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The Process of TiB_2-Cu Composite Phase and Structure Formation during Combustion Synthesis

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Journal of Wuhan university of technology(Materials science) 2006年第4期21卷 113-116页

作者：徐强 School of Materials science and Engineering Beijing Insitute of TechnologyBeijing 100081China

The reaction process of combustion synthesis for TiB2 -Cu was investigated in detail using combustion-wave arresting experiment, X-ray diffraction （ XRD ） analysis, SEM analysis and differential thermal analysis （ DTA ）. The XRD analysis results for the different parts of the quenched specimen show that TiCux intermetallic phase firstly forms with the propagation of combustion wave, and then Ti1.87 B50 and Ti3B4.metastable phases come forth due to the diffusion of B atoms and finally the stable TiB2 phase forms because of the continuous diffusion of B atoms. The formation of TiB2 phase is uot completed by one step, but undergoes several transient processes. The process of reaction synthesis for Ti-B-Cu ternary system can be divided into three main stages： melting of Cu and Ti , and the formation of Cu- Ti melt and few TiCux , TiBx intermetallic phases ; large numbers of TiCux intermetallic phases formation and some fine TiB2 particles precipitation ; and the TiB2 particles coarsening and the stable TiB2 and Cu two phases formation in the final product.

关键词： combustion synthesis reaction process TiB2 phase combustion-wave arresting experiment

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Orthogonally linear polarized lasers (I)——principle and devices

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Progress in Natural science:Materials International 2005年第7期15卷 586-595页

作者： ZHANG Shulian and XU Ting (State Key Laboratory of Precision Measurement technology and Instruments, Department of Precision Instruments, tsinghua university, beijing 100084, {4.) State Key Laboratory of Precision Measurement technology and Instruments Department of Precision Instruments Tsinghua University Beijing 100084 China

Two kinds of orthogonally polarized lasers, i. e. Zeeman dual-frequency lasers and four-frequency ring lasers (laser gyros) have been developed since the invention of lasers, in which circularly polarized lights oscillate. This paper summarizes recent progress of the study on orthogonally linear polarized lasers with the standing wave cavity. Firstly, the expression of producing orthogonally linear polarized lights in standing wave cavity, i. e. laser frequency splitting, is given. Almost all the birefringence effects made in laser cavity are used to produce orthogonally linear polarized lights. The effect includes quartz crystal birefringence effect, calcite birefringence effect, stress (photo-elastic) birefringence effect and electro-optical birefringence effect. Secondly, several physical phenomena of orthogonally linear polarized lasers are discovered such as aberrance of frequency splitting curves caused by optical activity of quartz crystal, order-passing of longitudinal modes with frequency splitting and strong modes competition. Finally, because the traditional Zeeman dual frequency laser cannot output frequency difference larger than 3 MHz, the approaches of obtaining larger frequency difference are studied. The sequential results, several kinds of orthogonally polarized lasers, are described, such as birefringence dual frequency lasers outputting a frequency difference from 4. MHz to hundreds of megahertz, birefringence-Zeeman dual frequency lasers outputting a frequency difference from 1 MHz to hundreds of megahertz, the LD pumped YAG birefringence dual frequency laser outputting frequency difference of several gigahertz, and the lasers whose longitudinal mode spacing is c/4. instead of c/2L .

关键词： orthogonally polarized laser dual frequency laser intra-cavity birefringence Zeeman effect photo-elastic birefringence electro-optical birefringence frequency splitting.

A multiple user sharing behaviors based approach for fake file detection in P2P environments

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science china(information sciences) 2010年第11期53卷 2169-2184页

作者： JIANG Jing, LI YongJun, FENG QinYuan, HUANG Peng & DAI YaFei Department of computer science and technology, Peking university, {4. 100871, china 1. Department of computer science and technology Peking University Beijing 100871 China

