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The Coagulation Process of Nascent Fibers in PAN Wet-spinning

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Journal of Wuhan university of Technology(materials {2.) 2010年第2期25卷 200-205页

作者：陈娟葛曷一 School of material science and {2. University of Jinan

The evolvement of microstructure and properties of nascent fibers during coagulation process in the polyacrylonitrile （PAN） wet-spinning and the effect of coagulation bath conditions on the structure and properties of the nascent fibers were investigated by the means of X-ray diffraction （XRD）, scanning electron microscope （SEM）, fiber fineness machine, fiber tensile strength machine, etc. The experimental results indicate that the nascent fibers become denser and have fewer inner defects, the diameter of nascent fibers shrink and the crystallization degree of nascent fibers gradually increases with the increasing of coagulation time. Too large spinning tension leads to grooves occurring on surface of fibers. To obtain circular cross-section of nascent fibers the optimal coagulation conditions are 50 ℃, 65% （concentration） and 0.9 （draw ratio）.

关键词： PAN wet-spinning coagulation nascent fibers

A complex variable meshless method for fracture problems

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science China(Physics,Mechanics & Astronomy) 2006年第1期49卷 46-59页

作者： CHENG Yumin1 & LI Jiuhong2.1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai university, Shanghai 2.0072. China 2. department of Building {2., Xi’an university of Technology, Xi’an 710048, China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai China department of Building engineering Xi’an University of Technology Xi’an China

Based on the moving least-square (MLS) approximation, the complex variable moving least-square approximation (CVMLS) is discussed in this paper. The complex variable moving least-square approximation cannot form ill-conditioned equations, and has greater precision and computational efficiency. Using the analytical solution near the tip of a crack, the trial functions in the complex variable moving least-square approxi- mation are extended, and the corresponding approximation function is obtained. And from the minimum potential energy principle, a complex variable meshless method for fracture problems is presented, and the formulae of the complex variable meshless method are obtained. The complex variable meshless method in this paper has greater precision and computational efficiency than the conventional meshless method. Some examples are given.

关键词： moving least-square approximation, complex variable moving least-square approximation, meshless method, complex variable meshless method, fracture.

Boundary element-free method for elastodynamics

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science China(Physics,Mechanics & Astronomy) 2005年第6期48卷 641-657页

作者： CHENG Yumin1 & PENG Miaojuan2.1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai university, Shanghai 2.0072. China 2. department of Civil {2., Shanghai university, Shanghai 2.0072. China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai China department of Civil engineering Shanghai University Shanghai China

The moving least-square approximation is discussed first. Sometimes the method can form an ill-conditioned equation system, and thus the solution cannot be obtained correctly. A Hilbert space is presented on which an orthogonal function system mixed a weight function is defined. Next the improved moving least-square approximation is discussed in detail. The improved method has higher computational efficiency and precision than the old method, and cannot form an ill-conditioned equation system. A boundary element-free method (BEFM) for elastodynamics problems is presented by combining the boundary integral equation method for elastodynamics and the improved moving least-square approximation. The boundary element-free method is a meshless method of boundary integral equation and is a direct numerical method compared with others, in which the basic unknowns are the real solutions of the nodal variables and the boundary conditions can be applied easily. The boundary element-free method has a higher computational efficiency and precision. In addition, the numerical procedure of the boundary element-free method for elastodynamics problems is presented in this paper. Finally, some numerical examples are given.

关键词： moving least-square approximation, improved moving least-square approximation, elastodynamics, boundary integral equation, meshless method, boundary element-free method, Fourier eigen transform.

Preliminary examination of electrochemical and spectroscopic features of trithiocarbonate collectors for sulfide mineral flotation

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中国有色金属学会会刊：英文版 2000年第S1期10卷 12-18页

作者： R. Du Plessis 1, J.D. Miller 1, J.C.Davidtz 2.1. department of Metallurgical engineering, {2. of Utah, Salt Lake City, Utah 84102. USA 2. department of materials science and Metallurgical engineering, {2. of Pretoria, Pretoria 0002 Univ Utah Dept Met Engn Salt Lake City UT 84102 USA Univ Pretoria Dept Met Engn & Mat Sci ZA-0002 Pretoria South Africa

The redox potentials of xanthate/dixanthogen (dithiocarbonate/di dithiocarbonate, DTC/(DTC) 2. and trithiocarbonate/di trithiocarbonate (TTC/(TTC) 2. couples have been measured for the potassium salts. The spectroscopic characteristics of these sulfide mineral collectors were determined by FTIR and UV analysis. Electrochemically controlled contact angle measurements at a pyrite surface provided the basis to analyze the effect of the functional group ( O CS 2.versus S CS 2. on the hydrophobic surface state. Results from this preliminary examination are discussed with respect to the nature of collector adsorption and the pyrite flotation response.

