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Structural stability of intermetallic compounds of Mg-Al-Ca alloy

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中国有色金属学会会刊：英文版 2007年第2期17卷 250-256页

作者：周惦武刘金水张健彭平 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University School of Materials Science and Engineering Hunan University

A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the energetic and electronic structures of intermetallic compounds of Mg-Al-Ca alloy, such as Al2Ca, Al4Ca and Mg2Ca. The negative formation heat, the cohesive energies and Gibbs energies of these compounds were estimated from the electronic structure calculations, and their structural stability was also analyzed. The results show that Al2Ca phase has the strongest alloying ability as well as the highest structural stability, next Al4Ca, finally Mg2Ca. After comparing the density of states of Al2Ca, Al4Ca and Mg2Ca phases, it is found that the highest structural stability of Al2Ca is attributed to an increase in the bonding electron numbers in lower energy range below Fermi level, which mainly originates from the contribution of valence electron numbers of Ca(s) and Ca(p) orbits, while the lowest structural stability of Mg2Ca is resulted from the least bonding electron numbers near Fermi level.

关键词：金属间化合物 Mg-Al-Ca合金结构稳定性电子结构

First-principles study on structural stability of 3d transition metal alloying magnesium hydride

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中国有色金属学会会刊：英文版 2006年第1期16卷 23-32页

作者：周惦武彭平刘金水陈律胡艳军 School of Materials Science and Engineering Hunan University Changsha 410082 China

A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the energy and electronic structure of magnesium hydride (MgH2) alloyed by 3d transition metal elements. Through calculations of the negative heat formation of magnesium hydride alloyed by X (X denotes 3d transition metal) element, it is found that when a little X (not including Sc) dissolves into magnesium hydride, the structural stability of alloying systems decreases, which indicates that the dehydrogenation properties of MgH2 can be improved. After comparing the densities of states(DOS) and the charge distribution of MgH2 with or without X alloying, it is found that the improvement for the dehydrogenation properties of MgH2 alloyed by X attributes to the fact that the weakened bonding between magnesium and hydrogen is caused by the stronger interactions between X (not including Cu) and hydrogen. The calculation results of the improvement for the dehydrogenation properties of MgH2-X (X=Ti, V, Mn, Fe, Co, Ni, Cu) systems are in agreement with the experimental results. Hence, the dehydrogenation properties of MgH2 are expected to be improved by addition of Cr, Zn alloying elements.

关键词： MgH2 镁合金合金化结构稳定性密度功能理论电子结构热加工

Efficient design of rotary traveling wave oscillator array via geometric programming

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第12期10卷 1815-1823页

作者： Li-jia CHEN Hua-feng ZHANG Jin-fang ZHOU Kang-sheng CHEN Department o fin formation Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

This paper presents an efficient method for globally optimizing and automating component sizing for rotary traveling wave oscillator arrays. The lumped equivalent model of transmission lines loaded by inverter pairs is evaluated and posynomial functions for oscillation frequency, power dissipation, phase noise, etc. are formulated using transmission line theory. The re- sulting design problem can be posed as a geometric programJning problem, which can be efficiently solved with a convex opti- mization solver. The proposed method can compute the global optima more efficiently than the traditional iterative scheme and various design problems can be solved with the same circuit model. The globally optimal trade-off curves between competing objectives are also computed to carry out robust designs and quickly explore the design space.

关键词： Rotary traveling wave oscillator array (RTWOA) Clock distribution Transmission line resonator Global optimi-zation Geometric programming (GP)

SUPERCONVERGENCE ANALYSIS OF FINITE ELEMENT METHODS FOR OPTIMAL CONTROL PROBLEMS OF THE STATIONARY B(?)NARD TYPE

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Journal of Computational Mathematics 2008年第5期26卷 660-676页

作者： Yanzhen Chang Danping Yang School of Mathematics and System Science Shandong University Jinan 250100 China Department of Mathematics East China Normal University Shanghai 200062 China

In this paper, we consider the finite element approximation of the distributed optimal control problems of the stationary Benard type under the pointwise control constraint. The states and the co-states are approximated by polynomial functions of lowest-order mixed finite element space or piecewise linear functions and the control is approximated by piecewise constant functions. We give the superconvergence analysis for the control; it is proved that the approximation has a second-order rate of convergence. We further give the superconvergence analysis for the states and the co-states. Then we derive error estimates in L^∞-norm and optimal error estimates in L^2-norm.

关键词： Optimal control problem The stationary Benard problem Nonlinear coupled system Finite element approximation Superconvergence.

Isotope systematics and metallogenetic age of Zhuanghe gold deposit, Liaoning province, china

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Journal of Central South University of Technology 2007年第1期14卷 104-110页

作者：魏俊浩谭文娟郭大招谭俊李闫华鄢云飞 Faculty of Earth Resources China University of Geosciences

Based on the metallogenetic geology conditions, the H, O, C and S isotopic compositions were measured by MAT-251 mass spectrometer, and Pb isotope and Rb-Sr dating were carried with MAT-261 multi-acceptor mass spectrometer. The results show that the δ^180 values of gold-bearing vein quartz from different levels are 1.19%-1.42%. The calculated δ^180 values of ore fluids are 0.55%-0.78%, and 319 values are from -8.64% to -6.66%. The calculated values of δ^34SH2s by the δ^34Spy values in quartz veins display sulfur isotope compositions from -0.053% to ＋0.413%. Carbon isotope compositions of carbonates are from -0.612% to 0.140%. The mole ratios of ^206Pb to ^204Pb, ^207Pb to ^204Pb and ^208Pb to ^204Pb in auriferous quartz vein are 16.987-17.545, 15.342-15.623, and 38.254-38.744, respectively. The age of the Zhuanghe gold deposit determined by Rb-Sr isochron of the fluid inclusions in quartzes is （143.0±5.8） Ma. These isotopic data suggest that the metallogenetic fluids are generated from magmatic hydrotherm and the origin of ore-forming matters is related to the deep-derived magmatic activities. Meanwhile, the metallogenetic epoch of the Zhuanghe gold deposit is in Yanshanian period.

