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131.
喷射沉积Al-8.5Fe-1.3V-1.7Si(8009)耐热铝合金板坯是由基体金属和孔隙、少量颗粒边界的氧化膜组成的,微观组织缺乏良好的冶金结合,直接采用轧制使其致密化产生塑性变形,在工艺上存在极大的难度,轧制时易出现板坯表面裂纹及边裂。本文研究了8009合金的包套轧制、交叉横轧工艺,实验结果表明:采用包套轧制、交叉横轧工艺,有效地改善了喷射沉积板坯的轧制成形性能,成功制备出厚度为0.6~1.0mm的薄板。 相似文献
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《Land Degradation \u0026amp; Development》2017,28(8):2432-2445
We combine high‐resolution soil sampling with lead (Pb) analyses (concentrations and stable isotopes) in two temperate podzols, together with previous data obtained with selective Al and Fe dissolution techniques. We aim to assess how atmospheric Pb is incorporated into the soils during pedogenesis. Partial least squares modelling for Pb concentrations shows that the podzolization process has the largest effect on Pb concentration (80·3% of the variance). The proportion of inorganic secondary compounds, the input of fresh organic matter from the soil surface and the relative abundance of Fe versus Al are responsible for a small part of the Pb concentration variance. Lead isotopic composition (206Pb/207Pb ratios) depends on soil organic matter content either fresh/poorly humified (57·3% of the variance) or humified (24·7% of the variance). The Pb linked to inorganic compounds and the overall podzolization process play a minor role in isotopic signature (5·3 and 3·7% of the variance respectively). Soil pH appears to be the controlling variable of the different transport and retention mechanisms. The relatively low isotopic ratios observed in spodic horizons result from geogenic Pb released through the preferential dissolution of the isotopically distinct most weatherable minerals of the parent material in the eluvial horizons, which undergoes downward mobilization. An accurate knowledge of soil reactive components and formation mechanisms is essential to a correct diagnose of the scope of Pb pollution and a more effective design of remediation strategies. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
135.
Research on the disease called shimao zheng, which had resulted in widespread fleece-eating and shedding by sheep and goats in the Haizi area of Akesa County of Gansu Province of China, was carried out by both laboratory studies and pathological observations. There was a marked deficiency of sulfur in the wool and tissues of the affected animals. The pathological changes were mainly loss of fleece, exposure of the skin, keratinization of the epidermal cells, narrowing and reduced numbers of the fleece follicles, and fewer sebaceous glands and sweat glands. Histologically, there was atrophy of the striated and cardiac muscles and of the epithelium of the convoluted tubules of the kidney, together with a glomerulonephritis. The disease was considered to be a local nutritional and metabolic disorder, probably mainly caused by sulfur deficiency. 相似文献
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太湖地区地表水氮污染源的评论 总被引:11,自引:0,他引:11
The nitrogen (N) pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system (GPS). The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region. 相似文献
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D. Fowler I. D. Leith J. Binnie A. Crossley D. W. F. Inglis T. W. Choularton M. Gay J. W. S. Longhurst D. E. Conland 《Water, air, and soil pollution》1995,85(4):2107-2112
Continuous monitoring of cloud and rain samples at three mountain sites in the UK has allowed consideration of the long term impact of the enhancement of the wet deposition of pollutants by orographie effects, specifically the scavenging of cap cloud droplets by rain falling from above (the seeder-feeder effects). The concentration of the major pollutant ions in the cloud water is related to the relative proximity of each site to marine and anthropogenic sources of aerosol. In general, the concentrations of major ions in precipitation at summit sites exceed those in precipitation to low ground nearby by 20% to 50%. Concentrations in orographie cloud exceed those in upwind rain by between a factor of five and ten. The results are consistent with seeder-feeder scavenging of hill cloud by falling precipitation in which the average concentration of ions in scavenged hill cloud exceed those in precipitation upwind by a factor of 1.7 to 2.3 for sulphate and nitrate respectively at Dunslair Heights and 1.5 to 1.8 for sulphate and nitrate at Holme Moss. The results suggest that the parameterisation of this relationship with scavenged feeder cloud water concentrations assumed to exceed those in seeder rain by a factor of two for the production of predictive maps of wet deposition in mountainous regions of the U.K. is satisfactory. 相似文献
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Our research examined the role of acidic deposition as a primary, or predisposing, stress on 8–12 week old cuttings of hybrid poplar (Populos deltoides x nigra). Firstly, we examined the role of acidic deposition as a primary stress in terms of physiological indicators (gas exchange, chlorophyll concentrations, chlorophyll-a fluorescence). Our results suggest that levels of acid precipitation of > pH 3.5 did not act as a primary stress. Secondly, we hypothesized that acidic deposition could act by making trees more susceptible to drought. An acid treatment exposure regime was followed by 3–4 days of drought stress in a controlled environment. Preexposure to acidic deposition did not increase the degree, or rate of appearance, of water stress as indicated by predawn xylem pressure potentials and leaf conductances. Examination of cuticular water loss from excised leaves suggested that this parameter was insensitive to acidic deposition from pH 3.0 to 5.5. 相似文献