DTPA-MA／PVDF共混膜对Ni^2＋吸附性能的研究

采用溶液共混和相转移技术,经二乙烯三胺五乙酸（DTPA）和三聚氰胺（MA）共价键合作用,制备了具有螯合配位作用的改性聚偏氟乙烯共混膜（DTPA-MA／PVDF）,研究了DTPA-MA／PVDF共混膜对水溶液中Ni^2＋的吸附性能、吸附热力学及吸附动力学。结果表明,DTPA-MA／PVDF共混膜对Ni^2＋具有优良的吸附性能,吸附量随温度升高而下降。热力学参数△G^0〈0、△H^0〈0、△S^0〉0,证实了DTPA-MA／PVDF共混膜对Ni^2＋的吸附为自发的放热过程。DTPA-MA／PVDF共混膜对Ni^2＋的等温吸附较好地符合Langmuir等温吸附模型,D-R等温吸附表明该吸附过程为离子交换反应,该吸附过程的动力学符合准二级动力学方程。经4次吸附／脱附循环后,DTPA-MA／PVDF共混膜对Ni^2＋吸附量仍大于0．025mg／cm^2,脱附率仍超过90％。     

活性氧化镁除氟条件的研究

采用自制的活性氧化镁[XMgO.YMg(OH)2]对含氟饮用水进行除氟处理,试验表明:活化温度设定为440℃,煅烧中间产物碱式碳酸镁[Mg5(CO3)4(OH).24H2O]1.5h所得活性氧化镁0.3g投入100ml 5mg/L的含氟水,处理40min可使F-降至0.06mg/L;当活化温度设定430℃,保温1.5h时,0.4g的活性氧化镁处理pH=5～8的含氟水,净化后水含氟量为0.16～0.44 mgF-/L,除氟容量为1.21～1.14 mgF-/g,pH保持在8～9,有益于人体健康;当含氟水pH=9时,除氟容量降至0.51 mgF-/g;而当含氟水pH=3～4时,不适宜用活性氧化镁除氟.当原水浓度为12.5mgF-/L时,除氟容量为2.33mgF-/g,这个值高于文献中以层析硅胶为载体,活性氧化镁为吸附质,动态除氟容量1.72mgF-/g.     

氟离子透入预防学龄前儿童龋齿的效果评价

目的评价氟离子透入预防学龄前儿童龋齿的效果。方法随机抽取泰州市海陵区12所幼儿园3-4岁儿童共1283名为实验组,另外11所幼儿园3-4岁儿童共1198名为对照组,实验组使用NF-Ⅱ型护齿仪进行氟离子透入防龋治疗,对照组不做任何防龋措施。结果经过3年跟踪调查,实验组儿童每年患龋增长率呈逐年下降的趋势,而对照组儿童呈逐渐升高的趋势。实验组儿童的患龋率、龋均均低于对照组,有显著性差异（X~2=110.36;P〈0.005）。结论氟离子透入预防儿童龋齿效果显著,该方法防龋工作效率高,无创伤,安全卫生,避免交叉感染,幼儿易于接受,适宜在幼儿园群体防治。     

北京市近年来大气颗粒物污染水平变化规律

北京市大气颗粒物的污染状况一直是社会各界关心的话题。以2001年3月-2009年2月空气质量日报数据为依据,分析了近年来北京市大气颗粒物的质量浓度变化规律和空气质量等级的变化特征。结果表明:2001-2008年间,北京市环境空气质量总体上趋于好转;好于Ⅱ级天气的天数上升,低于Ⅲ级天数降低;冬季和春季空气质量比夏季和秋季差;好于Ⅱ级的天气占总天数的比例在夏季较高,秋季和冬季的比例差不多,春季最低。     

管理者持股、国家股及股权集中度与资本结构关系的实证研究——来自江苏省上市公司的经验数据

基于资本结构理论,结合江苏省上市公司特点,实证分析了管理者持股、国家股及股权集中度与资本结构之间的关系。结果表明：江苏省上市公司的管理者持股、国家股及股权集中度对资本结构有着重要影响,两者关系紧密。MHSR、A1和A10与资本结构呈负相关的;SHSR与资本结构呈正相关,但不显著。     

Static recrystallization process comparison of AZ31 magnesium alloy deformed by cold compression and cold forging

We deformed AZ31 magnesium alloys by cold forging and cold compression process, and investigated their static recrystallization kinetics during the annealing process. The results demonstrate that the relationship between the annealing time and the fraction of recrystal grains can be described by the Johnson-Mehl-Avrami-Kolmogorov （JMAK） equation. Based on the kinetics analysis, we calculated that the activation energy of recrystallization by cold forging and cold compression were about 53.5 kJ/mol and 85.0 kJ/mol, respectively. The activation energy of cold compression process was higher than that of the cold forging process because the latter had high-rate deformation, which caused more energy storage during deformation.     

Optimizing neural networks by genetic algorithms for predicting particulate matter concentration in summer in Beijing

We developed and tested an improved neural network to predict the average concentration of PM10 （particulate matter with diameter smaller than 10 μm） several hours in advance in summer in Beijing. A genetic algorithm optimization procedure for optimizing initial weights and thresholds of the neural network was also evaluated. This research was based upon the PM10 data from seven monitoring sites in Beijing urban region and meteorological observation data, which were recorded every 3 h during summer of 2002. Two neural network models were developed. Model I was built for predicting PM10 concentrations 3 h in advance while Model II for one day in advance. The predictions of both models were found to be consistent with observations. Percent errors in forecasting the numerical value were about 20%. This brings us to the conclusion that short-term fluctuations of PM10 concentrations in Beijing urban region in summer are to a large extent driven by meteorological conditions. Moreover, the predicted results of Model II were compared with the ones provided by the Models-3 Community Multiscale Air Quality （CMAQ） modeling system. The mean relative errors of both models were 0.21 and 0.26, respectively. The performance of the neural network model was similar to numerical models, when applied to short-time prediction of PM10 concentration.     

Sn_xNi_yCo_z负极材料的制备与性能

采用化学还原共沉积法制备SnxNiyCoz（x∶y∶z=4∶3∶1.5,4∶2∶1,4∶2∶2,4∶1∶2）三元合金材料,通过充放电测试对比材料的电化学性能。结果表明：呈较均匀分散性和表面疏松的Sn4Ni2Co材料的电化学性能最好;第20次循环,Sn4Ni2Co合金电极可逆容量为346mAh.g-1,库仑效率为94.2%。     

考察不同氮源对咔唑法测定透明质酸浓度的影响

通过在植物氮源的水溶液中不加入和加入透明质酸的对比实验,用两种处理方式考察了溶液中不同氮源对透明质酸浓度测定的影响,并对结果进行了讨论。     

镁表面耐腐蚀性能的研究

纯镁及AZ61镁合金在磷酸盐中形成转化膜后,分别在水、碱溶液及钒盐溶液中进行封闭处理.采用点滴腐蚀试验、孔隙率测试和模拟海水浸泡法对封闭后的膜层的耐腐蚀性能进行研究,用显微镜对腐蚀前后的微观形貌进行了观察,讨论了腐蚀机理.试验表明,在水中封闭的膜层的耐蚀性最好,膜层的孔隙率最低;纯镁的表面转化膜层的耐海水腐蚀性能比镁合金AZ61的表面转化膜层耐海水腐蚀性能好.