Spatial distribution of chromium in soils contaminated by chromium-containing slag

To evaluate the metal chromium (Cr) contamination of soil at a chromium-containing slag site by ferrochromium production, the contaminated sites, under slag heap, in the vicinity of slag heap and arable soils near the outlet of sewer channel, and unpolluted site 5 km away from one ferroalloy plant in Hunan Province, China, were selected. The concentrations of total Cr and water soluble Cr in bulk soil samples and profile depth samples were determined. The results show that the soils in the vicinity of slag heap have the highest total Cr content followed by the soils under the slag heap and near the outlet of sewer channel of the factory. The mean concentrations of total Cr in the top soils at above three contaminated locations exceed the critical level of Secondary Environmental Quality Standard for Soil in China by 3.5, 5.4 and 1.8 times. In most Cr polluted soils, total Cr has a relative accumulation in soil depth of 40-60 cm, but this trend is not found in unpolluted soils. The average concentrations of water soluble Cr (Ⅵ) in top soils under slag heap and in the vicinity of slag heap are 176.9 times and 52.7 times higher than that in the uncontaminated soils, respectively. However, water soluble Cr (Ⅵ) contents in soils near sewer channel are all low and the values are close to that in the uncontaminated soils. Although water soluble Cr (Ⅵ) content in soil profiles decreases with soil depths, it in soils under slag heap maintains a high level even at a depth of 100-150 cm. The results imply that the transportation of Cr (Ⅵ) can result in a potential risk of groundwater system in this area.     

Inhibitory effect of Cr（Ⅵ） on activities of soil enzymes

To evaluate the influence of various Cr(VI) concentrations (0.05, 0.25, 0.50, 1.00 and 2.00 g/kg) on the activity of soil enzymes, the activities of catalase, polyphenol oxidase, dehydrogenase, alkaline phosphatase in soils were investigated in the incubation experiment with a period of 35 d. The results indicate that all the tested Cr(VI) concentrations significantly inhibit dehydrogenase activity by over 70% after 35 d. The activity of alkaline phosphatase is slightly inhibited during the whole experiment except for on the day 7. Cr(VI) has no obvious effect on the activity of catalase in soil. On the contrary, Cr(VI) stimulates the activity of polyphenol oxidase. The results suggest that dehydrogenase activity can be used as an indicator for assessing the severity of chromium pollution. Foundation item: Projects(2006AA06Z374, 2007AA021304) supported by the National High-Tech Research and Development Program of China; Project(2008SK2007) supported by the Key Program of Science and Technology of Hunan Province, China     

多盘转子系统的随机响应灵敏度分析

对于具有偏心质量、轴承刚度和阻尼的三盘转子系统,采用有限元法建立转子系统的动力学方程,研究圆盘质心径向位移随时间变化的趋势,采用蒙特卡罗(Monte Carlo)法进行随机抽样,得到圆盘径向位移的均值与标准差的变化曲线.结合灵敏度技术,推导出系统响应的灵敏度公式,获得了转子系统随机响应相对于随机参数的灵敏度变化曲线,研究了随机参数的统计特性对圆盘径向位移的影响规律.分析结果表明,在转子系统中对其径向位移影响较大的因素是圆盘的质量与偏心距.因此,在实际生产中应严格控制这些参数.     

瘤细胞内长间距胶原与原始肌节的鉴别诊断

本文着重讨论了效率南内长间距胶原与原始肌节的鉴别诊断。我们的研究表明，瘤细胞内长间距胶原与原始肌节十分相似，但在超微结构上又有许多不同之处。（１）含长间距胶原的瘤细胞富含粗面内质网，而线粒体和糖原少；含原始肌节的瘤细胞线粒体和糖原丰富，粗面同质网少。（２）长间距胶原中Ｚ线样结构呈“一”字型、粗细一致，而在原始肌节中则为不规则型，粗细不一，形状各异，排列混乱。（３）构成长间距胶原的细丝为直径约１０ｎ     

双极型64×32位集成电路存贮器模型

一、引言随着计算技术和集成电路技术的发展,要求提供一种存取周期性短,读写速度快,使用方便灵活的存贮体能与运算部件的工作相匹配,作为慢速大容量存贮器的缓冲。目前双极集成电路存贮器已被广泛采用。我们和半导体器件研制单位的同志们一起,以毛主席的实践论为武器,通过大量试     

亚毫微秒逻辑电路(F100K)性能的分析

<正> 引言随着计算机系统向高速大型机方向发展,对集成电路性能的要求也越来越高。MECL10K 电路是目前广泛使用的 ECL 电路系列,这种电路典型门的传输延迟为2.5ns,而且由于它没有电源,温度补偿性能,对于工作环境的要求是比较严格的。在研制高速大型计算机系统时,必须考虑这方面的要求。F100K 电路是现在世界上已能大量生产并已用于大型计算机系统的亚毫微秒 ECL电路系列。它的典型门的传输延迟为0.7ns,比起 MC10K 来要快得多。因此,在系统     

基于谐波理论的轴孔特征误差分离与表面形貌预测

轴孔零件作为机械产品中应用最为广泛的核心零件趋于向高精度、高强度、多元化方向发展,其质量控制和质量评价至关重要。针对轴孔零件的形位误差分离问题,在研究了传统的误差分离技术和谐波理论的基础上,提出了轴孔零件形位误差的谐波分离方法。根据在零件上测得的周期性数据,分析了各次谐波误差的产生机理,提出了控制低次谐波误差的措施。利用空间点矢量法获得了测量点实际位置,结合拟合算法对零件表面形貌进行了预测。通过实验验证了形位误差谐波分离和表面形貌预测方法的准确性和合理性,为轴孔零件的表面质量评价和预测提供一种新的思路。     

飞机角接头尺寸参数对其强度的影响分析

为了确保飞机角接头的强度和结构的安全性,采用ANSYS软件建立了角接头的力学分析模型,研究了在水平拉力作用下,尺寸参数如紧固件孔直径、接头端部厚度、圆角半径对角接头连接强度的影响规律。通过仿真分析,确定了角接头的危险位置,通过对不同工况的分析,改进了底板紧固件孔的布局,降低了29.74%的最大Von Mises应力,从而为角接头的底板紧固件孔布局设计提供一种参考依据。     

孔缝结构对电磁屏蔽的影响

介绍屏蔽设计原理和屏蔽效能的计算及测试方法,针对电磁兼容性设计中孔缝结构对电磁屏蔽效能的影响进行分析,在屏蔽效能设计阶段提出了实用的设计方法和建议,指出合理设计对电磁屏蔽具有十分重要的意义。通过仿真和工程实例中线路和结构设计两方面的技术介绍,分析孔缝效应的形成机制和应采取的有效技术手段。     

腐植酸钾对黄冠梨土壤肥力的影响

研究腐植酸钾对黄冠梨土壤中腐植质、氮、磷、钾含量的影响。结果表明：腐植酸钾显著提高土壤腐植质含量和速效氮、磷、钾含量,对土壤中全量养分影响不大。腐植酸钾具有改良土壤,增加肥效作用。