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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 {2. of Precision Measurement Technology and Instruments, Department of Precision Instruments, tsinghua university, beijing 100084, china) state key {2. 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 40 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/4L instead of c/2. .

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

Preparation of MWNTs/Al_2._3 composites and their mechanical and electrical properties

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Science china(Technological Sciences) 2005年第6期48卷 622-631页

作者： FAN Jinpeng1,2. ZHAO Daqing1,2. XU Zening1,2.& WU Minsheng1,2.1. Department of Mechanical Engineering, tsinghua university, beijing 100084,{2. 2. key laboratory for Advanced Manufacturing by Materials Processing Technology, tsinghua university, beijing 100084,{2. 1. Department of Mechanical Engineering Tsinghua University 100084 Beijing China 2. key laboratory for Advanced Manufacturing by Materials Processing Technology Tsinghua University 100084 Beijing China

The mechanical and electrical properties of MWNTs/Al2.3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1/2. which is 80% higher than that of pure Al2.3 obtained in the same conditions. The main toughening mechanism is CNTs’ pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2.t% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1/2. Furthermore, the electrical resistivity is as low as 8.4×10?3 ?·m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

关键词： MWNTs, alumina, composite, fracture toughness, electrical properties.

An integrated turbocharger design approach to improve engine performance

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Science china(Technological Sciences) 2010年第1期53卷 69-74页

作者： ZHANG YangJun1,CHEN Tao1,ZHUGE WeiLin1,ZHANG ShuYong2.& XU JianZhong3 1 state key {2. of automotive safety and energy,tsinghua university,beijing 100084,china 2.National key {2. of Diesel Engine Turbocharging Technology,P.O.B.2.,Datong 037036,china 3 Institute of Engineering Thermophysics,Chinese Academy of Sciences,beijing 100190,china 1. state key {2. of automotive safety and energy Tsinghua University Beijing 100084 China2. National Key Laboratory of Diesel Engine Turbocharging Technology P.O.B. 22 Datong 037036 China3. Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China

Turbocharging technology is today considered as a promising way for internal combustion engine energy saving and CO2.*** design is a major challenge for turbocharged engine performance *** turbocharger designer must draw upon the information of engine operation conditions,and an appropriate link between the engine requirements and design features must be carefully developed to generate the most suitable design *** objective of this research is to develop a turbocharger design approach for better turbocharger matching to an internal combustion *** development of the approach is based on the concept of turbocharger design and interaction links between engine cycle requirements and design parameter values.A turbocharger through flow model is then used to generate the design *** integrated method has been applied with success to a gasoline engine turbocharger assembly.

关键词： turbocharger design internal combustion engine integrated method through flow model

Fusion tracking in color and infrared images using joint sparse representation

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Science china(Information Sciences) 2012年第3期55卷 590-599页

作者： LIU HuaPing1,2.3 & SUN FuChun1,2.3 1Department of Computer Science and Technology, tsinghua university, beijing 100084,{2. 2.3} key laboratory of Intelligent Technology and Systems, beijing 100084,{2. 3tsinghua National laboratory for Information Science and Technology, beijing 100084,{2. 1. Department of Computer Science and Technology Tsinghua University Beijing 100084 China2. State Key Laboratory of Intelligent Technology and Systems Beijing 100084 China3. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

Currently sparse signal reconstruction gains considerable interest and is applied in many fields. In this paper, a similarity induced by joint sparse representation is designed to construct the likelihood function of particle filter tracker so that the color visual spectrum and thermal spectrum images can be fused for object tracking. The proposed fusion scheme performs joint sparse representation calculation on both modalities and the resultant tracking results are fused using min operation on the sparse representation coefficients. In addition, a co-learning approach is proposed to update the reference templates of both modality and enhance the tracking robustness. The proposed fusion scheme outperforms state-of-the-art approaches, and its effectiveness is verified using OTCBVS database.

关键词： joint sparse representation fusion tracking color image infrared image

Effects of fluvial processes and human activities on stream macro-invertebrates

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International Journal of Sediment Research 2011年第4期26卷 416-430页

作者： Xue-hua DUAN,Zhao-Yin WANG,and Meng-zhen XU 1 Ph.D.,state key {2. of Hydroscience and Engineering,tsinghua university,beijing 100084,china Jiangyin Water Conservancy and Farm Machinery Bureau,Jiangyin 2.4431 china, 2.Prof,state key {2. of Hydroscience and Engineering,tsinghua university,beijing 100084,china, 3 Doctoral candidate,state key {2. of Hydroscience and Engineering,tsinghua university,beijing 100084,china, [a] Ph.D. State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China Jiangyin Water Conservancy and Farm Machinery Bureau Jiangyin 214431 China Tel: 86-*** (M) [b] Prof. State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China [c] Doctoral candidate State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China

Benthic macro-invertebrates are vital components of river *** effects of fluvial processes and human activities on the distribution of macro-invertebrates were studied through field investigations and ***-one sampling sites on 31 rivers in china were selected to investigate the structures of macro-invertebrate *** rivers,according to their fluvial conditions,are classified as streams with a stable channel bed,degrading channel bed,aggrading channel bed,and intensive bed load *** structures of macro-invertebrate fauna for the four types of rivers are very *** rivers have a large number of individuals,abundant fauna, and high biodiversity;while the density and taxa richness for degrading rivers are small,and those for aggrading rivers are much less;whereas the ecology of rivers with intensive bed load motion are the *** paper proposes that streambed stability is the primary influential factor shaping the structure of benthic macro-invertebrate *** pollution can obviously result in the decrease of biodiversity,in the simplification of macro-invertebrate structures,and in the distortion of functional feeding group *** a river with high total nitrogen content,the relative abundance of collector-gatherers is high,and that of collector-filterers,scrapers,shredders,and predators are ***,shredders,and predators disappear in severely polluted *** isolation of aquatic habitat results in a distinct decrease of individual numbers and taxa *** result demonstrates that the connectivity of aquatic habitat significantly affects macro-invertebrate assemblages.A practical method to calculate a Habitat Suitability Index(HSI) is proposed,integrating the effects of the primary physical(including biotic and abiotic) and chemical *** biodiversity and taxa richness increase non-linearly with HSI.

