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The Stamping Formability of AZ31 Magnesium Alloy Sheet Improved by Equal-channel Angular Pressing

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Journal of Wuhan university of Technology(Materials science) 2010年第2期25卷 234-237页

作者：刘英 Department of Material science and engineering Jinan University

Equal channel angular pressing （ECAP） processing and annealing were applied to the AZ31 magnesium alloy sheets to evaluate the potential improvement in the mechanical properties and formability. The ECAP experiment was conducted at 300 ℃ in a die having an included angle of 90o between two channels by the BCZ route with the sheets rotated by 90°about the normal axis of plate plane. The tensile tests and conical cup tests were conducted at various temperatures from 2. to 2.0 ℃. The experimental results indicated that improving the working temperatures could lead to the soft in the material and the enhancement of ductility. Comparatively, the ECAPed AZ31 alloy sheets showed the lower yield strength and smaller conical cup value （CCV） than the unECAPed counterpart in the room temperature. The difference in yield strength between them became small in the elevated temperature, but the ECAPed samples still had the smaller CCV value, implying the improved formability. The texture of the AZ31 alloy sheets could be modified by ECAP and the decrease in the yield strength and more uniform deformation realized in the material, so the formability of AZ31 alloy sheets was improved.

关键词： AZ31 magnesium alloy sheets equal-channel angular pressing mechanical properties conical cup value (CCV)

Direct gray-scale extraction of topographic features for vein recognition

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science China(information sciences) 2010年第10期53卷 2062-2074页

作者： KANG WenXiong 1, LI HuaSong 2.& DENG FeiQi 1 1 College of Automation science and engineering,{2. China university of Technology, guangzhou 510640, China 2.school of information engineering, Wuyi university, Jiangmen 52.000, China 1. College of Automation science and engineering South China University of Technology Guangzhou 510640 China2. School of Information Engineering Wuyi University Jiangmen 529000 China

Binarization processing is a key step in most vein pattern recognition, but may create flaws such as leakage of some feature information. In order to overcome this problem, a new approach is explored in this paper which can extract topographic features directly from gray-scale vein images without binarization processing. First, an extreme graph of directional fields (EGDF) is calculated according to neighborhood information of every pixel, and then the intravenous main ridge of the image can be separated step by step from EGDF with the defined constraint template sets. After that, the sub-ridge is extracted from end points of the main ridge in range constraint image with the tracing method of maximal neighboring point. According to contrast experiment the proposed method is better than the traditional processing (performing binarization first and then skeletonization), in that it can overcome the problem that some separate vein lines are extracted incorrectly, and it can avoid extracting two neighboring vein lines as one ridge. As such, the proposed method is an effective way to extract topographic features for vein recognition

关键词： vein recognition feature extraction directional fields

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,{2. 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

Power functions with low uniformity on odd characteristic finite fields

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science China Mathematics 2010年第8期53卷 1931-1940页

作者： ZHA ZhengBang 1,3 & WANG XueLi 2.1 school of Mathematical sciences,Luoyang{2. university,Luoyang 47102.,China 2.school of Mathematical sciences,south China{2. university,guangzhou 510631,China 3 State Key Laboratory of information Security,Graduate university of Chinese Academy of sciences,Beijing 100049,China 1. school of Mathematical sciences Luoyang Normal University Luoyang 471022 China3. State Key Laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China2. School of Mathematical Sciences South China Normal University Guangzhou 510631 China

In this paper,we give some new low differential uniformity of some power functions defined on finite fields with odd *** corollaries of the uniformity,we obtain two families of almost perfect nonlinear functions in GF... 详细信息

关键词： almost perfect nonlinear function differential uniform function finite field

THE REGULARITY OF THE FREE BOUNDARY FOR STRIKE RESET OPTION

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Acta Mathematica Scientia 2010年第5期30卷 1721-1729页

作者：杨舟 school of Mathematical sciences South China Normal University

A strike reset option is an option that allows its holder to reset the strike price to the prevailing underlying asset price at a moment chosen by the holder. The pricing model of the option can be formulated as a parabolic variational inequality and the optimal reset strategy is the free boundary. The smoothness of the free boundary in some cases was showed in our article published in JDE. We would prove its smoothness in the other case in this paper by a generalized comparison principle for the variational inequality.

关键词： strike reset option free boundary variational inequality the comparison principle

Stability of impulsive stochastic functional differential systems in terms of two measures via comparison approach

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science China(information sciences) 2012年第6期55卷 1313-1322页

作者： YAO FengQi 1,2.& DENG FeiQi 1 1 Institute of System engineering,south China{2. of Technology,guangzhou 510640,China 2.school of Electrical engineering and information,Anhui{2. of Technology,Maanshan 2.3032.China 1. Institute of System engineering South China University of Technology Guangzhou 510640 China2. School of Electrical Engineering and Information Anhui University of Technology Maanshan 243032 China

Comparison principles for general impulsive stochastic functional differential systems are *** the comparison principles and the theory of differential inequalities,stability and instability,involving two measures,of impulsive stochastic functional differential systems are *** stability and instability criteria are obtained,and two examples are also given to illustrate our results.

