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A molecular dynamics study on melting point and specific heat of Ni_3Al alloy

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Science china(Physics,mechanics & Astronomy) 2007年第4期50卷 407-413页

作者： YANG Hong,Lü YongJun,CHEN Min & GUO ZengYuan department of engineering {2.,Tsinghua university,beijing 100084,china 1. department of engineering {2. Tsinghua University Beijing 100084 China

Using the Embedding Atom Method(EAM)for highly undercooled Ni3Al alloy,the melting point and the specific heat were studied by a molecular dynamics *** simulation of melting point was carried out by means of the sandwich method and the NVE ensemble method,and the results show a good agreement,whereas are larger than the experimental value of 1663 *** difference is attrib-uted to the influence of surface melting on experimental results,which causes the smaller measurements compared with the thermodynamic melting *** simulated specific heat of Ni3Al alloy weakly and linearly increases with the in-crease of undercooling in the temperature range from 800 K to 2.00 K.

关键词： Ni3Al alloy undercooled melting point specific heat

Stability　Analysis　of　Nonlinear　Vibrations　of　a　Deploying　Flexible　Beam

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Communications in Nonlinear Science and Numerical Simulation 1996年第4期1卷 32-35页

作者： Junfeng LI & Zhaolin WANG (department of engineering {2., Tsinghua university, beijing 100084,china) E-mail: lijf@*** department of engineering {2. Tsinghua university beijing 100084 china

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ＳｔａｂｉｌｉｔｙＡｎａｌｙｓｉｓｏｆＮｏｎｌｉｎｅａｒＶｉｂｒａｔｉｏｎｓｏｆａＤｅｐｌｏｙｉｎｇＦｌｅｘｉｂｌｅＢｅａｍ１，２１ＰｒｏｊｅｃｔｓｕｐｐｏｒｔｅｄｂｙｔｈｅＮａｔｉｏｎａｌＮａｔｕｒａｌＳｃｉｅｎｃｅＦｏｕｎｄａｔｉｏｎｏｆＣｈｉｎ...

关键词： Deploying flexible beam Rigid-flexible coupled system Partial stability

Effect of Post-spinning Modification on the PAN Precursors and Resulting Carbon Fibers

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Journal of Wuhan university of Technology(Materials Science) 2006年第3期21卷 44-48页

作者：张旺玺 department of mechanics {2. Zhongyuan Institute of TechnologyZhengzhou 450070China

The impregnation of a special grade PAN precursor,fibers wus carried out in a 8 wt% KMnO4 aqueous solution to obtain modified PAN precursor fibers. The effects of modification on the chemical stncture and the mechanical properties of precursor fibers thermally stabilized and their resulting carbon fibers u＇ere characterized by the combiination use of densities, wide-angle X-ray diffraction （WAXD）, X-ray photoelectron speetroscopy （XPS）, elemental analysis （ EA ）, Fourier traasform infrared spectroscopy （FT-IR） and scanning electron microscope （SEM）, ***4 as a strong oxidizer can swell, oxidize and corrode the skin of a ***, and transform C≡N groups to C≡N ones, meamchile , it can decreuse the crystal .size increuse the orientation index and the costallinity index, furthermore it can increuse the densities of modified PAN precursors and resuhing thermally stabilized fibers. As a result, the carbon fibers developed from modified PAN fibers show an improvement in tensile strength of 31.2. % and an improvement in elongation of 77.78 % , but a decrease of 16. 52. in Young＇s modulus.

关键词： carbon fibers carbon precursor chemical treatment mechanical properties

Bitstream decoding and SEU-induced failure analysis in SRAM-based FPGAs

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Science china(Information Sciences) 2012年第4期55卷 971-982页

作者： WANG ZhongMing 1,2.YAO ZhiBin 2.GUO HongXia 2.& LV Min 1 1 department of engineering Physics,Tsinghua {2.,beijing 100084,china 2.Northwest Institute of Nuclear Technology,Xi'an 71002.,china 1. department of engineering Physics Tsinghua University Beijing 100084 China2. Northwest Institute of Nuclear Technology Xi’an 710024 China

Reconfigurable SRAM-based FPGAs are highly susceptible to radiation induced single-event upsets (SEUs) in space *** bit flip in FPGAs configuration memory may alter user circuit permanently without proper bitstream reparation,which is a completely different phenomenon from upsets in traditional memory *** is important to find the relationship between a programmable resource and corresponding control bit in order to understand the impact of this *** this paper,a method is proposed to decode the bitstream of FPGAs from Xilinx Corporation,and then an analysis program is developed to parse the netlist of a specific design to get the configuration state of occupied programmable logic and *** that,an SEU propagation rule is established according to the resource type to identify critical logic nodes and paths,which could destroy the circuit topological *** decoded relationship is stored in a *** database is queried to get the sensitive bits of a specific *** result can be used to represent the vulnerability of the system and predict the on orbit system failure *** analysis tool was validated through fault injection and accelerator irradiation experiment.

