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Preparation of nanocrystalline BaTiO_3 ceramics

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science china(Technological sciences) 2009年第6期52卷 1730-1734页

作者： DEng XiangYun1,2,LI DeJun1,LI JianBao2,WAng XiaoHui3 & LI LongTu3 1 College of Physics and Electronic information,Tianjin Normal University,Tianjin 300387,china 2 Materials and Chemical Engineering Institute,Key laboratory for Hainan Advantage Resources and Applied technology in Chemical Engineering Material of Ministry of Education,Hainan Provincial Key laboratory of Research on Utilization of Si-Zr-Ti,Hainan University,Haikou 570228,china 3 Department of Materials science and Engineering,tsinghua University,beij.ng 100084,china College of Physics and Electronic information Tianjin Normal University Tianjin 300387 China Materials and Chemical Engineering Institute Key Laboratory for Hainan Advantage Resources and Applied Technology in Chemical Engineering Material of Ministry of Education Hainan Provincial Key Laboratory of Research on Utilization of Si-Zr-Ti Hainan University Haikou 570228 China Department of Materials science and Engineering Tsinghua University Beijing 100084 China

The high-dense nanocrystalline BaTiO3(BT)ceramics with grain size smaller than 100nm have been successfully prepared by the two step sintering and the spark plasma sintering(SPS)*** successive transitions in nanograin BT ceramics from rhombohedral to orthorhombic,tetragonal and cubic transitions,similar to those in coarse BT ceramics,were revealed by in-situ temperature dependent Raman *** multiphase coexistence and the diffused phase transition character were demonstrated in the 8nm nanocrystalline BT ceramics.

关键词： nanocrystalline BaTiO3 ceramics preparation microstructure size effect

Predistortion of high speed optical OFDM signal for aliasing-free receiving in multiple low-bandwidth receiver system

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Chinese Optics Letters 2010年第4期8卷 377-380页

作者：程林闻和郑小平张汉一郭奕理 State Key laboratory on Integrated Optoelectronics/tsinghua national laboratory for information science and technology Department of Electronic EngineeringTsinghua University

A cost-effective method of multi-receiver optical orthogonal frequency-division multiplexing（OOFDM） system is proposed to reduce the requirement for the speed of the receiver and the size of fast Fourier transform（FFT）.The sampling rate of analog-to-digital converters（ADCs） can be reduced to 1/N of the original signal bandwidth in an N-receiver *** by signal predistortion at the transmitter, aliasing-free signal can be retrieved independently and directly at the low speed receivers.A back-to-back experimental result is given for a two-receiver *** effect of the electrical filters added before the ADC is studied and the analysis for filters optimization is given.

关键词： Cost reduction Fast Fourier transforms Orthogonal frequency division multiplexing

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,beij.ng University of technology,beij.ng 100124,china 2 State Key laboratory of Networking and Switching technology,beij.ng University of Posts and Tele-communications,beij.ng 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) ,beij.ng 100049,china 1. College of Computer science and technology Beijing University of Technology Beijing 100124 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 2. State Key laboratory of Networking and Switching technology Beijing University of Posts and Telecommunications Beijing 100876 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

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, beij.ng University of technology, beij.ng 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), beij.ng 100049, china 4 State Key laboratory of Networking and Switching technology, beij.ng University of Posts and Tele-communications, beij.ng 100876, china College of Computer science and technology Beijing University of Technology Beijing 100124 China State Key laboratory of Integrated Services Network Xidian University Xi’an 710071 China State Key laboratory of information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China State Key laboratory of Networking and Switching technology Beijing University of Posts and Telecommunications Beijing 100876 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

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,beij.ng University of technology,beij.ng 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),beij.ng 100049,china 4 State Key laboratory of Networking and Switching technology,beij.ng University of Posts and Tele-communications,beij.ng 100876,china College of Computer science and technology Beijing University of Technology Beijing 100124 China State Key laboratory of Integrated Services Network Xidian University Xi’an 710071 China State Key laboratory of information Security (Graduate University of Chinese Academy of sciences) Beijing 100049 China State Key laboratory of Networking and Switching technology Beijing University of Posts and Telecommunications Beijing 100876 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