File pollution is a problem that is threatening security and availability in peer-to-peer environments, and could eventually be fatal to the survival of these systems. Current methods of fake file detection, which are based on trust mechanisms or file characteristics, do not consider the problems such as interference of multiple user sharing behaviors, the difficulty in obtaining large amounts of raw data, and malicious fraud immediately after version publication. This is the first time that differences in the sharing habits of users and particularly long retention time for individual files have been detected, which impact fake file detection. This paper proposes a pollution prevention model based on multiple user sharing behaviors, which reduces interference in multiple user sharing behaviors and malicious fraud immediately after version publication. It designs a low-cost implementation mechanism for use in structured peer-to-peer networks, which automatically collects a large amount of user file-sharing information and alleviates difficulties in obtaining large quantities of raw data. A parameter configuration is also given in this paper. Simulation experiments use realistic system logs and prove that this approach detects fake files accurately and quickly, thus decreasing download times of fake files, effectively guaranteeing almost 100% real file downloads and resisting file pollution.

关键词： peer-to-peer file pollution user sharing behavior

RST transforms resistant image watermarking based on centroid and sector-shaped partition

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science china(information sciences) 2012年第3期55卷 650-662页

作者： ZHAO Yao1,2*, NI RongRong1,2* & ZHU ZhenFeng1,2* 1Institute of information science, beijing Jiaotong university, beijing 10004., china 2beijing Key Laboratory of Advanced information science and Network technology, beijing 10004., china 1. Institute of information science Beijing Jiaotong University Beijing 100044 China2. Beijing Key Laboratory of Advanced Information Science and Network Technology Beijing 100044 China

A novel digital watermarking scheme featuring centroid-based sectoring is proposed in this paper. To get higher robustness against geometric attacks, such as rotation, scaling, and translation (RST), a delicate synchronization mechanism was developed and incorporated into the proposed approach. During the process of watermark embedding, the original image was partitioned into sectors based on the image centroid. Synchronization information as well as the message bits is then embedded into these sectors. With the help of the centroid-based sectoring and synchronization information, the proposed approach is capable of restoring the correct sectoring even if it has experienced severe geometric distortion. This attribute ensures the correct recovery of embedded watermarks and contributes to the robustness of the proposed scheme. A series of experiments have been conducted to verify the feasibility and effectiveness of the proposed approach. Experimental results show that the proposed scheme possesses good robustness against RST attacks and considerable robustness against other common image processing attacks.

关键词： digital watermarking geometrical transform attacks RST transforms

Texture Analysis of Superconducting Films Based on YBCO System

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International Journal of Minerals,Metallurgy and Materials 2000年第2期14卷 107-109页

作者： Nan Chen Weimin Mao(Material science and Engineering School, university of science and Technol0gy beijing, beijing 100083 china)(Department of Materials science and Engineering, university of Petroleum, beijing 102200, china) Material science and Engineering School University of Science and Technology Beijing Beijing 100083 China Department of Materials science and Engineering University of Petroleum Beijing 102200 China

Textures in different layers of superconductors based on YBCO system are analyzed using the methods of pole figure and con-ventional φ scans. It is shown that the φ scanning technology has only 1-dimensional description and could omit some information of3-dimensional orientaion distribution, which will influence the superconductor quality The pole figure method, in contrast, demonstra-tes the orientation distribution 2-dimensionally and gives a comprehensive view of thin filIn textUr, which is a much bettCr method fortexture analysis in superconducting films, in which there is commonly an unique high sharpness textur component.

关键词： superconductor thin film texture YBCO pole figure

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Multi-objective robust control based on fuzzy singularly perturbed models for hypersonic vehicles

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science china(information sciences) 2011年第3期54卷 563-576页

作者： HU YeNan 1 , YUAN Yuan 2 , MIN HaiBo 2,3 & SUN FuChun 1 1 Department of computer science and technology, tsinghua university, {4. 100084, china 2 Department of Automation, Xi’an Research Institute of High-Tech, Xi’an, Shaanxi 710025, china 3 {4. Institute of Astronautical System Engineering, {4. 100076, china 1. Department of computer science and technology Tsinghua University Beijing 100084 China2. Department of Automation Xi’an Research Institute of High-Tech Xi’an Shaanxi 710025 China3. Beijing Institute of Astronautical System Engineering Beijing 100076 China

In this paper, we propose a multi-objective robust controller based on fuzzy singularly perturbed models (FSPM) for the longitudinal motion of an air-breathing hypersonic vehicle. The control objective is to provide velocity and altitude tracking in the presence of the uncertainties and unknown nonlinearities in the model caused by variations in flight conditions. By approximating the multi-time-scale model with FSPM, ill-posed matrix calculations are circumvented. Under this framework, a fuzzy multi-objective robust controller is developed, and the linear matrix inequalities (LMI) condition is derived. Numerical simulation using the longitudinal model of a hypersonic aircraft is provided to demonstrate the effectiveness of the proposed strategy.

