基于主逻辑图的安全风险建模研究

概率风险评估已成为研究复杂系统安全风险较为成熟的方法 ,其风险模型的建立是基于故障树/事件树的 ,风险分析具有众多的静态特性。然而 ,大的复杂系统往往存在诸多动态因素 ,在风险研究需要考虑这些动态因素的情况下 ,基于传统故障树 /事件树的模型则难以提供支持。笔者对此进行了分析 ,提出了基于主逻辑图的安全风险建模 ;主要介绍了主逻辑图的概念及其建模方法 ,并对模型进行了分析 ;在此基础上 ,基于主逻辑图分析事故场景 ,对场景风险的量化评估进行了简要介绍 ,并结合某核反应堆例子进行了分析。     

铁路集装箱空箱安全高效调拨的计算机算法

铁路集装箱安全运输的重要内容是确保集装箱运输的连续性 ,而集装箱空箱的高效率、低成本的调拨是铁路集装箱运输连续性的重要前提。为此 ,笔者提出了一种解决铁路路网上集装箱空箱调拨问题的计算机算法 ,该算法将此类问题视为一种特定的运输问题去求解 ,其目标是使得调拨集装箱的运输费用 (箱·公里 )最小 ,费用系数是两个相关站点的最短运输距离 ,并给出集装箱调拨的算例 ,实例证明了该算法是富有效率且可行性好 ,能够满足铁路集装箱运输的高效、快速、便捷运输要求。     

近断层强震速度脉冲效应及连续梁桥减隔震特性分析

应用非线性时程分析的方法 ,对于减、隔震连续桥梁在近场地震作用下的有效性和响应特性 ,作了深入的研究。通过有代表性的脉冲型近场强震记录时程分析 ,提出了用速度脉冲峰值及其周期之积来表示速度脉冲能量的方法 ,计算表明近场地震速度脉冲波能近似表征地震动破坏能力的大小 ,它和桥梁结构承受的地震响应大体成正比例关系。铅芯橡胶隔震支座在近场地震作用下仍然适用 ,但对于个别脉冲型强震记录效果不够明显 ,支座参数有必要进行优化。     

How does eliminating mercury from artisanal and small-scale gold mining lead to achieving sustainable development goals?

Artisanal and small-scale gold mining (ASGM) is the principal anthropogenic activity that globally contributes to overloading our environment with mercury. Although the Minamata Convention, led by the United Nations, is a crucial instrument to eliminate its use progressively, novel approaches to accelerate this difficult transition are welcome. This article proposes a framework for policy-making or improvement, fostering the enforcement of mercury elimination through the lens of the 17 Sustainable Development Goals (SDGs), focusing on the excluded artisanal and small-scale gold miners and their dependents. We move forward with a literature review of the Artisanal and Small Mining topic, taking each SDG as a unit of analysis. Understanding the problem as a puzzle of four sets of pieces, namely: (1) social, (2) environmental, (3) economic, and (4) institutional, the paper offers potential opportunities for the decision-makers and practitioners to accelerate the substitution of this heavy metal and develop sustainable futures for the ASGM communities. We conclude by proposing a pragmatic framework that synthesizes the means, actions, and ends to accelerate a sustainable transition.     

Prenatal diagnosis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in a family with a previous fatal case of sudden unexpected death in childhood

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a potentially fatal inherited disease with a carrier frequency of approximately 1:100 in most Caucasian populations. The disease is implicated in sudden unexpected death in childhood. A prevalent disease-causing point mutation (A985G) in the MCAD gene has been characterized, thus rendering diagnosis easy in the majority of cases. Since the clinical spectrum of MCAD deficiency ranges from death in the first days of life to an asymptomatic life, there are probably other genetic factors—in addition to MCAD mutations—involved in the expression of the disease. Thus, families who have experienced the death of a child from MCAD deficiency might have an increased risk of a seriously affected subsequent child. In such a family we have therefore performed a prenatal diagnosis on a chorionic villus sample by a highly specific and sensitive polymerase chain reaction (PCR) assay for the G985 mutation. The analysis was positive and resulted in abortion. We verified the diagnosis by direct analysis on blood spots and other tissue material from the aborted fetus and from family members.     

