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Chinese Physics B 2014年第11期23卷 332-338页

作者：苟斗斗杨四刚张磊王小建陈宏伟陈明华谢世钟陈伟罗文勇 tsinghua national laboratory for information science and technology (TNList) Department of Electronic EngineeringTsinghua University FiberHome Telecommunication Technologies CO. Ltd

We demonstrate a cost effective, linearly tunable fiber optical parametric oscillator based on a home-made photonic crystal fiber pumped with a mode-locked ytterbium-doped fiber laser, providing linely tuning ranges from 1018 nm to 1038 nm for the idler wavelength and from 1097 nm to 1117 nm for the signal wavelength by tuning the pump wavelength and the cavity length. In order to obtain the desired fiber with a zero dispersion wavelength around 1060 rim, eight sam- ples of photonic crystal fibers with gradually changed structural parameters are fabricated for the reason that it is difficult to accurately customize the structural dimensions during fabrication. We verify the usability of the fabricated fiber experimen- tally via optical parametric generation and conclude a successful procedure of design, fabirication, and verification. A seed source of home-made all-normal-dispersion mode-locked ytterbium-doped fiber laser with 38.57 ps pulsewidth around the 1064 nm wavelength is used to pump the fiber optical parametric oscillator. The wide picosecond pulse pump laser enables a larger walk-off tolerance between the pump light and the oscillating light as well as a longer photonic crystal fiber of 20 m superior to the femtosecond pulse lasers, resulting in a larger parametric amplification and a lower threshold pump power of 15.8 dBm of the fiber optical parametric oscillator.

关键词： fiber optical parametric oscillator photonic crystal fiber mode-locked fiber laser

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The Effect of p-InGaN layer on ITO based ohmic contacts to p-GaN

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The Effect of p-InGaN layer on ITO based ohmic contacts to p...

Tissue P systems with cell separation: attacking the partition problem

国际纳光电子学研讨会

作者： Yanjun Han~* Zhongtao Liu Yi Luo Hongxia Ma Xianpeng zhang Lai Wang State Key laboratory on Integrated Optoelectronics/tsinghua national laboratory for information science and technology tsinghua University Beijing China 100084.

＜正＞By epitaxy of a thin p-lnGaN layer on p-GaN surface and optimization of InGaN/GaN heterostructures annealing condition,ohmic contact to p-GaN with high transparency was obtained by using electron beam evaporated...

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science China(information sciences) 2011年第2期54卷 293-304页

作者： ZHANG XingYi1, WANG Shuo2, NIU YunYun2 & PAN LinQiang2 1Key lab of Intelligent Computing and Signal Processing of Ministry of Education, School of Computer science and technology, Anhui University, Hefei 230039, China 2Image Processing and Intelligent Control Key laboratory of Education Ministry of China, Department of Control science and Engineering, Huazhong University of science and technology, Wuhan 430074, China 1. Key lab of Intelligent Computing and Signal Processing of Ministry of Education School of Computer Science and Technology Anhui University Hefei 230039 China2. Image Processing and Intelligent Control Key Laboratory of Education Ministry of China Department of Control Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China

Tissue P systems are distributed parallel and non-deterministic computing models in the framework of membrane computing, which are inspired by intercellular communication and cooperation between neurons. Recently, cell separation is introduced into tissue P systems, which enables systems to generate an exponential workspace in a polynomial time. In this work, the computational power of tissue P systems with cell separation is investigated. Specifically, a uniform family of tissue P systems with cell separation is constructed for effciently solving a well-known NP-complete problem, the partition problem.