关键词： FSPM multi-objective robust control intelligent control hypersonic vehicle

Predicting the behavior of large scale P2P systems by parallel discrete event simulation

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science china(information sciences) 2010年第6期53卷 1109-1121页

作者： ZHENG WeiMin1,YU HongLiang1,SHI GuangYu2 & CHEN Jian2 1Department of computer science and technology,tsinghua university,{4. 2Huawei Technologies Co.,Ltd,Shenzhen 518129,china 1. Department of computer science and technology Tsinghua University Beijing 100084 China2. Huawei Technologies Co. Ltd Shenzhen 518129 China

P2P systems are becoming the dominator of *** systems are typically composed of thousands to millions of physical computers,which make it difficult to predict their behaviors without a large scale distributed system *** paper is an attempt to predict the behavior of large scale P2P systems by building a novel parallel simulator:AegeanSim,which provides parallel discrete event simulation of such systems on high performance server *** abstract the execution of P2P applications with a specific event model,and parallel the simulation of events in a cluster,thus expanding the simulation scale and boosting the simulation process dramatically.A 1-stage synchronization method is proposed to improve the *** event callback interface is designed to implement their application logic easily while keeping the simulator *** use AegeanSim to predict the behavior of a typical P2P system:*** comparing the simulation behavior of BT with that of related BT studies and verifying its efficiency,scalability and accuracy,we make predictions about the behavior of BT system assuming they are assaulted by different man-made system *** reasonable results are found:(1) Tracker isolation can hardly work because of its short attacking time window.(2) Limiting the bandwidth of BT may be an efficient way to control it.

关键词： P2P simulation parallel

Inverse Modeling of Nonlinear Systems and Application

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International Journal of Minerals,Metallurgy and Materials 1999年第4期13卷 302-305页

作者： Jianping Wei Huade Li Datai Yu(information Engineering school, university’ of science and technology’ Beijng, {4. 1 00083, china) information Engineering School University of Science and Technology Beijing Beijing 100083 China

Inverse modeling is discussed based on neural networks. U-D factorization Kalman filter learning algorithm is introduced totrain a feed forward multilayer neural network, which is used as inverse models. A scheme of D... 详细信息

关键词： neural network modeling control DC EAF

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Cloning, sequencing and expression of the coat protein gene of Cocksfoot mottle virus

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Progress in Natural science:Materials International 2007年第2期17卷 222-225页

作者： DONG Zhi, GUO Xiaoyu, ZHANG Hailong and ZHANG Feiyun ( college of Life science, Capital Normal university, beijing 100037, {4. college of Resources Environment and Tourism, Capital Normal university, beijing 100037, {4. beijing Key Laboratory for Resources Environment and Geography information System, beijing 100037, {4.) [a]college of Life science Capital Normal University Beijing China [b]college of Resources Environment and Tourism Capital Normal University Beijing China [c]beijing Key Laboratory for Resources Environment and Geography information System Beijing China

The coat protein (CP) gene of Cocksfoot mottle virus (CfMV) was amplified by RT-PCR and inserted into expression vector pGEX-4.-1, and the resulting plasmid was designated as pGEXCfMV-JANCP. The fusion protein GST-CP was expressed in BL21 (DE3) pLysS after IPTG induction. The results of SDS-PAGE and Western blot analysis showed that the CfMV-CP gene was efficiently expressed in E. coli BL21 (DE3) pLysS through IPTG induction and the 56.0 kD protein was obtained.

关键词： Cocksfoot mottle virus sequence analysis prokaryotic expression.