氨气在4A分子筛上的吸附动力学研究

采用固定床中4A分子筛吸附的方法,研究不同NH3浓度和吸附床温度条件对分子筛吸附效果的影响.通过吸附穿透曲线和吸附床中的吸附平衡质量测定分子筛的吸附容量,并利用Langmuir等温方程对吸附等温线进行拟合.结果表明:分子筛的吸附容量随吸附床温度升高而降低,随吸附质初始浓度升高而升高,吸附平衡符合Langmuir方程.     

具R（X）〈2的自反Banach空间中的M不动点性质

对于Banach空间中的两个有界闭凸集,首先引入一个新的度量,并且在这种新的度量下重新定义非扩张映射,称它为肘非扩张映射,并且证明在一个自反的Banach空间中,当R（X）〈2时,它有肘不动点性质．     

Novel fixed‐carrier membranes for CO2 separation

A new membrane material having two kinds of CO₂ carriers was obtained. Composite membranes were prepared with the material and support membranes. The facilitated transport of CO₂ through these membranes was performed with pure CH₄ and CO₂ as well as CH₄/CO₂ mixtures containing 50 vol % CO₂. The results show that the membranes possess better CO₂ permeance than that of other fixed carrier membranes reported in the literature. In the measurements with pure gases, at 26°C, 0.013 atm of CO₂ pressure, the membrane with polysulfone support displays a CO₂ permeance of 7.93 × 10^?4 cm³ /cm² s cmHg and CO₂/CH₄ ideal selectivity of 212.1. In the measurements with mixed gases, at 26°C, 0.016 atm of CO₂ partial pressure, the membrane displays a CO₂ permeance of 1.69 × 10^?4 cm³ /cm² s cmHg and CO₂/CH₄ selectivity of 48.1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2222–2226, 2002     

Manipulation of gasification coal feed in order to increase the ash fusion temperature of the coal enabling the gasifiers to operate at higher temperatures

Coal is a crucial feedstock for South Africa’s unique synfuels and petrochemicals industry and used by Sasol as a feedstock to produce synthesis gas via the Sasol-Lurgi Fixed Bed Dry Bottom (FBDB) gasification process. The ash fusion temperature (AFT) gives detail information on the suitability of a coal source for gasification purposes, and specifically to which extent ash agglomeration or clinkering is likely to occur within the gasifier. Ash clinkering inside the gasifier can cause channel burning and unstable operation.Sasol-Lurgi FBDB gasifiers are currently operated with the philosophy of adding an excess of steam to the process to control the H₂/CO ratio of the syngas produced, but indirectly also to control the maximum gasifier temperature below the AFT of the coal. An opportunity exists to increase the AFT of the coal fed to the gasifiers by adding AFT increasing minerals to the coal blend before it is fed into the gasification process. For the aim of this study a South African coal source was investigated, as being used by the gasification operations in Secunda.With the specific aim of this study, to increase the AFT, the determination of the AFT of the coal blends where acidic components such as silica (SiO₂), alumina (Al₂O₃) and titania (TiO₂) were added was conducted. The Al₂O₃ had the biggest and most significant effect on the AFT with the least addition to the coal blend. The effect of SiO₂ and TiO₂ were very similar, but the effect was much smaller and further Al₂O₃ was needed to increase the AFT to a similar AFT level in comparison to the SiO₂ used. Kaolinite, roof and floor components (containing mainly Al₂O₃ and SiO₂) were also added, also showing an increase in the AFT with up to 4 mass% addition. Another observation was that the AFT was non-additive (not a linear weighted calculated average) and not the weighted average AFT as was expected for the other coal properties such as the ash content, for example. The ash slagging characteristics is a non-additive property of individual coal sources in the blend and therefore difficult to predict.In general it can be concluded that the unique opportunity exists to increase the AFT, was tested, proven and mechanistically outlined in this study on the coal source fed to the Sasol-Lurgi FBDB gasifiers. The AFT can be increased to >1350 °C by adding AFT increasing minerals or species to the coal blend before it is fed into the gasification process. By increasing the AFT, the direct effect will be that steam consumption can be decreased, which in turn will improve carbon utilization.     

