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Electronic structure and magnetism of Fe-doped SiC nanotubes

science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 1582-1589页

作者： ZHANG WeiHu1,2,3,ZHANG FuChun3,ZHANG ZhiYong4,LU ShuYuan5 & YANG YanNing3 1 xi’an Institute of Optics and Precision Mechanics,Chinese Academy of sciences,xi’an 710068,china 2 Graduate university of Chinese Academy of sciences,Beijing 100049,china 3 College of Physics and Electronic information,Yan’an university,Yan’an 716000,china 4 information science and technology institution,northwest university,xi’an 710127,china 5 Department of Telecommunications,xi’an Institute of Posts and Telecommunications,xi’an 710121,china xi"an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Graduate university of Chinese Academy of sciences College of Physics and Electronic information Yan"an University information science and technology institution Northwest

The electronic structure and magnetic properties of Fe-doped SiC nanotubes are investigated by using the first-principles method based on density functional theory(DFT) in the local spin density approximation(LSDA).The calculation results indicate that the SiC nanotube of Fe substitution for C exhibits antiferromagnetism while ferromagnetism features prominently when Fe substitutes *** is a kind of half-metal magnetic *** formation energy calculation results show that the formation energy of ferromagnetic structure is 3.2 eV lower than that of antiferromagnetic *** atoms are more likely to replace Si ***-orbit coupling induces electron spin polarization in the ground ***,the doping Fe atoms make relaxation towards the outside of the tube to some extent and larger geometric distortion occurs when Fe substitutes C,but the whole geometric structure of SiC nanotubes is not damaged due to the *** is revealed in the calculation of energy band structure and density of states that more dispersed distribution of energy levels is produced near the Fermi *** Fe substitution for Si,obviously there are spin-split and intense p-d hybrid effects by Si 3p electron spins and Fe 3d electron spins localized at the exchanging interactions between magnetic transitional metal(TM) *** electronic density results indicate that system magnetic moments are mainly generated by the unpaired 3d electrons of Fe *** these results show that the transition metal doping SiC nanotube could be a potential route to fabricating the promising magnetic materials.

关键词： SiC nanotube the first-principles doped magnetic properties

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L1/2 regularization

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science china(information sciences) 2010年第6期53卷 1159-1169页

作者： XU ZongBen 1 , ZHANG Hai 1,2 , WANG Yao 1 , CHANG xiangYu 1 & LIANG Yong 3 1 Institute of information and System science, xi'an Jiaotong university, xi'an 710049, china 2 Department of Mathematics, northwest university, xi'an 710069, china 3 university of science and technology, Macau 999078, china Institute of information and System science Xi’an Jiaotong University Xi’an China Department of Mathematics Northwest University Xi’an China university of science and technology Macau China

In this paper we propose an L1 /2 regularizer which has a nonconvex *** L 1/2 regularizer is shown to have many promising properties such as unbiasedness, sparsity and oracle properties.A reweighed iterative algorithm is proposed so that the solution of the L 1/2 regularizer can be solved through transforming it into the solution of a series of L 1 *** solution of the L 1/2 regularizer is more sparse than that of the L 1 regularizer, while solving the L 1/2 regularizer is much simpler than solving the L 0 *** experiments show that the L 1/2 regularizer is very useful and efficient, and can be taken as a representative of the Lp(0 < p < 1) regularizer.

关键词： machine learning variable selection regularizer compressed sensing

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The essential ability of sparse reconstruction of different compressive sensing strategies

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science china(information sciences) 2012年第11期55卷 2582-2589页

作者： ZHANG Hai1,2,LIANG Yong3,GOU HaiLiang1 & XU ZongBen1 1 Institute for information and System science,xi'an Jiaotong university,xi'an 710049,china 2Department of Mathematics,northwest university,xi'an 710069,china 3university of science and technology,Macau 999078,china Institute for information and System science Xi’an Jiaotong University Xi’an China Department of Mathematics Northwest University Xi’an China university of science and technology Macau China

We show the essential ability of sparse signal reconstruction of different compressive sensing strategies,which include the L1 regularization,the L0 regularization(thresholding iteration algorithm and OMP algorithm),the Lq(0 < q ≤ 1) regularizations,the Log regularization and the SCAD *** phase diagram as the basic tool for analysis,we find that(i) the solutions of the L0 regularization using hard thresholding algorithm and OMP algorithm are similar to those of the L1 regularization;(ii) the Lq regularization with the decreasing value of q,the Log regularization and the SCAD regularization can attain sparser solutions than the L1 regularization;(iii) the L1/2 regularization can be taken as a representative of the Lq(0 < q < 1) *** 1/2 < q < 1,the L1/2 regularization always yields the sparsest solutions and when 0 < q < 1/2 the performance of the regularizations takes no significant *** results of this paper provide experimental evidence for our previous work.

