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Progress in Natural Science:materials International 2011年第5期21卷 368-374页

作者： Zhen WANG,Xue-feng LIU,Jian-xin XIE key laboratory for advanced materials Processing,Ministry of Education, university of Science and technology beijing,beijing 100083,china key laboratory for advanced materials Processing Ministry of Education University of Science and Technology Beijing Beijing 100083 China

Effects of melt temperature and casting speed on microstructure and mechanical properties of Cu-14%Al-3.8%Ni(mass fraction) alloy wires fabricated by continuous unidirectional solidification technology were *** was found that the average size of columnar grain in the alloy decreased and grain boundary turned clear and straight with increasing the casting speed at a given melt *** the melt temperature was up to 1 280℃,theβ1phase gradually transformed into lozenged and lanciformγ’1martensite,as well as parallel-sided plateβ’*** alloy with numerous coarsely dendriticγ2phase has poor mechanical properties due to the difficulty of stress-induced martensitic *** the amount of theγ2phase reduced and the coarse dendriteγ2phase evolved into the fine square particles,the elongation of the alloy increased gradually with a decrease in tensile ***,the plasticity of the alloy could also be improved by increasing the amount and size of martensites,particularly the lanciformγ’*** the alloy was almost composed of coarse lanciformγ’1martensite,the tensile strength and elongation of the alloy could be up to 772 MPa and 18.9%,respectively,and the tensile curve consisted of three transformation platforms.

关键词： shape memory alloy continuous unidirectional solidification columnar grain martensitic transformation

Review of metal matrix composites with high thermal conductivity for thermal management applications

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Progress in Natural Science:materials International 2011年第3期21卷 189-197页

作者： Xuan-hui QU,Lin ZHANG,Mao WU,Shu-bin REN State key laboratory for advanced Metals and materials, beijing key laboratory for Powder Metallurgy and Particulate materials, university of Science and technology beijing,beijing 100083,china State key laboratory for advanced Metals and materials Beijing Key Laboratory for Powder Metallurgy and Particulate Materials University of Science and Technology Beijing Beijing 100083 China

Metal matrix composites with high thermal conductivity and tailorable coefficient of thermal expansion are found widespread applications in electronic package and thermal *** latest advances in manufacturing process,thermal properties and brazing technology of SiC/metal,carbon/metal and diamond/metal composites were *** factors controlling the thermo-physical properties were discussed in *** problems involved in the fabrication and the brazing of these composites were elucidated and the main focus was put on the discussion of the methods to overcome these *** review shows that the combination of pressureless infiltration and powder injection molding offers the benefits to produce near-net shape composites. Improving wettability and optimizing interfacial structure are prerequisites for successful fabrication and further enhancement of thermal properties.A new Ag-Cu-Sn brazing alloy with low melting point is found to be effective to braze Al-matrix composites.

关键词： metal matrix composites electronic packaging thermal conductivity coefficient of thermal expansion brazing

Effect of additive elements on exchange coupling and spin reorientation transition of nanocrystalline single-phase Nd-Fe-B alloy

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Science china(Technological Sciences) 2010年第9期53卷 2323-2327页

作者： BAO XiaoQian,GAO XueXu,ZHU Jie & ZHOU ShouZeng State key laboratory for advanced Metals and materials,university of Science and technology beijing,beijing 100083,china State key laboratory for advanced Metals and materials University of Science and Technology Beijing Beijing China

Nd12.3Fe81.7-xZrxB6.0 (x=0,1.5) and (NdDyTb)12.3(FeZrNbCu)81.7-yCoyB6.0 (y=0,12) ribbons were prepared by melt spinning at 22 m/s and subsequent *** influences of Zr,Dy/Tb and Co substitutions on magnetic properties and spin reorientation transitions of nanophase Nd2Fe14B have been systematically *** with Zr-free sample,the remanence,intrinsic coercivity and maximum energy product for Nd12.3Fe80.2Zr1.5B6.0 ribbon increase by 10.8 %,17.8 % and 60.2 %,*** significant improvement of magnetic properties originates from the finer grains of the sample by introducing Zr,which leads to the stronger exchange coupling between neighboring *** intrinsic coercivity for (DyTb)-substituted ribbon is significantly increased although the remanence is reduced,which could be compensated by the substitution of Co for *** spin reorientation temperature Tsr of nanocrystalline Nd2Fe14B alloys was determined by measuring the ac magnetic *** was found to be lower than that of bulk *** substitutions of Zr,Dy/Tb and Co result in reduction of *** smaller the grain size,the lower the Tsr will *** of spin reorientation on magnetization characteristics of nanophase Nd2Fe14B was discussed.

