检索结果-南通市图书馆

VISCOELASTIC BEHAVIOR OF THE NON-HOOKE DEFORMATION BEFORE YIELDING IN UNIAXIAL DRAWING OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE)

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2001年第4期19卷 399-405页

作者： Zhen-hua Yuan De-yan Shen Ren-yuan Qian Polymer Physics laboratory Center for molecular Science, Institute of Chemistry Chinese Academy of sciences, beijing 100080 China Chinese Acad Sci Inst Chem Ctr Mol Sci Polymer Phys Lab Beijing 100080 Peoples R China

Viscoelastic behavior of the non-Hooke deformation of amorphous PET film before yield was investigated in the temperature region 74-80.5 degreesC around the glass transition temperature. The film specimen was drawn to yield point followed by unloading to zero stress, then the residual deformation was held constant; while the subsequent evolution of the stress was recorded. An induction period was found in the course of stress evolution followed by a stress step-increase. The induction period decreases with increasing drawing temperature with an activation energy of 1.10 MJ/mol.K, which is attributed to the time needed for the relaxation of rubbery deformation through cooperative internal rotations. At temperatures lower than 74 degreesC, there is no stress increase or the induction period becomes too long to be observed. Thus the nature of anelasticity in the non-Hooke region before yielding is attributed to stress induced rubbery deformation. The experimental results are interpreted in terms of Perez' theological model of a series connected Hooks spring and a Voigt element consisting of a parallel connected elastic spring and a dashpot.

关键词： pre-yield deformation PET uniaxial drawing non-Hooke deformation viscoelasticity stress induced rubbery deformation

An efficient quantum secret sharing protocol with orthogonal product states

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2007年第3期50卷 331-338页

作者： YANG YuGuang1,2, WEN QiaoYan3 & ZHU FuChen4 1 School of Computer, beijing University of Technology, beijing 100022, China 2 State Key laboratory of Information Security, Graduate University of Chinese Academy of sciences, beijing 100022, China 3 School of Science, beijing University of Posts and Telecommunications, beijing 100876, China 4 national Key laboratory for Modern Communications, Chengdu 610041, China 1. School of Computer Beijing University of Technology Beijing 100022 China 2. State Key laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100022 China 3. School of Science Beijing University of Posts and Telecommunications Beijing 100876 China 4. national Key laboratory for Modern Communications Chengdu 610041 China

An efficient quantum secret sharing protocol with orthogonal product states in the 33 Hilbert space is presented. The particles in the orthogonal product states form two particle sequences. One sequence is sent to Bob and the other is sent to Charlie after rearranging the particle orders. With the help of Alice, Bob and Charlie make the corresponding local measurement to obtain the information of the or- thogonal product states prepared. This protocol has many distinct features such as great capacity and high efficiency.

关键词： quantum secret sharing orthogonal product state orthogonal measurement

A new trust region algorithm for image restoration

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2005年第2期48卷 169-184页

作者： WEN Zaiwen & WANG Yanfei State Key laboratory of Scientific Engineering Computing, Institute of Computational Mathematics and Scientific/Engineering Computing, Academy of Mathematics and System sciences, Chinese Academy of sciences, beijing 100080, China national Key laboratory on Remote Sensing Science, Institute of Remote Sensing Applications, Chinese Academy of sciences, beijing 100101, China 1. State Key laboratory of Scientific Engineering Computing Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and System Sciences Chinese Academy of Sciences 100080 Beijing China 2. national Key laboratory on Remote Sensing Science Institute of Remote Sensing Applications Chinese Academy of Sciences 100101 Beijing China

The image restoration problems play an important role in remote sensing and astronomical image analysis. One common method for the recovery of a true image from corrupted or blurred image is the least squares error (LSE) method. But the LSE method is unstable in practical applications. A popular way to overcome instability is the Tikhonov regularization. However, difficulties will encounter when adjusting the so-called regularization parameter a. Moreover, how to truncate the iteration at appropriate steps is also challenging. In this paper we use the trust region method to deal with the image restoration problem, meanwhile, the trust region subproblem is solved by the truncated Lanczos method and the preconditioned truncated Lanczos method. We also develop a fast algorithm for evaluating the Kronecker matrix-vector product when the matrix is banded. The trust region method is very stable and robust, and it has the nice property of updating the trust region automatically. This releases us from tedious finding the regularization parameters and truncation levels. Some numerical tests on remotely sensed images are given to show that the trust region method is promising.

关键词： trust region algorithm, image restoration, Lanczos method, Kronecker matrix-vector product, preconditioning.