关键词： membrane computing tissue P system cell separation partition problem

A New hcp Phase Formed in the Ni-Nb System during Ion-beam-assisted Deposition

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Journal of Materials science & technology 2004年第5期20卷 577-579页

作者： Bin ZHAO, Kuiwei GENG, Fei ZENG and Feng PANlaboratory of Advanced Materials, Department of Materials science and Engineering, tsinghua University, Beijing 100084, China lab. of Adv. Mat. Dept. of Mat. Sci. and Eng. Tsinghua Univ. Beijing 100084 China

The Ni80Nb20 films were prepared by ion beam assisted deposition (IBAD) with various Ar+ ion energies. A phase evolution of fcc→amorphous→Ni+Nb→Ni+hcp was observed with the increasing of ion beam energy from 2 keV to 8 keV. When bombarded by Ar+ ions of 8 keV during deposition, a new crystalline phase with hcp structure was obtained, of which the lattice parameters are a=0.286 nm and c=0.483 nm, different from those of the similar A3B-type hcp phase previously reported. The experimental results were discussed in terms of thermodynamics and restricted kinetic conditions in the far-from-equilibrium process of IBAD. The formation of hep phase may also be related to the valence electron effect.

关键词： Hcp phase Ni-Nb Ion beam assisted deposition Thermodynamics Valence electron effect

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VMckpt:lightweight and live virtual machine checkpointing

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science China(information sciences) 2012年第12期55卷 2865-2880页

作者： LIU HaiKun 1,JIN Hai 1,LIAO XiaoFei 1,MA Bo 1 & XU ChengZhong 2 1 Services Computing technology and System lab,Cluster and Grid Computing lab,School of Computer science and technology,Huazhong University of science and technology,Wuhan 430074,China 2 Department of Electrical and Computer Engineering,Wayne State University,Detroit,MI 48202,USA 1. Services Computing technology and System lab Cluster and Grid Computing Lab School of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China2. Department of Electrical and Computer Engineering Wayne State University Detroit MI [48202 USA

Recent advance of virtualization technology provides a new approach to check-point/restart at the virtual machine(VM) *** contrast to traditional process-level checkpointing,checkpointing at the virtualization layer brings up several advantages,such as compatibility,transparence,flexibility and ***,because the virtualization layer has little semantic knowledge about the operation system and the applications running atop,VM-layer checkpointing requires saving the entire operating system state rather than a single *** overhead may render the approach *** reduce the size of VM checkpoint,in this paper we propose a page eviction scheme and an incremental checkpointing mechanism to avoid saving unnecessary VM pages in the *** keep the system online transparently,we propose a live checkpointing mechanism by saving the memory image in a copy-on-write(COW) *** implement the performance optimization mechanisms in a prototype system,called *** results with a group of representative applications show that our page eviction scheme and incremental checkpointing can significantly reduce the checkpoint file size by up to 87% and shorten the total checkpointing/restart time by a factor of up to 71%,in comparison with the Xens default checkpointing *** observed application downtimes due to checkpointing can be reduced to as small as 300 ms.

关键词： checkpoint/restart copy-on-write page eviction virtual machine

Key technologies of light field capture for 3D reconstruction in microscopic scene

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science China(information sciences) 2010年第10期53卷 1917-1930页

作者： WANG Yu, JI XiangYang & DAI QiongHai Broadband Networks & Digital Media lab of Automation Department, tsinghua University, Beijing 100084, China 1. Broadband Networks & Digital Media lab of Automation Department Tsinghua University Beijing 100084 China

Light field capture for 3D reconstruction in microscopic scene is a very promising and useful technology, which can be extensively applied to life sciences, medicine, materials science, etc. This paper summarizes the key technologies in the evolution of microscopes for capturing 3D information, including wavefrontreconstruction, holography, fluorescence, tomography and so on. To give in-depth insights into them, detailed analyses and comparisons are provided. Finally, some future potential work in terms of light field capture and its application are discussed at length.

关键词： light field 3D reconstruction microscopy

Protocol of Steganography in Streaming Media on VOIP Network Based on Variable Length Coding

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Protocol of Steganography in Streaming Media on VOIP Network...

