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991.
以凹凸棒粘土作为高水速凝固化充填材料的悬浮稳定剂,考察了不同制浆机械对凹凸棒粘土制浆率的影响。采用高剪切混合乳化机预制的1%凹凸棒粘土浆配制高水速凝固化充填材料甲、已料单浆可获得满意的悬浮稳定效果。其充填体结石抗压强度早期发展迅速,后期持续增长。采用此工艺,注浆料的材料成本仅增加2%。  相似文献   
992.
Rare earth exchanged Na–Y zeolites, H-mordenite, K-10 montmorillonite clay and amorphous silica-alumina were effectively employed for the continuous synthesis of nitriles. Dehydration of benzaldoxime and 4-methoxybenzaldoxime were carried out on these catalysts at 473 K. Benzonitrile (dehydration product) was obtained in near quantitative yield with benzaldoxime whereas; 4-methoxybenzaldoxime produces both Beckmann rearrangement (4-methoxyphenylformamide) as well as dehydration products (4-methoxy benzonitrile) in quantitative yields. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream (TOS) studies show decline in the activity of the catalysts due to neutralization of acid sites by the basic reactant and product molecules and water formed during the dehydration of aldoximes.  相似文献   
993.
UHMWPE微粉辐照接枝MAH的研究   总被引:2,自引:0,他引:2  
采用辐照方法在超高分子量聚乙烯(UHMWPE)微粉表面接枝马来酸酐(MAH),用水在UHMWPE膜上的润湿角作为目标函数,依据试验优化设计和灰色系统控制理论,研究了辐照剂量、微粉的粒度和MAH单体的浓度对润湿角的影响。研究结果表明:所考查的三因数对润湿角的影响程度是不同的,影响顺序为:辐照剂量>UHMWPE微粉粒度>MAH浓度。从关联角度看,三因素对润湿角的关联度没有明显的差别,表明在UHMWPE微粉辐照接枝的反应过程中,所考查的三因素对接枝反应过程的影响是互相促进、互相影响、互相补充的。由于辐照剂量在UHMWPE的接枝反应中是比较重要的因素,因此在接枝反应中要严格控制其辐照剂量,其次注意微粉粒度,适当调整单体加入量。至于交互作用,尚需进一步进行研究探讨。  相似文献   
994.
本文根据溶液缩聚基本原理及反应过程的基本事实,用随机过程方法,得到缩聚产物分子量分布函数,并对分子量及其分布的控制作了讨论。  相似文献   
995.
利用HCl在甲醇中稀溶液的活度系数,通过Pitzer的缔合模型,关联出298.15K HCl在甲醇中的缔合常数Kx=1.7×10~2,然后利用HCl在甲醇中浓溶液的活度系数关联出近程作用单参数,进而推算溶剂甲醇的活度系数及溶液总压,均得到满意的结果,说明HCl甲醇浓溶液的热力学关联必须考虑HCl的部分离解效应。  相似文献   
996.
Summary Polysilanes with an optically active alkoxy group, i.e., (S)-(+)-2-butoxy, (R)-(-)-2-butoxy, (S)-(-)-2-methyl-1-butoxy, and (S)-(+)-3,7-dimethyl-1-octoxy, at the terminal positions, the chiral carbon centers of which were located at the α, β, and γ positions relative to the oxygen, respectively, were prepared, and the effect of the position of chiral center of the terminal optically active group on the induction of optical activity in polysilanes was investigated. The circular dichroism (CD) spectra of these polymers showed positive Cotton signals around 340 nm at temperatures below -20 °C, but the intensities were small, indicating that the optically active groups at the terminal positions have some ability, albeit small, to induce optical activity to the polysilanes. Further, the optically active (S)-(+)-2-butoxy and (R)-(-)-2-butoxy groups did not control the helical sense direction of the polymers, despite the different chiral stimuli from the 2-butoxy groups introduced to the terminal positions. To control the helical structure of polysilanes by the use of optically active terminal groups, appropriate optically active groups are required.  相似文献   
997.
A field experiment was conducted in Gampela (Burkina Faso) in 2000 and 2001 to assess the impact of organic and mineral sources of nutrients and combinations thereof in optimising crop production in till and no-till systems and to assess the economic benefit of these options. The study showed that under conditions of rainfall deficiency, the use of a single organic resource at an equivalent dose of 40 kg N ha−1 better secured crop yield than the application of an equivalent amount as urea-N, while a combination of organic resources and fertiliser was better in increasing crop yield than the application of the same N amount in the form of urea. In a year of rainfall deficiency, a mix of organic resources and fertiliser in both till and no-till systems increased crop water use efficiency, with the result that the farmer was able to purchase only half of the normal quantity of N fertiliser to obtain a higher yield that he would have done when all of the N was supplied in the form of urea. Under conditions where soil N is deficient, an economic benefit was achieved when urea was combined with easily decomposable organic material (e.g. sheep dung); mixing the urea at a dose of 40 kg N ha−1 with maize straw was not sufficient in alleviating the negative interaction due to the enhanced N immobilisation. The results demonstrate that the use of N fertiliser alone was risky and that a higher yield, with the accompanying economic benefit, was scarcely achieved under the prevailing rainfall conditions. The application of soil and water conservation measures can contribute greatly to increasing the economic benefit of mineral, organic or combined organic and mineral-derived nutrient application under semi-arid conditions.  相似文献   
998.
Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO4 were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO4 reached its maximum conductivity, 1.51 × 10?5 S cm?1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007  相似文献   
999.
通过对客户机/服务器模式和浏览器/服务器模式的比较,选择浏览器/服务器模式组建了基于Internt/Intranet的远程橡胶加工网络测控系统,并介绍了系统的开发模式、方法和注意事项。  相似文献   
1000.
张钦辉  刘波  周实  徐玉恒 《硅酸盐学报》2007,35(11):1526-1530
采用提拉法生长出光学质量的Nd:ZnWO4,Ce:ZnWO4和Ce:Nd:ZnWO4晶体.通过X射线衍射仪对晶体样品的微观结构进行了分析.测试了晶体的吸收光谱、电感耦合等离子体原子发射光谱和荧光光谱.根据Judd-Ofelt理论计算出Nd:ZnWO4晶体中Nd3 的强度参数为:Ω2=6.820 2×10-20 cm2,Ω4=0.463 3×10-20 cm2,Ω6=0.443 5×10-20 cm2.研究了Ce3 和Nd3 之间的能量转移现象.结果表明:Nd3 在850 nm激发时产生上转换发射峰位于474 nm和572 nm处,分别对应于2G9/2,4K13/2到基态能级4I9/2跃迁,计算出该峰的自发辐射几率为1 360 s-1,荧光寿命为7.353×10-4 s,发射截面为0.905 9×10-23 cm2.  相似文献   
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