Study on the design of anti-sticking structures in MEMS under different forces

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science china Mathematics 2001年第S1期44卷 436-442页

作者： DIng Jianning MEng Yonggang WEN Shizhu national Tribology laboratory, tsinghua University, beij.ng 100084, china Correspondence should be addressed to Ding Jianning tsinghua Univ Natl Tribol Lab Beijing 100084 Peoples R China

Mechanical stability and sticking are the troublesome problems in microfabrication andoperation processes when separations of components in MEMS are in the sub-micrometer *** mechanical effects including quantum mechanical effect should be taken into account forsolving the problems. The influence of capillary forces on sticking of a surface micromachined mi-crocantilever in ambient environment or the rinse liquid and the influence of quantum mechanicaleffect such as the Casimir effect on sticking and stability of a micro membrane strip cavity structurein vacuum were investigated. A factual rough model theory about sticking problem under theCasimir effect was suggested for the first time. The study on the design of anti-sticking structuresunder different forces shows that sticking and stability of microcantilevers and micro membranestrip cavities has something to do with Young’s modulus of materials, surface properties, length ofstructures, thickness of structures and separation between the fixed surface and the deflectingcomponent. But, it is independent of width of structures. The map of the size design of anti-stickingstructures was put forward for the first time. This also provides a way to design a MEMS structurewith high resistance to collapse.

关键词： capillary force casimir force MEMS mechanical stability sticking

Effect of streambed sediment on benthic ecology

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International Journal of Sediment Research 2009年第3期24卷 325-338页

作者： Xuehua DUAN1, Zhao-Yin WAng2, Mengzhen XU3, and Kang ZHAng41 Ph.D., Jiangyin Environmental Monitoring Station, Jiangyin 214431, china, Dept. of Hydraulic Engineering, tsinghua University,2 Prof., State Key laboratory of Hydroscience and Engineering, tsinghua University, beij.ng 100084, china, 3 Doctoral candidate, State Key laboratory of Hydroscience and Engineering, tsinghua University, beij.ng 100084, china,4 Doctoral candidate, State Key laboratory of Hydroscience and Engineering, tsinghua University, beij.ng 100084, china [a] Ph.D. Jiangyin Environmental Monitoring Station Jiangyin 214431 china Dept. of Hydraulic Engineering tsinghua University [b] Prof. State Key laboratory of Hydroscience and Engineering tsinghua University beij.ng 100084 china Tel: 86-10-62773448(O) [c] Doctoral candidate State Key laboratory of Hydroscience and Engineering tsinghua University beij.ng 100084 china [d] Doctoral candidate State Key laboratory of Hydroscience and Engineering tsinghua University beij.ng 100084 china

Benthic macroinvertebrates have been commonly used as indicator species for assessment of aquatic ecology. Streambed sediment, or substrate, plays an important role in habitat conditions for macroinvertebrate communities. Field investigations were done to study the benthic diversity and macroinvertebrate compositions in various stream substrata. Sampling sites with different bed sediment, latitude, and climate were selected along the Yangtze River, the Yellow River, the East River, and the Juma River, in china. The results show that benthic community structures found in different substrata clearly differ, while those found in substrata of similar composition and flow conditions but in different macroclimates are similar. The study, thus, demonstrates that the benthic macroinvertebrate community is mainly affected by substrate composition and flow conditions, but is generally unaffected by latitudinal position and macroclimate. Taxa richness of the macroinvertebrate community was found to be the highest on hydrophyte-covered cobbles, high on moss-covered bedrock, and low on clay beds and cobble beds devoid of plant biomass. Sandy beds are compact and unstable, thus, no benthic macroinvertebrates were found colonizing such substrata. Aquatic insects account for most of the macroinvertebrates collected in these rivers. Different insects dominate in different types of substrata: mainly EPT species (Ephemeroptera, Plecoptera, Trichoptera) in cobble, gravel, and moss-covered bedrock; and Chironomidae larvae in clay beds. The relation between the number of species in the samples and the size of the sampling area fits a power function of the species area. One square meter (1m2) is suggested as the minimum sampling area. A substrate suitability index is proposed by integrating the suitability of sediment, periphyton, and benthic organic materials for macroinvertebrates. The biodiversity of macroinvertebrates increases linearly with the substrate suitability index. Benthic ta