Fuzzy dynamic characteristic model based attitude control of hypersonic vehicle in gliding phase

在线全文

学校读者我要写书评

暂无评论

Science China(Information sciences) 2011年第3期54卷 448-459页

作者： LUO Xiong 1,2 & LI Jiang 1 1 Department of Computer Science and Technology, Key laboratory of Advanced Control of Iron and Steel Process (Ministry of Education), University of Science and Technology beijing, beijing 100083, China 2 national laboratory of Space Intelligent Control, beijing 100190, China 1. Department of Computer Science and Technology Key Laboratory of Advanced Control of Iron and Steel Process (Ministry of Education) University of Science and Technology Beijing Beijing 100083 China2. National Laboratory of Space Intelligent Control Beijing 100190 China

The intelligent autonomous control of hypersonic vehicles has aroused great interest from the field of spacecraft. To solve the problem of longitudinal attitude control of hypersonic vehicle in gliding phase, a new intelligent controller is proposed in this paper. This new controller is based on the fuzzy dynamic characteristic modeling method. The fuzzy logic is introduced into the characteristic modeling by dividing the whole restriction range into several subspaces. Simulations show that this modification greatly improves the performance of the original method. With the same whole restriction range the fuzzy dynamic characteristic modeling decreases the time of convergence, and at the same time makes the attitude angle tracing more precise and robust. Since the sub-model is a characteristic model that has stronger adaptiveness than a fixed local model, the number of fuzzy rules is greatly reduced. Our model sharply reduces the complexity in constructing a fuzzy dynamic model. Finally, simulation results are given to show the effectiveness of the proposed approach in dealing with the attitude control problem of hypersonic vehicle in gliding phase.

关键词： hypersonic vehicle gliding attitude control fuzzy dynamic characteristic modeling

molecular Gas and Dust in the Massive Star Forming Region S 233 IR

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2004年第5期4卷 440-454页

作者： Rui-Qing Mao and Qin Zeng1 Purple Mountain Observatory, Chinese Academy of sciences, Nanjing 210008 2 national Astronomical Observatories, Chinese Academy of sciences, beijing 100012 national Astronomical Observatories CAS NAOC Beijing 100012 China

The massive star forming region S 233 IR is observed in the molecular lines CO J = 2–1, 3–2, NH3 (1,1), (2,2) and the 870 um dust continuum. Four submillimeter continuum sources, labelled SMM 1–4, are revealed in the 870 um dust emission. The main core, SMM1, is found to be associated with a deeply embedded near infrared cluster in the northeast; while the weaker source SMM2 coincides with a more evolved cluster in the southwest. The best fit spectral energy distribution of SMM1 gives an emissivity of β = 1.6, and temperatures of 32 K and 92 K for the cold- and hot-dust components. An SMM1 core mass of 246 M☉, and a total mass of 445 M☉ are estimated from the 870 um dust continuum emission. SMM1 is found to have a temperature gradient decreasing from inside out, indicative of the presence of interior heating sources. The total outflow gas mass as traced by the CO J = 3–2 emission is estimated to be 35 M☉. Low velocity outflows are also found in the NH3 (1,1) emission. The non-thermal dominant NH3 line width as well as the substantial core mass suggest that the SMM1 core is a ``turbulent, massive dense core', in the process of forming a group or a cluster of stars. The much higher star formation efficiency found in the southwest cluster supports the suggestion that this cluster is more evolved than the northeast one. Large near infrared photometric variations found in the source PCS-IR93, a previously found highly polarized nebulosity, indicate an underlying star showing the FU Orionis type of behavior.

关键词： ISM: jets and outflows ISM: molecules ISM: dust, extinction stars:formation ISM: individual

Simulation of aerodynamic performance affected by vortex generators on blunt trailing-edge airfoils

在线全文

学校读者我要写书评

暂无评论

Science China(Technological sciences) 2010年第1期53卷 1-7页

作者： YANG Ke1,2,ZHANG Lei1,3 & XU JianZhong1,2 1 Institute of Engineering Thermophysics,Chinese Academy of sciences,beijing 100190,China 2 Key laboratory of Wind Energy Utilization,Chinese Academy of sciences,beijing 100190,China 3 Graduate School of Chinese Academy of sciences,beijing 100190,China 1. Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China2. Key Laboratory of Wind Energy Utilization Chinese Academy of Sciences Beijing 100190 China3. Graduate School of Chinese Academy of Sciences Beijing 100190 China

An investigation was carried out by numerical simulation on a wind turbine airfoil and a blunt trailing-edge airfoil with and without vortex generators (VGs), and the performance of the airfoils was analyzed. By the simulation of airfoil DU 91-W2-250 it was verified that the numerical method and model were credible. Based on this airfoil, a new one with a blunt trailing edge of 6% chord was blended by symmetrically adding thickness, and its characteristics curves were obtained through computing at key angles of attack. Additionally, the pressure distribution on blended airfoil was analyzed by comparing to the airfoil without blend. The interaction of streamwise vortices induced by VGs with trailing vortex or separation vortex was considered, followed by the uncovery of how VGs can suppress the boundary layer separation.