关键词： nanocrystalline Nd-Fe-B magnet exchange coupling spin reorientation transition magnetic properties

Multiparty simultaneous quantum identity authentication with secret sharing

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Science china(Physics,Mechanics & Astronomy) 2008年第3期51卷 321-327页

作者： YANG YuGuang1,2,WEN QiaoYan3 & ZHANG Xing4,5 1 College of Computer Science and technology,beijing university of technology,beijing 100022,china 2 State key laboratory of Information Security (Graduate university of the Chinese Academy of Sciences),beijing 100049,china 3 School of Science,beijing university of Posts and Telecommunications,beijing 100876,china 4 Institute of Electronic technology,Information Engineering university,Zhengzhou 450004,china 5 Trusted Computing laboratory,beijing university of technology,beijing 100022,china College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Information Security (Graduate university of the Chinese Academy of Sciences) Beijing China School of Science Beijing University of Posts and Telecommunications Beijing China Institute of Electronic technology Information Engineering University Zhengzhou China Trusted Computing laboratory Beijing University of Technology Beijing China

Two multiparty simultaneous quantum identity authentication (MSQIA) protocols based on secret sharing are presented. All the users can be authenticated by a trusted third party (TTP) simultaneously. In the first protocol,the TTP shares a random key K with all the users using quantum secret sharing. The ith share acts as the authentication key of the ith user. When it is necessary to perform MSQIA,the TTP generates a random number R secretly and sends a sequence of single photons encoded with K and R to all the users. According to his share,each user performs the corresponding unitary operations on the single photon sequence sequentially. At last,the TTP can judge whether the impersonator exists. The sec-ond protocol is a modified version with a circular structure. The two protocols can be efficiently used for MSQIA in a network. They are feasible with current technol-ogy.

关键词： quantum identity authentication secret sharing quantum cryptography

Microstructure refinement and magnetic properties enhancement of nanocrystalline Nd_(12.3)Fe_(81.7)B_(6.0) ribbons by addition of Zr

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Science china(Technological Sciences) 2009年第7期52卷 1891-1896页

作者： BAO XiaoQian, QIAO Yi, GAO XueXu, ZHU Jie & ZHOU ShouZeng State key laboratory for advanced Metals and materials, university of Science and technology beijing, beijing 100083, china State key laboratory for advanced Metals and materials University of Science and Technology Beijing Beijing China

Effects of Zr addition and annealing treatment on the formation, microstructure and magnetic properties of Nd12.3Fe81.7?xZrxB6.0 (x=0―3.0) ribbons melt-spun and annealed have been systematically investigated by means of vibrating sample magnetometer (VSM), differential scanning calorimeter (DSC), X-ray diffraction (XRD), and high resolution scanning electron microscopy (HRSEM). Phase analysis reveals that Nd2Fe14B is single-phase material. It has been found that the intrinsic coercivity Hci of the optimally processed Nd12.3Fe81.7?xZrxB6.0 ribbons increases monotonically from 751.7 kA/m for x=0 to 1005.3 kA/m for x=3.0. The remanence polarization Jr and maximum energy product (BH)max increase first with Zr addition, then slightly decrease with further increasing Zr content. Optimum magnetic properties with Jr=1.041 T, Hci=887.5 kA/m and (BH)max=175.2 kJ/m3 have been achieved for the ribbons with x=1.5. The significant improvement of magnetic properties originates from the finer grains of the ribbons by introducing Zr.

关键词： Nd-Fe-B magnets nanocrystalline microstructure magnetic properties

Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

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Science china(Physics,Mechanics & Astronomy) 2009年第7期52卷 987-992页

作者： TAN GuoTai1,2, CHEN ZhengHao3 & ZHANG XiaoZhong4,5 1 key laboratory of Beam technology & materials Modification of the Ministry of Education, Institute of Low Energy Nuclear Physics, beijing Normal university, beijing 100875, china 2 beijing Radiation Center, beijing 100875, china 3 laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, beijing 100080, china 4 key laboratory of advanced materials of the Ministry of Education, Department of materials Science and Engineering, Tsinghua university, beijing 100084, china 5 beijing National Center for Electron Microscopy, Tsinghua university, beijing 100084, china key laboratory of Beam technology & materials Modification of the Ministry of Education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing China beijing Radiation Center Beijing China laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing China key laboratory of advanced materials of the Ministry of Education Department of Materials Science and Engineering Tsinghua University Beijing China beijing National Center for Electron Microscopy Tsinghua University Beijing China

The LaMn1-xTexO3+δ (x=0.1, 0.2, 0.3) were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te4+, and Mn3+ ions are partly converted into Mn2+ and Mn4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn2+, Mn3+ and Mn4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn3+ is much larger or less than the sum of Mn2+ and Mn4+; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn3+ is close to the sum of Mn2+ and Mn4+. These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.

