材料期刊网

OPTIMIZATION OF AUTOBODY PANEL STAMPING PROCESS BASED ON DYNAMIC EXPLICIT FINITE ELEMENT METHOD

X. G. Bao , D. N. He , D. Lu , C. X. Li , J. L. Cheng and J. Y. Jiang( 1) National Mold and Dies CAD Engineering Research Center , Shanghai 200030 , China 2) Shanghai Volkswagen Automotive Company Ltd.(SVW) , Shanghai 201805 , China)

金属学报(英文版)

Taking CPU time cost and analysis accuracy into account, dynamic explicit finite ele- ment method is adopted to optimize the forming process of autobody panels that often have large sizes and complex geometry. In this paper, for the sake of illustrating in detail how dynamic explicit finite element method is applied to the numerical simulation of the autobody panel forming process,an example of optimization of stamping process pain meters of an inner door panel is presented. Using dynamic explicit finite element code Ls-DYNA3D, the inner door panel has been optimized by adapting pa- rameters such as the initial blank geometry and position, blank-holder forces and the location of drawbeads, and satisfied results are obtained.

关键词: dynamic explicit finite element method , null , null , null

Calculation of EPR parameters g factors for Ce3+ ion in YBa2Cu3O6+x superconductor

International Journal of Modern Physics B

The perturbation formulae of EPR parameters g factors g(x), g(y) and g(z) for the lowest Kramers doublet of 4f(1) ion in orthorhombic symmetry are established. In these formulae, the contributions of the covalency effects, the admixture between J = 7/2 and J = 5/2 states as well as the second-order perturbation (which is not considered in the previous works) via crystal-field and orbital angular momentum interactions are all included. According to these formulae, and by using the superposition model, the g-factors g., g(y) and g(z) for Ce3+ center in YBa2CU3O6+x superconductor are calculated. The results are discussed.

关键词: YBa2Cu3O6+x;EPR;superposition model;Ce3+;crystal-field

BaO含量对Ba改性Al2O3及其负载的Pt-Rh密偶催化剂性能的影响

姚艳玲 , 何胜楠 , 史忠华 , 龚茂初 , 陈耀强

催化学报 doi:10.3724/SP.J.1088.2011.01122

采用胶溶法制备了不同BaO含量的Ba改性的Al2O3样品(Ba-Al2O3).采用低温N2吸附-脱附、X射线衍射和氨程序升温脱附对样品进行了表征.结果表明,BaO的添加量为8%时,Ba-Al2O3样品具有最佳的织构性质、最大的表面酸量和最强的表面酸性;经1273 K焙烧5 h后,其比表面积和孔体积分别为142 m2/g和0.45 ml/g;于1373 K焙烧5 h后分别为114 m2/g和0.37 ml/g.以Ba-Al2O3材料为载体,采用浸渍法制备了Pt-Rh含量为1.5 g/L的密偶催化剂.催化剂活性测试结果表明,BaO的添加可有效提高催化剂上丙烷的转化活性,且当BaO含量为8%时,催化剂活性最高,新鲜和老化的催化剂上丙烷的起燃温度分别为513和557 K.

关键词: 氧化铝 , 氧化钡 , 铂 , 铑 , 密偶催化剂 , 热稳定性 , 丙烷

In situ observation of G. P. zones in an Al-Zn-Mg alloy under irradiation of electron beam

Journal of Materials Science Letters

关键词:

Explanations of the optical spectra and g factor for V3+ ions in ZnX (X = S, Se, Te) crystals

Physica B-Condensed Matter

This paper presents a cluster approach for the calculations of the absorption band positions and the g factor of d(2) tetrahedral cluster. In the approach, the different modifications of e and t(2) orbitals of d electrons and the contribution from the spin-orbit coupling of ligands to the EPR g factor due to the mixing of d(2) ions with the ligands are considered. The calculated band positions and g factor for ZnX : V3+ (X = S, Se, Te) crystals show good agreement with the observed values by using only two adjustable parameters. The contribution from the spin-orbit coupling of ligands to the g factor is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

关键词: crystal- and ligand-field theory;optical spectra;electron paramagnetic;resonance;spin-orbit coupling;V3+ ZnX (X = S, Se, Te);vanadium centers;znte crystals

INVESTIGATIONS ON THE g FACTORS AND THE SUPERHYPERFINE PARAMETERS FOR THE TETRAGONAL Pd(3+) CENTERS IN AgX (X = Cl, Br)

International Journal of Modern Physics B

The g factors and the superhyperfine parameters for the tetragonal Pd(3+) centers in AgX (X = Cl, Br) are theoretically investigated from the perturbation formulas of these parameters for a 4d(7) ion in tetragonally elongated octahedra In the calculations, the related molecular or coefficients and the unpaired spin densities of the ligands are determined quantitatively from the cluster approach in a uniform way. Both centers originate from substitutional Pd(3+) on Ag(+) site in AgX, with no charge compensator (silver vacancy) nearby. The [PdX(6)](3-) clusters suffer a relative elongation of 0.01 angstrom (or 0.06 angstrom) along [1 0 0] (or C(4)) axis for X = Cl (or Br) due to the Jahn-Teller effect The calculated g factors and the superhyperfine parameters based on the above Jahn-Teller elongations show good agreement with the experimental data.