关键词： vortex generators airfoil blunt trailing-edge

Topography and functional information of plasma membrane

在线全文

学校读者我要写书评

暂无评论

Science China(Life sciences) 2008年第2期51卷 95-103页

作者： SUN DeLan1, CHEN JianMin1, SONG YanMei1, ZHU ChuanFeng2, PAN GeBo2 & WAN LiJun2 1 Key laboratory of Photosynthesis and Environmental molecular Physiology, Institute of Botany, Chinese Academy of sciences, beijing 100093, China 2 Institute of Chemistry, Chinese Academy of sciences, beijing 100080, China 1. Key laboratory of Photosynthesis and Environmental molecular Physiology Institute of Botany Chinese Academy of Sciences Beijing 100093 China 2. Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China

By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12―40 nm for their diameter and 0.7―2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we clas

关键词： atomic force microscope winter wheat protoplast plasma membrane surface membrane protein invaginated pits

Terrestrial transect study on driving mechanism of vegetation changes

在线全文

学校读者我要写书评

暂无评论

Science China Earth sciences 2008年第7期51卷 984-991页

作者： ZHANG YuJin1,2 & ZHOU GuangSheng1 1 State Key laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of sciences, beijing 100093, China 2 Graduate University of Chinese Academy of sciences, beijing 100049, China 1. State Key laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing 100093 China 2. Graduate University of Chinese Academy of sciences Beijing 100049 China

In terms of Chinese climate-vegetation model based on the classification of plant functional types, to- gether with climatic data from 1951 to 1980 and two future climatic scenarios (SRES-A2 and SRES-B2) in China from the highest and the lowest emission scenarios of greenhouse gases, the distribution patterns of vegetation types and their changes along the Northeast China Transect (NECT) and the North-South Transect of Eastern China (NSTEC) were simulated in order to understand the driving mechanisms of vegetation changes under climatic change. The results indicated that the vegetation distribution patterns would change significantly under future climate, and the major factors driving the vegetation changes were water and heat. However, the responses of various vegetation types to the changes in water and heat factors were obviously different. The vegetation changes were more sensi- tive to heat factors than to water factors. Thus, in the future climate warming will significantly affect vegetation distribution patterns.

关键词： driving mechanism vegetation terrestrial transect climatic change plant functional types

Calcitonin gene-related peptide inhibits interleukin-1β-induced interleukin-8 secretion in human type Ⅱ alveolar epithelial cells

在线全文

学校读者我要写书评

暂无评论

Acta Pharmacologica Sinica 2006年第10期27卷 1340-1345页

作者： Wen-jing LI Teng-ke WANG Xian WANG~2 Department of Physiology,School of Basic Medical sciences,Peking University,Key laboratory of molecular Cardiovascular Science,Ministry of Education,beijing 100083,China Department of Physiology School of Basic Medical Sciences Peking University Key Laboratory of Molecular Cardiovascular Science Ministry of Education Beijing 100083 China

Aim:Our previous data have shown that type Ⅱ alveolar epithelial(AEⅡ)cellsexpress neuropeptide calcitonin gene-related peptide(CGRP),and that pro-in-flammatory factor interleukin 1-β(IL-1β)induces CGRP secretion in the A549 hu-man AEⅡ cell *** the present study,we investigated the effect of endogenousand exogenous CGRP on IL-1β-induced chemokine interleukin-8(IL-8)***:We used enzyme-linked immunosorbent assay(ELISA)and RT-PCR todetect IL-8 protein and mRNA levels,respectively,siRNA and the stably trans-fected cell line were used to knock down and overexpress the CGRP gene,respectively,and chemiluminescence assay was used to detect reactive oxygenspecies(ROS)***:CGRP-1 receptor antagonist hCGRP8-37(0.1-1nmol·L-1)greatly amplified IL-1β-induced IL-8 *** inhibition of CGRPexpression by siRNA significantly increased IL-8 secretion upon IL-1β ***,cell clones stably transfected with CGRP showed significantly inhibitedmRNA and protein levels of IL-8 induced by 1L-1β.Conclusion:These data implythat AEⅡ cell-derived CGRP suppress IL-1β-induced IL-8 secretion in an autocrine/paracrine *** investigation showed that CGRP attenuated IL-1β-arousedROS formation,which is an early indication of pro-inflammatory factor signaling.

关键词： type Ⅱ alveolar epithelial cells interleukinl interleukin-8 calcitonin gene-related peptide anti-inflammation lung reactive oxygen species