong kong,hong kong,china [a]School of Mechanical Engineering South China University of Technology Guangzhou 510640 China [b]Department of Physics Materials Science City University of Hong Kong Hong Kong China

Layered LiCoO2（HT-LiCoO2）films were grown on Pt-metalized silicon（PMS）substrates and polished bulk nickel（PBN）substrates by pulsed laser *** effects of substrate temperature,oxygen pressure,and substrate surface roughness on the microstructure of LiCoO2 films were *** has been found that a higher substrate temperature and a higher oxygen pressure favor the formation of better crystallized and less lithium-deficient HT-LiCoO2 *** HT-LiCoO2 film deposited on PBN substrates consists of large randomly orientated equiaxial grains,whereas on PMS substrate,it is made up of loosely packed highly[001]preferential orientated triangular shaped grains with the average grain size less than 100 *** measurements show that the highly[001]preferentially orientated nanostructured HT-LiCoO2 thin film grown on PMS substrate has good structural stability upon lithium insertion/extraction and can deliver an initial discharge capacity of approximately 45μA·h·cm-2·μm-1with a cycling efficiency of above 99% at the charge/discharge rate of 0.5 C.

关键词： thin film LiCoO2 pulsed laser deposition electrochemical properties thin film growth

Chaos-based encryption for fractal image coding

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Chinese Physics B 2012年第1期21卷 115-126页

作者：袁正雄黄国和 department of Electronic Engineering City University of Hong Kong

A chaos-based cryptosystem for fractal image coding is proposed. The Renyi chaotic map is employed to determine the order of processing the range blocks and to generate the keystream for masking the encoded sequence. Compared with the standard approach of fraetal image coding followed by the Advanced Encryption Standard, our scheme offers a higher sensitivity to both plaintext and ciphertext at a comparable operating efficiency. The keystream generated by the Renyi chaotic map passes the randomness tests set by the United States National Institute of Standards and Technology, and so the proposed scheme is sensitive to the key.

关键词： chaos cryptography joint image compression and encryption fractal image coding

Electrolyte Design for Low‑Temperature Li‑Metal Batteries:Challenges and Prospects

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Nano-Micro Letters 2024年第2期16卷 365-382页

作者： Siyu Sun Kehan Wang Zhanglian hong Mingjia Zhi Kai Zhang Jijian Xu department of Chemistry City University of Hong KongHong Kong 999077People’s Republic of China State Key Laboratory of Silicon Materials School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027People’s Republic of China State Key Laboratory of Advanced Chemical Power Sources Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education)Haihe Laboratory of Sustainable Chemical TransformationsCollaborative Innovation Center of Chemical Science and Engineering(Tianjin)College of ChemistryNankai UniversityTianjin 300071People’s Republic of China department of Chemical and Biomolecular Engineering University of Maryland College ParkCollege ParkMD 20742USA

Electrolyte design holds the greatest opportunity for the development of batteries that are capable of sub-zero temperature *** get the most energy storage out of the battery at low temperatures,improvements in electrolyte chemistry need to be coupled with optimized electrode materials and tailored electrolyte/electrode ***,this review critically outlines electrolytes’limiting factors,including reduced ionic conductivity,large de-solvation energy,sluggish charge transfer,and slow Li-ion transportation across the electrolyte/electrode interphases,which affect the low-temperature performance of Li-metal *** theoretical derivations that explain the explicit influence of temperature on battery performance are presented to deepen *** improvement strategies from the aspects of electrolyte design and electrolyte/electrode interphase engineering are summarized and rigorously *** on future research are proposed to guide the ongoing exploration for better low-temperature Li-metal batteries.

关键词： Solid electrolyte interphase Li metal Low temperature Electrolyte design Batteries

Combined perturbation bounds:Ⅱ.Polar decompositions

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Science china Mathematics 2007年第9期50卷 1339-1346页

作者： Wen LI~(1+) Wei-wei SUN~2 1 School of Mathematical Sciences,South china Normal university,Guangzhou 510631,china 2 department of Mathematics,city university of hong kong,hong kong,china School of Mathematical Sciences South China Normal University Guangzhou China department of Mathematics City University of Hong Kong Hong Kong China

In this paper,we study the perturbation bounds for the polar decomposition A=QH where Q is unitary and H is *** optimal (asymptotic) bounds obtained in previous works for the unitary factor,the Hermitian factor and singular values of A areσ_r^2||ΔQ||_F^2≤||ΔA||_F^2, 1/2||ΔH||_F^2≤||ΔA||_F^2 and ||Δ∑||_F^2≤||ΔA||_F^2,respectively,where∑=diag(σ_1,σ_2,...,σ_r,0,...,0) is the singular value matrix of A andσ_r denotes the smallest nonzero singular *** we present some new combined (asymptotic) perturbation boundsσ_r^2||ΔQ||_F^2+1/2||ΔH||_F^2≤||ΔA||_F^2 andσ_r^2||ΔQ||_F^2+||Δ∑||_F^2≤||ΔA||_F^2 which are optimal for each *** corresponding absolute perturbation bounds are also given.

关键词： polar decomposition perturbation singular value