关键词： isotope systematics metallogenetic age Zhuanghe gold deposit

Separation of chiral drugs with β-CD phosphate by capillary electrophoresis

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Chinese Chemical Letters 2000年第2期11卷 153-156页

作者： Xue Qin REN1 Xiao Dan SU1 Al Jin HUANG1 Yi Liang SUN1 Zeng Pei SUNZ2 (1 Department of Chemistry, Peking University, Beijing 100871 2 National Institute for the Control of pharmaceutical and Biological Products, Beijing 100050) Department of Chemistry Peking University Beijing 100871 China Natl. Inst. Contr. Pharmaceutical B. Beijing 100050 China

β-Cyclodextrin phosphate (β-CD-phosphate) was used as a selector for separating chiral drugs by capillary electrophoresis (CE). A solution comprising of 120 mmol/L Britton Robinson buffer (BRB) containing 10 mmol/L 0-CD phosphate with the pH adjusted to 7.0 was used as the background electrolyte (BGE), and a small amount of analyte was injected (600v/1s). Triethylamine, diethylamine, triethanolamine, diethanolamine, Tris added as modifier were compared. Isoprenaline, methoxamine, oxprenolol, practolol were successfully resolved.

关键词： Capillary electrophoresis chiral separation β-cyclodextrin-phosphate isoprenaline methoxamine oxprenolol practolol.

Theoretical study on phase conjugation in weakly injected vertical-cavity surface-emitting lasers

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Chinese Physics B 2008年第5期17卷 1821-1825页

作者：张伟利潘炜罗斌李孝峰邹喜华王梦遥 School of Information Science & Technology Southwest Jiaotong University

This paper gives a detailed theoretical investigation on phase conjugation induced by nearly degenerate fourwave mixing in single mode vertical-cavity surface-emitting lasers （VCSELs） with weak optical injection. Considering VCSELs that can work in linearly polarized or elliptically polarized states, it derives the theoretical expression of the conjugated field by small signal analysis based on the vectoral rate equations-the spin-flip model. For linearly polarized state, VCSELs show similar conjugate spectra to edge-emitting semiconductor lasers. For the elliptically polarized state, dichroism and birefringence parameters as well as the spin-flip rate can change the conjugate spectra. Especially, when frequency detuning of the probe and pump waves is between the positive and negative relaxation oscillation frequency, changes are evident. For specific values of parameters, conjugate efficiency between 20 dB to 40 dB are obtained.

关键词： phase conjugate VCSELs polarization four-wave mixing

Pretreatment of hypersaline mustard wastewater with integrated bioreactor

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Journal of Central South University 2012年第6期19卷 1673-1678页

作者：何强张婷婷柴宏祥杨士伟周健杜国军 Key Laboratory of Three Gorges Reservoir Region's Eco-Environment(Chongqing University) Ministry of Education

A full-scale experimental study of treating mustard wastewater by the integrated bioreactor with designed scale of 1 000 m3/d is conducted combined with a demonstration project. The systematical researches on the efficiency of combined operation conditions of anaerobic-aerobic and anaerobic-aerobic-flocculation as well as chemical phosphorus removal of hypersaline mustard wastewater are conducted. The optimal operation condition and parameters in pretreatment of mustard wastewater in winter （the water temperature ranges 8-15 ~C） are determined： the anaerobic load is 3.0 kg （COD）/（m3.d）, the average COD and phosphate concentration of the inflow are respectively 3 883 mg/L and 35.53 mg/L and the dosage of flocculent （PAC） is 400 mg/L. The anaerobic-aerobic-flocculation combined operation condition and postpositive phosphorous removal with ferrous sulfate are employed. After treatment, the COD of the effluent is 470 mg/L and the average phosphate concentration is 5.09 mg/L. The effluent could achieve the third-level of Integrated Wastewater Discharge Standard （GB 8978--1996）.

关键词： mustard wastewater aerobic treatment anaerobic treatment integrated bioreactor chemical phosphorus removal

A QR DECOMPOSITION BASED SOLVER FOR THE LEAST SQUARES PROBLEMS FROM THE MINIMAL RESIDUAL METHOD FOR THE SYLVESTER EQUATION

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Journal of Computational Mathematics 2007年第5期25卷 531-542页

作者： Zhongxiao Jia Yuquan Sun Department of Mathematical Sciences Tsinghua University Beijing 100084 China

Based on the generalized minimal residual （GMRES） principle, Hu and Reichel proposed a minimal residual algorithm for the Sylvester equation. The algorithm requires the solution of a structured least squares problem. They form the normal equations of the least squares problem and then solve it by a direct solver, so it is susceptible to instability. In this paper, by exploiting the special structure of the least squares problem and working on the problem directly, a numerically stable QR decomposition based algorithm is presented for the problem. The new algorithm is more stable than the normal equations algorithm of Hu and Reichel. Numerical experiments are reported to confirm the superior stability of the new algorithm.

关键词： Least-squares solution Preconditioning Generalized singular value decomposition.