关键词: Electron paramagnetic resonance;crystal and ligand fields;Pd(3+);AgCl;AgBr;transition-metal ions;epr spectroscopic investigations;electron-paramagnetic-resonance;atomic screening constants;laser-light;generation;color image-formation;silver bromide;superposition model;scf functions;agbr

Theoretical investigations of the g factors and the local structure for the trigonal Zr(3+) center in X-ray irradiated YSZ

Journal of Alloys and Compounds

The electron paramagnetic resonance (EPR) g factors g(parallel to) and gperpendicular to and the local structure for the trigonal Zr(3+) center in X-ray irradiated yttria-stabilized zirconia (YSZ) are theoretically investigated from the perturbation formulas of the g factors for a 4d(1) ion in trigonally distorted octahedra. Based on the studies, in this trigonal center (characterized as [ZrO(6)](9-) cluster associated with two oxygen vacancies V(o) along the [ 111] axis), the O(2-) ions in the ligand triangles are found to displace towards the neighbouring Vo by about 0.42 Angstrom due to the electrostatic attraction of the V(o). The above displacement is comparable with that (approximate to 0.36 Angstrom) obtained from neutron diffraction measurements and those (approximate to 0.24-0.37 Angstrom) based on the optical spectral analysis and crystal-field calculations in the previous works. Particularly, partial quenching of the spin-orbit (SO) coupling interaction (i.e., gamma(SO) approximate to 0.44) due to the dynamic Jahn-Teller effect (DJTE) and its influence on the g factors, which were ignored by the previous authors, are taken into account in the present work. The validity of the results is discussed. (C) 2004 Elsevier B.V. All rights reserved.

关键词: electron paramagnetic resonance (EPR);defect structure;crystal-fields;and spin Hamiltonian;Zr(3+);yttria-stabilized zirconia (YSZ);oxide fuel-cells;paramagnetic-resonance spectra;yttria-stabilized;zirconia;spin-orbit interaction;single-crystals;electron traps;ions;epr;fabrication;impurity

PVC／PP-g-MAH共混物X射线能谱微区分析

赵敏 , 姚子华 , 张荣珍 , 高俊刚

高分子材料科学与工程

用X射线能谱微区分析方法对PVC／PP-g-MA H共混物进行了研究,得到了共混物断面氯元素的面分布图,并对面分布图像进行了相分析,从 亚微观层次揭示了PVC／PP-g-MAH共混物的相结构。通过对元素面分布图的面积计算,研究 了共混组成与相容性的关系,并初步探讨了共混物力学性能与面分布的相关性。

关键词: X射线能谱 , 微区分析 , 面分布 , 相结构 , PV C/PP-g-MAH

Investigations of the g factors for the orthorhombic Co2+ center in YBa2Cu2.7Co0.3O7-x at room temperature

Physica C-Superconductivity and Its Applications

The anisotropic g factors g(x), g(y) and g(z) for the orthorhombic Co2+ center on the Cu(l) site in YBa2Cu2.7CO0.3O7-x at room temperature are theoretically investigated from the perturbation formulae of the g factors for a 3d(7) ion having low spin (S = 1/2) under octahedra with orthorhombic distortion. In these formulae, the contributions to the g factors from the orthorhombic crystal-fields as well as the ligand orbitals and spin-orbit coupling are taken into account based on the cluster approach. This center may be attributed to Co2+ located in a moderately compressed oxygen octahedron with additional orthorhombic distortion. The significant decline (characterized by the reduction factor y approximate to 0.13) of the energy separations due to the Jahn-Teller effect is suggested, by analyzing the experimental g factors. The calculated g factors based on the above contributions show good agreement with the observed values. In addition, the pronounced decrease in the intensity and the remarkable nonlinear increase in the g, of Co2+ EPR spectra as the temperature is lowered from room temperature to 150 K are also mentioned, in view of the opening of the spin gap due to antiferromagnetic interactions. (c) 2007 Elsevier B.V. All rights reserved.

关键词: electron paramagnetic resonance;crystal fields and spin hamiltonians;Co2+;YBa2Cu2.7Co0.3O7-x;atomic screening constants;d-orbital theory;paramagnetic-resonance;scf functions;spin gap;field;ions;0-less-than-or-equal-to-x-less-than-or-equal-to-0.30;yba2cu3o7-delta;la2-xsrxcuo4

Investigations of the electron paramagnetic resonance parameters and defect structures for Ni(2+) ions in CdX(2) (X = Cl, Br) crystals

Journal of Magnetism and Magnetic Materials

The high-order perturbation formulas of electron paramagnetic resonance (EPR) parameters (g factors g(parallel to), g(perpendicular to) and zero-field splitting D) for 3d(8) ions in trigonal octahedral clusters are established. These formulas contain the contributions not only from the crystal-field (CF) mechanism, but also from the charge-transfer (CT) mechanism (which is not considered in the widely used CF theory). From these formulas, the EPR parameters and the impurity-induced defect structures for Ni(2+) ions in CdX(2) (X = Cl, Br) crystals are studied. The calculated EPR parameters are coincident with the experimental values, and the defect structure of Ni(2+) impurity center obtained from the calculation is different from the corresponding structure in the host crystal. The sign of Q(CT) (Q = Delta g(parallel to), Delta g(perpendicular to), or D) due to CT mechanism agrees with that of the corresponding Q(CF) due to CF mechanism and the relative importance of CT mechanism (characterized by Q(CT)/Q(CF)) increases with increasing covalence of 3d(8) clusters and hence with raising atomic number of ligand X. So, in the explanations of the EPR parameters of 3d(8) (or other 3d(n)) ions in crystals with the heavy-element ligand ion (e. g., Br(-)), the calculated formulas based on the two-mechanism (CF and CT mechanisms) model are preferable to those based on only the CF mechanism in the CF theory. (C) 2008 Elsevier B. V. All rights reserved.

关键词: electron paramagnetic resonance (EPR);crystal- and ligand-field theory;charge-transfer mechanism;defect structure;Ni(2+);CdCl(2);CdBr(2);atomic screening constants;single-crystals;local-structure;scf;functions;spectra;transition;cadmium;cdcl2;epr