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881.
有色金属铸件有效浇注时间计算公式探讨 总被引:6,自引:2,他引:4
重点阐述了铝、铜合金铸件生产中较常应用的五种浇注时间计算公式的特点和存在的不足,分析了这几种公式在各自的材质铸件使用范围内出现的缺点及不足。研究及阐述了铝、镁合金和铜、锌合金铸件各自的通用有效浇注时间计算公式,及其良好的适用性和宽阔的适用范围。 相似文献
882.
贵金属浆料测评系统概述 总被引:1,自引:0,他引:1
贵金属浆料品质的测评系统由新近发布的浆料规范和系列测试方法国家标准组成。测试方法包括固体含量,粘度,细度,方阻,分辨率,可焊性和耐焊性,附着力的测定。同时与国内外相关技术比较,分析和评价系统的技术特点。 相似文献
883.
在差示热分析仪上安装1个高稳定度的直流电路,对DTA的试样支架结构作相应改造,建成一套适合于测量贵金属细丝电阻-温度特性曲线的装置。该装置的工作温度范围为室温-1500℃。 相似文献
884.
铝及铝合金在亚铁盐溶液中电解着色 总被引:3,自引:3,他引:0
铝及铝合金在含有2g/L的SB添加剂的150~180g/LH2SO4溶液中进行阳极氧化,得到多孔且无阻挡层的氧化铝膜。该膜在含有FesO4的溶液中进行交流电解着色,得到系列棕色膜。关键词##4铝;;阳极氧化;;电解着色;;硫酸亚铁;;棕色膜 相似文献
885.
Eino Mälkönen John Derome Hannu Fritze Heljä-Sisko Helmisaari Mikko Kukkola Anna Saarsalmi Maija Salemaa 《Nutrient Cycling in Agroecosystems》1999,55(3):239-268
The results from four compensatory fertilization experiments located at different distances (0.5, 2, 4 and 8 km) along a heavy metal deposition gradient extending from the Harjavalta Cu-Ni smelter in SW Finland are presented. The experiments were established in middle-age Scots pine stands growing on dryish sites of sorted glaciofluvial sediments. The soil type in all the experiments is ferric podsol. The treatments in the experiments consisted of liming, a powdered slow-release mineral mixture and stand-specific fertilization which comprised at least methylene urea and ammonium nitrate.Monitoring of deposition and soil solution and studies on soil chemical and microbiological properties, on the nutrient status of trees and needle litterfall, on fine root dynamics and on the growth of the tree stands were carried out during a 5-year period.There was a severe shortage of exchangeable Ca and Mg in the organic layer of the most polluted stands. Although the uppermost mineral soil layer had relatively high exchangeable Ca and Mg concentrations, the trees were not able to utilize these nutrient reserves presumably due to the toxic effects of Cu and Ni on the plant roots and mycorrhizas.The treatments that included limestone markedly decreased the Cu and Ni concentrations in the soil solution and soil organic layer, presumably due to immobilisation through precipitation or absorption. The Ca and Mg concentrations correspondingly increased, which certainly contributed to the partial recovery of fine root and stand growth. The powdered mineral mixture and the combination of methylene urea and ammonium nitrate had no short-term effect on the microbial biomass and activity. All the fertilizer treatments increased volume growth in the most polluted stand. The stand-specific fertilization increased needle mass in heavily polluted stands, but the response of the needle mass to fertilizer treatments was low in the less polluted stands. No clear evidence was found to support the role of nutrient status in tree resistance. 相似文献
886.
Neyman Konstantin M. Vent Stefan Rösch Notker Pacchioni Gianfranco 《Topics in Catalysis》1999,9(3-4):153-161
The interaction of isolated Pd atoms and of a square Pd4 cluster with the (001) surface of MgO is investigated by means of density functional (DF) calculations. The oxide surface
is represented by various model clusters and the effect of the surrounding is taken into account by embedding the cluster
in point charges and total ion model potentials. The calculations are performed at the relativistic level using the Becke–Perdew
exchange-correlation functional. The adsorption properties determined with this computational scheme are compared with other
DF results. The bonding of the Pd atoms and clusters with the surface is analyzed in terms of charge density difference plots.
It is found that the polarization of the metal adsorbate due to the surface electric field provides an important contribution
to the metal–oxide adhesion energy.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
887.
Environmental impact of mining activity on the pollution of the Medjerda River, north-west Tunisia 总被引:2,自引:0,他引:2
E. A. Jdid P. Blazy S. Kamoun A. Guedria B. Marouf S. Kitane 《Bulletin of Engineering Geology and the Environment》1999,57(3):273-280
In the Fej Hcine mining area of north-west Tunisia, the Medjerda River and its principal tributary, El Melah, are polluted
by heavy metals and arsenic. The geochemical studies undertaken have indicated pronounced falls in the concentrations of metals
since the mining activities ceased, although the river sediments still contain higher levels than the local host rocks, particularly
arsenic and zinc. At the Tunisia/Algeria border, arsenic concentrations in the Medjerda waters can exceed 1 mg/l. Leaching
tests on samples of ore, flotation tailings and an arseniferous mass indicate that whilst Zn, Pb, Cu and Cd concentrations
do not exceed 1 mg/l in the leachate solutions, arsenic levels reach 5, 344 and 9,400 mg/l respectively. The study has shown
that the pollution originates not only from the mining activities but also from the mineral occurrences present in the mining
district and from another source within Algeria.
Received: 18 May 1998 · Accepted: 24 June 1998 相似文献
888.
889.
随着锂离子电池行业的快速发展,废旧锂离子电池数量将呈现爆炸式增长趋势,从废旧锂离子电池中资源化回收有价金属对经济和环境都具有显著意义。为了实现废旧锂电池过程中各种有价金属(锂、钴、镍、锰等)高效无害化分离回收,针对各种金属离子的湿化学分离技术进行系统性总结,介绍了各类技术在浸出液中金属离子分离的应用工艺和发展现状,主要包括化学沉淀法、溶剂萃取法、吸附分离法、膜分离法和电沉积分离法等。分析了废旧锂电池有价金属分离过程中各类技术优缺点、关键性问题和发展趋势,表明当前分离技术关键点在于有价金属性质相似导致提纯困难、分离试剂昂贵导致工艺成本加大等,各种分离技术发展趋势在于开发新型低成本、环境友好的分离技术。 相似文献
890.
基于柠檬酸-铕金属有机纳米配体聚合物(citrate/europium lanthanide coordination polymer nanoparticles,Cit/Eu LCP NPs)构建快速检测肉品汤煲中5’-肌苷酸(inosine-5’-monophosphate,5’-IMP)的荧光探针。研究结果表明,5’-IMP对Cit/Eu?LCP?NPs有良好的荧光猝灭作用。在最佳条件下,该荧光探针在5’-IMP?2.5~200?μg/mL的质量浓度范围内呈现出良好的线性关系,检出限为0.17?μg/mL,且具备良好的抗干扰、稳定性和重复性。为了验证方法可行性,将该方法应用于实际鸡汤样品中的5’-IMP检测,测得加标回收率为97.85%~103.95%,可为快速检测肉品汤煲中5’-IMP提供新的思路和方法。 相似文献