关键词： radiation effect single-event effect single-event upset SRAM-based FPGA fault injection

New evidence for lack of CMB power on large scales

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Science china(Physics,mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： LIU Hao1 & LI TiPei1,2.3 1 Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, beijing 100049, china {2. of Physics & Center for Astrophysics, Tsinghua university, beijing 100084, china 3 department of engineering Physics & Center for Astrophysics, Tsinghua university, beijing 100084, china 1. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China2. Department of Physics & Center for Astrophysics Tsinghua University Beijing 100084 China3. Department of Engineering Physics & Center for Astrophysics Tsinghua University Beijing 100084 China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

The complex variable reproducing kernel particle method for elasto-plasticity problems

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Science china(Physics,mechanics & Astronomy) 2010年第5期53卷 954-965页

作者： CHEN Li1 & CHENG YuMin2.1 department of engineering {2.,Chang’an university,Xi’an 710064,china 2.Shanghai Institute of Applied Mathematics and {2.,Shanghai university,Shanghai 2.0072.china 1. department of engineering {2. Chang’an University Xi’an 710064 China2. Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

On the basis of reproducing kernel particle method(RKPM),using complex variable theory,the complex variable reproducing kernel particle method(CVRKPM) is discussed in this *** advantage of the CVRKPM is that the correction function of a two-dimensional problem is formed with one-dimensional basis function when the shape function is *** the CVRKPM is applied to solve two-dimensional elasto-plasticity *** Galerkin weak form is employed to obtain the discretized system equation,the penalty method is used to apply the essential boundary *** then,the CVRKPM for two-dimensional elasto-plasticity problems is formed,the corresponding formulae are obtained,and the Newton-Raphson method is used in the numerical *** numerical examples are given to show that this method in this paper is effective for elasto-plasticity analysis.

关键词： meshless method reproducing kernel particle method(RKPM) complex variable reproducing kernel particle method(CVRKPM) correction function elasto-plasticity

Analysis on cohesive crack opening displacement considering the strain softening effect

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Science china(Physics,mechanics & Astronomy) 2006年第1期49卷 88-101页

作者： WANG Limin1, XU Shilang2.& ZHAO Xiqiang3 1. mechanics department, Shandong {2. of Technology, Zibo 2.5049, china 2. Civil engineering department, Dalian {2. of Technology, Dalian 11602., china 3. Mathematics department, Ocean {2. of china, Qingdao 2.6071, china mechanics department Shandong University of Technology Zibo 255049 China Civil engineering department Dalian University of Technology Dalian 116024 China Mathematics department Ocean University of China Qingdao 266071 China

In order to investigate the crack propagation in quasi-brittle materials like rock, ceramic and concrete, Hillerborg and his co-researchers abstracted the fracture process zone in front of a stress free crack in terms of a “fictitious crack zone”. On the fictitious crack zone, cohesive stresses distribute following a given softening relationship of stress vs. crack opening. Based on the polynomial or power series expression of cohesive crack opening displacement, the relationship of the cohesive stress vs. the crack opening displacement is established using elastic theory and integral equation, and some unknown physics variables are obtained using variation approach. The calculation results gained in this paper are close to the experimentally test ones.

关键词： cohesive crack, softening, dissipation work, variation approach.

Micromechanical analysis of interaction energy for SMA reinforced composite

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Science china(Technological Sciences) 2009年第3期52卷 610-616页

作者： ZHU YuPing1,2. DUI GuanSuo1 & DUO Liu3 1 Institute of mechanics, beijing Jiaotong {2., beijing 100044, china 2.department of engineering mechanics, Jiangsu {2., Zhenjiang 2.2.13, china 3 State Key Lab of Crystal Materials, Shandong {2., Jinan 2.0100, china Institute of mechanics Beijing Jiaotong University Beijing 100044 China department of engineering {2. Jiangsu University Jiangsu Zhenjiang 212013 China State Key Lab of Crystal Materials Shandong University Jinan 250100 China

The energy of the interaction between the matrix and the inclusions in shape memory alloy (SMA) re- inforced composite is one of the most important and complicated parts in thermodynamic constitutive theory. In this paper, the interaction energy is derived based on the classical theory of micromechanics and the thermodynamic theory. The SMA composite is treated as three phases, namely the austenitic phase, the martensite phase and the matrix phase. The interaction among the three phases is analyzed in a way close to the fact. The present expression is used to calculate the interaction energy of a typical SMA composite with attentions paid to understand of the effects of the matrix material, the fiber ge- ometry, and the fiber/matrix volume ratio. It is shown that the method developed in this paper is credible compared with the references. Some useful conclusions are obtained.

关键词： shape memory alloy interaction energy SMA composite micromechanics thermodynamics

A study of mechanical behavior of rock-fill materials with reference to particle crushing

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Science china(Technological Sciences) 2007年第z1期50卷 125-135页

作者： HUANG WenXiong1?, REN QingWen1 & SUN DeAn2.1 department of engineering {2., Hohai university, Nanjing 2.0098, china 2.department of Civil engineering, Shanghai university, Shanghai 2.0072. china department of engineering {2. Hohai University Nanjing 210098 China department of Civil engineering Shanghai University Shanghai 200072 China

In rock-fill dams of 2.0 to 300 m high, maximum compressive stress can exceed 6 MPa. At such a high stress level, rock-fill materials may experience particle crushing during shear. The material behavior is highly sophisticated exhibiting pressure and density dependency as well as particle crushing effects. Through scrutinizing the relevant experimental data on rock-fill materials and sands published in the literatures, this paper is focused on understanding basic mechanical characteristics of this sort of materials in the light of constitutive modelling.

关键词： rock-fill materials granular materials compressibility shear dilatancy particle crushing