环境对MgB_2氧化过程中MgO晶须生长形状的影响

用扫描电镜研究了在 Mg B2 氧化过程中环境对 Mg O晶须生长形状的影响。仅有 Mg B2 时 ,在 80 0℃左右空气气氛中 ,可生长出纳米尺寸的 Mg O晶须。若把 Mg B2 添加到氧化铝陶瓷基体中 ,则生长成竹节状晶须。Mg O晶须生长形状的差别可能是由于氧浓度以及位错等因素造成的。     

流动注射区域采样法测定镀锌钝化液中高浓度锌

本文建立了流动注射二甲酚橙光度法测定镀锌纯化液中Ｚｎ￣２＋的自动分析方法。利用区域采样技术和调整管路参数自动完成对样品的上千倍稀释，确定了最佳分析条件并研究了干扰离子的影响及消除办法。所建方法仪器简单，分析速度为８４次／小时，变异系数（Ｚｎ￣２＋１６．０ｇ／Ｌ，ｎ＝２０）为１．Ｏ％，用于实际钝化液分析，相对误差小于±１０％。     

化学计量一级站量值传递工作及经验

介绍了国防科工委化学计量一级站为保证化学量值的准确与统一,在计量标准建立、标准物质研制、测量方法研究等方面所做的工作和经验。     

Thermogravimetric study on perovskite-like oxygen permeation ceramic membranes

The oxygen permeation properties of mixed-conducting ceramics SrFeCo_0.5O_3−δ (SFCO), Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO), La_0.2Sr_0.8Co_0.8Fe_0.2O_3−δ (LSCFO) and Ba_0.95Ca_0.05Co_0.8Fe_0.2O_3−δ (BCCFO) were studied by thermogravimetric method in the temperature range 600–900 °C. The results show that the oxygen adsorption rate constants k_a of all material are larger than oxygen desorption rate constants k_d and both k_a and k_d are not strongly dependent on temperature in the studied temperature range. The oxygen vacancy contents δ(N₂) and δ(O₂) in nitrogen and oxygen and their difference Δδ = δ(N₂) − δ(O₂) play an important role in determining the temperature behavior of oxygen permeation flux J_O2.     

纳米二氧化硅标准物质候选物的制备

以正硅酸乙酯和去离子水为反应物,氨水为催化剂,乙醇为共溶剂,通过沉淀反应制备窄分布的纳米二氧化硅标准物质候选物。利用扫描电子显微镜分析考察了氨水的用量对制备的二氧化硅粒度的影响。     

Improvement of the weighted essentially nonoscillatory scheme based on the interaction of smoothness indicators

The weighted essentially nonoscillatory scheme is improved by introducing new smoothness indicators that evaluate the interactions among the classical smoothness indicators suggested by Jiang and Shu. The effect of the key parameters in the new smoothness indicators on the scheme is systematically investigated. The improved scheme has smaller dissipation with larger weight assignment to the discontinuous stencils and higher numerical accuracy with weights closer to the ideal weights. To verify the theory, benchmark problems governed by the linear transport equation, the 1‐dimensional nonlinear Burgers equation, and the Euler equations are conducted and analyzed, respectively. Better computational performances both on numerical resolution and accuracy are shown in the comparisons with other classical weighted essentially nonoscillatory schemes.     

A numerical solution for the simultaneous disturbance decoupling and row-by-row decoupling problem

The numerical computation of the simultaneous disturbance decoupling and row-by-row decoupling problem is considered. Based on a condensed form for the system matrices the solvability of the simultaneous disturbance decoupling and row-by-row decoupling problem is reduced to the verification of an integer equality and the nonsingularity of a lower-dimensional constant matrix. The condensed form we use is computed using only orthogonal transformations, which can be implemented in a numerically stable way. Hence, it leads directly to an effective numerical method for solving the disturbance decoupling and row-by-row decoupling problem using existing tools such as LAPACK and Matlab. Our result complements existing geometric and structural approaches which are of a theoretical nature and are not suitable for numerical computation.     

A wire microcalorimetric study of catalytic ignition of methane–air mixtures over palladium oxide

Catalytic ignition and heat release of methane oxidation over a Pd wire covered with a 1–2 μm PdO surface layer were investigated by wire microcalorimetry over the temperature range of 600–770 K and pressure range of 0.5–4 atm. Ignition temperatures and heat release rates for different methane concentrations (1–4 vol.% in dry air) were determined, showing that the ignition temperatures decrease with increasing the methane concentration and increasing ambient pressure. At total pressure of 1 atm and 2% methane concentration, the global activation energy for the catalytic reaction is 21.5 ± 0.9 kcal/mol and 14.3 ± 0.2 kcal/mol in the temperature ranges of 600–670 K and 670–770 K, respectively. The reaction order for methane is 0.9 ± 0.1 over the temperature range of 630–770 K.