检索结果-南通市图书馆

An Explicit Function Expression for dc Bias and Temperature Dependence of Magnetoresistances in Magnetic Tunnel Junctions

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2002年第6期18卷 497-501页

作者： Xiufeng HANstate key laboratory of Magnetism, institute of Physics and Center of Condensed Matter Physics, chinese academy of sciences, beijing 100080, china chinese Acad Sci Inst Phys State Key Lab Magnetism Beijing 100080 Peoples R China chinese Acad Sci Ctr Condensed Matter Phys Beijing 100080 Peoples R China

An explicit function expression for the bias voltage or/and temperature dependences of tunnel magnetoresistance ratio and resistances were obtained with a unique set of intrinsic parameters. Two of these intrinsic parameters are the Curie temperature TC and the density of state (DOS) for itinerant majority and minority electrons ξ(ρM/ρm), which are the eigen parameters of ferromagnetic electrodes. Others are the spin-dependent matrix-element ratio (i.e., |Td|2/|TJ|2 ) and the anisotropic-wavelength-cutoff energy ECγ of spin-wave spectrum in magnetic tunnel junction (MTJ), which are the structure parameters of an MTJ. These intrinsic parameters can be predetermined using the experimental measurement or, in principle, using the first-principle calculation method for an MTJ with the three key layers of FM/I/FM. Furthermore, a series of experimental data for an MTJ, for example, a spin-valve-type MTJ of Ta (5 nm)/Ni79Fe21(25 nm)/lr22Mn78(12 nm)/Co75Fe25(4 nm)/AI(0.8 nm)-oxide/Co75Fe25(4 nm)/Ni79Fe21(20 nm)/Ta (5 nm) in this work, can be self-consistently evaluated and explained using such concise explicit function formulations.

关键词： Magnetic tunnel junction TMR Spin-electron transport Magnon excitation Spin-polarization Magnetotransport

Spectroscopic evidence for triplet excitation energy transfer among carotenoids in the LH2 complex from photosynthetic bacterium Rhodopseudomonas palustris

在线全文

学校读者我要写书评

暂无评论

Science china Chemistry 2004年第1期47卷 80-90页

作者： FENG Juan, WANG Qian, ZHANG Xujia, HUANG Youguo, Al Xicheng, ZHANG Xingkang & ZHANG Jianpingstate key laboratory for Structural Chemistry of Unstable and Stable Species, institute of Chemistry, chinese academy of sciences, beijing 100080, china National laboratory of Biomacromolecules, institute of Biophysics, chinese academy of sciences, beijing 100101, china state key laboratory for Structural Chemistry of Unstable and Stable Species institute of Chemistry Chinese Academy of Sciences Beijing China National laboratory of Biomacromolecules institute of Biophysics Chinese Academy of Sciences Beijing China

The LH2 complex from Rhodopsudomonas (Rps.) palustris is unique in the heterogeneous carotenoid compositions. The dynamics of triplet excited state Carotenoids (3Car* has been investigated by means of sub-microsecond time-resolved absorption spectroscopy both at physiological temperature (295 K) and at cryogenic temperature (77K). Broad and asymmetric T n ←T 1 transient absorption was observed at room temperature following the photo-excitation of Car at 532 nm, which suggests the contribution from various carotenoid compositions having different numbers of conjugated C=C double bonds (Nc=c). The triplet absorption bands of different carotenoids, which superimposed at room temperature, could be clearly distinguished upon decreasing the temperature down to 77 K. At room temperature the shorter-wavelength side of the main Tn04T1 absorption band decayed rapidly to reach a spectral equilibration with a characteristic time constant of ∽1 μs, the same spectral dynamics, however, was not observed at 77 K. The aforementioned spectral dynamics can be explained in terms of the triplet-excitation transfer among heterogeneous carotenoid compositions. Global spectral analysis was applied to the time-resolved spectra at room temperature, which revealed two spectral components peaked at 545 and 565 nm, and assignable to the Tn04 T1 absorption of Cars with Nc=c=11 and Nc=c=13, respectively. Surprisingly, the decay time constant of a shorter-conjugated Car, i.e. 0.72 ?s (aerobic) and 1.36 ?s (anaerobic), is smaller than that of a longer-conjugated Car, i.e. 2.12 us (aerobic) and 3.75 ?s (anaerobic), which is contradictory to the general rule of carotenoids and relative polyenes. The results are explained in terms of triplet-excitation transfer among different types of Cars. It is postulated that two Cars with different conjugation lengths coexist in an α, β-subunit in the LH2 complex.

