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Mesh-dependence of Material with Softening Behavior

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Chinese Journal of Aeronautics 2010年第1期23卷 46-53页

作者： Fu Li,Du Xingwen center for Composite Materials,Harbin Institute of technology,Harbin 150001,china [a] center for Composite Materials Harbin Institute of Technology Harbin 150001 China

The issue of mesh-dependence emerges when the conventional continuum damage model is applied to handling the softening behavior. In order to circumvent the mesh-dependence, the non-local theory is introduced into the conventional damage model and the finite element formulas are derived for two-dimensional gradient-enhanced damage model. A new element is proposed in which the basic unknown quantities are displacement, non-local equivalent strain and the gradient of non-local equivalent strain. The element and constitutive equation proposed in this article are added to the finite element software ABAQUS through user subroutine UEL. Numerical results show that the gradient-enhanced damage model can eliminate the mesh-dependence and is effective for dealing with the issue of softening behavior.

关键词： non-local theory gradient dependence softening behavior mesh-dependence Hermitian element finite element method

A formal method to real-time protocol interoperability testing

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Science in china(Series F) 2008年第11期51卷 1723-1744页

作者： WANG ZhiLiang1,3,YIN Xia2,3 & JING ChuanMing2,3 1 Network Research center,Tsinghua University,Beijing 100084,china 2 Department of Computer Science and technology,Tsinghua University,Beijing 100084,china 3 Tsinghua National Laboratory for Information Science and technology(TNList) ,Beijing 100084,china 1. Network Research center Tsinghua University Beijing 100084 China 3. Tsinghua National Laboratory for Information Science and technology (TNList) Beijing 100084 China 2. Department of Computer Science and technology Tsinghua University Beijing 100084 China

Interoperability testing is an important technique to ensure the quality of implementations of network communication protocol. In the next generation Internet protocol, real-time applications should be supported effectively. However, time constraints were not considered in the related studies of protocol interoperability testing, so existing interoperability testing methods are difficult to be applied in real-time protocol interoperability testing. In this paper, a formal method to real-time protocol interoperability testing is proposed. Firstly, a formal model CMpTIOA （communicating multi-port timed input output automata） is defined to specify the system under test （SUT） in real-time protocol interoperability testing; based on this model, timed interoperability relation is then defined. In order to check this relation, a test generation method is presented to generate a parameterized test behavior tree from SUT model; a mechanism of executability pre-determination is also integrated in the test generation method to alleviate state space explosion problem to some extent. The proposed theory and method are then applied in interoperability testing of IPv6 neighbor discovery protocol to show the feasibility of this method.

关键词： protocol testing interoperability testing real-time testing test generation timed input output automata(TIOA)

Stability of linear discrete switched systems with delays based on average dwell time method

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Science china(Information Sciences) 2010年第6期53卷 1216-1223页

作者： WANG Yong 1 , WANG Wei 1 & LIU GuoPing 2,3 1 Research center of Information and Control, Dalian University of technology, Dalian 116024, china 2 Faculty of Advanced technology, University of Glamorgan, Pontypridd, CF37 1DL, UK 3 CTGT center in Harbin Institute of technology, Harbin 150001, china 1. Research center of Information and Control Dalian University of Technology Dalian 116024 China2. Faculty of Advanced Technology University of Glamorgan Pontypridd CF37 1DL UK3. CTGT Center in Harbin Institute of Technology Harbin 150001 China

This paper deals with the problem of exponential stability for a class of linear discrete switched systems with constant *** switched systems consist of stable and unstable *** on the average dwell time method, some switching signals will be found to guarantee exponential stability of these *** explicit state decay estimation is also given in the form of the solutions of linear matrix inequalities(LMIs).An example relating to networked control systems(NCSs) illustrates the effectiveness of the proposed method.

