摘要：
The microstructure evolution of NiA-2.5Ta-7.5Cr alloy during annealing at different temperatures was investigated.It is found that the microstructure of the as-cast alloy consists of coarse Laves phase Ta(CrNiAI)2 with C14 structure at grain boundaries and Cr-rich particles with sizes in the range of 400-500 nm in the NiAI matrix.The Ta and Cr concentrations in the NiAl are-0.6% and-2.5% (at%),respectively.When the alloy is annealed at the temperature above 1000 ℃,fine rod-like Laves phases with C15 structure begin to precipitate dispersively in the NiAl.After annealing at 1200 ℃ for 2 h,the volume fraction of the particles increases,and in the mean time,the Ta concentration in NiAl matrix reduces to ~0.2at%.As the annealing temperature further increases to 1400 ℃,the Laves phase precipitates dissolve in the NiAl matrix completely.Therefore,the precipitation of Laves phase in NiAI during the annealing in the temperature range of 1000-1300 ℃ may be attributed to the diffusing followed by the supersaturation of Ta in NiAl after the solidification.
作者机构：
[沈连丰; 邓曙光; 李俊超] National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China;[邓曙光] Department of Physics and Telecommunication Engineering, Hunan City University, Yiyang 413000, China
通讯机构：
[Shen, L.] N;National Mobile Communications Research Laboratory, Southeast University, China
作者机构：
[万小军] Department of Physics and Telecommunication Engineering, Hunan City University, Yiyang 413000, China;[林建国; 王锋华; 万小军] Faculty of Material and Photoelectronic Physics, Xiangtan University, Xiangtan 411105, China
通讯机构：
Department of Physics and Telecommunication Engineering, Hunan City University, China
摘要：
BN coated Al2O3 fibre-reinforced NiAl-alloy composites were fabricated by hot pressing at 1 200-1 400 (C, and the interfacial microstructure and chemical stability of BN coated Al2O3 fibre-reinforced NiAl-alloy composites were investigated by scanning electron microscopy (SEM) and analytical transmission electron microscopy (TEM). It was found that the complicated chemical reactions and diffusion processes happened in the interface area between BN-layer and Ni25.8Al9.6Ta8.3 during the hot pressing at 1 200-1 400 (C. A continuous AlN-layer was formed at the interface due to the reaction between NiAl and BN. At the same time, Cr diffused extensively into the BN-layer and reacted with boron to form Cr boride precipitates (Cr5B3). In addition, a few particles of Ta-rich phase were also precipitated in NiAl matrix near the interface.
作者机构：
[Cai Jian-Le; Huang Wei-Li] Hangzhou Normal Univ, Coll Sci, Hangzhou 310018, Zhejiang, Peoples R China.;[Huang Wei-Li] Hunan City Univ, Dept Phys & Telecom Engn, Yiyang 413000, Peoples R China.
通讯机构：
[Cai Jian-Le] H;Hangzhou Normal Univ, Coll Sci, Hangzhou 310018, Zhejiang, Peoples R China.
关键词：
Higher-Order Lagrange Systems;Lie Point Transformation
摘要：
Conformal invariance and conserved quantities for a higher-order Lagrange system by Lie point transformation of groups are studied. The differential equation of motion for the higher-order Lagrange system is introduced. The definition of conformal invariance for the system together with its determining equations and conformal factor are provided. The necessary and sufficient condition that the system's conformal invariance would be Lie symmetry by the infinitesimal one-parameter point transformation group is deduced. The conserved quantity of the system is derived using the structural equation satisfied by the gauge function. An example of a higher-order mechanical system is offered to illustrate the application of the result.
摘要：
Porous Ti35Nb alloy with a porosity of 66% was made by a powder metallurgical method, and then it was treated by a standard treatment for activating the surface of Ti implant materials involving alkali and heat treatment. The alkali and heat treatment causes damages of the struts of the porous Ti35Nb in the form of reaction products layer, grain-pullout and cracks. Consequently, it leads to a significant degradation of the strength of the porous alloy. The effect of the alkali and heat treatment on the strength of the porous alloy was discussed.
作者机构：
[高攀; 周文芳; 柳清菊; 吴晶] Yunnan Key Laboratory of Nanomaterials and Technology, Yunnan University, Kunming 650091, China;[张学军] Department of Physics and Electric Information Engineering, Hunan City University, Yiyang 413000, China
通讯机构：
[Liu, QJ ] ;Yunnan Key Laboratory of Nanomaterials and Technology, Yunnan University, China
关键词：
TiO_2;N+Yb-doped;first-principle
摘要：
Crystal structures, electronic structures and optical properties of nitrogen and ytterbium doping anatase TiO_2 were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on the density functional theory. The calculated results show that the octahedral dipole moments in TiO_2 increase due to the changes in lattice parameters, bond length and charges on atoms, which is very effective for the separation of photoexcited electron-hole pairs and the improvement of the photocatalytic activity of TiO_2. The interband transition between OP_π states and Yb4f states make nitrogen and ytterbium doped TiO_2 manifest greater absorption coefficients in the visible-light region.
作者机构：
[欧阳竞成; 林亚平; 张建明] College of Computer and Communication, Hu'nan University, Changsha 410082, China;[林亚平; 周四望] College of Software, Hu'nan University, Changsha 410082, China;[张建明] Department of Computer Science, Hu'nan City University, Yiyang 413000, China
通讯机构：
College of Computer and Communication, Hu'nan University, China
作者机构：
[黄龙杨; 刘慧; 程恩] Key Laboratory of Underwater Acoustic Communication and Marine Information Technology, Xiamen University, Xiamen 361005, Fujian, China;[李梦醒] Department of Physics and Telecommunications, Hunan City University, Yiyang 413000, Hunan, China
通讯机构：
Key Laboratory of Underwater Acoustic Communication and Marine Information Technology, Xiamen University, China
作者机构：
[刘泽民; 李梦醒] School of Telecommunication Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China;[程恩; 黄龙杨] Laboratory of Underwater Acoustic Communication and Marine Information Technology, Ministry of Education, Fujian Xiamen 361005, China;[李梦醒] Department of Physics and Telecommunication Engineering, Hunan City University, Hunan Yiyang 413000, China
通讯机构：
[Li, M.-X.] S;School of Telecommunication Engineering, Beijing University of Posts and Telecommunications, China