关键词： compressive sensing regularization sparsity L1/2 regularization

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Design and analysis of a wideband photonic crystal waveguide with low group-velocity and low dispersion

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science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 481-485页

作者： Lü ShuYuan, ZHAO JianLin & ZHANG Dong Institute of Optical information science and technology, Shanxi Key Laboratory of Optical information technology, School of science, northwestern Polytechnical university, xi’an 710072, china Institute of Optical information science and technology Shanxi Key Laboratory of Optical Information Technology School of Science Northwestern Polytechnical University Xi’an China

The slow light propagation in a line waveguide in the two-dimensional triangular photonic crystal has been numerically studied, based on which a wideband photonic crystal waveguide with low group-velocity and low dispersion is proposed. The numerical simulation analysis shows that it is possible to maximize the group index and minimize the group-velocity dispersion in wide bandwidth by increasing the radius of the basic air hole and changing the position of the first two rows of air holes in photonic crystal waveguides. Such a photonic crystal waveguide exhibits low group velocity and low group-velocity dispersion over a broad wavelength range. A larger group index-bandwidth product is achieved in this type of waveguide structure. The numerically computed results present the normalized bandwidth as 0.32%, 0.48% and 0.642% corresponding to the group index of 85, 58 and 45, respectively.

关键词： photonic crystal waveguide slow light group-velocity group-velocity dispersion group index

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A STUDY OF OSCILLATING FLOWS OVER PROPAGATING RIPPLES:PART Ⅱ. VORTICITY DYNAMICS

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Journal of Hydrodynamics 2000年第1期12卷 8-15页

作者： Lu xi yun Department of Modern Mechanics, university of science and technology of china, Hefei 230026, P.R.china Univ of science and technology of China Hefei China

Vortex shedding for an oscillating flow over ripples is numerically investigated by solving 2 D time dependent incompressible Navier Stokes equations in curvilinear coordinates. The dynamics of vortex structures generated by flow separation is studied in order to understand some phenomena which take place near the bottom and in particular to get insight into the mechanism through which sediment grains are lifted up and maintained in suspension. Based on our calculated results, some important phenomena, such as vortex shedding, vortices pairing, vortices coalescence, vortex interaction with the free shear layer and so on, can be found. The behaviors of energy dissipation in the flow field and of shear stress along the ripple surface are also discussed for studying the dynamics of sediment grains in suspension and to obtain new information on the suspended load over the ripples.

关键词： oscillating flow ripple vorticity dynamics separation flow

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Threshold proxy quantum signature scheme with threshold shared verification

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science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 1079-1088页

作者： YANG YuGuang1,3,4 & WEN QiaoYan2 1 College of Computer science and technology,Beijing university of technology,Beijing 100124,china 2 State Key Laboratory of Networking and Switching technology,Beijing university of Posts and Tele-communications,Beijing 100876,china 3 State Key Laboratory of Integrated Services Network,xidian university,xi’an 710071,china 4 State Key Laboratory of information Security(Graduate university of Chinese Academy of sciences) ,Beijing 100049,china College of Computer science and technology Beijing University of Technology Beijing China State Key Laboratory of Integrated Services Network Xidian University Xi’an China State Key Laboratory of information Security (Graduate university of Chinese Academy of sciences) Beijing China State Key Laboratory of Networking and Switching technology Beijing University of Posts and Telecommunications Beijing China

A threshold proxy quantum signature scheme with threshold shared verification is proposed. An original signer could authorize a group as its proxy signers. Then only t or more of n persons in the proxy group can generate the proxy signature on behalf of the original signer and any t-1 or fewer ones cannot do that. When the proxy signature needs to be verified,any t or more of n persons belonging to the verification group can verify the message and any t-1 or fewer ones cannot verify the validity of the proxy signature.

关键词： quantum signature threshold proxy quantum group signature threshold shared verification

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Quantum threshold group signature

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science china(Physics,Mechanics & Astronomy) 2008年第10期51卷 1505-1514页

作者： YANG YuGuang1,2,3 & WEN QiaoYan4 1 College of Computer science and technology, Beijing university of technology, Beijing 100124, china 2 State Key Laboratory of Integrated Services Network, xidian university, xi’an 710071, china 3 State Key Laboratory of information Security (Graduate university of Chinese Academy of sciences), Beijing 100049, china 4 State Key Laboratory of Networking and Switching technology, Beijing university of Posts and Tele-communications, Beijing 100876, china College of Computer science and technology Beijing University of Technology Beijing China State Key Laboratory of Integrated Services Network Xidian University Xi’an China State Key Laboratory of information Security Graduate University of Chinese Academy of Sciences Beijing China State Key Laboratory of Networking and Switching technology Beijing University of Posts and Telecommunications Beijing China

In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t-1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t-1 or fewer receivers cannot verify the validity of the signature.