关键词： Macro-invertebrate Streambed stability Substratum Isolation Habitat suitability Water pollution

Fuzzy tracking control design for hypersonic vehicles via T-S model

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Science china(Information Sciences) 2011年第3期54卷 521-528页

作者： GAO DaoXiang 1 & SUN ZengQi 2.1 School of Technology, beijing Forestry university, beijing 100083, china 2.state key laboratory of Intelligent Technology and System, Department of Computer Science and Technology, tsinghua university, beijing 100084, china 1. School of Technology Beijing Forestry University Beijing 100083 China2. State Key Laboratory of Intelligent Technology and System Department of Computer Science and Technology Tsinghua University Beijing 100084 China

The main focus of this paper is on designing a T-S fuzzy controller for the hypersonic vehicle. The longitudinal dynamics of the vehicle are studied using time-scale decomposition to reduce the complexity of T-S modeling. The dynamic inversion with PI control technique is applied for the slow dynamics to derive the flight path angle command and throttle setting by taking the pilot altitude and velocity command as its inputs. The T-S fuzzy controller is designed for the fast dynamics to derive the elevator deflection to track the flight path angle command. The discrepancy between the T-S model and real vehicle model is considered by using sliding mode control for the system stability. Simulation results are included to show the effectiveness of the controller.

关键词： fuzzy control T-S model sliding mode control hypersonic vehicle

Negative regulation of TGF-β signaling in development

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Cell Research 2004年第6期14卷 441-449页

作者： Ye Guang CHEN, An Ming MENG The state key {2. of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, tsinghua university, beijing 100084, china Department of Biological Sciences and Biotechnology The State Key Laboratory of Biomembrane and Membrane Biotechnology Tsinghua University Beijing 100084 China

The TGF-β superfamily members have important roles in controlling patterning and tissue formation in both invertebrates and vertebrates. Two types of signal transducers, receptors and Smads, mediate the signaling to regulate expression of their target genes. Despite of the relatively simple signal transduction pathway, many modulators have been found to contribute to a tight regulation of this pathway in a variety of mechanisms. This article reviews the negative regulation of TGF-β signaling with focus on its roles in vertebrate development.

关键词： TGF-β BMP Nodal Activin antagonist development negative regulation.

Contact ratio and deformation of asperity in nano-partia lubrication

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Science china Mathematics 2001年第S1期44卷 78-85页

作者： LUO Jianbin LIU Shan WEN Shizhu state key {2. of Tribology, tsinghua university, beijing 100084, china tsinghua Univ State Key Lab Tribol Beijing 100084 Peoples R China

Partial lubrication or mixed lubrication in the nano-scale is discussed, which is consti-tuted from dry contact, boundary lubrication, thin film lubrication. A dynamic contact ratio has beenused to describe such lubrication, and the relationship between the contact ratio and its influencefactors was investigated. Experimental results indicate that the dynamic contact ratio increaseswith the decrease of film thickness by the exponential function. The decrease of speed and lubri-cant viscosity, and the increase of loads will enlarge the value of the contact ratio. When the polaradditives are added into the basic oil, the contact ratio decreases. In addition, the contact ratio ofthe surfaces with small roughness is larger than that of the surfaces with large roughness at verylow speed. However, the contact ratio of smooth surfaces decreases more quickly with speed thanthat of rough surfaces, and therefore, it will become smaller than that of rough surfaces after speedincreases over a certain degree.

关键词： mixed lubrication nano-tribology thin film lubrication

Electrophysiological research of synapse formation from beginning to maturity

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Chinese Science Bulletin 1998年第1期43卷 55-59页

作者： XIE Zuoping and ZHENG Yufang state key {2. of Biomembrane and Membrane Biotechnique Department of Biological Sciences and Biotechnology, tsinghua university, beijing 100084, china state key {2. of Biomembrane and Membrane Biotechnique Tsinghua University Beijing China Department of Biological Sciences and Biotechnology Tsinghua University Beijing China

The development of synapses is an important question in neurobiology. We employ patchclamp technique to record MEPCs and EPCs of myoballs in Xenopus cell culture. The rate of EPC/MEPC is related with synapses maturation. Accordingly, we define the mature synapses as those whose rate of presynaptic membrane’s EPC to MEPC is more than 8. The process of maturation needs about 2.5 h after neurites contact with myoballs. We divide the development of synapses into three stages: young, developing and mature. The neurotransmitters stack gradually and increase by hundreds of times along with young synapses growing into maturity. So the process of synapses maturation should include presynaptic membrane specialization, postsynaptic membrane specialization and neurotransmitters stack.

关键词： definition of mature synapse α latrotoxin (α LTX) neurotransmitter stack.