Comparing the Extent and Permanence of Headwater Streams From Two Field Surveys to Values From Hydrographic Databases and Maps

Supreme Court cases have questioned if jurisdiction under the Clean Water Act extends to water bodies such as streams without year‐round flow. Headwater streams are central to this issue because many periodically dry, and because little is known about their influence on navigable waters. An accurate account of the extent and flow permanence of headwater streams is critical to estimating downstream contributions. We compared the extent and permanence of headwater streams from two field surveys with values from databases and maps. The first used data from 29 headwater streams in nine U.S. forests, whereas the second had data from 178 headwater streams in Oregon. Synthetic networks developed from the nine‐forest survey indicated that 33 to 93% of the channel lacked year‐round flow. Seven of the nine forests were predicted to have >200% more channel length than portrayed in the high‐resolution National Hydrography Dataset (NHD). The NHD and topographic map classifications of permanence agreed with ~50% of the field determinations across ~300 headwater sites. Classification agreement with the field determinations generally increased with increasing resolution. However, the flow classification on soil maps only agreed with ~30% of the field determination despite depicting greater channel extent than other maps. Maps that include streams regardless of permanence and size will aid regulatory decisions and are fundamental to improving water quality monitoring and models.     

Vertebrate diet decreases winter torpor use in a desert marsupial

One of the energetic benefits of daily torpor over prolonged hibernation is that it enables animals to regularly forage and, therefore, replenish food reserves between bouts of torpor. However, little is known about the diet of predators undergoing torpor or whether differences in prey composition among individuals influence torpor characteristics. Here, we test the hypothesis that prey composition affects winter torpor use and patterns of a population of carnivorous marsupial, the brush-tailed mulgara (Dasycercus blythi), in the Great Sandy Desert, Australia. Mulgaras in the study population captured a wide range of prey including vertebrates (mammals, reptiles, birds), seven insect orders, spiders and centipedes. The proportion of vertebrates in the diet was negatively correlated with both frequency of torpor use and maximum bout duration. This variation in torpor use with diet can be explained by the higher energetic content of vertebrates as well as their larger size. Even assuming uniform intake of prey biomass among individuals, those that subsisted on an invertebrate-dominated diet during winter apparently suffered energetic shortages as a result of the scarcity of invertebrate taxa with high energy content (such as insect larvae). Our study is the first to demonstrate a link between diet composition and daily torpor use in a free-ranging mammal.     

Introduction of early amniocentesis to routine prenatal diagnosis

With growing awareness of the problems associated with prenatal cytogenetic diagnoses after CVS, attempts have been made to provide early amniocentesis as an alternative to CVS. Since 1990, at our clinic the gestational age limit for routine diagnostic amniocentesis has been successively lowered, first to 14 and then to 13 weeks of gestation. Thus, 811 prenatal diagnoses were performed after early amniocentesis at 13 weeks (n = 217) and at 14 weeks of gestation (n = 594). No problems were encountered. Culture failure was never observed in the early samples. Using the criteria ‘number of colonies’ and ‘culture duration until harvest’, early samples taken at 14 weeks did not differ significantly from the controls after standard amniocentesis performed at 15 and 16 weeks, respectively, whereas a minority of samples taken at 13 weeks experienced some delay in culturing. However, in each group at least 85 per cent of samples led to a diagnosis fulfilling our standard criteria of a safe diagnosis (at least 20 metaphases of at least five colonies from at least one primary culture after trypsinization) within 15 days. Some differences between the different groups can be recognized: culture duration of less than 11 days tends to be increasing after standard amniocentesis, whereas long culture duration (more than 20 days) is more often associated with early amniocentesis. However, this trend is only minimal and did not result in an increased risk of missing a diagnosis.