关键词： threshold quantum signature trusted party quantum cryptography

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Threshold quantum secret sharing between multi-party and multi-party

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science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1308-1315页

作者： YANG YuGuang1,2,3 & WEN QiaoYan4 1 College of Computer science and technology,Beijing university of technology,Beijing 100124,china 2 State Key Laboratory of Integrated Services Network,xidian university,xi’an 710071,china 3 State Key Laboratory of information Security (Graduate university of Chinese Academy of sciences),Beijing 100049,china 4 State Key Laboratory of Networking and Switching technology,Beijing university of Posts and Tele-communications,Beijing 100876,china College of Computer science and technology Beijing University of Technology Beijing China State Key Laboratory of Integrated Services Network Xidian University Xi’an China State Key Laboratory of information Security (Graduate university of Chinese Academy of sciences) Beijing China State Key Laboratory of Networking and Switching technology Beijing University of Posts and Telecommunications Beijing China

A threshold quantum secret sharing (TQSS) scheme between multi-party and multi-party was proposed using a sequence of single photons,which is useful and efficient when the parties of communication are not all present. We described the process of this TQSS scheme and discussed its security. It was shown that entan-glement is not necessary for quantum secret sharing. Moreover,the theoretic effi-ciency was improved to approach 100% as almost all the instances can be used for generating the private key,and each photon can carry one bit of information. This protocol is feasible with the present-day technique.

关键词： threshold quantum secret sharing quantum cryptography single photon multi-party and multi-party

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Refractive index changes induced by sheet beams with various intensity distributions in LiNbO_(3):Fe crystal

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science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 399-412页

作者： ZHANG Peng1, ZHAO Jianlin1, XU Honglai1, SUN Yidong2, YANG Dexing1 & WANG Meirong1 1. Institute of Optical information science and technology, School of science, northwestern Polytechnical university, xi’an 710072, china 2. School of science, xi’an Jiaotong university, xi’an 710049, china Institute of Optical information science and Technology School of Science Northwestern Polytechnical University Xi’an China School of science Xi’an Jiaotong University Xi’an China

According to the Kukhtarev equations and a simplified model based on the photovoltaic charge carriers transport mechanism, the distributions of the index changes (DICs) in LiNbO3:Fe crystals induced by sheet beams with various intensity profiles are theoretically analyzed. The numerically simulated results coincide with the analytic expressions deduced from the simplified model. The DICs in a LiNbO3:Fe crystal induced by sheet beams with rectangular, Gaussian and square law profiles are measured by using the interferometric method. By employing the analytic expressions, the experimental data points are well fitted. By utilizing the angular spectrum theory and the ray equation, the uniformities of the intensity profiles of the writing beams along the propagation directions and the influences of the self-defocusing effect of the crystal are numerically simulated, respectively. The results show that the experimental results are reliable. The numerically simulated method and the analytic expressions can be both employed to predict the DICs induced by sheet beams with various light intensity profiles. Furthermore, utilizing writing beams with proper intensity profiles, any desired index distributions could be obtained.

关键词： LiNbO3:Fe crystal, light intensity profile, distribution of refractive index changes, sheet beam.

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Parameter-Free Shifted Laplacian Reconstruction for Multiple Kernel Clustering

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 1072-1074页

作者： xi Wu Zhenwen Ren F.Richard Yu the School of National Defence science and technology Southwest University of Science and TechnologyMianyang 621010China the School of National Defence science and technology Southwest University of Science and TechnologyMianyang 621010 the Guangxi Key Laboratory of Machine Vision and Intelligent Control Wuzhou UniversityWuzhou 543002 the Guangdong Laboratory of Artificial Intelligence and Digital Economy(SZ) Shenzhen 518060China

Dear Editor,This letter proposes a parameter-free multiple kernel clustering(MKC)method by using shifted Laplacian *** MKC can effectively cluster nonlinear data,but it faces two main challenges:1)As an unsupervised method,it is up against parameter problems which makes the parameters intractable to tune and is unfeasible in real-life applications;2)Only considers the clustering information,but ignores the interference of noise within Laplacian.

关键词： parameter letter Parameter

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