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381.
目的 针对包含模糊样本的复合抽检型产品开展贮存寿命评估。方法 针对批次产品中的出厂失效数据和贮存失效数据,开展批次数据的相容性检验。通过出厂失效样本数随机化处理,量化贮存过程中模糊样本的不确定性。将出厂试验数据作为先验信息,贮存过程中的出厂试验数据作为观测信息,基于Bayes融合方法,更新出厂失效概率。通过更新后的出厂失效概率,确定模糊样本的组成,筛选出贮存失效概率样本。针对筛选后的样本,基于样本量加权最小二乘方法,开展贮存寿命评估。结果 将所提方法应用于某弹箭产品案例,有效评估了批次出厂失效概率及其估计方差,并给出了可靠寿命评估结果。结论 所提Bayes评估方法融合了出厂抽检数据和贮存抽检数据,有效解决了含模糊样本的失效概率估计问题,提高了估计的精确性,基于样本量权重的加权最小二乘法,考虑了样本的可信程度,提升了方法的科学性。 相似文献
382.
This article examines whether it is possible to target vulnerable households within a geographically defined area. It looks first at the justification for targeting and then reviews recent practical experience in actually trying to reach vulnerable groups. As complex emergencies increasingly last longer, strategies to target vulnerable households are common in the protracted phase of the emergency. While this is often necessary because of a decline in resources, it is not always justified by an improvement in nutritional status or food security of the beneficiary population.
Common target groups are the poor and the malnourished, but in complex emergencies these are not always the most vulnerable. Moreover, recent practical experience has shown considerable difficulties in targeting the poor. Methods to target the poor rely on community-based relief committees, whose priorities are not necessarily the same as those of external agencies. This paper gives examples of such targeted assistance programmes in Kenya, south Sudan and Tanzania. The paper concludes that situations where targeting vulnerable households is justified and feasible are extremely limited. It is suggested that if targeting has to be done because of scarce resources, this should be done on a geographical basis and on the basis of nutritional status. Case-study material shows that it is essential to understand the political determinants of vulnerability and to design methods that will reach the most vulnerable. 相似文献
Common target groups are the poor and the malnourished, but in complex emergencies these are not always the most vulnerable. Moreover, recent practical experience has shown considerable difficulties in targeting the poor. Methods to target the poor rely on community-based relief committees, whose priorities are not necessarily the same as those of external agencies. This paper gives examples of such targeted assistance programmes in Kenya, south Sudan and Tanzania. The paper concludes that situations where targeting vulnerable households is justified and feasible are extremely limited. It is suggested that if targeting has to be done because of scarce resources, this should be done on a geographical basis and on the basis of nutritional status. Case-study material shows that it is essential to understand the political determinants of vulnerability and to design methods that will reach the most vulnerable. 相似文献
383.
研究了SUMMA罐采样-全二维气相色谱-飞行时间质谱法测定环境空气中有机硫化物。采用SUMMA罐采集样品,自动进样器进样,三级冷阱预浓缩样品,全二维气相色谱-飞行时间质谱法(GC×GC-TOFMS)测试分析,以较长的非极性柱Rxi-5MS(30 m×320μm×1.0μm)作为第一维柱,较短的中等极性柱DB-17MS(2.0 m×0.1 mm×0.1μm)作为第二维柱,对环境空气中的有机硫化物进行了定性定量分析。结果表明,该方法特性不仅满足方法学要求,而且比《空气和废气监测分析方法》(第4版)推荐的方法更加优异,能够准确、快速地检测环境空气中有机硫化物。 相似文献
384.
以珠海码头作为调查船舶防污漆使用影响的对象,分析了珠海周边海域码头内表层沉积物与海水中的重金属含量,以Cu元素为讨论重点,对其进行污染程度与潜在生态危害的评估。结果表明,码头内表层沉积物中Cu含量明显高于码头外沉积物,离市区较近的香洲码头和金沙滩码头内沉积物受到中等至较高程度的Cu污染,海岛东澳岛码头海水易流通,因此受污染程度较低。使用Hakanson生态危害指数法对沉积物进行评估的结果为低潜在生态危害,但码头内海水中Cu元素含量已高于生态安全限值。 相似文献
385.
