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Strong Convergence Theorems for Strictly Asymptotically Pseudocontractive Mappings in Hilbert Spaces

Acta Mathematica Sinica,English Series 2011年第7期27卷 1367-1378页

作者： shi sheng ZHANG Department of Mathematics Yibin University Yibin 644007 P. R. China

The purpose of this paper is by using CSQ method to study the strong convergence problem of iterative sequences for a pair of strictly asymptotically pseudocontractive mappings to approximate a common fixed point in a Hilbert space. Under suitable conditions some strong convergence theorems are proved. The results presented in the paper are new which extend and improve some recent results of Acedo and Xu [Iterative methods for strict pseudo-contractions in Hilbert spaces. Nonlinear Anal., 67（7）, 2258-2271 （2007）], Kim and Xu [Strong convergence of modified Mann iterations for asymptoti- cally nonexpansive mappings and semigroups. Nonlinear Anal., 64, 1140-1152 （2006）], Martinez-Yanes and Xu [Strong convergence of the CQ method for fixed point iteration processes. Nonlinear Anal., 64, 2400-2411 （2006）], Nakajo and Takahashi pings and nonexpansive semigroups. J. Math [Strong convergence theorems for nonexpansive map- Anal. Appl., 279, 372-379 （2003）], Marino and Xu [Weak and strong convergence theorems for strict pseudocontractions in Hilbert spaces. J. Math. Anal. Appl., 329（1）, 336-346 （2007）], Osilike et al. [Demiclosedness principle and convergence theorems for k-strictly asymptotically pseudocontractive maps. J. Math. Anal. Appl., 326, 1334-1345 （2007）], Liu [Convergence theorems of the sequence of iterates for asymptotically demicontractive and hemicontractive mappings. Nonlinear Anal., 26（11）, 1835-1842 （1996）], Osilike et al. [Fixed points of demi-contractive mappings in arbitrary Banach spaces. Panamer Math. J., 12（2）, 77-88 （2002）], Gu [The new composite implicit iteration process strictly pseudocontractive mappings. J. Math with errors for common fixed points of a finite family of Anal. Appl., 329, 766-776 （2007）].

关键词： Strictly asymptotically pseudocontractive mapping strictly pseudocontractive mapping of Browder Petryshyn type CSQ methods common fixed point

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Unicyclic Graphs of Minimal Spectral Radius

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Acta Mathematica Sinica,English Series 2013年第2期29卷 281-286页

作者： Ling sheng shi Department of Mathematical Sciences Tsinghua University

It was conjectured by Li and Feng in 1979 that the unicyclic graph formed by a cycle of order g linking to an endvertex of a path of length k minimizes the spectral radius of all unicyclic graphs of order g ＋ k and girth g. In 1987, Cao proved that this conjecture is true for k ≥ g（g - 2）/8 and false for k = 2 and sufficiently large g. In this note, we show that g 〉12 suffices for the counterexample and give more counterexamples with large girth for any integer k 〉 1.

关键词： Extremal graph Li-Feng's conjecture spectral radius unicyclic

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Weak Convergence Theorem for Lipschizian Pseudocontraction Semigroups in Banach Spaces

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Acta Mathematica Sinica,English Series 2010年第2期26卷 337-344页

作者： shi sheng ZHANG Department of Mathematics Yibin University Yibin 644007 Sichuan P. R. China

The purpose of this paper is to study the weak convergence problems of the irnplicity iteration process for Lipschitzian pseudocontraction semigroups in general Banach spaces. The results presented in this paper extend and improve the corresponding results of Zhou [Nonlinear Anal., 68, 2977-2983 （2008）], Chen, et ah [J. Math. Anal. Appl., 314, 701 709 （2006）], Xu and Ori [Numer. Funct. Anal. Optim, 22, 767-773 （2001）] and Osilike [J. Math. Anal. Appl., 294, 73-81 （2004）]. Keywords

关键词： Lipschitzian pseudocontraction semigroup demi-closed principle common fixed point Opial condition strongly pseudocontractive mapping implicit iteration process

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Additive manufacturing of a Co-Cr-W alloy by selective laser melting:In-situ oxidation,precipitation and the corresponding strengthening effects

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Journal of Materials Science & Technology 2022年第30期125卷 171-181页