关键词： switched systems average dwell time time delay LMI

Isomerization of B_6,B_6^- and B_6^+ clusters

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Science china Chemistry 2010年第1期53卷 202-209页

作者： WEI GongMin1,PU ZhiFeng2,ZOU Rong3,LI GuoLiang2,3 & LUO Qiong2,3 1Department of Physics,Capital Normal University,Beijing 100048,china 2State Key Laboratory of Explosion Science and technology Beijing Institute of technology,Beijing 100081,china 3center for Computational Quantum Chemistry,South china Normal University,Guangzhou 510631,china 1. Department of Physics Capital Normal University Beijing 100048 China2. State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China3. Center for Computational Quantum Chemistry South China Normal University Guangzhou 510631 China

The interconversions between isomers with the same spin multiplicity of neutral B6 and charged B6-and B6+ clusters have been investigated at the B3LYP/6-311+G level of theory,including determination of the minimum energy pathways with transition states connecting the corresponding reactants and *** dynamic calculations,26 isomers were optimized,including 11 novel *** order to further refine the energies,single-point B3LYP/6-311+G(3df) calculations were carried out on the corresponding B3LYP/6-311+G geometries of all isomers of B6,B6-and B6+ and the corresponding isomerization transition *** stability of each isomer of B6(singlet and triplet states),B6-(doublet state) and B6+(doublet state) was analyzed from both thermodynamic and dynamic viewpoints.

关键词： B6 transition state intrinsic reaction coordinate barrier height

BRST quantization and canonical Ward identity of the supersymmetric electromagnetic interaction system

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Science china(Physics,Mechanics & Astronomy) 2007年第3期50卷 339-347页

作者： HUANG YongChang1,3,4, JIANG YunGuo1 & LI XinGuo2,3 1 Institute of Theoretical Physics, College of Applied Sciences, Beijing University of technology, Beijing 100022, china 2 Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, china 3 center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Collisions, Chinese Academy of Sciences, Lanzhou 730000, china 4 china center of Advanced Science and technology (World Laboratory), Beijing 100080, china 1. Institute of Theoretical Physics College of Applied Sciences Beijing University of Technology Beijing 100022 China 3. center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Collisions Chinese Academy of Sciences Lanzhou 730000 China 4. china center of Advanced Science and technology (World Laboratory) Beijing 100080 China 2. Institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China

According to the method of path integral quantization for the canonical constrained system in Becchi-Rouet-Stora-Tyutin scheme, the supersymmetric electromagnetic interaction system was quantized. Both the Hamiltonian of the supersymmetric electromagnetic interaction system in phase space and the quantization procedure were simplified. The BRST generator was constructed, and the BRST transforma- tions of supersymmetric fields were gotten; the effective action was calculated, and the generating functional for the Green function was achieved; also, the gauge generator was constructed, and the gauge transformation of the system was ob- tained. Finally, the Ward-Takahashi identities based on the canonical Noether theorem were calculated, and two relations between proper vertices and propaga- tors were obtained.

关键词： supersymmetric electromagnetic interaction BRST quantization Ward identity

Friction Stir Welding of Aluminum Alloys

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Journal of Wuhan University of technology(Materials Science) 2004年第1期19卷 61-64页

作者：傅志红 Zhuzhou Institute of technology

Friction stir welding(FSW),a new solid-state welding technology invited in the early 1990s,enables us weld aluminum alloys and titanium alloys *** processing of FSW,the microstructure in FSW alloys and the factors inf... 详细信息

关键词： friction stir welding stir-welding head aluminum alloy microstructure

A TTCN-3-based protocol testing system and its extension

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Science in china(Series F) 2008年第11期51卷 1703-1722页

作者： YIN Xia1,3,WANG ZhiLiang2,3,JING ChuanMing1,3 & SHI XinGang2,3 1 Department of Computer Science and technology,Tsinghua University,Beijing 100084,china 2 Network Research center,Tsinghua University,Beijing 100084,china 3 Tsinghua National Laboratory for Information Science and technology(TNList) ,Beijing 100084,china 1. Department of Computer Science and technology Tsinghua University Beijing 100084 China 3. ]Tsinghua National Laboratory for Information Science and technology (TNList) Beijing 100084 China 2. Network Research center Tsinghua University Beijing 100084 China

The protocol testing technology used in the next generation Internet should satisfy some new challenges and requirements. This paper focuses on the test suite description and test implementation techniques. TTCN-3 is chosen as the test suite description language and extended in both syntax and semantics to satisfy the requirements of protocol robustness testing. PITSv3, a protocol integrated testing system based on TTCN-3, is developed, and the extensions for robustness testing are implemented. Finally, two practical test applications are presented.