基于相空间神经网络耦合模型的径流降尺度分析 总被引:3,自引:0,他引:3
基于混沌理论和神经网络理论,研究水文科学的尺度问题,将混沌神经网络分析方法应用于径流的降尺度分析。首先通过对年径流量分解到月径流量的分解系数的分析,证明了分解系数具有混沌特性;其次利用相空间BP神经网络模型对分解系数进行预测,并根据预测结果进行月径流量的降尺度计算。实例研究表明,用神经网络拟合分解系数相空间的相点演化非线性关系和用相空间神经网络模型对径流作降尺度分析是可行的。 相似文献
386.
Microbiologically influenced corrosion (MIC) is a microbial community assisted degradation of materials affecting chemical processing and oil and gas industries. MIC has been implicated in incidents involving loss of containment of hazardous hydrocarbons which have led to fires and explosions, economic and environmental impact. The interplay between abiotic environmental factors and dynamic biotic factors in MIC are poorly understood. There is a lack of mechanistic understanding of MIC and very few models are available to predict or assess MIC threat. Here we report on the development of a model to assess the susceptibility to MIC. The high-resolution model utilizes 60 independent nodes, including operational and historical failure analysis data, and is built by combining empirical relationships between the abiotic and biotic variables impacting MIC. Both static and dynamic Bayesian-network (BN) approaches were used to combine heuristic and quantitative states of variables to ultimately yield a susceptibility measure for MIC. A confidence-in-information metric was generated to reflect the amount of data used in the estimation. A susceptibility to MIC of 45%–60% was estimated by the model for ten different scenarios simulated using case-studies from literature. The susceptibility to MIC estimated by these scenarios was further interpreted in the context of these cases. This systems-based MIC model can be utilized as an independent estimator of susceptibility or can be incorporated as a sub-model within comprehensive safety threat assessment models currently utilized in industry. 相似文献
387.
为了解决矿用水泥基封孔材料的抗冲击性问题,利用DTM-1000落锤冲击试验机研究不同掺量聚丙烯纤维对水泥基封孔材料抗冲击性能的影响,试验更接近于工程实际。在试验基础上初步探讨纤维素对水泥基材料的抗冲击性能提升的机理,为了进一步提高水泥基封孔材料的抗冲击性,利用试验研究不同玻璃纤维和聚丙烯纤维的混合比例对封孔材料抗冲击性的影响。最终得出当聚丙烯纤维和玻璃纤维混合比在1.5∶1为最佳提高水泥基材料的抗冲击性的比例。矿用改性水泥基封孔材料的抗冲击性能试验对提高水泥基封孔材料的抗冲击性能研究具有重要的参考意义。 相似文献
388.
Michael Urban Stephan Hann Helmut Rost 《Journal of environmental science and health. Part. B》2019,54(2):98-111
In this study, a two-dimensional liquid chromatography tandem mass spectrometry method was developed and validated for the determination of pesticide residues and contaminants in whole wheat grains and oats. The samples were extracted with a mixture of acetonitrile and water and were injected into the two-dimensional LC-MS/MS system without any further clean-up or sample preparation. Samples were analyzed with four different matrix matched calibrations. Matrix effects were evaluated by comparing analyte signals in the respective matrix matched standard with the neat solvent standards. The final method was validated according to the current Eurachem validation guide and SANTE document. The number of successfully validated analytes throughout all three validation levels in oats and wheat, respectively, were as follows: 330 and 316 out of 370 pesticides, 6 and 13 out of 18 pyrrolizidine alkaloids and 7 out of 9 regulated mycotoxins. Moreover, both plant growth regulators mepiquat and chlormequat as well as the tropane alkaloids atropine and scopolamine met the validation criteria. The majority of pesticides showed limits of detection below 1?µg kg?1, pyrrolizidine alkaloids below 0.7?µg kg?1, tropane alkaloids below 0.2?µg kg?1, growth regulators below 0.7?µg kg?1 and mycotoxins below 8?µg kg?1 in both matrices. 相似文献
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390.