关键词： Streambed sediment Macroinvertebrates Benthic ecology Substrate suitability Biodiversity

Mathematical Delineation of the Thermophysical Process of Electron Beam Welding

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稀有金属材料与工程 2011年第S4期40卷 134-137页

作者： Wang Xuedong1,2,Fu Pengfei 1,Shi Qingyu 2 1national Key laboratory of science and technology on Power Beam Processes,beij.ng Aeronautical Manufacturing Research Institute,beij.ng 100024,china2 Department of Mechanical Engineering,tsinghua University,beij.ng 100084,china beij.ng Aeronaut Mfg Res Inst Natl Key Lab Sci & Technol Power Beam Proc Beijing 100024 Peoples R China tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China

Multiple factors and complicated coupling relationships exist in the weldment during EBW,in order to comprehend this process,a mathematical delineation method based on a main line was presented in this *** on the main line,the complicated coupling relationships existing in EBW were reproduced by mathematical *** calculational results were in well agreement with the experimental *** mathematical delineation was an effective method to comprehend the features and essence of EBW.

关键词： electron beam welding mass transfer identification of phase interface keyhole

Research on the Long Time Swelling Properties of Poly (vinyl alcohol)/Hydroxylapatite Composite Hydrogel

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Journal of Bionic Engineering 2009年第1期6卷 22-28页

作者： De-kun Zhang~(1,3), Da-gang Wang~2, Jun-jie Duan~(1,3), Shi-rong Ge~(2,3)1. School of Materials science and Engineering, china University of Mining and technology, Xuzhou 221116, P. R. china2. School of Mechanical and Electrical Engineering, china University of Mining and technology, Xuzhou 221116, P. R. china3. Biotribology Center, national Key laboratory of Tribology, tsinghua University, beij.ng 100083, P. R. china [a]School of Materials science and Engineering China University of Mining and Technology Xuzhou 221116 P. R. China [b]School of Mechanical and Electrical Engineering China University of Mining and Technology Xuzhou 221116 P. R. China [c]Biotribology Center National Key Laboratory of Tribology Tsinghua University Beijing 100083 P. R. China

Poly(vinyl alcohol)/hydroxylapatite(PVA/HA)composite hydrogel was prepared by repeated freezing and *** water loss properties of the resultant hydrogel were investigated by using optical *** time immersion tests of PVA/HA composite hydrogel were carried out in the diluted calf serum solution to study the change laws of swelling properties with the freezing-thawing cycles and HA *** micro-morphologies of PVA/HA composite hydrogel after long time immersion were observed by means of the high-accuracy 3D *** results show that the swelling process of PVA/HA composite hydrogel is the converse process of its water *** time swelling ratio curves of PVA/HA composite hydrogel in the calf serum solution are manifested as four stages of quick increase,decrease,slow decrease and stable balance,and its equilibrium swelling ratio decreases with the increase of freezing-thawing cycles and HA *** is revealed that the network structure of the composite hydrogel immersed for a long period is significantly improved with the increase of HA content. Perfect network structures of PVA/HA composite hydrogel as well as full and equilibrium tissues after swelling equilibrium are obtained when the HA content is 3% and the number of freezing-thawing cycles is 7.

关键词： poly (vinyl alcohol) hydroxyapatite composite hydrogel swelling property morphology