关键词： colossal magnetoresistance La-Te-Mn-O magnetotransport

Thermodynamic properties and phase stability of nanocrystalline metals

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Rare Metals 2006年第5期25卷 582-586页

作者： SONG Xiaoyan LI Lingmei ZHANG Jiuxing College of materials Science and Engineering Key Lab of Advanced Functional Materials Miniswy of Education Beijing University of TechnologyBeijing 100022 China

The fundamental thermodynamic functions of enthalpy, entropy, and Gibbs free energy, as functions of the excess free volume at interfaces, temperature, and grain size, have been derived for single-phase metal nanocrystals. The model was applied to predict the thermal features of nano-grain boundaries and the characteristics of phase transformation in nanocrystalline metals, such as the transformation temperature and the critical grain size for phase transformation at a given temperature. The model predictions have been verified by experimental studies on the β-Co ←→α-Co phase transformation in nanocrystalline Co prepared by ball milling.

关键词： thermodynamics phase transformation metal nanocrystals nano-scale effect

Quasi-secure quantum dialogue using single photons

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Science china(Physics,Mechanics & Astronomy) 2007年第5期50卷 558-562页

作者： YANG YuGuang1,2 & WEN QiaoYan31 College of Computer Science and technology, beijing university of technology, beijing 100022, china 2 State key laboratory of Information Security, Graduate university of the Chinese Academy of Sciences, beijing 100049, china 3 School of Science, beijing university of Posts and Telecommunications, beijing 100876, china College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Information Security Graduate University of the Chinese Academy of Sciences Beijing China School of Science Beijing University of Posts and Telecommunications Beijing China

A quasi-secure quantum dialogue protocol using single photons was proposed. Different from the previous entanglement-based protocols, the present protocol uses batches of single photons which run back and forth between the two parties. A round run for each photon makes the two parties each obtain a classical bit of information. So the efficiency of information transmission can be increased. The present scheme is practical and well within the present-day technology.

关键词： quantum dialogue, single photon, quantum secure direct communication

Characterization of γ′ precipitates in a nickel base superalloy quenching from aging temperature at different rates

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Rare Metals 2010年第2期29卷 204-208页

作者： LI Hongyu, SONG Xiping, WANG Yanli, and CHEN Guoliang State key Lab for advanced Metals and materials, university of Science and technology beijing, beijing 100083, china State key Lab for advanced Metals and materials University of Science and Technology Beijing Beijing China

The characteristics of γ′ precipitates in a superalloy quenched from 1050°C at different rates were investigated using field emission scanning electron microscope（FESEM）.When quenched from 1050°C, the size of primary aging γ′ precipitates has a small increase in the specimens that experienced iced-brine-quenching, oil-quenching, and air-cooling-quenching conditions and a drastic increase in the specimen that experienced a furnace-cooling-quenching *** cooling γ′ precipitates have unimodal distributions after quenching at the air-cooling rate and bimodal distributions after quenching at the furnace-cooling rate, but there are not these distributions in the specimens that experienced iced-brine-quenching and oil-quenching *** aging at 760°C, the size of primary aging γ′ precipitates appears unaffected in the specimens that experienced iced-brine-quenching, oil-quenching, and air-cooling-quenching ***, it has a drastic increase in the specimen that experienced a furnace-cooling-quenching condition, and it is interesting that the bigger cooling γ′ precipitates have a coalescence and octodendritic *** microhardness study indicates that the hardness has no variation in the specimens that experienced iced-brine-quenching, oil-quenching, and air-cooling-quenching conditions and has a drastic decrease in the specimens that experienced a furnace-cooling-quenching condition and obtains the minimum microhardness value 390.8 HV.

关键词： superalloys precipitates quenching rate microhardness

Threshold quantum secure direct communication without entanglement

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Science china(Physics,Mechanics & Astronomy) 2008年第2期51卷 176-183页

作者： YANG YuGuang1,3 & WEN QiaoYan2 1 College of Computer Science and technology, beijing university of technology, beijing 100022, china 2 School of Science, beijing university of Posts and Telecommunications, beijing 100876, china 3 State key laboratory of Information Security (Graduate School of Chinese Academy of Sciences), beijing 100049, china College of Computer Science and technology Beijing University of Technology Beijing China State key laboratory of Information Security (Graduate School of Chinese Academy of Sciences) Beijing China School of Science Beijing University of Posts and Telecommunications Beijing China

For the first time, a threshold quantum secure direct communication (TQSDC) scheme is presented. Similar to the classical Shamir's secret sharing scheme, the sender makes n shares, S1, …, Sn of secret key K and each receiver keeps a share secretly. If the sender wants to send a secret message M to the receivers, he en-codes the information of K and M on a single photon sequence and sends it to one of the receivers. According to the secret shares, the t receivers sequentially per-form the corresponding unitary operations on the single photon sequence and ob-tain the secret message M. The shared shares may be reusable if it can be judged that there is no eavesdropper in line. We discuss that our protocol is feasible with current technology.

关键词： quantum secure direct communication threshold secure direct communication quantum secret sharing