Cement-stabilized fly ash base courses

Various demonstration projects have been carried out in The Netherlands with cement-stabilized fly ash as a base course. Usually these courses were made of 100 parts by mass of fly ash; 10 parts by mass of cement; 20 to 30 parts by mass of water. However, the projects were not quite successful since delamination was observed, and long-term strength, after a period of six years of performance, appears to be much smaller than expected on the basis of preliminary laboratory research. A model for pozzolanic reaction of fly ash recently developed by Fraay and Bijen pointed out that the reactivity of fly ash is influenced greatly by the pH value of the pore water. A pH of at least 13 is required to initiate fly ash pozzolanic reaction in a Portland cement environment. Pore water extraction measurements showed that the pH of cement-stabilized fly ash often has a substantially lower value. In this high-volume fly ash application the effect of the acidity of fly ash is much greater than in ordinary concrete with cement replaced by fly ash up to 30%. By addition of NaOH and/or sodium silicate to the mixing water, the pH value can be increased above the ‘threshold’ value.

Tests were carried out with different types of class-F fly ashes and with different NaOH concentrations in the mixing water. The results show an increase in compressive strength of up to 300% depending on the type of fly ash, and a substantial decrease in the rate of water absorption.     

Honeywell先进控制技术的应用

介绍了Ｈｏｎｅｙｗｅｌｌ先进控制技术ＲＭＰＣＴ在大庆石化公司炼油厂（简称炼油厂）重油催化装置吸收稳定系统上的应用，包括方案设计，阶跃测试和模型辨识等，并论述了Ｈｏｎｅｙｗｅｌｌ先进控制技术ＲＭＰＣＴ的功能及特点以及采用该技术后所能产生的社会效益和经济效益。     

迅速发展的我国合成材料制造业

从合成材料制造业的产量、产值、行业结构、生产企业、消费５个方面，阐述了该行业的发展状况，并预测了合成材料在近期内的需求。     

Synergistic thermal stabilization effect of polyamide/melamine on polyoxymethylene

The synergistic thermal stabilization effect of polyamide (PA) and melamine (MA) on polyoxymethylene (POM) was studied by isothermal weight loss analysis and nonisothermal thermogravimetric analysis, which showed that the complex stabilizer PA/MA was more efficient than the single‐use formaldehyde absorbents MA or PA in improving the thermal stability of POM. The nonisothermal degradation kinetics study further demonstrated the synergistic thermal stabilization effect of PA/MA on POM. The mechanical property investigation showed that the addition of a proper amount of PA or the proper reduction of MA content improved the impact strength of POM. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2387–2391, 2005     

一种便携式天然伽马能谱测量仪及其稳谱原理

介绍了一种便携式天然伽马能谱测量仪的框图原理。在稳谱方面，首先利用刻度过的温度与光电倍增管负高压的关系曲线，控制光电倍增管的负高压，使仪器系统增益稳定，达到稳谱粗调的目的；其次利用天然伽马射线特征峰的固定谱位，对采集到的数据曲线的能量轴重新标定，实现了把脉冲幅度计数率曲线直接转换为伽马射线能谱曲线，省去了同类仪器稳谱细调的过程。因此，在同样的统计涨落误差条件下，该方法大大地提高了仪器的数据采集速度。     

Effect of Organic Surface Load on Process Performance of Pilot-Scale Algae and Duckweed-Based Waste Stabilization Ponds

Removal efficiencies in pilot scale algae-based ponds (ABPs) and duckweed-based ponds (DBPs) were assessed during two periods of 4 months each. During Periods 1 and 2, the effect of low and high organic loading was studied. A linear correlation between ponds organic surface loading rates and the corresponding biochemical oxygen demand (BOD) removal rates was observed in both systems. For both periods, higher BOD and total suspended solids (TSS) removal efficiencies were found in DBPs compared to ABPs. Nitrogen removal rates (λr) in ABPs were linearly correlated with BOD surface loading rates (λs,BOD) and nitrogen loading rates (λs,N), while in DBPs, N removal rates were almost constant irrespective of λs,BOD or λs,N. Overall N removal rate in the algae system was significantly higher than that in duckweed system. Organic loading had no effect on total phosphorus removal efficiency in both systems. Higher P removal efficiency was achieved in the duckweed system than in the algae system. In ABPs as well as DBPs, fecal coliforms were better removed during low organic loading in comparison with high organic loading. During the two operational periods, higher fecal coliform removal efficiency in the algae system than in the duckweed system was observed.     

滨江公园护岸破坏原因分析

滨江公园护岸在施工过程中发生护岸的沉降及向外位移,危及结构整体稳定和安全。依据现场沉降和位移观测资料,结合边坡稳定分析表明,地基压缩变形和深层滑动是造成护岸沉降和水平位移的根本原因,建议采用抗滑桩进行除险加固。     

Post spinning modification of PAN fibres — a review

Post spinning modifications play an important role in improving the mechanical properties, density and structure of PAN fibres. Post spinning modifications affect the thermal and kinetic parameters during stabilization and alter the overall stabilization mechanism. The present paper presents a review of the different types of post spinning modifications previously attempted on PAN fibres and the effects of these modifications on the resulting carbon fibres.