关键词： protocol testing TTCN-3 PITSv3 robustness testing

Mesh theory of angle modified dual tori double-enveloping toroidal worm drive

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Science china(Technological Sciences) 2010年第7期53卷 1913-1927页

作者： ZHAO YaPing1, SU DaiZhong2, ZHANG Zhao1, WEI WenJun3 & DONG XueZhu3 1 College of Machinery and Automation, Wuhan University of Science and technology, Wuhan 430081, china 2 Advanced Design and Manufacturing Engineering center, Nottingham Trent University, Nottingham NG1 4BU, UK 3 College of Engineering, china agricultural University, Beijing 100083, china 1. College of Machinery and Automation Wuhan University of Science and Technology Wuhan 430081 China2. Advanced Design and Manufacturing Engineering Center Nottingham Trent University Nottingham NG1 4BU UK3. College of Engineering China Agricultural University Beijing 100083 China

In this paper, the meshing theory of the angle modified hourglass worm drive is enriched and developed. The ordinary condition of the angle modification is derived and the physical significance of the modification is interpreted. A normal section methodology is proposed for meshing analysis, which can be used to compute the normal distance near a singular meshing point of a conjugate surface couple. By means of the method and after analyzing the normal transversals, it is specified that the worm helicoid, the nominal former contact zone and the new contact zone intersect each other along the locus of singular points of the instantaneous contact lines of an angle-modified worm pair. As a result, it is explained clearly that those three osculate each other but the osculations are different in degree. Moreover, the mechanism of removing the twice-contacted zone from the worm gear tooth surface is clarified and the reason of shortening the worm working length is also elucidated. With the help of the theory described in the present paper and the thorough and systematic research on the relevant meshing characteristics, the angle modified dual tori double-enveloping toroidal worm drive has been shown to be an excellent new-fashioned hourglass worm set.

关键词： hourglass worm angle modification double-enveloping osculation normal transversal

Influence of Ru addition on microstructure and stress-rupture property of Ni-based single crystal superalloys

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Progress in Natural Science:Materials International 2010年第1期20卷 61-69页

作者： Jing-yang CHEN~1,Qiang FENG~(1,2),La-mei CAO~3,Zu-qing SUN~1 1.State Key Laboratory for Advanced Metals and Materials,University of Science and technology Beijing, Beijing 100083,china 2.National center for Materials service Safety,University of Science and technology Beijing,Beijing 100083,china 3.National Key Laboratory of Science and technology on Advanced High Temperature Structural Materials, Beijing Institute of Aeronautical Materials,Beijing 100095,china Univ Sci & Technol Beijing State Key Lab Adv Met & Mat Beijing 100083 Peoples R China Univ Sci & Technol Beijing Natl Ctr Mat Serv Safety Beijing 100083 Peoples R China Beijing Inst Aeronaut Mat Natl Key Lab Sci & Technol Adv High Temp Struct M Beijing 100095 Peoples R China

The effects of Ru on the microstructure and stress-rupture property were investigated in two experimental Ni-based single crystal superalloys with and without Ru addition(5.1%,mass fraction).The results indicate that the morphology ofγ' precipitates in the dendrite core and interdendritic region are intermediate and nearly spherical,respectively,in the Ru-free alloy after being aged at 1100℃for 8 *** Re partitioning ratio increases due to Ru addition and Ru partitioned preferentially to theγphase in both dendrite core and interdendritic region of the Ru-containing alloy,which results in more negative lattice misfit and more cuboidalγ' ***,theγ' volume fraction increases while the precipitate size and y channel width decreases due to Ru addition in both dendrite core and interdendritic *** addition improves the stress-rupture life at 1100℃/140 MPa significantly due to higherγ' volume fraction,more negative lattice misfit and a well rafting structure as well as lessγchannel width.

关键词： Ni-based superalloys ruthenium elemental partitioning ratio lattice misfit γ’ morphology stress-rupture property