植物对金的萃取机理研究进展

特定的植物群落可以从含金属的土壤中萃取金属。植物萃取能开采无法用传统采矿方法开采的低品位矿石、矿化土壤和尾矿,还可以指示土壤基质中的金属含量,开拓新的采矿区域。植物萃取金属达到一定含量能产生“生物矿石”,生物矿石几乎不含硫且金属含量高于传统矿石,因此利用植物萃取积累金属是一种经济环保的采矿方式。国外对金的植物采矿技术研究已趋于成熟,国内相关的研究较少。本文综述了植物对金的萃取、积累机理研究进展,讨论了植物萃取金的应用和经济前景。     

考虑线路运行状态的智能电网调度自适应控制研究

当前智能电网调度均忽略线路运行状态的影响,其自适应控制过程存在缺陷。该文充分考虑影响输电线路运行状态的内在、外在因素,从自然老化、健康状态、天气条件以及负载电流四个方面分析线路运行状态;利用所确定的线路运行状态,从并网时与孤岛时线路潮流优化控制两方面,建立智能电网调度模型,并利用模型预测控制方法中的域参数设置,求解智能电网调度模型;从自适应控制时域长度与自适应控制间隔长度两方面,保证域参数恒定,实现智能电网调度的自适应控制。实例分析结果表明,所研究方法可充分考虑线路运行状态,实现智能电网调度的自适应控制,确保智能电网可靠、稳定的运行状态。     

Effect of ignition timing and hydrogen fraction on combustion and emission characteristics of natural gas direct-injection engine

An experimental study on the combustion and emission characteristics of a direct-injection spark-ignited engine fueled with natural gas/hydrogen blends under various ignition timings was conducted. The results show that ignition timing has a significant influence on engine performance, combustion and emissions. The interval between the end of fuel injection and ignition timing is a very important parameter for direct-injection natural gas engines. The turbulent flow in the combustion chamber generated by the fuel jet remains high and relative strong mixture stratification is introduced when decreasing the angle interval between the end of fuel injection and ignition timing giving fast burning rates and high thermal efficiencies. The maximum cylinder gas pressure, maximum mean gas temperature, maximum rate of pressure rise and maximum heat release rate increase with the advancing of ignition timing. However, these parameters do not vary much with hydrogen addition under specific ignition timing indicating that a small hydrogen fraction addition of less than 20% in the present experiment has little influence on combustion parameters under specific ignition timing. The exhaust HC emission decreases while the exhaust CO₂ concentration increases with the advancing of ignition timing. In the lean combustion condition, the exhaust CO does not vary much with ignition timing. At the same ignition timing, the exhaust HC decreases with hydrogen addition while the exhaust CO and CO₂ do not vary much with hydrogen addition. The exhaust NOx increases with the advancing of ignition timing and the behavior tends to be more obvious at large ignition advance angle. The brake mean effective pressure and the effective thermal efficiency of natural gas/hydrogen mixture combustion increase compared with those of natural gas combustion when the hydrogen fraction is over 10%. __________ Translated from Transactions of CSICE, 2006, 24(5): 394–401 [译自:内燃机学报]     

共轭有机高聚物PPQ薄膜非线性吸收的Z-扫描测量

用 Z-扫描方法在 532 nm波长测量了共轭高聚物 PPQ( polyphenylquinoxalines)薄膜的三阶光学非线性参数 ,发现其较强的非线性 (双光子 )吸收系数β≈ 0 .59cm/ MW。同时得到 Kerr系数n2 ≈ 9.5× 10 -10 esu,与用其他方法的测量结果较好地吻合。     

Molecular dynamics in chlorinated butyl rubber containing organophilic montmorillonite nanoparticles