作者： Kefeng Li zhi Wang Kaikai Song Khashayar Khanlari Xu-sheng Yang Qi shi Xin Liu Xinhua Mao Institute of New Materials Guangdong Academy of SciencesGuangzhou 510650China National Engineering Research Center of Powder Metallurgy of Titanium and Rare Metals Guangzhou 510650China Guangdong Key Laboratory for Advanced Metallic Materials Processing South China University of TechnologyGuangzhou 510641China School of Mechanical Electrical and Information EngineeringShandong UniversityWeihai 264209China Advanced Manufacturing Technology Research Center Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518000China

Additive manufacturing exhibits great potentials for the fabrication of novel materials due to its unique non-equilibrium solidification and heating *** this work,a novel nano-oxides dispersion strengthened Co28 Cr9 W1.5 Si(wt.%)alloy,fabricated by laser powder bed fusion(LPBF),was comprehensively *** the layer-by-layer featured process,in-situ formation of Si rich,amorphous,nano-oxide inclusions was observed,whose formation is ascribed to the high affinity of Si to ***,distinctive body-centered cubic(BCC)Co5 Cr3 Si2 nano-precipitates with an 8-fold symmetry were also confirmed to *** precipitates,rarely reported in previous studied Co-Cr alloys,were found to tightly bond with the in-situ ***,the morphologies,the size distributions as well as the microstructure of the interface between the matrix and the inclusions were investigated in detail and their influence on the tensile deformation was also *** existence of transition boundaries between these inclusions and the matrix strongly blocked the movement of dislocations,thereby increasing the strength of the *** was understood that when the plastic deformation proceeds,the fracture occurs in the vicinity of the oxide inclusions where dislocations accumulate.A quantitative analysis of the strengthening mechanism was also established,in which an additional important contribution to strength(~169 MPa)caused by the effects of in-situ formed oxide inclusions was calculated.

关键词： Co-Cr-W-Si alloy Selective laser melting Oxide inclusion Precipitation Strengthening mechanisms

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XAFS applications in semiconductors

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Nuclear Science and Techniques 2006年第6期17卷 370-388页

作者： WEI shi-Qiang SUN zhi-Hu PAN zhi-Yun ZHANG Xin-Yi YAN Wen-sheng ZHONG Wen-Jie National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei 230029 China Department of Physics Surface Physics Laboratory （National Key laboratory） and Synchrotron Radiation Research Center Fudan University Shanghai 200433. China

X-ray absorption fine structure (XAFS) has experienced a rapid development in the last three decades and has proven to be a powerful structural characterization technique nowadays. In this review, the XAFS basic principles including the theory, the data analysis, and the experiments have been introduced in detail. To show its strength as a local structure probe, the XAFS applications in semiconductors are summarized comprehensively, that is, thin films, quantum wells and dots, dilute magnetic semiconductors, and so on. In addition, certain new XAFS-related techniques, such as in-situ XAFS, micro-XAFS, and time-resolved XAFS are also shown.

关键词： XAFS应用半导体 X射线吸收基本原理

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Orbital angular momentum photonic quantum interface

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Light(Science & Applications) 2016年第1期5卷 723-729页

作者： zhi-Yuan Zhou Yan Li Dong-sheng Ding Wei Zhang Shuai shi Bao-Sen shi Guang-Can Guo Key Laboratory of Quantum Information University of Science and Technology of ChinaHefeiAnhui 230026China Synergetic Innovation Center of Quantum Information&Quantum Physics University of Science and Technology of ChinaHefeiAnhui 230026China

Light-carrying orbital angular momentum(OAM)has great potential in enhancing the information channel capacity in both classical and quantum optical *** distance optical communication requires the wavelengths of light are situated in the low-loss communication windows,but most quantum memories currently being developed for use in a quantum repeater work at different wavelengths,so a quantum interface to bridge the wavelength gap is *** far,such an interface for OAM-carried light has not been realized ***,we report the first experimental realization of a quantum interface for a heralded single photon carrying OAM using a nonlinear crystal in an optical *** spatial structures of input and output photons exhibit strong *** importantly,single-photon coherence is preserved during up-conversion as demonstrated.