关键词： purple photosynthetic bacteria, carotenoid, excited-state, time-resolved spectroscopy.

Improved multi-pass fast correlation attacks with applications

在线全文

学校读者我要写书评

暂无评论

Science china(Information sciences) 2011年第8期54卷 1635-1644页

作者： ZHANG Bin & FENG DengGuo state key laboratory of Information Security,institute of Software,chinese academy of sciences,beijing 100190,china state key laboratory of Information Security Institute of Software Chinese Academy of Sciences

In this paper we propose two new algorithms for multi-pass fast correlation attacks on stream *** first algorithm aims at fast symbol-wise decoding in the circumstances that the noise is not very high and we have little resource for *** second algorithm deals with the practical decoding problem in the high noise and limited keystream *** new algorithms are applicable to arbitrary form LFSR and compare favorably to the previously known algorithms in the scenarios under *** applications,we demonstrate new key recovery attacks on one-level Bluetooth E0 and LILI-128,*** 2 37 -bit keystream and 2 28-byte memory,our attack against one-level E0 needs 2 35.1 *** 2 24-bit keystream and 2 24.5 -byte memory,our attack on LILI-128 has time complexity 2 70.6 operations.

关键词： stream cipher fast correlation attacks linear feedback shift register (LFSR) Bluetooth E0 LILI-128

Security model and modular design of fair authentication key exchange protocols

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(Information sciences) 2010年第2期53卷 278-287页

作者： FENG DengGuo & CHEN WeiDong state key laboratory of Information Security, institute of Software, chinese academy of sciences, beijing 100190, china state key laboratory of Information Security Institute of Software Chinese Academy of Sciences

It is traditionally assumed that the legal two parties in authentication key exchange (AKE) communications are both credible. However, in more and more network applications nowadays, it is often required that such protocols be run under the circumstances where ones do not trust in each other. Therefore, in this paper we propose the idea of fair authentication key exchange (FAKE), which has not only the basic properties of AKE protocols, but also some new properties: the "session proof" embedded in the input of protocols by the customer; and if not revealed, the protocols have the deniability, otherwise the transcript of protocol is binding for the identifications. Such a method is capable of solving the contradiction between protecting privacy and the dissension on network service. Then the security model of FAKE protocols is formulated systematically and a flaw of the security model of current signature schemes proposed by Kudla is also corrected. Finally, a kind of FAKE protocol based on current signature schemes is designed and the mBJM-AK security, conditional deniability and fairness of FAKE protocols are proved in the random oracle model.

关键词： authentication key exchange protocols deniability fairness concurrent signature provable security

Study on the atmospheric photochemical reaction of CF_3 radicals using ultraviolet photoelectron and photoionization mass spectrometer

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Chemistry 2008年第4期51卷 316-321页

作者： YAO Li1,2, DU Lin1,2, YIN Shi1,2 & GE MaoFa1 1 beijing National laboratory for Molecular sciences (BNLMS), state key laboratory for Structural Chemistry of Unstable and Stable Species, institute of Chemistry, chinese academy of sciences, beijing 100080, china 2 Graduate University of chinese academy of sciences, beijing 100080, china beijing National laboratory for Molecular sciences (BNLMS) State Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

A study of the atmospheric photochemical reaction of CF3 radical with CO and O2 was performed by using a homemade ultraviolet photoelectron spectrometer-photoionization mass spectrometer (PES- PIMS). The electronic structures and mechanism of ionization and dissociation of CF3OC(O)OOC(O)- OCF3 were investigated. It was indicated that the two bands on the photoelectron spectrum of CF3OC(O)OOC(O)OCF3 are the result of ionization of an electron from a lone pair of oxygen and a fluo- rine lone pair of CF3 group. The outermost electrons reside in the oxygen lone pair. The experimental and theoretical first vertical ionization energy is 13.21 and 13.178 eV, respectively, with the PES and OVGF method. They are in good agreement. The photo ionization and dissociation processes were discussed with the help of theoretical calculations and PES-PIMS experiment. After ionization, the parent ions prefer the dissociation of the C-O bond and giving the fragments CF3OCO+ and CF3+. It demonstrated that the ultraviolet photoelectron and photoionization mass spectrometer could be ap- plied widely in the study of atmospheric photochemical reaction.

