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排序方式: 共有113条查询结果,搜索用时 15 毫秒
61.
为了定性和定量的描述药柱燃面、密度、燃速等因素对固体火箭发动机(SRM)内弹道性能的影响,在HTPB复合固体推进剂老化研究和SRM内弹道性能预估研究的基础上,分析了HTPB推进剂因贮存老化引起的SRM内弹道性能偏差,建立了性能偏差计算模型。结果表明,老化引起的药柱燃面、密度、燃速变化以及侵蚀燃烧引起的喷喉烧蚀是SRM贮存过程中影响内弹道性能偏差的直接因素,老化引起它们微小的波动都会引起发动机内弹道性能较大的偏离。在发动机寿命预估和进行可靠性分析时必须考虑老化对内弹道性能的影响。 相似文献
62.
高晟 《安全.健康和环境》2012,12(1):42-45
介绍了危险与可操作性分析(HA-ZOP)的程序以及在溴化丁基橡胶装置的应用,根据分析结果提出相应的安全措施。 相似文献
63.
冯滨 《安全.健康和环境》2012,(10):43-45,50
介绍HAZOP分析方法在聚丙烯装置的应用,根据分析结果,有效地识别聚丙烯装置运行过程中存在的风险,并提出了降低风险的措施和建议。 相似文献
64.
可持续发展评价指标(体系)及其确定方法的探讨 总被引:23,自引:0,他引:23
通过对目前已有的可持续发展指标体系的研究,指出现有指标体系忽略了可持续性内涵、环境的限制作用、社会公平性及经济增长的影响作用等主要内容.提出采用离差法来计算可持续发展评价指标.建议采用限制型指标、发展型指标、协调型指标来评价系统的可持续性;标准值或参考值采用反映系统不可持续性状态的底线值以及反映整个人类状况的全球、区域或国家现时平均值.同时还提出了不可持续性标准值、不可持续状态、远离不可持续状态、迈进可持续发展过程等概念.强调单项指标的重要性,指出单项指标离差度对系统可持续性的指示作用. 相似文献
65.
通过实验验证了盐酸副玫瑰苯胺分光光度法测定大气中SO2的标准方法中,用EDTA代替CDTA去掩蔽金属离子的干扰是可行的,即方便,又经济。 相似文献
66.
Whitfield Slund M Celejewski M Lankadurai BP Simpson AJ Simpson MJ 《Chemosphere》2011,83(8):1096-1101
1H NMR metabolomics can be used to assess the sub-lethal toxicity of contaminants to earthworms by identifying alterations in the metabolic profiles of contaminant- exposed earthworms in contrast to those of healthy (control) individuals. In support of this method this study sought to better characterize the baseline metabolic profile of healthy, mature earthworms of the species, Eisenia fetida, which is recommended for both acute and sub-lethal toxicity testing for soil contaminants. Profiles of D2O-buffer extracted metabolites were determined using 1H NMR spectroscopy and both inter-individual metabolic variability and pair-wise metabolic correlations were assessed. The control earthworm extracts exhibited low overall inter-individual metabolic variability, with a spectrum-wide median relative standard deviation (%RSD = standard deviation/mean × 100) of 14%, which suggests that the metabolic profile of E. fetida earthworms is well controlled in laboratory conditions and supports further use of this organism in environmental metabolomics research. In addition, strong positive correlations were detected between the levels of maltose, betaine, glycine, and glutamate as well as between the levels of lactate, valine, leucine, alanine, lysine, tyrosine, and phenylalanine which had not previously been reported. Since comparison of pair-wise metabolic correlations between control and treated organisms can reveal changes in the underlying pattern of biochemical relationships between the metabolites, identification of these significant metabolic correlations in control earthworms provides an additional characteristic that may be applied to delineate between control and treated earthworms in future NMR-based metabolomic studies. 相似文献
67.
Cigarette smoke is a risk factor for human health, and many studies were conducted to investigate its adverse effects on humans and other mammals. However, since large amounts of cigarette products are produced and consumed, it is possible that tobacco chemicals can end up in aquatic environments through several routes, thus influencing aquatic organisms. In this study, the presence of tobacco-specific nitrosamine (TSNA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in aquatic environment was demonstrated. Since toxic effects on and distribution patterns of tobacco chemicals in aquatic organisms were rarely studied, after results of an acute toxicity pretest were obtained, experiment was conducted to investigate the bioaccumulation pattern of NNK and distribution patterns of its metabolites, mainly 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), in NNK-treated freshwater planarians, Dugesia japonica. Results from in vivo and in vitro studies showed that NNK was readily converted to NNAL through the carbonyl reduction in bodies of NNK-treated planarians. Tissue concentrations of both chemicals increased in time- and dose-dependent manners. Furthermore, we examined the end products of NNK/NNAL α-hydroxylation in NNK-treated planarians, but only 1-(3-pyridyl)-1,4-butanediol was detected, suggesting that NNK metabolism in planarians partially differs from that in mammalian systems. This is the first report on NNK metabolism in an aquatic organism and can be used as a foundation for developing freshwater planarians as a new in vivo model for the study of NNK toxicology in the future. 相似文献
68.
Árpád Ambrus Zsuzsanna Horváth Zsuzsa Farkas István J. Szabó Enikő Dorogházi Mária Szeitzné-Szabó 《Journal of environmental science and health. Part. B》2013,48(4):229-244
The supervised trial datasets (1950), consisting of a minimum of five residue values and selected by the experts of FAO/WHO Joint Meeting on Pesticide Residues for recommending maximum residue levels between 1997 and 2011, were evaluated to obtain information on the typical spread of residue values in individual datasets. The typical relative standard deviation, CV, of field-to-field variation of pesticide residues was about 80%. The spread of residues in datasets is independent from the chemical structure of pesticides, residue level, pre-harvest interval and number of values in the datasets. The CV ranges within the Codex commodity groups and between groups overlapped and their difference were not statistically significant. The number of residues below the limit of quantification (LOQ) affects the CV at various extents depending on the ratio of LOQ/R mean. The combined uncertainty of the highest residue in a dataset significantly affects the CV of the dataset. The lowest and intermediate ones have less influence. The residues in different fields receiving the same treatment vary within large range: 55%, 72%, 78%, 86% and 89% of the 25,766 residues values were, respectively, within 3, 4, 5, 6 and 7 times the median value of the corresponding dataset. 相似文献
69.
70.
以全国两次湿地资源调查数据为基础,借助ArcGIS可视化平台,采用标准差椭圆和空间自相关等方法,分析中国湿地变化的空间格局,揭示湿地变化的空间关联性.结果表明:①中国湿地存在明显的动态变化和分区特征,总湿地椭圆中心向正西方向移动,自然湿地与人工湿地的空间分异程度在增加;②人工湿地变化不存在显著的空间自相关性,自然湿地变化则存在显著的空间正相关性,表现出空间集聚状态,并产生了1个热点集聚区分布于青海、西藏和四川,1个独立热点区分布在内蒙古和1个冷点区分布在河南.Moran''s I统计表明自然湿地变化表现出空间变化上的连续性,人工湿地变化表现为空间随机性;③自然湿地保护效果表现出湿地保护高效区、低效区和不稳定区三大类分级特征,可细分为5小类.Moran统计能有效识别自然湿地变化的空间关联性,划定湿地保护效果,从而有利于明确湿地保护的地区差距,为系统制定湿地保护与管理决策提供依据,也为湿地保护效果评定研究提供新方法应用. 相似文献