B/TiO2摩尔比对Al-TiO2-B系XD合成过程及其力学性能的影响

主要讨论了B/TiO₂摩尔比对Al-TiO₂-B系XD(热扩散反应)合成过程及其力学性能的影响。随着B/TiO₂摩尔比从0增加到2,Al基体的晶粒细化,反应产物 Al₂O₃分布的均匀性提高;棒状物Al₃Ti的量逐渐减少直至消失;同时,该反应系的实际燃烧温度下降,反应速度减小,反应产物的致密度提高,力学性能明显改善,其抗拉强度由224.5MPa上升到354.5MPa,延伸率由3.2 %升高到5.6 %,断口中棒状物Al₃Ti逐渐消失,形成的韧窝细小而密集。     

侵彻原理在气动矛穿越过程中的应用

以侵彻原理为基础建立起气动矛有效工作约束条件;在土动力学基础上,以饱和砂土为例建立起气动矛受土壤力的模型,分析了在不同土壤力学特性下,气动矛穿越土质及穿越过程中受土壤力大小的影响因素.     

Dilution effect of air stream on NO emission characteristic in H2/Ar counterflow diffusion flame

The dilution effect of air stream according to agent type on flame structure and NO emission behaviour is numerically analysed with detailed chemistry. The adopted fuel is hydrogen diluted with the argon of volume percentage 50 per cent and the volume percentage of diluents (H₂O, CO₂ and N₂) in air stream is systematically changed from 10 to 50. The radiative heat loss term, based on an optically thin model, is included to clearly describe the flame structure and NO emission behaviour, especially at low strain rates. The effect of dilution of air stream on the decrease of maximum flame temperature varies as CO₂>H₂O>N₂. The qualitative tendency of the numerically predicted mole fractions of H, O and OH is well described using a simplified formula, based on a partial equilibrium concept. It is seen that the H₂O addition to air stream is the most effective for reducing NO emission. In the case of the addition of H₂O and N₂ the NO emission behaviour is governed by the thermal effect and in the case of CO₂ addition it is governed by both the thermal effect and the chemical effect. But the chemical effect, which is mainly attributed by the Fenimore mechanism to the breakdown of CO₂, is much more predominant in comparison with the thermal effect. Copyright © 2002 John Wiley & Sons, Ltd.     

Large signal and noise properties of heterojunction AlxGa1-xAs/GaAs DDRIMPATTs

Simulation studies are carried out on the large signal and noise properties of heterojunction (HT) Al_xGa_1-xAs/GaAs double drift region (DDR) IMPATT devices at V-band (60 GHz). The dependence of Al mole fraction on the aforementioned properties of the device has been investigated. A full simulation software package has been indigenously developed for this purpose. The large signal simulation is based on a non-sinusoidal voltage excitation model. Three mole fractions of Al and two complementary HT DDR structures for each mole fraction i.e., six DDR structures are considered in this study. The purpose is to discover the most suitable structure and corresponding mole fraction at which high power, high efficiency and low noise are obtained from the device. The noise spectral density and noise measure of all six HT DDR structures are obtained from a noise model and simulation method. Similar studies are carried out on homojunction (HM) DDR GaAs IMPATTs at 60 GHz to compare their RF properties with those of HT DDR devices. The results show that the HT DDR device based on N-Al_xGa_1-xAs/p-GaAs with 30% mole fraction of Al is the best one so far as large signal power output, DC to RF conversion efficiency and noise level are concerned.     

Zn与Ti摩尔比对磁控溅射TiO2-ZnO异质复合薄膜微观结构及光催化性能的影响

利用磁控溅射离子镀技术制备系列TiO 2-ZnO异质复合薄膜,通过调节溅射靶材电流的大小控制薄膜中n（Zn）/n（Ti）值。采用AFM﹑SEM﹑Raman和XPS手段表征薄膜的微观形貌和结构,并以甲基橙作为光催化污染物,研究n（Zn）/n（Ti）对TiO 2-ZnO复合薄膜微观结构及光催化性能的影响。结果表明：随着n（Zn）/n（Ti）的增大,复合薄膜的晶粒尺寸先减小而后增大,其粗糙度也先增大而后减小,且均在n（Zn）/n（Ti）为1/9.3时达到极值;n（Zn）/n（Ti）对薄膜中元素Ti和Zn的价态无明显影响,均以TiO 2和ZnO形式存在,但比值的大小影响薄膜退火后TiO 2中锐钛矿/金红石异质结的数量;n（Zn）/n（Ti）越大,复合薄膜的光响应范围及吸光度越大,其响应光谱最大可扩展150 nm,波长可至450 nm,但异质复合薄膜光催化效果与其并不对应,取决于ZnO对TiO 2复合薄膜微观结构的影响,当n（Zn）/n（Ti）为1/9.3时,薄膜的降解速率最大,光催化能力最好。     