关键词： photochemical reaction CF3 radical ultraviolet photoelectron and photoionization mass spectroscopy transient species

EXPERIMENTAL STUDY OF THE ASYNCHRONOUS MULTISPLITTING RELAXATION METHODS FOR THE LINEAR COMPLEMENTARITY PROBLEMS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2002年第6期20卷 561-574页

作者： Zhong-zhi Bai(state key laboratory of Scientific/Engineering Computing, institute of Computational Mathematicsand Scientific/Engineering Computing, academy of Mathematics and System sciences, chineseacademy of sciences, beijing 100080, china) institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and System Sciences Chinese Academy of Sciences State Key Laboratory of Scientific/Engineering ComputingCAS 北京 100080

Presents a study of the numerical behaviors of the relaxed asynchronous multisplitting methods for linear complementarity problems by solving typical problems from practical applications on a real multiprocessor system. Description of the tested problems and computing environment used in the computations; Description of the asynchronous multisplitting unsymmetric accelerated overrelaxation method; Discussion of results.

关键词： linear complementarity problem matrix multisplitting asynchronous iterative methods numerical experiment

MOLECULAR SIMULATION STUDY ON THE CHANGE OF POLYMER STRUCTURE DURING YIELDING

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5期19卷 527-529页

作者： Chen-guang Xu Tai-ning Liang Juan Sun Xiao-zhen Yang state key laboratory of Polymer Physics and Chemistry Center for Molecular Science, institute of Chemistry chinese academy of sciences, beijing 100080 china 中科院化学所高分子物理与化学国家重点实验室北京

A better understanding of a recently raised argument on whether there occurs a structure change during yielding has been acquired by using molecular simulation. That is, when monitoring the displacements of all atoms before and after the yield, a structure transition does occur, which is the 'atomic jump' that coordinates the amount of the atoms in the polymer and makes a large step beyond similar to0.05 nm for all those atoms. Results indicate that the complex of polymer chain packing induces the multiple atomic jumps around the yield point. This explains why polymers have a broader yielding peak.

关键词： polymer deformation yield structure transition atomic jump multiple yields

The theoretical research of basic function method in incompressible viscous flow and its simulations in three-dimensional aneurysms

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,mechanics & Astronomy) 2009年第6期52卷 909-918页

作者： SHEN Fang1 & WU WangYi2 1 state key laboratory for Space Weather, Center for Space Science and Applied Research, chinese academy of sciences, beijing 100190, china 2 state key laboratory of Turbulence and Complex Systems & Department of mechanics and Engineering Science, Peking University, beijing 100871, china state key laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China state key laboratory of Turbulence and Complex Systems & Department of mechanics and Engineering Science Peking University Beijing China

Basic function method is developed to treat the incompressible viscous flow. Artificial compressibility coefficient, the technique of flux splitting method and the combination of central and upwind schemes are applied to construct the basic function scheme of trigonometric function type for solving three-dimensional incompressible Navier-Stokes equations numerically. To prove the method, flows in finite-length-pipe are calculated, the velocity and pressure distribution of which solved by our method quite coincide with the exact solutions of Poiseuille flow except in the areas of entrance and exit. After the method is proved elementary, the hemodynamics in two-and three-dimensional aneurysms is researched numerically by using the basic function method of trigonometric function type and unstructured grids generation technique. The distributions of velocity, pressure and shear force in steady flow of aneurysms are calculated, and the influence of the shape of the aneurysms on the hemodynamics is studied.

关键词： basic function unstructured grid aneurysm viscous incompressible flow artificial compressibility flux splitting

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 state key laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing 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