The influence of slope collapse on water exchange between a pit lake and a heterogeneous aquifer

Slope collapse will reduce the water exchange. Slope collapse will affect the spatial distribution of the water exchange. Precipitation have the most impact on the dynamics of the water exchange. Due to the increase in open pit mining, pit lakes have become common surface water features, posing a potential risk to subsurface aquifer. In this study, a pit lake–groundwater interaction model is built based on the general program MODFLOW with the LAK3 package. For the first time, the effects of lake-slope collapse and aquifer heterogeneity on pit lake–groundwater interactions are analyzed by dividing the lake into six water exchange zones based on the aquifer lithology and groundwater level. Our investigation and simulations reveal a total water exchange from groundwater to the lake of 349000 m³/a without collapse of the pit lake slope, while the total net water exchange under slope collapse conditions is 248000 m³/a (i.e., a reduction of 1.40-fold). The monthly net water exchange per unit width from groundwater to the lake reaches the largest in April, shifting to negative values in zone IV from June to August and in zone V in June and July. Moreover, the monthly net water exchange per unit width decreases from north to south, and the direction and magnitude of water exchange are found to depend on the hydraulic gradients between the lake and groundwater and the hydraulic conductivity of the slope collapse.     

基于云模型的隧道塌方风险等级评价

针对造成隧道塌方事故影响因子的复杂性和模糊性,基于云模型理论,选取影响隧道塌方风险的10项因子,建立了4个风险等级的隧道塌方风险评价模型。根据云模型的数字特征计算规则计算各因子隶属于不同风险等级的云模型数字特征,结合正向正态云发生器和各项评价因子的权重,获得云模型的综合确定度,最终由最大综合确定度确定隧道塌方风险等级。工程实例样本应用中,构建的隧道塌方风险评价云模型和模糊综合评价模型的评价结果相符,同时与相应的设计施工方案和施工安全风险评估报告的结果相吻合,表明该模型的可行性与有效性,体现出云模型中定性语言描述和定量数值间不确定转换的优点,且结果便于工程应用。     

Metrics for quantifying how much different threats contribute to red lists of species and ecosystems

Red lists are a crucial tool for the management of threatened species and ecosystems. Among the information red lists provide, the threats affecting the listed species or ecosystem, such as pollution or hunting, are of special relevance. This information can be used to quantify the relative contribution of different threat factors to biodiversity loss by disaggregating the cumulative extinction risk across species into components that can be attributed to certain threats. We devised and compared 3 metrics that accomplish this and may be used as indicators. The first metric calculates the portion of the temporal change in red list index (RLI) values that is caused by each threat. The second metric attributes the deviation of an RLI value from its reference value to different threats. The third metric uses extinction probabilities that are inferred from red list categories to estimate the contribution of a threat to the expected loss of species or ecosystems within 50 years. We used data from Norwegian Red Lists to test and evaluate these metrics. The first metric captured only a minor portion of the biodiversity loss caused by threats because it ignores species whose red list category does not change. Management authorities will often be interested in the contribution of a given threat to the total deviation from the optimal state. This was measured by the remaining metrics. The second metric was best suited for comparisons across countries or taxonomic groups. The third metric conveyed the same information but uses numbers of species or ecosystem as its unit, which is likely more intuitive to lay people and may be preferred when communicating with stakeholders or the general public.     

基于需求时间的隧道塌方应急资源分级调度研究

为打破对物资送达时间的绝对性限制,均衡关注关键考量因素,提出需求时间的概念,借助ArcGIS绘制需求时间服务范围;考虑救援需求的不确定性,在需求时间服务范围内建立模型对应急资源进行分级调度,并对关键路段及交叉口制定应急交通管控预案.模型包括2部分,在路径决策方面,建立带需求时间和畅通可靠度阈值约束的路径选择决策综合评价...     

动态安全系统理论的研究与应用

将量子纠缠理论引入安全理论中,提出安全与危险纠缠机制;指出人们当前所处的“安全”的状态,实质上是“安全与风险叠加”的状态,是不确定的;而相对于当前的状态,之前的状态实质上是安全的,是确定的,由此重新给出了安全的新认知。再以安危纠缠和安全新认知为理论基础,建立了动态安全系统理论,给安全管理与事故预防提供了新思想和新方向。然后借由塔吊生产系统,展示了动态安全系统理论的应用,定量分析系统内部安全程度,从而使安全管理步入动态的定量化管理阶段。     

淮南大通浅覆盖岩溶区塌陷分布及土地利用可行性

通过地质调查、钻探、物探等方法对淮南大通浅覆盖岩溶区岩溶塌陷的分布特征及诱因进行了分析,结果表明,大通浅覆盖岩溶区岩溶塌陷主要分布于下伏奥陶系马家沟组地层之上,以及构造发育区和松散层粉土含量较高区,岩溶塌陷主要受岩石溶蚀程度、强烈地下水动力条件及松散层厚度、成分等控制。结合岩溶塌陷发育特征及场地具体条件,探讨了大通浅覆盖型岩溶区土地利用的可行性,为土地综合开发利用提供参考。     

