Ab initio study of the effects of Ag/Mn doping on the electronic structure of LiFePO_4

Based on density functional theory (DFT) of the first-principle for the cathode materials of lithium ion battery, the electronic structures of Li(Fe1-xMex)PO4 (Me = Ag/Mn, x = 0―0.40) are calculated by plane wave pseudo-potential method using Cambridge serial total energy package (CASTEP) program. The calculated results show that the Fermi level of mixed atoms Fe1-xAgx moves into its conduction bands (CBs) due to the Ag doping. The Li(Fe1-xAgx)PO4 system displays the periodic direct semiconductor characteristic with the increase of Ag-doped concentration. However, for Fe1-xMnx mixed atoms, the Fermi level is pined at the bottom of conduction bands (CBs), which is ascribed to the interaction be-tween Mn(3d) electrons and Fe(4s) electrons. The intensity of the partial density of states (PDOS) near the bottom of CBs becomes stronger with the increase of Mn-doped concentration. The Fermi energy of the Li(Fe1-xMnx)PO4 reaches maximum at x = 0.25, which is consistent with the experimental value of x = 0.20. The whole conduction property of Mn-doped LiFePO4 is superior to that of Ag-doped LiFePO4 cathode material, but the structural stability is reverse.     

碱土金属化合物晶格能计算的新方法——离子贡献法

本文提出了一种计算碱土金属化合物品格能的新方法——离子贡献法。该方法只需本文提供的离子贡献值即可计算得到晶格能,而不需要任何实验数据。对碱土金属氧化物、卤化物、氢化物、氢氧化物、硫酸盐、碳酸盐、磷酸盐等十九类75种化合物的计算结果表明,计算值与实验值之间的一致性令人满意,计算结果的平均相对误差仅0.79%,小于目前已有的所有方法的计算误差。     

离子选择电极法测定牙膏中的含氟量

采用氟离子选择电极法测定氟含量，具有简便、快速、灵敏、选择性好等优点，最低检出浓度为0.05mg／L，适用浓度范围宽，在测定牙膏含氟量中取得良好效果。     

金属工件内部残余应力的振动消除研究

本文针对传统的消除金属工作内部残余应力的热时效处理法的不足，从激振角度，运用材料力学、动力学中的振动理论等知识，并通过大量试验验证，研究了振动消除应力的方法－－振动时效法的原理及其有关问题。说明这种新的方法具有节能、高效等一系列优点。     

震区中小跨径桥梁墩柱配筋率取值范围

为研究配筋率对钢筋混凝土桥梁延性抗震性能的影响,并在不同设防烈度对主筋配筋率的合理取值进行细分。以钢筋混凝土桥梁为研究对象,通过拟静力模型试验与有限元数值分析的方法,研究竖向钢筋(主筋)配筋率对桥墩延性的影响,提出典型桥墩的多级性能水平量化指标;并探究在氯离子侵蚀的恶劣环境下,不同配筋率对桥梁抗震性能所带来的影响,从而对氯离子侵蚀环境下的震区中小跨径桥梁墩柱配筋率取值范围提供参考建议。结果表明：考虑氯离子侵蚀作用下的恢复力模型能够较好地反映刚度的退化特性,墩柱的最佳配筋率取值范围为1.11%～2.72%;当加速度为0.3g(g为重力加速度)时,仅从配筋率的角度已无法满足墩柱的损伤指标,建议采用减隔震体系进行抗震设计,如采用延性体系时配筋率不得小于2.64%。研究结果可为中小跨径连续桥梁抗震设计提供参考。     

回流充气法处理中,高量含铁地下水的研究

本文介绍一种深井回流充气工艺,它兼具充氧和除铁综合性能的新型工艺形式,能改善含铁地下水的过滤性能.在此基础上提出了深井回流充气稳定期的概念,建立了深井回流充气系统中氧量的平衡关系.通过正交试验,提出了处理中、高量含铁地下水的推荐工艺流程和工艺参数.采用χ—射线衍射方法测试了井内铁泥和成熟滤料表面滤膜的成分和形态,分析了"充气"和"过滤》两过程中的除铁机理.     

贮氢合金的开发与研究进展

贮氢合金是近年来开发的一类新型高性能材料。本文介绍了贮氢合金的开发和研究的最新进展,论述了它在氢的提纯、热泵、空调、压缩机和镍—氢化物电池等高技术领域中的应用前景。     

Effect of lanthanum ions on tRNAphe structure: Imino proton NMR spectroscopy

The effect of lanthanum ions on the structural and conformational change of yeast tRNA Phe was studied by 1H NMR. The results suggest that the tertiary base pair (G-15)(C-48), which was located in the terminal in the augmented dihydrouridine helix (D-helix), was markedly affected by adding La 3+ and shifted 0.33 downfield. Based pair (U-8)(A-14), which is associated with a tertiary interaction, links the base of the acceptor stem to the D-stem and anchors the elbow of the L structure, shifted 0.20 upfield. Another imino proton that may be affected by La 3+ in tRNA Phe is the tertiary base pair (G-19)(C-56). The assignment of this resonance is tentative since it is located in the region of highly overlapping resonances between 12.6 and 12.2. This base pair helps to anchor the D-loop to the TΨC loop.     

微量钠离子浓度测量方法

从能斯特方程出发,考虑到国产ＣＮａ电极的离散性,给出实用的数学模型,并用ＭＣＳ－５１单片机构成高性能价格比的微量钠离子检测仪。     

Pathways of proton transfer in the light-driven pump bacteriorhodopsin

The mechanism of proton transport in the light-driven pump bacteriorhodopsin is beginning to be understood. Light causes the all-trans to 13-cis isomerization of the retinal chromophore. This sets off a sequential and directed series of transient decreases in the pK_a's of a) the retinal Schiff base, b) an extracellular proton release complex which includes asp-85, and c) a cytoplasmic proton uptake complex which includes asp-96. The timing of these pK changes during the photoreaction cycle causes sequential proton transfers which result in the net movement of a proton across the protein, from the cytoplasmic to the extracellular surface.