水性无机富锌底漆研制及其在重防腐领域的应用

用高模数硅酸钾溶液、锌粉及功能填料制备了水性无机富锌涂料,研究了水性无机富锌涂料性能特点,并与环氧富锌涂料进行了性能对比,阐述了水性无机富锌涂料在重防腐领域的应用情况。     

‘It’s possible to play the game marvellously and at the same time look pretty and be perfectly fit’: Sport,Women and Fashion in Inter-war Britain

Abstract

This article will examine the development of women’s increasing participation in sport and its impact on the subsequent emergence of sportswear for women in inter-war Britain. It will explore the public discourses which surrounded these women and their clothes in order to point up the complex nature of the problems women faced when making decisions about what to wear for sports activities.     

Optimum Cut of Separating Element as Function of Total Separation Factor and Mole Fraction of Component to be Separated

For a simplified model of separating elements where a total separation factor αβ is independent of values of cut ? (0≤?≤1), an optimum cut ?_opt in the sense that the cut makes a separative power δU maximum, was derived in terms of αβ, and a mole fraction x_F (0≤x _F≤1) of the component to be separated. When values of x^F is nearly equal to zero, the optimum cut ?^xF _opt?0 decreases and approaches to near 0, as the total separation factor becomes larger. On the contrary, when x_F is nearly equal to 1, the optimum cut ?^xF _opt?1 was found from calculation to be 1-?^xF _opt?0, and increases and approaches to near 1, as the total separation factor becomes larger. Moreover, in the case of x_F =0.5, the optimum cut is 0.5 regardless of αβ. Generally, the optimum cut ?_opt(x_F ) was solved to be in the form of a linear interpolation of the boundary values, ?x^F _opt?0 and ?x^F _opt?1.     

镁铝比例对造纸阻燃剂镁铝水滑石性能的影响

用共沉淀法合成了原始镁铝比例分别为3:1、2:1、1:1、1:2和1:3的水滑石试样,分析了其成分组成和晶体性质,并将其以浆内添加的方式应用于阻燃纸的抄造中,测试了其对阻燃纸性能的影响。结果表明,不同原始镁铝比例下所合成的镁铝水滑石均具有典型的水滑石的结构,粒径均在200nm左右且具有较高的正电荷密度。原始镁铝比例为3:1的水滑石的阻燃性最好,并且具有较高的白度,当其加入量为20%时,阻燃纸的白度为81.6%,相对空白纸样提高了3.68%,阻燃纸的氧指数为25.1%,达到难燃级。     

Chemical effects of added CO2 on the extinction characteristics of H2/CO/CO2 syngas diffusion flames

Chemical effects of added CO₂ on flame extinction characteristics are numerically studied in H₂/CO syngas diffusion flames diluted with CO₂. The two representative syngas flames of 80% H₂ + 20% CO and 20% H₂ + 80% CO are inspected according to the composition of fuel mixture diluted with CO₂ and global strain rate. Particular concerns are focused on impact of chemical effects of added CO₂ on flame extinction characteristics through the comparison of the flame characteristics between well-burning flames far from extinction limit and flames at extinction. It is seen that chemical effects of added CO₂ reduce critical CO₂ mole fraction at flame extinction and thus extinguish the flame at higher flame temperature irrespective of global strain rate. This is attributed by the suppression of the reaction rate of the principal chain branching reaction through the augmented consumption of H-atom from the reaction CO₂ + H→CO + OH. As a result the overall reaction rate decreases. These chemical effects of added CO₂ are similar in both well-burning flames far from extinction limit and flames at extinction. There is a mismatching in the behaviors between critical CO₂ mole fraction and maximum flame temperature at extinction. This anomalous phenomenon is also discussed in detail.