Fixed‐time synchronization for complex‐valued BAM neural networks with time delays

In this paper, the fixed‐time synchronization for complex‐valued bidirectional associative memory (BAM) neural networks with time delays is studied. Based on the fixed‐time stability, the Lyapunov functional method and some inequality techniques, a new criterion is presented to guarantee that the addressed systems achieve synchronization in fixed time and a more accurate estimation independent of the initial conditions is given for the settling time. Meanwhile, a new nonlinear delayed controller different from the existing ones is designed. In the end, two numerical examples are provided to illustrate the effectiveness of the obtained result.     

适用于飞行自组网的闲置时隙预约TDMA协议

在飞行自组网中,固定时隙分配时分多址接入（TDMA）协议存在闲置时隙无法成功使用的问题。通过对TDMA协议引入闲置时隙预约机制,提出一种支持业务优先级传输机制的闲置时隙预约TDMA协议。采用短帧长的方式满足协同与控制业务的低时延传输需求,并利用闲置时隙预约机制允许节点使用闲置时隙传输感知业务,从而满足感知业务的高吞吐量传输性能要求。仿真结果表明,与CF-MAC和CTMAC协议相比,该协议能够在降低传输时延的同时,有效提高信道利用率和网络吞吐量。     

热轧齿轮齿形拉尖的影响因素

针对工艺参数对热轧齿轮齿形拉尖的影响,采用有限元数值模拟分析方法,引入无量纲量影响因子,对不同工况下热轧齿轮齿顶相对拉高进行了方差分析,并对不同影响因素进行了显著性分析.结果表明,轧辊转速和摩擦系数对齿形拉尖的影响最为显著,其次为进给速度和轧辊齿顶圆角,而轧制温度和坯料材料对齿形拉尖的影响并不显著.通过提高坯料材料的变形抗力或减小摩擦系数,均可以削弱热轧齿轮的齿形拉尖现象,且减小摩擦系数的影响效果更为明显,进一步验证了影响因素显著性分析的准确性.     

钢管混凝土拱抗冲击影响因素

为研究钢管混凝土拱的抗冲击力学性能,在试验结果验证的基础上,采用有限元分析方法,研究了集中冲击荷载作用下矢跨比、混凝土强度等级、钢材屈服强度和冲击质量4个因素对钢管混凝土拱抗冲击力学性能的影响.计算结果表明:相同冲击能量下,钢管混凝土拱存在着一个矢跨比阈值f,当试件矢跨比大于f时,试件的抗冲击性能基本相同;与钢管混凝土梁、柱类似,增大混凝土强度对提高试件的抗冲击性能影响不明显,而增大钢材屈服强度可以使试件的抗冲击性能明显改善;随着冲击质量增加,试件的冲击力峰值变化不大,挠度变大,冲击持续时间变长,冲击质量与跨中挠度成线性关系.     

外钳式管道坡口机定圈的有限元分析及结构优化

外钳式管道切割坡口机是油气集输与抢险作业的重要设备,而定圈是外钳式管道切割坡口机的核心部件,其截面形状及大小是影响外钳式管道坡口机可靠性和便携性的关键因素。为此,采用现代设计手段,建立了定圈的三维计算模型,并按照设备在工作中的受力情况进行有限元分析,对不同截面形状和面积的定圈进行结构对照优化。结果表明:合理的定圈截面形状不仅可有效提高定圈的刚度,增加设备的可靠性,同时还能减小定圈重量,提高携带性能。     

基于Mindlin解的单桩侧阻应力系数埋深效应初探

Geddes解采用的集中荷载,起始点在弹性半无限空间表面.应用于工程实践时,计算埋深较浅桩在土中产生应力的影响误差较小,随着建筑群桩基础埋置越深,有的已超35 m,误差会更大.此外基桩侧阻模式分布比较复杂,常常需要分解为几个基本侧阻形式,有的侧阻应力起点并不在地表.以Mindlin解为基础,参考Geddes解,将积分起点设在距离空间表面一定深度a处,从而得到具有埋深a的Geddes解析解,并与原Geddes解进行了简单比较.相对于沿袭Geddes解的做法,本计算式显然更为精确.