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81.
The improvement of safety in the process industries is related to assessment and reduction of risk in a cost-effective manner. This paper addresses the trade-off between risk and cost related to standby safety systems. An age-dependent unavailability model that integrates the effects of the test and maintenance (T&M) activities as well as component ageing is developed and represents the basis for calculating risk. The repair “same-as-new” process is considered regarding the T&M activities. Costs are expressed as a function of the selected risk measure. The time-averaged function of the selected risk measure is obtained from probabilistic safety assessment, i.e. the fault tree analysis. This function is further extended with inclusion of additional parameters related to T&M activities as well as ageing parameters related to component ageing. In that sense, a new model of system unavailability, incorporating component ageing and T&M costs, is presented. The testing strategy is also addressed. Sequential and staggered testings are compared. The developed approach is applied on a standard safety system in nuclear power plant although the method is applicable to standby safety systems that are tested and maintained in other industries as well. The results show that the risk-informed surveillance requirements differ from existing ones in technical specifications, which are deterministically based. Moreover, the presented approach achieves a significant reduction in system unavailability over a relatively small increase of total T&M costs. 相似文献
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83.
溶解性有机物(DOM)与区域土地利用的关系:基于三维荧光-平行因子分析(EEM-PARAFAC) 总被引:1,自引:0,他引:1
溶解性有机物(DOM)是水体质量的综合性指标,反映了流域内经济发展和治理保护等多方面因素,可为流域水体保护提供依据.本研究采集了宁波市4个不同城市化程度的区域内的河流样本,运用三维荧光结合平行因子分析法(EEM-PARAFAC)对水体中DOM进行解析,探讨了区域土地利用与DOM的关系.结果表明城市化在含量和组成两方面影响了流域水体中DOM的特征.城市区域(DOC=3.18 mg·L-1)和城乡结合区域(DOC=7.45 mg·L-1)水体中DOM的浓度远高于城市化程度较低的农村区域(DOC为2.16~2.62 mg·L-1,ANOVA,P<0.001).EEM-PARAFAC解析得到7个荧光组分,主要可归为类腐殖质和类蛋白质类物质.其中,城市区域DOM以类腐殖质物质为主,占比达到61.3%;而城乡结合区域由于受到更多的生活污水排放影响,类蛋白质物质的比例最高为59.4%;相比之下,农村区域虽然DOM浓度相对较低,但类腐殖质物质占比达63.6%~65.7%,面源污染是主要原因.主成分分析表明城市化发展对水质具有重要影响,在城市化初期污染主要来源于生活和工业污染源,当城市化到一定水平污染物更多来源于路面径流.本研究表明EEM-PARAFAC可以半定量辨析水体污染源,可为不同的区域水质恢复与治水策略制定提供针对性数据支撑. 相似文献
84.
四斗朱水库蓝藻水华爆发成因分析及治理对策研究 总被引:1,自引:0,他引:1
作为饮用水源的小型水库四斗朱连续几年在早春即开始爆发严重束丝藻水华(属于蓝藻)。水质分析发现,四斗朱水库的水质参数如总氮(TN)、总磷(TP)、氨氮(NH4^+-N)以及BOD和COD浓度并不高,但明显高于其上游的石门塘水库,这说明在四斗朱水库的集水区存在污染源。本文分析了在低营养盐浓度情况下四斗朱水库蓝藻水华爆发的原因,认为由于集水区内的农业、生活、水土淋失以及自然沉降等途径导致水库营养浓度升高。并由于未知营养、气温回升以及水库生态系统失衡等因素,导致蓝藻水华暴发。最后,提出了相应的综合治理对策。 相似文献
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在常态化疫情防控背景下,为避免本土病例造成区域不同需求主体防护物资短缺问题,构建最小化医院物资集散点需求未满足率加权和、最大化物资购买集中点分配公平性的储备库选址-分配模型,并基于某市相关数据,利用改进的非支配排序遗传算法(NSGA-Ⅱ)进行仿真研究。结果表明:某市应选择储备库数目为5,在物资分配时考虑物资防护等级要求,可减少医院物资集散点物资浪费,增加物资购买集中点获得量。 相似文献
87.
Species distribution modeling (SDM) is increasingly used to reveal biogeographical relationships, for example the sympatric range for species coexistence, and fundamental questions about niche evolution between related species. We explored the sympatric ranges between three Procapra species (Procapra przewalskii, Procapra Picticaudata, and Procapra gutturosa) via two methods of defining the study region (method 1, in which models were developed in a larger region including the whole geographic range of Procapra, and method 2 in which a smaller region surrounding focal species’ localities was used and then projected to the larger region). We also quantified environmental niche divergence between gazelles across the whole range in Procapra. Models for gazelles generally performed well. Compared with method 2, method 1 led to larger predicted areas with high suitability and was less concentrated around known localities. Clamping, which deals with variables outside the training range, varied between gazelles and occurred primarily in regions unsuitable for respective species. For all gazelle pairs, models revealed an overlap zone where more than one species should occur, while the estimates varied between the two methods. Moreover, we found that the niche overlap was closely associated with geographic distance but not with phylogenetic distance among gazelles. Our findings indicate that SDM is a useful tool for testing whether related species tend to be in sympatry at large scales, with method 1 leading to more realistic predictions for Procapra. This study provides evidence of a distinct niche divergence among related species and supports the theory that ecological speciation plays a significant role in lineage generation. 相似文献
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89.
Kan Yuna Zhai Shengcheng Chen Bingwei Pan Mingzhu Fan Xiaodong Leng Weiqi 《Journal of Polymers and the Environment》2022,30(6):2355-2365
Journal of Polymers and the Environment - The study investigated the effect of lignocellulosic biomass filler decayed by brown-rot fungi on the preparation and properties of polyurethane (PU) foam.... 相似文献
90.
香蕉茎秆、桉树皮和猪粪不同配比堆肥研究 总被引:1,自引:0,他引:1
通过固定猪粪添加量,依次增加桉树皮添加量,减少香蕉茎秆添加量,研究了桉树皮、香蕉茎秆和猪粪不同配比,不同C/N比值等对堆肥温度、pH值、微生物数量以及种子发芽率等堆肥发酵指标的影响,并用腐熟的有机肥进行香蕉幼苗盆栽试验。结果表明,堆肥材料C/N比值为25.24和27.01的处理堆肥温度较高,均达到56℃以上,持续高温时间分别为10和11 d,堆肥中各养分含量相对较高,达到NY 525—2012《有机肥料》标准。盆栽试验也表明,利用堆肥材料C/N比值为25.24和27.01的堆肥配制的有机肥对盆栽香蕉幼苗有一定的促生效果。 相似文献