关键词： frequency conversion spontaneous parametric down conversion sum frequency generation orbital angular momentum

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High-dimensional entanglement between distant atomic-ensemble memories

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Light(Science & Applications) 2016年第1期5卷 451-457页

作者： Dong-sheng Ding Wei Zhang Shuai shi zhi-Yuan Zhou Yan Li Bao-Sen shi Guang-Can Guo Key Laboratory of Quantum Information University of Science and Technology of ChinaHefeiAnhui 230026China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of ChinaHefeiAnhui 230026China

Entangled quantum states in high-dimensional space show many advantages compared with entangled states in two-dimensional *** former enable quantum communication with higher channel capacity,enable more efficient quantum-information processing and are more feasible for closing the detection loophole in Bell test *** high-dimensional entangled memories is essential for long-distance communication,but its experimental realization is *** experimentally established high-dimensional entanglement in orbital angular momentum space between two atomic ensembles separated by 1 *** reconstructed the density matrix for a three-dimensional entanglement and obtained an entanglement fidelity of(83.9±2.9)%.More importantly,we confirmed the successful preparation of a state entangled in more than three-dimensional space(up to seven-dimensional)using entanglement *** high-dimensional entanglement represents a significant step toward a high-capacity quantum network.

关键词： high-dimensional entanglement orbital angular momentum quantum memory

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A Multiparty Controlled Bidirectional Quantum Secure Direct Communicationand Authentication Protocol Based on EPR Pairs

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Chinese Physics Letters 2013年第6期30卷 9-12页

作者： CHANG Yan ZHANG shi-Bin YAN Li-Li sheng zhi-Wei Department of Network Engineering Chengdu University of Information TechnologyChengdu 610225

A multiparty controlled bidirectional quantum secure direct communication and authentication protocol is proposed based on EPR pair and entanglement *** legitimate identities of communicating parties are encoded to Bell states which act as a detection *** messages are transmitted by using the classical XOR operation,which serves as a *** photon with secret information transmits in the quantum *** with the protocols proposed by Wang et al.[Acta ***.56(2007)673;***.266(2006)732],the protocol in this study implements bidirectional communication and authentication,which defends most attacks including the‘man-in-the-middle’attack efficiently.

关键词： quantum Quantum EPR

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NUMERICAL SIMULATION OF BATOID LOCOMOTION

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Journal of Hydrodynamics 2011年第5期23卷 594-600页

作者： CHEN Wei-shan WU zhi-jun LIU Jun-kao shi sheng-jun ZHOU Yang State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150001 China

The hydrodynamics of batoid swimming motions is investigated using the three-dimensional simulation of a self-propelled body in still water. The kinematics of batoid swimming is characterized by large amplitude undulations of the pectoral fins while the middle part of the body remains straight. The majority of the thrust is generated by pectoral fins. Linear and quadratic amplitude variations are used for the pectoral fins in analyzing the locomotion of the batoid. Navier-Stokes equations are used to solve the unsteady fluid flow. A user defined function and a dynamic mesh method are applied to track the batoid locomotion. The mean swimming velocities of 1.6 BL/s and 1.3 BL/s are achieved, respectively, with thrust coefficients of 0.13 in and 0.095 in the dynamical simulation, where BL/s is the body length per second. The maximum propulsive efficiency 19% is achieved when the frequency of the undulation is 2.2 Hz in both amplitude variations.

关键词： batoid fish undulation pectoral fin dynamical simulation

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Design,fabrication and kinematics of a bio-inspired robotic bat wing

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Science China(Technological Sciences) 2016年第12期59卷 1921-1930页

作者： YIN Dong Fu ZHANG zhi sheng School of Mechanical Engineering Southeast University

The current work is oriented toward the development of a novel biologically inspired bat aerial robot with morphing wings. Based on the flight characteristics data of natural bats(Eptesicus fuscus), a novel four degrees of freedom robotic bat wing was developed to emulate the movements of bat wing. The design, fabrication, programing and wind tunnel experiments of the robot bat wing are described in this paper. Based on this robotic wing, the influence of flap amplitude, wind speed, flight frequency, downstroke ratio and stroke plane angle as well as the contributions of flap, elbow, sweep and wrist motions on the aerodynamic force and mechanical power were studied and analyzed. Results of wind tunnel experiments validated that higher lift would bring greater power consumption, and the flap motion would generate the most force and need more energy expenditure compared with other motions of bat. The experimental results suggest that the flap and fold motions are indispensable to make a robotic bat wing that has a better flight performance. This study provides some implications and a better understanding for the future robotic bat.

关键词： bio-inspiration wing robotic bat flight kinematics wrist motion

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