多高层钢结构耐火性能的子结构分析模型与分析方法

基于整体钢结构在局部火灾下的反应规律,将高层钢结构的初始倒塌破坏类型进行了分类(中间柱初始倒塌、边柱初始倒塌以及梁柱同时倒塌),根据整体结构约束影响和荷载影响,提出局部火灾下多高层钢结构耐火性能分析的相应子结构分析模型及其分析方法。子结构模型的边界充分考虑周围约束的影响,尤其是周围梁和上层柱构件以及层数的影响。针对不同类型的子结构模型,通过建立相应的具体子结构有限元模型,合理考虑边界条件的影响。最后基于建立的数值模型,研究了子结构的火灾反应规律与破坏机理,并与整体结构的分析结果进行了比较,结果表明:子结构分析模型与分析方法可以合理准确地分析整体结构的耐火性能。     

石膏矿采空区上覆岩层冒落规律与危险性评价

为对上覆岩层冒落的危险性进行有效评价,在工程实勘的基础上,将石膏矿上覆岩层的自然冒落作为一个逐级发展的过程来处理,并根据普氏平衡拱理论对各级拱形作出2点假定,即冒落拱顶部弧线为抛物线,矿柱按θ角剥蚀。提出以临界松散系数K作为其危险性评价因子,并根据所建立的一般冒落拱模型,分别推导得到条带矿柱及间隔点柱区域关于K的计算公式。最后,将该评价因子用于工程实际,实现对邵东石膏矿采空区的危险性分级。该评价体系,即可对石膏矿地表塌陷作出有效预测,也可对石膏矿地表危险程度进行合理分级。     

Loss of an ecological baseline through the eradication of oyster reefs from coastal ecosystems and human memory

Oyster reefs form over extensive areas and the diversity and productivity of sheltered coasts depend on them. Due to the relatively recent population growth of coastal settlements in Australia, we were able to evaluate the collapse and extirpation of native oyster reefs (Ostrea angasi) over the course of a commercial fishery. We used historical records to quantify commercial catch of O. angasi in southern Australia from early colonization, around 1836, to some of the last recorded catches in 1944 and used our estimates of catch and effort to map their past distribution and assess oyster abundance over 180 years. Significant declines in catch and effort occurred from 1886 to 1946 and no native oyster reefs occur today, but historically oyster reefs extended across more than 1,500 km of coastline. That oyster reefs were characteristic of much of the coastline of South Australia from 1836 to 1910 appears not to be known because there is no contemporary consideration of their ecological and economic value. Based on the concept of a shifted baseline, we consider this contemporary state to reflect a collective, intergenerational amnesia. Our model of generational amnesia accounts for differences in intergenerational expectations of food, economic value, and ecosystem services of nearshore areas. An ecological system that once surrounded much of the coast and possibly the past presence of oyster reefs altogether may be forgotten and could not only undermine progress towards their recovery, but also reduce our expectations of these coastal ecosystems. La Pérdida de una Línea de Base Ecológica por Medio de la Erradicación de Arrecifes de Ostión de los Ecosistemas Costeros y la Memoria Humana     

Risk Assessment of Inbreeding and Outbreeding Depression in a Captive‐Breeding Program

Captive‐breeding programs can be implemented to preserve the genetic diversity of endangered populations such that the controlled release of captive‐bred individuals into the wild may promote recovery. A common difficulty, however, is that programs are founded with limited wild broodstock, and inbreeding can become increasingly difficult to avoid with successive generations in captivity. Program managers must choose between maintaining the genetic purity of populations, at the risk of inbreeding depression, or interbreeding populations, at the risk of outbreeding depression. We evaluate these relative risks in a captive‐breeding program for 3 endangered populations of Atlantic salmon (Salmo salar). In each of 2 years, we released juvenile F₁ and F₂ interpopulation hybrids, backcrosses, as well as inbred and noninbred within‐population crosstypes into 9 wild streams. Juvenile size and survival was quantified in each year. Few crosstype effects were observed, but interestingly, the relative fitness consequences of inbreeding and outbreeding varied from year to year. Temporal variation in environmental quality might have driven some of these annual differences, by exacerbating the importance of maternal effects on juvenile fitness in a year of low environmental quality and by affecting the severity of inbreeding depression differently in different years. Nonetheless, inbreeding was more consistently associated with a negative effect on fitness, whereas the consequences of outbreeding were less predictable. Considering the challenges associated with a sound risk assessment in the wild and given that the effect of inbreeding on fitness is relatively predictable, we suggest that risk can be weighted more strongly in terms of the probable outcome of outbreeding. Factors such as genetic similarities between populations and the number of generations in isolation can sometimes be used to assess outbreeding risk, in lieu of experimentation. Evaluación del Riesgo de Depresión por Endogamia y Exogamia en un Programa de Reproducción en Cautiverio