关键词： stochastic systems impulsive functional differential systems comparison principle stability in terms of two measures instability

Theoretical study on homoleptic mononuclear and binuclear ruthenium carbonyls Ru(CO)_n(n=3―5) and Ru_2.CO)_n(n=8,9)

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science China Chemistry 2009年第11期52卷 1938-1944页

作者： PENG Bin1,GU FengLong1,ZHANG XiuHui2.LUO Qiong2.& LI QianShu1,2.1 school of Chemistry and Environment,south China{2. university,guangzhou 510631,China 2.Beijing Institute of Technology,Beijing 100081,China 1. school of Chemistry and Environment South China Normal University Guangzhou 510631 China 2. Beijing Institute of Technology Beijing 100081 China

Homoleptic mononuclear and binuclear ruthenium carbonyls Ru(CO)n(n=3―5) and Ru2.CO)n(n=8,9) have been investigated using density functional *** isomers are *** Ru(CO)5,the lowest-energy structure is the singlet D3h trigonal *** to Os(CO)5,the distorted square pyramid isomer with C2. symmetry lies ～7 kJ·mol-1 higher in *** the unsaturated mononuclear ruthenium carbonyls Ru(CO)4 and Ru(CO)3,a singlet structure with C2. symmetry and a Cs bent Tshaped structure are the lowest-energy structures,*** global minimum for the Ru2.CO)9 is a singly bridged(CO)4Ru(μ-CO)Ru(CO)4 structure.A triply bridged Ru2.CO)6(μ-CO)3 structure analogous to the known Fe2.CO)9 structure is predicted to lie very close in energy to the global *** Ru2.CO)8,the doubly bridged C2.structure is predicted to be the global *** the lowest-energy structures of M2.CO)n(M=Fe,Ru,Os,n=9,8),it is found that both iron and ruthenium are favored to form structures containing more bridging carbonyl groups,while osmium prefers to have structures with less bridging carbonyl *** study of dissociation energy shows that the dissociation of Ru2.CO)9 into the mononuclear fragments Ru(CO)5+Ru(CO)4 is a less energetically demanding process than the dissociation of one carbonyl group from Ru2.CO)9 to give Ru2.CO)8.

关键词： dinuclear ruthenium carbonyls DFT theoretical study

On the new results of global attractive set and positive invariant set of the Lorenz chaotic system and the applications to chaos control and synchronization

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science in China(Series F) 2005年第3期48卷 304-321页

作者： LIAO Xiaoxin 1, 2. 3 , FU Yuli 4 & XIE Shengli 4 1. Department of Control science & Control engineering, Huazhong{2. of science & Technology, Wuhan 430074, China 2. school of Automation, Wuhan{2. of science & Technology, Wuhan 430070, China 3. school of information, Central south{2. of Economy, Politics and Law, Wuhan 430064, China 4. school of Electronics & information engineering, south China{2. of Technology, guangzhou 510640, China Correspondence should be addressed to Liao Xiaoxin (email: xiaoxin_liao@***) 1. Department of Control science & Control engineering Huazhong University of Science & Technology 430074 Wuhan China 2. school of Automation Wuhan University of Science & Technology 430070 Wuhan China 3. school of information Central South University of Economy Politics and Law 430064 Wuhan China 4. school of Electronics & information{2. South China University of Technology 510640 Guangzhou China

Constructing a family of generalized Lyapunov functions, a new method is proposed to obtain new global attractive set and positive invariant set of the Lorenz chaotic system. The method we proposed greatly simplifies the complex proofs of the two famous estimations presented by the Russian scholar Leonov. Our uniform formula can derive a series of the new estimations. Employing the idea of intersection in set theory, we extract a new Leonov formula-like estimation from the family of the estimations. With our method and the new estimation, one can confirm that there are no equilibrium, periodic solutions, almost periodic motions, wandering motions or other chaotic attractors outside the global attractive set. The Lorenz butterfly-like singular attractors are located in the global attractive set only. This result is applied to the chaos control and chaos synchronization. Some feedback control laws are obtained to guarantee that all the trajectories of the Lorenz systems track a periodic solution, or globally stabilize an unstable (or locally stable but not globally asymptotically stable) equilibrium. Further, some new global exponential chaos synchronization results are presented. Our new method and the new results are expected to be applied in real secure communication systems.

关键词： Lorenz chaotic system global attractive set positive invariant set globally exponential tracking globally exponential synchronization.

Twisted Ate pairing on hyperelliptic curves and applications

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science China(information sciences) 2010年第8期53卷 1528-1538页

作者： ZHANG FangGuo 1,2.1 school of information{2. and Technology, Sun Yat-Sen university, guangzhou 5102.5, China 2.Guangdong Key Laboratory of information Security Technology, guangzhou 5102.5, China 1. school of information{2. and Technology Sun Yat-Sen University Guangzhou 510275 China2. Guangdong Key Laboratory of Information Security Technology Guangzhou 510275 China

In this paper we show that the twisted Ate pairing on elliptic curves can be generalized to hyperelliptic curves, and give a series of variations of the hyperelliptic Ate and twisted Ate pairings. Using the hyperelliptic Ate pairing and twisted Ate pairing, we propose a new approach to speeding up the Weil pairing computation. For some hyperelliptic curves with high degree twist, computing Weil pairing by our approach may be faster than Tate pairing, Ate pairing, and all other known pairings.

关键词： Ate pairing Weil pairing hyperelliptic curves pairing-based cryptosystems twisted curves