Competent predicate abstraction in model checking

2012 national Conference on information technology and Computer science

作者： Zhen Yang 1,2 1 Department of Electronic Engineering,tsinghua University,Beijing,100084,China 2 national laboratory for information science and technology Huaizhou Tao 1,2 1 Department of Electronic Engineering,tsinghua University,Beijing,100084,China 2 national laboratory for information science and technology Yongfeng Huang 1,2 1 Department of Electronic Engineering,tsinghua University,Beijing,100084,China 2 national laboratory for information science and technology Wanxia Yang 3 3 Engineering Institute of Gansu Agricultural University,Lanzhou,730070,China

Based on the three-layer model theory for steganography communication system,this paper designs a new steganography transmission protocol,to achieve a more effective frame structure,more reliable transmitting *** text message dialogue and file transmission communication based on the proposed method are reliable while the performance is also corresponding *** experimental results has proved theoretical prediction that the proposed protocol is able to achieve reliable and efficient steganography on VoIP network.

关键词： protocol variable length coding steganography VoIP information hiding

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science China(information sciences) 2011年第2期54卷 258-267页

作者： LI Li1,2,3, SONG XiaoYu4, GU Ming2,3 & LUO XiangYu2,3 1Department of Computer science & technology, tsinghua University, Beijing 100084, China 2Key laboratory for information System Security, Ministry of Education of China, Beijing 100084, China 3School of Software, tsinghua University, Beijing 100084, China 4Department of ECE, Portland State University, Portland, Oregon 97207, USA 1. Department of Computer science & technology Tsinghua University Beijing 100084 China2. Key Laboratory for Information System Security Ministry of Education of China Beijing 100084 China3. School of Software Tsinghua University Beijing 100084 China4. Department of ECE Portland State University Portland Oregon 97207 USA

The paper presents a new approach to computing the abstract state and a maximum weight heuristic method for finding the shortest counter-example in verification of imperative programs. The strategy is incorporated in a verification system based on the counterexample-guided abstraction refinement method. The proposed method slashes both the size of the abstract state space and the number of invokes of a decision procedure. A number of benchmarks are employed to evaluate the effectiveness of the approach.

关键词： program model checking predicate abstraction weight heuristic

Effect of Carbon on Dynamic Recrystallization Behavior of Vanadium Microalloy Steels

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Journal of Iron and Steel Research International 2011年第S1期18卷 129-134页

作者： LIU Guo-quan 1,2,ZHAO Hai-tao 1,WU Jin-bin 1,WANG Cheng-yang 1,XU Lei 1,3 (1.School of Materials science and Engineering,University of science and technology Beijing,Beijing 100083,China 2.State Key laboratory for Advanced Metals and Materials,University of science and technology Beijing,Beijing 100083,China 3.Department of Materials science and Engineering,tsinghua University,Beijing 100084,China) Univ Sci & Technol Beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China Univ Sci & Technol Beijing State Key Lab Adv Met & Mat Beijing 100083 Peoples R China tsinghua Univ Dept Mat Sci & Engn Beijing 100084 Peoples R China

The hot working behavior especially dynamic recrystallization of low-carbon and medium-carbon vanadium microalloy steels has been studied by performing isothermally compression tests and Avrami *** Avrami plots of the two experiment steels have been constructed based on flow stress curves following a new approach (Jonas,et *** Mater.,2009,57(2):2748-2756;Wu et al,Acta ***.,2010,46(7):838-843).It is experimentally found that the carbon effect on dynamic recrystallization is opposite to each other in lower and higher strain ranges:Carbon causes a softening effect at low strain rates (0.01,0.1,and 1.0 s-1),and a hardening effect at high strain rates (10.0 and 30.0 s-1).Correspondingly,carbon promotes the dynamic recrystallization at low strain rates and retards the dynamic recrystallization at high strain rates in the experimental *** phenomenon is then tentatively explained based on the possible mechanisms of dynamic process at different strain rates.

关键词： vanadium microalloy steels hot working dynamic recrystallization carbon strain rate Avrami modeling

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