关键词： redox potential trithiocarbonate collector sulfide mineral flotation

The influence of laser pulse on the photoabsorption spectra of Li atom in strong external field

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science China(Physics,Mechanics & Astronomy) 2006年第2期49卷 178-186页

作者： WANG Dehua1 & LIN Shenglu2.1. School of Physics and Electronic engineering, Yantai Normal university, Yantai 2.402., China 2. {2. of Physics, Shandong Normal university, Jinan 2.0014, China School of Physics and Electronic engineering Yantai Normal University Yantai China department of Physics Shandong Normal University Jinan China

Using the time-dependent perturbation theory and the calculation formula of the single- and double-pulse absorption spectra of the atom in strong external fields, we calculate the single- and double-pulse absorption spectra of Li atom in strong magnetic field for different pulse widths. The results show that a pulse of some width can reduce the contribution of the short period closed orbits and eliminate the contribution of the long period orbits. Compared with the single-pulse absorption spectra, we found that for some phase differences, the double-pulse laser absorption spectra are strengthened; while for others, they are reduced. Therefore, we can use the pulse laser to control the oscillation of the absorption spectra and obtain the optimization object.

关键词： laser pulse closed orbit absorption spectra.

Effect of Limestone Powder on Microstructure of Concrete

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Journal of Wuhan university of Technology(materials {2.) 2010年第2期25卷 328-331页

作者：刘数华 State Key Laboratory of Water Resource and Hydropower engineering science Wuhan University

The effect of limestone powder on microstructure of concrete was studied by using mercury intrusion porosimetry （MIP）, backscattering scanning electron（BSE）, scanning electron mi- croscopy （SEM） and X-ray diffraction （XRD） techniques. The experimental results show that the compressive strength of concrete containing 100 kg/m3 limestone powder can meet the strength requirement. Limestone powder has not pozzolanic activity; it is still unhydrated at the age of 2. days. But its filling effect can make the paste matrix and the interfacial transition zone between matrix and aggregate denser, which will improve the performance of concrete.

关键词： concrete limestone powder microstructure filling effect hydration characteristic

Electro-mechanical response of functionally graded beams with imperfectly integrated surface piezoelectric layers

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science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 513-525页

作者： YAN Wei1 & CHEN Weiqiu1,2.1. department of Civil engineering, Zhejiang {2., Hangzhou 31002., China 2. State Key Lab of CAD & CG, Zhejiang {2., Hangzhou 31002., China department of Civil engineering Zhejiang University Hangzhou China State Key Lab of CAD & CG Zhejiang University Hangzhou China

The time-dependent behavior of a simply-supported functionally graded beam bonded with piezoelectric sensors and actuators is studied using the state-space method. The creep behavior of bonding adhesives between piezoelectric layers and beam is characterized by a Kelvin-Voigt viscoelastic model, which is practical in a high temperature circumstance. Both the host elastic functionally graded beam and the piezoelectric layers are orthotropic and in a state of plane stress, with the former being inhomogeneous along the thickness direction. A laminate model is employed to approximate the host beam. Moreover, the coupling effect between the elastic deformation and electric field in piezoelectric layers is considered. Results indicate that the viscoelastic property of interfacial adhesives has a significant effect on the function of bonded actuators and sensors with time elapsing.

关键词： functionally graded beam piezoelectric layers Kelvin-Voigt model state-space method

Characterzation and separation of Al_(13) species using gel-filtration chromatography

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science China Chemistry 2006年第4期49卷 326-331页

作者： CHU Yongbao1,2. GAO Baoyu1, YUE Qinyan1, WANG Yan1 & WANG Shuguang1 1. School of Environmental science and engineering, Shandong {2., Jinan 2.0100, China 2. College of material and Environment, Qingdao {2. of science and Technology, Qingdao 2.6042. China School of Environmental science and engineering Shandong University Jinan China College of material and Environment Qingdao University of Science and Technology Qingdao China

A polyaluminum chloride (PAC) sample was prepared using a slow alkalinetitration method. The Bio-Gel P-100 gel column chromatographic technique was used to separate andcharacterize the various forms of aluminum present in the prepared PAC solution. The effluents froma gel column were monitored using online chemical method: AI-Ferron timed complexationspectropho-tometry and by ^(2.)Al nuclear magnetic resonance (NMR) spectroscopy. Effects ofdifferent experimental conditions such as eluent flow rate, ionic strength and pH on separation ofAl_(13) were investigated. Experimental results indicated that molecule size exclusion was not theonly parameter affecting the column chromatographic separation efficiency of Al_(13) but moleculecharge as well. Reducing the eluent flow rate, increasing the ionic strength and suitable pHresulted in increase in the separation efficiency. Experimental results clearly indicated that byvarying the experimental conditions, it is possible to produce pure Al_(13) species using a gelcolumn chromatographic technique.

关键词： Al13 species, column chromatography, polyaluminum chloride (PAC), separation and purification.

Thermal-stress Simulation of Direct-chill Casting of AZ31 Magnesium Alloy Billets

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Journal of Wuhan university of Technology(materials {2.) 2009年第3期24卷 376-382页

作者：胡红军 College of materials science and {2. Chongqing University National engineering Research Center for Magnesium Alloys Chongqing University College of material science and {2. Chongqing University of Technology

Two-dimensional （2.） transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill （DC） casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters （at pouring temperature of 680 ℃, casting speed of 2.min/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m^2.℃^-1）. The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.

关键词： magnesium alloy direct-chill casting temperature and stress fields numerical simulation solidification model