The dynamic mechanical loss tangent (tanδ) of chlorinated butyl rubber (CIIR) shows an asymmetrical double-peak structure with a shoulder on the low-temperature side and a maximum on the high-temperature side, which are attributed to local segmental motion and Rouse modes, respectively. To study the effect of nanoparticles on these two different modes of molecular motion, organophilic montmorillonite nanoparticles (OMMT) were incorporated into CIIR. With the increase of OMMT weight fraction, a filler network is formed and becomes more and more compact in the CIIR matrix, which exerts significant effect on the molecular dynamics of CIIR. The maximum and the shoulder of the tanδ peak are both suppressed by the filler network, but the maximum is suppressed to a higher extent and finally even becomes lower than the shoulder at high filler loading. The temperature position of the maximum is also shifted toward lower temperature with the formation of the filler network, while that of the shoulder remains nearly constant. These phenomena can be interpreted in terms of the different restriction extents of the filler network on the different modes of molecular motion.     

黄河强烈游荡,严重淤积的原因

强烈游荡，严重淤积，是黄河下游河道的两个主要特征，也是黄河一切灾难的主要原因。前是断面太宽浅而直接引起的问题，是由来水来沙搭配关系决定的。水沙关系ｍ值小于２．５的属于大水来沙偏少而小水来沙偏多，滩地不易淤高而河槽易于淤浅，形成多汊宽线游荡性河流；反之，ｍ大于２．５的则形成单股窄深蠕动性河流。黄河下游ｍ约为２，故成为强烈游荡的宽浅河道。后则是河道输沙能力的形成问题，是由纵横断面的配合决定的，黄河     

三种常用润滑剂对聚氯乙烯熔合特性的影响

通过对硬脂酸钙、硬脂酸和石蜡3种常用润滑剂对聚氯乙烯（PVC）熔合行为的影响的研究,建议使用硬脂酸指数（SAI）作为评价润滑剂加工性能的指标,即在PVC配混料中只单独添加1.0份硬酯酸作为润滑剂,把其流变曲线的熔合扭矩、熔合时间等特征参数值作为基数（1.0）,然后以同样的实验条件测得同一配混料加入其他润滑剂或润滑剂组合的各特征参数值与之比较.     

Computer simulation of hydrogen physisorption in a Li-doped single walled carbon nanotube array

Hydrogen physisorption in a Li-doped single walled carbon nanotube (SWCNT) array is investigated by grand canonical Monte Carlo simulation. The optimization of hydrogen storage capacity at normal temperature and moderate pressure as a function of Li doping arrangement, doping-site position, doping ratio, and SWCNT array configuration is discussed and explained.     

Structural and electrical properties of Pb(Zr0.53Ti0.47)O3 films prepared on La0.5Sr0.5CoO3 coated Si substrates

PbZr_0.53Ti_0.47O₃ (PZT) thin films with thickness of 0.9 μm were prepared on La_0.5Sr_0.5CoO₃ (LSCO) coated Si substrates. Both PZT and LSCO were prepared by the sol–gel method. The concentration of LSCO sol was varied from 0.3 to 0.1 mol/L, which could modify the preferential orientation of PZT thin films and consequently affect the dielectric and ferroelectric properties. The LSCO electrode layers derived from lower sol concentration of 0.1 mol/L have much more densified structure, which facilitates the formation of (1 0 0) textured PZT films with smooth and compact columnar grains. PZT thin films prepared on the optimized LSCO films exhibit the enhanced dielectric constant and remnant polarization of 980 and 20 μC/cm², respectively.     

植物乳杆菌亚油酸异构酶的分离纯化及其性质研究

经硫酸铵分级沉淀、阴离子交换层析和凝胶过滤,由植物乳杆菌(LactobacillusplantarumL 2 9)分离纯化得到亚油酸异构酶,分子量为4 3ku。对其酶学性质进行研究,结果表明,温度37℃、pH 6 0时酶活性较高;Co2 + 、Fe2 + 可提高酶的活性,Cu2 + 、Zn2 + 则对酶活力有抑制作用;该酶作用于亚油酸的Km=2 5 3×10 -5mol/L ,Vmax=2 5 7×10 -8mol/ (min·mg)。