水土保持工程施工阶段的设计变更

通过对水土保持工程施工阶段设计变更原因的分析，指出水土保持生态工程施工阶段变更的必要性和建设、监理单位对变更管理的重要性。通过对变更设计的程序和原则进行的分析，阐述了变更设计涉及的几个主要问题。     

朗江电站水库洪水调度探讨

文章根据朗江水库工程实际情况,介绍了水库洪水成因及特性,通过洪水设计、调洪演算计算分析,指出了闸门操作程序,对"以峰控制"的中、小型水库的洪水调度具有一定的参考价值。     

Breast feeding: Mo, As, Mn, Zn and Cu concentrations in milk of economically poor Indian tribal and urban women

The breast milk of 86 economically poor Indian women was analysed by neutron activation analyses for Mo, As, Mn, Zn, and Cu concentrations. The colostrum of 10 tribal women contained 0.27 microgram Cu/g, 2.1 micrograms Zn/g, 19.9 ng Mn/g, 0.73 ng As/g and 5.4 ng Mo/g, whereas 19 urban women had corresponding concentrations of 0.91 microgram Cu/g, 7.3 micrograms Zn/g, 15.3 ng Mn/g, 0.5 ng As/g and 15.3 ng Mo/g. A survey of mature milk between 1 and 6 months, 6 and 12 months and 1 and 2.5 years indicated decreasing concentrations of Zn and Mo, but increasing Mn concentrations as the post-partum period progressed. Malnourished infants received breast milk containing less Cu, Zn and Mn than those who were better nourished and of the same age group. The results, therefore, imply the necessity of supplementing breast feeds in the economically poorer groups.     

铁路信号电缆断线故障在线监测与定位方法研究

铁路信号电缆是保证列车安全运营的重要组成部分,其故障严重影响列车的安全运营;由于其经多个分线盒接线柱连接的敷设特点,存在中间接头过多,致使传统的电缆故障检测方法应用受到了极大的限制;为此,通过在电缆中间分线盒的备用芯线对接线柱中接入固定阻值的电阻,将备用芯线对形成闭合回路网络,然后在线监测其电阻阻值,利用回路阻值的变化来反映电缆状态,并以在线监测备用芯线对代替在用芯线对,进而在不影响正常列控信号传输的情况下实现了信号电缆的故障在线监测;经实际测试,有效地解决了铁路信号电缆断线故障的在线监测及定位。     

铝合金挤压铸造用电磁泵定量浇注技术

为了开发研制铝合金挤压铸造用电磁泵定量浇注控制系统,应用试验研究和数学分析的方法,建立了电磁泵流量计算的数学模型,开发了电磁泵定量浇注控制程序.结果表明,电磁泵定量浇注挤压铸件质量精度达到2%.该项技术在铝合金挤压铸造中的应用能有效提高铸件的品质和质量精度,提高材料的利用率和铸件生产率.     

High-temperature oxidation of aluminum electroplated Fe-Mn alloys

Austenitic Mn-Al alloys (20–32 W/O Mn, 7–10 Al, 2–3 Si, 1C) were found to have satisfactory oxidation resistance up to 950°C under isothermal conditions in air. Surface enrichment of aluminum is a necessary condition for obtaining an almost pure alumina scale for uses at higher temperatures. Four different Mn-steels were Al-coated by the Capuano electroplating process. In all the steels there was an increase in the hot-oxidation resistance. The best results were obtained with steels containing both Al and Si, and this for temperatures up to 1100°C. No spalling was noticed during rapid cooling of the test pieces. Silicon was found to act as a diffusion barrier to outward iron diffusion. It appears that there is formation of a pure, thin film of alumina from the matrix which interacts with the aluminum diffusing from the superimposed, coating for the formation of good bonds.     

萘降解菌的筛选及降解性能的初步研究

微生物降解是多环芳烃从土壤和水环境中消失的主要途径。本文从加油站废油排放口附近被污染土壤中筛选到两种降解萘的混合菌H1、H2并从中分离出一株纯菌C_1。研究发现,利用纯无机盐培养基加萘作为唯一碳源要比加入其它营养物质的培养基对于筛选萘降解菌更为有利。H_1、H_2和C_1均能以萘为唯一碳源生长,在萘初始浓度为1000mg/L的纯无机盐培养基中培养40h后,培养液中微生物数量分别增长10倍以上,利用气相色谱测得萘的降解率都达到99．6％以上。     

Effect of the matrix crystallinity on the percolation threshold and dielectric behavior in percolative composites

Through the use of polyethylenes with different crystallinities as matrices, the effects of the matrix crystallinity on the percolation threshold and dielectric behavior of percolative composites have been investigated. The results suggest that the percolation threshold is negatively related to the matrix crystallinity, whereas the enhancement of the dielectric constant is positively related to the matrix crystallinity. A two‐dimensional diagram is proposed to illustrate such relationships. In addition, it has been found that the insulator–conductor transition is much flatter in low‐crystallinity‐matrix‐based composites, and this may be favorable for preparing threshold composites with a high dielectric constant and a low loss tangent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Morphologies and microstructures of tree-like carbon produced at different reaction conditions in a CVD process

Centimeter-size multi-branched tree-like carbon structures have been generated by the catalytic chemical vapor deposition of toluene using ferrocene as the catalyst precursor and investigated by means of SEM, TEM, and EDX. It is found that a temperature of 1000-1200 °C and a carrier gas flow rate of 1000-2500 ml/min are necessary for the generation of the carbon trees. Their morphologies and microstructures change greatly with the changing reaction conditions. The fractal dimensions of the trees are calculated to quantitatively investigate the influence of different reaction temperatures on the morphologies.